While these samples are representative of the content of Science.gov,

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of Science.gov

to obtain the most current and comprehensive results.

Last update: August 15, 2014.

1

For bottom-up proteomics there are a wide variety of database searching algorithms in use for matching peptide sequences to tandem MS spectra. Likewise, there are numerous strategies being employed to produce a confident list of peptide identifications from the different search algorithm outputs. Here we introduce a grid search approach for determining optimal database filtering criteria in shotgun proteomics data analyses that is easily adaptable to any search. Systematic Trial and Error Parameter Selection - referred to as STEPS - utilizes user-defined parameter ranges to test a wide array of parameter combinations to arrive at an optimal "parameter set" for data filtering, thus maximizing confident identifications. The benefits of this approach in terms of numbers of true positive identifications are demonstrated using datasets derived from immunoaffinity-depleted blood serum and a bacterial cell lysate, two common proteomics sample types.

Piehowski, Paul D.; Petyuk, Vladislav A.; Sandoval, John D.; Burnum, Kristin E.; Kiebel, Gary R.; Monroe, Matthew E.; Anderson, Gordon A.; Camp, David G.; Smith, Richard D.

2013-03-01

2

Optimum digital recursive filters for step scan phased array radars

A design method for recursive filters with optimum clutter rejection is presented. The designed filters are suitable for MTI (moving target indication) systems in step scan phased array radars. The designed filters are optimized for a given clutter power spectrum and a finite number of samples without initialization. The performance of the designed filters was studied by considering their clutter

Hussian Al-Ahmad; Gordon B. Lockhart

1991-01-01

3

We derive optimal filters on the sphere in the context of detecting compact objects embedded in a stochastic background process. The matched filter and the scale adaptiv e filter are derived on the sphere in the most general setting, allowing for directional template profiles and filters. The p erfor- mance and relative merits of the two optimal filters are discu

Jason D. Mcewen; Michael P. Hobson; Anthony N. Lasenby

2008-01-01

4

National Technical Information Service (NTIS)

This report summarizes the results obtained during the contract No. F 19628-88-K-0018 entitled 'Optimal Phase-only Filters'. This research was focused on Phase-only Filters (POFs) and Binary Phase-only Filters (BPOFs). We prove in this report that the con...

B. V. Kumar Z. Bahri

1990-01-01

5

Optimal filtering and filter stability of linear stochastic delay systems

NASA Technical Reports Server (NTRS)

Optimal filtering equations are obtained for very general linear stochastic delay systems. Stability of the optimal filter is studied in the case where there are no delays in the observations. Using the duality between linear filtering and control, asymptotic stability of the optimal filter is proved. Finally, the cascade of the optimal filter and the deterministic optimal quadratic control system is shown to be asymptotically stable as well.

Kwong, R. H.-S.; Willsky, A. S.

1977-01-01

6

Optimal real correlation filters

NASA Technical Reports Server (NTRS)

Expressions are derived for real filters that have a maximum correlation signal to noise ratio. Both continuous and discrete cases are treated and shown to have similar forms. The signal can be complex, and the case of a real signal is considered and related to previous results.

Juday, Richard D.; Vijaya Kumar, B. V. K.; Rajan, P. Karivaratha

1991-01-01

7

Stepped Triangular CIC-Cosine Decimation Filter

This paper presents a new two-stage CIC-cosine decimation filter. The original CIC filter is replaced by a two-stage CIC structure where the first section is realized in a nonrecursive form, and the second section is a CIC filter which works at lower rate that depends on the decimation factor of the first stage. Using the polyphase decomposition, the subfilters of

G. J. Dolecek; S. K. Mitra

2006-01-01

8

Optimal PHD filter for single-target detection and tracking

NASA Astrophysics Data System (ADS)

The PHD filter has attracted much international interest since its introduction in 2000. It is based on two approximations. First, it is a first-order approximation of the multitarget Bayes filter. Second, to achieve closed-form formulas for the Bayes data-update step, the predicted multitarget probability distribution must be assumed Poisson. In this paper we show how to derive an optimal PHD (OPHD) filter, given that target number does not exceed one. (That is, we restrict ourselves to the single-target detection and tracking problem.) We further show that, assuming no more than a single target, the following are identical: (1) the multitarget Bayes filter; (2) the OPHD filter; (3) the CPHD filter; and (4) the multi-hypothesis correlation (MHC) filter. We also note that all of these are generalizations of the probabilistic data association (IPDA) filter of Musicki, Evans, and Stankovic.

Maher, Ronald

2007-08-01

9

OPTIMIZATION OF ADVANCED FILTER SYSTEMS

Two advanced, hot gas, barrier filter system concepts have been proposed by the Siemens Westinghouse Power Corporation to improve the reliability and availability of barrier filter systems in applications such as PFBC and IGCC power generation. The two hot gas, barrier filter system concepts, the inverted candle filter system and the sheet filter system, were the focus of bench-scale testing, data evaluations, and commercial cost evaluations to assess their feasibility as viable barrier filter systems. The program results show that the inverted candle filter system has high potential to be a highly reliable, commercially successful, hot gas, barrier filter system. Some types of thin-walled, standard candle filter elements can be used directly as inverted candle filter elements, and the development of a new type of filter element is not a requirement of this technology. Six types of inverted candle filter elements were procured and assessed in the program in cold flow and high-temperature test campaigns. The thin-walled McDermott 610 CFCC inverted candle filter elements, and the thin-walled Pall iron aluminide inverted candle filter elements are the best candidates for demonstration of the technology. Although the capital cost of the inverted candle filter system is estimated to range from about 0 to 15% greater than the capital cost of the standard candle filter system, the operating cost and life-cycle cost of the inverted candle filter system is expected to be superior to that of the standard candle filter system. Improved hot gas, barrier filter system availability will result in improved overall power plant economics. The inverted candle filter system is recommended for continued development through larger-scale testing in a coal-fueled test facility, and inverted candle containment equipment has been fabricated and shipped to a gasifier development site for potential future testing. Two types of sheet filter elements were procured and assessed in the program through cold flow and high-temperature testing. The Blasch, mullite-bonded alumina sheet filter element is the only candidate currently approaching qualification for demonstration, although this oxide-based, monolithic sheet filter element may be restricted to operating temperatures of 538 C (1000 F) or less. Many other types of ceramic and intermetallic sheet filter elements could be fabricated. The estimated capital cost of the sheet filter system is comparable to the capital cost of the standard candle filter system, although this cost estimate is very uncertain because the commercial price of sheet filter element manufacturing has not been established. The development of the sheet filter system could result in a higher reliability and availability than the standard candle filter system, but not as high as that of the inverted candle filter system. The sheet filter system has not reached the same level of development as the inverted candle filter system, and it will require more design development, filter element fabrication development, small-scale testing and evaluation before larger-scale testing could be recommended.

R.A. Newby; M.A. Alvin; G.J. Bruck; T.E. Lippert; E.E. Smeltzer; M.E. Stampahar

2002-06-30

10

Stepped Triangular CIC Filter for Rational Sample Rate Conversion

The modification of the conventional CIC (cascaded-integrator-comb) filter for rational sample rate conversion (SRC) is presented here, where the conversion factor is a ratio of two mutually prime numbers. Specifically, we consider the case where the decimation factor M can be expressed as a product of two integers. The overall filter realization is based on a stepped triangular form of

Gordana Jovanovic-dolecek; Sanjit K. Mitra

2006-01-01

11

Quantum Filtering and Optimal Control

NASA Astrophysics Data System (ADS)

Quantum mechanical systems exhibit an inherently probabilistic nature upon measurement which excludes in principle the singular direct observability case. Quantum theory of time continuous measurements and quantum filtering developed by VPB on the basis of semi-Markov independent increment models for quantum noise and quantum nondemolition (QND) observability is generalized for demolition indirect measurements of quantum unstable systems satisfying the microcausality principle. The reduced quantum feedback-controlled dynamics is described both by linear semi-Markov and nonlinear conditionally-Markov stochastic master equations. Using this scheme for diffusive and counting measurement to describe the stochastic evolution of the open quantum system under the continuous indirect observation and working in parallel with classical indeterministic control theory, we show the conditionally-Markov Bellman equations for optimal feedback control of the a posteriori stochastic quantum states conditioned upon these measurements. The resulting Bellman equation for the diffusive observation is then applied to the explicitly solvable quantum linear-quadratic-Gaussian (LQG) problem which emphasizes many similarities with the corresponding classical control problem.

Belavkin, Viacheslav P.; Edwards, Simon

2008-08-01

12

Estimation of optimal Kalman filter gain from non-optimal filter residuals

NASA Technical Reports Server (NTRS)

This paper presents a novel method of estimating the optimal steady state Kalman filter gain of a linear discrete time-invariant system from a non-optimal Kalman filter residual sequence. The relation between the optimal residual sequence and a signal derived from the non-optimal residual sequence is described by a Moving Average (MA) model whose coefficients are expressed in terms of the state space parameters and the optimal steady state Kalman filter gain. In order to identify the MA model, a whitening filter of the derived signal, which corresponds to an AutoRegressive (AR) model of the signal, is first identified using the least-squares method. Then the inverse filter of the whitening filter, which corresponds to the MA model, is calculated. From the coefficients of the identified MA model, the optimal steady state Kalman filter gain can be obtained. Numerical example is provided to illustrate the feasibility of this approach.

Chen, Chung-Wen; Huang, Jen-Kuang

1991-01-01

13

Optimal approximation algorithms for digital filter design

NASA Astrophysics Data System (ADS)

Several new algorithms are presented for the optimal approximation and design of various classes of digital filters. An iterative algorithm is developed for the efficient design of unconstrained and constrained infinite impulse response (IIR) digital filters. Both in the unconstrained and constrained cases, the numerator and denominator of the filter transfer function are designed iteratively by recourse to the Remez algorithm and to appropriate design parameters and criteria, at each iteration. This makes it possible for the algorithm to be implemented by means of a short main program which uses (at each iteration) the linear phase FIR filter design algorithm of McClellan et al. as a subroutine. The approach taken also permits the filter to be designed with a desired ripple ratio. Also, the algorithm determines automatically the minimum passband ripple corresponding to the prescribed orders and band edges of the filter. The filter is designed directly without guessing the passband ripple or stopband ripple.

Liang, J. K.

14

Steps Toward Optimal Competitive Scheduling

NASA Technical Reports Server (NTRS)

This paper is concerned with the problem of allocating a unit capacity resource to multiple users within a pre-defined time period. The resource is indivisible, so that at most one user can use it at each time instance. However, different users may use it at different times. The users have independent, se@sh preferences for when and for how long they are allocated this resource. Thus, they value different resource access durations differently, and they value different time slots differently. We seek an optimal allocation schedule for this resource. This problem arises in many institutional settings where, e.g., different departments, agencies, or personal, compete for a single resource. We are particularly motivated by the problem of scheduling NASA's Deep Space Satellite Network (DSN) among different users within NASA. Access to DSN is needed for transmitting data from various space missions to Earth. Each mission has different needs for DSN time, depending on satellite and planetary orbits. Typically, the DSN is over-subscribed, in that not all missions will be allocated as much time as they want. This leads to various inefficiencies - missions spend much time and resource lobbying for their time, often exaggerating their needs. NASA, on the other hand, would like to make optimal use of this resource, ensuring that the good for NASA is maximized. This raises the thorny problem of how to measure the utility to NASA of each allocation. In the typical case, it is difficult for the central agency, NASA in our case, to assess the value of each interval to each user - this is really only known to the users who understand their needs. Thus, our problem is more precisely formulated as follows: find an allocation schedule for the resource that maximizes the sum of users preferences, when the preference values are private information of the users. We bypass this problem by making the assumptions that one can assign money to customers. This assumption is reasonable; a committee is usually in charge of deciding the priority of each mission competing for access to the DSN within a time period while scheduling. Instead, we can assume that the committee assigns a budget to each mission.This paper is concerned with the problem of allocating a unit capacity resource to multiple users within a pre-defined time period. The resource is indivisible, so that at most one user can use it at each time instance. However, different users may use it at different times. The users have independent, se@sh preferences for when and for how long they are allocated this resource. Thus, they value different resource access durations differently, and they value different time slots differently. We seek an optimal allocation schedule for this resource. This problem arises in many institutional settings where, e.g., different departments, agencies, or personal, compete for a single resource. We are particularly motivated by the problem of scheduling NASA's Deep Space Satellite Network (DSN) among different users within NASA. Access to DSN is needed for transmitting data from various space missions to Earth. Each mission has different needs for DSN time, depending on satellite and planetary orbits. Typically, the DSN is over-subscribed, in that not all missions will be allocated as much time as they want. This leads to various inefficiencies - missions spend much time and resource lobbying for their time, often exaggerating their needs. NASA, on the other hand, would like to make optimal use of this resource, ensuring that the good for NASA is maximized. This raises the thorny problem of how to measure the utility to NASA of each allocation. In the typical case, it is difficult for the central agency, NASA in our case, to assess the value of each interval to each user - this is really only known to the users who understand their needs. Thus, our problem is more precisely formulated as follows: find an allocation schedule for the resource that maximizes the sum ofsers preferences, when the preference values are private information of the users. We bypass this

Frank, Jeremy; Crawford, James; Khatib, Lina; Brafman, Ronen

2006-01-01

15

Spectral optimized asymmetric segmented phase-only correlation filter.

We suggest a new type of optimized composite filter, i.e., the asymmetric segmented phase-only filter (ASPOF), for improving the effectiveness of a VanderLugt correlator (VLC) when used for face identification. Basically, it consists in merging several reference images after application of a specific spectral optimization method. After segmentation of the spectral filter plane to several areas, each area is assigned to a single winner reference according to a new optimized criterion. The point of the paper is to show that this method offers a significant performance improvement on standard composite filters for face identification. We first briefly revisit composite filters [adapted, phase-only, inverse, compromise optimal, segmented, minimum average correlation energy, optimal trade-off maximum average correlation, and amplitude-modulated phase-only (AMPOF)], which are tools of choice for face recognition based on correlation techniques, and compare their performances with those of the ASPOF. We illustrate some of the drawbacks of current filters for several binary and grayscale image identifications. Next, we describe the optimization steps and introduce the ASPOF that can overcome these technical issues to improve the quality and the reliability of the correlation-based decision. We derive performance measures, i.e., PCE values and receiver operating characteristic curves, to confirm consistency of the results. We numerically find that this filter increases the recognition rate and decreases the false alarm rate. The results show that the discrimination of the ASPOF is comparable to that of the AMPOF, but the ASPOF is more robust than the trade-off maximum average correlation height against rotation and various types of noise sources. Our method has several features that make it amenable to experimental implementation using a VLC. PMID:22614484

Leonard, I; Alfalou, A; Brosseau, C

2012-05-10

16

Optimal Approximation Algorithms for Digital Filter Design.

NASA Astrophysics Data System (ADS)

Several new algorithms are presented for the optimal approximation and design of various classes of digital filters. An iterative algorithm is developed for the efficient design of unconstrained and constrained infinite impulse response (IIR) digital filters. Both in the unconstrained and constrained cases, the numerator and denominator of the filter transfer function are designed iteratively by recourse to the Remez algorithm and to appropriate design parameters and criteria, at each iteration. This makes it possible for the algorithm to be implemented by means of a short main program which uses (at each iteration) the linear phase FIR filter design algorithm of McClellan et al. as a subroutine. The approach taken also permits the filter to be designed with a desired ripple ratio. Also, the algorithm determines automatically the minimum passband ripple corresponding to the prescribed orders and band edges of the filter. The filter is designed directly without guessing the passband ripple or stopband ripple. Another algorithm, based on similar principles, is developed for the design of a nonlinear phase finite impulse response (FIR) filter, whose transfer function optimally approximates a desired magnitude response, there being no constraints imposed on the phase response. A similar algorithm is presented for the design of two new classes of FIR digital filters, one linear phase and the other nonlinear phase. A filter of either class has significantly reduced number of multiplications compared to the one obtained by its conventional counterpart, with respect to a given frequency response. In the case of linear phase, by introducing the new class of digital filters into the design of multistage decimators and interpolators for narrow-band filter implementation, it is found that an efficient narrow-band filter requiring considerably lower multiplication rate than the conventional linear phase FIR design can be obtained. The amount of data storage required by the new class of nonlinear phase FIR filters is significantly less than its linear phase counterpart. Finally, the design of a (finite-impulse-response) FIR digital filter with some of the coefficients constrained to zero is formulated as a linear programming (LP) problem and the LP technique is then used to design this class of constrained FIR digital filters. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI.

Liang, Junn-Kuen

17

On Optimal Infinite Impulse Response Edge Detection Filters

The authors outline the design of an optimal, computationally efficient, infinite impulse response edge detection filter. The optimal filter is computed based on Canny's high signal to noise ratio, good localization criteria, and a criterion on the spurious response of the filter to noise. An expression for the width of the filter, which is appropriate for infinite-length filters, is incorporated

Sudeep Sarkar; Kim L. Boyer

1991-01-01

18

MEDOF - MINIMUM EUCLIDEAN DISTANCE OPTIMAL FILTER

NASA Technical Reports Server (NTRS)

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 values of amplitude and phase for the k whose metric was largest, as well as consistency checks, are reported. A finer search can be done in the neighborhood of the optimal k if desired. The filter finally selected is written to disk in terms of drive values, not in terms of the filter's complex transmittance. Optionally, the impulse response of the filter may be created to permit users to examine the response for the features the algorithm deems important to the recognition process under the selected metric, limitations of the filter SLM, etc. MEDOF uses the filter SLM to its greatest potential, therefore filter competence is not compromised for simplicity of computation. MEDOF is written in C-language for Sun series computers running SunOS. With slight modifications, it has been implemented on DEC VAX series computers using the DEC-C v3.30 compiler, although the documentation does not currently support this platform. MEDOF can also be compiled using Borland International Inc.'s Turbo C++ v1.0, but IBM PC memory restrictions greatly reduce the maximum size of the reference images from which the filters can be calculated. MEDOF requires a two dimensional Fast Fourier Transform (2DFFT). One 2DFFT routine which has been used successfully with MEDOF is a routine found in "Numerical Recipes in C: The Art of Scientific Programming," which is available from Cambridge University Press, New Rochelle, NY 10801. The standard distribution medium for MEDOF is a .25 inch streaming magnetic tape cartridge (Sun QIC-24) in UNIX tar format. MEDOF was developed in 1992-1993.

Barton, R. S.

1994-01-01

19

Optimal design of active EMC filters

NASA Astrophysics Data System (ADS)

A recent trend in automotive industry is adding electrical drive systems to conventional drives. The electrification allows an expansion of energy sources and provides great opportunities for environmental friendly mobility. The electrical powertrain and its components can also cause disturbances which couple into nearby electronic control units and communication cables. Therefore the communication can be degraded or even permanently disrupted. To minimize these interferences, different approaches are possible. One possibility is to use EMC filters. However, the diversity of filters is very large and the determination of an appropriate filter for each application is time-consuming. Therefore, the filter design is determined by using a simulation tool including an effective optimization algorithm. This method leads to improvements in terms of weight, volume and cost.

Chand, B.; Kut, T.; Dickmann, S.

2013-07-01

20

We have proposed an effective method to synthesize and optimize multichannel fiber Bragg grating filters (MCFBGFs). The novel method contains two steps, i.e., the discrete layer peeling algorithm generates the excellent initial guess values and, successively, the nonlinear least squares method reconstructs and optimizes the expected fiber Bragg grating parameters from the initial guess in the previous step. Design examples

Yongkang Gong; Xueming Liu; Leiran Wang; Xiaohong Hu; Aoxiang Lin; Wei Zhao

2009-01-01

21

On optimal infinite impulse response edge detection filters

NASA Technical Reports Server (NTRS)

The authors outline the design of an optimal, computationally efficient, infinite impulse response edge detection filter. The optimal filter is computed based on Canny's high signal to noise ratio, good localization criteria, and a criterion on the spurious response of the filter to noise. An expression for the width of the filter, which is appropriate for infinite-length filters, is incorporated directly in the expression for spurious responses. The three criteria are maximized using the variational method and nonlinear constrained optimization. The optimal filter parameters are tabulated for various values of the filter performance criteria. A complete methodology for implementing the optimal filter using approximating recursive digital filtering is presented. The approximating recursive digital filter is separable into two linear filters operating in two orthogonal directions. The implementation is very simple and computationally efficient, has a constant time of execution for different sizes of the operator, and is readily amenable to real-time hardware implementation.

Sarkar, Sudeep; Boyer, Kim L.

1991-01-01

22

NASA Astrophysics Data System (ADS)

The objective of this work is to analyze the improvement in the performance of the particle filter by including a resample-move step or by using a modified Gaussian particle filter. Specifically, the standard particle filter structure is altered by the inclusion of the Markov chain Monte Carlo move step. The second choice adopted in this study uses the moments of an ensemble Kalman filter analysis to define the importance density function within the Gaussian particle filter structure. Both variants of the standard particle filter are used in the assimilation of densely sampled discharge records into a conceptual rainfall-runoff model. In order to quantify the obtained improvement, discharge root mean square errors are compared for different particle filters, as well as for the ensemble Kalman filter. First, a synthetic experiment is carried out. The results indicate that the performance of the standard particle filter can be improved by the inclusion of the resample-move step, but its effectiveness is limited to situations with limited particle impoverishment. The results also show that the modified Gaussian particle filter outperforms the rest of the filters. Second, a real experiment is carried out in order to validate the findings from the synthetic experiment. The addition of the resample-move step does not show a considerable improvement due to performance limitations in the standard particle filter with real data. On the other hand, when an optimal importance density function is used in the Gaussian particle filter, the results show a considerably improved performance of the particle filter.

Plaza Guingla, D. A.; Pauwels, V. R.; De Lannoy, G. J.; Matgen, P.; Giustarini, L.; De Keyser, R.

2012-12-01

23

Triple band microstrip tri-section bandpass filter using stepped impedance resonators (SIRs) is designed, simulated, built, and measured using hair pin structure. The complete design procedure is given from analytical stage to implementation stage with details The coupling between SIRs is investigated for the first time in detail by studying their effect on the filter characteristics including bandwidth, and attenuation to optimize the filter perfomance. The simulation of the filler is performed using method of moment based 2.5D planar electromagnetic simulator The filter is then implemented on RO4003 material and measured The simulation, and measured results are compared and found to be my close. The effect of coupling on the filter performance is then investigated using electromagnetic simulator It is shown that the coupling effect between SIRs can be used as a design knob to obtain a bandpass Idler with a better performance jar the desired frequency band using the proposed filter topology The results of this work can used in wireless communication systems where multiple frequency bandy are needed

Eroglu, Abdullah [ORNL

2010-01-01

24

Optimal wavelet filter bank design for image fusion

NASA Astrophysics Data System (ADS)

A novel optimization-based method for designing wavelet filter banks in image fusion is proposed. The filter bank design is formulated as a nonlinear optimization problem. The objective function of the optimization problem consists of both the performance metrics of the image fusion, such as the root mean square error (RMSE), and those of individual filters. The optimization problem is solved using simulating annealing.

Liu, Gang; Lv, Xueqin; Huang, Guohong

2007-11-01

25

Program Computes SLM Inputs To Implement Optimal Filters

NASA Technical Reports Server (NTRS)

Minimum Euclidean Distance Optimal Filter (MEDOF) program generates filters for use in optical correlators. Analytically optimizes filters on arbitrary spatial light modulators (SLMs) of such types as coupled, binary, fully complex, and fractional-2pi-phase. Written in C language.

Barton, R. Shane; Juday, Richard D.; Alvarez, Jennifer L.

1995-01-01

26

An optimal receiver using a time-dependent adaptive filter

The optimal time-dependent receiver (OTDR) is presented and shown to be superior to the conventional matched filter receiver when cyclostationary interference is present. This performance advantage is explained by viewing both the OTDR and the conventional matched filter receiver as time-dependent filters that use the spectral correlation properties of the signal. The matched filter is periodic at the baud rate

C. D. Greene; J. H. Reed; T. C. Hsia

1989-01-01

27

Optimal filters with heuristic 1-norm sparsity constraints

NASA Astrophysics Data System (ADS)

We present a design method for sparse optimal Finite Impulse Response (FIR) filters that improve the visibility of a desired stochastic signal corrupted with white Gaussian noise. We emphasize that the filters we seek are of high-order but sparse, thus significantly reducing computational complexity. An optimal FIR filter for the estimation of a desired signal corrupted with white noise can be designed by maximizing the signal-to-noise ratio (SNR) of the filter output with the constraint that the magnitude (in 2-norm) of the FIR filter coefficients are set to unity.1, 2 This optimization problem is in essence maximizing the Rayleigh quotient and is thus equivalent to finding the eigenvector with the largest eigenvalue.3 While such filters are optimal, they are rarely sparse. To ensure sparsity, one must introduce a cardinality constraint in the optimization procedure. For high order filters such constraints are computationally burdensome due to the combinatorial search space. We relax the cardinality constraint by using the 1-norm approximation of the cardinality function. This is a relaxation heuristic similar to the recent sparse filter design work of Baran, Wei, and Oppenheim.4 The advantage of this relaxation heuristic is that the solutions tend to be sparse and the optimization procedure reduces to a convex program, thus ensuring global optimality. In addition to our proposed optimization procedure for deriving sparse FIR filters, we show examples where sparse high-order filters significantly perform better than low-order filters, whereas complexity is reduced by a factor of 10.

Yazdani, Mehrdad; Hecht-Nielsen, Robert

2011-09-01

28

NASA Technical Reports Server (NTRS)

This estimator breaks a nonlinear estimation problem into a set of over determined 'first step' states which are linear in the observations and 'second step' states which are ultimately the states of interest. Linear estimation methods are applied to filter the observations and produce the optimal first step state estimate. The 'second step' states are obtained through iterative nonlinear parameter estimation considering the first step states as observations. It has been shown that this process exactly minimizes the least squares cost function for static problems and provides a better solution than the iterated extended Kalman filter (EKF) for dynamic problems. The two step filter is applied in this paper to process range and range rate measurements between the two spacecraft. Details of the application of the two step estimator to this problem will be given, highlighting the use of a test for ill-conditioned covariance estimates that can result from the first order covariance propagation. A comparison will be made between the performance of the two step filter and the IEKF.

Garrison, James L.; Axelrad, Penina

1997-01-01

29

Computations of Two-Dimensional Step Flow Preceding an Air Filter

Computations were performed for two-dimensional step flows with part of the downstream domain an air filter. The study was motivated by the problems of flow separation and flow distribution through filters in automotive air filter housings. A second-order accurate, two-step, time-split, finite difference method was used to solve the Navier-Stokes equations. The filter is modeled as a homogeneous porous medium

S. Yao; F. W. Chambers

1998-01-01

30

Optimal filters for detecting cosmic bubble collisions

NASA Astrophysics Data System (ADS)

A number of well-motivated extensions of the ?CDM concordance cosmological model postulate the existence of a population of sources embedded in the cosmic microwave background. One such example is the signature of cosmic bubble collisions which arise in models of eternal inflation. The most unambiguous way to test these scenarios is to evaluate the full posterior probability distribution of the global parameters defining the theory; however, a direct evaluation is computationally impractical on large datasets, such as those obtained by the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck. A method to approximate the full posterior has been developed recently, which requires as an input a set of candidate sources which are most likely to give the largest contribution to the likelihood. In this article, we present an improved algorithm for detecting candidate sources using optimal filters, and apply it to detect candidate bubble collision signatures in WMAP 7-year observations. We show both theoretically and through simulations that this algorithm provides an enhancement in sensitivity over previous methods by a factor of approximately two. Moreover, no other filter-based approach can provide a superior enhancement of these signatures. Applying our algorithm to WMAP 7-year observations, we detect eight new candidate bubble collision signatures for follow-up analysis.

McEwen, J. D.; Feeney, S. M.; Johnson, M. C.; Peiris, H. V.

2012-05-01

31

Fast analysis and optimization of combline filters using FEM

We analyze a combline filter using the Finite Element Method (FEM) with ports where the tuning screws would normally be. The filter is tuned with a circuit simulator using the multiport S-parameter data and lumped capacitors at the ports. We can then optimize the combline filter very rapidly by mapping the “coarse” circuit model to the “fine” FEM model. This

Daniel G. Swanson; Robert J. Wenzel

2001-01-01

32

A monothically integrated dual-wavelength photodetector with a step-shaped Fabry-Pérot filter

NASA Astrophysics Data System (ADS)

A novel long wavelength photodetector with dual-wavelength response has been designed and fabricated, which can be realized by a step-shaped Fabry-Perot (F-P) filter structure. By using low pressure metal organic chemical vapor deposition (LP-MOCVD), the step-shaped GaAs/AlGaAs distributed Bragg reflectors (DBR) and the InP PIN photodetector are grown on a GaAs substrate, and by employing a thin low temperature buffer layer, the high quality GaAs/InP heteroepitaxy is realized. The structure of the photodetector is optimized by theoretical simulation. This device has a dual-peak distance of 19nm (1558, 1577 nm). The peak quantum efficiency of 8.5% around 1558 nm and 8.6% around 1577 nm, the 3dB bandwidth of 16 GHz are simultaneously obtained.

Fan, Xinye; Huang, Yongqing; Ren, Xiaomin; Duan, Xiaofeng; Hu, Fuquan; Wang, Qi; Cai, Shiwei

2012-10-01

33

Application of Stepped-Impedance Technique for Bandwidth Control of Dual-Band Filters

This paper demonstrates application of the popular stepped-impedance technique to control the bandwidths of dual-band filters independently. Unlike previous dual-band stepped-impedance filters, the role of the stepped-impedance technique is to control the bandwidths of the two bands rather than to provide dual-band performance. The exact relationship between stepped-impedance ratios and the ratio of the two absolute bandwidths is obtained through

Jungje Ha; Seungku Lee; Byung-Wook Min; Yongshik Lee

2012-01-01

34

A new approach to optimal nonlinear filtering

The classical approach to designing filters for systems where system equations are linear and measurement equations are nonlinear is to linearise measurement equations, and apply an extended Kalman filter (EKF). This results in suboptimal, biased, and often divergent filters. Many schemes proposed to improve the performance of the EKF concentrated on better linearisation techniques, iterative techniques and adaptive schemes. The

Subhash Challa; Farhan A. Faruqi

1997-01-01

35

Computations of Two-Dimensional Step Flow Preceding an Air Filter

NASA Astrophysics Data System (ADS)

Computations were performed for two-dimensional step flows with part of the downstream domain an air filter. The study was motivated by the problems of flow separation and flow distribution through filters in automotive air filter housings. A second-order accurate, two-step, time-split, finite difference method was used to solve the Navier-Stokes equations. The filter is modeled as a homogeneous porous medium using an extended Darcy's law. The entire flow domain, including the filter, is solved simultaneously. At the interfaces, the boundary conditions are the continuities of velocity, shear stress, and normal stress. The effects of the filter on the separated velocity and pressure fields were studied for step height Reynolds numbers of 100 to 800. When the filter is far downstream, it has no apparent effect on the separated flow field and the pressure is nearly uniformly increased before the filter. When the filter is close to the attachment point at the step- side wall or to the vortex at the non-step wall, the velocity field is changed significantly. The presence of a filter enhances the recirculatory flow. However, recirculatory flow was not found to extend into the filter.

Yao, S.; Chambers, F. W.

1998-11-01

36

A novel discrete multi-objective Particle Swarm Optimization (MOPSO) of optimal shunt power filter

In this paper, a novel discrete optimization approach is developed to optimally solve the optimization problem of power system shunt filter design based on discrete multi objective particle swarm optimization MOPSO technique to ensure harmonic current reduction and noise mitigation on electrical utility grid. In this novel optimization approach, multi objective particle swarm optimization MOPSO is implemented to tackle a

Adel M. Sharaf; Adel A. A. El-Gammal

2009-01-01

37

Optimization-based tuning of LPV fault detection filters for civil transport aircraft

NASA Astrophysics Data System (ADS)

In this paper, a two-step optimal synthesis approach of robust fault detection (FD) filters for the model based diagnosis of sensor faults for an augmented civil aircraft is suggested. In the first step, a direct analytic synthesis of a linear parameter varying (LPV) FD filter is performed for the open-loop aircraft using an extension of the nullspace based synthesis method to LPV systems. In the second step, a multiobjective optimization problem is solved for the optimal tuning of the LPV detector parameters to ensure satisfactory FD performance for the augmented nonlinear closed-loop aircraft. Worst-case global search has been employed to assess the robustness of the fault detection system in the presence of aerodynamics uncertainties and estimation errors in the aircraft parameters. An application of the proposed method is presented for the detection of failures in the angle-of-attack sensor.

Ossmann, D.; Varga, A.

2013-12-01

38

Automatic layout optimization of an EMC filter

The transfer function of an EMC (Electro-Magnetic Compatibility) filter is strongly disturbed in high frequency due to stray electromagnetic phenomena. On the one hand the imperfections of the components but also all magnetic couplings on the other hand. Although these effects seem to be negative, it is possible to reduce the impacts of these imperfections on the filter response, and

Thomas DE OLIVEIRA; Jean-Luc SCHANEN; Jean-Michel GUICHON; Laurent GERBAUD

2010-01-01

39

The paper presents a novel discrete search optimization and approach to solve the problem of the hybrid power filter compensator with design a C-type filter and fixed capacitor bank using discrete multi objective particle swarm optimization MOPSO method. This is to ensure both loss reduction and harmonic current mitigation on electrical utility grid. This novel optimization approach, a multi objective

Adel M. Sharaf; Adel A. A. El-Gammal

2009-01-01

40

Optimal filter bandwidth for pulse oximetry

NASA Astrophysics Data System (ADS)

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.

Stuban, Norbert; Niwayama, Masatsugu

2012-10-01

41

NASA Astrophysics Data System (ADS)

This paper extends the recently introduced variable step-size (VSS) approach to the family of adaptive filter algorithms. This method uses prior knowledge of the channel impulse response statistic. Accordingly, optimal step-size vector is obtained by minimizing the mean-square deviation (MSD). The presented algorithms are the VSS affine projection algorithm (VSS-APA), the VSS selective partial update NLMS (VSS-SPU-NLMS), the VSS-SPU-APA, and the VSS selective regressor APA (VSS-SR-APA). In VSS-SPU adaptive algorithms the filter coefficients are partially updated which reduce the computational complexity. In VSS-SR-APA, the optimal selection of input regressors is performed during the adaptation. The presented algorithms have good convergence speed, low steady state mean square error (MSE), and low computational complexity features. We demonstrate the good performance of the proposed algorithms through several simulations in system identification scenario.

Shams Esfand Abadi, Mohammad; AbbasZadeh Arani, Seyed Ali Asghar

2011-12-01

42

Optimal deconvolution filter design under parameters perturbation in transmission channels

An optimal deconvolution filter design method is proposed in this paper for signal transmission systems with small perturbation of parameters. The perturbative parameters of the transmission channel and noise model are of probabilistic structures. A realizable filter is derived to minimize the mean square estimation error from the viewpoint of frequency domain. The calculus of variation technique and the spectral

Bor-Sen Chen; Chin-Wei Lin

1996-01-01

43

Numerically reliable methods for optimal design of fault detection filters

The design problem of fault detection and isolation filters is formulated as a model matching problem and solved using an H2-or H?-norm optimization approach. A systematic procedure is proposed to choose appropriate filter specifications which guarantee the existence of proper and stable solutions of the model matching problem. This selection is integral part of numerically reliable computational methods to design

A. Varga

2005-01-01

44

Particle Filter versus Particle Swarm Optimization for Object Tracking

Recently, Particle Swarm Optimization (PSO) is introduced as an alternative to Particle Filter (PF) for object tracking. In this work, we compare a PSO tracker with two PF trackers, a classical PF tracker and an Enhanced Particle Filter (EPF) tracker, introduced in this paper. The accuracy of the tracking and, in particular, occlusion handling are considered. The different trackers are

Howida A. Abd El-Halym; Imbaby I. Mahmoud; A. AbdelTawab; D. Habib

45

Initial steps of inactivation at the K+ channel selectivity filter.

K(+) efflux through K(+) channels can be controlled by C-type inactivation, which is thought to arise from a conformational change near the channel's selectivity filter. Inactivation is modulated by ion binding near the selectivity filter; however, the molecular forces that initiate inactivation remain unclear. We probe these driving forces by electrophysiology and molecular simulation of MthK, a prototypical K(+) channel. Either Mg(2+) or Ca(2+) can reduce K(+) efflux through MthK channels. However, Ca(2+), but not Mg(2+), can enhance entry to the inactivated state. Molecular simulations illustrate that, in the MthK pore, Ca(2+) ions can partially dehydrate, enabling selective accessibility of Ca(2+) to a site at the entry to the selectivity filter. Ca(2+) binding at the site interacts with K(+) ions in the selectivity filter, facilitating a conformational change within the filter and subsequent inactivation. These results support an ionic mechanism that precedes changes in channel conformation to initiate inactivation. PMID:24733889

Thomson, Andrew S; Heer, Florian T; Smith, Frank J; Hendron, Eunan; Bernèche, Simon; Rothberg, Brad S

2014-04-29

46

Time-optimal control of a stepping motor

Time-optimal control for multiple stepping of a variable-reluctance type stepping motor is discussed. A controller with phase-position feedback is designed and built for the minimum-time control of the motor. Experimental results showed that the controlled motor is capable of traveling a prescribed number of steps in near minimum time by the injection of one or two single pulses and the

B. Kuo; R. Yackel; G. Singh

1969-01-01

47

Joint fundamental frequency and order estimation using optimal filtering

NASA Astrophysics Data System (ADS)

In this paper, the problem of jointly estimating the number of harmonics and the fundamental frequency of periodic signals is considered. We show how this problem can be solved using a number of methods that either are or can be interpreted as filtering methods in combination with a statistical model selection criterion. The methods in question are the classical comb filtering method, a maximum likelihood method, and some filtering methods based on optimal filtering that have recently been proposed, while the model selection criterion is derived herein from the maximum a posteriori principle. The asymptotic properties of the optimal filtering methods are analyzed and an order-recursive efficient implementation is derived. Finally, the estimators have been compared in computer simulations that show that the optimal filtering methods perform well under various conditions. It has previously been demonstrated that the optimal filtering methods perform extremely well with respect to fundamental frequency estimation under adverse conditions, and this fact, combined with the new results on model order estimation and efficient implementation, suggests that these methods form an appealing alternative to classical methods for analyzing multi-pitch signals.

Græsbøll Christensen, Mads; Højvang, Lisby Jesper; Jakobsson, Andreas; Holdt Jensen, Søren

2011-12-01

48

Geomagnetic modeling by optimal recursive filtering

NASA Technical Reports Server (NTRS)

The results of a preliminary study to determine the feasibility of using Kalman filter techniques for geomagnetic field modeling are given. Specifically, five separate field models were computed using observatory annual means, satellite, survey and airborne data for the years 1950 to 1976. Each of the individual field models used approximately five years of data. These five models were combined using a recursive information filter (a Kalman filter written in terms of information matrices rather than covariance matrices.) The resulting estimate of the geomagnetic field and its secular variation was propogated four years past the data to the time of the MAGSAT data. The accuracy with which this field model matched the MAGSAT data was evaluated by comparisons with predictions from other pre-MAGSAT field models. The field estimate obtained by recursive estimation was found to be superior to all other models.

Gibbs, B. P.; Estes, R. H.

1981-01-01

49

Optimal Sharpening of Compensated Comb Decimation Filters: Analysis and Design

Comb filters are a class of low-complexity filters especially useful for multistage decimation processes. However, the magnitude response of comb filters presents a droop in the passband region and low stopband attenuation, which is undesirable in many applications. In this work, it is shown that, for stringent magnitude specifications, sharpening compensated comb filters requires a lower-degree sharpening polynomial compared to sharpening comb filters without compensation, resulting in a solution with lower computational complexity. Using a simple three-addition compensator and an optimization-based derivation of sharpening polynomials, we introduce an effective low-complexity filtering scheme. Design examples are presented in order to show the performance improvement in terms of passband distortion and selectivity compared to other methods based on the traditional Kaiser-Hamming sharpening and the Chebyshev sharpening techniques recently introduced in the literature.

Troncoso Romero, David Ernesto

2014-01-01

50

Production of retroviral vectors for clinical use requires removal of cells and cellular debris. We combined a series of filters of decreasing pore size using commercially available blood banking filters approved for clinical use. The collection bag and filters can be connected to create a sterile, closed system using clinically approved tubing and sealing systems. Even when challenged with a large number of vector producer cells (2.38 x 10(9)cells), no viable cells are passed through the system. The step filtration system developed minimizes the titer reduction associated with filtration, provides rapid flow rates, and was cost effective when filtering volumes in excess of 2 liters. PMID:11175310

Reeves, L; Cornetta, K

2000-12-01

51

Ares-I Bending Filter Design using a Constrained Optimization Approach

NASA Technical Reports Server (NTRS)

The Ares-I launch vehicle represents a challenging flex-body structural environment for control system design. Software filtering of the inertial sensor output is required to ensure adequate stable response to guidance commands while minimizing trajectory deviations. This paper presents a design methodology employing numerical optimization to develop the Ares-I bending filters. The design objectives include attitude tracking accuracy and robust stability with respect to rigid body dynamics, propellant slosh, and flex. Under the assumption that the Ares-I time-varying dynamics and control system can be frozen over a short period of time, the bending filters are designed to stabilize all the selected frozen-time launch control systems in the presence of parameter uncertainty. To ensure adequate response to guidance command, step response specifications are introduced as constraints in the optimization problem. Imposing these constrains minimizes performance degradation caused by the addition of the bending filters. The first stage bending filter design achieves stability by adding lag to the first structural frequency to phase stabilize the first flex mode while gain stabilizing the higher modes. The upper stage bending filter design gain stabilizes all the flex bending modes. The bending filter designs provided here have been demonstrated to provide stable first and second stage control systems in both Draper Ares Stability Analysis Tool (ASAT) and the MSFC MAVERIC 6DOF nonlinear time domain simulation.

Hall, Charles; Jang, Jiann-Woei; Hall, Robert; Bedrossian, Nazareth

2008-01-01

52

Identifying Optimal Measurement Subspace for the Ensemble Kalman Filter

To reduce the computational load of the ensemble Kalman filter while maintaining its efficacy, an optimization algorithm based on the generalized eigenvalue decomposition method is proposed for identifying the most informative measurement subspace. When the number of measurements is large, the proposed algorithm can be used to make an effective tradeoff between computational complexity and estimation accuracy. This algorithm also can be extended to other Kalman filters for measurement subspace selection.

Zhou, Ning; Huang, Zhenyu; Welch, Greg; Zhang, J.

2012-05-24

53

Design of optimal correlation filters for hybrid vision systems

NASA Technical Reports Server (NTRS)

Research is underway at the NASA Johnson Space Center on the development of vision systems that recognize objects and estimate their position by processing their images. This is a crucial task in many space applications such as autonomous landing on Mars sites, satellite inspection and repair, and docking of space shuttle and space station. Currently available algorithms and hardware are too slow to be suitable for these tasks. Electronic digital hardware exhibits superior performance in computing and control; however, they take too much time to carry out important signal processing operations such as Fourier transformation of image data and calculation of correlation between two images. Fortunately, because of the inherent parallelism, optical devices can carry out these operations very fast, although they are not quite suitable for computation and control type operations. Hence, investigations are currently being conducted on the development of hybrid vision systems that utilize both optical techniques and digital processing jointly to carry out the object recognition tasks in real time. Algorithms for the design of optimal filters for use in hybrid vision systems were developed. Specifically, an algorithm was developed for the design of real-valued frequency plane correlation filters. Furthermore, research was also conducted on designing correlation filters optimal in the sense of providing maximum signal-to-nose ratio when noise is present in the detectors in the correlation plane. Algorithms were developed for the design of different types of optimal filters: complex filters, real-value filters, phase-only filters, ternary-valued filters, coupled filters. This report presents some of these algorithms in detail along with their derivations.

Rajan, Periasamy K.

1990-01-01

54

Optimally smooth symmetric quadrature mirror filters for image coding

NASA Astrophysics Data System (ADS)

Symmetric quadrature mirror filters (QMFs) offer several advantages for wavelet-based image coding. Symmetry and odd-length contribute to efficient boundary handling and preservation of edge detail. Symmetric QMFs can be obtained by mildly relaxing the filter bank orthogonality conditions. We describe a computational algorithm for these filter banks which is also symmetric in the sense that the analysis and synthesis operations have identical implementations, up to a delay. The essence of a wavelet transform is its multiresolution decomposition, obtained by iterating the lowpass filter. This allows one to introduce a new design criterion, smoothness (good behavior) of the lowpass filter under iteration. This design constraint can be expressed solely in terms of the lowpass filter tap values (via the eigenvalue decomposition of a certain finite-dimensional matrix). Our innovation is to design near- orthogonal QMFs with linear-phase symmetry which are optimized for smoothness under iteration, not for stopband rejection. The new class of optimally smooth QMF filter banks yields high performance in a practical image compression system.

Heller, Peter N.; Shapiro, Jerome M.; Wells, Raymond O., Jr.

1995-04-01

55

Optimal Signal Processing of Frequency-Stepped CW Radar Data

NASA Technical Reports Server (NTRS)

An optimal signal processing algorithm is derived for estimating the time delay and amplitude of each scatterer reflection using a frequency-stepped CW system. The channel is assumed to be composed of abrupt changes in the reflection coefficient profile. The optimization technique is intended to maximize the target range resolution achievable from any set of frequency-stepped CW radar measurements made in such an environment. The algorithm is composed of an iterative two-step procedure. First, the amplitudes of the echoes are optimized by solving an overdetermined least squares set of equations. Then, a nonlinear objective function is scanned in an organized fashion to find its global minimum. The result is a set of echo strengths and time delay estimates. Although this paper addresses the specific problem of resolving the time delay between the two echoes, the derivation is general in the number of echoes. Performance of the optimization approach is illustrated using measured data obtained from an HP-851O network analyzer. It is demonstrated that the optimization approach offers a significant resolution enhancement over the standard processing approach that employs an IFFT. Degradation in the performance of the algorithm due to suboptimal model order selection and the effects of additive white Gaussion noise are addressed.

Ybarra, Gary A.; Wu, Shawkang M.; Bilbro, Griff L.; Ardalan, Sasan H.; Hearn, Chase P.; Neece, Robert T.

1995-01-01

56

Optimal Signal Processing of Frequency-Stepped CW Radar Data

NASA Technical Reports Server (NTRS)

An optimal signal processing algorithm is derived for estimating the time delay and amplitude of each scatterer reflection using a frequency-stepped CW system. The channel is assumed to be composed of abrupt changes in the reflection coefficient profile. The optimization technique is intended to maximize the target range resolution achievable from any set of frequency-stepped CW radar measurements made in such an environment. The algorithm is composed of an iterative two-step procedure. First, the amplitudes of the echoes are optimized by solving an overdetermined least squares set of equations. Then, a nonlinear objective function is scanned in an organized fashion to find its global minimum. The result is a set of echo strengths and time delay estimates. Although this paper addresses the specific problem of resolving the time delay between the first two echoes, the derivation is general in the number of echoes. Performance of the optimization approach is illustrated using measured data obtained from an HP-X510 network analyzer. It is demonstrated that the optimization approach offers a significant resolution enhancement over the standard processing approach that employs an IFFT. Degradation in the performance of the algorithm due to suboptimal model order selection and the effects of additive white Gaussion noise are addressed.

Ybarra, Gary A.; Wu, Shawkang M.; Bilbro, Griff L.; Ardalan, Sasan H.; Hearn, Chase P.; Neece, Robert T.

1995-01-01

57

Swarm Intelligence for Optimizing Hybridized Smoothing Filter in Image Edge Enhancement

NASA Astrophysics Data System (ADS)

In this modern era, image transmission and processing plays a major role. It would be impossible to retrieve information from satellite and medical images without the help of image processing techniques. Edge enhancement is an image processing step that enhances the edge contrast of an image or video in an attempt to improve its acutance. Edges are the representations of the discontinuities of image intensity functions. For processing these discontinuities in an image, a good edge enhancement technique is essential. The proposed work uses a new idea for edge enhancement using hybridized smoothening filters and we introduce a promising technique of obtaining best hybrid filter using swarm algorithms (Artificial Bee Colony (ABC), Particle Swarm Optimization (PSO) and Ant Colony Optimization (ACO)) to search for an optimal sequence of filters from among a set of rather simple, representative image processing filters. This paper deals with the analysis of the swarm intelligence techniques through the combination of hybrid filters generated by these algorithms for image edge enhancement.

Rao, B. Tirumala; Dehuri, S.; Dileep, M.; Vindhya, A.

58

Optimal filtering in multipulse sequences for nuclear quadrupole resonance detection

NASA Astrophysics Data System (ADS)

The application of the multipulse sequences in nuclear quadrupole resonance (NQR) detection of explosive and narcotic substances has been studied. Various approaches to increase the signal to noise ratio (SNR) of signal detection are considered. We discussed two modifications of the phase-alternated multiple-pulse sequence (PAMS): the 180° pulse sequence with a preparatory pulse and the 90° pulse sequence. The advantages of optimal filtering to detect NQR in the case of the coherent steady-state precession have been analyzed. It has been shown that this technique is effective in filtering high-frequency and low-frequency noise and increasing the reliability of NQR detection. Our analysis also shows the PAMS with 180° pulses is more effective than PSL sequence from point of view of the application of optimal filtering procedure to the steady-state NQR signal.

Osokin, D. Ya.; Khusnutdinov, R. R.; Mozzhukhin, G. V.; Rameev, B. Z.

2014-05-01

59

Optimized linear-phase filter banks for wavelet image coding

NASA Astrophysics Data System (ADS)

In this paper, we address the issue of designing a two- channel linear phase biorthogonal filter bank that maximizes the two most desired properties for the wavelet transform in image coding applications, namely, orthogonality and energy compaction. Proper cost functions are formulated for these two criteria and an efficient signal-adaptive optimization algorithm is proposed. Our algorithm is motivated by a number of interesting properties of the correlation matrix of typical image signals, and uses lifting operations to efficiently represent the degrees of freedom subject to perfect reconstruction conditions. In addition, it offers a successive tradeoff between our two optimization goals. Experimental results on the popular Daubechies 9-7 and 10-18 filter banks reveal that considerable improvements in terms of both orthogonality and energy compaction can be achieved through the proposed optimization technique.

Yang, Xuguang; Ramchandran, Kannan

1998-01-01

60

Multidisciplinary Analysis and Optimization Generation 1 and Next Steps

NASA Technical Reports Server (NTRS)

The Multidisciplinary Analysis & Optimization Working Group (MDAO WG) of the Systems Analysis Design & Optimization (SAD&O) discipline in the Fundamental Aeronautics Program s Subsonic Fixed Wing (SFW) project completed three major milestones during Fiscal Year (FY)08: "Requirements Definition" Milestone (1/31/08); "GEN 1 Integrated Multi-disciplinary Toolset" (Annual Performance Goal) (6/30/08); and "Define Architecture & Interfaces for Next Generation Open Source MDAO Framework" Milestone (9/30/08). Details of all three milestones are explained including documentation available, potential partner collaborations, and next steps in FY09.

Naiman, Cynthia Gutierrez

2008-01-01

61

Optimizing wavelength-selective filters for luminescent solar concentrators

NASA Astrophysics Data System (ADS)

In a Luminescent Solar Concentrator, short-wavelength light is converted by a luminescent material into longwavelength light, which is light guided towards a photovoltaic cell. In principle, a Luminescent Solar Concentrator allows for high concentration, since the heat generated by the conversion process can be used to lower the entropy of light. However, less controlled loss mechanisms prevent high concentration factors in practice. One important loss mechanism is the escape of luminescent radiation into directions that do not stay inside the light guide. To reduce this amount, wavelength-selective filters can be applied that reflect the luminescent radiation back into the light guide while transmitting the incident sunlight. However, a filter optimized for reflecting as much as possible luminescent radiation will reflect part of the incident sunlight at high angles. Depending on the luminophore properties, it may be possible to design a suitable filter. In this paper, the interdependence of the luminophore and filter properties will be clarified and quantified using simulations. Optimal luminophore-filter combinations will be discussed, as well as the feasibility to realize them in practice.

de Boer, Dick K. G.

2010-04-01

62

FIR filter optimization for video processing on FPGAs

NASA Astrophysics Data System (ADS)

Two-dimensional finite impulse response (FIR) filters are an important component in many image and video processing systems. The processing of complex video applications in real time requires high computational power, which can be provided using field programmable gate arrays (FPGAs) due to their inherent parallelism. The most resource-intensive components in computing FIR filters are the multiplications of the folding operation. This work proposes two optimization techniques for high-speed implementations of the required multiplications with the least possible number of FPGA components. Both methods use integer linear programming formulations which can be optimally solved by standard solvers. In the first method, a formulation for the pipelined multiple constant multiplication problem is presented. In the second method, also multiplication structures based on look-up tables are taken into account. Due to the low coefficient word size in video processing filters of typically 8 to 12 bits, an optimal solution is found for most of the filters in the benchmark used. A complexity reduction of 8.5% for a Xilinx Virtex 6 FPGA could be achieved compared to state-of-the-art heuristics.

Kumm, Martin; Fanghänel, Diana; Möller, Konrad; Zipf, Peter; Meyer-Baese, Uwe

2013-12-01

63

3D target recognition using quasi-optimal visual filters

NASA Astrophysics Data System (ADS)

We describe a general approach for the representation and recognition of 3D objects, as it applies to Automatic Target Recognition (ATR) tasks. The method is based on locally adaptive target segmentation, biologically motivated image processing and a novel view selection mechanism that develops 'visual filters' responsive to specific target classes to encode the complete viewing sphere with a small number of prototypical examples. The optimal set of visual filters is found via a cross-validation-like data reduction algorithm used to train banks of back propagation (BP) neural networks. Experimental results on synthetic and real-world imagery demonstrate the feasibility of our approach.

Takacs, Barnabas; Sadovnik, Lev S.

1998-09-01

64

NASA Astrophysics Data System (ADS)

The aim of this study was to evaluate the effectiveness and efficiency in inverse IMRT planning of one-step optimization with the step-and-shoot (SS) technique as compared to traditional two-step optimization using the sliding windows (SW) technique. The Pinnacle IMRT TPS allows both one-step and two-step approaches. The same beam setup for five head-and-neck tumor patients and dose-volume constraints were applied for all optimization methods. Two-step plans were produced converting the ideal fluence with or without a smoothing filter into the SW sequence. One-step plans, based on direct machine parameter optimization (DMPO), had the maximum number of segments per beam set at 8, 10, 12, producing a directly deliverable sequence. Moreover, the plans were generated whether a split-beam was used or not. Total monitor units (MUs), overall treatment time, cost function and dose-volume histograms (DVHs) were estimated for each plan. PTV conformality and homogeneity indexes and normal tissue complication probability (NTCP) that are the basis for improving therapeutic gain, as well as non-tumor integral dose (NTID), were evaluated. A two-sided t-test was used to compare quantitative variables. All plans showed similar target coverage. Compared to two-step SW optimization, the DMPO-SS plans resulted in lower MUs (20%), NTID (4%) as well as NTCP values. Differences of about 15-20% in the treatment delivery time were registered. DMPO generates less complex plans with identical PTV coverage, providing lower NTCP and NTID, which is expected to reduce the risk of secondary cancer. It is an effective and efficient method and, if available, it should be favored over the two-step IMRT planning.

Abate, A.; Pressello, M. C.; Benassi, M.; Strigari, L.

2009-12-01

65

Millimeter-wave GaAs stepped-impedance hairpin resonator filters using surface micromachining

NASA Astrophysics Data System (ADS)

In this paper, microstrip stepped-impedance hairpin resonator (SIR) low-pass filter (LPF) and slow-wave band-pass filter (BPF) using dielectric supported air-gapped microstrip line (DAML) of surface micromachining on GaAs substrate are proposed. The DAML structure, which is a new low-loss micromachining transmission line, is useful for the integration of MEMS and/or MMIC components. Design parameters for the proposed SIR low-pass and slow-wave band-pass filters are derived based on stepped-impedance theory. The proposed slow-wave BPF is designed to produce a passband of 10% at the fundamental frequency of 60 GHz. and a new SIR LPF with aperture and IDC (inter-digital capacitor) is designed for 3-dB cutoff frequency of 33 GHz. The measurement results of the BPF filter and LPF filter agree well with simulation results. These filters are useful for many millimeter-wave system applications.

Cho, Ju-Hyun; Yun, Tae-Soon; Baek, Tae-Jong; Ko, Back-Seok; Shin, Dong-Hoon; Lee, Jong-Chul

2005-05-01

66

System-level optimization of baseband filters for communication applications

NASA Astrophysics Data System (ADS)

In this paper, we present a design approach for the high-level synthesis of programmable continuous-time Gm-C and active-RC filters with optimum trade-off among dynamic range, distortion products generation, area consumption and power dissipation, thus meeting the needs of more demanding baseband filter realizations. Further, the proposed technique guarantees that under all programming configurations, transconductors (in Gm-C filters) and resistors (in active-RC filters) as well as capacitors, are related by integer ratios in order to reduce the sensitivity to mismatch of the monolithic implementation. In order to solve the aforementioned trade-off, the filter must be properly scaled at each configuration. It means that filter node impedances must be conveniently altered so that the noise contribution of each node to the filter output be as low as possible, while avoiding that peak amplitudes at such nodes be so high as to drive active circuits into saturation. Additionally, in order to not degrade the distortion performance of the filter (in particular, if it is implemented using Gm-C techniques) node impedances can not be scaled independently from each other but restrictions must be imposed according to the principle of nonlinear cancellation. Altogether, the high-level synthesis can be seen as a constrained optimization problem where some of the variables, namely, the ratios among similar components, are restricted to discrete values. The proposed approach to accomplish optimum filter scaling under all programming configurations, relies on matrix methods for network representation, which allows an easy estimation of performance features such as dynamic range and power dissipation, as well as other network properties such as sensitivity to parameter variations and non-ideal effects of integrators blocks; and the use of a simulated annealing algorithm to explore the design space defined by the transfer and group delay specifications. It must be noted that such design space also includes most common approximation methods and network synthesis approaches as optimization variables, in order to make as widespread as possible the search for optimum solutions. The proposed methodology has been partially developed in MATLAB, taking advantage of the routines available in the signal processing and control toolboxes, and C++. The validity of the methodology and companying software will be demonstrated at the Conference and reported in the paper, using as a tailoring example the design of a programmable bank of filters for a high-performance powerline modem.

Delgado-Restituto, Manuel; Fernandez-Bootello, Juan F.; Rodríguez-Vázquez, Angel

2003-04-01

67

We apply a matched filter based SAR algorithm to process ground penetrating radar data. The algorithm discussed is for a stepped frequency type radar although it can be applied to other types with few modifications. The selection of the synthetic aperture length considering the ground attenuation, antenna beam pattern and the scattering pattern of the object being imaged is also

Aruna Gunawardena; Dennis Longstaff

1995-01-01

68

Particle Filter (PF) is a sophisticated model estimation technique based on simulation. Due to the natural limitations of\\u000a PF, two problems, namely particle impoverishment and sample size dependency, frequently occur during the particles updating\\u000a stage and these problems will limit the accuracy of the estimation results. In order to alleviate these problems, Ant Colony\\u000a Optimization is incorporated into the generic

Junpei Zhong; Yu-fai Fung; Mingjun Dai

2010-01-01

69

NASA Technical Reports Server (NTRS)

We propose an analytical design for a microstrip broadband spurious-suppression filter. The proposed design uses every section of the transmission lines as both a coupling and a spurious suppression element, which creates a very compact, planar filter. While a traditional filter length is greater than the multiple of the quarter wavelength at the center passband frequency (lambda(sub g)/4), the proposed filter length is less than (order n(Ssup th) + l)center dot lambda(sub g)/8. The filter s spurious response and physical dimension are controlled by the step impedance ratio (R) between two transmission line sections as a lambda(sub g)/4 resonator. The experimental result shows that, with R of 0.2, the out-of-band attenuation is greater than 40 dB; and the first spurious mode is shifted to more than 5 times the fundamental frequency. Moreover, it is the most compact planar filter design to date. The results also indicate a low in-band insertion loss.

U-Yen, Kongpop; Wollack, Edward J.; Doiron, Terence; Papapolymerou, John; Laskar, Joy

2005-01-01

70

A multi-dimensional procedure for BNCT filter optimization

An initial version of an optimization code utilizing two-dimensional radiation transport methods has been completed. This code is capable of predicting material compositions of a beam tube-filter geometry which can be used in a boron neutron capture therapy treatment facility to improve the ratio of the average radiation dose in a brain tumor to that in the healthy tissue surrounding the tumor. The optimization algorithm employed by the code is very straightforward. After an estimate of the gradient of the dose ratio with respect to the nuclide densities in the beam tube-filter geometry is obtained, changes in the nuclide densities are made based on: (1) the magnitude and sign of the components of the dose ratio gradient, (2) the magnitude of the nuclide densities, (3) the upper and lower bound of each nuclide density, and (4) the linear constraint that the sum of the nuclide density fractions in each material zone be less than or equal to 1.0. A local optimal solution is assumed to be found when one of the following conditions is satisfied in every material zone: (1) the maximum positive component of the gradient corresponds to a nuclide at its maximum density and the sum of the density fractions equals 1.0 or, and (2) the positive and negative components of the gradient correspond to nuclides densities at their upper and lower bounds, respectively, and the remaining components of the gradient are sufficiently small. The optimization procedure has been applied to a beam tube-filter geometry coupled to a simple tumor-patient head model and an improvement of 50% in the dose ratio was obtained.

Lille, R.A.

1998-02-01

71

The multi-dimensional quality open linear dynamical system with observation and feedback along a quantum linear transmission line is studied in discrete time. The linear least squares filtering and optimal control strategies are obtained as quantum analogies of the Kalman filter and Bellman dynamical programming. The duality of quantum filtering and optimal feedback control is observed for this particular case.

Simon C. Edwards; Viacheslav P. Belavkin

2003-01-01

72

A new method of genetic algorithm (GA) optimized the extended Kalman particle filter (EKPF) is proposed in this paper. The algorithm of extended Kalman particle filter is a suboptimal filtering algorithm with good performance for target tracking and non-linear tracking problem. In the implementation of the extended Kalman particle filter, a re-sampling scheme is used to decrease the degeneracy phenomenon

Shuying Yang; Wenjuan Huang; Qin Ma

2009-01-01

73

Optimization of adenovirus 40 and 41 recovery from tap water using small disk filters.

Currently, the U.S. Environmental Protection Agency's Information Collection Rule (ICR) for the primary concentration of viruses from drinking and surface waters uses the 1MDS filter, but a more cost effective option, the NanoCeram® filter, has been shown to recover comparable levels of enterovirus and norovirus from both matrices. In order to achieve the highest viral recoveries, filtration methods require the identification of optimal concentration conditions that are unique for each virus type. This study evaluated the effectiveness of 1MDS and NanoCeram filters in recovering adenovirus (AdV) 40 and 41 from tap water, and optimized two secondary concentration procedures the celite and organic flocculation method. Adjustments in pH were made to both virus elution solutions and sample matrices to determine which resulted in higher virus recovery. Samples were analyzed by quantitative PCR (qPCR) and Most Probable Number (MPN) techniques and AdV recoveries were determined by comparing levels of virus in sample concentrates to that in the initial input. The recovery of adenovirus was highest for samples in unconditioned tap water (pH 8) using the 1MDS filter and celite for secondary concentration. Elution buffer containing 0.1% sodium polyphosphate at pH 10.0 was determined to be most effective overall for both AdV types. Under these conditions, the average recovery for AdV40 and 41 was 49% and 60%, respectively. By optimizing secondary elution steps, AdV recovery from tap water could be improved at least two-fold compared to the currently used methodology. Identification of the optimal concentration conditions for human AdV (HAdV) is important for timely and sensitive detection of these viruses from both surface and drinking waters. PMID:23796954

McMinn, Brian R

2013-11-01

74

Neuromuscular fiber segmentation through particle filtering and discrete optimization

NASA Astrophysics Data System (ADS)

We present an algorithm to segment a set of parallel, intertwined and bifurcating fibers from 3D images, targeted for the identification of neuronal fibers in very large sets of 3D confocal microscopy images. The method consists of preprocessing, local calculation of fiber probabilities, seed detection, tracking by particle filtering, global supervised seed clustering and final voxel segmentation. The preprocessing uses a novel random local probability filtering (RLPF). The fiber probabilities computation is performed by means of SVM using steerable filters and the RLPF outputs as features. The global segmentation is solved by discrete optimization. The combination of global and local approaches makes the segmentation robust, yet the individual data blocks can be processed sequentially, limiting memory consumption. The method is automatic but efficient manual interactions are possible if needed. The method is validated on the Neuromuscular Projection Fibers dataset from the Diadem Challenge. On the 15 first blocks present, our method has a 99.4% detection rate. We also compare our segmentation results to a state-of-the-art method. On average, the performances of our method are either higher or equivalent to that of the state-of-the-art method but less user interactions is needed in our approach.

Dietenbeck, Thomas; Varray, François; Kybic, Jan; Basset, Olivier; Cachard, Christian

2014-03-01

75

Quantum demolition filtering and optimal control of unstable systems.

A brief account of the quantum information dynamics and dynamical programming methods for optimal control of quantum unstable systems is given to both open loop and feedback control schemes corresponding respectively to deterministic and stochastic semi-Markov dynamics of stable or unstable systems. For the quantum feedback control scheme, we exploit the separation theorem of filtering and control aspects as in the usual case of quantum stable systems with non-demolition observation. This allows us to start with the Belavkin quantum filtering equation generalized to demolition observations and derive the generalized Hamilton-Jacobi-Bellman equation using standard arguments of classical control theory. This is equivalent to a Hamilton-Jacobi equation with an extra linear dissipative term if the control is restricted to Hamiltonian terms in the filtering equation. An unstable controlled qubit is considered as an example throughout the development of the formalism. Finally, we discuss optimum observation strategies to obtain a pure quantum qubit state from a mixed one. PMID:23091216

Belavkin, V P

2012-11-28

76

Optimal linear combination of order statistics filters and their relationship to the Delta-operator

NASA Astrophysics Data System (ADS)

Linear Combination of Order Statistics (LOS) filters are a special case of the Choquet integral filters. LOS are a class of nonlinear filters parameterized by a set of n weights. Different values of the weights lead to different filters. Examples include the median and other order statistic filters, local averaging filters, and trimmed average filters. Differences of LOS filters have been used in the past as target detection filters by nonlinearly comparing a small, targets size region with the surrounding region. The delta operator, proposed by Gelenbe et. al. for land mine detection, can be represented as a special case of a difference of LOS operators. Weights of LOS operators can be determined by solving an optimization problem, represented as a quadratic program. In this paper, experiments are conducted in determining optimal differences of LOS operators using the DARPA backgrounds data. The results are that the delta-operator is the solution of the optimization problem for this data set.

Hocaoglu, Ali K.; Gader, Paul D.; Gelenbe, Erol; Kocak, Taskin

1999-08-01

77

Cat Swarm Optimization algorithm for optimal linear phase FIR filter design.

In this paper a new meta-heuristic search method, called Cat Swarm Optimization (CSO) algorithm is applied to determine the best optimal impulse response coefficients of FIR low pass, high pass, band pass and band stop filters, trying to meet the respective ideal frequency response characteristics. CSO is generated by observing the behaviour of cats and composed of two sub-models. In CSO, one can decide how many cats are used in the iteration. Every cat has its' own position composed of M dimensions, velocities for each dimension, a fitness value which represents the accommodation of the cat to the fitness function, and a flag to identify whether the cat is in seeking mode or tracing mode. The final solution would be the best position of one of the cats. CSO keeps the best solution until it reaches the end of the iteration. The results of the proposed CSO based approach have been compared to those of other well-known optimization methods such as Real Coded Genetic Algorithm (RGA), standard Particle Swarm Optimization (PSO) and Differential Evolution (DE). The CSO based results confirm the superiority of the proposed CSO for solving FIR filter design problems. The performances of the CSO based designed FIR filters have proven to be superior as compared to those obtained by RGA, conventional PSO and DE. The simulation results also demonstrate that the CSO is the best optimizer among other relevant techniques, not only in the convergence speed but also in the optimal performances of the designed filters. PMID:23958491

Saha, Suman Kumar; Ghoshal, Sakti Prasad; Kar, Rajib; Mandal, Durbadal

2013-11-01

78

Combining classical Kalman filter with NIR analysis technology, a new method of characteristic wavelength variable selection, namely Kalman filtering method, is presented. The principle of Kalman filter for selecting optimal wavelength variable was analyzed. The wavelength selection algorithm was designed and applied to NIR detection of soybean oil acid value. First, the PLS (partial leastsquares) models were established by using different absorption bands of oil. The 4 472-5 000 cm(-1) characteristic band of oil acid value, including 132 wavelengths, was selected preliminarily. Then the Kalman filter was used to select characteristic wavelengths further. The PLS calibration model was established using selected 22 characteristic wavelength variables, the determination coefficient R2 of prediction set and RMSEP (root mean squared error of prediction) are 0.970 8 and 0.125 4 respectively, equivalent to that of 132 wavelengths, however, the number of wavelength variables was reduced to 16.67%. This algorithm is deterministic iteration, without complex parameters setting and randomicity of variable selection, and its physical significance was well defined. The modeling using a few selected characteristic wavelength variables which affected modeling effect heavily, instead of total spectrum, can make the complexity of model decreased, meanwhile the robustness of model improved. The research offered important reference for developing special oil near infrared spectroscopy analysis instruments on next step. PMID:25007608

Wang, Li-Qi; Ge, Hui-Fang; Li, Gui-Bin; Yu, Dian-Yu; Hu, Li-Zhi; Jiang, Lian-Zhou

2014-04-01

79

NASA Astrophysics Data System (ADS)

We outline a method, using simulated annealing algorithm, to optimize the dilation factor of the wavelet function, from a number of images. The optimized dilation factor has been used to obtain wavelet matched filters (WMFs) for different fingerprint images. A single WMF instead of a bank of filters can be used for identifying each image. The filter performance was tested in terms of discrimination ratio, peak-to-correlation plane energy ratio, peak-to-sidelobe ratio and average similarity measure with digitally degraded fingerprints. The performance has been compared with that of a classical matched filter and a phase only filter. The filter performance has also been tested for noisy images.

Pohit, M.; Singh, K.

2001-01-01

80

NASA Astrophysics Data System (ADS)

We introduce the use of complex-step method (CSM) in the context of a low-rank extended Kalman filter (CSM-SEEK).We describe the application of CSM-SEEK in subsurface flow and transport models.We implement the new algorithm for a state-parameter estimation problem.CSM-SEEK provides more accurate estimates than FD- and CD-SEEK filters.CSM-SEEK outperforms the EnKF when the filter's ensemble/rank is small.

Gharamti, M. E.; Hoteit, I.

2014-02-01

81

Intelligent Optimization Algorithm (IOA) mainly includes Immune Algorithm (IA) and Genetic Algorithm (GA). One of the most important characteristics of MRI is the complicated changes of gray level. Traditional filtering algorithms are not fit for MRI. Adaptive Template Filtering Method (ATFM) is an appropriate denoising method for MRI. However, selecting threshold for ATFM is a complicated problem which directly affects the denoising result. Threshold selection has been based on experience. Thus, it was lack of solid theoretical foundation. In this paper, 2 kinds of IOA are proposed for threshold optimization respectively. As our experiment demonstrates, they can effectively solve the problem of threshold selection and perfect ATFM. Through algorithm analysis, the performance of IA surpasses the performance of GA. As a new kind of IOA, IA exhibits its great potential in image processing. PMID:17945854

Guo, Lei; Wu, Youxi; Liu, Xuena; Li, Ying; Xu, Guizhi; Yan, Weili

2006-01-01

82

Effects of Rate-Limiting Steps in Transcription Initiation on Genetic Filter Motifs

The behavior of genetic motifs is determined not only by the gene-gene interactions, but also by the expression patterns of the constituent genes. Live single-molecule measurements have provided evidence that transcription initiation is a sequential process, whose kinetics plays a key role in the dynamics of mRNA and protein numbers. The extent to which it affects the behavior of cellular motifs is unknown. Here, we examine how the kinetics of transcription initiation affects the behavior of motifs performing filtering in amplitude and frequency domain. We find that the performance of each filter is degraded as transcript levels are lowered. This effect can be reduced by having a transcription process with more steps. In addition, we show that the kinetics of the stepwise transcription initiation process affects features such as filter cutoffs. These results constitute an assessment of the range of behaviors of genetic motifs as a function of the kinetics of transcription initiation, and thus will aid in tuning of synthetic motifs to attain specific characteristics without affecting their protein products.

Hakkinen, Antti; Tran, Huy; Yli-Harja, Olli; Ribeiro, Andre S.

2013-01-01

83

Effects of rate-limiting steps in transcription initiation on genetic filter motifs.

The behavior of genetic motifs is determined not only by the gene-gene interactions, but also by the expression patterns of the constituent genes. Live single-molecule measurements have provided evidence that transcription initiation is a sequential process, whose kinetics plays a key role in the dynamics of mRNA and protein numbers. The extent to which it affects the behavior of cellular motifs is unknown. Here, we examine how the kinetics of transcription initiation affects the behavior of motifs performing filtering in amplitude and frequency domain. We find that the performance of each filter is degraded as transcript levels are lowered. This effect can be reduced by having a transcription process with more steps. In addition, we show that the kinetics of the stepwise transcription initiation process affects features such as filter cutoffs. These results constitute an assessment of the range of behaviors of genetic motifs as a function of the kinetics of transcription initiation, and thus will aid in tuning of synthetic motifs to attain specific characteristics without affecting their protein products. PMID:23940576

Häkkinen, Antti; Tran, Huy; Yli-Harja, Olli; Ribeiro, Andre S

2013-01-01

84

Design of waveguide filters by using genetically optimized frequency selective surfaces

A new optimization procedure suitable for the design of waveguide filters is presented. The filter structure consists of a frequency selective surface (FSS), placed on the transverse plane of a rectangular waveguide, so introducing a filtering behavior of the waveguide. Due to the boundary conditions imposed by the metallic waveguide walls, the FSS results to be infinite in extent, allowing

Agostino Monorchio; Giuliano Manara; Umberto Serra; Giovanni Marola; Enrico Pagana

2005-01-01

85

NASA Technical Reports Server (NTRS)

A general form of an optimal washout filter is derived using state-space linear optimal control theory, and this is applied to the design of washout filters of various types of moving base motion simulators, including the NASA's vertical motion simulator. Attention is given to the linear elements of a washout filter. One of the nonlinearities considered is braking which may be required near the end of the simulator excursion to prevent a crash. Although the general form of the optimal washout filter is applicable to time-variant system, the applications analyzed in the study are restricted to time-invariant cases.

Kurosaki, M.

1979-01-01

86

Correlation methods are becoming increasingly attractive tools for image recognition and location. This renewed interest in correlation methods is spurred by the availability of high-speed image processors and the emergence of correlation filter designs that can optimize relevant figures of merit. In this paper, a new correlation filter design method is presented that allows one to optimally tradeoff among potentially

B. V. K. Vijaya Kumar; Abhijit Mahalanobis; Alex Takessian

2000-01-01

87

NASA Astrophysics Data System (ADS)

This paper presents a triple-band bandpass filter for applications of GSM, WiMAX, and WLAN systems. The proposed filter comprises of the tri-section step-impedance and capacitively loaded step-impedance resonators, which are combined using the cross coupling technique. Additionally, tapered lines are used to connect at both ports of the filter in order to enhance matching for the tri-band resonant frequencies. The filter can operate at the resonant frequencies of 1.8 GHz, 3.7 GHz, and 5.5 GHz. At resonant frequencies, the measured values of S11 are -17.2 dB, -33.6 dB, and -17.9 dB, while the measured values of S21 are -2.23 dB, -2.98 dB, and -3.31 dB, respectively. Moreover, the presented filter has compact size compared with the conventional open-loop cross coupling triple band bandpass filters

Chomtong, P.; Akkaraekthalin, P.

2014-05-01

88

A class of variable step-size algorithms for complex-valued nonlinear neural adaptive finite impulse response (FIR) filters realised as a dynamical perceptron is proposed. The adaptive step-size is updated using gradient descent to give variable step-size complex-valued nonlinear gradient descent (VSCNGD) algorithms. These algorithms are shown to be capable of tracking signals with rich and unknown dynamics, and exhibit faster convergence

Su Lee Goh; Danilo P. Mandic

2005-01-01

89

A class of variable step-size learning algorithms for complex-valued nonlinear adaptive finite impulse response (FIR) filters is proposed. To achieve this, first a general complex-valued nonlinear gradient-descent (CNGD) algorithm with a fully complex nonlinear activation function is derived. To improve the convergence and robustness of CNGD, we further introduce a gradient-adaptive step size to give a class of variable step-size

Su Lee Goh; Danilo P. Mandic

2007-01-01

90

Optimization of spatial filter with volume Bragg gratings in photo-thermo-refractive glass.

We present a method for optimizing spatial filter performance by inserting volume Bragg gratings (VBGs) in front of the traditional spatial filters. The experimental results show that the cutoff frequency is modified with the insertion of VBGs. We also demonstrate the optimization of filtering performance in both the spatial and frequency domains, with detailed comparison of near-field modulation, contrast ratio, and power spectral density of output laser beams. PMID:24487893

Zhang, Xiang; Yuan, Xiao; Feng, Jiansheng; Gao, Fan; Xiong, Baoxing; Zou, Kuaisheng

2014-02-01

91

In this paper conditional hidden Markov model (HMM) filters and conditional Kalman filters (KF) are coupled together to improve demodulation of differential encoded signals in noisy fading channels. We present an indicator matrix representation for differential encoded signals and the optimal HMM filter for demodulation. The filter requires O(N^{3<\\/sup>) calculations per time iteration, where N is the number of message}

Jason Ford; John Moore

1998-01-01

92

Optimal measurement of signal over noise ratio with constrained filter transfer functions

NASA Astrophysics Data System (ADS)

The problem of optimal measurement of a signal in presence of noise is treated in detail by Baldinger and Franzen (Adv. Electron. Electron Phys. 8 (1956) 225), Radeka and Karlovac (Nucl. Instr. and Meth. 52 (1967) 86) and Gatti and Manfredi (La Rivista Nuovo Cimento 9(1) (1986) 1), and the filter transfer function optimizing the signal over noise ratio is well known. These calculations deals with unconstrained optimization, that is the filter transfer function may assume any value. In this paper functional analysis techniques are applied to optimize the filter transfer function in presence of linear constraints.

Cattaneo, Paolo Walter

2002-03-01

93

Optimal Filters For Gradient-Based Motion Estimation

Gradient based approaches for motion estimation (optical-flow) estimate the motion of an image sequence based on local changes in the image intensities. In order to best evaluate local changes in the intensities, specific filters are applied to the image sequence. These filters are typically composed of spatio-temporal derivatives. The design of these filters plays an important role in the estimation

Michael Elad; Patrick C. Teo; Yacov Hel-Or

1999-01-01

94

On the Optimality of Motion-Based Particle Filtering

Particle filters have revolutionized object tracking in video sequences. The conventional particle filter, also called the CONDENSATION filter, uses the state transition distribu- tion as the proposal distribution, from which the particles are drawn at each iteration. However, the transition distribution does not take into account the current observations, and thus many particles can be wasted in low likelihood regions.

Nidhal Bouaynaya; Dan Schonfeld

2009-01-01

95

Optimizing spatial filters with kernel methods for BCI applications

NASA Astrophysics Data System (ADS)

Brain Computer Interface (BCI) is a communication or control system in which the user's messages or commands do not depend on the brain's normal output channels. The key step of BCI technology is to find a reliable method to detect the particular brain signals, such as the alpha, beta and mu components in EEG/ECOG trials, and then translate it into usable control signals. In this paper, our objective is to introduce a novel approach that is able to extract the discriminative pattern from the non-stationary EEG signals based on the common spatial patterns(CSP) analysis combined with kernel methods. The basic idea of our Kernel CSP method is performing a nonlinear form of CSP by the use of kernel methods that can efficiently compute the common and distinct components in high dimensional feature spaces related to input space by some nonlinear map. The algorithm described here is tested off-line with dataset I from the BCI Competition 2005. Our experiments show that the spatial filters employed with kernel CSP can effectively extract discriminatory information from single-trial EGOG recorded during imagined movements. The high recognition of linear discriminative rates and computational simplicity of "Kernel Trick" make it a promising method for BCI systems.

Zhang, Jiacai; Tang, Jianjun; Yao, Li

2007-11-01

96

Approximation of optimal step size control for acoustic echo cancellation

One of the most widely used gradient-based adaptation algorithms is the so called normalized least mean square (NLMS) algorithm. The rate of convergence, misadjustment and noise insensitivity of the NLMS-type algorithm depend on the proper choice of the step size parameter, which controls the weighting applied to each coefficient update. Different step size methods have been proposed to improve the

Christiane Antweiler; Jorn Grunwald; Holger Quack

1997-01-01

97

NASA Astrophysics Data System (ADS)

The present research work presents a novel control scheme for tuning PID controllers using Internal Model control with the filter time constant optimized using Bee colony Optimization technique. PID controllers are used widely in Industrial Processes. Tuning of PID controllers is accomplished using Internal Model control scheme. IMC includes tuning of filter constant ?. Compromise is made in selecting the filter constant ? since an increased value of ? results in a sluggish response whereas decreased value of filter constant leads in an aggressive action. In the present work, an attempt has been made to optimize the value of the ? by Bee colony optimization technique. Simulation results show the validity of the proposed scheme for the PID controller tuning.

Banu, U. Sabura; Uma, G.

98

Three-Dimensional Micro Propeller Design by Using Efficient Two Step Optimization

A practical and efficient optimal design procedure is presented for three-dimensional micro-propeller. To manage many design related variables and operating conditions efficiently, the design procedure consists of two steps for optimization of operating conditions and blade geometries. First, operating condition points are extracted from the design-of-experiments, and provided as the input data of the geometry optimization step. Next, in the

Ki-Hak Lee; Yong-Hee Jeon; Kyu-Hong Kim; Dong-Ho Lee; Kyung-Tae Lee

2007-01-01

99

Dual optimality of the phase-only filter

A measure of the peak-to-sidelobe performance for correlation filters is defined. The phase-only filter is then shown to be optimum with respect to the peak-to-sidelobe criterion. The phase-only filter has been previously shown to give optimum signal-to-noise performance. Thus, under the assumption of a unit modulus phase device, optimum peak-to-sidelobe and signal-to-noise performance can be obtained simultaneously.

Fred M. Dickey; Louis A. Romero

1989-01-01

100

Thin film characterization for modeling and optimization of silver-dielectric color filters.

We investigate the most appropriate way to optically characterize the materials and predict the spectral responses of metal-dielectric filters in the visible range. Special attention is given to thin silver layers that have a major impact on the filter's spectral transmittance and reflectance. Two characterization approaches are compared, based either on single layers, or on multilayer stacks, in approaching the filter design. The second approach is preferred, because it gives the best way to predict filter characteristics. Meanwhile, it provides a stack model and dispersion relations that can be used for filter design optimization. PMID:24663425

Frey, Laurent; Parrein, Pascale; Virot, Léopold; Pellé, Catherine; Raby, Jacques

2014-03-10

101

NASA Astrophysics Data System (ADS)

Computer simulations of photorefractive thresholding filters for the reduction of artifact or dust noise demonstrate an increase in signal-to-noise ratio (SNR) of 70% to 95%, respectively, of that provided by the Wiener filter for inputs with a SNR of approximately 3. These simple, nearly optimal filters use a spectral thresholding profile that is proportional to the envelope of the noise spectrum. Alternative nonlinear filters with either 1/ nu or constant thresholding profiles increase the SNR almost as much as the noise-envelope thresholding filter.

Fu, Jack; Khoury, Jehad; Cronin-Golomb, Mark; Woods, Charles L.

1995-01-01

102

An optimized low voltage and High Frequency CCII based multifunction Filters

In this paper, a low voltage current conveyor (CCII) based multifunction filter is presented. Firstly, thanks to an optimizing heuristic, an optimal sizing of a low voltage low power CMOS current conveyor (CCII) was done. Hence, we improve static and dynamic performances of this configuration. The optimized CCII configuration has a current bandwidth of 1.103 GHz and a voltage bandwidth

Samir Ben Salem; Dorra Sellami Masmoudi; Ashwek Ben Saïd; Mourad Loulou

2006-01-01

103

Bayesian-Optimal Image Reconstruction for Translational-Symmetric Filters

Translational-symmetric filters provide a foundation for various kinds of image processing. When a filtered image containing noise is observed, the original one can be reconstructed by Bayesian inference. Furthermore, hyperparameters such as the smoothness of the image and the noise level in the communication channel through which the image observed can be estimated from the observed image by setting a

Satohiro Tajima; Masato Inoue; Masato Okada

2008-01-01

104

An optimal modification of a Kalman filter for time scales

NASA Technical Reports Server (NTRS)

The Kalman filter in question, which was implemented in the time scale algorithm TA(NIST), produces time scales with poor short-term stability. A simple modification of the error covariance matrix allows the filter to produce time scales with good stability at all averaging times, as verified by simulations of clock ensembles.

Greenhall, C. A.

2003-01-01

105

NASA Astrophysics Data System (ADS)

We address p-shift finite impulse response optimal (OFIR) and unbiased (UFIR) algorithms for predictive filtering ( p > 0), filtering ( p = 0), and smoothing filtering ( p < 0) at a discrete point n over N neighboring points. The algorithms were designed for linear time-invariant state-space signal models with white Gaussian noise. The OFIR filter self-determines the initial mean square state function by solving the discrete algebraic Riccati equation. The UFIR one represented both in the batch and iterative Kalman-like forms does not require the noise covariances and initial errors. An example of applications is given for smoothing and predictive filtering of a two-state polynomial model. Based upon this example, we show that exact optimality is redundant when N ? 1 and still a nice suboptimal estimate can fairly be provided with a UFIR filter at a much lower cost.

Shmaliy, Yuriy S.; Ibarra-Manzano, Oscar

2012-12-01

106

Optease vena cava filter optimal indwelling time and retrievability.

The purpose of this study was to assess the indwelling time and retrievability of the Optease IVC filter. Between 2002 and 2009, a total of 811 Optease filters were inserted: 382 for prophylaxis in multitrauma patients and 429 for patients with venous thromboembolic (VTE) disease. In 139 patients [97 men and 42 women; mean age, 36 (range, 17-82) years], filter retrieval was attempted. They were divided into two groups to compare change in retrieval policy during the years: group A, 60 patients with filter retrievals performed before December 31 2006; and group B, 79 patients with filter retrievals from January 2007 to October 2009. A total of 128 filters were successfully removed (57 in group A, and 71 in group B). The mean filter indwelling time in the study group was 25 (range, 3-122) days. In group A the mean indwelling time was 18 (range, 7-55) days and in group B 31 days (range, 8-122). There were 11 retrieval failures: 4 for inability to engage the filter hook and 7 for inability to sheathe the filter due to intimal overgrowth. The mean indwelling time of group A retrieval failures was 16 (range, 15-18) days and in group B 54 (range, 17-122) days. Mean fluoroscopy time for successful retrieval was 3.5 (range, 1-16.6) min and for retrieval failures 25.2 (range, 7.2-62) min. Attempts to retrieve the Optease filter can be performed up to 60 days, but more failures will be encountered with this approach. PMID:20556385

Rimon, Uri; Bensaid, Paul; Golan, Gil; Garniek, Alexander; Khaitovich, Boris; Dotan, Zohar; Konen, Eli

2011-06-01

107

An optimal washout filter design for a motion platform with senseless and angular scaling maneuvers

The motion cueing algorithms are often applied in the motion simulators. In this paper, an optimal washout filter, taking into account the limitation of the simulator's workspace, is designed for the motion platform aiming to minimize human's perception error in order to provide realistic behavior. The filtering algorithm compares the human's perception of driving simulated vehicles realized by the motion

Sung-Hua Chen; Li-Chen Fu

2010-01-01

108

An optimal filtering algorithm for non-parametric observation models in robot localization

The lack of a parameterized observation model in robot localization using occupancy grids requires the application of sampling-based methods, or particle filters. This work addresses the problem of optimal Bayesian filtering for dynamic systems with observation models that cannot be approximated properly as any parameterized distribution, which includes localization and SLAM with occupancy grids. By integrating ideas from previous works

Jose-luis Blanco; Javier Gonzalez; Juan-antonio Fernandez-madrigal

2008-01-01

109

An Optimal Frequency Domain Filter for Edge Detection in Digital Pictures

Edge detection and enhancement are widely used in image processing applications. In this paper we consider the problem of optimizing spatial frequency domain filters for detecting edges in digital pictures. The filter is optimum in that it produces maximum energy within a resolution interval of specified width in the vicinity of the edge. We show that, in the continuous case,

K. Sam Shanmugam; Fred M. Dickey; James A. Green

1979-01-01

110

Optimal Filters with Multiple Packet Losses and its Application in Wireless Sensor Networks

This paper is concerned with the filtering problem for both discrete-time stochastic linear (DTSL) systems and discrete-time stochastic nonlinear (DTSN) systems. In DTSL systems, an linear optimal filter with multiple packet losses is designed based on the orthogonal principle analysis approach over unreliable wireless sensor networks (WSNs), and the experience result verifies feasibility and effectiveness of the proposed linear filter; in DTSN systems, an extended minimum variance filter with multiple packet losses is derived, and the filter is extended to the nonlinear case by the first order Taylor series approximation, which is successfully applied to unreliable WSNs. An application example is given and the corresponding simulation results show that, compared with extended Kalman filter (EKF), the proposed extended minimum variance filter is feasible and effective in WSNs.

Liu, Yonggui; Xu, Bugong; Feng, Linfang; Li, Shanbin

2010-01-01

111

Hybrid Kalman/H?filter in designing optimal navigation of vehicle in PRT System

NASA Astrophysics Data System (ADS)

PRT( Personal Rapid Transit ) system is a automated operation, so that it is important exactly finding position of vehicle. Many of PRT system has accepted the GPS system for a position, speed, and direction. in this paper, we propose a combination of Kalman Filter and H? Filter known as Hybrid Kalman/ H? Filter for applying to GPS navigation algorithm. For disturbance cancellation, Kalman Filter is optimal but it requires the statistical information about process and measurement noises while H? Filter only minimizes the "worst-case" error and requires that the noises are bounded. The new Hybrid Filter is expected to reduce the worst-case error and exploit the incomplete knowledge about noises to provide a better estimation. The experiment shows us the ability of Hybrid Filter in GPS navigation algorithm.

Kim, Hyunsoo; Nguyen, Hoang Hieu; Nguyen, Phi Long; Kim, Han Sil; Jang, Young Hwan; Ryu, Myungseon; Choi, Changho

2007-12-01

112

A method for optimizing multipass laser amplifier output utilizes a spectral filter in early passes but not in later passes. The pulses shift position slightly for each pass through the amplifier, and the filter is placed such that early passes intersect the filter while later passes bypass it. The filter position may be adjust offline in order to adjust the number of passes in each category. The filter may be optimized for use in a cryogenic amplifier.

Backus, Sterling J. (Erie, CO) [Erie, CO; Kapteyn, Henry C. (Boulder, CO) [Boulder, CO

2007-07-10

113

NASA Astrophysics Data System (ADS)

A unifying algorithm has been developed to systematize the collection of compact Daubechies wavelets computable by spectral factorization of a symmetric positive polynomial. This collection comprises all classes of real and complex orthogonal and biorthogonal wavelet filters with maximal flatness for their minimal length. The main algorithm incorporates spectral factorization of the Daubechies product filter into analysis and synthesis filters. The spectral factors are found for search-optimized families by examining a desired criterion over combinatorial subsets of roots indexed by binary codes, and for constraint-selected families by imposing sufficient constraints on the roots without any optimizing search for an extremal property. Daubechies wavelet filter families have been systematized to include those constraint-selected by the principle of separably disjoint roots, and those search-optimized for time-domain regularity, frequency-domain selectivity, time-frequency uncertainty, and phase nonlinearity. The latter criterion permits construction of the least and most asymmetric and least and most symmetric real and complex orthogonal filters. Biorthogonal symmetric spline and balanced-length filters with linear phase are also computable by these methods. This systematized collection has been developed in the context of a general framework enabling evaluation of the equivalence of constraint-selected and search-optimized families with respect to the filter coefficients and roots and their characteristics. Some of the constraint-selected families have been demonstrated to be equivalent to some of the search-optimized families, thereby obviating the necessity for any search in their computation.

Taswell, Carl

2000-09-01

114

Direct EM based optimization of advanced waffle-iron and rectangular combline filters

A fast hybrid mode-matching (MM)\\/finite-element (FE) method is applied for the direct EM based optimization of advanced waffle-iron filters and coax-fed rectangular combline filters. The proposed technique, which combines the efficiency of the MM with the flexibility of the FE technique, achieves the direct EM based optimization of these components within typically an overnight run on a PC. The CAD

F. Arndt; Joem Brandt

2002-01-01

115

Algorithmic and architectural optimizations for computationally efficient particle filtering.

In this paper, we analyze the computational challenges in implementing particle filtering, especially to video sequences. Particle filtering is a technique used for filtering nonlinear dynamical systems driven by non-Gaussian noise processes. It has found widespread applications in detection, navigation, and tracking problems. Although, in general, particle filtering methods yield improved results, it is difficult to achieve real time performance. In this paper, we analyze the computational drawbacks of traditional particle filtering algorithms, and present a method for implementing the particle filter using the Independent Metropolis Hastings sampler, that is highly amenable to pipelined implementations and parallelization. We analyze the implementations of the proposed algorithm, and, in particular, concentrate on implementations that have minimum processing times. It is shown that the design parameters for the fastest implementation can be chosen by solving a set of convex programs. The proposed computational methodology was verified using a cluster of PCs for the application of visual tracking. We demonstrate a linear speed-up of the algorithm using the methodology proposed in the paper. PMID:18390378

Sankaranarayanan, Aswin C; Srivastava, Ankur; Chellappa, Rama

2008-05-01

116

Bayesian-Optimal Image Reconstruction for Translational-Symmetric Filters

NASA Astrophysics Data System (ADS)

Translational-symmetric filters provide a foundation for various kinds of image processing. When a filtered image containing noise is observed, the original one can be reconstructed by Bayesian inference. Furthermore, hyperparameters such as the smoothness of the image and the noise level in the communication channel through which the image observed can be estimated from the observed image by setting a criterion of maximizing marginalized likelihood. In this article we apply a diagonalization technique with the Fourier transform to this image reconstruction problem. This diagonalization not only reduces computational costs but also facilitates theoretical analyses of the estimation and reconstruction performances. We take as an example the Mexican-hat shaped neural cell receptive field seen in the early visual systems of animals, and we compare the reconstruction performances obtained under various hyperparameter and filter parameter conditions with each other and with the corresponding performances obtained under no-filter conditions. The results show that the using a Mexican-hat filter can reduce reconstruction error.

Tajima, Satohiro; Inoue, Masato; Okada, Masato

2008-05-01

117

Optimizing The Number Of Steps In Learning Tasks For Complex Skills

ERIC Educational Resources Information Center

Background: Carrying out whole tasks is often too difficult for novice learners attempting to acquire complex skills. The common solution is to split up the tasks into a number of smaller steps. The number of steps must be optimized for efficient and effective learning. Aim: The aim of the study is to investigate the relation between the number of…

Nadolski, Rob J.; Kirschner, Paul A.; van Merrienboer, Jeroen J.G.

2005-01-01

118

Optimal PID controller for high-speed rail pantograph system with notch filter

The pantograph device must exert enough upward force to maintain sliding contact with the catenary at all times to avoid loss of contact due to excessive transient motion. This paper presented a global-oriented particle swarm optimization (GPSO) technique with Cauchy mutation for tuning the optimal control gains of PID controller in a high-speed rail pantograph device with notch filter. The

Zwe-Lee Gaing; Rung-Fang Chang

2009-01-01

119

Optimal measurement of signal over noise ratio with constrained filter transfer functions

The problem of optimal measurement of a signal in presence of noise is treated in detail by Baldinger and Franzen (Adv. Electron. Electron Phys. 8 (1956) 225), Radeka and Karlovac (Nucl. Instr. and Meth. 52 (1967) 86) and Gatti and Manfredi (La Rivista Nuovo Cimento 9(1) (1986) 1), and the filter transfer function optimizing the signal over noise ratio is

Paolo Walter Cattaneo

2002-01-01

120

An infeasible interior-point algorithm with full-Newton step for linear optimization

NASA Astrophysics Data System (ADS)

Recently, Roos (SIAM J Optim 16(4):1110?1136, 2006) presented a primal-dual infeasible interior-point algorithm that uses full-Newton steps and whose iteration bound coincides with the best known bound for infeasible interior-point algorithms. In the current paper we use a different feasibility step such that the definition of the feasibility step in Mansouri and Roos (Optim Methods Softw 22(3):519?530, 2007) is a special case of our definition, and show that the same result on the order of iteration complexity can be obtained.

Liu, Zhongyi; Sun, Wenyu

2007-10-01

121

3D target recognition using quasi-optimal visual filters

We describe a general approach for the representation and recognition of 3D objects, as it applies to Automatic Target Recognition (ATR) tasks. The method is based on locally adaptive target segmentation, biologically motivated image processing and a novel view selection mechanism that develops 'visual filters' responsive to specific target classes to encode the complete viewing sphere with a small number

Barnabas Takacs; Lev S. Sadovnik

1998-01-01

122

Matched Filtering and Optimal Use of an Antenna.

National Technical Information Service (NTIS)

This study lies in that area of research that is concerned with the improvement of long-range detection techniques. By extending the well-known concept of a matched filter to include a receiver with several elements and by using a few simple examples, it ...

H. Mermoz

1966-01-01

123

This thesis solves the problem of finding the optimal linear noise-reduction filter for linear tomographic image reconstruction. The optimization is data dependent and results in minimizing the mean-square error of the reconstructed image. The error is defined as the difference between the result and the best possible reconstruction. Applications for the optimal filter include reconstructions of positron emission tomographic (PET), X-ray computed tomographic, single-photon emission tomographic, and nuclear magnetic resonance imaging. Using high resolution PET as an example, the optimal filter is derived and presented for the convolution backprojection, Moore-Penrose pseudoinverse, and the natural-pixel basis set reconstruction methods. Simulations and experimental results are presented for the convolution backprojection method.

Sun, W.Y. [Lawrence Berkeley Lab., CA (United States)]|[California Univ., Berkeley, CA (United States). Dept. of Electrical Engineering and Computer Sciences

1993-04-01

124

National Technical Information Service (NTIS)

The implementation of a sub-optimal analog or hybrid Kalman filter is described stressing reliability, robustness, and speed requirements. The filter is designed assuming mismatched dynamics, noise, drift, and computational errors. The state estimation er...

L. F. Pau

1979-01-01

125

Poly-phase codes and optimal filters for multiple user ranging

NASA Astrophysics Data System (ADS)

A technique is introduced to select poly-phase codes and optimal filters of a pulse compression system that have specific temporal and frequency characteristics. In the particular problem under study, multiple vehicles are assigned unique codes and receiver filters that have nearly orthogonal signatures. Narrowband users, that act as interference, are also present within the system. A code selection algorithm is used to select codes which have low autocorrelation sidelobes and low cross correlation peaks. Optimal mismatched filters are designed for these codes which minimize the peak values in the autocorrelation and the cross correlation functions. An adjustment to the filter design technique produces filters with nulls in their frequency response, in addition to having low correlation peaks. The method produces good codes and filters for a four-user system with length 34 four-phase codes. There is considerable improvement in cross and autocorrelation sidelobe levels over the matched filter case with only a slight decrease in the signal-to-noise ratio (SNR) of the system. The mismatched filter design also allows the design of frequency nulls at any frequency with arbitrary null attenuation, null width, and sidelobe level, at the cost of a slight decrease in processing gain.

Griep, Karl R.; Ritcey, James A.; Burlingame, John J.

1995-04-01

126

An alternative to the well-established Fourier transform infrared (FT-IR) spectrometry, termed discrete frequency infrared (DFIR) spectrometry, has recently been proposed. This approach uses narrowband mid-infrared reflectance filters based on guided-mode resonance (GMR) in waveguide gratings, but filters designed and fabricated have not attained the spectral selectivity (? 32 cm?1) commonly employed for measurements of condensed matter using FT-IR spectroscopy. With the incorporation of dispersion and optical absorption of materials, we present here optimal design of double-layer surface-relief silicon nitride-based GMR filters in the mid-IR for various narrow bandwidths below 32 cm?1. Both shift of the filter resonance wavelengths arising from the dispersion effect and reduction of peak reflection efficiency and electric field enhancement due to the absorption effect show that the optical characteristics of materials must be taken into consideration rigorously for accurate design of narrowband GMR filters. By incorporating considerations for background reflections, the optimally designed GMR filters can have bandwidth narrower than the designed filter by the antireflection equivalence method based on the same index modulation magnitude, without sacrificing low sideband reflections near resonance. The reported work will enable use of GMR filters-based instrumentation for common measurements of condensed matter, including tissues and polymer samples.

Liu, Jui-Nung; Schulmerich, Matthew V.; Bhargava, Rohit; Cunningham, Brian T.

2011-01-01

127

Many signal processing problems are tackled by filtering the signal for subsequent feature classification or regression. Both steps are critical and need to be designed carefully to deal with the particular statistical characteristics of both signal and noise. Optimal design of the filter and the classifier are typically aborded in a separated way, thus leading to suboptimal classification schemes. This

Rémi Flamary; Devis Tuia; Benjamin Labbe; Gustavo Camps-Valls; Alain Rakotomamonjy

2012-01-01

128

On the application of optimal wavelet filter banks for ECG signal classification

NASA Astrophysics Data System (ADS)

This paper discusses ECG signal classification after parametrizing the ECG waveforms in the wavelet domain. Signal decomposition using perfect reconstruction quadrature mirror filter banks can provide a very parsimonious representation of ECG signals. In the current work, the filter parameters are adjusted by a numerical optimization algorithm in order to minimize a cost function associated to the filter cut-off sharpness. The goal consists of achieving a better compromise between frequency selectivity and time resolution at each decomposition level than standard orthogonal filter banks such as those of the Daubechies and Coiflet families. Our aim is to optimally decompose the signals in the wavelet domain so that they can be subsequently used as inputs for training to a neural network classifier.

Hadjiloucas, S.; Jannah, N.; Hwang, F.; Galvão, R. K. H.

2014-03-01

129

Optimal implementation approach for discrete wavelet transform using FIR filter banks on FPGAs

NASA Astrophysics Data System (ADS)

We present a wavelet transform implementation approach using a FIR filter bank that uses a Wallace Tree structure for fast multiplication. VHDL models targeted specifically for synthesize have been written for clocked data registers, adders and the multiplier. Symmetric wavelets like Biorthogonal wavelets can be implemented using this design. By changing the input filter coefficients different wavelet decompositions may be implemented. The design is mapped onto the ORCA series FPGA after synthesis and optimization for timing and area.

Sargunaraj, Joe J.; Rao, Sathyanarayana S.

1998-10-01

130

On optimal filtering of GPS dual frequency observations without using orbit information

The concept of optimal filtering of observations collected with a dual frequency GPS P-code receiver is investigated in comparison\\u000a to an approach for C\\/A-code units. The filter presented here uses only data gathered between one receiver and one satellite.\\u000a The estimated state vector consists of a one-way pseudorange, ionospheric influence, and ambiguity biases. Neither orbit information\\u000a nor station information is

Hans-Juergen Eueler; Clyde C. Goad

1991-01-01

131

An improved particle filtering algorithm based on observation inversion optimal sampling

According to the effective sampling of particles and the particles impoverishment caused by re-sampling in particle filter,\\u000a an improved particle filtering algorithm based on observation inversion optimal sampling was proposed. Firstly, virtual observations\\u000a were generated from the latest observation, and two sampling strategies were presented. Then, the previous time particles\\u000a were sampled by utilizing the function inversion relationship between observation

Zhen-tao Hu; Quan Pan; Feng Yang; Yong-mei Cheng

2009-01-01

132

Design of almost symmetric orthogonal wavelet filter bank via direct optimization.

It is a well-known fact that (compact-support) dyadic wavelets [based on the two channel filter banks (FBs)] cannot be simultaneously orthogonal and symmetric. Although orthogonal wavelets have the energy preservation property, biorthogonal wavelets are preferred in image processing applications because of their symmetric property. In this paper, a novel method is presented for the design of almost symmetric orthogonal wavelet FB. Orthogonality is structurally imposed by using the unnormalized lattice structure, and this leads to an objective function, which is relatively simple to optimize. The designed filters have good frequency response, flat group delay, almost symmetric filter coefficients, and symmetric wavelet function. PMID:22345542

Murugesan, Selvaraaju; Tay, David B H

2012-05-01

133

NASA Astrophysics Data System (ADS)

A sample fiber Bragg grating (SFBG) with Gaussian apodization profile is designed and optimized for the narrowband wavelength filter, and the relevant conclusions provide a guide for the further filter fabrication. With the grating length limited, a narrowband (5 GHz) grating filter used in the radio over fiber (ROF) system is fabricated, which has insertion loss of 3.463 dB, sideband suppression of 24.21dB, 3 dB bandwidth of 40 pm, and 20 dB bandwidth of 106.3 pm.

Chen, Peng; Wang, Rong; Pu, Tao; Lu, Lin; Fang, Tao; Zheng, Jilin; Gan, Zhi-Chun

2009-11-01

134

Optimizing spatial filters with kernel methods for BCI applications

Brain Computer Interface (BCI) is a communication or control system in which the user's messages or commands do not depend on the brain's normal output channels. The key step of BCI technology is to find a reliable method to detect the particular brain signals, such as the alpha, beta and mu components in EEG\\/ECOG trials, and then translate it into

Jiacai Zhang; Jianjun Tang; Li Yao

2007-01-01

135

Optimal-adaptive filters for modelling spectral shape, site amplification, and source scaling

This paper introduces some applications of optimal filtering techniques to earthquake engineering by using the so-called ARMAX models. Three applications are presented: (a) spectral modelling of ground accelerations, (b) site amplification (i.e., the relationship between two records obtained at different sites during an earthquake), and (c) source scaling (i.e., the relationship between two records obtained at a site during two different earthquakes). A numerical example for each application is presented by using recorded ground motions. The results show that the optimal filtering techniques provide elegant solutions to above problems, and can be a useful tool in earthquake engineering.

Safak, Erdal

1989-01-01

136

Modeling a Dynamic Design System Using the Mahalanobis Taguchi System - Two-Step Optimal Algorithm

\\u000a This work presents a novel algorithm, the Mahalanobis Taguchi System- Two Step Optimal algorithm (MTS-TSO), which combines\\u000a the Mahalanobis Taguchi System (MTS) and Two-Step Optimal (TSO) algorithm for parameter selection of product design, and parameter\\u000a adjustment under the dynamic service industry environments.\\u000a \\u000a \\u000a From the results of the confirm experiment, a service industry company is adopted to applies in the methodology,

Tsung-Shin Hsu; Ching-Lien Huang

2010-01-01

137

Code optimization for direct sequence spread spectrum and SAW-matched filter implementation.

This paper introduces a new optimization algorithm for the minimization of the time sidelobes of the correlation function of a pseudonoise (PN) sequence by applying dynamic weighting to the sequence. The resulting optimized time sidelobe level sequences are to be used in direct sequence spread spectrum (DS-SS) systems with digital modulations such as BPSK, DPSK, QPSK, etc. The new optimization algorithm starts with a PN sequence. It first optimizes the correlation time sidelobes for the case where the consecutive data bits are identical (11 or 00). It then optimizes the correlation time sidelobes for the case of alternating consecutive data bits (10 or 01). The suppressed time sidelobe level sequences are derived by iterating these algorithms alternately starting from the initial PN sequence. The derived suppressed time sidelobe sequences show excellent correlation characteristics when compared to conventional PN sequences such as maximal length sequences, Gold sequences and Barker codes. Surface acoustic wave (SAW) devices were used to implement the optimized time sidelobe level sequences in a matched filter pair. The design of the apodized SAW-matched filters and their predicted second order effects are presented. The experimental results for the SAW-matched filters for the optimized time sidelobe level sequences derived from a Barker code were found to be in good agreement with the theoretical predictions from this new algorithm. PMID:18238632

Hikino, O; Belkerdid, M A; Malocha, D C

2000-01-01

138

Extended and unscented filtering algorithms using one-step randomly delayed observations

In this paper, the least squares filtering problem is investigated for a class of nonlinear discrete-time stochastic systems using observations with stochastic delays contaminated by additive white noise. The delay is considered to be random and modelled by a binary white noise with values of zero or one; these values indicate that the measurement arrives on time or that it

Aurora Hermoso-carazo; Josefa Linares-pérez

2007-01-01

139

NSDL National Science Digital Library

All About Circuits is a website that Ã¢ÂÂprovides a series of online textbooks covering electricity and electronics.Ã¢ÂÂ Written by Tony R. Kuphaldt, the textbooks available here are wonderful resources for students, teachers, and anyone who is interested in learning more about electronics. This specific section, Filters, is the eighth chapter in Volume II Ã¢ÂÂAlternating Current (AC). A few of the topics covered in this chapter include: Low-pass filters, High-pass filters, Band-pass filters, Band-stop filters, and Resonant filters. Diagrams and detailed descriptions of concepts are included throughout the chapter to provide users with a comprehensive lesson. Visitors to the site are also encouraged to discuss concepts and topics using the All About Circuits discussion forums (registration with the site is required to post materials).

Kuphaldt, Tony R.

2008-07-02

140

Using the innovation analysis method in the time domain, based on the autoregressive moving average (ARMA) innovation model, this paper presents a unified white noise estimation theory that includes both input and measurement white noise estimators, and presents a new steady-state optimal state estimation theory. Non-recursive optimal state estimators are given, whose recursive version gives a steady-state Kalman filter, where

Zi-Li Deng; Huan-Shui Zhang; Shu-Jun Liu; Lu Zhou

1996-01-01

141

Comparison of optimal and local search methods for designing finite wordlength FIR digital filters

This paper presents a comparison between an optimal (branch-and-bound) algorithm and a suboptimal (local search) algorithm for the design of finite wordlength finite-impulse-response (FIR) digital filters. Experimental results are described for 11 examples of length 15 to 35. It is concluded that when computer resources are not available for the optimal method, it is still worth applying the local search

D. Kodek; K. Steiglitz

1981-01-01

142

Global optimization using homotopy with 2-step predictor-corrector method

NASA Astrophysics Data System (ADS)

In this research, we suggest a new method for solving global optimization problem by improving Homotopy Optimization with Perturbations and Ensembles (HOPE) method. Our new method, named as Homotopy 2-Step Predictor-corrector Method (HSPM) is based on the intermediate Value Theorem (IVT) coupled with modified Predictor-Corrector Halley method (PCH) for solving global optimization problem. HSPM does not require a good initial guess since it contains the element of homotopy, which is a globally convergent method. This paper discusses the time complexity of the new algorithm, which makes it more efficient than HOPE.

Chang, Kerk Lee; Ahmad, Rohanin Bt.

2014-06-01

143

Insights into HER2 signaling from step-by-step optimization of anti-HER2 antibodies.

HER2, a ligand-free tyrosine kinase receptor of the HER family, is frequently overexpressed in breast cancer. The anti-HER2 antibody trastuzumab has shown significant clinical benefits in metastatic breast cancer; however, resistance to trastuzumab is common. The development of monoclonal antibodies that have complementary mechanisms of action results in a more comprehensive blockade of ErbB2 signaling, especially HER2/HER3 signaling. Use of such antibodies may have clinical benefits if these antibodies can become widely accepted. Here, we describe a novel anti-HER2 antibody, hHERmAb-F0178C1, which was isolated from a screen of a phage display library. A step-by-step optimization method was employed to maximize the inhibitory effect of this anti-HER2 antibody. Crystallographic analysis was used to determine the three-dimensional structure to 3.5 Å resolution, confirming that the epitope of this antibody is in domain III of HER2. Moreover, this novel anti-HER2 antibody exhibits superior efficacy in blocking HER2/HER3 heterodimerization and signaling, and its use in combination with pertuzumab has a synergistic effect. Characterization of this antibody revealed the important role of a ligand binding site within domain III of HER2. The results of this study clearly indicate the unique potential of hHERmAb-F0178C1, and its complementary inhibition effect on HER2/HER3 signaling warrants its consideration as a promising clinical treatment. PMID:24838231

Fu, Wenyan; Wang, Yuxiao; Zhang, Yunshan; Xiong, Lijuan; Takeda, Hiroaki; Ding, Li; Xu, Qunfang; He, Lidong; Tan, Wenlong; Bethune, Augus N; Zhou, Lijun

2014-07-01

144

An optimal target-filter system for electron beam generated x-ray spectra

An electron beam generated x-ray spectrum consists of characteristic x rays of the target and continuous bremsstrahlung. The percentage of characteristic x rays over the entire energy spectrum depends on the beam energy and the filter thickness. To determine the optimal electron beam energy and filter thickness, one can either conduct many experimental measurements, or perform a series of Monte Carlo simulations. Monte Carlo simulations are shown to be an efficient tool for determining the optimal target-filter system for electron beam generated x-ray spectra. Three of the most commonly used low-energy x-ray metal targets (Cu, Zn and Mo) are chosen for this study to illustrate the power of Monte Carlo simulations.

Hsu, Hsiao-Hua; Vasilik, D.G. [Los Alamos National Lab., NM (United States); Chen, J. [GSF, Institut fur Strahlenbiologie, Neuherberg (Germany)

1994-04-01

145

A triparametric family of three-step optimal eighth-order methods for solving nonlinear equations

A new triparametric family of three-step optimal eighth-order iterative methods free from second derivatives are proposed in this paper, to find a simple root of nonlinear equations. Convergence analysis as well as numerical experiments confirms the eighth-order convergence and asymptotic error constants.

Young Ik Kim

2012-01-01

146

NASA Technical Reports Server (NTRS)

Telban and Cardullo have developed and successfully implemented the non-linear optimal motion cueing algorithm at the Visual Motion Simulator (VMS) at the NASA Langley Research Center in 2005. The latest version of the non-linear algorithm performed filtering of motion cues in all degrees-of-freedom except for pitch and roll. This manuscript describes the development and implementation of the non-linear optimal motion cueing algorithm for the pitch and roll degrees of freedom. Presented results indicate improved cues in the specified channels as compared to the original design. To further advance motion cueing in general, this manuscript describes modifications to the existing algorithm, which allow for filtering at the location of the pilot's head as opposed to the centroid of the motion platform. The rational for such modification to the cueing algorithms is that the location of the pilot's vestibular system must be taken into account as opposed to the off-set of the centroid of the cockpit relative to the center of rotation alone. Results provided in this report suggest improved performance of the motion cueing algorithm.

Zaychik, Kirill B.; Cardullo, Frank M.

2012-01-01

147

HUMAN MOVEMENT TRACKING AND ANALYSIS WITH KALMAN FILTERING AND GLOBAL OPTIMIZATION TECHNIQUES

This paper addresses the problem of tracking feature points along image sequences to analyze the undergoing human movement. An approach based on Kalman filtering performs the estimation and correction of the feature point's movement in every image frame, and optimizes the incorporation of the measured data in order to establish the best global correspondence. We propose a criterion to establish

Raquel R. Pinho; João Manuel; R. S. Tavares; Miguel V. Correia

148

Optimal Switched Dynamic Modulated Power Filter Compensator for Radial Distribution System

This paper presents a novel pulse width switched modulated power filter compensator (MPFC) for the voltage stability enhancement, energy utilization, loss reduction, and power factor correction in a radial distribution network using the Particle Swarm Optimization (PSO) technique. The MPFC is controlled by a novel dynamic tri-loop error driven controller. The dynamic controller is regulated to minimize the switching current

Adel M. Sharaf; Adel A. A. El-gammal

2009-01-01

149

Synthesis and Optimization of 2D Filter Designs for Heterogeneous FPGAs

Many image processing applications require fast convolution of an image with one or more 2D filters. Field-Programmable Gate Arrays (FPGAs) are often used to achieve this goal due to their fine grain parallelism and reconfigurability. However, the heterogeneous nature of modern reconfigurable devices is not usually considered during design optimization. This article proposes an algorithm that explores the space of

Christos-savvas Bouganis; Sung-boem Park; George A. Constantinides; Peter Y. K. Cheung

2009-01-01

150

Dynamic positioning of floating vessles based on Kalman filtering and optimal control

This paper describes computer-based, dynamic positioning system for floating vessels. The system is based on a detailed mathematical model of vessel motion in response to forces from thrusters, wind, waves and water current. The system uses a Kalman filter for optimal estimation of vessel motions and environmental forces from wind, waves and current. The control system is based on feedback

Jens G. Balchen; Nils A. Jenssen; Eldar Mathisen; Steinar Saelid

1980-01-01

151

Studies of an Optimally Unbiased MA Filter Intended for GPS-Based Timekeeping.

National Technical Information Service (NTIS)

In this paper, we examine one of the possible approaches to design an optimally unbiased moving average (MA) filter intended for the time error online estimating and synchronization in timekeeping. The approach is based on the slowly changing nature of a ...

O. Ibarra-Manzano R. Rojas-Laguana R. Vazguez- Bautista Y. Shmaliy

2001-01-01

152

Harmonic-suppression LTCC filter with the step-impedance quarter-wavelength open stub

An effective method to design a low-temperature co-fired ceramic RF bandpass filter with suppression of the harmonic frequency is demonstrated in this paper. The second harmonic, which appears in the frequency band of 4.8-5.0 GHz, is very significant and should be reduced in the 2.4-GHz wireless local area network and Bluetooth application. This feature of harmonic frequency suppression is very

Ching-Wen Tang

2004-01-01

153

Optimization of Optical Filters for the LIBEAM Diagnostic

NASA Astrophysics Data System (ADS)

In tokamak plasmas with an edge transport barrier, a measurement of the edge current density is necessary to understand plasma stability. A LIBEAM diagnostic system has been deployed on DIII-D that measures Zeeman polarimetry of the 2S-2P lithium resonance line in order to determine the magnetic field and corresponding current density within the edge pedestal region. Emission of the lithium resonance line is split by the local magnetic field producing three closely spaced spectral components; isolation of the &-circ; spectral component is required for measurement of the local magnetic field. A double Fabry-Perot etalon system is currently used for this purpose but a narrower bandpass is desired. This research will determine whether the installation of an exit pinhole will improve the etalon's finesse. However, transmitted light intensity is near a minimum threshold and the efficiency of the entire optical system must be examined and maximized. Optimization may include the installation of new detectors, lenses and fibers.

McGuire, Sean; Petty, C. C.; Thomas, D. M.; Hudson, B.

2009-11-01

154

Design Optimization of Vena Cava Filters: An application to dual filtration devices

Pulmonary embolism (PE) is a significant medical problem that results in over 300,000 fatalities per year. A common preventative treatment for PE is the insertion of a metallic filter into the inferior vena cava that traps thrombi before they reach the lungs. The goal of this work is to use methods of mathematical modeling and design optimization to determine the configuration of trapped thrombi that minimizes the hemodynamic disruption. The resulting configuration has implications for constructing an optimally designed vena cava filter. Computational fluid dynamics is coupled with a nonlinear optimization algorithm to determine the optimal configuration of trapped model thrombus in the inferior vena cava. The location and shape of the thrombus are parameterized, and an objective function, based on wall shear stresses, determines the worthiness of a given configuration. The methods are fully automated and demonstrate the capabilities of a design optimization framework that is broadly applicable. Changes to thrombus location and shape alter the velocity contours and wall shear stress profiles significantly. For vena cava filters that trap two thrombi simultaneously, the undesirable flow dynamics past one thrombus can be mitigated by leveraging the flow past the other thrombus. Streamlining the shape of thrombus trapped along the cava wall reduces the disruption to the flow, but increases the area exposed to abnormal wall shear stress. Computer-based design optimization is a useful tool for developing vena cava filters. Characterizing and parameterizing the design requirements and constraints is essential for constructing devices that address clinical complications. In addition, formulating a well-defined objective function that quantifies clinical risks and benefits is needed for designing devices that are clinically viable.

Singer, M A; Wang, S L; Diachin, D P

2009-12-03

155

Optimal filter framework for automated, instantaneous detection of lesions in retinal images.

Automated detection of lesions in retinal images is a crucial step towards efficient early detection, or screening, of large at-risk populations. In particular, the detection of microaneurysms, usually the first sign of diabetic retinopathy (DR), and the detection of drusen, the hallmark of age-related macular degeneration (AMD), are of primary importance. In spite of substantial progress made, detection algorithms still produce 1) false positives-target lesions are mixed up with other normal or abnormal structures in the eye, and 2) false negatives-the large variability in the appearance of the lesions causes a subset of these target lesions to be missed. We propose a general framework for detecting and characterizing target lesions almost instantaneously. This framework relies on a feature space automatically derived from a set of reference image samples representing target lesions, including atypical target lesions, and those eye structures that are similar looking but are not target lesions. The reference image samples are obtained either from an expert- or a data-driven approach. Factor analysis is used to derive the filters generating this feature space from reference samples. Previously unseen image samples are then classified in this feature space. We tested this approach by training it to detect microaneurysms. On a set of images from 2739 patients including 67 with referable DR, DR detection area under the receiver-operating characteristic curve (AUC) was comparable (AUC=0.927) to our previously published red lesion detection algorithm (AUC=0.929). We also tested the approach on the detection of AMD, by training it to differentiate drusen from Stargardt's disease lesions, and achieved an AUC=0.850 on a set of 300 manually detected drusen and 300 manually detected flecks. The entire image processing sequence takes less than a second on a standard PC compared to minutes in our previous approach, allowing instantaneous detection. Free-response receiver-operating characteristic analysis showed the superiority of this approach over a framework where false positives and the atypical lesions are not explicitly modeled. A greater performance was achieved by the expert-driven approach for DR detection, where the designer had sound expert knowledge. However, for both problems, a comparable performance was obtained for both expert- and data-driven approaches. This indicates that annotation of a limited number of lesions suffices for building a detection system for any type of lesion in retinal images, if no expert-knowledge is available. We are studying whether the optimal filter framework also generalizes to the detection of any structure in other domains. PMID:21292586

Quellec, Gwénolé; Russell, Stephen R; Abramoff, Michael D

2011-02-01

156

Fast automatic estimation of the optimization step size for nonrigid image registration

NASA Astrophysics Data System (ADS)

Image registration is often used in the clinic, for example during radiotherapy and image-guide surgery, but also for general image analysis. Currently, this process is often very slow, yet for intra-operative procedures the speed is crucial. For intensity-based image registration, a nonlinear optimization problem should be solved, usually by (stochastic) gradient descent. This procedure relies on a proper setting of a parameter which controls the optimization step size. This parameter is difficult to choose manually however, since it depends on the input data, optimization metric and transformation model. Previously, the Adaptive Stochastic Gradient Descent (ASGD) method has been proposed that automatically chooses the step size, but it comes at high computational cost. In this paper, we propose a new computationally efficient method to automatically determine the step size, by considering the observed distribution of the voxel displacements between iterations. A relation between the step size and the expectation and variance of the observed distribution is then derived. Experiments have been performed on 3D lung CT data (19 patients) using a nonrigid B-spline transformation model. For all tested dissimilarity metrics (mean squared distance, normalized correlation, mutual information, normalized mutual information), we obtained similar accuracy as ASGD. Compared to ASGD whose estimation time is progressively increasing with the number of parameters, the estimation time of the proposed method is substantially reduced to an almost constant time, from 40 seconds to no more than 1 second when the number of parameters is 105.

Qiao, Y.; Lelieveldt, B. P. F.; Staring, M.

2014-03-01

157

The accurate localization of anatomical landmarks is a challenging task, often solved by domain specific approaches. We propose a method for the automatic localization of landmarks in complex, repetitive anatomical structures. The key idea is to combine three steps: (1) a classifier for pre-filtering anatomical landmark positions that (2) are refined through a Hough regression model, together with (3) a parts-based model of the global landmark topology to select the final landmark positions. During training landmarks are annotated in a set of example volumes. A classifier learns local landmark appearance, and Hough regressors are trained to aggregate neighborhood information to a precise landmark coordinate position. A non-parametric geometric model encodes the spatial relationships between the landmarks and derives a topology which connects mutually predictive landmarks. During the global search we classify all voxels in the query volume, and perform regression-based agglomeration of landmark probabilities to highly accurate and specific candidate points at potential landmark locations. We encode the candidates’ weights together with the conformity of the connecting edges to the learnt geometric model in a Markov Random Field (MRF). By solving the corresponding discrete optimization problem, the most probable location for each model landmark is found in the query volume. We show that this approach is able to consistently localize the model landmarks despite the complex and repetitive character of the anatomical structures on three challenging data sets (hand radiographs, hand CTs, and whole body CTs), with a median localization error of 0.80 mm, 1.19 mm and 2.71 mm, respectively.

Donner, Rene; Menze, Bjoern H.; Bischof, Horst; Langs, Georg

2013-01-01

158

Improved particle filters for ballistic target tracking

We present in this paper two improved particle filter algorithms for ballistic target tracking. The first algorithm is a sampling\\/importance resampling (SIR) filter that uses an optimized importance function plus residual resampling to combat particle degeneracy, and also incorporates a Metropolis-Hastings (MH) move step to reduce particle impoverishment. The second proposed algorithm is an auxiliary particle filter (APF). Both algorithms

Marcelo G. S. Bruno; Anton Pavlov

2004-01-01

159

Optimal configurations of filter cavity in future gravitational-wave detectors

Sensitivity of future laser interferometric gravitational wave detectors can be improved using squeezed light with frequency-dependent squeeze angle and/or amplitude, which can be created using additional so-called filter cavities. Here we compare performances of several variants of this scheme, proposed during the last few years, assuming the case of a single relatively short (tens of meters) filter cavity suitable for implementation already during the life cycle of the second-generation detectors, like Advanced LIGO. Using numerical optimization, we show that the phase filtering scheme proposed by Kimble et al [H. J. Kimble, Yu. Levin, A. B. Matsko, K. S. Thorne, and S. P. Vyatchanin, Phys. Rev. D 65, 022002 (2001).] looks like the best candidate for this scenario.

Khalili, F. Ya. [Physics Faculty, Moscow State University, Moscow 119992 (Russian Federation)

2010-06-15

160

Performance evaluation of optimal filters for target detection using SAR imagery

NASA Astrophysics Data System (ADS)

Various matched filter based architectures have been proposed over the last two decades to optimize the target detection and recognition performance. While these techniques provide excellent performance with respect to one or more parameters, a unified and synergistic approach to evaluate the performance of these techniques under the same constraints is yet to be done. Consequently, in this paper, we used a set of generalized performance metrics for comparing the performance of the recently reported matched filter based techniques using various types of infrared and SAR datasets. Test results obtained using the aforementioned datasets and performance metrics provide excellent information with respect to the suitability of existing filter based techniques for various target detection and tracking practical applications.

Alam, Mohammad S.; Khoury, Jed; Banerjee, Partha P.; Durant, William M.; Martin, Daniel M.; Nehmetallah, Georges T.

2014-04-01

161

STEPPED-FREQUENCY ISAR MOTION COMPENSATION USING PARTICLE SWARM OPTIMIZATION WITH AN ISLAND MODEL

Abstract—This paper proposes a motion compensation method,to compensate,for the inter-pulse phase errors caused by the target movement in stepped-frequency ISAR imaging. For this purpose, genetic algorithm, particle swarm optimization (PSO) and PSO with an island model (PSOI) were applied in the proposed procedure. Simulation results using point scatterers and measured data show that PSOI is the most efficient in the

Sang-Hong Park; Hyo-Tae Kim; Kyung-Tae Kim

2008-01-01

162

An optimized method of harvesting vibrational energy with a piezoelectric element using a step-down DC-DC converter is presented. In this configuration, the converter regulates the power flow from the piezoelectric element to the desired electronic load. Analysis of the converter in discontinuous current conduction mode results in an expression for the duty cycle-power relationship. Using parameters of the mechanical system,

Geffrey K. Ottman; Heath F. Hofmann; George A. Lesieutre

2003-01-01

163

Background Malaria remains a major cause of morbidity and mortality worldwide. Flow cytometry-based assays that take advantage of fluorescent protein (FP)-expressing malaria parasites have proven to be valuable tools for quantification and sorting of specific subpopulations of parasite-infected red blood cells. However, identification of rare subpopulations of parasites using green fluorescent protein (GFP) labelling is complicated by autofluorescence (AF) of red blood cells and low signal from transgenic parasites. It has been suggested that cell sorting yield could be improved by using filters that precisely match the emission spectrum of GFP. Methods Detection of transgenic Plasmodium falciparum parasites expressing either tdTomato or GFP was performed using a flow cytometer with interchangeable optical filters. Parasitaemia was evaluated using different optical filters and, after optimization of optics, the GFP-expressing parasites were sorted and analysed by microscopy after cytospin preparation and by imaging cytometry. Results A new approach to evaluate filter performance in flow cytometry using two-dimensional dot blot was developed. By selecting optical filters with narrow bandpass (BP) and maximum position of filter emission close to GFP maximum emission in the FL1 channel (510/20, 512/20 and 517/20; dichroics 502LP and 466LP), AF was markedly decreased and signal-background improve dramatically. Sorting of GFP-expressing parasite populations in infected red blood cells at 90 or 95% purity with these filters resulted in 50-150% increased yield when compared to the standard filter set-up. The purity of the sorted population was confirmed using imaging cytometry and microscopy of cytospin preparations of sorted red blood cells infected with transgenic malaria parasites. Discussion Filter optimization is particularly important for applications where the FP signal and percentage of positive events are relatively low, such as analysis of parasite-infected samples with in the intention of gene-expression profiling and analysis. The approach outlined here results in substantially improved yield of GFP-expressing parasites, and requires decreased sorting time in comparison to standard methods. It is anticipated that this protocol will be useful for a wide range of applications involving rare events.

2012-01-01

164

NASA Astrophysics Data System (ADS)

Terrestrial ecosystem models have been widely used to simulate carbon, water and energy fluxes and climate-ecosystem interactions. In these models, some vegetation and soil parameters are determined based on limited studies from literatures without consideration of their seasonal variations. Data assimilation (DA) provides an effective way to optimize these parameters at different time scales . In this study, an ensemble Kalman filter (EnKF) is developed and applied to optimize two key parameters of an ecosystem model, namely the Boreal Ecosystem Productivity Simulator (BEPS): (1) the maximum photosynthetic carboxylation rate (Vcmax) at 25 °C, and (2) the soil water stress factor (fw) for stomatal conductance formulation. These parameters are optimized through assimilating observations of gross primary productivity (GPP) and latent heat (LE) fluxes measured in a 74 year-old pine forest, which is part of the Turkey Point Flux Station's age-sequence sites. Vcmax is related to leaf nitrogen concentration and varies slowly over the season and from year to year. In contrast, fw varies rapidly in response to soil moisture dynamics in the root-zone. Earlier studies suggested that DA of vegetation parameters at daily time steps leads to Vcmax values that are unrealistic. To overcome the problem, we developed a three-step scheme to optimize Vcmax and fw. First, the EnKF is applied daily to obtain precursor estimates of Vcmax and fw. Then Vcmax is optimized at different time scales assuming fw is unchanged from first step. The best temporal period or window size is then determined by analyzing the magnitude of the minimized cost-function, and the coefficient of determination (R2) and Root-mean-square deviation (RMSE) of GPP and LE between simulation and observation. Finally, the daily fw value is optimized for rain free days corresponding to the Vcmax curve from the best window size. The optimized fw is then used to model its relationship with soil moisture. We found that the optimized fw is best correlated linearly to soil water content at 5 to 10 cm depth. We also found that both the temporal scale or window size and the priori uncertainty of Vcmax (given as its standard deviation) are important in determining the seasonal trajectory of Vcmax. During the leaf expansion stage, an appropriate window size leads to reasonable estimate of Vcmax. In the summer, the fluctuation of optimized Vcmax is mainly caused by the uncertainties in Vcmax but not the window size. Our study suggests that a smooth Vcmax curve optimized from an optimal time window size is close to the reality though the RMSE of GPP at this window is not the minimum. It also suggests that for the accurate optimization of Vcmax, it is necessary to set appropriate levels of uncertainty of Vcmax in the spring and summer because the rate of leaf nitrogen concentration change is different over the season. Parameter optimizations for more sites and multi-years are in progress.

He, L.; Chen, J. M.; Liu, J.; Mo, G.; Zhen, T.; Chen, B.; Wang, R.; Arain, M.

2013-12-01

165

Filter Design and Analysis in Frequency Domain for Server Scheduling and Optimization

Internet traffic often exhibits a structure with rich high-order statistical properties like self-similarity and long-range dependency (LRD). This greatly complicates the problem of server performance modeling and optimization. Existing tools like queuing models in most cases only hold in mean value analysis under the assumption of simplified traffic structures. In this paper, we present a filter model to characterize the

Cheng-Zhong Xu; Minghua Xu; Le Yi Wang; George Yin

2010-01-01

166

A New Method Based on Ant Colony Optimization for the Probability Hypothesis Density Filter

\\u000a A new approximating estimate method based on ant colony optimization algorithm for probability hypothesis density (PHD) filter\\u000a is investigated and applied to estimate the time-varying number of targets and their states in clutter environment. Four key\\u000a process phases are included: generation of candidates, initiation, extremum search and state extraction. Numerical simulations\\u000a show the performance of the proposed method is closed

Jihong Zhu; Benlian Xu; Fei Wang; Qiquan Wang

167

Optimizing binary phase and amplitude filters for PCE, SNR, and discrimination

NASA Technical Reports Server (NTRS)

Binary phase-only filters (BPOFs) have generated much study because of their implementation on currently available spatial light modulator devices. On polarization-rotating devices such as the magneto-optic spatial light modulator (SLM), it is also possible to encode binary amplitude information into two SLM transmission states, in addition to the binary phase information. This is done by varying the rotation angle of the polarization analyzer following the SLM in the optical train. Through this parameter, a continuum of filters may be designed that span the space of binary phase and amplitude filters (BPAFs) between BPOFs and binary amplitude filters. In this study, we investigate the design of optimal BPAFs for the key correlation characteristics of peak sharpness (through the peak-to-correlation energy (PCE) metric), signal-to-noise ratio (SNR), and discrimination between in-class and out-of-class images. We present simulation results illustrating improvements obtained over conventional BPOFs, and trade-offs between the different performance criteria in terms of the filter design parameter.

Downie, John D.

1992-01-01

168

Multi-Bandwidth Frequency Selective Surfaces for Near Infrared Filtering: Design and Optimization

NASA Technical Reports Server (NTRS)

Frequency selective surfaces are widely used in the microwave and millimeter wave regions of the spectrum for filtering signals. They are used in telecommunication systems for multi-frequency operation or in instrument detectors for spectroscopy. The frequency selective surface operation depends on a periodic array of elements resonating at prescribed wavelengths producing a filter response. The size of the elements is on the order of half the electrical wavelength, and the array period is typically less than a wavelength for efficient operation. When operating in the optical region, diffraction gratings are used for filtering. In this regime the period of the grating may be several wavelengths producing multiple orders of light in reflection or transmission. In regions between these bands (specifically in the infrared band) frequency selective filters consisting of patterned metal layers fabricated using electron beam lithography are beginning to be developed. The operation is completely analogous to surfaces made in the microwave and millimeter wave region except for the choice of materials used and the fabrication process. In addition, the lithography process allows an arbitrary distribution of patterns corresponding to resonances at various wavelengths to be produced. The design of sub-millimeter filters follows the design methods used in the microwave region. Exacting modal matching, integral equation or finite element methods can be used for design. A major difference though is the introduction of material parameters and thicknesses tha_ may not be important in longer wavelength designs. This paper describes the design of multi-bandwidth filters operating in the I-5 micrometer wavelength range. This work follows on previous design [1,2]. In this paper extensions based on further optimization and an examination of the specific shape of the element in the periodic cell will be reported. Results from the design, manufacture and test of linear wedge filters built using micro-lithographic techniques and used ir spectral imaging applications will be presented.

Cwik, Tom; Fernandez, Salvador; Ksendzov, A.; LaBaw, Clayton C.; Maker, Paul D.; Muller, Richard E.

1999-01-01

169

Multi-Bandwidth Frequency Selective Surfaces for Near Infrared Filtering: Design and Optimization

NASA Technical Reports Server (NTRS)

Frequency selective surfaces are widely used in the microwave and millimeter wave regions of the spectrum for filtering signals. They are used in telecommunication systems for multi-frequency operation or in instrument detectors for spectroscopy. The frequency selective surface operation depends on a periodic array of elements resonating at prescribed wavelengths producing a filter response. The size of the elements is on the order of half the electrical wavelength, and the array period is typically less than a wavelength for efficient operation. When operating in the optical region, diffraction gratings are used for filtering. In this regime the period of the grating may be several wavelengths producing multiple orders of light in reflection or transmission. In regions between these bands (specifically in the infrared band) frequency selective filters consisting of patterned metal layers fabricated using electron beam lithography are beginning to be developed. The operation is completely analogous to surfaces made in the microwave and millimeter wave region except for the choice of materials used and the fabrication process. In addition, the lithography process allows an arbitrary distribution of patterns corresponding to resonances at various wavelengths to be produced. The design of sub-millimeter filters follows the design methods used in the microwave region. Exacting modal matching, integral equation or finite element methods can be used for design. A major difference though is the introduction of material parameters and thicknesses that may not be important in longer wavelength designs. This paper describes the design of multi- bandwidth filters operating in the 1-5 micrometer wavelength range. This work follows on a previous design. In this paper extensions based on further optimization and an examination of the specific shape of the element in the periodic cell will be reported. Results from the design, manufacture and test of linear wedge filters built using microlithographic techniques and used in spectral imaging applications will be presented.

Cwik, Tom; Fernandez, Salvador; Ksendzov, A.; LaBaw, Clayton C.; Maker, Paul D.; Muller, Richard E.

1998-01-01

170

Objectives Quantifying testicular homogenization resistant spermatid heads (HRSH) is a powerful indicator of spermatogenesis. These counts have traditionally been performed manually using a hemocytometer, but this method can be time consuming and biased. We aimed to develop a protocol to reduce debris for the application of automated counting, which would allow for efficient and unbiased quantification of rat HRSH. Findings We developed a filter-lysis protocol that effectively removes debris from rat testicular homogenates. After filtering and lysing the homogenates, we found no statistical differences between manual (classic and filter-lysis) and automated (filter-lysis) counts using one-way ANOVA with Bonferroni’s multiple comparison test. In addition, Pearson’s correlation coefficients were calculated to compare the counting methods and there was a strong correlation between the classic manual counts and the filter-lysis manual (r = 0.85, p = 0.002) and the filter-lysis automated (r = 0.89, p = 0.0005) counts. We also tested the utility of the automated method in a low dose exposure model known to decrease HRSH. Adult Fischer 344 rats exposed to 0.33% 2,5-hexanedione (HD) in the drinking water for 12 weeks demonstrated decreased body (p = 0.02) and testes (p = 0.002) weights. In addition, there was a significant reduction in the number of HRSH per testis (p = 0.002) when compared to control. Conclusions A filter-lysis protocol was optimized to purify rat testicular homogenates for automated HRSH counts. Automated counting systems yield unbiased data and can be applied to detect changes in the testis after low dose toxicant exposure.

Pacheco, Sara E.; Anderson, Linnea M.; Boekelheide, Kim

2013-01-01

171

Optimization of a blanching step to maximize sulforaphane synthesis in broccoli florets.

A blanching step was designed to favor sulforaphane synthesis in broccoli. Blanching was optimised through a central composite design, and the effects of temperature (50-70 °C) and immersion time in water (5-15 min) on the content of total glucosinolates, glucoraphanin, sulforaphane, and myrosinase activity were determined. Results were analysed by ANOVA and the optimal condition was determined through response surface methodology. Temperature between 50 and 60 °C significantly increased sulforaphane content (p<0.05), whilst blanching at 70 and 74 °C diminished significantly this content, compared to fresh broccoli. The optimal blanching conditions given by the statistical model were immersion in water at 57 °C for 13 min; coinciding with the minimum glucosinolates and glucoraphanin content, and with the maximum myrosinase activity. In the optimal conditions, the predicted response of 4.0 ?mol sulforaphane/g dry matter was confirmed experimentally. This value represents a 237% increase with respect to the fresh vegetable. PMID:24128476

Pérez, Carmen; Barrientos, Herna; Román, Juan; Mahn, Andrea

2014-02-15

172

Optimized particle-mesh Ewald/multiple-time step integration for molecular dynamics simulations

NASA Astrophysics Data System (ADS)

We develop an efficient multiple time step (MTS) force splitting scheme for biological applications in the AMBER program in the context of the particle-mesh Ewald (PME) algorithm. Our method applies a symmetric Trotter factorization of the Liouville operator based on the position-Verlet scheme to Newtonian and Langevin dynamics. Following a brief review of the MTS and PME algorithms, we discuss performance speedup and the force balancing involved to maximize accuracy, maintain long-time stability, and accelerate computational times. Compared to prior MTS efforts in the context of the AMBER program, advances are possible by optimizing PME parameters for MTS applications and by using the position-Verlet, rather than velocity-Verlet, scheme for the inner loop. Moreover, ideas from the Langevin/MTS algorithm LN are applied to Newtonian formulations here. The algorithm's performance is optimized and tested on water, solvated DNA, and solvated protein systems. We find CPU speedup ratios of over 3 for Newtonian formulations when compared to a 1 fs single-step Verlet algorithm using outer time steps of 6 fs in a three-class splitting scheme; accurate conservation of energies is demonstrated over simulations of length several hundred ps. With modest Langevin forces, we obtain stable trajectories for outer time steps up to 12 fs and corresponding speedup ratios approaching 5. We end by suggesting that modified Ewald formulations, using tailored alternatives to the Gaussian screening functions for the Coulombic terms, may allow larger time steps and thus further speedups for both Newtonian and Langevin protocols; such developments are reported separately.

Batcho, Paul F.; Case, David A.; Schlick, Tamar

2001-09-01

173

Implicit application of polynomial filters in a k-step Arnoldi method

NASA Technical Reports Server (NTRS)

The Arnoldi process is a well known technique for approximating a few eigenvalues and corresponding eigenvectors of a general square matrix. Numerical difficulties such as loss of orthogonality and assessment of the numerical quality of the approximations as well as a potential for unbounded growth in storage have limited the applicability of the method. These issues are addressed by fixing the number of steps in the Arnoldi process at a prescribed value k and then treating the residual vector as a function of the initial Arnoldi vector. This starting vector is then updated through an iterative scheme that is designed to force convergence of the residual to zero. The iterative scheme is shown to be a truncation of the standard implicitly shifted QR-iteration for dense problems and it avoids the need to explicitly restart the Arnoldi sequence. The main emphasis of this paper is on the derivation and analysis of this scheme. However, there are obvious ways to exploit parallelism through the matrix-vector operations that comprise the majority of the work in the algorithm. Preliminary computational results are given for a few problems on some parallel and vector computers.

Sorensen, D. C.

1990-01-01

174

An Optimized Blockwise Non Local Means Denoising Filter for 3D Magnetic Resonance Images

ó A critical issue in image restoration is the problem of noise removal while keeping the integrity of relevant image information. Denoising is a crucial step to increase image quality and to improve the performance of all the tasks needed for quantitative imaging analysis. The method proposed in this paper is based on a 3D optimized blockwise version of the

Pierrick Coupe; Pierre Yger; Sylvain Prima; Pierre Hellier; Charles Kervrann; Christian Barillot

2008-01-01

175

Optimization of EFTEM image acquisition by using elastically filtered images for drift correction.

Because of its high spatial resolution, energy-filtering transmission electron microscopy (EFTEM) has become widely used for the analysis of the chemical composition of nanostructures. To obtain the best spatial resolution, the precise correction of instrumental influences and the optimization of the data acquisition procedure are very important. In this publication, we discuss a modified image acquisition procedure that optimizes the acquisition process of the EFTEM images, especially for long exposure times and measurements that are affected by large spatial drift. To alleviate the blurring of the image caused by the spatial drift, we propose to take several EFTEM images with a shorter exposure time (sub-images) and merge these sub-images afterwards. To correct for the drift between these sub-images, elastically filtered images are acquired between two subsequent sub-images. These elastically filtered images are highly suitable for spatial drift correction based on the cross-correlation method. The use of the drift information between two elastically filtered images permits to merge the drift-corrected sub-images automatically and with high accuracy, resulting in sharper edges and an improved signal intensity in the final EFTEM image. Artefacts that are caused by prominent noise-peaks in the dark reference image have been suppressed by calculating the dark reference image from three images. Furthermore, using the information given by the elastically filtered images, it is possible to drift-correct a set of EFTEM images already during the acquisition. This simplifies the post-processing for elemental mapping and offers the possibility for active drift correction using the image shift function of the microscope, leading to an increased field of view. PMID:20392564

Heil, Tobias; Kohl, Helmut

2010-06-01

176

This paper introduces an original supervised classification method based on the optimization of the Fisher ratio under the Volterra filtering model. Optimum Volterra filters are derived for the problem of discriminating 2 classes. They have properties yielding some decision strategy that aims to reject (i.e. take no decision) data corresponding to unlearned classes. An original extension of this solution is

Cyrille J. Enderli; Radar Dpt

2007-01-01

177

A Two-Step Double Filter Method to Extract Open Water Surfaces from Landsat ETM+ Imagery

NASA Astrophysics Data System (ADS)

In arid and semi-arid areas, lakes and temporal ponds play a significant role in agriculture and livelihood of local communities as well as in ecology. Monitoring the changes of these open water bodies allows to draw conclusions on water use as well as climatic impacts and can assist in the formulation of a sustainable resource management strategy. The simultaneous monitoring of larger numbers of water bodies with respect to their stage and area is feasible with the aid of remote sensing. Here the monitoring of lake surface areas is discussed. Landsat TM and ETM+ images provide a medium resolution of 30m, and offer an easily available data source to monitor the long term changes of water surfaces in arid and semi-arid regions. In the past great effort was put into developing simple indices to extract water surfaces from satellite images. However, there is a common problem in achieving accurate results with these indices: How to select a threshold value for water pixels without introducing excessive subjective judgment. The threshold value would also have to vary with location, land features and seasons, allowing for inherent uncertainty. A new method was developed using Landsat ETM+ imaginary (30 meter resolution) to extract open water surfaces. This method uses the Normalized Difference of Vegetation Index (NDVI) as the basis for an objective way of selecting threshold values of Modified Normalized Difference of Water Index (MNDWI) and Stress Degree Days (SDD), which were used as a combined filter to extract open water surfaces. We choose two study areas to verify the method. One study area is in Northeast China, where bigger lakes, smaller muddy ponds and wetlands are interspersed with agricultural land and salt crusts. The other one is Kafue Flats in Zambia, where seasonal floods of the Zambezi River create seasonal wetlands in addition to the more permanent water ponds and river channels. For both sites digital globe images of 0.5 meter resolution are available, which were taken within a few days of Landsat passing dates and which will serve here as ground truth information. On their basis the new method was compared to other available methods for extracting water pixels. Compared to the other methods, the new method can extract water surface not only from deep lakes/reservoirs and wetlands but also from small mud ponds in alkali flats and irrigation ponds in the fields. For the big and deep lakes, the extracted boundary of the lakes fits accurately the observed boundary. Five test sites in the study area in Northeast China with only shallow water surfaces were chosen and tested. The extracted water surfaces were compared with each site's digital globe maps, respectively to determine the accuracy of the method. The comparison shows that the method could extract all completely wet pixels (water area covering 100% of the pixel area) in all test sites. For partially wet pixels (50-100% of pixel area), the model can detect 91% of all pixels. No dry pixels were mistaken by the model as water pixels. Keywords: Remote sensing, Landsat ETM+ imaginary, Water Surface, NDVI, MNDWI, and SDD

Wang, Haijing; Kinzelbach, Wolfgang

2010-05-01

178

Optimal hydrograph separation filter to evaluate transport routines of hydrological models

NASA Astrophysics Data System (ADS)

Hydrograph separation (HS) using recursive digital filter approaches focuses on trying to distinguish between the rapidly occurring discharge components like surface runoff, and the slowly changing discharge originating from interflow and groundwater. Filter approaches are mathematical procedures, which perform the HS using a set of separation parameters. The first goal of this study is an attempt to minimize the subjective influence that a user of the filter technique exerts on the results by the choice of such filter parameters. A simple optimal HS (OHS) technique for the estimation of the separation parameters was introduced, relying on measured stream hydrochemistry. The second goal is to use the OHS parameters to develop a benchmark model that can be used as a geochemical model itself, or to test the performance of process based hydro-geochemical models. The benchmark model quantifies the degree of knowledge that the stream flow time series itself contributes to the hydrochemical analysis. Results of the OHS show that the two HS fractions ("rapid" and "slow") differ according to the geochemical substances which were selected. The OHS parameters were then used to demonstrate how to develop benchmark model for hydro-chemical predictions. Finally, predictions of solute transport from a process-based hydrological model were compared to the proposed benchmark model. Our results indicate that the benchmark model illustrated and quantified the contribution of the modeling procedure better than only using traditional measures like r2 or the Nash-Sutcliffe efficiency.

Rimmer, Alon; Hartmann, Andreas

2014-05-01

179

CELISA, or cellular enzyme-linked immunosorbent assay, is a powerful and easy to use technique to study cell surface antigens under different stimulations. Nevertheless, some factors must be discussed and optimized prior to reaching a reproducible CELISA. These include the choice of cell density, fixative agent, blocking agent, culture medium, optimal antibody dilutions, and incubation time. In this paper, we first present a short review of some references devoted to CELISA by means of a comparison of these parameters, followed by their description. Then, we describe and study these different parameters using practical examples comparing TNF-induced ICAM-1 expression as an end point, on HBL melanoma and HUVEC. These cell lines were also chosen because they differ in their ability to grow as discontinuous and continuous layers, respectively. Furthermore, we designed a comprehensive flow chart, as well as a complete step-by-step protocol for CELISA optimization. PMID:11816800

Morandini, R; Boeynaems, J M; Wérenne, J; Ghanem, G

2001-01-01

180

Towards optimal explicit time-stepping schemes for the gyrokinetic equations

NASA Astrophysics Data System (ADS)

The nonlinear gyrokinetic equations describe plasma turbulence in laboratory and astrophysical plasmas. To solve these equations, massively parallel codes have been developed and run on present-day supercomputers. This paper describes measures to improve the efficiency of such computations, thereby making them more realistic. Explicit Runge-Kutta schemes are considered to be well suited for time-stepping. Although the numerical algorithms are often highly optimized, performance can still be improved by a suitable choice of the time-stepping scheme, based on the spectral analysis of the underlying operator. Here, an operator splitting technique is introduced to combine first-order Runge-Kutta-Chebychev schemes for the collision term with fourth-order schemes for the remaining terms. In the nonlinear regime, based on the observation of eigenvalue shifts due to the (generalized) E×B advection term, an accurate and robust estimate for the nonlinear timestep is developed. The presented techniques can reduce simulation times by factors of up to three in realistic cases. This substantial speedup encourages the use of similar timestep optimized explicit schemes not only for the gyrokinetic equation, but also for other applications with comparable properties.

Doerk, H.; Jenko, F.

2014-07-01

181

NASA Astrophysics Data System (ADS)

The photorefractive joint transform correlator (JTC) combines two features. The first is embedded semi-adaptive optimality which weighs the correlation against clutter and noise in the input and the second is the intrinsic dynamic range compression nonlinearity which improves several metrics simultaneously without metric tradeoff. The performance of this two-beam coupling joint transform correlator scheme is evaluated against several other well-known correlation filters that have been developed during the last three decades. The result shows that the two-beam coupling joint transform scheme is a very robust correlator with respect to standard evaluation metrics for different sets of data.

Khoury, Jed; Alam, Mohammad S.; Banerjee, Partha P.; Nehmetallah, Georges T.; Durant, William M.; Martin, Daniel M.; Donoghue, John; Peyghambarian, N.; Yamamoto, M.

2014-04-01

182

Optimized model of oriented-line-target detection using vertical and horizontal filters

NASA Astrophysics Data System (ADS)

A line-element target differing sufficiently in orientation from a background of line elements can be visually detected easily and quickly; orientation thresholds for such detection are lowest when the background elements are all vertical or all horizontal. A simple quantitative model of this performance was constructed from two classes of anisotropic filters, (2) nonlinear point transformation, and (3) estimation of a signal-to-noise ratio based on responses to images with and without a target. A Monte Carlo optimization procedure (simulated annealing) was used to determine the model parameter values required for providing an accurate description of psychophysical data on orientation increment thresholds.

Westland, Stephen; Foster, David H.

1995-08-01

183

NASA Astrophysics Data System (ADS)

A frequency domain implementation of the Optimal Trade-off Maximum Average Correlation Height (OT-MACH) filter has been optimized to classify target vehicles acquired from a Forward Looking Infra Red (FLIR) sensor. The clutter noise does not have a white spectrum and models employing the power spectral density of the background clutter require a predefined threshold. A method of automatically adjusting the noise model in the filter by using the input image statistical information has been introduced. Parameter surfaces for the remaining OT-MACH variables are calculated in order to determine optimal operating conditions for the view independent recognition of vehicles in highly cluttered FLIR imagery.

Alkandri, Ahmad; Gardezi, Akber; Birch, Philip; Young, Rupert; Chatwin, Chris

2011-04-01

184

High-frequency ultrasound (HFUS) in the 20 MHz to 100 MHz range has to meet the opposite requirements of good spatial resolution and of high penetration depth for in vivo ultrasound biomicroscopy (UBM) of skin. The attenuation of water, which serves as sound propagation medium between utilized single element transducers and the skin, becomes very eminent with increasing frequency. Furthermore, the spectra of acquired radio frequency (rf) echo signals change over depth because of the diffracted sound field characteristics. The reduction of the system's center frequency and bandwidth causes a significant loss of spatial resolution over depth. In this paper, the spectral characteristics of HFUS imaging systems and the potential of inverse echo signal filtering for the optimization of pulse-echo measurements is analyzed and validated. A Gaussian model of the system's transfer function, which takes into account the frequency-dependent attenuation of the water path, was developed. Predictions of system performance are derived from this model and compared with measurement results. The design of a HFUS skin imaging system with a 100 MHz range transducer and a broadband driving electronics is discussed. A time-variant filter for inverse rf echo signal filtering was designed to compensate the system's depth-dependent imaging properties. Results of in vivo measurements are shown and discussed. PMID:17703658

Vogt, Michael; Ermert, Helmut

2007-08-01

185

The aim of the present study was to investigate the suitability of a Biological Aerated Filter (BAF) plant as an alternative process or an upgrading step for the treatment of domestic wastewater from the city of Rome, Italy. The results obtained through a three years experimental activity on a pilot-scale BAF plant fed with real wastewater showed high process efficiencies and stable performance for both carbon and ammonia oxidation. The effluent quality met, on average basis, 68 mg/L total COD (COD(tot)), 37 mg/L Total Suspended Solids (TSS), 3.3mg/L ammonia-nitrogen (NH(4)(+)-N) and 21.1mg/L nitrate-nitrogen (NO(3)(-)-N). Despite the good performance, the high content of suspended solids in the influent stream caused filter bed clogging and frequent backwashing operations were required. Therefore, in the last part of the experimental activity a pre-treatment step was adopted prior to the biological step, consisting of chemical precipitation by lime addition. The influent quality parameters were consequently modified; for instance the particulate matter content was reduced by about 73%. The process efficiency of both ammonia and organic carbon oxidation did not modify appreciably; however, a beneficial effect was obtained on the frequency of the backwashing phase, which could be reduced by half. Since the new combined chemical-biological system demonstrated to be a valid alternative to the activated sludge treatment plant, a modeling activity was finally performed with the aim of evaluating the design parameters of a full-scale BAF plant fed with the same pre-treated wastewater as used in the experimental activity. The results of this phase are also herewith presented and discussed. PMID:19631453

Farabegoli, G; Chiavola, A; Rolle, E

2009-11-15

186

NASA Astrophysics Data System (ADS)

In communications systems, the message signal is sometimes spread over a large bandwidth in order to realize performance gains in the presence of narrowband interference, multipath propagation, and multiuser interference. The extent to which performance is improved is highly dependent upon the spreading code implemented. Traditionally, the spreading codes have consisted of pseudo-noise (PN) sequences whose chip values are limited to bipolar values. Recently, however, alternatives to the PN sequences have been studied including wavelet based and PR-QMF based spreading codes. The spreading codes implemented are the basis functions of a particular wavelet transform or PR-QMF bank. Since the choice of available basis functions is much larger than that of PN sequences, it is hoped that better performance can be achieved by choosing a basis tailored to the system requirements mentioned above. In this paper, a design method is presented to construct a PR-QMF bank which will generate spreading codes optimized for operating in a multiuser interference environment. Objective functions are developed for the design criteria and a multivariable constrained optimization problem is employed to generate the coefficients used in the filter bank. Once the filter bank is complete, the spreading codes are extracted and implemented in the spread spectrum system. System bit error rate (BER) curves are generated from computer simulation for analysis. Curves are generated for both the single user and the CDMA environment and performance is compared to that attained using gold codes.

Hetling, Kenneth J.; Saulnier, Gary J.; Das, Pankaj K.

1995-04-01

187

Optimal hydrograph separation filter to evaluate transport routines of hydrological models

NASA Astrophysics Data System (ADS)

Hydrograph separation (HS) using recursive digital filter approaches focuses on trying to distinguish between the rapidly occurring discharge components like surface runoff, and the slowly changing discharge originating from interflow and groundwater. Filter approaches are mathematical procedures, which perform the HS using a set of separation parameters. The first goal of this study is to minimize the subjective influence that a user of the filter technique exerts on the results by the choice of such filter parameters. A simple optimal HS (OHS) technique for the estimation of the separation parameters was introduced, relying on measured stream hydrochemistry. The second goal is to use the OHS parameters to benchmark the performance of process-based hydro-geochemical (HG) models. The new HG routine can be used to quantify the degree of knowledge that the stream flow time series itself contributes to the HG analysis, using newly developed benchmark geochemistry efficiency (BGE). Results of the OHS show that the two HS fractions (“rapid” and “slow”) differ according to the HG substances which were selected. The BFImax parameter (long-term ratio of baseflow to total streamflow) ranged from 0.26 to 0.94 for SO4-2 and total suspended solids, TSS, respectively. Then, predictions of SO4-2 transport from a process-based hydrological model were benchmarked with the proposed HG routine, in order to evaluate the significance of the HG routines in the process-based model. This comparison provides valuable quality test that would not be obvious when using the traditional measures like r2 or the NSE (Nash-Sutcliffe efficiency). The process-based model resulted in r2 = 0.65 and NSE = 0.65, while the benchmark routine results were slightly lower with r2 = 0.61 and NSE = 0.58. However, the comparison between the two model resulted in obvious advantage for the process-based model with BGE = 0.15.

Rimmer, Alon; Hartmann, Andreas

2014-06-01

188

A filter housing design technique has been developed that computes the housing geometry required to provide a user-specified velocity distribution through the filter. Appropriate control of the flow field across the filter can improve filter efficiency. Two-dimensional computational designs have been performed specifying a uniform velocity distribution through the filter. This distribution corresponds to a uniform, constant pressure drop across

A. AL-SARKHI; F. W. CHAMBERS

2004-01-01

189

The ARTcrystal process is a new approach for the production of drug nanocrystals. It is a combination of a special pre-treatment step with subsequent high pressure homogenization (HPH) at low pressures. In the pre-treatment step the particle size is already reduced to the nanometer range by use of the newly developed ART MICCRA rotor-stator system. In this study, the running parameters for the ART MICCRA system are systematically studied, i.e. temperature, stirring speed, flow rate, foaming effects, size of starting material, valve position from 0° to 45°. The antioxidant rutin was used as model drug. Applying optimized parameters, the pre-milling yielded already a nanosuspension with a photon correlation spectroscopy (PCS) diameter of about 650 nm. On lab scale production time was 5 min for 1L nanosuspension (5% rutin content), i.e. the capacity of the setup is also suitable for medium industrial scale production. Compared to other nanocrystal production methods (bead milling, HPH, etc.), similar sizes are achievable, but the process is more cost-effective, faster in time and easily scale-able, thus being an interesting novel process for nanocrystal production on lab and industrial scale. PMID:24556175

Scholz, Patrik; Arntjen, Anja; Müller, Rainer H; Keck, Cornelia M

2014-04-25

190

NASA Technical Reports Server (NTRS)

We propose an ultra compact single-layer spurious suppression band pass filter design which has the following benefit: 1) Effective coupling area can be increased with no fabrication limitation and no effect on the spurious response; 2) Two fundamental poles are introduced to suppress spurs; 3) Filter can be designed with up to 30% bandwidth; 4) The Filter length is reduced by at least 100% when compared to the conventional filter; 5) Spurious modes are suppressed up to at the seven times the fundamental frequency; and 6) It uses only one layer of metallization which minimize the fabrication cost.

U-Yen, Kongpop; Wollack, Ed; Papapolymerou, John; Laskar, Joy

2005-01-01

191

Optimal Tuner Selection for Kalman-Filter-Based Aircraft Engine Performance Estimation

NASA Technical Reports Server (NTRS)

An emerging approach in the field of aircraft engine controls and system health management is the inclusion of real-time, onboard models for the inflight estimation of engine performance variations. This technology, typically based on Kalman-filter concepts, enables the estimation of unmeasured engine performance parameters that can be directly utilized by controls, prognostics, and health-management applications. A challenge that complicates this practice is the fact that an aircraft engine s performance is affected by its level of degradation, generally described in terms of unmeasurable health parameters such as efficiencies and flow capacities related to each major engine module. Through Kalman-filter-based estimation techniques, the level of engine performance degradation can be estimated, given that there are at least as many sensors as health parameters to be estimated. However, in an aircraft engine, the number of sensors available is typically less than the number of health parameters, presenting an under-determined estimation problem. A common approach to address this shortcoming is to estimate a subset of the health parameters, referred to as model tuning parameters. The problem/objective is to optimally select the model tuning parameters to minimize Kalman-filterbased estimation error. A tuner selection technique has been developed that specifically addresses the under-determined estimation problem, where there are more unknown parameters than available sensor measurements. A systematic approach is applied to produce a model tuning parameter vector of appropriate dimension to enable estimation by a Kalman filter, while minimizing the estimation error in the parameters of interest. Tuning parameter selection is performed using a multi-variable iterative search routine that seeks to minimize the theoretical mean-squared estimation error of the Kalman filter. This approach can significantly reduce the error in onboard aircraft engine parameter estimation applications such as model-based diagnostic, controls, and life usage calculations. The advantage of the innovation is the significant reduction in estimation errors that it can provide relative to the conventional approach of selecting a subset of health parameters to serve as the model tuning parameter vector. Because this technique needs only to be performed during the system design process, it places no additional computation burden on the onboard Kalman filter implementation. The technique has been developed for aircraft engine onboard estimation applications, as this application typically presents an under-determined estimation problem. However, this generic technique could be applied to other industries using gas turbine engine technology.

Simon, Donald L.; Garg, Sanjay

2011-01-01

192

To focus ultrasonic waves in an unknown heterogeneous medium using a phased array, one has to calculate the optimal set of signals to be applied on the transducers of the array. (In most applications of ultrasound, medical imaging, medical therapy, nondestructive testing, the first step consists of focusing a broadband ultrasound beam deeply inside the medium to be investigated.) Focusing in a homogeneous medium simply requires to compensate for the varying focus-array elements geometrical distances. Nevertheless, heterogeneities in the medium, in terms of speed of sound, density, or absorption, may strongly degrade the focusing. Different techniques have been developed in order to correct such aberrations induced by heterogeneous media (time reversal, speckle brightness, for example). In the companion to this paper, a new broadband focusing technique was investigated: the spatio-temporal inverse filter. Experimental results obtained in various media, such as reverberating and absorbing media, are presented here. In particular, intraplate echoes suppression and high-quality focusing through a human skull, as well as hyper-resolution in a reverberating medium, will be shown. It is important to notice that all these experiments were performed with fully programmable multichannel electronics whose use is required to fully exploit the spatio-temporal technique. PMID:11508973

Aubry, J F; Tanter, M; Gerber, J; Thomas, J L; Fink, M

2001-07-01

193

NASA Astrophysics Data System (ADS)

Compressible flow based image registration operates under the assumption that the mass of the imaged material is conserved from one image to the next. Depending on how the mass conservation assumption is modeled, the performance of existing compressible flow methods is limited by factors such as image quality, noise, large magnitude voxel displacements, and computational requirements. The Least Median of Squares Filtered Compressible Flow (LFC) method introduced here is based on a localized, nonlinear least squares, compressible flow model that describes the displacement of a single voxel that lends itself to a simple grid search (block matching) optimization strategy. Spatially inaccurate grid search point matches, corresponding to erroneous local minimizers of the nonlinear compressible flow model, are removed by a novel filtering approach based on least median of squares fitting and the forward search outlier detection method. The spatial accuracy of the method is measured using ten thoracic CT image sets and large samples of expert determined landmarks (available at www.dir-lab.com). The LFC method produces an average error within the intra-observer error on eight of the ten cases, indicating that the method is capable of achieving a high spatial accuracy for thoracic CT registration.

Castillo, Edward; Castillo, Richard; White, Benjamin; Rojo, Javier; Guerrero, Thomas

2012-08-01

194

Application of digital tomosynthesis (DTS) of optimal deblurring filters for dental X-ray imaging

NASA Astrophysics Data System (ADS)

Digital tomosynthesis (DTS) is a limited-angle tomographic technique that provides some of the tomographic benefits of computed tomography (CT) but at reduced dose and cost. Thus, the potential for application of DTS to dental X-ray imaging seems promising. As a continuation of our dental radiography R&D, we developed an effective DTS reconstruction algorithm and implemented it in conjunction with a commercial dental CT system for potential use in dental implant placement. The reconstruction algorithm employed a backprojection filtering (BPF) method based upon optimal deblurring filters to suppress effectively both the blur artifacts originating from the out-focus planes and the high-frequency noise. To verify the usefulness of the reconstruction algorithm, we performed systematic simulation works and evaluated the image characteristics. We also performed experimental works in which DTS images of enhanced anatomical resolution were successfully obtained by using the algorithm and were promising to our ongoing applications to dental X-ray imaging. In this paper, our approach to the development of the DTS reconstruction algorithm and the results are described in detail.

Oh, J. E.; Cho, H. S.; Kim, D. S.; Choi, S. I.; Je, U. K.

2012-04-01

195

A pseudo-dynamic sub-optimal filter for elastography under static loading and measurements

NASA Astrophysics Data System (ADS)

We propose a pseudo-dynamic form of a sub-optimal Kalman filter for elastography of plane-strain models of soft tissues under strictly static deformations and partial measurements. Since the tissue material is nearly incompressible and is thus prone to volumetric locking via standard displacement-based finite element formulations, we use a Cosserat point approach for deriving the static equilibrium equations. A pseudo-dynamical form of the equilibrium equations, with added noise and appropriate augmentation by the discretized shear modulus as additional states, is then adopted as the process equation such that its steady-state solution approaches the static response of the plane-strain model. A fictitious noise of small intensity is also added to the measurement equation and, following linearization of the process equation, a Kalman filter is applied to reconstruct the shear modulus profile. We present several numerical experiments, some of which also bring forth the relative advantages of the proposed approach over a deterministic reconstruction based on a quasi-Newton search.

Banerjee, B.; Roy, D.; Vasu, R. M.

2009-01-01

196

Compressible flow based image registration operates under the assumption that the mass of the imaged material is conserved from one image to the next. Depending on how the mass conservation assumption is modeled, the performance of existing compressible flow methods is limited by factors such as image quality, noise, large magnitude voxel displacements, and computational requirements. The Least Median of Squares Filtered Compressible Flow (LFC) method introduced here is based on a localized, nonlinear least squares, compressible flow model that describes the displacement of a single voxel that lends itself to a simple grid search (block matching) optimization strategy. Spatially inaccurate grid search point matches, corresponding to erroneous local minimizers of the nonlinear compressible flow model, are removed by a novel filtering approach based on least median of squares fitting and the forward search outlier detection method. The spatial accuracy of the method is measured using ten thoracic CT image sets and large samples of expert determined landmarks (available at www.dir-lab.com). The LFC method produces an average error within the intra-observer error on eight of the ten cases, indicating that the method is capable of achieving a high spatial accuracy for thoracic CT registration.

Castillo, Edward; Castillo, Richard; White, Benjamin; Rojo, Javier; Guerrero, Thomas

2012-01-01

197

A hydrodynamically levitated centrifugal blood pump with a semi-open impeller has been developed for mechanical circulatory assistance. However, a narrow bearing gap has the potential to cause hemolysis. The purpose of the present study is to optimize the geometric configuration of the hydrodynamic step bearing in order to reduce hemolysis by expansion of the bearing gap. First, a numerical analysis of the step bearing, based on lubrication theory, was performed to determine the optimal design. Second, in order to assess the accuracy of the numerical analysis, the hydrodynamic forces calculated in the numerical analysis were compared with those obtained in an actual measurement test using impellers having step lengths of 0%, 33%, and 67% of the vane length. Finally, a bearing gap measurement test and a hemolysis test were performed. As a result, the numerical analysis revealed that the hydrodynamic force was the largest when the step length was approximately 70%. The hydrodynamic force calculated in the numerical analysis was approximately equivalent to that obtained in the measurement test. In the measurement test and the hemolysis test, the blood pump having a step length of 67% achieved the maximum bearing gap and reduced hemolysis, as compared with the pumps having step lengths of 0% and 33%. It was confirmed that the numerical analysis of the step bearing was effective, and the developed blood pump having a step length of approximately 70% was found to be a suitable configuration for the reduction of hemolysis. PMID:23834855

Kosaka, Ryo; Yada, Toru; Nishida, Masahiro; Maruyama, Osamu; Yamane, Takashi

2013-09-01

198

Do Humans Optimally Exploit Redundancy to Control Step Variability in Walking?

It is widely accepted that humans and animals minimize energetic cost while walking. While such principles predict average behavior, they do not explain the variability observed in walking. For robust performance, walking movements must adapt at each step, not just on average. Here, we propose an analytical framework that reconciles issues of optimality, redundancy, and stochasticity. For human treadmill walking, we defined a goal function to formulate a precise mathematical definition of one possible control strategy: maintain constant speed at each stride. We recorded stride times and stride lengths from healthy subjects walking at five speeds. The specified goal function yielded a decomposition of stride-to-stride variations into new gait variables explicitly related to achieving the hypothesized strategy. Subjects exhibited greatly decreased variability for goal-relevant gait fluctuations directly related to achieving this strategy, but far greater variability for goal-irrelevant fluctuations. More importantly, humans immediately corrected goal-relevant deviations at each successive stride, while allowing goal-irrelevant deviations to persist across multiple strides. To demonstrate that this was not the only strategy people could have used to successfully accomplish the task, we created three surrogate data sets. Each tested a specific alternative hypothesis that subjects used a different strategy that made no reference to the hypothesized goal function. Humans did not adopt any of these viable alternative strategies. Finally, we developed a sequence of stochastic control models of stride-to-stride variability for walking, based on the Minimum Intervention Principle. We demonstrate that healthy humans are not precisely “optimal,” but instead consistently slightly over-correct small deviations in walking speed at each stride. Our results reveal a new governing principle for regulating stride-to-stride fluctuations in human walking that acts independently of, but in parallel with, minimizing energetic cost. Thus, humans exploit task redundancies to achieve robust control while minimizing effort and allowing potentially beneficial motor variability.

Dingwell, Jonathan B.; John, Joby; Cusumano, Joseph P.

2010-01-01

199

The first on-site evaluation of a new filter optimized for TARC and developer

NASA Astrophysics Data System (ADS)

In previous studies, we identified filter properties that have a strong effect on microbubble formation on the downstream side of the filter membrane. A new Highly Asymmetric Polyarylsulfone (HAPAS) filter was developed based on the findings. In the current study, we evaluated newly-developed HAPAS filter in environmentally preferred non-PFOS TARC in a laboratory setting. Test results confirmed that microbubble counts downstream of the filter were lower than those of a conventional HDPE filter. Further testing in a manufacturing environment confirmed that HAPAS filtration of TARC at point of use was able to reduce defectivity caused by microbubbles on both unpatterned and patterned wafers, compared with a HDPE filter.

Umeda, Toru; Ishibashi, Takeo; Nakamura, Atsushi; Ide, Junichi; Nagano, Masaru; Omura, Koichi; Tsuzuki, Shuichi; Numaguchi, Toru

2008-11-01

200

Data-driven temporal filtering approaches based on a specific optimization criterion have been shown to be capable of enhancing the discrimination and robustness of speech features in speech recognition. The filters in these approaches are often obtained with the statistics of the features in the temporal domain. In this paper, we derive new data-driven temporal filters that employ the statistics of

Jeih-weih Hung; Nantou Hsien

2007-01-01

201

Independent component analysis (ICA) aims at decomposing an observed random vector into statistically independent variables. Deflation-based implementations, such as the popular one-unit FastICA algorithm and its variants, extract the independent components one after another. A novel method for deflationary ICA, referred to as RobustICA, is put forward in this paper. This simple technique consists of performing exact line search optimization of the kurtosis contrast function. The step size leading to the global maximum of the contrast along the search direction is found among the roots of a fourth-degree polynomial. This polynomial rooting can be performed algebraically, and thus at low cost, at each iteration. Among other practical benefits, RobustICA can avoid prewhitening and deals with real- and complex-valued mixtures of possibly noncircular sources alike. The absence of prewhitening improves asymptotic performance. The algorithm is robust to local extrema and shows a very high convergence speed in terms of the computational cost required to reach a given source extraction quality, particularly for short data records. These features are demonstrated by a comparative numerical analysis on synthetic data. RobustICA's capabilities in processing real-world data involving noncircular complex strongly super-Gaussian sources are illustrated by the biomedical problem of atrial activity (AA) extraction in atrial fibrillation (AF) electrocardiograms (ECGs), where it outperforms an alternative ICA-based technique. PMID:20028621

Zarzoso, Vicente; Comon, Pierre

2010-02-01

202

NASA Technical Reports Server (NTRS)

The determination of optimum filtering characteristics for guidance system design is generally a tedious process which cannot usually be carried out in general terms. In this report a simple explicit solution is given which is applicable to many different types of problems. It is shown to be applicable to problems which involve optimization of constant-coefficient guidance systems and time-varying homing type systems for several stationary and nonstationary inputs. The solution is also applicable to off-design performance, that is, the evaluation of system performance for inputs for which the system was not specifically optimized. The solution is given in generalized form in terms of the minimum theoretical error, the optimum transfer functions, and the optimum transient response. The effects of input signal, contaminating noise, and limitations on the response are included. From the results given, it is possible in an interception problem, for example, to rapidly assess the effects on minimum theoretical error of such factors as target noise and missile acceleration. It is also possible to answer important questions regarding the effect of type of target maneuver on optimum performance.

Stewart, Elwood C.

1961-01-01

203

NASA Astrophysics Data System (ADS)

Correlation filters with three transmittance levels (+1, 0, and -1) are of interest in optical pattern recognition because they can be implemented on available spatial light modulators and because the zero level allows us to include a region of support (ROS). The ROS can provide additional control over the filter's noise tolerance and peak sharpness. A new algorithm based on optimizing a compromise average performance measure (CAPM) is proposed for designing three-level composite filters. The performance of this algorithm is compared to other three-level composite filter designs using a common image database and using figures of merit such as the Fisher ratio, error rate, and light efficiency. It is shown that the CAPM algorithm yields better results.

Hendrix, Charles D.; Vijaya Kumar, B. V. K.

1994-06-01

204

NASA Astrophysics Data System (ADS)

Five-zone binary phase filters (FBPFs) are proposed for decreasing the spot size and/or increasing the focal depth of the near-field optical storage system with a hemisphere solid immersion lens (SIL). The design of filters is based on the vector diffraction theory and the MATLAB optimizing toolbox. Three FBPFs with rotationally symmetrical pupil function have been designed, where the one FBPF is for increasing the focal depth as big as possible, the second FBPF is for improving the resolution as high as possible, and the third FBPF integrate the increase of focal depth with the improvement of resolution. Numerical results show that compared with the three-zone amplitude filter, the designed five-zone binary phase-only filters have more prominent performances in improving the focal depth and the resolution of the near-field SIL optical storage system.

Fang, Chaolong; Zhang, Yaoju; Zhu, Haiyong

2012-06-01

205

A solution is derived to the problems of H? -optimal linear state regulation and filtering. The solution method for both problems is based on a transfer function approach which applies standard spectral factorization. Return difference relations are given which are extensions of the relations associated with the linear quadratic problem

Isaac Yaesh; Uri Shaked

1991-01-01

206

In this paper, the first real-time implementation and perceptual evaluation of a singular value decomposition (SVD)-based optimal filtering technique for noise reduction in a dual microphone behind-the-ear (BTE) hearing aid is presented. This evaluation was carried out for a speech weighted noise and multitalker babble, for single and multiple jammer sound source scenarios. Two basic microphone configurations in the hearing aid were used. The SVD-based optimal filtering technique was compared against an adaptive beamformer, which is known to give significant improvements in speech intelligibility in noisy environment. The optimal filtering technique works without assumptions about a speaker position, unlike the two-stage adaptive beamformer. However this strategy needs a robust voice activity detector (VAD). A method to improve the performance of the VAD was presented and evaluated physically. By connecting the VAD to the output of the noise reduction algorithms, a good discrimination between the speech-and-noise periods and the noise-only periods of the signals was obtained. The perceptual experiments demonstrated that the SVD-based optimal filtering technique could perform as well as the adaptive beamformer in a single noise source scenario, i.e., the ideal scenario for the latter technique, and could outperform the adaptive beamformer in multiple noise source scenarios. PMID:16189969

Maj, Jean-Baptiste; Royackers, Liesbeth; Moonen, Marc; Wouters, Jan

2005-09-01

207

This paper proposes a novel grid synchronization scheme using a new phase-locked loop (PLL) scheme based on the adaptive linear optimal filtering (ALOF) technique. The problem formulation of the proposed ALOF is based on decomposing grid voltage signal into inner product of two vectors, namely, the vector of trigonometric functions and the vector of coefficients, corresponding to the input vector

Yang Han; Lin Xu; Muhammad Mansoor Khan; Gang Yao; Li-Dan Zhou; Chen Chen

2009-01-01

208

This paper proposes a novel hybrid learning algorithm with stable learning laws for Adaptive Network-based Fuzzy Inference System (ANFIS) as a system identifier. The proposed hybrid learning algorithm is based on the particle swarm optimization (PSO) for training the antecedent part and the extended Kalman filter (EKF) for training the conclusion part. Lyapunov stability theory is used to study the

Mahdi Aliyari Shoorehdeli; Mohammad Teshnehlab; Ali Khaki Sedigh

2009-01-01

209

NSDL National Science Digital Library

Students learn how CCD cameras use color filters to create astronomical images in this Moveable Museum unit. The four-page PDF guide includes suggested general background readings for educators, activity notes, and step-by-step directions. Students look at black-and-white photos to understand gray scale and construct simple red and green cellophane filters and observe magazine images through them.

210

Particle Swarm Optimization aided unscented kalman filter for ballistic target tracking

Tracking of a ballistic target in its reentry phase by considering the radar measurements is a highly complex problem in nonlinear filtering. Kalman Filter (KF) is used to estimate the positions of the target when the measurements are corrupted with noise. If the measurements (range and bearing) are nonlinear then Unscented Kalman filter (UKF) can be used. For obtaining reliable

Ravi Kumar Jatoth; D. N. Rao; K. S. Kumar

2010-01-01

211

Optimality of the maximum average correlation height filter for detection of targets in noise

A statistical analysis is provided for the properties of the recently developed maximum average correlation height (MACH) filter (Mahalanobis et al. 1994). It is shown that the MACH filter can be interpreted as an optimum filter for the detection of targets in additive noise. A rationale is given for using a popular peak-to-sidelobe ratio metric to characterize the output of

Abhijit Mahalanobis; B. V. K. Vijaya Kumar

1997-01-01

212

Three new concepts — breakdown points, breakdown probabilities, and midpoint sensitivity curves — for stack filter analysis are introduced and analyzed in this paper. Breakdown points and probabilities can be used as measures of the robustness of stack filters. Midpoint sensitivity curves in turn give information on how sensitive the output of a stack filter is to the changes of

Pauli Kuosmanen; Jaakko Astola

1996-01-01

213

NASA Astrophysics Data System (ADS)

This paper proposes Hybrid Genetic Algorithm (GA)-Adaptive Particle Swarm Optimization (APSO) aided Unscented Kalman Filter (UKF) to estimate the harmonic components present in power system voltage/current waveforms. The initial choice of the process and measurement error covariance matrices Q and R (called tuning of the filter) plays a vital role in removal of noise. Hence, hybrid GA-APSO algorithm is used to estimate the error covariance matrices by minimizing the Root Mean Square Error(RMSE) of the UKF. Simulation results are presented to demonstrate the estimation accuracy is significantly improved in comparison with that of conventional UKF.

Jatoth, Ravi Kumar; Reddy, Gogulamudi Anudeep

214

NASA Astrophysics Data System (ADS)

With well-determined hydraulic parameters in a hydrologic model, a traditional data assimilation method (such as the Kalman filter and its extensions) can be used to retrieve root zone soil moisture under uncertain initial state variables (e.g., initial soil moisture content) and good simulated results can be achieved. However, when the key soil hydraulic parameters are incorrect, the error is non-Gaussian, as the Kalman filter will produce a persistent bias in its predictions. In this paper, we propose a method coupling optimal parameters and extended Kalman filter data assimilation (OP-EKF) by combining optimal parameter estimation, the extended Kalman filter (EKF) assimilation method, a particle swarm optimization (PSO) algorithm, and Richards' equation. We examine the accuracy of estimating root zone soil moisture through the optimal parameters and extended Kalman filter data assimilation method by using observed in situ data at the Meiling experimental station, China. Results indicate that merely using EKF for assimilating surface soil moisture content to obtain soil moisture content in the root zone will produce a persistent bias between simulated and observed values. Using the OP-EKF assimilation method, estimates were clearly improved. If the soil profile is heterogeneous, soil moisture retrieval is accurate in the 0-50 cm soil profile and is inaccurate at 100 cm depth. Results indicate that the method is useful for retrieving root zone soil moisture over large areas and long timescales even when available soil moisture data are limited to the surface layer, and soil moisture content are uncertain and soil hydraulic parameters are incorrect.

Lü, Haishen; Yu, Zhongbo; Zhu, Yonghua; Drake, Sam; Hao, Zhenchun; Sudicky, Edward A.

2011-03-01

215

Selection of plants for optimization of vegetative filter strips treating runoff from turfgrass.

Runoff from turf environments, such as golf courses, is of increasing concern due to the associated chemical contamination of lakes, reservoirs, rivers, and ground water. Pesticide runoff due to fungicides, herbicides, and insecticides used to maintain golf courses in acceptable playing condition is a particular concern. One possible approach to mitigate such contamination is through the implementation of effective vegetative filter strips (VFS) on golf courses and other recreational turf environments. The objective of the current study was to screen ten aesthetically acceptable plant species for their ability to remove four commonly-used and degradable pesticides: chlorpyrifos (CP), chlorothalonil (CT), pendimethalin (PE), and propiconazole (PR) from soil in a greenhouse setting, thus providing invaluable information as to the species composition that would be most efficacious for use in VFS surrounding turf environments. Our results revealed that blue flag iris (Iris versicolor) (76% CP, 94% CT, 48% PE, and 33% PR were lost from soil after 3 mo of plant growth), eastern gama grass (Tripsacum dactyloides) (47% CP, 95% CT, 17% PE, and 22% PR were lost from soil after 3 mo of plant growth), and big blue stem (Andropogon gerardii) (52% CP, 91% CT, 19% PE, and 30% PR were lost from soil after 3 mo of plant growth) were excellent candidates for the optimization of VFS as buffer zones abutting turf environments. Blue flag iris was most effective at removing selected pesticides from soil and had the highest aesthetic value of the plants tested. PMID:18689747

Smith, Katy E; Putnam, Raymond A; Phaneuf, Clifford; Lanza, Guy R; Dhankher, Om P; Clark, John M

2008-01-01

216

Optimizing single mode robustness of the distributed modal filtering rod fiber amplifier.

High-power fiber amplifiers for pulsed applications require large mode area (LMA) fibers having high pump absorption and near diffraction limited output. Photonic crystal fibers allow realization of short LMA fiber amplifiers having high pump absorption through a pump cladding that is decoupled from the outer fiber diameter. However, achieving ultra low NA for single mode (SM) guidance is challenging, thus different design strategies must be applied. The distributed modal filtering (DMF) design enables SM guidance in ultra low NA fibers with very large cores, where large preform tolerances can be compensated during the fiber draw. Design optimization of the SM bandwidth of the DMF rod fiber is presented. Analysis of band gap properties results in a fourfold increase of the SM bandwidth compared to previous results, achieved by utilizing the first band of cladding modes, which can cover a large fraction of the Yb emission band including wavelengths of 1030 nm and 1064 nm. Design parameters tolerating refractive index fabrication uncertainties of ± 10?? are targeted to yield stable SM bandwidths. PMID:22453408

Jørgensen, Mette Marie; Petersen, Sidsel Rübner; Laurila, Marko; Lægsgaard, Jesper; Alkeskjold, Thomas Tanggaard

2012-03-26

217

The Touro 12-Step: A Systematic Guide to Optimizing Survey Research with Online Discussion Boards

The Internet, in particular discussion boards, can provide a unique opportunity for recruiting participants in online research surveys. Despite its outreach potential, there are significant barriers which can limit its success. Trust, participation, and visibility issues can all hinder the recruitment process; the Touro 12-Step was developed to address these potential hurdles. By following this step-by-step approach, researchers will be able to minimize these pitfalls and maximize their recruitment potential via online discussion boards.

Ip, Eric J; Tenerowicz, Michael J; Perry, Paul J

2010-01-01

218

We have developed a hydrodynamic levitation centrifugal blood pump with a semi-open impeller for a mechanically circulatory assist. The impeller levitated with original hydrodynamic bearings without any complicated control and sensors. However, narrow bearing gap has the potential for causing hemolysis. The purpose of the study is to investigate the geometric configuration of the hydrodynamic step bearing to minimize hemolysis by expansion of the bearing gap. Firstly, we performed the numerical analysis of the step bearing based on Reynolds equation, and measured the actual hydrodynamic force of the step bearing. Secondly, the bearing gap measurement test and the hemolysis test were performed to the blood pumps, whose step length were 0 %, 33 % and 67 % of the vane length respectively. As a result, in the numerical analysis, the hydrodynamic force was the largest, when the step bearing was around 70 %. In the actual evaluation tests, the blood pump having step 67 % obtained the maximum bearing gap, and was able to improve the hemolysis, compared to those having step 0% and 33%. We confirmed that the numerical analysis of the step bearing worked effectively, and the blood pump having step 67 % was suitable configuration to minimize hemolysis, because it realized the largest bearing gap. PMID:22254562

Kosaka, Ryo; Yada, Toru; Nishida, Masahiro; Maruyama, Osamu; Yamane, Takashi

2011-01-01

219

National Technical Information Service (NTIS)

Telban and Cardullo have developed and successfully implemented the non-linear optimal motion cueing algorithm at the Visual Motion Simulator (VMS) at the NASA Langley Research Center in 2005. The latest version of the non-linear algorithm performed filte...

F. M. Cardullo K. B. Zaychik

2012-01-01

220

NASA Astrophysics Data System (ADS)

The paper describes the development of periodic structure mechanical filter (PSMF) that has the potential to reduce vibration transmission and sound radiation at resonances of the foundation in a two-degree-of-freedom (2dof) vibration isolation system by using the band gaps of the periodic structure. The transmission matrix method is used to model vibration transmission of the 2dof system and an analytical expression of sound radiation from the foundation plate is derived. The multi-layer PSMF composed of rigid plates and curved beams is represented by an equivalent m- k- c (viscous damping) model. The propagation/attenuation zones and attenuation ability of PSMF are expressed in the propagation scenario and the iso-attenuation curves by exploiting the unit cell transfer matrix invariant. Influence of the number of unit cells, viscous damping on the mobility of PSMF and vibro-acoustic behavior of the 2dof system is extensively studied. And under the constraints of installation space and stability of the whole system, the more the number of the unit cells, the better attenuation ability in the band gap can be obtained. The interaction between PSMF and the 2dof system is analyzed by the substructure method and contribution of frequency component from different substructures is identified by setting different level of damping for each substructure. Factors influencing the first mounting frequency of the 2dof system with PSMF are discussed and three styles of installing PSMF are studied. The performance of piecewise periodic PSMF and quasi-periodic PSMF is also studied in an attempt to eliminate new-born resonances by PSMF. An optimization scheme involving sensitivity analysis is applied to obtain the optimal values of m and k. And the optimization is effective. The experiment of detecting the band gap of PSMF and the comparative trial of a 2dof system with a flexible plate as the foundation with/without PSMF are carried out. Both numerical and experimental simulation results have demonstrated that by use of PSMF, the vibration transmission at resonances is reduced and the radiation of the foundation at resonances is suppressed.

Xiuchang, Huang; Aihua, Jiang; Zhiyi, Zhang; Hongxing, Hua

2011-09-01

221

Filtering of Defects in Semipolar (11-22) GaN Using 2-Steps Lateral Epitaxial Overgrowth

Good-quality (11?22) semipolar GaN sample was obtained using epitaxial lateral overgrowth. The growth conditions were chosen to enhance the growth rate along the [0001] inclined direction. Thus, the coalescence boundaries stop the propagation of basal stacking faults. The faults filtering and the improvement of the crystalline quality were attested by transmission electron microscopy and low temperature photoluminescence. The temperature dependence of the luminescence polarization under normal incidence was also studied.

2010-01-01

222

NASA Astrophysics Data System (ADS)

This dissertation deals with aspects of sequential data assimilation (in particular ensemble Kalman filtering) and numerical weather forecasting. In the first part, the recently formulated Ensemble Kalman-Bucy (EnKBF) filter is revisited. It is shown that the previously used numerical integration scheme fails when the magnitude of the background error covariance grows beyond that of the observational error covariance in the forecast window. Therefore, we present a suitable integration scheme that handles the stiffening of the differential equations involved and doesn't represent further computational expense. Moreover, a transform-based alternative to the EnKBF is developed: under this scheme, the operations are performed in the ensemble space instead of in the state space. Advantages of this formulation are explained. For the first time, the EnKBF is implemented in an atmospheric model. The second part of this work deals with ensemble clustering, a phenomenon that arises when performing data assimilation using of deterministic ensemble square root filters in highly nonlinear forecast models. Namely, an M-member ensemble detaches into an outlier and a cluster of M-1 members. Previous works may suggest that this issue represents a failure of EnSRFs; this work dispels that notion. It is shown that ensemble clustering can be reverted also due to nonlinear processes, in particular the alternation between nonlinear expansion and compression of the ensemble for different regions of the attractor. Some EnSRFs that use random rotations have been developed to overcome this issue; these formulations are analyzed and their advantages and disadvantages with respect to common EnSRFs are discussed. The third and last part contains the implementation of the Robert-Asselin-Williams (RAW) filter in an atmospheric model. The RAW filter is an improvement to the widely popular Robert-Asselin filter that successfully suppresses spurious computational waves while avoiding any distortion in the mean value of the function. Using statistical significance tests both at the local and field level, it is shown that the climatology of the SPEEDY model is not modified by the changed time stepping scheme; hence, no retuning of the parameterizations is required. It is found the accuracy of the medium-term forecasts is increased by using the RAW filter.

Amezcua, Javier

223

This paper proposes a new distributed Kalman filtering fusion with random state transition and measurement matrices, i.e., random parameter matrices Kalman filtering. It is proved that under a mild condition the fused state estimate is equivalent to the centralized Kalman filtering using all sensor measurements; therefore, it achieves the best performance. More importantly, this result can be applied to Kalman filtering with uncertain observations including the measurement with a false alarm probability as a special case, as well as, randomly variant dynamic systems with multiple models. Numerical examples are given which support our analysis and show significant performance loss of ignoring the randomness of the parameter matrices.

Luo, Yingting; Zhu, Yunmin; Luo, Dandan; Zhou, Jie; Song, Enbin; Wang, Donghua

2008-01-01

224

Optical feedback to the laser source in tunable diode laser spectroscopy (TDLS) is known to create intensity modulation noise due to elatoning and optical feedback (i.e., multiplicative technical noise) that usually limits spectral signal-to-noise (S/N). The large technical noise often limits absorption spectroscopy to noise floors 100-fold greater than the Poisson shot noise limit due to fluctuations in the laser intensity. The high output powers generated from quantum cascade (QC) lasers, along with their high gain, makes these injection laser systems especially susceptible to technical noise. In this article we discuss a method of using optimal filtering to reduce technical noise. We have observed S/N enhancements ranging from {approx}20% to a factor of {approx}50. The degree to which optimal filtering will enhance S/N depends on the similarity between the Fourier components of the technical noise and those of the signal, with lower S/N enhancements observed for more similar Fourier decompositions of the signal and technical noise. We also examine the linearity of optimal filtered spectra for both time and intensity. This was accomplished by creating a synthetic spectrum for the species being studied (CH4, N2O, CO2, H2O in ambient air) utilizing line-positions and line-widths with an assumed Voight-profile from a previous database (HITRAN). Agreement better than 0.036% in wavenumber, and 1.64% in intensity (up to a 260-fold intensity ratio employed), was observed. Our results suggest that rapid ex post facto digital optimal filtering can be used to enhance S/N for routine trace gas detection.

Disselkamp, Robert S.; Kelly, James F.; Sams, Robert L.; Anderson, Gordon A.

2002-09-01

225

This paper proposes the employment of the differential evolution (DE) to offline optimize the covariance matrices of a new reduced delayed-state Kalman-filter (DSKF)-based algorithm which estimates the stator-flux linkage components, in the stationary reference frame, to realize sensorless control of induction motors (IMs). The DSKF-based algorithm uses the derivatives of the stator-flux components as mathematical model and the stator-voltage equations

Nadia Salvatore; Andrea Caponio; Ferrante Neri; Silvio Stasi; Giuseppe Leonardo Cascella

2010-01-01

226

NASA Astrophysics Data System (ADS)

Two strategies to focus time harmonic scalar fields in known inhomogeneous lossy media are compared. The first one is the Inverse Filter (IF) method, which faces the focusing task as the synthesis of a nominal field. The second one is the Constrained Power Focusing Optimization (CPFO) method, which tackles the problem in terms of constrained mask constrained power optimization. Numerical examples representative of focusing in noninvasive microwave hyperthermia are provided to show that CPFO is able to outperform IF, thanks to the additional degrees of freedom arising from the adopted power synthesis formulation.

Iero, D. A. M.; Isernia, T.; Crocco, L.

2013-08-01

227

Step-voltage-optimized Lightning Protection earth-termination systems analysis and simulation

Earth-Termination Systems as an important part of the Lightning Protection Systems must be designed in a way that lightning currents are safely diverted into the ground without generating step-voltages on the surface of the soil that would be dangerous to human beings. The paper considers safety limits for step-voltages and examines the effectiveness of several design principles of earth-termination systems

Ralph Brocke; Volker Hinrichsen; Sebastian Suchanek; Jing Gao

2011-01-01

228

The purpose of this report is to evaluate the hemodynamic effects of renal vein inflow and filter position on unoccluded and partially occluded IVC filters using three-dimensional computational fluid dynamics. Three-dimensional models of the TrapEase and Gunther Celect IVC filters, spherical thrombi, and an IVC with renal veins were constructed. Hemodynamics of steady-state flow was examined for unoccluded and partially occluded TrapEase and Gunther Celect IVC filters in varying proximity to the renal veins. Flow past the unoccluded filters demonstrated minimal disruption. Natural regions of stagnant/recirculating flow in the IVC are observed superior to the bilateral renal vein inflows, and high flow velocities and elevated shear stresses are observed in the vicinity of renal inflow. Spherical thrombi induce stagnant and/or recirculating flow downstream of the thrombus. Placement of the TrapEase filter in the suprarenal vein position resulted in a large area of low shear stress/stagnant flow within the filter just downstream of thrombus trapped in the upstream trapping position. Filter position with respect to renal vein inflow influences the hemodynamics of filter trapping. Placement of the TrapEase filter in a suprarenal location may be thrombogenic with redundant areas of stagnant/recirculating flow and low shear stress along the caval wall due to the upstream trapping position and the naturally occurring region of stagnant flow from the renal veins. Infrarenal vein placement of IVC filters in a near juxtarenal position with the downstream cone near the renal vein inflow likely confers increased levels of mechanical lysis of trapped thrombi due to increased shear stress from renal vein inflow.

Wang, S L; Singer, M A

2009-07-13

229

NASA Astrophysics Data System (ADS)

The authors demonstrate a simple passive technique for increasing the transmission distance in fiber wireless links through the application of a narrowband fiber Bragg grating (FBG) with high reflectivity (90-99%). They are applied in a conventional downstream link and also for the upstream in a wavelength-reused scheme. In the conventional nonwavelength-reused system, the grating is used to optimize the optical modulation depth and, hence, the receiver sensitivity in the downstream transmitted signal by reducing the power of the optical carrier before fiber transmission. In the wavelength-reused systems, the highly reflective FBGs can be effectively used at the base stations to recover a major portion of the optical carrier (as high as 99% of the downlink carrier) for uplink transmission from a weakly modulated downstream signal. In the latter case, the penalty in the downstream signal due to the large extraction of carrier power is partially offset by the sensitivity enhancement obtained in the filtering process. The authors present experimental results for the increased transmission performance for both the nonwavelength-reused and wavelength-reused scenarios. The increase in the sensitivity (at {bit error rate} = 10-9) in the nonwavelength-reused scheme for a given launch channel power that facilitates the increased transmission distance can be as large as 7 dB. The relative increase in the power margin for the upstream signal can be up to 4 dB in the wavelength-reused scheme. This would more than double the currently demonstrated transmission distances in such wavelength-reused systems without any optical amplification. The scheme is applicable to a wide range of radio frequencies and modulation depths.

Attygalle, Manik; Lim, Christina; Nirmalathas, Ampalavanapillai Thas

2006-04-01

230

NASA Astrophysics Data System (ADS)

Quasicrystalline solids were first observed in nature in 1980s. Their lattice geometry is devoid of translational symmetry; however it possesses long-range order as well as certain orders of rotational symmetry forbidden by translational symmetry. Mathematically, such lattices are related to aperiodic tilings. Since their discovery there has been great interest in utilizing aperiodic geometries for a wide variety of electromagnetic (EM) and optical applications. The first thrust of this dissertation addresses applications of quasicrystalline geometries for wideband antenna arrays and plasmonic nano-spherical arrays. The first application considered is the design of suitable antenna arrays for micro-UAV (unmanned aerial vehicle) swarms based on perturbation of certain types of aperiodic tilings. Due to safety reasons and to avoid possible collision between micro-UAVs it is desirable to keep the minimum separation distance between the elements several wavelengths. As a result typical periodic planar arrays are not suitable, since for periodic arrays increasing the minimum element spacing beyond one wavelength will lead to the appearance of grating lobes in the radiation pattern. It will be shown that using this method antenna arrays with very wide bandwidths and low sidelobe levels can be designed. It will also be shown that in conjunction with a phase compensation method these arrays show a large degree of versatility to positional noise. Next aperiodic aggregates of gold nano-spheres are studied. Since traditional unit cell approaches cannot be used for aperiodic geometries, we start be developing new analytical tools for aperiodic arrays. A modified version of generalized Mie theory (GMT) is developed which defines scattering coefficients for aperiodic spherical arrays. Next two specific properties of quasicrystalline gold nano-spherical arrays are considered. The optical response of these arrays can be explained in terms of the grating response of the array (photonic resonance) and the plasmonic response of the spheres (plasmonic resonance). In particular the couplings between the photonic and plasmonic modes are studied. In periodic arrays this coupling leads to the formation of a so called photonic-plasmonic hybrid mode. The formation of hybrid modes is studied in quasicrystalline arrays. Quasicrystalline structures in essence possess several periodicities which in some cases can lead to the formation of multiple hybrid modes with wider bandwidths. It is also demonstrated that the performance of these arrays can be further enhanced by employing a perturbation method. The second property considered is local field enhancements in quasicrystalline arrays of gold nanospheres. It will be shown that despite a considerably smaller filling factor quasicrystalline arrays generate larger local field enhancements which can be even further enhanced by optimally placing perturbing spheres within the prototiles that comprise the aperiodic arrays. The second thrust of research in this dissertation focuses on designing all-dielectric filters and metamaterial coatings for the optical range. In higher frequencies metals tend to have a high loss and thus they are not suitable for many applications. Hence dielectrics are used for applications in optical frequencies. In particular we focus on designing two types of structures. First a near-perfect optical mirror is designed. The design is based on optimizing a subwavelength periodic dielectric grating to obtain appropriate effective parameters that will satisfy the desired perfect mirror condition. Second, a broadband anti-reflective all-dielectric grating with wide field of view is designed. The second design is based on a new computationally efficient genetic algorithm (GA) optimization method which shapes the sidewalls of the grating based on optimizing the roots of polynomial functions.

Namin, Frank Farhad A.

231

National Technical Information Service (NTIS)

Monolithic, macroscopic, nanoporous nanotube filters are fabricated having radially aligned carbon nanotube walls. The freestanding filters have diameters and lengths up to several centimeters. A single-step filtering process was demonstrated in two impor...

A. Srivastava O. N. Srivastava P. M. Ajayan R. Vajtal S. Talapatra

2005-01-01

232

Optimal-tradeoff circular harmonic function filters for 3D target recognition

NASA Astrophysics Data System (ADS)

3D target recognition is of significant interest because representing the object in 3D space couuld essentially provide a solution to pose variation and self-occlusion problems that are big challenges in 2D pattern recognition. Correlation filers have been used in a variety of 2D pattern matching applications and many correlation filter designs have been developed to handle problems such as rotations. Correlation filters also offer other benefits such as shift-invariance, graceful degradation and closed-form solutions. The 3D extension of correlation filter is a natural extension to handle 3D pattern recognition problem. In this paper, we propose a 3D correlation filter design method based on cylindrical circular harmonic function (CCHF) and use LADAR imagery to illustrate the good performance of CCHF filters.

Vijaya Kumar, Bhagavatula V. K.; Xie, Chunyan; Mahalanobis, Abhijit

2003-09-01

233

NASA Astrophysics Data System (ADS)

The greatest impediment to extracting high-quality fetal signals from fetal magnetocardiography (fMCG) is environmental magnetic noise, which may have peak-to-peak intensity comparable to fetal QRS amplitude. Being an unstructured Gaussian signal with large disturbances at specific frequencies, ambient field noise can be reduced with hardware-based approaches and/or with software algorithms that digitally filter magnetocardiographic recordings. At present, no systematic evaluation of filters' performances on shielded and unshielded fMCG is available. We designed high-pass and low-pass Chebychev II-type filters with zero-phase and stable impulse response; the most commonly used band-pass filters were implemented combining high-pass and low-pass filters. The achieved ambient noise reduction in shielded and unshielded recordings was quantified, and the corresponding signal-to-noise ratio (SNR) and signal-to-distortion ratio (SDR) of the retrieved fetal signals was evaluated. The study regarded 66 fMCG datasets at different gestational ages (22-37 weeks). Since the spectral structures of shielded and unshielded magnetic noise were very similar, we concluded that the same filter setting might be applied to both conditions. Band-pass filters (1.0-100 Hz) and (2.0-100 Hz) provided the best combinations of fetal signal detection rates, SNR and SDR; however, the former should be preferred in the case of arrhythmic fetuses, which might present spectral components below 2 Hz.

Comani, S.; Mantini, D.; Alleva, G.; Di Luzio, S.; Romani, G. L.

2005-12-01

234

Optimized design of a band-pass filter with low frequency and narrow bandwidth

NASA Astrophysics Data System (ADS)

An underwater metal pipeline detector is designed based on the principle of artificial source electromagnetic detection, which is used for detecting the deeply buried in underwater metal pipes. Narrowband band-pass filter in the receiver can well separate the specific frequency signal from mixed signal which is containing strong noise. Authors deduced the narrowband filter transfer function and simulated in computer, and the detector was applied in instrument prototype. Experiment results show that the error of the center frequency of the band-pass filter is small, and the gain is stable. In conclusion the detector has good performance.

Tian, Biao; Fu, Guo-hong; Liao, Xiu-ying; Cheng, Hui; Li, Guang

2013-10-01

235

NASA Astrophysics Data System (ADS)

Optimization and field application of a filter pack system for the simultaneous collection of atmospheric gas-phase HN0 3, NH 3 and S0 2 have been studied. A Teflon prefilter was used to remove particulate matter. Nylon filter, oxalic-acid-treated Whatman 41 filter and sodium-carbonate-treated Whatman 41 filter were used for the collection of HN0 3, NH 3 and S0 2, respectively. For the collection of gas-phase HN0 3, nylon filters had better efficiency and capacity as compared to NaCl-impregnated Whatman 41 filters for long sampling periods of more than 30 h. All treated filters and nylon filters worked with the collection efficiencies of greater than 95%. About 2% of the gas-phase ammonia has been retained by the nylon filters during simultaneous collection experiments done in the laboratory but the retained ammonia on the nylon filter sometimes reached to about 25% of the gaseous total ammonia collected on the oxalic-acid-impregnated filter in the field experiments. Other than ammonia no significant retention or volatilization from the filter pack system was observed during the simultaneous experiments carried out in an urban atmosphere.

Karaka?, Duran; Tuncel, Semra G.

236

SUMMARY The primary objectives of the present exposition are to: (i) provide a generalized unied mathematical framework and setting leading to the unique design of computational algorithms for structural dynamic problems encompassing the broad scope of linear multi-step (LMS) methods and within the limitation of the Dahlquist barrier theorem (Reference (3), G. Dahlquist, BIT 1963; 3:27), and also leading to

X. Zhou; K. K. Tamma

2004-01-01

237

Design of linear tracking filters via robust H\\/sub 2\\/ optimization

The design of a velocity-acceleration tracking filter is considered. The filler achieves real-time smoothing of noisy velocity measurements by using acceleration measurements. Robust H 2-filtering is used which keeps the bias that occurs in the velocity estimation in maneuvers small, for low-cost accelerometers that attain large scale factors. Three methods of robust H 2 estimation are applied, and their results,

I. Yaesh; U. Shaked

1996-01-01

238

Pyramid Implementation Of Optimal Step Conjugate Search Algorithms For Some Computer Vision Problems

Optimization of a cost function arises in several computer vision problems. The cost functions in these problems are usually derived from discretization of functionals obtained from regularization principles or stochastic estimation techniques using Markov random field models. In this paper we present a parallel implementation on a pyramid of the line search conjugate gradient algorithm for minimizing the cost functions

T. Simchony; R. Chellappa; Z. Lichtenstein

1988-01-01

239

Optimization of 3D laser scanning speed by use of combined variable step

NASA Astrophysics Data System (ADS)

The problem of 3D TVS slow functioning caused by constant small scanning step becomes its solution in the presented research. It can be achieved by combined scanning step application for the fast search of n obstacles in unknown surroundings. Such a problem is of keynote importance in automatic robot navigation. To maintain a reasonable speed robots must detect dangerous obstacles as soon as possible, but all known scanners able to measure distances with sufficient accuracy are unable to do it in real time. So, the related technical task of the scanning with variable speed and precise digital mapping only for selected spatial sectors is under consideration. A wide range of simulations in MATLAB 7.12.0 of several variants of hypothetic scenes with variable n obstacles in each scene (including variation of shapes and sizes) and scanning with incremented angle value (0.6° up to 15°) is provided. The aim of such simulation was to detect which angular values of interval still permit getting the maximal information about obstacles without undesired time losses. Three of such local maximums were obtained in simulations and then rectified by application of neuronal network formalism (Levenberg-Marquradt Algorithm). The obtained results in its turn were applied to MET (Micro-Electro-mechanical Transmission) design for practical realization of variable combined step scanning on an experimental prototype of our previously known laser scanner.

Garcia-Cruz, X. M.; Sergiyenko, O. Yu.; Tyrsa, Vera; Rivas-Lopez, M.; Hernandez-Balbuena, D.; Rodriguez-Quiñonez, J. C.; Basaca-Preciado, L. C.; Mercorelli, P.

2014-03-01

240

NASA Astrophysics Data System (ADS)

This paper shows the improvements in imaging performance on the ASML PAS5500/800TM, the PAS5500/850BTM and the TWINSCANTM AT:850BTM Step & Scan systems. During setup, the lens aberrations are measured by the TAMIS technique and optimized. This gives excellent imaging performance for aberration sensitive features such as 'two bar,' the DRAM isolation pattern and isolated lines printed with alternating PSM. Lithographic tests based on these features were developed and tested on a number of 800 and 850 systems and gave results well within specification limits. Consequently, the imaging performance has been improved for a wide range of applications.

van Ingen Schenau, Koen; Bakker, Hans; Zellenrath, Mark; Moerman, Richard; Linders, Jeroen; Rohe, Thomas; Emer, Wolfgang

2002-07-01

241

NASA Astrophysics Data System (ADS)

The layout optimization with the ON-OFF information of magnetic material in finite elements is one of the most attractive tools in initial conceptual and practical design of electrical machinery for engineers. The heuristic algorithms based on the random search allow the engineers to define the general-purpose objects, however, there are many iterations of finite element analysis, and it is difficult to realize the practical solution without island and void distribution by using direct search method, for example, simulated annealing (SA), genetic algorithm (GA), and so on. This paper presents the layout optimization method based on GA. Proposed method can arrive at the practical solution by means of multi-step utilization of GA, and the convergence speed is considerably improved by using the combination with the reduction process of design space.

Okamoto, Yoshifumi; Tominaga, Yusuke; Sato, Shuji

242

Wind-hydrothermal power system dispatching has received intensive attention in recent years because it can help develop various reasonable plans to schedule the power generation efficiency. But future data such as wind power output and power load would not be accurately predicted and the nonlinear nature involved in the complex multiobjective scheduling model; therefore, to achieve accurate solution to such complex problem is a very difficult task. This paper presents an interval programming model with 2-step optimization algorithm to solve multiobjective dispatching. Initially, we represented the future data into interval numbers and simplified the object function to a linear programming problem to search the feasible and preliminary solutions to construct the Pareto set. Then the simulated annealing method was used to search the optimal solution of initial model. Thorough experimental results suggest that the proposed method performed reasonably well in terms of both operating efficiency and precision.

Jihong, Qu

2014-01-01

243

Wind-hydrothermal power system dispatching has received intensive attention in recent years because it can help develop various reasonable plans to schedule the power generation efficiency. But future data such as wind power output and power load would not be accurately predicted and the nonlinear nature involved in the complex multiobjective scheduling model; therefore, to achieve accurate solution to such complex problem is a very difficult task. This paper presents an interval programming model with 2-step optimization algorithm to solve multiobjective dispatching. Initially, we represented the future data into interval numbers and simplified the object function to a linear programming problem to search the feasible and preliminary solutions to construct the Pareto set. Then the simulated annealing method was used to search the optimal solution of initial model. Thorough experimental results suggest that the proposed method performed reasonably well in terms of both operating efficiency and precision. PMID:24895663

Ren, Kun; Jihong, Qu

2014-01-01

244

National Technical Information Service (NTIS)

The overall management program of an optimal correction step equalizer for INTEL 8080 microprocessor is described. The flow diagram of the management program and the listing of the overall program are presented. The equalizer work starts with a training p...

F. Cascio G. Martinelli G. Orlandi M. Salerno

1980-01-01

245

Independent component analysis (ICA) aims at decomposing an observed random\\u000avector into statistically independent variables. Deflation-based\\u000aimplementations, such as the popular one-unit FastICA algorithm and its\\u000avariants, extract the independent components one after another. A novel method\\u000afor deflationary ICA, referred to as RobustICA, is put forward in this paper.\\u000aThis simple technique consists of performing exact line search optimization

Vicente Zarzoso; Pierre Comon

2010-01-01

246

Initiating basal insulin therapy in type 2 diabetes: practical steps to optimize glycemic control.

Primary care practitioners are increasingly responsible for the management of the escalating numbers of patients with type 2 diabetes. The majority of these patients will require insulin replacement therapy as their disease progresses, because glycemic control is often unsustainable using oral antidiabetic drugs. This review explains the practicalities of initiating and optimizing basal insulin in clinical practice, emphasizing the need for regular glycated hemoglobin (A1c) monitoring to allow timely initiation of insulin when the A1c target is not met. The importance of patient education in overcoming barriers to insulin is discussed, as well as the choice of available basal insulins and the necessity to optimize basal insulin dosage by self-titration. The traditional view of insulin therapy as a last resort is challenged with the modern basal insulin analogues (insulin detemir and insulin glargine), which offer simple and effective glycemic control with a reduced risk of hypoglycemia compared with older insulin formulations such as neutral protamine Hagedorn. PMID:23953076

Philis-Tsimikas, Athena

2013-09-01

247

Optimized mRNA isolation and assessment methodology with two-step real time PCR.

Messenger ribonucleic acid (mRNA) isolation from tomato seeds was performed with the PolyATtract System 1000 and was evaluated in two-step Real Time PCR using the fluoresence dye Sybr Green. The proposed isolation method resulted in cDNA production with Sybr Green 11-fold higher fluorescence intensity, having 87% lower standard deviation in the recorded fluorescence signals, and PCR efficiency improved by 21% in comparison to mRNA samples obtained with the manufacturer's protocol. The method for the assessment of the mRNA isolation procedure and the proposed mathematical analysis of the data are applicable to gene identification and expression studies for biotechnological applications. PMID:16239192

Psallida, Charoula; Argyropoulos, Dimitris

2005-01-01

248

In this paper we address the problem of tracking feature points along image sequences. To analyze the undergoing movement we use a common approach based on Kalman filtering which performs the estimation and correction of the feature point's movement in every image frame. The criterion proposed to establish correspondences, between the group of estimates in each image and the new

Raquel R. Pinho; João Manuel; R. S. Tavares; Miguel V. Correia

2005-01-01

249

Improved design and optimization of subsurface flow constructed wetlands and sand filters

Subsurface flow constructed wetlands and sand filters are engineered systems capable of eliminating a wide range of pollutants from wastewater. These devices are easy to operate, flexible and have low maintenance costs. For these reasons, they are particularly suitable for small settlements and isolated farms and their use has substantially increased in the last 15 years. Furthermore, they are also

A. Brovelli; O. Carranza-Díaz; L. Rossi; D. A. Barry

2010-01-01

250

Multiple targets tracking by optimized particle filter based on multi-scan JPDA

In this paper, the particle filter is used to solve the nonlinear and nonGaussian estimation problem in multiple targets tracking and multiple sensor fusion process. The weight of the particle is evaluated through the combination of Joint Probability Data Association (JPDA) and multiple hypothesis tracking (MHT), which makes the probabilistic assignment based on all reasonable hypotheses in a sliding window

Liu Jing; Prahlad Vadakkepat

2004-01-01

251

The standard (STD) 5 × 5 hybrid median filter (HMF) was previously described as a nonparametric local backestimator of spatially arrayed microtiter plate (MTP) data. As such, the HMF is a useful tool for mitigating global and sporadic systematic error in MTP data arrays. Presented here is the first known HMF correction of a primary screen suffering from systematic error best described as gradient vectors. Application of the STD 5 × 5 HMF to the primary screen raw data reduced background signal deviation, thereby improving the assay dynamic range and hit confirmation rate. While this HMF can correct gradient vectors, it does not properly correct periodic patterns that may present in other screening campaigns. To address this issue, 1 × 7 median and a row/column 5 × 5 hybrid median filter kernels (1 × 7 MF and RC 5 × 5 HMF) were designed ad hoc, to better fit periodic error patterns. The correction data show periodic error in simulated MTP data arrays is reduced by these alternative filter designs and that multiple corrective filters can be combined in serial operations for progressive reduction of complex error patterns in a MTP data array.

Bushway, Paul J.; Azimi, Behrad; Heynen-Genel, Susanne

2014-01-01

252

NASA Technical Reports Server (NTRS)

Three algorithms are developed for designing finite impulse response digital filters to be used for pulse shaping and channel equalization. The first is the Minimax algorithm which uses linear programming to design a frequency-sampling filter with a pulse shape that approximates the specification in a minimax sense. Design examples are included which accurately approximate a specified impulse response with a maximum error of 0.03 using only six resonators. The second algorithm is an extension of the Minimax algorithm to design preset equalizers for channels with known impulse responses. Both transversal and frequency-sampling equalizer structures are designed to produce a minimax approximation of a specified channel output waveform. Examples of these designs are compared as to the accuracy of the approximation, the resultant intersymbol interference (ISI), and the required transmitted energy. While the transversal designs are slightly more accurate, the frequency-sampling designs using six resonators have smaller ISI and energy values.

Houts, R. C.; Vaughn, G. L.

1974-01-01

253

Optimal design of IIR digital filters with robust stability using conic quadratic programming

In this paper, minimax design of infinite-impulse-response (IIR) filters with prescribed stability margin is formulated as a conic quadratic programming (CQP) problem. CQP is known as a class of well-structured convex programming problems for which efficient interior-point solvers are available. By considering factorized denominators, the proposed formulation incorporates a set of linear constraints that are sufficient and near necessary for

Wu-Sheng Lu; Takao Hinanioto

2003-01-01

254

In this paper, minimax design of infinite-impulse-response (IIR) filters with prescribed stability margin is formulated as a conic quadratic programming (CQP) problem. CQP is known as a class of well-structured convex programming problems for which efficient interior-point solvers are available. By considering factorized denominators, the proposed formulation incorporates a set of linear constraints that are sufficient and near necessary for

Wu-Sheng Lu; Takao Hinamoto

2003-01-01

255

Optimization of the Gamma-Gamma MAP filter for SAR image clutters

The Gamma-Gamma Maximum a posteriori filter provides an estimate of the speckle-free radar cross-section when both the radar reflectivity and the speckle distributions are gamma-distributed. In this Letter, it is shown that a factor greater than two in precision can be typically gained in the radar cross-section estimate in the case of natural land Synthetic Aperture Radar (SAR) clutters. This

M. Beauchemin; K. P. B. Thomson; G. Edwards

1996-01-01

256

The matched-filter bound on optimal space-time processing in correlated fading channels

This paper presents a theoretical analysis of the matched-filter bound on N-branch space-time processing receivers in a frequency-selective correlated fading environment. The development is based on a Karhunen-Loe`ve expansion in the frequency domain. Although many other works are based on similar expansions, we present a more general analytical framework in the frequency domain covering Rayleigh and Rician fading scenarios, with

Sébastien Roy; David D. Falconer

2004-01-01

257

Simulation of RF data with tissue motion for optimizing stationary echo canceling filters.

Blood velocity estimation is complicated by the strong echoes received from tissue surrounding the vessel under investigation. Proper blood velocity estimation necessitates use of a filter for separation of the different signal components. Development of these filters and new estimators requires RF-data, where the tissue component is known. In vivo RF-data does not have this property. Instead simulated data incorporating all relevant features of the measurement situation can be employed. One feature is the motion in the surrounding tissue induced by pulsation, heartbeat, and breathing. This study has developed models for the motions and incorporated them into the RF simulation program Field II, thereby obtaining realistic simulated data. A powerful tool for evaluation of different filters and estimators is then available. The model parameters can be varied according to the physical situation with respect to scan-site and the individual to be scanned. The nature of pulsation is discussed, and a relation between the pressure in the carotid artery and the experienced vessel wall motion is derived. PMID:12853077

Schlaikjer, M; Torp-Pedersen, S; Jensen, J A

2003-08-01

258

Topology optimization of dielectric substrates for filters and antennas using SIMP

Summary In this paper a novel design procedure based on the integration of full wave Finite Element Analysis (FEA) and a topology\\u000a design method employing Sequential Linear Programming (SLP) is introduced. The employed design method is the Solid Isotropic\\u000a Material with Penalization (SIMP) technique formulated as a general non-linear optimization problem. SLP is used to solve\\u000a the optimization problem with the

G. Kiziltas; N. Kikuchi; J. L. Volakis; J. Halloran

2004-01-01

259

The authors have investigated the use of a time-domain optimal filtering method to simultaneously minimize both the baseline variation and high-frequency noise in near-infrared (NIR) spectrophotometric absorption data of glucose dissolved in a simple aqueous (deionized water) matrix. By coupling a third-order (6-pole) digital Butterworth bandpass filter with partial least-squares (PLS) regression modeling, glucose concentrations were determined for a set

Fredric M. Ham; Ivica N. Kostanic; Glenn M. Cohen; Brent R. Gooch

1997-01-01

260

NASA Technical Reports Server (NTRS)

This paper describes and illustrates two matched-filter-theory based schemes for obtaining maximized and time-correlated gust-loads for a nonlinear airplane. The first scheme is computationally fast because it uses a simple one-dimensional search procedure to obtain its answers. The second scheme is computationally slow because it uses a more complex multidimensional search procedure to obtain its answers, but it consistently provides slightly higher maximum loads than the first scheme. Both schemes are illustrated with numerical examples involving a nonlinear control system.

Scott, Robert C.; Perry, Boyd, III; Pototzky, Anthony S.

1991-01-01

261

NASA Technical Reports Server (NTRS)

Two matched filter theory based schemes are described and illustrated for obtaining maximized and time correlated gust loads for a nonlinear aircraft. The first scheme is computationally fast because it uses a simple 1-D search procedure to obtain its answers. The second scheme is computationally slow because it uses a more complex multi-dimensional search procedure to obtain its answers, but it consistently provides slightly higher maximum loads than the first scheme. Both schemes are illustrated with numerical examples involving a nonlinear control system.

Scott, Robert C.; Pototzky, Anthony S.; Perry, Boyd, III

1991-01-01

262

NASA Astrophysics Data System (ADS)

There is little information in scientific literature regarding the modifications induced by check dam systems in flow regimes within restored gully reaches, despite it being a crucial issue for the design of gully restoration measures. Here, we develop a conceptual model to classify flow regimes in straight rectangular channels for initial and dam-filling conditions as well as a method of estimating efficiency in order to provide design guidelines. The model integrates several previous mathematical approaches for assessing the main processes involved (hydraulic jump, impact flow, gradually varied flows). Ten main classifications of flow regimes were identified, producing similar results when compared with the IBER model. An interval for optimal energy dissipation (ODI) was observed when the steepness factor c was plotted against the design number (DN, ratio between the height and the product of slope and critical depth). The ODI was characterized by maximum energy dissipation and total influence conditions. Our findings support the hypothesis of a maximum flow resistance principle valid for a range of spacing rather than for a unique configuration. A value of c = 1 and DN ~ 100 was found to economically meet the ODI conditions throughout the different sedimentation stages of the structure. When our model was applied using the same parameters to the range typical of step-pool systems, the predicted results fell within a similar region to that observed in field experiments. The conceptual model helps to explain the spacing frequency distribution as well as the often-cited trend to lower c for increasing slopes in step-pool systems. This reinforces the hypothesis of a close link between stable configurations of step-pool units and man-made interventions through check dams.

Castillo, C.; Pérez, R.; Gómez, J. A.

2014-05-01

263

NASA Astrophysics Data System (ADS)

Conducted electromagnetic interference (EMI) generated by PWM inverter-fed induction motor drive systems, which are currently widely used in many industrial and/or avionic applications, causes severe parasitic current problems, especially at high frequencies (HF). These restrict power electronic drive's evolution. In order to reduce or minimize these EMI problems, several techniques can be applied. In this paper, insertion of an optimized passive EMI filter is proposed. This filter is optimized by taking into account real impedances of each part of a considered AC motor drive system contrarily to commercial EMI filters designed by considering internal impedance of disturbance source and load, equal to 50?. Employing the latter EMI filter would make EMI minimization less effective. The proposed EMI filter optimization is mainly dedicated to minimize common mode (CM) currents due to its most dominant effects in this kind of system. The efficiency of the proposed optimization method using two-port network approach is deduced by comparing the minimized CM current spectra to an applied normative level (ex. DO-160D in aeronautics).

Jettanasen, C.; Ngaopitakkul, A.

2010-10-01

264

Noise from motion artifacts is currently one of the main challenges in the field of ambulatory ECG recording. To address this problem, we propose the use of two different approaches. First, an adaptive filter with electrode-skin impedance as a reference signal is described. Secondly, a multi-channel ECG algorithm based on Independent Component Analysis is introduced. Both algorithms have been designed and further optimized for real-time work embedded in a dedicated Digital Signal Processor. We show that both algorithms improve the performance of a beat detection algorithm when applied in high noise conditions. In addition, an efficient way of choosing this methods is suggested with the aim of reduce the overall total system power consumption. PMID:23367417

Berset, Torfinn; Geng, Di; Romero, Iñaki

2012-01-01

265

Metrics for comparing plasma mass filters

NASA Astrophysics Data System (ADS)

High-throughput mass separation of nuclear waste may be useful for optimal storage, disposal, or environmental remediation. The most dangerous part of nuclear waste is the fission product, which produces most of the heat and medium-term radiation. Plasmas are well-suited to separating nuclear waste because they can separate many different species in a single step. A number of plasma devices have been designed for such mass separation, but there has been no standardized comparison between these devices. We define a standard metric, the separative power per unit volume, and derive it for three different plasma mass filters: the plasma centrifuge, Ohkawa filter, and the magnetic centrifugal mass filter.

Fetterman, Abraham J.; Fisch, Nathaniel J.

2011-10-01

266

Metrics For Comparing Plasma Mass Filters

High-throughput mass separation of nuclear waste may be useful for optimal storage, disposal, or environmental remediation. The most dangerous part of nuclear waste is the fission product, which produces most of the heat and medium-term radiation. Plasmas are well-suited to separating nuclear waste because they can separate many different species in a single step. A number of plasma devices have been designed for such mass separation, but there has been no standardized comparison between these devices. We define a standard metric, the separative power per unit volume, and derive it for three different plasma mass filters: the plasma centrifuge, Ohkawa filter, and the magnetic centrifugal mass filter. __________________________________________________

Abraham J. Fetterman and Nathaniel J. Fisch

2012-08-15

267

Metrics for comparing plasma mass filters

High-throughput mass separation of nuclear waste may be useful for optimal storage, disposal, or environmental remediation. The most dangerous part of nuclear waste is the fission product, which produces most of the heat and medium-term radiation. Plasmas are well-suited to separating nuclear waste because they can separate many different species in a single step. A number of plasma devices have been designed for such mass separation, but there has been no standardized comparison between these devices. We define a standard metric, the separative power per unit volume, and derive it for three different plasma mass filters: the plasma centrifuge, Ohkawa filter, and the magnetic centrifugal mass filter.

Fetterman, Abraham J.; Fisch, Nathaniel J. [Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08540 (United States)

2011-10-15

268

Optimal spatial filtering and transfer function for SAR ocean wave spectra

NASA Technical Reports Server (NTRS)

The impulse response of the SAR system is not a delta function and the spectra represent the product of the underlying image spectrum with the transform of the impulse response which must be removed. A digitally computed spectrum of SEASAT imagery of the Atlantic Ocean east of Cape Hatteras was smoothed with a 5 x 5 convolution filter and the trend was sampled in a direction normal to the predominant wave direction. This yielded a transform of a noise-like process. The smoothed value of this trend is the transform of the impulse response. This trend is fit with either a second- or fourth-order polynomial which is then used to correct the entire spectrum. A 16 x 16 smoothing of the spectrum shows the presence of two distinct swells. Correction of the effects of speckle is effected by the subtraction of a bias from the spectrum.

Beal, R. C.; Tilley, D. G.

1981-01-01

269

Porous ceramic samples were prepared from aqueous foam incorporated alumina suspension for application as hot aerosol filtering membrane. The procedure for establishment of membrane features required to maintain a desired flow condition was theoretically described and experimental work was designed to prepare ceramic membranes to meet the predicted criteria. Two best membranes, thus prepared, were selected for permeability tests up to 700 degrees C and their total and fractional collection efficiencies were experimentally evaluated. Reasonably good performance was achieved at room temperature, while at 700 degrees C, increased permeability was obtained with significant reduction in collection efficiency, which was explained by a combination of thermal expansion of the structure and changes in the gas properties. PMID:18565647

Innocentini, Murilo D M; Rodrigues, Vanessa P; Romano, Roberto C O; Pileggi, Rafael G; Silva, Gracinda M C; Coury, José R

2009-02-15

270

Optimal spatial filtering for brain oscillatory activity using the Relevance Vector Machine.

Over the past decade, various techniques have been proposed for localization of cerebral sources of oscillatory activity on the basis of magnetoencephalography (MEG) or electroencephalography recordings. Beamformers in the frequency domain, in particular, have proved useful in this endeavor. However, the localization accuracy and efficacy of such spatial filters can be markedly limited by bias from correlation between cerebral sources and short duration of source activity, both essential issues in the localization of brain data. Here, we evaluate a method for frequency-domain localization of oscillatory neural activity based on the relevance vector machine (RVM). RVM is a Bayesian algorithm for learning sparse models from possibly overcomplete data sets. The performance of our frequency-domain RVM method (fdRVM) was compared with that of dynamic imaging of coherent sources (DICS), a frequency-domain spatial filter that employs a minimum variance adaptive beamformer (MVAB) approach. The methods were tested both on simulated and real data. Two types of simulated MEG data sets were generated, one with continuous source activity and the other with transiently active sources. The real data sets were from slow finger movements and resting state. Results from simulations show comparable performance for DICS and fdRVM at high signal-to-noise ratios and low correlation. At low SNR or in conditions of high correlation between sources, fdRVM performs markedly better. fdRVM was successful on real data as well, indicating salient focal activations in the sensorimotor area. The resulting high spatial resolution of fdRVM and its sensitivity to low-SNR transient signals could be particularly beneficial when mapping event-related changes of oscillatory activity. PMID:23729235

Belardinelli, P; Jalava, A; Gross, J; Kujala, J; Salmelin, R

2013-11-01

271

Microbubble in filtering Tetra Methyl Ammonium Hydroxide (TMAH) were counted to find the filter which generates the lowest microbubble in resist development process. Hydrophilic Highly Asymmetric Poly Aryl Sulfone (HAPAS) filter was developed and tested. The result showed that generation of microbubbles was as low as that of the Nylon 6,6 filter which had the best performance to date. Microbubbles

Toru Umeda; Shuichi Tsuzuki; Mikal Boucher; Hung Dinh; L. C. Ma; Russell Boten

2006-01-01

272

NASA Astrophysics Data System (ADS)

This study contributes the ASSIST (Adaptive Strategies for Sampling in Space and Time) framework for improving long-term groundwater monitoring decisions across space and time while accounting for the influences of systematic model errors (or predictive bias). The new framework combines contaminant flow-and-transport modeling, bias-aware ensemble Kalman filtering (EnKF), many-objective evolutionary optimization, and visual analytics-based decision support. The ASSIST framework allows decision makers to forecast the value of investments in new observations for many objectives simultaneously. Information tradeoffs are evaluated using an EnKF to forecast plume transport in space and time in the presence of uncertain and biased model predictions that are conditioned on uncertain measurement data. This study demonstrates the ASSIST framework using a laboratory-based physical aquifer tracer experiment. In this initial demonstration, the position and frequency of tracer sampling was optimized to: (1) minimize monitoring costs, (2) maximize the information provided to the EnKF, (3) minimize failures to detect the tracer, (4) maximize the detection of tracer fluxes, (5) minimize error in quantifying tracer mass, and (6) minimize error in quantifying the centroid of the tracer plume. Our results demonstrate that the forecasting, search, and visualization components of the ASSIST framework represent a significant advance for observation network design that has a strong potential to innovate our characterization, prediction, and management of groundwater systems.

Kollat, J. B.; Reed, P. M.; Maxwell, R. M.

2010-12-01

273

Optimization of polarized helium-3 neutron spin filters for neutron scattering

NASA Astrophysics Data System (ADS)

Nuclear spin-polarized 3He gas has been widely used in neutron scattering experiments. Spin-exchange optical pumping (SEOP) is one of the primary methods to produce polarized 3He. In SEOP, 3He is polarized via spin exchange collisions with optically pumped rubidium (Rb) atoms. At Indiana University, we have developed a boat system and a compact system based on the SEOP method to produce hyperpolarized 3He. A nuclear magnetic resonance (NMR) system has been built to monitor the relative 3He polarization as well as to flip the polarization. In order to get an absolute measure of the 3He polarization, an electron paramagnetic resonance (EPR) system has also been constructed. The NMR and EPR combined offer a robust 3He polarimetry to our SEOP systems. To get better performance, a new SEOP method called Hybrid SEOP is applied, which uses a rubidium/potassium (K) mixture instead of a pure Rb vapor. We have successfully achieved up to 69% 3He polarization with this method on our compact system. One important application of polarized 3He is used as neutron spin filters. We provided a neutron polarizer imbedded with a NMR-based neutron spin flipper for the HB-2A powder diffractometer at Oak Ridge National Laboratory, which make the HB-2A the first powder diffractometer in US capable of performing polarized studies.

Jiang, Chenyang

274

Optimized multiple-quantum filter for robust selective excitation of metabolite signals

NASA Astrophysics Data System (ADS)

The selective excitation of metabolite signals in vivo requires the use of specially adapted pulse techniques, in particular when the signals are weak and the resonances overlap with those of unwanted molecules. Several pulse sequences have been proposed for this spectral editing task. However, their performance is strongly degraded by unavoidable experimental imperfections. Here, we show that optimal control theory can be used to generate pulses and sequences that perform almost ideally over a range of rf field strengths and frequency offsets that can be chosen according to the specifics of the spectrometer or scanner being used. We demonstrate this scheme by applying it to lactate editing. In addition to the robust excitation, we also have designed the pulses to minimize the signal of unwanted molecular species.

Holbach, Mirjam; Lambert, Jörg; Suter, Dieter

2014-06-01

275

NASA Astrophysics Data System (ADS)

Marshes are ubiquitous landforms in estuaries and lagoons, where important hydrological, morphological and ecological processes take place. These areas attenuate sea action on the coast and act as sediment trapping zones. Due to their ecosystem functions and effects on coastal stabilization, marshes are crucial structures in tidal environments, both biologically and geomorphologically, and are fundamental elements in wetland restoration and coastal realignment schemes. The spatially-distributed study of the geomorphology of intertidal areas using remotely-sensed digital terrain models remains problematic, owing to their small relief, often of the order of a few tens of centimetres, and to the presence of short and dense vegetation, which strongly reduces the number of resolvable ground returns. Here, we use high-resolution Terrestrial Laser Scanning (˜ 200 returns/m 2) to retrieve a high-resolution and high-accuracy Digital Terrain Model within a tidal marsh in the Venice lagoon. To this aim we apply a new filtering scheme to Terrestrial Laser Scanner data which selects the lowest values within moving windows, whose optimal size is determined with the aid of a limited number of ancillary Differential GPS data in order to maximize resolution while ensuring the identification of true ground returns. The accuracy of the filtered data is further refined using classifications of the intensity of the returns to extract additional information on the surface (ground or canopy) originating the returning laser beam. Validations against about 200 reference Differential GPS ground elevation observations indicates that the best separation of canopy and ground signals is obtained using a low-pass filter with window size of the order of 1 m and the maximum likelihood classifier to further refine the detection of ground returns. In this case the average estimation error is about 1 cm (slight overestimation of ground elevation), while its standard deviation is about 3 cm. Our approach allows the separation of laser returns coming from the low marsh vegetation from those coming from the marsh surface. The overall result is a new observation technique producing Digital Terrain and Digital Surface Models in areas with very small relief, which is shown to provide unprecedented high-resolution and high-accuracy characterizations of marsh morphology.

Guarnieri, A.; Vettore, A.; Pirotti, F.; Menenti, M.; Marani, M.

2009-12-01

276

Moment tensor solutions estimated using optimal filter theory for 51 selected earthquakes, 1980-1984

The 51 global events that occurred from January 1980 to March 1984, which were chosen by the convenors of the Symposium on Seismological Theory and Practice, have been analyzed using a moment tensor inversion algorithm (Sipkin). Many of the events were routinely analyzed as part of the National Earthquake Information Center's (NEIC) efforts to publish moment tensor and first-motion fault-plane solutions for all moderate- to large-sized (mb>5.7) earthquakes. In routine use only long-period P-waves are used and the source-time function is constrained to be a step-function at the source (??-function in the far-field). Four of the events were of special interest, and long-period P, SH-wave solutions were obtained. For three of these events, an unconstrained inversion was performed. The resulting time-dependent solutions indicated that, for many cases, departures of the solutions from pure double-couples are caused by source complexity that has not been adequately modeled. These solutions also indicate that source complexity of moderate-sized events can be determined from long-period data. Finally, for one of the events of special interest, an inversion of the broadband P-waveforms was also performed, demonstrating the potential for using broadband waveform data in inversion procedures. ?? 1987.

Sipkin, S. A.

1987-01-01

277

Band Pass Filter Design and Optimization on High-Resistivity Silicon for 5GHz RF Front End Receiver

Low-cost and compact size is endlessly requested by new wireless and mobile communication systems. These requirements are critical for some specific application such as bandpass filter(BPF). Most of today embedded filters in SIP are made on low temperature co-fired ceramics (LTCC) technology, which eliminates Surface Mount Technology (SMT) and reduces the size of the filter. While LTCC filter can reduce

Zhou Jinchang; Xiao Xianghua; Liu Shiguo; K. Nagaya; Y. Tsuchiya; Y. Mano; Khoo Yee Mong; Li Hongyu

2008-01-01

278

NASA Astrophysics Data System (ADS)

Microbubble in filtering Tetra Methyl Ammonium Hydroxide (TMAH) were counted to find the filter which generates the lowest microbubble in resist development process. Hydrophilic Highly Asymmetric Poly Aryl Sulfone (HAPAS) filter was developed and tested. The result showed that generation of microbubbles was as low as that of the Nylon 6,6 filter which had the best performance to date. Microbubbles in TARC are counted using the same method as the developer testing described above except for mainstream flow rate and the counter model. The results show that counts in the small channel could be reduced by smaller pore size filter such as conventional 0.02um rated filter. However, counts in the larger channel could be reduced by larger pore size filter such as 0.1um rated filter. Based on the above results, 0.02um rated asymmetric nylon 6,6 filter was developed. As a result, 0.02um rated asymmetric Nylon 6,6 filter achieved relatively lower count at any channel as compared to the standard 0.04um rated Nylon 6,6 filter. Nylon 6,6 filters were installed in resist as an improvement for preventive maintenance (PM) at Wafertech, L.L.C. instead of the currently used filter which has more hydrophobic membrane material. Using the Nylon 6,6 membrane, the number of defects immediately after filter change greatly decreased from 493 pcs of the more hydrophobic filter to 6 pcs/wafer, then after purging with about 250ml, the number of defects reduced within the process specification while the more hydrophobic filter had required 2L purging and 12-36 hours of PM time.

Umeda, Toru; Tsuzuki, Shuichi; Boucher, Mikal; Dinh, Hung; Ma, L. C.; Boten, Russell

2006-03-01

279

NASA Technical Reports Server (NTRS)

This paper covers the development of a model-based engine control (MBEC) methodology featuring a self tuning on-board model applied to an aircraft turbofan engine simulation. Here, the Commercial Modular Aero-Propulsion System Simulation 40,000 (CMAPSS40k) serves as the MBEC application engine. CMAPSS40k is capable of modeling realistic engine performance, allowing for a verification of the MBEC over a wide range of operating points. The on-board model is a piece-wise linear model derived from CMAPSS40k and updated using an optimal tuner Kalman Filter (OTKF) estimation routine, which enables the on-board model to self-tune to account for engine performance variations. The focus here is on developing a methodology for MBEC with direct control of estimated parameters of interest such as thrust and stall margins. Investigations using the MBEC to provide a stall margin limit for the controller protection logic are presented that could provide benefits over a simple acceleration schedule that is currently used in traditional engine control architectures.

Connolly, Joseph W.; Csank, Jeffrey Thomas; Chicatelli, Amy; Kilver, Jacob

2013-01-01

280

The optimal design method of the indoor thermal environment using CFD coupled simulation and genetic algorithms (GA) is developed in this study. CFD could analyze the thermal environment considering the distribution of temperature and air flow in a room. Therefore, it would be appropriate to use CFD for the optimal design method considering their distribution. In this study, the optimal

Taeyeon Kim; Doosam Song; Shinsuke Kato; Shuzo Murakami

2007-01-01

281

Inadequacies in health care practices have been reported despite existing guidelines to manage hip or knee osteoarthritis. To facilitate guideline implementation and improve utilization of non-surgical treatment options a care strategy should be developed. This study describes the development of an evidence-based, multidisciplinary, patient-centered, stepped care strategy. A national, multidisciplinary, steering group developed the strategy in three phases: (1) consensus among steering group members (first draft); (2) written consultation of 23 representatives of patient organizations and professional associations involved in osteoarthritis care (second draft); (3) consensus of the final draft after discussion in two rounds during a conference with representatives from the different disciplines. The final stepped care strategy presents, in three tiers, the optimal order for non-surgical treatment modalities. It recommends that more advanced options should only be considered if options listed in previous steps failed to produce satisfactory results. Hence, the first step treatment options can be offered to all patients but may also be provided through self care (education, life style advice, and acetaminophen). The second step (exercise therapy, dietary therapy, and non-steroidal anti-inflammatory drugs) and third step treatment options (multidisciplinary care, intra-articular injections, and transcutaneous electrical nerve stimulation) can be considered for people with persisting complaints. Trough a consensus procedure, we succeeded to develop a multidisciplinary, patient-centered, stepped care strategy based on national guidelines. This strategy provides a framework for health care providers and patients with hip or knee osteoarthritis to discuss the optimal timing of the various treatment options. PMID:21887488

Smink, Agnes J; van den Ende, Cornelia H M; Vliet Vlieland, Thea P M; Swierstra, Bart A; Kortland, Joke H; Bijlsma, Johannes W J; Voorn, Theo B; Schers, Henk J; Bierma-Zeinstra, Sita M A; Dekker, Joost

2011-12-01

282

This article presents multipole ring resonator planar active filters. We show how the noise factor of this category of filters can be analytically derived and effectively minimized by using appropriate unbalanced power couplers and amplifiers. Topologies of devices achieving a minimum noise factor with a maximum gain are presented. We validate our approach with simulated examples for each topology

L. Nenert; D. Denis; L. Billonnet; B. Jarry; P. Guillon

1999-01-01

283

NASA Astrophysics Data System (ADS)

We propose a two-step method for digital filtering of phase-shift keyed signals filtering in the problem of determination of the time delay during the multichannel propagation. The first step is realized as an information-optimal linear filter with complex coefficients, while the second step, as a quadratic filter based on the minimum-variance criterion. The e.ciency of the proposed method is demonstrated for short PSK signals with various carrier frequencies against the background of additive and multiplicative noise. The developed algorithm can easily be implemented in real time on the basis of a digital signal processor.

Loginov, A. A.; Morozov, O. A.; Soldatov, E. A.; Khmelev, S. L.

2007-03-01

284

NASA Astrophysics Data System (ADS)

We present a new least-mean-square algorithm of adaptive filtering to improve the signal to noise ratio for magnetocardiography data collected with high-temperature SQUID-based magnetometers. By frequently adjusting the adaptive parameter ? to systematic optimum values in the course of the programmed procedure, the convergence is accelerated with a highest speed and the minimum steady-state error is obtained simultaneously. This algorithm may be applied to eliminate other non-steady relevant noises as well.

Li, Zhuo; Chen, Geng-Hua; Zhang, Li-Hua; Yang, Qian-Sheng; Feng, Ji

2006-02-01

285

NASA Astrophysics Data System (ADS)

The use of polarized protons as neutron spin filter is an attractive alternative to the well established neutron polarization techniques, as the large, spin-dependent neutron scattering cross-section for protons is useful up to the sub-MeV region. Employing optically excited triplet states for the dynamic nuclear polarization (DNP) of the protons relieves the stringent requirements of classical DNP schemes, i.e low temperatures and strong magnetic fields, making technically simpler systems with open geometries possible. Using triplet DNP a record polarization of 71% has been achieved in a pentacene doped naphthalene single crystal at a field of 0.36 T using a simple helium flow cryostat for cooling. Furthermore, by placing the polarized crystal in a neutron optics focus and de-focus scheme, the actual sample cross-section could be increased by a factor 35 corresponding to an effective spin filter cross-section of 18×18 mm2.

Eichhorn, T. R.; Niketic, N.; van den Brandt, B.; Filges, U.; Panzner, T.; Rantsiou, E.; Wenckebach, W. Th.; Hautle, P.

2014-08-01

286

An improved Particle filter tracking algorithm

In target tracking, if the dynamic model satisfies the Kalman filter assumptions, Kalman filter is optimal, Particle filter is a second-best. Usually, systems are often unable to meet the best, at this time particle filter is usually better than any other filtering method. In order to solve the degradation and deprivation of particle filter in Iteration. This article introduces crossover

Gao Bingkun; Li Wenchao; Wang Shuai

2010-01-01

287

National Technical Information Service (NTIS)

This research develops and attempts to implement a Kalman filter integration of a Phase III Global Positioning System (GPS) five-channel receiver and an LN-94 Inertial Navigation System (INS). The GPS provides highly accurate position and velocity informa...

J. L. Hirning

1990-01-01

288

This paper shows applied sensitivity analysis for easier design and practical application of a planar half-wavelength low-pass filter (LPF) using defected ground structure (DGS). Typically, it is difficult to deploy planar half-wavelength low-pass filters when high power durability is required because of the very narrow line-widths of high impedance transmission line. Here, we propose a new configuration for the high

Jin-Kyu Byun; Jae-Hyeong Ko; Hyang-Beom Lee; Jun-Seok Park; Hyeong-Seok Kim

2009-01-01

289

A method for achieving optimal design of a wide-angle narrow-bandpass optical detection system composed of a spherical interference filter and a circular photodetector is introduced. It was found that there is an optimal photodetector diameter that maximizes the signal-to-noise ratio (SNR) for a given filter configuration. We show how to optimize optical detection systems based on spherical interference filters for all the important parameters simultaneously. The SNR values of these systems are compared with the SNR values of spherical-step-filter-based detection systems. When large silicon photodetectors are used, the two systems have equal SNR values so that the more economical step-filter systems are preferable. The results given here in the near-infrared region can be used for the optimization of any configuration of a detection system based on a spherical interference filter and a silicon photodetector working at the same wavelength range, without further calculations. PMID:18337966

Schweitzer, N; Arieli, Y

2000-02-20

290

ERIC Educational Resources Information Center

The Optimal Aging Program (OAP) at the University of Arizona, College of Medicine is a longitudinal mentoring program that pairs students with older adults who are considered to be aging "successfully." This credit-bearing elective was initially established in 2001 through a grant from the John A. Hartford Foundation, and aims to expand the…

Sikora, Stephanie

2006-01-01

291

NASA Astrophysics Data System (ADS)

This paper builds upon our recent data assimilation work with the extended Kalman filter (EKF) method [J. Kao, D. Flicker, R. Henninger, S. Frey, M. Ghil, K. Ide, Data assimilation with an extended Kalman filter for an impact-produced shock-wave study, J. Comp. Phys. 196 (2004) 705-723.]. The purpose is to test the capability of EKF in optimizing a model's physical parameters. The problem is to simulate the evolution of a shock produced through a high-speed flyer plate. In the earlier work, we have showed that the EKF allows one to estimate the evolving state of the shock wave from a single pressure measurement, assuming that all model parameters are known. In the present paper, we show that imperfectly known model parameters can also be estimated accordingly, along with the evolving model state, from the same single measurement. The model parameter optimization using the EKF can be achieved through a simple modification of the original EKF formalism by including the model parameters into an augmented state variable vector. While the regular state variables are governed by both deterministic and stochastic forcing mechanisms, the parameters are only subject to the latter. The optimally estimated model parameters are thus obtained through a unified assimilation operation. We show that improving the accuracy of the model parameters also improves the state estimate. The time variation of the optimized model parameters results from blending the data and the corresponding values generated from the model and lies within a small range, of less than 2%, from the parameter values of the original model. The solution computed with the optimized parameters performs considerably better and has a smaller total variance than its counterpart using the original time-constant parameters. These results indicate that the model parameters play a dominant role in the performance of the shock-wave hydrodynamic code at hand.

Kao, Jim; Flicker, Dawn; Ide, Kayo; Ghil, Michael

2006-05-01

292

This paper builds upon our recent data assimilation work with the extended Kalman filter (EKF) method [J. Kao, D. Flicker, R. Henninger, S. Frey, M. Ghil, K. Ide, Data assimilation with an extended Kalman filter for an impact-produced shock-wave study, J. Comp. Phys. 196 (2004) 705-723.]. The purpose is to test the capability of EKF in optimizing a model's physical parameters. The problem is to simulate the evolution of a shock produced through a high-speed flyer plate. In the earlier work, we have showed that the EKF allows one to estimate the evolving state of the shock wave from a single pressure measurement, assuming that all model parameters are known. In the present paper, we show that imperfectly known model parameters can also be estimated accordingly, along with the evolving model state, from the same single measurement. The model parameter optimization using the EKF can be achieved through a simple modification of the original EKF formalism by including the model parameters into an augmented state variable vector. While the regular state variables are governed by both deterministic and stochastic forcing mechanisms, the parameters are only subject to the latter. The optimally estimated model parameters are thus obtained through a unified assimilation operation. We show that improving the accuracy of the model parameters also improves the state estimate. The time variation of the optimized model parameters results from blending the data and the corresponding values generated from the model and lies within a small range, of less than 2%, from the parameter values of the original model. The solution computed with the optimized parameters performs considerably better and has a smaller total variance than its counterpart using the original time-constant parameters. These results indicate that the model parameters play a dominant role in the performance of the shock-wave hydrodynamic code at hand.

Kao, Jim [Los Alamos National Laboratory, Applied Physics Division, P.O. Box 1663, MS T086, Los Alamos, NM 87545 (United States)]. E-mail: kao@lanl.gov; Flicker, Dawn [Los Alamos National Laboratory, Applied Physics Division, P.O. Box 1663, MS T086, Los Alamos, NM 87545 (United States); Ide, Kayo [University of California at Los Angeles (United States); Ghil, Michael [University of California at Los Angeles (United States)

2006-05-20

293

NASA Astrophysics Data System (ADS)

It is utilized the morphology filter and self-adaptive genetic algorithm to present the morphology filter with selfoptimized genetic algorithms (MFGA) for detecting IR image signature of the target. According to training the structuring element from original image data, some constraint conditions such as the prior knowledge and statistics laws , we summarize a judgment rule on finding out the best of structuring elements. As two special applications about IR image signature of the detections, one is detected solid thruster plume IR image and the other is weak-small infrared target under complex background. Compared the experimental results of the MFGA with those of the morphology filter (MF), we find that the MFGA has high convergence speed, greatly enhanced the Signal Noise ratio of target detection and effectively detecting target from complex background. And the experimental results and methods have a great significance in aerial forecasting and space defense.

Wang, Ming-Jun; Wu, Zhen-Sen; Li, Ying-Le; Wang, Yun-Qiang

2009-07-01

294

NASA Technical Reports Server (NTRS)

A digital automatic control law to capture a steep glideslope and track the glideslope to a specified altitude is developed for the longitudinal/vertical dynamics of a CTOL aircraft using modern estimation and control techniques. The control law uses a constant gain Kalman filter to process guidance information from the microwave landing system, and acceleration from body mounted accelerometer data. The filter outputs navigation data and wind velocity estimates which are used in controlling the aircraft. Results from a digital simulation of the aircraft dynamics and the control law are presented for various wind conditions.

Halyo, N.

1976-01-01

295

This paper proposes and develops two simple efficient techniques for optimizing the closed-loop transient response of three-stage amplifiers for large capacitive load applications. The proposed approaches exploit a current comparator in the inner amplifier nodes to sense the input voltage transients and switch on an auxiliary driving device providing slew-rate enhancement and settling time improvement without extra static power dissipation.

Davide Marano; Gaetano Palumbo; Salvatore Pennisi

2009-01-01

296

Finite element analysis and optimal design of the mudsill and bracket of large-scale bag filter

By using the finite element analysis software ANSYS, the model of the mudsill and bracket of large-scale bag filter was established, and the stress distribution and deformation of the structure were analyzed. Then under the prerequisite of the mudsill and bracket structure satisfied in possessing enough strength and stiffness and taking the mass of the structure to be the lightest

Wang Shijie; Zhang Zhichen; Liao Shanmei; Zhang Lei; Lv Guosheng; Liu Linzhi

2010-01-01

297

The influence of magnetic filter configuration on the beam uniformity was examined to improve beam uniformity in a large Cs-seeded negative-ion source. By reducing the filter strength of the transverse magnetic field used in a typical negative-ion source, the beam uniformity was largely improved with the improvement of the plasma uniformity while the beam intensity was kept to be nearly constant. However, the coextracted electron current greatly increased. To suppress the coextracted electron current, a tent-shaped magnetic filter was applied together with modifications in the cusp magnets to form a typical multicusp positive-ion source arrangement. The uniformity in longitudinal beam profile was improved with the deviation of local beam intensity within 16% that was nearly equal to the deviation obtained at 50 G cm of the transverse filter strength. In the meantime, the coextracted electron current was kept to be the same as the H{sup -} ion current. The present result suggests that the uniformity of H{sup -} ion-beam profile is affected by the uniformity of atoms or protons in the source plasma, which are the primary species of negative ions under Cs-seeded surface production.

Hanada, M.; Seki, T.; Takado, N.; Inoue, T.; Tobari, H.; Mizuno, T.; Hatayama, A.; Dairaku, M.; Kashiwagi, M.; Sakamoto, K.; Taniguchi, M.; Watanabe, K. [Japan Atomic Energy Agency, Naka, Ibaraki 311-0193 (Japan); Keio University, Yokohama 223-8522 (Japan); Japan Atomic Energy Agency, Naka, Ibaraki 311-0193 (Japan); Keio University, Yokohama 223-8522 (Japan); Japan Atomic Energy Agency, Naka, Ibaraki 311-0193 (Japan)

2006-03-15

298

A filter family designed for use in quadrature mirror filter banks

This paper discusses a family of filters that have been designed for Quadrature Mirror Filter (QMF) Banks. These filters provide a significant improvement over conventional optimal equiripple and window designs when used in QMF banks. The performance criterion for these filters differ from those usually used for filter design in a way which makes the usual filter design techniques difficult

J. D. Johnston

1980-01-01

299

Biological and biomedical applications of accelerator mass spectrometry (AMS) use isotope ratio mass spectrometry to quantify minute amounts of long-lived radioisotopes such as (14)C. AMS target preparation involves first the oxidation of carbon (in sample of interest) to CO 2 and second the reduction of CO 2 to filamentous, fluffy, fuzzy, or firm graphite-like substances that coat a -400-mesh spherical iron powder (-400MSIP) catalyst. Until now, the quality of AMS targets has been variable; consequently, they often failed to produce robust ion currents that are required for reliable, accurate, precise, and high-throughput AMS for biological/biomedical applications. Therefore, we described our optimized method for reduction of CO 2 to high-quality uniform AMS targets whose morphology we visualized using scanning electron microscope pictures. Key features of our optimized method were to reduce CO 2 (from a sample of interest that provided 1 mg of C) using 100 +/- 1.3 mg of Zn dust, 5 +/- 0.4 mg of -400MSIP, and a reduction temperature of 500 degrees C for 3 h. The thermodynamics of our optimized method were more favorable for production of graphite-coated iron powders (GCIP) than those of previous methods. All AMS targets from our optimized method were of 100% GCIP, the graphitization yield exceeded 90%, and delta (13)C was -17.9 +/- 0.3 per thousand. The GCIP reliably produced strong (12)C (-) currents and accurate and precise F m values. The observed F m value for oxalic acid II NIST SRM deviated from its accepted F m value of 1.3407 by only 0.0003 +/- 0.0027 (mean +/- SE, n = 32), limit of detection of (14)C was 0.04 amol, and limit of quantification was 0.07 amol, and a skilled analyst can prepare as many as 270 AMS targets per day. More information on the physical (hardness/color), morphological (SEMs), and structural (FT-IR, Raman, XRD spectra) characteristics of our AMS targets that determine accurate, precise, and high-hroughput AMS measurement are in the companion paper. PMID:18785761

Kim, Seung-Hyun; Kelly, Peter B; Clifford, Andrew J

2008-10-15

300

Comparison of Filtering Methods for Extracellular Gastric Slow Wave Recordings

Background Extracellular recordings are used to define gastric slow wave propagation. Signal filtering is a key step in the analysis and interpretation of extracellular slow wave data; however, there is controversy and uncertainty regarding the appropriate filtering settings. This study investigated the effect of various standard filters on the morphology and measurement of extracellular gastric slow waves. Methods Experimental extracellular gastric slow waves were recorded from the serosal surface of the stomach from pigs and humans. Four digital filters: finite impulse response filter (0.05–1 Hz); Savitzky-Golay filter (0–1.98 Hz); Bessel filter (2–100 Hz); and Butterworth filter (5–100 Hz); were applied on extracellular gastric slow wave signals to compare the changes temporally (morphology of the signal) and spectrally (signals in the frequency domain). Key Results The extracellular slow wave activity/morphology is represented in the frequency domain by a dominant frequency and its associated harmonics in diminishing power. Optimal filters apply cutoff frequencies consistent with the dominant slow wave frequency (3–5cpm) and main harmonics (up to ~2Hz). Applying filters with cutoff frequencies above or below the dominant and harmonic frequencies was found to distort or eliminate slow wave signal content. Conclusions and Inferences Investigators must be cognizant of these optimal filtering practices when detecting, analyzing and interpreting extracellular slow wave recordings. The use of frequency domain analysis is important for identifying the dominant and harmonics of the signal of interest. Capturing the dominant frequency and major harmonics of slow wave is crucial for accurate representation of slow wave activity in the time domain. Standardized filter settings should be determined.

Paskaranandavadivel, Niranchan; O'Grady, Gregory; Du, Peng; Cheng, Leo K

2012-01-01

301

NASA Astrophysics Data System (ADS)

A video-stream associated with an Unmanned System or Full Motion Video can support the extraction of ground coordinates of a target of interest. The sensor metadata associated with the video-stream includes a time series of estimates of sensor position and attitude, required for down-stream single frame or multi-frame ground point extraction, such as stereo extraction using two frames in the video-stream that are separated in both time and imaging geometry. The sensor metadata may also include a corresponding time history of sensor position and attitude estimate accuracy (error covariance). This is required for optimal down-stream target extraction as well as corresponding reliable predictions of extraction accuracy. However, for multi-frame extraction, this is only a necessary condition. The temporal correlation of estimate errors (error cross-covariance) between an arbitrary pair of video frames is also required. When the estimates of sensor position and attitude are from a Kalman filter, as typically the case, the corresponding error covariances are automatically computed and available. However, the cross-covariances are not. This paper presents an efficient method for their exact representation in the metadata using additional, easily computed, data from the Kalman filter. The paper also presents an optimal weighted least squares extraction algorithm that correctly accounts for the temporal correlation, given the additional metadata. Simulation-based examples are presented that show the importance of correctly accounting for temporal correlation in multi-frame extraction algorithms.

Dolloff, J. T.

2012-05-01

302

NASA Astrophysics Data System (ADS)

Although tapered fins transfer more rate of heat per unit volume, they are not found in every practical application because of the difficulty in manufacturing and fabrications. Therefore, there is a scope to modify the geometry of a constant thickness fin in view of the less difficulty in manufacturing and fabrication as well as betterment of heat transfer rate per unit volume of the fin material. For the better utilization of fin material, it is proposed a modified geometry of new fin with a step change in thickness (SF) in the literature. In the present paper, the homotopy perturbation method has been used to evaluate the temperature distribution within the straight radiating fins with a step change in thickness and variable thermal conductivity. The temperature profile has an abrupt change in the temperature gradient where the step change in thickness occurs and thermal conductivity parameter describing the variation of thermal conductivity has an important role on the temperature profile and the heat transfer rate. The optimum geometry which maximizes the heat transfer rate for a given fin volume has been found. The derived condition of optimality gives an open choice to the designer.

Arslanturk, Cihat

2011-02-01

303

Pretreatment is necessary for lignocellulose to achieve a highly efficient enzymatic hydrolysis and fermentation. However, coincident with pretreatment, compounds inhibiting microorganism growth are formed. Some tissues or cells, such as thin-walled cells that easily hydrolyze, will be excessively degraded because of the structural heterogeneity of lignocellulose, and some inhibitors will be generated under the same pretreatment conditions. Results showed, compared with one-step steam explosion (1.2 MPa/8 min), two-step steam explosion with an intermediate separation of fiber cells (ISFC) (1.1 Mpa/4 min-ISFC-1.2 MPa/4 min) can increase enzymatic hydrolyzation by 12.82%, reduce inhibitor conversion by 33%, and increase fermentation product (2,3-butanediol) conversion by 209%. Thus, the two-step steam explosion with ISFC process is proposed to optimize the hydrolysis process of lignocellulose by modifying the raw material from the origin. This novel process reduces the inhibitor content, promotes the biotransformation of lignocellulose, and simplifies the process of excluding the detoxification unit operation. PMID:22858472

Zhang, Yuzhen; Fu, Xiaoguo; Chen, Hongzhang

2012-10-01

304

NASA Astrophysics Data System (ADS)

To estimate the surface carbon flux in Asia and investigate the effect of the nesting domain on carbon flux analyses in Asia, two experiments with different nesting domains were conducted using the CarbonTracker developed by the National Oceanic and Atmospheric Administration. CarbonTracker is an inverse modeling system that uses an ensemble Kalman filter (EnKF) to estimate surface carbon fluxes from surface CO2 observations. One experiment was conducted with a nesting domain centered in Asia and the other with a nesting domain centered in North America. Both experiments analyzed the surface carbon fluxes in Asia from 2001 to 2006. The results showed that prior surface carbon fluxes were underestimated in Asia compared with the optimized fluxes. The optimized biosphere fluxes of the two experiments exhibited roughly similar spatial patterns but different magnitudes. Weekly cumulative optimized fluxes showed more diverse patterns than the prior fluxes, indicating that more detailed flux analyses were conducted during the optimization. The nesting domain in Asia produced a detailed estimate of the surface carbon fluxes in Asia and exhibited better agreement with the CO2 observations. Finally, the simulated background atmospheric CO2 concentrations in the experiment with the nesting domain in Asia were more consistent with the observed CO2 concentrations than those in the experiment with the nesting domain in North America. The results of this study suggest that surface carbon fluxes in Asia can be estimated more accurately using an EnKF when the nesting domain is centered in Asian regions.

Kim, Jinwoong; Kim, Hyun Mee; Cho, Chun-Ho

2014-05-01

305

Exact Moments of Filtered Laser Phase Noise

NASA Astrophysics Data System (ADS)

In this paper, we derive an exact finite power series expression of the n th-order moment of a complex filtered phase noise random variable. This random variable is usually encountered in the error probability analysis of coherent heterodyne optical receivers. The result is then used to derive an infinite power series expression for the moment generating function of the same random variable. The two expressions represent a novel full statistical characterization of filtered phase noise. They also constitute an important step toward deriving optimal heterodyne receiver designs in the presence of phase noise. In a previous work Banat (J. Opt. Commun., vol. 5, 267 271, Dec. 2004), the author presented an approximate finite power series moment expression for filtered laser phase noise. The new results will be compared to those of Banat (J. Opt. Commun., vol. 5, 267 271, Dec. 2004).

Banat, Mohammad M.

2007-02-01

306

NASA Astrophysics Data System (ADS)

For a specific manipulation of friction surfaces it is important to measure and calculate geometrical parameters to derive the tribological behavior. The new functional approach presented in this paper is the calculation of the characteristic lateral extension of the real contact surface as well as the representative contact radius by applying morphological filters to a 3D-set of data. All surface characteristics, including form, waviness, roughness as well as defined microstructures, are extracted holistically with a 3D Coordinate Measuring Instrument or a Form Measuring Instrument, but with the smallest available tip radius. The paper presents the benefit of this holistic extraction method and the application of morphological filtering for the description of the contact form (plateau or sphere), the real contact surface, number of contacts, the typical contact radius and the typical lateral extension of the micro contact plateaus.

Gröger, S.; Burkhardt, T.; Dietzsch, M.

2011-08-01

307

Study of Washout Filters for a Simulator Motion Base.

National Technical Information Service (NTIS)

The conventional linear washout filter and coordinated adaptive washout filter for a six-degree-of-freedom flight simulator are surveyed. A nonlinear optimal washout filter based on nonlinear regulator and optimal control theories has been synthesized. Th...

Z. Q. Liu

1983-01-01

308

Multi-Step Look-Ahead Trajectory Planning in SLAM: Possibility and Necessity

Abstract— In this paper, the possibility and necessity of multi- step trajectory planning in Extended Kalman Filter (EKF) based SLAM is investigated. The objective of the trajectory planning here is to minimize the estimation error of the robot and landmark locations subject to a given time horizon. We show that the problem can be regarded as an optimization problem for

Shoudong Huang; Ngai Ming Kwok; Gamini Dissanayake; Q. P. Ha; Gu Fang

2005-01-01

309

Abstract: In this book, the extended Kalman filter (EKF) has been used as the standard technique for performing recursive nonlinear estimation. The EKF algorithm, however, provides only an approximation to optimal nonlinear estimation. In this chapter, we point out the underlying assumptions and flaws in the EKF, and present an alternative filter with performance superior to that of the EKF.

E. Wan; R. Van Der Merwe

2001-01-01

310

We report a low-temperature fluorescence spectroscopy study of the PAS-GAF-PHY sensory module of Cph1 phytochrome, its Y263F mutant (both with known 3D structures) as well as Y263H and Y263S to connect their photochemical parameters with intramolecular interactions. None of the holoproteins showed photochemical activity at low temperature, and the activation barriers for the Pr?lumi-R photoreaction (2.5-3.1 kJ mol(-1) ) and fluorescence quantum yields (0.29-0.42) were similar. The effect of the mutations on Pr?Pfr photoconversion efficiency (?Pr?Pfr ) was observed primarily at the prelumi-R S0 bifurcation point corresponding to the conical intersection of the energy surfaces at which the molecule relaxes to form lumi-R or Pr, lowering ?Pr?Pfr from 0.13 in the wild type to 0.05-0.07 in the mutants. We suggest that the Ea activation barrier in the Pr* S1 excited state might correspond to the D-ring (C19) carbonyl - H290 hydrogen bond or possibly to the hindrance caused by the C13(1) /C17(1) methyl groups of the C and D rings. The critical role of the tyrosine hydroxyl group can be at the prelumi-R bifurcation point to optimize the yield of the photoprocess and energy storage in the form of lumi-R for subsequent rearrangement processes culminating in Pfr formation. PMID:24571438

Sineshchekov, Vitaly; Mailliet, Joel; Psakis, Georgios; Feilke, Kathleen; Kopycki, Jakub; Zeidler, Mathias; Essen, Lars-Oliver; Hughes, Jon

2014-07-01

311

The aim of this study was to compare IMRT optimization in the CMS XiO radiotherapy treatment planning system, with and without segment weight optimization. Twenty-one prostate cancer patients were selected for this study. All patients were initially planned with step-and-shoot IMRT (S-IMRT). A new plan was then created for each patient by applying the segment weight optimization tool (SWO-IMRT). Analysis was performed on the (SWO-IMRT) and (S-IMRT) plans by comparing the total number of segments, monitor units, rectal and bladder dose. The study showed a statistically significant reduction in the total number of segments (mean: 25.3%; range: 16.8%-31.1%) with SWO-IMRT as compared to S-IMRT (p < 0.0001). Similarly, a mean reduction of 3.8% (range: 0.4%-7.7%) in the total MU was observed with SWO-IMRT (p < 0.0001). The study showed an average rectal dose decrease of 13.7% (range: 7.9%-21.4%) with SWO-IMRT (p < 0.0001). We also observed a statistically significant reduction of 26.7% (range: 16.0%-41.4%; p < 0.0001) in the mean dose to the posterior one-third rectum and an overall reduction in mean bladder dose of 2.2% (range: 0.1%-6.1%) for SWO-IMRT (p < 0.0001). This study shows that the segment weight optimization method significantly reduces the total number of segments and the dose to the rectum for IMRT prostate cancer. It also resulted in fewer monitor units for most of the prostate cases observed in this study. PMID:22231214

Prabhakar, Ramachandran; Cramb, Jim; Gehrke, Christopher; Anderson, Justin; Andrews, Judy

2012-01-01

312

Babcock and Wilcox Technical Services Group (B and W) has identified aqueous homogeneous reactors (AHRs) as a technology well suited to produce the medical isotope molybdenum 99 (Mo-99). AHRs have never been specifically designed or built for this specialized purpose. However, AHRs have a proven history of being safe research reactors. In fact, in 1958, AHRs had 'a longer history of operation than any other type of research reactor using enriched fuel' and had 'experimentally demonstrated to be among the safest of all various type of research reactor now in use [1].' While AHRs have been modeled effectively using simplified 'Level 1' tools, the complex interactions between fluids, neutronics, and solid structures are important (but not necessarily safety significant). These interactions require a 'Level 2' modeling tool. Imperial College London (ICL) has developed such a tool: Finite Element Transient Criticality (FETCH). FETCH couples the radiation transport code EVENT with the computational fluid dynamics code (Fluidity), the result is a code capable of modeling sub-critical, critical, and super-critical solutions in both two-and three-dimensions. Using FETCH, ICL researchers and B and W engineers have studied many fissioning solution systems include the Tokaimura criticality accident, the Y12 accident, SILENE, TRACY, and SUPO. These modeling efforts will ultimately be incorporated into FETCH'S extensive automated verification and validation (V and V) test suite expanding FETCH'S area of applicability to include all relevant physics associated with AHRs. These efforts parallel B and W's engineering effort to design and optimize an AHR to produce Mo99. (authors)

Nygaard, E. T. [Babcock and Wilcox Technical Services Group, 800 Main Street, Lynchburg, VA 24504 (United States); Pain, C. C.; Eaton, M. D.; Gomes, J. L. M. A.; Goddard, A. J. H.; Gorman, G.; Tollit, B.; Buchan, A. G.; Cooling, C. M. [Applied Modelling and Computation Group, Dept. of Earth Science and Engineering, Imperial College London, SW7 2AZ (United Kingdom); Angelo, P. L. [Y-12 National Security Complex, Oak Ridge, TN 37831 (United States)

2012-07-01

313

An improved Rao-Blackwellized particle filtering (RBPF) is proposed track the mobility of mobile station (MS) in mixed line-of-sight (LOS) or non-line-of-sight (NLOS) conditions in cellular network. The algorithm first estimates the sight condition state using particle filtering method, in which particles are sampled by the optimal trial distribution and selected by one-step backward prediction. Then, by applying decentralized extended Kalman

Chen Liang; Wu Lenan

2009-01-01

314

In this work, phenylboronic acid (PBA) was thoroughly investigated as a synthetic ligand for the purification of an immunoglobulin G (IgG) from a clarified cell supernatant from Chinese Hamster Ovary (CHO) cell cultures. In particular, the study was focused on the development of a washing step and in the optimization of the elution step using a serum containing supernatant. From the different conditions tested, best recoveries - 99% - and purifications - protein purity of 81% and a purification factor of 16 out of a maximum of 20 - were achieved using 100mM d-sorbitol in 10mM Tris-HCl as washing buffer and 0.5M d-sorbitol with 150mM NaCl in 10mM Tris-HCl as elution buffer. The purification outcome was also compared with protein A chromatography that revealed a recovery of 99%, 87% protein purity and 29 out of a maximum of 33 purification factor. Following the main purification, purified IgG was characterized in terms of isoelectric point, size and activity. In the end, a proof of concept was performed using two different mAbs from serum-free CHO cell cultures. PMID:24947887

Dos Santos, Raquel; Rosa, Sara A S L; Aires-Barros, M Raquel; Tover, Andres; Azevedo, Ana M

2014-08-15

315

NASA Technical Reports Server (NTRS)

Time-correlated gust loads are time histories of two or more load quantities due to the same disturbance time history. Time correlation provides knowledge of the value (magnitude and sign) of one load when another is maximum. At least two analysis methods have been identified that are capable of computing maximized time-correlated gust loads for linear aircraft. Both methods solve for the unit-energy gust profile (gust velocity as a function of time) that produces the maximum load at a given location on a linear airplane. Time-correlated gust loads are obtained by re-applying this gust profile to the airplane and computing multiple simultaneous load responses. Such time histories are physically realizable and may be applied to aircraft structures. Within the past several years there has been much interest in obtaining a practical analysis method which is capable of solving the analogous problem for nonlinear aircraft. Such an analysis method has been the focus of an international committee of gust loads specialists formed by the U.S. Federal Aviation Administration and was the topic of a panel discussion at the Gust and Buffet Loads session at the 1989 SDM Conference in Mobile, Alabama. The kinds of nonlinearities common on modern transport aircraft are indicated. The Statical Discrete Gust method is capable of being, but so far has not been, applied to nonlinear aircraft. To make the method practical for nonlinear applications, a search procedure is essential. Another method is based on Matched Filter Theory and, in its current form, is applicable to linear systems only. The purpose here is to present the status of an attempt to extend the matched filter approach to nonlinear systems. The extension uses Matched Filter Theory as a starting point and then employs a constrained optimization algorithm to attack the nonlinear problem.

Pototzky, Anthony S.; Heeg, Jennifer; Perry, Boyd, III

1990-01-01

316

NASA Astrophysics Data System (ADS)

The existence of insoluble residues as intermediate products produced during the wet etching process is the main quality-reducing and structure-patterning issue for lead zirconate titanate (PZT) thin films. A one-step wet etching process using the solutions of buffered HF (BHF) and HNO3 acid was developed for patterning PZT thin films for microelectomechanical system (MEMS) applications. PZT thin films with 1 µm thickness were prepared on the Pt/Ti/SiO2/Si substrate by the sol-gel process for compatibility with Si micromachining. Various compositions of the etchant were investigated and the patterns were examined to optimize the etching process. The optimal result is demonstrated by a high etch rate (3.3 µm min-1) and low undercutting (1.1: 1). The patterned PZT thin film exhibits a remnant polarization of 24 µC cm-2, a coercive field of 53 kV cm-1, a leakage current density of 4.7 × 10-8 A cm-2 at 320 kV cm-1 and a dielectric constant of 1100 at 1 KHz.

Che, L.; Halvorsen, E.; Chen, X.

2011-10-01

317

Filter designing for image processing based on multidimensional linear extrapolation

NASA Astrophysics Data System (ADS)

This article is proposed to develop a method of the synthesis of the prediction filter based on the multidimensional linear extrapolation to improve the accuracy of the pixel value prediction, as well as to assess the effectiveness of the proposed predictive filters depending on the prediction step and the dimension of training vectors to minimize the prediction error and the entropy of the differential signal. The article contain a solution of the special cases for a number of elements of the vector prediction, statistical dependence of the vector dimension and prediction filter order from the mean square error and the entropy of the differential signal are determined. Optimal prediction step is founded based on the experimental data and all the results are being analyzed.

Bagmanov, Valery Kh.; Zainullin, Airat R.; Meshkov, Ivan K.; Sultanov, Albert Kh.

2014-04-01

318

We address the problem of automated detection of biological macromolecules imaged with an electron microscope. These types of images are characterized by a low signal-to-noise ratio (0 dB), a low and varying contrast, in-plane rotated and densely distributed objects in the scene, strong object deformations, and the possible occurrence of false class objects and object agglomerations. We propose a two-step

Arne Stoschek; T. P. Y. Yu; R. Hegerl

1996-01-01

319

Modelling of diffraction grating based optical filters for fluorescence detection of biomolecules

The detection of biomolecules based on fluorescence measurements is a powerful diagnostic tool for the acquisition of genetic, proteomic and cellular information. One key performance limiting factor remains the integrated optical filter, which is designed to reject strong excitation light while transmitting weak emission (fluorescent) light to the photodetector. Conventional filters have several disadvantages. For instance absorbing filters, like those made from amorphous silicon carbide, exhibit low rejection ratios, especially in the case of small Stokes’ shift fluorophores (e.g. green fluorescent protein GFP with ?exc = 480 nm and ?em = 510 nm), whereas interference filters comprising many layers require complex fabrication. This paper describes an alternative solution based on dielectric diffraction gratings. These filters are not only highly efficient but require a smaller number of manufacturing steps. Using FEM-based optical modelling as a design optimization tool, three filtering concepts are explored: (i) a diffraction grating fabricated on the surface of an absorbing filter, (ii) a diffraction grating embedded in a host material with a low refractive index, and (iii) a combination of an embedded grating and an absorbing filter. Both concepts involving an embedded grating show high rejection ratios (over 100,000) for the case of GFP, but also high sensitivity to manufacturing errors and variations in the incident angle of the excitation light. Despite this, simulations show that a 60 times improvement in the rejection ratio relative to a conventional flat absorbing filter can be obtained using an optimized embedded diffraction grating fabricated on top of an absorbing filter.

Kovacic, M.; Krc, J.; Lipovsek, B.; Topic, M.

2014-01-01

320

Estimation and filter stability of stochastic delay systems

NASA Technical Reports Server (NTRS)

Linear and nonlinear filtering for stochastic delay systems are studied. A representation theorem for conditional moment functionals is obtained, which, in turn, is used to derive stochastic differential equations describing the optimal linear or nonlinear filter. A complete characterization of the optimal filter is given for linear systems with Gaussian noise. Stability of the optimal filter is studied in the case where there are no delays in the observations. Using the duality between linear filtering and control, asymptotic stability of the optimal filter is proved. Finally, the cascade of the optimal filter and the deterministic optimal quadratic control system is shown to be asymptotically stable as well.

Kwong, R. H.; Willsky, A. S.

1978-01-01

321

Adaptive kalman filter with the filter gain correction applied to UAV flight dynamics

In normal operation conditions of an UAV (Unmanned Aerial Vehicle), Optimal Kalman Filter gives sufficiently good estimation results. However, in case, where measurements are faulty, filter outputs become inaccurate and even the filter may fail. This study, introduces an Adaptive Kalman Filter algorithm with the filter gain correction for the case of measurement malfunctions. By the use of a defined

Chingiz Hajiyev; Halil Ersin Soken

2009-01-01

322

Research on filter processing of LIDAR data

The aim of the filter processing to LIDAR dataset is to divide the dataset into ground points and non-ground points. So, the filtering of LIDAR dataset is a crucial step to obtain the DEM with high precision. Over the last few years, some algorithms have been developed to filter LIDAR data. This paper studies three filtering algorithms that are used

Jie Yu; Guoning Zhang; Pingxiang Li; Kun Qin; Haiquan Yang

2006-01-01

323

Design of withdrawal-weighted SAW filters.

This paper presents a new design algorithm for a withdrawal-weighted surface acoustic wave (SAW) transversal filter. The proposed algorithm is based on the effective transmission loss theory and a delta function model of a SAW transversal filter. The design process consists of three steps, which eventually determine eight geometrical design parameters for the filter in order to satisfy given performance specifications. First, the number of fingers in the input and output interdigital transducers (IDTs), plus their geometrical sizes is determined using the insertion loss specification. Second, the number and positions of the polarity reverses in the output IDT are determined using the bandwidth and ripple specifications. Third, the number and position for withdrawing and switching specific fingers in the output IDT and attached electrode area are determined to achieve the desired sidelobe level. The efficiency of the technique is illustrated using a sample design of an IF filter consisting of a uniform input IDT and withdrawal-weighted output IDT. The proposed algorithm is distinct from conventional techniques in that it can optimize the structural geometry of a withdrawal-weighted SAW filter in a direct manner by considering all the performance specifications simultaneously. PMID:12322883

Lee, Youngjin; Lee, Seunghee; Roh, Yongrae

2002-03-01

324

NASA Astrophysics Data System (ADS)

A series of microporous carbons (MPCs) were successfully prepared by an efficient one-step condensation and activation strategy using commercially available dialdehyde and diamine as carbon sources. The resulting MPCs have large surface areas (up to 1881 m2 g-1), micropore volumes (up to 0.78 cm3 g-1), and narrow micropore size distributions (0.7-1.1 nm). The CO2 uptakes of the MPCs prepared at high temperatures (700-750 °C) are higher than those prepared under mild conditions (600-650 °C), because the former samples possess optimal micropore sizes (0.7-0.8 nm) that are highly suitable for CO2 capture due to enhanced adsorbate-adsorbent interactions. At 1 bar, MPC-750 prepared at 750 °C demonstrates the best CO2 capture performance and can efficiently adsorb CO2 molecules at 2.86 mmol g-1 and 4.92 mmol g-1 at 25 and 0 °C, respectively. In particular, the MPCs with optimal micropore sizes (0.7-0.8 nm) have extremely high CO2/N2 adsorption ratios (47 and 52 at 25 and 0 °C, respectively) at 1 bar, and initial CO2/N2 adsorption selectivities of up to 81 and 119 at 25 °C and 0 °C, respectively, which are far superior to previously reported values for various porous solids. These excellent results, combined with good adsorption capacities and efficient regeneration/recyclability, make these carbons amongst the most promising sorbents reported so far for selective CO2 adsorption in practical applications.A series of microporous carbons (MPCs) were successfully prepared by an efficient one-step condensation and activation strategy using commercially available dialdehyde and diamine as carbon sources. The resulting MPCs have large surface areas (up to 1881 m2 g-1), micropore volumes (up to 0.78 cm3 g-1), and narrow micropore size distributions (0.7-1.1 nm). The CO2 uptakes of the MPCs prepared at high temperatures (700-750 °C) are higher than those prepared under mild conditions (600-650 °C), because the former samples possess optimal micropore sizes (0.7-0.8 nm) that are highly suitable for CO2 capture due to enhanced adsorbate-adsorbent interactions. At 1 bar, MPC-750 prepared at 750 °C demonstrates the best CO2 capture performance and can efficiently adsorb CO2 molecules at 2.86 mmol g-1 and 4.92 mmol g-1 at 25 and 0 °C, respectively. In particular, the MPCs with optimal micropore sizes (0.7-0.8 nm) have extremely high CO2/N2 adsorption ratios (47 and 52 at 25 and 0 °C, respectively) at 1 bar, and initial CO2/N2 adsorption selectivities of up to 81 and 119 at 25 °C and 0 °C, respectively, which are far superior to previously reported values for various porous solids. These excellent results, combined with good adsorption capacities and efficient regeneration/recyclability, make these carbons amongst the most promising sorbents reported so far for selective CO2 adsorption in practical applications. Electronic supplementary information (ESI) available: Fig. S1-13 and Table S1. See DOI: 10.1039/c3nr05825e

Wang, Jiacheng; Liu, Qian

2014-03-01

325

A series of microporous carbons (MPCs) were successfully prepared by an efficient one-step condensation and activation strategy using commercially available dialdehyde and diamine as carbon sources. The resulting MPCs have large surface areas (up to 1881 m(2) g(-1)), micropore volumes (up to 0.78 cm(3) g(-1)), and narrow micropore size distributions (0.7-1.1 nm). The CO2 uptakes of the MPCs prepared at high temperatures (700-750 °C) are higher than those prepared under mild conditions (600-650 °C), because the former samples possess optimal micropore sizes (0.7-0.8 nm) that are highly suitable for CO2 capture due to enhanced adsorbate-adsorbent interactions. At 1 bar, MPC-750 prepared at 750 °C demonstrates the best CO2 capture performance and can efficiently adsorb CO2 molecules at 2.86 mmol g(-1) and 4.92 mmol g(-1) at 25 and 0 °C, respectively. In particular, the MPCs with optimal micropore sizes (0.7-0.8 nm) have extremely high CO2/N2 adsorption ratios (47 and 52 at 25 and 0 °C, respectively) at 1 bar, and initial CO2/N2 adsorption selectivities of up to 81 and 119 at 25 °C and 0 °C, respectively, which are far superior to previously reported values for various porous solids. These excellent results, combined with good adsorption capacities and efficient regeneration/recyclability, make these carbons amongst the most promising sorbents reported so far for selective CO2 adsorption in practical applications. PMID:24603950

Wang, Jiacheng; Liu, Qian

2014-04-21

326

High accuracy motor controller for positioning optical filters in the CLAES Spectrometer

NASA Technical Reports Server (NTRS)

The Etalon Drive Motor (EDM), a precision etalon control system designed for accurate positioning of etalon filters in the IR spectrometer of the Cryogenic Limb Array Etalon Spectrometer (CLAES) experiment is described. The EDM includes a brushless dc torque motor, which has an infinite resolution for setting an etalon filter to any desired angle, a four-filter etalon wheel, and an electromechanical resolver for angle information. An 18-bit control loop provides high accuracy, resolution, and stability. Dynamic computer interaction allows the user to optimize the step response. A block diagram of the motor controller is presented along with a schematic of the digital/analog converter circuit.

Thatcher, John B.

1989-01-01

327

Scale-up and optimization of an acoustic filter for 200 L/day perfusion of a CHO cell culture.

Acoustic cell retention devices have provided a practical alternative for up to 50 L/day perfusion cultures but further scale-up has been limited. A novel temperature-controlled and larger-scale acoustic separator was evaluated at up to 400 L/day for a 10(7) CHO cell/mL perfusion culture using a 100-L bioreactor that produced up to 34 g/day recombinant protein. The increased active volume of this scaled-up separator was divided into four parallel compartments for improved fluid dynamics. Operational settings of the acoustic separator were optimized and the limits of robust operations explored. The performance was not influenced over wide ranges of duty cycle stop and run times. The maximum performance of 96% separation efficiency at 200 L/day was obtained by setting the separator temperature to 35.1 degrees C, the recirculation rate to three times the harvest rate, and the power to 90 W. While there was no detectable effect on culture viability, viable cells were selectively retained, especially at 50 L/day, where there was a 5-fold higher nonviable washout efficiency. Overall, the new temperature-controlled and scaled-up separator design performed reliably in a way similar to smaller-scale acoustic separators. These results provide strong support for the feasibility of much greater scale-up of acoustic separations. PMID:12325152

Gorenflo, Volker M; Smith, Laura; Dedinsky, Bob; Persson, Bo; Piret, James M

2002-11-20

328

Factoring wavelet transforms into lifting steps

This article is essentially tutorial in nature. We show how any discrete wavelet transform or two band subband filtering with\\u000a finite filters can be decomposed into a finite sequence of simple filtering steps, which we call lifting steps but that are\\u000a also known as ladder structures. This decomposition corresponds to a factorization of the polyphase matrix of the wavelet\\u000a or

Ingrid Daubechies; Wim Sweldens

1998-01-01

329

An electric disk filter provides a high efficiency at high temperature. A hollow outer filter of fibrous stainless steel forms the ground electrode. A refractory filter material is placed between the outer electrode and the inner electrically isolated high voltage electrode. Air flows through the outer filter surfaces through the electrified refractory filter media and between the high voltage electrodes and is removed from a space in the high voltage electrode.

Bergman, W.

1985-01-09

330

A generalized adaptive mathematical morphological filter for LIDAR data

NASA Astrophysics Data System (ADS)

Airborne Light Detection and Ranging (LIDAR) technology has become the primary method to derive high-resolution Digital Terrain Models (DTMs), which are essential for studying Earth's surface processes, such as flooding and landslides. The critical step in generating a DTM is to separate ground and non-ground measurements in a voluminous point LIDAR dataset, using a filter, because the DTM is created by interpolating ground points. As one of widely used filtering methods, the progressive morphological (PM) filter has the advantages of classifying the LIDAR data at the point level, a linear computational complexity, and preserving the geometric shapes of terrain features. The filter works well in an urban setting with a gentle slope and a mixture of vegetation and buildings. However, the PM filter often removes ground measurements incorrectly at the topographic high area, along with large sizes of non-ground objects, because it uses a constant threshold slope, resulting in "cut-off" errors. A novel cluster analysis method was developed in this study and incorporated into the PM filter to prevent the removal of the ground measurements at topographic highs. Furthermore, to obtain the optimal filtering results for an area with undulating terrain, a trend analysis method was developed to adaptively estimate the slope-related thresholds of the PM filter based on changes of topographic slopes and the characteristics of non-terrain objects. The comparison of the PM and generalized adaptive PM (GAPM) filters for selected study areas indicates that the GAPM filter preserves the most "cut-off" points removed incorrectly by the PM filter. The application of the GAPM filter to seven ISPRS benchmark datasets shows that the GAPM filter reduces the filtering error by 20% on average, compared with the method used by the popular commercial software TerraScan. The combination of the cluster method, adaptive trend analysis, and the PM filter allows users without much experience in processing LIDAR data to effectively and efficiently identify ground measurements for the complex terrains in a large LIDAR data set. The GAPM filter is highly automatic and requires little human input. Therefore, it can significantly reduce the effort of manually processing voluminous LIDAR measurements.

Cui, Zheng

331

NASA Technical Reports Server (NTRS)

The Aquaspace H2OME Guardian Water Filter, available through Western Water International, Inc., reduces lead in water supplies. The filter is mounted on the faucet and the filter cartridge is placed in the "dead space" between sink and wall. This filter is one of several new filtration devices using the Aquaspace compound filter media, which combines company developed and NASA technology. Aquaspace filters are used in industrial, commercial, residential, and recreational environments as well as by developing nations where water is highly contaminated.

1993-01-01

332

National Technical Information Service (NTIS)

An electrical filter is described for removing noise from voice communications signals. Filtering is accomplished by adding balanced, with respect to a midpoint sample, spaced pairs of the sampled signal values, and then multiplying each pair by a selecte...

T. R. Edwards H. W. Zeanah

1974-01-01

333

ERIC Educational Resources Information Center

Presents the 1978 literature review of wastewater treatment. The review is concerned with biological filters, and it covers: (1) trickling filters; (2) rotating biological contractors; and (3) miscellaneous reactors. A list of 14 references is also presented. (HM)

Klemetson, S. L.

1978-01-01

334

A step-by-step guide to systematically identify all relevant animal studies.

Before starting a new animal experiment, thorough analysis of previously performed experiments is essential from a scientific as well as from an ethical point of view. The method that is most suitable to carry out such a thorough analysis of the literature is a systematic review (SR). An essential first step in an SR is to search and find all potentially relevant studies. It is important to include all available evidence in an SR to minimize bias and reduce hampered interpretation of experimental outcomes. Despite the recent development of search filters to find animal studies in PubMed and EMBASE, searching for all available animal studies remains a challenge. Available guidelines from the clinical field cannot be copied directly to the situation within animal research, and although there are plenty of books and courses on searching the literature, there is no compact guide available to search and find relevant animal studies. Therefore, in order to facilitate a structured, thorough and transparent search for animal studies (in both preclinical and fundamental science), an easy-to-use, step-by-step guide was prepared and optimized using feedback from scientists in the field of animal experimentation. The step-by-step guide will assist scientists in performing a comprehensive literature search and, consequently, improve the scientific quality of the resulting review and prevent unnecessary animal use in the future. PMID:22037056

Leenaars, Marlies; Hooijmans, Carlijn R; van Veggel, Nieky; ter Riet, Gerben; Leeflang, Mariska; Hooft, Lotty; van der Wilt, Gert Jan; Tillema, Alice; Ritskes-Hoitinga, Merel

2012-01-01

335

A step-by-step guide to systematically identify all relevant animal studies

Before starting a new animal experiment, thorough analysis of previously performed experiments is essential from a scientific as well as from an ethical point of view. The method that is most suitable to carry out such a thorough analysis of the literature is a systematic review (SR). An essential first step in an SR is to search and find all potentially relevant studies. It is important to include all available evidence in an SR to minimize bias and reduce hampered interpretation of experimental outcomes. Despite the recent development of search filters to find animal studies in PubMed and EMBASE, searching for all available animal studies remains a challenge. Available guidelines from the clinical field cannot be copied directly to the situation within animal research, and although there are plenty of books and courses on searching the literature, there is no compact guide available to search and find relevant animal studies. Therefore, in order to facilitate a structured, thorough and transparent search for animal studies (in both preclinical and fundamental science), an easy-to-use, step-by-step guide was prepared and optimized using feedback from scientists in the field of animal experimentation. The step-by-step guide will assist scientists in performing a comprehensive literature search and, consequently, improve the scientific quality of the resulting review and prevent unnecessary animal use in the future.

Leenaars, Marlies; Hooijmans, Carlijn R; van Veggel, Nieky; ter Riet, Gerben; Leeflang, Mariska; Hooft, Lotty; van der Wilt, Gert Jan; Tillema, Alice; Ritskes-Hoitinga, Merel

2012-01-01

336

Particle Kalman Filtering: A Nonlinear Bayesian Framework for Ensemble Kalman Filters

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

Ibrahim Hoteit; Xiaodong Luo; Dinh-Tuan Pham

2011-01-01

337

NASA Technical Reports Server (NTRS)

The improvement of accuracy in using the smoothing filter instead of the Kalman filter is discussed. Factors of improvement for velocity errors of up to four are shown for position measurements. Smoothing equations are presented, and it is shown that smoothing equations for the smoothing filter appear to be stable.

Lear, W. H.

1980-01-01

338

NASA Astrophysics Data System (ADS)

Iterative image reconstruction with the total-variation (TV) constraint has become an active research area in recent years, especially in x-ray CT and MRI. Based on Green's one-step-late algorithm, this paper develops a transmission noise weighted iterative algorithm with a TV prior. This paper compares the reconstructions from this iterative TV algorithm with reconstructions from our previously developed non-iterative reconstruction method that consists of a noise-weighted filtered backprojection (FBP) reconstruction algorithm and a nonlinear edge-preserving post filtering algorithm. This paper gives a mathematical proof that the noise-weighted FBP provides an optimal solution. The results from both methods are compared using clinical data and computer simulation data. The two methods give comparable image quality, while the non-iterative method has the advantage of requiring much shorter computation times.

Zeng, Gengsheng L.; Li, Ya; Zamyatin, Alex

2013-05-01

339

Generalized linear correlation filters

NASA Astrophysics Data System (ADS)

We present two generalized linear correlation filters (CFs) that encompass most of the state-of-the-art linear CFs. The common criteria that arc used in linear CF design are the mean squared error (MSE), output noise variance (ONV), and average similarity measure (ASM). We present a simple formulation that uses an optimal tradeoff among these criteria both constraining and not constraining the correlation peak value, and refer to them as generalized Constrained Correlation Filter (CCF) and Unconstrained Couelation Filter (UCF). We show that most state-of-the-art linear CFs arc subsets of these filters. We present a technique for efficient UCF computation. We also introduce the modified CCF (mCCF) that chooses a unique correlation peak value for each training image, and show that mCCF usually outperforms both UCF and CCF.

Rodriguez, Andres; Vijaya Kumar, B. V. K.

2013-05-01

340

Hot-gas filter manufacturing assessments: Volume 5. Final report, April 15, 1997

The development of advanced filtration media for advanced fossil-fueled power generating systems is a critical step in meeting the performance and emissions requirements for these systems. While porous metal and ceramic candle-filters have been available for some time, the next generation of filters will include ceramic-matrix composites (CMCs), intermetallic alloys, and alternate filter geometries. The goal of this effort was to perform a cursory review of the manufacturing processes used by 5 companies developing advanced filters from the perspective of process repeatability and the ability for their processes to be scale-up to production volumes. It was found that all of the filter manufacturers had a solid understanding of the product development path. Given that these filters are largely developmental, significant additional work is necessary to understand the process-performance relationships and projecting manufacturing costs. While each organization had specific needs, some common among all of the filter manufacturers were access to performance testing of the filters to aide process/product development, a better understanding of the stresses the filters will see in service for use in structural design of the components, and a strong process sensitivity study to allow optimization of processing.

Boss, D.E.

1997-12-31

341

Pratical high temperature superconductor filters

NASA Astrophysics Data System (ADS)

Thin-film high temperature superconductor (HTS) microwave filters were developed for military communications and electronic warfare systems, where the inherently high Q of the HTS resonator can dramatically improve circuit performance. To make this near-perfect high performance filter available for commerical use, steps were taken to adapt the components by adding additional functions and eliminating the need for liquid nitrogen through use of a closed-loop cooling system. This paper outline further development of the filter, and describes cellular base station and switchable filter applications.

Madden, Joseph M.

1994-10-01

342

We have successfully implemented Fluidigm's SlingShot™ technology into our 454 sequencing process at two key junctions: sub-optimal sample quantitation and replacement of the library titration. This implementation has allowed us to process previously failed samples (Roche recommends samples be between 3ug and 5ug) and replace the costly titration step, saving us processing time (up to 2 days) plus the cost

Joseph F. Boland; Casey A. Matthews; Jennifer A. Bacior; Victor Lonsberry; Zuoming Deng; Laufey Amundadottir; Stephen J. Chanock

343

Validation of a sterilizing filtration process is critical since it is impossible with currently available technology to measure the sterility of each filled container; therefore, sterility assurance of the filtered product must be achieved through validation of the filtration process. Validating a pharmaceutical sterile filtration process involves three things: determining the effect of the liquid on the filter, determining the effect of the filter on the liquid, and demonstrating that the filter removes all microorganisms from the liquid under actual processing conditions. PMID:16570864

Madsen, Russell E

2006-01-01

344

A fast matched filter in time domain

This paper presents a fast matched filter algorithm in time domain. Matched filters compute correlation of signals for optimal detection of signals in noise, for extracting ranging measurements, synchronisation, etc. We consider matched filters in the context of Global Positioning System (GPS) receivers, but the algorithms presented here can be used for other applications as no constraining assumptions are made

David Akopian; SOS Agaian

2004-01-01

345

Multiresolution Bilateral Filtering for Image Denoising

The bilateral filter is a nonlinear filter that does spatial averaging without smoothing edges; it has shown to be an effective image denoising technique. An important issue with the application of the bilateral filter is the selection of the filter parameters, which affect the results significantly. There are two main contributions of this paper. The first contribution is an empirical study of the optimal bilateral filter parameter selection in image denoising applications. The second contribution is an extension of the bilateral filter: multiresolution bilateral filter, where bilateral filtering is applied to the approximation (low-frequency) subbands of a signal decomposed using a wavelet filter bank. The multiresolution bilateral filter is combined with wavelet thresholding to form a new image denoising framework, which turns out to be very effective in eliminating noise in real noisy images. Experimental results with both simulated and real data are provided.

Zhang, Ming; Gunturk, Bahadir K.

2008-01-01

346

Digital filters for synthetic aperture radar

NASA Astrophysics Data System (ADS)

An organized approach is discussed for designing a set of optimal digital filters that can accommodate a wide range of synthetic-aperture radar (SAR) geometries. The basic SAR signal processing functions are reviewed since they are the basis for the filter design problems. Special digital filter optimality criteria are described that are tailored to the SAR environment. The results from recent filter design publications related to these critria are summarized and examples are included to demonstrate the effectiveness of this approach to designing filters for SAR processors.

Adams, J. W.; Medlin, G. W.; Bayma, R. W.

347

Filtering, stability, and robustness

NASA Astrophysics Data System (ADS)

The theory of nonlinear filtering concerns the optimal estimation of a Markov signal in noisy observations. Such estimates necessarily depend on the model that is chosen for the signal and observations processes. This thesis studies the sensitivity of the filter to the choice of underlying model over long periods of time, within the framework of continuous time filtering with white noise type observations. The first topic of this thesis is the asymptotic stability of the filter, which is studied using the theory of conditional diffusions. This leads to improvements on pathwise stability bounds, and to new insight into existing stability results in a fully probabilistic setting. Furthermore, I develop in detail the theory of conditional diffusions for finite-state Markov signals and clarify the duality between estimation and stochastic control in this context. The second topic of this thesis is the sensitivity of the nonlinear filter to the model parameters of the signal and observations processes. This section concentrates on the finite state case, where the corresponding model parameters are the jump rates of the signal, the observation function, and the initial measure. The main result is that the expected difference between the filters with the true and modified model parameters is bounded uniformly on the infinite time interval, provided that the signal process satisfies a mixing property. The proof uses properties of the stochastic flow generated by the filter on the simplex, as well as the Malliavin calculus and anticipative stochastic calculus. The third and final topic of this thesis is the asymptotic stability of quantum filters. I begin by developing quantum filtering theory using reference probability methods. The stability of the resulting filters is not easily studied using the preceding methods, as smoothing violates the nondemolition requirement. Fortunately, progress can be made by randomizing the initial state of the filter. Using this technique, I prove that the filtered estimate of the measurement observable is stable regardless of the underlying model, provided that the initial states are absolutely continuous in a suitable sense.

van Handel, Ramon

348

Output statistics of a line enhancer based on a combination of two adaptive filters

NASA Astrophysics Data System (ADS)

This paper studies output statistics of an adaptive line enhancer that is based on an affine combination of two NLMS adaptive filters. Combination of adaptive filters is a new interesting way of improving the performance of adaptive algorithms. The structure consists of two adaptive filters that adapt on the same input signal, one with a large and the other one with a small step size. Such a combination is capable of achieving fast initial convergence and small steady state error at the same time. In this paper we investigate the second order statistics of the output signal of adaptive line enhancer based on the combination in steady state. The result is given in terms of the parameters of the adaptive combination, input process statistics, and the optimal Wiener filter weights for the problem at hands.

Tõnu, Trump

2011-09-01

349

NSDL National Science Digital Library

In this engineering activity, challenge learners to invent a water filter that cleans dirty water. Learners construct a filter device out of a 2-liter bottle and then experiment with different materials like gravel, sand, and cotton balls to see which is the most effective. Safety note: An adult's help is needed for this activity.

Boston, Wgbh

2002-01-01

350

A radiation source emits a beam of penetrating radiation toward an examination object. A protective filter, fabricated of yttrium foil attached to a bakelite card, is positioned in the path of the radiation beam between the source and the examination object. The yttrium filter has a preselected critical absorption edge operable to obstruct from the beam photon energy below 20 keV and permit a filtered beam having a photon energy above 20 keV to pass through the examination object. The filtered radiation emerging from the examination object is detected by preselected means, such as illuminated film, an X-ray intensifier, a CT scanner, or the like. The detector generates an output signal corresponding to the intensity of the emerging filtered radiation. An image processor converts the output signals to a radiographic image displaying the examination object.

Hartwell, G.

1985-02-12

351

The synthesis of fatty acid ethyl esters (FAEEs) by a two-step in situ (reactive) esterification/transesterification from Jatropha curcas L. (JCL) seeds using microwave system has been investigated. Free fatty acid was reduced from 14% to less than 1% in the first step using H2SO4 as acid catalyst after 35 min of microwave irradiation heating. The organic phase in the first step was subjected to a second reaction by adding 5 N KOH in ethanol as the basic catalyst. Response surface methodology (RSM) based on central composite design (CCD) was utilized to design the experiments and analyze the influence of process variables (particles seed size, time of irradiation, agitation speed and catalyst loading) on conversion of triglycerides (TGs) in the second step. The highest triglycerides conversion to fatty acid ethyl esters (FAEEs) was 97.29% at the optimum conditions:<0.5mm seed size, 12.21 min irradiation time, 8.15 ml KOH catalyst loading and 331.52 rpm agitation speed in the 110 W microwave power system. PMID:23567732

Jaliliannosrati, Hamidreza; Amin, Nor Aishah Saidina; Talebian-Kiakalaieh, Amin; Noshadi, Iman

2013-05-01

352

Parametric Bayesian filters for nonlinear stochastic dynamical systems: a survey.

Nonlinear stochastic dynamical systems are commonly used to model physical processes. For linear and Gaussian systems, the Kalman filter is optimal in minimum mean squared error sense. However, for nonlinear or non-Gaussian systems, the estimation of states or parameters is a challenging problem. Furthermore, it is often required to process data online. Therefore, apart from being accurate, the feasible estimation algorithm also needs to be fast. In this paper, we review Bayesian filters that possess the aforementioned properties. Each filter is presented in an easy way to implement algorithmic form. We focus on parametric methods, among which we distinguish three types of filters: filters based on analytical approximations (extended Kalman filter, iterated extended Kalman filter), filters based on statistical approximations (unscented Kalman filter, central difference filter, Gauss-Hermite filter), and filters based on the Gaussian sum approximation (Gaussian sum filter). We discuss each of these filters, and compare them with illustrative examples. PMID:23757593

Stano, Pawe; Lendek, Zsófia; Braaksma, Jelmer; Babuska, Robert; de Keizer, Cees; den Dekker, Arnold J

2013-12-01

353

Recursive Implementations of the Consider Filter

NASA Technical Reports Server (NTRS)

One method to account for parameters errors in the Kalman filter is to consider their effect in the so-called Schmidt-Kalman filter. This work addresses issues that arise when implementing a consider Kalman filter as a real-time, recursive algorithm. A favorite implementation of the Kalman filter as an onboard navigation subsystem is the UDU formulation. A new way to implement a UDU consider filter is proposed. The non-optimality of the recursive consider filter is also analyzed, and a modified algorithm is proposed to overcome this limitation.

Zanetti, Renato; DSouza, Chris

2012-01-01

354

Method for transforming bandpass filters to facilitate their production and resulting devices

US Patent & Trademark Office Database

The invention concerns a method for optimizing elements of a narrow or intermediate band bandpass filter whereof the LC prototype has been determined. The invention is characterized in that it comprises steps which consist in: (i) breaking down several parallel or series capacitors of resonators with X elements, (ii) inserting pairs of transformers between the first and second separated element and the rest of the resonator, (iii) displacing the residual transformers to modify the impedance levels of the resonators, and (iv) absorbing the residual transformers by transformation. The invention also concerns the resulting filters.

2005-03-22

355

Correlation Filters With Controlled Scale Response

Correlation filtering methods are becoming increasingly popular for image recognition and location. The recent introduction of optimal tradeoff circular harmonic function filters allowed the user to specify the response of a correlation filter to in-plane rotation distortion. In this paper we introduce a new correlation filter design that can provide a user-specified response to in-plane scale distortion. The design is

Ryan A. Kerekes; B. V. K. Vijaya Kumar

2006-01-01

356

An Iterated Extended Risk-Sensitive Filters for Nonlinear Filtering Problems

The problem for filtering certain classes of systems which incorporate nonlinear, uncertainty initial condition is addressed. An extended risk-sensitive filter (ERSF) is reexamined and, new iterated version of that ERSF called the iterated extended risk sensitive filters (IERSF) is developed. An ERSF weakness specifically accumulation error in the computing of innovation steps due to approximating nonlinear functions at recently available

M. Srinivasan; M. K. Tyagi; K. Radha Rani; M. Suman; B. Loveswara Rao

2008-01-01

357

An improved particle filter based on diversity guidance

Particle filter has been widely applied into many fields in recent years. Combined with the deficiency analysis of particle filter, an improved particle filter based on diversity guidance is proposed. Firstly, the adaptive resampling step in particle filter is tuned based on two diversity measures which are effective sample size and population diversity factor. Moreover, the operation of particle mutation

Jin-Xia Yu; Yong-Li Tang; Xian-Cha Liu; Qian Zhao

2011-01-01

358

New filter efficiency test for future nuclear grade HEPA filters

We have developed a new test procedure for evaluating filter penetrations as low as 10/sup /minus/9/ at 0.1-..mu..m particle diameter. In comparison, the present US nuclear filter certification test has a lower penetration limit of 10/sup /minus/5/. Our new test procedure is unique not only in its much higher sensitivity, but also in avoiding the undesirable effect of clogging the filter. Our new test procedure consists of a two-step process: (1) We challenge the test filter with a very high concentration of heterodisperse aerosol for a short time while passing all or a significant portion of the filtered exhaust into an inflatable bag; (2) We then measure the aerosol concentration in the bag using a new laser particle counter sensitive to 0.07-..mu..m diameter. The ratio of particle concentration in the bag to the concentration challenging the filter gives the filter penetration as a function of particle diameter. The bad functions as a particle accumulator for subsequent analysis to minimize the filter exposure time. We have studied the particle losses in the bag over time and find that they are negligible when the measurements are taken within one hour. We also compared filter penetration measurements taken in the conventional direct-sampling method with the indirect bag-sampling method and found excellent agreement. 6 refs., 18 figs., 1 tab.

Bergman, W.; Foiles, L.; Mariner, C.; Kincy, M.

1988-08-17

359

Aquatic Plants Aid Sewage Filter

NASA Technical Reports Server (NTRS)

Method of wastewater treatment combines micro-organisms and aquatic plant roots in filter bed. Treatment occurs as liquid flows up through system. Micro-organisms, attached themselves to rocky base material of filter, act in several steps to decompose organic matter in wastewater. Vascular aquatic plants (typically, reeds, rushes, cattails, or water hyacinths) absorb nitrogen, phosphorus, other nutrients, and heavy metals from water through finely divided roots.

Wolverton, B. C.

1985-01-01

360

Choquet integral representations of nonlinear filters with applications to ladar image processing

NASA Astrophysics Data System (ADS)

The paper describes the application of Choquet integral filters to automatic object detection in laser radar (LADAR) imagery. Choquet integrals are nonlinear integrals with respect to non-additive measures. These integrals can be used to represent typical nonlinear filters such as order statistic filters, linear combination of order statistic filters, weighted median filters and others. A Choquet integral filter is characterized by a measure. The representation of these filters as integrals with respect to measures provides an opportunity for optimizing the filters by finding optimal measures. Both optimal and heuristic filters are designed and compared on real data.

Hocaoglu, Ali K.; Gader, Paul D.

1998-04-01

361

Metal-dielectric photonic devices for spatial filtering and image contrast enhancement

NASA Astrophysics Data System (ADS)

Propagation of light through layered metamaterials consisting of a metal-dielectric stack may be described as linear spatial filtering. We present the modelling and optimization strategy for engineering such metamaterials, as well as the measurement results of spatial filters consisting of titanium oxide and silver layers evaporated with PVD. Depending on the point spread function, the metamaterial can be applied for subdiffraction spatial filtering or for classical spatial filtering operations. We optimize the metamaterial with respect to the shape of the complex amplitude transfer function, the average transmission coefficient and to average reflections. The shape of the point spread function can only be tailored in a limited degree, due to the limited number of the degrees of freedom contained in the structure, and only in one, planarly or radially oriented dimension. The metamaterial optimised for high-pass filtering consists of several substructures, each of which is an individual cavity, and is optimized by tuning the resonance order of these cavities. In this way we obtain a high transmission for a broad range of spatial frequencies. This metamaterial can be applied to modify the contrast of the object or to introduce a phase-contrast. It may be used for far-field imaging. As an example, we propose to apply it as a novel phase-step visualization photonic element.

Pastuszczak, Anna; Wróbel, Piotr; Stefaniuk, Tomasz; Stolarek, Marcin; Wlaz?o, Mateusz; Koty?ski, Rafa?

2013-05-01

362

Track probability hypothesis density filter for multi-target tracking

The probability hypothesis density (PHD) filter is a practical alternative to the theoretically optimal multi-target Bayesian filter based on random finite sets (RFS) for multi- target tracking. In this paper, we propose Track PHD (TPHD) filter based on a track state space consisted of target position history and it propagates the multi-target intensity function of track RFS. The new filter

Yan Wang; Huadong Meng; Hao Zhang; Xiqin Wang

2011-01-01

363

Low-cost waveguide filters with printed-circuit inserts

An easy to manufacture waveguide filter is presented. This type of filter is based on printed-circuit-board inserts with resonator strips. The electromagnetic properties of the strips interacting with the electromagnetic field inside the waveguide are described by equivalent circuit elements. Filter synthesis and computer optimization is applied to design band-stop filters. Finally simulated results are compared with measurements

H. Schmiedel; M. Muller; A. Anufriev

1996-01-01

364

Initial Ares I Bending Filter Design

NASA Technical Reports Server (NTRS)

The Ares-I launch vehicle represents a challenging flex-body structural environment for control system design. Software filtering of the inertial sensor output will be required to ensure control system stability and adequate performance. This paper presents a design methodology employing numerical optimization to develop the Ares-I bending filters. The filter design methodology was based on a numerical constrained optimization approach to maximize stability margins while meeting performance requirements. The resulting bending filter designs achieved stability by adding lag to the first structural frequency and hence phase stabilizing the first Ares-I flex mode. To minimize rigid body performance impacts, a priority was placed via constraints in the optimization algorithm to minimize bandwidth decrease with the addition of the bending filters. The bending filters provided here have been demonstrated to provide a stable first stage control system in both the frequency domain and the MSFC MAVERIC time domain simulation.

Jang, Jiann-Woei; Bedrossian, Nazareth; Hall, Robert; Norris, H. Lee; Hall, Charles; Jackson, Mark

2007-01-01

365

Regularized multitarget particle filter for sensor management

NASA Astrophysics Data System (ADS)

Sensor management in support of Level 1 data fusion (multisensor integration), or Level 2 data fusion (situation assessment) requires a computationally tractable multitarget filter. The theoretically optimal approach to this multi-target filtering is a suitable generalization of the recursive Bayes nonlinear filter. However, this optimal filter is intractable and computationally challenging that it must usually be approximated. We report on the approximation of a multi-target non-linear filtering for Sensor Management that is based on the particle filter implementation of Stein-Winter probability hypothesis densities (PHDs). Our main focus is on the operational utility of the implementation, and its computational efficiency and robustness for sensor management applications. We present a multitarget Particle Filter (PF) implementation of the PHD that include clustering, regularization, and computational efficiency. We present some open problems, and suggest future developments. Sensor management demonstrations using a simulated multi-target scenario are presented.

El-Fallah, A.; Zatezalo, A.; Mahler, R.; Mehra, R. K.; Alford, M.

2006-06-01

366

Optimal biorthogonal wavelet analysis

NASA Astrophysics Data System (ADS)

The paper investigates the design of filter banks generating the optimal signal representation by M-band one-dimensional and multi-dimensional biorthogonal wavelet frames. Criterion of optimality is the minimization of the average mean-square approximation error at each level of the decomposition. Preliminary results of the application of such filter banks to two- dimensional image compression are included.

Strintzis, Michael G.

1994-09-01

367

NASA Astrophysics Data System (ADS)

Rolling element bearings are the most important components used in machinery. Bearing faults, once they have developed, quickly become severe and can result in fatal breakdowns. Envelope spectrum analysis is one effective approach to detect early bearing faults through the identification of bearing fault characteristic frequencies (BFCFs). To achieve this, it is necessary to find a band-pass filter to retain a resonant frequency band for the enhancement of weak bearing fault signatures. In Part 1 paper, the wavelet packet filters with fixed center frequencies and bandwidths used in a sparsogram may not cover a whole bearing resonant frequency band. Besides, a bearing resonant frequency band may be split into two adjacent imperfect orthogonal frequency bands, which reduce the bearing fault features. Considering the above two reasons, a sparsity measurement based optimal wavelet filter is required to be designed for providing more flexible center frequency and bandwidth for covering a bearing resonant frequency band. Part 2 paper presents an automatic selection process for finding the optimal complex Morlet wavelet filter with the help of genetic algorithm that maximizes the sparsity measurement value. Then, the modulus of the wavelet coefficients obtained by the optimal wavelet filter is used to extract the envelope. Finally, a non-linear function is introduced to enhance the visual inspection ability of BFCFs. The convergence of the optimal filter is fastened by the center frequencies and bandwidths of the optimal wavelet packet nodes established by the new sparsogram. Previous case studies including a simulated bearing fault signal and real bearing fault signals were used to show that the effectiveness of the optimal wavelet filtering method in detecting bearing faults. Finally, the results obtained from comparison studies are presented to verify that the proposed method is superior to the other three popular methods.

Tse, Peter W.; Wang, Dong

2013-11-01

368

Following autophagy step by step

Autophagy is an evolutionarily conserved lysosomal degradation route for soluble components of the cytosol and organelles. There is great interest in identifying compounds that modulate autophagy because they may have applications in the treatment of major diseases including cancer and neurodegenerative disease. Hundeshagen and colleagues describe this month in BMC Biology a screening assay based on flow cytometry that makes it possible to track distinct steps in the autophagic process and thereby identify novel modulators of autophagy. See research article: http://www.biomedcentral.com/1741-7007/9/38

2011-01-01

369

An insert which allows a supersonic nozzle of a rocket propulsion system to operate at two or more different nozzle area ratios. This provides an improved vehicle flight performance or increased payload. The insert has significant advantages over existing devices for increasing nozzle area ratios. The insert is temporarily fastened by a simple retaining mechanism to the aft end of the diverging segment of the nozzle and provides for a multi-step variation of nozzle area ratio. When mounted in place, the insert provides the nozzle with a low nozzle area ratio. During flight, the retaining mechanism is released and the insert ejected thereby providing a high nozzle area ratio in the diverging nozzle segment.

Sutton, George P. (Danville, CA)

1998-01-01

370

An insert is described which allows a supersonic nozzle of a rocket propulsion system to operate at two or more different nozzle area ratios. This provides an improved vehicle flight performance or increased payload. The insert has significant advantages over existing devices for increasing nozzle area ratios. The insert is temporarily fastened by a simple retaining mechanism to the aft end of the diverging segment of the nozzle and provides for a multi-step variation of nozzle area ratio. When mounted in place, the insert provides the nozzle with a low nozzle area ratio. During flight, the retaining mechanism is released and the insert ejected thereby providing a high nozzle area ratio in the diverging nozzle segment. 5 figs.

Sutton, G.P.

1998-07-14

371

NASA Astrophysics Data System (ADS)

Over the past decade of nanotube research, a variety of organized nanotube architectures have been fabricated using chemical vapour deposition. The idea of using nanotube structures in separation technology has been proposed, but building macroscopic structures that have controlled geometric shapes, density and dimensions for specific applications still remains a challenge. Here we report the fabrication of freestanding monolithic uniform macroscopic hollow cylinders having radially aligned carbon nanotube walls, with diameters and lengths up to several centimetres. These cylindrical membranes are used as filters to demonstrate their utility in two important settings: the elimination of multiple components of heavy hydrocarbons from petroleum-a crucial step in post-distillation of crude oil-with a single-step filtering process, and the filtration of bacterial contaminants such as Escherichia coli or the nanometre-sized poliovirus (~25 nm) from water. These macro filters can be cleaned for repeated filtration through ultrasonication and autoclaving. The exceptional thermal and mechanical stability of nanotubes, and the high surface area, ease and cost-effective fabrication of the nanotube membranes may allow them to compete with ceramic- and polymer-based separation membranes used commercially.

Srivastava, A.; Srivastava, O. N.; Talapatra, S.; Vajtai, R.; Ajayan, P. M.

2004-09-01

372

Deconvolution filtering: Temporal smoothing revisited.

Inferences made from analysis of BOLD data regarding neural processes are potentially confounded by multiple competing sources: cardiac and respiratory signals, thermal effects, scanner drift, and motion-induced signal intensity changes. To address this problem, we propose deconvolution filtering, a process of systematically deconvolving and reconvolving the BOLD signal via the hemodynamic response function such that the resultant signal is composed of maximally likely neural and neurovascular signals. To test the validity of this approach, we compared the accuracy of BOLD signal variants (i.e., unfiltered, deconvolution filtered, band-pass filtered, and optimized band-pass filtered BOLD signals) in identifying useful properties of highly confounded, simulated BOLD data: (1) reconstructing the true, unconfounded BOLD signal, (2) correlation with the true, unconfounded BOLD signal, and (3) reconstructing the true functional connectivity of a three-node neural system. We also tested this approach by detecting task activation in BOLD data recorded from healthy adolescent girls (control) during an emotion processing task. Results for the estimation of functional connectivity of simulated BOLD data demonstrated that analysis (via standard estimation methods) using deconvolution filtered BOLD data achieved superior performance to analysis performed using unfiltered BOLD data and was statistically similar to well-tuned band-pass filtered BOLD data. Contrary to band-pass filtering, however, deconvolution filtering is built upon physiological arguments and has the potential, at low TR, to match the performance of an optimal band-pass filter. The results from task estimation on real BOLD data suggest that deconvolution filtering provides superior or equivalent detection of task activations relative to comparable analyses on unfiltered signals and also provides decreased variance over the estimate. In turn, these results suggest that standard preprocessing of the BOLD signal ignores significant sources of noise that can be effectively removed without damaging the underlying signal. PMID:24768215

Bush, Keith; Cisler, Josh

2014-07-01

373

Time optimal, parameters-insensitive digital controller for DC-DC buck converters

In this paper a digital control approach is investigated for time-optimal load step response of DC-DC synchronous buck converters intended for point-of-load applications employing low-ESR ceramic output capacitors. Unlike previously reported approaches, the proposed technique is insensitive to the power stage parameters, as its operation does not rely on the knowledge of the output filter inductance or capacitance. The time-optimal

A. Costabeber; L. Corradini; P. Mattavelli; S. Saggini

2008-01-01

374

Noroviruses (NoVs) are an important human pathogen associated with acute viral gastroenteritis worldwide. NoVs display a significant amount of genetic heterogeneity, making it difficult to develop comprehensive detection assays. In this study, primer sets and probes were designed for a TaqMan(®)-based real-time reverse transcription-polymerase chain reaction (RT-PCR) for norovirus detection purposes. The assay was optimized and utilized as a multiplex real-time RT-PCR assay for genogroup I (GI) detection, and a singleplex real-time RT-PCR assay for genogroup II (GII) detection. The assays showed high specificity for NoV detection and no cross-reactivity was observed between GI and GII. The detection limit of the assay was as low as 10 and 50 RNA copies per reaction for GI and GII, respectively. The optimized protocol was employed to assess the presence of NoV strains in clinical samples collected throughout Thailand during December 2005 to November 2006. The percentage of NoV infections among children with acute gastroenteritis (case) was 23.8% (119/500) and for children without acute gastroenteritis (control) it was 6.8% (30/441). The frequency of NoV infections varied geographically, with the highest frequency observed in the central region and the lowest frequency in the northern region (P>0.0001). Of the 149 positive case and control specimens, GII was found to be the predominant genogroup (98.6%). Partial capsid sequences were successfully obtained from 67 NoV-positive specimens and a phylogenetic analysis was performed to genotype the viral strains. GII.4 was the most common genotype detected. PMID:24070785

Neesanant, Pimmnapar; Sirinarumitr, Theerapol; Chantakru, Siriruk; Boonyaprakob, Ukadaj; Chuwongkomon, Kaittawee; Bodhidatta, Ladaporn; Sethabutr, Orntipa; Abente, Eugenio J; Supawat, Krongkaew; Mason, Carl J

2013-12-01

375

NASA Technical Reports Server (NTRS)

Seeking to find a more effective method of filtering potable water that was highly contaminated, Mike Pedersen, founder of Western Water International, learned that NASA had conducted extensive research in methods of purifying water on board manned spacecraft. The key is Aquaspace Compound, a proprietary WWI formula that scientifically blends various types of glandular activated charcoal with other active and inert ingredients. Aquaspace systems remove some substances; chlorine, by atomic adsorption, other types of organic chemicals by mechanical filtration and still others by catalytic reaction. Aquaspace filters are finding wide acceptance in industrial, commercial, residential and recreational applications in the U.S. and abroad.

1988-01-01

376

Unscented Kalman Filter and Particle Filter for Chaotic Synchronization

The first and foremost step in developing a chaotic communication system is to establish synchronization of the chaotic systems\\/maps at the transmitter and receiver. Extended Kalman filter (EKF) is a widely studied nonlinear observer for chaotic synchronization. Since this scheme depends on the first order Taylor series approximation of the nonlinear function, it may introduce large errors in the state

Ajeesh P. Kurian; Sadasivan Puthusserypady

2006-01-01

377

NASA Technical Reports Server (NTRS)

A notch filter for the selective attenuation of a narrow band of frequencies out of a larger band was developed. A helical resonator is connected to an input circuit and an output circuit through discrete and equal capacitors, and a resistor is connected between the input and the output circuits.

Shelton, G. B. (inventor)

1977-01-01

378

A novel proposal distribution for particle filter

In order to solve the problem of degeneracy in particle filtering algorithm, a novel proposal distribution is designed in this paper. The principal idea of the proposal distribution is to fuse the latest observations together with the previous filtering estimate and the prior model information. In that case, the one-step smoothing estimate of the state is employed. Simulation results show

Bing Ju; Zenghui Zhang; Jubo Zhu

2010-01-01

379

Unscented grid filtering and elman recurrent networks

This paper develops an unscented grid-based filter for improved recurrent neural network modeling of time series. The filter approximates directly the weight posterior distribution as a linear mixture using deterministic unscented sampling. The weight posterior is obtained in one step, without linearisation through derivatives. An expectation maximisation algorithm is formulated for evaluation of the complete data likelihood and finding the

Nikolay Y. Nikolaev; Derrick Mirikitani; Evgueni Smirnov

2010-01-01

380

The Optimization of a Three-Phase Surfactant Washing System

In this analysis, the economics of MBI International's three-phase surfactant washing system for the removal of polychlorinated biphenyls (PCBs) from sediment was optimized. The system, which consists of a screw washer, an oil\\/water separator, and a vacuum filter, transfers PCBs to a sacrificial oil layer through two individual two-phase partitioning steps. At the completion of the washing process, the sacrificial

Tylisha Baber; Melinda Baker; Keya Belcher; Rebekah Stephenson

381

Filtered Backprojection Reconstruction with Depth-Dependent Filtering*

A direct filtered-backprojection (FBP) reconstruction algorithm is presented for circular cone-beam computed tomography (CB-CT) that allows the filter operation to be applied efficiently with shift-variant band-pass characteristics on the kernel function. Our algorithm is derived from the ramp-filter based FBP method of Feldkamp et al. and obtained by decomposing the ramp filtering into a convolution involving the Hilbert kernel (global operation) and a subsequent differentiation operation (local operation). The differentiation is implemented as a finite difference of two (Hilbert filtered) data samples and carried out as part of the backprojection step. The spacing between the two samples, which defines the low-pass characteristics of the filter operation, can thus be selected individually for each point in the image volume. We here define the sample spacing to follow the magnification of the divergent-beam geometry and thus obtain a novel, depth-dependent filtering algorithm for circular CB-CT. We evaluate this resulting algorithm using computer-simulated CB data and demonstrate that our algorithm yields results where spatial resolution and image noise are distributed much more uniformly over the field-of-view, compared to Feldkamp’s approach.

Dennerlein, Frank; Kunze, Holger; Noo, Frederic

2010-01-01

382

Improving retrieval rates for retrievable inferior vena cava filters.

The introduction of retrievable inferior vena cava (IVC) filters was an important step in the evolution of deep vein thrombosis/pulmonary embolism management. Their removability makes them preferred to permanent filters in many cases. IVC filter retrieval often occurs at a suboptimal rate, leading to complications associated with long-term placement. Improving retrievability includes solutions for patients being lost to follow-up, filter malpositioning, need arising for permanent IVC filtration, filtration requiring longer than the filter's window of retrievability, and filter compromise by the presence of a large trapped clot. This review explores these strategies for retrieval in detail in hopes of improving IVC filter retrieval rates. PMID:23278230

Dixon, Austin; Stavropoulos, S William

2013-01-01

383

An approach to the approximation problem for nonrecursive digital filters

A direct design procedure for nonrecursive digital filters, based primarily on the frequency-response characteristic of the desired filters, is presented. An optimization technique is used to minimize the maximum deviation of the synthesized filter from the ideal filter over some frequence range. Using this frequency-sampling technique, a wide variety of low-pass and bandpass filters have been designed, as well as

LAWRENCE R. RABINER; BERNARD GOLD; C. McGonegal

1970-01-01

384

A pharmacokinetic-pharmacodynamic (PKPD) model that characterizes the full time course of in vitro time-kill curve experiments of antibacterial drugs was here evaluated in its capacity to predict the previously determined PK/PD indices. Six drugs (benzylpenicillin, cefuroxime, erythromycin, gentamicin, moxifloxacin, and vancomycin), representing a broad selection of mechanisms of action and PK and PD characteristics, were investigated. For each drug, a dose fractionation study was simulated, using a wide range of total daily doses given as intermittent doses (dosing intervals of 4, 8, 12, or 24 h) or as a constant drug exposure. The time course of the drug concentration (PK model) as well as the bacterial response to drug exposure (in vitro PKPD model) was predicted. Nonlinear least-squares regression analyses determined the PK/PD index (the maximal unbound drug concentration [fCmax]/MIC, the area under the unbound drug concentration-time curve [fAUC]/MIC, or the percentage of a 24-h time period that the unbound drug concentration exceeds the MIC [fT>MIC]) that was most predictive of the effect. The in silico predictions based on the in vitro PKPD model identified the previously determined PK/PD indices, with fT>MIC being the best predictor of the effect for ?-lactams and fAUC/MIC being the best predictor for the four remaining evaluated drugs. The selection and magnitude of the PK/PD index were, however, shown to be sensitive to differences in PK in subpopulations, uncertainty in MICs, and investigated dosing intervals. In comparison with the use of the PK/PD indices, a model-based approach, where the full time course of effect can be predicted, has a lower sensitivity to study design and allows for PK differences in subpopulations to be considered directly. This study supports the use of PKPD models built from in vitro time-kill curves in the development of optimal dosing regimens for antibacterial drugs.

Nielsen, Elisabet I.; Cars, Otto; Friberg, Lena E.

2011-01-01

385

The intractable cigarette 'filter problem'

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 production. The synthetic plastic cellulose acetate became the fundamental cigarette filter material. By the mid-1960s, the meaning of the phrase ‘filter problem’ changed, such that the effort to develop effective filters became a campaign to market cigarette designs that would sustain the myth of cigarette filter efficacy. Conclusions This study indicates that cigarette designers at Philip Morris, British-American Tobacco, Lorillard and other companies believed for a time that they might be able to reduce some of the most dangerous substances in mainstream smoke through advanced engineering of filter tips. In their attempts to accomplish this, they developed the now ubiquitous cellulose acetate cigarette filter. By the mid-1960s cigarette designers realised that the intractability of the ‘filter problem’ derived from a simple fact: that which is harmful in mainstream smoke and that which provides the smoker with ‘satisfaction’ are essentially one and the same. Only in the wake of this realisation did the agenda of cigarette designers appear to transition away from mitigating the health hazards of smoking and towards the perpetuation of the notion that cigarette filters are effective in reducing these hazards. Filters became a marketing tool, designed to keep and recruit smokers as consumers of these hazardous products.

2011-01-01

386

The Lockheed alternate partial polarizer universal filter

NASA Technical Reports Server (NTRS)

A tunable birefringent filter using an alternate partial polarizer design has been built. The filter has a transmission of 38% in polarized light. Its full width at half maximum is .09A at 5500A. It is tunable from 4500 to 8500A by means of stepping motor actuated rotating half wave plates and polarizers. Wave length commands and thermal compensation commands are generated by a PPD 11/10 minicomputer. The alternate partial polarizer universal filter is compared with the universal birefringent filter and the design techniques, construction methods, and filter performance are discussed in some detail. Based on the experience of this filter some conclusions regarding the future of birefringent filters are elaborated.

Title, A. M.

1976-01-01

387

Nonlinear Bayesian filtering with applications to estimation and navigation

NASA Astrophysics Data System (ADS)

In principle, general approaches to optimal nonlinear filtering can be described in a unified way from the recursive Bayesian approach. The central idea to this recursive Bayesian estimation is to determine the probability density function of the state vector of the nonlinear systems conditioned on the available measurements. However, the optimal exact solution to this Bayesian filtering problem is intractable since it requires an infinite dimensional process. For practical nonlinear filtering applications approximate solutions are required. Recently efficient and accurate approximate nonlinear filters as alternatives to the extended Kalman filter are proposed for recursive nonlinear estimation of the states and parameters of dynamical systems. First, as sampling-based nonlinear filters, the sigma point filters, the unscented Kalman filter and the divided difference filter are investigated. Secondly, a direct numerical nonlinear filter is introduced where the state conditional probability density is calculated by applying fast numerical solvers to the Fokker-Planck equation in continuous-discrete system models. As simulation-based nonlinear filters, a universally effective algorithm, called the sequential Monte Carlo filter, that recursively utilizes a set of weighted samples to approximate the distributions of the state variables or parameters, is investigated for dealing with nonlinear and non-Gaussian systems. Recent particle filtering algorithms, which are developed independently in various engineering fields, are investigated in a unified way. Furthermore, a new type of particle filter is proposed by integrating the divided difference filter with a particle filtering framework, leading to the divided difference particle filter. Sub-optimality of the approximate nonlinear filters due to unknown system uncertainties can be compensated by using an adaptive filtering method that estimates both the state and system error statistics. For accurate identification of the time-varying parameters of dynamic systems, new adaptive nonlinear filters that integrate the presented nonlinear filtering algorithms with noise estimation algorithms are derived. For qualitative and quantitative performance analysis among the proposed nonlinear filters, systematic methods for measuring the nonlinearities, biasness, and optimality of the proposed nonlinear filters are introduced. The proposed nonlinear optimal and sub-optimal filtering algorithms with applications to spacecraft orbit estimation and autonomous navigation are investigated. Simulation results indicate that the advantages of the proposed nonlinear filters make these attractive alternatives to the extended Kalman filter.

Lee, Deok-Jin

388

Method and system for training dynamic nonlinear adaptive filters which have embedded memory

NASA Technical Reports Server (NTRS)

Described herein is a method and system for training nonlinear adaptive filters (or neural networks) which have embedded memory. Such memory can arise in a multi-layer finite impulse response (FIR) architecture, or an infinite impulse response (IIR) architecture. We focus on filter architectures with separate linear dynamic components and static nonlinear components. Such filters can be structured so as to restrict their degrees of computational freedom based on a priori knowledge about the dynamic operation to be emulated. The method is detailed for an FIR architecture which consists of linear FIR filters together with nonlinear generalized single layer subnets. For the IIR case, we extend the methodology to a general nonlinear architecture which uses feedback. For these dynamic architectures, we describe how one can apply optimization techniques which make updates closer to the Newton direction than those of a steepest descent method, such as backpropagation. We detail a novel adaptive modified Gauss-Newton optimization technique, which uses an adaptive learning rate to determine both the magnitude and direction of update steps. For a wide range of adaptive filtering applications, the new training algorithm converges faster and to a smaller value of cost than both steepest-descent methods such as backpropagation-through-time, and standard quasi-Newton methods. We apply the algorithm to modeling the inverse of a nonlinear dynamic tracking system 5, as well as a nonlinear amplifier 6.

Rabinowitz, Matthew (Inventor)

2002-01-01

389

Collaborative emitter tracking using Rao-Blackwellized random exchange diffusion particle filtering

NASA Astrophysics Data System (ADS)

We introduce in this paper the fully distributed, random exchange diffusion particle filter (ReDif-PF) to track a moving emitter using multiple received signal strength (RSS) sensors. We consider scenarios with both known and unknown sensor model parameters. In the unknown parameter case, a Rao-Blackwellized (RB) version of the random exchange diffusion particle filter, referred to as the RB ReDif-PF, is introduced. In a simulated scenario with a partially connected network, the proposed ReDif-PF outperformed a PF tracker that assimilates local neighboring measurements only and also outperformed a linearized random exchange distributed extended Kalman filter (ReDif-EKF). Furthermore, the novel ReDif-PF matched the tracking error performance of alternative suboptimal distributed PFs based respectively on iterative Markov chain move steps and selective average gossiping with an inter-node communication cost that is roughly two orders of magnitude lower than the corresponding cost for the Markov chain and selective gossip filters. Compared to a broadcast-based filter which exactly mimics the optimal centralized tracker or its equivalent (exact) consensus-based implementations, ReDif-PF showed a degradation in steady-state error performance. However, compared to the optimal consensus-based trackers, ReDif-PF is better suited for real-time applications since it does not require iterative inter-node communication between measurement arrivals.

Bruno, Marcelo G. S.; Dias, Stiven S.

2014-12-01

390

NASA Technical Reports Server (NTRS)

Biomedical Optical Company of America's suntiger lenses eliminate more than 99% of harmful light wavelengths. NASA derived lenses make scenes more vivid in color and also increase the wearer's visual acuity. Distant objects, even on hazy days, appear crisp and clear; mountains seem closer, glare is greatly reduced, clouds stand out. Daytime use protects the retina from bleaching in bright light, thus improving night vision. Filtering helps prevent a variety of eye disorders, in particular cataracts and age related macular degeneration.

1987-01-01

391

Evaluating hydraulic losses in FRKDI bag filters

Methods for evaluating and reducing the hydraulic resistance and optimizing the power consumption of FRKDI filters were assessed. Hydraulic losses were calculated by determining local hydraulic resistances along the gas flow from the inlet to the outlet of the filter and summing these values. The hydraulic resistance was at a maximum in the inlet and outlet nozzles. The design variations

Yu. I. Gromov; S. V. Obichkin

1988-01-01

392

Performance Analysis of Adaptive Polarization Filters.

National Technical Information Service (NTIS)

In the dynamic electromagnetic environments, a polarization estimator is usually utilized by an adaptive polarization filter to acquire the knowledge of the polarization of the interference field, then optimal polarization is calculated for polarization f...

X. Wang Z. Xu D. Dai S. Xiao Z. Zhuang

2005-01-01

393

Polynomial distance classifier correlation filter for pattern recognition

NASA Astrophysics Data System (ADS)

We introduce what is to our knowledge a new nonlinear shift-invariant classifier called the polynomial distance classifier correlation filter (PDCCF). The underlying theory extends the original linear distance classifier correlation filter [Appl. Opt. 35, 3127 (1996)] to include nonlinear functions of the input pattern. This new filter provides a framework (for combining different classification filters) that takes advantage of the individual filter strengths. In this new filter design, all filters are optimized jointly. We demonstrate the advantage of the new PDCCF method using simulated and real multi-class synthetic aperture radar images.

Alkanhal, Mohamed; Vijaya Kumar, B. V. K.

2003-08-01

394

Generalized particle flow for nonlinear filters

NASA Astrophysics Data System (ADS)

We generalize the theory of particle flow to stabilize the nonlinear filter. We have invented a new nonlinear filter that is vastly superior to the classic particle filter and the extended Kalman filter (EKF). In particular, the computational complexity of the new filter is many orders of magnitude less than the classic particle filter with optimal estimation accuracy for problems with dimension greater than 4. Our accuracy is typically several orders of magnitude better than the EKF for nonlinear problems. We do not resample, and we do not use any proposal density from an EKF or UKF or other filter. Moreover, our new algorithm is deterministic, and we do not use any MCMC methods; this is a radical departure from other particle filters. The new filter implements Bayes' rule using particle flow rather than with a pointwise multiplication of two functions; this avoids one of the fundamental and well known problems in particle filters, namely "particle degeneracy." In addition, we explicitly stabilize our particle filter using negative feedback, unlike standard particle filters, which are generally very inaccurate for plants with slow mixing or unstable dynamics. This stabilization improves performance by several orders of magnitude for difficult problems.

Daum, Fred; Huang, Jim

2010-04-01

395

Consistency checks for particle filters with application to image stabilization

An ‘inconsistent’ particle filter produces – in a statistical sense – larger estimation errors than predicted by the model on which the filter is based. Inconsistent behavior of a particle filter can be detected online by checking whether the predicted measurements (derived from the particles that represent the one-step-ahead prediction pdf) comply in a statistical sense with the observed measurements.

Heijden van der Ferdinand

2005-01-01

396

A Sequential Ensemble Kalman Filter for Atmospheric Data Assimilation

An ensemble Kalman filter may be considered for the 4D assimilation of atmospheric data. In this paper, an efficient implementation of the analysis step of the filter is proposed. It employs a Schur (elementwise) product of the covariances of the background error calculated from the ensemble and a correlation function having local support to filter the small (and noisy) background-error

P. L. Houtekamer; Herschel L. Mitchell

2001-01-01

397

Improved particle filters for multi-target tracking

We present a novel approach for improving particle filters for multi-target tracking. The suggested approach is based on drift homotopy for stochastic differential equations. Drift homotopy is used to design a Markov Chain Monte Carlo step which is appended to the particle filter and aims to bring the particle filter samples closer to the observations while at the same time

Vasileios Maroulas; Panos Stinis

398

ON THE CONVERGENCE OF THE ENSEMBLE KALMAN FILTER

Convergence of the ensemble Kalman filter in the limit for large ensembles to the Kalman filter is proved. In each step of the filter, convergence of the ensemble sample covariance follows from a weak law of large numbers for exchangeable random variables, the continuous mapping theorem gives convergence in probability of the ensemble members, and Lp bounds on the ensemble then give Lp convergence.

Mandel, Jan; Cobb, Loren; Beezley, Jonathan D.

2013-01-01

399

A method, for producing a filter having partially different apparent densities, comprises the steps assembling at least two kinds of foamed bodies having different cell densities, which are formed of an organic compound such as urethane, into a three dimensional structure. The obtained composite body immersed into a slurry composed of ceramic such as cordierite so that the slurry is attached to the surface of the composite body, which is fired to burn off the foamed bodies. By selecting the portion to be formed into high density, mechanical strength and exhaust gas purifying efficiency of the filter can be improved.

Tomita, M.; Wakayama, M.

1983-08-02

400

NASA Astrophysics Data System (ADS)

In this study, we present the concurrent effects of the number of segments (NS) and the least segment area (LSA) for step-and-shoot head-and-neck intensity-modulated radiation therapy (IMRT) planning using the direct machine parameter optimization (DMPO), on which basis we suggest the optimal NS and LSA ranges. We selected three head-and-neck patients who had received IMRT via the simultaneous integrated boost (SIB) technique and classified them as easy, intermediate, and difficult cases. We formulated a benchmark plan and made 11 additional plans by re-optimizing the benchmark by varying the NS and the LSA for each case. Clinical and physical plan-quality evaluation parameters were considered separately: the conformality index (CI), the homogeneity index (HI) and the maximum or mean doses for the organs-at-risk were the clinical factors, and these were summarized as plan-quality parameter, Q. The modulation index (MI), the total monitor units (MUs), and the final composite cost function F were employed as parameters in the evaluation of the physical aspects. A 2-way analysis of variance (2-way ANOVA) was used to determine the effects of the NS and the LSA concurrently. Pearson's correlations among the total MU, MI, F, and Q were examined as well. Overall plan-efficiency factor ? was defined to estimate the optimal NS and LSA by considering the plan's quality and the beam delivery efficiency together. Plans with simple targets or a small number of beams (NB) were affected by the LSA whereas plans with complex targets or large NB were affected by the NS. Moreover, smaller NS and smaller LSA were advantageous for simple plans whereas larger NS and smaller LSA were beneficial for complex plans. When we consider the plan's quality and the beam delivery efficiency, {NS = 60-80, LSA = 8-12 cm2} are the proper ranges for head-and-neck IMRT planning with DMPO; however, the combination may differ based on the complexity of a given plan.

Cheong, Kwang-Ho; Kang, Sei-Kwon; Lee, MeYeon; Kim, Haeyoung; Bae, Hoonsik; Park, SoAh; Hwang, Taejin; Kim, KyoungJu; Han, Taejin

2013-05-01

401

Optimum Low Cost Two Channel IIR Orthonormal Filter Bank.

National Technical Information Service (NTIS)

In this paper, we statistically optimize a well known class of IIR two channel orthonormal filter banks parameterized by a single coefficient when subband quantizers are present. The optimization procedure is extremely simple and very fast compared for ex...

J. Tuqan P. P. Vaidyanathan

1997-01-01

402

Smoothing filter for digital to analog conversion

NASA Technical Reports Server (NTRS)

An electronic filter comprised of three active filter sections to smooth the stepped signal from a digital to analog converter is described. The first section has a noninverting low pass filter transfer function, and the second has an inverting transfer function designed to pass a narrow frequency band centered at the step frequency of the stepped output signal with sharp cutoff of either side of that narrow band. The third section adds the noninverted output of the first section to the inverted output of the second section. This third section has a lead-lag transfer function designed to reduce the phase angle between the signal at its output terminal and the stepped signal at the input of the first section.

Wagner, C. A. (inventor)

1981-01-01

403

US Patent & Trademark Office Database

A backwash filter system includes a filter array comprising a plurality of filter units each having a housing, a filter element unit and a process liquid inlet port and a filtered liquid outlet port connected respectively with process liquid inlet and filtered liquid outlet sides of the filter element unit for filtering process liquid. A process liquid inlet header connects to the process liquid inlet ports of the filter units. A filtered liquid outlet header connects to the filtered liquid outlet ports of the filter units. A first valve unit on the process liquid inlet header is switchable for connecting same alternatively to a process liquid source and a backwash liquid drain. The filtered liquid outlet header can communicate with a filtered liquid receiver.

1998-08-11

404

NASA Technical Reports Server (NTRS)

This article reviews the types and capabilities of birefringent filters. The general operating principles of Lyot (perfect polarizers), partial polarizing, and Solc (no internal polarizers) filters are introduced. Appropriate techniques for tuning each filter type are presented. Field of view of birefringent filters is discussed and is compared to Fabry-Perot and interference filters. The transmission and throughput advantages of birefringent filters are shown. Finally, the current state of the art in practical filters is reviewed.

Title, A. M.; Rosenberg, W. J.

1981-01-01

405

Mathematical methods for the design of color scanning filters

The problem of the design of color scanning filters is addressed in this paper. The problem is posed within the framework of the vector space approach to color systems. The measure of the goodness of a set of color scanning filters presented in earlier work is used as an optimization criterion to design color scanning filters modeled in terms of

Poorvi L. Vora; H. Joel Trussell

1997-01-01

406

Novel Data Association Schemes for the Probability Hypothesis Density Filter

The probability hypothesis density (PHD) filter is a practical alternative to the optimal Bayesian multi-target filter based on finite set statistics. It propagates the PHD function, a first order moment of the full multi-target posterior density. The peaks of the PHD function give estimates of the target states. However, the PHD filter keeps no record of target identities and hence

Kusha Panta; Ba-Ngu Vo; Sumeetpal Singh

2006-01-01

407

Mixed Particle Filtering for Maneuvering Target Tracking in Clutter

The particle filtering (PF) is a recursive sub-optimal Bayesian estimator. The multiple model particle filtering (MMPF) has been proposed for tracking a maneuvering target. In a cluttered environment, probabilistic data association (PDA) is incorporated into MMPF to overcome the measurement-origin uncertainty. While the particle filtering is fairly easy to implement, its main drawback is that it is quite computation intensive,

Xiaojun Yang; Xiangmo Zhao

2008-01-01

408

Improvement of Chinese spam filtering method based on Bayesian classification

The paper described the basic principle of Naive Bayesian spam filter, and analyzed some major factors which influence Chinese spam filter mostly. On the basis of these, proposed a method to optimize the feature databases. Some experiments were designed to study the filter performance on correctness and efficiency. Some detailed analysis of the experiments also presented in this paper. The

Wu Jiansheng; Zhao Xingwen

2010-01-01

409

An analytical formula for the design of quadrature mirror filters

Quadrature mirror filters have an outstanding relevance in the implementation of filter banks for dividing the speech signal into frequency bands and for reconstructing it from these subbands. An analytical formula is given, which allows one to optimize the design of the basic low-pass FIR filter by means of a straight nonlinear minimization procedure.

GIANCARLO PIRANI; VALERIO ZINGARELLI

1984-01-01

410

Digital filter designs for the pre-filter MTI technique with SAR

NASA Astrophysics Data System (ADS)

An optimal filter design technique for the prefilter moving target indication (MTI) method used in synthetic aperture radar (SAR) systems is presented. The technique is general, so that the data resampling ratio can be an arbitrary rational number. The digital filters have linear phase and are based on a two-stage design process involving an interpolation and a decimation. A filter is designed for each stage and the final, optimized design is the convolution of the single stage filters. The proposed filters are used when the pulse repetition frequency is a rational multiple of the clutter bandwidth. The filters show good clutter cancellation and minimal aliased overlap between MTI bands. An example is provided which demonstrates the effectiveness of the design technique.

Medlin, Gregory

411

Application of the implicit particle filter to a model of nearshore circulation

NASA Astrophysics Data System (ADS)

implicit particle filter is applied to a stochastically forced shallow water model of nearshore flow, and found to produce reliable state estimates with tens of particles. The state vector of this model consists of a height anomaly and two horizontal velocity components at each point on a 128 × 98 regular rectangular grid, making for a state dimension O(104). The particle filter was applied to the model with two parameter choices representing two distinct dynamical regimes, and performed well in both. Demands on computing resources were manageable. Simulations with as many as a hundred particles ran overnight on a modestly configured workstation. In this case of observations defined by a linear function of the state vector, taken every time step of the numerical model, the implicit particle filter is equivalent to the optimal importance filter, i.e., at each step any given particle is drawn from the density of the system conditioned jointly upon observations and the state of that particle at the previous time. Even in this ideal case, the sample occasionally collapses to a single particle, and resampling is necessary. In those cases, the sample rapidly reinflates, and the analysis never loses track. In both dynamical regimes, the ensembles of particles deviated significantly from normality.

Miller, R. N.; Ehret, L. L.

2014-04-01

412

Design of FIR filters with discrete coefficients via sphere relaxation

A method for designing FIR digital filters, with each coefficient a sum of signed power-of-2 terms, by sphere relaxation is proposed. To justify the design methodology, we present an analysis showing that the globally optimal design always lies in a vicinity of the optimal FIR filter with continuous coefficients. The design problem at hand is then addressed using a new

Wu-sheng Lu

2006-01-01

413

Ensemble sizes required for particle filters in high dimensions

NASA Astrophysics Data System (ADS)

Particle filters are ensemble-based state-estimation techniques that in principle approximate the correct Bayesian analysis step for general non-Gaussian probability distributions. We investigate the ensemble size necessary for the particle filter as the state dimension increases. For the simplest particle-filter algorithm, in which the prior distribution (i.e. the distribution of the state at the present time, conditioned on previous observations) is used a the proposal distribution, simulations and asymptotic analysis (following Bengtsson, Bickel and collaborators) demonstrate that the required ensemble size scales exponentially with a certain measure of the problem size. When each component of the state vector is independent, Gaussian, and of unit variance and the observations are of each state component separately with independent, Gaussian errors, the required ensemble size scales exponentially with the state dimension and simulations show that at least 1011 members when applied to a 200-dimensional state. In more general cases, the asymptotic theory reveals that the ensemble size must scale exponentially with the variance of the observation log likelihood rather than with the state dimension per se. A proposal density sufficiently close to the correct posterior would alleviate these difficulties, although there is no theoretical guidance for what sufficiently close means as the state dimension increases. Simulations indicate that the "optimal" proposal density of Doucet, which minimizes the variance of the particle weights after resampling, also suffers from an exponential increase of the necessary ensemble size.

Snyder, C.; Bengtsson, T.; Bickel, P.; Anderson, J.

2009-04-01

414

Probability hypothesis density filter versus multiple hypothesis tracking

The probability hypothesis density (PHD) filter is a practical alternative to the optimal Bayesian multi-target filter based on finite set statistics. It propagates only the first order moment instead of the full multi-target posterior. Recently, a sequential Monte Carlo (SMC) implementation of PHD filter has been used in multi-target filtering with promising results. In this paper, we will compare the

Kusha Panta; Ba-Ngu Vo; Sumeetpal Singh; Arnaud Doucet

2004-01-01

415

Auxiliary Particle Implementation of the Probability Hypothesis Density Filter

Optimal Bayesian multi-target filtering is, in general, computationally impractical due to the high dimensionality of the multi-target state. Recently Mahler, [9], introduced a filter which propagates the first moment of the multi-target posterior distribution, which he called the Probability Hypothesis Density (PHD) filter. While this reduces the dimensionality of the problem, the PHD filter still involves intractable integrals in many

N. Whiteley; S. Singh; S. Godsill

2007-01-01

416

The unscented Kalman filtering in extended noise environments

This paper introduces an extended environment for the unscented Kalman filtering that considers also the presence of additive noise on input observations in order to solve the problem of optimal estimation of noise-corrupted input and output sequences. This environment includes as sub-cases both errors-in-variables filtering and unscented Kalman filtering. The unscented Kalman filtering to the presence of additive noise on

Yucheng Zhou; Jiahe Xu; Yuanwei Jing; Georgi M. Dimirovski

2009-01-01

417

NASA Astrophysics Data System (ADS)

We present and release co-added images of the Sloan Digital Sky Survey (SDSS) Stripe 82. Stripe 82 covers an area of ~300 deg2 on the celestial equator, and has been repeatedly scanned 70-90 times in the ugriz bands by the SDSS imaging survey. By making use of all available data in the SDSS archive, our co-added images are optimized for depth. Input single-epoch frames were properly processed and weighted based on seeing, sky transparency, and background noise before co-addition. The resultant products are co-added science images and their associated weight images that record relative weights at individual pixels. The depths of the co-adds, measured as the 5? detection limits of the aperture (3.''2 diameter) magnitudes for point sources, are roughly 23.9, 25.1, 24.6, 24.1, and 22.8 AB magnitudes in the five bands, respectively. They are 1.9-2.2 mag deeper than the best SDSS single-epoch data. The co-added images have good image quality, with an average point-spread function FWHM of ~1'' in the r, i, and z bands. We also release object catalogs that were made with SExtractor. These co-added products have many potential uses for studies of galaxies, quasars, and Galactic structure. We further present and release near-IR J-band images that cover ~90 deg2 of Stripe 82. These images were obtained using the NEWFIRM camera on the NOAO 4 m Mayall telescope, and have a depth of about 20.0-20.5 Vega magnitudes (also 5? detection limits for point sources).

Jiang, Linhua; Fan, Xiaohui; Bian, Fuyan; McGreer, Ian D.; Strauss, Michael A.; Annis, James; Buck, Zoë; Green, Richard; Hodge, Jacqueline A.; Myers, Adam D.; Rafiee, Alireza; Richards, Gordon

2014-07-01

418

Feasibility of nanofluid-based optical filters.

In this article we report recent modeling and design work indicating that mixtures of nanoparticles in liquids can be used as an alternative to conventional optical filters. The major motivation for creating liquid optical filters is that they can be pumped in and out of a system to meet transient needs in an application. To demonstrate the versatility of this new class of filters, we present the design of nanofluids for use as long-pass, short-pass, and bandpass optical filters using a simple Monte Carlo optimization procedure. With relatively simple mixtures, we achieve filters with <15% mean-squared deviation in transmittance from conventional filters. We also discuss the current commercial feasibility of nanofluid-based optical filters by including an estimation of today's off-the-shelf cost of the materials. While the limited availability of quality commercial nanoparticles makes it hard to compete with conventional filters, new synthesis methods and economies of scale could enable nanofluid-based optical filters in the near future. As such, this study lays the groundwork for creating a new class of selective optical filters for a wide range of applications, namely communications, electronics, optical sensors, lighting, photography, medicine, and many more. PMID:23458793

Taylor, Robert A; Otanicar, Todd P; Herukerrupu, Yasitha; Bremond, Fabienne; Rosengarten, Gary; Hawkes, Evatt R; Jiang, Xuchuan; Coulombe, Sylvain

2013-03-01

419

National Technical Information Service (NTIS)

A filter assembly for fluid containing microbial agents comprises a base defining a first broad filter supporting surface for receiving an appropriate microbial filter membrane, and at least one fluid drain disposed therebeneath to conduct the fluid carry...

M. Shepel

1981-01-01

420

Quantum neural network-based EEG filtering for a brain-computer interface.

A novel neural information processing architecture inspired by quantum mechanics and incorporating the well-known Schrodinger wave equation is proposed in this paper. The proposed architecture referred to as recurrent quantum neural network (RQNN) can characterize a nonstationary stochastic signal as time-varying wave packets. A robust unsupervised learning algorithm enables the RQNN to effectively capture the statistical behavior of the input signal and facilitates the estimation of signal embedded in noise with unknown characteristics. The results from a number of benchmark tests show that simple signals such as dc, staircase dc, and sinusoidal signals embedded within high noise can be accurately filtered and particle swarm optimization can be employed to select model parameters. The RQNN filtering procedure is applied in a two-class motor imagery-based brain-computer interface where the objective was to filter electroencephalogram (EEG) signals before feature extraction and classification to increase signal separability. A two-step inner-outer fivefold cross-validation approach is utilized to select the algorithm parameters subject-specifically for nine subjects. It is shown that the subject-specific RQNN EEG filtering significantly improves brain-computer interface performance compared to using only the raw EEG or Savitzky-Golay filtered EEG across multiple sessions. PMID:24807028

Gandhi, Vaibhav; Prasad, Girijesh; Coyle, Damien; Behera, Laxmidhar; McGinnity, Thomas Martin

2014-02-01

421

Filtered multitensor tractography.

We describe a technique that uses tractography to drive the local fiber model estimation. Existing techniques use independent estimation at each voxel so there is no running knowledge of confidence in the estimated model fit. We formulate fiber tracking as recursive estimation: at each step of tracing the fiber, the current estimate is guided by those previous. To do this we perform tractography within a filter framework and use a discrete mixture of Gaussian tensors to model the signal. Starting from a seed point, each fiber is traced to its termination using an unscented Kalman filter to simultaneously fit the local model to the signal and propagate in the most consistent direction. Despite the presence of noise and uncertainty, this provides a causal estimate of the local structure at each point along the fiber. Using two- and three-fiber models we demonstrate in synthetic experiments that this approach significantly improves the angular resolution at crossings and branchings. In vivo experiments confirm the ability to trace through regions known to contain such crossing and branching while providing inherent path regularization. PMID:20805043

Malcolm, James G; Shenton, Martha E; Rathi, Yogesh

2010-09-01

422

The use of filter media to determine filter cleanliness

NASA Astrophysics Data System (ADS)

It is general believed that a sand filter starts its life with new, perfectly clean media, which becomes gradually clogged with each filtration cycle, eventually getting to a point where either head loss or filtrate quality starts to deteriorate. At this point the backwash cycle is initiated and, through the combined action of air and water, returns the media to its original perfectly clean state. Reality, however, dictates otherwise. Many treatment plants visited a decade or more after commissioning are found to have unacceptably dirty filter sand and backwash systems incapable of returning the filter media to a desired state of cleanliness. In some cases, these problems are common ones encountered in filtration plants but many reasons for media deterioration remain elusive, falling outside of these common problems. The South African conditions of highly eutrophic surface waters at high temperatures, however, exacerbate the problems with dirty filter media. Such conditions often lead to the formation of biofilm in the filter media, which is shown to inhibit the effective backwashing of sand and carbon filters. A systematic investigation into filter media cleanliness was therefore started in 2002, ending in 2005, at the University of Johannesburg (the then Rand Afrikaans University). This involved media from eight South African Water Treatment Plants, varying between sand and sand-anthracite combinations and raw water types from eutrophic through turbid to low-turbidity waters. Five states of cleanliness and four fractions of specific deposit were identified relating to in situ washing, column washing, cylinder inversion and acid-immersion techniques. These were measured and the results compared to acceptable limits for specific deposit, as determined in previous studies, though expressed in kg/m 3. These values were used to determine the state of the filters. In order to gain greater insight into the composition of the specific deposits stripped from the media, a four-point characterisation step was introduced for the resultant suspensions based on acid-solubility and volatility. Results showed that a reasonably effective backwash removed a median specific deposit of 0.89 kg/m 3. Further washing in a laboratory column removed a median specific deposit of 1.34 kg/m 3. Media subjected to a standardised cylinder inversion procedure removed a median specific deposit of 2.41 kg/m 3. Immersion in a strong acid removed a median specific deposit of 35.2 kg/m 3. The four-point characterisation step showed that the soluble-volatile fraction was consistently small in relation to the other fractions. The organic fraction was quite high at the RG treatment plant and the soluble-non-volatile fraction was particularly high at the BK treatment plant.

Van Staden, S. J.; Haarhoff, J.

423

In-place testing of off-gas iodine filters

At the Idaho National Engineering Laboratory, both charcoal and silver zeolite (AgX) filters are used for radioactive iodine off-gas cleanup of reactor systems. These filters are used in facilities which are conducting research in the areas of reactor fuel failure, reactor fuel inspection, and loss of fluids from reactor vessels. Iodine retention efficiency testing of these filters is dictated by prudent safety practices and regulatory guidelines. A procedure for determining iodine off-gas filter efficiency in-place has been developed and tested on both AgX and charcoal filters. The procedure involves establishing sample points upstream and downstream of the filter to be tested. A step-by-step approach for filter efficiency testing is presented.