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1

Centroid finding method for position-sensitive detectors  

International Nuclear Information System (INIS)

A new centroid finding method for all detectors where the signal charge is collected or induced on strips or wires, or on subdivided resistive electrodes, is presented. The centroid of charge is determined by convolution of the sequentially switched outputs from these subdivisions or from the strips with a linear centroid finding filter. The position line width is inversely proportional to N3sup(/)2, where N is the number of subdivisions. (orig.)

2

A new timing readout method for TCD (triple charge division) a novel centroid finding method  

International Nuclear Information System (INIS)

We have shown that timing readout for triple charge division centroid finding method by using the ratio to time response of transmission line is possible. Attention must be drawn toward the threshold voltages of discriminators and the best results are taken when this voltage is one second of the summation of both sides' signals. This summation, for charge division readout, is almost constant. In future program, we will expand the TCD pattern toward long range position sensing and generalize the GCD readout method. (author)

3

Modification of backgammon shape cathode and graded charge division readout method for a novel triple charge division centroid finding method  

International Nuclear Information System (INIS)

Triple Charge Division (TCD) centroid finding method that uses modified pattern of Backgammon Shape Cathode (MBSC) is introduced for medium range length position sensitive detectors with optimum numbers of cathode segments. MBSC pattern has three separated areas and uses saw tooth like insulator gaps for separating the areas. Side areas of the MBSC pattern are severed by a central common area. Size of the central area is twice of the size of both sides. Whereas central area is the widest area among three, both sides' areas have the main role in position sensing. With the same resolution and linearity, active region of original Backgammon pattern increases twice by using MBSC pattern, and with the same length, linearity of TCD centroid finding is much better than Backgammon charge division readout method. Linearity prediction of TCD centroid finding and experimental results conducted us to find an optimum truncation of the apices of MBCS pattern in the central area. The TCD centroid finding has an especial readout method since charges must be collected from two segments in both sides and from three segments in the central area of MBSC pattern. The so called Graded Charge Division (GCD) is the especial readout method for TCD. The GCD readout is a combination of the charge division readout and sequence grading of serial segments. Position sensing with TCD centroid finding and GCD readout were done by two sizes MBSC patterns (200mm and 80mm) and Spatial resolution about 1m and 80mm) and Spatial resolution about 1% of the detector length is achieved

4

High-position-resolution scintillation neutron-imaging detector by crossed-fiber readout with novel centroid-finding method  

CERN Document Server

Aiming at high-position-resolution and high-counting-rate neutron imaging, a novel centroid-finding method is proposed for a scintillation neutron-imaging detector with crossed-fiber readout. Crossed wavelength-shifting fibers are arranged on and under the scintillator. Luminescences generated in the scintillator are emitted and detected by a few fibers surrounding the incident point of a neutron. In the novel method, X and Y positions of the incident neutron are decided by coincidence of a central signal and neighboring signals, respectively. By fundamental experiments using a ZnS:Ag/ sup 6 LiF scintillator of 0.5-mm thickness and crossed wavelength-shifting fibers with a size of 0.5 x 0.5 mm sup 2 , it was confirmed that the position resolution is about 0.5 mm and the limitation of the neutron-counting rate is 320 kcps. (orig.)

Katagiri, M; Sakasai, K; Matsubayashi, M; Birumachi, A; Takahashi, H; Nakazawa, M

2002-01-01

5

High-position-resolution scintillation neutron-imaging detector by crossed-fiber readout with novel centroid-finding method  

International Nuclear Information System (INIS)

Aiming at high-position-resolution and high-counting-rate neutron imaging, a novel centroid-finding method is proposed for a scintillation neutron-imaging detector with crossed-fiber readout. Crossed wavelength-shifting fibers are arranged on and under the scintillator. Luminescences generated in the scintillator are emitted and detected by a few fibers surrounding the incident point of a neutron. In the novel method, X and Y positions of the incident neutron are decided by coincidence of a central signal and neighboring signals, respectively. By fundamental experiments using a ZnS:Ag/6LiF scintillator of 0.5-mm thickness and crossed wavelength-shifting fibers with a size of 0.5 x 0.5 mm2, it was confirmed that the position resolution is about 0.5 mm and the limitation of the neutron-counting rate is 320 kcps. (orig.)

6

A new type of centroid finding method for position sensitive detectors  

International Nuclear Information System (INIS)

A new method is introduced for determining the position of events in all detectors where the signals are collected through strips or wires or subdivided electrodes.Signals issued from a position-sensitive detector are processed to construct two pulses. Then, the position is determined by the time interval between these two waveforms. This method is a generalization of the delay line one used mostly in MWPC. However, the new method allows higher rates. The delay can be adjusted to smaller values (24 ns for our prototype).Tests were performed with 1D gas-filled detector with 100 mm length, designed for SAXS experiment at the ESRF synchrotron in Grenoble. The induced signal on a segmented cathode was collected through a resistor network similar to the charge division. The left and the right signals were used to determine the position using the new method based prototype. A spatial resolution of 0.67 mm at FWHM was obtained. Good linearity was achieved after correction of the U-distortion observed on a homogeneous irradiation of the detector. (orig.)

7

An Integrated Centroid Finding and Particle Overlap Decomposition Algorithm for Stereo Imaging Velocimetry  

Science.gov (United States)

An integrated algorithm for decomposing overlapping particle images (multi-particle objects) along with determining each object s constituent particle centroid(s) has been developed using image analysis techniques. The centroid finding algorithm uses a modified eight-direction search method for finding the perimeter of any enclosed object. The centroid is calculated using the intensity-weighted center of mass of the object. The overlap decomposition algorithm further analyzes the object data and breaks it down into its constituent particle centroid(s). This is accomplished with an artificial neural network, feature based technique and provides an efficient way of decomposing overlapping particles. Combining the centroid finding and overlap decomposition routines into a single algorithm allows us to accurately predict the error associated with finding the centroid(s) of particles in our experiments. This algorithm has been tested using real, simulated, and synthetic data and the results are presented and discussed.

McDowell, Mark

2004-01-01

8

Method for measuring centroid algorithm accuracy  

Science.gov (United States)

This paper will describe such a method for measuring the accuracy of centroid algorithms using a relatively inexpensive setup consisting of a white light source, lenses, a CCD camea, an electro-strictive actuator, and a DAC (Digital-to-Analog Converter), and employing embedded PowerPC, VxWorks, and Solaris based software.

Klein, S.; Liewer, K.

2002-01-01

9

Digital centroid-finding electronics for high-rate detectors  

International Nuclear Information System (INIS)

Fast centroid-finding electronics are being developed for a range of position-sensitive gas proportional detectors. Each cathode strip feeds a preamplifier, shaper and a free-running ADC. Increased total count rate is achieved by dividing the detector into several segments with parallel processing that introduces no common dead time. Each segment has central-channel finding logic and event listing realized in a FPGA, followed by a DSP that performs the centroid calculation and histogramming. Measured count-rate per segment exceeds 106 per second, with virtually no dead time

10

Capacitive charge division in centroid finding cathode readouts in MWPCs  

International Nuclear Information System (INIS)

A technique is described in which the centroid of induced charge on cathode strips in a proportional chamber can be determined with reduced differential and integral nonlinearity, without increasing the number of readout channels. It is based on capacitive charge division from intermediate cathode strips to adjacent readout strips, and may be applied to a variety of position readout principles

11

Radar attenuation tomography using the centroid frequency downshift method  

Science.gov (United States)

A method for tomographically estimating electromagnetic (EM) wave attenuation based on analysis of centroid frequency downshift (CFDS) of impulse radar signals is described and applied to cross-hole radar data. The method is based on a constant-Q model, which assumes a linear frequency dependence of attenuation for EM wave propagation above the transition frequency. The method uses the CFDS to construct the projection function. In comparison with other methods for estimating attenuation, the CFDS method is relatively insensitive to the effects of geometric spreading, instrument response, and antenna coupling and radiation pattern, but requires the data to be broadband so that the frequency shift and variance can be easily measured. The method is well-suited for difference tomography experiments using electrically conductive tracers. The CFDS method was tested using cross-hole radar data collected at the U.S. Geological Survey Fractured Rock Research Site at Mirror Lake, New Hampshire (NH) during a saline-tracer injection experiment. The attenuation-difference tomogram created with the CFDS method outlines the spatial distribution of saline tracer within the tomography plane. ?? 1998 Elsevier Science B.V. All rights reserved.

Liu, L.; Lane, J.W.; Quan, Y.

1998-01-01

12

Expand the measurement range of a critical angle refractometer by a centroid method for transparent fluids  

Science.gov (United States)

A simple approach to expand the measurement range of a critical angle refractometer (CAR) is demonstrated. Our method is based on measuring the centroid point of the angular reflective ratio of the CAR. According to the Snell's reflective law, the CAR with a divergent beam source has a limited measurement range. When the refractive index (RI) is higher than the upper limit, the reflective ratio curve is gradual changing without cutoff edge between the total internal reflection (TIR) and non-TIR. We find that the centroid point of the gradual changing curve is associated with the RI value of a liquid. Theorectical analysis and experimental results on sugar solutions with RI that varying from 1.359 to 1.3766 show that this method is effective and accurate to expand the measurement range.

Ye, Junwei; Yang, Kecheng; Liu, Hao; Dai, Jie; Guo, Wenping; Li, Wei; Xia, Min

2015-01-01

13

A Method for Analog Implementation of Centroid Tracking Algorithm in a Video Signal  

Directory of Open Access Journals (Sweden)

Full Text Available The main goal of a video tracking algorithm is finding the location of a predefined target in successive video frames. Centroid pointing is one of the most efficient methods in the target tracking. This method can be simply implemented by a digital video processing system that includes a video memory and a powerful digital processor. Usually, the cost and the complexity of the digital video processor is high and in some applications, using analog video processor that includes only electronic devices like OPAMP, diodes, transistors, resistors and capacitors has lower cost, more efficient and more reliable. Implementing of the centroid in an analog video processor is not as simple as digital one, therefore in this paper, we introduce a novel formulation of the centroid that can be implemented in an analog video processor. We simulate the proposed method by MatLab simulink and compare the results with the area-based tracking that is usually used in analog video processors. The simulation results show that the proposed method is more reliable and accurate.

Payman Moallem

2007-06-01

14

Alteração no método centroide de avaliação da adaptabilidade genotípica / Alteration of the centroid method to evaluate genotypic adaptability  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O objetivo deste trabalho foi alterar o método centroide de avaliação da adaptabilidade e estabilidade fenotípica de genótipos, para deixá-lo com maior sentido biológico e melhorar aspectos quantitativos e qualitativos de sua análise. A alteração se deu pela adição de mais três ideótipos, definidos [...] de acordo com valores médios dos genótipos nos ambientes. Foram utilizados dados provenientes de um experimento sobre produção de matéria seca de 92 genótipos de alfafa (Medicago sativa) realizado em blocos ao acaso, com duas repetições. Os genótipos foram submetidos a 20 cortes, no período de novembro de 2004 a junho de 2006. Cada corte foi considerado um ambiente. A inclusão dos ideótipos de maior sentido biológico (valores médios nos ambientes) resultou em uma dispersão gráfica em forma de uma seta voltada para a direita, na qual os genótipos mais produtivos ficaram próximos à ponta da seta. Com a alteração, apenas cinco genótipos foram classificados nas mesmas classes do método centroide original. A figura em forma de seta proporciona uma comparação direta dos genótipos, por meio da formação de um gradiente de produtividade. A alteração no método mantém a facilidade de interpretação dos resultados para a recomendação dos genótipos presente no método original e não permite duplicidade de interpretação dos resultados. Abstract in english ABSTRACT The objective of this work was to modify the centroid method of evaluation of phenotypic adaptability and the phenotype stability of genotypes in order for the method to make greater biological sense and improve its quantitative and qualitative performance. The method was modified by means [...] of the inclusion of three additional ideotypes defined in accordance with the genotypes' average yield in the environments tested. The alfalfa (Medicago sativa L.) forage yield of 92 genotypes was used. The trial had a randomized block design, with two replicates, and the data were used to test the method. The genotypes underwent 20 cuts, from November 2004 to June 2006. Each cut was considered an environment. The inclusion of ideotypes of greater biological average production in the environments produced an arrow-shaped graphical dispersion directed to the right in which the most productive genotypes were placed near the tip of the arrow. With the alteration only five genotypes were classified into the former classes of the original centroid method. The arrow-shaped figure allowed a direct comparison of genotypes throughout the productivity gradient. The alteration performed in the method preserved the easy interpretation of results for genotype recommendations of the original method, and does leaves no room for ambiguity in interpretation of the results.

Moysés, Nascimento; Cosme Damião, Cruz; Ana Carolina Mota, Campana; Rafael Simões, Tomaz; Caio Césio, Salgado; Reinaldo de Paula, Ferreira.

2009-03-01

15

Star sub-pixel centroid calculation based on multi-step minimum energy difference method  

Science.gov (United States)

The star's centroid plays a vital role in celestial navigation, star images which be gotten during daytime, due to the strong sky background, have a low SNR, and the star objectives are nearly submerged in the background, takes a great trouble to the centroid localization. Traditional methods, such as a moment method, weighted centroid calculation method is simple but has a big error, especially in the condition of a low SNR. Gaussian method has a high positioning accuracy, but the computational complexity. Analysis of the energy distribution in star image, a location method for star target centroids based on multi-step minimum energy difference is proposed. This method uses the linear superposition to narrow the centroid area, in the certain narrow area uses a certain number of interpolation to pixels for the pixels' segmentation, and then using the symmetry of the stellar energy distribution, tentatively to get the centroid position: assume that the current pixel is the star centroid position, and then calculates and gets the difference of the sum of the energy which in the symmetric direction(in this paper we take the two directions of transverse and longitudinal) and the equal step length(which can be decided through different conditions, the paper takes 9 as the step length) of the current pixel, and obtain the centroid position in this direction when the minimum difference appears, and so do the other directions, then the validation comparison of simulated star images, and compare with several traditional methods, experiments shows that the positioning accuracy of the method up to 0.001 pixel, has good effect to calculate the centroid of low SNR conditions; at the same time, uses this method on a star map which got at the fixed observation site during daytime in near-infrared band, compare the results of the paper's method with the position messages which were known of the star, it shows that :the multi-step minimum energy difference method achieves a better effect.

Wang, Duo; Han, YanLi; Sun, Tengfei

2013-09-01

16

A further investigation of the centroid-to-centroid method for stereotactic lung radiotherapy: A phantom study  

Energy Technology Data Exchange (ETDEWEB)

Purpose: Our previous study [B. Lu et al., “A patient alignment solution for lung SBRT setups based on a deformable registration technique,” Med. Phys. 39(12), 7379–7389 (2012)] proposed a deformable-registration-based patient setup strategy called the centroid-to-centroid (CTC) method, which can perform an accurate alignment of internal-target-volume (ITV) centroids between averaged four-dimensional computed tomography and cone-beam computed tomography (CBCT) images. Scenarios with variations between CBCT and simulation CT caused by irregular breathing and/or tumor change were not specifically considered in the patient study [B. Lu et al., “A patient alignment solution for lung SBRT setups based on a deformable registration technique,” Med. Phys. 39(12), 7379–7389 (2012)] due to the lack of both a sufficiently large patient data sample and a method of tumor tracking. The aim of this study is to thoroughly investigate and compare the impacts of breathing pattern and tumor change on both the CTC and the translation-only (T-only) gray-value mode strategies by employing a four-dimensional (4D) lung phantom.Methods: A sophisticated anthropomorphic 4D phantom (CIRS Dynamic Thorax Phantom model 008) was employed to simulate all desired respiratory variations. The variation scenarios were classified into four groups: inspiration to expiration ratio (IE ratio) change, tumor trajectory change, tumor position change, tumor size change, and the combination of these changes. For each category the authors designed several scenarios to demonstrate the effects of different levels of breathing variation on both of the T-only and the CTC methods. Each scenario utilized 4DCT and CBCT scans. The ITV centroid alignment discrepancies for CTC and T-only were evaluated. The dose-volume-histograms (DVHs) of ITVs for two extreme cases were analyzed.Results: Except for some extreme cases in the combined group, the accuracy of the CTC registration was about 2 mm for all cases for both the single and the combined scenarios. The performance of the CTC method was insensitive to region-of-registration (ROR) size selections, as suggested by the comparable accuracy between 1 and 2 cm expansions of the ROR selections for the method. The T-only method was suitable for some single scenarios, such as trajectory variation, position variation, and size variation. However, for combined scenarios and/or a large variation in the IE ratio, the T-only method failed to produce reasonable registration results (within 3 mm). The discrepancy was close to, or even greater than, 1 cm. In addition, unlike the CTC method, the T-only method was sensitive to the ROR size selection. The DVH analysis suggested that a large ITV to PTV margin should be considered if a breathing pattern variation is observed.Conclusions: The phantom study demonstrated that the CTC method was reliable for scenarios in which breathing pattern variation was involved. The T-only gray value method worked for some scenarios, but not for scenarios that involved an IE ratio variation. For scenarios involving position variation, the T-only method worked only with a careful selection of the ROR, whereas the CTC method was independent of ROR size as long as the ITVs were included in the ROR. One indication of the dose consequence analysis was that a large ITV to PTV margin should be considered if a breathing pattern variation is observed.

Lu, Bo; Samant, Sanjiv; Mittauer, Kathryn; Lee, Soyoung; Huang, Yin; Li, Jonathan; Kahler, Darren; Liu, Chihray [Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, Florida 32610 (United States)

2013-10-15

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A further investigation of the centroid-to-centroid method for stereotactic lung radiotherapy: A phantom study  

International Nuclear Information System (INIS)

Purpose: Our previous study [B. Lu et al., “A patient alignment solution for lung SBRT setups based on a deformable registration technique,” Med. Phys. 39(12), 7379–7389 (2012)] proposed a deformable-registration-based patient setup strategy called the centroid-to-centroid (CTC) method, which can perform an accurate alignment of internal-target-volume (ITV) centroids between averaged four-dimensional computed tomography and cone-beam computed tomography (CBCT) images. Scenarios with variations between CBCT and simulation CT caused by irregular breathing and/or tumor change were not specifically considered in the patient study [B. Lu et al., “A patient alignment solution for lung SBRT setups based on a deformable registration technique,” Med. Phys. 39(12), 7379–7389 (2012)] due to the lack of both a sufficiently large patient data sample and a method of tumor tracking. The aim of this study is to thoroughly investigate and compare the impacts of breathing pattern and tumor change on both the CTC and the translation-only (T-only) gray-value mode strategies by employing a four-dimensional (4D) lung phantom.Methods: A sophisticated anthropomorphic 4D phantom (CIRS Dynamic Thorax Phantom model 008) was employed to simulate all desired respiratory variations. The variation scenarios were classified into four groups: inspiration to expiration ratio (IE ratio) change, tumor trajectory change, tumor position change, tumor size change, and the combination of these changes. For each category the authors designed several scenarios to demonstrate the effects of different levels of breathing variation on both of the T-only and the CTC methods. Each scenario utilized 4DCT and CBCT scans. The ITV centroid alignment discrepancies for CTC and T-only were evaluated. The dose-volume-histograms (DVHs) of ITVs for two extreme cases were analyzed.Results: Except for some extreme cases in the combined group, the accuracy of the CTC registration was about 2 mm for all cases for both the single and the combined scenarios. The performance of the CTC method was insensitive to region-of-registration (ROR) size selections, as suggested by the comparable accuracy between 1 and 2 cm expansions of the ROR selections for the method. The T-only method was suitable for some single scenarios, such as trajectory variation, position variation, and size variation. However, for combined scenarios and/or a large variation in the IE ratio, the T-only method failed to produce reasonable registration results (within 3 mm). The discrepancy was close to, or even greater than, 1 cm. In addition, unlike the CTC method, the T-only method was sensitive to the ROR size selection. The DVH analysis suggested that a large ITV to PTV margin should be considered if a breathing pattern variation is observed.Conclusions: The phantom study demonstrated that the CTC method was reliable for scenarios in which breathing pattern variation was involved. The T-only gray value method worked for some scenarios, but not for scenarios that involved an IE ratio variation. For scenarios involving position variation, the T-only method worked only with a careful selection of the ROR, whereas the CTC method was independent of ROR size as long as the ITVs were included in the ROR. One indication of the dose consequence analysis was that a large ITV to PTV margin should be considered if a breathing pattern variation is observed

18

Statistical analysis of x-ray stress measurement by centroid method  

International Nuclear Information System (INIS)

The X-ray technique allows a nondestructive and rapid measurement of residual stresses in metallic materials. The centroid method has an advantage over other X-ray methods in that it can determine the angular position of a diffraction line, from which the stress is calculated, even with an asymmetrical line profile. An equation for the standard deviation of the angular position of a diffraction line, ?sub(p), caused by statistical fluctuation was derived, which is a fundamental source of scatter in X-ray stress measurements. This equation shows that an increase of X-ray counts by a factor of k results in a decrease of ?sub(p) by a factor of 1/?k. It also shows that ?sub(p) increases rapidly as the angular range used in calculating the centroid increases. It is therefore important to calculate the centroid using the narrow angular range between the two ends of the diffraction line where it starts to deviate from the straight background line. By using quenched structural steels JIS S35C and S45C, the residual stresses and their standard deviations were calculated by the centroid, parabola, Gaussian curve, and half-width methods, and the results were compared. The centroid of a diffraction line was affected greatly by the background line used. The standard deviation of the stress measured by the centroid method was found to be the largest among the four methods. (author)

19

Fast centroid algorithm for determining the surface plasmon resonance angle using the fixed-boundary method  

International Nuclear Information System (INIS)

To simplify the algorithm for determining the surface plasmon resonance (SPR) angle for special applications and development trends, a fast method for determining an SPR angle, called the fixed-boundary centroid algorithm, has been proposed. Two experiments were conducted to compare three centroid algorithms from the aspects of the operation time, sensitivity to shot noise, signal-to-noise ratio (SNR), resolution, and measurement range. Although the measurement range of this method was narrower, the other performance indices were all better than the other two centroid methods. This method has outstanding performance, high speed, good conformity, low error and a high SNR and resolution. It thus has the potential to be widely adopted

20

Lifetime measurements in Cr and V isotopes using centroid shift method and DSAM  

International Nuclear Information System (INIS)

The growing interest in studying properties of fp shell nuclei is prompted by the possibility of observing different aspects of complex phenomena through different modes of excitation. Some interesting observations motivated to undertake the present experiment to measure the lifetime of several levels in 48,49V and 50,51Cr using centroid shift method and DSAM analysis

 
 
 
 
21

Shack-Hartmann centroid detection method based on high dynamic range imaging and normalization techniques  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the optical quality measuring process of an optical system, including diamond-turning components, the use of a laser light source can produce an undesirable speckle effect in a Shack-Hartmann (SH) CCD sensor. This speckle noise can deteriorate the precision and accuracy of the wavefront sensor measurement. Here we present a SH centroid detection method founded on computer-based techniques and capable of measurement in the presence of strong speckle noise. The method extends the dynamic ran...

Quiroga Mellado, Juan Antonio; Vargas, Javier; Gonza?lez Ferna?ndez, Luis M.; Belenguer Da?vila, Toma?s

2010-01-01

22

Noninvasive measurement of cardiopulmonary blood volume: evaluation of the centroid method  

International Nuclear Information System (INIS)

Cardiopulmonary blood volume (CPV) and mean pulmonary transit time (MTT) determined by radionuclide measurements (Tc-99m HSA) were compared with values obtained from simultaneous dye-dilution (DD) studies (indocyanine green). The mean transit time was obtained from radionuclide curves by two methods: the peak-to-peak time and the interval between the two centroids determined from the right and left-ventricular time-concentration curves. Correlation of dye-dilution MTT and peak-to-peak time was significant (r = 0.79, p < 0.001), but its correlation with centroid-derived values was better (r = 0.86, p < 0.001). CPV values (using the centroid method for radionuclide technique) correlated significantly with values derived from dye-dilution curves (r = 0.74, p < 0.001). Discrepancies between the two were greater the more rapid the circulation (r = 0.61, p < 0.01), suggesting that minor inaccuracies of dye-dilution methods, due to positioning or delay of the system, can become magnified in hyperkinetic conditions. The radionuclide method is simple, repeatable, and noninvasive, and it provides simultaneous evaluation of pulmonary and systemic hemodynamics. Further, calculation of the ratio of cardiopulmonary to total blood volume can be used as an index of overall venous distensibility and relocation of intravascular blood volume

23

The generalized centroid shift method for lifetime measurements in heavy ion reactions  

International Nuclear Information System (INIS)

An application of the generalized centroid shift method for lifetime measurements in the nano-second and subnanosecond region in HI reactions on the Rutgers tandem is described. Delayed ??-coincidence measurements using plastic scintillators (start) and a germanium detector (stop) are discussed. Details of the analysis including treatment of the time background (random coincidences) and the choice of range of analysis of the time distributions are considered. (orig./WL)

24

Wedge-and-strip anodes for centroid-finding position-sensitive photon and particle detectors  

Science.gov (United States)

The paper examines geometries employing position-dependent charge partitioning to obtain a two-dimensional position signal from each detected photon or particle. Requiring three or four anode electrodes and signal paths, images have little distortion and resolution is not limited by thermal noise. An analysis of the geometrical image nonlinearity between event centroid location and the charge partition ratios is presented. In addition, fabrication and testing of two wedge-and-strip anode systems are discussed. Images obtained with EUV radiation and microchannel plates verify the predicted performance, with further resolution improvements achieved by adopting low noise signal circuitry. Also discussed are the designs of practical X-ray, EUV, and charged particle image systems.

Martin, C.; Jelinsky, P.; Lampton, M.; Malina, R. F.

1981-01-01

25

Adaptive thresholding and dynamic windowing method for automatic centroid detection of digital Shack-Hartmann wavefront sensor  

International Nuclear Information System (INIS)

A Shack-Hartmann wavefront sensor (SWHS) splits the incident wavefront into many subsections and transfers the distorted wavefront detection into the centroid measurement. The accuracy of the centroid measurement determines the accuracy of the SWHS. Many methods have been presented to improve the accuracy of the wavefront centroid measurement. However, most of these methods are discussed from the point of view of optics, based on the assumption that the spot intensity of the SHWS has a Gaussian distribution, which is not applicable to the digital SHWS. In this paper, we present a centroid measurement algorithm based on the adaptive thresholding and dynamic windowing method by utilizing image processing techniques for practical application of the digital SHWS in surface profile measurement. The method can detect the centroid of each focal spot precisely and robustly by eliminating the influence of various noises, such as diffraction of the digital SHWS, unevenness and instability of the light source, as well as deviation between the centroid of the focal spot and the center of the detection area. The experimental results demonstrate that the algorithm has better precision, repeatability, and stability compared with other commonly used centroid methods, such as the statistical averaging, thresholding, and windowing algorithms.

26

Optimal Citing Of Distribution Generation Units In Distribution Networks Based On Load Centroid Method  

Directory of Open Access Journals (Sweden)

Full Text Available The Distribution System Load Flow (DSLF methods take special care to overcome the ill- conditioned nature arising due to high R/X ratios of the feeders, which makes the fast decoupled Newton method often not valid. The DSLF methods also exploit the radial nature of the distribution networks. Centroid method of Distribution Load Flow Extensive research has been conducted to identify optimal DG allocation. Almost All known methods model the task as an optimization problem based on certain objective function(s and constraints. The formulated optimization problem is commonly solved using various versions of heuristic techniques like SA, GA, PSO, ABC, etc. All these techniques are iterative methods that form a heavy computational burden and are very time consuming especially for fairly big networks. In this paper an analytical expression to calculate the optimal size and a methodology to identify the corresponding optimum location for DG placement for minimizing the total power losses in distribution systems based on the new concept of load centroid method is presented. The analytical expression and the methodology are based on the exact loss formula. This methodology can only identify the best location for a single DG. Case studies are performed on 12, 22, 33 bus radial distribution systems.

N. Prema Kumar

2013-12-01

27

Shack-Hartmann centroid detection method based on high dynamic range imaging and normalization techniques  

International Nuclear Information System (INIS)

In the optical quality measuring process of an optical system, including diamond-turning components, the use of a laser light source can produce an undesirable speckle effect in a Shack-Hartmann (SH) CCD sensor. This speckle noise can deteriorate the precision and accuracy of the wavefront sensor measurement. Here we present a SH centroid detection method founded on computer-based techniques and capable of measurement in the presence of strong speckle noise. The method extends the dynamic range imaging capabilities of the SH sensor through the use of a set of different CCD integration times. The resultant extended range spot map is normalized to accurately obtain the spot centroids. The proposed method has been applied to measure the optical quality of the main optical system (MOS) of the mid-infrared instrument telescope smulator. The wavefront at the exit of this optical system is affected by speckle noise when it is illuminated by a laser source and by air turbulence because it has a long back focal length (3017 mm). Using the proposed technique, the MOS wavefront error was measured and satisfactory results were obtained.

28

Localization Methods of Weighted Centroid of dBZ on Weather-Radar Echo Maps in Vector Format  

Directory of Open Access Journals (Sweden)

Full Text Available Fast generation of weather-radar echo maps in vector format and accurate localization of weighted centroid of dBZ (dBZ stands for decibels of reflectivity of a radar signal reflected off a remote object are the basis of studying the characteristic tracking algorithms which are based on the vector echoes. The authors principally studied the approach to generating the vector echo map, and discussed the localization methods of weighted centroid of dBZ on vector echo maps. First, based on the traditional calculation method on raster echo data, some new localization methods of weighted centroid of dBZ on vector echo data were proposed by considering the weights of features’ area and distance from their location to radar center. Second, taking the base reflectivity products of CINRAD/SA weather radar in Meizhou city of China as data sources, they illustrated the storage structure of this type of echo data and studied the drawing mode of changing this type of data into vector format files under the polar coordinate system in detail. Third, using the same vector echo maps created by the above method, the weighted centroid of the same area was calculated by the above localization methods. In the end, Compared with the calculated value of the same area by traditional method which is based on raster echo maps, the three new calculated results and the sources of error were analyzed in detail and two conclusions were drawn: the echo’s precision in vector format is much higher than that in raster format and it is more accurate to take the features’ area and distance to radar center as weights during the calculation of weighted centroid of dBZ on echo maps in vector format.

Xue-tao Yu

2013-02-01

29

A walk-free centroid method for lifetime measurements with pulsed beams  

International Nuclear Information System (INIS)

A delayed-coincidence lifetime measurement method based on a comparison of walk-free centroids of time spectra is presented. The time is measured between the cyclotron RF signal and the pulse from a plastic scintillation detector followed by a fixed energy selection. The events to be time-analyzed are selected from the associated charge-particle spectrum of a silicon detector which is operated in coincidence with the scintillator, i.e., independently of the formation of the signal containing the time information. With this technique, with the micropulse FWHM of typically 500 to 700 ps, half-lives down to the 10 ps region can be measured. The following half-lives are obtained with the new method: 160+-6 ps for the 2032 keV level in 209Pb; 45+-10 ps and 160+-20 ps for the 1756.8 keV (02+) and 2027.3 keV (03+) levels in 116Sn, respectively. (author)

30

A multi-resolution method for climate system modeling: application of spherical centroidal Voronoi tessellations  

Energy Technology Data Exchange (ETDEWEB)

During the next decade and beyond, climate system models will be challenged to resolve scales and processes that are far beyond their current scope. Each climate system component has its prototypical example of an unresolved process that may strongly influence the global climate system, ranging from eddy activity within ocean models, to ice streams within ice sheet models, to surface hydrological processes within land system models, to cloud processes within atmosphere models. These new demands will almost certainly result in the develop of multiresolution schemes that are able, at least regionally, to faithfully simulate these fine-scale processes. Spherical centroidal Voronoi tessellations (SCVTs) offer one potential path toward the development of a robust, multiresolution climate system model components. SCVTs allow for the generation of high quality Voronoi diagrams and Delaunay triangulations through the use of an intuitive, user-defined density function. In each of the examples provided, this method results in high-quality meshes where the quality measures are guaranteed to improve as the number of nodes is increased. Real-world examples are developed for the Greenland ice sheet and the North Atlantic ocean. Idealized examples are developed for ocean–ice shelf interaction and for regional atmospheric modeling. In addition to defining, developing, and exhibiting SCVTs, we pair this mesh generation technique with a previously developed finite-volume method. Our numerical example is based on the nonlinear, shallow water equations spanning the entire surface of the sphere. This example is used to elucidate both the potential benefits of this multiresolution method and the challenges ahead.

Ringler, Todd [Los Alamos National Laboratory; Ju, Lili [University of South Carolina; Gunzburger, Max [Florida State University

2008-01-01

31

Centroid and full-width at half maximum uncertainties of histogrammed data with an underlying Gaussian distribution -- The moments method  

International Nuclear Information System (INIS)

The effect of approximating a continuous Gaussian distribution with histogrammed data are studied. The expressions for theoretical uncertainties in centroid and full-width at half maximum (FWHM), as determined by calculation of moments, are derived using the error propagation method for a histogrammed Gaussian distribution. The results are compared with the corresponding pseudo-experimental uncertainties for computer-generated histogrammed Gaussian peaks to demonstrate the effect of binning the data. It is shown that increasing the number of bins in the histogram improves the continuous distribution approximation. For example, a FWHM ? 9 and FWHM ? 12 bins are needed to reduce the pseudo-experimental standard deviation of FWHM to within ?5% and ?1%, respectively, of the theoretical value for a peak containing 10,000 counts. In addition, the uncertainties in the centroid and FWHM as a function of peak area are studied. Finally, Sheppard's correction is applied to partially correct for the binning effect

32

A method for centroid-shift time measurements with magnetic plus Si(Li) combination conversion-electron spectrometer  

International Nuclear Information System (INIS)

A centroid timing method has been developed for use in connection with a magnetic plus Si(Li) combination conversion-electron spectrometer. In in-beam measurements, the time intervals between the Si(Li) output and cyclotron rf pulses are measured. The properties of the walk curves, isochronism and time-dependent background of the instrument are described. No inherent delay between total-absorption (peak) and partial-absorption (tail) events is observed. The region of applicability and advantages of the method as compared with direct Ge(Li) timing are discussed. In favourable cases, half-lives can be determined to an accuracy of about 10 ps. (orig.)

33

Numerical Optical Centroid Measurements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Optical imaging methods are typically restricted to a resolution of order of the probing light wavelength $\\lambda_p$ by the Rayleigh diffraction limit. This limit can be circumvented by making use of multiphoton detection of correlated $N$-photon states, having an effective wavelength $\\lambda_p/N$. But the required $N$-photon detection usually renders these schemes impractical. To overcome this limitation, recently, so-called optical centroid measurements (OCM) have been p...

Gulfam, Qurrat-ul-ain; Evers, Jo?rg

2013-01-01

34

Characterizing charge centroids from lightning using a slow antenna network and the Levenberg-Marquardt inverse method  

Science.gov (United States)

Researchers have long studied the copious and complex electric field waveforms caused by lightning. By combining electric-field measurements taken at many different locations on the ground simultaneously [Krehbiel et al., 1979], we hope to learn more about charge sources for lightning flashes. The Langmuir Electric Field Array (LEFA) is a network of nine field-change measurement stations (slow-antennas) arranged around Langmuir Laboratory near Magdalena, New Mexico. Using a mathematical method called the Levenberg-Marquardt (LM) method, we can invert the electric field data to determine the magnitude and position of the charge centroid removed from the cloud. We analyzed three return strokes (RS) following a dart-leader from a storm occurring on October 21st 2011. RS 'A' occurred at 07:17:00.63 UT. The altitude of the charge centroid was estimated to be 5 km via LMA data. Because the LM method requires a prediction, the code was run with a wide range of values to verify the robustness of the method. Predictions varied from ±3 C for the charge magnitude and ±20 km N-S and E-W for the position (with the coordinate origin being the Langmuir Laboratory Annex). The LM method converged to a charge magnitude of -5.5 C and a centroid position of 3.3 km E-W and 12 km, N-S for that RS. RS 'B' occurred at 07:20:05.9 UT. With an altitude of 4 km, the predictions were again varied; ±3 C, ±15 km N-S and E-W. Most runs converged to -27.5 C, 4 km E-W, and 10.9 km N-S. Finally, while results seem best for events right over the array, success was had locating more distant events. RS 'C' occurred at 02:42:46.8 UT. Assuming an altitude of 5 km and varying the predictions as with RS 'A', the results converged to -9.2 C, 35.5 km E-W, and 9 km N-S. All of these results are broadly consistent with the LMA and the NLDN. By continuing this type of analysis, we hope to learn more about how lightning channels propagate and how the charges in the cloud respond to the sudden change in charge distribution after a CG flash. Reference Krehbiel, P.R., M. Brook, and R. A. McCrory (1979), An analysis of the charge structure of lightning discharges to ground, J. Geophys. Res., 84(C5), 2432-2456. We gratefully acknowledge support from the National Science Foundation Grant No. 0724771.

Lapierre, J. L.; Sonnenfeld, R. G.; Hager, W. W.; Morris, K.

2011-12-01

35

Weighted Centroid Modified Simplex and Linear Constrained Response Surface Optimization Methods for the Xbar-R Chart Variable Determination  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: Although economic Xbar-R chart designs do guarantee the minimal operating cost, they typically have poor levels of statistical performance measures. The obvious limitation of the economic design is that the Type I error rate seems to be very high for many situations and will cause a large number of false alarms. This situation leads to an investigation of appropriate levels of control chart variables which consist of a sample size, an interval between samples or sampling frequency and the control chart limits. Approach: Evolutionary operations via the weighed centroid modified simplex, WCMSM and linear constrained response surface optimization, LCRSOM, methods are applied to optimize the Xbar-R chart variables in the analytical model called as the operating cost function. WCMSM allows the simplex to converge more rapidly towards an optimum via the weighted centroid of the hyperface by expansion and multiple ways of simplex contraction along the line of conventional reflection in order to speed up the convergence. LCRSOM is a combination of the principles of experimental designs, least squares and related mathematical programming models to approach the optimum. Results: The computational results for economic Xbar-R charts via both methods reveal that the process quality level affects the total cost more than relevant errors from selecting and inspecting samples including identifying assignable causes. However, total costs obtained from the LCRSOM seem to be better for all process scenarios. Conclusions: On Xbar-R charts, if a process is at the high quality level the total cost is better than a process with a low quality level without a consideration of errors from selecting/inspecting samples and identifying assignable causes.

Pongchanun Luangpaiboon

2011-01-01

36

A novel, view-independent method for strain mapping in myocardial elastography: eliminating angle and centroid dependence  

Energy Technology Data Exchange (ETDEWEB)

Robust indices of regional and global cardiac function are a key factor in detection and treatment of heart disease as well as understanding of the fundamental mechanisms of a healthy heart. Myocardial elastography provides a noninvasive method for imaging and measuring displacement and strain of the myocardium for the early detection of cardiovascular disease. However, two-dimensional in-plane axial and lateral strains measured depend on the sonographic view used. This becomes especially critical in a clinical setting and may induce large variations in the measured strains, potentially leading to false diagnoses. A novel method in myocardial elastography is proposed for eliminating this view dependence by deriving the polar, principal and classified principal strains. The performance of the proposed methodology is assessed by employing 3D finite-element left-ventricular models of a control and an ischemic canine heart. Although polar strains are angle-independent, they are sensitive to the selected reference coordinate system, which requires the definition of a centroid of the left ventricle (LV). In contrast, principal strains derived through eigenvalue decomposition exhibit the inherent characteristic of coordinate system independence, offering view (i.e., angle and centroid)-independent strain measurements. Classified principal strains are obtained by assigning the principal components in the physical ventricular coordinate system. An extensive strain analysis illustrates the improvement in interpretation and visualization of the full-field myocardial deformation by using the classified principal strains, clearly depicting the ischemic and non-ischemic regions. Strain maps, independent of sonographic views and imaging planes, that can be used to accurately detect regional contractile dysfunction are demonstrated.

Zervantonakis, I K; Fung-Kee-Fung, S D; Lee, W-N; Konofagou, E E [Department of Biomedical Engineering, Columbia University, New York, NY (United States)

2007-07-21

37

A novel, view-independent method for strain mapping in myocardial elastography: eliminating angle and centroid dependence  

International Nuclear Information System (INIS)

Robust indices of regional and global cardiac function are a key factor in detection and treatment of heart disease as well as understanding of the fundamental mechanisms of a healthy heart. Myocardial elastography provides a noninvasive method for imaging and measuring displacement and strain of the myocardium for the early detection of cardiovascular disease. However, two-dimensional in-plane axial and lateral strains measured depend on the sonographic view used. This becomes especially critical in a clinical setting and may induce large variations in the measured strains, potentially leading to false diagnoses. A novel method in myocardial elastography is proposed for eliminating this view dependence by deriving the polar, principal and classified principal strains. The performance of the proposed methodology is assessed by employing 3D finite-element left-ventricular models of a control and an ischemic canine heart. Although polar strains are angle-independent, they are sensitive to the selected reference coordinate system, which requires the definition of a centroid of the left ventricle (LV). In contrast, principal strains derived through eigenvalue decomposition exhibit the inherent characteristic of coordinate system independence, offering view (i.e., angle and centroid)-independent strain measurements. Classified principal strains are obtained by assigning the principal components in the physical ventricular coordinate system. An extensive strain analysis ille system. An extensive strain analysis illustrates the improvement in interpretation and visualization of the full-field myocardial deformation by using the classified principal strains, clearly depicting the ischemic and non-ischemic regions. Strain maps, independent of sonographic views and imaging planes, that can be used to accurately detect regional contractile dysfunction are demonstrated

38

The mirror symmetric centroid difference method for picosecond lifetime measurements via ?-? coincidences using very fast LaBr3(Ce) scintillator detectors  

International Nuclear Information System (INIS)

The ultra-fast timing technique was introduced in the 1980s and is capable of measuring picosecond lifetimes of nuclear excited states with about 3 ps accuracy. Very fast scintillator detectors are connected to an electronic timing circuit and detector vs. detector time spectra are analyzed by means of the centroid shift method. The very good 3% energy resolution of the nowadays available LaBr3(Ce) scintillator detectors for ?-rays has made possible an extension of the well-established fast timing technique. The energy dependent fast timing characteristics or the prompt curve, respectively, of the LaBr3(Ce) scintillator detector has been measured using a standard 152Eu ?-ray source. For any energy combination in the range of 200keV?<1500keV, the ?-? fast timing characteristics is calibrated as a function of energy with an accuracy of 2-4 ps. An extension of the centroid shift method providing very attractive features for picosecond lifetime measurements is presented. The mirror symmetric centroid difference method takes advantage of the symmetry obtained when performing ?-? lifetime measurements using a pair of almost identical very fast scintillator detectors. In particular cases, the use of the mirror symmetric centroid difference method also allows the direct determination of picosecond lifetimes, hence without the need of calibrating the prompt curve.

39

Selection of Initial Centroids for k-Means Algorithm?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Clustering is one of the important data mining techniques. k-Means [1] is one of the mostimportant algorithm for Clustering. Traditional k-Means algorithm selects initial centroids randomly and ink-Means algorithm result of clustering highly depends on selection of initial centroids. k-Means algorithm issensitive to initial centroids so proper selection of initial centroids is necessary. This paper introduces anefficient method to start the k-Means with good initial centroids. Good initial ce...

Baswade, Anand M.; Nalwade?, Prakash S.

2013-01-01

40

Geogebra: Calculation of Centroid  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Our paper is result of the research done in a special direction for solving problems of physics by using GeoGebra programme: calculation of centroid. Lots of simulations of physical phenomena from the class of Mechanics can be performed and computational problems can be solved with GeoGebra. GeoGebra offers many commands and one of them is the command “centroid” to calculate the coordinates of the centroid of a polygon but, we have created a new tool to calculate the coordinates of the c...

Qamil Kllogjeri; Pellumb Kllogjeri

2012-01-01

 
 
 
 
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Application example: Preliminary Results of ISOLA use to find moment tensor solutions and centroid depth applied to aftershocks of Mw=8.8 February 27 2010, Maule Earthquake  

Science.gov (United States)

We selected seven aftershocks from Maule earthquake between 33.5°S to 35°S from May to September to find single source inversion. The data were provided by XY Chile Ramp Experiment* which was deployed after great Maule earthquake. Waveform data are from 13 broad band stations chosen from the 58 broad band stations deployed by IRIS-PASCAL from April to September 2010. Stations are placed above the normal subduction section south of ~33.5°S. Events were located with an iterative software called Hypocenter using one dimensional local model, obtained above for the forearc region between 33°S to 35°S. We used ISOLA which is a fortran code with a Matlab interface to obtain moment tensors solutions, optimum position and time of the subevents. Values depth obtained by a grid search of centroid position show range values which are compatibles with the interplate seismogenic zone. Double-Couple focal mechanism solutions (Figure 1) show 4 thrust events which can be associated with that zone. However, only one of them has strike, dip and rake of 358°, 27° and 101 respectively, appropriate to be expected for interplate seismogenic zone. On the other hand, the other 3 events show strike and normal double-couple focal mechanism solutions (Figure 1). This last topic makes association to those events to the contact of the Nazca and South American plate difficult. Nevertheless, in a first stage, their depths may allow possibility of an origin there. * The facilities of the IRIS Data Management System, and specifically the IRIS Data Management Center, were used for access to waveform, metadata or products required in this study. The IRIS DMS is funded through the National Science Foundation and specifically the GEO Directorate through the Instrumentation and Facilities Program of the National Science Foundation under Cooperative Agreement EAR-0552316. Some activities of are supported by the National Science Foundation EarthScope Program under Cooperative Agreement EAR-0733069. Figure 1. Doble-Couple focal mechanisms solutions from Moment Tensor Inversion using ISOLA. Triangles show broad band stations used in this work from IRIS-PASSCAL.

Nacif, S. V.; Sanchez, M. A.

2013-05-01

42

Geogebra: Calculation of Centroid  

Directory of Open Access Journals (Sweden)

Full Text Available Our paper is result of the research done in a special direction for solving problems of physics by using GeoGebra programme: calculation of centroid. Lots of simulations of physical phenomena from the class of Mechanics can be performed and computational problems can be solved with GeoGebra. GeoGebra offers many commands and one of them is the command “centroid” to calculate the coordinates of the centroid of a polygon but, we have created a new tool to calculate the coordinates of the centroid of a plane region bounded by curves. Our work is part of the passionate work of many GeoGebra users which will result with a very rich fund of GeoGebra virtual tools, examples and experiences that will be worldwidely available for many teachers and practioners.

Qamil Kllogjeri

2012-09-01

43

Centroid motion in periodically focused beams  

International Nuclear Information System (INIS)

The role of the centroid dynamics in the transport of periodically focused particle beams is investigated. A Kapchinskij-Vladimirskij equilibrium distribution for an off-axis beam is derived. It is shown that centroid and envelope dynamics are uncoupled and that unstable regions for the centroid dynamics overlap with previously stable regions for the envelope dynamics alone. Multiparticle simulations validate the findings. The effects of a conducting pipe encapsulating the beam are also investigated. It is shown that the charge induced at the pipe may generate chaotic orbits which can be detrimental to the adequate functioning of the transport mechanism

44

Centroid Based Text Clustering  

Directory of Open Access Journals (Sweden)

Full Text Available Web mining is a burgeoning new field that attempts to glean meaningful information from natural language text. Web mining refers generally to the process of extracting interesting information and knowledge from unstructured text. Text clustering is one of the important Web mining functionalities. Text clustering is the task in which texts are classified into groups of similar objects based on their contents. Current research in the area of Web mining is tacklesproblems of text data representation, classification, clustering, information extraction or the search for and modeling of hidden patterns. In this paper we propose for mining large document collections it is necessary to pre-process the web documents and store the information in a data structure, which is more appropriate for further processing than a plain web file. In this paper we developed a php-mySql based utility to convert unstructured web documents into structured tabular representation by preprocessing, indexing .We apply centroid based web clustering method on preprocessed data. We apply three methods for clustering. Finally we proposed a method that can increase accuracy based on clustering ofdocuments.

Priti Maheshwari

2010-09-01

45

The generalized centroid difference method for picosecond sensitive determination of lifetimes of nuclear excited states using large fast-timing arrays  

International Nuclear Information System (INIS)

A novel method for direct electronic “fast-timing” lifetime measurements of nuclear excited states via ?–? coincidences using an array equipped with N?N equally shaped very fast high-resolution LaBr3(Ce) scintillator detectors is presented. Analogous to the mirror symmetric centroid difference method, the generalized centroid difference method provides two independent “start” and “stop” time spectra obtained by a superposition of the N(N?1)?–? time difference spectra of the N detector fast-timing system. The two fast-timing array time spectra correspond to a forward and reverse gating of a specific ?–? cascade. Provided that the energy response and the electronic time pick-off of the detectors are almost equal, a mean prompt response difference between start and stop events is calibrated and used as a single correction for lifetime determination. These combined fast-timing arrays mean ?–? time-walk characteristics can be determined for 40keV?152Eu ?-ray source. Due to reduction and cancellation of many possible systematic errors, the lifetime determination limit of the method over the total dynamic range is mainly determined by the statistics. The setup of an N=4 detector fast-timing array delivered an absolute time resolving power of 3 ps for 10 000 ?–? events per total fast timing array start and stop time spectrum. The new method is tested over the total dynamic range by the measurements of known picosecond lifetimes in standard ?-ray sources

46

Transverse motion of electron beam centroid: corkscrew  

International Nuclear Information System (INIS)

In a solenoidal focusing field, the centroid of any slice in an electron beam will execute cyclotron oscillation if the magnetic-axis is tilted from the axis of accelerator. The energy variation within the beam pulse will make cyclotron oscillation develop corkscrew oscillation. The trajectory of beam centroid is analytically found, the expression of the effective radius for an electron beam is given, and the method to reduce corkscrew oscillation is simply discussed

47

Research on Centroid Position for Stairs Climbing Stability of Search and Rescue Robot  

Directory of Open Access Journals (Sweden)

Full Text Available This paper represents the relationship between the stability of stairs climbing and the centroid position of the search and rescue robot. The robot system is considered as a mass point-plane model and the kinematics features are analyzed to find the relationship between centroid position and the maximal pitch angle of stairs the robot could climb up. A computable function about this relationship is given in this paper. During the stairs climbing, there is a maximal stability-keeping angle depends on the centroid position and the pitch angle of stairs, and the numerical formula is developed about the relationship between the maximal stability-keeping angle and the centroid position and pitch angle of stairs. The experiment demonstrates the trustworthy and correction of the method in the paper.

Yan Guo

2011-01-01

48

1990 CENSUS BLOCK CENTROIDS  

Science.gov (United States)

The block_cen layer in the EPA New England database provides the centroids of block boundaries coverage based on the U.S. Bureau of the Census Public Law (PL) 94-171 data. The block_cen layer is an ARC/INFO point coverage....

49

Centroids, moments, and radii of gyration  

Science.gov (United States)

Computer program finds area, centroid, moments of inertia, product of inertia, and radii of gyration of closed curve given in graphical form such as on engineering drawing or strip chart. System is applicable when finding volume and center of gravity for liquid tanks, or for detecting buoyancy of hull sections.

Patch, R. W.

1979-01-01

50

A quantum generalization of intrinsic reaction coordinate using path integral centroid coordinates.  

Science.gov (United States)

We propose a generalization of the intrinsic reaction coordinate (IRC) for quantum many-body systems described in terms of the mass-weighted ring polymer centroids in the imaginary-time path integral theory. This novel kind of reaction coordinate, which may be called the "centroid IRC," corresponds to the minimum free energy path connecting reactant and product states with a least amount of reversible work applied to the center of masses of the quantum nuclei, i.e., the centroids. We provide a numerical procedure to obtain the centroid IRC based on first principles by combining ab initio path integral simulation with the string method. This approach is applied to NH(3) molecule and N(2)H(5) (-) ion as well as their deuterated isotopomers to study the importance of nuclear quantum effects in the intramolecular and intermolecular proton transfer reactions. We find that, in the intramolecular proton transfer (inversion) of NH(3), the free energy barrier for the centroid variables decreases with an amount of about 20% compared to the classical one at the room temperature. In the intermolecular proton transfer of N(2)H(5) (-), the centroid IRC is largely deviated from the "classical" IRC, and the free energy barrier is reduced by the quantum effects even more drastically. PMID:22583273

Shiga, Motoyuki; Fujisaki, Hiroshi

2012-05-14

51

A quantum generalization of intrinsic reaction coordinate using path integral centroid coordinates  

International Nuclear Information System (INIS)

We propose a generalization of the intrinsic reaction coordinate (IRC) for quantum many-body systems described in terms of the mass-weighted ring polymer centroids in the imaginary-time path integral theory. This novel kind of reaction coordinate, which may be called the ''centroid IRC,'' corresponds to the minimum free energy path connecting reactant and product states with a least amount of reversible work applied to the center of masses of the quantum nuclei, i.e., the centroids. We provide a numerical procedure to obtain the centroid IRC based on first principles by combining ab initio path integral simulation with the string method. This approach is applied to NH3 molecule and N2H5- ion as well as their deuterated isotopomers to study the importance of nuclear quantum effects in the intramolecular and intermolecular proton transfer reactions. We find that, in the intramolecular proton transfer (inversion) of NH3, the free energy barrier for the centroid variables decreases with an amount of about 20% compared to the classical one at the room temperature. In the intermolecular proton transfer of N2H5-, the centroid IRC is largely deviated from the ''classical'' IRC, and the free energy barrier is reduced by the quantum effects even more drastically.

52

Multiple Centroid Methodology to analyze genotype adaptability  

Directory of Open Access Journals (Sweden)

Full Text Available This study was carried out to propose a modification of the centroid method. The method is modified in thechoice of the ideotype, to be defined according to the researcher's interest, using the bi-segmented regression model, ratherthan based on experimental data, which limit the comparison of genotypes. To illustrate the method, one trait was simulatedin 25 genotypes in 8 environments. For the simulations and statistical analyses the software package GENES was used. Themultiple centroid is more flexible than the original centroid method, since it can be used according to the researcher's objectiveand the desired recommendation strategy. It is also readily interpretable for recommendation and unambiguous. Besides, thenumber of genotypes of interest can be compared, making a detailed study possible, by separating the genotypes intorecommendation classes.

Moysés Nascimento

2009-01-01

53

On Computing the Vertex Centroid of a Polyhedron  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Let $\\mathcal{P}$ be an $\\mathcal{H}$-polytope in $\\mathbb{R}^d$ with vertex set $V$. The vertex centroid is defined as the average of the vertices in $V$. We prove that computing the vertex centroid of an $\\mathcal{H}$-polytope is #P-hard. Moreover, we show that even just checking whether the vertex centroid lies in a given halfspace is already #P-hard for $\\mathcal{H}$-polytopes. We also consider the problem of approximating the vertex centroid by finding a point within an...

Elbassioni, Khaled; Tiwary, Hans Raj

2008-01-01

54

An efficient g-centroid location algorithm for cographs  

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Full Text Available In 1998, Pandu Rangan et al. Proved that locating the g-centroid for an arbitrary graph is 𝒩𝒫-hard by reducing the problem of finding the maximum clique size of a graph to the g-centroid location problem. They have also given an efficient polynomial time algorithm for locating the g-centroid for maximal outerplanar graphs, Ptolemaic graphs, and split graphs. In this paper, we present an O(nm time algorithm for locating the g-centroid for cographs, where n is the number of vertices and m is the number of edges of the graph.

V. Prakash

2005-07-01

55

An efficient g-centroid location algorithm for cographs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In 1998, Pandu Rangan et al. Proved that locating the g-centroid for an arbitrary graph is 𝒩𝒫-hard by reducing the problem of finding the maximum clique size of a graph to the g-centroid location problem. They have also given an efficient polynomial time algorithm for locating the g-centroid for maximal outerplanar graphs, Ptolemaic graphs, and split graphs. In this paper, we present an O(nm) time algorithm for locating the g-centroid for cographs, where n is...

Prakash, V.

2005-01-01

56

Weighted Centroid Correction Localization in Cellular Systems  

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Full Text Available Problem statement: There is a large demand for wireless Location-Based Service (LBS and it is provided by many wireless cellular systems. In process of positioning a Mobile Station (MS, the computing speed is as important as the positioning accuracy and the algorithm should also be resistant to environmental influences. Approach: A new positioning method based on Weighted Centroid Correction Localization (WCCL for wireless cellular systems is introduced in this article. Firstly, referring to the receiving-state of an MS in cellular systems, it computes a weighted centroid of surrounding Base Stations (BSs as a rough approximate position of the MS. Then, according to the distances between the MS and the BSs being less or bigger than the computed distances between the BSs and the weighted centroid, it corrects the coordinate of the weighted centroid towards the directions of the BSs by moving it closer or farther in turn. Results: According to our experiments, WCCL improves the positioning accuracy, as well as to provide a better resistance to environmental influences. Conclusion: As a modified centroid-based localization algorithm, WCCL obtains weighting factors from the receiving-state of MS in multi-cells structured cellular systems and obtains a better positioning result in cellular systems without updating the network equipment. Therefore, for the cellular positioning problem, WCCL algorithm can be an alternate solution.

Rong-Zheng Li

2011-01-01

57

Evidence for subduction beneath Gibraltar Arc and Andean regions from k-means earthquake centroids  

Science.gov (United States)

k-Means algorithms are widely used for determining clusters in broad types of datasets. Since zones of high seismic activity as plate boundary present diffuse seismicity patterns, the use of k-algorithm is a way to classify earthquakes in terms of centroids. Mapping centroids improves seismic visibility for further tectonic interpretation. We used selected datasets of earthquakes and determined the number of clusters or values of k by introducing the silhouette index method to check the validity of cluster numbers. By introducing magnitude size in the vectorial attributes, k-means algorithm provides a map of centroids that represents the location of high seismic energy, which is useful in seismic risk assessment. By including the depth of seismic events as the main attribute, we obtained spatiotemporal variations of centroids, which improve the image resolution of seismicity at depth to find out the underlying dynamic process. This has been achieved in subduction zone of Chile where the presence of slab is reflected by centroid distribution. The method is particularly relevant to complex seismic zones where controversial geodynamic models are reported such as the Gibraltar Arc. Resulting model supports W-oriented subduction underlying many parts of the Gibraltar zone.

Ramdani, Faiçal; Kettani, Omar; Tadili, Benaissa

2015-01-01

58

CHARGE CENTROID DETERMINATION IN FIELD-EFFECT EXPERIMENTS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents a new method for making field-effect measurements in low-conductivity materials. The method complements conventional field effect methods by providing for the determination of the charge centroid of the field-induced charge.

Senturia, S.; Rubinstein, J.; Azoury, S.; Adler, D.

1981-01-01

59

A variational centroid density procedure for the calculation of transmission coefficients for asymmetric barriers at low temperature  

International Nuclear Information System (INIS)

The low temperature behavior of the centroid density method of Voth, Chandler, and Miller (VCM) [J. Chem. Phys. 91, 7749 (1989)] is investigated for tunneling through a one-dimensional barrier. We find that the bottleneck for a quantum activated process as defined by VCM does not correspond to the classical bottleneck for the case of an asymmetric barrier. If the centroid density is constrained to be at the classical bottleneck for an asymmetric barrier, the centroid density method can give transmission coefficients that are too large by as much as five orders of magnitude. We follow a variational procedure, as suggested by VCM, whereby the best transmission coefficient is found by varying the position of the centroid until the minimum value for this transmission coefficient is obtained. This is a procedure that is readily generalizable to multidimensional systems. We present calculations on several test systems which show that this variational procedure greatly enhances the accuracy of the centroid density method compared to when the centroid is constrained to be at the barrier top. Furthermore, the relation of this procedure to the low temperature periodic orbit or ''instanton'' approach is discussed. copyright 1995 American Institute of Physics

60

Comparação dos métodos de determinação da estabilidade oxidativa de biodiesel B100, em mistura com antioxidantes sintéticos: aplicação do delineamento simplex-centroide com variável de processo Comparison of methods for determination of oxidative stability of B100 biodiesel mixed with synthetic antioxidants: application of simplex-centroid design with process variable  

Directory of Open Access Journals (Sweden)

Full Text Available The Rancimat and accelerated stove tests were used to determine the oxidative stability of B100 biodiesel mixed with synthetic antioxidants. The predictive equations, with process variable, were obtained by applying a simplex-centroid design. Regardless of the antioxidant used, all assays carried out with the accelerated stove test presented storage time longer than 177.88 d, the greatest value obtained by applying the Rancimat test. The t test, applied to the parameters containing the process variable, showed a statistically significant difference (at the level of 5% between the methods used.

João Rafael de Moraes Cini

2013-01-01

 
 
 
 
61

Comparação dos métodos de determinação da estabilidade oxidativa de biodiesel B100, em mistura com antioxidantes sintéticos: aplicação do delineamento simplex-centroide com variável de processo / Comparison of methods for determination of oxidative stability of B100 biodiesel mixed with synthetic antioxidants: application of simplex-centroid design with process variable  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese [...] Abstract in english The Rancimat and accelerated stove tests were used to determine the oxidative stability of B100 biodiesel mixed with synthetic antioxidants. The predictive equations, with process variable, were obtained by applying a simplex-centroid design. Regardless of the antioxidant used, all assays carried ou [...] t with the accelerated stove test presented storage time longer than 177.88 d, the greatest value obtained by applying the Rancimat test. The t test, applied to the parameters containing the process variable, showed a statistically significant difference (at the level of 5%) between the methods used.

João Rafael de Moraes, Cini; Dionísio, Borsato; Carmen Luísa Barbosa, Guedes; Hágata Cremasco da, Silva; Rodolfo Lopes, Coppo.

62

Constructing Centroid of a Triangle  

Science.gov (United States)

The page features and series of small photographs that automatically advance to illustrate, step by step, the construction of the centroid of a triangle. The illustration shows proper use of compass and straightedge.

Kocmoud's Math Page

2009-07-31

63

Halftoning with Weighted Centroidal Voronoi Tessellations  

Science.gov (United States)

We propose a method for halftoning grayscale images by drawing weighted centroidal Voronoi tessellations (WCVTs) with black lines on white image planes. Based on the fact that CVT approaches a uniform hexagonal lattice asymptotically, we derive a relationship of darkness between input grayscale images and the corresponding halftone images. Then the derived relationship is used for adjusting the contrast of the halftone images. Experimental results show that the generated halftone images can reproduce the original tone in the input images faithfully.

Inoue, Kohei; Urahama, Kiichi

64

Weighted Centroid Correction Localization in Cellular Systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Problem statement: There is a large demand for wireless Location-Based Service (LBS) and it is provided by many wireless cellular systems. In process of positioning a Mobile Station (MS), the computing speed is as important as the positioning accuracy and the algorithm should also be resistant to environmental influences. Approach: A new positioning method based on Weighted Centroid Correction Localization (WCCL) for wireless cellular systems is introduced in...

Rong-Zheng Li; Xin-Long Luo; Jia-Ru Lin

2011-01-01

65

Variable centroid control scheme over hypersonic tactical missile  

Science.gov (United States)

This paper presents a brand-new tactical missile control scheme—variable centroid vector control according to the international highlight in the field of missile control and the research status of hypersonic missile control in China. Four critical problems related with the new control method are included: improving phase control in the spinning missile single-channel control; establishing variable centroid controlled spinning missile attitude dynamics equations; analyzing variable centroid control strategies and analyzing the stability of the controlled missile and implementing robust control. The achievements and results obtained are valuable and helpful to the theoretical explorations and engineering applications.

Yi, Yan; Zhou, Fengqi

2003-12-01

66

Point estimation of root finding methods  

CERN Document Server

This book sets out to state computationally verifiable initial conditions for predicting the immediate appearance of the guaranteed and fast convergence of iterative root finding methods. Attention is paid to iterative methods for simultaneous determination of polynomial zeros in the spirit of Smale's point estimation theory, introduced in 1986. Some basic concepts and Smale's theory for Newton's method, together with its modifications and higher-order methods, are presented in the first two chapters. The remaining chapters contain the recent author's results on initial conditions guaranteing convergence of a wide class of iterative methods for solving algebraic equations. These conditions are of practical interest since they depend only on available data, the information of a function whose zeros are sought and initial approximations. The convergence approach presented can be applied in designing a package for the simultaneous approximation of polynomial zeros.

2008-01-01

67

Analysis of the positon resolution in centroid measurements in MWPC  

International Nuclear Information System (INIS)

Resolution limits in avalanche localization along the anode wires of an MWPC with cathodes connected by resistors and equally spaced amplifiers, are evaluated. A simple weighted-centroid method and a highly linear method based on a linear centroid finding filter, are considered. The contributions to the variance of the estimator of the avalanche position, due to the series noise of the amplifiers and to the thermal noise of the resistive line are separately calculated and compared. A comparison is made with the resolution of the MWPC with isolated cathodes. The calculations are performed with a distributed model of the diffusive line formed by the cathodes and the resistors. A comparison is also made with the results obtained with a simple lumped model of the diffusive line. A number of graphs useful in determining the best parameters of a MWPC, with a specified position and time resolution, are given. It has been found that, for short resolution times, an MWPC with cathodes connected by resitors presents better resolution (lower variance of the estimator of the avalanche position) than an MWPC with isolated cathodes. Conversely, for long resolution times, the variance of the estimator of the avalanche position is lower in an MWPC with isolated cathodes. (orig.)

68

Centroid of a Polygon--Three Views.  

Science.gov (United States)

Investigates the idea of the center of mass of a polygon and illustrates centroids of polygons. Connects physics, mathematics, and technology to produces results that serve to generalize the notion of centroid to polygons other than triangles. (KHR)

Shilgalis, Thomas W.; Benson, Carol T.

2001-01-01

69

Comparison of Blaugrund and Monte Carlo centroid-shift calculations  

International Nuclear Information System (INIS)

A comparison of Blaugrund and Monte Carlo centroid-shift calculations is presented. We find that the two methods of calculation agree to within 15% if the lifetime is greater than several times the flight time between collisions. The differences are systematic and hence predictable. These discrepancies depend only weakly on the reduced energy parameter epsilon and are a function of the mass ratio only when the projectile-target mass ratio is close to unity. Furthermore, the discrepancies between these methods of calculation only show a weak dependence on the choice of atomic interaction potential. On the other hand, for lifetimes that are shorter than a few times the flight time between collisions, the situation is more complex. (orig.)

70

Maser Source Finding Methods in HOPS  

CERN Document Server

The {\\bf H}$_2${\\bf O} Southern Galactic {\\bf P}lane {\\bf S}urvey (HOPS) has observed 100 square degrees of the Galactic plane, using the Mopra radio telescope to search for emission from multiple spectral lines in the 12\\,mm band (19.5\\,--\\,27.5\\,GHz). Perhaps the most important of these spectral lines is the 22.2\\,GHz water maser transition. We describe the methods used to identify water maser candidates and subsequent confirmation of the sources. Our methods involve a simple determination of likely candidates by searching peak emission maps, utilising the intrinsic nature of water maser emission - spatially unresolved and spectrally narrow-lined. We estimate completeness limits and compare our method with results from the {\\sc Duchamp} source finder. We find that the two methods perform similarly. We conclude that the similarity in performance is due to the intrinsic limitation of the noise characteristics of the data. The advantages of our method are that it is slightly more efficient in eliminating spuri...

Walsh, Andrew J; Longmore, Steven; Jordan, Christopher H; Lowe, Vicki

2011-01-01

71

Method for finding bunched beam instability thresholds  

International Nuclear Information System (INIS)

At high intensity, a short range wake field can distort the beam's potential well and thereby change the stationary distribution. It is now known that if this is not taken into account, instability thresholds will be incorrectly predicted. A numerical method exists for solving the linearized Vlasov equation for the self-consistent case, including the distortion to the stationary distribution, and finding such thresholds. We have found physical explanations for the eigenmodes and instability thresholds predicted in this method. As a result, a much simpler stability criterion has been found. The criterion is simple in that it depends only on the stationary distribution and does not require solution of the linearized Vlasov equation. (author)

72

Content Based Image Retrieval by using Multi Layer Centroid Contour Distance  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper we present a new approach to measuring similarity between two shape of object. In conventional method, centroid contour distance (CCD is formed by measuring distance between centroid (center and boundary of object, but this method cannot capture if an object have multiple boundary in the same angle. We develop a novel approach feature shape by measuring distance between centroid (center and boundary of object that can capture multiple boundaries in the same angle or multi-layer centroid contour distance (MLCCD. The experiment result on simulation dataset and plankton dataset show that the proposed method (MLCCD better than the conventional method (CCD.

Kohei Arai

2013-03-01

73

Content Based Image Retrieval by using Multi Layer Centroid Contour Distance  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we present a new approach to measuring similarity between two shape of object. In conventional method, centroid contour distance (CCD) is formed by measuring distance between centroid (center) and boundary of object, but this method cannot capture if an object have multiple boundary in the same angle. We develop a novel approach feature shape by measuring distance between centroid (center) and boundary of object that can capture multiple boundaries in the same angle or multi-lay...

Kohei Arai; Cahya Rahmad

2013-01-01

74

Quantum spatial superresolution by optical centroid measurements  

CERN Document Server

Quantum lithography (QL) has been suggested as a means of achieving enhanced spatial resolution for optical imaging, but its realization has been held back by the low multi-photon detection rates of recording materials. Recently, an optical centroid measurement (OCM) procedure was proposed as a way to obtain spatial resolution enhancement identical to that of QL but with higher detection efficiency (M. Tsang, Phys. Rev. Lett. 102, 253601, 2009). Here we describe a variation of the OCM method with still higher detection efficiency based on the use of photon-number-resolving detection. We also report laboratory results for two-photon interference. We compare these results with those of the standard QL method based on multi-photon detection and show that the new method leads to superresolution but with higher detection efficiency.

Shin, Heedeuk; Chang, Hye Jeong; Boyd, Robert W

2011-01-01

75

Intelligent systems for analyzing soccer games: The weighted centroid  

Directory of Open Access Journals (Sweden)

Full Text Available New, intelligent systems have been developed recently to improve the quality of match analysis. These systems analyze the tactical behavior of the teams. However, the existing methods leave room for improvement. Thus, the main goal of this study is to refine the team centroid metric by considering all of the players on the team and the ball position. Furthermore, this study analyzes the relation-ship between the centroids of the two opposing teams. One 11-on-11 soccer match was analyzed to test the new centroid algorithm. The results provided strong evidence of the positive relation between the centroids of the two teams over time in the x-axis (rs= 0.781 and the x-axis (rs= 0.707. This study confirmed the results of previous studies that analyzed the relationship between team centroids. Furthermore, it was possible to prove the effectiveness of the new tactical metric and its relevance for adding information during a match.

Filipe Manuel Clemente

2014-11-01

76

Maser Source Finding Methods in HOPS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The {\\bf H}$_2${\\bf O} Southern Galactic {\\bf P}lane {\\bf S}urvey (HOPS) has observed 100 square degrees of the Galactic plane, using the Mopra radio telescope to search for emission from multiple spectral lines in the 12\\,mm band (19.5\\,--\\,27.5\\,GHz). Perhaps the most important of these spectral lines is the 22.2\\,GHz water maser transition. We describe the methods used to identify water maser candidates and subsequent confirmation of the sources. Our methods involve a sim...

Walsh, Andrew J.; Purcell, Cormac; Longmore, Steven; Jordan, Christopher H.; Lowe, Vicki

2011-01-01

77

On Centroidal Voronoi Tessellation--Energy Smoothness and Fast Computation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Centroidal Voronoi tessellation (CVT) is a particular type of Voronoi tessellation that has many applications in computational sciences and engineering, including computer graphics. The prevail- ing method for computing CVT is Lloyd's method, which has linear convergence and is inefficient in practice. We develop new efficient methods for CVT computation and demonstrate the fast convergence of these methods. Specifically, we show that the CVT energy function has 2nd order smoothness for conve...

Liu, Yang; Wang, Wenping; Le?vy, Bruno; Sun, Feng; Yan, Dong-ming; Lu, Lin; Yang, Chenglei

2009-01-01

78

A Doppler centroid estimation algorithm for SAR systems optimized for the quasi-homogeneous source  

Science.gov (United States)

Radar signal processing applications frequently require an estimate of the Doppler centroid of a received signal. The Doppler centroid estimate is required for synthetic aperture radar (SAR) processing. It is also required for some applications involving target motion estimation and antenna pointing direction estimation. In some cases, the Doppler centroid can be accurately estimated based on available information regarding the terrain topography, the relative motion between the sensor and the terrain, and the antenna pointing direction. Often, the accuracy of the Doppler centroid estimate can be improved by analyzing the characteristics of the received SAR signal. This kind of signal processing is also referred to as clutterlock processing. A Doppler centroid estimation (DCE) algorithm is described which contains a linear estimator optimized for the type of terrain surface that can be modeled by a quasi-homogeneous source (QHS). Information on the following topics is presented: (1) an introduction to the theory of Doppler centroid estimation; (2) analysis of the performance characteristics of previously reported DCE algorithms; (3) comparison of these analysis results with experimental results; (4) a description and performance analysis of a Doppler centroid estimator which is optimized for a QHS; and (5) comparison of the performance of the optimal QHS Doppler centroid estimator with that of previously reported methods.

Jin, Michael Y.

1989-01-01

79

Particle identification by modified Bragg-curve centroid detection  

International Nuclear Information System (INIS)

A new article identification method based on the measurement of Bragg-curve centroids using a gas-filled ionization chamber has been improved for detection of low-energy particles around 1 MeV per nucleon by introducing a nonuniform distribution of resistance on the anode electrode. Almost the same quality of Z-resolutions as in the conventional ?E-E method could be obtained up to Z=19. (orig.)

80

Statistical Properties of Line Centroid Velocities and Centroid Velocity Increments in Compressible Turbulence  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have calculated probability density functions (PDFs) of centroid velociti and centroid velocity increments of line profiles computed from the output of a 512 simulation of compressible turbulence. The PDFs of centroid velocities calculated over the whole data cube are roughly Gaussian. On a smaller scale, non-Gaussian PDFs are observed in some cases. However, this is far from being the rule, and most of the distributions show relatively minor deviations from a Gaussian. By contrast, PDFs o...

Lis, D. C.; Pety, J.; Phillips, T. G.; Falgarone, E.

1996-01-01

 
 
 
 
81

Systematic shifts of evaluated charge centroid for the cathode read-out multiwire proportional chamber  

International Nuclear Information System (INIS)

We have investigated the systematic error associtated with the charge centroid evaluation for the cathode read-out multiwire proportional chamber. Correction curves for the systematic error according to six centroid finding algorithms have been obtained by using the charge distribution calculated in a simple electrostatic mode. They have been experimentally examined and proved to be essential for the accurate determination of the irradiated position. (orig.)

82

Properties of Planet-induced Deviations in the Astrometric Microlensing Centroid Shift Trajectory  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we investigate the properties of the planet-induced deviations in the trajectory of the microlensed source star centroid motion (astrometric curve) and the correlations between the astrometric and photometric deviations. For this, we construct vector field maps of excess centroid shifts. Fromthe investigation of the maps, we find that the astrometric deviation is closely correlated with the photometric one. The astrometric deviation increases as the photometri...

Han, Cheongho; Lee, Chunguk

2001-01-01

83

Measuring the centroid gain of a Shack-Hartmann quad-cell wavefront sensor by using slope discrepancy  

Science.gov (United States)

Shack-Hartmann wavefront sensors (SH WFS) are used by many adaptive optics (AO) systems to measure the wavefront. In this WFS, the centroid of the spots is proportional to the wavefront slope. If the detectors consist of 2×2 quad cells, as is the case in most astronomical AO systems, then the centroid measurement is proportional to the centroid gain. This quantity varies with the strength of the atmospheric turbulence and the angular extent of the beacon. The benefits of knowing the centroid gain and current techniques to measure it are discussed. A new method is presented, which takes advantage of the fact that, in a SH-WFS-based AO system, there are usually more measurements than actuators. Centroids in the null space of the wavefront reconstructor, called slope discrepancy measurements, contain information about the centroid gain. Tests using the W. M. Keck Observatory AO system demonstrate the accuracy of the algorithm.

van Dam, Marcos A.

2005-08-01

84

Improving the Initial Centroids of k-means Clustering Algorithm to Generalize its Applicability  

Science.gov (United States)

k-means is one of the most widely used partition based clustering algorithm. But the initial centroids generated randomly by the k-means algorithm cause the algorithm to converge at the local optimum. So to make k-means algorithm globally optimum, the initial centroids must be selected carefully rather than randomly. Though many researchers have already been carried out for the enhancement of k-means algorithm, they have their own limitations. In this paper a new method to formulate the initial centroids is proposed which results in better clusters equally for uniform and non-uniform data sets.

Goyal, M.; Kumar, S.

2014-12-01

85

Centroid estimation by model-fitting from undersampled wavefront sensing images  

Science.gov (United States)

Wavefront sensing using a Shack-Hartmann sensor is a common method for estimating atmospheric phase distortion. A key step in processing the wavefront sensing data is to centroid the spots captured by a detector array. These centroids are used to estimate the local slopes which are then combined to give the overall wavefront reconstruction. The location of the centroid is however sensitive to the pixelisation of the detector array, especially in the presence of noise and when the measurements are aliased. We investigate how modelling can be employed to estimate the mean spot as well as the centroids. This approach is shown to be particularly advantageous when the object is extended. Both simulated and real data are used to verify the proposed method.

Leung, W.-Y. V.; Tallon, M.; Lane, R. G.

2002-01-01

86

CentroidHomfold-LAST: accurate prediction of RNA secondary structure using automatically collected homologous sequences  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Although secondary structure predictions of an individual RNA sequence have been widely used in a number of sequence analyses of RNAs, accuracy is still limited. Recently, we proposed a method (called ‘CentroidHomfold’), which includes information about homologous sequences into the prediction of the secondary structure of the target sequence, and showed that it substantially improved the performance of secondary structure predictions. CentroidHomfold, however, forces users to prepare hom...

Hamada, Michiaki; Yamada, Koichiro; Sato, Kengo; Frith, Martin C.; Asai, Kiyoshi

2011-01-01

87

Conjugate gradient method for finding fundamental solitary waves  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Conjugate Gradient method (CGM) is known to be the fastest generic iterative method for solving linear systems with symmetric sign definite matrices. In this paper, we modify this method so that it could find fundamental solitary waves of nonlinear Hamiltonian equations. The main obstacle that such a modified CGM overcomes is that the operator of the equation linearized about a solitary wave is not sign definite. Instead, it has a finite number of eigenvalues on the oppo...

Lakoba, Taras I.

2009-01-01

88

Radiographic measures of thoracic kyphosis in osteoporosis: Cobb and vertebral centroid angles  

International Nuclear Information System (INIS)

Several measures can quantify thoracic kyphosis from radiographs, yet their suitability for people with osteoporosis remains uncertain. The aim of this study was to examine the validity and reliability of the vertebral centroid and Cobb angles in people with osteoporosis. Lateral radiographs of the thoracic spine were captured in 31 elderly women with osteoporosis. Thoracic kyphosis was measured globally (T1-T12) and regionally (T4-T9) using Cobb and vertebral centroid angles. Multisegmental curvature was also measured by fitting polynomial functions to the thoracic curvature profile. Canonical and Pearson correlations were used to examine correspondence; agreement between measures was examined with linear regression. Moderate to high intra- and inter-rater reliability was achieved (SEM = 0.9-4.0 ). Concurrent validity of the simple measures was established against multisegmental curvature (r = 0.88-0.98). Strong association was observed between the Cobb and centroid angles globally (r = 0.84) and regionally (r 0.83). Correspondence between measures was moderate for the Cobb method (r 0.72), yet stronger for the centroid method (r = 0.80). The Cobb angle was 20% greater for regional measures due to the influence of endplate tilt. Regional Cobb and centroid angles are valid and reliable measures of thoracic kyphosis in people with osteoporosis. However, the Cobb angle is biased by endplate tilt, suggesting that the centroid angle is more appropriate for this populationle is more appropriate for this population. (orig.)

89

A new method for finding vacua in string phenomenology  

Energy Technology Data Exchange (ETDEWEB)

One of the central problems of string-phenomenology is to find stable vacua in the four dimensional effective theories which result from compactification. We present an algorithmic method to find all of the vacua of any given string-phenomenological system in a huge class. In particular, this paper reviews and then extends hep-th/0606122 to include various nonperturbative effects. These include gaugino condensation and instantonic contributions to the superpotential. (authors)

Gray, James [Institut d' Astrophysique de Paris and APC, Universite de Paris 7, 98 bis, Bd. Arago 75014, Paris (France); He, Yang-Hui [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom)]|[Merton College, Oxford, OX1 4JD and Mathematical Institute, Oxford University, Oxford (United Kingdom); Ilderton, Anton [School of Mathematics and Statistics, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Lukas, Andre [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom)

2007-05-15

90

A new method for finding vacua in string phenomenology  

International Nuclear Information System (INIS)

One of the central problems of string-phenomenology is to find stable vacua in the four dimensional effective theories which result from compactification. We present an algorithmic method to find all of the vacua of any given string-phenomenological system in a huge class. In particular, this paper reviews and then extends hep-th/0606122 to include various nonperturbative effects. These include gaugino condensation and instantonic contributions to the superpotential. (authors)

91

Global Optimization of Centroidal Voronoi Tessellation with Monte Carlo Approach.  

Science.gov (United States)

Centroidal Voronoi tessellation (CVT) is a widely used geometric structure in applications including mesh generation, vector quantization and image processing. Global optimization of the CVT function is important in these applications. With numerical evidences, we show that the CVT function is highly non-convex and has many local minima and therefore the global optimization of the CVT function is nontrivial. We apply the method of {\\em Monte Carlo with minimization} (MCM) to optimizing the CVT function globally and demonstrate its efficacy in producing much improved results compared with two other global optimization methods. PMID:22291151

Lu, Lin; Sun, Feng; Pan, Hao; Wang, Wenping

2012-01-26

92

The centroid of extended affine and root graded Lie algebras  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We develop general results on centroids of Lie algebras and apply them to determine the centroid of extended affine Lie algebras, loop-like and Kac-Moody Lie algebras, and Lie algebras graded by finite root systems.

Benkart, Georgia; Neher, Erhard

2005-01-01

93

Biased gradient squared descent saddle point finding method.  

Science.gov (United States)

The harmonic approximation to transition state theory simplifies the problem of calculating a chemical reaction rate to identifying relevant low energy saddle points in a chemical system. Here, we present a saddle point finding method which does not require knowledge of specific product states. In the method, the potential energy landscape is transformed into the square of the gradient, which converts all critical points of the original potential energy surface into global minima. A biasing term is added to the gradient squared landscape to stabilize the low energy saddle points near a minimum of interest, and destabilize other critical points. We demonstrate that this method is competitive with the dimer min-mode following method in terms of the number of force evaluations required to find a set of low-energy saddle points around a reactant minimum. PMID:24852525

Duncan, Juliana; Wu, Qiliang; Promislow, Keith; Henkelman, Graeme

2014-05-21

94

Path finding methods accounting for stoichiometry in metabolic networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Graph-based methods have been widely used for the analysis of biological networks. Their application to metabolic networks has been much discussed, in particular noting that an important weakness in such methods is that reaction stoichiometry is neglected. In this study, we show that reaction stoichiometry can be incorporated into path-finding approaches via mixed-integer linear programming. This major advance at the modeling level results in improved prediction of topological and functional ...

Pey, Jon; Prada, Joaqui?n; Beasley, John E.; Planes, Francisco J.

2011-01-01

95

EPA flow reference method testing and analysis: Findings report. Appendices  

International Nuclear Information System (INIS)

In the summer of 1997, the US Environmental Protection Agency (EPA) conducted a series of week-long field tests at three electric utility sites to evaluate potential improvements to Method 2, EPA's test method for measuring flue gas volumetric flow in stacks. The findings from that study are presented in document EPA/430-R-99-009a (NTIS Order Number PB99-150286). This document contains 10 appendices for that report

96

Centroid neural network for unsupervised competitive learning.  

Science.gov (United States)

An unsupervised competitive learning algorithm based on the classical -means clustering algorithm is proposed. The proposed learning algorithm called the centroid neural network (CNN) estimates centroids of the related cluster groups in training date. This paper also explains algorithmic relationships among the CNN and some of the conventional unsupervised competitive learning algorithms including Kohonen's self-organizing map (SOM) and Kosko's differential competitive learning (DCL) algorithm. The CNN algorithm requires neither a predetermined schedule for learning coefficient nor a total number of iterations for clustering. The simulation results on clustering problems and image compression problems show that CNN converges much faster than conventional algorithms with compatible clustering quality while other algorithms may give unstable results depending on the initial values of the learning coefficient and the total number of iterations. PMID:18249781

Park, D C

2000-01-01

97

Centroid tracking with area array detectors  

Science.gov (United States)

A computer program (ALGEVAL) has been developed to simulate the position estimating behavior of a centroid estimator algorithm using data typical of optical point spread function data recorded by an area array detector. Typical results are shown of varying detector properties and optical point spread function types. The detector parameters currently available for study include read noise mean value, dark current mean value and spatial variation, charge transfer efficiency and point spread function location, saturation level, signal level and pixel size. The program is capable of calculating any order centroid using an array size from 2 x 2 to 15 x 15 pixels. The output of the program is either a performance map, histogram data or tabluar data. A number of further developments are recommended.

Glavich, T. A.

1986-01-01

98

The Burbea-Rao and Bhattacharyya centroids  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the centroid with respect to the class of information-theoretic Burbea-Rao divergences that generalize the celebrated Jensen-Shannon divergence by measuring the non-negative Jensen difference induced by a strictly convex and differentiable function. Although those Burbea-Rao divergences are symmetric by construction, they are not metric since they fail to satisfy the triangle inequality. We first explain how a particular symmetrization of Bregman divergences called ...

Nielsen, Frank; Boltz, Sylvain

2010-01-01

99

Comparing the performance of open loop centroiding techniques in the Raven MOAO system  

Science.gov (United States)

Raven is a multi-object adaptive optics (MOAO) demonstrator that will be mounted on the NIR Nasmyth platform of the Subaru telescope in May, 2014. Raven can use three open-loop NGS WFSs and an on-axis LGS WFS to control DMs in two separate science pick-off arms. Centroiding in open loop AO systems like Raven is more difficult than in closed loop AO systems because the Shack-Hartmann spots will not be driven to the same spot on a detector. Rather the spots can fall on any combination of pixels because the WFSs need to have sufficient dynamic range to measure the full turbulence. In this paper, we compare correlation and thresholded center of gravity (tCOG) centroiding methods in simulation, with Raven using its calibration unit, and on-sky. Each method has its own advantages. Correlation centroiding is superior to tCOG centroiding for faint NGSs and for extended sources (Raven open loop WFSs do not contain ADCs so spots will become elongated). We expect that correlation centroiding will push the limiting magnitude of Raven NGSs fainter by roughly one magnitude. Correlation centroiding is computationally more intensive, however, and actually will limit Raven's sampling rate for shorter integrations. Therefore, for bright stars with sufficiently high signal-to-noise, Raven can be run significantly faster and with superior performance using the tCOG method. Here we quantify both the performance and timing differences of these two centroiding methods in simulation, in the lab and on sky using Raven.

Andersen, David R.; Bradley, Colin; Gamroth, Darryl; Kerley, Dan; Lardière, Olivier; Véran, Jean-Pierre

2014-08-01

100

Findings  

Science.gov (United States)

... News & Meetings Science Education About NIGMS NIGMS Home > Science Education > Findings Findings All Issues Featured Scientists Multimedia Puzzles & Quizzes Subscribe Search all issues: Search by issue or topic Print Magazine Subscribe & Order a Free Copy Download PDF Version ...

 
 
 
 
101

Centroidal Voronoi Tesselation of Line Segments and Graphs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Centroidal Voronoi Tesselation (CVT) of points has many applications in geometry processing, including re-meshing and segmentation to name but a few. In this paper, we propose a new extension of CVT, generalized to graphs. Given a graph and a 3D polygonal surface, our method optimizes the placement of the vertices of the graph in such a way that the graph segments best approximate the shape of the surface. We formulate the computation of CVT for graphs as a continuous variational problem, and...

Lu, Lin; Le?vy, Bruno; Wang, Wenping

2009-01-01

102

Modified string method for finding minimum energy path  

CERN Document Server

We present an efficient algorithm to calculate minimum energy path (MEP) and energy barriers between locally minimum points on the multidimensional potential energy surface (PES). Our method dwells the original idea of the String method [Phys. Rev. B 66, 052301 (2002)] to evolve a smooth string along a direction normal to the string. The algorithm works by identifying hyperplanes, at each discretized point, normal to path. The intermediate configurations at these discretized points are then relaxed with their motion confined to their corresponding hyperplanes. Thus the problem of finding MEP on the PES is remodeled as a set of constrained minimization problem. This provides the flexibility of using minimization algorithms faster than the steepest descent method used in the simplified string method [J. Chem. Phys.,126(16),164103 (2007)]. In our method, since each intermediate image relaxes independently, if their step lengths are not controlled kinks can form easily. We propose using a mixing scheme to advance...

Samanta, Amit

2010-01-01

103

ASTROMETRIC IMAGE CENTROID DISPLACEMENTS DUE TO GRAVITATIONAL MICROLENSING BY THE ELLIS WORMHOLE  

International Nuclear Information System (INIS)

Continuing work initiated in an earlier publication, we study the gravitational microlensing effects of the Ellis wormhole in the weak-field limit. First, we find a suitable coordinate transformation, such that the lens equation and analytic expressions of the lensed image positions can become much simpler. Second, we prove that two images always appear for the weak-field lens by the Ellis wormhole. By using these analytic results, we discuss astrometric image centroid displacements due to gravitational microlensing by the Ellis wormhole. The astrometric image centroid trajectory by the Ellis wormhole is different from the standard one by a spherical lensing object that is expressed by the Schwarzschild metric. The anomalous shift of the image centroid by the Ellis wormhole lens is smaller than that by the Schwarzschild lens, provided that the impact parameter and the Einstein ring radius are the same. Therefore, the lensed image centroid by the Ellis wormhole moves slower. Such a difference, although it is very small, will be, in principle, applicable for detecting or constraining the Ellis wormhole by using future high-precision astrometry observations. In particular, the image centroid position gives us additional information, so that the parameter degeneracy existing in photometric microlensing can be partially broken. The anomalous shift reaches the order of a few micro arcseconds, if our galaxy hosts a wormhole with throat radius larger than 105 km. Wat radius larger than 105 km. When the source moves tangentially to the Einstein ring, for instance, the maximum position shift of the image centroid by the Ellis wormhole is 0.18 normalized by the Einstein ring radius. For the same source trajectory, the maximum difference between the centroid displacement by the Ellis wormhole lens and that by the Schwarzschild one with the same Einstein ring radius is -0.16 in the units of the Einstein radius, where the negative means that the astrometric displacement by the Ellis wormhole lens is smaller than that by the Schwarzschild one.

104

Computed tomographic methods and findings in adenomyomatosis of the gallbladder  

International Nuclear Information System (INIS)

Objective: To describe the characteristic CT imaging of adenomyomatosis of gallbladder and to improve the diagnostic knowledge of the disease. Methods: Eleven (5 males and 6 females, mean age = 43 years) patients with adenomyomatosis of gallbladder (4 diffuse, 2 segmental, and 5 fundal) confirmed by histopathology and performed by CT examination including plain, dynamic or multiphase enhancement and/or oral chole-graphic agent were reviewed. Results: Correct diagnosis was made in 7 of 11 patients (3 diffuse, 1 segmental, and 3 fundal). CT findings included segmental or diffuse gallbladder wall thickening in the involved area, associated with well defined and regular borders at both of the inner and outer layers. Significant CT findings of this entity were marked enhancement of wall layers during triphase contrast CT scanning, especially at delayed scans. Rokitansky-Aschoff sinuses were clearly shown by CT, Presenting as characteristic 'aureola' sign, when performed with application of a chole-graphic agent. Conclusion: Understanding the CT findings and using the optimal methods, the authors can use CT scan as a valuable method to help make the diagnosis in most cases of adenomyomatosis

105

S-curve centroiding error correction for star sensor  

Science.gov (United States)

A star centroiding error is a critical error in determining the accuracy of star sensors. As an important component of the systematic centroiding errors, the S-curve error is known for its well-regulated sine shape in a period of a pixel. On the basis of the frequency domain analysis, the analytical expression of an S-curve error is given in this paper. Accordingly, the sources resulting in the S-curve error are comprehensively investigated in this study along with their specific role in determining the characteristics of the S-curve error. Experiments are carried out using a real star sensor with the help of a precise turning table and a starlight simulator. The S-curve error data are collected, and a corresponding correction model in the form of a sine function is developed on the basis of the analytical expression. The correction of the S-curve error is well verified by the additional collected test data in the entire field of view (FOV) with an improvement of at least 35.7% in the star centroiding accuracy. Consequently, the calibration accuracy of the star sensor is also improved by 31.7% after the S-curve error correction. Further experiments are performed to investigate the S-curve errors of stars having saturated pixel energy, and the results of these experiments agree with those of the simulations to a large extent. All the analytical and experimental results indicate that the S-curve error has significant regularity and can be corrected using the proposed method.

Wei, Xinguo; Xu, Jia; Li, Jian; Yan, Jinyun; Zhang, Guangjun

2014-06-01

106

Basin constrained ?-dimer method for saddle point finding  

Science.gov (United States)

Within the harmonic approximation to transition state theory, the rate of escape from a reactant is calculated from local information at saddle points on the boundary of the state. The dimer minimum-mode following method can be used to find such saddle points. But as we show, dimer searches that are initiated from a reactant state of interest can converge to saddles that are not on the boundary of the reactant state. These disconnected saddles are not directly useful for calculating the escape rate. Additionally, the ratio of disconnected saddles can be large, especially when the dimer searches are initiated far from the reactant minimum. The reason that the method finds disconnected saddles is a result of the fact that the dimer method tracks local ridges, defined as the set of points where the force is perpendicular to the negative curvature mode, and not the true ridge, defined as the boundary of the set of points which minimize to the reactant. The local ridges tend to deviate from the true ridge away from saddle points. Furthermore, the local ridge can be discontinuous and have holes which allow the dimer to cross the true ridge and escape the initial state. To solve this problem, we employ an alternative definition of a local ridge based upon the minimum directional curvature of the isopotential hyperplane, ?, which provides additional local information to tune the dimer dynamics. We find that hyperplanes of ? = 0 pass through all saddle points but rarely intersect with the true ridge elsewhere. By restraining the dimer within the ? saddles is significantly reduced and the efficiency of finding connected saddles is increased.

Xiao, Penghao; Wu, Qiliang; Henkelman, Graeme

2014-10-01

107

Computing 2D Periodic Centroidal Voronoi Tessellation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we propose an efficient algorithm to compute the centroidal Voronoi tessellation in 2D periodic space. We first present a simple algorithm for constructing the periodic Voronoi diagram (PVD) from a Euclidean Voronoi diagram. The presented PVD algorithm considers only a small set of periodic copies of the input sites, which is more efficient than previous approaches requiring full copies of the sites (9 in 2D and 27 in 3D). The presented PVD algorithm is applied in a fast Newton...

Yan, Dong-ming; Wang, Kai; Le?vy, Bruno; Alonso, Laurent

2011-01-01

108

Comparison of decision tree methods for finding active objects  

CERN Document Server

The automated classification of objects from large catalogues or survey projects is an important task in many astronomical surveys. Faced with various classification algorithms, astronomers should select the method according to their requirements. Here we describe several kinds of decision trees for finding active objects by multi-wavelength data, such as REPTree, Random Tree, Decision Stump, Random Forest, J48, NBTree, AdTree. All decision tree approaches investigated are in the WEKA package. The classification performance of the methods is presented. In the process of classification by decision tree methods, the classification rules are easily obtained, moreover these rules are clear and easy to understand for astronomers. As a result, astronomers are inclined to prefer and apply them, thus know which attributes are important to discriminate celestial objects. The experimental results show that when various decision trees are applied in discriminating active objects (quasars, BL Lac objects and active galax...

Zhao, Y

2007-01-01

109

Automatic centroid detection and surface measurement with a digital Shack–Hartmann wavefront sensor  

International Nuclear Information System (INIS)

With the breakthrough of manufacturing technologies, the measurement of surface profiles is becoming a big issue. A Shack–Hartmann wavefront sensor (SHWS) provides a promising technology for non-contact surface measurement with a number of advantages over interferometry. The SHWS splits the incident wavefront into many subsections and transfers the distorted wavefront detection into the centroid measurement. So the accuracy of the centroid measurement determines the accuracy of the SHWS. In this paper, we have presented a new centroid measurement algorithm based on an adaptive thresholding and dynamic windowing method by utilizing image-processing techniques. Based on this centroid detection method, we have developed a digital SHWS system which can automatically detect centroids of focal spots, reconstruct the wavefront and measure the 3D profile of the surface. The system has been tested with various simulated and real surfaces such as flat surfaces, spherical and aspherical surfaces as well as deformable surfaces. The experimental results demonstrate that the system has good accuracy, repeatability and immunity to optical misalignment. The system is also suitable for on-line applications of surface measurement

110

A method for finding three-dimensional magnetic skeletons  

International Nuclear Information System (INIS)

Magnetic fields are an essential component of a plasma. In many astrophysical, solar, magnetospheric, and laboratory situations the magnetic field in the plasma can be very dynamic and form highly complex structures. One approach to unraveling these structures is to determine the magnetic skeleton of the field, a set of topological features that divide the magnetic field into topologically distinct domains. In general, the features of the magnetic skeleton are difficult to locate, in particular those given by numerical experiments. In this paper, we propose a new set of tools to find the skeleton of general magnetic fields including null points, spines, separatrix surfaces, and separators. This set of tools is found to be considerably better at finding the skeleton than the currently favored methods used in magnetohydrodynamics.

111

Reducing Centroid Error Through Model-Based Noise Reduction  

Science.gov (United States)

A method of processing the digitized output of a charge-coupled device (CCD) image detector has been devised to enable reduction of the error in computed centroid of the image of a point source of light. The method involves model-based estimation of, and correction for, the contributions of bias and noise to the image data. The method could be used to advantage in any of a variety of applications in which there are requirements for measuring precise locations of, and/or precisely aiming optical instruments toward, point light sources. In the present method, prior to normal operations of the CCD, one measures the point-spread function (PSF) of the telescope or other optical system used to project images on the CCD. The PSF is used to construct a database of spot models representing the nominal CCD pixel outputs for a point light source projected onto the CCD at various positions incremented by small fractions of a pixel.

Lee, Shinhak

2006-01-01

112

The effect of suprathreshold contrast on stimulus centroid and its implications for the perceived location of objects.  

Science.gov (United States)

Using an alignment task, we investigate the role of suprathreshold contrast upon the perceived location of asymmetric Gaussian-windowed stimuli. A model which extracts the centroid of the stimulus envelope between limits defined by contrast threshold accounts well for the observed variation in perceived position. This finding helps to explain previous discrepancies in the literature regarding the validity of stimulus centroid as a determinant of visual location. PMID:9893792

Whitaker, D; McGraw, P V

1998-11-01

113

Differential methods for finding independent sets in hypergraphs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

It is shown by using differential methods that if H is a double linear, r-uniform hypergraph with degree sequence {dv} such that any subhypergraph induced by a neighborhood has maximum degree less than m, then its independence number is at least ?vfr,m(dv), where fr,m(x) is a convex function satisfying fr,m(x) ? (logx)/x if r = 2 and c/x1/(r-1) if r ? 3, as x ? ?, and c = c(r, m) > 0 is a constant. The proof yields a polynomial-time algorithm for finding such an independent set in H....

Zang, W.; Li, Y.

2006-01-01

114

Centroid velocity statistics of molecular clouds  

Science.gov (United States)

We compute structure functions and Fourier spectra of 2D centroid velocity maps in order to study the gas dynamics of typical molecular clouds in numerical simulations. We account for a simplified treatment of time-dependent chemistry and the non-isothermal nature of the gas and use a 3D radiative transfer tool to model the CO line emission in a post-processing step. We perform simulations using three different initial mean number densities of n0 = 30, 100 and 300 cm-3 to span a range of typical values for dense gas clouds in the solar neighbourhood. We compute slopes of the centroid velocity increment structure functions (CVISF) and of Fourier spectra for different chemical components: the total density, H2 number density, 12CO number density as well as the integrated intensity of 12CO (J = 1 ? 0) and 13CO (J = 1 ? 0). We show that optical depth effects can significantly affect the slopes derived for the CVISF, which also leads to different scaling properties for the Fourier spectra. The slopes of CVISF and Fourier spectra for H2 are significantly steeper than those for the different CO tracers, independent of the density and the numerical resolution. This is due to the larger space-filling factor of H2 as it is better able to self-shield in diffuse regions, leading to a larger fractal co-dimension compared to CO.

Bertram, Erik; Konstandin, Lukas; Shetty, Rahul; Glover, Simon C. O.; Klessen, Ralf S.

2015-02-01

115

Measurement of centroid trajectory of Dragon-I electron beam  

International Nuclear Information System (INIS)

The control of the electron beam in an intense current linear induction accelerator (LIA) is very important. The center position of the electron beam and the beam profile are two important parameters which should be measured accurately. The setup of a time-resolved measurement system and a data processing method for determining the beam center position are introduced for the purpose of obtaining Dragon-I electron beam trajectory including beam profile. The actual results show that the centroid position error can be controlled in one to two pixels. the time-resolved beam centroid trajectory of Dragon-I (18.5 MeV, 2 kA, 90 ns) is obtained recently in 10 ns interval, 3 ns exposure time with a multi-frame gated camera. The results show that the screw movement of the electron beam is mainly limited in an area with a radius of 0.5 mm and the time-resolved diameters of the beam are 8.4 mm, 8.8 mm, 8.5 mm, 9.3 mm and 7.6 mm. These results have provided a very important support to several research areas such as beam trajectory tuning and beam transmission. (authors)

116

Transverse centroid oscillations in solenoidially focused beam transport lattices  

International Nuclear Information System (INIS)

Transverse centroid oscillations are analyzed for a beam in a solenoid transport lattice. Linear equations of motion are derived that describe small-amplitude centroid oscillations induced by displacement and rotational misalignments of the focusing solenoids in the transport lattice, dipole steering elements, and initial centroid offset errors. These equations are analyzed in a local rotating Larmor frame to derive complex-variable 'alignment functions' and 'bending functions' that efficiently describe the characteristics of the centroid oscillations induced by both mechanical misalignments of the solenoids and dipole steering elements. The alignment and bending functions depend only on the properties of the ideal lattice in the absence of errors and steering, and have associated expansion amplitudes set by the misalignments and steering fields, respectively. Applications of this formulation are presented for statistical analysis of centroid oscillations, calculation of actual lattice misalignments from centroid measurements, and optimal beam steering.

117

Interstellar cloud structure: The statistics of centroid velocities  

CERN Document Server

The investigation of the statistical properties of maps of line centroids has been used for almost 50 years, but there is still no general agreement on their interpretation. We try to quantify which properties of underlying turbulent velocity fields can be derived from centroid velocity maps, and we test conditions under which the scaling behaviour of the centroid velocities matches the scaling of the three-dimensional velocity field. Using fractal cloud models we study systematically the relation between three-dimensional density and velocity fields and the statistical properties of the produced line centroid maps. We put special attention to cases with large density fluctuations resembling supersonic interstellar turbulence. Starting from the Delta-variance analysis we derive a new tool to compute the scaling behaviour of the three-dimensional velocity field from observed intensity and centroid velocity maps. We provide two criteria to decide whether the information from the centroid velocities directly ref...

Ossenkopf, V; Lazarian, A; Stutzki, J

2006-01-01

118

Optimization of Existing Centroiding Algorithms for Shack Hartmann Sensor  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Three centroiding techniques to estimate the position of the spots in a Shack Hartmann sensor: Normalized Centre of Gravity (CoG), Iteratively Weighted Centre of Gravity (IWCoG) and Intensity Weighted (IWC) centroiding are studied in comparison. The spot pattern at the focal plane of a Shack Hartmann sensor was simulated by including the effect of a background noise. We present the results of optimization of the performance of each of the centroiding techniques as a function...

Vyas, Akondi; Roopashree, M. B.; Prasad, B. R.

2009-01-01

119

An Improved Centroid Algorithm in Wireless Sensor Network  

Directory of Open Access Journals (Sweden)

Full Text Available Due to the anisotropic network, the distribution of nodes is completely random, network topology is not uniform, through the centroid algorithm there are some errors between estimated position and actual position of nodes, "cluster effect" error is prone to made in the positioning process. In order to overcome the positioning error resulting, a modified centroid algorithm is proposed that adds the stage of a correction of node estimated position on the basis of the traditional centroid algorithm positioning completion.

Siwei Peng

2013-01-01

120

Micro-pixel accuracy centroid displacement estimation and detector calibration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Precise centroid estimation plays a critical role in accurate astrometry using telescope images. Conventional centroid estimation fits a template point spread function (PSF) to the image data. Because the PSF is typically not known to high accuracy due to wavefront aberrations and uncertainties in optical system, a simple Gaussian function is commonly used. PSF knowledge error leads to systematic errors in the conventional centroid estimation. In this paper, we present an ac...

Zhai, Chengxing; Shao, Mike; Goullioud, Renaud; Nemati, Bijan

2011-01-01

 
 
 
 
121

An Improved Centroid Algorithm in Wireless Sensor Network  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Due to the anisotropic network, the distribution of nodes is completely random, network topology is not uniform, through the centroid algorithm there are some errors between estimated position and actual position of nodes, "cluster effect" error is prone to made in the positioning process. In order to overcome the positioning error resulting, a modified centroid algorithm is proposed that adds the stage of a correction of node estimated position on the basis of the traditional centroid algori...

Siwei Peng; Hui Liu

2013-01-01

122

Accurate Alignment of Plasma Channels Based on Laser Centroid Oscillations  

International Nuclear Information System (INIS)

A technique has been developed to accurately align a laser beam through a plasma channel by minimizing the shift in laser centroid and angle at the channel outptut. If only the shift in centroid or angle is measured, then accurate alignment is provided by minimizing laser centroid motion at the channel exit as the channel properties are scanned. The improvement in alignment accuracy provided by this technique is important for minimizing electron beam pointing errors in laser plasma accelerators.

123

Star point centroid algorithm based on background forecast  

Science.gov (United States)

The calculation of star point centroid is a key step of improving star tracker measuring error. A star map photoed by APS detector includes several noises which have a great impact on veracity of calculation of star point centroid. Through analysis of characteristic of star map noise, an algorithm of calculation of star point centroid based on background forecast is presented in this paper. The experiment proves the validity of the algorithm. Comparing with classic algorithm, this algorithm not only improves veracity of calculation of star point centroid, but also does not need calibration data memory. This algorithm is applied successfully in a certain star tracker.

Wang, Jin; Zhao, Rujin; Zhu, Nan

2014-09-01

124

Comparison of decision tree methods for finding active objects  

Science.gov (United States)

The automated classification of objects from large catalogs or survey projects is an important task in many astronomical surveys. Faced with various classification algorithms, astronomers should select the method according to their requirements. Here we describe several kinds of decision trees for finding active objects by multi-wavelength data, such as REPTree, Random Tree, Decision Stump, Random Forest, J48, NBTree, AdTree. All decision tree approaches investigated are in the WEKA package. The classification performance of the methods is presented. In the process of classification by decision tree methods, the classification rules are easily obtained, moreover these rules are clear and easy to understand for astronomers. As a result, astronomers are inclined to prefer and apply them, thus know which attributes are important to discriminate celestial objects. The experimental results show that when various decision trees are applied in discriminating active objects (quasars, BL Lac objects and active galaxies) from non-active objects (stars and galaxies), ADTree is the best only in terms of accuracy, Decision Stump is the best only considering speed, J48 is the optimal choice considering both accuracy and speed.

Zhao, Yongheng; Zhang, Yanxia

125

Finding and characterising WHIM structures using the luminosity density method  

CERN Document Server

We have developed a new method to approach the missing baryons problem. We assume that the missing baryons reside in a form of Warm Hot Intergalactic Medium, i.e. the WHIM. Our method consists of (a) detecting the coherent large scale structure in the spatial distribution of galaxies that traces the Cosmic Web and that in hydrodynamical simulations is associated to the WHIM, (b) map its luminosity into a galaxy luminosity density field, (c) use numerical simulations to relate the luminosity density to the density of the WHIM, (d) apply this relation to real data to trace the WHIM using the observed galaxy luminosities in the Sloan Digital Sky Survey and 2dF redshift surveys. In our application we find evidence for the WHIM along the line of sight to the Sculptor Wall, at redshifts consistent with the recently reported X-ray absorption line detections. Our indirect WHIM detection technique complements the standard method based on the detection of characteristic X-ray absorption lines, showing that the galaxy l...

Nevalainen, J; Tempel, E; Branchini, E; Roncarelli, M; Giocoli, C; Heinamaki, P; Saar, E; Bonamente, M; Einasto, M; Finoguenov, A; Kaastra, J; Lindfors, E; Nurmi, P; Ueda, Y

2014-01-01

126

Centroid and moments of an area using a digitizer  

Science.gov (United States)

The centroid and moments of an area program provides the centroid, moments of inertia, product of inertia, radii of gyration, and area of any closed planar geometric figure. The figure must be available in graphic form and is digitized once with chart digitizer (graphic tablet). The digitizer origin may be set anywhere on the digitizer table. After digitizing, fifteen quantities are calculated and displayed: (1) area (2) moment of inertia of area with respect to digitizer x-axis, (3) moment of inertia of area with respect to digitizer y-axis, (4) product of inertia of area with respect to digitizer axes, (5) first moment of x for digitizer axes, (6) first moment of y for digitizer axes, (7) x coordinate of centroid, (8) y coordinate of centroid, (9) moment of area inertia of with respect to x axis through centroid, (10) moment of inertia of area with respect to y axis through centroid, (11) product inertia of area with respect to x and y axes through centroid, (12) polar moment of inertia of area around centroid, (13) radius of gyration about digitizer x axis, (14) radius of gyration about digitizer y-axis; and (15) variance in the x-direction.

Patch, R. W.

1976-01-01

127

Transverse centroid oscillations in solenoidially focused beam transport lattices  

International Nuclear Information System (INIS)

Linear equations of motion are derived that describe small-amplitude centroid oscillations induced by displacement and rotational misalignments of the focusing solenoids in the transport lattice, dipole steering elements, and initial centroid offset errors. These equations are analyzed in a local rotating Larmor frame to derive complex-variable 'alignment functions' and 'bending functions' that efficiently describe the characteristics of the centroid oscillations induced by mechanical misalignments of the solenoids and dipole steering elements. The alignment and bending functions depend only on properties of the ideal lattice in the absence of errors and steering and have associated expansion amplitudes set by the misalignments and steering fields. Applications of this formulation are presented for statistical analysis of centroid deviations, calculation of actual lattice misalignments from centroid measurements, and optimal beam steering

128

Ambiguity Of Doppler Centroid In Synthetic-Aperture Radar  

Science.gov (United States)

Paper discusses performances of two algorithms for resolution of ambiguity in estimated Doppler centroid frequency of echoes in synthetic-aperture radar. One based on range-cross-correlation technique, other based on multiple-pulse-repetition-frequency technique.

Chang, Chi-Yung; Curlander, John C.

1991-01-01

129

Centroid-moment tensor solutions for April-June 1989  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Centroid-moment tensor solutions are presented for 226 earthquakes that occurred during the second quarter of 1989. The solutions are obtained using corrections for aspherical Earth structure. © 1990.

Dziewonski, Am; Ekstro?m, G.; Woodhouse, Jh; Zwart, G.

1990-01-01

130

#A #characterization of the centroid of a prime ring  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We characterize certain maps by their action on a fixed polynomial in noncommuting variables on algebras satisfying certain d -freeness condition. Consequently, a characterization of the centroid of a prime ring is obtained.

Benkovic?, Dominik; Eremita, Daniel; Vukman, Joso

2012-01-01

131

Refinement of Magellan radiometric correction using range centroid estimation  

Science.gov (United States)

The Magellan (MGN) synthetic aperture radar (SAR) processing radiometric compensation algorithm is described, and the effective pointing error caused by the terrain is examined. It is shown how the range centroid can be computed from spacecraft ancillary data with an accurate topographic model. In cases where such data are not available, a technique is presented to estimate the range centroid from the coherent radar echoes. This technique is demonstrated using MGN SAR data.

Cheng, T.; Jin, M.; Curlander, J.

1992-01-01

132

Finding the Stationary States of Markov Chains by Iterative Methods  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we develop new methods for approximating dominant eigenvector of column-stochastic matrices. We analyze the Google matrix, and present an averaging scheme with linear rate of convergence in terms of 1-norm distance. For extending this convergence result onto general case, we assume existence of a positive row in the matrix. Our new numerical scheme, the Reduced Power Method (RPM), can be seen as a proper averaging of the power iterates of a reduced stochastic matrix. We analyze...

Nesterov, Yurii; Nemirovski, Arkadi

2012-01-01

133

Modified string method for finding minimum energy path  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present an efficient algorithm for calculating the minimum energy path (MEP) and energy barriers between local minima on a multidimensional potential energy surface (PES). Such paths play a central role in the understanding of transition pathways between metastable states. Our method relies on the original formulation of the string method [Phys. Rev. B ${\\bf 66}$, 052301 (2002)], i.e. to evolve a smooth curve along a direction normal to the curve. The algorithm works by p...

Samanta, Amit; E, Weinan

2010-01-01

134

Class hierarchy method to find Change-Proneness  

Directory of Open Access Journals (Sweden)

Full Text Available Finding Proneness of software is necessary to identify fault prone and change prone classes at earlier stages of development, so that those classes can be given special attention. Also to improves the quality and reliability of the software. For corrective and adaptive maintenance we require to make changes during the software evolution.As such changes cluster around number of key components in software, it is important to analyze the frequency of changes in individual classes and also to identify and show related changes in multiple classes. Early detection of fault prone and change prone classes can enables the developers and experts to spend their valuable time and resources on these areas of software. Prediction of change-prone and fault prone classes of a software is an active topic in the area of software engineering. Such prediction can be used to predict changes to different classes of a system from one release of software to the next release. Identifying the change-prone and fault prone classes in advance can helps to focus attention on these classes.In this paper we are focusing on finding dependency of software that can be chieved by estimating the proneness of Object Oriented Software. Two main types of proneness are associated with OO software. Fault Proneness and Change Proneness.

Malan V.Gaikwad

2011-01-01

135

Spectral-Element Centroid-Moment Tensor Inversions  

Science.gov (United States)

The recently developed spectral-element method (SEM) accurately simulates wave propagation in 3-D global and regional Earth models. In general, these 3-D synthetics significantly improve the waveform fit to the data. In this study, we use the SEM to calculate Fréchet derivatives for earthquake source parameters in fully 3-D Earth models. This enables us to perform Centroid-Moment Tensor (CMT) inversions for global and regional events. We use a variety of misfit criteria to obtain a robust estimate of the source parameters. On a global scale, we test the method for the deep 1994 Bolivia earthquake and the shallow 2001 Buj, India, event. We use 3-D model S20RTS (Ritsema et al. 1999) and crustal model CRUST2.0 (Bassin et al. 2000). The synthetics incorporate effects due to ellipticity, topography and bathymetry, attenuation, the oceans, rotation, and self-gravitation. In Southern California, we test the CMT algorithm for several small local events by using the new 3-D LA basin model developed by Süss et al. We use a local version of the SEM that honors the deep geometry of the basement and incorporates topography and bathymetry, attenuation, and shallow sediments.

Liu, Q.; Komatitsch, D.; Tromp, J.

2002-12-01

136

Bias in the centroid moment tensor for central Asian earthquakes: Evidence from regional surface wave data  

International Nuclear Information System (INIS)

Surface waves recorded on the Chinese Digital Seismic Network (CDSN) station Urumqi (WMQ) are analyzed for 26 centroid moment tensor (CMT) earthquakes located within an epicentral distance of 1300 km. Applying a simple grid search method for source parameter retrieval, I obtain revised estimates of the focal depth, fault strike, and seismic moment (M0) from amplitude spectra of Love and Rayleigh waves and compare these estimates with the CMT best double-couple solutions. The comparisons show that residuals are unbiased for focal depth and fault strike, where population spreads are ±13 km and ±17 degree, respectively. On the other hand, M0 estimates are found to be biased, with CMT M0 larger than regional estimates by an average of 0.27±0.04 log units. The results for focal depth and strike are consistent with previous global and regional studies comparing independent estimates with CMT results. Recent full-waveform modeling studies for central Asian earthquakes support the findings of bias in M0 estimates. I suggest that causes for M0 bias may be related to great thicknesses of continental crust in Hindu Kush and Tien Shan regions and to data censoring practices at small magnitudes. M0:mb scaling relationships for central Asian earthquakes show better agreement with western U.S. scaling when M0 estimates determined in this study are used. copyright 1998 American Geophysical Unioopyright 1998 American Geophysical Union

137

Variational method for finding periodic orbits in a general flow  

CERN Document Server

A variational principle for determining unstable periodic orbits of flows as well as unstable spatio-temporally periodic solutions of extended systems is proposed and implemented. An initial loop approximating a periodic solution is evolved in the space of loops toward a true periodic solution by a minimization of local errors along the loop. The ``\\descent'' partial differential equation that governs this evolution is an infinitesimal step version of the damped Newton-Raphson iteration. The feasibility of the method is demonstrated by its application to the H\\'enon-Heiles system, the circular restricted three-body problem, and the Kuramoto-Sivashinsky system in a weakly turbulent regime.

Lan, Y

2004-01-01

138

Esthesioneuroblastoma methods of intracranial extension: CT and MR imaging findings  

International Nuclear Information System (INIS)

Esthesioneuroblastoma (ENB) is an aggressive neuroectodermal malignancy in the upper nasal cavity with local infiltration and lymphatic or hematogenous metastasis. The purpose of this paper is to document three types of direct intracranial extensions by ENB using computed tomography (CT) and magnetic resonance imaging (MRI). Eleven patients with pathologically confirmed ENB were admitted in our hospital between December 2002 and December 2008. Their magnetic resonance (MR; n = 10) and CT (n = 8) images were retrospectively reviewed, and particular attention was paid to tumor location and extension, enhancement pattern, cervical lymph node metastasis, and Kadish stage. The majority of patients were male (8/11) with Kadish stage C tumor (10/11). Three types of direct intracranial extension by ENBs were put forward according to their MR and CT findings. The primary tumors were well-defined soft-tissue masses centered in the roof of the nasal cavity eroding into the paranasal sinuses (11/11), the contralateral nasal cavity (4/11), the cranial cavity (5/11), and the fossa orbitalis (3/11). The tumor parenchyma were hypointensity on T1-weighted images, heterogeneous hyperintensity on T2-weighted images, and isodensity or slight hyperdensity on CT images with scattered necroses (4/11) and marginal cysts(4/11). Their enhancements were significant and inhomogeneous. Cervical lymph nodes metastases were observed in four patients (4/11), but no pathologically proved distant meta but no pathologically proved distant metastasis was observed. Three types of direct intracranial extensions by ENB can be found on CT and MRI: cranio-orbital-nasal-communicating ENB, cranio-nasal-communicating ENB, and orbital-nasal-communicating ENB. (orig.)

139

Esthesioneuroblastoma methods of intracranial extension: CT and MR imaging findings  

Energy Technology Data Exchange (ETDEWEB)

Esthesioneuroblastoma (ENB) is an aggressive neuroectodermal malignancy in the upper nasal cavity with local infiltration and lymphatic or hematogenous metastasis. The purpose of this paper is to document three types of direct intracranial extensions by ENB using computed tomography (CT) and magnetic resonance imaging (MRI). Eleven patients with pathologically confirmed ENB were admitted in our hospital between December 2002 and December 2008. Their magnetic resonance (MR; n = 10) and CT (n = 8) images were retrospectively reviewed, and particular attention was paid to tumor location and extension, enhancement pattern, cervical lymph node metastasis, and Kadish stage. The majority of patients were male (8/11) with Kadish stage C tumor (10/11). Three types of direct intracranial extension by ENBs were put forward according to their MR and CT findings. The primary tumors were well-defined soft-tissue masses centered in the roof of the nasal cavity eroding into the paranasal sinuses (11/11), the contralateral nasal cavity (4/11), the cranial cavity (5/11), and the fossa orbitalis (3/11). The tumor parenchyma were hypointensity on T1-weighted images, heterogeneous hyperintensity on T2-weighted images, and isodensity or slight hyperdensity on CT images with scattered necroses (4/11) and marginal cysts(4/11). Their enhancements were significant and inhomogeneous. Cervical lymph nodes metastases were observed in four patients (4/11), but no pathologically proved distant metastasis was observed. Three types of direct intracranial extensions by ENB can be found on CT and MRI: cranio-orbital-nasal-communicating ENB, cranio-nasal-communicating ENB, and orbital-nasal-communicating ENB. (orig.)

Yu, Tian; Xu, Yi-Kai; Jia, Fei-Ge; Yang, Rui-Meng; Feng, Jie; Ye, Xiang-Hua; Qiu, Ying-Wei [Southern Medical University, Department of Medical Imaging Center, Nan Fang Hospital, Guangzhou, Guangdong (China); Li, Long [Chinese People' s Armed Police Forces, Department of Radiology, Guangdong Provincial Corps Hospital, Guangzhou (China); Duan, Gang; Wu, Yuan-Kui [Southern Medical University, Department of Radiology, Nan Fang Hospital, Guangzhou (China); Li, Hua-Yu [No. 458 Hospital of PLA, Department of Medical Imaging Center, Guangzhou (China)

2009-12-15

140

r-centroids and Franck-Condon factors of the SiO molecule  

International Nuclear Information System (INIS)

The r-centroids and Franck-Condon factors for the bands of the E1?+-X1?+ and a 3PIsub(r) - X1?+ systems of the astrophysically important SiO molecule have been determined. The characteristic bands of this molecule are found in the sunspots. The Franck-Condon factors are determined by the approximate analytical method of Jarmain and Fraser. The absence of the bands in these systems is explained. (orig.)

 
 
 
 
141

Gradient of the Objective Function for an Anisotropic Centroidal Voronoi Tessellation (CVT) - A revised, detailed derivation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In their recent article (2010), Levy and Liu introduced a generalization of Centroidal Voronoi Tessellation (CVT) - namely the Lp-CVT - that allows the computation of an anisotropic CVT over a sound mathematical framework. In this article a new objective function is defined, and both this function and its gradient are derived in closed-form for surfaces and volumes. This method opens a wide range of possibilities, also described in the paper, such as quad-dominant surface re...

Parigi, Giacomo; Piastra, Marco

2014-01-01

142

Accuracy Evaluation for Region Centroid-Based Registration of Fluorescent CLSM Imagery  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present an accuracy evaluation of a semiautomatic registration technique for 3D volume reconstruction from fluorescent confocal laser scanning microscope (CLSM) imagery. The presented semiautomatic method is designed based on our observations that (a) an accurate point selection is much harder than an accurate region (segment) selection for a human, (b) a centroid selection of any region is less accurate by a human than by a computer, and (c) registration based on structural shape ...

Lin Amy; Folberg Robert; Lee Sang-Chul; Bajcsy Peter

2006-01-01

143

Optimal properties of centroid-based classifiers for very high-dimensional data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We show that scale-adjusted versions of the centroid-based classifier enjoys optimal properties when used to discriminate between two very high-dimensional populations where the principal differences are in location. The scale adjustment removes the tendency of scale differences to confound differences in means. Certain other distance-based methods, for example, those founded on nearest-neighbor distance, do not have optimal performance in the sense that we propose. Our resu...

Hall, Peter; Pham, Tung

2010-01-01

144

A evolutionary method for finding communities in bipartite networks  

CERN Document Server

Common practice in community structure detection is to develop different methods for different classes of networks. Here, we first show that unipartite networks and directed networks can be uniformly represented as bipartite networks, and their modularity completely consist with that for bipartite networks. To optimize the bipartite modularity, we then present a modified adaptive genetic algorithm, called as MMOGA, which is especially suited for community structure detection. In MMOGA, we introduce a new measure for the informativeness of a locus instead of the standard deviation, which can exactly determine those loci to mutate. This measure is the bias between the distribution of a locus over the current population and the uniform distribution of the locus, i.e., Kull-back Divergence between them. Moreover, we develop a reassignment technique for differentiating the informative state a locus has attained from the random state at initial phase. Also we present a modified mutation rule which incorporating rel...

WeiHua, Zhan; Jihong, Guan; Shuigeng, Zhou

2010-01-01

145

A Statistical Study of Beam Centroid Oscillations in a Solenoid Transport Channel  

International Nuclear Information System (INIS)

A recent theory of transverse centroid oscillations in solenoidally focused beam transport lattices presented in Ref. (1) is applied to statistically analyze properties of the centroid orbit in the Neutralized Drift Compression Experiment (NDCX) at the Lawrence Berkeley National Laboratory. Contributions to the amplitude of the centroid oscillations from mechanical misalignments and initial centroid errors exiting the injector are analyzed. Measured values of the centroid appear consistent with expected alignment tolerances. Correction of these errors is discussed

146

Trunk muscle geometry and centroid location when twisting.  

Science.gov (United States)

The trunk muscles of the lumbar region were studied using magnetic resonance imaging (MRI) in five male volunteers placed in neutral and in two twisted postures. Using a CAD digitizing system, the positions of trunk muscle centroids and the cross-sectional areas of these muscles were measured from the transverse scans at 1 cm intervals from L2 to S1. Muscle lines of action were created by connecting the muscle centroids from the successive sections. Changes in cross-sectional areas and displacements of centroids in a three-dimensional coordinate system and the local two-dimensional coordinate system were estimated at each disc level. In the three-dimensional coordinate system, all muscle centroids were displaced when twisting. Thus, the locations and orientations of all muscle lines of action changed. In the local two-dimensional coordinate system, only the muscle centroids of four abdominal muscles were displaced. Most of these displacements occurred in the first 25 degrees of twisting. Higher up in the lumbar spine, the displacement was greater. The changes in moment arms were sometimes as great as twofold. Only the abdominal oblique muscles (AOM) changed their cross-sectional area significantly; the area of the right AOM ipsilateral to the side of twisting increased, while that of the left AOM was decreased. PMID:8478355

Tsuang, Y H; Novak, G J; Schipplein, O D; Hafezi, A; Trafimow, J H; Andersson, G B

1993-01-01

147

Plasma Channel Diagnostic Based on Laser Centroid Oscillations  

Science.gov (United States)

A technique has been developed for measuring the properties of discharge-based plasma channels by monitoring the centroid location of a laser beam exiting the channel as a function of input alignment offset between the laser and the channel. The centroid position of low-intensity (positions recorded to determine the channel shape and depth with an accuracy of a few %. In addition, accurate alignment of the laser beam through the plasma channel can be provided by minimizing laser centroid motion at the channel exit as the channel depth is scanned either by scanning the plasma density or the discharge timing. The improvement in alignment accuracy provided by this technique will be crucial for minimizing electron beam pointing errors in laser plasma accelerators.

Gonsalves, A. J.; Nakamura, K.; Lin, C.; Osterhoff, J.; Shiraishi, S.; Schroeder, C. B.; Geddes, C. G. R.; Tóth, Cs.; Esarey, E.; Leemans, W. P.

2010-11-01

148

Plasma channel diagnostic based on laser centroid oscillationsa)  

Science.gov (United States)

A technique has been developed for measuring the properties of discharge-based plasma channels by monitoring the centroid location of a laser beam exiting the channel as a function of input alignment offset between the laser and the channel. Experiments were performed using low-intensity (centroid position at the input of the channel and recording the exit position allow determination of the channel depth with an accuracy of a few percent, measurement of the transverse channel shape, and inference of the matched spot size. In addition, accurate alignment of the laser beam through the plasma channel is provided by minimizing laser centroid motion at the channel exit as the channel depth is scanned either by scanning the plasma density or the discharge timing. The improvement in alignment accuracy provided by this technique will be crucial for minimizing electron beam pointing errors in laser plasma accelerators.

Gonsalves, A. J.; Nakamura, K.; Lin, C.; Osterhoff, J.; Shiraishi, S.; Schroeder, C. B.; Geddes, C. G. R.; Tóth, Cs.; Esarey, E.; Leemans, W. P.

2010-05-01

149

Plasma Channel Diagnostic Based on Laser Centroid Oscillations  

International Nuclear Information System (INIS)

A technique has been developed for measuring the properties of discharge-based plasma channels by monitoring the centroid location of a laser beam exiting the channel as a function of input alignment offset between the laser and the channel. The centroid position of low-intensity (14Wcm-2) laser pulses focused at the input of a hydrogen-filled capillary discharge waveguide was scanned and the exit positions recorded to determine the channel shape and depth with an accuracy of a few %. In addition, accurate alignment of the laser beam through the plasma channel can be provided by minimizing laser centroid motion at the channel exit as the channel depth is scanned either by scanning the plasma density or the discharge timing. The improvement in alignment accuracy provided by this technique will be crucial for minimizing electron beam pointing errors in laser plasma accelerators.

150

Doppler centroid estimation ambiguity for synthetic aperture radars  

Science.gov (United States)

A technique for estimation of the Doppler centroid of an SAR in the presence of large uncertainty in antenna boresight pointing is described. Also investigated is the image degradation resulting from data processing that uses an ambiguous centroid. Two approaches for resolving ambiguities in Doppler centroid estimation (DCE) are presented: the range cross-correlation technique and the multiple-PRF (pulse repetition frequency) technique. Because other design factors control the PRF selection for SAR, a generalized algorithm is derived for PRFs not containing a common divisor. An example using the SIR-C parameters illustrates that this algorithm is capable of resolving the C-band DCE ambiguities for antenna pointing uncertainties of about 2-3 deg.

Chang, C. Y.; Curlander, J. C.

1989-01-01

151

Plasma Channel Diagnostic Based on Laser Centroid Oscillations  

International Nuclear Information System (INIS)

A technique has been developed for measuring the properties of discharge-based plasma channels by monitoring the centroid location of a laser beam exiting the channel as a function of input alignment offset between the laser and the channel. The centroid position of low-intensity (14 W cm-2) laser pulses focused at the input of a hydrogen-filled capillary discharge waveguide was scanned and the exit positions recorded to determine the channel shape and depth with an accuracy of a few %. In addition, accurate alignment of the laser beam through the plasma channel can be provided by minimizing laser centroid motion at the channel exit as the channel depth is scanned either by scanning the plasma density or the discharge timing. The improvement in alignment accuracy provided by this technique will be crucial for minimizing electron beam pointing errors in laser plasma accelerators.

152

A Prolog-based centroid algorithm for isovolume extraction from finite element torso simulations.  

Science.gov (United States)

Computer modeling and simulation of the human torso provides a rapid and non-invasive means to observe the effects of implanted defibrillators. The objective of this study was to improve a method of extracting data from an implanted defibrillator simulation for subsequent visualization. Electrical quantities, such as the potential and gradient fields, are computed at points throughout various regions of a three-dimensional (3-D) torso model via a finite element solution. Software is then implemented in the Prolog language to extract and visualize a subset of the data, from within any subregion of the model, satisfying a given declarative constraint. In past work, membership in these subsets had been determined solely by the electrical quantities at the vertices of the tetrahedral elements within the model along with an arbitrary choice made by the user. However, this study expands upon previous work to utilize an alternative means of classification, calculating the centroid of each tetrahedron and assigning electrical properties to these centroids based on the distances of each centroid to the four corners of the tetrahedron. After the modifications, it is expected that the extracted subsets of the model will represent the data in a more realistic and conservative manner and provide more insight into the process of defibrillation than previous methods of data extraction and visualization. PMID:11809317

Russomanno, David J; Hicks, Kathryn

2002-02-01

153

Relation between medium fluid temperature and centroid subchannel temperatures of a nuclear fuel bundle mock-up  

International Nuclear Information System (INIS)

The subchannel method used in nuclear fuel bundle thermal-hydraulic analysis lies in the statement that subchannel fluid temperatures are taken at mixed mean values. However, the development of mixing correlations and code assessment procedures are, sometimes in the literature, based upon the assumption of identity between lumped and local (subchannel centroid) temperature values. The present paper is concerned with the presentation of an approach for correlating lumped to centroid subchannel temperatures, based upon previously formulated models by the author, applied to a nine heated tube bundle experimental data set. (Author)

154

Optimizing the calculation of point source count-centroid in pixel size measurement  

International Nuclear Information System (INIS)

Pixel size is an important parameter of gamma camera and SPECT. A number of methods are used for its accurate measurement. In the original count-centroid method, where the image of a point source (PS) is acquired and its count-centroid calculated to represent PS position in the image, background counts are inevitable. Thus the measured count-centroid (Xm) is an approximation of the true count-centroid (Xp) of the PS, i.e. Xm=Xp + (Xb-Xp)/(1+Rp/Rb), where Rp is the net counting rate of the PS, Xb the background count-centroid and Rb the background counting. To get accurate measurement, Rp must be very big, which is unpractical, resulting in the variation of measured pixel size. Rp-independent calculation of PS count-centroid is desired. Methods: The proposed method attempted to eliminate the effect of the term (Xb-Xp)/(1 + Rp/Rb) by bringing Xb closer to Xp and by reducing Rb. In the acquired PS image, a circular ROI was generated to enclose the PS, the pixel with the maximum count being the center of the ROI. To choose the diameter (D) of the ROI, a Gaussian count distribution was assumed for the PS, accordingly, K=1-(0.5)D/R percent of the total PS counts was in the ROI, R being the full width at half maximum of the PS count distribution. D was set to be 6*R to ount distribution. D was set to be 6*R to enclose most (K=98.4%) of the PS counts. The count-centroid of the ROI was calculated to represent Xp. The proposed method was tested in measuring the pixel size of a well-tuned SPECT, whose pixel size was estimated to be 3.02 mm according to its mechanical and electronic setting (128 x 128 matrix, 387 mm UFOV, ZOOM=1). For comparison, the original method, which was use in the former versions of some commercial SPECT software, was also tested. 12 PSs were prepared and their image acquired and stored. The net counting rate of the PSs increased from 10 cps to 1183 cps. Results: Using the proposed method, the measured pixel size (in mm) varied only between 3.00 and 3.01 (mean = 3.01 ± 0.00) as Rp increased, and the difference between the measured and estimated pixel size was 1%. While using the original method, the measured pixel size decreased from 23.11 to 3.10 (mean=7.07 ± 6.35) as Rp increased, and the difference between the measured and estimated pixel size was much bigger. Conclusions: The proposed method is not only Rp-independent, but also accurate and precise. (authors)

155

Metrology calibration and very high accuracy centroiding with the NEAT testbed  

CERN Document Server

NEAT is an astrometric mission proposed to ESA with the objectives of detecting Earth-like exoplanets in the habitable zone of nearby solar-type stars. NEAT requires the capability to measure stellar centroids at the precision of 5e-6 pixel. Current state-of-the-art methods for centroid estimation have reached a precision of about 2e-5 pixel at two times Nyquist sampling, this was shown at the JPL by the VESTA experiment. A metrology system was used to calibrate intra and inter pixel quantum efficiency variations in order to correct pixelation errors. The European part of the NEAT consortium is building a testbed in vacuum in order to achieve 5e-6 pixel precision for the centroid estimation. The goal is to provide a proof of concept for the precision requirement of the NEAT spacecraft. The testbed consists of two main sub-systems. The first one produces pseudo stars: a blackbody source is fed into a large core fiber and lights-up a pinhole mask in the object plane, which is imaged by a mirror on the CCD. The ...

Crouzier, A; Preis, O; Henault, F; Kern, P; Martin, G; Feautrier, P; Stadler, E; Lafrasse, S; Delboulbe, A; Behar, E; Saint-Pe, M; Dupont, J; Potin, S; Cara, C; Donati, M; Doumayrou, E; Lagage, P O; Léger, A; LeDuigou, J M; Shao, M; Goullioud, R

2014-01-01

156

Centroid based Categorization Approach for Extraction of Body Sensor Network Data  

Directory of Open Access Journals (Sweden)

Full Text Available Monitoring human activities using wearable wireless sensor nodes has the potential to enable many useful applications for everyday situations. The long-term lifestyle categorization can greatly improve healthcare by gathering information about quality of life; aiding the diagnosis and tracking of certain diseases. The deployment of an automatic and computationally-efficient algorithm reduces the complexities involved in the detection and recognition of human activities in a distributed on Body sensor network server. Directory service is a useful aid human looking for information on Network Data. A directory services is a pre-categorized list of topics containing many links for each topic. However, most directory services are maintained manually now and face many drawbacks. Therefore the task of automatic categorization of new data into the topics of directory services becomes very necessary. BSN data categorization is more difficult due to a large variation of noisy information embedded in Sensor network data. This paper suggests a new Centroid based approach for Categorization for BSN data. We further introduce a new algorithm through centroid based approach for extraction of BSN data categorization and show that it achieves about more improvement over other BSN data categorization methods. Experimental results show that our proposed Centroid-based BSN data categorization algorithm achieves an approximately 13.8% improvement for BSN data categorization algorithm.

Setu Ku. Chaturvedi

2010-01-01

157

Interfractional Variations of Tumor Centroid Position and Tumor Regression during Stereotactic Body Radiotherapy for Lung Tumor  

Science.gov (United States)

Purpose. To determine interfractional changes of lung tumor centroid position and tumor regression during stereotactic body radiation therapy (SBRT). Methods and Materials. 34 patients were treated by SBRT in 4-5 fractions to a median dose of 50?Gy. The CT scans acquired for verification were registered with simulation CT scans. The gross target volume (GTV) was contoured on all verification CT scans and compared to the initial GTV in treatment plan system. Results. The mean (±standard deviation, SD) three-dimension vector shift was 5.2 ± 3.1?mm. The mean (±SD) interfractional variations of tumor centroid position were ?0.7 ± 4.5?mm in anterior-posterior (AP) direction, 0.2 ± 3.1?mm in superior-inferior (SI) direction, and 0.4 ± 2.4?mm in right-left (RL) direction. Large interfractional variations (?5?mm) were observed in 5 fractions (3.3%) in RL direction, 16 fractions (10.5%) in SI direction, and 36 fractions (23.5%) in AP direction. Tumor volume did not decrease significantly during lung SBRT. Conclusions. Small but insignificant tumor volume regression was observed during lung SBRT. While the mean interfractional variations of tumor centroid position were minimal in three directions, variations more than 5?mm account for approximately a third of all, indicating additional margin for PTV, especially in AP direction. PMID:25548770

Sun, Yanan; Lu, Yufei; Cheng, Siguo; Guo, Wei; Ye, Ke; Zhao, Huiyun; Zheng, Xiaoli; Li, Dingjie; Wang, Shujuan; Yang, Chengliang; Ge, Hong

2014-01-01

158

Centroids and the Rapid Decay property in mapping class groups  

CERN Document Server

We study a notion of a Lipschitz, permutation-invariant "centroid" for triples of points in mapping class groups MCG(S), which satisfies a certain polynomial growth bound. A consequence (via work of Drutu-Sapir) is the Rapid Decay Property for MCG(S).

Behrstock, Jason A

2008-01-01

159

Determination of depths to centroids of three-dimensional sources of potential-field anomalies with examples from environmental and geologic applications  

Science.gov (United States)

A method is developed for determining the depth to the centroid (the geometric center) of `semi-compact' sources. The method, called the anomaly attenuation rate (AAR) method, involves computing radial averages of AARs with increasing distances from a range of assumed source centers. For well-isolated magnetic anomalies from `semi-compact' sources, the theoretical AARs range from ˜2 (close to the sources) to ˜3 (in the far-field region); the corresponding theoretical range of AARs for gravity anomalies is ˜1 to ˜2. When the estimated source centroid is incorrect, the AARs either exceed or fall short of the theoretical values. The levelling-off of the far-field AARs near their theoretical maximum values indicates the upper (deeper) bound of the centroid location. Similarly, near-field AARs lower than the theoretical minimum indicate the lower (shallower) bound of the centroid location. It is not always possible to determine usable upper and lower bounds of the centroids because the method depends on characteristics of sources/anomalies and the noise level of the data. For the environmental magnetic examples considered in this study, the determined deeper bounds were within 4% of the true centroid-to-observation distance. For the case of the gravity anomaly from the Bloomfield Pluton, Missouri, USA, determination of only the shallower bound of the centroid location (˜7 km) was possible. This estimate agrees closely with the centroid of a previously determined three-dimensional model of the Bloomfield Pluton. For satellite magnetic anomalies, the method is appropriate only for high-amplitude, near-circular anomalies due to the inherent low signal-to-noise ratio of satellite magnetic anomalies. Model studies indicate that the AAR method is able to place depths within ±20-30 km of actual center locations from a 400-km observation altitude. Thus, the method may be able to discriminate between upper crustal, lower crustal, and mantle magnetic sources. The results from the prominent Kentucky anomaly are relatively well-resolved (centroid depth ˜30 km below the Earth's surface). For the Kiruna Magsat anomaly, the deleterious effects from neighboring anomalies make a determination difficult (possible depth could be between 20 and 30 km). The centroid depths are deeper for the Kursk anomaly (˜40-50 km). These depths may indicate that magnetic anomalies from the near-surface Kursk iron formations (a known contributor) and deep crustal magnetic sources could combine to form the Kursk Magsat anomaly.

Ravat, D.; Taylor, Patrick T.

1998-09-01

160

Content-Based Image Retrieval Using Salient Boundary and Centroid-Radii Model  

Science.gov (United States)

In view of the instability and low efficiency of the present image retrieval method, especially for simple image comparison with some salient shapes, a new image retrieval algorithm based on salient closed boundary is presented. Firstly, the Canny operator is performed to detect edges. Secondly, the ratio contour is used to extract the most salient closed boundary of some shape from the image. Finally, the similarities are measured by feature vector of the salient closed boundary based on the centroid-radii model. Preliminary experimental results demonstrate that the proposed method is quite suitable for many professional image retrieval systems and has a good performance in both retrieval efficiency and effectiveness.

Wang, Qing; Ye, Haijian; Wang, Yan; Zhang, Hua

 
 
 
 
161

Classification of open clusters by centroid method of taxonomical analysis  

International Nuclear Information System (INIS)

Distributions of open clusters of the Galaxy in spaces with coordinates being mass, absolute magnitude, integrated colour index, diameter, metallicity, and age, are considered. Majority of clusters are shown to enter several taxons (classes) with narrow enough limits of these parameters. The classes form a linear sequence by age and two-dimensional sequence on colour - magnitude diagram. They are not isolated but transit into each other continuously. It possibly means an absence of significant gaps in cluster formation process. Bifurcation of age sequence of classes depending on mass and diameter values is found. This allows an evolutionary interpretation

162

The RPC space resolution with the charge centroid method  

Science.gov (United States)

RPC detectors were originally developed to exploit the very good intrinsic time resolution of the plane geometry and have been used as muon trigger in most of their high energy physics applications, disregarding the detector space resolution. Due to the high luminosity of future colliders, new experiments will be very demanding in terms of momentum selection of the muon spectrometer. For this reason, trigger detectors will be required to have a sub-millimeter space resolution as well as a sub-nanosecond time resolution. RPCs are good candidates for these applications, as it can be shown that they have excellent intrinsic space resolution, while the actual results depend mostly on the front-end electronics performance. Here we present a beam test carried out on a small size RPC. The results are consistent with a space resolution of ~ 130 ?m.

Aielli, G.; Cardarelli, R.; Di Stante, L.; Liberti, B.; Paolozzi, L.; Pastori, E.; Santonico, R.

2014-09-01

163

Centroid Detection by Gaussian Pattern Matching in Adaptive Optics  

CERN Document Server

Shack Hartmann wavefront sensor is a two dimensional array of lenslets which is used to detect the incoming phase distorted wavefront through local tilt measurements made by recording the spot pattern near the focal plane. Wavefront reconstruction is performed in two stages - (a) image centroiding to calculate local slopes, (b) formation of the wavefront shape from local slope measurement. Centroiding accuracy contributes to most of the wavefront reconstruction error in Shack Hartmann sensor based adaptive optics system with readout and background noise. It becomes even more difficult in atmospheric adaptive optics case, where scintillation effects may also occur. In this paper we used a denoising technique based on thresholded Zernike reconstructor to minimize the effects due to readout and background noise. At low signal to noise ratio, this denoising technique can be improved further by taking the advantage of the shape of the spot. Assuming a Gaussian pattern for individual spots, it is shown that the cen...

Vyas, Akondi; Prasad, B Raghavendra

2009-01-01

164

Beam centroid motion estimate for a high current LIA  

International Nuclear Information System (INIS)

A high current linear induction accelerator now is being constructed in Institute of Fluid Physics. It consists of 18 blocks, totally 72 induction accelerating cells, and 18 connection cells with ports for beam diagnostic hardware and vacuum pump. The goal of the facility is to obtain high quality, high current pulse electron beams. In order to reduce corkscrew motion caused by energy spread and misalignment of a focusing system some measures to control the transverse motion of beam centroid must be taken. At first magnetic alignment is performed by using pulsed-wire technique very carefully, then the tilt errors is corrected by a pair of steering coils, which are located inside each cell, after that based on the alignment data a simple estimate of the beam centroid motion has been done by transfer matrix algorithm. In this paper, the calculated and analysis results are presented

165

Uncertain Centroid based Partitional Clustering of Uncertain Data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Clustering uncertain data has emerged as a challenging task in uncertain data management and mining. Thanks to a computational complexity advantage over other clustering paradigms, partitional clustering has been particularly studied and a number of algorithms have been developed. While existing proposals differ mainly in the notions of cluster centroid and clustering objective function, little attention has been given to an analysis of their characteristics and limits. In t...

Gullo, Francesco; Tagarelli, Andrea

2012-01-01

166

Direct assessment of quantum nuclear effects on hydrogen bond strength by constrained-centroid ab initio path integral molecular dynamics  

Science.gov (United States)

The impact of quantum nuclear effects on hydrogen (H-) bond strength has been inferred in earlier work from bond lengths obtained from path integral molecular dynamics (PIMD) simulations. To obtain a direct quantitative assessment of such effects, we use constrained-centroid PIMD simulations to calculate the free energy changes upon breaking the H-bonds in dimers of HF and water. Comparing ab initio simulations performed using PIMD and classical nucleus molecular dynamics (MD), we find smaller dissociation free energies with the PIMD method. Specifically, at 50 K, the H-bond in (HF)2 is about 30% weaker when quantum nuclear effects are included, while that in (H2O)2 is about 15% weaker. In a complementary set of simulations, we compare unconstrained PIMD and classical nucleus MD simulations to assess the influence of quantum nuclei on the structures of these systems. We find increased heavy atom distances, indicating weakening of the H-bond consistent with that observed by direct calculation of the free energies of dissociation.

Walker, Brent; Michaelides, Angelos

2010-11-01

167

Plasma channel diagnostic based on laser centroid oscillations  

International Nuclear Information System (INIS)

A technique has been developed for measuring the properties of discharge-based plasma channels by monitoring the centroid location of a laser beam exiting the channel as a function of input alignment offset between the laser and the channel. Experiments were performed using low-intensity (14 W cm-2) laser pulses focused onto the entrance of a hydrogen-filled capillary discharge waveguide. Scanning the laser centroid position at the input of the channel and recording the exit position allow determination of the channel depth with an accuracy of a few percent, measurement of the transverse channel shape, and inference of the matched spot size. In addition, accurate alignment of the laser beam through the plasma channel is provided by minimizing laser centroid motion at the channel exit as the channel depth is scanned either by scanning the plasma density or the discharge timing. The improvement in alignment accuracy provided by this technique will be crucial for minimizing electron beam pointing errors in laser plasma accelerators.

168

Improved envelope and centroid equations for high current beams  

International Nuclear Information System (INIS)

The standard envelope equation for charged particle beams (e.g., Lee-Cooper) neglects self-field contributions from the beam rotation and the slope of the beam envelope. We have carried out an expansion that includes these effects to first order, resulting in a new equation for the edge radius. The change in beam kinetic energy due to space-charge depression as the beam radius varies is also included. For the centroid equation, we have included the 'self-steering' effect due to the curvature of the beam orbit. To leading order, there is a cancellation between the self-steering effect and the space-charge depression of the beam energy, so that a more accurate centroid equation is obtained by using the undepressed value of the energy (i.e., the total beam energy) to calculate the orbit. We have implemented the envelope and centroid equations in the Lamda code. The effect of the new terms will be illustrated with calculations for the DARHT accelerators at the Los Alamos National Laboratory

169

Model Independent Analysis of Beam Centroid Dynamics in Accelerators  

International Nuclear Information System (INIS)

Fundamental issues in Beam-Position-Monitor (BPM)-based beam dynamics observations are studied in this dissertation. The major topic is the Model-Independent Analysis (MIA) of beam centroid dynamics. Conventional beam dynamics analysis requires a certain machine model, which itself of ten needs to be refined by beam measurements. Instead of using any particular machine model, MIA relies on a statistical analysis of the vast amount of BPM data that often can be collected non-invasively during normal machine operation. There are two major parts in MIA. One is noise reduction and degrees-of-freedom analysis using a singular value decomposition of a BPM-data matrix, which constitutes a principal component analysis of BPM data. The other is a physical base decomposition of the BPM-data matrix based on the time structure of pulse-by-pulse beam and/or machine parameters. The combination of these two methods allows one to break the resolution limit set by individual BPMs and observe beam dynamics at more accurate levels. A physical base decomposition is particularly useful for understanding various beam dynamics issues. MIA improves observation and analysis of beam dynamics and thus leads to better understanding and control of beams in both linacs and rings. The statistical nature of MIA makes it potentially useful in other fields. Another important topic discussed in this dissertation is the measurement of a nonlinear Poincare section (one-turn) map in circular accelerators.n (one-turn) map in circular accelerators. The beam dynamics in a ring is intrinsically nonlinear. In fact, nonlinearities are a major factor that limits stability and influences the dynamics of halos. The Poincare section map plays a basic role in characterizing and analyzing such a periodic nonlinear system. Although many kinds of nonlinear beam dynamics experiments have been conducted, no direct measurement of a nonlinear map has been reported for a ring in normal operation mode. This dissertation analyzes various issues concerning map measurements and shows that it is possible to measure the Poincare section map (in terms of Taylor series) of a circular accelerator to a surprisingly high order and accuracy based on present BPM technology. MIA can overcome the inherent limit of BPM resolution. Nonlinear map measurements will advance understanding of the beam dynamics of a ring

170

An Efficient Range Partitioning Method for Finding Frequent Patterns from Huge Database  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Data mining is finding increasing acceptance in science and business areas that need to analyze large amounts of data to discover trends that they could not otherwise find. Different applications may require different data mining techniques. The kinds of knowledge that could be discovered from a database are categorized into association rules mining, sequential patterns mining, classification, and clustering. In this paper we present an efficient range partitioning method for finding frequent...

Ms. Ruchita Gupta; Satsangi, Dr C. S.

2012-01-01

171

Optimized shooting method for finding periodic orbits of nonlinear dynamical systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An alternative numerical method is developed to find stable and unstable periodic orbits of nonlinear dynamical systems. The method exploits the high-efficiency of the Levenberg-Marquardt algorithm for medium-sized problems and has the additional advantage of being relatively simple to implement. It is also applicable to both autonomous and non-autonomous systems. As an example of its use, it is employed to find periodic orbits in the R\\"ossler system, a coupled R\\"ossler sy...

Dednam, W.; Botha, A. E.

2014-01-01

172

Finding-equal regression method and its application in predication of U resources  

International Nuclear Information System (INIS)

The commonly adopted deposit model method in mineral resources predication has two main part: one is model data that show up geological mineralization law for deposit, the other is statistics predication method that accords with characters of the data namely pretty regression method. This kind of regression method may be called finding-equal regression, which is made of the linear regression and distribution finding-equal method. Because distribution finding-equal method is a data pretreatment which accords with advanced mathematical precondition for the linear regression namely equal distribution theory, and this kind of data pretreatment is possible of realization. Therefore finding-equal regression not only can overcome nonlinear limitations, that are commonly occurred in traditional linear regression or other regression and always have no solution, but also can distinguish outliers and eliminate its weak influence, which would usually appeared when Robust regression possesses outlier in independent variables. Thus this newly finding-equal regression stands the best status in all kind of regression methods. Finally, two good examples of U resource quantitative predication are provided

173

Improved shrunken centroid classifiers for high-dimensional class-imbalanced data  

Science.gov (United States)

Background PAM, a nearest shrunken centroid method (NSC), is a popular classification method for high-dimensional data. ALP and AHP are NSC algorithms that were proposed to improve upon PAM. The NSC methods base their classification rules on shrunken centroids; in practice the amount of shrinkage is estimated minimizing the overall cross-validated (CV) error rate. Results We show that when data are class-imbalanced the three NSC classifiers are biased towards the majority class. The bias is larger when the number of variables or class-imbalance is larger and/or the differences between classes are smaller. To diminish the class-imbalance problem of the NSC classifiers we propose to estimate the amount of shrinkage by maximizing the CV geometric mean of the class-specific predictive accuracies (g-means). Conclusions The results obtained on simulated and real high-dimensional class-imbalanced data show that our approach outperforms the currently used strategy based on the minimization of the overall error rate when NSC classifiers are biased towards the majority class. The number of variables included in the NSC classifiers when using our approach is much smaller than with the original approach. This result is supported by experiments on simulated and real high-dimensional class-imbalanced data. PMID:23433084

2013-01-01

174

An Inversion-Free Method for Finding Positive Definite Solution of a Rational Matrix Equation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new iterative scheme has been constructed for finding minimal solution of a rational matrix equation of the form X + A*X?1A = I. The new method is inversion-free per computing step. The convergence of the method has been studied and tested via numerical experiments.

Fazlollah Soleymani; Mahdi Sharifi; Solat Karimi Vanani; Farhad Khaksar Haghani; Xe Man, Adem K. X. L. X.

2014-01-01

175

An Inversion-Free Method for Finding Positive Definite Solution of a Rational Matrix Equation  

Science.gov (United States)

A new iterative scheme has been constructed for finding minimal solution of a rational matrix equation of the form X + A*X?1A = I. The new method is inversion-free per computing step. The convergence of the method has been studied and tested via numerical experiments. PMID:25215323

Sharifi, Mahdi; Karimi Vanani, Solat; Khaksar Haghani, Farhad; K?l?çman, Adem

2014-01-01

176

User Manual and Supporting Information for Library of Codes for Centroidal Voronoi Point Placement and Associated Zeroth, First, and Second Moment Determination; TOPICAL  

International Nuclear Information System (INIS)

The theory, numerical algorithm, and user documentation are provided for a new ''Centroidal Voronoi Tessellation (CVT)'' method of filling a region of space (2D or 3D) with particles at any desired particle density. ''Clumping'' is entirely avoided and the boundary is optimally resolved. This particle placement capability is needed for any so-called ''mesh-free'' method in which physical fields are discretized via arbitrary-connectivity discrete points. CVT exploits efficient statistical methods to avoid expensive generation of Voronoi diagrams. Nevertheless, if a CVT particle's Voronoi cell were to be explicitly computed, then it would have a centroid that coincides with the particle itself and a minimized rotational moment. The CVT code provides each particle's volume and centroid, and also the rotational moment matrix needed to approximate a particle by an ellipsoid (instead of a simple sphere). DIATOM region specification is supported

177

Nonlinear force density method for the form-finding of minimal surface membrane structures  

Science.gov (United States)

We develop an alternative approach for the form-finding of the minimal surface membranes (including cable membranes) using discrete models and nonlinear force density method. Two directed weighted graphs with 3 and 4-sided regional cycles, corresponding to triangular and quadrilateral finite element meshes are introduced as computational models for the form-finding problem. The triangular graph model is closely related to the triangular computational models available in the literature whilst the quadrilateral graph uses a novel averaging approach for the form-finding of membrane structures within the context of nonlinear force density method. The viability of the mentioned discrete models for form-finding are studied through two solution methods including a fixed-point iteration method and the Newton-Raphson method with backtracking. We suggest a hybrid version of these methods as an effective solution strategy. Examples of the formation of certain well-known minimal surfaces are presented whilst the results obtained are compared and contrasted with analytical solutions in order to verify the accuracy and viability of the suggested methods.

Koohestani, K.

2014-06-01

178

Localization Algorithm based on Improved Weighted Centroid in Wireless Sensor Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Location technology is becoming more and more important in wireless sensor networks. The weighted centroid localization offers a fast and simple algorithm for the location equipment in wireless sensor networks. The algorithm derives from the centroid measurement and calculation device of the adjacent anchor in the average coordinate. After the analysis of the radio propagation loss model, the most appropriate log-distance distribution model is selected to simulate the signal propagation. Based on the centroid algorithm and the weighted centroid algorithm, this paper proposes an ellipse centroid localization algorithm. This algorithm makes use of ellipse’s characteristic to estimate the unknown node’s coordinate. The main idea of ellipse centroid localization algorithm is the precision control factor that can control the algorithm’s location precision. In ellipse centroid localization algorithm, node is extended as anchor in order to strengthen anchor density’s dynamic characteristic. The simulation result shows the ellipse centroid localization algorithm is more effective than the centroid algorithm and the weighted centroid precision algorithm

Shyi-Ching Liang

2014-01-01

179

Assessing the uncertainties on seismic source parameters: Towards realistic error estimates for centroid-moment-tensor determinations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The centroid-moment-tensor (CMT) algorithm provides a straightforward, rapid method for the determination of seismic source parameters from waveform data. As such, it has found widespread application, and catalogues of CMT solutions – particularly the catalogue maintained by the Global CMT Project – are routinely used by geoscientists. However, there have been few attempts to quantify the uncertainties associated with any given CMT determination: whilst catalogues typically qu...

Valentine, A. P.; Trampert, J.

2012-01-01

180

Nano-JASMINE: cosmic radiation degradation of CCD performance and centroid detection  

Science.gov (United States)

Nano-JASMINE (NJ) is a very small astrometry satellite project led by the National Astronomical Observatory of Japan. The satellite is ready for launch, and the launch is currently scheduled for late 2013 or early 2014. The satellite is equipped with a fully depleted CCD and is expected to perform astrometry observations for stars brighter than 9 mag in the zw-band (0.6 µm-1.0 µm). Distances of stars located within 100 pc of the Sun can be determined by using annual parallax measurements. The targeted accuracy for the position determination of stars brighter than 7.5 mag is 3 mas, which is equivalent to measuring the positions of stars with an accuracy of less than one five-hundredth of the CCD pixel size. The position measurements of stars are performed by centroiding the stellar images taken by the CCD that operates in the time and delay integration mode. The degradation of charge transfer performance due to cosmic radiation damage in orbit is proved experimentally. A method is then required to compensate for the effects of performance degradation. One of the most effective ways of achieving this is to simulate observed stellar outputs, including the effect of CCD degradation, and then formulate our centroiding algorithm and evaluate the accuracies of the measurements. We report here the planned procedure to simulate the outputs of the NJ observations. We also developed a CCD performance-measuring system and present preliminary results obtained using the system.

Kobayashi, Yukiyasu; Shimura, Yuki; Niwa, Yoshito; Yano, Taihei; Gouda, Naoteru; Yamada, Yoshiyuki

2012-09-01

 
 
 
 
181

A fast algorithm to compute precise type-2 centroids for real-time control applications.  

Science.gov (United States)

An interval type-2 fuzzy set (IT2 FS) is characterized by its upper and lower membership functions containing all possible embedded fuzzy sets, which together is referred to as the footprint of uncertainty (FOU). The FOU results in a span of uncertainty measured in the defuzzified space and is determined by the positional difference of the centroids of all the embedded fuzzy sets taken together. This paper provides a closed-form formula to evaluate the span of uncertainty of an IT2 FS. The closed-form formula offers a precise measurement of the degree of uncertainty in an IT2 FS with a runtime complexity less than that of the classical iterative Karnik-Mendel algorithm and other formulations employing the iterative Newton-Raphson algorithm. This paper also demonstrates a real-time control application using the proposed closed-form formula of centroids with reduced root mean square error and computational overhead than those of the existing methods. Computer simulations for this real-time control application indicate that parallel realization of the IT2 defuzzification outperforms its competitors with respect to maximum overshoot even at high sampling rates. Furthermore, in the presence of measurement noise in system (plant) states, the proposed IT2 FS based scheme outperforms its type-1 counterpart with respect to peak overshoot and root mean square error in plant response. PMID:24691554

Chakraborty, Sumantra; Konar, Amit; Ralescu, Anca; Pal, Nikhil R

2015-02-01

182

Combined centroid-envelope dynamics of intense, magnetically focused charged beams surrounded by conducting walls  

International Nuclear Information System (INIS)

In this paper we analyze the combined envelope-centroid dynamics of magnetically focused high-intensity charged beams surrounded by conducting walls. Similar to the case where conducting walls are absent, it is shown that the envelope and centroid dynamics decouple from each other. Mismatched envelopes still decay into equilibrium with simultaneous emittance growth, but the centroid keeps oscillating with no appreciable energy loss. Some estimates are performed to analytically obtain characteristics of halo formation seen in the full simulations

183

The Schr\\"odinger formulation of the Feynman path centroid density  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present an analysis of the Feynman path centroid density that provides new insight into the correspondence between the path integral and the Schr\\"odinger formulations of statistical mechanics. The path centroid density is a central concept for several approximations (centroid molecular dynamics, quantum transition state theory, and pure quantum self-consistent harmonic approximation) that are used in path integral studies of thermodynamic and dynamical properties of quan...

Rami?rez, Rafael; Lo?pez-ciudad, Telesforo

1999-01-01

184

Nudged-elastic band method with two climbing images: finding transition states in complex energy landscapes  

CERN Document Server

The nudged-elastic band (NEB) method is modified with concomitant two climbing images (C2-NEB) to find a transition state (TS) in complex energy landscapes, such as those with serpentine minimal energy path (MEP). If a single climbing image (C1-NEB) successfully finds the TS, C2-NEB finds it with higher stability and accuracy. However, C2-NEB is suitable for more complex cases, where C1-NEB misses the TS because the MEP and NEB directions near the saddle point are different. Generally, C2-NEB not only finds the TS but guarantees that the climbing images approach it from the opposite sides along the MEP, and it estimates accuracy from the three images: the highest-energy one and its climbing neighbors. C2-NEB is suitable for fixed-cell NEB and the generalized solid-state NEB (SS-NEB).

Zarkevich, Nikolai A

2014-01-01

185

A new exhaustive method and strategy for finding motifs in ChIP-enriched regions.  

Science.gov (United States)

ChIP-seq, which combines chromatin immunoprecipitation (ChIP) with next-generation parallel sequencing, allows for the genome-wide identification of protein-DNA interactions. This technology poses new challenges for the development of novel motif-finding algorithms and methods for determining exact protein-DNA binding sites from ChIP-enriched sequencing data. State-of-the-art heuristic, exhaustive search algorithms have limited application for the identification of short (l, d) motifs (l ? 10, d ? 2) contained in ChIP-enriched regions. In this work we have developed a more powerful exhaustive method (FMotif) for finding long (l, d) motifs in DNA sequences. In conjunction with our method, we have adopted a simple ChIP-enriched sampling strategy for finding these motifs in large-scale ChIP-enriched regions. Empirical studies on synthetic samples and applications using several ChIP data sets including 16 TF (transcription factor) ChIP-seq data sets and five TF ChIP-exo data sets have demonstrated that our proposed method is capable of finding these motifs with high efficiency and accuracy. The source code for FMotif is available at http://211.71.76.45/FMotif/. PMID:24475069

Jia, Caiyan; Carson, Matthew B; Wang, Yang; Lin, Youfang; Lu, Hui

2014-01-01

186

Error-finding and error-correcting methods for the start-up of the SLC  

International Nuclear Information System (INIS)

During the commissioning of an accelerator, storage ring, or beam transfer line, one of the important tasks of an accelertor physicist is to check the first-order optics of the beam line and to look for errors in the system. Conceptually, it is important to distinguish between techniques for finding the machine errors that are the cause of the problem and techniques for correcting the beam errors that are the result of the machine errors. In this paper we will limit our presentation to certain applications of these two methods for finding or correcting beam-focus errors and beam-kick errors that affect the profile and trajectory of the beam respectively. Many of these methods have been used successfully in the commissioning of SLC systems. In order not to waste expensive beam time we have developed and used a beam-line simulator to test the ideas that have not been tested experimentally. To save valuable physicist's time we have further automated the beam-kick error-finding procedures by adopting methods from the field of artificial intelligence to develop a prototype expert system. Our experience with this prototype has demonstrated the usefulness of expert systems in solving accelerator control problems. The expert system is able to find the same solutions as an expert physicist but in a more systematic fashion. The methods used in these procedures and some of the recent applications will be described in this paper

187

Level set methods for finding saddle points of general Morse index  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For a real valued function, a point is critical if its derivatives are zero, and a critical point is a saddle point if it is not a local extrema. In this paper, we study algorithms to find saddle points of general Morse index. Our approach is motivated by the multidimensional mountain pass theorem, and extends our earlier work on methods (based on studying the level sets) to find saddle points of mountain pass type. We prove the convergence of our algorithms in the nonsmooth...

Pang, C. H. Jeffrey

2010-01-01

188

An improved centroid location algorithm for Infrared LED feature points  

Science.gov (United States)

The precision of centroid location for infrared LED point images is an important factor, which affects the precision of the light-pen Coordinate Measuring Machining (CMM) .In this paper, the error model using the traditional center of mass (COM) algorithm is analyzed and it is shown that there are systematic error and random error. This paper analyzes the systematic error and random error, and then adopts the Gaussian surface fitting (GSF) algorithm and weighted centre-ofgravity (WCOG) algorithm to compensate systematic errors, meanwhile it analyzes how to reduce random error. The simulation results show that the accuracy of the infrared LED point position can be enhanced from 1/ 20 pixel to 1/100 pixel using the new algorithm.

Wang, Shaoqiong; Yan, Bixi; Dong, Mingli; Wang, Jun; Sun, Peng

2013-10-01

189

Beam centroid trajectory control for a high current LIA  

International Nuclear Information System (INIS)

In order to reduce the amplitude of corkscrew motion to obtain a high current pulsed electron beam with good quality, both simulation and experimental work were done based on the beam transport system of 'Dragon-I', which is a pulsed high current electron LIA. The beam centroid motion was controlled by adjusting the current fed into two pairs of steering coils located inside the accelerator cavities. The two pairs of steering coils are perpendicular to each other. The principle of the adjustments, simulations and experiments are introduced in this paper. Corkscrew amplitude of the output electron beam with 50 ns pulse flattop is reduced from 4 mm to less than 1 mm. (authors)

190

A Tabu Search Method for Finding Minimal Multi-Homogeneous Bézout Number  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: A homotopy method has proven to be reliable for computing all of the isolated solutions of a multivariate polynomial system. The multi-homogeneous Bézout number of a polynomial system is the number of paths that one has to trace in order to compute all of its isolated solutions. Each partition of the variables corresponds to a multi-homogeneous Bézout number. It is a crucial problem to find a partition with the minimum multi-homogeneous Bézout number since the size of the space of all the partitions increases exponentially. Approach: This study presented a new method by producing the Tabu Search Method (TSM as a powerful technique for finding minimum multi-homogeneous Bézout number. Results: A comparison is made between the new method and some recent methods. It is shown that our algorithm is superior to the latter, besides being simple and efficient in the implementation. Conclusion: Furthermore the present study extended the applicability of the Tabu search method.

Hassan M.S. Bawazir

2010-01-01

191

Finite difference method to find period-one gait cycles of simple passive walkers  

Science.gov (United States)

Passive dynamic walking refers to a class of bipedal robots that can walk down an incline with no actuation or control input. These bipeds are sensitive to initial conditions due to their style of walking. According to small basin of attraction of passive limit cycles, it is important to start with an initial condition in the basin of attraction of stable walking (limit cycle). This paper presents a study of the simplest passive walker with point and curved feet. A new approach is proposed to find proper initial conditions for a pair of stable and unstable period-one gait limit cycles. This methodology is based on finite difference method which can solve the nonlinear differential equations of motion on a discrete time. Also, to investigate the physical configurations of the walkers and the environmental influence such as the slope angle, the parameter analysis is applied. Numerical simulations reveal the performance of the presented method in finding two stable and unstable gait patterns.

Dardel, Morteza; Safartoobi, Masoumeh; Pashaei, Mohammad Hadi; Ghasemi, Mohammad Hassan; Navaei, Mostafa Kazemi

2015-01-01

192

Application of a Bayesian Method to Absorption Spectral-Line Finding in Simulated ASKAP Data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The large spectral bandwidth and wide field of view of the Australian SKA Pathfinder radio telescope will open up a completely new parameter space for large extragalactic HI surveys. Here we focus on identifying and parametrising HI absorption lines which occur in the line of sight towards strong radio continuum sources. We have developed a method for simultaneously finding and fitting HI absorption lines in radio data by using multi-nested sampling, a Bayesian Monte Carlo a...

Allison, J. R.; Sadler, E. M.; Whiting, M. T.

2011-01-01

193

A method for finding the ridge between saddle points applied to rare event rate estimates  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A method is presented for finding the ridge between first order saddle points on a multidimensional surface. For atomic scale systems, such saddle points on the energy surface correspond to atomic rearrangement mechanisms. Information about the ridge can be used to test the validity of the harmonic approximation to transition state theory, in particular to verify that second order saddle points—maxima along the ridge—are high enough compared to the first order saddle points. New minima al...

Maronsson, Jon Bergmann; Jo?nsson, Hannes; Vegge, Tejs

2012-01-01

194

A Root-MUSIC-Like Direction Finding Method for Cyclostationary Signals  

Directory of Open Access Journals (Sweden)

Full Text Available We propose a new root-MUSIC-like direction finding algorithm that exploits cyclostationarity in order to improve the direction-of-arrival estimation. The proposed cyclic method is signal selective, it allows to increase the resolution power and the noise robustness significantly, and it is also able to handle more sources than the number of sensors. Computer simulations are used to show the performance of the algorithm.

Yide Wang

2005-01-01

195

A method for finding bounds on critical values for non-attractive interacting particle systems  

International Nuclear Information System (INIS)

The method is to use a computer to find a function for the process that always has negative expectation by considering all relevant configurations of 0's and 1's at the boundary of a finite process in one dimension. It is shown that a branching annihilating random walk will die out if the diffusion parameter ? is greater than 0.176. The method may also be applied to attractive processes, and is used for the contact process in one dimension obtaining the same values as Ziezold and Grillenberger (1988) for up to 10 places in from the boundaries. (author)

196

The impact of the in-orbit background and the X-ray source intensity on the centroiding accuracy of the Swift X-ray telescope  

International Nuclear Information System (INIS)

The optical components of the Swift Gamma Ray Burst Explorer X-ray Telescope (XRT), consisting of the JET-X spare flight mirror and a charge coupled device of the type used in the EPIC program, were used in a re-calibration study carried out at the Panter facility, which is part of the Max Plank Institute for Extraterrestrial Physics. The objective of this study was to check the focal length and the off axis performance of the mirrors and to show that the half energy width (HEW) of the on-axis point spread function (PSF) was of the order of 16 arcsec at 1.5 keV (Nucl. Instr. and Meth. A 488 (2002) 543; SPIE 4140 (2000) 64) and that a centroiding accuracy better that 1 arcsec could be achieved within the 4 arcmin sampling area designated by the Burst Alert Telescope (Nucl. Instr. and Meth. A 488 (2002) 543). The centroiding accuracy of the Swift XRT's optical components was tested as a function of distance from the focus and off axis position of the PSF (Nucl. Instr. and Meth. A 488 (2002) 543). The presence of background events in the image frame introduced errors in the centroiding process, making the choice of centroiding algorithm important (Nucl. Instr. and Meth. A 488 (2002) 543). Since the objective of Swift is to rapidly investigate the X-ray afterglows of Gamma Ray Bursts the possibility of detecting a bright source with intensity greater than 25 Crab could not be excluded and therefore the impact of a saturated PSF core on the centroiding accuracy was investire on the centroiding accuracy was investigated by experimental methods

197

Changes of the centroid position of laser beams propagating through an optical system in turbulent atmosphere  

Science.gov (United States)

In this paper, the effects of atmospheric turbulence, initial field amplitude, optical system and thermal blooming on the centroid position of laser beams propagating through the atmosphere are studied in detail. With the average over the ensemble of the turbulent medium, the centroid position is independent of turbulence. However, the centroid position depends on the centroid positions at the source plane and in the far-field, and the elements of ray-transfer-matrix. The physical reason why the centroid position changes on propagation is that the far-field centroid position is not located on the propagation z-axis due to the field phase distortion and the decentred intensity. The centroid position of laser beams with the spherical aberration and the decentred intensity is examined analytically. When laser beams with the decentred intensity propagate through the atmosphere, the effect of thermal blooming on the centroid position is investigated by using the four-dimensional (4D) computer code of the time-dependent propagation of high power laser beams through the atmosphere.

Ji, Xiaoling; Baykal, Yahya; Jia, Xinhong

2013-12-01

198

A Nearest-Centroid Technique for Evaluating the Minimum-Variance Clustering Procedure.  

Science.gov (United States)

Two data sets are cluster-analyzed by the minimum variance procedure, and centroid vectors for the first are calculated. The objects of the second are assigned to the nearest centroid calculated in the first data set, and the results are evaluated in terms of stability and accuracy. (Author/BW)

McIntyre, Robert M.; Blashfield, Roger K.

1980-01-01

199

Centroid offset estimation in the Fourier domain for a highly sensitive Shack–Hartmann wavefront sensor  

International Nuclear Information System (INIS)

The estimation of the centroid offset can have an effect on the accuracy of wavefront measurements conducted by highly sensitive Shack–Hartmann wavefront sensors. In this paper, a novel offset estimation algorithm processed in the Fourier domain is proposed. This method can be used to process the offset estimation in the Fourier domain and is efficient in noise suppression. The principle of the algorithm is described in detail. Comparisons between the technique and two other widely used algorithms, the best-threshold center of gravity algorithm and the correlation algorithm, are performed theoretically using numerical simulation and experimentally using a Shack–Hartmann wavefront sensor. The results show that the proposed offset estimation algorithm is unbiased, as robust as the correlation algorithm, as fast as the best-threshold center of gravity algorithm, and achieves a good balance between precision and speed. (paper)

200

Franck–Condon factors and r-centroids for the diatomic fluorides of germanium and silicon  

Directory of Open Access Journals (Sweden)

Full Text Available A suitable potential energy function was found by analysing the potential functions proposed by Morse, Mohammad and Rafi et al. for the A2?+–X2?3/2 and B2?+–X2?3/2 band systems of GeF and the 1?–1? band system of SiF. It was found that the potential proposed by Rafi et al. is in close agreement with the Rydberg–Klein–Rees (R–K–R potential. Using this potential, the wave functions were evaluated by the Wentzel–Kramer–Brillouin (W–K–B method. The Franck–Condon factors and r-centroids were computed by a numerical integration technique. The results are compared with available theoretical values. The intensities of the various bands were investigated.

S. KANAGAPRABHA

2008-05-01

 
 
 
 
201

A framework for fast probabilistic centroid-moment-tensor determination—inversion of regional static displacement measurements  

Science.gov (United States)

The determination of earthquake source parameters is an important task in seismology. For many applications, it is also valuable to understand the uncertainties associated with these determinations, and this is particularly true in the context of earthquake early warning (EEW) and hazard mitigation. In this paper, we develop a framework for probabilistic moment tensor point source inversions in near real time. Our methodology allows us to find an approximation to p(m|d), the conditional probability of source models (m) given observations (d). This is obtained by smoothly interpolating a set of random prior samples, using Mixture Density Networks (MDNs)-a class of neural networks which output the parameters of a Gaussian mixture model. By combining multiple networks as `committees', we are able to obtain a significant improvement in performance over that of a single MDN. Once a committee has been constructed, new observations can be inverted within milliseconds on a standard desktop computer. The method is therefore well suited for use in situations such as EEW, where inversions must be performed routinely and rapidly for a fixed station geometry. To demonstrate the method, we invert regional static GPS displacement data for the 2010 MW 7.2 El Mayor Cucapah earthquake in Baja California to obtain estimates of magnitude, centroid location and depth and focal mechanism. We investigate the extent to which we can constrain moment tensor point sources with static displacement observations under realistic conditions. Our inversion results agree well with published point source solutions for this event, once the uncertainty bounds of each are taken into account.

Käufl, Paul; Valentine, Andrew P.; O'Toole, Thomas B.; Trampert, Jeannot

2014-03-01

202

Centroid distortion of a wavefront with varying amplitude due to asymmetry in lens diffraction.  

Science.gov (United States)

It is often of interest to measure the centroid of a light intensity pattern in order to deduce physical properties. Examples are the Hartmann-Shack sensor, which measures the wavefront slopes, and position sensors. We investigate whether amplitude changes of the incoming electromagnetic field can affect the location of the centroid, and we show that the effect is strongly dependent on the relative size of the diffraction pattern in relation to the lenslet size. We show that if the phase varies slowly in space-and the focal spot size relative to the centroid integration area approaches zero-this variation does not affect the centroid. This is a consequence of symmetry properties of the Fresnel operator. We then show that when the focal width is not infinitely small, changes in the field amplitude can exacerbate distortion of the centroid results. PMID:19109604

Carmon, Yuval; Ribak, Erez N

2009-01-01

203

New Method for Finding an Optimal Solution to Quadratic Programming Problems  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study is to present a new method for finding an optimal solution to quadratic programming problems. The principle of the method is based on calculating the value of critical point. If the critical point belongs to the set of feasible solutions, so the optimal solution to our problem is the critical point itself. If the critical point is not at in the feasible solution set, a new feasible constraint set is built by a homographic transform, in such a way that the projection of the critical point of the objective function onto this set produces the exact solution to the problem on hand. It should be noted here that the objective function may be convex or not convex. On the other hand the search for the optimal solution is to find the hyper plane separating the convex and the critical point. Notice that one does not need to transform the quadratic problem into an equivalent linear one as in the numerical methods; the method is purely analytical and avoids the usage of initial solution. An algorithm computing the optimal solution of the concave function has given.

R. Mekki

2010-01-01

204

Observations of sensor bias dependent cluster centroid shifts in a prototype sensor for the LHCb Vertex Locator detector  

CERN Document Server

We present results from a recent beam test of a prototype sensor for the LHCb Vertex Locator detector, read out with the Beetle 1.3 front-end chip. We have studied the effect of the sensor bias voltage on the reconstructed cluster positions in a sensor placed in a 120GeV pion beam at a 10° incidence angle. We find an unexplained sysematic shift in the reconstructed cluster centroid when increasing the bias voltage on an already overdepleted sensor. The shift is independent of strip pitch and sensor thickness.

Papadelis, Aras

2006-01-01

205

Observations of sensor bias dependent cluster centroid shifts in a prototype sensor for the LHCb Vertex Locator detector  

International Nuclear Information System (INIS)

We present results from a recent beam test of a prototype sensor for the LHCb Vertex Locator detector, read out with the Beetle1.3 front-end chip. We have studied the effect of the sensor bias voltage on the reconstructed cluster positions in a sensor placed in a 120GeV pion beam at a 10-bar incidence angle. We find an unexplained systematic shift in the reconstructed cluster centroid when increasing the bias voltage on an already overdepleted sensor. The shift is independent of strip pitch and sensor thickness

206

Numerical method for finding decoherence-free subspaces and its applications  

Science.gov (United States)

In this work, inspired by the study of semidefinite programming for block-diagonalizing matrix *-algebras, we propose an algorithm that can find the algebraic structure of decoherence-free subspaces (DFS's) for a given noisy quantum channel. We prove that this algorithm will work for all cases with probability 1, and it is more efficient than the algorithm proposed by J. A. Holbrook, D. W. Kribs, and R. Laflamme, [Quantum. Inf. Proc.1570-075510.1023/B:QINP.0000022737.53723.b4 80, 381 (2003)]. In fact, our results reveal that this previous algorithm only works for special cases. As an application, we discuss how this method can be applied to increase the efficiency of an optimization procedure for finding an approximate DFS.

Wang, Xiaoting; Byrd, Mark; Jacobs, Kurt

2013-01-01

207

Minima Hopping Accelerated Path Search: An Efficient Method for Finding Complex Chemical Reaction Pathways  

CERN Document Server

Based on Minima Hopping and its capabilities of exploring potential energy surfaces we have developed Minima Hopping Accelerated Path Search (MHAPS) which is a novel algorithm for efficiently finding the reaction paths of complex chemical reactions by sampling collections of energetically low-lying minima and first order saddle points of potential energy surfaces. For this new reaction path search method we developed a highly reliable approach for computing saddle points which is based on the idea of a bar rolling downwards the potential energy landscape. For Lennard-Jones benchmark systems, Minima Hopping Accelerated Path Search was compared to a known mode-following based approach for sampling collections of minima and first order transition states. Although we used a stabilized mode-following technique that reliably allows to follow distinct directions that are defined by the eigenvectors of the Hessian matrix, we observed that Minima Hopping Accelerated Path Search is far superior in finding lowest-barrie...

Schaefer, Bastian; Amsler, Maximilian; Goedecker, Stefan

2014-01-01

208

A method for finding the ridge between saddle points applied to rare event rate estimates.  

Science.gov (United States)

A method is presented for finding the ridge between first order saddle points on a multidimensional surface. For atomic scale systems, such saddle points on the energy surface correspond to atomic rearrangement mechanisms. Information about the ridge can be used to test the validity of the harmonic approximation to transition state theory, in particular to verify that second order saddle points--maxima along the ridge--are high enough compared to the first order saddle points. New minima along the ridge can also be identified during the path optimisation, thereby revealing additional transition mechanisms. The method is based on a string of discretisation points along a path between the first order saddle points and using an iterative optimisation which requires only the force acting on the atoms. At each iteration during the optimisation, the force is inverted along an unstable eigenmode perpendicular to the path. The method is applied to Al adatom diffusion on the Al(100) surface to find the ridge between 2-, 3- and 4-atom concerted displacements and hop mechanisms. A correction to the harmonic approximation of transition state theory was estimated by direct evaluation of the configuration integral along the ridge. PMID:22262088

Maronsson, Jón Bergmann; Jónsson, Hannes; Vegge, Tejs

2012-02-28

209

A method for finding the ridge between saddle points applied to rare event rate estimates  

DEFF Research Database (Denmark)

A method is presented for finding the ridge between first order saddle points on a multidimensional surface. For atomic scale systems, such saddle points on the energy surface correspond to atomic rearrangement mechanisms. Information about the ridge can be used to test the validity of the harmonic approximation to transition state theory, in particular to verify that second order saddle points—maxima along the ridge—are high enough compared to the first order saddle points. New minima along the ridge can also be identified during the path optimisation, thereby revealing additional transition mechanisms. The method is based on a string of discretisation points along a path between the first order saddle points and using an iterative optimisation which requires only the force acting on the atoms. At each iteration during the optimisation, the force is inverted along an unstable eigenmode perpendicular to the path. The method is applied to Al adatom diffusion on the Al(100) surface to find the ridge between 2-,3- and 4-atom concerted displacements and hop mechanisms. A correction to the harmonic approximation of transition state theory was estimated by direct evaluation of the configuration integral along the ridge.

Maronsson, Jon Bergmann; Jónsson, Hannes

2012-01-01

210

Optimization of the fermentation media for sophorolipid production from Candida bombicola ATCC 22214 using a simplex centroid design.  

Science.gov (United States)

This article describes the use of a simplex centroid mixture experimental design to optimize the fermentation medium in the production of sophorolipids (SLs) using Candida bombicola. In the first stage, 16 media ingredients were screened for the ones that have the most positive influence on the SL production. The sixteen ingredients that were chosen are five different carbohydrates (fructose, glucose, glycerol, lactose, and sucrose), five different nitrogen sources (malt extract, peptone extract, soytone, urea, and yeast extract), two lipid sources (mineral oil and oleic acid), two phosphorus sources (K(2)HPO(4) and KH(2)PO(4)), MgSO(4), and CaCl(2). Multiple regression analysis and centroid effect analysis were carried out to find the sugar, lipid, nitrogen source, phosphorus source, and metals having the most positive influence. Sucrose, malt extract, oleic acid, K(2)HPO(4), and CaCl(2) were selected for the second stage of experiments. An augmented simplex centroid design for five ingredients requiring 16 experiments was used for the optimization stage. This produced a quadratic model developed to help understand the interaction amongst the ingredients and find the optimal media concentrations. In addition, the top three results from the optimization experiments were used to obtain constraints that identify an optimal region. The model together with the optimal region constraints predicts the maximum production of SLs when the fermentation media is composed of sucrose, 125 g/L; malt extract, 25 g/L; oleic acid, 166.67 g/L; K(2)HPO(4), 1.5 g/L; and CaCl(2), 2.5 g/L. The optimal media was validated experimentally and a yield of 177 g/L was obtained. PMID:20205261

Rispoli, Fred J; Badia, Daniel; Shah, Vishal

2010-01-01

211

Minima hopping guided path search: An efficient method for finding complex chemical reaction pathways  

Science.gov (United States)

The Minima Hopping global optimization method uses physically realizable molecular dynamics moves in combination with an energy feedback that guarantees the escape from any potential energy funnel. For the purpose of finding reaction pathways, we argue that Minima Hopping is particularly suitable as a guide through the potential energy landscape and as a generator for pairs of minima that can be used as input structures for methods capable of finding transition states between two minima. For Lennard-Jones benchmark systems we compared this Minima Hopping guided path search method to a known approach for the exploration of potential energy landscapes that is based on deterministic mode-following. Although we used a stabilized mode-following technique that reliably allows to follow distinct directions when escaping from a local minimum, we observed that Minima Hopping guided path search is far superior in finding lowest-barrier reaction pathways. We, therefore, suggest that Minima Hopping guided path search can be used as a simple and efficient way to identify energetically low-lying chemical reaction pathways. Finally, we applied the Minima Hopping guided path search approach to 75-atom and 102-atom Lennard-Jones systems. For the 75-atom system we found pathways whose highest energies are significantly lower than the highest energy along the previously published lowest-barrier pathway. Furthermore, many of these pathways contain a smaller number of intermediate transition states than the previously publish lowest-barrier pathway. In case of the 102-atom system Minima Hopping guided path search found a previously unknown and energetically low-lying funnel.

Schaefer, Bastian; Mohr, Stephan; Amsler, Maximilian; Goedecker, Stefan

2014-06-01

212

Neutron radiography with sub-15 ?m resolution through event centroiding  

Science.gov (United States)

Conversion of thermal and cold neutrons into a strong ˜1 ns electron pulse with an absolute neutron detection efficiency as high as 50-70% makes detectors with 10B-doped Microchannel Plates (MCPs) very attractive for neutron radiography and microtomography applications. The subsequent signal amplification preserves the location of the event within the MCP pore (typically 6-10 ?m in diameter), providing the possibility to perform neutron counting with high spatial resolution. Different event centroiding techniques of the charge landing on a patterned anode enable accurate reconstruction of the neutron position, provided the charge footprints do not overlap within the time required for event processing. The new fast 2×2 Timepix readout with >1.2 kHz frame rates provides the unique possibility to detect neutrons with sub-15 ?m resolution at several MHz/cm2 counting rates. The results of high resolution neutron radiography experiments presented in this paper, demonstrate the sub-15 ?m resolution capability of our detection system. The high degree of collimation and cold spectrum of ICON and BOA beamlines combined with the high spatial resolution and detection efficiency of MCP-Timepix detectors are crucial for high contrast neutron radiography and microtomography with high spatial resolution. The next generation of Timepix electronics with sparsified readout should enable counting rates in excess of 107 n/cm2/s taking full advantage of high beam intensity of present brightest neutron imaging facilities.

Tremsin, Anton S.; McPhate, Jason B.; Vallerga, John V.; Siegmund, Oswald H. W.; Bruce Feller, W.; Lehmann, Eberhard; Kaestner, Anders; Boillat, Pierre; Panzner, Tobias; Filges, Uwe

2012-10-01

213

Beam centroid and envelope model for the SLIA accelerator  

Science.gov (United States)

The RAM computer code has been developed to model the Spiral Line Induction Accelerator (SLIA), which is under development at Pulse Sciences Inc. (PSI). The code advances the beam centroid and envelope equations for a complete current pulse in this high-current recirculating accelerator. Since the beam cross-section is elliptical, in general, and the transverse x-y motions are coupled via an axial magnetic field, the beam envelope is modeled using a 4 × 4 covariance matrix. The envelope equation includes a correction for beam diamagnetism. Toroidal self-field contributions to the bending field and the transverse frequencies have been calculated; the results retain terms which were inconsistently omitted in previous derivations, leading to incorrect frequencies. The code uses a circuit model to compute the beam-loading effect on the accelerating voltage at each gap. The transverse gap forces, which drive the beam breakup (BBU) instability are also computed. Realistic field maps for all beamline elements (solenoids, stellarator coils, bending fields, and matching quadrupoles) are incorporated.

Hughes, Thomas P.; Genoni, Thomas C.

1996-05-01

214

Application of a Bayesian method to absorption spectral-line finding in simulated ASKAP data  

CERN Document Server

The large spectral bandwidth and wide field-of-view of the Australian SKA Pathfinder radio telescope will open up a completely new parameter space for large extragalactic HI surveys. Here we focus on identifying and parametrising HI absorption-lines which occur in the line of sight towards strong radio continuum sources. We have developed a method for simultaneously finding and fitting HI absorption-lines in radio data by using multi-nested sampling, a Bayesian Monte-arlo algorithm. The method is tested on a simulated ASKAP data cube, and is shown to be reliable at detecting absorption-lines in low signal-to-noise data without the need to smooth or alter the data. Estimation of the local Bayesian evidence statistic provides a quantitative criterion for assigning significance to a detection and selecting between competing analytical line-profile models.

Allison, J R; Whiting, M T

2011-01-01

215

An automated method to find transition states using chemical dynamics simulations.  

Science.gov (United States)

A procedure to automatically find the transition states (TSs) of a molecular system (MS) is proposed. It has two components: high-energy chemical dynamics simulations (CDS), and an algorithm that analyzes the geometries along the trajectories to find reactive pathways. Two levels of electronic structure calculations are involved: a low level (LL) is used to integrate the trajectories and also to optimize the TSs, and a higher level (HL) is used to reoptimize the structures. The method has been tested in three MSs: formaldehyde, formic acid (FA), and vinyl cyanide (VC), using MOPAC2012 and Gaussian09 to run the LL and HL calculations, respectively. Both the efficacy and efficiency of the method are very good, with around 15 TS structures optimized every 10 trajectories, which gives a total of 7, 12, and 83 TSs for formaldehyde, FA, and VC, respectively. The use of CDS makes it a powerful tool to unveil possible nonstatistical behavior of the system under study. © 2014 Wiley Periodicals, Inc. PMID:25413470

Martínez-Núñez, Emilio

2014-11-21

216

BAYESIAN DATA AUGMENTATION DOSE FINDING WITH CONTINUAL REASSESSMENT METHOD AND DELAYED TOXICITY  

Science.gov (United States)

A major practical impediment when implementing adaptive dose-finding designs is that the toxicity outcome used by the decision rules may not be observed shortly after the initiation of the treatment. To address this issue, we propose the data augmentation continual re-assessment method (DA-CRM) for dose finding. By naturally treating the unobserved toxicities as missing data, we show that such missing data are nonignorable in the sense that the missingness depends on the unobserved outcomes. The Bayesian data augmentation approach is used to sample both the missing data and model parameters from their posterior full conditional distributions. We evaluate the performance of the DA-CRM through extensive simulation studies, and also compare it with other existing methods. The results show that the proposed design satisfactorily resolves the issues related to late-onset toxicities and possesses desirable operating characteristics: treating patients more safely, and also selecting the maximum tolerated dose with a higher probability. The new DA-CRM is illustrated with two phase I cancer clinical trials. PMID:24707327

Liu, Suyu; Yin, Guosheng; Yuan, Ying

2014-01-01

217

Reducing false-positive incidental findings with ensemble genotyping and logistic regression based variant filtering methods.  

Science.gov (United States)

As whole genome sequencing (WGS) uncovers variants associated with rare and common diseases, an immediate challenge is to minimize false-positive findings due to sequencing and variant calling errors. False positives can be reduced by combining results from orthogonal sequencing methods, but costly. Here, we present variant filtering approaches using logistic regression (LR) and ensemble genotyping to minimize false positives without sacrificing sensitivity. We evaluated the methods using paired WGS datasets of an extended family prepared using two sequencing platforms and a validated set of variants in NA12878. Using LR or ensemble genotyping based filtering, false-negative rates were significantly reduced by 1.1- to 17.8-fold at the same levels of false discovery rates (5.4% for heterozygous and 4.5% for homozygous single nucleotide variants (SNVs); 30.0% for heterozygous and 18.7% for homozygous insertions; 25.2% for heterozygous and 16.6% for homozygous deletions) compared to the filtering based on genotype quality scores. Moreover, ensemble genotyping excluded > 98% (105,080 of 107,167) of false positives while retaining > 95% (897 of 937) of true positives in de novo mutation (DNM) discovery in NA12878, and performed better than a consensus method using two sequencing platforms. Our proposed methods were effective in prioritizing phenotype-associated variants, and an ensemble genotyping would be essential to minimize false-positive DNM candidates. PMID:24829188

Hwang, Kyu-Baek; Lee, In-Hee; Park, Jin-Ho; Hambuch, Tina; Choe, Yongjoon; Kim, MinHyeok; Lee, Kyungjoon; Song, Taemin; Neu, Matthew B; Gupta, Neha; Kohane, Isaac S; Green, Robert C; Kong, Sek Won

2014-08-01

218

Seismotectonics of Morocco from regional centroid moment tensors  

Science.gov (United States)

We have obtained new regional centroid moment tensors (RCMTs) for 35 earthquakes occurred in Morocco and vicinity between 2008 and 2012. During this time period an unprecedented number of broadband stations (more than 100) were operating in the region, providing high-quality waveform data that were used to obtain RCMTs from waveform inversion. The main part of this dataset was composed of temporary broadband stations that were concurrently deployed in different seismic experiments (i.e. IberArray, PICASSO, Muenster, Bristol). The events analyzed in this study are moderate in size, ranging in moment magnitude Mw from 3.5 to 4.8. Their predominant mechanisms correspond to reverse and strike-slip faulting, although normal and "mixed" mechanisms are also observed. In spite of this variability in mechanism type, when analyzed in terms of the orientation of the P (compression) axes two major groups can be distinguished. The first group, corresponding to earthquakes in the Altas and NE Morocco is characterized by near-horizontal P axes oriented in an approximately NW-SE direction that coincides with the direction of convergence between Africa and Eurasia. A small clockwise rotation of the orientation of the P axes is observed from eastern Morocco to the western Atlas. The second group corresponds to earthquakes in the western Rif, that are characterized also by horizontal P axes, but oriented in a SW-NE direction, almost perpendicular to the first group. These earthquakes are part of a cluster located north of Ouezzane. The mechanisms in this second cluster are consistent with recent GPS results that show that the western Rif is moving in a SW direction with respect to the African (Nubia) plate.

Villaseñor, Antonio; el Moudnib, Lahcen; Herrmann, Robert B.; Harnafi, Mimoun

2014-05-01

219

An experiment in systematic study of global seismicity: centroid- moment tensor solutions for 201 moderate and large earthquakes in 1981.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Data from the Global Digital Seismograph Network were used to obtain 'centroid-moment tensor' solutions using the method of Dziewonski et al (1981). Results were obtained for 201 earthquakes ranging in seismic moment from 7 X 1023-3 X 1027 dyne-cm. The wide dynamic range of the SRO/ASRO stations allows us to investigate, using the same algorithm, series of events among which the smallest and the largest may differ in moment by a factor as large as 1000. Among the events studied is a particula...

Dziewonski, Am; Woodhouse, Jh

1983-01-01

220

GeneWaltz--A new method for reducing the false positives of gene finding  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Identifying protein-coding regions in genomic sequences is an essential step in genome analysis. It is well known that the proportion of false positives among genes predicted by current methods is high, especially when the exons are short. These false positives are problematic because they waste time and resources of experimental studies. Methods We developed GeneWaltz, a new filtering method that reduces the risk of false positives in gene finding. GeneWaltz utilizes a codon-to-codon substitution matrix that was constructed by comparing protein-coding regions from orthologous gene pairs between mouse and human genomes. Using this matrix, a scoring scheme was developed; it assigned higher scores to coding regions and lower scores to non-coding regions. The regions with high scores were considered candidate coding regions. One-dimensional Karlin-Altschul statistics was used to test the significance of the coding regions identified by GeneWaltz. Results The proportion of false positives among genes predicted by GENSCAN and Twinscan were high, especially when the exons were short. GeneWaltz significantly reduced the ratio of false positives to all positives predicted by GENSCAN and Twinscan, especially when the exons were short. Conclusions GeneWaltz will be helpful in experimental genomic studies. GeneWaltz binaries and the matrix are available online at http://en.sourceforge.jp/projects/genewaltz/.

Misawa Kazuharu

2010-09-01

 
 
 
 
221

Using a complete spectroscopic survey to find red quasars and test the KX method  

CERN Document Server

We present an investigation of quasar colour-redshift parameter space in order to search for radio-quiet red quasars and to test the ability of a variant of the KX quasar selection method to detect quasars over a full range of colour without bias. This is achieved by combining IRIS2 imaging with the complete Fornax Cluster Spectroscopic Survey to probe parameter space unavailable to other surveys. We construct a new sample of 69 quasars with measured bJ - K colours. We show that the colour distribution of these quasars is significantly different from that of the Large Bright Quasar Survey's quasars at a 99.9% confidence level. We find 11 of our sample of 69 quasars have signifcantly red colours (bJ - K >= 3.5) and from this, we estimate the red quasar fraction of the K <= 18.4 quasar population to be 31%, and robustly constrain it to be at least 22%. We show that the KX method variant used here is more effective than the UVX selection method, and has less colour bias than optical colour-colour selection me...

Jurek, Russell J; Francis, Paul J; Pimbblet, Kevin A

2007-01-01

222

THE LOCATION OF CENTROIDS IN PHOTON AND ELECTRON MAPS OF SOLAR FLARES  

International Nuclear Information System (INIS)

We explore the use of centroid coordinates as a means to identify the 'locations' of electron-proton bremsstrahlung hard X-ray sources in solar flares. Differences between the coordinates of the electron and photon centroids are derived and explained. For electron propagation in a collision-dominated target, with either a uniform or an exponential density profile, the position of the electron centroid can be calculated analytically. We compare these analytic forms to data from a flare event on 2002 February 20. We first spectrally invert the native photon visibility data to obtain 'electron visibilities', which are in turn used to construct electron flux images at various electron energies E. Centroids of these maps are then obtained by straightforward numerical integration over the electron maps. This comparison allows us to infer the density structure in the two compact sources visible, and we discuss the (somewhat unexpected) results thus obtained.

223

Measurements of ultrasonic backscattered spectral centroid shift from spine in vivo: methodology and preliminary results  

Science.gov (United States)

We have developed a technique to measure backscattered ultrasound from lumbar vertebrae using a commercial ultrasound scanner. The spectral centroid shift between the spine and reference phantom data is an index of attenuation within the spine. From measurements from 11 vertebrae, we found a correlation coefficient of r = -0.61 between spectral centroid shift and bone mineral density (BMD). This negative correlation is expected as denser, more highly attenuating bone would be expected to produce greater downshifts in spectral centroid. This is the first technique performing quantitative ultrasound measurements on trabecular bone in the spine. This study shows that (1) acquisition of ultrasonic backscatter data from human spine in vivo is feasible, and (2) spectral centroid shift exhibits a moderate negative correlation with BMD in accordance with expectations.

Wear, Keith A.; Garra, Brian S.; Pinet, Melanie C.; Felker, Steven; Mai, Jonathan

2003-05-01

224

A Computer Program to Create a Population with Any Desired Centroid and Covariance Matrix  

Science.gov (United States)

A Computer program written in FORTRAN IV is presented which will create a population of desired size with marginally normal score vectors manifesting any desired centroid and covariance matrix. Uses and documentation are provided. (Author)

Morris, John D.

1975-01-01

225

Centroiding algorithms for high speed crossed strip readout of microchannel plate detectors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Imaging microchannel plate (MCP) detectors with cross strip (XS) readout anodes require centroiding algorithms to determine the location of the amplified charge cloud from the incident radiation, be it photon or particle. We have developed a massively parallel XS readout electronic system that employs an amplifier and ADC for each strip and uses this digital data to calculate the centroid of each event in real time using a field programmable gate array (FPGA). Doing the calculations in real t...

Vallerga, John; Tremsin, Anton; Raffanti, Rick; Siegmund, Oswald

2011-01-01

226

Optimal Estimation Of Range And Doppler Centroid In ScanSAR  

Science.gov (United States)

Algorithm processes synthetic-aperture-radar (SAR) returns into optimal estimates of ranges, pointing angles, and Doppler centroids. Derives radar-beam-pointing angles partly from SAR data. Exploits information available in overlapping regions between adjacent image bursts or, equivalently, between adjacent radar beams corresponding to adjacent image bursts. Range or Doppler centroid obtained from estimate of range or Doppler value at which intensity in one image burst equals that in adjacent burst.

Jin, Michael Y.

1995-01-01

227

Localization Algorithm based on Improved Weighted Centroid in Wireless Sensor Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Location technology is becoming more and more important in wireless sensor networks. The weighted centroid localization offers a fast and simple algorithm for the location equipment in wireless sensor networks. The algorithm derives from the centroid measurement and calculation device of the adjacent anchor in the average coordinate. After the analysis of the radio propagation loss model, the most appropriate log-distance distribution model is selected to simulate the signal propagation. Base...

Shyi-Ching Liang; LunHao Liao; Yen-Chun Lee

2014-01-01

228

Optical Range and Doppler Centroid Estimation for a ScanSAR System  

Science.gov (United States)

This paper presents a new range and Doppler centroid estimation algorithm for a ScanSAR system. Its accurate range and Doppler centroid estimates lead to refined radar pointing angles, which enables the ScanSAR imagery meeting its radiometric reuirements. This algorithm attains an accuracy equal to the cramer Rao's lower bound for both the homogeneous and quasi-homogeneous targets. This algorithm is also efficient in computation and easy for implementation.

Jin, Michael Y.

1994-01-01

229

Multiple-precision zero-finding methods and the complexity of elementary function evaluation  

CERN Document Server

We consider methods for finding high-precision approximations to simple zeros of smooth functions. As an application, we give fast methods for evaluating the elementary functions log(x), exp(x), sin(x) etc. to high precision. For example, if x is a positive floating-point number with an n-bit fraction, then (under rather weak assumptions) an n-bit approximation to log(x) or exp(x) may be computed in time asymptotically equal to 13M(n)lg(n), where M(n) is the time required to multiply floating-point numbers with n-bit fractions. Similar results are given for the other elementary functions. Some analogies with operations on formal power series (over a field of characteristic zero) are discussed. In particular, it is possible to compute the first n terms in log(1 + a_1.x + ...) or exp(a_1.x + ...) in time O(M(n)), where M(n) is the time required to multiply two polynomials of degree n - 1. It follows that the first n terms in a q-th power (1 + a_1.x + ...)^q can be computed in time O(M(n)), independent of q. One...

Brent, Richard P

2010-01-01

230

The evolution of the transverse centroid of asymmetric laser field in plasmas with various density distributions  

International Nuclear Information System (INIS)

The propagation of asymmetric relativistic intense laser beams in nonuniform and uniform underdense cold plasmas is studied. After simplifying the wave equation, we obtain the evolution equation of the transverse centroid of laser beams in terms of variational approaches. Theoretical analysis shows that in uniform plasmas a laser beam with an asymmetric initial phase has a constant centroid drift velocity, at which the centroid of the laser beam drifts away from the light axis in a fixed direction; the centroid drift velocity of a laser beam with symmetric initial phase, but either symmetric or asymmetric amplitude, is always zero, i.e., the symmetric features of the laser field is retained. Furthermore, the channel-like symmetric plasma plays a role like a restoring force to confine the laser centroid around the density channel axis so the centroid of the laser beam with asymmetric amplitude or phase is going to oscillate with damp around the channel axis. The nonlinear effect can symmetrize initially asymmetric laser beams and the steeper effective density gradient is more beneficial to the symmetrizing process. Finally, the analytic results are checked and confirmed by numerical simulations with finite difference to the wave equation and two-dimensional particle-in-cell code

231

Novas abordagens da avaliação do comportamento tático no futebol: análise do centroid e índice de dispersão / Towards a new evaluation of the football' tactical behaviour: analysis of the centroid and stretch index  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese A tendência evolutiva do futebol determina as necessidades de produzir ferramentas inovadoras que aumentem substancialmente a eficiência da análise de jogo. Considerando os métodos tradicionais notacionais como limitados para a interpretação dos processos de jogo, a investigação carece de novos méto [...] dos nos quais prevaleça a análise do processo. Dessa forma, o presente trabalho propõe-se a analisar novas métricas quantitativas e automáticas de avaliação tática no futebol, nomeadamente o centroid de equipe e o índice de dispersão. Abstract in english The evolutionary tendency of the football game determines the conception of the new tools that increase the efficiency of the match analysis. The traditional notational analysis, actually, are limited to understand the true dynamic of the football match, thus the investigation lacks by new methods t [...] o understand the process and not just the product. Therefore, this work aims analyze new automatically tactical metrics, specifically the centroid and the stretch index method.

Rui Manuel, Mendes; Filipe Manuel, Clemente; Micael Santos, Couceiro; Fernando Manuel Lourenço, Martins.

2013-12-01

232

Time delay and magnification centroid due to gravitational lensing by black holes and naked singularities  

International Nuclear Information System (INIS)

We model the massive dark object at the center of the Galaxy as a Schwarzschild black hole as well as Janis-Newman-Winicour naked singularities, characterized by the mass and scalar charge parameters, and study gravitational lensing (particularly time delay, magnification centroid, and total magnification) by them. We find that the lensing features are qualitatively similar (though quantitatively different) for Schwarzschild black holes, weakly naked, and marginally strongly naked singularities. However, the lensing characteristics of strongly naked singularities are qualitatively very different from those due to Schwarzschild black holes. The images produced by Schwarzschild black hole lenses and weakly naked and marginally strongly naked singularity lenses always have positive time delays. On the other hand, strongly naked singularity lenses can give rise to images with positive, zero, or negative time delays. In particular, for a large angular source position the direct image (the outermost image on the same side as the source) due to strongly naked singularity lensing always has a negative time delay. We also found that the scalar field decreases the time delay and increases the total magnification of images; this result could have important implications for cosmology. As the Janis-Newman-Winicour metric also describes the exterior gravitational field of a scalar star, naked singularities as well as scalar star lenses, if these exist in nature, will serve as more these exist in nature, will serve as more efficient cosmic telescopes than regular gravitational lenses

233

SAFT Based Imaging and Centroid Technique for Classification of UT Signals from the Steam Generator of a Nuclear Power Plant  

International Nuclear Information System (INIS)

Many technical methods are used for nondestructive testing field for solid materials. Among those, ultrasonic inspection methods are widely used and one of the popular methods involves the extraction of an appropriate set of features followed by the use of a neural network for the classification of the signals in the feature space. This paper describes an approach which uses LMS method to determine the coordinates of the ultrasonic probe followed by the use of SAFT with centroid technique to estimate the location of the ultrasonic reflector. The method is employed for classifying UT-NDE signals from the steam generator tubes in a nuclear power plant. The classification results are presented for the ultrasonic signals from cracks and deposits within steam generator tubes.

234

A measure of variable planar locations anchored on the centroid of the vowel space : A sociophonetic research tool  

DEFF Research Database (Denmark)

This paper presents part of an ongoing research program which aims to apply mathematical and geometrical analytic methods to vowel formant data to enable the quantification of parameters of variation of interest to sociophoneticians. We open with an overview of recent research working towards a set of desiderata for choice of normalization algorithm(s) based on replicable procedures. We then present the principles of centroid-based normalization and account for its performance in recent road tests. In sections 4 and 5 we introduce a method that utilizes the centroid of the speaker’s vowel space as an anchor point or vertex for calculation of planar locations on formant plots, permitting quantification of the distribution of vowel tokens within the space. This information, along with details such as Euclidean distances, can then be used to precisely pinpoint the trajectories of diachronic change, for instance over a set of speakers in different age groups within a defined speech community. This has the advantage of mathematical reproducibility, and reduces the level of subjectivity in visual analyses of formant plots used in investigations of vowel variability and change in progress.

Watt, Dominic; Fabricius, Anne

2011-01-01

235

Subtractive clustering analysis: a novel data mining method for finding cell subpopulations  

Science.gov (United States)

A novel data mining program called "subtractive clustering" picks out the most important differences between two or more flow cytometry listmode data files. While making no assumptions about the data, the program uses a variable weight and skew metric in the determination of bin size allowing for subtractive clustering of data without the need for bit-reduction or projection. In contrast, other subtraction methods, such as channel-by-channel subtraction, are dependent upon dimensionality and resolution, which can lead to an overestimation of positive cells because they do not account for the overall distribution of the test and control data sets. By taking into account human visual inspection of the data it is possible for the experimenter to choose an optimal subtraction by choosing an appropriate weight and skew metric, but without allowing direct modification of the results. By maximizing a bin size which can still differentiate clusters, it is possible to minimize computation while still removing data. The choice of control weight allows for different levels of bin destruction during the subtraction stage, the smaller the number the more conservative the subtraction, the larger, the more liberal. Three data sets illustrate full dimensional subtraction, single step biological data and multi-stage subtraction to show definitive test results. Subtractive clustering was able to conservatively remove control information leaving populations of interest. Subtractive clustering provides a powerful comparison of clusters and is a first step for finding non-obvious (hidden) differences and minimizing human prejudice during the analysis.

Smith, Jacob N.; Reece, Lisa; Szaniszlo, Peter; Leary, Rosemary C.; Leary, James F.

2005-03-01

236

Velocity Field Statistics in Star-forming Regions. I. Centroid Velocity Observations  

Science.gov (United States)

The probability density functions (pdfs) of molecular line centroid velocity fluctuations, and of line centroid velocity fluctuation differences at different spatial lags, are estimated for several nearby molecular clouds with active internal star formation. The data consist of over 75,000 13CO line profiles divided among 12 spatially and/or kinematically distinct regions. These regions range in size from less than 1 to more than 40 pc and are all substantially supersonic, with centroid fluctuation Mach numbers ranging from about 1.5 to 7. The centroid pdfs are constructed using three different types of estimators. Although three regions (all in Mon R2) exhibit nearly Gaussian centroid pdfs, the other regions show strong evidence for non-Gaussian pdfs, often nearly exponential, with possible evidence for power-law contributions in the far tails. Evidence for nearly exponential centroid pdfs in the neutral H I component of the interstellar medium is also presented, based on older published data for optical absorption lines and H I emission and absorption lines. These strongly non-Gaussian pdfs disagree with the nearly Gaussian behavior found for incompressible turbulence (except possibly shear flow turbulence) and simulations of decaying mildly supersonic turbulence. Spatial images of the largest magnitude centroid velocity differences for the star-forming regions appear less filamentary than predicted by decay simulations dominated by vortical interactions. No evidence for the scaling of difference pdf kurtosis with Reynolds number, as found in incompressible turbulence experiments and simulations, is found. We conclude that turbulence in both star-forming molecular clouds and diffuse H I regions involves physical processes that are not adequately captured by incompressible turbulence or by mildly supersonic decay simulations. The variation with lag of the variance and kurtosis of the difference pdfs is presented as a constraint on future simulations, and we evaluate and discuss the implications of the large scale and Taylor scale Reynolds numbers for the regions studied here.

Miesch, Mark S.; Scalo, John; Bally, John

1999-10-01

237

Infant feeding experiences among teen mothers in North Carolina: Findings from a mixed-methods study  

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Full Text Available Abstract Background Adolescent mothers in the U.S. are much less likely to initiate breastfeeding than older mothers, and teens who do initiate breastfeeding tend to breastfeed for shorter durations. The purpose of this mixed-methods study is to investigate breastfeeding practices, barriers and facilitators among adolescent mothers ages 17 and younger. Methods Quantitative descriptive analyses are conducted using data from the North Carolina Pregnancy Risk Assessment Monitoring System (PRAMS. The population-based sample comprises 389 teens ages 13-17 giving birth to a live born infant in North Carolina in 2000 - 2005 and in 2007. Qualitative analyses are based on in-depth interviews with 22 Black, White and Hispanic teen mothers residing in rural and urban areas of North Carolina conducted between November 2007 and February 2009. Results In quantitative analyses, 52% (196 of 389 of North Carolina teen mothers initiated breastfeeding, but half of those who initiated breastfeeding (92/196 stopped within the first month postpartum. Hispanic teens (44/52 or 89% were much more likely than Black (61/159 or 41% or White teens (87/164 or 52% to initiate breastfeeding and to continue for a longer duration. Nearly sixty two percent (29/52 of Hispanic respondents breastfed for greater than four weeks as compared to 16% (29/159 of Black respondents and 26% (39/164 of White respondents. Common barriers to breastfeeding initiation and continuation included not liking breastfeeding, returning to school, nipple pain, and insufficient milk. Qualitative data provided context for the quantitative findings, elucidating the barriers and facilitators to breastfeeding from the teens' perspective and insight into the ways in which breastfeeding support to teens could be enhanced. Conclusions The large number of adolescents ceasing breastfeeding within the first month points to the need for more individualized follow-up after hospital discharge in the first few days postpartum, to address common technical challenges and to provide assistance managing the transition back to school. Provision of an extra home visit or outpatient visit for teens within the first few days following hospital discharge, and advocacy to make schools more compatible with breastfeeding, could potentially help teens who desire to breastfeed to successfully continue. These interventions warrant further research to test their effectiveness among adolescents.

Samandari Ghazaleh

2011-09-01

238

Iterative Approaches to Find Zeros of Maximal Monotone Operators by Hybrid Approximate Proximal Point Methods  

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The purpose of this paper is to introduce and investigate two kinds of iterative algorithms for the problem of finding zeros of maximal monotone operators. Weak and strong convergence theorems are established in a real Hilbert space. As applications, we consider a problem of finding a minimizer of a convex function.

Lu Chuan Ceng; Yeong Cheng Liou; Eskandar Naraghirad

2011-01-01

239

Study of centroiding algorithms to optimize Shack-Hartmann WFS in the context of ELTs  

Science.gov (United States)

Along with the expected ELTs comes the diversification of Adaptive Optics (AO) systems. Mo%J 1st AO are beginning to make extensive use of laser guide stars (LGS), to increase sky coverage and produce a bright beacon in order to reduce wavefront measurement errors and improve performance. However, because of the larger size of the next generation of telescopes, the elongation seen in a Shack-Hartmann Wavefront Sensor is larger, i.e up to 7” for a 30m telescope. With such an elongation, both photon and read noise will increase and distribution variations of sodium atoms in the sodium layer start to matter. In this paper, we conduct ShackHartmann simulations at the sub-aperture level made with real sodium profiles taken at Lick Observatory. We will compare focus on two methods of centroiders: the matched filter and the correlation. We then compare results with data taken form a real bench at Uvic in the particular case of NFIRAOS AO system for TMT. The goal is to better understand the impact of such variations on the final error budget for the WFS.

Thomas, Sandrine; Lardiere, Olivier; Gavel, Donald; Conan, Rodolphe

240

Detection of a surface breaking crack by using the centroid variations of laser ultrasonic spectrums  

International Nuclear Information System (INIS)

A laser ultrasonic system is a non-contact inspection device with a wide-band spectrum and a high spatial resolution. It provides absolute measurements of the moving distance and it can be applied to hard-to-access locations including curved or rough surfaces like in a nuclear power plant. In this paper, we have investigated the detection methods of the depth of a surface-breaking crack by using the surface wave of a laser ultrasound. The filtering function of a surface-breaking crack is a kind of a low-pass filter. The higher frequency components are more highly decreased in proportion to the crack depth. Also, the center frequency value of each ultrasound spectrum is decreased in proportion to the crack depth. We extracted the depth information of a surface-breaking crack by observing the centroid variation of the frequency spectrum. We describe the experimental results to detect the crack depth information by using the peak-to-valley values in the time domain and the center frequency values in the frequency domain.

 
 
 
 
241

New algorithm for centroiding in elongated spots for Shack-Hartmann wavefront sensors using artificial neural networks  

Science.gov (United States)

To recover the resolution lost in a ground-based telescopes due to the atmospheric turbulence, it is necessary to use a technique known as Adaptive Optics (AO). The next generation of telescopes will have primary mirrors of more than 30 meter in diameter and will require AO systems from the ground up (Nelson et al. 2006). There are a number of challenges to implement an AO system at these scales. One of these challenges is the accurate measurement of the aberrated wavefronts using a laser guide star and a Shack-Hartmann wavefront sensor. Due to the diameter of the telescope and the use of the sodium layer in the upper atmosphere as photon return for the laser guide stars, the image of the guide star will appear elongated in the wavefront sensor. Typical centroiding algorithms such as Center of Gravity do not perform well under these conditions (Thomas et al. 2008). We present a new technique based on artificial neural networks for measuring the spot position with better accuracy than existing methods. Simulation results confirms that the new algorithm incurs in smaller errors with respect to other centroiding techniques in use.

Mello, A. T.; Kanaan, A.; Guzmán, D.

2014-10-01

242

Correcting the beam centroid motion in an induction accelerator and reducing the beam breakup instability  

Science.gov (United States)

Axial beam centroid and beam breakup (BBU) measurements were conducted on an 80 ns FWHM, intense relativistic electron bunch with an injected energy of 3.8 MV and current of 2.9 kA. The intense relativistic electron bunch is accelerated and transported through a nested solenoid and ferrite induction core lattice consisting of 64 elements, exiting the accelerator with a nominal energy of 19.8 MeV. The principal objective of these experiments is to quantify the coupling of the beam centroid motion to the BBU instability and validate the theory of this coupling for the first time. Time resolved centroid measurements indicate a reduction in the BBU amplitude, ???, of 19% and a reduction in the BBU growth rate (?) of 4% by reducing beam centroid misalignments ˜50% throughout the accelerator. An investigation into the contribution of the misaligned elements is made. An alignment algorithm is presented in addition to a qualitative comparison of experimental and calculated results which include axial beam centroid oscillations, BBU amplitude, and growth with different dipole steering.

Coleman, J. E.; Ekdahl, C. A.; Moir, D. C.; Sullivan, G. W.; Crawford, M. T.

2014-09-01

243

Southern Ocean jets and how to find them: Improving and comparing common jet detection methods  

Science.gov (United States)

study undertakes a detailed comparison of different methods used for detecting and tracking oceanic jets in the Southern Ocean. The methods under consideration are the gradient thresholding method, the probability density function (PDF) method, and the contour method. Some weaknesses of the gradient thresholding method are discussed and an enhancement (the WHOSE method), based on techniques from signal processing, is proposed. The WHOSE method is then compared to the other three methods. Quantitative comparison is undertaken using synthetic sea-surface height fields. The WHOSE method and the contour method are found to perform well even in the presence of a strong eddy field. In contrast, the standard gradient thresholding and PDF methods only perform well in high signal-to-noise ratio situations. The WHOSE, PDF, and the contour methods are then applied to data from the eddy-resolving Ocean General Circulation Model for the Earth Simulator. While the three methods are in broad agreement on the location of the main ACC jets, the nature of the jet fields they produce differ. In particular, the WHOSE method reveals a fine-scale jet field with complex braiding behavior. It is argued that this fine-scale jet field may affect the calculation of eddy diffusivities. Finally, recommendations based on this study are made. The WHOSE and gradient thresholding methods are more suitable for the study of jets as localized strong currents, useful for studies of tracer fluxes. The contour and PDF methods are recommended for studies linking jets to hydrographic fronts.

Chapman, Christopher C.

2014-07-01

244

Estimation Normal Vector of Triangular Mesh Vertex by Angle and Centroid Weights and its Application  

Directory of Open Access Journals (Sweden)

Full Text Available To compute vertex normal of triangular meshes more accurately, this paper presents an improved algorithm based on angle and centroid weights. Firstly, four representational algorithms are analyzed by comparing their weighting characteristics such as angles, areas and centroids. The drawbacks of each algorithm are discussed. Following that, an improved algorithm is put forward based on angle and centroid weights. Finally, by taking the deviation angle between the nominal normal vector and the estimated one as the error evaluation standard factor, the triangular mesh models of spheres, ellipsoids, paraboloids and cylinders are used to analyze the performance of all these estimation algorithms. The machining and inspection operations of one mould part are conducted to verify the improved algorithm. Experimental results demonstrate that the algorithm is effective.

Yueping Chen

2013-04-01

245

Parallel algorithms for planar and spherical Delaunay construction with an application to centroidal Voronoi tessellations  

Directory of Open Access Journals (Sweden)

Full Text Available A new algorithm, featuring overlapping domain decompositions, for the parallel construction of Delaunay and Voronoi tessellations is developed. Overlapping allows for the seamless stitching of the partial Delaunay tessellations constructed by individual processors. The algorithm is then modified, by the addition of stereographic projections, to handle the parallel construction of spherical Delaunay and Voronoi tessellations. The algorithms are then embedded into algorithms for the parallel construction of planar and spherical centroidal Voronoi tessellations that require multiple constructions of Delaunay tessellations. Computational tests are used to demonstrate the efficiency and scalability of the algorithms for spherical Delaunay and centroidal Voronoi tessellations. Compared to serial versions of the algorithm and to the STRIPACK-based approaches, the new parallel algorithm results in significant speedups for the construction of spherical centroidal Voronoi tessellations.

D. W. Jacobsen

2013-02-01

246

Centroid propagation through optical systems with ABCD kernels and non-uniform or finite apertures  

Science.gov (United States)

Determining the precise location of irradiance centroids is a key step for optical triangulation and wavefront sensing based on wavefront slope measurements (as e.g. in Hartmann-Shack aberrometry). Since most aberrometers include some kind of optical relay system to reimage the irradiance distributions provided by the wavefront sampling element onto the irradiance detector, it is esential to ensure that the centroid position and momentum information is preserved along this operation. In optical systems with ABCD difrraction kernels the centroids propagate according to an effective geometrical optics rule. However, the presence of finite apertures partially blocking the incoming beam or non-uniform transmittances unevenly altering its original irradiance distribution may give rise to potentially significant departures from this simple geometrical picture. The potential magnitude of this bias makes it advisable to take proper steps to counteract it in the design of aberrometric setups.

Lancis, Jesús; Martínez-Cuenca, Raúl; Ares, Jorge; Bará, Salvador

2011-05-01

247

Effects of window size and shape on accuracy of subpixel centroid estimation of target images  

Science.gov (United States)

A new algorithm is presented for increasing the accuracy of subpixel centroid estimation of (nearly) point target images in cases where the signal-to-noise ratio is low and the signal amplitude and shape vary from frame to frame. In the algorithm, the centroid is calculated over a data window that is matched in width to the image distribution. Fourier analysis is used to explain the dependency of the centroid estimate on the size of the data window, and simulation and experimental results are presented which demonstrate the effects of window size for two different noise models. The effects of window shape were also investigated for uniform and Gaussian-shaped windows. The new algorithm was developed to improve the dynamic range of a close-range photogrammetric tracking system that provides feedback for control of a large gap magnetic suspension system (LGMSS).

Welch, Sharon S.

1993-01-01

248

Beyond Field Effect: Analysis of Shrunken Centroids in Normal Esophageal Epithelia Detects Concomitant Esophageal Adenocarcinoma  

Directory of Open Access Journals (Sweden)

Full Text Available Background and Aims: Because of the extremely low neoplastic progression rate in Barrett’s esophagus, it is difficult to diagnose patients with concomitant adenocarcinoma early in their disease course. If biomarkers existed in normal squamous esophageal epithelium to identify patients with concomitant esophageal adenocarcinoma, potential applications would be far-reaching. The aim of the current study was to identify global gene expression patterns in normal esophageal epithelium capable of revealing simultaneous esophageal adenocarcinoma, even located remotely in the esophagus.Methods: Tissues comprised normal esophageal epithelia from 9 patients with esophageal adenocarcinoma, 8 patients lacking esophageal adenocarcinoma or Barrett’s, and 6 patients with Barrett’s esophagus alone. cDNA microarrays were performed, and pattern recognition in each of these subgroups was achieved using shrunken nearest centroid predictors. Results: Our method accurately discriminated normal esophageal epithelia of 8/8 patients without esophageal adenocarcinoma or Barrett’s esophagus and of 6/6 patients with Barrett’s esophagus alone from normal esophageal epithelia of 9/9 patients with Barrett’s esophagus and concomitant esophageal adenocarcinoma. Moreover, we identified genes differentially expressed between the above subgroups. Thus, based on their corresponding normal esophageal epithelia alone, our method accurately diagnosed patients who had concomitant esophageal adenocarcinoma.Conclusions: These global gene expression patterns, along with individual genes culled from them, represent potential biomarkers for the early diagnosis of esophageal adenocarcinoma from normal esophageal epithelia. Genes discovered in normal esophagus that are differentially expressed in patients with vs. without esophageal adenocarcinoma merit further pursuit in molecular genetic, functional, and therapeutic interventional studies.

Florin M. Selaru

2007-01-01

249

Fast Simulators for Satellite Cloud Optical Centroid Pressure Retrievals, 1. Evaluation of OMI Cloud Retrievals  

Science.gov (United States)

The cloud Optical Centroid Pressure (OCP), also known as the effective cloud pressure, is a satellite-derived parameter that is commonly used in trace-gas retrievals to account for the effects of clouds on near-infrared through ultraviolet radiance measurements. Fast simulators are desirable to further expand the use of cloud OCP retrievals into the operational and climate communities for applications such as data assimilation and evaluation of cloud vertical structure in general circulation models. In this paper, we develop and validate fast simulators that provide estimates of the cloud OCP given a vertical profile of optical extinction. We use a pressure-weighting scheme where the weights depend upon optical parameters of clouds and/or aerosol. A cloud weighting function is easily extracted using this formulation. We then use fast simulators to compare two different satellite cloud OCP retrievals from the Ozone Monitoring Instrument (OMI) with estimates based on collocated cloud extinction profiles from a combination of CloudS at radar and MODIS visible radiance data. These comparisons are made over a wide range of conditions to provide a comprehensive validation of the OMI cloud OCP retrievals. We find generally good agreement between OMI cloud OCPs and those predicted by CloudSat. However, the OMI cloud OCPs from the two independent algorithms agree better with each other than either does with the estimates from CloudSat/MODIS. Differences between OMI cloud OCPs and those based on CloudSat/MODIS may result from undetected snow/ice at the surface, cloud 3-D effects, low altitude clouds missed by CloudSat, and the fact that CloudSat only observes a relatively small fraction of an OMI field-of-view.

Joiner, J.; Vasilkov, A.; Gupta, P.; Bhartia, P. K.; Veefkind, P.; Sneep, M.; de Haan, J.; Polonsky, I.; Spurr, R.

2012-01-01

250

Study of Functional Variable Method for Finding Exact Solutions of Nonlinear Evolution Equations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A direct method, called the functional variable method, has been used to construct the exact solutions of nonlinear evolution equations (NLEEs) in mathematical physics. To illustrate the validity and advantages of this method, the (2+1) dimensional Boussinesq-Kadomtsev-Petviashvili (BKP) equations and the new coupled Konno-Oono (KO) equations are considered. The obtained solutions contain an explicit function of the variables in the considered equations. It has been shown ...

Khan, Kamruzzaman; Ali Akbar, M.

2015-01-01

251

GeneWaltz--A new method for reducing the false positives of gene finding  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Identifying protein-coding regions in genomic sequences is an essential step in genome analysis. It is well known that the proportion of false positives among genes predicted by current methods is high, especially when the exons are short. These false positives are problematic because they waste time and resources of experimental studies. Methods We developed GeneWaltz, a new filtering method that reduces the risk of false positives in gene f...

Misawa Kazuharu; Kikuno Reiko F

2010-01-01

252

Study of Functional Variable Method for Finding Exact Solutions of Nonlinear Evolution Equations  

Directory of Open Access Journals (Sweden)

Full Text Available A direct method, called the functional variable method, has been used to construct the exact solutions of nonlinear evolution equations (NLEEs in mathematical physics. To illustrate the validity and advantages of this method, the (2+1 dimensional Boussinesq-Kadomtsev-Petviashvili (BKP equations and the new coupled Konno-Oono (KO equations are considered. The obtained solutions contain an explicit function of the variables in the considered equations. It has been shown that the method provides a powerful mathematical tool for solving NLEEs in mathematical physics and engineering fields without the help of computer algebra system.

Kamruzzaman KHAN

2015-03-01

253

Quantum Imaging beyond the Diffraction Limit by Optical Centroid Measurements  

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I propose a quantum imaging method that can beat the Rayleigh-Abbe diffraction limit and achieve de Broglie resolution without requiring a multi-photon absorber or coincidence detection. Using the same non-classical states of light as those for quantum lithography, the proposed method requires only optical intensity measurements, followed by image post-processing, to produce the same complex quantum interference patterns as those in quantum lithography. The method is expected to b...

Tsang, Mankei

2009-01-01

254

Finding the Right Mix: Teaching Methods as Predictors for Student Progress on Learning Objectives  

Science.gov (United States)

This study extends existing student ratings research by exploring how teaching methods, individually and collectively, influence a minimum standard of student achievement on learning objectives and how class size impacts this influence. Twenty teaching methods were used to predict substantial or exceptional progress on each of 12 learning…

Glover, Jacob I.

2012-01-01

255

Mechanical form-Finding of the Timber Fabric Structures with Dynamic Relaxation Method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Timber Fabric structures (TFS) initiate from a correspondence between textile principles and recent industrial developments in producing cross laminated timber panels. Several individual timber strips are interlaced according to a pattern and result in an innovative space structure. The obtained three-dimensional geometry can be regarded as the relaxed configuration of deformed panels under the imposed boundary conditions. We herein propose a form-finding procedure, which reproduces this def...

Nabaei, Seyed Sina; Baverel, Olivier; Weinand, Yves

2013-01-01

256

Thermal analysis of parabolic concentrator for finding optical efficiency by different methods with varying parameters.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Parabolic concentrator is used to utilize the solar energy for heating purpose. Thermal tests are performed on concentrator at different time periods and at different masses to find the variation in the optical efficiency and heat loss factor. The results verified by graphical test can be used to design the concentrator for the desired output. It was found that the system gave almost the same values of optical efficiency, for the various masses of water on different days. The value of optical...

Abhijeet Auti; Singh, Dr T. P.; Pangavhane, Dr Dilip R.

2013-01-01

257

A Method to Find Longevity-Selected Positions in the Mammalian Proteome  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Evolutionary theory suggests that the force of natural selection decreases with age. To explore the extent to which this prediction directly affects protein structure and function, we used multiple regression to find longevity-selected positions, defined as the columns of a sequence alignment conserved in long-lived but not short-lived mammal species. We analyzed 7,590 orthologous protein families in 33 mammalian species, accounting for body mass, phylogeny, and species-specific mutation rate...

Semeiks, Jeremy; Grishin, Nick V.

2012-01-01

258

Method for finding the critical temperature of the island in a SET structure  

CERN Document Server

We present a method to measure the critical temperature of the island of a superconducting single electron transistor. The method is based on a sharp change in the slope of the zero-bias conductance as a function of temperature. We have used this method to determine the superconducting phase transition temperature of the Nb island of an superconducting single electron transistor with Al leads. We obtain $T_\\mathrm{c}^\\mathrm{Nb}$ as high as 8.5 K and gap energies up to $\\Delta_\\mathrm{Nb}\\simeq 1.45$ meV. By looking at the zero bias conductance as a function of magnetic field instead of temperature, also the critical field of the island can be determined. Using the orthodox theory, we have performed extensive numerical simulations of charge transport properties in the SET at temperatures comparable to the gap, which match very well the data, therefore providing a solid theoretical basis for our method.

Toppari, J J; Halvari, A P; Paraoanu, G S

2008-01-01

259

Centroid-based summarization of multiple documents sentence extraction, utility-based evaluation and user studies  

CERN Document Server

We present a multi-document summarizer, called MEAD, which generates summaries using cluster centroids produced by a topic detection and tracking system. We also describe two new techniques, based on sentence utility and subsumption, which we have applied to the evaluation of both single and multiple document summaries. Finally, we describe two user studies that test our models of multi-document summarization.

Radev, D R; Budzikowska, M; Radev, Dragomir R.; Jing, Hongyan; Budzikowska, Malgorzata

2000-01-01

260

Optimal Doppler centroid estimation for SAR data from a quasi-homogeneous source  

Science.gov (United States)

This correspondence briefly describes two Doppler centroid estimation (DCE) algorithms, provides a performance summary for these algorithms, and presents the experimental results. These algorithms include that of Li et al. (1985) and a newly developed one that is optimized for quasi-homogeneous sources. The performance enhancement achieved by the optimal DCE algorithm is clearly demonstrated by the experimental results.

Jin, M. Y.

1986-01-01

 
 
 
 
261

A numerical method for finding sign-changing solutions of superlinear Dirichlet problems  

Energy Technology Data Exchange (ETDEWEB)

In a recent result it was shown via a variational argument that a class of superlinear elliptic boundary value problems has at least three nontrivial solutions, a pair of one sign and one which sign changes exactly once. These three and all other nontrivial solutions are saddle points of an action functional, and are characterized as local minima of that functional restricted to a codimension one submanifold of the Hilbert space H-0-1-2, or an appropriate higher codimension subset of that manifold. In this paper, we present a numerical Sobolev steepest descent algorithm for finding these three solutions.

Neuberger, J.M.

1996-12-31

262

Finding ultracool brown dwarfs with MegaCam on CFHT: method and first results  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present the first results of a wide field survey for cool brown dwarfs with the MegaCam camera on the CFHT telescope, the Canada-France Brown Dwarf Survey, hereafter CFBDS. Our objectives are to find ultracool brown dwarfs and to constrain the field-brown dwarf mass function thanks to a larger sample of L and T dwarfs. We identify candidates in CFHT/MegaCam i' and z' images using optimised psf-fitting within Source Extractor, and follow them up with pointed near-infrared ...

Delorme, Philippe; Willott, Chris; Forveille, Thierry; Delfosse, Xavier; Reyle?, Ce?line; Bertin, Emmanuel; Albert, Loic; Artigau, Etienne; Robin, Annie; Allard, France; Doyon, Rene; Hill, Gary

2008-01-01

263

Who Is Using Long-Acting Reversible Contraceptive Methods? Findings from Nine Low-Fertility Countries  

Science.gov (United States)

CONTEXT Long-acting reversible contraceptive (LARC) methods—IUDs and implants—are more effective than other reversible methods, yet are little used in the United States. Examining which U.S. women use LARC methods and how they differ from users in other low-fertility countries may help point the way toward increasing use. METHODS Data from married or cohabiting women participating in the National Survey of Family Growth (2008–2010) and in eight countries’ Generations and Gender Programme surveys (2004–2010) were used in bivariate and multinomial logistic regression analyses examining LARC use within each setting. RESULTS The proportion of contraceptive use accounted for by LARC methods was generally greater in Europe (10–32%) than in the United States (10%) and Australia (7%). Compared with LARC use among comparable groups in other countries, use was particularly low among U.S. women who were married, were aged 40–44 or had had three or more children, yet was comparatively high among 18–24-year-olds. Among U.S. women, those aged 35–39 or 40–44 were more likely than 18–29-year-olds to rely on sterilization rather than on LARC methods (odds ratios, 3.0 and 10.7, respectively), those who had had three or more children were more likely to do so than were those who had had none or one (4.9), and women who had completed college were less likely than those who had not finished high school to do so (0.4). CONCLUSIONS Certain subgroups of U.S. women may benefit from the reversibility and effectiveness of LARC methods. PMID:25040454

Eeckhaut, Mieke C. W.; Sweeney, Megan M.; Gipson, Jessica D.

2014-01-01

264

High-sensitivity fiber Bragg grating transverse force sensor based on centroid measurement of polarization-dependent loss  

International Nuclear Information System (INIS)

The transverse force measurement by virtue of 'stress-induced birefringence effects' of a fiber Bragg grating (FBG) written in a standard telecom single-mode fiber is attractive in the field of internal strain sensing in materials and structures. However, the measurement suffers from the drawback of low transverse force sensitivity of the FBG. In this paper, we propose utilizing the centroid information of the polarization-dependent loss (PDL) evolution of FBG for transverse force measurements. The evolution of the PDL with wavelength for the transmitted signals with respect to transverse force was analyzed and numerically simulated. Experiments were carried out to verify the reasonability and feasibility of the measurement method. Good agreement between experimental results and numerical simulations has been obtained

265

DiffCoEx: a simple and sensitive method to find differentially coexpressed gene modules  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Large microarray datasets have enabled gene regulation to be studied through coexpression analysis. While numerous methods have been developed for identifying differentially expressed genes between two conditions, the field of differential coexpression analysis is still relatively new. More specifically, there is so far no sensitive and untargeted method to identify gene modules (also known as gene sets or clusters that are differentially coexpressed between two conditions. Here, sensitive and untargeted means that the method should be able to construct de novo modules by grouping genes based on shared, but subtle, differential correlation patterns. Results We present DiffCoEx, a novel method for identifying correlation pattern changes, which builds on the commonly used Weighted Gene Coexpression Network Analysis (WGCNA framework for coexpression analysis. We demonstrate its usefulness by identifying biologically relevant, differentially coexpressed modules in a rat cancer dataset. Conclusions DiffCoEx is a simple and sensitive method to identify gene coexpression differences between multiple conditions.

Breitling Rainer

2010-10-01

266

Nudged-elastic band method with two climbing images: Finding transition states in complex energy landscapes a)  

Science.gov (United States)

The nudged-elastic band (NEB) method is modified with concomitant two climbing images (C2-NEB) to find a transition state (TS) in complex energy landscapes, such as those with a serpentine minimal energy path (MEP). If a single climbing image (C1-NEB) successfully finds the TS, then C2-NEB finds it too. However, improved stability of C2-NEB makes it suitable for more complex cases, where C1-NEB misses the TS because the MEP and NEB directions near the saddle point are different. Generally, C2-NEB not only finds the TS, but also guarantees, by construction, that the climbing images approach it from the opposite sides along the MEP. In addition, C2-NEB provides an accuracy estimate from the three images: the highest-energy one and its climbing neighbors. C2-NEB is suitable for fixed-cell NEB and the generalized solid-state NEB.

Zarkevich, Nikolai A.; Johnson, Duane D.

2015-01-01

267

A Monte Carlo Method to Find Mass Flux Variability in the North Atlantic and Southern Oceans  

Science.gov (United States)

Using the concept of transit-time distributions (TTDs), we estimate the volume transports and spreading rates of Labrador Sea Water (LSW), Antarctic Intermediate Water (AAIW), and North Atlantic Deep Water (NADW) through different repeat hydrographic-sections of the ocean with observations of transient tracers and model output from the National Center for Atmospheric Research (NCAR) high resolution Parallel Ocean Program (POP) model. We estimate the TTDs using inverse Gaussians (IGs) that are observationally informed from pCFC and statistically estimated Helium-3/Tritium ages. The Helium-3/Tritium ages are estimated using a nonparametric statistical model that works well with sparse observations and quantifies uncertainty associated with mapping. In areas where water masses of vastly different ages mix, this representation is extended to a mixture of two IGs. Using the NCAR POP model TTDs as priors, we arrive at a Bayesian estimate of a multiple peaked TTD and estimate the mean ages and Peclet number at each location and depth. We find that once a mean age of about 50 years is surpassed, statistically estimated Helium-3/Tritium serves to add more information than CFCs would have alone, but the uncertainties on the IG parameters below the thermocline can often be large enough to not be able to distinguish the Peclet number from zero. We also find smaller average spreading rates than those inferred from previous studies with intra-annual variability larger for NADW than AAIW and LSW with the smallest, assuming steady-state for each snapshot.

Trossman, D. S.; Thompson, L.; Bryan, F. O.; Mecking, S.; Warner, M. J.; Peacock, S.

2010-12-01

268

Nondestructive Testing Method for Finding out the Defects in a Composite Liner  

Directory of Open Access Journals (Sweden)

Full Text Available A composite liner of carbon phenolic has been inspected by ultrasonic, X-ray radiography andX-ray computed tomography (CT to find defects like delaminations, debonds, voids, foreign inclusions, etc.The geometry, detection of multiple defects and porosity of the liner make ultrasonic testing (pulse-echo anddrycoupling difficult for inspection. X-ray radiography being a non-contact technique finds multiple defectsbut compresses the structural information of 3-D volume into a 2-D image and interferes with overlyingand underlying areas of the object. X-ray CT generates an image of a thin and cross-sectional slice ofan object. R e linear attenuation coefficients in terms of Hounsfield values have been measured, comparedand correlated with CT images at the contrasts observed. 3-D images can be generated by stacking2-D cross-sectional images of the slices. These 3-D images can be cut at any angle of choice for mappingthe extent of delaminated/debonded areas. This type of information is difficult to obtain with conventionalnon-destructive testing techniques.

C. Muralidhar

2013-04-01

269

An efficient search method for finding the critical slip surface using the compositional Monte Carlo technique  

International Nuclear Information System (INIS)

Locating the critical slip surface and the associated minimum factor of safety are two complementary parts in a slope stability analysis. A large number of computer programs exist to solve slope stability problems. Most of these programs, however, have used inefficient and unreliable search procedures to locate the global minimum factor of safety. This paper presents an efficient and reliable method to determine the global minimum factor of safety coupled with a modified version of the Monte Carlo technique. Examples arc presented to illustrate the reliability of the proposed method

270

A Simple Method to Find out when an Ordinary Differential Equation Is Separable  

Science.gov (United States)

We present an alternative method to that of Scott (D. Scott, "When is an ordinary differential equation separable?", "Amer. Math. Monthly" 92 (1985), pp. 422-423) to teach the students how to discover whether a differential equation y[prime] = f(x,y) is separable or not when the nonlinearity f(x, y) is not explicitly factorized. Our approach is…

Cid, Jose Angel

2009-01-01

271

Method for finding the critical temperature of the island in a SET structure  

International Nuclear Information System (INIS)

We present a method to measure the critical temperature of the island of a superconducting single electron transistor. The method is based on a sharp change in the slope of the zero-bias conductance as a function of temperature. We have used this method to determine the superconducting phase transition temperature of the Nb island of an superconducting single electron transistor with Al leads. We obtain TcNb as high as 8.5 K and gap energies up to ?Nb ? 1.45 meV. By looking at the zero bias conductance as a function of magnetic field instead of temperature, also the critical field of the island can be determined. Using the orthodox theory, we have performed extensive numerical simulations of charge transport properties in the SET at temperatures comparable to the gap, which match very well the data, therefore providing a solid theoretical basis for our method. PACS: 73.23.Hk,73.40.Gk,74.50.+r

272

Paediatric cardiac CT examinations: impact of the iterative reconstruction method ASIR on image quality - preliminary findings  

International Nuclear Information System (INIS)

Radiation dose exposure is of particular concern in children due to the possible harmful effects of ionizing radiation. The adaptive statistical iterative reconstruction (ASIR) method is a promising new technique that reduces image noise and produces better overall image quality compared with routine-dose contrast-enhanced methods. To assess the benefits of ASIR on the diagnostic image quality in paediatric cardiac CT examinations. Four paediatric radiologists based at two major hospitals evaluated ten low-dose paediatric cardiac examinations (80 kVp, CTDIvol 4.8-7.9 mGy, DLP 37.1-178.9 mGy.cm). The average age of the cohort studied was 2.6 years (range 1 day to 7 years). Acquisitions were performed on a 64-MDCT scanner. All images were reconstructed at various ASIR percentages (0-100%). For each examination, radiologists scored 19 anatomical structures using the relative visual grading analysis method. To estimate the potential for dose reduction, acquisitions were also performed on a Catphan phantom and a paediatric phantom. The best image quality for all clinical images was obtained with 20% and 40% ASIR (p < 0.001) whereas with ASIR above 50%, image quality significantly decreased (p < 0.001). With 100% ASIR, a strong noise-free appearance of the structures reduced image conspicuity. A potential for dose reduction of about 36% is predicted for a 2- to 3-year-old child when using 40% ASIR rather than the standard filtered back-projection method. Reconstr filtered back-projection method. Reconstruction including 20% to 40% ASIR slightly improved the conspicuity of various paediatric cardiac structures in newborns and children with respect to conventional reconstruction (filtered back-projection) alone. (orig.)

273

A few basic considerations on the method of finding the law - Einige Grundüberlegungen zur Methode der Rechtsfindung  

Directory of Open Access Journals (Sweden)

Full Text Available The contribution attempts to illustrate why it is appropriate to speak of finding, re-cognising and application, or applying, of the law. Reservations have been articulated about this use of language as a consequence of ontologically sceptical assumptions, which raise doubts as to the level of reality contained in these terms. “Legal ontology” is used as a knock-down argument in certain pointed aspects of this scepticism. However, there is no reason to do so.Der Beitrag versucht zu verdeutlichen, warum es in Ordnung ist, von Rechtsfindung, Rechtserkenntnis und Rechtsanwendung zu sprechen. Bedenken gegenüber diesem Sprachgebrauch sind in der Folge ontologieskeptischer Annahmen artikuliert worden, die Zweifel am Realitätsgehalt der genannten Begriffe anmelden. „Rechtsontologie” wird in bestimmten Pointierungen dieser Skepsis als Knock-down-Argument eingesetzt. Dafür gibt es aber keinen Grund.

Jochen Bung

2009-09-01

274

Finding a Needle in a Haystack: Toward a Psychologically Informed Method for Aviation Security Screening.  

Science.gov (United States)

Current aviation security systems identify behavioral indicators of deception to assess risks to flights, but they lack a strong psychological basis or empirical validation. We present a new method that tests the veracity of passenger accounts. In an in vivo double-blind randomized-control trial conducted in international airports, security agents detected 66% of deceptive passengers using the veracity test method compared with less than 5% using behavioral indicator recognition. As well as revealing advantages of veracity testing over behavioral indicator identification, the study provides the highest levels to date of deception detection in a realistic setting where the known base rate of deceptive individuals is low. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:25365531

Ormerod, Thomas C; Dando, Coral J

2014-11-01

275

THE STATISTICAL METHOD FOR FINDING THE RESPONSE FOR N RANDOM EXCITATION OF THE INVERTED PENDULUM  

Directory of Open Access Journals (Sweden)

Full Text Available We present a method for estimating the power spectral density of the stationary response of oscillatorwith a nonlinear restoring force under external stochastic wide-band excitation. An equivalent linear system isderived, from which the power spectral density is deduced. We consider an inverted pendulum suspendedsubjected to white noise excitation with a random number n random excitations simultaneously applied. Themethod will be briefly discussed in the following sections

Marinic? STAN

2013-05-01

276

THE STATISTICAL METHOD FOR FINDING THE RESPONSE FOR N RANDOM EXCITATION OF THE INVERTED PENDULUM  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a method for estimating the power spectral density of the stationary response of oscillatorwith a nonlinear restoring force under external stochastic wide-band excitation. An equivalent linear system isderived, from which the power spectral density is deduced. We consider an inverted pendulum suspendedsubjected to white noise excitation with a random number n random excitations simultaneously applied. Themethod will be briefly discussed in the following sections

Stan, Marinica?; Stan, Petre

2013-01-01

277

The chronic painful Achilles tendon : sonographic findings and new methods for treatment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of the present thesis was to evaluate sonographic methods for investigation of the chronic painful Achilles tendon. In a prospective study on patients with chronic painful mid-portion Achilles tendinosis, grey-scale ultrasound (US) showed a decreased tendon thickness and a “normalized” structure in the majority of patients successfully treated with eccentric calf-muscle training. By combining US with colour Doppler examination (CDV), a neovascularisation was shown in the region wi...

O?hberg, Lars

2003-01-01

278

A heuristic method for finding the optimal number of clusters with application in medical data.  

Science.gov (United States)

In this paper, a heuristic method for determining the optimal number of clusters is proposed. Four clustering algorithms, namely K-means, Growing Neural Gas, Simulated Annealing based technique, and Fuzzy C-means in conjunction with three well known cluster validity indices, namely Davies-Bouldin index, Calinski-Harabasz index, Maulik-Bandyopadhyay index, in addition to the proposed index are used. Our simulations evaluate capability of mentioned indices in some artificial and medical datasets. PMID:19163761

Bayati, Hamidreza; Davoudi, Heydar; Fatemizadeh, Emad

2008-01-01

279

The relationship between vocational interests and intelligence: Do findings generalize across different assessment methods?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of this study was to further explore the relationship between vocational interests and intelligence. There is some evidence in literature on the stable relationships between vocational interests and intelligence (cf. Ackerman & Heggestad, 1997). It should be noted that the majority of the previous studies have only used questionnaires for the assessment of vocational interests. Thus, it is of interest whether the results are also stable when different assessment methods are used. Ther...

Proyer, Rene? T.

2006-01-01

280

4D tumor centroid tracking using orthogonal 2D dynamic MRI: Implications for radiotherapy planning  

Energy Technology Data Exchange (ETDEWEB)

Purpose: Current pretreatment, 4D imaging techniques are suboptimal in that they sample breathing motion over a very limited “snapshot” in time. Heretofore, long-duration, 4D motion characterization for radiotherapy planning, margin optimization, and validation have been impractical for safety reasons, requiring invasive markers imaged under x-ray fluoroscopy. To characterize 3D tumor motion and associated variability over durations more consistent with treatments, the authors have developed a practical dynamic MRI (dMRI) technique employing two orthogonal planes acquired in a continuous, interleaved fashion.Methods: 2D balanced steady-state free precession MRI was acquired continuously over 9–14 min at approximately 4 Hz in three healthy volunteers using a commercial 1.5 T system; alternating orthogonal imaging planes (sagittal, coronal, sagittal, etc.) were employed. The 2D in-plane pixel resolution was 2 × 2 mm{sup 2} with a 5 mm slice profile. Simultaneous with image acquisition, the authors monitored a 1D surrogate respiratory signal using a device available with the MRI system. 2D template matching-based anatomic feature registration, or tracking, was performed independently in each orientation. 4D feature tracking at the raw frame rate was derived using spline interpolation.Results: Tracking vascular features in the lung for two volunteers and pancreatic features in one volunteer, the authors have successfully demonstrated this method. Registration error, defined here as the difference between the sagittal and coronal tracking result in the SI direction, ranged from 0.7 to 1.6 mm (1?) which was less than the acquired image resolution. Although the healthy volunteers were instructed to relax and breathe normally, significantly variable respiration was observed. To demonstrate potential applications of this technique, the authors subsequently explored the intrafraction stability of hypothetical tumoral internal target volumes and 3D spatial probability distribution functions. The surrogate respiratory information allowed the authors to show how this technique can be used to study correlations between internal and external (surrogate) information over these prolonged durations. However, compared against the gold standard of the time stamps in the dMRI frames, the temporal synchronization of the surrogate 1D respiratory information was shown to be likely unreliable.Conclusions: The authors have established viability of a novel and practical pretreatment, 4D tumor centroid tracking method employing a commercially available dynamic MRI sequence. Further developments from the vendor are likely needed to provide a reliably synchronized surrogate 1D respiratory signal, which will likely broaden the utility of this method in the pretreatment radiotherapy planning context.

Tryggestad, Erik [Department of Radiation Oncology and Molecular Radiation Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21231 and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota 55905 (United States); Flammang, Aaron; Shea, Steven M. [Center for Applied Medical Imaging, Siemens Corporation, Corporate Technology, Baltimore, Maryland 21205 (United States); Hales, Russell; Herman, Joseph; Lee, Junghoon; McNutt, Todd; Roland, Teboh; Wong, John [Department of Radiation Oncology and Molecular Radiation Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21231 (United States)

2013-09-15

 
 
 
 
281

A comparative method for finding and folding RNA secondary structures within protein-coding regions  

Science.gov (United States)

Existing computational methods for RNA secondary-structure prediction tacitly assume RNA to only encode functional RNA structures. However, experimental studies have revealed that some RNA sequences, e.g. compact viral genomes, can simultaneously encode functional RNA structures as well as proteins, and evidence is accumulating that this phenomenon may also be found in Eukaryotes. We here present the first comparative method, called RNA-Decoder, which explicitly takes the known protein-coding context of an RNA-sequence alignment into account in order to predict evolutionarily conserved secondary-structure elements, which may span both coding and non-coding regions. RNA-Decoder employs a stochastic context-free grammar together with a set of carefully devised phylogenetic substitution-models, which can disentangle and evaluate the different kinds of overlapping evolutionary constraints which arise. We show that RNA-Decoder's parameters can be automatically trained to successfully fold known secondary structures within the HCV genome. We scan the genomes of HCV and polio virus for conserved secondary-structure elements, and analyze performance as a function of available evolutionary information. On known secondary structures, RNA-Decoder shows a sensitivity similar to the programs Mfold, Pfold and RNAalifold. When scanning the entire genomes of HCV and polio virus for structure elements, RNA-Decoder's results indicate a markedly higher specificity than Mfold, Pfold and RNAalifold. PMID:15448187

Pedersen, Jakob Skou; Meyer, Irmtraud Margret; Forsberg, Roald; Simmonds, Peter; Hein, Jotun

2004-01-01

282

A comparative method for finding and folding RNA secondary structures within protein-coding regions  

DEFF Research Database (Denmark)

Existing computational methods for RNA secondary-structure prediction tacitly assume RNA to only encode functional RNA structures. However, experimental studies have revealed that some RNA sequences, e.g. compact viral genomes, can simultaneously encode functional RNA structures as well as proteins, and evidence is accumulating that this phenomenon may also be found in Eukaryotes. We here present the first comparative method, called RNA-DECODER, which explicitly takes the known protein-coding context of an RNA-sequence alignment into account in order to predict evolutionarily conserved secondary-structure elements, which may span both coding and non-coding regions. RNA-DECODER employs a stochastic context-free grammar together with a set of carefully devised phylogenetic substitution-models, which can disentangle and evaluate the different kinds of overlapping evolutionary constraints which arise. We show that RNA-DECODER's parameters can be automatically trained to successfully fold known secondary structures within the HCV genome. We scan the genomes of HCV and polio virus for conserved secondary-structure elements, and analyze performance as a function of available evolutionary information. On known secondary structures, RNA-DECODER shows a sensitivity similar to the programs MFOLD, PFOLD and RNAALIFOLD. When scanning the entire genomes of HCV and polio virus for structure elements, RNA-DECODER's results indicate a markedly higher specificity than MFOLD, PFOLD and RNAALIFOLD.

Pedersen, Jakob Skou; Meyer, Irmtraud Margret

2004-01-01

283

The relationship between vocational interests and intelligence: Do findings generalize across different assessment methods?  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study was to further explore the relationship between vocational interests and intelligence. There is some evidence in literature on the stable relationships between vocational interests and intelligence (cf. Ackerman & Heggestad, 1997. It should be noted that the majority of the previous studies have only used questionnaires for the assessment of vocational interests. Thus, it is of interest whether the results are also stable when different assessment methods are used. Therefore, a nonverbal test was used in this study together with two questionnaires. Additionally, tests for general intelligence, verbal, numeric, and spatial ability, and memory were used. A sample of N = 138 persons was tested in a computerized setting. Results indicate that there is a positive relation between Realistic and Investigative interests and spatial ability. This result was found for both the questionnaires as well as the nonverbal test. Therefore, it can be assumed that this relation is stable for different assessment methods. The data is discussed with respect to current literature.

RENÉ T. PROYER

2006-12-01

284

Is dark matter present in NGC4736? An iterative spectral method for finding mass distribution in spiral galaxies  

CERN Document Server

We present Iterative Spectral Method of reconstructing mass distribution in spiral galaxies in an infinitely thin axial symmetric disk approximation. The method, without extra assumptions and free parameters, overcomes all problems encountered in standard use of disk model and utilises only information that is available observationally. As an example we apply the method to the ringed Sab-type galaxy NGC4736 that breaks sphericity condition at larger radii. We find mass distribution in NGC4736 that agrees perfectly with its high resolution rotation curve (high resolution, however, is not a must in our method). Given the distribution one finds rotational velocity which is the same as the observed rotation curve (!). The obtained surface mass density is consistent with the I-band luminosity profile (M/L_I=0.7 in Solar units) and with the amount of hydrogen observed in outermost regions where rotation curve is not measured. In the framework of Newtonian gravitation, these findings put in question the presence of ...

Bratek, L; Kutschera, M; Bratek, Lukasz; Jalocha, Joanna; Kutschera, Marek

2006-01-01

285

Glucose metabolism following human traumatic brain injury: methods of assessment and pathophysiological findings.  

Science.gov (United States)

The pathophysiology of traumatic brain (TBI) injury involves changes to glucose uptake into the brain and its subsequent metabolism. We review the methods used to study cerebral glucose metabolism with a focus on those used in clinical TBI studies. Arterio-venous measurements provide a global measure of glucose uptake into the brain. Microdialysis allows the in vivo sampling of brain extracellular fluid and is well suited to the longitudinal assessment of metabolism after TBI in the clinical setting. A recent novel development is the use of microdialysis to deliver glucose and other energy substrates labelled with carbon-13, which allows the metabolism of glucose and other substrates to be tracked. Positron emission tomography and magnetic resonance spectroscopy allow regional differences in metabolism to be assessed. We summarise the data published from these techniques and review their potential uses in the clinical setting. PMID:25413449

Jalloh, Ibrahim; Carpenter, Keri L H; Helmy, Adel; Carpenter, T Adrian; Menon, David K; Hutchinson, Peter J

2014-11-21

286

Three-Dimensional Computed Tomography as a Method for Finding Die Attach Voids in Diodes  

Science.gov (United States)

NASA analyzes electrical, electronic, and electromechanical (EEE) parts used in space vehicles to understand failure modes of these components. The diode is an EEE part critical to NASA missions that can fail due to excessive voiding in the die attach. Metallography, one established method for studying the die attach, is a time-intensive, destructive, and equivocal process whereby mechanical grinding of the diodes is performed to reveal voiding in the die attach. Problems such as die attach pull-out tend to complicate results and can lead to erroneous conclusions. The objective of this study is to determine if three-dimensional computed tomography (3DCT), a nondestructive technique, is a viable alternative to metallography for detecting die attach voiding. The die attach voiding in two- dimensional planes created from 3DCT scans was compared to several physical cross sections of the same diode to determine if the 3DCT scan accurately recreates die attach volumetric variability

Brahm, E. N.; Rolin, T. D.

2010-01-01

287

Combined Calibration Method and its Realization for Direction Finding Antenna Systems with Patch Antennas  

Directory of Open Access Journals (Sweden)

Full Text Available A novel radio channel compensation method aiming to give optimal calibration for microstrip antenna array systems is presented in this paper, realized for an actual DOA measurement antenna system using microstrip antennas to sample the electromagnetic field, operating at 4.5GHz. This new approach considers mismatch between antennas and channel RF ports, channel transmission inequalities, and also decreases the effects of multipath propagation components of calibration reference signals by placing the calibration reference signal feeding network on the microstrip antenna array bearer, directly beside the antenna patches. It is combined with orthogonal spread spectrum calibration signal utility for continuous uninterrupted measurements. The spread spectrum calibration signal is orthogonal to the continuous wave (CW signal to be measured, therefore, the 2 signals can be separated in the receiver, enabling them to be present simultaneously. DOA measurement results are shown, measured with the realized integrated microstrip patch antenna array with calibration network hardware.

R. Seller

2007-09-01

288

Finding disease variants in Mendelian disorders by using sequence data: methods and applications.  

Science.gov (United States)

Many sequencing studies are now underway to identify the genetic causes for both Mendelian and complex traits. Via exome-sequencing, genes harboring variants implicated in several Mendelian traits have already been identified. The underlying methodology in these studies is a multistep algorithm based on filtering variants identified in a small number of affected individuals and depends on whether they are novel (not yet seen in public resources such as dbSNP), shared among affected individuals, and other external functional information on the variants. Although intuitive, these filter-based methods are nonoptimal and do not provide any measure of statistical uncertainty. We describe here a formal statistical approach that has several distinct advantages: (1) it provides fast computation of approximate p values for individual genes, (2) it adjusts for the background variation in each gene, (3) it allows for incorporation of functional or linkage-based information, and (4) it accommodates designs based on both affected relative pairs and unrelated affected individuals. We show via simulations that the proposed approach can be used in conjunction with the existing filter-based methods to achieve a substantially better ranking of a gene relevant for disease when compared to currently used filter-based approaches, this is especially so in the presence of disease locus heterogeneity. We revisit recent studies on three Mendelian diseases and show that the proposed approach results in the implicated gene being ranked first in all studies, and approximate p values of 10(-6) for the Miller Syndrome gene, 1.0 × 10(-4) for the Freeman-Sheldon Syndrome gene, and 3.5 × 10(-5) for the Kabuki Syndrome gene. PMID:22137099

Ionita-Laza, Iuliana; Makarov, Vlad; Yoon, Seungtai; Raby, Benjamin; Buxbaum, Joseph; Nicolae, Dan L; Lin, Xihong

2011-12-01

289

Finding an optimal method for imaging lymphatic vessels of the upper limb  

International Nuclear Information System (INIS)

Lymphoscintigraphy involves interstitial injection of radiolabelled particulate materials or radioproteins. Although several variations in the technique have been described, their place in clinical practice remains controversial. Traditional diagnostic criteria are based primarily on lymph node appearances but in situations such as breast cancer, where lymph nodes may have been excised, these criteria are of limited use. In these circumstances, lymphatic vessel morphology takes on greater importance as a clinical endpoint, so a method that gives good definition of lymphatic vessels would be useful. In patients with breast cancer, for example, such a method, used before and after lymph node resection, may assist in predicting the development of breast cancer-related lymphoedema. The aim of this study was to optimise a method for the visualisation of lymphatic vessels. Subcutaneous (sc) and intradermal (id) injection sites were compared, and technetium-99m nanocolloid, a particulate material, was compared with 99mTc-human immunoglobulin (HIG), which is a soluble macromolecule. Twelve normal volunteers were each studied on two occasions. In three subjects, id 99mTc-HIG was compared with sc 99mTc-HIG, in three id 99mTc-nanocolloid was compared with sc 99mTc-nanocolloid, in three id 99mTc-HIG was compared with id 99mTc-nanocolloid and in three sc 99mTc-HIG was compared with sc 99mTc-HIG was compared with sc 99mTc-nanocolloid. Endpoints were quality of lymphatic vessel definition, the time after injection at which vessels were most clearly visualised, the rate constant of depot disappearance (k) and the systemic blood accumulation rate as measured by gamma camera imaging over the liver or cardiac blood pool. Excellent definition of lymphatic vessels was obtained following id injection of either radiopharmaceutical, an injection route that was clearly superior to sc. Differences between radiopharmaceuticals were less clear, although after id injection, 99mTc-HIG gave images that were marginally but significantly better than those given by 99mTc-nanocolloid. Image quality correlated inversely with time after injection at which the best image was obtained, consistent with the notion that good vessel definition was dependent on a ''narrow'' bolus width. k was approximately three times higher after id injection than after sc injection but it was not significantly different between radiopharmaceuticals for either injection route. Intradermal 99mTc-HIG gave a cardiac blood pool signal that, over the first 60 min, increased about five times faster than that with sc 99mTc-HIG, but no clear difference was observed in the rate of increase in hepatic activity between id 99mTc-nanocolloid and sc 99mTc-nanocolloid. We conclude that id injection provides rapid access of radiotracers to lymphatic vessels, which is ideal for imaging lymphatic vessel morphology. 99mTc-HIG is marginally superior to nanocolloid for this purpose and, in drainage basins from which lymph nodes have been excised, is not handicapped by a potentially inferior ability, compared with radiocolloid, to image lymph nodes. (orig.)

290

Finding an optimal method for imaging lymphatic vessels of the upper limb  

Energy Technology Data Exchange (ETDEWEB)

Lymphoscintigraphy involves interstitial injection of radiolabelled particulate materials or radioproteins. Although several variations in the technique have been described, their place in clinical practice remains controversial. Traditional diagnostic criteria are based primarily on lymph node appearances but in situations such as breast cancer, where lymph nodes may have been excised, these criteria are of limited use. In these circumstances, lymphatic vessel morphology takes on greater importance as a clinical endpoint, so a method that gives good definition of lymphatic vessels would be useful. In patients with breast cancer, for example, such a method, used before and after lymph node resection, may assist in predicting the development of breast cancer-related lymphoedema. The aim of this study was to optimise a method for the visualisation of lymphatic vessels. Subcutaneous (sc) and intradermal (id) injection sites were compared, and technetium-99m nanocolloid, a particulate material, was compared with {sup 99m}Tc-human immunoglobulin (HIG), which is a soluble macromolecule. Twelve normal volunteers were each studied on two occasions. In three subjects, id {sup 99m}Tc-HIG was compared with sc {sup 99m}Tc-HIG, in three id {sup 99m}Tc-nanocolloid was compared with sc {sup 99m}Tc-nanocolloid, in three id {sup 99m}Tc-HIG was compared with id {sup 99m}Tc-nanocolloid and in three sc {sup 99m}Tc-HIG was compared with sc {sup 99m}Tc-nanocolloid. Endpoints were quality of lymphatic vessel definition, the time after injection at which vessels were most clearly visualised, the rate constant of depot disappearance (k) and the systemic blood accumulation rate as measured by gamma camera imaging over the liver or cardiac blood pool. Excellent definition of lymphatic vessels was obtained following id injection of either radiopharmaceutical, an injection route that was clearly superior to sc. Differences between radiopharmaceuticals were less clear, although after id injection, {sup 99m}Tc-HIG gave images that were marginally but significantly better than those given by {sup 99m}Tc-nanocolloid. Image quality correlated inversely with time after injection at which the best image was obtained, consistent with the notion that good vessel definition was dependent on a ''narrow'' bolus width. k was approximately three times higher after id injection than after sc injection but it was not significantly different between radiopharmaceuticals for either injection route. Intradermal {sup 99m}Tc-HIG gave a cardiac blood pool signal that, over the first 60 min, increased about five times faster than that with sc {sup 99m}Tc-HIG, but no clear difference was observed in the rate of increase in hepatic activity between id {sup 99m}Tc-nanocolloid and sc {sup 99m}Tc-nanocolloid. We conclude that id injection provides rapid access of radiotracers to lymphatic vessels, which is ideal for imaging lymphatic vessel morphology. {sup 99m}Tc-HIG is marginally superior to nanocolloid for this purpose and, in drainage basins from which lymph nodes have been excised, is not handicapped by a potentially inferior ability, compared with radiocolloid, to image lymph nodes. (orig.)

O' Mahony, Susan; Purushotham, Arnie D. [Cambridge Breast Unit, Addenbrooke' s Hospital, Cambridge (United Kingdom); Rose, Sarah L.; Chilvers, Alison J.; Ballinger, James R.; Solanki, Chandra K.; Barber, Robert W.; Peters, A. Michael [Department of Nuclear Medicine, Addenbrooke' s Hospital, Hills Road, CB2 2QQ, Cambridge (United Kingdom); Mortimer, Peter S. [Department of Medicine, St George' s Hospital, London (United Kingdom)

2004-04-01

291

Interprofessional mental health training in rural primary care: findings from a mixed methods study.  

Science.gov (United States)

Abstract The benefits of interprofessional care in providing mental health services have been widely recognized, particularly in rural communities where access to health services is limited. There continues to be a need for more continuing interprofessional education in mental health intervention in rural areas. There have been few reports of rural programs in which mental health content has been combined with training in collaborative practice. The current study used a sequential mixed-method and quasi-experimental design to evaluate the impact of an interprofessional, intersectoral education program designed to enhance collaborative mental health capacity in six rural sites. Quantitative results reveal a significant increase in positive attitudes toward interprofessional mental health care teams and self-reported increases in knowledge and understanding about collaborative mental health care delivery. The analysis of qualitative data collected following completion of the program, reinforced the value of teaching mental health content within the context of collaborative practice and revealed practice changes, including more interprofessional and intersectoral collaboration. This study suggests that imbedding explicit training in collaborative care in content focused continuing professional education for more complex and chronic health issues may increase the likelihood that professionals will work together to effectively meet client needs. PMID:25291262

Heath, Olga; Church, Elizabeth; Curran, Vernon; Hollett, Ann; Cornish, Peter; Callanan, Terrence; Bethune, Cheri; Younghusband, Lynda

2014-10-01

292

Novel survey method finds dramatic decline of wild cotton-top tamarin population.  

Science.gov (United States)

The cotton-top tamarin (Saguinus oedipus) is a critically endangered primate, endemic to the tropical forests of Colombia. Population monitoring is essential to evaluate the success of conservation efforts, yet standard survey methods are ineffective because animals flee silently before they are seen. We developed a novel technique that combines the use of playbacks of territorial vocalizations with traditional transect surveys. We used remote sensing to identify potential habitat within the species' historic range, and visited the 27% that we could survey safely. Of this, only 99 km(2) was extant forest, containing an estimated 2,045 animals (95% confidence interval 1,587-2,634). Assuming comparable densities in non-surveyed areas, approximately 7,394 wild cotton-top tamarins remain in Colombia. With 20-30,000 animals exported to the United States in the late 1960s, this must represent a precipitous decline. Habitat destruction and capture for the illegal pet trade are ongoing. Urgent conservation measures are required to prevent extinction in the wild. PMID:20975684

Savage, Anne; Thomas, Len; Leighty, Katherine A; Soto, Luis H; Medina, Felix S

2010-01-01

293

Method for Finding Metabolic Properties Based on the General Growth Law. Liver Examples. A General Framework for Biological Modeling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We propose a method for finding metabolic parameters of cells, organs and whole organisms, which is based on the earlier discovered general growth law. Based on the obtained results and analysis of available biological models, we propose a general framework for modeling biological phenomena and discuss how it can be used in Virtual Liver Network project. The foundational idea of the study is that growth of cells, organs, systems and whole organisms, besides biomolecular machinery, is influenc...

Shestopaloff, Yuri K.

2014-01-01

294

The Pade approximant method for finding the Hilbert-Schmidt eigenvalues and eigenfunctions in two- and three-body problems  

International Nuclear Information System (INIS)

An approach is proposed which makes it possible to obtain the Hilbert-Schmidt (or Sturm-Liouville) eigenvalue and eigenfunctions for two-or three-body systems over the entire domain of analyticity of these functions in energy on the basis of calculations of bound states only. It is shown how this method may be used to find the two- and three-body resonances and the near-threshold states. (orig.)

295

The Shortlist Method for fast computation of the Earth Mover's Distance and finding optimal solutions to transportation problems.  

Science.gov (United States)

Finding solutions to the classical transportation problem is of great importance, since this optimization problem arises in many engineering and computer science applications. Especially the Earth Mover's Distance is used in a plethora of applications ranging from content-based image retrieval, shape matching, fingerprint recognition, object tracking and phishing web page detection to computing color differences in linguistics and biology. Our starting point is the well-known revised simplex algorithm, which iteratively improves a feasible solution to optimality. The Shortlist Method that we propose substantially reduces the number of candidates inspected for improving the solution, while at the same time balancing the number of pivots required. Tests on simulated benchmarks demonstrate a considerable reduction in computation time for the new method as compared to the usual revised simplex algorithm implemented with state-of-the-art initialization and pivot strategies. As a consequence, the Shortlist Method facilitates the computation of large scale transportation problems in viable time. In addition we describe a novel method for finding an initial feasible solution which we coin Modified Russell's Method. PMID:25310106

Gottschlich, Carsten; Schuhmacher, Dominic

2014-01-01

296

Artificial neural networks for centroiding elongated spots in Shack-Hartmann wavefront sensors  

CERN Document Server

The use of Adaptive Optics in Extremely Large Telescopes brings new challenges, one of which is the treatment of Shack-Hartmann Wavefront sensors images. When using this type of sensors in conjunction with laser guide stars for sampling the pupil of telescopes with 30+ m in diameter, it is necessary to compute the centroid of elongated spots, whose elongation angle and aspect ratio are changing across the telescope pupil. Existing techniques such as Matched Filter have been considered as the best technique to compute the centroid of elongated spots, however they are not good at coping with the effect of a variation in the Sodium profile. In this work we propose a new technique using artificial neural networks, which take advantage of the neural network's ability to cope with changing conditions, outperforming existing techniques in this context. We have developed comprehensive simulations to explore this technique and compare it with existing algorithms.

Mello, A T; Guzman, D; Guesalaga, A

2014-01-01

297

A numerical study of bunched beam transverse e-p instability based on the centroid model  

International Nuclear Information System (INIS)

In a recent theoretical study of the transverse electron-proton (e-p) instability, an asymptotic solution has been found for the equations describing the centroid motion of the traversing proton bunch and the stationary background electrons. It was shown that the combination of finite proton bunch length, non-uniform proton line density, and the single-pass e-p interaction cause the instability to evolve intricately in space and time even in the linear regime. This paper reports a numerical study of the e-p instability based on the same centroid equations. The purpose of the work is to compare the numerical solution with the analytic solution and to use the numerical approach to investigate the early development of the instability not covered by the asymptotic solution. In particular, the instability threshold and the initial growth of the instability are studied for various proton-beam conditions, fraction of charge neutralization, and initial perturbations.

298

Centroid and Envelope Dynamics of High-Intensity Charged-Particle Beams in an External Focusing Lattice and Oscillating Wobbler  

International Nuclear Information System (INIS)

The centroid and envelope dynamics of a high-intensity charged-particle beam are investigated as a beam smoothing technique to achieve uniform illumination over a suitably chosen region of the target for applications to ion-beam-driven high energy density physics and heavy ion fusion. The motion of the beam centroid projected onto the target follows a smooth pattern to achieve the desired illumination, for improved stability properties during the beam-target interaction. The centroid dynamics is controlled by an oscillating 'wobbler', a set of electrically biased plates driven by rf voltage.

299

Centroid and Envelope Dynamics of High-intensity Charged Particle Beams in an External Focusing Lattice and Oscillating Wobbler  

International Nuclear Information System (INIS)

The centroid and envelope dynamics of a high-intensity charged particle beam are investigated as a beam smoothing technique to achieve uniform illumination over a suitably chosen region of the target for applications to ion-beam-driven high energy density physics and heavy ion fusion. The motion of the beam centroid projected onto the target follows a smooth pattern to achieve the desired illumination, for improved stability properties during the beam-target interaction. The centroid dynamics is controlled by an oscillating 'wobbler', a set of electrically-biased plates driven by RF voltage.

300

Fast simulators for satellite cloud optical centroid pressure retrievals; evaluation of OMI cloud retrievals  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The cloud Optical Centroid Pressure (OCP) is a satellite-derived parameter that is commonly used in trace-gas retrievals to account for the effects of clouds on near-infrared through ultraviolet radiance measurements. Fast simulators are desirable to further expand the use of cloud OCP retrievals into the operational and climate communities for applications such as data assimilation and evaluation of cloud vertical structure in general circulation models. In this paper, w...

Joiner, J.; Vasilkov, A. P.; Gupta, P.; Bhartia, P. K.; Veefkind, P.; Sneep, M.; Haan, J.; Polonsky, I.; Spurr, R.

2012-01-01

 
 
 
 
301

A Localization Strategy Based on N-times Trilateral Centroid with Weight  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Localization based on received signal strength indication (RSSI) is a low cost and low complexity technology, and it is widely applied in distance-based localization of wireless sensor networks (WSNs). Error of existed localization technologies is significant. This paper presents the N-times trilateral centroid weighted localization algorithm (NTCWLA), which can reduce the error considerably. Considering the instability of RSSI, we use the weighted average of many RSSIs as c...

Qiu, Tie; Zhou, Yu; Xia, Feng; Jin, Naigao; Feng, Lin

2013-01-01

302

Vertex-centroid finite volume scheme on tetrahedral grids for conservation laws  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Vertex-centroid schemes are cell-centered finite volume schemes for conservation laws which make use of vertex values to construct high resolution schemes. The vertex values must be obtained through a consistent averaging (interpolation) procedure. A modified interpolation scheme is proposed which is better than existing schemes in giving positive weights in the interpolation formula. A simplified reconstruction scheme is also proposed which is also more accurate and efficie...

Chandrashekar, Praveen; Garg, Ashish

2011-01-01

303

On the approximation of a polytope by its dual $L_{p}$-centroid bodies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We show that the rate of convergence on the approximation of volumes of a convex symmetric polytope P in R^n by its dual L_{p$-centroid bodies is independent of the geometry of P. In particular we show that if P has volume 1, lim_{p\\rightarrow \\infty} \\frac{p}{\\log{p}} (\\frac{|Z_{p}^{\\circ}(P)|}{|P^{\\circ}|} -1) = n^{2}. We provide an application to the approximation of polytopes by uniformly convex sets.

Paouris, Grigoris; Werner, Elisabeth M.

2011-01-01

304

Velocity Field Statistics in Star-Forming Regions. I. Centroid Velocity Observations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The probability density functions (pdfs) of molecular line centroid velocity fluctuations and fluctuation differences at different spatial lags are estimated for several nearby molecular clouds with active internal star formation. The data consist of over 75,000 $^{13}$CO line profiles divided among twelve spatially and/or kinematically distinct regions. Although three regions (all in Mon R2) appear nearly Gaussian, the others show strong evidence for non-Gaussian, often nea...

Miesch, M. S.; Scalo, J. M.; Bally, J.

1998-01-01

305

Exponential Tails in the Centroid Velocity Distributions of Star-Forming Regions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Probability density functions (pdfs) of $^{13}CO$ emission line centroid (line-of-sight, intensity-weighted average) velocities are presented for several densely sampled molecular clouds as quantitative descriptors of their underlying dynamics. Although some are approximately Gaussian in form, most of the pdfs exhibit relatively broader, often nearly exponential, tails, similar to the pdfs of velocity {\\em differences} and {\\em derivatives} (but not the velocity field itself...

Miesch, Mark S.; Scalo, John M.

1994-01-01

306

Fast simulators for satellite cloud optical centroid pressure retrievals, 1. evaluation of OMI cloud retrievals  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The cloud Optical Centroid Pressure (OCP) is a satellite-derived parameter that is commonly used in trace-gas retrievals to account for the effects of clouds on near-infrared through ultraviolet radiance measurements. A fast simulator is desirable in order to further expand the use of cloud OCP retrievals into the operational and climate communities for applications such as data assimilation and evaluation of cloud vertical structure in general circulation models. In this paper, we ...

Joiner, J.; Vasilkov, A. P.; Gupta, P.; Bhartia, P. K.; Veefkind, P.; Sneep, M.; Haan, J.; Polonsky, I.; Spurr, R.

2011-01-01

307

Parallel algorithms for planar and spherical Delaunay construction with an application to centroidal Voronoi tessellations  

Directory of Open Access Journals (Sweden)

Full Text Available A new algorithm, featuring overlapping domain decompositions, for the parallel construction of Delaunay and Voronoi tessellations is developed. Overlapping allows for the seamless stitching of the partial pieces of the global Delaunay tessellations constructed by individual processors. The algorithm is then modified, by the addition of stereographic projections, to handle the parallel construction of spherical Delaunay and Voronoi tessellations. The algorithms are then embedded into algorithms for the parallel construction of planar and spherical centroidal Voronoi tessellations that require multiple constructions of Delaunay tessellations. This combination of overlapping domain decompositions with stereographic projections provides a unique algorithm for the construction of spherical meshes that can be used in climate simulations. Computational tests are used to demonstrate the efficiency and scalability of the algorithms for spherical Delaunay and centroidal Voronoi tessellations. Compared to serial versions of the algorithm and to STRIPACK-based approaches, the new parallel algorithm results in speedups for the construction of spherical centroidal Voronoi tessellations and spherical Delaunay triangulations.

D. W. Jacobsen

2013-08-01

308

Enhancing spatial resolution of soft x-ray CCD detectors by single-photon centroid determination  

CERN Document Server

In Charge Coupled Device (CCD) detectors the electrons excited upon absorption of a single x-ray photon quickly diffuse and generate charge-spots often larger than pixel dimensions. In the soft x-ray range this phenomenon drastically limits the effective spatial resolution to approximately 25\\mu m, irrespective of the pixel size. For very low fluence the charge-cloud centroid determination can be used, on each individual spot, to estimate the actual photon impact position with sub-pixel precision. The readout noise and speed, together with the charge and spatial undersampling, are the main factors limiting the accuracy of this procedure in commercial devices. We have developed and extensively tested an algorithm for efficient centroid reconstruction on images acquired by low noise detectors not designed for single photon counting. We have thus measured a position uncertainty of 6-7\\mu m in CCDs with 13.5\\mu m and 20.0\\mu m pixel size, around 1 keV photon energy. We have analyzed the centroid calculation perfo...

Amorese, Andrea; Braicovich, Lucio; Ghiringhelli, Giacomo

2014-01-01

309

Centroiding algorithms for high speed crossed strip readout of microchannel plate detectors.  

Science.gov (United States)

Imaging microchannel plate (MCP) detectors with cross strip (XS) readout anodes require centroiding algorithms to determine the location of the amplified charge cloud from the incident radiation, be it photon or particle. We have developed a massively parallel XS readout electronic system that employs an amplifier and ADC for each strip and uses this digital data to calculate the centroid of each event in real time using a field programmable gate array (FPGA). Doing the calculations in real time in the front end electronics using an FPGA enables a much higher input event rate, nearly two orders of magnitude faster, by avoiding the bandwidth limitations of the raw data transfer to a computer. We report on our detailed efforts to optimize the algorithms used on both an 18 mm and 40 mm diameter XS MCP detector with strip pitch of 640 microns and read out with multiple 32 channel "Preshape32" ASIC amplifiers (developed at Rutherford Appleton Laboratory). Each strip electrode is continuously digitized to 12 bits at 50 MHz with all 64 digital channels (128 for the 40 mm detector) transferred to a Xilinx Virtex 5 FPGA. We describe how events are detected in the continuous data stream and then multiplexed into firmware modules that spatially and temporally filter and weight the input after applying offset and gain corrections. We will contrast a windowed "center of gravity" algorithm to a convolution with a special centroiding kernel in terms of resolution and distortion and show results with 1 MHz. PMID:21918588

Vallerga, John; Tremsin, Anton; Raffanti, Rick; Siegmund, Oswald

2011-05-01

310

Determination of the centroid of interaction of crystals in block detectors for PET  

International Nuclear Information System (INIS)

Cut blocks of bismuth germanate (BGO) are the most common detectors used in current positron emission tomography (PET) imaging systems. The distribution of light received by four photo-multiplier (PMT) cathodes is used to assign each gamma ray to one crystal. Most 511-keV gamma rays undergo Compton scattering in the crystal before being photoelectrically absorbed. This, and the effects of dense metal septa between blocks change the response of the crystals depending on their position in the block and the angle of incidence of gamma rays on the block. For each projection, the authors used Monte Carlo simulation to determine the ''centroid of interaction'' for each crystal in the block. The authors found the crystals appear to be packed slightly closer in each block than their geometrical distance. The authors found the location of the crystal's centroid relative to its center changes along each projection. The authors simulated the 4 x 4 crystal arrays of the Scanditronix PC2048-B, determined the centroid of interaction for each crystal, then modified the reconstruction program's interpolation parameters. The spatial resolution improved by up to 10%, and a distortion of 1.5 mm at the edge of the imaging field was eliminated

311

Centroiding algorithms for high speed crossed-strip readout of microchannel plate detectors  

International Nuclear Information System (INIS)

Imaging microchannel plate (MCP) detectors with cross-strip (XS) readout anodes require centroiding algorithms to determine the location of the amplified charge cloud from the incident radiation, be it photon or particle. We have developed a massively parallel XS readout electronic system that employs an amplifier and ADC for each strip and uses this digital data to calculate the centroid of each event in real time using a field programmable gate array (FPGA). Doing the calculations in real time in the front end electronics using an FPGA enables a much higher input event rate, nearly two orders of magnitude faster by avoiding the bandwidth limitations of the raw data transfer to a computer. We report on our detailed efforts to optimize the algorithms used on both 18 and 40 mm diameter XS MCP detector with strip pitch of 640 ?m and readout with multiple 32 channel 'Preshape32' ASIC amplifiers (developed at Rutherford Appleton Laboratory). Each strip electrode is continuously digitized to 12 bits at 50 MHz with all 64 digital channels (128 for the 40 mm detector) transferred to a Xilinx Virtex 5 FPGA. We describe how events are detected in the continuous data stream and then multiplexed into firmware modules that spatially and temporally filter and weight the input after applying offset and gain corrections. We will contrast a windowed 'center of gravity' algorithm to a convolution with a special centroiding kernel in terms of resolution and distortion and show resultsesolution and distortion and show results with1 MHz.

312

Statistical Properties of Line Centroid Velocity Increments in the rho Ophiuchi Cloud  

Science.gov (United States)

We present a comparison of histograms of CO (2-1) line centroid velocity increments in the rho Ophiuchi molecular cloud with those computed for spectra synthesized from a three-dimensional, compressible, but non-starforming and non-gravitating hydrodynamic simulation. Histograms of centroid velocity increments in the rho Ophiuchi cloud show clearly non-Gaussian wings, similar to those found in histograms of velocity increments and derivatives in experimental studies of laboratory and atmospheric flows, as well as numerical simulations of turbulence. The magnitude of these wings increases monotonically with decreasing separation, down to the angular resolution of the data. This behavior is consistent with that found in the phase of the simulation which has most of the properties of incompressible turbulence. The time evolution of the magnitude of the non-Gaussian wings in the histograms of centroid velocity increments in the simulation is consistent with the evolution of the vorticity in the flow. However, we cannot exclude the possibility that the wings are associated with the shock interaction regions. Moreover, in an active starforming region like the rho Ophiuchi cloud, the effects of shocks may be more important than in the simulation. However, being able to identify shock interaction regions in the interstellar medium is also important, since numerical simulations show that vorticity is generated in shock interactions.

Lis, D. C.; Keene, Jocelyn; Li, Y.; Phillips, T. G.; Pety, J.

1998-01-01

313

Inclusion of inversion symmetry in centroid molecular dynamics: A possible avenue to recover quantum coherence  

International Nuclear Information System (INIS)

Inversion symmetry is included in the operator formulation of the centroid molecular dynamics (CMD). This work involves the development of a symmetry-adapted CMD (SA-CMD), here particularly for symmetrization and antisymmetrization projections. A symmetry-adapted quasidensity operator, as defined by Blinov and Roy [J. Chem. Phys. 115, 7822 (2001)], is employed to obtain the centroid representation of quantum mechanical operators. Numerical examples are given for a single particle confined to one-dimensional symmetric quartic and symmetric double-well potentials. Two SA-CMD simulations are performed separately for both projections, and centroid position autocorrelation functions are obtained. For each projection, the quality of the approximation as well as the accuracy are similar to those of regular CMD. It is shown that individual trajectories from two separate SA-CMD simulations can be properly combined to recover trajectories for Boltzmann statistics. Position autocorrelation functions are compared to the exact quantum mechanical ones. This explicit account of inversion symmetry provides a qualitative improvement on the conventional CMD approach and allows the recovery of some quantum coherence

314

Centers and centroids of the cone-beam projection of a ball  

International Nuclear Information System (INIS)

In geometric calibration of cone-beam (CB) scanners, point-like marker objects such as small balls are imaged to obtain positioning information from which the unknown geometric parameters are extracted. The procedure is sensitive to errors in the positioning information, and one source of error is a small bias which can occur in estimating the detector locations of the CB projections of the centers of the balls. We call these detector locations the center projections. In general, the CB projection of a ball of uniform density onto a flat detector forms an ellipse. Inside the ellipse lie the center projection M, the ellipse center C and the centroid G of the intensity values inside the ellipse. The center projection is invariably estimated from C or G which are much easier to extract directly from the data. In this work, we quantify the errors incurred in using C or G to estimate M. We prove mathematically that the points C, G, M and O are always distinct and lie on the major axis of the ellipse, where O is the detector origin, defined as the orthogonal projection of the cone vertex onto the detector. (The ellipse can only degenerate to a circle if the ball is along the direct line of sight to O, and in this case all four points coincide.) The points always lie in the same order: O, M, G, C which establishes that the centroid has less geometric bias than the ellipse center for estimating M. However, our numerical studies indicate that the centroid bias is only 20% lesste that the centroid bias is only 20% less than the ellipse center bias so the benefit in using centroid estimates is not substantial. For the purposes of quantifying the bias in practice, we show that the ellipse center bias ||CM|| can be conveniently estimated by eA/(? f-tilde) where A is the area of the elliptical projection, e is the eccentricity of the ellipse and f-tilde is an estimate of the focal length of the system. Finally, we discuss how these results are affected by physical factors such as beam hardening, and indicate extensions to balls of non-uniform density.

315

A Novel Systematic Error Compensation Algorithm Based on Least Squares Support Vector Regression for Star Sensor Image Centroid Estimation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The star centroid estimation is the most important operation, which directly affects the precision of attitude determination for star sensors. This paper presents a theoretical study of the systematic error introduced by the star centroid estimation algorithm. The systematic error is analyzed through a frequency domain approach and numerical simulations. It is shown that the systematic error consists of the approximation error and truncation error which resulted from the discretization approx...

Jingyan Song; Bin Liang; Tao Zhang; Jun Yang

2011-01-01

316

Centers and centroids of the cone-beam projection of a ball  

Science.gov (United States)

In geometric calibration of cone-beam (CB) scanners, point-like marker objects such as small balls are imaged to obtain positioning information from which the unknown geometric parameters are extracted. The procedure is sensitive to errors in the positioning information, and one source of error is a small bias which can occur in estimating the detector locations of the CB projections of the centers of the balls. We call these detector locations the center projections. In general, the CB projection of a ball of uniform density onto a flat detector forms an ellipse. Inside the ellipse lie the center projection M, the ellipse center C and the centroid G of the intensity values inside the ellipse. The center projection is invariably estimated from C or G which are much easier to extract directly from the data. In this work, we quantify the errors incurred in using C or G to estimate M. We prove mathematically that the points C, G, M and O are always distinct and lie on the major axis of the ellipse, where O is the detector origin, defined as the orthogonal projection of the cone vertex onto the detector. (The ellipse can only degenerate to a circle if the ball is along the direct line of sight to O, and in this case all four points coincide.) The points always lie in the same order: O, M, G, C which establishes that the centroid has less geometric bias than the ellipse center for estimating M. However, our numerical studies indicate that the centroid bias is only 20% less than the ellipse center bias so the benefit in using centroid estimates is not substantial. For the purposes of quantifying the bias in practice, we show that the ellipse center bias ||CM|| can be conveniently estimated by eA/(\\pi \\skew4\\tilde{f}) where A is the area of the elliptical projection, e is the eccentricity of the ellipse and \\skew4\\tilde{f} is an estimate of the focal length of the system. Finally, we discuss how these results are affected by physical factors such as beam hardening, and indicate extensions to balls of non-uniform density.

Clackdoyle, R.; Mennessier, C.

2011-12-01

317

Geometry of the $L_q$-centroid bodies of an isotropic log-concave measure  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study some geometric properties of the $L_q$-centroid bodies $Z_q(\\mu)$ of an isotropic log-concave measure $\\mu $ on ${\\mathbb R}^n$. For any $2\\ls q\\ls\\sqrt{n}$ and for $\\varepsilon \\in (\\varepsilon_0(q,n),1)$ we determine the inradius of a random $(1-\\varepsilon)n$-dimensional projection of $Z_q(\\mu)$ up to a constant depending polynomially on $\\varepsilon $. Using this fact we obtain estimates for the covering numbers $N(\\sqrt{\\smash[b]{q}}B_2^n,tZ_q(\\mu))$, $t\\gr 1$,...

Giannopoulos, Apostolos; Stavrakakis, Pantelis; Tsolomitis, Antonis; Vritsiou, Beatrice-helen

2013-01-01

318

Determination of the beam centroid of an obstructed focused Gaussian laser beam  

International Nuclear Information System (INIS)

Diffraction of an obstructed focused Gaussian laser beam has been treated theoretically using the Huygens-Fresnel diffraction integral and was found to be in good agreement with experimental measurements. The obstruction is a vertically oriented opaque cylinder treated as a flat hard aperture. Measurements and calculations are compared for the diffracted irradiance profile and the beam centroid as a function of cylinder diameter and lateral and longitudinal placement along the optic axis. The cylinders used were gauge pins and/or wires with diameters from 0.5 to 100 mil.

319

FISH Amyloid – a new method for finding amyloidogenic segments in proteins based on site specific co-occurence of aminoacids  

Science.gov (United States)

Background Amyloids are proteins capable of forming fibrils whose intramolecular contact sites assume densely packed zipper pattern. Their oligomers can underlie serious diseases, e.g. Alzheimer’s and Parkinson’s diseases. Recent studies show that short segments of aminoacids can be responsible for amyloidogenic properties of a protein. A few hundreds of such peptides have been experimentally found but experimental testing of all candidates is currently not feasible. Here we propose an original machine learning method for classification of aminoacid sequences, based on discovering a segment with a discriminative pattern of site-specific co-occurrences between sequence elements. The pattern is based on the positions of residues with correlated occurrence over a sliding window of a specified length. The algorithm first recognizes the most relevant training segment in each positive training instance. Then the classification is based on maximal distances between co-occurrence matrix of the relevant segments in positive training sequences and the matrix from negative training segments. The method was applied for studying sequences of aminoacids with regard to their amyloidogenic properties. Results Our method was first trained on available datasets of hexapeptides with the amyloidogenic classification, using 5 or 6-residue sliding windows. Depending on the choice of training and testing datasets, the area under ROC curve obtained the value up to 0.80 for experimental, and 0.95 for computationally generated (with 3D profile method) datasets. Importantly, the results on 5-residue segments were not significantly worse, although the classification required that algorithm first recognized the most relevant training segments. The dataset of long sequences, such as sup35 prion and a few other amyloid proteins, were applied to test the method and gave encouraging results. Our web tool FISH Amyloid was trained on all available experimental data 4-10 residues long, offers prediction of amyloidogenic segments in protein sequences. Conclusions We proposed a new original classification method which recognizes co-occurrence patterns in sequences. The method reveals characteristic classification pattern of the data and finds the segments where its scoring is the strongest, also in long training sequences. Applied to the problem of amyloidogenic segments recognition, it showed a good potential for classification problems in bioinformatics. PMID:24564523

2014-01-01

320

Centroid Localization of Uncooperative Nodes in Wireless Networks Using a Relative Span Weighting Method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Increasingly ubiquitous wireless technologies require novel localization techniques to pinpoint the position of an uncooperative node, whether the target is a malicious device engaging in a security exploit or a low-battery handset in the middle of a critical emergency. Such scenarios necessitate that a radio signal source be localized by other network nodes efficiently, using minimal information. We propose two new algorithms for estimating the position of an uncooperative transmitte...

Laurendeau Christine; Barbeau Michel

2010-01-01

 
 
 
 
321

Using quantitative and qualitative data in health services research – what happens when mixed method findings conflict? [ISRCTN61522618  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background In this methodological paper we document the interpretation of a mixed methods study and outline an approach to dealing with apparent discrepancies between qualitative and quantitative research data in a pilot study evaluating whether welfare rights advice has an impact on health and social outcomes among a population aged 60 and over. Methods Quantitative and qualitative data were collected contemporaneously. Quantitative data were collected from 126 men and women aged over 60 within a randomised controlled trial. Participants received a full welfare benefits assessment which successfully identified additional financial and non-financial resources for 60% of them. A range of demographic, health and social outcome measures were assessed at baseline, 6, 12 and 24 month follow up. Qualitative data were collected from a sub-sample of 25 participants purposively selected to take part in individual interviews to examine the perceived impact of welfare rights advice. Results Separate analysis of the quantitative and qualitative data revealed discrepant findings. The quantitative data showed little evidence of significant differences of a size that would be of practical or clinical interest, suggesting that the intervention had no impact on these outcome measures. The qualitative data suggested wide-ranging impacts, indicating that the intervention had a positive effect. Six ways of further exploring these data were considered: (i treating the methods as fundamentally different; (ii exploring the methodological rigour of each component; (iii exploring dataset comparability; (iv collecting further data and making further comparisons; (v exploring the process of the intervention; and (vi exploring whether the outcomes of the two components match. Conclusion The study demonstrates how using mixed methods can lead to different and sometimes conflicting accounts and, using this six step approach, how such discrepancies can be harnessed to interrogate each dataset more fully. Not only does this enhance the robustness of the study, it may lead to different conclusions from those that would have been drawn through relying on one method alone and demonstrates the value of collecting both types of data within a single study. More widespread use of mixed methods in trials of complex interventions is likely to enhance the overall quality of the evidence base.

Howel Denise

2006-03-01

322

Microlensed image centroid motions by an exotic lens object with negative convergence or negative mass  

CERN Document Server

Gravitational lens models with negative convergence (surface mass density projected onto the lens plane) inspired by modified gravity theories, exotic matter and energy have been recently examined to discuss possible demagnification of images and gravitational lensing shear, in such a way that a static and spherically symmetric modified spacetime metric depends on the inverse distance to the power of positive $n$ ($n=1$ for Schwarzschild metric, $n=2$ for Ellis wormhole) in the weak-field approximation [Kitamura, Nakajima and Asada, PRD 87, 027501 (2013), Izumi et al. to be published in PRD (2013)]. Some of the exotic lens models cause the attractive force on light rays like a convex lens, whereas the others are repulsive on light rays like a concave lens. The present paper considers microlensed image centroid motions by the exotic lens models. Numerical calculations show that, for large $n$ cases in the convex-type models, the centroid shift from the source position might move on a multiply-connected curve l...

Kitamura, Takao; Nakajima, Koki; Hagiwara, Chisaki; Asada, Hideki

2013-01-01

323

Iteratively Weighted Centroiding for Shack-Hartmann Wave-Front Sensors  

Energy Technology Data Exchange (ETDEWEB)

Several techniques have been used with Shack-Hartmann wavefront sensors to determine the local wave-front gradient across each lenslet. In this article we introduce an iterative weighted technique which is specifically targeted for open-loop applications such as aberrometers and metrology. In this article the iterative centroiding technique is compared to existing techniques such as center-of-mass with thresholding, weighted center-of-gravity, matched filter and cross-correlation. Under conditions of low signal-to-noise ratio, the iterative weighted centroiding algorithm is demonstrated to produce a lower variance in the reconstructed phase than existing techniques. The iteratively weighted algorithm was also compared in closed-loop and demonstrated to have the lowest error variance along with the weighted center-of-gravity, however, the iteratively weighted algorithm removes the bulk of the aberration in roughly half the iterations than the weighted center-of-gravity algorithm. This iterative weighted algorithm is also well suited to applications such as guiding on telescopes.

Baker, K L; Moallem, M M

2007-02-28

324

Application of the multiple PRF technique to resolve Doppler centroid estimation ambiguity for spaceborne SAR  

Science.gov (United States)

Estimation of the Doppler centroid ambiguity is a necessary element of the signal processing for SAR systems with large antenna pointing errors. Without proper resolution of the Doppler centroid estimation (DCE) ambiguity, the image quality will be degraded in the system impulse response function and the geometric fidelity. Two techniques for resolution of DCE ambiguity for the spaceborne SAR are presented; they include a brief review of the range cross-correlation technique and presentation of a new technique using multiple pulse repetition frequencies (PRFs). For SAR systems, where other performance factors control selection of the PRF's, an algorithm is devised to resolve the ambiguity that uses PRF's of arbitrary numerical values. The performance of this multiple PRF technique is analyzed based on a statistical error model. An example is presented that demonstrates for the Shuttle Imaging Radar-C (SIR-C) C-band SAR, the probability of correct ambiguity resolution is higher than 95 percent for antenna attitude errors as large as 3 deg.

Chang, C. Y.; Curlander, J. C.

1992-01-01

325

Finding possible transition states of defects in silicon-carbide and alpha-iron using the dimer method  

CERN Document Server

Energetic primary recoil atoms from ion implantation or fast neutron irradiation produce isolated point defects and clusters of both vacancies and interstitials. The migration energies and mechanisms for these defects are crucial to successful multiscale modeling of microstructural evolution during ion-implantation, thermal annealing, or under irradiation over long periods of time. The dimer method is employed to search for possible transition states of interstitials and small interstitial clusters in SiC and alpha-Fe. The method uses only the first derivatives of the potential energy to find saddle points without knowledge of the final state of the transition. In SiC, the possible migration pathway for the C interstitial is found to consist of the first neighbor jump via a Si site or second neighbor jump, but the relative probability for the second neighbor jump is very low. In alpha-Fe, the possible transition states are studied as a function of interstitial cluster size, and the lowest energy barriers corr...

Gao Fei; Weber, W J; Corrales, L R; Jonsson, H

2003-01-01

326

Radiation organ doses received in a nationwide cohort of u.s. Radiologic technologists: methods and findings.  

Science.gov (United States)

In this article, we describe recent methodological enhancements and findings from the dose reconstruction component of a study of health risks among U.S. radiologic technologists. An earlier version of the dosimetry published in 2006 used physical and statistical models, literature-reported exposure measurements for the years before 1960, and archival personnel monitoring badge data from cohort members through 1984. The data and models previously described were used to estimate annual occupational radiation doses for 90,000 radiological technologists, incorporating information about each individual's employment practices based on a baseline survey conducted in the mid-1980s. The dosimetry methods presented here, while using many of the same methods as before, now estimate 2.23 million annual badge doses (personal dose equivalent) for the years 1916-1997 for 110,374 technologists, but with numerous methodological improvements. Every technologist's annual dose is estimated as a probability density function to reflect uncertainty about the true dose. Multiple realizations of the entire cohort distribution were derived to account for shared uncertainties and possible biases in the input data and assumptions used. Major improvements in the dosimetry methods from the earlier version include: A substantial increase in the number of cohort member annual badge dose measurements; Additional information on individual apron usage obtained from surveys conducted in the mid-1990s and mid-2000s; Refined modeling to develop lognormal annual badge dose probability density functions using censored data regression models; Refinements of cohort-based annual badge probability density functions to reflect individual work patterns and practices reported on questionnaires and to more accurately assess minimum detection limits; and Extensive refinements in organ dose conversion coefficients to account for uncertainties in radiographic machine settings for the radiographic techniques employed. For organ dose estimation, we rely on well-researched assumptions about critical exposure-related variables and their changes over the decades, including the peak kilovoltage and filtration typically used in conducting radiographic examinations, and the usual body location for wearing radiation monitoring badges, the latter based on both literature and national recommendations. We have derived organ dose conversion coefficients based on air-kerma weighting of photon fluences from published X-ray spectra and derived energy-dependent transmission factors for protective lead aprons of different thicknesses. Findings are presented on estimated organ doses for 12 organs and tissues: red bone marrow, female breast, thyroid, brain, lung, heart, colon, ovary, testes, skin of trunk, skin of head and neck and arms, and lens of the eye. PMID:25361400

Simon, Steven L; Preston, Dale L; Linet, Martha S; Miller, Jeremy S; Sigurdson, Alice J; Alexander, Bruce H; Kwon, Deukwoo; Yoder, R Craig; Bhatti, Parveen; Little, Mark P; Rajaraman, Preetha; Melo, Dunstana; Drozdovitch, Vladimir; Weinstock, Robert M; Doody, Michele M

2014-11-01

327

Mixed methods evaluation of targeted case finding for cardiovascular disease prevention using a stepped wedged cluster RCT  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background A pilot project cardiovascular prevention was implemented in Sandwell (West Midlands, UK. This used electronic primary care records to identify untreated patients at high risk of cardiovascular disease then invited these high risk patients for assessment by a nurse in their own general practice. Those found to be eligible for treatment were offered treatment. During the pilot a higher proportion of high risk patients were started on treatment in the intervention practices than in control practices. Following the apparent success of the prevention project, it was intended to extend the service to all practices across the Sandwell area. However the pilot project was not a robust evaluation. There was a need for an efficient evaluation that would not disrupt the planned rollout of the project. Methods/design Project nurses will sequentially implement targeted cardiovascular case finding in a phased way across all general practices, with the sequence of general practices determined randomly. This is a stepped wedge randomised controlled trial design. The target population is patients aged 35 to 74, without diabetes or cardiovascular disease whose ten-year cardiovascular risk, (determined from data in their electronic records is ?20%. The primary outcome is the number of high risk patients started on treatment, because these data could be efficiently obtained from electronic primary care records. From this we can determine the effects of the case finding programme on the proportion of high risk patients started on treatment in practices before and after implementation of targeted case finding. Cost-effectiveness will be modelled from the predicted effects of treatments on cardiovascular events and associated health service costs. Alongside the implementation it is intended to interview clinical staff and patients who participated in the programme in order to determine acceptability to patients and clinicians. Practical considerations meant that 26 practices in Sandwell could be randomised, including about 6,250 patients at high risk of cardiovascular disease. This gives sufficient power for evaluation. Discussion It is possible to design a stepped wedge randomised controlled trial using routine data to determine the primary outcome to evaluate implementation of a cardiovascular prevention programme.

Marshall Tom

2012-10-01

328

The energy dependence of the centroid frequency and phase lag of the QPOs in GRS 1915+105  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a study of the centroid frequencies and phase lags of the quasi-periodic oscillations (QPOs) as functions of photon energy for GRS 1915+105. It is found that the centroid frequencies of the 0.5-10 Hz QPOs and their phase lags are both energy dependent, and there exists an anti-correlation between the QPO frequency and phase lag. These new results challenge the popular QPO models, because none of them can fully explain the observed properties. We suggest that the o...

Qu, J. L.; Lu, F. J.; Lu, Y.; Song, M. L.; Zhang, S.; Ding, G. Q.

2009-01-01

329

Weighted Centroid Algorithm for Estimating Primary User Location: Theoretical Analysis and Distributed Implementation  

CERN Document Server

Information about primary user (PU) location is crucial in enabling several key capabilities in dynamic spectrum access networks, including improved spatio-temporal sensing, intelligent location-aware routing, as well as aiding spectrum policy enforcement. Compared to other proposed non-interactive localization algorithms, the weighted centroid localization (WCL) scheme uses only received signal strength information, which makes it simple and robust to variations in the propagation environment. In contrast to prior work, which focused mainly on proposing algorithmic variations and verifying their performance through simulations, in this paper we present the first theoretical framework for WCL performance analysis in terms of its localization error distribution parameterized by node density, node placement, shadowing variance and correlation distance. Using this analysis, we quantify the robustness of WCL to various physical conditions and provide guidelines, such as node placement, for practical deployment of...

Wang, Jun; Han, Yuxing; ?abri?, Danijela

2010-01-01

330

Path integral centroid molecular dynamics simulations of semiinfinite slab and bulk liquid of para-hydrogen  

Energy Technology Data Exchange (ETDEWEB)

It has been unsuccessful to solve a set of time-dependent Schroedinger equations numerically for many-body quantum systems which involve, e.g., a number of hydrogen molecules, protons, and excess electrons at a low temperature, where quantum effect evidently appears. This undesirable situation is fatal for the investigation of real low-temperature chemical systems because they are essentially composed of many quantum degrees of freedom. However, if we use a new technique called `path integral centroid molecular dynamics (CMD) simulation` proposed by Cao and Voth in 1994, the real-time semi-classical dynamics of many degrees of freedom can be computed by utilizing the techniques already developed in the traditional classical molecular dynamics (MD) simulations. Therefore, the CMD simulation is expected to be very powerful tool for the quantum dynamics studies or real substances. (J.P.N.)

Kinugawa, Kenichi [Nara Women`s Univ., Nara (Japan). Dept. of Chemistry

1998-10-01

331

Path integral centroid molecular dynamics simulations of semiinfinite slab and bulk liquid of para-hydrogen  

International Nuclear Information System (INIS)

It has been unsuccessful to solve a set of time-dependent Schroedinger equations numerically for many-body quantum systems which involve, e.g., a number of hydrogen molecules, protons, and excess electrons at a low temperature, where quantum effect evidently appears. This undesirable situation is fatal for the investigation of real low-temperature chemical systems because they are essentially composed of many quantum degrees of freedom. However, if we use a new technique called 'path integral centroid molecular dynamics (CMD) simulation' proposed by Cao and Voth in 1994, the real-time semi-classical dynamics of many degrees of freedom can be computed by utilizing the techniques already developed in the traditional classical molecular dynamics (MD) simulations. Therefore, the CMD simulation is expected to be very powerful tool for the quantum dynamics studies or real substances. (J.P.N.)

332

Acquisition and Initial Analysis of H+- and H--Beam Centroid Jitter at LANSCE  

International Nuclear Information System (INIS)

During the 2005 Los Alamos Neutron Science Center (LANSCE) beam runs, beam current and centroid-jitter data were observed, acquired, analyzed, and documented for both the LANSCE H+ and H- beams. These data were acquired using three beam position monitors (BPMs) from the 100-MeV Isotope Production Facility (IPF) beam line and three BPMs from the Switchyard transport line at the end of the LANSCE 800-MeV linac. The two types of data acquired, intermacropulse and intramacropulse, were analyzed for statistical and frequency characteristics as well as various other correlations including comparing their phase-space like characteristics in a coordinate system of transverse angle versus transverse position. This paper will briefly describe the measurements required to acquire these data, the initial analysis of these jitter data, and some interesting dilemmas these data presented

333

Centroid Detector Assembly for the AXAF-I Alignment Test System  

Science.gov (United States)

The High Resolution Mirror Assembly (HRMA) of the Advanced X-ray Astrophysics Facility (imaging) (AXAF-I) consists of four nested paraboloids and four nested hyperboloids, all of meter-class size, and all of which are to be assembled and aligned in a special 15 meter tower at Eastman Kodak Company in Rochester, NY. The goals of the alignment are (1) to make the images of the four telescopes coincident; (2) to remove coma from each image individually; and (3) to control and determine the final position of the composite focus. This will be accomplished by the HRMA Aligment Test System (HATS) which is essentially a scanning Hartmann test system. The scanning laser source and the focal plane of the HATS are part of the Centroid Detector Assembly (CDA) which also includes processing electronics and software. In this paper we discuss the design and the measured performance of the CDA.

Glenn, Paul

1995-01-01

334

Centroid position measurements and subpixel sensitivity variations with the MAMA detector  

Science.gov (United States)

Initial measurements of the position sensitivity of a visible-light multianode microchannel array detector show that centroid calculations for image spots are accurate to better than 0.04 pixels even with sources that are essentially delta functions at the photocathode.Subpixel sensitivity variations of 10-15 percent are typically found for pixels in the array. Variations as large as 30 percent are possible in the worst conditions. These variations limit the photometric accuracy of the detector when very small scale features are observed. The photometric accuracy and the position sensitivity of the detector appear to be limited by cross-coupling effects within the anode array. Initial measurements with more recent designs of the detector show that most or all of this cross-coupling has been eliminated.

Morgan, Jeffrey S.; Slater, D. C.; Timothy, John G.; Jenkins, E. B.

1989-01-01

335

Luminescence properties, centroid shift and energy transfer of Ce3+ in aqueous chloride solutions  

International Nuclear Information System (INIS)

This paper focuses upon three themes: all related to aqueous cerium chloride solutions. First, the features in the absorption spectra of CeCl3 solutions do not shift noticeably with concentration and are at similar energies to bands in the solid-state absorption spectrum of Ce(H2O)93+, with the exception of the weak band at 297 nm which is due to Ce(H2O)83+. The broad emission band in solution is only due to [Ce(H2O)83+]? and the emission quenches at concentrations >0.06 M. Bands in the excitation spectra of aqueous CeCl3 solutions apparently change position with increasing concentration, due to absorption by Ce(H2O)93+ which does not contribute to emission. At concentrations above 1 M, there is total extinction of incident radiation for wavelengths shorter than 310 nm. Second, this system is chosen to illustrate the revised calculation of centroid shift, by taking into account the vibronic nature of spectral features, in contrast with the pure electronic transition of the free ion. Similar calculations are applicable to other Ce3+ systems. Thirdly, excitation spectra are employed to demonstrate the energy transfer occurring from Ce3+ to Tb3+ and Eu3+ in aqueous chloride solutions, which is an unusual energy transfer, occurring from 5d to 4f states and between hydrated lanthanide ions in solution. -- Highlights: • Excitation spectra of aqueous CeCl3 reveal photodissociation and emission only from [Ce(H2O)83+]?. • Revised calculation of centroid shift is given for general cases. • Excitation spectra demonstrate the energy transfer occurring from Ce3+ to Tb3+ and Eu3+ in aqueous chloride solutions. • This is an unusual energy transfer, occurring from 5d to 4f states and between hydrated lanthanide ions in solution

336

Use of a Hybrid Edge Node-Centroid Node Approach to Thermal Modeling  

Science.gov (United States)

A recent proposal submitted for an ESA mission required that models be delivered in ESARAD/ESATAN formats. ThermalDesktop was the preferable analysis code to be used for model development with a conversion done as the final step before delivery. However, due to some differences between the capabilities of the two codes, a unique approach was developed to take advantage of the edge node capability of ThermalDesktop while maintaining the centroid node approach used by ESARAD. In essence, two separate meshes were used: one for conduction and one for radiation. The conduction calculations were eliminated from the radiation surfaces and the capacitance and radiative calculations were eliminated from the conduction surfaces. The resulting conduction surface nodes were coincident with all nodes of the radiation surface and were subsequently merged, while the nodes along the edges remained free. Merging of nodes on the edges of adjacent surfaces provided the conductive links between surfaces. Lastly, all nodes along edges were placed into the subnetwork and the resulting supernetwork included only the nodes associated with radiation surfaces. This approach had both benefits and disadvantages. The use of centroid, surface based radiation reduces the overall size of the radiation network, which is often the most computationally intensive part of the modeling process. Furthermore, using the conduction surfaces and allowing ThermalDesktop to calculate the conduction network can save significant time by not having to manually generate the couplings. Lastly, the resulting GMM/TMM models can be exported to formats which do not support edge nodes. One drawback, however, is the necessity to maintain two sets of surfaces. This requires additional care on the part of the analyst to ensure communication between the conductive and radiative surfaces in the resulting overall network. However, with more frequent use of this technique, the benefits of this approach can far outweigh the additional effort.

Peabody, Hume L.

2010-01-01

337

A Novel Systematic Error Compensation Algorithm Based on Least Squares Support Vector Regression for Star Sensor Image Centroid Estimation  

Directory of Open Access Journals (Sweden)

Full Text Available The star centroid estimation is the most important operation, which directly affects the precision of attitude determination for star sensors. This paper presents a theoretical study of the systematic error introduced by the star centroid estimation algorithm. The systematic error is analyzed through a frequency domain approach and numerical simulations. It is shown that the systematic error consists of the approximation error and truncation error which resulted from the discretization approximation and sampling window limitations, respectively. A criterion for choosing the size of the sampling window to reduce the truncation error is given in this paper. The systematic error can be evaluated as a function of the actual star centroid positions under different Gaussian widths of star intensity distribution. In order to eliminate the systematic error, a novel compensation algorithm based on the least squares support vector regression (LSSVR with Radial Basis Function (RBF kernel is proposed. Simulation results show that when the compensation algorithm is applied to the 5-pixel star sampling window, the accuracy of star centroid estimation is improved from 0.06 to 6 × 10?5 pixels.

Jingyan Song

2011-07-01

338

Kinetic and thermodynamic parameters of biodiesel oxidation with synthetic antioxidants: simplex centroid mixture design  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A influência da temperatura sobre a oxidação de biodiesel foi avaliada pelos parâmetros cinéticos e termodinâmicos do biocombustível de óleo de soja e gordura suína com antioxidantes sintéticos: 3-terc-butil-4-hidroxianisol (BHA), 3,5-di-terc-butil-hidroxitolueno (BHT), 2-terc-butil-hidroquinona (TB [...] HQ) e galato de propila (PG), de acordo com delineamento de mistura simplex-centróide. Os parâmetros cinéticos foram determinados considerando-se reação de primeira ordem e aplicando a equação de Arrhenius. A adição de antioxidantes promoveu o aumento da energia de ativação (Ea), sendo TBHQ e PG os mais eficientes, apresentando efeito sinérgico. BHT e BHA foram os menos eficientes, assim como suas misturas. Os parâmetros termodinâmicos de ativação, avaliados pela equação de Eyring, não indicaram processos espontâneos (?G‡ > 0) com valores de ?H‡ positivos, e ?S‡ positivos e negativos. O delineamento simplex-centróide indicou valor otimizado de 174,46 kJ mol-1 para a mistura contendo 33,33 e 66,67% de TBHQ e PG, respectivamente. Abstract in english Temperature's influence on biodiesel oxidation was evaluated by kinetic and thermodynamic data in biofuel from soybean oil and lard with synthetic antioxidants: butylatedhydroxyanisol (BHA), butylatedhydroxytoluene (BHT), tert-butylhydroquinone (TBHQ), and propylgallate (PG) by simplex centroid mixt [...] ure design. The kinetic parameters ware obtained by Arrhenius equation and showed that addition of antioxidants in all tests increased activation energy (Ea) and that TBHQ and PG were more efficient and presented synergistic effect. BHT and BHA were the least efficient, as well as their mixtures. The thermodynamic activation parameters of the reactions, evaluated by the Eyring equation and based on the theory of the activated complex (ACT), indicated no spontaneous processes (?G‡ > 0) with positive ?H‡ values and positive and negative ?S‡ values. The application of simplex centroid mixture design, using Ea as response, showed the optimised value of 174.46 kJ mol-1 for a mixture containing 33.33 and 66.67% of TBHQ and PG, respectively.

Dionisio, Borsato; Diego, Galvan; Jaqueline L., Pereira; Juliane R., Orives; Karina G., Angilelli; Rodolfo L., Coppo.

1984-19-01

339

Luminescence properties, centroid shift and energy transfer of Ce{sup 3+} in aqueous chloride solutions  

Energy Technology Data Exchange (ETDEWEB)

This paper focuses upon three themes: all related to aqueous cerium chloride solutions. First, the features in the absorption spectra of CeCl{sub 3} solutions do not shift noticeably with concentration and are at similar energies to bands in the solid-state absorption spectrum of Ce(H{sub 2}O){sub 9}{sup 3+}, with the exception of the weak band at 297 nm which is due to Ce(H{sub 2}O){sub 8}{sup 3+}. The broad emission band in solution is only due to [Ce(H{sub 2}O){sub 8}{sup 3+}]{sup ?} and the emission quenches at concentrations >0.06 M. Bands in the excitation spectra of aqueous CeCl{sub 3} solutions apparently change position with increasing concentration, due to absorption by Ce(H{sub 2}O){sub 9}{sup 3+} which does not contribute to emission. At concentrations above 1 M, there is total extinction of incident radiation for wavelengths shorter than 310 nm. Second, this system is chosen to illustrate the revised calculation of centroid shift, by taking into account the vibronic nature of spectral features, in contrast with the pure electronic transition of the free ion. Similar calculations are applicable to other Ce{sup 3+} systems. Thirdly, excitation spectra are employed to demonstrate the energy transfer occurring from Ce{sup 3+} to Tb{sup 3+} and Eu{sup 3+} in aqueous chloride solutions, which is an unusual energy transfer, occurring from 5d to 4f states and between hydrated lanthanide ions in solution. -- Highlights: • Excitation spectra of aqueous CeCl{sub 3} reveal photodissociation and emission only from [Ce(H{sub 2}O){sub 8}{sup 3+}]{sup ?}. • Revised calculation of centroid shift is given for general cases. • Excitation spectra demonstrate the energy transfer occurring from Ce{sup 3+} to Tb{sup 3+} and Eu{sup 3+} in aqueous chloride solutions. • This is an unusual energy transfer, occurring from 5d to 4f states and between hydrated lanthanide ions in solution.

Wang, Jiwei; Mei, Yong [Faculty of Physics, Liaoning University, Shenyang 110036 (China); Tanner, Peter A., E-mail: peter.a.tanner@gmail.com [Department of Science and Environmental Studies, The Hong Kong Institute of Education, 10 Lo Ping Road, Tai Po, New Territories, Hong Kong S. A. R. (China)

2014-02-15

340

An algebraic method for finding a series of exact solutions to integrable and nonintegrable nonlinear evolution equations  

International Nuclear Information System (INIS)

An algebraic method is devised to uniformly construct a series of exact solutions for general integrable and nonintegrable nonlinear evolution equations. Compared with most existing tanh methods, the Jacobi function expansion method or other sophisticated methods, the proposed method not only gives new and more general solutions, but also provides a guideline to classify the various types of the solutions according to the values of some parameters. The solutions obtained in this paper include (a) polynomial solutions, (b) exponential solutions, (c) rational solutions, (d) triangular periodic wave solutions, (e) hyperbolic and solitary wave solutions and (f) Jacobi and Weierstrass doubly periodic wave solutions. The efficiency of the method can be demonstrated on a large variety of nonlinear equations such as those considered in this paper, new (2 + 1)-dimensional Calogero-KdV equation, (3 + 1)-dimensional Jimbo-Miwa equation, symmetric regular long wave equation, Drinfel'd-Sokolov-Wilson equation, (2 + 1)-dimensional generalized dispersive long wave equation, double sine-Gordon equation, Calogero-Degasperis-Fokas equation and coupled Schroedinger-Boussinesq equation. In addition, the links among our proposed method, the tanh method, the extended method and the Jacobi function expansion method are also clarified generally

 
 
 
 
341

A hybrid method for the exact planted (l, d) motif finding problem and its parallelization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Given a set of DNA sequences s1, ..., st, the (l, d) motif problem is to find an l-length motif sequence M , not necessary existing in any of the input sequences, such that for each sequence si, 1 ? i ? t, there is at least one subsequence differing with at most d mismatches from M. Many exact algorithms have been develope...

Abbas Mostafa M; Abouelhoda Mohamed; Bahig Hazem M

2012-01-01

342

A genetic-algorithm-based method to find unitary transformations for any desired quantum computation and application to a one-bit oracle decision problem  

Science.gov (United States)

We propose a genetic-algorithm-based method to find the unitary transformations for any desired quantum computation. We formulate a simple genetic algorithm by introducing the "genetic parameter vector" of the unitary transformations to be found. In the genetic algorithm process, all components of the genetic parameter vectors are supposed to evolve to the solution parameters of the unitary transformations. We apply our method to find the optimal unitary transformations and to generalize the corresponding quantum algorithms for a realistic problem, the one-bit oracle decision problem, or the often-called Deutsch problem. By numerical simulations, we can faithfully find the appropriate unitary transformations to solve the problem by using our method. We analyze the quantum algorithms identified by the found unitary transformations and generalize the variant models of the original Deutsch's algorithm.

Bang, Jeongho; Yoo, Seokwon

2014-12-01

343

Power centroid radar and its rise from the universal cybernetics duality  

Science.gov (United States)

Power centroid radar (PC-Radar) is a fast and powerful adaptive radar scheme that naturally surfaced from the recent discovery of the time-dual for information theory which has been named "latency theory." Latency theory itself was born from the universal cybernetics duality (UC-Duality), first identified in the late 1970s, that has also delivered a time dual for thermodynamics that has been named "lingerdynamics" and anchors an emerging lifespan theory for biological systems. In this paper the rise of PC-Radar from the UC-Duality is described. The development of PC-Radar, US patented, started with Defense Advanced Research Projects Agency (DARPA) funded research on knowledge-aided (KA) adaptive radar of the last decade. The outstanding signal to interference plus noise ratio (SINR) performance of PC-Radar under severely taxing environmental disturbances will be established. More specifically, it will be seen that the SINR performance of PC-Radar, either KA or knowledgeunaided (KU), approximates that of an optimum KA radar scheme. The explanation for this remarkable result is that PC-Radar inherently arises from the UC-Duality, which advances a "first principles" duality guidance theory for the derivation of synergistic storage-space/computational-time compression solutions. Real-world synthetic aperture radar (SAR) images will be used as prior-knowledge to illustrate these results.

Feria, Erlan H.

2014-05-01

344

Rapid Centroids and the Refined Position Accuracy of the Swift Gamma-ray Burst Catalogue  

International Nuclear Information System (INIS)

The Swift X-ray Telescope autonomously refines the Burst Alert Telescope positions (?1-4' uncertainty) to better than 5 arcsec, within 5 seconds of target acquisition by the observatory for typical bursts. The results of the rapid positioning capability of the XRT are presented here for both known sources and newly discovered GRBs, demonstrating the ability to automatically utilise one of two integration times according to the burst brightness, and to correct the position for alignment offsets caused by the fast pointing performance and variable thermal environment of the satellite as measured by the Telescope Alignment Monitor. We present an evaluation of the position accuracy for both the onboard centroiding software and the ground software for the calibration targets and show that a significant improvement in position accuracy is obtained if the boresight detector position is optimised relative to the spacecraft pointing. Finally, we present an updated catalogue of Swift GRB X-ray positions obtained in Photon Counting Mode using the improved, calibrated boresight

345

Collective centroid oscillations as an emittance preservation diagnostic in linear collider linacs  

International Nuclear Information System (INIS)

Transverse bunch centroid oscillations, induced at operating beam currents at which transverse wakefields are substantial, and observed at Beam Position Monitors, are sensitive to the actual magnetic focusing, energy gain, and rf phase profiles in a linac, and are insensitive to misalignments and jitter sources. In the pulse stealing set-up implemented at the SLC, they thus allow the frequent monitoring of the stability of the in-place emittance growth inhibiting or mitigating measures--primarily the energy scaled magnetic lattice and the rf phases necessary for BNS damping--independent of the actual emittance growth as driven by misalignments and jitter. The authors have developed a physically based analysis technique to meaningfully reduce the data. Oscillation beta-beating is a primary indicator of beam energy errors; shifts in the invariant amplitude reflect differential internal motion along the longitudinally extended bunch and thus are a sensitive indicator of the real rf phases in the machine; shifts in betatron phase advance contain corroborative information sensitive to both effects

346

THE VELOCITY CENTROID PERIODICITY OF L2 PUPPIS' SiO MASER EMISSION  

International Nuclear Information System (INIS)

We report the first short term velocity centroid (VC) periodicity derived from SiO maser emission. L2 Puppis, a semi-regular AGB star, was observed using the Mopra radio telescope of the Australia Telescope National Facility in the SiO v = 1, J = 1-0 and v = 1, J = 2-1 transitions. It exhibits a 139 day period in its SiO maser VC based on a period folding analysis and a Lomb Scargle analysis. L2 Pup's SiO maser emission has an unusually large velocity range and an unusual three-peaked spectrum. To create the change in VC the entire spectrum does not shift in velocity, but changes in the relative emission of the peaks generate the variation. The changes in the VC may be due to differential illumination, an asymmetric circumstellar distribution of material, or a mixture of causes. The unusual velocity structure, similar to that observed in Orion source 1, may be due to revolution of the circumstellar material or asymmetries in the circumstellar environment

347

For a reasoned development of experimental methods in information and communication sciences Some epistemological findings of methodological pluralism  

Directory of Open Access Journals (Sweden)

Full Text Available If multidisciplinarity is necessary, first, for studying the widest possible set of communication phenomena (organizational, in groups, interpersonal, media, computer-mediated communication... and, secondly, for grasping the complexity of the different moments of the same phenomenon of communication (production, content, reception, circulation ..., methodological pluralism is also important. However, French research in communication sciences leaves in the shade a number of phenomena and moments of communication that could be better understood thanks to the experimental method. We will underline that the epistemological issues related to rational use of the experimental method in communication sciences are not negligible: it allows the study of objects that cannot be investigated with other methods and offers the opportunity to build knowledge by the refutation of hypotheses and theoretical propositions. We will clarify some epistemological misunderstandings concerning this method. First, it is actually a method of studying complex systems and communication processes. Secondly, its use is not incompatible with constructivism.

Didier COURBET

2013-07-01

348

PyMGC3: Finding stellar streams in the Galactic Halo using a family of Great Circle Cell counts methods  

Science.gov (United States)

PyMGC3 is a Python toolkit to apply the Modified Great Circle Cell Counts (mGC3) method to search for tidal streams in the Galactic Halo. The code computes pole count maps using the full mGC3/nGC3/GC3 family of methods. The original GC3 method (Johnston et al., 1996) uses positional information to search for 'great-circle-cell structures'; mGC3 makes use of full 6D data and nGC3 uses positional and proper motion data.

Mateu, C.

2014-11-01

349

Centroid and Envelope Eynamics of Charged Particle Beams in an Oscillating Wobbler and External Focusing Lattice for Heavy Ion Fusion Applications  

International Nuclear Information System (INIS)

Recent heavy ion fusion target studies show that it is possible to achieve ignition with direct drive and energy gain larger than 100 at 1MJ. To realize these advanced, high-gain schemes based on direct drive, it is necessary to develop a reliable beam smoothing technique to mitigate instabilities and facilitate uniform deposition on the target. The dynamics of the beam centroid can be explored as a possible beam smoothing technique to achieve a uniform illumination over a suitably chosen region of the target. The basic idea of this technique is to induce an oscillatory motion of the centroid for each transverse slice of the beam in such a way that the centroids of different slices strike different locations on the target. The centroid dynamics is controlled by a set of biased electrical plates called 'wobblers'. Using a model based on moments of the Vlasov-Maxwell equations, we show that the wobbler deflection force acts only on the centroid motion, and that the envelope dynamics are independent of the wobbler fields. If the conducting wall is far away from the beam, then the envelope dynamics and centroid dynamics are completely decoupled. This is a preferred situation for the beam wobbling technique, because the wobbler system can be designed to generate the desired centroid motion on the target without considering its effects on the envelope and emittance. A conceptual design of the wobbler system for a heavy ion fusion driver is briefly summarized.

350

Using quantitative and qualitative data in health services research – what happens when mixed method findings conflict? [ISRCTN61522618  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background In this methodological paper we document the interpretation of a mixed methods study and outline an approach to dealing with apparent discrepancies between qualitative and quantitative research data in a pilot study evaluating whether welfare rights advice has an impact on health and social outcomes among a population aged 60 and over. Methods Quantitative and qualitative data were collected contemporaneously. Quantitative data were collected...

Howel Denise; Mackintosh Joan; White Martin; Moffatt Suzanne

2006-01-01

351

K-nearest Neighbour Method of Analysing the ECG Signal (To Find out the Different Disorders Related to Heart)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Heart attack is very common thing now-a-days. This results because of many disorders occurring in the heart. These disorders can be found out by analysing the ECG signal. The conventional method of analysing the ECG signal is done by the doctors who are expert in that. So far there is no systematic procedure for analysing the ECG signal. The main goal of this study is to obtain a systematic method of analysing the Electrocardiogram (ECG) from the patient an...

Jayalalitha, S.; Susan, D.; Shalini Kumari; Archana, B.

2014-01-01

352

A fast and versatile wire chamber space point finding processor  

International Nuclear Information System (INIS)

A four plane, four metre square, multiwire proportional counter at the CERN Omega spectrometer is used to digitize the spatial position of charged particles and generate a fast second level trigger. The coordinates of cluster centroids are fed into a modular space point finding processor which can analyse a ten particle event in 40 ?s. The detector and the algorithms are described in the first part of this paper, the hardware implementation and the performance are then discussed. (orig.)

353

Diagnostic methods in finding out the causes of infertility, results of HSG examination and laparoscopy in infertile women examined at the Gynecological Ward of the City Hospital  

International Nuclear Information System (INIS)

The paper presents diagnostic methods and the results of hysterosalpingography (HSG) and laparoscopy examination, with special attention being drawn to the usefulness of these methods in finding out the causes of infertility. 51 patients with primary and second infertility were examined. HSG and laparoscopy make it possible to diagnose correctly the cause of infertility. They also enable adequate and early classification of patients for further diagnosis and treatment at highly specialized centers dealing with the problems of infertility. (author)

354

A quantitative assessment of the accuracy of centroid molecular dynamics for the calculation of the infrared spectrum of liquid water.  

Science.gov (United States)

A detailed analysis of the infrared lineshapes corresponding to the intramolecular bond vibrations of HOD in either H(2)O or D(2)O is presented here in order to quantitatively assess the accuracy of centroid molecular dynamics in reproducing the correct features of the infrared spectrum of water at ambient conditions. Through a direct comparison with the results obtained from mixed quantum-classical calculations, it is shown that centroid molecular dynamics provides accurate vibrational shifts and lineshapes when the intramolecular bond stretching vibrations are described by a physically reasonable anharmonic potential. Artificially large redshifts due to a so-called "curvature problem" are instead obtained with an unphysical shifted harmonic potential because the latter allows substantial probability density at zero bond lengths. PMID:20078147

Paesani, Francesco; Voth, Gregory A

2010-01-01

355

Quantum size correction to the work function and the centroid of excess charge in positively ionized simple metal clusters  

Directory of Open Access Journals (Sweden)

Full Text Available  In this work, we have shown the important role of the finite-size correction to the work function in predicting the correct position of the centroid of excess charge in positively charged simple metal clusters with different values . For this purpose, firstly we have calculated the self-consistent Kohn-Sham energies of neutral and singly-ionized clusters with sizes in the framework of local spin-density approximation and stabilized jellium model (SJM as well as simple jellium model (JM with rigid jellium. Secondly, we have fitted our results to the asymptotic ionization formulas both with and without the size correction to the work function. The results of fittings show that the formula containing the size correction predict a correct position of the centroid inside the jellium while the other predicts a false position, outside the jellium sphere.

M. Payami

2003-12-01

356

4fn-15d centroid shift in lanthanides and relation with anion polarizability, covalency, and cation electronegativity  

International Nuclear Information System (INIS)

Data collected on the centroid shift of the 5d-configuration of Ce3+ in oxide and fluoride compounds were recently analyzed with a model involving the correlated motion between 5d-electron and ligand electrons. The correlation effects are proportional to the polarizability of the anion ligands and it leads, like covalency, to lowering of the 5d-orbital energies. By means of ab initio Hartree-Fock-LCAO calculations including configuration interaction the contribution from covalency and correlated motion to the centroid shift are determined separately for Ce3+ in various compounds. It will be shown that in fluoride compounds, covalency provides an insignificant contribution. In oxides, polarizability appears to be of comparable importance as covalency

357

Quantum size correction to the work function and centroid of excess charge in positively ionized simple metal clusters  

International Nuclear Information System (INIS)

In this work, we have shown the important role of the finite-size correction to the work function in predicting the correct position of the centroid of excess charge in positively charged simple metal clusters with different rs values (2? rs? 7). For this purpose, firstly we have calculated the self-consistent Kohn-Sham energies of neutral and singly-ionized clusters with sizes 2? N ?100 in the framework of local spin-density approximation and stabilized jellium model as well as simple jellium model with rigid jellium. Secondly, we have fitted our results to the asymptotic ionization formulas both with and without the size correction to the work function. The results of fittings show that the formula containing the size correction predict a correct position of the centroid inside the jellium while the other predicts a false position, outside the jellium sphere

358

OMERACT 10 sharp symposium: important findings in examination of imaging methods for measurement of joint damage in rheumatoid arthritis  

DEFF Research Database (Denmark)

The Sharp Symposium was held at the Outcome Measures in Rheumatology Clinical Trials 2010 meeting (OMERACT 10) in honor of the late John Sharp, consummate rheumatologist and researcher. The symposium focused on the status of current scoring methods in radiography, magnetic resonance imaging (MRI), and ultrasound (US) in rheumatoid arthritis (RA), as well as on the use of soluble and tissue biomarkers in RA, with the aim of updating recommendations regarding methods for enhanced detection, monitoring, and prediction of joint damage in clinical trials.

Strand, Vibeke; Kingsbury, Sarah R

2011-01-01

359

Franck-Condon factors and r-centroids for certain band systems of gallium and indium mono-fluorides  

International Nuclear Information System (INIS)

For the first time, the Franck-Condon factors and r-centroids, which are very closely related to vibrational transition probabilities, have been evaluated for the bands of A3?+0 - Xl ?+, B3 ?-1 - Xl ?+, and C1? - Xl ?+ systems of Ga F and In F molecules. A numerical integration procedure is followed to evaluate these transition probability parameters, using a suitable potential. (Author)

360

A Method for Finding Solutions of the Hermitian Theory of Relativity which Depend on Three Co-ordinates  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A method is presented, which can generate solutions of the Hermitian theory of relativity from known solutions of the general theory of relativity, when the latter depend on three co-ordinates and are invariant under reversal of the fourth one.

Antoci, S.

2001-01-01

 
 
 
 
361

Tomography methods for diagnostic examination of cerebrovascular disease: a comparative evaluation of SPECT, PET and MR/CT findings  

International Nuclear Information System (INIS)

Single Photon Emissions Computerized Tomography (SPECT), Positron Emissions Tomography (PET), Magnetic Resonance Tomography (MR), and Transmission Computerized Tomography (CT) complement each other and lead to a consideration of the cerebrovascular disease under patho-physiological aspects. Indications for the combined application of functionally oriented (SPECT/PET) and morphologically oriented (CT/MR) examination methods with cerebrovascular disease are presented. (orig./MG)

362

Assessing the impacts of regional characteristics on the location of manufacturing facilities: A review of recent methods and findings  

Energy Technology Data Exchange (ETDEWEB)

This report gives federal agencies background information to help them assess the impacts that siting a nuclear-waste storage facility could have on industries making location decisions in various regions of influence. It reviews two major research methods used to analyze reasons for location choices: economic-based or econometric methods and survey-based factor-ranking methods. It summarizes the results of studies that have used these methods, identifying and ranking factors shown to be important to industries making location decisions throughout the nation and in western states. Neither economic-based nor survey-based studies have shown the public`s perceptions of a region to be an important determinant in the selection of new manufacturing sites, although consideration of the level of amenities is gaining importance in the West. In general, available studies are inconclusive with respect to the extent to which perceptions about hazards play a role in the location of manufacturing facilities in any region of the nation.

Calzonetti, F.J. [West Virginia Univ., Morgantown, WV (United States). Dept. of Geology and Geography; Hemphill, R.C. [Argonne National Lab., IL (United States). Environmental Assessment and Information Sciences Div.

1992-01-01

363

Assessing the impacts of regional characteristics on the location of manufacturing facilities: A review of recent methods and findings  

Energy Technology Data Exchange (ETDEWEB)

This report gives federal agencies background information to help them assess the impacts that siting a nuclear-waste storage facility could have on industries making location decisions in various regions of influence. It reviews two major research methods used to analyze reasons for location choices: economic-based or econometric methods and survey-based factor-ranking methods. It summarizes the results of studies that have used these methods, identifying and ranking factors shown to be important to industries making location decisions throughout the nation and in western states. Neither economic-based nor survey-based studies have shown the public's perceptions of a region to be an important determinant in the selection of new manufacturing sites, although consideration of the level of amenities is gaining importance in the West. In general, available studies are inconclusive with respect to the extent to which perceptions about hazards play a role in the location of manufacturing facilities in any region of the nation.

Calzonetti, F.J. (West Virginia Univ., Morgantown, WV (United States). Dept. of Geology and Geography); Hemphill, R.C. (Argonne National Lab., IL (United States). Environmental Assessment and Information Sciences Div.)

1992-01-01

364

Neutron radiography with sub-15 {mu}m resolution through event centroiding  

Energy Technology Data Exchange (ETDEWEB)

Conversion of thermal and cold neutrons into a strong {approx}1 ns electron pulse with an absolute neutron detection efficiency as high as 50-70% makes detectors with {sup 10}B-doped Microchannel Plates (MCPs) very attractive for neutron radiography and microtomography applications. The subsequent signal amplification preserves the location of the event within the MCP pore (typically 6-10 {mu}m in diameter), providing the possibility to perform neutron counting with high spatial resolution. Different event centroiding techniques of the charge landing on a patterned anode enable accurate reconstruction of the neutron position, provided the charge footprints do not overlap within the time required for event processing. The new fast 2 Multiplication-Sign 2 Timepix readout with >1.2 kHz frame rates provides the unique possibility to detect neutrons with sub-15 {mu}m resolution at several MHz/cm{sup 2} counting rates. The results of high resolution neutron radiography experiments presented in this paper, demonstrate the sub-15 {mu}m resolution capability of our detection system. The high degree of collimation and cold spectrum of ICON and BOA beamlines combined with the high spatial resolution and detection efficiency of MCP-Timepix detectors are crucial for high contrast neutron radiography and microtomography with high spatial resolution. The next generation of Timepix electronics with sparsified readout should enable counting rates in excess of 10{sup 7} n/cm{sup 2}/s taking full advantage of high beam intensity of present brightest neutron imaging facilities.

Tremsin, Anton S., E-mail: ast@ssl.berkeley.edu [Space Sciences Laboratory, University of California at Berkeley, Berkeley, CA 94720 (United States); McPhate, Jason B.; Vallerga, John V.; Siegmund, Oswald H.W. [Space Sciences Laboratory, University of California at Berkeley, Berkeley, CA 94720 (United States); Bruce Feller, W. [NOVA Scientific, Inc. 10 Picker Road, Sturbridge, MA 01566 (United States); Lehmann, Eberhard; Kaestner, Anders; Boillat, Pierre; Panzner, Tobias; Filges, Uwe [Spallation Neutron Source Division, Paul Scherrer Institute, CH-5232 Villigen (Switzerland)

2012-10-01

365

Finding Factors Influencing Risk: Comparing Variable Selection Methods Applied to Logistic Regression Models of Cases and Controls  

Digital Repository Infrastructure Vision for European Research (DRIVER)

When modeling the risk of a disease, the very act of selecting the factors to include can heavily impact the results. This study compares the performance of several variable selection techniques applied to logistic regression. We performed realistic simulation studies to compare five methods of variable selection: (1) a confidence interval approach for significant coefficients (CI), (2) backward selection, (3) forward selection, (4) stepwise selection, and (5) Bayesian stochastic search varia...

Swartz, Michael D.; Yu, Robert K.; Shete, Sanjay

2008-01-01

366

Finding the low-energy forms of avian pancreatic polypeptide with the diffusion-process-controlled Monte Carlo method  

Science.gov (United States)

Ab initio folding of the avian pancreatic polypeptide using a diffusion-process-controlled Monte Carlo method is presented. This method differs from other Monte Carlo methods in that two successive conformations must be kinetically connected in a small period of time. The 36-residue polypeptide is represented using a hybrid level of structure description: the backbone is treated at an all-atom level, while the side chains are modeled as spheres. The conformations are evaluated on the basis of pairwise contact energies between the side chains, a main chain hydrogen bonding potential, and local bonded potentials. Starting from various extended conformations, the chain reaches the basin of lowest energy in ˜1000-3500 Monte Carlo steps and the predicted conformations deviate by ˜3.0 Å rms from the x-ray structure. The eight trajectories suggest a three-step mechanism: (1) early formation of the ? helix in the region 14-33, (2) cooperative formation of long-range interactions, and (3) stabilization of the polyprolinelike conformation in the region 1-8 in the final steps of folding.

Derreumaux, Philippe

1998-07-01

367

Characterization of a millefiori glass find from Aquincum by SEM-EDX and micro-PIXE methods  

Energy Technology Data Exchange (ETDEWEB)

Research has been focused on the analysis of archaeological glasses from the Roman age and medieval times. Study of ancient millefiori type glasses from the collection of Hungarian Museums has been started. A test measurement, carried out on a glass fragment supposedly part of a dish, was performed by SEM-EDX and micro-PIXE methods. Complementary analytical data were obtained for texture and composition. Results suggest that Roman and Mesopotamian techniques were used together. Our data contribute to data bases of millefiori glasses.

Uzonyi, I., E-mail: uzonyi@atomki.hu [Institute of Nuclear Research of the Hungarian Academy of Sciences, H-4026 Debrecen, Bem ter 18/C (Hungary); Csontos, K.; Verebes, A. [Budapest History Museum, Aquincum Museum H-8211 Budapest, Zahony u. 4. (Hungary); Cserhati, C. [Department of Solid State Physics, University of Debrecen H-4032 Debrecen, Bem ter 18/B (Hungary); Csedreki, L.; Kis-Varga, M.; Kiss, A.Z. [Institute of Nuclear Research of the Hungarian Academy of Sciences, H-4026 Debrecen, Bem ter 18/C (Hungary)

2011-10-15

368

Pseudometrically Constrained Centroidal Voronoi Tessellations: Generating uniform antipodally symmetric points on the unit sphere with a novel acceleration strategy and its applications to Diffusion and 3D radial MRI  

CERN Document Server

Purpose: The purpose of this work is to investigate the hypothesis that uniform sampling measurements that are endowed with antipodal symmetry play an important role when the raw data and image data are related through the Fourier relationship as in q-space diffusion MRI and 3D radial MRI. Currently, it is extremely challenging to generate large uniform antipodally symmetric point sets suitable for 3D radial MRI. A novel approach is proposed to solve this important and long-standing problem. Methods: The proposed method is based upon constrained centroidal Voronoi tessellations of the upper hemisphere with a novel pseudometric. Geometrically intuitive approach to tessellating the upper hemisphere is also proposed. Results: The average time complexity of the proposed centroidal tessellations was shown to be effectively on the order of the product of the number of iterations and the number of generators. For small sample size, the proposed method was comparable to the state-of-the-art iterative method in terms ...

Koay, Cheng Guan

2012-01-01

369

A vision-based hybrid particle tracking velocimetry (PTV) technique using a modified cascade correlation peak-finding method  

Energy Technology Data Exchange (ETDEWEB)

A novel technique for particle tracking velocimetry is presented in this paper to overcome the issue of overlapping particle images encountered in the flows with high particle density or under volumetric illumination conditions. To achieve this goal, algorithms for particle identification and tracking are developed based on current methods and validated with both synthetic and experimental image sets. The results from synthetic image tests show that the particle identification algorithm is able to resolve overlapped particle images up to 50 % under noisy conditions, while keeping the root mean square peak location error under 0.07 pixels. The algorithm is also robust to the size changes up to a size ratio of 5. The tracking method developed from a classic computer vision matching algorithm is capable of capturing a velocity gradient up to 0.3 while maintaining the error under 0.2 pixels. Sensitivity tests were performed to describe the optimum conditions for the technique in terms of particle image density, particle image sizes and velocity gradients, also its sensitivity to errors of the PIV results that guide the tracking process. The comparison with other existing tracking techniques demonstrates that this technique is able to resolve more vectors out of a dense particle image field. (orig.)

Lei, Y.C. [University of Washington, Department of Aeronautics and Astronautics, Seattle, WA (United States); Canadian Aviation Electronics Inc., Performance Group Division, Quebec, CA (Canada); Tien, W.H.; Dabiri, D. [University of Washington, Department of Aeronautics and Astronautics, Seattle, WA (United States); Duncan, J. [University of Washington, Department of Aeronautics and Astronautics, Seattle, WA (United States); Edwards Air Force Base, CA (United States); Paul, M. [University of Washington, Department of Aeronautics and Astronautics, Seattle, WA (United States); Eglin Air Force Base, FL (United States); Ponchaut, N. [Exponent, Natick, MA (United States); Mouton, C. [RAND Corporation, Santa Monica, CA (United States); Roesgen, T. [ETH Zurich, Institute of Fluid Dynamics, Zurich (Switzerland); Hove, J. [University of Cincinnati College of Medicine, Molecular and Cellular Physiology, Cincinnati, OH (United States)

2012-11-15

370

Improvements and new findings in Monte Carlo method with complex-valued weights for neutron leakage-corrected assembly calculations  

International Nuclear Information System (INIS)

The author of this paper recently proposed a Monte Carlo calculation algorithm to solve a complex transport equation with complex-valued weights. The algorithm enables one to generate neutron leakage-corrected group constants and anisotropic diffusion coefficients for a unit fuel pin cell or assembly. The group constants are subsequently used for multi-group deterministic core calculations. The technique, however, had some limitations in applying itself to general problems. Some improvements have been done in this paper. The reflective boundary condition has newly become available. It has been found that a cumbersome weight cancellation of fission sources with positive and negative weights can be omitted in general fuel assembly geometries. A homogenization method of diffusion coefficients for a fuel assembly has been proposed. (author)

371

The centroid shift of the 5d levels of Ce sup 3 sup + with respect to the 4f levels in ionic crystals, a theoretical investigation  

CERN Document Server

The centroid shifts of the 5d level of Ce sup 3 sup + in BaF sub 2 , LaAlO sub 3 and LaCl sub 3 have been calculated using the ionic cluster approach. By applying configuration interaction as extension of the basic HF-LCAO approach the dynamical polarization contribution to the centroid shift was calculated. This was found to be only successful if basis sets are used optimized for polarization of the anions.

Andriessen, J; Eijk, C W E

2002-01-01

372

Franck-Condon factors and r-centroids for the B-X bands of 10B18O and 11B18O molecules  

Directory of Open Access Journals (Sweden)

Full Text Available Frank–Condon factors and r-centroids have been calculated for the B2S+ –X2S+ bands of the 10B18O and 11B18O isotopic molecules assuming that both the B and X states follow a Morse potential curve. The calculated q n'n" values are compared with observed band intensities and the relationship between the r-centroids and the band positions has been determined and is discussed.

VOJISLAV BOJOVIC

2005-05-01

373

The centroid shift of the 5d levels of Ce3+ with respect to the 4f levels in ionic crystals, a theoretical investigation  

International Nuclear Information System (INIS)

The centroid shifts of the 5d level of Ce3+ in BaF2, LaAlO3 and LaCl3 have been calculated using the ionic cluster approach. By applying configuration interaction as extension of the basic HF-LCAO approach the dynamical polarization contribution to the centroid shift was calculated. This was found to be only successful if basis sets are used optimized for polarization of the anions

374

Rock Finding  

Science.gov (United States)

In this article, the authors discuss a literature-based activity that helps students discover the importance of making detailed observations. In an inspiring children's classic book, "Everybody Needs a Rock" by Byrd Baylor (1974), the author invites readers to go "rock finding," laying out 10 rules for finding a "perfect" rock. In this way, the…

Rommel-Esham, Katie; Constable, Susan D.

2006-01-01

375

Automatic NC-Data generation method for 5-axis cutting of turbine-blades by finding Safe heel-angles and adaptive path-intervals  

International Nuclear Information System (INIS)

In this paper, an efficient method for generating 5-axis cutting data for a turbine blade is presented. The interference elimination of 5-axis cutting currently is very complicated, and it takes up a lot of time. The proposed method can generate an interference-free tool path, within an allowance range. Generating the cutting data just point to the cutting process and using it to obtain NC data by calculating the feed rate, allows us to maintain the proper feed rate of the 5-axis machine. This paper includes the algorithms for: (1) CL data generation by detecting an interference-free heel angle, (2) finding the optimal tool path interval considering the cusp-height, (3) finding the adaptive feed rate values for each cutter path, and (4) the inverse kinematics depending on the structure of the 5-axis machine, for generating the NC data

376

Interpreting regional myocardial magnetic resonance imaging data: A new method for collation with angiographic findings in patients with coronary artery disease  

International Nuclear Information System (INIS)

The magnetic resonance imaging (MRI) assessment of myocardial function and perfusion is a valuable complementary technique to coronary angiography. We describe a method of presenting and collating regional MRI data with the angiographic findings as annotated by the Green Lane reporting system. Routine clinical use of this approach is likely to increase the accuracy of MRI data interpretation and to influence both medical and interventional treatment strategies. Sensky, P.R. (2002)

377

Quantum size correction to the work function and the centroid of excess charge in positively ionized simple metal clusters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this work, we have shown the important role of the finite-size correction to the work function in predicting the correct positions of the centroid of excess charge in positively charged simple metal clusters with different $r_s$ values ($2\\le r_s\\le7$). For this purpose, firstly we have calculated the self-consistent Kohn-Sham energies of neutral and singly-ionized clusters with sizes $2\\le N\\le 100$ in the framework of local spin-density approximation and stabilized jell...

Payami, M.

2002-01-01

378

A colorimetric method for highly sensitive and accurate detection of iodide by finding the critical color in a color change process using silver triangular nanoplates  

Energy Technology Data Exchange (ETDEWEB)

Graphical abstract: -- Highlights: •Demonstrated a new colorimetric strategy for iodide detection by silver nanoplates. •The colorimetric strategy is to find the critical color in a color change process. •The colorimetric strategy is more accurate and sensitive than common colorimetry. •Discovered a new morphological transformation phenomenon of silver nanoplates. -- Abstract: In this contribution, we demonstrated a novel colorimetric method for highly sensitive and accurate detection of iodide using citrate-stabilized silver triangular nanoplates (silver TNPs). Very lower concentration of iodide can induce an appreciable color change of silver TNPs solution from blue to yellow by fusing of silver TNPs to nanoparticles, as confirmed by UV–vis absorption spectroscopy and transmission electron microscopy (TEM). The principle of this colorimetric assay is not an ordinary colorimetry, but a new colorimetric strategy by finding the critical color in a color change process. With this strategy, 0.1 ?M of iodide can be recognized within 30 min by naked-eyes observation, and lower concentration of iodide down to 8.8 nM can be detected using a spectrophotometer. Furthermore, this high sensitive colorimetric assay has good accuracy, stability and reproducibility comparing with other ordinary colorimetry. We believe this new colorimetric method will open up a fresh insight of simple, rapid and reliable detection of iodide and can find its future application in the biochemical analysis or clinical diagnosis.

Yang, Xiu-Hua; Ling, Jian, E-mail: lingjian@ynu.edu.cn; Peng, Jun; Cao, Qiu-E., E-mail: qecao@ynu.edu.cn; Ding, Zhong-Tao; Bian, Long-Chun

2013-10-10

379

A colorimetric method for highly sensitive and accurate detection of iodide by finding the critical color in a color change process using silver triangular nanoplates  

International Nuclear Information System (INIS)

Graphical abstract: -- Highlights: •Demonstrated a new colorimetric strategy for iodide detection by silver nanoplates. •The colorimetric strategy is to find the critical color in a color change process. •The colorimetric strategy is more accurate and sensitive than common colorimetry. •Discovered a new morphological transformation phenomenon of silver nanoplates. -- Abstract: In this contribution, we demonstrated a novel colorimetric method for highly sensitive and accurate detection of iodide using citrate-stabilized silver triangular nanoplates (silver TNPs). Very lower concentration of iodide can induce an appreciable color change of silver TNPs solution from blue to yellow by fusing of silver TNPs to nanoparticles, as confirmed by UV–vis absorption spectroscopy and transmission electron microscopy (TEM). The principle of this colorimetric assay is not an ordinary colorimetry, but a new colorimetric strategy by finding the critical color in a color change process. With this strategy, 0.1 ?M of iodide can be recognized within 30 min by naked-eyes observation, and lower concentration of iodide down to 8.8 nM can be detected using a spectrophotometer. Furthermore, this high sensitive colorimetric assay has good accuracy, stability and reproducibility comparing with other ordinary colorimetry. We believe this new colorimetric method will open up a fresh insight of simple, rapid and reliable detection of iodide and can find its future application in the biochemical analysis or clinical diagnosis

380

Evidence-informed health policy 1 – Synthesis of findings from a multi-method study of organizations that support the use of research evidence  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Organizations have been established in many countries and internationally to support the use of research evidence by producing clinical practice guidelines, undertaking health technology assessments, and/or directly supporting the use of research evidence in developing health policy on an international, national, and state or provincial level. Learning from these organizations can reduce the need to 'reinvent the wheel' and inform decisions about how best to organize support for such organizations, particularly in low- and middle-income countries (LMICs. Methods We undertook a multi-method study in three phases – a survey, interviews, and case descriptions that drew on site visits – and in each of the second and third phases we focused on a purposive sample of those involved in the previous phase. We used the seven main recommendations that emerged from the advice offered in the interviews to organize much of the synthesis of findings across phases and methods. We used a constant comparative method to identify themes from across phases and methods. Results Seven recommendations emerged for those involved in establishing or leading organizations that support the use of research evidence in developing health policy: 1 collaborate with other organizations; 2 establish strong links with policymakers and involve stakeholders in the work; 3 be independent and manage conflicts of interest among those involved in the work; 4 build capacity among those working in the organization; 5 use good methods and be transparent in the work; 6 start small, have a clear audience and scope, and address important questions; and 7 be attentive to implementation considerations, even if implementation is not a remit. Four recommendations emerged for the World Health Organization (WHO and other international organizations and networks: 1 support collaborations among organizations; 2 support local adaptation efforts; 3 mobilize support; and 4 create global public goods. Conclusion This synthesis of findings from a multi-method study, along with the more detailed findings from each of the three phases of the study (which are reported in the three following articles in the series, provide a strong basis on which researchers, policymakers, international organizations (and networks like WHO can respond to the growing chorus of voices calling for efforts to support the use of research evidence in developing health policy.

Moynihan Ray

2008-12-01

 
 
 
 
381

The New Multi-HAzard and MulTi-RIsK Assessment MethodS for Europe (MATRIX) Project - An overview of its major findings  

Science.gov (United States)

Recent major natural disasters, such as the 2011 T?hoku earthquake, tsunami and subsequent Fukushima nuclear accident, have raised awareness of the frequent and potentially far-reaching interconnections between natural hazards. Such interactions occur at the hazard level, where an initial hazard may trigger other events (e.g., an earthquake triggering a tsunami) or several events may occur concurrently (or nearly so), e.g., severe weather around the same time as an earthquake. Interactions also occur at the vulnerability level, where the initial event may make the affected community more susceptible to the negative consequences of another event (e.g., an earthquake weakens buildings, which are then damaged further by windstorms). There is also a temporal element involved, where changes in exposure may alter the total risk to a given area. In short, there is the likelihood that the total risk estimated when considering multiple hazard and risks and their interactions is greater than the sum of their individual parts. It is with these issues in mind that the European Commission, under their FP7 program, supported the New Multi-HAzard and MulTi-RIsK Assessment MethodS for Europe or MATRIX project (10.2010 to 12.2013). MATRIX set out to tackle multiple natural hazards (i.e., those of concern to Europe, namely earthquakes, landslides, volcanos, tsunamis, wild fires, storms and fluvial and coastal flooding) and risks within a common theoretical framework. The MATRIX work plan proceeded from an assessment of single-type risk methodologies (including how uncertainties should be treated), cascade effects within a multi-hazard environment, time-dependent vulnerability, decision making and support for multi-hazard mitigation and adaption, and an assessment of how the multi-hazard and risk viewpoint may be integrated into current decision making and risk mitigation programs, considering the existing single-hazard and risk focus. Three test sites were considered during the project: Naples, Cologne, and the French West Indies. In addition, a software platform, the MATRIX-Common IT sYstem (MATRIX-CITY), was developed to allow the evaluation of characteristic multi-hazard and risk scenarios in comparison to single-type analyses. This presentation therefore outlines the more significant outcomes of the project, in particular those dealing with the harmonization of single-type hazards, cascade event analysis, time-dependent vulnerability changes and the response of the disaster management community to the MATRIX point of view.

Fleming, Kevin; Zschau, Jochen; Gasparini, Paolo

2014-05-01

382

Finding Perimeter  

Science.gov (United States)

In this lesson, students will explore a real world problem based on the Marilyn Burns book Spaghetti and Meatballs for All!. The problem and further practice finding the distance around rectangles will lead them to discover efficient strategies and formulas for solving perimeter.

Strickland, Susanna

2012-07-27

383

Reliability of change in lumbar MRI findings over time in patients with and without disc prosthesis - comparing two different image evaluation methods  

Energy Technology Data Exchange (ETDEWEB)

To assess the reliability of change in lumbar magnetic resonance imaging (MRI) findings evaluated retrospectively by direct comparison of images and by non-comparison. Pre-treatment and 2-year follow-up MRI was performed in 126 patients randomized to disc prosthesis surgery or non-surgical treatment. Two experienced radiologists independently evaluated progress and regress for Modic changes, disc findings, and facet arthropathy (FA) at L3/L4, L4/L5, and L5/S1, both by non-comparison and by comparison of initial and follow-up images. FA was evaluated at all levels, and other findings at non-operated levels. We calculated prevalence- and bias-adjusted kappa (PABAK) values for interobserver agreement. The impact of an adjacent prosthesis (which causes artefacts) and image evaluation method on PABAK was assessed using generalized estimating equations. Image comparison indicated good interobserver agreement on progress and regress (PABAK 0.63-1.00) for Modic changes, posterior high-intensity zone, disc height, and disc contour at L3-S1 and for nucleus pulposus signal and FA at L3/L4; and moderate interobserver agreement (PABAK 0.46-0.59) on decreasing nucleus signal and increasing FA at L4-S1. Image comparison indicated lower (but fair) interobserver agreement (PABAK 0.29) only for increasing FA at L5/S1 in patients with prosthesis in L4/L5 and/or L5/S1. An adjacent prosthesis had no overall impact on PABAK values (p {>=} 0.22). Comparison yielded higher PABAK values than non-comparison (p < 0.001). Regarding changes in lumbar MRI findings over time, comparison of images can provide moderate or good interobserver agreement, and better agreement than non-comparison. An adjacent prosthesis may not reduce agreement on change for most findings. (orig.)

Berg, Linda; Espeland, Ansgar [Haukeland University Hospital, Department of Radiology, Bergen (Norway); University of Bergen, Section for Radiology, Department of Surgical Sciences, Bergen (Norway); Gjertsen, Oeivind [Oslo University Hospital, Department of Neuroradiology, Oslo (Norway); Hellum, Christian [Oslo University Hospital, Department of Orthopaedics, Oslo (Norway); University of Oslo, Department of Orthopaedics, Oslo (Norway); Neckelmann, Gesche [Haukeland University Hospital, Department of Radiology, Bergen (Norway); Johnsen, Lars G. [University Hospital of Trondheim, National Centre for Diseases of the Spine, Trondheim (Norway); University Hospital of Trondheim, Orthopaedic Department, Trondheim (Norway); Eide, Geir E. [Haukeland University Hospital, Centre for Clinical Research, Bergen (Norway); University of Bergen, Department of Public Health and Primary Health Care, Bergen (Norway)

2012-12-15

384

Vital sign sensing method based on EMD in terahertz band  

Science.gov (United States)

Non-contact respiration and heartbeat rates detection could be applied to find survivors trapped in the disaster or the remote monitoring of the respiration and heartbeat of a patient. This study presents an improved algorithm that extracts the respiration and heartbeat rates of humans by utilizing the terahertz radar, which further lessens the effects of noise, suppresses the cross-term, and enhances the detection accuracy. A human target echo model for the terahertz radar is first presented. Combining the over-sampling method, low-pass filter, and Empirical Mode Decomposition improves the signal-to-noise ratio. The smoothed pseudo Wigner-Ville distribution time-frequency technique and the centroid of the spectrogram are used to estimate the instantaneous velocity of the target's cardiopulmonary motion. The down-sampling method is adopted to prevent serious distortion. Finally, a second time-frequency analysis is applied to the centroid curve to extract the respiration and heartbeat rates of the individual. Simulation results show that compared with the previously presented vital sign sensing method, the improved algorithm enhances the signal-to-noise ratio to 1 dB with a detection accuracy of 80%. The improved algorithm is an effective approach for the detection of respiration and heartbeat signal in a complicated environment.

Xu, Zhengwu; Liu, Tong

2014-12-01

385

Tibiofemoral centroid velocity correlates more consistently with cartilage damage than does contact path length in two ovine models of stifle injury.  

Science.gov (United States)

Anterior cruciate ligament (ACL) rupture and/or meniscal injury are known risk factors for post-traumatic osteoarthritis. We tested the hypothesis that increasingly abnormal tibiofemoral centroid path lengths and velocities would correlate with the severity of cartilage damage in injured sheep. Six sheep underwent combined ACL/medial collateral ligament transection (ACL/MCLx), five complete lateral meniscectomy (Mx), and four sham arthrotomy (Sham). Weighted centroids were used to estimate in vivo tibiofemoral cartilage contact path length during stance and the velocity of relative motion. Cartilage morphology was graded at dissection. Ligament transection significantly elongated plateau centroid path lengths and velocities, whereas condyle paths and velocities were reduced. Differences between plateau and femoral velocities (relative centroid velocity) were increased up to 10-fold over baseline values in the medial compartment. Reductions in Mx lateral compartment paths were significantly different from ACL/MCLx paths, but not relative to baseline or Sham values. Importantly, only centroid velocities consistently correlated with cartilage damage in either injury model, suggesting that while path length is valuable in detecting changes in the envelope of joint motion, it may average out meaningful peaks in the rate of relative motion that more closely relate to the mechanisms that might be damaging articular cartilage in these models. PMID:23832294

Beveridge, Jillian E; Heard, Bryan J; Shrive, Nigel G; Frank, Cyril B

2013-11-01

386

Reconstruction of an Object From Its Noisy Fourier Modulus: Ideal Estimate of the Object to Be Reconstructed and a Method That Attempts to Find That Estimate  

Science.gov (United States)

In general, the problem of reconstructing an object from its Fourier modulus has no solution when the Fourier modulus is contaminated by noise. Therefore a quasi solution, which we call the ideal estimate of the object to be reconstructed, is defined here based on the concept of territories of the convergence objects of the error-reduction algorithm, and a method that attempts to find that solution is presented. Keeping in mind that the ideal estimate is one of the output-stagnation objects of the hybrid input output algorithm, we modify the hybrid input output algorithm so that the output-stagnation objects can be located even when the value of the feedback parameter is not infinitesimally small, and this modified algorithm is combined with the hybrid input output algorithm itself. The results of computer simulations carried out to test the performance of the proposed method are shown.

Takajo, Hiroaki; Shizuma, Takao; Takahashi, Tohru; Takahata, Seiji

1999-09-01

387

Magnetic resonance imaging of anterior cruciate ligament tears: reevaluation of quantitative parameters and imaging findings including a simplified method for measuring the anterior cruciate ligament angle.  

Science.gov (United States)

We evaluated the diagnostic utility of magnetic resonance imaging (MRI) for predicting anterior cruciate ligament (ACL) tears using both quantitative parameters and nonquantitative imaging findings. MRI examinations were retrospectively evaluated in a group of patients with arthroscopically confirmed complete ACL tear and in a control group with arthroscopically confirmed intact ACL. We evaluated multiple MRI features to compare their sensitivity and specificity for detecting ACL tears. Particular emphasis is put on the evaluation of three different quantitative parameters, including a simplified method for measuring the ACL angle. With a threshold value of 45 degrees the ACL angle reached a sensitivity and specificity of 100% for detecting ACL tears. With a threshold value of 0 degrees the Blumensaat angle had a sensitivity of 90% and a specificity of 98%. Finally, a threshold value of 115 degrees gave the posterior cruciate ligament angle a sensitivity of 70% and a specificity of 82%. Discontinuity was found to be the most useful of the ACL abnormalities. Of the secondary findings anterior tibial displacement was the best predictor of ligamentous injury. However, ACL abnormalities and secondary findings, alone or combined, failed to surpass the diagnostic value of the ACL angle for predicting ACL tears. Quantitative parameters are thus good predictors of ACL tears and may increase the overall sensitivity and specificity of MRI. The ACL angle may be confidently measured in a single MRI section and can be considered to be the most reliable quantitative parameter for detecting ACL tears. PMID:14530852

Mellado, J M; Calmet, J; Olona, M; Giné, J; Saurí, A

2004-05-01

388

Method of transient identification based on a possibilistic approach, optimized by genetic algorithm  

International Nuclear Information System (INIS)

This work develops a method for transient identification based on a possible approach, optimized by Genetic Algorithm to optimize the number of the centroids of the classes that represent the transients. The basic idea of the proposed method is to optimize the partition of the search space, generating subsets in the classes within a partition, defined as subclasses, whose centroids are able to distinguish the classes with the maximum correct classifications. The interpretation of the subclasses as fuzzy sets and the possible approach provided a heuristic to establish influence zones of the centroids, allowing to achieve the 'don't know' answer for unknown transients, that is, outside the training set. (author)

389

Point spread function and centroiding accuracy measurements with the JET-X mirror and MOS CCD detector of the Swift gamma ray burst explorer's X-ray telescope  

International Nuclear Information System (INIS)

The optical components of the Swift X-ray telescope (XRT) are already developed items. They are the flight spare X-ray mirror from the JET-X/Spectrum-X program and an MOS CCD (CCD22) of the type currently operating in orbit as part of the EPIC focal plane camera on XMM-Newton (SPIE 4140 (2000) 64). The JET-X mirrors were first calibrated at the Max Plank Institute for Extraterrestrial Physics' (MPE) Panter facility, Garching, Germany in 1996 (SPIE 2805 (1996) 56; SPIE 3114 (1997) 392). Half-energy widths of 16 arcsec at 1.5 keV were confirmed for the two flight mirrors and the flight spare. The calibration of the flight spare was repeated at Panter in July 2000 in order to establish whether any changes had occurred during the 4 yr that the mirror had been in storage at the OAB, Milan, Italy. The results reported in this paper confirm that the resolution of the JET-X mirrors has remained stable over this storage period. In an extension of this test program, the flight spare EPIC camera was installed at the focus of the JET-X mirror to simulate the optical system of the Swift XRT. Tolerances in the mirror focal length, the on-axis and off-axis point spread functions were measured and calibration data sets were used to obtain centroid positions of X-ray point sources. The results confirmed Swift's ability to determine the centroid positions of sources at 100 mCrab brightness to better than 1 arcsec and provided a calibration of the centroiding process as a function of sohe centroiding process as a function of source flux and off-axis angle. The presence of background events in the image frame introduced errors in the centroiding process and this was accounted for by reducing the sampling area used for the centroiding algorithm

390

THE ENERGY DEPENDENCE OF THE CENTROID FREQUENCY AND PHASE LAG OF THE QUASI-PERIODIC OSCILLATIONS IN GRS 1915+105  

International Nuclear Information System (INIS)

We present a study of the centroid frequencies and phase lags of quasi-periodic oscillations (QPOs) as functions of photon energy for GRS 1915+105. It is found that the centroid frequencies of the 0.5-10 Hz QPOs and their phase lags are both energy dependent, and there exists an anticorrelation between the QPO frequency and phase lag. These new results challenge the popular QPO models, because none of them can fully explain the observed properties. We suggest that the observed QPO phase lags are partially due to the variation of the QPO frequency with energy, especially for those with frequency higher than 3.5 Hz.

391

Oscar — Using Byte Pairs to Find File Type and Camera Make of Data Fragments  

Science.gov (United States)

Mapping out the contents of fragmented storage media is hard if the file system has been corrupted, especially as the current forensic tools rely on meta information to do their job. If it was possible to find all fragments belonging to a certain file type, it would also be possible to recover a lost file. Such a tool could for example be used in the hunt for child pornography. The Oscar method identifies the file type of data fragments based solely on statistics calculated from their structure. The method does not need any meta data to work. We have previously used the byte frequency distribution and the rate of change between consecutive bytes as basis for the statistics, as well as calculating the 2-gram frequency distribution to create a model of different file types. This paper present a variant of the 2-gram method, in that it uses a dynamic smoothing factor. In this way we take the amount of data used to create the centroid into consideration. A previous experiment on file type identification is extended with .mp3 files reaching a detection rate of 76% with a false positives rate of 0.4%. We also use the method to identify the camera make used to capture a .jpg picture from a fragment of the picture. The result shows that we can clearly separate a picture fragment coming from a Fuji or Olympus cameras from a fragment of a picture of the other camera makes used in our test.

Karresand, Martin; Shahmehri, Nahid

392

High performance liquid chromatography (HPLC) method for confirming thin layer chromatography (TLC) findings in inborn errors of metabolism children in Malaysia.  

Science.gov (United States)

High performance liquid chromatography (HPLC) with phenylisothiocyanate (PITC) is recently used for confirming the diagnosis of inborn errors of metabolism (IEM) especially amino acid disorders in Malaysian children. The method of HPLC used is a precolumn derivatization of amino acids with phenylisothiocyanate and is separated by reversed phase chromatography using 3.9 x 300 mm free amino acid columns and is detected by a UV/Vis detector. The samples are obtained from cases suspected of inborn errors of metabolism, especially of amino acid disorders, which are detected clinically by pediatricians. Initially, samples from patients suspected of inborn errors of metabolism, either urine or serum, are run on one-dimensional thin layer chromatography and supplementary chemical tests to detect the abnormal bands and associated abnormalities respectively. Positive samples are further run on HPLC to determine the specific amino acids abnormality. An examples of a case of maple syrup urine disease is discussed, based on the thin layer chromatography findings and HPLC findings. PMID:8629091

Yahya, N A; Ismail, Z; Embong, K H; Mohamad, S A

1995-01-01

393

Weighted Centroid Modified Simplex and Linear Constrained Response Surface Optimization Methods for the Xbar-R Chart Variable Determination  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Problem statement: Although economic Xbar-R chart designs do guarantee the minimal operating cost, they typically have poor levels of statistical performance measures. The obvious limitation of the economic design is that the Type I error rate seems to be very high for many situations and will cause a large number of false alarms. This situation leads to an investigation of appropriate levels of control chart variables which consist of a sample ...

Pongchanun Luangpaiboon

2011-01-01

394

Hide and vanish: data sets where the most parsimonious tree is known but hard to find, and their implications for tree search methods.  

Science.gov (United States)

Three different types of data sets, for which the uniquely most parsimonious tree can be known exactly but is hard to find with heuristic tree search methods, are studied. Tree searches are complicated more by the shape of the tree landscape (i.e. the distribution of homoplasy on different trees) than by the sheer abundance of homoplasy or character conflict. Data sets of Type 1 are those constructed by Radel et al. (2013). Data sets of Type 2 present a very rugged landscape, with narrow peaks and valleys, but relatively low amounts of homoplasy. For such a tree landscape, subjecting the trees to TBR and saving suboptimal trees produces much better results when the sequence of clipping for the tree branches is randomized instead of fixed. An unexpected finding for data sets of Types 1 and 2 is that starting a search from a random tree instead of a random addition sequence Wagner tree may increase the probability that the search finds the most parsimonious tree; a small artificial example where these probabilities can be calculated exactly is presented. Data sets of Type 3, the most difficult data sets studied here, comprise only congruent characters, and a single island with only one most parsimonious tree. Even if there is a single island, missing entries create a very flat landscape which is difficult to traverse with tree search algorithms because the number of equally parsimonious trees that need to be saved and swapped to effectively move around the plateaus is too large. Minor modifications of the parameters of tree drifting, ratchet, and sectorial searches allow travelling around these plateaus much more efficiently than saving and swapping large numbers of equally parsimonious trees with TBR. For these data sets, two new related criteria for selecting taxon addition sequences in Wagner trees (the "selected" and "informative" addition sequences) produce much better results than the standard random or closest addition sequences. These new methods for Wagner trees and for moving around plateaus can be useful when analyzing phylogenomic data sets formed by concatenation of genes with uneven taxon representation ("sparse" supermatrices), which are likely to present a tree landscape with extensive plateaus. PMID:24952317

Goloboff, Pablo A

2014-10-01

395

Analytic continuation average spectrum method for transport in quantum liquids  

International Nuclear Information System (INIS)

Recently, we have applied the analytic continuation averaged spectrum method (ASM) to calculate collective density fluctuations in quantum liquid . Unlike the maximum entropy (MaxEnt) method, the ASM approach is capable of revealing resolved modes in the dynamic structure factor in agreement with experiments. In this work we further develop the ASM to study single-particle dynamics in quantum liquids with dynamical susceptibilities that are characterized by a smooth spectrum. Surprisingly, we find that for the power spectrum of the velocity autocorrelation function there are pronounced differences in comparison with the MaxEnt approach, even for this simple case of smooth unimodal dynamic response. We show that for liquid para-hydrogen the ASM is closer to the centroid molecular dynamics (CMD) result while for normal liquid helium it agrees better with the quantum mode coupling theory (QMCT) and with the MaxEnt approach.

396

Robust of Doppler Centroid for Mapping Sea Surface Current by Using Radar Satellite Data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Problem statement: Sea surface current retrieving from Synthetic Aperture Radar (SAR) is required standard methods due to the complexity of sea surface ocean imaging in SAR data. In this context, various analytical models have been developed which describe overall effects of sea surface roughness on the Doppler signal mechanisms. Nevertheless, such models are limited in the complexity of the sea surface current estimation that can be used. In fact, the resolution of the sea surface Dop...

Mazlan Hashim; Maged Marghany

2009-01-01

397

Implementation of Multi-Centroid Moment Invariants in Thermal-Based Face Identification System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Problem statement: Current paramount methods and approaches in face identification field rely on facial characteristics; such as location of eyes, length of nose and mouth, regardless the type of medium used to acquire the facial images. The visibility of these facial characteristics varies significantly with environmental factors (e.g., lighting elements). Various researches have been devoted to develop methodologies for addressing these problems. Despite the overwhelming effort to ov...

Abas, Khairul H.; Osamu Ono

2010-01-01

398

Image motion compensation by area correlation and centroid tracking of solar surface features  

Science.gov (United States)

An experimental solar correlation tracker was tested and evaluated on a ground-based solar magnetograph. Using sunspots as fixed targets, tracking error signals were derived by which the telescope image was stabilized against wind induced perturbations. Two methods of stabilization were investigated; mechanical stabilization of the image by controlled two-axes motion of an active optical element in the telescope beam, and electronic stabilization by biasing of the electron scan in the recording camera. Both approaches have demonstrated telescope stability of about 0.6 arc sec under random perturbations which can cause the unstabilized image to move up to 120 arc sec at frequencies up to 30 Hz.

Nein, M. E.; Mcintosh, W. R.; Cumings, N. P.

1983-01-01

399

Combined radioimmunoassay of 17-alpha-hydroxyprogesterone and 11-desoxycortisol, and of dehydroepiandrosterone-sulphate: Methods and some novel clinical findings  

International Nuclear Information System (INIS)

The radioimmunoassay (RIA) methods for determining 17-alpha-hydroxyprogesterone (17HOP), 11-desoxycortisol (Cpd.-S), and dehydroepiandrosterone-sulphate, are reported. The plasma levels of these hormones were measured in a series of 15 diagnostic groups including adrenal diseases, fertility-related problems and human growth hormone (HGH) deficiency states. The relations of DHEA-S and growth hormone were studied in a group of children with growth retardation who presented an absent response to HGH stimulation tests. The DHEA-S level found in these patients was significantly lower than that of their age-matched controls. Furthermore, in an etiologically different entity, i.e. head-injury patients, similar findings were also made. In a single case with HGH deficiency due to antibodies against HGH, DHEA-S levels were not detectable. It is suggested that the determination of DHEA-S plasma levels can provide further insight into the classification of patients with fertility-related problems. Furthermore, it appears that DHEA-S can be taken as an indicator for the availability of bioactive human growth hormone. The various forms of congenital adrenal hyperplasia (CAH) can be successfully screened and detected by the determination of the plasma levels of 17-alpha-hydroxyprogesterone (17HOP), of 11-desoxycortisol (Cpd.-S), and of dehydroepiandrosterone-sulphate (DHEA-S). These tests are also relevant in the investigation of patients with hirsutism, hyperandrogenism, and amenorth hirsutism, hyperandrogenism, and amenorrhea. RIA procedures for the measurement of these hormones are described and new clinical data on DHEA-S are presented in relation to fertility problems both in men and women, such as oligozoospermia, oligomenorrhea and aspermia and, in cases of human growth hormone (HGH), deficiency states such as retarded growth, head-injury patients and, in one case, HGH deficiency due to antibodies directed against HGH. The relations between normo- and hyperprolactinaemia and DHEA-S are also examined

400

Accelerated steered response power method for sound source localization via clustering search  

Science.gov (United States)

The steered response power-phase transform (SRP-PHAT) sound source localization algorithm is robust in a real environment. However, the large computation complexity limits the practical application of SRP-PHAT. For a microphone array, each location corresponds to a set of time differences of arrival (TDOAs), and this paper collects them into a TDOA vector. Since the TDOA vectors in the adjacent regions are similar, we present a fast algorithm based on clustering search to reduce the computation complexity of SRP-PHAT. In the training stage, the K-means or Iterative Self-Organizing Data Analysis Technique (ISODATA) clustering algorithm is used to find the centroid in each cluster with similar TDOA vectors. In the procedure of sound localization, the optimal cluster is found by comparing the steered response powers (SRPs) of all centroids. The SRPs of all candidate locations in the optimal cluster are compared to localize the sound source. Experiments both in simulation environments and real environments have been performed to compare the localization accuracy and computational load of the proposed method with those of the conventional SRP-PHAT algorithm. The results show that the proposed method is able to reduce the computational load drastically and maintains almost the same localization accuracy and robustness as those of the conventional SRP-PHAT algorithm. The difference in localization performance brought by different clustering algorithms used in the training stage is trivial.

Zhao, XiaoYan; Tang, Jie; Zhou, Lin; Wu, ZhenYang

2013-07-01

 
 
 
 
401

An object-oriented C++ implementation of Davidson method for finding a few selected extreme eigenpairs of a large, sparse, real, symmetric matrix  

Science.gov (United States)

A C++ class named Davidson is presented for determining a few eigenpairs with lowest or alternatively highest values of a large, real, symmetric matrix. The algorithm described by Stathopoulos and Fischer is used. The exception mechanism is involved to report the errors. The class is written in ANSI C++, so it is fully portable. In addition a console program as well as a program with graphical user interface for Microsoft Windows is attached, which allow one to calculate the lowest eigenstates of time-independent Schrödinger equation for a given binding potential in one, two or three spatial dimensions. The package contains the classes providing often used potential functions (model atom potential, Coulomb potential, square well potential and Kramers-Henneberger well potential) as well as a possibility to use any potential stored in a file (then any dimensionality of the problem is allowed). The described code is the subject of M.Sc. thesis of T.D. prepared under the supervision of J.M. Program summaryProgram title: Davidson Catalogue identifier: ADZM_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADZM_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3 037 055 No. of bytes in distributed program, including test data, etc.: 20 002 609 Distribution format: tar.gz Programming language: C++ Computer: All Operating system: Any RAM: User's parameters dependent Word size: 32 and 64 bits Supplementary material: Test results for the 2D and 3D cases is available Classification: 4, 4.8 Nature of problem: Finding a few extreme eigenpairs of a real, symmetric, sparse matrix. Examples in quantum optics (interaction of matter with a laser field). Solution method: Davidson algorithm Running time: The test example included in the distribution package (1D matrix) takes approximately 30 minutes to run. 2D matrix calculations can take hours and 3D, days, to run.

Dziubak, Tomasz; Matulewski, Jacek

2007-10-01

402

Ce3+ 5d-centroid shift and vacuum referred 4f-electron binding energies of all lanthanide impurities in 150 different compounds  

International Nuclear Information System (INIS)

A review on the wavelengths of all five 4f–5d transitions for Ce3+ in about 150 different inorganic compounds (fluorides, chlorides, bromides, iodides, oxides, sulfides, selenides, nitrides) is presented. It provides data on the centroid shift and the crystal field splitting of the 5d-configuration which are then used to estimate the Eu2+ inter 4f-electron Coulomb repulsion energy U(6,A) in compound A. The four semi-empirical models (the redshift model, the centroid shift model, the charge transfer model, and the chemical shift model) on lanthanide levels that were developed past 12 years are briefly reviewed. It will be demonstrated how those models together with the collected data of this work and elsewhere can be united to construct schemes that contain the binding energy of electrons in the 4f and 5d states for each divalent and each trivalent lanthanide ion relative to the vacuum energy. As example the vacuum referred binding energy schemes for LaF3 and La2O3 will be constructed. - Highlights: ? An compilation on all five Ce3+ 4f–5d energies in 150 inorganic compounds is presented. ? The relationship between the 5d centroid shift and host cation electronegativity id demonstrated. ? The electronic structure scheme of the lanthanides in La2O3 and LaF3 is presented.

403

Finding seed points for organ segmentation using example annotations  

Science.gov (United States)

Organ segmentation is important in diagnostic medicine to make current decision-support tools more effective and efficient. Performing it automatically can save time and labor. In this paper, a method to perform automatic identification of seed points for the segmentation of organs in three-dimensional (3D) non-annotated, full- body magnetic resonance (MR) and computed tomography (CT) volumes is presented. It uses 3D MR and CT acquisitions along with corresponding organ annotations from the Visual Concept Extraction Challenge in Radiology (VISCERAL) banchmark. A training MR or CT volume is first registered affinely with a carefully-chosen reference volume. The registration transform obtained is then used to warp the annotations accompanying that training volume. The process is repeated for several other training volumes. For each organ of interest, an overlap volume is created by merging the warped training annotations corresponding to it. Next, a 3D probability map for organ location on the reference volume is derived from each overlap volume. The centroid of each probability map is determined and it represents a suitable seed point for segmentation of each organ. Afterwards, the reference volume can be affinely mapped onto any non-annotated volume and the mapping applied to the pre-computed volume containing the centroid and the probability distribution for an organ of interest. Segmentation on the non-annotated volume may then be started using existing region-growing segmentation algorithms with the warped centroid as the seed point and the warped probability distribution as an aid to the stopping criterion. The approach yields very promising results.

Joyseeree, Ranveer; Müller, Henning

2014-03-01

404

Finding Cyclic Frequent Itemsets  

Directory of Open Access Journals (Sweden)

Full Text Available Mining various types of association rules from supermarket datasets is an important data mining problem. One similar problem involves finding frequent itemsets and then deriving rules from frequent itemsets. The supermarket data is temporal. Considering time attributes in the supermarket dataset some association rules can be extracted which may hold for a small time interval and not throughout the data gathering period. Such rules are called as local association rules and corresponding frequent itemsets as locally frequent itemsets. Mahanta et al proposes an algorithm for extracting all locally frequent itemsets where each locally frequent itemset is associated with sequence time intervals in which it is frequent. The sequence of time intervals associated with a locally frequent itemsets may exhibit some interesting properties e.g. the itemsets may be cyclic in nature. In this paper we propose an alternative method of finding such cyclic frequent itemsets. The efficacy of the method is established through experimental results.

Mazarbhuiya, F. A.

2012-11-01

405

Radiological findings after gastrectomy  

Energy Technology Data Exchange (ETDEWEB)

In 63 patients after total gastrectomy and reconstruction of the small bowel described by Beal-Longmire, Roux and Tomoda radiological findings were correlated with clinical symptoms. No correlation could be found between clinical symptoms of dumping and oesophagitis caused by reflux on one side and increased length of intestinal transit time, increased diameter of intestinal loops and gastro-oesophageal reflux on the other side. Enlarged blind loops after termino-lateral oesophago-jejunostomy and insufficient ligations (operation technique by Tomoda) were correlated with higher incidence of pains. Patients operated by the method of Beal-Longmire and Roux showed better results than those operated with the method of Tomoda.

Riedl, P.; Polterauer, P.; Funovics, J.

1980-06-01

406

Radiological findings after gastrectomy  

International Nuclear Information System (INIS)

In 63 patients after total gastrectomy and reconstruction of the small bowel described by Beal-Longmire, Roux and Tomoda radiological findings were correlated with clinical symptoms. No correlation could be found between clinical symptoms if dumping and oesophagitis caused by reflux on one side and increased length of intestinal transit time, increased diameter of intestinal loops and gastro-oesophageal reflux on the other side. Enlarged blind loops after termino-lateral oesophago-jejunostomy and insufficient ligations (operation technique by Tomoda) were correlated with higher incidence of pains. Patients operated by the method of Beal-Longmire and Roux showed better results than those operated with the method of Tomoda. (orig.)

407

Method of particle trajectory recognition in particle flows of high particle concentration using a candidate trajectory tree process with variable search areas  

Energy Technology Data Exchange (ETDEWEB)

The application relates to particle trajectory recognition from a Centroid Population comprised of Centroids having an (x, y, t) or (x, y, f) coordinate. The method is applicable to visualization and measurement of particle flow fields of high particle. In one embodiment, the centroids are generated from particle images recorded on camera frames. The application encompasses digital computer systems and distribution mediums implementing the method disclosed and is particularly applicable to recognizing trajectories of particles in particle flows of high particle concentration. The method accomplishes trajectory recognition by forming Candidate Trajectory Trees and repeated searches at varying Search Velocities, such that initial search areas are set to a minimum size in order to recognize only the slowest, least accelerating particles which produce higher local concentrations. When a trajectory is recognized, the centroids in that trajectory are removed from consideration in future searches.

Shaffer, Franklin D.

2013-03-12

408

Granulomatous mastitis: radiological findings  

Energy Technology Data Exchange (ETDEWEB)

Purpose: To evaluate the radiological, ultrasonographic, and magnetic resonance imaging (MRI) findings of idiopathic granulomatous mastitis. Material and Methods: Between April 2002 and June 2005, the mammography, ultrasound, color Doppler ultrasound, non enhanced MR, and dynamic MR findings of nine patients with the preliminary clinical diagnosis of malignancy and the final diagnosis of granulomatous mastitis were evaluated. Results: On mammography, asymmetrical focal densities with no distinct margins, ill-defined masses with spiculated contours, and bilateral multiple ill-defined nodules were seen. On ultrasound, in four patients a discrete, heterogenous hypoechoic mass, in two patients multiple abscesses, in one patient bilateral multiple central hypo peripheral hyperechoic lesions, in two patients heterogeneous hypo- and hyperechoic areas together with parenchymal distortion, and in one patient irregular hypoechoic masses with tubular extensions and abscess cavities were seen. Five of the lesions were vascular on color Doppler ultrasound. On MR mammography, the most frequent finding was focal or diffuse asymmetrical signal intensity changes that were hypointense on T1W images and hyperintense on T2W images, without significant mass effect. Nodular lesions were also seen. On dynamic contrast-enhanced mammography, mass-like enhancement, ring-like enhancement, and nodular enhancement were seen. The time-intensity curves differed from patient to patient and from lesion to lesion. Conclusion: The imaging findings of idiopathic granulomatous mastitis have a wide spectrum, and they are inconclusive for differentiating malignant and benign lesions.

Ozturk, M.; Mavili, E.; Kahriman, G.; Akcan, A.C.; Ozturk, F. [Depts. of Radiology, Surgery, and Pathology, Erciyes Univ. Medical Faculty, Kayseri (Turkey)

2007-02-15

409

Granulomatous mastitis: radiological findings  

International Nuclear Information System (INIS)

Purpose: To evaluate the radiological, ultrasonographic, and magnetic resonance imaging (MRI) findings of idiopathic granulomatous mastitis. Material and Methods: Between April 2002 and June 2005, the mammography, ultrasound, color Doppler ultrasound, non enhanced MR, and dynamic MR findings of nine patients with the preliminary clinical diagnosis of malignancy and the final diagnosis of granulomatous mastitis were evaluated. Results: On mammography, asymmetrical focal densities with no distinct margins, ill-defined masses with spiculated contours, and bilateral multiple ill-defined nodules were seen. On ultrasound, in four patients a discrete, heterogenous hypoechoic mass, in two patients multiple abscesses, in one patient bilateral multiple central hypo peripheral hyperechoic lesions, in two patients heterogeneous hypo- and hyperechoic areas together with parenchymal distortion, and in one patient irregular hypoechoic masses with tubular extensions and abscess cavities were seen. Five of the lesions were vascular on color Doppler ultrasound. On MR mammography, the most frequent finding was focal or diffuse asymmetrical signal intensity changes that were hypointense on T1W images and hyperintense on T2W images, without significant mass effect. Nodular lesions were also seen. On dynamic contrast-enhanced mammography, mass-like enhancement, ring-like enhancement, and nodular enhancement were seen. The time-intensity curves differed from patient to patient and from lesiered from patient to patient and from lesion to lesion. Conclusion: The imaging findings of idiopathic granulomatous mastitis have a wide spectrum, and they are inconclusive for differentiating malignant and benign lesions

410

Logic and intuitive methods of management systems study during direction finding of companies’ modernization development in health resort and tourism sphere  

Directory of Open Access Journals (Sweden)

Full Text Available The article analyses existing approaches to companies’ management systems in health resort and tourism sphere, gives general characteristic of fundamental updating companies, representing some scheme of companies description according to certain set of characteristics, including those from cited logic and intuitive methods.

Alexander S. Varyukhin

2011-02-01

411

Ce{sup 3+} 5d-centroid shift and vacuum referred 4f-electron binding energies of all lanthanide impurities in 150 different compounds  

Energy Technology Data Exchange (ETDEWEB)

A review on the wavelengths of all five 4f-5d transitions for Ce{sup 3+} in about 150 different inorganic compounds (fluorides, chlorides, bromides, iodides, oxides, sulfides, selenides, nitrides) is presented. It provides data on the centroid shift and the crystal field splitting of the 5d-configuration which are then used to estimate the Eu{sup 2+} inter 4f-electron Coulomb repulsion energy U(6,A) in compound A. The four semi-empirical models (the redshift model, the centroid shift model, the charge transfer model, and the chemical shift model) on lanthanide levels that were developed past 12 years are briefly reviewed. It will be demonstrated how those models together with the collected data of this work and elsewhere can be united to construct schemes that contain the binding energy of electrons in the 4f and 5d states for each divalent and each trivalent lanthanide ion relative to the vacuum energy. As example the vacuum referred binding energy schemes for LaF{sub 3} and La{sub 2}O{sub 3} will be constructed. - Highlights: Black-Right-Pointing-Pointer An compilation on all five Ce{sup 3+} 4f-5d energies in 150 inorganic compounds is presented. Black-Right-Pointing-Pointer The relationship between the 5d centroid shift and host cation electronegativity id demonstrated. Black-Right-Pointing-Pointer The electronic structure scheme of the lanthanides in La{sub 2}O{sub 3} and LaF{sub 3} is presented.

Dorenbos, Pieter, E-mail: P.Dorenbos@tudelft.nl [Luminescence Materials Research group, Department of RRR, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands)

2013-03-15

412

Finding Extreme Subdwarfs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

I develop a new technique to identify M-type extreme subdwarfs (esdMs) and demonstrate that it is substantially more efficient than previous methods. I begin by obtaining spectroscopy and improved photometry of a sample of 54 late-type halo candidates using the rNLTT reduced proper motion (RPM) diagram. From spectroscopy, I find that four of these are esdMs, three of which were previously unknown. From the improved photometry, I show that all four lie in a narrow RPM corri...

Marshall, J. L.

2007-01-01

413

Assessment of prior learning in vocational education and training : Findings from a study about methods for assessing prior learning in preparation for vocational qualifications (VET)  

DEFF Research Database (Denmark)

The article deals about the results of a study of the assessment of prior learning among adult workers who want to obtain formal qualifications as skilled workers. The study contributes to developing methods for assessing prior learning including both the teachers’ ways of eliciting the students’ knowledge, skills and competences during the students’ performances and the methods that the teachers apply in order to assess the students’ prior learning in relation to the regulations of the current VET-program. In particular the study focuses on how to assess not only the students’ explicated knowledge and skills but also their competences, i.e. the way the students use their skills and knowledge to perform in practice. Based on a description of the assessment procedures the article discusses central issues in relation to the assessment of prior learning. The empirical data have been obtained in the VET programs for gastronomes respectively child-care assistants.

Aarkrog, Vibe; Wahlgren, Bjarne

414

Finding of experience of the use of computer-integrated forms and methods of teaching in the process of preparation of future teachers of initial school  

Directory of Open Access Journals (Sweden)

Full Text Available Theoretically grounded and experimentally examined that one of the trends of future teachers training for the integrated activity is gaining experience in using the integrated organization forms of learning. It is realized in the process of specially organized student's learning and during their pedagogical practice. It was promoted by conducting the special course The integrated forms of learning organization in primary school with the use of interactive forms and methods of learning, fulfilling the aimed tasks while passing pedagogical practice.

Sinopalnikova N.N.

2010-06-01

415

Metáforas e Linguística de Corpus: metodologia de análise aplicada a um gênero de negócios Metaphors and Corpus Linguistics: a method for finding metaphors in a business genre  

Directory of Open Access Journals (Sweden)

Full Text Available O presente trabalho visa a relatar o desenvolvimento de uma metodologia de identificação de metáforas em corpora eletrônicos. Como exemplo, foi tomado o gênero teleconferências de apresentação de resultados financeiros. A metodologia é do tipo "bottom-up" / "corpus-driven" e se baseia na identificação de palavras com frequência marcante (palavras-chave e de seus padrões de co-ocorrência, seguido do cálculo de similaridade semântica entre essas palavras. Com isso, chega-se a um conjunto de palavras que são então interpretadas em seu co-texto, por meio de concordâncias.This paper aims at reporting the development of a method for metaphor identification in computer corpora. The method was tested on a particular corpus, namely of investment conference calls, and comprises procedures that work from the bottom up, and rely on marked frequency, collocation and semantic similarity as signalling devices for metaphor. As such, the method is an example of corpus-driven research into metaphor. The application of these procedures yields a number of metaphor candidates, which are then checked manually through concordances.

Tony Berber Sardinha

2011-01-01

416

Differences in male and female nurses' responses to physical assault by psychiatric patients: a supplemental finding of a mixed-methods study.  

Science.gov (United States)

In one segment of a multifactor study conducted in 2011 at five psychiatric sites in three counties of Long Island, New York, 110 nurses were interviewed about their experiences with physical assault by psychiatric patients. Marked differences were identified between the male and female nurse participants who were assaulted. Women expressed feelings of inadequacy and questioned their competence. They felt blamed by administration and sometimes even colleagues. In addition, many did not report the incident for fear of reprisal. Women believed that violence was to be expected, and they considered it part of the job. On the other hand, men did not question their competency. They blamed external factors, such as poor staffing or unsafe design of the unit, or they stated that the patient was inadequately medicated and impossible to control. The male nurses did not feel blamed for the incident. All but one male nurse formally reported the incidents. They believed that violence in psychiatry is to be expected but should not be considered part of the job. These findings may be explained by Weiner's Attribution Theory. PMID:25250791

Moylan, Lois Biggin; Cullinan, Meritta B; Kimpel, Jeanne E

2014-12-01

417

Uni and multivariate methods applied to studies of phenotypic adaptability in maize (Zea mays L.)=Métodos uni e multivariados aplicados em estudos de adaptabilidade fenotípica em milho (Zea mays L.).  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of this study was to evaluate the performance of 15 maize cultivars in seven locations in Paraná State, Brazil. Towards this aim, grain yield trials were conducted during two crop seasons, and centroid (multivariate) and bissegmented regression (univariate) methods were used to evaluate possible divergences among results obtained. The genotypes were evaluated in randomized complete blocks with three replications. The centroid method was effective for indicating productive poten...

Antonio Carlos Gerage; Pedro Mário de Araújo; Deoclécio Domingos Garbuglio; Esmael Lopes dos Santos; Pedro Sentaro Shioga; Cássio Egidio Cavenaghi Prete

2011-01-01

418

The impact of the in-orbit background and the X-ray source intensity on the centroiding accuracy of the Swift X-ray telescope  

CERN Document Server

The optical components of the Swift Gamma Ray Burst Explorer X-ray Telescope (XRT), consisting of the JET-X spare flight mirror and a charge coupled device of the type used in the EPIC program, were used in a re-calibration study carried out at the Panter facility, which is part of the Max Planck Institute for Extraterrestrial Physics. The objective of this study was to check the focal length and the off axis performance of the mirrors and to show that the half energy width (HEW) of the on-axis point spread function (PSF) was of the order of 16 arcsec at 1.5 keV (Nucl. Instr. and Meth. A 488 (2002) 543; SPIE 4140 (2000) 64) and that a centroiding accuracy better that 1 arcsec could be achieved within the 4 arcmin sampling area designated by the Burst Alert Telescope (Nucl. Instr. and Meth. A 488 (2002) 543). The centroiding accuracy of the Swift XRT's optical components was tested as a function of distance from the focus and off axis position of the PSF (Nucl. Instr. and Meth. A 488 (2002) 543). The presence ...

Ambrosi, R M; Hill, J; Cheruvu, C; Abbey, A F; Short, A D T

2002-01-01

419

Form finding and analysis of extensible membranes attached to 2-D and 3-D frames intended for micro air vehicles via experimentally validated finite element methods  

Science.gov (United States)

This work is concerned with a new method to apply consistent and known pretension to silicone rubber membranes intended for micro air vehicles as well as an understanding in the science of developed pre-tension in membranes constrained by 2- D and 3-D frames and structures. Pre-tension has a marked effect on the static and dynamic response of membrane wings and controls the overall deflections, as such control and measurement of the membrane pre-tension is important. Two different 2-D frame geometries were fabricated to evaluate the technique. For open-cell frames, the pretension was not uniform, whereas it was for closed-cell frames. Results show developed full-field stress and strain fields as a function of membrane attachment temperature and frame geometry along with experimental iterations to prove repeatability. The membranes can be stretched to a specific pretension according to the temperature at which it adheres to frames. Strain fields in membranes attached to 3-D frames at various temperatures are modeled through FEA utilizing Abaqus to be able to predict the developed membrane deformations, stresses, and strains. Rigid frames with various curvatures are built via appropriate molds and then adhered to silicone rubber membranes and elevated to various temperatures to achieve different pre-strains for experimental validation. Additional experiments are conducted for more complex frame geometries involving both convex and concave topologies embedded within frames. Results are then compared with the Abaqus outputs to validate the accuracy of the FEA model. Highly compliant wings have been used for MAV platforms, where the wing structure is determined by some combination of carbon fiber composites and a membrane skin, adhered in between the layers of composite material. Another new technique of attaching membranes firmly on wing structures is introduced, which involves the application of a technology known as corona treatment coupled with another method of tensioning silicone membranes on any given frame geometry. Corona treatment provided a means of increasing adhesion of silicone on carbon fiber through the use of a high-frequency high-voltage air plasma discharge. The silicone membrane is co-cured with carbon fiber under vacuum pressure at an elevated temperature. After cool down, the membrane is tensioned.

Abudaram, Yaakov Jack

420

A histogram-based segmentation method for characterization of self-assembled hexagonal lattices  

Science.gov (United States)

Lattice characterization techniques are often used to quantify the effects of different anodization conditions on nano-porous anodized aluminum oxides. In this work, we develop a comprehensive hexagonal lattice characterization method to evaluate the amount of ordering of the lattice and localize the domains of the image and report their characteristics. A robust preprocessing is proposed to find pores' centroids. Different domains of SEM images usually have different orientations. Pores orientation distribution is analyzed using angle-histogram. The valleys of angle-histogram are employed as thresholds to separate different dominant orientations. We show that using orientation as a distinguishing feature of different domains, significantly improves the robustness of the algorithm against tolerance parameters. Some new parameters are introduced to exactly characterize each of the domains and the whole lattice.

Abdollahifard, Mohammad J.; Faez, Karim; Pourfard, Mohammadreza; Abdollahi, Mojtaba

2011-10-01