NASA Technical Reports Server (NTRS)
Bagri, Durgadas S.; Majid, Walid
2009-01-01
At present spacecraft angular position with Deep Space Network (DSN) is determined using group delay estimates from very long baseline interferometer (VLBI) phase measurements employing differential one way ranging (DOR) tones. As an alternative to this approach, we propose estimating position of a spacecraft to half a fringe cycle accuracy using time variations between measured and calculated phases as the Earth rotates using DSN VLBI baseline(s). Combining fringe location of the target with the phase allows high accuracy for spacecraft angular position estimate. This can be achieved using telemetry signals of at least 4-8 MSamples/sec data rate or DOR tones.
Accurate maser positions for MALT-45
NASA Astrophysics Data System (ADS)
Jordan, Christopher; Bains, Indra; Voronkov, Maxim; Lo, Nadia; Jones, Paul; Muller, Erik; Cunningham, Maria; Burton, Michael; Brooks, Kate; Green, James; Fuller, Gary; Barnes, Peter; Ellingsen, Simon; Urquhart, James; Morgan, Larry; Rowell, Gavin; Walsh, Andrew; Loenen, Edo; Baan, Willem; Hill, Tracey; Purcell, Cormac; Breen, Shari; Peretto, Nicolas; Jackson, James; Lowe, Vicki; Longmore, Steven
2013-10-01
MALT-45 is an untargeted survey, mapping the Galactic plane in CS (1-0), Class I methanol masers, SiO masers and thermal emission, and high frequency continuum emission. After obtaining images from the survey, a number of masers were detected, but without accurate positions. This project seeks to resolve each maser and its environment, with the ultimate goal of placing the Class I methanol maser into a timeline of high mass star formation.
How Accurate are SuperCOSMOS Positions?
NASA Astrophysics Data System (ADS)
Schaefer, Adam; Hunstead, Richard; Johnston, Helen
2014-02-01
Optical positions from the SuperCOSMOS Sky Survey have been compared in detail with accurate radio positions that define the second realisation of the International Celestial Reference Frame (ICRF2). The comparison was limited to the IIIaJ plates from the UK/AAO and Oschin (Palomar) Schmidt telescopes. A total of 1 373 ICRF2 sources was used, with the sample restricted to stellar objects brighter than BJ = 20 and Galactic latitudes |b| > 10°. Position differences showed an rms scatter of
Accurate Telescope Mount Positioning with MEMS Accelerometers
NASA Astrophysics Data System (ADS)
Mészáros, L.; Jaskó, A.; Pál, A.; Csépány, G.
2014-08-01
This paper describes the advantages and challenges of applying microelectromechanical accelerometer systems (MEMS accelerometers) in order to attain precise, accurate, and stateless positioning of telescope mounts. This provides a completely independent method from other forms of electronic, optical, mechanical or magnetic feedback or real-time astrometry. Our goal is to reach the subarcminute range which is considerably smaller than the field-of-view of conventional imaging telescope systems. Here we present how this subarcminute accuracy can be achieved with very cheap MEMS sensors and we also detail how our procedures can be extended in order to attain even finer measurements. In addition, our paper discusses how can a complete system design be implemented in order to be a part of a telescope control system.
MEMS accelerometers in accurate mount positioning systems
NASA Astrophysics Data System (ADS)
Mészáros, László; Pál, András.; Jaskó, Attila
2014-07-01
In order to attain precise, accurate and stateless positioning of telescope mounts we apply microelectromechanical accelerometer systems (also known as MEMS accelerometers). In common practice, feedback from the mount position is provided by electronic, optical or magneto-mechanical systems or via real-time astrometric solution based on the acquired images. Hence, MEMS-based systems are completely independent from these mechanisms. Our goal is to investigate the advantages and challenges of applying such devices and to reach the sub-arcminute range { that is well smaller than the field-of-view of conventional imaging telescope systems. We present how this sub-arcminute accuracy can be achieved with very cheap MEMS sensors. Basically, these sensors yield raw output within an accuracy of a few degrees. We show what kind of calibration procedures could exploit spherical and cylindrical constraints between accelerometer output channels in order to achieve the previously mentioned accuracy level. We also demonstrate how can our implementation be inserted in a telescope control system. Although this attainable precision is less than both the resolution of telescope mount drive mechanics and the accuracy of astrometric solutions, the independent nature of attitude determination could significantly increase the reliability of autonomous or remotely operated astronomical observations.
Optimal Centroid Position Estimation
Candy, J V; McClay, W A; Awwal, A S; Ferguson, S W
2004-07-23
The alignment of high energy laser beams for potential fusion experiments demand high precision and accuracy by the underlying positioning algorithms. This paper discusses the feasibility of employing online optimal position estimators in the form of model-based processors to achieve the desired results. Here we discuss the modeling, development, implementation and processing of model-based processors applied to both simulated and actual beam line data.
Accurate radio and optical positions for southern radio sources
NASA Technical Reports Server (NTRS)
Harvey, Bruce R.; Jauncey, David L.; White, Graeme L.; Nothnagel, Axel; Nicolson, George D.; Reynolds, John E.; Morabito, David D.; Bartel, Norbert
1992-01-01
Accurate radio positions with a precision of about 0.01 arcsec are reported for eight compact extragalactic radio sources south of -45-deg declination. The radio positions were determined using VLBI at 8.4 GHz on the 9589 km Tidbinbilla (Australia) to Hartebeesthoek (South Africa) baseline. The sources were selected from the Parkes Catalogue to be strong, flat-spectrum radio sources with bright optical QSO counterparts. Optical positions of the QSOs were also measured from the ESO B Sky Survey plates with respect to stars from the Perth 70 Catalogue, to an accuracy of about 0.19 arcsec rms. These radio and optical positions are as precise as any presently available in the far southern sky. A comparison of the radio and optical positions confirms the estimated optical position errors and shows that there is overall agreement at the 0.1-arcsec level between the radio and Perth 70 optical reference frames in the far south.
Accurate pose estimation for forensic identification
NASA Astrophysics Data System (ADS)
Merckx, Gert; Hermans, Jeroen; Vandermeulen, Dirk
2010-04-01
In forensic authentication, one aims to identify the perpetrator among a series of suspects or distractors. A fundamental problem in any recognition system that aims for identification of subjects in a natural scene is the lack of constrains on viewing and imaging conditions. In forensic applications, identification proves even more challenging, since most surveillance footage is of abysmal quality. In this context, robust methods for pose estimation are paramount. In this paper we will therefore present a new pose estimation strategy for very low quality footage. Our approach uses 3D-2D registration of a textured 3D face model with the surveillance image to obtain accurate far field pose alignment. Starting from an inaccurate initial estimate, the technique uses novel similarity measures based on the monogenic signal to guide a pose optimization process. We will illustrate the descriptive strength of the introduced similarity measures by using them directly as a recognition metric. Through validation, using both real and synthetic surveillance footage, our pose estimation method is shown to be accurate, and robust to lighting changes and image degradation.
Accurate water maser positions from HOPS
NASA Astrophysics Data System (ADS)
Walsh, Andrew J.; Purcell, Cormac R.; Longmore, Steven N.; Breen, Shari L.; Green, James A.; Harvey-Smith, Lisa; Jordan, Christopher H.; Macpherson, Christopher
2014-08-01
We report on high spatial resolution water maser observations, using the Australia Telescope Compact Array, towards water maser sites previously identified in the H2O southern Galactic Plane Survey (HOPS). Of the 540 masers identified in the single-dish observations of Walsh et al., we detect emission in all but 31 fields. We report on 2790 spectral features (maser spots), with brightnesses ranging from 0.06 to 576 Jy and with velocities ranging from -238.5 to +300.5 km s-1. These spectral features are grouped into 631 maser sites. We have compared the positions of these sites to the literature to associate the sites with astrophysical objects. We identify 433 (69 per cent) with star formation, 121 (19 per cent) with evolved stars and 77 (12 per cent) as unknown. We find that maser sites associated with evolved stars tend to have more maser spots and have smaller angular sizes than those associated with star formation. We present evidence that maser sites associated with evolved stars show an increased likelihood of having a velocity range between 15 and 35 km s-1 compared to other maser sites. Of the 31 non-detections, we conclude they were not detected due to intrinsic variability and confirm previous results showing that such variable masers tend to be weaker and have simpler spectra with fewer peaks.
Accurate estimation of sigma(exp 0) using AIRSAR data
NASA Technical Reports Server (NTRS)
Holecz, Francesco; Rignot, Eric
1995-01-01
During recent years signature analysis, classification, and modeling of Synthetic Aperture Radar (SAR) data as well as estimation of geophysical parameters from SAR data have received a great deal of interest. An important requirement for the quantitative use of SAR data is the accurate estimation of the backscattering coefficient sigma(exp 0). In terrain with relief variations radar signals are distorted due to the projection of the scene topography into the slant range-Doppler plane. The effect of these variations is to change the physical size of the scattering area, leading to errors in the radar backscatter values and incidence angle. For this reason the local incidence angle, derived from sensor position and Digital Elevation Model (DEM) data must always be considered. Especially in the airborne case, the antenna gain pattern can be an additional source of radiometric error, because the radar look angle is not known precisely as a result of the the aircraft motions and the local surface topography. Consequently, radiometric distortions due to the antenna gain pattern must also be corrected for each resolution cell, by taking into account aircraft displacements (position and attitude) and position of the backscatter element, defined by the DEM data. In this paper, a method to derive an accurate estimation of the backscattering coefficient using NASA/JPL AIRSAR data is presented. The results are evaluated in terms of geometric accuracy, radiometric variations of sigma(exp 0), and precision of the estimated forest biomass.
31 CFR 205.24 - How are accurate estimates maintained?
Code of Federal Regulations, 2010 CFR
2010-07-01
... 31 Money and Finance: Treasury 2 2010-07-01 2010-07-01 false How are accurate estimates maintained... Treasury-State Agreement § 205.24 How are accurate estimates maintained? (a) If a State has knowledge that an estimate does not reasonably correspond to the State's cash needs for a Federal assistance...
Accurate Biomass Estimation via Bayesian Adaptive Sampling
NASA Technical Reports Server (NTRS)
Wheeler, Kevin R.; Knuth, Kevin H.; Castle, Joseph P.; Lvov, Nikolay
2005-01-01
The following concepts were introduced: a) Bayesian adaptive sampling for solving biomass estimation; b) Characterization of MISR Rahman model parameters conditioned upon MODIS landcover. c) Rigorous non-parametric Bayesian approach to analytic mixture model determination. d) Unique U.S. asset for science product validation and verification.
Micromagnetometer calibration for accurate orientation estimation.
Zhang, Zhi-Qiang; Yang, Guang-Zhong
2015-02-01
Micromagnetometers, together with inertial sensors, are widely used for attitude estimation for a wide variety of applications. However, appropriate sensor calibration, which is essential to the accuracy of attitude reconstruction, must be performed in advance. Thus far, many different magnetometer calibration methods have been proposed to compensate for errors such as scale, offset, and nonorthogonality. They have also been used for obviate magnetic errors due to soft and hard iron. However, in order to combine the magnetometer with inertial sensor for attitude reconstruction, alignment difference between the magnetometer and the axes of the inertial sensor must be determined as well. This paper proposes a practical means of sensor error correction by simultaneous consideration of sensor errors, magnetic errors, and alignment difference. We take the summation of the offset and hard iron error as the combined bias and then amalgamate the alignment difference and all the other errors as a transformation matrix. A two-step approach is presented to determine the combined bias and transformation matrix separately. In the first step, the combined bias is determined by finding an optimal ellipsoid that can best fit the sensor readings. In the second step, the intrinsic relationships of the raw sensor readings are explored to estimate the transformation matrix as a homogeneous linear least-squares problem. Singular value decomposition is then applied to estimate both the transformation matrix and magnetic vector. The proposed method is then applied to calibrate our sensor node. Although there is no ground truth for the combined bias and transformation matrix for our node, the consistency of calibration results among different trials and less than 3(°) root mean square error for orientation estimation have been achieved, which illustrates the effectiveness of the proposed sensor calibration method for practical applications. PMID:25265625
Extremely Accurate On-Orbit Position Accuracy using TDRSS
NASA Technical Reports Server (NTRS)
Stocklin, Frank; Toral, Marco; Bar-Sever, Yoaz; Rush, John
2006-01-01
NASA is planning to launch a new service for Earth satellites providing them with precise GPS differential corrections and other ancillary information enabling decimeter level orbit determination accuracy and nanosecond time-transfer accuracy, onboard, in real-time. The TDRSS Augmentation Service for Satellites (TASS) will broadcast its message on the S-band multiple access forward channel of NASA s Tracking and Data Relay Satellite System (TDRSS). The satellite's phase array antenna has been configured to provide a wide beam, extending coverage up to 1000 km altitude over the poles. Global coverage will be ensured with broadcast from three or more TDRSS satellites. The GPS differential corrections are provided by the NASA Global Differential GPS (GDGPS) System, developed and operated by JPL. The GDGPS System employs global ground network of more than 70 GPS receivers to monitor the GPS constellation in real time. The system provides real-time estimates of the GPS satellite states, as well as many other real-time products such as differential corrections, global ionospheric maps, and integrity monitoring. The unique multiply redundant architecture of the GDGPS System ensures very high reliability, with 99.999% demonstrated since the inception of the system in early 2000. The estimated real time GPS orbit and clock states provided by the GDGPS system are accurate to better than 20 cm 3D RMS, and have been demonstrated to support sub-decimeter real time positioning and orbit determination for a variety of terrestrial, airborne, and spaceborne applications. In addition to the GPS differential corrections, TASS will provide real-time Earth orientation and solar flux information that enable precise onboard knowledge of the Earth-fixed position of the spacecraft, and precise orbit prediction and planning capabilities. TASS will also provide 5 seconds alarms for GPS integrity failures based on the unique GPS integrity monitoring service of the GDGPS System.
Accurate positioning of long, flexible ARM's (Articulated Robotic Manipulator)
NASA Technical Reports Server (NTRS)
Malachowski, Michael J.
1988-01-01
An articulated robotic manipulator (ARM) system is being designed for space applications. Work being done on a concept utilizing an infinitely stiff laser beam for position reference is summarized. The laser beam is projected along the segments of the ARM, and the position is sensed by the beam rider modules (BRM) mounted on the distal ends of the segments. The BRM concept is the heart of the system. It utilizes a combination of lateral displacements and rotational and distance measurement sensors. These determine the relative position of the two ends of the segments with respect to each other in six degrees of freedom. The BRM measurement devices contain microprocessor controlled data acquisition and active positioning components. An indirect adaptive controller is used to accurately control the position of the ARM.
Improvements in Accurate GPS Positioning Using Time Series Analysis
NASA Astrophysics Data System (ADS)
Koyama, Yuichiro; Tanaka, Toshiyuki
Although the Global Positioning System (GPS) is used widely in car navigation systems, cell phones, surveying, and other areas, several issues still exist. We focus on the continuous data received in public use of GPS, and propose a new positioning algorithm that uses time series analysis. By fitting an autoregressive model to the time series model of the pseudorange, we propose an appropriate state-space model. We apply the Kalman filter to the state-space model and use the pseudorange estimated by the filter in our positioning calculations. The results of the authors' positioning experiment show that the accuracy of the proposed method is much better than that of the standard method. In addition, as we can obtain valid values estimated by time series analysis using the state-space model, the proposed state-space model can be applied to several other fields.
Quantifying Accurate Calorie Estimation Using the "Think Aloud" Method
ERIC Educational Resources Information Center
Holmstrup, Michael E.; Stearns-Bruening, Kay; Rozelle, Jeffrey
2013-01-01
Objective: Clients often have limited time in a nutrition education setting. An improved understanding of the strategies used to accurately estimate calories may help to identify areas of focused instruction to improve nutrition knowledge. Methods: A "Think Aloud" exercise was recorded during the estimation of calories in a standard dinner meal…
Multimodal Spatial Calibration for Accurately Registering EEG Sensor Positions
Chen, Shengyong; Xiao, Gang; Li, Xiaoli
2014-01-01
This paper proposes a fast and accurate calibration method to calibrate multiple multimodal sensors using a novel photogrammetry system for fast localization of EEG sensors. The EEG sensors are placed on human head and multimodal sensors are installed around the head to simultaneously obtain all EEG sensor positions. A multiple views' calibration process is implemented to obtain the transformations of multiple views. We first develop an efficient local repair algorithm to improve the depth map, and then a special calibration body is designed. Based on them, accurate and robust calibration results can be achieved. We evaluate the proposed method by corners of a chessboard calibration plate. Experimental results demonstrate that the proposed method can achieve good performance, which can be further applied to EEG source localization applications on human brain. PMID:24803954
Multimodal spatial calibration for accurately registering EEG sensor positions.
Zhang, Jianhua; Chen, Jian; Chen, Shengyong; Xiao, Gang; Li, Xiaoli
2014-01-01
This paper proposes a fast and accurate calibration method to calibrate multiple multimodal sensors using a novel photogrammetry system for fast localization of EEG sensors. The EEG sensors are placed on human head and multimodal sensors are installed around the head to simultaneously obtain all EEG sensor positions. A multiple views' calibration process is implemented to obtain the transformations of multiple views. We first develop an efficient local repair algorithm to improve the depth map, and then a special calibration body is designed. Based on them, accurate and robust calibration results can be achieved. We evaluate the proposed method by corners of a chessboard calibration plate. Experimental results demonstrate that the proposed method can achieve good performance, which can be further applied to EEG source localization applications on human brain. PMID:24803954
Efficient and Accurate WLAN Positioning with Weighted Graphs
NASA Astrophysics Data System (ADS)
Hansen, René; Thomsen, Bent
This paper concerns indoor location determination by using existing WLAN infrastructures and WLAN enabled mobile devices. The location fingerprinting technique performs localization by first constructing a radio map of signal strengths from nearby access points. The radio map is subsequently searched using a classification algorithm to determine a location estimate. This paper addresses two distinct challenges of location fingerprinting incurred by positioning moving users. Firstly, movement affects the positioning accuracy negatively due to increased signal strength fluctuations. Secondly, tracking moving users requires a low-latency overhead which translates into efficient computations to be done on a mobile device with limited capabilities. We present a technique to simultaneously improve the positioning accuracy and computational efficiency. The technique utilizes a weighted graph model of the indoor environment to improve positioning accuracy and computational efficiency by only considering the subset of locations in the radio map that are feasible to reach from a previously estimated position. The technique is general and can be used on top of any existing location system. Our results indicate that we are able to achieve similar dynamic localization accuracy to static localization. Effectively, we are able to counter the adverse effects of added signal fluctuations caused by movement. However, as some of our experiments testify, any location system is fundamentally constrained by the underlying environment. We give pointers to research which allows such problems to be detected early and thereby avoided before deploying a system.
Accurate parameter estimation for unbalanced three-phase system.
Chen, Yuan; So, Hing Cheung
2014-01-01
Smart grid is an intelligent power generation and control console in modern electricity networks, where the unbalanced three-phase power system is the commonly used model. Here, parameter estimation for this system is addressed. After converting the three-phase waveforms into a pair of orthogonal signals via the α β-transformation, the nonlinear least squares (NLS) estimator is developed for accurately finding the frequency, phase, and voltage parameters. The estimator is realized by the Newton-Raphson scheme, whose global convergence is studied in this paper. Computer simulations show that the mean square error performance of NLS method can attain the Cramér-Rao lower bound. Moreover, our proposal provides more accurate frequency estimation when compared with the complex least mean square (CLMS) and augmented CLMS. PMID:25162056
Cook, Andrea J.; Elmore, Joann G.; Zhu, Weiwei; Jackson, Sara L.; Carney, Patricia A.; Flowers, Chris; Onega, Tracy; Geller, Berta; Rosenberg, Robert D.; Miglioretti, Diana L.
2013-01-01
Objective To determine if U.S. radiologists accurately estimate their own interpretive performance of screening mammography and how they compare their performance to their peers’. Materials and Methods 174 radiologists from six Breast Cancer Surveillance Consortium (BCSC) registries completed a mailed survey between 2005 and 2006. Radiologists’ estimated and actual recall, false positive, and cancer detection rates and positive predictive value of biopsy recommendation (PPV2) for screening mammography were compared. Radiologists’ ratings of their performance as lower, similar, or higher than their peers were compared to their actual performance. Associations with radiologist characteristics were estimated using weighted generalized linear models. The study was approved by the institutional review boards of the participating sites, informed consent was obtained from radiologists, and procedures were HIPAA compliant. Results While most radiologists accurately estimated their cancer detection and recall rates (74% and 78% of radiologists), fewer accurately estimated their false positive rate and PPV2 (19% and 26%). Radiologists reported having similar (43%) or lower (31%) recall rates and similar (52%) or lower (33%) false positive rates compared to their peers, and similar (72%) or higher (23%) cancer detection rates and similar (72%) or higher (38%) PPV2. Estimation accuracy did not differ by radiologists’ characteristics except radiologists who interpret ≤1,000 mammograms annually were less accurate at estimating their recall rates. Conclusion Radiologists perceive their performance to be better than it actually is and at least as good as their peers. Radiologists have particular difficulty estimating their false positive rates and PPV2. PMID:22915414
Accurate pose estimation using single marker single camera calibration system
NASA Astrophysics Data System (ADS)
Pati, Sarthak; Erat, Okan; Wang, Lejing; Weidert, Simon; Euler, Ekkehard; Navab, Nassir; Fallavollita, Pascal
2013-03-01
Visual marker based tracking is one of the most widely used tracking techniques in Augmented Reality (AR) applications. Generally, multiple square markers are needed to perform robust and accurate tracking. Various marker based methods for calibrating relative marker poses have already been proposed. However, the calibration accuracy of these methods relies on the order of the image sequence and pre-evaluation of pose-estimation errors, making the method offline. Several studies have shown that the accuracy of pose estimation for an individual square marker depends on camera distance and viewing angle. We propose a method to accurately model the error in the estimated pose and translation of a camera using a single marker via an online method based on the Scaled Unscented Transform (SUT). Thus, the pose estimation for each marker can be estimated with highly accurate calibration results independent of the order of image sequences compared to cases when this knowledge is not used. This removes the need for having multiple markers and an offline estimation system to calculate camera pose in an AR application.
An Accurate Link Correlation Estimator for Improving Wireless Protocol Performance
Zhao, Zhiwei; Xu, Xianghua; Dong, Wei; Bu, Jiajun
2015-01-01
Wireless link correlation has shown significant impact on the performance of various sensor network protocols. Many works have been devoted to exploiting link correlation for protocol improvements. However, the effectiveness of these designs heavily relies on the accuracy of link correlation measurement. In this paper, we investigate state-of-the-art link correlation measurement and analyze the limitations of existing works. We then propose a novel lightweight and accurate link correlation estimation (LACE) approach based on the reasoning of link correlation formation. LACE combines both long-term and short-term link behaviors for link correlation estimation. We implement LACE as a stand-alone interface in TinyOS and incorporate it into both routing and flooding protocols. Simulation and testbed results show that LACE: (1) achieves more accurate and lightweight link correlation measurements than the state-of-the-art work; and (2) greatly improves the performance of protocols exploiting link correlation. PMID:25686314
An accurate link correlation estimator for improving wireless protocol performance.
Zhao, Zhiwei; Xu, Xianghua; Dong, Wei; Bu, Jiajun
2015-01-01
Wireless link correlation has shown significant impact on the performance of various sensor network protocols. Many works have been devoted to exploiting link correlation for protocol improvements. However, the effectiveness of these designs heavily relies on the accuracy of link correlation measurement. In this paper, we investigate state-of-the-art link correlation measurement and analyze the limitations of existing works. We then propose a novel lightweight and accurate link correlation estimation (LACE) approach based on the reasoning of link correlation formation. LACE combines both long-term and short-term link behaviors for link correlation estimation. We implement LACE as a stand-alone interface in TinyOS and incorporate it into both routing and flooding protocols. Simulation and testbed results show that LACE: (1) achieves more accurate and lightweight link correlation measurements than the state-of-the-art work; and (2) greatly improves the performance of protocols exploiting link correlation. PMID:25686314
Fast and accurate estimation for astrophysical problems in large databases
NASA Astrophysics Data System (ADS)
Richards, Joseph W.
2010-10-01
A recent flood of astronomical data has created much demand for sophisticated statistical and machine learning tools that can rapidly draw accurate inferences from large databases of high-dimensional data. In this Ph.D. thesis, methods for statistical inference in such databases will be proposed, studied, and applied to real data. I use methods for low-dimensional parametrization of complex, high-dimensional data that are based on the notion of preserving the connectivity of data points in the context of a Markov random walk over the data set. I show how this simple parameterization of data can be exploited to: define appropriate prototypes for use in complex mixture models, determine data-driven eigenfunctions for accurate nonparametric regression, and find a set of suitable features to use in a statistical classifier. In this thesis, methods for each of these tasks are built up from simple principles, compared to existing methods in the literature, and applied to data from astronomical all-sky surveys. I examine several important problems in astrophysics, such as estimation of star formation history parameters for galaxies, prediction of redshifts of galaxies using photometric data, and classification of different types of supernovae based on their photometric light curves. Fast methods for high-dimensional data analysis are crucial in each of these problems because they all involve the analysis of complicated high-dimensional data in large, all-sky surveys. Specifically, I estimate the star formation history parameters for the nearly 800,000 galaxies in the Sloan Digital Sky Survey (SDSS) Data Release 7 spectroscopic catalog, determine redshifts for over 300,000 galaxies in the SDSS photometric catalog, and estimate the types of 20,000 supernovae as part of the Supernova Photometric Classification Challenge. Accurate predictions and classifications are imperative in each of these examples because these estimates are utilized in broader inference problems
Accurate and robust estimation of camera parameters using RANSAC
NASA Astrophysics Data System (ADS)
Zhou, Fuqiang; Cui, Yi; Wang, Yexin; Liu, Liu; Gao, He
2013-03-01
Camera calibration plays an important role in the field of machine vision applications. The popularly used calibration approach based on 2D planar target sometimes fails to give reliable and accurate results due to the inaccurate or incorrect localization of feature points. To solve this problem, an accurate and robust estimation method for camera parameters based on RANSAC algorithm is proposed to detect the unreliability and provide the corresponding solutions. Through this method, most of the outliers are removed and the calibration errors that are the main factors influencing measurement accuracy are reduced. Both simulative and real experiments have been carried out to evaluate the performance of the proposed method and the results show that the proposed method is robust under large noise condition and quite efficient to improve the calibration accuracy compared with the original state.
Accurate Satellite-Derived Estimates of Tropospheric Ozone Radiative Forcing
NASA Technical Reports Server (NTRS)
Joiner, Joanna; Schoeberl, Mark R.; Vasilkov, Alexander P.; Oreopoulos, Lazaros; Platnick, Steven; Livesey, Nathaniel J.; Levelt, Pieternel F.
2008-01-01
Estimates of the radiative forcing due to anthropogenically-produced tropospheric O3 are derived primarily from models. Here, we use tropospheric ozone and cloud data from several instruments in the A-train constellation of satellites as well as information from the GEOS-5 Data Assimilation System to accurately estimate the instantaneous radiative forcing from tropospheric O3 for January and July 2005. We improve upon previous estimates of tropospheric ozone mixing ratios from a residual approach using the NASA Earth Observing System (EOS) Aura Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) by incorporating cloud pressure information from OMI. Since we cannot distinguish between natural and anthropogenic sources with the satellite data, our estimates reflect the total forcing due to tropospheric O3. We focus specifically on the magnitude and spatial structure of the cloud effect on both the shortand long-wave radiative forcing. The estimates presented here can be used to validate present day O3 radiative forcing produced by models.
Robust ODF smoothing for accurate estimation of fiber orientation.
Beladi, Somaieh; Pathirana, Pubudu N; Brotchie, Peter
2010-01-01
Q-ball imaging was presented as a model free, linear and multimodal diffusion sensitive approach to reconstruct diffusion orientation distribution function (ODF) using diffusion weighted MRI data. The ODFs are widely used to estimate the fiber orientations. However, the smoothness constraint was proposed to achieve a balance between the angular resolution and noise stability for ODF constructs. Different regularization methods were proposed for this purpose. However, these methods are not robust and quite sensitive to the global regularization parameter. Although, numerical methods such as L-curve test are used to define a globally appropriate regularization parameter, it cannot serve as a universal value suitable for all regions of interest. This may result in over smoothing and potentially end up in neglecting an existing fiber population. In this paper, we propose to include an interpolation step prior to the spherical harmonic decomposition. This interpolation based approach is based on Delaunay triangulation provides a reliable, robust and accurate smoothing approach. This method is easy to implement and does not require other numerical methods to define the required parameters. Also, the fiber orientations estimated using this approach are more accurate compared to other common approaches. PMID:21096202
Accurate estimators of correlation functions in Fourier space
NASA Astrophysics Data System (ADS)
Sefusatti, E.; Crocce, M.; Scoccimarro, R.; Couchman, H. M. P.
2016-08-01
Efficient estimators of Fourier-space statistics for large number of objects rely on fast Fourier transforms (FFTs), which are affected by aliasing from unresolved small-scale modes due to the finite FFT grid. Aliasing takes the form of a sum over images, each of them corresponding to the Fourier content displaced by increasing multiples of the sampling frequency of the grid. These spurious contributions limit the accuracy in the estimation of Fourier-space statistics, and are typically ameliorated by simultaneously increasing grid size and discarding high-frequency modes. This results in inefficient estimates for e.g. the power spectrum when desired systematic biases are well under per cent level. We show that using interlaced grids removes odd images, which include the dominant contribution to aliasing. In addition, we discuss the choice of interpolation kernel used to define density perturbations on the FFT grid and demonstrate that using higher order interpolation kernels than the standard Cloud-In-Cell algorithm results in significant reduction of the remaining images. We show that combining fourth-order interpolation with interlacing gives very accurate Fourier amplitudes and phases of density perturbations. This results in power spectrum and bispectrum estimates that have systematic biases below 0.01 per cent all the way to the Nyquist frequency of the grid, thus maximizing the use of unbiased Fourier coefficients for a given grid size and greatly reducing systematics for applications to large cosmological data sets.
Position Estimation Using Image Derivative
NASA Technical Reports Server (NTRS)
Mortari, Daniele; deDilectis, Francesco; Zanetti, Renato
2015-01-01
This paper describes an image processing algorithm to process Moon and/or Earth images. The theory presented is based on the fact that Moon hard edge points are characterized by the highest values of the image derivative. Outliers are eliminated by two sequential filters. Moon center and radius are then estimated by nonlinear least-squares using circular sigmoid functions. The proposed image processing has been applied and validated using real and synthetic Moon images.
Accurate recovery of articulator positions from acoustics: New conclusions based on human data
Hogden, J.; Lofqvist, A.; Gracco, V.; Zlokarnik, I.; Rubin, P.; Saltzman, E.
1996-09-01
Vocal tract models are often used to study the problem of mapping from the acoustic transfer function to the vocal tract area function (inverse mapping). Unfortunately, results based on vocal tract models are strongly affected by the assumptions underlying the models. In this study, the mapping from acoustics (digitized speech samples) to articulation (measurements of the positions of receiver coils placed on the tongue, jaw, and lips) is examined using human data from a single speaker: Simultaneous acoustic and articulator measurements made for vowel-to-vowel transitions, /g/ closures, and transitions into and out of /g/ closures. Articulator positions were measured using an EMMA system to track coils placed on the lips, jaw, and tongue. Using these data, look-up tables were created that allow articulator positions to be estimated from acoustic signals. On a data set not used for making look-up tables, correlations between estimated and actual coil positions of around 94{percent} and root-mean-squared errors around 2 mm are common for coils on the tongue. An error source evaluation shows that estimating articulator positions from quantized acoustics gives root-mean-squared errors that are typically less than 1 mm greater than the errors that would be obtained from quantizing the articulator positions themselves. This study agrees with and extends previous studies of human data by showing that for the data studied, speech acoustics can be used to accurately recover articulator positions. {copyright} {ital 1996 Acoustical Society of America.}
Estimation of base station position using timing advance measurements
NASA Astrophysics Data System (ADS)
Raitoharju, Matti; Ali-Löytty, Simo; Wirola, Lauri
2011-10-01
Timing Advance is used in TDMA (Time Division Multiple Access) systems, such as GSM and LTE, to synchronize the mobile phone to the cellular BS (Base Station). Mobile phone positioning can use TA measurements if BS positions are known, but in many cases BS positions are not in the public domain. In this work we study how to use a set of TA measurements taken by mobile phones at known positions to estimate the position of a BS. This paper describes two methods -- GMF (Gaussian Mixture Filter) and PMF (Point Mass Filter) for estimation of the BS position. Positioning performance is evaluated using simulated and real measurements. In suburban field tests, TA measurements suffice to determine BS position with an error comparable to the TA granularity (550m). GMF computes BS position much faster than PMF and is only slightly less accurate.
Using GPS To Teach More Than Accurate Positions.
ERIC Educational Resources Information Center
Johnson, Marie C.; Guth, Peter L.
2002-01-01
Undergraduate science majors need practice in critical thinking, quantitative analysis, and judging whether their calculated answers are physically reasonable. Develops exercises using handheld Global Positioning System (GPS) receivers. Reinforces students' abilities to think quantitatively, make realistic "back of the envelope" assumptions, and…
Accurate Orientation Estimation Using AHRS under Conditions of Magnetic Distortion
Yadav, Nagesh; Bleakley, Chris
2014-01-01
Low cost, compact attitude heading reference systems (AHRS) are now being used to track human body movements in indoor environments by estimation of the 3D orientation of body segments. In many of these systems, heading estimation is achieved by monitoring the strength of the Earth's magnetic field. However, the Earth's magnetic field can be locally distorted due to the proximity of ferrous and/or magnetic objects. Herein, we propose a novel method for accurate 3D orientation estimation using an AHRS, comprised of an accelerometer, gyroscope and magnetometer, under conditions of magnetic field distortion. The system performs online detection and compensation for magnetic disturbances, due to, for example, the presence of ferrous objects. The magnetic distortions are detected by exploiting variations in magnetic dip angle, relative to the gravity vector, and in magnetic strength. We investigate and show the advantages of using both magnetic strength and magnetic dip angle for detecting the presence of magnetic distortions. The correction method is based on a particle filter, which performs the correction using an adaptive cost function and by adapting the variance during particle resampling, so as to place more emphasis on the results of dead reckoning of the gyroscope measurements and less on the magnetometer readings. The proposed method was tested in an indoor environment in the presence of various magnetic distortions and under various accelerations (up to 3 g). In the experiments, the proposed algorithm achieves <2° static peak-to-peak error and <5° dynamic peak-to-peak error, significantly outperforming previous methods. PMID:25347584
Accurate Position Sensing of Defocused Beams Using Simulated Beam Templates
Awwal, A; Candy, J; Haynam, C; Widmayer, C; Bliss, E; Burkhart, S
2004-09-29
In position detection using matched filtering one is faced with the challenge of determining the best position in the presence of distortions such as defocus and diffraction noise. This work evaluates the performance of simulated defocused images as the template against the real defocused beam. It was found that an amplitude modulated phase-only filter is better equipped to deal with real defocused images that suffer from diffraction noise effects resulting in a textured spot intensity pattern. It is shown that the there is a tradeoff of performance dependent upon the type and size of the defocused image. A novel automated system was developed that can automatically select the right template type and size. Results of this automation for real defocused images are presented.
Accurate aircraft wind measurements using the global positioning system (GPS)
Dobosy, R.J.; Crawford, T.L., McMillen, R.T., Dumas, E.J.
1996-11-01
High accuracy measurements of the spatial distribution of wind speed are required in the study of turbulent exchange between the atmosphere and the earth. The use of a differential global positioning system (GPS) to determine the sensor velocity vector component of wind speed is discussed in this paper. The results of noise and rocking testing are summarized, and fluxes obtained from the GPS-based methods are compared to those measured from systems on towers and airplanes. The GPS-based methods provided usable measurements that compared well with tower and aircraft data at a significantly lower cost. 21 refs., 1 fig., 2 tabs.
Chen, Weizhong; Liu, Yi; Zhu, Shanshan; Green, Christopher D; Wei, Gang; Han, Jing-Dong Jackie
2014-01-01
Accurate determination of genome-wide nucleosome positioning can provide important insights into global gene regulation. Here, we describe the development of an improved nucleosome-positioning algorithm-iNPS-which achieves significantly better performance than the widely used NPS package. By determining nucleosome boundaries more precisely and merging or separating shoulder peaks based on local MNase-seq signals, iNPS can unambiguously detect 60% more nucleosomes. The detected nucleosomes display better nucleosome 'widths' and neighbouring centre-centre distance distributions, giving rise to sharper patterns and better phasing of average nucleosome profiles and higher consistency between independent data subsets. In addition to its unique advantage in classifying nucleosomes by shape to reveal their different biological properties, iNPS also achieves higher significance and lower false positive rates than previously published methods. The application of iNPS to T-cell activation data demonstrates a greater ability to facilitate detection of nucleosome repositioning, uncovering additional biological features underlying the activation process. PMID:25233085
Position Estimation of Tranceivers in Communication Networks
Kent, C A; Dowla, F U
2003-10-13
With the rapid development in wireless sensor networks, there is an important need for transceiver position estimation independent of Global Positioning Systems (GPS) [1,3]. While GPS might be useful for outdoor sensor nodes, it is not for indoor node localization. In this case, position estimation is possible through network range estimates from time-of-flight (TOF) measurements, a technique well suited to large bandwidth physical links, such as in ultra-wideband (UWB) communications. For example, in our UWB systems, with pulse duration less than 200 pico-seconds, range can easily be resolved to less than a foot. Assuming an encoded UWB or spread spectrum physical layer, we developed algorithms and simulation tools to test transceiver position localization. Simulations were designed to lend insight into system characteristics such as position error sensitivities to network geometry, to range estimation errors, and to number of sensor nodes.
Accurate estimation of object location in an image sequence using helicopter flight data
NASA Technical Reports Server (NTRS)
Tang, Yuan-Liang; Kasturi, Rangachar
1994-01-01
In autonomous navigation, it is essential to obtain a three-dimensional (3D) description of the static environment in which the vehicle is traveling. For a rotorcraft conducting low-latitude flight, this description is particularly useful for obstacle detection and avoidance. In this paper, we address the problem of 3D position estimation for static objects from a monocular sequence of images captured from a low-latitude flying helicopter. Since the environment is static, it is well known that the optical flow in the image will produce a radiating pattern from the focus of expansion. We propose a motion analysis system which utilizes the epipolar constraint to accurately estimate 3D positions of scene objects in a real world image sequence taken from a low-altitude flying helicopter. Results show that this approach gives good estimates of object positions near the rotorcraft's intended flight-path.
Detecting Positioning Errors and Estimating Correct Positions by Moving Window
Song, Ha Yoon; Lee, Jun Seok
2015-01-01
In recent times, improvements in smart mobile devices have led to new functionalities related to their embedded positioning abilities. Many related applications that use positioning data have been introduced and are widely being used. However, the positioning data acquired by such devices are prone to erroneous values caused by environmental factors. In this research, a detection algorithm is implemented to detect erroneous data over a continuous positioning data set with several options. Our algorithm is based on a moving window for speed values derived by consecutive positioning data. Both the moving average of the speed and standard deviation in a moving window compose a moving significant interval at a given time, which is utilized to detect erroneous positioning data along with other parameters by checking the newly obtained speed value. In order to fulfill the designated operation, we need to examine the physical parameters and also determine the parameters for the moving windows. Along with the detection of erroneous speed data, estimations of correct positioning are presented. The proposed algorithm first estimates the speed, and then the correct positions. In addition, it removes the effect of errors on the moving window statistics in order to maintain accuracy. Experimental verifications based on our algorithm are presented in various ways. We hope that our approach can help other researchers with regard to positioning applications and human mobility research. PMID:26624282
Detecting Positioning Errors and Estimating Correct Positions by Moving Window.
Song, Ha Yoon; Lee, Jun Seok
2015-01-01
In recent times, improvements in smart mobile devices have led to new functionalities related to their embedded positioning abilities. Many related applications that use positioning data have been introduced and are widely being used. However, the positioning data acquired by such devices are prone to erroneous values caused by environmental factors. In this research, a detection algorithm is implemented to detect erroneous data over a continuous positioning data set with several options. Our algorithm is based on a moving window for speed values derived by consecutive positioning data. Both the moving average of the speed and standard deviation in a moving window compose a moving significant interval at a given time, which is utilized to detect erroneous positioning data along with other parameters by checking the newly obtained speed value. In order to fulfill the designated operation, we need to examine the physical parameters and also determine the parameters for the moving windows. Along with the detection of erroneous speed data, estimations of correct positioning are presented. The proposed algorithm first estimates the speed, and then the correct positions. In addition, it removes the effect of errors on the moving window statistics in order to maintain accuracy. Experimental verifications based on our algorithm are presented in various ways. We hope that our approach can help other researchers with regard to positioning applications and human mobility research. PMID:26624282
Bioaccessibility tests accurately estimate bioavailability of lead to quail
Beyer, W. Nelson; Basta, Nicholas T; Chaney, Rufus L.; Henry, Paula F.; Mosby, David; Rattner, Barnett A.; Scheckel, Kirk G.; Sprague, Dan; Weber, John
2016-01-01
Hazards of soil-borne Pb to wild birds may be more accurately quantified if the bioavailability of that Pb is known. To better understand the bioavailability of Pb to birds, we measured blood Pb concentrations in Japanese quail (Coturnix japonica) fed diets containing Pb-contaminated soils. Relative bioavailabilities were expressed by comparison with blood Pb concentrations in quail fed a Pb acetate reference diet. Diets containing soil from five Pb-contaminated Superfund sites had relative bioavailabilities from 33%-63%, with a mean of about 50%. Treatment of two of the soils with phosphorus significantly reduced the bioavailability of Pb. Bioaccessibility of Pb in the test soils was then measured in six in vitro tests and regressed on bioavailability. They were: the “Relative Bioavailability Leaching Procedure” (RBALP) at pH 1.5, the same test conducted at pH 2.5, the “Ohio State University In vitro Gastrointestinal” method (OSU IVG), the “Urban Soil Bioaccessible Lead Test”, the modified “Physiologically Based Extraction Test” and the “Waterfowl Physiologically Based Extraction Test.” All regressions had positive slopes. Based on criteria of slope and coefficient of determination, the RBALP pH 2.5 and OSU IVG tests performed very well. Speciation by X-ray absorption spectroscopy demonstrated that, on average, most of the Pb in the sampled soils was sorbed to minerals (30%), bound to organic matter (24%), or present as Pb sulfate (18%). Additional Pb was associated with P (chloropyromorphite, hydroxypyromorphite and tertiary Pb phosphate), and with Pb carbonates, leadhillite (a lead sulfate carbonate hydroxide), and Pb sulfide. The formation of chloropyromorphite reduced the bioavailability of Pb and the amendment of Pb-contaminated soils with P may be a thermodynamically favored means to sequester Pb.
Bioaccessibility tests accurately estimate bioavailability of lead to quail.
Beyer, W Nelson; Basta, Nicholas T; Chaney, Rufus L; Henry, Paula F P; Mosby, David E; Rattner, Barnett A; Scheckel, Kirk G; Sprague, Daniel T; Weber, John S
2016-09-01
Hazards of soil-borne lead (Pb) to wild birds may be more accurately quantified if the bioavailability of that Pb is known. To better understand the bioavailability of Pb to birds, the authors measured blood Pb concentrations in Japanese quail (Coturnix japonica) fed diets containing Pb-contaminated soils. Relative bioavailabilities were expressed by comparison with blood Pb concentrations in quail fed a Pb acetate reference diet. Diets containing soil from 5 Pb-contaminated Superfund sites had relative bioavailabilities from 33% to 63%, with a mean of approximately 50%. Treatment of 2 of the soils with phosphorus (P) significantly reduced the bioavailability of Pb. Bioaccessibility of Pb in the test soils was then measured in 6 in vitro tests and regressed on bioavailability: the relative bioavailability leaching procedure at pH 1.5, the same test conducted at pH 2.5, the Ohio State University in vitro gastrointestinal method, the urban soil bioaccessible lead test, the modified physiologically based extraction test, and the waterfowl physiologically based extraction test. All regressions had positive slopes. Based on criteria of slope and coefficient of determination, the relative bioavailability leaching procedure at pH 2.5 and Ohio State University in vitro gastrointestinal tests performed very well. Speciation by X-ray absorption spectroscopy demonstrated that, on average, most of the Pb in the sampled soils was sorbed to minerals (30%), bound to organic matter (24%), or present as Pb sulfate (18%). Additional Pb was associated with P (chloropyromorphite, hydroxypyromorphite, and tertiary Pb phosphate) and with Pb carbonates, leadhillite (a lead sulfate carbonate hydroxide), and Pb sulfide. The formation of chloropyromorphite reduced the bioavailability of Pb, and the amendment of Pb-contaminated soils with P may be a thermodynamically favored means to sequester Pb. Environ Toxicol Chem 2016;35:2311-2319. Published 2016 Wiley Periodicals Inc. on behalf of
Fast and Accurate Learning When Making Discrete Numerical Estimates.
Sanborn, Adam N; Beierholm, Ulrik R
2016-04-01
Many everyday estimation tasks have an inherently discrete nature, whether the task is counting objects (e.g., a number of paint buckets) or estimating discretized continuous variables (e.g., the number of paint buckets needed to paint a room). While Bayesian inference is often used for modeling estimates made along continuous scales, discrete numerical estimates have not received as much attention, despite their common everyday occurrence. Using two tasks, a numerosity task and an area estimation task, we invoke Bayesian decision theory to characterize how people learn discrete numerical distributions and make numerical estimates. Across three experiments with novel stimulus distributions we found that participants fell between two common decision functions for converting their uncertain representation into a response: drawing a sample from their posterior distribution and taking the maximum of their posterior distribution. While this was consistent with the decision function found in previous work using continuous estimation tasks, surprisingly the prior distributions learned by participants in our experiments were much more adaptive: When making continuous estimates, participants have required thousands of trials to learn bimodal priors, but in our tasks participants learned discrete bimodal and even discrete quadrimodal priors within a few hundred trials. This makes discrete numerical estimation tasks good testbeds for investigating how people learn and make estimates. PMID:27070155
Fast and Accurate Learning When Making Discrete Numerical Estimates
Sanborn, Adam N.; Beierholm, Ulrik R.
2016-01-01
Many everyday estimation tasks have an inherently discrete nature, whether the task is counting objects (e.g., a number of paint buckets) or estimating discretized continuous variables (e.g., the number of paint buckets needed to paint a room). While Bayesian inference is often used for modeling estimates made along continuous scales, discrete numerical estimates have not received as much attention, despite their common everyday occurrence. Using two tasks, a numerosity task and an area estimation task, we invoke Bayesian decision theory to characterize how people learn discrete numerical distributions and make numerical estimates. Across three experiments with novel stimulus distributions we found that participants fell between two common decision functions for converting their uncertain representation into a response: drawing a sample from their posterior distribution and taking the maximum of their posterior distribution. While this was consistent with the decision function found in previous work using continuous estimation tasks, surprisingly the prior distributions learned by participants in our experiments were much more adaptive: When making continuous estimates, participants have required thousands of trials to learn bimodal priors, but in our tasks participants learned discrete bimodal and even discrete quadrimodal priors within a few hundred trials. This makes discrete numerical estimation tasks good testbeds for investigating how people learn and make estimates. PMID:27070155
Bioaccessibility tests accurately estimate bioavailability of lead to quail
Technology Transfer Automated Retrieval System (TEKTRAN)
Hazards of soil-borne Pb to wild birds may be more accurately quantified if the bioavailability of that Pb is known. To better understand the bioavailability of Pb, we incorporated Pb-contaminated soils or Pb acetate into diets for Japanese quail (Coturnix japonica), fed the quail for 15 days, and ...
BIOACCESSIBILITY TESTS ACCURATELY ESTIMATE BIOAVAILABILITY OF LEAD TO QUAIL
Hazards of soil-borne Pb to wild birds may be more accurately quantified if the bioavailability of that Pb is known. To better understand the bioavailability of Pb to birds, we measured blood Pb concentrations in Japanese quail (Coturnix japonica) fed diets containing Pb-contami...
Position estimation of transceivers in communication networks
Kent, Claudia A.; Dowla, Farid
2008-06-03
This invention provides a system and method using wireless communication interfaces coupled with statistical processing of time-of-flight data to locate by position estimation unknown wireless receivers. Such an invention can be applied in sensor network applications, such as environmental monitoring of water in the soil or chemicals in the air where the position of the network nodes is deemed critical. Moreover, the present invention can be arranged to operate in areas where a Global Positioning System (GPS) is not available, such as inside buildings, caves, and tunnels.
Synthetic Estimation Filters For Determination Of Position
NASA Technical Reports Server (NTRS)
Juday, Richard D.; Monroe, Stanley E., Jr.
1989-01-01
Concept of synthetic estimation filter (SEF) proposed to extend concept of matched filter from mere recognition of object to recognition of position and orientation relative to observing apparatus. Optical filter of this general type correlated with input image to obtain signal indicative of match between input and filter images.
How Accurately Do Spectral Methods Estimate Effective Elastic Thickness?
NASA Astrophysics Data System (ADS)
Perez-Gussinye, M.; Lowry, A. R.; Watts, A. B.; Velicogna, I.
2002-12-01
The effective elastic thickness, Te, is an important parameter that has the potential to provide information on the long-term thermal and mechanical properties of the the lithosphere. Previous studies have estimated Te using both forward and inverse (spectral) methods. While there is generally good agreement between the results obtained using these methods, spectral methods are limited because they depend on the spectral estimator and the window size chosen for analysis. In order to address this problem, we have used a multitaper technique which yields optimal estimates of the bias and variance of the Bouguer coherence function relating topography and gravity anomaly data. The technique has been tested using realistic synthetic topography and gravity. Synthetic data were generated assuming surface and sub-surface (buried) loading of an elastic plate with fractal statistics consistent with real data sets. The cases of uniform and spatially varying Te are examined. The topography and gravity anomaly data consist of 2000x2000 km grids sampled at 8 km interval. The bias in the Te estimate is assessed from the difference between the true Te value and the mean from analyzing 100 overlapping windows within the 2000x2000 km data grids. For the case in which Te is uniform, the bias and variance decrease with window size and increase with increasing true Te value. In the case of a spatially varying Te, however, there is a trade-off between spatial resolution and variance. With increasing window size the variance of the Te estimate decreases, but the spatial changes in Te are smeared out. We find that for a Te distribution consisting of a strong central circular region of Te=50 km (radius 600 km) and progressively smaller Te towards its edges, the 800x800 and 1000x1000 km window gave the best compromise between spatial resolution and variance. Our studies demonstrate that assumed stationarity of the relationship between gravity and topography data yields good results even in
Position estimator for underground mine equipment
Shaffer, G.K.; Stentz, A.; Whittaker, W.L.; Fitzpatrick, K.W. )
1992-10-01
This paper describes a 2-D perception system that exploits the accuracy and resolution of a laser range sensor to determine the position and orientation of a mobile robot in a mine environment. The perception system detects features from range sensor data and matches the features to a map of the mine to compute the sensor position. The features used are line segments and corners, which represent the typical geometry of the mine walls and intersections found in room-0and-pillar type mining. The position estimate is refined by minimizing the error between the map and sensed features. This position information can be used for autonomous navigation when a map of the mine is available or to survey the mine to build such a map. The technique is applied to robot navigation in a mine mockup. A refinement of this system could guide machines to yield productive, safe mining operations.
Wolf, Max; Kurvers, Ralf H. J. M.; Ward, Ashley J. W.; Krause, Stefan; Krause, Jens
2013-01-01
In a wide range of contexts, including predator avoidance, medical decision-making and security screening, decision accuracy is fundamentally constrained by the trade-off between true and false positives. Increased true positives are possible only at the cost of increased false positives; conversely, decreased false positives are associated with decreased true positives. We use an integrated theoretical and experimental approach to show that a group of decision-makers can overcome this basic limitation. Using a mathematical model, we show that a simple quorum decision rule enables individuals in groups to simultaneously increase true positives and decrease false positives. The results from a predator-detection experiment that we performed with humans are in line with these predictions: (i) after observing the choices of the other group members, individuals both increase true positives and decrease false positives, (ii) this effect gets stronger as group size increases, (iii) individuals use a quorum threshold set between the average true- and false-positive rates of the other group members, and (iv) individuals adjust their quorum adaptively to the performance of the group. Our results have broad implications for our understanding of the ecology and evolution of group-living animals and lend themselves for applications in the human domain such as the design of improved screening methods in medical, forensic, security and business applications. PMID:23407830
Accurate feature detection and estimation using nonlinear and multiresolution analysis
NASA Astrophysics Data System (ADS)
Rudin, Leonid; Osher, Stanley
1994-11-01
A program for feature detection and estimation using nonlinear and multiscale analysis was completed. The state-of-the-art edge detection was combined with multiscale restoration (as suggested by the first author) and robust results in the presence of noise were obtained. Successful applications to numerous images of interest to DOD were made. Also, a new market in the criminal justice field was developed, based in part, on this work.
Accurate tempo estimation based on harmonic + noise decomposition
NASA Astrophysics Data System (ADS)
Alonso, Miguel; Richard, Gael; David, Bertrand
2006-12-01
We present an innovative tempo estimation system that processes acoustic audio signals and does not use any high-level musical knowledge. Our proposal relies on a harmonic + noise decomposition of the audio signal by means of a subspace analysis method. Then, a technique to measure the degree of musical accentuation as a function of time is developed and separately applied to the harmonic and noise parts of the input signal. This is followed by a periodicity estimation block that calculates the salience of musical accents for a large number of potential periods. Next, a multipath dynamic programming searches among all the potential periodicities for the most consistent prospects through time, and finally the most energetic candidate is selected as tempo. Our proposal is validated using a manually annotated test-base containing 961 music signals from various musical genres. In addition, the performance of the algorithm under different configurations is compared. The robustness of the algorithm when processing signals of degraded quality is also measured.
Integration Window Position Estimation in TR Receivers
Nekoogar, F; Dowla, F; Spiridon, A
2005-03-15
Transmitted-reference (TR) receivers avoid the stringent synchronization requirements that exist in conventional pulse detection schemes. However, the performance of such receivers is highly sensitive to precise timing acquisition and tracking as well as the length of their integration window. This window in TR receivers defines the limits of the finite integrator prior to the final decision making block. In this paper, we propose a novel technique that allows us to extract the timing information of the integration window very accurately in UWB-TR receivers in the presence of channel noise. The principles of the method are presented and the BER performance of a modified UWB-TR receiver is investigated by computer simulation. Our studies show that the proposed estimation technique adds value to the conventional TR receiver structure with modest increase in complexity.
Accurate reconstruction of viral quasispecies spectra through improved estimation of strain richness
2015-01-01
Background Estimating the number of different species (richness) in a mixed microbial population has been a main focus in metagenomic research. Existing methods of species richness estimation ride on the assumption that the reads in each assembled contig correspond to only one of the microbial genomes in the population. This assumption and the underlying probabilistic formulations of existing methods are not useful for quasispecies populations where the strains are highly genetically related. The lack of knowledge on the number of different strains in a quasispecies population is observed to hinder the precision of existing Viral Quasispecies Spectrum Reconstruction (QSR) methods due to the uncontrolled reconstruction of a large number of in silico false positives. In this work, we formulated a novel probabilistic method for strain richness estimation specifically targeting viral quasispecies. By using this approach we improved our recently proposed spectrum reconstruction pipeline ViQuaS to achieve higher levels of precision in reconstructed quasispecies spectra without compromising the recall rates. We also discuss how one other existing popular QSR method named ShoRAH can be improved using this new approach. Results On benchmark data sets, our estimation method provided accurate richness estimates (< 0.2 median estimation error) and improved the precision of ViQuaS by 2%-13% and F-score by 1%-9% without compromising the recall rates. We also demonstrate that our estimation method can be used to improve the precision and F-score of ShoRAH by 0%-7% and 0%-5% respectively. Conclusions The proposed probabilistic estimation method can be used to estimate the richness of viral populations with a quasispecies behavior and to improve the accuracy of the quasispecies spectra reconstructed by the existing methods ViQuaS and ShoRAH in the presence of a moderate level of technical sequencing errors. Availability http://sourceforge.net/projects/viquas/ PMID:26678073
Li, Kui; Wang, Lei; Lv, Yanhong; Gao, Pengyu; Song, Tianxiao
2015-01-01
Getting a land vehicle’s accurate position, azimuth and attitude rapidly is significant for vehicle based weapons’ combat effectiveness. In this paper, a new approach to acquire vehicle’s accurate position and orientation is proposed. It uses biaxial optical detection platform (BODP) to aim at and lock in no less than three pre-set cooperative targets, whose accurate positions are measured beforehand. Then, it calculates the vehicle’s accurate position, azimuth and attitudes by the rough position and orientation provided by vehicle based navigation systems and no less than three couples of azimuth and pitch angles measured by BODP. The proposed approach does not depend on Global Navigation Satellite System (GNSS), thus it is autonomous and difficult to interfere. Meanwhile, it only needs a rough position and orientation as algorithm’s iterative initial value, consequently, it does not have high performance requirement for Inertial Navigation System (INS), odometer and other vehicle based navigation systems, even in high precise applications. This paper described the system’s working procedure, presented theoretical deviation of the algorithm, and then verified its effectiveness through simulation and vehicle experiments. The simulation and experimental results indicate that the proposed approach can achieve positioning and orientation accuracy of 0.2 m and 20″ respectively in less than 3 min. PMID:26492249
Li, Kui; Wang, Lei; Lv, Yanhong; Gao, Pengyu; Song, Tianxiao
2015-01-01
Getting a land vehicle's accurate position, azimuth and attitude rapidly is significant for vehicle based weapons' combat effectiveness. In this paper, a new approach to acquire vehicle's accurate position and orientation is proposed. It uses biaxial optical detection platform (BODP) to aim at and lock in no less than three pre-set cooperative targets, whose accurate positions are measured beforehand. Then, it calculates the vehicle's accurate position, azimuth and attitudes by the rough position and orientation provided by vehicle based navigation systems and no less than three couples of azimuth and pitch angles measured by BODP. The proposed approach does not depend on Global Navigation Satellite System (GNSS), thus it is autonomous and difficult to interfere. Meanwhile, it only needs a rough position and orientation as algorithm's iterative initial value, consequently, it does not have high performance requirement for Inertial Navigation System (INS), odometer and other vehicle based navigation systems, even in high precise applications. This paper described the system's working procedure, presented theoretical deviation of the algorithm, and then verified its effectiveness through simulation and vehicle experiments. The simulation and experimental results indicate that the proposed approach can achieve positioning and orientation accuracy of 0.2 m and 20″ respectively in less than 3 min. PMID:26492249
Approaches to relativistic positioning around Earth and error estimations
NASA Astrophysics Data System (ADS)
Puchades, Neus; Sáez, Diego
2016-01-01
In the context of relativistic positioning, the coordinates of a given user may be calculated by using suitable information broadcast by a 4-tuple of satellites. Our 4-tuples belong to the Galileo constellation. Recently, we estimated the positioning errors due to uncertainties in the satellite world lines (U-errors). A distribution of U-errors was obtained, at various times, in a set of points covering a large region surrounding Earth. Here, the positioning errors associated to the simplifying assumption that photons move in Minkowski space-time (S-errors) are estimated and compared with the U-errors. Both errors have been calculated for the same points and times to make comparisons possible. For a certain realistic modeling of the world line uncertainties, the estimated S-errors have proved to be smaller than the U-errors, which shows that the approach based on the assumption that the Earth's gravitational field produces negligible effects on photons may be used in a large region surrounding Earth. The applicability of this approach - which simplifies numerical calculations - to positioning problems, and the usefulness of our S-error maps, are pointed out. A better approach, based on the assumption that photons move in the Schwarzschild space-time governed by an idealized Earth, is also analyzed. More accurate descriptions of photon propagation involving non symmetric space-time structures are not necessary for ordinary positioning and spacecraft navigation around Earth.
Position Estimation of Transceivers in Communication Networks
Dowla, F; Kent, C
2004-01-20
With rapid developments in wireless sensor networks, there is a growing need for transceiver position estimation independent of GPS, which may not be available in indoor networks. Our approach is to use range estimates from time-of-flight (TOF) measurements, a technique well suited to large bandwidth physical links, such as in ultra-wideband (UWB) systems. In our UWB systems, pulse duration less than 200 psecs can easily be resolved to less than a foot. Assuming an encoded UWB physical layer, we first test positioning accuracy using simulations. We are interested in sensitivity to range errors and the required number of ranging nodes, and we show that in a high-precision environment, such as UWB, the optimal number of transmitters is four. Four transmitters with {+-}20ft. range error can locate a receiver to within one or two feet. We then implement these algorithms on an 802.11 wireless network and demonstrate the ability to locate a network access point to approximately 20 feet.
Accurate biopsy-needle depth estimation in limited-angle tomography using multi-view geometry
NASA Astrophysics Data System (ADS)
van der Sommen, Fons; Zinger, Sveta; de With, Peter H. N.
2016-03-01
Recently, compressed-sensing based algorithms have enabled volume reconstruction from projection images acquired over a relatively small angle (θ < 20°). These methods enable accurate depth estimation of surgical tools with respect to anatomical structures. However, they are computationally expensive and time consuming, rendering them unattractive for image-guided interventions. We propose an alternative approach for depth estimation of biopsy needles during image-guided interventions, in which we split the problem into two parts and solve them independently: needle-depth estimation and volume reconstruction. The complete proposed system consists of the previous two steps, preceded by needle extraction. First, we detect the biopsy needle in the projection images and remove it by interpolation. Next, we exploit epipolar geometry to find point-to-point correspondences in the projection images to triangulate the 3D position of the needle in the volume. Finally, we use the interpolated projection images to reconstruct the local anatomical structures and indicate the position of the needle within this volume. For validation of the algorithm, we have recorded a full CT scan of a phantom with an inserted biopsy needle. The performance of our approach ranges from a median error of 2.94 mm for an distributed viewing angle of 1° down to an error of 0.30 mm for an angle larger than 10°. Based on the results of this initial phantom study, we conclude that multi-view geometry offers an attractive alternative to time-consuming iterative methods for the depth estimation of surgical tools during C-arm-based image-guided interventions.
NASA Astrophysics Data System (ADS)
Kawasaki, Makoto; Kohno, Ryuji
Wireless communication devices in the field of medical implant, such as cardiac pacemakers and capsule endoscopes, have been studied and developed to improve healthcare systems. Especially it is very important to know the range and position of each device because it will contribute to an optimization of the transmission power. We adopt the time-based approach of position estimation using ultra wideband signals. However, the propagation velocity inside the human body differs in each tissue and each frequency. Furthermore, the human body is formed of various tissues with complex structures. For this reason, propagation velocity is different at a different point inside human body and the received signal so distorted through the channel inside human body. In this paper, we apply an adaptive template synthesis method in multipath channel for calculate the propagation time accurately based on the output of the correlator between the transmitter and the receiver. Furthermore, we propose a position estimation method using an estimation of the propagation velocity inside the human body. In addition, we show by computer simulation that the proposal method can perform accurate positioning with a size of medical implanted devices such as a medicine capsule.
NASA Astrophysics Data System (ADS)
Zhao, Xiang; Lin, Jiming
2016-04-01
Image sensor-based visible light positioning can be applied not only to indoor environments but also to outdoor environments. To determine the performance bounds of the positioning accuracy from the view of statistical optimization for an outdoor image sensor-based visible light positioning system, we analyze and derive the maximum likelihood estimation and corresponding Cramér-Rao lower bounds of vehicle position, under the condition that the observation values of the light-emitting diode (LED) imaging points are affected by white Gaussian noise. For typical parameters of an LED traffic light and in-vehicle camera image sensor, simulation results show that accurate estimates are available, with positioning error generally less than 0.1 m at a communication distance of 30 m between the LED array transmitter and the camera receiver. With the communication distance being constant, the positioning accuracy depends on the number of LEDs used, the focal length of the lens, the pixel size, and the frame rate of the camera receiver.
Monocular camera and IMU integration for indoor position estimation.
Zhang, Yinlong; Tan, Jindong; Zeng, Ziming; Liang, Wei; Xia, Ye
2014-01-01
This paper presents a monocular camera (MC) and inertial measurement unit (IMU) integrated approach for indoor position estimation. Unlike the traditional estimation methods, we fix the monocular camera downward to the floor and collect successive frames where textures are orderly distributed and feature points robustly detected, rather than using forward oriented camera in sampling unknown and disordered scenes with pre-determined frame rate and auto-focus metric scale. Meanwhile, camera adopts the constant metric scale and adaptive frame rate determined by IMU data. Furthermore, the corresponding distinctive image feature point matching approaches are employed for visual localizing, i.e., optical flow for fast motion mode; Canny Edge Detector & Harris Feature Point Detector & Sift Descriptor for slow motion mode. For superfast motion and abrupt rotation where images from camera are blurred and unusable, the Extended Kalman Filter is exploited to estimate IMU outputs and to derive the corresponding trajectory. Experimental results validate that our proposed method is effective and accurate in indoor positioning. Since our system is computationally efficient and in compact size, it's well suited for visually impaired people indoor navigation and wheelchaired people indoor localization. PMID:25570179
Direct Rotor-Position Estimation Method for Salient Pole PM Motor by Using High-Frequency Voltage
NASA Astrophysics Data System (ADS)
Ito, Masato; Kinpara, Yoshihiko
Recently, a number of methods have been proposed for estimating the rotor position of a salient pole PM motor, and methods using a high-frequency voltage can estimate the rotor position accurately, even at low speeds. In the conventional method, the rotor position is estimated indirectly by minimizing the position error signal associated with the difference between the estimated position and the real one. This paper proposes a novel direct rotor-position estimation method for salient pole PM motors. In this method, a rotating high-frequency voltage is supplied to the motor, and the rotor position is estimated directly from the high-frequency current in the motor.
Accurate Visual Heading Estimation at High Rotation Rate Without Oculomotor or Static-Depth Cues
NASA Technical Reports Server (NTRS)
Stone, Leland S.; Perrone, John A.; Null, Cynthia H. (Technical Monitor)
1995-01-01
It has been claimed that either oculomotor or static depth cues provide the signals about self-rotation necessary approx.-1 deg/s. We tested this hypothesis by simulating self-motion along a curved path with the eyes fixed in the head (plus or minus 16 deg/s of rotation). Curvilinear motion offers two advantages: 1) heading remains constant in retinotopic coordinates, and 2) there is no visual-oculomotor conflict (both actual and simulated eye position remain stationary). We simulated 400 ms of rotation combined with 16 m/s of translation at fixed angles with respect to gaze towards two vertical planes of random dots initially 12 and 24 m away, with a field of view of 45 degrees. Four subjects were asked to fixate a central cross and to respond whether they were translating to the left or right of straight-ahead gaze. From the psychometric curves, heading bias (mean) and precision (semi-interquartile) were derived. The mean bias over 2-5 runs was 3.0, 4.0, -2.0, -0.4 deg for the first author and three naive subjects, respectively (positive indicating towards the rotation direction). The mean precision was 2.0, 1.9, 3.1, 1.6 deg. respectively. The ability of observers to make relatively accurate and precise heading judgments, despite the large rotational flow component, refutes the view that extra-flow-field information is necessary for human visual heading estimation at high rotation rates. Our results support models that process combined translational/rotational flow to estimate heading, but should not be construed to suggest that other cues do not play an important role when they are available to the observer.
NASA Astrophysics Data System (ADS)
Jauncey, David L.; White, Graeme L.; Preston, Robert A.; Niell, Arthur E.; Harvey, Bruce R.; Morabito, David D.; Meier, David L.; Slade, Martin A.; Stolz, Artur; Tzioumis, Anastasios K.
1989-07-01
Radio positions measured on a 275 km baseline are given for six extragalactic sources south of declination -45°. The measurements were made using very long baseline interferometry (VLBI) at 2.3 and 8.4 GHz between the 64 m antennas at Parkes and Tidbinbilla, Australia. Positions with accuracies of ±0.11 arcsec in right ascension and ±0.08 arcsec in declination are given with respect to the JPL VLBI reference frame. This program is a first step in establishing an accurate radio reference frame in the mid-latitude to polar regions of the southern hemisphere. Accurate optical positions have also been determined from glass plate copies of the ESO B Schmidt atlas using reference stars from the Perth 70 catalog. A comparison between the optical and radio positions yields mean differences (optical - radio) of -0.02 ± 0.09 and 0.05 ± 0.13 arcsec in right ascension and declination, respectively. On average, the optical reference frame south of -45°, the FK4 as defined by the Perth 70 catalog, and the VLBI radio reference frame as defined by the present six sources, appear to be consistent at the tenth of an arcsecond level.
Browning, Sharon R.; Browning, Brian L.
2015-01-01
Existing methods for estimating historical effective population size from genetic data have been unable to accurately estimate effective population size during the most recent past. We present a non-parametric method for accurately estimating recent effective population size by using inferred long segments of identity by descent (IBD). We found that inferred segments of IBD contain information about effective population size from around 4 generations to around 50 generations ago for SNP array data and to over 200 generations ago for sequence data. In human populations that we examined, the estimates of effective size were approximately one-third of the census size. We estimate the effective population size of European-ancestry individuals in the UK four generations ago to be eight million and the effective population size of Finland four generations ago to be 0.7 million. Our method is implemented in the open-source IBDNe software package. PMID:26299365
NASA Astrophysics Data System (ADS)
Vizireanu, D. N.; Halunga, S. V.
2012-04-01
A simple, fast and accurate amplitude estimation algorithm of sinusoidal signals for DSP based instrumentation is proposed. It is shown that eight samples, used in two steps, are sufficient. A practical analytical formula for amplitude estimation is obtained. Numerical results are presented. Simulations have been performed when the sampled signal is affected by white Gaussian noise and when the samples are quantized on a given number of bits.
Lossius, Hans Morten; Wemmelund, Kristian; Stokkeland, Paal Johan; Knudsen, Lars; Sloth, Erik
2013-01-01
Background: Although thoracic ultrasonography accurately determines the size and extent of occult pneumothoraces (PTXs) in spontaneously breathing patients, there is uncertainty about patients receiving positive pressure ventilation. We compared the lung point (ie, the area where the collapsed lung still adheres to the inside of the chest wall) using the two modalities ultrasonography and CT scanning to determine whether ultrasonography can be used reliably to assess PTX progression in a positive-pressure-ventilated porcine model. Methods: Air was introduced in incremental steps into five hemithoraces in three intubated porcine models. The lung point was identified on ultrasound imaging and referenced against the lateral limit of the intrapleural air space identified on the CT scans. The distance from the sternum to the lung point (S-LP) was measured on the CT scans and correlated to the insufflated air volume. Results: The mean total difference between the 131 ultrasound and CT scan lung points was 6.8 mm (SD, 7.1 mm; range, 0.0-29.3 mm). A mixed-model regression analysis showed a linear relationship between the S-LP distances and the PTX volume (P < .001). Conclusions: In an experimental porcine model, we found a linear relation between the PTX size and the lateral position of the lung point. The accuracy of thoracic ultrasonography for identifying the lung point (and, thus, the PTX extent) was comparable to that of CT imaging. These clinically relevant results suggest that ultrasonography may be safe and accurate in monitoring PTX progression during positive pressure ventilation. PMID:23188058
On the accurate estimation of gap fraction during daytime with digital cover photography
NASA Astrophysics Data System (ADS)
Hwang, Y. R.; Ryu, Y.; Kimm, H.; Macfarlane, C.; Lang, M.; Sonnentag, O.
2015-12-01
Digital cover photography (DCP) has emerged as an indirect method to obtain gap fraction accurately. Thus far, however, the intervention of subjectivity, such as determining the camera relative exposure value (REV) and threshold in the histogram, hindered computing accurate gap fraction. Here we propose a novel method that enables us to measure gap fraction accurately during daytime under various sky conditions by DCP. The novel method computes gap fraction using a single DCP unsaturated raw image which is corrected for scattering effects by canopies and a reconstructed sky image from the raw format image. To test the sensitivity of the novel method derived gap fraction to diverse REVs, solar zenith angles and canopy structures, we took photos in one hour interval between sunrise to midday under dense and sparse canopies with REV 0 to -5. The novel method showed little variation of gap fraction across different REVs in both dense and spares canopies across diverse range of solar zenith angles. The perforated panel experiment, which was used to test the accuracy of the estimated gap fraction, confirmed that the novel method resulted in the accurate and consistent gap fractions across different hole sizes, gap fractions and solar zenith angles. These findings highlight that the novel method opens new opportunities to estimate gap fraction accurately during daytime from sparse to dense canopies, which will be useful in monitoring LAI precisely and validating satellite remote sensing LAI products efficiently.
A new geometric-based model to accurately estimate arm and leg inertial estimates.
Wicke, Jason; Dumas, Geneviève A
2014-06-01
Segment estimates of mass, center of mass and moment of inertia are required input parameters to analyze the forces and moments acting across the joints. The objectives of this study were to propose a new geometric model for limb segments, to evaluate it against criterion values obtained from DXA, and to compare its performance to five other popular models. Twenty five female and 24 male college students participated in the study. For the criterion measures, the participants underwent a whole body DXA scan, and estimates for segment mass, center of mass location, and moment of inertia (frontal plane) were directly computed from the DXA mass units. For the new model, the volume was determined from two standing frontal and sagittal photographs. Each segment was modeled as a stack of slices, the sections of which were ellipses if they are not adjoining another segment and sectioned ellipses if they were adjoining another segment (e.g. upper arm and trunk). Length of axes of the ellipses was obtained from the photographs. In addition, a sex-specific, non-uniform density function was developed for each segment. A series of anthropometric measurements were also taken by directly following the definitions provided of the different body segment models tested, and the same parameters determined for each model. Comparison of models showed that estimates from the new model were consistently closer to the DXA criterion than those from the other models, with an error of less than 5% for mass and moment of inertia and less than about 6% for center of mass location. PMID:24735506
Accurate Estimation of the Entropy of Rotation-Translation Probability Distributions.
Fogolari, Federico; Dongmo Foumthuim, Cedrix Jurgal; Fortuna, Sara; Soler, Miguel Angel; Corazza, Alessandra; Esposito, Gennaro
2016-01-12
The estimation of rotational and translational entropies in the context of ligand binding has been the subject of long-time investigations. The high dimensionality (six) of the problem and the limited amount of sampling often prevent the required resolution to provide accurate estimates by the histogram method. Recently, the nearest-neighbor distance method has been applied to the problem, but the solutions provided either address rotation and translation separately, therefore lacking correlations, or use a heuristic approach. Here we address rotational-translational entropy estimation in the context of nearest-neighbor-based entropy estimation, solve the problem numerically, and provide an exact and an approximate method to estimate the full rotational-translational entropy. PMID:26605696
Damon, Bruce M.; Heemskerk, Anneriet M.; Ding, Zhaohua
2012-01-01
Fiber curvature is a functionally significant muscle structural property, but its estimation from diffusion-tensor MRI fiber tracking data may be confounded by noise. The purpose of this study was to investigate the use of polynomial fitting of fiber tracts for improving the accuracy and precision of fiber curvature (κ) measurements. Simulated image datasets were created in order to provide data with known values for κ and pennation angle (θ). Simulations were designed to test the effects of increasing inherent fiber curvature (3.8, 7.9, 11.8, and 15.3 m−1), signal-to-noise ratio (50, 75, 100, and 150), and voxel geometry (13.8 and 27.0 mm3 voxel volume with isotropic resolution; 13.5 mm3 volume with an aspect ratio of 4.0) on κ and θ measurements. In the originally reconstructed tracts, θ was estimated accurately under most curvature and all imaging conditions studied; however, the estimates of κ were imprecise and inaccurate. Fitting the tracts to 2nd order polynomial functions provided accurate and precise estimates of κ for all conditions except very high curvature (κ=15.3 m−1), while preserving the accuracy of the θ estimates. Similarly, polynomial fitting of in vivo fiber tracking data reduced the κ values of fitted tracts from those of unfitted tracts and did not change the θ values. Polynomial fitting of fiber tracts allows accurate estimation of physiologically reasonable values of κ, while preserving the accuracy of θ estimation. PMID:22503094
NASA Astrophysics Data System (ADS)
Donoso, Guillermo; Ladera, Celso L.
2016-09-01
An accurate linear optical displacement transducer of about 0.2 mm resolution over a range of ∼40 mm is presented. This device consists of a stack of thin cellulose acetate strips, each strip longitudinally slid ∼0.5 mm over the precedent one so that one end of the stack becomes a stepped wedge of constant step. A narrowed light beam from a white LED orthogonally incident crosses the wedge at a known point, the transmitted intensity being detected with a phototransistor whose emitter is connected to a diode. We present the interesting analytical proof that the voltage across the diode is linearly dependent upon the ordinate of the point where the light beam falls on the wedge, as well as the experimental validation of such a theoretical proof. Applications to nonlinear oscillations are then presented—including the interesting case of a body moving under dry friction, and the more advanced case of an oscillator in a quartic energy potential—whose time-varying positions were accurately measured with our transducer. Our sensing device can resolve the dynamics of an object attached to it with great accuracy and precision at a cost considerably less than that of a linear neutral density wedge. The technique used to assemble the wedge of acetate strips is described.
NASA Technical Reports Server (NTRS)
Lee, Harry
1994-01-01
A highly accurate transmission line fault locator based on the traveling-wave principle was developed and successfully operated within B.C. Hydro. A transmission line fault produces a fast-risetime traveling wave at the fault point which propagates along the transmission line. This fault locator system consists of traveling wave detectors located at key substations which detect and time tag the leading edge of the fault-generated traveling wave as if passes through. A master station gathers the time-tagged information from the remote detectors and determines the location of the fault. Precise time is a key element to the success of this system. This fault locator system derives its timing from the Global Positioning System (GPS) satellites. System tests confirmed the accuracy of locating faults to within the design objective of +/-300 meters.
Simultaneous, accurate measurement of the 3D position and orientation of single molecules
Backlund, Mikael P.; Lew, Matthew D.; Backer, Adam S.; Sahl, Steffen J.; Grover, Ginni; Agrawal, Anurag; Piestun, Rafael; Moerner, W. E.
2012-01-01
Recently, single molecule-based superresolution fluorescence microscopy has surpassed the diffraction limit to improve resolution to the order of 20 nm or better. These methods typically use image fitting that assumes an isotropic emission pattern from the single emitters as well as control of the emitter concentration. However, anisotropic single-molecule emission patterns arise from the transition dipole when it is rotationally immobile, depending highly on the molecule’s 3D orientation and z position. Failure to account for this fact can lead to significant lateral (x, y) mislocalizations (up to ∼50–200 nm). This systematic error can cause distortions in the reconstructed images, which can translate into degraded resolution. Using parameters uniquely inherent in the double-lobed nature of the Double-Helix Point Spread Function, we account for such mislocalizations and simultaneously measure 3D molecular orientation and 3D position. Mislocalizations during an axial scan of a single molecule manifest themselves as an apparent lateral shift in its position, which causes the standard deviation (SD) of its lateral position to appear larger than the SD expected from photon shot noise. By correcting each localization based on an estimated orientation, we are able to improve SDs in lateral localization from ∼2× worse than photon-limited precision (48 vs. 25 nm) to within 5 nm of photon-limited precision. Furthermore, by averaging many estimations of orientation over different depths, we are able to improve from a lateral SD of 116 (∼4× worse than the photon-limited precision; 28 nm) to 34 nm (within 6 nm of the photon limit). PMID:23129640
NASA Astrophysics Data System (ADS)
Moreira, António H. J.; Queirós, Sandro; Morais, Pedro; Rodrigues, Nuno F.; Correia, André Ricardo; Fernandes, Valter; Pinho, A. C. M.; Fonseca, Jaime C.; Vilaça, João. L.
2015-03-01
The success of dental implant-supported prosthesis is directly linked to the accuracy obtained during implant's pose estimation (position and orientation). Although traditional impression techniques and recent digital acquisition methods are acceptably accurate, a simultaneously fast, accurate and operator-independent methodology is still lacking. Hereto, an image-based framework is proposed to estimate the patient-specific implant's pose using cone-beam computed tomography (CBCT) and prior knowledge of implanted model. The pose estimation is accomplished in a threestep approach: (1) a region-of-interest is extracted from the CBCT data using 2 operator-defined points at the implant's main axis; (2) a simulated CBCT volume of the known implanted model is generated through Feldkamp-Davis-Kress reconstruction and coarsely aligned to the defined axis; and (3) a voxel-based rigid registration is performed to optimally align both patient and simulated CBCT data, extracting the implant's pose from the optimal transformation. Three experiments were performed to evaluate the framework: (1) an in silico study using 48 implants distributed through 12 tridimensional synthetic mandibular models; (2) an in vitro study using an artificial mandible with 2 dental implants acquired with an i-CAT system; and (3) two clinical case studies. The results shown positional errors of 67+/-34μm and 108μm, and angular misfits of 0.15+/-0.08° and 1.4°, for experiment 1 and 2, respectively. Moreover, in experiment 3, visual assessment of clinical data results shown a coherent alignment of the reference implant. Overall, a novel image-based framework for implants' pose estimation from CBCT data was proposed, showing accurate results in agreement with dental prosthesis modelling requirements.
Accurate estimation of forest carbon stocks by 3-D remote sensing of individual trees.
Omasa, Kenji; Qiu, Guo Yu; Watanuki, Kenichi; Yoshimi, Kenji; Akiyama, Yukihide
2003-03-15
Forests are one of the most important carbon sinks on Earth. However, owing to the complex structure, variable geography, and large area of forests, accurate estimation of forest carbon stocks is still a challenge for both site surveying and remote sensing. For these reasons, the Kyoto Protocol requires the establishment of methodologies for estimating the carbon stocks of forests (Kyoto Protocol, Article 5). A possible solution to this challenge is to remotely measure the carbon stocks of every tree in an entire forest. Here, we present a methodology for estimating carbon stocks of a Japanese cedar forest by using a high-resolution, helicopter-borne 3-dimensional (3-D) scanning lidar system that measures the 3-D canopy structure of every tree in a forest. Results show that a digital image (10-cm mesh) of woody canopy can be acquired. The treetop can be detected automatically with a reasonable accuracy. The absolute error ranges for tree height measurements are within 42 cm. Allometric relationships of height to carbon stocks then permit estimation of total carbon storage by measurement of carbon stocks of every tree. Thus, we suggest that our methodology can be used to accurately estimate the carbon stocks of Japanese cedar forests at a stand scale. Periodic measurements will reveal changes in forest carbon stocks. PMID:12680675
Hwang, Beomsoo; Jeon, Doyoung
2015-01-01
In exoskeletal robots, the quantification of the user's muscular effort is important to recognize the user's motion intentions and evaluate motor abilities. In this paper, we attempt to estimate users' muscular efforts accurately using joint torque sensor which contains the measurements of dynamic effect of human body such as the inertial, Coriolis, and gravitational torques as well as torque by active muscular effort. It is important to extract the dynamic effects of the user's limb accurately from the measured torque. The user's limb dynamics are formulated and a convenient method of identifying user-specific parameters is suggested for estimating the user's muscular torque in robotic exoskeletons. Experiments were carried out on a wheelchair-integrated lower limb exoskeleton, EXOwheel, which was equipped with torque sensors in the hip and knee joints. The proposed methods were evaluated by 10 healthy participants during body weight-supported gait training. The experimental results show that the torque sensors are to estimate the muscular torque accurately in cases of relaxed and activated muscle conditions. PMID:25860074
Technical note: tree truthing: how accurate are substrate estimates in primate field studies?
Bezanson, Michelle; Watts, Sean M; Jobin, Matthew J
2012-04-01
Field studies of primate positional behavior typically rely on ground-level estimates of substrate size, angle, and canopy location. These estimates potentially influence the identification of positional modes by the observer recording behaviors. In this study we aim to test ground-level estimates against direct measurements of support angles, diameters, and canopy heights in trees at La Suerte Biological Research Station in Costa Rica. After reviewing methods that have been used by past researchers, we provide data collected within trees that are compared to estimates obtained from the ground. We climbed five trees and measured 20 supports. Four observers collected measurements of each support from different locations on the ground. Diameter estimates varied from the direct tree measures by 0-28 cm (Mean: 5.44 ± 4.55). Substrate angles varied by 1-55° (Mean: 14.76 ± 14.02). Height in the tree was best estimated using a clinometer as estimates with a two-meter reference placed by the tree varied by 3-11 meters (Mean: 5.31 ± 2.44). We determined that the best support size estimates were those generated relative to the size of the focal animal and divided into broader categories. Support angles were best estimated in 5° increments and then checked using a Haglöf clinometer in combination with a laser pointer. We conclude that three major factors should be addressed when estimating support features: observer error (e.g., experience and distance from the target), support deformity, and how support size and angle influence the positional mode selected by a primate individual. individual. PMID:22371099
Underwater terrain positioning method based on least squares estimation for AUV
NASA Astrophysics Data System (ADS)
Chen, Peng-yun; Li, Ye; Su, Yu-min; Chen, Xiao-long; Jiang, Yan-qing
2015-12-01
To achieve accurate positioning of autonomous underwater vehicles, an appropriate underwater terrain database storage format for underwater terrain-matching positioning is established using multi-beam data as underwater terrainmatching data. An underwater terrain interpolation error compensation method based on fractional Brownian motion is proposed for defects of normal terrain interpolation, and an underwater terrain-matching positioning method based on least squares estimation (LSE) is proposed for correlation analysis of topographic features. The Fisher method is introduced as a secondary criterion for pseudo localization appearing in a topographic features flat area, effectively reducing the impact of pseudo positioning points on matching accuracy and improving the positioning accuracy of terrain flat areas. Simulation experiments based on electronic chart and multi-beam sea trial data show that drift errors of an inertial navigation system can be corrected effectively using the proposed method. The positioning accuracy and practicality are high, satisfying the requirement of underwater accurate positioning.
Yu, Jihnhee; Yang, Luge; Vexler, Albert; Hutson, Alan D
2016-06-15
The receiver operating characteristic (ROC) curve is a popular technique with applications, for example, investigating an accuracy of a biomarker to delineate between disease and non-disease groups. A common measure of accuracy of a given diagnostic marker is the area under the ROC curve (AUC). In contrast with the AUC, the partial area under the ROC curve (pAUC) looks into the area with certain specificities (i.e., true negative rate) only, and it can be often clinically more relevant than examining the entire ROC curve. The pAUC is commonly estimated based on a U-statistic with the plug-in sample quantile, making the estimator a non-traditional U-statistic. In this article, we propose an accurate and easy method to obtain the variance of the nonparametric pAUC estimator. The proposed method is easy to implement for both one biomarker test and the comparison of two correlated biomarkers because it simply adapts the existing variance estimator of U-statistics. In this article, we show accuracy and other advantages of the proposed variance estimation method by broadly comparing it with previously existing methods. Further, we develop an empirical likelihood inference method based on the proposed variance estimator through a simple implementation. In an application, we demonstrate that, depending on the inferences by either the AUC or pAUC, we can make a different decision on a prognostic ability of a same set of biomarkers. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26790540
Estimating the Effective Permittivity for Reconstructing Accurate Microwave-Radar Images.
Lavoie, Benjamin R; Okoniewski, Michal; Fear, Elise C
2016-01-01
We present preliminary results from a method for estimating the optimal effective permittivity for reconstructing microwave-radar images. Using knowledge of how microwave-radar images are formed, we identify characteristics that are typical of good images, and define a fitness function to measure the relative image quality. We build a polynomial interpolant of the fitness function in order to identify the most likely permittivity values of the tissue. To make the estimation process more efficient, the polynomial interpolant is constructed using a locally and dimensionally adaptive sampling method that is a novel combination of stochastic collocation and polynomial chaos. Examples, using a series of simulated, experimental and patient data collected using the Tissue Sensing Adaptive Radar system, which is under development at the University of Calgary, are presented. These examples show how, using our method, accurate images can be reconstructed starting with only a broad estimate of the permittivity range. PMID:27611785
Effective Echo Detection and Accurate Orbit Estimation Algorithms for Space Debris Radar
NASA Astrophysics Data System (ADS)
Isoda, Kentaro; Sakamoto, Takuya; Sato, Toru
Orbit estimation of space debris, objects of no inherent value orbiting the earth, is a task that is important for avoiding collisions with spacecraft. The Kamisaibara Spaceguard Center radar system was built in 2004 as the first radar facility in Japan devoted to the observation of space debris. In order to detect the smaller debris, coherent integration is effective in improving SNR (Signal-to-Noise Ratio). However, it is difficult to apply coherent integration to real data because the motions of the targets are unknown. An effective algorithm is proposed for echo detection and orbit estimation of the faint echoes from space debris. The characteristics of the evaluation function are utilized by the algorithm. Experiments show the proposed algorithm improves SNR by 8.32dB and enables estimation of orbital parameters accurately to allow for re-tracking with a single radar.
Loewe, Axel; Wilhelms, Mathias; Schmid, Jochen; Krause, Mathias J.; Fischer, Fathima; Thomas, Dierk; Scholz, Eberhard P.; Dössel, Olaf; Seemann, Gunnar
2016-01-01
Computational models of cardiac electrophysiology provided insights into arrhythmogenesis and paved the way toward tailored therapies in the last years. To fully leverage in silico models in future research, these models need to be adapted to reflect pathologies, genetic alterations, or pharmacological effects, however. A common approach is to leave the structure of established models unaltered and estimate the values of a set of parameters. Today’s high-throughput patch clamp data acquisition methods require robust, unsupervised algorithms that estimate parameters both accurately and reliably. In this work, two classes of optimization approaches are evaluated: gradient-based trust-region-reflective and derivative-free particle swarm algorithms. Using synthetic input data and different ion current formulations from the Courtemanche et al. electrophysiological model of human atrial myocytes, we show that neither of the two schemes alone succeeds to meet all requirements. Sequential combination of the two algorithms did improve the performance to some extent but not satisfactorily. Thus, we propose a novel hybrid approach coupling the two algorithms in each iteration. This hybrid approach yielded very accurate estimates with minimal dependency on the initial guess using synthetic input data for which a ground truth parameter set exists. When applied to measured data, the hybrid approach yielded the best fit, again with minimal variation. Using the proposed algorithm, a single run is sufficient to estimate the parameters. The degree of superiority over the other investigated algorithms in terms of accuracy and robustness depended on the type of current. In contrast to the non-hybrid approaches, the proposed method proved to be optimal for data of arbitrary signal to noise ratio. The hybrid algorithm proposed in this work provides an important tool to integrate experimental data into computational models both accurately and robustly allowing to assess the often non
NASA Technical Reports Server (NTRS)
Savage, A.
1986-01-01
Several programs are making use of UKST Sky Survey plates to identify southern radio sources. The fine-grain modern plates and accurate radio positions give a much improved identification rate. It seems that it will very soon be possible to determine whether or not there is a quasar redshift cut-off at z of about 4. There is an urgent need for more accurate fundamental reference star positions in the South.
NASA Astrophysics Data System (ADS)
Yang, Que; Wang, Shanshan; Wang, Kai; Zhang, Chunyu; Zhang, Lu; Meng, Qingyu; Zhu, Qiudong
2015-08-01
For normal eyes without history of any ocular surgery, traditional equations for calculating intraocular lens (IOL) power, such as SRK-T, Holladay, Higis, SRK-II, et al., all were relativley accurate. However, for eyes underwent refractive surgeries, such as LASIK, or eyes diagnosed as keratoconus, these equations may cause significant postoperative refractive error, which may cause poor satisfaction after cataract surgery. Although some methods have been carried out to solve this problem, such as Hagis-L equation[1], or using preoperative data (data before LASIK) to estimate K value[2], no precise equations were available for these eyes. Here, we introduced a novel intraocular lens power estimation method by accurate ray tracing with optical design software ZEMAX. Instead of using traditional regression formula, we adopted the exact measured corneal elevation distribution, central corneal thickness, anterior chamber depth, axial length, and estimated effective lens plane as the input parameters. The calculation of intraocular lens power for a patient with keratoconus and another LASIK postoperative patient met very well with their visual capacity after cataract surgery.
NASA Astrophysics Data System (ADS)
Kasaragod, Deepa; Sugiyama, Satoshi; Ikuno, Yasushi; Alonso-Caneiro, David; Yamanari, Masahiro; Fukuda, Shinichi; Oshika, Tetsuro; Hong, Young-Joo; Li, En; Makita, Shuichi; Miura, Masahiro; Yasuno, Yoshiaki
2016-03-01
Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of OCT that contrasts the polarization properties of tissues. It has been applied to ophthalmology, cardiology, etc. Proper quantitative imaging is required for a widespread clinical utility. However, the conventional method of averaging to improve the signal to noise ratio (SNR) and the contrast of the phase retardation (or birefringence) images introduce a noise bias offset from the true value. This bias reduces the effectiveness of birefringence contrast for a quantitative study. Although coherent averaging of Jones matrix tomography has been widely utilized and has improved the image quality, the fundamental limitation of nonlinear dependency of phase retardation and birefringence to the SNR was not overcome. So the birefringence obtained by PS-OCT was still not accurate for a quantitative imaging. The nonlinear effect of SNR to phase retardation and birefringence measurement was previously formulated in detail for a Jones matrix OCT (JM-OCT) [1]. Based on this, we had developed a maximum a-posteriori (MAP) estimator and quantitative birefringence imaging was demonstrated [2]. However, this first version of estimator had a theoretical shortcoming. It did not take into account the stochastic nature of SNR of OCT signal. In this paper, we present an improved version of the MAP estimator which takes into account the stochastic property of SNR. This estimator uses a probability distribution function (PDF) of true local retardation, which is proportional to birefringence, under a specific set of measurements of the birefringence and SNR. The PDF was pre-computed by a Monte-Carlo (MC) simulation based on the mathematical model of JM-OCT before the measurement. A comparison between this new MAP estimator, our previous MAP estimator [2], and the standard mean estimator is presented. The comparisons are performed both by numerical simulation and in vivo measurements of anterior and
Regularization Based Iterative Point Match Weighting for Accurate Rigid Transformation Estimation.
Liu, Yonghuai; De Dominicis, Luigi; Wei, Baogang; Chen, Liang; Martin, Ralph R
2015-09-01
Feature extraction and matching (FEM) for 3D shapes finds numerous applications in computer graphics and vision for object modeling, retrieval, morphing, and recognition. However, unavoidable incorrect matches lead to inaccurate estimation of the transformation relating different datasets. Inspired by AdaBoost, this paper proposes a novel iterative re-weighting method to tackle the challenging problem of evaluating point matches established by typical FEM methods. Weights are used to indicate the degree of belief that each point match is correct. Our method has three key steps: (i) estimation of the underlying transformation using weighted least squares, (ii) penalty parameter estimation via minimization of the weighted variance of the matching errors, and (iii) weight re-estimation taking into account both matching errors and information learnt in previous iterations. A comparative study, based on real shapes captured by two laser scanners, shows that the proposed method outperforms four other state-of-the-art methods in terms of evaluating point matches between overlapping shapes established by two typical FEM methods, resulting in more accurate estimates of the underlying transformation. This improved transformation can be used to better initialize the iterative closest point algorithm and its variants, making 3D shape registration more likely to succeed. PMID:26357287
Positional estimation techniques for an autonomous mobile robot
NASA Technical Reports Server (NTRS)
Nandhakumar, N.; Aggarwal, J. K.
1990-01-01
Techniques for positional estimation of a mobile robot navigation in an indoor environment are described. A comprehensive review of the various positional estimation techniques studied in the literature is first presented. The techniques are divided into four different types and each of them is discussed briefly. Two different kinds of environments are considered for positional estimation; mountainous natural terrain and an urban, man-made environment with polyhedral buildings. In both cases, the robot is assumed to be equipped with single visual camera that can be panned and tilted and also a 3-D description (world model) of the environment is given. Such a description could be obtained from a stereo pair of aerial images or from the architectural plans of the buildings. Techniques for positional estimation using the camera input and the world model are presented.
Estimating Relative Positions of Outer-Space Structures
NASA Technical Reports Server (NTRS)
Balian, Harry; Breckenridge, William; Brugarolas, Paul
2009-01-01
A computer program estimates the relative position and orientation of two structures from measurements, made by use of electronic cameras and laser range finders on one structure, of distances and angular positions of fiducial objects on the other structure. The program was written specifically for use in determining errors in the alignment of large structures deployed in outer space from a space shuttle. The program is based partly on equations for transformations among the various coordinate systems involved in the measurements and on equations that account for errors in the transformation operators. It computes a least-squares estimate of the relative position and orientation. Sequential least-squares estimates, acquired at a measurement rate of 4 Hz, are averaged by passing them through a fourth-order Butterworth filter. The program is executed in a computer aboard the space shuttle, and its position and orientation estimates are displayed to astronauts on a graphical user interface.
Cancilla, John C; Díaz-Rodríguez, Pablo; Matute, Gemma; Torrecilla, José S
2015-02-14
The estimation of the density and refractive index of ternary mixtures comprising the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate, 2-propanol, and water at a fixed temperature of 298.15 K has been attempted through artificial neural networks. The obtained results indicate that the selection of this mathematical approach was a well-suited option. The mean prediction errors obtained, after simulating with a dataset never involved in the training process of the model, were 0.050% and 0.227% for refractive index and density estimation, respectively. These accurate results, which have been attained only using the composition of the dissolutions (mass fractions), imply that, most likely, ternary mixtures similar to the one analyzed, can be easily evaluated utilizing this algorithmic tool. In addition, different chemical processes involving ILs can be monitored precisely, and furthermore, the purity of the compounds in the studied mixtures can be indirectly assessed thanks to the high accuracy of the model. PMID:25583241
Sansone, Giuseppe; Maschio, Lorenzo; Usvyat, Denis; Schütz, Martin; Karttunen, Antti
2016-01-01
The black phosphorus (black-P) crystal is formed of covalently bound layers of phosphorene stacked together by weak van der Waals interactions. An experimental measurement of the exfoliation energy of black-P is not available presently, making theoretical studies the most important source of information for the optimization of phosphorene production. Here, we provide an accurate estimate of the exfoliation energy of black-P on the basis of multilevel quantum chemical calculations, which include the periodic local Møller-Plesset perturbation theory of second order, augmented by higher-order corrections, which are evaluated with finite clusters mimicking the crystal. Very similar results are also obtained by density functional theory with the D3-version of Grimme's empirical dispersion correction. Our estimate of the exfoliation energy for black-P of -151 meV/atom is substantially larger than that of graphite, suggesting the need for different strategies to generate isolated layers for these two systems. PMID:26651397
Lamb mode selection for accurate wall loss estimation via guided wave tomography
Huthwaite, P.; Ribichini, R.; Lowe, M. J. S.; Cawley, P.
2014-02-18
Guided wave tomography offers a method to accurately quantify wall thickness losses in pipes and vessels caused by corrosion. This is achieved using ultrasonic waves transmitted over distances of approximately 1–2m, which are measured by an array of transducers and then used to reconstruct a map of wall thickness throughout the inspected region. To achieve accurate estimations of remnant wall thickness, it is vital that a suitable Lamb mode is chosen. This paper presents a detailed evaluation of the fundamental modes, S{sub 0} and A{sub 0}, which are of primary interest in guided wave tomography thickness estimates since the higher order modes do not exist at all thicknesses, to compare their performance using both numerical and experimental data while considering a range of challenging phenomena. The sensitivity of A{sub 0} to thickness variations was shown to be superior to S{sub 0}, however, the attenuation from A{sub 0} when a liquid loading was present was much higher than S{sub 0}. A{sub 0} was less sensitive to the presence of coatings on the surface of than S{sub 0}.
Lamb mode selection for accurate wall loss estimation via guided wave tomography
NASA Astrophysics Data System (ADS)
Huthwaite, P.; Ribichini, R.; Lowe, M. J. S.; Cawley, P.
2014-02-01
Guided wave tomography offers a method to accurately quantify wall thickness losses in pipes and vessels caused by corrosion. This is achieved using ultrasonic waves transmitted over distances of approximately 1-2m, which are measured by an array of transducers and then used to reconstruct a map of wall thickness throughout the inspected region. To achieve accurate estimations of remnant wall thickness, it is vital that a suitable Lamb mode is chosen. This paper presents a detailed evaluation of the fundamental modes, S0 and A0, which are of primary interest in guided wave tomography thickness estimates since the higher order modes do not exist at all thicknesses, to compare their performance using both numerical and experimental data while considering a range of challenging phenomena. The sensitivity of A0 to thickness variations was shown to be superior to S0, however, the attenuation from A0 when a liquid loading was present was much higher than S0. A0 was less sensitive to the presence of coatings on the surface of than S0.
Removing the thermal component from heart rate provides an accurate VO2 estimation in forest work.
Dubé, Philippe-Antoine; Imbeau, Daniel; Dubeau, Denise; Lebel, Luc; Kolus, Ahmet
2016-05-01
Heart rate (HR) was monitored continuously in 41 forest workers performing brushcutting or tree planting work. 10-min seated rest periods were imposed during the workday to estimate the HR thermal component (ΔHRT) per Vogt et al. (1970, 1973). VO2 was measured using a portable gas analyzer during a morning submaximal step-test conducted at the work site, during a work bout over the course of the day (range: 9-74 min), and during an ensuing 10-min rest pause taken at the worksite. The VO2 estimated, from measured HR and from corrected HR (thermal component removed), were compared to VO2 measured during work and rest. Varied levels of HR thermal component (ΔHRTavg range: 0-38 bpm) originating from a wide range of ambient thermal conditions, thermal clothing insulation worn, and physical load exerted during work were observed. Using raw HR significantly overestimated measured work VO2 by 30% on average (range: 1%-64%). 74% of VO2 prediction error variance was explained by the HR thermal component. VO2 estimated from corrected HR, was not statistically different from measured VO2. Work VO2 can be estimated accurately in the presence of thermal stress using Vogt et al.'s method, which can be implemented easily by the practitioner with inexpensive instruments. PMID:26851474
Granata, Daniele; Carnevale, Vincenzo
2016-01-01
The collective behavior of a large number of degrees of freedom can be often described by a handful of variables. This observation justifies the use of dimensionality reduction approaches to model complex systems and motivates the search for a small set of relevant “collective” variables. Here, we analyze this issue by focusing on the optimal number of variable needed to capture the salient features of a generic dataset and develop a novel estimator for the intrinsic dimension (ID). By approximating geodesics with minimum distance paths on a graph, we analyze the distribution of pairwise distances around the maximum and exploit its dependency on the dimensionality to obtain an ID estimate. We show that the estimator does not depend on the shape of the intrinsic manifold and is highly accurate, even for exceedingly small sample sizes. We apply the method to several relevant datasets from image recognition databases and protein multiple sequence alignments and discuss possible interpretations for the estimated dimension in light of the correlations among input variables and of the information content of the dataset. PMID:27510265
Hybridization modeling of oligonucleotide SNP arrays for accurate DNA copy number estimation
Wan, Lin; Sun, Kelian; Ding, Qi; Cui, Yuehua; Li, Ming; Wen, Yalu; Elston, Robert C.; Qian, Minping; Fu, Wenjiang J
2009-01-01
Affymetrix SNP arrays have been widely used for single-nucleotide polymorphism (SNP) genotype calling and DNA copy number variation inference. Although numerous methods have achieved high accuracy in these fields, most studies have paid little attention to the modeling of hybridization of probes to off-target allele sequences, which can affect the accuracy greatly. In this study, we address this issue and demonstrate that hybridization with mismatch nucleotides (HWMMN) occurs in all SNP probe-sets and has a critical effect on the estimation of allelic concentrations (ACs). We study sequence binding through binding free energy and then binding affinity, and develop a probe intensity composite representation (PICR) model. The PICR model allows the estimation of ACs at a given SNP through statistical regression. Furthermore, we demonstrate with cell-line data of known true copy numbers that the PICR model can achieve reasonable accuracy in copy number estimation at a single SNP locus, by using the ratio of the estimated AC of each sample to that of the reference sample, and can reveal subtle genotype structure of SNPs at abnormal loci. We also demonstrate with HapMap data that the PICR model yields accurate SNP genotype calls consistently across samples, laboratories and even across array platforms. PMID:19586935
Granata, Daniele; Carnevale, Vincenzo
2016-01-01
The collective behavior of a large number of degrees of freedom can be often described by a handful of variables. This observation justifies the use of dimensionality reduction approaches to model complex systems and motivates the search for a small set of relevant "collective" variables. Here, we analyze this issue by focusing on the optimal number of variable needed to capture the salient features of a generic dataset and develop a novel estimator for the intrinsic dimension (ID). By approximating geodesics with minimum distance paths on a graph, we analyze the distribution of pairwise distances around the maximum and exploit its dependency on the dimensionality to obtain an ID estimate. We show that the estimator does not depend on the shape of the intrinsic manifold and is highly accurate, even for exceedingly small sample sizes. We apply the method to several relevant datasets from image recognition databases and protein multiple sequence alignments and discuss possible interpretations for the estimated dimension in light of the correlations among input variables and of the information content of the dataset. PMID:27510265
Methods for accurate estimation of net discharge in a tidal channel
Simpson, M.R.; Bland, R.
2000-01-01
Accurate estimates of net residual discharge in tidally affected rivers and estuaries are possible because of recently developed ultrasonic discharge measurement techniques. Previous discharge estimates using conventional mechanical current meters and methods based on stage/discharge relations or water slope measurements often yielded errors that were as great as or greater than the computed residual discharge. Ultrasonic measurement methods consist of: 1) the use of ultrasonic instruments for the measurement of a representative 'index' velocity used for in situ estimation of mean water velocity and 2) the use of the acoustic Doppler current discharge measurement system to calibrate the index velocity measurement data. Methods used to calibrate (rate) the index velocity to the channel velocity measured using the Acoustic Doppler Current Profiler are the most critical factors affecting the accuracy of net discharge estimation. The index velocity first must be related to mean channel velocity and then used to calculate instantaneous channel discharge. Finally, discharge is low-pass filtered to remove the effects of the tides. An ultrasonic velocity meter discharge-measurement site in a tidally affected region of the Sacramento-San Joaquin Rivers was used to study the accuracy of the index velocity calibration procedure. Calibration data consisting of ultrasonic velocity meter index velocity and concurrent acoustic Doppler discharge measurement data were collected during three time periods. Two sets of data were collected during a spring tide (monthly maximum tidal current) and one of data collected during a neap tide (monthly minimum tidal current). The relative magnitude of instrumental errors, acoustic Doppler discharge measurement errors, and calibration errors were evaluated. Calibration error was found to be the most significant source of error in estimating net discharge. Using a comprehensive calibration method, net discharge estimates developed from the three
MIDAS robust trend estimator for accurate GPS station velocities without step detection
NASA Astrophysics Data System (ADS)
Blewitt, Geoffrey; Kreemer, Corné; Hammond, William C.; Gazeaux, Julien
2016-03-01
Automatic estimation of velocities from GPS coordinate time series is becoming required to cope with the exponentially increasing flood of available data, but problems detectable to the human eye are often overlooked. This motivates us to find an automatic and accurate estimator of trend that is resistant to common problems such as step discontinuities, outliers, seasonality, skewness, and heteroscedasticity. Developed here, Median Interannual Difference Adjusted for Skewness (MIDAS) is a variant of the Theil-Sen median trend estimator, for which the ordinary version is the median of slopes vij = (xj-xi)/(tj-ti) computed between all data pairs i > j. For normally distributed data, Theil-Sen and least squares trend estimates are statistically identical, but unlike least squares, Theil-Sen is resistant to undetected data problems. To mitigate both seasonality and step discontinuities, MIDAS selects data pairs separated by 1 year. This condition is relaxed for time series with gaps so that all data are used. Slopes from data pairs spanning a step function produce one-sided outliers that can bias the median. To reduce bias, MIDAS removes outliers and recomputes the median. MIDAS also computes a robust and realistic estimate of trend uncertainty. Statistical tests using GPS data in the rigid North American plate interior show ±0.23 mm/yr root-mean-square (RMS) accuracy in horizontal velocity. In blind tests using synthetic data, MIDAS velocities have an RMS accuracy of ±0.33 mm/yr horizontal, ±1.1 mm/yr up, with a 5th percentile range smaller than all 20 automatic estimators tested. Considering its general nature, MIDAS has the potential for broader application in the geosciences.
High-Resolution Tsunami Inundation Simulations Based on Accurate Estimations of Coastal Waveforms
NASA Astrophysics Data System (ADS)
Oishi, Y.; Imamura, F.; Sugawara, D.; Furumura, T.
2015-12-01
We evaluate the accuracy of high-resolution tsunami inundation simulations in detail using the actual observational data of the 2011 Tohoku-Oki earthquake (Mw9.0) and investigate the methodologies to improve the simulation accuracy.Due to the recent development of parallel computing technologies, high-resolution tsunami inundation simulations are conducted more commonly than before. To evaluate how accurately these simulations can reproduce inundation processes, we test several types of simulation configurations on a parallel computer, where we can utilize the observational data (e.g., offshore and coastal waveforms and inundation properties) that are recorded during the Tohoku-Oki earthquake.Before discussing the accuracy of inundation processes on land, the incident waves at coastal sites must be accurately estimated. However, for megathrust earthquakes, it is difficult to find the tsunami source that can provide accurate estimations of tsunami waveforms at every coastal site because of the complex spatiotemporal distribution of the source and the limitation of observation. To overcome this issue, we employ a site-specific source inversion approach that increases the estimation accuracy within a specific coastal site by applying appropriate weighting to the observational data in the inversion process.We applied our source inversion technique to the Tohoku tsunami and conducted inundation simulations using 5-m resolution digital elevation model data (DEM) for the coastal area around Miyako Bay and Sendai Bay. The estimated waveforms at the coastal wave gauges of these bays successfully agree with the observed waveforms. However, the simulations overestimate the inundation extent indicating the necessity to improve the inundation model. We find that the value of Manning's roughness coefficient should be modified from the often-used value of n = 0.025 to n = 0.033 to obtain proper results at both cities.In this presentation, the simulation results with several
Huber's M-estimation in relative GPS positioning: computational aspects
NASA Astrophysics Data System (ADS)
Chang, X.-W.; Guo, Y.
2005-08-01
When GPS signal measurements have outliers, using least squares (LS) estimation is likely to give poor position estimates. One of the typical approaches to handle this problem is to use robust estimation techniques. We study the computational issues of Huber’s M-estimation applied to relative GPS positioning. First for code-based relative positioning, we use simulation results to show that Newton’s method usually converges faster than the iteratively reweighted least squares (IRLS) method, which is often used in geodesy for computing robust estimates of parameters. Then for code- and carrier-phase-based relative positioning, we present a recursive modified Newton method to compute Huber’s M-estimates of the positions. The structures of the model are exploited to make the method efficient, and orthogonal transformations are used to ensure numerical reliability of the method. Economical use of computer memory is also taken into account in designing the method. Simulation results show that the method is effective.
A new sensor system for accurate and precise determination of sediment dynamics and position.
NASA Astrophysics Data System (ADS)
Maniatis, Georgios; Hoey, Trevor; Sventek, Joseph; Hodge, Rebecca
2014-05-01
Sediment transport processes control many significant geomorphological changes. Consequently, sediment transport dynamics are studied across a wide range of scales leading to application of a variety of conceptually different mathematical descriptions (models) and data acquisition techniques (sensing). For river sediment transport processes both Eulerian and Lagrangian formulations are used. Data are gathered using a very wide range of sensing techniques that are not always compatible with the conceptual formulation applied. We are concerned with small to medium sediment grain-scale motion in gravel-bed rivers, and other coarse-grained environments, and: a) are developing a customised environmental sensor capable of providing coherent data that reliably record the motion; and, b) provide a mathematical framework in which these data can be analysed and interpreted, this being compatible with current stochastic approaches to sediment transport theory. Here we present results from three different aspects of the above developmental process. Firstly, we present a requirement analysis for the sensor based on the state of the art of the existing technologies. We focus on the factors that enhance data coherence and representativeness, extending the common practice for optimization which is based exclusively on electronics/computing related criteria. This analysis leads to formalization of a method that permits accurate control on the physical properties of the sensor using contemporary rapid prototyping techniques [Maniatis et al. 2013]. Secondly the first results are presented from a series of entrainment experiments in a 5 x 0.8 m flume in which a prototype sensor was deployed to monitor entrainment dynamics under increasing flow conditions (0.037 m3.s-1). The sensor was enclosed in an idealized spherical case (111 mm diameter) and placed on a constructed bed of hemispheres of the same diameter. We measured 3-axial inertial acceleration (as a measure of flow stress
Accurate estimation of the RMS emittance from single current amplifier data
Stockli, Martin P.; Welton, R.F.; Keller, R.; Letchford, A.P.; Thomae, R.W.; Thomason, J.W.G.
2002-05-31
This paper presents the SCUBEEx rms emittance analysis, a self-consistent, unbiased elliptical exclusion method, which combines traditional data-reduction methods with statistical methods to obtain accurate estimates for the rms emittance. Rather than considering individual data, the method tracks the average current density outside a well-selected, variable boundary to separate the measured beam halo from the background. The average outside current density is assumed to be part of a uniform background and not part of the particle beam. Therefore the average outside current is subtracted from the data before evaluating the rms emittance within the boundary. As the boundary area is increased, the average outside current and the inside rms emittance form plateaus when all data containing part of the particle beam are inside the boundary. These plateaus mark the smallest acceptable exclusion boundary and provide unbiased estimates for the average background and the rms emittance. Small, trendless variations within the plateaus allow for determining the uncertainties of the estimates caused by variations of the measured background outside the smallest acceptable exclusion boundary. The robustness of the method is established with complementary variations of the exclusion boundary. This paper presents a detailed comparison between traditional data reduction methods and SCUBEEx by analyzing two complementary sets of emittance data obtained with a Lawrence Berkeley National Laboratory and an ISIS H{sup -} ion source.
Accurate estimation of motion blur parameters in noisy remote sensing image
NASA Astrophysics Data System (ADS)
Shi, Xueyan; Wang, Lin; Shao, Xiaopeng; Wang, Huilin; Tao, Zhong
2015-05-01
The relative motion between remote sensing satellite sensor and objects is one of the most common reasons for remote sensing image degradation. It seriously weakens image data interpretation and information extraction. In practice, point spread function (PSF) should be estimated firstly for image restoration. Identifying motion blur direction and length accurately is very crucial for PSF and restoring image with precision. In general, the regular light-and-dark stripes in the spectrum can be employed to obtain the parameters by using Radon transform. However, serious noise existing in actual remote sensing images often causes the stripes unobvious. The parameters would be difficult to calculate and the error of the result relatively big. In this paper, an improved motion blur parameter identification method to noisy remote sensing image is proposed to solve this problem. The spectrum characteristic of noisy remote sensing image is analyzed firstly. An interactive image segmentation method based on graph theory called GrabCut is adopted to effectively extract the edge of the light center in the spectrum. Motion blur direction is estimated by applying Radon transform on the segmentation result. In order to reduce random error, a method based on whole column statistics is used during calculating blur length. Finally, Lucy-Richardson algorithm is applied to restore the remote sensing images of the moon after estimating blur parameters. The experimental results verify the effectiveness and robustness of our algorithm.
Schütt, Heiko H; Harmeling, Stefan; Macke, Jakob H; Wichmann, Felix A
2016-05-01
The psychometric function describes how an experimental variable, such as stimulus strength, influences the behaviour of an observer. Estimation of psychometric functions from experimental data plays a central role in fields such as psychophysics, experimental psychology and in the behavioural neurosciences. Experimental data may exhibit substantial overdispersion, which may result from non-stationarity in the behaviour of observers. Here we extend the standard binomial model which is typically used for psychometric function estimation to a beta-binomial model. We show that the use of the beta-binomial model makes it possible to determine accurate credible intervals even in data which exhibit substantial overdispersion. This goes beyond classical measures for overdispersion-goodness-of-fit-which can detect overdispersion but provide no method to do correct inference for overdispersed data. We use Bayesian inference methods for estimating the posterior distribution of the parameters of the psychometric function. Unlike previous Bayesian psychometric inference methods our software implementation-psignifit 4-performs numerical integration of the posterior within automatically determined bounds. This avoids the use of Markov chain Monte Carlo (MCMC) methods typically requiring expert knowledge. Extensive numerical tests show the validity of the approach and we discuss implications of overdispersion for experimental design. A comprehensive MATLAB toolbox implementing the method is freely available; a python implementation providing the basic capabilities is also available. PMID:27013261
Accurate estimation of human body orientation from RGB-D sensors.
Liu, Wu; Zhang, Yongdong; Tang, Sheng; Tang, Jinhui; Hong, Richang; Li, Jintao
2013-10-01
Accurate estimation of human body orientation can significantly enhance the analysis of human behavior, which is a fundamental task in the field of computer vision. However, existing orientation estimation methods cannot handle the various body poses and appearances. In this paper, we propose an innovative RGB-D-based orientation estimation method to address these challenges. By utilizing the RGB-D information, which can be real time acquired by RGB-D sensors, our method is robust to cluttered environment, illumination change and partial occlusions. Specifically, efficient static and motion cue extraction methods are proposed based on the RGB-D superpixels to reduce the noise of depth data. Since it is hard to discriminate all the 360 (°) orientation using static cues or motion cues independently, we propose to utilize a dynamic Bayesian network system (DBNS) to effectively employ the complementary nature of both static and motion cues. In order to verify our proposed method, we build a RGB-D-based human body orientation dataset that covers a wide diversity of poses and appearances. Our intensive experimental evaluations on this dataset demonstrate the effectiveness and efficiency of the proposed method. PMID:23893759
Quick and accurate estimation of the elastic constants using the minimum image method
NASA Astrophysics Data System (ADS)
Tretiakov, Konstantin V.; Wojciechowski, Krzysztof W.
2015-04-01
A method for determining the elastic properties using the minimum image method (MIM) is proposed and tested on a model system of particles interacting by the Lennard-Jones (LJ) potential. The elastic constants of the LJ system are determined in the thermodynamic limit, N → ∞, using the Monte Carlo (MC) method in the NVT and NPT ensembles. The simulation results show that when determining the elastic constants, the contribution of long-range interactions cannot be ignored, because that would lead to erroneous results. In addition, the simulations have revealed that the inclusion of further interactions of each particle with all its minimum image neighbors even in case of small systems leads to results which are very close to the values of elastic constants in the thermodynamic limit. This enables one for a quick and accurate estimation of the elastic constants using very small samples.
Rapid position estimation and tracking for autonomous driving
NASA Astrophysics Data System (ADS)
Wang, Patrick K.; Torrione, Peter A.; Collins, Leslie M.; Morton, Kenneth D., Jr.
2012-06-01
A method is presented for determining the position and orientation of a vehicle from a single, color video taken from the hood of the vehicle, for the purpose of assisting its autonomous operation at very high speeds on rural roads. An implicit perspective transformation allows estimation of the vehicle's orientation and cross-road image features. From these, an adaptive road model is built and the horizontal position of the vehicle can be estimated. This method makes very few assumptions about the structure of the road or the path of the vehicle. In a realistic, simulated environment, good road model construction and vehicle position estimation are achieved at frame rates suitable for real-time high speed driving.
A Simple yet Accurate Method for the Estimation of the Biovolume of Planktonic Microorganisms.
Saccà, Alessandro
2016-01-01
Determining the biomass of microbial plankton is central to the study of fluxes of energy and materials in aquatic ecosystems. This is typically accomplished by applying proper volume-to-carbon conversion factors to group-specific abundances and biovolumes. A critical step in this approach is the accurate estimation of biovolume from two-dimensional (2D) data such as those available through conventional microscopy techniques or flow-through imaging systems. This paper describes a simple yet accurate method for the assessment of the biovolume of planktonic microorganisms, which works with any image analysis system allowing for the measurement of linear distances and the estimation of the cross sectional area of an object from a 2D digital image. The proposed method is based on Archimedes' principle about the relationship between the volume of a sphere and that of a cylinder in which the sphere is inscribed, plus a coefficient of 'unellipticity' introduced here. Validation and careful evaluation of the method are provided using a variety of approaches. The new method proved to be highly precise with all convex shapes characterised by approximate rotational symmetry, and combining it with an existing method specific for highly concave or branched shapes allows covering the great majority of cases with good reliability. Thanks to its accuracy, consistency, and low resources demand, the new method can conveniently be used in substitution of any extant method designed for convex shapes, and can readily be coupled with automated cell imaging technologies, including state-of-the-art flow-through imaging devices. PMID:27195667
A Simple yet Accurate Method for the Estimation of the Biovolume of Planktonic Microorganisms
2016-01-01
Determining the biomass of microbial plankton is central to the study of fluxes of energy and materials in aquatic ecosystems. This is typically accomplished by applying proper volume-to-carbon conversion factors to group-specific abundances and biovolumes. A critical step in this approach is the accurate estimation of biovolume from two-dimensional (2D) data such as those available through conventional microscopy techniques or flow-through imaging systems. This paper describes a simple yet accurate method for the assessment of the biovolume of planktonic microorganisms, which works with any image analysis system allowing for the measurement of linear distances and the estimation of the cross sectional area of an object from a 2D digital image. The proposed method is based on Archimedes’ principle about the relationship between the volume of a sphere and that of a cylinder in which the sphere is inscribed, plus a coefficient of ‘unellipticity’ introduced here. Validation and careful evaluation of the method are provided using a variety of approaches. The new method proved to be highly precise with all convex shapes characterised by approximate rotational symmetry, and combining it with an existing method specific for highly concave or branched shapes allows covering the great majority of cases with good reliability. Thanks to its accuracy, consistency, and low resources demand, the new method can conveniently be used in substitution of any extant method designed for convex shapes, and can readily be coupled with automated cell imaging technologies, including state-of-the-art flow-through imaging devices. PMID:27195667
Accurate Estimation of the Fine Layering Effect on the Wave Propagation in the Carbonate Rocks
NASA Astrophysics Data System (ADS)
Bouchaala, F.; Ali, M. Y.
2014-12-01
The attenuation caused to the seismic wave during its propagation can be mainly divided into two parts, the scattering and the intrinsic attenuation. The scattering is an elastic redistribution of the energy due to the medium heterogeneities. However the intrinsic attenuation is an inelastic phenomenon, mainly due to the fluid-grain friction during the wave passage. The intrinsic attenuation is directly related to the physical characteristics of the medium, so this parameter is very can be used for media characterization and fluid detection, which is beneficial for the oil and gas industry. The intrinsic attenuation is estimated by subtracting the scattering from the total attenuation, therefore the accuracy of the intrinsic attenuation is directly dependent on the accuracy of the total attenuation and the scattering. The total attenuation can be estimated from the recorded waves, by using in-situ methods as the spectral ratio and frequency shift methods. The scattering is estimated by assuming the heterogeneities as a succession of stacked layers, each layer is characterized by a single density and velocity. The accuracy of the scattering is strongly dependent on the layer thicknesses, especially in the case of the media composed of carbonate rocks, such media are known for their strong heterogeneity. Previous studies gave some assumptions for the choice of the layer thickness, but they showed some limitations especially in the case of carbonate rocks. In this study we established a relationship between the layer thicknesses and the frequency of the propagation, after certain mathematical development of the Generalized O'Doherty-Anstey formula. We validated this relationship through some synthetic tests and real data provided from a VSP carried out over an onshore oilfield in the emirate of Abu Dhabi in the United Arab Emirates, primarily composed of carbonate rocks. The results showed the utility of our relationship for an accurate estimation of the scattering
Deng, Zhi-An; Wang, Guofeng; Hu, Ying; Cui, Yang
2016-01-01
This paper proposes a novel heading estimation approach for indoor pedestrian navigation using the built-in inertial sensors on a smartphone. Unlike previous approaches constraining the carrying position of a smartphone on the user’s body, our approach gives the user a larger freedom by implementing automatic recognition of the device carrying position and subsequent selection of an optimal strategy for heading estimation. We firstly predetermine the motion state by a decision tree using an accelerometer and a barometer. Then, to enable accurate and computational lightweight carrying position recognition, we combine a position classifier with a novel position transition detection algorithm, which may also be used to avoid the confusion between position transition and user turn during pedestrian walking. For a device placed in the trouser pockets or held in a swinging hand, the heading estimation is achieved by deploying a principal component analysis (PCA)-based approach. For a device held in the hand or against the ear during a phone call, user heading is directly estimated by adding the yaw angle of the device to the related heading offset. Experimental results show that our approach can automatically detect carrying positions with high accuracy, and outperforms previous heading estimation approaches in terms of accuracy and applicability. PMID:27187391
Deng, Zhi-An; Wang, Guofeng; Hu, Ying; Cui, Yang
2016-01-01
This paper proposes a novel heading estimation approach for indoor pedestrian navigation using the built-in inertial sensors on a smartphone. Unlike previous approaches constraining the carrying position of a smartphone on the user's body, our approach gives the user a larger freedom by implementing automatic recognition of the device carrying position and subsequent selection of an optimal strategy for heading estimation. We firstly predetermine the motion state by a decision tree using an accelerometer and a barometer. Then, to enable accurate and computational lightweight carrying position recognition, we combine a position classifier with a novel position transition detection algorithm, which may also be used to avoid the confusion between position transition and user turn during pedestrian walking. For a device placed in the trouser pockets or held in a swinging hand, the heading estimation is achieved by deploying a principal component analysis (PCA)-based approach. For a device held in the hand or against the ear during a phone call, user heading is directly estimated by adding the yaw angle of the device to the related heading offset. Experimental results show that our approach can automatically detect carrying positions with high accuracy, and outperforms previous heading estimation approaches in terms of accuracy and applicability. PMID:27187391
Kashima RAy-Tracing Service (KARATS) for high accurate GNSS positioning
NASA Astrophysics Data System (ADS)
Ichikawa, R.; Hobiger, T.; Hasegawa, S.; Tsutsumi, M.; Koyama, Y.; Kondo, T.
2010-12-01
Radio signal delays associated with the neutral atmosphere are one of the major error sources of space geodesy such as GPS, GLONASS, GALILEO, VLBI, In-SAR measurements. We have developed a state-of-art tool to estimate the atmospheric path delays by ray-tracing through JMA meso-scale analysis (MANAL data) data. The tools, which we have named 'KAshima RAytracing Tools (KARAT)', are capable of calculating total slant delays and ray-bending angles considering real atmospheric phenomena. Numerical weather models such as MANAL data have undergone a significant improvement of accuracy and spatial resolution, which makes it feasible to utilize them for the correction of atmosphere excess path delays. In the previous studies for evaluating KARAT performance, the KARAT solutions are slightly better than the solutions using VMF1 and GMF with linear gradient model for horizontal and height positions. Based on these results we have started the web-based online service, 'KAshima RAytracing Service (KARATS)' for providing the atmospheric delay correction of RINEX files on Jan 27th, 2010. The KARATS receives user's RINEX data via a proper web site (http://vps.nict.go.jp/karats/index.html) and processes user's data files using KARAT for reducing atmospheric slant delays. The reduced RINEX files are archived in the specific directory for each user on the KARATS server. Once the processing is finished the information of data archive is sent privately via email to each user. If user want to process a large amount of data files, user can prepare own server which archives them. The KARATS can get these files from the user's server using GNU ¥emph{wget} and performs ray-traced corrections. We will present a brief status of the KARATS and summarize first experiences gained after this service went operational in December 2009. In addition, we will also demonstrate the newest KARAT performance based on the 5km MANAL data which has been operational from April 7th, 2009 and an outlook on
Accurate position for the globular cluster X-ray source M15 - 211/X2127 + 119
NASA Astrophysics Data System (ADS)
Geffert, M.; Auriere, M.; Ilovaisky, S. A.; Terzan, A.
1989-01-01
Two new and improved determinations of the position of the globular cluster X-ray source X2127+119/M15:AC211 are presented. The positions were determined using long focus exposures on CCD frames and photographic and image tube plates. Stars from the SAO and AGK 3 catalogues were taken to derive positions of faint reference stars in the surroundings of the X-ray source. The uncertainty of the best position (in the AGK 3 system) is 0.20 arcsec in alpha and delta. The nominal separation of the optical position and the X-ray position is found to be 2 arcsec, but with an uncertainty of about 1.5 arcsec from the Einstein determination.
Accurate motion parameter estimation for colonoscopy tracking using a regression method
NASA Astrophysics Data System (ADS)
Liu, Jianfei; Subramanian, Kalpathi R.; Yoo, Terry S.
2010-03-01
Co-located optical and virtual colonoscopy images have the potential to provide important clinical information during routine colonoscopy procedures. In our earlier work, we presented an optical flow based algorithm to compute egomotion from live colonoscopy video, permitting navigation and visualization of the corresponding patient anatomy. In the original algorithm, motion parameters were estimated using the traditional Least Sum of squares(LS) procedure which can be unstable in the context of optical flow vectors with large errors. In the improved algorithm, we use the Least Median of Squares (LMS) method, a robust regression method for motion parameter estimation. Using the LMS method, we iteratively analyze and converge toward the main distribution of the flow vectors, while disregarding outliers. We show through three experiments the improvement in tracking results obtained using the LMS method, in comparison to the LS estimator. The first experiment demonstrates better spatial accuracy in positioning the virtual camera in the sigmoid colon. The second and third experiments demonstrate the robustness of this estimator, resulting in longer tracked sequences: from 300 to 1310 in the ascending colon, and 410 to 1316 in the transverse colon.
Use of vehicle magnetic signatures for position estimation
NASA Astrophysics Data System (ADS)
Taghvaeeyan, S.; Rajamani, R.
2011-09-01
This letter analyzes the magnetic signatures of cars and investigates the use of anisotropic magnetoresistive sensors to estimate the relative position of a vehicle from its magnetic signature. Theoretical analysis and experimental measurements both show that vehicle magnetic field has a first order inverse relationship with distance at small distances. However, the parameters in the magnetic field-distance relationship vary significantly with the type and size of car. A sensor system consisting of 2 magnetoresistive sensors and an extended Kalman filter can adaptively estimate these parameters in real-time. Experimental results from tests with various vehicles show that the developed sensor system can reliably estimate vehicle distance from magnetic field measurements.
Can student health professionals accurately estimate alcohol content in commonly occurring drinks?
Sinclair, Julia; Searle, Emma
2016-01-01
Objectives: Correct identification of alcohol as a contributor to, or comorbidity of, many psychiatric diseases requires health professionals to be competent and confident to take an accurate alcohol history. Being able to estimate (or calculate) the alcohol content in commonly consumed drinks is a prerequisite for quantifying levels of alcohol consumption. The aim of this study was to assess this ability in medical and nursing students. Methods: A cross-sectional survey of 891 medical and nursing students across different years of training was conducted. Students were asked the alcohol content of 10 different alcoholic drinks by seeing a slide of the drink (with picture, volume and percentage of alcohol by volume) for 30 s. Results: Overall, the mean number of correctly estimated drinks (out of the 10 tested) was 2.4, increasing to just over 3 if a 10% margin of error was used. Wine and premium strength beers were underestimated by over 50% of students. Those who drank alcohol themselves, or who were further on in their clinical training, did better on the task, but overall the levels remained low. Conclusions: Knowledge of, or the ability to work out, the alcohol content of commonly consumed drinks is poor, and further research is needed to understand the reasons for this and the impact this may have on the likelihood to undertake screening or initiate treatment. PMID:27536344
Ultrasound Fetal Weight Estimation: How Accurate Are We Now Under Emergency Conditions?
Dimassi, Kaouther; Douik, Fatma; Ajroudi, Mariem; Triki, Amel; Gara, Mohamed Faouzi
2015-10-01
The primary aim of this study was to evaluate the accuracy of sonographic estimation of fetal weight when performed at due date by first-line sonographers. This was a prospective study including 500 singleton pregnancies. Ultrasound examinations were performed by residents on delivery day. Estimated fetal weights (EFWs) were calculated and compared with the corresponding birth weights. The median absolute difference between EFW and birth weight was 200 g (100-330). This difference was within ±10% in 75.2% of the cases. The median absolute percentage error was 5.53% (2.70%-10.03%). Linear regression analysis revealed a good correlation between EFW and birth weight (r = 0.79, p < 0.0001). According to Bland-Altman analysis, bias was -85.06 g (95% limits of agreement: -663.33 to 494.21). In conclusion, EFWs calculated by residents were as accurate as those calculated by experienced sonographers. Nevertheless, predictive performance remains limited, with a low sensitivity in the diagnosis of macrosomia. PMID:26164286
NASA Astrophysics Data System (ADS)
Hu, Yongxiang; Behrenfeld, Mike; Hostetler, Chris; Pelon, Jacques; Trepte, Charles; Hair, John; Slade, Wayne; Cetinic, Ivona; Vaughan, Mark; Lu, Xiaomei; Zhai, Pengwang; Weimer, Carl; Winker, David; Verhappen, Carolus C.; Butler, Carolyn; Liu, Zhaoyan; Hunt, Bill; Omar, Ali; Rodier, Sharon; Lifermann, Anne; Josset, Damien; Hou, Weilin; MacDonnell, David; Rhew, Ray
2016-06-01
Beam attenuation coefficient, c, provides an important optical index of plankton standing stocks, such as phytoplankton biomass and total particulate carbon concentration. Unfortunately, c has proven difficult to quantify through remote sensing. Here, we introduce an innovative approach for estimating c using lidar depolarization measurements and diffuse attenuation coefficients from ocean color products or lidar measurements of Brillouin scattering. The new approach is based on a theoretical formula established from Monte Carlo simulations that links the depolarization ratio of sea water to the ratio of diffuse attenuation Kd and beam attenuation C (i.e., a multiple scattering factor). On July 17, 2014, the CALIPSO satellite was tilted 30° off-nadir for one nighttime orbit in order to minimize ocean surface backscatter and demonstrate the lidar ocean subsurface measurement concept from space. Depolarization ratios of ocean subsurface backscatter are measured accurately. Beam attenuation coefficients computed from the depolarization ratio measurements compare well with empirical estimates from ocean color measurements. We further verify the beam attenuation coefficient retrievals using aircraft-based high spectral resolution lidar (HSRL) data that are collocated with in-water optical measurements.
Accurate definition of brain regions position through the functional landmark approach.
Thirion, Bertrand; Varoquaux, Gaël; Poline, Jean-Baptiste
2010-01-01
In many application of functional Magnetic Resonance Imaging (fMRI), including clinical or pharmacological studies, the definition of the location of the functional activity between subjects is crucial. While current acquisition and normalization procedures improve the accuracy of the functional signal localization, it is also important to ensure that functional foci detection yields accurate results, and reflects between-subject variability. Here we introduce a fast functional landmark detection procedure, that explicitly models the spatial variability of activation foci in the observed population. We compare this detection approach to standard statistical maps peak extraction procedures: we show that it yields more accurate results on simulations, and more reproducible results on a large cohort of subjects. These results demonstrate that explicit functional landmark modeling approaches are more effective than standard statistical mapping for brain functional focus detection. PMID:20879321
VizieR Online Data Catalog: Accurate positions for 17124 galaxies (Paturel+, 2000)
NASA Astrophysics Data System (ADS)
Paturel, G.; Petit, C.; Garnier, R.; Prugniel, P.
2000-04-01
This paper gives accurate coordinates and diameters for 3301 galaxies, companions of UGC galaxies. (about 2764 companions were not yet available in electronic form). In addition previously poor equatorial coordinates are re-measured for 13823 galaxies. These coordinates which have an accuracy of 5'' or better will be used for facilitating the cross-identification with forthcoming catalogues of millions of galaxies. (2 data files).
What Can We Learn From The Shape Of A Correlation Peak For Position Estimation?
Awwal, A S
2009-08-25
Matched filtering is a robust technique to identify and locate objects in the presence of noise. Traditionally, the amplitude of the correlation peak is used for detection of a match. However, when distinguishing objects that are not significantly different or detecting objects under high noise imaging conditions, the normalized peak amplitude alone may not provide sufficient discrimination. In this paper, we demonstrate that measurements derived from the shape of the correlation peak offer not only higher levels of discrimination but also accurate position estimation. To our knowledge, this is the first time such features have been used in a real-time system, like the National Ignition Facility, where such techniques enable real-time, accurate position estimation and alignment under challenging imaging conditions. It is envisioned that systems utilizing matched filtering will greatly benefit from incorporating additional shape based information.
Discrete state model and accurate estimation of loop entropy of RNA secondary structures.
Zhang, Jian; Lin, Ming; Chen, Rong; Wang, Wei; Liang, Jie
2008-03-28
Conformational entropy makes important contribution to the stability and folding of RNA molecule, but it is challenging to either measure or compute conformational entropy associated with long loops. We develop optimized discrete k-state models of RNA backbone based on known RNA structures for computing entropy of loops, which are modeled as self-avoiding walks. To estimate entropy of hairpin, bulge, internal loop, and multibranch loop of long length (up to 50), we develop an efficient sampling method based on the sequential Monte Carlo principle. Our method considers excluded volume effect. It is general and can be applied to calculating entropy of loops with longer length and arbitrary complexity. For loops of short length, our results are in good agreement with a recent theoretical model and experimental measurement. For long loops, our estimated entropy of hairpin loops is in excellent agreement with the Jacobson-Stockmayer extrapolation model. However, for bulge loops and more complex secondary structures such as internal and multibranch loops, we find that the Jacobson-Stockmayer extrapolation model has large errors. Based on estimated entropy, we have developed empirical formulae for accurate calculation of entropy of long loops in different secondary structures. Our study on the effect of asymmetric size of loops suggest that loop entropy of internal loops is largely determined by the total loop length, and is only marginally affected by the asymmetric size of the two loops. Our finding suggests that the significant asymmetric effects of loop length in internal loops measured by experiments are likely to be partially enthalpic. Our method can be applied to develop improved energy parameters important for studying RNA stability and folding, and for predicting RNA secondary and tertiary structures. The discrete model and the program used to calculate loop entropy can be downloaded at http://gila.bioengr.uic.edu/resources/RNA.html. PMID:18376982
Estimating the absolute position of a mobile robot using position probability grids
Burgard, W.; Fox, D.; Hennig, D.; Schmidt, T.
1996-12-31
In order to re-use existing models of the environment mobile robots must be able to estimate their position and orientation in such models. Most of the existing methods for position estimation are based on special purpose sensors or aim at tracking the robot`s position relative to the known starting point. This paper describes the position probability grid approach to estimating the robot`s absolute position and orientation in a metric model of the environment. Our method is designed to work with standard sensors and is independent of any knowledge about the starting point. It is a Bayesian approach based on certainty grids. In each cell of such a grid we store the probability that this cell refers to the current position of the robot. These probabilities are obtained by integrating the likelihoods of sensor readings over time. Results described in this paper show that our technique is able to reliably estimate the position of a robot in complex environments. Our approach has proven to be robust with respect to inaccurate environmental models, noisy sensors, and ambiguous situations.
Accurate positions of H2 O masers in the Large Magellanic Cloud
NASA Astrophysics Data System (ADS)
Lazendic, J. S.; Whiteoak, J. B.; Klamer, I.; Harbison, P. D.; Kuiper, T. B. H.
2002-04-01
Positions with subarcsecond accuracy have been measured for seven 22-GHz H2 O masers associated with Hii regions in the Large Magellanic Cloud (LMC); two of the masers are new detections. Initial position measurements were obtained with the 70-m antenna of the Canberra NASA Deep Space Network during a period of more than two years in which the antenna was used to monitor the maser emission. The positions were further improved using 22-GHz observations involving three antennas of the Australia Telescope Compact Array. The positions have been compared with those of 1.6-GHz continuum emission and other LMC masers (of OH and CH3 OH). The H2 O maser positions range from within 1arcsec (270mpc) of the centre of a compact Hii component to beyond the boundary of significant continuum emission. Three of the four masers located near continuum peaks are close to OH masers. In two cases the positional agreement is better than 0.2arcsec (53mpc) in the third case the agreement is worse (0.9arcsec) but the positions of the individual H2 O features appear to be spread over more than 1arcsec. The velocities of the OH masers are within the spread of the H2 O velocities. The three H2 O masers offset from continuum centres are located 3-7arcsec from optical or infrared phenomena probably associated with very early stages of star formation; no other molecular masers are known in these directions.
A machine learning approach to the accurate prediction of multi-leaf collimator positional errors
NASA Astrophysics Data System (ADS)
Carlson, Joel N. K.; Park, Jong Min; Park, So-Yeon; In Park, Jong; Choi, Yunseok; Ye, Sung-Joon
2016-03-01
Discrepancies between planned and delivered movements of multi-leaf collimators (MLCs) are an important source of errors in dose distributions during radiotherapy. In this work we used machine learning techniques to train models to predict these discrepancies, assessed the accuracy of the model predictions, and examined the impact these errors have on quality assurance (QA) procedures and dosimetry. Predictive leaf motion parameters for the models were calculated from the plan files, such as leaf position and velocity, whether the leaf was moving towards or away from the isocenter of the MLC, and many others. Differences in positions between synchronized DICOM-RT planning files and DynaLog files reported during QA delivery were used as a target response for training of the models. The final model is capable of predicting MLC positions during delivery to a high degree of accuracy. For moving MLC leaves, predicted positions were shown to be significantly closer to delivered positions than were planned positions. By incorporating predicted positions into dose calculations in the TPS, increases were shown in gamma passing rates against measured dose distributions recorded during QA delivery. For instance, head and neck plans with 1%/2 mm gamma criteria had an average increase in passing rate of 4.17% (SD = 1.54%). This indicates that the inclusion of predictions during dose calculation leads to a more realistic representation of plan delivery. To assess impact on the patient, dose volumetric histograms (DVH) using delivered positions were calculated for comparison with planned and predicted DVHs. In all cases, predicted dose volumetric parameters were in closer agreement to the delivered parameters than were the planned parameters, particularly for organs at risk on the periphery of the treatment area. By incorporating the predicted positions into the TPS, the treatment planner is given a more realistic view of the dose distribution as it will truly be
A machine learning approach to the accurate prediction of multi-leaf collimator positional errors.
Carlson, Joel N K; Park, Jong Min; Park, So-Yeon; Park, Jong In; Choi, Yunseok; Ye, Sung-Joon
2016-03-21
Discrepancies between planned and delivered movements of multi-leaf collimators (MLCs) are an important source of errors in dose distributions during radiotherapy. In this work we used machine learning techniques to train models to predict these discrepancies, assessed the accuracy of the model predictions, and examined the impact these errors have on quality assurance (QA) procedures and dosimetry. Predictive leaf motion parameters for the models were calculated from the plan files, such as leaf position and velocity, whether the leaf was moving towards or away from the isocenter of the MLC, and many others. Differences in positions between synchronized DICOM-RT planning files and DynaLog files reported during QA delivery were used as a target response for training of the models. The final model is capable of predicting MLC positions during delivery to a high degree of accuracy. For moving MLC leaves, predicted positions were shown to be significantly closer to delivered positions than were planned positions. By incorporating predicted positions into dose calculations in the TPS, increases were shown in gamma passing rates against measured dose distributions recorded during QA delivery. For instance, head and neck plans with 1%/2 mm gamma criteria had an average increase in passing rate of 4.17% (SD = 1.54%). This indicates that the inclusion of predictions during dose calculation leads to a more realistic representation of plan delivery. To assess impact on the patient, dose volumetric histograms (DVH) using delivered positions were calculated for comparison with planned and predicted DVHs. In all cases, predicted dose volumetric parameters were in closer agreement to the delivered parameters than were the planned parameters, particularly for organs at risk on the periphery of the treatment area. By incorporating the predicted positions into the TPS, the treatment planner is given a more realistic view of the dose distribution as it will truly be
Estimating missing marker positions using low dimensional Kalman smoothing.
Burke, M; Lasenby, J
2016-06-14
Motion capture is frequently used for studies in biomechanics, and has proved particularly useful in understanding human motion. Unfortunately, motion capture approaches often fail when markers are occluded or missing and a mechanism by which the position of missing markers can be estimated is highly desirable. Of particular interest is the problem of estimating missing marker positions when no prior knowledge of marker placement is known. Existing approaches to marker completion in this scenario can be broadly divided into tracking approaches using dynamical modelling, and low rank matrix completion. This paper shows that these approaches can be combined to provide a marker completion algorithm that not only outperforms its respective components, but also solves the problem of incremental position error typically associated with tracking approaches. PMID:27155749
Method for accurately positioning a device at a desired area of interest
Jones, Gary D.; Houston, Jack E.; Gillen, Kenneth T.
2000-01-01
A method for positioning a first device utilizing a surface having a viewing translation stage, the surface being movable between a first position where the viewing stage is in operational alignment with a first device and a second position where the viewing stage is in operational alignment with a second device. The movable surface is placed in the first position and an image is produced with the first device of an identifiable characteristic of a calibration object on the viewing stage. The moveable surface is then placed in the second position and only the second device is moved until an image of the identifiable characteristic in the second device matches the image from the first device. The calibration object is then replaced on the stage of the surface with a test object, and the viewing translation stage is adjusted until the second device images the area of interest. The surface is then moved to the first position where the test object is scanned with the first device to image the area of interest. An alternative embodiment where the devices move is also disclosed.
Accurate calculation of phase shifts for electron collisions with positive ions
NASA Astrophysics Data System (ADS)
Gien, T. T.
2003-06-01
The Harris-Nesbet variational method was considered for the calculation of phase shifts of electron collisions with hydrogen-like ions (Li2+, Be3+, and B4+). Calculations were carried out for both singlet and triplet scattering. Very accurate results of phase shift of electron collisions with these ionic targets were obtained for the first time for partial waves of L up to six. The phase shifts that we obtained for low partial wave (S, P, and D) scattering were compared with those available in the literature by a few other research groups employing different numerical methods.
NASA Astrophysics Data System (ADS)
Paturel, G.; Petit, C.; Garnier, R.; Prugniel, P.
2000-06-01
This paper gives accurate coordinates and diameters for 3301 galaxies, companions of UGC galaxies. (about 2764 companions were not yet available in electronic form). In addition previously poor equatorial coordinates are re-measured for 13823 galaxies. These coordinates which have an accuracy of 5'' or better will be used for facilitating the cross-identification with forthcoming catalogues of millions of galaxies. Full Tables 1 and 2 are available in electronic form at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
nuMap: a web platform for accurate prediction of nucleosome positioning.
Alharbi, Bader A; Alshammari, Thamir H; Felton, Nathan L; Zhurkin, Victor B; Cui, Feng
2014-10-01
Nucleosome positioning is critical for gene expression and of major biological interest. The high cost of experimentally mapping nucleosomal arrangement signifies the need for computational approaches to predict nucleosome positions at high resolution. Here, we present a web-based application to fulfill this need by implementing two models, YR and W/S schemes, for the translational and rotational positioning of nucleosomes, respectively. Our methods are based on sequence-dependent anisotropic bending that dictates how DNA is wrapped around a histone octamer. This application allows users to specify a number of options such as schemes and parameters for threading calculation and provides multiple layout formats. The nuMap is implemented in Java/Perl/MySQL and is freely available for public use at http://numap.rit.edu. The user manual, implementation notes, description of the methodology and examples are available at the site. PMID:25220945
A Proposed Frequency Synthesis Approach to Accurately Measure the Angular Position of a Spacecraft
NASA Technical Reports Server (NTRS)
Bagri, D. S.
2005-01-01
This article describes an approach for measuring the angular position of a spacecraft with reference to a nearby calibration source (quasar) with an accuracy of a few tenths of a nanoradian using a very long baseline interferometer of two antennas that measures the interferometer phase with a modest accuracy. It employs (1) radio frequency phase to determine the spacecraft position with high precision and (2) multiple delay measurements using either frequency tones or telemetry signals at different frequency spacings to resolve ambiguity of the location of the fringe (cycle) containing the direction of the spacecraft.
NASA Astrophysics Data System (ADS)
Wang, Wei; Huang, Peter
2016-02-01
Evanescent wave nano-velocimetry offers a unique three-dimensional measurement capability that allows for inferring tracer position distribution through the imaged particle intensities. Our previous study suggested that tracer polydispersity and failure to account for a near-wall tracer depletion layer would lead to compromised measurement accuracy. In this work, we report on a hybrid algorithm that converts the measured tracer intensities as a whole into their overall position distribution. The algorithm achieves a superior accuracy by using tracer size variation as a statistical analysis parameter.
A Landmark Based Position Estimation for Pinpoint Landing on Mars
NASA Technical Reports Server (NTRS)
Cheng, Yang; Ansar, Adnan
2005-01-01
Real-time position estimation for a descent lander is a critical technological need for many of NASA's planned in situ missions including landing on a number of bodies at locations of greatest scientific interest and sample return. In particular, it enables the capability to land precisely and safely in a scientifically promising but hazardous site and is a key technology to be demonstrated by NASA in the next decade. The key challenge of pinpoint landing (PPL) is how to localize the lander by recognizing the landmarks (craters) in the landing area and match them positively to a preexisting landmark database while the spacecraft is descending. In this paper, a real-time landmark based position estimation technique for pinpoint landing is suggested. This system includes three crucial components: (1) real time landmark detection, (2) real-time landmark matching and (3) state (both position and velocity) estimation. We discuss the performance analysis of this system. Finally, we show that the suggested technology is able to deliver a spacecraft to less than 100 m from a pre-selected landing site on Mars.
Estimating the spatial position of marine mammals based on digital camera recordings
Hoekendijk, Jeroen P A; de Vries, Jurre; van der Bolt, Krissy; Greinert, Jens; Brasseur, Sophie; Camphuysen, Kees C J; Aarts, Geert
2015-01-01
Estimating the spatial position of organisms is essential to quantify interactions between the organism and the characteristics of its surroundings, for example, predator–prey interactions, habitat selection, and social associations. Because marine mammals spend most of their time under water and may appear at the surface only briefly, determining their exact geographic location can be challenging. Here, we developed a photogrammetric method to accurately estimate the spatial position of marine mammals or birds at the sea surface. Digital recordings containing landscape features with known geographic coordinates can be used to estimate the distance and bearing of each sighting relative to the observation point. The method can correct for frame rotation, estimates pixel size based on the reference points, and can be applied to scenarios with and without a visible horizon. A set of R functions was written to process the images and obtain accurate geographic coordinates for each sighting. The method is applied to estimate the spatiotemporal fine-scale distribution of harbour porpoises in a tidal inlet. Video recordings of harbour porpoises were made from land, using a standard digital single-lens reflex (DSLR) camera, positioned at a height of 9.59 m above mean sea level. Porpoises were detected up to a distance of ∽3136 m (mean 596 m), with a mean location error of 12 m. The method presented here allows for multiple detections of different individuals within a single video frame and for tracking movements of individuals based on repeated sightings. In comparison with traditional methods, this method only requires a digital camera to provide accurate location estimates. It especially has great potential in regions with ample data on local (a)biotic conditions, to help resolve functional mechanisms underlying habitat selection and other behaviors in marine mammals in coastal areas. PMID:25691982
Estimating the spatial position of marine mammals based on digital camera recordings.
Hoekendijk, Jeroen P A; de Vries, Jurre; van der Bolt, Krissy; Greinert, Jens; Brasseur, Sophie; Camphuysen, Kees C J; Aarts, Geert
2015-02-01
Estimating the spatial position of organisms is essential to quantify interactions between the organism and the characteristics of its surroundings, for example, predator-prey interactions, habitat selection, and social associations. Because marine mammals spend most of their time under water and may appear at the surface only briefly, determining their exact geographic location can be challenging. Here, we developed a photogrammetric method to accurately estimate the spatial position of marine mammals or birds at the sea surface. Digital recordings containing landscape features with known geographic coordinates can be used to estimate the distance and bearing of each sighting relative to the observation point. The method can correct for frame rotation, estimates pixel size based on the reference points, and can be applied to scenarios with and without a visible horizon. A set of R functions was written to process the images and obtain accurate geographic coordinates for each sighting. The method is applied to estimate the spatiotemporal fine-scale distribution of harbour porpoises in a tidal inlet. Video recordings of harbour porpoises were made from land, using a standard digital single-lens reflex (DSLR) camera, positioned at a height of 9.59 m above mean sea level. Porpoises were detected up to a distance of ∽3136 m (mean 596 m), with a mean location error of 12 m. The method presented here allows for multiple detections of different individuals within a single video frame and for tracking movements of individuals based on repeated sightings. In comparison with traditional methods, this method only requires a digital camera to provide accurate location estimates. It especially has great potential in regions with ample data on local (a)biotic conditions, to help resolve functional mechanisms underlying habitat selection and other behaviors in marine mammals in coastal areas. PMID:25691982
NASA Technical Reports Server (NTRS)
Malachowski, M. J.
1990-01-01
Laser beam positioning and beam rider modules were incorporated into the long hollow flexible segment of an articulated robot manipulator (ARM). Using a single laser beam, the system determined the position of the distal ARM endtip, with millimetric precision, in six degrees of freedom, at distances of up to 10 meters. Preliminary designs, using space rated technology for the critical systems, of a two segmented physical ARM, with a single and a dual degree of freedom articulation, were developed, prototyped, and tested. To control the positioning of the physical ARM, an indirect adaptive controller, which used the mismatch between the position of the laser beam under static and dynamic conditions, was devised. To predict the behavior of the system and test the concept, a computer simulation model was constructed. A hierarchical artificially intelligent real time ADA operating system program structure was created. The software was designed for implementation on a dedicated VME bus based Intel 80386 administered parallel processing multi-tasking computer system.
ERIC Educational Resources Information Center
Friedman, Lee; Harvey, Robert J.
1986-01-01
Job-naive raters provided with job descriptive information made Position Analysis Questionnaire (PAQ) ratings which were validated against ratings of job analysts who were also job content experts. None of the reduced job descriptive information conditions enabled job-naive raters to obtain either acceptable levels of convergent validity with…
Accurate radio and optical positions for the radio star HD 36705 (AB Doradus)
NASA Technical Reports Server (NTRS)
White, Graeme L.; Jauncey, David L.; Batty, Michael J.; Peters, W. L.; Gulkis, S.
1988-01-01
Arc-second position measurements of the active star HD 36705 (AB Dor) and of the variable radio source found nearby are presented. These measurements show that the radio source is clearly identified with HD 36705 and not with the nearby red-dwarf star Rst 137B.
Hyperbolic Position Location Estimation in the Multipath Propagation Environment
NASA Astrophysics Data System (ADS)
Stefański, Jacek
The efficiency analysis a hyperbolic position location estimation in the multipath propagation environment in the wideband code division multiple access (WCDMA) interface was presented. Four, the most popular methods: Chan’s [1], Foy’s [2], Fang’s [3] and Friedlander’s [4] were considered. These algorithms enable the calculation of the geographical position of a mobile station (MS) using the time differences of arrival (TDOA) between several base stations (BS) and MS. The simulation model is outlined and simulation results are presented.
Predictive Attitude Estimation Using Global Positioning System Signals
NASA Technical Reports Server (NTRS)
Crassidis, John L.; Markley, F. Landis; Lightsey, E. Glenn; Ketchum, Eleanor
1997-01-01
In this paper, a new algorithm is developed for attitude estimation using Global Positioning System (GPS) signals. The new algorithm is based on a predictive filtering scheme designed for spacecraft without rate measuring devices. The major advantage of this new algorithm over traditional Kalman filter approaches is that the model error is not assumed to represented by an unbiased Gaussian noise process with known covariance, but instead is determined during the estimation process. This is achieved by simultaneously solving system optimality conditions and an output error constraint. This approach is well suited for GPS attitude estimation since some error sources that contribute to attitude inaccuracy, such as signal multipath, are known to be non-Gaussian processes. Also, the predictive filter scheme can use either GPS signals or vector observations or a combination of both for attitude estimation, so that performance characteristics can be maintained during periods of GPS attitude sensor outage. The performance of the new algorithm is tested using flight data from the REX-2 spacecraft. Results are shown using the predictive filter to estimate the attitude from both GPS signals and magnetometer measurements, and comparing that solution to a magnetometer-only based solution. Results using the new estimation algorithm indicate that GPS-based solutions are verified to within 2 degrees using the magnetometer cross-check for the REX-2 spacecraft. GPS attitude accuracy of better than 1 degree is expected per axis, but cannot be reliably proven due to inaccuracies in the magnetic field model.
Wang, Ping; Chen, Xiaowu; Sun, Beiwang; Liu, Yanmin
2015-01-01
To explore the clinical effect of percutaneous transhepatic cholangioscopic lithotomy (PTCSL) combined with rigid choledochoscope and accurate positioning in the treatment of calculus of bile duct. This study retrospectively reviewed 162 patients with hepatolithiasis at the First Affiliated Hospital of Guangzhou Medical University between 2001 and 2013 were assigned to hard lens group or traditional PTCSL group. Compared with the traditional PTCSL, PTCSL with rigid choledochoscope can shorten the interval time which limit the PTCSL application. The operation time (45 vs 78, P=0.003), the number of operation (1.62 vs 1.97, P=0.031), and blood loss (37.8 vs 55.1, P=0.022) were better in hard lens group while the stone residual and complication had no significant differences. Rigid choledochoscope is a safe, minimally invasive and effective method in the treatment of bile duct stones. Accurate positioning method can effectively shorten operation process time. PMID:26629183
Time-based position estimation in monolithic scintillator detectors.
Tabacchini, Valerio; Borghi, Giacomo; Schaart, Dennis R
2015-07-21
Gamma-ray detectors based on bright monolithic scintillation crystals coupled to pixelated photodetectors are currently being considered for several applications in the medical imaging field. In a typical monolithic detector, both the light intensity and the time of arrival of the earliest scintillation photons can be recorded by each of the photosensor pixels every time a gamma interaction occurs. Generally, the time stamps are used to determine the gamma interaction time while the light intensities are used to estimate the 3D position of the interaction point. In this work we show that the spatio-temporal distribution of the time stamps also carries information on the location of the gamma interaction point and thus the time stamps can be used as explanatory variables for position estimation. We present a model for the spatial resolution obtainable when the interaction position is estimated using exclusively the time stamp of the first photon detected on each of the photosensor pixels. The model is shown to be in agreement with experimental measurements on a 16 mm × 16 mm × 10 mm LSO : Ce,0.2%Ca crystal coupled to a digital photon counter (DPC) array where a spatial resolution of 3 mm (root mean squared error) is obtained. Finally we discuss the effects of the main parameters such as scintillator rise and decay time, light output and photosensor single photon time resolution and pixel size. PMID:26133784
Time-based position estimation in monolithic scintillator detectors
NASA Astrophysics Data System (ADS)
Tabacchini, Valerio; Borghi, Giacomo; Schaart, Dennis R.
2015-07-01
Gamma-ray detectors based on bright monolithic scintillation crystals coupled to pixelated photodetectors are currently being considered for several applications in the medical imaging field. In a typical monolithic detector, both the light intensity and the time of arrival of the earliest scintillation photons can be recorded by each of the photosensor pixels every time a gamma interaction occurs. Generally, the time stamps are used to determine the gamma interaction time while the light intensities are used to estimate the 3D position of the interaction point. In this work we show that the spatio-temporal distribution of the time stamps also carries information on the location of the gamma interaction point and thus the time stamps can be used as explanatory variables for position estimation. We present a model for the spatial resolution obtainable when the interaction position is estimated using exclusively the time stamp of the first photon detected on each of the photosensor pixels. The model is shown to be in agreement with experimental measurements on a 16 mm × 16 mm × 10 mm LSO : Ce,0.2%Ca crystal coupled to a digital photon counter (DPC) array where a spatial resolution of 3 mm (root mean squared error) is obtained. Finally we discuss the effects of the main parameters such as scintillator rise and decay time, light output and photosensor single photon time resolution and pixel size.
NASA Astrophysics Data System (ADS)
Drizdal, T.; Paulides, M. M.; Linthorst, M.; van Rhoon, G. C.
2012-05-01
In the current clinical practice, prior to superficial hyperthermia treatments (HT), temperature probes are placed in tissue to document a thermal dose. To investigate whether the painful procedure of catheter placement can be replaced by superficial HT planning, we study if the specific absorption rate (SAR) coverage is predictive for treatment outcome. An absolute requirement for such a study is the accurate reconstruction of the applicator setup. The purpose of this study was to investigate the feasibility of the applicator setup reconstruction from multiple-view images. The accuracy of the multiple-view reconstruction method has been assessed for two experimental setups using six lucite cone applicators (LCAs) representing the largest array applied at our clinic and also the most difficult scenario for the reconstruction. For the two experimental setups and 112 distances, the mean difference between photogrametry reconstructed and manually measured distances was 0.25 ± 0.79 mm (mean±1 standard deviation). By a parameter study of translation T (mm) and rotation R (°) of LCAs, we showed that these inaccuracies are clinically acceptable, i.e. they are either from ±1.02 mm error in translation or ±0.48° in rotation, or combinations expressed by 4.35R2 + 0.97T2 = 1. We anticipate that such small errors will not have a relevant influence on the SAR distribution in the treated region. The clinical applicability of the procedure is shown on a patient with a breast cancer recurrence treated with reirradiation plus superficial hyperthermia using the six-LCA array. The total reconstruction procedure of six LCAs from a set of ten photos currently takes around 1.5 h. We conclude that the reconstruction of superficial HT setup from multiple-view images is feasible and only minor errors are found that will have a negligible influence on treatment planning quality.
NASA Astrophysics Data System (ADS)
Choi, Seung-Bok; Seong, Min-Sang; Ha, Sung Hoon
2013-04-01
In this work, position control of a one-link flexible arm is undertaken by considering the field-dependent hysteresis behavior of a piezoceramic actuator (piezoactuator in short). The proposed arm is controlled by two actuators: a motor mounted at the hub and a piezoceramic bonded to the surface of the flexible link. In the modeling process, two transfer functions: one from the input torque to output hub angle and the other from the input voltage to the output tip deflection are obtained. The hysteretic behavior of the piezoactuator is experimentally identified using the Preisach model, and the first-order descending (FOD) curves are obtained that are required to design a hysteresis compensator. After establishing the overall control block diagram for the position control of the flexible arm, a quantitative feedback theory (QFT) controller is designed by treating parameter variations and external disturbances as uncertainties. Subsequently, a hysteresis compensator that produces additional control input to the piezoactuator is designed to enhance the vibration control performance. An experimental realization of the proposed control scheme is undertaken and the effect of the hysteresis compensator on vibration control of the flexible arm is evaluated in the time domain.
Imani, Farsad; Karimi Rouzbahani, Hamid Reza; Goudarzi, Mehrdad; Tarrahi, Mohammad Javad; Ebrahim Soltani, Alireza
2016-01-01
Background: During anesthesia, continuous body temperature monitoring is essential, especially in children. Anesthesia can increase the risk of loss of body temperature by three to four times. Hypothermia in children results in increased morbidity and mortality. Since the measurement points of the core body temperature are not easily accessible, near core sites, like rectum, are used. Objectives: The purpose of this study was to measure skin temperature over the carotid artery and compare it with the rectum temperature, in order to propose a model for accurate estimation of near core body temperature. Patients and Methods: Totally, 124 patients within the age range of 2 - 6 years, undergoing elective surgery, were selected. Temperature of rectum and skin over the carotid artery was measured. Then, the patients were randomly divided into two groups (each including 62 subjects), namely modeling (MG) and validation groups (VG). First, in the modeling group, the average temperature of the rectum and skin over the carotid artery were measured separately. The appropriate model was determined, according to the significance of the model’s coefficients. The obtained model was used to predict the rectum temperature in the second group (VG group). Correlation of the predicted values with the real values (the measured rectum temperature) in the second group was investigated. Also, the difference in the average values of these two groups was examined in terms of significance. Results: In the modeling group, the average rectum and carotid temperatures were 36.47 ± 0.54°C and 35.45 ± 0.62°C, respectively. The final model was obtained, as follows: Carotid temperature × 0.561 + 16.583 = Rectum temperature. The predicted value was calculated based on the regression model and then compared with the measured rectum value, which showed no significant difference (P = 0.361). Conclusions: The present study was the first research, in which rectum temperature was compared with that
Global positioning system watches for estimating energy expenditure.
Hongu, Nobuko; Orr, Barron J; Roe, Denise J; Reed, Rebecca G; Going, Scott B
2013-11-01
Global positioning system (GPS) watches have been introduced commercially, converting frequent measurements of time, location, speed (pace), and elevation into energy expenditure (EE) estimates. The purpose of this study was to compare EE estimates of 4 different GPS watches (Forerunner, Suunto, Polar, Adeo), at various walking speeds, with EE estimate from a triaxial accelerometer (RT3), which was used as a reference measure in this study. Sixteen healthy young adults completed the study. Participants wore 4 different GPS watches and an RT3 accelerometer and walked at 6-minute intervals on an outdoor track at 3 speeds (3, 5, and 7 km/hr). The statistical significance of differences in EE between the 3 watches was assessed using linear contrasts of the coefficients from the overall model. Reliability across trials for a given device was assessed using intraclass correlation coefficients as estimated in the mixed model. The GPS watches demonstrated lower reliability (intraclass correlation coefficient) across trials when compared with the RT3, particularly at the higher speed, 7 km/hr. Three GPS watches (Forerunner, Polar, and Suunto) significantly and consistently underestimated EE compared with the reference EE given by the RT3 accelerometer (average mean difference: Garmin, -50.5%; Polar, -41.7%; and Suunto, -41.7%; all p < 0.001). Results suggested that caution should be exercised when using commercial GPS watches to estimate EE in athletes during field-based testing and training. PMID:23439338
Crop area estimation based on remotely-sensed data with an accurate but costly subsample
NASA Technical Reports Server (NTRS)
Gunst, R. F.
1983-01-01
Alternatives to sampling-theory stratified and regression estimators of crop production and timber biomass were examined. An alternative estimator which is viewed as especially promising is the errors-in-variable regression estimator. Investigations established the need for caution with this estimator when the ratio of two error variances is not precisely known.
Using Visual Odometry to Estimate Position and Attitude
NASA Technical Reports Server (NTRS)
Maimone, Mark; Cheng, Yang; Matthies, Larry; Schoppers, Marcel; Olson, Clark
2007-01-01
A computer program in the guidance system of a mobile robot generates estimates of the position and attitude of the robot, using features of the terrain on which the robot is moving, by processing digitized images acquired by a stereoscopic pair of electronic cameras mounted rigidly on the robot. Developed for use in localizing the Mars Exploration Rover (MER) vehicles on Martian terrain, the program can also be used for similar purposes on terrestrial robots moving in sufficiently visually textured environments: examples include low-flying robotic aircraft and wheeled robots moving on rocky terrain or inside buildings. In simplified terms, the program automatically detects visual features and tracks them across stereoscopic pairs of images acquired by the cameras. The 3D locations of the tracked features are then robustly processed into an estimate of overall vehicle motion. Testing has shown that by use of this software, the error in the estimate of the position of the robot can be limited to no more than 2 percent of the distance traveled, provided that the terrain is sufficiently rich in features. This software has proven extremely useful on the MER vehicles during driving on sandy and highly sloped terrains on Mars.
Gordon, Brett Ashley; Bruce, Lyndell; Benson, Amanda Clare
2016-08-01
Monitoring physical activity is important to better individualise health and fitness benefits. This study assessed the concurrent validity of a smartphone global positioning system (GPS) 'app' and a sport-specific GPS device with a similar sampling rate, to measure physical activity components of speed and distance, compared to a higher sampling sport-specific GPS device. Thirty-eight (21 female, 17 male) participants, mean age of 24.68, s = 6.46 years, completed two 2.400 km trials around an all-weather athletics track wearing GPSports Pro™ (PRO), GPSports WiSpi™ (WISPI) and an iPhone™ with a Motion X GPS™ 'app' (MOTIONX). Statistical agreement, assessed using t-tests and Bland-Altman plots, indicated an (mean; 95% LOA) underestimation of 2% for average speed (0.126 km·h(-1); -0.389 to 0.642; p < .001), 1.7% for maximal speed (0.442 km·h(-1); -2.676 to 3.561; p = .018) and 1.9% for distance (0.045 km; -0.140 to 0.232; p < .001) by MOTIONX compared to that measured by PRO. In contrast, compared to PRO, WISPI overestimated average speed (0.232 km·h(-1); -0.376 to 0.088; p < .001) and distance (0.083 km; -0.129 to -0.038; p < .001) by 3.5% whilst underestimating maximal speed by 2.5% (0.474 km·h(-1); -1.152 to 2.099; p < .001). Despite the statistically significant difference, the MOTIONX measures intensity of physical activity, with a similar error as WISPI, to an acceptable level for population-based monitoring in unimpeded open-air environments. This presents a low-cost, minimal burden opportunity to remotely monitor physical activity participation to improve the prescription of exercise as medicine. PMID:26505223
Position, velocity and acceleration estimates from the noisy radar measurements
NASA Astrophysics Data System (ADS)
Ramachandra, K. V.
1984-04-01
A two-dimensional Kalman tracking filter is described for obtaining optimum estimates of position, velocity and acceleration of an aircraft whose acceleration is perturbed due to maneuvers and/or other random factors. In a track-while-scan operation, a two-dimensional radar sensor is assumed to measure the range and bearing of the vehicle at uniform sampling intervals of time T seconds through random noise. The steady-state gain characteristics of the filter have been analytically obtained and the computer results are presented.
Precision of vertical position estimates from very long baseline interferometry
NASA Technical Reports Server (NTRS)
Herring, T. A.
1986-01-01
It is found that the precision of VLBI measurements of vertical crustal motions is limited by errors in the modeling of the propagation delay through the earth's neutral atmosphere, and by errors in finding the orientation of a fixed crust coordinate system in the VLBI reference frame. The repeatability of baseline length measurements study indicates a vertical position precision of about 8 cm, averaged over 13 sites and 4.5 years of data, while the repeatability of vertical position estimates for a Richmond, FL site is found to yield a precision of about 7 cm for 42 observations made over an 11-month period. An overall precision of 8 cm for a 24-hour VLBI observing session is obtained, and the effects of earth orientation parameter errors is contingent on the distances between the VLBI sites.
Subramanian, Swetha; Mast, T Douglas
2015-10-01
Computational finite element models are commonly used for the simulation of radiofrequency ablation (RFA) treatments. However, the accuracy of these simulations is limited by the lack of precise knowledge of tissue parameters. In this technical note, an inverse solver based on the unscented Kalman filter (UKF) is proposed to optimize values for specific heat, thermal conductivity, and electrical conductivity resulting in accurately simulated temperature elevations. A total of 15 RFA treatments were performed on ex vivo bovine liver tissue. For each RFA treatment, 15 finite-element simulations were performed using a set of deterministically chosen tissue parameters to estimate the mean and variance of the resulting tissue ablation. The UKF was implemented as an inverse solver to recover the specific heat, thermal conductivity, and electrical conductivity corresponding to the measured area of the ablated tissue region, as determined from gross tissue histology. These tissue parameters were then employed in the finite element model to simulate the position- and time-dependent tissue temperature. Results show good agreement between simulated and measured temperature. PMID:26352462
NASA Astrophysics Data System (ADS)
Subramanian, Swetha; Mast, T. Douglas
2015-09-01
Computational finite element models are commonly used for the simulation of radiofrequency ablation (RFA) treatments. However, the accuracy of these simulations is limited by the lack of precise knowledge of tissue parameters. In this technical note, an inverse solver based on the unscented Kalman filter (UKF) is proposed to optimize values for specific heat, thermal conductivity, and electrical conductivity resulting in accurately simulated temperature elevations. A total of 15 RFA treatments were performed on ex vivo bovine liver tissue. For each RFA treatment, 15 finite-element simulations were performed using a set of deterministically chosen tissue parameters to estimate the mean and variance of the resulting tissue ablation. The UKF was implemented as an inverse solver to recover the specific heat, thermal conductivity, and electrical conductivity corresponding to the measured area of the ablated tissue region, as determined from gross tissue histology. These tissue parameters were then employed in the finite element model to simulate the position- and time-dependent tissue temperature. Results show good agreement between simulated and measured temperature.
Sensor fusion method for off-road vehicle position estimation
NASA Astrophysics Data System (ADS)
Guo, Linsong; Zhang, Qin; Han, Shufeng
2002-07-01
A FOG-aided GPS fusion system was developed for positioning an off-road vehicle, which consists of a six-axis inertial measurement unit (IMU) and a Garmin global positioning system (GPS). An observation-based Kalman filter was designed to integrate the readings from both sensors so that the noise in GPS signal was smoothed out, the redundant information was fused and a high update rate of output signals was obtained. The drift error of FOG was also compensated. By using this system, a low cost GPS can be used to replace expensive GPS with a higher accuracy. Measurement and fusion results showed that the positioning error of the vehicle estimated using this fusion system was greatly reduced from a GPS-only system. At a vehicle speed of about 1.34 m/s, the mean bias in East axis of the fusion system was 0.48 m comparing to the GPS mean bias of 1.28 m, and the mean bias in North axis was reduced to 0.32 m from 1.48 m. The update frequency of the fusion system was increased to 9 Hz from 1 Hz of the GPS. A prototype system was installed on a sprayer for vehicle positioning measurement.
NASA Technical Reports Server (NTRS)
Howard, David E. (Inventor); Smith, Dennis A. (Inventor)
1991-01-01
The invention disclosed is a digital circuit which emulates a synchro signal in a synchro-resolver follower system for precise control of shaft position and rotation at very low rotational rates. The invention replaces the synchro and drive motor in a synchro-resolver follower system with a digital and analog synchro emulation circuit for generating the resolver control signal. The synchro emulation circuit includes amplitude modulation means to provide relatively high frequency resolver excitation signals for accurate resolver response even with very low shaft rotation rates.
NASA Technical Reports Server (NTRS)
Howard, David E. (Inventor); Smith, Dennis A. (Inventor)
1992-01-01
The invention herein disclosed is a digital circuit which emulates a synchro signal in a synchro-resolver follower system for precise control of shaft position and rotation at very low rotational rates. The subject invention replaces the synchro and drive motor in a synchroresolver follower system with a digital and analog synchro emulation circuit for generating the resolver control signal. The synchro emulation circuit includes amplitude modulation means to provide relatively high frequency resolver excitation signals for accurate resolver response even with very low shaft rotation rates.
NASA Astrophysics Data System (ADS)
Grasso, Robert J.; Russo, Leonard P.; Barrett, John L.; Odhner, Jefferson E.; Egbert, Paul I.
2007-09-01
BAE Systems presents the results of a program to model the performance of Raman LIDAR systems for the remote detection of atmospheric gases, air polluting hydrocarbons, chemical and biological weapons, and other molecular species of interest. Our model, which integrates remote Raman spectroscopy, 2D and 3D LADAR, and USAF atmospheric propagation codes permits accurate determination of the performance of a Raman LIDAR system. The very high predictive performance accuracy of our model is due to the very accurate calculation of the differential scattering cross section for the specie of interest at user selected wavelengths. We show excellent correlation of our calculated cross section data, used in our model, with experimental data obtained from both laboratory measurements and the published literature. In addition, the use of standard USAF atmospheric models provides very accurate determination of the atmospheric extinction at both the excitation and Raman shifted wavelengths.
Meckley, Trevor D.; Holbrook, Christopher M.; Wagner, C. Michael; Binder, Thomas R.
2014-01-01
The use of position precision estimates that reflect the confidence in the positioning process should be considered prior to the use of biological filters that rely on a priori expectations of the subject’s movement capacities and tendencies. Position confidence goals should be determined based upon the needs of the research questions and analysis requirements versus arbitrary selection, in which filters of previous studies are adopted. Data filtering with this approach ensures that data quality is sufficient for the selected analyses and presents the opportunity to adjust or identify a different analysis in the event that the requisite precision was not attained. Ignoring these steps puts a practitioner at risk of reporting errant findings.
Bi-fluorescence imaging for estimating accurately the nuclear condition of Rhizoctonia spp.
Technology Transfer Automated Retrieval System (TEKTRAN)
Aims: To simplify the determination of the nuclear condition of the pathogenic Rhizoctonia, which currently needs to be performed either using two fluorescent dyes, thus is more costly and time-consuming, or using only one fluorescent dye, and thus less accurate. Methods and Results: A red primary ...
Shen, Yan; Lou, Shuqin; Wang, Xin
2014-03-20
The evaluation accuracy of real optical properties of photonic crystal fibers (PCFs) is determined by the accurate extraction of air hole edges from microscope images of cross sections of practical PCFs. A novel estimation method of point spread function (PSF) based on Kalman filter is presented to rebuild the micrograph image of the PCF cross-section and thus evaluate real optical properties for practical PCFs. Through tests on both artificially degraded images and microscope images of cross sections of practical PCFs, we prove that the proposed method can achieve more accurate PSF estimation and lower PSF variance than the traditional Bayesian estimation method, and thus also reduce the defocus effect. With this method, we rebuild the microscope images of two kinds of commercial PCFs produced by Crystal Fiber and analyze the real optical properties of these PCFs. Numerical results are in accord with the product parameters. PMID:24663461
Accurate state estimation for a hydraulic actuator via a SDRE nonlinear filter
NASA Astrophysics Data System (ADS)
Strano, Salvatore; Terzo, Mario
2016-06-01
The state estimation in hydraulic actuators is a fundamental tool for the detection of faults or a valid alternative to the installation of sensors. Due to the hard nonlinearities that characterize the hydraulic actuators, the performances of the linear/linearization based techniques for the state estimation are strongly limited. In order to overcome these limits, this paper focuses on an alternative nonlinear estimation method based on the State-Dependent-Riccati-Equation (SDRE). The technique is able to fully take into account the system nonlinearities and the measurement noise. A fifth order nonlinear model is derived and employed for the synthesis of the estimator. Simulations and experimental tests have been conducted and comparisons with the largely used Extended Kalman Filter (EKF) are illustrated. The results show the effectiveness of the SDRE based technique for applications characterized by not negligible nonlinearities such as dead zone and frictions.
Erwin, Andrew; Sup, Frank C
2015-01-01
In this paper, a novel haptic feedback scheme, used for accurately positioning a 1DOF virtual wrist prosthesis through sensory substitution, is presented. The scheme employs a three-node tactor array and discretely and selectively modulates the stimulation frequency of each tactor to relay 11 discrete haptic stimuli to the user. Able-bodied participants were able to move the virtual wrist prosthesis via a surface electromyography based controller. The participants evaluated the feedback scheme without visual or audio feedback and relied solely on the haptic feedback alone to correctly position the hand. The scheme was evaluated through both normal (perpendicular) and shear (lateral) stimulations applied on the forearm. Normal stimulations were applied through a prototype device previously developed by the authors while shear stimulations were generated using an ubiquitous coin motor vibrotactor. Trials with no feedback served as a baseline to compare results within the study and to the literature. The results indicated that using normal and shear stimulations resulted in accurately positioning the virtual wrist, but were not significantly different. Using haptic feedback was substantially better than no feedback. The results found in this study are significant since the feedback scheme allows for using relatively few tactors to relay rich haptic information to the user and can be learned easily despite a relatively short amount of training. Additionally, the results are important for the haptic community since they contradict the common conception in the literature that normal stimulation is inferior to shear. From an ergonomic perspective normal stimulation has the potential to benefit upper limb amputees since it can operate at lower frequencies than shear-based vibrotactors while also generating less noise. Through further tuning of the novel haptic feedback scheme and normal stimulation device, a compact and comfortable sensory substitution device for upper
Erwin, Andrew; Sup, Frank C.
2015-01-01
In this paper, a novel haptic feedback scheme, used for accurately positioning a 1DOF virtual wrist prosthesis through sensory substitution, is presented. The scheme employs a three-node tactor array and discretely and selectively modulates the stimulation frequency of each tactor to relay 11 discrete haptic stimuli to the user. Able-bodied participants were able to move the virtual wrist prosthesis via a surface electromyography based controller. The participants evaluated the feedback scheme without visual or audio feedback and relied solely on the haptic feedback alone to correctly position the hand. The scheme was evaluated through both normal (perpendicular) and shear (lateral) stimulations applied on the forearm. Normal stimulations were applied through a prototype device previously developed by the authors while shear stimulations were generated using an ubiquitous coin motor vibrotactor. Trials with no feedback served as a baseline to compare results within the study and to the literature. The results indicated that using normal and shear stimulations resulted in accurately positioning the virtual wrist, but were not significantly different. Using haptic feedback was substantially better than no feedback. The results found in this study are significant since the feedback scheme allows for using relatively few tactors to relay rich haptic information to the user and can be learned easily despite a relatively short amount of training. Additionally, the results are important for the haptic community since they contradict the common conception in the literature that normal stimulation is inferior to shear. From an ergonomic perspective normal stimulation has the potential to benefit upper limb amputees since it can operate at lower frequencies than shear-based vibrotactors while also generating less noise. Through further tuning of the novel haptic feedback scheme and normal stimulation device, a compact and comfortable sensory substitution device for upper
FAST TRACK COMMUNICATION Accurate estimate of α variation and isotope shift parameters in Na and Mg+
NASA Astrophysics Data System (ADS)
Sahoo, B. K.
2010-12-01
We present accurate calculations of fine-structure constant variation coefficients and isotope shifts in Na and Mg+ using the relativistic coupled-cluster method. In our approach, we are able to discover the roles of various correlation effects explicitly to all orders in these calculations. Most of the results, especially for the excited states, are reported for the first time. It is possible to ascertain suitable anchor and probe lines for the studies of possible variation in the fine-structure constant by using the above results in the considered systems.
Nazareth, D; Malhotra, H; French, S; Hoffmann, K; Merrow, C
2014-06-01
Purpose: Breast radiotherapy, particularly electronic compensation, may involve large dose gradients and difficult patient positioning problems. We have developed a simple self-calibrating augmented-reality system, which assists in accurately and reproducibly positioning the patient, by displaying her live image from a single camera superimposed on the correct perspective projection of her 3D CT data. Our method requires only a standard digital camera capable of live-view mode, installed in the treatment suite at an approximately-known orientation and position (rotation R; translation T). Methods: A 10-sphere calibration jig was constructed and CT imaged to provide a 3D model. The (R,T) relating the camera to the CT coordinate system were determined by acquiring a photograph of the jig and optimizing an objective function, which compares the true image points to points calculated with a given candidate R and T geometry. Using this geometric information, 3D CT patient data, viewed from the camera's perspective, is plotted using a Matlab routine. This image data is superimposed onto the real-time patient image, acquired by the camera, and displayed using standard live-view software. This enables the therapists to view both the patient's current and desired positions, and guide the patient into assuming the correct position. The method was evaluated using an in-house developed bolus-like breast phantom, mounted on a supporting platform, which could be tilted at various angles to simulate treatment-like geometries. Results: Our system allowed breast phantom alignment, with an accuracy of about 0.5 cm and 1 ± 0.5 degree. Better resolution could be possible using a camera with higher-zoom capabilities. Conclusion: We have developed an augmented-reality system, which combines a perspective projection of a CT image with a patient's real-time optical image. This system has the potential to improve patient setup accuracy during breast radiotherapy, and could possibly be
Accurate State Estimation and Tracking of a Non-Cooperative Target Vehicle
NASA Technical Reports Server (NTRS)
Thienel, Julie K.; Sanner, Robert M.
2006-01-01
Autonomous space rendezvous scenarios require knowledge of the target vehicle state in order to safely dock with the chaser vehicle. Ideally, the target vehicle state information is derived from telemetered data, or with the use of known tracking points on the target vehicle. However, if the target vehicle is non-cooperative and does not have the ability to maintain attitude control, or transmit attitude knowledge, the docking becomes more challenging. This work presents a nonlinear approach for estimating the body rates of a non-cooperative target vehicle, and coupling this estimation to a tracking control scheme. The approach is tested with the robotic servicing mission concept for the Hubble Space Telescope (HST). Such a mission would not only require estimates of the HST attitude and rates, but also precision control to achieve the desired rate and maintain the orientation to successfully dock with HST.
Precision Pointing Control to and Accurate Target Estimation of a Non-Cooperative Vehicle
NASA Technical Reports Server (NTRS)
VanEepoel, John; Thienel, Julie; Sanner, Robert M.
2006-01-01
In 2004, NASA began investigating a robotic servicing mission for the Hubble Space Telescope (HST). Such a mission would not only require estimates of the HST attitude and rates in order to achieve capture by the proposed Hubble Robotic Vehicle (HRV), but also precision control to achieve the desired rate and maintain the orientation to successfully dock with HST. To generalize the situation, HST is the target vehicle and HRV is the chaser. This work presents a nonlinear approach for estimating the body rates of a non-cooperative target vehicle, and coupling this estimation to a control scheme. Non-cooperative in this context relates to the target vehicle no longer having the ability to maintain attitude control or transmit attitude knowledge.
A microbial clock provides an accurate estimate of the postmortem interval in a mouse model system
Metcalf, Jessica L; Wegener Parfrey, Laura; Gonzalez, Antonio; Lauber, Christian L; Knights, Dan; Ackermann, Gail; Humphrey, Gregory C; Gebert, Matthew J; Van Treuren, Will; Berg-Lyons, Donna; Keepers, Kyle; Guo, Yan; Bullard, James; Fierer, Noah; Carter, David O; Knight, Rob
2013-01-01
Establishing the time since death is critical in every death investigation, yet existing techniques are susceptible to a range of errors and biases. For example, forensic entomology is widely used to assess the postmortem interval (PMI), but errors can range from days to months. Microbes may provide a novel method for estimating PMI that avoids many of these limitations. Here we show that postmortem microbial community changes are dramatic, measurable, and repeatable in a mouse model system, allowing PMI to be estimated within approximately 3 days over 48 days. Our results provide a detailed understanding of bacterial and microbial eukaryotic ecology within a decomposing corpse system and suggest that microbial community data can be developed into a forensic tool for estimating PMI. DOI: http://dx.doi.org/10.7554/eLife.01104.001 PMID:24137541
Fast and accurate probability density estimation in large high dimensional astronomical datasets
NASA Astrophysics Data System (ADS)
Gupta, Pramod; Connolly, Andrew J.; Gardner, Jeffrey P.
2015-01-01
Astronomical surveys will generate measurements of hundreds of attributes (e.g. color, size, shape) on hundreds of millions of sources. Analyzing these large, high dimensional data sets will require efficient algorithms for data analysis. An example of this is probability density estimation that is at the heart of many classification problems such as the separation of stars and quasars based on their colors. Popular density estimation techniques use binning or kernel density estimation. Kernel density estimation has a small memory footprint but often requires large computational resources. Binning has small computational requirements but usually binning is implemented with multi-dimensional arrays which leads to memory requirements which scale exponentially with the number of dimensions. Hence both techniques do not scale well to large data sets in high dimensions. We present an alternative approach of binning implemented with hash tables (BASH tables). This approach uses the sparseness of data in the high dimensional space to ensure that the memory requirements are small. However hashing requires some extra computation so a priori it is not clear if the reduction in memory requirements will lead to increased computational requirements. Through an implementation of BASH tables in C++ we show that the additional computational requirements of hashing are negligible. Hence this approach has small memory and computational requirements. We apply our density estimation technique to photometric selection of quasars using non-parametric Bayesian classification and show that the accuracy of the classification is same as the accuracy of earlier approaches. Since the BASH table approach is one to three orders of magnitude faster than the earlier approaches it may be useful in various other applications of density estimation in astrostatistics.
Spectral estimation from laser scanner data for accurate color rendering of objects
NASA Astrophysics Data System (ADS)
Baribeau, Rejean
2002-06-01
Estimation methods are studied for the recovery of the spectral reflectance across the visible range from the sensing at just three discrete laser wavelengths. Methods based on principal component analysis and on spline interpolation are judged based on the CIE94 color differences for some reference data sets. These include the Macbeth color checker, the OSA-UCS color charts, some artist pigments, and a collection of miscellaneous surface colors. The optimal three sampling wavelengths are also investigated. It is found that color can be estimated with average accuracy ΔE94 = 2.3 when optimal wavelengths 455 nm, 540 n, and 610 nm are used.
Crop area estimation based on remotely-sensed data with an accurate but costly subsample
NASA Technical Reports Server (NTRS)
Gunst, R. F.
1985-01-01
Research activities conducted under the auspices of National Aeronautics and Space Administration Cooperative Agreement NCC 9-9 are discussed. During this contract period research efforts are concentrated in two primary areas. The first are is an investigation of the use of measurement error models as alternatives to least squares regression estimators of crop production or timber biomass. The secondary primary area of investigation is on the estimation of the mixing proportion of two-component mixture models. This report lists publications, technical reports, submitted manuscripts, and oral presentation generated by these research efforts. Possible areas of future research are mentioned.
NASA Astrophysics Data System (ADS)
Omori, Takayuki; Sano, Katsuhiro; Yoneda, Minoru
2014-05-01
This paper presents new correction approaches for "early" radiocarbon ages to reconstruct the Paleolithic absolute chronology. In order to discuss time-space distribution about the replacement of archaic humans, including Neanderthals in Europe, by the modern humans, a massive data, which covers a wide-area, would be needed. Today, some radiocarbon databases focused on the Paleolithic have been published and used for chronological studies. From a viewpoint of current analytical technology, however, the any database have unreliable results that make interpretation of radiocarbon dates difficult. Most of these unreliable ages had been published in the early days of radiocarbon analysis. In recent years, new analytical methods to determine highly-accurate dates have been developed. Ultrafiltration and ABOx-SC methods, as new sample pretreatments for bone and charcoal respectively, have attracted attention because they could remove imperceptible contaminates and derive reliable accurately ages. In order to evaluate the reliability of "early" data, we investigated the differences and variabilities of radiocarbon ages on different pretreatments, and attempted to develop correction functions for the assessment of the reliability. It can be expected that reliability of the corrected age is increased and the age applied to chronological research together with recent ages. Here, we introduce the methodological frameworks and archaeological applications.
Zhang, Peng; Zhou, Ning; Abdollahi, Ali
2013-09-10
A Generalized Subspace-Least Mean Square (GSLMS) method is presented for accurate and robust estimation of oscillation modes from exponentially damped power system signals. The method is based on orthogonality of signal and noise eigenvectors of the signal autocorrelation matrix. Performance of the proposed method is evaluated using Monte Carlo simulation and compared with Prony method. Test results show that the GSLMS is highly resilient to noise and significantly dominates Prony method in tracking power system modes under noisy environments.
How Accurate and Robust Are the Phylogenetic Estimates of Austronesian Language Relationships?
Greenhill, Simon J.; Drummond, Alexei J.; Gray, Russell D.
2010-01-01
We recently used computational phylogenetic methods on lexical data to test between two scenarios for the peopling of the Pacific. Our analyses of lexical data supported a pulse-pause scenario of Pacific settlement in which the Austronesian speakers originated in Taiwan around 5,200 years ago and rapidly spread through the Pacific in a series of expansion pulses and settlement pauses. We claimed that there was high congruence between traditional language subgroups and those observed in the language phylogenies, and that the estimated age of the Austronesian expansion at 5,200 years ago was consistent with the archaeological evidence. However, the congruence between the language phylogenies and the evidence from historical linguistics was not quantitatively assessed using tree comparison metrics. The robustness of the divergence time estimates to different calibration points was also not investigated exhaustively. Here we address these limitations by using a systematic tree comparison metric to calculate the similarity between the Bayesian phylogenetic trees and the subgroups proposed by historical linguistics, and by re-estimating the age of the Austronesian expansion using only the most robust calibrations. The results show that the Austronesian language phylogenies are highly congruent with the traditional subgroupings, and the date estimates are robust even when calculated using a restricted set of historical calibrations. PMID:20224774
Accurate Angle Estimator for High-Frame-Rate 2-D Vector Flow Imaging.
Villagomez Hoyos, Carlos Armando; Stuart, Matthias Bo; Hansen, Kristoffer Lindskov; Nielsen, Michael Bachmann; Jensen, Jorgen Arendt
2016-06-01
This paper presents a novel approach for estimating 2-D flow angles using a high-frame-rate ultrasound method. The angle estimator features high accuracy and low standard deviation (SD) over the full 360° range. The method is validated on Field II simulations and phantom measurements using the experimental ultrasound scanner SARUS and a flow rig before being tested in vivo. An 8-MHz linear array transducer is used with defocused beam emissions. In the simulations of a spinning disk phantom, a 360° uniform behavior on the angle estimation is observed with a median angle bias of 1.01° and a median angle SD of 1.8°. Similar results are obtained on a straight vessel for both simulations and measurements, where the obtained angle biases are below 1.5° with SDs around 1°. Estimated velocity magnitudes are also kept under 10% bias and 5% relative SD in both simulations and measurements. An in vivo measurement is performed on a carotid bifurcation of a healthy individual. A 3-s acquisition during three heart cycles is captured. A consistent and repetitive vortex is observed in the carotid bulb during systoles. PMID:27093598
Ouellette, Karli J; de Linage, Caroline; Famiglietti, James S
2013-01-01
[1] Accurate estimation of the characteristics of the winter snowpack is crucial for prediction of available water supply, flooding, and climate feedbacks. Remote sensing of snow has been most successful for quantifying the spatial extent of the snowpack, although satellite estimation of snow water equivalent (SWE), fractional snow covered area, and snow depth is improving. Here we show that GPS observations of vertical land surface loading reveal seasonal responses of the land surface to the total weight of snow, providing information about the stored SWE. We demonstrate that the seasonal signal in Scripps Orbit and Permanent Array Center (SOPAC) GPS vertical land surface position time series at six locations in the western United States is driven by elastic loading of the crust by the snowpack. GPS observations of land surface deformation are then used to predict the water load as a function of time at each location of interest and compared for validation to nearby Snowpack Telemetry observations of SWE. Estimates of soil moisture are included in the analysis and result in considerable improvement in the prediction of SWE. Citation: Ouellette, K. J., C. de Linage, and J. S. Famiglietti (2013), Estimating snow water equivalent from GPS vertical site-position observations in the western United States, Water Resour. Res., 49, 2508–2518, doi:10.1002/wrcr.20173. PMID:24223442
Ouellette, Karli J; de Linage, Caroline; Famiglietti, James S
2013-05-01
[1] Accurate estimation of the characteristics of the winter snowpack is crucial for prediction of available water supply, flooding, and climate feedbacks. Remote sensing of snow has been most successful for quantifying the spatial extent of the snowpack, although satellite estimation of snow water equivalent (SWE), fractional snow covered area, and snow depth is improving. Here we show that GPS observations of vertical land surface loading reveal seasonal responses of the land surface to the total weight of snow, providing information about the stored SWE. We demonstrate that the seasonal signal in Scripps Orbit and Permanent Array Center (SOPAC) GPS vertical land surface position time series at six locations in the western United States is driven by elastic loading of the crust by the snowpack. GPS observations of land surface deformation are then used to predict the water load as a function of time at each location of interest and compared for validation to nearby Snowpack Telemetry observations of SWE. Estimates of soil moisture are included in the analysis and result in considerable improvement in the prediction of SWE. Citation: Ouellette, K. J., C. de Linage, and J. S. Famiglietti (2013), Estimating snow water equivalent from GPS vertical site-position observations in the western United States, Water Resour. Res., 49, 2508-2518, doi:10.1002/wrcr.20173. PMID:24223442
Fetal position and size data for dose estimation.
Osei, E K; Faulkner, K
1999-04-01
In order to establish both positional and size data for estimation of fetal absorbed dose from radiological examinations, the depth from the mother's anterior surface to the mid-line of the fetal head and abdomen were measured from ultrasound scans in 215 pregnant women. Depths were measured along a ray path projected in the anteroposterior (AP) direction from the mother's abdomen. The fetal size was estimated from measurements of the fetal abdominal and head circumference, femur length and the biparietal diameter. The effects of fetal presentation, maternal bladder volume, placenta location, gestational age and maternal AP thickness on fetal depth and size were analysed. The fetal position from the anterior surface of the mother's abdomen is shorter for posterior placenta and empty bladder volume, but longer for anterior placenta and full bladder volume. Mean fetal depth (MFD) observed for all bladder volumes, fetal presentations and placenta locations increased from 6.5 +/- 0.5 cm to 10.2 +/- 0.7 cm over the duration of pregnancy. Similarly, mean fetal skull depth (FSD) increased from 6.6 +/- 0.6 cm to 9.8 +/- 0.6 cm over the period of pregnancy, but only from about 6.6 cm to 7.8 cm over the period (8-25 weeks) when damage to the developing brain has been observed to result in mental retardation. Using the range of mean fetal depth (4.7-13.9 cm) observed in this study and depth dose data at 75 kVp and 3.0 mmAl half value thickness (HVT), fetal absorbed dose would be overestimated by up to 66% or underestimated by up to 77% if the mean value of MFD (8.1 cm) is used rather than actual individual values. These errors increase with lower tube potential and filtration up to over 90% overestimation and up to 100% underestimation at 60 kVp and 1.0 mmAl filtration. PMID:10474497
Accurate estimation of influenza epidemics using Google search data via ARGO.
Yang, Shihao; Santillana, Mauricio; Kou, S C
2015-11-24
Accurate real-time tracking of influenza outbreaks helps public health officials make timely and meaningful decisions that could save lives. We propose an influenza tracking model, ARGO (AutoRegression with GOogle search data), that uses publicly available online search data. In addition to having a rigorous statistical foundation, ARGO outperforms all previously available Google-search-based tracking models, including the latest version of Google Flu Trends, even though it uses only low-quality search data as input from publicly available Google Trends and Google Correlate websites. ARGO not only incorporates the seasonality in influenza epidemics but also captures changes in people's online search behavior over time. ARGO is also flexible, self-correcting, robust, and scalable, making it a potentially powerful tool that can be used for real-time tracking of other social events at multiple temporal and spatial resolutions. PMID:26553980
Accurate estimation of influenza epidemics using Google search data via ARGO
Yang, Shihao; Santillana, Mauricio; Kou, S. C.
2015-01-01
Accurate real-time tracking of influenza outbreaks helps public health officials make timely and meaningful decisions that could save lives. We propose an influenza tracking model, ARGO (AutoRegression with GOogle search data), that uses publicly available online search data. In addition to having a rigorous statistical foundation, ARGO outperforms all previously available Google-search–based tracking models, including the latest version of Google Flu Trends, even though it uses only low-quality search data as input from publicly available Google Trends and Google Correlate websites. ARGO not only incorporates the seasonality in influenza epidemics but also captures changes in people’s online search behavior over time. ARGO is also flexible, self-correcting, robust, and scalable, making it a potentially powerful tool that can be used for real-time tracking of other social events at multiple temporal and spatial resolutions. PMID:26553980
Raman spectroscopy for highly accurate estimation of the age of refrigerated porcine muscle
NASA Astrophysics Data System (ADS)
Timinis, Constantinos; Pitris, Costas
2016-03-01
The high water content of meat, combined with all the nutrients it contains, make it vulnerable to spoilage at all stages of production and storage even when refrigerated at 5 °C. A non-destructive and in situ tool for meat sample testing, which could provide an accurate indication of the storage time of meat, would be very useful for the control of meat quality as well as for consumer safety. The proposed solution is based on Raman spectroscopy which is non-invasive and can be applied in situ. For the purposes of this project, 42 meat samples from 14 animals were obtained and three Raman spectra per sample were collected every two days for two weeks. The spectra were subsequently processed and the sample age was calculated using a set of linear differential equations. In addition, the samples were classified in categories corresponding to the age in 2-day steps (i.e., 0, 2, 4, 6, 8, 10, 12 or 14 days old), using linear discriminant analysis and cross-validation. Contrary to other studies, where the samples were simply grouped into two categories (higher or lower quality, suitable or unsuitable for human consumption, etc.), in this study, the age was predicted with a mean error of ~ 1 day (20%) or classified, in 2-day steps, with 100% accuracy. Although Raman spectroscopy has been used in the past for the analysis of meat samples, the proposed methodology has resulted in a prediction of the sample age far more accurately than any report in the literature.
Techniques for accurate estimation of net discharge in a tidal channel
Simpson, Michael R.; Bland, Roger
1999-01-01
An ultrasonic velocity meter discharge-measurement site in a tidally affected region of the Sacramento-San Joaquin rivers was used to study the accuracy of the index velocity calibration procedure. Calibration data consisting of ultrasonic velocity meter index velocity and concurrent acoustic Doppler discharge measurement data were collected during three time periods. The relative magnitude of equipment errors, acoustic Doppler discharge measurement errors, and calibration errors were evaluated. Calibration error was the most significant source of error in estimating net discharge. Using a comprehensive calibration method, net discharge estimates developed from the three sets of calibration data differed by less than an average of 4 cubic meters per second. Typical maximum flow rates during the data-collection period averaged 750 cubic meters per second.
Lower bound on reliability for Weibull distribution when shape parameter is not estimated accurately
NASA Technical Reports Server (NTRS)
Huang, Zhaofeng; Porter, Albert A.
1991-01-01
The mathematical relationships between the shape parameter Beta and estimates of reliability and a life limit lower bound for the two parameter Weibull distribution are investigated. It is shown that under rather general conditions, both the reliability lower bound and the allowable life limit lower bound (often called a tolerance limit) have unique global minimums over a range of Beta. Hence lower bound solutions can be obtained without assuming or estimating Beta. The existence and uniqueness of these lower bounds are proven. Some real data examples are given to show how these lower bounds can be easily established and to demonstrate their practicality. The method developed here has proven to be extremely useful when using the Weibull distribution in analysis of no-failure or few-failures data. The results are applicable not only in the aerospace industry but anywhere that system reliabilities are high.
Lower bound on reliability for Weibull distribution when shape parameter is not estimated accurately
NASA Technical Reports Server (NTRS)
Huang, Zhaofeng; Porter, Albert A.
1990-01-01
The mathematical relationships between the shape parameter Beta and estimates of reliability and a life limit lower bound for the two parameter Weibull distribution are investigated. It is shown that under rather general conditions, both the reliability lower bound and the allowable life limit lower bound (often called a tolerance limit) have unique global minimums over a range of Beta. Hence lower bound solutions can be obtained without assuming or estimating Beta. The existence and uniqueness of these lower bounds are proven. Some real data examples are given to show how these lower bounds can be easily established and to demonstrate their practicality. The method developed here has proven to be extremely useful when using the Weibull distribution in analysis of no-failure or few-failures data. The results are applicable not only in the aerospace industry but anywhere that system reliabilities are high.
Are satellite based rainfall estimates accurate enough for crop modelling under Sahelian climate?
NASA Astrophysics Data System (ADS)
Ramarohetra, J.; Sultan, B.
2012-04-01
Agriculture is considered as the most climate dependant human activity. In West Africa and especially in the sudano-sahelian zone, rain-fed agriculture - that represents 93% of cultivated areas and is the means of support of 70% of the active population - is highly vulnerable to precipitation variability. To better understand and anticipate climate impacts on agriculture, crop models - that estimate crop yield from climate information (e.g rainfall, temperature, insolation, humidity) - have been developed. These crop models are useful (i) in ex ante analysis to quantify the impact of different strategies implementation - crop management (e.g. choice of varieties, sowing date), crop insurance or medium-range weather forecast - on yields, (ii) for early warning systems and to (iii) assess future food security. Yet, the successful application of these models depends on the accuracy of their climatic drivers. In the sudano-sahelian zone , the quality of precipitation estimations is then a key factor to understand and anticipate climate impacts on agriculture via crop modelling and yield estimations. Different kinds of precipitation estimations can be used. Ground measurements have long-time series but an insufficient network density, a large proportion of missing values, delay in reporting time, and they have limited availability. An answer to these shortcomings may lie in the field of remote sensing that provides satellite-based precipitation estimations. However, satellite-based rainfall estimates (SRFE) are not a direct measurement but rather an estimation of precipitation. Used as an input for crop models, it determines the performance of the simulated yield, hence SRFE require validation. The SARRAH crop model is used to model three different varieties of pearl millet (HKP, MTDO, Souna3) in a square degree centred on 13.5°N and 2.5°E, in Niger. Eight satellite-based rainfall daily products (PERSIANN, CMORPH, TRMM 3b42-RT, GSMAP MKV+, GPCP, TRMM 3b42v6, RFEv2 and
Plant DNA Barcodes Can Accurately Estimate Species Richness in Poorly Known Floras
Costion, Craig; Ford, Andrew; Cross, Hugh; Crayn, Darren; Harrington, Mark; Lowe, Andrew
2011-01-01
Background Widespread uptake of DNA barcoding technology for vascular plants has been slow due to the relatively poor resolution of species discrimination (∼70%) and low sequencing and amplification success of one of the two official barcoding loci, matK. Studies to date have mostly focused on finding a solution to these intrinsic limitations of the markers, rather than posing questions that can maximize the utility of DNA barcodes for plants with the current technology. Methodology/Principal Findings Here we test the ability of plant DNA barcodes using the two official barcoding loci, rbcLa and matK, plus an alternative barcoding locus, trnH-psbA, to estimate the species diversity of trees in a tropical rainforest plot. Species discrimination accuracy was similar to findings from previous studies but species richness estimation accuracy proved higher, up to 89%. All combinations which included the trnH-psbA locus performed better at both species discrimination and richness estimation than matK, which showed little enhanced species discriminatory power when concatenated with rbcLa. The utility of the trnH-psbA locus is limited however, by the occurrence of intraspecific variation observed in some angiosperm families to occur as an inversion that obscures the monophyly of species. Conclusions/Significance We demonstrate for the first time, using a case study, the potential of plant DNA barcodes for the rapid estimation of species richness in taxonomically poorly known areas or cryptic populations revealing a powerful new tool for rapid biodiversity assessment. The combination of the rbcLa and trnH-psbA loci performed better for this purpose than any two-locus combination that included matK. We show that although DNA barcodes fail to discriminate all species of plants, new perspectives and methods on biodiversity value and quantification may overshadow some of these shortcomings by applying barcode data in new ways. PMID:22096501
Lupaşcu, Carmen Alina; Tegolo, Domenico; Trucco, Emanuele
2013-12-01
We present an algorithm estimating the width of retinal vessels in fundus camera images. The algorithm uses a novel parametric surface model of the cross-sectional intensities of vessels, and ensembles of bagged decision trees to estimate the local width from the parameters of the best-fit surface. We report comparative tests with REVIEW, currently the public database of reference for retinal width estimation, containing 16 images with 193 annotated vessel segments and 5066 profile points annotated manually by three independent experts. Comparative tests are reported also with our own set of 378 vessel widths selected sparsely in 38 images from the Tayside Scotland diabetic retinopathy screening programme and annotated manually by two clinicians. We obtain considerably better accuracies compared to leading methods in REVIEW tests and in Tayside tests. An important advantage of our method is its stability (success rate, i.e., meaningful measurement returned, of 100% on all REVIEW data sets and on the Tayside data set) compared to a variety of methods from the literature. We also find that results depend crucially on testing data and conditions, and discuss criteria for selecting a training set yielding optimal accuracy. PMID:24001930
Chon, K H; Cohen, R J; Holstein-Rathlou, N H
1997-01-01
A linear and nonlinear autoregressive moving average (ARMA) identification algorithm is developed for modeling time series data. The algorithm uses Laguerre expansion of kernals (LEK) to estimate Volterra-Wiener kernals. However, instead of estimating linear and nonlinear system dynamics via moving average models, as is the case for the Volterra-Wiener analysis, we propose an ARMA model-based approach. The proposed algorithm is essentially the same as LEK, but this algorithm is extended to include past values of the output as well. Thus, all of the advantages associated with using the Laguerre function remain with our algorithm; but, by extending the algorithm to the linear and nonlinear ARMA model, a significant reduction in the number of Laguerre functions can be made, compared with the Volterra-Wiener approach. This translates into a more compact system representation and makes the physiological interpretation of higher order kernels easier. Furthermore, simulation results show better performance of the proposed approach in estimating the system dynamics than LEK in certain cases, and it remains effective in the presence of significant additive measurement noise. PMID:9236985
NASA Astrophysics Data System (ADS)
Rosenthal, Yair; Lohmann, George P.
2002-09-01
Paired δ18O and Mg/Ca measurements on the same foraminiferal shells offer the ability to independently estimate sea surface temperature (SST) changes and assess their temporal relationship to the growth and decay of continental ice sheets. The accuracy of this method is confounded, however, by the absence of a quantitative method to correct Mg/Ca records for alteration by dissolution. Here we describe dissolution-corrected calibrations for Mg/Ca-paleothermometry in which the preexponent constant is a function of size-normalized shell weight: (1) for G. ruber (212-300 μm) (Mg/Ca)ruber = (0.025 wt + 0.11) e0.095T and (b) for G. sacculifer (355-425 μm) (Mg/Ca)sacc = (0.0032 wt + 0.181) e0.095T. The new calibrations improve the accuracy of SST estimates and are globally applicable. With this correction, eastern equatorial Atlantic SST during the Last Glacial Maximum is estimated to be 2.9° ± 0.4°C colder than today.
Using identity by descent estimation with dense genotype data to detect positive selection.
Han, Lide; Abney, Mark
2013-02-01
Identification of genomic loci and segments that are identical by descent (IBD) allows inference on problems such as relatedness detection, IBD disease mapping, heritability estimation and detection of recent or ongoing positive selection. Here, employing a novel statistical method, we use IBD to find signals of selection in the Maasai from Kinyawa, Kenya (MKK). In doing so, we demonstrate the advantage of statistical tools that can probabilistically estimate IBD sharing without having to thin genotype data because of linkage disequilibrium (LD), and that allow for both inbreeding and more than one allele to be shared IBD. We use our novel method, GIBDLD, to estimate IBD sharing between all pairs of individuals at all genotyped SNPs in the MKK, and, by looking for genomic regions showing excess IBD sharing in unrelated pairs, find loci that are known to have undergone recent selection (eg, the LCT gene and the HLA region) as well as many novel loci. Intriguingly, those loci that show the highest amount of excess IBD, with the exception of HLA, also show a substantial number of unrelated pairs sharing all four of their alleles IBD. In contrast to other IBD detection methods, GIBDLD provides accurate probabilistic estimates at each locus for all nine possible IBD sharing states between a pair of individuals, thus allowing for consanguinity, while also modeling LD, thus removing the need to thin SNPs. These characteristics will prove valuable for those doing genetic studies, and estimating IBD, in the wide variety of human populations. PMID:22781100
Higher Accurate Estimation of Axial and Bending Stiffnesses of Plates Clamped by Bolts
NASA Astrophysics Data System (ADS)
Naruse, Tomohiro; Shibutani, Yoji
Equivalent stiffness of clamped plates should be prescribed not only to evaluate the strength of bolted joints by the scheme of “joint diagram” but also to make structural analyses for practical structures with many bolted joints. We estimated the axial stiffness and bending stiffness of clamped plates by using Finite Element (FE) analyses while taking the contact condition on bearing surfaces and between the plates into account. The FE models were constructed for bolted joints tightened with M8, 10, 12 and 16 bolts and plate thicknesses of 3.2, 4.5, 6.0 and 9.0 mm, and the axial and bending compliances were precisely evaluated. These compliances of clamped plates were compared with those from VDI 2230 (2003) code, in which the equivalent conical compressive stress field in the plate has been assumed. The code gives larger axial stiffness for 11% and larger bending stiffness for 22%, and it cannot apply to the clamped plates with different thickness. Thus the code shall give lower bolt stress (unsafe estimation). We modified the vertical angle tangent, tanφ, of the equivalent conical by adding a term of the logarithm of thickness ratio t1/t2 and by fitting to the analysis results. The modified tanφ can estimate the axial compliance with the error from -1.5% to 6.8% and the bending compliance with the error from -6.5% to 10%. Furthermore, the modified tanφ can take the thickness difference into consideration.
Accurate estimation of airborne ultrasonic time-of-flight for overlapping echoes.
Sarabia, Esther G; Llata, Jose R; Robla, Sandra; Torre-Ferrero, Carlos; Oria, Juan P
2013-01-01
In this work, an analysis of the transmission of ultrasonic signals generated by piezoelectric sensors for air applications is presented. Based on this analysis, an ultrasonic response model is obtained for its application to the recognition of objects and structured environments for navigation by autonomous mobile robots. This model enables the analysis of the ultrasonic response that is generated using a pair of sensors in transmitter-receiver configuration using the pulse-echo technique. This is very interesting for recognizing surfaces that simultaneously generate a multiple echo response. This model takes into account the effect of the radiation pattern, the resonant frequency of the sensor, the number of cycles of the excitation pulse, the dynamics of the sensor and the attenuation with distance in the medium. This model has been developed, programmed and verified through a battery of experimental tests. Using this model a new procedure for obtaining accurate time of flight is proposed. This new method is compared with traditional ones, such as threshold or correlation, to highlight its advantages and drawbacks. Finally the advantages of this method are demonstrated for calculating multiple times of flight when the echo is formed by several overlapping echoes. PMID:24284774
Accurate Estimation of Airborne Ultrasonic Time-of-Flight for Overlapping Echoes
Sarabia, Esther G.; Llata, Jose R.; Robla, Sandra; Torre-Ferrero, Carlos; Oria, Juan P.
2013-01-01
In this work, an analysis of the transmission of ultrasonic signals generated by piezoelectric sensors for air applications is presented. Based on this analysis, an ultrasonic response model is obtained for its application to the recognition of objects and structured environments for navigation by autonomous mobile robots. This model enables the analysis of the ultrasonic response that is generated using a pair of sensors in transmitter-receiver configuration using the pulse-echo technique. This is very interesting for recognizing surfaces that simultaneously generate a multiple echo response. This model takes into account the effect of the radiation pattern, the resonant frequency of the sensor, the number of cycles of the excitation pulse, the dynamics of the sensor and the attenuation with distance in the medium. This model has been developed, programmed and verified through a battery of experimental tests. Using this model a new procedure for obtaining accurate time of flight is proposed. This new method is compared with traditional ones, such as threshold or correlation, to highlight its advantages and drawbacks. Finally the advantages of this method are demonstrated for calculating multiple times of flight when the echo is formed by several overlapping echoes. PMID:24284774
Daily estimates of the earth's pole position with the Global Positioning System
NASA Technical Reports Server (NTRS)
Lindqwister, Ulf J.; Freedman, Adam P.; Blewitt, Geoffrey
1992-01-01
Daily estimates of the earth's pole position have been obtained with measurements from a worldwide network of GPS receivers, obtained during the three week GIG '91 experiment in January-February 1991. For this short-term study, the GPS based polar motion series agrees with the other space based geodetic techniques (Very Long Baseline Interferometry and Satellite Laser Ranging) to about 0.4 mas rms, after the removal of mean biases of order 1-3 mas. The small error in day-to-day variability is not sensitive to the fiducial strategy used, nor are fiducial sites even necessary for monitoring high frequency pole position variability. The small biases indicate that the applied reference frames of the three geodetic techniques are nearly aligned, that the GPS fiducial errors are small, and that systematic errors in GPS are also small (of order 5 ppb). A well determined reference frame is necessary for monitoring the long-term stability of polar motion and for separating it from other long-term signals such as tectonic motion and internal systematic errors.
An Energy-Efficient Strategy for Accurate Distance Estimation in Wireless Sensor Networks
Tarrío, Paula; Bernardos, Ana M.; Casar, José R.
2012-01-01
In line with recent research efforts made to conceive energy saving protocols and algorithms and power sensitive network architectures, in this paper we propose a transmission strategy to minimize the energy consumption in a sensor network when using a localization technique based on the measurement of the strength (RSS) or the time of arrival (TOA) of the received signal. In particular, we find the transmission power and the packet transmission rate that jointly minimize the total consumed energy, while ensuring at the same time a desired accuracy in the RSS or TOA measurements. We also propose some corrections to these theoretical results to take into account the effects of shadowing and packet loss in the propagation channel. The proposed strategy is shown to be effective in realistic scenarios providing energy savings with respect to other transmission strategies, and also guaranteeing a given accuracy in the distance estimations, which will serve to guarantee a desired accuracy in the localization result. PMID:23202218
Indoor Positioning in Wireless Local Area Networks with Online Path-Loss Parameter Estimation
Bruno, Luigi
2014-01-01
Location based services are gathering an even wider interest also in indoor environments and urban canyons, where satellite systems like GPS are no longer accurate. A much addressed solution for estimating the user position exploits the received signal strengths (RSS) in wireless local area networks (WLANs), which are very common nowadays. However, the performances of RSS based location systems are still unsatisfactory for many applications, due to the difficult modeling of the propagation channel, whose features are affected by severe changes. In this paper we propose a localization algorithm which takes into account the nonstationarity of the working conditions by estimating and tracking the key parameters of RSS propagation. It is based on a Sequential Monte Carlo realization of the optimal Bayesian estimation scheme, whose functioning is improved by exploiting the Rao-Blackwellization rationale. Two key statistical models for RSS characterization are deeply analyzed, by presenting effective implementations of the proposed scheme and by assessing the positioning accuracy by extensive computer experiments. Many different working conditions are analyzed by simulated data and corroborated through the validation in a real world scenario. PMID:25165755
Indoor positioning in wireless local area networks with online path-loss parameter estimation.
Bruno, Luigi; Addesso, Paolo; Restaino, Rocco
2014-01-01
Location based services are gathering an even wider interest also in indoor environments and urban canyons, where satellite systems like GPS are no longer accurate. A much addressed solution for estimating the user position exploits the received signal strengths (RSS) in wireless local area networks (WLANs), which are very common nowadays. However, the performances of RSS based location systems are still unsatisfactory for many applications, due to the difficult modeling of the propagation channel, whose features are affected by severe changes. In this paper we propose a localization algorithm which takes into account the nonstationarity of the working conditions by estimating and tracking the key parameters of RSS propagation. It is based on a Sequential Monte Carlo realization of the optimal Bayesian estimation scheme, whose functioning is improved by exploiting the Rao-Blackwellization rationale. Two key statistical models for RSS characterization are deeply analyzed, by presenting effective implementations of the proposed scheme and by assessing the positioning accuracy by extensive computer experiments. Many different working conditions are analyzed by simulated data and corroborated through the validation in a real world scenario. PMID:25165755
[Research on maize multispectral image accurate segmentation and chlorophyll index estimation].
Wu, Qian; Sun, Hong; Li, Min-zan; Song, Yuan-yuan; Zhang, Yan-e
2015-01-01
In order to rapidly acquire maize growing information in the field, a non-destructive method of maize chlorophyll content index measurement was conducted based on multi-spectral imaging technique and imaging processing technology. The experiment was conducted at Yangling in Shaanxi province of China and the crop was Zheng-dan 958 planted in about 1 000 m X 600 m experiment field. Firstly, a 2-CCD multi-spectral image monitoring system was available to acquire the canopy images. The system was based on a dichroic prism, allowing precise separation of the visible (Blue (B), Green (G), Red (R): 400-700 nm) and near-infrared (NIR, 760-1 000 nm) band. The multispectral images were output as RGB and NIR images via the system vertically fixed to the ground with vertical distance of 2 m and angular field of 50°. SPAD index of each sample was'measured synchronously to show the chlorophyll content index. Secondly, after the image smoothing using adaptive smooth filtering algorithm, the NIR maize image was selected to segment the maize leaves from background, because there was a big difference showed in gray histogram between plant and soil background. The NIR image segmentation algorithm was conducted following steps of preliminary and accuracy segmentation: (1) The results of OTSU image segmentation method and the variable threshold algorithm were discussed. It was revealed that the latter was better one in corn plant and weed segmentation. As a result, the variable threshold algorithm based on local statistics was selected for the preliminary image segmentation. The expansion and corrosion were used to optimize the segmented image. (2) The region labeling algorithm was used to segment corn plants from soil and weed background with an accuracy of 95. 59 %. And then, the multi-spectral image of maize canopy was accurately segmented in R, G and B band separately. Thirdly, the image parameters were abstracted based on the segmented visible and NIR images. The average gray
The challenges of accurately estimating time of long bone injury in children.
Pickett, Tracy A
2015-07-01
The ability to determine the time an injury occurred can be of crucial significance in forensic medicine and holds special relevance to the investigation of child abuse. However, dating paediatric long bone injury, including fractures, is nuanced by complexities specific to the paediatric population. These challenges include the ability to identify bone injury in a growing or only partially-calcified skeleton, different injury patterns seen within the spectrum of the paediatric population, the effects of bone growth on healing as a separate entity from injury, differential healing rates seen at different ages, and the relative scarcity of information regarding healing rates in children, especially the very young. The challenges posed by these factors are compounded by a lack of consistency in defining and categorizing healing parameters. This paper sets out the primary limitations of existing knowledge regarding estimating timing of paediatric bone injury. Consideration and understanding of the multitude of factors affecting bone injury and healing in children will assist those providing opinion in the medical-legal forum. PMID:26048508
NASA Astrophysics Data System (ADS)
Vuye, Cedric; Vanlanduit, Steve; Guillaume, Patrick
2009-06-01
When using optical measurements of the sound fields inside a glass tube, near the material under test, to estimate the reflection and absorption coefficients, not only these acoustical parameters but also confidence intervals can be determined. The sound fields are visualized using a scanning laser Doppler vibrometer (SLDV). In this paper the influence of different test signals on the quality of the results, obtained with this technique, is examined. The amount of data gathered during one measurement scan makes a thorough statistical analysis possible leading to the knowledge of confidence intervals. The use of a multi-sine, constructed on the resonance frequencies of the test tube, shows to be a very good alternative for the traditional periodic chirp. This signal offers the ability to obtain data for multiple frequencies in one measurement, without the danger of a low signal-to-noise ratio. The variability analysis in this paper clearly shows the advantages of the proposed multi-sine compared to the periodic chirp. The measurement procedure and the statistical analysis are validated by measuring the reflection ratio at a closed end and comparing the results with the theoretical value. Results of the testing of two building materials (an acoustic ceiling tile and linoleum) are presented and compared to supplier data.
Accurate Estimation of Protein Folding and Unfolding Times: Beyond Markov State Models.
Suárez, Ernesto; Adelman, Joshua L; Zuckerman, Daniel M
2016-08-01
Because standard molecular dynamics (MD) simulations are unable to access time scales of interest in complex biomolecular systems, it is common to "stitch together" information from multiple shorter trajectories using approximate Markov state model (MSM) analysis. However, MSMs may require significant tuning and can yield biased results. Here, by analyzing some of the longest protein MD data sets available (>100 μs per protein), we show that estimators constructed based on exact non-Markovian (NM) principles can yield significantly improved mean first-passage times (MFPTs) for protein folding and unfolding. In some cases, MSM bias of more than an order of magnitude can be corrected when identical trajectory data are reanalyzed by non-Markovian approaches. The NM analysis includes "history" information, higher order time correlations compared to MSMs, that is available in every MD trajectory. The NM strategy is insensitive to fine details of the states used and works well when a fine time-discretization (i.e., small "lag time") is used. PMID:27340835
Thermal Conductivities in Solids from First Principles: Accurate Computations and Rapid Estimates
NASA Astrophysics Data System (ADS)
Carbogno, Christian; Scheffler, Matthias
In spite of significant research efforts, a first-principles determination of the thermal conductivity κ at high temperatures has remained elusive. Boltzmann transport techniques that account for anharmonicity perturbatively become inaccurate under such conditions. Ab initio molecular dynamics (MD) techniques using the Green-Kubo (GK) formalism capture the full anharmonicity, but can become prohibitively costly to converge in time and size. We developed a formalism that accelerates such GK simulations by several orders of magnitude and that thus enables its application within the limited time and length scales accessible in ab initio MD. For this purpose, we determine the effective harmonic potential occurring during the MD, the associated temperature-dependent phonon properties and lifetimes. Interpolation in reciprocal and frequency space then allows to extrapolate to the macroscopic scale. For both force-field and ab initio MD, we validate this approach by computing κ for Si and ZrO2, two materials known for their particularly harmonic and anharmonic character. Eventually, we demonstrate how these techniques facilitate reasonable estimates of κ from existing MD calculations at virtually no additional computational cost.
Estimated SLR station position and network frame sensitivity to time-varying gravity
NASA Astrophysics Data System (ADS)
Zelensky, Nikita P.; Lemoine, Frank G.; Chinn, Douglas S.; Melachroinos, Stavros; Beckley, Brian D.; Beall, Jennifer Wiser; Bordyugov, Oleg
2014-06-01
This paper evaluates the sensitivity of ITRF2008-based satellite laser ranging (SLR) station positions estimated weekly using LAGEOS-1/2 data from 1993 to 2012 to non-tidal time-varying gravity (TVG). Two primary methods for modeling TVG from degree-2 are employed. The operational approach applies an annual GRACE-derived field, and IERS recommended linear rates for five coefficients. The experimental approach uses low-order/degree coefficients estimated weekly from SLR and DORIS processing of up to 11 satellites (tvg4x4). This study shows that the LAGEOS-1/2 orbits and the weekly station solutions are sensitive to more detailed modeling of TVG than prescribed in the current IERS standards. Over 1993-2012 tvg4x4 improves SLR residuals by 18 % and shows 10 % RMS improvement in station stability. Tests suggest that the improved stability of the tvg4x4 POD solution frame may help clarify geophysical signals present in the estimated station position time series. The signals include linear and seasonal station motion, and motion of the TRF origin, particularly in Z. The effect on both POD and the station solutions becomes increasingly evident starting in 2006. Over 2008-2012, the tvg4x4 series improves SLR residuals by 29 %. Use of the GRGS RL02 series shows similar improvement in POD. Using tvg4x4, secular changes in the TRF origin Z component double over the last decade and although not conclusive, it is consistent with increased geocenter rate expected due to continental ice melt. The test results indicate that accurate modeling of TVG is necessary for improvement of station position estimation using SLR data.
ProViDE: A software tool for accurate estimation of viral diversity in metagenomic samples
Ghosh, Tarini Shankar; Mohammed, Monzoorul Haque; Komanduri, Dinakar; Mande, Sharmila Shekhar
2011-01-01
Given the absence of universal marker genes in the viral kingdom, researchers typically use BLAST (with stringent E-values) for taxonomic classification of viral metagenomic sequences. Since majority of metagenomic sequences originate from hitherto unknown viral groups, using stringent e-values results in most sequences remaining unclassified. Furthermore, using less stringent e-values results in a high number of incorrect taxonomic assignments. The SOrt-ITEMS algorithm provides an approach to address the above issues. Based on alignment parameters, SOrt-ITEMS follows an elaborate work-flow for assigning reads originating from hitherto unknown archaeal/bacterial genomes. In SOrt-ITEMS, alignment parameter thresholds were generated by observing patterns of sequence divergence within and across various taxonomic groups belonging to bacterial and archaeal kingdoms. However, many taxonomic groups within the viral kingdom lack a typical Linnean-like taxonomic hierarchy. In this paper, we present ProViDE (Program for Viral Diversity Estimation), an algorithm that uses a customized set of alignment parameter thresholds, specifically suited for viral metagenomic sequences. These thresholds capture the pattern of sequence divergence and the non-uniform taxonomic hierarchy observed within/across various taxonomic groups of the viral kingdom. Validation results indicate that the percentage of ‘correct’ assignments by ProViDE is around 1.7 to 3 times higher than that by the widely used similarity based method MEGAN. The misclassification rate of ProViDE is around 3 to 19% (as compared to 5 to 42% by MEGAN) indicating significantly better assignment accuracy. ProViDE software and a supplementary file (containing supplementary figures and tables referred to in this article) is available for download from http://metagenomics.atc.tcs.com/binning/ProViDE/ PMID:21544173
A new method based on the subpixel Gaussian model for accurate estimation of asteroid coordinates
NASA Astrophysics Data System (ADS)
Savanevych, V. E.; Briukhovetskyi, O. B.; Sokovikova, N. S.; Bezkrovny, M. M.; Vavilova, I. B.; Ivashchenko, Yu. M.; Elenin, L. V.; Khlamov, S. V.; Movsesian, Ia. S.; Dashkova, A. M.; Pogorelov, A. V.
2015-08-01
We describe a new iteration method to estimate asteroid coordinates, based on a subpixel Gaussian model of the discrete object image. The method operates by continuous parameters (asteroid coordinates) in a discrete observational space (the set of pixel potentials) of the CCD frame. In this model, the kind of coordinate distribution of the photons hitting a pixel of the CCD frame is known a priori, while the associated parameters are determined from a real digital object image. The method that is developed, which is flexible in adapting to any form of object image, has a high measurement accuracy along with a low calculating complexity, due to the maximum-likelihood procedure that is implemented to obtain the best fit instead of a least-squares method and Levenberg-Marquardt algorithm for minimization of the quadratic form. Since 2010, the method has been tested as the basis of our Collection Light Technology (COLITEC) software, which has been installed at several observatories across the world with the aim of the automatic discovery of asteroids and comets in sets of CCD frames. As a result, four comets (C/2010 X1 (Elenin), P/2011 NO1(Elenin), C/2012 S1 (ISON) and P/2013 V3 (Nevski)) as well as more than 1500 small Solar system bodies (including five near-Earth objects (NEOs), 21 Trojan asteroids of Jupiter and one Centaur object) have been discovered. We discuss these results, which allowed us to compare the accuracy parameters of the new method and confirm its efficiency. In 2014, the COLITEC software was recommended to all members of the Gaia-FUN-SSO network for analysing observations as a tool to detect faint moving objects in frames.
Figure of merit of diamond power devices based on accurately estimated impact ionization processes
NASA Astrophysics Data System (ADS)
Hiraiwa, Atsushi; Kawarada, Hiroshi
2013-07-01
Although a high breakdown voltage or field is considered as a major advantage of diamond, there has been a large difference in breakdown voltages or fields of diamond devices in literature. Most of these apparently contradictory results did not correctly reflect material properties because of specific device designs, such as punch-through structure and insufficient edge termination. Once these data were removed, the remaining few results, including a record-high breakdown field of 20 MV/cm, were theoretically reproduced, exactly calculating ionization integrals based on the ionization coefficients that were obtained after compensating for possible errors involved in reported theoretical values. In this compensation, we newly developed a method for extracting an ionization coefficient from an arbitrary relationship between breakdown voltage and doping density in the Chynoweth's framework. The breakdown field of diamond was estimated to depend on the doping density more than other materials, and accordingly required to be compared at the same doping density. The figure of merit (FOM) of diamond devices, obtained using these breakdown data, was comparable to the FOMs of 4H-SiC and Wurtzite-GaN devices at room temperature, but was projected to be larger than the latter by more than one order of magnitude at higher temperatures about 300 °C. Considering the relatively undeveloped state of diamond technology, there is room for further enhancement of the diamond FOM, improving breakdown voltage and mobility. Through these investigations, junction breakdown was found to be initiated by electrons or holes in a p--type or n--type drift layer, respectively. The breakdown voltages in the two types of drift layers differed from each other in a strict sense but were practically the same. Hence, we do not need to care about the conduction type of drift layers, but should rather exactly calculate the ionization integral without approximating ionization coefficients by a power
Wind effect on PV module temperature: Analysis of different techniques for an accurate estimation.
NASA Astrophysics Data System (ADS)
Schwingshackl, Clemens; Petitta, Marcello; Ernst Wagner, Jochen; Belluardo, Giorgio; Moser, David; Castelli, Mariapina; Zebisch, Marc; Tetzlaff, Anke
2013-04-01
temperature estimation using meteorological parameters. References: [1] Skoplaki, E. et al., 2008: A simple correlation for the operating temperature of photovoltaic modules of arbitrary mounting, Solar Energy Materials & Solar Cells 92, 1393-1402 [2] Skoplaki, E. et al., 2008: Operating temperature of photovoltaic modules: A survey of pertinent correlations, Renewable Energy 34, 23-29 [3] Koehl, M. et al., 2011: Modeling of the nominal operating cell temperature based on outdoor weathering, Solar Energy Materials & Solar Cells 95, 1638-1646 [4] Mattei, M. et al., 2005: Calculation of the polycrystalline PV module temperature using a simple method of energy balance, Renewable Energy 31, 553-567 [5] Kurtz, S. et al.: Evaluation of high-temperature exposure of rack-mounted photovoltaic modules
NASA Astrophysics Data System (ADS)
Guarnieri, A.; Milan, N.; Pirotti, F.; Vettore, A.
2011-12-01
In the automotive sector, especially in these last decade, a growing number of investigations have taken into account electronic systems to check and correct the behavior of drivers, increasing road safety. The possibility to identify with high accuracy the vehicle position in a mapping reference frame for driving directions and best-route analysis is also another topic which attracts lot of interest from the research and development sector. To reach the objective of accurate vehicle positioning and integrate response events, it is necessary to estimate time by time the position, orientation and velocity of the system. To this aim low cost GPS and MEMS (sensors can be used. In comparison to a four wheel vehicle, the dynamics of a two wheel vehicle (e.g. a scooter) feature a higher level of complexity. Indeed more degrees of freedom must be taken into account to describe the motion of the latter. For example a scooter can twist sideways, thus generating a roll angle. A slight pitch angle has to be considered as well, since wheel suspensions have a higher degree of motion with respect to four wheel vehicles. In this paper we present a method for the accurate reconstruction of the trajectory of a motorcycle ("Vespa" scooter), which can be used as alternative to the "classical" approach based on the integration of GPS and INS sensors. Position and orientation of the scooter are derived from MEMS data and images acquired by on-board digital camera. A Bayesian filter provides the means for integrating the data from MEMS-based orientation sensor and the GPS receiver.
COMPARISON OF RECURSIVE ESTIMATION TECHNIQUES FOR POSITION TRACKING RADIOACTIVE SOURCES
K. MUSKE; J. HOWSE
2000-09-01
This paper compares the performance of recursive state estimation techniques for tracking the physical location of a radioactive source within a room based on radiation measurements obtained from a series of detectors at fixed locations. Specifically, the extended Kalman filter, algebraic observer, and nonlinear least squares techniques are investigated. The results of this study indicate that recursive least squares estimation significantly outperforms the other techniques due to the severe model nonlinearity.
Sahu, Nityananda; Singh, Gurmeet; Nandi, Apurba; Gadre, Shridhar R
2016-07-21
Owing to the steep scaling behavior, highly accurate CCSD(T) calculations, the contemporary gold standard of quantum chemistry, are prohibitively difficult for moderate- and large-sized water clusters even with the high-end hardware. The molecular tailoring approach (MTA), a fragmentation-based technique is found to be useful for enabling such high-level ab initio calculations. The present work reports the CCSD(T) level binding energies of many low-lying isomers of large (H2O)n (n = 16, 17, and 25) clusters employing aug-cc-pVDZ and aug-cc-pVTZ basis sets within the MTA framework. Accurate estimation of the CCSD(T) level binding energies [within 0.3 kcal/mol of the respective full calculation (FC) results] is achieved after effecting the grafting procedure, a protocol for minimizing the errors in the MTA-derived energies arising due to the approximate nature of MTA. The CCSD(T) level grafting procedure presented here hinges upon the well-known fact that the MP2 method, which scales as O(N(5)), can be a suitable starting point for approximating to the highly accurate CCSD(T) [that scale as O(N(7))] energies. On account of the requirement of only an MP2-level FC on the entire cluster, the current methodology ultimately leads to a cost-effective solution for the CCSD(T) level accurate binding energies of large-sized water clusters even at the complete basis set limit utilizing off-the-shelf hardware. PMID:27351269
Mou, Weimin; Zhang, Lei
2014-12-01
This project examined the roles of idiothetic cues due to individuals' movement and allothetic cues independent of individuals' movement in individuals' estimations of their position and heading during locomotion. In an immersive virtual environment, participants learned the locations of five objects and then moved along two legs of a path before positioning the origin and the objects. Participants' estimations of their test position and their test heading were calculated based on the responded objects' locations, using a method of dissociating position estimation and heading estimation developed in this project. Results showed that when a conflicting visual orientation cue was presented after walking, participants relied on the allothetic cues (i.e., the visual orientation cue) for their heading estimation, but on idiothetic cues for their position estimation. These results indicate that after participants updated their position in terms the origin of the path (homing vector) via path integration, they estimated their heading. These results are inconsistent with the theoretical models stipulating that homing vectors are specified in terms of participants' body coordinate systems, but are consistent with the models stipulating that both homing vectors and participants' heading are specified in terms of a fixed reference direction in the environment. PMID:25215931
NASA Astrophysics Data System (ADS)
Khalaf-Allah, Mohamed
2007-12-01
The mobile terminal positioning problem is categorized into three different types according to the availability of (1) initial accurate location information and (2) motion measurement data. Location estimation refers to the mobile positioning problem when both the initial location and motion measurement data are not available. If both are available, the positioning problem is referred to as position tracking. When only motion measurements are available, the problem is known as global localization. These positioning problems were solved within the Bayesian filtering framework. Filter derivation and implementation algorithms are provided with emphasis on the mapping approach. The radio maps of the experimental area have been created by a 3D deterministic radio propagation tool with a grid resolution of 5 m. Real-world experimentation was conducted in a GSM network deployed in a semiurban environment in order to investigate the performance of the different positioning algorithms.
Wood, Nathan A.; del Agua, Diego Moral; Zenati, Marco A.; Riviere, Cameron N.
2012-01-01
HeartLander, a small mobile robot designed to provide treatments to the surface of the beating heart, overcomes a major difficulty of minimally invasive cardiac surgery, providing a stable operating platform. This is achieved inherently in the way the robot adheres to and crawls over the surface of the heart. This mode of operation does not require physiological motion compensation to provide this stable environment; however, modeling of physiological motion is advantageous in providing more accurate position estimation as well as synchronization of motion to the physiological cycles. The work presented uses an Extended Kalman Filter framework to estimate parameters of non-stationary Fourier series models of the motion of the heart due to the respiratory and cardiac cycles as well as the position of the robot as it moves over the surface of the heart. The proposed method is demonstrated in the laboratory with HeartLander operating on a physiological motion simulator. Improved performance is demonstrated in comparison to the filtering methods previously used with HeartLander. The use of detected physiological cycle phases to synchronize locomotion of HeartLander is also described. PMID:23066511
Novel rotor position estimation technique for switched reluctance motor (SRM)
NASA Astrophysics Data System (ADS)
Moradi, Hassan; Afjei, Ebrahim
2011-09-01
This article presents a new and novel method which is designed to detect the rotor position at standstill and at low speeds in switched reluctance motor. Since the inductance parameter plays a significant role both in the steady state and in the dynamic characteristics of an electromagnetic device, the rotor position can be determined using inductance bridge systems to measure unknown inductance and resistance values. In this method we use motor winding in Maxwell-Wien Bridge, with the standard capacitor and the resistor in parallel with it adjusted to achieve balance in an aligned position when the maximum inductance occurs. The supply voltage, in conjunction with the drive transistor, produces short pulses for this AC bridge. The condition of the balanced bridge v 0 = 0 leads to the relation between the impedances of the bridge branches. The phase inductance varies with the rotor position. Therefore the motor goes into an unaligned position and the Maxwell-Wien Bridge goes into an unbalanced condition thus causing variation in the state of the bridge output. It then continues to sense the rotor position with the motor running by applying the same procedure, but only to the un-energised phases winding. The simulation and experimentally obtained results demonstrate the feasibility and practicability of this method.
Steinmetz, Melissa; Czupryna, Anna; Bigambo, Machunde; Mzimbiri, Imam; Powell, George; Gwakisa, Paul
2015-01-01
In this study we show that incentives (dog collars and owner wristbands) are effective at increasing owner participation in mass dog rabies vaccination clinics and we conclude that household questionnaire surveys and the mark-re-sight (transect survey) method for estimating post-vaccination coverage are accurate when all dogs, including puppies, are included. Incentives were distributed during central-point rabies vaccination clinics in northern Tanzania to quantify their effect on owner participation. In villages where incentives were handed out participation increased, with an average of 34 more dogs being vaccinated. Through economies of scale, this represents a reduction in the cost-per-dog of $0.47. This represents the price-threshold under which the cost of the incentive used must fall to be economically viable. Additionally, vaccination coverage levels were determined in ten villages through the gold-standard village-wide census technique, as well as through two cheaper and quicker methods (randomized household questionnaire and the transect survey). Cost data were also collected. Both non-gold standard methods were found to be accurate when puppies were included in the calculations, although the transect survey and the household questionnaire survey over- and under-estimated the coverage respectively. Given that additional demographic data can be collected through the household questionnaire survey, and that its estimate of coverage is more conservative, we recommend this method. Despite the use of incentives the average vaccination coverage was below the 70% threshold for eliminating rabies. We discuss the reasons and suggest solutions to improve coverage. Given recent international targets to eliminate rabies, this study provides valuable and timely data to help improve mass dog vaccination programs in Africa and elsewhere. PMID:26633821
Minyoo, Abel B; Steinmetz, Melissa; Czupryna, Anna; Bigambo, Machunde; Mzimbiri, Imam; Powell, George; Gwakisa, Paul; Lankester, Felix
2015-12-01
In this study we show that incentives (dog collars and owner wristbands) are effective at increasing owner participation in mass dog rabies vaccination clinics and we conclude that household questionnaire surveys and the mark-re-sight (transect survey) method for estimating post-vaccination coverage are accurate when all dogs, including puppies, are included. Incentives were distributed during central-point rabies vaccination clinics in northern Tanzania to quantify their effect on owner participation. In villages where incentives were handed out participation increased, with an average of 34 more dogs being vaccinated. Through economies of scale, this represents a reduction in the cost-per-dog of $0.47. This represents the price-threshold under which the cost of the incentive used must fall to be economically viable. Additionally, vaccination coverage levels were determined in ten villages through the gold-standard village-wide census technique, as well as through two cheaper and quicker methods (randomized household questionnaire and the transect survey). Cost data were also collected. Both non-gold standard methods were found to be accurate when puppies were included in the calculations, although the transect survey and the household questionnaire survey over- and under-estimated the coverage respectively. Given that additional demographic data can be collected through the household questionnaire survey, and that its estimate of coverage is more conservative, we recommend this method. Despite the use of incentives the average vaccination coverage was below the 70% threshold for eliminating rabies. We discuss the reasons and suggest solutions to improve coverage. Given recent international targets to eliminate rabies, this study provides valuable and timely data to help improve mass dog vaccination programs in Africa and elsewhere. PMID:26633821
Mars lander position estimation in the presence of ephemeris biases.
NASA Technical Reports Server (NTRS)
Blackshear, W. T.; Tolson, R. H.; Day, G. M.
1972-01-01
The process of estimating the location of a spacecraft landed on the surface of Mars is investigated through the application of statistical estimation techniques to earth-based radio tracking data. The spacecraft location and the tracking geometry and schedule are consistent with Viking-type mission constraints. With mission control requirements in mind, the investigation is restricted to analysis of a short data arc (approximately 3 days). Statistics of the spacecraft location are obtained through analysis of (direct-link) tracking data for the landed spacecraft and through simultaneous analysis of tracking data for both a landed and an orbiting spacecraft. These estimates include the effects of model uncertainties in the ephemeris of Mars, tracking station locations, the Mars rotational period, the Mars gravity field, and the orientation of Mars axis of rotation. The most significant of these effects is shown to be due to the Mars ephemeris uncertainty. A dual spacecraft tracking technique is presented for substantially reducing these ephemeris effects.
Extension of synthetic estimation filters for relative position measurements
NASA Technical Reports Server (NTRS)
Monroe, Stanley E., Jr.; Juday, Richard D.
1988-01-01
The construction of synthetic estimation filters (SEF) for out-of-plane rotation is reported. When images corresponding to rotations between the angles which were used to construct the estimator were input to the simulator, the yaw measurement accuracy was a little better than one-half of a degree over the five degree range. If individual phase-only filters were used and the only criteria for yaw angle was 'best correlation', 11 filter would be required for the same range and accuracy. The technique proposed here is invariant to translation.
The Joint Position-Amplitude Formulation for Hurricane State Estimation
NASA Astrophysics Data System (ADS)
Ravela, S.; Williams, J.; Emanuel, K.
2008-12-01
Classical formulations of data assimilation, whether sequential, ensemble-based or variational, are amplitude adjustment methods. Such approaches can perform poorly when forecast locations of weather systems are displaced from their observations. Compensating position errors by adjusting amplitudes can produce unacceptably 'distorted' states, adversely affecting analysis, verification and subsequent forecasts. There are many sources of position error. It is non-trivial to decompose position error into constituent sources and yet correcting position errors during assimilation can be essential for operationally predicting strong, localized weather events such as tropical cyclones. We will argue and show that if we assume a perfect world where forecast errors do not have position errors and have a Gaussian uncertainty, then in the real world, the bias or variance induced by position errors is the only reason for suboptimal performance of contemporary assimilation methods. Therefore, we propose a method that accounts for both position and amplitude errors using a variational approach. We show that the objective can be solved for position and amplitude decision variables using stochastic methods, thus corresponding with ensemble data assimilation. We then show that if an Euler-Lagrange approximation is made, can solve the objective nearly as well in two steps. This approach is entirely consistent with contemporary data assimilation practice. In the two-step approach, the first step is field alignment, where the current model state is aligned with observations by adjusting a continuous field of local displacements, subject to certain constraints. The second step is amplitude adjustment, where contemporary assimilation approaches are used. We will then demonstrate several choices of constraints on the displacement field, first starting with fluid-like viscous constraints and then proceeding to a multiscale wavelet representation that allows better balance in the
Distributed estimation of sensors position in underwater wireless sensor network
NASA Astrophysics Data System (ADS)
Zandi, Rahman; Kamarei, Mahmoud; Amiri, Hadi
2016-05-01
In this paper, a localisation method for determining the position of fixed sensor nodes in an underwater wireless sensor network (UWSN) is introduced. In this simple and range-free scheme, the node localisation is achieved by utilising an autonomous underwater vehicle (AUV) that transverses through the network deployment area, and that periodically emits a message block via four directional acoustic beams. A message block contains the actual known AUV position as well as a directional dependent marker that allows a node to identify the respective transmit beam. The beams form a fixed angle with the AUV body. If a node passively receives message blocks, it could calculate the arithmetic mean of the coordinates existing in each messages sequence, to find coordinates at two different time instants via two different successive beams. The node position can be derived from the two computed positions of the AUV. The major advantage of the proposed localisation algorithm is that it is silent, which leads to energy efficiency for sensor nodes. The proposed method does not require any synchronisation among the nodes owing to being silent. Simulation results, using MATLAB, demonstrated that the proposed method had better performance than other similar AUV-based localisation methods in terms of the rates of well-localised sensor nodes and positional root mean square error.
Application of NTR ZTD estimates from GBAS network to improve fast-static GNSS positioning
NASA Astrophysics Data System (ADS)
Wielgosz, P.; Paziewski, J.; Stepniak, K.; Krukowska, M.; Kaplon, J.; Sierny, J.; Hadas, T.; Bosy, J.
2012-04-01
of kilometers were processed in fast-static mode using in-house developed GINPOS software. A 24-h data set was divided into 288 sessions, each of 1- or 5-minute long. Each session was processed independently and the obtained coordinate residuals were analysed. Four different approaches to the troposphere modelling were applied and tested: a) using a standard mathematical atmosphere model, b) using ZTD estimates based on GNSS data, c) using NRT ZTD estimates based on GNSS data, d) using NRT ZTD estimates based on meteorological data. The results show that NRT ZTD products can improve both the accuracy and the reliability of the fast-static positioning, what is of special interest to field surveyors. The most noticeable effect is observed in the station height component estimation. In some extreme cases, mismodelling of the troposphere may even disrupt ambiguity resolution and, therefore, prevents user from obtaining accurate position.
Bayesian Estimation of the Logistic Positive Exponent IRT Model
ERIC Educational Resources Information Center
Bolfarine, Heleno; Bazan, Jorge Luis
2010-01-01
A Bayesian inference approach using Markov Chain Monte Carlo (MCMC) is developed for the logistic positive exponent (LPE) model proposed by Samejima and for a new skewed Logistic Item Response Theory (IRT) model, named Reflection LPE model. Both models lead to asymmetric item characteristic curves (ICC) and can be appropriate because a symmetric…
2011-01-01
Background Data assimilation refers to methods for updating the state vector (initial condition) of a complex spatiotemporal model (such as a numerical weather model) by combining new observations with one or more prior forecasts. We consider the potential feasibility of this approach for making short-term (60-day) forecasts of the growth and spread of a malignant brain cancer (glioblastoma multiforme) in individual patient cases, where the observations are synthetic magnetic resonance images of a hypothetical tumor. Results We apply a modern state estimation algorithm (the Local Ensemble Transform Kalman Filter), previously developed for numerical weather prediction, to two different mathematical models of glioblastoma, taking into account likely errors in model parameters and measurement uncertainties in magnetic resonance imaging. The filter can accurately shadow the growth of a representative synthetic tumor for 360 days (six 60-day forecast/update cycles) in the presence of a moderate degree of systematic model error and measurement noise. Conclusions The mathematical methodology described here may prove useful for other modeling efforts in biology and oncology. An accurate forecast system for glioblastoma may prove useful in clinical settings for treatment planning and patient counseling. Reviewers This article was reviewed by Anthony Almudevar, Tomas Radivoyevitch, and Kristin Swanson (nominated by Georg Luebeck). PMID:22185645
Regularized Positive-Definite Fourth Order Tensor Field Estimation from DW-MRI★
Barmpoutis, Angelos; Vemuri, Baba C.; Howland, Dena; Forder, John R.
2009-01-01
In Diffusion Weighted Magnetic Resonance Image (DW-MRI) processing, a 2nd order tensor has been commonly used to approximate the diffusivity function at each lattice point of the DW-MRI data. From this tensor approximation, one can compute useful scalar quantities (e.g. anisotropy, mean diffusivity) which have been clinically used for monitoring encephalopathy, sclerosis, ischemia and other brain disorders. It is now well known that this 2nd-order tensor approximation fails to capture complex local tissue structures, e.g. crossing fibers, and as a result, the scalar quantities derived from these tensors are grossly inaccurate at such locations. In this paper we employ a 4th order symmetric positive-definite (SPD) tensor approximation to represent the diffusivity function and present a novel technique to estimate these tensors from the DW-MRI data guaranteeing the SPD property. Several articles have been reported in literature on higher order tensor approximations of the diffusivity function but none of them guarantee the positivity of the estimates, which is a fundamental constraint since negative values of the diffusivity are not meaningful. In this paper we represent the 4th-order tensors as ternary quartics and then apply Hilbert’s theorem on ternary quartics along with the Iwasawa parametrization to guarantee an SPD 4th-order tensor approximation from the DW-MRI data. The performance of this model is depicted on synthetic data as well as real DW-MRIs from a set of excised control and injured rat spinal cords, showing accurate estimation of scalar quantities such as generalized anisotropy and trace as well as fiber orientations. PMID:19063978
Noise estimation of beam position monitors at RHIC
Shen, X.; Bai, M.; Lee, S. Y.
2014-02-10
Beam position monitors (BPM) are used to record the average orbits and transverse turn-by-turn displacements of the beam centroid motion. The Relativistic Hadron Ion Collider (RHIC) has 160 BPMs for each plane in each of the Blue and Yellow rings: 72 dual-plane BPMs in the insertion regions (IR) and 176 single-plane modules in the arcs. Each BPM is able to acquire 1024 or 4096 consecutive turn-by-turn beam positions. Inevitably, there are broadband noisy signals in the turn-by-turn data due to BPM electronics as well as other sources. A detailed study of the BPM noise performance is critical for reliable optics measurement and beam dynamics analysis based on turn-by-turn data.
NASA Astrophysics Data System (ADS)
Omoniyi, Bayonle; Stow, Dorrik
2016-04-01
One of the major challenges in the assessment of and production from turbidite reservoirs is to take full account of thin and medium-bedded turbidites (<10cm and <30cm respectively). Although such thinner, low-pay sands may comprise a significant proportion of the reservoir succession, they can go unnoticed by conventional analysis and so negatively impact on reserve estimation, particularly in fields producing from prolific thick-bedded turbidite reservoirs. Field development plans often take little note of such thin beds, which are therefore bypassed by mainstream production. In fact, the trapped and bypassed fluids can be vital where maximising field value and optimising production are key business drivers. We have studied in detail, a succession of thin-bedded turbidites associated with thicker-bedded reservoir facies in the North Brae Field, UKCS, using a combination of conventional logs and cores to assess the significance of thin-bedded turbidites in computing hydrocarbon pore thickness (HPT). This quantity, being an indirect measure of thickness, is critical for an accurate estimation of original-oil-in-place (OOIP). By using a combination of conventional and unconventional logging analysis techniques, we obtain three different results for the reservoir intervals studied. These results include estimated net sand thickness, average sand thickness, and their distribution trend within a 3D structural grid. The net sand thickness varies from 205 to 380 ft, and HPT ranges from 21.53 to 39.90 ft. We observe that an integrated approach (neutron-density cross plots conditioned to cores) to HPT quantification reduces the associated uncertainties significantly, resulting in estimation of 96% of actual HPT. Further work will focus on assessing the 3D dynamic connectivity of the low-pay sands with the surrounding thick-bedded turbidite facies.
Logan, Corina J; Palmstrom, Christin R
2015-01-01
There is an increasing need to validate and collect data approximating brain size on individuals in the field to understand what evolutionary factors drive brain size variation within and across species. We investigated whether we could accurately estimate endocranial volume (a proxy for brain size), as measured by computerized tomography (CT) scans, using external skull measurements and/or by filling skulls with beads and pouring them out into a graduated cylinder for male and female great-tailed grackles. We found that while females had higher correlations than males, estimations of endocranial volume from external skull measurements or beads did not tightly correlate with CT volumes. We found no accuracy in the ability of external skull measures to predict CT volumes because the prediction intervals for most data points overlapped extensively. We conclude that we are unable to detect individual differences in endocranial volume using external skull measurements. These results emphasize the importance of validating and explicitly quantifying the predictive accuracy of brain size proxies for each species and each sex. PMID:26082858
A plan for accurate estimation of daily area-mean rainfall during the CaPE experiment
NASA Technical Reports Server (NTRS)
Duchon, Claude E.
1992-01-01
The Convection and Precipitation/Electrification (CaPE) experiment took place in east central Florida from 8 July to 18 August, 1991. There were five research themes associated with CaPE. In broad terms they are: investigation of the evolution of the electric field in convective clouds, determination of meteorological and electrical conditions associated with lightning, development of mesoscale numerical forecasts (2-12 hr) and nowcasts (less than 2 hr) of convective initiation and remote estimation of rainfall. It is the last theme coupled with numerous raingage and streamgage measurements, satellite and aircraft remote sensing, radiosondes and other meteorological measurements in the atmospheric boundary layer that provide the basis for determining the hydrologic cycle for the CaPE experiment area. The largest component of the hydrologic cycle in this region is rainfall. An accurate determination of daily area-mean rainfall is important in correctly modeling its apportionment into runoff, infiltration and evapotranspiration. In order to achieve this goal a research plan was devised and initial analysis begun. The overall research plan is discussed with special emphasis placed on the adjustment of radar rainfall estimates to raingage rainfall.
Estimation of Subdaily Polar Motion with the Global Positioning System During the Spoch '92 Campaign
NASA Technical Reports Server (NTRS)
Ibanez-Meier, R.; Freedman, A. P.; Herring, T. A.; Gross, R. S.; Lichten, S. M.; Lindqwister, U. J.
1994-01-01
Data collected over six days from a worldwide Global Positioning System (GPS) tracking network during the Epoch '92 campaign are used to estimate variations of the Earth's pole position every 30 minutes.
Position estimation and driving of an autonomous vehicle by monocular vision
NASA Astrophysics Data System (ADS)
Hanan, Jay C.; Kayathi, Pavan; Hughlett, Casey L.
2007-04-01
Automatic adaptive tracking in real-time for target recognition provided autonomous control of a scale model electric truck. The two-wheel drive truck was modified as an autonomous rover test-bed for vision based guidance and navigation. Methods were implemented to monitor tracking error and ensure a safe, accurate arrival at the intended science target. Some methods are situation independent relying only on the confidence error of the target recognition algorithm. Other methods take advantage of the scenario of combined motion and tracking to filter out anomalies. In either case, only a single calibrated camera was needed for position estimation. Results from real-time autonomous driving tests on the JPL simulated Mars yard are presented. Recognition error was often situation dependent. For the rover case, the background was in motion and may be characterized to provide visual cues on rover travel such as rate, pitch, roll, and distance to objects of interest or hazards. Objects in the scene may be used as landmarks, or waypoints, for such estimations. As objects are approached, their scale increases and their orientation may change. In addition, particularly on rough terrain, these orientation and scale changes may be unpredictable. Feature extraction combined with the neural network algorithm was successful in providing visual odometry in the simulated Mars environment.
Reliable estimation of shock position in shock-capturing compressible hydrodynamics codes
Nelson, Eric M
2008-01-01
The displacement method for estimating shock position in a shock-capturing compressible hydrodynamics code is introduced. Common estimates use simulation data within the captured shock, but the displacement method uses data behind the shock, making the estimate consistent with and as reliable as estimates of material parameters obtained from averages or fits behind the shock. The displacement method is described in the context of a steady shock in a one-dimensional lagrangian hydrodynamics code, and demonstrated on a piston problem and a spherical blast wave.The displacement method's estimates of shock position are much better than common estimates in such applications.
NASA Astrophysics Data System (ADS)
Li, Damei; Lu, Jun-An; Wu, Xiaoqun; Chen, Guanrong
2006-11-01
To estimate the ultimate bound and positively invariant set for a dynamic system is an important but quite challenging task in general. In this paper, we attempt to investigate the ultimate bound and positively invariant set for two specific systems, the Lorenz system and a unified chaotic system. We derive an ellipsoidal estimate of the ultimate bound and positively invariant set for the Lorenz system, for all the positive values of its parameters a, b and c, and obtain the minimum value of volume for the ellipsoid. Comparing with the best results in the current literature [D. Li, J. Lu, X. Wu, G. Chen, Estimating the bounds for the Lorenz family of chaotic systems, Chaos Solitons Fractals 23 (2005) 529-534; X. Liao, On the global basin of attraction and positively invariant set for the Lorenz chaotic system and its application in chaos control and synchronization, Sci. China Ser. E 34 (2004) 1404-1419], our new results fill up the gap of the estimate for the cases of 0positively invariant set for the Lorenz chaotic system and its application in chaos control and synchronization, Sci. China Ser. E 34 (2004) 1404-1419]. Furthermore, the estimation derived here contains the results given in [D. Li, J. Lu, X. Wu, G. Chen, Estimating the bounds for the Lorenz family of chaotic systems, Chaos Solitons Fractals 23 (2005) 529-534] and [X. Liao, On the global basin of attraction and positively invariant set for the Lorenz chaotic system and its application in chaos control and synchronization, Sci. China Ser. E 34 (2004) 1404-1419] as special cases. Along the same line, we also provide estimates of cylindrical and ellipsoidal bounds for a unified chaotic system, for its parameter range , and obtain the minimum value of volume for the ellipsoid. The estimate is more accurate than and also extends the result of [D. Li, J. Lu, X. Wu, G. Chen, Estimating the bounds for the Lorenz family of chaotic systems, Chaos
Nakano, Alberto Yoshihiro; Nakagawa, Seiichi; Yamamoto, Kazumasa
2009-12-01
A method which automatically provides the position and orientation of a directional acoustic source in an enclosed environment is proposed. In this method, different combinations of the estimated parameters from the received signals and the microphone positions of each array are used as inputs to the artificial neural network (ANN). The estimated parameters are composed of time delay estimates (TDEs), source position estimates, distance estimates, and energy features. The outputs of the ANN are the source orientation (one out of four possible orientations shifted by 90 degrees and either the best array which is defined as the nearest to the source) or the source position in two dimensional/three dimensional (2D/3D) space. This paper studies the position and orientation estimation performances of the ANN for different input/output combinations (and different numbers of hidden units). The best combination of parameters (TDEs and microphone positions) yields 21.8% reduction in the average position error compared to the following baselines and a correct orientation ratio greater than 99%. Position localization baselines consist of a time delay of arrival based method with an average position error of 34.1 cm and the steered response power with phase transform method with an average position error of 29.8 cm in 3D space. PMID:20000922
NASA Astrophysics Data System (ADS)
Kassinopoulos, Michalis; Pitris, Costas
2016-03-01
The modulations appearing on the backscattering spectrum originating from a scatterer are related to its diameter as described by Mie theory for spherical particles. Many metrics for Spectroscopic Optical Coherence Tomography (SOCT) take advantage of this observation in order to enhance the contrast of Optical Coherence Tomography (OCT) images. However, none of these metrics has achieved high accuracy when calculating the scatterer size. In this work, Mie theory was used to further investigate the relationship between the degree of modulation in the spectrum and the scatterer size. From this study, a new spectroscopic metric, the bandwidth of the Correlation of the Derivative (COD) was developed which is more robust and accurate, compared to previously reported techniques, in the estimation of scatterer size. The self-normalizing nature of the derivative and the robustness of the first minimum of the correlation as a measure of its width, offer significant advantages over other spectral analysis approaches especially for scatterer sizes above 3 μm. The feasibility of this technique was demonstrated using phantom samples containing 6, 10 and 16 μm diameter microspheres as well as images of normal and cancerous human colon. The results are very promising, suggesting that the proposed metric could be implemented in OCT spectral analysis for measuring nuclear size distribution in biological tissues. A technique providing such information would be of great clinical significance since it would allow the detection of nuclear enlargement at the earliest stages of precancerous development.
NASA Astrophysics Data System (ADS)
Mindur, B.; Alimov, S.; Fiutowski, T.; Schulz, C.; Wilpert, T.
2014-12-01
A two-dimensional (2D) position sensitive detector for neutron scattering applications based on low-pressure gas amplification and micro-strip technology was built and tested with an innovative readout electronics and data acquisition system. This detector contains a thin solid neutron converter and was developed for time- and thus wavelength-resolved neutron detection in single-event counting mode, which improves the image contrast in comparison with integrating detectors. The prototype detector of a Micro-Strip Gas Chamber (MSGC) was built with a solid natGd/CsI thermal neutron converter for spatial resolutions of about 100 μm and counting rates up to 107 neutrons/s. For attaining very high spatial resolutions and counting rates via micro-strip readout with centre-of-gravity evaluation of the signal amplitude distributions, a fast, channel-wise, self-triggering ASIC was developed. The front-end chips (MSGCROCs), which are very first signal processing components, are read out into powerful ADC-FPGA boards for on-line data processing and thereafter via Gigabit Ethernet link into the data receiving PC. The workstation PC is controlled by a modular, high performance dedicated software suite. Such a fast and accurate system is crucial for efficient radiography/tomography, diffraction or imaging applications based on high flux thermal neutron beam. In this paper a brief description of the detector concept with its operation principles, readout electronics requirements and design together with the signals processing stages performed in hardware and software are presented. In more detail the neutron test beam conditions and measurement results are reported. The focus of this paper is on the system integration, two dimensional spatial resolution, the time resolution of the readout system and the imaging capabilities of the overall setup. The detection efficiency of the detector prototype is estimated as well.
NASA Astrophysics Data System (ADS)
Rozov, Alexey; Demeshkina, Natalia; Khusainov, Iskander; Westhof, Eric; Yusupov, Marat; Yusupova, Gulnara
2016-01-01
Posttranscriptional modifications at the wobble position of transfer RNAs play a substantial role in deciphering the degenerate genetic code on the ribosome. The number and variety of modifications suggest different mechanisms of action during messenger RNA decoding, of which only a few were described so far. Here, on the basis of several 70S ribosome complex X-ray structures, we demonstrate how Escherichia coli tRNALysUUU with hypermodified 5-methylaminomethyl-2-thiouridine (mnm5s2U) at the wobble position discriminates between cognate codons AAA and AAG, and near-cognate stop codon UAA or isoleucine codon AUA, with which it forms pyrimidine-pyrimidine mismatches. We show that mnm5s2U forms an unusual pair with guanosine at the wobble position that expands general knowledge on the degeneracy of the genetic code and specifies a powerful role of tRNA modifications in translation. Our models consolidate the translational fidelity mechanism proposed previously where the steric complementarity and shape acceptance dominate the decoding mechanism.
Rozov, Alexey; Demeshkina, Natalia; Khusainov, Iskander; Westhof, Eric; Yusupov, Marat; Yusupova, Gulnara
2016-01-01
Posttranscriptional modifications at the wobble position of transfer RNAs play a substantial role in deciphering the degenerate genetic code on the ribosome. The number and variety of modifications suggest different mechanisms of action during messenger RNA decoding, of which only a few were described so far. Here, on the basis of several 70S ribosome complex X-ray structures, we demonstrate how Escherichia coli tRNA(Lys)(UUU) with hypermodified 5-methylaminomethyl-2-thiouridine (mnm(5)s(2)U) at the wobble position discriminates between cognate codons AAA and AAG, and near-cognate stop codon UAA or isoleucine codon AUA, with which it forms pyrimidine-pyrimidine mismatches. We show that mnm(5)s(2)U forms an unusual pair with guanosine at the wobble position that expands general knowledge on the degeneracy of the genetic code and specifies a powerful role of tRNA modifications in translation. Our models consolidate the translational fidelity mechanism proposed previously where the steric complementarity and shape acceptance dominate the decoding mechanism. PMID:26791911
Rozov, Alexey; Demeshkina, Natalia; Khusainov, Iskander; Westhof, Eric; Yusupov, Marat; Yusupova, Gulnara
2016-01-01
Posttranscriptional modifications at the wobble position of transfer RNAs play a substantial role in deciphering the degenerate genetic code on the ribosome. The number and variety of modifications suggest different mechanisms of action during messenger RNA decoding, of which only a few were described so far. Here, on the basis of several 70S ribosome complex X-ray structures, we demonstrate how Escherichia coli tRNALysUUU with hypermodified 5-methylaminomethyl-2-thiouridine (mnm5s2U) at the wobble position discriminates between cognate codons AAA and AAG, and near-cognate stop codon UAA or isoleucine codon AUA, with which it forms pyrimidine–pyrimidine mismatches. We show that mnm5s2U forms an unusual pair with guanosine at the wobble position that expands general knowledge on the degeneracy of the genetic code and specifies a powerful role of tRNA modifications in translation. Our models consolidate the translational fidelity mechanism proposed previously where the steric complementarity and shape acceptance dominate the decoding mechanism. PMID:26791911
Piñero, David P; Camps, Vicente J; Ramón, María L; Mateo, Verónica; Pérez-Cambrodí, Rafael J
2015-01-01
Purpose: To evaluate the predictability of the refractive correction achieved with a positional accommodating intraocular lenses (IOL) and to develop a potential optimization of it by minimizing the error associated with the keratometric estimation of the corneal power and by developing a predictive formula for the effective lens position (ELP). Materials and Methods: Clinical data from 25 eyes of 14 patients (age range, 52–77 years) and undergoing cataract surgery with implantation of the accommodating IOL Crystalens HD (Bausch and Lomb) were retrospectively reviewed. In all cases, the calculation of an adjusted IOL power (PIOLadj) based on Gaussian optics considering the residual refractive error was done using a variable keratometric index value (nkadj) for corneal power estimation with and without using an estimation algorithm for ELP obtained by multiple regression analysis (ELPadj). PIOLadj was compared to the real IOL power implanted (PIOLReal, calculated with the SRK-T formula) and also to the values estimated by the Haigis, HofferQ, and Holladay I formulas. Results: No statistically significant differences were found between PIOLReal and PIOLadj when ELPadj was used (P = 0.10), with a range of agreement between calculations of 1.23 D. In contrast, PIOLReal was significantly higher when compared to PIOLadj without using ELPadj and also compared to the values estimated by the other formulas. Conclusions: Predictable refractive outcomes can be obtained with the accommodating IOL Crystalens HD using a variable keratometric index for corneal power estimation and by estimating ELP with an algorithm dependent on anatomical factors and age. PMID:26139807
In-Flight Estimation of Center of Gravity Position Using All-Accelerometers
Al-Rawashdeh, Yazan Mohammad; Elshafei, Moustafa; Al-Malki, Mohammad Fahad
2014-01-01
Changing the position of the Center of Gravity (CoG) for an aerial vehicle is a challenging part in navigation, and control of such vehicles. In this paper, an all-accelerometers-based inertial measurement unit is presented, with a proposed method for on-line estimation of the position of the CoG. The accelerometers' readings are used to find and correct the vehicle's angular velocity and acceleration using an Extended Kalman Filter. Next, the accelerometers' readings along with the estimated angular velocity and acceleration are used in an identification scheme to estimate the position of the CoG and the vehicle's linear acceleration. The estimated position of the CoG and motion measurements can then be used to update the control rules to achieve better trim conditions for the air vehicle. PMID:25244585
NASA Astrophysics Data System (ADS)
Wang, Shi-tai; Peng, Jun-huan
2015-12-01
The characterization of ionosphere delay estimated with precise point positioning is analyzed in this paper. The estimation, interpolation and application of the ionosphere delay are studied based on the processing of 24-h data from 5 observation stations. The results show that the estimated ionosphere delay is affected by the hardware delay bias from receiver so that there is a difference between the estimated and interpolated results. The results also show that the RMSs (root mean squares) are bigger, while the STDs (standard deviations) are better than 0.11 m. When the satellite difference is used, the hardware delay bias can be canceled. The interpolated satellite-differenced ionosphere delay is better than 0.11 m. Although there is a difference between the between the estimated and interpolated ionosphere delay results it cannot affect its application in single-frequency positioning and the positioning accuracy can reach cm level.
NASA Astrophysics Data System (ADS)
Zaksek, K.; Pick, L.; Lombardo, V.; Hort, M. K.
2015-12-01
Measuring the heat emission from active volcanic features on the basis of infrared satellite images contributes to the volcano's hazard assessment. Because these thermal anomalies only occupy a small fraction (< 1 %) of a typically resolved target pixel (e.g. from Landsat 7, MODIS) the accurate determination of the hotspot's size and temperature is however problematic. Conventionally this is overcome by comparing observations in at least two separate infrared spectral wavebands (Dual-Band method). We investigate the resolution limits of this thermal un-mixing technique by means of a uniquely designed indoor analog experiment. Therein the volcanic feature is simulated by an electrical heating alloy of 0.5 mm diameter installed on a plywood panel of high emissivity. Two thermographic cameras (VarioCam high resolution and ImageIR 8300 by Infratec) record images of the artificial heat source in wavebands comparable to those available from satellite data. These range from the short-wave infrared (1.4-3 µm) over the mid-wave infrared (3-8 µm) to the thermal infrared (8-15 µm). In the conducted experiment the pixel fraction of the hotspot was successively reduced by increasing the camera-to-target distance from 3 m to 35 m. On the basis of an individual target pixel the expected decrease of the hotspot pixel area with distance at a relatively constant wire temperature of around 600 °C was confirmed. The deviation of the hotspot's pixel fraction yielded by the Dual-Band method from the theoretically calculated one was found to be within 20 % up until a target distance of 25 m. This means that a reliable estimation of the hotspot size is only possible if the hotspot is larger than about 3 % of the pixel area, a resolution boundary most remotely sensed volcanic hotspots fall below. Future efforts will focus on the investigation of a resolution limit for the hotspot's temperature by varying the alloy's amperage. Moreover, the un-mixing results for more realistic multi
Fu, Jun; Yao, Rongyan; Luo, Yanyun; Yang, Dantong; Cao, Yang; Qiu, Yi; Song, Wei; Miao, Shiying; Gu, Yiqun; Wang, Linfang
2016-01-01
Infertility is currently a major public health problem. Anti-sperm antibodies (ASAs) markedly reduce sperm quality, which can subsequently lead to male and/or female infertility. The accurate detection of ASAs derived from specific spermatozoa is, therefore, clinically useful. We have focused on the spermatozoa-specific expression protein ACTL7a for many years and have developed an enzyme-linked immunosorbent assay (ELISA) to detect the concentration of anti-ACTL7a antibodies in fertile sera (n = 267) and infertile sera (n = 193). Infertile sera were collected from the positive sera of tray agglutination tests (TAT), which is a routine ASA screening methodology. We found that the concentration of anti-ACTL7a antibodies was significantly higher in the infertile sera (than in the fertile sera, P < 0.0001) and much higher in the TAT ≥ 16 infertile sera. The ELISA was much better for male sera detection (AUC = 0.9899). If we set the standard at a strongly positive value (calculated by ROC curve), the positive predictive value of the antibody detection reached 100 percent, with a false positive rate of zero. The developed ELISA method for anti-ACTL7a antibody detection is therefore sensitive, accurate, and easy to perform, making it an excellent potential tool for future clinical use. PMID:26957350
Fu, Jun; Yao, Rongyan; Luo, Yanyun; Yang, Dantong; Cao, Yang; Qiu, Yi; Song, Wei; Miao, Shiying; Gu, Yiqun; Wang, Linfang
2016-01-01
Infertility is currently a major public health problem. Anti-sperm antibodies (ASAs) markedly reduce sperm quality, which can subsequently lead to male and/or female infertility. The accurate detection of ASAs derived from specific spermatozoa is, therefore, clinically useful. We have focused on the spermatozoa-specific expression protein ACTL7a for many years and have developed an enzyme-linked immunosorbent assay (ELISA) to detect the concentration of anti-ACTL7a antibodies in fertile sera (n = 267) and infertile sera (n = 193). Infertile sera were collected from the positive sera of tray agglutination tests (TAT), which is a routine ASA screening methodology. We found that the concentration of anti-ACTL7a antibodies was significantly higher in the infertile sera (than in the fertile sera, P < 0.0001) and much higher in the TAT ≥ 16 infertile sera. The ELISA was much better for male sera detection (AUC = 0.9899). If we set the standard at a strongly positive value (calculated by ROC curve), the positive predictive value of the antibody detection reached 100 percent, with a false positive rate of zero. The developed ELISA method for anti-ACTL7a antibody detection is therefore sensitive, accurate, and easy to perform, making it an excellent potential tool for future clinical use. PMID:26957350
A Novel Position Estimation Method Based on Displacement Correction in AIS
Jiang, Yi; Zhang, Shufang; Yang, Dongkai
2014-01-01
A new position estimation method by using the signals from two automatic identification system (AIS) stations is proposed in this paper. The time of arrival (TOA) method is enhanced with the displacement correction, so that the vessel's position can be determined even for the situation where it can receive the signals from only two AIS base stations. Its implementation scheme based on the mathematical model is presented. Furthermore, performance analysis is carried out to illustrate the relation between the positioning errors and the displacement vector provided by auxiliary sensors. Finally, the positioning method is verified and its performance is evaluated by simulation. The results show that the positioning accuracy is acceptable. PMID:25232913
Estimating Position of Mobile Robots From Omnidirectional Vision Using an Adaptive Algorithm.
Li, Luyang; Liu, Yun-Hui; Wang, Kai; Fang, Mu
2015-08-01
This paper presents a novel and simple adaptive algorithm for estimating the position of a mobile robot with high accuracy in an unknown and unstructured environment by fusing images of an omnidirectional vision system with measurements of odometry and inertial sensors. Based on a new derivation where the omnidirectional projection can be linearly parameterized by the positions of the robot and natural feature points, we propose a novel adaptive algorithm, which is similar to the Slotine-Li algorithm in model-based adaptive control, to estimate the robot's position by using the tracked feature points in image sequence, the robot's velocity, and orientation angles measured by odometry and inertial sensors. It is proved that the adaptive algorithm leads to global exponential convergence of the position estimation errors to zero. Simulations and real-world experiments are performed to demonstrate the performance of the proposed algorithm. PMID:25265622
Altini, Marco; Penders, Julien; Vullers, Ruud; Amft, Oliver
2015-01-01
Several methods to estimate energy expenditure (EE) using body-worn sensors exist; however, quantifications of the differences in estimation error are missing. In this paper, we compare three prevalent EE estimation methods and five body locations to provide a basis for selecting among methods, sensors number, and positioning. We considered 1) counts-based estimation methods, 2) activity-specific estimation methods using METs lookup, and 3) activity-specific estimation methods using accelerometer features. The latter two estimation methods utilize subsequent activity classification and EE estimation steps. Furthermore, we analyzed accelerometer sensors number and on-body positioning to derive optimal EE estimation results during various daily activities. To evaluate our approach, we implemented a study with 15 participants that wore five accelerometer sensors while performing a wide range of sedentary, household, lifestyle, and gym activities at different intensities. Indirect calorimetry was used in parallel to obtain EE reference data. Results show that activity-specific estimation methods using accelerometer features can outperform counts-based methods by 88% and activity-specific methods using METs lookup for active clusters by 23%. No differences were found between activity-specific methods using METs lookup and using accelerometer features for sedentary clusters. For activity-specific estimation methods using accelerometer features, differences in EE estimation error between the best combinations of each number of sensors (1 to 5), analyzed with repeated measures ANOVA, were not significant. Thus, we conclude that choosing the best performing single sensor does not reduce EE estimation accuracy compared to a five sensors system and can reliably be used. However, EE estimation errors can increase up to 80% if a nonoptimal sensor location is chosen. PMID:24691168
Experimental verification of an interpolation algorithm for improved estimates of animal position.
Schell, Chad; Jaffe, Jules S
2004-07-01
This article presents experimental verification of an interpolation algorithm that was previously proposed in Jaffe [J. Acoust. Soc. Am. 105, 3168-3175 (1999)]. The goal of the algorithm is to improve estimates of both target position and target strength by minimizing a least-squares residual between noise-corrupted target measurement data and the output of a model of the sonar's amplitude response to a target at a set of known locations. Although this positional estimator was shown to be a maximum likelihood estimator, in principle, experimental verification was desired because of interest in understanding its true performance. Here, the accuracy of the algorithm is investigated by analyzing the correspondence between a target's true position and the algorithm's estimate. True target position was measured by precise translation of a small test target (bead) or from the analysis of images of fish from a coregistered optical imaging system. Results with the stationary spherical test bead in a high signal-to-noise environment indicate that a large increase in resolution is possible, while results with commercial aquarium fish indicate a smaller increase is obtainable. However, in both experiments the algorithm provides improved estimates of target position over those obtained by simply accepting the angular positions of the sonar beam with maximum output as target position. In addition, increased accuracy in target strength estimation is possible by considering the effects of the sonar beam patterns relative to the interpolated position. A benefit of the algorithm is that it can be applied "ex post facto" to existing data sets from commercial multibeam sonar systems when only the beam intensities have been stored after suitable calibration. PMID:15295985
Experimental verification of an interpolation algorithm for improved estimates of animal position
NASA Astrophysics Data System (ADS)
Schell, Chad; Jaffe, Jules S.
2004-07-01
This article presents experimental verification of an interpolation algorithm that was previously proposed in Jaffe [J. Acoust. Soc. Am. 105, 3168-3175 (1999)]. The goal of the algorithm is to improve estimates of both target position and target strength by minimizing a least-squares residual between noise-corrupted target measurement data and the output of a model of the sonar's amplitude response to a target at a set of known locations. Although this positional estimator was shown to be a maximum likelihood estimator, in principle, experimental verification was desired because of interest in understanding its true performance. Here, the accuracy of the algorithm is investigated by analyzing the correspondence between a target's true position and the algorithm's estimate. True target position was measured by precise translation of a small test target (bead) or from the analysis of images of fish from a coregistered optical imaging system. Results with the stationary spherical test bead in a high signal-to-noise environment indicate that a large increase in resolution is possible, while results with commercial aquarium fish indicate a smaller increase is obtainable. However, in both experiments the algorithm provides improved estimates of target position over those obtained by simply accepting the angular positions of the sonar beam with maximum output as target position. In addition, increased accuracy in target strength estimation is possible by considering the effects of the sonar beam patterns relative to the interpolated position. A benefit of the algorithm is that it can be applied ``ex post facto'' to existing data sets from commercial multibeam sonar systems when only the beam intensities have been stored after suitable calibration.
NASA Astrophysics Data System (ADS)
Heida, M.; Jonker, P. G.; Torres, M. A. P.; Mineo, S.
2012-08-01
In this paper, we report accurate Chandra positions for two ultraluminous X-ray sources (ULXs): NGC 7319-X4 at Right Ascension (RA) = 339?029 17(2), Declination (Dec.) = 33?974 76(2) and NGC 5474-X1 at RA = 211?248 59(3), Dec. = 53?635 84(3). We perform bore-sight corrections on the Chandra X-ray satellite observations of these sources to get these accurate positions of the X-ray sources and match these positions with archival optical data from the Wide Field Planetary Camera 2 (WFPC2) onboard the Hubble Space Telescope. We do not find the optical counterparts; the limiting absolute magnitudes of the observations in the WFPC2 standard magnitude system are B=-7.9, V=-8.7 and I=-9.3 for NGC 7319-X4 and U=-6.4 for NGC 5474-X1. We report on the X-ray spectral properties and find evidence for X-ray variability in NGC 5474-X1. Finally, we briefly discuss several options for the nature of these ULXs.
Byun, Yeun-Sub; Jeong, Rag-Gyo; Kang, Seok-Won
2015-01-01
The real-time recognition of absolute (or relative) position and orientation on a network of roads is a core technology for fully automated or driving-assisted vehicles. This paper presents an empirical investigation of the design, implementation, and evaluation of a self-positioning system based on a magnetic marker reference sensing method for an autonomous vehicle. Specifically, the estimation accuracy of the magnetic sensing ruler (MSR) in the up-to-date estimation of the actual position was successfully enhanced by compensating for time delays in signal processing when detecting the vertical magnetic field (VMF) in an array of signals. In this study, the signal processing scheme was developed to minimize the effects of the distortion of measured signals when estimating the relative positional information based on magnetic signals obtained using the MSR. In other words, the center point in a 2D magnetic field contour plot corresponding to the actual position of magnetic markers was estimated by tracking the errors between pre-defined reference models and measured magnetic signals. The algorithm proposed in this study was validated by experimental measurements using a test vehicle on a pilot network of roads. From the results, the positioning error was found to be less than 0.04 m on average in an operational test. PMID:26580622
Byun, Yeun-Sub; Jeong, Rag-Gyo; Kang, Seok-Won
2015-01-01
The real-time recognition of absolute (or relative) position and orientation on a network of roads is a core technology for fully automated or driving-assisted vehicles. This paper presents an empirical investigation of the design, implementation, and evaluation of a self-positioning system based on a magnetic marker reference sensing method for an autonomous vehicle. Specifically, the estimation accuracy of the magnetic sensing ruler (MSR) in the up-to-date estimation of the actual position was successfully enhanced by compensating for time delays in signal processing when detecting the vertical magnetic field (VMF) in an array of signals. In this study, the signal processing scheme was developed to minimize the effects of the distortion of measured signals when estimating the relative positional information based on magnetic signals obtained using the MSR. In other words, the center point in a 2D magnetic field contour plot corresponding to the actual position of magnetic markers was estimated by tracking the errors between pre-defined reference models and measured magnetic signals. The algorithm proposed in this study was validated by experimental measurements using a test vehicle on a pilot network of roads. From the results, the positioning error was found to be less than 0.04 m on average in an operational test. PMID:26580622
Position Estimation and Local Mapping Using Omnidirectional Images and Global Appearance Descriptors
Berenguer, Yerai; Payá, Luis; Ballesta, Mónica; Reinoso, Oscar
2015-01-01
This work presents some methods to create local maps and to estimate the position of a mobile robot, using the global appearance of omnidirectional images. We use a robot that carries an omnidirectional vision system on it. Every omnidirectional image acquired by the robot is described only with one global appearance descriptor, based on the Radon transform. In the work presented in this paper, two different possibilities have been considered. In the first one, we assume the existence of a map previously built composed of omnidirectional images that have been captured from previously-known positions. The purpose in this case consists of estimating the nearest position of the map to the current position of the robot, making use of the visual information acquired by the robot from its current (unknown) position. In the second one, we assume that we have a model of the environment composed of omnidirectional images, but with no information about the location of where the images were acquired. The purpose in this case consists of building a local map and estimating the position of the robot within this map. Both methods are tested with different databases (including virtual and real images) taking into consideration the changes of the position of different objects in the environment, different lighting conditions and occlusions. The results show the effectiveness and the robustness of both methods. PMID:26501289
Berenguer, Yerai; Payá, Luis; Ballesta, Mónica; Reinoso, Oscar
2015-01-01
This work presents some methods to create local maps and to estimate the position of a mobile robot, using the global appearance of omnidirectional images. We use a robot that carries an omnidirectional vision system on it. Every omnidirectional image acquired by the robot is described only with one global appearance descriptor, based on the Radon transform. In the work presented in this paper, two different possibilities have been considered. In the first one, we assume the existence of a map previously built composed of omnidirectional images that have been captured from previously-known positions. The purpose in this case consists of estimating the nearest position of the map to the current position of the robot, making use of the visual information acquired by the robot from its current (unknown) position. In the second one, we assume that we have a model of the environment composed of omnidirectional images, but with no information about the location of where the images were acquired. The purpose in this case consists of building a local map and estimating the position of the robot within this map. Both methods are tested with different databases (including virtual and real images) taking into consideration the changes of the position of different objects in the environment, different lighting conditions and occlusions. The results show the effectiveness and the robustness of both methods. PMID:26501289
NASA Astrophysics Data System (ADS)
Qiao, Bing; Tang, Shuren; Ma, Kexin; Liu, Zhenya
2013-10-01
The capacity to acquire the relative position and attitude information between the chaser and the target satellites in real time is one of the necessary prerequisites for the successful implementation of autonomous rendezvous and docking. This paper addresses a vision based relative position and attitude estimation algorithm for the final phase of spacecraft rendezvous and docking. By assuming that the images of feature points on the target satellite lie within the convex regions, the estimation of the relative position and attitude is converted into solving a convex optimization problem in which the dual quaternion method is employed to represent the rotational and translational transformation between the chaser body frame and the target body frame. Due to the point-to-region correspondence instead of the point-to-point correspondence is used, the proposed estimation algorithm shows good performance in robustness which is verified through computer simulations.
NASA Astrophysics Data System (ADS)
de Leeuw, Hendrik; Moerland, Marinus A.; van Vulpen, Marco; Seevinck, Peter R.; Bakker, Chris J. G.
2013-11-01
Effective high-dose-rate (HDR) treatment requires accurate and independent treatment verification to ensure that the treatment proceeds as prescribed, in particular if a high dose is given, as in single fraction therapy. Contrary to CT imaging and fluoroscopy, MR imaging provides high soft tissue contrast. Conventional MR techniques, however, do not offer the temporal resolution in combination with the 3D spatial resolution required for accurate brachytherapy source localization. We have developed an MR imaging method (center-out RAdial Sampling with Off-Resonance (co-RASOR)) that generates high positive contrast in the geometrical center of field perturbing objects, such as HDR brachytherapy sources. co-RASOR generates high positive contrast in the geometric center of an Ir-192 source by applying a frequency offset to center-out encoded data. To obtain high spatial accuracy in 3D with adequate temporal resolution, two orthogonal center-out encoded 2D images are applied instead of a full 3D acquisition. Its accuracy in 3D is demonstrated by 3D MRI and CT. The 2D images show high positive contrast in the geometric center of non-radioactive Ir-192 sources, with signal intensities up to 160% of the average signal intensity in the surrounding medium. The accuracy with which the center of the Ir-192 source is located by the dual-plane MRI acquisition corresponds closely to the accuracy obtained by 3D MRI and CT imaging. The positive contrast is shown to be obtained in homogeneous and in heterogeneous tissue. The dual-plane MRI technique allows the brachytherapy source to be tracked in 3D with millimeter accuracy with a temporal resolution of approximately 4 s.
Yuan, Xuebing; Yu, Shuai; Zhang, Shengzhi; Wang, Guoping; Liu, Sheng
2015-01-01
Inertial navigation based on micro-electromechanical system (MEMS) inertial measurement units (IMUs) has attracted numerous researchers due to its high reliability and independence. The heading estimation, as one of the most important parts of inertial navigation, has been a research focus in this field. Heading estimation using magnetometers is perturbed by magnetic disturbances, such as indoor concrete structures and electronic equipment. The MEMS gyroscope is also used for heading estimation. However, the accuracy of gyroscope is unreliable with time. In this paper, a wearable multi-sensor system has been designed to obtain the high-accuracy indoor heading estimation, according to a quaternion-based unscented Kalman filter (UKF) algorithm. The proposed multi-sensor system including one three-axis accelerometer, three single-axis gyroscopes, one three-axis magnetometer and one microprocessor minimizes the size and cost. The wearable multi-sensor system was fixed on waist of pedestrian and the quadrotor unmanned aerial vehicle (UAV) for heading estimation experiments in our college building. The results show that the mean heading estimation errors are less 10° and 5° to multi-sensor system fixed on waist of pedestrian and the quadrotor UAV, respectively, compared to the reference path. PMID:25961384
Yuan, Xuebing; Yu, Shuai; Zhang, Shengzhi; Wang, Guoping; Liu, Sheng
2015-01-01
Inertial navigation based on micro-electromechanical system (MEMS) inertial measurement units (IMUs) has attracted numerous researchers due to its high reliability and independence. The heading estimation, as one of the most important parts of inertial navigation, has been a research focus in this field. Heading estimation using magnetometers is perturbed by magnetic disturbances, such as indoor concrete structures and electronic equipment. The MEMS gyroscope is also used for heading estimation. However, the accuracy of gyroscope is unreliable with time. In this paper, a wearable multi-sensor system has been designed to obtain the high-accuracy indoor heading estimation, according to a quaternion-based unscented Kalman filter (UKF) algorithm. The proposed multi-sensor system including one three-axis accelerometer, three single-axis gyroscopes, one three-axis magnetometer and one microprocessor minimizes the size and cost. The wearable multi-sensor system was fixed on waist of pedestrian and the quadrotor unmanned aerial vehicle (UAV) for heading estimation experiments in our college building. The results show that the mean heading estimation errors are less 10° and 5° to multi-sensor system fixed on waist of pedestrian and the quadrotor UAV, respectively, compared to the reference path. PMID:25961384
Estimation of the absolute position of mobile systems by an optoelectronic processor
NASA Technical Reports Server (NTRS)
Feng, Liqiang; Fainman, Yeshaiahu; Koren, Yoram
1992-01-01
A method that determine the absolute position of a mobile system with a hybrid optoelectronic processor has been developed. Position estimates are based on an analysis of circular landmarks that are detected by a TV camera attached to the mobile system. The difference between the known shape of the landmark and its image provides the information needed to determine the absolute position of the mobile system. For robust operation, the parameters of the landmark image are extracted at high speeds using an optical processor that performs an optical Hough transform. The coordinates of the mobile system are computed from these parameters in a digital co-processor using fast algorithms. Different sources of position estimation errors have also been analyzed, and consequent algorithms to improve the navigation performance of the mobile system have been developed and evaluated by both computer simulation and experiments.
A demonstration of position angle-only weak lensing shear estimators on the GREAT3 simulations
NASA Astrophysics Data System (ADS)
Whittaker, Lee; Brown, Michael L.; Battye, Richard A.
2015-12-01
We develop and apply the position angle-only shear estimator of Whittaker, Brown & Battye to realistic galaxy images. This is done by demonstrating the method on the simulations of the third GRavitational lEnsing Accuracy Testing (GREAT3) challenge, which include contributions from anisotropic point spread functions (PSFs). We measure the position angles of the galaxies using three distinct methods - the integrated light method, quadrupole moments of surface brightness, and using model-based ellipticity measurements provided by IM3SHAPE. A weighting scheme is adopted to address biases in the position angle measurements which arise in the presence of an anisotropic PSF. Biases on the shear estimates, due to measurement errors on the position angles and correlations between the measurement errors and the true position angles, are corrected for using simulated galaxy images and an iterative procedure. The properties of the simulations are estimated using the deep field images provided as part of the challenge. A method is developed to match the distributions of galaxy fluxes and half-light radii from the deep fields to the corresponding distributions in the field of interest. We recover angle-only shear estimates with a performance close to current well-established model and moments-based methods for all three angle measurement techniques. The Q-values for all three methods are found to be Q ˜ 400. The code is freely available online at http://www.jb.man.ac.uk/mbrown/angle_only_shear/.
3D position estimation using an artificial neural network for a continuous scintillator PET detector
NASA Astrophysics Data System (ADS)
Wang, Y.; Zhu, W.; Cheng, X.; Li, D.
2013-03-01
Continuous crystal based PET detectors have features of simple design, low cost, good energy resolution and high detection efficiency. Through single-end readout of scintillation light, direct three-dimensional (3D) position estimation could be another advantage that the continuous crystal detector would have. In this paper, we propose to use artificial neural networks to simultaneously estimate the plane coordinate and DOI coordinate of incident γ photons with detected scintillation light. Using our experimental setup with an ‘8 + 8’ simplified signal readout scheme, the training data of perpendicular irradiation on the front surface and one side surface are obtained, and the plane (x, y) networks and DOI networks are trained and evaluated. The test results show that the artificial neural network for DOI estimation is as effective as for plane estimation. The performance of both estimators is presented by resolution and bias. Without bias correction, the resolution of the plane estimator is on average better than 2 mm and that of the DOI estimator is about 2 mm over the whole area of the detector. With bias correction, the resolution at the edge area for plane estimation or at the end of the block away from the readout PMT for DOI estimation becomes worse, as we expect. The comprehensive performance of the 3D positioning by a neural network is accessed by the experimental test data of oblique irradiations. To show the combined effect of the 3D positioning over the whole area of the detector, the 2D flood images of oblique irradiation are presented with and without bias correction.
Gorresen, P. Marcos; Camp, Richard J.; Brinck, Kevin W.; Farmer, Chris
2012-01-01
Point-transect surveys indicated that millerbirds were more abundant than shown by the striptransect method, and were estimated at 802 birds in 2010 (95%CI = 652 – 964) and 704 birds in 2011 (95%CI = 579 – 837). Point-transect surveys yielded population estimates with improved precision which will permit trends to be detected in shorter time periods and with greater statistical power than is available from strip-transect survey methods. Mean finch population estimates and associated uncertainty were not markedly different among the three survey methods, but the performance of models used to estimate density and population size are expected to improve as the data from additional surveys are incorporated. Using the pointtransect survey, the mean finch population size was estimated at 2,917 birds in 2010 (95%CI = 2,037 – 3,965) and 2,461 birds in 2011 (95%CI = 1,682 – 3,348). Preliminary testing of the line-transect method in 2011 showed that it would not generate sufficient detections to effectively model bird density, and consequently, relatively precise population size estimates. Both species were fairly evenly distributed across Nihoa and appear to occur in all or nearly all available habitat. The time expended and area traversed by observers was similar among survey methods; however, point-transect surveys do not require that observers walk a straight transect line, thereby allowing them to avoid culturally or biologically sensitive areas and minimize the adverse effects of recurrent travel to any particular area. In general, pointtransect surveys detect more birds than strip-survey methods, thereby improving precision and resulting population size and trend estimation. The method is also better suited for the steep and uneven terrain of Nihoa
Zhao, Lin; Guan, Dongxue; Landry, René; Cheng, Jianhua; Sydorenko, Kostyantyn
2015-01-01
Target positioning systems based on MEMS gyros and laser rangefinders (LRs) have extensive prospects due to their advantages of low cost, small size and easy realization. The target positioning accuracy is mainly determined by the LR's attitude derived by the gyros. However, the attitude error is large due to the inherent noises from isolated MEMS gyros. In this paper, both accelerometer/magnetometer and LR attitude aiding systems are introduced to aid MEMS gyros. A no-reset Federated Kalman Filter (FKF) is employed, which consists of two local Kalman Filters (KF) and a Master Filter (MF). The local KFs are designed by using the Direction Cosine Matrix (DCM)-based dynamic equations and the measurements from the two aiding systems. The KFs can estimate the attitude simultaneously to limit the attitude errors resulting from the gyros. Then, the MF fuses the redundant attitude estimates to yield globally optimal estimates. Simulation and experimental results demonstrate that the FKF-based system can improve the target positioning accuracy effectively and allow for good fault-tolerant capability. PMID:26512672
Zhao, Lin; Guan, Dongxue; Landry, René Jr.; Cheng, Jianhua; Sydorenko, Kostyantyn
2015-01-01
Target positioning systems based on MEMS gyros and laser rangefinders (LRs) have extensive prospects due to their advantages of low cost, small size and easy realization. The target positioning accuracy is mainly determined by the LR’s attitude derived by the gyros. However, the attitude error is large due to the inherent noises from isolated MEMS gyros. In this paper, both accelerometer/magnetometer and LR attitude aiding systems are introduced to aid MEMS gyros. A no-reset Federated Kalman Filter (FKF) is employed, which consists of two local Kalman Filters (KF) and a Master Filter (MF). The local KFs are designed by using the Direction Cosine Matrix (DCM)-based dynamic equations and the measurements from the two aiding systems. The KFs can estimate the attitude simultaneously to limit the attitude errors resulting from the gyros. Then, the MF fuses the redundant attitude estimates to yield globally optimal estimates. Simulation and experimental results demonstrate that the FKF-based system can improve the target positioning accuracy effectively and allow for good fault-tolerant capability. PMID:26512672
NASA Astrophysics Data System (ADS)
Bloßfeld, Mathis; Panzetta, Francesca; Müller, Horst; Gerstl, Michael
2016-04-01
The GGOS vision is to integrate geometric and gravimetric observation techniques to estimate consistent geodetic-geophysical parameters. In order to reach this goal, the common estimation of station coordinates, Stokes coefficients and Earth Orientation Parameters (EOP) is necessary. Satellite Laser Ranging (SLR) provides the ability to study correlations between the different parameter groups since the observed satellite orbit dynamics are sensitive to the above mentioned geodetic parameters. To decrease the correlations, SLR observations to multiple satellites have to be combined. In this paper, we compare the estimated EOP of (i) single satellite SLR solutions and (ii) multi-satellite SLR solutions. Therefore, we jointly estimate station coordinates, EOP, Stokes coefficients and orbit parameters using different satellite constellations. A special focus in this investigation is put on the de-correlation of different geodetic parameter groups due to the combination of SLR observations. Besides SLR observations to spherical satellites (commonly used), we discuss the impact of SLR observations to non-spherical satellites such as, e.g., the JASON-2 satellite. The goal of this study is to discuss the existing parameter interactions and to present a strategy how to obtain reliable estimates of station coordinates, EOP, orbit parameter and Stokes coefficients in one common adjustment. Thereby, the benefits of a multi-satellite SLR solution are evaluated.
Mello, Beatriz; Schrago, Carlos G
2014-01-01
Divergence time estimation has become an essential tool for understanding macroevolutionary events. Molecular dating aims to obtain reliable inferences, which, within a statistical framework, means jointly increasing the accuracy and precision of estimates. Bayesian dating methods exhibit the propriety of a linear relationship between uncertainty and estimated divergence dates. This relationship occurs even if the number of sites approaches infinity and places a limit on the maximum precision of node ages. However, how the placement of calibration information may affect the precision of divergence time estimates remains an open question. In this study, relying on simulated and empirical data, we investigated how the location of calibration within a phylogeny affects the accuracy and precision of time estimates. We found that calibration priors set at median and deep phylogenetic nodes were associated with higher precision values compared to analyses involving calibration at the shallowest node. The results were independent of the tree symmetry. An empirical mammalian dataset produced results that were consistent with those generated by the simulated sequences. Assigning time information to the deeper nodes of a tree is crucial to guarantee the accuracy and precision of divergence times. This finding highlights the importance of the appropriate choice of outgroups in molecular dating. PMID:24855333
Estimation of shoreline position and change using airborne topographic lidar data
Stockdon, H.F.; Sallenger, A.H., Jr.; List, J.H.; Holman, R.A.
2002-01-01
A method has been developed for estimating shoreline position from airborne scanning laser data. This technique allows rapid estimation of objective, GPS-based shoreline positions over hundreds of kilometers of coast, essential for the assessment of large-scale coastal behavior. Shoreline position, defined as the cross-shore position of a vertical shoreline datum, is found by fitting a function to cross-shore profiles of laser altimetry data located in a vertical range around the datum and then evaluating the function at the specified datum. Error bars on horizontal position are directly calculated as the 95% confidence interval on the mean value based on the Student's t distribution of the errors of the regression. The technique was tested using lidar data collected with NASA's Airborne Topographic Mapper (ATM) in September 1997 on the Outer Banks of North Carolina. Estimated lidar-based shoreline position was compared to shoreline position as measured by a ground-based GPS vehicle survey system. The two methods agreed closely with a root mean square difference of 2.9 m. The mean 95% confidence interval for shoreline position was ?? 1.4 m. The technique has been applied to a study of shoreline change on Assateague Island, Maryland/Virginia, where three ATM data sets were used to assess the statistics of large-scale shoreline change caused by a major 'northeaster' winter storm. The accuracy of both the lidar system and the technique described provides measures of shoreline position and change that are ideal for studying storm-scale variability over large spatial scales.
How Accurate Are German Work-Time Data? A Comparison of Time-Diary Reports and Stylized Estimates
ERIC Educational Resources Information Center
Otterbach, Steffen; Sousa-Poza, Alfonso
2010-01-01
This study compares work time data collected by the German Time Use Survey (GTUS) using the diary method with stylized work time estimates from the GTUS, the German Socio-Economic Panel, and the German Microcensus. Although on average the differences between the time-diary data and the interview data is not large, our results show that significant…
Markov Jump Linear Systems-Based Position Estimation for Lower Limb Exoskeletons
Nogueira, Samuel L.; Siqueira, Adriano A. G.; Inoue, Roberto S.; Terra, Marco H.
2014-01-01
In this paper, we deal with Markov Jump Linear Systems-based filtering applied to robotic rehabilitation. The angular positions of an impedance-controlled exoskeleton, designed to help stroke and spinal cord injured patients during walking rehabilitation, are estimated. Standard position estimate approaches adopt Kalman filters (KF) to improve the performance of inertial measurement units (IMUs) based on individual link configurations. Consequently, for a multi-body system, like a lower limb exoskeleton, the inertial measurements of one link (e.g., the shank) are not taken into account in other link position estimation (e.g., the foot). In this paper, we propose a collective modeling of all inertial sensors attached to the exoskeleton, combining them in a Markovian estimation model in order to get the best information from each sensor. In order to demonstrate the effectiveness of our approach, simulation results regarding a set of human footsteps, with four IMUs and three encoders attached to the lower limb exoskeleton, are presented. A comparative study between the Markovian estimation system and the standard one is performed considering a wide range of parametric uncertainties. PMID:24451469
NASA Astrophysics Data System (ADS)
Jakobsen, Jakob; Jensen, Anna B. O.; Nielsen, Allan Aasbjerg
2015-05-01
The paper describes the development and testing of a simulation tool, called QualiSIM. The tool estimates GNSS-based position accuracy based on a simulation of the environment surrounding the GNSS antenna, with a special focus on city-scape environments with large amounts of signal reflections from non-line-of-sight satellites. The signal reflections are implemented using the extended geometric path length of the signal path caused by reflections from the surrounding buildings. Based on real GPS satellite positions, simulated Galileo satellite positions, models of atmospheric effect on the satellite signals, designs of representative environments e.g. urban and rural scenarios, and a method to simulate reflection of satellite signals within the environment we are able to estimate the position accuracy given several prerequisites as described in the paper. The result is a modelling of the signal path from satellite to receiver, the satellite availability, the extended pseudoranges caused by signal reflection, and an estimate of the position accuracy based on a least squares adjustment of the extended pseudoranges. The paper describes the models and algorithms used and a verification test where the results of QualiSIM are compared with results from collection of real GPS data in an environment with much signal reflection.
NASA Astrophysics Data System (ADS)
Wu, Shunguang; Hong, Lang
2008-04-01
A framework of simultaneously estimating the motion and structure parameters of a 3D object by using high range resolution (HRR) and ground moving target indicator (GMTI) measurements with template information is given. By decoupling the motion and structure information and employing rigid-body constraints, we have developed the kinematic and measurement equations of the problem. Since the kinematic system is unobservable by using only one scan HRR and GMTI measurements, we designed an architecture to run the motion and structure filters in parallel by using multi-scan measurements. Moreover, to improve the estimation accuracy in large noise and/or false alarm environments, an interacting multi-template joint tracking (IMTJT) algorithm is proposed. Simulation results have shown that the averaged root mean square errors for both motion and structure state vectors have been significantly reduced by using the template information.
NASA Astrophysics Data System (ADS)
Cofaru, Corneliu; Philips, Wilfried; Van Paepegem, Wim
2011-09-01
Digital image processing methods represent a viable and well acknowledged alternative to strain gauges and interferometric techniques for determining full-field displacements and strains in materials under stress. This paper presents an image adaptive technique for dense motion and strain estimation using high-resolution speckle images that show the analyzed material in its original and deformed states. The algorithm starts by dividing the speckle image showing the original state into irregular cells taking into consideration both spatial and gradient image information present. Subsequently the Newton-Raphson digital image correlation technique is applied to calculate the corresponding motion for each cell. Adaptive spatial regularization in the form of the Geman- McClure robust spatial estimator is employed to increase the spatial consistency of the motion components of a cell with respect to the components of neighbouring cells. To obtain the final strain information, local least-squares fitting using a linear displacement model is performed on the horizontal and vertical displacement fields. To evaluate the presented image partitioning and strain estimation techniques two numerical and two real experiments are employed. The numerical experiments simulate the deformation of a specimen with constant strain across the surface as well as small rigid-body rotations present while real experiments consist specimens that undergo uniaxial stress. The results indicate very good accuracy of the recovered strains as well as better rotation insensitivity compared to classical techniques.
A maximum likelihood approach to estimating articulator positions from speech acoustics
Hogden, J.
1996-09-23
This proposal presents an algorithm called maximum likelihood continuity mapping (MALCOM) which recovers the positions of the tongue, jaw, lips, and other speech articulators from measurements of the sound-pressure waveform of speech. MALCOM differs from other techniques for recovering articulator positions from speech in three critical respects: it does not require training on measured or modeled articulator positions, it does not rely on any particular model of sound propagation through the vocal tract, and it recovers a mapping from acoustics to articulator positions that is linearly, not topographically, related to the actual mapping from acoustics to articulation. The approach categorizes short-time windows of speech into a finite number of sound types, and assumes the probability of using any articulator position to produce a given sound type can be described by a parameterized probability density function. MALCOM then uses maximum likelihood estimation techniques to: (1) find the most likely smooth articulator path given a speech sample and a set of distribution functions (one distribution function for each sound type), and (2) change the parameters of the distribution functions to better account for the data. Using this technique improves the accuracy of articulator position estimates compared to continuity mapping -- the only other technique that learns the relationship between acoustics and articulation solely from acoustics. The technique has potential application to computer speech recognition, speech synthesis and coding, teaching the hearing impaired to speak, improving foreign language instruction, and teaching dyslexics to read. 34 refs., 7 figs.
Estimation of Rotor Position in a 3-Phase SRM at Standstill and Low Speeds
NASA Astrophysics Data System (ADS)
Komatsuzaki, Akitomo; Bamba, Tatsunori; Miki, Ichiro
Switched reluctance motors (SRMs) are widely employed as industrial drives because they are inexpensive, simple, and sturdy, further, they deliver a robust and reliable performance. SRMs are controlled with a rotor position sensor attached to the motor shaft. Normally, encoders, resolvers, or Hall sensors are used as position sensors. The use of these sensors, however, increases the size and cost of the machine and degrades its performance. Therefore, to overcome these difficulties, several sensorless drive techniques have been reported. In this paper, a method for estimating the position of a rotor in an SRM; this method is based on calculation of the space vector of phase inductance at standstill and low speeds. The position at standstill is obtained simply without making use of the magnetic characteristics of the motor or any additional hardware. Assuming the inductance waveform to be a sine wave, the position of rotor at standstill is obtained from the phase inductance vectors of all phases. At low speeds, position estimation is carried out by applying a DC link voltage to the unenergized phases. The validity of the proposed method is experimentally verified.
NASA Technical Reports Server (NTRS)
Lichten, S. M.
1991-01-01
Data from the Global Positioning System (GPS) were used to determine precise polar motion estimates. Conservatively calculated formal errors of the GPS least squares solution are approx. 10 cm. The GPS estimates agree with independently determined polar motion values from very long baseline interferometry (VLBI) at the 5 cm level. The data were obtained from a partial constellation of GPS satellites and from a sparse worldwide distribution of ground stations. The accuracy of the GPS estimates should continue to improve as more satellites and ground receivers become operational, and eventually a near real time GPS capability should be available. Because the GPS data are obtained and processed independently from the large radio antennas at the Deep Space Network (DSN), GPS estimation could provide very precise measurements of Earth orientation for calibration of deep space tracking data and could significantly relieve the ever growing burden on the DSN radio telescopes to provide Earth platform calibrations.
Clisby, Nathan
2010-02-01
We introduce a fast implementation of the pivot algorithm for self-avoiding walks, which we use to obtain large samples of walks on the cubic lattice of up to 33x10{6} steps. Consequently the critical exponent nu for three-dimensional self-avoiding walks is determined to great accuracy; the final estimate is nu=0.587 597(7). The method can be adapted to other models of polymers with short-range interactions, on the lattice or in the continuum. PMID:20366773
Impact of the Fano Factor on Position and Energy Estimation in Scintillation Detectors
Bora, Vaibhav; Barrett, Harrison H.; Jha, Abhinav K.; Clarkson, Eric
2015-01-01
The Fano factor for an integer-valued random variable is defined as the ratio of its variance to its mean. Light from various scintillation crystals have been reported to have Fano factors from sub-Poisson (Fano factor < 1) to super-Poisson (Fano factor > 1). For a given mean, a smaller Fano factor implies a smaller variance and thus less noise. We investigated if lower noise in the scintillation light will result in better spatial and energy resolutions. The impact of Fano factor on the estimation of position of interaction and energy deposited in simple gamma-camera geometries is estimated by two methods - calculating the Cramér-Rao bound and estimating the variance of a maximum likelihood estimator. The methods are consistent with each other and indicate that when estimating the position of interaction and energy deposited by a gamma-ray photon, the Fano factor of a scintillator does not affect the spatial resolution. A smaller Fano factor results in a better energy resolution. PMID:26523069
Impact of the Fano Factor on Position and Energy Estimation in Scintillation Detectors.
Bora, Vaibhav; Barrett, Harrison H; Jha, Abhinav K; Clarkson, Eric
2015-02-01
The Fano factor for an integer-valued random variable is defined as the ratio of its variance to its mean. Light from various scintillation crystals have been reported to have Fano factors from sub-Poisson (Fano factor < 1) to super-Poisson (Fano factor > 1). For a given mean, a smaller Fano factor implies a smaller variance and thus less noise. We investigated if lower noise in the scintillation light will result in better spatial and energy resolutions. The impact of Fano factor on the estimation of position of interaction and energy deposited in simple gamma-camera geometries is estimated by two methods - calculating the Cramér-Rao bound and estimating the variance of a maximum likelihood estimator. The methods are consistent with each other and indicate that when estimating the position of interaction and energy deposited by a gamma-ray photon, the Fano factor of a scintillator does not affect the spatial resolution. A smaller Fano factor results in a better energy resolution. PMID:26523069
Precise Point Positioning with Ionosphere Estimation and application of Regional Ionospheric Maps
NASA Astrophysics Data System (ADS)
Galera Monico, J. F.; Marques, H. A.; Rocha, G. D. D. C.
2015-12-01
The ionosphere is one of most difficult source of errors to be modelled in the GPS positioning, mainly when applying data collected by single frequency receivers. Considering Precise Point Positioning (PPP) with single frequency data the options available include, for example, the use of Klobuchar model or applying Global Ionosphere Maps (GIM). The GIM contains Vertical Electron Content (VTEC) values that are commonly estimated considering a global network with poor covering in certain regions. For this reason Regional Ionosphere Maps (RIM) have been developed considering local GNSS network, for instance, the La Plata Ionospheric Model (LPIM) developed inside the context of SIRGAS (Geocentric Reference System for Americas). The South American RIM are produced with data from nearly 50 GPS ground receivers and considering these maps are generated for each hour with spatial resolution of one degree it is expected to provide better accuracy in GPS positioning for such region. Another possibility to correct for ionosphere effects in the PPP is to apply the ionosphere estimation technique based on Kalman filter. In this case, the ionosphere can be treated as a stochastic process and a good initial guess is necessary what can be obtained from an ionospheric map. In this paper we present the methodology involved with ionosphere estimation by using Kalman filter and also the application of global and regional ionospheric maps in the PPP as first guess. The ionosphere estimation strategy was implemented in the house software called RT_PPP that is capable of accomplishing PPP either for single or dual frequency data. GPS data from Brazilian station near equatorial region were processed and results with regional maps were compared with those by using global maps. Improvements of the order 15% were observed. In case of ionosphere estimation, the estimated coordinates were compared with ionosphere free solution and after PPP convergence the results reached centimeter accuracy.
Network-based estimation of time-dependent noise in GPS position time series
NASA Astrophysics Data System (ADS)
Dmitrieva, Ksenia; Segall, Paul; DeMets, Charles
2015-06-01
Some estimates of GPS velocity uncertainties are very low, 0.1 mm/year with 10 years of data. Yet, residual velocities relative to rigid plate models in nominally stable plate interiors can be an order of magnitude larger. This discrepancy could be caused by underestimating low-frequency time-dependent noise in position time series, such as random walk. We show that traditional estimators, based on individual time series, are insensitive to low-amplitude random walk, yet such noise significantly increases GPS velocity uncertainties. Here, we develop a method for determining representative noise parameters in GPS position time series, by analyzing an entire network simultaneously, which we refer to as the network noise estimator (NNE). We analyze data from the aseismic central-eastern USA, assuming that residual motions relative to North America, corrected for glacial isostatic adjustment (GIA), represent noise. The position time series are decomposed into signal (plate rotation and GIA) and noise components. NNE simultaneously processes multiple stations with a Kalman filter and solves for average noise components for the network by maximum likelihood estimation. Synthetic tests show that NNE correctly estimates even low-level random walk, thus providing better estimates of velocity uncertainties than conventional, single station methods. To test NNE on actual data, we analyze a heterogeneous 15 station GPS network from the central-eastern USA, assuming the noise is a sum of random walk, flicker and white noise. For the horizontal time series, NNE finds higher average random walk than the standard individual station-based method, leading to velocity uncertainties a factor of 2 higher than traditional methods.
Indoor patient position estimation using particle filtering and wireless body area networks.
Ren, Hongliang; Meng, Max Q H; Xu, Lisheng
2007-01-01
Wireless Body Area Network (WBAN) has been recently promoted to monitor the physiological parameters of patient in an unobtrusive and natural way. This paper towards to make advantage of those ongoing wireless communication links between the body sensors to provide estimated position information of patients or particular body area networks, which make daily activity surveillance possible for further analysis. The proposed particle filtering based localization algorithm just picks up the received radio signal strength information from beacons or its neighbors to infer its own pose, which do not require additional hardware or instruments. Theoretical analysis and simulation experiments are presented to examine the performance of location estimating method. PMID:18002445
Vector Observation-Aided/Attitude-Rate Estimation Using Global Positioning System Signals
NASA Technical Reports Server (NTRS)
Oshman, Yaakov; Markley, F. Landis
1997-01-01
A sequential filtering algorithm is presented for attitude and attitude-rate estimation from Global Positioning System (GPS) differential carrier phase measurements. A third-order, minimal-parameter method for solving the attitude matrix kinematic equation is used to parameterize the filter's state, which renders the resulting estimator computationally efficient. Borrowing from tracking theory concepts, the angular acceleration is modeled as an exponentially autocorrelated stochastic process, thus avoiding the use of the uncertain spacecraft dynamic model. The new formulation facilitates the use of aiding vector observations in a unified filtering algorithm, which can enhance the method's robustness and accuracy. Numerical examples are used to demonstrate the performance of the method.
Hu Tao; Shao Zhengyi; Peng Qiuhe E-mail: taohu.nju@gmail.com
2013-01-10
The inclination (i) and position angle (PA) of the Whirlpool galaxy (M51) are critical to modeling and interpreting observations. Here we make improved estimates of these parameters by fitting logarithmic spirals to the main arms. From separate fits to each major arm, we obtain i = 20. Degree-Sign 3 {+-} 2. Degree-Sign 8 and PA = 12. Degree-Sign 0 {+-} 2. Degree-Sign 5. We then use Poisson's equation for the logarithmic perturbation of the density to estimate the mean vertical scale height (H) of M51 to be 95-178 pc.
Abd Rahman, Azrin N; Tett, Susan E; Staatz, Christine E
2014-03-01
Mycophenolic acid (MPA) is a potent immunosuppressant agent, which is increasingly being used in the treatment of patients with various autoimmune diseases. Dosing to achieve a specific target MPA area under the concentration-time curve from 0 to 12 h post-dose (AUC12) is likely to lead to better treatment outcomes in patients with autoimmune disease than a standard fixed-dose strategy. This review summarizes the available published data around concentration monitoring strategies for MPA in patients with autoimmune disease and examines the accuracy and precision of methods reported to date using limited concentration-time points to estimate MPA AUC12. A total of 13 studies were identified that assessed the correlation between single time points and MPA AUC12 and/or examined the predictive performance of limited sampling strategies in estimating MPA AUC12. The majority of studies investigated mycophenolate mofetil (MMF) rather than the enteric-coated mycophenolate sodium (EC-MPS) formulation of MPA. Correlations between MPA trough concentrations and MPA AUC12 estimated by full concentration-time profiling ranged from 0.13 to 0.94 across ten studies, with the highest associations (r (2) = 0.90-0.94) observed in lupus nephritis patients. Correlations were generally higher in autoimmune disease patients compared with renal allograft recipients and higher after MMF compared with EC-MPS intake. Four studies investigated use of a limited sampling strategy to predict MPA AUC12 determined by full concentration-time profiling. Three studies used a limited sampling strategy consisting of a maximum combination of three sampling time points with the latest sample drawn 3-6 h after MMF intake, whereas the remaining study tested all combinations of sampling times. MPA AUC12 was best predicted when three samples were taken at pre-dose and at 1 and 3 h post-dose with a mean bias and imprecision of 0.8 and 22.6 % for multiple linear regression analysis and of -5.5 and 23.0 % for
Optimal Position Estimation for the Automatic Alignment of a High Energy Laser
Candy, J V; Mcclay, W A; Awwal, A S; Ferguson, S W
2004-07-20
The alignment of high energy laser beams for potential fusion experiments demand high precision and accuracy by the underlying positioning algorithms whether it be for actuator control or monitoring the beam line for potential anomalies. This paper discusses the feasibility of employing on-line optimal position estimators in the form of model-based processors to achieve the desired results. Here we discuss the modeling, development, implementation and processing of model-based processors applied to both simulated and actual beam line data.
NASA Technical Reports Server (NTRS)
Galante, Joseph M.; Van Eepoel, John; D' Souza, Chris; Patrick, Bryan
2016-01-01
The Raven ISS Hosted Payload will feature several pose measurement sensors on a pan/tilt gimbal which will be used to autonomously track resupply vehicles as they approach and depart the International Space Station. This paper discusses the derivation of a Relative Navigation Filter (RNF) to fuse measurements from the different pose measurement sensors to produce relative position and attitude estimates. The RNF relies on relative translation and orientation kinematics and careful pose sensor modeling to eliminate dependence on orbital position information and associated orbital dynamics models. The filter state is augmented with sensor biases to provide a mechanism for the filter to estimate and mitigate the offset between the measurements from different pose sensors.
NASA Technical Reports Server (NTRS)
Galante, Joseph M.; Van Eepoel, John; D'Souza, Chris; Patrick, Bryan
2016-01-01
The Raven ISS Hosted Payload will feature several pose measurement sensors on a pan/tilt gimbal which will be used to autonomously track resupply vehicles as they approach and depart the International Space Station. This paper discusses the derivation of a Relative Navigation Filter (RNF) to fuse measurements from the different pose measurement sensors to produce relative position and attitude estimates. The RNF relies on relative translation and orientation kinematics and careful pose sensor modeling to eliminate dependence on orbital position information and associated orbital dynamics models. The filter state is augmented with sensor biases to provide a mechanism for the filter to estimate and mitigate the offset between the measurements from different pose sensors
Indoor positioning system using WLAN channel estimates as fingerprints for mobile devices
NASA Astrophysics Data System (ADS)
Schmidt, Erick; Akopian, David
2015-03-01
With the growing integration of location based services (LBS) such as GPS in mobile devices, indoor position systems (IPS) have become an important role for research. There are several IPS methods such as AOA, TOA, TDOA, which use trilateration for indoor location estimation but are generally based on line-of-sight. Other methods rely on classification such as fingerprinting which uses WLAN indoor signals. This paper re-examines the classical WLAN fingerprinting accuracy which uses received signal strength (RSS) measurements by introducing channel estimates for improvements in the classification of indoor locations. The purpose of this paper is to improve existing classification algorithms used in fingerprinting by introducing channel estimates when there are a low number of APs available. The channel impulse response, or in this case the channel estimation from the receiver, should characterize a complex indoor area which usually has multipath, thus providing a unique signature for each location which proves useful for better pattern recognition. In this experiment, channel estimates are extracted from a Software-Defined Radio (SDR) environment, thus exploiting the benefits of SDR from a NI-USRP model and LabVIEW software. Measurements are taken from a known building, and several scenarios with one and two access points (APs) are used in this experiment. Also, three granularities in distance between locations are analyzed. A Support Vector Machine (SVM) is used as the algorithm for pattern recognition of different locations based on the samples taken from RSS and channel estimation coefficients.
ERIC Educational Resources Information Center
Conone, Ruth M.
The key to positioning is the creation of a clear benefit image in the consumer's mind. One positioning strategy is creating in the prospect's mind a position that takes into consideration the company's or agency's strengths and weaknesses as well as those of its competitors. Another strategy is to gain entry into a position ladder owned by…
Deneux, Thomas; Kaszas, Attila; Szalay, Gergely; Katona, Gergely; Lakner, Tamás; Grinvald, Amiram; Rózsa, Balázs; Vanzetta, Ivo
2016-01-01
Extracting neuronal spiking activity from large-scale two-photon recordings remains challenging, especially in mammals in vivo, where large noises often contaminate the signals. We propose a method, MLspike, which returns the most likely spike train underlying the measured calcium fluorescence. It relies on a physiological model including baseline fluctuations and distinct nonlinearities for synthetic and genetically encoded indicators. Model parameters can be either provided by the user or estimated from the data themselves. MLspike is computationally efficient thanks to its original discretization of probability representations; moreover, it can also return spike probabilities or samples. Benchmarked on extensive simulations and real data from seven different preparations, it outperformed state-of-the-art algorithms. Combined with the finding obtained from systematic data investigation (noise level, spiking rate and so on) that photonic noise is not necessarily the main limiting factor, our method allows spike extraction from large-scale recordings, as demonstrated on acousto-optical three-dimensional recordings of over 1,000 neurons in vivo. PMID:27432255
Deneux, Thomas; Kaszas, Attila; Szalay, Gergely; Katona, Gergely; Lakner, Tamás; Grinvald, Amiram; Rózsa, Balázs; Vanzetta, Ivo
2016-01-01
Extracting neuronal spiking activity from large-scale two-photon recordings remains challenging, especially in mammals in vivo, where large noises often contaminate the signals. We propose a method, MLspike, which returns the most likely spike train underlying the measured calcium fluorescence. It relies on a physiological model including baseline fluctuations and distinct nonlinearities for synthetic and genetically encoded indicators. Model parameters can be either provided by the user or estimated from the data themselves. MLspike is computationally efficient thanks to its original discretization of probability representations; moreover, it can also return spike probabilities or samples. Benchmarked on extensive simulations and real data from seven different preparations, it outperformed state-of-the-art algorithms. Combined with the finding obtained from systematic data investigation (noise level, spiking rate and so on) that photonic noise is not necessarily the main limiting factor, our method allows spike extraction from large-scale recordings, as demonstrated on acousto-optical three-dimensional recordings of over 1,000 neurons in vivo. PMID:27432255
Woerner, Michael; Sendtner, Ernst; Springorum, Robert; Craiovan, Benjamin; Worlicek, Michael; Renkawitz, Tobias; Grifka, Joachim; Weber, Markus
2016-06-01
Background and purpose - In hip arthroplasty, acetabular inclination and anteversion-and also femoral stem torsion-are generally assessed by eye intraoperatively. We assessed whether visual estimation of cup and stem position is reliable. Patients and methods - In the course of a subgroup analysis of a prospective clinical trial, 65 patients underwent cementless hip arthroplasty using a minimally invasive anterolateral approach in lateral decubitus position. Altogether, 4 experienced surgeons assessed cup position intraoperatively according to the operative definition by Murray in the anterior pelvic plane and stem torsion in relation to the femoral condylar plane. Inclination, anteversion, and stem torsion were measured blind postoperatively on 3D-CT and compared to intraoperative results. Results - The mean difference between the 3D-CT results and intraoperative estimations by eye was -4.9° (-18 to 8.7) for inclination, 9.7° (-16 to 41) for anteversion, and -7.3° (-34 to 15) for stem torsion. We found an overestimation of > 5° for cup inclination in 32 hips, an overestimation of > 5° for stem torsion in 40 hips, and an underestimation < 5° for cup anteversion in 42 hips. The level of professional experience and patient characteristics had no clinically relevant effect on the accuracy of estimation by eye. Altogether, 46 stems were located outside the native norm of 10-20° as defined by Tönnis, measured on 3D-CT. Interpretation - Even an experienced surgeon's intraoperative estimation of cup and stem position by eye is not reliable compared to 3D-CT in minimally invasive THA. The use of mechanical insertion jigs, intraoperative fluoroscopy, or imageless navigation is recommended for correct implant insertion. PMID:26848628
Position Estimation of Access Points in 802.11 Wireless Networks
Kent, C A; Dowla, F U; Atwal, P K; Lennon, W J
2003-12-05
We developed a technique to locate wireless network nodes using multiple time-of-flight range measurements in a position estimate. When used with communication methods that allow propagation through walls, such as Ultra-Wideband and 802.11, we can locate network nodes in buildings and in caves where GPS is unavailable. This paper details the implementation on an 802.11a network where we demonstrated the ability to locate a network access point to within 20 feet.
Woerner, Michael; Sendtner, Ernst; Springorum, Robert; Craiovan, Benjamin; Worlicek, Michael; Renkawitz, Tobias; Grifka, Joachim; Weber, Markus
2016-01-01
Background and purpose In hip arthroplasty, acetabular inclination and anteversion—and also femoral stem torsion—are generally assessed by eye intraoperatively. We assessed whether visual estimation of cup and stem position is reliable. Patients and methods In the course of a subgroup analysis of a prospective clinical trial, 65 patients underwent cementless hip arthroplasty using a minimally invasive anterolateral approach in lateral decubitus position. Altogether, 4 experienced surgeons assessed cup position intraoperatively according to the operative definition by Murray in the anterior pelvic plane and stem torsion in relation to the femoral condylar plane. Inclination, anteversion, and stem torsion were measured blind postoperatively on 3D-CT and compared to intraoperative results. Results The mean difference between the 3D-CT results and intraoperative estimations by eye was −4.9° (−18 to 8.7) for inclination, 9.7° (−16 to 41) for anteversion, and −7.3° (−34 to 15) for stem torsion. We found an overestimation of > 5° for cup inclination in 32 hips, an overestimation of > 5° for stem torsion in 40 hips, and an underestimation < 5° for cup anteversion in 42 hips. The level of professional experience and patient characteristics had no clinically relevant effect on the accuracy of estimation by eye. Altogether, 46 stems were located outside the native norm of 10–20° as defined by Tönnis, measured on 3D-CT. Interpretation Even an experienced surgeon’s intraoperative estimation of cup and stem position by eye is not reliable compared to 3D-CT in minimally invasive THA. The use of mechanical insertion jigs, intraoperative fluoroscopy, or imageless navigation is recommended for correct implant insertion. PMID:26848628
Initial rotor position estimation and sliding preventing for elevators with surface-mounted PMSMs
NASA Astrophysics Data System (ADS)
Liu, Feng; Shen, Anwen; Tang, Qipeng; Xu, Jinbang
2016-03-01
Improved methods of initial rotor position estimation and sliding prevention are presented in this paper for elevators with surface-mounted permanent magnet synchronous machines (SPMSMs). In contrast to most of the existing literature, in this paper, estimation errors caused by stator resistance and dead time are analysed in detail. The improved estimation method can reduce the errors greatly without dead-time compensations and knowledge of motor parameters. Besides, an observer-based feedforward compensation of load torque is introduced to elevator applications to prevent sliding during the starting process. Since the torque observer is widely used in other motor applications, we focus on the impact caused by the change in inertia. Finally, a series of experiments are performed on a testing system with two 13.4 kW SPMSMs and drivers to illustrate the effectiveness and improvement of the method.
High-precision position estimation in PET using artificial neural networks
NASA Astrophysics Data System (ADS)
Mateo, F.; Aliaga, R. J.; Ferrando, N.; Martínez, J. D.; Herrero, V.; Lerche, Ch. W.; Colom, R. J.; Monzó, J. M.; Sebastiá, A.; Gadea, R.
2009-06-01
Traditionally, the most popular technique to predict the impact position of gamma photons on a PET detector has been Anger's logic. However, it introduces nonlinearities that compress the light distribution, reducing the useful field of view and the spatial resolution, especially at the edges of the scintillator crystal. In this work, we make use of neural networks to address a bias-corrected position estimation from real stimulus obtained from a 2D PET system setup. The preprocessing and data acquisition were performed by separate custom boards, especially designed for this application. The results show that neural networks yield a more uniform field of view while improving the systematic error and the spatial resolution. Therefore, they stand as a better performing and readily available alternative to classic positioning methods.
Inter-system biases estimation in multi-GNSS relative positioning with GPS and Galileo
NASA Astrophysics Data System (ADS)
Deprez, Cecile; Warnant, Rene
2016-04-01
The recent increase in the number of Global Navigation Satellite Systems (GNSS) opens new perspectives in the field of high precision positioning. Particularly, the European Galileo program has experienced major progress in 2015 with the launch of 6 satellites belonging to the new Full Operational Capability (FOC) generation. Associated with the ongoing GPS modernization, many more frequencies and satellites are now available. Therefore, multi-GNSS relative positioning based on GPS and Galileo overlapping frequencies should entail better accuracy and reliability in position estimations. However, the differences between satellite systems induce inter-system biases (ISBs) inside the multi-GNSS equations of observation. Once these biases estimated and removed from the model, a solution involving a unique pivot satellite for the two considered constellations can be obtained. Such an approach implies that the addition of even one single Galileo satellite to the GPS-only model will strengthen it. The combined use of L1 and L5 from GPS with E1 and E5a from Galileo in zero baseline double differences (ZB DD) based on a unique pivot satellite is employed to resolve ISBs. This model removes all the satellite- and receiver-dependant error sources by differentiating and the zero baseline configuration allows atmospheric and multipath effects elimination. An analysis of the long-term stability of ISBs is conducted on various pairs of receivers over large time spans. The possible influence of temperature variations inside the receivers over ISB values is also investigated. Our study is based on the 5 multi-GNSS receivers (2 Septentrio PolaRx4, 1 Septentrio PolaRxS and 2 Trimble NetR9) installed on the roof of our building in Liege. The estimated ISBs are then used as corrections in the multi-GNSS observation model and the resulting accuracy of multi-GNSS positioning is compared to GPS and Galileo standalone solutions.
Kamphuis, Claudia; Burke, Jennie K; Taukiri, Sarah; Petch, Susan-Fay; Turner, Sally-Anne
2016-08-01
Dairy cows grazing pasture and milked using automated milking systems (AMS) have lower milking frequencies than indoor fed cows milked using AMS. Therefore, milk recording intervals used for herd testing indoor fed cows may not be suitable for cows on pasture based farms. We hypothesised that accurate standardised 24 h estimates could be determined for AMS herds with milk recording intervals of less than the Gold Standard (48 hs), but that the optimum milk recording interval would depend on the herd average for milking frequency. The Gold Standard protocol was applied on five commercial dairy farms with AMS, between December 2011 and February 2013. From 12 milk recording test periods, involving 2211 cow-test days and 8049 cow milkings, standardised 24 h estimates for milk volume and milk composition were calculated for the Gold Standard protocol and compared with those collected during nine alternative sampling scenarios, including six shorter sampling periods and three in which a fixed number of milk samples per cow were collected. Results infer a 48 h milk recording protocol is unnecessarily long for collecting accurate estimates during milk recording on pasture based AMS farms. Collection of two milk samples only per cow was optimal in terms of high concordance correlation coefficients for milk volume and components and a low proportion of missed cow-test days. Further research is required to determine the effects of diurnal variations in milk composition on standardised 24 h estimates for milk volume and components, before a protocol based on a fixed number of samples could be considered. Based on the results of this study New Zealand have adopted a split protocol for herd testing based on the average milking frequency for the herd (NZ Herd Test Standard 8100:2015). PMID:27600967
Hussain, Zahra; Svensson, Carl-Magnus; Besle, Julien; Webb, Ben S.; Barrett, Brendan T.; McGraw, Paul V.
2015-01-01
We describe a method for deriving the linear cortical magnification factor from positional error across the visual field. We compared magnification obtained from this method between normally sighted individuals and amblyopic individuals, who receive atypical visual input during development. The cortical magnification factor was derived for each subject from positional error at 32 locations in the visual field, using an established model of conformal mapping between retinal and cortical coordinates. Magnification of the normally sighted group matched estimates from previous physiological and neuroimaging studies in humans, confirming the validity of the approach. The estimate of magnification for the amblyopic group was significantly lower than the normal group: by 4.4 mm deg−1 at 1° eccentricity, assuming a constant scaling factor for both groups. These estimates, if correct, suggest a role for early visual experience in establishing retinotopic mapping in cortex. We discuss the implications of altered cortical magnification for cortical size, and consider other neural changes that may account for the amblyopic results. PMID:25761341
Ultra-wideband radios for time-of-flight-ranging and network position estimation
Hertzog, Claudia A.; Dowla, Farid U.; Dallum, Gregory E.; Romero, Carlos E.
2011-06-14
This invention provides a novel high-accuracy indoor ranging device that uses ultra-wideband (UWB) RF pulsing with low-power and low-cost electronics. A unique of the present invention is that it exploits multiple measurements in time and space for very accurate ranging. The wideband radio signals utilized herein are particularly suited to ranging in harsh RF environments because they allow signal reconstruction in spite of multipath propagation distortion. Furthermore, the ranging and positioning techniques discussed herein directly address many of the known technical challenges encountered in UWB localization regarding synchronization and sampling. In the method developed, noisy, corrupted signals can be recovered by repeating range measurements across a channel, and the distance measurements are combined from many locations surrounding the target in a way that minimizes the range biases associated to indirect flight paths and through-wall propagation delays.
NASA Astrophysics Data System (ADS)
Kiso, Atsushi; Taniguchi, Yu; Seki, Hirokazu
This paper describes the estimation of the optimal measurement position by discriminant analysis based on Wilks' lambda for myoelectric hand control. In previous studies, for motion discrimination, the myoelectric signals were measured at the same positions. However, the optimal measurement positions of the myoelectric signals for motion discrimination differ depending on the remaining muscles of amputees. Therefore, the purpose of this study is to estimate the optimal and fewer measurement positions for precise motion discrimination of a human forearm. This study proposes a method for estimating the optimal measurement positions by discriminant analysis based on Wilks' lambda, using the myoelectric signals measured at multiple positions. The results of some experiments on the myoelectric hand simulator show the effectiveness of the proposed optimal measurement position estimation method.
NASA Technical Reports Server (NTRS)
Battin, R. H.; Croopnick, S. R.; Edwards, J. A.
1977-01-01
The formulation of a recursive maximum likelihood navigation system employing reference position and velocity vectors as state variables is presented. Convenient forms of the required variational equations of motion are developed together with an explicit form of the associated state transition matrix needed to refer measurement data from the measurement time to the epoch time. Computational advantages accrue from this design in that the usual forward extrapolation of the covariance matrix of estimation errors can be avoided without incurring unacceptable system errors. Simulation data for earth orbiting satellites are provided to substantiate this assertion.
Iqbal, Sumaiya; Hoque, Md Tamjidul
2016-01-01
A set of features computed from the primary amino acid sequence of proteins, is crucial in the process of inducing a machine learning model that is capable of accurately predicting three-dimensional protein structures. Solutions for existing protein structure prediction problems are in need of features that can capture the complexity of molecular level interactions. With a view to this, we propose a novel approach to estimate position specific estimated energy (PSEE) of a residue using contact energy and predicted relative solvent accessibility (RSA). Furthermore, we demonstrate PSEE can be reasonably estimated based on sequence information alone. PSEE is useful in identifying the structured as well as unstructured or, intrinsically disordered region of a protein by computing favorable and unfavorable energy respectively, characterized by appropriate threshold. The most intriguing finding, verified empirically, is the indication that the PSEE feature can effectively classify disorder versus ordered residues and can segregate different secondary structure type residues by computing the constituent energies. PSEE values for each amino acid strongly correlate with the hydrophobicity value of the corresponding amino acid. Further, PSEE can be used to detect the existence of critical binding regions that essentially undergo disorder-to-order transitions to perform crucial biological functions. Towards an application of disorder prediction using the PSEE feature, we have rigorously tested and found that a support vector machine model informed by a set of features including PSEE consistently outperforms a model with an identical set of features with PSEE removed. In addition, the new disorder predictor, DisPredict2, shows competitive performance in predicting protein disorder when compared with six existing disordered protein predictors. PMID:27588752
Using Spitzer to Estimate the Kepler False Positive Rate and to Validate Kepler Candidates.
NASA Astrophysics Data System (ADS)
Desert, Jean-Michel; Charbonneau, D.; Fressin, F.; Torres, G.
2012-01-01
I present the results from an ongoing large campaign with the Spitzer Space Telescope to gather near-infrared photometric measurements of Kepler Objects of Interest (KOI). Our goals are (1) to validate the planetary status of these Kepler candidates, (2) to estimate observationally the false positive rate, and (3) to study the atmospheres of confirmed planets through measurements of their secondary eclipses. Our target list spans of wide range of candidate sizes and periods orbiting various spectral type stars. The Spitzer observations provide constraints on the possibility of astrophysical false positives resulting from stellar blends, including eclipsing binaries and hierarchical triples. The number of possible blends per star is estimated using stellar population synthesis models and observational probes of the KOI close environments from direct imaging (e.g. Adaptive Optics, Speckle images, Kepler centroids). Combining all the above information with the shape of the transit lightcurves from the Kepler photometry, we compute odd ratios for the 34 candidates we observed in order to determine their false positive probability. Our results suggest that the Kepler false positive rate in this subset of candidates is low. I finally present a new list of Kepler candidates that we were able to validate using this method. This work is based on observations made with the Spitzer, which is operated by JPL/Caltech, under a contract with NASA. Support was provided by NASA through an award issued by JPL/Caltech. Kepler was selected as the 10th mission of the Discovery Program. Funding for this mission is provided by NASA, Science Mission Directorate.
Gibson, A; Jorm, L; McIntyre, P
2015-09-01
Meningococcal disease is a rare, rapidly progressing condition which may be difficult to diagnose, disproportionally affects children, and has high morbidity and mortality. Accurate incidence estimates are needed to monitor the effectiveness of vaccination and treatment. We used linked notification, hospital, mortality and birth data for all children of an Australian state (2000-2007) to estimate the incidence of meningococcal disease. A total of 595 cases were notified, 684 cases had a hospital diagnosis, and 26 cases died from meningococcal disease. All deaths were notified, but only 68% (466/684) of hospitalized cases. Of non-notified hospitalized cases with more than one clinical admission, most (90%, 103/114) did not have meningococcal disease recorded as their final diagnosis, consistent with initial 'false-positive' hospital meningococcal disease diagnosis. After adjusting for false-positive rates in hospital data, capture-recapture estimation suggested that up to four cases of meningococcal disease may not have been captured in either notification or hospital records. The estimated incidence of meningococcal disease in NSW-born and -resident children aged 0-14 years was 5·1-5·4 cases/100 000 child-years at risk, comparable to international estimates using similar methods, but lower than estimates based on hospital data. PMID:25573266
NASA Technical Reports Server (NTRS)
Chen, Lingli; Fathpour, Nanaz; Mehra, Raman K.
2005-01-01
As more and more nonlinear estimation techniques become available, our interest is in finding out what performance improvement, if any, they can provide for practical nonlinear problems that have been traditionally solved using linear methods. In this paper we examine the problem of estimating spacecraft position using conical scan (conscan) for NASA's Deep Space Network antennas. We show that for additive disturbances on antenna power measurement, the problem can be transformed into a linear one, and we present a general solution to this problem, with the least square solution reported in literature as a special case. We also show that for additive disturbances on antenna position, the problem is a truly nonlinear one, and we present two approximate solutions based on linearization and Unscented Transformation respectively, and one 'exact' solution based on Markov Chain Monte Carlo (MCMC) method. Simulations show that, with the amount of data collected in practice, linear methods perform almost the same as MCMC methods. It is only when we artificially reduce the amount of collected data and increase the level of noise that nonlinear methods show significantly better accuracy than that achieved by linear methods, at the expense of more computation.
A Simple Interface for 3D Position Estimation of a Mobile Robot with Single Camera.
Chao, Chun-Tang; Chung, Ming-Hsuan; Chiou, Juing-Shian; Wang, Chi-Jo
2016-01-01
In recent years, there has been an increase in the number of mobile robots controlled by a smart phone or tablet. This paper proposes a visual control interface for a mobile robot with a single camera to easily control the robot actions and estimate the 3D position of a target. In this proposal, the mobile robot employed an Arduino Yun as the core processor and was remote-controlled by a tablet with an Android operating system. In addition, the robot was fitted with a three-axis robotic arm for grasping. Both the real-time control signal and video transmission are transmitted via Wi-Fi. We show that with a properly calibrated camera and the proposed prototype procedures, the users can click on a desired position or object on the touchscreen and estimate its 3D coordinates in the real world by simple analytic geometry instead of a complicated algorithm. The results of the measurement verification demonstrates that this approach has great potential for mobile robots. PMID:27023556
A Simple Interface for 3D Position Estimation of a Mobile Robot with Single Camera
Chao, Chun-Tang; Chung, Ming-Hsuan; Chiou, Juing-Shian; Wang, Chi-Jo
2016-01-01
In recent years, there has been an increase in the number of mobile robots controlled by a smart phone or tablet. This paper proposes a visual control interface for a mobile robot with a single camera to easily control the robot actions and estimate the 3D position of a target. In this proposal, the mobile robot employed an Arduino Yun as the core processor and was remote-controlled by a tablet with an Android operating system. In addition, the robot was fitted with a three-axis robotic arm for grasping. Both the real-time control signal and video transmission are transmitted via Wi-Fi. We show that with a properly calibrated camera and the proposed prototype procedures, the users can click on a desired position or object on the touchscreen and estimate its 3D coordinates in the real world by simple analytic geometry instead of a complicated algorithm. The results of the measurement verification demonstrates that this approach has great potential for mobile robots. PMID:27023556
Airdata sensor based position estimation and fault diagnosis in aerial refueling
NASA Astrophysics Data System (ADS)
Sevil, Hakki Erhan
Aerial refueling is the process of transferring fuel from one aircraft (the tanker) to another (the receiver) during flight. In aerial refueling operations, the receiver aircraft is exposed to nonuniform wind field induced by tanker aircraft, and this nonuniform wind field leads to differences in readings of airdata sensors placed at different locations on the receiver aircraft. There are advantages and disadvantages of this phenomenon. As an advantage, it is used as a mechanism to estimate relative position of the receiver aircraft inside the nonuniform wind field behind the tanker. Using the difference in the measurements from multiple identical sensors, a model of the nonuniform wind field that is organized as maps of the airspeed, side slip angle and angle of attack as functions of the relative position is prepared. Then, using the developed algorithms, preformed maps and instant sensor readings, the relative position receiver aircraft is determined. The disadvantage of the phenomenon is that the differences in readings of airdata sensors cause false fault detections in a redundant-sensor-based Fault Detection and Isolation (FDI) system developed based on the assumption of identical sensor readings from three airdata sensors. Such FDI algorithm successfully performs detection and isolation of sensor faults when the receiver aircraft flies solo or outside the wake of the tanker aircraft. However, the FDI algorithm yields false fault detection when the receiver aircraft enters the tanker's wake. This problem can be eliminated by modifying the FDI algorithm. For the robustness, the expected values of the sensor measurements are incorporated in the FDI algorithm, instead of the assumption of identical measurements from the sensors. The expected values, which depend on the position of the receiver relative to the tanker, are obtained from the maps of the nonuniform wind field as functions of the relative position. The new robust FDI detects and isolates sensor
Needle position estimation from sub-sampled k-space data for MRI-guided interventions
NASA Astrophysics Data System (ADS)
Schmitt, Sebastian; Choli, Morwan; Overhoff, Heinrich M.
2015-03-01
MRI-guided interventions have gained much interest. They profit from intervention synchronous data acquisition and image visualization. Due to long data acquisition durations, ergonomic limitations may occur. For a trueFISP MRI-data acquisition sequence, a time sparing sub-sampling strategy has been developed that is adapted to amagnetic needle detection. A symmetrical and contrast rich susceptibility needle artifact, i.e. an approximately rectangular gray scale profile is assumed. The 1-D-Fourier transformed of a rectangular function is a sinc-function. Its periodicity is exploited by sampling only along a few orthogonal trajectories in k-space. Because a needle moves during intervention, its tip region resembles a rectangle in a time-difference image that is reconstructed from such sub-sampled k-spaces acquired at different time stamps. In different phantom experiments, a needle was pushed forward along a reference trajectory, which was determined from a needle holders geometric parameters. In addition, the trajectory of the needle tip was estimated by the method described above. Only ca. 4 to 5% of the entire k-space data was used for needle tip estimation. The misalignment of needle orientation and needle tip position, i.e. the differences between reference and estimated values, is small and even in its worst case less than 2 mm. The results show that the method is applicable under nearly real conditions. Next steps are addressed to the validation of the method for clinical data.
Plate Motion and Crustal Deformation Estimated with Geodetic Data from the Global Positioning System
NASA Technical Reports Server (NTRS)
Argus, Donald F.; Heflin, Michael B.
1995-01-01
We use geodetic data taken over four years with the Global Positioning System (GPS) to estimate: (1) motion between six major plates and (2) motion relative to these plates of ten sites in plate boundary zones. The degree of consistency between geodetic velocities and rigid plates requires the (one-dimensional) standard errors in horizontal velocities to be approx. 2 mm/yr. Each of the 15 angular velocities describing motion between plate pairs that we estimate with GPS differs insignificantly from the corresponding angular velocity in global plate motion model NUVEL-1A, which averages motion over the past 3 m.y. The motion of the Pacific plate relative to both the Eurasian and North American plates is observed to be faster than predicted by NUVEL-1A, supporting the inference from Very Long B ase- line Interferometry (VLBI) that motion of the Pacific plate has speed up over the past few m.y. The Eurasia-North America pole of rotation is estimated to be north of NUVEL-1A, consistent with the independent hypothesis that the pole has recently migrated northward across northeast Asia to near the Lena River delta. Victoria, which lies above the main thrust at the Cascadia subduction zone, moves relative to the interior of the overriding plate at 30% of the velocity of the subducting plate, reinforcing the conclusion that the thrust there is locked beneath the continental shelf and slope.
NASA Astrophysics Data System (ADS)
Rybynok, V. O.; Kyriacou, P. A.
2007-10-01
Diabetes is one of the biggest health challenges of the 21st century. The obesity epidemic, sedentary lifestyles and an ageing population mean prevalence of the condition is currently doubling every generation. Diabetes is associated with serious chronic ill health, disability and premature mortality. Long-term complications including heart disease, stroke, blindness, kidney disease and amputations, make the greatest contribution to the costs of diabetes care. Many of these long-term effects could be avoided with earlier, more effective monitoring and treatment. Currently, blood glucose can only be monitored through the use of invasive techniques. To date there is no widely accepted and readily available non-invasive monitoring technique to measure blood glucose despite the many attempts. This paper challenges one of the most difficult non-invasive monitoring techniques, that of blood glucose, and proposes a new novel approach that will enable the accurate, and calibration free estimation of glucose concentration in blood. This approach is based on spectroscopic techniques and a new adaptive modelling scheme. The theoretical implementation and the effectiveness of the adaptive modelling scheme for this application has been described and a detailed mathematical evaluation has been employed to prove that such a scheme has the capability of extracting accurately the concentration of glucose from a complex biological media.
Locating the position of objects in non-line-of-sight based on time delay estimation
NASA Astrophysics Data System (ADS)
Wang, Xue-Feng; Wang, Yuan-Qing; Su, Jin-Shan; Yang, Xing-Yu
2016-08-01
Non-line-of-sight imaging detection is to detect hidden objects by indirect light and intermediary surface (diffuser). It has very important significance in indirect access to an object or dangerous object detection, such as medical treatment and rescue. An approach to locating the positions of hidden objects is proposed based on time delay estimation. The time delays between the received signals and the source signal can be obtained by correlation analysis, and then the positions of hidden objects will be located. Compared with earlier systems and methods, the proposed approach has some modifications and provides significant improvements, such as quick data acquisition, simple system structure and low cost, and can locate the positions of hidden objects as well: this technology lays a good foundation for developing a practical system that can be used in real applications. Project supported by the National Science and Technology Major Project of China (Grant No. AHJ2011Z001) and the Major Research Project of Yili Normal University (Grant No. 2016YSZD05).
Estimation of trapping position in three-dimensional off-axis trapping with optical vortices
NASA Astrophysics Data System (ADS)
Ando, Taro; Otsu, Tomoko; Takiguchi, Yu; Ohtake, Yoshiyuki; Toyoda, Haruyoshi; Itoh, Hiroyasu
2014-08-01
Dynamics of micrometer-sized dielectric objects can be controlled by optical tweezers with scanning light, however, the trapped objects fail to track the scan when drag exceeds the trapping by too quick movement. On the other hand, optical vortices (OVs), which have a property of carrying angular momenta, can directly control torque on objects rather than their position. Laguerre-Gaussian (LG) beams are the most familiar examples of OV and have been studied extensively so far. Revolution of the objects trapped by the LG beams provides typical models of nonequilibrium statistical system, but stable mid-water trapping by the LG beams becomes essential to evaluate physical properties of the system without extrinsic hydrodynamic effects,. Nevertheless, off-axis revolutions of small objects trapped in mid-water by the LG beams have not yet been established with secure evidences. Here we report stable off-axis trapping of dielectric spheres in mid-water using high-quality LG beams generated by a holographic complex-amplitude modulation method. Direct evidence of the three-dimensional off-axis LG trapping was established via estimating the trapping position by measuring the change of revolution radii upon pressing the spheres onto glass walls. Resultantly, the axial trapping position was determined as about half the wavelength behind the beam waist position. This result provides a direct scientific evidence for possibility of off-axis three-dimensional trapping with a single LG beam, moreover, suggests applications as powerful tools for studying energy-conversion mechanisms and nonequilibrium nature in biological molecules under torque.
Laitinen, Elina; Lohan, Elena Simona
2016-01-01
The positioning based on Wireless Local Area Networks (WLAN) is one of the most promising technologies for indoor location-based services, generally using the information carried by Received Signal Strengths (RSS). One challenge, however, is the huge amount of data in the radiomap database due to the enormous number of hearable Access Points (AP) that could make the positioning system very complex. This paper concentrates on WLAN-based indoor location by comparing fingerprinting, path loss and weighted centroid based positioning approaches in terms of complexity and performance and studying the effects of grid size and AP reduction with several choices for appropriate selection criterion. All results are based on real field measurements in three multi-floor buildings. We validate our earlier findings concerning several different AP selection criteria and conclude that the best results are obtained with a maximum RSS-based criterion, which also proved to be the most consistent among the different investigated approaches. We show that the weighted centroid based low-complexity method is very sensitive to AP reduction, while the path loss-based method is also very robust to high percentage removals. Indeed, for fingerprinting, 50% of the APs can be removed safely with a properly chosen removal criterion without increasing the positioning error much. PMID:27213395
Laitinen, Elina; Lohan, Elena Simona
2016-01-01
The positioning based on Wireless Local Area Networks (WLAN) is one of the most promising technologies for indoor location-based services, generally using the information carried by Received Signal Strengths (RSS). One challenge, however, is the huge amount of data in the radiomap database due to the enormous number of hearable Access Points (AP) that could make the positioning system very complex. This paper concentrates on WLAN-based indoor location by comparing fingerprinting, path loss and weighted centroid based positioning approaches in terms of complexity and performance and studying the effects of grid size and AP reduction with several choices for appropriate selection criterion. All results are based on real field measurements in three multi-floor buildings. We validate our earlier findings concerning several different AP selection criteria and conclude that the best results are obtained with a maximum RSS-based criterion, which also proved to be the most consistent among the different investigated approaches. We show that the weighted centroid based low-complexity method is very sensitive to AP reduction, while the path loss-based method is also very robust to high percentage removals. Indeed, for fingerprinting, 50% of the APs can be removed safely with a properly chosen removal criterion without increasing the positioning error much. PMID:27213395
The power of being positive: Robust state estimation made possible by quantum mechanics
NASA Astrophysics Data System (ADS)
Kalev, Amir; Baldwin, Charles
Quantum-state tomography (QST) is generally expensive to implement experimentally. Nevertheless, in state-of-the-art experiments in quantum information science the goal is not to produce arbitrary states but states that have very high purity. Including this prior information in QST results in more manageable tomography protocols. In the context of pure-state tomography, and more generally, of bounded-rank states (states with rank <= r) tomography, a natural notion of informational completeness emerges, rank- r completeness. The purpose of this contribution is two fold. First, to prove and emphasize the significance of a less intuitive, yet more powerful, notion of completeness for practical QST, rank- r strict-completeness. This notion is made possible due to the positive semidefinite property of density matrices. Strictly-complete quantum measurements ensure a robust estimation of the state of the system, regardless of the convex estimator we use. Thus, pragmatically, quantum state tomography should be done using these kind of measurements. Second, to argue, based on strong numerical indication, that it is fairly straightforward to experimentally implement such measurements by measuring only few random orthonormal bases. For example, in our numerical experi This work was supported by NSF Grants PHY-1212445, PHY-1521016, and PHY-1521431.
A positional estimation technique for an autonomous land vehicle in an unstructured environment
NASA Technical Reports Server (NTRS)
Talluri, Raj; Aggarwal, J. K.
1990-01-01
This paper presents a solution to the positional estimation problem of an autonomous land vehicle navigating in an unstructured mountainous terrain. A Digital Elevation Map (DEM) of the area in which the robot is to navigate is assumed to be given. It is also assumed that the robot is equipped with a camera that can be panned and tilted, and a device to measure the elevation of the robot above the ground surface. No recognizable landmarks are assumed to be present in the environment in which the robot is to navigate. The solution presented makes use of the DEM information, and structures the problem as a heuristic search in the DEM for the possible robot location. The shape and position of the horizon line in the image plane and the known camera geometry of the perspective projection are used as parameters to search the DEM. Various heuristics drawn from the geometric constraints are used to prune the search space significantly. The algorithm is made robust to errors in the imaging process by accounting for the worst care errors. The approach is tested using DEM data of areas in Colorado and Texas. The method is suitable for use in outdoor mobile robots and planetary rovers.
Estimating fresh grass/herb biomass from HYMAP data using the red edge position
NASA Astrophysics Data System (ADS)
Cho, Moses A.; Sobhan, Istiak M.; Skidmore, Andrew K.
2006-08-01
Remote sensing of grass/herb quantity is essential for rangeland management of livestock and wildlife. Spectral indices such as NDVI, determined from red and near infrared bands are affected by variable soil and atmospheric conditions and saturate in dense vegetation. Alternatively, the wavelength of maximum slope in the red-NIR transition, termed the red edge position (REP) has potential to mitigate these effects. But the utility of the REP using air- and space-borne imagery is determined by the availability of narrow bands in the region of the red edge and the simplicity of the extraction method. Very recently, we proposed a simple technique for extracting the REP called the linear extrapolation method [Cho and Skidmore, Remote Sens. Environ., 101(2006)118.]. The purpose of this study was to evaluate the potential of the linear extrapolation method for estimating fresh grass/herb biomass and compare its performance with the four-point linear interpolation and three-point Lagrangian interpolation methods. The REPs were derived from atmospherically corrected HYMAP images collected over Majella National Park, Italy in July 2004. The predictive capabilities of various REP linear regression models were evaluated using leave-one-out cross validation and test set validation methods. For both validation methods, the linear extrapolation REP models produced higher correlations with grass/herb biomass and lower prediction errors compared with the linear interpolation and Lagrangian REP models. This study demonstrates the potential of REPs extracted by the linear extrapolation method using HYMAP data for estimating fresh grass/herb biomass.
Robust 3D Position Estimation in Wide and Unconstrained Indoor Environments
Mossel, Annette
2015-01-01
In this paper, a system for 3D position estimation in wide, unconstrained indoor environments is presented that employs infrared optical outside-in tracking of rigid-body targets with a stereo camera rig. To overcome limitations of state-of-the-art optical tracking systems, a pipeline for robust target identification and 3D point reconstruction has been investigated that enables camera calibration and tracking in environments with poor illumination, static and moving ambient light sources, occlusions and harsh conditions, such as fog. For evaluation, the system has been successfully applied in three different wide and unconstrained indoor environments, (1) user tracking for virtual and augmented reality applications, (2) handheld target tracking for tunneling and (3) machine guidance for mining. The results of each use case are discussed to embed the presented approach into a larger technological and application context. The experimental results demonstrate the system’s capabilities to track targets up to 100 m. Comparing the proposed approach to prior art in optical tracking in terms of range coverage and accuracy, it significantly extends the available tracking range, while only requiring two cameras and providing a relative 3D point accuracy with sub-centimeter deviation up to 30 m and low-centimeter deviation up to 100 m. PMID:26694388
NASA Astrophysics Data System (ADS)
Oda, Hirokuni; Xuan, Chuang; Yamamoto, Yuhji
2016-07-01
Pass-through superconducting rock magnetometers (SRM) offer rapid and high-precision remanence measurements for continuous samples that are essential for modern paleomagnetism studies. However, continuous SRM measurements are inevitably smoothed and distorted due to the convolution effect of SRM sensor response. Deconvolution is necessary to restore accurate magnetization from pass-through SRM data, and robust deconvolution requires reliable estimate of SRM sensor response as well as understanding of uncertainties associated with the SRM measurement system. In this paper, we use the SRM at Kochi Core Center (KCC), Japan, as an example to introduce new tool and procedure for accurate and efficient estimate of SRM sensor response. To quantify uncertainties associated with the SRM measurement due to track positioning errors and test their effects on deconvolution, we employed laser interferometry for precise monitoring of track positions both with and without placing a u-channel sample on the SRM tray. The acquired KCC SRM sensor response shows significant cross-term of Z-axis magnetization on the X-axis pick-up coil and full widths of ~46-54 mm at half-maximum response for the three pick-up coils, which are significantly narrower than those (~73-80 mm) for the liquid He-free SRM at Oregon State University. Laser interferometry measurements on the KCC SRM tracking system indicate positioning uncertainties of ~0.1-0.2 and ~0.5 mm for tracking with and without u-channel sample on the tray, respectively. Positioning errors appear to have reproducible components of up to ~0.5 mm possibly due to patterns or damages on tray surface or rope used for the tracking system. Deconvolution of 50,000 simulated measurement data with realistic error introduced based on the position uncertainties indicates that although the SRM tracking system has recognizable positioning uncertainties, they do not significantly debilitate the use of deconvolution to accurately restore high
Okeme, Joseph O; Parnis, J Mark; Poole, Justen; Diamond, Miriam L; Jantunen, Liisa M
2016-08-01
Polydimethylsiloxane (PDMS) shows promise for use as a passive air sampler (PAS) for semi-volatile organic compounds (SVOCs). To use PDMS as a PAS, knowledge of its chemical-specific partitioning behaviour and time to equilibrium is needed. Here we report on the effectiveness of two approaches for estimating the partitioning properties of polydimethylsiloxane (PDMS), values of PDMS-to-air partition ratios or coefficients (KPDMS-Air), and time to equilibrium of a range of SVOCs. Measured values of KPDMS-Air, Exp' at 25 °C obtained using the gas chromatography retention method (GC-RT) were compared with estimates from a poly-parameter free energy relationship (pp-FLER) and a COSMO-RS oligomer-based model. Target SVOCs included novel flame retardants (NFRs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), organophosphate flame retardants (OPFRs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). Significant positive relationships were found between log KPDMS-Air, Exp' and estimates made using the pp-FLER model (log KPDMS-Air, pp-LFER) and the COSMOtherm program (log KPDMS-Air, COSMOtherm). The discrepancy and bias between measured and predicted values were much higher for COSMO-RS than the pp-LFER model, indicating the anticipated better performance of the pp-LFER model than COSMO-RS. Calculations made using measured KPDMS-Air, Exp' values show that a PDMS PAS of 0.1 cm thickness will reach 25% of its equilibrium capacity in ∼1 day for alpha-hexachlorocyclohexane (α-HCH) to ∼ 500 years for tris (4-tert-butylphenyl) phosphate (TTBPP), which brackets the volatility range of all compounds tested. The results presented show the utility of GC-RT method for rapid and precise measurements of KPDMS-Air. PMID:27179237
Estimated Position Replacement Costs for Technician Personnel in a State's Public Facilities
ERIC Educational Resources Information Center
Zaharia, E. S.; Baumeister, A. A.
1978-01-01
Estimates and fiscal data were gathered from three public institutions for the developmentally disabled to estimate technician replacement costs in the residential service delivery system of a southeastern state. (Author/SBH)
NASA Technical Reports Server (NTRS)
Boland, J. S., III
1975-01-01
A general simulation program is presented (GSP) involving nonlinear state estimation for space vehicle flight navigation systems. A complete explanation of the iterative guidance mode guidance law, derivation of the dynamics, coordinate frames, and state estimation routines are given so as to fully clarify the assumptions and approximations involved so that simulation results can be placed in their proper perspective. A complete set of computer acronyms and their definitions as well as explanations of the subroutines used in the GSP simulator are included. To facilitate input/output, a complete set of compatable numbers, with units, are included to aid in data development. Format specifications, output data phrase meanings and purposes, and computer card data input are clearly spelled out. A large number of simulation and analytical studies were used to determine the validity of the simulator itself as well as various data runs.
Zapata, Julián; Lopez, Ricardo; Herrero, Paula; Ferreira, Vicente
2012-11-30
An automated headspace in-tube extraction (ITEX) method combined with multiple headspace extraction (MHE) has been developed to provide simultaneously information about the accurate wine content in 20 relevant aroma compounds and about their relative transfer rates to the headspace and hence about the relative strength of their interactions with the matrix. In the method, 5 μL (for alcohols, acetates and carbonyl alcohols) or 200 μL (for ethyl esters) of wine sample were introduced in a 2 mL vial, heated at 35°C and extracted with 32 (for alcohols, acetates and carbonyl alcohols) or 16 (for ethyl esters) 0.5 mL pumping strokes in four consecutive extraction and analysis cycles. The application of the classical theory of Multiple Extractions makes it possible to obtain a highly reliable estimate of the total amount of volatile compound present in the sample and a second parameter, β, which is simply the proportion of volatile not transferred to the trap in one extraction cycle, but that seems to be a reliable indicator of the actual volatility of the compound in that particular wine. A study with 20 wines of different types and 1 synthetic sample has revealed the existence of significant differences in the relative volatility of 15 out of 20 odorants. Differences are particularly intense for acetaldehyde and other carbonyls, but are also notable for alcohols and long chain fatty acid ethyl esters. It is expected that these differences, linked likely to sulphur dioxide and some unknown specific compositional aspects of the wine matrix, can be responsible for relevant sensory changes, and may even be the cause explaining why the same aroma composition can produce different aroma perceptions in two different wines. PMID:23102525
NASA Astrophysics Data System (ADS)
Collilieux, Xavier; Lebarbier, Emilie; Coulot, David; Bernard, Etienne
2014-05-01
GNSS position time series computed from permanent station observations have been shown to be affected by a significant number of offsets that can be explained (equipment changes, antenna malfunction, earthquakes) or not. If not corrected, velocities or inter-annual signals estimated from the series will be biased. In addition to these offsets, GNSS position series show dominant periodic signals at seasonal and specific frequencies related to real ground displacements or systematic errors. As a consequence, it is relevant to estimate both the frequencies of the periodic signals and the positions of the offsets. This supplies a synthetic description of the series and should improve the velocity determination. In this poster, we propose to study two methods that rely on two different approaches on real and synthetic series in order to solve this problem. We then propose to quantify if the estimation of low-frequency signals could help to improve the offsets detection.
Relich, Peter K; Olah, Mark J; Cutler, Patrick J; Lidke, Keith A
2016-04-01
The movement of a particle described by Brownian motion is quantified by a single parameter, D, the diffusion constant. The estimation of D from a discrete sequence of noisy observations is a fundamental problem in biological single-particle tracking experiments since it can provide information on the environment and/or the state of the particle itself via the hydrodynamic radius. Here, we present a method to estimate D that takes into account several effects that occur in practice, important for the correct estimation of D, and that have hitherto not been combined together for an estimation of D. These effects are motion blur from the finite integration time of the camera, intermittent trajectories, and time-dependent localization uncertainty. Our estimation procedure, a maximum-likelihood estimation with an information-based confidence interval, follows directly from the likelihood expression for a discretely observed Brownian trajectory that explicitly includes these effects. We begin with the formulation of the likelihood expression and then present three methods to find the exact solution. Each method has its own advantages in either computational robustness, theoretical insight, or the estimation of hidden variables. The Fisher information for this likelihood distribution is calculated and analyzed to show that localization uncertainties impose a lower bound on the estimation of D. Confidence intervals are established and then used to evaluate our estimator on simulated data with experimentally relevant camera effects to demonstrate the benefit of incorporating variable localization errors. PMID:27176323
NASA Astrophysics Data System (ADS)
Relich, Peter K.; Olah, Mark J.; Cutler, Patrick J.; Lidke, Keith A.
2016-04-01
The movement of a particle described by Brownian motion is quantified by a single parameter, D , the diffusion constant. The estimation of D from a discrete sequence of noisy observations is a fundamental problem in biological single-particle tracking experiments since it can provide information on the environment and/or the state of the particle itself via the hydrodynamic radius. Here, we present a method to estimate D that takes into account several effects that occur in practice, important for the correct estimation of D , and that have hitherto not been combined together for an estimation of D . These effects are motion blur from the finite integration time of the camera, intermittent trajectories, and time-dependent localization uncertainty. Our estimation procedure, a maximum-likelihood estimation with an information-based confidence interval, follows directly from the likelihood expression for a discretely observed Brownian trajectory that explicitly includes these effects. We begin with the formulation of the likelihood expression and then present three methods to find the exact solution. Each method has its own advantages in either computational robustness, theoretical insight, or the estimation of hidden variables. The Fisher information for this likelihood distribution is calculated and analyzed to show that localization uncertainties impose a lower bound on the estimation of D . Confidence intervals are established and then used to evaluate our estimator on simulated data with experimentally relevant camera effects to demonstrate the benefit of incorporating variable localization errors.
Time-Dependent Noise in GPS Position Time Series By a Network Noise Estimator
NASA Astrophysics Data System (ADS)
Dmitrieva, K.; Segall, P.
2014-12-01
Some current estimates of GPS velocity uncertainties for continuous stations with more than a decade of data can be very low, < 0.1 mm per year. Yet, velocities with respect to rigid plates can be an order of magnitude larger, even in nominally stable plate interiors. This could be caused by underestimating low frequency, time-dependent noise, such as random walk. Traditional estimators, based on individual time series, are insensitive to low amplitude random walk, yet such noise significantly increases GPS velocity uncertainties. We develop a new approach to estimating noise in GPS time series, focusing on areas where the signal in the data is well characterized. We analyze data from the seismically inactive parts of central US. The data is decomposed into signal, plate rotation and Glacial Isostatic Adjustment (GIA), and various noise components. Our method processes multiple stations simultaneously with a Kalman Filter, and estimates average noise components for the network by maximum likelihood. Currently, we model white noise, flicker noise and random walk. Synthetic tests show that this approach correctly estimates the velocity uncertainty by determining a good estimate of random walk variance, even when it is too small to be correctly estimated by traditional approaches. We present preliminary results from a network of 15 GPS stations in the central USA. The data is in a North America fixed reference frame, we subtract seasonal components and GIA displacements used in the SNARF model. Hence, all data in this reference frame is treated as noise. We estimate random walk of 0.82 mm/yr0.5, flicker noise of 3.96 mm/yr0.25 and white noise of 1.05 mm. From these noise parameters the estimated velocity uncertainty is 0.29 mm/yr for 10 years of daily data. This uncertainty is significantly greater than estimated by the traditional methods, at 0.12 mm/yr. The estimated uncertainty is still less than the median residual velocity in the North America fixed reference
A sensorless initial rotor position's estimation for permanent magnet synchronous machines
NASA Astrophysics Data System (ADS)
Krasnov, I.; Langraf, S.; Odnolopylov, I.; Koltun, V.
2015-10-01
Permanent magnet synchronous motors for the effective start require information about the initial position of a rotor. In this regard, most systems use position sensors, which substantially increase entirely a cost of an electrical drive [1-3]. The aim of this article is to develop a new method, allowing determining the absolute angular position of the permanent magnet synchronous motors’ rotor [4,5]. With a certain voltage pulses applied to the motor, its stator is magnetized by currents leakage in the windings. This allows using a special algorithm to calculate the absolute position of the rotor without using any motor parameters [6]. Simulation results prove the simplicity and efficiency of this method for determining an initial position of the permanent magnet synchronous motors’ rotor. Thus, this method can be widely used in the electrical industry.
Imaida, K; Tatematsu, M; Kato, T; Tsuda, H; Ito, N
1989-04-01
The applicability to a medium-term bioassay for liver carcinogens of mathematical formulae for the calculation of numbers of foci per volume was examined in F344 rats. Two weeks after initiation with diethylnitrosamine, animals were given test compounds for 6 weeks, partial hepatectomy being performed at week 3. At week 8, the rats were killed, the livers removed and stained immunohistochemically for assessment of glutathione S-transferase P form (GST-P)-positive foci development. Numbers and areas of lesions were measured two-dimensionally using a color image analyzer, and the Enzmann and Campbell formulae for estimation of number and volume per cm3 were applied to the results. In addition, three-dimensional reconstruction of individual foci was performed using up to 150 GST-P stained foci, with the aid of a computerized graphic system. Both two- and three-dimensionally expressed quantitative results were found to adequately demonstrate the modifying potential of test chemicals on hepatocarcinogenesis. The three-dimensional approach was only more accurate if most of the foci were small and the liver was enlarged by compound treatment. Stereological reconstruction revealed that the shape of GST-P-positive foci, especially if relatively large, is not always spherical but that many demonstrate irregular branching forms, so that the assumptions behind stereological estimation are not met. The results therefore show that care must be taken in applying mathematical formulae for the calculation of three-dimensional data. PMID:2501249
Koehlinger, Keegan; Oleson, Jacob; McCreery, Ryan; Moeller, Mary Pat
2015-01-01
Purpose Production accuracy of s-related morphemes was examined in 3-year-olds with mild-to-severe hearing loss, focusing on perceptibility, articulation, and input frequency. Method Morphemes with /s/, /z/, and /ɪz/ as allomorphs (plural, possessive, third-person singular –s, and auxiliary and copula “is”) were analyzed from language samples gathered from 51 children (ages: 2;10 [years;months] to 3;8) who are hard of hearing (HH), all of whom used amplification. Articulation was assessed via the Goldman-Fristoe Test of Articulation–Second Edition, and monomorphemic word final /s/ and /z/ production. Hearing was measured via better ear pure tone average, unaided Speech Intelligibility Index, and aided sensation level of speech at 4 kHz. Results Unlike results reported for children with normal hearing, the group of children who are HH correctly produced the /ɪz/ allomorph more than /s/ and /z/ allomorphs. Relative accuracy levels for morphemes and sentence positions paralleled those of children with normal hearing. The 4-kHz sensation level scores (but not the better ear pure tone average or Speech Intelligibility Index), the Goldman-Fristoe Test of Articulation–Second Edition, and word final s/z use all predicted accuracy. Conclusions Both better hearing and higher articulation scores are associated with improved morpheme production, and better aided audibility in the high frequencies and word final production of s/z are particularly critical for morpheme acquisition in children who are HH. PMID:25650750
A blowing-based method of detecting trunk and estimating root position for weeding mobile robots
NASA Astrophysics Data System (ADS)
Zhang, Fan; Matsushita, Akihiko; Kaneko, Shun'ichi; Tanaka, Takayuki
2008-11-01
Due to the area of the vineyard in Hokkaido is extremely large, it is very difficult and hard to eradicate weeds by human being. In order to solve this problem, we developed a dynamic image measure technique, which can be applied to the weeding robots in vineyards. The outstanding of this technique is that it can discriminate the weed and the trunk correctly and efficiently. Meanwhile, we also attempt to measure the root of trunk accurately. And a new method to measure the blocked trunk of grapes in vineyards has also been developed in this paper.
Nam, Kyung-Tae; Lee, Seung-Joon; Kuc, Tae-Yong; Kim, Hyungjong
2015-01-01
In this paper, we consider the state estimation problem for flexible joint manipulators that involve nonlinear characteristics in their stiffness. The two key ideas of our design are that (a) an accelerometer is used in order that the estimation error dynamics do not depend on nonlinearities at the link part of the manipulators and (b) the model of the nonlinear stiffness is indeed a Lipschitz function. Based on the measured acceleration, we propose a nonlinear observer under the Lipschitz condition of the nonlinear stiffness. In addition, in order to effectively compensate for the estimation error, the gain of the proposed observer is chosen from the ARE (algebraic Riccati equations) which depend on the Lipschitz constant. Comparative experimental results verify the effectiveness of the proposed method. PMID:26729125
NASA Astrophysics Data System (ADS)
Rebello, N. Sanjay
2012-02-01
Research has shown students' beliefs regarding their own abilities in math and science can influence their performance in these disciplines. I investigated the relationship between students' estimated performance and actual performance on five exams in a second semester calculus-based physics class. Students in a second-semester calculus-based physics class were given about 72 hours after the completion of each of five exams, to estimate their individual and class mean score on each exam. Students were given extra credit worth 1% of the exam points for estimating their score correct within 2% of the actual score and another 1% extra credit for estimating the class mean score within 2% of the correct value. I compared students' individual and mean score estimations with the actual scores to investigate the relationship between estimation accuracies and exam performance of the students as well as trends over the semester.
NASA Technical Reports Server (NTRS)
Mach, Douglas M.; Rust, W. D.
1993-01-01
Velocities, optical risetimes, and transmission line model peak currents for seven natural positive return strokes are reported. The average 2D positive return stroke velocity for channel segments of less than 500 m in length starting near the base of the channel is 0.8 +/- 0.3 x 10 exp 8 m/s, which is slower than the present corresponding average velocity for natural negative first return strokes of 1.7 +/- 0.7 x 10 exp 8/s. It is inferred that positive stroke peak currents in the literature, which assume the same velocity as negative strokes, are low by a factor of 2. The average 2D positive return stroke velocity for channel segments of greater than 500 m starting near the base of the channel is 0.9 +/- 0.4 x 10 exp 8 m/s. The corresponding average velocity for the present natural negative first strokes is 1.2 +/- 0.6 x 10 exp 8 m/s. No significant velocity change with height is found for positive return strokes.
Impact of orbit modeling on DORIS station position and Earth rotation estimates
NASA Astrophysics Data System (ADS)
Štěpánek, Petr; Rodriguez-Solano, Carlos Javier; Hugentobler, Urs; Filler, Vratislav
2014-04-01
The high precision of estimated station coordinates and Earth rotation parameters (ERP) obtained from satellite geodetic techniques is based on the precise determination of the satellite orbit. This paper focuses on the analysis of the impact of different orbit parameterizations on the accuracy of station coordinates and the ERPs derived from DORIS observations. In a series of experiments the DORIS data from the complete year 2011 were processed with different orbit model settings. First, the impact of precise modeling of the non-conservative forces on geodetic parameters was compared with results obtained with an empirical-stochastic modeling approach. Second, the temporal spacing of drag scaling parameters was tested. Third, the impact of estimating once-per-revolution harmonic accelerations in cross-track direction was analyzed. And fourth, two different approaches for solar radiation pressure (SRP) handling were compared, namely adjusting SRP scaling parameter or fixing it on pre-defined values. Our analyses confirm that the empirical-stochastic orbit modeling approach, which does not require satellite attitude information and macro models, results for most of the monitored station parameters in comparable accuracy as the dynamical model that employs precise non-conservative force modeling. However, the dynamical orbit model leads to a reduction of the RMS values for the estimated rotation pole coordinates by 17% for x-pole and 12% for y-pole. The experiments show that adjusting atmospheric drag scaling parameters each 30 min is appropriate for DORIS solutions. Moreover, it was shown that the adjustment of cross-track once-per-revolution empirical parameter increases the RMS of the estimated Earth rotation pole coordinates. With recent data it was however not possible to confirm the previously known high annual variation in the estimated geocenter z-translation series as well as its mitigation by fixing the SRP parameters on pre-defined values.
NASA Technical Reports Server (NTRS)
Gaines, Joseph; Johnston, Nick
1999-01-01
The Video Guidance Sensor, part of the Automated Rendezvous and Capture mechanism, is due to undergo formal qualification testing at Marshall Space Flight Center. Before it undergoes this qualification, a test was needed to verify repeatability of the sensor, and to allow different sensor configurations to be compared. This test was developed at the Flight Robotics Laboratory. The test uses a software script to drive the sensor target to the same position and thus allows sensor runs to be compared. The sensor target is the Dynamic Overhead Target Simulator. The simulator uses encoders as its position indicator. Distance Measuring Device's were used to independently verify the software script, the sensor reading, and the target position. The test area, sensor, and other test equipment are briefly described. The actual data is tabulated and will serve as a baseline for future tests. The software script was found to be adequate for the test. Position repeatability was acceptable for all the equipment. The system test is now ready to be used in formal qualification testing.
Ng, L.C.; Kelly, M.F.
1988-03-01
The report summarized the mathematical algorithm and the computed results developed for the prediction of a balloon's position uncertainty as a function of time from a given statistical wind velocity profile. The predicted results were used for mission plannings in support of a recent ship launch ballon observation experiment. 30 figs.
Paglia, Gianluca; Rohl, Andrew L.; Gale, Julian D.; Buckley, Craig E.
2005-06-01
We have performed an extensive computational study of {gamma}-Al{sub 2}O{sub 3}, beginning with the geometric analysis of approximately 1.47 billion spinel-based structural candidates, followed by derivative method energy minimization calculations of approximately 122 000 structures. Optimization of the spinel-based structural models demonstrated that structures exhibiting nonspinel site occupancy after simulation were more energetically favorable, as suggested in other computational studies. More importantly, none of the spinel structures exhibited simulated diffraction patterns that were characteristic of {gamma}-Al{sub 2}O{sub 3}. This suggests that cations of {gamma}-Al{sub 2}O{sub 3} are not exclusively held in spinel positions, that the spinel model of {gamma}-Al{sub 2}O{sub 3} does not accurately reflect its structure, and that a representative structure cannot be achieved from molecular modeling when the spinel representation is used as the starting structure. The latter two of these three findings are extremely important when trying to accurately model the structure. A second set of starting models were generated with a large number of cations occupying c symmetry positions, based on the findings from recent experiments. Optimization of the new c symmetry-based structural models resulted in simulated diffraction patterns that were characteristic of {gamma}-Al{sub 2}O{sub 3}. The modeling, conducted using supercells, yields a more accurate and complete determination of the defect structure of {gamma}-Al{sub 2}O{sub 3} than can be achieved with current experimental techniques. The results show that on average over 40% of the cations in the structure occupy nonspinel positions, and approximately two-thirds of these occupy c symmetry positions. The structures exhibit variable occupancy in the site positions that follow local symmetry exclusion rules. This variation was predominantly represented by a migration of cations away from a symmetry positions to other
NASA Astrophysics Data System (ADS)
Paglia, Gianluca; Rohl, Andrew L.; Buckley, Craig E.; Gale, Julian D.
2005-06-01
We have performed an extensive computational study of γ-Al2O3 , beginning with the geometric analysis of approximately 1.47 billion spinel-based structural candidates, followed by derivative method energy minimization calculations of approximately 122 000 structures. Optimization of the spinel-based structural models demonstrated that structures exhibiting nonspinel site occupancy after simulation were more energetically favorable, as suggested in other computational studies. More importantly, none of the spinel structures exhibited simulated diffraction patterns that were characteristic of γ-Al2O3 . This suggests that cations of γ-Al2O3 are not exclusively held in spinel positions, that the spinel model of γ-Al2O3 does not accurately reflect its structure, and that a representative structure cannot be achieved from molecular modeling when the spinel representation is used as the starting structure. The latter two of these three findings are extremely important when trying to accurately model the structure. A second set of starting models were generated with a large number of cations occupying c symmetry positions, based on the findings from recent experiments. Optimization of the new c symmetry-based structural models resulted in simulated diffraction patterns that were characteristic of γ-Al2O3 . The modeling, conducted using supercells, yields a more accurate and complete determination of the defect structure of γ-Al2O3 than can be achieved with current experimental techniques. The results show that on average over 40% of the cations in the structure occupy nonspinel positions, and approximately two-thirds of these occupy c symmetry positions. The structures exhibit variable occupancy in the site positions that follow local symmetry exclusion rules. This variation was predominantly represented by a migration of cations away from a symmetry positions to other tetrahedral site positions during optimization which were found not to affect the diffraction
Epstein, Ariel Tessler, Nir Einziger, Pinchas D.; Roberts, Matthew
2014-06-14
We present an analytical method for evaluating the first and second moments of the effective exciton spatial distribution in organic light-emitting diodes (OLED) from measured emission patterns. Specifically, the suggested algorithm estimates the emission zone mean position and width, respectively, from two distinct features of the pattern produced by interference between the emission sources and their images (induced by the reflective cathode): the angles in which interference extrema are observed, and the prominence of interference fringes. The relations between these parameters are derived rigorously for a general OLED structure, indicating that extrema angles are related to the mean position of the radiating excitons via Bragg's condition, and the spatial broadening is related to the attenuation of the image-source interference prominence due to an averaging effect. The method is applied successfully both on simulated emission patterns and on experimental data, exhibiting a very good agreement with the results obtained by numerical techniques. We investigate the method performance in detail, showing that it is capable of producing accurate estimations for a wide range of source-cathode separation distances, provided that the measured spectral interval is large enough; guidelines for achieving reliable evaluations are deduced from these results as well. As opposed to numerical fitting tools employed to perform similar tasks to date, our approximate method explicitly utilizes physical intuition and requires far less computational effort (no fitting is involved). Hence, applications that do not require highly resolved estimations, e.g., preliminary design and production-line verification, can benefit substantially from the analytical algorithm, when applicable. This introduces a novel set of efficient tools for OLED engineering, highly important in the view of the crucial role the exciton distribution plays in determining the device performance.
NASA Technical Reports Server (NTRS)
Gage, K. S.; Jasperson, W. H.
1977-01-01
An analysis is presented of the tropospheric turbulence data obtained by the Metrac positioning system, a radio location system which employs the Doppler principle to track inexpensive expendable balloon-borne transmitters. A Minneapolis field test of the Metrac system provided one-second samples of transmitter frequency from balloons tracked by four ground stations for more than an hour. The derivation of diffusion coefficients from the turbulence data was conducted by two methods, yielding highly consistent results.
NASA Astrophysics Data System (ADS)
Kamath, T.; Broek, T.; McCarthy, M.
2012-12-01
Compound Specific Isotope Analysis of Amino Acids (CSI-AA) has emerged as a highly precise new method of determining trophic levels of both aquatic and terrestrial organisms. Multiple studies have now shown that δ15N values for glutamic acid (Glu) and phenylalanine (Phe) can be coupled to provide extremely precise estimates of trophic position in diverse food web studies. The standard gas chromatography—isotope ratio mass spectrometer (GC-IRMS) approach is presently limited to a select number of labs since necessary equipment is both expensive and not widely accessible. Furthermore, typical GC-IRMS δ15N precision (±1‰) is significantly lower than usual bulk δ15N values (±0.1‰), thus presenting a considerable setback for precise trophic level calculations. In this study, we develop a new dual-column method to purify Glu and Phe using high performance liquid chromatography (HPLC). Phe is purified using an analytical scale reverse phase column embedded with anionic ion-pairing reagents and collected using automated fraction collection. Glu is separated from the non-polar amino acids using the same column and further purified using a hydrophilic interaction liquid chromatography (HILIC) cation and anion-exchange column and collected via automated fraction collection. Isotopic analysis of the purified AAs is then conducted on an elemental analyzer—isotope ratio mass spectrometer (EA-IRMS). As a test of this method, we present and compare the trophic position of five marine organisms—cyanobacteria, deep-sea bamboo coral, juvenile and adult white sea bass, and harbor seal, calculated using Glu and Phe δ15N values produced by both GC-IRMS and our HPLC-EA-IRMS approach. The preliminary results of this study suggest that the HPLC-EA-IRMS method is a viable alternative to GC-IRMS, which should allow accurate trophic position estimates to be made by more researchers using more readily available instrumentation.
A Two-dimensional Position Estimate of Two Sound Sources Using Two Microphones with Reflectors
NASA Astrophysics Data System (ADS)
Nakashima, Hiromichi; Kawamoto, Mitsuru; Ito, Masanori; Mukai, Toshiharu
Human beings and living things have the capability of identifying the directions of two or more sounds by a certain amount of correctness with only two ears. However it is difficult to give this capability to robots. Almost all the robots which have been proposed until now have three or more microphones in order to localize sound sources. In this paper, we propose a technique of estimating two kinds of directions, that is, vertical and horizontal directions, using a robot head consisted of two microphones, where the microphones of the robot head have reflectors working like the pinna.
NASA Astrophysics Data System (ADS)
Webb, S. R.; Penna, N. T.; Clarke, P. J.; Webster, S.; Martin, I.
2013-12-01
The estimation of total precipitable water vapour (PWV) using kinematic GNSS has been investigated since around 2001, aiming to extend the use of static ground-based GNSS, from which PWV estimates are now operationally assimilated into numerical weather prediction models. To date, kinematic GNSS PWV studies suggest a PWV measurement agreement with radiosondes of 2-3 mm, almost commensurate with static GNSS measurement accuracy, but only shipborne experiments have so far been carried out. As a first step towards extending such sea level-based studies to platforms that operate at a range of altitudes, such as airplanes or land based vehicles, the kinematic GNSS estimation of PWV over an exactly repeated trajectory is considered. A data set was collected from a GNSS receiver and antenna mounted on a carriage of the Snowdon Mountain Railway, UK, which continually ascends and descends through 950 m of vertical relief. Static GNSS reference receivers were installed at the top and bottom of the altitude profile, and derived zenith wet delay (ZWD) was interpolated to the altitude of the train to provide reference values together with profile estimates from the 100 m resolution runs of the Met Office's Unified Model. We demonstrate similar GNSS accuracies as obtained from previous shipborne studies, namely a double difference relative kinematic GNSS ZWD accuracy within 14 mm, and a kinematic GNSS precise point positioning ZWD accuracy within 15 mm. The latter is a more typical airborne PWV estimation scenario i.e. without the reliance on ground-based GNSS reference stations. We show that the kinematic GPS-only precise point positioning ZWD estimation is enhanced by also incorporating GLONASS observations.
NASA Astrophysics Data System (ADS)
He, Qian; Hu, Jianbin; Blum, Rick S.; Wu, Yonggang
2016-04-01
In this paper, we derive the Cramer-Rao bound (CRB) for joint target position and velocity estimation using an active or passive distributed radar network under more general, and practically occurring, conditions than assumed in previous work. In particular, the presented results allow nonorthogonal signals, spatially dependent Gaussian reflection coefficients, and spatially dependent Gaussian clutter-plus-noise. These bounds allow designers to compare the performance of their developed approaches, which are deemed to be of acceptable complexity, to the best achievable performance. If their developed approaches lead to performance close to the bounds, these developed approaches can be deemed "good enough". A particular recent study where algorithms have been developed for a practical radar application which must involve nonorthogonal signals, for which the best performance is unknown, is a great example. The presented results in our paper do not make any assumptions about the approximate location of the target being known from previous target detection signal processing. In addition, for situations in which we do not know some parameters accurately, we also derive the mismatched CRB. Numerical investigations of the mean squared error of the maximum likelihood estimation are employed to support the validity of the CRBs. In order to demonstrate the utility of the provided results to a topic of great current interest, the numerical results focus on a passive radar system using the Global System for Mobile communication (GSM) cellar system.
NASA Astrophysics Data System (ADS)
Kassem Jebai, Al; Malrait, François; Martin, Philippe; Rouchon, Pierre
2016-03-01
Sensorless control of permanent-magnet synchronous motors at low velocity remains a challenging task. A now well-established method consists of injecting a high-frequency signal and using the rotor saliency, both geometric and magnetic-saturation induced. This paper proposes a clear and original analysis based on second-order averaging of how to recover the position information from signal injection; this analysis blends well with a general model of magnetic saturation. It also proposes a simple parametric model of the saturated motor, based on an energy function which simply encompasses saturation and cross-saturation effects. Experimental results on a surface-mounted motor and an interior magnet motor illustrate the relevance of the approach.
NASA Technical Reports Server (NTRS)
Larson, Kristine M.; Freymueller, Jeff
1995-01-01
Global Positioning System (GPS) measurements spanning approximately 3 years have been used to determine velocities for 7 sites on the Australian, Pacific and Antarctic plates. The site velocities agree with both plate model predictions and other space geodetic techniques. We find no evidence for internal deformation of the interior of the Australian plate. Wellington, New Zealand, located in the Australian-Pacific plate boundary zone, moves 20 +/- 5 mm/yr west-southwest relative to the Australian plate. Its velocity lies midway between the predicted velocities of the two plates. Relative Euler vectors for the Australia-Antarctica and Pacific-Antarctica plates agree within one standard deviation with the NUVEL-1A predictions.
NASA Astrophysics Data System (ADS)
Olesen, Jacob Bjerring; Villagomez-Hoyos, Carlos Armando; Traberg, Marie Sand; Chee, Adrian J. Y.; Yiu, Billy Y. S.; Ho, Chung Kit; Yu, Alfred C. H.; Jensen, Jørgen Arendt
2016-04-01
This paper presents a method for measuring pressure changes in deep-tissue vessels using vector velocity ultrasound data. The large penetration depth is ensured by acquiring data using a low frequency phased array transducer. Vascular pressure changes are then calculated from 2-D angle-independent vector velocity fields using a model based on the Navier-Stokes equations. Experimental scans are performed on a fabricated flow phantom having a constriction of 36% at a depth of 100 mm. Scans are carried out using a phased array transducer connected to the experimental scanner, SARUS. 2-D fields of angle-independent vector velocities are acquired using directional synthetic aperture vector flow imaging. The obtained results are evaluated by comparison to a 3-D numerical simulation model with equivalent geometry as the designed phantom. The study showed pressure drops across the constricted phantom varying from -40 Pa to 15 Pa with a standard deviation of 32%, and a bias of 25% found relative to the peak simulated pressure drop. This preliminary study shows that pressure can be estimated non-invasively to a depth that enables cardiac scans, and thereby, the possibility of detecting the pressure drops across the mitral valve.
NASA Astrophysics Data System (ADS)
Sage, J. P.; Mayles, W. P. M.; Mayles, H. M.; Syndikus, I.
2014-10-01
Maximum likelihood estimation (MLE) is presented as a statistical tool to evaluate the contribution of measurement error to any measurement series where the same quantity is measured using different independent methods. The technique was tested against artificial data sets; generated for values of underlying variation in the quantity and measurement error between 0.5 mm and 3 mm. In each case the simulation parameters were determined within 0.1 mm. The technique was applied to analyzing external random positioning errors from positional audit data for 112 pelvic radiotherapy patients. Patient position offsets were measured using portal imaging analysis and external body surface measures. Using MLE to analyze all methods in parallel it was possible to ascertain the measurement error for each method and the underlying positional variation. In the (AP / Lat / SI) directions the standard deviations of the measured patient position errors from portal imaging were (3.3 mm / 2.3 mm / 1.9 mm), arising from underlying variations of (2.7 mm / 1.5 mm / 1.4 mm) and measurement uncertainties of (1.8 mm / 1.8 mm / 1.3 mm), respectively. The measurement errors agree well with published studies. MLE used in this manner could be applied to any study in which the same quantity is measured using independent methods.
De Neve, Jan-Emmanuel; Oswald, Andrew J.
2012-01-01
The question of whether there is a connection between income and psychological well-being is a long-studied issue across the social, psychological, and behavioral sciences. Much research has found that richer people tend to be happier. However, relatively little attention has been paid to whether happier individuals perform better financially in the first place. This possibility of reverse causality is arguably understudied. Using data from a large US representative panel, we show that adolescents and young adults who report higher life satisfaction or positive affect grow up to earn significantly higher levels of income later in life. We focus on earnings approximately one decade after the person’s well-being is measured; we exploit the availability of sibling clusters to introduce family fixed effects; we account for the human capacity to imagine later socioeconomic outcomes and to anticipate the resulting feelings in current well-being. The study’s results are robust to the inclusion of controls such as education, intelligence quotient, physical health, height, self-esteem, and later happiness. We consider how psychological well-being may influence income. Sobel–Goodman mediation tests reveal direct and indirect effects that carry the influence from happiness to income. Significant mediating pathways include a higher probability of obtaining a college degree, getting hired and promoted, having higher degrees of optimism and extraversion, and less neuroticism. PMID:23169627
NASA Astrophysics Data System (ADS)
Ng, J. A.; Booth, J.; Poulsen, P.; Kuncic, Z.; Keall, P. J.
2013-09-01
Kilovoltage intratreatment monitoring (KIM) is a novel real-time localization modality where the tumor position is continuously measured during intensity modulated radiation therapy (IMRT) or intensity modulated arc therapy (IMAT) by a kilovoltage (kV) x-ray imager. Adding kV imaging during therapy adds radiation dose. The additional effective dose is quantified for prostate radiotherapy and compared to dose from other localization modalities. The software PCXMC 2.0 was used to calculate the effective dose delivered to a phantom as a function of imager angle and field size for a Varian On-Board Imager. The average angular effective dose was calculated for a field size of 6 cm × 6 cm. The average angular effective dose was used in calculations for different treatment scenarios. Treatment scenarios considered were treatment type and fractionation. For all treatment scenarios, (i.e. conventionally fractionated and stereotactic body radiotherapy (SBRT), IMRT and IMAT), the total KIM dose at 1 Hz ranged from 2-10 mSv. This imaging dose is less than the Navotek radioactive implant dose (64 mSv) and a standard SBRT cone beam computed tomography pretreatment scan dose (22 mSv) over an entire treatment regime. KIM delivers an acceptably low effective dose for daily use as a real-time image-guidance method for prostate radiotherapy.
Makeev, Andrey; Clajus, Martin; Snyder, Scott; Wang, Xiaolang; Glick, Stephen J.
2015-01-01
Abstract. Semiconductor photon-counting detectors based on high atomic number, high density materials [cadmium zinc telluride (CZT)/cadmium telluride (CdTe)] for x-ray computed tomography (CT) provide advantages over conventional energy-integrating detectors, including reduced electronic and Swank noise, wider dynamic range, capability of spectral CT, and improved signal-to-noise ratio. Certain CT applications require high spatial resolution. In breast CT, for example, visualization of microcalcifications and assessment of tumor microvasculature after contrast enhancement require resolution on the order of 100 μm. A straightforward approach to increasing spatial resolution of pixellated CZT-based radiation detectors by merely decreasing the pixel size leads to two problems: (1) fabricating circuitry with small pixels becomes costly and (2) inter-pixel charge spreading can obviate any improvement in spatial resolution. We have used computer simulations to investigate position estimation algorithms that utilize charge sharing to achieve subpixel position resolution. To study these algorithms, we model a simple detector geometry with a 5×5 array of 200 μm pixels, and use a conditional probability function to model charge transport in CZT. We used COMSOL finite element method software to map the distribution of charge pulses and the Monte Carlo package PENELOPE for simulating fluorescent radiation. Performance of two x-ray interaction position estimation algorithms was evaluated: the method of maximum-likelihood estimation and a fast, practical algorithm that can be implemented in a readout application-specific integrated circuit and allows for identification of a quadrant of the pixel in which the interaction occurred. Both methods demonstrate good subpixel resolution; however, their actual efficiency is limited by the presence of fluorescent K-escape photons. Current experimental breast CT systems typically use detectors with a pixel size of 194
Makeev, Andrey; Clajus, Martin; Snyder, Scott; Wang, Xiaolang; Glick, Stephen J
2015-04-01
Semiconductor photon-counting detectors based on high atomic number, high density materials [cadmium zinc telluride (CZT)/cadmium telluride (CdTe)] for x-ray computed tomography (CT) provide advantages over conventional energy-integrating detectors, including reduced electronic and Swank noise, wider dynamic range, capability of spectral CT, and improved signal-to-noise ratio. Certain CT applications require high spatial resolution. In breast CT, for example, visualization of microcalcifications and assessment of tumor microvasculature after contrast enhancement require resolution on the order of [Formula: see text]. A straightforward approach to increasing spatial resolution of pixellated CZT-based radiation detectors by merely decreasing the pixel size leads to two problems: (1) fabricating circuitry with small pixels becomes costly and (2) inter-pixel charge spreading can obviate any improvement in spatial resolution. We have used computer simulations to investigate position estimation algorithms that utilize charge sharing to achieve subpixel position resolution. To study these algorithms, we model a simple detector geometry with a [Formula: see text] array of [Formula: see text] pixels, and use a conditional probability function to model charge transport in CZT. We used COMSOL finite element method software to map the distribution of charge pulses and the Monte Carlo package PENELOPE for simulating fluorescent radiation. Performance of two x-ray interaction position estimation algorithms was evaluated: the method of maximum-likelihood estimation and a fast, practical algorithm that can be implemented in a readout application-specific integrated circuit and allows for identification of a quadrant of the pixel in which the interaction occurred. Both methods demonstrate good subpixel resolution; however, their actual efficiency is limited by the presence of fluorescent [Formula: see text]-escape photons. Current experimental breast CT systems typically use
NASA Astrophysics Data System (ADS)
Iwata, Akitoshi; Ichikawa, Shinji; Tomita, Mutuwo; Doki, Shinji; Okuma, Shigeru
This paper presents a novel on-line parameter identification method for sensorless control of Synchronous Reluctance Motors (SynRMs). Although conventional sensorless control methods based on mathematical models usually need some complex measurements of motor parameters in advance, the proposed identification method does not require them and can be realized on-line. The proposed method identifies motor parameters under sensorless control, so rotor position and velocity can not be used to identify these parameters. However, the proposed method does not need rotor position and veocity, identified parameters are not affected by these estimation errors. The sensorless control using identified motor parameters is realized, and effective of the proposed method is verified by experimental results.
Broeckx, B J G; Verhoeven, G; Coopman, F; Van Haeringen, W; Bosmans, T; Gielen, I; Henckens, S; Saunders, J H; van Bree, H; Van Ryssen, B; Verbeke, V; Van Steendam, K; Van Nieuwerburgh, F; Deforce, D
2014-09-01
Although the prevalence of canine hip dysplasia (HD) has been the subject of a number of published studies, estimates vary widely. This study evaluated several possible causes for these differences. Sixty Belgian, Dutch and German veterinarians were asked to submit all hip radiographs obtained for screening purposes (irrespective of HD status) over a 2-year period, resulting in a database of 583 dogs. Each set of radiographs was accompanied by information on the reason for screening (breeding soundness examination, clinical complaint, assistance dogs, or other reasons), and dog breed, date of birth and age. Dog positioning exerted an effect at multiple levels. The agreement among different observers regarding correct or incorrect positioning was limited and incorrect positioning itself reduced the inter-observer agreement for radiographic hip conformation. Dysplastic dogs were more commonly positioned incorrectly than non-dysplastic dogs. The clinical complaint population had a high prevalence of dysplastic dogs (>70%) compared with the breeding population (11%) and the assistance dogs (6%). There was a significantly lower prevalence of HD among cases referred by veterinarians who frequently submitted hip-extended radiographs for evaluation (P = 0.002) compared to those who refer less frequently. However, this was likely to be selection bias, as radiographs that were from dogs suspected to be dysplastic were not submitted by frequent senders. The prevalence of dysplastic dogs varied widely between breeds (16.7-71.4%). Dogs diagnosed with dysplasia were significantly older than dogs considered healthy (P = 0.001) and dogs classified as borderline dysplastic (P = 0.035). Inter-observer agreement for hip conformation was moderately low, resulting in >7% variation in prevalence estimates for dysplasia. PMID:24986314
Nielsen, Jens M; Popp, Brian N; Winder, Monika
2015-07-01
Estimating trophic structures is a common approach used to retrieve information regarding energy pathways, predation, and competition in complex ecosystems. The application of amino acid (AA) compound-specific nitrogen (N) isotope analysis (CSIA) is a relatively new method used to estimate trophic position (TP) and feeding relationships in diverse organisms. Here, we conducted the first meta-analysis of δ(15)N AA values from measurements of 359 marine species covering four trophic levels, and compared TP estimates from AA-CSIA to literature values derived from food items, gut or stomach content analysis. We tested whether the AA trophic enrichment factor (TEF), or the (15)N enrichment among different individual AAs is constant across trophic levels and whether inclusion of δ(15)N values from multiple AAs improves TP estimation. For the TEF of glutamic acid relative to phenylalanine (Phe) we found an average value of 6.6‰ across all taxa, which is significantly lower than the commonly applied 7.6‰. We found that organism feeding ecology influences TEF values of several trophic AAs relative to Phe, with significantly higher TEF values for herbivores compared to omnivores and carnivores, while TEF values were also significantly lower for animals excreting urea compared to ammonium. Based on the comparison of multiple model structures using the metadata of δ(15)N AA values we show that increasing the number of AAs in principle improves precision in TP estimation. This meta-analysis clarifies the advantages and limitations of using individual δ(15)N AA values as tools in trophic ecology and provides a guideline for the future application of AA-CSIA to food web studies. PMID:25843809
NASA Astrophysics Data System (ADS)
Shi, Junbo; Xu, Chaoqian; Li, Yihe; Gao, Yang
2015-08-01
Global Positioning System (GPS) has become a cost-effective tool to determine troposphere zenith total delay (ZTD) with accuracy comparable to other atmospheric sensors such as the radiosonde, the water vapor radiometer, the radio occultation and so on. However, the high accuracy of GPS troposphere ZTD estimates relies on the precise satellite orbit and clock products available with various latencies. Although the International GNSS Service (IGS) can provide predicted orbit and clock products for real-time applications, the predicted clock accuracy of 3 ns cannot always guarantee the high accuracy of troposphere ZTD estimates. Such limitations could be overcome by the use of the newly launched IGS real-time service which provides 5 cm orbit and 0.2-1.0 ns (an equivalent range error of 6-30 cm) clock products in real time. Considering the relatively larger magnitude of the clock error than that of the orbit error, this paper investigates the effect of real-time satellite clock errors on the GPS precise point positioning (PPP)-based troposphere ZTD estimation. Meanwhile, how the real-time satellite clock errors impact the GPS PPP-based troposphere ZTD estimation has also been studied to obtain the most precise ZTD solutions. First, two types of real-time satellite clock products are assessed with respect to the IGS final clock product in terms of accuracy and precision. Second, the real-time GPS PPP-based troposphere ZTD estimation is conducted using data from 34 selected IGS stations over three independent weeks in April, July and October, 2013. Numerical results demonstrate that the precision, rather than the accuracy, of the real-time satellite clock products impacts the real-time PPP-based ZTD solutions more significantly. In other words, the real-time satellite clock product with better precision leads to more precise real-time PPP-based troposphere ZTD solutions. Therefore, it is suggested that users should select and apply real-time satellite products with
NASA Astrophysics Data System (ADS)
Charbonneau, David; Harps-N Collaboration
2015-01-01
Although the NASA Kepler Mission has determined the physical sizes of hundreds of small planets, and we have in many cases characterized the star in detail, we know virtually nothing about the planetary masses: There are only 7 planets smaller than 2.5 Earth radii for which there exist published mass estimates with a precision better than 20 percent, the bare minimum value required to begin to distinguish between different models of composition.HARPS-N is an ultra-stable fiber-fed high-resolution spectrograph optimized for the measurement of very precise radial velocities. We have 80 nights of guaranteed time per year, of which half are dedicated to the study of small Kepler planets.In preparation for the 2014 season, we compared all available Kepler Objects of Interest to identify the ones for which our 40 nights could be used most profitably. We analyzed the Kepler light curves to constrain the stellar rotation periods, the lifetimes of active regions on the stellar surface, and the noise that would result in our radial velocities. We assumed various mass-radius relations to estimate the observing time required to achieve a mass measurement with a precision of 15%, giving preference to stars that had been well characterized through asteroseismology. We began by monitoring our long list of targets. Based on preliminary results we then selected our final short list, gathering typically 70 observations per target during summer 2014.These resulting mass measurements will have a signifcant impact on our understanding of these so-called super-Earths and small Neptunes. They would form a core dataset with which the international astronomical community can meaningfully seek to understand these objects and their formation in a quantitative fashion.HARPS-N was funded by the Swiss Space Office, the Harvard Origin of Life Initiative, the Scottish Universities Physics Alliance, the University of Geneva, the Smithsonian Astrophysical Observatory, the Italian National
NASA Astrophysics Data System (ADS)
Khan, Yasin; Nur Budiman, Firmansiah; Béroual, Abderrahmane; Hussain Malik, Nazar; Al-Arainy, Abdulrehman Ali
2013-05-01
The presence of metallic particles has been recognized as a dangerous threat in gas-insulated substation (GIS). Such particles are initially free and move toward higher electric field regions such as triple junction i.e., spacer-electrode-gas interface. However, once these particles reach the spacer surface, they adhere to the spacer easily due to electrostatic image forces. From insulation point of view, the triple junction is the weakest point in GIS. The presence of such metallic particles on the spacer surface deteriorates the insulation strength. Thus, in order to improve the reliability of GIS, it is important to identify the size and the position of the particle adhering to the insulating spacer surface. One of the most promising methods to carry out such identification is by recognizing the partial discharges (PDs) provoked by such particles. This paper is aimed to discuss the particle size and position estimation by using the PD patterns and statistical analysis. The PD patterns were acquired using IEC 60270 method. Measurements were made to determine various PD signals caused by particle of different sizes at different locations on the spacer surface. The acquired PD patterns were characterized by a number of statistical parameters. The results show that the implemented technique could be used to distinguish between various particle sizes and positions at different SF6 pressures with a fairly high accuracy.
Accurate Evaluation of Quantum Integrals
NASA Technical Reports Server (NTRS)
Galant, David C.; Goorvitch, D.
1994-01-01
Combining an appropriate finite difference method with Richardson's extrapolation results in a simple, highly accurate numerical method for solving a Schr\\"{o}dinger's equation. Important results are that error estimates are provided, and that one can extrapolate expectation values rather than the wavefunctions to obtain highly accurate expectation values. We discuss the eigenvalues, the error growth in repeated Richardson's extrapolation, and show that the expectation values calculated on a crude mesh can be extrapolated to obtain expectation values of high accuracy.
Improving the Accuracy of Estimated 3d Positions Using Multi-Temporal Alos/prism Triplet Images
NASA Astrophysics Data System (ADS)
Susaki, J.; Kishimoto, H.
2015-03-01
In this paper, we present a method to improve the accuracy of a digital surface model (DSM) by utilizing multi-temporal triplet images. The Advanced Land Observing Satellite (ALOS) / Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) measures triplet images in the forward, nadir, and backward view directions, and a DSM is generated from the obtained set of triplet images. To generate a certain period of DSM, multiple DSMs generated from individual triplet images are compared, and outliers are removed. Our proposed method uses a traditional surveying approach to increase observations and solves multiple observation equations from all triplet images via the bias-corrected rational polynomial coefficient (RPC) model. Experimental results from using five sets of PRISM triplet images taken of the area around Saitama, north of Tokyo, Japan, showed that the average planimetric and height errors in the coordinates estimated from multi-temporal triplet images were 3.26 m and 2.71 m, respectively, and that they were smaller than those generated by using each set of triplet images individually. As a result, we conclude that the proposed method is effective for stably generating accurate DSMs from multi-temporal triplet images.
Daly, Megan E.; Luxton, Gary; Choi, Clara Y.H.; Gibbs, Iris C.; Chang, Steven D.; Adler, John R.; Soltys, Scott G.
2012-04-01
traditionally used to estimate spinal cord NTCP may not apply to the dosimetry of SRS. Further research with additional NTCP models is needed.
NASA Astrophysics Data System (ADS)
Itano, Wayne M.; Ramsey, Norman F.
1993-07-01
The paper discusses current methods for accurate measurements of time by conventional atomic clocks, with particular attention given to the principles of operation of atomic-beam frequency standards, atomic hydrogen masers, and atomic fountain and to the potential use of strings of trapped mercury ions as a time device more stable than conventional atomic clocks. The areas of application of the ultraprecise and ultrastable time-measuring devices that tax the capacity of modern atomic clocks include radio astronomy and tests of relativity. The paper also discusses practical applications of ultraprecise clocks, such as navigation of space vehicles and pinpointing the exact position of ships and other objects on earth using the GPS.
NASA Astrophysics Data System (ADS)
Désert, Jean-Michel; Charbonneau, David; Torres, Guillermo; Fressin, François; Ballard, Sarah; Bryson, Stephen T.; Knutson, Heather A.; Batalha, Natalie M.; Borucki, William J.; Brown, Timothy M.; Deming, Drake; Ford, Eric B.; Fortney, Jonathan J.; Gilliland, Ronald L.; Latham, David W.; Seager, Sara
2015-05-01
NASA’s Kepler mission has provided several thousand transiting planet candidates during the 4 yr of its nominal mission, yet only a small subset of these candidates have been confirmed as true planets. Therefore, the most fundamental question about these candidates is the fraction of bona fide planets. Estimating the rate of false positives of the overall Kepler sample is necessary to derive the planet occurrence rate. We present the results from two large observational campaigns that were conducted with the Spitzer Space Telescope during the the Kepler mission. These observations are dedicated to estimating the false positive rate (FPR) among the Kepler candidates. We select a sub-sample of 51 candidates, spanning wide ranges in stellar, orbital, and planetary parameter space, and we observe their transits with Spitzer at 4.5 μm. We use these observations to measures the candidate’s transit depths and infrared magnitudes. An authentic planet produces an achromatic transit depth (neglecting the modest effect of limb darkening). Conversely a bandpass-dependent depth alerts us to the potential presence of a blending star that could be the source of the observed eclipse: a false positive scenario. For most of the candidates (85%), the transit depths measured with Kepler are consistent with the transit depths measured with Spitzer as expected for planetary objects, while we find that the most discrepant measurements are due to the presence of unresolved stars that dilute the photometry. The Spitzer constraints on their own yield FPRs between 5% and depending on the Kepler Objects of Interest. By considering the population of the Kepler field stars, and by combining follow-up observations (imaging) when available, we find that the overall FPR of our sample is low. The measured upper limit on the FPR of our sample is 8.8% at a confidence level of 3σ. This observational result, which uses the achromatic property of planetary transit signals that is not investigated
NASA Technical Reports Server (NTRS)
Goad, Clyde C.; Chadwell, C. David
1993-01-01
GEODYNII is a conventional batch least-squares differential corrector computer program with deterministic models of the physical environment. Conventional algorithms were used to process differenced phase and pseudorange data to determine eight-day Global Positioning system (GPS) orbits with several meter accuracy. However, random physical processes drive the errors whose magnitudes prevent improving the GPS orbit accuracy. To improve the orbit accuracy, these random processes should be modeled stochastically. The conventional batch least-squares algorithm cannot accommodate stochastic models, only a stochastic estimation algorithm is suitable, such as a sequential filter/smoother. Also, GEODYNII cannot currently model the correlation among data values. Differenced pseudorange, and especially differenced phase, are precise data types that can be used to improve the GPS orbit precision. To overcome these limitations and improve the accuracy of GPS orbits computed using GEODYNII, we proposed to develop a sequential stochastic filter/smoother processor by using GEODYNII as a type of trajectory preprocessor. Our proposed processor is now completed. It contains a correlated double difference range processing capability, first order Gauss Markov models for the solar radiation pressure scale coefficient and y-bias acceleration, and a random walk model for the tropospheric refraction correction. The development approach was to interface the standard GEODYNII output files (measurement partials and variationals) with software modules containing the stochastic estimator, the stochastic models, and a double differenced phase range processing routine. Thus, no modifications to the original GEODYNII software were required. A schematic of the development is shown. The observational data are edited in the preprocessor and the data are passed to GEODYNII as one of its standard data types. A reference orbit is determined using GEODYNII as a batch least-squares processor and the
NASA Astrophysics Data System (ADS)
Mancinelli, Giorgio; Vizzini, Salvatrice; Mazzola, Antonio; Maci, Stefano; Basset, Alberto
2013-12-01
FishBase, a relational database freely available on the Internet, is to date widely used as a source of quantitative information on the trophic position of marine fish species. Here, we compared FishBase estimates for an assemblage of 30 fish species sampled in a Mediterranean lagoon (Acquatina lagoon, SE Italy) with their trophic positions calculated using nitrogen stable isotopes.
NASA Astrophysics Data System (ADS)
Kale, David; Stork, David G.
2009-02-01
The problems of estimating the position of an illuminant and the direction of illumination in realist paintings have been addressed using algorithms from computer vision. These algorithms fall into two general categories: In model-independent methods (cast-shadow analysis, occluding-contour analysis, ...), one does not need to know or assume the three-dimensional shapes of the objects in the scene. In model-dependent methods (shape-fromshading, full computer graphics synthesis, ...), one does need to know or assume the three-dimensional shapes. We explore the intermediate- or weak-model condition, where the three-dimensional object rendered is so simple one can very confidently assume its three-dimensional shape and, further, that this shape admits an analytic derivation of the appearance model. Specifically, we can assume that floors and walls are flat and that they are horizontal and vertical, respectively. We derived the maximum-likelihood estimator for the two-dimensional spatial location of a point source in an image as a function of the pattern of brightness (or grayscale value) over such a planar surface. We applied our methods to two paintings of the Baroque, paintings for which the question of the illuminant position is of interest to art historians: Georges de la Tour's Christ in the carpenter's studio (1645) and Caravaggio's The calling of St. Matthew (1599-1600). Our analyses show that a single point source (somewhat near to the depicted candle) is a slightly better explanation of the pattern of brightness on the floor in Christ than are two point sources, one in place of each of the figures. The luminance pattern on the rear wall in The calling implies the source is local, a few meters outside the picture frame-not the infinitely distant sun. Both results are consistent with previous rebuttals of the recent art historical claim that these paintings were executed by means of tracing optically projected images. Our method is the first application of such
NASA Astrophysics Data System (ADS)
Fu, Wanyi; Tian, Xiaoyu; Sturgeon, Gregory; Agasthya, Greeshma; Segars, William Paul; Goodsitt, Mitchell M.; Kazerooni, Ella A.; Samei, Ehsan
2016-04-01
In thoracic CT, organ-based tube current modulation (OTCM) reduces breast dose by lowering the tube current in the 120° anterior dose reduction zone of patients. However, in practice the breasts usually expand to an angle larger than the dose reduction zone. This work aims to simulate a breast positioning technique (BPT) to constrain the breast tissue to within the dose reduction zone for OTCM and to evaluate the corresponding potential reduction in breast dose. Thirteen female anthropomorphic computational phantoms were studied (age range: 27-65 y.o., weight range: 52-105.8 kg). Each phantom was modeled in the supine position with and without application of the BPT. Attenuation-based tube current (ATCM, reference mA) was generated by a ray-tracing program, taking into account the patient attenuation change in the longitudinal and angular plane (CAREDose4D, Siemens Healthcare). OTCM was generated by reducing the mA to 20% between +/- 60° anterior of the patient and increasing the mA in the remaining projections correspondingly (X-CARE, Siemens Healthcare) to maintain the mean tube current. Breast tissue dose was estimated using a validated Monte Carlo program for a commercial scanner (SOMATOM Definition Flash, Siemens Healthcare). Compared to standard tube current modulation, breast dose was significantly reduced using OTCM by 19.8+/-4.7%. With the BPT, breast dose was reduced by an additional 20.4+/-6.5% to 37.1+/-6.9%, using the same CTDIvol. BPT was more effective for phantoms simulating women with larger breasts with the average breast dose reduction of 30.2%, 39.2%, and 49.2% from OTCMBP to ATCM, using the same CTDIvol for phantoms with 0.5, 1.5, and 2.5 kg breasts, respectively. This study shows that a specially designed BPT improves the effectiveness of OTCM.
NASA Astrophysics Data System (ADS)
Boese, Margot; Hardt, Jacob
2015-04-01
In the classical research area of glacial morphology south of the Baltic Sea, the supposed main ice-marginal positions of the Weichselian glaciation have been documented on various maps. The lines in the maps suggest a similar timing of the ice margin along these hypothetical lines and represent a traditional morphostratigraphical approach. Nevertheless, more recent research resulting in stratigraphical interpretations of the related sediments give controversial results about the connectivity of ice-marginal features in the landscape. In addition, the development of new dating techniques reveals more diversified ice dynamics of the Scandinavian ice sheet as well as a time transgressiveness of the formation of major end moraine belts. On the other hand, age estimates generated by various methods don't give an unambiguous pattern of ice advances and retreat phases. The interpretation of geochronological data is a highly sensitive challenge in respect to the methods themselves and in respect to landscape processes induced by Late Glacial climatic phases, the relief, and by human impact during the Holocene. The Pomeranian ice margin will be taken as an example for the diverse interpretations of data obtained by Surface Exposure Dating, Optically Stimulated Luminescence, and Radiocarbon data. The dating methods require material of different origin, such as boulders at the surface, fine grained sediment, and organic material. All methods have been applied for dating the same ice marginal position. The remaining question is to which extent the reactions of the ice margins of the Scandinavian Ice Sheet can be brought into accordance with the general climatic record of long term climate archives or whether local weather conditions linked to changes in the atmospheric flow pattern influenced small scale ice advances or retreat along the fringe of the Scandinavian Ice Sheet.
Poulsen, Per Rugaard Cho, Byungchul; Keall, Paul J.
2008-12-01
Purpose: To develop a probability-based method for estimating the mean position, motion magnitude, and trajectory of a tumor using cone-beam CT (CBCT) projections. Method and Materials: CBCT acquisition was simulated for more than 80 hours of patient-measured trajectories for thoracic/abdominal tumors and prostate. The trajectories were divided into 60-second segments for which CBCT was simulated by projecting the tumor position onto a rotating imager. Tumor (surrogate) visibility on all projections was assumed. The mean and standard deviation of the tumor position and motion correlation along the three axes were determined with maximum likelihood estimation based on the projection data, assuming a Gaussian spatial distribution. The unknown position component along the imager axis was approximated by its expectation value, determined by the Gaussian distribution. Transformation of the resulting three-dimensional position to patient coordinates provided the estimated trajectory. Two trajectories were experimentally investigated by CBCT acquisition of a phantom. Results: The root-mean-square error of the estimated mean position was 0.05 mm. The root-mean-square error of the trajectories was <1 mm in 99.1% of the thorax/abdomen cases and in 99.7% of the prostate cases. The experimental trajectory estimation agreed with the actual phantom trajectory within 0.44 mm in any direction. Clinical applicability was demonstrated by estimating the tumor trajectory for a pancreas cancer case. Conclusions: A method for estimation of mean position, motion magnitude, and trajectory of a tumor from CBCT projections has been developed. The accuracy was typically much better than 1 mm. The method is applicable to motion-inclusive, respiratory-gated, and tumor-tracking radiotherapy.
NASA Technical Reports Server (NTRS)
Tralli, David M.; Dixon, Timothy H.; Stephens, Scott A.
1988-01-01
Surface Meteorological (SM) and Water Vapor Radiometer (WVR) measurements are used to provide an independent means of calibrating the GPS signal for the wet tropospheric path delay in a study of geodetic baseline measurements in the Gulf of California using GPS in which high tropospheric water vapor content yielded wet path delays in excess of 20 cm at zenith. Residual wet delays at zenith are estimated as constants and as first-order exponentially correlated stochastic processes. Calibration with WVR data is found to yield the best repeatabilities, with improved results possible if combined carrier phase and pseudorange data are used. Although SM measurements can introduce significant errors in baseline solutions if used with a simple atmospheric model and estimation of residual zenith delays as constants, SM calibration and stochastic estimation for residual zenith wet delays may be adequate for precise estimation of GPS baselines. For dry locations, WVRs may not be required to accurately model tropospheric effects on GPS baselines.
NASA Astrophysics Data System (ADS)
Ikari, Yohei; Hirata, Shinnosuke; Hachiya, Hiroyuki
2015-07-01
Pulse compression using a maximum-length sequence (M-sequence) can improve the signal-to-noise ratio (SNR) of the reflected echo in the pulse-echo method. In the case of a moving object, however, the echo is modulated owing to the Doppler effect. The Doppler-shifted M-sequence-modulated signal cannot be correlated with the reference signal that corresponds to the transmitted M-sequence-modulated signal. Therefore, Doppler velocity estimation by spectrum-pattern analysis of a cyclic M-sequence-modulated signal and cross correlations with Doppler-shifted reference signals that correspond to the estimated Doppler velocities has been proposed. In this paper, measurements of the position and velocity of a moving object by the proposed method are described. First, Doppler velocities of the object are estimated using a microphone array. Secondly, the received signal from each microphone is correlated with each Doppler-shifted reference signal. Then, the position of the object is determined from the B-mode image formed from all cross-correlation functions. After that, the velocity of the object is calculated from velocity components estimated from the Doppler velocities and the position. Finally, the estimated Doppler velocities, determined positions, and calculated velocities are evaluated.
Liu, Ruijie Rachel; Erwin, William D
2006-08-01
) error in radial position for eight patient scans without truncation were 3.37 cm (12.9%) for PM and 1.99 cm (8.6%) for BF, indicating BF is superior to PM in the absence of truncation. For two patient scans with truncation, the rms error was 3.24 cm (12.2%) for PM and 4.10 cm (18.2%) for BF. The slightly better performance of PM in the case of truncation is anomalous, due to FOV edge truncation artifacts in the CT reconstruction, and thus is suspect. The calculated NCO contour for a patient SPECT/CT scan was used with an iterative reconstruction algorithm that incorporated compensation for system resolution. The resulting image was qualitatively superior to the image obtained by reconstructing the data using the fixed radius stored by the scanner. The result was also superior to the image reconstructed using the iterative algorithm provided with the system, which does not incorporate resolution modeling. These results suggest that, under conditions of no or only mild lateral truncation of the CT scan, the algorithm is capable of providing radius estimates suitable for iterative SPECT reconstruction collimator geometric resolution modeling. PMID:16964856
Liu Ruijie Rachel; Erwin, William D.
2006-08-15
in radial position for eight patient scans without truncation were 3.37 cm (12.9%) for PM and 1.99 cm (8.6%) for BF, indicating BF is superior to PM in the absence of truncation. For two patient scans with truncation, the rms error was 3.24 cm (12.2%) for PM and 4.10 cm (18.2%) for BF. The slightly better performance of PM in the case of truncation is anomalous, due to FOV edge truncation artifacts in the CT reconstruction, and thus is suspect. The calculated NCO contour for a patient SPECT/CT scan was used with an iterative reconstruction algorithm that incorporated compensation for system resolution. The resulting image was qualitatively superior to the image obtained by reconstructing the data using the fixed radius stored by the scanner. The result was also superior to the image reconstructed using the iterative algorithm provided with the system, which does not incorporate resolution modeling. These results suggest that, under conditions of no or only mild lateral truncation of the CT scan, the algorithm is capable of providing radius estimates suitable for iterative SPECT reconstruction collimator geometric resolution modeling.
NASA Technical Reports Server (NTRS)
Elyasberg, P. Y.; Kugayenko, B. V.; Voyskovskiy, M. I.
1975-01-01
The effects of disturbing forces on position calculation, and errors in the initial conditions of motion and in the selected assignment calculation schemes are estimated. It is shown that the main disturbing effects on the accuracy are due to density variations of the upper atmosphere. Recommendations are presented for estimating the calculation accuracy along with an example of such an estimate for the Interkosmos-7 artificial earth satellite. Other factors considered include the adopted scheme and computational algorithms used, effects of disturbing forces not taken into account earlier, and errors in the values of constants and in models of disturbing forces.
NASA Astrophysics Data System (ADS)
Tralli, David M.; Lichten, Stephen M.; Herring, Thomas A.
1992-12-01
Kalman filter estimates of zenith nondispersive atmospheric path delays at Westford, Massachusetts, Fort Davis, Texas, and Mojave, California, were obtained from independent analyses of data collected during January and February 1988 using the GPS and VLBI. The apparent accuracy of the path delays is inferred by examining the estimates and covariances from both sets of data. The ability of the geodetic data to resolve zenith path delay fluctuations is determined by comparing further the GPS Kalman filter estimates with corresponding wet path delays derived from water vapor radiometric data available at Mojave over two 8-hour data spans within the comparison period. GPS and VLBI zenith path delay estimates agree well within one standard deviation formal uncertainties (from 10-20 mm for GPS and 3-15 mm for VLBI) in four out of the five possible comparisons, with maximum differences of 5 and 21 mm over 8- to 12-hour data spans.
NASA Technical Reports Server (NTRS)
Tralli, David M.; Lichten, Stephen M.; Herring, Thomas A.
1992-01-01
Kalman filter estimates of zenith nondispersive atmospheric path delays at Westford, Massachusetts, Fort Davis, Texas, and Mojave, California, were obtained from independent analyses of data collected during January and February 1988 using the GPS and VLBI. The apparent accuracy of the path delays is inferred by examining the estimates and covariances from both sets of data. The ability of the geodetic data to resolve zenith path delay fluctuations is determined by comparing further the GPS Kalman filter estimates with corresponding wet path delays derived from water vapor radiometric data available at Mojave over two 8-hour data spans within the comparison period. GPS and VLBI zenith path delay estimates agree well within one standard deviation formal uncertainties (from 10-20 mm for GPS and 3-15 mm for VLBI) in four out of the five possible comparisons, with maximum differences of 5 and 21 mm over 8- to 12-hour data spans.
Cho, Byungchul; Poulsen, Per Rugaard; Sawant, Amit; Ruan, Dan; Keall, Paul J.
2011-01-01
Purpose: To develop a real-time target position estimation method using stereoscopic kilovoltage (kV)/megavoltage (MV) imaging and external respiratory monitoring, and to investigate the performance of a dynamic multileaf collimator tracking system using this method. Methods and Materials: The real-time three-dimensional internal target position estimation was established by creating a time-varying correlation model that connected the external respiratory signals with the internal target motion measured intermittently using kV/MV imaging. The method was integrated into a dynamic multileaf collimator tracking system. Tracking experiments were performed for 10 thoracic/abdominal traces. A three-dimensional motion platform carrying a gold marker and a separate one-dimensional motion platform were used to reproduce the target and external respiratory motion, respectively. The target positions were detected by kV (1 Hz) and MV (5.2 Hz) imaging, and external respiratory motion was captured by an optical system (30 Hz). The beam-target alignment error was quantified as the positional difference between the target and circular beam center on the MV images acquired during tracking. The correlation model error was quantified by comparing a model estimate and measured target positions. Results: The root-mean-square errors in the beam-target alignment that had ranged from 3.1 to 7.6 mm without tracking were reduced to <1.5 mm with tracking, except during the model building period (6 s). The root-mean-square error in the correlation model was submillimeters in all directions. Conclusion: A novel real-time target position estimation method was developed and integrated into a dynamic multileaf collimator tracking system and demonstrated an average submillimeter geometric accuracy after initializing the internal/external correlation model. The method used hardware tools available on linear accelerators and therefore shows promise for clinical implementation.
van Sighem, Ard; Thiebaut, Rodolphe; Smith, Colette; Ratmann, Oliver; Cambiano, Valentina; Albert, Jan; Amato-Gauci, Andrew; Bezemer, Daniela; Campbell, Colin; Commenges, Daniel; Donoghoe, Martin; Ford, Deborah; Kouyos, Roger; Lodwick, Rebecca; Lundgren, Jens; Pantazis, Nikos; Pharris, Anastasia; Quinten, Chantal; Thorne, Claire; Touloumi, Giota; Delpech, Valerie; Phillips, Andrew
2016-01-01
It is important not only to collect epidemiologic data on HIV but to also fully utilize such information to understand the epidemic over time and to help inform and monitor the impact of policies and interventions. We describe and apply a novel method to estimate the size and characteristics of HIV-positive populations. The method was applied to data on men who have sex with men living in the UK and to a pseudo dataset to assess performance for different data availability. The individual-based simulation model was calibrated using an approximate Bayesian computation-based approach. In 2013, 48,310 (90% plausibility range: 39,900–45,560) men who have sex with men were estimated to be living with HIV in the UK, of whom 10,400 (6,160–17,350) were undiagnosed. There were an estimated 3,210 (1,730–5,350) infections per year on average between 2010 and 2013. Sixty-two percent of the total HIV-positive population are thought to have viral load <500 copies/ml. In the pseudo-epidemic example, HIV estimates have narrower plausibility ranges and are closer to the true number, the greater the data availability to calibrate the model. We demonstrate that our method can be applied to settings with less data, however plausibility ranges for estimates will be wider to reflect greater uncertainty of the data used to fit the model. PMID:26605814
Hyer, Daniel E.; Hintenlang, David E.
2010-09-15
Purpose: The purpose of this study was to develop a practical method for estimating organ doses from kilovoltage cone-beam CT (CBCT) that can be performed with readily available phantoms and dosimeters. The accuracy of organ dose estimates made using the ImPACT patient dose calculator was also evaluated. Methods: A 100 mm pencil chamber and standard CT dose index (CTDI) phantoms were used to measure the cone-beam dose index (CBDI). A weighted CBDI (CBDI{sup w}) was then calculated from these measurements to represent the average volumetric dose in the CTDI phantom. By comparing CBDI{sup w} to the previously published organ doses, organ dose conversion coefficients were developed. The measured CBDI values were also used as inputs for the ImPACT calculator to estimate organ doses. All CBDI dose measurements were performed on both the Elekta XVI and Varian OBI at three clinically relevant locations: Head, chest, and pelvis. Results: The head, chest, and pelvis protocols yielded CBDI{sup w} values of 0.98, 16.62, and 24.13 mGy for the XVI system and 5.17, 6.14, and 21.57 mGy for the OBI system, respectively. Organ doses estimated with the ImPACT CT dose calculator showed a large range of variation from the previously measured organ doses, demonstrating its limitations for use with CBCT. Conclusions: The organ dose conversion coefficients developed in this work relate CBDI{sup w} values to organ doses previously measured using the same clinical protocols. Ultimately, these coefficients will allow for the quick estimation of organ doses from routine measurements performed using standard CTDI phantoms and pencil chambers.
NASA Technical Reports Server (NTRS)
Lear, W. M.
1974-01-01
The integration is discussed of the vector differential equation X = F(x, t) from time t sub i to t sub (i = 1) where only the values of x sub i are available for the the integration. No previous values of x or x prime are used. Using an orbit integration problem, comparisons are made between Taylor series integrators and various types and orders of Runge-Kutta integrators. A fourth order Runge-Kutta type integrator for orbital work is presented, and approximate (there may be no exact) fifth order Runge-Kutta integrators are discussed. Also discussed and compared is a self starting integrator ising delta f/delta x. A numerical method for controlling the accuracy of integration is given, and the special equations for accurately integrating accelerometer data are shown.
Lott, S; Musshoff, F; Madea, B
2012-09-10
There is no toxicological analysis of gamma-hydroxybutyrate (GHB) applied routinely in cases of driving under influence (DUI); therefore the extent of consumption of this drug might be underestimated. Its consumption is described as occurring often concurrently with amphetamine or ecstasy. This study examines 196 serum samples which were collected by police during road side testing for GHB. The samples subject to this study have already been found to be positive for amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA) and/or 3,4-methylenedioxyethamphetamine (MDEA). Analysis has been performed by LC/MS/MS in the multiple reaction monitoring (MRM) mode. Due to its polarity, chromatographic separation of GHB was achieved by a HILIC column. To differentiate endogenous and exogenous levels of GHB, a cut-off concentration of 4μg/ml was applied. Of the 196 samples, two have been found to be positive for GHB. Of these samples, one sample was also positive for amphetamine and one for MDMA. Whilst other amphetamine derivates were not detected in these samples, both samples were found to be positive for cannabinoids. These results suggest that co-consumption of GHB with amphetamine or ecstasy is relatively low (1%) for the collective of this study. PMID:22554869
Leslie, Hannah H.; Karasek, Deborah A.; Harris, Laura F.; Chang, Emily; Abdulrahim, Naila; Maloba, May; Huchko, Megan J.
2014-01-01
Objective To demonstrate the application of causal inference methods to observational data in the obstetrics and gynecology field, particularly causal modeling and semi-parametric estimation. Background Human immunodeficiency virus (HIV)-positive women are at increased risk for cervical cancer and its treatable precursors. Determining whether potential risk factors such as hormonal contraception are true causes is critical for informing public health strategies as longevity increases among HIV-positive women in developing countries. Methods We developed a causal model of the factors related to combined oral contraceptive (COC) use and cervical intraepithelial neoplasia 2 or greater (CIN2+) and modified the model to fit the observed data, drawn from women in a cervical cancer screening program at HIV clinics in Kenya. Assumptions required for substantiation of a causal relationship were assessed. We estimated the population-level association using semi-parametric methods: g-computation, inverse probability of treatment weighting, and targeted maximum likelihood estimation. Results We identified 2 plausible causal paths from COC use to CIN2+: via HPV infection and via increased disease progression. Study data enabled estimation of the latter only with strong assumptions of no unmeasured confounding. Of 2,519 women under 50 screened per protocol, 219 (8.7%) were diagnosed with CIN2+. Marginal modeling suggested a 2.9% (95% confidence interval 0.1%, 6.9%) increase in prevalence of CIN2+ if all women under 50 were exposed to COC; the significance of this association was sensitive to method of estimation and exposure misclassification. Conclusion Use of causal modeling enabled clear representation of the causal relationship of interest and the assumptions required to estimate that relationship from the observed data. Semi-parametric estimation methods provided flexibility and reduced reliance on correct model form. Although selected results suggest an increased
Binder, Thomas R.; Holbrook, Christopher M.; Miehls, Scott M.; Thompson, Henry T.; Krueger, Charles C.
2014-01-01
Our results satisfied the three assumptions of oviduct tagging and suggested that oviduct transmitters can be used with positional telemetry to estimate time and location of spawning in lake trout and other species. In situations where oviduct transmitters may be difficult to position once expelled into substrate, pairing oviduct transmitters with a normal-sized fish transmitter that remains in the fish is recommended, with spawning inferred when the two tags separate in space. Optimal transmitter delay will depend on expected degree of spawning site residency and swim speed.
ERIC Educational Resources Information Center
Rom, Mark Carl
2011-01-01
Grades matter. College grading systems, however, are often ad hoc and prone to mistakes. This essay focuses on one factor that contributes to high-quality grading systems: grading accuracy (or "efficiency"). I proceed in several steps. First, I discuss the elements of "efficient" (i.e., accurate) grading. Next, I present analytical results…
Predict amine solution properties accurately
Cheng, S.; Meisen, A.; Chakma, A.
1996-02-01
Improved process design begins with using accurate physical property data. Especially in the preliminary design stage, physical property data such as density viscosity, thermal conductivity and specific heat can affect the overall performance of absorbers, heat exchangers, reboilers and pump. These properties can also influence temperature profiles in heat transfer equipment and thus control or affect the rate of amine breakdown. Aqueous-amine solution physical property data are available in graphical form. However, it is not convenient to use with computer-based calculations. Developed equations allow improved correlations of derived physical property estimates with published data. Expressions are given which can be used to estimate physical properties of methyldiethanolamine (MDEA), monoethanolamine (MEA) and diglycolamine (DGA) solutions.
NASA Astrophysics Data System (ADS)
Balachandar, Settu; Shivaprakash, N. C.; Kameswara Rao, L.
2016-01-01
A new approach is proposed to estimate the thermal diffusivity of optically transparent solids at ambient temperature based on the velocity of an effective temperature point (ETP), and by using a two-beam interferometer the proposed concept is corroborated. 1D unsteady heat flow via step-temperature excitation is interpreted as a ‘micro-scale rectilinear translatory motion’ of an ETP. The velocity dependent function is extracted by revisiting the Fourier heat diffusion equation. The relationship between the velocity of the ETP with thermal diffusivity is modeled using a standard solution. Under optimized thermal excitation, the product of the ‘velocity of the ETP’ and the distance is a new constitutive equation for the thermal diffusivity of the solid. The experimental approach involves the establishment of a 1D unsteady heat flow inside the sample through step-temperature excitation. In the moving isothermal surfaces, the ETP is identified using a two-beam interferometer. The arrival-time of the ETP to reach a fixed distance away from heat source is measured, and its velocity is calculated. The velocity of the ETP and a given distance is sufficient to estimate the thermal diffusivity of a solid. The proposed method is experimentally verified for BK7 glass samples and the measured results are found to match closely with the reported value.
Accurate monotone cubic interpolation
NASA Technical Reports Server (NTRS)
Huynh, Hung T.
1991-01-01
Monotone piecewise cubic interpolants are simple and effective. They are generally third-order accurate, except near strict local extrema where accuracy degenerates to second-order due to the monotonicity constraint. Algorithms for piecewise cubic interpolants, which preserve monotonicity as well as uniform third and fourth-order accuracy are presented. The gain of accuracy is obtained by relaxing the monotonicity constraint in a geometric framework in which the median function plays a crucial role.
Accurate Finite Difference Algorithms
NASA Technical Reports Server (NTRS)
Goodrich, John W.
1996-01-01
Two families of finite difference algorithms for computational aeroacoustics are presented and compared. All of the algorithms are single step explicit methods, they have the same order of accuracy in both space and time, with examples up to eleventh order, and they have multidimensional extensions. One of the algorithm families has spectral like high resolution. Propagation with high order and high resolution algorithms can produce accurate results after O(10(exp 6)) periods of propagation with eight grid points per wavelength.
Detection and accurate localization of harmonic chipless tags
NASA Astrophysics Data System (ADS)
Dardari, Davide
2015-12-01
We investigate the detection and localization properties of harmonic tags working at microwave frequencies. A two-tone interrogation signal and a dedicated signal processing scheme at the receiver are proposed to eliminate phase ambiguities caused by the short signal wavelength and to provide accurate distance/position estimation even in the presence of clutter and multipath. The theoretical limits on tag detection and localization accuracy are investigated starting from a concise characterization of harmonic backscattered signals. Numerical results show that accuracies in the order of centimeters are feasible within an operational range of a few meters in the RFID UHF band.
NASA Astrophysics Data System (ADS)
Cellmer, S.
2012-01-01
On-the-fly ambiguity resolution (OTF AR) is based on a small data set, obtained from a very short observation session or even from a single epoch observation. In these cases, a classical approach to ambiguity resolution (e.g. the Lambda method) can meet some numerical problems. The basis of the Lambda method is an integer decorrelation of the positive definite ambiguity covariance matrix (ACM). The necessary condition for the proper performing of this procedure is a positive definiteness of ACM. However, this condition is not satisfied in cases of very short observation sessions or single epoch positioning if phase-only observations are used. The subject of this contribution is such a case where phase-only observations are used in the final part of the computational process. The modification of ACM is proposed in order to ensure its positive definiteness. An estimator of modified ACM is a good ACM approximation for the purpose of performing the LAMBDA method. Another problem of short sessions (or a single epoch) positioning is the poor quality of the float solution. In this paper, a cascade adjustment with wide-lane combinations of signals L1 and L2 as a method of solving this problem is presented.
NASA Astrophysics Data System (ADS)
Gu, Shengfeng; Lou, Yidong; Shi, Chuang; Liu, Jingnan
2015-10-01
At present, the BeiDou system (BDS) enables the practical application of triple-frequency observable in the Asia-Pacific region, of many possible benefits from the additional signal; this study focuses on exploiting the contribution of zero difference (ZD) ambiguity resolution (AR) to the precise point positioning (PPP). A general modeling strategy for multi-frequency PPP AR is presented, in which, the least squares ambiguity decorrelation adjustment (LAMBDA) method is employed in ambiguity fixing based on the full variance-covariance ambiguity matrix generated from the raw data processing model. Because of the reliable fixing of BDS L1 ambiguity faces more difficulty, the LAMBDA method with partial ambiguity fixing is proposed to enable the independent and instantaneous resolution of extra wide-lane (EWL) and wide-lane (WL). This mechanism of sequential ambiguity fixing is demonstrated for resolving ZD satellite phase bias and performing triple-frequency PPP AR with two reference station networks with a typical baseline of up to 400 and 800 km, respectively. Tests show that about of the EWL and WL phase bias of BDS has a consistency of better than 0.1 cycle, and this value decreases to 80 % for L1 phase bias for Experiment I, while all the solutions of Experiment II have a similar RMS of about 0.12 cycles. In addition, the repeatability of the daily mean phase bias agree to 0.093 cycles and 0.095 cycles for EWL and WL on average, which is much smaller than 0.20 cycles of L1. To assess the improvement of fixed PPP brought by applying the third frequency signal as well as the above phase bias, various ambiguity fixing strategy are considered in the numerical demonstration. It is shown that the impact of the additional signal is almost negligible when only float solution involved. It is also shown that by fixing EWL and WL together, as opposed to the single ambiguity fixing, will leads to an improvement in PPP accuracy by about on average. Attributed to the efficient
Samb, Rawane; Khadraoui, Khader; Belleau, Pascal; Deschênes, Astrid; Lakhal-Chaieb, Lajmi; Droit, Arnaud
2015-12-01
Genome-wide mapping of nucleosomes has revealed a great deal about the relationships between chromatin structure and control of gene expression. Recent next generation CHIP-chip and CHIP-Seq technologies have accelerated our understanding of basic principles of chromatin organization. These technologies have taught us that nucleosomes play a crucial role in gene regulation by allowing physical access to transcription factors. Recent methods and experimental advancements allow the determination of nucleosome positions for a given genome area. However, most of these methods estimate the number of nucleosomes either by an EM algorithm using a BIC criterion or an effective heuristic strategy. Here, we introduce a Bayesian method for identifying nucleosome positions. The proposed model is based on a Multinomial-Dirichlet classification and a hierarchical mixture distributions. The number and the positions of nucleosomes are estimated using a reversible jump Markov chain Monte Carlo simulation technique. We compare the performance of our method on simulated data and MNase-Seq data from Saccharomyces cerevisiae against PING and NOrMAL methods. PMID:26656614
Jensen, Bente R; Hovgaard-Hansen, Line; Cappelen, Katrine L
2016-08-01
Running on a lower-body positive-pressure (LBPP) treadmill allows effects of weight support on leg muscle activation to be assessed systematically, and has the potential to facilitate rehabilitation and prevent overloading. The aim was to study the effect of running with weight support on leg muscle activation and to estimate relative knee and ankle joint forces. Runners performed 6-min running sessions at 2.22 m/s and 3.33 m/s, at 100%, 80%, 60%, 40%, and 20% body weight (BW). Surface electromyography, ground reaction force, and running characteristics were measured. Relative knee and ankle joint forces were estimated. Leg muscles responded differently to unweighting during running, reflecting different relative contribution to propulsion and antigravity forces. At 20% BW, knee extensor EMGpeak decreased to 22% at 2.22 m/s and 28% at 3.33 m/s of 100% BW values. Plantar flexors decreased to 52% and 58% at 20% BW, while activity of biceps femoris muscle remained unchanged. Unweighting with LBPP reduced estimated joint force significantly although less than proportional to the degree of weight support (ankle). It was concluded that leg muscle activation adapted to the new biomechanical environment, and the effect of unweighting on estimated knee force was more pronounced than on ankle force. PMID:26957520
NASA Astrophysics Data System (ADS)
Lorrain, Anne; Graham, Brittany S.; Popp, Brian N.; Allain, Valérie; Olson, Robert J.; Hunt, Brian P. V.; Potier, Michel; Fry, Brian; Galván-Magaña, Felipe; Menkes, Christophe E. R.; Kaehler, Sven; Ménard, Frédéric
2015-03-01
Assessment of isotopic compositions at the base of food webs is a prerequisite for using stable isotope analysis to assess foraging locations and trophic positions of marine organisms. Our study represents a unique application of stable-isotope analyses across multiple trophic levels (primary producer, primary consumer and tertiary consumer) and over a large spatial scale in two pelagic marine ecosystems. We found that δ15N values of particulate organic matter (POM), barnacles and phenylalanine from the muscle tissue of yellowfin tuna all showed similar spatial patterns. This consistency suggests that isotopic analysis of any of these can provide a reasonable proxy for isotopic variability at the base of the food web. Secondly, variations in the δ15N values of yellowfin tuna bulk-muscle tissues paralleled the spatial trends observed in all of these isotopic baseline proxies. Variation in isotopic composition at the base of the food web, rather than differences in tuna diet, explained the 11‰ variability observed in the bulk-tissue δ15N values of yellowfin tuna. Evaluating the trophic position of yellowfin tuna using amino-acid isotopic compositions across the western Indian and equatorial Pacific Oceans strongly suggests these tuna occupy similar trophic positions, albeit absolute trophic positions estimated by this method were lower than expected. This study reinforces the importance of considering isotopic baseline variability for diet studies, and provides new insights into methods that can be applied to generate nitrogen isoscapes for worldwide comparisons of top predators in marine ecosystems.
Skar, Helena; Albert, Jan; Leitner, Thomas
2013-01-01
Estimating date of infection for HIV-1-infected patients is vital for disease tracking and informed public health decisions, but is difficult to obtain because most patients have an established infection of unknown duration at diagnosis. Previous studies have used HIV-1-specific immunoglobulin G (IgG) levels as measured by the IgG capture BED enzyme immunoassay (BED assay) to indicate if a patient was infected recently, but a time-continuous model has not been available. Therefore, we developed a logistic model of IgG production over time. We used previously published metadata from 792 patients for whom the HIV-1-specific IgG levels had been longitudinally measured using the BED assay. To account for patient variability, we used mixed effects modeling to estimate general population parameters. The typical patient IgG production rate was estimated at r = 6.72[approximate 95% CI 6.17,7.33]×10−3 OD-n units day−1, and the carrying capacity at K = 1.84[1.75,1.95] OD-n units, predicting how recently patients seroconverted in the interval ∧t = (31,711) days. Final model selection and validation was performed on new BED data from a population of 819 Swedish HIV-1 patients diagnosed in 2002–2010. On an appropriate subset of 350 patients, the best model parameterization had an accuracy of 94% finding a realistic seroconversion date. We found that seroconversion on average is at the midpoint between last negative and first positive HIV-1 test for patients diagnosed in prospective/cohort studies such as those included in the training dataset. In contrast, seroconversion is strongly skewed towards the first positive sample for patients identified by regular public health diagnostic testing as illustrated in the validation dataset. Our model opens the door to more accurate estimates of date of infection for HIV-1 patients, which may facilitate a better understanding of HIV-1 epidemiology on a population level and individualized prevention, such as guidance
Accurate quantum chemical calculations
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.
1989-01-01
An important goal of quantum chemical calculations is to provide an understanding of chemical bonding and molecular electronic structure. A second goal, the prediction of energy differences to chemical accuracy, has been much harder to attain. First, the computational resources required to achieve such accuracy are very large, and second, it is not straightforward to demonstrate that an apparently accurate result, in terms of agreement with experiment, does not result from a cancellation of errors. Recent advances in electronic structure methodology, coupled with the power of vector supercomputers, have made it possible to solve a number of electronic structure problems exactly using the full configuration interaction (FCI) method within a subspace of the complete Hilbert space. These exact results can be used to benchmark approximate techniques that are applicable to a wider range of chemical and physical problems. The methodology of many-electron quantum chemistry is reviewed. Methods are considered in detail for performing FCI calculations. The application of FCI methods to several three-electron problems in molecular physics are discussed. A number of benchmark applications of FCI wave functions are described. Atomic basis sets and the development of improved methods for handling very large basis sets are discussed: these are then applied to a number of chemical and spectroscopic problems; to transition metals; and to problems involving potential energy surfaces. Although the experiences described give considerable grounds for optimism about the general ability to perform accurate calculations, there are several problems that have proved less tractable, at least with current computer resources, and these and possible solutions are discussed.
Analysis of strand positions in CIC conductor
NASA Astrophysics Data System (ADS)
Teshima, S.; Nakazawa, S.; Tsuda, M.; Hamajima, T.; Yagai, T.; Nunoya, Y.; Okuno, K.; Takahata, K.
2011-11-01
Information of 3D strand locations in a Cable-in-Conduit (CIC) conductor is necessary for accurate estimation of conductor performance, e.g., AC losses, current distribution or strain effect. However, it is difficult to derive strand positions after compaction, and there have been no analytical methods to accurately estimate strand positions. In our previous work, we measured strand positions in the CIC conductor, whose length is about 1 m, with 81 NbTi strands and it was verified that some strands were displaced from their original positions. In order to estimate strand locations in a long conductor, we developed a method to analyze three dimensional strand positions taking into account the cable deformation caused by compaction. In this method, we use strand positions in only one cross section of conductor and twist pitches of each sub-cable to calculate the center of gravity of each sub-cable. The strand positions are obtained in a manner that the same order sub-cables rotate around the center of gravity of one order higher sub-cable according to a function of the cabling pitch. We derive the twist pitches after compaction by using measured and calculated strand positions. The calculated strand locations by using the derived twist pitches agree well with the measured ones, with errors of about 0.7 mm.
2013-01-01
Background We estimated sufficient setup margins for head-and-neck cancer (HNC) radiotherapy (RT) when 2D kV images are utilized for routine patient setup verification. As another goal we estimated a threshold for the displacements of the most important bony landmarks related to the target volumes requiring immediate attention. Methods We analyzed 1491 orthogonal x-ray images utilized in RT treatment guidance for 80 HNC patients. We estimated overall setup errors and errors for four subregions to account for patient rotation and deformation: the vertebrae C1-2, C5-7, the occiput bone and the mandible. Setup margins were estimated for two 2D image guidance protocols: i) imaging at first three fractions and weekly thereafter and ii) daily imaging. Two 2D image matching principles were investigated: i) to the vertebrae in the middle of planning target volume (PTV) (MID_PTV) and ii) minimizing maximal position error for the four subregions (MIN_MAX). The threshold for the position errors was calculated with two previously unpublished methods based on the van Herk’s formula and clinical data by retaining a margin of 5 mm sufficient for each subregion. Results Sufficient setup margins to compensate the displacements of the subregions were approximately two times larger than were needed to compensate setup errors for rigid target. Adequate margins varied from 2.7 mm to 9.6 mm depending on the subregions related to the target, applied image guidance protocol and early correction of clinically important systematic 3D displacements of the subregions exceeding 4 mm. The MIN_MAX match resulted in smaller margins but caused an overall shift of 2.5 mm for the target center. Margins ≤ 5mm were sufficient with the MID_PTV match only through application of daily 2D imaging and the threshold of 4 mm to correct systematic displacement of a subregion. Conclusions Adequate setup margins depend remarkably on the subregions related to the target volume. When the systematic 3D
Piñero, David P.; Camps, Vicente J.; Ramón, María L.; Mateo, Verónica; Pérez-Cambrodí, Rafael J.
2015-01-01
AIM To evaluate the prediction error in intraocular lens (IOL) power calculation for a rotationally asymmetric refractive multifocal IOL and the impact on this error of the optimization of the keratometric estimation of the corneal power and the prediction of the effective lens position (ELP). METHODS Retrospective study including a total of 25 eyes of 13 patients (age, 50 to 83y) with previous cataract surgery with implantation of the Lentis Mplus LS-312 IOL (Oculentis GmbH, Germany). In all cases, an adjusted IOL power (PIOLadj) was calculated based on Gaussian optics using a variable keratometric index value (nkadj) for the estimation of the corneal power (Pkadj) and on a new value for ELP (ELPadj) obtained by multiple regression analysis. This PIOLadj was compared with the IOL power implanted (PIOLReal) and the value proposed by three conventional formulas (Haigis, Hoffer Q and Holladay I). RESULTS PIOLReal was not significantly different than PIOLadj and Holladay IOL power (P>0.05). In the Bland and Altman analysis, PIOLadj showed lower mean difference (-0.07 D) and limits of agreement (of 1.47 and -1.61 D) when compared to PIOLReal than the IOL power value obtained with the Holladay formula. Furthermore, ELPadj was significantly lower than ELP calculated with other conventional formulas (P<0.01) and was found to be dependent on axial length, anterior chamber depth and Pkadj. CONCLUSION Refractive outcomes after cataract surgery with implantation of the multifocal IOL Lentis Mplus LS-312 can be optimized by minimizing the keratometric error and by estimating ELP using a mathematical expression dependent on anatomical factors. PMID:26085998
Disparity fusion using depth and stereo cameras for accurate stereo correspondence
NASA Astrophysics Data System (ADS)
Jang, Woo-Seok; Ho, Yo-Sung
2015-03-01
Three-dimensional content (3D) creation has received a lot of attention due to numerous successes of 3D entertainment. Accurate stereo correspondence is necessary for efficient 3D content creation. In this paper, we propose a disparity map estimation method based on stereo correspondence. The proposed system utilizes depth and stereo camera sets. While the stereo set carries out disparity estimation, depth camera information is projected to left and right camera positions using 3D transformation and upsampling is processed in accordance with the image size. The upsampled depth is used for obtaining disparity data of left and right positions. Finally, disparity data from each depth sensor are combined. In order to evaluate the proposed method, we applied view synthesis from the acquired disparity map. The experimental results demonstrate that our method produces more accurate disparity maps compared to the conventional approaches which use the single depth sensors.
Cheong, Kit-Leong; Wu, Ding-Tao; Zhao, Jing; Li, Shao-Ping
2015-06-26
In this study, a rapid and accurate method for quantitative analysis of natural polysaccharides and their different fractions was developed. Firstly, high performance size exclusion chromatography (HPSEC) was utilized to separate natural polysaccharides. And then the molecular masses of their fractions were determined by multi-angle laser light scattering (MALLS). Finally, quantification of polysaccharides or their fractions was performed based on their response to refractive index detector (RID) and their universal refractive index increment (dn/dc). Accuracy of the developed method for the quantification of individual and mixed polysaccharide standards, including konjac glucomannan, CM-arabinan, xyloglucan, larch arabinogalactan, oat β-glucan, dextran (410, 270, and 25 kDa), mixed xyloglucan and CM-arabinan, and mixed dextran 270 K and CM-arabinan was determined, and their average recoveries were between 90.6% and 98.3%. The limits of detection (LOD) and quantification (LOQ) were ranging from 10.68 to 20.25 μg/mL, and 42.70 to 68.85 μg/mL, respectively. Comparing to the conventional phenol sulfuric acid assay and HPSEC coupled with evaporative light scattering detection (HPSEC-ELSD) analysis, the developed HPSEC-MALLS-RID method based on universal dn/dc for the quantification of polysaccharides and their fractions is much more simple, rapid, and accurate with no need of individual polysaccharide standard, as well as free of calibration curve. The developed method was also successfully utilized for quantitative analysis of polysaccharides and their different fractions from three medicinal plants of Panax genus, Panax ginseng, Panax notoginseng and Panax quinquefolius. The results suggested that the HPSEC-MALLS-RID method based on universal dn/dc could be used as a routine technique for the quantification of polysaccharides and their fractions in natural resources. PMID:25990349
Flores, Cintia; Caixach, Josep
2015-08-14
An integrated high resolution mass spectrometry (HRMS) strategy has been developed for rapid and accurate determination of free and cell-bound microcystins (MCs) and related peptides in water blooms. The natural samples (water and algae) were filtered for independent analysis of aqueous and sestonic fractions. These fractions were analyzed by MALDI-TOF/TOF-MS and ESI-Orbitrap-HCD-MS. MALDI, ESI and the study of fragmentation sequences have been provided crucial structural information. The potential of combined positive and negative ionization modes, full scan and fragmentation acquisition modes (TOF/TOF and HCD) by HRMS and high resolution and accurate mass was investigated in order to allow unequivocal determination of MCs. Besides, a reliable quantitation has been possible by HRMS. This composition helped to decrease the probability of false positives and negatives, as alternative to commonly used LC-ESI-MS/MS methods. The analysis was non-target, therefore covered the possibility to analyze all MC analogs concurrently without any pre-selection of target MC. Furthermore, archived data was subjected to retrospective "post-targeted" analysis and a screening of other potential toxins and related peptides as anabaenopeptins in the samples was done. Finally, the MS protocol and identification tools suggested were applied to the analysis of characteristic water blooms from Spanish reservoirs. PMID:26141269
Michael, Denna; Kanjala, Chifundo; Calvert, Clara; Pretorius, Carel; Wringe, Alison; Todd, Jim; Mtenga, Balthazar; Isingo, Raphael; Zaba, Basia; Urassa, Mark
2014-01-01
Introduction Spectrum epidemiological models are used by UNAIDS to provide global, regional and national HIV estimates and projections, which are then used for evidence-based health planning for HIV services. However, there are no validations of the Spectrum model against empirical serological and mortality data from populations in sub-Saharan Africa. Methods Serologic, demographic and verbal autopsy data have been regularly collected among over 30,000 residents in north-western Tanzania since 1994. Five-year age-specific mortality rates (ASMRs) per 1,000 person years and the probability of dying between 15 and 60 years of age (45Q15,) were calculated and compared with the Spectrum model outputs. Mortality trends by HIV status are shown for periods before the introduction of antiretroviral therapy (1994–1999, 2000–2005) and the first 5 years afterwards (2005–2009). Results Among 30–34 year olds of both sexes, observed ASMRs per 1,000 person years were 13.33 (95% CI: 10.75–16.52) in the period 1994–1999, 11.03 (95% CI: 8.84–13.77) in 2000–2004, and 6.22 (95% CI; 4.75–8.15) in 2005–2009. Among the same age group, the ASMRs estimated by the Spectrum model were 10.55, 11.13 and 8.15 for the periods 1994–1999, 2000–2004 and 2005–2009, respectively. The cohort data, for both sexes combined, showed that the 45Q15 declined from 39% (95% CI: 27–55%) in 1994 to 22% (95% CI: 17–29%) in 2009, whereas the Spectrum model predicted a decline from 43% in 1994 to 37% in 2009. Conclusion From 1994 to 2009, the observed decrease in ASMRs was steeper in younger age groups than that predicted by the Spectrum model, perhaps because the Spectrum model under-estimated the ASMRs in 30–34 year olds in 1994–99. However, the Spectrum model predicted a greater decrease in 45Q15 mortality than observed in the cohort, although the reasons for this over-estimate are unclear. PMID:24438873
Estimating potential evapotranspiration with improved radiation estimation
Technology Transfer Automated Retrieval System (TEKTRAN)
Potential evapotranspiration (PET) is of great importance to estimation of surface energy budget and water balance calculation. The accurate estimation of PET will facilitate efficient irrigation scheduling, drainage design, and other agricultural and meteorological applications. However, accuracy o...
Positive position control of robotic manipulators
NASA Technical Reports Server (NTRS)
Baz, A.; Gumusel, L.
1989-01-01
The present, simple and accurate position-control algorithm, which is applicable to fast-moving and lightly damped robot arms, is based on the positive position feedback (PPF) strategy and relies solely on position sensors to monitor joint angles of robotic arms to furnish stable position control. The optimized tuned filters, in the form of a set of difference equations, manipulate position signals for robotic system performance. Attention is given to comparisons between this PPF-algorithm controller's experimentally ascertained performance characteristics and those of a conventional proportional controller.
NASA Astrophysics Data System (ADS)
Schlittenhardt, J.
- A comparison of regional and teleseismic log rms (root-mean-square) Lg amplitude measurements have been made for 14 underground nuclear explosions from the East Kazakh test site recorded both by the BRV (Borovoye) station in Kazakhstan and the GRF (Gräfenberg) array in Germany. The log rms Lg amplitudes observed at the BRV regional station at a distance of 690km and at the teleseismic GRF array at a distance exceeding 4700km show very similar relative values (standard deviation 0.048 magnitude units) for underground explosions of different sizes at the Shagan River test site. This result as well as the comparison of BRV rms Lg magnitudes (which were calculated from the log rms amplitudes using an appropriate calibration) with magnitude determinations for P waves of global seismic networks (standard deviation 0.054 magnitude units) point to a high precision in estimating the relative source sizes of explosions from Lg-based single station data. Similar results were also obtained by other investigators (Patton, 1988; Ringdaletal., 1992) using Lg data from different stations at different distances.Additionally, GRF log rms Lg and P-coda amplitude measurements were made for a larger data set from Novaya Zemlya and East Kazakh explosions, which were supplemented with mb(Lg) amplitude measurements using a modified version of Nuttli's (1973, 1986a) method. From this test of the relative performance of the three different magnitude scales, it was found that the Lg and P-coda based magnitudes performed equally well, whereas the modified Nuttli mb(Lg) magnitudes show greater scatter when compared to the worldwide mb reference magnitudes. Whether this result indicates that the rms amplitude measurements are superior to the zero-to-peak amplitude measurement of a single cycle used for the modified Nuttli method, however, cannot be finally assessed, since the calculated mb(Lg) magnitudes are only preliminary until appropriate attenuation corrections are available for the
NASA Astrophysics Data System (ADS)
Dautermann, Thomas; Calais, Eric; Mattioli, Glen S.
2009-02-01
Volcanic explosions or shallow earthquakes are known to trigger acoustic and gravity waves that propagate in the atmosphere at infrasonic speeds. At ionospheric heights, coupling between neutral particles and free electrons induces variations of electron density detectable with dual-frequency Global Positioning System (GPS) measurements. Using GPS data collected in the Caribbean, we identified an ionospheric perturbation after a major volcanic explosion at the Soufrière Hills Volcano (Montserrat, Lesser Antilles) on 13 July 2003. Spectral analysis reveals peaks centered at 1 and 4 mHz, similar to those in previous observations and consistent with theory, suggesting both gravity and acoustic wave components. We retrieve a horizontal velocity of ˜624 m/s for the acoustic component, which implies upward propagation at ˜33°, consistent with ray-tracing results. We model the acoustic wave using an N-wave pressure source at ground level combined with ray tracing to propagate the neutral pressure wave; this accounts for the dispersive characteristics of the atmosphere while conserving total acoustic energy. Plasma velocity is derived from neutral velocity using a finite difference solution of the magnetohydrodynamic momentum equation. The continuity equation for charge densities is used to compute corresponding electron density variations, which are then numerically integrated along satellite-to-receiver line of sights, simultaneously accounting for the satellite displacements. We minimize the misfit between observed and model waveforms to estimate a total acoustic energy release of 1.53 × 1010 J for the primary explosion event at Soufrière Hills Volcano associated with the peak dome collapse. This method can be applied to any explosion of sufficient magnitude, provided GPS data are available at near to medium range from the source.
NNLOPS accurate associated HW production
NASA Astrophysics Data System (ADS)
Astill, William; Bizon, Wojciech; Re, Emanuele; Zanderighi, Giulia
2016-06-01
We present a next-to-next-to-leading order accurate description of associated HW production consistently matched to a parton shower. The method is based on reweighting events obtained with the HW plus one jet NLO accurate calculation implemented in POWHEG, extended with the MiNLO procedure, to reproduce NNLO accurate Born distributions. Since the Born kinematics is more complex than the cases treated before, we use a parametrization of the Collins-Soper angles to reduce the number of variables required for the reweighting. We present phenomenological results at 13 TeV, with cuts suggested by the Higgs Cross section Working Group.
Human Pose Estimation from Video and IMUs.
Marcard, Timo von; Pons-Moll, Gerard; Rosenhahn, Bodo
2016-08-01
In this work, we present an approach to fuse video with sparse orientation data obtained from inertial sensors to improve and stabilize full-body human motion capture. Even though video data is a strong cue for motion analysis, tracking artifacts occur frequently due to ambiguities in the images, rapid motions, occlusions or noise. As a complementary data source, inertial sensors allow for accurate estimation of limb orientations even under fast motions. However, accurate position information cannot be obtained in continuous operation. Therefore, we propose a hybrid tracker that combines video with a small number of inertial units to compensate for the drawbacks of each sensor type: on the one hand, we obtain drift-free and accurate position information from video data and, on the other hand, we obtain accurate limb orientations and good performance under fast motions from inertial sensors. In several experiments we demonstrate the increased performance and stability of our human motion tracker. PMID:26829774
How to accurately bypass damage
Broyde, Suse; Patel, Dinshaw J.
2016-01-01
Ultraviolet radiation can cause cancer through DNA damage — specifically, by linking adjacent thymine bases. Crystal structures show how the enzyme DNA polymerase η accurately bypasses such lesions, offering protection. PMID:20577203
Apparatus for accurately measuring high temperatures
Smith, Douglas D.
1985-01-01
The present invention is a thermometer used for measuring furnace temperaes in the range of about 1800.degree. to 2700.degree. C. The thermometer comprises a broadband multicolor thermal radiation sensor positioned to be in optical alignment with the end of a blackbody sight tube extending into the furnace. A valve-shutter arrangement is positioned between the radiation sensor and the sight tube and a chamber for containing a charge of high pressure gas is positioned between the valve-shutter arrangement and the radiation sensor. A momentary opening of the valve shutter arrangement allows a pulse of the high gas to purge the sight tube of air-borne thermal radiation contaminants which permits the radiation sensor to accurately measure the thermal radiation emanating from the end of the sight tube.
Apparatus for accurately measuring high temperatures
Smith, D.D.
The present invention is a thermometer used for measuring furnace temperatures in the range of about 1800/sup 0/ to 2700/sup 0/C. The thermometer comprises a broadband multicolor thermal radiation sensor positioned to be in optical alignment with the end of a blackbody sight tube extending into the furnace. A valve-shutter arrangement is positioned between the radiation sensor and the sight tube and a chamber for containing a charge of high pressure gas is positioned between the valve-shutter arrangement and the radiation sensor. A momentary opening of the valve shutter arrangement allows a pulse of the high gas to purge the sight tube of air-borne thermal radiation contaminants which permits the radiation sensor to accurately measure the thermal radiation emanating from the end of the sight tube.
NASA Astrophysics Data System (ADS)
Guha, Abhinav
-San Joaquin River Delta in the Central Valley. Through analysis of these field measurements, this dissertation presents the apportionment of observed CH4 and N2O concentration enhancements into major source categories along with direct emissions estimates from airborne observations. We perform high-precision measurements of greenhouse gases using gas analyzers based on absorption spectroscopy, and other source marker volatile organic compounds (VOCs) using state of the art VOC measurement systems (e.g. proton transfer reaction mass spectrometry). We combine these measurements with a statistical source apportionment technique called positive matrix factorization (PMF) to evaluate and investigate the major local sources of CH4 and N2O during CalNex and Walnut Grove campaigns. In the CABERNET study, we combine measurements with an airborne approach to a well-established micrometeorological technique (eddy-covariance method) to derive CH4 fluxes over different source regions in the Central Valley. In the CalNex experiments, we demonstrate that dairy and livestock remains the largest source sector of non-CO2 greenhouse gases in the San Joaquin Valley contributing most of the CH4 and much of the measured N2O at Bakersfield. Agriculture is observed to provide another major source of N2O, while vehicle emissions are found to be an insignificant source of N2O, contrary to the current statewide greenhouse gas inventory which includes vehicles as a major source. Our PMF source apportionment also produces an evaporative/fugitive factor but its relative lack of CH4 contributions points to removal processes from vented emissions in the surrounding O&G industry and the overwhelming dominance of the dairy CH4 source. In the CABERNET experiments, we report enhancements of CH4 from a number of sources spread across the spatial domain of the Central Valley that improves our understanding of their distribution and relative strengths. We observe large enhancements of CH4 mixing ratios over the
Two-dimensional location and direction estimating method.
Haga, Teruhiro; Tsukamoto, Sosuke; Hoshino, Hiroshi
2008-01-01
In this paper, a method of estimating both the position and the rotation angle of an object on a measurement stage was proposed. The system utilizes the radio communication technology and the directivity of an antenna. As a prototype system, a measurement stage (a circle 240mm in diameter) with 36 antennas that placed in each 10 degrees was developed. Two transmitter antennas are settled in a right angle on the stage as the target object, and the position and the rotation angle is estimated by measuring efficiency of the radio communication of each 36 antennas. The experimental result revealed that even when the estimated location is not so accurate (about a 30 mm error), the rotation angle is accurately estimated (about 2.33 degree error on average). The result suggests that the proposed method will be useful for estimating the location and the direction of an object. PMID:19162938
NASA Astrophysics Data System (ADS)
Guha, Abhinav
-San Joaquin River Delta in the Central Valley. Through analysis of these field measurements, this dissertation presents the apportionment of observed CH4 and N2O concentration enhancements into major source categories along with direct emissions estimates from airborne observations. We perform high-precision measurements of greenhouse gases using gas analyzers based on absorption spectroscopy, and other source marker volatile organic compounds (VOCs) using state of the art VOC measurement systems (e.g. proton transfer reaction mass spectrometry). We combine these measurements with a statistical source apportionment technique called positive matrix factorization (PMF) to evaluate and investigate the major local sources of CH4 and N2O during CalNex and Walnut Grove campaigns. In the CABERNET study, we combine measurements with an airborne approach to a well-established micrometeorological technique (eddy-covariance method) to derive CH4 fluxes over different source regions in the Central Valley. In the CalNex experiments, we demonstrate that dairy and livestock remains the largest source sector of non-CO2 greenhouse gases in the San Joaquin Valley contributing most of the CH4 and much of the measured N2O at Bakersfield. Agriculture is observed to provide another major source of N2O, while vehicle emissions are found to be an insignificant source of N2O, contrary to the current statewide greenhouse gas inventory which includes vehicles as a major source. Our PMF source apportionment also produces an evaporative/fugitive factor but its relative lack of CH4 contributions points to removal processes from vented emissions in the surrounding O&G industry and the overwhelming dominance of the dairy CH4 source. In the CABERNET experiments, we report enhancements of CH4 from a number of sources spread across the spatial domain of the Central Valley that improves our understanding of their distribution and relative strengths. We observe large enhancements of CH4 mixing ratios over the
High-precision positioning of radar scatterers
NASA Astrophysics Data System (ADS)
Dheenathayalan, Prabu; Small, David; Schubert, Adrian; Hanssen, Ramon F.
2016-05-01
Remote sensing radar satellites cover wide areas and provide spatially dense measurements, with millions of scatterers. Knowledge of the precise position of each radar scatterer is essential to identify the corresponding object and interpret the estimated deformation. The absolute position accuracy of synthetic aperture radar (SAR) scatterers in a 2D radar coordinate system, after compensating for atmosphere and tidal effects, is in the order of centimeters for TerraSAR-X (TSX) spotlight images. However, the absolute positioning in 3D and its quality description are not well known. Here, we exploit time-series interferometric SAR to enhance the positioning capability in three dimensions. The 3D positioning precision is parameterized by a variance-covariance matrix and visualized as an error ellipsoid centered at the estimated position. The intersection of the error ellipsoid with objects in the field is exploited to link radar scatterers to real-world objects. We demonstrate the estimation of scatterer position and its quality using 20 months of TSX stripmap acquisitions over Delft, the Netherlands. Using trihedral corner reflectors (CR) for validation, the accuracy of absolute positioning in 2D is about 7 cm. In 3D, an absolute accuracy of up to ˜ 66 cm is realized, with a cigar-shaped error ellipsoid having centimeter precision in azimuth and range dimensions, and elongated in cross-range dimension with a precision in the order of meters (the ratio of the ellipsoid axis lengths is 1/3/213, respectively). The CR absolute 3D position, along with the associated error ellipsoid, is found to be accurate and agree with the ground truth position at a 99 % confidence level. For other non-CR coherent scatterers, the error ellipsoid concept is validated using 3D building models. In both cases, the error ellipsoid not only serves as a quality descriptor, but can also help to associate radar scatterers to real-world objects.
Laaksomaa, Marko; Kapanen, Mika; Skyttä, Tanja; Peltola, Seppo; Hyödynmaa, Simo; Kellokumpu-Lehtinen, Pirkko-Liisa
2014-01-01
Aim The aim was to find an optimal setup image matching position and minimal setup margins to maximally spare the organs at risk in breast radiotherapy. Background Radiotherapy of breast cancer is a routine task but has many challenges. We investigated residual position errors in whole breast radiotherapy when orthogonal setup images were matched to different bony landmarks. Materials and methods A total of 1111 orthogonal setup image pairs and tangential field images were analyzed retrospectively for 50 consecutive patients. Residual errors in the treatment field images were determined by matching the orthogonal setup images to the vertebrae, sternum, ribs and their compromises. The most important region was the chest wall as it is crucial for the dose delivered to the heart and the ipsilateral lung. Inter-observer variation in online image matching was investigated. Results The best general image matching position was the compromise of the vertebrae, ribs and sternum, while the worst position was the vertebrae alone (p ≤ 0.03). The setup margins required for the chest wall varied from 4.3 mm to 5.5 mm in the lung direction while in the superior–inferior (SI) direction the margins varied from 5.1 mm to 7.6 mm. The inter-observer variation increased the minimal margins by approximately 1 mm. The margin of the lymph node areas should be at least 4.8 mm. Conclusions Setup margins can be reduced by proper selection of a matching position for the orthogonal setup images. To retain the minimal margins sufficient, systematic error of the chest wall should not exceed 4 mm in the tangential field image. PMID:25337409
Huang, Ai-Chun; Chen, Yu-Yawn; Chuang, Chih-Lin; Chiang, Li-Ming; Lu, Hsueh-Kuan; Lin, Hung-Chi; Chen, Kuen-Tsann; Hsiao, An-Chi; Hsieh, Kuen-Chang
2015-11-01
Bioelectrical impedance analysis (BIA) is commonly used to assess body composition. Cross-mode (left hand to right foot, Z(CR)) BIA presumably uses the longest current path in the human body, which may generate better results when estimating fat-free mass (FFM). We compared the cross-mode with the hand-to-foot mode (right hand to right foot, Z(HF)) using dual-energy x-ray absorptiometry (DXA) as the reference. We hypothesized that when comparing anthropometric parameters using stepwise regression analysis, the impedance value from the cross-mode analysis would have better prediction accuracy than that from the hand-to-foot mode analysis. We studied 264 men and 232 women (mean ages, 32.19 ± 14.95 and 34.51 ± 14.96 years, respectively; mean body mass indexes, 24.54 ± 3.74 and 23.44 ± 4.61 kg/m2, respectively). The DXA-measured FFMs in men and women were 58.85 ± 8.15 and 40.48 ± 5.64 kg, respectively. Multiple stepwise linear regression analyses were performed to construct sex-specific FFM equations. The correlations of FFM measured by DXA vs. FFM from hand-to-foot mode and estimated FFM by cross-mode were 0.85 and 0.86 in women, with standard errors of estimate of 2.96 and 2.92 kg, respectively. In men, they were 0.91 and 0.91, with standard errors of the estimates of 3.34 and 3.48 kg, respectively. Bland-Altman plots showed limits of agreement of -6.78 to 6.78 kg for FFM from hand-to-foot mode and -7.06 to 7.06 kg for estimated FFM by cross-mode for men, and -5.91 to 5.91 and -5.84 to 5.84 kg, respectively, for women. Paired t tests showed no significant differences between the 2 modes (P > .05). Hence, cross-mode BIA appears to represent a reasonable and practical application for assessing FFM in Chinese populations. PMID:26409342
NASA Astrophysics Data System (ADS)
Nair, B. G.; Winter, N.; Daniel, B.; Ward, R. M.
2016-07-01
Direct measurement of the flow of electric current during VAR is extremely difficult due to the aggressive environment as the arc process itself controls the distribution of current. In previous studies the technique of “magnetic source tomography” was presented; this was shown to be effective but it used a computationally intensive iterative method to analyse the distribution of arc centre position. In this paper we present faster computational methods requiring less numerical optimisation to determine the centre position of a single distributed arc both numerically and experimentally. Numerical validation of the algorithms were done on models and experimental validation on measurements based on titanium and nickel alloys (Ti6Al4V and INCONEL 718). The results are used to comment on the effects of process parameters on arc behaviour during VAR.
Accurate calculation of diffraction-limited encircled and ensquared energy.
Andersen, Torben B
2015-09-01
Mathematical properties of the encircled and ensquared energy functions for the diffraction-limited point-spread function (PSF) are presented. These include power series and a set of linear differential equations that facilitate the accurate calculation of these functions. Asymptotic expressions are derived that provide very accurate estimates for the relative amount of energy in the diffraction PSF that fall outside a square or rectangular large detector. Tables with accurate values of the encircled and ensquared energy functions are also presented. PMID:26368873
Can Selforganizing Maps Accurately Predict Photometric Redshifts?
NASA Technical Reports Server (NTRS)
Way, Michael J.; Klose, Christian
2012-01-01
We present an unsupervised machine-learning approach that can be employed for estimating photometric redshifts. The proposed method is based on a vector quantization called the self-organizing-map (SOM) approach. A variety of photometrically derived input values were utilized from the Sloan Digital Sky Survey's main galaxy sample, luminous red galaxy, and quasar samples, along with the PHAT0 data set from the Photo-z Accuracy Testing project. Regression results obtained with this new approach were evaluated in terms of root-mean-square error (RMSE) to estimate the accuracy of the photometric redshift estimates. The results demonstrate competitive RMSE and outlier percentages when compared with several other popular approaches, such as artificial neural networks and Gaussian process regression. SOM RMSE results (using delta(z) = z(sub phot) - z(sub spec)) are 0.023 for the main galaxy sample, 0.027 for the luminous red galaxy sample, 0.418 for quasars, and 0.022 for PHAT0 synthetic data. The results demonstrate that there are nonunique solutions for estimating SOM RMSEs. Further research is needed in order to find more robust estimation techniques using SOMs, but the results herein are a positive indication of their capabilities when compared with other well-known methods
Fast and Accurate Construction of Confidence Intervals for Heritability.
Schweiger, Regev; Kaufman, Shachar; Laaksonen, Reijo; Kleber, Marcus E; März, Winfried; Eskin, Eleazar; Rosset, Saharon; Halperin, Eran
2016-06-01
Estimation of heritability is fundamental in genetic studies. Recently, heritability estimation using linear mixed models (LMMs) has gained popularity because these estimates can be obtained from unrelated individuals collected in genome-wide association studies. Typically, heritability estimation under LMMs uses the restricted maximum likelihood (REML) approach. Existing methods for the construction of confidence intervals and estimators of SEs for REML rely on asymptotic properties. However, these assumptions are often violated because of the bounded parameter space, statistical dependencies, and limited sample size, leading to biased estimates and inflated or deflated confidence intervals. Here, we show that the estimation of confidence intervals by state-of-the-art methods is inaccurate, especially when the true heritability is relatively low or relatively high. We further show that these inaccuracies occur in datasets including thousands of individuals. Such biases are present, for example, in estimates of heritability of gene expression in the Genotype-Tissue Expression project and of lipid profiles in the Ludwigshafen Risk and Cardiovascular Health study. We also show that often the probability that the genetic component is estimated as 0 is high even when the true heritability is bounded away from 0, emphasizing the need for accurate confidence intervals. We propose a computationally efficient method, ALBI (accurate LMM-based heritability bootstrap confidence intervals), for estimating the distribution of the heritability estimator and for constructing accurate confidence intervals. Our method can be used as an add-on to existing methods for estimating heritability and variance components, such as GCTA, FaST-LMM, GEMMA, or EMMAX. PMID:27259052
Accurate wavelength calibration method for flat-field grating spectrometers.
Du, Xuewei; Li, Chaoyang; Xu, Zhe; Wang, Qiuping
2011-09-01
A portable spectrometer prototype is built to study wavelength calibration for flat-field grating spectrometers. An accurate calibration method called parameter fitting is presented. Both optical and structural parameters of the spectrometer are included in the wavelength calibration model, which accurately describes the relationship between wavelength and pixel position. Along with higher calibration accuracy, the proposed calibration method can provide information about errors in the installation of the optical components, which will be helpful for spectrometer alignment. PMID:21929865
Toward Accurate and Quantitative Comparative Metagenomics.
Nayfach, Stephen; Pollard, Katherine S
2016-08-25
Shotgun metagenomics and computational analysis are used to compare the taxonomic and functional profiles of microbial communities. Leveraging this approach to understand roles of microbes in human biology and other environments requires quantitative data summaries whose values are comparable across samples and studies. Comparability is currently hampered by the use of abundance statistics that do not estimate a meaningful parameter of the microbial community and biases introduced by experimental protocols and data-cleaning approaches. Addressing these challenges, along with improving study design, data access, metadata standardization, and analysis tools, will enable accurate comparative metagenomics. We envision a future in which microbiome studies are replicable and new metagenomes are easily and rapidly integrated with existing data. Only then can the potential of metagenomics for predictive ecological modeling, well-powered association studies, and effective microbiome medicine be fully realized. PMID:27565341
Accurate thickness measurement of graphene
NASA Astrophysics Data System (ADS)
Shearer, Cameron J.; Slattery, Ashley D.; Stapleton, Andrew J.; Shapter, Joseph G.; Gibson, Christopher T.
2016-03-01
Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.
Towards an accurate bioimpedance identification
NASA Astrophysics Data System (ADS)
Sanchez, B.; Louarroudi, E.; Bragos, R.; Pintelon, R.
2013-04-01
This paper describes the local polynomial method (LPM) for estimating the time-invariant bioimpedance frequency response function (FRF) considering both the output-error (OE) and the errors-in-variables (EIV) identification framework and compare it with the traditional cross— and autocorrelation spectral analysis techniques. The bioimpedance FRF is measured with the multisine electrical impedance spectroscopy (EIS) technique. To show the overwhelming accuracy of the LPM approach, both the LPM and the classical cross— and autocorrelation spectral analysis technique are evaluated through the same experimental data coming from a nonsteady-state measurement of time-varying in vivo myocardial tissue. The estimated error sources at the measurement frequencies due to noise, σnZ, and the stochastic nonlinear distortions, σZNL, have been converted to Ω and plotted over the bioimpedance spectrum for each framework. Ultimately, the impedance spectra have been fitted to a Cole impedance model using both an unweighted and a weighted complex nonlinear least square (CNLS) algorithm. A table is provided with the relative standard errors on the estimated parameters to reveal the importance of which system identification frameworks should be used.
GPS Position and Heading Circuitry for Ships
NASA Technical Reports Server (NTRS)
Cooke, Michael P.; Yim, Hester J.; Gomez, Susan F.
2003-01-01
Circuit boards that contain radio-frequency (RF) and digital circuitry have been developed by NASA to satisfy a requirement of the Port of Houston Authority for relatively inexpensive Global Positioning System (GPS) receivers that indicate the azimuthal headings as well as the positions of ships. The receiver design utilizes the unique architecture of the Mitel commercial chip-set, which provides for an accurate GPS-based heading-determination device. The major components include two RF front ends (each connected to a separate antenna), a surface-acoustic-wave intermediate-frequency filter between second- and third-stage mixers, a correlator, and a reduced-instruction- set computer. One of the RF front ends operates as a master, the other as a slave. Both RF front ends share a 10-MHz sinusoidal clock oscillator, which provides for more accurate carrier phase measurements between the two antennas. The outputs of the RF front ends are subjected to conventional GPS processing. The commercial-based chip-set design approach provides an inexpensive open architecture GPS platform, which can be used in developing and implementing unique GPS-heading and attitude-determination algorithms for specific applications. The heading is estimated from the GPS position solutions of the two antennas by an algorithm developed specifically for this application. If a third (and preferably a fourth) antenna were added, it would be possible to estimate the attitude of the GPS receiver in three dimensions instead of only its heading in a horizontal plane.
Technology Transfer Automated Retrieval System (TEKTRAN)
Having accurate estimates of the cost of irrigation is important when making irrigation decisions. Estimates of fixed costs are critical for investment decisions. Operating cost estimates can assist in decisions regarding additional irrigations. This fact sheet examines the costs associated with ...
NASA Technical Reports Server (NTRS)
Chamberlain, R. G.; Aster, R. W.; Firnett, P. J.; Miller, M. A.
1985-01-01
Improved Price Estimation Guidelines, IPEG4, program provides comparatively simple, yet relatively accurate estimate of price of manufactured product. IPEG4 processes user supplied input data to determine estimate of price per unit of production. Input data include equipment cost, space required, labor cost, materials and supplies cost, utility expenses, and production volume on industry wide or process wide basis.
Highly accurate articulated coordinate measuring machine
Bieg, Lothar F.; Jokiel, Jr., Bernhard; Ensz, Mark T.; Watson, Robert D.
2003-12-30
Disclosed is a highly accurate articulated coordinate measuring machine, comprising a revolute joint, comprising a circular encoder wheel, having an axis of rotation; a plurality of marks disposed around at least a portion of the circumference of the encoder wheel; bearing means for supporting the encoder wheel, while permitting free rotation of the encoder wheel about the wheel's axis of rotation; and a sensor, rigidly attached to the bearing means, for detecting the motion of at least some of the marks as the encoder wheel rotates; a probe arm, having a proximal end rigidly attached to the encoder wheel, and having a distal end with a probe tip attached thereto; and coordinate processing means, operatively connected to the sensor, for converting the output of the sensor into a set of cylindrical coordinates representing the position of the probe tip relative to a reference cylindrical coordinate system.
Two Types of Motor Strategy for Accurate Dart Throwing
Nasu, Daiki; Matsuo, Tomoyuki; Kadota, Koji
2014-01-01
This study investigated whether expert dart players utilize hand trajectory patterns that can compensate for the inherent variability in their release timing. In this study, we compared the timing error and hand trajectory patterns of expert players with those of novices. Eight experts and eight novices each made 60 dart throws, aiming at the bull’s-eye. The movements of the dart and index finger were captured using seven 480-Hz cameras. The data were interpolated using a cubic spline function and analyzed by the millisecond. The estimated vertical errors on the dartboard were calculated as a time-series by using the state variables of the index finger (position, velocity, and direction of motion). This time-series error represents the hand trajectory pattern. Two variables assessing the performance outcome in the vertical plane and two variables related to the timing control were quantified on the basis of the time-series error. The results revealed two typical types of motor strategies in the expert group. The timing error of some experts was similar to that of novices; however, these experts had a longer window of time in which to release an accurately thrown dart. These subjects selected hand trajectory patterns that could compensate for the timing error. Other experts did not select the complementary hand trajectories, but greatly reduced their error in release timing. PMID:24533102
Accurate adiabatic correction in the hydrogen molecule
Pachucki, Krzysztof; Komasa, Jacek
2014-12-14
A new formalism for the accurate treatment of adiabatic effects in the hydrogen molecule is presented, in which the electronic wave function is expanded in the James-Coolidge basis functions. Systematic increase in the size of the basis set permits estimation of the accuracy. Numerical results for the adiabatic correction to the Born-Oppenheimer interaction energy reveal a relative precision of 10{sup −12} at an arbitrary internuclear distance. Such calculations have been performed for 88 internuclear distances in the range of 0 < R ⩽ 12 bohrs to construct the adiabatic correction potential and to solve the nuclear Schrödinger equation. Finally, the adiabatic correction to the dissociation energies of all rovibrational levels in H{sub 2}, HD, HT, D{sub 2}, DT, and T{sub 2} has been determined. For the ground state of H{sub 2} the estimated precision is 3 × 10{sup −7} cm{sup −1}, which is almost three orders of magnitude higher than that of the best previous result. The achieved accuracy removes the adiabatic contribution from the overall error budget of the present day theoretical predictions for the rovibrational levels.
Accurate adiabatic correction in the hydrogen molecule
NASA Astrophysics Data System (ADS)
Pachucki, Krzysztof; Komasa, Jacek
2014-12-01
A new formalism for the accurate treatment of adiabatic effects in the hydrogen molecule is presented, in which the electronic wave function is expanded in the James-Coolidge basis functions. Systematic increase in the size of the basis set permits estimation of the accuracy. Numerical results for the adiabatic correction to the Born-Oppenheimer interaction energy reveal a relative precision of 10-12 at an arbitrary internuclear distance. Such calculations have been performed for 88 internuclear distances in the range of 0 < R ⩽ 12 bohrs to construct the adiabatic correction potential and to solve the nuclear Schrödinger equation. Finally, the adiabatic correction to the dissociation energies of all rovibrational levels in H2, HD, HT, D2, DT, and T2 has been determined. For the ground state of H2 the estimated precision is 3 × 10-7 cm-1, which is almost three orders of magnitude higher than that of the best previous result. The achieved accuracy removes the adiabatic contribution from the overall error budget of the present day theoretical predictions for the rovibrational levels.
Accurate ab Initio Spin Densities
2012-01-01
We present an approach for the calculation of spin density distributions for molecules that require very large active spaces for a qualitatively correct description of their electronic structure. Our approach is based on the density-matrix renormalization group (DMRG) algorithm to calculate the spin density matrix elements as a basic quantity for the spatially resolved spin density distribution. The spin density matrix elements are directly determined from the second-quantized elementary operators optimized by the DMRG algorithm. As an analytic convergence criterion for the spin density distribution, we employ our recently developed sampling-reconstruction scheme [J. Chem. Phys.2011, 134, 224101] to build an accurate complete-active-space configuration-interaction (CASCI) wave function from the optimized matrix product states. The spin density matrix elements can then also be determined as an expectation value employing the reconstructed wave function expansion. Furthermore, the explicit reconstruction of a CASCI-type wave function provides insight into chemically interesting features of the molecule under study such as the distribution of α and β electrons in terms of Slater determinants, CI coefficients, and natural orbitals. The methodology is applied to an iron nitrosyl complex which we have identified as a challenging system for standard approaches [J. Chem. Theory Comput.2011, 7, 2740]. PMID:22707921
Attitude and Trajectory Determination using Magnetometers and Estimated Rates
NASA Technical Reports Server (NTRS)
Schierman, J. D.; Schmidt, D. K.; Deutschmann, J.
1997-01-01
A simultaneous attitude and orbit determination algorithm which uses magnetometer measurements and estimated attitude rates is presented. This is an extension of an algorithm which uses magnetometer and rate gyro measurements. The new algorithm is intended for gyroless spacecraft, or in the case of gyro failures/saturation. Torque control input data is used in forming the rate estimates. Simulation tests of the algorithm are presented. First, tests were performed using the 'true' rate values at each time step. This simulated using accurate gyro measurements. Then, tests were performed estimating the rates. Using estimated rates rather than 'gyro measurements' did not significantly degrade the algorithm's performance if accurate estimates of the initial rates were available. An initial Root-Sum-Square (RSS) position error of 1,400 km was reduced to an average error of approximately 100 km within the first two minutes. The RSS attitude error converged to less than 1.5 degrees within three orbits.
NASA Astrophysics Data System (ADS)
Lasemi, Ali; Xue, Deyi; Gu, Peihua
2016-05-01
Five-axis CNC machine tools are widely used in manufacturing of parts with free-form surfaces. Geometric errors of machine tools have significant effects on the quality of manufactured parts. This research focuses on development of a new method to accurately identify geometric errors of 5-axis CNC machines, especially the errors due to rotary axes, using the magnetic double ball bar. A theoretical model for identification of geometric errors is provided. In this model, both position-independent errors and position-dependent errors are considered as the error sources. This model is simplified by identification and removal of the correlated and insignificant error sources of the machine. Insignificant error sources are identified using the sensitivity analysis technique. Simulation results reveal that the simplified error identification model can result in more accurate estimations of the error parameters. Experiments on a 5-axis CNC machine tool also demonstrate significant reduction in the volumetric error after error compensation.
Precise and Accurate Density Determination of Explosives Using Hydrostatic Weighing
B. Olinger
2005-07-01
Precise and accurate density determination requires weight measurements in air and water using sufficiently precise analytical balances, knowledge of the densities of air and water, knowledge of thermal expansions, availability of a density standard, and a method to estimate the time to achieve thermal equilibrium with water. Density distributions in pressed explosives are inferred from the densities of elements from a central slice.
2012-01-01
Background Gefitinib, a tyrosine kinase inhibitor, is an effective treatment in advanced non-small cell lung cancer (NSCLC) patients with an activating mutation in the epidermal growth factor receptor (EGFR). Randomised clinical trials showed a benefit in progression free survival for gefitinib versus doublet chemotherapy regimens in patients with an activated EGFR mutation (EGFR M+). From a patient perspective, progression free survival is important, but so is health-related quality of life. Therefore, this analysis evaluates the Quality Adjusted progression free survival of gefitinib versus three relevant doublet chemotherapies (gemcitabine/cisplatin (Gem/Cis); pemetrexed/cisplatin (Pem/Cis); paclitaxel/carboplatin (Pac/Carb)) in a Dutch health care setting in patients with EGFR M+ stage IIIB/IV NSCLC. This study uses progression free survival rather than overall survival for its time frame in order to better compare the treatments and to account for the influence that subsequent treatment lines would have on overall survival analysis. Methods Mean progression free survival for Pac/Carb was obtained by extrapolating the median progression free survival as reported in the Iressa-Pan-Asia Study (IPASS). Data from a network meta-analysis was used to estimate the mean progression free survival for therapies of interest relative to Pac/Carb. Adjustment for health-related quality of life was done by incorporating utilities for the Dutch population, obtained by converting FACT-L data (from IPASS) to utility values and multiplying these with the mean progression free survival for each treatment arm to determine the Quality Adjusted progression free survival. Probabilistic sensitivity analysis was carried out to determine 95% credibility intervals. Results The Quality Adjusted progression free survival (PFS) (mean, (95% credibility interval)) was 5.2 months (4.5; 5.8) for Gem/Cis, 5.3 months (4.6; 6.1) for Pem/Cis; 4.9 months (4.4; 5.5) for Pac/Carb and 8.3 (7.0; 9.9) for
Geskus, Ronald B.; González, Cristina; Torres, Montserrat; Del Romero, Jorge; Viciana, Pompeyo; Masiá, Mar; Blanco, José R.; Iribarren, Mauricio; De Sanjosé, Silvia; Hernández-Novoa, Beatriz; Ortiz, Marta; Del Amo, Julia
2016-01-01
Background: To estimate incidence and clearance of high-risk human papillomavirus (HR-HPV), and their risk factors, in men who have sex with men (MSM) recently infected by HIV in Spain; 2007–2013. Methods: Multicenter cohort. HR-HPV infection was determined and genotyped with linear array. Two-state Markov models and Poisson regression were used. Results: We analysed 1570 HR-HPV measurements of 612 MSM over 13 608 person-months (p-m) of follow-up. Median (mean) number of measurements was 2 (2.6), median time interval between measurements was 1.1 years (interquartile range: 0.89–1.4). Incidence ranged from 9.0 [95% confidence interval (CI) 6.8–11.8] per 1000 p-m for HPV59 to 15.9 (11.7–21.8) per 1000 p-m for HPV51. HPV16 and HPV18 had slightly above average incidence: 11.9/1000 p-m and 12.8/1000 p-m. HPV16 showed the lowest clearance for both ‘prevalent positive’ (15.7/1000 p-m; 95% CI 12.0–20.5) and ‘incident positive’ infections (22.1/1000 p-m; 95% CI 11.8–41.1). More sexual partners increased HR-HPV incidence, although it was not statistically significant. Age had a strong effect on clearance (P-value < 0.001) due to the elevated rate in MSM under age 25; the effect of HIV-RNA viral load was more gradual, with clearance rate decreasing at higher HIV-RNA viral load (P-value 0.008). Conclusion: No large variation in incidence by HR-HPV type was seen. The most common incident types were HPV51, HPV52, HPV31, HPV18 and HPV16. No major variation in clearance by type was observed, with the exception of HPV16 which had the highest persistence and potentially, the strongest oncogenic capacity. Those aged below 25 or with low HIV-RNA- viral load had the highest clearance. PMID:26355673
Accurate paleointensities - the multi-method approach
NASA Astrophysics Data System (ADS)
de Groot, Lennart
2016-04-01
The accuracy of models describing rapid changes in the geomagnetic field over the past millennia critically depends on the availability of reliable paleointensity estimates. Over the past decade methods to derive paleointensities from lavas (the only recorder of the geomagnetic field that is available all over the globe and through geologic times) have seen significant improvements and various alternative techniques were proposed. The 'classical' Thellier-style approach was optimized and selection criteria were defined in the 'Standard Paleointensity Definitions' (Paterson et al, 2014). The Multispecimen approach was validated and the importance of additional tests and criteria to assess Multispecimen results must be emphasized. Recently, a non-heating, relative paleointensity technique was proposed -the pseudo-Thellier protocol- which shows great potential in both accuracy and efficiency, but currently lacks a solid theoretical underpinning. Here I present work using all three of the aforementioned paleointensity methods on suites of young lavas taken from the volcanic islands of Hawaii, La Palma, Gran Canaria, Tenerife, and Terceira. Many of the sampled cooling units are <100 years old, the actual field strength at the time of cooling is therefore reasonably well known. Rather intuitively, flows that produce coherent results from two or more different paleointensity methods yield the most accurate estimates of the paleofield. Furthermore, the results for some flows pass the selection criteria for one method, but fail in other techniques. Scrutinizing and combing all acceptable results yielded reliable paleointensity estimates for 60-70% of all sampled cooling units - an exceptionally high success rate. This 'multi-method paleointensity approach' therefore has high potential to provide the much-needed paleointensities to improve geomagnetic field models for the Holocene.
Smirenin, S A; Khabova, Z S; Fetisov, V A
2015-01-01
above morphological signs for the objective determination of the passenger position inside the car passenger compartment during traffic accidents and thereby to improve the quality of expert conclusions and the results of forensic medical examination of the injuries inflicted in car crashes. PMID:26245101
Accurate Inventories Of Irrigated Land
NASA Technical Reports Server (NTRS)
Wall, S.; Thomas, R.; Brown, C.
1992-01-01
System for taking land-use inventories overcomes two problems in estimating extent of irrigated land: only small portion of large state surveyed in given year, and aerial photographs made on 1 day out of year do not provide adequate picture of areas growing more than one crop per year. Developed for state of California as guide to controlling, protecting, conserving, and distributing water within state. Adapted to any large area in which large amounts of irrigation water needed for agriculture. Combination of satellite images, aerial photography, and ground surveys yields data for computer analysis. Analyst also consults agricultural statistics, current farm reports, weather reports, and maps. These information sources aid in interpreting patterns, colors, textures, and shapes on Landsat-images.
Landsiedel, F.W.; Wolff, H.
1960-06-28
An apparatus is described for automatically accomplishing the final accurate horizontal positioning of a crane after the latter has been placed to within 1/8 in. of its selected position. For this purpose there is provided a tiltable member on the crane mast for lowering into contact with a stationary probe. Misalignment of the tiltable member, with respect to the probe as the member is lowered, causes tilting of the latter to actuate appropriate switches that energize motors for bringing the mast into proper position. When properly aligned the member is not tilted and a central switch is actuated to indicate the final alignment of the crane.
Error compensation algorithm for patient positioning robotics system
NASA Astrophysics Data System (ADS)
Murty, Pilaka V.; Talpasanu, Ilie; Roz, Mugur A.
2009-03-01
Surgeons in various medical areas (orthopedic surgery, neurosurgery, dentistry etc.) are using motor-driven drilling tools to make perforations in hard tissues (bone, enamel, dentine, cementum etc.) When the penetration requires very precise angles and accurate alignment with respect to different targets, precision cannot be obtained by using visual estimation and hand-held tools. Robots have been designed to allow for very accurate relative positioning of the patient and the surgical tools, and in certain classes of applications the location of bone target and inclination of the surgical tool can be accurately specified with respect to an inertial frame of reference. However, patient positioning errors as well as position changes during surgery can jeopardize the precision of the operation, and drilling parameters have to be dynamically adjusted. In this paper the authors present a quantitative method to evaluate the corrected position and inclination of the drilling tool, to account for translational and rotational errors in displaced target position. The compensation algorithm applies principles of inverse kinematics wherein a faulty axis in space caused by the translational and rotational errors of the target position is identified with an imaginary true axis in space by enforcing identity through a modified trajectory. In the absence of any specific application, this algorithm is verified on Solid Works, a commercial CAD tool and found to be correct. An example problem given at the end vindicates this statement.
Accurate localization of in-body medical implants based on spatial sparsity.
Pourhomayoun, Mohammad; Jin, Zhanpeng; Fowler, Mark L
2014-02-01
Wearable and implantable wireless communication devices have in recent years gained increasing attention for medical diagnostics and therapeutics. In particular, wireless capsule endoscopy has become a popular method to visualize and diagnose the human gastrointestinal tract. Estimating the exact position of the capsule when each image is taken is a very critical issue in capsule endoscopy. Several approaches have been developed by researchers to estimate the capsule location. However, some unique challenges exist for in-body localization, such as the severe multipath issue caused by the boundaries of different organs, inconsistency of signal propagation velocity and path loss parameters inside the human body, and the regulatory restrictions on using high-bandwidth or high-power signals. In this paper, we propose a novel localization method based on spatial sparsity. We directly estimate the location of the capsule without going through the usual intermediate stage of first estimating time-of-arrival or received-signal strength, and then a second stage of estimating the location. We demonstrate the accuracy of the proposed method through extensive Monte Carlo simulations for radio frequency emission signals within the required power and bandwidth range. The results show that the proposed method is effective and accurate, even in massive multipath conditions. PMID:24108709
The high cost of accurate knowledge.
Sutcliffe, Kathleen M; Weber, Klaus
2003-05-01
Many business thinkers believe it's the role of senior managers to scan the external environment to monitor contingencies and constraints, and to use that precise knowledge to modify the company's strategy and design. As these thinkers see it, managers need accurate and abundant information to carry out that role. According to that logic, it makes sense to invest heavily in systems for collecting and organizing competitive information. Another school of pundits contends that, since today's complex information often isn't precise anyway, it's not worth going overboard with such investments. In other words, it's not the accuracy and abundance of information that should matter most to top executives--rather, it's how that information is interpreted. After all, the role of senior managers isn't just to make decisions; it's to set direction and motivate others in the face of ambiguities and conflicting demands. Top executives must interpret information and communicate those interpretations--they must manage meaning more than they must manage information. So which of these competing views is the right one? Research conducted by academics Sutcliffe and Weber found that how accurate senior executives are about their competitive environments is indeed less important for strategy and corresponding organizational changes than the way in which they interpret information about their environments. Investments in shaping those interpretations, therefore, may create a more durable competitive advantage than investments in obtaining and organizing more information. And what kinds of interpretations are most closely linked with high performance? Their research suggests that high performers respond positively to opportunities, yet they aren't overconfident in their abilities to take advantage of those opportunities. PMID:12747164
LWR-PV damage estimate methodology
Wagschal, J.J.; Maerker, R.E.; Broadhead, B.L.
1980-01-01
A credible estimate of the pressure vessel lifetime due to neutron-induced embrittlement is studied. The first step toward this goal is the accurate prediction of fluence and neutron energy spectrum at the pressure vessel. This, in turn, is obtained from least squares unfolding techniques of dosimetry measurements at a surveillance position, transport calculations, and a translation of information obtained at the surveillance position to the damage position. Including a prototypic neutron field like the ORNL Pool Critical Assembly, in which measurements are performed to serve as benchmarks for the LWR-PV surveillance dosimetry program, involves the use of approximate calculational methods. These approximate methods are supplemented by correction factors also known as calculational bias factors, the proper utilization of which requires estimated uncertainties of these biases as well. The source of a few biases for the PCA and some biases and correlations for the group fluxes at two PCA locations are presented.
Hydrogen atoms can be located accurately and precisely by x-ray crystallography.
Woińska, Magdalena; Grabowsky, Simon; Dominiak, Paulina M; Woźniak, Krzysztof; Jayatilaka, Dylan
2016-05-01
Precise and accurate structural information on hydrogen atoms is crucial to the study of energies of interactions important for crystal engineering, materials science, medicine, and pharmacy, and to the estimation of physical and chemical properties in solids. However, hydrogen atoms only scatter x-radiation weakly, so x-rays have not been used routinely to locate them accurately. Textbooks and teaching classes still emphasize that hydrogen atoms cannot be located with x-rays close to heavy elements; instead, neutron diffraction is needed. We show that, contrary to widespread expectation, hydrogen atoms can be located very accurately using x-ray diffraction, yielding bond lengths involving hydrogen atoms (A-H) that are in agreement with results from neutron diffraction mostly within a single standard deviation. The precision of the determination is also comparable between x-ray and neutron diffraction results. This has been achieved at resolutions as low as 0.8 Å using Hirshfeld atom refinement (HAR). We have applied HAR to 81 crystal structures of organic molecules and compared the A-H bond lengths with those from neutron measurements for A-H bonds sorted into bonds of the same class. We further show in a selection of inorganic compounds that hydrogen atoms can be located in bridging positions and close to heavy transition metals accurately and precisely. We anticipate that, in the future, conventional x-radiation sources at in-house diffractometers can be used routinely for locating hydrogen atoms in small molecules accurately instead of large-scale facilities such as spallation sources or nuclear reactors. PMID:27386545
Hydrogen atoms can be located accurately and precisely by x-ray crystallography
Woińska, Magdalena; Grabowsky, Simon; Dominiak, Paulina M.; Woźniak, Krzysztof; Jayatilaka, Dylan
2016-01-01
Precise and accurate structural information on hydrogen atoms is crucial to the study of energies of interactions important for crystal engineering, materials science, medicine, and pharmacy, and to the estimation of physical and chemical properties in solids. However, hydrogen atoms only scatter x-radiation weakly, so x-rays have not been used routinely to locate them accurately. Textbooks and teaching classes still emphasize that hydrogen atoms cannot be located with x-rays close to heavy elements; instead, neutron diffraction is needed. We show that, contrary to widespread expectation, hydrogen atoms can be located very accurately using x-ray diffraction, yielding bond lengths involving hydrogen atoms (A–H) that are in agreement with results from neutron diffraction mostly within a single standard deviation. The precision of the determination is also comparable between x-ray and neutron diffraction results. This has been achieved at resolutions as low as 0.8 Å using Hirshfeld atom refinement (HAR). We have applied HAR to 81 crystal structures of organic molecules and compared the A–H bond lengths with those from neutron measurements for A–H bonds sorted into bonds of the same class. We further show in a selection of inorganic compounds that hydrogen atoms can be located in bridging positions and close to heavy transition metals accurately and precisely. We anticipate that, in the future, conventional x-radiation sources at in-house diffractometers can be used routinely for locating hydrogen atoms in small molecules accurately instead of large-scale facilities such as spallation sources or nuclear reactors. PMID:27386545
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
Geometrical Positioning Schemes Based on Hybrid Lines of Position
NASA Astrophysics Data System (ADS)
Chen, Chien-Sheng; Lin, Jium-Ming; Liu, Wen-Hsiung; Chi, Ching-Lung
To achieve more accurate measurements of the mobile station (MS) location, it is possible to integrate many kinds of measurements. In this paper we proposed several simpler methods that utilized time of arrival (TOA) at three base stations (BSs) and the angle of arrival (AOA) information at the serving BS to give location estimation of the MS in non-line-of-sight (NLOS) environments. From the viewpoint of geometric approach, for each a TOA value measured at any BS, one can generate a circle. Rather than applying the nonlinear circular lines of position (LOP), the proposed methods are much easier by using linear LOP to determine the MS. Numerical results demonstrate that the calculation time of using linear LOP is much less than employing circular LOP. Although the location precision of using linear LOP is only reduced slightly. However, the proposed efficient methods by using linear LOP can still provide precise solution of MS location and reduce the computational effort greatly. In addition, the proposed methods with less effort can mitigate the NLOS effect, simply by applying the weighted sum of the intersections between different linear LOP and the AOA line, without requiring priori knowledge of NLOS error statistics. Simulation results show that the proposed methods can always yield superior performance in comparison with Taylor series algorithm (TSA) and the hybrid lines of position algorithm (HLOP).
Fast and Provably Accurate Bilateral Filtering
NASA Astrophysics Data System (ADS)
Chaudhury, Kunal N.; Dabhade, Swapnil D.
2016-06-01
The bilateral filter is a non-linear filter that uses a range filter along with a spatial filter to perform edge-preserving smoothing of images. A direct computation of the bilateral filter requires $O(S)$ operations per pixel, where $S$ is the size of the support of the spatial filter. In this paper, we present a fast and provably accurate algorithm for approximating the bilateral filter when the range kernel is Gaussian. In particular, for box and Gaussian spatial filters, the proposed algorithm can cut down the complexity to $O(1)$ per pixel for any arbitrary $S$. The algorithm has a simple implementation involving $N+1$ spatial filterings, where $N$ is the approximation order. We give a detailed analysis of the filtering accuracy that can be achieved by the proposed approximation in relation to the target bilateral filter. This allows us to to estimate the order $N$ required to obtain a given accuracy. We also present comprehensive numerical results to demonstrate that the proposed algorithm is competitive with state-of-the-art methods in terms of speed and accuracy.
Fast and Provably Accurate Bilateral Filtering.
Chaudhury, Kunal N; Dabhade, Swapnil D
2016-06-01
The bilateral filter is a non-linear filter that uses a range filter along with a spatial filter to perform edge-preserving smoothing of images. A direct computation of the bilateral filter requires O(S) operations per pixel, where S is the size of the support of the spatial filter. In this paper, we present a fast and provably accurate algorithm for approximating the bilateral filter when the range kernel is Gaussian. In particular, for box and Gaussian spatial filters, the proposed algorithm can cut down the complexity to O(1) per pixel for any arbitrary S . The algorithm has a simple implementation involving N+1 spatial filterings, where N is the approximation order. We give a detailed analysis of the filtering accuracy that can be achieved by the proposed approximation in relation to the target bilateral filter. This allows us to estimate the order N required to obtain a given accuracy. We also present comprehensive numerical results to demonstrate that the proposed algorithm is competitive with the state-of-the-art methods in terms of speed and accuracy. PMID:27093722
... Story" 5 Things to Know About Zika & Pregnancy Nursing Positions KidsHealth > For Parents > Nursing Positions Print A ... and actually needs to feed. Getting Comfortable With Breastfeeding Nursing can be one of the most challenging ...
Beam Profile Monitor With Accurate Horizontal And Vertical Beam Profiles
Havener, Charles C [Knoxville, TN; Al-Rejoub, Riad [Oak Ridge, TN
2005-12-26
A widely used scanner device that rotates a single helically shaped wire probe in and out of a particle beam at different beamline positions to give a pair of mutually perpendicular beam profiles is modified by the addition of a second wire probe. As a result, a pair of mutually perpendicular beam profiles is obtained at a first beamline position, and a second pair of mutually perpendicular beam profiles is obtained at a second beamline position. The simple modification not only provides more accurate beam profiles, but also provides a measurement of the beam divergence and quality in a single compact device.
Fixed-Wing Micro Aerial Vehicle for Accurate Corridor Mapping
NASA Astrophysics Data System (ADS)
Rehak, M.; Skaloud, J.
2015-08-01
In this study we present a Micro Aerial Vehicle (MAV) equipped with precise position and attitude sensors that together with a pre-calibrated camera enables accurate corridor mapping. The design of the platform is based on widely available model components to which we integrate an open-source autopilot, customized mass-market camera and navigation sensors. We adapt the concepts of system calibration from larger mapping platforms to MAV and evaluate them practically for their achievable accuracy. We present case studies for accurate mapping without ground control points: first for a block configuration, later for a narrow corridor. We evaluate the mapping accuracy with respect to checkpoints and digital terrain model. We show that while it is possible to achieve pixel (3-5 cm) mapping accuracy in both cases, precise aerial position control is sufficient for block configuration, the precise position and attitude control is required for corridor mapping.
RFID-Based Vehicle Positioning and Its Applications in Connected Vehicles
Wang, Jianqiang; Ni, Daiheng; Li, Keqiang
2014-01-01
This paper proposed an RFID-based vehicle positioning approach to facilitate connected vehicles applications. When a vehicle passes over an RFID tag, the vehicle position is given by the accurate position stored in the tag. At locations without RFID coverage, the vehicle position is estimated from the most recent tag location using a kinematics integration algorithm till updates from the next tag. The accuracy of RFID positioning is verified empirically in two independent ways with one using radar and the other a photoelectric switch. The former is designed to verify whether the dynamic position obtained from RFID tags matches the position measured by radar that is regarded as accurate. The latter aims to verify whether the position estimated from the kinematics integration matches the position obtained from RFID tags. Both means supports the accuracy of RFID-based positioning. As a supplement to GPS which suffers from issues such as inaccuracy and loss of signal, RFID positioning is promising in facilitating connected vehicles applications. Two conceptual applications are provided here with one in vehicle operational control and the other in Level IV intersection control. PMID:24599188
RFID-based vehicle positioning and its applications in connected vehicles.
Wang, Jianqiang; Ni, Daiheng; Li, Keqiang
2014-01-01
This paper proposed an RFID-based vehicle positioning approach to facilitate connected vehicles applications. When a vehicle passes over an RFID tag, the vehicle position is given by the accurate position stored in the tag. At locations without RFID coverage, the vehicle position is estimated from the most recent tag location using a kinematics integration algorithm till updates from the next tag. The accuracy of RFID positioning is verified empirically in two independent ways with one using radar and the other a photoelectric switch. The former is designed to verify whether the dynamic position obtained from RFID tags matches the position measured by radar that is regarded as accurate. The latter aims to verify whether the position estimated from the kinematics integration matches the position obtained from RFID tags. Both means supports the accuracy of RFID-based positioning. As a supplement to GPS which suffers from issues such as inaccuracy and loss of signal, RFID positioning is promising in facilitating connected vehicles applications. Two conceptual applications are provided here with one in vehicle operational control and the other in Level IV intersection control. PMID:24599188
ERIC Educational Resources Information Center
Peterson, Christopher
2009-01-01
Positive psychology is a deliberate correction to the focus of psychology on problems. Positive psychology does not deny the difficulties that people may experience but does suggest that sole attention to disorder leads to an incomplete view of the human condition. Positive psychologists concern themselves with four major topics: (1) positive…
How flatbed scanners upset accurate film dosimetry.
van Battum, L J; Huizenga, H; Verdaasdonk, R M; Heukelom, S
2016-01-21
Film is an excellent dosimeter for verification of dose distributions due to its high spatial resolution. Irradiated film can be digitized with low-cost, transmission, flatbed scanners. However, a disadvantage is their lateral scan effect (LSE): a scanner readout change over its lateral scan axis. Although anisotropic light scattering was presented as the origin of the LSE, this paper presents an alternative cause. Hereto, LSE for two flatbed scanners (Epson 1680 Expression Pro and Epson 10000XL), and Gafchromic film (EBT, EBT2, EBT3) was investigated, focused on three effects: cross talk, optical path length and polarization. Cross talk was examined using triangular sheets of various optical densities. The optical path length effect was studied using absorptive and reflective neutral density filters with well-defined optical characteristics (OD range 0.2-2.0). Linear polarizer sheets were used to investigate light polarization on the CCD signal in absence and presence of (un)irradiated Gafchromic film. Film dose values ranged between 0.2 to 9 Gy, i.e. an optical density range between 0.25 to 1.1. Measurements were performed in the scanner's transmission mode, with red-green-blue channels. LSE was found to depend on scanner construction and film type. Its magnitude depends on dose: for 9 Gy increasing up to 14% at maximum lateral position. Cross talk was only significant in high contrast regions, up to 2% for very small fields. The optical path length effect introduced by film on the scanner causes 3% for pixels in the extreme lateral position. Light polarization due to film and the scanner's optical mirror system is the main contributor, different in magnitude for the red, green and blue channel. We concluded that any Gafchromic EBT type film scanned with a flatbed scanner will face these optical effects. Accurate dosimetry requires correction of LSE, therefore, determination of the LSE per color channel and dose delivered to the film. PMID:26689962
How flatbed scanners upset accurate film dosimetry
NASA Astrophysics Data System (ADS)
van Battum, L. J.; Huizenga, H.; Verdaasdonk, R. M.; Heukelom, S.
2016-01-01
Film is an excellent dosimeter for verification of dose distributions due to its high spatial resolution. Irradiated film can be digitized with low-cost, transmission, flatbed scanners. However, a disadvantage is their lateral scan effect (LSE): a scanner readout change over its lateral scan axis. Although anisotropic light scattering was presented as the origin of the LSE, this paper presents an alternative cause. Hereto, LSE for two flatbed scanners (Epson 1680 Expression Pro and Epson 10000XL), and Gafchromic film (EBT, EBT2, EBT3) was investigated, focused on three effects: cross talk, optical path length and polarization. Cross talk was examined using triangular sheets of various optical densities. The optical path length effect was studied using absorptive and reflective neutral density filters with well-defined optical characteristics (OD range 0.2-2.0). Linear polarizer sheets were used to investigate light polarization on the CCD signal in absence and presence of (un)irradiated Gafchromic film. Film dose values ranged between 0.2 to 9 Gy, i.e. an optical density range between 0.25 to 1.1. Measurements were performed in the scanner’s transmission mode, with red-green-blue channels. LSE was found to depend on scanner construction and film type. Its magnitude depends on dose: for 9 Gy increasing up to 14% at maximum lateral position. Cross talk was only significant in high contrast regions, up to 2% for very small fields. The optical path length effect introduced by film on the scanner causes 3% for pixels in the extreme lateral position. Light polarization due to film and the scanner’s optical mirror system is the main contributor, different in magnitude for the red, green and blue channel. We concluded that any Gafchromic EBT type film scanned with a flatbed scanner will face these optical effects. Accurate dosimetry requires correction of LSE, therefore, determination of the LSE per color channel and dose delivered to the film.
Accurate and occlusion-robust multi-view stereo
NASA Astrophysics Data System (ADS)
Zhu, Zhaokun; Stamatopoulos, Christos; Fraser, Clive S.
2015-11-01
This paper proposes an accurate multi-view stereo method for image-based 3D reconstruction that features robustness in the presence of occlusions. The new method offers improvements in dealing with two fundamental image matching problems. The first concerns the selection of the support window model, while the second centers upon accurate visibility estimation for each pixel. The support window model is based on an approximate 3D support plane described by a depth and two per-pixel depth offsets. For the visibility estimation, the multi-view constraint is initially relaxed by generating separate support plane maps for each support image using a modified PatchMatch algorithm. Then the most likely visible support image, which represents the minimum visibility of each pixel, is extracted via a discrete Markov Random Field model and it is further augmented by parameter clustering. Once the visibility is estimated, multi-view optimization taking into account all redundant observations is conducted to achieve optimal accuracy in the 3D surface generation for both depth and surface normal estimates. Finally, multi-view consistency is utilized to eliminate any remaining observational outliers. The proposed method is experimentally evaluated using well-known Middlebury datasets, and results obtained demonstrate that it is amongst the most accurate of the methods thus far reported via the Middlebury MVS website. Moreover, the new method exhibits a high completeness rate.
Hwang, Jinsang; Yun, Hongsik; Suh, Yongcheol; Cho, Jeongho; Lee, Dongha
2012-01-01
This study developed a smartphone application that provides wireless communication, NRTIP client, and RTK processing features, and which can simplify the Network RTK-GPS system while reducing the required cost. A determination method for an error model in Network RTK measurements was proposed, considering both random and autocorrelation errors, to accurately calculate the coordinates measured by the application using state estimation filters. The performance evaluation of the developed application showed that it could perform high-precision real-time positioning, within several centimeters of error range at a frequency of 20 Hz. A Kalman Filter was applied to the coordinates measured from the application, to evaluate the appropriateness of the determination method for an error model, as proposed in this study. The results were more accurate, compared with those of the existing error model, which only considered the random error. PMID:23201981
Hwang, Jinsang; Yun, Hongsik; Suh, Yongcheol; Cho, Jeongho; Lee, Dongha
2012-01-01
This study developed a smartphone application that provides wireless communication, NRTIP client, and RTK processing features, and which can simplify the Network RTK-GPS system while reducing the required cost. A determination method for an error model in Network RTK measurements was proposed, considering both random and autocorrelation errors, to accurately calculate the coordinates measured by the application using state estimation filters. The performance evaluation of the developed application showed that it could perform high-precision real-time positioning, within several centimeters of error range at a frequency of 20 Hz. A Kalman Filter was applied to the coordinates measured from the application, to evaluate the appropriateness of the determination method for an error model, as proposed in this study. The results were more accurate, compared with those of the existing error model, which only considered the random error. PMID:23201981
Accurate Prediction of Docked Protein Structure Similarity.
Akbal-Delibas, Bahar; Pomplun, Marc; Haspel, Nurit
2015-09-01
One of the major challenges for protein-protein docking methods is to accurately discriminate nativelike structures. The protein docking community agrees on the existence of a relationship between various favorable intermolecular interactions (e.g. Van der Waals, electrostatic, desolvation forces, etc.) and the similarity of a conformation to its native structure. Different docking algorithms often formulate this relationship as a weighted sum of selected terms and calibrate their weights against specific training data to evaluate and rank candidate structures. However, the exact form of this relationship is unknown and the accuracy of such methods is impaired by the pervasiveness of false positives. Unlike the conventional scoring functions, we propose a novel machine learning approach that not only ranks the candidate structures relative to each other but also indicates how similar each candidate is to the native conformation. We trained the AccuRMSD neural network with an extensive dataset using the back-propagation learning algorithm. Our method achieved predicting RMSDs of unbound docked complexes with 0.4Å error margin. PMID:26335807
Cummings, Carl
2011-01-01
Cranial asymmetry occurring as a result of forces that deform skull shape in the supine position is known as deformational plagiocephaly. The risk of plagiocephaly may be modified by positioning the baby on alternate days with the head to the right or the left side, and by increasing time spent in the prone position during awake periods. When deformational plagiocephaly is already present, physiotherapy (including positioning equivalent to the preventive positioning, and exercises as needed for torticollis and positional preference) has been shown to be superior to counselling about preventive positioning only. Helmet therapy (moulding therapy) to reduce skull asymmetry has some drawbacks: it is expensive, significantly inconvenient due to the long hours of use per day and associated with skin complications. There is evidence that helmet therapy may increase the initial rate of improvement of asymmetry, but there is no evidence that it improves the final outcome for patients with moderate or severe plagiocephaly. PMID:23024590
Optical Enhancement of Exoskeleton-Based Estimation of Glenohumeral Angles
Cortés, Camilo; Unzueta, Luis; de los Reyes-Guzmán, Ana; Ruiz, Oscar E.; Flórez, Julián
2016-01-01
In Robot-Assisted Rehabilitation (RAR) the accurate estimation of the patient limb joint angles is critical for assessing therapy efficacy. In RAR, the use of classic motion capture systems (MOCAPs) (e.g., optical and electromagnetic) to estimate the Glenohumeral (GH) joint angles is hindered by the exoskeleton body, which causes occlusions and magnetic disturbances. Moreover, the exoskeleton posture does not accurately reflect limb posture, as their kinematic models differ. To address the said limitations in posture estimation, we propose installing the cameras of an optical marker-based MOCAP in the rehabilitation exoskeleton. Then, the GH joint angles are estimated by combining the estimated marker poses and exoskeleton Forward Kinematics. Such hybrid system prevents problems related to marker occlusions, reduced camera detection volume, and imprecise joint angle estimation due to the kinematic mismatch of the patient and exoskeleton models. This paper presents the formulation, simulation, and accuracy quantification of the proposed method with simulated human movements. In addition, a sensitivity analysis of the method accuracy to marker position estimation errors, due to system calibration errors and marker drifts, has been carried out. The results show that, even with significant errors in the marker position estimation, method accuracy is adequate for RAR. PMID:27403044
Optical Enhancement of Exoskeleton-Based Estimation of Glenohumeral Angles.
Cortés, Camilo; Unzueta, Luis; de Los Reyes-Guzmán, Ana; Ruiz, Oscar E; Flórez, Julián
2016-01-01
In Robot-Assisted Rehabilitation (RAR) the accurate estimation of the patient limb joint angles is critical for assessing therapy efficacy. In RAR, the use of classic motion capture systems (MOCAPs) (e.g., optical and electromagnetic) to estimate the Glenohumeral (GH) joint angles is hindered by the exoskeleton body, which causes occlusions and magnetic disturbances. Moreover, the exoskeleton posture does not accurately reflect limb posture, as their kinematic models differ. To address the said limitations in posture estimation, we propose installing the cameras of an optical marker-based MOCAP in the rehabilitation exoskeleton. Then, the GH joint angles are estimated by combining the estimated marker poses and exoskeleton Forward Kinematics. Such hybrid system prevents problems related to marker occlusions, reduced camera detection volume, and imprecise joint angle estimation due to the kinematic mismatch of the patient and exoskeleton models. This paper presents the formulation, simulation, and accuracy quantification of the proposed method with simulated human movements. In addition, a sensitivity analysis of the method accuracy to marker position estimation errors, due to system calibration errors and marker drifts, has been carried out. The results show that, even with significant errors in the marker position estimation, method accuracy is adequate for RAR. PMID:27403044
Leveraging Two Kinect Sensors for Accurate Full-Body Motion Capture
Gao, Zhiquan; Yu, Yao; Zhou, Yu; Du, Sidan
2015-01-01
Accurate motion capture plays an important role in sports analysis, the medical field and virtual reality. Current methods for motion capture often suffer from occlusions, which limits the accuracy of their pose estimation. In this paper, we propose a complete system to measure the pose parameters of the human body accurately. Different from previous monocular depth camera systems, we leverage two Kinect sensors to acquire more information about human movements, which ensures that we can still get an accurate estimation even when significant occlusion occurs. Because human motion is temporally constant, we adopt a learning analysis to mine the temporal information across the posture variations. Using this information, we estimate human pose parameters accurately, regardless of rapid movement. Our experimental results show that our system can perform an accurate pose estimation of the human body with the constraint of information from the temporal domain. PMID:26402681
Leveraging Two Kinect Sensors for Accurate Full-Body Motion Capture.
Gao, Zhiquan; Yu, Yao; Zhou, Yu; Du, Sidan
2015-01-01
Accurate motion capture plays an important role in sports analysis, the medical field and virtual reality. Current methods for motion capture often suffer from occlusions, which limits the accuracy of their pose estimation. In this paper, we propose a complete system to measure the pose parameters of the human body accurately. Different from previous monocular depth camera systems, we leverage two Kinect sensors to acquire more information about human movements, which ensures that we can still get an accurate estimation even when significant occlusion occurs. Because human motion is temporally constant, we adopt a learning analysis to mine the temporal information across the posture variations. Using this information, we estimate human pose parameters accurately, regardless of rapid movement. Our experimental results show that our system can perform an accurate pose estimation of the human body with the constraint of information from the temporal domain. PMID:26402681
Accurate Fiber Length Measurement Using Time-of-Flight Technique
NASA Astrophysics Data System (ADS)
Terra, Osama; Hussein, Hatem
2016-06-01
Fiber artifacts of very well-measured length are required for the calibration of optical time domain reflectometers (OTDR). In this paper accurate length measurement of different fiber lengths using the time-of-flight technique is performed. A setup is proposed to measure accurately lengths from 1 to 40 km at 1,550 and 1,310 nm using high-speed electro-optic modulator and photodetector. This setup offers traceability to the SI unit of time, the second (and hence to meter by definition), by locking the time interval counter to the Global Positioning System (GPS)-disciplined quartz oscillator. Additionally, the length of a recirculating loop artifact is measured and compared with the measurement made for the same fiber by the National Physical Laboratory of United Kingdom (NPL). Finally, a method is proposed to relatively correct the fiber refractive index to allow accurate fiber length measurement.
Strategy Guideline. Accurate Heating and Cooling Load Calculations
Burdick, Arlan
2011-06-01
This guide presents the key criteria required to create accurate heating and cooling load calculations and offers examples of the implications when inaccurate adjustments are applied to the HVAC design process. The guide shows, through realistic examples, how various defaults and arbitrary safety factors can lead to significant increases in the load estimate. Emphasis is placed on the risks incurred from inaccurate adjustments or ignoring critical inputs of the load calculation.
Accurate Insertion Loss Measurements of the Juno Patch Array Antennas
NASA Technical Reports Server (NTRS)
Chamberlain, Neil; Chen, Jacqueline; Hodges, Richard; Demas, John
2010-01-01
This paper describes two independent methods for estimating the insertion loss of patch array antennas that were developed for the Juno Microwave Radiometer instrument. One method is based principally on pattern measurements while the other method is based solely on network analyzer measurements. The methods are accurate to within 0.1 dB for the measured antennas and show good agreement (to within 0.1dB) of separate radiometric measurements.
Strategy Guideline: Accurate Heating and Cooling Load Calculations
Burdick, A.
2011-06-01
This guide presents the key criteria required to create accurate heating and cooling load calculations and offers examples of the implications when inaccurate adjustments are applied to the HVAC design process. The guide shows, through realistic examples, how various defaults and arbitrary safety factors can lead to significant increases in the load estimate. Emphasis is placed on the risks incurred from inaccurate adjustments or ignoring critical inputs of the load calculation.
NASA Technical Reports Server (NTRS)
Aster, R. W.; Chamberlain, R. G.; Zendejas, S. C.; Lee, T. S.; Malhotra, S.
1986-01-01
Company-wide or process-wide production simulated. Price Estimation Guidelines (IPEG) program provides simple, accurate estimates of prices of manufactured products. Simplification of SAMIS allows analyst with limited time and computing resources to perform greater number of sensitivity studies. Although developed for photovoltaic industry, readily adaptable to standard assembly-line type of manufacturing industry. IPEG program estimates annual production price per unit. IPEG/PC program written in TURBO PASCAL.
Important Nearby Galaxies without Accurate Distances
NASA Astrophysics Data System (ADS)
McQuinn, Kristen
2014-10-01
The Spitzer Infrared Nearby Galaxies Survey (SINGS) and its offspring programs (e.g., THINGS, HERACLES, KINGFISH) have resulted in a fundamental change in our view of star formation and the ISM in galaxies, and together they represent the most complete multi-wavelength data set yet assembled for a large sample of nearby galaxies. These great investments of observing time have been dedicated to the goal of understanding the interstellar medium, the star formation process, and, more generally, galactic evolution at the present epoch. Nearby galaxies provide the basis for which we interpret the distant universe, and the SINGS sample represents the best studied nearby galaxies.Accurate distances are fundamental to interpreting observations of galaxies. Surprisingly, many of the SINGS spiral galaxies have numerous distance estimates resulting in confusion. We can rectify this situation for 8 of the SINGS spiral galaxies within 10 Mpc at a very low cost through measurements of the tip of the red giant branch. The proposed observations will provide an accuracy of better than 0.1 in distance modulus. Our sample includes such well known galaxies as M51 (the Whirlpool), M63 (the Sunflower), M104 (the Sombrero), and M74 (the archetypal grand design spiral).We are also proposing coordinated parallel WFC3 UV observations of the central regions of the galaxies, rich with high-mass UV-bright stars. As a secondary science goal we will compare the resolved UV stellar populations with integrated UV emission measurements used in calibrating star formation rates. Our observations will complement the growing HST UV atlas of high resolution images of nearby galaxies.
Relativistic positioning systems: Numerical simulations
NASA Astrophysics Data System (ADS)
Puchades Colmenero, Neus
-time (ST) corresponding to an ideal static spherically symmetric Earth. Since this ST is asymptotically Minkowskian, as soon as Schwarzschild's metric is assumed, there is a reference system with origin in the Earth center, which is inertial from the theoretical point of view, and almost inertial - since the acceleration due to the Sun and other small effects are being neglected- from the physical point of view. In one of the models, the 0-order RPS, photons move in the Minkowski ST asymptotic to Schwarzschild, whereas in the second model (1-order RPS), photons move - as the satellites - in Schwarzschild's ST. In the context of RPS, error estimations seem to be more systematic than in the framework of CPS. In the scheme presented in this thesis, there are two types of positioning errors. The U-errors are due to deviations of the actual satellite world lines with respect to the nominal lines (which have been adequately defined); whereas the S-errors arise when some sources of the gravitational field are neglected and, consequently, the metric and the photon null geodesics are not fully accurate. For every user, the total error is the addition of the U and the S errors. We have found, represented, and studied, the distributions of bifurcation points, U-errors, and S-errors, inside a wide spherical region with a radius of 100.000 km, which is located around Earth and centered in an arbitrary point on Earth's surface; in this way, we have discussed - for the first time - spacecraft positioning in this region based on GPS and GALILEO 4-tuples. (Abstract shortened by UMI.).
ERIC Educational Resources Information Center
Seligman, Martin E. P.; Rashid, Tayyab; Parks, Acacia C.
2006-01-01
Positive psychotherapy (PPT) contrasts with standard interventions for depression by increasing positive emotion, engagement, and meaning rather than directly targeting depressive symptoms. The authors have tested the effects of these interventions in a variety of settings. In informal student and clinical settings, people not uncommonly reported…
Sampling designs matching species biology produce accurate and affordable abundance indices.
Harris, Grant; Farley, Sean; Russell, Gareth J; Butler, Matthew J; Selinger, Jeff
2013-01-01
Wildlife biologists often use grid-based designs to sample animals and generate abundance estimates. Although sampling in grids is theoretically sound, in application, the method can be logistically difficult and expensive when sampling elusive species inhabiting extensive areas. These factors make it challenging to sample animals and meet the statistical assumption of all individuals having an equal probability of capture. Violating this assumption biases results. Does an alternative exist? Perhaps by sampling only where resources attract animals (i.e., targeted sampling), it would provide accurate abundance estimates more efficiently and affordably. However, biases from this approach would also arise if individuals have an unequal probability of capture, especially if some failed to visit the sampling area. Since most biological programs are resource limited, and acquiring abundance data drives many conservation and management applications, it becomes imperative to identify economical and informative sampling designs. Therefore, we evaluated abundance estimates generated from grid and targeted sampling designs using simulations based on geographic positioning system (GPS) data from 42 Alaskan brown bears (Ursus arctos). Migratory salmon drew brown bears from the wider landscape, concentrating them at anadromous streams. This provided a scenario for testing the targeted approach. Grid and targeted sampling varied by trap amount, location (traps placed randomly, systematically or by expert opinion), and traps stationary or moved between capture sessions. We began by identifying when to sample, and if bears had equal probability of capture. We compared abundance estimates against seven criteria: bias, precision, accuracy, effort, plus encounter rates, and probabilities of capture and recapture. One grid (49 km(2) cells) and one targeted configuration provided the most accurate results. Both placed traps by expert opinion and moved traps between capture sessions
Sampling designs matching species biology produce accurate and affordable abundance indices
Farley, Sean; Russell, Gareth J.; Butler, Matthew J.; Selinger, Jeff
2013-01-01
Wildlife biologists often use grid-based designs to sample animals and generate abundance estimates. Although sampling in grids is theoretically sound, in application, the method can be logistically difficult and expensive when sampling elusive species inhabiting extensive areas. These factors make it challenging to sample animals and meet the statistical assumption of all individuals having an equal probability of capture. Violating this assumption biases results. Does an alternative exist? Perhaps by sampling only where resources attract animals (i.e., targeted sampling), it would provide accurate abundance estimates more efficiently and affordably. However, biases from this approach would also arise if individuals have an unequal probability of capture, especially if some failed to visit the sampling area. Since most biological programs are resource limited, and acquiring abundance data drives many conservation and management applications, it becomes imperative to identify economical and informative sampling designs. Therefore, we evaluated abundance estimates generated from grid and targeted sampling designs using simulations based on geographic positioning system (GPS) data from 42 Alaskan brown bears (Ursus arctos). Migratory salmon drew brown bears from the wider landscape, concentrating them at anadromous streams. This provided a scenario for testing the targeted approach. Grid and targeted sampling varied by trap amount, location (traps placed randomly, systematically or by expert opinion), and traps stationary or moved between capture sessions. We began by identifying when to sample, and if bears had equal probability of capture. We compared abundance estimates against seven criteria: bias, precision, accuracy, effort, plus encounter rates, and probabilities of capture and recapture. One grid (49 km2 cells) and one targeted configuration provided the most accurate results. Both placed traps by expert opinion and moved traps between capture sessions, which
Human leader and robot follower team: correcting leader's position from follower's heading
NASA Astrophysics Data System (ADS)
Borenstein, Johann; Thomas, David; Sights, Brandon; Ojeda, Lauro; Bankole, Peter; Fellars, Donald
2010-04-01
In multi-agent scenarios, there can be a disparity in the quality of position estimation amongst the various agents. Here, we consider the case of two agents - a leader and a follower - following the same path, in which the follower has a significantly better estimate of position and heading. This may be applicable to many situations, such as a robotic "mule" following a soldier. Another example is that of a convoy, in which only one vehicle (not necessarily the leading one) is instrumented with precision navigation instruments while all other vehicles use lower-precision instruments. We present an algorithm, called Follower-derived Heading Correction (FDHC), which substantially improves estimates of the leader's heading and, subsequently, position. Specifically, FHDC produces a very accurate estimate of heading errors caused by slow-changing errors (e.g., those caused by drift in gyros) of the leader's navigation system and corrects those errors.
Accurate orbit propagation with planetary close encounters
NASA Astrophysics Data System (ADS)
Baù, Giulio; Milani Comparetti, Andrea; Guerra, Francesca
2015-08-01
We tackle the problem of accurately propagating the motion of those small bodies that undergo close approaches with a planet. The literature is lacking on this topic and the reliability of the numerical results is not sufficiently discussed. The high-frequency components of the perturbation generated by a close encounter makes the propagation particularly challenging both from the point of view of the dynamical stability of the formulation and the numerical stability of the integrator. In our approach a fixed step-size and order multistep integrator is combined with a regularized formulation of the perturbed two-body problem. When the propagated object enters the region of influence of a celestial body, the latter becomes the new primary body of attraction. Moreover, the formulation and the step-size will also be changed if necessary. We present: 1) the restarter procedure applied to the multistep integrator whenever the primary body is changed; 2) new analytical formulae for setting the step-size (given the order of the multistep, formulation and initial osculating orbit) in order to control the accumulation of the local truncation error and guarantee the numerical stability during the propagation; 3) a new definition of the region of influence in the phase space. We test the propagator with some real asteroids subject to the gravitational attraction of the planets, the Yarkovsky and relativistic perturbations. Our goal is to show that the proposed approach improves the performance of both the propagator implemented in the OrbFit software package (which is currently used by the NEODyS service) and of the propagator represented by a variable step-size and order multistep method combined with Cowell's formulation (i.e. direct integration of position and velocity in either the physical or a fictitious time).
Accurate TOA-Based UWB Localization System in Coal Mine Based on WSN
NASA Astrophysics Data System (ADS)
Cheng, Guangliang
Over the last years, there has been a great deal of interest in Ultra Wideband (UWB) wireless communication and Wireless Sensor Networks(WSN), especially following the proposing of the internet of things by the MIT (Massachusetts Institute of Technology) in 1999, hich is also result in an increasing research on UWB and WSN applications. This article mainly introduced the accurate UWB Localization System based on WSN in coal mine. Firstly, we briefly introduced UWB and WSN Localization technology. Secondly, the advantages and disadvantages of the previous personnel localization technology in coal mine was analyzed and contrasted, and then the suitable personnel localization system in coal mine based on UWB signal and TOA estimate positioning scheme are presented. At last the rationality and feasibility of this scheme was proved through the simulation results.
NASA Astrophysics Data System (ADS)
Cai, Jun; Deng, Zhiquan
2015-02-01
Accurate rotor position signal is highly required for controlling the switched reluctance motor (SRM). The use of galvanic isolated sensing coils can provide independent circuit for position estimation without affecting the SRM actuation. However, the cross-coupling between main winding and sensing coil, and the mutual coupling between adjacent phase sensing coils may affect the position estimation performance seriously. In this paper, three sensing coil configurations in a 12/8 structure SRM are analyzed and compared for selecting an optimal configuration that can effectively minimize the bad effects of the cross-coupling factors. The finite element analysis and experimental results are provided for verification.
Cai, Jun; Deng, Zhiquan
2015-02-01
Accurate rotor position signal is highly required for controlling the switched reluctance motor (SRM). The use of galvanic isolated sensing coils can provide independent circuit for position estimation without affecting the SRM actuation. However, the cross-coupling between main winding and sensing coil, and the mutual coupling between adjacent phase sensing coils may affect the position estimation performance seriously. In this paper, three sensing coil configurations in a 12/8 structure SRM are analyzed and compared for selecting an optimal configuration that can effectively minimize the bad effects of the cross-coupling factors. The finite element analysis and experimental results are provided for verification. PMID:25725876