Accurate absolute GPS positioning through satellite clock error estimation
NASA Astrophysics Data System (ADS)
Han, S.-C.; Kwon, J. H.; Jekeli, C.
2001-05-01
An algorithm for very accurate absolute positioning through Global Positioning System (GPS) satellite clock estimation has been developed. Using International GPS Service (IGS) precise orbits and measurements, GPS clock errors were estimated at 30-s intervals. Compared to values determined by the Jet Propulsion Laboratory, the agreement was at the level of about 0.1 ns (3 cm). The clock error estimates were then applied to an absolute positioning algorithm in both static and kinematic modes. For the static case, an IGS station was selected and the coordinates were estimated every 30 s. The estimated absolute position coordinates and the known values had a mean difference of up to 18 cm with standard deviation less than 2 cm. For the kinematic case, data obtained every second from a GPS buoy were tested and the result from the absolute positioning was compared to a differential GPS (DGPS) solution. The mean differences between the coordinates estimated by the two methods are less than 40 cm and the standard deviations are less than 25 cm. It was verified that this poorer standard deviation on 1-s position results is due to the clock error interpolation from 30-s estimates with Selective Availability (SA). After SA was turned off, higher-rate clock error estimates (such as 1 s) could be obtained by a simple interpolation with negligible corruption. Therefore, the proposed absolute positioning technique can be used to within a few centimeters' precision at any rate by estimating 30-s satellite clock errors and interpolating them.
BIOACCESSIBILITY TESTS ACCURATELY ESTIMATE ...
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 P significantly reduced the bioavailability of Pb. The bioaccessibility of the 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%. Ad
Accurate radio positions with the Tidbinbilla interferometer
NASA Technical Reports Server (NTRS)
Batty, M. J.; Gulkis, S.; Jauncey, D. L.; Rayner, P. T.
1979-01-01
The Tidbinbilla interferometer (Batty et al., 1977) is designed specifically to provide accurate radio position measurements of compact radio sources in the Southern Hemisphere with high sensitivity. The interferometer uses the 26-m and 64-m antennas of the Deep Space Network at Tidbinbilla, near Canberra. The two antennas are separated by 200 m on a north-south baseline. By utilizing the existing antennas and the low-noise traveling-wave masers at 2.29 GHz, it has been possible to produce a high-sensitivity instrument with a minimum of capital expenditure. The north-south baseline ensures that a good range of UV coverage is obtained, so that sources lying in the declination range between about -80 and +30 deg may be observed with nearly orthogonal projected baselines of no less than about 1000 lambda. The instrument also provides high-accuracy flux density measurements for compact radio sources.
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 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 Biomass Estimation via Bayesian Adaptive Sampling
NASA Astrophysics Data System (ADS)
Wheeler, K.; Knuth, K.; Castle, P.
2005-12-01
and IKONOS imagery and the 3-D volume estimates. The combination of these then allow for a rapid and hopefully very accurate estimation of biomass.
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 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.
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.
Preparing Rapid, Accurate Construction Cost Estimates with a Personal Computer.
ERIC Educational Resources Information Center
Gerstel, Sanford M.
1986-01-01
An inexpensive and rapid method for preparing accurate cost estimates of construction projects in a university setting, using a personal computer, purchased software, and one estimator, is described. The case against defined estimates, the rapid estimating system, and adjusting standard unit costs are discussed. (MLW)
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.
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.
Accurate genome relative abundance estimation based on shotgun metagenomic reads.
Xia, Li C; Cram, Jacob A; Chen, Ting; Fuhrman, Jed A; Sun, Fengzhu
2011-01-01
Accurate estimation of microbial community composition based on metagenomic sequencing data is fundamental for subsequent metagenomics analysis. Prevalent estimation methods are mainly based on directly summarizing alignment results or its variants; often result in biased and/or unstable estimates. We have developed a unified probabilistic framework (named GRAMMy) by explicitly modeling read assignment ambiguities, genome size biases and read distributions along the genomes. Maximum likelihood method is employed to compute Genome Relative Abundance of microbial communities using the Mixture Model theory (GRAMMy). GRAMMy has been demonstrated to give estimates that are accurate and robust across both simulated and real read benchmark datasets. We applied GRAMMy to a collection of 34 metagenomic read sets from four metagenomics projects and identified 99 frequent species (minimally 0.5% abundant in at least 50% of the data-sets) in the human gut samples. Our results show substantial improvements over previous studies, such as adjusting the over-estimated abundance for Bacteroides species for human gut samples, by providing a new reference-based strategy for metagenomic sample comparisons. GRAMMy can be used flexibly with many read assignment tools (mapping, alignment or composition-based) even with low-sensitivity mapping results from huge short-read datasets. It will be increasingly useful as an accurate and robust tool for abundance estimation with the growing size of read sets and the expanding database of reference genomes.
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 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.
Towards accurate and precise estimates of lion density.
Elliot, Nicholas B; Gopalaswamy, Arjun M
2016-12-13
Reliable estimates of animal density are fundamental to our understanding of ecological processes and population dynamics. Furthermore, their accuracy is vital to conservation biology since wildlife authorities rely on these figures to make decisions. However, it is notoriously difficult to accurately estimate density for wide-ranging species such as carnivores that occur at low densities. In recent years, significant progress has been made in density estimation of Asian carnivores, but the methods have not been widely adapted to African carnivores. African lions (Panthera leo) provide an excellent example as although abundance indices have been shown to produce poor inferences, they continue to be used to estimate lion density and inform management and policy. In this study we adapt a Bayesian spatially explicit capture-recapture model to estimate lion density in the Maasai Mara National Reserve (MMNR) and surrounding conservancies in Kenya. We utilize sightings data from a three-month survey period to produce statistically rigorous spatial density estimates. Overall posterior mean lion density was estimated to be 16.85 (posterior standard deviation = 1.30) lions over one year of age per 100km(2) with a sex ratio of 2.2♀:1♂. We argue that such methods should be developed, improved and favored over less reliable methods such as track and call-up surveys. We caution against trend analyses based on surveys of differing reliability and call for a unified framework to assess lion numbers across their range in order for better informed management and policy decisions to be made. This article is protected by copyright. All rights reserved.
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.
How utilities can achieve more accurate decommissioning cost estimates
Knight, R.
1999-07-01
The number of commercial nuclear power plants that are undergoing decommissioning coupled with the economic pressure of deregulation has increased the focus on adequate funding for decommissioning. The introduction of spent-fuel storage and disposal of low-level radioactive waste into the cost analysis places even greater concern as to the accuracy of the fund calculation basis. The size and adequacy of the decommissioning fund have also played a major part in the negotiations for transfer of plant ownership. For all of these reasons, it is important that the operating plant owner reduce the margin of error in the preparation of decommissioning cost estimates. To data, all of these estimates have been prepared via the building block method. That is, numerous individual calculations defining the planning, engineering, removal, and disposal of plant systems and structures are performed. These activity costs are supplemented by the period-dependent costs reflecting the administration, control, licensing, and permitting of the program. This method will continue to be used in the foreseeable future until adequate performance data are available. The accuracy of the activity cost calculation is directly related to the accuracy of the inventory of plant system component, piping and equipment, and plant structural composition. Typically, it is left up to the cost-estimating contractor to develop this plant inventory. The data are generated by searching and analyzing property asset records, plant databases, piping and instrumentation drawings, piping system isometric drawings, and component assembly drawings. However, experience has shown that these sources may not be up to date, discrepancies may exist, there may be missing data, and the level of detail may not be sufficient. Again, typically, the time constraints associated with the development of the cost estimate preclude perfect resolution of the inventory questions. Another problem area in achieving accurate cost
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.}
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"…
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.
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.
Estimation of bone permeability using accurate microstructural measurements.
Beno, Thoma; Yoon, Young-June; Cowin, Stephen C; Fritton, Susannah P
2006-01-01
While interstitial fluid flow is necessary for the viability of osteocytes, it is also believed to play a role in bone's mechanosensory system by shearing bone cell membranes or causing cytoskeleton deformation and thus activating biochemical responses that lead to the process of bone adaptation. However, the fluid flow properties that regulate bone's adaptive response are poorly understood. In this paper, we present an analytical approach to determine the degree of anisotropy of the permeability of the lacunar-canalicular porosity in bone. First, we estimate the total number of canaliculi emanating from each osteocyte lacuna based on published measurements from parallel-fibered shaft bones of several species (chick, rabbit, bovine, horse, dog, and human). Next, we determine the local three-dimensional permeability of the lacunar-canalicular porosity for these species using recent microstructural measurements and adapting a previously developed model. Results demonstrated that the number of canaliculi per osteocyte lacuna ranged from 41 for human to 115 for horse. Permeability coefficients were found to be different in three local principal directions, indicating local orthotropic symmetry of bone permeability in parallel-fibered cortical bone for all species examined. For the range of parameters investigated, the local lacunar-canalicular permeability varied more than three orders of magnitude, with the osteocyte lacunar shape and size along with the 3-D canalicular distribution determining the degree of anisotropy of the local permeability. This two-step theoretical approach to determine the degree of anisotropy of the permeability of the lacunar-canalicular porosity will be useful for accurate quantification of interstitial fluid movement in bone.
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.
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.
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.
Chen, Weizhong; Liu, Yi; Zhu, Shanshan; Green, Christopher D; Wei, Gang; Han, Jing-Dong Jackie
2014-09-18
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.
Accurate OH Maser Positions from the SPLASH Pilot Region
NASA Astrophysics Data System (ADS)
Qiao, Hai-Hua; Walsh, Andrew J.; Green, James A.; Breen, Shari L.; Dawson, J. R.; Ellingsen, Simon P.; Gómez, José F.; Jordan, Christopher H.; Shen, Zhi-Qiang; Lowe, Vicki; Jones, Paul A.
2016-12-01
We report on high spatial resolution observations, using the Australia Telescope Compact Array (ATCA), of ground-state OH masers. These observations were carried out toward 196 pointing centers previously identified in the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH) pilot region, between Galactic longitudes of 334° and 344° and Galactic latitudes of ‑2° and +2°. Supplementing our data with data from the MAGMO (Mapping the Galactic Magnetic field through OH masers) survey, we find maser emission toward 175 of the 196 target fields. We conclude that about half of the 21 nondetections were due to intrinsic variability. Due to the superior sensitivity of the followup ATCA observations, and the ability to resolve nearby sources into separate sites, we have identified 215 OH maser sites toward the 175 fields with detections. Among these 215 OH maser sites, 111 are new detections. After comparing the positions of these 215 maser sites to the literature, we identify 122 (57%) sites associated with evolved stars (one of which is a planetary nebula), 64 (30%) with star formation, two sites with supernova remnants, and 27 (13%) of unknown origin. The infrared colors of evolved star sites with symmetric maser profiles tend to be redder than those of evolved star sites with asymmetric maser profiles, which may indicate that symmetric sources are generally at an earlier evolutionary stage.
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.
2016-01-01
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
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.
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...
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 ...
How accurate are physical property estimation programs for organosilicon compounds?
Boethling, Robert; Meylan, William
2013-11-01
Organosilicon compounds are important in chemistry and commerce, and nearly 10% of new chemical substances for which premanufacture notifications are processed by the US Environmental Protection Agency (USEPA) contain silicon (Si). Yet, remarkably few measured values are submitted for key physical properties, and the accuracy of estimation programs such as the Estimation Programs Interface (EPI) Suite and the SPARC Performs Automated Reasoning in Chemistry (SPARC) system is largely unknown. To address this issue, the authors developed an extensive database of measured property values for organic compounds containing Si and evaluated the performance of no-cost estimation programs for several properties of importance in environmental assessment. These included melting point (mp), boiling point (bp), vapor pressure (vp), water solubility, n-octanol/water partition coefficient (log KOW ), and Henry's law constant. For bp and the larger of 2 vp datasets, SPARC, MPBPWIN, and the USEPA's Toxicity Estimation Software Tool (TEST) had similar accuracy. For log KOW and water solubility, the authors tested 11 and 6 no-cost estimators, respectively. The best performers were Molinspiration and WSKOWWIN, respectively. The TEST's consensus mp method outperformed that of MPBPWIN by a considerable margin. Generally, the best programs estimated the listed properties of diverse organosilicon compounds with accuracy sufficient for chemical screening. The results also highlight areas where improvement is most needed.
Erasing Errors due to Alignment Ambiguity When Estimating Positive Selection
Redelings, Benjamin
2014-01-01
Current estimates of diversifying positive selection rely on first having an accurate multiple sequence alignment. Simulation studies have shown that under biologically plausible conditions, relying on a single estimate of the alignment from commonly used alignment software can lead to unacceptably high false-positive rates in detecting diversifying positive selection. We present a novel statistical method that eliminates excess false positives resulting from alignment error by jointly estimating the degree of positive selection and the alignment under an evolutionary model. Our model treats both substitutions and insertions/deletions as sequence changes on a tree and allows site heterogeneity in the substitution process. We conduct inference starting from unaligned sequence data by integrating over all alignments. This approach naturally accounts for ambiguous alignments without requiring ambiguously aligned sites to be identified and removed prior to analysis. We take a Bayesian approach and conduct inference using Markov chain Monte Carlo to integrate over all alignments on a fixed evolutionary tree topology. We introduce a Bayesian version of the branch-site test and assess the evidence for positive selection using Bayes factors. We compare two models of differing dimensionality using a simple alternative to reversible-jump methods. We also describe a more accurate method of estimating the Bayes factor using Rao-Blackwellization. We then show using simulated data that jointly estimating the alignment and the presence of positive selection solves the problem with excessive false positives from erroneous alignments and has nearly the same power to detect positive selection as when the true alignment is known. We also show that samples taken from the posterior alignment distribution using the software BAli-Phy have substantially lower alignment error compared with MUSCLE, MAFFT, PRANK, and FSA alignments. PMID:24866534
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.
Sensorless position estimator applied to nonlinear IPMC model
NASA Astrophysics Data System (ADS)
Bernat, Jakub; Kolota, Jakub
2016-11-01
This paper addresses the issue of estimating position for an ionic polymer metal composite (IPMC) known as electro active polymer (EAP). The key step is the construction of a sensorless mode considering only current feedback. This work takes into account nonlinearities caused by electrochemical effects in the material. Owing to the recent observer design technique, the authors obtained both Lyapunov function based estimation law as well as sliding mode observer. To accomplish the observer design, the IPMC model was identified through a series of experiments. The research comprises time domain measurements. The identification process was completed by means of geometric scaling of three test samples. In the proposed design, the estimated position accurately tracks the polymer position, which is illustrated by the experiments.
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.
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.
Fast and Accurate Estimates of Divergence Times from Big Data.
Mello, Beatriz; Tao, Qiqing; Tamura, Koichiro; Kumar, Sudhir
2017-01-01
Ongoing advances in sequencing technology have led to an explosive expansion in the molecular data available for building increasingly larger and more comprehensive timetrees. However, Bayesian relaxed-clock approaches frequently used to infer these timetrees impose a large computational burden and discourage critical assessment of the robustness of inferred times to model assumptions, influence of calibrations, and selection of optimal data subsets. We analyzed eight large, recently published, empirical datasets to compare time estimates produced by RelTime (a non-Bayesian method) with those reported by using Bayesian approaches. We find that RelTime estimates are very similar to Bayesian approaches, yet RelTime requires orders of magnitude less computational time. This means that the use of RelTime will enable greater rigor in molecular dating, because faster computational speeds encourage more extensive testing of the robustness of inferred timetrees to prior assumptions (models and calibrations) and data subsets. Thus, RelTime provides a reliable and computationally thrifty approach for dating the tree of life using large-scale molecular datasets.
False Positive Mammograms and Detection Controlled Estimation
Kleit, Andrew N; Ruiz, James F
2003-01-01
Objective To investigate the causes of false positive in mammograms. Data Sources Secondary data collected from extracts from computerized medical records from 1999 from five thousand patients at a single hospital in a medium-sized Southern city. Study Design Retrospective analysis of electronic medical data on screening and diagnostic mammograms. Detection-controlled estimation (DCE) was used to compare the efficacy of alternative readers of mammogram films. Analysis was also conducted on follow-up exams of women who tested positive in the first stage of investigation. Key variables included whether the patient had had a prior mammogram, age of the patient, and identifiers for the individual physicians. Data Collection/Extraction Methods Hospital maintains electronic medical records (EMR) on all patients. Extracts were performed on this EMR system under the guidance of clinical expertise. Data were collected for all women who had mammograms in 1999. Random samples were employed for screening mammograms, and all data was used for diagnostic mammograms. Principal Findings Study results imply that access to a previous mammogram greatly reduces the incidence of false positives readings. This has important consequences for benefit-cost, and cost-effectiveness analysis of mammography. Were previous mammograms always available, the results imply the number of false positives would decrease by at least half. The results here also indicate that there is no reason to believe this decrease in false positive would be accompanied by an increase in the number of false negatives. Other attributes also affected the number of false positives. Mondays and Wednesdays appear to be more prone to false positives than the other days in the week. There is also some disparity in false positive outcomes among the five physicians studied. With respect to detection-controlled estimation, the results are mixed. With follow-up data, the DCE estimator appears to generate reasonable, robust
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.
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.
Li, Kui; Wang, Lei; Lv, Yanhong; Gao, Pengyu; Song, Tianxiao
2015-10-20
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.
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.
Position Estimation by Wearable Walking Navigation System for Visually Impaired with Sensor Fusion
NASA Astrophysics Data System (ADS)
Watanabe, Hiromi; Yamamoto, Yoshihiko; Tanzawa, Tsutomu; Kotani, Shinji
A wearable walking navigation system without any special infrastructures has been developed to guide visually impaired. It is important to estimate a position correctly so that safe navigation can be realized. In our system, different sensor data are fused to estimate a pedestrian's position. An image processing system and a laser range finder were used to estimate the positions indoors. In this paper, we introduce the concept of “similarity” between map information and sensor data. This similarity is used to estimate the positions. Experimental results show that highly accurate position estimation can be achieved by sensor fusion. The positions in a linear passage were estimated using image processing data, and when the passage turns, the positions were estimated using LRF data.
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.
Browning, Sharon R; Browning, Brian L
2015-09-03
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.
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
LSimpute: accurate estimation of missing values in microarray data with least squares methods.
Bø, Trond Hellem; Dysvik, Bjarte; Jonassen, Inge
2004-02-20
Microarray experiments generate data sets with information on the expression levels of thousands of genes in a set of biological samples. Unfortunately, such experiments often produce multiple missing expression values, normally due to various experimental problems. As many algorithms for gene expression analysis require a complete data matrix as input, the missing values have to be estimated in order to analyze the available data. Alternatively, genes and arrays can be removed until no missing values remain. However, for genes or arrays with only a small number of missing values, it is desirable to impute those values. For the subsequent analysis to be as informative as possible, it is essential that the estimates for the missing gene expression values are accurate. A small amount of badly estimated missing values in the data might be enough for clustering methods, such as hierachical clustering or K-means clustering, to produce misleading results. Thus, accurate methods for missing value estimation are needed. We present novel methods for estimation of missing values in microarray data sets that are based on the least squares principle, and that utilize correlations between both genes and arrays. For this set of methods, we use the common reference name LSimpute. We compare the estimation accuracy of our methods with the widely used KNNimpute on three complete data matrices from public data sets by randomly knocking out data (labeling as missing). From these tests, we conclude that our LSimpute methods produce estimates that consistently are more accurate than those obtained using KNNimpute. Additionally, we examine a more classic approach to missing value estimation based on expectation maximization (EM). We refer to our EM implementations as EMimpute, and the estimate errors using the EMimpute methods are compared with those our novel methods produce. The results indicate that on average, the estimates from our best performing LSimpute method are at least as
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.
A fast and accurate frequency estimation algorithm for sinusoidal signal with harmonic components
NASA Astrophysics Data System (ADS)
Hu, Jinghua; Pan, Mengchun; Zeng, Zhidun; Hu, Jiafei; Chen, Dixiang; Tian, Wugang; Zhao, Jianqiang; Du, Qingfa
2016-10-01
Frequency estimation is a fundamental problem in many applications, such as traditional vibration measurement, power system supervision, and microelectromechanical system sensors control. In this paper, a fast and accurate frequency estimation algorithm is proposed to deal with low efficiency problem in traditional methods. The proposed algorithm consists of coarse and fine frequency estimation steps, and we demonstrate that it is more efficient than conventional searching methods to achieve coarse frequency estimation (location peak of FFT amplitude) by applying modified zero-crossing technique. Thus, the proposed estimation algorithm requires less hardware and software sources and can achieve even higher efficiency when the experimental data increase. Experimental results with modulated magnetic signal show that the root mean square error of frequency estimation is below 0.032 Hz with the proposed algorithm, which has lower computational complexity and better global performance than conventional frequency estimation methods.
Sample Size Requirements for Accurate Estimation of Squared Semi-Partial Correlation Coefficients.
ERIC Educational Resources Information Center
Algina, James; Moulder, Bradley C.; Moser, Barry K.
2002-01-01
Studied the sample size requirements for accurate estimation of squared semi-partial correlation coefficients through simulation studies. Results show that the sample size necessary for adequate accuracy depends on: (1) the population squared multiple correlation coefficient (p squared); (2) the population increase in p squared; and (3) the…
Do We Know Whether Researchers and Reviewers are Estimating Risk and Benefit Accurately?
Hey, Spencer Phillips; Kimmelman, Jonathan
2016-10-01
Accurate estimation of risk and benefit is integral to good clinical research planning, ethical review, and study implementation. Some commentators have argued that various actors in clinical research systems are prone to biased or arbitrary risk/benefit estimation. In this commentary, we suggest the evidence supporting such claims is very limited. Most prior work has imputed risk/benefit beliefs based on past behavior or goals, rather than directly measuring them. We describe an approach - forecast analysis - that would enable direct and effective measure of the quality of risk/benefit estimation. We then consider some objections and limitations to the forecasting approach.
Askalany, Ahmed A; Saha, Bidyut B
2017-03-15
Accurate estimation of the isosteric heat of adsorption is mandatory for a good modeling of adsorption processes. In this paper a thermodynamic formalism on adsorbed phase volume which is a function of adsorption pressure and temperature has been proposed for the precise estimation of the isosteric heat of adsorption. The estimated isosteric heat of adsorption using the new correlation has been compared with measured values of prudently selected several adsorbent-refrigerant pairs from open literature. Results showed that the proposed isosteric heat of adsorption correlation fits the experimentally measured values better than the Clausius-Clapeyron equation.
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.
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.
[Guidelines for Accurate and Transparent Health Estimates Reporting: the GATHER Statement].
Stevens, Gretchen A; Alkema, Leontine; Black, Robert E; Boerma, J Ties; Collins, Gary S; Ezzati, Majid; Grove, John T; Hogan, Daniel R; Hogan, Margaret C; Horton, Richard; Lawn, Joy E; Marušic, Ana; Mathers, Colin D; Murray, Christopher J L; Rudan, Igor; Salomon, Joshua A; Simpson, Paul J; Vos, Theo; Welch, Vivian
2017-01-01
Measurements of health indicators are rarely available for every population and period of interest, and available data may not be comparable. The Guidelines for Accurate and Transparent Health Estimates Reporting (GATHER) define best reporting practices for studies that calculate health estimates for multiple populations (in time or space) using multiple information sources. Health estimates that fall within the scope of GATHER include all quantitative population-level estimates (including global, regional, national, or subnational estimates) of health indicators, including indicators of health status, incidence and prevalence of diseases, injuries, and disability and functioning; and indicators of health determinants, including health behaviours and health exposures. GATHER comprises a checklist of 18 items that are essential for best reporting practice. A more detailed explanation and elaboration document, describing the interpretation and rationale of each reporting item along with examples of good reporting, is available on the GATHER website (http://gather-statement.org).
Damon, Bruce M; Heemskerk, Anneriet M; Ding, Zhaohua
2012-06-01
Fiber curvature is a functionally significant muscle structural property, but its estimation from diffusion-tensor magnetic resonance imaging 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 data sets 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-mm(3) voxel volume with isotropic resolution; 13.5-mm(3) 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 second-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.
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
Robust and accurate fundamental frequency estimation based on dominant harmonic components.
Nakatani, Tomohiro; Irino, Toshio
2004-12-01
This paper presents a new method for robust and accurate fundamental frequency (F0) estimation in the presence of background noise and spectral distortion. Degree of dominance and dominance spectrum are defined based on instantaneous frequencies. The degree of dominance allows one to evaluate the magnitude of individual harmonic components of the speech signals relative to background noise while reducing the influence of spectral distortion. The fundamental frequency is more accurately estimated from reliable harmonic components which are easy to select given the dominance spectra. Experiments are performed using white and babble background noise with and without spectral distortion as produced by a SRAEN filter. The results show that the present method is better than previously reported methods in terms of both gross and fine F0 errors.
Development of Star Tracker System for Accurate Estimation of Spacecraft Attitude
2009-12-01
TRACKER SYSTEM FOR ACCURATE ESTIMATION OF SPACECRAFT ATTITUDE by Jack A. Tappe December 2009 Thesis Co-Advisors: Jae Jun Kim Brij N... Brij N. Agrawal Co-Advisor Dr. Knox T. Millsaps Chairman, Department of Mechanical and Astronautical Engineering iv THIS PAGE...much with my studies here. I would like to especially thank Professors Barry Leonard, Brij Agrawal, Grand Master Shin, and Comrade Oleg Yakimenko
Simons, Craig J; Cobb, Loren; Davidson, Bradley S
2014-04-01
In vivo measurement of lumbar spine configuration is useful for constructing quantitative biomechanical models. Positional magnetic resonance imaging (MRI) accommodates a larger range of movement in most joints than conventional MRI and does not require a supine position. However, this is achieved at the expense of image resolution and contrast. As a result, quantitative research using positional MRI has required long reconstruction times and is sensitive to incorrectly identifying the vertebral boundary due to low contrast between bone and surrounding tissue in the images. We present a semi-automated method used to obtain digitized reconstructions of lumbar vertebrae in any posture of interest. This method combines a high-resolution reference scan with a low-resolution postural scan to provide a detailed and accurate representation of the vertebrae in the posture of interest. Compared to a criterion standard, translational reconstruction error ranged from 0.7 to 1.6 mm and rotational reconstruction error ranged from 0.3 to 2.6°. Intraclass correlation coefficients indicated high interrater reliability for measurements within the imaging plane (ICC 0.97-0.99). Computational efficiency indicates that this method may be used to compile data sets large enough to account for population variance, and potentially expand the use of positional MRI as a quantitative biomechanics research tool.
Hwang, Beomsoo; Jeon, Doyoung
2015-04-09
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.
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.
Xing, Li; Hang, Yijun; Xiong, Zhi; Liu, Jianye; Wan, Zhong
2016-01-01
This paper describes a disturbance acceleration adaptive estimate and correction approach for an attitude reference system (ARS) so as to improve the attitude estimate precision under vehicle movement conditions. The proposed approach depends on a Kalman filter, where the attitude error, the gyroscope zero offset error and the disturbance acceleration error are estimated. By switching the filter decay coefficient of the disturbance acceleration model in different acceleration modes, the disturbance acceleration is adaptively estimated and corrected, and then the attitude estimate precision is improved. The filter was tested in three different disturbance acceleration modes (non-acceleration, vibration-acceleration and sustained-acceleration mode, respectively) by digital simulation. Moreover, the proposed approach was tested in a kinematic vehicle experiment as well. Using the designed simulations and kinematic vehicle experiments, it has been shown that the disturbance acceleration of each mode can be accurately estimated and corrected. Moreover, compared with the complementary filter, the experimental results have explicitly demonstrated the proposed approach further improves the attitude estimate precision under vehicle movement conditions. PMID:27754469
Helb, Danica A; Tetteh, Kevin K A; Felgner, Philip L; Skinner, Jeff; Hubbard, Alan; Arinaitwe, Emmanuel; Mayanja-Kizza, Harriet; Ssewanyana, Isaac; Kamya, Moses R; Beeson, James G; Tappero, Jordan; Smith, David L; Crompton, Peter D; Rosenthal, Philip J; Dorsey, Grant; Drakeley, Christopher J; Greenhouse, Bryan
2015-08-11
Tools to reliably measure Plasmodium falciparum (Pf) exposure in individuals and communities are needed to guide and evaluate malaria control interventions. Serologic assays can potentially produce precise exposure estimates at low cost; however, current approaches based on responses to a few characterized antigens are not designed to estimate exposure in individuals. Pf-specific antibody responses differ by antigen, suggesting that selection of antigens with defined kinetic profiles will improve estimates of Pf exposure. To identify novel serologic biomarkers of malaria exposure, we evaluated responses to 856 Pf antigens by protein microarray in 186 Ugandan children, for whom detailed Pf exposure data were available. Using data-adaptive statistical methods, we identified combinations of antibody responses that maximized information on an individual's recent exposure. Responses to three novel Pf antigens accurately classified whether an individual had been infected within the last 30, 90, or 365 d (cross-validated area under the curve = 0.86-0.93), whereas responses to six antigens accurately estimated an individual's malaria incidence in the prior year. Cross-validated incidence predictions for individuals in different communities provided accurate stratification of exposure between populations and suggest that precise estimates of community exposure can be obtained from sampling a small subset of that community. In addition, serologic incidence predictions from cross-sectional samples characterized heterogeneity within a community similarly to 1 y of continuous passive surveillance. Development of simple ELISA-based assays derived from the successful selection strategy outlined here offers the potential to generate rich epidemiologic surveillance data that will be widely accessible to malaria control programs.
Patient-tailored plate for bone fixation and accurate 3D positioning in corrective osteotomy.
Dobbe, J G G; Vroemen, J C; Strackee, S D; Streekstra, G J
2013-02-01
A bone fracture may lead to malunion of bone segments, which gives discomfort to the patient and may lead to chronic pain, reduced function and finally to early osteoarthritis. Corrective osteotomy is a treatment option to realign the bone segments. In this procedure, the surgeon tries to improve alignment by cutting the bone at, or near, the fracture location and fixates the bone segments in an improved position, using a plate and screws. Three-dimensional positioning is very complex and difficult to plan, perform and evaluate using standard 2D fluoroscopy imaging. This study introduces a new technique that uses preoperative 3D imaging to plan positioning and design a patient-tailored fixation plate that only fits in one way and realigns the bone segments as planned. The method is evaluated using artificial bones and renders realignment highly accurate and very reproducible (d(err) < 1.2 ± 0.8 mm and φ(err) < 1.8° ± 2.1°). Application of a patient-tailored plate is expected to be of great value for future corrective osteotomy surgeries.
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.
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
Accurate estimates of age at maturity from the growth trajectories of fishes and other ectotherms.
Honsey, Andrew E; Staples, David F; Venturelli, Paul A
2017-01-01
Age at maturity (AAM) is a key life history trait that provides insight into ecology, evolution, and population dynamics. However, maturity data can be costly to collect or may not be available. Life history theory suggests that growth is biphasic for many organisms, with a change-point in growth occurring at maturity. If so, then it should be possible to use a biphasic growth model to estimate AAM from growth data. To test this prediction, we used the Lester biphasic growth model in a likelihood profiling framework to estimate AAM from length at age data. We fit our model to simulated growth trajectories to determine minimum data requirements (in terms of sample size, precision in length at age, and the cost to somatic growth of maturity) for accurate AAM estimates. We then applied our method to a large walleye Sander vitreus data set and show that our AAM estimates are in close agreement with conventional estimates when our model fits well. Finally, we highlight the potential of our method by applying it to length at age data for a variety of ectotherms. Our method shows promise as a tool for estimating AAM and other life history traits from contemporary and historical samples.
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
Van Derlinden, E; Bernaerts, K; Van Impe, J F
2008-11-30
Prediction of the microbial growth rate as a response to changing temperatures is an important aspect in the control of food safety and food spoilage. Accurate model predictions of the microbial evolution ask for correct model structures and reliable parameter values with good statistical quality. Given the widely accepted validity of the Cardinal Temperature Model with Inflection (CTMI) [Rosso, L., Lobry, J. R., Bajard, S. and Flandrois, J. P., 1995. Convenient model to describe the combined effects of temperature and pH on microbial growth, Applied and Environmental Microbiology, 61: 610-616], this paper focuses on the accurate estimation of its four parameters (T(min), T(opt), T(max) and micro(opt)) by applying the technique of optimal experiment design for parameter estimation (OED/PE). This secondary model describes the influence of temperature on the microbial specific growth rate from the minimum to the maximum temperature for growth. Dynamic temperature profiles are optimized within two temperature regions ([15 degrees C, 43 degrees C] and [15 degrees C, 45 degrees C]), focusing on the minimization of the parameter estimation (co)variance (D-optimal design). The optimal temperature profiles are implemented in a computer controlled bioreactor, and the CTMI parameters are identified from the resulting experimental data. Approximately equal CTMI parameter values were derived irrespective of the temperature region, except for T(max). The latter could only be estimated accurately from the optimal experiments within [15 degrees C, 45 degrees C]. This observation underlines the importance of selecting the upper temperature constraint for OED/PE as close as possible to the true T(max). Cardinal temperature estimates resulting from designs within [15 degrees C, 45 degrees C] correspond with values found in literature, are characterized by a small uncertainty error and yield a good result during validation. As compared to estimates from non-optimized dynamic
Rashid, Mamoon; Pain, Arnab
2013-01-01
Summary: READSCAN is a highly scalable parallel program to identify non-host sequences (of potential pathogen origin) and estimate their genome relative abundance in high-throughput sequence datasets. READSCAN accurately classified human and viral sequences on a 20.1 million reads simulated dataset in <27 min using a small Beowulf compute cluster with 16 nodes (Supplementary Material). Availability: http://cbrc.kaust.edu.sa/readscan Contact: arnab.pain@kaust.edu.sa or raeece.naeem@gmail.com Supplementary information: Supplementary data are available at Bioinformatics online. PMID:23193222
The estimation of tumor cell percentage for molecular testing by pathologists is not accurate.
Smits, Alexander J J; Kummer, J Alain; de Bruin, Peter C; Bol, Mijke; van den Tweel, Jan G; Seldenrijk, Kees A; Willems, Stefan M; Offerhaus, G Johan A; de Weger, Roel A; van Diest, Paul J; Vink, Aryan
2014-02-01
Molecular pathology is becoming more and more important in present day pathology. A major challenge for any molecular test is its ability to reliably detect mutations in samples consisting of mixtures of tumor cells and normal cells, especially when the tumor content is low. The minimum percentage of tumor cells required to detect genetic abnormalities is a major variable. Information on tumor cell percentage is essential for a correct interpretation of the result. In daily practice, the percentage of tumor cells is estimated by pathologists on hematoxylin and eosin (H&E)-stained slides, the reliability of which has been questioned. This study aimed to determine the reliability of estimated tumor cell percentages in tissue samples by pathologists. On 47 H&E-stained slides of lung tumors a tumor area was marked. The percentage of tumor cells within this area was estimated independently by nine pathologists, using categories of 0-5%, 6-10%, 11-20%, 21-30%, and so on, until 91-100%. As gold standard, the percentage of tumor cells was counted manually. On average, the range between the lowest and the highest estimate per sample was 6.3 categories. In 33% of estimates, the deviation from the gold standard was at least three categories. The mean absolute deviation was 2.0 categories (range between observers 1.5-3.1 categories). There was a significant difference between the observers (P<0.001). If 20% of tumor cells were considered the lower limit to detect a mutation, samples with an insufficient tumor cell percentage (<20%) would have been estimated to contain enough tumor cells in 27/72 (38%) observations, possibly causing false negative results. In conclusion, estimates of tumor cell percentages on H&E-stained slides are not accurate, which could result in misinterpretation of test results. Reliability could possibly be improved by using a training set with feedback.
Sansone, Giuseppe; Maschio, Lorenzo; Usvyat, Denis; Schütz, Martin; Karttunen, Antti
2016-01-07
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.
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}.
Magnetic gaps in organic tri-radicals: From a simple model to accurate estimates
NASA Astrophysics Data System (ADS)
Barone, Vincenzo; Cacelli, Ivo; Ferretti, Alessandro; Prampolini, Giacomo
2017-03-01
The calculation of the energy gap between the magnetic states of organic poly-radicals still represents a challenging playground for quantum chemistry, and high-level techniques are required to obtain accurate estimates. On these grounds, the aim of the present study is twofold. From the one side, it shows that, thanks to recent algorithmic and technical improvements, we are able to compute reliable quantum mechanical results for the systems of current fundamental and technological interest. From the other side, proper parameterization of a simple Hubbard Hamiltonian allows for a sound rationalization of magnetic gaps in terms of basic physical effects, unraveling the role played by electron delocalization, Coulomb repulsion, and effective exchange in tuning the magnetic character of the ground state. As case studies, we have chosen three prototypical organic tri-radicals, namely, 1,3,5-trimethylenebenzene, 1,3,5-tridehydrobenzene, and 1,2,3-tridehydrobenzene, which differ either for geometric or electronic structure. After discussing the differences among the three species and their consequences on the magnetic properties in terms of the simple model mentioned above, accurate and reliable values for the energy gap between the lowest quartet and doublet states are computed by means of the so-called difference dedicated configuration interaction (DDCI) technique, and the final results are discussed and compared to both available experimental and computational estimates.
NASA Astrophysics Data System (ADS)
Bengulescu, Marc; Blanc, Philippe; Boilley, Alexandre; Wald, Lucien
2017-02-01
This study investigates the characteristic time-scales of variability found in long-term time-series of daily means of estimates of surface solar irradiance (SSI). The study is performed at various levels to better understand the causes of variability in the SSI. First, the variability of the solar irradiance at the top of the atmosphere is scrutinized. Then, estimates of the SSI in cloud-free conditions as provided by the McClear model are dealt with, in order to reveal the influence of the clear atmosphere (aerosols, water vapour, etc.). Lastly, the role of clouds on variability is inferred by the analysis of in-situ measurements. A description of how the atmosphere affects SSI variability is thus obtained on a time-scale basis. The analysis is also performed with estimates of the SSI provided by the satellite-derived HelioClim-3 database and by two numerical weather re-analyses: ERA-Interim and MERRA2. It is found that HelioClim-3 estimates render an accurate picture of the variability found in ground measurements, not only globally, but also with respect to individual characteristic time-scales. On the contrary, the variability found in re-analyses correlates poorly with all scales of ground measurements variability.
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.
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
NASA Astrophysics Data System (ADS)
Granata, Daniele; Carnevale, Vincenzo
2016-08-01
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.
MIDAS robust trend estimator for accurate GPS station velocities without step detection.
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.
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.
MIDAS robust trend estimator for accurate GPS station velocities without step detection
Kreemer, Corné; Hammond, William C.; Gazeaux, Julien
2016-01-01
Abstract 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. PMID:27668140
NASA Astrophysics Data System (ADS)
Gibbons, S. J.; Pabian, F.; Näsholm, S. P.; Kværna, T.; Mykkeltveit, S.
2017-01-01
velocity gradients reduce the residuals, the relative location uncertainties and the sensitivity to the combination of stations used. The traveltime gradients appear to be overestimated for the regional phases, and teleseismic relative location estimates are likely to be more accurate despite an apparent lower precision. Calibrations for regional phases are essential given that smaller magnitude events are likely not to be recorded teleseismically. We discuss the implications for the absolute event locations. Placing the 2006 event under a local maximum of overburden at 41.293°N, 129.105°E would imply a location of 41.299°N, 129.075°E for the January 2016 event, providing almost optimal overburden for the later four events.
NASA Astrophysics Data System (ADS)
Gibbons, S. J.; Pabian, F.; Näsholm, S. P.; Kværna', T.; Mykkeltveit, S.
2016-10-01
modified velocity gradients reduce the residuals, the relative location uncertainties, and the sensitivity to the combination of stations used. The traveltime gradients appear to be overestimated for the regional phases, and teleseismic relative location estimates are likely to be more accurate despite an apparent lower precision. Calibrations for regional phases are essential given that smaller magnitude events are likely not to be recorded teleseismically. We discuss the implications for the absolute event locations. Placing the 2006 event under a local maximum of overburden at 41.293°N, 129.105°E would imply a location of 41.299°N, 129.075°E for the January 2016 event, providing almost optimal overburden for the later four events.
High-accurate nonlocal timing and positioning using entangled photon pairs
NASA Astrophysics Data System (ADS)
Valencia Gonzalez, Alejandra C.
One of the most surprising consequences of quantum mechanics is the concept of entanglement. This concept has intrigued the scientific community since it was first proposed by Einstein, Podolsky and Rosen in 1935 because of its connection to fundamental aspects regarding our conception of the universe. Nowadays, there are still open questions about the fundamental issues of quantum mechanics. Nevertheless, the unique characteristics of entanglement have been proposed for practical applications in the last years. Spontaneous Parametric Down Conversion (SPDC) has been recognized as a convenient source of entangled photon pairs. SPDC is a nonlinear optical process in which a pump laser beam is shone into a nonlinear crystal and occasionally one pump photon is down-converted to a pair of lower frequency photons that are entangled. Two photons in an entangled state are characterized by a single two-photon effective wavefunction, or Biphoton. They cannot be considered as the simple juxtaposition of two individual systems. This is a consequence of the quantum correlations between the two photons and implies that a measurement in one of the subsystems affects the total state of the composite system and, therefore, affects the output of a measurement performed in the other photon. The purpose of this dissertation is to show the potential of entangled photon pairs for high-accurate timing and positioning measurements. The entangled nature of the two-photon states allows, in principle, precise space-time correlation measurements to the femtosecond level, providing the physical foundations for high-accurate nonlocal distant clock synchronization. In this dissertation, the proof-of-principle demonstration of a "one-way" distant clock synchronization protocol is presented. The novel method is based on the measurements of the second order correlation function of entangled photon pairs. An experimental study of the behavior of the Biphoton when it travels through a dispersive
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.
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.
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 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.
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.
Wang, Xu; Zhang, Chao; Wang, Chen; Huang, Jia Zhang; Ma, Xin
2016-01-01
INTRODUCTION Anatomical markers can help to guide lag screw placement during surgery for internal fixation of fifth metatarsal base fractures. This study aimed to identify the optimal anatomical markers and thus reduce radiation exposure. METHODS A total of 50 patients in Huashan Hospital, Shanghai, China, who underwent oblique foot radiography in the lateral position were randomly selected. The angles between the fifth metatarsal axis and cuboid articular surface were measured to determine the optimal lag screw placement relative to anatomical markers. RESULTS The line connecting the styloid process of the fifth metatarsal base with the second metatarsophalangeal (MTP) joint intersected with the fifth metatarsal base fracture line at an angle of 86.85° ± 5.44°. The line connecting the fifth metatarsal base styloid with the third and fourth MTP joints intersected with the fracture line at angles of 93.28° ± 5.24° and 100.95° ± 5.00°, respectively. The proximal articular surface of the fifth metatarsal base intersected with the line connecting the styloid process of the fifth metatarsal base with the second, third and fourth MTP joints at angles of 24.02° ± 4.77°, 30.79° ± 4.53° and 38.08° ± 4.54°, respectively. CONCLUSION The fifth metatarsal base styloid and third MTP joint can be used as anatomical markers for lag screw placement in fractures involving the fifth tarsometatarsal joint. The connection line, which is normally perpendicular to the fracture line, provides sufficient mechanical stability to facilitate accurate screw placement. The use of these anatomical markers could help to reduce unnecessary radiation exposure for patients and medical staff. PMID:26767892
Accurate and Robust Attitude Estimation Using MEMS Gyroscopes and a Monocular Camera
NASA Astrophysics Data System (ADS)
Kobori, Norimasa; Deguchi, Daisuke; Takahashi, Tomokazu; Ide, Ichiro; Murase, Hiroshi
In order to estimate accurate rotations of mobile robots and vehicle, we propose a hybrid system which combines a low-cost monocular camera with gyro sensors. Gyro sensors have drift errors that accumulate over time. On the other hand, a camera cannot obtain the rotation continuously in the case where feature points cannot be extracted from images, although the accuracy is better than gyro sensors. To solve these problems we propose a method for combining these sensors based on Extended Kalman Filter. The errors of the gyro sensors are corrected by referring to the rotations obtained from the camera. In addition, by using the reliability judgment of camera rotations and devising the state value of the Extended Kalman Filter, even when the rotation is not continuously observable from the camera, the proposed method shows a good performance. Experimental results showed the effectiveness of the proposed method.
Houairi, Kamel; Cassaing, Frédéric
2009-12-01
Two-wavelength interferometry combines measurement at two wavelengths lambda(1) and lambda(2) in order to increase the unambiguous range (UR) for the measurement of an optical path difference. With the usual algorithm, the UR is equal to the synthetic wavelength Lambda=lambda(1)lambda(2)/|lambda(1)-lambda(2)|, and the accuracy is a fraction of Lambda. We propose here a new analytical algorithm based on arithmetic properties, allowing estimation of the absolute fringe order of interference in a noniterative way. This algorithm has nice properties compared with the usual algorithm: it is at least as accurate as the most accurate measurement at one wavelength, whereas the UR is extended to several times the synthetic wavelength. The analysis presented shows how the actual UR depends on the wavelengths and different sources of error. The simulations presented are confirmed by experimental results, showing that the new algorithm has enabled us to reach an UR of 17.3 microm, much larger than the synthetic wavelength, which is only Lambda=2.2 microm. Applications to metrology and fringe tracking are discussed.
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
Numerical Estimation in Children for Both Positive and Negative Numbers
ERIC Educational Resources Information Center
Brez, Caitlin C.; Miller, Angela D.; Ramirez, Erin M.
2016-01-01
Numerical estimation has been used to study how children mentally represent numbers for many years (e.g., Siegler & Opfer, 2003). However, these studies have always presented children with positive numbers and positive number lines. Children's mental representation of negative numbers has never been addressed. The present study tested children…
Single-shot camera position estimation by crossed grating imaging
NASA Astrophysics Data System (ADS)
Juarez-Salazar, Rigoberto; Gaxiola, Leopoldo N.; Diaz-Ramirez, Victor H.
2017-01-01
A simple method to estimate the position of a camera device with respect to a reference plane is proposed. The method utilizes a crossed grating in the reference plane and exploits the coordinate transformation induced by the perspective projection. If the focal length is available, the position of the camera can be estimated with a single-shot. Otherwise, the focal length can be firstly estimated from few frames captured at different known displacements. The theoretical principles of the proposed method are given and the functionality of the approach is exhibited by correcting perspective-distorted images. The proposed method is computationally efficient and highly appropriate to be used in dynamic measurement systems.
Single-point position estimation in interplanetary trajectories using star trackers
NASA Astrophysics Data System (ADS)
Mortari, Daniele; Conway, Dylan
2016-11-01
This study provides a single-point position estimation technique for interplanetary missions by observing visible planets using star trackers. Closed-form least-squares solution is obtained by minimizing the sum of the expected object-space squared distance errors. A weighted least-squares solution is provided by an iterative procedure. The weights are evaluated using the distances to the planets estimated by the least-squares solution. It is shown that the weighted approach only requires one iteration to converge and results in significant accuracy gains compared to simple least squares approach. The light-time correction is taken into account while the star-light aberration cannot be implemented in single-point estimation as it requires knowledge of the observer velocity. The proposed method is numerically validated through a statistical scenario as follows. A three-dimensional grid of test cases is generated: two dimensions sweep through the ecliptic plane and the third dimension sweeps through time from January 1, 2018 to January 1, 2043 in 5-year increments. The observer position is estimated at each test case and the estimate error is recorded. The results obtained show that a large majority of positions are well suited to position estimation by using star trackers pointing to visible planets, and reliable and accurate single-point position estimations can be provided in interplanetary missions. The proposed approach is suitable to be used to initiate a filtering technique to increase the estimation accuracy.
The potential of more accurate InSAR covariance matrix estimation for land cover mapping
NASA Astrophysics Data System (ADS)
Jiang, Mi; Yong, Bin; Tian, Xin; Malhotra, Rakesh; Hu, Rui; Li, Zhiwei; Yu, Zhongbo; Zhang, Xinxin
2017-04-01
Synthetic aperture radar (SAR) and Interferometric SAR (InSAR) provide both structural and electromagnetic information for the ground surface and therefore have been widely used for land cover classification. However, relatively few studies have developed analyses that investigate SAR datasets over richly textured areas where heterogeneous land covers exist and intermingle over short distances. One of main difficulties is that the shapes of the structures in a SAR image cannot be represented in detail as mixed pixels are likely to occur when conventional InSAR parameter estimation methods are used. To solve this problem and further extend previous research into remote monitoring of urban environments, we address the use of accurate InSAR covariance matrix estimation to improve the accuracy of land cover mapping. The standard and updated methods were tested using the HH-polarization TerraSAR-X dataset and compared with each other using the random forest classifier. A detailed accuracy assessment complied for six types of surfaces shows that the updated method outperforms the standard approach by around 9%, with an overall accuracy of 82.46% over areas with rich texture in Zhuhai, China. This paper demonstrates that the accuracy of land cover mapping can benefit from the 3 enhancement of the quality of the observations in addition to classifiers selection and multi-source data ingratiation reported in previous studies.
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
Greater contrast in Martian hydrological history from more accurate estimates of paleodischarge
NASA Astrophysics Data System (ADS)
Jacobsen, R. E.; Burr, D. M.
2016-09-01
Correlative width-discharge relationships from the Missouri River Basin are commonly used to estimate fluvial paleodischarge on Mars. However, hydraulic geometry provides alternative, and causal, width-discharge relationships derived from broader samples of channels, including those in reduced-gravity (submarine) environments. Comparison of these relationships implies that causal relationships from hydraulic geometry should yield more accurate and more precise discharge estimates. Our remote analysis of a Martian-terrestrial analog channel, combined with in situ discharge data, substantiates this implication. Applied to Martian features, these results imply that paleodischarges of interior channels of Noachian-Hesperian (~3.7 Ga) valley networks have been underestimated by a factor of several, whereas paleodischarges for smaller fluvial deposits of the Late Hesperian-Early Amazonian (~3.0 Ga) have been overestimated. Thus, these new paleodischarges significantly magnify the contrast between early and late Martian hydrologic activity. Width-discharge relationships from hydraulic geometry represent validated tools for quantifying fluvial input near candidate landing sites of upcoming missions.
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.
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.
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
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 optical flow field estimation using mechanical properties of soft tissues
NASA Astrophysics Data System (ADS)
Mehrabian, Hatef; Karimi, Hirad; Samani, Abbas
2009-02-01
A novel optical flow based technique is presented in this paper to measure the nodal displacements of soft tissue undergoing large deformations. In hyperelasticity imaging, soft tissues maybe compressed extensively [1] and the deformation may exceed the number of pixels ordinary optical flow approaches can detect. Furthermore in most biomedical applications there is a large amount of image information that represent the geometry of the tissue and the number of tissue types present in the organ of interest. Such information is often ignored in applications such as image registration. In this work we incorporate the information pertaining to soft tissue mechanical behavior (Neo-Hookean hyperelastic model is used here) in addition to the tissue geometry before compression into a hierarchical Horn-Schunck optical flow method to overcome this large deformation detection weakness. Applying the proposed method to a phantom using several compression levels proved that it yields reasonably accurate displacement fields. Estimated displacement results of this phantom study obtained for displacement fields of 85 pixels/frame and 127 pixels/frame are reported and discussed in this paper.
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.
How accurately can we estimate energetic costs in a marine top predator, the king penguin?
Halsey, Lewis G; Fahlman, Andreas; Handrich, Yves; Schmidt, Alexander; Woakes, Anthony J; Butler, Patrick J
2007-01-01
King penguins (Aptenodytes patagonicus) are one of the greatest consumers of marine resources. However, while their influence on the marine ecosystem is likely to be significant, only an accurate knowledge of their energy demands will indicate their true food requirements. Energy consumption has been estimated for many marine species using the heart rate-rate of oxygen consumption (f(H) - V(O2)) technique, and the technique has been applied successfully to answer eco-physiological questions. However, previous studies on the energetics of king penguins, based on developing or applying this technique, have raised a number of issues about the degree of validity of the technique for this species. These include the predictive validity of the present f(H) - V(O2) equations across different seasons and individuals and during different modes of locomotion. In many cases, these issues also apply to other species for which the f(H) - V(O2) technique has been applied. In the present study, the accuracy of three prediction equations for king penguins was investigated based on validity studies and on estimates of V(O2) from published, field f(H) data. The major conclusions from the present study are: (1) in contrast to that for walking, the f(H) - V(O2) relationship for swimming king penguins is not affected by body mass; (2) prediction equation (1), log(V(O2) = -0.279 + 1.24log(f(H) + 0.0237t - 0.0157log(f(H)t, derived in a previous study, is the most suitable equation presently available for estimating V(O2) in king penguins for all locomotory and nutritional states. A number of possible problems associated with producing an f(H) - V(O2) relationship are discussed in the present study. Finally, a statistical method to include easy-to-measure morphometric characteristics, which may improve the accuracy of f(H) - V(O2) prediction equations, is explained.
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
Use of optoelectronic tweezers in manufacturing—accurate solder bead positioning
NASA Astrophysics Data System (ADS)
Zhang, Shuailong; Liu, Yongpeng; Juvert, Joan; Tian, Pengfei; Navarro, Jean-Claude; Cooper, Jonathan M.; Neale, Steven L.
2016-11-01
In this work, we analyze the use of optoelectronic tweezers (OETs) to manipulate 45 μm diameter Sn62Pb36Ag2 solder beads with light-induced dielectrophoresis force and we demonstrate high positioning accuracy. It was found that the positional deviation of the solder beads increases with the increase of the trap size. To clarify the underlying mechanism, simulations based on the integration of the Maxwell stress tensor were used to study the force profiles of OET traps with different sizes. It was found that the solder beads felt a 0.1 nN static friction or stiction force due to electrical forces pulling them towards the surface and that this force is not dependent on the size of the trap. The stiction limits the positioning accuracy; however, we show that by choosing a trap that is just larger than the solder bead sub-micron positional accuracy can be achieved.
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.
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
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.
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.
How accurate are X-rays to check NG tube positioning?
Rollins, Hazel; Arnold-Jellis, Jacqui; Taylor, Andrew
The position of a nasogastric tube is vitally important for patients' safety and wellbeing. X-rays are sometimes used to determine whether nasogastric tubes are correctly positioned, but how effective are they? To find out, we undertook an audit of data from the radiology information system, collating all reports that included the word "nasogastric" from 1 January 2010 until 15 May 2011. For each report the description of tube position was put in one of six categories from "fully compliant with NPSA [National Patient Safety Agency] requirements" to "image missing". In a second, smaller dataset (cases in which some anatomy was described), we investigated the position of the tube tip as classified using descriptions from radiology reports. None of the reports contained all of the information required to comply with NSPA's (2011) guidelines, but most nasogastric tubes (70%) were in the stomach. Twenty-one per cent were reported as being in the oesophagus; advice varied from advancing it further (if uncomplicated) to removing it (if coiled or looped). Four per cent of tubes were seen in the airways (lung or bronchus) with advice for immediate removal.
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.
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.
Muscle spindle responses in man to changes in load during accurate position maintenance.
Burke, D; Hagbarth, K E; Löfstedt, L
1978-03-01
1. Single unit and multi-unit recordings of muscle spindle activity were made from the peroneal nerves of human subjects. While the subjects attempted to maintain a constant ankle joint position, an external load on the receptor-bearing muscle was altered unexpectedly. 2. The spindle discharge produced by a sudden increase in load was of similar strength when the receptor-bearing muscle was relaxed as when it was contracting at the moment of the impact. A motor response at a latency consistent with a spinal reflex mechanism occurred only when the muscle was contracting. It is concluded that the potentiation of the reflex mechanism during contraction was not due primarily to a fusimotor action. 3. Sudden decrease in load produced a pause in spindle discharge followed by a pause in on-going e.m.g. activity at a latency consistent with spinal reflex mechanisms. 4. Slow changes in load produced parallel changes in e.m.g. and spindle discharge. It is suggested that the voluntary effort involved in maintaining joint position in the face of gradually changing loads results in corticospinal activity adjusted in strength to the opposing torque and operating on alpha and gamma motoneurones in parallel.
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.
NASA Astrophysics Data System (ADS)
Yu, Xiaolin; Zhang, Shaoqing; Lin, Xiaopei; Li, Mingkui
2017-03-01
The uncertainties in values of coupled model parameters are an important source of model bias that causes model climate drift. The values can be calibrated by a parameter estimation procedure that projects observational information onto model parameters. The signal-to-noise ratio of error covariance between the model state and the parameter being estimated directly determines whether the parameter estimation succeeds or not. With a conceptual climate model that couples the stochastic atmosphere and slow-varying ocean, this study examines the sensitivity of state-parameter covariance on the accuracy of estimated model states in different model components of a coupled system. Due to the interaction of multiple timescales, the fast-varying atmosphere
with a chaotic nature is the major source of the inaccuracy of estimated state-parameter covariance. Thus, enhancing the estimation accuracy of atmospheric states is very important for the success of coupled model parameter estimation, especially for the parameters in the air-sea interaction processes. The impact of chaotic-to-periodic ratio in state variability on parameter estimation is also discussed. This simple model study provides a guideline when real observations are used to optimize model parameters in a coupled general circulation model for improving climate analysis and predictions.
A signal strength priority based position estimation for mobile platforms
NASA Astrophysics Data System (ADS)
Kalgikar, Bhargav; Akopian, David; Chen, Philip
2010-01-01
Global Positioning System (GPS) products help to navigate while driving, hiking, boating, and flying. GPS uses a combination of orbiting satellites to determine position coordinates. This works great in most outdoor areas, but the satellite signals are not strong enough to penetrate inside most indoor environments. As a result, a new strain of indoor positioning technologies that make use of 802.11 wireless LANs (WLAN) is beginning to appear on the market. In WLAN positioning the system either monitors propagation delays between wireless access points and wireless device users to apply trilateration techniques or it maintains the database of location-specific signal fingerprints which is used to identify the most likely match of incoming signal data with those preliminary surveyed and saved in the database. In this paper we investigate the issue of deploying WLAN positioning software on mobile platforms with typically limited computational resources. We suggest a novel received signal strength rank order based location estimation system to reduce computational loads with a robust performance. The proposed system performance is compared to conventional approaches.
Accurate positioning for head and neck cancer patients using 2D and 3D image guidance
Kang, Hyejoo; Lovelock, Dale M.; Yorke, Ellen D.; Kriminiski, Sergey; Lee, Nancy; Amols, Howard I.
2011-01-01
Our goal is to determine an optimized image-guided setup by comparing setup errors determined by two-dimensional (2D) and three-dimensional (3D) image guidance for head and neck cancer (HNC) patients immobilized by customized thermoplastic masks. Nine patients received weekly imaging sessions, for a total of 54, throughout treatment. Patients were first set up by matching lasers to surface marks (initial) and then translationally corrected using manual registration of orthogonal kilovoltage (kV) radiographs with DRRs (2D-2D) on bony anatomy. A kV cone beam CT (kVCBCT) was acquired and manually registered to the simulation CT using only translations (3D-3D) on the same bony anatomy to determine further translational corrections. After treatment, a second set of kVCBCT was acquired to assess intrafractional motion. Averaged over all sessions, 2D-2D registration led to translational corrections from initial setup of 3.5 ± 2.2 (range 0–8) mm. The addition of 3D-3D registration resulted in only small incremental adjustment (0.8 ± 1.5 mm). We retrospectively calculated patient setup rotation errors using an automatic rigid-body algorithm with 6 degrees of freedom (DoF) on regions of interest (ROI) of in-field bony anatomy (mainly the C2 vertebral body). Small rotations were determined for most of the imaging sessions; however, occasionally rotations > 3° were observed. The calculated intrafractional motion with automatic registration was < 3.5 mm for eight patients, and < 2° for all patients. We conclude that daily manual 2D-2D registration on radiographs reduces positioning errors for mask-immobilized HNC patients in most cases, and is easily implemented. 3D-3D registration adds little improvement over 2D-2D registration without correcting rotational errors. We also conclude that thermoplastic masks are effective for patient immobilization. PMID:21330971
Klassen, Tara D.; Simpson, Lisa A.; Lim, Shannon B.; Louie, Dennis R.; Parappilly, Beena; Sakakibara, Brodie M.; Zbogar, Dominik
2016-01-01
Background As physical activity in people poststroke is low, devices that monitor and provide feedback of walking activity provide motivation to engage in exercise and may assist rehabilitation professionals in auditing walking activity. However, most feedback devices are not accurate at slow walking speeds. Objective This study assessed the accuracy of one accelerometer to measure walking steps of community-dwelling individuals poststroke. Design This was a cross-sectional study. Methods Two accelerometers were positioned on the nonparetic waist and ankle of participants (N=43), and walking steps from these devices were recorded at 7 speeds (0.3–0.9 m/s) and compared with video recordings (gold standard). Results When positioned at the waist, the accelerometer had more than 10% error at all speeds, except 0.8 and 0.9 m/s, and numerous participants recorded zero steps at 0.3 to 0.5 m/s. The device had 10% or less error when positioned at the ankle for all speeds between 0.4 and 0.9 m/s. Limitations Some participants were unable to complete the faster walking speeds due to their walking impairments and inability to maintain the requested walking speed. Conclusions Although not recommended by the manufacturer, positioning the accelerometer at the ankle (compared with the waist) may fill a long-standing need for a readily available device that provides accurate feedback for the altered and slow walking patterns that occur with stroke. PMID:26251478
Children Can Accurately Monitor and Control Their Number-Line Estimation Performance
ERIC Educational Resources Information Center
Wall, Jenna L.; Thompson, Clarissa A.; Dunlosky, John; Merriman, William E.
2016-01-01
Accurate monitoring and control are essential for effective self-regulated learning. These metacognitive abilities may be particularly important for developing math skills, such as when children are deciding whether a math task is difficult or whether they made a mistake on a particular item. The present experiments investigate children's ability…
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 ...
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.
Twin-beam real-time position estimation of micro-objects in 3D
NASA Astrophysics Data System (ADS)
Gurtner, Martin; Zemánek, Jiří
2016-12-01
Various optical methods for measuring positions of micro-objects in 3D have been reported in the literature. Nevertheless, the majority of them are not suitable for real-time operation, which is needed, for example, for feedback position control. In this paper, we present a method for real-time estimation of the position of micro-objects in 3D1; the method is based on twin-beam illumination and requires only a very simple hardware setup whose essential part is a standard image sensor without any lens. The performance of the proposed method is tested during a micro-manipulation task in which the estimated position served as feedback for the controller. The experiments show that the estimate is accurate to within ∼3 μm in the lateral position and ∼7 μm in the axial distance with the refresh rate of 10 Hz. Although the experiments are done using spherical objects, the presented method could be modified to handle non-spherical objects as well.
Bayesian parameter estimation of a k-ε model for accurate jet-in-crossflow simulations
Ray, Jaideep; Lefantzi, Sophia; Arunajatesan, Srinivasan; Dechant, Lawrence
2016-05-31
Reynolds-averaged Navier–Stokes models are not very accurate for high-Reynolds-number compressible jet-in-crossflow interactions. The inaccuracy arises from the use of inappropriate model parameters and model-form errors in the Reynolds-averaged Navier–Stokes model. In this study, the hypothesis is pursued that Reynolds-averaged Navier–Stokes predictions can be significantly improved by using parameters inferred from experimental measurements of a supersonic jet interacting with a transonic crossflow.
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.
Accurate liability estimation improves power in ascertained case-control studies.
Weissbrod, Omer; Lippert, Christoph; Geiger, Dan; Heckerman, David
2015-04-01
Linear mixed models (LMMs) have emerged as the method of choice for confounded genome-wide association studies. However, the performance of LMMs in nonrandomly ascertained case-control studies deteriorates with increasing sample size. We propose a framework called LEAP (liability estimator as a phenotype; https://github.com/omerwe/LEAP) that tests for association with estimated latent values corresponding to severity of phenotype, and we demonstrate that this can lead to a substantial power increase.
Robust and Accurate Vision-Based Pose Estimation Algorithm Based on Four Coplanar Feature Points
Zhang, Zimiao; Zhang, Shihai; Li, Qiu
2016-01-01
Vision-based pose estimation is an important application of machine vision. Currently, analytical and iterative methods are used to solve the object pose. The analytical solutions generally take less computation time. However, the analytical solutions are extremely susceptible to noise. The iterative solutions minimize the distance error between feature points based on 2D image pixel coordinates. However, the non-linear optimization needs a good initial estimate of the true solution, otherwise they are more time consuming than analytical solutions. Moreover, the image processing error grows rapidly with measurement range increase. This leads to pose estimation errors. All the reasons mentioned above will cause accuracy to decrease. To solve this problem, a novel pose estimation method based on four coplanar points is proposed. Firstly, the coordinates of feature points are determined according to the linear constraints formed by the four points. The initial coordinates of feature points acquired through the linear method are then optimized through an iterative method. Finally, the coordinate system of object motion is established and a method is introduced to solve the object pose. The growing image processing error causes pose estimation errors the measurement range increases. Through the coordinate system, the pose estimation errors could be decreased. The proposed method is compared with two other existing methods through experiments. Experimental results demonstrate that the proposed method works efficiently and stably. PMID:27999338
NASA Astrophysics Data System (ADS)
Wang, Benfeng; Jakobsen, Morten; Wu, Ru-Shan; Lu, Wenkai; Chen, Xiaohong
2017-03-01
Full waveform inversion (FWI) has been regarded as an effective tool to build the velocity model for the following pre-stack depth migration. Traditional inversion methods are built on Born approximation and are initial model dependent, while this problem can be avoided by introducing Transmission matrix (T-matrix), because the T-matrix includes all orders of scattering effects. The T-matrix can be estimated from the spatial aperture and frequency bandwidth limited seismic data using linear optimization methods. However the full T-matrix inversion method (FTIM) is always required in order to estimate velocity perturbations, which is very time consuming. The efficiency can be improved using the previously proposed inverse thin-slab propagator (ITSP) method, especially for large scale models. However, the ITSP method is currently designed for smooth media, therefore the estimation results are unsatisfactory when the velocity perturbation is relatively large. In this paper, we propose a domain decomposition method (DDM) to improve the efficiency of the velocity estimation for models with large perturbations, as well as guarantee the estimation accuracy. Numerical examples for smooth Gaussian ball models and a reservoir model with sharp boundaries are performed using the ITSP method, the proposed DDM and the FTIM. The estimated velocity distributions, the relative errors and the elapsed time all demonstrate the validity of the proposed DDM.
Kim, Dohyun; Lee, Jongshill; Park, Hoon Ki; Jang, Dong Pyo; Song, Soohwa; Cho, Baek Hwan; Jung, Yoo-Suk; Park, Rae-Woong; Joo, Nam-Seok; Kim, In Young
2016-08-24
The purpose of the study is to analyse how the standard of resting metabolic rate (RMR) affects estimation of the metabolic equivalent of task (MET) using an accelerometer. In order to investigate the effect on estimation according to intensity of activity, comparisons were conducted between the 3.5 ml O2 · kg(-1) · min(-1) and individually measured resting VO2 as the standard of 1 MET. MET was estimated by linear regression equations that were derived through five-fold cross-validation using 2 types of MET values and accelerations; the accuracy of estimation was analysed through cross-validation, Bland and Altman plot, and one-way ANOVA test. There were no significant differences in the RMS error after cross-validation. However, the individual RMR-based estimations had as many as 0.5 METs of mean difference in modified Bland and Altman plots than RMR of 3.5 ml O2 · kg(-1) · min(-1). Finally, the results of an ANOVA test indicated that the individual RMR-based estimations had less significant differences between the reference and estimated values at each intensity of activity. In conclusion, the RMR standard is a factor that affects accurate estimation of METs by acceleration; therefore, RMR requires individual specification when it is used for estimation of METs using an accelerometer.
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.
Goudar, Chetan T
2011-10-01
We have identified an error in the published integral form of the modified Michaelis-Menten equation that accounts for endogenous substrate production. The correct solution is presented and the error in both the substrate concentration, S, and the kinetic parameters Vm , Km , and R resulting from the incorrect solution was characterized. The incorrect integral form resulted in substrate concentration errors as high as 50% resulting in 7-50% error in kinetic parameter estimates. To better reflect experimental scenarios, noise containing substrate depletion data were analyzed by both the incorrect and correct integral equations. While both equations resulted in identical fits to substrate depletion data, the final estimates of Vm , Km , and R were different and Km and R estimates from the incorrect integral equation deviated substantially from the actual values. Another observation was that at R = 0, the incorrect integral equation reduced to the correct form of the Michaelis-Menten equation. We believe this combination of excellent fits to experimental data, albeit with incorrect kinetic parameter estimates, and the reduction to the Michaelis-Menten equation at R = 0 is primarily responsible for the incorrectness to go unnoticed. However, the resulting error in kinetic parameter estimates will lead to incorrect biological interpretation and we urge the use of the correct integral form presented in this study.
Alpha's standard error (ASE): an accurate and precise confidence interval estimate.
Duhachek, Adam; Lacobucci, Dawn
2004-10-01
This research presents the inferential statistics for Cronbach's coefficient alpha on the basis of the standard statistical assumption of multivariate normality. The estimation of alpha's standard error (ASE) and confidence intervals are described, and the authors analytically and empirically investigate the effects of the components of these equations. The authors then demonstrate the superiority of this estimate compared with previous derivations of ASE in a separate Monte Carlo simulation. The authors also present a sampling error and test statistic for a test of independent sample alphas. They conclude with a recommendation that all alpha coefficients be reported in conjunction with standard error or confidence interval estimates and offer SAS and SPSS programming codes for easy implementation.
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.
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.
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
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.
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.
Xiang, G.; Ferson, S.; Ginzburg, L.; Longpré, L.; Mayorga, E.; Kosheleva, O.
2013-01-01
To preserve privacy, the original data points (with exact values) are replaced by boxes containing each (inaccessible) data point. This privacy-motivated uncertainty leads to uncertainty in the statistical characteristics computed based on this data. In a previous paper, we described how to minimize this uncertainty under the assumption that we use the same standard statistical estimates for the desired characteristics. In this paper, we show that we can further decrease the resulting uncertainty if we allow fuzzy-motivated weighted estimates, and we explain how to optimally select the corresponding weights. PMID:25187183
Accurate and unbiased estimation of power-law exponents from single-emitter blinking data.
Hoogenboom, Jacob P; den Otter, Wouter K; Offerhaus, Herman L
2006-11-28
Single emitter blinking with a power-law distribution for the on and off times has been observed on a variety of systems including semiconductor nanocrystals, conjugated polymers, fluorescent proteins, and organic fluorophores. The origin of this behavior is still under debate. Reliable estimation of power exponents from experimental data is crucial in validating the various models under consideration. We derive a maximum likelihood estimator for power-law distributed data and analyze its accuracy as a function of data set size and power exponent both analytically and numerically. Results are compared to least-squares fitting of the double logarithmically transformed probability density. We demonstrate that least-squares fitting introduces a severe bias in the estimation result and that the maximum likelihood procedure is superior in retrieving the correct exponent and reducing the statistical error. For a data set as small as 50 data points, the error margins of the maximum likelihood estimator are already below 7%, giving the possibility to quantify blinking behavior when data set size is limited, e.g., due to photobleaching.
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
Satellite-map position estimation for the Mars rover
NASA Technical Reports Server (NTRS)
Hayashi, Akira; Dean, Thomas
1989-01-01
A method for locating the Mars rover using an elevation map generated from satellite data is described. In exploring its environment, the rover is assumed to generate a local rover-centered elevation map that can be used to extract information about the relative position and orientation of landmarks corresponding to local maxima. These landmarks are integrated into a stochastic map which is then matched with the satellite map to obtain an estimate of the robot's current location. The landmarks are not explicitly represented in the satellite map. The results of the matching algorithm correspond to a probabilistic assessment of whether or not the robot is located within a given region of the satellite map. By assigning a probabilistic interpretation to the information stored in the satellite map, researchers are able to provide a precise characterization of the results computed by the matching algorithm.
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
Do hand-held calorimeters provide reliable and accurate estimates of resting metabolic rate?
Van Loan, Marta D
2007-12-01
This paper provides an overview of a new technique for indirect calorimetry and the assessment of resting metabolic rate. Information from the research literature includes findings on the reliability and validity of a new hand-held indirect calorimeter as well as use in clinical and field settings. Research findings to date are of mixed results. The MedGem instrument has provided more consistent results when compared to the Douglas bag method of measuring metabolic rate. The BodyGem instrument has been shown to be less accurate when compared to standard metabolic carts. Furthermore, when the Body Gem has been used with clinical patients or with under nourished individuals the results have not been acceptable. Overall, there is not a large enough body of evidence to definitively support the use of these hand-held devices for assessment of metabolic rate in a wide variety of clinical or research environments.
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.
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.
Multiple candidates and multiple constraints based accurate depth estimation for multi-view stereo
NASA Astrophysics Data System (ADS)
Zhang, Chao; Zhou, Fugen; Xue, Bindang
2017-02-01
In this paper, we propose a depth estimation method for multi-view image sequence. To enhance the accuracy of dense matching and reduce the inaccurate matching which is produced by inaccurate feature description, we select multiple matching points to build candidate matching sets. Then we compute an optimal depth from a candidate matching set which satisfies multiple constraints (epipolar constraint, similarity constraint and depth consistency constraint). To further increase the accuracy of depth estimation, depth consistency constraint of neighbor pixels is used to filter the inaccurate matching. On this basis, in order to get more complete depth map, depth diffusion is performed by neighbor pixels' depth consistency constraint. Through experiments on the benchmark datasets for multiple view stereo, we demonstrate the superiority of proposed method over the state-of-the-art method in terms of accuracy.
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.
Accurate dynamic power estimation for CMOS combinational logic circuits with real gate delay model.
Fadl, Omnia S; Abu-Elyazeed, Mohamed F; Abdelhalim, Mohamed B; Amer, Hassanein H; Madian, Ahmed H
2016-01-01
Dynamic power estimation is essential in designing VLSI circuits where many parameters are involved but the only circuit parameter that is related to the circuit operation is the nodes' toggle rate. This paper discusses a deterministic and fast method to estimate the dynamic power consumption for CMOS combinational logic circuits using gate-level descriptions based on the Logic Pictures concept to obtain the circuit nodes' toggle rate. The delay model for the logic gates is the real-delay model. To validate the results, the method is applied to several circuits and compared against exhaustive, as well as Monte Carlo, simulations. The proposed technique was shown to save up to 96% processing time compared to exhaustive simulation.
Rogers, Kevin J; Finn, Anthony
2017-02-01
Acoustic atmospheric tomography calculates temperature and wind velocity fields in a slice or volume of atmosphere based on travel time estimates between strategically located sources and receivers. The technique discussed in this paper uses the natural acoustic signature of an unmanned aerial vehicle as it overflies an array of microphones on the ground. The sound emitted by the aircraft is recorded on-board and by the ground microphones. The group velocities of the intersecting sound rays are then derived by comparing these measurements. Tomographic inversion is used to estimate the temperature and wind fields from the group velocity measurements. This paper describes a technique for deriving travel time (and hence group velocity) with an accuracy of 0.1% using these assets. This is shown to be sufficient to obtain highly plausible tomographic inversion results that correlate well with independent SODAR measurements.
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.
NASA Astrophysics Data System (ADS)
Mickaelian, A. M.
2004-10-01
Accurate measurements of the positions of 1101 First Byurakan Survey (FBS) blue stellar objects (the Second part of the FBS) have been carried out on the DSS1 and DSS2 (red and blue images). To establish the accuracy of the DSS1 and DSS2, measurements have been made for 153 AGN for which absolute VLBI coordinates have been published. The rms errors are: 0.45 arcsec for DSS1, 0.33 arcsec for DSS2 red, and 0.59 arcsec for DSS2 blue in each coordinate, the corresponding total positional errors being 0.64 arcsec, 0.46 arcsec, and 0.83 arcsec, respectively. The highest accuracy (0.42 arcsec) is obtained by weighted averaging of the DSS1 and DSS2 red positions. It is shown that by using all three DSS images accidental errors can be significantly reduced. The comparison of DSS2 and DSS1 images made it possible to reveal positional differences and proper motions for 78 objects (for 62 of these for the first time), including new high-probability candidate white dwarfs, and to find objects showing strong variability, i.e. high-probability candidate cataclysmic variables. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/426/367
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
Low-Cost MEMS sensors and vision system for motion and position estimation of a scooter.
Guarnieri, Alberto; Pirotti, Francesco; Vettore, Antonio
2013-01-24
The possibility to identify with significant accuracy the position of a vehicle in a mapping reference frame for driving directions and best-route analysis is a topic which is attracting a 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 position, orientation and velocity of the system with high measurement rates. In this work we test a system which uses low-cost sensors, based on Micro Electro-Mechanical Systems (MEMS) technology, coupled with information derived from a video camera placed on a two-wheel motor vehicle (scooter). In comparison to a four-wheel vehicle; the dynamics of a two-wheel vehicle feature a higher level of complexity given that more degrees of freedom must be taken into account. For example a motorcycle 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 compared to four-wheel motor vehicles. In this paper we present a method for the accurate reconstruction of the trajectory of a "Vespa" scooter; which can be used as alternative to the "classical" approach based on GPS/INS sensor integration. Position and orientation of the scooter are obtained by integrating MEMS-based orientation sensor data with digital images through a cascade of a Kalman filter and a Bayesian particle filter.
Low-Cost MEMS Sensors and Vision System for Motion and Position Estimation of a Scooter
Guarnieri, Alberto; Pirotti, Francesco; Vettore, Antonio
2013-01-01
The possibility to identify with significant accuracy the position of a vehicle in a mapping reference frame for driving directions and best-route analysis is a topic which is attracting a 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 position, orientation and velocity of the system with high measurement rates. In this work we test a system which uses low-cost sensors, based on Micro Electro-Mechanical Systems (MEMS) technology, coupled with information derived from a video camera placed on a two-wheel motor vehicle (scooter). In comparison to a four-wheel vehicle; the dynamics of a two-wheel vehicle feature a higher level of complexity given that more degrees of freedom must be taken into account. For example a motorcycle 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 compared to four-wheel motor vehicles. In this paper we present a method for the accurate reconstruction of the trajectory of a “Vespa” scooter; which can be used as alternative to the “classical” approach based on GPS/INS sensor integration. Position and orientation of the scooter are obtained by integrating MEMS-based orientation sensor data with digital images through a cascade of a Kalman filter and a Bayesian particle filter. PMID:23348036
A Simple and Accurate Equation for Peak Capacity Estimation in Two Dimensional Liquid Chromatography
Li, Xiaoping; Stoll, Dwight R.; Carr, Peter W.
2009-01-01
Two dimensional liquid chromatography (2DLC) is a very powerful way to greatly increase the resolving power and overall peak capacity of liquid chromatography. The traditional “product rule” for peak capacity usually overestimates the true resolving power due to neglect of the often quite severe under-sampling effect and thus provides poor guidance for optimizing the separation and biases comparisons to optimized one dimensional gradient liquid chromatography. Here we derive a simple yet accurate equation for the effective two dimensional peak capacity that incorporates a correction for under-sampling of the first dimension. The results show that not only is the speed of the second dimension separation important for reducing the overall analysis time, but it plays a vital role in determining the overall peak capacity when the first dimension is under-sampled. A surprising subsidiary finding is that for relatively short 2DLC separations (much less than a couple of hours), the first dimension peak capacity is far less important than is commonly believed and need not be highly optimized, for example through use of long columns or very small particles. PMID:19053226
NASA Astrophysics Data System (ADS)
Visser, R.; Godart, J.; Wauben, D. J. L.; Langendijk, J. A.; van't Veld, A. A.; Korevaar, E. W.
2016-12-01
In pre-treatment dose verification, low resolution detector systems are unable to identify shifts of individual leafs of high resolution multi leaf collimator (MLC) systems from detected changes in the dose deposition. The goal of this study was to introduce an alternative approach (the shutter technique) combined with a previous described iterative reconstruction method to accurately reconstruct high resolution MLC leaf positions based on low resolution measurements. For the shutter technique, two additional radiotherapy treatment plans (RT-plans) were generated in addition to the original RT-plan; one with even MLC leafs closed for reconstructing uneven leaf positions and one with uneven MLC leafs closed for reconstructing even leaf positions. Reconstructed leaf positions were then implemented in the original RT-plan for 3D dose reconstruction. The shutter technique was evaluated for a 6 MV Elekta SLi linac with 5 mm MLC leafs (Agility™) in combination with the MatriXX Evolution detector with detector spacing of 7.62 mm. Dose reconstruction was performed with the COMPASS system (v2.0). The measurement setup allowed one row of ionization chambers to be affected by two adjacent leaf pairs. Measurements were obtained for various field sizes with MLC leaf position errors ranging from 1.0 mm to 10.0 mm. Furthermore, one clinical head and neck IMRT treatment beam with MLC introduced leaf position errors of 5.0 mm was evaluated to illustrate the impact of the shutter technique on 3D dose reconstruction. Without the shutter technique, MLC leaf position reconstruction showed reconstruction errors up to 6.0 mm. Introduction of the shutter technique allowed MLC leaf position reconstruction for the majority of leafs with sub-millimeter accuracy resulting in a reduction of dose reconstruction errors. The shutter technique in combination with the iterative reconstruction method allows high resolution MLC leaf position reconstruction using low resolution
Accurate Estimation of Expression Levels of Homologous Genes in RNA-seq Experiments
NASA Astrophysics Data System (ADS)
Paşaniuc, Bogdan; Zaitlen, Noah; Halperin, Eran
Next generation high throughput sequencing (NGS) is poised to replace array based technologies as the experiment of choice for measuring RNA expression levels. Several groups have demonstrated the power of this new approach (RNA-seq), making significant and novel contributions and simultaneously proposing methodologies for the analysis of RNA-seq data. In a typical experiment, millions of short sequences (reads) are sampled from RNA extracts and mapped back to a reference genome. The number of reads mapping to each gene is used as proxy for its corresponding RNA concentration. A significant challenge in analyzing RNA expression of homologous genes is the large fraction of the reads that map to multiple locations in the reference genome. Currently, these reads are either dropped from the analysis, or a naïve algorithm is used to estimate their underlying distribution. In this work, we present a rigorous alternative for handling the reads generated in an RNA-seq experiment within a probabilistic model for RNA-seq data; we develop maximum likelihood based methods for estimating the model parameters. In contrast to previous methods, our model takes into account the fact that the DNA of the sequenced individual is not a perfect copy of the reference sequence. We show with both simulated and real RNA-seq data that our new method improves the accuracy and power of RNA-seq experiments.
Accurate estimation of expression levels of homologous genes in RNA-seq experiments.
Paşaniuc, Bogdan; Zaitlen, Noah; Halperin, Eran
2011-03-01
Abstract Next generation high-throughput sequencing (NGS) is poised to replace array-based technologies as the experiment of choice for measuring RNA expression levels. Several groups have demonstrated the power of this new approach (RNA-seq), making significant and novel contributions and simultaneously proposing methodologies for the analysis of RNA-seq data. In a typical experiment, millions of short sequences (reads) are sampled from RNA extracts and mapped back to a reference genome. The number of reads mapping to each gene is used as proxy for its corresponding RNA concentration. A significant challenge in analyzing RNA expression of homologous genes is the large fraction of the reads that map to multiple locations in the reference genome. Currently, these reads are either dropped from the analysis, or a naive algorithm is used to estimate their underlying distribution. In this work, we present a rigorous alternative for handling the reads generated in an RNA-seq experiment within a probabilistic model for RNA-seq data; we develop maximum likelihood-based methods for estimating the model parameters. In contrast to previous methods, our model takes into account the fact that the DNA of the sequenced individual is not a perfect copy of the reference sequence. We show with both simulated and real RNA-seq data that our new method improves the accuracy and power of RNA-seq experiments.
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
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.
[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
Brahme, Anders; Nyman, Peter; Skatt, Björn
2008-05-01
A four-dimensional (4D) laser camera (LC) has been developed for accurate patient imaging in diagnostic and therapeutic radiology. A complementary metal-oxide semiconductor camera images the intersection of a scanned fan shaped laser beam with the surface of the patient and allows real time recording of movements in a three-dimensional (3D) or four-dimensional (4D) format (3D +time). The LC system was first designed as an accurate patient setup tool during diagnostic and therapeutic applications but was found to be of much wider applicability as a general 4D photon "tag" for the surface of the patient in different clinical procedures. It is presently used as a 3D or 4D optical benchmark or tag for accurate delineation of the patient surface as demonstrated for patient auto setup, breathing and heart motion detection. Furthermore, its future potential applications in gating, adaptive therapy, 3D or 4D image fusion between most imaging modalities and image processing are discussed. It is shown that the LC system has a geometrical resolution of about 0, 1 mm and that the rigid body repositioning accuracy is about 0, 5 mm below 20 mm displacements, 1 mm below 40 mm and better than 2 mm at 70 mm. This indicates a slight need for repeated repositioning when the initial error is larger than about 50 mm. The positioning accuracy with standard patient setup procedures for prostate cancer at Karolinska was found to be about 5-6 mm when independently measured using the LC system. The system was found valuable for positron emission tomography-computed tomography (PET-CT) in vivo tumor and dose delivery imaging where it potentially may allow effective correction for breathing artifacts in 4D PET-CT and image fusion with lymph node atlases for accurate target volume definition in oncology. With a LC system in all imaging and radiation therapy rooms, auto setup during repeated diagnostic and therapeutic procedures may save around 5 min per session, increase accuracy and allow
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.
NASA Astrophysics Data System (ADS)
Guerdoux, Simon; Fourment, Lionel
2007-05-01
An Arbitrary Lagrangian Eulerian (ALE) formulation is developed to simulate the different stages of the Friction Stir Welding (FSW) process with the FORGE3® F.E. software. A splitting method is utilized: a) the material velocity/pressure and temperature fields are calculated, b) the mesh velocity is derived from the domain boundary evolution and an adaptive refinement criterion provided by error estimation, c) P1 and P0 variables are remapped. Different velocity computation and remap techniques have been investigated, providing significant improvement with respect to more standard approaches. The proposed ALE formulation is applied to FSW simulation. Steady state welding, but also transient phases are simulated, showing good robustness and accuracy of the developed formulation. Friction parameters are identified for an Eulerian steady state simulation by comparison with experimental results. Void formation can be simulated. Simulations of the transient plunge and welding phases help to better understand the deposition process that occurs at the trailing edge of the probe. Flexibility and robustness of the model finally allows investigating the influence of new tooling designs on the deposition process.
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.
Pinkerton, Steven D; Galletly, Carol L; McAuliffe, Timothy L; DiFranceisco, Wayne; Raymond, H Fisher; Chesson, Harrell W
2010-02-01
The sexual behaviors of HIV/sexually transmitted infection (STI) prevention intervention participants can be assessed on a partner-by-partner basis: in aggregate (i.e., total numbers of sex acts, collapsed across partners) or using a combination of these two methods (e.g., assessing five partners in detail and any remaining partners in aggregate). There is a natural trade-off between the level of sexual behavior detail and the precision of HIV/STI acquisition risk estimates. The results of this study indicate that relatively simple aggregate data collection techniques suffice to adequately estimate HIV risk. For highly infectious STIs, in contrast, accurate STI risk assessment requires more intensive partner-by-partner methods.
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
Vieira, Vasco M. N. C. S.; Engelen, Aschwin H.; Huanel, Oscar R.; Guillemin, Marie-Laure
2016-01-01
Survival is a fundamental demographic component and the importance of its accurate estimation goes beyond the traditional estimation of life expectancy. The evolutionary stability of isomorphic biphasic life-cycles and the occurrence of its different ploidy phases at uneven abundances are hypothesized to be driven by differences in survival rates between haploids and diploids. We monitored Gracilaria chilensis, a commercially exploited red alga with an isomorphic biphasic life-cycle, having found density-dependent survival with competition and Allee effects. While estimating the linear-in-the-parameters survival function, all model I regression methods (i.e, vertical least squares) provided biased line-fits rendering them inappropriate for studies about ecology, evolution or population management. Hence, we developed an iterative two-step non-linear model II regression (i.e, oblique least squares), which provided improved line-fits and estimates of survival function parameters, while robust to the data aspects that usually turn the regression methods numerically unstable. PMID:27936048
Position estimation for timing belt drives of precision machinery using structured neural networks
NASA Astrophysics Data System (ADS)
Kilic, Ergin; Dogruer, Can Ulas; Dolen, Melik; Koku, Ahmet Bugra
2012-05-01
This paper focuses on a viable position estimation scheme for timing-belt drives using artificial neural networks. In this study, the position of a carriage (load) is calculated via a structured neural network topology accepting input from a position sensor on the actuator side of the timing belt. The paper presents a detailed discussion on the source of transmission errors. The characteristics of the error in different operation regimes are exploited to construct different network topologies. That is, a relevant neural network model is developed by the sketchy guidance of a priori knowledge on the process. The resulting structured neural network is shown to estimate the error of the carriage quite accurately whereas generic recurrent neural networks fail to capture the dynamics of the system under investigation altogether. Extensive testing demonstrates the effectiveness of proposed method when the drive system is not subjected to external loads while the operating conditions such as ambient temperature and belt tensions do not deviate from the experimental conditions.
Drift-free position estimation for periodic movements using inertial units.
Millor, Nora; Lecumberri, Pablo; Gomez, Marisol; Martinez-Ramirez, Alicia; Izquierdo, Mikel
2014-07-01
Latest advances in microelectromechanical systems have made inertial units (IUs) a powerful tool for human motion analysis. However, difficulties in handling their output signals must be overcome. The purpose of this study was to develop the novel "PB-algorithm" based on polynomial data fitting, splines interpolation, and the wavelet transform, one after the other, to cancel drift disturbances in position estimation for periodic movements. High-accuracy position measurements from an optical system (Vicon Nexus 1.0) were used to validate the proposed method and comparison with another drift-correction algorithm was provided. Results indicate the accuracy with respect to the Vicon's reference signal (euclidean error lower than 54.62 × 10(-3) m and correlation coefficient higher than 0.968). A reduction of the root-mean-square error of 68.74% was obtained when the proposed two-step method was compared with a modified-band limited Fourier linear combiner. All methods were applied to data from the 30-s chair stand test, which is one of the most used clinical tests dealing with lower body strength assessment, falls prediction, and gait disorders in older adults. The relevance of this study is that after cancelling drift disturbances, and obtaining an accurate Z-position estimation, it is possible to evaluate the sit-to-stand and stand-to-sit transitions from the whole test.
Walters, William A.; Lennon, Niall J.; Bochicchio, James; Krohn, Andrew; Pennanen, Taina
2016-01-01
ABSTRACT While high-throughput sequencing methods are revolutionizing fungal ecology, recovering accurate estimates of species richness and abundance has proven elusive. We sought to design internal transcribed spacer (ITS) primers and an Illumina protocol that would maximize coverage of the kingdom Fungi while minimizing nontarget eukaryotes. We inspected alignments of the 5.8S and large subunit (LSU) ribosomal genes and evaluated potential primers using PrimerProspector. We tested the resulting primers using tiered-abundance mock communities and five previously characterized soil samples. We recovered operational taxonomic units (OTUs) belonging to all 8 members in both mock communities, despite DNA abundances spanning 3 orders of magnitude. The expected and observed read counts were strongly correlated (r = 0.94 to 0.97). However, several taxa were consistently over- or underrepresented, likely due to variation in rRNA gene copy numbers. The Illumina data resulted in clustering of soil samples identical to that obtained with Sanger sequence clone library data using different primers. Furthermore, the two methods produced distance matrices with a Mantel correlation of 0.92. Nonfungal sequences comprised less than 0.5% of the soil data set, with most attributable to vascular plants. Our results suggest that high-throughput methods can produce fairly accurate estimates of fungal abundances in complex communities. Further improvements might be achieved through corrections for rRNA copy number and utilization of standardized mock communities. IMPORTANCE Fungi play numerous important roles in the environment. Improvements in sequencing methods are providing revolutionary insights into fungal biodiversity, yet accurate estimates of the number of fungal species (i.e., richness) and their relative abundances in an environmental sample (e.g., soil, roots, water, etc.) remain difficult to obtain. We present improved methods for high-throughput Illumina sequencing of the
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.
Lake, Douglas E; Moorman, J Randall
2011-01-01
Entropy estimation is useful but difficult in short time series. For example, automated detection of atrial fibrillation (AF) in very short heart beat interval time series would be useful in patients with cardiac implantable electronic devices that record only from the ventricle. Such devices require efficient algorithms, and the clinical situation demands accuracy. Toward these ends, we optimized the sample entropy measure, which reports the probability that short templates will match with others within the series. We developed general methods for the rational selection of the template length m and the tolerance matching r. The major innovation was to allow r to vary so that sufficient matches are found for confident entropy estimation, with conversion of the final probability to a density by dividing by the matching region volume, 2r(m). The optimized sample entropy estimate and the mean heart beat interval each contributed to accurate detection of AF in as few as 12 heartbeats. The final algorithm, called the coefficient of sample entropy (COSEn), was developed using the canonical MIT-BIH database and validated in a new and much larger set of consecutive Holter monitor recordings from the University of Virginia. In patients over the age of 40 yr old, COSEn has high degrees of accuracy in distinguishing AF from normal sinus rhythm in 12-beat calculations performed hourly. The most common errors are atrial or ventricular ectopy, which increase entropy despite sinus rhythm, and atrial flutter, which can have low or high entropy states depending on dynamics of atrioventricular conduction.
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.
NASA Astrophysics Data System (ADS)
Zhang, Zhisen; Wu, Tao; Wang, Qi; Pan, Haihua; Tang, Ruikang
2014-01-01
The interactions between proteins/peptides and materials are crucial to research and development in many biomedical engineering fields. The energetics of such interactions are key in the evaluation of new proteins/peptides and materials. Much research has recently focused on the quality of free energy profiles by Jarzynski's equality, a widely used equation in biosystems. In the present work, considerable discrepancies were observed between the results obtained by Jarzynski's equality and those derived by umbrella sampling in biomaterial-water model systems. Detailed analyses confirm that such discrepancies turn up only when the target molecule moves in the high-density water layer on a material surface. Then a hybrid scheme was adopted based on this observation. The agreement between the results of the hybrid scheme and umbrella sampling confirms the former observation, which indicates an approach to a fast and accurate estimation of adsorption free energy for large biomaterial interfacial systems.
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
Wood, Nathan A; Del Agua, Diego Moral; Zenati, Marco A; Riviere, Cameron N
2011-12-05
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.
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.
An accurate position for the black hole candidate XTE J1752-223: re-interpretation of the VLBI data
NASA Astrophysics Data System (ADS)
Miller-Jones, J. C. A.; Jonker, P. G.; Ratti, E. M.; Torres, M. A. P.; Brocksopp, C.; Yang, J.; Morrell, N. I.
2011-07-01
Using high-precision astrometric optical observations from the Walter Baade Magellan Telescope in conjunction with high-resolution very long baseline interferometric (VLBI) radio imaging with the Very Long Baseline Array (VLBA), we have located the core of the X-ray binary system XTE J1752-223. Compact radio emission from the core was detected following the state transition from the soft to the hard X-ray state. Its position to the south-east of all previously detected jet components mandated a re-analysis of the existing VLBI data. Our analysis suggests that the outburst comprised at least two ejection events prior to 2010 February 26. No radio-emitting components were detected to the south-east of the core at any epoch, suggesting that the receding jets were Doppler-deboosted below our sensitivity limit. From the ratio of the brightness of the detected components to the measured upper limits for the receding ejecta, we constrain the jet speed β > 0.66 and the inclination angle to the line of sight θ < 49°. Assuming that the initial ejection event occurred at the transition from the hard intermediate state to the soft intermediate state, an initial period of ballistic motion followed by a Sedov phase (i.e. self-similar adiabatic expansion) appears to fit the motion of the ejecta better than a uniform deceleration model. The accurate core location can provide a long time baseline for a future proper motion determination should the system show a second outburst, providing insights into the formation mechanism of the compact object.
Attitude and position estimation on the Mars Exploration Rovers
NASA Technical Reports Server (NTRS)
Ali, Khaled S.; Vanelli, C. Anthony; Biesiadecki, Jeffrey J.; Maimone, Mark W.; Cheng, Yang; San Martin, A. Miguel; Alexander, James W.
2005-01-01
This paper describes the techniques used by the rovers to acquire and maintain attitude and position knowledge, the accuracy which is obtainable, and lessons learned after more than one year in operation.
Attitude and position estimation on the Mars Exploration Rovers
NASA Technical Reports Server (NTRS)
Ali, Khaled S.; Vanelli, C. Anthony; Biesiadecki, Jeffrey J.; Maimone, Mark W.; Yang Cheng, A.; San Martin, Miguel; Alexander, James W.
2005-01-01
NASA/JPL 's Mars Exploration Rovers acquire their attitude upon command and autonomously propagate their attitude and position. The rovers use accelerometers and images of the sun to acquire attitude, autonomously searching the sky for the sun with a pointable camera. To propagate the attitude and position the rovers use either accelerometer and gyro readings or gyro readings and wheel odometiy, depending on the nature of the movement ground operators are commanding. Where necessary, visual odometry is performed on images to fine tune the position updates, particularly in high slip environments. The capability also exists for visual odometry attitude updates. This paper describes the techniques used by the rovers to acquire and maintain attitude and position knowledge, the accuracy which is obtainable, and lessons learned after more than one year in operation.
Estimation of Target Angular Position Under Mainbeam Jamming Conditions,
1995-12-01
technique, Multiple Signal Classification ( MUSIC ), is used to estimate the target Direction Of Arrival (DOA) from the processed data vectors. The model...used in the MUSIC technique takes into account the fact that the jammer has been cancelled in the target data vector. The performance of this algorithm
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
NASA Astrophysics Data System (ADS)
An, Zhe; Rey, Daniel; Ye, Jingxin; Abarbanel, Henry D. I.
2017-01-01
The problem of forecasting the behavior of a complex dynamical system through analysis of observational time-series data becomes difficult when the system expresses chaotic behavior and the measurements are sparse, in both space and/or time. Despite the fact that this situation is quite typical across many fields, including numerical weather prediction, the issue of whether the available observations are "sufficient" for generating successful forecasts is still not well understood. An analysis by Whartenby et al. (2013) found that in the context of the nonlinear shallow water equations on a β plane, standard nudging techniques require observing approximately 70 % of the full set of state variables. Here we examine the same system using a method introduced by Rey et al. (2014a), which generalizes standard nudging methods to utilize time delayed measurements. We show that in certain circumstances, it provides a sizable reduction in the number of observations required to construct accurate estimates and high-quality predictions. In particular, we find that this estimate of 70 % can be reduced to about 33 % using time delays, and even further if Lagrangian drifter locations are also used as measurements.
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.
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…
Regularized positive-definite fourth order tensor field estimation from DW-MRI.
Barmpoutis, Angelos; Hwang, Min Sig; Howland, Dena; Forder, John R; Vemuri, Baba C
2009-03-01
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.
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
2013-07-01
Simultaneous Position, Velocity, Attitude, Angular Rates, and Surface Parameter Estimation Using Astrometric and Photometric Observations...estimation is extended to include the various surface parameters associated with the bidirectional reflectance distribution function (BRDF... parameters are estimated simultaneously Keywords—estimation; data fusion; BRDF I. INTRODUCTION Wetterer and Jah [1] first demonstrated how brightness
NASA Astrophysics Data System (ADS)
Sollberger, S.; Perez, K.; Schubert, C. J.; Eugster, W.; Wehrli, B.; Del Sontro, T.
2013-12-01
Currently, carbon dioxide (CO2) and methane (CH4) emissions from lakes, reservoirs and rivers are readily investigated due to the global warming potential of those gases and the role these inland waters play in the carbon cycle. However, there is a lack of high spatiotemporally-resolved emission estimates, and how to accurately assess the gas transfer velocity (K) remains controversial. In anthropogenically-impacted systems where run-of-river reservoirs disrupt the flow of sediments by increasing the erosion and load accumulation patterns, the resulting production of carbonic greenhouse gases (GH-C) is likely to be enhanced. The GH-C flux is thus counteracting the terrestrial carbon sink in these environments that act as net carbon emitters. The aim of this project was to determine the GH-C emissions from a medium-sized river heavily impacted by several impoundments and channelization through a densely-populated region of Switzerland. Estimating gas emission from rivers is not trivial and recently several models have been put forth to do so; therefore a second goal of this project was to compare the river emission models available with direct measurements. Finally, we further validated the modeled fluxes by using a combined approach with water sampling, chamber measurements, and highly temporal GH-C monitoring using an equilibrator. We conducted monthly surveys along the 120 km of the lower Aare River where we sampled for dissolved CH4 (';manual' sampling) at a 5-km sampling resolution, and measured gas emissions directly with chambers over a 35 km section. We calculated fluxes (F) via the boundary layer equation (F=K×(Cw-Ceq)) that uses the water-air GH-C concentration (C) gradient (Cw-Ceq) and K, which is the most sensitive parameter. K was estimated using 11 different models found in the literature with varying dependencies on: river hydrology (n=7), wind (2), heat exchange (1), and river width (1). We found that chamber fluxes were always higher than boundary
NASA Astrophysics Data System (ADS)
Katata, Genki; Kajino, Mizuo; Hiraki, Takatoshi; Aikawa, Masahide; Kobayashi, Tomiki; Nagai, Haruyasu
2011-10-01
To apply a meteorological model to investigate fog occurrence, acidification and deposition in mountain forests, the meteorological model WRF was modified to calculate fog deposition accurately by the simple linear function of fog deposition onto vegetation derived from numerical experiments using the detailed multilayer atmosphere-vegetation-soil model (SOLVEG). The modified version of WRF that includes fog deposition (fog-WRF) was tested in a mountain forest on Mt. Rokko in Japan. fog-WRF provided a distinctly better prediction of liquid water content of fog (LWC) than the original version of WRF. It also successfully simulated throughfall observations due to fog deposition inside the forest during the summer season that excluded the effect of forest edges. Using the linear relationship between fog deposition and altitude given by the fog-WRF calculations and the data from throughfall observations at a given altitude, the vertical distribution of fog deposition can be roughly estimated in mountain forests. A meteorological model that includes fog deposition will be useful in mapping fog deposition in mountain cloud forests.
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.
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.
de Müllenheim, Pierre-Yves; Chaudru, Ségolène; Gernigon, Marie; Mahé, Guillaume; Bickert, Sandrine; Prioux, Jacques; Noury-Desvaux, Bénédicte; Le Faucheur, Alexis
2016-09-21
The aim of this study was to assess, for the first time, the accuracy of a low-cost global positioning system (GPS) receiver for estimating grade during outdoor walking. Thirty subjects completed outdoor walks (2.0, 3.5 and 5.0 km · h(-1)) in three randomized conditions: 1/level walking on a 0.0% grade; 2/graded (uphill and downhill) walking on a 3.4% grade; and 3/on a 10.4% grade. Subjects were equipped with a GPS receiver (DG100, GlobalSat Technology Corp., Taiwan; ~US$75). The GPS receiver was set to record at 1 Hz and its antenna was placed on the right shoulder. Grade was calculated from GPS speed and altitude data (grade = altitude variation/travelled distance × 100). Two methods were used for the grade calculation: one using uncorrected altitude data given by the GPS receiver and another one using corrected altitude data obtained using map projection software (CartoExploreur, version 3.11.0, build 2.6.6.22, Bayo Ltd, Appoigny, France, ~US$35). Linear regression of GPS-estimated versus actual grade with R (2) coefficients, bias with 95% limits of agreement (±95% LoA), and typical error of the estimate with 95% confidence interval (TEE (95% CI)) were computed to assess the accuracy of the GPS receiver. 444 walking periods were performed. Using uncorrected altitude data, we obtained: R (2) = 0.88 (p < 0.001), bias = 0.0 ± 6.6%, TEE between 1.9 (1.7-2.2)% and 4.2 (3.6-4.9)% according to the grade level. Using corrected altitude data, we obtained: R (2) = 0.98 (p < 0.001), bias = 0.2 ± 1.9%, TEE between 0.2 (0.2-0.3)% and 1.0 (0.9-1.2)% according to the grade level. The low-cost GPS receiver used was weakly accurate for estimating grade during outdoor walking when using uncorrected altitude data. However, the accuracy was greatly improved when using corrected altitude data. This study supports the potential interest of using GPS for estimating energy
How accurate is the estimation of anthropogenic carbon in the ocean? An evaluation of the ΔC* method
NASA Astrophysics Data System (ADS)
Matsumoto, Katsumi; Gruber, Nicolas
2005-09-01
The ΔC* method of Gruber et al. (1996) is widely used to estimate the distribution of anthropogenic carbon in the ocean; however, as yet, no thorough assessment of its accuracy has been made. Here we provide a critical re-assessment of the method and determine its accuracy by applying it to synthetic data from a global ocean biogeochemistry model, for which we know the "true" anthropogenic CO2 distribution. Our results indicate that the ΔC* method tends to overestimate anthropogenic carbon in relatively young waters but underestimate it in older waters. Main sources of these biases are (1) the time evolution of the air-sea CO2 disequilibrium, which is not properly accounted for in the ΔC* method, (2) a pCFC ventilation age bias that arises from mixing, and (3) errors in identifying the different end-member water types. We largely support the findings of Hall et al. (2004), who have also identified the first two bias sources. An extrapolation of the errors that we quantified on a number of representative isopycnals to the global ocean suggests a positive bias of about 7% in the ΔC*-derived global anthropogenic CO2 inventory. The magnitude of this bias is within the previously estimated 20% uncertainty of the method, but regional biases can be larger. Finally, we propose two improvements to the ΔC* method in order to account for the evolution of air-sea CO2 disequilibrium and the ventilation age mixing bias.
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)
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
Calibration Method for ML Estimation of 3D Interaction Position in a Thick Gamma-Ray Detector
Hunter, William C. J.; Barrett, Harrison H.; Furenlid, Lars R.
2010-01-01
High-energy (> 100 keV) photon detectors are often made thick relative to their lateral resolution in order to improve their photon-detection efficiency. To avoid issues of parallax and increased signal variance that result from random interaction depth, we must determine the 3D interaction position in the imaging detector. With this goal in mind, we examine a method of calibrating response statistics of a thick-detector gamma camera to produce a maximum-likelihood estimate of 3D interaction position. We parameterize the mean detector response as a function of 3D position, and we estimate these parameters by maximizing their likelihood given prior knowledge of the pathlength distribution and a complete list of camera signals for an ensemble of gamma-ray interactions. Furthermore, we describe an iterative method for removing multiple-interaction events from our calibration data and for refining our calibration of the mean detector response to single interactions. We demonstrate this calibration method with simulated gamma-camera data. We then show that the resulting calibration is accurate and can be used to produce unbiased estimates of 3D interaction position. PMID:20191099
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
Initial Rotor Position Estimation of Half-Wave Rectified Brushless Synchronous Motor
NASA Astrophysics Data System (ADS)
Abe, Takashi; Oyama, Jun; Higuchi, Tsuyoshi
This paper presents an initial rotor position estimation of Half-Wave Rectified Brushless Synchronous Motor. In the previous paper, we proposed this motor as AC servo motor, which is based on the half-wave rectified brushless excitation principle. The basic principle of this estimation technique utilizes the dependence of inductance on the rotor position. The bias frequency component of half-Wave rectified brushless excitation is used to estimate the rotor position error. The magnetic pole is discriminated by the switching condition of the diode inserted into the rotor field winding. This estimation technique is confirmed by simulation include inverter circuit, control program and motor model. Finally, the effectiveness of the proposed estimation technique has been verified by experiments.
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.
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)
Gorbachev, Alexey A.; Serikova, Mariya G.; Pantyushina, Ekaterina N.; Volkova, Daria A.
2016-04-01
Modern demands for railway track measurements require high accuracy (about 2-5 mm) of rails placement along the track to ensure smooth, safe and fast transportation. As a mean for railways geometry measurements we suggest a stereoscopic system which measures 3D position of fiducial marks arranged along the track by image processing algorithms. The system accuracy was verified during laboratory tests by comparison with precise laser tracker indications. The accuracy of +/-1.5 mm within a measurement volume 150×400×5000 mm was achieved during the tests. This confirmed that the stereoscopic system demonstrates good measurement accuracy and can be potentially used as fully automated mean for railway track inspection.
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
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
Ades, A E; Cliffe, S
2002-01-01
Decision models are usually populated 1 parameter at a time, with 1 item of information informing each parameter. Often, however, data may not be available on the parameters themselves but on several functions of parameters, and there may be more items of information than there are parameters to be estimated. The authors show how in these circumstances all the model parameters can be estimated simultaneously using Bayesian Markov chain Monte Carlo methods. Consistency of the information and/or the adequacy of the model can also be assessed within this framework. Statistical evidence synthesis using all available data should result in more precise estimates of parameters and functions of parameters, and is compatible with the emphasis currently placed on systematic use of evidence. To illustrate this, WinBUGS software is used to estimate a simple 9-parameter model of the epidemiology of HIV in women attending prenatal clinics, using information on 12 functions of parameters, and to thereby compute the expected net benefit of 2 alternative prenatal testing strategies, universal testing and targeted testing of high-risk groups. The authors demonstrate improved precision of estimates, and lower estimates of the expected value of perfect information, resulting from the use of all available data.
Yuan, Xuebing; Yu, Shuai; Zhang, Shengzhi; Wang, Guoping; Liu, Sheng
2015-05-07
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.
Van Uffelen, Lora J; Nosal, Eva-Marie; Howe, Bruce M; Carter, Glenn S; Worcester, Peter F; Dzieciuch, Matthew A; Heaney, Kevin D; Campbell, Richard L; Cross, Patrick S
2013-10-01
Four acoustic Seagliders were deployed in the Philippine Sea November 2010 to April 2011 in the vicinity of an acoustic tomography array. The gliders recorded over 2000 broadband transmissions at ranges up to 700 km from moored acoustic sources as they transited between mooring sites. The precision of glider positioning at the time of acoustic reception is important to resolve the fundamental ambiguity between position and sound speed. The Seagliders utilized GPS at the surface and a kinematic model below for positioning. The gliders were typically underwater for about 6.4 h, diving to depths of 1000 m and traveling on average 3.6 km during a dive. Measured acoustic arrival peaks were unambiguously associated with predicted ray arrivals. Statistics of travel-time offsets between received arrivals and acoustic predictions were used to estimate range uncertainty. Range (travel time) uncertainty between the source and the glider position from the kinematic model is estimated to be 639 m (426 ms) rms. Least-squares solutions for glider position estimated from acoustically derived ranges from 5 sources differed by 914 m rms from modeled positions, with estimated uncertainty of 106 m rms in horizontal position. Error analysis included 70 ms rms of uncertainty due to oceanic sound-speed variability.
The Impact of Estimating High-Resolution Tropospheric Gradients on Multi-GNSS Precise Positioning.
Zhou, Feng; Li, Xingxing; Li, Weiwei; Chen, Wen; Dong, Danan; Wickert, Jens; Schuh, Harald
2017-04-03
Benefits from the modernized US Global Positioning System (GPS), the revitalized Russian GLObal NAvigation Satellite System (GLONASS), and the newly-developed Chinese BeiDou Navigation Satellite System (BDS) and European Galileo, multi-constellation Global Navigation Satellite System (GNSS) has emerged as a powerful tool not only in positioning, navigation, and timing (PNT), but also in remote sensing of the atmosphere and ionosphere. Both precise positioning and the derivation of atmospheric parameters can benefit from multi-GNSS observations. In this contribution, extensive evaluations are conducted with multi-GNSS datasets collected from 134 globally-distributed ground stations of the International GNSS Service (IGS) Multi-GNSS Experiment (MGEX) network in July 2016. The datasets are processed in six different constellation combinations, i.e., GPS-, GLONASS-, BDS-only, GPS + GLONASS, GPS + BDS, and GPS + GLONASS + BDS + Galileo precise point positioning (PPP). Tropospheric gradients are estimated with eight different temporal resolutions, from 1 h to 24 h, to investigate the impact of estimating high-resolution gradients on position estimates. The standard deviation (STD) is used as an indicator of positioning repeatability. The results show that estimating tropospheric gradients with high temporal resolution can achieve better positioning performance than the traditional strategy in which tropospheric gradients are estimated on a daily basis. Moreover, the impact of estimating tropospheric gradients with different temporal resolutions at various elevation cutoff angles (from 3° to 20°) is investigated. It can be observed that with increasing elevation cutoff angles, the improvement in positioning repeatability is decreased.
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.
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
Dorval, Alan D
2008-08-15
The maximal information that the spike train of any neuron can pass on to subsequent neurons can be quantified as the neuronal firing pattern entropy. Difficulties associated with estimating entropy from small datasets have proven an obstacle to the widespread reporting of firing pattern entropies and more generally, the use of information theory within the neuroscience community. In the most accessible class of entropy estimation techniques, spike trains are partitioned linearly in time and entropy is estimated from the probability distribution of firing patterns within a partition. Ample previous work has focused on various techniques to minimize the finite dataset bias and standard deviation of entropy estimates from under-sampled probability distributions on spike timing events partitioned linearly in time. In this manuscript we present evidence that all distribution-based techniques would benefit from inter-spike intervals being partitioned in logarithmic time. We show that with logarithmic partitioning, firing rate changes become independent of firing pattern entropy. We delineate the entire entropy estimation process with two example neuronal models, demonstrating the robust improvements in bias and standard deviation that the logarithmic time method yields over two widely used linearly partitioned time approaches.
Distributed bounded-error state estimation based on practical robust positive invariance
NASA Astrophysics Data System (ADS)
Riverso, Stefano; Rubini, Daria; Ferrari-Trecate, Giancarlo
2015-11-01
We propose a state estimator for linear discrete-time systems composed by coupled subsystems affected by bounded disturbances. The architecture is distributed in the sense that each subsystem is equipped with a local state estimator that exploits suitable pieces of information from parent subsystems. Furthermore, each local estimator reconstructs the state of the corresponding subsystem only. Different from methods based on moving horizon estimation, our approach does not require the online solution to optimisation problems. Our state estimation scheme, which is based on the notion of practical robust positive invariance, also guarantees satisfaction of constraints on local estimation errors and it can be updated with a limited computational effort when subsystems are added or removed.
Byun, Yeun-Sub; Jeong, Rag-Gyo; Kang, Seok-Won
2015-11-13
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.
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
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…
A simple method for accurate liver volume estimation by use of curve-fitting: a pilot study.
Aoyama, Masahito; Nakayama, Yoshiharu; Awai, Kazuo; Inomata, Yukihiro; Yamashita, Yasuyuki
2013-01-01
In this paper, we describe the effectiveness of our curve-fitting method by comparing liver volumes estimated by our new technique to volumes obtained with the standard manual contour-tracing method. Hepatic parenchymal-phase images of 13 patients were obtained with multi-detector CT scanners after intravenous bolus administration of 120-150 mL of contrast material (300 mgI/mL). The liver contours of all sections were traced manually by an abdominal radiologist, and the liver volume was computed by summing of the volumes inside the contours. The section number between the first and last slice was then divided into 100 equal parts, and each volume was re-sampled by use of linear interpolation. We generated 13 model profile curves by averaging 12 cases, leaving out one case, and we estimated the profile curve for each patient by fitting the volume values at 4 points using a scale and translation transform. Finally, we determined the liver volume by integrating the sampling points of the profile curve. We used Bland-Altman analysis to evaluate the agreement between the volumes estimated with our curve-fitting method and the volumes measured by the manual contour-tracing method. The correlation between the volume measured by manual tracing and that estimated with our curve-fitting method was relatively high (r = 0.98; slope 0.97; p < 0.001). The mean difference between the manual tracing and our method was -22.9 cm(3) (SD of the difference, 46.2 cm(3)). Our volume-estimating technique that requires the tracing of only 4 images exhibited a relatively high linear correlation with the manual tracing technique.
Haasl, Ryan J; Payseur, Bret A
2010-12-01
Theoretical work focused on microsatellite variation has produced a number of important results, including the expected distribution of repeat sizes and the expected squared difference in repeat size between two randomly selected samples. However, closed-form expressions for the sampling distribution and frequency spectrum of microsatellite variation have not been identified. Here, we use coalescent simulations of the stepwise mutation model to develop gamma and exponential approximations of the microsatellite allele frequency spectrum, a distribution central to the description of microsatellite variation across the genome. For both approximations, the parameter of biological relevance is the number of alleles at a locus, which we express as a function of θ, the population-scaled mutation rate, based on simulated data. Discovered relationships between θ, the number of alleles, and the frequency spectrum support the development of three new estimators of microsatellite θ. The three estimators exhibit roughly similar mean squared errors (MSEs) and all are biased. However, across a broad range of sample sizes and θ values, the MSEs of these estimators are frequently lower than all other estimators tested. The new estimators are also reasonably robust to mutation that includes step sizes greater than one. Finally, our approximation to the microsatellite allele frequency spectrum provides a null distribution of microsatellite variation. In this context, a preliminary analysis of the effects of demographic change on the frequency spectrum is performed. We suggest that simulations of the microsatellite frequency spectrum under evolutionary scenarios of interest may guide investigators to the use of relevant and sometimes novel summary statistics.
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
2015-10-16
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.
The dynamic research and position estimation of the towed array during the U-turn process
NASA Astrophysics Data System (ADS)
Yang, J. X.; Shuai, C. G.; He, L.; Zhang, S. K.; Zhou, S. T.
2016-09-01
A dynamic model for estimating position of ship towed array during U-turn manoeuvre is introduced and developed. Based on this model, the influences of the parameters such as time step and segment length on the numerical simulation are analysed. The results indicate that decreasing the time step has little effect on the simulation accuracy but will increase the computational time. The selection of segment length has a great influence on the estimation of ship towed array position during U-turn manoeuvre. Reducing the segment length somewhat increases the computational complexity and significantly improves simulation precision.
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.
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.
NASA Astrophysics Data System (ADS)
Cortez, Celia Martins; Fragoso, Viviane Muniz S.; Silva, Dilson
2014-10-01
In this work, we used a mathematical model to study the interaction of risperidone with human and bovine serum albumins estimating the relative position of the primary binding site, based on the fluorescence quenching theory. Results have shown that the model was able to demonstrate that primary binding site for risperidone in HSA and BSA is very close to the position where is tryptophan 134 of BSA, possibly in domain 1B.
Formation control and collision avoidance for multi-agent systems based on position estimation.
Xia, Yuanqing; Na, Xitai; Sun, Zhongqi; Chen, Jing
2016-03-01
In this paper, formation control strategies based on position estimation for double-integrator systems are investigated. Firstly, an optimal control formation control strategy is derived based on the estimator. It is proven that the control inputs are able to drive the agents to the predefined formation and the controller is optimal even based on the estimation law if the estimator has converged to stable. Secondly, a consensus law based on the estimator is presented, which enables the agents converge to the formation in a cooperative manner. The stability can be guaranteed by proper parameters. Thirdly, extra control input for inter collision avoidance is added into the derived consensus control strategy, and efficacy analysis are provided in detail. Finally, the effectiveness of the strategies proposed are shown by simulation and experiment results.
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)
Blockley, Simon P. E.; Bronk Ramsey, C.; Pyle, D. M.
2008-10-01
The role of tephrochronology, as a dating and stratigraphic tool, in precise palaeoclimate and environmental reconstruction, has expanded significantly in recent years. The power of tephrochronology rests on the fact that a tephra layer can stratigraphically link records at the resolution of as little as a few years, and that the most precise age for a particular tephra can be imported into any site where it is found. In order to maximise the potential of tephras for this purpose it is necessary to have the most precise and robustly tested age estimate possible available for key tephras. Given the varying number and quality of dates associated with different tephras it is important to be able to build age models to test competing tephra dates. Recent advances in Bayesian age modelling of dates in sequence have radically extended our ability to build such stratigraphic age models. As an example of the potential here we use Bayesian methods, now widely applied, to examine the dating of some key Late Quaternary tephras from Italy. These are: the Agnano Monte Spina Tephra (AMST), the Neapolitan Yellow Tuff (NYT) and the Agnano Pomici Principali (APP), and all of them have multiple estimates of their true age. Further, we use the Bayesian approaches to generate a revised mixed radiocarbon/varve chronology for the important Lateglacial section of the Lago Grande Monticchio record, as a further illustration of what can be achieved by a Bayesian approach. With all three tephras we were able to produce viable model ages for the tephra, validate the proposed 40Ar/ 39Ar age ranges for these tephras, and provide relatively high precision age models. The results of the Bayesian integration of dating and stratigraphic information, suggest that the current best 95% confidence calendar age estimates for the AMST are 4690-4300 cal BP, the NYT 14320-13900 cal BP, and the APP 12380-12140 cal BP.
Hernández-Vicente, Adrián; Pérez-Isaac, Raúl; Santín-Medeiros, Fernanda; Cristi-Montero, Carlos; Casajús, Jose Antonio; Garatachea, Nuria
2017-01-01
Background The SenseWear Armband (SWA) is a monitor that can be used to estimate energy expenditure (EE); however, it has not been validated in healthy adults. The objective of this paper was to study the validity of the SWA for quantifying EE levels. Methods Twenty-three healthy adults (age 40–55 years, mean: 48±3.42 years) performed different types of standardized physical activity (PA) for 10 minutes (rest, walking at 3 and 5 km·h-1, running at 7 and 9 km·h-1, and sitting/standing at a rate of 30 cycle·min-1). Participants wore the SWA on their right arm, and their EE was measured by indirect calorimetry (IC) the gold standard. Results There were significant differences between the SWA and IC, except in the group that ran at 9 km·h-1 (>9 METs). Bland-Altman analysis showed a BIAS of 1.56 METs (±1.83 METs) and limits of agreement (LOA) at 95% of −2.03 to 5.16 METs. There were indications of heteroscedasticity (R2 =0.03; P<0.05). Analysis of the receiver operating characteristic (ROC) curves showed that the SWA seems to be not sensitive enough to estimate the level of EE at highest intensities. Conclusions The SWA is not as precise in estimating EE as IC, but it could be a useful tool to determine levels of EE at low intensities. PMID:28361062
Blache, Yoann; Bobbert, Maarten; Argaud, Sebastien; Pairot de Fontenay, Benoit; Monteil, Karine M
2013-08-01
In experiments investigating vertical squat jumping, the HAT segment is typically defined as a line drawn from the hip to some point proximally on the upper body (eg, the neck, the acromion), and the hip joint as the angle between this line and the upper legs (θUL-HAT). In reality, the hip joint is the angle between the pelvis and the upper legs (θUL-pelvis). This study aimed to estimate to what extent hip joint definition affects hip joint work in maximal squat jumping. Moreover, the initial pelvic tilt was manipulated to maximize the difference in hip joint work as a function of hip joint definition. Twenty-two male athletes performed maximum effort squat jumps in three different initial pelvic tilt conditions: backward (pelvisB), neutral (pelvisN), and forward (pelvisF). Hip joint work was calculated by integrating the hip net joint torque with respect to θUL-HAT (WUL-HAT) or with respect to θUL-pelvis (WUL-pelvis). θUL-HAT was greater than θUL-pelvis in all conditions. WUL-HAT overestimated WULpelvis by 33%, 39%, and 49% in conditions pelvisF, pelvisN, and pelvisB, respectively. It was concluded that θUL-pelvis should be measured when the mechanical output of hip extensor muscles is estimated.
Estimation of shoreline position and change using airborne topographic lidar data
Stockdon, H.F.; Sallenger, A.H.; 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.
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)
Perez-Quezada, Jorge F.; Brito, Carla E.; Cabezas, Julián; Galleguillos, Mauricio; Fuentes, Juan P.; Bown, Horacio E.; Franck, Nicolás
2016-12-01
Making accurate estimations of daily and annual Rs fluxes is key for understanding the carbon cycle process and projecting effects of climate change. In this study we used high-frequency sampling (24 measurements per day) of Rs in a temperate rainforest during 1 year, with the objective of answering the questions of when and how often measurements should be made to obtain accurate estimations of daily and annual Rs. We randomly selected data to simulate samplings of 1, 2, 4 or 6 measurements per day (distributed either during the whole day or only during daytime), combined with 4, 6, 12, 26 or 52 measurements per year. Based on the comparison of partial-data series with the full-data series, we estimated the performance of different partial sampling strategies based on bias, precision and accuracy. In the case of annual Rs estimation, we compared the performance of interpolation vs. using non-linear modelling based on soil temperature. The results show that, under our study conditions, sampling twice a day was enough to accurately estimate daily Rs (RMSE < 10 % of average daily flux), even if both measurements were done during daytime. The highest reduction in RMSE for the estimation of annual Rs was achieved when increasing from four to six measurements per year, but reductions were still relevant when further increasing the frequency of sampling. We found that increasing the number of field campaigns was more effective than increasing the number of measurements per day, provided a minimum of two measurements per day was used. Including night-time measurements significantly reduced the bias and was relevant in reducing the number of field campaigns when a lower level of acceptable error (RMSE < 5 %) was established. Using non-linear modelling instead of linear interpolation did improve the estimation of annual Rs, but not as expected. In conclusion, given that most of the studies of Rs use manual sampling techniques and apply only one measurement per day, we
Effects of linear trends on estimation of noise in GNSS position time-series
NASA Astrophysics Data System (ADS)
Dmitrieva, K.; Segall, P.; Bradley, A. M.
2017-01-01
A thorough understanding of time-dependent noise in Global Navigation Satellite System (GNSS) position time-series is necessary for computing uncertainties in any signals found in the data. However, estimation of time-correlated noise is a challenging task and is complicated by the difficulty in separating noise from signal, the features of greatest interest in the time-series. In this paper, we investigate how linear trends affect the estimation of noise in daily GNSS position time-series. We use synthetic time-series to study the relationship between linear trends and estimates of time-correlated noise for the six most commonly cited noise models. We find that the effects of added linear trends, or conversely de-trending, vary depending on the noise model. The commonly adopted model of random walk (RW), flicker noise (FN) and white noise (WN) is the most severely affected by de-trending, with estimates of low-amplitude RW most severely biased. FN plus WN is least affected by adding or removing trends. Non-integer power-law noise estimates are also less affected by de-trending, but are very sensitive to the addition of trend when the spectral index is less than one. We derive an analytical relationship between linear trends and the estimated RW variance for the special case of pure RW noise. Overall, we find that to ascertain the correct noise model for GNSS position time-series and to estimate the correct noise parameters, it is important to have independent constraints on the actual trends in the data.
Effects of linear trends on estimation of noise in GNSS position time series
NASA Astrophysics Data System (ADS)
Dmitrieva, K.; Segall, P.; Bradley, A. M.
2016-10-01
A thorough understanding of time dependent noise in Global Navigation Satellite System (GNSS) position time series is necessary for computing uncertainties in any signals found in the data. However, estimation of time-correlated noise is a challenging task and is complicated by the difficulty in separating noise from signal, the features of greatest interest in the time series. In this paper we investigate how linear trends affect the estimation of noise in daily GNSS position time series. We use synthetic time series to study the relationship between linear trends and estimates of time-correlated noise for the six most commonly cited noise models. We find that the effects of added linear trends, or conversely de-trending, vary depending on the noise model. The commonly adopted model of random walk (RW), flicker noise (FN), and white noise (WN) is the most severely affected by de-trending, with estimates of low amplitude RW most severely biased. Flicker noise plus white noise is least affected by adding or removing trends. Non-integer power-law noise estimates are also less affected by de-trending, but are very sensitive to the addition of trend when the spectral index is less than one. We derive an analytical relationship between linear trends and the estimated random walk variance for the special case of pure random walk noise. Overall, we find that to ascertain the correct noise model for GNSS position time series and to estimate the correct noise parameters, it is important to have independent constraints on the actual trends in the data.
Effects of linear trends on estimation of noise in GNSS position time-series
Dmitrieva, K.; Segall, P.; Bradley, A. M.
2016-10-20
A thorough understanding of time-dependent noise in Global Navigation Satellite System (GNSS) position time-series is necessary for computing uncertainties in any signals found in the data. However, estimation of time-correlated noise is a challenging task and is complicated by the difficulty in separating noise from signal, the features of greatest interest in the time-series. In this study, we investigate how linear trends affect the estimation of noise in daily GNSS position time-series. We use synthetic time-series to study the relationship between linear trends and estimates of time-correlated noise for the six most commonly cited noise models. We find that themore » effects of added linear trends, or conversely de-trending, vary depending on the noise model. The commonly adopted model of random walk (RW), flicker noise (FN) and white noise (WN) is the most severely affected by de-trending, with estimates of low-amplitude RW most severely biased. FN plus WN is least affected by adding or removing trends. Non-integer power-law noise estimates are also less affected by de-trending, but are very sensitive to the addition of trend when the spectral index is less than one. We derive an analytical relationship between linear trends and the estimated RW variance for the special case of pure RW noise. Finally, overall, we find that to ascertain the correct noise model for GNSS position time-series and to estimate the correct noise parameters, it is important to have independent constraints on the actual trends in the data.« less
Effects of linear trends on estimation of noise in GNSS position time-series
Dmitrieva, K.; Segall, P.; Bradley, A. M.
2016-10-20
A thorough understanding of time-dependent noise in Global Navigation Satellite System (GNSS) position time-series is necessary for computing uncertainties in any signals found in the data. However, estimation of time-correlated noise is a challenging task and is complicated by the difficulty in separating noise from signal, the features of greatest interest in the time-series. In this study, we investigate how linear trends affect the estimation of noise in daily GNSS position time-series. We use synthetic time-series to study the relationship between linear trends and estimates of time-correlated noise for the six most commonly cited noise models. We find that the effects of added linear trends, or conversely de-trending, vary depending on the noise model. The commonly adopted model of random walk (RW), flicker noise (FN) and white noise (WN) is the most severely affected by de-trending, with estimates of low-amplitude RW most severely biased. FN plus WN is least affected by adding or removing trends. Non-integer power-law noise estimates are also less affected by de-trending, but are very sensitive to the addition of trend when the spectral index is less than one. We derive an analytical relationship between linear trends and the estimated RW variance for the special case of pure RW noise. Finally, overall, we find that to ascertain the correct noise model for GNSS position time-series and to estimate the correct noise parameters, it is important to have independent constraints on the actual trends in the data.
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
NASA Astrophysics Data System (ADS)
Hamila, Ridha; Lakhzouri, Abdelmonaem; Lohan, Elena Simona; Renfors, Markku
2005-12-01
Line-of-sight signal delay estimation is a crucial element for any mobile positioning system. Estimating correctly the delay of the first arriving path is a challenging topic in severe propagation environments, such as closely spaced multipaths in multiuser scenario. Previous studies showed that there are many linear and nonlinear techniques able to solve closely spaced multipaths when the system is not bandlimited. However, using root raised cosine (RRC) pulse shaping introduces additional errors in the delay estimation process compared to the case with rectangular pulse shaping due to the inherent bandwidth limitation. In this paper, we introduce a novel technique for asynchronous WCDMA multipath delay estimation based on deconvolution with a suitable pulse shape, followed by Teager-Kaiser operator. The deconvolution stage is employed to reduce the effect of the bandlimiting pulse shape.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Carson, Jeffrey J. L.; Ephrat, Pinhas; Seabrook, Adam
2008-02-01
Source localization by photoacoustic tomography is dependent on time-of-flight pressure data collected by one or more transducers at multiple positions about the imaged object. Errors in transducer position lead directly to errors in source localization. The objective of this work was to develop a method for experimental determination of transducer position for the purpose of (i) comparison of the measured to the expected transducer position, and (ii) automated calibration of transducer position in scanning and array setups. Our approach was to acquire the time of arrival data at each transducer using a small, point-like photoacoustic source from many locations in the imaged volume. Source placement was controlled with a 3D robotic gantry (accuracy +/-0.01 mm). Time of arrival data for all source locations was used to compute a vector of source-transducer distances. The coordinates of each transducer location were then found by nonlinear parameter estimation for a function that related the source distance to the known source location and the unknown transducer location. Application of the method to a planar array of 14 transducers resulted in identification of the position of each element in the transducer array. This finding suggested that the method may be useful for (i) mapping transducer positions during validation and calibration studies, (ii) measuring the effective position of transducers that are asymmetric or have fabrication errors, and (iii) obtaining the mapping relationship between the imaging system and the imaging volume in situations where coregistration of image data from other modalities is desired.
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.
3D position estimation using a single coil and two magnetic field sensors.
Tadayon, P; Staude, G; Felderhoff, T
2015-01-01
This paper presents an algorithm which enables the estimation of relative 3D position of a sensor module with two magnetic sensors with respect to a magnetic field source using a single transmitting coil. Starting with the description of the ambiguity problem caused by using a single coil, a system concept comprising two sensors having a fixed spatial relation to each other is introduced which enables the unique determination of the sensors' position in 3D space. For this purpose, an iterative two-step algorithm is presented: In a first step, the data of one sensor is used to limit the number of possible position solutions. In a second step, the spatial relation between the sensors is used to determine the correct sensor position.
Vargas, Alfredo; Krivokapic, Itana; Hauser, Andreas; Lawson Daku, Latévi Max
2013-03-21
We report a detailed DFT study of the energetic and structural properties of the spin-crossover Co(ii) complex [Co(tpy)(2)](2+) (tpy = 2,2':6',2''-terpyridine) in the low-spin (LS) and the high-spin (HS) states, using several generalized gradient approximation and hybrid functionals. In either spin-state, the results obtained with the functionals are consistent with one another and in good agreement with available experimental data. Although the different functionals correctly predict the LS state as the electronic ground state of [Co(tpy)(2)](2+), they give estimates of the HS-LS zero-point energy difference which strongly depend on the functional used. This dependency on the functional was also reported for the DFT estimates of the zero-point energy difference in the HS complex [Co(bpy)(3)](2+) (bpy = 2,2'-bipyridine) [A. Vargas, A. Hauser and L. M. Lawson Daku, J. Chem. Theory Comput., 2009, 5, 97]. The comparison of the and estimates showed that all functionals correctly predict an increase of the zero-point energy difference upon the bpy → tpy ligand substitution, which furthermore weakly depends on the functionals, amounting to . From these results and basic thermodynamic considerations, we establish that, despite their limitations, current DFT methods can be applied to the accurate determination of the spin-state energetics of complexes of a transition metal ion, or of these complexes in different environments, provided that the spin-state energetics is accurately known in one case. Thus, making use of the availability of a highly accurate ab initio estimate of the HS-LS energy difference in the complex [Co(NCH)(6)](2+) [L. M. Lawson Daku, F. Aquilante, T. W. Robinson and A. Hauser, J. Chem. Theory Comput., 2012, 8, 4216], we obtain for [Co(tpy)(2)](2+) and [Co(bpy)(3)](2+) best estimates of and , in good agreement with the known magnetic behaviour of the two complexes.
NASA Astrophysics Data System (ADS)
Zhang, W.; Haase, J. S.; Hertzog, A.; Lou, Y.; Vincent, R. A.
2015-12-01
Gravity waves (GWs) play an important role in transferring energy and momentum from the troposphere to the middle atmosphere. However, shorter period GWs are generally not explicitly resolved in general circulation models but need to be parameterized instead. Super pressure balloons, which float on the isopycnal surfaces, provide a direct access to measure GW characteristics as a function of wave intrinsic frequency that are needed for these parameterizations. The 30 s sampling rate of the GPS receivers carried on the balloons deployed in 2010 Concordiasi campaign in the Antarctic region is much higher compared to the previous campaigns and can cover the full range of the GW spectrum. Two among 19 balloons in the Concordiasi campaign are also equipped with the high-accuracy dual-frequency GPS receivers initially developed for GPS radio occultation research in addition to the regular single-frequency receivers, which enables us to expect a better accuracy of balloon positions for the purpose of GW momentum flux estimates. The positions are estimated using the Precise Point Positioning with Ambiguity Resolution (PPPAR) method based on the GPS data. Improvements of the positions are significant, from ~3-10 m to ~0.1-0.2 m in 3-D positions, which makes it possible to resolve the Eulerian pressure independently of height for the estimation of the intrinsic phase speed. The impacts of the position improvements on the final GW parameters (momentum flux and intrinsic phase speed) retrievals are highlighted, with ~0.54 mPa difference of the mean absolute momentum flux in Antarctic region and considerable difference in the distribution of the intrinsic phase speed.
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.
Regularized estimation of vertical total electron content from Global Positioning System data
NASA Astrophysics Data System (ADS)
Arikan, F.; Erol, C. B.; Arikan, O.
2003-12-01
A novel regularization technique which can combine signals from all Global Positioning System (GPS) satellites for a given instant and a given receiver is developed to estimate the vertical total electron content (VTEC) values for the 24-hour period without missing any important features in the temporal domain. The algorithm is based on the minimization of a cost function which also includes a high pass penalty filter. Optional weighting function and sliding window median filter are added to enrich the processing and smoothing of the data. The developed regularized estimation algorithm is applied to GPS data for various locations for the solar maximum week of 23-28 April 2001. The parameter set that is required by the estimation algorithm is chosen optimally using appropriate error functions. This robust and optimum parameter set can be used for all latitudes and for both quiet and disturbed days. It is observed that the estimated TEC values are in general accordance with the TEC estimates from other global ionospheric maps, especially for quiet days and midlatitudes. Owing to its 30 s time resolution, the regularized VTEC estimates from the developed algorithm are very successful in representation and tracking of sudden temporal variations of the ionosphere, especially for high latitudes and during ionospheric disturbances.
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.
Wang, Zhihua; Yang, Zhaochu; Dong, Tao
2017-01-01
Rapid growth of the aged population has caused an immense increase in the demand for healthcare services. Generally, the elderly are more prone to health problems compared to other age groups. With effective monitoring and alarm systems, the adverse effects of unpredictable events such as sudden illnesses, falls, and so on can be ameliorated to some extent. Recently, advances in wearable and sensor technologies have improved the prospects of these service systems for assisting elderly people. In this article, we review state-of-the-art wearable technologies that can be used for elderly care. These technologies are categorized into three types: indoor positioning, activity recognition and real time vital sign monitoring. Positioning is the process of accurate localization and is particularly important for elderly people so that they can be found in a timely manner. Activity recognition not only helps ensure that sudden events (e.g., falls) will raise alarms but also functions as a feasible way to guide people’s activities so that they avoid dangerous behaviors. Since most elderly people suffer from age-related problems, some vital signs that can be monitored comfortably and continuously via existing techniques are also summarized. Finally, we discussed a series of considerations and future trends with regard to the construction of “smart clothing” system. PMID:28208620
Wang, Zhihua; Yang, Zhaochu; Dong, Tao
2017-02-10
Rapid growth of the aged population has caused an immense increase in the demand for healthcare services. Generally, the elderly are more prone to health problems compared to other age groups. With effective monitoring and alarm systems, the adverse effects of unpredictable events such as sudden illnesses, falls, and so on can be ameliorated to some extent. Recently, advances in wearable and sensor technologies have improved the prospects of these service systems for assisting elderly people. In this article, we review state-of-the-art wearable technologies that can be used for elderly care. These technologies are categorized into three types: indoor positioning, activity recognition and real time vital sign monitoring. Positioning is the process of accurate localization and is particularly important for elderly people so that they can be found in a timely manner. Activity recognition not only helps ensure that sudden events (e.g., falls) will raise alarms but also functions as a feasible way to guide people's activities so that they avoid dangerous behaviors. Since most elderly people suffer from age-related problems, some vital signs that can be monitored comfortably and continuously via existing techniques are also summarized. Finally, we discussed a series of considerations and future trends with regard to the construction of "smart clothing" system.
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
NASA Astrophysics Data System (ADS)
Zeng, Dong; Gong, Changfei; Bian, Zhaoying; Huang, Jing; Zhang, Xinyu; Zhang, Hua; Lu, Lijun; Niu, Shanzhou; Zhang, Zhang; Liang, Zhengrong; Feng, Qianjin; Chen, Wufan; Ma, Jianhua
2016-11-01
Dynamic myocardial perfusion computed tomography (MPCT) is a promising technique for quick diagnosis and risk stratification of coronary artery disease. However, one major drawback of dynamic MPCT imaging is the heavy radiation dose to patients due to its dynamic image acquisition protocol. In this work, to address this issue, we present a robust dynamic MPCT deconvolution algorithm via adaptive-weighted tensor total variation (AwTTV) regularization for accurate residue function estimation with low-mA s data acquisitions. For simplicity, the presented method is termed ‘MPD-AwTTV’. More specifically, the gains of the AwTTV regularization over the original tensor total variation regularization are from the anisotropic edge property of the sequential MPCT images. To minimize the associative objective function we propose an efficient iterative optimization strategy with fast convergence rate in the framework of an iterative shrinkage/thresholding algorithm. We validate and evaluate the presented algorithm using both digital XCAT phantom and preclinical porcine data. The preliminary experimental results have demonstrated that the presented MPD-AwTTV deconvolution algorithm can achieve remarkable gains in noise-induced artifact suppression, edge detail preservation, and accurate flow-scaled residue function and MPHM estimation as compared with the other existing deconvolution algorithms in digital phantom studies, and similar gains can be obtained in the porcine data experiment.
McMillan, K; Bostani, M; McNitt-Gray, M; McCollough, C
2015-06-15
Purpose: Most patient models used in Monte Carlo-based estimates of CT dose, including computational phantoms, do not have tube current modulation (TCM) data associated with them. While not a problem for fixed tube current simulations, this is a limitation when modeling the effects of TCM. Therefore, the purpose of this work was to develop and validate methods to estimate TCM schemes for any voxelized patient model. Methods: For 10 patients who received clinically-indicated chest (n=5) and abdomen/pelvis (n=5) scans on a Siemens CT scanner, both CT localizer radiograph (“topogram”) and image data were collected. Methods were devised to estimate the complete x-y-z TCM scheme using patient attenuation data: (a) available in the Siemens CT localizer radiograph/topogram itself (“actual-topo”) and (b) from a simulated topogram (“sim-topo”) derived from a projection of the image data. For comparison, the actual TCM scheme was extracted from the projection data of each patient. For validation, Monte Carlo simulations were performed using each TCM scheme to estimate dose to the lungs (chest scans) and liver (abdomen/pelvis scans). Organ doses from simulations using the actual TCM were compared to those using each of the estimated TCM methods (“actual-topo” and “sim-topo”). Results: For chest scans, the average differences between doses estimated using actual TCM schemes and estimated TCM schemes (“actual-topo” and “sim-topo”) were 3.70% and 4.98%, respectively. For abdomen/pelvis scans, the average differences were 5.55% and 6.97%, respectively. Conclusion: Strong agreement between doses estimated using actual and estimated TCM schemes validates the methods for simulating Siemens topograms and converting attenuation data into TCM schemes. This indicates that the methods developed in this work can be used to accurately estimate TCM schemes for any patient model or computational phantom, whether a CT localizer radiograph is available or not
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.
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.
The role of internal forward models and proprioception in hand position estimation.
Yavari, Fatemeh; Towhidkhah, Farzad; Ahmadi-Pajouh, Mohammad-Ali; Darainy, Mohammad
2015-09-01
Our ability to properly move and react in different situations is largely dependent on our perception of our limbs' position. At least three sources - vision, proprioception, and internal forward models (FMs) - seem to contribute to this perception. To the best of our knowledge, the effect of each source has not been studied individually. Specifically, role of FM has been ignored in some previous studies. We hypothesized that FM has a critical role in subjects' perception which needs to be considered in the relevant studies to obtain more reliable results. Therefore, we designed an experiment with the goal of investigating FM and proprioception role in subjects' perception of their hand's position. Three groups of subjects were recruited in the study. Based on the experiment design, it was supposed that subjects in different groups relied on proprioception, FM, and both of them for estimating their unseen hand's position. Comparing the results of three groups revealed significant difference between their estimation' errors. FM provided minimum estimation error, while proprioception had a bias error in the tested region. Integrating proprioception with FM decreased this error. Integration of two Gaussian functions, fitted to the error distribution of FM and proprioception groups, was simulated and created a mean error value almost similar to the experimental observation. These results suggest that FM role needs to be considered when studying the perceived position of the limbs. This can lead to gain better insights into the mechanisms underlying the perception of our limbs' position which might have potential clinical and rehabilitation applications, e.g., in the postural control of elderly which are at high risk of falls and injury because of deterioration of their perception with age.
Chan, Yi-Hsin; Tsai, Wei-Chung; Shen, Changyu; Han, Seongwook; Chen, Lan S.; Lin, Shien-Fong; Chen, Peng-Sheng
2015-01-01
Background We recently reported that subcutaneous nerve activity (SCNA) can be used to estimate sympathetic tone. Objectives To test the hypothesis that left thoracic SCNA is more accurate than heart rate variability (HRV) in estimating cardiac sympathetic tone in ambulatory dogs with myocardial infarction (MI). Methods We used an implanted radiotransmitter to study left stellate ganglion nerve activity (SGNA), vagal nerve activity (VNA), and thoracic SCNA in 9 dogs at baseline and up to 8 weeks after MI. HRV was determined based by time-domain, frequency-domain and non-linear analyses. Results The correlation coefficients between integrated SGNA and SCNA averaged 0.74 (95% confidence interval (CI), 0.41–1.06) at baseline and 0.82 (95% CI, 0.63–1.01) after MI (P<.05 for both). The absolute values of the correlation coefficients were significant larger than that between SGNA and HRV analysis based on time-domain, frequency-domain and non-linear analyses, respectively, at baseline (P<.05 for all) and after MI (P<.05 for all). There was a clear increment of SGNA and SCNA at 2, 4, 6 and 8 weeks after MI, while HRV parameters showed no significant changes. Significant circadian variations were noted in SCNA, SGNA and all HRV parameters at baseline and after MI, respectively. Atrial tachycardia (AT) episodes were invariably preceded by the SCNA and SGNA, which were progressively increased from 120th, 90th, 60th to 30th s before the AT onset. No such changes of HRV parameters were observed before AT onset. Conclusion SCNA is more accurate than HRV in estimating cardiac sympathetic tone in ambulatory dogs with MI. PMID:25778433
A method of rapidly estimating the position of the laminar separation point
NASA Technical Reports Server (NTRS)
Von Doenhoff, Albert E
1938-01-01
A method is described of rapidly estimating the position of the laminar separation point from the given pressure distribution along a body; the method is applicable to a fairly wide variety of cases. The laminar separation point is found by the von Karman-Millikan method for a series of velocity distributions along a flat plate, which consist of a region of uniform velocity followed by a region of uniform decreased velocity. It is shown that such a velocity distribution can frequently replace the actual velocity distribution along a body insofar as the effects on laminar separation are concerned. An example of the application of the method is given by using it to calculate the position of the laminar separation point on the NACA 0012 airfoil section at zero lift. The agreement between the position of the separation point calculated according to the present method and that found from more elaborate computations is very good.
Method for quantitative estimation of position perception using a joystick during linear movement.
Wada, Y; Tanaka, M; Mori, S; Chen, Y; Sumigama, S; Naito, H; Maeda, M; Yamamoto, M; Watanabe, S; Kajitani, N
1996-12-01
We designed a method for quantitatively estimating self-motion perceptions during passive body movement on a sled. The subjects were instructed to tilt a joystick in proportion to perceived displacement from a giving starting position during linear movement with varying displacements of 4 m, 10 m and 16 m induced by constant acceleration of 0.02 g, 0.05 g and 0.08 g along the antero-posterior axis. With this method, we could monitor not only subjective position perceptions but also response latencies for the beginning (RLbgn) and end (RLend) of the linear movement. Perceived body position fitted Stevens' power law, where R=kSn (R is output of the joystick, k is a constant, S is the displacement from the linear movement and n is an exponent). RLbgn decreased as linear acceleration increased. We conclude that this method is useful in analyzing the features and sensitivities of self-motion perceptions during movement.
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.
NASA Astrophysics Data System (ADS)
Ganguli, Anurag; Saha, Bhaskar; Raghavan, Ajay; Kiesel, Peter; Arakaki, Kyle; Schuh, Andreas; Schwartz, Julian; Hegyi, Alex; Sommer, Lars Wilko; Lochbaum, Alexander; Sahu, Saroj; Alamgir, Mohamed
2017-02-01
A key challenge hindering the mass adoption of Lithium-ion and other next-gen chemistries in advanced battery applications such as hybrid/electric vehicles (xEVs) has been management of their functional performance for more effective battery utilization and control over their life. Contemporary battery management systems (BMS) reliant on monitoring external parameters such as voltage and current to ensure safe battery operation with the required performance usually result in overdesign and inefficient use of capacity. More informative embedded sensors are desirable for internal cell state monitoring, which could provide accurate state-of-charge (SOC) and state-of-health (SOH) estimates and early failure indicators. Here we present a promising new embedded sensing option developed by our team for cell monitoring, fiber-optic (FO) sensors. High-performance large-format pouch cells with embedded FO sensors were fabricated. This second part of the paper focuses on the internal signals obtained from these FO sensors. The details of the method to isolate intercalation strain and temperature signals are discussed. Data collected under various xEV operational conditions are presented. An algorithm employing dynamic time warping and Kalman filtering was used to estimate state-of-charge with high accuracy from these internal FO signals. Their utility for high-accuracy, predictive state-of-health estimation is also explored.
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)
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.
Smith, C.A.
1987-01-01
The ionosphere delays transmissions from the Global Positioning System (GPS), as well as those from other satellite systems. At the GPS frequencies (L-Band), this delay is directly proportional to the total ionospheric electron content (TEC) along the line-of-sight to the satellite. Classified receivers have access to 2 frequencies to allow them to measure this delay through the difference in the ionospheric effect at the 2 frequencies, but commercial, single-frequency receivers have had no direct method for estimating the ionospheric delay; they have had to rely on a TEC prediction. Two methods are described for single-frequency GPS receivers to estimate the ionospheric TEC directly. These methods take advantage of the dispersive nature of the ionosphere at L-Band frequencies, which causes a phase advance of the carrier that is opposite to the group delay of the GPS code and data.
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…
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.
Harrow, Lisa; Espie, Colin
2010-03-01
The 'quarter-hour rule' (QHR) instructs the person with insomnia to get out of bed after 15 min of wakefulness and return to bed only when sleep feels imminent. Recent research has identified that sleep can be significantly improved using this simple intervention (Malaffo and Espie, Sleep, 27(s), 2004, 280; Sleep, 29 (s), 2006, 257), but successful implementation depends on estimating time without clock monitoring, and the insomnia literature indicates poor time perception is a maintaining factor in primary insomnia (Harvey, Behav. Res. Ther., 40, 2002, 869). This study expands upon previous research with the aim of identifying whether people with insomnia can accurately perceive a 15-min interval during the sleep-onset period, and therefore successfully implements the QHR. A mixed models anova design was applied with between-participants factor of group (insomnia versus good sleepers) and within-participants factor of context (night versus day). Results indicated no differences between groups and contexts on time estimation tasks. This was despite an increase in arousal in the night context for both groups, and tentative support for the impact of arousal in inducing underestimations of time. These results provide promising support for the successful application of the QHR in people with insomnia. The results are discussed in terms of whether the design employed successfully accessed the processes that are involved in distorting time perception in insomnia. Suggestions for future research are provided and limitations of the current study discussed.
NASA Astrophysics Data System (ADS)
Craig, Norman C.; Demaison, Jean; Groner, Peter; Rudolph, Heinz Dieter; Vogt, Natalja
2015-06-01
An accurate equilibrium structure of trans-hexatriene has been determined by the mixed estimation method with rotational constants from 8 deuterium and carbon isotopologues and high-level quantum chemical calculations. In the mixed estimation method bond parameters are fit concurrently to moments of inertia of various isotopologues and to theoretical bond parameters, each data set carrying appropriate uncertainties. The accuracy of this structure is 0.001 Å and 0.1°. Structures of similar accuracy have been computed for the cis,cis, trans,trans, and cis,trans isomers of octatetraene at the CCSD(T) level with a basis set of wCVQZ(ae) quality adjusted in accord with the experience gained with trans-hexatriene. The structures are compared with butadiene and with cis-hexatriene to show how increasing the length of the chain in polyenes leads to increased blurring of the difference between single and double bonds in the carbon chain. In trans-hexatriene r(“C_1=C_2") = 1.339 Å and r(“C_3=C_4") = 1.346 Å compared to 1.338 Å for the “double" bond in butadiene; r(“C_2-C_3") = 1.449 Å compared to 1.454 Å for the “single" bond in butadiene. “Double" bonds increase in length; “single" bonds decrease in length.
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.
Position estimation for fiducial marks based on high intensity retroreflective tape
NASA Astrophysics Data System (ADS)
Trushkina, Anna; Serikova, Mariya; Pantyushin, Anton
2016-04-01
3D position estimation of an object usually involve computer vision techniques, which require fiducial markers attached to the objects surface. Modern technology provides a high intensity retroreflective material in the form of a tape which is easy to mount to the object and can be used as a base for fiducial marks. But inevitable drawback of the tapes with the highest retroreflective intensity is the presence of technological pattern which affects spatial distribution of retroreflected light and deforms border of any print on tape's surface. In this work we compare various shapes of metrological pattern and examine Fourier descriptors based image processing to obtain estimation of accuracy of mark image position. To verify results we developed a setup consisting of a camera based on Sony ICX274 CCD, 25 mm lens, 800 nm LED lightning and high intensity microprismatic tape. The experiment showed that there is no significant difference between proposed mark shapes as well as between direct and indirect contrast when proposed image processing is used. The experiments confirmed that the image processing implemented without elimination of non-reflective netting pattern can only provide an accuracy of coordinates extraction close to 1 pix.
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
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.
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.
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
Glos, Martin; Romberg, Dietrich; Endres, Susanne; Fietze, Ingo
2007-02-01
To determine the short-term effects of non-invasive positive pressure ventilation (PPV) on spontaneous baroreflex sensitivity, we acquired time series of RR interval and beat-to-beat blood pressure in 55 healthy volunteers (mean age 46.5+/-10.5 years), who performed breathing tests on four occasions at frequencies of 12 and 15/min, with application of PPV of 5 mbar, and without positive pressure (control). Using spectral and transfer function analysis, we estimated RR interval variability (HRV) and systolic blood pressure variability (SBPV), as well as the gain (alpha-index) and phase shift (Phi) of the baroreceptor reflex for low- (LF) and high-frequency (HF) bands. Compared to control breathing, PPV at 12 and 15/min led to an increase in mean RR (p<0.001) and blood pressure (p<0.05). The alpha-index in the HF band increased significantly due to PPV for both respiratory frequencies (p<0.05). Phase shifts did not show significant changes in response to pressure ventilation. These results indicate that short-term administration of PPV in normal subjects elicits significant enhancement in the HF index of baroreflex gain. These findings may contribute to understanding the mechanisms, indications, and effectiveness of positive pressure breathing strategies in treating cardiorespiratory and other disease conditions.
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).
NASA Astrophysics Data System (ADS)
McGee, D.; Donohoe, A.; Marshall, J.; Ferreira, D.
2012-12-01
The mean position and seasonal migration of the Intertropical Convergence Zone (ITCZ) govern the intensity, spatial distribution and seasonality of precipitation throughout the tropics as well as the magnitude and direction of interhemispheric atmospheric heat transport (AHT). As a result of these links to global tropical precipitation and hemispheric heat budgets, paleoclimate studies have commonly sought to use reconstructions of local precipitation and surface winds to identify past shifts in the ITCZ's mean position or seasonal extent. Records indicate close ties between ITCZ position and interhemispheric surface temperature gradients in past climates, with the ITCZ shifting toward the warmer hemisphere. This shift would increase AHT into the cooler hemisphere to at least partially compensate for cooling there. Despite widespread qualitative evidence consistent with ITCZ shifts, few proxy records offer quantitative estimates of the distance of these shifts or of the associated changes in AHT. Here we present a strategy for placing quantitative limits on past changes in mean annual ITCZ position and interhemispheric AHT based on explorations of the modern seasonal cycle and models of present and past climates. We use reconstructions of tropical sea surface temperature gradients to place bounds on globally averaged ITCZ position and interhemispheric AHT during the Last Glacial Maximum, Heinrich Stadial 1, and the Mid-Holocene (6 ka). Though limited by the small number of SST records available, our results suggest that past shifts in the global mean ITCZ were small, typically less than 1 degree of latitude. Past changes in interhemispheric AHT may have been substantial, with anomalies approximately equal to the magnitude of modern interhemispheric AHT. Using constraints on the invariance of the total (ocean+atmosphere) heat transport we suggest possible bounds on fluctuations of the OHT and AMOC during Heinrich Stadial 1. We also explore ITCZ shifts in models and
NASA Technical Reports Server (NTRS)
Knox, C. E.; Vicroy, D. D.; Scanlon, C.
1984-01-01
Simulation and flight tests were conducted to compare the accuracy of two algorithms designed to compute a position estimate with an airborne navigation computer. Both algorithms used ILS localizer and DME radio signals to compute a position difference vector to be used as an input to the navigation computer position estimate filter. The results of these tests show that the position estimate accuracy and response to artificially induced errors are improved when the position estimate is computed by an algorithm that geometrically combines DME and ILS localizer information to form a single component of error rather than by an algorithm that produces two independent components of error, one from a DMD input and the other from the ILS localizer input.
Beretta, Elisa; De Momi, Elena; Camomilla, Valentina; Cereatti, Andrea; Cappozzo, Aurelio; Ferrigno, Giancarlo
2014-09-01
In computer-assisted knee surgery, the accuracy of the localization of the femur centre of rotation relative to the hip-bone (hip joint centre) is affected by the unavoidable and untracked pelvic movements because only the femoral pose is acquired during passive pivoting manoeuvres. We present a dual unscented Kalman filter algorithm that allows the estimation of the hip joint centre also using as input the position of a pelvic reference point that can be acquired with a skin marker placed on the hip, without increasing the invasiveness of the surgical procedure. A comparative assessment of the algorithm was carried out using data provided by in vitro experiments mimicking in vivo surgical conditions. Soft tissue artefacts were simulated and superimposed onto the position of a pelvic landmark. Femoral pivoting made of a sequence of star-like quasi-planar movements followed by a circumduction was performed. The dual unscented Kalman filter method proved to be less sensitive to pelvic displacements, which were shown to be larger during the manoeuvres in which the femur was more adducted. Comparable accuracy between all the analysed methods resulted for hip joint centre displacements smaller than 1 mm (error: 2.2 ± [0.2; 0.3] mm, median ± [inter-quartile range 25%; inter-quartile range 75%]) and between 1 and 6 mm (error: 4.8 ± [0.5; 0.8] mm) during planar movements. When the hip joint centre displacement exceeded 6 mm, the dual unscented Kalman filter proved to be more accurate than the other methods by 30% during multi-planar movements (error: 5.2 ± [1.2; 1] mm).
Belge, Bénédicte; Coche, Emmanuel; Pasquet, Agnès; Vanoverschelde, Jean-Louis J; Gerber, Bernhard L
2006-07-01
Retrospective reconstruction of ECG-gated images at different parts of the cardiac cycle allows the assessment of cardiac function by multi-detector row CT (MDCT) at the time of non-invasive coronary imaging. We compared the accuracy of such measurements by MDCT to cine magnetic resonance (MR). Forty patients underwent the assessment of global and regional cardiac function by 16-slice MDCT and cine MR. Left ventricular (LV) end-diastolic and end-systolic volumes estimated by MDCT (134+/-51 and 67+/-56 ml) were similar to those by MR (137+/-57 and 70+/-60 ml, respectively; both P=NS) and strongly correlated (r=0.92 and r=0.95, respectively; both P<0.001). Consequently, LV ejection fractions by MDCT and MR were also similar (55+/-21 vs. 56+/-21%; P=NS) and highly correlated (r=0.95; P<0.001). Regional end-diastolic and end-systolic wall thicknesses by MDCT were highly correlated (r=0.84 and r=0.92, respectively; both P<0.001), but significantly lower than by MR (8.3+/-1.8 vs. 8.8+/-1.9 mm and 12.7+/-3.4 vs. 13.3+/-3.5 mm, respectively; both P<0.001). Values of regional wall thickening by MDCT and MR were similar (54+/-30 vs. 51+/-31%; P=NS) and also correlated well (r=0.91; P<0.001). Retrospectively gated MDCT can accurately estimate LV volumes, EF and regional LV wall thickening compared to cine MR.
Howarth, Samuel J; Graham, Ryan B
2015-04-13
Application of non-linear dynamics analyses to study human movement has increased recently, which necessitates an understanding of how dependent measures may be influenced by experimental design and setup. Quantifying local dynamic stability for a multi-articulated structure such as the spine presents the possibility for estimates to be influenced by positioning of kinematic sensors used to measure spine angular kinematics. Oftentimes researchers will also choose to constrain the spine's movement by physically restraining the pelvis and/or using targets to control movement endpoints. Ten healthy participants were recruited, and asked to perform separate trials of 35 consecutive cycles of spine flexion under both constrained and unconstrained conditions. Electromagnetic sensors that measure three-dimensional angular orientations were positioned over the pelvis and the spinous processes of L3, L1, and T11. Using the pelvic sensor as a reference, each sensor location on the spine was used to obtain a different representation of the three-dimensional spine angular kinematics. Local dynamic stability of each kinematic time-series was determined by calculating the maximum finite-time Lyapunov exponent (λmax). Estimates for λmax were significantly lower (i.e. dynamically more stable) for spine kinematic data obtained from the L3 sensor than those obtained from kinematic data using either the L1 or T11 sensors. Likewise, λmax was lower when the movement was constrained. These results emphasize the importance of proper placement of instrumentation for quantifying local dynamic stability of spine kinematics and are especially relevant for repeated measures designs where data are obtained from the same individual on multiple days.
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.
Estimating False Positive Contamination in Crater Annotations from Citizen Science Data
NASA Astrophysics Data System (ADS)
Tar, P. D.; Bugiolacchi, R.; Thacker, N. A.; Gilmour, J. D.
2017-01-01
Web-based citizen science often involves the classification of image features by large numbers of minimally trained volunteers, such as the identification of lunar impact craters under the Moon Zoo project. Whilst such approaches facilitate the analysis of large image data sets, the inexperience of users and ambiguity in image content can lead to contamination from false positive identifications. We give an approach, using Linear Poisson Models and image template matching, that can quantify levels of false positive contamination in citizen science Moon Zoo crater annotations. Linear Poisson Models are a form of machine learning which supports predictive error modelling and goodness-of-fits, unlike most alternative machine learning methods. The proposed supervised learning system can reduce the variability in crater counts whilst providing predictive error assessments of estimated quantities of remaining true verses false annotations. In an area of research influenced by human subjectivity, the proposed method provides a level of objectivity through the utilisation of image evidence, guided by candidate crater identifications.
Estimating False Positive Contamination in Crater Annotations from Citizen Science Data
NASA Astrophysics Data System (ADS)
Tar, P. D.; Bugiolacchi, R.; Thacker, N. A.; Gilmour, J. D.
2016-11-01
Web-based citizen science often involves the classification of image features by large numbers of minimally trained volunteers, such as the identification of lunar impact craters under the Moon Zoo project. Whilst such approaches facilitate the analysis of large image data sets, the inexperience of users and ambiguity in image content can lead to contamination from false positive identifications. We give an approach, using Linear Poisson Models and image template matching, that can quantify levels of false positive contamination in citizen science Moon Zoo crater annotations. Linear Poisson Models are a form of machine learning which supports predictive error modelling and goodness-of-fits, unlike most alternative machine learning methods. The proposed supervised learning system can reduce the variability in crater counts whilst providing predictive error assessments of estimated quantities of remaining true verses false annotations. In an area of research influenced by human subjectivity, the proposed method provides a level of objectivity through the utilisation of image evidence, guided by candidate crater identifications.
Tomasić, Ivan; Frljak, Sabina; Trobec, Roman
2013-12-01
A methodology is presented for estimating the wireless body electrode (WE) positions and for calculating the linear transformations that enable the synthesis of a 12-lead ECG or a multichannel ECG from three WEs, which in turn simplifies and improves the acquisition of ECGs. We present, compare, and evaluate three approaches to the synthesis: fully personalized, fully universal, and combined with universal leads and personalized transformations. The evaluation results show that WEs are an acceptable alternative to the standard 12-lead ECG device for patients with chronic myocardial ischemia, if either the fully personalized or combined approach is used. The median correlation coefficients are all higher than 0.94 and 0.92 for the fully personalized and combined approaches, respectively. The corresponding kappa and percentual diagnostic agreements between the synthesized and target 12-lead ECGs are 0.88 (95%) and 0.83 (92%), respectively. The evaluation additionally shows that the personalization of the transformations has more impact on the quality of the synthesized ECGs than the personalization of the WEs' positions.
Multi-User Identification-Based Eye-Tracking Algorithm Using Position Estimation
Kang, Suk-Ju
2016-01-01
This paper proposes a new multi-user eye-tracking algorithm using position estimation. Conventional eye-tracking algorithms are typically suitable only for a single user, and thereby cannot be used for a multi-user system. Even though they can be used to track the eyes of multiple users, their detection accuracy is low and they cannot identify multiple users individually. The proposed algorithm solves these problems and enhances the detection accuracy. Specifically, the proposed algorithm adopts a classifier to detect faces for the red, green, and blue (RGB) and depth images. Then, it calculates features based on the histogram of the oriented gradient for the detected facial region to identify multiple users, and selects the template that best matches the users from a pre-determined face database. Finally, the proposed algorithm extracts the final eye positions based on anatomical proportions. Simulation results show that the proposed algorithm improved the average F1 score by up to 0.490, compared with benchmark algorithms. PMID:28035979
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
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.
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.
Sperduto, Paul W.; Kased, Norbert; Roberge, David; Xu, Zhiyuan; Shanley, Ryan; Luo, Xianghua; Sneed, Penny K.; Chao, Samuel T.; Weil, Robert J.; Suh, John; Bhatt, Amit; Jensen, Ashley W.; Brown, Paul D.; Shih, Helen A.; Kirkpatrick, John; Gaspar, Laurie E.; Fiveash, John B.; Chiang, Veronica; Knisely, Jonathan P.S.; Sperduto, Christina Maria; Lin, Nancy; Mehta, Minesh
2012-01-01
Purpose Our group has previously published the Graded Prognostic Assessment (GPA), a prognostic index for patients with brain metastases. Updates have been published with refinements to create diagnosis-specific Graded Prognostic Assessment indices. The purpose of this report is to present the updated diagnosis-specific GPA indices in a single, unified, user-friendly report to allow ease of access and use by treating physicians. Methods A multi-institutional retrospective (1985 to 2007) database of 3,940 patients with newly diagnosed brain metastases underwent univariate and multivariate analyses of prognostic factors associated with outcomes by primary site and treatment. Significant prognostic factors were used to define the diagnosis-specific GPA prognostic indices. A GPA of 4.0 correlates with the best prognosis, whereas a GPA of 0.0 corresponds with the worst prognosis. Results Significant prognostic factors varied by diagnosis. For lung cancer, prognostic factors were Karnofsky performance score, age, presence of extracranial metastases, and number of brain metastases, confirming the original Lung-GPA. For melanoma and renal cell cancer, prognostic factors were Karnofsky performance score and the number of brain metastases. For breast cancer, prognostic factors were tumor subtype, Karnofsky performance score, and age. For GI cancer, the only prognostic factor was the Karnofsky performance score. The median survival times by GPA score and diagnosis were determined. Conclusion Prognostic factors for patients with brain metastases vary by diagnosis, and for each diagnosis, a robust separation into different GPA scores was discerned, implying considerable heterogeneity in outcome, even within a single tumor type. In summary, these indices and related worksheet provide an accurate and facile diagnosis-specific tool to estimate survival, potentially select appropriate treatment, and stratify clinical trials for patients with brain metastases. PMID:22203767
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
Bolboacă, Sorana; Jäntschi, Lorentz
2005-01-01
Likelihood Ratio medical key parameters calculated on categorical results from diagnostic tests are usually express accompanied with their confidence intervals, computed using the normal distribution approximation of binomial distribution. The approximation creates known anomalies,especially for limit cases. In order to improve the quality of estimation, four new methods (called here RPAC, RPAC0, RPAC1, and RPAC2) were developed and compared with the classical method (called here RPWald), using an exact probability calculation algorithm.Computer implementations of the methods use the PHP language. We defined and implemented the functions of the four new methods and the five criterions of confidence interval assessment. The experiments run for samples sizes which vary in 14 - 34 range, 90 - 100 range (0 < X < m, 0< Y < n), as well as for random numbers for samples sizes (4m, n positive and negative likelihood ratios.
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
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.
Ionospheric Slant Total Electron Content Analysis Using Global Positioning System Based Estimation
NASA Technical Reports Server (NTRS)
Sparks, Lawrence C. (Inventor); Mannucci, Anthony J. (Inventor); Komjathy, Attila (Inventor)
2017-01-01
A method, system, apparatus, and computer program product provide the ability to analyze ionospheric slant total electron content (TEC) using global navigation satellite systems (GNSS)-based estimation. Slant TEC is estimated for a given set of raypath geometries by fitting historical GNSS data to a specified delay model. The accuracy of the specified delay model is estimated by computing delay estimate residuals and plotting a behavior of the delay estimate residuals. An ionospheric threat model is computed based on the specified delay model. Ionospheric grid delays (IGDs) and grid ionospheric vertical errors (GIVEs) are computed based on the ionospheric threat model.
Position and volume estimation of atmospheric nuclear detonations from video reconstruction
NASA Astrophysics Data System (ADS)
Schmitt, Daniel T.
Recent work in digitizing films of foundational atmospheric nuclear detonations from the 1950s provides an opportunity to perform deeper analysis on these historical tests. This work leverages multi-view geometry and computer vision techniques to provide an automated means to perform three-dimensional analysis of the blasts for several points in time. The accomplishment of this requires careful alignment of the films in time, detection of features in the images, matching of features, and multi-view reconstruction. Sub-explosion features can be detected with a 67% hit rate and 22% false alarm rate. Hotspot features can be detected with a 71.95% hit rate, 86.03% precision and a 0.015% false positive rate. Detected hotspots are matched across 57-109 degree viewpoints with 76.63% average correct matching by defining their location relative to the center of the explosion, rotating them to the alternative viewpoint, and matching them collectively. When 3D reconstruction is applied to the hotspot matching it completes an automated process that has been used to create 168 3D point clouds with 31.6 points per reconstruction with each point having an accuracy of 0.62 meters with 0.35, 0.24, and 0.34 meters of accuracy in the x-, y- and z-direction respectively. As a demonstration of using the point clouds for analysis, volumes are estimated and shown to be consistent with radius-based models and in some cases improve on the level of uncertainty in the yield calculation.
GPS position time-series analysis based on asymptotic normality of M-estimation
NASA Astrophysics Data System (ADS)
Khodabandeh, A.; Amiri-Simkooei, A. R.; Sharifi, M. A.
2012-01-01
The efficacy of robust M-estimators is a well-known issue when dealing with observational blunders. When the number of observations is considerably large—long time series for instance—one can take advantage of the asymptotic normality of the M-estimation and compute reasonable estimates for the unknown parameters of interest. A few leading M-estimators have been employed to identify the most likely functional model for GPS coordinate time series. This includes the simultaneous detection of periodic patterns and offsets in the GPS time series. Estimates of white noise, flicker noise, and random walk noise components are also achieved using the robust M-estimators of (co)variance components, developed in the framework of the least-squares variance component estimation (LS-VCE) theory. The method allows one to compute confidence interval for the (co)variance components in asymptotic sense. Simulated time series using white noise plus flicker noise show that the estimates of random walk noise fluctuate more than those of flicker noise for different M-estimators. This is because random walk noise is not an appropriate noise structure for the series. The same phenomenon is observed using the results of real GPS time series, which implies that the combination of white plus flicker noise is well described for GPS time series. Some of the estimated noise components of LS-VCE differ significantly from those of other M- estimators. This reveals that there are a large number of outliers in the series. This conclusion is also affirmed by performing the statistical tests, which detect (large) parts of the outliers but can also leave parts to be undetected.
NASA Astrophysics Data System (ADS)
Shrestha, Shanker Man; Arai, Ikuo
2003-12-01
Super-resolution is very important for the signal processing of GPR (ground penetration radar) to resolve closely buried targets. However, it is not easy to get high resolution as GPR signals are very weak and enveloped by the noise. The MUSIC (multiple signal classification) algorithm, which is well known for its super-resolution capacity, has been implemented for signal and image processing of GPR. In addition, conventional spectral estimation technique, FFT (fast Fourier transform), has also been implemented for high-precision receiving signal level. In this paper, we propose CPM (combined processing method), which combines time domain response of MUSIC algorithm and conventional IFFT (inverse fast Fourier transform) to obtain a super-resolution and high-precision signal level. In order to support the proposal, detailed simulation was performed analyzing SNR (signal-to-noise ratio). Moreover, a field experiment at a research field and a laboratory experiment at the University of Electro-Communications, Tokyo, were also performed for thorough investigation and supported the proposed method. All the simulation and experimental results are presented.
NASA Astrophysics Data System (ADS)
Dutta, Ivy; Chowdhury, Anirban Roy; Kumbhakar, Dharmadas
2013-03-01
Using Chebyshev power series approach, accurate description for the first higher order (LP11) mode of graded index fibers having three different profile shape functions are presented in this paper and applied to predict their propagation characteristics. These characteristics include fractional power guided through the core, excitation efficiency and Petermann I and II spot sizes with their approximate analytic formulations. We have shown that where two and three Chebyshev points in LP11 mode approximation present fairly accurate results, the values based on our calculations involving four Chebyshev points match excellently with available exact numerical results.
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.
van der Loos, Chris M; de Boer, Onno J; Mackaaij, Claire; Hoekstra, Lisette T; van Gulik, Thomas M; Verheij, Joanne
2013-01-01
Determination of hepatocyte proliferation activity is hampered by the presence of Ki67-positive non-parenchymal cells. We validated a multicolor immunohistochemical (IHC) approach using multispectral tissue and cell segmentation software. Portal vein branches to the cranial liver lobes of 10 rabbits were embolized, leading to atrophy of the cranial lobes and hyperplasia of the caudal lobes. Slides from cranial and caudal lobes (n=20) were double-stained (CK8+18 and Ki67) and triple-stained (CK8+18, Ki67, and CD31). The Ki67 proliferation index was calculated using automated tissue and cell segmentation software and compared with manual counting by two independent observers. A substantial variation was seen in the number of Ki67-positive hepatocytes in the different specimens in both double and triple staining (range, 0-50). Correlation coefficients between manual counting and the digital analysis were 0.76 for observer 1 (p<0.001) and 0.78 for observer 2 (p<0.001) with double staining and R(2) = 0.91 for observer 1 and R(2) = 0.89 for observer 2, p<0.001 with triple staining. In conclusion, in rabbit, the hepatocellular proliferation index can be reliably determined using automated tissue and cell segmentation software in combination with IHC multiple staining. Our findings may be useful in clinical practice when Ki67 proliferation index yields prognostic significance.
NASA Astrophysics Data System (ADS)
Harrison, R. G.
2015-07-01
A mean-field positive-feedback (PFB) theory of ferromagnetism is used to explain the origin of Barkhausen noise (BN) and to show why it is most pronounced in the irreversible regions of the hysteresis loop. By incorporating the ABBM-Sablik model of BN into the PFB theory, we obtain analytical solutions that simultaneously describe both the major hysteresis loop and, by calculating separate expressions for the differential susceptibility in the irreversible and reversible regions, the BN power response at all points of the loop. The PFB theory depends on summing components of the applied field, in particular, the non-monotonic field-magnetization relationship characterizing hysteresis, associated with physical processes occurring in the material. The resulting physical model is then validated by detailed comparisons with measured single-peak BN data in three different steels. It also agrees with the well-known influence of a demagnetizing field on the position and shape of these peaks. The results could form the basis of a physics-based method for modeling and understanding the significance of the observed single-peak (and in multi-constituent materials, multi-peak) BN envelope responses seen in contemporary applications of BN, such as quality control in manufacturing, non-destructive testing, and monitoring the microstructural state of ferromagnetic materials.
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.
Markova-Raina, Penka; Petrov, Dmitri
2011-01-01
We investigate the effect of aligner choice on inferences of positive selection using site-specific models of molecular evolution. We find that independently of the choice of aligner, the rate of false positives is unacceptably high. Our study is a whole-genome analysis of all protein-coding genes in 12 Drosophila genomes annotated in either all 12 species (∼6690 genes) or in the six melanogaster group species. We compare six popular aligners: PRANK, T-Coffee, ClustalW, ProbCons, AMAP, and MUSCLE, and find that the aligner choice strongly influences the estimates of positive selection. Differences persist when we use (1) different stringency cutoffs, (2) different selection inference models, (3) alignments with or without gaps, and/or additional masking, (4) per-site versus per-gene statistics, (5) closely related melanogaster group species versus more distant 12 Drosophila genomes. Furthermore, we find that these differences are consequential for downstream analyses such as determination of over/under-represented GO terms associated with positive selection. Visual analysis indicates that most sites inferred as positively selected are, in fact, misaligned at the codon level, resulting in false positive rates of 48%–82%. PRANK, which has been reported to outperform other aligners in simulations, performed best in our empirical study as well. Unfortunately, PRANK still had a high, and unacceptable for most applications, false positives rate of 50%–55%. We identify misannotations and indels, many of which appear to be located in disordered protein regions, as primary culprits for the high misalignment-related error levels and discuss possible workaround approaches to this apparently pervasive problem in genome-wide evolutionary analyses. PMID:21393387
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
Nam, Kyung-Tae; Lee, Seung-Joon; Kuc, Tae-Yong; Kim, Hyungjong
2015-12-31
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.
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)
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.
Rapid position estimation using electromagnetic induction data from the MetalMapper in dynamic mode
NASA Astrophysics Data System (ADS)
Grzegorczyk, Tomasz M.; Barrowes, Benjamin; George, David; Shubitidze, Fridon; Fernández, J. P.; O'Neill, Kevin
2011-06-01
Dynamic data from the MetalMapper electromagnetic induction sensor are analyzed using a fast inversion algorithm in order to obtain position information of buried anomalies. After validating the algorithm by comparing static and dynamic inversions from reference measurements at Camp San Luis Obispo, the algorithm is applied to realistic dynamic measurements from Camp Butner. A sequence of 939 data points are inverted as the MetalMapper travels along a calibration lane, flagging a few positions as corresponding to buried anomalies. An a posteriori comparison with field plots reveals a good agreement between the flagged positions and the field peak values, suggesting the efficacy of the algorithm at detecting a large variety of anomalies from dynamic data.
NASA Astrophysics Data System (ADS)
Tanaka, Takuro; Takahashi, Hisashi
In some motor applications, it is very difficult to attach a position sensor to the motor in housing. One of the examples of such applications is the dental handpiece-motor. In those designs, it is necessary to drive highly efficiency at low speed and variable load condition without a position sensor. We developed a method to control a motor high-efficient and smoothly at low speed without a position sensor. In this paper, the method in which permanent magnet synchronous motor is controlled smoothly and high-efficient by using torque angle control in synchronized operation is shown. The usefulness is confirmed by experimental results. In conclusion, the proposed sensor-less control method has been achieved to be very efficiently and smoothly.
Effects of body position on lung density estimated from EIT data
NASA Astrophysics Data System (ADS)
Noshiro, Makoto; Ebihara, Kei; Sato, Ena; Nebuya, Satoru; Brown, Brian H.
2010-04-01
Normal subjects took the sitting, supine, prone, right lateral and left lateral positions during the measurement procedure. One minute epochs of EIT data were collected at the levels of the 3rd, 4th, 5th and 6th intercostal spaces in each position during normal tidal breathing. Lung density was then determined from the EIT data using the method proposed by Brown5. Lung density at the electrode level of the 6th intercostal space was different from that at almost any other levels in both male and female subjects, and lung density at the electrode levels of the 4th and 5th intercostal spaces in male subjects did not depend upon position.
1989-02-01
carried out by Mayflower Communications Company, Inc. for the Air Force Geophysics Laboratory, under contract number F19628-86-C-0136. The Mayflower effort ...in each axis. A detailed error analysis of the effect of measurement errors on the Shuttle acceleration estimation accuracy was carried out which... carried out . The results of the error analysis, hardware selection and Shuttle , (OVER) 20. DISTRIBUTION IAVAIL*SIUTY OF ABSTRACT 21. ABSTRACT SECURITY
Vazquez, Alejandro; Statton, Matthew A.; Busgang, Stefanie A.
2015-01-01
Motor learning during reaching not only recalibrates movement but can also lead to small but consistent changes in the sense of arm position. Studies have suggested that this sensory effect may be the result of recalibration of a forward model that associates motor commands with their sensory consequences. Here we investigated whether similar perceptual changes occur in the lower limbs after learning a new walking pattern on a split-belt treadmill—a task that critically involves proprioception. Specifically, we studied how this motor learning task affects perception of leg speed during walking, perception of leg position during standing or walking, and perception of contact force during stepping. Our results show that split-belt adaptation leads to robust motor aftereffects and alters the perception of leg speed during walking. This is specific to the direction of walking that was trained during adaptation (i.e., backward or forward). The change in leg speed perception accounts for roughly half of the observed motor aftereffect. In contrast, split-belt adaptation does not alter the perception of leg position during standing or walking and does not change the perception of stepping force. Our results demonstrate that there is a recalibration of a sensory percept specific to the domain of the perturbation that was applied during walking (i.e., speed but not position or force). Furthermore, the motor and sensory consequences of locomotor adaptation may be linked, suggesting overlapping mechanisms driving changes in the motor and sensory domains. PMID:26424576
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.
ERIC Educational Resources Information Center
Warne, Russell T.
2016-01-01
Recently Kim (2016) published a meta-analysis on the effects of enrichment programs for gifted students. She found that these programs produced substantial effects for academic achievement (g = 0.96) and socioemotional outcomes (g = 0.55). However, given current theory and empirical research these estimates of the benefits of enrichment programs…
Scott, P K; Finley, B L; Sung, H M; Schulze, R H; Turner, D B
1997-07-01
The primary health concern associated with chromite ore processing residues (COPR) at sites in Hudson County, NJ, is the inhalation of Cr(VI) suspended from surface soils. Since health-based soil standards for Cr(VI) will be derived using the inhalation pathway, soil suspension modeling will be necessary to estimate site-specific, health-based soil cleanup levels (HBSCLs). The purpose of this study was to identify the most appropriate particulate emission and air dispersion models for estimating soil suspension at these sites based on their theoretical underpinnings, scientific acceptability, and past performance. The identified modeling approach, the AP-42 particulate emission model and the fugitive dust model (FDM), was used to calculate concentrations of airborne Cr(VI) and TSP at two COPR sites. These estimated concentrations were then compared to concentrations measured at each site. The TSP concentrations calculated using the AP-42/FDM soil suspension modeling approach were all within a factor of 3 of the measured concentrations. The majority of the estimated air concentrations were greater than the measured, indicating that the AP-42/FDM approach tends to overestimate on-site concentrations. The site-specific Cr(VI) HBSCLs for these two sites calculated using this conservative soil suspension modeling approach ranged from 190 to 420 mg/kg.
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.
Position Estimation for Projectiles Using Low-cost Sensors and Flight Dynamics
2012-04-01
performance. Conditions of the simulation were similar to the experiments. Monte Carlo analysis was undertaken with 500 repetitions of each case. 3.4...uncertainty in flight and measurements used in the Monte Carlo simulations is given in table 1. These error budgets are based on laboratory...equations (i.e., no filtering). Position errors from these Monte Carlo simulations are on the same order of magnitude as the experimental result as shown
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.
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.
Position of cytogenetic examination of cosmonauts for the space radiation exposure estimate
NASA Astrophysics Data System (ADS)
Snigiryova, Galina; Novitskaya, Natalia; Fedorenko, Boris
The cytogenetic monitoring was carried out to evaluate of radiation induced stable and un-stable chromosome aberration frequency in peripheral blood lymphocytes of cosmonauts who participated in flights on Mir Orbital Station and ISS (International Space Station). In the period of 1992 -2008 chromosome aberrations in 202 blood samples from 48 cosmonauts were analyzed using the conventional method. In addition 23 blood samples from 12 cosmonauts were analyzed using FISH (fluorescence in situ hybridization) technique. Whole chromosome painting probes for chromosomes 1, 4 and 12 were used simultaneously with a pancentromeric probe. Samples taken before and after the flights were analyzed. Long-term space flights led to an increase of stable (FISH method) and unstable (conventional method) chromosome aber-ration frequencies. The frequencies of dicentrics and centric rings depend on the space flight duration and accumulated dose value. Extravehicular activity also adds to chromosome aber-ration frequency in blood lymphocytes of cosmonauts. Several years after the space flight the increased level of unstable chromosome aberrations is still apparent. The radiation load was decreased for cosmonauts after taking ISS over from MIR station. The cytogenetic results were in agreement with data of physical dosimetry. The dose interval after the first flight, estimated by the frequency of dicentrics, was 113-227 mSv for long-term flights (73 -199 days) and 53-107 mSv for short-term flights (1 -21 days). According to the frequency of FISH translocations, the average dose after the first long-term flight was 186 mSv, which is comparable with estimates made from the dicentric assay. Cytogenetic examination of cosmonauts, including analysis of dicentrics (conventional method) and translocations (FISH method) should find wider applica-tion to assessment of radiation effects associated with long-term space flights such as flights to Mars.
NASA Astrophysics Data System (ADS)
McCook, G. P.; Guinan, E. F.; Saumon, D.; Kang, Y. W.
1997-05-01
CM Draconis (Gl 630.1; Vmax = +12.93) is an important eclipsing binary consisting of two dM4.5e stars with an orbital period of 1.2684 days. This binary is a high velocity star (s= 164 km/s) and the brighter member of a common proper motion pair with a cool faint white dwarf companion (LP 101-16). CM Dra and its white dwarf companion were once considered by Zwicky to belong to a class of "pygmy stars", but they turned out to be ordinary old, cool white dwarfs or faint red dwarfs. Lacy (ApJ 218,444L) determined the first orbital and physical properties of CM Dra from the analysis of his light and radial velocity curves. In addition to providing directly measured masses, radii, and luminosities for low mass stars, CM Dra was also recognized by Lacy and later by Paczynski and Sienkiewicz (ApJ 286,332) as an important laboratory for cosmology, as a possible old Pop II object where it may be possible to determine the primordial helium abundance. Recently, Metcalfe et al.(ApJ 456,356) obtained accurate RV measures for CM Dra and recomputed refined elements along with its helium abundance. Starting in 1995, we have been carrying out intensive RI photoelectric photometry of CM Dra to obtain well defined, accurate light curves so that its fundamental properties can be improved, and at the same time, to search for evidence of planets around the binary from planetary transit eclipses. During 1996 and 1997 well defined light curves were secured and these were combined with the RV measures of Metcalfe et al. (1996) to determine the orbital and physical parameters of the system, including a refined orbital period. A recent version of the Wilson-Devinney program was used to analyze the data. New radii, masses, mean densities, Teff, and luminosities were found as well as a re-determination of the helium abundance (Y). The results of the recent analyses of the light and RV curves will be presented and modelling results discussed. This research is supported by NSF grants AST-9315365
Miller, David A W; Nichols, James D; Gude, Justin A; Rich, Lindsey N; Podruzny, Kevin M; Hines, James E; Mitchell, Michael S
2013-01-01
Large-scale presence-absence monitoring programs have great promise for many conservation applications. Their value can be limited by potential incorrect inferences owing to observational errors, especially when data are collected by the public. To combat this, previous analytical methods have focused on addressing non-detection from public survey data. Misclassification errors have received less attention but are also likely to be a common component of public surveys, as well as many other data types. We derive estimators for dynamic occupancy parameters (extinction and colonization), focusing on the case where certainty can be assumed for a subset of detections. We demonstrate how to simultaneously account for non-detection (false negatives) and misclassification (false positives) when estimating occurrence parameters for gray wolves in northern Montana from 2007-2010. Our primary data source for the analysis was observations by deer and elk hunters, reported as part of the state's annual hunter survey. This data was supplemented with data from known locations of radio-collared wolves. We found that occupancy was relatively stable during the years of the study and wolves were largely restricted to the highest quality habitats in the study area. Transitions in the occupancy status of sites were rare, as occupied sites almost always remained occupied and unoccupied sites remained unoccupied. Failing to account for false positives led to over estimation of both the area inhabited by wolves and the frequency of turnover. The ability to properly account for both false negatives and false positives is an important step to improve inferences for conservation from large-scale public surveys. The approach we propose will improve our understanding of the status of wolf populations and is relevant to many other data types where false positives are a component of observations.
Miller, David A. W.; Nichols, James D.; Gude, Justin A.; Rich, Lindsey N.; Podruzny, Kevin M.; Hines, James E.; Mitchell, Michael S.
2013-01-01
Large-scale presence-absence monitoring programs have great promise for many conservation applications. Their value can be limited by potential incorrect inferences owing to observational errors, especially when data are collected by the public. To combat this, previous analytical methods have focused on addressing non-detection from public survey data. Misclassification errors have received less attention but are also likely to be a common component of public surveys, as well as many other data types. We derive estimators for dynamic occupancy parameters (extinction and colonization), focusing on the case where certainty can be assumed for a subset of detections. We demonstrate how to simultaneously account for non-detection (false negatives) and misclassification (false positives) when estimating occurrence parameters for gray wolves in northern Montana from 2007–2010. Our primary data source for the analysis was observations by deer and elk hunters, reported as part of the state’s annual hunter survey. This data was supplemented with data from known locations of radio-collared wolves. We found that occupancy was relatively stable during the years of the study and wolves were largely restricted to the highest quality habitats in the study area. Transitions in the occupancy status of sites were rare, as occupied sites almost always remained occupied and unoccupied sites remained unoccupied. Failing to account for false positives led to over estimation of both the area inhabited by wolves and the frequency of turnover. The ability to properly account for both false negatives and false positives is an important step to improve inferences for conservation from large-scale public surveys. The approach we propose will improve our understanding of the status of wolf populations and is relevant to many other data types where false positives are a component of observations. PMID:23840372
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)
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 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)
Sugimoto, S.; Tadokoro, K.; Ikuta, R.; Watanabe, T.; Okuda, T.; Sayanagi, K.; Miyata, K.; Nagao, T.
2009-12-01
We have been developing an observation system with the GPS/Acoustic combination technique for monitoring of seafloor crustal deformation. We installed two sets of triangular array of acoustic transponders as geodetic reference sites on the Suruga trough, central Japan, where the Philippine Sea plate is subducting beneath the Eurasian plate at a rate of 2 cm/yr. In our campaign observation, we measured ranges to acoustic transponders from an on-board acoustic transducer whose position was determined by kinematic GPS. Repeated our campaign observations can reveal directly seafloor crustal deformation in focal area of subduction zone. Present analysis method simultaneously estimates temporal variation of acoustic velocity and positions of acoustic transponders assuming the horizontally-layered structure of acoustic velocity. However, actual structure might have stable spatial variation due to oceanic current and internal wave. The stable spatial variation causes bias error on the positioning. For reduction of the bias error and shortening observation time, we should measure and/or estimate the spatial variation of acoustic velocity. In this presentation, for an investigation of horizontal scales of the spatial variation of acoustic velocity, we estimated spectrum of oceanic internal wave using by continuous measurements of temperature and pressure in ocean. In addition, we evaluate a new seafloor positioning method which simultaneously estimates spatiotemporal variation of acoustic velocity through numerical experiments. The continuous measurements in parallel with acoustic ranging were conducted by mooring temperature and pressure sensors attached rope with an interval of 50 m. The continuous measurements were made for five hours with a sampling interval of three seconds in each day in August and October 2008. For reduction of measurement noise, we carried out two-dimensional B-spline fitting of temperature and pressure with ABIC minimization. By the fitting, we
Forman, Michele R; Zhu, Yeyi; Hernandez, Ladia M; Himes, John H; Dong, Yongquan; Danish, Robert K; James, Kyla E; Caulfield, Laura E; Kerver, Jean M; Arab, Lenore; Voss, Paula; Hale, Daniel E; Kanafani, Nadim; Hirschfeld, Steven
2014-09-01
Surrogate measures are needed when recumbent length or height is unobtainable or unreliable. Arm span has been used as a surrogate but is not feasible in children with shoulder or arm contractures. Ulnar length is not usually impaired by joint deformities, yet its utility as a surrogate has not been adequately studied. In this cross-sectional study, we aimed to examine the accuracy and reliability of ulnar length measured by different tools as a surrogate measure of recumbent length and height. Anthropometrics [recumbent length, height, arm span, and ulnar length by caliper (ULC), ruler (ULR), and grid (ULG)] were measured in 1479 healthy infants and children aged <6 y across 8 study centers in the United States. Multivariate mixed-effects linear regression models for recumbent length and height were developed by using ulnar length and arm span as surrogate measures. The agreement between the measured length or height and the predicted values by ULC, ULR, ULG, and arm span were examined by Bland-Altman plots. All 3 measures of ulnar length and arm span were highly correlated with length and height. The degree of precision of prediction equations for length by ULC, ULR, and ULG (R(2) = 0.95, 0.95, and 0.92, respectively) was comparable with that by arm span (R(2) = 0.97) using age, sex, and ethnicity as covariates; however, height prediction by ULC (R(2) = 0.87), ULR (R(2) = 0.85), and ULG (R(2) = 0.88) was less comparable with arm span (R(2) = 0.94). Our study demonstrates that arm span and ULC, ULR, or ULG can serve as accurate and reliable surrogate measures of recumbent length and height in healthy children; however, ULC, ULR, and ULG tend to slightly overestimate length and height in young infants and children. Further testing of ulnar length as a surrogate is warranted in physically impaired or nonambulatory children.
Fowler, T; Edeghere, O; Inglis, N; Bradshaw, S
2013-03-01
Advances in technology have raised the possibility of including gonorrhoea testing as part of chlamydia screening. In England this is recommended only where the positive predictive value (PPV) of the test is ≥90%. This study assessed the PPV for gonorrhoea testing using routine testing data. Routine data (including gonorrhoea testing) from the Greater Manchester Chlamydia Screening Programme (GMCSP) in 2009/2010, were used to estimate the PPV for gonorrhoea testing. Of those screened, 0.3% (59/18044) of men and 0.4% (174/41873) of women tested positive for gonorrhoea. The PPV was 82.3% in women and 73.6% in men, in those who also tested positive for chlamydia. For women and men testing negative for chlamydia the PPV for a positive gonorrhoea test was incalculable. The low PPV observed in most groups suggests that where population testing for gonorrhoea occurs there is a need for further confirmatory testing of positive results before treatment decisions are made. Clinicians should be aware of screening test result limitations in this context.
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.
Position of cytogenetic examination of cosmonauts for the space radiation expose estimate
NASA Astrophysics Data System (ADS)
Snigireva, Galina; Novitskaya, Natalia; Ivanov, Alexander
Analysis of chromosome aberrations in human peripheral blood lymphocytes is widely used for the indication and quantitative assessment of radiation. The dose, as estimated by the frequency of chromosome aberrations takes into account not only the physical impact of radiation on the human body but also its individual characteristics, such as radiation sensitivity and functional conditions during irradiation. The purpose of this study was to evaluate the influence of radiation on the chromosome aberration frequency in peripheral blood lymphocytes of the cosmonauts who participated in flights on the ISS (International Space Station). Cytogenetic examination was performed in the period 1992-2013 and included the analysis of chromosome aberrations using conventional Giemsa staining method in blood samples from 38 cosmonauts who participated in flights on the ISS. The cytogenetic examination results showed that cosmic flights lead to an increase of chromosome aberrations in the lymphocytes of cosmonauts. Compared with the pre-flight levels frequencies of dicentrics and centric rings (the radiation exposure markers) are about 4 times higher for cosmonauts after flights. The frequency of chromosome aberrations depends on the length of the flight and, correspondingly, on the accumulated dose of cosmic irradiation. Between flights, a decrease in the chromosome aberration frequency is observed, but even several years after a flight, the level of chromosome aberrations in the lymphocytes of cosmonauts remains high. Cytogenetic monitoring of cosmonauts can undoubtedly play an important role in comprehensive medical surveys of these individuals if we take into account the possible connection of higher levels of chromosomal aberrations with the risk of oncological diseases. Analysis of chromosome aberration dynamics after flights will allow the determination of individuals with an increased cancerogenese risk and provision of required treatments.
Ng, J A; Booth, J; Poulsen, P; Kuncic, Z; Keall, P J
2013-01-01
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 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 CBCT 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. PMID:23938470
De Neve, Jan-Emmanuel; Oswald, Andrew J
2012-12-04
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.
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.
Romero-Vivas, C M E; Llinás, H; Falconar, A K I
2007-11-01
The ability of a simple sweeping method, coupled to calibration factors, to accurately estimate the total numbers of Aedes aegypti (L.) (Diptera: Culicidae) pupae in water-storage containers (20-6412-liter capacities at different water levels) throughout their main dengue virus transmission temperature range was evaluated. Using this method, one set of three calibration factors were derived that could accurately estimate the total Ae. aegypti pupae in their principal breeding sites, large water-storage containers, found throughout the world. No significant differences were obtained using the method at different altitudes (14-1630 m above sea level) that included the range of temperatures (20-30 degrees C) at which dengue virus transmission occurs in the world. In addition, no significant differences were found in the results obtained between and within the 10 different teams that applied this method; therefore, this method was extremely robust. One person could estimate the Ae. aegypti pupae in each of the large water-storage containers in only 5 min by using this method, compared with two people requiring between 45 and 90 min to collect and count the total pupae population in each of them. Because the method was both rapid to perform and did not disturb the sediment layers in these domestic water-storage containers, it was more acceptable by the residents, and, therefore, ideally suited for routine surveillance purposes and to assess the efficacy of Ae. aegypti control programs in dengue virus-endemic areas throughout the world.
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
NASA Astrophysics Data System (ADS)
Heidrich, P.; Wolfersdorf, J. v.; Schmidt, S.; Schnieder, M.
2008-11-01
This paper describes a non-invasive, non-destructive, transient inverse measurement technique that allows one to determine internal heat transfer coefficients and rib positions of real gas turbine blades from outer surface temperature measurements after a sudden flow heating. The determination of internal heat transfer coefficients is important during the design process to adjust local heat transfer to spatial thermal load. The detection of rib positions is important during production to fulfill design and quality requirements. For the analysis the one-dimensional transient heat transfer problem inside of the turbine blade's wall was solved. This solution was combined with the Levenberg-Marquardt method to estimate the unknown boundary condition by an inverse technique. The method was tested with artificial data to determine uncertainties with positive results. Then experimental testing with a reference model was carried out. Based on the results, it is concluded that the presented inverse technique could be used to determine internal heat transfer coefficients and to detect rib positions of real turbine blades.
Accurate Evaluation of Quantum Integrals
NASA Technical Reports Server (NTRS)
Galant, D. C.; Goorvitch, D.; Witteborn, Fred C. (Technical Monitor)
1995-01-01
Combining an appropriate finite difference method with Richardson's extrapolation results in a simple, highly accurate numerical method for solving a Schrodinger'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.
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.
Park, Jung Hwan; Kim, Yong Chul; Koo, Ho Seok; Oh, Se Won; Kim, Suhnggwon; Chin, Ho Jun
2014-09-01
Stomach cancer is one of the most common cancers in Korea. The aim of this study was to identify the association between the prevalence of cancer, particularly stomach cancer, and the amount of 24-hr urine sodium excretion estimated from spot urine specimens. The study included 19,083 subjects who took part in the Korean National Health and Nutritional Examination Survey between 2009 and 2011. The total amount of urine sodium excreted in a 24-hr period was estimated by using two equations based on the values for spot urine sodium and creatinine. In subjects who had an estimated 24-hr urine sodium excretion of more than two standard deviations above the mean (group 2), the prevalence of stomach cancer was higher than in subjects with lower 24-hr sodium excretion (group 1). By using the Tanaka equation to estimate it, the prevalence of stomach cancer was 0.6% (114/18,331) in group 1, whereas it was 1.6% (9/568) in group 2 (P=0.006). By using the Korean equation, the prevalence was 0.6% (115/18,392) in group 1, and 1.6% in group 2 (8/507) (P=0.010). By using the Tanaka equation, breast cancer in women is more prevalent in group 2 (1.9%, 6/324) than group 1 (0.8%, 78/9,985, P=0.039). Higher salt intake, as defined by the estimated amount of 24-hr urine sodium excretion, is positively correlated with a higher prevalence of stomach or breast cancer in the Korean population.
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)
Fan, Lei; Li, Min; Wang, Cheng; Shi, Chuang
2017-02-01
The differential code bias (DCB) of BeiDou satellite is an important topic to make better use of BeiDou system (BDS) for many practical applications. This paper proposes a new method to estimate the BDS satellite DCBs based on triple-frequency uncombined precise point positioning (UPPP). A general model of both triple-frequency UPPP and Geometry-Free linear combination of Phase-Smoothed Range (GFPSR) is presented, in which, the ionospheric observable and the combination of triple-frequency satellite and receiver DCBs (TF-SRDCBs) are derived. Then the satellite and receiver DCBs (SRDCBs) are estimated together with the ionospheric delay that is modeled at each individual station in a weighted least-squares estimator, and the satellite DCBs are determined by introducing the zero-mean condition of all available BDS satellites. To validate the new method, 90 day's real tracking GNSS data (from January to March in 2014) collected from 9 Multi-GNSS Experiment (MGEX) stations (equipped with Trimble NETR9 receiver) is used, and the BDS satellite DCB products from German Aerospace Center (DLR) are taken as reference values for comparison. Results show that the proposed method is able to precisely estimate BDS satellite DCBs: (1) the mean value of the day-to-day scattering for all available BDS satellites is about 0.24 ns, which is reduced in average by 23% when compared with the results derived by only GFPSR. Moreover, the mean value of the day-to-day scattering of IGSO satellites is lower than that of GEO and MEO satellites; (2) the mean value of RMS of the difference with respect to DLR DCB products is about 0.39 ns, which is improved by an average of 11% when compared with the results derived by only GFPSR. Besides, the RMS of IGSO and MEO satellites is at the same level which is better than that of GEO satellites.
Software Estimation: Developing an Accurate, Reliable Method
2011-08-01
level 5 organizations. Defects identified here for CMM level 1 and level 5 are captured from Capers Jones who has identified software delivered... Capers , “Software Assessments, Benchmarks, and Best Practices”, Addison-Wesley Professional, April 2000. 1. At the AV-8B Joint System Support
Barton, Karen L; Wrieden, Wendy L; Sherriff, Andrea; Armstrong, Julie; Anderson, Annie S
2014-07-14
Frequent consumption of energy-dense foods has been strongly implicated in the global increase of obesity. The World Cancer Research Fund suggests a population-level energy density (ED) goal for diets of 523 kJ/100 g (125 kcal/100 g) as desirable for reducing weight gain and related co-morbidities. However, there is limited information about the ED of diets of contemporary populations. The aims of the present study were to (1) estimate the mean ED of the Scottish diet, (2) assess differences in ED over time by socio-economic position, by household (HH) composition and for HH meeting dietary targets for fat and fruit and vegetables, and (3) assess the relationship between ED and the consumption of foods and nutrients, which are indicative of diet quality. ED of the diet was estimated from food (including milk) from UK food purchase survey data. The average ED of the Scottish diet was estimated as 718 kJ/100 g with no change between the survey periods 2001 and 2009. Individuals living in the most deprived areas had a higher mean ED than those living in the least deprived areas (737 v. 696 kJ/100 g). Single-parent HH had the highest mean ED (765 kJ/100 g) of all the HH surveyed. The mean ED of HH achieving dietary targets for fat and fruit and vegetables was 576 kJ/100 g compared with 731 kJ/100 g for non-achievers. HH within the lowest quintile of ED were, on average, closest to meeting most dietary guidelines. Food purchase data can be used to monitor the quality of the diet in terms of dietary ED of the population and subgroups defined by an area-based measure of socio-economic status.
Estimation of position resolution for DOI-PET detector using diameter 0.2 mm WLS fibers
Kaneko, Naomi; Ito, Hiroshi; Kawai, Hideyuki; Kamada, Kei
2015-07-01
We have been developing sub mm resolution and $ 1 million DOI-PET detector using wavelength shifting fibers (WLSF), scintillation crystals of plate shape and SiPM (MPPC: HAMAMATSU K. K.). Conventional design of DOI-PET detector is obtained about mm{sup 3} of resolution by using some blocks detecting gamma-ray in mm 3 voxel. It requires the production cost of $ a few ten million or more for high technique of processing crystal and a lot of number of photo-devices, and this technology is reaching the limit of the resolution. Both higher resolution and lower cost of DOI-PET detector production is challenging for PET diagnosis population. We propose two type of detector. One is a whole body PET system, and the other for brain or small animal. Both PET system consist 6 blocks. the former consist of 6 layers 300 mm x 300 mm x 4 mm crystal plate. The latter consist 16 crystal layers, 4 x 4 crystal array. The size of crystal plate is 40 mm x 40 mm x 1 mm.The WLSF sheets connect to upper and lower plane. The whole PET systems connect 8 SiPMs are bonded on each side. For the brain PET, 9 WLSF fibers are bond on the each side. The expected position resolution maybe less than 1 mm at the former. We have estimation experimental performance the system using {sup 22}Na radioactive source. The collection efficiency of WLSF (R-3) sheet was achieved 10% with GAGG at 511 keV. The relation between reconstruction position and incident position is obtained linearity and achieved the resolution of 0.7 mm FWHM for x-axis of DOI by readout WLSF. (authors)
Désert, Jean-Michel; Brown, Timothy M.; Charbonneau, David; Torres, Guillermo; Fressin, François; Ballard, Sarah; Latham, David W.; Bryson, Stephen T.; Borucki, William J.; Knutson, Heather A.; Batalha, Natalie M.; Deming, Drake; Ford, Eric B.; Fortney, Jonathan J.; Gilliland, Ronald L.; 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 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)
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)
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)
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 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.
Dudka, A. P.; Mill', B. V.
2013-07-15
The accurate X-ray diffraction study of a Ca{sub 3}Ga{sub 2}Ge{sub 4}O{sub 14} crystal (sp. gr. P321, Z = 1) has been performed using repeated X-ray diffraction data sets collected on a diffractometer equipped with a CCD area detector at 295 and 100 K. The asymmetric disorder in the atomic positions in Ca{sub 3}Ga{sub 2}Ge{sub 4}O{sub 14} is described in two alternative ways: with the use of anharmonic atomic displacements (at 295 K R/wR = 0.68/0.60%, 3754 reflections; at 100 K R/wR = 0.90/0.70%, 3632 reflections) and using a split model (SM) (at 295 K R/wR = 0.74/0.67%; at 100 K R/wR = 0.95/0.74%). An analysis of the probability density function that defines the probability of finding an atom at a particular point in space shows that, at 295 K, five of the seven independent atoms in the unit cell are asymmetrically disordered in the vicinity of their sites, whereas only three atoms are disordered at 100 K. At both temperatures the largest disorder is observed at the 3f site on a twofold axis, which is a prerequisite for the formation of helicoidal chains of atoms along the c axis of the crystal and can serve as a structural basis for multiferroic properties of this family of crystals with magnetic ions.
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.
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.
Nakagawa, Fumiyo; 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
2016-03-01
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.
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
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.
Breinholt, Jesse W.; Kawahara, Akito Y.
2013-01-01
Recent advancements in molecular sequencing techniques have led to a surge in the number of phylogenetic studies that incorporate large amounts of genetic data. We test the assumption that analyzing large number of genes will lead to improvements in tree resolution and branch support using moths in the superfamily Bombycoidea, a group with some interfamilial relationships that have been difficult to resolve. Specifically, we use a next-gen data set that included 19 taxa and 938 genes (∼1.2M bp) to examine how codon position and saturation might influence resolution and node support among three key families. Maximum likelihood, parsimony, and species tree analysis using gene tree parsimony, on different nucleotide and amino acid data sets, resulted in largely congruent topologies with high bootstrap support compared with prior studies that included fewer loci. However, for a few shallow nodes, nucleotide and amino acid data provided high support for conflicting relationships. The third codon position was saturated and phylogenetic analysis of this position alone supported a completely different, potentially misleading sister group relationship. We used the program RADICAL to assess the number of genes needed to fix some of these difficult nodes. One such node originally needed a total of 850 genes but only required 250 when synonymous signal was removed. Our study shows that, in order to effectively use next-gen data to correctly resolve difficult phylogenetic relationships, it is necessary to assess the effects of synonymous substitutions and third codon positions. PMID:24148944
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.
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.
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.
NASA Astrophysics Data System (ADS)
Shi, C. G.; Salous, S.; Wang, F.; Zhou, J. J.
2017-01-01
Owing to the increased deployment and the favorable range and Doppler resolutions, orthogonal frequency-division multiplexing (OFDM)-based L band digital aeronautical communication system type 1 (LDACS1) stations have become attractive systems for target surveillance in passive radar applications. This paper investigates the problem of joint parameter (position and velocity) estimation of a Rician target in OFDM-based passive radar network systems with multichannel receivers placed on moving platforms, which are composed of multiple OFDM-based LDACS1 transmitters of opportunity and multiple radar receivers. The modified Cramér-Rao lower bounds (MCRLBs) on the Cartesian coordinates of target position and velocity are computed, where the received signal from the target is composed of dominant scatterer (DS) component and weak isotropic scatterers (WIS) component. Simulation results are provided to demonstrate that the target parameter estimation accuracy can be improved by exploiting the DS component. It also shows that the joint MCRLB is not only a function of the transmitted waveform parameters, target radar cross section, and signal-to-noise ratio but also a function of the relative geometry between the target and the passive radar networks. The analytical expressions of MCRLB can be utilized as a performance metric to access the target parameter estimation in OFDM-based passive radar networks in that they enable the selection of optimal transmitter-receiver pairs for target estimation.
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.
Safren, Steven A; Hughes, James P; Mimiaga, Matthew J; Moore, Ayana T; Friedman, Ruth Khalili; Srithanaviboonchai, Kriengkrai; Limbada, Mohammed; Williamson, Brian D; Elharrar, Vanessa; Cummings, Vanessa; Magidson, Jessica F; Gaydos, Charlotte A; Celentano, David D; Mayer, Kenneth H
2016-01-01
Introduction Successful global treatment as prevention (TasP) requires identifying HIV-positive individuals at high risk for transmitting HIV, and having impact via potential infections averted. This study estimated the frequency and predictors of numbers of HIV transmissions and bacterial sexually transmitted infection (STI) acquisition among sexually active HIV-positive individuals in care from three representative global settings. Methods HIV-positive individuals (n=749), including heterosexual men, heterosexual women and men who have sex with men (MSM) in HIV care, were recruited from Chiang Mai (Thailand), Rio De Janeiro (Brazil) and Lusaka (Zambia). Participants were assessed on HIV and STI sexual transmission risk variables, psychosocial characteristics and bacterial STIs at enrolment and quarterly for 12 months (covering 15 months). Estimated numbers of HIV transmissions per person were calculated using reported numbers of partners and sex acts together with estimates of HIV transmissibility, accounting for ART treatment and condom use. Results An estimated 3.81 (standard error, (SE)=0.63) HIV transmissions occurred for every 100 participants over the 15 months, which decreased over time. The highest rate was 19.50 (SE=1.68) for every 100 MSM in Brazil. In a multivariable model, country×risk group interactions emerged: in Brazil, MSM had 2.85 (95% CI=1.45, 4.25, p<0.0001) more estimated transmissions than heterosexual men and 3.37 (95% CI=2.01, 4.74, p<0.0001) more than heterosexual women over the 15 months. For MSM and heterosexual women, the combined 12-month STI incidence rate for the sample was 22.4% (95% CI=18.1%, 27.3%; incidence deemed negligible in heterosexual men). In the multivariable model, MSM had 12.3 times greater odds (95% CI=4.44, 33.98) of acquiring an STI than women, but this was not significant in Brazil. Higher alcohol use on the Alcohol Use Disorders Identification Test (OR=1.04, 95% CI=1.01, 1.08) was also significantly associated
Vogel, Stephan E; Grabner, Roland H; Schneider, Michael; Siegler, Robert S; Ansari, Daniel
2013-04-01
How are numerical and non-numerical magnitudes processed in the brain? Brain imaging research, primarily using comparison paradigms (i.e. judging which of two magnitudes is larger), has provided strong evidence demonstrating that the intraparietal sulcus (IPS) is a key region for processing both numerical (e.g. Arabic numerals, arrays of dots) and non-numerical magnitudes (e.g. height, brightness). These studies have suggested that there is both activation overlap and segregation in the brain regions involved in processing different dimensions of magnitude. In the present functional Magnetic Resonance Imaging (fMRI) study, we extended this line of investigation by probing the brain mechanisms underlying the mapping of numerical (Arabic numerals) and non-numerical magnitudes (brightness levels) onto a number line. Consistent with previous studies the present results revealed that number and brightness estimation was associated with overlapping activation within right lateralized areas of the posterior IPS. In addition, the contrast between number and brightness estimation revealed that bilateral anterior regions of the IPS are specifically involved in the process of estimating the position of symbolic numbers onto a number line. Furthermore, we found a significant influence of landmark reference points (0, 50 and 100) on brain activation in the right IPS for number estimation only. No regions were found to be specifically associated with brightness estimation. The results of this study reveal that the estimation of both numerical and non-numerical magnitude are associated with the engagement of a right lateralized magnitude system, but that symbolic number estimation is associated with additional engagement of bilateral regions of the anterior IPS.
Yonetani, Shota; Okazaki, Mitsuhiro; Araki, Koji; Makino, Hiroshi; Fukugawa, Yoko; Okuyama, Takahiro; Ohnishi, Hiroaki; Watanabe, Takashi
2012-06-01
This study describes a direct inoculation method using the automated BacT/ALERT 3D and the BD Phoenix System in combination for identification and susceptibility testing of isolates from positive blood cultures. Organism identification and susceptibility results were compared with the conventional method for 211 positive aerobic blood cultures. Of 110 Gram-positive cocci (GPCs), 98 (89.1%) isolates were correctly identified to the species level. Of 101 Gram-negative rods (GNRs), 98 (97.0%) isolates were correctly identified to the species level. The overall categorical agreement in antimicrobial susceptibility testing among the 110 GPCs was 92.7%, with 0.04% very major and 0.7% major error rates. The overall categorical agreement among 78 isolates of enterobacteria and 23 isolates of nonfermenters in GNRs was 99.5% and 91.1%, respectively, with no major errors identified. We conclude that, compared with previously reported direct inoculation methods, our method is superior in identification and susceptibility testing of GPCs.
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
Melius, E J; Davis, S I; Redd, J T; Lewin, M; Herlihy, R; Henderson, A; Sobel, J; Gold, B; Cheek, J E
2013-03-01
We investigated a possible outbreak of H. pylori in a rural Northern Plains community. In a cross-sectional survey, we randomly sampled 244 households from a geocoded emergency medical system database. We used a complex survey design and global positioning system units to locate houses and randomly selected one eligible household member to administer a questionnaire and a 13C-urea breath test for active H. pylori infection (n = 166). In weighted analyses, active H. pylori infection was detected in 55·0% of the sample. Factors associated with infection on multivariate analysis included using a public drinking-water supply [odds ratio (OR) 12·2, 95% confidence interval (CI) 2·9-50·7] and current cigarette smoking (OR 4·1, 95% CI 1·7-9·6). People who lived in houses with more rooms, a possible indicator of decreased crowding in the home, were less likely to have active H. pylori infections (OR 0·7, 95% CI 0·5-0·9 for each additional room).
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.
NASA Astrophysics Data System (ADS)
Brunini, C.; Crespi, M.; Mazzoni, A.
2008-12-01
It is well know that GNSS permanent networks for real-time positioning were mainly designed to generate and transmit products for RTK (or Network-RTK) positioning. In this context, RTK products are restricted to users equipped with geodetic-class receivers. This work is a first step toward using a local network of permanent GNSS stations to generate and transmit real time products that could remarkably improve positioning accuracy for C/A receiver users. A simple experiment was carried out based on 3 consecutive days of data from 3 permanent stations that belong to the RESNAP-GPS network (w3.uniroma1.it/resnap-gps), located at the Lazio Region (Central Italy) and managed by DITS-Area di Geodesia e Geomatica, Sapienza University of Rome. In the first step the RINEX files were corrected for the differential code biases according to IGS recommendations and then processed with Bernese 5.0 CODSPP module (single point positioning using code measurements), using IGS precise ephemeris and clocks. One position per epoch (every 30 seconds) was estimated for P1 and for the ionosphere free combination (P3). The accuracy obtained with the P3 combination for the vertical component, which ranged from -1 to +1 m, was taken as the reference for the following discussion. For P1 observations, the vertical coordinate errors showed a typical signature due to the ionospheric activity: higher errors for day-time (up to 5 m) and smaller ones for night-time (around 1.5 m). In order to improve the accuracy of the P1 solution, ionospheric corrections were estimated using the La Plata Ionospheric Model, based on the dual-frequency observations from the RESNAP-GPS network. Those corrections were applied to the RINEX files of a probing station located within the reference network. With this procedure, the vertical coordinate errors were reduced to the range from -0.8 to 0.8 m. This methodological approach shows the possibility to remarkably improve the real time positioning based on Code
NASA Astrophysics Data System (ADS)
Brunini, C.; Crespi, M.; Mazzoni, A.
2009-04-01
It is well know that GNSS permanent networks for real-time positioning were mainly designed to generate and transmit products for RTK (or Network-RTK) positioning. In this context, RTK products are restricted to users equipped with geodetic-class receivers. This work is a first step toward using a local network of permanent GNSS stations to generate and transmit real time products that could remarkably improve positioning accuracy for C/A receiver users. A simple experiment was carried out based on 3 consecutive days of data from 3 permanent stations that belong to the RESNAP-GPS network (w3.uniroma1.it/resnap-gps), located at the Lazio Region (Central Italy) and managed by DITS-Area di Geodesia e Geomatica, Sapienza University of Rome. In the first step the RINEX files were corrected for the differential code biases according to IGS recommendations and then processed with Bernese 5.0 CODSPP module (single point positioning using code measurements), using IGS precise ephemeris and clocks. One position per epoch (every 30 seconds) was estimated for P1 and for the ionosphere free combination (P3). The accuracy obtained with the P3• combination for the vertical component, which ranged from -1 to +1 m, was taken as the reference for the following discussion. For P1 observations, the vertical coordinate errors showed a typical signature due to the ionospheric activity: higher errors for day-time (up to 5 m) and smaller ones for night-time (around 1.5 m). In order to improve the accuracy of the P1 solution, ionospheric corrections were estimated using the La Plata Ionospheric Model, based on the dual-frequency observations from the RESNAP-GPS network. Those corrections were applied to the RINEX files of a probing station located within the reference network. With this procedure, the vertical coordinate errors were reduced to the range from -0.8 to 0.8 m. This methodological approach shows the possibility to remarkably improve the real time positioning based on Code
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.
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.
NASA Astrophysics Data System (ADS)
Inaniwa, Taku; Kohno, Toshiyuki; Tomitani, Takehiro
2005-12-01
In radiation therapy with hadron beams, conformal irradiation to a tumour can be achieved by using the properties of incident ions such as the high dose concentration around the Bragg peak. For the effective utilization of such properties, it is necessary to evaluate the volume irradiated with hadron beams and the deposited dose distribution in a patient's body. Several methods have been proposed for this purpose, one of which uses the positron emitters generated through fragmentation reactions between incident ions and target nuclei. In the previous paper, we showed that the maximum likelihood estimation (MLE) method could be applicable to the estimation of beam end-point from the measured positron emitting activity distribution for mono-energetic beam irradiations. In a practical treatment, a spread-out Bragg peak (SOBP) beam is used to achieve a uniform biological dose distribution in the whole target volume. Therefore, in the present paper, we proposed to extend the MLE method to estimations of the position of the distal and proximal edges of the SOBP from the detected annihilation gamma ray distribution. We confirmed the effectiveness of the method by means of simulations. Although polyethylene was adopted as a substitute for a soft tissue target in validating the method, the proposed method is equally applicable to general cases, provided that the reaction cross sections between the incident ions and the target nuclei are known. The relative advantage of incident beam species to determine the position of the distal and the proximal edges was compared. Furthermore, we ascertained the validity of applying the MLE method to determinations of the position of the distal and the proximal edges of an SOBP by simulations and we gave a physical explanation of the distal and the proximal information.
Extracting Time-Accurate Acceleration Vectors From Nontrivial Accelerometer Arrangements.
Franck, Jennifer A; Blume, Janet; Crisco, Joseph J; Franck, Christian
2015-09-01
Sports-related concussions are of significant concern in many impact sports, and their detection relies on accurate measurements of the head kinematics during impact. Among the most prevalent recording technologies are videography, and more recently, the use of single-axis accelerometers mounted in a helmet, such as the HIT system. Successful extraction of the linear and angular impact accelerations depends on an accurate analysis methodology governed by the equations of motion. Current algorithms are able to estimate the magnitude of acceleration and hit location, but make assumptions about the hit orientation and are often limited in the position and/or orientation of the accelerometers. The newly formulated algorithm presented in this manuscript accurately extracts the full linear and rotational acceleration vectors from a broad arrangement of six single-axis accelerometers directly from the governing set of kinematic equations. The new formulation linearizes the nonlinear centripetal acceleration term with a finite-difference approximation and provides a fast and accurate solution for all six components of acceleration over long time periods (>250 ms). The approximation of the nonlinear centripetal acceleration term provides an accurate computation of the rotational velocity as a function of time and allows for reconstruction of a multiple-impact signal. Furthermore, the algorithm determines the impact location and orientation and can distinguish between glancing, high rotational velocity impacts, or direct impacts through the center of mass. Results are shown for ten simulated impact locations on a headform geometry computed with three different accelerometer configurations in varying degrees of signal noise. Since the algorithm does not require simplifications of the actual impacted geometry, the impact vector, or a specific arrangement of accelerometer orientations, it can be easily applied to many impact investigations in which accurate kinematics need to
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.
Accurate spectral color measurements
NASA Astrophysics Data System (ADS)
Hiltunen, Jouni; Jaeaeskelaeinen, Timo; Parkkinen, Jussi P. S.
1999-08-01
Surface color measurement is of importance in a very wide range of industrial applications including paint, paper, printing, photography, textiles, plastics and so on. For a demanding color measurements spectral approach is often needed. One can measure a color spectrum with a spectrophotometer using calibrated standard samples as a reference. Because it is impossible to define absolute color values of a sample, we always work with approximations. The human eye can perceive color difference as small as 0.5 CIELAB units and thus distinguish millions of colors. This 0.5 unit difference should be a goal for the precise color measurements. This limit is not a problem if we only want to measure the color difference of two samples, but if we want to know in a same time exact color coordinate values accuracy problems arise. The values of two instruments can be astonishingly different. The accuracy of the instrument used in color measurement may depend on various errors such as photometric non-linearity, wavelength error, integrating sphere dark level error, integrating sphere error in both specular included and specular excluded modes. Thus the correction formulas should be used to get more accurate results. Another question is how many channels i.e. wavelengths we are using to measure a spectrum. It is obvious that the sampling interval should be short to get more precise results. Furthermore, the result we get is always compromise of measuring time, conditions and cost. Sometimes we have to use portable syste or the shape and the size of samples makes it impossible to use sensitive equipment. In this study a small set of calibrated color tiles measured with the Perkin Elmer Lamda 18 and the Minolta CM-2002 spectrophotometers are compared. In the paper we explain the typical error sources of spectral color measurements, and show which are the accuracy demands a good colorimeter should have.
Chu, Haitao; Zhou, Yijie; Cole, Stephen R; Ibrahim, Joseph G
2010-05-20
To evaluate the probabilities of a disease state, ideally all subjects in a study should be diagnosed by a definitive diagnostic or gold standard test. However, since definitive diagnostic tests are often invasive and expensive, it is generally unethical to apply them to subjects whose screening tests are negative. In this article, we consider latent class models for screening studies with two imperfect binary diagnostic tests and a definitive categorical disease status measured only for those with at least one positive screening test. Specifically, we discuss a conditional-independent and three homogeneous conditional-dependent latent class models and assess the impact of misspecification of the dependence structure on the estimation of disease category probabilities using frequentist and Bayesian approaches. Interestingly, the three homogeneous-dependent models can provide identical goodness-of-fit but substantively different estimates for a given study. However, the parametric form of the assumed dependence structure itself is not 'testable' from the data, and thus the dependence structure modeling considered here can only be viewed as a sensitivity analysis concerning a more complicated non-identifiable model potentially involving a heterogeneous dependence structure. Furthermore, we discuss Bayesian model averaging together with its limitations as an alternative way to partially address this particularly challenging problem. The methods are applied to two cancer screening studies, and simulations are conducted to evaluate the performance of these methods. In summary, further research is needed to reduce the impact of model misspecification on the estimation of disease prevalence in such settings.
Numerical Estimation in Deaf and Hearing Adults.
Bull, Rebecca; Marschark, Marc; Sapere, Patty; Davidson, Wendy A; Murphy, Derek; Nordmann, Emily
2011-08-01
Deaf students often lag behind hearing peers in numerical and mathematical abilities. Studies of hearing children with mathematical difficulties highlight the importance of estimation skills as the foundation for formal mathematical abilities, but research with adults is limited. Deaf and hearing college students were assessed on the Number-to-Position task as a measure of estimation, and completed standardised assessments of arithmetical and mathematical reasoning. Deaf students performed significantly more poorly on all measures, including making less accurate number-line estimates. For deaf students, there was also a strong relationship showing that those more accurate in making number-line estimates achieved higher scores on the math achievement tests. No such relationship was apparent for hearing students. Further insights into the estimation abilities of deaf individuals should be made, including tasks that require symbolic and non-symbolic estimation and which address the quality of estimation strategies being used.
Three Position Estimation Procedures. Revision,
1986-02-01
the direc-. tion 6 of the major axis and the size is given in terms of the lengths SMJ and SMI of the semi-major and semi-minor axes and the confidence...6 - 1800 and a-, > a^1 y x. With an order relation and a value for p, values for a^ and 0i, can be determined with values for SMJ and SMI. With...nautical miles. And, for k = 2:xy SMJ = 20.56 nautical miles, SMI = 12.42 nautical miles and 6 = 1190. The composite confidence region and its three com
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.
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
NASA Astrophysics Data System (ADS)
Luce, H.; RöTtger, J.; Crochet, M.; Yamamoto, M.; Fukao, S.
2000-09-01
In the companion paper (part 1), theoretical studies on the dual frequency domain interferometry (FDI) technique have been presented. Two possible causes of biases in the layer thickness and position estimations by FDI have been considered: the limited extent of the scattering structure in the horizontal plane and the advection of this structure by the wind. In the present work, we study the effects of the tilts of the scattering layer from horizontal. It is shown that in case of large tilt angles, substantial biases on position and thickness can occur. The model, first developed by Liu and Pan [1993] but more extensively described in this paper, can also be used for a prediction of the variations of the FDI coherence with the zenith angle and their relation to the anisotropy of the scatterers. Some preliminary observations of the zenith angle dependence of the FDI coherence and echo power obtained with the middle and upper atmosphere (MU) radar from the vertical up to 28° off zenith with a step of 2° are shown and discussed. In principle, comparisons between the observed power and coherence variations with those given by the model could give more information on the structures that contribute around and far from the zenith.
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...
Accurate Coordinates and Predicted Position of Navigation Satellites NNSS,
1980-11-28
orbital elements of satellites No.s 13 , 14, 12, 19 and 20. The elements of SN-18 were given in Table 2. All these data refer to satellites operating in...December 1975. Table 4 lists transmitted orbital elements of satellites No.s 20, 14, 13 , 12 and 19 observed in January 1976. In Tables 3 and 4, the...equation 0s) - M*) + ( -mhI) (( 13 ) Let the longitude of the node Xw be its longitude at the first transit of the SN through the equator from South to
Kaneko, Naomi; Ito, H.; Han, S.; Kawai, H.; Kodama, S.; Kobayashi, A.; Tabata, M.; Kamada, K.; Shoji, Y.; Yoshikawa, A.
2015-07-01
We have been developing a submillimeter resolution and low-cost DOI-PET detector using wavelength shifting fibers (WLSF), scintillating crystal plates and MPPCs (Hamamatsu Photonics). Conventional design of DOI-PET detectors had approximately mm{sup 3} of resolution by using some scintillating blocks with a volume of 1 mm{sup 3}, which detects gamma-ray. They are expensive due to difficulties in processing scintillating crystals and a large number of photo-detectors, and these technologies are likely to reach the limit of the resolution. Development of a lower cost DOI-PET detector with higher resolution is challenging to popularize the PET diagnosis. We propose two type of PET detector. One is a whole body PET system, and the other is a PET system for brain or small animals. Each PET system consists 6 blocks. The former consists of 6 layers of crystal plates with 300 mm x 300 mm x 4 mm. The latter consists of 16 crystal layers, forming 4 x 4 crystal arrays. The size of the crystal plate is 40 mm x 40 mm x 1 mm. Wavelength shifting fiber (WLSF) sheets are attached to above and up and down side of crystal planes. The whole PET system has 8 MPPCs attached on each side. For the brain PET detector, 9 WLSF fibers are attached on the each side. The expected position resolution would be less than 1 mm at the former system. We have performed an experimental performance estimation for the system component using {sup 22}Na radioactive source. We achieved a collection efficiency of 10% using the WLSF sheet and Ce:Gd{sub 3}(Al,Ga){sub 5}O{sub 12} (GAGG) crystals at 511 keV. The linear relationship between reconstruction position and incident position was obtained, and a resolution of 0.7 mm (FWHM) for x-axis of DOI by the WLSF readout was achieved. (authors)
Shirai, Yoshiro; Kuriki, Kiyonori; Endoh, Kaori; Miyauchi, Rie; Kasezawa, Nobuhiko; Tohyama, Kazushige; Goda, Toshinao
2016-03-01
The relationship between drinking frequency and amount of alcohol consumption (i.e., drinking habits) and the risk of chronic kidney disease (CKD) remains unclear. We aimed to clarify either a linear or J-shaped dose-response relationship between drinking habits and estimated glomerular filtration rate (eGFR) as a biomarker for identifying individuals at high risk of CKD. In a large-scale cross-sectional study, 403 men and 121 women with an eGFR of 30-60 mL/min per 1.73 m(2) were defined as cases, and 1209 men and 363 women with ≥60 mL/min/1.73 m(2) were randomly extracted as controls (one case subject was matched with three control subjects, matched according to age and season of data collection). We calculated multivariate-adjusted CKD risk and the corresponding mean eGFR according to drinking habits. In men, negative and positive linear relationships with drinking habits were found for CKD risk and mean eGFR (p < 0.001 for all linear terms), respectively, but there were no corresponding J-shaped relationships (not significant for all quadratic terms). In regard to the mean eGFR, however, positive linear relationships were only shown in men in the highest eGFR quartile (p < 0.05 and p < 0.01 for drinking frequency and amount of alcohol consumption, respectively). In women, no association was found. Regarding each drinking habit, we found a positive linear dose-response relationship to eGFR in middle-aged men with an eGFR ≥30 mL/min/1.73 m(2).
Forman, Michele R.; Zhu, Yeyi; Hernandez, Ladia M.; Himes, John H.; Dong, Yongquan; Danish, Robert K.; James, Kyla E.; Caulfield, Laura E.; Kerver, Jean M.; Arab, Lenore; Voss, Paula; Hale, Daniel E.; Kanafani, Nadim; Hirschfeld, Steven
2014-01-01
Surrogate measures are needed when recumbent length or height is unobtainable or unreliable. Arm span has been used as a surrogate but is not feasible in children with shoulder or arm contractures. Ulnar length is not usually impaired by joint deformities, yet its utility as a surrogate has not been adequately studied. In this cross-sectional study, we aimed to examine the accuracy and reliability of ulnar length measured by different tools as a surrogate measure of recumbent length and height. Anthropometrics [recumbent length, height, arm span, and ulnar length by caliper (ULC), ruler (ULR), and grid (ULG)] were measured in 1479 healthy infants and children aged <6 y across 8 study centers in the United States. Multivariate mixed-effects linear regression models for recumbent length and height were developed by using ulnar length and arm span as surrogate measures. The agreement between the measured length or height and the predicted values by ULC, ULR, ULG, and arm span were examined by Bland-Altman plots. All 3 measures of ulnar length and arm span were highly correlated with length and height. The degree of precision of prediction equations for length by ULC, ULR, and ULG (R2 = 0.95, 0.95, and 0.92, respectively) was comparable with that by arm span (R2 = 0.97) using age, sex, and ethnicity as covariates; however, height prediction by ULC (R2 = 0.87), ULR (R2 = 0.85), and ULG (R2 = 0.88) was less comparable with arm span (R2 = 0.94). Our study demonstrates that arm span and ULC, ULR, or ULG can serve as accurate and reliable surrogate measures of recumbent length and height in healthy children; however, ULC, ULR, and ULG tend to slightly overestimate length and height in young infants and children. Further testing of ulnar length as a surrogate is warranted in physically impaired or nonambulatory children. PMID:25031329
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.
The importance of the seated condylar position in orthodontic correction.
Cordray, Frank E
2002-04-01
It has been proposed that the discrepancy between the seated and unseated condylar position be identified and eliminated when the occlusion is reorganized. Identification of this discrepancy is most accurately accomplished through the use of diagnostic casts that have been taken from a deprogrammed patient and mounted in the seated condylar position on a semiadjustable articulator through an estimated facebow transfer. The amount and direction of any discrepancy is determined three dimensionally with condylar position instrumentation.
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.
Accurate estimation of the elastic properties of porous fibers
Thissell, W.R.; Zurek, A.K.; Addessio, F.
1997-05-01
A procedure is described to calculate polycrystalline anisotropic fiber elastic properties with cylindrical symmetry and porosity. It uses a preferred orientation model (Tome ellipsoidal self-consistent model) for the determination of anisotropic elastic properties for the case of highly oriented carbon fibers. The model predictions, corrected for porosity, are compared to back-calculated fiber elastic properties of an IM6/3501-6 unidirectional composite whose elastic properties have been determined via resonant ultrasound spectroscopy. The Halpin-Tsai equations used to back-calculated fiber elastic properties are found to be inappropriate for anisotropic composite constituents. Modifications are proposed to the Halpin-Tsai equations to expand their applicability to anisotropic reinforcement materials.
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.
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.
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
Benn, P A; Ying, J; Beazoglou, T; Egan, J F
2001-01-01
Second trimester screening for fetal Down syndrome and trisomy 18 is available through separate protocols that combine the maternal age-specific risk and the analysis of maternal serum markers. We have determined the extent to which additional Down syndrome affected pregnancies may be identified through trisomy 18 screening, and the extent to which additional cases of trisomy 18 may be screen-positive for Down syndrome. The combined false-positive rate, taking into consideration those pregnancies that are screen-positive by both protocols, has also been determined. Sensitivity and false-positive rates were determined by computer simulation of results that incorporated previously published statistical variables into the model. Using second trimester risk cut-offs of 1:270 for Down syndrome and 1:100 for trisomy 18, it was found that few additional cases of Down syndrome are identified through trisomy 18 screening. However, approximately 6-10% of trisomy 18 affected pregnancies will be screen-positive for Down syndrome but screen-negative for trisomy 18. For women aged 40 or more, the false-positive rate for trisomy 18 exceeds 1% and approximately half of these cases will also be screen-positive for Down syndrome. For a population with maternal ages equivalent to that in the United States in 1998, after adjusting for the cross-identification, the sensitivity for three-analyte trisomy 18 screening is 78%. If this testing is performed in conjunction with Down syndrome "triple" screening, the Down syndrome sensitivity is 75% and the combined false-positive rate is 8.5%. If the three-analyte trisomy 18 screening is performed with the Down syndrome "quad" screen, the trisomy 18 sensitivity remains at 78%, the Down syndrome sensitivity is 79%, and combined false-positive rate is 7.5%. Sensitivity and false-positive rates are also provided for other widely used Down syndrome and trisomy 18 risk cut-offs. Sensitivity and false-positive rates that take into consideration
FPGA Accelerated Discrete-SURF for Real-Time Homography Estimation
2015-03-26
tracking methods homography estimation required to determine relative position and orientation. The analysis concludes as current challenges in the area set...Communication between platforms with their own on-board inertial navigation systems (INS) is a common solution to relative navigation that is cheap in...accurate estimation of movement and position. By communicating their enhanced pose estimation, many platforms can navigate relative to one another
LOST2: A positioning system for underwater vessels
NASA Astrophysics Data System (ADS)
Beckman, Richard Robert
2001-10-01
The LOST2 system is a new accurate underwater positioning system that nonlinearly combines parts of dead-reckoning, acoustic-based positioning, and terrain-based positioning. The system is composed of two major subsystems, a system observer and a constrained extended Kalman filter. Inputs to the system are as follows: (1)high resolution bathymetry, (2)measured ocean depth at the position of the vessel, (3)measured or estimated vessel velocity, (4)slant range to and position of a known point, and (5)an initial prediction of the vessel's location. The system development, simulation studies, results from sea trials and some suggestions for future work are presented. The system is capable of providing position estimates with the same degree of accuracy as present methods, with significantly less hardware. These results prove the concept of the system as a new method to position underwater vessels.
Fast and accurate registration techniques for affine and nonrigid alignment of MR brain images.
Liu, Jia-Xiu; Chen, Yong-Sheng; Chen, Li-Fen
2010-01-01
Registration of magnetic resonance brain images is a geometric operation that determines point-wise correspondences between two brains. It remains a difficult task due to the highly convoluted structure of the brain. This paper presents novel methods, Brain Image Registration Tools (BIRT), that can rapidly and accurately register brain images by utilizing the brain structure information estimated from image derivatives. Source and target image spaces are related by affine transformation and non-rigid deformation. The deformation field is modeled by a set of Wendland's radial basis functions hierarchically deployed near the salient brain structures. In general, nonlinear optimization is heavily engaged in the parameter estimation for affine/non-rigid transformation and good initial estimates are thus essential to registration performance. In this work, the affine registration is initialized by a rigid transformation, which can robustly estimate the orientation and position differences of brain images. The parameters of the affine/non-rigid transformation are then hierarchically estimated in a coarse-to-fine manner by maximizing an image similarity measure, the correlation ratio, between the involved images. T1-weighted brain magnetic resonance images were utilized for performance evaluation. Our experimental results using four 3-D image sets demonstrated that BIRT can efficiently align images with high accuracy compared to several other algorithms, and thus is adequate to the applications which apply registration process intensively. Moreover, a voxel-based morphometric study quantitatively indicated that accurate registration can improve both the sensitivity and specificity of the statistical inference results.
2013-10-18
area of 3D point estimation of flapping- wing UASs. The benefits of designing and developing such a system is instrumental in researching various...are many benefits to us- ing SIFT in tracking. It detects features that are invariant to image scale and rotation, and are shown to provide robust...provided to estimate background motion for optical flow background subtraction. The experiments with the static background showed minute benefit in
NASA Astrophysics Data System (ADS)
Carlowicz, Michael
The U.S. Global Positioning System (GPS) will soon become more accurate for civilian users, improving the quality of navigation and of some types of scientific research. The Clinton Administration announced March 29 that within a decade, the federal government will stop degrading the civilian GPS signal and will allow nonmilitary users access to the same clear signals that U.S. troops rely upon.Designed as dual-use system with primary use by the American military, the GPS is a constellation of 24 satellites that allows soldiers to determine their exact positions (in latitude and longitude) anywhere in the world. While the GPS is operated by the Department of Defense (DoD), scientists and adventurous civilians have been able to purchase small, portable GPS devices. However, the U.S. military has kept to itself a capability known as “selective availability” that provides a much more precise signal than is available to the public. According to the White House, that selected signal will be available to all users within 4-10 years.
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
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.
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.
Toward Accurate and Quantitative Comparative Metagenomics
Nayfach, Stephen; Pollard, Katherine S.
2016-01-01
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
Sparse and accurate high resolution SAR imaging
NASA Astrophysics Data System (ADS)
Vu, Duc; Zhao, Kexin; Rowe, William; Li, Jian
2012-05-01
We investigate the usage of an adaptive method, the Iterative Adaptive Approach (IAA), in combination with a maximum a posteriori (MAP) estimate to reconstruct high resolution SAR images that are both sparse and accurate. IAA is a nonparametric weighted least squares algorithm that is robust and user parameter-free. IAA has been shown to reconstruct SAR images with excellent side lobes suppression and high resolution enhancement. We first reconstruct the SAR images using IAA, and then we enforce sparsity by using MAP with a sparsity inducing prior. By coupling these two methods, we can produce a sparse and accurate high resolution image that are conducive for feature extractions and target classification applications. In addition, we show how IAA can be made computationally efficient without sacrificing accuracies, a desirable property for SAR applications where the size of the problems is quite large. We demonstrate the success of our approach using the Air Force Research Lab's "Gotcha Volumetric SAR Data Set Version 1.0" challenge dataset. Via the widely used FFT, individual vehicles contained in the scene are barely recognizable due to the poor resolution and high side lobe nature of FFT. However with our approach clear edges, boundaries, and textures of the vehicles are obtained.
On numerically accurate finite element
NASA Technical Reports Server (NTRS)
Nagtegaal, J. C.; Parks, D. M.; Rice, J. R.
1974-01-01
A general criterion for testing a mesh with topologically similar repeat units is given, and the analysis shows that only a few conventional element types and arrangements are, or can be made suitable for computations in the fully plastic range. Further, a new variational principle, which can easily and simply be incorporated into an existing finite element program, is presented. This allows accurate computations to be made even for element designs that would not normally be suitable. Numerical results are given for three plane strain problems, namely pure bending of a beam, a thick-walled tube under pressure, and a deep double edge cracked tensile specimen. The effects of various element designs and of the new variational procedure are illustrated. Elastic-plastic computation at finite strain are discussed.
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.
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.
Comparison of Low-Cost Computer Algorithms for Global Positioning System Users.
The Global Positioning System ( GPS ) is a navigation system which relies on range and range-rate measurements between satellites and the GPS -user in...order to determine his position and velocity. Using extensive support equipment, GPS is anticipated to achieve extremely accurate results. However... position estimates (dead-reckoning) for the first two approaches. The Kalman filter was modelled with fixed covariance matrices. The approaches were
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.
Accurate method for computing correlated color temperature.
Li, Changjun; Cui, Guihua; Melgosa, Manuel; Ruan, Xiukai; Zhang, Yaoju; Ma, Long; Xiao, Kaida; Luo, M Ronnier
2016-06-27
For the correlated color temperature (CCT) of a light source to be estimated, a nonlinear optimization problem must be solved. In all previous methods available to compute CCT, the objective function has only been approximated, and their predictions have achieved limited accuracy. For example, different unacceptable CCT values have been predicted for light sources located on the same isotemperature line. In this paper, we propose to compute CCT using the Newton method, which requires the first and second derivatives of the objective function. Following the current recommendation by the International Commission on Illumination (CIE) for the computation of tristimulus values (summations at 1 nm steps from 360 nm to 830 nm), the objective function and its first and second derivatives are explicitly given and used in our computations. Comprehensive tests demonstrate that the proposed method, together with an initial estimation of CCT using Robertson's method [J. Opt. Soc. Am. 58, 1528-1535 (1968)], gives highly accurate predictions below 0.0012 K for light sources with CCTs ranging from 500 K to 10^{6} K.
A quick accurate model of nozzle backflow
NASA Technical Reports Server (NTRS)
Kuharski, R. A.
1991-01-01
Backflow from nozzles is a major source of contamination on spacecraft. If the craft contains any exposed high voltages, the neutral density produced by the nozzles in the vicinity of the craft needs to be known in order to assess the possibility of Paschen breakdown or the probability of sheath ionization around a region of the craft that collects electrons for the plasma. A model for backflow has been developed for incorporation into the Environment-Power System Analysis Tool (EPSAT) which quickly estimates both the magnitude of the backflow and the species makeup of the flow. By combining the backflow model with the Simons (1972) model for continuum flow it is possible to quickly estimate the density of each species from a nozzle at any position in space. The model requires only a few physical parameters of the nozzle and the gas as inputs and is therefore ideal for engineering applications.
Accurate ab Initio Spin Densities.
Boguslawski, Katharina; Marti, Konrad H; Legeza, Ors; Reiher, Markus
2012-06-12
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].
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.
Position Error Covariance Matrix Validation and Correction
NASA Technical Reports Server (NTRS)
Frisbee, Joe, Jr.
2016-01-01
In order to calculate operationally accurate collision probabilities, the position error covariance matrices predicted at times of closest approach must be sufficiently accurate representations of the position uncertainties. This presentation will discuss why the Gaussian distribution is a reasonable expectation for the position uncertainty and how this assumed distribution type is used in the validation and correction of position error covariance matrices.
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.
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
Høstmark, Arne Torbjørn
2010-12-01
A previous finding that soft drink intake is associated with increased serum triglycerides and decreased high-density-lipoprotein (HDL) cholesterol, both components of the metabolic syndrome (MetS), raises the question of whether other aspects of an unhealthy diet might be associated with MetS. Main MetS requirements are central obesity and 2 of the following: increased triglycerides, low HDL, increased systolic or diastolic blood pressure, and elevated fasting blood glucose. Of the 18 770 participants in the Oslo Health Study, there were 13 170 respondents (5997 men and 7173 women) with data on MetS factors (except fasting glucose) and on the components used to determine the Dietary Index score (calculated as the intake estimate of soft drinks divided by the sum of intake estimates of fruits and vegetables). MetSRisk was calculated as the sum of arbitrarily weighted factors positively associated with MetS divided by HDL cholesterol. Using regression analyses, the association of the Dietary Index with MetSRisk, with the number of MetS requirements present, and with the complete MetS was studied. In young, middle-aged, and senior men and women, there was, in general, a positive association (p < 0.001) between the Dietary Index and the MetS estimates, which persisted in regression models adjusted for sex, age, time since the last meal, intake of cheese, intake of fatty fish, intake of coffee, intake of alcohol, smoking, physical activity, education, and birthplace. Thus, an index reflecting a high intake of soft drinks and a low intake of fruit and vegetables was positively and independently associated with aspects of MetS.
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.
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.
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, 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...
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, 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, 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...
Global Positioning System Status
2011-04-27
GPS : FREE – DEPENDABLE – RELIABLE - ACCURATE 1 GLOBAL POSITIONING SYSTEM STATUS Benjamin Barbour Major, United States Air Force Schriever AFB... Global Positioning System Service Interface Committee (CGSIC) held in Groton, CT, April 2011 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY...Continuing work with international GNSS community Maintains Backward Compatibility Managing GPS systems and supporting stakeholders Committed to responsible stewardship of GPS
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.
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
Does a pneumotach accurately characterize voice function?
NASA Astrophysics Data System (ADS)
Walters, Gage; Krane, Michael
2016-11-01
A study is presented which addresses how a pneumotach might adversely affect clinical measurements of voice function. A pneumotach is a device, typically a mask, worn over the mouth, in order to measure time-varying glottal volume flow. By measuring the time-varying difference in pressure across a known aerodynamic resistance element in the mask, the glottal volume flow waveform is estimated. Because it adds aerodynamic resistance to the vocal system, there is some concern that using a pneumotach may not accurately portray the behavior of the voice. To test this hypothesis, experiments were performed in a simplified airway model with the principal dimensions of an adult human upper airway. A compliant constriction, fabricated from silicone rubber, modeled the vocal folds. Variations of transglottal pressure, time-averaged volume flow, model vocal fold vibration amplitude, and radiated sound with subglottal pressure were performed, with and without the pneumotach in place, and differences noted. Acknowledge support of NIH Grant 2R01DC005642-10A1.
Accurate equilibrium structures for piperidine and cyclohexane.
Demaison, Jean; Craig, Norman C; Groner, Peter; Écija, Patricia; Cocinero, Emilio J; Lesarri, Alberto; Rudolph, Heinz Dieter
2015-03-05
Extended and improved microwave (MW) measurements are reported for the isotopologues of piperidine. New ground state (GS) rotational constants are fitted to MW transitions with quartic centrifugal distortion constants taken from ab initio calculations. Predicate values for the geometric parameters of piperidine and cyclohexane are found from a high level of ab initio theory including adjustments for basis set dependence and for correlation of the core electrons. Equilibrium rotational constants are obtained from GS rotational constants corrected for vibration-rotation interactions and electronic contributions. Equilibrium structures for piperidine and cyclohexane are fitted by the mixed estimation method. In this method, structural parameters are fitted concurrently to predicate parameters (with appropriate uncertainties) and moments of inertia (with uncertainties). The new structures are regarded as being accurate to 0.001 Å and 0.2°. Comparisons are made between bond parameters in equatorial piperidine and cyclohexane. Another interesting result of this study is that a structure determination is an effective way to check the accuracy of the ground state experimental rotational constants.
Multiple-hit parameter estimation in monolithic detectors
Hunter, William C. J.; Barrett, Harrison H.; Miyaoka, Robert S.; Lewellen, Tom K.
2012-01-01
We examine a maximum-a-priori (MAP) method for estimating the primary interaction position of gamma rays with multiple-interaction sites (hits) in a monolithic detector. In assessing the performance of a multiple-hit estimator over that of a conventional one-hit estimator, we consider a few different detector and readout configurations of a 50-mm-wide square LSO block. For this study, we use simulated data from SCOUT, a Monte-Carlo tool for photon tracking and modeling scintillation-camera output. With this tool, we determine estimate bias and variance for a multiple-hit estimator and compare these with similar metrics for a conventional ML estimator, which assumes full energy deposition in one hit. We also examine the effect of event filtering on these metrics; for this purpose, we use a likelihood threshold to reject signals that are not likely to have been produced under the assumed likelihood model. Depending on detector design, we observe a 1–12% improvement of intrinsic resolution for a 1-or-2-hit estimator as compared with a 1-hit estimator. We also observe improved differentiation of photopeak events using a 1-or-2-hit estimator as compared with the 1-hit estimator; more than 6% of photopeak events that were rejected by likelihood filtering for the 1-hit estimator were accurately identified as photo peak events and positioned without loss of resolution by a 1-or-2-hit estimator. PMID:23238325
Moving target parameter estimation of SAR after two looks cancellation
NASA Astrophysics Data System (ADS)
Gan, Rongbing; Wang, Jianguo; Gao, Xiang
2005-11-01
Moving target detection of synthetic aperture radar (SAR) by two looks cancellation is studied. First, two looks are got by the first and second half of the synthetic aperture. After two looks cancellation, the moving targets are reserved and stationary targets are removed. After that, a Constant False Alarm Rate (CFAR) detector detects moving targets. The ground range velocity and cross-range velocity of moving target can be got by the position shift between the two looks. We developed a method to estimate the cross-range shift due to slant range moving. we estimate cross-range shift by Doppler frequency center. Wigner-Ville Distribution (WVD) is used to estimate the Doppler frequency center (DFC). Because the range position and cross range before correction is known, estimation of DFC is much easier and efficient. Finally experiments results show that our algorithms have good performance. With the algorithms we can estimate the moving target parameter accurately.
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.
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
Range and Size Estimation Based on a Coordinate Transformation Model for Driving Assistance Systems
NASA Astrophysics Data System (ADS)
Wu, Bing-Fei; Lin, Chuan-Tsai; Chen, Yen-Lin
This paper presents new approaches for the estimation of range between the preceding vehicle and the experimental vehicle, estimation of vehicle size and its projective size, and dynamic camera calibration. First, our proposed approaches adopt a camera model to transform coordinates from the ground plane onto the image plane to estimate the relative position between the detected vehicle and the camera. Then, to estimate the actual and projective size of the preceding vehicle, we propose a new estimation method. This method can estimate the range from a preceding vehicle to the camera based on contact points between its tires and the ground and then estimate the actual size of the vehicle according to the positions of its vertexes in the image. Because the projective size of a vehicle varies with respect to its distance to the camera, we also present a simple and rapid method of estimating a vehicle's projective height, which allows a reduction in computational time for size estimation in real-time systems. Errors caused by the application of different camera parameters are also estimated and analyzed in this study. The estimation results are used to determine suitable parameters during camera installation to suppress estimation errors. Finally, to guarantee robustness of the detection system, a new efficient approach to dynamic calibration is presented to obtain accurate camera parameters, even when they are changed by camera vibration owing to on-road driving. Experimental results demonstrate that our approaches can provide accurate and robust estimation results of range and size of target vehicles.
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 glucose detection in a small etalon
NASA Astrophysics Data System (ADS)
Martini, Joerg; Kuebler, Sebastian; Recht, Michael; Torres, Francisco; Roe, Jeffrey; Kiesel, Peter; Bruce, Richard
2010-02-01
We are developing a continuous glucose monitor for subcutaneous long-term implantation. This detector contains a double chamber Fabry-Perot-etalon that measures the differential refractive index (RI) between a reference and a measurement chamber at 850 nm. The etalon chambers have wavelength dependent transmission maxima which dependent linearly on the RI of their contents. An RI difference of ▵n=1.5.10-6 changes the spectral position of a transmission maximum by 1pm in our measurement. By sweeping the wavelength of a single-mode Vertical-Cavity-Surface-Emitting-Laser (VCSEL) linearly in time and detecting the maximum transmission peaks of the etalon we are able to measure the RI of a liquid. We have demonstrated accuracy of ▵n=+/-3.5.10-6 over a ▵n-range of 0 to 1.75.10-4 and an accuracy of 2% over a ▵nrange of 1.75.10-4 to 9.8.10-4. The accuracy is primarily limited by the reference measurement. The RI difference between the etalon chambers is made specific to glucose by the competitive, reversible release of Concanavalin A (ConA) from an immobilized dextran matrix. The matrix and ConA bound to it, is positioned outside the optical detection path. ConA is released from the matrix by reacting with glucose and diffuses into the optical path to change the RI in the etalon. Factors such as temperature affect the RI in measurement and detection chamber equally but do not affect the differential measurement. A typical standard deviation in RI is +/-1.4.10-6 over the range 32°C to 42°C. The detector enables an accurate glucose specific concentration measurement.
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.
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.
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.
Diagnosing Dementia--Positive Signs
... Navigation Bar Home Current Issue Past Issues Diagnosing Dementia—Positive Signs Past Issues / Fall 2007 Table of ... easy, affordable blood test that could accurately diagnose Alzheimer's disease (AD)—even before symptoms began to show? Researchers ...
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.
Acoustic Sensor Network Design for Position Estimation
2009-05-01
utility is K(ñ) = ( T∑ t=1 ω̃1,tñt )( T∑ t=1 ω̃2,tñt )ρ . (17) We start by noting that the following is a necessary KKT condition for the op- timal...Analysis]: Optimization —Constrained optimization , convex pro- gramming, integer programming, nonlinear programming; G.3 [Probability and Statistics...subsections describe general multiple-objective optimization , exact integer programming methods to find the “ optimal ” designs, and approximate non
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.
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.
Optical Fiber Geometry: Accurate Measurement of Cladding Diameter
Young, Matt; Hale, Paul D.; Mechels, Steven E.
1993-01-01
We have developed three instruments for accurate measurement of optieal fiber cladding diameter: a contact micrometer, a scanning confocal microscope, and a white-light interference microscope. Each instrument has an estimated uncertainty (3 standard deviations) of 50 nm or less, but the confocal microscope may display a 20 nm systematic error as well. The micrometer is used to generate Standard Reference Materials that are commercially available. PMID:28053467
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