Science.gov

Sample records for absolute positioning accuracy

  1. Absolute Positioning Using the Global Positioning System

    DTIC Science & Technology

    1994-04-01

    Global Positioning System ( GPS ) has becom a useful tool In providing relativ survey...Includes the development of a low cost navigator for wheeled vehicles. ABSTRACT The Global Positioning System ( GPS ) has become a useful tool In providing...technique of absolute or point positioning involves the use of a single Global Positioning System ( GPS ) receiver to determine the three-dimenslonal

  2. Achieving Climate Change Absolute Accuracy in Orbit

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C. O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jennings, D.; Jin, Z.; Johnson, D. G.; Jucks, K.; Kato, S.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Roithmayr, C. M.; Sandford, S.; Taylor, P. C.; Xiong, X.

    2013-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5-50 micron), the spectrum of solar radiation reflected by the Earth and its atmosphere (320-2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST [National Institute of Standards and Technology] in orbit." CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

  3. Absolute GPS Positioning Using Genetic Algorithms

    NASA Astrophysics Data System (ADS)

    Ramillien, G.

    A new inverse approach for restoring the absolute coordinates of a ground -based station from three or four observed GPS pseudo-ranges is proposed. This stochastic method is based on simulations of natural evolution named genetic algorithms (GA). These iterative procedures provide fairly good and robust estimates of the absolute positions in the Earth's geocentric reference system. For comparison/validation, GA results are compared to the ones obtained using the classical linearized least-square scheme for the determination of the XYZ location proposed by Bancroft (1985) which is strongly limited by the number of available observations (i.e. here, the number of input pseudo-ranges must be four). The r.m.s. accuracy of the non -linear cost function reached by this latter method is typically ~10-4 m2 corresponding to ~300-500-m accuracies for each geocentric coordinate. However, GA can provide more acceptable solutions (r.m.s. errors < 10-5 m2), even when only three instantaneous pseudo-ranges are used, such as a lost of lock during a GPS survey. Tuned GA parameters used in different simulations are N=1000 starting individuals, as well as Pc=60-70% and Pm=30-40% for the crossover probability and mutation rate, respectively. Statistical tests on the ability of GA to recover acceptable coordinates in presence of important levels of noise are made simulating nearly 3000 random samples of erroneous pseudo-ranges. Here, two main sources of measurement errors are considered in the inversion: (1) typical satellite-clock errors and/or 300-metre variance atmospheric delays, and (2) Geometrical Dilution of Precision (GDOP) due to the particular GPS satellite configuration at the time of acquisition. Extracting valuable information and even from low-quality starting range observations, GA offer an interesting alternative for high -precision GPS positioning.

  4. Individual Differences in Absolute and Relative Metacomprehension Accuracy

    ERIC Educational Resources Information Center

    Maki, Ruth H.; Shields, Micheal; Wheeler, Amanda Easton; Zacchilli, Tammy Lowery

    2005-01-01

    The authors investigated absolute and relative metacomprehension accuracy as a function of verbal ability in college students. Students read hard texts, revised texts, or a mixed set of texts. They then predicted their performance, took a multiple-choice test on the texts, and made posttest judgments about their performance. With hard texts,…

  5. Simultaneously improving the sensitivity and absolute accuracy of CPT magnetometer.

    PubMed

    Liang, Shang-Qing; Yang, Guo-Qing; Xu, Yun-Fei; Lin, Qiang; Liu, Zhi-Heng; Chen, Zheng-Xiang

    2014-03-24

    A new method to improve the sensitivity and absolute accuracy simultaneously for coherent population trapping (CPT) magnetometer based on the differential detection method is presented. Two modulated optical beams with orthogonal circular polarizations are applied, in one of which two magnetic resonances are excited simultaneously by modulating a 3.4GHz microwave with Larmor frequency. When a microwave frequency shift is introduced, the difference in the power transmitted through the cell in each beam shows a low noise resonance. The sensitivity of 2pT/Hz @ 10Hz is achieved. Meanwhile, the absolute accuracy of ± 0.5nT within the magnetic field ranging from 20000nT to 100000nT is realized.

  6. Alaska national hydrography dataset positional accuracy assessment study

    USGS Publications Warehouse

    Arundel, Samantha; Yamamoto, Kristina H.; Constance, Eric; Mantey, Kim; Vinyard-Houx, Jeremy

    2013-01-01

    Initial visual assessments Wide range in the quality of fit between features in NHD and these new image sources. No statistical analysis has been performed to actually quantify accuracy Determining absolute accuracy is cost prohibitive (must collect independent, well defined test points) Quantitative analysis of relative positional error is feasible.

  7. Constraint on Absolute Accuracy of Metacomprehension Assessments: The Anchoring and Adjustment Model vs. the Standards Model

    ERIC Educational Resources Information Center

    Kwon, Heekyung

    2011-01-01

    The objective of this study is to provide a systematic account of three typical phenomena surrounding absolute accuracy of metacomprehension assessments: (1) the absolute accuracy of predictions is typically quite low; (2) there exist individual differences in absolute accuracy of predictions as a function of reading skill; and (3) postdictions…

  8. Absolute positioning using DORIS tracking of the SPOT-2 satellite

    NASA Technical Reports Server (NTRS)

    Watkins, M. M.; Ries, J. C.; Davis, G. W.

    1992-01-01

    The ability of the French DORIS system operating on the SPOT-2 satellite to provide absolute site positioning at the 20-30-centimeter level using 80 d of data is demonstrated. The accuracy of the vertical component is comparable to that of the horizontal components, indicating that residual troposphere error is not a limiting factor. The translation parameters indicate that the DORIS network realizes a geocentric frame to about 50 nm in each component. The considerable amount of data provided by the nearly global, all-weather DORIS network allowed this complex parameterization required to reduce the unmodeled forces acting on the low-earth satellite. Site velocities with accuracies better than 10 mm/yr should certainly be possible using the multiyear span of the SPOT series and Topex/Poseidon missions.

  9. Astronomic Position Accuracy Capability Study.

    DTIC Science & Technology

    1979-10-01

    portion of F. E. Warren AFB, Wyoming. The three points were called THEODORE ECC , TRACY, and JIM and consisted of metal tribrachs plastered to cinder...sets were computed as a deviation from the standard. Accuracy figures were determined from these residuals. Homo - geneity of variances was tested using

  10. Positioning, alignment and absolute pointing of the ANTARES neutrino telescope

    NASA Astrophysics Data System (ADS)

    Fehr, F.; Distefano, C.; Antares Collaboration

    2010-01-01

    A precise detector alignment and absolute pointing is crucial for point-source searches. The ANTARES neutrino telescope utilises an array of hydrophones, tiltmeters and compasses for the relative positioning of the optical sensors. The absolute calibration is accomplished by long-baseline low-frequency triangulation of the acoustic reference devices in the deep-sea with a differential GPS system at the sea surface. The absolute pointing can be independently verified by detecting the shadow of the Moon in cosmic rays.

  11. Absolute Position Encoders With Vertical Image Binning

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    2005-01-01

    Improved optoelectronic patternrecognition encoders that measure rotary and linear 1-dimensional positions at conversion rates (numbers of readings per unit time) exceeding 20 kHz have been invented. Heretofore, optoelectronic pattern-recognition absoluteposition encoders have been limited to conversion rates <15 Hz -- too low for emerging industrial applications in which conversion rates ranging from 1 kHz to as much as 100 kHz are required. The high conversion rates of the improved encoders are made possible, in part, by use of vertically compressible or binnable (as described below) scale patterns in combination with modified readout sequences of the image sensors [charge-coupled devices (CCDs)] used to read the scale patterns. The modified readout sequences and the processing of the images thus read out are amenable to implementation by use of modern, high-speed, ultra-compact microprocessors and digital signal processors or field-programmable gate arrays. This combination of improvements makes it possible to greatly increase conversion rates through substantial reductions in all three components of conversion time: exposure time, image-readout time, and image-processing time.

  12. System and method for calibrating a rotary absolute position sensor

    NASA Technical Reports Server (NTRS)

    Davis, Donald R. (Inventor); Permenter, Frank Noble (Inventor); Radford, Nicolaus A (Inventor)

    2012-01-01

    A system includes a rotary device, a rotary absolute position (RAP) sensor generating encoded pairs of voltage signals describing positional data of the rotary device, a host machine, and an algorithm. The algorithm calculates calibration parameters usable to determine an absolute position of the rotary device using the encoded pairs, and is adapted for linearly-mapping an ellipse defined by the encoded pairs to thereby calculate the calibration parameters. A method of calibrating the RAP sensor includes measuring the rotary position as encoded pairs of voltage signals, linearly-mapping an ellipse defined by the encoded pairs to thereby calculate the calibration parameters, and calculating an absolute position of the rotary device using the calibration parameters. The calibration parameters include a positive definite matrix (A) and a center point (q) of the ellipse. The voltage signals may include an encoded sine and cosine of a rotary angle of the rotary device.

  13. 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.

  14. Cavity ring-down spectroscopy of Doppler-broadened absorption line with sub-MHz absolute frequency accuracy.

    PubMed

    Cheng, C-F; Sun, Y R; Pan, H; Lu, Y; Li, X-F; Wang, J; Liu, A-W; Hu, S-M

    2012-04-23

    A continuous-wave cavity ring-down spectrometer has been built for precise determination of absolute frequencies of Doppler-broadened absorption lines. Using a thermo-stabilized Fabry-Pérot interferometer and Rb frequency references at the 780 nm and 795 nm, 0.1 - 0.6 MHz absolute frequency accuracy has been achieved in the 775-800 nm region. A water absorption line at 12579 cm(-1) is studied to test the performance of the spectrometer. The line position at zero-pressure limit is determined with an uncertainty of 0.3 MHz (relative accuracy of 0.8 × 10(-9)).

  15. HST Stellar Standards with 1% Accuracy in Absolute Flux

    NASA Astrophysics Data System (ADS)

    Bohlin, R. C.

    2007-04-01

    Free of any atmospheric contamination, the {Hubble Space Telescope} provides the best available spectrophotometry from the far-UV to the near-IR for stars as faint as V˜16. The HST CALSPEC standard star network is based on three standard candles: the hot, pure hydrogen white dwarf (WD) stars G 191B2B, GD 153, and GD 71, which have Hubeny NLTE flux calculations that require the atomic physics for only one atom. These model flux distributions are normalized to the absolute flux for Vega of 3.46×10-9 erg cm-2 s-1 Å-1 at 5556 Å using precise Landolt V band photometry and the V bandpass function corrected for atmospheric transmission by M. Cohen. The three primary WD standards provide absolute flux calibrations for FOS, STIS and NICMOS spectrophotometry from these instruments on the HST. About 32 stellar spectral energy distributions (SEDs) have been constructed with a primary pedigree from the STIS data, which extends from 1150 Å for the hot stars to a long wavelength limit of 1 μm. NICMOS grism spectrophotometry provides an extension to 1.9 μm in the IR for 17 of the HST standards and longward to 2.5 μm for a few of the brighter stars. Included among these HST standards are Vega, the Sloan standard BD+17 4708, three bright solar analog candidates, three cool stars of type M or later, and five hot WDs. In addition, four K giants and four main sequence A-stars have NICMOS spectrophotometry from 0.8-2.5 μm. The WD fluxes are compared to their modeled SEDs and demonstrate an internal precision of 1-2%, while the A-stars agree with the Cohen IR fluxes to ˜2%. Three solar analog candidate stars differ from the solar spectrum by up to 10% in the region of heavy line blanketing from 3000-4000 Å and show differences in shape of ˜5% in the IR around 1.8 μm.

  16. MSTAR: an absolute metrology sensor with sub-micron accuracy for space-based applications

    NASA Technical Reports Server (NTRS)

    Peters, Robert D.; Lay, Oliver P.; Dubovitsky, Serge; Burger, Johan P.; Jeganathan, Muthu

    2004-01-01

    The MSTAR sensor is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with subnanometer accuracy.

  17. Positional Accuracy Assessment of Googleearth in Riyadh

    NASA Astrophysics Data System (ADS)

    Farah, Ashraf; Algarni, Dafer

    2014-06-01

    Google Earth is a virtual globe, map and geographical information program that is controlled by Google corporation. It maps the Earth by the superimposition of images obtained from satellite imagery, aerial photography and GIS 3D globe. With millions of users all around the globe, GoogleEarth® has become the ultimate source of spatial data and information for private and public decision-support systems besides many types and forms of social interactions. Many users mostly in developing countries are also using it for surveying applications, the matter that raises questions about the positional accuracy of the Google Earth program. This research presents a small-scale assessment study of the positional accuracy of GoogleEarth® Imagery in Riyadh; capital of Kingdom of Saudi Arabia (KSA). The results show that the RMSE of the GoogleEarth imagery is 2.18 m and 1.51 m for the horizontal and height coordinates respectively.

  18. Speed and Accuracy of Absolute Pitch Judgments: Some Latter-Day Results.

    ERIC Educational Resources Information Center

    Carroll, John B.

    Nine subjects, 5 of whom claimed absolute pitch (AP) ability were instructed to rapidly strike notes on the piano to match randomized tape-recorded piano notes. Stimulus set sizes were 64, 16, or 4 consecutive semitones, or 7 diatonic notes of a designated octave. A control task involved motor movements to notes announced in advance. Accuracy,…

  19. Positioning accuracy of the neurotron 1000

    SciTech Connect

    Cox, R.S.; Murphy, M.J.

    1995-12-31

    The Neuotron 1000 is a novel treatment machine under development for frameless stereotaxic radiosurgery that consists of a compact X-band accelerator mounted on a robotic arm. The therapy beam is guided to the lesion by an imaging system, which included two diagnostic x-ray cameras that view the patient during treatment. Patient position and motion are measured by the imaging system and appropriate corrections are communicated in real time to the robotic arm for beam targeting and motion tracking. The three tests reported here measured the pointing accuracy of the therapy beam and the present capability of the imaging guidance system. The positioning and pointing test measured the ability of the robotic arm to direct the beam through a test isocenter from arbitrary arm positions. The test isocenter was marked by a small light-sensitive crystal and the beam axis was simulated by a laser.

  20. Accuracy of the LPM tracking system considering dynamic position changes.

    PubMed

    Ogris, Georg; Leser, Roland; Horsak, Brian; Kornfeind, Philipp; Heller, Mario; Baca, Arnold

    2012-01-01

    This study investigates the accuracy of the tracking system LPM (local position measurement). The goal was to determine detailed error values of the system in the context of sports performance analyses. Six moderately trained male soccer players (amateur level) performed 276 runs on three different courses at six different speeds. Additionally, ten small-sided game plays were carried out. All runs and game plays were recorded with the LPM tracking system and the motion capture system VICON simultaneously. VICON served as the reference system. The absolute error of all LPM position estimations was on average 23.4±20.7 cm. The estimation for average velocities varied between 0.01 km h(-1) and 0.23 km h(-1), the maximum speed estimations differed by up to 2.71 km h(-1). In addition, the results showed that the accuracy of the LPM system is highly dependent on the instantaneous dynamics of the player and decreases in the margins of the observation field. These dependencies were quantified. Considering commonly used applications of position tracking systems in sports (Leser, Ogris, & Baca, 2011), the accuracy of LPM is acceptable for position and velocity estimations. The system provides valuable results for average velocities but seems to be far less reliable when dealing with high dynamic movements and measuring instantaneous velocities.

  1. Accuracy of maxillary positioning in bimaxillary surgery.

    PubMed

    Kretschmer, W B; Zoder, W; Baciut, G; Bacuit, Mihaela; Wangerin, K

    2009-09-01

    The aim of the study was to investigate the accuracy of a modified pin system for the vertical control of maxillary repositioning in bimaxillary osteotomies. The preoperative cephalograms of 239 consecutive patients who were to have bimaxillary osteotomies were superimposed on the postoperative films. Planned and observed vertical and horizontal movements of the upper incisor were analysed statistically. The mean deviations of -0.07 mm (95% confidence intervals (CIs) -0.17 to 0.04 mm) for the vertical movement and 0.12 mm (95% CI -0.06 to 0.30 mm) for the horizontal movement did not differ significantly from zero. Comparison of the two variances between intrusion and extrusion of the maxilla did not differ significantly either (p=0.51). These results suggest that the modified pin system for vertical control combined with interocclusal splints provides accurate vertical positioning of the anterior maxilla in orthognathic surgery.

  2. Using AIRS and IASI Data to Evaluate Absolute Radiometric Accuracy and Stability for Climate Applications

    NASA Technical Reports Server (NTRS)

    Aumann, Hartmut H.; Pagano, Thomas S.

    2008-01-01

    The creation of multi-decadal data sets for climate research requires better than 100 mK absolute calibration accuracy for the full range of spectral temperatures encountered under global conditions. Validation that this accuracy is achieved by the operational hyperspectral sounders from polar orbit is facilitated by comparing data from two instruments. Extreme radiometric calibration stability is critical to allow a long time series of noisy, but presumably long-term accurate truth measurements to be used for the validation of absolute accuracy at the 100 mK level. We use the RTGSST in the tropical oceans as ground truth. The difference between the AIRS derived sst2616 and the RTGSST based on six years of data shows a systematic cold bias of about 250 mK, but better than 4 mK/year stability. The double difference between AIRS and the RTGSST and IASI and the RTGSST with less than one year of data already allows statements at the 100 mK absolute level. It shows a 60 mK difference between the AIRS and the IASI calibration at 2616 cm-(sup 1) and 300 K, with a statistically insignificant 20 mK shift in six months.

  3. Time and position accuracy using codeless GPS

    NASA Technical Reports Server (NTRS)

    Dunn, C. E.; Jefferson, D. C.; Lichten, S. M.; Thomas, J. B.; Vigue, Y.; Young, L. E.

    1994-01-01

    The Global Positioning System has allowed scientists and engineers to make measurements having accuracy far beyond the original 15 meter goal of the system. Using global networks of P-Code capable receivers and extensive post-processing, geodesists have achieved baseline precision of a few parts per billion, and clock offsets have been measured at the nanosecond level over intercontinental distances. A cloud hangs over this picture, however. The Department of Defense plans to encrypt the P-Code (called Anti-Spoofing, or AS) in the fall of 1993. After this event, geodetic and time measurements will have to be made using codeless GPS receivers. However, there appears to be a silver lining to the cloud. In response to the anticipated encryption of the P-Code, the geodetic and GPS receiver community has developed some remarkably effective means of coping with AS without classified information. We will discuss various codeless techniques currently available and the data noise resulting from each. We will review some geodetic results obtained using only codeless data, and discuss the implications for time measurements. Finally, we will present the status of GPS research at JPL in relation to codeless clock measurements.

  4. High Accuracy, Absolute, Cryogenic Refractive Index Measurements of Infrared Lens Materials for JWST NIRCam using CHARMS

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas; Frey, Bradley

    2005-01-01

    The current refractive optical design of the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam) uses three infrared materials in its lenses: LiF, BaF2, and ZnSe. In order to provide the instrument s optical designers with accurate, heretofore unavailable data for absolute refractive index based on actual cryogenic measurements, two prismatic samples of each material were measured using the cryogenic, high accuracy, refraction measuring system (CHARMS) at NASA GSFC, densely covering the temperature range from 15 to 320 K and wavelength range from 0.4 to 5.6 microns. Measurement methods are discussed and graphical and tabulated data for absolute refractive index, dispersion, and thermo-optic coefficient for these three materials are presented along with estimates of uncertainty. Coefficients for second order polynomial fits of measured index to temperature are provided for many wavelengths to allow accurate interpolation of index to other wavelengths and temperatures.

  5. A microwave position sensor with submillimeter accuracy

    NASA Astrophysics Data System (ADS)

    Stelzer, A.; Diskus, C. G.; Lubke, K.; Thim, H. W.

    1999-12-01

    Design and characteristics of a prototype distance sensor are presented in this paper. The radar front-end operates at 35 GHz and applies six-port technology and direct frequency measurement. The sensor makes use of both frequency-modulated continuous wave and interferometer principles and is capable of measuring distance with a very high accuracy of ±0.1 mm.

  6. Absolute Positioning by Collecting Global Positioning System (GPS) Data Along Short Baselines

    DTIC Science & Technology

    1993-09-01

    BASELINES BY BRUCE R . HERMANN AND ALAN G. EVANS STRATEGIC AND SPACE SYSTEMS DEPARTMENT SEPTEMBER 1993 DTI I . ELECT’ ]0CT 22 1993 Approved for public release...NSWCDD/TR-93/309 ABSOLUTE POSITIONING BY COLLECTING GLOBAL POSITIONING SYSTEM (GPS) DATA ALONG SHORT BASELINES BY BRUCE R . HERMANN AND ALAN G. EVANS...Branch; Mr. T. Sims, Head, Space Sciences Branch; and Mr. J. Sloop, Head, Space and Surface Systems Division. ,- o" Fo, .. ,, ,Approved by: B~y. ’ " - R

  7. Superharp — A wire scanner with absolute position readout for beam energy measurement at CEBAF

    NASA Astrophysics Data System (ADS)

    Yan, C.; Adderley, P.; Barker, D.; Beaufait, J.; Capek, K.; Carlini, R.; Dahlberg, J.; Feldl, E.; Jordan, K.; Kross, B.; Oren, W.; Wojcik, R.; VanDyke, J.

    1995-02-01

    The CEBAF superharp is an upgraded beam wire scanner which provides absolute beam position readout using a shaft encoder. Superharps allow for high precision measurements of the beam's profile and position ( Δx ˜ 10 μm). The Hall C endstation at CEBAF will use three pairs of superharps to perform beam energy measurements with 10 -3 accuracy. The three pairs are installed at the beginning, the mid-point and the end of the Hall C arc beamline. Using superharps in conjunction with a dual sensor system: the direct current pick-up and the bremsstrahlung detectors, beam profile measurements can be obtained over a wide beam current range of 1 ˜ 200 μA.

  8. High-accuracy absolute distance measurement with a mode-resolved optical frequency comb

    NASA Astrophysics Data System (ADS)

    Voigt, Dirk; van den Berg, Steven A.; Lešundák, Adam; van Eldik, Sjoerd; Bhattacharya, Nandini

    2016-04-01

    Optical interferometry enables highly accurate non-contact displacement measurement. The optical phase ambiguity needs to be resolved for absolute distance ranging. In controlled laboratory conditions and for short distances it is possible to track a non-interrupted displacement from a reference position to a remote target. With large distances covered in field applications this may not be feasible, e.g. in structure monitoring, large scale industrial manufacturing or aerospace navigation and attitude control. We use an optical frequency comb source to explore absolute distance measurement by means of a combined spectral and multi-wavelength homodyne interferometry. This relaxes the absolute distance ambiguity to a few tens of centimeters, covered by simpler electronic distance meters, while maintaining highly accurate optical phase measuring capability. A virtually imaged phased array spectrometer records a spatially dispersed interferogram in a single exposure and allows for resolving the modes of our near infrared comb source with 1 GHz mode separation. This enables measurements with direct traceability of the atomic clock referenced comb source. We observed agreement within 500 nm in comparison with a commercial displacement interferometer for target distances up to 50 m. Furthermore, we report on current work toward applicability in less controlled conditions. A filter cavity decimates the comb source to an increased mode separation larger than 20 GHz. A simple grating spectrometer then allows to record mode-resolved interferograms.

  9. Handheld Reflective Foil Emissometer with 0.007 Absolute Accuracy at 0.05

    NASA Astrophysics Data System (ADS)

    van der Ham, E. W. M.; Ballico, M. J.

    2014-07-01

    The development and performance of a handheld emissometer for the measurement of the emissivity of highly reflective metallic foils used for the insulation of domestic and commercial buildings are described. Reflective roofing insulation based on a thin coating of metal on a more robust substrate is very widely used in hotter climates to reduce the radiant heat transfer between the ceiling and roof in commercial and residential buildings. The required normal emissivity of these foils is generally below 0.05, so stray reflected ambient infrared radiation (IR) makes traditional reflectance-based measurements of emissivity very difficult to achieve with the required accuracy. Many manufacturers apply additional coatings onto the metallic foil to reduce visible glare during installation on a roof, and to provide protection to the thin reflective layer; however, this layer can also substantially increase the IR emissivity. The system as developed at the National Measurement Institute, Australia (NMIA) is based on the principle of measurement of the modulation in thermal infrared radiation, as the sample is thermally modulated by hot and cold air streams. A commercial infrared to band radiation thermometer with a highly specialized stray and reflected radiation shroud attachment is used as the detector system, allowing for convenient handheld field measurements. The performance and accuracy of the system have been compared with NMIA's reference emissometer systems for a number of typical material samples, demonstrating its capability to measure the absolute thermal emissivity of these very highly reflective foils with an uncertainty of better than.

  10. Single-track absolute position encoding method based on spatial frequency of stripes

    NASA Astrophysics Data System (ADS)

    Xiang, Xiansong; Lu, Yancong; Wei, Chunlong; Zhou, Changhe

    2014-11-01

    A new method of single-track absolute position encoding based on spatial frequency of stripes is proposed. Instead of using pseudorandom-sequence arranged stripes as in conventional situations, this kind of encoding method stores the location information in the frequency space of the stripes, which means the spatial frequency of stripes varies with position and indicates position. This encoding method has a strong fault-tolerant capability with single-stripe detecting errors. The method can be applied to absolute linear encoders, absolute photoelectric angle encoders or two-dimensional absolute linear encoders. The measuring apparatus includes a CCD image sensor and a microscope system, and the method of decoding this frequency code is based on FFT algorithm. This method should be highly interesting for practical applications as an absolute position encoding method.

  11. Observational constraints on atmospheric radiaitve feedbacks: absolute accuracy and next-generation observing systems

    NASA Astrophysics Data System (ADS)

    Dykema, J. A.; Hanssen, L. M.; Mekhontsev, S.; Anderson, J.

    2012-12-01

    The central role of atmospheric radiative feedbacks to understanding and projecting climate change calls for a robust observational system. Recent studies have shown the value of space-based measurements for putting quantitative constraints on a range of radiative feedback processes through a fingerprinting method applied to long-term observational records. More recent work has suggested the value of demonstrably accurate measurements to disentangle model error from observational uncertainties within reanalysis systems, potentially yielding improved representations of feedback processes within just a few years. Both of these methods rely on space-based measurements that can be objectively tested for accuracy on-orbit. A new class of mission has been proposed that incorporates the same type of empirical tests for accuracy as used in the laboratory into a space-based sensor. One example of such a mission is the Climate Absolute Radiance and Refractivity Observatory (CLARREO), a new mission suggested by the 2006 National Research Council Decadal Survey. CLARREO includes three sensor types: thermal infrared, microwave, and reflected shortwave. This paper presents a laboratory demonstration of prototype systems for testing the on-orbit accuracy of a thermal infrared sensor for CLARREO. These systems utilize infrared lasers to provide monochromatic light sources to quantitatively determine the optical properties of materials. These infrared optical properties are major determinants of the on-orbit radiometric performance of a thermal infrared sensor. For this reason, reliable quantitative information (including uncertainty) that tracks any changes in relevant infrared materials over the mission lifetime is essential to objective assessment of instrument accuracy. The practicality of mid-infrared lasers for these applications is due to the availability and continued evolution of compact, high-efficiency Quantum Cascade Lasers (QCLs). These lasers can provide over 100 m

  12. Absolute Position of Targets Measured Through a Chamber Window Using Lidar Metrology Systems

    NASA Technical Reports Server (NTRS)

    Kubalak, David; Hadjimichael, Theodore; Ohl, Raymond; Slotwinski, Anthony; Telfer, Randal; Hayden, Joseph

    2012-01-01

    Lidar is a useful tool for taking metrology measurements without the need for physical contact with the parts under test. Lidar instruments are aimed at a target using azimuth and elevation stages, then focus a beam of coherent, frequency modulated laser energy onto the target, such as the surface of a mechanical structure. Energy from the reflected beam is mixed with an optical reference signal that travels in a fiber path internal to the instrument, and the range to the target is calculated based on the difference in the frequency of the returned and reference signals. In cases when the parts are in extreme environments, additional steps need to be taken to separate the operator and lidar from that environment. A model has been developed that accurately reduces the lidar data to an absolute position and accounts for the three media in the testbed air, fused silica, and vacuum but the approach can be adapted for any environment or material. The accuracy of laser metrology measurements depends upon knowing the parameters of the media through which the measurement beam travels. Under normal conditions, this means knowledge of the temperature, pressure, and humidity of the air in the measurement volume. In the past, chamber windows have been used to separate the measuring device from the extreme environment within the chamber and still permit optical measurement, but, so far, only relative changes have been diagnosed. The ability to make accurate measurements through a window presents a challenge as there are a number of factors to consider. In the case of the lidar, the window will increase the time-of-flight of the laser beam causing a ranging error, and refract the direction of the beam causing angular positioning errors. In addition, differences in pressure, temperature, and humidity on each side of the window will cause slight atmospheric index changes and induce deformation and a refractive index gradient within the window. Also, since the window is a

  13. Absolute distance measurement with micrometer accuracy using a Michelson interferometer and the iterative synthetic wavelength principle.

    PubMed

    Alzahrani, Khaled; Burton, David; Lilley, Francis; Gdeisat, Munther; Bezombes, Frederic; Qudeisat, Mohammad

    2012-02-27

    We present a novel system that can measure absolute distances of up to 300 mm with an uncertainty of the order of one micrometer, within a timeframe of 40 seconds. The proposed system uses a Michelson interferometer, a tunable laser, a wavelength meter and a computer for analysis. The principle of synthetic wave creation is used in a novel way in that the system employs an initial low precision estimate of the distance, obtained using a triangulation, or time-of-flight, laser system, or similar, and then iterates through a sequence of progressively smaller synthetic wavelengths until it reaches micrometer uncertainties in the determination of the distance. A further novel feature of the system is its use of Fourier transform phase analysis techniques to achieve sub-wavelength accuracy. This method has the major advantages of being relatively simple to realize, offering demonstrated high relative precisions better than 5 × 10(-5). Finally, the fact that this device does not require a continuous line-of-sight to the target as is the case with other configurations offers significant advantages.

  14. High accuracy autonomous navigation using the global positioning system (GPS)

    NASA Technical Reports Server (NTRS)

    Truong, Son H.; Hart, Roger C.; Shoan, Wendy C.; Wood, Terri; Long, Anne C.; Oza, Dipak H.; Lee, Taesul

    1997-01-01

    The application of global positioning system (GPS) technology to the improvement of the accuracy and economy of spacecraft navigation, is reported. High-accuracy autonomous navigation algorithms are currently being qualified in conjunction with the GPS attitude determination flyer (GADFLY) experiment for the small satellite technology initiative Lewis spacecraft. Preflight performance assessments indicated that these algorithms are able to provide a real time total position accuracy of better than 10 m and a velocity accuracy of better than 0.01 m/s, with selective availability at typical levels. It is expected that the position accuracy will be increased to 2 m if corrections are provided by the GPS wide area augmentation system.

  15. System providing limit switch function with simultaneous absolute position output

    NASA Technical Reports Server (NTRS)

    Alhorn, Dean C. (Inventor); Howard, David E. (Inventor); Smith, Dennis A. (Inventor)

    2006-01-01

    A limit and position sensing system includes a sensor assembly and an emitter. The sensor assembly includes first and second electrical conductors arranged in opposing parallel planes. The first electrical conductor is coiled outwardly from either end thereof in a clockwise fashion to form a first coil region and a second coil region. The second electrical conductor forms a single coil with portions of the single coil's rings lying between the first end and second end of the first electrical conductor being parallel to an axis of the first electrical conductor's plane. Ferromagnetic material is aligned with the first and second electrical conductors and spans beyond (a) the first and second ends of the first electrical conductor, and (b) the portions of the rings of the second electrical conductor's single coil that lie between the first end and second end of the first electrical conductor. The emitter is spaced apart from the sensor assembly and transmits a periodic electromagnetic wave towards the sensor assembly.

  16. A Comparative Study of Precise Point Positioning (PPP) Accuracy Using Online Services

    NASA Astrophysics Data System (ADS)

    Malinowski, Marcin; Kwiecień, Janusz

    2016-12-01

    Precise Point Positioning (PPP) is a technique used to determine the position of receiver antenna without communication with the reference station. It may be an alternative solution to differential measurements, where maintaining a connection with a single RTK station or a regional network of reference stations RTN is necessary. This situation is especially common in areas with poorly developed infrastructure of ground stations. A lot of research conducted so far on the use of the PPP technique has been concerned about the development of entire day observation sessions. However, this paper presents the results of a comparative analysis of accuracy of absolute determination of position from observations which last between 1 to 7 hours with the use of four permanent services which execute calculations with PPP technique such as: Automatic Precise Positioning Service (APPS), Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP), GNSS Analysis and Positioning Software (GAPS) and magicPPP - Precise Point Positioning Solution (magicGNSS). On the basis of acquired results of measurements, it can be concluded that at least two-hour long measurements allow acquiring an absolute position with an accuracy of 2-4 cm. An evaluation of the impact on the accuracy of simultaneous positioning of three points test network on the change of the horizontal distance and the relative height difference between measured triangle vertices was also conducted. Distances and relative height differences between points of the triangular test network measured with a laser station Leica TDRA6000 were adopted as references. The analyses of results show that at least two hours long measurement sessions can be used to determine the horizontal distance or the difference in height with an accuracy of 1-2 cm. Rapid products employed in calculations conducted with PPP technique reached the accuracy of determining coordinates on a close level as in elaborations which employ Final products.

  17. The most appropriate position and number for absolute anchorages for orthodontic tooth movements.

    PubMed

    Yu, Jian-Hong; Takakuda, Kazuo; Miyairi, Hiroo; Soma, Kunimichi

    2003-04-01

    Absolute anchorages proved to be very effective for orthodontic tooth movements. We used a 3D digitizer to record each tooth on pre-treatment diagnostic and post-treatment predictive setup models and then 3D coordinate system conversion was performed to make the coordinate values comparable. An arithmetic calculation of vector and moment based on the orthodontic forces and the tooth displacement under preliminary premises undertaken to decide the most favorable position and number for absolute anchorages. Position--For two-dimensional and three-dimensional calculations, the most appropriate positions for absolute anchorages should theoretically be on the line of resultant force (2D) and the plane (3D) where the total moment effect tends to be zero. Number--As for the number of the absolute anchorages needed, it depends on the number of target teeth. Different combinations of target teeth provide different sets of results.

  18. Absolute thickness metrology with submicrometer accuracy using a low-coherence distance measuring interferometer.

    PubMed

    Zhao, Yang; Schmidt, Greg; Moore, Duncan T; Ellis, Jonathan D

    2015-09-01

    Absolute physical thickness across the sample aperture is critical in determining the index of a refraction profile from the optical path length profile for gradient index (GRIN) materials, which have a designed inhomogeneous refractive index. Motivated by this application, instrumentation was established to measure the absolute thickness of samples with nominally plane-parallel surfaces up to 50 mm thick. The current system is capable of measuring absolute thickness with 120 nm (1σ) repeatability and submicrometer expanded measurement uncertainty. Beside GRIN materials, this method is also capable of measuring other inhomogeneous and opaque materials.

  19. Absolute and relative height-pixel accuracy of SRTM-GL1 over the South American Andean Plateau

    NASA Astrophysics Data System (ADS)

    Satge, Frédéric; Denezine, Matheus; Pillco, Ramiro; Timouk, Franck; Pinel, Sébastien; Molina, Jorge; Garnier, Jérémie; Seyler, Frédérique; Bonnet, Marie-Paule

    2016-11-01

    Previously available only over the Continental United States (CONUS), the 1 arc-second mesh size (spatial resolution) SRTM-GL1 (Shuttle Radar Topographic Mission - Global 1) product has been freely available worldwide since November 2014. With a relatively small mesh size, this digital elevation model (DEM) provides valuable topographic information over remote regions. SRTM-GL1 is assessed for the first time over the South American Andean Plateau in terms of both the absolute and relative vertical point-to-point accuracies at the regional scale and for different slope classes. For comparison, SRTM-v4 and GDEM-v2 Global DEM version 2 (GDEM-v2) generated by ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) are also considered. A total of approximately 160,000 ICESat/GLAS (Ice, Cloud and Land Elevation Satellite/Geoscience Laser Altimeter System) data are used as ground reference measurements. Relative error is often neglected in DEM assessments due to the lack of reference data. A new methodology is proposed to assess the relative accuracies of SRTM-GL1, SRTM-v4 and GDEM-v2 based on a comparison with ICESat/GLAS measurements. Slope values derived from DEMs and ICESat/GLAS measurements from approximately 265,000 ICESat/GLAS point pairs are compared using quantitative and categorical statistical analysis introducing a new index: the False Slope Ratio (FSR). Additionally, a reference hydrological network is derived from Google Earth and compared with river networks derived from the DEMs to assess each DEM's potential for hydrological applications over the region. In terms of the absolute vertical accuracy on a global scale, GDEM-v2 is the most accurate DEM, while SRTM-GL1 is more accurate than SRTM-v4. However, a simple bias correction makes SRTM-GL1 the most accurate DEM over the region in terms of vertical accuracy. The relative accuracy results generally did not corroborate the absolute vertical accuracy. GDEM-v2 presents the lowest statistical

  20. Influence of Ephemeris Error on GPS Single Point Positioning Accuracy

    NASA Astrophysics Data System (ADS)

    Lihua, Ma; Wang, Meng

    2013-09-01

    The Global Positioning System (GPS) user makes use of the navigation message transmitted from GPS satellites to achieve its location. Because the receiver uses the satellite's location in position calculations, an ephemeris error, a difference between the expected and actual orbital position of a GPS satellite, reduces user accuracy. The influence extent is decided by the precision of broadcast ephemeris from the control station upload. Simulation analysis with the Yuma almanac show that maximum positioning error exists in the case where the ephemeris error is along the line-of-sight (LOS) direction. Meanwhile, the error is dependent on the relationship between the observer and spatial constellation at some time period.

  1. Superharp: A wire scanner with absolute position readout for beam energy measurement at CEBAF

    SciTech Connect

    Yan, C.

    1994-09-07

    Superharp is an upgrade CEBAF wire scanner with absolute position readout from shaft encoder. As high precision absolute beam position probe ({Delta}x {approximately} 10{mu}m), three pairs of superharps are installed at the entrance, the mid-point, and the exit of Hall C arc beamline in beam switch yard, which will be tuned in dispersive mode as energy spectrometer performing 10{sup {minus}3} beam energy measurement. With dual sensor system: the direct current pickup and the bremsstrahlung detection electronics, beam profile can be obtained by superharp at wide beam current range from 1 {mu}A to 100 {mu}A.

  2. Accuracy in fixing ship's positions by camera survey of bearings

    NASA Astrophysics Data System (ADS)

    Naus, Krzysztof; Wąż, Mariusz

    2011-01-01

    The paper presents the results of research on the possibilities of fixing ship position coordinates based on results of surveying bearings on navigational marks with the use of the CCD camera. Accuracy of the determination of ship position coordinates, expressed in terms of the mean error, was assumed to be the basic criterion of this estimation. The first part of the paper describes the method of the determination of the resolution and the mean error of the angle measurement, taken with a camera, and also the method of the determination of the mean error of position coordinates when two or more bearings were measured. There have been defined three software applications assigned for the development of navigational sea charts with accuracy areas mapped on. The second part contains the results of studying accuracy in fixing ship position coordinates, carried out in the Gulf of Gdansk, with the use of bearings taken obtained with the Rolleiflex and Sony cameras. The results are presented in a form of diagrams of the mean error of angle measurement, also in the form of navigational charts with accuracy fields mapped on. In the final part, basing on results obtained, the applicability of CCD cameras in automation of coastal navigation performance process is discussed.

  3. Low Cost, High Accuracy Positioning In Urban Environments

    NASA Astrophysics Data System (ADS)

    Hide, Chris; Moore, Terry; Hill, Chris; Park, David

    It is well known that GPS measurements are regularly obstructed in urban environments. Positioning accuracy in such environments is significantly degraded and in many areas, it is not possible to obtain a GPS position fix at all. There are currently two methods that can be used to improve availability in the urban environment. Firstly, GPS receivers can be augmented with dead reckoning sensors such as an INS. Alternatively, High Sensitivity GPS (HSGPS) receivers can be used which are able to acquire and track very weak signals. This paper assesses the performance obtained from a GPS and low cost INS integrated system and a HSGPS receiver in an urban environment in Nottingham, UK. The navigation systems are compared to a high accuracy integrated GPS/INS system which is used to provide a reference trajectory. It is demonstrated that the differential GPS and low cost INS system can provide horizontal positioning accuracy of better than 2·5 m RMS in real-time, and better than 1 m RMS in post-processing, whereas the non-differential HSGPS receiver provides a real-time performance of 5 m RMS. These results were obtained in an environment where, with conventional GPS receivers, a position solution is only available 48·4% of the time. Operational considerations such as initial alignment of the GPS and low cost INS are also discussed when comparing the two systems for urban positioning applications.

  4. Reticle flexure influence on pattern positioning accuracy for reticle writing

    NASA Astrophysics Data System (ADS)

    Hirano, Ryoichi; Matsuki, Kazuto; Yoshitake, Shusuke; Takahashi, Yoshihiko; Tamamushi, Shuichi; Ogawa, Yoji; Tojo, Toru

    1995-07-01

    This paper presents a method for estimating the influence of reticle flexure on pattern positioning accuracy, and evaluates the method by measuring patterned reticles. Reticle flexure causes the pattern shift which occurs by stretching or compression of the reticle surface. A height-mapping function of an electron beam (EB) writing system and a measuring machine are used to calculate the pattern shift due to reticle flexure. The bent shape of a reticle on the EB-writing system differs from that on the measuring machine, so that the patten shifts on the two machines are different. The pattern shifts caused by the bent shape difference were excluded from the measurement result of pattern positioning errors. The values of pattern positioning accuracy evaluation parameters, x, y-scaling and orthogonality, are calculated among several reticles (5 inches, 0.09 inches thick). The deviations of these three values are reduced to less than 50% of their uncompensated values.

  5. Absolute Binding Free Energy Calculations: On the Accuracy of Computational Scoring of Protein-ligand Interactions

    PubMed Central

    Singh, Nidhi; Warshel, Arieh

    2010-01-01

    Calculating the absolute binding free energies is a challenging task. Reliable estimates of binding free energies should provide a guide for rational drug design. It should also provide us with deeper understanding of the correlation between protein structure and its function. Further applications may include identifying novel molecular scaffolds and optimizing lead compounds in computer-aided drug design. Available options to evaluate the absolute binding free energies range from the rigorous but expensive free energy perturbation to the microscopic Linear Response Approximation (LRA/β version) and its variants including the Linear Interaction Energy (LIE) to the more approximated and considerably faster scaled Protein Dipoles Langevin Dipoles (PDLD/S-LRA version), as well as the less rigorous Molecular Mechanics Poisson–Boltzmann/Surface Area (MM/PBSA) and Generalized Born/Surface Area (MM/GBSA) to the less accurate scoring functions. There is a need for an assessment of the performance of different approaches in terms of computer time and reliability. We present a comparative study of the LRA/β, the LIE, the PDLD/S-LRA/β and the more widely used MM/PBSA and assess their abilities to estimate the absolute binding energies. The LRA and LIE methods perform reasonably well but require specialized parameterization for the non-electrostatic term. On the average, the PDLD/S-LRA/β performs effectively. Our assessment of the MM/PBSA is less optimistic. This approach appears to provide erroneous estimates of the absolute binding energies due to its incorrect entropies and the problematic treatment of electrostatic energies. Overall, the PDLD/S-LRA/β appears to offer an appealing option for the final stages of massive screening approaches. PMID:20186976

  6. Absolute instability from linear conversion of counter-propagating positive and negative energy waves

    SciTech Connect

    Kaufman, A.N.; Brizard, A.J.; Morehead, J.J.; Tracy, E.R.

    1997-12-31

    The resonant interaction of a negative-energy wave with a positive-energy wave gives rise to a linear instability. Whereas a single crossing of rays in a nonuniform medium leads to a convectively saturated instability, we show that a double crossing can yield an absolute instability.

  7. 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.

  8. Accuracy, Precision, Sensitivity, and Specificity of Noninvasive ICP Absolute Value Measurements.

    PubMed

    Krakauskaite, Solventa; Petkus, Vytautas; Bartusis, Laimonas; Zakelis, Rolandas; Chomskis, Romanas; Preiksaitis, Aidanas; Ragauskas, Arminas; Matijosaitis, Vaidas; Petrikonis, Kestutis; Rastenyte, Daiva

    2016-01-01

    An innovative absolute intracranial pressure (ICP) value measurement method has been validated by multicenter comparative clinical studies. The method is based on two-depth transcranial Doppler (TCD) technology and uses intracranial and extracranial segments of the ophthalmic artery as pressure sensors. The ophthalmic artery is used as a natural pair of "scales" that compares ICP with controlled pressure Pe, which is externally applied to the orbit. To balance the scales, ICP = Pe a special two-depth TCD device was used as a pressure balance indicator. The proposed method is the only noninvasive ICP measurement method that does not need patient-specific calibration.

  9. Absolute continuity for operator valued completely positive maps on C∗-algebras

    NASA Astrophysics Data System (ADS)

    Gheondea, Aurelian; Kavruk, Ali Şamil

    2009-02-01

    Motivated by applicability to quantum operations, quantum information, and quantum probability, we investigate the notion of absolute continuity for operator valued completely positive maps on C∗-algebras, previously introduced by Parthasarathy [in Athens Conference on Applied Probability and Time Series Analysis I (Springer-Verlag, Berlin, 1996), pp. 34-54]. We obtain an intrinsic definition of absolute continuity, we show that the Lebesgue decomposition defined by Parthasarathy is the maximal one among all other Lebesgue-type decompositions and that this maximal Lebesgue decomposition does not depend on the jointly dominating completely positive map, we obtain more flexible formulas for calculating the maximal Lebesgue decomposition, and we point out the nonuniqueness of the Lebesgue decomposition as well as a sufficient condition for uniqueness. In addition, we consider Radon-Nikodym derivatives for absolutely continuous completely positive maps that, in general, are unbounded positive self-adjoint operators affiliated to a certain von Neumann algebra, and we obtain a spectral approximation by bounded Radon-Nikodym derivatives. An application to the existence of the infimum of two completely positive maps is indicated, and formulas in terms of Choi's matrices for the Lebesgue decomposition of completely positive maps in matrix algebras are obtained.

  10. Positioning Accuracy in Otosurgery Measured with Optical Tracking

    PubMed Central

    Óvári, Attila; Neményi, Dóra; Just, Tino; Schuldt, Tobias; Buhr, Anne; Mlynski, Robert; Csókay, András; Pau, Hans-Wilhelm; Valálik, István

    2016-01-01

    Objectives To assess positioning accuracy in otosurgery and to test the impact of the two-handed instrument holding technique and the instrument support technique on surgical precision. To test an otologic training model with optical tracking. Study Design In total, 14 ENT surgeons in the same department with different levels of surgical experience performed static and dynamic tasks with otologic microinstruments under simulated otosurgical conditions. Methods Tip motion of the microinstrument was registered in three dimensions by optical tracking during 10 different tasks simulating surgical steps such as prosthesis crimping and dissection of the middle ear using formalin-fixed temporal bone. Instrument marker trajectories were compared within groups of experienced and less experienced surgeons performing uncompensated or compensated exercises. Results Experienced surgeons have significantly better positioning accuracy than novice ear surgeons in terms of mean displacement values of marker trajectories. The instrument support and the two-handed instrument holding techniques significantly reduce surgeons’ tremor. The laboratory set-up presented in this study provides precise feedback for otosurgeons about their surgical skills and proved to be a useful device for otosurgical training. Conclusions Simple tremor compensation techniques may offer trainees the potential to improve their positioning accuracy to the level of more experienced surgeons. Training in an experimental otologic environment with optical tracking may aid acquisition of technical skills in middle ear surgery and potentially shorten the learning curve. Thus, simulated exercises of surgical steps should be integrated into the training of otosurgeons. PMID:27027500

  11. Absolute positioning by multi-wavelength interferometry referenced to the frequency comb of a femtosecond laser.

    PubMed

    Wang, Guochao; Jang, Yoon-Soo; Hyun, Sangwon; Chun, Byung Jae; Kang, Hyun Jay; Yan, Shuhua; Kim, Seung-Woo; Kim, Young-Jin

    2015-04-06

    A multi-wavelength interferometer utilizing the frequency comb of a femtosecond laser as the wavelength ruler is tested for its capability of ultra-precision positioning for machine axis control. The interferometer uses four different wavelengths phase-locked to the frequency comb and then determines the absolute position through a multi-channel scheme of detecting interference phases in parallel so as to enable fast, precise and stable measurements continuously over a few meters of axis-travel. Test results show that the proposed interferometer proves itself as a potential candidate of absolute-type position transducer needed for next-generation ultra-precision machine axis control, demonstrating linear errors of less than 61.9 nm in peak-to-valley over a 1-meter travel with an update rate of 100 Hz when compared to an incremental-type He-Ne laser interferometer.

  12. Accuracy of WAAS-enabled GPS for the determination of position and speed over ground.

    PubMed

    Witte, T H; Wilson, A M

    2005-08-01

    The Global Positioning System (GPS) offers many advantages over conventional methods for the determination of subject speed during biomechanical studies. Recent advances in GPS technology, in particular the implementation of the Wide-Angle Augmentation System and European Geostationary Navigation Overlay Service (WAAS/EGNOS), mean that small, highly portable units are available offering the potential of superior accuracy in the determination of both position and speed. This study set out to examine the accuracy of a WAAS-enabled GPS unit for the determination of position and speed. Comparison with the new and published data showed significant enhancements in both position and speed accuracy over a non-WAAS system. Position data collected during straight line cycling showed significantly lower sample-to-sample variation (mean absolute deviation from straight line 0.11 vs. 0.78 m) and greater repeatability from trial to trial (mean absolute deviation from actual path 0.37 vs. 4.8 m) for the WAAS-enabled unit compared to the non-WAAS unit. The speed determined by the WAAS-enabled GPS receiver during cycling in a straight line was within 0.2 ms(-1) of the actual speed measured for 57% of the values with 82% lying within 0.4 ms(-1), however, the data tended towards underestimation of speed during circle cycling, with 65% of values within 0.2 ms(-1) and 87% within 0.4 ms(-1) of the actual value. Local dGPS and dual frequency techniques are more accurate still, however, traditional differential GPS (dGPS), employing FM radio transmission of correction data to a separate receiver, now offers no advantage over WAAS and appears redundant.

  13. Approximating relational observables by absolute quantities: a quantum accuracy-size trade-off

    NASA Astrophysics Data System (ADS)

    Miyadera, Takayuki; Loveridge, Leon; Busch, Paul

    2016-05-01

    The notion that any physical quantity is defined and measured relative to a reference frame is traditionally not explicitly reflected in the theoretical description of physical experiments where, instead, the relevant observables are typically represented as ‘absolute’ quantities. However, the emergence of the resource theory of quantum reference frames as a new branch of quantum information science in recent years has highlighted the need to identify the physical conditions under which a quantum system can serve as a good reference. Here we investigate the conditions under which, in quantum theory, an account in terms of absolute quantities can provide a good approximation of relative quantities. We find that this requires the reference system to be large in a suitable sense.

  14. Horizontal Positional Accuracy of Google Earth's High-Resolution Imagery Archive.

    PubMed

    Potere, David

    2008-12-08

    Google Earth now hosts high-resolution imagery that spans twenty percent of the Earth's landmass and more than a third of the human population. This contemporary highresolution archive represents a significant, rapidly expanding, cost-free and largely unexploited resource for scientific inquiry. To increase the scientific utility of this archive, we address horizontal positional accuracy (georegistration) by comparing Google Earth with Landsat GeoCover scenes over a global sample of 436 control points located in 109 cities worldwide. Landsat GeoCover is an orthorectified product with known absolute positional accuracy of less than 50 meters root-mean-squared error (RMSE). Relative to Landsat GeoCover, the 436 Google Earth control points have a positional accuracy of 39.7 meters RMSE (error magnitudes range from 0.4 to 171.6 meters). The control points derived from satellite imagery have an accuracy of 22.8 meters RMSE, which is significantly more accurate than the 48 control-points based on aerial photography (41.3 meters RMSE; t-test p-value < 0.01). The accuracy of control points in more-developed countries is 24.1 meters RMSE, which is significantly more accurate than the control points in developing countries (44.4 meters RMSE; t-test p-value < 0.01). These findings indicate that Google Earth highresolution imagery has a horizontal positional accuracy that is sufficient for assessing moderate-resolution remote sensing products across most of the world's peri-urban areas.

  15. Accuracy of distal radius positioning using an anatomical plate.

    PubMed

    Vroemen, Joy C; Dobbe, Johannes G G; Sierevelt, Inger N; Strackee, Simon D; Streekstra, Geert J

    2013-04-01

    Over the past decade, several anatomical plates have been introduced to improve the result of open reduction and internal fixation of the distal radius. Using 3-dimensional imaging techniques, the authors studied the accuracy and reproducibility of distal radius positioning using anatomical plates.Distal radius fractures and the correction of these fractures were simulated with plastic bone models of radii. The authors simulated a defect by removing an arbitrary wedge shape from the artificial radii. Two surgeons corrected these fractures by placing 2 anatomical plate types according to the plate manufacturers' instructions. The residual positioning errors of the distal segment in relation to the unaffected radii were determined using 3-dimensional imaging and were compared with naturally occurring bilateral radius differences in healthy individuals. In many cases, positioning does not agree with differences based on bilateral asymmetry in healthy patients.This study indicated the accuracy of anatomical plates. Positioning an anatomical plate may lead to considerable residual errors in individual patients. Volar distal radius plate shapes differ among plate manufacturers. Therefore, one plate may perform better than another in an individual.

  16. Dependence of Orbit Determination Accuracy on the Observer Position

    NASA Astrophysics Data System (ADS)

    Vananti, Alessandro; Schildknecht, Thomas

    2013-08-01

    The Astronomical Institute of the University of Bern (AIUB) is conducting several search campaigns for space debris in Geostationary (GEO) and Medium Earth Orbits (MEO). Usually, to improve the quality of the determined orbits for newly discovered objects, follow-up observations are conducted. The latter take place at different times during the discovery night or in subsequent nights. The time interval between the observations plays an important role in the accuracy of the calculated orbits. Another essential parameter to consider is the position of the observer at the observation time. In this paper, the accuracy of the orbit determination with respect to the position of the observer is analyzed. The same observing site at varying epochs or multiple site locations involve different distances from the target object and a different observing angle with respect to its orbital plane and trajectory. The formal error in the orbit determination process is, among other dependencies, a function of the latter parameters. The analysis of this dependence is important to choose the appropriate observation strategy. One of the main questions that arises is e.g. whether observing the same object from different stations results in better determined orbits and, if yes, how big is the improvement. Another question is e.g. whether the observation from multiple sites needs to be simultaneous or not for a better orbit accuracy.

  17. Absolute accuracy of the Cyberware WB4 whole-body scanner

    NASA Astrophysics Data System (ADS)

    Daanen, Hein A. M.; Taylor, Stacie E.; Brunsman, Matthew A.; Nurre, Joseph H.

    1997-03-01

    The Cyberware WB4 whole body scanner is one of the first scanning systems in the world that generates a high resolution data set of the outer surface of the human body. The Computerized Anthropometric Research and Design (CARD) Laboratory of Wright-Patterson AFB intends to use the scanner to enable quick and reliable acquisition of anthropometric data. For this purpose, a validation study was initiated to check the accuracy, reliability and errors of the system. A calibration object, consisting of two boxes and a cylinder, was scanned in several locations in the scanning space. The object dimensions in the resulting scans compared favorably to the actual dimensions of the calibration object.

  18. Correction to Method of Establishing the Absolute Radiometric Accuracy of Remote Sensing Systems While On-orbit Using Characterized Stellar Sources

    NASA Technical Reports Server (NTRS)

    Bowen, Howard S.; Cunningham, Douglas M.

    2007-01-01

    The contents include: 1) Brief history of related events; 2) Overview of original method used to establish absolute radiometric accuracy of remote sensing instruments using stellar sources; and 3) Considerations to improve the stellar calibration approach.

  19. Electroelastic optical fiber positioning with submicrometer accuracy: Model and experiment

    NASA Astrophysics Data System (ADS)

    Kofod, Guggi; Mc Carthy, Denis N.; Krissler, Jan; Lang, Günter; Jordan, Grace

    2009-05-01

    We present accurate electromechanical measurements on a balanced push-pull dielectric elastomer actuator, demonstrating submicrometer accurate position control. An analytical model based on a simplified pure-shear dielectric elastomer film with prestretch is found to capture the voltage-displacement behavior, with reduced output due to the boundary conditions. Two complementary experiments show that actuation coefficients of 0.5-1 nm/V2 are obtainable with the demonstrated device, enabling motion control with submicrometer accuracy in a voltage range below 200 V.

  20. Accuracy of patient positioning in mantle field irradiation.

    PubMed

    Creutzberg, C L; Visser, A G; De Porre, P M; Meerwaldt, J H; Althof, V G; Levendag, P C

    1992-04-01

    A prospective study of the accuracy of patient positioning in mantle field irradiation was carried out in 13 lymphoma patients treated with curative radiotherapy. Patients were treated in the supine and prone position for anterior and posterior fields, respectively. Individually shaped divergent shielding blocks were placed in a fixed position in a template which was positioned on a tray above the patient. A total number of 94 megavoltage portal films (MV) was analysed and compared to 26 simulation films (SIM). MV-SIM differences were larger for posterior fields than for anterior fields. Regarding the position of the lung shielding blocks, mean MV-SIM differences ranged from 1.3 to 4.4 mm and errors exceeding 1 cm were found in 7.2% of cases. Most discrepancies appeared to be randomly distributed. A 4-5 mm systematic cranial shift of patients in the posterior treatment position was noted. Discrepancies in the position of the laryngeal block, spinal cord shielding block and humerus blocks were small with mean MV-SIM differences ranging from 0.3 to 2.7 mm. Differences between simulation set-up and treatment set-up were modest as compared to error rates reported in the literature. Shielding of tumour-bearing areas did not occur. It was concluded that the present standardised technique of patient positioning and the design of treatment fields results in acceptable error rates. Attention should be directed towards increasing the stability of patients in the prone treatment position in order to further reduce both systematic and random error rates.

  1. Position error correction in absolute surface measurement based on a multi-angle averaging method

    NASA Astrophysics Data System (ADS)

    Wang, Weibo; Wu, Biwei; Liu, Pengfei; Liu, Jian; Tan, Jiubin

    2017-04-01

    We present a method for position error correction in absolute surface measurement based on a multi-angle averaging method. Differences in shear rotation measurements at overlapping areas can be used to estimate the unknown relative position errors of the measurements. The model and the solving of the estimation algorithm have been discussed in detail. The estimation algorithm adopts a least-squares technique to eliminate azimuthal errors caused by rotation inaccuracy. The cost functions can be minimized to determine the true values of the unknowns of Zernike polynomial coefficients and rotation angle. Experimental results show the validity of the method proposed.

  2. Cadastral Positioning Accuracy Improvement: a Case Study in Malaysia

    NASA Astrophysics Data System (ADS)

    Hashim, N. M.; Omar, A. H.; Omar, K. M.; Abdullah, N. M.; Yatim, M. H. M.

    2016-09-01

    Cadastral map is a parcel-based information which is specifically designed to define the limitation of boundaries. In Malaysia, the cadastral map is under authority of the Department of Surveying and Mapping Malaysia (DSMM). With the growth of spatial based technology especially Geographical Information System (GIS), DSMM decided to modernize and reform its cadastral legacy datasets by generating an accurate digital based representation of cadastral parcels. These legacy databases usually are derived from paper parcel maps known as certified plan. The cadastral modernization will result in the new cadastral database no longer being based on single and static parcel paper maps, but on a global digital map. Despite the strict process of the cadastral modernization, this reform has raised unexpected queries that remain essential to be addressed. The main focus of this study is to review the issues that have been generated by this transition. The transformed cadastral database should be additionally treated to minimize inherent errors and to fit them to the new satellite based coordinate system with high positional accuracy. This review result will be applied as a foundation for investigation to study the systematic and effectiveness method for Positional Accuracy Improvement (PAI) in cadastral database modernization.

  3. Precision and accuracy in the quantitative analysis of biological samples by accelerator mass spectrometry: application in microdose absolute bioavailability studies.

    PubMed

    Gao, Lan; Li, Jing; Kasserra, Claudia; Song, Qi; Arjomand, Ali; Hesk, David; Chowdhury, Swapan K

    2011-07-15

    Determination of the pharmacokinetics and absolute bioavailability of an experimental compound, SCH 900518, following a 89.7 nCi (100 μg) intravenous (iv) dose of (14)C-SCH 900518 2 h post 200 mg oral administration of nonradiolabeled SCH 900518 to six healthy male subjects has been described. The plasma concentration of SCH 900518 was measured using a validated LC-MS/MS system, and accelerator mass spectrometry (AMS) was used for quantitative plasma (14)C-SCH 900518 concentration determination. Calibration standards and quality controls were included for every batch of sample analysis by AMS to ensure acceptable quality of the assay. Plasma (14)C-SCH 900518 concentrations were derived from the regression function established from the calibration standards, rather than directly from isotopic ratios from AMS measurement. The precision and accuracy of quality controls and calibration standards met the requirements of bioanalytical guidance (U.S. Department of Health and Human Services, Food and Drug Administration, Center for Drug Evaluation and Research, Center for Veterinary Medicine. Guidance for Industry: Bioanalytical Method Validation (ucm070107), May 2001. http://www.fda.gov/downloads/Drugs/GuidanceCompilanceRegulatoryInformation/Guidances/ucm070107.pdf ). The AMS measurement had a linear response range from 0.0159 to 9.07 dpm/mL for plasma (14)C-SCH 900158 concentrations. The CV and accuracy were 3.4-8.5% and 94-108% (82-119% for the lower limit of quantitation (LLOQ)), respectively, with a correlation coefficient of 0.9998. The absolute bioavailability was calculated from the dose-normalized area under the curve of iv and oral doses after the plasma concentrations were plotted vs the sampling time post oral dose. The mean absolute bioavailability of SCH 900518 was 40.8% (range 16.8-60.6%). The typical accuracy and standard deviation in AMS quantitative analysis of drugs from human plasma samples have been reported for the first time, and the impact of these

  4. Parametric Characterization of SGP4 Theory and TLE Positional Accuracy

    NASA Astrophysics Data System (ADS)

    Oltrogge, D.; Ramrath, J.

    2014-09-01

    Two-Line Elements, or TLEs, contain mean element state vectors compatible with General Perturbations (GP) singly-averaged semi-analytic orbit theory. This theory, embodied in the SGP4 orbit propagator, provides sufficient accuracy for some (but perhaps not all) orbit operations and SSA tasks. For more demanding tasks, higher accuracy orbit and force model approaches (i.e. Special Perturbations numerical integration or SP) may be required. In recent times, the suitability of TLEs or GP theory for any SSA analysis has been increasingly questioned. Meanwhile, SP is touted as being of high quality and well-suited for most, if not all, SSA applications. Yet the lack of truth or well-known reference orbits that haven't already been adopted for radar and optical sensor network calibration has typically prevented a truly unbiased assessment of such assertions. To gain better insight into the practical limits of applicability for TLEs, SGP4 and the underlying GP theory, the native SGP4 accuracy is parametrically examined for the statistically-significant range of RSO orbit inclinations experienced as a function of all orbit altitudes from LEO through GEO disposal altitude. For each orbit altitude, reference or truth orbits were generated using full force modeling, time-varying space weather, and AGIs HPOP numerical integration orbit propagator. Then, TLEs were optimally fit to these truth orbits. The resulting TLEs were then propagated and positionally differenced with the truth orbits to determine how well the GP theory was able to fit the truth orbits. Resultant statistics characterizing these empirically-derived accuracies are provided. This TLE fit process of truth orbits was intentionally designed to be similar to the JSpOC process operationally used to generate Enhanced GP TLEs for debris objects. This allows us to draw additional conclusions of the expected accuracies of EGP TLEs. In the real world, Orbit Determination (OD) programs aren't provided with dense optical

  5. SU-E-T-89: Accuracy of Absolute Three-Dimensional Dose Distribution Measurement Using the Delta4

    SciTech Connect

    Uehara, R; Tachibana, H; Ohyoshi, H; Matsumoto, S; Baba, H; Tanaka, F; Ariji, T

    2015-06-15

    Purpose: In this study, we investigated the accuracy of the absolute dose distribution measurement using the Delta4 phantom compared to the measurements using a ionization chamber and EDR2 film Methods: Several conventional and intensity-modulated radiation therapy plans were used to compare the dose distribution measured using the Delta4 phantom to the absolute point dose using the chamber and the relative two-dimensional dose distribution using the EDR2 film. For the absolute dose distribution evaluation, the measurements using the Delta4, the chamber and the film were performed in similar measurement geometry. For point dose measurement using the chamber, an acrylic slab phantom with the PTW Semiflex chamber was inserted into the Delta4 phantom, alternative to the Delta4 main unit. Similarly, for dose distribution measurement using the film, the EDR2 film sandwiched with two acrylic slab phantoms were inserted to the phantom. Dose difference and gamma analysis were done for point dose and relative dose distribution comparisons, respectively. Results: The point dose measurements show slight negative systematic dose difference of −0.5 ± 0.1% and −1.0 ± 0.4% in the conventional and the IMRT plans, respectively. The additional measurement for direction dependency for Delta4 shows similar negative systematic dose difference even the phantom analysis software consider the directional dependency. The pass rate of the gamma evaluation was 77.7 ± 5.8% and 88.8±3.3% in the conventional and the IMRT plans, respectively. Conclusions: The Delta4 phantom shows a 1%-systematic dose difference derived from directional dependency and lower resolution compared to the film. Thus it is necessary to comprehensively evaluate the phantom to verify the IMRT/VMAT plans. Especially, the dosimetry tool is needed to have high resolution and high measurement accuracy in IMRT/VMAT-SBRT plan with small fields using intensity modulation in which the analysis area is limited and the

  6. SAR image registration in absolute coordinates using GPS carrier phase position and velocity information

    SciTech Connect

    Burgett, S.; Meindl, M.

    1994-09-01

    It is useful in a variety of military and commercial application to accurately register the position of synthetic aperture radar (SAR) imagery in absolute coordinates. The two basic SAR measurements, range and doppler, can be used to solve for the position of the SAR image. Imprecise knowledge of the SAR collection platform`s position and velocity vectors introduce errors in the range and doppler measurements and can cause the apparent location of the SAR image on the ground to be in error by tens of meters. Recent advances in carrier phase GPS techniques can provide an accurate description of the collection vehicle`s trajectory during the image formation process. In this paper, highly accurate carrier phase GPS trajectory information is used in conjunction with SAR imagery to demonstrate a technique for accurate registration of SAR images in WGS-84 coordinates. Flight test data will be presented that demonstrates SAR image registration errors of less than 4 meters.

  7. Two-modality laser diode interferometer for high-accuracy measurement of long-range absolute distance

    NASA Astrophysics Data System (ADS)

    Wang, Bofan; Li, Zhongliang; Wang, Xiangzhao; Bu, Peng

    2010-08-01

    This paper presents a two-modality laser diode (LD) interferometer which combine as two-wavelength sinusoidal phase modulating (SPM) interferometer with a wavelength scanning interferometer (WSI) for measurement of distance over long range with high accuracy. Moreover, the intensity modulation due to power changes of LD is suppressed by appropriately choosing the modulation amplitude of injection current (IC) of LD. Triangle wave is used to modulate the IC of one LD with that of the other LD being constant at first. Thus the interferometer works as a wavelength scanning interferometer. An initial estimate of the distance can be obtained from the phase change of the interference signal. Then sinusoidal wave is used for modulating IC of both LDs to realize a two-wavelength SPM interferometer. However, the modulation of the IC of two LDs results in not only the wavelength modulation but also the intensity modulation. This intensity modulation will cause a measured phase error. To eliminate this error, SPM depths are appropriately chosen, therefore the distance to be measured can be accurately obtained with synthetic-wavelength algorithm. Experimental results indicate that an absolute distance measurement accuracy of 1μm can be achieved over the range of 40mm to 100mm.

  8. Vehicle Position Estimation Based on Magnetic Markers: Enhanced Accuracy by Compensation of Time Delays.

    PubMed

    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.

  9. Vehicle Position Estimation Based on Magnetic Markers: Enhanced Accuracy by Compensation of Time Delays

    PubMed Central

    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

  10. Absolute reliability of isokinetic knee flexion and extension measurements adopting a prone position.

    PubMed

    Ayala, F; De Ste Croix, M; Sainz de Baranda, P; Santonja, F

    2013-01-01

    The main purpose of this study was to determine the absolute and relative reliability of isokinetic peak torque (PT), angle of peak torque (APT), average power (PW) and total work (TW) for knee flexion and extension during concentric and eccentric actions measured in a prone position at 60, 180 and 240° s(-1). A total of 50 recreational athletes completed the study. PT, APT, PW and TW for concentric and eccentric knee extension and flexion were recorded at three different angular velocities (60, 180 and 240° s(-1)) on three different occasions with a 72- to 96-h rest interval between consecutive testing sessions. Absolute reliability was examined through typical percentage error (CV(TE)), percentage change in the mean (ChM) and relative reliability with intraclass correlations (ICC(3,1)). For both the knee extensor and flexor muscle groups, all strength data (except APT during knee flexion movements) demonstrated moderate absolute reliability (ChM < 3%; ICCs > 0·70; and CV(TE) < 20%) independent of the knee movement (flexion and extension), type of muscle action (concentric and eccentric) and angular velocity (60, 180 and 240° s(-1)). Therefore, the current study suggests that the CV(TE) values reported for PT (8-20%), APT (8-18%) (only during knee extension movements), PW (14-20%) and TW (12-28%) may be acceptable to detect the large changes usually observed after rehabilitation programmes, but not acceptable to examine the effect of preventative training programmes in healthy individuals.

  11. Soccer-specific accuracy and validity of the local position measurement (LPM) system.

    PubMed

    Frencken, Wouter G P; Lemmink, Koen A P M; Delleman, Nico J

    2010-11-01

    Limited data is available on accuracy and validity of video-based, GPS and electronic tracking systems, particularly with reference to curved courses and short high intensity running activities. The main goal of this study was to assess soccer-specific accuracy and validity of the radio-frequency based local position measurement (LPM) system (1000Hz) for measuring distance and speed during walking and sprinting. Three males walked and sprinted 4 soccer-specific courses 10 times each. Distance and speed recorded by LPM were compared to actual distance and speed measured by measuring tape and timing gates. In addition, accuracy was assessed. The static accuracy (SD of the mean) is 1cm for devices put on the pitch and 2-3 cm when worn by participants. LPM underestimates actual distance (mean difference at most -1.6%). Coefficient of variation becomes larger at higher speed and increased turning angle. With regard to speed, validity correlations are high (range: 0.71-0.97). The LPM speed is significantly and systematically lower, although absolute and relative differences are small, between -0.1 km h⁻¹ (-1.3%) and -0.6 km h⁻¹ (-3.9%). The typical error of the estimate increases with increased speed, but does not increase with increased turning angle. Because the reported differences are small, we conclude that the LPM-system produces highly accurate position and speed data in static and dynamic conditions and is a valid tool for player tracking in soccer and ball team sports in general.

  12. New low-cost dimensionally stable composite linear absolute position encoder scale

    NASA Astrophysics Data System (ADS)

    Hassler, William L., Jr.; Nakayama, Robert K.

    1990-11-01

    A major problem in the use of standard linear position encoders is that the etched glass scales they use have a coefficient of thermal expansion (C. T. E. ) of about 1 1 . Oppm/ C. This means that their position measurements drift with changes in environmental temperature proportional to their C. T. E. . A new low cost dimensionally stable composite scale was made for use in a new absolute linear position encoder. The unidirectional Polyphenylene Sulfide/AS4 carbon fiber composite material that this scale is made of was tested for dimensional stability with respect to changes in temperature humidity and creep. The C. T. E. of the scale material was measured to be nominally 0. 29 ppm/ C with a standard deviation of 0. 12 over the operating temperature range of -2 to 62 C. The overall displacement strain due to 98 moisture absorption relative to 0 moisture absorption was measured to be 9 ppm. The strain due to stress-relief creep was found to be a maximum of 3 ppm over a period of 173 days. These results show that a linear position encoder scale made of this material is superior to those made of the standard glass currently being used and more cost effective than fused silica for most applications. 1.

  13. High-accuracy absolute rotation rate measurements with a large ring laser gyro: establishing the scale factor.

    PubMed

    Hurst, Robert B; Mayerbacher, Marinus; Gebauer, Andre; Schreiber, K Ulrich; Wells, Jon-Paul R

    2017-02-01

    Large ring lasers have exceeded the performance of navigational gyroscopes by several orders of magnitude and have become useful tools for geodesy. In order to apply them to tests in fundamental physics, remaining systematic errors have to be significantly reduced. We derive a modified expression for the Sagnac frequency of a square ring laser gyro under Earth rotation. The modifications include corrections for dispersion (of both the gain medium and the mirrors), for the Goos-Hänchen effect in the mirrors, and for refractive index of the gas filling the cavity. The corrections were measured and calculated for the 16  m2 Grossring laser located at the Geodetic Observatory Wettzell. The optical frequency and the free spectral range of this laser were measured, allowing unique determination of the longitudinal mode number, and measurement of the dispersion. Ultimately we find that the absolute scale factor of the gyroscope can be estimated to an accuracy of approximately 1 part in 108.

  14. Absolute position calculation for a desktop mobile rehabilitation robot based on three optical mouse sensors.

    PubMed

    Zabaleta, Haritz; Valencia, David; Perry, Joel; Veneman, Jan; Keller, Thierry

    2011-01-01

    ArmAssist is a wireless robot for post stroke upper limb rehabilitation. Knowing the position of the arm is essential for any rehabilitation device. In this paper, we describe a method based on an artificial landmark navigation system. The navigation system uses three optical mouse sensors. This enables the building of a cheap but reliable position sensor. Two of the sensors are the data source for odometry calculations, and the third optical mouse sensor takes very low resolution pictures of a custom designed mat. These pictures are processed by an optical symbol recognition algorithm which will estimate the orientation of the robot and recognize the landmarks placed on the mat. The data fusion strategy is described to detect the misclassifications of the landmarks in order to fuse only reliable information. The orientation given by the optical symbol recognition (OSR) algorithm is used to improve significantly the odometry and the recognition of the landmarks is used to reference the odometry to a absolute coordinate system. The system was tested using a 3D motion capture system. With the actual mat configuration, in a field of motion of 710 × 450 mm, the maximum error in position estimation was 49.61 mm with an average error of 36.70 ± 22.50 mm. The average test duration was 36.5 seconds and the average path length was 4173 mm.

  15. White-light scanning fiber Michelson interferometer for absolute position-distance measurement.

    PubMed

    Li, T; Wang, A; Murphy, K; Claus, R

    1995-04-01

    A white-light fiber interferometer working in the spatial domain, using two fiber ends in a hollow tube as the sensing head and an electric magnetic actuator-mirror reflector as the path-compensation-measurement element, is presented. Analysis and preliminary experiments have demonstrated a repeatability of 0.5 microm (2sigma) for position-distance measurement, and the measurement uncertainty was estimated to be 1.5 microm (2sigma) over a distance range of 150 microm. Suggestions for further improving the measurement accuracy and response speed are also given.

  16. White-light scanning fiber Michelson interferometer for absolute position-distance measurement

    NASA Astrophysics Data System (ADS)

    Li, Tianchu; Wang, Anbo; Murphy, Kent; Claus, Richard

    1995-04-01

    A white-light fiber interferometer working in the spatial domain, using two fiber ends in a hollow tube as the sensing head and an electric magnetic actuator-mirror reflector as the path-compensation-measurement element, is presented. Analysis and preliminary experiments have demonstrated a repeatability of 0.5 mu m (2 sigma ) for position-distance measurement, and the measurement uncertainty was estimated to be 1.5 mu m (2 sigma ) over a distance range of 150 mu m. Suggestions for further improving the measurement accuracy and response speed are also given.

  17. Positioning accuracy of primary mirror actuators for large-aperture space-based optical instruments

    NASA Astrophysics Data System (ADS)

    Hatheway, Alson E.

    2000-10-01

    This paper describes the Rubicontm actuator, discusses its test data and derives from the data the actuator's accuracy function based upon the observed accuracy of long and short stroke motion commands. The accuracy is described in terms of the rms positioning error (in nanometers) for moves of a given size, regardless of position in the stroke.

  18. Tracking Accuracy of a Real-Time Fiducial Tracking System for Patient Positioning and Monitoring in Radiation Therapy

    SciTech Connect

    Shchory, Tal; Schifter, Dan; Lichtman, Rinat; Neustadter, David; Corn, Benjamin W.

    2010-11-15

    Purpose: In radiation therapy there is a need to accurately know the location of the target in real time. A novel radioactive tracking technology has been developed to answer this need. The technology consists of a radioactive implanted fiducial marker designed to minimize migration and a linac mounted tracking device. This study measured the static and dynamic accuracy of the new tracking technology in a clinical radiation therapy environment. Methods and Materials: The tracking device was installed on the linac gantry. The radioactive marker was located in a tissue equivalent phantom. Marker location was measured simultaneously by the radioactive tracking system and by a Microscribe G2 coordinate measuring machine (certified spatial accuracy of 0.38 mm). Localization consistency throughout a volume and absolute accuracy in the Fixed coordinate system were measured at multiple gantry angles over volumes of at least 10 cm in diameter centered at isocenter. Dynamic accuracy was measured with the marker located inside a breathing phantom. Results: The mean consistency for the static source was 0.58 mm throughout the tested region at all measured gantry angles. The mean absolute position error in the Fixed coordinate system for all gantry angles was 0.97 mm. The mean real-time tracking error for the dynamic source within the breathing phantom was less than 1 mm. Conclusions: This novel radioactive tracking technology has the potential to be useful in accurate target localization and real-time monitoring for radiation therapy.

  19. How a GNSS Receiver Is Held May Affect Static Horizontal Position Accuracy.

    PubMed

    Weaver, Steven A; Ucar, Zennure; Bettinger, Pete; Merry, Krista

    2015-01-01

    The static horizontal position accuracy of a mapping-grade GNSS receiver was tested in two forest types over two seasons, and subsequently was tested in one forest type against open sky conditions in the winter season. The main objective was to determine whether the holding position during data collection would result in significantly different static horizontal position accuracy. Additionally, we wanted to determine whether the time of year (season), forest type, or environmental variables had an influence on accuracy. In general, the F4Devices Flint GNSS receiver was found to have mean static horizontal position accuracy levels within the ranges typically expected for this general type of receiver (3 to 5 m) when differential correction was not employed. When used under forest cover, in some cases the GNSS receiver provided a higher level of static horizontal position accuracy when held vertically, as opposed to held at an angle or horizontally (the more natural positions), perhaps due to the orientation of the antenna within the receiver, or in part due to multipath or the inability to use certain satellite signals. Therefore, due to the fact that numerous variables may affect static horizontal position accuracy, we only conclude that there is weak to moderate evidence that the results of holding position are significant. Statistical test results also suggest that the season of data collection had no significant effect on static horizontal position accuracy, and results suggest that atmospheric variables had weak correlation with horizontal position accuracy. Forest type was found to have a significant effect on static horizontal position accuracy in one aspect of one test, yet otherwise there was little evidence that forest type affected horizontal position accuracy. Since the holding position was found in some cases to be significant with regard to the static horizontal position accuracy of positions collected in forests, it may be beneficial to have an

  20. Absolute Side-chain Structure at Position 13 Is Required for the Inhibitory Activity of Bromein*

    PubMed Central

    Sawano, Yoriko; Hatano, Ken-ichi; Miyakawa, Takuya; Tanokura, Masaru

    2008-01-01

    Bromelain isoinhibitor (bromein), a cysteine proteinase inhibitor from pineapple stem, has a unique double-chain structure. The bromein precursor protein includes three homologous inhibitor domains, each containing an interchain peptide between the light and heavy chains. The interchain peptide in the single-chain precursor is immediately processed by bromelain, a target proteinase. In the present study, to clarify the essential inhibitory site of bromein, we constructed 44 kinds of site-directed and deletion mutants and investigated the inhibitory activity of each toward bromelain. As a result, the complete chemical structure of Leu13 in the light chain was revealed to be essential for inhibition. Pro12 prior to the leucine residue was also involved in the inhibitory activity and would control the location of the leucine side chain by the fixed φ dihedral angle of proline. Furthermore, the five-residue length of the interchain peptide was strictly required for the inhibitory activity. On the other hand, no inhibitory activity against bromelain was observed by the substitution of proline for the N terminus residue Thr15 of the interchain peptide. In summary, these mutational analyses of bromein demonstrated that the appropriate position and conformation of Leu13 are absolutely crucial for bromelain inhibition. PMID:18948264

  1. Analysis of Current Position Determination Accuracy in Natural Resources Canada Precise Point Positioning Service

    NASA Astrophysics Data System (ADS)

    Krzan, Grzegorz; Dawidowicz, Karol; Krzysztof, Świaţek

    2013-09-01

    Precise Point Positioning (PPP) is a technique used to determine highprecision position with a single GNSS receiver. Unlike DGPS or RTK, satellite observations conducted by the PPP technique are not differentiated, therefore they require that parameter models should be used in data processing, such as satellite clock and orbit corrections. Apart from explaining the theory of the PPP technique, this paper describes the available web-based online services used in the post-processing of observation results. The results obtained in the post-processing of satellite observations at three points, with different characteristics of environment conditions, using the CSRS-PPP service, will be presented as the results of the experiment. This study examines the effect of the duration of the measurement session on the results and compares the results obtained by working out observations made by the GPS system and the combined observations from GPS and GLONASS. It also presents the analysis of the position determination accuracy using one and two measurement frequencies

  2. Optimal design of the absolute positioning sensor for a high-speed maglev train and research on its fault diagnosis.

    PubMed

    Zhang, Dapeng; Long, Zhiqiang; Xue, Song; Zhang, Junge

    2012-01-01

    This paper studies an absolute positioning sensor for a high-speed maglev train and its fault diagnosis method. The absolute positioning sensor is an important sensor for the high-speed maglev train to accomplish its synchronous traction. It is used to calibrate the error of the relative positioning sensor which is used to provide the magnetic phase signal. On the basis of the analysis for the principle of the absolute positioning sensor, the paper describes the design of the sending and receiving coils and realizes the hardware and the software for the sensor. In order to enhance the reliability of the sensor, a support vector machine is used to recognize the fault characters, and the signal flow method is used to locate the faulty parts. The diagnosis information not only can be sent to an upper center control computer to evaluate the reliability of the sensors, but also can realize on-line diagnosis for debugging and the quick detection when the maglev train is off-line. The absolute positioning sensor we study has been used in the actual project.

  3. Optimal Design of the Absolute Positioning Sensor for a High-Speed Maglev Train and Research on Its Fault Diagnosis

    PubMed Central

    Zhang, Dapeng; Long, Zhiqiang; Xue, Song; Zhang, Junge

    2012-01-01

    This paper studies an absolute positioning sensor for a high-speed maglev train and its fault diagnosis method. The absolute positioning sensor is an important sensor for the high-speed maglev train to accomplish its synchronous traction. It is used to calibrate the error of the relative positioning sensor which is used to provide the magnetic phase signal. On the basis of the analysis for the principle of the absolute positioning sensor, the paper describes the design of the sending and receiving coils and realizes the hardware and the software for the sensor. In order to enhance the reliability of the sensor, a support vector machine is used to recognize the fault characters, and the signal flow method is used to locate the faulty parts. The diagnosis information not only can be sent to an upper center control computer to evaluate the reliability of the sensors, but also can realize on-line diagnosis for debugging and the quick detection when the maglev train is off-line. The absolute positioning sensor we study has been used in the actual project. PMID:23112619

  4. Global positioning system measurements for crustal deformation: Precision and accuracy

    USGS Publications Warehouse

    Prescott, W.H.; Davis, J.L.; Svarc, J.L.

    1989-01-01

    Analysis of 27 repeated observations of Global Positioning System (GPS) position-difference vectors, up to 11 kilometers in length, indicates that the standard deviation of the measurements is 4 millimeters for the north component, 6 millimeters for the east component, and 10 to 20 millimeters for the vertical component. The uncertainty grows slowly with increasing vector length. At 225 kilometers, the standard deviation of the measurement is 6, 11, and 40 millimeters for the north, east, and up components, respectively. Measurements with GPS and Geodolite, an electromagnetic distance-measuring system, over distances of 10 to 40 kilometers agree within 0.2 part per million. Measurements with GPS and very long baseline interferometry of the 225-kilometer vector agree within 0.05 part per million.

  5. Accuracy aspects of recent laser station positioning experiments

    NASA Astrophysics Data System (ADS)

    Ambrosius, B. A. C.; Noomen, R.; Wakker, K. F.; Papazissi, E.

    1987-12-01

    Over the past few years, the contribution of the European laser ranging systems to the total amount of global observations of the LAGEOS geodynamics satellite has increased considerably. In the studies described in this paper selected samples of the data are used to derive the positions of the European stations within the framework of a global coordinates solution and to determine accurate baselines between these stations. Recent improvements in the dynamic models of the motion of the earth and LAGEOS, and the high quality of the laser data, are shown to result in monthly global coordinate solutions with a consistency of better than 5 cm. The repeatability of monthly solutions of the European baselines is demonstrated to be even better than 3.5 cm. A combined global station coordinate solution is presented, based on the tracking data of the first three months of 1986 and denoted by DUT/SOM LSC 87.1. Also the effects of tectonic plate motions are shown to be detectable from the analysis of data covering a period of less than 2 years. The results for the baseline from Monument Peak to Quincy, which crosses the San Andreas fault, are highlighted.

  6. An evaluation of the accuracy of geomagnetic data obtained from an unattended, automated, quasi-absolute station

    USGS Publications Warehouse

    Herzog, D.C.

    1990-01-01

    A comparison is made of geomagnetic calibration data obtained from a high-sensitivity proton magnetometer enclosed within an orthogonal bias coil system, with data obtained from standard procedures at a mid-latitude U.S. Geological Survey magnetic observatory using a quartz horizontal magnetometer, a Ruska magnetometer, and a total field magnetometer. The orthogonal coil arrangement is used with the proton magnetometer to provide Deflected-Inclination-Deflected-Declination (DIDD) data from which quasi-absolute values of declination, horizontal intensity, and vertical intensity can be derived. Vector magnetometers provide the ordinate values to yield baseline calibrations for both the DIDD and standard observatory processes. Results obtained from a prototype system over a period of several months indicate that the DIDD unit can furnish adequate absolute field values for maintaining observatory calibration data, thus providing baseline control for unattended, remote stations. ?? 1990.

  7. High-accuracy interferometer with a prism pair for measurement of the absolute refractive index of glass

    SciTech Connect

    Hori, Yasuaki; Hirai, Akiko; Minoshima, Kaoru; Matsumoto, Hirokazu

    2009-04-10

    We propose a variable-path interferometric technique for the measurement of the absolute refractive index of optical glasses. We use two interferometers to decide the ratio between changes in the optical path in a prism-shaped sample glass and in air resulting from displacement of the sample. The method allows precise measurements to be made without prior knowledge of the properties of the sample. The combined standard uncertainty of the proposed method is 1.6x10{sup -6}.

  8. Absolute Measurement of Electron Cloud Density in aPositively-Charged Particle Beam

    SciTech Connect

    Kireeff Covo, Michel; Molvik, Arthur W.; Friedman, Alex; Vay,Jean-Luc; Seidl, Peter A.; Logan, Grant; Baca, David; Vujic, Jasmina L.

    2006-04-27

    Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the depressed beam potential and gives the dynamic cloud density. Clearing electrode current reveals the static background cloud density, allowing the first absolute measurement of the time-dependent electron cloud density during the beam pulse.

  9. Absolute Measurement of Electron Cloud Density in a Positively-Charged Particle Beam

    SciTech Connect

    Covo, M K; Molvik, A W; Friedman, A; Vay, J; Seidl, P A; Logan, B G; Baca, D; Vujic, J L

    2006-05-18

    Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the depressed beam potential and gives the dynamic cloud density. Clearing electrode current reveals the static background cloud density, allowing the first absolute measurement of the time-dependent electron cloud density during the beam pulse.

  10. Absolute measurement of electron-cloud density in a positively charged particle beam.

    PubMed

    Kireeff Covo, Michel; Molvik, Arthur W; Friedman, Alex; Vay, Jean-Luc; Seidl, Peter A; Logan, Grant; Baca, David; Vujic, Jasmina L

    2006-08-04

    Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron-cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the depressed beam potential and gives the dynamic cloud density. Clearing electrode current reveals the static background cloud density, allowing the first absolute measurement of the time-dependent electron-cloud density during the beam pulse.

  11. Accuracy and Fluency in List and Context Reading of Skilled and RD Groups: Absolute and Relative Performance Levels.

    ERIC Educational Resources Information Center

    Jenkins, Joseph R.; Fuchs, Lynn S.; van den Broek, Paul; Espin, Christine; Deno, Stanley L.

    2003-01-01

    Twenty-four students with reading difficulties (grade 4) and 85 skilled readers completed a reading comprehension test, read aloud a folktale, and read aloud a list of the folktale's words. Skilled readers read three times more correct words per minute in context and showed higher accuracy and rates on all measures. (Contains references.)…

  12. High-accuracy indoor positioning system based on visible light communication

    NASA Astrophysics Data System (ADS)

    Wei, Ling; Zhang, Hongming; Yu, Bingyan; Guan, Yang

    2015-11-01

    A visible light communication (VLC)-based high-accuracy indoor positioning system is proposed and demonstrated. In this system, the light-emitting diode identification (LED-ID) indicating the position information of the LED can be transmitted to the receiver by the illumination LED through VLC. In the meantime, with the aid of a camera and angular sensors of the mobile device, a coordinate transform can be employed to calculate the relative position between the receiver and the reference LED so that the position of the receiver can be determined. Finally, the experimental results show that 2-cm positioning accuracy can be achieved and the simulation results indicate that the positioning error can be limited within 4.7 cm when the accuracy of angular sensors is 1 deg.

  13. Improve the Absolute Accuracy of Ozone Intensities in the 9-11 μm Region via Mw/ir Multi-Wavelength Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Drouin, Brian

    2016-06-01

    Ozone (O_3) is crucial for studies of air quality, human and crop health, and radiative forcing. Spectroscopic remote sensing techniques have been extensively employed to investigate ozone globally and regionally. Infrared intensities of ≤1% accuracy are desired by the remote sensing community. The accuracy of the current state-of-the-art infrared ozone intensities is on the order of 4-10%, resulting in ad hoc intensity scaling factors for consistent atmospheric retrievals. The large uncertainties on the infrared ozone intensities arise from the fact that pure ozone is very difficult to generate and sustain in the laboratory. Best estimates have employed IR/UV cross beam experiments to determine the accurate O_3 volume mixing ratio of the sample through its standard cross section value at 254 nm. This presentation reports our effort to improve the absolute accuracy of ozone intensities in the 9-11 μm region via a transfer of the precision of the rotational dipole moment onto the infrared measurement (MW/IR). Our approach was to use MW/IR cross beam experiments and determine the O_3 mixing ratio through alternately measuring pure rotation ozone lines from 692 to 779 GHz. The uncertainty of these pure rotation line intensities is better than 0.1%. The sample cell was a slow flow cross cell and the total pressure inside the sample cell was maintained constant through a proportional-integral-derivative (PID) flow control. Five infrared O_3 spectra were obtained, with a path length of 3.74 m, pressures ranging from 30 to 120 mTorr, and mixing ratio ranging from 0.5 to 0.9. A multi spectrum fitting technique was employed to fit all the FTS spectra simultaneously. The results show that we can determine intensities of the 9.6μm band with absolute accuracy better than 4%.

  14. SU-E-T-189: First Experimental Verification of the Accuracy of Absolute Dose Reconstruction From PET-CT Imaging of Yttrium 90 Microspheres

    SciTech Connect

    Veltchev, I; Fourkal, E; Doss, M; Ma, C; Meyer, J; Yu, M; Horwitz, E

    2014-06-01

    Purpose: In the past few years there have been numerous proposals for 3D dose reconstruction from the PET-CT imaging of patients undergoing radioembolization treatment of the liver with yttrium-90 microspheres. One of the most promising techniques uses convolution of the measured PET activity distribution with a pre-calculated Monte Carlo dose deposition kernel. The goal of the present study is to experimentally verify the accuracy of this method and to analyze the significance of various error sources. Methods: Optically stimulated luminescence detectors (OSLD) were used (NanoDot, Landauer) in this experiment. Two detectors were mounted on the central axis of a cylinder filled with water solution of yttrium-90 chloride. The total initial activity was 90mCi. The cylinder was inserted in a larger water phantom and scanned on a Siemens Biograph 16 Truepoint PET-CT scanner. Scans were performed daily over a period of 20 days to build a calibration curve for the measured absolute activity spanning 7 yttrium-90 half-lives. The OSLDs were mounted in the phantom for a predetermined period of time in order to record 2Gy dose. The measured dose was then compared to the dose reconstructed from the activity density at the location of each dosimeter. Results: Thorough error analysis of the dose reconstruction algorithm takes into account the uncertainties in the absolute PET activity, branching ratios, and nonlinearity of the calibration curve. The measured dose for 105-minute exposure on day 10 of the experiment was 219(11)cGy, while the reconstructed dose at the location of the detector was 215(47)cGy. Conclusion: We present the first experimental verification of the accuracy of the convolution algorithm for absolute dose reconstruction of yttrium-90 microspheres. The excellent agreement between the measured and calculated point doses will encourage the broad clinical adoption of the convolution-based dose reconstruction algorithm, making future quantitative dose

  15. Accuracy of Linear Measurements of Galileos Cone Beam Computed Tomography in Normal and Different Head Positions

    PubMed Central

    Sheikhi, Mahnaz; Ghorbanizadeh, Sajad; Abdinian, Mehrdad; Goroohi, Hossein; Badrian, Hamid

    2012-01-01

    Introduction. The aim of this study was to determine the accuracy of linear measurements in dry human skulls in ideal position and different deviated positions of the skull. Methods. 6 dry human skulls were included in the study. Opaque markers were attached to alveolar bone. Buccolingual and mesiodistal distances and heights were measured in 5 different regions of either jaws using a digital caliper. Radiographic distances were measured in ideal, rotation, tilt, flexion, and extension positions of the skulls. The physical and radiographic measurements were compared to estimate linear measurement accuracy. Results. The mean difference between physical measurements and radiographic measurements was 0.05 ± 0.45. There was a significant difference between physical measurements and radiographic measurements in ideal, rotation, tilt, and extension positions (P   value < 0.05). Conclusions. The accuracy of measurements in GALILEOUS CBCT machine varies when the position of the skull deviates from ideal; however, the differences are not clinically significant. PMID:22844282

  16. In vitro measurements of absolute blood oxygen saturation using pulsed near-infrared photoacoustic spectroscopy: accuracy and resolution.

    PubMed

    Laufer, Jan; Elwell, Clare; Delpy, Dave; Beard, Paul

    2005-09-21

    Pulsed photoacoustic spectroscopy was used to measure blood oxygen saturation in vitro. An optical parametric oscillator laser system provided nanosecond excitation pulses over the wavelength range 740-1040 nm which were used to generate photoacoustic signals in a cuvette through which a saline suspension of red blood cells was circulated. The signal amplitude and the effective attenuation coefficient were extracted from the photoacoustic signals as a function of wavelength to provide photoacoustic spectra of the blood. From these, the relative concentrations of oxy- and deoxyhaemoglobin, and therefore blood oxygen saturation (SO2), were determined using forward models of the absorbed energy distribution based on diffusion theory. A standard linear model of the dependence of absorbance on the concentration of chromophores was also used to calculate the blood oxygen saturation from the signal amplitude spectra. The diffusion approximation model was shown to produce the highest accuracy in blood SO2. The photoacoustically determined oxygen saturation was found to have an accuracy of +/-4% SO2 for signal amplitude data and +/-2.5% SO2 for effective attenuation spectra. The smallest change in oxygen saturation that can be measured using this technique was +/-1% SO2.

  17. A phantom study on the positioning accuracy of the Novalis Body system.

    PubMed

    Yan, Hui; Yin, Fang-Fang; Kim, Jae Ho

    2003-12-01

    A phantom study was conducted to investigate inherent positioning accuracy of an image-guided patient positioning system-the Novalis Body system for three-dimensional (3-D) conformal radiotherapy. This positioning system consists of two infrared (IR) cameras and one video camera and two kV x-ray imaging devices. The initial patient setup was guided by the IR camera system and the target localization was accomplished using the kV x-ray imaging system. In this study, the IR marker shift and phantom rotation were simulated and their effects on the positioning accuracy were examined by a Rando phantom. The effects of CT slice thickness and treatment sites on the positioning accuracy were tested. In addition, the internal target shift was simulated and its effect on the positioning accuracy was examined by a water tank. With the application of the Novalis Body system, the positioning error of the planned isocenter was significantly reduced. The experimental results with the simulated IR marker shifts indicated that the positioning errors of the planned isocenter were 0.6 +/- 0.3, 0.5 +/- 0.2, and 0.7 +/- 0.2 mm along the lateral, longitudinal, and vertical axes, respectively. The experimental results with the simulated phantom rotations indicated that the positioning errors of the planned isocenter were 0.6 +/- 0.3, 0.7 +/- 0.2, and 0.5 +/- 0.2 mm along the three axes, respectively. The experimental results with the simulated target shifts indicated that the positioning errors of the planned isocenter were 0.6 +/- 0.3, 0.7 +/- 0.2, and 0.5 +/- 0.2 mm along the three axes, respectively. On average, the positioning accuracy of 1 mm for the planned isocenter was achieved using the Novalis Body system.

  18. Income and Well-Being: Relative Income and Absolute Income Weaken Negative Emotion, but Only Relative Income Improves Positive Emotion

    PubMed Central

    Yu, Zonghuo; Chen, Li

    2016-01-01

    Whether relative income or absolute income could affect subjective well-being has been a bone of contention for years. Life satisfaction and the relative frequency of positive and negative emotions are parts of subjective well-being. According to the prospect theory, hedonic adaptation helps to explain why positive emotion is often so hard to be maintained, and negative emotion wouldn’t be easy to be eliminated. So we expect the relationship between income and positive emotion is different from that between income and negative emotion. Given that regional reference is the main comparison mechanism, effects of regional average income on regional average subjective well-being should be potentially zero if only relative income matters. Using multilevel analysis, we tested the hypotheses with a dataset of 30,144 individuals from 162 counties in China. The results suggested that household income at the individual level is associated with life satisfaction, happiness and negative emotions. On the contrary, at a county level, household income is only associated with negative emotion. In other words, happiness and life satisfaction was only associated with relative income, but negative emotion was associated with relative income and absolute income. Without social comparison, income doesn’t improve happiness, but it could weaken negative emotion. Therefore, it is possible for economic growth to weaken negative emotion without improving happiness. These findings also contribute to the current debate about the “Esterling paradox.” PMID:28066312

  19. Income and Well-Being: Relative Income and Absolute Income Weaken Negative Emotion, but Only Relative Income Improves Positive Emotion.

    PubMed

    Yu, Zonghuo; Chen, Li

    2016-01-01

    Whether relative income or absolute income could affect subjective well-being has been a bone of contention for years. Life satisfaction and the relative frequency of positive and negative emotions are parts of subjective well-being. According to the prospect theory, hedonic adaptation helps to explain why positive emotion is often so hard to be maintained, and negative emotion wouldn't be easy to be eliminated. So we expect the relationship between income and positive emotion is different from that between income and negative emotion. Given that regional reference is the main comparison mechanism, effects of regional average income on regional average subjective well-being should be potentially zero if only relative income matters. Using multilevel analysis, we tested the hypotheses with a dataset of 30,144 individuals from 162 counties in China. The results suggested that household income at the individual level is associated with life satisfaction, happiness and negative emotions. On the contrary, at a county level, household income is only associated with negative emotion. In other words, happiness and life satisfaction was only associated with relative income, but negative emotion was associated with relative income and absolute income. Without social comparison, income doesn't improve happiness, but it could weaken negative emotion. Therefore, it is possible for economic growth to weaken negative emotion without improving happiness. These findings also contribute to the current debate about the "Esterling paradox."

  20. Accuracy and stability of positioning in radiosurgery: Long term results of the Gamma Knife system

    SciTech Connect

    Heck, Bernhard; Jess-Hempen, Anja; Kreiner, Hans Juerg; Schoepgens, Hans; Mack, Andreas

    2007-04-15

    The primary aim of this investigation was to determine the long term overall accuracy of an irradiation position of Gamma Knife systems. The mechanical accuracy of the system as well as the overall accuracy of an irradiation position was examined by irradiating radiosensitive films. To measure the mechanical accuracy, the GafChromic registered film was fixed by a special tool at the unit center point (UCP). For overall accuracy the film was mounted inside a phantom at a target position given by a two-dimensional cross. Its position was determined by CT or MRI scans, a treatment was planned to hit this target by use of the standard planning software and the radiation was finally delivered. This procedure is named ''system test'' according to DIN 6875-1 and is equivalent to a treatment simulation. The used GafChromic registered films were evaluated by high resolution densitometric measurements. The Munich Gamma Knife UCP coincided within x;y;z: -0.014{+-}0.09 mm; 0.013{+-}0.09 mm; -0.002{+-}0.06 mm (mean{+-}SD) to the center of dose distribution. There was no trend in the measured data observed over more than ten years. All measured data were within a sphere of 0.2 mm radius. When basing the target definition in the system test on MRI scans, we obtained an overall accuracy of an irradiation position in the x direction of 0.21{+-}0.32 mm and in the y direction 0.15{+-}0.26 mm (mean{+-}SD). When a CT-based target definition was used, we measured distances in x direction 0.06{+-}0.09 mm and in y direction 0.04{+-}0.09 mm (mean{+-}SD), respectively. These results were compared with those obtained with a Gamma Knife equipped with an automatic positioning system (APS) by use of a different phantom. This phantom was found to be slightly less accurate due to its mechanical construction and the soft fixation into the frame. The phantom related position deviation was found to be about {+-}0.2 mm, and therefore the measured accuracy of the APS Gamma Knife was evidently less

  1. Positioning accuracy assessment for the 4GEO/5IGSO/2MEO constellation of COMPASS

    NASA Astrophysics Data System (ADS)

    Zhou, ShanShi; Cao, YueLing; Zhou, JianHua; Hu, XiaoGong; Tang, ChengPan; Liu, Li; Guo, Rui; He, Feng; Chen, JunPing; Wu, Bin

    2012-12-01

    Determined to become a new member of the well-established GNSS family, COMPASS (or BeiDou-2) is developing its capabilities to provide high accuracy positioning services. Two positioning modes are investigated in this study to assess the positioning accuracy of COMPASS' 4GEO/5IGSO/2MEO constellation. Precise Point Positioning (PPP) for geodetic users and real-time positioning for common navigation users are utilized. To evaluate PPP accuracy, coordinate time series repeatability and discrepancies with GPS' precise positioning are computed. Experiments show that COMPASS PPP repeatability for the east, north and up components of a receiver within mainland China is better than 2 cm, 2 cm and 5 cm, respectively. Apparent systematic offsets of several centimeters exist between COMPASS precise positioning and GPS precise positioning, indicating errors remaining in the treatments of COMPASS measurement and dynamic models and reference frame differences existing between two systems. For common positioning users, COMPASS provides both open and authorized services with rapid differential corrections and integrity information available to authorized users. Our assessment shows that in open service positioning accuracy of dual-frequency and single-frequency users is about 5 m and 6 m (RMS), respectively, which may be improved to about 3 m and 4 m (RMS) with the addition of differential corrections. Less accurate Signal In Space User Ranging Error (SIS URE) and Geometric Dilution of Precision (GDOP) contribute to the relatively inferior accuracy of COMPASS as compared to GPS. Since the deployment of the remaining 1 GEO and 2 MEO is not able to significantly improve GDOP, the performance gap could only be overcome either by the use of differential corrections or improvement of the SIS URE, or both.

  2. On the absolute accuracy of Zernike polynomials to characterize the corneal surface and the optical aberrations of the human eye

    NASA Astrophysics Data System (ADS)

    Carvalho, Luis A.

    2005-06-01

    Zernike Polynomials have been successfully used for many years in optics. Nevertheless there are some recent discussions regarding their accuracy when applied to surfaces such as the human cornea. A set of synthetic surfaces resembling several common corneal anomalies was sampled and was also used to compute the optical path difference using a simple ray-tracing procedure. The Root Mean Square Error between the Zernike Polynomials fit and the theoretical elevation and WF error surface was computed for both surfaces and for all number of Zernike terms. We have found that RMSE for the simplest, most symmetric corneal surface (spherical shape) and for the most complex shape (post-radial keratotomy) both the optical path difference and surface elevation, for 1 through 36 Zernike terms, range from: 421.4 to 0.8 microns, and 421.4 to 8.2 microns, respectively; mean RMSE for maximum Zernike terms for both surfaces were 4.5 microns. Computations in this work suggest that, for surfaces such as post-RK, keratoconus or post-keratoplasty, even more than 36 terms may be necessary in order to obtain minimum precision requirements. We suggest that the number of Zernike Polynomial should not be a global fixed conventional value but rather based on specific surface properties.

  3. Combined adjustment of multi-resolution satellite imagery for improved geo-positioning accuracy

    NASA Astrophysics Data System (ADS)

    Tang, Shengjun; Wu, Bo; Zhu, Qing

    2016-04-01

    Due to the widespread availability of satellite imagery nowadays, it is common for regions to be covered by satellite imagery from multiple sources with multiple resolutions. This paper presents a combined adjustment approach to integrate multi-source multi-resolution satellite imagery for improved geo-positioning accuracy without the use of ground control points (GCPs). Instead of using all the rational polynomial coefficients (RPCs) of images for processing, only those dominating the geo-positioning accuracy are used in the combined adjustment. They, together with tie points identified in the images, are used as observations in the adjustment model. Proper weights are determined for each observation, and ridge parameters are determined for better convergence of the adjustment solution. The outputs from the combined adjustment are the improved dominating RPCs of images, from which improved geo-positioning accuracy can be obtained. Experiments using ZY-3, SPOT-7 and Pleiades-1 imagery in Hong Kong, and Cartosat-1 and Worldview-1 imagery in Catalonia, Spain demonstrate that the proposed method is able to effectively improve the geo-positioning accuracy of satellite images. The combined adjustment approach offers an alternative method to improve geo-positioning accuracy of satellite images. The approach enables the integration of multi-source and multi-resolution satellite imagery for generating more precise and consistent 3D spatial information, which permits the comparative and synergistic use of multi-resolution satellite images from multiple sources.

  4. The Positioning Accuracy of BAUV Using Fusion of Data from USBL System and Movement Parameters Measurements.

    PubMed

    Krzysztof, Naus; Aleksander, Nowak

    2016-08-15

    The article presents a study of the accuracy of estimating the position coordinates of BAUV (Biomimetic Autonomous Underwater Vehicle) by the extended Kalman filter (EKF) method. The fusion of movement parameters measurements and position coordinates fixes was applied. The movement parameters measurements are carried out by on-board navigation devices, while the position coordinates fixes are done by the USBL (Ultra Short Base Line) system. The problem of underwater positioning and the conceptual design of the BAUV navigation system constructed at the Naval Academy (Polish Naval Academy-PNA) are presented in the first part of the paper. The second part consists of description of the evaluation results of positioning accuracy, the genesis of the problem of selecting method for underwater positioning, and the mathematical description of the method of estimating the position coordinates using the EKF method by the fusion of measurements with on-board navigation and measurements obtained with the USBL system. The main part contains a description of experimental research. It consists of a simulation program of navigational parameter measurements carried out during the BAUV passage along the test section. Next, the article covers the determination of position coordinates on the basis of simulated parameters, using EKF and DR methods and the USBL system, which are then subjected to a comparative analysis of accuracy. The final part contains systemic conclusions justifying the desirability of applying the proposed fusion method of navigation parameters for the BAUV positioning.

  5. The Positioning Accuracy of BAUV Using Fusion of Data from USBL System and Movement Parameters Measurements

    PubMed Central

    Krzysztof, Naus; Aleksander, Nowak

    2016-01-01

    The article presents a study of the accuracy of estimating the position coordinates of BAUV (Biomimetic Autonomous Underwater Vehicle) by the extended Kalman filter (EKF) method. The fusion of movement parameters measurements and position coordinates fixes was applied. The movement parameters measurements are carried out by on-board navigation devices, while the position coordinates fixes are done by the USBL (Ultra Short Base Line) system. The problem of underwater positioning and the conceptual design of the BAUV navigation system constructed at the Naval Academy (Polish Naval Academy—PNA) are presented in the first part of the paper. The second part consists of description of the evaluation results of positioning accuracy, the genesis of the problem of selecting method for underwater positioning, and the mathematical description of the method of estimating the position coordinates using the EKF method by the fusion of measurements with on-board navigation and measurements obtained with the USBL system. The main part contains a description of experimental research. It consists of a simulation program of navigational parameter measurements carried out during the BAUV passage along the test section. Next, the article covers the determination of position coordinates on the basis of simulated parameters, using EKF and DR methods and the USBL system, which are then subjected to a comparative analysis of accuracy. The final part contains systemic conclusions justifying the desirability of applying the proposed fusion method of navigation parameters for the BAUV positioning. PMID:27537884

  6. Angles-Only Navigation: Position and Velocity Solution from Absolute Triangulation

    DTIC Science & Technology

    2011-01-01

    for automated farming. A specific proposed application for open-sea ship navigation would use the angular posi- tions of Earth satellites observed...navigation would use the angular positions of Earth satellites observed optically against a star background. Such a system could provide a supplement to... Earth , so that observations can be col- lected over extended tracks. The paper is organized by sections as follows. First, some possible applications

  7. Positional Accuracy of Airborne Integrated Global Positioning and Inertial Navigation Systems for Mapping in Glen Canyon, Arizona

    USGS Publications Warehouse

    Sanchez, Richard D.; Hothem, Larry D.

    2002-01-01

    High-resolution airborne and satellite image sensor systems integrated with onboard data collection based on the Global Positioning System (GPS) and inertial navigation systems (INS) may offer a quick and cost-effective way to gather accurate topographic map information without ground control or aerial triangulation. The Applanix Corporation?s Position and Orientation Solutions for Direct Georeferencing of aerial photography was used in this project to examine the positional accuracy of integrated GPS/INS for terrain mapping in Glen Canyon, Arizona. The research application in this study yielded important information on the usefulness and limits of airborne integrated GPS/INS data-capture systems for mapping.

  8. An Effective Approach to Improving Low-Cost GPS Positioning Accuracy in Real-Time Navigation

    PubMed Central

    Islam, Md. Rashedul; Kim, Jong-Myon

    2014-01-01

    Positioning accuracy is a challenging issue for location-based applications using a low-cost global positioning system (GPS). This paper presents an effective approach to improving the positioning accuracy of a low-cost GPS receiver for real-time navigation. The proposed method precisely estimates position by combining vehicle movement direction, velocity averaging, and distance between waypoints using coordinate data (latitude, longitude, time, and velocity) of the GPS receiver. The previously estimated precious reference point, coordinate translation, and invalid data check also improve accuracy. In order to evaluate the performance of the proposed method, we conducted an experiment using a GARMIN GPS 19xHVS receiver attached to a car and used Google Maps to plot the processed data. The proposed method achieved improvement of 4–10 meters in several experiments. In addition, we compared the proposed approach with two other state-of-the-art methods: recursive averaging and ARMA interpolation. The experimental results show that the proposed approach outperforms other state-of-the-art methods in terms of positioning accuracy. PMID:25136679

  9. The effect of different Global Navigation Satellite System methods on positioning accuracy in elite alpine skiing.

    PubMed

    Gilgien, Matthias; Spörri, Jörg; Limpach, Philippe; Geiger, Alain; Müller, Erich

    2014-10-03

    In sport science, Global Navigation Satellite Systems (GNSS) are frequently applied to capture athletes' position, velocity and acceleration. Application of GNSS includes a large range of different GNSS technologies and methods. To date no study has comprehensively compared the different GNSS methods applied. Therefore, the aim of the current study was to investigate the effect of differential and non-differential solutions, different satellite systems and different GNSS signal frequencies on position accuracy. Twelve alpine ski racers were equipped with high-end GNSS devices while performing runs on a giant slalom course. The skiers' GNSS antenna positions were calculated in three satellite signal obstruction conditions using five different GNSS methods. The GNSS antenna positions were compared to a video-based photogrammetric reference system over one turn and against the most valid GNSS method over the entire run. Furthermore, the time for acquisitioning differential GNSS solutions was assessed for four differential methods. The only GNSS method that consistently yielded sub-decimetre position accuracy in typical alpine skiing conditions was a differential method using American (GPS) and Russian (GLONASS) satellite systems and the satellite signal frequencies L1 and L2. Under conditions of minimal satellite signal obstruction, valid results were also achieved when either the satellite system GLONASS or the frequency L2 was dropped from the best configuration. All other methods failed to fulfill the accuracy requirements needed to detect relevant differences in the kinematics of alpine skiers, even in conditions favorable for GNSS measurements. The methods with good positioning accuracy had also the shortest times to compute differential solutions. This paper highlights the importance to choose appropriate methods to meet the accuracy requirements for sport applications.

  10. The Effect of Different Global Navigation Satellite System Methods on Positioning Accuracy in Elite Alpine Skiing

    PubMed Central

    Gilgien, Matthias; Spörri, Jörg; Limpach, Philippe; Geiger, Alain; Müller, Erich

    2014-01-01

    In sport science, Global Navigation Satellite Systems (GNSS) are frequently applied to capture athletes' position, velocity and acceleration. Application of GNSS includes a large range of different GNSS technologies and methods. To date no study has comprehensively compared the different GNSS methods applied. Therefore, the aim of the current study was to investigate the effect of differential and non-differential solutions, different satellite systems and different GNSS signal frequencies on position accuracy. Twelve alpine ski racers were equipped with high-end GNSS devices while performing runs on a giant slalom course. The skiers' GNSS antenna positions were calculated in three satellite signal obstruction conditions using five different GNSS methods. The GNSS antenna positions were compared to a video-based photogrammetric reference system over one turn and against the most valid GNSS method over the entire run. Furthermore, the time for acquisitioning differential GNSS solutions was assessed for four differential methods. The only GNSS method that consistently yielded sub-decimetre position accuracy in typical alpine skiing conditions was a differential method using American (GPS) and Russian (GLONASS) satellite systems and the satellite signal frequencies L1 and L2. Under conditions of minimal satellite signal obstruction, valid results were also achieved when either the satellite system GLONASS or the frequency L2 was dropped from the best configuration. All other methods failed to fulfill the accuracy requirements needed to detect relevant differences in the kinematics of alpine skiers, even in conditions favorable for GNSS measurements. The methods with good positioning accuracy had also the shortest times to compute differential solutions. This paper highlights the importance to choose appropriate methods to meet the accuracy requirements for sport applications. PMID:25285461

  11. Accuracy of velocities from repeated GPS surveys: relative positioning is concerned

    NASA Astrophysics Data System (ADS)

    Duman, Huseyin; Ugur Sanli, D.

    2016-04-01

    Over more than a decade, researchers have been interested in studying the accuracy of GPS positioning solutions. Recently, reporting the accuracy of GPS velocities has been added to this. Researchers studying landslide motion, tectonic motion, uplift, sea level rise, and subsidence still report results from GPS experiments in which repeated GPS measurements from short sessions are used. This motivated some other researchers to study the accuracy of GPS deformation rates/velocities from various repeated GPS surveys. In one of the efforts, the velocity accuracy was derived from repeated GPS static surveys using short observation sessions and Precise Point Positioning mode of GPS software. Velocities from short GPS sessions were compared with the velocities from 24 h sessions. The accuracy of velocities was obtained using statistical hypothesis testing and quantifying the accuracy of least squares estimation models. The results reveal that 45-60 % of the horizontal and none of the vertical solutions comply with the results from 24 h solutions. We argue that this case in which the data was evaluated using PPP should also apply to the case in which the data belonging to long GPS base lengths is processed using fundamental relative point positioning. To test this idea we chose the two IGS stations ANKR and NICO and derive their velocities from the reference stations held fixed in the stable EURASIAN plate. The University of Bern's GNSS software BERNESE was used to produce relative positioning solutions, and the results are compared with those of GIPSY/OASIS II PPP results. First impressions indicate that it is worth designing a global experiment and test these ideas in detail.

  12. Teaching High-Accuracy Global Positioning System to Undergraduates Using Online Processing Services

    ERIC Educational Resources Information Center

    Wang, Guoquan

    2013-01-01

    High-accuracy Global Positioning System (GPS) has become an important geoscientific tool used to measure ground motions associated with plate movements, glacial movements, volcanoes, active faults, landslides, subsidence, slow earthquake events, as well as large earthquakes. Complex calculations are required in order to achieve high-precision…

  13. Portable device to assess dynamic accuracy of global positioning systems (GPS) receivers used in agricultural aircraft

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A device was designed to test the dynamic accuracy of Global Positioning System (GPS) receivers used in aerial vehicles. The system works by directing a sun-reflected light beam from the ground to the aircraft using mirrors. A photodetector is placed pointing downward from the aircraft and circuitry...

  14. The Impact of Ionospheric Disturbances on High Accuracy Positioning in Brazil

    NASA Astrophysics Data System (ADS)

    Yang, L.; Park, J.; Susnik, A.; Aquino, M. H.; Dodson, A.

    2013-12-01

    High positioning accuracy is a key requirement to a number of applications with a high economic impact, such as precision agriculture, surveying, geodesy, land management, off-shore operations. Global Navigation Satellite Systems (GNSS) carrier phase measurement based techniques, such as Real Time Kinematic (RTK), Network-RTK (NRTK) and Precise Point Positioning (PPP), have played an important role in providing centimetre-level positioning accuracy, and become the core of the above applications. However these techniques are especially sensitive to ionospheric perturbations, in particular scintillation. Brazil sits in one of the most affected regions of the Earth and can be regarded as a test-bed for scenarios of the severe ionospheric condition. Over the Brazilian territory, the ionosphere behaves in a considerably unpredictable way and scintillation activity is very prominent, occurring especially after sunset hours. NRTK services may not be able to provide satisfactory accuracy, or even continuous positioning during strong scintillation periods. CALIBRA (Countering GNSS high Accuracy applications Limitations due to Ionospheric disturbances in BRAzil) started in late 2012 and is a project funded by the GSA (European GNSS Agency) and the European Commission under the Framework Program 7 to deliver improvements on carrier phase based high accuracy algorithms and their implementation in GNSS receivers, aiming to counter the adverse ionospheric effects over Brazil. As the first stage of this project, the ionospheric disturbances, which affect the applications of RTK, NRTK or PPP, are characterized. Typical problems include degraded positioning accuracy, difficulties in ambiguity fixing, NRTK network interpolation errors, long PPP convergence time etc. It will identify how GNSS observables and existing algorithms are degraded by ionosphere related phenomena, evaluating the impact on positioning techniques in terms of accuracy, integrity and availability. Through the

  15. Positioning Accuracy in Stereotactic Radiotherapy Using a Mask System With Added Vacuum Mouth Piece and Stereoscopic X-Ray Positioning

    SciTech Connect

    Santvoort, Jan van Wiggenraad, Ruud; Bos, Petra

    2008-09-01

    Purpose: For cranial patients receiving stereotactic radiotherapy, we use the Exactrac stereoscopic X-ray system to optimize patient positioning. Patients are immobilized with the BrainLAB Mask System (BrainLAB, Feldkirchen, Germany). We have developed an adapter to this system that accommodates a vacuum mouth piece (VMP). Measurements with the Exactrac system have been performed to study the positioning accuracy after corrections with this system and to evaluate the accuracy of the VMP vs. the standard available upper jaw support (UJS). Methods and Materials: Positioning results were collected for 20 patients with the UJS and 20 patients with the VMP, before treatment (1,122 fractions) and after treatment (400 fractions). For all 6 degrees of freedom the average, the random error and systematic error were calculated. Results: The average vector length before and after correction with the Exactrac system was 2.1 {+-} 1.2 mm and 0.7 {+-} 0.6 mm respectively for UJS and 1.7 {+-} 0.7 mm and 0.4 {+-} 0.4 mm for VMP. Interfraction positioning for translations was greatly improved after correction with the Exactrac system (p < 0.0005) and is better with VMP than with UJS (p = 0.005). Outliers were greatly reduced. Interfraction rotations were significantly smaller for VMP. Intrafraction errors for vertical and longitudinal translations and for rotations were smaller for the VMP. Conclusions: Positioning correction using the Exactrac X-ray system greatly improves accuracy. Adding the VMP results in even better patient fixation and smaller rotations, making it a useful addition to the Mask System. Combined, this is a convenient and accurate alternative to invasive fixation methods.

  16. High accuracy position response calibration method for a micro-channel plate ion detector

    NASA Astrophysics Data System (ADS)

    Hong, R.; Leredde, A.; Bagdasarova, Y.; Fléchard, X.; García, A.; Müller, P.; Knecht, A.; Liénard, E.; Kossin, M.; Sternberg, M. G.; Swanson, H. E.; Zumwalt, D. W.

    2016-11-01

    We have developed a position response calibration method for a micro-channel plate (MCP) detector with a delay-line anode position readout scheme. Using an in situ calibration mask, an accuracy of 8 μm and a resolution of 85 μm (FWHM) have been achieved for MeV-scale α particles and ions with energies of ∼10 keV. At this level of accuracy, the difference between the MCP position responses to high-energy α particles and low-energy ions is significant. The improved performance of the MCP detector can find applications in many fields of AMO and nuclear physics. In our case, it helps reducing systematic uncertainties in a high-precision nuclear β-decay experiment.

  17. Accuracy analysis of a mobile tracking system for angular position determination of flying targets

    NASA Astrophysics Data System (ADS)

    Walther, Andreas; Buske, Ivo; Riede, Wolfgang

    2016-10-01

    Lasers arouse an increasing interest in remote sensing applications. In order to deliver as much as possible of the available laser power onto a flying object the subsystems of a beam control system have to operate precisely together. One important subsystem is responsible for determination of the target's angular position. Here, we focus on an optical system for measuring precisely the angular position of flying objects. We designed this subunit of a beam control system exclusively from readily available commercial-off-the-shelf components. Two industrial cameras were used for angle measuring and for guiding the system to the position of the flying object. Both cameras are mounted on a modified astronomical mount with high-precision angle encoders. To achieve a high accuracy we temporally synchronize the acquisition of the angle from the pan tilt unit with the exposure of the camera. Therefore, a FPGA-based readout device for the rotary encoders was designed and implemented. Additionally, we determined and evaluated the influence of the distortion of the lenses to the measurement. We investigated various scenarios to determine the accuracy and the limitations of our system for angular position determination of flying targets. Performance tests were taken indoor and outdoor at our test sites. A target can be mounted on a fast moving linear stage. The position of this linear stage is continuously read out by a high resolution encoder so we know the target's position with a dynamic accuracy in the range of a few μm. With this setup we evaluated the spatial resolution of our tracking system. We showed that the presented system can determine the angular position of fast flying objects with an uncertainty of only 2 μrad RMS. With this mobile tracking system for angular position determination of flying targets we designed an accurate cost-efficient opportunity for further developments.

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

    NASA Technical Reports Server (NTRS)

    Hill, J. E.; Angelini, L.; Moretti, A.; Morris, D. C.; Racusin, J.; Burrows, D. N.; Beardmore, A. P.; Campana, S.; Capalbi, M.; Kennea, J. A.

    2005-01-01

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

  19. SU-E-T-33: An EPID-Based Method for Testing Absolute Leaf Position for MLC Without Backup Jaws

    SciTech Connect

    Hancock, S; Whitaker, M

    2014-06-01

    Purpose: Methods in common use for MLC leaf position QA are limited to measurements relative to an arbitrary reference position. The authors previously presented an EPID-based method for efficiently testing accuracy of leaf position relative to the mechanical isocenter for MLC with backup jaws. The purpose of this work is to extend that method to the general case of MLC without backup jaws. Methods: A pair of collimator walkout images is used to determine the location of the mechanical isocenter relative to the center of one field using a parameter called X-offset. The method allows for shift of the imager panel to cover subsets of MLC leaves within the limited field of view of the imager. For a shifted panel position, an image of three beam strips defined by a subset of MLC leaves allows determination of the position of each leaf relative to the isocenter. The location of the isocenter is determined by applying X-offset to an image of a single rectangular field obtained at that panel position. The method can also be used to test backup jaws instead of MLC leaves. A software tool was developed to efficiently analyze the images. Results: The software tool reports leaf position and deviation from nominal position, and provides visual displays to facilitate rapid qualitative interpretation. Test results using this method agree well with results using the previous method requiring backup jaws. Test results have been successfully used to recalibrate one model MLC (Elekta MLCi2™). Work in progress includes extension of the software tool to other MLC models, and quantification of reproducibility of the measurements. Conclusion: This work successfully demonstrates a method to efficiently and accurately measure MLC leaf position, or backup jaw position, relative to the mechanical isocenter of the collimator.

  20. Relationship of hand preference to accuracy on a thumb-positioning task.

    PubMed

    Riolo-Quinn, L

    1991-08-01

    This study was designed to examine the relationship of hand preference to performance on a thumb-positioning task. Two hypotheses were proposed on the basis of hemispheric lateralization. The first stated that all subjects would perform the task more accurately using the left thumb, regardless of hand preference. The second hypothesis tested was that left-handed subjects would perform more accurately than right-handed subjects. Each of 20 neurologically intact adults grouped by hand preference reproduced a criterion thumb position with both thumbs simultaneously. Absolute error, recorded for each movement and analyzed by mixed analysis of variance, did support the first hypothesis. However, the left-handed group did not perform statistically differently from right-handed subjects. Factors influencing the data are discussed and recommendations for further studies are made.

  1. Absolute Zero

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell J.; Sheibley, D.; Belloni, M.; Stamper-Kurn, D.; Vinen, W. F.

    2006-12-01

    Absolute Zero is a two hour PBS special attempting to bring to the general public some of the advances made in 400 years of thermodynamics. It is based on the book “Absolute Zero and the Conquest of Cold” by Tom Shachtman. Absolute Zero will call long-overdue attention to the remarkable strides that have been made in low-temperature physics, a field that has produced 27 Nobel Prizes. It will explore the ongoing interplay between science and technology through historical examples including refrigerators, ice machines, frozen foods, liquid oxygen and nitrogen as well as much colder fluids such as liquid hydrogen and liquid helium. A website has been established to promote the series: www.absolutezerocampaign.org. It contains information on the series, aimed primarily at students at the middle school level. There is a wealth of material here and we hope interested teachers will draw their student’s attention to this website and its substantial contents, which have been carefully vetted for accuracy.

  2. Enhanced Positioning Algorithm of ARPS for Improving Accuracy and Expanding Service Coverage

    PubMed Central

    Lee, Kyuman; Baek, Hoki; Lim, Jaesung

    2016-01-01

    The airborne relay-based positioning system (ARPS), which employs the relaying of navigation signals, was proposed as an alternative positioning system. However, the ARPS has limitations, such as relatively large vertical error and service restrictions, because firstly, the user position is estimated based on airborne relays that are located in one direction, and secondly, the positioning is processed using only relayed navigation signals. In this paper, we propose an enhanced positioning algorithm to improve the performance of the ARPS. The main idea of the enhanced algorithm is the adaptable use of either virtual or direct measurements of reference stations in the calculation process based on the structural features of the ARPS. Unlike the existing two-step algorithm for airborne relay and user positioning, the enhanced algorithm is divided into two cases based on whether the required number of navigation signals for user positioning is met. In the first case, where the number of signals is greater than four, the user first estimates the positions of the airborne relays and its own initial position. Then, the user position is re-estimated by integrating a virtual measurement of a reference station that is calculated using the initial estimated user position and known reference positions. To prevent performance degradation, the re-estimation is performed after determining its requirement through comparing the expected position errors. If the navigation signals are insufficient, such as when the user is outside of airborne relay coverage, the user position is estimated by additionally using direct signal measurements of the reference stations in place of absent relayed signals. The simulation results demonstrate that a higher accuracy level can be achieved because the user position is estimated based on the measurements of airborne relays and a ground station. Furthermore, the service coverage is expanded by using direct measurements of reference stations for user

  3. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  4. Accuracy of an acoustic location system for monitoring the position of duetting songbirds in tropical forest

    PubMed Central

    Mennill, Daniel J.; Burt, John M.; Fristrup, Kurt M.; Vehrencamp, Sandra L.

    2008-01-01

    A field test was conducted on the accuracy of an eight-microphone acoustic location system designed to triangulate the position of duetting rufous-and-white wrens (Thryothorus rufalbus) in Costa Rica’s humid evergreen forest. Eight microphones were set up in the breeding territories of twenty pairs of wrens, with an average inter-microphone distance of 75.2±2.6 m. The array of microphones was used to record antiphonal duets broadcast through stereo loudspeakers. The positions of the loudspeakers were then estimated by evaluating the delay with which the eight microphones recorded the broadcast sounds. Position estimates were compared to coordinates surveyed with a global-positioning system (GPS). The acoustic location system estimated the position of loudspeakers with an error of 2.82±0.26 m and calculated the distance between the “male” and “female” loudspeakers with an error of 2.12±0.42 m. Given the large range of distances between duetting birds, this relatively low level of error demonstrates that the acoustic location system is a useful tool for studying avian duets. Location error was influenced partly by the difficulties inherent in collecting high accuracy GPS coordinates of microphone positions underneath a lush tropical canopy, and partly by the complicating influence of irregular topography and thick vegetation on sound transmission. PMID:16708941

  5. Accuracies of Positioning and Geodata Using Helicopters for Geodetic and Geophysical Surveys

    NASA Astrophysics Data System (ADS)

    Bielenberg, O.; Meyer, U.; Vasterling, M.

    2010-12-01

    : Helicopters are frequently used for airborne surveys in geodesy and geophysics. The range of accuracies needed for proper data reconstruction is wide spread from some meters for airborne magnetics to centimeters for laser scanner measurements. This study lists up to date methods of online and offline positioning, discusses their accuracies that may be achieved and relates them to different geodetic as geophysical surveys in different types of terrain. The goal is to match helicopter positioning methods with the given survey task to optimize results and work efficiency. Some fundamental studies have been conducted on helicopter work during the DESIRE (Dead Sea Integrated Research) project in Israel and Jordan which have been continued in Germany. These studies include the impact of vibrations on INS, IMU and gravity meter systems as well as the choice of antenna locations on the shell of the helicopter.

  6. Accuracy in GPS/Acoustic positioning on a moored buoy moving around far from the optimal position

    NASA Astrophysics Data System (ADS)

    Imano, M.; Kido, M.; Ohta, Y.; Takahashi, N.; Fukuda, T.; Ochi, H.; Hino, R.

    2015-12-01

    For detecting the seafloor crustal deformation and Tsunami associated with large earthquakes in real-time, it is necessary to monitor them just above the possible source region. For this purpose, we have been dedicated in developing a real-time continuous observation system using a multi-purpose moored buoy. Sea-trials of the system have been carried out near the Nanakai trough in 2013 and 2014 (Takahashi et al., 2014). We especially focused on the GPS/Acoustic measurement (GPS/A) in the system for horizontal crustal movement. The GPS/A on a moored buoy has a critical drawback compared to the traditional ones, in which the data can be stacked over ranging points fixed at an optimal position. Accuracy in positioning with a single ranging from an arbitrary point is the subject to be improved in this study. Here, we report the positioning results in the buoy system using data in the 2014 sea-trial and demonstrate the improvement of the result. We also address the potential resolving power in the positioning using synthetic tests. The target GPS/A site consists of six seafloor transponders (PXPs) forming a small inner- and a large outer-triangles. The bottom of the moored cable is anchored nearly the center of the triangles. In the sea-trial, 11 times successive ranging was scheduled once a week, and we plotted positioning results from different buoy position. We confirmed that scatter in positioning using six PXPs simultaneously is ten times smaller than that using individual triangle separately. Next, we modified the definition of the PXP array geometry using data obtained in a campaign observation. Definition of an array geometry is insensitive as far as ranging is made in the same position, however, severely affects the positioning when ranging is made from various positions like the moored buoy. The modified PXP array is slightly smaller and 2m deeper than the original one. We found that the scatter of positioning results in the sea-trial is reduced from 4m to 1

  7. Position Accuracy Improvement by Implementing the DGNSS-CP Algorithm in Smartphones

    PubMed Central

    Yoon, Donghwan; Kee, Changdon; Seo, Jiwon; Park, Byungwoon

    2016-01-01

    The position accuracy of Global Navigation Satellite System (GNSS) modules is one of the most significant factors in determining the feasibility of new location-based services for smartphones. Considering the structure of current smartphones, it is impossible to apply the ordinary range-domain Differential GNSS (DGNSS) method. Therefore, this paper describes and applies a DGNSS-correction projection method to a commercial smartphone. First, the local line-of-sight unit vector is calculated using the elevation and azimuth angle provided in the position-related output of Android’s LocationManager, and this is transformed to Earth-centered, Earth-fixed coordinates for use. To achieve position-domain correction for satellite systems other than GPS, such as GLONASS and BeiDou, the relevant line-of-sight unit vectors are used to construct an observation matrix suitable for multiple constellations. The results of static and dynamic tests show that the standalone GNSS accuracy is improved by about 30%–60%, thereby reducing the existing error of 3–4 m to just 1 m. The proposed algorithm enables the position error to be directly corrected via software, without the need to alter the hardware and infrastructure of the smartphone. This method of implementation and the subsequent improvement in performance are expected to be highly effective to portability and cost saving. PMID:27322284

  8. Position Accuracy Improvement by Implementing the DGNSS-CP Algorithm in Smartphones.

    PubMed

    Yoon, Donghwan; Kee, Changdon; Seo, Jiwon; Park, Byungwoon

    2016-06-18

    The position accuracy of Global Navigation Satellite System (GNSS) modules is one of the most significant factors in determining the feasibility of new location-based services for smartphones. Considering the structure of current smartphones, it is impossible to apply the ordinary range-domain Differential GNSS (DGNSS) method. Therefore, this paper describes and applies a DGNSS-correction projection method to a commercial smartphone. First, the local line-of-sight unit vector is calculated using the elevation and azimuth angle provided in the position-related output of Android's LocationManager, and this is transformed to Earth-centered, Earth-fixed coordinates for use. To achieve position-domain correction for satellite systems other than GPS, such as GLONASS and BeiDou, the relevant line-of-sight unit vectors are used to construct an observation matrix suitable for multiple constellations. The results of static and dynamic tests show that the standalone GNSS accuracy is improved by about 30%-60%, thereby reducing the existing error of 3-4 m to just 1 m. The proposed algorithm enables the position error to be directly corrected via software, without the need to alter the hardware and infrastructure of the smartphone. This method of implementation and the subsequent improvement in performance are expected to be highly effective to portability and cost saving.

  9. A new source difference artificial neural network for enhanced positioning accuracy

    NASA Astrophysics Data System (ADS)

    Bhatt, Deepak; Aggarwal, Priyanka; Devabhaktuni, Vijay; Bhattacharya, Prabir

    2012-10-01

    Integrated inertial navigation system (INS) and global positioning system (GPS) units provide reliable navigation solution compared to standalone INS or GPS. Traditional Kalman filter-based INS/GPS integration schemes have several inadequacies related to sensor error model and immunity to noise. Alternatively, multi-layer perceptron (MLP) neural networks with three layers have been implemented to improve the position accuracy of the integrated system. However, MLP neural networks show poor accuracy for low-cost INS because of the large inherent sensor errors. For the first time the paper demonstrates the use of knowledge-based source difference artificial neural network (SDANN) to improve navigation performance of low-cost sensor, with or without external aiding sources. Unlike the conventional MLP or artificial neural networks (ANN), the structure of SDANN consists of two MLP neural networks called the coarse model and the difference model. The coarse model learns the input-output data relationship whereas the difference model adds knowledge to the system and fine-tunes the coarse model output by learning the associated training or estimation error. Our proposed SDANN model illustrated a significant improvement in navigation accuracy of up to 81% over conventional MLP. The results demonstrate that the proposed SDANN method is effective for GPS/INS integration schemes using low-cost inertial sensors, with and without GPS.

  10. Influence of Pedometer Position on Pedometer Accuracy at Various Walking Speeds: A Comparative Study

    PubMed Central

    Lovis, Christian

    2016-01-01

    Background Demographic growth in conjunction with the rise of chronic diseases is increasing the pressure on health care systems in most OECD countries. Physical activity is known to be an essential factor in improving or maintaining good health. Walking is especially recommended, as it is an activity that can easily be performed by most people without constraints. Pedometers have been extensively used as an incentive to motivate people to become more active. However, a recognized problem with these devices is their diminishing accuracy associated with decreased walking speed. The arrival on the consumer market of new devices, worn indifferently either at the waist, wrist, or as a necklace, gives rise to new questions regarding their accuracy at these different positions. Objective Our objective was to assess the performance of 4 pedometers (iHealth activity monitor, Withings Pulse O2, Misfit Shine, and Garmin vívofit) and compare their accuracy according to their position worn, and at various walking speeds. Methods We conducted this study in a controlled environment with 21 healthy adults required to walk 100 m at 3 different paces (0.4 m/s, 0.6 m/s, and 0.8 m/s) regulated by means of a string attached between their legs at the level of their ankles and a metronome ticking the cadence. To obtain baseline values, we asked the participants to walk 200 m at their own pace. Results A decrease of accuracy was positively correlated with reduced speed for all pedometers (12% mean error at self-selected pace, 27% mean error at 0.8 m/s, 52% mean error at 0.6 m/s, and 76% mean error at 0.4 m/s). Although the position of the pedometer on the person did not significantly influence its accuracy, some interesting tendencies can be highlighted in 2 settings: (1) positioning the pedometer at the waist at a speed greater than 0.8 m/s or as a necklace at preferred speed tended to produce lower mean errors than at the wrist position; and (2) at a slow speed (0.4 m/s), pedometers

  11. Laser adjustable actuators for high-accuracy positioning of micro components

    NASA Astrophysics Data System (ADS)

    Esser, Gerd; Schmidt, Michael; Dirscherl, Manfred

    2003-11-01

    High-precision adjustment of smallest optical and electronic components is increasingly recognized as one of the key issues facing micromachining technology. As even narrow production tolerances for all individual parts are often not sufficient to match the tightly specified positioning accuracies of the complete assembly, in situ adjustment techniques are gaining more and more attention. Together with research partners from industry and science, the BLZ is developing a contact-free, laser-based adjustment method which allows high-accuracy adjustment of components mounted on specifically designed actuators. The underlying mechanisms do not depend on thermal effects but on selective laser ablation of prestressed layers of actuator substrate. This way, slightest deformations or modifications of particular mechanical properties can be initiated. The method promises to be more accurate and less time consuming than thermally induced laser bending.

  12. Validation of dosimetric field matching accuracy from proton therapy using a robotic patient positioning system.

    PubMed

    Farr, Jonathan B; O'Ryan-Blair, Avril; Jesseph, Frederick; Hsi, Wen-Chien; Allgower, Chris E; Mascia, Anthony E; Thornton, Allan F; Schreuder, Andreas N

    2010-04-12

    Large area, shallow fields are well suited to proton therapy. However, due to beam production limitations, such volumes typically require multiple matched fields. This is problematic due to the relatively narrow beam penumbra at shallow depths compared to electron and photon beams. Therefore, highly accurate dose planning and delivery is required. As the dose delivery includes shifting the patient for matched fields, accuracy at the 1-2 millimeter level in patient positioning is also required. This study investigates the dosimetric accuracy of such proton field matching by an innovative robotic patient positioner system (RPPS). The dosimetric comparisons were made between treatment planning system calculations, radiographic film and ionization chamber measurements. The results indicated good agreement amongst the methods and suggest that proton field matching by a RPPS is accurate and efficient.

  13. Multi-sensor fusion with interacting multiple model filter for improved aircraft position accuracy.

    PubMed

    Cho, Taehwan; Lee, Changho; Choi, Sangbang

    2013-03-27

    The International Civil Aviation Organization (ICAO) has decided to adopt Communications, Navigation, and Surveillance/Air Traffic Management (CNS/ATM) as the 21st century standard for navigation. Accordingly, ICAO members have provided an impetus to develop related technology and build sufficient infrastructure. For aviation surveillance with CNS/ATM, Ground-Based Augmentation System (GBAS), Automatic Dependent Surveillance-Broadcast (ADS-B), multilateration (MLAT) and wide-area multilateration (WAM) systems are being established. These sensors can track aircraft positions more accurately than existing radar and can compensate for the blind spots in aircraft surveillance. In this paper, we applied a novel sensor fusion method with Interacting Multiple Model (IMM) filter to GBAS, ADS-B, MLAT, and WAM data in order to improve the reliability of the aircraft position. Results of performance analysis show that the position accuracy is improved by the proposed sensor fusion method with the IMM filter.

  14. Estimated results analysis and application of the precise point positioning based high-accuracy ionosphere delay

    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.

  15. Multi-Sensor Fusion with Interacting Multiple Model Filter for Improved Aircraft Position Accuracy

    PubMed Central

    Cho, Taehwan; Lee, Changho; Choi, Sangbang

    2013-01-01

    The International Civil Aviation Organization (ICAO) has decided to adopt Communications, Navigation, and Surveillance/Air Traffic Management (CNS/ATM) as the 21st century standard for navigation. Accordingly, ICAO members have provided an impetus to develop related technology and build sufficient infrastructure. For aviation surveillance with CNS/ATM, Ground-Based Augmentation System (GBAS), Automatic Dependent Surveillance-Broadcast (ADS-B), multilateration (MLAT) and wide-area multilateration (WAM) systems are being established. These sensors can track aircraft positions more accurately than existing radar and can compensate for the blind spots in aircraft surveillance. In this paper, we applied a novel sensor fusion method with Interacting Multiple Model (IMM) filter to GBAS, ADS-B, MLAT, and WAM data in order to improve the reliability of the aircraft position. Results of performance analysis show that the position accuracy is improved by the proposed sensor fusion method with the IMM filter. PMID:23535715

  16. Mapping stream habitats with a global positioning system: Accuracy, precision, and comparison with traditional methods

    USGS Publications Warehouse

    Dauwalter, D.C.; Fisher, W.L.; Belt, K.C.

    2006-01-01

    We tested the precision and accuracy of the Trimble GeoXT??? global positioning system (GPS) handheld receiver on point and area features and compared estimates of stream habitat dimensions (e.g., lengths and areas of riffles and pools) that were made in three different Oklahoma streams using the GPS receiver and a tape measure. The precision of differentially corrected GPS (DGPS) points was not affected by the number of GPS position fixes (i.e., geographic location estimates) averaged per DGPS point. Horizontal error of points ranged from 0.03 to 2.77 m and did not differ with the number of position fixes per point. The error of area measurements ranged from 0.1% to 110.1% but decreased as the area increased. Again, error was independent of the number of position fixes averaged per polygon corner. The estimates of habitat lengths, widths, and areas did not differ when measured using two methods of data collection (GPS and a tape measure), nor did the differences among methods change at three stream sites with contrasting morphologies. Measuring features with a GPS receiver was up to 3.3 times faster on average than using a tape measure, although signal interference from high streambanks or overhanging vegetation occasionally limited satellite signal availability and prolonged measurements with a GPS receiver. There were also no differences in precision of habitat dimensions when mapped using a continuous versus a position fix average GPS data collection method. Despite there being some disadvantages to using the GPS in stream habitat studies, measuring stream habitats with a GPS resulted in spatially referenced data that allowed the assessment of relative habitat position and changes in habitats over time, and was often faster than using a tape measure. For most spatial scales of interest, the precision and accuracy of DGPS data are adequate and have logistical advantages when compared to traditional methods of measurement. ?? 2006 Springer Science+Business Media

  17. The Quantitative Relationship Between ISO 15197 Accuracy Criteria and Mean Absolute Relative Difference (MARD) in the Evaluation of Analytical Performance of Self-Monitoring of Blood Glucose (SMBG) Systems.

    PubMed

    Pardo, Scott; Simmons, David A

    2016-09-01

    The relationship between International Organization for Standardization (ISO) accuracy criteria and mean absolute relative difference (MARD), 2 methods for assessing the accuracy of blood glucose meters, is complex. While lower MARD values are generally better than higher MARD values, it is not possible to define a particular MARD value that ensures a blood glucose meter will satisfy the ISO accuracy criteria. The MARD value that ensures passing the ISO accuracy test can be described only as a probabilistic range. In this work, a Bayesian model is presented to represent the relationship between ISO accuracy criteria and MARD. Under the assumptions made in this work, there is nearly a 100% chance of satisfying ISO 15197:2013 accuracy requirements if the MARD value is between 3.25% and 5.25%.

  18. Absolute Photometry

    NASA Astrophysics Data System (ADS)

    Hartig, George

    1990-12-01

    The absolute sensitivity of the FOS will be determined in SV by observing 2 stars at 3 epochs, first in 3 apertures (1.0", 0.5", and 0.3" circular) and then in 1 aperture (1.0" circular). In cycle 1, one star, BD+28D4211 will be observed in the 1.0" aperture to establish the stability of the sensitivity and flat field characteristics and improve the accuracy obtained in SV. This star will also be observed through the paired apertures since these are not calibrated in SV. The stars will be observed in most detector/grating combinations. The data will be averaged to form the inverse sensitivity functions required by RSDP.

  19. High accuracy integrated global positioning system/inertial navigation system LDRD: Final report

    SciTech Connect

    Owen, T.E.; Meindl, M.A.; Fellerhoff, J.R.

    1997-03-01

    This report contains the results of a Sandia National Laboratories Directed Research and Development (LDRD) program to investigate the integration of Global Positioning System (GPS) and inertial navigation system (INS) technologies toward the goal of optimizing the navigational accuracy of the combined GPSANS system. The approach undertaken is to integrate the data from an INS, which has long term drifts, but excellent short term accuracy, with GPS carrier phase signal information, which is accurate to the sub-centimeter level, but requires continuous tracking of the GPS signals. The goal is to maintain a sub-meter accurate navigation solution while the vehicle is in motion by using the GPS measurements to estimate the INS navigation errors and then using the refined INS data to aid the GPS carrier phase cycle slip detection and correction and bridge dropouts in the GPS data. The work was expanded to look at GPS-based attitude determination, using multiple GPS receivers and antennas on a single platform, as a possible navigation aid. Efforts included not only the development of data processing algorithms and software, but also the collection and analysis of GPS and INS flight data aboard a Twin Otter aircraft. Finally, the application of improved navigation system accuracy to synthetic aperture radar (SAR) target location is examined.

  20. Accuracy of relative positioning by interferometry with GPS Double-blind test results

    NASA Technical Reports Server (NTRS)

    Counselman, C. C., III; Gourevitch, S. A.; Herring, T. A.; King, B. W.; Shapiro, I. I.; Cappallo, R. J.; Rogers, A. E. E.; Whitney, A. R.; Greenspan, R. L.; Snyder, R. E.

    1983-01-01

    MITES (Miniature Interferometer Terminals for Earth Surveying) observations conducted on December 17 and 29, 1980, are analyzed. It is noted that the time span of the observations used on each day was 78 minutes, during which five satellites were always above 20 deg elevation. The observations are analyzed to determine the intersite position vectors by means of the algorithm described by Couselman and Gourevitch (1981). The average of the MITES results from the two days is presented. The rms differences between the two determinations of the components of the three vectors, which were about 65, 92, and 124 m long, were 8 mm for the north, 3 mm for the east, and 6 mm for the vertical. It is concluded that, at least for short distances, relative positioning by interferometry with GPS can be done reliably with subcentimeter accuracy.

  1. Effect of Traffic Position Accuracy for Conducting Safe Airport Surface Operations

    NASA Technical Reports Server (NTRS)

    Jones, Denise R.; Prinzel, Lawrence J., III; Bailey, Randall E.; Arthur, Jarvis J., III; Barnes, James R.

    2014-01-01

    The Next Generation Air Transportation System (NextGen) concept proposes many revolutionary operational concepts and technologies, such as display of traffic information and movements, airport moving maps (AMM), and proactive alerts of runway incursions and surface traffic conflicts, to deliver an overall increase in system capacity and safety. A piloted simulation study was conducted at the National Aeronautics and Space Administration (NASA) Langley Research Center to evaluate the ability to conduct safe and efficient airport surface operations while utilizing an AMM displaying traffic of various position accuracies as well as the effect of traffic position accuracy on airport conflict detection and resolution (CD&R) capability. Nominal scenarios and off-nominal conflict scenarios were conducted using 12 airline crews operating in a simulated Memphis International Airport terminal environment. The data suggest that all traffic should be shown on the airport moving map, whether qualified or unqualified, and conflict detection and resolution technologies provide significant safety benefits. Despite the presence of traffic information on the map, collisions or near collisions still occurred; when indications or alerts were generated in these same scenarios, the incidences were averted.

  2. Stimulus Probability Effects in Absolute Identification

    ERIC Educational Resources Information Center

    Kent, Christopher; Lamberts, Koen

    2016-01-01

    This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of…

  3. Exploring the Relationship between Absolute and Relative Position and Late-Life Depression: Evidence from 10 European Countries

    ERIC Educational Resources Information Center

    Ladin, Keren; Daniels, Norman; Kawachi, Ichiro

    2010-01-01

    Purpose: Socioeconomic inequality has been associated with higher levels of morbidity and mortality. This study explores the role of absolute and relative deprivation in predicting late-life depression on both individual and country levels. Design and Methods: Country- and individual-level inequality indicators were used in multivariate logistic…

  4. Millimetre Level Accuracy GNSS Positioning with the Blind Adaptive Beamforming Method in Interference Environments.

    PubMed

    Daneshmand, Saeed; Marathe, Thyagaraja; Lachapelle, Gérard

    2016-10-31

    The use of antenna arrays in Global Navigation Satellite System (GNSS) applications is gaining significant attention due to its superior capability to suppress both narrowband and wideband interference. However, the phase distortions resulting from array processing may limit the applicability of these methods for high precision applications using carrier phase based positioning techniques. This paper studies the phase distortions occurring with the adaptive blind beamforming method in which satellite angle of arrival (AoA) information is not employed in the optimization problem. To cater to non-stationary interference scenarios, the array weights of the adaptive beamformer are continuously updated. The effects of these continuous updates on the tracking parameters of a GNSS receiver are analyzed. The second part of this paper focuses on reducing the phase distortions during the blind beamforming process in order to allow the receiver to perform carrier phase based positioning by applying a constraint on the structure of the array configuration and by compensating the array uncertainties. Limitations of the previous methods are studied and a new method is proposed that keeps the simplicity of the blind beamformer structure and, at the same time, reduces tracking degradations while achieving millimetre level positioning accuracy in interference environments. To verify the applicability of the proposed method and analyze the degradations, array signals corresponding to the GPS L1 band are generated using a combination of hardware and software simulators. Furthermore, the amount of degradation and performance of the proposed method under different conditions are evaluated based on Monte Carlo simulations.

  5. Millimetre Level Accuracy GNSS Positioning with the Blind Adaptive Beamforming Method in Interference Environments

    PubMed Central

    Daneshmand, Saeed; Marathe, Thyagaraja; Lachapelle, Gérard

    2016-01-01

    The use of antenna arrays in Global Navigation Satellite System (GNSS) applications is gaining significant attention due to its superior capability to suppress both narrowband and wideband interference. However, the phase distortions resulting from array processing may limit the applicability of these methods for high precision applications using carrier phase based positioning techniques. This paper studies the phase distortions occurring with the adaptive blind beamforming method in which satellite angle of arrival (AoA) information is not employed in the optimization problem. To cater to non-stationary interference scenarios, the array weights of the adaptive beamformer are continuously updated. The effects of these continuous updates on the tracking parameters of a GNSS receiver are analyzed. The second part of this paper focuses on reducing the phase distortions during the blind beamforming process in order to allow the receiver to perform carrier phase based positioning by applying a constraint on the structure of the array configuration and by compensating the array uncertainties. Limitations of the previous methods are studied and a new method is proposed that keeps the simplicity of the blind beamformer structure and, at the same time, reduces tracking degradations while achieving millimetre level positioning accuracy in interference environments. To verify the applicability of the proposed method and analyze the degradations, array signals corresponding to the GPS L1 band are generated using a combination of hardware and software simulators. Furthermore, the amount of degradation and performance of the proposed method under different conditions are evaluated based on Monte Carlo simulations. PMID:27809252

  6. Openstage: A Low-Cost Motorized Microscope Stage with Sub-Micron Positioning Accuracy

    PubMed Central

    Campbell, Robert A. A.; Eifert, Robert W.; Turner, Glenn C.

    2014-01-01

    Recent progress in intracellular calcium sensors and other fluorophores has promoted the widespread adoption of functional optical imaging in the life sciences. Home-built multiphoton microscopes are easy to build, highly customizable, and cost effective. For many imaging applications a 3-axis motorized stage is critical, but commercially available motorization hardware (motorized translators, controller boxes, etc) are often very expensive. Furthermore, the firmware on commercial motor controllers cannot easily be altered and is not usually designed with a microscope stage in mind. Here we describe an open-source motorization solution that is simple to construct, yet far cheaper and more customizable than commercial offerings. The cost of the controller and motorization hardware are under $1000. Hardware costs are kept low by replacing linear actuators with high quality stepper motors. Electronics are assembled from commonly available hobby components, which are easy to work with. Here we describe assembly of the system and quantify the positioning accuracy of all three axes. We obtain positioning repeatability of the order of in X/Y and in Z. A hand-held control-pad allows the user to direct stage motion precisely over a wide range of speeds ( to ), rapidly store and return to different locations, and execute “jumps” of a fixed size. In addition, the system can be controlled from a PC serial port. Our “OpenStage” controller is sufficiently flexible that it could be used to drive other devices, such as micro-manipulators, with minimal modifications. PMID:24586468

  7. Influence of both angle and position error of pentaprism on accuracy of pentaprism scanning system

    NASA Astrophysics Data System (ADS)

    Xu, Kun; Han, Sen; Zhang, Qiyuan; Wu, Quanying

    2014-11-01

    Pentaprism scanning system has been widely used in the measurement of large flat and wavefront, based on its property that the deviated beam will have no motion in the pitch direction. But the manufacturing and position errors of pentaprisms will bring error to the measurement and so a good error analysis method is indispensable. In this paper, we propose a new method of building mathematic models of pentaprism and through which the size and angle errors of a pentaprism can be put into the model as parameters. 4 size parameters are selected to determine the size and 11 angle parameters are selected to determine the angles of a pentaprism. Yaw, Roll and Pitch are used to describe the position error of a pentaprism and an autocollimator. A pentaprism scanning system of wavefront test is simulated by ray tracing using matlab. We design a method of separating the constant from the measurement results which will improve the measurement accuracy and analyze the system error by Monte Carlo method. This method is simple, rapid, accurate and convenient for computer programming.

  8. Accuracy of Implant Position Transfer and Surface Detail Reproduction with Different Impression Materials and Techniques

    PubMed Central

    Alikhasi, Marzieh; Siadat, Hakimeh; Kharazifard, Mohammad Javad

    2015-01-01

    Objectives: The purpose of this study was to compare the accuracy of implant position transfer and surface detail reproduction using two impression techniques and materials. Materials and Methods: A metal model with two implants and three grooves of 0.25, 0.50 and 0.75 mm in depth on the flat superior surface of a die was fabricated. Ten regular-body polyether (PE) and 10 regular-body polyvinyl siloxane (PVS) impressions with square and conical transfer copings using open tray and closed tray techniques were made for each group. Impressions were poured with type IV stone, and linear and angular displacements of the replica heads were evaluated using a coordinate measuring machine (CMM). Also, accurate reproduction of the grooves was evaluated by a video measuring machine (VMM). These measurements were compared with the measurements calculated on the reference model that served as control, and the data were analyzed with two-way ANOVA and t-test at P= 0.05. Results: There was less linear displacement for PVS and less angular displacement for PE in closed-tray technique, and less linear displacement for PE in open tray technique (P<0.001). Also, the open tray technique showed less angular displacement with the use of PVS impression material. Detail reproduction accuracy was the same in all the groups (P>0.05). Conclusion: The open tray technique was more accurate using PE, and also both closed tray and open tray techniques had acceptable results with the use of PVS. The choice of impression material and technique made no significant difference in surface detail reproduction. PMID:27252761

  9. Absolute airborne gravimetry

    NASA Astrophysics Data System (ADS)

    Baumann, Henri

    This work consists of a feasibility study of a first stage prototype airborne absolute gravimeter system. In contrast to relative systems, which are using spring gravimeters, the measurements acquired by absolute systems are uncorrelated and the instrument is not suffering from problems like instrumental drift, frequency response of the spring and possible variation of the calibration factor. The major problem we had to resolve were to reduce the influence of the non-gravitational accelerations included in the measurements. We studied two different approaches to resolve it: direct mechanical filtering, and post-processing digital compensation. The first part of the work describes in detail the different mechanical passive filters of vibrations, which were studied and tested in the laboratory and later in a small truck in movement. For these tests as well as for the airborne measurements an absolute gravimeter FG5-L from Micro-G Ltd was used together with an Inertial navigation system Litton-200, a vertical accelerometer EpiSensor, and GPS receivers for positioning. These tests showed that only the use of an optical table gives acceptable results. However, it is unable to compensate for the effects of the accelerations of the drag free chamber. The second part describes the strategy of the data processing. It is based on modeling the perturbing accelerations by means of GPS, EpiSensor and INS data. In the third part the airborne experiment is described in detail, from the mounting in the aircraft and data processing to the different problems encountered during the evaluation of the quality and accuracy of the results. In the part of data processing the different steps conducted from the raw apparent gravity data and the trajectories to the estimation of the true gravity are explained. A comparison between the estimated airborne data and those obtained by ground upward continuation at flight altitude allows to state that airborne absolute gravimetry is feasible and

  10. Accuracy of a low-cost global positioning system receiver for estimating grade during outdoor walking.

    PubMed

    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

  11. Accuracy of positioning and irradiation targeting for multiple targets in intracranial image-guided radiation therapy: a phantom study.

    PubMed

    Tominaga, Hirofumi; Araki, Fujio; Shimohigashi, Yoshinobu; Ishihara, Terunobu; Kawasaki, Keiichi; Kanetake, Nagisa; Sakata, Junichi; Iwashita, Yuki

    2014-12-21

    This study investigated the accuracy of positioning and irradiation targeting for multiple off-isocenter targets in intracranial image-guided radiation therapy (IGRT). A phantom with nine circular targets was created to evaluate both accuracies. First, the central point of the isocenter target was positioned with a combination of an ExacTrac x-ray (ETX) and a 6D couch. The positioning accuracy was determined from the deviations of coordinates of the central point in each target obtained from the kV-cone beam computed tomography (kV-CBCT) for IGRT and the planning CT. Similarly, the irradiation targeting accuracy was evaluated from the deviations of the coordinates between the central point of each target and the central point of each multi-leaf collimator (MLC) field for multiple targets. Secondly, the 6D couch was intentionally rotated together with both roll and pitch angles of 0.5° and 1° at the isocenter and similarly the deviations were evaluated. The positioning accuracy for all targets was less than 1 mm after 6D positioning corrections. The irradiation targeting accuracy was up to 1.3 mm in the anteroposterior (AP) direction for a target 87 mm away from isocenter. For the 6D couch rotations with both roll and pitch angles of 0.5° and 1°, the positioning accuracy was up to 1.0 mm and 2.3 mm in the AP direction for the target 87 mm away from the isocenter, respectively. The irradiation targeting accuracy was up to 2.1 mm and 2.6 mm in the AP direction for the target 87 mm away from the isocenter, respectively. The off-isocenter irradiation targeting accuracy became worse than the positioning accuracy. Both off-isocenter accuracies worsened in proportion to rotation angles and the distance from the isocenter to the targets. It is necessary to examine the set-up margin for off-isocenter multiple targets at each institution because irradiation targeting accuracy is peculiar to the linac machine.

  12. Accuracy of positioning and irradiation targeting for multiple targets in intracranial image-guided radiation therapy: a phantom study

    NASA Astrophysics Data System (ADS)

    Tominaga, Hirofumi; Araki, Fujio; Shimohigashi, Yoshinobu; Ishihara, Terunobu; Kawasaki, Keiichi; Kanetake, Nagisa; Sakata, Junichi; Iwashita, Yuki

    2014-12-01

    This study investigated the accuracy of positioning and irradiation targeting for multiple off-isocenter targets in intracranial image-guided radiation therapy (IGRT). A phantom with nine circular targets was created to evaluate both accuracies. First, the central point of the isocenter target was positioned with a combination of an ExacTrac x-ray (ETX) and a 6D couch. The positioning accuracy was determined from the deviations of coordinates of the central point in each target obtained from the kV-cone beam computed tomography (kV-CBCT) for IGRT and the planning CT. Similarly, the irradiation targeting accuracy was evaluated from the deviations of the coordinates between the central point of each target and the central point of each multi-leaf collimator (MLC) field for multiple targets. Secondly, the 6D couch was intentionally rotated together with both roll and pitch angles of 0.5° and 1° at the isocenter and similarly the deviations were evaluated. The positioning accuracy for all targets was less than 1 mm after 6D positioning corrections. The irradiation targeting accuracy was up to 1.3 mm in the anteroposterior (AP) direction for a target 87 mm away from isocenter. For the 6D couch rotations with both roll and pitch angles of 0.5° and 1°, the positioning accuracy was up to 1.0 mm and 2.3 mm in the AP direction for the target 87 mm away from the isocenter, respectively. The irradiation targeting accuracy was up to 2.1 mm and 2.6 mm in the AP direction for the target 87 mm away from the isocenter, respectively. The off-isocenter irradiation targeting accuracy became worse than the positioning accuracy. Both off-isocenter accuracies worsened in proportion to rotation angles and the distance from the isocenter to the targets. It is necessary to examine the set-up margin for off-isocenter multiple targets at each institution because irradiation targeting accuracy is peculiar to the linac machine.

  13. Development of a video image-based QA system for the positional accuracy of dynamic tumor tracking irradiation in the Vero4DRT system

    SciTech Connect

    Ebe, Kazuyu Tokuyama, Katsuichi; Baba, Ryuta; Ogihara, Yoshisada; Ichikawa, Kosuke; Toyama, Joji; Sugimoto, Satoru; Utsunomiya, Satoru; Kagamu, Hiroshi; Aoyama, Hidefumi; Court, Laurence

    2015-08-15

    Purpose: To develop and evaluate a new video image-based QA system, including in-house software, that can display a tracking state visually and quantify the positional accuracy of dynamic tumor tracking irradiation in the Vero4DRT system. Methods: Sixteen trajectories in six patients with pulmonary cancer were obtained with the ExacTrac in the Vero4DRT system. Motion data in the cranio–caudal direction (Y direction) were used as the input for a programmable motion table (Quasar). A target phantom was placed on the motion table, which was placed on the 2D ionization chamber array (MatriXX). Then, the 4D modeling procedure was performed on the target phantom during a reproduction of the patient’s tumor motion. A substitute target with the patient’s tumor motion was irradiated with 6-MV x-rays under the surrogate infrared system. The 2D dose images obtained from the MatriXX (33 frames/s; 40 s) were exported to in-house video-image analyzing software. The absolute differences in the Y direction between the center of the exposed target and the center of the exposed field were calculated. Positional errors were observed. The authors’ QA results were compared to 4D modeling function errors and gimbal motion errors obtained from log analyses in the ExacTrac to verify the accuracy of their QA system. The patients’ tumor motions were evaluated in the wave forms, and the peak-to-peak distances were also measured to verify their reproducibility. Results: Thirteen of sixteen trajectories (81.3%) were successfully reproduced with Quasar. The peak-to-peak distances ranged from 2.7 to 29.0 mm. Three trajectories (18.7%) were not successfully reproduced due to the limited motions of the Quasar. Thus, 13 of 16 trajectories were summarized. The mean number of video images used for analysis was 1156. The positional errors (absolute mean difference + 2 standard deviation) ranged from 0.54 to 1.55 mm. The error values differed by less than 1 mm from 4D modeling function errors

  14. Assessment of Completeness and Positional Accuracy of Linear Features in Volunteered Geographic Information (vgi)

    NASA Astrophysics Data System (ADS)

    Eshghi, M.; Alesheikh, A. A.

    2015-12-01

    Recent advances in spatial data collection technologies and online services dramatically increase the contribution of ordinary people to produce, share, and use geographic information. Collecting spatial data as well as disseminating them on the internet by citizens has led to a huge source of spatial data termed as Volunteered Geographic Information (VGI) by Mike Goodchild. Although, VGI has produced previously unavailable data assets, and enriched existing ones. But its quality can be highly variable and challengeable. This presents several challenges to potential end users who are concerned about the validation and the quality assurance of the data which are collected. Almost, all the existing researches are based on how to find accurate VGI data from existing VGI data which consist of a) comparing the VGI data with the accurate official data, or b) in cases that there is no access to correct data; therefore, looking for an alternative way to determine the quality of VGI data is essential, and so forth. In this paper it has been attempt to develop a useful method to reach this goal. In this process, the positional accuracy of linear feature of Iran, Tehran OSM data have been analyzed.

  15. The accuracy of image-guided navigation for maxillary positioning in bimaxillary surgery.

    PubMed

    Sun, Yi; Luebbers, Heinz-Theo; Agbaje, Jimoh Olubanwo; Lambrichts, Ivo; Politis, Constantinus

    2014-05-01

    The aim of our study was to evaluate the accuracy of image-guided maxillary positioning in sagittal, vertical, and mediolateral direction. Between May 2011 and July 2012, 17 patients (11 males, 6 females) underwent bimaxillary surgery with the use of intraoperative surgical navigation. During Le Fort I osteotomy, the Kolibri navigation system was used to measure movement of the maxilla at the edge of the upper central upper incisor in sagittal (buccal surface), vertical (incisor edge), and mediolateral (dental midline) direction. Six weeks after surgery, a postoperative CBCT scan was taken and registered to the preoperative cone-beam computed tomography scan to identify the actual surgical movement of the maxilla. Student 2-tailed paired t test was used to evaluate differences between the measured result from navigation system and actual surgical movement of the maxilla, which were 0.44 ± 0.35 mm (P = 0.82) in the sagittal, 0.50 ± 0.35 mm (P = 0.85) in the vertical, and 0.56 ± 0.36 mm (P = 0.81) in the mediolateral direction. Our finding demonstrates that intraoperative computer navigation is a promising tool for measuring the surgical change of the maxilla in bimaxillary surgery.

  16. Accuracy of time comparison derived from reception of LORAN-C and Global Positioning System time signals

    NASA Astrophysics Data System (ADS)

    Horiai, Koji

    1992-10-01

    The accuracy of time comparison by means of the reception of common time signals, namely, LORAN-C and Global Positioning System (GPS), is examined. Differences of UTC from the emission times of these two radio wave signals measured at four Japanese stations and one U.S. station are analyzed and compared with the clock comparison reports published by the Bureau International des Poids et Mesures. The accuracy of the time comparison via LORAN-C signals of the northwest Pacific chain is about 3.61 microns and that via GPS is 0.14 microns. The accuracy analysis reveals the existence of systematic errors at the individual stations. In LORAN-C, the most serious error comes from those in the delay time calibration of receiving instruments and estimation of the propagation delay over land. Calibration of the clocks by a portable clock improves the accuracy of the GPS method to the accuracy of the GPS signals.

  17. Consonant Production Accuracy in Young Cochlear Implant Recipients: Developmental Sound Classes and Word Position Effects

    ERIC Educational Resources Information Center

    Ertmer, David J.; Kloiber, Diana True; Jung, Jongmin; Kirleis, Katie Connell; Bradford, Denise

    2012-01-01

    Purpose: To compare young cochlear implant (CI) recipients' consonant production accuracy with that of age- and gender-matched peers who were typically developing (TD). In addition to examining initial consonants, the authors compiled new data regarding the accuracy of final consonants and the order of consonant acquisition. Methods: Eleven young…

  18. Measurement of the absolute accuracy (to <0.5%) of a clip-level beam profiler using Fresnel diffraction by a wide slit

    NASA Astrophysics Data System (ADS)

    Johnston, Thomas F., Jr.; Fleischer, John M.

    1995-04-01

    By comparing the measured width of an optical test patten to the known width, the absolute error of a clip-level profiler is determined to be (-0.1 +/- 0.3)%. An expanded fundamental mode beam illuminates a pair of opposed knife edges (a wide slit) to generate the test pattern by Fresnel diffraction. Analysis of the diffraction pattern gives 18.2% as the appropriate clip level to read the geometrical shadow width between edges (with additional small adjustments for illumination non-uniformity and the finite size of the scanning aperture). The separation between the edges is determined by mechanical translation edge to edge through a focused beam. 3

  19. MLC positional accuracy evaluation through the Picket Fence test on EBT2 films and a 3D volumetric phantom.

    PubMed

    Antypas, Christos; Floros, Ioannis; Rouchota, Maritina; Armpilia, Christina; Lyra, Maria

    2015-03-08

    The accuracy of MLC positions during radiotherapy is important as even small positional deviations can translate into considerable dose delivery errors. This becomes crucial when radiosensitive organs are located near the treated volume and especially during IMRT, where dose gradients are steep. A test commonly conducted to measure the positional accuracy of the MLCs is the Picket Fence test. In this study two alterations of the Picket Fence test were performed and evaluated, the first one using radiochromic EBT2 films and the second one the Delta4PT diode array phantom and its software. Our results showed that EBT2 films provide a relatively fast, qualitative visual inspection of the significant leaf dispositions. When slight inaccuracies need to be revealed or precise numerical results for each leaf position are needed, Delta4PT provides the desired accuracy of 1 mm. In treatment modalities where a higher accuracy is required in the delivered dose distribution, such as in IMRT, precise numerical values of the measurements for the MLC positional inspection are required.

  20. Multi-channel absolute distance measurement system with sub ppm-accuracy and 20 m range using frequency scanning interferometry and gas absorption cells.

    PubMed

    Dale, John; Hughes, Ben; Lancaster, Andrew J; Lewis, Andrew J; Reichold, Armin J H; Warden, Matthew S

    2014-10-06

    We present an implementation of an absolute distance measurement system which uses frequency scanning interferometry (FSI). The technique, referred to as dynamic FSI, uses two frequency scanning lasers, a gas absorption cell and a reference interferometer to determine the unknown optical path length difference (OPD) of one or many measurement interferometers. The gas absorption cell is the length reference for the measurement system and is traceable to international standards through knowledge of the frequencies of its absorption features. The OPD of the measurement interferometers can vary during the measurement and the variation is measured at the sampling rate of the system (2.77 MHz in the system described here). The system is shown to measure distances from 0.2 m to 20 m with a combined relative uncertainty of 0.41 × 10⁻⁶ at the two sigma level (k = 2). It will be shown that within a scan the change in OPD of the measurement interferometer can be determined to a resolution of 40 nm.

  1. Assessing the impact of relative social position and absolute community resources on depression and obesity among smokers.

    PubMed

    Aguilera, Adrian; Leykin, Yan; Adler, Nancy; Muñoz, Ricardo F

    2012-09-01

    We tested two competing hypotheses-relative social position and community resources-in regards to their effect on two co-occurring health problems (depression, and obesity) in a sample of smokers participating in an online smoking cessation intervention. Income and education data at the zip code level from the 2000 Census was linked with individual level data. Logistic regression models were used for each co-occurring problem to determine how each SES variable (individually and interactively) was associated with the presence of co-occurring health problems. We found that lower individual education was related to poorer health for all outcomes (Depression: OR = 1.25; Obesity: OR = 1.24; Both: OR = 1.46), lower community education was only related to obesity (OR = 1.20). Lower individual income was related to higher rates of depressive symptoms (OR = 1.64) and both health problems (OR = 1.55); a significant interaction of individual and community income (Wald = 6.13, p < .05) revealed that high income individuals were less likely to be depressed if they lived in lower-income communities and became more likely to be so as community income increased. Relative social position was confirmed for depression, whereas community resources were prominent only for obesity. Higher individual education most consistently predicted positive health outcomes, making it a potentially powerful target to reduce health disparities.

  2. Increasing shape modelling accuracy by adjusting for subject positioning: an application to the analysis of radiographic proximal femur symmetry using data from the Osteoarthritis Initiative.

    PubMed

    Lindner, C; Wallis, G A; Cootes, T F

    2014-04-01

    In total hip arthroplasty, the shape of the contra-lateral femur frequently serves as a template for preoperative planning. Previous research on contra-lateral femoral symmetry has been based on conventional hip geometric measurements (which reduce shape to a series of linear measurements) and did not take the effect of subject positioning on radiographic femur shape into account. The aim of this study was to analyse proximal femur symmetry based on statistical shape models (SSMs) which quantify global femoral shape while also adjusting for differences in subject positioning during image acquisition. We applied our recently developed fully automatic shape model matching (FASMM) system to automatically segment the proximal femur from AP pelvic radiographs to generate SSMs of the proximal femurs of 1258 Caucasian females (mean age: 61.3 SD=9.0). We used a combined SSM (capturing the left and right femurs) to identify and adjust for shape variation attributable to subject positioning as well as a single SSM (including all femurs as left femurs) to analyse proximal femur symmetry. We also calculated conventional hip geometric measurements (head diameter, neck width, shaft width and neck-shaft angle) using the output of the FASMM system. The combined SSM revealed two modes that were clearly attributable to subject positioning. The average difference (mean point-to-curve distance) between left and right femur shape was 1.0mm before and 0.8mm after adjusting for these two modes. The automatic calculation of conventional hip geometric measurements after adjustment gave an average absolute percent asymmetry of within 3.1% and an average absolute difference of within 1.1mm or 2.9° for all measurements. We conclude that (i) for Caucasian females the global shape of the right and left proximal femurs is symmetric without isolated locations of asymmetry; (ii) a combined left-right SSM can be used to adjust for radiographic shape variation due to subject positioning; and (iii

  3. Method to quantify accuracy of position feedback signals of a three-dimensional two-photon laser-scanning microscope

    PubMed Central

    Kummer, Michael; Kirmse, Knut; Witte, Otto W.; Haueisen, Jens; Holthoff, Knut

    2015-01-01

    Two-photon laser-scanning microscopy enables to record neuronal network activity in three-dimensional space while maintaining single-cellular resolution. One of the proposed approaches combines galvanometric x-y scanning with piezo-driven objective movements and employs hardware feedback signals for position monitoring. However, readily applicable methods to quantify the accuracy of those feedback signals are currently lacking. Here we provide techniques based on contact-free laser reflection and laser triangulation for the quantification of positioning accuracy of each spatial axis. We found that the lateral feedback signals are sufficiently accurate (defined as <2.5 µm) for a wide range of scan trajectories and frequencies. We further show that axial positioning accuracy does not only depend on objective acceleration and mass but also its geometry. We conclude that the introduced methods allow a reliable quantification of position feedback signals in a cost-efficient, easy-to-install manner and should be applicable for a wide range of two-photon laser scanning microscopes. PMID:26504620

  4. Method to quantify accuracy of position feedback signals of a three-dimensional two-photon laser-scanning microscope.

    PubMed

    Kummer, Michael; Kirmse, Knut; Witte, Otto W; Haueisen, Jens; Holthoff, Knut

    2015-10-01

    Two-photon laser-scanning microscopy enables to record neuronal network activity in three-dimensional space while maintaining single-cellular resolution. One of the proposed approaches combines galvanometric x-y scanning with piezo-driven objective movements and employs hardware feedback signals for position monitoring. However, readily applicable methods to quantify the accuracy of those feedback signals are currently lacking. Here we provide techniques based on contact-free laser reflection and laser triangulation for the quantification of positioning accuracy of each spatial axis. We found that the lateral feedback signals are sufficiently accurate (defined as <2.5 µm) for a wide range of scan trajectories and frequencies. We further show that axial positioning accuracy does not only depend on objective acceleration and mass but also its geometry. We conclude that the introduced methods allow a reliable quantification of position feedback signals in a cost-efficient, easy-to-install manner and should be applicable for a wide range of two-photon laser scanning microscopes.

  5. SU-E-J-118: Verification of Intrafractional Positional Accuracy Using Ultrasound Autoscan Tracking for Prostate Cancer Treatment

    SciTech Connect

    Yu, S; Hristov, D; Phillips, T

    2014-06-01

    Purpose: Transperineal ultrasound imaging is attractive option for imageguided radiation therapy as there is no need to implant fiducials, no extra imaging dose, and real time continuous imaging is possible during treatment. The aim of this study is to verify the tracking accuracy of a commercial ultrasound system under treatment conditions with a male pelvic phantom. Methods: A CT and ultrasound scan were acquired for the male pelvic phantom. The phantom was then placed in a treatment mimicking position on a motion platform. The axial and lateral tracking accuracy of the ultrasound system were verified using an independent optical tracking system. The tracking accuracy was evaluated by tracking the phantom position detected by the ultrasound system, and comparing it to the optical tracking system under the conditions of beam on (15 MV), beam off, poor image quality with an acoustic shadow introduced, and different phantom motion cycles (10 and 20 second periods). Additionally, the time lag between the ultrasound-detected and actual phantom motion was investigated. Results: Displacement amplitudes reported by the ultrasound system and optical system were within 0.5 mm of each other for both directions and all conditions. The ultrasound tracking performance in axial direction was better than in lateral direction. Radiation did not interfere with ultrasound tracking while image quality affected tracking accuracy. The tracking accuracy was better for periodic motion with 20 second period. The time delay between the ultrasound tracking system and the phantom motion was clinically acceptable. Conclusion: Intrafractional prostate motion is a potential source of treatment error especially in the context of emerging SBRT regimens. It is feasible to use transperineal ultrasound daily to monitor prostate motion during treatment. Our results verify the tracking accuracy of a commercial ultrasound system to be better than 1 mm under typical external beam treatment conditions.

  6. Accuracy of determination of position and width of molecular groups in biological and lipid membranes via neutron diffraction.

    PubMed

    Gordeliy, V I; Chernov, N I

    1997-07-01

    Neutron diffraction combined with the deuterium-labelled molecular groups of biological and model membrane components allows one to detect with high accuracy the structure of these objects. Experiments of this kind are only possible at unique high-flux neutron sources, and the planning of neutron-diffraction experiments must take into account some special requirements primarily related to the duration of the experiment and the accuracy of estimation of membrane structure parameters as a result of finite time of the measurements. This paper deals with the question of statistical accuracy of the position x(0) and width v of the distribution of deuterium labels in membranes along the normal of their plane, which are determined in a neutron diffraction experiment. It is shown that the accuracy of x(0) and v estimation does not depend on membrane constitution. It is dependent only on the scattering amplitude of the deuterium label, the label position x(0) and the distribution width v. Analytic calculations show that the statistical errors Deltax(0) and Deltav are inversely proportional to the scattering amplitude of the label and, as usual, to the square root of measurement time. The question of Deltax0 and Deltav dependence on the number of structure factors used in the calculations of x(0) and v is also studied. It is shown that, the accuracy of x(0) estimation is approximately constant with down to four structure factors used, and, with the number of the factors below four, it deteriorates drastically. Analogous is the behaviour of Deltav(h(max)) relation with one exception: abrupt deterioration of the accuracy occurs beginning with five structure factors used. One does not have to measure the highest diffraction reflections which takes a much longer time compared with the first ones. It is an important result. All the problems mentioned above have also been considered for the case of two different deuterium labels in membranes.

  7. Accuracy of time comparison derived from reception of LORAN-C and Global Positioning System time signals.

    NASA Astrophysics Data System (ADS)

    Horiai, K.

    1992-10-01

    The accuracy of time comparison by means of the reception of common time signals, namely, LORAN-C and Global Positioning System (GPS), is examined. Differences of UTC from the emission times of these two radio wave signals measured at four Japanese stations and one U.S. station are analyzed and compared with the clock comparison reports published by the Bureau International des Poids et Mesures. The accuracy of the time comparison via LORAN-C signals of the northwest Pacific chain is about 3.61 μs and that via GPS is 0.14 μs. The accuracy analysis reveals the existence of systematic errors at the individual stations. In LORAN-C, the most serious error comes from those in the delay time calibration of receiving instruments and estimation of the propagation delay over land. Calibration of the clocks by a portable clock improves the accuracy of the GPS method to the accuracy of the GPS signals.

  8. Development of a Heterogeneous sUAS High-Accuracy Positional Flight Data Acquisition System

    NASA Technical Reports Server (NTRS)

    McSwain, Robert G.; Grosveld, Ferdinand W.

    2016-01-01

    Recently, a heterogeneous FDAS, consisting of a diverse range of instruments was developed to support acoustic flight research programs at NASA Langley Research Center. In addition to a conventional GPS to measure latitude, longitude and altitude, the FDAS also utilizes a small, light-weight, low-cost DGPS system to obtain centimeter accuracy to measure the distance traveled by sound from a sUAS vehicle to a microphone on the ground. Acoustic flight testing using the FDAS installed on several different sUAS platforms has been conducted in support of the NASA CAS DELIVER and ERA ITD projects (Reference 1). The first FDAS prototype was assembled and implemented in the acoustic/flight measurement system in December 2014 to support DELIVER acoustic flight tests. Evaluation of the system performance and results from the data analyses were used to further test, develop and enhance the FDAS over a six-month period to support acoustic flight research for the ERA.

  9. Examination of the Position Accuracy of Implant Abutments Reproduced by Intra-Oral Optical Impression

    PubMed Central

    Odaira, Chikayuki; Kobayashi, Takuya; Kondo, Hisatomo

    2016-01-01

    An impression technique called optical impression using intraoral scanner has attracted attention in digital dentistry. This study aimed to evaluate the accuracy of the optical impression, comparing a virtual model reproduced by an intraoral scanner to a working cast made by conventional silicone impression technique. Two implants were placed on a master model. Working casts made of plaster were fabricated from the master model by silicone impression. The distance between the ball abutments and the angulation between the healing abutments of 5 mm and 7 mm height at master model were measured using Computer Numerical Control Coordinate Measuring Machine (CNCCMM) as control. Working casts were then measured using CNCCMM, and virtual models via stereo lithography data of master model were measured by a three-dimensional analyzing software. The distance between ball abutments of the master model was 9634.9 ± 1.2 μm. The mean values of trueness of the Lava COS and working casts were 64.5 μm and 22.5 μm, respectively, greater than that of control. The mean of precision values of the Lava COS and working casts were 15.6 μm and 13.5 μm, respectively. In the case of a 5-mm-height healing abutment, mean angulation error of the Lava COS was greater than that of the working cast, resulting in significant differences in trueness and precision. However, in the case of a 7-mm-height abutment, mean angulation errors of the Lava COS and the working cast were not significantly different in trueness and precision. Therefore, distance errors of the optical impression were slightly greater than those of conventional impression. Moreover, the trueness and precision of angulation error could be improved in the optical impression using longer healing abutments. In the near future, the development of information technology could enable improvement in the accuracy of the optical impression with intraoral scanners. PMID:27706225

  10. An investigation of airborne GPS/INS for high accuracy position and velocity determination

    SciTech Connect

    Sun, H.; Cannon, M.E.; Owen, T.E.; Meindl, M.A.

    1993-12-31

    An airborne test using a differential GPS-INS system in a Twin Otter was conducted by Sandia National Laboratories to assess the feasibility of using the integrated system for cm-level position and cm/s velocity. The INS is a miniaturized ring-laser gyro IMU jointly developed by Sandia and Honeywell while the GPS system consists of the NovAtel GPSCard{trademark}. INS position, velocity and attitude data were computed using Sandia`s SANDAC flight computer system and logged at 4 Hz and GPS data was acquired at a 1 Hz rate. The mission was approximately 2.5 hours in duration and the aircraft reached separations of up to 19 km from the base station. The data was post-processed using a centralized Kalman filter approach in which the double differenced carrier phase measurements are used to update the INS data. The INS position is in turn used to detect and correct GPS carrier phase cycle slips and also to bridge GPS outages. Results are presented for the GPS-only case and also for integrated GPS/INS.

  11. Sharp Chandra View of ROSAT All-Sky Survey Bright Sources — I. Improvement of Positional Accuracy

    NASA Astrophysics Data System (ADS)

    Gao, Shuang; Wang, Song; Liu, Ji-Feng

    2016-12-01

    The ROSAT All-Sky Survey (RASS) represents one of the most complete and sensitive soft X-ray all-sky surveys to date. However, the deficient positional accuracy of the RASS Bright Source Catalog (BSC) and subsequent lack of firm optical identifications affect multi-wavelength studies of X-ray sources. The widely used positional errors σpos based on the Tycho Reference Catalog (Tycho-1) have previously been applied for identifying objects in the optical band. The considerably sharper Chandra view covers a fraction of RASS sources, whose σpos could be improved by utilizing the sub-arcsec positional accuracy of Chandra observations. We cross-match X-ray objects between the BSC and Chandra sources extracted from the Advanced CCD Imaging Spectrometer (ACIS) archival observations. A combined list of counterparts (BSCxACIS) with Chandra spatial positions weighted by the X-ray flux of multiple counterparts is employed to evaluate and improve the former identifications of BSC when used with other surveys. Based on these identification evaluations, we suggest that the point-source likeness of BSC sources and INS (isolated neutron star) candidates should be carefully reconsidered.

  12. Changing within-trial array location and target object position enhances rats' (Rattus norvegicus) missing object recognition accuracy.

    PubMed

    Arain, Marium; Parameswaran, Varakini; Cohen, Jerome

    2012-09-01

    Six rats were trained to find a previously missing target or 'jackpot' object in a square array of four identical or different objects (the test segment of a trial) after first visiting and collecting sunflower seeds from under the other three objects (the study segment of a trial). During training, objects' local positions within the array and their global positions within the larger foraging array were varied over trials but were not changed between segments within a trial. Following this training, rats were tested on their accuracy for finding the target object when a trial's test array was sometimes moved to a different location in the foraging arena or when the position of the target object within the test array had been changed. Either of these manipulations initially slightly reduced rats' accuracy for finding the missing object but then enhanced it. Relocating test arrays of identical objects enhanced rats' performance only after 10-min inter-segment intervals (ISIs). Relocating test arrays of different objects enhanced rats' performance only after 2-min ISIs. Rats also improved their performance when they encountered the target object in a new position in test arrays of different objects. This enhancement effect occurred after either 2- or 30-min ISIs. These findings suggest that rats separately retrieved a missing (target) object's spatial and non-spatial information when they were relevant but not when they were irrelevant in a trial. The enhancement effects provide evidence for rats' limited retrieval capacity in their visuo-spatial working memory.

  13. Detecting recent positive selection with high accuracy and reliability by conditional coalescent tree.

    PubMed

    Wang, Minxian; Huang, Xin; Li, Ran; Xu, Hongyang; Jin, Li; He, Yungang

    2014-11-01

    Studies of natural selection, followed by functional validation, are shedding light on understanding of genetic mechanisms underlying human evolution and adaptation. Classic methods for detecting selection, such as the integrated haplotype score (iHS) and Fay and Wu's H statistic, are useful for candidate gene searching underlying positive selection. These methods, however, have limited capability to localize causal variants in selection target regions. In this study, we developed a novel method based on conditional coalescent tree to detect recent positive selection by counting unbalanced mutations on coalescent gene genealogies. Extensive simulation studies revealed that our method is more robust than many other approaches against biases due to various demographic effects, including population bottleneck, expansion, or stratification, while not sacrificing its power. Furthermore, our method demonstrated its superiority in localizing causal variants from massive linked genetic variants. The rate of successful localization was about 20-40% higher than that of other state-of-the-art methods on simulated data sets. On empirical data, validated functional causal variants of four well-known positive selected genes were all successfully localized by our method, such as ADH1B, MCM6, APOL1, and HBB. Finally, the computational efficiency of this new method was much higher than that of iHS implementations, that is, 24-66 times faster than the REHH package, and more than 10,000 times faster than the original iHS implementation. These magnitudes make our method suitable for applying on large sequencing data sets. Software can be downloaded from https://github.com/wavefancy/scct.

  14. Position of helical kinks in membrane protein crystal structures and the accuracy of computational prediction.

    PubMed

    Hall, Spencer E; Roberts, Kyle; Vaidehi, Nagarajan

    2009-01-01

    The structural features of helical transmembrane (TM) proteins, such as helical kinks, tilts, and rotational orientations are important in modulation of their function and these structural features give rise to functional diversity in membrane proteins with similar topology. In particular, the helical kinks caused by breaking of the backbone hydrogen bonds lead to hinge bending flexibility in these helices. Therefore it is important to understand the nature of the helical kinks and to be able to reproduce these kinks in structural models of membrane proteins. We have analyzed the position and extent of helical kinks in the transmembrane helices of all the crystal structures of membrane proteins taken from the MPtopo database, which are about 405 individual helices of length between 19 and 35 residues. 44% of the crystal structures of TM helices showed a significant helical kink, and 35% of these kinks are caused by prolines. Many of the non-proline helical kinks are caused by other residues like Ser and Gly that are located at the center of helical kinks. The side chain of Ser makes a hydrogen bond with the main chain carbonyl of the i - 4th or i + 4th residue thus making a kink. We have also studied how well molecular dynamics (MD) simulations on isolated helices can reproduce the position of the helical kinks in TM helices. Such a method is useful for structure prediction of membrane proteins. We performed MD simulations, starting from a canonical helix for the 405 TM helices. 1 ns of MD simulation results show that we can reproduce about 79% of the proline kinks, only 59% of the vestigial proline kinks and 18% of the non-proline helical kinks. We found that similar results can be obtained from choosing the lowest potential energy structure from the MD simulation. 4-14% more of the vestigial prolines were reproduced by replacing them with prolines before performing MD simulations, and changing the amino acid back to proline after the MD simulations. From these

  15. Absolute measurement of length with nanometric resolution

    NASA Astrophysics Data System (ADS)

    Apostol, D.; Garoi, F.; Timcu, A.; Damian, V.; Logofatu, P. C.; Nascov, V.

    2005-08-01

    Laser interferometer displacement measuring transducers have a well-defined traceability route to the definition of the meter. The laser interferometer is de-facto length scale for applications in micro and nano technologies. However their physical unit -half lambda is too large for nanometric resolution. Fringe interpolation-usual technique to improve the resolution-lack of reproducibility could be avoided using the principles of absolute distance measurement. Absolute distance refers to the use of interferometric techniques for determining the position of an object without the necessity of measuring continuous displacements between points. The interference pattern as produced by the interference of two point-like coherent sources is fitted to a geometric model so as to determine the longitudinal location of the target by minimizing least square errors. The longitudinal coordinate of the target was measured with accuracy better than 1 nm, for a target position range of 0.4μm.

  16. Direct measurement of the position accuracy for low energy X-ray photons with a pnCCD

    NASA Astrophysics Data System (ADS)

    Ihle, S.; Holl, P.; Kalok, D.; Hartmann, R.; Ryll, H.; Steigenhöfer, D.; Strüder, L.

    2017-02-01

    We undertook a comparative study on optimizing the position accuracy of pnCCDs for single X-ray photon measurements. Various methods were analyzed by Monte Carlo simulations and related to experimental data obtained with a focused X-ray beam. Even with low energy photons of 1320 eV, a position accuracy much smaller than the actual pixel size of 48 μm × 48 μm can be achieved. This is possible since signal charges from a single photon interaction spread into more than one pixel, allowing a reconstruction of the original point of interaction. We found that a) making a decision on which pixels to use for the reconstruction and b) choosing a centroiding algorithm for carrying out the reconstruction were particularly crucial. For a) we introduce a new and superior method using a two step analysis with an adaptive pattern. It is compared to using a threshold or a fixed pattern. For b) we present a Center-of-Gravity method with a Gaussian correction taking into account the shape of the signal charge cloud. Both methods are also optimized for fast execution by implementing lookup tables rather than time consuming calculations. Our results show that with the appropriate analysis an uncertainty of the position measurement of better than 3.0 μm rms for 1320 eV photons is possible.

  17. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  18. Evaluation of the Positional Accuracy and Dosimetric Properties of a Three-dimensional Printed Device for Head and Neck Immobilization.

    PubMed

    Sato, Kiyokazu; Takeda, Ken; Dobashi, Suguru; Kadoya, Noriyuki; Ito, Kengo; Chiba, Mizuki; Kishi, Kazuma; Yanagawa, Isao; Jingu, Keiichi

    2017-01-01

    Our aim was to investigate the feasibility of a three-dimensional (3D) -printed head-and-neck (HN) immobilization device by comparing its positional accuracy and dosimetric properties with those of a conventional immobilization device (CID). We prepared a 3D-printed immobilization device (3DID) consisting of a mask and headrest with acrylonitrile-butadiene-styrene resin developed from the computed tomography data obtained by imaging a HN phantom. For comparison, a CID comprising a thermoplastic mask and headrest was prepared using the same HN phantom. We measured the setup error using the ExacTrac X-ray image system. Furthermore, using the ionization chamber and the water-equivalent phantom, we measured the changes in the dose due to the difference in the immobilization device material from the photon of 4 MV and 6 MV. The positional accuracy of the two devices were almost similar in each direction except in the vertical, lateral, and pitch directions (t-test, p<0.0001), and the maximum difference was 1 mm, and 1°. The standard deviations were not statistically different in each direction except in the longitudinal (F-test, p=0.034) and roll directions (F-test, p<0.0001). When the thickness was the same, the dose difference was almost similar at a 50 mm depth. At a 1 mm depth, the 3DID-plate had a 2.9-4.2% lower dose than the CID-plate. This study suggested that the positional accuracy and dosimetric properties of 3DID were almost similar to those of CID.

  19. Measuring the accuracy of particle position and force in optical tweezers using high-speed video microscopy.

    PubMed

    Gibson, Graham M; Leach, Jonathan; Keen, Stephen; Wright, Amanda J; Padgett, Miles J

    2008-09-15

    We assess the performance of a CMOS camera for the measurement of particle position within optical tweezers and the associated autocorrelation function and power spectrum. Measurement of the displacement of the particle from the trap center can also be related to the applied force. By considering the Allan variance of these measurements, we show that such cameras are capable of reaching the thermal limits of nanometer and femtonewton accuracies, and hence are suitable for many of the applications that traditionally use quadrant photodiodes. As an example of a multi-particle measurement we show the hydrodynamic coupling between two particles.

  20. Ultrasound Indoor Positioning System Based on a Low-Power Wireless Sensor Network Providing Sub-Centimeter Accuracy

    PubMed Central

    Medina, Carlos; Segura, José Carlos; De la Torre, Ángel

    2013-01-01

    This paper describes the TELIAMADE system, a new indoor positioning system based on time-of-flight (TOF) of ultrasonic signal to estimate the distance between a receiver node and a transmitter node. TELIAMADE system consists of a set of wireless nodes equipped with a radio module for communication and a module for the transmission and reception of ultrasound. The access to the ultrasonic channel is managed by applying a synchronization algorithm based on a time-division multiplexing (TDMA) scheme. The ultrasonic signal is transmitted using a carrier frequency of 40 kHz and the TOF measurement is estimated by applying a quadrature detector to the signal obtained at the A/D converter output. Low sampling frequencies of 17.78 kHz or even 12.31 kHz are possible using quadrature sampling in order to optimize memory requirements and to reduce the computational cost in signal processing. The distance is calculated from the TOF taking into account the speed of sound. An excellent accuracy in the estimation of the TOF is achieved using parabolic interpolation to detect of maximum of the signal envelope at the matched filter output. The signal phase information is also used for enhancing the TOF measurement accuracy. Experimental results show a root mean square error (rmse) less than 2 mm and a standard deviation less than 0.3 mm for pseudorange measurements in the range of distances between 2 and 6 m. The system location accuracy is also evaluated by applying multilateration. A sub-centimeter location accuracy is achieved with an average rmse of 9.6 mm. PMID:23486218

  1. Ultrasound indoor positioning system based on a low-power wireless sensor network providing sub-centimeter accuracy.

    PubMed

    Medina, Carlos; Segura, José Carlos; De la Torre, Ángel

    2013-03-13

    This paper describes the TELIAMADE system, a new indoor positioning system based on time-of-flight (TOF) of ultrasonic signal to estimate the distance between a receiver node and a transmitter node. TELIAMADE system consists of a set of wireless nodes equipped with a radio module for communication and a module for the transmission and reception of ultrasound. The access to the ultrasonic channel is managed by applying a synchronization algorithm based on a time-division multiplexing (TDMA) scheme. The ultrasonic signal is transmitted using a carrier frequency of 40 kHz and the TOF measurement is estimated by applying a quadrature detector to the signal obtained at the A/D converter output. Low sampling frequencies of 17.78 kHz or even 12.31 kHz are possible using quadrature sampling in order to optimize memory requirements and to reduce the computational cost in signal processing. The distance is calculated from the TOF taking into account the speed of sound. An excellent accuracy in the estimation of the TOF is achieved using parabolic interpolation to detect of maximum of the signal envelope at the matched filter output. The signal phase information is also used for enhancing the TOF measurement accuracy. Experimental results show a root mean square error (rmse) less than 2 mm and a standard deviation less than 0.3 mm for pseudorange measurements in the range of distances between 2 and 6 m. The system location accuracy is also evaluated by applying multilateration. A sub-centimeter location accuracy is achieved with an average rmse of 9.6 mm.

  2. High-Accuracy Self-Calibration for Smart, Optical Orbiting Payloads Integrated with Attitude and Position Determination

    PubMed Central

    Li, Jin; Xing, Fei; Chu, Daping; Liu, Zilong

    2016-01-01

    A high-accuracy space smart payload integrated with attitude and position (SSPIAP) is a new type of optical remote sensor that can autonomously complete image positioning. Inner orientation parameters (IOPs) are a prerequisite for image position determination of an SSPIAP. The calibration of IOPs significantly influences the precision of image position determination of SSPIAPs. IOPs can be precisely measured and calibrated in a laboratory. However, they may drift to a significant degree because of vibrations during complicated launches and on-orbit functioning. Therefore, laboratory calibration methods are not suitable for on-orbit functioning. We propose an on-orbit self-calibration method for SSPIAPs. Our method is based on an auto-collimating dichroic filter combined with a micro-electro-mechanical system (MEMS) point-source focal plane. A MEMS procedure is used to manufacture a light transceiver focal plane, which integrates with point light sources and a complementary metal oxide semiconductor (CMOS) sensor. A dichroic filter is used to fabricate an auto-collimation light reflection element. The dichroic filter and the MEMS point light sources focal plane are integrated into an SSPIAP so it can perform integrated self-calibration. Experiments show that our method can achieve micrometer-level precision, which is good enough to complete real-time calibration without temporal or spatial limitations. PMID:27472339

  3. Accuracy and reliability of multi-GNSS real-time precise positioning: GPS, GLONASS, BeiDou, and Galileo

    NASA Astrophysics Data System (ADS)

    Li, Xingxing; Ge, Maorong; Dai, Xiaolei; Ren, Xiaodong; Fritsche, Mathias; Wickert, Jens; Schuh, Harald

    2015-06-01

    In this contribution, we present a GPS+GLONASS+BeiDou+Galileo four-system model to fully exploit the observations of all these four navigation satellite systems for real-time precise orbit determination, clock estimation and positioning. A rigorous multi-GNSS analysis is performed to achieve the best possible consistency by processing the observations from different GNSS together in one common parameter estimation procedure. Meanwhile, an efficient multi-GNSS real-time precise positioning service system is designed and demonstrated by using the multi-GNSS Experiment, BeiDou Experimental Tracking Network, and International GNSS Service networks including stations all over the world. The statistical analysis of the 6-h predicted orbits show that the radial and cross root mean square (RMS) values are smaller than 10 cm for BeiDou and Galileo, and smaller than 5 cm for both GLONASS and GPS satellites, respectively. The RMS values of the clock differences between real-time and batch-processed solutions for GPS satellites are about 0.10 ns, while the RMS values for BeiDou, Galileo and GLONASS are 0.13, 0.13 and 0.14 ns, respectively. The addition of the BeiDou, Galileo and GLONASS systems to the standard GPS-only processing, reduces the convergence time almost by 70 %, while the positioning accuracy is improved by about 25 %. Some outliers in the GPS-only solutions vanish when multi-GNSS observations are processed simultaneous. The availability and reliability of GPS precise positioning decrease dramatically as the elevation cutoff increases. However, the accuracy of multi-GNSS precise point positioning (PPP) is hardly decreased and few centimeter are still achievable in the horizontal components even with 40 elevation cutoff. At 30 and 40 elevation cutoffs, the availability rates of GPS-only solution drop significantly to only around 70 and 40 %, respectively. However, multi-GNSS PPP can provide precise position estimates continuously (availability rate is more than 99

  4. Evaluation of MLC leaf positioning accuracy for static and dynamic IMRT treatments using DAVID in vivo dosimetric system.

    PubMed

    Karagoz, Gulay; Zorlu, Faruk; Yeginer, Mete; Yildiz, Demet; Ozyigit, Gokhan

    2016-03-08

    Accuracy and precision of leaf positioning in multileaf collimators (MLCs) are significant factors for the accuracy of IMRT treatments. This study aimed to inves-tigate the accuracy and repeatability of the MLC leaf positioning via the DAVID invivo dosimetric system for dynamic and static MLC systems. The DAVID system was designed as multiwire transmission ionization chamber which is placed in accessory holder of linear accelerators. Each wire of DAVID system corresponds to a MLC leaf-pair to verify the leaf positioning accuracy during IMRT treatment and QA. In this study, verifications of IMRT plans of five head and neck (H&N) and five prostate patients treated in a Varian DHX linear accelerator with 80-leaf MLC were performed using DAVID system. Before DAVID-based dosimetry, Electronics Portal Imaging Device (EPID) and PTW 2D ARRAY dosimetry system were used for 2D verification of each plan. The measurements taken by DAVID system in the first day of the treatments were used as reference for the following measurements taken over the next four weeks. The deviations in leaf positioning were evaluated by "Total Deviation (TD)" parameter calculated by DAVID software. The delivered IMRT plans were originally prepared using dynamic MLC method. The same plans were subsequently calculated based on static MLC method with three different intensity levels of five (IL5), 10 (IL10) and 20 (IL20) in order to compare the performances of MLC leaf positioning repeatability for dynamic and static IMRT plans. The leaf positioning accuracy is also evaluated by analyzing DynaLog files based on error histograms and root mean square (RMS) errors of leaf pairs' positions. Moreover, a correlation analysis between simultaneously taken DAVID and EPID measurements and DynaLog file recordings was subsequently performed. In the analysis of DAVID outputs, the overall deviations of dynamic MLC-based IMRT calculated from the deviations of the four weeks were found as 0.55% ± 0.57% and 1.48% ± 0

  5. Evaluation of MLC leaf positioning accuracy for static and dynamic IMRT treatments using DAVID in vivo dosimetric system.

    PubMed

    Karagoz, Gulay; Zorlu, Faruk; Yeginer, Mete; Yildiz, Demet; Ozyigit, Gokhan

    2016-03-01

    Accuracy and precision of leaf positioning in multileaf collimators (MLCs) are significant factors for the accuracy of IMRT treatments. This study aimed to investigate the accuracy and repeatability of the MLC leaf positioning via the DAVID in vivo dosimetric system for dynamic and static MLC systems. The DAVID system was designed as multiwire transmission ionization chamber which is placed in accessory holder of linear accelerators. Each wire of DAVID system corresponds to a MLC leaf-pair to verify the leaf positioning accuracy during IMRT treatment and QA. In this study, verifications of IMRT plans of five head and neck (H&N) and five prostate patients treated in a Varian DHX linear accelerator with 80-leaf MLC were performed using DAVID system. Before DAVID-based dosimetry, Electronics Portal Imaging Device (EPID) and PTW 2D ARRAY dosimetry system were used for 2D verification of each plan. The measurements taken by DAVID system in the first day of the treatments were used as reference for the following measurements taken over the next four weeks. The deviations in leaf positioning were evaluated by "Total Deviation (TD)" parameter calculated by DAVID software. The delivered IMRT plans were originally prepared using dynamic MLC method. The same plans were subsequently calculated based on static MLC method with three different intensity levels of five (IL5), 10 (IL10) and 20 (IL20) in order to compare the performances of MLC leaf positioning repeatability for dynamic and static IMRT plans. The leaf positioning accuracy is also evaluated by analyzing DynaLog files based on error histograms and root mean square (RMS) errors of leaf pairs' positions. Moreover, a correlation analysis between simultaneously taken DAVID and EPID measurements and DynaLog file recordings was subsequently performed. In the analysis of DAVID outputs, the overall deviations of dynamic MLC-based IMRT calculated from the deviations of the four weeks were found as 0.55%±0.57% and 1.48%±0

  6. Performance characterization of precision micro robot using a machine vision system over the Internet for guaranteed positioning accuracy

    NASA Astrophysics Data System (ADS)

    Kwon, Yongjin; Chiou, Richard; Rauniar, Shreepud; Sosa, Horacio

    2005-11-01

    There is a missing link between a virtual development environment (e.g., a CAD/CAM driven offline robotic programming) and production requirements of the actual robotic workcell. Simulated robot path planning and generation of pick-and-place coordinate points will not exactly coincide with the robot performance due to lack of consideration in variations in individual robot repeatability and thermal expansion of robot linkages. This is especially important when robots are controlled and programmed remotely (e.g., through Internet or Ethernet) since remote users have no physical contact with robotic systems. Using the current technology in Internet-based manufacturing that is limited to a web camera for live image transfer has been a significant challenge for the robot task performance. Consequently, the calibration and accuracy quantification of robot critical to precision assembly have to be performed on-site and the verification of robot positioning accuracy cannot be ascertained remotely. In worst case, the remote users have to assume the robot performance envelope provided by the manufacturers, which may causes a potentially serious hazard for system crash and damage to the parts and robot arms. Currently, there is no reliable methodology for remotely calibrating the robot performance. The objective of this research is, therefore, to advance the current state-of-the-art in Internet-based control and monitoring technology, with a specific aim in the accuracy calibration of micro precision robotic system for the development of a novel methodology utilizing Ethernet-based smart image sensors and other advanced precision sensory control network.

  7. Optimization of the Coverage and Accuracy of an Indoor Positioning System with a Variable Number of Sensors

    PubMed Central

    Domingo-Perez, Francisco; Lazaro-Galilea, Jose Luis; Bravo, Ignacio; Gardel, Alfredo; Rodriguez, David

    2016-01-01

    This paper focuses on optimal sensor deployment for indoor localization with a multi-objective evolutionary algorithm. Our goal is to obtain an algorithm to deploy sensors taking the number of sensors, accuracy and coverage into account. Contrary to most works in the literature, we consider the presence of obstacles in the region of interest (ROI) that can cause occlusions between the target and some sensors. In addition, we aim to obtain all of the Pareto optimal solutions regarding the number of sensors, coverage and accuracy. To deal with a variable number of sensors, we add speciation and structural mutations to the well-known non-dominated sorting genetic algorithm (NSGA-II). Speciation allows one to keep the evolution of sensor sets under control and to apply genetic operators to them so that they compete with other sets of the same size. We show some case studies of the sensor placement of an infrared range-difference indoor positioning system with a fairly complex model of the error of the measurements. The results obtained by our algorithm are compared to sensor placement patterns obtained with random deployment to highlight the relevance of using such a deployment algorithm. PMID:27338414

  8. Pitfalls at the root of facial assessment on photographs: a quantitative study of accuracy in positioning facial landmarks.

    PubMed

    Cummaudo, M; Guerzoni, M; Marasciuolo, L; Gibelli, D; Cigada, A; Obertovà, Z; Ratnayake, M; Poppa, P; Gabriel, P; Ritz-Timme, S; Cattaneo, C

    2013-05-01

    In the last years, facial analysis has gained great interest also for forensic anthropology. The application of facial landmarks may bring about relevant advantages for the analysis of 2D images by measuring distances and extracting quantitative indices. However, this is a complex task which depends upon the variability in positioning facial landmarks. In addition, literature provides only general indications concerning the reliability in positioning facial landmarks on photographic material, and no study is available concerning the specific errors which may be encountered in such an operation. The aim of this study is to analyze the inter- and intra-observer error in defining facial landmarks on photographs by using a software specifically developed for this purpose. Twenty-four operators were requested to define 22 facial landmarks on frontal view photographs and 11 on lateral view images; in addition, three operators repeated the procedure on the same photographs 20 times (at distance of 24 h). In the frontal view, the landmarks with less dispersion were the pupil, cheilion, endocanthion, and stomion (sto), and the landmarks with the highest dispersion were gonion, zygion, frontotemporale, tragion, and selion (se). In the lateral view, the landmarks with the least dispersion were se, pronasale, subnasale, and sto, whereas landmarks with the highest dispersion were gnathion, pogonion, and tragion. Results confirm that few anatomical points can be defined with the highest accuracy and show the importance of the preliminary investigation of reliability in positioning facial landmarks.

  9. Positioning System Accuracy Assessment for the Runway Incursion Prevention System Flight Test at the Dallas/Ft. Worth International Airport

    NASA Technical Reports Server (NTRS)

    Quach, Cuong C.

    2004-01-01

    NASA/Langley Research Center collaborated with the Federal Aviation Administration (FAA) to test a Runway Incursion Prevention System (RIPS) at the Dallas Fort Worth International Airport (DFW) in October 2000. The RIPS combines airborne and ground sensor data with various cockpit displays to improve pilots' awareness of traffic conditions on the airport surface. The systems tested at DFW involved surface radar and data systems that gather and send surface traffic information to a research aircraft outfitted with the RIPS software, cockpit displays, and data link transceivers. The data sent to the airborne systems contained identification and GPS location of traffic. This information was compared with the own-ship location from airborne GPS receivers to generate incursion alerts. A total of 93 test tracks were flown while operating RIPS. This report compares the accuracy of the airborne GPS systems that gave the own-ship position of the research aircraft for the 93 test tracks.

  10. Absolute Antenna Calibration at the US National Geodetic Survey

    NASA Astrophysics Data System (ADS)

    Mader, G. L.; Bilich, A. L.

    2012-12-01

    Geodetic GNSS applications routinely demand millimeter precision and extremely high levels of accuracy. To achieve these accuracies, measurement and instrument biases at the centimeter to millimeter level must be understood. One of these biases is the antenna phase center, the apparent point of signal reception for a GNSS antenna. It has been well established that phase center patterns differ between antenna models and manufacturers; additional research suggests that the addition of a radome or the choice of antenna mount can significantly alter those a priori phase center patterns. For the more demanding GNSS positioning applications and especially in cases of mixed-antenna networks, it is all the more important to know antenna phase center variations as a function of both elevation and azimuth in the antenna reference frame and incorporate these models into analysis software. Determination of antenna phase center behavior is known as "antenna calibration". Since 1994, NGS has computed relative antenna calibrations for more than 350 antennas. In recent years, the geodetic community has moved to absolute calibrations - the IGS adopted absolute antenna phase center calibrations in 2006 for use in their orbit and clock products, and NGS's CORS group began using absolute antenna calibration upon the release of the new CORS coordinates in IGS08 epoch 2005.00 and NAD 83(2011,MA11,PA11) epoch 2010.00. Although NGS relative calibrations can be and have been converted to absolute, it is considered best practice to independently measure phase center characteristics in an absolute sense. Consequently, NGS has developed and operates an absolute calibration system. These absolute antenna calibrations accommodate the demand for greater accuracy and for 2-dimensional (elevation and azimuth) parameterization. NGS will continue to provide calibration values via the NGS web site www.ngs.noaa.gov/ANTCAL, and will publish calibrations in the ANTEX format as well as the legacy ANTINFO

  11. Mathematical Model for Absolute Magnetic Measuring Systems in Industrial Applications

    NASA Astrophysics Data System (ADS)

    Fügenschuh, Armin; Fügenschuh, Marzena; Ludszuweit, Marina; Mojsic, Aleksandar; Sokół, Joanna

    2015-09-01

    Scales for measuring systems are either based on incremental or absolute measuring methods. Incremental scales need to initialize a measurement cycle at a reference point. From there, the position is computed by counting increments of a periodic graduation. Absolute methods do not need reference points, since the position can be read directly from the scale. The positions on the complete scales are encoded using two incremental tracks with different graduation. We present a new method for absolute measuring using only one track for position encoding up to micrometre range. Instead of the common perpendicular magnetic areas, we use a pattern of trapezoidal magnetic areas, to store more complex information. For positioning, we use the magnetic field where every position is characterized by a set of values measured by a hall sensor array. We implement a method for reconstruction of absolute positions from the set of unique measured values. We compare two patterns with respect to uniqueness, accuracy, stability and robustness of positioning. We discuss how stability and robustness are influenced by different errors during the measurement in real applications and how those errors can be compensated.

  12. Computer-assisted orthognathic surgery: waferless maxillary positioning, versatility, and accuracy of an image-guided visualisation display.

    PubMed

    Zinser, Max J; Mischkowski, Robert A; Dreiseidler, Timo; Thamm, Oliver C; Rothamel, Daniel; Zöller, Joachim E

    2013-12-01

    There may well be a shift towards 3-dimensional orthognathic surgery when virtual surgical planning can be applied clinically. We present a computer-assisted protocol that uses surgical navigation supplemented by an interactive image-guided visualisation display (IGVD) to transfer virtual maxillary planning precisely. The aim of this study was to analyse its accuracy and versatility in vivo. The protocol consists of maxillofacial imaging, diagnosis, planning of virtual treatment, and intraoperative surgical transfer using an IGV display. The advantage of the interactive IGV display is that the virtually planned maxilla and its real position can be completely superimposed during operation through a video graphics array (VGA) camera, thereby augmenting the surgeon's 3-dimensional perception. Sixteen adult class III patients were treated with by bimaxillary osteotomy. Seven hard tissue variables were chosen to compare (ΔT1-T0) the virtual maxillary planning (T0) with the postoperative result (T1) using 3-dimensional cephalometry. Clinically acceptable precision for the surgical planning transfer of the maxilla (<0.35 mm) was seen in the anteroposterior and mediolateral angles, and in relation to the skull base (<0.35°), and marginal precision was seen in the orthogonal dimension (<0.64 mm). An interactive IGV display complemented surgical navigation, augmented virtual and real-time reality, and provided a precise technique of waferless stereotactic maxillary positioning, which may offer an alternative approach to the use of arbitrary splints and 2-dimensional orthognathic planning.

  13. Single-frequency receivers as master permanent stations in GNSS networks: precision and accuracy of the positioning in mixed networks

    NASA Astrophysics Data System (ADS)

    Dabove, Paolo; Manzino, Ambrogio Maria

    2015-04-01

    The use of GPS/GNSS instruments is a common practice in the world at both a commercial and academic research level. Since last ten years, Continuous Operating Reference Stations (CORSs) networks were born in order to achieve the possibility to extend a precise positioning more than 15 km far from the master station. In this context, the Geomatics Research Group of DIATI at the Politecnico di Torino has carried out several experiments in order to evaluate the achievable precision obtainable with different GNSS receivers (geodetic and mass-market) and antennas if a CORSs network is considered. This work starts from the research above described, in particular focusing the attention on the usefulness of single frequency permanent stations in order to thicken the existing CORSs, especially for monitoring purposes. Two different types of CORSs network are available today in Italy: the first one is the so called "regional network" and the second one is the "national network", where the mean inter-station distances are about 25/30 and 50/70 km respectively. These distances are useful for many applications (e.g. mobile mapping) if geodetic instruments are considered but become less useful if mass-market instruments are used or if the inter-station distance between master and rover increases. In this context, some innovative GNSS networks were developed and tested, analyzing the performance of rover's positioning in terms of quality, accuracy and reliability both in real-time and post-processing approach. The use of single frequency GNSS receivers leads to have some limits, especially due to a limited baseline length, the possibility to obtain a correct fixing of the phase ambiguity for the network and to fix the phase ambiguity correctly also for the rover. These factors play a crucial role in order to reach a positioning with a good level of accuracy (as centimetric o better) in a short time and with an high reliability. The goal of this work is to investigate about the

  14. Absolute transition probabilities of phosphorus.

    NASA Technical Reports Server (NTRS)

    Miller, M. H.; Roig, R. A.; Bengtson, R. D.

    1971-01-01

    Use of a gas-driven shock tube to measure the absolute strengths of 21 P I lines and 126 P II lines (from 3300 to 6900 A). Accuracy for prominent, isolated neutral and ionic lines is estimated to be 28 to 40% and 18 to 30%, respectively. The data and the corresponding theoretical predictions are examined for conformity with the sum rules.-

  15. Absolute multilateration between spheres

    NASA Astrophysics Data System (ADS)

    Muelaner, Jody; Wadsworth, William; Azini, Maria; Mullineux, Glen; Hughes, Ben; Reichold, Armin

    2017-04-01

    Environmental effects typically limit the accuracy of large scale coordinate measurements in applications such as aircraft production and particle accelerator alignment. This paper presents an initial design for a novel measurement technique with analysis and simulation showing that that it could overcome the environmental limitations to provide a step change in large scale coordinate measurement accuracy. Referred to as absolute multilateration between spheres (AMS), it involves using absolute distance interferometry to directly measure the distances between pairs of plain steel spheres. A large portion of each sphere remains accessible as a reference datum, while the laser path can be shielded from environmental disturbances. As a single scale bar this can provide accurate scale information to be used for instrument verification or network measurement scaling. Since spheres can be simultaneously measured from multiple directions, it also allows highly accurate multilateration-based coordinate measurements to act as a large scale datum structure for localized measurements, or to be integrated within assembly tooling, coordinate measurement machines or robotic machinery. Analysis and simulation show that AMS can be self-aligned to achieve a theoretical combined standard uncertainty for the independent uncertainties of an individual 1 m scale bar of approximately 0.49 µm. It is also shown that combined with a 1 µm m‑1 standard uncertainty in the central reference system this could result in coordinate standard uncertainty magnitudes of 42 µm over a slender 1 m by 20 m network. This would be a sufficient step change in accuracy to enable next generation aerospace structures with natural laminar flow and part-to-part interchangeability.

  16. MAGSAT: Vector magnetometer absolute sensor alignment determination

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.

    1981-01-01

    A procedure is described for accurately determining the absolute alignment of the magnetic axes of a triaxial magnetometer sensor with respect to an external, fixed, reference coordinate system. The method does not require that the magnetic field vector orientation, as generated by a triaxial calibration coil system, be known to better than a few degrees from its true position, and minimizes the number of positions through which a sensor assembly must be rotated to obtain a solution. Computer simulations show that accuracies of better than 0.4 seconds of arc can be achieved under typical test conditions associated with existing magnetic test facilities. The basic approach is similar in nature to that presented by McPherron and Snare (1978) except that only three sensor positions are required and the system of equations to be solved is considerably simplified. Applications of the method to the case of the MAGSAT Vector Magnetometer are presented and the problems encountered discussed.

  17. Assessment of the accuracy of PPP for very-high-frequency dynamic, satellite positioning and earthquake modeling

    NASA Astrophysics Data System (ADS)

    Moschas, F.; Avallone, A.; Moschonas, N.; Saltogianni, V.; Stiros, S.

    2012-04-01

    With the advent of various GPS/GNSS Point Positioning techniques, it became possible to model the dynamic displacement history of specific points during large and rather moderate earthquakes using satellite positioning, 1Hz and occasionally 10Hz sampling data. While there is evidence that the obtained data are precise, experience from monitoring of engineering structures like bridges, indicates that GPS/GNSS records are contaminated by coloured (mostly background noise) noise even in the cases of differential-type analysis of the satellite signals. This made the necessary the assessment of the results of different PPP processing using supervised learning techniques. Our work was based on a modification of an experiment first made to assess the potential of GPS to measure oscillations of civil engineering structures. A 10Hz GNSS antenna-receiver unit was mounted on the top of a vertical rod, fixed on the ground and forced to controlled oscillations. Oscillations were also recorded by a robotic theodolite and an accelerometer, and the whole experiment was video-recorded. A second 10Hz GNSS antenna-receiver unit was left on stable ground, in a nearby position. The rod was forced to semi-static motion (bending) and then was left to oscillate freely until still, and the whole movement was recorded by all sensors. GNSS data were analyzed both in kinematic mode and in PPP mode, using the GIPSY-OASIS II (http://gipsy-oasis.jpl.nasa.gov) (only GPS) and the PPP CRCS facility (GPS + GLONAS). Recorded PPP and differential kinematic processing coordinates (apparent displacements) were found to follow the real motion, but to be contaminated by a long-period noise. On the contrary, the short-period component of the apparent PPP displacements, obtained using high-pass filtering, were very much consistent with the real motion, with sub-mm mean deviation, though occasionally contaminated by clipping. The assessment of the very-high frequency GPS noise will provide useful information

  18. Design and implementation of a two-axis micromanipulator to enhance the gripper positional accuracy of a single flexible link

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoying

    1994-05-01

    Accurate and versatile robots are required to perform advanced assembly and manufacturing tasks. To improve the end effector positional accuracy of lightweight robot arms, a two-axis micro-manipulator is mounted between the robot wrist and its manipulator. The rationale is to reduce the wrist sensitivity to the structural deflections of the robotic manipulator. In an attempt to separate the problem of the end-of-arm deflections from the overall control problem of multi-link systems, the micromanipulator is tested on a single flexible link. A laser head with a dual axis photodetector is used to provide direct measurements of the transverse deflections at the free-end of the beam and to detect mechanical inaccuracies caused by manufacturing imperfections and assembly misalignment. The advantages of the integrated system of the micro-manipulator with a single compliant beam are demonstrated and compared to the one without the micro-manipulator for two different control schemes, 'rigid body controller (RBC)' and 'rigid and flexible motion controller (RFMC)' . Both theoretical and experimental results have proven the capability of the micro-manipulator in significantly improving the gripper positional accuracy. Furthermore, it was demonstrated that the micromanipulator tends to complement rather than overlap the effort exerted by the host beam controller. The experimental results have revealed the significant adverse effects of the backlash in gearing on the overall performance of the macro- and micro-manipulators. To address this problem, the dynamic model of the macro- and micro-manipulators is modified to include the dynamics of joint actuators along with the effects of backlash in the indirect drive mechanism of the compliant beam. A general method is developed to handle the dynamic characteristics of backlash in gearing. It entails the derivation of a variable structure model with one auxiliary degree-of-freedom. The latter serves to increase the number of degrees

  19. Criterion validity and accuracy of global positioning satellite and data logging devices for wheelchair tennis court movement

    PubMed Central

    Sindall, Paul; Lenton, John P.; Whytock, Katie; Tolfrey, Keith; Oyster, Michelle L.; Cooper, Rory A.; Goosey-Tolfrey, Victoria L.

    2013-01-01

    Purpose To compare the criterion validity and accuracy of a 1 Hz non-differential global positioning system (GPS) and data logger device (DL) for the measurement of wheelchair tennis court movement variables. Methods Initial validation of the DL device was performed. GPS and DL were fitted to the wheelchair and used to record distance (m) and speed (m/second) during (a) tennis field (b) linear track, and (c) match-play test scenarios. Fifteen participants were monitored at the Wheelchair British Tennis Open. Results Data logging validation showed underestimations for distance in right (DLR) and left (DLL) logging devices at speeds >2.5 m/second. In tennis-field tests, GPS underestimated distance in five drills. DLL was lower than both (a) criterion and (b) DLR in drills moving forward. Reversing drill direction showed that DLR was lower than (a) criterion and (b) DLL. GPS values for distance and average speed for match play were significantly lower than equivalent values obtained by DL (distance: 2816 (844) vs. 3952 (1109) m, P = 0.0001; average speed: 0.7 (0.2) vs. 1.0 (0.2) m/second, P = 0.0001). Higher peak speeds were observed in DL (3.4 (0.4) vs. 3.1 (0.5) m/second, P = 0.004) during tennis match play. Conclusions Sampling frequencies of 1 Hz are too low to accurately measure distance and speed during wheelchair tennis. GPS units with a higher sampling rate should be advocated in further studies. Modifications to existing DL devices may be required to increase measurement precision. Further research into the validity of movement devices during match play will further inform the demands and movement patterns associated with wheelchair tennis. PMID:23820154

  20. Positional Accuracy Assessment of the Openstreetmap Buildings Layer Through Automatic Homologous Pairs Detection: the Method and a Case Study

    NASA Astrophysics Data System (ADS)

    Brovelli, M. A.; Minghini, M.; Molinari, M. E.; Zamboni, G.

    2016-06-01

    OpenStreetMap (OSM) is currently the largest openly licensed collection of geospatial data. Being OSM increasingly exploited in a variety of applications, research has placed great attention on the assessment of its quality. This work focuses on assessing the quality of OSM buildings. While most of the studies available in literature are limited to the evaluation of OSM building completeness, this work proposes an original approach to assess the positional accuracy of OSM buildings based on comparison with a reference dataset. The comparison relies on a quasi-automated detection of homologous pairs on the two datasets. Based on the homologous pairs found, warping algorithms like e.g. affine transformations and multi-resolution splines can be applied to the OSM buildings to generate a new version having an optimal local match to the reference layer. A quality assessment of the OSM buildings of Milan Municipality (Northern Italy), having an area of about 180 km2, is then presented. After computing some measures of completeness, the algorithm based on homologous points is run using the building layer of the official vector cartography of Milan Municipality as the reference dataset. Approximately 100000 homologous points are found, which show a systematic translation of about 0.4 m on both the X and Y directions and a mean distance of about 0.8 m between the datasets. Besides its efficiency and high degree of automation, the algorithm generates a warped version of OSM buildings which, having by definition a closest match to the reference buildings, can be eventually integrated in the OSM database.

  1. Absolute optical metrology : nanometers to kilometers

    NASA Technical Reports Server (NTRS)

    Dubovitsky, Serge; Lay, O. P.; Peters, R. D.; Liebe, C. C.

    2005-01-01

    We provide and overview of the developments in the field of high-accuracy absolute optical metrology with emphasis on space-based applications. Specific work on the Modulation Sideband Technology for Absolute Ranging (MSTAR) sensor is described along with novel applications of the sensor.

  2. Electronic Absolute Cartesian Autocollimator

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    2006-01-01

    An electronic absolute Cartesian autocollimator performs the same basic optical function as does a conventional all-optical or a conventional electronic autocollimator but differs in the nature of its optical target and the manner in which the position of the image of the target is measured. The term absolute in the name of this apparatus reflects the nature of the position measurement, which, unlike in a conventional electronic autocollimator, is based absolutely on the position of the image rather than on an assumed proportionality between the position and the levels of processed analog electronic signals. The term Cartesian in the name of this apparatus reflects the nature of its optical target. Figure 1 depicts the electronic functional blocks of an electronic absolute Cartesian autocollimator along with its basic optical layout, which is the same as that of a conventional autocollimator. Referring first to the optical layout and functions only, this or any autocollimator is used to measure the compound angular deviation of a flat datum mirror with respect to the optical axis of the autocollimator itself. The optical components include an illuminated target, a beam splitter, an objective or collimating lens, and a viewer or detector (described in more detail below) at a viewing plane. The target and the viewing planes are focal planes of the lens. Target light reflected by the datum mirror is imaged on the viewing plane at unit magnification by the collimating lens. If the normal to the datum mirror is parallel to the optical axis of the autocollimator, then the target image is centered on the viewing plane. Any angular deviation of the normal from the optical axis manifests itself as a lateral displacement of the target image from the center. The magnitude of the displacement is proportional to the focal length and to the magnitude (assumed to be small) of the angular deviation. The direction of the displacement is perpendicular to the axis about which the

  3. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  4. Smart Device-Supported BDS/GNSS Real-Time Kinematic Positioning for Sub-Meter-Level Accuracy in Urban Location-Based Services

    PubMed Central

    Wang, Liang; Li, Zishen; Zhao, Jiaojiao; Zhou, Kai; Wang, Zhiyu; Yuan, Hong

    2016-01-01

    Using mobile smart devices to provide urban location-based services (LBS) with sub-meter-level accuracy (around 0.5 m) is a major application field for future global navigation satellite system (GNSS) development. Real-time kinematic (RTK) positioning, which is a widely used GNSS-based positioning approach, can improve the accuracy from about 10–20 m (achieved by the standard positioning services) to about 3–5 cm based on the geodetic receivers. In using the smart devices to achieve positioning with sub-meter-level accuracy, a feasible solution of combining the low-cost GNSS module and the smart device is proposed in this work and a user-side GNSS RTK positioning software was developed from scratch based on the Android platform. Its real-time positioning performance was validated by BeiDou Navigation Satellite System/Global Positioning System (BDS/GPS) combined RTK positioning under the conditions of a static and kinematic (the velocity of the rover was 50–80 km/h) mode in a real urban environment with a SAMSUNG Galaxy A7 smartphone. The results show that the fixed-rates of ambiguity resolution (the proportion of epochs of ambiguities fixed) for BDS/GPS combined RTK in the static and kinematic tests were about 97% and 90%, respectively, and the average positioning accuracies (RMS) were better than 0.15 m (horizontal) and 0.25 m (vertical) for the static test, and 0.30 m (horizontal) and 0.45 m (vertical) for the kinematic test. PMID:28009835

  5. Smart Device-Supported BDS/GNSS Real-Time Kinematic Positioning for Sub-Meter-Level Accuracy in Urban Location-Based Services.

    PubMed

    Wang, Liang; Li, Zishen; Zhao, Jiaojiao; Zhou, Kai; Wang, Zhiyu; Yuan, Hong

    2016-12-21

    Using mobile smart devices to provide urban location-based services (LBS) with sub-meter-level accuracy (around 0.5 m) is a major application field for future global navigation satellite system (GNSS) development. Real-time kinematic (RTK) positioning, which is a widely used GNSS-based positioning approach, can improve the accuracy from about 10-20 m (achieved by the standard positioning services) to about 3-5 cm based on the geodetic receivers. In using the smart devices to achieve positioning with sub-meter-level accuracy, a feasible solution of combining the low-cost GNSS module and the smart device is proposed in this work and a user-side GNSS RTK positioning software was developed from scratch based on the Android platform. Its real-time positioning performance was validated by BeiDou Navigation Satellite System/Global Positioning System (BDS/GPS) combined RTK positioning under the conditions of a static and kinematic (the velocity of the rover was 50-80 km/h) mode in a real urban environment with a SAMSUNG Galaxy A7 smartphone. The results show that the fixed-rates of ambiguity resolution (the proportion of epochs of ambiguities fixed) for BDS/GPS combined RTK in the static and kinematic tests were about 97% and 90%, respectively, and the average positioning accuracies (RMS) were better than 0.15 m (horizontal) and 0.25 m (vertical) for the static test, and 0.30 m (horizontal) and 0.45 m (vertical) for the kinematic test.

  6. Accuracy of time comparison derived from reception of LORAN-C and Global Positioning System time signals.

    NASA Astrophysics Data System (ADS)

    Horiai, K.

    1992-10-01

    The accuracy of time comparison by means of the reception of common time signals, namely, LORAN-C and GPS, is examined. Differences of UTC from the emission times of these two radio wave signals measured at four Japanese stations and one US station are analyzed and compared with the clock comparison reports published by the Bureau International des Poids et Mesures. The accuracy of the time comparison via LORAN-C signals of the northwest Pacific chain is about 3.61 μs and that via GPS is 0.14 μs.

  7. Absolute Standards for Climate Measurements

    NASA Astrophysics Data System (ADS)

    Leckey, J.

    2016-10-01

    In a world of changing climate, political uncertainty, and ever-changing budgets, the benefit of measurements traceable to SI standards increases by the day. To truly resolve climate change trends on a decadal time scale, on-orbit measurements need to be referenced to something that is both absolute and unchanging. One such mission is the Climate Absolute Radiance and Refractivity Observatory (CLARREO) that will measure a variety of climate variables with an unprecedented accuracy to definitively quantify climate change. In the CLARREO mission, we will utilize phase change cells in which a material is melted to calibrate the temperature of a blackbody that can then be observed by a spectrometer. A material's melting point is an unchanging physical constant that, through a series of transfers, can ultimately calibrate a spectrometer on an absolute scale. CLARREO consists of two primary instruments: an infrared (IR) spectrometer and a reflected solar (RS) spectrometer. The mission will contain orbiting radiometers with sufficient accuracy to calibrate other space-based instrumentation and thus transferring the absolute traceability. The status of various mission options will be presented.

  8. Accuracy and efficiency of an infrared based positioning and tracking system for patient set-up and monitoring in image guided radiotherapy

    NASA Astrophysics Data System (ADS)

    Jia, Jing; Xu, Gongming; Pei, Xi; Cao, Ruifen; Hu, Liqin; Wu, Yican

    2015-03-01

    An infrared based positioning and tracking (IPT) system was introduced and its accuracy and efficiency for patient setup and monitoring were tested for daily radiotherapy treatment. The IPT system consists of a pair of floor mounted infrared stereoscopic cameras, passive infrared markers and tools used for acquiring localization information as well as a custom controlled software which can perform the positioning and tracking functions. The evaluation of IPT system characteristics was conducted based on the AAPM 147 task report. Experiments on spatial drift and reproducibility as well as static and dynamic localization accuracy were carried out to test the efficiency of the IPT system. Measurements of known translational (up to 55.0 mm) set-up errors in three dimensions have been performed on a calibration phantom. The accuracy of positioning was evaluated on an anthropomorphic phantom with five markers attached to the surface; the precision of the tracking ability was investigated through a sinusoidal motion platform. For the monitoring of the respiration, three volunteers contributed to the breathing testing in real time. The spatial drift of the IPT system was 0.65 mm within 60 min to be stable. The reproducibility of position variations were between 0.01 and 0.04 mm. The standard deviation of static marker localization was 0.26 mm. The repositioning accuracy was 0.19 mm, 0.29 mm, and 0.53 mm in the left/right (L/R), superior/inferior (S/I) and anterior/posterior (A/P) directions, respectively. The measured dynamic accuracy was 0.57 mm and discrepancies measured for the respiratory motion tracking was better than 1 mm. The overall positioning accuracy of the IPT system was within 2 mm. In conclusion, the IPT system is an accurate and effective tool for assisting patient positioning in the treatment room. The characteristics of the IPT system can successfully meet the needs for real time external marker tracking and patient positioning as well as respiration

  9. Absolute-structure reports.

    PubMed

    Flack, Howard D

    2013-08-01

    All the 139 noncentrosymmetric crystal structures published in Acta Crystallographica Section C between January 2011 and November 2012 inclusive have been used as the basis of a detailed study of the reporting of absolute structure. These structure determinations cover a wide range of space groups, chemical composition and resonant-scattering contribution. Defining A and D as the average and difference of the intensities of Friedel opposites, their level of fit has been examined using 2AD and selected-D plots. It was found, regardless of the expected resonant-scattering contribution to Friedel opposites, that the Friedel-difference intensities are often dominated by random uncertainty and systematic error. An analysis of data collection strategy is provided. It is found that crystal-structure determinations resulting in a Flack parameter close to 0.5 may not necessarily be from crystals twinned by inversion. Friedifstat is shown to be a robust estimator of the resonant-scattering contribution to Friedel opposites, very little affected by the particular space group of a structure nor by the occupation of special positions. There is considerable confusion in the text of papers presenting achiral noncentrosymmetric crystal structures. Recommendations are provided for the optimal way of treating noncentrosymmetric crystal structures for which the experimenter has no interest in determining the absolute structure.

  10. A high-accuracy two-position alignment inertial navigation system for lunar rovers aided by a star sensor with a calibration and positioning function

    NASA Astrophysics Data System (ADS)

    Lu, Jiazhen; Lei, Chaohua; Yang, Yanqiang; Liu, Ming

    2016-12-01

    An integrated inertial/celestial navigation system (INS/CNS) has wide applicability in lunar rovers as it provides accurate and autonomous navigational information. Initialization is particularly vital for a INS. This paper proposes a two-position initialization method based on a standard Kalman filter. The difference between the computed star vector and the measured star vector is measured. With the aid of a star sensor and the two positions, the attitudinal and positional errors can be greatly reduced, and the biases of three gyros and accelerometers can also be estimated. The semi-physical simulation results show that the positional and attitudinal errors converge within 0.07″ and 0.1 m, respectively, when the given initial positional error is 1 km and the attitudinal error is 10°. These good results show that the proposed method can accomplish alignment, positioning and calibration functions simultaneously. Thus the proposed two-position initialization method has the potential for application in lunar rover navigation.

  11. Accuracy of surface registration compared to conventional volumetric registration in patient positioning for head-and-neck radiotherapy: A simulation study using patient data

    SciTech Connect

    Kim, Youngjun; Li, Ruijiang; Na, Yong Hum; Xing, Lei; Lee, Rena

    2014-12-15

    Purpose: 3D optical surface imaging has been applied to patient positioning in radiation therapy (RT). The optical patient positioning system is advantageous over conventional method using cone-beam computed tomography (CBCT) in that it is radiation free, frameless, and is capable of real-time monitoring. While the conventional radiographic method uses volumetric registration, the optical system uses surface matching for patient alignment. The relative accuracy of these two methods has not yet been sufficiently investigated. This study aims to investigate the theoretical accuracy of the surface registration based on a simulation study using patient data. Methods: This study compares the relative accuracy of surface and volumetric registration in head-and-neck RT. The authors examined 26 patient data sets, each consisting of planning CT data acquired before treatment and patient setup CBCT data acquired at the time of treatment. As input data of surface registration, patient’s skin surfaces were created by contouring patient skin from planning CT and treatment CBCT. Surface registration was performed using the iterative closest points algorithm by point–plane closest, which minimizes the normal distance between source points and target surfaces. Six degrees of freedom (three translations and three rotations) were used in both surface and volumetric registrations and the results were compared. The accuracy of each method was estimated by digital phantom tests. Results: Based on the results of 26 patients, the authors found that the average and maximum root-mean-square translation deviation between the surface and volumetric registrations were 2.7 and 5.2 mm, respectively. The residual error of the surface registration was calculated to have an average of 0.9 mm and a maximum of 1.7 mm. Conclusions: Surface registration may lead to results different from those of the conventional volumetric registration. Only limited accuracy can be achieved for patient

  12. Evaluating the velocity accuracy of an integrated GPS/INS system: Flight test results. [Global positioning system/inertial navigation systems (GPS/INS)

    SciTech Connect

    Owen, T.E.; Wardlaw, R.

    1991-01-01

    Verifying the velocity accuracy of a GPS receiver or an integrated GPS/INS system in a dynamic environment is a difficult proposition when many of the commonly used reference systems have velocity uncertainities of the same order of magnitude or greater than the GPS system. The results of flight tests aboard an aircraft in which multiple reference systems simultaneously collected data to evaluate the accuracy of an integrated GPS/INS system are reported. Emphasis is placed on obtaining high accuracy estimates of the velocity error of the integrated system in order to verify that velocity accuracy is maintained during both linear and circular trajectories. Three different reference systems operating in parallel during flight tests are used to independently determine the position and velocity of an aircraft in flight. They are a transponder/interrogator ranging system, a laser tracker, and GPS carrier phase processing. Results obtained from these reference systems are compared against each other and against an integrated real time differential based GPS/INS system to arrive at a set of conclusions about the accuracy of the integrated system.

  13. Study on desirable ionospheric corrections accuracy for network-RTK positioning and its impact on time-to-fix and probability of successful single-epoch ambiguity resolution

    NASA Astrophysics Data System (ADS)

    Paziewski, Jacek

    2016-02-01

    The mitigation of ionospheric delay is still of crucial interest in GNSS positioning, especially in precise solutions such as instantaneous RTK positioning. Thus, several effective algorithms and functional models were developed, and also numerous investigations of ionospheric correction properties in RTK positioning have been performed so far. One of the most highly effective approaches in precise relative positioning is the application of the ionosphere-weighted model with network-derived corrections. This contribution investigates the impact of the accuracy of the network ionospheric corrections on time-to-fix in RTK-OTF positioning. Also, an attempt has been made to estimate the desirable accuracy of the network ionospheric corrections, allowing for reliable instantaneous ambiguity resolution. The experiment is based on a multi-baseline GPS RTK positioning supported with network-derived ionospheric corrections for medium length baselines. The results show that in such scenario, the double-differenced ionospheric correction residuals should not exceed ∼1/3 of the L1 wavelength for successful single-epoch ambiguity resolution.

  14. Absolutely classical spin states

    NASA Astrophysics Data System (ADS)

    Bohnet-Waldraff, F.; Giraud, O.; Braun, D.

    2017-01-01

    We introduce the concept of "absolutely classical" spin states, in analogy to absolutely separable states of bipartite quantum systems. Absolutely classical states are states that remain classical (i.e., a convex sum of projectors on coherent states of a spin j ) under any unitary transformation applied to them. We investigate the maximal size of the ball of absolutely classical states centered on the maximally mixed state and derive a lower bound for its radius as a function of the total spin quantum number. We also obtain a numerical estimate of this maximal radius and compare it to the case of absolutely separable states.

  15. Accuracy of three-dimensional measurements obtained from cone beam computed tomography surface-rendered images for cephalometric analysis: influence of patient scanning position.

    PubMed

    Hassan, Bassam; van der Stelt, Paul; Sanderink, Gerard

    2009-04-01

    The aims of this study were to assess the accuracy of linear measurements on three-dimensional (3D) surface-rendered images generated from cone beam computed tomography (CBCT) in comparison with two-dimensional (2D) slices and 2D lateral and postero-anterior (PA) cephalometric projections, and to investigate the influence of patient head position in the scanner on measurement accuracy. Eight dry human skulls were scanned twice using NewTom 3G CBCT in an ideal and a rotated position and the resulting datasets were used to create 3D surface-rendered images, 2D tomographic slices, and 2D lateral and PA projections. Ten linear distances were defined for cephalometric measurements. The physical and radiographic measurements were repeated twice by three independent observers and were compared using repeated measures analysis of variance (P=0.05). The radiographic measurements were also compared between the ideal and the rotated scan positions. The radiographic measurements of the 3D images were closer to the physical measurements than the 2D slices and 2D projection images. No statistically significant difference was found between the ideal and the rotated scan measurements for the 3D images and the 2D tomographic slices. A statistically significant difference (P<0.001) was observed between the ideal and rotated scan positions for the 2D projection images. The findings indicate that measurements based on 3D CBCT surface images are accurate and that small variations in the patient's head position do not influence measurement accuracy.

  16. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

    2012-05-15

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  17. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2010-07-13

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  18. Development of X-Y servo pneumatic-piezoelectric hybrid actuators for position control with high response, large stroke and nanometer accuracy.

    PubMed

    Chiang, Mao-Hsiung

    2010-01-01

    This study aims to develop a X-Y dual-axial intelligent servo pneumatic-piezoelectric hybrid actuator for position control with high response, large stroke (250 mm, 200 mm) and nanometer accuracy (20 nm). In each axis, the rodless pneumatic actuator serves to position in coarse stroke and the piezoelectric actuator compensates in fine stroke. Thus, the overall control systems of the single axis become a dual-input single-output (DISO) system. Although the rodless pneumatic actuator has relatively larger friction force, it has the advantage of mechanism for multi-axial development. Thus, the X-Y dual-axial positioning system is developed based on the servo pneumatic-piezoelectric hybrid actuator. In addition, the decoupling self-organizing fuzzy sliding mode control is developed as the intelligent control strategies. Finally, the proposed novel intelligent X-Y dual-axial servo pneumatic-piezoelectric hybrid actuators are implemented and verified experimentally.

  19. Study of accuracy in the position determination with SALSA, a γ-scanning system for the characterization of segmented HPGe detectors

    NASA Astrophysics Data System (ADS)

    Hernandez-Prieto, A.; Quintana, B.; Martìn, S.; Domingo-Pardo, C.

    2016-07-01

    Accurate characterization of the electric response of segmented high-purity germanium (HPGe) detectors as a function of the interaction position is one of the current goals of the Nuclear Physics community seeking to perform γ-ray tracking or even imaging with these detectors. For this purpose, scanning devices must be developed to achieve the signal-position association with the highest precision. With a view to studying the accuracy achieved with SALSA, the SAlamanca Lyso-based Scanning Array, here we report a detailed study on the uncertainty sources and their effect in the position determination inside the HPGe detector to be scanned. The optimization performed on the design of SALSA, aimed at minimizing the effect of the uncertainty sources, afforded an intrinsic uncertainty of ∼2 mm for large coaxial detectors and ∼1 mm for planar ones.

  20. Improved accuracy and speed in scanning probe microscopy by image reconstruction from non-gridded position sensor data

    NASA Astrophysics Data System (ADS)

    Ziegler, Dominik; Meyer, Travis R.; Farnham, Rodrigo; Brune, Christoph; Bertozzi, Andrea L.; Ashby, Paul D.

    2013-08-01

    Scanning probe microscopy (SPM) has facilitated many scientific discoveries utilizing its strengths of spatial resolution, non-destructive characterization and realistic in situ environments. However, accurate spatial data are required for quantitative applications but this is challenging for SPM especially when imaging at higher frame rates. We present a new operation mode for scanning probe microscopy that uses advanced image processing techniques to render accurate images based on position sensor data. This technique, which we call sensor inpainting, frees the scanner to no longer be at a specific location at a given time. This drastically reduces the engineering effort of position control and enables the use of scan waveforms that are better suited for the high inertia nanopositioners of SPM. While in raster scanning, typically only trace or retrace images are used for display, in Archimedean spiral scans 100% of the data can be displayed and at least a two-fold increase in temporal or spatial resolution is achieved. In the new mode, the grid size of the final generated image is an independent variable. Inpainting to a few times more pixels than the samples creates images that more accurately represent the ground truth.

  1. Electromagnetic Real-Time Tumor Position Monitoring and Dynamic Multileaf Collimator Tracking Using a Siemens 160 MLC: Geometric and Dosimetric Accuracy of an Integrated System

    SciTech Connect

    Krauss, Andreas; Nill, Simeon; Tacke, Martin; Oelfke, Uwe

    2011-02-01

    Purpose: Dynamic multileaf collimator tracking represents a promising method for high-precision radiotherapy to moving tumors. In the present study, we report on the integration of electromagnetic real-time tumor position monitoring into a multileaf collimator-based tracking system. Methods and Materials: The integrated system was characterized in terms of its geometric and radiologic accuracy. The former was assessed from portal images acquired during radiation delivery to a phantom in tracking mode. The tracking errors were calculated from the positions of the tracking field and of the phantom as extracted from the portal images. Radiologic accuracy was evaluated from film dosimetry performed for conformal and intensity-modulated radiotherapy applied to different phantoms moving on sinusoidal trajectories. A static radiation delivery to the nonmoving target served as a reference for the delivery to the moving phantom with and without tracking applied. Results: Submillimeter tracking accuracy was observed for two-dimensional target motion despite the relatively large system latency of 500 ms. Film dosimetry yielded almost complete recovery of a circular dose distribution with tracking in two dimensions applied: 2%/2 mm gamma-failure rates could be reduced from 59.7% to 3.3%. For single-beam intensity-modulated radiotherapy delivery, accuracy was limited by the finite leaf width. A 2%/2 mm gamma-failure rate of 15.6% remained with tracking applied. Conclusion: The integrated system we have presented marks a major step toward the clinical implementation of high-precision dynamic multileaf collimator tracking. However, several challenges such as irregular motion traces or a thorough quality assurance still need to be addressed.

  2. Accuracy of Ultrasound-Based Image Guidance for Daily Positioning of the Upper Abdomen: An Online Comparison With Cone Beam CT

    SciTech Connect

    Boda-Heggemann, Judit Mennemeyer, Philipp; Wertz, Hansjoerg; Riesenacker, Nadja; Kuepper, Beate; Lohr, Frank; Wenz, Frederik

    2009-07-01

    Purpose: Image-guided intensity-modulated radiotherapy can improve protection of organs at risk when large abdominal target volumes are irradiated. We estimated the daily positioning accuracy of ultrasound-based image guidance for abdominal target volumes by a direct comparison of daily imaging obtained with cone beam computed tomography (CBCT). Methods and Materials: Daily positioning (n = 83 positionings) of 15 patients was completed by using ultrasound guidance after an initial CBCT was obtained. Residual error after ultrasound was estimated by comparison with a second CBCT. Ultrasound image quality was visually rated using a scale of 1 to 4. Results: Of 15 patients, 7 patients had good sonographic imaging quality, 5 patients had satisfactory sonographic quality, and 3 patients were excluded because of unsatisfactory sonographic quality. When image quality was good, residual errors after ultrasound were -0.1 {+-} 3.11 mm in the x direction (left-right; group systematic error M = -0.09 mm; standard deviation [SD] of systematic error, {sigma} = 1.37 mm; SD of the random error, {sigma} = 2.99 mm), 0.93 {+-} 4.31 mm in the y direction (superior-inferior, M = 1.12 mm; {sigma} = 2.96 mm; {sigma} = 3.39 mm), and 0.71 {+-} 3.15 mm in the z direction (anteroposterior; M = 1.01 mm; {sigma} = 2.46 mm; {sigma} = 2.24 mm). For patients with satisfactory image quality, residual error after ultrasound was -0.6 {+-} 5.26 mm in the x (M = 0.07 mm; {sigma} = 5.67 mm; {sigma} = 4.86 mm), 1.76 {+-} 4.92 mm in the y (M = 3.54 mm; {sigma} = 4.1 mm; {sigma} = 5.29 mm), and 1.19 {+-} 4.75 mm in the z (M = 0.82 mm; {sigma} = 2.86 mm; {sigma} = 3.05 mm) directions. Conclusions: In patients from whom good sonographic image quality could be obtained, ultrasound improved daily positioning accuracy. In the case of satisfactory image quality, ultrasound guidance improved accuracy compared to that of skin marks only minimally. If sonographic image quality was unsatisfactory, daily CBCT

  3. Accuracy of an infrared marker-based patient positioning system (ExacTrac®) for stereotactic body radiotherapy in localizing the planned isocenter using fiducial markers

    SciTech Connect

    Montes-Rodríguez, María de los Ángeles Mitsoura, Eleni; Hernández-Bojórquez, Mariana; Martínez-Gómez, Alma Angélica; Contreras-Pérez, Agustín; Negrete-Hernández, Ingrid Mireya; Hernández-Oviedo, Jorge Omar; Santiago-Concha, Bernardino Gabriel

    2014-11-07

    Stereotactic Body Radiation Therapy (SBRT) requires a controlled immobilization and position monitoring of patient and target. The purpose of this work is to analyze the performance of the imaging system ExacTrac® (ETX) using infrared and fiducial markers. Materials and methods: In order to assure the accuracy of isocenter localization, a Quality Assurance procedure was applied using an infrared marker-based positioning system. Scans were acquired of an inhouse-agar gel and solid water phantom with infrared spheres. In the inner part of the phantom, three reference markers were delineated as reference and one pellet was place internally; which was assigned as the isocenter. The iPlan® RT Dose treatment planning system. Images were exported to the ETX console. Images were acquired with the ETX to check the correctness of the isocenter placement. Adjustments were made in 6D the reference markers were used to fuse the images. Couch shifts were registered. The procedure was repeated for verification purposes. Results: The data recorded of the verifications in translational and rotational movements showed averaged 3D spatial uncertainties of 0.31 ± 0.42 mm respectively 0.82° ± 0.46° in the phantom and the first correction of these uncertainties were of 1.51 ± 1.14 mm respectively and 1.37° ± 0.61°. Conclusions: This study shows a high accuracy and repeatability in positioning the selected isocenter. The ETX-system for verifying the treatment isocenter position has the ability to monitor the tracing position of interest, making it possible to be used for SBRT positioning within uncertainty ≤1mm.

  4. Accuracy of an infrared marker-based patient positioning system (ExacTrac®) for stereotactic body radiotherapy in localizing the planned isocenter using fiducial markers

    NASA Astrophysics Data System (ADS)

    Montes-Rodríguez, María de los Ángeles; Hernández-Bojórquez, Mariana; Martínez-Gómez, Alma Angélica; Contreras-Pérez, Agustín; Negrete-Hernández, Ingrid Mireya; Hernández-Oviedo, Jorge Omar; Mitsoura, Eleni; Santiago-Concha, Bernardino Gabriel

    2014-11-01

    Stereotactic Body Radiation Therapy (SBRT) requires a controlled immobilization and position monitoring of patient and target. The purpose of this work is to analyze the performance of the imaging system ExacTrac® (ETX) using infrared and fiducial markers. Materials and methods: In order to assure the accuracy of isocenter localization, a Quality Assurance procedure was applied using an infrared marker-based positioning system. Scans were acquired of an inhouse-agar gel and solid water phantom with infrared spheres. In the inner part of the phantom, three reference markers were delineated as reference and one pellet was place internally; which was assigned as the isocenter. The iPlan® RT Dose treatment planning system. Images were exported to the ETX console. Images were acquired with the ETX to check the correctness of the isocenter placement. Adjustments were made in 6D the reference markers were used to fuse the images. Couch shifts were registered. The procedure was repeated for verification purposes. Results: The data recorded of the verifications in translational and rotational movements showed averaged 3D spatial uncertainties of 0.31 ± 0.42 mm respectively 0.82° ± 0.46° in the phantom and the first correction of these uncertainties were of 1.51 ± 1.14 mm respectively and 1.37° ± 0.61°. Conclusions: This study shows a high accuracy and repeatability in positioning the selected isocenter. The ETX-system for verifying the treatment isocenter position has the ability to monitor the tracing position of interest, making it possible to be used for SBRT positioning within uncertainty ≤1mm.

  5. Positioning.

    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…

  6. Navigated non-image-based registration of the position of the pelvis during THR. An accuracy and reproducibility study.

    PubMed

    Jenny, Jean-Yves; Boeri, Cyril; Ciobanu, Eugen

    2008-05-01

    The precise recording of the position of the pelvis is a prerequisite for total hip replacement (THR). The anterior pelvic plane is an accepted reference for determining the 3D pelvic orientation. We hypothesized that cutaneous palpation of this plane was accurate and reproducible. Ten consecutive navigated implantations of THR prostheses were studied. In each case, four palpations of both anterior iliac spines and the pubic symphysis were performed with a navigated stylus. The first palpation was made on actual bone contours through a skin puncture and was considered as the reference. The other three palpations were made over the intact skin as a normal intra-operative procedure. There was no significant difference between the pelvic orientations measured by the three cutaneous palpations, or between the orientations measured by transcutaneous palpation and the mean result with cutaneous palpation. Cutaneous palpation can be considered as a reliable technique for the definition of pelvic orientation during THR with the non-image-based system employed.

  7. Disturbance in hitting accuracy by professional and collegiate baseball players due to intentional change of target position.

    PubMed

    Higuchi, Takatoshi; Nagami, Tomoyuki; Morohoshi, Jun; Nakata, Hiroki; Kanosue, Kazuyuki

    2013-04-01

    The present study investigated bat control of skilled baseball batters during tee batting, faced with an intentional change in target position. Twelve, skilled, male baseball players (M age = 24 yr., SD = 4) participated in the study. Participants were instructed to hit a baseball off a tee 0.8 m from the ground (Hitting condition), and also to deliberately swing just above the ball (Air Swing condition). The task for the participants was to perform, in alternate order, 15 swings at a real baseball on a stationary tee and 15 swings at an imaginary ball that was said to be on top of the real baseball. The participants were instructed to hit the ball toward center field just as they would hit in a game. While most participants could hit the real ball in the sweet area of the bat, only one participant did so in the Air Swing condition. Average distances from the center of the sweet area to ball center at the moment of ball-bat contact in the Air Swing condition (85 mm) were significantly greater than the distance in the Hitting condition (38 mm). The larger error in hitting an imaginary ball in the sweet area could be due to perceptual changes following the batter's altered focus, expectation of a lack of contact, and/or lack of feedback from the swing. It was suggested that baseball batters should be aware of the possible error in hitting accurately when they intentionally shifted the target.

  8. Ionospheric corrections estimation in a local GNSS permanent stations network: improvement of Code Point Positioning at sub-metric accuracy level

    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

  9. Ionospheric corrections estimation in a local GNSS permanent stations network: improvement of Code Point Positioning at sub-metric accuracy level

    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

  10. Interplay effects between dose distribution quality and positioning accuracy in total marrow irradiation with volumetric modulated arc therapy

    SciTech Connect

    Mancosu, Pietro; Navarria, Piera; Reggiori, Giacomo; Tomatis, Stefano; Alongi, Filippo; Scorsetti, Marta; Castagna, Luca; Sarina, Barbara; Nicolini, Giorgia; Fogliata, Antonella; Cozzi, Luca

    2013-11-15

    Purpose: To evaluate the dosimetric consequences of inaccurate isocenter positioning during treatment of total marrow (lymph-node) irradiation (TMI-TMLI) using volumetric modulated arc therapy (VMAT).Methods: Four patients treated with TMI and TMLI were randomly selected from the internal database. Plans were optimized with VMAT technique. Planning target volume (PTV) included all the body bones; for TMLI, lymph nodes and spleen were considered into the target, too. Dose prescription to PTV was 12 Gy in six fractions, two times per day for TMI, and 2 Gy in single fraction for TMLI. Ten arcs on five isocenters (two arcs for isocenter) were used to cover the upper part of PTV (i.e., from cranium to middle femurs). For each plan, three series of random shifts with values between −3 and +3 mm and three between −5 and +5 mm were applied to the five isocenters simulating involuntary patient motion during treatment. The shifts were applied separately in the three directions: left–right (L-R), anterior–posterior (A-P), and cranial–caudal (C-C). The worst case scenario with simultaneous random shifts in all directions simultaneously was considered too. Doses were recalculated for the 96 shifted plans (24 for each patient).Results: For all shifts, differences <0.5% were found for mean doses to PTV, body, and organs at risk with volumes >100 cm{sup 3}. Maximum doses increased up to 15% for C-C shifted plans. PTV covered by the 95% isodose decreased of 2%–8% revealing target underdosage with the highest values in C-C direction.Conclusions: The correct isocenter repositioning of TMI-TMLI patients is fundamental, in particular in C-C direction, in order to avoid over- and underdosages especially in the overlap regions. For this reason, a dedicated immobilization system was developed in the authors' center to best immobilize the patient.

  11. Magnifying absolute instruments for optically homogeneous regions

    SciTech Connect

    Tyc, Tomas

    2011-09-15

    We propose a class of magnifying absolute optical instruments with a positive isotropic refractive index. They create magnified stigmatic images, either virtual or real, of optically homogeneous three-dimensional spatial regions within geometrical optics.

  12. An analysis on combined GPS/COMPASS data quality and its effect on single point positioning accuracy under different observing conditions

    NASA Astrophysics Data System (ADS)

    Cai, Changsheng; Gao, Yang; Pan, Lin; Dai, Wujiao

    2014-09-01

    With the rapid development of the COMPASS system, it is currently capable of providing regional navigation services. In order to test its data quality and performance for single point positioning (SPP), experiments have been conducted under different observing conditions including open sky, under trees, nearby a glass wall, nearby a large area of water, under high-voltage lines and under a signal transmitting tower. To assess the COMPASS data quality, the code multipath, cycle slip occurrence rate and data availability were analyzed and compared to GPS data. The datasets obtained from the experiments have also been utilized to perform combined GPS/COMPASS SPP on an epoch-by-epoch basis using unsmoothed single-frequency code observations. The investigation on the regional navigation performance aims at low-accuracy applications and all tests are made in Changsha, China, using the “SOUTH S82-C” GPS/COMPASS receivers. The results show that adding COMPASS observations can significantly improve the positioning accuracy of single-frequency GPS-only SPP in environments with limited satellite visibility. Since the COMPASS system is still in an initial operational stage, all results are obtained based on a fairly limited amount of data.

  13. Performance and Accuracy of Lightweight and Low-Cost GPS Data Loggers According to Antenna Positions, Fix Intervals, Habitats and Animal Movements.

    PubMed

    Forin-Wiart, Marie-Amélie; Hubert, Pauline; Sirguey, Pascal; Poulle, Marie-Lazarine

    2015-01-01

    Recently developed low-cost Global Positioning System (GPS) data loggers are promising tools for wildlife research because of their affordability for low-budget projects and ability to simultaneously track a greater number of individuals compared with expensive built-in wildlife GPS. However, the reliability of these devices must be carefully examined because they were not developed to track wildlife. This study aimed to assess the performance and accuracy of commercially available GPS data loggers for the first time using the same methods applied to test built-in wildlife GPS. The effects of antenna position, fix interval and habitat on the fix-success rate (FSR) and location error (LE) of CatLog data loggers were investigated in stationary tests, whereas the effects of animal movements on these errors were investigated in motion tests. The units operated well and presented consistent performance and accuracy over time in stationary tests, and the FSR was good for all antenna positions and fix intervals. However, the LE was affected by the GPS antenna and fix interval. Furthermore, completely or partially obstructed habitats reduced the FSR by up to 80% in households and increased the LE. Movement across habitats had no effect on the FSR, whereas forest habitat influenced the LE. Finally, the mean FSR (0.90 ± 0.26) and LE (15.4 ± 10.1 m) values from low-cost GPS data loggers were comparable to those of built-in wildlife GPS collars (71.6% of fixes with LE < 10 m for motion tests), thus confirming their suitability for use in wildlife studies.

  14. Performance and Accuracy of Lightweight and Low-Cost GPS Data Loggers According to Antenna Positions, Fix Intervals, Habitats and Animal Movements

    PubMed Central

    Forin-Wiart, Marie-Amélie; Hubert, Pauline; Sirguey, Pascal; Poulle, Marie-Lazarine

    2015-01-01

    Recently developed low-cost Global Positioning System (GPS) data loggers are promising tools for wildlife research because of their affordability for low-budget projects and ability to simultaneously track a greater number of individuals compared with expensive built-in wildlife GPS. However, the reliability of these devices must be carefully examined because they were not developed to track wildlife. This study aimed to assess the performance and accuracy of commercially available GPS data loggers for the first time using the same methods applied to test built-in wildlife GPS. The effects of antenna position, fix interval and habitat on the fix-success rate (FSR) and location error (LE) of CatLog data loggers were investigated in stationary tests, whereas the effects of animal movements on these errors were investigated in motion tests. The units operated well and presented consistent performance and accuracy over time in stationary tests, and the FSR was good for all antenna positions and fix intervals. However, the LE was affected by the GPS antenna and fix interval. Furthermore, completely or partially obstructed habitats reduced the FSR by up to 80% in households and increased the LE. Movement across habitats had no effect on the FSR, whereas forest habitat influenced the LE. Finally, the mean FSR (0.90 ± 0.26) and LE (15.4 ± 10.1 m) values from low-cost GPS data loggers were comparable to those of built-in wildlife GPS collars (71.6% of fixes with LE < 10 m for motion tests), thus confirming their suitability for use in wildlife studies. PMID:26086958

  15. High-accuracy and real-time 3D positioning, tracking system for medical imaging applications based on 3D digital image correlation

    NASA Astrophysics Data System (ADS)

    Xue, Yuan; Cheng, Teng; Xu, Xiaohai; Gao, Zeren; Li, Qianqian; Liu, Xiaojing; Wang, Xing; Song, Rui; Ju, Xiangyang; Zhang, Qingchuan

    2017-01-01

    This paper presents a system for positioning markers and tracking the pose of a rigid object with 6 degrees of freedom in real-time using 3D digital image correlation, with two examples for medical imaging applications. Traditional DIC method was improved to meet the requirements of the real-time by simplifying the computations of integral pixel search. Experiments were carried out and the results indicated that the new method improved the computational efficiency by about 4-10 times in comparison with the traditional DIC method. The system was aimed for orthognathic surgery navigation in order to track the maxilla segment after LeFort I osteotomy. Experiments showed noise for the static point was at the level of 10-3 mm and the measurement accuracy was 0.009 mm. The system was demonstrated on skin surface shape evaluation of a hand for finger stretching exercises, which indicated a great potential on tracking muscle and skin movements.

  16. Absolute and relative blindsight.

    PubMed

    Balsdon, Tarryn; Azzopardi, Paul

    2015-03-01

    The concept of relative blindsight, referring to a difference in conscious awareness between conditions otherwise matched for performance, was introduced by Lau and Passingham (2006) as a way of identifying the neural correlates of consciousness (NCC) in fMRI experiments. By analogy, absolute blindsight refers to a difference between performance and awareness regardless of whether it is possible to match performance across conditions. Here, we address the question of whether relative and absolute blindsight in normal observers can be accounted for by response bias. In our replication of Lau and Passingham's experiment, the relative blindsight effect was abolished when performance was assessed by means of a bias-free 2AFC task or when the criterion for awareness was varied. Furthermore, there was no evidence of either relative or absolute blindsight when both performance and awareness were assessed with bias-free measures derived from confidence ratings using signal detection theory. This suggests that both relative and absolute blindsight in normal observers amount to no more than variations in response bias in the assessment of performance and awareness. Consideration of the properties of psychometric functions reveals a number of ways in which relative and absolute blindsight could arise trivially and elucidates a basis for the distinction between Type 1 and Type 2 blindsight.

  17. Absolute neutrino mass scale

    NASA Astrophysics Data System (ADS)

    Capelli, Silvia; Di Bari, Pasquale

    2013-04-01

    Neutrino oscillation experiments firmly established non-vanishing neutrino masses, a result that can be regarded as a strong motivation to extend the Standard Model. In spite of being the lightest massive particles, neutrinos likely represent an important bridge to new physics at very high energies and offer new opportunities to address some of the current cosmological puzzles, such as the matter-antimatter asymmetry of the Universe and Dark Matter. In this context, the determination of the absolute neutrino mass scale is a key issue within modern High Energy Physics. The talks in this parallel session well describe the current exciting experimental activity aiming to determining the absolute neutrino mass scale and offer an overview of a few models beyond the Standard Model that have been proposed in order to explain the neutrino masses giving a prediction for the absolute neutrino mass scale and solving the cosmological puzzles.

  18. The absolute path command

    SciTech Connect

    Moody, A.

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it can provide the absolute path to a relative directory from the current working directory.

  19. Absolute Distance Measurement with the MSTAR Sensor

    NASA Technical Reports Server (NTRS)

    Lay, Oliver P.; Dubovitsky, Serge; Peters, Robert; Burger, Johan; Ahn, Seh-Won; Steier, William H.; Fetterman, Harrold R.; Chang, Yian

    2003-01-01

    The MSTAR sensor (Modulation Sideband Technology for Absolute Ranging) is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with sub-nanometer accuracy. The sensor uses a single laser in conjunction with fast phase modulators and low frequency detectors. We describe the design of the system - the principle of operation, the metrology source, beamlaunching optics, and signal processing - and show results for target distances up to 1 meter. We then demonstrate how the system can be scaled to kilometer-scale distances.

  20. 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.

  1. Precise determination of the absolute isotopic abundance ratio and the atomic weight of chlorine in three international reference materials by the positive thermal ionization mass spectrometer-Cs2Cl+-graphite method.

    PubMed

    Wei, Hai-Zhen; Jiang, Shao-Yong; Xiao, Ying-Kai; Wang, Jun; Lu, Hai; Wu, Bin; Wu, He-Pin; Li, Qing; Luo, Chong-Guang

    2012-12-04

    Because the variation in chlorine isotopic abundances of naturally occurring chlorine bearing substances is significant, the IUPAC Inorganic Chemistry Division, Commission on Isotopic Abundances and Atomic Weights (CIAAW-IUPAC) decided that the uncertainty of atomic weight of chlorine (A(r)(Cl)) should be increased so that the implied range was related to terrestrial variability in 1999 (Coplen, T. B. Atomic weights of the elements 1999 (IUPAC Technical Report), Pure Appl. Chem.2001, 73(4), 667-683; and then, it emphasized that the standard atomic weights of ten elements including chlorine were not constants of nature but depend upon the physical, chemical, and nuclear history of the materials in 2009 (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396). According to the agreement by CIAAW that an atomic weight could be defined for one specified sample of terrestrial origin (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396), the absolute isotope ratios and atomic weight of chlorine in standard reference materials (NIST 975, NIST 975a, ISL 354) were accurately determined using the high-precision positive thermal ionization mass spectrometer (PTIMS)-Cs(2)Cl(+)-graphite method. After eliminating the weighing error caused from evaporation by designing a special weighing container and accurately determining the chlorine contents in two highly enriched Na(37)Cl and Na(35)Cl salts by the current constant coulometric titration, one series of gravimetric synthetic mixtures prepared from two highly enriched Na(37)Cl and Na(35)Cl salts was used to calibrate two thermal ionization mass spectrometers in two individual laboratories. The correction factors (i.e., K(37/35) = R(37/35meas)/R(37/35calc)) were obtained from five cycles of iterative calculations on the basis of calculated and determined R((37)Cl/(35)Cl) values in gravimetric synthetic mixtures. The absolute R((37)Cl/(35)Cl) ratios for NIST SRM 975, NIST 975a, and ISL 354 by the precise

  2. Absolute calibration of optical tweezers

    SciTech Connect

    Viana, N.B.; Mazolli, A.; Maia Neto, P.A.; Nussenzveig, H.M.; Rocha, M.S.; Mesquita, O.N.

    2006-03-27

    As a step toward absolute calibration of optical tweezers, a first-principles theory of trapping forces with no adjustable parameters, corrected for spherical aberration, is experimentally tested. Employing two very different setups, we find generally very good agreement for the transverse trap stiffness as a function of microsphere radius for a broad range of radii, including the values employed in practice, and at different sample chamber depths. The domain of validity of the WKB ('geometrical optics') approximation to the theory is verified. Theoretical predictions for the trapping threshold, peak position, depth variation, multiple equilibria, and 'jump' effects are also confirmed.

  3. Advancing the prediction accuracy of protein-protein interactions by utilizing evolutionary information from position-specific scoring matrix and ensemble classifier.

    PubMed

    Wang, Lei; You, Zhu-Hong; Xia, Shi-Xiong; Liu, Feng; Chen, Xing; Yan, Xin; Zhou, Yong

    2017-04-07

    Protein-Protein Interactions (PPIs) are essential to most biological processes and play a critical role in most cellular functions. With the development of high-throughput biological techniques and in silico methods, a large number of PPI data have been generated for various organisms, but many problems remain unsolved. These factors promoted the development of the in silico methods based on machine learning to predict PPIs. In this study, we propose a novel method by combining ensemble Rotation Forest (RF) classifier and Discrete Cosine Transform (DCT) algorithm to predict the interactions among proteins. Specifically, the protein amino acids sequence is transformed into Position-Specific Scoring Matrix (PSSM) containing biological evolution information, and then the feature vector is extracted to present protein evolutionary information using DCT algorithm; finally, the ensemble rotation forest model is used to predict whether a given protein pair is interacting or not. When performed on Yeast and H. pylori data sets, the proposed method achieved excellent results with an average accuracy of 98.54% and 88.27%. In addition, we achieved good prediction accuracy of 98.08%, 92.75%, 98.87% and 98.72% on independent data sets (C.elegans, E.coli, H.sapiens and M.musculus). In order to further evaluate the performance of our method, we compare it with the state-of-the-art Support Vector Machine (SVM) classifier and get good results. As a web server, the source code and Yeast data sets used in this article are freely available at http://202.119.201.126:8888/DCTRF/.

  4. On the accuracy of approximation of motion of a small celestial body by intermediate perturbed orbits calculated on the basis of three position vectors and three observations

    NASA Astrophysics Data System (ADS)

    Shefer, V. A.; Shefer, O. V.

    2016-05-01

    Intermediate perturbed orbits, which were proposed earlier by the first author and are calculated based on three position vectors and three measurements of angular coordinates of a small celestial body, are examined. Provided that the reference time interval encompassing the measurements is short, these orbits are close in the accuracy of approximation of actual motion to an orbit with fourth-order tangency. The shorter the reference time interval is, the better is the approximation. The laws of variation of the errors of methods for constructing such intermediate orbits with the length of the reference time interval are formulated. According to these laws, the rate of convergence of the methods to an exact solution in the process of shortening of the reference time interval is, in general, three orders of magnitude higher than that of conventional methods relying on an unperturbed Keplerian orbit. The considered orbits are among the most accurate of their class that is defined by the order of tangency. The obtained theoretical results are verified by numerical experiments on determining the orbit of 99942 Apophis.

  5. Absolute Calibration Accuracy for Hyperspectral Imagers in the Solar Reflective

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis

    2009-01-01

    The characterization and calibration of hyperspectral imagers is a challenging one that is expected to become even more challenging as needs increase for highly-accurate radiometric data from such systems. The preflight calibration of the Advanced Responsive Tactically Effective Military Imaging Spectrometer (ARTEMIS) is used as an example of the difficulties to calibrate hyperspectrally. Results from a preflight solar radiation-based calibration are presented with a discussion of the uncertainties in such a method including the NISI-traceable and SItraceable aspects. Expansion on the concept of solar-based calibration is given with descriptions of methods that view the solar disk directly, illuminate a solar diffuser that is part of the sensor's inflight calibration, and illuminate an external diffuser that is imaged by the sensor. The results of error analysis show that it is feasible to achieve preflight calibration using the sun as a source at the same level of uncertainty as those of lamp-based approaches. The error analysis is evaluated and verified through the solar-radiation-based calibration of several of laboratory grade radiometers. Application of these approaches to NASA's upcoming CLARREO mission are discussed including proposed methods for significantly reducing the uncertainties to allow CLARREO data to be used for climate data records.

  6. Integrated Navigation System Design for Micro Planetary Rovers: Comparison of Absolute Heading Estimation Algorithms and Nonlinear Filtering

    PubMed Central

    Ilyas, Muhammad; Hong, Beomjin; Cho, Kuk; Baeg, Seung-Ho; Park, Sangdeok

    2016-01-01

    This paper provides algorithms to fuse relative and absolute microelectromechanical systems (MEMS) navigation sensors, suitable for micro planetary rovers, to provide a more accurate estimation of navigation information, specifically, attitude and position. Planetary rovers have extremely slow speed (~1 cm/s) and lack conventional navigation sensors/systems, hence the general methods of terrestrial navigation may not be applicable to these applications. While relative attitude and position can be tracked in a way similar to those for ground robots, absolute navigation information is hard to achieve on a remote celestial body, like Moon or Mars, in contrast to terrestrial applications. In this study, two absolute attitude estimation algorithms were developed and compared for accuracy and robustness. The estimated absolute attitude was fused with the relative attitude sensors in a framework of nonlinear filters. The nonlinear Extended Kalman filter (EKF) and Unscented Kalman filter (UKF) were compared in pursuit of better accuracy and reliability in this nonlinear estimation problem, using only on-board low cost MEMS sensors. Experimental results confirmed the viability of the proposed algorithms and the sensor suite, for low cost and low weight micro planetary rovers. It is demonstrated that integrating the relative and absolute navigation MEMS sensors reduces the navigation errors to the desired level. PMID:27223293

  7. Integrated Navigation System Design for Micro Planetary Rovers: Comparison of Absolute Heading Estimation Algorithms and Nonlinear Filtering.

    PubMed

    Ilyas, Muhammad; Hong, Beomjin; Cho, Kuk; Baeg, Seung-Ho; Park, Sangdeok

    2016-05-23

    This paper provides algorithms to fuse relative and absolute microelectromechanical systems (MEMS) navigation sensors, suitable for micro planetary rovers, to provide a more accurate estimation of navigation information, specifically, attitude and position. Planetary rovers have extremely slow speed (~1 cm/s) and lack conventional navigation sensors/systems, hence the general methods of terrestrial navigation may not be applicable to these applications. While relative attitude and position can be tracked in a way similar to those for ground robots, absolute navigation information is hard to achieve on a remote celestial body, like Moon or Mars, in contrast to terrestrial applications. In this study, two absolute attitude estimation algorithms were developed and compared for accuracy and robustness. The estimated absolute attitude was fused with the relative attitude sensors in a framework of nonlinear filters. The nonlinear Extended Kalman filter (EKF) and Unscented Kalman filter (UKF) were compared in pursuit of better accuracy and reliability in this nonlinear estimation problem, using only on-board low cost MEMS sensors. Experimental results confirmed the viability of the proposed algorithms and the sensor suite, for low cost and low weight micro planetary rovers. It is demonstrated that integrating the relative and absolute navigation MEMS sensors reduces the navigation errors to the desired level.

  8. Enhancing and evaluating diagnostic accuracy.

    PubMed

    Swets, J A; Getty, D J; Pickett, R M; D'Orsi, C J; Seltzer, S E; McNeil, B J

    1991-01-01

    Techniques that may enhance diagnostic accuracy in clinical settings were tested in the context of mammography. Statistical information about the relevant features among those visible in a mammogram and about their relative importances in the diagnosis of breast cancer was the basis of two decision aids for radiologists: a checklist that guides the radiologist in assigning a scale value to each significant feature of the images of a particular case, and a computer program that merges those scale values optimally to estimate a probability of malignancy. A test set of approximately 150 proven cases (including normals and benign and malignant lesions) was interpreted by six radiologists, first in their usual manner and later with the decision aids. The enhancing effect of these feature-analytic techniques was analyzed across subsets of cases that were restricted progressively to more and more difficult cases, where difficulty was defined in terms of the radiologists' judgements in the standard reading condition. Accuracy in both standard and enhanced conditions decreased regularly and substantially as case difficulty increased, but differentially, such that the enhancement effect grew regularly and substantially. For the most difficult case sets, the observed increases in accuracy translated into an increase of about 0.15 in sensitivity (true-positive proportion) for a selected specificity (true-negative proportion) of 0.85 or a similar increase in specificity for a selected sensitivity of 0.85. That measured accuracy can depend on case-set difficulty to different degrees for two diagnostic approaches has general implications for evaluation in clinical medicine. Comparative, as well as absolute, assessments of diagnostic performances--for example, of alternative imaging techniques--may be distorted by inadequate treatments of this experimental variable. Subset analysis, as defined and illustrated here, can be useful in alleviating the problem.

  9. The effects of domain knowledge on metacomprehension accuracy.

    PubMed

    Griffin, Thomas D; Jee, Benjamin D; Wiley, Jennifer

    2009-10-01

    In the present research, we examined the relationship between readers' domain knowledge and their ability to judge their comprehension of novel domain-related material. Participants with varying degrees of baseball knowledge read five texts on baseball-related topics and five texts on non-baseball-related topics, predicted their performance, and completed tests for each text. Baseball knowledge was positively related to absolute accuracy within the baseball domain but was unrelated to relative accuracy within the baseball domain. Also, the readers showed a general underconfidence bias, but the bias was less extreme for higher knowledge readers. The results challenge common assumptions that experts' metacognitive judgments are less accurate than novices'. Results involving topic familiarity ratings and a no-reading control group suggest that higher knowledge readers are not more likely to ignore text-specific cues in favor of a domain familiarity heuristic, but they do appear to make more effective use of domain familiarity in predicting absolute performance levels.

  10. Climate Absolute Radiance and Refractivity Observatory (CLARREO)

    NASA Technical Reports Server (NTRS)

    Leckey, John P.

    2015-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a mission, led and developed by NASA, that will measure a variety of climate variables with an unprecedented accuracy to quantify and attribute climate change. CLARREO consists of three separate instruments: an infrared (IR) spectrometer, a reflected solar (RS) spectrometer, and a radio occultation (RO) instrument. The mission will contain orbiting radiometers with sufficient accuracy, including on orbit verification, to calibrate other space-based instrumentation, increasing their respective accuracy by as much as an order of magnitude. The IR spectrometer is a Fourier Transform spectrometer (FTS) working in the 5 to 50 microns wavelength region with a goal of 0.1 K (k = 3) accuracy. The FTS will achieve this accuracy using phase change cells to verify thermistor accuracy and heated halos to verify blackbody emissivity, both on orbit. The RS spectrometer will measure the reflectance of the atmosphere in the 0.32 to 2.3 microns wavelength region with an accuracy of 0.3% (k = 2). The status of the instrumentation packages and potential mission options will be presented.

  11. Absolute Equilibrium Entropy

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    1997-01-01

    The entropy associated with absolute equilibrium ensemble theories of ideal, homogeneous, fluid and magneto-fluid turbulence is discussed and the three-dimensional fluid case is examined in detail. A sigma-function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H-theorems of ideal turbulence). It is shown that the two approaches are complimentary though conceptually different: H-theorems show that an isolated system tends to equilibrium while sigma-functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids.

  12. Optimizing geometric accuracy of four-dimensional CT scans acquired using the wall- and couch-mounted Varian® Real-time Position Management™ camera systems

    PubMed Central

    Irvine, D M; Cole, A J; Hanna, G G; McGarry, C K

    2015-01-01

    Objective: The aim of this study was to identify sources of anatomical misrepresentation owing to the location of camera mounting, tumour motion velocity and image processing artefacts in order to optimize the four-dimensional CT (4DCT) scan protocol and improve geometrical–temporal accuracy. Methods: A phantom with an imaging insert was driven with a sinusoidal superior–inferior motion of varying amplitude and period for 4DCT scanning. The length of a high-density cube within the insert was measured using treatment planning software to determine the accuracy of its spatial representation. Scan parameters were varied, including the tube rotation period and the cine time between reconstructed images. A CT image quality phantom was used to measure various image quality signatures under the scan parameters tested. Results: No significant difference in spatial accuracy was found for 4DCT scans carried out using the wall- or couch-mounted camera for sinusoidal target motion. Greater spatial accuracy was found for 4DCT scans carried out using a tube rotation speed of 0.5 s rather than 1.0 s. The reduction in image quality when using a faster rotation speed was not enough to require an increase in patient dose. Conclusion: The 4DCT accuracy may be increased by optimizing scan parameters, including choosing faster tube rotation speeds. Peak misidentification in the recorded breathing trace may lead to spatial artefacts, and this risk can be reduced by using a couch-mounted infrared camera. Advances in knowledge: This study explicitly shows that 4DCT scan accuracy is improved by scanning with a faster CT tube rotation speed. PMID:25470359

  13. Absolute and relative dosimetry for ELIMED

    NASA Astrophysics Data System (ADS)

    Cirrone, G. A. P.; Cuttone, G.; Candiano, G.; Carpinelli, M.; Leonora, E.; Lo Presti, D.; Musumarra, A.; Pisciotta, P.; Raffaele, L.; Randazzo, N.; Romano, F.; Schillaci, F.; Scuderi, V.; Tramontana, A.; Cirio, R.; Marchetto, F.; Sacchi, R.; Giordanengo, S.; Monaco, V.

    2013-07-01

    The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.

  14. Estimating Absolute Site Effects

    SciTech Connect

    Malagnini, L; Mayeda, K M; Akinci, A; Bragato, P L

    2004-07-15

    The authors use previously determined direct-wave attenuation functions as well as stable, coda-derived source excitation spectra to isolate the absolute S-wave site effect for the horizontal and vertical components of weak ground motion. They used selected stations in the seismic network of the eastern Alps, and find the following: (1) all ''hard rock'' sites exhibited deamplification phenomena due to absorption at frequencies ranging between 0.5 and 12 Hz (the available bandwidth), on both the horizontal and vertical components; (2) ''hard rock'' site transfer functions showed large variability at high-frequency; (3) vertical-motion site transfer functions show strong frequency-dependence, and (4) H/V spectral ratios do not reproduce the characteristics of the true horizontal site transfer functions; (5) traditional, relative site terms obtained by using reference ''rock sites'' can be misleading in inferring the behaviors of true site transfer functions, since most rock sites have non-flat responses due to shallow heterogeneities resulting from varying degrees of weathering. They also use their stable source spectra to estimate total radiated seismic energy and compare against previous results. they find that the earthquakes in this region exhibit non-constant dynamic stress drop scaling which gives further support for a fundamental difference in rupture dynamics between small and large earthquakes. To correct the vertical and horizontal S-wave spectra for attenuation, they used detailed regional attenuation functions derived by Malagnini et al. (2002) who determined frequency-dependent geometrical spreading and Q for the region. These corrections account for the gross path effects (i.e., all distance-dependent effects), although the source and site effects are still present in the distance-corrected spectra. The main goal of this study is to isolate the absolute site effect (as a function of frequency) by removing the source spectrum (moment-rate spectrum) from

  15. Accuracy Assessment of Mobile Mapping Point Clouds Using the Existing Environment as Terrestrial Reference

    NASA Astrophysics Data System (ADS)

    Hofmann, S.; Brenner, C.

    2016-06-01

    Mobile mapping data is widely used in various applications, what makes it especially important for data users to get a statistically verified quality statement on the geometric accuracy of the acquired point clouds or its processed products. The accuracy of point clouds can be divided into an absolute and a relative quality, where the absolute quality describes the position of the point cloud in a world coordinate system such as WGS84 or UTM, whereas the relative accuracy describes the accuracy within the point cloud itself. Furthermore, the quality of processed products such as segmented features depends on the global accuracy of the point cloud but mainly on the quality of the processing steps. Several data sources with different characteristics and quality can be thought of as potential reference data, such as cadastral maps, orthophoto, artificial control objects or terrestrial surveys using a total station. In this work a test field in a selected residential area was acquired as reference data in a terrestrial survey using a total station. In order to reach high accuracy the stationing of the total station was based on a newly made geodetic network with a local accuracy of less than 3 mm. The global position of the network was determined using a long time GNSS survey reaching an accuracy of 8 mm. Based on this geodetic network a 3D test field with facades and street profiles was measured with a total station, each point with a two-dimensional position and altitude. In addition, the surface of poles of street lights, traffic signs and trees was acquired using the scanning mode of the total station. Comparing this reference data to the acquired mobile mapping point clouds of several measurement campaigns a detailed quality statement on the accuracy of the point cloud data is made. Additionally, the advantages and disadvantages of the described reference data source concerning availability, cost, accuracy and applicability are discussed.

  16. Pointing to double-step visual stimuli from a standing position: motor corrections when the speed-accuracy trade-off is unexpectedly modified in-flight. A breakdown of the perception-action coupling.

    PubMed

    Fautrelle, L; Barbieri, G; Ballay, Y; Bonnetblanc, F

    2011-10-27

    The time required to complete a fast and accurate movement is a function of its amplitude and the target size. This phenomenon refers to the well known speed-accuracy trade-off. Some interpretations have suggested that the speed-accuracy trade-off is already integrated into the movement planning phase. More specifically, pointing movements may be planned to minimize the variance of the final hand position. However, goal-directed movements can be altered at any time, if for instance, the target location is changed during execution. Thus, one possible limitation of these interpretations may be that they underestimate feedback processes. To further investigate this hypothesis we designed an experiment in which the speed-accuracy trade-off was unexpectedly varied at the hand movement onset by modifying separately the target distance or size, or by modifying both of them simultaneously. These pointing movements were executed from an upright standing position. Our main results showed that the movement time increased when there was a change to the size or location of the target. In addition, the terminal variability of finger position did not change. In other words, it showed that the movement velocity is modulated according to the target size and distance during motor programming or during the final approach, independently of the final variability of the hand position. It suggests that when the speed-accuracy trade-off is unexpectedly modified, terminal feedbacks based on intermediate representations of the endpoint velocity are used to monitor and control the hand displacement. There is clearly no obvious perception-action coupling in this case but rather intermediate processing that may be involved.

  17. Accuracy of the VITEK® 2 system for a rapid and direct identification and susceptibility testing of Gramnegative rods and Gram-positive cocci in blood samples.

    PubMed

    Nimer, N A; Al-Saa'da, R J; Abuelaish, O

    2016-06-15

    The performance of the VITEK® 2 system for direct rapid identification and antimicrobial susceptibility testing of the bacteria responsible for blood infections was determined. The isolates studied included 166 Gram-negative rods and 74 Gram-positive cocci from inpatients. Specially treated monomicrobial samples from positive blood culture bottles were directly inoculated into the VITEK 2 system and the results were compared with those from cards inoculated with standardized bacterial suspensions. Compared with the standard method, 95.8% of Gram-negative rods were correctly identified by VITEK 2 and the overall level of agreement between the two methods in susceptibility testing was 92.0%. For Gram-positive bacteria, 89.2% were correctly identified by VITEK 2 and susceptibility testing revealed an overall agreement rate of 91.3%. These results suggest that VITEK 2 cards inoculated with fluids sampled directly from positive blood culture bottles are suitable for speedy identification and susceptibility testing of Gram-negative bacilli and Gram-positive cocci.

  18. Monochromator-Based Absolute Calibration of Radiation Thermometers

    NASA Astrophysics Data System (ADS)

    Keawprasert, T.; Anhalt, K.; Taubert, D. R.; Hartmann, J.

    2011-08-01

    A monochromator integrating-sphere-based spectral comparator facility has been developed to calibrate standard radiation thermometers in terms of the absolute spectral radiance responsivity, traceable to the PTB cryogenic radiometer. The absolute responsivity calibration has been improved using a 75 W xenon lamp with a reflective mirror and imaging optics to a relative standard uncertainty at the peak wavelength of approximately 0.17 % ( k = 1). Via a relative measurement of the out-of-band responsivity, the spectral responsivity of radiation thermometers can be fully characterized. To verify the calibration accuracy, the absolutely calibrated radiation thermometer is used to measure Au and Cu freezing-point temperatures and then to compare the obtained results with the values obtained by absolute methods, resulting in T - T 90 values of +52 mK and -50 mK for the gold and copper fixed points, respectively.

  19. Cryogenic, Absolute, High Pressure Sensor

    NASA Technical Reports Server (NTRS)

    Chapman, John J. (Inventor); Shams. Qamar A. (Inventor); Powers, William T. (Inventor)

    2001-01-01

    A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

  20. Toward robust deconvolution of pass-through paleomagnetic measurements: new tool to estimate magnetometer sensor response and laser interferometry of sample positioning accuracy

    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

  1. Negative absolute temperature for mobile particles

    NASA Astrophysics Data System (ADS)

    Braun, Simon; Ronzheimer, Philipp; Schreiber, Michael; Hodgman, Sean; Bloch, Immanuel; Schneider, Ulrich

    2013-05-01

    Absolute temperature is usually bound to be strictly positive. However, negative absolute temperature states, where the occupation probability of states increases with their energy, are possible in systems with an upper energy bound. So far, such states have only been demonstrated in localized spin systems with finite, discrete spectra. We realized a negative absolute temperature state for motional degrees of freedom with ultracold bosonic 39K atoms in an optical lattice, by implementing the attractive Bose-Hubbard Hamiltonian. This new state strikingly revealed itself by a quasimomentum distribution that is peaked at maximum kinetic energy. The measured kinetic energy distribution and the extracted negative temperature indicate that the ensemble is close to degeneracy, with coherence over several lattice sites. The state is as stable as a corresponding positive temperature state: The negative temperature stabilizes the system against mean-field collapse driven by negative pressure. Negative temperatures open up new parameter regimes for cold atoms, enabling fundamentally new many-body states. Additionally, they give rise to several counterintuitive effects such as heat engines with above unity efficiency.

  2. Consistent thermostatistics forbids negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Dunkel, Jörn; Hilbert, Stefan

    2014-01-01

    Over the past 60 years, a considerable number of theories and experiments have claimed the existence of negative absolute temperature in spin systems and ultracold quantum gases. This has led to speculation that ultracold gases may be dark-energy analogues and also suggests the feasibility of heat engines with efficiencies larger than one. Here, we prove that all previous negative temperature claims and their implications are invalid as they arise from the use of an entropy definition that is inconsistent both mathematically and thermodynamically. We show that the underlying conceptual deficiencies can be overcome if one adopts a microcanonical entropy functional originally derived by Gibbs. The resulting thermodynamic framework is self-consistent and implies that absolute temperature remains positive even for systems with a bounded spectrum. In addition, we propose a minimal quantum thermometer that can be implemented with available experimental techniques.

  3. Diagnostic accuracy of plasma free metanephrines in a seated position compared with 24-hour urinary metanephrines in the investigation of pheochromocytoma.

    PubMed

    Kim, Hye Jeong; Lee, Ji In; Cho, Yoon Young; Lee, Soo Youn; Kim, Jung Han; Jung, Byong Chang; Kim, Sun Wook; Chung, Jae Hoon; Min, Yong-Ki; Lee, Myung-Shik; Lee, Moon-Kyu; Kim, Jae Hyeon

    2015-01-01

    The aim of this study was to determine the diagnostic efficacy of free metanephrines in plasma samples drawn in the seated position compared with 24-h urinary metanephrines in detecting pheochromocytomas in Asian patients. This prospective study was conducted at Samsung Medical Center between May 2010 and July 2011. The study contained 245 subjects, including 28 patients with histologically-proven pheochromocytoma, 44 with histologically-proven non-pheochromocytoma, 112 controls suspected of having tumors but with negative investigations during two or more years of follow-up, and 45 healthy normotensive volunteers. Plasma-free metanephrines were measured by LC-MS/MS. The cut-off values with optimal sensitivity and specificity for plasma metanephrine and plasma normetanephrine were 0.33 nmol/L and 0.61 nmol/L, respectively. Both the plasma metanephrines measurement and urinary metanephrines measurement had a sensitivity of 96.4% (p = 1.00). However, the urinary metanephrines measurement was significantly more specific than the plasma metanephrines measurement (94.2% vs. 75.6%; p < 0.001). When we applied cut-off values based on BMI, specificity improved from 75.6% to 87.2%, with a comparable gain in sensitivity. From a diagnostic perspective, measurement of free metanephrines in plasma drawn in the seated position is highly sensitive but insufficiently specific when compared with measurement of 24-h urinary fractionated metanephrines. The specificity may be improved by applying cut-off values based on BMI. We suggest that free metanephrines in plasma drawn from seated position can also be used as an initial screening test to ensure that pheochromocytomas are not missed in Asian patients.

  4. Enhancing Positioning Accuracy in Urban Terrain by Fusing Data from a GPS Receiver, Inertial Sensors, Stereo-Camera and Digital Maps for Pedestrian Navigation

    PubMed Central

    Przemyslaw, Baranski; Pawel, Strumillo

    2012-01-01

    The paper presents an algorithm for estimating a pedestrian location in an urban environment. The algorithm is based on the particle filter and uses different data sources: a GPS receiver, inertial sensors, probability maps and a stereo camera. Inertial sensors are used to estimate a relative displacement of a pedestrian. A gyroscope estimates a change in the heading direction. An accelerometer is used to count a pedestrian's steps and their lengths. The so-called probability maps help to limit GPS inaccuracy by imposing constraints on pedestrian kinematics, e.g., it is assumed that a pedestrian cannot cross buildings, fences etc. This limits position inaccuracy to ca. 10 m. Incorporation of depth estimates derived from a stereo camera that are compared to the 3D model of an environment has enabled further reduction of positioning errors. As a result, for 90% of the time, the algorithm is able to estimate a pedestrian location with an error smaller than 2 m, compared to an error of 6.5 m for a navigation based solely on GPS. PMID:22969321

  5. Elevation correction factor for absolute pressure measurements

    NASA Technical Reports Server (NTRS)

    Panek, Joseph W.; Sorrells, Mark R.

    1996-01-01

    With the arrival of highly accurate multi-port pressure measurement systems, conditions that previously did not affect overall system accuracy must now be scrutinized closely. Errors caused by elevation differences between pressure sensing elements and model pressure taps can be quantified and corrected. With multi-port pressure measurement systems, the sensing elements are connected to pressure taps that may be many feet away. The measurement system may be at a different elevation than the pressure taps due to laboratory space or test article constraints. This difference produces a pressure gradient that is inversely proportional to height within the interface tube. The pressure at the bottom of the tube will be higher than the pressure at the top due to the weight of the tube's column of air. Tubes with higher pressures will exhibit larger absolute errors due to the higher air density. The above effect is well documented but has generally been taken into account with large elevations only. With error analysis techniques, the loss in accuracy from elevation can be easily quantified. Correction factors can be applied to maintain the high accuracies of new pressure measurement systems.

  6. SU-E-P-54: Evaluation of the Accuracy and Precision of IGPS-O X-Ray Image-Guided Positioning System by Comparison with On-Board Imager Cone-Beam Computed Tomography

    SciTech Connect

    Zhang, D; Wang, W; Jiang, B; Fu, D

    2015-06-15

    Purpose: The purpose of this study is to assess the positioning accuracy and precision of IGPS-O system which is a novel radiographic kilo-voltage x-ray image-guided positioning system developed for clinical IGRT applications. Methods: IGPS-O x-ray image-guided positioning system consists of two oblique sets of radiographic kilo-voltage x-ray projecting and imaging devices which were equiped on the ground and ceiling of treatment room. This system can determine the positioning error in the form of three translations and three rotations according to the registration of two X-ray images acquired online and the planning CT image. An anthropomorphic head phantom and an anthropomorphic thorax phantom were used for this study. The phantom was set up on the treatment table with correct position and various “planned” setup errors. Both IGPS-O x-ray image-guided positioning system and the commercial On-board Imager Cone-beam Computed Tomography (OBI CBCT) were used to obtain the setup errors of the phantom. Difference of the Result between the two image-guided positioning systems were computed and analyzed. Results: The setup errors measured by IGPS-O x-ray image-guided positioning system and the OBI CBCT system showed a general agreement, the means and standard errors of the discrepancies between the two systems in the left-right, anterior-posterior, superior-inferior directions were −0.13±0.09mm, 0.03±0.25mm, 0.04±0.31mm, respectively. The maximum difference was only 0.51mm in all the directions and the angular discrepancy was 0.3±0.5° between the two systems. Conclusion: The spatial and angular discrepancies between IGPS-O system and OBI CBCT for setup error correction was minimal. There is a general agreement between the two positioning system. IGPS-O x-ray image-guided positioning system can achieve as good accuracy as CBCT and can be used in the clinical IGRT applications.

  7. Improved setup and positioning accuracy using a three-point customized cushion/mask/bite-block immobilization system for stereotactic reirradiation of head and neck cancer.

    PubMed

    Wang, He; Wang, Congjun; Tung, Samuel; Dimmitt, Andrew Wilson; Wong, Pei Fong; Edson, Mark A; Garden, Adam S; Rosenthal, David I; Fuller, Clifton D; Gunn, Gary B; Takiar, Vinita; Wang, Xin A; Luo, Dershan; Yang, James N; Wong, Jennifer; Phan, Jack

    2016-05-08

    The purpose of this study was to investigate the setup and positioning uncertainty of a custom cushion/mask/bite-block (CMB) immobilization system and determine PTV margin for image-guided head and neck stereotactic ablative radiotherapy (HN-SABR). We analyzed 105 treatment sessions among 21 patients treated with HN-SABR for recurrent head and neck cancers using a custom CMB immobilization system. Initial patient setup was performed using the ExacTrac infrared (IR) tracking system and initial setup errors were based on comparison of ExacTrac IR tracking system to corrected online ExacTrac X-rays images registered to treatment plans. Residual setup errors were determined using repeat verification X-ray. The online ExacTrac corrections were compared to cone-beam CT (CBCT) before treatment to assess agreement. Intrafractional positioning errors were determined using prebeam X-rays. The systematic and random errors were analyzed. The initial translational setup errors were -0.8 ± 1.3 mm, -0.8 ± 1.6 mm, and 0.3 ± 1.9 mm in AP, CC, and LR directions, respectively, with a three-dimensional (3D) vector of 2.7 ± 1.4 mm. The initial rotational errors were up to 2.4° if 6D couch is not available. CBCT agreed with ExacTrac X-ray images to within 2 mm and 2.5°. The intrafractional uncertainties were 0.1 ± 0.6 mm, 0.1 ± 0.6 mm, and 0.2 ± 0.5 mm in AP, CC, and LR directions, respectively, and 0.0° ± 0.5°, 0.0° ± 0.6°, and -0.1° ± 0.4° in yaw, roll, and pitch direction, respectively. The translational vector was 0.9 ± 0.6 mm. The calculated PTV margins mPTV(90,95) were within 1.6 mm when using image guidance for online setup correction. The use of image guidance for online setup correction, in combination with our customized CMB device, highly restricted target motion during treatments and provided robust immobilization to ensure minimum dose of 95% to target volume with 2.0 mm PTV margin for HN-SABR.

  8. Improved setup and positioning accuracy using a three-point customized cushion/mask/bite-block immobilization system for stereotactic reirradiation of head and neck cancer.

    PubMed

    Wang, He; Wang, Congjun; Tung, Samuel; Dimmitt, Andrew Wilson; Wong, Pei Fong; Edson, Mark A; Garden, Adam S; Rosenthal, David I; Fuller, Clifton D; Gunn, Gary B; Takiar, Vinita; Wang, Xin A; Luo, Dershan; Yang, James N; Wong, Jennifer; Phan, Jack

    2016-05-01

    The purpose of this study was to investigate the setup and positioning uncertainty of a custom cushion/mask/bite-block (CMB) immobilization system and determine PTV margin for image-guided head and neck stereotactic ablative radiotherapy (HN-SABR). We analyzed 105 treatment sessions among 21 patients treated with HN-SABR for recurrent head and neck cancers using a custom CMB immobilization system. Initial patient setup was performed using the ExacTrac infrared (IR) tracking system and initial setup errors were based on comparison of ExacTrac IR tracking system to corrected online ExacTrac X-rays images registered to treatment plans. Residual setup errors were determined using repeat verification X-ray. The online ExacTrac corrections were compared to cone-beam CT (CBCT) before treatment to assess agreement. Intrafractional positioning errors were determined using prebeam X-rays. The systematic and random errors were analyzed. The initial translational setup errors were -0.8±1.3 mm, -0.8±1.6 mm, and 0.3±1.9 mm in AP, CC, and LR directions, respectively, with a three-dimensional (3D) vector of 2.7±1.4 mm. The initial rotational errors were up to 2.4° if 6D couch is not available. CBCT agreed with ExacTrac X-ray images to within 2 mm and 2.5°. The intrafractional uncertainties were 0.1±0.6 mm, 0.1±0.6 mm, and 0.2±0.5 mm in AP, CC, and LR directions, respectively, and 0.0∘±0.5°, 0.0∘±0.6°, and -0.1∘±0.4∘ in yaw, roll, and pitch direction, respectively. The translational vector was 0.9±0.6 mm. The calculated PTV margins mPTV(90,95) were within 1.6 mm when using image guidance for online setup correction. The use of image guidance for online setup correction, in combination with our customized CMB device, highly restricted target motion during treatments and provided robust immobilization to ensure minimum dose of 95% to target volume with 2.0 mm PTV margin for HN-SABR. PACS number(s): 87.55.ne.

  9. Database applicaton for absolute spectrophotometry

    NASA Astrophysics Data System (ADS)

    Bochkov, Valery V.; Shumko, Sergiy

    2002-12-01

    32-bit database application with multidocument interface for Windows has been developed to calculate absolute energy distributions of observed spectra. The original database contains wavelength calibrated observed spectra which had been already passed through apparatus reductions such as flatfielding, background and apparatus noise subtracting. Absolute energy distributions of observed spectra are defined in unique scale by means of registering them simultaneously with artificial intensity standard. Observations of sequence of spectrophotometric standards are used to define absolute energy of the artificial standard. Observations of spectrophotometric standards are used to define optical extinction in selected moments. FFT algorithm implemented in the application allows performing convolution (deconvolution) spectra with user-defined PSF. The object-oriented interface has been created using facilities of C++ libraries. Client/server model with Windows Socket functionality based on TCP/IP protocol is used to develop the application. It supports Dynamic Data Exchange conversation in server mode and uses Microsoft Exchange communication facilities.

  10. Four Years of Absolutely Calibrated Hyperspectral Data from the Atmospheric Infrared Sounder (AIRS) on the Eos Aqua

    NASA Technical Reports Server (NTRS)

    Aumann, Hartmut H.; Broberg, Steve; Elliott, Denis; Gregorich, Dave

    2006-01-01

    This viewgraph presentation reviews four years of absolute calibration of hyperspectral data from the AIRS instrument located on the EOS AQUA spacecraft. The following topics are discussed: 1) A quick overview of AIRS; 2) What absolute calibration accuracy and stability are required for climate applications?; 3) Validating of radiance accuracy and stability: Results from four years of AIRS data; and 4) Conclusions.

  11. Absolute classification with unsupervised clustering

    NASA Technical Reports Server (NTRS)

    Jeon, Byeungwoo; Landgrebe, D. A.

    1992-01-01

    An absolute classification algorithm is proposed in which the class definition through training samples or otherwise is required only for a particular class of interest. The absolute classification is considered as a problem of unsupervised clustering when one cluster is known initially. The definitions and statistics of the other classes are automatically developed through the weighted unsupervised clustering procedure, which is developed to keep the cluster corresponding to the class of interest from losing its identity as the class of interest. Once all the classes are developed, a conventional relative classifier such as the maximum-likelihood classifier is used in the classification.

  12. Absolute Radiometric Calibration of EUNIS-06

    NASA Technical Reports Server (NTRS)

    Thomas, R. J.; Rabin, D. M.; Kent, B. J.; Paustian, W.

    2007-01-01

    The Extreme-Ultraviolet Normal-Incidence Spectrometer (EUNIS) is a soundingrocket payload that obtains imaged high-resolution spectra of individual solar features, providing information about the Sun's corona and upper transition region. Shortly after its successful initial flight last year, a complete end-to-end calibration was carried out to determine the instrument's absolute radiometric response over its Longwave bandpass of 300 - 370A. The measurements were done at the Rutherford-Appleton Laboratory (RAL) in England, using the same vacuum facility and EUV radiation source used in the pre-flight calibrations of both SOHO/CDS and Hinode/EIS, as well as in three post-flight calibrations of our SERTS sounding rocket payload, the precursor to EUNIS. The unique radiation source provided by the Physikalisch-Technische Bundesanstalt (PTB) had been calibrated to an absolute accuracy of 7% (l-sigma) at 12 wavelengths covering our bandpass directly against the Berlin electron storage ring BESSY, which is itself a primary radiometric source standard. Scans of the EUNIS aperture were made to determine the instrument's absolute spectral sensitivity to +- 25%, considering all sources of error, and demonstrate that EUNIS-06 was the most sensitive solar E W spectrometer yet flown. The results will be matched against prior calibrations which relied on combining measurements of individual optical components, and on comparisons with theoretically predicted 'insensitive' line ratios. Coordinated observations were made during the EUNIS-06 flight by SOHO/CDS and EIT that will allow re-calibrations of those instruments as well. In addition, future EUNIS flights will provide similar calibration updates for TRACE, Hinode/EIS, and STEREO/SECCHI/EUVI.

  13. An estimate of global absolute dynamic topography

    NASA Technical Reports Server (NTRS)

    Tai, C.-K.; Wunsch, C.

    1984-01-01

    The absolute dynamic topography of the world ocean is estimated from the largest scales to a short-wavelength cutoff of about 6700 km for the period July through September, 1978. The data base consisted of the time-averaged sea-surface topography determined by Seasat and geoid estimates made at the Goddard Space Flight Center. The issues are those of accuracy and resolution. Use of the altimetric surface as a geoid estimate beyond the short-wavelength cutoff reduces the spectral leakage in the estimated dynamic topography from erroneous small-scale geoid estimates without contaminating the low wavenumbers. Comparison of the result with a similarly filtered version of Levitus' (1982) historical average dynamic topography shows good qualitative agreement. There is quantitative disagreement, but it is within the estimated errors of both methods of calculation.

  14. Micron Accurate Absolute Ranging System: Range Extension

    NASA Technical Reports Server (NTRS)

    Smalley, Larry L.; Smith, Kely L.

    1999-01-01

    The purpose of this research is to investigate Fresnel diffraction as a means of obtaining absolute distance measurements with micron or greater accuracy. It is believed that such a system would prove useful to the Next Generation Space Telescope (NGST) as a non-intrusive, non-contact measuring system for use with secondary concentrator station-keeping systems. The present research attempts to validate past experiments and develop ways to apply the phenomena of Fresnel diffraction to micron accurate measurement. This report discusses past research on the phenomena, and the basis of the use Fresnel diffraction distance metrology. The apparatus used in the recent investigations, experimental procedures used, preliminary results are discussed in detail. Continued research and equipment requirements on the extension of the effective range of the Fresnel diffraction systems is also described.

  15. Absolute Spectrophotometry of 237 Open Cluster Stars

    NASA Astrophysics Data System (ADS)

    Clampitt, L.; Burstein, D.

    1994-12-01

    We present absolute spectrophotometry of 237 stars in 7 nearby open clusters: Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, and M 39. The observations were taken using the Wampler single-channel scanner (Wampler 1966) on the Crossley 0.9m telescope at Lick Observatory from July 1973 through December 1974. 21 bandpasses spanning the spectral range 3500 Angstroms to 7780 Angstroms were observed for each star, with bandwiths ranging from 32Angstroms to 64 Angstroms. Data are standardized to the Hayes--Latham (1975) system. Our measurements are compared to filter colors on the Johnson BV, Stromgren ubvy, and Geneva U V B_1 B_2 V_1 G systems, as well as to spectrophotometry of a few stars published by Gunn, Stryker & Tinsley and in the Spectrophotometric Standards Catalog (Adelman; as distributed by the NSSDC). Both internal and external comparisons to the filter systems indicate a formal statistical accuracy per bandpass of 0.01 to 0.02 mag, with apparent larger ( ~ 0.03 mag) differences in absolute calibration between this data set and existing spectrophotometry. These data will comprise part of the spectrophotometry that will be used to calibrate the Beijing-Arizona-Taipei-Connecticut Color Survey of the Sky (see separate paper by Burstein et al. at this meeting).

  16. Swarm's Absolute Scalar Magnetometers Burst Mode Results

    NASA Astrophysics Data System (ADS)

    Coisson, P.; Vigneron, P.; Hulot, G.; Crespo Grau, R.; Brocco, L.; Lalanne, X.; Sirol, O.; Leger, J. M.; Jager, T.; Bertrand, F.; Boness, A.; Fratter, I.

    2014-12-01

    Each of the three Swarm satellites embarks an Absolute Scalar Magnetometer (ASM) to provide absolute scalar measurements of the magnetic field with high accuracy and stability. Nominal data acquisition of these ASMs is 1 Hz. But they can also run in a so-called "burst mode" and provide data at 250 Hz. During the commissioning phase of the mission, seven burst mode acquisition campaigns have been run simultaneously for all satellites, obtaining a total of ten days of burs-mode data. These campaigns allowed the identification of issues related to the operations of the piezo-electric motor and the heaters connected to the ASM, that do not impact the nominal 1 Hz scalar data. We analyze the burst mode data to identify high frequency geomagnetic signals, focusing the analysis in two regions: the low latitudes, where we seek signatures of ionospheric irregularities, and the high latitudes, to identify high frequency signals related to polar region currents. Since these campaigns have been conducted during the initial months of the mission, the three satellites where still close to each other, allowing to analyze the spatial coherency of the signals. Wavelet analysis have revealed 31 Hz signals appearing in the night-side in the equatorial region.

  17. Accuracy evaluation of 3D lidar data from small UAV

    NASA Astrophysics Data System (ADS)

    Tulldahl, H. M.; Bissmarck, Fredrik; Larsson, Hâkan; Grönwall, Christina; Tolt, Gustav

    2015-10-01

    A UAV (Unmanned Aerial Vehicle) with an integrated lidar can be an efficient system for collection of high-resolution and accurate three-dimensional (3D) data. In this paper we evaluate the accuracy of a system consisting of a lidar sensor on a small UAV. High geometric accuracy in the produced point cloud is a fundamental qualification for detection and recognition of objects in a single-flight dataset as well as for change detection using two or several data collections over the same scene. Our work presented here has two purposes: first to relate the point cloud accuracy to data processing parameters and second, to examine the influence on accuracy from the UAV platform parameters. In our work, the accuracy is numerically quantified as local surface smoothness on planar surfaces, and as distance and relative height accuracy using data from a terrestrial laser scanner as reference. The UAV lidar system used is the Velodyne HDL-32E lidar on a multirotor UAV with a total weight of 7 kg. For processing of data into a geographically referenced point cloud, positioning and orientation of the lidar sensor is based on inertial navigation system (INS) data combined with lidar data. The combination of INS and lidar data is achieved in a dynamic calibration process that minimizes the navigation errors in six degrees of freedom, namely the errors of the absolute position (x, y, z) and the orientation (pitch, roll, yaw) measured by GPS/INS. Our results show that low-cost and light-weight MEMS based (microelectromechanical systems) INS equipment with a dynamic calibration process can obtain significantly improved accuracy compared to processing based solely on INS data.

  18. Relativistic Absolutism in Moral Education.

    ERIC Educational Resources Information Center

    Vogt, W. Paul

    1982-01-01

    Discusses Emile Durkheim's "Moral Education: A Study in the Theory and Application of the Sociology of Education," which holds that morally healthy societies may vary in culture and organization but must possess absolute rules of moral behavior. Compares this moral theory with current theory and practice of American educators. (MJL)

  19. Droplet digital PCR for absolute quantification of pathogens.

    PubMed

    Gutiérrez-Aguirre, Ion; Rački, Nejc; Dreo, Tanja; Ravnikar, Maja

    2015-01-01

    The recent advent of different digital PCR (dPCR) platforms is enabling the expansion of this technology for research and diagnostic applications worldwide. The main principle of dPCR, as in other PCR-based methods including quantitative PCR (qPCR), is the specific amplification of a nucleic acid target. The distinctive feature of dPCR is the separation of the reaction mixture into thousands to millions of partitions which is followed by a real time or end point detection of the amplification. The distribution of target sequences into partitions is described by the Poisson distribution, thus allowing accurate and absolute quantification of the target from the ratio of positive against all partitions at the end of the reaction. This omits the need to use reference materials with known target concentrations and increases the accuracy of quantification at low target concentrations compared to qPCR. dPCR has also shown higher resilience to inhibitors in a number of different types of samples. In this chapter we describe the droplet digital PCR (ddPCR) workflow for the detection and quantification of pathogens using the droplet digital Bio-Rad platform QX100. We present as an example the quantification of the quarantine plant pathogenic bacterium, Erwinia amylovora.

  20. Quasi-absolute surface figure test with two orthogonal transverse spatial shifts

    NASA Astrophysics Data System (ADS)

    Xue, Shuai; Chen, Shanyong; Zhai, Dede; Shi, Feng

    2017-04-01

    A new zonal wavefront reconstruction algorithm with pixel-level spatial resolution and high accuracy is proposed, which is able to reconstruct the original wavefront of general aperture shape from only two difference wavefronts measured at two orthogonal shear directions with shear amounts equaling arbitrary moderate integral multiples of the sample interval. Based on this algorithm, a quasi-absolute surface figure test method is presented, which requires only two additional translational measurements with shifts of arbitrary moderate integral multiples of sample interval along x and y directions besides the original position measurement. Optical schemes of the proposed method for testing flat, spherical and cylindrical surfaces are investigated, and special considerations and challenges for calibrating spheres and cylinders are also briefly formulated theoretically. Thorough errors analysis is formulated for obtaining high accuracy test result. Simulations and experiments on a flat surface are conducted to validate the proposed algorithm and method. Compared with existing absolute test methods with Pseudo-Shear Interferometry (PSI) technique, the presented method has advantages, like, less number of measurements, arbitrary moderate shear amounts and the high signal-to-noise ratio it can reach.

  1. Absolute calibration of optical flats

    DOEpatents

    Sommargren, Gary E.

    2005-04-05

    The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.

  2. The Absolute Spectrum Polarimeter (ASP)

    NASA Technical Reports Server (NTRS)

    Kogut, A. J.

    2010-01-01

    The Absolute Spectrum Polarimeter (ASP) is an Explorer-class mission to map the absolute intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from 30 GHz to 5 THz. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much greater than 1O(raised to the power of { -3}) and Compton distortion y < 10 (raised to the power of{-6}). We describe the ASP instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.

  3. Physics of negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Abraham, Eitan; Penrose, Oliver

    2017-01-01

    Negative absolute temperatures were introduced into experimental physics by Purcell and Pound, who successfully applied this concept to nuclear spins; nevertheless, the concept has proved controversial: a recent article aroused considerable interest by its claim, based on a classical entropy formula (the "volume entropy") due to Gibbs, that negative temperatures violated basic principles of statistical thermodynamics. Here we give a thermodynamic analysis that confirms the negative-temperature interpretation of the Purcell-Pound experiments. We also examine the principal arguments that have been advanced against the negative temperature concept; we find that these arguments are not logically compelling, and moreover that the underlying "volume" entropy formula leads to predictions inconsistent with existing experimental results on nuclear spins. We conclude that, despite the counterarguments, negative absolute temperatures make good theoretical sense and did occur in the experiments designed to produce them.

  4. Optomechanics for absolute rotation detection

    NASA Astrophysics Data System (ADS)

    Davuluri, Sankar

    2016-07-01

    In this article, we present an application of optomechanical cavity for the absolute rotation detection. The optomechanical cavity is arranged in a Michelson interferometer in such a way that the classical centrifugal force due to rotation changes the length of the optomechanical cavity. The change in the cavity length induces a shift in the frequency of the cavity mode. The phase shift corresponding to the frequency shift in the cavity mode is measured at the interferometer output to estimate the angular velocity of absolute rotation. We derived an analytic expression to estimate the minimum detectable rotation rate in our scheme for a given optomechanical cavity. Temperature dependence of the rotation detection sensitivity is studied.

  5. Strategy for the absolute neutron emission measurement on ITER.

    PubMed

    Sasao, M; Bertalot, L; Ishikawa, M; Popovichev, S

    2010-10-01

    Accuracy of 10% is demanded to the absolute fusion measurement on ITER. To achieve this accuracy, a functional combination of several types of neutron measurement subsystem, cross calibration among them, and in situ calibration are needed. Neutron transport calculation shows the suitable calibration source is a DT/DD neutron generator of source strength higher than 10(10) n/s (neutron/second) for DT and 10(8) n/s for DD. It will take eight weeks at the minimum with this source to calibrate flux monitors, profile monitors, and the activation system.

  6. An absolute photometric system at 10 and 20 microns

    NASA Technical Reports Server (NTRS)

    Rieke, G. H.; Lebofsky, M. J.; Low, F. J.

    1985-01-01

    Two new direct calibrations at 10 and 20 microns are presented in which terrestrial flux standards are referred to infrared standard stars. These measurements give both good agreement and higher accuracy when compared with previous direct calibrations. As a result, the absolute calibrations at 10 and 20 microns have now been determined with accuracies of 3 and 8 percent, respectively. A variety of absolute calibrations based on extrapolation of stellar spectra from the visible to 10 microns are reviewed. Current atmospheric models of A-type stars underestimate their fluxes by about 10 percent at 10 microns, whereas models of solar-type stars agree well with the direct calibrations. The calibration at 20 microns can probably be determined to about 5 percent by extrapolation from the more accurate result at 10 microns. The photometric system at 10 and 20 microns is updated to reflect the new absolute calibration, to base its zero point directly on the colors of A0 stars, and to improve the accuracy in the comparison of the standard stars.

  7. Absolute stereochemistry of altersolanol A and alterporriols.

    PubMed

    Kanamaru, Saki; Honma, Miho; Murakami, Takanori; Tsushima, Taro; Kudo, Shinji; Tanaka, Kazuaki; Nihei, Ken-Ichi; Nehira, Tatsuo; Hashimoto, Masaru

    2012-02-01

    The absolute stereochemistry of altersolanol A (1) was established by observing a positive exciton couplet in the circular dichroism (CD) spectrum of the C3,C4-O-bis(2-naphthoyl) derivative 10 and by chemical correlations with known compound 8. Before the discussion, the relative stereochemistry of 1 was confirmed by X-ray crystallographic analysis. The shielding effect at C7'-OMe group by C1-O-benzoylation established the relative stereochemical relationship between the C8-C8' axial bonding and the C1-C4/C1'-C4' polyol moieties of alterporriols E (3), an atropisomer of the C8-C8' dimer of 1. As 3 could be obtained by dimerization of 1 in vitro, the absolute configuration of its central chirality elements (C1-C4) must be identical to those of 1. Spectral comparison between the experimental and theoretical CD spectra supported the above conclusion. Axial stereochemistry of novel C4-O-deoxy dimeric derivatives, alterporriols F (4) and G (5), were also revealed by comparison of their CD spectra to those of 2 and 3.

  8. Absolute Positioning Using The Earth’s Magnetic Anomaly Field

    DTIC Science & Technology

    2016-09-15

    systems do not have. Furthermore, the magnetic anomaly signal is available at all times of the day and under all weather conditions. The general...space weather effects, most magnetic surveys take steps to avoid man- made sources corrupting the measurements, and temporal variations are recorded at a...temporal variations caused by space and ionospheric weather conditions. From 54 Figure 27. World Digital Magnetic Anomaly Map [43] 55 a practical standpoint

  9. Absolute Gravity Datum in the Age of Cold Atom Gravimeters

    NASA Astrophysics Data System (ADS)

    Childers, V. A.; Eckl, M. C.

    2014-12-01

    The international gravity datum is defined today by the International Gravity Standardization Net of 1971 (IGSN-71). The data supporting this network was measured in the 1950s and 60s using pendulum and spring-based gravimeter ties (plus some new ballistic absolute meters) to replace the prior protocol of referencing all gravity values to the earlier Potsdam value. Since this time, gravimeter technology has advanced significantly with the development and refinement of the FG-5 (the current standard of the industry) and again with the soon-to-be-available cold atom interferometric absolute gravimeters. This latest development is anticipated to provide improvement in the range of two orders of magnitude as compared to the measurement accuracy of technology utilized to develop ISGN-71. In this presentation, we will explore how the IGSN-71 might best be "modernized" given today's requirements and available instruments and resources. The National Geodetic Survey (NGS), along with other relevant US Government agencies, is concerned about establishing gravity control to establish and maintain high order geodetic networks as part of the nation's essential infrastructure. The need to modernize the nation's geodetic infrastructure was highlighted in "Precise Geodetic Infrastructure, National Requirements for a Shared Resource" National Academy of Science, 2010. The NGS mission, as dictated by Congress, is to establish and maintain the National Spatial Reference System, which includes gravity measurements. Absolute gravimeters measure the total gravity field directly and do not involve ties to other measurements. Periodic "intercomparisons" of multiple absolute gravimeters at reference gravity sites are used to constrain the behavior of the instruments to ensure that each would yield reasonably similar measurements of the same location (i.e. yield a sufficiently consistent datum when measured in disparate locales). New atomic interferometric gravimeters promise a significant

  10. Development and Testing of a High-Precision Position and Attitude Measuring System for a Space Mechanism

    NASA Technical Reports Server (NTRS)

    Khanenya, Nikolay; Paciotti, Gabriel; Forzani, Eugenio; Blecha, Luc

    2016-01-01

    This paper describes a high-precision optical metrology system - a unique ground test equipment which was designed and implemented for simultaneous precise contactless measurements of 6 degrees-of-freedom (3 translational + 3 rotational) of a space mechanism end-effector [1] in a thermally controlled ISO 5 clean environment. The developed contactless method reconstructs both position and attitude of the specimen from three cross-sections measured by 2D distance sensors [2]. The cleanliness is preserved by the hermetic test chamber filled with high purity nitrogen. The specimen's temperature is controlled by the thermostat [7]. The developed method excludes errors caused by the thermal deformations and manufacturing inaccuracies of the test jig. Tests and simulations show that the measurement accuracy of an object absolute position is of 20 micron in in-plane measurement (XY) and about 50 micron out of plane (Z). The typical absolute attitude is determined with an accuracy better than 3 arcmin in rotation around X and Y and better than 10 arcmin in Z. The metrology system is able to determine relative position and movement with an accuracy one order of magnitude lower than the absolute accuracy. Typical relative displacement measurement accuracies are better than 1 micron in X and Y and about 2 micron in Z. Finally, the relative rotation can be measured with accuracy better than 20 arcsec in any direction.

  11. The Absolute Gravimeter FG5 - Adjustment and Residual Data Evaluation

    NASA Astrophysics Data System (ADS)

    Orlob, M.; Braun, A.; Henton, J.; Courtier, N.; Liard, J.

    2009-05-01

    The most widely used method of direct terrestrial gravity determination is performed by using a ballistic absolute gravimeter. Today, the FG5 (Micro-g LaCoste; Lafayette, CO) is the most common free-fall absolute gravimeter. It uses the Michelson-type interferometer to determine the absolute gravity value with accuracies up to one part- per-billion of g. Furthermore, absolute gravimeter measurements can be used to assist in the validation and interpretation of temporal variations of the global gravity field, e.g. from the GRACE mission. In addition, absolute gravimetry allows for monitoring gravity changes which are caused by subsurface mass redistributions and/or vertical displacements. In this study,adjustment software was developed and applied to the raw data sets of FG5#106 and FG5#236, made available by Natural Resources Canada. Both data sets have been collected at the same time and place which leads to an intercomparison of the instruments performance. The adjustment software was validated against the official FG5 software package developed by Micro-g Lacoste. In order to identify potential environmental or instrument disturbances in the observed time series, a Lomb- Scargle periodogram analysis was employed. The absolute gravimeter FG5 is particularly sensitive to low frequencies between 0-3Hz. Hence, the focus of the analysis is to detect signals in the band of 0-100 Hz. An artificial signal was added to the measurements for demonstration purposes. Both the performance of the adjustment software and the Lomb-Scargle analysis will be discussed.

  12. Cosmology with negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony

    2016-08-01

    Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < -1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.

  13. Absolute configuration determination of angular dihydrocoumarins from Peucedanum praeruptorum.

    PubMed

    Lou, Hong-Xiang; Sun, Long-Ru; Yu, Wen-Tao; Fan, Pei-Hong; Cui, Lei; Gao, Yan-Hui; Ma, Bin; Ren, Dong-Mei; Ji, Mei

    2004-09-01

    From Peucedanum praeruptorum, one new khellactone ester (3'R)-O-acetyl-(4'S)-O-angeloylkhellactone (3), as well as four known angular dihydropyranocoumarins (1, 2, 4, 5) have been isolated. On the basis of NMR spectra and X-ray crystallography, their structures were determined. We have elucidated their absolute configuration by either chiral separation of their alkaline hydrolysis products with Rp-18 HPLC eluted with 5% hydroxypropyl-beta-cyclodextrin (beta-HCD) or by measurement of their CD spectra. A general rule relating the position and absolute streochemistry of the khellactone esters to the sign of their Cotton effects in CD curves is proposed.

  14. a Portable Apparatus for Absolute Measurements of the Earth's Gravity.

    NASA Astrophysics Data System (ADS)

    Zumberge, Mark Andrew

    We have developed a new, portable apparatus for making absolute measurements of the acceleration due to the earth's gravity. We use the method of interferometrically determining the acceleration of a freely falling corner -cube prism. The falling object is surrounded by a chamber which is driven vertically inside a fixed vacuum chamber. This falling chamber is servoed to track the falling corner -cube to shield it from drag due to background gas. In addition, the drag-free falling chamber removes the need for a magnetic release, shields the falling object from electrostatic forces, and provides a means of both gently arresting the falling object and quickly returning it to its start position, to allow rapid acquisition of data. A synthesized long period isolation device reduces the noise due to seismic oscillations. A new type of Zeeman laser is used as the light source in the interferometer, and is compared with the wavelength of an iodine stabilized laser. The times of occurrence of 45 interference fringes are measured to within 0.2 nsec over a 20 cm drop and are fit to a quadratic by an on-line minicomputer. 150 drops can be made in ten minutes resulting in a value of g having a precision of 3 to 6 parts in 10('9). Systematic errors have been determined to be less than 5 parts in 10('9) through extensive tests. Three months of gravity data have been obtained with a reproducibility ranging from 5 to 10 parts in 10('9). The apparatus has been designed to be easily portable. Field measurements are planned for the immediate future. An accuracy of 6 parts in 10('9) corresponds to a height sensitivity of 2 cm. Vertical motions in the earth's crust and tectonic density changes that may precede earthquakes are to be investigated using this apparatus.

  15. Accuracy of three-dimensional soft tissue simulation in bimaxillary osteotomies.

    PubMed

    Liebregts, Jeroen; Xi, Tong; Timmermans, Maarten; de Koning, Martien; Bergé, Stefaan; Hoppenreijs, Theo; Maal, Thomas

    2015-04-01

    The purpose of this study was to evaluate the accuracy of an algorithm based on the mass tensor model (MTM) for computerized 3D simulation of soft-tissue changes following bimaxillary osteotomy, and to identify patient and surgery-related factors that may affect the accuracy of the simulation. Sixty patients (mean age 26.0 years) who had undergone bimaxillary osteotomy, participated in this study. Cone beam CT scans were acquired pre- and one year postoperatively. The 3D rendered pre- and postoperative scans were matched. The maxilla and mandible were segmented and aligned to the postoperative position. 3D distance maps and cephalometric analyses were used to quantify the simulation error. The mean absolute error between the 3D simulation and the actual postoperative facial profile was 0.81 ± 0.22 mm for the face as a whole. The accuracy of the simulation (average absolute error ≤2 mm) for the whole face and for the upper lip, lower lip and chin subregions were 100%, 93%, 90% and 95%, respectively. The predictability was correlated with the magnitude of the maxillary and mandibular advancement, age and V-Y closure. It was concluded that the MTM-based soft tissue simulation for bimaxillary surgery was accurate for clinical use, though patients should be informed of possible variation in the predicted lip position.

  16. Absolute distance sensing by two laser optical interferometry.

    PubMed

    Thurner, Klaus; Braun, Pierre-François; Karrai, Khaled

    2013-11-01

    We have developed a method for absolute distance sensing by two laser optical interferometry. A particularity of this technique is that a target distance is determined in absolute and is no longer limited to within an ambiguity range affecting usually multiple wavelength interferometers. We implemented the technique in a low-finesse Fabry-Pérot miniature fiber based interferometer. We used two diode lasers, both operating in the 1550 nm wavelength range. The wavelength difference is chosen to create a 25 μm long periodic beating interferometric pattern allowing a nanometer precise position measurement but limited to within an ambiguity range of 25 μm. The ambiguity is then eliminated by scanning one of the wavelengths over a small range (3.4 nm). We measured absolute distances in the sub-meter range and this with just few nanometer repeatability.

  17. Method and apparatus for two-dimensional absolute optical encoding

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B. (Inventor)

    2004-01-01

    This invention presents a two-dimensional absolute optical encoder and a method for determining position of an object in accordance with information from the encoder. The encoder of the present invention comprises a scale having a pattern being predetermined to indicate an absolute location on the scale, means for illuminating the scale, means for forming an image of the pattern; and detector means for outputting signals derived from the portion of the image of the pattern which lies within a field of view of the detector means, the field of view defining an image reference coordinate system, and analyzing means, receiving the signals from the detector means, for determining the absolute location of the object. There are two types of scale patterns presented in this invention: grid type and starfield type.

  18. Absolute and relative family affluence and psychosomatic symptoms in adolescents.

    PubMed

    Elgar, Frank J; De Clercq, Bart; Schnohr, Christina W; Bird, Phillippa; Pickett, Kate E; Torsheim, Torbjørn; Hofmann, Felix; Currie, Candace

    2013-08-01

    Previous research on the links between income inequality and health and socioeconomic differences in health suggests that relative differences in affluence impact health and well-being more than absolute affluence. This study explored whether self-reported psychosomatic symptoms in adolescents relate more closely to relative affluence (i.e., relative deprivation or rank affluence within regions or schools) than to absolute affluence. Data on family material assets and psychosomatic symptoms were collected from 48,523 adolescents in eight countries (Austria, Belgium, Canada, Norway, Scotland, Poland, Turkey, and Ukraine) as part of the 2009/10 Health Behaviour in School-aged Children study. Multilevel regression analyses of the data showed that relative deprivation (Yitzhaki Index, calculated in regions and in schools) and rank affluence (in regions) (1) related more closely to symptoms than absolute affluence, and (2) related to symptoms after differences in absolute affluence were held constant. However, differences in family material assets, whether they are measured in absolute or relative terms, account for a significant variation in adolescent psychosomatic symptoms. Conceptual and empirical issues relating to the use of material affluence indices to estimate socioeconomic position are discussed.

  19. High speed image acquisition system of absolute encoder

    NASA Astrophysics Data System (ADS)

    Liao, Jianxiang; Chen, Xin; Chen, Xindu; Zhang, Fangjian; Wang, Han

    2017-01-01

    Absolute optical encoder as a product of optical, mechanical and electronic integration has been widely used in displacement measuring fields. However, how to improve the measurement velocity and reduce the manufacturing cost of absolute optical encoder is the key problem to be solved. To improve the measurement speed, a novel absolute optical encoder image acquisition system is proposed. The proposed acquisition system includes a linear CCD sensor is applied for capturing coding pattern images, an optical magnifying system is used for enlarging the grating stripes, an analog-digital conversion(ADC) module is used for processing the CCD analogy signal, a field programmable gate array(FPGA) device and other peripherals perform driving task. An absolute position measurement experiment was set up to verify and evaluate the proposed image acquisition system. The experimental result indicates that the proposed absolute optical encoder image acquisition system has the image acquisition speed of more than 9500fp/s with well reliability and lower manufacture cost.

  20. Absolute Instability in Swept Leading-Edge Boundary Layers

    NASA Astrophysics Data System (ADS)

    Lin, R.-S.; Li, F.; Malik, M. R.

    1997-11-01

    Absolute instabilities in the swept Hiemenz flow and flows over Poll's swept cylinder are studied. It is assumed that the span is infinite and the laminar flow field is subjected to a line impulsive excitation so that the spanwise wavenumber (β) is taken to be real, which is akin to the rotating disk study made by Lingwood.footnote Lingwood, R. J., J. Fluid Mech., 299, 17, 1995. We found that these flows can be absolutely unstable in the chordwise (x) direction. The pinch-point singularities formed by the coalescence of two distinct spatial branches can lie either below or above the real α-axis. The pinch points with a positive αi imply the existence of an unstable disturbance propagating against the mainstream, which has never been observed before. It is found that singularities of pinch type occur in a region very close to the leading edge, therefore the attachment-line Reynolds number is used to correlate the onset of absolute instability. The critical Reynolds number for absolute instability is found to be about R=540 compared to 583 for the attachment-line instability. Provided the non-linear behavior of this absolute instability is sufficient to trigger the laminar to turbulent transition, then it would cause a complete loss of laminar flow on a swept wing as does the attachment-line instability.

  1. The absolute radiometric calibration of the advanced very high resolution radiometer

    NASA Technical Reports Server (NTRS)

    Slater, P. N.; Teillet, P. M.; Ding, Y.

    1988-01-01

    The need for independent, redundant absolute radiometric calibration methods is discussed with reference to the Thematic Mapper. Uncertainty requirements for absolute calibration of between 0.5 and 4 percent are defined based on the accuracy of reflectance retrievals at an agricultural site. It is shown that even very approximate atmospheric corrections can reduce the error in reflectance retrieval to 0.02 over the reflectance range 0 to 0.4.

  2. Absolute magnitude calibration using trigonometric parallax - Incomplete, spectroscopic samples

    NASA Technical Reports Server (NTRS)

    Ratnatunga, Kavan U.; Casertano, Stefano

    1991-01-01

    A new numerical algorithm is used to calibrate the absolute magnitude of spectroscopically selected stars from their observed trigonometric parallax. This procedure, based on maximum-likelihood estimation, can retrieve unbiased estimates of the intrinsic absolute magnitude and its dispersion even from incomplete samples suffering from selection biases in apparent magnitude and color. It can also make full use of low accuracy and negative parallaxes and incorporate censorship on reported parallax values. Accurate error estimates are derived for each of the fitted parameters. The algorithm allows an a posteriori check of whether the fitted model gives a good representation of the observations. The procedure is described in general and applied to both real and simulated data.

  3. Determination of absolute internal conversion coefficients using the SAGE spectrometer

    NASA Astrophysics Data System (ADS)

    Sorri, J.; Greenlees, P. T.; Papadakis, P.; Konki, J.; Cox, D. M.; Auranen, K.; Partanen, J.; Sandzelius, M.; Pakarinen, J.; Rahkila, P.; Uusitalo, J.; Herzberg, R.-D.; Smallcombe, J.; Davies, P. J.; Barton, C. J.; Jenkins, D. G.

    2016-03-01

    A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of 154Sm, 152Sm and 166Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for ground-state band E2 transitions show that the absolute internal conversion coefficients can be extracted using the methods described with a reasonable accuracy. In some cases of less intense transitions only an upper limit for the internal conversion coefficient could be given.

  4. Measured and modelled absolute gravity in Greenland

    NASA Astrophysics Data System (ADS)

    Nielsen, E.; Forsberg, R.; Strykowski, G.

    2012-12-01

    Present day changes in the ice volume in glaciated areas like Greenland will change the load on the Earth and to this change the lithosphere will respond elastically. The Earth also responds to changes in the ice volume over a millennial time scale. This response is due to the viscous properties of the mantle and is known as Glaical Isostatic Adjustment (GIA). Both signals are present in GPS and absolute gravity (AG) measurements and they will give an uncertainty in mass balance estimates calculated from these data types. It is possible to separate the two signals if both gravity and Global Positioning System (GPS) time series are available. DTU Space acquired an A10 absolute gravimeter in 2008. One purpose of this instrument is to establish AG time series in Greenland and the first measurements were conducted in 2009. Since then are 18 different Greenland GPS Network (GNET) stations visited and six of these are visited more then once. The gravity signal consists of three signals; the elastic signal, the viscous signal and the direct attraction from the ice masses. All of these signals can be modelled using various techniques. The viscous signal is modelled by solving the Sea Level Equation with an appropriate ice history and Earth model. The free code SELEN is used for this. The elastic signal is modelled as a convolution of the elastic Greens function for gravity and a model of present day ice mass changes. The direct attraction is the same as the Newtonian attraction and is calculated as this. Here we will present the preliminary results of the AG measurements in Greenland. We will also present modelled estimates of the direct attraction, the elastic and the viscous signals.

  5. Improved accuracies for satellite tracking

    NASA Technical Reports Server (NTRS)

    Kammeyer, P. C.; Fiala, A. D.; Seidelmann, P. K.

    1991-01-01

    A charge coupled device (CCD) camera on an optical telescope which follows the stars can be used to provide high accuracy comparisons between the line of sight to a satellite, over a large range of satellite altitudes, and lines of sight to nearby stars. The CCD camera can be rotated so the motion of the satellite is down columns of the CCD chip, and charge can be moved from row to row of the chip at a rate which matches the motion of the optical image of the satellite across the chip. Measurement of satellite and star images, together with accurate timing of charge motion, provides accurate comparisons of lines of sight. Given lines of sight to stars near the satellite, the satellite line of sight may be determined. Initial experiments with this technique, using an 18 cm telescope, have produced TDRS-4 observations which have an rms error of 0.5 arc second, 100 m at synchronous altitude. Use of a mosaic of CCD chips, each having its own rate of charge motion, in the focal place of a telescope would allow point images of a geosynchronous satellite and of stars to be formed simultaneously in the same telescope. The line of sight of such a satellite could be measured relative to nearby star lines of sight with an accuracy of approximately 0.03 arc second. Development of a star catalog with 0.04 arc second rms accuracy and perhaps ten stars per square degree would allow determination of satellite lines of sight with 0.05 arc second rms absolute accuracy, corresponding to 10 m at synchronous altitude. Multiple station time transfers through a communications satellite can provide accurate distances from the satellite to the ground stations. Such observations can, if calibrated for delays, determine satellite orbits to an accuracy approaching 10 m rms.

  6. Next-generation inductive transducers for position measurement

    NASA Astrophysics Data System (ADS)

    Howard, Mark A.

    2012-06-01

    Position transducers are common but critical elements in defence, aerospace, security and surveillance equipment. Traditional solutions such as potentiometers, optical encoders and inductive detectors, struggle to match the high operational, environmental and lifetime requirements demanded by such equipment. This paper outlines a radically new approach to position measurement suitable for a wide variety of shapes and sizes including rotary, linear, 2D and 3D geometries. The technology's main components are arrays of printed conductors on thin, lightweight flexible substrates. The result is a non-contact, absolute measurement technique which offers high reliability, accuracy and robust operation in a compact, non-ITAR and lightweight form.

  7. Interferometric attitude determination using the global positioning system - A new gyrotheodolite

    NASA Astrophysics Data System (ADS)

    Brown, A. K.; Thorvaldsen, T. P.; Bowles, W. M.

    A GPS receiver can measure absolute position to 5 meters. However, it is possible to measure relative position more accurately by using interferometry on the GPS carrier to measure heading. Simulation has shown that a dynamically aided, three antennae, short baselength GPS interferometer can measure heading to an accuracy of 50 microrad. Relative position can be determined from this heading measurement by sighting onto control stations with a theodolite mounted on the interferometer. If the control stations were 1 km distant it would be possible to measure relative position, using a GPS interferometer, to within 5 cm.

  8. ON A SUFFICIENT CONDITION FOR ABSOLUTE CONTINUITY.

    DTIC Science & Technology

    The formulation of a condition which yields absolute continuity when combined with continuity and bounded variation is the problem considered in the...Briefly, the formulation is achieved through a discussion which develops a proof by contradiction of a sufficiently theorem for absolute continuity which uses in its hypothesis the condition of continuity and bounded variation .

  9. Introducing the Mean Absolute Deviation "Effect" Size

    ERIC Educational Resources Information Center

    Gorard, Stephen

    2015-01-01

    This paper revisits the use of effect sizes in the analysis of experimental and similar results, and reminds readers of the relative advantages of the mean absolute deviation as a measure of variation, as opposed to the more complex standard deviation. The mean absolute deviation is easier to use and understand, and more tolerant of extreme…

  10. Monolithically integrated absolute frequency comb laser system

    SciTech Connect

    Wanke, Michael C.

    2016-07-12

    Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.

  11. Absolute instability of the Gaussian wake profile

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Aggarwal, Arun K.

    1987-01-01

    Linear parallel-flow stability theory has been used to investigate the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution. The type of local instability, i.e., convective or absolute, is determined by the location of a branch-point singularity with zero group velocity of the complex dispersion relation for the instability waves. The effects of viscosity were found to be weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake half-width, larger than about 400. Absolute instability occurs only for sufficiently large values of the center-line wake defect. The critical value of this parameter increases with decreasing wake Reynolds number, thereby indicating a shrinking region of absolute instability with decreasing wake Reynolds number. If backflow is not allowed, absolute instability does not occur for wake Reynolds numbers smaller than about 38.

  12. Assessing and Ensuring GOES-R Magnetometer Accuracy

    NASA Technical Reports Server (NTRS)

    Carter, Delano R.; Todirita, Monica; Kronenwetter, Jeffrey; Chu, Donald

    2016-01-01

    The GOES-R magnetometer subsystem accuracy requirement is 1.7 nanoteslas (nT). During quiet times (100 nT), accuracy is defined as absolute mean plus 3 sigma. During storms (300 nT), accuracy is defined as absolute mean plus 2 sigma. Error comes both from outside the magnetometers, e.g. spacecraft fields and misalignments, as well as inside, e.g. zero offset and scale factor errors. Because zero offset and scale factor drift over time, it will be necessary to perform annual calibration maneuvers. To predict performance before launch, we have used Monte Carlo simulations and covariance analysis. Both behave as expected, and their accuracy predictions agree within 30%. With the proposed calibration regimen, both suggest that the GOES-R magnetometer subsystem will meet its accuracy requirements.

  13. Assessing and Ensuring GOES-R Magnetometer Accuracy

    NASA Technical Reports Server (NTRS)

    Kronenwetter, Jeffrey; Carter, Delano R.; Todirita, Monica; Chu, Donald

    2016-01-01

    The GOES-R magnetometer accuracy requirement is 1.7 nanoteslas (nT). During quiet times (100 nT), accuracy is defined as absolute mean plus 3 sigma. During storms (300 nT), accuracy is defined as absolute mean plus 2 sigma. To achieve this, the sensor itself has better than 1 nT accuracy. Because zero offset and scale factor drift over time, it is also necessary to perform annual calibration maneuvers. To predict performance, we used covariance analysis and attempted to corroborate it with simulations. Although not perfect, the two generally agree and show the expected behaviors. With the annual calibration regimen, these predictions suggest that the magnetometers will meet their accuracy requirements.

  14. An absolute sensitivity calibration of the JET VUV SPRED spectrometer

    NASA Astrophysics Data System (ADS)

    Lawson, K. D.; Coffey, I. H.; Zacks, J.; Stamp, M. F.; contributors, JET-EFDA

    2009-04-01

    The determination of a good relative and absolute sensitivity calibration for wideband VUV spectrometers is challenging. On JET, the possible T and Be contamination of the VUV spectrometer precludes its removal to a synchrotron source and, consequently, a range of alternative in situ techniques have been investigated in depth. This has resulted in a reliable calibration for the complete spectral range, the relative calibration at short wavelengths being particularly accurate. At these wavelengths, a novel approach is used, in which the calibration is extended using a number of Na- and Li-like metal doublets. At longer wavelengths, the Li-like doublets of Ar and Ne have been used in conjunction with CII, CIII and CIV line intensity ratios. Unexplained discrepancies between the measured and modelled C results have meant that the exceptional short wavelength accuracy has not be repeated at these longer wavelengths. The absolute sensitivity has been determined from branching ratios to an absolutely calibrated visible spectrometer. The long term stability of the calibration is discussed.

  15. Mini-implants and miniplates generate sub-absolute and absolute anchorage.

    PubMed

    Consolaro, Alberto

    2014-01-01

    The functional demand imposed on bone promotes changes in the spatial properties of osteocytes as well as in their extensions uniformly distributed throughout the mineralized surface. Once spatial deformation is established, osteocytes create the need for structural adaptations that result in bone formation and resorption that happen to meet the functional demands. The endosteum and the periosteum are the effectors responsible for stimulating adaptive osteocytes in the inner and outer surfaces. Changes in shape, volume and position of the jaws as a result of skeletal correction of the maxilla and mandible require anchorage to allow bone remodeling to redefine morphology, esthetics and function as a result of spatial deformation conducted by orthodontic appliances. Examining the degree of changes in shape, volume and structural relationship of areas where mini-implants and miniplates are placed allows us to classify mini-implants as devices of subabsolute anchorage and miniplates as devices of absolute anchorage.

  16. Absolute quantitation of protein posttranslational modification isoform.

    PubMed

    Yang, Zhu; Li, Ning

    2015-01-01

    Mass spectrometry has been widely applied in characterization and quantification of proteins from complex biological samples. Because the numbers of absolute amounts of proteins are needed in construction of mathematical models for molecular systems of various biological phenotypes and phenomena, a number of quantitative proteomic methods have been adopted to measure absolute quantities of proteins using mass spectrometry. The liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with internal peptide standards, i.e., the stable isotope-coded peptide dilution series, which was originated from the field of analytical chemistry, becomes a widely applied method in absolute quantitative proteomics research. This approach provides more and more absolute protein quantitation results of high confidence. As quantitative study of posttranslational modification (PTM) that modulates the biological activity of proteins is crucial for biological science and each isoform may contribute a unique biological function, degradation, and/or subcellular location, the absolute quantitation of protein PTM isoforms has become more relevant to its biological significance. In order to obtain the absolute cellular amount of a PTM isoform of a protein accurately, impacts of protein fractionation, protein enrichment, and proteolytic digestion yield should be taken into consideration and those effects before differentially stable isotope-coded PTM peptide standards are spiked into sample peptides have to be corrected. Assisted with stable isotope-labeled peptide standards, the absolute quantitation of isoforms of posttranslationally modified protein (AQUIP) method takes all these factors into account and determines the absolute amount of a protein PTM isoform from the absolute amount of the protein of interest and the PTM occupancy at the site of the protein. The absolute amount of the protein of interest is inferred by quantifying both the absolute amounts of a few PTM

  17. An ultrasonic system for measurement of absolute myocardial thickness using a single transducer.

    PubMed

    Pitsillides, K F; Longhurst, J C

    1995-03-01

    We have developed an ultrasonic instrument that can measure absolute regional myocardial wall motion throughout the cardiac cycle using a single epicardial piezoelectric transducer. The methods in place currently that utilize ultrasound to measure myocardial wall thickness are the transit-time sonomicrometer (TTS) and, more recently, the Doppler echo displacement method. Both methods have inherent disadvantages. To address the need for an instrument that can measure absolute dimensions of myocardial wall at any depth, an ultrasonic single-crystal sonomicrometer (SCS) system was developed. This system can identify and track the boundary of the endocardial muscle-blood interface. With this instrument, it is possible to obtain, from a single epicardial transducer, measurement of myocardial wall motion that is calibrated in absolute dimensional units. The operating principles of the proposed myocardial dimension measurement system are as follows. A short duration ultrasonic burst having a frequency of 10 MHz is transmitted from the piezoelectric transducer. Reflected echoes are sampled at two distinct time intervals to generate reference and interface sample volumes. During steady state, the two sample volumes are adjusted so that the reference volume remains entirely within the myocardium, whereas half of the interface sampled volume is located within the myocardium. After amplification and filtering, the true root mean square values of both signals are compared and an error signal is generated. A closed-loop circuit uses the integrated error signal to continuously adjust the position of the two sample volumes. We have compared our system in vitro against a known signal and in vivo against the two-crystal TTS system during control, suppression (ischemia), and enhancement (isoproterenol) of myocardial function. Results were obtained in vitro for accuracy (> 99%), signal linearity (r = 0.99), and frequency response to heart rates > 450 beats/min, and in vivo data were

  18. Absolute realization of low BRDF value

    NASA Astrophysics Data System (ADS)

    Liu, Zilong; Liao, Ningfang; Li, Ping; Wang, Yu

    2010-10-01

    Low BRDF value is widespread used in many critical domains such as space and military fairs. These values below 0.1 Sr-1 . So the Absolute realization of these value is the most critical issue in the absolute measurement of BRDF. To develop the Absolute value realization theory of BRDF , defining an arithmetic operators of BRDF , achieving an absolute measurement Eq. of BRDF based on radiance. This is a new theory method to solve the realization problem of low BRDF value. This theory method is realized on a self-designed common double orientation structure in space. By designing an adding structure to extend the range of the measurement system and a control and processing software, Absolute realization of low BRDF value is achieved. A material of low BRDF value is measured in this measurement system and the spectral BRDF value are showed within different angles allover the space. All these values are below 0.4 Sr-1 . This process is a representative procedure about the measurement of low BRDF value. A corresponding uncertainty analysis of this measurement data is given depend on the new theory of absolute realization and the performance of the measurement system. The relative expand uncertainty of the measurement data is 0.078. This uncertainty analysis is suitable for all measurements using the new theory of absolute realization and the corresponding measurement system.

  19. Accuracy of the correlation method of the thermal neutron absorption cross-section determination for rocks

    NASA Astrophysics Data System (ADS)

    Krynicka, Ewa

    1995-08-01

    The influence of various random errors on the accuracy of thermal neutron absorption cross-sections determined by a correlation method is discussed. It is considered either as an absolute accuracy, when all experimental errors arc taken into account, or as an experimental assay accuracy, when the reference moderator parameters are assumed as the invariant data fixed for all experiments. The estimated accuracy is compared with the accuracy of results obtained for the same rock sample by Czubek's measurement method.

  20. Absolute Temperature Monitoring Using RF Radiometry in the MRI Scanner

    PubMed Central

    El-Sharkawy, AbdEl-Monem M.; Sotiriadis, Paul P.; Bottomley, Paul A.; Atalar, Ergin

    2007-01-01

    Temperature detection using microwave radiometry has proven value for noninvasively measuring the absolute temperature of tissues inside the body. However, current clinical radiometers operate in the gigahertz range, which limits their depth of penetration. We have designed and built a noninvasive radiometer which operates at radio frequencies (64 MHz) with ∼100-kHz bandwidth, using an external RF loop coil as a thermal detector. The core of the radiometer is an accurate impedance measurement and automatic matching circuit of 0.05 Ω accuracy to compensate for any load variations. The radiometer permits temperature measurements with accuracy of ±0.1°K, over a tested physiological range of 28° C–40° C in saline phantoms whose electric properties match those of tissue. Because 1.5 T magnetic resonance imaging (MRI) scanners also operate at 64 MHz, we demonstrate the feasibility of integrating our radiometer with an MRI scanner to monitor RF power deposition and temperature dosimetry, obtaining coarse, spatially resolved, absolute thermal maps in the physiological range. We conclude that RF radiometry offers promise as a direct, noninvasive method of monitoring tissue heating during MRI studies and thereby providing an independent means of verifying patient-safe operation. Other potential applications include titration of hyper- and hypo-therapies. PMID:18026562

  1. Error analysis in newborn screening: can quotients support the absolute values?

    PubMed

    Arneth, Borros; Hintz, Martin

    2017-03-01

    Newborn screening is performed using modern tandem mass spectrometry, which can simultaneously detect a variety of analytes, including several amino acids and fatty acids. Tandem mass spectrometry measures the diagnostic parameters as absolute concentrations and produces fragments which are used as markers of specific substances. Several prominent quotients can also be derived, which are quotients of two absolute measured concentrations. In this study, we determined the precision of both the absolute concentrations and the derived quotients. First, the measurement error of the absolute concentrations and the measurement error of the ratios were practically determined. Then, the Gaussian theory of error calculation was used. Finally, these errors were compared with one another. The practical analytical accuracies of the quotients were significantly higher (e.g., coefficient of variation (CV) = 5.1% for the phenylalanine to tyrosine (Phe/Tyr) quotient and CV = 5.6% for the Fisher quotient) than the accuracies of the absolute measured concentrations (mean CVs = 12%). According to our results, the ratios are analytically correct and, from an analytical point of view, can support the absolute values in finding the correct diagnosis.

  2. Measurement accuracies in band-limited extrapolation

    NASA Technical Reports Server (NTRS)

    Kritikos, H. N.

    1982-01-01

    The problem of numerical instability associated with extrapolation algorithms is addressed. An attempt is made to estimate the bounds for the acceptable errors and to place a ceiling on the measurement accuracy and computational accuracy needed for the extrapolation. It is shown that in band limited (or visible angle limited) extrapolation the larger effective aperture L' that can be realized from a finite aperture L by over sampling is a function of the accuracy of measurements. It is shown that for sampling in the interval L/b absolute value of xL, b1 the signal must be known within an error e sub N given by e sub N squared approximately = 1/4(2kL') cubed (e/8b L/L')(2kL') where L is the physical aperture, L' is the extrapolated aperture, and k = 2pi lambda.

  3. Absolute flatness testing of skip-flat interferometry by matrix analysis in polar coordinates.

    PubMed

    Han, Zhi-Gang; Yin, Lu; Chen, Lei; Zhu, Ri-Hong

    2016-03-20

    A new method utilizing matrix analysis in polar coordinates has been presented for absolute testing of skip-flat interferometry. The retrieval of the absolute profile mainly includes three steps: (1) transform the wavefront maps of the two cavity measurements into data in polar coordinates; (2) retrieve the profile of the reflective flat in polar coordinates by matrix analysis; and (3) transform the profile of the reflective flat back into data in Cartesian coordinates and retrieve the profile of the sample. Simulation of synthetic surface data has been provided, showing the capability of the approach to achieve an accuracy of the order of 0.01 nm RMS. The absolute profile can be retrieved by a set of closed mathematical formulas without polynomial fitting of wavefront maps or the iterative evaluation of an error function, making the new method more efficient for absolute testing.

  4. IMPROVEMENT OF SMVGEAR II ON VECTOR AND SCALAR MACHINES THROUGH ABSOLUTE ERROR TOLERANCE CONTROL (R823186)

    EPA Science Inventory

    The computer speed of SMVGEAR II was improved markedly on scalar and vector machines with relatively little loss in accuracy. The improvement was due to a method of frequently recalculating the absolute error tolerance instead of keeping it constant for a given set of chemistry. ...

  5. Demonstrating the Error Budget for the Climate Absolute Radiance and Refractivity Observatory Through Solar Irradiance Measurements

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; McCorkel, Joel; McAndrew, Brendan

    2016-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission addresses the need to observe highaccuracy, long-term climate change trends and to use decadal change observations as a method to determine the accuracy of climate change. A CLARREO objective is to improve the accuracy of SI-traceable, absolute calibration at infrared and reflected solar wavelengths to reach on-orbit accuracies required to allow climate change observations to survive data gaps and observe climate change at the limit of natural variability. Such an effort will also demonstrate National Institute of Standards and Technology (NIST) approaches for use in future spaceborne instruments. The current work describes the results of laboratory and field measurements with the Solar, Lunar for Absolute Reflectance Imaging Spectroradiometer (SOLARIS) which is the calibration demonstration system (CDS) for the reflected solar portion of CLARREO. SOLARIS allows testing and evaluation of calibration approaches, alternate design and/or implementation approaches and components for the CLARREO mission. SOLARIS also provides a test-bed for detector technologies, non-linearity determination and uncertainties, and application of future technology developments and suggested spacecraft instrument design modifications. Results of laboratory calibration measurements are provided to demonstrate key assumptions about instrument behavior that are needed to achieve CLARREO's climate measurement requirements. Absolute radiometric response is determined using laser-based calibration sources and applied to direct solar views for comparison with accepted solar irradiance models to demonstrate accuracy values giving confidence in the error budget for the CLARREO reflectance retrieval.

  6. Electrical Noise and the Measurement of Absolute Temperature, Boltzmann's Constant and Avogadro's Number.

    ERIC Educational Resources Information Center

    Ericson, T. J.

    1988-01-01

    Describes an apparatus capable of measuring absolute temperatures of a tungsten filament bulb up to normal running temperature and measuring Botzmann's constant to an accuracy of a few percent. Shows that electrical noise techniques are convenient to demonstrate how the concept of temperature is related to the micro- and macroscopic world. (CW)

  7. A New Gimmick for Assigning Absolute Configuration.

    ERIC Educational Resources Information Center

    Ayorinde, F. O.

    1983-01-01

    A five-step procedure is provided to help students in making the assignment absolute configuration less bothersome. Examples for both single (2-butanol) and multi-chiral carbon (3-chloro-2-butanol) molecules are included. (JN)

  8. The Simplicity Argument and Absolute Morality

    ERIC Educational Resources Information Center

    Mijuskovic, Ben

    1975-01-01

    In this paper the author has maintained that there is a similarity of thought to be found in the writings of Cudworth, Emerson, and Husserl in his investigation of an absolute system of morality. (Author/RK)

  9. Absolute cross sections of compound nucleus reactions

    NASA Astrophysics Data System (ADS)

    Capurro, O. A.

    1993-11-01

    The program SEEF is a Fortran IV computer code for the extraction of absolute cross sections of compound nucleus reactions. When the evaporation residue is fed by its parents, only cumulative cross sections will be obtained from off-line gamma ray measurements. But, if one has the parent excitation function (experimental or calculated), this code will make it possible to determine absolute cross sections of any exit channel.

  10. Kelvin and the absolute temperature scale

    NASA Astrophysics Data System (ADS)

    Erlichson, Herman

    2001-07-01

    This paper describes the absolute temperature scale of Kelvin (William Thomson). Kelvin found that Carnot's axiom about heat being a conserved quantity had to be abandoned. Nevertheless, he found that Carnot's fundamental work on heat engines was correct. Using the concept of a Carnot engine Kelvin found that Q1/Q2 = T1/T2. Thermometers are not used to obtain absolute temperatures since they are calculated temperatures.

  11. Reticence, Accuracy and Efficacy

    NASA Astrophysics Data System (ADS)

    Oreskes, N.; Lewandowsky, S.

    2015-12-01

    James Hansen has cautioned the scientific community against "reticence," by which he means a reluctance to speak in public about the threat of climate change. This may contribute to social inaction, with the result that society fails to respond appropriately to threats that are well understood scientifically. Against this, others have warned against the dangers of "crying wolf," suggesting that reticence protects scientific credibility. We argue that both these positions are missing an important point: that reticence is not only a matter of style but also of substance. In previous work, Bysse et al. (2013) showed that scientific projections of key indicators of climate change have been skewed towards the low end of actual events, suggesting a bias in scientific work. More recently, we have shown that scientific efforts to be responsive to contrarian challenges have led scientists to adopt the terminology of a "pause" or "hiatus" in climate warming, despite the lack of evidence to support such a conclusion (Lewandowsky et al., 2015a. 2015b). In the former case, scientific conservatism has led to under-estimation of climate related changes. In the latter case, the use of misleading terminology has perpetuated scientific misunderstanding and hindered effective communication. Scientific communication should embody two equally important goals: 1) accuracy in communicating scientific information and 2) efficacy in expressing what that information means. Scientists should strive to be neither conservative nor adventurous but to be accurate, and to communicate that accurate information effectively.

  12. Orion Absolute Navigation System Progress and Challenge

    NASA Technical Reports Server (NTRS)

    Holt, Greg N.; D'Souza, Christopher

    2012-01-01

    The absolute navigation design of NASA's Orion vehicle is described. It has undergone several iterations and modifications since its inception, and continues as a work-in-progress. This paper seeks to benchmark the current state of the design and some of the rationale and analysis behind it. There are specific challenges to address when preparing a timely and effective design for the Exploration Flight Test (EFT-1), while still looking ahead and providing software extensibility for future exploration missions. The primary onboard measurements in a Near-Earth or Mid-Earth environment consist of GPS pseudo-range and delta-range, but for future explorations missions the use of star-tracker and optical navigation sources need to be considered. Discussions are presented for state size and composition, processing techniques, and consider states. A presentation is given for the processing technique using the computationally stable and robust UDU formulation with an Agee-Turner Rank-One update. This allows for computational savings when dealing with many parameters which are modeled as slowly varying Gauss-Markov processes. Preliminary analysis shows up to a 50% reduction in computation versus a more traditional formulation. Several state elements are discussed and evaluated, including position, velocity, attitude, clock bias/drift, and GPS measurement biases in addition to bias, scale factor, misalignment, and non-orthogonalities of the accelerometers and gyroscopes. Another consideration is the initialization of the EKF in various scenarios. Scenarios such as single-event upset, ground command, and cold start are discussed as are strategies for whole and partial state updates as well as covariance considerations. Strategies are given for dealing with latent measurements and high-rate propagation using multi-rate architecture. The details of the rate groups and the data ow between the elements is discussed and evaluated.

  13. Assessing and ensuring GOES-R magnetometer accuracy

    NASA Astrophysics Data System (ADS)

    Carter, Delano; Todirita, Monica; Kronenwetter, Jeffrey; Dahya, Melissa; Chu, Donald

    2016-05-01

    The GOES-R magnetometer subsystem accuracy requirement is 1.7 nanoteslas (nT). During quiet times (100 nT), accuracy is defined as absolute mean plus 3 sigma error per axis. During storms (300 nT), accuracy is defined as absolute mean plus 2 sigma error per axis. Error comes both from outside the magnetometers, e.g. spacecraft fields and misalignments, as well as inside, e.g. zero offset and scale factor errors. Because zero offset and scale factor drift over time, it will be necessary to perform annual calibration maneuvers. To predict performance before launch, we have used Monte Carlo simulations and covariance analysis. With the proposed calibration regimen, both suggest that the magnetometer subsystem will meet its accuracy requirements.

  14. Oblique-incidence sounder measurements with absolute propagation delay timing

    SciTech Connect

    Daehler, M.

    1990-05-03

    Timing from the Global Position Satellite (GPS) system has been applied to HF oblique incidence sounder measurements to produce ionograms whose propagation delay time scale is absolutely calibrated. Such a calibration is useful for interpreting ionograms in terms of the electron density true-height profile for the ionosphere responsible for the propagation. Use of the time variations in the shape of the electron density profile, in conjunction with an HF propagation model, is expected to provide better near-term (1-24 hour) HF propagation forecasts than are available from current updating systems, which use only the MUF. Such a capability may provide the basis for HF frequency management techniques which are more efficient than current methods. Absolute timing and other techniques applicable to automatic extraction of the electron-density profile from an ionogram will be discussed.

  15. Usage tests of oak moss absolutes containing high and low levels of atranol and chloroatranol.

    PubMed

    Mowitz, Martin; Svedman, Cecilia; Zimerson, Erik; Bruze, Magnus

    2014-07-01

    Atranol and chloroatranol are strong contact allergens in oak moss absolute, a lichen extract used in perfumery. Fifteen subjects with contact allergy to oak moss absolute underwent a repeated open application test (ROAT) using solutions of an untreated oak moss absolute (sample A) and an oak moss absolute with reduced content of atranol and chloroatranol (sample B). All subjects were in addition patch-tested with serial dilutions of samples A and B. Statistically significantly more subjects reacted to sample A than to sample B in the patch tests. No corresponding difference was observed in the ROAT, though there was a significant difference in the time required to elicit a positive reaction. Still, the ROAT indicates that the use of a cosmetic product containing oak moss absolute with reduced levels of atranol and chloroatranol is capable of eliciting an allergic reaction in previously sensitised individuals.

  16. Accuracy of the Cloud Integrating Nephelometer

    NASA Technical Reports Server (NTRS)

    Gerber, Hermann E.

    2004-01-01

    Potential error sources for measurements with the Cloud Integrating Nephelometer (CIN) are discussed and analyzed, including systematic errors of the measurement approach, flow and particle-trajectory deviations at flight velocity, ice-crystal breakup on probe surfaces, and errors in calibration and developing scaling constants. It is concluded that errors are minimal, and that the accuracy of the CIN should be close to the systematic behavior of the CIN derived in Gerber et al (2000). Absolute calibration of the CIN with a transmissometer operating co-located in a mountain-top cloud shows that the earlier scaling constant for the optical extinction coefficient obtained by other means is within 5% of the absolute calibration value, and that the CIN measurements on the Citation aircraft flights during the CRYSTAL-FACE study are accurate.

  17. Matching accuracy in hemiparetic cerebral palsy during unimanual and bimanual movements with (mirror) visual feedback.

    PubMed

    Smorenburg, Ana R P; Ledebt, Annick; Deconinck, Frederik J A; Savelsbergh, Geert J P

    2012-01-01

    In the present study participants with Spastic Hemiparetic Cerebral Palsy (SHCP) were asked to match the position of a target either with the impaired arm only (unimanual condition) or with both arms at the same time (bimanual condition). The target was placed at 4 different locations scaled to the individual maximum reaching distance. To test the effect of mirror visual feedback of the less-impaired arm on the matching accuracy, an opaque screen or a mirror was placed in between the arms which masked vision of the impaired arm. Absolute endpoint error was smaller in the bimanual condition compared to the unimanual condition, but there was no effect of mirror visual feedback. Inspection of the individual data, however, showed that 13 out of 23 participants did experience a positive effect of mirror visual feedback. A positive correlation between the baseline error (screen) and the improvement in accuracy with mirror visual feedback seems to suggest that individuals with lower proprioceptive accuracy in the baseline condition may benefit more from mirror visual feedback. Together these findings indicate that bimanual therapy and therapy with mirror visual feedback might be valuable approaches for rehabilitation for a subset of the individuals with SHCP.

  18. Jasminum flexile flower absolute from India--a detailed comparison with three other jasmine absolutes.

    PubMed

    Braun, Norbert A; Kohlenberg, Birgit; Sim, Sherina; Meier, Manfred; Hammerschmidt, Franz-Josef

    2009-09-01

    Jasminum flexile flower absolute from the south of India and the corresponding vacuum headspace (VHS) sample of the absolute were analyzed using GC and GC-MS. Three other commercially available Indian jasmine absolutes from the species: J. sambac, J. officinale subsp. grandiflorum, and J. auriculatum and the respective VHS samples were used for comparison purposes. One hundred and twenty-one compounds were characterized in J. flexile flower absolute, with methyl linolate, benzyl salicylate, benzyl benzoate, (2E,6E)-farnesol, and benzyl acetate as the main constituents. A detailed olfactory evaluation was also performed.

  19. Geolocation Accuracy Evaluations of OrbView-3, EROS-A, and SPOT-5 Imagery

    NASA Technical Reports Server (NTRS)

    Bresnahan, Paul

    2007-01-01

    This viewgraph presentation evaluates absolute geolocation accuracy of OrbView-3, EROS-A, and SPOT-5 by comparing test imagery-derived ground coordinates to Ground Control Points using SOCET set photogrammetric software.

  20. Improvement in absolute calibration accuracy of Landsat-5 TM with Landsat-7 ETM+ data

    USGS Publications Warehouse

    Chander, G.; Markham, B.L.; Micijevic, E.; Teillet, P.M.; Helder, D.L.; ,

    2005-01-01

    The ability to detect and quantify changes in the Earth's environment depends on satellites sensors that can provide calibrated, consistent measurements of Earth's surface features through time. A critical step in this process is to put image data from subsequent generations of sensors onto a common radiometric scale. To evaluate Landsat-5 (L5) Thematic Mapper's (TM) utility in this role, image pairs from the L5 TM and Landsat-7 (L7) Enhanced Thematic Mapper Plus (ETM+) sensors were compared. This approach involves comparison of surface observations based on image statistics from large common areas observed eight days apart by the two sensors. The results indicate a significant improvement in the consistency of L5 TM data with respect to L7 ETM+ data, achieved using a revised Look-Up-Table (LUT) procedure as opposed to the historical Internal Calibrator (IC) procedure previously used in the L5 TM product generation system. The average percent difference in reflectance estimates obtained from the L5 TM agree with those from the L7 ETM+ in the Visible and Near Infrared (VNIR) bands to within four percent and in the Short Wave Infrared (SWIR) bands to within six percent.

  1. Radiometric absolute noise-temperature measurement system features improved accuracy and calibration ease

    NASA Technical Reports Server (NTRS)

    Brown, W.; Ewen, H.; Haroules, G.

    1970-01-01

    Radiometric receiver system, which measures noise temperatures in degrees Kelvin, does not require cryogenic noise sources for routine operation. It eliminates radiometer calibration errors associated with RF attenuation measurements. Calibrated noise source is required only for laboratory adjustment and calibration.

  2. Absolute Radiometric Calibration of ALS Intensity Data: Effects on Accuracy and Target Classification

    PubMed Central

    Kaasalainen, Sanna; Pyysalo, Ulla; Krooks, Anssi; Vain, Ants; Kukko, Antero; Hyyppä, Juha; Kaasalainen, Mikko

    2011-01-01

    Radiometric calibration of airborne laser scanning (ALS) intensity data aims at retrieving a value related to the target scattering properties, which is independent on the instrument or flight parameters. The aim of a calibration procedure is also to be able to compare results from different flights and instruments, but practical applications are sparsely available, and the performance of calibration methods for this purpose needs to be further assessed. We have studied the radiometric calibration with data from three separate flights and two different instruments using external calibration targets. We find that the intensity data from different flights and instruments can be compared to each other only after a radiometric calibration process using separate calibration targets carefully selected for each flight. The calibration is also necessary for target classification purposes, such as separating vegetation from sand using intensity data from different flights. The classification results are meaningful only for calibrated intensity data. PMID:22346660

  3. Universal Cosmic Absolute and Modern Science

    NASA Astrophysics Data System (ADS)

    Kostro, Ludwik

    The official Sciences, especially all natural sciences, respect in their researches the principle of methodic naturalism i.e. they consider all phenomena as entirely natural and therefore in their scientific explanations they do never adduce or cite supernatural entities and forces. The purpose of this paper is to show that Modern Science has its own self-existent, self-acting, and self-sufficient Natural All-in Being or Omni-Being i.e. the entire Nature as a Whole that justifies the scientific methodic naturalism. Since this Natural All-in Being is one and only It should be considered as the own scientifically justified Natural Absolute of Science and should be called, in my opinion, the Universal Cosmic Absolute of Modern Science. It will be also shown that the Universal Cosmic Absolute is ontologically enormously stratified and is in its ultimate i.e. in its most fundamental stratum trans-reistic and trans-personal. It means that in its basic stratum. It is neither a Thing or a Person although It contains in Itself all things and persons with all other sentient and conscious individuals as well, On the turn of the 20th century the Science has begun to look for a theory of everything, for a final theory, for a master theory. In my opinion the natural Universal Cosmic Absolute will constitute in such a theory the radical all penetrating Ultimate Basic Reality and will substitute step by step the traditional supernatural personal Absolute.

  4. Analysis of absolute flatness testing in sub-stitching interferometer

    NASA Astrophysics Data System (ADS)

    Jia, Xin; Xu, Fuchao; Xie, Weimin; Xing, Tingwen

    2016-09-01

    Sub-aperture stitching is an effective way to extend the lateral and vertical dynamic range of a conventional interferometer. The test accuracy can be achieved by removing the error of reference surface by the absolute testing method. When the testing accuracy (repeatability and reproducibility) is close to 1nm, in addition to the reference surface, other factors will also affect the measuring accuracy such as environment, zoom magnification, stitching precision, tooling and fixture, the characteristics of optical materials and so on. In the thousand level cleanroom, we establish a good environment system. Long time stability, temperature controlled at 22°+/-0.02°.The humidity and noise are controlled in a certain range. We establish a stitching system in the clean room. The vibration testing system is used to test the vibration. The air pressure testing system is also used. In the motion system, we control the tilt error no more than 4 second to reduce the error. The angle error can be tested by the autocollimator and double grating reading head.

  5. Diagnostic accuracy of pre-exercise screening questionnaire: emphasis on educational level and cognitive status.

    PubMed

    Maranhao Neto, Geraldo A; Luz, Leonardo Gomes Oliveira; Farinatti, Paulo T V

    2013-01-01

    The physical activity readiness questionnaire (PAR-Q) has been the most popular simple method of screening for people who intend to engage in exercise programs. Despite of the recommendations indicating that the instrument should be applied in the age range from 15 to 69 years, the questionnaire has been widely used in elderly people. The aim of this study was to assess the diagnostic accuracy of PAR-Q in elderly women with respect to absolute and relative contraindications to exercise and verify the influence of educational level and cognitive status. Eighty-nine subjects (61-89 years) participated in the study and went through clinical exams and exercise testing. The influence of educational status, age and cognitive state (Mini-Mental State Examination, MMSE) on the PAR-Q responses was analyzed by logistic regression. The occurrences of absolute and relative contraindications were respectively 9% and 22%. The Sensitivity and Specificity were 75.0% and 19.8% (absolute) and 77.8% and 19.7% (relative). The PAR-Q results were not influenced by low educational status; age, or cognitive state. In conclusion, although the usefulness and easy applicability of the PAR-Q's questions, the responses to the questionnaire led to a high number of false positive and false negative cases, suggesting that it would not be adequate as a pre-participation screening tool in elder samples.

  6. Quantitative standards for absolute linguistic universals.

    PubMed

    Piantadosi, Steven T; Gibson, Edward

    2014-01-01

    Absolute linguistic universals are often justified by cross-linguistic analysis: If all observed languages exhibit a property, the property is taken to be a likely universal, perhaps specified in the cognitive or linguistic systems of language learners and users. In many cases, these patterns are then taken to motivate linguistic theory. Here, we show that cross-linguistic analysis will very rarely be able to statistically justify absolute, inviolable patterns in language. We formalize two statistical methods--frequentist and Bayesian--and show that in both it is possible to find strict linguistic universals, but that the numbers of independent languages necessary to do so is generally unachievable. This suggests that methods other than typological statistics are necessary to establish absolute properties of human language, and thus that many of the purported universals in linguistics have not received sufficient empirical justification.

  7. Comparative Accuracy Evaluation of Fine-Scale Global and Local Digital Surface Models: The Tshwane Case Study I

    NASA Astrophysics Data System (ADS)

    Breytenbach, A.

    2016-10-01

    Conducted in the City of Tshwane, South Africa, this study set about to test the accuracy of DSMs derived from different remotely sensed data locally. VHR digital mapping camera stereo-pairs, tri-stereo imagery collected by a Pléiades satellite and data detected from the Tandem-X InSAR satellite configuration were fundamental in the construction of seamless DSM products at different postings, namely 2 m, 4 m and 12 m. The three DSMs were sampled against independent control points originating from validated airborne LiDAR data. The reference surfaces were derived from the same dense point cloud at grid resolutions corresponding to those of the samples. The absolute and relative positional accuracies were computed using well-known DEM error metrics and accuracy statistics. Overall vertical accuracies were also assessed and compared across seven slope classes and nine primary land cover classes. Although all three DSMs displayed significantly more vertical errors where solid waterbodies, dense natural and/or alien woody vegetation and, in a lesser degree, urban residential areas with significant canopy cover were encountered, all three surpassed their expected positional accuracies overall.

  8. Absolute flux density calibrations of radio sources: 2.3 GHz

    NASA Technical Reports Server (NTRS)

    Freiley, A. J.; Batelaan, P. D.; Bathker, D. A.

    1977-01-01

    A detailed description of a NASA/JPL Deep Space Network program to improve S-band gain calibrations of large aperture antennas is reported. The program is considered unique in at least three ways; first, absolute gain calibrations of high quality suppressed-sidelobe dual mode horns first provide a high accuracy foundation to the foundation to the program. Second, a very careful transfer calibration technique using an artificial far-field coherent-wave source was used to accurately obtain the gain of one large (26 m) aperture. Third, using the calibrated large aperture directly, the absolute flux density of five selected galactic and extragalactic natural radio sources was determined with an absolute accuracy better than 2 percent, now quoted at the familiar 1 sigma confidence level. The follow-on considerations to apply these results to an operational network of ground antennas are discussed. It is concluded that absolute gain accuracies within + or - 0.30 to 0.40 db are possible, depending primarily on the repeatability (scatter) in the field data from Deep Space Network user stations.

  9. High-rate precise point positioning (PPP) to measure seismic wave motions: An experimental comparison of GPS PPP with inertial measurement units

    NASA Astrophysics Data System (ADS)

    Xu, Peiliang; Shi, Chuang; Fang, Rongxin; Liu, Jingnan; Niu, Xiaoji; Zhang, Quan; Yanagidani, Takashi

    2013-04-01

    High-rate GPS has been widely used to construct displacement waveforms and to invert for source parameters of earthquakes. Almost all works on internal and external evaluation of high-rate GPS accuracy are based on GPS relative positioning. We build an experimental platform to externally evaluate the accuracy of 50 Hz PPP displacement waveforms. Since the shake table allows motion in any of six degrees of freedom, we install an inertial measurement unit (IMU) to measure the attitude of the platform and transform the IMU displacements into the GPS coordinate system. The experimental results have shown that high-rate PPP can produce absolute horizontal displacement waveforms at the accuracy of 2 to 4 millimeters and absolute vertical displacement waveforms at the sub-centimeter level of accuracy within a short period of time. The significance of the experiments indicates that high-rate PPP is capable of detecting absolute seismic displacement waveforms at the same high accuracy as GPS relative positioning techniques but requires no fixed datum station. We have also found a small scaling error of IMU and a small time offset of misalignment between high-rate PPP and IMU displacement waveforms by comparing the amplitudes of and cross-correlating both the displacement waveforms. For more details on this talk, one can now get access to the on-line-first version of our Journal of Geodesy paper: J Geod, DOI 10.1007/s00190-012-0606-z

  10. Absolute length measurement using manually decided stereo correspondence for endoscopy

    NASA Astrophysics Data System (ADS)

    Sasaki, M.; Koishi, T.; Nakaguchi, T.; Tsumura, N.; Miyake, Y.

    2009-02-01

    In recent years, various kinds of endoscope have been developed and widely used to endoscopic biopsy, endoscopic operation and endoscopy. The size of the inflammatory part is important to determine a method of medical treatment. However, it is not easy to measure absolute size of inflammatory part such as ulcer, cancer and polyp from the endoscopic image. Therefore, it is required measuring the size of those part in endoscopy. In this paper, we propose a new method to measure the absolute length in a straight line between arbitrary two points based on the photogrammetry using endoscope with magnetic tracking sensor which gives camera position and angle. In this method, the stereo-corresponding points between two endoscopic images are determined by the endoscopist without any apparatus of projection and calculation to find the stereo correspondences, then the absolute length can be calculated on the basis of the photogrammetry. The evaluation experiment using a checkerboard showed that the errors of the measurements are less than 2% of the target length when the baseline is sufficiently-long.

  11. Absolutely relative or relatively absolute: violations of value invariance in human decision making.

    PubMed

    Teodorescu, Andrei R; Moran, Rani; Usher, Marius

    2016-02-01

    Making decisions based on relative rather than absolute information processing is tied to choice optimality via the accumulation of evidence differences and to canonical neural processing via accumulation of evidence ratios. These theoretical frameworks predict invariance of decision latencies to absolute intensities that maintain differences and ratios, respectively. While information about the absolute values of the choice alternatives is not necessary for choosing the best alternative, it may nevertheless hold valuable information about the context of the decision. To test the sensitivity of human decision making to absolute values, we manipulated the intensities of brightness stimuli pairs while preserving either their differences or their ratios. Although asked to choose the brighter alternative relative to the other, participants responded faster to higher absolute values. Thus, our results provide empirical evidence for human sensitivity to task irrelevant absolute values indicating a hard-wired mechanism that precedes executive control. Computational investigations of several modelling architectures reveal two alternative accounts for this phenomenon, which combine absolute and relative processing. One account involves accumulation of differences with activation dependent processing noise and the other emerges from accumulation of absolute values subject to the temporal dynamics of lateral inhibition. The potential adaptive role of such choice mechanisms is discussed.

  12. A Multilaboratory Comparison of Calibration Accuracy and the Performance of External References in Analytical Ultracentrifugation

    PubMed Central

    Zhao, Huaying; Ghirlando, Rodolfo; Alfonso, Carlos; Arisaka, Fumio; Attali, Ilan; Bain, David L.; Bakhtina, Marina M.; Becker, Donald F.; Bedwell, Gregory J.; Bekdemir, Ahmet; Besong, Tabot M. D.; Birck, Catherine; Brautigam, Chad A.; Brennerman, William; Byron, Olwyn; Bzowska, Agnieszka; Chaires, Jonathan B.; Chaton, Catherine T.; Cölfen, Helmut; Connaghan, Keith D.; Crowley, Kimberly A.; Curth, Ute; Daviter, Tina; Dean, William L.; Díez, Ana I.; Ebel, Christine; Eckert, Debra M.; Eisele, Leslie E.; Eisenstein, Edward; England, Patrick; Escalante, Carlos; Fagan, Jeffrey A.; Fairman, Robert; Finn, Ron M.; Fischle, Wolfgang; de la Torre, José García; Gor, Jayesh; Gustafsson, Henning; Hall, Damien; Harding, Stephen E.; Cifre, José G. Hernández; Herr, Andrew B.; Howell, Elizabeth E.; Isaac, Richard S.; Jao, Shu-Chuan; Jose, Davis; Kim, Soon-Jong; Kokona, Bashkim; Kornblatt, Jack A.; Kosek, Dalibor; Krayukhina, Elena; Krzizike, Daniel; Kusznir, Eric A.; Kwon, Hyewon; Larson, Adam; Laue, Thomas M.; Le Roy, Aline; Leech, Andrew P.; Lilie, Hauke; Luger, Karolin; Luque-Ortega, Juan R.; Ma, Jia; May, Carrie A.; Maynard, Ernest L.; Modrak-Wojcik, Anna; Mok, Yee-Foong; Mücke, Norbert; Nagel-Steger, Luitgard; Narlikar, Geeta J.; Noda, Masanori; Nourse, Amanda; Obsil, Tomas; Park, Chad K.; Park, Jin-Ku; Pawelek, Peter D.; Perdue, Erby E.; Perkins, Stephen J.; Perugini, Matthew A.; Peterson, Craig L.; Peverelli, Martin G.; Piszczek, Grzegorz; Prag, Gali; Prevelige, Peter E.; Raynal, Bertrand D. E.; Rezabkova, Lenka; Richter, Klaus; Ringel, Alison E.; Rosenberg, Rose; Rowe, Arthur J.; Rufer, Arne C.; Scott, David J.; Seravalli, Javier G.; Solovyova, Alexandra S.; Song, Renjie; Staunton, David; Stoddard, Caitlin; Stott, Katherine; Strauss, Holger M.; Streicher, Werner W.; Sumida, John P.; Swygert, Sarah G.; Szczepanowski, Roman H.; Tessmer, Ingrid; Toth, Ronald T.; Tripathy, Ashutosh; Uchiyama, Susumu; Uebel, Stephan F. W.; Unzai, Satoru; Gruber, Anna Vitlin; von Hippel, Peter H.; Wandrey, Christine; Wang, Szu-Huan; Weitzel, Steven E.; Wielgus-Kutrowska, Beata; Wolberger, Cynthia; Wolff, Martin; Wright, Edward; Wu, Yu-Sung; Wubben, Jacinta M.; Schuck, Peter

    2015-01-01

    Analytical ultracentrifugation (AUC) is a first principles based method to determine absolute sedimentation coefficients and buoyant molar masses of macromolecules and their complexes, reporting on their size and shape in free solution. The purpose of this multi-laboratory study was to establish the precision and accuracy of basic data dimensions in AUC and validate previously proposed calibration techniques. Three kits of AUC cell assemblies containing radial and temperature calibration tools and a bovine serum albumin (BSA) reference sample were shared among 67 laboratories, generating 129 comprehensive data sets. These allowed for an assessment of many parameters of instrument performance, including accuracy of the reported scan time after the start of centrifugation, the accuracy of the temperature calibration, and the accuracy of the radial magnification. The range of sedimentation coefficients obtained for BSA monomer in different instruments and using different optical systems was from 3.655 S to 4.949 S, with a mean and standard deviation of (4.304 ± 0.188) S (4.4%). After the combined application of correction factors derived from the external calibration references for elapsed time, scan velocity, temperature, and radial magnification, the range of s-values was reduced 7-fold with a mean of 4.325 S and a 6-fold reduced standard deviation of ± 0.030 S (0.7%). In addition, the large data set provided an opportunity to determine the instrument-to-instrument variation of the absolute radial positions reported in the scan files, the precision of photometric or refractometric signal magnitudes, and the precision of the calculated apparent molar mass of BSA monomer and the fraction of BSA dimers. These results highlight the necessity and effectiveness of independent calibration of basic AUC data dimensions for reliable quantitative studies. PMID:25997164

  13. A multilaboratory comparison of calibration accuracy and the performance of external references in analytical ultracentrifugation.

    PubMed

    Zhao, Huaying; Ghirlando, Rodolfo; Alfonso, Carlos; Arisaka, Fumio; Attali, Ilan; Bain, David L; Bakhtina, Marina M; Becker, Donald F; Bedwell, Gregory J; Bekdemir, Ahmet; Besong, Tabot M D; Birck, Catherine; Brautigam, Chad A; Brennerman, William; Byron, Olwyn; Bzowska, Agnieszka; Chaires, Jonathan B; Chaton, Catherine T; Cölfen, Helmut; Connaghan, Keith D; Crowley, Kimberly A; Curth, Ute; Daviter, Tina; Dean, William L; Díez, Ana I; Ebel, Christine; Eckert, Debra M; Eisele, Leslie E; Eisenstein, Edward; England, Patrick; Escalante, Carlos; Fagan, Jeffrey A; Fairman, Robert; Finn, Ron M; Fischle, Wolfgang; de la Torre, José García; Gor, Jayesh; Gustafsson, Henning; Hall, Damien; Harding, Stephen E; Cifre, José G Hernández; Herr, Andrew B; Howell, Elizabeth E; Isaac, Richard S; Jao, Shu-Chuan; Jose, Davis; Kim, Soon-Jong; Kokona, Bashkim; Kornblatt, Jack A; Kosek, Dalibor; Krayukhina, Elena; Krzizike, Daniel; Kusznir, Eric A; Kwon, Hyewon; Larson, Adam; Laue, Thomas M; Le Roy, Aline; Leech, Andrew P; Lilie, Hauke; Luger, Karolin; Luque-Ortega, Juan R; Ma, Jia; May, Carrie A; Maynard, Ernest L; Modrak-Wojcik, Anna; Mok, Yee-Foong; Mücke, Norbert; Nagel-Steger, Luitgard; Narlikar, Geeta J; Noda, Masanori; Nourse, Amanda; Obsil, Tomas; Park, Chad K; Park, Jin-Ku; Pawelek, Peter D; Perdue, Erby E; Perkins, Stephen J; Perugini, Matthew A; Peterson, Craig L; Peverelli, Martin G; Piszczek, Grzegorz; Prag, Gali; Prevelige, Peter E; Raynal, Bertrand D E; Rezabkova, Lenka; Richter, Klaus; Ringel, Alison E; Rosenberg, Rose; Rowe, Arthur J; Rufer, Arne C; Scott, David J; Seravalli, Javier G; Solovyova, Alexandra S; Song, Renjie; Staunton, David; Stoddard, Caitlin; Stott, Katherine; Strauss, Holger M; Streicher, Werner W; Sumida, John P; Swygert, Sarah G; Szczepanowski, Roman H; Tessmer, Ingrid; Toth, Ronald T; Tripathy, Ashutosh; Uchiyama, Susumu; Uebel, Stephan F W; Unzai, Satoru; Gruber, Anna Vitlin; von Hippel, Peter H; Wandrey, Christine; Wang, Szu-Huan; Weitzel, Steven E; Wielgus-Kutrowska, Beata; Wolberger, Cynthia; Wolff, Martin; Wright, Edward; Wu, Yu-Sung; Wubben, Jacinta M; Schuck, Peter

    2015-01-01

    Analytical ultracentrifugation (AUC) is a first principles based method to determine absolute sedimentation coefficients and buoyant molar masses of macromolecules and their complexes, reporting on their size and shape in free solution. The purpose of this multi-laboratory study was to establish the precision and accuracy of basic data dimensions in AUC and validate previously proposed calibration techniques. Three kits of AUC cell assemblies containing radial and temperature calibration tools and a bovine serum albumin (BSA) reference sample were shared among 67 laboratories, generating 129 comprehensive data sets. These allowed for an assessment of many parameters of instrument performance, including accuracy of the reported scan time after the start of centrifugation, the accuracy of the temperature calibration, and the accuracy of the radial magnification. The range of sedimentation coefficients obtained for BSA monomer in different instruments and using different optical systems was from 3.655 S to 4.949 S, with a mean and standard deviation of (4.304 ± 0.188) S (4.4%). After the combined application of correction factors derived from the external calibration references for elapsed time, scan velocity, temperature, and radial magnification, the range of s-values was reduced 7-fold with a mean of 4.325 S and a 6-fold reduced standard deviation of ± 0.030 S (0.7%). In addition, the large data set provided an opportunity to determine the instrument-to-instrument variation of the absolute radial positions reported in the scan files, the precision of photometric or refractometric signal magnitudes, and the precision of the calculated apparent molar mass of BSA monomer and the fraction of BSA dimers. These results highlight the necessity and effectiveness of independent calibration of basic AUC data dimensions for reliable quantitative studies.

  14. Accuracy of three-dimensional facial soft tissue simulation in post-traumatic zygoma reconstruction.

    PubMed

    Li, P; Zhou, Z W; Ren, J Y; Zhang, Y; Tian, W D; Tang, W

    2016-12-01

    The aim of this study was to evaluate the accuracy of novel software-CMF-preCADS-for the prediction of soft tissue changes following repositioning surgery for zygomatic fractures. Twenty patients who had sustained an isolated zygomatic fracture accompanied by facial deformity and who were treated with repositioning surgery participated in this study. Cone beam computed tomography (CBCT) scans and three-dimensional (3D) stereophotographs were acquired preoperatively and postoperatively. The 3D skeletal model from the preoperative CBCT data was matched with the postoperative one, and the fractured zygomatic fragments were segmented and aligned to the postoperative position for prediction. Then, the predicted model was matched with the postoperative 3D stereophotograph for quantification of the simulation error. The mean absolute error in the zygomatic soft tissue region between the predicted model and the real one was 1.42±1.56mm for all cases. The accuracy of the prediction (mean absolute error ≤2mm) was 87%. In the subjective assessment it was found that the majority of evaluators considered the predicted model and the postoperative model to be 'very similar'. CMF-preCADS software can provide a realistic, accurate prediction of the facial soft tissue appearance after repositioning surgery for zygomatic fractures. The reliability of this software for other types of repositioning surgery for maxillofacial fractures should be validated in the future.

  15. Absolute properties of the triple star HP Aurigae

    SciTech Connect

    Lacy, Claud H. Sandberg; Burks, Charles L.; Torres, Guillermo; Wolf, Marek E-mail: clburks@email.uark.edu E-mail: wolf@cesnet.cz

    2014-01-01

    New photometric, spectroscopic, and eclipse timing observations of the eclipsing binary star HP Aur allow for very accurate orbital determinations, even in the presence of a third body and transient starspot activity. The eclipsing binary masses are determined to an accuracy of ±0.4% and the radii to ±0.6%. The masses are 0.9543 ± 0.0041 and 0.8094 ± 0.0036 solar masses, and the radii are 1.0278 ± 0.0042 and 0.7758 ± 0.0034 solar radii, respectively. The orbital period in the outer orbit is accurately determined for the first time: 4.332 ± 0.011 yr. A comparison with current theories of stellar evolution shows that the components' absolute properties can be well-matched by the current models at an age of about 7 billion years.

  16. Landsat-5 TM reflective-band absolute radiometric calibration

    USGS Publications Warehouse

    Chander, G.; Helder, D.L.; Markham, B.L.; Dewald, J.D.; Kaita, E.; Thome, K.J.; Micijevic, E.; Ruggles, T.A.

    2004-01-01

    The Landsat-5 Thematic Mapper (TM) sensor provides the longest running continuous dataset of moderate spatial resolution remote sensing imagery, dating back to its launch in March 1984. Historically, the radiometric calibration procedure for this imagery used the instrument's response to the Internal Calibrator (IC) on a scene-by-scene basis to determine the gain and offset of each detector. Due to observed degradations in the IC, a new procedure was implemented for U.S.-processed data in May 2003. This new calibration procedure is based on a lifetime radiometric calibration model for the instrument's reflective bands (1-5 and 7) and is derived, in part, from the IC response without the related degradation effects and is tied to the cross calibration with the Landsat-7 Enhanced Thematic Mapper Plus. Reflective-band absolute radiometric accuracy of the instrument tends to be on the order of 7% to 10%, based on a variety of calibration methods.

  17. Sub-nanometer periodic nonlinearity error in absolute distance interferometers.

    PubMed

    Yang, Hongxing; Huang, Kaiqi; Hu, Pengcheng; Zhu, Pengfei; Tan, Jiubin; Fan, Zhigang

    2015-05-01

    Periodic nonlinearity which can result in error in nanometer scale has become a main problem limiting the absolute distance measurement accuracy. In order to eliminate this error, a new integrated interferometer with non-polarizing beam splitter is developed. This leads to disappearing of the frequency and/or polarization mixing. Furthermore, a strict requirement on the laser source polarization is highly reduced. By combining retro-reflector and angel prism, reference and measuring beams can be spatially separated, and therefore, their optical paths are not overlapped. So, the main cause of the periodic nonlinearity error, i.e., the frequency and/or polarization mixing and leakage of beam, is eliminated. Experimental results indicate that the periodic phase error is kept within 0.0018°.

  18. Assignment of absolute stereostructures through quantum mechanics electronic and vibrational circular dichroism calculations.

    PubMed

    Dai, Peng; Jiang, Nan; Tan, Ren-Xiang

    2016-01-01

    Elucidation of absolute configuration of chiral molecules including structurally complex natural products remains a challenging problem in organic chemistry. A reliable method for assigning the absolute stereostructure is to combine the experimental circular dichroism (CD) techniques such as electronic and vibrational CD (ECD and VCD), with quantum mechanics (QM) ECD and VCD calculations. The traditional QM methods as well as their continuing developments make them more applicable with accuracy. Taking some chiral natural products with diverse conformations as examples, this review describes the basic concepts and new developments of QM approaches for ECD and VCD calculations in solution and solid states.

  19. Optical scanning extrinsic Fabry-Perot interferometer for absolute microdisplacement measurement.

    PubMed

    Li, T; May, R G; Wang, A; Claus, R O

    1997-12-01

    We report an optical-scanning, dual-fiber, extrinsic Fabry-Perot interferometer system for absolute measurement of microdisplacement. The system involves two air-gapped Fabry-Perot cavities, formed by fiber end faces, functioning as sensing and reference elements. Taking the scanning wavelength as an interconverter to compare the gap length of the sensing head with the reference-cavity length yields the absolute measurement of the sensing-cavity length. The measurement is independent of the wavelength-scanning accuracy, and the reference-cavity length can be self-calibrated simply by one's changing the sensing-head length by an accurate value.

  20. The study of absolute distance measurement based on the self-mixing interference in laser diode

    NASA Astrophysics Data System (ADS)

    Wang, Ting-ting; Zhang, Chuang

    2009-07-01

    In this work, an absolute distance measurement method based on the self-mixing interference is presented. The principles of the method used three-mirror cavity equivalent model are studied in this paper, and the mathematical model is given. Wavelength modulation of the laser beam is obtained by saw-tooth modulating the infection current of the laser diode. Absolute distance of the external target is determined by Fourier analysis method. The frequency of signal from PD is linearly dependent on absolute distance, but also affected by temperature and fluctuation of current source. A dual-path method which uses the reference technique for absolute distance measurement has been proposed. The theoretical analysis shows that the method can eliminate errors resulting from distance-independent variations in the setup. Accuracy and stability can be improved. Simulated results show that a resolution of +/-0.2mm can be achieved for absolute distance ranging from 250mm to 500mm. In the same measurement range, the resolution we obtained is better than other absolute distance measurement system proposed base on self-mixing interference.

  1. Game theory and evolution: finite size and absolute fitness measures.

    PubMed

    Demetrius, L; Gundlach, V M

    2000-11-01

    This article is concerned with the characterization and existence of evolutionarily stable strategies (ESS) in Games against Nature, a class of models described by finite size populations and absolute fitness measures. We address these problems in terms of a new formalism which revolves around the concept evolutionary entropy, a measure of the diversity of options associated with a strategy pure - strategies have zero entropy, mixed strategies positive entropy. We invoke this formalism to show that ESS are characterized by extremal states of entropy. We illustrate this characterization of ESS by an analysis of the evolution of the sex ratio and the evolution of seed size.

  2. Mitigation of Atmospheric Delay in SAR Absolute Ranging Using Global Numerical Weather Prediction Data: Corner Reflector Experiments at 3 Different Test Sites

    NASA Astrophysics Data System (ADS)

    Cong, Xiaoying; Balss, Ulrich; Eineder, Michael

    2015-04-01

    The atmospheric delay due to vertical stratification, the so-called stratified atmospheric delay, has a great impact on both interferometric and absolute range measurements. In our current researches [1][2][3], centimeter-range accuracy has been proven based on Corner Reflector (CR) based measurements by applying atmospheric delay correction using the Zenith Path Delay (ZPD) corrections derived from nearby Global Positioning System (GPS) stations. For a global usage, an effective method has been introduced to estimate the stratified delay based on global 4-dimensional Numerical Weather Prediction (NWP) products: the direct integration method [4][5]. Two products, ERA-Interim and operational data, provided by European Centre for Medium-Range Weather Forecast (ECMWF) are used to integrate the stratified delay. In order to access the integration accuracy, a validation approach is investigated based on ZPD derived from six permanent GPS stations located in different meteorological conditions. Range accuracy at centimeter level is demonstrated using both ECMWF products. Further experiments have been carried out in order to determine the best interpolation method by analyzing the temporal and spatial correlation of atmospheric delay using both ECMWF and GPS ZPD. Finally, the integrated atmospheric delays in slant direction (Slant Path Delay, SPD) have been applied instead of the GPS ZPD for CR experiments at three different test sites with more than 200 TerraSAR-X High Resolution SpotLight (HRSL) images. The delay accuracy is around 1-3 cm depending on the location of test site due to the local water vapor variation and the acquisition time/date. [1] Eineder M., Minet C., Steigenberger P., et al. Imaging geodesy - Toward centimeter-level ranging accuracy with TerraSAR-X. Geoscience and Remote Sensing, IEEE Transactions on, 2011, 49(2): 661-671. [2] Balss U., Gisinger C., Cong X. Y., et al. Precise Measurements on the Absolute Localization Accuracy of TerraSAR-X on the

  3. Comparative vs. Absolute Judgments of Trait Desirability

    ERIC Educational Resources Information Center

    Hofstee, Willem K. B.

    1970-01-01

    Reversals of trait desirability are studied. Terms indicating conservativw behavior appeared to be judged relatively desirable in comparative judgement, while traits indicating dynamic and expansive behavior benefited from absolute judgement. The reversal effect was shown to be a general one, i.e. reversals were not dependent upon the specific…

  4. New Techniques for Absolute Gravity Measurements.

    DTIC Science & Technology

    1983-01-07

    Hammond, J.A. (1978) Bollettino Di Geofisica Teorica ed Applicata Vol. XX. 8. Hammond, J. A., and Iliff, R. L. (1979) The AFGL absolute gravity system...International Gravimetric Bureau, No. L:I-43. 7. Hammond. J.A. (1978) Bollettino Di Geofisica Teorica ed Applicata Vol. XX. 8. Hammond, J.A., and

  5. An Absolute Electrometer for the Physics Laboratory

    ERIC Educational Resources Information Center

    Straulino, S.; Cartacci, A.

    2009-01-01

    A low-cost, easy-to-use absolute electrometer is presented: two thin metallic plates and an electronic balance, usually available in a laboratory, are used. We report on the very good performance of the device that allows precise measurements of the force acting between two charged plates. (Contains 5 footnotes, 2 tables, and 6 figures.)

  6. GEOSPATIAL DATA ACCURACY ASSESSMENT

    EPA Science Inventory

    The development of robust accuracy assessment methods for the validation of spatial data represent's a difficult scientific challenge for the geospatial science community. The importance and timeliness of this issue is related directly to the dramatic escalation in the developmen...

  7. Landsat wildland mapping accuracy

    USGS Publications Warehouse

    Todd, William J.; Gehring, Dale G.; Haman, J. F.

    1980-01-01

    A Landsat-aided classification of ten wildland resource classes was developed for the Shivwits Plateau region of the Lake Mead National Recreation Area. Single stage cluster sampling (without replacement) was used to verify the accuracy of each class.

  8. [Design and accuracy analysis of upper slicing system of MSCT].

    PubMed

    Jiang, Rongjian

    2013-05-01

    The upper slicing system is the main components of the optical system in MSCT. This paper focuses on the design of upper slicing system and its accuracy analysis to improve the accuracy of imaging. The error of slice thickness and ray center by bearings, screw and control system were analyzed and tested. In fact, the accumulated error measured is less than 1 microm, absolute error measured is less than 10 microm. Improving the accuracy of the upper slicing system contributes to the appropriate treatment methods and success rate of treatment.

  9. Development of a GPS-aided motion measurement, pointing, and stabilization system for a Synthetic Aperture Radar. [Global Positioning System (GPS)

    SciTech Connect

    Fellerhoff, J.R.; Kohler, S.M.

    1991-01-01

    An advanced Synthetic Aperture Radar Motion Compensation System has been developed by Sandia National Laboratories (SNL). The system includes a miniaturized high accuracy ring laser gyro inertial measurement unit, a three axis gimbal pointing and stabilization assembly, a differential Global Positioning System (GPS) navigation aiding system, and a pilot guidance system. The system provides several improvements over previous SNL motion compensation systems and is capable of antenna stabilization to less than 0.01 degrees RMS and absolute position measurement to less than 5.0 meters RMS. These accuracies have been demonstrated in recent flight testing aboard a DHC-6-300 Twin Otter'' aircraft.

  10. Accuracy control in Monte Carlo radiative calculations

    NASA Technical Reports Server (NTRS)

    Almazan, P. Planas

    1993-01-01

    The general accuracy law that rules the Monte Carlo, ray-tracing algorithms used commonly for the calculation of the radiative entities in the thermal analysis of spacecraft are presented. These entities involve transfer of radiative energy either from a single source to a target (e.g., the configuration factors). or from several sources to a target (e.g., the absorbed heat fluxes). In fact, the former is just a particular case of the latter. The accuracy model is later applied to the calculation of some specific radiative entities. Furthermore, some issues related to the implementation of such a model in a software tool are discussed. Although only the relative error is considered through the discussion, similar results can be derived for the absolute error.

  11. Inertial Measures of Motion for Clinical Biomechanics: Comparative Assessment of Accuracy under Controlled Conditions – Changes in Accuracy over Time

    PubMed Central

    Lebel, Karina; Boissy, Patrick; Hamel, Mathieu; Duval, Christian

    2015-01-01

    Background Interest in 3D inertial motion tracking devices (AHRS) has been growing rapidly among the biomechanical community. Although the convenience of such tracking devices seems to open a whole new world of possibilities for evaluation in clinical biomechanics, its limitations haven’t been extensively documented. The objectives of this study are: 1) to assess the change in absolute and relative accuracy of multiple units of 3 commercially available AHRS over time; and 2) to identify different sources of errors affecting AHRS accuracy and to document how they may affect the measurements over time. Methods This study used an instrumented Gimbal table on which AHRS modules were carefully attached and put through a series of velocity-controlled sustained motions including 2 minutes motion trials (2MT) and 12 minutes multiple dynamic phases motion trials (12MDP). Absolute accuracy was assessed by comparison of the AHRS orientation measurements to those of an optical gold standard. Relative accuracy was evaluated using the variation in relative orientation between modules during the trials. Findings Both absolute and relative accuracy decreased over time during 2MT. 12MDP trials showed a significant decrease in accuracy over multiple phases, but accuracy could be enhanced significantly by resetting the reference point and/or compensating for initial Inertial frame estimation reference for each phase. Interpretation The variation in AHRS accuracy observed between the different systems and with time can be attributed in part to the dynamic estimation error, but also and foremost, to the ability of AHRS units to locate the same Inertial frame. Conclusions Mean accuracies obtained under the Gimbal table sustained conditions of motion suggest that AHRS are promising tools for clinical mobility assessment under constrained conditions of use. However, improvement in magnetic compensation and alignment between AHRS modules are desirable in order for AHRS to reach their

  12. In-situ absolute calibration of electric-field amplitude measurements with the LPDA radio detector stations of the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Briechle, Florian

    2017-03-01

    With the Auger Engineering Radio Array (AERA) located at the Pierre Auger Observatory, radio emission of extensive air showers is observed. To exploit the physics potential of AERA, electric-field amplitude measurements with the radio detector stations need to be well-calibrated on an absolute level. A convenient tool for far-field calibration campaigns is a flying drone. Here we make use of an octocopter to place a calibrated source at freely chosen positions above the radio detector array. Special emphasis is put on the reconstruction of the octocopter position and its accuracy during the flights. The antenna response pattern of the radio detector stations was measured in a recent calibration campaign. Results of these measurements are presented and compared to simulations. It is found that measurements and simulations are in good agreement.

  13. Measuring true localization accuracy in super resolution microscopy with DNA-origami nanostructures

    NASA Astrophysics Data System (ADS)

    Reuss, Matthias; Fördős, Ferenc; Blom, Hans; Öktem, Ozan; Högberg, Björn; Brismar, Hjalmar

    2017-02-01

    A common method to assess the performance of (super resolution) microscopes is to use the localization precision of emitters as an estimate for the achieved resolution. Naturally, this is widely used in super resolution methods based on single molecule stochastic switching. This concept suffers from the fact that it is hard to calibrate measures against a real sample (a phantom), because true absolute positions of emitters are almost always unknown. For this reason, resolution estimates are potentially biased in an image since one is blind to true position accuracy, i.e. deviation in position measurement from true positions. We have solved this issue by imaging nanorods fabricated with DNA-origami. The nanorods used are designed to have emitters attached at each end in a well-defined and highly conserved distance. These structures are widely used to gauge localization precision. Here, we additionally determined the true achievable localization accuracy and compared this figure of merit to localization precision values for two common super resolution microscope methods STED and STORM.

  14. Overlay accuracy fundamentals

    NASA Astrophysics Data System (ADS)

    Kandel, Daniel; Levinski, Vladimir; Sapiens, Noam; Cohen, Guy; Amit, Eran; Klein, Dana; Vakshtein, Irina

    2012-03-01

    Currently, the performance of overlay metrology is evaluated mainly based on random error contributions such as precision and TIS variability. With the expected shrinkage of the overlay metrology budget to < 0.5nm, it becomes crucial to include also systematic error contributions which affect the accuracy of the metrology. Here we discuss fundamental aspects of overlay accuracy and a methodology to improve accuracy significantly. We identify overlay mark imperfections and their interaction with the metrology technology, as the main source of overlay inaccuracy. The most important type of mark imperfection is mark asymmetry. Overlay mark asymmetry leads to a geometrical ambiguity in the definition of overlay, which can be ~1nm or less. It is shown theoretically and in simulations that the metrology may enhance the effect of overlay mark asymmetry significantly and lead to metrology inaccuracy ~10nm, much larger than the geometrical ambiguity. The analysis is carried out for two different overlay metrology technologies: Imaging overlay and DBO (1st order diffraction based overlay). It is demonstrated that the sensitivity of DBO to overlay mark asymmetry is larger than the sensitivity of imaging overlay. Finally, we show that a recently developed measurement quality metric serves as a valuable tool for improving overlay metrology accuracy. Simulation results demonstrate that the accuracy of imaging overlay can be improved significantly by recipe setup optimized using the quality metric. We conclude that imaging overlay metrology, complemented by appropriate use of measurement quality metric, results in optimal overlay accuracy.

  15. Absolute Radiation Thermometry in the NIR

    NASA Astrophysics Data System (ADS)

    Bünger, L.; Taubert, R. D.; Gutschwager, B.; Anhalt, K.; Briaudeau, S.; Sadli, M.

    2017-04-01

    A near infrared (NIR) radiation thermometer (RT) for temperature measurements in the range from 773 K up to 1235 K was characterized and calibrated in terms of the "Mise en Pratique for the definition of the Kelvin" (MeP-K) by measuring its absolute spectral radiance responsivity. Using Planck's law of thermal radiation allows the direct measurement of the thermodynamic temperature independently of any ITS-90 fixed-point. To determine the absolute spectral radiance responsivity of the radiation thermometer in the NIR spectral region, an existing PTB monochromator-based calibration setup was upgraded with a supercontinuum laser system (0.45 μm to 2.4 μm) resulting in a significantly improved signal-to-noise ratio. The RT was characterized with respect to its nonlinearity, size-of-source effect, distance effect, and the consistency of its individual temperature measuring ranges. To further improve the calibration setup, a new tool for the aperture alignment and distance measurement was developed. Furthermore, the diffraction correction as well as the impedance correction of the current-to-voltage converter is considered. The calibration scheme and the corresponding uncertainty budget of the absolute spectral responsivity are presented. A relative standard uncertainty of 0.1 % (k=1) for the absolute spectral radiance responsivity was achieved. The absolute radiometric calibration was validated at four temperature values with respect to the ITS-90 via a variable temperature heatpipe blackbody (773 K ...1235 K) and at a gold fixed-point blackbody radiator (1337.33 K).

  16. Accuracy analysis of the space shuttle solid rocket motor profile measuring device

    NASA Technical Reports Server (NTRS)

    Estler, W. Tyler

    1989-01-01

    The Profile Measuring Device (PMD) was developed at the George C. Marshall Space Flight Center following the loss of the Space Shuttle Challenger. It is a rotating gauge used to measure the absolute diameters of mating features of redesigned Solid Rocket Motor field joints. Diameter tolerance of these features are typically + or - 0.005 inches and it is required that the PMD absolute measurement uncertainty be within this tolerance. In this analysis, the absolute accuracy of these measurements were found to be + or - 0.00375 inches, worst case, with a potential accuracy of + or - 0.0021 inches achievable by improved temperature control.

  17. In-Flight Measurement of the Absolute Energy Scale of the Fermi Large Area Telescope

    SciTech Connect

    Ackermann, M.; Ajello, M.; Allafort, A.; Atwood, W.B.; Axelsson, M.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E.D.; Bonamente, E.; Borgland, A.W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; /more authors..

    2012-09-20

    The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to survey the gamma-ray sky from 20 MeV to several hundreds of GeV. In this energy band there are no astronomical sources with sufficiently well known and sharp spectral features to allow an absolute calibration of the LAT energy scale. However, the geomagnetic cutoff in the cosmic ray electron-plus-positron (CRE) spectrum in low Earth orbit does provide such a spectral feature. The energy and spectral shape of this cutoff can be calculated with the aid of a numerical code tracing charged particles in the Earth's magnetic field. By comparing the cutoff value with that measured by the LAT in different geomagnetic positions, we have obtained several calibration points between {approx}6 and {approx}13 GeV with an estimated uncertainty of {approx}2%. An energy calibration with such high accuracy reduces the systematic uncertainty in LAT measurements of, for example, the spectral cutoff in the emission from gamma ray pulsars.

  18. In-Flight Measurement of the Absolute Energy Scale of the Fermi Large Area Telescope

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Ajello, M.; Allafort, A.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Barbielini, G; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B,; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Gehrels, N.; Hays, E.; McEnery, J. E.; Thompson, D. J.; Troja, E. J.

    2012-01-01

    The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to survey the gamma-ray sky from 20 MeV to several hundreds of GeV. In this energy band there are no astronomical sources with sufficiently well known and sharp spectral features to allow an absolute calibration of the LAT energy scale. However, the geomagnetic cutoff in the cosmic ray electron- plus-positron (CRE) spectrum in low Earth orbit does provide such a spectral feature. The energy and spectral shape of this cutoff can be calculated with the aid of a numerical code tracing charged particles in the Earth's magnetic field. By comparing the cutoff value with that measured by the LAT in different geomagnetic positions, we have obtained several calibration points between approx. 6 and approx. 13 GeV with an estimated uncertainty of approx. 2%. An energy calibration with such high accuracy reduces the systematic uncertainty in LAT measurements of, for example, the spectral cutoff in the emission from gamma ray pulsars.

  19. Facing the Sunrise: Cultural Worldview Underlying Intrinsic-Based Encoding of Absolute Frames of Reference in Aymara

    ERIC Educational Resources Information Center

    Nunez, Rafael E.; Cornejo, Carlos

    2012-01-01

    The Aymara of the Andes use absolute (cardinal) frames of reference for describing the relative position of ordinary objects. However, rather than encoding them in available absolute lexemes, they do it in lexemes that are intrinsic to the body: "nayra" ("front") and "qhipa" ("back"), denoting east and west,…

  20. High accuracy gaseous x-ray detectors

    SciTech Connect

    Smith, G.C.

    1983-11-01

    An outline is given of the design and operation of high accuracy position-sensitive x-ray detectors suitable for experiments using synchrotron radiation. They are based on the gas proportional detector, with position readout using a delay line; a detailed examination is made of factors which limit spatial resolution. Individual wire readout may be used for extremely high counting rates.

  1. The Absolute Vector Magnetometers on Board Swarm, Lessons Learned From Two Years in Space.

    NASA Astrophysics Data System (ADS)

    Hulot, G.; Leger, J. M.; Vigneron, P.; Brocco, L.; Olsen, N.; Jager, T.; Bertrand, F.; Fratter, I.; Sirol, O.; Lalanne, X.

    2015-12-01

    ESA's Swarm satellites carry 4He absolute magnetometers (ASM), designed by CEA-Léti and developed in partnership with CNES. These instruments are the first-ever space-born magnetometers to use a common sensor to simultaneously deliver 1Hz independent absolute scalar and vector readings of the magnetic field. They have provided the very high accuracy scalar field data nominally required by the mission (for both science and calibration purposes, since each satellite also carries a low noise high frequency fluxgate magnetometer designed by DTU), but also very useful experimental absolute vector data. In this presentation, we will report on the status of the instruments, as well as on the various tests and investigations carried out using these experimental data since launch in November 2013. In particular, we will illustrate the advantages of flying ASM instruments on space-born magnetic missions for nominal data quality checks, geomagnetic field modeling and science objectives.

  2. Predict Gram-Positive and Gram-Negative Subcellular Localization via Incorporating Evolutionary Information and Physicochemical Features Into Chou's General PseAAC.

    PubMed

    Sharma, Ronesh; Dehzangi, Abdollah; Lyons, James; Paliwal, Kuldip; Tsunoda, Tatsuhiko; Sharma, Alok

    2015-12-01

    In this study, we used structural and evolutionary based features to represent the sequences of gram-positive and gram-negative subcellular localizations. To do this, we proposed a normalization method to construct a normalize Position Specific Scoring Matrix (PSSM) using the information from original PSSM. To investigate the effectiveness of the proposed method we compute feature vectors from normalize PSSM and by applying support vector machine (SVM) and naïve Bayes classifier, respectively, we compared achieved results with the previously reported results. We also computed features from original PSSM and normalized PSSM and compared their results. The archived results show enhancement in gram-positive and gram-negative subcellular localizations. Evaluating localization for each feature, our results indicate that employing SVM and concatenating features (amino acid composition feature, Dubchak feature (physicochemical-based features), normalized PSSM based auto-covariance feature and normalized PSSM based bigram feature) have higher accuracy while employing naïve Bayes classifier with normalized PSSM based auto-covariance feature proves to have high sensitivity for both benchmarks. Our reported results in terms of overall locative accuracy is 84.8% and overall absolute accuracy is 85.16% for gram-positive dataset; and, for gram-negative dataset, overall locative accuracy is 85.4% and overall absolute accuracy is 86.3%.

  3. Dichotomy and perceptual distortions in absolute pitch ability

    PubMed Central

    Athos, E. Alexandra; Levinson, Barbara; Kistler, Amy; Zemansky, Jason; Bostrom, Alan; Freimer, Nelson; Gitschier, Jane

    2007-01-01

    Absolute pitch (AP) is the rare ability to identify the pitch of a tone without the aid of a reference tone. Understanding both the nature and genesis of AP can provide insights into neuroplasticity in the auditory system. We explored factors that may influence the accuracy of pitch perception in AP subjects both during the development of the trait and in later age. We used a Web-based survey and a pitch-labeling test to collect perceptual data from 2,213 individuals, 981 (44%) of whom proved to have extraordinary pitch-naming ability. The bimodal distribution in pitch-naming ability signifies AP as a distinct perceptual trait, with possible implications for its genetic basis. The wealth of these data has allowed us to uncover unsuspected note-naming irregularities suggestive of a “perceptual magnet” centered at the note “A.” In addition, we document a gradual decline in pitch-naming accuracy with age, characterized by a perceptual shift in the “sharp” direction. These findings speak both to the process of acquisition of AP and to its stability. PMID:17724340

  4. Dichotomy and perceptual distortions in absolute pitch ability.

    PubMed

    Athos, E Alexandra; Levinson, Barbara; Kistler, Amy; Zemansky, Jason; Bostrom, Alan; Freimer, Nelson; Gitschier, Jane

    2007-09-11

    Absolute pitch (AP) is the rare ability to identify the pitch of a tone without the aid of a reference tone. Understanding both the nature and genesis of AP can provide insights into neuroplasticity in the auditory system. We explored factors that may influence the accuracy of pitch perception in AP subjects both during the development of the trait and in later age. We used a Web-based survey and a pitch-labeling test to collect perceptual data from 2,213 individuals, 981 (44%) of whom proved to have extraordinary pitch-naming ability. The bimodal distribution in pitch-naming ability signifies AP as a distinct perceptual trait, with possible implications for its genetic basis. The wealth of these data has allowed us to uncover unsuspected note-naming irregularities suggestive of a "perceptual magnet" centered at the note "A." In addition, we document a gradual decline in pitch-naming accuracy with age, characterized by a perceptual shift in the "sharp" direction. These findings speak both to the process of acquisition of AP and to its stability.

  5. Prospects for the Moon as an SI-Traceable Absolute Spectroradiometric Standard for Satellite Remote Sensing

    NASA Astrophysics Data System (ADS)

    Cramer, C. E.; Stone, T. C.; Lykke, K.; Woodward, J. T.

    2015-12-01

    The Earth's Moon has many physical properties that make it suitable for use as a reference light source for radiometric calibration of remote sensing satellite instruments. Lunar calibration has been successfully applied to many imagers in orbit, including both MODIS instruments and NPP-VIIRS, using the USGS ROLO model to predict the reference exoatmospheric lunar irradiance. Sensor response trending was developed for SeaWIFS with a relative accuracy better than 0.1 % per year with lunar calibration techniques. However, the Moon rarely is used as an absolute reference for on-orbit calibration, primarily due to uncertainties in the ROLO model absolute scale of 5%-10%. But this limitation lies only with the models - the Moon itself is radiometrically stable, and development of a high-accuracy absolute lunar reference is inherently feasible. A program has been undertaken by NIST to collect absolute measurements of the lunar spectral irradiance with absolute accuracy <1 % (k=2), traceable to SI radiometric units. Initial Moon observations were acquired from the Whipple Observatory on Mt. Hopkins, Arizona, elevation 2367 meters, with continuous spectral coverage from 380 nm to 1040 nm at ~3 nm resolution. The lunar spectrometer acquired calibration measurements several times each observing night by pointing to a calibrated integrating sphere source. The lunar spectral irradiance at the top of the atmosphere was derived from a time series of ground-based measurements by a Langley analysis that incorporated measured atmospheric conditions and ROLO model predictions for the change in irradiance resulting from the changing Sun-Moon-Observer geometry throughout each night. Two nights were selected for further study. An extensive error analysis, which includes instrument calibration and atmospheric correction terms, shows a combined standard uncertainty under 1 % over most of the spectral range. Comparison of these two nights' spectral irradiance measurements with predictions

  6. Numerical accuracy assessment

    NASA Astrophysics Data System (ADS)

    Boerstoel, J. W.

    1988-12-01

    A framework is provided for numerical accuracy assessment. The purpose of numerical flow simulations is formulated. This formulation concerns the classes of aeronautical configurations (boundaries), the desired flow physics (flow equations and their properties), the classes of flow conditions on flow boundaries (boundary conditions), and the initial flow conditions. Next, accuracy and economical performance requirements are defined; the final numerical flow simulation results of interest should have a guaranteed accuracy, and be produced for an acceptable FLOP-price. Within this context, the validation of numerical processes with respect to the well known topics of consistency, stability, and convergence when the mesh is refined must be done by numerical experimentation because theory gives only partial answers. This requires careful design of text cases for numerical experimentation. Finally, the results of a few recent evaluation exercises of numerical experiments with a large number of codes on a few test cases are summarized.

  7. From Hubble's NGSL to Absolute Fluxes

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Lindler, Don

    2012-01-01

    Hubble's Next Generation Spectral Library (NGSL) consists of R-l000 spectra of 374 stars of assorted temperature, gravity, and metallicity. Each spectrum covers the wavelength range, 0.18-1.00 microns. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsll. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We are therefore developing an observing procedure that should yield fluxes with uncertainties less than 1 % and will take part in an HST proposal to observe up to 15 stars using this new procedure.

  8. Asteroid absolute magnitudes and slope parameters

    NASA Technical Reports Server (NTRS)

    Tedesco, Edward F.

    1991-01-01

    A new listing of absolute magnitudes (H) and slope parameters (G) has been created and published in the Minor Planet Circulars; this same listing will appear in the 1992 Ephemerides of Minor Planets. Unlike previous listings, the values of the current list were derived from fits of data at the V band. All observations were reduced in the same fashion using, where appropriate, a single basis default value of 0.15 for the slope parameter. Distances and phase angles were computed for each observation. The data for 113 asteroids was of sufficiently high quality to permit derivation of their H and G. These improved absolute magnitudes and slope parameters will be used to deduce the most reliable bias-corrected asteroid size-frequency distribution yet made.

  9. Computer processing of spectrograms for absolute intensities.

    PubMed

    Guttman, A; Golden, J; Galbraith, H J

    1967-09-01

    A computer program was developed to process photographically recorded spectra for absolute intensity. Test and calibration films are subjected to densitometric scans that provide digitally recorded densities on magnetic tapes. The nonlinear calibration data are fitted by least-squares cubic polynomials to yield a good approximation to the monochromatic H&D curves for commonly used emulsions (2475 recording film, Royal-X, Tri-X, 4-X). Several test cases were made. Results of these cases show that the machine processed absolute intensities are accurate to within 15%o. Arbitrarily raising the sensitivity threshold by 0.1 density units above gross fog yields cubic polynomial fits to the H&D curves that are radiometrically accurate within 10%. In addition, curves of gamma vs wavelength for 2475, Tri-X, and 4-X emulsions were made. These data show slight evidence of the photographic Purkinje effect in the 2475 emulsion.

  10. An absolute measure for a key currency

    NASA Astrophysics Data System (ADS)

    Oya, Shunsuke; Aihara, Kazuyuki; Hirata, Yoshito

    It is generally considered that the US dollar and the euro are the key currencies in the world and in Europe, respectively. However, there is no absolute general measure for a key currency. Here, we investigate the 24-hour periodicity of foreign exchange markets using a recurrence plot, and define an absolute measure for a key currency based on the strength of the periodicity. Moreover, we analyze the time evolution of this measure. The results show that the credibility of the US dollar has not decreased significantly since the Lehman shock, when the Lehman Brothers bankrupted and influenced the economic markets, and has increased even relatively better than that of the euro and that of the Japanese yen.

  11. Probing absolute spin polarization at the nanoscale.

    PubMed

    Eltschka, Matthias; Jäck, Berthold; Assig, Maximilian; Kondrashov, Oleg V; Skvortsov, Mikhail A; Etzkorn, Markus; Ast, Christian R; Kern, Klaus

    2014-12-10

    Probing absolute values of spin polarization at the nanoscale offers insight into the fundamental mechanisms of spin-dependent transport. Employing the Zeeman splitting in superconducting tips (Meservey-Tedrow-Fulde effect), we introduce a novel spin-polarized scanning tunneling microscopy that combines the probing capability of the absolute values of spin polarization with precise control at the atomic scale. We utilize our novel approach to measure the locally resolved spin polarization of magnetic Co nanoislands on Cu(111). We find that the spin polarization is enhanced by 65% when increasing the width of the tunnel barrier by only 2.3 Å due to the different decay of the electron orbitals into vacuum.

  12. Improving metacomprehension accuracy in an undergraduate course context.

    PubMed

    Wiley, Jennifer; Griffin, Thomas D; Jaeger, Allison J; Jarosz, Andrew F; Cushen, Patrick J; Thiede, Keith W

    2016-12-01

    Students tend to have poor metacomprehension when learning from text, meaning they are not able to distinguish between what they have understood well and what they have not. Although there are a good number of studies that have explored comprehension monitoring accuracy in laboratory experiments, fewer studies have explored this in authentic course contexts. This study investigated the effect of an instructional condition that encouraged comprehension-test-expectancy and self-explanation during study on metacomprehension accuracy in the context of an undergraduate course in research methods. Results indicated that when students received this instructional condition, relative metacomprehension accuracy was better than in a comparison condition. In addition, differences were also seen in absolute metacomprehension accuracy measures, strategic study behaviors, and learning outcomes. The results of the current study demonstrate that a condition that has improved relative metacomprehension accuracy in laboratory contexts may have value in real classroom contexts as well. (PsycINFO Database Record

  13. Silicon Absolute X-Ray Detectors

    SciTech Connect

    Seely, John F.; Korde, Raj; Sprunck, Jacob; Medjoubi, Kadda; Hustache, Stephanie

    2010-06-23

    The responsivity of silicon photodiodes having no loss in the entrance window, measured using synchrotron radiation in the 1.75 to 60 keV range, was compared to the responsivity calculated using the silicon thickness measured using near-infrared light. The measured and calculated responsivities agree with an average difference of 1.3%. This enables their use as absolute x-ray detectors.

  14. Absolute distance measurement using frequency-sweeping heterodyne interferometer calibrated by an optical frequency comb.

    PubMed

    Wu, Xuejian; Wei, Haoyun; Zhang, Hongyuan; Ren, Libing; Li, Yan; Zhang, Jitao

    2013-04-01

    We present a frequency-sweeping heterodyne interferometer to measure an absolute distance based on a frequency-tunable diode laser calibrated by an optical frequency comb (OFC) and an interferometric phase measurement system. The laser frequency-sweeping process is calibrated by the OFC within a range of 200 GHz and an accuracy of 1.3 kHz, which brings about a precise temporal synthetic wavelength of 1.499 mm. The interferometric phase measurement system consisting of the analog signal processing circuit and the digital phase meter achieves a phase difference resolution better than 0.1 deg. As the laser frequency is sweeping, the absolute distance can be determined by measuring the phase difference variation of the interference signals. In the laboratory condition, our experimental scheme realizes micrometer accuracy over meter distance.

  15. Simple and accurate empirical absolute volume calibration of a multi-sensor fringe projection system

    NASA Astrophysics Data System (ADS)

    Gdeisat, Munther; Qudeisat, Mohammad; AlSa`d, Mohammed; Burton, David; Lilley, Francis; Ammous, Marwan M. M.

    2016-05-01

    This paper suggests a novel absolute empirical calibration method for a multi-sensor fringe projection system. The optical setup of the projector-camera sensor can be arbitrary. The term absolute calibration here means that the centre of the three dimensional coordinates in the resultant calibrated volume coincides with a preset centre to the three-dimensional real-world coordinate system. The use of a zero-phase fringe marking spot is proposed to increase depth calibration accuracy, where the spot centre is determined with sub-pixel accuracy. Also, a new method is proposed for transversal calibration. Depth and transversal calibration methods have been tested using both single sensor and three-sensor fringe projection systems. The standard deviation of the error produced by this system is 0.25 mm. The calibrated volume produced by this method is 400 mm×400 mm×140 mm.

  16. Measurement of absolute gravity acceleration in Firenze

    NASA Astrophysics Data System (ADS)

    de Angelis, M.; Greco, F.; Pistorio, A.; Poli, N.; Prevedelli, M.; Saccorotti, G.; Sorrentino, F.; Tino, G. M.

    2011-01-01

    This paper reports the results from the accurate measurement of the acceleration of gravity g taken at two separate premises in the Polo Scientifico of the University of Firenze (Italy). In these laboratories, two separate experiments aiming at measuring the Newtonian constant and testing the Newtonian law at short distances are in progress. Both experiments require an independent knowledge on the local value of g. The only available datum, pertaining to the italian zero-order gravity network, was taken more than 20 years ago at a distance of more than 60 km from the study site. Gravity measurements were conducted using an FG5 absolute gravimeter, and accompanied by seismic recordings for evaluating the noise condition at the site. The absolute accelerations of gravity at the two laboratories are (980 492 160.6 ± 4.0) μGal and (980 492 048.3 ± 3.0) μGal for the European Laboratory for Non-Linear Spectroscopy (LENS) and Dipartimento di Fisica e Astronomia, respectively. Other than for the two referenced experiments, the data here presented will serve as a benchmark for any future study requiring an accurate knowledge of the absolute value of the acceleration of gravity in the study region.

  17. System for absolute measurements by interferometric sensors

    NASA Astrophysics Data System (ADS)

    Norton, Douglas A.

    1993-03-01

    The most common problem of interferometric sensors is their inability to measure absolute path imbalance. Presented in this paper is a signal processing system that gives absolute, unambiguous reading of optical path difference for almost any style of interferometric sensor. Key components are a wide band (incoherent) optical source, a polychromator, and FFT electronics. Advantages include no moving parts in the signal processor, no active components at the sensor location, and the use of standard single mode fiber for sensor illumination and signal transmission. Actual absolute path imbalance of the interferometer is determined without using fringe counting or other inferential techniques. The polychromator extracts the interference information that occurs at each discrete wavelength within the spectral band of the optical source. The signal processing consists of analog and digital filtering, Fast Fourier analysis, and a peak detection and interpolation algorithm. This system was originally designed for use in a remote pressure sensing application that employed a totally passive fiber optic interferometer. A performance qualification was made using a Fabry-Perot interferometer and a commercially available laser interferometer to measure the reference displacement.

  18. Chemical composition of French mimosa absolute oil.

    PubMed

    Perriot, Rodolphe; Breme, Katharina; Meierhenrich, Uwe J; Carenini, Elise; Ferrando, Georges; Baldovini, Nicolas

    2010-02-10

    Since decades mimosa (Acacia dealbata) absolute oil has been used in the flavor and perfume industry. Today, it finds an application in over 80 perfumes, and its worldwide industrial production is estimated five tons per year. Here we report on the chemical composition of French mimosa absolute oil. Straight-chain analogues from C6 to C26 with different functional groups (hydrocarbons, esters, aldehydes, diethyl acetals, alcohols, and ketones) were identified in the volatile fraction. Most of them are long-chain molecules: (Z)-heptadec-8-ene, heptadecane, nonadecane, and palmitic acid are the most abundant, and constituents such as 2-phenethyl alcohol, methyl anisate, and ethyl palmitate are present in smaller amounts. The heavier constituents were mainly triterpenoids such as lupenone and lupeol, which were identified as two of the main components. (Z)-Heptadec-8-ene, lupenone, and lupeol were quantified by GC-MS in SIM mode using external standards and represents 6%, 20%, and 7.8% (w/w) of the absolute oil. Moreover, odorant compounds were extracted by SPME and analyzed by GC-sniffing leading to the perception of 57 odorant zones, of which 37 compounds were identified by their odorant description, mass spectrum, retention index, and injection of the reference compound.

  19. Constrained Least Absolute Deviation Neural Networks

    PubMed Central

    Wang, Zhishun; Peterson, Bradley S.

    2008-01-01

    It is well known that least absolute deviation (LAD) criterion or L1-norm used for estimation of parameters is characterized by robustness, i.e., the estimated parameters are totally resistant (insensitive) to large changes in the sampled data. This is an extremely useful feature, especially, when the sampled data are known to be contaminated by occasionally occurring outliers or by spiky noise. In our previous works, we have proposed the least absolute deviation neural network (LADNN) to solve unconstrained LAD problems. The theoretical proofs and numerical simulations have shown that the LADNN is Lyapunov-stable and it can globally converge to the exact solution to a given unconstrained LAD problem. We have also demonstrated its excellent application value in time-delay estimation. More generally, a practical LAD application problem may contain some linear constraints, such as a set of equalities and/or inequalities, which is called constrained LAD problem, whereas the unconstrained LAD can be considered as a special form of the constrained LAD. In this paper, we present a new neural network called constrained least absolute deviation neural network (CLADNN) to solve general constrained LAD problems. Theoretical proofs and numerical simulations demonstrate that the proposed CLADNN is Lyapunov stable and globally converges to the exact solution to a given constrained LAD problem, independent of initial values. The numerical simulations have also illustrated that the proposed CLADNN can be used to robustly estimate parameters for nonlinear curve fitting, which is extensively used in signal and image processing. PMID:18269958

  20. Accuracy rates of US-guided vacuum-assisted breast biopsy.

    PubMed

    Bonifacino, Adriana; Petrocelli, Viviana; Pisani, Tiziana; Giannerini, Simone; Giovagnoli, Alessandra; Vecchione, Aldo; Mingazzini, Pietro L; Giovagnoli, Maria Rosaria

    2005-01-01

    A prospective study designed to measure the accuracy of mammography (MRx), ultrasound (US), fine-needle aspiration cytology (FNAC) and one of the most recently introduced techniques, vacuum biopsy (VB), in the diagnosis of breast cancer is reported. A sample of 146 breast lesions on 135 patients were examined. The design of the study made it possible to compare MRx, US, FNAC and VB directly, because it excluded several confounding variables. Statistical indicators--sensitivity, specificity, predictive values (PPV and NPV), false-negative and false-positive rates (FN and FP), suspicious plus indeterminate rate and likelihood ratios (LR)--were calculated. The NPV of MRx and US were remarkably high (92.4% and 97.9%, respectively), confirming previous reports. The complete sensitivity of FNAC was 80%, while specificity was 99.1% and LR of positive tests 88.8. The combined score of FNAC, US and MRx resulted in a good increase in complete sensitivity (97.1%), when compared with the results of the single diagnostic tests evaluated separately. The absolute sensitivity of VB was 97.1% and specificity was 100%. In conclusion, considered together, MRx, US and FNAC appear to be reliable diagnostic procedures and, when they are all negative, the possibility of a cancer is extremely low, although it cannot be completely ruled out. The VB test had the highest absolute sensitivity among all the methods compared. Therefore, this technique could be considered conclusive in diagnostically doubtful cases, avoiding open surgical biopsy.

  1. Prelaunch absolute radiometric calibration of the reflective bands on the LANDSAT-4 protoflight Thematic Mapper

    NASA Technical Reports Server (NTRS)

    Barker, J. L.; Ball, D. L.; Leung, K. C.; Walker, J. A.

    1984-01-01

    The results of the absolute radiometric calibration of the LANDSAT 4 thematic mapper, as determined during pre-launch tests with a 122 cm integrating sphere, are presented. Detailed results for the best calibration of the protoflight TM are given, as well as summaries of other tests performed on the sensor. The dynamic range of the TM is within a few per cent of that required in all bands, except bands 1 and 3. Three detectors failed to pass the minimum SNR specified for their respective bands: band 5, channel 3 (dead), band 2, and channels 2 and 4 (noisy or slow response). Estimates of the absolute calibration accuracy for the TM show that the detectors are typically calibrated to 5% absolute error for the reflective bands; 10% full-scale accuracy was specified. Ten tests performed to transfer the detector absolute calibration to the internal calibrator show a 5% range at full scale in the transfer calibration; however, in two cases band 5 showed a 10% and a 7% difference.

  2. Accuracy and coverage of the modernized Polish Maritime differential GPS system

    NASA Astrophysics Data System (ADS)

    Specht, Cezary

    2011-01-01

    The DGPS navigation service augments The NAVSTAR Global Positioning System by providing localized pseudorange correction factors and ancillary information which are broadcast over selected marine reference stations. The DGPS service position and integrity information satisfy requirements in coastal navigation and hydrographic surveys. Polish Maritime DGPS system has been established in 1994 and modernized (in 2009) to meet the requirements set out in IMO resolution for a future GNSS, but also to preserve backward signal compatibility of user equipment. Having finalized installation of the new technology L1, L2 reference equipment performance tests were performed.The paper presents results of the coverage modeling and accuracy measuring campaign based on long-term signal analyses of the DGPS reference station Rozewie, which was performed for 26 days in July 2009. Final results allowed to verify the coverage area of the differential signal from reference station and calculated repeatable and absolute accuracy of the system, after the technical modernization. Obtained field strength level area and position statistics (215,000 fixes) were compared to past measurements performed in 2002 (coverage) and 2005 (accuracy), when previous system infrastructure was in operation.So far, no campaigns were performed on differential Galileo. However, as signals, signal processing and receiver techniques are comparable to those know from DGPS. Because all satellite differential GNSS systems use the same transmission standard (RTCM), maritime DGPS Radiobeacons are standardized in all radio communication aspects (frequency, binary rate, modulation), then the accuracy results of differential Galileo can be expected as a similar to DGPS.Coverage of the reference station was calculated based on unique software, which calculate the signal strength level based on transmitter parameters or field signal strength measurement campaign, done in the representative points. The software works

  3. The Influence of External Loads on Movement Precision During Active Shoulder Internal Rotation Movements as Measured by 3 Indices of Accuracy

    PubMed Central

    Brindle, Timothy J; Uhl, Timothy L; Nitz, Arthur J; Shapiro, Robert

    2006-01-01

    Context: Using constant, variable, and absolute error to measure movement accuracy might provide a more complete description of joint position sense than any of these values alone. Objective: To determine the effect of loaded movements and type of feedback on shoulder joint position sense and movement velocity. Design: Applied study with repeated measures comparing type of feedback and the presence of a load. Setting: Laboratory. Patients or Other Participants: Twenty healthy subjects (age = 27.2 ± 3.3 years, height = 173.2 ± 18.1 cm, mass = 70.8 ± 14.5 kg) were seated with their arms in a custom shoulder wheel. Intervention(s): Subjects internally rotated 27° in the plane of the scapula, with either visual feedback provided by a video monitor or proprioceptive feedback provided by prior passive positioning, to a target at 48° of external rotation. Subjects performed the internal rotation movements with video feedback and proprioceptive feedback and with and without load (5% of body weight). Main Outcome Measure(s): High-speed motion analysis recorded peak rotational velocity and accuracy. Constant, variable, and absolute error for joint position sense was calculated from the final position. Results: Unloaded movements demonstrated significantly greater variable error than for loaded movements (2.0 ± 0.7° and 1.5 ± 0.4°, respectively) (P < .05), but there were no differences in constant or absolute error. Peak velocity was greater for movements with proprioceptive feedback (45.6 ± 2.9°/s) than visual feedback (39.1 ± 2.1°/s) and for unloaded (47.8 ± 3.6°/s) than loaded (36.9 ± 1.0°/s) movements (P < .05). Conclusions: Shoulder joint position sense demonstrated greater variable error unloaded versus loaded movements. Both visual feedback and additional loads decreased peak rotational velocity. PMID:16619096

  4. A quantitative method for evaluating numerical simulation accuracy of time-transient Lamb wave propagation with its applications to selecting appropriate element size and time step.

    PubMed

    Wan, Xiang; Xu, Guanghua; Zhang, Qing; Tse, Peter W; Tan, Haihui

    2016-01-01

    Lamb wave technique has been widely used in non-destructive evaluation (NDE) and structural health monitoring (SHM). However, due to the multi-mode characteristics and dispersive nature, Lamb wave propagation behavior is much more complex than that of bulk waves. Numerous numerical simulations on Lamb wave propagation have been conducted to study its physical principles. However, few quantitative studies on evaluating the accuracy of these numerical simulations were reported. In this paper, a method based on cross correlation analysis for quantitatively evaluating the simulation accuracy of time-transient Lamb waves propagation is proposed. Two kinds of error, affecting the position and shape accuracies are firstly identified. Consequently, two quantitative indices, i.e., the GVE (group velocity error) and MACCC (maximum absolute value of cross correlation coefficient) derived from cross correlation analysis between a simulated signal and a reference waveform, are proposed to assess the position and shape errors of the simulated signal. In this way, the simulation accuracy on the position and shape is quantitatively evaluated. In order to apply this proposed method to select appropriate element size and time step, a specialized 2D-FEM program combined with the proposed method is developed. Then, the proper element size considering different element types and time step considering different time integration schemes are selected. These results proved that the proposed method is feasible and effective, and can be used as an efficient tool for quantitatively evaluating and verifying the simulation accuracy of time-transient Lamb wave propagation.

  5. Inertial Measures of Motion for Clinical Biomechanics: Comparative Assessment of Accuracy under Controlled Conditions - Effect of Velocity

    PubMed Central

    Lebel, Karina; Boissy, Patrick; Hamel, Mathieu; Duval, Christian

    2013-01-01

    Background Inertial measurement of motion with Attitude and Heading Reference Systems (AHRS) is emerging as an alternative to 3D motion capture systems in biomechanics. The objectives of this study are: 1) to describe the absolute and relative accuracy of multiple units of commercially available AHRS under various types of motion; and 2) to evaluate the effect of motion velocity on the accuracy of these measurements. Methods The criterion validity of accuracy was established under controlled conditions using an instrumented Gimbal table. AHRS modules were carefully attached to the center plate of the Gimbal table and put through experimental static and dynamic conditions. Static and absolute accuracy was assessed by comparing the AHRS orientation measurement to those obtained using an optical gold standard. Relative accuracy was assessed by measuring the variation in relative orientation between modules during trials. Findings Evaluated AHRS systems demonstrated good absolute static accuracy (mean error < 0.5o) and clinically acceptable absolute accuracy under condition of slow motions (mean error between 0.5o and 3.1o). In slow motions, relative accuracy varied from 2o to 7o depending on the type of AHRS and the type of rotation. Absolute and relative accuracy were significantly affected (p<0.05) by velocity during sustained motions. The extent of that effect varied across AHRS. Interpretation Absolute and relative accuracy of AHRS are affected by environmental magnetic perturbations and conditions of motions. Relative accuracy of AHRS is mostly affected by the ability of all modules to locate the same global reference coordinate system at all time. Conclusions Existing AHRS systems can be considered for use in clinical biomechanics under constrained conditions of use. While their individual capacity to track absolute motion is relatively consistent, the use of multiple AHRS modules to compute relative motion between rigid bodies needs to be optimized according to

  6. Accuracy Assessment of Altimeter Derived Geostrophic Velocities

    NASA Astrophysics Data System (ADS)

    Leben, R. R.; Powell, B. S.; Born, G. H.; Guinasso, N. L.

    2002-12-01

    Along track sea surface height anomaly gradients are proportional to cross track geostrophic velocity anomalies allowing satellite altimetry to provide much needed satellite observations of changes in the geostrophic component of surface ocean currents. Often, surface height gradients are computed from altimeter data archives that have been corrected to give the most accurate absolute sea level, a practice that may unnecessarily increase the error in the cross track velocity anomalies and thereby require excessive smoothing to mitigate noise. Because differentiation along track acts as a high-pass filter, many of the path length corrections applied to altimeter data for absolute height accuracy are unnecessary for the corresponding gradient calculations. We report on a study to investigate appropriate altimetric corrections and processing techniques for improving geostrophic velocity accuracy. Accuracy is assessed by comparing cross track current measurements from two moorings placed along the descending TOPEX/POSEIDON ground track number 52 in the Gulf of Mexico to the corresponding altimeter velocity estimates. The buoys are deployed and maintained by the Texas Automated Buoy System (TABS) under Interagency Contracts with Texas A&M University. The buoys telemeter observations in near real-time via satellite to the TABS station located at the Geochemical and Environmental Research Group (GERG) at Texas A&M. Buoy M is located in shelf waters of 57 m depth with a second, Buoy N, 38 km away on the shelf break at 105 m depth. Buoy N has been operational since the beginning of 2002 and has a current meter at 2m depth providing in situ measurements of surface velocities coincident with Jason and TOPEX/POSEIDON altimeter over flights. This allows one of the first detailed comparisons of shallow water near surface current meter time series to coincident altimetry.

  7. Seasonal Effects on GPS PPP Accuracy

    NASA Astrophysics Data System (ADS)

    Saracoglu, Aziz; Ugur Sanli, D.

    2016-04-01

    GPS Precise Point Positioning (PPP) is now routinely used in many geophysical applications. Static positioning and 24 h data are requested for high precision results however real life situations do not always let us collect 24 h data. Thus repeated GPS surveys of 8-10 h observation sessions are still used by some research groups. Positioning solutions from shorter data spans are subject to various systematic influences, and the positioning quality as well as the estimated velocity is degraded. Researchers pay attention to the accuracy of GPS positions and of the estimated velocities derived from short observation sessions. Recently some research groups turned their attention to the study of seasonal effects (i.e. meteorological seasons) on GPS solutions. Up to now usually regional studies have been reported. In this study, we adopt a global approach and study the various seasonal effects (including the effect of the annual signal) on GPS solutions produced from short observation sessions. We use the PPP module of the NASA/JPL's GIPSY/OASIS II software and globally distributed GPS stations' data of the International GNSS Service. Accuracy studies previously performed with 10-30 consecutive days of continuous data. Here, data from each month of a year, incorporating two years in succession, is used in the analysis. Our major conclusion is that a reformulation for the GPS positioning accuracy is necessary when taking into account the seasonal effects, and typical one term accuracy formulation is expanded to a two-term one.

  8. Demonstrating the error budget for the climate absolute radiance and refractivity observatory through solar irradiance measurements (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Thome, Kurtis J.; McCorkel, Joel; Angal, Amit

    2016-09-01

    The goal of the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission is to provide high-accuracy data for evaluation of long-term climate change trends. Essential to the CLARREO project is demonstration of SI-traceable, reflected measurements that are a factor of 10 more accurate than current state-of-the-art sensors. The CLARREO approach relies on accurate, monochromatic absolute radiance calibration in the laboratory transferred to orbit via solar irradiance knowledge. The current work describes the results of field measurements with the Solar, Lunar for Absolute Reflectance Imaging Spectroradiometer (SOLARIS) that is the calibration demonstration system (CDS) for the reflected solar portion of CLARREO. Recent measurements of absolute spectral solar irradiance using SOLARIS are presented. The ground-based SOLARIS data are corrected to top-of-atmosphere values using AERONET data collected within 5 km of the SOLARIS operation. The SOLARIS data are converted to absolute irradiance using laboratory calibrations based on the Goddard Laser for Absolute Measurement of Radiance (GLAMR). Results are compared to accepted solar irradiance models to demonstrate accuracy values giving confidence in the error budget for the CLARREO reflectance retrieval.

  9. A fast RCS accuracy assessment method for passive radar calibrators

    NASA Astrophysics Data System (ADS)

    Zhou, Yongsheng; Li, Chuanrong; Tang, Lingli; Ma, Lingling; Liu, QI

    2016-10-01

    In microwave radar radiometric calibration, the corner reflector acts as the standard reference target but its structure is usually deformed during the transportation and installation, or deformed by wind and gravity while permanently installed outdoor, which will decrease the RCS accuracy and therefore the radiometric calibration accuracy. A fast RCS accuracy measurement method based on 3-D measuring instrument and RCS simulation was proposed in this paper for tracking the characteristic variation of the corner reflector. In the first step, RCS simulation algorithm was selected and its simulation accuracy was assessed. In the second step, the 3-D measuring instrument was selected and its measuring accuracy was evaluated. Once the accuracy of the selected RCS simulation algorithm and 3-D measuring instrument was satisfied for the RCS accuracy assessment, the 3-D structure of the corner reflector would be obtained by the 3-D measuring instrument, and then the RCSs of the obtained 3-D structure and corresponding ideal structure would be calculated respectively based on the selected RCS simulation algorithm. The final RCS accuracy was the absolute difference of the two RCS calculation results. The advantage of the proposed method was that it could be applied outdoor easily, avoiding the correlation among the plate edge length error, plate orthogonality error, plate curvature error. The accuracy of this method is higher than the method using distortion equation. In the end of the paper, a measurement example was presented in order to show the performance of the proposed method.

  10. Swarm Absolute Scalar Magnetometers first in-orbit results

    NASA Astrophysics Data System (ADS)

    Fratter, Isabelle; Léger, Jean-Michel; Bertrand, François; Jager, Thomas; Hulot, Gauthier; Brocco, Laura; Vigneron, Pierre

    2016-04-01

    The ESA Swarm mission will provide the best ever survey of the Earth's magnetic field and its temporal evolution. This will be achieved by a constellation of three identical satellites, launched together on the 22nd of November 2013. In order to observe the magnetic field thoroughly, each satellite carries two magnetometers: a Vector Field Magnetometer (VFM) coupled with a star tracker camera, to measure the direction of the magnetic field in space, and an Absolute Scalar Magnetometer (ASM), to measure its intensity. The ASM is the French contribution to the Swarm mission. This new generation instrument was designed by CEA-Leti and developed in close partnership with CNES, with scientific support from IPGP. Its operating principle is based on the atomic spectroscopy of the helium 4 metastable state. It makes use of the Zeeman's effect to transduce the magnetic field into a frequency, the signal being amplified by optical pumping. The primary role of the ASM is to provide absolute measurements of the magnetic field's strength at 1 Hz, for the in-flight calibration of the VFM. As the Swarm magnetic reference, the ASM scalar performance is crucial for the mission's success. Thanks to its innovative design, the ASM offers the best precision, resolution and absolute accuracy ever attained in space, with similar performance all along the orbit. In addition, thanks to an original architecture, the ASM implements on an experimental basis a capacity for providing simultaneously vector measurements at 1 Hz. This new feature makes it the first instrument capable of delivering both scalar and vector measurements simultaneously at the same point. Swarm offers a unique opportunity to validate the ASM vector data in orbit by comparison with the VFM's. Furthermore, the ASM can provide scalar data at a much higher sampling rate, when run in "burst" mode at 250 Hz, with a 100 Hz measurement bandwidth. An analysis of the spectral content of the magnetic field above 1 Hz becomes thus

  11. Absolute Calibration of the AXAF Telescope Effective Area

    NASA Technical Reports Server (NTRS)

    Kellogg, E.; Cohen, L.; Edgar, R.; Evans, I.; Freeman, M.; Gaetz, T.; Jerius, D.; McDermott, W. C.; McKinnon, P.; Murray, S.; Podgorski, W.; Schwartz, D.; VanSpeybroeck, L.; Wargelin, B.; Zombeck, M.; Weisskopf, M.; Elsner, R.; ODell, S.; Tennant, A.; Kolodziejczak, J.

    1997-01-01

    The prelaunch calibration of AXAF encompasses many aspects of the telescope. In principle, all that is needed is the complete point response function. This is, however, a function of energy, off-axis angle of the source, and operating mode of the facility. No single measurement would yield the entire result. Also, any calibration made prior to launch will be affected by changes in conditions after launch, such as the change from one g to zero g. The reflectivity of the mirror and perhaps even the detectors can change as well, for example by addition or removal of small amounts of material deposited on their surfaces. In this paper, we give a broad view of the issues in performing such a calibration, and discuss how they are being addressed in prelaunch preparation of AXAF. As our title indicates, we concentrate here on the total throughput of the observatory. This can be thought of as the integral of the point response function, i.e. the encircled energy, out ot the largest practical solid angle for an observation. Since there is no standard x-ray source in the sky whose flux is known to the -1% accuracy we are trying to achieve, we must do this calibration on the ground. we also must provide a means for monitoring any possible changes in this calibration from pre-launch until on-orbit operation can transfer the calibration to a celestial x-ray source whose emission is stable. In this paper, we analyze the elements of the absolute throughput calibration, which we call Effective Area. We review the requirements for calibrations of components or subsystems of the AXAF facility, including mirror, detectors, and gratings. We show how it is necessary to calibrate this ground-based detection system at standard man-made x-ray sources, such as electron storage rings. We present the status of all these calibrations, with indications of the measurements remaining to be done, even though the measurements on the AXAF flight optics and detectors will have been completed by the

  12. Clock time is absolute and universal

    NASA Astrophysics Data System (ADS)

    Shen, Xinhang

    2015-09-01

    A critical error is found in the Special Theory of Relativity (STR): mixing up the concepts of the STR abstract time of a reference frame and the displayed time of a physical clock, which leads to use the properties of the abstract time to predict time dilation on physical clocks and all other physical processes. Actually, a clock can never directly measure the abstract time, but can only record the result of a physical process during a period of the abstract time such as the number of cycles of oscillation which is the multiplication of the abstract time and the frequency of oscillation. After Lorentz Transformation, the abstract time of a reference frame expands by a factor gamma, but the frequency of a clock decreases by the same factor gamma, and the resulting multiplication i.e. the displayed time of a moving clock remains unchanged. That is, the displayed time of any physical clock is an invariant of Lorentz Transformation. The Lorentz invariance of the displayed times of clocks can further prove within the framework of STR our earth based standard physical time is absolute, universal and independent of inertial reference frames as confirmed by both the physical fact of the universal synchronization of clocks on the GPS satellites and clocks on the earth, and the theoretical existence of the absolute and universal Galilean time in STR which has proved that time dilation and space contraction are pure illusions of STR. The existence of the absolute and universal time in STR has directly denied that the reference frame dependent abstract time of STR is the physical time, and therefore, STR is wrong and all its predictions can never happen in the physical world.

  13. Brownian motion: Absolute negative particle mobility

    NASA Astrophysics Data System (ADS)

    Ros, Alexandra; Eichhorn, Ralf; Regtmeier, Jan; Duong, Thanh Tu; Reimann, Peter; Anselmetti, Dario

    2005-08-01

    Noise effects in technological applications, far from being a nuisance, can be exploited with advantage - for example, unavoidable thermal fluctuations have found application in the transport and sorting of colloidal particles and biomolecules. Here we use a microfluidic system to demonstrate a paradoxical migration mechanism in which particles always move in a direction opposite to the net acting force (`absolute negative mobility') as a result of an interplay between thermal noise, a periodic and symmetric microstructure, and a biased alternating-current electric field. This counterintuitive phenomenon could be used for bioanalytical purposes, for example in the separation and fractionation of colloids, biological molecules and cells.

  14. Arbitrary segments of absolute negative mobility

    NASA Astrophysics Data System (ADS)

    Chen, Ruyin; Nie, Linru; Chen, Chongyang; Wang, Chaojie

    2017-01-01

    In previous research work, investigators have reported only one or two segments of absolute negative mobility (ANM) in a periodic potential. In fact, many segments of ANM also occur in the system considered here. We investigate transport of an inertial particle in a gating ratchet periodic potential subjected to a constant bias force. Our numerical results show that its mean velocity can decrease with the bias force increasing, i.e. ANM phenomenon. Furthermore, the ANM can take place arbitrary segments, even up to more than thirty. Intrinsic physical mechanism and conditions for arbitrary segments of ANM to occur are discussed in detail.

  15. Absolute quantification of myocardial blood flow.

    PubMed

    Yoshinaga, Keiichiro; Manabe, Osamu; Tamaki, Nagara

    2016-07-21

    With the increasing availability of positron emission tomography (PET) myocardial perfusion imaging, the absolute quantification of myocardial blood flow (MBF) has become popular in clinical settings. Quantitative MBF provides an important additional diagnostic or prognostic information over conventional visual assessment. The success of MBF quantification using PET/computed tomography (CT) has increased the demand for this quantitative diagnostic approach to be more accessible. In this regard, MBF quantification approaches have been developed using several other diagnostic imaging modalities including single-photon emission computed tomography, CT, and cardiac magnetic resonance. This review will address the clinical aspects of PET MBF quantification and the new approaches to MBF quantification.

  16. An absolute radius scale for Saturn's rings

    NASA Technical Reports Server (NTRS)

    Nicholson, Philip D.; Cooke, Maren L.; Pelton, Emily

    1990-01-01

    Radio and stellar occultation observations of Saturn's rings made by the Voyager spacecraft are discussed. The data reveal systematic discrepancies of almost 10 km in some parts of the rings, limiting some of the investigations. A revised solution for Saturn's rotation pole has been proposed which removes the discrepancies between the stellar and radio occultation profiles. Corrections to previously published radii vary from -2 to -10 km for the radio occultation, and +5 to -6 km for the stellar occultation. An examination of spiral density waves in the outer A Ring supports that the revised absolute radii are in error by no more than 2 km.

  17. Absolute Rate Theories of Epigenetic Stability

    NASA Astrophysics Data System (ADS)

    Walczak, Aleksandra M.; Onuchic, Jose N.; Wolynes, Peter G.

    2006-03-01

    Spontaneous switching events in most characterized genetic switches are rare, resulting in extremely stable epigenetic properties. We show how simple arguments lead to theories of the rate of such events much like the absolute rate theory of chemical reactions corrected by a transmission factor. Both the probability of the rare cellular states that allow epigenetic escape, and the transmission factor, depend on the rates of DNA binding and unbinding events and on the rates of protein synthesis and degradation. Different mechanisms of escape from the stable attractors occur in the nonadiabatic, weakly adiabatic and strictly adiabatic regimes, characterized by the relative values of those input rates.

  18. Absolute rate theories of epigenetic stability

    NASA Astrophysics Data System (ADS)

    Walczak, Aleksandra M.; Onuchic, José N.; Wolynes, Peter G.

    2005-12-01

    Spontaneous switching events in most characterized genetic switches are rare, resulting in extremely stable epigenetic properties. We show how simple arguments lead to theories of the rate of such events much like the absolute rate theory of chemical reactions corrected by a transmission factor. Both the probability of the rare cellular states that allow epigenetic escape and the transmission factor depend on the rates of DNA binding and unbinding events and on the rates of protein synthesis and degradation. Different mechanisms of escape from the stable attractors occur in the nonadiabatic, weakly adiabatic, and strictly adiabatic regimes, characterized by the relative values of those input rates. rate theory | stochastic gene expression | gene switches

  19. Absolute method of measuring magnetic susceptibility

    USGS Publications Warehouse

    Thorpe, A.; Senftle, F.E.

    1959-01-01

    An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved. ?? 1959 The American Institute of Physics.

  20. Absolute Priority for a Vehicle in VANET

    NASA Astrophysics Data System (ADS)

    Shirani, Rostam; Hendessi, Faramarz; Montazeri, Mohammad Ali; Sheikh Zefreh, Mohammad

    In today's world, traffic jams waste hundreds of hours of our life. This causes many researchers try to resolve the problem with the idea of Intelligent Transportation System. For some applications like a travelling ambulance, it is important to reduce delay even for a second. In this paper, we propose a completely infrastructure-less approach for finding shortest path and controlling traffic light to provide absolute priority for an emergency vehicle. We use the idea of vehicular ad-hoc networking to reduce the imposed travelling time. Then, we simulate our proposed protocol and compare it with a centrally controlled traffic light system.

  1. Accuracy Analysis and Validation of the Mars Science Laboratory (MSL) Robotic Arm

    NASA Technical Reports Server (NTRS)

    Collins, Curtis L.; Robinson, Matthew L.

    2013-01-01

    The Mars Science Laboratory (MSL) Curiosity Rover is currently exploring the surface of Mars with a suite of tools and instruments mounted to the end of a five degree-of-freedom robotic arm. To verify and meet a set of end-to-end system level accuracy requirements, a detailed positioning uncertainty model of the arm was developed and exercised over the arm operational workspace. Error sources at each link in the arm kinematic chain were estimated and their effects propagated to the tool frames.A rigorous test and measurement program was developed and implemented to collect data to characterize and calibrate the kinematic and stiffness parameters of the arm. Numerous absolute and relative accuracy and repeatability requirements were validated with a combination of analysis and test data extrapolated to the Mars gravity and thermal environment. Initial results of arm accuracy and repeatability on Mars demonstrate the effectiveness of the modeling and test program as the rover continues to explore the foothills of Mount Sharp.

  2. A Method for Selecting between Fisher's Linear Classification Functions and Least Absolute Deviation in Predictive Discriminant Analysis.

    ERIC Educational Resources Information Center

    Meshbane, Alice; Morris, John D.

    A method for comparing the cross-validated classification accuracy of Fisher's linear classification functions (FLCFs) and the least absolute deviation is presented under varying data conditions for the two-group classification problem. With this method, separate-group as well as total-sample proportions of current classifications can be compared…

  3. Linear ultrasonic motor for absolute gravimeter.

    PubMed

    Jian, Yue; Yao, Zhiyuan; Silberschmidt, Vadim V

    2017-02-01

    Thanks to their compactness and suitability for vacuum applications, linear ultrasonic motors are considered as substitutes for classical electromagnetic motors as driving elements in absolute gravimeters. Still, their application is prevented by relatively low power output. To overcome this limitation and provide better stability, a V-type linear ultrasonic motor with a new clamping method is proposed for a gravimeter. In this paper, a mechanical model of stators with flexible clamping components is suggested, according to a design criterion for clamps of linear ultrasonic motors. After that, an effect of tangential and normal rigidity of the clamping components on mechanical output is studied. It is followed by discussion of a new clamping method with sufficient tangential rigidity and a capability to facilitate pre-load. Additionally, a prototype of the motor with the proposed clamping method was fabricated and the performance tests in vertical direction were implemented. Experimental results show that the suggested motor has structural stability and high dynamic performance, such as no-load speed of 1.4m/s and maximal thrust of 43N, meeting the requirements for absolute gravimeters.

  4. Why to compare absolute numbers of mitochondria.

    PubMed

    Schmitt, Sabine; Schulz, Sabine; Schropp, Eva-Maria; Eberhagen, Carola; Simmons, Alisha; Beisker, Wolfgang; Aichler, Michaela; Zischka, Hans

    2014-11-01

    Prompted by pronounced structural differences between rat liver and rat hepatocellular carcinoma mitochondria, we suspected these mitochondrial populations to differ massively in their molecular composition. Aiming to reveal these mitochondrial differences, we came across the issue on how to normalize such comparisons and decided to focus on the absolute number of mitochondria. To this end, fluorescently stained mitochondria were quantified by flow cytometry. For rat liver mitochondria, this approach resulted in mitochondrial protein contents comparable to earlier reports using alternative methods. We determined similar protein contents for rat liver, heart and kidney mitochondria. In contrast, however, lower protein contents were determined for rat brain mitochondria and for mitochondria from the rat hepatocellular carcinoma cell line McA 7777. This result challenges mitochondrial comparisons that rely on equal protein amounts as a typical normalization method. Exemplarily, we therefore compared the activity and susceptibility toward inhibition of complex II of rat liver and hepatocellular carcinoma mitochondria and obtained significant discrepancies by either normalizing to protein amount or to absolute mitochondrial number. Importantly, the latter normalization, in contrast to the former, demonstrated a lower complex II activity and higher susceptibility toward inhibition in hepatocellular carcinoma mitochondria compared to liver mitochondria. These findings demonstrate that solely normalizing to protein amount may obscure essential molecular differences between mitochondrial populations.

  5. The absolute threshold of cone vision

    PubMed Central

    Koeing, Darran; Hofer, Heidi

    2013-01-01

    We report measurements of the absolute threshold of cone vision, which has been previously underestimated due to sub-optimal conditions or overly strict subjective response criteria. We avoided these limitations by using optimized stimuli and experimental conditions while having subjects respond within a rating scale framework. Small (1′ fwhm), brief (34 msec), monochromatic (550 nm) stimuli were foveally presented at multiple intensities in dark-adapted retina for 5 subjects. For comparison, 4 subjects underwent similar testing with rod-optimized stimuli. Cone absolute threshold, that is, the minimum light energy for which subjects were just able to detect a visual stimulus with any response criterion, was 203 ± 38 photons at the cornea, ∼0.47 log units lower than previously reported. Two-alternative forced-choice measurements in a subset of subjects yielded consistent results. Cone thresholds were less responsive to criterion changes than rod thresholds, suggesting a limit to the stimulus information recoverable from the cone mosaic in addition to the limit imposed by Poisson noise. Results were consistent with expectations for detection in the face of stimulus uncertainty. We discuss implications of these findings for modeling the first stages of human cone vision and interpreting psychophysical data acquired with adaptive optics at the spatial scale of the receptor mosaic. PMID:21270115

  6. [Estimation of absolute risk for fracture].

    PubMed

    Fujiwara, Saeko

    2009-03-01

    Osteoporosis treatment aims to prevent fractures and maintain the QOL of the elderly. However, persons at high risk of future fracture cannot be effectively identified on the basis of bone density (BMD) alone, although BMD is used as an diagnostic criterion. Therefore, the WHO recommended that absolute risk for fracture (10-year probability of fracture) for each individual be evaluated and used as an index for intervention threshold. The 10-year probability of fracture is calculated based on age, sex, BMD at the femoral neck (body mass index if BMD is not available), history of previous fractures, parental hip fracture history, smoking, steroid use, rheumatoid arthritis, secondary osteoporosis and alcohol consumption. The WHO has just announced the development of a calculation tool (FRAX: WHO Fracture Risk Assessment Tool) in February this year. Fractures could be prevented more effectively if, based on each country's medical circumstances, an absolute risk value for fracture to determine when to start medical treatment is established and persons at high risk of fracture are identified and treated accordingly.

  7. Absolute Electron Extraction Efficiency of Liquid Xenon

    NASA Astrophysics Data System (ADS)

    Kamdin, Katayun; Mizrachi, Eli; Morad, James; Sorensen, Peter

    2016-03-01

    Dual phase liquid/gas xenon time projection chambers (TPCs) currently set the world's most sensitive limits on weakly interacting massive particles (WIMPs), a favored dark matter candidate. These detectors rely on extracting electrons from liquid xenon into gaseous xenon, where they produce proportional scintillation. The proportional scintillation from the extracted electrons serves to internally amplify the WIMP signal; even a single extracted electron is detectable. Credible dark matter searches can proceed with electron extraction efficiency (EEE) lower than 100%. However, electrons systematically left at the liquid/gas boundary are a concern. Possible effects include spontaneous single or multi-electron proportional scintillation signals in the gas, or charging of the liquid/gas interface or detector materials. Understanding EEE is consequently a serious concern for this class of rare event search detectors. Previous EEE measurements have mostly been relative, not absolute, assuming efficiency plateaus at 100%. I will present an absolute EEE measurement with a small liquid/gas xenon TPC test bed located at Lawrence Berkeley National Laboratory.

  8. Standardization of the cumulative absolute velocity

    SciTech Connect

    O'Hara, T.F.; Jacobson, J.P. )

    1991-12-01

    EPRI NP-5930, A Criterion for Determining Exceedance of the Operating Basis Earthquake,'' was published in July 1988. As defined in that report, the Operating Basis Earthquake (OBE) is exceeded when both a response spectrum parameter and a second damage parameter, referred to as the Cumulative Absolute Velocity (CAV), are exceeded. In the review process of the above report, it was noted that the calculation of CAV could be confounded by time history records of long duration containing low (nondamaging) acceleration. Therefore, it is necessary to standardize the method of calculating CAV to account for record length. This standardized methodology allows consistent comparisons between future CAV calculations and the adjusted CAV threshold value based upon applying the standardized methodology to the data set presented in EPRI NP-5930. The recommended method to standardize the CAV calculation is to window its calculation on a second-by-second basis for a given time history. If the absolute acceleration exceeds 0.025g at any time during each one second interval, the earthquake records used in EPRI NP-5930 have been reanalyzed and the adjusted threshold of damage for CAV was found to be 0.16g-set.

  9. Alternatives to accuracy and bias metrics based on percentage errors for radiation belt modeling applications

    SciTech Connect

    Morley, Steven Karl

    2016-07-01

    This report reviews existing literature describing forecast accuracy metrics, concentrating on those based on relative errors and percentage errors. We then review how the most common of these metrics, the mean absolute percentage error (MAPE), has been applied in recent radiation belt modeling literature. Finally, we describe metrics based on the ratios of predicted to observed values (the accuracy ratio) that address the drawbacks inherent in using MAPE. Specifically, we define and recommend the median log accuracy ratio as a measure of bias and the median symmetric accuracy as a measure of accuracy.

  10. Extracting infrared absolute reflectance from relative reflectance measurements.

    PubMed

    Berets, Susan L; Milosevic, Milan

    2012-06-01

    Absolute reflectance measurements are valuable to the optics industry for development of new materials and optical coatings. Yet, absolute reflectance measurements are notoriously difficult to make. In this paper, we investigate the feasibility of extracting the absolute reflectance from a relative reflectance measurement using a reference material with known refractive index.

  11. A Conceptual Approach to Absolute Value Equations and Inequalities

    ERIC Educational Resources Information Center

    Ellis, Mark W.; Bryson, Janet L.

    2011-01-01

    The absolute value learning objective in high school mathematics requires students to solve far more complex absolute value equations and inequalities. When absolute value problems become more complex, students often do not have sufficient conceptual understanding to make any sense of what is happening mathematically. The authors suggest that the…

  12. Critical thinking and accuracy of nurses' diagnoses.

    PubMed

    Lunney, Margaret

    2003-01-01

    Interpretations of patient data are complex and diverse, contributing to a risk of low accuracy nursing diagnoses. This risk is confirmed in research findings that accuracy of nurses' diagnoses varied widely from high to low. Highly accurate diagnoses are essential, however, to guide nursing interventions for the achievement of positive health outcomes. Development of critical thinking abilities is likely to improve accuracy of nurses' diagnoses. New views of critical thinking serve as a basis for critical thinking in nursing. Seven cognitive skills and ten habits of mind are identified as dimensions of critical thinking for use in the diagnostic process. Application of the cognitive skills of critical thinking illustrates the importance of using critical thinking for accuracy of nurses' diagnoses. Ten strategies are proposed for self-development of critical thinking abilities.

  13. What do we mean by accuracy in geomagnetic measurements?

    USGS Publications Warehouse

    Green, A.W.

    1990-01-01

    High accuracy is what distinguishes measurements made at the world's magnetic observatories from other types of geomagnetic measurements. High accuracy in determining the absolute values of the components of the Earth's magnetic field is essential to studying geomagnetic secular variation and processes at the core mantle boundary, as well as some magnetospheric processes. In some applications of geomagnetic data, precision (or resolution) of measurements may also be important. In addition to accuracy and resolution in the amplitude domain, it is necessary to consider these same quantities in the frequency and space domains. New developments in geomagnetic instruments and communications make real-time, high accuracy, global geomagnetic observatory data sets a real possibility. There is a growing realization in the scientific community of the unique relevance of geomagnetic observatory data to the principal contemporary problems in solid Earth and space physics. Together, these factors provide the promise of a 'renaissance' of the world's geomagnetic observatory system. ?? 1990.

  14. EOS mapping accuracy study

    NASA Technical Reports Server (NTRS)

    Forrest, R. B.; Eppes, T. A.; Ouellette, R. J.

    1973-01-01

    Studies were performed to evaluate various image positioning methods for possible use in the earth observatory satellite (EOS) program and other earth resource imaging satellite programs. The primary goal is the generation of geometrically corrected and registered images, positioned with respect to the earth's surface. The EOS sensors which were considered were the thematic mapper, the return beam vidicon camera, and the high resolution pointable imager. The image positioning methods evaluated consisted of various combinations of satellite data and ground control points. It was concluded that EOS attitude control system design must be considered as a part of the image positioning problem for EOS, along with image sensor design and ground image processing system design. Study results show that, with suitable efficiency for ground control point selection and matching activities during data processing, extensive reliance should be placed on use of ground control points for positioning the images obtained from EOS and similar programs.

  15. Negative absolute temperature for motional degrees of freedom.

    PubMed

    Braun, S; Ronzheimer, J P; Schreiber, M; Hodgman, S S; Rom, T; Bloch, I; Schneider, U

    2013-01-04

    Absolute temperature is usually bound to be positive. Under special conditions, however, negative temperatures-in which high-energy states are more occupied than low-energy states-are also possible. Such states have been demonstrated in localized systems with finite, discrete spectra. Here, we prepared a negative temperature state for motional degrees of freedom. By tailoring the Bose-Hubbard Hamiltonian, we created an attractively interacting ensemble of ultracold bosons at negative temperature that is stable against collapse for arbitrary atom numbers. The quasimomentum distribution develops sharp peaks at the upper band edge, revealing thermal equilibrium and bosonic coherence over several lattice sites. Negative temperatures imply negative pressures and open up new parameter regimes for cold atoms, enabling fundamentally new many-body states.

  16. High accuracy OMEGA timekeeping

    NASA Technical Reports Server (NTRS)

    Imbier, E. A.

    1982-01-01

    The Smithsonian Astrophysical Observatory (SAO) operates a worldwide satellite tracking network which uses a combination of OMEGA as a frequency reference, dual timing channels, and portable clock comparisons to maintain accurate epoch time. Propagational charts from the U.S. Coast Guard OMEGA monitor program minimize diurnal and seasonal effects. Daily phase value publications of the U.S. Naval Observatory provide corrections to the field collected timing data to produce an averaged time line comprised of straight line segments called a time history file (station clock minus UTC). Depending upon clock location, reduced time data accuracies of between two and eight microseconds are typical.

  17. Accuracy of perturbative master equations.

    PubMed

    Fleming, C H; Cummings, N I

    2011-03-01

    We consider open quantum systems with dynamics described by master equations that have perturbative expansions in the system-environment interaction. We show that, contrary to intuition, full-time solutions of order-2n accuracy require an order-(2n+2) master equation. We give two examples of such inaccuracies in the solutions to an order-2n master equation: order-2n inaccuracies in the steady state of the system and order-2n positivity violations. We show how these arise in a specific example for which exact solutions are available. This result has a wide-ranging impact on the validity of coupling (or friction) sensitive results derived from second-order convolutionless, Nakajima-Zwanzig, Redfield, and Born-Markov master equations.

  18. Noninvasive absolute cerebral oximetry with frequency-domain near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Hallacoglu, Bertan

    Near-infrared spectroscopy (NIRS) measurements of absolute concentrations of oxy-hemoglobin and deoxy-hemoglobin in the human brain can provide critical information about cerebral physiology in terms of cerebral blood volume, blood flow, oxygen delivery, and metabolic rate of oxygen. We developed several frequency domain NIRS data acquisition and analysis methods aimed at absolute measurements of hemoglobin concentration and saturation in cerebral tissue of adult human subjects. Extensive experimental investigations were carried out in various homogenous and two-layered tissue-mimicking phantoms, and biological tissues. The advantages and limitations of commonly used homogenous models and inversion strategies were thoroughly investigated. Prior to human subjects, extensive studies were carried out in in vivo animal models. In rabbits, absolute hemoglobin oxygen desaturation was shown to depend strongly on surgically induced testicular torsion. Methods developed in this study were then adapted for measurements in the rat brain. Absolute values were demonstrated to discern cerebrovascular impairment in a rat model of diet-induced vascular cognitive impairment. These results facilitated the development of clinically useful optical measures of cerebrovascular health. In a large group of human subjects, employing a homogeneous model for absolute measurements was shown to be reliable and robust. However, it was also shown to be limited due to the relatively thick extracerebral tissue. The procedure we develop in this work and the thesis thereof performs a nonlinear inversion procedure with six unknown parameters with no other prior knowledge for the retrieval of the optical coefficients and top layer thickness with high accuracy on two-layered media. Our absolute measurements of cerebral hemoglobin concentration and saturation are based on the discrimination of extracerebral and cerebral tissue layers, and they can enhance the impact of NIRS for cerebral hemodynamics and

  19. Ridge-spotting: A new test for Pacific absolute plate motion models

    NASA Astrophysics Data System (ADS)

    Wessel, Paul; Müller, R. Dietmar

    2016-06-01

    Relative plate motions provide high-resolution descriptions of motions of plates relative to other plates. Yet geodynamically, motions of plates relative to the mantle are required since such motions can be attributed to forces (e.g., slab pull and ridge push) acting upon the plates. Various reference frames have been proposed, such as the hot spot reference frame, to link plate motions to a mantle framework. Unfortunately, both accuracy and precision of absolute plate motion models lag behind those of relative plate motion models. Consequently, it is paramount to use relative plate motions in improving our understanding of absolute plate motions. A new technique called "ridge-spotting" combines absolute and relative plate motions and examines the viability of proposed absolute plate motion models. We test the method on six published Pacific absolute plate motions models, including fixed and moving hot spot models as well as a geodynamically derived model. Ridge-spotting reconstructs the Pacific-Farallon and Pacific-Antarctica ridge systems over the last 80 Myr. All six absolute plate motion models predict large amounts of northward migration and monotonic clockwise rotation for the Pacific-Farallon ridge. A geodynamic implication of our ridge migration predictions is that the suggestion that the Pacific-Farallon ridge may have been pinned by a large mantle upwelling is not supported. Unexpected or erratic ridge behaviors may be tied to limitations in the models themselves or (for Indo-Atlantic models) discrepancies in the plate circuits used to project models into the Pacific realm. Ridge-spotting is promising and will be extended to include more plates and other ocean basins.

  20. Use of Absolute and Comparative Performance Feedback in Absolute and Comparative Judgments and Decisions

    ERIC Educational Resources Information Center

    Moore, Don A.; Klein, William M. P.

    2008-01-01

    Which matters more--beliefs about absolute ability or ability relative to others? This study set out to compare the effects of such beliefs on satisfaction with performance, self-evaluations, and bets on future performance. In Experiment 1, undergraduate participants were told they had answered 20% correct, 80% correct, or were not given their…

  1. Absolute localization of ground robots by matching LiDAR and image data in dense forested environments

    NASA Astrophysics Data System (ADS)

    Hussein, Marwan; Renner, Matthew; Iagnemma, Karl

    2014-06-01

    A method for the autonomous geolocation of ground vehicles in forest environments is discussed. The method provides an estimate of the global horizontal position of a vehicle strictly based on finding a geometric match between a map of observed tree stems, scanned in 3D by Light Detection and Ranging (LiDAR) sensors onboard the vehicle, to another stem map generated from the structure of tree crowns analyzed from high resolution aerial orthoimagery of the forest canopy. Extraction of stems from 3D data is achieved by using Support Vector Machine (SVM) classifiers and height above ground filters that separate ground points from vertical stem features. Identification of stems from overhead imagery is achieved by finding the centroids of tree crowns extracted using a watershed segmentation algorithm. Matching of the two maps is achieved by using a robust Iterative Closest Point (ICP) algorithm that determines the rotation and translation vectors to align the datasets. The alignment is used to calculate the absolute horizontal location of the vehicle. The method has been tested with real-world data and has been able to estimate vehicle geoposition with an average error of less than 2 m. It is noted that the algorithm's accuracy performance is currently limited by the accuracy and resolution of aerial orthoimagery used. The method can be used in real-time as a complement to the Global Positioning System (GPS) in areas where signal coverage is inadequate due to attenuation by the forest canopy, or due to intentional denied access. The method has two key properties that are significant: i) It does not require a priori knowledge of the area surrounding the robot. ii) Uses the geometry of detected tree stems as the only input to determine horizontal geoposition.

  2. Absolute activity measurement of radon gas at IRA-METAS

    NASA Astrophysics Data System (ADS)

    Spring, Philippe; Nedjadi, Youcef; Bailat, Claude; Triscone, Gilles; Bochud, François

    2006-12-01

    This paper describes the system of the Swiss national metrological institute (IRA-METAS) for the absolute standardisation of radon gas. This method relies on condensing radon under vacuum conditions within a specified cold area using a cryogenerator, and detecting its alpha particles with an ion-implanted silicon detector, through a very accurately defined solid angle. The accuracy of this defined solid angle standardisation technique was corroborated by another primary measurement method involving 4 πγ NaI(Tl) integral counting and Monte Carlo efficiency calculations. The 222Rn standard submitted by IRA-METAS to the Système International de Référence (SIR) at the Bureau International des Poids et Mesures (BIPM) has also been found to be consistent with an analogous standard submitted by the German national metrological institute (PTB). IRA-METAS is able to deliver radon standards, with activities ranging from a few kBq to 350 kBq, in NIST-Type ampoules, and glass or steel containers usable for calibrating radon-measuring instruments.

  3. Scanning micro-resonator direct-comb absolute spectroscopy

    NASA Astrophysics Data System (ADS)

    Gambetta, Alessio; Cassinerio, Marco; Gatti, Davide; Laporta, Paolo; Galzerano, Gianluca

    2016-10-01

    Direct optical Frequency Comb Spectroscopy (DFCS) is proving to be a fundamental tool in many areas of science and technology thanks to its unique performance in terms of ultra-broadband, high-speed detection and frequency accuracy, allowing for high-fidelity mapping of atomic and molecular energy structure. Here we present a novel DFCS approach based on a scanning Fabry-Pérot micro-cavity resonator (SMART) providing a simple, compact and accurate method to resolve the mode structure of an optical frequency comb. The SMART approach, while drastically reducing system complexity, allows for a straightforward absolute calibration of the optical-frequency axis with an ultimate resolution limited by the micro-resonator resonance linewidth and can be used in any spectral region from UV to THz. We present an application to high-precision spectroscopy of acetylene at 1.54 μm, demonstrating performances comparable or even better than current state-of-the-art DFCS systems in terms of sensitivity, optical bandwidth and frequency-resolution.

  4. Scanning micro-resonator direct-comb absolute spectroscopy

    PubMed Central

    Gambetta, Alessio; Cassinerio, Marco; Gatti, Davide; Laporta, Paolo; Galzerano, Gianluca

    2016-01-01

    Direct optical Frequency Comb Spectroscopy (DFCS) is proving to be a fundamental tool in many areas of science and technology thanks to its unique performance in terms of ultra-broadband, high-speed detection and frequency accuracy, allowing for high-fidelity mapping of atomic and molecular energy structure. Here we present a novel DFCS approach based on a scanning Fabry-Pérot micro-cavity resonator (SMART) providing a simple, compact and accurate method to resolve the mode structure of an optical frequency comb. The SMART approach, while drastically reducing system complexity, allows for a straightforward absolute calibration of the optical-frequency axis with an ultimate resolution limited by the micro-resonator resonance linewidth and can be used in any spectral region from UV to THz. We present an application to high-precision spectroscopy of acetylene at 1.54 μm, demonstrating performances comparable or even better than current state-of-the-art DFCS systems in terms of sensitivity, optical bandwidth and frequency-resolution. PMID:27752132

  5. Alignment and absolute wavelength calibration of imaging Bragg spectrometers

    NASA Astrophysics Data System (ADS)

    Bertschinger, G.; Marchuk, O.; Barnsley, R.

    2016-11-01

    In the present and the next generation of fusion devices, imaging Bragg spectrometers are key diagnostics to measure plasma parameters in the hot core, especially ion temperature and plasma rotation. The latter quantities are routinely obtained using the Doppler-width and -shift of the emitted spectral lines, respectively. Line shift measurements require absolute accuracies Δλ/λ of about 10 ppm, where λ-is the observed wavelength. For ITER and the present fusion devices, spectral lines of He-and H-like argon, iron, and krypton as well as Ne-like tungsten are foreseen for the measurements. For these lines, Kα lines can be found, some in higher order, which fit into the narrow energy window of the spectrometers. For arbitrary wavelength settings, Kα lines are also used to measure the miscut of the spherical crystals; afterwards the spectrometers can be set according to the geometrical imaging properties using coordinate measurement machines. For the spectrometers measuring Lyα lines of H-like ions, fluorescence targets can provide in situ localized calibration lines on the spectra. The fluorescence targets are used best in transmission and are excited by the thermal x-ray radiation of the plasma. An analytic theory of fluorescence is worked out.

  6. Absolute nonlocality via distributed computing without communication

    NASA Astrophysics Data System (ADS)

    Czekaj, Ł.; Pawłowski, M.; Vértesi, T.; Grudka, A.; Horodecki, M.; Horodecki, R.

    2015-09-01

    Understanding the role that quantum entanglement plays as a resource in various information processing tasks is one of the crucial goals of quantum information theory. Here we propose an alternative perspective for studying quantum entanglement: distributed computation of functions without communication between nodes. To formalize this approach, we propose identity games. Surprisingly, despite no signaling, we obtain that nonlocal quantum strategies beat classical ones in terms of winning probability for identity games originating from certain bipartite and multipartite functions. Moreover we show that, for a majority of functions, access to general nonsignaling resources boosts success probability two times in comparison to classical ones for a number of large enough outputs. Because there are no constraints on the inputs and no processing of the outputs in the identity games, they detect very strong types of correlations: absolute nonlocality.

  7. In vivo absorption spectroscopy for absolute measurement.

    PubMed

    Furukawa, Hiromitsu; Fukuda, Takashi

    2012-10-01

    In in vivo spectroscopy, there are differences between individual subjects in parameters such as tissue scattering and sample concentration. We propose a method that can provide the absolute value of a particular substance concentration, independent of these individual differences. Thus, it is not necessary to use the typical statistical calibration curve, which assumes an average level of scattering and an averaged concentration over individual subjects. This method is expected to greatly reduce the difficulties encountered during in vivo measurements. As an example, for in vivo absorption spectroscopy, the method was applied to the reflectance measurement in retinal vessels to monitor their oxygen saturation levels. This method was then validated by applying it to the tissue phantom under a variety of absorbance values and scattering efficiencies.

  8. Determining Absolute Zero Using a Tuning Fork

    NASA Astrophysics Data System (ADS)

    Goldader, Jeffrey D.

    2008-04-01

    The Celsius and Kelvin temperature scales, we tell our students, are related. We explain that a change in temperature of 1°C corresponds to a change of 1 Kelvin and that atoms and molecules have zero kinetic energy at zero Kelvin, -273°C. In this paper, we will show how students can derive the relationship between the Celsius and Kelvin temperature scales using a simple, well-known physics experiment. By making multiple measurements of the speed of sound at different temperatures, using the classic physics experiment of determining the speed of sound with a tuning fork and variable-length tube, they can determine the temperature at which the speed of sound is zero—absolute zero.

  9. Absolute measurements of fast neutrons using yttrium.

    PubMed

    Roshan, M V; Springham, S V; Rawat, R S; Lee, P; Krishnan, M

    2010-08-01

    Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be f(n) approximately 4.1x10(-4) with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 10(8) neutrons per discharge.

  10. Absolute bioavailability of quinine formulations in Nigeria.

    PubMed

    Babalola, C P; Bolaji, O O; Ogunbona, F A; Ezeomah, E

    2004-09-01

    This study compared the absolute bioavailability of quinine sulphate as capsule and as tablet against the intravenous (i.v.) infusion of the drug in twelve male volunteers. Six of the volunteers received intravenous infusion over 4 h as well as the capsule formulation of the drug in a cross-over manner, while the other six received the tablet formulation. Blood samples were taken at predetermined time intervals and plasma analysed for quinine (QN) using reversed-phase HPLC method. QN was rapidly absorbed after the two oral formulations with average t(max) of 2.67 h for both capsule and tablet. The mean elimination half-life of QN from the i.v. and oral dosage forms varied between 10 and 13.5 hr and were not statistically different (P > 0.05). On the contrary, the maximum plasma concentration (C(max)) and area under the curve (AUC) from capsule were comparable to those from i.v. (P > 0.05), while these values were markedly higher than values from tablet formulation (P < 0.05). The therapeutic QN plasma levels were not achieved with the tablet formulation. The absolute bioavailability (F) were 73% (C.l., 53.3 - 92.4%) and 39 % (C.I., 21.7 - 56.6%) for the capsule and tablet respectively and the difference was significant (P < 0.05). The subtherapeutic levels obtained from the tablet form used in this study may cause treatment failure during malaria and caution should be taken when predictions are made from results obtained from different formulations of QN.

  11. Test Plan for a Calibration Demonstration System for the Reflected Solar Instrument for the Climate Absolute Radiance and Refractivity Observatory

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; McCorkel, Joel; Hair, Jason; McAndrew, Brendan; Daw, Adrian; Jennings, Donald; Rabin, Douglas

    2012-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission addresses the need to observe high-accuracy, long-term climate change trends and to use decadal change observations as the most critical method to determine the accuracy of climate change. One of the major objectives of CLARREO is to advance the accuracy of SI traceable absolute calibration at infrared and reflected solar wavelengths. This advance is required to reach the on-orbit absolute accuracy required to allow climate change observations to survive data gaps while remaining sufficiently accurate to observe climate change to within the uncertainty of the limit of natural variability. While these capabilities exist at NIST in the laboratory, there is a need to demonstrate that it can move successfully from NIST to NASA and/or instrument vendor capabilities for future spaceborne instruments. The current work describes the test plan for the Solar, Lunar for Absolute Reflectance Imaging Spectroradiometer (SOLARIS) which is the calibration demonstration system (CDS) for the reflected solar portion of CLARREO. The goal of the CDS is to allow the testing and evaluation of calibration approaches , alternate design and/or implementation approaches and components for the CLARREO mission. SOLARIS also provides a test-bed for detector technologies, non-linearity determination and uncertainties, and application of future technology developments and suggested spacecraft instrument design modifications. The end result of efforts with the SOLARIS CDS will be an SI-traceable error budget for reflectance retrieval using solar irradiance as a reference and methods for laboratory-based, absolute calibration suitable for climate-quality data collections. The CLARREO mission addresses the need to observe high-accuracy, long-term climate change trends and advance the accuracy of SI traceable absolute calibration. The current work describes the test plan for the SOLARIS which is the calibration demonstration

  12. Multi-Channel Optical Coherence Elastography Using Relative and Absolute Shear-Wave Time of Flight

    PubMed Central

    Elyas, Eli; Grimwood, Alex; Erler, Janine T.; Robinson, Simon P.; Cox, Thomas R.; Woods, Daniel; Clowes, Peter; De Luca, Ramona; Marinozzi, Franco; Fromageau, Jérémie; Bamber, Jeffrey C.

    2017-01-01

    Elastography, the imaging of elastic properties of soft tissues, is well developed for macroscopic clinical imaging of soft tissues and can provide useful information about various pathological processes which is complementary to that provided by the original modality. Scaling down of this technique should ply the field of cellular biology with valuable information with regard to elastic properties of cells and their environment. This paper evaluates the potential to develop such a tool by modifying a commercial optical coherence tomography (OCT) device to measure the speed of shear waves propagating in a three-dimensional (3D) medium. A needle, embedded in the gel, was excited to vibrate along its long axis and the displacement as a function of time and distance from the needle associated with the resulting shear waves was detected using four M-mode images acquired simultaneously using a commercial four-channel swept-source OCT system. Shear-wave time of arrival (TOA) was detected by tracking the axial OCT-speckle motion using cross-correlation methods. Shear-wave speed was then calculated from inter-channel differences of TOA for a single burst (the relative TOA method) and compared with the shear-wave speed determined from positional differences of TOA for a single channel over multiple bursts (the absolute TOA method). For homogeneous gels the relative method provided shear-wave speed with acceptable precision and accuracy when judged against the expected linear dependence of shear modulus on gelatine concentration (R2 = 0.95) and ultimate resolution capabilities limited by 184μm inter-channel distance. This overall approach shows promise for its eventual provision as a research tool in cancer cell biology. Further work is required to optimize parameters such as vibration frequency, burst length and amplitude, and to assess the lateral and axial resolutions of this type of device as well as to create 3D elastograms. PMID:28107368

  13. Multi-Channel Optical Coherence Elastography Using Relative and Absolute Shear-Wave Time of Flight.

    PubMed

    Elyas, Eli; Grimwood, Alex; Erler, Janine T; Robinson, Simon P; Cox, Thomas R; Woods, Daniel; Clowes, Peter; De Luca, Ramona; Marinozzi, Franco; Fromageau, Jérémie; Bamber, Jeffrey C

    2017-01-01

    Elastography, the imaging of elastic properties of soft tissues, is well developed for macroscopic clinical imaging of soft tissues and can provide useful information about various pathological processes which is complementary to that provided by the original modality. Scaling down of this technique should ply the field of cellular biology with valuable information with regard to elastic properties of cells and their environment. This paper evaluates the potential to develop such a tool by modifying a commercial optical coherence tomography (OCT) device to measure the speed of shear waves propagating in a three-dimensional (3D) medium. A needle, embedded in the gel, was excited to vibrate along its long axis and the displacement as a function of time and distance from the needle associated with the resulting shear waves was detected using four M-mode images acquired simultaneously using a commercial four-channel swept-source OCT system. Shear-wave time of arrival (TOA) was detected by tracking the axial OCT-speckle motion using cross-correlation methods. Shear-wave speed was then calculated from inter-channel differences of TOA for a single burst (the relative TOA method) and compared with the shear-wave speed determined from positional differences of TOA for a single channel over multiple bursts (the absolute TOA method). For homogeneous gels the relative method provided shear-wave speed with acceptable precision and accuracy when judged against the expected linear dependence of shear modulus on gelatine concentration (R2 = 0.95) and ultimate resolution capabilities limited by 184μm inter-channel distance. This overall approach shows promise for its eventual provision as a research tool in cancer cell biology. Further work is required to optimize parameters such as vibration frequency, burst length and amplitude, and to assess the lateral and axial resolutions of this type of device as well as to create 3D elastograms.

  14. Fully distributed absolute blood flow velocity measurement for middle cerebral arteries using Doppler optical coherence tomography

    PubMed Central

    Qi, Li; Zhu, Jiang; Hancock, Aneeka M.; Dai, Cuixia; Zhang, Xuping; Frostig, Ron D.; Chen, Zhongping

    2016-01-01

    Doppler optical coherence tomography (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow velocity at a high accuracy. However, the measurement of total absolute blood flow velocity (BFV) of major cerebral arteries is still a difficult problem since it is related to vessel geometry. In this paper, we present a volumetric vessel reconstruction approach that is capable of measuring the absolute BFV distributed along the entire middle cerebral artery (MCA) within a large field-of-view. The Doppler angle at each point of the MCA, representing the vessel geometry, is derived analytically by localizing the artery from pure DOCT images through vessel segmentation and skeletonization. Our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches. Experiments on rodents using swept-source optical coherence tomography showed that our approach was able to reveal the consequences of permanent MCA occlusion with absolute BFV measurement. PMID:26977365

  15. Radiocarbon dating accuracy improved

    NASA Astrophysics Data System (ADS)

    Scientists have extended the accuracy of carbon-14 (14C) dating by correlating dates older than 8,000 years with uranium-thorium dates that span from 8,000 to 30,000 years before present (ybp, present = 1950). Edouard Bard, Bruno Hamelin, Richard Fairbanks and Alan Zindler, working at Columbia University's Lamont-Doherty Geological Observatory, dated corals from reefs off Barbados using both 14C and uranium-234/thorium-230 by thermal ionization mass spectrometry techniques. They found that the two age data sets deviated in a regular way, allowing the scientists to correlate the two sets of ages. The 14C dates were consistently younger than those determined by uranium-thorium, and the discrepancy increased to about 3,500 years at 20,000 ybp.

  16. Accuracy of eye position for saccades and smooth pursuit

    PubMed Central

    Shanidze, Natela; Ghahghaei, Saeideh; Verghese, Preeti

    2016-01-01

    In this study, we address the question of whether a target is foveated during smooth pursuit. Specifically, we examine whether smooth pursuit eye movements land near the center-of-mass of the target, as is the case for saccades. To that end, we instructed eight untrained, healthy participants to follow moving targets, presented monocularly in a scanning laser ophthalmoscope. Stimuli moved either in a modified step-ramp (smooth pursuit), or made a single step (saccade), stepping 6° from the center. Targets were ring-shaped and either 0.6° or 1.7° in diameter. In an additional set of experiments, two participants collected more extensive data on smooth pursuit and saccades for a larger range of target sizes (0.6°, 1.7°, or 4.3°). During pursuit, eyes were rarely placed at target center, even when participants' fixational stability was taken into account. Furthermore, there was a clear tendency for distance from target center to increase with target size. This outcome was in contrast to saccades, where there was no effect of target size across participants. The difference in foveal placement between the two types of eye movements is consistent with their different purposes: closer inspection of the target for saccades versus maintenance of the target in the visual field for smooth pursuit. PMID:28006073

  17. Accuracy Test of Microsoft Kinect for Human Morphologic Measurements

    NASA Astrophysics Data System (ADS)

    Molnár, B.; Toth, C. K.; Detrekői, A.

    2012-08-01

    The Microsoft Kinect sensor, a popular gaming console, is widely used in a large number of applications, including close-range 3D measurements. This low-end device is rather inexpensive compared to similar active imaging systems. The Kinect sensors include an RGB camera, an IR projector, an IR camera and an audio unit. The human morphologic measurements require high accuracy with fast data acquisition rate. To achieve the highest accuracy, the depth sensor and the RGB camera should be calibrated and co-registered to achieve high-quality 3D point cloud as well as optical imagery. Since this is a low-end sensor, developed for different purpose, the accuracy could be critical for 3D measurement-based applications. Therefore, two types of accuracy test are performed: (1) for describing the absolute accuracy, the ranging accuracy of the device in the range of 0.4 to 15 m should be estimated, and (2) the relative accuracy of points depending on the range should be characterized. For the accuracy investigation, a test field was created with two spheres, while the relative accuracy is described by sphere fitting performance and the distance estimation between the sphere center points. Some other factors can be also considered, such as the angle of incidence or the material used in these tests. The non-ambiguity range of the sensor is from 0.3 to 4 m, but, based on our experiences, it can be extended up to 20 m. Obviously, this methodology raises some accuracy issues which make accuracy testing really important.

  18. First report on Swarm's Absolute Scalar Magnetometers and their various operating modes

    NASA Astrophysics Data System (ADS)

    Hulot, Gauthier; Léger, Jean-Michel; Fratter, Isabelle; Jager, Thomas; Bertrand, François; Vigneron, Pierre; Brocco, Laura; Crespo-Grau, Raul; Chulliat, Arnaud; Lalanne, Xavier; Boness, Axel

    2014-05-01

    Each of the three ESA Swarm satellites carries a vector field magnetometer (VFM) and an absolute scalar magnetometer (ASM), positioned on a boom away from the body of the satellite to minimize undesired magnetic perturbations, and distant enough from each other to avoid crosstalk. The VFM further shares an optical bench with a star imager (STR), to which it is thus rigidly attached. The primary role of the ASM is to provide precise 1 Hz absolute field intensity measurements, while the VFM and STR provide the additional data needed to accurately reconstruct the vector field. Each ASM instrument, however, can also produce 1 Hz experimental vector data without affecting its ability to deliver absolute scalar data. If requested, it can also run a 250 Hz scalar burst mode. Both these capacities have been operated on the three Swarm satellites during commissioning. In this talk, we will present and discuss early results from these various operating modes.

  19. Bayesian Methods for Medical Test Accuracy

    PubMed Central

    Broemeling, Lyle D.

    2011-01-01

    Bayesian methods for medical test accuracy are presented, beginning with the basic measures for tests with binary scores: true positive fraction, false positive fraction, positive predictive values, and negative predictive value. The Bayesian approach is taken because of its efficient use of prior information, and the analysis is executed with a Bayesian software package WinBUGS®. The ROC (receiver operating characteristic) curve gives the intrinsic accuracy of medical tests that have ordinal or continuous scores, and the Bayesian approach is illustrated with many examples from cancer and other diseases. Medical tests include X-ray, mammography, ultrasound, computed tomography, magnetic resonance imaging, nuclear medicine and tests based on biomarkers, such as blood glucose values for diabetes. The presentation continues with more specialized methods suitable for measuring the accuracies of clinical studies that have verification bias, and medical tests without a gold standard. Lastly, the review is concluded with Bayesian methods for measuring the accuracy of the combination of two or more tests. PMID:26859485

  20. Calibration of the Reflected Solar Instrument for the Climate Absolute Radiance and Refractivity Observatory

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; Barnes, Robert; Baize, Rosemary; O'Connell, Joseph; Hair, Jason

    2010-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) plans to observe climate change trends over decadal time scales to determine the accuracy of climate projections. The project relies on spaceborne earth observations of SI-traceable variables sensitive to key decadal change parameters. The mission includes a reflected solar instrument retrieving at-sensor reflectance over the 320 to 2300 nm spectral range with 500-m spatial resolution and 100-km swath. Reflectance is obtained from the ratio of measurements of the earth s surface to those while viewing the sun relying on a calibration approach that retrieves reflectance with uncertainties less than 0.3%. The calibration is predicated on heritage hardware, reduction of sensor complexity, adherence to detector-based calibration standards, and an ability to simulate in the laboratory on-orbit sources in both size and brightness to provide the basis of a transfer to orbit of the laboratory calibration including a link to absolute solar irradiance measurements.

  1. A novel absolute measurement for the low-frequency figure correction of aspheric surfaces

    NASA Astrophysics Data System (ADS)

    Lin, Wei-Cheng; Chang, Shenq-Tsong; Ho, Cheng-Fang; Kuo, Ching-Hsiang; Chung, Chien-Kai; Hsu, Wei-Yao; Tseng, Shih-Feng; Sung, Cheng-Kuo

    2015-07-01

    This study proposes an absolute measurement method with a computer-generated hologram (CGHs) to assist the identification of manufacturing form error, and gravity and mounting resulted distortions for a 300 mm aspherical mirror. This method adopts the frequency of peaks and valleys of each Zernike coefficient grabbed by the measurement with various orientations of the mirror in horizontal optical-axis configuration. In addition, the rotational-symmetric aberration (spherical aberration) is calibrated with random ball test method. According to the measured absolute surface figure, a high accuracy aspherical surface with peak to valley (P-V) value of 1/8 wave @ 632.8 nm was fabricated after surface figure correction with the reconstructed error map.

  2. Sample positioning in neutron diffraction experiments using a multi-material fiducial marker

    NASA Astrophysics Data System (ADS)

    Marais, D.; Venter, A. M.; Markgraaff, J.; James, J.

    2017-01-01

    An alternative sample positioning method is reported for use in conjunction with sample positioning and experiment planning software systems deployed on some neutron diffraction strain scanners. In this approach, the spherical fiducial markers and location trackers used with optical metrology hardware are replaced with a specifically designed multi-material fiducial marker that requires one diffraction measurement. In a blind setting, the marker position can be determined within an accuracy of ±164 μm with respect to the instrument gauge volume. The scheme is based on a pre-determined relationship that links the diffracted peak intensity to the absolute positioning of the fiducial marker with respect to the instrument gauge volume. Two methods for establishing the linking relationship are presented, respectively based on fitting multi-dimensional quadratic functions and a cross-correlation artificial neural network.

  3. Accuracy analysis for DSM and orthoimages derived from SPOT HRS stereo data using direct georeferencing

    NASA Astrophysics Data System (ADS)

    Reinartz, Peter; Müller, Rupert; Lehner, Manfred; Schroeder, Manfred

    During the HRS (High Resolution Stereo) Scientific Assessment Program the French space agency CNES delivered data sets from the HRS camera system with high precision ancillary data. Two test data sets from this program were evaluated: one is located in Germany, the other in Spain. The first goal was to derive orthoimages and digital surface models (DSM) from the along track stereo data by applying the rigorous model with direct georeferencing and without ground control points (GCPs). For the derivation of DSM, the stereo processing software, developed at DLR for the MOMS-2P three line stereo camera was used. As a first step, the interior and exterior orientation of the camera, delivered as ancillary data from positioning and attitude systems were extracted. A dense image matching, using nearly all pixels as kernel centers provided the parallaxes. The quality of the stereo tie points was controlled by forward and backward matching of the two stereo partners using the local least squares matching method. Forward intersection lead to points in object space which are subsequently interpolated to a DSM in a regular grid. DEM filtering methods were also applied and evaluations carried out differentiating between accuracies in forest and other areas. Additionally, orthoimages were generated from the images of the two stereo looking directions. The orthoimage and DSM accuracy was determined by using GCPs and available reference DEMs of superior accuracy (DEM derived from laser data and/or classical airborne photogrammetry). As expected the results obtained without using GCPs showed a bias in the order of 5-20 m to the reference data for all three coordinates. By image matching it could be shown that the two independently derived orthoimages exhibit a very constant shift behavior. In a second step few GCPs (3-4) were used to calculate boresight alignment angles, introduced into the direct georeferencing process of each image independently. This method improved the absolute

  4. Head and neck position sense.

    PubMed

    Armstrong, Bridget; McNair, Peter; Taylor, Denise

    2008-01-01

    fails to be appropriately integrated in the CNS, errors in head position may occur, resulting in an inaccurate reference for HNPS, and conversely if neck proprioceptive information is inaccurate, then control of head position may be affected. The cerebellum and cortex also play a role in control of head position, providing feed-forward and modulatory influences depending on the task requirements. Position-matching tasks have been the most popular means of testing position sense in the cervical spine. These allow the appreciation of absolute, constant and variable errors in positioning and have been shown to be reliable. The results of such tests indicate that errors are relatively low (2-5 degrees). It is apparent that error is not consistently affected by age, a finding similar to studies undertaken in peripheral joints. Furthermore, the range of motion in which subjects are tested does not consistently affect accuracy in a predictable manner. However, it is evident that impairments in position sense are observed in individuals who have experienced whiplash-type injuries and individuals with chronic head and neck pain of non-traumatic origin (e.g. cervical spondylosis). While researchers advocate comprehensive retraining protocols, which include eye and neck motion targeting tasks and coordination exercises, as well as co-contraction exercises to reduce such impairments, some studies show that more general exercises and manipulation may be of benefit. Overall, there is limited information concerning the efficacy of treatment programmes.

  5. Absolute calibration of forces in optical tweezers

    NASA Astrophysics Data System (ADS)

    Dutra, R. S.; Viana, N. B.; Maia Neto, P. A.; Nussenzveig, H. M.

    2014-07-01

    Optical tweezers are highly versatile laser traps for neutral microparticles, with fundamental applications in physics and in single molecule cell biology. Force measurements are performed by converting the stiffness response to displacement of trapped transparent microspheres, employed as force transducers. Usually, calibration is indirect, by comparison with fluid drag forces. This can lead to discrepancies by sizable factors. Progress achieved in a program aiming at absolute calibration, conducted over the past 15 years, is briefly reviewed. Here we overcome its last major obstacle, a theoretical overestimation of the peak stiffness, within the most employed range for applications, and we perform experimental validation. The discrepancy is traced to the effect of primary aberrations of the optical system, which are now included in the theory. All required experimental parameters are readily accessible. Astigmatism, the dominant effect, is measured by analyzing reflected images of the focused laser spot, adapting frequently employed video microscopy techniques. Combined with interface spherical aberration, it reveals a previously unknown window of instability for trapping. Comparison with experimental data leads to an overall agreement within error bars, with no fitting, for a broad range of microsphere radii, from the Rayleigh regime to the ray optics one, for different polarizations and trapping heights, including all commonly employed parameter domains. Besides signaling full first-principles theoretical understanding of optical tweezers operation, the results may lead to improved instrument design and control over experiments, as well as to an extended domain of applicability, allowing reliable force measurements, in principle, from femtonewtons to nanonewtons.

  6. What is Needed for Absolute Paleointensity?

    NASA Astrophysics Data System (ADS)

    Valet, J. P.

    2015-12-01

    Many alternative approaches to the Thellier and Thellier technique for absolute paleointensity have been proposed during the past twenty years. One reason is the time consuming aspect of the experiments. Another reason is to avoid uncertainties in determinations of the paleofield which are mostly linked to the presence of multidomain grains. Despite great care taken by these new techniques, there is no indication that they always provide the right answer and in fact sometimes fail. We are convinced that the most valid approach remains the original double heating Thellier protocol provided that natural remanence is controlled by pure magnetite with a narrow distribution of small grain sizes, mostly single domains. The presence of titanium, even in small amount generates biases which yield incorrect field values. Single domain grains frequently dominate the magnetization of glass samples, which explains the success of this selective approach. They are also present in volcanic lava flows but much less frequently, and therefore contribute to the low success rate of most experiments. However the loss of at least 70% of the magnetization at very high temperatures prior to the Curie point appears to be an essential prerequisite that increases the success rate to almost 100% and has been validated from historical flows and from recent studies. This requirement can easily be tested by thermal demagnetization while low temperature experiments can document the detection of single domain magnetite using the δFC/δZFC parameter as suggested (Moskowitz et al, 1993) for biogenic magnetite.

  7. Gyrokinetic Statistical Absolute Equilibrium and Turbulence

    SciTech Connect

    Jian-Zhou Zhu and Gregory W. Hammett

    2011-01-10

    A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence [T.-D. Lee, "On some statistical properties of hydrodynamical and magnetohydrodynamical fields," Q. Appl. Math. 10, 69 (1952)] is taken to study gyrokinetic plasma turbulence: A finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N + 1 quantities are conserved, corresponding to an energy invariant and N entropy-related invariants), the negative temperature states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.

  8. Absolute flux measurements for swift atoms

    NASA Technical Reports Server (NTRS)

    Fink, M.; Kohl, D. A.; Keto, J. W.; Antoniewicz, P.

    1987-01-01

    While a torsion balance in vacuum can easily measure the momentum transfer from a gas beam impinging on a surface attached to the balance, this measurement depends on the accommodation coefficients of the atoms with the surface and the distribution of the recoil. A torsion balance is described for making absolute flux measurements independent of recoil effects. The torsion balance is a conventional taut suspension wire design and the Young modulus of the wire determines the relationship between the displacement and the applied torque. A compensating magnetic field is applied to maintain zero displacement and provide critical damping. The unique feature is to couple the impinging gas beam to the torsion balance via a Wood's horn, i.e., a thin wall tube with a gradual 90 deg bend. Just as light is trapped in a Wood's horn by specular reflection from the curved surfaces, the gas beam diffuses through the tube. Instead of trapping the beam, the end of the tube is open so that the atoms exit the tube at 90 deg to their original direction. Therefore, all of the forward momentum of the gas beam is transferred to the torsion balance independent of the angle of reflection from the surfaces inside the tube.

  9. Absolute Geodetic Rotation Measurement Using Atom Interferometry

    SciTech Connect

    Stockton, J. K.; Takase, K.; Kasevich, M. A.

    2011-09-23

    We demonstrate a cold-atom interferometer gyroscope which overcomes accuracy and dynamic range limitations of previous atom interferometer gyroscopes. We show how the instrument can be used for precise determination of latitude, azimuth (true north), and Earth's rotation rate. Spurious noise terms related to multiple-path interferences are suppressed by employing a novel time-skewed pulse sequence. Extended versions of this instrument appear capable of meeting the stringent requirements for inertial navigation, geodetic applications of Earth's rotation rate determination, and tests of general relativity.

  10. Groves model accuracy study

    NASA Astrophysics Data System (ADS)

    Peterson, Matthew C.

    1991-08-01

    The United States Air Force Environmental Technical Applications Center (USAFETAC) was tasked to review the scientific literature for studies of the Groves Neutral Density Climatology Model and compare the Groves Model with others in the 30-60 km range. The tasking included a request to investigate the merits of comparing accuracy of the Groves Model to rocketsonde data. USAFETAC analysts found the Groves Model to be state of the art for middle-atmospheric climatological models. In reviewing previous comparisons with other models and with space shuttle-derived atmospheric densities, good density vs altitude agreement was found in almost all cases. A simple technique involving comparison of the model with range reference atmospheres was found to be the most economical way to compare the Groves Model with rocketsonde data; an example of this type is provided. The Groves 85 Model is used routinely in USAFETAC's Improved Point Analysis Model (IPAM). To create this model, Dr. Gerald Vann Groves produced tabulations of atmospheric density based on data derived from satellite observations and modified by rocketsonde observations. Neutral Density as presented here refers to the monthly mean density in 10-degree latitude bands as a function of altitude. The Groves 85 Model zonal mean density tabulations are given in their entirety.

  11. Absolute nuclear material assay using count distribution (LAMBDA) space

    DOEpatents

    Prasad, Mano K.; Snyderman, Neal J.; Rowland, Mark S.

    2015-12-01

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  12. Absolute nuclear material assay using count distribution (LAMBDA) space

    DOEpatents

    Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

    2012-06-05

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  13. A novel scanning system using an industrial robot and the workspace measurement and positioning system

    NASA Astrophysics Data System (ADS)

    Zhao, Ziyue; Zhu, Jigui; Yang, Linghui; Lin, Jiarui

    2015-10-01

    The present scanning system consists of an industrial robot and a line-structured laser sensor which uses the industrial robot as a position instrument to guarantee the accuracy. However, the absolute accuracy of an industrial robot is relatively poor compared with the good repeatability in the manufacturing industry. This paper proposes a novel method using the workspace measurement and positioning system (wMPS) to remedy the lack of accuracy of the industrial robot. In order to guarantee the positioning accuracy of the system, the wMPS which is a laser-based measurement technology designed for large-volume metrology applications is brought in. Benefitting from the wMPS, this system can measure different cell-areas by the line-structured laser sensor and fuse the measurement data of different cell-areas by using the wMPS accurately. The system calibration which is the procedure to acquire and optimize the structure parameters of the scanning system is also stated in detail in this paper. In order to verify the feasibility of the system for scanning the large free-form surface, an experiment is designed to scan the internal surface of the door of a car-body in white. The final results show that the measurement data of the whole measuring areas have been jointed perfectly and there is no mismatch in the figure especially in the hole measuring areas. This experiment has verified the rationality of the system scheme, the correctness and effectiveness of the relevant methods.

  14. Absolute and Convective Instability of a Liquid Jet

    NASA Technical Reports Server (NTRS)

    Lin, S. P.; Hudman, M.; Chen, J. N.

    1999-01-01

    The existence of absolute instability in a liquid jet has been predicted for some time. The disturbance grows in time and propagates both upstream and downstream in an absolutely unstable liquid jet. The image of absolute instability is captured in the NASA 2.2 sec drop tower and reported here. The transition from convective to absolute instability is observed experimentally. The experimental results are compared with the theoretical predictions on the transition Weber number as functions of the Reynolds number. The role of interfacial shear relative to all other relevant forces which cause the onset of jet breakup is explained.

  15. Absolute calorimetric calibration of low energy brachytherapy sources

    NASA Astrophysics Data System (ADS)

    Stump, Kurt E.

    the current instrument to direct further work in this field. It has been found that for sources with powers above approximately 2 muW the instrument is able to determine the source power in agreement to within less than 7% of what is expected based upon the current source strength standard. For lower power sources, the agreement is still within the uncertainty of the power measurement, but the calorimeter noise dominates. Thus, to provide absolute calibration of lower power sources additional measures must be taken. The conclusion of this thesis describes these measures and how they will improve the factors that limit the current instrument. The results of the work presented in this thesis establish the methodology of active radiometric calorimetey for the absolute calibration of radioactive sources. The method is an improvement over previous techniques in that there is no reliance upon the thermal properties of the materials used or the heat flow pathways on the source measurements. The initial work presented here will help to shape future refinements of this technique to allow lower power sources to be calibrated with high precision and high accuracy.

  16. High Accuracy Wavelength Calibration For A Scanning Visible Spectrometer

    SciTech Connect

    Filippo Scotti and Ronald Bell

    2010-07-29

    Spectroscopic applications for plasma velocity measurements often require wavelength accuracies ≤ 0.2Â. An automated calibration for a scanning spectrometer has been developed to achieve a high wavelength accuracy overr the visible spectrum, stable over time and environmental conditions, without the need to recalibrate after each grating movement. The method fits all relevant spectrometer paraameters using multiple calibration spectra. With a steping-motor controlled sine-drive, accuracies of ~0.025 Â have been demonstrated. With the addition of high resolution (0.075 aresec) optical encoder on the grading stage, greater precision (~0.005 Â) is possible, allowing absolute velocity measurements with ~0.3 km/s. This level of precision requires monitoring of atmospheric temperature and pressure and of grating bulk temperature to correct for changes in the refractive index of air and the groove density, respectively.

  17. Ozone absorption coefficients' role in Dobson instrument ozone measurement accuracy

    NASA Astrophysics Data System (ADS)

    Basher, R. E.

    1982-11-01

    The differences of 10% or more between the laboratory measurements of UV absorption coefficients by different investigators indicate accuracies that are quite inadequate for current needs in the measurement of atmospheric ozone. The standard band-integrated set of coefficients now used with the Dobson instrument are mutually consistent to about 2%, but their absolute accuracy is still in question. The accurate calculation of band-integrated coefficients must take account of their dependence on source spectral irradiance, atmospheric spectral transmittance, mean ozone temperature, and instrument spectral transmittance. A careful examination shows that Komhyr's (1980) case for an error of about +5% in the standard Dobson AD ozone estimation is subject to large uncertainties and certain lacks of independence. The obvious solution to this accuracy problem lies in better laboratory measurements of ozone absorption.

  18. Absolute total electron scattering cross sections for N/sub 2/ between 0. 5 and 50 eV

    SciTech Connect

    Kennerly, R.E.

    1980-06-01

    Absolute total electron scattering cross sections for N/sub 2/ from 0.5 to 50 eV have been measured with an estimated uncertainty of +- 3% using a transmission time-of-flight method previously described. The results are compared to previous experimental results and to recent calculations. The positions of the /sup 2/Pi/sub g/ resonance peaks were determined with much greater accuracy ( +- 15 meV) than in previous transmission measurements. The structure reported by Golden (1966) below the /sup 2/Pi/sub g/ resonance was clearly not present, indicating that, if real, these features are not a property of the N/sub 2/ ground vibronic state. The shape resonance predicted at 11 eV by Dill and Dehmer (1977) was not seen, perhaps because it was too weakly manifested in the total cross section. A weak broad band centered at 25 eV may be interpreted as being due to a sigma/sub u/ shape resonance as predicted by Dehmer, Siegel, Welch, and Dill.

  19. Absolute pitch among students at the Shanghai Conservatory of Music: a large-scale direct-test study.

    PubMed

    Deutsch, Diana; Li, Xiaonuo; Shen, Jing

    2013-11-01

    This paper reports a large-scale direct-test study of absolute pitch (AP) in students at the Shanghai Conservatory of Music. Overall note-naming scores were very high, with high scores correlating positively with early onset of musical training. Students who had begun training at age ≤5 yr scored 83% correct not allowing for semitone errors and 90% correct allowing for semitone errors. Performance levels were higher for white key pitches than for black key pitches. This effect was greater for orchestral performers than for pianists, indicating that it cannot be attributed to early training on the piano. Rather, accuracy in identifying notes of different names (C, C#, D, etc.) correlated with their frequency of occurrence in a large sample of music taken from the Western tonal repertoire. There was also an effect of pitch range, so that performance on tones in the two-octave range beginning on Middle C was higher than on tones in the octave below Middle C. In addition, semitone errors tended to be on the sharp side. The evidence also ran counter to the hypothesis, previously advanced by others, that the note A plays a special role in pitch identification judgments.

  20. Towards Experimental Accuracy from the First Principles

    NASA Astrophysics Data System (ADS)

    Polyansky, O. L.; Lodi, L.; Tennyson, J.; Zobov, N. F.

    2013-06-01

    Producing ab initio ro-vibrational energy levels of small, gas-phase molecules with an accuracy of 0.10 cm^{-1} would constitute a significant step forward in theoretical spectroscopy and would place calculated line positions considerably closer to typical experimental accuracy. Such an accuracy has been recently achieved for the H_3^+ molecular ion for line positions up to 17 000 cm ^{-1}. However, since H_3^+ is a two-electron system, the electronic structure methods used in this study are not applicable to larger molecules. A major breakthrough was reported in ref., where an accuracy of 0.10 cm^{-1} was achieved ab initio for seven water isotopologues. Calculated vibrational and rotational energy levels up to 15 000 cm^{-1} and J=25 resulted in a standard deviation of 0.08 cm^{-1} with respect to accurate reference data. As far as line intensities are concerned, we have already achieved for water a typical accuracy of 1% which supersedes average experimental accuracy. Our results are being actively extended along two major directions. First, there are clear indications that our results for water can be improved to an accuracy of the order of 0.01 cm^{-1} by further, detailed ab initio studies. Such level of accuracy would already be competitive with experimental results in some situations. A second, major, direction of study is the extension of such a 0.1 cm^{-1} accuracy to molecules containg more electrons or more than one non-hydrogen atom, or both. As examples of such developments we will present new results for CO, HCN and H_2S, as well as preliminary results for NH_3 and CH_4. O.L. Polyansky, A. Alijah, N.F. Zobov, I.I. Mizus, R. Ovsyannikov, J. Tennyson, L. Lodi, T. Szidarovszky and A.G. Csaszar, Phil. Trans. Royal Soc. London A, {370}, 5014-5027 (2012). O.L. Polyansky, R.I. Ovsyannikov, A.A. Kyuberis, L. Lodi, J. Tennyson and N.F. Zobov, J. Phys. Chem. A, (in press). L. Lodi, J. Tennyson and O.L. Polyansky, J. Chem. Phys. {135}, 034113 (2011).

  1. Climate Change Accuracy: Requirements and Economic Value

    NASA Astrophysics Data System (ADS)

    Wielicki, B. A.; Cooke, R.; Mlynczak, M. G.; Lukashin, C.; Thome, K. J.; Baize, R. R.

    2014-12-01

    Higher than normal accuracy is required to rigorously observe decadal climate change. But what level is needed? How can this be quantified? This presentation will summarize a new more rigorous and quantitative approach to determining the required accuracy for climate change observations (Wielicki et al., 2013, BAMS). Most current global satellite observations cannot meet this accuracy level. A proposed new satellite mission to resolve this challenge is CLARREO (Climate Absolute Radiance and Refractivity Observatory). CLARREO is designed to achieve advances of a factor of 10 for reflected solar spectra and a factor of 3 to 5 for thermal infrared spectra (Wielicki et al., Oct. 2013 BAMS). The CLARREO spectrometers are designed to serve as SI traceable benchmarks for the Global Satellite Intercalibration System (GSICS) and to greatly improve the utility of a wide range of LEO and GEO infrared and reflected solar passive satellite sensors for climate change observations (e.g. CERES, MODIS, VIIIRS, CrIS, IASI, Landsat, SPOT, etc). Providing more accurate decadal change trends can in turn lead to more rapid narrowing of key climate science uncertainties such as cloud feedback and climate sensitivity. A study has been carried out to quantify the economic benefits of such an advance as part of a rigorous and complete climate observing system. The study concludes that the economic value is $12 Trillion U.S. dollars in Net Present Value for a nominal discount rate of 3% (Cooke et al. 2013, J. Env. Sys. Dec.). A brief summary of these two studies and their implications for the future of climate science will be presented.

  2. Monitoring of absolute mirror alignment at COMPASS RICH-1 detector

    NASA Astrophysics Data System (ADS)

    Alexeev, M.; Birsa, R.; Bradamante, F.; Bressan, A.; Chiosso, M.; Ciliberti, P.; Dalla Torre, S.; Denisov, O.; Duic, V.; Ferrero, A.; Finger, M.; Finger, M.; Gayde, J. Ch.; Giorgi, M.; Gobbo, B.; Levorato, S.; Maggiora, A.; Martin, A.; Menon, G.; Panzieri, D.; Pesaro, G.; Polak, J.; Rocco, E.; Sbrizzai, G.; Schiavon, P.; Slunecka, M.; Sozzi, F.; Steiger, L.; Sulc, M.; Takekawa, S.; Tessarotto, F.

    2014-12-01

    The gaseous COMPASS RICH-1 detector uses two spherical mirror surfaces, segmented into 116 individual mirrors, to focus the Cherenkov photons onto the detector plane. Any mirror misalignment directly affects the detector resolution. The on-line Continuous Line Alignment and Monitoring (CLAM) photogrammetry-based method has been implemented to measure the alignment of individual mirrors which can be characterized by the center of curvature. The mirror wall reflects a regular grid of retroreflective strips placed inside the detector vessel. Then, the position of each mirror is determined from the image of the grid reflection. The images are collected by four cameras. Any small mirror misalignment results in changes of the grid lines' positions in the image. The accuracy limits of the CLAM method were checked by laser interferometry and are below 0.1 mrad.

  3. Absolute Plate Velocities from Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Kreemer, Corné; Zheng, Lin; Gordon, Richard

    2015-04-01

    The orientation of seismic anisotropy inferred beneath plate interiors may provide a means to estimate the motions of the plate relative to the sub-asthenospheric mantle. Here we analyze two global sets of shear-wave splitting data, that of Kreemer [2009] and an updated and expanded data set, to estimate plate motions and to better understand the dispersion of the data, correlations in the errors, and their relation to plate speed. We also explore the effect of using geologically current plate velocities (i.e., the MORVEL set of angular velocities [DeMets et al. 2010]) compared with geodetically current plate velocities (i.e., the GSRM v1.2 angular velocities [Kreemer et al. 2014]). We demonstrate that the errors in plate motion azimuths inferred from shear-wave splitting beneath any one tectonic plate are correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining relative plate angular velocities to consistency with the MORVEL relative plate angular velocities. The SKS-MORVEL absolute plate angular velocities (based on the Kreemer [2009] data set) are determined from the poles from eight plates weighted proportionally to the root-mean-square velocity of each plate. SKS-MORVEL indicates that eight plates (Amur, Antarctica, Caribbean, Eurasia, Lwandle, Somalia, Sundaland, and Yangtze) have angular velocities that differ insignificantly from zero. The net rotation of the lithosphere is 0.25±0.11° Ma-1 (95% confidence limits) right-handed about 57.1°S, 68.6°E. The within-plate dispersion of seismic anisotropy for oceanic lithosphere (σ=19.2° ) differs insignificantly from that for continental lithosphere (σ=21.6° ). The between-plate dispersion, however, is significantly smaller for oceanic lithosphere (σ=7.4° ) than for continental

  4. Evaluation of the Absolute Regional Temperature Potential

    NASA Technical Reports Server (NTRS)

    Shindell, D. T.

    2012-01-01

    The Absolute Regional Temperature Potential (ARTP) is one of the few climate metrics that provides estimates of impacts at a sub-global scale. The ARTP presented here gives the time-dependent temperature response in four latitude bands (90-28degS, 28degS-28degN, 28-60degN and 60-90degN) as a function of emissions based on the forcing in those bands caused by the emissions. It is based on a large set of simulations performed with a single atmosphere-ocean climate model to derive regional forcing/response relationships. Here I evaluate the robustness of those relationships using the forcing/response portion of the ARTP to estimate regional temperature responses to the historic aerosol forcing in three independent climate models. These ARTP results are in good accord with the actual responses in those models. Nearly all ARTP estimates fall within +/-20%of the actual responses, though there are some exceptions for 90-28degS and the Arctic, and in the latter the ARTP may vary with forcing agent. However, for the tropics and the Northern Hemisphere mid-latitudes in particular, the +/-20% range appears to be roughly consistent with the 95% confidence interval. Land areas within these two bands respond 39-45% and 9-39% more than the latitude band as a whole. The ARTP, presented here in a slightly revised form, thus appears to provide a relatively robust estimate for the responses of large-scale latitude bands and land areas within those bands to inhomogeneous radiative forcing and thus potentially to emissions as well. Hence this metric could allow rapid evaluation of the effects of emissions policies at a finer scale than global metrics without requiring use of a full climate model.

  5. Absolute determination of local tropospheric OH concentrations

    NASA Technical Reports Server (NTRS)

    Armerding, Wolfgang; Comes, Franz-Josef

    1994-01-01

    Long path absorption (LPA) according to Lambert Beer's law is a method to determine absolute concentrations of trace gases such as tropospheric OH. We have developed a LPA instrument which is based on a rapid tuning of the light source which is a frequency doubled dye laser. The laser is tuned across two or three OH absorption features around 308 nm with a scanning speed of 0.07 cm(exp -1)/microsecond and a repetition rate of 1.3 kHz. This high scanning speed greatly reduces the fluctuation of the light intensity caused by the atmosphere. To obtain the required high sensitivity the laser output power is additionally made constant and stabilized by an electro-optical modulator. The present sensitivity is of the order of a few times 10(exp 5) OH per cm(exp 3) for an acquisition time of a minute and an absorption path length of only 1200 meters so that a folding of the optical path in a multireflection cell was possible leading to a lateral dimension of the cell of a few meters. This allows local measurements to be made. Tropospheric measurements have been carried out in 1991 resulting in the determination of OH diurnal variation at specific days in late summer. Comparison with model calculations have been made. Interferences are mainly due to SO2 absorption. The problem of OH self generation in the multireflection cell is of minor extent. This could be shown by using different experimental methods. The minimum-maximum signal to noise ratio is about 8 x 10(exp -4) for a single scan. Due to the small size of the absorption cell the realization of an open air laboratory is possible in which by use of an additional UV light source or by additional fluxes of trace gases the chemistry can be changed under controlled conditions allowing kinetic studies of tropospheric photochemistry to be made in open air.

  6. Absolute Radiometric Calibration of KOMPSAT-3A

    NASA Astrophysics Data System (ADS)

    Ahn, H. Y.; Shin, D. Y.; Kim, J. S.; Seo, D. C.; Choi, C. U.

    2016-06-01

    This paper presents a vicarious radiometric calibration of the Korea Multi-Purpose Satellite-3A (KOMPSAT-3A) performed by the Korea Aerospace Research Institute (KARI) and the Pukyong National University Remote Sensing Group (PKNU RSG) in 2015.The primary stages of this study are summarized as follows: (1) A field campaign to determine radiometric calibrated target fields was undertaken in Mongolia and South Korea. Surface reflectance data obtained in the campaign were input to a radiative transfer code that predicted at-sensor radiance. Through this process, equations and parameters were derived for the KOMPSAT-3A sensor to enable the conversion of calibrated DN to physical units, such as at-sensor radiance or TOA reflectance. (2) To validate the absolute calibration coefficients for the KOMPSAT-3A sensor, we performed a radiometric validation with a comparison of KOMPSAT-3A and Landsat-8 TOA reflectance using one of the six PICS (Libya 4). Correlations between top-of-atmosphere (TOA) radiances and the spectral band responses of the KOMPSAT-3A sensors at the Zuunmod, Mongolia and Goheung, South Korea sites were significant for multispectral bands. The average difference in TOA reflectance between KOMPSAT-3A and Landsat-8 image over the Libya 4, Libya site in the red-green-blue (RGB) region was under 3%, whereas in the NIR band, the TOA reflectance of KOMPSAT-3A was lower than the that of Landsat-8 due to the difference in the band passes of two sensors. The KOMPSAT-3Aensor includes a band pass near 940 nm that can be strongly absorbed by water vapor and therefore displayed low reflectance. Toovercome this, we need to undertake a detailed analysis using rescale methods, such as the spectral bandwidth adjustment factor.

  7. High accuracy plasma density measurement using hybrid Langmuir probe and microwave interferometer method.

    PubMed

    Deline, C; Gilchrist, B E; Dobson, C; Jones, J E; Chavers, D G

    2007-11-01

    High spatial resolution plasma density measurements have been taken as part of an investigation into magnetic nozzle physics at the NASA/MSFC Propulsion Research Center. These measurements utilized a Langmuir triple probe scanned across the measurement chord of either of two stationary rf interferometers. By normalizing the scanned profile to the microwave interferometer line-integrated density measurement for each electrostatic probe measurement, the effect of shot-to-shot variation of the line-integrated density can be removed. In addition, by summing the voltage readings at each radial position in a transverse scan, the line density can be reconstituted, allowing the absolute density to be determined, assuming that the shape of the profile is constant from shot to shot. The spatial and temporal resolutions of this measurement technique depend on the resolutions of the scanned electrostatic probe and the interferometer. The measurement accuracy is 9%-15%, which is on the order of the accuracy of the rf interferometer. The measurement technique was compared directly with both scanning rf interferometer and standard Langmuir probe theory. The hybrid technique compares favorably with the scanning rf interferometer, and appears more accurate than probe theory alone. Additionally, our measurement technique is generally applicable even for nonaxisymmetric plasmas.

  8. System for absolute measurement of electrolytic conductivity in aqueous solutions based on van der Pauw's theory

    NASA Astrophysics Data System (ADS)

    Zhang, Bing; Lin, Zhen; Zhang, Xiao; Yu, Xiang; Wei, Jiali; Wang, Xiaoping

    2014-05-01

    Based on an innovative application of van der Pauw's theory, a system was developed for the absolute measurement of electrolytic conductivity in aqueous solutions. An electrolytic conductivity meter was designed that uses a four-electrode system with an axial-radial two-dimensional adjustment structure coupled to an ac voltage excitation source and signal collecting circuit. The measurement accuracy, resolution and repeatability of the measurement system were examined through a series of experiments. Moreover, the measurement system and a high-precision electrolytic conductivity meter were compared using some actual water samples.

  9. Many-wavelength interferometry with thousands of lasers for absolute distance measurement.

    PubMed

    van den Berg, S A; Persijn, S T; Kok, G J P; Zeitouny, M G; Bhattacharya, N

    2012-05-04

    We demonstrate a new technique for absolute distance measurement with a femtosecond frequency comb laser, based on unraveling the output of an interferometer to distinct comb modes with 1 GHz spacing. From the fringe patterns that are captured with a camera, a distance is derived by combining spectral and homodyne interferometry, exploiting about 9000 continuous wave lasers. This results in a measurement accuracy far within an optical fringe (λ/30), combined with a large range of nonambiguity (15 cm). Our technique merges multiwavelength interferometry and spectral interferometry, within a single scheme.

  10. Laser induced deflection technique for absolute thin film absorption measurement: optimized concepts and experimental results

    SciTech Connect

    Muehlig, Christian; Kufert, Siegfried; Bublitz, Simon; Speck, Uwe

    2011-03-20

    Using experimental results and numerical simulations, two measuring concepts of the laser induced deflection (LID) technique are introduced and optimized for absolute thin film absorption measurements from deep ultraviolet to IR wavelengths. For transparent optical coatings, a particular probe beam deflection direction allows the absorption measurement with virtually no influence of the substrate absorption, yielding improved accuracy compared to the common techniques of separating bulk and coating absorption. For high-reflection coatings, where substrate absorption contributions are negligible, a different probe beam deflection is chosen to achieve a better signal-to-noise ratio. Various experimental results for the two different measurement concepts are presented.

  11. Phylogenetic Tree Reconstruction Accuracy and Model Fit when Proportions of Variable Sites Change across the Tree

    PubMed Central

    Grievink, Liat Shavit; Penny, David; Hendy, Michael D.; Holland, Barbara R.

    2010-01-01

    Commonly used phylogenetic models assume a homogeneous process through time in all parts of the tree. However, it is known that these models can be too simplistic as they do not account for nonhomogeneous lineage-specific properties. In particular, it is now widely recognized that as constraints on sequences evolve, the proportion and positions of variable sites can vary between lineages causing heterotachy. The extent to which this model misspecification affects tree reconstruction is still unknown. Here, we evaluate the effect of changes in the proportions and positions of variable sites on model fit and tree estimation. We consider 5 current models of nucleotide sequence evolution in a Bayesian Markov chain Monte Carlo framework as well as maximum parsimony (MP). We show that for a tree with 4 lineages where 2 nonsister taxa undergo a change in the proportion of variable sites tree reconstruction under the best-fitting model, which is chosen using a relative test, often results in the wrong tree. In this case, we found that an absolute test of model fit is a better predictor of tree estimation accuracy. We also found further evidence that MP is not immune to heterotachy. In addition, we show that increased sampling of taxa that have undergone a change in proportion and positions of variable sites is critical for accurate tree reconstruction. PMID:20525636

  12. Predictions of Ligand Selectivity from Absolute Binding Free Energy Calculations

    PubMed Central

    2016-01-01

    Binding selectivity is a requirement for the development of a safe drug, and it is a critical property for chemical probes used in preclinical target validation. Engineering selectivity adds considerable complexity to the rational design of new drugs, as it involves the optimization of multiple binding affinities. Computationally, the prediction of binding selectivity is a challenge, and generally applicable methodologies are still not available to the computational and medicinal chemistry communities. Absolute binding free energy calculations based on alchemical pathways provide a rigorous framework for affinity predictions and could thus offer a general approach to the problem. We evaluated the performance of free energy calculations based on molecular dynamics for the prediction of selectivity by estimating the affinity profile of three bromodomain inhibitors across multiple bromodomain families, and by comparing the results to isothermal titration calorimetry data. Two case studies were considered. In the first one, the affinities of two similar ligands for seven bromodomains were calculated and returned excellent agreement with experiment (mean unsigned error of 0.81 kcal/mol and Pearson correlation of 0.75). In this test case, we also show how the preferred binding orientation of a ligand for different proteins can be estimated via free energy calculations. In the second case, the affinities of a broad-spectrum inhibitor for 22 bromodomains were calculated and returned a more modest accuracy (mean unsigned error of 1.76 kcal/mol and Pearson correlation of 0.48); however, the reparametrization of a sulfonamide moiety improved the agreement with experiment. PMID:28009512

  13. Characterizing flow in oil reservoir rock using SPH: absolute permeability

    NASA Astrophysics Data System (ADS)

    Holmes, David W.; Williams, John R.; Tilke, Peter; Leonardi, Christopher R.

    2016-04-01

    In this paper, a three-dimensional smooth particle hydrodynamics (SPH) simulator for modeling grain scale fluid flow in porous rock is presented. The versatility of the SPH method has driven its use in increasingly complex areas of flow analysis, including flows related to permeable rock for both groundwater and petroleum reservoir research. While previous approaches to such problems using SPH have involved the use of idealized pore geometries (cylinder/sphere packs etc), in this paper we detail the characterization of flow in models with geometries taken from 3D X-ray microtomographic imaging of actual porous rock; specifically 25.12 % porosity dolomite. This particular rock type has been well characterized experimentally and described in the literature, thus providing a practical `real world' means of verification of SPH that will be key to its acceptance by industry as a viable alternative to traditional reservoir modeling tools. The true advantages of SPH are realized when adding the complexity of multiple fluid phases, however, the accuracy of SPH for single phase flow is, as yet, under developed in the literature and will be the primary focus of this paper. Flow in reservoir rock will typically occur in the range of low Reynolds numbers, making the enforcement of no-slip boundary conditions an important factor in simulation. To this end, we detail the development of a new, robust, and numerically efficient method for implementing no-slip boundary conditions in SPH that can handle the degree of complexity of boundary surfaces, characteristic of an actual permeable rock sample. A study of the effect of particle density is carried out and simulation results for absolute permeability are presented and compared to those from experimentation showing good agreement and validating the method for such applications.

  14. Accuracy of Digital vs. Conventional Implant Impressions

    PubMed Central

    Lee, Sang J.; Betensky, Rebecca A.; Gianneschi, Grace E.; Gallucci, German O.

    2015-01-01

    The accuracy of digital impressions greatly influences the clinical viability in implant restorations. The aim of this study is to compare the accuracy of gypsum models acquired from the conventional implant impression to digitally milled models created from direct digitalization by three-dimensional analysis. Thirty gypsum and 30 digitally milled models impressed directly from a reference model were prepared. The models were scanned by a laboratory scanner and 30 STL datasets from each group were imported to an inspection software. The datasets were aligned to the reference dataset by a repeated best fit algorithm and 10 specified contact locations of interest were measured in mean volumetric deviations. The areas were pooled by cusps, fossae, interproximal contacts, horizontal and vertical axes of implant position and angulation. The pooled areas were statistically analysed by comparing each group to the reference model to investigate the mean volumetric deviations accounting for accuracy and standard deviations for precision. Milled models from digital impressions had comparable accuracy to gypsum models from conventional impressions. However, differences in fossae and vertical displacement of the implant position from the gypsum and digitally milled models compared to the reference model, exhibited statistical significance (p<0.001, p=0.020 respectively). PMID:24720423

  15. Assisting personal positioning in indoor environments using map matching

    NASA Astrophysics Data System (ADS)

    Attia, M.; Moussa, A.; Zhao, X.; El-Sheimy, N.

    2011-12-01

    Personal positioning is facing a huge challenge to maintain a reliable accuracy through all applications. Although in outdoor applications, several mobile navigation devices can provide acceptable positioning accuracy, the situation in indoor environment is not the same. Mobile navigation devices mainly contain a global positioning system (GPS) receiver and an inertial measurement unit (IMU). The main drawback in indoor navigation applications is the unavailability of the GNSS signals, which decreases the possibility of obtaining an accurate absolute position solution, as the inertial system (INS) solution will drift with time in the absence of external updates. Several alternatives were presented lately to update the inertial solution such as using Wi-Fi, UWB, RFID, several self-contained sensors, imaging aiding and spatial information aiding. In order to achieve accurate position solution, with low-cost and usable technique, an integrated mobile navigation system integrating GPS/IMU/Wi-Fi and map-matching was developed. The developed system uses the prior knowledge of the indoor geometrical and topological information, as a threshold for the navigation solution, forcing the provided solution to be mostly on the right track. The geometrical and topological information for the building was used to build the geospatial data model. The use of this model was performed by developing a map matching algorithm which uses the geometrical and topological characteristics of the building to locate the user position on the building map. This algorithm was developed based on the geospatial information of the Engineering building, University of Calgary, where the field test occurred. The map-matching algorithm was evaluated by processing and comparing two separate navigation solutions through the study area, one using only the GPS/IMU/Wi-Fi system, and second solution was assisted with the map-matching algorithm which shows significant enhancement in the position solution for

  16. In-flight quality and accuracy of attitude measurements from the CHAMP advanced stellar compass

    NASA Astrophysics Data System (ADS)

    Jørgensen, Peter S.; Jørgensen, John L.; Denver, Troelz; Betto, Maurizio

    2005-01-01

    The German geo-observations satellite CHAMP carries highly accurate vector instruments. The orientation of these relative to the inertial reference frame is obtained using star trackers. These advanced stellar compasses (ASC) are fully autonomous units, which provide, in real time, the absolute attitude with accuracy in the arc second range. In order to investigate the in-flight accuracy of the ASC, the terminology to characterize noise and biases is introduced. Relative instrument accuracy (RIA) and absolute instrument accuracy (AIA) can in principle be determined in-flight. However problems with modeling external noise sources often arise. The special CHAMP configuration with two star tracker cameras mounted fixed together provides an excellent opportunity to determine the AIA in-flight using the inter boresight angle.

  17. Presenting a high accuracy Theta-Phi-style fiber-positioner prototype with a 15-mm pitch

    NASA Astrophysics Data System (ADS)

    Haeuser, Marco; Lang-Bardl, Florian; Richter, Josef; Hess, Hans-Joachim; Degwert, Adrian; Karasz, Adolf; Kosyra, Ralf; Hopp, Ulrich; Bender, Ralf

    2014-07-01

    We present a Θ - Φ-style fiber-positioner prototype, which will be controlled via the EMI-robust CAN-Bus. Our positioner points without iterations or a metrology system. Due to the overlapping patrol disc of 17.3 mm diameter, we reach a filling factor of 100 %. The positioners diameter is 14.6 mm, containing the control electronics on a contemporary PCB of 13.5 mm width. While moving, the power consumption does not lead to a significant rise in temperature. Given a mechanical reference point measured by stall detection, the absolute accuracy is 27 μm (1σ = 14 µm) and pointings are repeatable with 7 μm (1σ = 4 μm). Better positioning may be reachable with upcoming calibration.

  18. Determination of Absolute Zero Using a Computer-Based Laboratory

    ERIC Educational Resources Information Center

    Amrani, D.

    2007-01-01

    We present a simple computer-based laboratory experiment for evaluating absolute zero in degrees Celsius, which can be performed in college and undergraduate physical sciences laboratory courses. With a computer, absolute zero apparatus can help demonstrators or students to observe the relationship between temperature and pressure and use…

  19. A Global Forecast of Absolute Poverty and Employment.

    ERIC Educational Resources Information Center

    Hopkins, M. J. D.

    1980-01-01

    Estimates are made of absolute poverty and employment under the hypothesis that existing trends continue. Concludes that while the number of people in absolute poverty is not likely to decline by 2000, the proportion will fall. Jobs will have to grow 3.9% per year in developing countries to achieve full employment. (JOW)

  20. Absolute Humidity and the Seasonality of Influenza (Invited)

    NASA Astrophysics Data System (ADS)

    Shaman, J. L.; Pitzer, V.; Viboud, C.; Grenfell, B.; Goldstein, E.; Lipsitch, M.

    2010-12-01

    Much of the observed wintertime increase of mortality in temperate regions is attributed to seasonal influenza. A recent re-analysis of laboratory experiments indicates that absolute humidity strongly modulates the airborne survival and transmission of the influenza virus. Here we show that the onset of increased wintertime influenza-related mortality in the United States is associated with anomalously low absolute humidity levels during the prior weeks. We then use an epidemiological model, in which observed absolute humidity conditions temper influenza transmission rates, to successfully simulate the seasonal cycle of observed influenza-related mortality. The model results indicate that direct modulation of influenza transmissibility by absolute humidity alone is sufficient to produce this observed seasonality. These findings provide epidemiological support for the hypothesis that absolute humidity drives seasonal variations of influenza transmission in temperate regions. In addition, we show that variations of the basic and effective reproductive numbers for influenza, caused by seasonal changes in absolute humidity, are consistent with the general timing of pandemic influenza outbreaks observed for 2009 A/H1N1 in temperate regions. Indeed, absolute humidity conditions correctly identify the region of the United States vulnerable to a third, wintertime wave of pandemic influenza. These findings suggest that the timing of pandemic influenza outbreaks is controlled by a combination of absolute humidity conditions, levels of susceptibility and changes in population mixing and contact rates.