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1

Evaluation of Precise, Kinematic GPS Point Positioning  

Microsoft Academic Search

We present the results of precise static and kinematic point-positioning solutions obtained in post-processing, with a recursive Kalman filter and smoother estimator (i.e., a state space approach). The observations are dual- frequency GPS carrier phase and pseudo-range, treated as two distinct data types, each with its own measurement equations. The receiver data is single-differenced between satellites, to eliminate the receiver

Oscar L. Colombo; Andrew W. Sutter; Alan G. Evans

2

Precise Point Positioning Using IGS Orbit and Clock Products  

Microsoft Academic Search

  The contribution details a post-processing approach that used undifferentiated dual-frequency pseudorange and carrier phase\\u000a observations along with IGS procise orbit products, for stand-alone precise geodetic point positioning (static or kinematic)\\u000a with cm precision. This is possible if one takes advantage of the satellite clock estimates available with the satellite coordinates\\u000a in the IGS precise orbit products and models systematic effects

Jan Kouba; Pierre Héroux

2001-01-01

3

Flight evaluation of GPS precise point positioning for helicopter navigation  

Microsoft Academic Search

We reported development and assessment of a precise point positioning (PPP) software for land vehicular navigation in 2006. This paper presents one phase of the continued study at NDA for further extension of the software to helicopter navigation. For 3D users, the height-dependent tropospheric delay is a critical factor, and so the sophisticated correction models and parameter estimation strategies have

Yutaka Shimizu; Masaaki Murata

2007-01-01

4

Analyzing GNSS data in precise point positioning software  

Microsoft Academic Search

This work demonstrates that precise point positioning (PPP) can be used not only for positioning, but for a variety of other\\u000a tasks, such as signal analysis. The fact that the observation model used for accurate error modeling has to take into consideration\\u000a the several effects present in GPS signals, and that observations are undifferenced, makes PPP a powerful data analysis

Rodrigo F. Leandro; Marcelo C. Santos; Richard B. Langley

2011-01-01

5

Deterministic and Stochastic Receiver Clock Modeling in Precise Point Positioning  

NASA Astrophysics Data System (ADS)

The traditional GNSS (Global Navigation Satellite System) data analysis assumes an independent set of clock corrections for each epoch. This introduces a huge number of parameters that are highly correlated with station height and troposphere parameters. If the number of clock parameters can be reduced, the GNSS processing procedure may be stabilized. Experiments with kinematic solutions for stations equipped with H-Maser clocks have confirmed this. On the other hand, static coordinates do not significantly benefit from changing the strategy in handling the clock parameter. In the current GNSS constellation only GIOVE-B and the GPS Block IIF satellite clocks seem to be good enough to be modeled instead of freely estimated for each epoch without losing accuracy at the level of phase measurements. With the Galileo constellation this will change in future. In this context, ESA (European Space Agency) funded a project on "Satellite and Station Clock Modelling for GNSS". In the frame of this project, various deterministic and stochastic clock models have been evaluated, implemented and assessed for both, station and satellite clocks. In this paper we focus on the impact of modeling the receiver clock in the processing of GNSS data in static and kinematic precise point positioning (PPP) modes. Initial results show that for stations connected to an H-Maser clock the stability of the vertical position for kinematic PPP could be improved by up to 60%. The impact of clock modeling on the estimation of troposphere parameters is also investigated, along with the role of the tropospheric modeling itself, by testing various sampling rates and relative constraints for the troposphere parameters. Finally, we investigate the convergence time of PPP when deterministic or stochastic clock modeling is applied to the receiver clock.

Orliac, E.; Dach, R.; Wang, K.; Rothacher, M.; Voithenleitner, D.; Hugentobler, U.; Heinze, M.; Svehla, D.

2012-04-01

6

Establishing ground control points for high-resolution satellite imagery using GPS precise point positioning  

Microsoft Academic Search

A GPS measurement and processing technique of precise point positioning (PPP) accurate to 2.5 m is developed for the purpose of establishing ground control points (GCPs) for rectifying medium and high resolution satellite imageries. In practice, the coordinates necessary in geometric rectification are usually derived from medium scale maps such as 1;50,000 or 1:25,000 scale topographic maps. However, the total

Chalermchon Satirapod; I. Trisirisatayawong; P. Homniam

2003-01-01

7

GPS Precise Point Positioning Methods Using IGS Products for Vehicular Navigation Application  

Microsoft Academic Search

Recently, GPS precise point positioning (PPP) has attracted the precision GPS community as it can provide the cm-dm level positioning accuracy with a single GPS receiver, which is almost comparable to that obtained by DGPS. We have developed a generic PPP software. Assuming a dual frequency receiver and using IGS precise satellite ephemeris and clock, the software estimates position vector

Masatoshi Honda; Masaaki Murata; Y. Mizukura

2006-01-01

8

Development of Precise Point Positioning Method Using Global Positioning System Measurements  

NASA Astrophysics Data System (ADS)

Precise point positioning (PPP) is increasingly used in several parts such as monitoring of crustal movement and maintaining an international terrestrial reference frame using global positioning system (GPS) measurements. An accuracy of PPP data processing has been increased due to the use of the more precise satellite orbit/clock products. In this study we developed PPP algorithm that utilizes data collected by a GPS receiver. The measurement error modelling including the tropospheric error and the tidal model in data processing was considered to improve the positioning accuracy. The extended Kalman filter has been also employed to estimate the state parameters such as positioning information and float ambiguities. For the verification, we compared our results to other of International GNSS Service analysis center. As a result, the mean errors of the estimated position on the East-West, North-South and Up-Down direction for the five days were 0.9 cm, 0.32 cm, and 1.14 cm in 95% confidence level.

Choi, Byung-Kyu; Back, Jeong-Ho; Cho, Sung-Ki; Park, Jong-Uk; Park, Pil-Ho

2011-09-01

9

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

NASA Astrophysics Data System (ADS)

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

Krzan, Grzegorz; Dawidowicz, Karol; Krzysztof, ?wia¸tek

2013-09-01

10

Surface Ice Flow Velocity and Tide Retrieval of the Amery Ice Shelf using Precise Point Positioning  

Microsoft Academic Search

Five days of continuous GPS observation data were collected in the frontal zone of the Amery ice shelf and subsequently post-processed using precise point position (PPP) technology based on precise orbit and clock products from the International GNSS service. The surface ice flow velocity of the observed point was derived from PPP to be 2.25 m\\/day toward the northeast with an

Xiaohong Zhang; Ole B. Andersen

2006-01-01

11

Errors Analysis in GPS Precise Point Positioning: Impact of Ambiguity Fixing  

Microsoft Academic Search

GNSS geodetic positioning using the classical double-difference approach may have some limitations. For example, fixing ambiguities can be challenging for long baselines, while processing short baseline only give the relative displacement between the two stations. In this context and thanks to the continuous improvement of IGS GNSS orbit and clock products, the Precise Point Positioning (PPP) technique appears in the

F. Perosanz; F. Fund; F. Mercier; S. Loyer; H. Capdeville

2010-01-01

12

An improved approach to model regional ionosphere and accelerate convergence for precise point positioning  

NASA Astrophysics Data System (ADS)

Given the severe effects of the ionosphere on global navigation satellite system (GNSS) signals, single-frequency (SF) precise point positioning (PPP) users can only achieve decimeter-level positioning results. Ionosphere-free combinations can eliminate the majority of ionospheric delay, but increase observation noise and slow down dual-frequency (DF) PPP convergence. In this paper, we develop a regional ionosphere modeling and rapid convergence approach to improve SF PPP (SFPPP) accuracy and accelerate DF PPP (DFPPP) convergence speed. Instead of area model, ionospheric delay is modeled for each satellite to be used as a priori correction. With the ionospheric, wide-lane uncalibrated phase delay (UPD) and residuals satellite DCBs product, the wide-lane observations for DF users change to be high-precision pseudorange observations. The validation of a continuously operating reference station (CORS) network was analyzed. The experimental results confirm that the approach considerably improves the accuracy of SFPPP. For DF users, convergence time is substantially reduced.

Yao, Yibin; Zhang, Rui; Song, Weiwei; Shi, Chuang; Lou, Yidong

2013-10-01

13

Flight Evaluation of GPS Precise Point Positioning Software for Helicopter Navigation  

NASA Astrophysics Data System (ADS)

In 2007 development and assessment of a precise point positioning (PPP) software for land vehicular navigation have been reported. This paper presents one phase of the continued study at NDA for further extension of the software to helicopter navigation. For 3D users, the height-dependent tropospheric delay is a critical factor, and so the sophisticated correction models and parameter estimation strategies have to be investigated to mitigate the delay effect. Since the precise positioning results become available only after the filter convergence and the filter generally converges rather slowly, speeding up the convergence has to be taken into special attention. In this paper we propose some new ideas to cope with this problem, and report the test using GPS helicopter flight data in post-processing. With proposed techniques including the variable Q and pseudo-observation concept, we show that point positioning accuracy at about decimeter level both horizontally and vertically can be achieved with improved convergence within about half an hour. We also show that the use of the high-rate (30-second) satellite clocks rather than the 5-minute clocks further improves positioning accuracy at sub-decimeter level in each 3D coordinate.

Shimizu, Yutaka; Murata, Masaaki

14

Regional reference network augmented precise point positioning for instantaneous ambiguity resolution  

NASA Astrophysics Data System (ADS)

Integer ambiguity fixing can significantly shorten the initialization time and improve the accuracy of precise point positioning (PPP), but it still takes approximate 15 min of time to achieve reliable integer ambiguity solutions. In this contribution, we present a new strategy to augment PPP estimation with a regional reference network, so that instantaneous ambiguity fixing is achievable for users within the network coverage. In the proposed method, precise zero-differenced atmospheric delays are derived from the PPP fixed solution of the reference stations, which are disseminated to, and interpolated at user stations to correct for L1, L2 phase observations or their combinations. With the corrected observations, instantaneous ambiguity resolution can be carried out within the user PPP software, thus achieving the position solutions equivalent to the network real-time kinematic positioning (NRTK). The strategy is validated experimentally. The derived atmospheric delays and the interpolated corrections are investigated. The ambiguity fixing performance and the resulted position accuracy are assessed. The validation confirms that the new strategy can provide comparable service with NRTK. Therefore, with this new processing strategy, it is possible to integrate PPP and NRTK into a seamless positioning service, which can provide an accuracy of about 10 cm anywhere, and upgrade to a few centimeters within a regional network.

Li, Xingxing; Zhang, Xiaohong; Ge, Maorong

2011-03-01

15

An Analysis of the Impact of AN Improved Gnss Constellation on Precise Point Positioning  

NASA Astrophysics Data System (ADS)

During the past few years there have been an increasing number of GNSS research studies on the predicted impact on positioning due to the implementation and use of Galileo and GLONASS alongside GPS. It is expected that some years from now these other two satellite constellations will be complete and therefore there would be around about three times more GNSS satellites in the sky compared to those provided by GPS alone, which would bring a considerable improvement in terms of satellite geometry at any location on the globe. Most of the research studies on the simultaneous use GPS and Galileo measurements, for example, have been carried out through signal simulation, by means of either software or hardware simulators. In order to analyze the impact of the larger number of available satellites, but using actual satellite signals, we have used a different technique in which the current GPS constellation is virtually doubled. This means that we are simulating a second GNSS system with the same orbital characteristics as GPS (but not considering any improved signal characteristics it may have) in different geometry condition - in effect, a doubling of the GPS constellation. The exact procedure is explained in this paper. The main advantages of this technique are that it does not require the use of a simulator; it is based on real satellite signals; and it is reasonably simple to perform if the appropriate positioning engine is available. Using this technique, we are able to analyze the possible impact of a second GNSS constellation. Although it is not possible to derive immutable numbers to quantify this improvement (a shared limitation of any other simulation analysis), due to the nature of the analysis technique, it is possible to have a reasonably clear idea of what the positioning performance will actually look like. Precise point positioning (PPP) is one of the existing techniques for determining point coordinates using a GPS receiver. In this technique, observations produced by a single receiver are used to determine the three coordinate components, as well as other parameters, such as the receiver clock error and the total neutral atmosphere delay. The word "precise" was first used, in the late 1990s, to provide a different qualification of this new technique from conventional point positioning using broadcast satellite orbits and clocks. So the technique was said to be "precise" because precise (i.e., post-fit) satellite orbits and clock corrections were used in the data processing. The results proved to be significantly more precise and accurate than using broadcast orbits and clocks. PPP has come a long way over the past decade to reach the current level of achievable accuracy depending on the type of positioning and quality of satellite information. This has been made possible through the use of more sophisticated observational models, the use of carrier-phase measurements instead of pseudoranges, and also benefiting from the enhancement of the quality of orbit and clock corrections made available, with the resulting positioning errors matching the quality of the orbits and clocks used. The main tool which is used in this work is our PPP package, called GAPS (GPS Analysis and Positioning Software). GAPS has been developed at UNB over the past 3 years, and its main advantage is that it is not only a positioning application, but also a data analysis tool. In this paper, we present the analysis of data from a mimicked double constellation using the current GPS satellites (actually observed during two different time intervals, but analyzed as if the two constellations were observed simultaneously), assessing the performance results with GAPS. The outcome of our analysis provides a perspective on the likely impact of multiple GNSS systems on PPP, in terms of accuracies achievable and convergence times.

Garcia, Carlos; Leandro, Rodrigo; Santos, Marcelo; Langley, Richard

16

Precise point positioning for the efficient and robust analysis of GPS data from large networks  

Microsoft Academic Search

Networks of dozens to hundreds of permanently operating precision Global Positioning System (GPS) receivers are emerging at spatial scales that range from 100 to 10  km. To keep the computational burden associated with the analysis of such data economically feasible, one approach is to first determine precise GPS satellite positions and clock corrections from a globally distributed network of

J. F. Zumberge; M. B. Heflin; D. C. Jefferson; M. M. Watkins; F. H. Webb

1997-01-01

17

Detection of Ocean Tide Loading Constituents Based on Precise Point Positioning by GPS  

NASA Astrophysics Data System (ADS)

In this study, the Ocean Tide Loading (OTL) constituents were detected by the Precise Point Positioning (PPP) technique using GPS. Then, the GPS estimates of OTL constituents were compared with the predictions of the ocean tide models. We picked three permanent GPS stations as test sites and they are ICNW, SEOS, and CJUN. To detect the OTL constituents using GPS, we created vertical coordinate time series at 10-minute intervals using the PPP approach implemented in the GIPSY software. Through the tidal harmonic analysis of this height time series, the four major constituents (M2; S2;K1;O1) were determined. The amplitude obtained from the GPS height time series of the OTL constituents showed best match with the model predictions at CJUN, while the phase showed closest match at ICNW. The amplitude accuracy of the M2, which is the dominant factor out of the 11 major constituents, was 24.8 on average.

Won, Jihye; Park, Kwan-Dong

2009-12-01

18

Flight Test Evaluation of Precise Point Positioning Techniques Using Optical Ranging  

NASA Astrophysics Data System (ADS)

This article reports on a flight test for the purpose of validating single-vehicle Global Positioning System (GPS) precise point positioning (PPP) of an aircraft using JPL's Global Navigation Satellite System (GNSS)-Inferred Positioning System (GIPSY) software and postprocessed satellite products. The article provides a comparison of a laser ranging device to GPS position estimates relative to a fixed ground station. The range data derived independently from the laser and GPS techniques agree to an average of 6.6 cm (RMS). The flight test was conducted on a Cessna aircraft circling the laser ranging device installed at Table Mountain in Wrightwood, California, at a range of approximately 6 km while the aircraft flew at an altitude of about 4.3 km. An error budget is presented based on the GPS, laser, meteorology, and inertial sensors employed. The survey of the locations of the instruments and associated error is presented. The range error of 6.6 cm RMS is consistent with the error in the instruments and survey.

Williamson, W.; Haines, B.; Wilson, K.; Kovalik, J.; Wright, M.; Meyer, R.; Bar-Sever, Y.

2012-11-01

19

Evaluation of Kinematic Airborne GPS Data Processing Using Precise Point Positioning Approach  

Microsoft Academic Search

The airborne GPS receiver is used to get the position information of an aircraft in the calibration flight test of radars. The position information is obtained by the carrier phase differential GPS techniques (CDGPS), which needs a network of GPS receivers as reference stations. Usually at least two GPS receivers are needed to get position information of decimeter level precision.

Xianqin Tu; Qinghai Meng; Dongyun Yi; Haiyin Zhou

2012-01-01

20

Real-time Precise Point Positioning with Ambiguity Resolution for Geosciences  

NASA Astrophysics Data System (ADS)

Real-time provision of information on large scale crustal deformation during an earthquake can be crucial in assessing property damage and managing relief operations. Moreover, such a real-time monitoring system may even lead to the accurate prediction of earthquakes in future and help the subsequent studies on the mechanism involved. During the past two decades, Global Positioning System (GPS) measurements have been extensively applied to investigate such processes in the geosciences. Precise point positioning (PPP) using GPS based on single stations can achieve comparable accuracies to conventional relative positioning, when precise satellite orbits and clocks, and Earth rotation products are used. Thus, PPP does not need any reference stations to achieve high positioning accuracy, e.g. at the millimetre level in static and centimetre level in kinematic applications. This has both technical and economic advantages and may be the only feasible option in some specific applications such as Tsunami early warning systems. However, unlike relative positioning, PPP suffers from unresolved integer ambiguities, which prevented further accuracy improvements within short observation periods or in real-time. On account of the great potential of PPP, we developed a prototype real-time PPP system which also employs ambiguity resolution at a single station. This development is based on the PANDA (Positioning And Navigation Data Analyst) software, which was originally developed at Wuhan University in China, and has been significantly refined by the authors. To assess this system, about 30 stations from the EUREF Permanent Network Internet Protocol (EUREF-IP) pilot project are used to produce the real-time satellite clocks, with satellite orbits and Earth rotation parameters (ERP) fixed to the predicted part of the IGS (International GNSS Service) ultra-rapid products. This is followed by the estimation of the uncalibrated hardware delays (UHD), which are crucial in resolving the ambiguities. Finally, all products (clocks, orbits, UHDs and ERPs) are provided in real-time to allow PPP with ambiguity resolution. Through the simulation of this prototype real-time PPP system, we show that significant accuracy improvements can be achieved, which are of significance to real-time applications in the geosciences.

Geng, J.; Meng, X.; Teferle, F. N.; Dodson, A. H.; Ge, M.; Shi, C.; Liu, J.

2009-04-01

21

Satellite- and epoch differenced precise point positioning based on a regional augmentation network.  

PubMed

Precise Point Positioning (PPP) has been demonstrated as a simple and effective approach for user positioning. The key issue in PPP is how to shorten convergence time and improve positioning efficiency. Recent researches mainly focus on the ambiguity resolution by correcting residual phase errors at a single station. The success of this approach (referred to hereafter as NORM-PPP) is subject to how rapidly one can fix wide-lane and narrow-lane ambiguities to achieve the first ambiguity-fixed solution. The convergence time of NORM-PPP is receiver type dependent, and normally takes 15-20 min. Different from the general algorithm and theory by which the float ambiguities are estimated and the integer ambiguities are fixed, we concentrate on a differential PPP approach: the satellite- and epoch differenced (SDED) approach. In general, the SDED approach eliminates receiver clocks and ambiguity parameters and thus avoids the complicated residual phase modeling procedure. As a further development of the SDED approach, we use a regional augmentation network to derive tropospheric delay and remaining un-modeled errors at user sites. By adding these corrections and applying the Robust estimation, the weak mathematic properties due to the ED operation is much improved. Implementing this new approach, we need only two epochs of data to achieve PPP positioning converging to centimeter-positioning accuracy. Using seven days of GPS data at six CORS stations in Shanghai, we demonstrate the success rate, defined as the case when three directions converging to desired positioning accuracy of 10 cm, reaches 100% when the interval between the two epochs is longer than 15 min. Comparing the results of 15 min' interval to that of 10 min', it is observed that the position RMS improves from 2.47, 3.95, 5.78 cm to 2.21, 3.93, 4.90 cm in the North, East and Up directions, respectively. Combining the SDED coordinates at the starting point and the ED relative coordinates thereafter, we demonstrate the performance of RTK PPP with standard deviation of 0.80, 1.34, 0.97 cm in the North, East and Up directions. PMID:22969358

Li, Haojun; Chen, Junping; Wang, Jiexian; Wu, Bin

2012-06-04

22

Satellite- and Epoch Differenced Precise Point Positioning Based on a Regional Augmentation Network  

PubMed Central

Precise Point Positioning (PPP) has been demonstrated as a simple and effective approach for user positioning. The key issue in PPP is how to shorten convergence time and improve positioning efficiency. Recent researches mainly focus on the ambiguity resolution by correcting residual phase errors at a single station. The success of this approach (referred to hereafter as NORM-PPP) is subject to how rapidly one can fix wide-lane and narrow-lane ambiguities to achieve the first ambiguity-fixed solution. The convergence time of NORM-PPP is receiver type dependent, and normally takes 15–20 min. Different from the general algorithm and theory by which the float ambiguities are estimated and the integer ambiguities are fixed, we concentrate on a differential PPP approach: the satellite- and epoch differenced (SDED) approach. In general, the SDED approach eliminates receiver clocks and ambiguity parameters and thus avoids the complicated residual phase modeling procedure. As a further development of the SDED approach, we use a regional augmentation network to derive tropospheric delay and remaining un-modeled errors at user sites. By adding these corrections and applying the Robust estimation, the weak mathematic properties due to the ED operation is much improved. Implementing this new approach, we need only two epochs of data to achieve PPP positioning converging to centimeter-positioning accuracy. Using seven days of GPS data at six CORS stations in Shanghai, we demonstrate the success rate, defined as the case when three directions converging to desired positioning accuracy of 10 cm, reaches 100% when the interval between the two epochs is longer than 15 min. Comparing the results of 15 min' interval to that of 10 min', it is observed that the position RMS improves from 2.47, 3.95, 5.78 cm to 2.21, 3.93, 4.90 cm in the North, East and Up directions, respectively. Combining the SDED coordinates at the starting point and the ED relative coordinates thereafter, we demonstrate the performance of RTK PPP with standard deviation of 0.80, 1.34, 0.97 cm in the North, East and Up directions.

Li, Haojun; Chen, Junping; Wang, Jiexian; Wu, Bin

2012-01-01

23

Triple-frequency GPS precise point positioning with rapid ambiguity resolution  

NASA Astrophysics Data System (ADS)

At present, reliable ambiguity resolution in real-time GPS precise point positioning (PPP) can only be achieved after an initial observation period of a few tens of minutes. In this study, we propose a method where the incoming triple-frequency GPS signals are exploited to enable rapid convergences to ambiguity-fixed solutions in real-time PPP. Specifically, extra-wide-lane ambiguity resolution can be first achieved almost instantaneously with the Melbourne-Wübbena combination observable on L2 and L5. Then the resultant unambiguous extra-wide-lane carrier-phase is combined with the wide-lane carrier-phase on L1 and L2 to form an ionosphere-free observable with a wavelength of about 3.4 m. Although the noise of this observable is around 100 times the raw carrier-phase noise, its wide-lane ambiguity can still be resolved very efficiently, and the resultant ambiguity-fixed observable can assist much better than pseudorange in speeding up succeeding narrow-lane ambiguity resolution. To validate this method, we use an advanced hardware simulator to generate triple-frequency signals and a high-grade receiver to collect 1-Hz data. When the carrier-phase precisions on L1, L2 and L5 are as poor as 1.5, 6.3 and 1.5 mm, respectively, wide-lane ambiguity resolution can still reach a correctness rate of over 99 % within 20 s. As a result, the correctness rate of narrow-lane ambiguity resolution achieves 99 % within 65 s, in contrast to only 64 % within 150 s in dual-frequency PPP. In addition, we also simulate a multipath-contaminated data set and introduce new ambiguities for all satellites every 120 s. We find that when multipath effects are strong, ambiguity-fixed solutions are achieved at 78 % of all epochs in triple-frequency PPP whilst almost no ambiguities are resolved in dual-frequency PPP. Therefore, we demonstrate that triple-frequency PPP has the potential to achieve ambiguity-fixed solutions within a few minutes, or even shorter if raw carrier-phase precisions are around 1 mm. In either case, we conclude that the efficiency of ambiguity resolution in triple-frequency PPP is much higher than that in dual-frequency PPP.

Geng, Jianghui; Bock, Yehuda

2013-05-01

24

Study of the azimuthal heterogeneity of tropospheric delays by GPS precise-point-positioning  

NASA Astrophysics Data System (ADS)

In recent years it has been shown that models for the tropospheric delays based on data from numerical weather models improve the accuracy of station coordinates derived from GPS analysis on a global as well as a regional (e.g. European) scale. However, there is no recommendation in terms of azimuthal asymmetries, i.e., as far as tropospheric (hydrostatic and wet) gradients are concerned. This work will investigate the non-homogeneous behaviour in azimuth for slant tropospheric delays in order to enhance the gradient models in GPS processing, in particular for the west of France. This is a region where GPS measurements are under influence of maritime meteorology. Satellites can be located above the Atlantic Ocean as well as above the European continent. Meteorological conditions affecting these areas are different; thus, the work deals with impact of satellites choices on tropospheric delays and station coordinates. The GIPSY software will be used to treat observations with the precise-point-positioning (PPP) procedure and the GAMIT software will be applied in a classical way for comparison. The final goal and perspective is to assess current methods and to eventually propose a new tropospheric model to better take into account the azimuthal tropospheric heterogeneity.

Morel, Laurent; Fund, Francois; Boehm, Johannes

2010-05-01

25

Determination of earthquake magnitude using GPS displacement waveforms from real-time precise point positioning  

NASA Astrophysics Data System (ADS)

For earthquake and tsunami early warning and emergency response, earthquake magnitude is the crucial parameter to be determined rapidly and correctly. However, a reliable and rapid measurement of the magnitude of an earthquake is a challenging problem, especially for large earthquakes (M > 8). Here, the magnitude is determined based on the GPS displacement waveform derived from real-time precise point positioning (RTPPP). RTPPP results are evaluated with an accuracy of 1 cm in the horizontal components and 2-3 cm in the vertical components, indicating that the RTPPP is capable of detecting seismic waves with amplitude of 1 cm horizontally and 2-3 cm vertically with a confidence level of 95 per cent. In order to estimate the magnitude, the unique information provided by the GPS displacement waveform is the horizontal peak displacement amplitude. We show that the empirical relation of Gutenberg (1945) between peak displacement and magnitude holds up to nearly magnitude 9.0 when displacements are measured with GPS. We tested the proposed method for three large earthquakes. For the 2010 Mw 7.2 El Mayor-Cucapah earthquake, our method provides a magnitude of M7.18 ± 0.18. For the 2011 Mw 9.0 Tohoku-oki earthquake the estimated magnitude is M8.74 ± 0.06, and for the 2010 Mw 8.8 Maule earthquake the value is M8.7 ± 0.1 after excluding some near-field stations. We, therefore, conclude that depending on the availability of high-rate GPS observations, a robust value of magnitude up to 9.0 for a point source earthquake can be estimated within tens of seconds or a few minutes after an event using a few GPS stations close to the epicentre. The rapid magnitude could be as a pre-requisite for tsunami early warning, fast source inversion and emergency response is feasible.

Fang, Rongxin; Shi, Chuang; Song, Weiwei; Wang, Guangxing; Liu, Jingnan

2013-10-01

26

Real Time Precise Point Positioning: Preliminary Results for the Brazilian Region  

NASA Astrophysics Data System (ADS)

GNSS positioning can be carried out in relative or absolute approach. In the last years, more attention has been driven to the real time precise point positioning (PPP). To achieve centimeter accuracy with this method in real time it is necessary to have available the satellites precise coordinates as well as satellites clocks corrections. The coordinates can be used from the predicted IGU ephemeris, but the satellites clocks must be estimated in a real time. It can be made from a GNSS network as can be seen from EUREF Permanent Network. The infra-structure to realize the PPP in real time is being available in Brazil through the Brazilian Continuous Monitoring Network (RBMC) together with the Sao Paulo State GNSS network which are transmitting GNSS data using NTRIP (Networked Transport of RTCM via Internet Protocol) caster. Based on this information it was proposed a PhD thesis in the Univ. Estadual Paulista (UNESP) aiming to investigate and develop the methodology to estimate the satellites clocks and realize PPP in real time. Then, software is being developed to process GNSS data in the real time PPP mode. A preliminary version of the software was called PPP_RT and is able to process GNSS code and phase data using precise ephemeris and satellites clocks. The PPP processing can be accomplished considering the absolute satellite antenna Phase Center Variation (PCV), Ocean Tide Loading (OTL), Earth Body Tide, among others. The first order ionospheric effects can be eliminated or minimized by ion-free combination or parameterized in the receiver-satellite direction using a stochastic process, e.g. random walk or white noise. In the case of ionosphere estimation, a pseudo-observable is introduced in the mathematical model for each satellite and the initial value can be computed from Klobuchar model or from Global Ionospheric Map (GIM). The adjustment is realized in the recursive mode and the DIA (Detection Identification and Adaptation) is used for quality control. In this paper our proposition is to present the mathematical models implemented in the PPP_RT software and some proposal to accomplish the PPP in real time as for example using tropospheric model from Brazilian Numerical Weather Forecast Model (BNWFM) and estimating the ionosphere using stochastic process. GPS data sample from the Brazilian region was processed using the PPP_RT software considering periods under low and high ionospheric activities and the results estimating the ionosphere were compared with the ion-free combination. The PPP results also were analyzed considering the strategy of the troposphere estimation, Hopfield model or using the BNWFM. For the troposphere case, the values from BNWFM can reach similar results when estimating the troposphere. For the ionosphere case, the results have shown that ionosphere estimation can improve the time convergence of the PPP processing what is very important for PPP in real time.

Marques, Haroldo; Monico, João.; Hirokazu Shimabukuro, Milton; Aquino, Marcio

2010-05-01

27

Assessment of correct fixing rate for precise point positioning ambiguity resolution on a global scale  

NASA Astrophysics Data System (ADS)

Ambiguity resolution (AR) for a single receiver has been a popular topic in Global Positioning System (GPS) recently. Ambiguity-resolution methods for precise point positioning (PPP) have been well documented in recent years, demonstrating that it can improve the accuracy of PPP. However, users are often concerned about the reliability of ambiguity-fixed PPP solution in practical applications. If ambiguities are fixed to wrong integers, large errors would be introduced into position estimates. In this paper, we aim to assess the correct fixing rate (CFR), i.e., number of ambiguities correctly fixing to the total number of ambiguities correctly and incorrectly fixing, for PPP user ambiguity resolution on a global scale. A practical procedure is presented to evaluate the CFR of PPP user ambiguity resolution. GPS data of the first 3 days in each month of 2010 from about 390 IGS stations are used for experiments. Firstly, we use GPS data collected from about 320 IGS stations to estimate global single-differenced (SD) wide-lane and narrow-lane satellite uncalibrated phase delays (UPDs). The quality of UPDs is evaluated. We found that wide-lane UPD estimates have a rather small standard deviation (Std) between 0.003 and 0.004 cycles while most of Std of narrow-lane estimates are from 0.01 to 0.02 cycles. Secondly, many experiments have been conducted to investigate the CFR of integer ambiguity resolution we can achieve under different conditions, including reference station density, observation session length and the ionospheric activity. The results show that the CFR of PPP can exceed 98.0 % with only 1 h of observations for most user stations. No obvious correlation between the CFR and the reference station density is found. Therefore, nearly homogeneous CFR can be achieved in PPP AR for global users. At user end, higher CFR could be achieved with longer observations. The average CFR for 30-min, 1-h, 2-h and 4-h observation is 92.3, 98.2, 99.5 and 99.7 %, respectively. In order to get acceptable CFR, 1 h is a recommended minimum observation time. Furthermore, the CFR of PPP can be affected by diurnal variation and geomagnetic latitude variation in the ionosphere. During one day at the hours when rapid ionospheric variations occur or in low geomagnetic latitude regions where equatorial electron density irregularities are produced relatively frequently, a significant degradation of the CFR is demonstrated.

Zhang, Xiaohong; Li, Pan

2013-06-01

28

Tightly Coupled Processing of Precise Point Position (PPP) and INS Data  

Microsoft Academic Search

This paper looks at the implementation and results from processing un-differenced GPS data (PPP) with Inertial Measurement Unit (IMU) data using a tightly coupled filter in an airborne environment. With the use of precise orbit and clock products, PPP has matured from a research topic to a practical GPS processing methodology. The major advantage of PPP GPS processing is that

Hugh Martell

29

Trimble’s Rtk And Dgps Solutions In Comparison With Precise Point Positioning  

Microsoft Academic Search

Differential GPS (DGPS) and Real-Time-Kinematic (RTK) solutions are widely accepted methods for accurate positioning and navigation.\\u000a Initially these methods were based on single reference stations. A big breakthrough in performance and accuracy was achieved\\u000a by the introduction of network solutions. Today, the use of the Virtual Reference Station method is a standard technology\\u000a applied in a large number of regional

Herbert Landau; Xiaoming Chen; Sören Klose; Rodrigo Leandro; Ulrich Vollath

30

First results from Virtual Reference Station (VRS) and Precise Point Positioning (PPP) GPS research at the Western Australian Centre for Geodesy  

Microsoft Academic Search

Over the past 18 months, a team in the Western Australian Centre for Geodesy at Curtin University of Technology, Perth, has been researching the optimum configurations to achieve long-range and precise GPS- based aircraft positioning for subsequent airborne mapping projects. Three parallel strategies have been adopted to solve this problem: virtual reference stations (VRS), precise point positioning (PPP), and multiple

N. Castleden; G. R. Hu; W. E. Featherstone; D. A. Abbey; C. J. Earls; D. Weihing; O. Øvstedal

2004-01-01

31

A reference station-based GNSS computing mode to support unified precise point positioning and real-time kinematic services  

NASA Astrophysics Data System (ADS)

Currently, the GNSS computing modes are of two classes: network-based data processing and user receiver-based processing. A GNSS reference receiver station essentially contributes raw measurement data in either the RINEX file format or as real-time data streams in the RTCM format. Very little computation is carried out by the reference station. The existing network-based processing modes, regardless of whether they are executed in real-time or post-processed modes, are centralised or sequential. This paper describes a distributed GNSS computing framework that incorporates three GNSS modes: reference station-based, user receiver-based and network-based data processing. Raw data streams from each GNSS reference receiver station are processed in a distributed manner, i.e., either at the station itself or at a hosting data server/processor, to generate station-based solutions, or reference receiver-specific parameters. These may include precise receiver clock, zenith tropospheric delay, differential code biases, ambiguity parameters, ionospheric delays, as well as line-of-sight information such as azimuth and elevation angles. Covariance information for estimated parameters may also be optionally provided. In such a mode the nearby precise point positioning (PPP) or real-time kinematic (RTK) users can directly use the corrections from all or some of the stations for real-time precise positioning via a data server. At the user receiver, PPP and RTK techniques are unified under the same observation models, and the distinction is how the user receiver software deals with corrections from the reference station solutions and the ambiguity estimation in the observation equations. Numerical tests demonstrate good convergence behaviour for differential code bias and ambiguity estimates derived individually with single reference stations. With station-based solutions from three reference stations within distances of 22-103 km the user receiver positioning results, with various schemes, show an accuracy improvement of the proposed station-augmented PPP and ambiguity-fixed PPP solutions with respect to the standard float PPP solutions without station augmentation and ambiguity resolutions. Overall, the proposed reference station-based GNSS computing mode can support PPP and RTK positioning services as a simpler alternative to the existing network-based RTK or regionally augmented PPP systems.

Feng, Yanming; Gu, Shengfeng; Shi, Chuang; Rizos, Chris

2013-09-01

32

Precise Point Positioning (PPP) - an alternative processing technique to estimate the tropospheric wet delay of GNSS signals  

NASA Astrophysics Data System (ADS)

Microwave signals of the GNSS satellites (GPS, GLONASS and in future GALILEO) are time delayed when passing the atmosphere. Based on this signal delay, e.g. the humidity distribution within the troposphere can be determined. It has already been shown that delivery of the Zenith Wet Delays derived from a network solution with hourly resolution and accuracy of 1mm PW is achievable. In the case of very large networks along with an increased number of observation and computational demands, an alternative processing technique has to be applied - Precise Point Positioning (PPP). In this presentation we investigate how the atmospheric precipitable water content derived from GNSS data can be assimilated within an operational Nowcasting system (INCA) and how PPP results compare to the network solution. It is to be expected that the accuracy of the PPP estimates decreases due to several effects (satellite clocks, biases, no ambiguity resolution), but independency from the reference station data will significantly shorten the latency of the results (few min), and provide the regional/national service to enhance the prognosis in the numerical forecast model. It has been proved that e.g. passing weather fronts can be analysed much better by introduced GNSS derived tropospheric wet delays because this data is influenced by changes in humidity in the free atmosphere, whereas the data at the meteorological ground stations reacts to these changes with a considerable time delay. This allows to forecast heavy rainfall causing potentially local floodings more reliable and to narrow down the affected region.

Karabatic, A.; Weber, R.

2009-04-01

33

GPS single frequency precise orbit determination of LEO satellites with the cm-level accuracy and comparison with the precise point positioning  

NASA Astrophysics Data System (ADS)

Using single frequency GPS measurements from the CHAMP satellite it was demonstrated before that during the solar maximum the LEO orbit can be determined with an accuracy below 10 cm RMS (1D). The first order ionosphere effect is removed by linear combination of pseudorange and carrier phase measurements using the so-called LP linear combination. The main limitation of this POD approach is the high noise of the pseudorange measurements. By forming the LP linear combination, noise in the pseudorange measurements is reduced by 50%, and by estimating half-cycle phase ambiguities an additional reduction can be expected in all systematic effects (e.g. multipath, group delay variations, etc.). Furthermore, thanks to the high quality GPS measurements from the GRACE mission, it was demonstrated that the orbit of a LEO satellite can be determined using single frequency measurements with an accuracy of 5 cm RMS (1D). This is very close to the cm-level accuracy of the LEO orbits based on dual-frequency carrier phase measurements. Here we show that based on the latest gravity field models short term perturbations can very accurately be modelled in the numerical integration, considerably reducing the number of empirical parameters. This allows to average errors in the pseudorange measurements over a longer period of time and further increase the accuracy of GRACE orbit down to 3 cm RMS (1D) and beyond. However, at this level of accuracy systematic errors in the code to carrier coherence play a crucial role, especially in terms of signal group delay variations of GPS satellite and LEO antenna. Here we demonstrate a novel approach in the code to carrier calibration based on a geometry and ionosphere free linear combination. We show that it is possible to separate the group delay variations of the GPS satellite antenna from the group delay variations of a LEO or a ground antenna. This leads to very accurate mean group delay maps of the GPS satellite antennas. Validation of the code to carrier coherence calibration is carried out with the independent measurements from a high-gain steerable ground antenna. Here we show how code to phase coherence calibration improves LEO orbit determination based on single frequency measurements and compare our results with the ground precise point positioning based on single-frequency GPS measurements. A typical performance curve relating convergence time and accuracy is derived for PPP, as well as POD of the GRACE satellites during the solar minimum and maximum.

Svehla, Drazen; Escobar, Diego A.; Dow, John M.

34

Ultra-precision positioning assembly  

DOEpatents

An apparatus and method is disclosed for ultra-precision positioning. A slide base provides a foundational support. A slide plate moves with respect to the slide base along a first geometric axis. Either a ball-screw or a piezoelectric actuator working separate or in conjunction displaces the slide plate with respect to the slide base along the first geometric axis. A linking device directs a primary force vector into a center-line of the ball-screw. The linking device consists of a first link which directs a first portion of the primary force vector to an apex point, located along the center-line of the ball-screw, and a second link for directing a second portion of the primary force vector to the apex point. A set of rails, oriented substantially parallel to the center-line of the ball-screw, direct movement of the slide plate with respect to the slide base along the first geometric axis and are positioned such that the apex point falls within a geometric plane formed by the rails. The slide base, the slide plate, the ball-screw, and the linking device together form a slide assembly. Multiple slide assemblies can be distributed about a platform. In such a configuration, the platform may be raised and lowered, or tipped and tilted by jointly or independently displacing the slide plates.

Montesanti, Richard C. (San Francisco, CA); Locke, Stanley F. (Livermore, CA); Thompson, Samuel L. (Pleasanton, CA)

2002-01-01

35

Precision pointing mechanism for intersatellite optical communication  

NASA Astrophysics Data System (ADS)

The SILEX project is an experimental communication system aimed at demonstrating, in orbit, the feasibility of intersatellite optical communications using semiconductor lasers. As part of this project, a precision mechanism has been developed to point the transmitted beam ahead of the current receiving satellite position. This is necessary due to the relative motion of the satellites, the narrow beam, and the finite velocity of light. The design and construction of a prototype of this device is discussed along with measurements of performance. The technique as described can be used in many applications requiring precision beam steering or rotation control.

Hicks, T.; O'Sullivan, B.; Russell, J.; Scholl, L.

1989-09-01

36

Precision pointing mechanism for laser communication mission  

NASA Astrophysics Data System (ADS)

This paper describes the design, development and testing of a precision steering mirror used to provide laser pointing in a laser communication link. The mechanism is used to steer a 9 mm output laser beam about two orthogonal axes using an open loop command. The pointing error budget is 13 (mu) rad over the +/- 6.5 mrad pointing region. The mirror is mounted on a 2-axis flexure suspension system and driven by linear actuators. Position sensors measure the mirror position with respect to the base. The drive electronics utilize redundant servo electronics cards. This paper provides a general overview of the mechanism pointing requirements. After the requirements definition, an overview of the hardware configuration is given, followed by critical performance summaries and test results.

Harvison, Douglas A.; Hardy, Bruce

1996-10-01

37

Millimeter-accuracy GPS landslide monitoring using Precise Point Positioning with Single Receiver Phase Ambiguity (PPP-SRPA) resolution: a case study in Puerto Rico  

NASA Astrophysics Data System (ADS)

Continuous Global Positioning System (GPS) monitoring is essential for establishing the rate and pattern of superficial movements of landslides. This study demonstrates a technique which uses a stand-alone GPS station to conduct millimeter-accuracy landslide monitoring. The Precise Point Positioning with Single Receiver Phase Ambiguity (PPP-SRPA) resolution employed by the GIPSY/OASIS software package (V6.1.2) was applied in this study. Two-years of continuous GPS data collected at a creeping landslide were used to evaluate the accuracy of the PPP-SRPA solutions. The criterion for accuracy was the root-mean-square (RMS) of residuals of the PPP-SRPA solutions with respect to "true" landslide displacements over the two-year period. RMS is often regarded as repeatability or precision in GPS literature. However, when contrasted with a known "true" position or displacement it could be termed RMS accuracy or simply accuracy. This study indicated that the PPP-SRPA resolution can provide an accuracy of 2 to 3 mm horizontally and 8 mm vertically for 24-hour sessions with few outliers (< 1%) in the Puerto Rico region. Horizontal accuracy below 5 mm can be stably achieved with 4-hour or longer sessions if avoiding the collection of data during extreme weather conditions. Vertical accuracy below 10 mm can be achieved with 8-hour or longer sessions. This study indicates that the PPP-SRPA resolution is competitive with the conventional carrier-phase double-difference network resolution for static (longer than 4 hours) landslide monitoring while maintaining many advantages. It is evident that the PPP-SRPA method would become an attractive alternative to the conventional carrier-phase double-difference method for landslide monitoring, notably in remote areas or developing countries.

Wang, G. Q.

2013-03-01

38

PRECISION POINTING OF IBEX-Lo OBSERVATIONS  

SciTech Connect

Post-launch boresight of the IBEX-Lo instrument on board the Interstellar Boundary Explorer (IBEX) is determined based on IBEX-Lo Star Sensor observations. Accurate information on the boresight of the neutral gas camera is essential for precise determination of interstellar gas flow parameters. Utilizing spin-phase information from the spacecraft attitude control system (ACS), positions of stars observed by the Star Sensor during two years of IBEX measurements were analyzed and compared with positions obtained from a star catalog. No statistically significant differences were observed beyond those expected from the pre-launch uncertainty in the Star Sensor mounting. Based on the star observations and their positions in the spacecraft reference system, pointing of the IBEX satellite spin axis was determined and compared with the pointing obtained from the ACS. Again, no statistically significant deviations were observed. We conclude that no systematic correction for boresight geometry is needed in the analysis of IBEX-Lo observations to determine neutral interstellar gas flow properties. A stack-up of uncertainties in attitude knowledge shows that the instantaneous IBEX-Lo pointing is determined to within {approx}0.{sup 0}1 in both spin angle and elevation using either the Star Sensor or the ACS. Further, the Star Sensor can be used to independently determine the spacecraft spin axis. Thus, Star Sensor data can be used reliably to correct the spin phase when the Star Tracker (used by the ACS) is disabled by bright objects in its field of view. The Star Sensor can also determine the spin axis during most orbits and thus provides redundancy for the Star Tracker.

Hlond, M.; Bzowski, M. [Space Research Centre of the Polish Academy of Sciences, 18A Bartycka, 00-716 Warsaw (Poland); Moebius, E.; Kucharek, H.; Heirtzler, D.; Schwadron, N. A.; Neill, M. E. O'; Clark, G. [Space Science Center and Department of Physics, University of New Hampshire, Morse Hall, 8 College Road, Durham, NH 03824 (United States); Crew, G. B. [Haystack Observatory, Massachusetts Institute of Technology, Route 40, Westford, MA 01886 (United States); Fuselier, S. [Lockheed Martin, Space Physics Lab, 3251 Hanover Street, Palo Alto, CA 94304 (United States); McComas, D. J., E-mail: mhlond@cbk.waw.pl, E-mail: eberhard.moebius@unh.edu, E-mail: gbc@haystack.mit.edu, E-mail: stephen.a.fuselier@linco.com, E-mail: DMcComas@swri.edu, E-mail: DMcComas@swri.edu [Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78228 (United States)

2012-02-01

39

Precision Pointing of IBEX-Lo Observations  

NASA Astrophysics Data System (ADS)

Post-launch boresight of the IBEX-Lo instrument on board the Interstellar Boundary Explorer (IBEX) is determined based on IBEX-Lo Star Sensor observations. Accurate information on the boresight of the neutral gas camera is essential for precise determination of interstellar gas flow parameters. Utilizing spin-phase information from the spacecraft attitude control system (ACS), positions of stars observed by the Star Sensor during two years of IBEX measurements were analyzed and compared with positions obtained from a star catalog. No statistically significant differences were observed beyond those expected from the pre-launch uncertainty in the Star Sensor mounting. Based on the star observations and their positions in the spacecraft reference system, pointing of the IBEX satellite spin axis was determined and compared with the pointing obtained from the ACS. Again, no statistically significant deviations were observed. We conclude that no systematic correction for boresight geometry is needed in the analysis of IBEX-Lo observations to determine neutral interstellar gas flow properties. A stack-up of uncertainties in attitude knowledge shows that the instantaneous IBEX-Lo pointing is determined to within ~0fdg1 in both spin angle and elevation using either the Star Sensor or the ACS. Further, the Star Sensor can be used to independently determine the spacecraft spin axis. Thus, Star Sensor data can be used reliably to correct the spin phase when the Star Tracker (used by the ACS) is disabled by bright objects in its field of view. The Star Sensor can also determine the spin axis during most orbits and thus provides redundancy for the Star Tracker.

H?ond, M.; Bzowski, M.; Möbius, E.; Kucharek, H.; Heirtzler, D.; Schwadron, N. A.; O'Neill, M. E.; Clark, G.; Crew, G. B.; Fuselier, S.; McComas, D. J.

2012-02-01

40

Active Thermal Management for Precision Positioning  

Microsoft Academic Search

Precision positioning systems are inevitably subject to various thermal disturbances including heating from motors, friction between components, and ambient temperature fluctuations. Thermal disturbances cause unwanted thermal expansion and contraction; the resulting distortion of the components in the positioning system could lead to degraded positioning accuracy. This paper explores the application of estimation and control techniques to address thermally-induced positioning error.

Rongliang Zhou; Bill Gressick; John T. Wen; Michael Jensen; Joe Frankel; Grey Lerner; Mark Unrath

2007-01-01

41

Using Handheld GPS Receivers for Precise Positioning  

Microsoft Academic Search

SUMMARY In general handheld GPS receivers are used for absolute positioning or for relative positioning using DGPS-services or WAAS\\/EGNOS signals. The positioning is realized using code pseudo-ranges. Moreover it is well known that some of the handheld receivers use phase-smoothed code for positioning. This means that the phase signal is available and may be used for Precise Differential GPS (PDGPS)

Volker SCHWIEGER

2003-01-01

42

High precision positioning with a sensor network  

Microsoft Academic Search

We present an experimental high-precision ultrasonic positioning system based on a sensor network. The network can track an object moving along a straight line with an accuracy of 1 cm. The bulk of the position calculation is distributed, with sensor nodes exchanging only the times-of-flight of the ultrasonic pulses, and state information.

Julio I. Concha; Jae-Hyuk Oh

2004-01-01

43

Combined GPS and GALILEO instantaneous precise positioning  

NASA Astrophysics Data System (ADS)

This presentation provides results of the research aimed at precise positioning using single-epoch GPS and Galileo observations. The main goal was to develop algorithms that allow obtaining reliable centimeter-level position when using just a single epoch of pseudorange and carrier phase GPS and Galileo data in a single functional model. The presented algorithms are based on relative precise positioning using double-differenced observations in both single baseline and network mode. Fast and reliable ambiguity resolution is the key for rapid and single-epoch precise positioning. In order to support ambiguity resolution using small amount of data, special emphasis was put on mitigation of ionospheric and tropospheric delays. The functional model was based on constrained least squares estimation. The LAMBDA method was applied for ambiguity resolution and a multi-criteria statistical tests are used for ambiguity validation. These algorithms were implemented in GINPOS software developed at the University of Warmia and Mazury in Olsztyn. The results of combined GPS+Galileo processing were compared to the solutions obtained using GPS-only and Galileo-only data. Since there are just two test Galileo satellites on orbit, Spirent multi-GNSS simulator was used to obtain Galileo and GPS signals. The processed baselines reached up to 35-70 km. The results based on the simulated data show that even though single-epoch precise positioning is possible with GPS only, adding Galileo data increases availability and reliability of the user position.

Wielgosz, P.; Paziewski, J.; Stepniak, K.

2011-12-01

44

Precise positioning of patients for radiation therapy  

SciTech Connect

A number of immobilization schemes which permit precise daily positioning of patients for radiation therapy are discussed. Pretreatment and post-treatment radiographs have been taken with the patient in the treatment position and analyzed to determine the amount of intratreatment movement. Studies of patients in the supine, seated and decubitus positions indicate mean movements of less than 1 mm with a standard deviation of less than 1 mm. Patients immobilized in the seated position with a bite block and a mask have a mean movement of about 0.5 mm +/- 0.3 mm (s.d.), and patients immobilized in the supine position with their necks hyperextended for submental therapy evidence a mean movement of about 1.4 mm +/- 0.9 mm (s.d.). With the exception of those used for the decubitus position, the immobilization devices are simply fabricated out of thermoplastic casting materials readily available from orthopedic supply houses. A study of day-to-day reproducibility of patient position using laser alignment and pretreatment radiographs for final verification of position indicates that the initial laser alignment can be used to position a patient within 2.2 mm +/- 1.4 mm (s.d.) of the intended position. These results indicate that rigid immobilization devices can improve the precision of radiotherapy, which would be advantageous with respect to both tumor and normal tissue coverage in certain situations.

Verhey, L.J.; Goitein, M.; McNulty, P.; Munzenrider, J.E.; Suit, H.D.

1982-02-01

45

Precise Positioning of Ships for Maritime Disasters Prevention Using GPS  

NASA Astrophysics Data System (ADS)

Most ships use the marine DGPS (Differential Global Positioning System) service to know position information in the sea. In Korea, the Ministry of Land Transport and Maritime Affairs (MLTM) provides the nationwide DGPS (NDGPS) service to users trying to secure the safety of traffic of ships. The precision of ship position information obtained by the MLTM NDGPS system is about 1-2m. When ships pass through courses under bridges, ship collisions can occur with the bridges because of the few meter-level precision of position information. In this study, as a feasibility test, we estimated positions of ships at sea to predict the collisions between ships and bridges using DGPS, carrier phase DGPS (CDGPS), and precise point positioning (PPP) techniques were used. We conducted ship borne GPS observations in the south sea of Korea. To process the GPS data, GIPSY-OASIS (GPS Inferred Positioning System-Orbit Analysis and Simulation Software) developed by the Jet Propulsion Laboratory and CDGPS MATLAB program developed by Korea Space Research Institute were used. Antenna phase center variations, ocean tidal loading displacements, and azimuthal gradients of the atmosphere were corrected or estimated as standard procedures of high-precision GIPSY-OASIS data processing. As a result, the position precision decreased to decimeter-level with increasing the quantity of motion such as velocity, pitch and roll of the ship and buoys.

Ha, J.; Heo, M.; Chun, S.; Park, S.; Cho, D.

2010-12-01

46

Precision Positioning for Shallow Water Drilling  

NASA Astrophysics Data System (ADS)

The science-driven requirement for sediment cores on continental shelves has led to the Active Heave Compensation (AHC) upgrade Global LAke Drilling (GLAD)-800 drilling system. The AHC-GLAD800 drill rig was developed for installation on the largest vessels in the UNOLS fleet and was tested in the November 2001 on the R/V Knorr. Evaluation of the results of that test cruise pointed out the need for a significant increase in the accuracy and repeatability of the real-time navigation input to the vessel?s dynamic positioning (DP) system. An shore-based evaluation of different Global Positioning System (GPS) receivers including P-Code, US Coast Guard broadcast differential GPS (DGPS) and commercial satellite distributed DGPS was used to develop an approach for real-time system that flags and excludes outliers in order to maintain the tight input requirements for the DP system. Analysis of the data collected from the shore-based experiments and the at-sea field program will be presented.

Chayes, D. N.; Schmidt, V. E.

2002-12-01

47

Technology and design needs for precision pointing systems  

Microsoft Academic Search

World War II and the ensuing Cold War drove the development of sensing and weapon directing systems to the microradian level when the pointing systems are mounted on very dynamic hosts. Precision pointing, like all areas of aerospace-high technology, has come to be driven by the need to bring reliable, low risk, technically adequate systems to marketplace quickly and inexpensively.

Ronald Cubalchini

1995-01-01

48

Fast Precise GPS Positioning in the Presence of Ionospheric Delays.  

National Technical Information Service (NTIS)

This thesis deals about geodetic applications of the Global Positioning System (GPS), in which the position of the GPS receiver must be determined with cm-precision. This requires a relative measurement setup, together with an advanced processing strategy...

D. Odijk

2002-01-01

49

Precision absolute positional measurement of laser beams.  

PubMed

We describe an instrument which, coupled with a suitable coordinate measuring machine, facilitates the absolute measurement within the machine frame of the propagation direction of a millimeter-scale laser beam to an accuracy of around ±4 ?m in position and ±20 ?rad in angle. PMID:23669658

Fitzsimons, Ewan D; Bogenstahl, Johanna; Hough, James; Killow, Christian J; Perreur-Lloyd, Michael; Robertson, David I; Ward, Henry

2013-04-20

50

Precise centromere positioning on chicken chromosome 3.  

PubMed

Despite the progress of the chicken (Gallus gallus) genome sequencing project, the centromeric sequences of most macrochromosomes remain unknown. This makes it difficult to determine centromere positions in the genome sequence assembly. Using giant lampbrush chromosomes from growing oocytes, we analyzed in detail the pericentromeric region of chicken chromosome 3. Without knowing the DNA sequence, the centromeres at the lampbrush stage are detectable by immunostaining with antibodies against cohesin subunits. Immunostaining for cohesin followed by FISH with 23 BAC clones, covering the region from 0 to 23 Mb on chicken chromosome 3 (GGA3), allowed us to map the GGA3 centromere between BAC clones WAG38P15 and WAG54M22 located at position 2.3 and 2.5 Mb, respectively. This corresponds to the gap between 2 supercontigs at the 2.4-Mb position in the current GGA3 sequence assembly (build 2.1). Furthermore, we have determined that the current putative centromeric gap at position 11.6-13.1 Mb corresponds in fact to a long cluster of tandem chicken erythrocyte nuclear membrane repeats (CNM). PMID:20606388

Zlotina, A; Galkina, S; Krasikova, A; Crooijmans, R P M A; Groenen, M A M; Gaginskaya, E; Deryusheva, S

2010-07-03

51

A precision positioning system for fiber fed multi object spectroscopy  

NASA Astrophysics Data System (ADS)

This paper describes a high-precision fiber-positioning system currently being constructed for fiber-fed multiple-object spectroscopy, that will position optical fibers with an accuracy of better than 10 microns. The subsystems of this positioning system, which consists of mechanical frame, the x-y positioning system, fiber button gripper assembly for z positioning, and measurement system, are described in detail. This high-precision positioning system is mechanically stable and is essentially invariant to environmental conditions while in use.

Craig, W. W.; Hailey, C. J.; Stewart, R. E.; Blaedel, K. L.; Brodie, J. P.

52

Magnetic levitated high precision positioning system based on antagonistic mechanism  

Microsoft Academic Search

A six degree-of-freedom magnetically levitated high precision micro positioning system is designed to get rid of the friction which is one of the important factors limiting the resolution and accuracy of positioning devices. Since magnetic levitation systems are inherently unstable, most of the emphasis is placed on a magnetic circuit design so as to increase the system dynamic stability. For

Kee-Bong Choi; Soo-Hyun Kim; Yoon Keun Kwak

1996-01-01

53

An optimal GPS data processing technique for precise positioning  

Microsoft Academic Search

A mathematical formula for optimally combining dual-frequency Global Positioning System (GPS) pseudorange and carrier phase data streams into a single data stream is derived in closed form. The data combination reduces the data volume and computing time in the filtering process for parameter estimation by a factor of four while preserving the full data strength for precise positioning. The resulting

Sien-Chong Wu; William G. Melbourne

1993-01-01

54

Development of Real-Time Precise Positioning Algorithm Using GPS L1 Carrier Phase Data  

NASA Astrophysics Data System (ADS)

We have developed Real-time Phase DAta Processor(RPDAP) for GPS L1 carrier. And also, we tested the RPDAP's positioning accuracy compared with results of real time kinematic(RTK) positioning. While quality of the conventional L1 RTK positioning highly depend on receiving condition, the RPDAP can gives more stable positioning result because of different set of common GPS satellites, which searched by elevation mask angle and signal strength. In this paper, we demonstrated characteristics of the RPDAP compared with the L1 RTK technique. And we discussed several improvement ways to apply the RPDAP to precise real-time positioning using low-cost GPS receiver. With correcting the discussed weak points in near future, the RPDAP will be used in the field of precise real-time application, such as precise car navigation and precise personal location services.

Joh, Jeong-Ho; Choi, Byung-Kyu; Park, Jong-Uk; Pakr, Kwan-Dong Park; Lim, Hyung-Chul; Pakr, Pil-Ho

2002-12-01

55

The instrument pointing system: Precision attitude control in space  

NASA Astrophysics Data System (ADS)

The Spacelab Instrument Pointing System (IPS) is a three axes gimbal system providing pointing and stabilization in the arcsec range to a variety of space experiments with a mass of up to 7000 kg. The IPS demonstrated its control performance during the maiden flight in July 1985, the Spacelab 2 mission on board the Space Shuttle Challenger. The most challenging problem for attitude control in space is the disturbance compensation in the presence of structural flexibilities. Kalman filtering based on optical sensor and gyro measurements as well as flexible mode attenuation and feedforward control were indispensable to achieve high precision. To further enhance the IPS pointing performance and versatility, a new, more autonomous computer and sensor concept has been conceived providing the capacity for a higher degree of automation as well as improved pointing and closed loop tracking control. The autonomy and control capacity of the enhanced IPS establish the basis to accommodate the IPS as long-term available tracking and pointing platform on the International Space Station Freedom (ISF).

Hartmann, Ralf; Woelker, Albrecht

1990-06-01

56

Precision Measurement of Positioning on the Desktop Microrobot Factory  

NASA Astrophysics Data System (ADS)

Today, there is variety of “nanotechnology” field such as semiconductor, biochemistry, material and so on. However, measurement and sensing technologies in nano-scale positioning are common technologies for establishing nanotechnology in each field. In this report, precise measurement technologies in positioning for “Desktop micro robots factory” are described. Non-contact position measurement techniques such as image tracking, optical encoder, and magnetic encoder are reviewed. By employing several measurement techniques in position measurement, it enables cm order to nm order positioning seamlessly. Some advantages of “Desktop micro robots factory” as a production system for nanotechnology are also reviewed.

Fuchiwaki, Ohmi

57

Airborne Supplemental Navigation Equipment Using the Global Positioning System (GPS)/Precise Positioning Service (PPS).  

National Technical Information Service (NTIS)

This Military Standard Order (MSO) prescribes the minimum performance standard that airborne supplemental area navigation equipment using Global Positioning System (GPS) / Precise Positioning Service (PPS) must meet in order to be identified with the appl...

2005-01-01

58

Airborne Supplemental Navigation Equipment Using The Global Positioning System (GPS) Precise Positioning Service (PPS).  

National Technical Information Service (NTIS)

This Military Standard Order (MSO) prescribes the minimum performance standard that airborne supplemental area navigation equipment using Global Positioning System (GPS) / Precise Positioning Service (PPS) must meet in order to be identified with the appl...

2002-01-01

59

GPS-Based Satellite Tracking System for Precise Positioning  

Microsoft Academic Search

NASA is developing a Global Positioning System (GPS) based measurement system to provide precise determination of Earth satellite orbits, geodetic baselines, ionospheric electron content, and clock offsets between worldwide tracking sites. The system will employ variations on the differential GPS observing technique and will use a network of nine fixed ground terminals. Satellite applications will require either a GPS flight

THOMAS P. YUNCK; WILLIAM G. MELBOURNE; C. L. Thoenton

1985-01-01

60

Higher order ionospheric effects in precise GNSS positioning  

Microsoft Academic Search

With the increasing number of precise navigation and positioning applications using Global Navigation Satellite Systems (GNSS)\\u000a such as the Global Positioning System (GPS), higher order ionospheric effects and their correction become more and more important.\\u000a Whereas the first-order error can be completely eliminated by a linear combination of dual- frequency measurements, the second-\\u000a and third-order residual effects remain uncorrected in

M. Mainul Hoque; N. Jakowski

2007-01-01

61

Precise CCD positions of Galilean satellite-pairs  

NASA Astrophysics Data System (ADS)

In this paper, we present 526 precise CCD positions of Galilean satellite-pairs of Jupiter, which have been extracted from 441 CCD frames captured by a 1-m telescope at the Yunnan Observatory from 2002 to 2010. The four Galilean satellites (Io, Europa, Ganymede and Callisto) are used to calibrate the CCD field of view by comparing their pixel positions with their theoretical positions computed from two modern ephemerides of the Galilean satellites, L2 and JUP230, which have been developed by the Institut de Méchanique Céleste et de Calcul des Éphémérides and the Jet Propulsion Laboratory, respectively. In this paper, we focus on the relative position of a pair of satellites with short separation (less than 85 arcsec) for good internal precision. The mean (O - C) (observed minus computed) values of all these satellite-pairs in right ascension and declination are found to be no larger than 6 mas and 2 mas, respectively, for each ephemeris. The estimated precision for one single observation is better than 30 mas in each direction.

Peng, Q. Y.; He, H. F.; Lainey, V.; Vienne, A.

2012-01-01

62

Impact of the Combined GPS + Galileo Satellite Geometry on Positioning Precision  

Microsoft Academic Search

The improvement in positioning precision that can be expected from extending the GPS constellation with Galileo satellites will be treated in this paper. The influence of the pure geometric aspect, i.e. the effect of having more available satellites, will be assessed, while the effect of the availability of new signals will be ignored. From this point of view, two scenarios

S. Daghay; M. Moins; C. Bruyninx; Y. Rolain; F. Roosbeek

63

Sequence-controlled polymerization using dendritic macromonomers: precise chain-positioning of bulky functional clusters.  

PubMed

A simple strategy to insert functional dendrons at precise positions along a linear polymer backbone is reported. Sequence controlled copolymerization of styrene and polyester dendrons containing a maleimide unit at their focal points was utilized to yield such polymers. PMID:23775396

Baradel, Nathalie; Gok, Ozgul; Zamfir, Mirela; Sanyal, Amitav; Lutz, Jean-François

2013-08-25

64

Precise Positioning Control Using Auto-Tuned Fuzzy Logic Controller  

NASA Astrophysics Data System (ADS)

Nonlinear friction, resonant vibration modes, in addition to dead time of a positioning mechanism deteriorate the control performance in the microscopic displacement range. A control scheme composed of two types of control methodology is proposed in this paper in order to obtain high speed and high precision positioning of a ball-screw-driven mechanism: a feedforward compensator, based on coprime factorization of the positioning mechanism with dead time compensator, and a feedback compensator, an auto-tuned PDFLC (Proportional plus Derivative Fuzzy Logic Controller) based on real coded genetic algorithm as an optimization technique, with nonlinear friction compensation by using inverse model-based disturbance observer. Experimental results verified the effectiveness and robustness of the proposed control system against the difference of the nonlinear friction accompanied with the repetitive motion.

Abd-Elhameed, Esam H.; Iwasaki, Makoto

65

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

USGS Publications Warehouse

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, Inc.

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

2006-01-01

66

Active structures for vibration suppression and precision positioning  

NASA Astrophysics Data System (ADS)

This paper addresses the problem of precision positioning of space structures in the presence of quasi-static and dynamic perturbations, with particular emphasis on achieving robust active damping. The first part of the paper discusses the pole-zero pattern of non-colocated control systems. The beneficial consequences of the minimum-phase alternating pattern of colocated systems on the robustness with respect to parametric uncertainty is emphasized. The second part describes some colocated algorithms for robust active damping. These schemes do not rely on a model of the structure and have guaranteed stability properties, even for large changes in the parameters of the structure. Finally, the paper emphasizes the role of damping on dynamic disturbance rejection and illustrates how active damping can be embedded in a position control loop to achieve better performance.

Preumont, Andre

1993-10-01

67

Closed loop high precision position control system with optical scale  

NASA Astrophysics Data System (ADS)

With the developments of science of art, there are more and more demands on the high resolution control of position of object to be controlled, such as lathe, product line, elements in the optical resonant cavity, telescope, and so on. As one device with high resolution, the optical scale has more and more utility within the industrial and civil applications. With one optical scale and small DC servo motor, one closed loop high resolution position control system is constructed. This apparatus is used to control the position of the elements of optical system. The optical scale is attached on the object or reference guide way. The object position is sampled by a readhead of non-contact optical encoder. Control system processes the position information and control the position of object through the motion control of servo DC motor. The DC motor is controlled by one controller which is connected to an industrial computer. And the micro frictionless slide table does support the smooth motion of object to be controlled. The control algorithm of system is PID (Proportional-Integral-Differential) methods. The PID control methods have well ROBUST. The needed data to control are position, velocity and acceleration of the object. These three parameters correspond to the PID characters respectively. After the accomplishments of hardware, GUI (Graphical user interface), that is, the software of control system is also programmed. The whole system is assembled by specialized worker. Through calibration experiments, the coefficients of PID are obtained respectively. And then the precision of position control of the system is about 0.1?m.

Ge, Cheng-liang; Liao, Yuan; He, Zhong-wu; Luo, Zhong-xiang; Huang, Zhi-wei; Wan, Min; Hu, Xiao-yang; Fan, Guo-bin; Liang, Zheng

2008-03-01

68

Electrostatic microactuators for precise positioning of neural microelectrodes.  

PubMed

Microelectrode arrays used for monitoring single and multineuronal action potentials often fail to record from the same population of neurons over a period of time likely due to micromotion of neurons away from the microelectrode, gliosis around the recording site and also brain movement due to behavior. We report here novel electrostatic microactuated microelectrodes that will enable precise repositioning of the microelectrodes within the brain tissue. Electrostatic comb-drive microactuators and associated microelectrodes are fabricated using the SUMMiT V (Sandia's Ultraplanar Multilevel MEMS Technology) process, a five-layer polysilicon micromachining technology of the Sandia National labs, NM. The microfabricated microactuators enable precise bidirectional positioning of the microelectrodes in the brain with accuracy in the order of 1 microm. The microactuators allow for a linear translation of the microelectrodes of up to 5 mm in either direction making it suitable for positioning microelectrodes in deep structures of a rodent brain. The overall translation was reduced to approximately 2 mm after insulation of the microelectrodes with epoxy for monitoring multiunit activity. The microactuators are capable of driving the microelectrodes in the brain tissue with forces in the order of several micro-Newtons. Single unit recordings were obtained from the somatosensory cortex of adult rats in acute experiments demonstrating the feasibility of this technology. Further optimization of the insulation, packaging and interconnect issues will be necessary before this technology can be validated in long-term experiments. PMID:16235660

Muthuswamy, Jit; Okandan, Murat; Jain, Tilak; Gilletti, Aaron

2005-10-01

69

Multi-GNSS precise single-epoch positioning  

NASA Astrophysics Data System (ADS)

An instantaneous (single-epoch) long-range RTK positioning using data from multiple Global Navigation Satellite Systems (GNSS) is currently being implemented and tested in the GINPOS software, developed at the University of Warmia and Mazury in Olsztyn. The instantaneous ambiguity resolution has several advantages; it is resistant to negative effects of cycle slips, receiver loss of lock, power and communications outages and there is no need for re-initialization immediately following loss-of-lock. The use of several GNSS systems in instantaneous kinematic positioning significantly increases the distance over which carrier-phase ambiguities can be recovered to their integer values. It also improves the reliability and integrity of the ambiguity resolution. In this work, satellite data from GPS and Galileo systems were processed. Since currently there are just two Galileo In-Orbit Validation (IOV) satellites on orbit, Spirent multi-GNSS hardware simulator was used to obtain Galileo and GPS signals from full constellations. The observations were obtained for several locations allowing to form baselines reaching up to 100 km. The results based on the processing of the simulated data show that even though single-epoch precise positioning is possible with any single system, combining data for both systems increases positioning availability and reliability.

Paziewski, J.; Stepniak, K.; Wielgosz, P.; Krypiak-Gregorczyk, A.; Krukowska, M.

2012-04-01

70

Single-frequency, single-receiver terrestrial and spaceborne point positioning  

Microsoft Academic Search

High-accuracy, point positioning has been an attractive research topic in the GPS community for a number of years. The overall quality of precise point positioning results is also dependent on the quality of the GPS measurements and the user's processing software. Dual-frequency, geodetic-quality GPS receivers are routinely used both in static and kinematic applications for high-accuracy point positioning. However, use

Tomas Beran

2008-01-01

71

Precise Positioning of Myosin VI on Endocytic Vesicles In Vivo  

PubMed Central

Myosin VI has been studied in both a monomeric and a dimeric form in vitro. Because the functional characteristics of the motor are dramatically different for these two forms, it is important to understand whether myosin VI heavy chains are brought together on endocytic vesicles. We have used fluorescence anisotropy measurements to detect fluorescence resonance energy transfer between identical fluorophores (homoFRET) resulting from myosin VI heavy chains being brought into close proximity. We observed that, when associated with clathrin-mediated endocytic vesicles, myosin VI heavy chains are precisely positioned to bring their tail domains in close proximity. Our data show that on endocytic vesicles, myosin VI heavy chains are brought together in an orientation that previous in vitro studies have shown causes dimerization of the motor. Our results are therefore consistent with vesicle-associated myosin VI existing as a processive dimer, capable of its known trafficking function.

Hasson, Tama; Spudich, James A; Mayor, Satyajit

2007-01-01

72

Precise measurement and calculation of coincidence summing corrections for point and linear sources.  

PubMed

Point sources of (60)Co, (133)Ba, (134)Cs and (152)Eu, calibrated at Physikalisch-Technische Bundesanstalt were measured in 13 positions on the axis of a 50% relative efficiency p-type detector. The peak and total efficiencies were calibrated using single photon emitting nuclides. Precise experimental values of the coincidence summing corrections were evaluated in each geometry. Synthetic linear source data, as well as the corresponding peak and total efficiency curves, were prepared using the dependence of the count rates on the position of the emitting point. The coincidence summing corrections for the linear sources were computed, analyzed with respect to different approximations and compared with simulations carried out with GESPECOR. PMID:22405956

Sima, Octavian; Arnold, Dirk

2012-02-27

73

Airborne gravity and precise positioning for geologic applications  

NASA Astrophysics Data System (ADS)

Airborne gravimetry has become an important geophysical tool primarily because of advancements in methodology and instrumentation made in the past decade. Airborne gravity is especially useful when measured in conjunction with other geophysical data, such as magnetics, radar, and laser altimetry. The aerogeophysical survey over the West Antarctic ice sheet described in this paper is one such interdisciplinary study. This paper outlines in detail the instrumentation, survey and data processing methodology employed to perform airborne gravimetry from the multi-instrumented Twin Otter aircraft. Precise positioning from carrier-phase Global Positioning System (GPS) observations are combined with measurements of acceleration made by the gravity meter in the aircraft to obtain the free-air gravity anomaly measurement at aircraft altitude. GPS data are processed using the Kinematic and Rapid Static (KARS) software program, and aircraft vertical acceleration and corrections for gravity data reduction are calculated from the GPS position solution. Accuracies for the free-air anomaly are determined from crossover analysis after significant editing (2.98 mGal rms) and from a repeat track (1.39 mGal rms). The aerogeophysical survey covered a 300,000 km2 region in West Antarctica over the course of five field seasons. The gravity data from the West Antarctic survey reveal the major geologic structures of the West Antarctic rift system, including the Whitmore Mountains, the Byrd Subglacial Basin, the Sinuous Ridge, the Ross Embayment, and Siple Dome. These measurements, in conjunction with magnetics and ice-penetrating radar, provide the information required to reveal the tectonic fabric and history of this important region.

Bell, R. E.; Childers, V. A.; Arko, R. A.; Blankenship, D. D.; Brozena, J. M.

1999-07-01

74

Study on global control network precision positioning method in visual shape measurement  

NASA Astrophysics Data System (ADS)

Large-size visual shape measurement based on ICP (iterative closest point) mosaicing algorithm generally has a larger cumulative error; however, this problem can be well solved by precision positioning global control network. Therefore, this method is widely used in large-size visual shape measurement. Since the positioning accuracy of the global control network is the key influencing factor of the final measurement accuracy, the method of precision positioning global control network is researched, which is dependent on the principle of portable close-range photogrammetry. The precision positioning theory and mathematical model of global control network are investigated in this paper. Bundle adjustment optimization algorithm is the core of this measurement system, the solution method of this algorithm is introduced in detail, which can improve the model solution accuracy. As is known, the initial value of the algorithm has a direct influence on the convergence of the result, so obtaining the initial value is a key part of the measurement system, including control points matching technology, stations orientation technology and the technology of obtaining the initial value of the three-dimensional coordinates of global control points. New technological breakthroughs were made based on the existing researches to get a more precious and stable initial value. Firstly, a nonlinear adjustment model based control points matching method is proposed, which significantly improves the correct matching rate when the control points distribute intensively. Secondly, a new station orientation method without using an external orientation device is studied, which greatly improves the shooting freedom and expands the range of the spatial distribution of the measurement stations. Finally, a camera calibration method independent with the imaging model is explored, which converts image coordinate information into image angle information. Thus, the initial value calculation accuracy of the three-dimensional coordinates of the control points is not affected by the lens distortion and measurement distance. A large number of experiments were carried out using a high-resolution digital camera, and the experimental results show that the measurement accuracy of this method can reach 0.02mm (3m * 3m range), and the root mean square is about 0.015mm. Consequently we conclude that this method can achieve the precise positioning of the global control network and help to improve the accuracy of large-size visual shape measurement.

Long, Chang-yu; Zhu, Ji-gui

2013-08-01

75

New amplified piezoelectric actuator for precision positioning and active damping  

NASA Astrophysics Data System (ADS)

Two typical characteristics of direct piezoelectric actuators are displacements of ten micrometers and high stiffnesses. Recently, multilayer actuators have been improved, and they now display strains of approximately 1200 ppm at low excitation levels (less than two hundred volts). Thus, they are well suited to perform precise positioning of optical devices. But for industrial needs, this performance is still insufficient for positioning devices with larger displacements (in the range of several hundred micrometers). Numerous designs of mechanical amplifier devices based on the use of flexural hinges have been proposed. Due to their low stiffness, these devices cannot be used in space applications because they would not survive during takeoff. The amplified piezoelectric actuator which we designed and tested, eliminated the low stiffness drawback and ensures good force transmission. Due to the stiffness of the amplifier, the efficiency of the electromechanical transduction is significantly higher than those of conventional amplifier mechanisms. To design this actuator, we performed a numerical finite element simulation that included the piezoelectric effect. Among other things, this model shows the displacement as a function of the excitation and the electrical admittance. The static and the dynamic behaviors were determined. The main features of the actuator are a no-load displacement of 180 micrometers and stiffness of 5 N/m. These characteristics were experimentally verified using an electromechanical test bench including a laser Doppler interferometer, thus confirming the design method. Technological aspects, like the compressive force applied to the piezoelectric material, were considered. Many applications for this amplified actuator already exist. For example, an active mechanism using this actuator can be used to tilt a mirror. Another application of the amplified actuator is in the field of active damping of structures. In this case, the actuator is connected to a resistive shunt so that electrical damping is obtained through the direct piezoelectric effect. The experimental results show that the actuator is interesting because of its high electromechanical coupling, and, consequently, its ability to perform active damping.

Leletty, R.; Claeyssen, F.; Lhermet, N.; Bouchilloux, Philippe

1997-06-01

76

The MATPHOT Algorithm for Accurate and Precise Stellar Photometry and Astrometry Using Discrete Point Spread Functions  

NASA Astrophysics Data System (ADS)

I describe the key features of my MATPHOT algorithm for accurate and precise stellar photometry and astrometry using discrete Point Spread Functions. A discrete Point Spread Function (PSF) is a sampled version of a continuous two-dimensional PSF. The shape information about the photon scattering pattern of a discrete PSF is typically encoded using a numerical table (matrix) or a FITS image file. The MATPHOT algorithm shifts discrete PSFs within an observational model using a 21-pixel-wide damped sinc function and position partial derivatives are computed using a five-point numerical differentiation formula. The MATPHOT algorithm achieves accurate and precise stellar photometry and astrometry of undersampled CCD observations by using supersampled discrete PSFs that are sampled 2, 3, or more times more finely than the observational data. I have written a C-language computer program called MPD which is based on the current implementation of the MATPHOT algorithm; all source code and documentation for MPD and support software is freely available at the following website: http://www.noao.edu/staff/mighell/matphot . I demonstrate the use of MPD and present a detailed MATPHOT analysis of simulated James Webb Space Telescope observations which demonstrates that millipixel relative astrometry and millimag photometric accuracy is achievable with very complicated space-based discrete PSFs. This work was supported by a grant from the National Aeronautics and Space Administration (NASA), Interagency Order No. S-13811-G, which was awarded by the Applied Information Systems Research (AISR) Program of NASA's Science Mission Directorate.

Mighell, K. J.

2004-12-01

77

Precision SUSY measurements at LHC:Point 3  

SciTech Connect

This paper, which is one of a series, presents detailed studies of mass reconstructions and other measurements in a case study illustrating the power of the ATLAS detector to perform measurements of supersymmetric particle production. A particular point in the parameter space of the Minimal Supergravity inspired model is used. Reconstruction of gluino, sbottom and light squarks and the measurement of neutral ion mass differences is shown.

Hinchliffe, I.; Paige, F.E.; Nagy, E.; Shapiro, M.D.; Soderqvist, J.; Yao, W.

1998-11-01

78

Pointing Control System for a High Precision Flight Telescope  

SciTech Connect

A pointing control system is developed and tested for a flying gimbaled telescope. The two-axis pointing system is capable of sub-microradian pointing stability and high accuracy in the presence of large host vehicle jitter. The telescope also has high agility--it is capable of a 50-degree retarget (in both axes simultaneously) in less than 2 seconds. To achieve the design specifications, high-accuracy, high-resolution, two-speed resolvers were used, resulting in gimbal-angle measurements stable to 1.5 microradians. In addition, on-axis inertial angle displacement sensors were mounted on the telescope to provide host-vehicle jitter cancellation. The inertial angle sensors are accurate to about 100 nanoradians, but do not measure low frequency displacements below 2 Hz. The gimbal command signal includes host-vehicle attitude information, which is band-limited. This provides jitter data below 20 Hz, but includes a variable latency between 15 and 25 milliseconds. One of the most challenging aspects of this design was to combine the inertial-angle-sensor data with the less perfect information in the command signal to achieve maximum jitter reduction. The optimum blending of these two signals, along with the feedback compensation were designed using Quantitative Feedback Theory.

BENTLEY,ANTHONY E.; WILCOXEN,JEFFREY LEE

2000-12-01

79

A precision pointing system for space telescope class optical trackers  

NASA Astrophysics Data System (ADS)

This paper reports on the results of a study effort whose main objective was to develop a conceptual design for a space based, large-payload (3000 kg) pointing system capable of both rapid slew maneuvers (0.35 rad/sec-squared) and very stable tracking (1 microrad, 1 sigma, each axis). The key features of the resulting solution are: (1) cross elevation over elevation gimbal system, (2) closed cross elevation gimbal ring, (3) graphite-epoxy structure, (4) two-motor reactionless joint torquers, (5) payload mounted vernier reaction wheel, and (6) gyrostabilized model following control system.

Sevaston, George E.; Schier, J. Alan; Iskenderian, Theodore C.; Lin, Yu-Hwan; Satter, Celeste M.

80

PreCisIon: PREdiction of CIS-regulatory elements improved by gene's positION  

PubMed Central

Conventional approaches to predict transcriptional regulatory interactions usually rely on the definition of a shared motif sequence on the target genes of a transcription factor (TF). These efforts have been frustrated by the limited availability and accuracy of TF binding site motifs, usually represented as position-specific scoring matrices, which may match large numbers of sites and produce an unreliable list of target genes. To improve the prediction of binding sites, we propose to additionally use the unrelated knowledge of the genome layout. Indeed, it has been shown that co-regulated genes tend to be either neighbors or periodically spaced along the whole chromosome. This study demonstrates that respective gene positioning carries significant information. This novel type of information is combined with traditional sequence information by a machine learning algorithm called PreCisIon. To optimize this combination, PreCisIon builds a strong gene target classifier by adaptively combining weak classifiers based on either local binding sequence or global gene position. This strategy generically paves the way to the optimized incorporation of any future advances in gene target prediction based on local sequence, genome layout or on novel criteria. With the current state of the art, PreCisIon consistently improves methods based on sequence information only. This is shown by implementing a cross-validation analysis of the 20 major TFs from two phylogenetically remote model organisms. For Bacillus subtilis and Escherichia coli, respectively, PreCisIon achieves on average an area under the receiver operating characteristic curve of 70 and 60%, a sensitivity of 80 and 70% and a specificity of 60 and 56%. The newly predicted gene targets are demonstrated to be functionally consistent with previously known targets, as assessed by analysis of Gene Ontology enrichment or of the relevant literature and databases.

Elati, Mohamed; Nicolle, Remy; Junier, Ivan; Fernandez, David; Fekih, Rim; Font, Julio; Kepes, Francois

2013-01-01

81

Dynamic positioning in single-point moorings  

SciTech Connect

This paper deals with the concept of and a system for complete control of the slowly varying bow motion of a bow-moored ship using dynamic positioning. System performance is shown by simulated case studies with an offshore loading tanker. Significant improvements of motion behaviour and mooring force performance are demonstrated. A complete positioning system is presently running successfully onboard a 125000 dwt tanker in the North Sea. Some preliminary results are shown.

Sorheim, H.R.; Gregersen, S.; Jenssen, N.A.

1983-05-01

82

On Intermediate Precision Required for Correctly-Rounding Decimal-to-Binary Floating-Point Conversion  

Microsoft Academic Search

The algorithms developed ten years ago in preparation for IBM's support of IEEE Floating-Point on its mainframe S\\/390 processors use an overly conservative inter- mediate precision to guarantee correctly-rounded results across the entire exponent range. Here we study the minimal requirement for both bounded and unbounded precision on the decimal side (converting to machine precision on the binary side). An

Michel Hack

83

The GFZ real-time GNSS precise positioning service system and its adaption for COMPASS  

NASA Astrophysics Data System (ADS)

Motivated by the IGS real-time Pilot Project, GFZ has been developing its own real-time precise positioning service for various applications. An operational system at GFZ is now broadcasting real-time orbits, clocks, global ionospheric model, uncalibrated phase delays and regional atmospheric corrections for standard PPP, PPP with ambiguity fixing, single-frequency PPP and regional augmented PPP. To avoid developing various algorithms for different applications, we proposed a uniform algorithm and implemented it into our real-time software. In the new processing scheme, we employed un-differenced raw observations with atmospheric delays as parameters, which are properly constrained by real-time derived global ionospheric model or regional atmospheric corrections and by the empirical characteristics of the atmospheric delay variation in time and space. The positioning performance in terms of convergence time and ambiguity fixing depends mainly on the quality of the received atmospheric information and the spatial and temporal constraints. The un-differenced raw observation model can not only integrate PPP and NRTK into a seamless positioning service, but also syncretize these two techniques into a unique model and algorithm. Furthermore, it is suitable for both dual-frequency and sing-frequency receivers. Based on the real-time data streams from IGS, EUREF and SAPOS reference networks, we can provide services of global precise point positioning (PPP) with 5-10 cm accuracy, PPP with ambiguity-fixing of 2-5 cm accuracy, PPP using single-frequency receiver with accuracy of better than 50 cm and PPP with regional augmentation for instantaneous ambiguity resolution of 1-3 cm accuracy. We adapted the system for current COMPASS to provide PPP service. COMPASS observations from a regional network of nine stations are used for precise orbit determination and clock estimation in simulated real-time mode, the orbit and clock products are applied for real-time precise point positioning. The simulated real-time PPP service confirms that real-time positioning services of accuracy at dm-level and even cm-level is achievable with COMPASS only.

Li, Xingxing; Ge, Maorong; Zhang, Hongping; Nischan, Thomas; Wickert, Jens

2013-03-01

84

Three-dimensional localization precision of the double-helix point spread function versus astigmatism and biplane.  

PubMed

Wide-field microscopy with a double-helix point spread function (DH-PSF) provides three-dimensional (3D) position information beyond the optical diffraction limit. We compare the theoretical localization precision for an unbiased estimator of the DH-PSF to that for 3D localization by astigmatic and biplane imaging using Fisher information analysis including pixelation and varying levels of background. The DH-PSF results in almost constant localization precision in all three dimensions for a 2 ?m thick depth of field while astigmatism and biplane improve the axial localization precision over smaller axial ranges. For high signal-to-background ratio, the DH-PSF on average achieves better localization precision. PMID:21079725

Badieirostami, Majid; Lew, Matthew D; Thompson, Michael A; Moerner, W E

2010-10-18

85

Laser-interferometer position-feedback for precision machine tools  

SciTech Connect

Diamond turning of off-axis parabolic mirrors is used to provide high-quality turning and focusing optics for the Los Alamos Scientific Laboratory's laser-fusion research. These mirrors are fabricated at the Oak Ridge Y-12 Plant on a large machine tool that incorporates lasers, air bearings, and linear-motor slide-drives to meet the part specifications of 0.63 ..mu..m (25 ..mu..in) on contour and 63 nm (2.5 ..mu..in) on surface finish. This report discusses the application of lasers to this machine and other precision machine tools.

Barkman, W.E.

1980-04-15

86

The MATPHOT Algorithm for Accurate and Precise Stellar Photometry and Astrometry Using Discrete Point Spread Functions  

Microsoft Academic Search

I describe the key features of my MATPHOT algorithm for accurate and precise stellar photometry and astrometry using discrete Point Spread Functions. A discrete Point Spread Function (PSF) is a sampled version of a continuous two-dimensional PSF. The shape information about the photon scattering pattern of a discrete PSF is typically encoded using a numerical table (matrix) or a FITS

K. J. Mighell

2004-01-01

87

PRECISE ORIENTATION OF SPOT PANCHROMATIC IMAGES WITH TIE POINTS TO A SAR IMAGE  

Microsoft Academic Search

The extraction of spatial data from satellite imagery requires that precise sensor models are used to orientate images. This is particularly important with images acquired by linear sensors, such as SPOT, frequently pointed with large incidence angles. Image orientation with pixel accuracy requires that accurate ground control points are used. The acquisition of ground control is especially difficult in remote

J. A. Gonçalves; I. Dowman

88

LAMOST fiber unit positional precision passive detection exploiting the technique of template matching  

NASA Astrophysics Data System (ADS)

The large sky area multi-object fiber spectroscopic telescope (LAMOST) is an innovative reflecting schmidt telescope, promising a very high spectrum acquiring rate of several ten-thousands of spectra per night. By using the parallel controllable fiber positioning technique, LAMOST makes reconfiguration of fibers accurately according to the positions of objects in minutes and fine adjusting the fibers. As a key problem, High precision positioning detection of LAMOST fiber positioning unit has always been highly regarded and some detection schemes have been proposed. Among these, active detection method, which determines the final accurate position of optical fiber end with the help of lighting the fiber, has been most widely researched, but this kind of method could not be applied in LAMOST real-time observation because it needs projecting light into fiber. A novel detection idea exploiting the technique of template matching is presented in this paper. As we know, final position of a specific fiber end can be easily inferred by its corresponding revolving angles of the central revolving axle and bias revolving axle in double revolving style, so the key point in this problem is converted to the accurate determination of these revolving angles. Template matching technique are explored to acquire the matching parameters for its real-time collected imagery, and thus determine the corresponding revolving angle of the central revolving axle and bias revolving axle respectively. Experiments results obtained with data acquired from LAMOST site are used to verify the feasibility and effectiveness of this novel method.

Wang, Mengxin; Zhao, Yongheng; Luo, Ali

2012-09-01

89

The Integration of Positioning Technologies for Precise Location Identification  

Microsoft Academic Search

With the growing trend towards a world where people, vehicles, and other mobile objects are getting more and more interconnected, location information is increasingly becoming a recognized need for providing rapid and timely information to the mobile workforce. More and more products are present in the market that allows location identifications. Positioning technologies differ in their capacity to identify. Some

T. Y. Chew

2005-01-01

90

THE PRECISE SATELLITE POSITIONING SYSTEM ASG-EUPOS  

Microsoft Academic Search

Nowadays, the use of the Global Navigation Satellite Systems (GNSS) is the fastest and easiest way to determine position. Yet, their accuracy is still limited, because it is dependent on a number of various factors, mostly ionospheric and tropospheric delays. To improve the accuracy of GNSS, the systems based on reference networks are being built. Such networks consist of a

Marcin Ryczywolski; Artur Oruba

91

Precise acoustic ranging and positioning: a progress report  

Microsoft Academic Search

The authors carried out an experiment in April 1999 by using a 2 m-square surface buoy and the RV Tansei-maru, Ocean Research Institute, University of Tokyo. Three GPS antennae were fixed on the top of the buoy and an acoustic transducer on the bottom. GPS reference station for kinematic GPS positioning from the study area was set at Aburatsubo, about

Yukihito Osada; Hiromi Fujimoto; Kin-ichiro Koizumi; Toshihiko Kanazawa; Hideyuki Murakami

2000-01-01

92

Global positioning system measurements for crustal deformation: Precision and accuracy  

USGS Publications Warehouse

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.

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

1989-01-01

93

GPS doppler processing for precise positioning in dynamic applications  

Microsoft Academic Search

A doppler processing technique for smoothing the GPS code-phase measurements is presented. It is shown that this technique can enhance the resolution of C\\/A pseudo-range measurements to better than 1 centimeter. Data is presented to show that it is possible to obtain position fixes with an runs scatter of a few centimeters from the C\\/A code. Although the presented technique

J. Ashjaee

1985-01-01

94

Influence of Ephemeris Error on GPS Single Point Positioning Accuracy  

NASA Astrophysics Data System (ADS)

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.

Lihua, Ma; Wang, Meng

2013-09-01

95

Input shaping for three-dimensional slew maneuvers of a precision pointing flexible spacecraft.  

National Technical Information Service (NTIS)

A method is presented for input torque shaping for three-dimensional slew maneuvers of a precision pointing flexible spacecraft. The method determines the torque profiles for fixed-time, rest-to-rest maneuvers which minimizes a specified performance index...

C. R. Dohrmann R. D. Robinett

1994-01-01

96

Precise mean sea level measurements using the Global Positioning System  

NASA Astrophysics Data System (ADS)

This paper describes the results of a sea level measurement test conducted off La Jolla, California, in November of 1991. The purpose of this test was to determine accurate sea level measurements using a Global Positioning System (GPS) equipped buoy. These measurements were intended to be used as the sea level component for calibration of the ERS 1 satellite altimeter. Measurements were collected on November 25 and 28 when the ERS 1 satellite overflew the calibration area. Two different types of buoys were used. A waverider design was used on November 25 and a spar design on November 28. This provided the opportunity to examine how dynamic effects of the measurement platform might affect the sea level accuracy. The two buoys were deployed at locations approximately 1.2 km apart and about 15 km west of a reference GPS receiver located on the rooftop of the Institute of Geophysics and Planetary Physics at the Scripps Institute of Oceanography. GPS solutions were computed for 45 minutes on each day and used to produce two sea level time series. An estimate of the mean sea level at both locations was computed by subtracting tide gage data collected at the Scripps Pier from the GPS-determined sea level measurements and then filtering out the high-frequency components due to waves and buoy dynamics. In both cases the GPS estimate differed from Rapp's mean altimetric surface by 0.06 m. Thus the gradient in the GPS measurements matched the gradient in Rapp's surface. These results suggest that accurate sea level can be determined using GPS on widely differing platforms as long as care is taken to determine the height of the GPS antenna phase center above water level. Application areas include measurement of absolute sea level, of temporal variations in sea level, and of sea level gradients (dominantly the geoid). Specific applications would include ocean altimeter calibration, monitoring of sea level in remote regions, and regional experiments requiring spatial and temporal resolution higher than that available from altimeter data.

Kelecy, Thomas M.; Born, George H.; Parke, Michael E.; Rocken, Christian

1994-04-01

97

Rigorous high-precision enclosures of fixed points and their invariant manifolds  

NASA Astrophysics Data System (ADS)

The well established concept of Taylor Models is introduced, which offer highly accurate C0 enclosures of functional dependencies, combining high-order polynomial approximation of functions and rigorous estimates of the truncation error, performed using verified arithmetic. The focus of this work is on the application of Taylor Models in algorithms for strongly non-linear dynamical systems. A method is proposed to extend the existing implementation of Taylor Models in COSY INFINITY from double precision coefficients to arbitrary precision coefficients. Great care is taken to maintain the highest efficiency possible by adaptively adjusting the precision of higher order coefficients in the polynomial expansion. High precision operations are based on clever combinations of elementary floating point operations yielding exact values for round-off errors. An experimental high precision interval data type is developed and implemented. Algorithms for the verified computation of intrinsic functions based on the High Precision Interval datatype are developed and described in detail. The application of these operations in the implementation of High Precision Taylor Models is discussed. An application of Taylor Model methods to the verification of fixed points is presented by verifying the existence of a period 15 fixed point in a near standard Henon map. Verification is performed using different verified methods such as double precision Taylor Models, High Precision intervals and High Precision Taylor Models. Results and performance of each method are compared. An automated rigorous fixed point finder is implemented, allowing the fully automated search for all fixed points of a function within a given domain. It returns a list of verified enclosures of each fixed point, optionally verifying uniqueness within these enclosures. An application of the fixed point finder to the rigorous analysis of beam transfer maps in accelerator physics is presented. Previous work done by Johannes Grote is extended to compute very accurate polynomial approximations to invariant manifolds of discrete maps of arbitrary dimension around hyperbolic fixed points. The algorithm presented allows for automatic removal of resonances occurring during construction. A method for the rigorous enclosure of invariant manifolds of continuous systems is introduced. Using methods developed for discrete maps, polynomial approximations of invariant manifolds of hyperbolic fixed points of ODEs are obtained. These approximations are outfit with a sharp error bound which is verified to rigorously contain the manifolds. While we focus on the three dimensional case, verification in higher dimensions is possible using similar techniques. Integrating the resulting enclosures using the verified COSY VI integrator, the initial manifold enclosures are expanded to yield sharp enclosures of large parts of the stable and unstable manifolds. To demonstrate the effectiveness of this method, we construct enclosures of the invariant manifolds of the Lorenz system and show pictures of the resulting manifold enclosures. To the best of our knowledge, these enclosures are the largest verified enclosures of manifolds in the Lorenz system in existence.

Wittig, Alexander N.

98

Dynamic implications of customer order decoupling point positioning  

Microsoft Academic Search

Purpose – The positioning of the customer order decoupling point (CODP) is an important strategic consideration for supply chains. Recently, research has focused only on the static effects of CODP positioning. The purpose of this paper is to expand the body of knowledge by describing the dynamic consequences that arise from shifting the CODP upstream or downstream. Design\\/methodology\\/approach – A

Philip Hedenstierna; Amos H. C. Ng

2011-01-01

99

Precise positioning surveillance in 3-D using night-vision stereoscopic photogrammetry  

NASA Astrophysics Data System (ADS)

A 3-D imaging technique is presented which pairs high-resolution night-vision cameras with GPS to increase the capabilities of passive imaging surveillance. Camera models and GPS are used to derive a registered point cloud from multiple night-vision images. These point clouds are used to generate 3-D scene models and extract real-world positions of mission critical objects. Analysis shows accuracies rivaling laser scanning even in near-total darkness. The technique has been tested on stereoscopic 3-D video collections as well. Because this technique does not rely on active laser emissions it is more portable, less complex, less costly, and less detectable than laser scanning. This study investigates close-range photogrammetry under night-vision lighting conditions using practical use-case examples of terrain modeling, covert facility surveillance, and stand-off facial recognition. The examples serve as the context for discussion of a standard processing workflow. Results include completed, geo-referenced 3-D models, assessments of related accuracy and precision, and a discussion of future activities.

Schwartz, Jason M.

2011-05-01

100

A High-Speed and High-Precision Position Control Using Sliding Mode Compensator  

NASA Astrophysics Data System (ADS)

To achieve high-speed and high-precision position control for semiconductor product machines and industrial robots, the full-closed feedback control is applied. Many control methods have been proposed for such a system. In general, P,PI/I-PI control which is one of PID control is applied to a lot of industrial applications. However, in case of changing mechanical characters of control target, the parameters of P,PI/I-PI control have to be changed for keeping a good motion performance. In this paper, we propose a new P,PI/I-P control method which is with nonlinear compensator. The algorithm of nonlinear compensator is based on sliding mode control with chattering compensation. The effectiveness of proposed control method is evaluated by using full-closed single axis slider system via point to point control and contour control in the case of changing load. From the experimental results, the proposed control method has robustness in the case of changing acceleration/deceleration of control reference, changing load and low velocity contouring motion.

Tsuruta, Kazuhiro; Sato, Kazuya; Ushimi, Nobuhiro; Fujimoto, Takashi

101

Clinical precision of myofascial trigger point location in the trapezius muscle  

Microsoft Academic Search

Myofascial trigger points (TrPs) have been clinically described as discrete areas of muscle tenderness presenting in taut bands of skeletal muscle. Using well-defined clinical criteria, prior investigations have demonstrated interrater reliability in the diagnosis of TrPs within a given muscle. No reports exist, however, with respect to the precision with which experienced clinicians can determine the anatomic locations of TrPs

Veronica M Sciotti; Veronica L Mittak; Lisa DiMarco; Lillian M Ford; Julie Plezbert; Eileen Santipadri; Janet Wigglesworth; Kevin Ball

2001-01-01

102

Ion beam machining of single-point diamond tools for nano-precision turning  

Microsoft Academic Search

In order to obtain single-point diamond tools (SPDT) with cutting edges of sharp or small negative land for ultra-precision turning of soft materials, machining of the SPDT by an argon ion beam of 1.0 keV has been investigated. The edge radius of the SPDT was measured using a profile SEM (scanning electron microscope having two secondary electron detectors). By this

I. Miyamoto; T. Ezawa; K. Nishimura

1990-01-01

103

Geo-referencing point clouds with transformational and positional uncertainties  

NASA Astrophysics Data System (ADS)

The paper presents an iterative matching method to improve a direct geo-referencing approach for stationary terrestrial 3D laser scans by means of the positional and transformational uncertainties of two 3D point clouds. In this approach, a geo-referenced point cloud from a station inherits the following stochastic information: (1) transformational uncertainties from processed GNSS data through the Kalman filter and (2) positional uncertainties through the range and angular uncertainties from the terrestrial laser scanner as well as the incident angle of the laser beam to a surface. This stochastic information from two (pre-) geo-referenced 3D point clouds is implemented within a novel iterative matching algorithm, named Geo-referencing ICP with Helmert 3D transformation, for subsequent post-processing procedures such as segmentation and further calibration.

Paffenholz, Jens-André; Bae, Kwang-Ho

2012-03-01

104

High precision position control of voice coil motor based on single neuron PID  

NASA Astrophysics Data System (ADS)

Voice coil motor(VCM) is widely used in high-speed and high-precision positioning control system in recent years. However, there are system uncertainty, nonlinear, modeling error, and external disturbances in the high-precision positioning control system, traditional PID control method is difficult to achieve precise positioning control. In this paper, a new position control strategy with a single neuron controller which has the capability of self-studying and self-adapting composed with PID controller is put forward, and the feedforward compensator is added to improve the dynamic response of the system in the position loop. Moreover, the disturbance observer is designed to suppress model parameter uncertainty and external disturbance signal in the current loop. In addition, the problem of high precision position control of VCM under the influence of significant disturbances is addressed, which including the gas-lubricated damping, the spring, the back EMF and ripple forces, on the basis, the mathematical model of VCM is established accurately. The simulation results show that this kind of controller can improve the dynamic characteristic and strengthen the robustness of the system, and the current loop with disturbance observer can also restrain disturbance and high frequency.

Li, Liyi; Chen, Qiming; Tan, Guangjun; Zhu, He

2013-01-01

105

Development of stewart platforms for active vibration isolation and precision pointing  

NASA Astrophysics Data System (ADS)

Vibration isolation and extreme precision pointing is needed for future space telescopes, imaging sensors, laser communication, space-borne optical interferometer, and other sensitive payloads which have increased performance, depending on sustained sub-microradian pointing accuracy and stability. However, the vibration sources are increased due to the large flexible structures, truss-type structures and motion devices. The spatial Stewart platform (hexapod), built by smart materials and smart structures, is a promising way to address these issues, especially for the six degree-of-freedom control purpose, since the platform offers several advantages over the serial counterparts and other methods. Jet Propulsion Laboratory (JPL), Air Force Research Laboratory (AFRL), Naval Postgraduate School (NPS), University of Washington, the Hexapod Research Group of University of Wyoming, CSA Engineering Inc, Honeywell Satellite Systems Operation and other groups have done a lot of research, this paper provides a representative look at the state-of-the-art technology and research in active vibration isolation and precision pointing applied in space.

Liu, Lei; Wang, Benli

2007-10-01

106

Improving the Accuracy of Position Detection of Point Light Sources on Digital Images  

NASA Astrophysics Data System (ADS)

The determination of accurate positions of stars is an essential task to obtain a reference coordinate system for precise navigation of ships, airplanes, satellites and space crafts. Stellar positions and proper motions will also help to investigate the structure and evolution of matter in the universe. From astronomical observations systematic errors have been reported by different authors using different techniques to detect and measure positions of point-light sources from digital images. An overview of this problem of image processing is given. The relative subpixel deviation will be defined and described. It provides interesting characteristics independent from the method of position retrieval or point spread introduced by any image deterioration. The relative subpixel deviation defines the lower limit of the achievable precision of positions. The function is the error correction term by itself, which yields a new concept of the error correction. A concept of a new simulation software is presented to further investigate the relative subpixel deviation. Features of the core framework are: support of different optical systems, sources of noise, and detectors types, like monochrome or color CCD and CMOS imagers, their pixel geometry, gaps and varying subpixel sensitivity functions. First results from the simulator software as well as results from new astronomical observations are presented as a proof of concept of the proposed approach to improve the current limit of position accuracy in the order of a few 1/100 of a pixel.

Bauer, Thilo

107

Improvement of GPS/acoustic seafloor positioning precision through controlling the ship's track line  

NASA Astrophysics Data System (ADS)

The precision of GPS/acoustic seafloor positioning was improved by introducing a hull-mounted onboard system in March 2008, which allows us to conduct acoustic ranging measurements with the vessel sailing along the pre-determined track lines, while the early system before 2008 could only adopt the uncontrollable drifting observation. The continuity of the positioning results due to the transition was first confirmed through the comparison between results from sailing and drifting observations conducted in parallel. Using the data acquired for about 3 years since 2008, the repeatability of the determined position for the sailing observation was evaluated to be about 2 cm in root mean squares in the horizontal component, significantly better than that for the early drifting observation. The improvement of positioning precision probably resulted from the improvement of geometric distribution of acoustic ranging data by controlling the track lines. It was also shown that the sailing observation allows to obtain reliable results with a smaller amount of data. Comparison between the results in different sea regions suggests that positioning precision is better in the region along the Nankai Trough than in the region along the Japan Trench, probably because of the complicated acoustic velocity structure of seawater often observed in the latter. Furthermore, the precision of height determination was also improved, which leads us to expect that vertical crustal movement will be detectable in the future through accumulation of data as well as further technology development.

Sato, M.; Fujita, M.; Matsumoto, Y.; Saito, H.; Ishikawa, T.; Asakura, T.

2013-09-01

108

Input shaping for three-dimensional slew maneuvers of a precision pointing flexible spacecraft  

NASA Astrophysics Data System (ADS)

A method is presented for input torque shaping for three-dimensional slew maneuvers of a precision pointing flexible spacecraft. The method determines the torque profiles for fixed-time, rest-to-rest maneuvers which minimizes a specified performance index. Spacecraft dynamics are formulated in such a manner that the rigid body and flexible motions are decoupled. Furthermore, assembly by making use of finite element analysis results. Input torque profiles are determined by solving an associated optimization problem using dynamic programming. Three example problems are provided to demonstrate the application of the method.

Dohrmann, C. R.; Robinett, R. D.

109

Compact Integration of a GSM-19 Magnetic Sensor with High-Precision Positioning using VRS GNSS Technology  

PubMed Central

Magnetic data consists of a sequence of collected points with spatial coordinates and magnetic information. The spatial location of these points needs to be as exact as possible in order to develop a precise interpretation of magnetic anomalies. GPS is a valuable tool for accomplishing this objective, especially if the RTK approach is used. In this paper the VRS (Virtual Reference Station) technique is introduced as a new approach for real-time positioning of magnetic sensors. The main advantages of the VRS approach are, firstly, that only a single GPS receiver is needed (no base station is necessary), reducing field work and equipment costs. Secondly, VRS can operate at distances separated 50–70 km from the reference stations without degrading accuracy. A compact integration of a GSM-19 magnetometer sensor with a geodetic GPS antenna is presented; this integration does not diminish the operational flexibility of the original magnetometer and can work with the VRS approach. The coupled devices were tested in marshlands around Gandia, a city located approximately 100 km South of Valencia (Spain), thought to be the site of a Roman cemetery. The results obtained show adequate geometry and high-precision positioning for the structures to be studied (a comparison with the original low precision GPS of the magnetometer is presented). Finally, the results of the magnetic survey are of great interest for archaeological purposes.

Martin, Angel; Padin, Jorge; Anquela, Ana Belen; Sanchez, Juan; Belda, Santiago

2009-01-01

110

Compact Integration of a GSM-19 Magnetic Sensor with High-Precision Positioning using VRS GNSS Technology.  

PubMed

Magnetic data consists of a sequence of collected points with spatial coordinates and magnetic information. The spatial location of these points needs to be as exact as possible in order to develop a precise interpretation of magnetic anomalies. GPS is a valuable tool for accomplishing this objective, especially if the RTK approach is used. In this paper the VRS (Virtual Reference Station) technique is introduced as a new approach for real-time positioning of magnetic sensors. The main advantages of the VRS approach are, firstly, that only a single GPS receiver is needed (no base station is necessary), reducing field work and equipment costs. Secondly, VRS can operate at distances separated 50-70 km from the reference stations without degrading accuracy. A compact integration of a GSM-19 magnetometer sensor with a geodetic GPS antenna is presented; this integration does not diminish the operational flexibility of the original magnetometer and can work with the VRS approach. The coupled devices were tested in marshlands around Gandia, a city located approximately 100 km South of Valencia (Spain), thought to be the site of a Roman cemetery. The results obtained show adequate geometry and high-precision positioning for the structures to be studied (a comparison with the original low precision GPS of the magnetometer is presented). Finally, the results of the magnetic survey are of great interest for archaeological purposes. PMID:22574055

Martín, Angel; Padín, Jorge; Anquela, Ana Belén; Sánchez, Juán; Belda, Santiago

2009-04-22

111

Tobacco point of sale advertising increases positive brand user imagery  

PubMed Central

Objectives: To determine the potential impact of point of sale advertising on adolescents so as to inform changes to the Tobacco Control Act. Design: Participants were randomly assigned to one of two conditions. In the control condition, students were exposed to a photograph of a packet of cigarettes; in the intervention condition, students were exposed to an ad for cigarettes, typical of point of sale advertising posters. All students then rated the brand user on a set of 12 bipolar adjectives. Two brands were used in the study: Benson & Hedges, and Marlboro. Subjects: One hundred year (grade) 6 and 7 students (age range 10–12 years), from four Western Australian metropolitan primary schools, participated in the study. Results: In a majority of the brand user descriptions, the cigarette advertisements increased brand user imagery in a positive way, especially for Benson & Hedges. For example, participants viewing the Benson & Hedges advertisement, as distinct from those viewing the Benson & Hedges pack only, were more likely to describe the Benson & Hedges user as relaxed, interesting, cool, rich, adventurous, and classy. Relative to the Marlboro pack only, the Marlboro ad increased positive perceptions of the Marlboro user on adventurous, interesting, and relaxed. Conclusions: The results presented here support restrictions being placed on advertising at point of sale, since such ads have the potential to increase positive brand user imagery directly in the situation where a product purchase can take place, and hence the potential to increase the likelihood of impulse purchasing.

Donovan, R; Jancey, J; Jones, S

2002-01-01

112

Precise Near-Earth Navigation with GPS (Global Positioning System): A Survey of Techniques.  

National Technical Information Service (NTIS)

The tracking accuracy of the low earth orbiters (below about 3000 km altitude) can be brought below 10 cm with a variety of differential techniques that exploit the Global Positioning System (GPS). All of these techniques require a precisely known global ...

T. P. Yunck S. C. Wu J. Wu

1987-01-01

113

546 precise astrometric positions of minor planets obtained at the GPO telescope of ESO - La Silla.  

NASA Astrophysics Data System (ADS)

Precise astrometric positions of minor planets: 383 Janina, 1111 Reinmuthia, 1586 Thiele, 1674 Groeneveld, 2682 Soromundi, 2911 1938 GJ, 3009 Coventry, 3032 Evans and 19 new ones, provisional designations 1986 QB1 - 1986 QC3 are presented. Photographic observations of minor planets were carried out in August and September 1986 with the Grand Prism Objective (GPO), 40/400 cm) at ESO.

Debehogne, H.; Olevi?, D.; Proti?-Benišek, V.

1989-12-01

114

Precise tracking of remote sensing satellites with the Global Positioning System  

Microsoft Academic Search

The Global Positioning System (GPS) can be applied in a number of ways to track remote sensing satellites at altitudes below 3000 km with accuracies of better than 10 cm. All techniques use a precise global network of GPS ground receivers operating in concert with a receiver aboard the user satellite, and all estimate the user orbit, GPS orbits, and

THOMAS P. YUNCK; SIEN-CHONG WU; JIUN-TSONG WU; CATHERINE L. THORNTON

1990-01-01

115

Combining bundle adjustment and laser tracker for precise position measurement of fiber ends  

NASA Astrophysics Data System (ADS)

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is a special quasi-meridian reflecting Schmidt telescope that is installed with 4000 optical fibers, and these fibers should precisely align the celestial target when the astronomical observation is performing. Hence, it is necessary to kwon the precise position of the fiber end for tracking the celestial target. The existence of various error sources can affect the process of camera calibration and measurement, causing the measurement results to be less accurate than expected. In order to acquire the precise position of the fiber end on the focal plane of LAMOST, a novel algorithm for fiber end positioning based on the bundle adjustment and laser tracker is proposed in this paper. We also need reduce some error sources. The bundle adjustment algorithm applied in the paper has been implemented with special emphasis on accuracy and performance efficiency. The preliminary results show that this new bundle adjustment algorithm can achieve better accuracy than conventional calibration method. The precision error of fibers position is less than 17?m on the plane of the mechanical structure movement.

Feng, MingChi; Gu, YongGang; Zhai, Chao

2013-06-01

116

NEW DESIGNS OF STAGE MIRRORS FOR HIGHEST PRECISION POSITIONING AND MEASURING MACHINES  

Microsoft Academic Search

Ultra high precision positioning and measuring ma- chines have to face the demand for increasing moving and measuring volumes while reaching accuracy in the nanometer range. For three dimensional measur- ing systems with the required accuracy a setup of three fixed laser interferometers and a moving mirror with three planes are in use in most cases. The mirror carries the

M. Lotz; T. Frank; T. Hackel; R. Theska; G. Höhne

117

Robust fast and precise positioning of ball screw-driven table system on machine stand  

Microsoft Academic Search

This paper presents a robust fast and precise positioning methodology for the ball screw-driven table system on machine stand. The position control system is composed of a robust 2-Degrees-of-Freedom (2DOF) compensator based on the coprime factorization description. In this system, a feedback compensator is mainly designed to ensure the robust control performance and to expand the servo bandwidth, where the

Kazuaki Itoh; Makoto Iwasaki; Nobuyuki Matsui

2004-01-01

118

High precision series solutions of differential equations: Ordinary and regular singular points of second order ODEs  

NASA Astrophysics Data System (ADS)

A subroutine for a very-high-precision numerical solution of a class of ordinary differential equations is provided. For a given evaluation point and equation parameters the memory requirement scales linearly with precision P, and the number of algebraic operations scales roughly linearly with P when P becomes sufficiently large. We discuss results from extensive tests of the code, and how one, for a given evaluation point and equation parameters, may estimate precision loss and computing time in advance.Program summaryProgram title: seriesSolveOde1Catalogue identifier: AEMW_v1_0Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEMW_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 991No. of bytes in distributed program, including test data, etc.: 488116Distribution format: tar.gzProgramming language: C++Computer: PC’s or higher performance computers.Operating system: Linux and MacOSRAM: Few to many megabytes (problem dependent).Classification: 2.7, 4.3External routines: CLN — Class Library for Numbers [1] built with the GNU MP library [2], and GSL — GNU Scientific Library [3] (only for time measurements).Nature of problem:The differential equation -s2(d2dz2+1-?+-?-zddz+?+?-z2)?(z)+1z?n=0Nvnzn?(z)=0, is solved numerically to very high precision. The evaluation point z and some or all of the equation parameters may be complex numbers; some or all of them may be represented exactly in terms of rational numbers.Solution method: The solution ?(z), and optionally ??(z), is evaluated at the point z by executing the recursion A(z)=s-2(m+1+?-?+)(m+1+?-?-)?n=0NVn(z)A(z),?(z)=?(z)+A(z), to sufficiently large m. Here ? is either ?+ or ?-, and Vn(z)=vnz. The recursion is initialized by A(z)=?z?,for n=0,1,…,N?(z)=A0(z). Restrictions: No solution is computed if z=0, or s=0, or if ?=?- (assuming Re?+?Re?-) with ?+-?- an integer, except when ?+-?-=1 and v0=0 (i.e. when z is an ordinary point for z?(z)).Additional comments: The code of the main algorithm is in the file seriesSolveOde1.cc, which “#include” the file checkForBreakOde1.cc. These routines, and the programs using them, must “#include” the file seriesSolveOde1.cc.Running time: On a Linux PC that is a few years old, at y=10 to an accuracy of P=200 decimal digits, evaluating the ground state wavefunction of the anharmonic oscillator (with the eigenvalue known in advance); (cf. Eq. (6)) takes about 2 ms, and about 40 min at an accuracy of P=100000 decimal digits.References:[1] B. Haible and R.B. Kreckel, CLN — Class Library for Numbers, http://www.ginac.de/CLN/[2] T. Granlund and collaborators, GMP — The GNU Multiple Precision Arithmetic Library, http://gmplib.org/[3] M. Galassi et al., GNU Scientific Library Reference Manual (3rd Ed.), ISBN 0954612078., http://www.gnu.org/software/gsl/

Noreen, Amna; Olaussen, Kåre

2012-10-01

119

DORIS-based point mascons for the long term stability of precise orbit solutions  

NASA Astrophysics Data System (ADS)

In recent years non-tidal Time Varying Gravity (TVG) has emerged as the most important contributor in the error budget of Precision Orbit Determination (POD) solutions for altimeter satellites' orbits. The Gravity Recovery And Climate Experiment (GRACE) mission has provided POD analysts with static and time-varying gravity models that are very accurate over the 2002-2012 time interval, but whose linear rates cannot be safely extrapolated before and after the GRACE lifespan. One such model based on a combination of data from GRACE and Lageos from 2002-2010, is used in the dynamic POD solutions developed for the Geophysical Data Records (GDRs) of the Jason series of altimeter missions and the equivalent products from lower altitude missions such as Envisat, Cryosat-2, and HY-2A. In order to accommodate long-term time-variable gravity variations not included in the background geopotential model, we assess the feasibility of using DORIS data to observe local mass variations using point mascons. In particular, we show that the point-mascon approach can stabilize the geographically correlated orbit errors which are of fundamental interest for the analysis of regional Mean Sea Level trends based on altimeter data, and can therefore provide an interim solution in the event of GRACE data loss. The time series of point-mass solutions for Greenland and Antarctica show good agreement with independent series derived from GRACE data, indicating a mass loss at rate of 210 Gt/year and 110 Gt/year respectively.

Cerri, L.; Lemoine, J. M.; Mercier, F.; Zelensky, N. P.; Lemoine, F. G.

2013-08-01

120

On-line point positioning with single frame camera data  

NASA Astrophysics Data System (ADS)

The project on-line point positioning with single frame camera data was concluded. The goal of the project was to develop a data processing concept for an on-line high accuracy point positioning system. An operational on-line system, installed in a UNIX environment under the programming language C, for aerial phototriangulation working on an analytical plotter or on a digital workstation should provide high speed of operation, accuracy of results, and ease of data management. Established tests showed that the Sun Microsystems workstations have sufficient memory capacity and speed performance to run on-line triangulation applications. The adopted algorithms in the on-line triangulation system for the computation of initial values, for the sequential and simultaneous adjustment and for quality control will be presented in this report. A description of the developed software modules and the program will also be given. Although this system was designed and developed specifically for aerial triangulation, it is anticipated that future applications for on-line triangulation algorithms and methods will be found in robotics and industrial quality control.

Gruen, A.

1992-03-01

121

A High Precision Position Sensor Design and Its Signal Processing Algorithm for a Maglev Train  

PubMed Central

High precision positioning technology for a kind of high speed maglev train with an electromagnetic suspension (EMS) system is studied. At first, the basic structure and functions of the position sensor are introduced and some key techniques to enhance the positioning precision are designed. Then, in order to further improve the positioning signal quality and the fault-tolerant ability of the sensor, a new kind of discrete-time tracking differentiator (TD) is proposed based on nonlinear optimal control theory. This new TD has good filtering and differentiating performances and a small calculation load. It is suitable for real-time signal processing. The stability, convergence property and frequency characteristics of the TD are studied and analyzed thoroughly. The delay constant of the TD is figured out and an effective time delay compensation algorithm is proposed. Based on the TD technology, a filtering process is introduced in to improve the positioning signal waveform when the sensor is under bad working conditions, and a two-sensor switching algorithm is designed to eliminate the positioning errors caused by the joint gaps of the long stator. The effectiveness and stability of the sensor and its signal processing algorithms are proved by the experiments on a test train during a long-term test run.

Xue, Song; Long, Zhiqiang; He, Ning; Chang, Wensen

2012-01-01

122

Precise VLA positions and flux-density measurements of the Jupiter system  

SciTech Connect

VLA C array configuration observations at 2 and 6 cm are presented for Europa, Ganymede, and Callisto at eastern and western elongations with respect to Jupiter, which allowed measurements in right ascension and declination of the satellites with an rms precision of about + or - 0.03 arcsec. The transfer of the mean offsets of Ganymede to Jupiter yields offsets of -0.185 + or - 0.03 arcsec and -0.06 + or - 0.03 arcsec, with respect to JPL-DE-200, at the mean epoch of April 28, 1983; the large offset in right ascension is a combination of the Jupiter ephemeris error and the error in the frame tie of the Jovian planets with the VLBI system of precise positions which was used as the absolute reference frame for the observations. A significant error is noted in the orbital position of Callisto with respect to Ganymede. 12 references.

Muhleman, D.O.; Berge, G.L.; Rudy, D.; Niell, A.E.

1986-12-01

123

A hand-held 3D laser scanning with global positioning system of subvoxel precision  

NASA Astrophysics Data System (ADS)

In this paper we propose a hand-held 3D laser scanner composed of an optical head device to extract 3D local surface information and a stereo vision system with subvoxel precision to measure the position and orientation of the 3D optical head. The optical head is manually scanned over the surface object by the operator. The orientation and position of the 3D optical head is determined by a phase-sensitive method using a 2D regular intensity pattern. This phase reference pattern is rigidly fixed to the optical head and allows their 3D location with subvoxel precision in the observation field of the stereo vision system. The 3D resolution achieved by the stereo vision system is about 33 microns at 1.8 m with an observation field of 60cm x 60cm.

Arias, Néstor; Meneses, Néstor; Meneses, Jaime; Gharbi, Tijani

2011-01-01

124

MEMS-based clamp with a passive hold function for precision position retaining of micro manipulators  

Microsoft Academic Search

In this paper the design, modeling and fabrication of a precision MEMS-based clamp with a relatively large clamping force are presented. The purpose of the clamp is to mechanically fix a six-degree-of-freedom (DOF) MEMS-based sample manipulator (Brouwer et al J. Int. Soc. Precis. Eng. Nanotechnol. submitted) once the sample has been positioned in all DOFs. The clamping force is generated

D. M. Brouwer; B. R. de Jong; M. J. de Boer; H. V. Jansen; J. van Dijk; G. J. M. Krijnen; H. M. J. R. Soemers

2009-01-01

125

Nano-motion stage for high speed and precision positioning on an X-Y plane  

Microsoft Academic Search

Precision positioning technology with high speed on an X-Y plane requires to a manufacturing inspection for semiconductor and flat display areas, and so on. The authors proposed a new actuator called ldquoNano-Motion Actuator (NMA)rdquo for track following on a spin-stand that evaluated magnetic heads and media for high density magnetic recording. We applied technologies of the NMA to a new

S. Mori; Y. Sato; A. Sakurada; A. Naganawa; Y. Shibuya; G. Obinata

2009-01-01

126

A Friction Compensation Method in Positioning Control of Nonresonant Ultrasonic Actuator-Driven Precise Stage  

NASA Astrophysics Data System (ADS)

This research has aimed at the control system development of a non-resonant ultrasonic motor (SPIDER)-driven precision stage. SPIDER is newly developed as an actuator to achieve the positioning performance required for next generation. In this paper, friction compensation is firstly realized considering integral effect of controllers. Next, the compensation is achieved based on the adaptive friction observer. Moreover it is experimentally verified that the stick-slip phenomenon is prevented for an environmental change by the proposal technique, and a quick positioning in the scale resolution becomes possible.

Hashimoto, Seiji; Ohishi, Kiyoshi; Kosaka, Koji; Ishikawa, Takeo; Kubota, Hiroshi; Ohmi, Tadahiro

127

Fast and Precise Positioning Using Sequential Adaptive Feedfoward Compensation for Disturbance  

NASA Astrophysics Data System (ADS)

This paper presents a performance improvement of trajectory tracking for the fast-response and high-precision positioning by a sequential adaptive compensation for disturbance. A mathematical disturbance model formulated and parameterized by an iterative learning process can estimate the actual disturbance, and the model can be sequentially adapted by a recursive least-squares method so that it shows the adaptive property against disturbance variations. The proposed positioning control approach involving disturbance modeling and compensation has been verified by experiments using a linear motor-driven table system.

Maebashi, Wataru; Ito, Kazuaki; Iwasaki, Makoto

128

The Use of Industrial Robot Arms for High Precision Patient Positioning  

SciTech Connect

The Indiana University Cyclotron Facility (IUCF) is in the process of designing and building the Midwest Proton Radiation Institute (MPRI) [1]. The design process includes the development of several patient treatment systems. This paper discusses the use of two such systems that provide for the high precision positioning of a patient. They are the Patient Positioner System and the X-ray system. The Patient Positioner System positions an immobilized patient on a support device to a treatment position based on a prescribed Treatment Plan. The X-ray system uses an industrial robot arm to position a Digital Radiography Panel to acquire an X-ray image to verify the location of the prescribed treatment volume in a patient by comparing the acquired images with reference images obtained from the patient's Treatment plan.

Katuin, J.E.; Schreuder, A.N.; Starks, W.M.; Doskow, J. [IUCF, 2401 Milo B Sampson Ln, Bloomington, IN 47408 (United States)

2003-08-26

129

Determination of precise photographic positions with the automatic measuring machine IRIS  

NASA Astrophysics Data System (ADS)

An important task in astrometry is related to the determination of precise photographic positions of solar system bodies. Positions of newly discovered objects provide a basis for the determination of orbits and the calculations for follow-up observations. A program for the determination of accurate positions of asteroids makes use of an automatic measuring machine IRIS and the interactive computer routine Asteroid, which allows automatized measurements and reductions of photographic positions. The Image Reading Instrument System (IRIS) was developed in the 1970s. IRIS represents a two-channel microdensitometer with vibrating prisms as scanning devices. A description of the interactive computer routine Asteroid is presented, taking into account the selection of bright stars, aspects of visual identification, coordinate transformation, the selection of reference stars, the identification of the unknown objects, automatic measurements, and details of data reduction.

Hahn, G.; Lagerkvist, C.-I.

1982-04-01

130

Image-processing techniques in precisely measuring positions of Jupiter and its Galilean satellites  

NASA Astrophysics Data System (ADS)

Two image-processing techniques are developed to measure precisely the positions of Jupiter and its Galilean satellites. One is used to detect the edge of Jupiter's CCD image and fit it with an ellipse, thereby obtaining the planetary center. The other is used to remove the positional effect of Jupiter's scattering light that has on the measurement of a close satellite. 133 frames of CCD images are measured by using these techniques, and these measured positions of Galilean satellites are compared to the ones computed with the ephemerides of Jacobson's JUP204 and Arlot's G5. Preliminary analysis of the data as Jupiter-satellite or inter-satellite positions shows that a standard error (i.e. internal precision) as small as 0.03 arcsec can be reached in right ascension and declination. It is believed that these techniques would be useful for astrometric and photometric CCD observations of Galilean satellites, especially for CCD observations in the forthcoming mutual phenomena of Galilean satellites.

Peng, Q. Y.; Han, Y. B.; Zhang, C. L.; Li, Z. L.

2003-04-01

131

Study on a joint synchronization algorithm in timedomain for OFDM-UWB based indoor precision positioning system receiver  

Microsoft Academic Search

According to the basic principle of Orthogonal Frequency Division Multiplexing Ultra Wide Band (OFDM-UWB) based indoor precision positioning system, a Symbol Timing Synchronization (STS) algorithm with the high synchronization precision of only a few (1~3) sampling intervals is required to achieve indoor centimeter-level precision positioning. The performance of existing synchronization algorithms of OFDM-UWB system is so far to fit the

Decai Zou; Feng Liu; Yun Li; Tao Han

2010-01-01

132

The design and finite element analysis of a compliant 3DOF spatial translational ultra-precise positioning platform  

Microsoft Academic Search

Ultra-precise positioning platform plays a significant role in ultra-precise operation and micro-operation. A new compliant 3-DOF spatial translational ultra-precise positioning platform is proposed and it overcomes the shortcomings of the general conventional drive and transmission such as low speed of response and low displacement resolution. The platform is consist of flexible hinges which provide elastic supporting, and with piezoelectric actuators

Chen Qiang; Huang Yong; Zhu Dachang; Zhou Mugui

2010-01-01

133

A design, fabrication and test of a precision positioning servo drive for a multiplexed imaging system  

NASA Astrophysics Data System (ADS)

In support of the development of a new initiative in the field of multiplexed image spectroscopy, a high torque, servo system was developed. Utilizing only a low resolution shaft position encoder, the system demonstrated an excellent ability to track a pulse input signal with high precision and stability. Ultimately, this servo system will be incorporated into a new generation of multiplexed imaging and imaging spectroscopy instruments. It will provide those instruments with the capability to accurately rotate into position a sequence of optical image encoding masks and it will tightly control that position, even in the presence of external perturbations. A computer will read the light intensity signals from a sensor and quickly decode the image for viewing and analysis. Further research into this technology should lead to full development of an extremely efficient infrared imaging system, with additional applications to passive surveillance, target signature identification, and airborne infrared astrophysics.

Sargent, Joseph P., Jr.

1991-09-01

134

Libration point orbits for lunar global positioning systems  

NASA Astrophysics Data System (ADS)

With the development of lunar exploration, a lunar global positioning system (LGPS) is demanded for both on-ground and in-flight lunar exploration missions. The traditional configuration of constellation requires at least eighteen satellites to cover the whole lunar surface continuously. In this paper, the configurations of the libration point orbits (LPOs) constellations are investigated. By using the constellations on the Earth-Moon L1 and L2 LPOs, the basic functions of the LGPS can be realized by using eight to fourteen satellites. First, the LPO and the combinations of LPOs, which can be used in the constellations of the LGPS, are investigated. The criteria and procedures of the configuration design are introduced. Second, the configurations of LPOs constellations are investigated in the Earth-Moon circular-restricted three-body problem (CR3BP). The size of the LPOs and the distribution of the satellites on these LPOs are determined by using an exhaustive algorithm and a global optimization method, respectively. The key performance parameters of these constellations are computed. Third, the constellations with good performance in the CR3BP are redesigned in the more accurate Earth-Moon based Sun-perturbed bicircular four-body problem (B4BP). Moreover, in order to avoid the ground coverage problem caused by the perturbation of the Sun, some modifications are implemented, and the configuration of the no blind area LGPS in the B4BP is obtained.

Ren, Yuan; Shan, Jinjun

2013-04-01

135

An Integration of GPS with INS Sensors for Precise Long-Baseline Kinematic Positioning  

PubMed Central

Integrating the precise GPS carrier phases and INS sensor technologies is a methodology that has been applied indispensably in those application fields requiring accurate and reliable position, velocity, and attitude information. However, conventional integration approaches with a single GPS reference station may not fulfil the demanding performance requirements, especially in the position component, when the baseline length between the reference station and mobile user’s GPS receiver is greater than a few tens of kilometres. This is because their positioning performance is primarily dependent on the common mode of errors of GPS measurements. To address this constraint, a novel GPS/INS integration scheme using multiple GPS reference stations is proposed here that can improve its positioning accuracy by modelling the baseline-dependent errors. In this paper, the technical issues concerned with implementing the proposed scheme are described, including the GPS network correction modelling and integrated GPS/INS filtering. In addition, the results from the processing of the simulated measurements are presented to characterise the system performance. As a result, it has been established that the integration of GPS/INS with multiple reference stations would make it possible to ensure centimetre-level positioning accuracy, even if the baseline length reaches about 100 km.

Lee, Hungkyu

2010-01-01

136

Design and Analysis of a Compact Precision Positioning Platform Integrating Strain Gauges and the Piezoactuator  

PubMed Central

Miniaturization precision positioning platforms are needed for in situ nanomechanical test applications. This paper proposes a compact precision positioning platform integrating strain gauges and the piezoactuator. Effects of geometric parameters of two parallel plates on Von Mises stress distribution as well as static and dynamic characteristics of the platform were studied by the finite element method. Results of the calibration experiment indicate that the strain gauge sensor has good linearity and its sensitivity is about 0.0468 mV/?m. A closed-loop control system was established to solve the problem of nonlinearity of the platform. Experimental results demonstrate that for the displacement control process, both the displacement increasing portion and the decreasing portion have good linearity, verifying that the control system is available. The developed platform has a compact structure but can realize displacement measurement with the embedded strain gauges, which is useful for the closed-loop control and structure miniaturization of piezo devices. It has potential applications in nanoindentation and nanoscratch tests, especially in the field of in situ nanomechanical testing which requires compact structures.

Huang, Hu; Zhao, Hongwei; Yang, Zhaojun; Fan, Zunqiang; Wan, Shunguang; Shi, Chengli; Ma, Zhichao

2012-01-01

137

A free jet (supersonic), molecular beam source with automatized, 50 nm precision nozzle-skimmer positioning  

NASA Astrophysics Data System (ADS)

Low energy (thermal) free jet (supersonic) molecular beams are used in a range of applications from surface science and surface deposition to quantum coherence and gas kinetics experiments. A free jet molecular beam is created by a gas expansion from a high pressure reservoir through a small aperture (nozzle). The nozzle typically has a diameter of 2-20 ?m. The central part of the beam is selected using a skimmer, typically up to 500 ?m in diameter. Recent years have seen the introduction of highly spatially confined beam sources based on micrometer skimmers and micrometer or even sub-micrometer nozzles. Such sources have been applied, for example, in the investigation of superfluidity and in neutral helium microscopy. However, up till now no source design allowing the precise positioning of the micro-skimmer relative to the nozzle has been available. This is an important issue because the relative position of skimmer and nozzle can influence the beam properties considerably. Here we present the design and implementation of a new molecular beam source, which allows an automatized, 50 nm precision positioning of the skimmer relative to the nozzle. The source is liquid nitrogen cooled and the temperature can be controlled between 110 K and 350 K with a temperature fluctuation of less than +/-0.1 K over several hours. Beam intensity measurements using a 5 ?m nozzle and a skimmer 5 ?m in diameter are presented for stagnation pressures po in the range 3-180 bars. A 2D beam profile scan, using a 9.5 ?m skimmer and a 5 ?m nozzle is presented as a further documentation of the versatility of the new design and as an illustration of the influence of the relative skimmer-nozzle position on the beam properties.

Eder, S. D.; Samelin, B.; Bracco, G.; Ansperger, K.; Holst, B.

2013-09-01

138

A free jet (supersonic), molecular beam source with automatized, 50 nm precision nozzle-skimmer positioning.  

PubMed

Low energy (thermal) free jet (supersonic) molecular beams are used in a range of applications from surface science and surface deposition to quantum coherence and gas kinetics experiments. A free jet molecular beam is created by a gas expansion from a high pressure reservoir through a small aperture (nozzle). The nozzle typically has a diameter of 2-20??m. The central part of the beam is selected using a skimmer, typically up to 500??m in diameter. Recent years have seen the introduction of highly spatially confined beam sources based on micrometer skimmers and micrometer or even sub-micrometer nozzles. Such sources have been applied, for example, in the investigation of superfluidity and in neutral helium microscopy. However, up till now no source design allowing the precise positioning of the micro-skimmer relative to the nozzle has been available. This is an important issue because the relative position of skimmer and nozzle can influence the beam properties considerably. Here we present the design and implementation of a new molecular beam source, which allows an automatized, 50?nm precision positioning of the skimmer relative to the nozzle. The source is liquid nitrogen cooled and the temperature can be controlled between 110?K and 350?K with a temperature fluctuation of less than ±0.1?K over several hours. Beam intensity measurements using a 5??m nozzle and a skimmer 5??m in diameter are presented for stagnation pressures po in the range 3-180?bars. A 2D beam profile scan, using a 9.5??m skimmer and a 5??m nozzle is presented as a further documentation of the versatility of the new design and as an illustration of the influence of the relative skimmer-nozzle position on the beam properties. PMID:24089819

Eder, S D; Samelin, B; Bracco, G; Ansperger, K; Holst, B

2013-09-01

139

On the role the friction plays in an ultra precision positioning system  

Microsoft Academic Search

Friction, due to its destabilizing and drastic magnitude variation between stick and slip, is commonly considered as a detrimental factor to a positioning system. This paper, based on the new knowledge about pre-sliding dynamics, tries to put forward another point of view; it shows that the spring-damper-like property in the pre-sliding phase makes it possible to achieve the so called

Chen Hsieh; Kang-Chin Yang

2009-01-01

140

Theoretical and experimental research on machine tool servo system for ultra-precision position compensation on CNC lathe  

Microsoft Academic Search

The theories and techniques for improving machining accuracy via position control of diamond tool's tip and raising resolution of cutting depth on precise CNC lathes have been extremely focused on. A new piezo-driven ultra-precision machine tool servo system is designed and tested to improve manufacturing accuracy of workpiece. The mathematical model of machine tool servo system is established and the

Zhichao Ma; Leilei Hu; Hongwei Zhao; Boda Wu; Zhenxing Peng; Xiaoqin Zhou; Hongguo Zhang; Shuai Zhu; Lifeng Xing; Huang Hu

2010-01-01

141

Positional and orientational referencing of multiple light sectioning systems for precision profile measurement  

NASA Astrophysics Data System (ADS)

Precision rolled strips are often intermediate products in the manufacturing of blades. In such cases the shape and size of these strips are essential to the functionality and quality of the blade and cutting workpiece. Although precision strips are normally produced in heavily automated rolling mills, their size and shape are still inspected manually with profile gauges and microscopes. In this paper we present a measurement setup with multiple light-sectioning systems, which is suitable for the inspection of all sides of a profiled strip. It consists of three measurement heads, which are used to inspect the upper side, the lower side and the back of the blade. The heads are calibrated individually; the focus of the work here is to determine the relative position and orientation of the heads with respect to each other. The first approach has been developed to reference two or more measurement heads. The calculation of the required transformations is based on the rotation of a suitable target. Due to the small depth of field, the location of the rotation axis must be pre-adjusted very precisely. To improve the accuracy and to simplify the process, a second referencing method was developed. The required target was manufactured by means of a 5-axis high speed milling machine and features a thickness tolerance of less than 1 micron. Both the referencing method and target are presented. Additionally, we demonstrate the all-side inspection of a blade. It will be shown that the approaches allow a robust and flexible referencing of multiple measurement heads to each other.

Tratnig, Mark; Hlobil, Helmut; Reisinger, Johann; O'Leary, Paul L.

2005-02-01

142

Large stroke and high precision pneumatic–piezoelectric hybrid positioning control using adaptive discrete variable structure control  

Microsoft Academic Search

This paper investigates a novel large stroke and high precision pneumatic–piezoelectric hybrid positioning control system that contains a pneumatic servo cylinder and a piezoelectric servo actuator combined in cascade. The pneumatic servo cylinder serves to positioning with high speed and large stroke; the piezoelectric actuator positions in fine stroke for compensating the influence of friction force so as to achieve

Mao-Hsiung Chiang; Chung-Chieh Chen; Tan-Ni Tsou

2005-01-01

143

Precision analog signal processor for beam position measurements in electron storage rings  

SciTech Connect

Beam position monitors (BPM) in electron and positron storage rings have evolved from simple systems composed of beam pickups, coaxial cables, multiplexing relays, and a single receiver (usually a analyzer) into very complex and costly systems of multiple receivers and processors. The older may have taken minutes to measure the circulating beam closed orbit. Today instrumentation designers are required to provide high-speed measurements of the beam orbit, often at the ring revolution frequency. In addition the instruments must have very high accuracy and resolution. A BPM has been developed for the Advanced Light Source (ALS) in Berkeley which features high resolution and relatively low cost. The instrument has a single purpose; to measure position of a stable stored beam. Because the pickup signals are multiplexed into a single receiver, and due to its narrow bandwidth, the receiver is not intended for single-turn studies. The receiver delivers normalized measurements of X and Y posit ion entirely by analog means at nominally 1 V/mm. No computers are involved. No software is required. Bergoz, a French company specializing in precision beam instrumentation, integrated the ALS design m their new BPM analog signal processor module. Performance comparisons were made on the ALS. In this paper we report on the architecture and performance of the ALS prototype BPM.

Hinkson, J.A. [Lawrence Berkeley Lab., CA (US); Unser, K.B. [Consultant, Genis-Pouilly (France)

1995-05-01

144

Nano-Motion Stage for High-Speed and Precision Positioning on an X-Y Plane  

Microsoft Academic Search

Precision positioning technology with high speed on an X-Y plane which was a coplanar coupling type required a manufacturing inspection for semiconductor and flat display areas, and so on. However, a precise positioning technology with high-speed motion had not been established on the X-Y plane which was coplanar without rotation around a Z axis yet. The authors proposed a new

Shigeki Mori; Yuudai Sato; Akira Sakurada; Akihiro Naganawa; Yotsugi Shibuya; Goro Obinata

2009-01-01

145

Precise Positioning Stage Driven by Multilayer Piezo Actuator using Strain Gauge  

NASA Astrophysics Data System (ADS)

A newly developed strain gauge with a Cr-N thin film was formed directly on a zirconia plate by sputtering without using any adhesive. Unevenness of sensitivity and drift caused by an adhesive layer could thus be suppressed. The gauge factor of the strain gauge was 6, three-fold that of a conventional strain gauge such as a Ni-Cu foil type. Four strain gauges were formed on one side of a zirconia plate. This zirconia plate was attached to sensor heads. When the sensor heads were moved, positive and negative strains were induced by a diaphram construction due to the use of a full-bridge circuit. A resistance of the strain gauge of 5 k? could be realized by thin and fine patterning in order to suppress joule heat. Therefore 10 V could be applied on a full-bridge circuit as bridge input voltage. The value was five-fold that of conventional bridge input voltage. By these improvements, higher sensitivity could be obtained and the S/N ratio could be improved. The precise positioning stage had a 5 nm resolution using this newly developed strain gauge as a displacement sensor.

Furuta, Atsushi; Munekata, Mutsuo; Higuchi, Toshiro

2002-10-01

146

Flight tests of GPS/GLONASS precise positioning versus dual frequency KGPS profile  

NASA Astrophysics Data System (ADS)

The benefits of combined use of the GLONASS and GPS navigation satellite constellations have become obvious for applications such as open-cast mining operations and highly dynamic vehicles such as spaceplanes. Moreover, using GLONASS satellites in addition to GPS is useful for long baseline applications since it increases the numbers of satellites in common view. Japan's National Aerospace Laboratory (NAL) has been conducting feasibility studies using combined GPS/GLONASS positioning for spaceplane landing systems and the precise navigation of stratospheric airships. This paper presents the results of the first Japanese kinematic GPS/GLONASS flight test. In the test, the difference in estimated position between dual frequency GPS and single frequency GPS/GLONASS systems was found to be within a few centimeters, indicating that GLONASS carrier phase ambiguities were correctly resolved. To demonstrate the benefits of combining GLONASS with GPS navigation, an on-the-fly (OTF) test of instantaneous ambiguity resolution with a 30 degree cutoff angle was performed. The OTF performance of the combined GPS/GLONASS system was found to be similar to that of a GPS system with a cutoff angle of 10 degrees, showing that augmentation of GPS with GLONASS will be useful for highly dynamic vehicle applications.

Tsujii, T.; Harigae, M.; Inagaki, T.; Kanai, T.

2000-10-01

147

Deterministic delivery of externally cold and precisely positioned single molecular ions  

NASA Astrophysics Data System (ADS)

We present the preparation and deterministic delivery of a selectable number of externally cold molecular ions. A laser cooled ensemble of 24Mg+ ions subsequently confined in several linear Paul traps inter-connected via a quadrupole guide serves as a cold bath for a single or up to a few hundred molecular ions. Sympathetic cooling embeds the molecular ions in the crystalline structure. 24MgH+ ions that serve as a model system for a large variety of other possible molecular ions, are cooled down close to the Doppler limit and are positioned with an accuracy of one micrometer. After the production process, severely compromising the vacuum conditions, the molecular ion is efficiently transferred into nearly background-free environment. The transfer of a molecular ion between different traps as well as the control of the molecular ions in the traps is demonstrated. Schemes, optimized for the transfer of a specific number of ions, are realized and their efficiencies are evaluated. This versatile source applicable for broad charge-to-mass ratios of externally cold and precisely positioned molecular ions can serve as a container-free target preparation device well suited for diffraction or spectroscopic measurements on individual molecular ions at high repetition rates (kHz).

Leschhorn, G.; Kahra, S.; Schaetz, T.

2012-08-01

148

A finite element analysis approach with integrated PID control for simultaneous precision positioning and vibration suppression of smart structures  

NASA Astrophysics Data System (ADS)

This paper focuses on the development of an ANSYS finite element analysis (FEA) environment with integrated PID control scheme for simultaneous precision positioning and vibration suppression of smart composite structures with piezoelectric flat patches acting as actuators. This environment includes three modules: structural modeling, PID controller design, and dynamic analysis of smart structures. Two types of PID controllers are investigated, namely, PID vibration suppression (PID-VS) controller and PID simultaneous precision positioning and vibration suppression (PIDSPPVS) controller. The PID-VS controller is suitable to perform only vibration suppression with no positioning capability. The PID-SPPVS controller is equipped with SPPVS capabilities. The characteristics of individual control gains and their behavior with respect to each other for the two PID controllers are also studied. The gain selection for the PID-VS controller is based on obtaining the best VS while the gain selection for the PID-SPPVS controller is based on achieving the best positioning accuracy and VS simultaneously. In this study, a horizontal cantilevered graphite/epoxy composite beam with one surface-mounted ACX piezoelectric flat patch located at the beam root is first modeled. Next, the FE modal analysis is performed to determine the natural frequencies and hence the time step interval needed for the FE transient analysis. During the transient analysis, the mid-point of the beam tip is subjected to different types of external excitations such as sine loadings with different frequencies as well as random forces to evaluate the two PID controller performances. It is demonstrated that the FEA model with integrated PID-SPPVS controller is able to reach the desired position in a much shorter time in comparison to the PID-VS controller. Vibration amplitude reduction capabilities for the both PID controllers are very similar, although the PID-VS controller performs slightly better. This study also implies that the integrated FEA environment, consisting of the structural modeling of active composite structures with piezoelectric flat patches, modal and transient analyses, controller design, and simulation, provides a powerful tool for the design, analysis, and control of smart structures with SPPVS capabilities.

Russ, Richard; Ma, Kougen; Ghasemi-Nejhad, Mehrdad N.

2006-04-01

149

Modeling, actuator optimization, and simultaneous precision positioning and vibration suppression of smart composite panels  

NASA Astrophysics Data System (ADS)

To improve the fuel consumption of a satellite, maintain the position and orientation and eliminate the unwanted thruster vibration, intelligent composite structure technology was proposed in the ADPICAS (Adaptive Damping and Positioning using Intelligent Composite Active Structures) project funded by the ONR (Office of Naval Research) in collaboration with the NRL (Naval Research Laboratory) in 2000. This dissertation introduces the author's research achievements in developing smart composite panels for the ADPICAS project, including modeling, actuator optimization, and vibration control. The method of separation of variables is presented to derive the analytical shape functions for complex composite structures with asymmetric constraints, i.e., the 2-D Adaptive Composite Circular Plate (ACCP) in cylindrical coordinates and the 3-D Adaptive Composite Satellite Dish (ACSD) in spherical coordinates. Following these solutions, two modeling approaches are developed to obtain the models of adaptive composite panels including an adaptive composite beam, the ACCP, and the ACSD. One model approach is to employ the Lagrange-Rayleigh-Ritz method based on the developed analytical shape functions. Meanwhile, the transfer function estimation technique, combining the finite element analyses, is applied to obtain the numerical model of the composite panels. Aiming at improving the actuation efficiency, a Genetic Algorithm is presented to optimize the piezoelectric actuator placement on the composite panels. Taking the inertia and stiffness characteristics of the piezoelectric actuators into account, this algorithm defines the performance index as a weighted summation of control error and control energy consumption, and obtained the optimal solution that minimizes the performance index. Furthermore, an adaptive disturbance observer/feed-forward (ADOB/FF) controller is proposed to achieve simultaneous precision positioning and vibration suppression of the adaptive composite panels. Numerical simulations and experiments are conducted. The optimal piezoelectric actuator configuration saves the control energy and reduces vibration of the composite panels substantially. The simulations and experiments show that the ADOB/FF provides a robust performance against the system parameter perturbations and environmental disturbances.

Yan, Su

150

A Laboratory Simulation of a Single-Axis Dual-Level Precision Pointing System.  

National Technical Information Service (NTIS)

The laboratory simulation of a scaled single-axis dual-level control system for a large space telescope is demonstrated. The dual-level control system consists of a coarse-body-pointing system and a fine-pointing system, which uses an image motion compens...

F. R. Morrell G. F. Bullock K. C. Romanczyk

1973-01-01

151

Precise integration method for a class of singular two-point boundary value problems  

NASA Astrophysics Data System (ADS)

In this paper we present a precise integration method based on high order multiple perturbation method and reduction method for solving a class of singular twopoint boundary value problems. Firstly, by employing the method of variable coefficient dimensional expanding, the non-homogeneous ordinary differential equations (ODEs) are transformed into homogeneous ODEs. Then the interval is divided evenly, and the transfer matrix in every subinterval is worked out using the high order multiple perturbation method, and a set of algebraic equations is given in the form of matrix by the precise integration relation for each segment, which is worked out by the reduction method. Finally numerical examples are elaboratedd to validate the present method.

Zhang, Wen-Zhi; Huang, Pei-Yan

2013-04-01

152

Tobacco point of sale advertising increases positive brand user imagery  

Microsoft Academic Search

Subjects: One hundred year (grade) 6 and 7 students (age range 10-12 years), from four Western Australian metropolitan primary schools, participated in the study. Results: In a majority of the brand user descriptions, the cigarette advertisements increased brand user imagery in a positive way, especially for Benson & Hedges. For example, participants viewing the Benson & Hedges advertisement, as distinct

R J Donovan; J Jancey; S Jones

2005-01-01

153

FPGA accelerating double\\/quad-double high precision floating-point applications for ExaScale computing  

Microsoft Academic Search

In this paper we explore the capability and flexibility of FPGA solutions in a sense to accelerate scientific computing applications which require very high precision arithmetic, based on 128-bit or even 256-bit floating-point number representation. This paper addresses the accuracy when performing LU decomposition on large-scale matrices. In future ExaScale computing environments, accuracy errors are expected to increase up to

Yong Dou; Yuanwu Lei; Guiming Wu; Song Guo; Jie Zhou; Li Shen

2010-01-01

154

The Effects of L2C Signal Tracking on High-Precision Carrier Phase GPS Positioning  

NASA Astrophysics Data System (ADS)

In 2005, the L2C signal was introduced to improve the accuracy, tracking and redundancy of the GPS system for civilian users. The L2C signal also provides improved SNR data when compared with the L2P(Y) legacy signal, comparable to that of the L1 C/A-code, which allows for better tracking at lower elevations. With the recent launch of the first block II-F satellite (SVN62/PRN25), there are 8 healthy satellites broadcasting L2C signals, or 25% of the constellation. However, GNSS network operators such as the UNAVCO Plate Boundary Observatory (PBO) have been hesitant to use the new signal as it is not well determined how tracking and logging L2C could affect the positions derived from L2 carrier phase measurements for a given receiver. The L2C carrier phase is in quadrature (90° out of phase) with the L2P(Y) phase that has been used by high-precision positioning software since the beginning of GPS. To complicate matters further, some receiver manufacturers (e.g. Trimble) correct for this when logging L2C phase while others (e.g. Topcon) do not. The L2C capability of receivers currently in widespread use in permanent networks can depend on firmware as well as hardware; in some cases receivers can simultaneously track L2C and L2P(Y) phases and some can track only one or the other, and the resulting observation files can depend on how individual operators configure the devices. In cases where both L2C and L2P(Y) are logged simultaneously, translation software (such as UNAVCO’s teqc) must be used carefully in order to select which L2 observation is written to RINEX (2.11) and used in positioning. Modifications were recently made to teqc to eliminate potential confusion in that part of the process; if L2C code observations appear in a RINEX (2.11) file produced by teqc, the L2 phase and S2 SNR observations were from the L2C carrier for those satellites. To date L2C analyses have been restricted to special applications such as snow depth and soil moisture using SNR data (Larson et al, 2010). We use several different methods to determine the effect that tracking and logging L2C has on carrier phase measurements and positioning for various receiver models and configurations. Our analyses use GAMIT and TRACK to calculate positions and baseline lengths including zero-length baselines, position time series from a subset of 10 PBO stations that have been L2C enabled, phase residual comparisons and direct comparisons of the L2 phase observable. Twenty-four hour zero-length baseline solutions using L2 show sub-millimeter differences in the mean positions for both the horizontal and vertical components. Direct comparisons of the L2 phase observable from RINEX (2.11) files with and without the L2C observable show sub-millicycle differences over a 24 hour mean with variations up to ~±0.06 cycles for satellites that broadcast L2C. Our results show that the magnitude of the variations increased at low elevations. Separate correlation of the L2 and L2C signals may explain this difference. The number of L2 observations increased when the L2C observable was recorded, while the number of cycle slips above 10 degrees in elevation decreased when L2C was recorded. The behavior of the L2P(Y) phase observations or positions from a given receiver was not affected by the enabling of L2C tracking.

Berglund, H.; Blume, F.; Estey, L. H.; Borsa, A. A.

2010-12-01

155

New extreme point results on robust strict positive realness  

Microsoft Academic Search

This paper considers the robust strict positive real (SPR) problem for a family of plants of the form G(s,q)=N(s,qn)D-1 (s,qd)-?, where N(s,qn) and D(s,qd) are multiaffine in uncertain parameters qn and qd, respectively, and ?>0. In the discrete-time setting, this problem plays an important role in digital quantization. Several results are presented. First, we prove that this plant family is

M. Fu; S. Dasgupta

1996-01-01

156

Super-resolution for a point source using positive refraction  

NASA Astrophysics Data System (ADS)

Leonhardt demonstrated (2009) that the 2D Maxwell Fish Eye lens (MFE) can focus perfectly 2D Helmholtz waves of arbitrary frequency, i.e., it can transport perfectly an outward (monopole) 2D Helmholtz wave field, generated by a point source, towards a receptor called "perfect drain" (PD) located at the corresponding MFE image point. The PD has the property of absorbing the complete radiation without radiation or scattering and it has been claimed as necessary to obtain super-resolution (SR) in the MFE. However, a prototype using a "drain" different from the PD has shown ?/5 resolution for microwave frequencies (Ma et al, 2010). Recently, the SR properties of a device equivalent to the MFE, called the Spherical Geodesic Waveguide (SGW) (Miñano et al, 2012) have been analyzed. The reported results show resolution up to ? /3000, for the SGW loaded with the perfect drain, and up to ? /500 for the SGW without perfect drain. The perfect drain was realized as a coaxial probe loaded with properly calculated impedance. The SGW provides SR only in a narrow band of frequencies close to the resonance Schumann frequencies. Here we analyze the SGW loaded with a small "perfect drain region" (González et al, 2011). This drain is designed as a region made of a material with complex permittivity. The comparative results show that there is no significant difference in the SR properties for both perfect drain designs.

Miñano, Juan C.; Benítez, Pablo; González, Juan C.; Grabovi?ki?, Dejan; Ahmadpanahi, Hamed

157

Image-guided system with miniature robot for precise positioning and targeting in keyhole neurosurgery.  

PubMed

This paper describes a novel image-guided system for precise automatic targeting in minimally invasive keyhole neurosurgery. The system consists of the MARS miniature robot fitted with a mechanical guide for needle, probe or catheter insertion. Intraoperatively, the robot is directly affixed to a head clamp or to the patient's skull. It automatically positions itself with respect to predefined targets in a preoperative CT/MRI image following an anatomical registration with an intraoperative 3D surface scan of the patient's facial features and registration jig. We present the system architecture, surgical protocol, custom hardware (targeting and registration jig), and software modules (preoperative planning, intraoperative execution, 3D surface scan processing, and three-way registration). We also describe a prototype implementation of the system and in vitro registration experiments. Our results indicate a system-wide target registration error of 1.7 mm (standard deviation = 0.7 mm), which is close to the required 1.0-1.5 mm clinical accuracy in many keyhole neurosurgical procedures. PMID:17038306

Joskowicz, L; Shamir, R; Freiman, M; Shoham, M; Zehavi, E; Umansky, F; Shoshan, Y

2006-07-01

158

Nonlinear control design techniques for precision formation flying at Lagrange points  

NASA Astrophysics Data System (ADS)

Precision spacecraft formation flying is an enabling technology for a variety of proposed space-based observatories, such as NASA's Terrestrial Planet Finder (TPF), the Micro-Arcsecond X-Ray Imaging Mission (MAXIM), and Stellar Imager (SI). This research specifically examines the precision formation flying control architecture, characterizing the relative performance of linear and nonlinear controllers. Controller design is based on a 6DOF control architecture, characteristic of precision formation flying control. In an effort to minimize the influence of design parameters in the comparison, analysis employs "equivalent" controller gains, and incorporates an integrator in the linear control design. Controller performance is evaluated through various simulations designed to reflect a realistic space environment. The simulation architecture includes a full gravitational model and solar pressure effects. Spacecraft model properties are based on realistic mission design parameters. Control actuators are modeled as a fixed set of thrusters for both translation and attitude control. Analysis includes impact on controller performance due to omitted dynamics in the model (gravitational sources and solar pressure) and model uncertainty (mass properties, thruster placement and thruster alignment). Linearized equations of relative motion are derived for spacecraft operating in the context of the Restricted Three Body Problem. Linearization is performed with respect to a reference spacecraft within the formation. Analysis demonstrates robust stability for the Linear Quadratic Regulator controller design based on the linearized dynamics. Nonlinear controllers are developed based on Lyapunov analysis, including both non-adaptive and adaptive designs. While the linear controller demonstrates greater robustness to model uncertainty, both nonlinear controllers exhibit superior performance. The adaptive controller provides the best performance. As a key feature, the adaptive controller design requires only relative navigation knowledge. Analysis demonstrates the ability of the nonlinear controller to compensate for unknown dynamics and model uncertainty. Results exhibit the potential of a nonlinear adaptive architecture for improving controller performance. Nonlinear adaptive control is a viable strategy for meeting the extreme control requirements associated with formation flying missions like MAXIM and Stellar Imager. Mission specific analysis from a systems perspective is required to determine the best controller design.

Luquette, Richard J.

159

Construction and Operation of a Simple High-Precision Copper-Point Blackbody and Furnace.  

National Technical Information Service (NTIS)

Detailed instructions for the construction and operation of an inexpensive copper-point blackbody and furnace are presented. Such a source may be expected to realize the radiance temperature of 1083.3C (Int. 48) with an uncertainty of 0.2C and a variation...

R. D. Lee

1969-01-01

160

Precision Measurement of VHF Gain and Pointing Accuracy of the NRL 150-Foot Parabolic Antenna.  

National Technical Information Service (NTIS)

Radio astronomy techniques were employed by accurately determine the gain, pointing error, and temperature of the CBA, NRL 150-foot parabolic antenna system. A frequency of 146 Mhz was chosen for measurements corresponding to one of the few 4-Mhz wide cha...

P. F. Nicholson

1965-01-01

161

The design of a precision pointing control system for the Space Infrared Telescope Facility  

Microsoft Academic Search

The design and performance simulation of the Space Infrared Telescope Facility pointing and control system are described. The system design is constrained by such considerations as image stability, maneuver capability, cryogen lifetime, and structural flexibility. The primary design driver is the requirement to rapidly execute small angle reorientations of the telescope's optical axis. The flexibility of the spacecraft was simulated

B. Sridhar; J.-N. Aurbrun; K. R. Lorell

1985-01-01

162

Differential and Precise Point Positioning in the South American Region with lonosphere Maps  

Microsoft Academic Search

This paper presents two strategies for improving GPS coordinate solutions using regional ionosphere maps in South America,\\u000a a region susceptible to strong ionospheric activity.\\u000a \\u000a Since 2005, the La Plata Ionospheric Model (LPIM) has been used to routinely generate Vertical Total Electron Content (VTEC)\\u000a maps at the La Plata Processing Center (CPLAT) using about 50 GPS stations in South America. VTEC

S. M Alves Costa; Alberto Luis da Silva; Newton José de Moura Jr; Mauricio Alfredo Gende; Claudio Antonio Brunini

163

The design of a precision pointing control system for the Space Infrared Telescope Facility  

NASA Astrophysics Data System (ADS)

The design and performance simulation of the Space Infrared Telescope Facility pointing and control system are described. The system design is constrained by such considerations as image stability, maneuver capability, cryogen lifetime, and structural flexibility. The primary design driver is the requirement to rapidly execute small angle reorientations of the telescope's optical axis. The flexibility of the spacecraft was simulated using a simplified multibody model which provided an approximation of the primary bending modes. The rather conventional attitude control system design of PID type with a 0.5 Hz bandwidth was enhanced to meet the small angle maneuver requirements by the use of three techniques: (1) a feedforward loop to improve the time response; (2) torque shaping to minimize structural excitation; and (3) active image stabilization to remove residual pointing error and jitter. Simulation results indicate that the system has the desired performance and can be designed using techniques and hardware well within the state-of-the-art.

Sridhar, B.; Aurbrun, J.-N.; Lorell, K. R.

164

Measurement of the Positive Muon Lifetime and Determination of the Fermi Constant to Part-per-Million Precision  

SciTech Connect

We report a measurement of the positive muon lifetime to a precision of 1.0 ppm; it is the most precise particle lifetime ever measured. The experiment used a time-structured, low-energy muon beam and a segmented plastic scintillator array to record more than 2x10{sup 12} decays. Two different stopping target configurations were employed in independent data-taking periods. The combined results give {tau}{sub {mu}}{sup +}(MuLan)=2 196 980.3(2.2) ps, more than 15 times as precise as any previous experiment. The muon lifetime gives the most precise value for the Fermi constant: G{sub F}(MuLan)=1.166 378 8(7)x10{sup -5} GeV{sup -2} (0.6 ppm). It is also used to extract the {mu}{sup -}p singlet capture rate, which determines the proton's weak induced pseudoscalar coupling g{sub P}.

Webber, D. M.; Chitwood, D. B.; Crnkovic, J.; Debevec, P. T.; Hertzog, D. W.; Kammel, P.; Kiburg, B.; Kizilgul, S.; Kunkle, J.; McNabb, R.; Winter, P.; Wolfe, B. [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Tishchenko, V.; Battu, S.; Dhamija, S.; Gorringe, T. P.; Rath, S. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506 (United States); Peng, Q.; Carey, R. M.; Earle, W. [Department of Physics, Boston University, Boston, Massachusetts 02215 (United States)

2011-01-28

165

Position control of linear switched reluctance motors for high-precision applications  

Microsoft Academic Search

Most advanced manufacturing processes require precise motions for material transfer, packaging, assembly, and electrical wiring. To achieve precise linear motions, most of these high-performance manufacturing machines use X-Y sliding tables with permanent-magnet rotary motors and rotary to linear couplers. Though this method is the most widely used, it has disadvantages of low accuracy, complex mechanical adjustments, high cost, and low

Wai-Chuen Gan; Norbert C. Cheung; Li Qiu

2003-01-01

166

Estimating the normal dispersion matrix and the precision matrix from a decision-theoretic point of view: a review  

Microsoft Academic Search

Based on a pxp Wishart matrix S ? Wp(?|n) and an independent vector\\u000a $$\\\\underset{\\\\raise0.3em\\\\hbox{$\\\\smash{\\\\scriptscriptstyle\\\\thicksim}$}}{X} \\\\sim N_p (\\\\underset{\\\\raise0.3em\\\\hbox{$\\\\smash{\\\\scriptscriptstyle\\\\thicksim}$}}{\\\\mu } ,\\\\Sigma )$$\\u000a , various point estimation methods are discussed in a decision-theoretic framework to estimate the dispersion matrix ? and\\u000a the precision matrix ??1. In this article we try to review the rich and vast literature on the above mentioned problems which

N. Pal

1993-01-01

167

Precise robot-assisted guide positioning for distal locking of intramedullary nails.  

PubMed

This paper presents a novel image-guided robot-based system to assist orthopedic surgeons in performing distal locking of long bone intramedullary nails. The system consists of a bone-mounted miniature robot fitted with a drill guide that provides rigid mechanical guidance for hand-held drilling of the distal screws' pilot holes. The robot is automatically positioned so that the drill guide and nail distal locking axes coincide, using a single fluoroscopic X-ray image. Since the robot is rigidly attached to the intramedullary nail or bone, no leg immobilization or real-time tracking is required. We describe the system and protocol and present a method for accurate and robust drill guide and nail hole localization and registration. The in vitro system accuracy experiments for fronto-parallel viewing show a mean angular error of 1.3 degrees (std = 0.4 degrees ) between the computed drill guide axes and the actual locking holes axes, and a mean 3.0 mm error (std = 1.1 mm) in the entry and exit drill point, which is adequate for successfully locking the nail. PMID:15889550

Yaniv, Ziv; Joskowicz, Leo

2005-05-01

168

Accurate determination of CT point-spread-function with high precision.  

PubMed

The measurement of modulation transfer functions (MTFs) in computed tomography (CT) is often performed by scanning a point source phantom such as a thin wire or a microbead. In these methods the region of interest (ROI) is generally placed on the scanned image to crop the point source response. The aim of the present study was to examine the effect of ROI size on MTF measurement, and to optimize the ROI size. Using a 4 multidetector-row CT, MTFs were measured by the wire and bead methods for three types of reconstruction kernels designated as 'smooth', 'standard', and 'edge-enhancement' kernels. The size of a square ROI was changed from 30 to 50 pixels (approximately 2.9 to 4.9 mm). The accuracies of the MTFs were evaluated using the verification method. The MTFs measured by the wire and bead methods were dependent on ROI size, particularly in MTF measurement for the 'edge-enhancement' kernel. MTF accuracy evaluated by the verification method changed with ROI size, and we were able to determine the optimum ROI size for each method (wire/bead) and for each kernel. Using these optimal ROI sizes, the MTF obtained by the wire method was in strong agreement with the MTF obtained by the bead method in each kernel. Our data demonstrate that the difficulties in obtaining accurate MTFs for some kernels such as edge-enhancement can be overcome by incorporating the verification method into the wire and bead methods, allowing optimization of the ROI size to accurately determine the MTF. PMID:23835372

Kayugawa, Akihiro; Ohkubo, Masaki; Wada, Shinichi

2013-07-08

169

Spatiotemporal precision and hemodynamic mechanism of optical point spreads in alert primates  

PubMed Central

In functional brain imaging there is controversy over which hemodynamic signal best represents neural activity. Intrinsic signal optical imaging (ISOI) suggests that the best signal is the early darkening observed at wavelengths absorbed preferentially by deoxyhemoglobin (HbR). It is assumed that this darkening or “initial dip” reports local conversion of oxyhemoglobin (HbO) to HbR, i.e., oxygen consumption caused by local neural activity, thus giving the most specific measure of such activity. The blood volume signal, by contrast, is believed to be more delayed and less specific. Here, we used multiwavelength ISOI to simultaneously map oxygenation and blood volume [i.e., total hemoglobin (HbT)] in primary visual cortex (V1) of the alert macaque. We found that the hemodynamic “point spread,” i.e., impulse response to a minimal visual stimulus, was as rapid and retinotopically specific when imaged by using blood volume as when using the initial dip. Quantitative separation of the imaged signal into HbR, HbO, and HbT showed, moreover, that the initial dip was dominated by a fast local increase in HbT, with no increase in HbR. We found only a delayed HbR decrease that was broader in retinotopic spread than HbO or HbT. Further, we show that the multiphasic time course of typical ISOI signals and the strength of the initial dip may reflect the temporal interplay of monophasic HbO, HbR, and HbT signals. Characterizing the hemodynamic response is important for understanding neurovascular coupling and elucidating the physiological basis of imaging techniques such as fMRI.

Sirotin, Yevgeniy B.; Hillman, Elizabeth M. C.; Bordier, Clemence; Das, Aniruddha

2009-01-01

170

Correlation matching method for high-precision position detection of optical vortex using Shack-Hartmann wavefront sensor.  

PubMed

We propose a new method for realizing high-spatial-resolution detection of singularity points in optical vortex beams. The method uses a Shack-Hartmann wavefront sensor (SHWS) to record a Hartmanngram. A map of evaluation values related to phase slope is then calculated from the Hartmanngram. The position of an optical vortex is determined by comparing the map with reference maps that are calculated from numerically created spiral phases having various positions. Optical experiments were carried out to verify the method. We displayed various spiral phase distribution patterns on a phase-only spatial light modulator and measured the resulting singularity point using the proposed method. The results showed good linearity in detecting the position of singularity points. The RMS error of the measured position of the singularity point was approximately 0.056, in units normalized to the lens size of the lenslet array used in the SHWS. PMID:23187465

Huang, Chenxi; Huang, Hongxin; Toyoda, Haruyoshi; Inoue, Takashi; Liu, Huafeng

2012-11-19

171

Determination of rigid-body pose from imprecise point position measurements  

Microsoft Academic Search

The determination of a rigid-body position and orientation from the position of a number of its points is one of the fundamental problems in kinematics. This problem arises in robotics, biomechanics, automatic guided vehicles, real-time control of space structures, etc. Under ideal conditions, it is possible to apply classical methods to find a body's position and orientation. However, in the

Anastasia Tegopoulou; Evangelos Papadopoulos

2011-01-01

172

Sensorless Maximum Power Point Tracking of Wind by DFIG Using Rotor Position Phase Lock Loop (PLL)  

Microsoft Academic Search

This paper presents an invention, the rotor position phase lock loop (PLL), which enables maximum power point (MPPT) tracking of wind by doubly-fed induction generators without needing a tachometer, an absolute position encoder, or an anemometer. The rotor position PLL is parameter variation insensitive, requiring only an estimate of the magnetization inductance for it to operate. It is also insensitive

Baike Shen; Bakari Mwinyiwiwa; Yongzheng Zhang; Boon-Teck Ooi

2009-01-01

173

Precision of high-resolution multibeam echo sounding coupled with high-accuracy positioning in a shallow water coastal environment  

NASA Astrophysics Data System (ADS)

Over 4 years, repetitive bathymetric measurements of a shipwreck in the Grådyb tidal inlet channel in the Danish Wadden Sea were carried out using a state-of-the-art high-resolution multibeam echosounder (MBES) coupled with a real-time long range kinematic (LRK™) global positioning system. Seven measurements during a single survey in 2003 ( n=7) revealed a horizontal and vertical precision of the MBES system of ±20 and ±2 cm, respectively, at a 95% confidence level. By contrast, four annual surveys from 2002 to 2005 ( n=4) yielded a horizontal and vertical precision (at 95% confidence level) of only ±30 and ±8 cm, respectively. This difference in precision can be explained by three main factors: (1) the dismounting of the system between the annual surveys, (2) rougher sea conditions during the survey in 2004 and (3) the limited number of annual surveys. In general, the precision achieved here did not correspond to the full potential of the MBES system, as this could certainly have been improved by an increase in coverage density (soundings/m2), achievable by reducing the survey speed of the vessel. Nevertheless, precision was higher than that reported to date for earlier offshore test surveys using comparable equipment.

Ernstsen, Verner B.; Noormets, Riko; Hebbeln, Dierk; Bartholomä, Alex; Flemming, Burg W.

2006-09-01

174

Multilateration with the wide-angle airborne laser ranging system: positioning precision and atmospheric effects.  

PubMed

Numerical simulations based on previously validated models for the wide-angle airborne laser ranging system are used here for assessing the precision in coordinate estimates of ground-based cube-corner retroreflectors (CCR's). It is shown that the precision can be optimized to first order as a function of instrument performance, number of laser shots (LS's), and network size. Laser beam divergence, aircraft altitude, and CCR density are only second-order parameters, provided that the number of echoes per LS is greater than 20. Thus precision in the vertical is approximately 1 mm, with a signal-to-noise ratio of 50 at nadir, a 10-km altitude, a 20 degrees beam divergence, and approximately 5 x 10(3) measurements. Scintillation and fair-weather cumulus clouds usually have negligible influence on the estimates. Laser biases and path delay are compensated for by adjustment of aircraft offsets. The predominant atmospheric effect is with mesoscale nonuniform horizontal temperature gradients, which might lead to biases near 0.5 mm. PMID:18319932

Bock, O

1999-05-20

175

Application of the nonlinear, double-dynamic Taguchi method to the precision positioning device using combined piezo-VCM actuator.  

PubMed

In this research, the nonlinear, double-dynamic Taguchi method was used as design and analysis methods for a high-precision positioning device using the combined piezo-voice-coil motor (VCM) actuator. An experimental investigation into the effects of two input signals and three control factors were carried out to determine the optimum parametric configuration of the positioning device. The double-dynamic Taguchi method, which permits optimization of several control factors concurrently, is particularly suitable for optimizing the performance of a positioning device with multiple actuators. In this study, matrix experiments were conducted with L9(3(4)) orthogonal arrays (OAs). The two most critical processes for the optimization of positioning device are the identification of the nonlinear ideal function and the combination of the double-dynamic signal factors for the ideal function's response. The driving voltage of the VCM and the waveform amplitude of the PZT actuator are combined into a single quality characteristic to evaluate the positioning response. The application of the double-dynamic Taguchi method, with dynamic signal-to-noise ratio (SNR) and L9(3(4)) OAs, reduced the number of necessary experiments. The analysis of variance (ANOVA) was applied to set the optimum parameters based on the high-precision positioning process. PMID:17328322

Liu, Yung-Tien; Fung, Rong-Fong; Wang, Chun-Chao

2007-02-01

176

Measuring precise sea level from a buoy using the global positioning system  

Microsoft Academic Search

High-accuracy sea surface positioning is required for sea floor geodesy, satellite altimeter verification, and the study of sea level. An experiment to study the feasibility of using the Global Positioning System (GPS) for accurate sea surface positioning was conducted. A GPS-equipped buoy (floater) was deployed off the Scripps pier at La Jolla, California during December 13–15, 1989. Two reference GPS

Christian Rocken; Thomas M. Kelecy; George H. Born; Larry E. Young; George H. Purcell Jr; Susan Kornreich Wolf

1990-01-01

177

Measuring precise sea level from a buoy using the global positioning system  

Microsoft Academic Search

High-accuracy sea surface positioning is required for sea floor geodesy, satellite altimeter verification, and the study of sea level. An experiment to study the feasibility of using the Global Positioning System (GPS) for accurate sea surface positioning was conducted. A GPS-equipped buoy (floater) was deployed off the Scripps pier at La Jolla, California during December 13-15, 1989. Two reference GPS

Christian Rocken; Thomas M. Kelecy; George H. Born; Larry E. Young; George H. Purcell; Susan Kornreich Wolf

1990-01-01

178

Effects of time pressure and precision demands during computer mouse work on muscle oxygenation and position sense  

Microsoft Academic Search

The present study investigated the effects of time pressure and precision demands during computer mouse work on muscle oxygenation and position sense in the upper extremity. Twenty-four healthy subjects (12 males and 12 females) performed a 45-min standardized mouse-operated computer task on two occasions. The task consisted of painting rectangles that were presented on the screen. On one occasion, time

M. Heiden; E. Lyskov; M. Djupsjöbacka; F. Hellström; A. G. Crenshaw

2005-01-01

179

QUICK AND PRECISE POSITION CONTROL OF ULTRASONIC MOTORS WITH TWO CONTROL INPUTS  

Microsoft Academic Search

Ultrasonic motor (USM) has an excellent performance and many useful features. Since this motor is superior in holding torque and high response characteristic, it has been expected to use as position servomotor for small motors.There have been reported some mathematical models of the ultrasonic motor. however, these models are too complex to apply for control of the motor. Therefore position

TOMONOBU SENJYU; HIROSHI MIYAZATO; KATSUMI UEZATO

1997-01-01

180

Precise Positioning and Compliance Synthesis for Automatic Assembly Using Lorentz Levitation.  

National Technical Information Service (NTIS)

Many manufacturing assembly tasks require fine compliant motion and fast, accurate positioning. Conventional robots perform poorly in these tasks because of their large mass, friction and backlash in gears, cogging in drive motors and other deleterious ef...

R. L. Hollis S. Salcudean

1992-01-01

181

RF device for precision location of the beam-position detectors in the Energy Saver  

SciTech Connect

The task is to measure the center line of the beam detector with respect to the magnetic centerline with a precision of +-0.2 mm; the measurement must be made on 250 magnets (they come in 6 lengths, from 25'' to 99'') by a technician. Optical, mechanical, and electrical techniques for carrying out this procedure were considered. An RF device operating at 53 MHZ was adopted for the following reasons: (a) it provides complete electrical checkout of the hardware at operating frequency, including the bidirectional operation of the pickup, (b) no mechanical contact with the strip lines is required, and (c) the demands of production measurements and maintenance of calibration are better matched to the skills of an average technician. We describe the conceptual design, fabrication, and performance of this device.

Kerns, Q.A.; Biallas, G.H.; Turkot, F.; Webber, R.C.; Wehmann, A.

1983-03-01

182

Kinematic calibration of precise 6-DOF Stewart platform-type positioning systems for radio telescope applications  

NASA Astrophysics Data System (ADS)

The pose accuracy of a parallel robot is a function of the mobile platform posture. Thus, there is no a single value of the robot's accuracy. In this paper, two novel methods for estimating the accuracy of parallel robots are presented. In the first method, the pose accuracy estimation is calculated by considering the propagation of each error, i.e., error variations are considered as a function of the actuator's stroke. In the second method, it is considered that each actuator has a constant error at any stroke. Both methods can predict pose accuracy of precise robots at design stages, and/or can reduce calibration time of existing robots. An example of a six degree-of-freedom parallel manipulator is included to show the application of the proposed methods.

Jáuregui, Juan Carlos; Hernández, Eusebio E.; Ceccarelli, Marco; López-Cajún, Carlos; García, Alejandro

2013-09-01

183

Apparatus for precision focussing and positioning of a beam waist on a target  

NASA Astrophysics Data System (ADS)

The invention relates to optical focussing apparatus and, more particularly, to optical apparatus for focussing a highly collimated Gaussian beam which provides independent and fine control over the focus waist diameter, the focus position both along the beam axis and transverse to the beam, and the focus angle. A beam focussing and positioning apparatus provides focussing and positioning for the waist of a waisted beam at a desired location on a target such as an optical fiber. The apparatus includes a first lens, having a focal plane f sub 1, disposed in the path of an incoming beam and a second lens, having a focal plane f sub 2 and being spaced downstream from the first lens by a distance at least equal to f sub 1 + 10 f sub 2, which cooperates with the first lens to focus the waist of the beam on the target. A rotatable optical device, disposed upstream of the first lens, adjusts the angular orientation of the beam waist. The transverse position of the first lens relative to the axis of the beam is varied to control the transverse position of the beam waist relative to the target (a fiber optic as shown) while the relative axial positions of the lenses are varied to control the diameter of the beam waist and to control the axial position of the beam waist. Mechanical controllers C sub 1, C sub 2, C sub 3, C sub 4, and C sub 5 control the elements of the optical system. How seven adjustments can be made to correctly couple a laser beam into an optical fiber is illustrated. Prior art systems employing optical techniques to couple a laser beam into an optical fiber or other target simply do not provide the seven necessary adjustments. The closest known prior art, a Newport coupler, provides only two of the seven required adjustments.

Lynch, Dana H.; Gunter, William D.; McAlister, Kenneth W.

1991-12-01

184

Measuring precise sea level from a buoy using the global positioning system  

SciTech Connect

High-accuracy sea surface positioning is required for sea floor geodesy, satellite altimeter verification, and the study of sea level. An experiment to study the feasibility of using the Global Positioning System (GPS) for accurate sea surface positioning was conducted. A GPS-equipped buoy (floater) was deployed off the Scripps pier at La Jolla, California during December 13-15, 1989. Two reference GPS receivers were placed on land, one within {approximately}100 m of the floater, and the other about 80 km inland at the laser ranging site on Monument Peak. The position of the floater was determined relative to the land-fixed receivers using: (a) kinematic GPS processing software developed at the National Geodetic Survey (NGS), and (b) the Jet Propulsion Laboratory's GIPSY (GPS Inferred Positioning SYstem) software. Sea level and ocean wave spectra were calculated from GPPS measurements. These results were compared to measurements made with a NOAA tide gauge and a Paros{trademark} pressure transducer (PPT). GPS sea level for the short 100-m baseline agrees with the PPT sea level at the 1-cm level and has an rms variation of 5 mm over a period of 4 hours. Agreement between results with the two independent GPS analyses is on the order of a few millimeters. Processing of the longer Monument Peak - floater baseline is in progress and will require orbit adjustments and tropospheric modeling to obtain results comparable to the short baseline.

Rocken, C.; Kelecy, T.M.; Born, G.H. (Univ. of Colorado, Boulder (USA)); Young, L.E.; Purcell, G.H. Jr.; Wolf, S.K. (California Inst. of Tech., Pasadena (USA))

1990-11-01

185

Application of shape memory alloy wire actuator for precision position control of a composite beam  

NASA Astrophysics Data System (ADS)

In this paper are presented the design and experimental results of using a shape memory alloy (SMA) wire as an actuator for position control of a composite beam. The composite beam is honeycomb structured, having wires of SMA embedded in one of its face sheets for the purposes of active actuation. Nickel-titanium SMA wires were chosen as actuating elements due to their high recovery stress (>700 MPa) and tolerance to high strain (up to 8%). A simple proportional and derivative controller plus a feed-forward current is designed and implemented for controlling the tip position of the composite beam. Experiments have demonstrated the effectiveness of the SMA wire as an actuator for active position control of a composite beam.

Song, Gangbing; Lam, P. C.; Srivatsan, T. S.; Kelly, B.; Agrawa, B. N.

2000-06-01

186

Improving precise positioning of surgical robotic instruments by a three-side-view presentation system on telesurgery.  

PubMed

For faultless collaboration among the surgeon, surgical staffs, and surgical robots in telesurgery, communication must include environmental information of the remote operating room, such as behavior of robots and staffs, vital information of a patient, named supporting information, in addition to view of surgical field. "Surgical Cockpit System, " which is a telesurgery support system that has been developed by the authors, is mainly focused on supporting information exchange between remote sites. Live video presentation is important technology for Surgical Cockpit System. Visualization method to give precise location/posture of surgical instruments is indispensable for accurate control and faultless operation. In this paper, the authors propose three-side-view presentation method for precise location/posture control of surgical instruments in telesurgery. The experimental results show that the proposed method improved accurate positioning of a telemanipulator. PMID:16235819

Hori, Kenta; Kuroda, Tomohiro; Oyama, Hiroshi; Ozaki, Yasuhiko; Nakamura, Takehiko; Takahashi, Takashi

2005-12-01

187

Quick and precise position control of ultrasonic motors with dual mode control  

Microsoft Academic Search

The ultrasonic motor (USM) is a new type motor that has many excellent performances and features which are not available in electromagnetic type motors. Therefore, it expected to be of practical use in small motor applications. The phase difference control of applied voltages seems to be most suitable for position control of this motor. However, it is difficult to carry

Tomonobu Senjyu; Hiroshi Miyazato; Katsumi Uezato

1995-01-01

188

Integrating External Position Information with GPS using Existing GPS Processing Software for Precision Agriculture Applications  

Microsoft Academic Search

The Integration of GPS with additional position technologies, such as Inertial Navigation Systems (INS), is an area of research that is well developed. The complimentary properties of the two systems, the long term stability and accuracy of GPS with the reliability and high data rates of the INS system, have meant they have been ideal candidates for integration in order

Anthony Cole

189

Low precision algorithm for determining the position of the most important bodies in the solar system  

NASA Astrophysics Data System (ADS)

A FORTRAN algorithm which gives the position of the ten most important bodies of the Solar System (Sun, Moon, and the planets) on an inertial geocentric system is presented. Comparison values were taken from the American Ephemeris and Nautical Almanac (AENA) for 1979.

Demedeiros, V. M.; Kuga, H. K.

1980-12-01

190

Precise determination of Earth's center of mass using measurements from the global positioning system  

Microsoft Academic Search

Global Positioning System (GPS) data from a worldwide geodetic experiment were collected during a 3 week period early in 1991. We estimated geocentric station coordinates using the GPS data, thus defining a dynamically determined reference frame origin which should coincide with the Earth center of mass, or geocenter. The 3-week GPS av- erage geocenter estimates agree to 7-13 cm with

Yvonne Vigue; Stephen M. Lichten; Geoffrey Blewitt; Michael B. Heflin; Rajendra P. Malla

1992-01-01

191

Precise positioning and compliance synthesis for automatic assembly using Lorentz levitation  

Microsoft Academic Search

Many manufacturing assembly tasks require fine compliant motion and fast, accurate positioning. Conventional robots perform poorly in these tasks because of their large mass, friction and backlash in gears, cogging in drive motors and other deleterious effects. Even robots equipped with special control systems enabling compliant operation offer only partial solutions. It is difficult or impossible to automate many product

R. L. Hollis; S. Salcudean

1992-01-01

192

High-Precision Resonant Cavity Beam Position, Emittance And Third-Moment Monitors  

SciTech Connect

Linear colliders and FEL facilities need fast, nondestructive beam position and profile monitors to facilitate machine tune-up, and for use with feedback control. FAR-TECH, Inc., in collaboration with SLAC, is developing a resonant cavity diagnostic to simultaneously measure the dipole, quadrupole and sextupole moments of the beam distribution. Measurements of dipole and quadrupole moments at multiple locations yield information about beam orbit and emittance. The sextupole moment can reveal information about beam asymmetry which is useful in diagnosing beam tail deflections caused by short-range dipole wakefields. In addition to the resonance enhancement of a single-cell cavity, use of a multi-cell standing-wave structure further enhances signal strength and improves the resolution of the device. An estimated resolution is better than 1 {micro}m in rms beam size and better than 1 nm in beam position.

Barov, N.; Kim, J.S.; Weidemann, A.W.; /FARTECH, San Diego; Miller, R.H.; Nantista, C.D.; /SLAC

2006-03-14

193

Precise Aircraft-to-Aircraft Positioning Using a Multiple Receiver Configuration  

Microsoft Academic Search

A configuration of four IO-channel single frequency C\\/A code narrow correlator spacing receivers is used to position two aircraft with respect to each other. The platforms used are U.S. Navy P-3 Orion aircraft cruising at speeds of 300 knots. Two receivers are mounted on each aircraft, with one antenna mounted on the fuselage and the other some 20 m aft

G. Lachapelle; H. Sun; M. E. Cannon; G. Lu

1994-01-01

194

UCAC2: a new high precision catalog of positions and proper motions  

Microsoft Academic Search

The U.S. Naval Observatory (USNO) CCD Astrograph Catalog (UCAC) project started observations of the southern sky in February 1998 from the Cerro Tololo Inter-American Observatory (CTIO). The last observing night at CTIO was 18\\/19 September 2001 and the telescope has now relocated to the USNO station in Flagstaff, AZ to complete the northern sky. A catalog of positions of about

N. Zacharias; M. I. Zacharias; S. E. Urban; T. J. Rafferty

2001-01-01

195

Time space position information data processor for precision optical platform slaving  

NASA Astrophysics Data System (ADS)

This paper describes the applications of the time space position information (TSPI) data processor (TDP), developed by the Wright Laboratory Armament Directorate, Instrumentation Technology Branch for optical platform tracking systems. The TDP provides common hardware and software for real-time Kalman filtering to be used on DoD test ranges. The design allows for easy integration of the TDP with existing range assets.

Williamson, Kenneth; Gross, Len

1993-01-01

196

Theoretical and experimental research on machine tool servo system for ultra-precision position compensation on CNC lathe  

NASA Astrophysics Data System (ADS)

The theories and techniques for improving machining accuracy via position control of diamond tool's tip and raising resolution of cutting depth on precise CNC lathes have been extremely focused on. A new piezo-driven ultra-precision machine tool servo system is designed and tested to improve manufacturing accuracy of workpiece. The mathematical model of machine tool servo system is established and the finite element analysis is carried out on parallel plate flexure hinges. The output position of diamond tool's tip driven by the machine tool servo system is tested via a contact capacitive displacement sensor. Proportional, integral, derivative (PID) feedback is also implemented to accommodate and compensate dynamical change owing cutting forces as well as the inherent non-linearity factors of the piezoelectric stack during cutting process. By closed loop feedback controlling strategy, the tracking error is limited to 0.8 ?m. Experimental results have shown the proposed machine tool servo system could provide a tool positioning resolution of 12 nm, which is much accurate than the inherent CNC resolution magnitude. The stepped shaft of aluminum specimen with a step increment of cutting depth of 1 ?m is tested, and the obtained contour illustrates the displacement command output from controller is accurately and real-time reflected on the machined part.

Ma, Zhichao; Hu, Leilei; Zhao, Hongwei; Wu, Boda; Peng, Zhenxing; Zhou, Xiaoqin; Zhang, Hongguo; Zhu, Shuai; Xing, Lifeng; Hu, Huang

2010-08-01

197

Integrated hybrid vibration isolator with feedforward compensation for fast high-precision positioning X/Y tables  

NASA Astrophysics Data System (ADS)

The design, realization and control technologies of a high-performance hybrid microvibration isolator for ultra-high-precision high-speed moving X/Y tables are presented in this paper—the novel isolator with integrated passive-active high level of damping. The passive damping was implemented using air-springs in both vertical and horizontal directions, with parallel linear motors in two directions to realize the active damping and the positioning functions. It is an actual hybrid isolation system because its air-spring can also be controlled through the pneumatic loop. The isolation servo system also has fast positioning capability via the feedforward compensation for the moving tables. Compared with the conventional filtered reference type control algorithms that rely on the assumption for the adaptive filter and the controlled system, in which the disturbance is estimated from the residual signal, the feedforward compensation here shows high effectiveness of vibration isolation and high-precision positioning performance for its platform. The performance of feedforward compensation has been enhanced via an efficient state estimation adaptive algorithm, the fast Kalman filter. Finally, experimental demonstration has been shown for the prototype system and the results have verified the effectiveness of the proposed isolator system design and the adaptive control algorithm for substantially enhanced damping of the platform system with the moving X/Y tables.

Yan, T. H.; Pu, H. Y.; Chen, X. D.; Li, Q.; Xu, C.

2010-06-01

198

GPS precision positioning in a regional net using pseudo-nonfiducial method  

NASA Astrophysics Data System (ADS)

The pseudo-nonfiducial positioning method is applied to a regional GPS net, and compared with conventional fiducial method. The conclusions are that there are respective characteristics and application area for both methods. The pseudo-nonfiducial method can avoid the problem of net shape twisting which is difficult to be overcome in the fiducial method, and the choice and changing of the transformation fiducial site as well as increasing or decreasing the number of transformation fiducial site are all very convenient and simple. It is valuable to spread the pseudo-nonfiducial method.

Cheng, Zongyi; Hu, Xiaogong; Zhu, Wenyao

199

Precise positioning and compliance synthesis for automatic assembly using Lorentz levitation  

NASA Astrophysics Data System (ADS)

Many manufacturing assembly tasks require fine compliant motion and fast, accurate positioning. Conventional robots perform poorly in these tasks because of their large mass, friction and backlash in gears, cogging in drive motors and other deleterious effects. Even robots equipped with special control systems enabling compliant operation offer only partial solutions. It is difficult or impossible to automate many product assemblies requiring fine, compliant motion. This problem can be greatly alleviated by dividing the manipulation system into coarse and fine domains. In this scenario, a standard industrial robot can serve as a coarse positioner which in turn carries a six degrees of freedom fine motion wrist. Thus the robot can access a workspace measured in meters at low bandwidth and low resolution while the wrist can move over millimeters at high bandwidth and high resolution during the final phase of the assembly operation. Work indicates that fine motion wrists using Lorentz levitation can greatly augment the accuracy and dexterity of robots because they are frictionless, have high bandwidths and have a single back drivable moving part. Also, since there is no contact between the moving and stationary parts, wear and contamination can be eliminated. The use of six Lorentz force actuators in combination with real time position and orientation sensing offers several important advantages over magnetic bearing approaches.

Hollis, R. L.; Salcudean, S.

1992-05-01

200

UCAC2: a new high precision catalog of positions and proper motions  

NASA Astrophysics Data System (ADS)

The U.S. Naval Observatory (USNO) CCD Astrograph Catalog (UCAC) project started observations of the southern sky in February 1998 from the Cerro Tololo Inter-American Observatory (CTIO). The last observing night at CTIO was 18/19 September 2001 and the telescope has now relocated to the USNO station in Flagstaff, AZ to complete the northern sky. A catalog of positions of about 40 million stars (8 to 16 mag) is being constructed based on all survey observations obtained at CTIO, with coverage from the south pole north to between +24 and +31 degrees declination, depending on the right ascension. Depending on magnitude, the positional accuracy is between 20 and 70 mas at mean epoch. Proper motions are being provided utilizing the Southern Proper Motion (SPM) first epoch and other catalog data (1 to 5 mas/yr). The UCAC2 will become available on 2 CD-ROMs in early 2002 and will supersede the UCAC1. Internal UCAC releases are already in use with the Sloan (SDSS) and 2MASS projects and for minor planet occulation predictions. The final UCAC will be the basis for the SIM input catalog.

Zacharias, N.; Zacharias, M. I.; Urban, S. E.; Rafferty, T. J.

2001-12-01

201

Influence of a high vacuum on the precise positioning using an ultrasonic linear motor  

NASA Astrophysics Data System (ADS)

This paper presents an investigation of the ultrasonic linear motor stage for use in a high vacuum environment. The slider table is driven by the hybrid bolt-clamped Langevin-type ultrasonic linear motor, which is excited with its different modes of natural frequencies in both lateral and longitudinal directions. In general, the friction behavior in a vacuum environment becomes different from that in an environment of atmospheric pressure and this difference significantly affects the performance of the ultrasonic linear motor. In this paper, to consistently provide stable and high power of output in a high vacuum, frequency matching was conducted. Moreover, to achieve the fine control performance in the vacuum environment, a modified nominal characteristic trajectory following control method was adopted. Finally, the stage was operated under high vacuum condition, and the operating performances were investigated compared with that of a conventional PI compensator. As a result, robustness of positioning was accomplished in a high vacuum condition with nanometer-level accuracy.

Kim, Wan-Soo; Lee, Dong-Jin; Lee, Sun-Kyu

2011-01-01

202

Crustal deformation measurements in Central Japan determined by a global positioning system fixed-point network  

Microsoft Academic Search

A Global Positioning System (GPS) fixed-point network has been operating in the Kanto and Tokai districts of central Japan since April 1988 to detect crustal deformation associated with the convergence of the Eurasian. Pacific, North American, and Philippine Sea plates and to monitor the deformation cycles of frequent large interplate and intraplate earthquakes. This 10-station network established by the National

Seiichi Shimada; Yehuda Bock

1992-01-01

203

Pointed water vapor radiometer corrections for accurate Global Positioning System surveying  

Microsoft Academic Search

Delay of the Global Positioning System (GPS) signal due to atmospheric water vapor is a major source of error in GPS surveying. Improved vertical accuracy is important for sea level and polar isostasy measurements, geodesy, normal fault motion, subsidence, earthquake studies, air and ground-based gravimetry, ice dynamics, and volcanology. We conducted a GPS survey using water vapor radiometers (WVRs) pointed

Randolph Ware; Christian Rocken; Fredrick Solheim; Teresa Van Hove; Chris Alber; James Johnson

1993-01-01

204

Regional gravity field modeling by the free-positioned point mass method  

NASA Astrophysics Data System (ADS)

The remove-compute-restore technique can be regarded as a state-of-the-art procedure for regional gravity field modeling, in which the long and short wavelength contributions from a spherical harmonic model and a DTM are first removed from the observations, then gravity field modeling techniques are applied to the residuals, and finally the corresponding long and short wavelength contributions are restored back. In this contribution the emphasis is on the second step, i.e., the compute or modeling step. Besides the classical integral and least-squares collocation (LSC) methods, the estimation based on radial basis functions is another interesting approach for regional gravity field modeling. The point mass method belongs to the latter category, where the basis functions with respect to the disturbing potential are the reciprocal distances between the function and observation locations. The choice of the positions and number of the point masses plays a crucial role in this method, and even in other related estimation methods. In order to solve this problem, the concept of the free-positioned point masses proposed by Barthelmes (1986) seems to be a good choice, in which the point masses are searched stepwise with simultaneous determination of the corresponding point mass positions and magnitudes within an iterative nonlinear least-squares approach. In this study, four different nonlinear iterative algorithms (Levenberg-Marquardt, L-BFGS, L-BFGS-B, and NLCG) have been implemented for regional gravity field modeling. The applicability and performance of each algorithm is demonstrated by two numerical tests with simulated and real data, respectively. In each test, different aspects (e.g., the use of original or reduced basis functions, the use of 2 or 4 parameters for each point mass), affecting the quality of the solutions, are discussed. Furthermore, the results are compared to the classical LSC solutions.

Lin, Miao; Denker, Heiner; Müller, Jürgen

2013-04-01

205

PRECISION CONSERVATION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Precision conservation utilizes a set of technologies and procedures that link mapped variables with analytical capabilities to appropriate management actions. It requires the integration of spatial technologies of global positioning systems, remote sensing and geographic information systems with t...

206

Positive solutions for a semipositone three-point fractional boundary value problem  

NASA Astrophysics Data System (ADS)

In this paper, we investigate the existence of positive solutions for the following nonlinear fractional semipositone boundary value problem: D0+?u(t) = -f(t,u),0(-?,+?) satisfies Carathéodory Condition and we also allow that the nonlinear term f is both semipositone and lower unbounded. By using the fixed point theorem in a cone, the existence of many positive solutions are obtained.

Al-Askar, Farah M.

2013-09-01

207

Position Estimation of Access Points in 802.11 Wireless Networks  

SciTech Connect

We developed a technique to locate wireless network nodes using multiple time-of-flight range measurements in a position estimate. When used with communication methods that allow propagation through walls, such as Ultra-Wideband and 802.11, we can locate network nodes in buildings and in caves where GPS is unavailable. This paper details the implementation on an 802.11a network where we demonstrated the ability to locate a network access point to within 20 feet.

Kent, C A; Dowla, F U; Atwal, P K; Lennon, W J

2003-12-05

208

Positive and Negative Point-to-Plane Corona in Pure and Impure Hydrogen, Nitrogen, and Argon  

Microsoft Academic Search

To extend knowledge concerning the positive and negative point-to-plane corona, studies were made of the discharge in very pure H2, N2, and A. Neither pre-onset streamers nor burst pulses were observed in pure H2 and N2, in accordance with present theories of these effects. At high fields weak streamers developed which ultimately led to breakdown. Adding traces of O2 to

Gerhard L. Weissler

1943-01-01

209

Low-energy electron point source microscope with position-sensitive electron energy analyzer  

Microsoft Academic Search

A low-energy electron point source microscope equipped with a position-sensitive energy analyzer is constructed. A nanometer-sized feature can be zoomed in and its energy-loss spectrum can be measured with a retarding field-type energy analyzer mounted in front of the imaging screen. The geometric and the electronic structures of carbon nanotubes are measured with the present system. Interference between the scattered

Jeong-Young Park; S. H. Kim; Y. D. Suh; W. G. Park; Y. Kuk

1999-01-01

210

Narrow nuclear resonance position or cross section shape measurements with a high precision computer controlled beam energy scanning system  

NASA Astrophysics Data System (ADS)

The relative positions, intensity and shape of narrow resonances (?~100eV) in (p,?), (p,??) and (p,p'?) reactions induced on the isotopes 13C, 15N, 18O, 19F, 23Na, 24Mg, 27Al, 29Si, 30Si and 52Cr were investigated in the energy range from 150 to 2500keV, using a fully automatic hysteresis free energy scanning system. The energy differences between the resonance positions were measured with optimum accuracy, down to around +/-100eV. The results are of interest for the easy and accurate calibration of accelerators and for determining the energy scale in the neighbourhood of resonances used for depth profiling experiments with high precision. The new set-up allows the automatic recording of nuclear reaction or elastic scattering excitation curves over wide energy ranges, up to +/-10% around any central energy. The results illustrate also how powerful a tool such a scanning system may be in various fields of ion beam analysis.

Amsel, G.; D'Artemare, E.; Battistig, G.; Girard, E.; Gosset, L. G.; Révész, P.

1998-03-01

211

On the influence of background electrolyte concentration on the position of the isoelectric point and the point of zero charge  

Microsoft Academic Search

In the case of a specific interaction of background electrolyte ions with the surface of a solid in an aqueous electrolyte solution a shift of the characteristic points, the isoelectric point (iep) and the point of zero charge (pzc), in an opposite direction was described by Lyklema (in: Th.F. Thadros (Ed.), Solid\\/Liquid Dispersions, Academic Press, London, 1987). In the present

Jürgen Sonnefeld

2001-01-01

212

Zitterbewegung of optical pulses near the Dirac point inside a negative-zero-positive index metamaterial  

NASA Astrophysics Data System (ADS)

By numerically solving Maxwell's equation with boundary conditions, we have demonstrated the optical Zitterbewegung effect by means of electromagnetic pulses propagating through a negative-zero-positive index metamaterial (NZPIM). We find that a finite pulse with frequencies near the Dirac point of the NZPIM diffuses and oscillates, and its output pulse from the finite NZPIM slab becomes an oscillating pulse with a characteristic frequency independent of the slab thickness. We further find that the oscillating properties of the optical Zitterbewegung effect are strongly dependent on the pulse parameters: such as pulse duration and pulse transverse spatial width. The physical nature of such oscillation effects is due to the interference between the upper and lower high-transmittance passbands at both sides of the Dirac point of the NZPIM slab, which is similar to the Zitterbewegung of electron wave packets.

Wang, Li-Gang; Wang, Zhi-Guo; Zhu, Shi-Yao

2009-05-01

213

Modeling and Control of Macro-micro Dual-Drive High Acceleration and High Precision Positioning Stage Using for IC Packaging  

Microsoft Academic Search

Macro-micro dual-drive positioning stage has particularly good potential application in high acceleration and high precision\\u000a positioning stage using for IC packaging. In this paper, the positioning stage which is composed by VCM (voice coil motor)\\u000a as macro driver and PZT as micro driver is used. Coupling characters of the stage are discussed by analyzing dynamic model\\u000a firstly, then models of

Yanjie Liu; Teng Li; Lining Sun

2008-01-01

214

Stochastic modelling considering ionospheric scintillation effects on GNSS relative and point positioning  

NASA Astrophysics Data System (ADS)

Global Navigation Satellite Systems (GNSS), in particular the Global Positioning System (GPS), have been widely used for high accuracy geodetic positioning. The Least Squares functional models related to the GNSS observables have been more extensively studied than the corresponding stochastic models, given that the development of the latter is significantly more complex. As a result, a simplified stochastic model is often used in GNSS positioning, which assumes that all the GNSS observables are statistically independent and of the same quality, i.e. a similar variance is assigned indiscriminately to all of the measurements. However, the definition of the stochastic model may be approached from a more detailed perspective, considering specific effects affecting each observable individually, as for example the effects of ionospheric scintillation. These effects relate to phase and amplitude fluctuations in the satellites signals that occur due to diffraction on electron density irregularities in the ionosphere and are particularly relevant at equatorial and high latitude regions, especially during periods of high solar activity. As a consequence, degraded measurement quality and poorer positioning accuracy may result. This paper takes advantage of the availability of specially designed GNSS receivers that provide parameters indicating the level of phase and amplitude scintillation on the signals, which therefore can be used to mitigate these effects through suitable improvements in the least squares stochastic model. The stochastic model considering ionospheric scintillation effects has been implemented following the approach described in Aquino et al. (2009), which is based on the computation of weights derived from the scintillation sensitive receiver tacking models of Conker et al. (2003). The methodology and algorithms to account for these effects in the stochastic model are described and results of experiments where GPS data were processed in both a relative and a point positioning mode are presented and discussed. Two programs have been developed to enable the analyses: GPSeq (currently under development at the FCT/UNESP Sao Paulo State University - Brazil) and PP_Sc (developed in a collaborative project between FCT/UNESP and Nottingham University - UK). The point positioning approach is based on an epoch by epoch solution, whereas the relative positioning on an accumulated solution using a Kalman Filter and the LAMBDA method to solve the Double Differences ambiguities. Additionally to the use of an improved stochastic model, all data processing in this paper were performed using an option implemented in both programs, to estimate, for each observable, an individual ionospheric parameter modelled as a stochastic process, using either the white noise or the random walk correlation models. Data from a network of GPS Ionospheric Scintillation and TEC Monitor (GISTM) receivers set up in Northern Europe as part of the ISACCO project (De Franceschi et al., 2006) were used in the experiments. The point positioning results have shown improvements of the order of 45% in height accuracy when the proposed stochastic model is applied. In the static relative positioning, improvements of the order of 50%, also in height accuracy, have been reached under moderate to strong scintillation conditions. These and further results are discussed in this paper.

da Silva, Heloísa Alves; de Oliveira Camargo, Paulo; Galera Monico, João Francisco; Aquino, Marcio; Marques, Haroldo Antonio; de Franceschi, Giorgiana; Dodson, Alan

2010-05-01

215

Performance assessment of the COAMPS numerical weather prediction model in precise GPS positioning: EUPOS network case study  

NASA Astrophysics Data System (ADS)

The Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) represents a complete three-dimensional data assimilation system comprised of data quality control, analysis, initialization, and forecast model components. COAMPS has been developed by the Marine Meteorology Division (MMD) of the Naval Research Laboratory (NRL). The U.S. Navy uses the system for short-term numerical weather predictions for various regions of the world. Currently COAMPS ver.3.1 is also operated and tested at the Department of Civil Engineering and Geodesy of the Military University of Technology, Warsaw, Poland (MUT). It is primarily used for military applications, but also a new module has been developed to provide tropospheric zenith total delays (ZTD) for stations of the Polish part of the European Position Determination System (EUPOS). ZTDs can be obtained in both near-real time and several hours ahead. In the highest-precision GPS applications tropospheric delays are usually estimated from satellite observables. When processing long baselines the common practice is to derive the hydrostatic component from any troposphere model and use it as a priori information. The non-hydrostatic part is estimated in the adjustment along with station coordinates. The change of satellite geometry during the observational session allows overcome high correlation between the tropospheric delays and the station height components. However, when processing very short sessions and medium baselines, this change is too small and does not allow estimating reliable ZTDs. Hence, ZTD are derived from troposphere models and used for correction of GPS data in the processing. This contribution presents the application of COAMPS-derived ZTDs in precise GPS positioning when using short data spans (1-5 minutes) and processing medium baselines (50-80 km). The presented tests were performed in two areas: Wielkopolska Lowland (all stations located at similar heights), and Carpathian Mountains (where station height differences run into several hundreds of meters). The ZTDs derived from COAMPS model were used for correcting GPS observations. The ZTDs were mapped into slant delays using several mapping functions also these derived from numerical weather models (NWM), namely: VMF1, GMF, UNBab and Niell. Mapping functions and ZTD based on NWMs are said to provide the best troposphere modeling nowadays. About 200 sessions were processed in order to analyze accuracy and repeatability of the derived station coordinates. The results were compared to the ones obtained with application of simple Modified Hopfield model as well as well-established UNB3m neutral atmosphere model. Another tested and compared approach was the modelling of the tropospheric delays at the reference station network and then providing the interpolated corrections to the user receiver. All the processing was performed with use of GINPOS software developed at the University of Warmia and Mazury in Olsztyn (UWM).

Wielgosz, Pawel; Paziewski, Jacek; Krankowski, Andrzej; Kroszczynski, Krzyszfof; Figurski, Mariusz

2010-05-01

216

The effect of aborting ongoing movements on end point position estimation.  

PubMed

The present study investigated the impact of motor commands to abort ongoing movement on position estimation. Participants carried out visually guided reaching movements on a horizontal plane with their eyes open. By setting a mirror above their arm, however, they could not see the arm, only the start and target points. They estimated the position of their fingertip based solely on proprioception after their reaching movement was stopped before reaching the target. The participants stopped reaching as soon as they heard an auditory cue or were mechanically prevented from moving any further by an obstacle in their path. These reaching movements were carried out at two different speeds (fast or slow). It was assumed that additional motor commands to abort ongoing movement were required and that their magnitude was high, low, and zero, in the auditory-fast condition, the auditory-slow condition, and both the obstacle conditions, respectively. There were two main results. (1) When the participants voluntarily stopped a fast movement in response to the auditory cue (the auditory-fast condition), they showed more underestimates than in the other three conditions. This underestimate effect was positively related to movement velocity. (2) An inverted-U-shaped bias pattern as a function of movement distance was observed consistently, except in the auditory-fast condition. These findings indicate that voluntarily stopping fast ongoing movement created a negative bias in the position estimate, supporting the idea that additional motor commands or efforts to abort planned movement are involved with the position estimation system. In addition, spatially probabilistic inference and signal-dependent noise may explain the underestimate effect of aborting ongoing movement. PMID:24057053

Itaguchi, Yoshihiro; Fukuzawa, Kazuyoshi

2013-09-22

217

Evolution of offshore wind waves tracked by surface drifters with a point-positioning GPS sensor  

NASA Astrophysics Data System (ADS)

Wind-generated waves have been recognized as one of the most important factors of the sea surface roughness which plays crucial roles in various air-sea interactions such as energy, momentum, heat and gas exchanges. At the same time, wind waves with extreme wave heights representatively called as freak or rogue waves have been a matter of great concern for many people involved in shipping, fishing, constracting, surfing and other marine activities, because such extreme waves frequently affect on the marine activities and sometimes cause serious disasters. Nevertheless, investigations of actual conditions for the evolution of wind waves in the offshore region are less and sparse in contrast to dense monitoring networks in the coastal regions because of difficulty of offshore observation with high accuracy. Recently accurate in situ observation of offshore wind waves is getting possible at low cost owing to a wave height and direction sensor developed by Harigae et al. (2004) by installing a point-positioning GPS receiver on a surface drifting buoy. The point-positioning GPS sensor can extract three dimensional movements of the buoy excited by ocean waves with minimizing effects of GPS point-positioning errors through the use of a high-pass filter. Two drifting buoys equipped with the GPS-based wave sensor charged by solar cells were drifted in the western North Pacific and one of them continued to observe wind waves during 16 months from Sep. 2007. The RMSE of the GPS-based wave sensor was less than 10cm in significant wave height and about 1s in significant wave period in comparison with other sensors, i.e. accelerometers installed on drifting buoys of Japan Meteorological Agency, ultrasonic sensors placed at the Hiratsuka observation station of the University of Tokyo and altimeter of the JASON-1. The GPS-based wave buoys enabled us to detect freak waves defined as waves whose height is more than twice the significant wave height. The observation conducted by the wave buoys in 2007-2008 indicated a little more frequent occurrence of freak waves comparing with Forristall’s (1978) empirical formula and Naess’s (1985) distribution for a narrow-band Gaussian sea. Fig.1. Time series of the ratio of the significant wave height to the maximum wave height in 20 minutes sampling period observed by a drifting buoy with a GPS sensor

Komatsu, K.

2009-12-01

218

The Apache Point Observatory Lunar Laser-ranging Operation: Testing General Relativity with Millimeter-precision Measurements of the Earth-Moon Separation.  

NASA Astrophysics Data System (ADS)

Based on the discovery of the accelerating universe and dark energy, along with our inability to unite quantum mechanics and General Relativity, there is a clear need to probe deeper into gravitational physics. The Earth-Moon-Sun system is a natural, fertile laboratory for such tests. The Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) bounces laser light off of man-made retro-reflectors on the lunar surface to measure the Earth-Moon separation with a precision of one millimeter. Such precise measurements of the lunar orbit allow us to improve constraints on gravitational phenomena such as the Weak Equivalence Principle, the Strong Equivalence Principle, de Sitter precession and dG/dt by an order of magnitude or better. I will describe the APOLLO project and its current status, as well as prospects for constraining PPN parameters and the universality of free-fall. This work was carried out under the financial support of NASA and NSF.

Battat, James B.; Murphy, T. W.; Adelberger, E. G.; Hoyle, C. D.; McMillan, R. J.; Michelsen, E.; Nordtvedt, K.; Orin, A.; Stubbs, C. W.; Swanson, H. E.

2006-12-01

219

The use of satellite laser ranging for single point positioning in short-arc analysis  

NASA Astrophysics Data System (ADS)

In order to reduce the effects of force model errors on the coordinate solution in satellite laser ranging, an extended Kalman filter is proposed with short arcs consisting of only a few consecutive passes of a satellite over a tracking station. This method for single-point positioning in short-arc analysis is used to estimate the geodetic coordinates of the transportable laser ranging station. Laser ranging data for the Lageos satellite were successfully obtained for two consecutive passes over the station on Februrary 5, 1980. The total number of range observations was 232 for the first pass and 278 for the second pass. The time gap between the passes was three hours, and the standard deviation of the observation noise was 20 cm. The height accuracy of the result was of order 1 m, while the longitude and latitude accuracy was of order 0.00002.

He, M.; Fong, C.

220

Cinderellas and ugly ducklings: positive turning points in students' educational careers—exploratory evidence and a future agenda  

Microsoft Academic Search

Positive turning points touch upon the essence of education. They epitomize its power and reflect its core agenda: maximizing human capital. Paradoxically, previous studies have not looked into this important phenomenon. The current exploratory study fills this lacuna by building on extensive empirical research of key educational experiences to shed light on four aspects of turning points in students' educational

Gad Yair

2009-01-01

221

Research of Confirming Height Rules of Human Characteristic Positions Based on 3D Point-Cloud Data  

Microsoft Academic Search

In this research, Point-cloud diagrams can be obtained by using 3D body scanner and then characteristic positions of the body (such as waist, abdomen and buttocks) can be confirmed. Then height of characteristic positions can be measured from diagrams by the software of Image-ware. The correlation relationship between height of characteristic positions and height can be analyzed by the software

Hai-yan Kong; Bing-fei Gu; Jun-qiang Su; Guo-lian Liu

2010-01-01

222

Crustal deformation measurements in Central Japan determined by a global positioning system fixed-point network  

NASA Astrophysics Data System (ADS)

A Global Positioning System (GPS) fixed-point network has been operating in the Kanto and Tokai districts of central Japan since April 1988 to detect crustal deformation associated with the convergence of the Eurasian. Pacific, North American, and Philippine Sea plates and to monitor the deformation cycles of frequent large interplate and intraplate earthquakes. This 10-station network established by the National Research Institute for Earth Science and Disaster Prevention (NIED) is the first continuously monitoring network of its kind. We determine deformation within the network using two consecutive days of data every 2 weeks for the first 17 months of operations. We use a station and orbit relaxation method which relies exclusively on data collected within the NIED network, except for 1 week of global GPS tracking data which is used to determine initial station positions with respect to the global refrence frame. We detect, relative to a station on the Eurasian plate in central Japan, significant westward motion of 28 mm/yr of the northern tip of the Philippine Sea plate, which is subducting beneath the Eurasian plate at the Suruga trough. Our results support finite element models of collision of the Izu Block with the Eruasian plate based on earthquake focal mechanisms and plate block motions of the Japanese archipelago determined from conventional geodetic measurements over the last century. We detect southwestward motion of 18 mm/yr of the southeastern tip of the Eurasian plate, confirming expected surface extension of the subducted plate parallel to the Suruga trough axis. Significant vertical uplift with a velocity of 20 mm/yr is suggested at a sites inland of the Tokai district located in the Akaishi uplift zone and at a site on Hatsushima Island in Sagami Bay. The general tendency of vertical movements of the other site agrees with vertical velocities obtained from 70 years of geodetic leveling and with Quaternary vertical displacements determined from geomorphological and other geological evidence. We detect no significant crustal motion across the Fossa Magna tectonic zone in central Japan (often considered a plate boundary), across the Tokyo metropolitan area, nor across the Sagami trough associated with the subduction of the Philippine Sea plate beneath northeast Japan. Our results demonstrate the power of regionally based, continuously monitoring GPS networks for obtaining temporally dense meausrements of small horizontal and vertical crustal movements across plate boundary zones.

Bock, Yehuda

1992-08-01

223

The Dynamic Properties of a Monolithic Mechanism with Notch Flexure Hinges for Precision Control of Orientation and Position  

NASA Astrophysics Data System (ADS)

An algorithm for estimating the elastic coefficient, eigen frequency and effect of disturbing vibrations in the environment is derived for a monolithic mechanism with notch flexure hinges used for precision adjustments. The feasibility of the algorithm for the actual design of mechanisms is confirmed by experiments on a mechanism consisting of a quadrilateral of links. The concept of reduction of a diagram is introduced to simplify design procedures for such mechanisms, and several important examples of the mechanisms are described. The generalized algorithm for estimating the dynamic properties of a link mechanism with notch flexure hinges is discussed with a view to developing a software system for computer-aided design.

Tanaka, Mitsuru

1983-01-01

224

High-precision kinematic GPS differential positioning and integration of GPS with a ring laser strapdown inertial system  

Microsoft Academic Search

Many fields, such as geodetic surveying, positioning of airborne sensors (photogrammetric cameras), laser bathymetry, airborne gravimetry, and hydrographic surveys, require accuracies in the decimeter or even centimeter range in differential positioning. Using the full potential of the GPS in a dynamic environment, the Institute of Astronomical and Physical Geodesy (IAPG) has carried out several kinematic tests with respect to land-based,

Guenter W. Hein; Gerald Baustert; Bernd Eissfeller; Herbert Landau

1989-01-01

225

[Protozoal antigen positivity in diarrheal patients admitted to emergency service: a point prevalence study].  

PubMed

Intestinal parasites are the important etiological agents of water and food related diarrhea cases which are frequently seen during summer/early autumn seasons in developing countries. This point prevalence study was aimed to determine the protozoal antigen positivity rate in diarrhea cases admitted to the emergency service in one single day. A total of 198 diarrheal patients (90 male, 108 female; age range: 1-82 years, mean age: 29 years) who were admitted to the emergency service of Ankara Training and Research Hospital were included in the study. Macroscopic and direct microscopic examinations were performed for the stool samples of patients, and the samples which yielded pathological microscopic findings (e.g. presence of leukocytes, erythrocytes, and trophozoits) were investigated in terms of Entamoeba histolytica adhesin antigen, Giardia intestinalis cyst antigen and Cryptosporidium oocyst antigen by commercial ELISA kits (Techlab, USA). Macroscopic examination of the stool samples revealed that 60 (30%) of them had blood and mucous, 137 (69%) were watery and one sample had normal appearance. Pathologic results were obtained for 96 (48.5%) of the samples by microscopic examination: 36 (37.5%) revealed erythrocytes, 90 (93.7%) had leukocytes and 3 (1.5%) had G.intestinalis trophozoites. Since Shigella spp. were cultured in two of these 96 samples, these two cases were omitted from the study and 94 samples were investigated by ELISA assays. G.intestinalis was detected in 13 (13.8%) and E.histolytica in 2 (2.1%) samples while Cryptosporidium antigen was not detected in any of the samples by the ELISA assays. It was concluded that ELISA antigen assays were rapid and cost-effective methods for the determination of the causative agent in cases of diarrhea. PMID:22090311

Koçak Tufan, Zeliha; Altun, Serife; Bulut, Cemal; K?n?kl?, Sami; Demiröz, Ali Pekcan

2011-10-01

226

Precision translator  

DOEpatents

A precision translator for focusing a beam of light on the end of a glass fiber which includes two turning fork-like members rigidly connected to each other. These members have two prongs each with its separation adjusted by a screw, thereby adjusting the orthogonal positioning of a glass fiber attached to one of the members. This translator is made of simple parts with capability to keep adjustment even in condition of rough handling.

Reedy, R.P.; Crawford, D.W.

1982-03-09

227

Precision translator  

DOEpatents

A precision translator for focusing a beam of light on the end of a glass fiber which includes two turning fork-like members rigidly connected to each other. These members have two prongs each with its separation adjusted by a screw, thereby adjusting the orthogonal positioning of a glass fiber attached to one of the members. This translator is made of simple parts with capability to keep adjustment even in condition of rough handling.

Reedy, Robert P. (Livermore, CA); Crawford, Daniel W. (Livermore, CA)

1984-01-01

228

Plans of the U.S. Government for the future radio navigation services Navstar GPS and consequences for the precise positioning and navigation at sea  

NASA Astrophysics Data System (ADS)

The developments considered in the present paper are of interest to a group of users who require accurate positioning and navigation data at sea and in areas in the vicinity of harbors. Such data are needed for hydrographic sea surveying activities, oceanography, seismic measurements, applications related to fishing, and the positioning of offshore platforms for oil-drilling operations. The requirements include demands for an absolute accuracy in the range from 5 to 15 meters. A source of information concerning the plans of the U.S. Government regarding its radio navigation services is provided by the 'Federal Radionavigation Plan' (FRP). Attention is given to the policies of the U.S. Government regarding the Global Positioning System (GPS), the utilization of the Precise Positioning Service by civil users, plans with respect to existing radio navigation services, details regarding navigational requirements, and cost considerations.

Rehmert, H.

229

DMAHTC (Defense Mapping Agency Hydrographic/Topographic Center) GPS Point Positioning Software: Initial Results.  

National Technical Information Service (NTIS)

Absolute positioning software written at the Defense Mapping Agency Hydrographic/Topographic Center (DMAHTC) was designed to process Texas Instruments 4100 (TI 4100) geodetic receiver phase and range observations. This paper describes absolute positioning...

T. E. Meyer G. T. Tennis J. A. Slater B. J. DeNoyer

1986-01-01

230

Atlas of the muscle motor points for the lower limb: implications for electrical stimulation procedures and electrode positioning.  

PubMed

The aim of the study was to investigate the uniformity of the muscle motor point location for lower limb muscles in healthy subjects. Fifty-three subjects of both genders (age range: 18-50 years) were recruited. The muscle motor points were identified for the following ten muscles of the lower limb (dominant side): vastus medialis, rectus femoris, and vastus lateralis of the quadriceps femoris, biceps femoris, semitendinosus, and semimembranosus of the hamstring muscles, tibialis anterior, peroneus longus, lateral and medial gastrocnemius. The muscle motor point was identified by scanning the skin surface with a stimulation pen electrode and corresponded to the location of the skin area above the muscle in which an electrical pulse evoked a muscle twitch with the least injected current. For each investigated muscle, 0.15 ms square pulses were delivered through the pen electrode at low current amplitude (<10 mA) and frequency (2 Hz). 16 motor points were identified in the 10 investigated muscles of almost all subjects: 3 motor points for the vastus lateralis, 2 motor points for rectus femoris, vastus medialis, biceps femoris, and tibialis anterior, 1 motor point for the remaining muscles. An important inter-individual variability was observed for the position of the following 4 out of 16 motor points: vastus lateralis (proximal), biceps femoris (short head), semimembranosus, and medial gastrocnemius. Possible implications for electrical stimulation procedures and electrode positioning different from those commonly applied for thigh and leg muscles are discussed. PMID:21796408

Botter, Alberto; Oprandi, Gianmosè; Lanfranco, Fabio; Allasia, Stefano; Maffiuletti, Nicola A; Minetto, Marco Alessandro

2011-07-28

231

The Speech Focus Position Effect on Jaw-Finger Coordination in a Pointing Task  

ERIC Educational Resources Information Center

Purpose: This article investigates jaw-finger coordination in a task involving pointing to a target while naming it with a 'CVCV (e.g., /'papa/) versus CV'CV (e.g., /pa'pa/) word. According to the authors' working hypothesis, the pointing apex (gesture extremum) would be synchronized with the apex of the jaw-opening gesture corresponding to the…

Rochet-Capellan, Amelie; Laboissiere, Rafael; Galvan, Arturo; Schwartz, Jean-Luc

2008-01-01

232

Estimation of the light source position on the basis of the light point figure  

Microsoft Academic Search

The light point figure is an image of a source of light seen in the reflector surface of a headlight. The source location is one of decisive parameters that influence the shape of the figure. The paper is an attempt to estimate the source of light location on the basis of the shape of the light point figure. The location

Dariusz Sawicki

2005-01-01

233

A study of the position of grass growing points in two species under different systems of management  

Microsoft Academic Search

A simple technique for measuring the position of grass growing points in relation to the soil surface was found to be satisfactory during internode elongation.Grazing or mowing treatments applied to Lolium (multiflorum xperenne) ‘Grasslands Manawa’ (short-rotation ryegrass) or Dactylis glomerata L. ‘Grasslands Apanui’(cocksfoot) plots revealed that, in mid-spring, the ryegrass growing points were near the soil surface, whereas in cocksfoot

D. B. Edmond; C. S. Hoveland

1972-01-01

234

Precision alignment of the LIGO 4 km arms using the dual-frequency differential global positioning system  

Microsoft Academic Search

The alignment of the Laser Interferometer Gravitational-Wave Observatory ~LIGO! using the global positioning system ~GPS! is described. The LIGO project is designed to detect gravitational waves from astrophysical sources by laser interferometry. There are two sites separated by 3002 km that will be operated in coincidence. At each site, laser beams propagate in two orthogonal 4 km long evacuated beam

W. E. Althouse

235

Precision alignment of the LIGO 4 km arms using the dual-frequency differential global positioning system  

Microsoft Academic Search

The alignment of the Laser Interferometer Gravitational-Wave Observatory (LIGO) using the global positioning system (GPS) is described. The LIGO project is designed to detect gravitational waves from astrophysical sources by laser interferometry. There are two sites separated by 3002 km that will be operated in coincidence. At each site, laser beams propagate in two orthogonal 4 km long evacuated beam

W. E. Althouse; S. D. Hand; L. K. Jones; A. Lazzarini; R. Weiss

2001-01-01

236

Comparison of ADOS (African Doppler Survey) Point Positioning Results from Various Softwares.  

National Technical Information Service (NTIS)

The African Doppler Survey project (ADOS) is a multi-national effort to establish primary control (via Doppler satellite observations) on the African continent. There are four Computing Centers under the ADOS project which use three different point positi...

T. J. Knopp

1986-01-01

237

Characterization of global positioning system earth surface multipath and cross correlation for aircraft precision approach operations using software radio technology  

NASA Astrophysics Data System (ADS)

A GPS Software Defined Radio (SDR) is designed for the analysis of GPS error sources, and is applied to evaluate earth-surface multipath errors and self-interference errors due to C/A code cross correlation for aircraft precision approach operations. The pseudorange error caused by earth-surface multipath is characterized for airborne GPS receivers. A detection algorithm that can estimate the strength of earth-surface multipath from the received signals is developed and implemented in the GPS SDR. The response to earth-surface multipath from different GPS receiver architectures is studied, from which it is determined that the pseudorange errors could be bounded to within a few decimeters with a careful selection of tracking algorithms. GPS self-interference caused by C/A code cross correlation is evaluated in the operational environment. The induced errors on pseudorange and Carrier to Noise Ratio estimation are characterized, and bounds are determined for relative signal strength, Doppler frequency, and Doppler change rate to limit the pseudorange errors to 0.2 m.

Zhu, Zhen

238

The precise computation of geoid undulation differences with comparison to results obtained from the global positioning system  

Microsoft Academic Search

Ellipsoidal height differences have been determined for 13 station pairs in the central Ohio region using measurements made with the Global Positioning System. This information was used to compute geoid undulation differences based on known orthometric heights. These differences were compared to gravimetrically-computed undulations (using a Stokes integration procedure, and least squares collocation having an internal r.m.s. agreement of plus

Theo Engelis; R. H. Rapp; C. C. Tscherning

1984-01-01

239

Asynchronous decoding of finger position and of EMG during precision grip using CM cell activity: application to robot control.  

PubMed

Recent brain-machine interfaces (BMI) have demonstrated the use of intracortical signals for the kinematic control of robotic arms. However, for potential restoration of manual dexterity, two issues remain to be addressed: (1) Can hand and digit movements for dexterous manipulation be controlled in a similar way to arm movements? (2) Can the potentially large signal space for decoding of the many degrees of freedom (dof) of hand and digit movements be minimized? The first question addresses BMI control of dexterous prosthetic devices, while the second addresses the problem of whether few, but identified, neurons might provide adequate decoding. Asynchronous decoding of precision grip finger movement kinematics from identified corticomotoneuronal (CM) cell activity was performed with an artificial neural network (ANN). After training over a given session, the ANNs successfully decoded trial-by-trial movement kinematics. Average accuracy over sessions was in the order of 80% and 50% for data sets of two monkeys respectively. Decoding accuracy increased as a function of (1) number of simultaneously recorded CM cells used for prediction, and (2) size of the sliding input window. Subsequently, a robot digit actuated by pneumatic artificial muscles, fed with the predicted trajectory, mimicked the recorded movement offline. Furthermore, CM cell signals were used for decoding of time-varying hand muscle EMG activity. The performance of EMG prediction tended to increase if CM cells that facilitated this particular muscle (compared to CM cells that facilitated other muscles) were used. These results provide evidence that an anthropomorphic robot finger can be controlled offline by spike trains recorded from identified corticospinal neurons. This represents a step towards neuroprosthetic devices for dexterous hand movements. PMID:22262537

Ouanezar, Sofiane; Eskiizmirliler, Selim; Maier, Marc A

2011-12-01

240

The use of global positioning system (GPS) to estimate point sources of selected biomass residues in the Philippines  

Microsoft Academic Search

A study (1) was made to identify point sources of biomass wastes in the Philippines from selected agricultural and forestry establishments with the use of differential global positioning system (DGPS). The identification of exact geographic location of the sources of biomass wastes makes it possible to have an accurate estimate of biomass resources and develop project feasibility studies more readily.

S. C. Capareda; Ralph P. Overend

241

Stereographic Targeting in Prostate Radiotherapy: Speed and Precision by Daily Automatic Positioning Corrections Using Kilovoltage/Megavoltage Image Pairs  

SciTech Connect

Purpose: A fully automated, fast, on-line prostate repositioning scheme using implanted markers, kilovoltage/megavoltage imaging, and remote couch movements has been developed and clinically applied. The initial clinical results of this stereographic targeting (SGT) method, as well as phantom evaluations, are presented. Methods and Materials: Using the SGT method, portal megavoltage images are acquired with the first two to six monitor units of a treatment beam, immediately followed by acquisition of an orthogonal kilovoltage image without gantry motion. The image pair is automatically analyzed to obtain the marker positions and three-dimensional prostate displacement and rotation. Remote control couch shifts are applied to correct for the displacement. The SGT performance was measured using both phantom images and images from 10 prostate cancer patients treated using SGT. Results: With phantom measurements, the accuracy of SGT was 0.5, 0.2, and 0.3 mm (standard deviation [SD]) for the left-right, craniocaudal, and anteroposterior directions, respectively, for translations and 0.5{sup o} (SD) for the rotations around all axes. Clinically, the success rate for automatic marker detection was 99.5%, and the accuracy was 0.3, 0.5 and 0.8 mm (SD) in the left-right, craniocaudal, and anteroposterior axes. The SDs of the systematic center-of-mass positioning errors ({sigma}) were reduced from 4.0 mm to <0.5 mm for all axes. The corresponding SD of the random ({sigma}) errors was reduced from 3.0 to <0.8 mm. These small residual errors were achieved with a treatment time extension of <1 min. Conclusion: Stereographic targeting yields systematic and random prostate positioning errors of <1 mm with <1 min of added treatment time.

Mutanga, Theodore F. [Department of Radiation Oncology, Division of Medical Physics, Erasmus Medical Center-Daniel den Hoed Oncology Center, Rotterdam (Netherlands)], E-mail: t.mutanga@erasmusmc.nl; Boer, Hans C.J. de [Department of Radiation Oncology, Division of Medical Physics, Erasmus Medical Center-Daniel den Hoed Oncology Center, Rotterdam (Netherlands); Wielen, Gerard J. van der [Department of Radiation Oncology, Erasmus Medical Center-Daniel den Hoed Oncology Center, Rotterdam (Netherlands); Wentzler, Davy; Barnhoorn, Jaco [Department of Radiation Oncology, Division of Medical Physics, Erasmus Medical Center-Daniel den Hoed Oncology Center, Rotterdam (Netherlands); Incrocci, Luca [Department of Radiation Oncology, Erasmus Medical Center-Daniel den Hoed Oncology Center, Rotterdam (Netherlands); Heijmen, Ben J.M. [Department of Radiation Oncology, Division of Medical Physics, Erasmus Medical Center-Daniel den Hoed Oncology Center, Rotterdam (Netherlands)

2008-07-15

242

Miniaturized suspension structure for precise flying height positioning measurement using a swing arm actuator with a holographic optical element module sensor  

NASA Astrophysics Data System (ADS)

This work presents a means of active actuation of the suspension structure with a holographic optical element (HOE) for the small-form-factor optical-disk drives. The proposed HOE module sensor is mounted on a swing arm swivel-drive mechanism with unique features, including a rotary actuator for tracking and a swing arm nutates along a pivot for focusing. The fabrication methodology for a cantilever-beam-like structure with HOE module sensor is investigated. Furthermore, the performances of optical module with swing arm-swivel actuation are experimentally evaluated to demonstrate the effectiveness of precise flying height positioning measurement method.

Chou, Po-Chien; Lin, Yu-Cheng; Cheng, Stone

2011-03-01

243

High performance and high precision ultrasonic motor-actuated positioning servo drive system using improved fuzzy-reasoning controller  

Microsoft Academic Search

This paper presents the latest significant developments of ultrasonic motor (USM)-actuated servo drives suitable for direct-drive motion systems, which effectively introduce the practical fuzzy-reasoning controller with speed and positional state-variable feedback schemes. The USM-actuated servo control system is schematically composed of the commercially-available travelling-wave type USM, mechanical loads, high-frequency DC-DC chopper regulator, two-phase high-frequency resonant inverter using parasitic piezo-electric load

Yuji Izuno; Mutsuo Nakaoka

1994-01-01

244

The NOVA satellite precise ephemeris  

NASA Astrophysics Data System (ADS)

An analysis of the NOVA satellite is presented emphasizing the generation of precise ephemeris and limited point positioning results. Forcing functions for the satellite for such parameters as accelerations due to the gravitational fields of the earth, moon and sun, lunar and solar tidal distortions, and vehicle thrust were easily modelled according to a modification of the CELEST program (O'Toole, 1976). The NOVA pole position solutions are almost a factor of two less noisy than those for Oscar satellite 30190. Initial position corrections were significantly reduced in magnitude and more constant.

Ziegler, R. E.

245

Dirac point in the photon dispersion relation of a negative\\/zero\\/positive-index plasmonic metamaterial  

Microsoft Academic Search

We report on the emergence of a Dirac point in the dispersion relation of a plasmonic metamaterial. It is realized as a three-dimensional crystal (cubic or orthorhombic) whose lattice sites are decorated by aggregates of gold nanoparticles embedded in a high-index dielectric material. The Dirac-type dispersion lines of the photon modes are not a result of diffraction as in photonic

Vassilios Yannopapas; Alexandros Vanakaras

2011-01-01

246

Super-resolution for a point source better than ?/500 using positive refraction  

NASA Astrophysics Data System (ADS)

Leonhardt (2009 New J. Phys. 11 093040) demonstrated that the two-dimensional (2D) Maxwell fish eye (MFE) lens can focus perfectly 2D Helmholtz waves of arbitrary frequency; that is, it can transport perfectly an outward (monopole) 2D Helmholtz wave field, generated by a point source, towards a ‘perfect point drain’ located at the corresponding image point. Moreover, a prototype with ?/5 super-resolution property for one microwave frequency has been manufactured and tested (Ma et al 2010 arXiv:1007.2530v1; Ma et al 2010 New J. Phys. 13 033016). However, neither software simulations nor experimental measurements for a broad band of frequencies have yet been reported. Here, we present steady-state simulations with a non-perfect drain for a device equivalent to the MFE, called the spherical geodesic waveguide (SGW), which predicts up to ?/500 super-resolution close to discrete frequencies. Out of these frequencies, the SGW does not show super-resolution in the analysis carried out.

Miñano, Juan C.; Marqués, Ricardo; González, Juan C.; Benítez, Pablo; Delgado, Vicente; Grabovickic, Dejan; Freire, Manuel

2011-12-01

247

Concurrent Validity of Office Discipline Referrals and Cut Points Used in Schoolwide Positive Behavior Support  

ERIC Educational Resources Information Center

Office discipline referrals (ODRs) are commonly used by school teams implementing schoolwide positive behavior support to indicate individual student need for additional behavior support. However, little is known about the technical adequacy of ODRs when used in this manner. In this study, the authors assessed (a) the concurrent validity of number…

McIntosh, Kent; Campbell, Amy L.; Carter, Deborah Russell; Zumbo, Bruno D.

2009-01-01

248

Concurrent Validity of Office Discipline Referrals and Cut Points Used in Schoolwide Positive Behavior Support  

Microsoft Academic Search

Office discipline referrals (ODRs) are commonly used by school teams implementing school-wide positive behavior support to indicate individual student need for additional behavior support. However, little is known about the technical adequacy of ODRs when used in this manner. In this study, the authors assessed a) the concurrent validity of number of ODRs received with a contemporary standardized behavior rating

Kent McIntosh; Amy L. Campbell; Deborah R. Carter; Bruno D. Zumbo

2009-01-01

249

Improved accuracy from Doppler satellite positioning  

NASA Astrophysics Data System (ADS)

The possibility of improving the accuracy and precision of Doppler satellite geodetic positioning is investigated, which includes point positioning and short arc network techniques with the use of both broadcast and precise ephemerides. An analysis of hardware characteristics and software modeling for both precise ephemeris determination and surveying techniques is presented. The role of fundamental constants and the use of the most recent values are examined for the purpose of making the broadcast and precise ephemerides compatible.

Ziegler, R. E.

1980-01-01

250

Global Positioning System Sensor with Instantaneous-Impact-Point Prediction for Sounding Rockets  

Microsoft Academic Search

The development and verification of a dedicated global positioning system (GPS) sensor for sounding rocket missions is described. It is based on the hardware design of a terrestrial low-cost, single-frequency coarse\\/acquisition (C\\/A) code receiver but operates an enhanced software that has been specifically adapted for high dynamics applications. Besides the navigation and timing function provided by traditional GPS receivers, the

Oliver Montenbruck; Markus Markgraf

2004-01-01

251

A decision support system for locating weapon and radar positions in stationary point air defence  

Microsoft Academic Search

In this study, a decision support system (DSS) based on the interactive use of location models and geographical information\\u000a systems (GIS) was developed to determine the optimal positions for air defence weapons and radars. In the location model,\\u000a the fire units are considered as the facilities to be located and the possible approach routes of air vehicles are treated\\u000a as

Türker Tanergüçlü; Hakan Mara?; Cevriye Gencer; Haluk Aygüne?

252

High Dynamics and Precision Optical Measurement Using a Position Sensitive Detector (PSD) in Reflection-Mode: Application to 2D Object Tracking over a Smart Surface  

PubMed Central

When related to a single and good contrast object or a laser spot, position sensing, or sensitive, detectors (PSDs) have a series of advantages over the classical camera sensors, including a good positioning accuracy for a fast response time and very simple signal conditioning circuits. To test the performance of this kind of sensor for microrobotics, we have made a comparative analysis between a precise but slow video camera and a custom-made fast PSD system applied to the tracking of a diffuse-reflectivity object transported by a pneumatic microconveyor called Smart-Surface. Until now, the fast system dynamics prevented the full control of the smart surface by visual servoing, unless using a very expensive high frame rate camera. We have built and tested a custom and low cost PSD-based embedded circuit, optically connected with a camera to a single objective by means of a beam splitter. A stroboscopic light source enhanced the resolution. The obtained results showed a good linearity and a fast (over 500 frames per second) response time which will enable future closed-loop control by using PSD.

Ivan, Ioan Alexandru; Ardeleanu, Mihai; Laurent, Guillaume J.

2012-01-01

253

Two distant and precisely positioned domains promote transcription of Xenopus laevis rRNA genes: analysis with linker-scanning mutants.  

PubMed

To examine the internal organization of the promoter of the Xenopus laevis rRNA gene, we constructed a series of linker-scanning mutants that traverse the rDNA initiation region. The mutant genes, which have 3 to 11 clustered base substitutions set within an otherwise unaltered rDNA promoter sequence, were injected into Xenopus oocyte nuclei, and their transcriptional capacity was assessed by S1 nuclease analysis of the resultant RNA. The data demonstrate that there are two essential promoter domains, the distal boundaries of which coincide with the promoter boundaries established previously by analysis of 5' and 3' deletion mutants. The upstream promoter domain is relatively small and extends from residues ca. -140 to -128. The downstream domain is considerably larger, encompassing residues ca. -36 to +10, and exactly corresponds in both size and position to the mammalian minimal promoter region. The Xenopus rDNA sequence between these two essential domains has a much smaller effect on the level of transcriptional initiation. In light of the fact that a large portion of this intervening region consists of a segment (residues -114 to -72) that is duplicated many times in the upstream spacer to form an rDNA enhancer sequence, it is noteworthy that a "-115/-77 linker scanner," in which virtually this entire segment is replaced by a polylinker sequence, has full promoter activity in the injected Xenopus borealis oocytes. Analysis of a parallel series of spacing change linker-scanning mutants revealed the unexpected result that the relative positions of the upstream and downstream promoter domains are very critical: all spacing alterations of more than 2 base pairs within this 100-base-pair region virtually abolish promoter activity. We conclude that the factors that bind to these two distant promoter domains must interact in a very precise stereospecific manner. PMID:3796610

Windle, J J; Sollner-Webb, B

1986-12-01

254

Precision Displacement Mechanism (PDM).  

National Technical Information Service (NTIS)

A mechanism designed to fulfill the requirements of the Precision Displacement Mechanism (PDM) for the Far Infrared and Submillimeter Space Telescope (FIRST) antenna is described. The PDM function is to perform the fine adjustment of the position of the m...

J. I. Bueno F. Delcampo P. Coste

1993-01-01

255

Effects of Meteorological Conditions and Measurement Precision on the Earth Trace of the Sonic Boom Wake (Extinction, Focalization) Influence des Conditions Meteorologiques et de Leur Precision sur la Position au Sol du Tapis de Bang (Extinction, Focallsation Sous Trace).  

National Technical Information Service (NTIS)

The influence of meteorological conditions and the precision of the measurement of meteorological parameters on the prediction of the aircraft sonic boom path on the ground is discussed. It was found that the sonic boom of the second sounding of the two d...

M. Schaffar F. Schlosser

1973-01-01

256

Precision Assessment of Near Real Time Precise Orbit Determination for Low Earth Orbiter  

NASA Astrophysics Data System (ADS)

The precise orbit determination (POD) of low earth orbiter (LEO) has complied with its required positioning accuracy by the double-differencing of observations between International GNSS Service (IGS) and LEO to eliminate the common clock error of the global positioning system (GPS) satellites and receiver. Using this method, we also have achieved the 1 m positioning accuracy of Korea Multi-Purpose Satellite (KOMPSAT)-2. However double-differencing POD has huge load of processing the global network of lots of ground stations because LEO turns around the Earth with rapid velocity. And both the centimeter accuracy and the near real time (NRT) processing have been needed in the LEO POD applications--atmospheric sounding or urgent image processing--as well as the surveying. An alternative to differential GPS for high accuracy NRT POD is precise point positioning (PPP) to use measurements from one satellite receiver only, to replace the broadcast navigation message with precise post processed values from IGS, and to have phase measurements of dual frequency GPS receiver. PPP can obtain positioning accuracy comparable to that of differential positioning. KOMPSAT-5 has a precise dual frequency GPS flight receiver (integrated GPS and occultation receiver, IGOR) to satisfy the accuracy requirements of 20 cm positioning accuracy for highly precise synthetic aperture radar image processing and to collect GPS radio occultation measurements for atmospheric sounding. In this paper we obtained about 3-5 cm positioning accuracies using the real GPS data of the Gravity Recover and Climate Experiment (GRACE) satellites loaded the Blackjack receiver, a predecessor of IGOR. And it is important to reduce the latency of orbit determination processing in the NRT POD. This latency is determined as the volume of GPS measurements. Thus changing the sampling intervals, we show their latency to able to reduce without the precision degradation as the assessment of their precision.

Choi, Jong-Yeoun; Lee, Sang-Jeong

2011-03-01

257

Precision Measurement  

NSDL National Science Digital Library

Precision Measurement is a lesson plan which introduces students to and provides practice in using various precision measurement instruments including the machinists steel rule, the protractor, the vernier caliper, and the one-inch external micrometer. After completing this module, students should be able to demonstrate their ability to make precision measurements using these instruments by measuring various parts and verifying conformance to tolerances. Note: This module is part of a modularized manufacturing technology curriculum created by the PSCME, found at www.pscme.org/educators.html.

2010-07-22

258

Precision manometer gauge  

DOEpatents

A precision manometer gauge which locates a zero height and a measured height of liquid using an open tube in communication with a reservoir adapted to receive the pressure to be measured. The open tube has a reference section carried on a positioning plate which is moved vertically with machine tool precision. Double scales are provided to read the height of the positioning plate accurately, the reference section being inclined for accurate meniscus adjustment, and means being provided to accurately locate a zero or reference position.

McPherson, M.J.; Bellman, R.A.

1982-09-27

259

Precision manometer gauge  

DOEpatents

A precision manometer gauge which locates a zero height and a measured height of liquid using an open tube in communication with a reservoir adapted to receive the pressure to be measured. The open tube has a reference section carried on a positioning plate which is moved vertically with machine tool precision. Double scales are provided to read the height of the positioning plate accurately, the reference section being inclined for accurate meniscus adjustment, and means being provided to accurately locate a zero or reference position.

McPherson, Malcolm J. (Lafayette, CA); Bellman, Robert A. (Berkeley, CA)

1984-01-01

260

MEASUREMENT AND PRECISION, EXPERIMENTAL VERSION.  

ERIC Educational Resources Information Center

|THIS DOCUMENT IS AN EXPERIMENTAL VERSION OF A PROGRAMED TEXT ON MEASUREMENT AND PRECISION. PART I CONTAINS 24 FRAMES DEALING WITH PRECISION AND SIGNIFICANT FIGURES ENCOUNTERED IN VARIOUS MATHEMATICAL COMPUTATIONS AND MEASUREMENTS. PART II BEGINS WITH A BRIEF SECTION ON EXPERIMENTAL DATA, COVERING SUCH POINTS AS (1) ESTABLISHING THE ZERO POINT,…

Harvard Univ., Cambridge, MA. Harvard Project Physics.

261

Precise Vectorial Magnetic Sensors  

Microsoft Academic Search

Precise magnetic sensors are required in many fields: besides the traditional geophysical magnetometers they serve for navigation,\\u000a position tracking, military and security. First a short review of basic practical rules and sensor parameters is given. Next\\u000a the most important semiconductor magnetic sensors (Hall sensors and semiconductor magnetoresistors) are discussed. Following\\u000a sections describe the most important precise magnetic sensors: ferromagnetic magnetoresistors

Pavel Ripka

262

Precision displacement reference system  

DOEpatents

A precision displacement reference system is described, which enables real time accountability over the applied displacement feedback system to precision machine tools, positioning mechanisms, motion devices, and related operations. As independent measurements of tool location is taken by a displacement feedback system, a rotating reference disk compares feedback counts with performed motion. These measurements are compared to characterize and analyze real time mechanical and control performance during operation.

Bieg, Lothar F. (Albuquerque, NM); Dubois, Robert R. (Albuquerque, NM); Strother, Jerry D. (Edgewood, NM)

2000-02-22

263

Comparison of point-of-care versus laboratory-based CD4 cell enumeration in HIV-positive pregnant women  

PubMed Central

Introduction Early initiation of antiretroviral therapy (ART) in eligible pregnant women is a key intervention for prevention of mother-to-child transmission (PMTCT) of HIV. However, in many settings in sub-Saharan Africa where ART-eligibility is determined by CD4 cell counts, limited access to laboratories presents a significant barrier to rapid ART initiation. Point-of-care (POC) CD4 cell count testing has been suggested as one approach to overcome this challenge, but there are few data on the agreement between POC CD4 cell enumeration and standard laboratory-based testing. Methods Working in a large antenatal clinic in Cape Town, South Africa, we compared POC CD4 cell enumeration (using the Alere PimaTM Analyzer) to laboratory-based flow cytometry in consecutive HIV-positive pregnant women. Bland–Altman methods were used to compare the two methods, including analyses by subgroups of participant gestational age. Results Among the 521 women participating, the median gestational age was 23 weeks, and the median CD4 cell count according to POC and laboratory-based methods was 388 and 402 cells/µL, respectively. On average, the Pima POC test underestimated CD4 cell count relative to flow cytometry: the mean difference (laboratory test minus Pima POC) was 22.7 cells/µL (95% CI, 16.1 to 29.2), and the limits of agreement were ?129.2 to 174.6 cells/µL. When analysed by gestational age categories, there was a trend towards increasing differences between laboratory and POC testing with increasing gestational age; in women more than 36 weeks’ gestation, the mean difference was 45.0 cells/µL (p=0.04). Discussion These data suggest reasonable overall agreement between Pima POC CD4 testing and laboratory-based flow cytometry among HIV-positive pregnant women. The finding for decreasing agreement with increasing gestational age requires further investigation, as does the operational role of POC CD4 testing to increase access to ART within PMTCT programmes.

Myer, Landon; Daskilewicz, Kristen; McIntyre, James; Bekker, Linda-Gail

2013-01-01

264

Application of Real-Time Precise Point Positioning and GIS for Rail Track Deformation Monitoring of the Qinghai-Tibet Railway  

Microsoft Academic Search

The Qinghai-Tibet railway is the highest railway in the world. The operational conditions of this railway are very harsh, such as occurrence of earthquake, potential melting of frozen soil, and severely cold and thin air. Real time monitoring the deformation of the railway system for maintaining safe operation has posed a big challenge. Extensive document review conducted by the authors

R. Gao; X. Meng; J. Geng; H.-S. Yu; L. Xu

2008-01-01

265

Precision metrology.  

PubMed

This article is a summary of the Satellite Meeting, which followed on from the Discussion Meeting at the Royal Society on 'Ultra-precision engineering: from physics to manufacture', held at the Kavli Royal Society International Centre, Chicheley Hall, Buckinghamshire, UK. The meeting was restricted to 18 invited experts in various aspects of precision metrology from academics from the UK and Sweden, Government Institutes from the UK and Germany and global aerospace industries. It examined and identified metrology problem areas that are, or may be, limiting future developments in precision engineering and, in particular, metrology. The Satellite Meeting was intended to produce a vision that will inspire academia and industry to address the solutions of those open-ended problems identified. The discussion covered three areas, namely the function of engineering parts, their measurement and their manufacture, as well as their interactions. PMID:22802506

Jiang, X; Whitehouse, D J

2012-08-28

266

Study on the special vision sensor for detecting position error in robot precise TIG welding of some key part of rocket engine  

NASA Astrophysics Data System (ADS)

Rocket engine is a hard-core part of aerospace transportation and thrusting system, whose research and development is very important in national defense, aviation and aerospace. A novel vision sensor is developed, which can be used for error detecting in arc length control and seam tracking in precise pulse TIG welding of the extending part of the rocket engine jet tube. The vision sensor has many advantages, such as imaging with high quality, compactness and multiple functions. The optics design, mechanism design and circuit design of the vision sensor have been described in detail. Utilizing the mirror imaging of Tungsten electrode in the weld pool, a novel method is proposed to detect the arc length and seam tracking error of Tungsten electrode to the center line of joint seam from a single weld image. A calculating model of the method is proposed according to the relation of the Tungsten electrode, weld pool, the mirror of Tungsten electrode in weld pool and joint seam. The new methodologies are given to detect the arc length and seam tracking error. Through analyzing the results of the experiments, a system error modifying method based on a linear function is developed to improve the detecting precise of arc length and seam tracking error. Experimental results show that the final precision of the system reaches 0.1 mm in detecting the arc length and the seam tracking error of Tungsten electrode to the center line of joint seam.

Zhang, Wenzeng; Chen, Nian; Wang, Bin; Cao, Yipeng

2005-01-01

267

A Flexure-Based Tool Holder for Sub-(micro)m Positioning of a Single Point Cutting Tool on a Four-axis Lathe  

SciTech Connect

A tool holder was designed to facilitate the machining of precision meso-scale components with complex three-dimensional shapes with sub-{micro}m accuracy on a four-axis lathe. A four-axis lathe incorporates a rotary table that allows the cutting tool to swivel with respect to the workpiece to enable the machining of complex workpiece forms, and accurately machining complex meso-scale parts often requires that the cutting tool be aligned precisely along the axis of rotation of the rotary table. The tool holder designed in this study has greatly simplified the process of setting the tool in the correct location with sub-{micro}m precision. The tool holder adjusts the tool position using flexures that were designed using finite element analyses. Two flexures adjust the lateral position of the tool to align the center of the nose of the tool with the axis of rotation of the B-axis, and another flexure adjusts the height of the tool. The flexures are driven by manual micrometer adjusters, each of which provides a minimum increment of motion of 20 nm. This tool holder has simplified the process of setting a tool with sub-{micro}m accuracy, and it has significantly reduced the time required to set a tool.

Bono, M J; Hibbard, R L

2005-12-05

268

Precision Nova operations  

SciTech Connect

To improve the symmetry of x-ray drive on indirectly driven ICF capsules, we have increased the accuracy of operating procedures and diagnostics on the Nova laser. Precision Nova operations includes routine precision power balance to within 10% rms in the ``foot`` and 5% nns in the peak of shaped pulses, beam synchronization to within 10 ps rms, and pointing of the beams onto targets to within 35 {mu}m rms. We have also added a ``fail-safe chirp`` system to avoid Stimulated Brillouin Scattering (SBS) in optical components during high energy shots.

Ehrlich, R.B.; Miller, J.L.; Saunders, R.L.; Thompson, C.E.; Weiland, T.L.; Laumann, C.W.

1995-09-01

269

A Case Example of the Implementation of Schoolwide Positive Behavior Support in a High School Setting Using Change Point Test Analysis  

ERIC Educational Resources Information Center

The purpose of this case study was to expand the literature base regarding the application of high school schoolwide positive behavior support in an urban setting for practitioners and policymakers to address behavior issues. In addition, the study describes the use of the Change Point Test as a method for analyzing time series data that are…

Bohanon, Hank; Fenning, Pamela; Hicks, Kira; Weber, Stacey; Thier, Kimberly; Aikins, Brigit; Morrissey, Kelly; Briggs, Alissa; Bartucci, Gina; McArdle, Lauren; Hoeper, Lisa; Irvin, Larry

2012-01-01

270

A Case Example of the Implementation of Schoolwide Positive Behavior Support in a High School Setting Using Change Point Test Analysis  

Microsoft Academic Search

The purpose of this case study was to expand the literature base regarding the application of high school schoolwide positive behavior support in an urban setting for practitioners and policymakers to address behavior issues. In addition, the study describes the use of the Change Point Test as a method for analyzing time series data that are dependent in nature. The

Hank Bohanon; Pamela Fenning; Kira Hicks; Stacey Weber; Kimberly Thier; Brigit Aikins; Kelly Morrissey; Alissa Briggs; Gina Bartucci; Lauren McArdle; Lisa Hoeper; Larry Irvin

2012-01-01

271

Dissemination of developed in VNIIOFI high temperature Fix-points based on Metal-Carbon Eutectics for Space Applications of ultra-precise Radiometry and Spectral Radiation Thermometry Measurements  

NASA Astrophysics Data System (ADS)

Several fixed-point cells (with 2 and 4 mm apertures for spectral-radiance application, and with 8 and 10 mm apertures (for the spectral irradiance measurements) have been designed and investigated at VNIIOFI consisted of a high- purity graphite crucibles containing Re-C ingots with nominal total impurity levels of 5,5N at the eutectic composition(s). It was investigated that fix-point reproducibility (freezing plateau level for all measured cells) was up to 0.01...0.02% between series of measurements / crucibles, and 0.002...0.004% within a sample measurement session, i.e. better than 100 mK. Measurements of high-temperature fixed points blackbodies based on Ir-C and Re-C eutectics were carried out to investigate their applicability as radiation sources for precision photometry and radiometry, in particular for astronomy and space applications, like long-term measurements of solar variability, etc. The measurement results encourage that the utilization of a new series of a high-temperature fix-point sources hand in hand with cryo-radiometer detector could cardinally change the situation in reproduction of spectral radiance, irradiance and temperature international scales. Several more high-temperature eutectics (e.g. TiC-C metal- carbon eutectics with T = 3057 C) are being investigated further for use as high- temperature fixed-point radiance and irradiance sources in o der to increase ther accuracy of radiometric and radiance-temperature scales above the conventionally assigned values of temperatures of ITS-90.

Sapritsky, V.; Ogarev, S.; Khlevnoy, B.

272

Shifting Positions to the Media Discourse on Terrorism: Critical Points in Audience Members' Meaning-making Experiences  

Microsoft Academic Search

In his essay on encoding\\/decoding, Hall (1980) acknowledges that events in the broader socio-political context influence the way audiences position themselves in relation to the dominant hegemonic discourse. This article reports on an investigation into how Australian audience members continuously reviewed and shifted their positions to media texts that contributed to an over-arching evolving and changing discourse of terrorism in

Anne Aly

2010-01-01

273

Arithmetic Operations Beyond Floating Point Number Precision  

Microsoft Academic Search

In basic computational physics classes, students often raise the question of how to compute a number that exceeds the numerical limit of the machine. While technique of avoiding overflow\\/underflow has practical application in the electrical and electronics engineering industries, it is not commonly utilized in scientific computing, because scientific notation is adequate in most cases. We present an undergraduate project

Chih-Yueh Wang; Chen-Yang Yin; Hong-Yu Chen; Yung-Ko Chen

2010-01-01

274

Higher Education-to-Work Transitions in the Knowledge Society: The Initial Transition and Positional Competition Point of View  

ERIC Educational Resources Information Center

|This article presents an analysis of the higher education-to-work transition from the perspective of the competition for job positions between students and degree holders. The conceptual framework used addresses two factors influencing the success of policies that aim to support higher education-to-work transition of youth in a knowledge society:…

Lindberg, Matti

2008-01-01

275

Comparisons of Line-of-Sight Water Vapor Observations Using the Global Positioning System and a Pointing Microwave Radiometer  

Microsoft Academic Search

Line-of-sight measurements of integrated water vapor from a global positioning system (GPS) receiver and a microwave radiometer are compared. These two instruments were collocated at the central facility of the Department of Energy's Atmospheric Radiation Measurement Program's Southern Great Plains region, near Lamont, Oklahoma. The comparison was made using 47 days of observations in May and June of 2000. Weather

John Braun; Christian Rocken; James Liljegren

2003-01-01

276

Precision vs. error in JPEG compression  

NASA Astrophysics Data System (ADS)

By mapping computations directly onto hardware, reconfigurable machines promise a tremendous speed-up over traditional computers. However, executing floating-point operations directly in hardware is a waste of resources. Variable precision fixed-point arithmetic operations can save gates and reduce clock cycle times. This paper investigates the relation between precision and error for image compression/decompression. More precisely, this paper investigates the relationship between error and bit- precision for the Discrete Cosine Transform and JPEG.

Bins, Jose C.; Draper, Bruce A.; Bohm, Willem A.; Najjar, Walid

1999-10-01

277

Staurosporine-induced apoptosis of HPV positive and negative human cervical cancer cells from different points in the cell cycle  

Microsoft Academic Search

In the present study, we compare the sensitivity of CaSki and HeLa cells (HPV positive, wild-type p53) and C33A cells (HPV negative, mutated p53) to a protein kinase inhibitor, the staurosporine (ST). We show that ST can reversibly arrest the three cervical-derived cell lines, either in G1 or in G2\\/M. Beyond certain ST concentrations or\\/and over 24 h exposure, the

B Bernard; T Fest; J-L Prétet; C Mougin

2001-01-01

278

Development of a GPS-aided motion measurement, pointing, and stabilization system for a Synthetic Aperture Radar. [Global Positioning System (GPS)  

SciTech Connect

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.

Fellerhoff, J.R.; Kohler, S.M.

1991-01-01

279

Correlation between energy positions of deep intrinsic point-defect levels and a limiting fermi level in irradiated III V semiconductors  

NASA Astrophysics Data System (ADS)

The energy levels of neutral anion (VA) and cation (VC) vacancies and antisite defects are calculated for the anion CA and cation AC sublattices of III V semiconductors. An averaged energy level position for these defects is estimated to be Eav abs = 4.9 eV. The position coincides with the local charge electroneutrality level. It is shown that the case, where the total energies of formation of VA, VC and antisite CA, AC defects in the sublattices of binary semiconductors are similar, corresponds to the point-defect equilibrium condition and stabilization of the Fermi level in the proximity of the local charge electroneutrality level.

Brudnyi, V. N.; Grinyaev, S. N.; Kolin, N. G.

2007-05-01

280

Measuring the body position, attitude and wing deformation of a free-flight dragonfly by combining a comb fringe pattern with sign points on the wing  

NASA Astrophysics Data System (ADS)

The simultaneous measurements of the body position, attitude and the wing kinematics of a free-flight insect are very important for analysing the flight performance. In this paper, a method based on combining a comb fringe pattern with sign points on the dragonfly wing has been developed to improve the accuracy in body position and attitude measurement or in construction of a local body-fixed coordinate system. Meanwhile, the wing kinematics can be measured simultaneously by the comb fringe pattern method. The method has been used successfully in the measurement of a free-flight dragonfly.

Wang, Hao; Zeng, Lijiang; Yin, Chunyong

2002-06-01

281

Flexures for high precision robotics  

Microsoft Academic Search

High precision robots are often used for complex assembly or positioning tasks. One way to achieve high motion precision is to design mechanical systems based on flexure joints. Flexure joints (or flexures) utilize the elastic properties of matter, which brings avoidance of dry friction. Nanometer scale motions are then possible, without wear, mechanical play or particle emission. Leading to high

Jean-Philippe Bacher; Cédric Joseph; Reymond Clavel

2002-01-01

282

A new method to detect object and estimate the position and the orientation from an image using a 3-D model having feature points  

Microsoft Academic Search

We propose an approach to detecting a three-dimensional (3-D) object and estimating its position and orientation. The proposed system can estimate the object's 3-D pose from a single input image by using 3-D model with feature points. The 3-D model is employed in order to represent a 3-D object, and the system can create 2-D models projected from various viewpoints.

MASASHI KAYANUMA; MASAFUMI HAGIWARA

1999-01-01

283

Transfer-matrix approach to estimating coverage discontinuities and multicritical-point positions in two-dimensional lattice-gas phase diagrams  

Microsoft Academic Search

We present a method of computing coverage discontinuities in two-dimensional lattice-gas phase diagrams using transfer matrices. By applying the method to Baxter's generalized hard-square model, we find good agreement with exact results. This method also can be used to estimate the position of multicritical points, and we again find good agreement with exact results and with previous work on the

N. C. Bartelt; T. L. Einstein; L. D. Roelofs

1986-01-01

284

Precision laser aiming system  

SciTech Connect

A precision laser aiming system comprises a disrupter tool, a reflector, and a laser fixture. The disrupter tool, the reflector and the laser fixture are configurable for iterative alignment and aiming toward an explosive device threat. The invention enables a disrupter to be quickly and accurately set up, aligned, and aimed in order to render safe or to disrupt a target from a standoff position.

Ahrens, Brandon R. (Albuquerque, NM); Todd, Steven N. (Rio Rancho, NM)

2009-04-28

285

Solid state NMR spectroscopy as a precise tool for assigning the tautomeric form and proton position in the intramolecular bridges of o-hydroxy Schiff bases.  

PubMed

Two analogous Schiff bases, (S,E)-2-((1-hydroxy-3-methyl-1,1-diphenylbutan-2-ylimino)methyl)phenol (1) and (S,Z)-2-hydroxy-6-((1-hydroxy-3-methyl-1,1-diphenylbutan-2-ylamino)methylene)cyclohexa-2,4-dienone (2), exist in the solid state as phenol-imine and keto-amine tautomers, respectively. Their crystal structures were solved using the X-ray diffraction method. Sample 1 forms orthorhombic crystals of space group P2(1)2(1)2(1), while 2 forms monoclinic crystals of space group P2(1). In each sample, one molecule is in the asymmetric unit of the crystal structure. One-dimensional and two-dimensional solid state NMR techniques were used for structure assignment and for inspection of the (13)C and (15)N ?(ii) of the chemical shift tensor (CST) values. NMR study indicates that the span (? = ?(11)-?(33)) and the skew (? = 3(?(22)-?(iso)/?) are extremely sensitive to change in the tautomeric form of the Schiff bases. Theoretical calculations of NMR shielding parameters for 1 and 2 and a model compound with reduced aliphatic residue were performed using the GIAO method with B3LYP functional and 6-311++g(d,p) basis sets. From comparative analysis of the experimental and theoretical parameters, it was concluded that the position of hydrogen in the intramolecular bridge has tremendous influence on (13)C and (15)N CST parameters. Inspection of ? and ? parameters allowed for the establishment of the nature of the hydrogen bonding and the assignment of the equilibrium proton position in the intramolecular bridges in the solid state. PMID:21049987

Jaworska, Magdalena; Hrynczyszyn, Pawe? B; We?niak, Miros?aw; Wojtczak, Andrzej; Nowicka, Katarzyna; Krasi?ski, Grzegorz; Kassassir, Hassan; Ciesielski, W?odzimierz; Potrzebowski, Marek J

2010-11-04

286

Point Mutations with Positive Selection Were a Major Force during the Evolution of a Receptor-Kinase Resistance Gene Family of Rice1[W  

PubMed Central

The rice (Oryza sativa) Xa26 gene, which confers resistance to bacterial blight disease and encodes a leucine-rich repeat (LRR) receptor kinase, resides at a locus clustered with tandem homologous genes. To investigate the evolution of this family, four haplotypes from the two subspecies of rice, indica and japonica, were analyzed. Comparative sequence analysis of 34 genes of 10 types of paralogs of the family revealed haplotype polymorphisms and pronounced paralog diversity. The orthologs in different haplotypes were more similar than the paralogs in the same haplotype. At least five types of paralogs were formed before the separation of indica and japonica subspecies. Only 7% of amino acid sites were detected to be under positive selection, which occurred in the extracytoplasmic domain. Approximately 74% of the positively selected sites were solvent-exposed amino acid residues of the LRR domain that have been proposed to be involved in pathogen recognition, and 73% of the hypervariable sites detected in the LRR domain were subject to positive selection. The family is formed by tandem duplication followed by diversification through recombination, deletion, and point mutation. Most variation among genes in the family is caused by point mutations and positive selection.

Sun, Xinli; Cao, Yinglong; Wang, Shiping

2006-01-01

287

The sharp rise of Lake Victoria, a positive indicator to solar Wolf-Gleissberg cycles turning points  

NASA Astrophysics Data System (ADS)

The Sun experiences cycles of the order 80-120 years known as the Wolf-Gleissberg (WG). Climate change occur at their turning points. 1878 marked the end of a WG cycle and the beginning of a series of four low activity solar cycles. The induced 1878 sharp rise in Lake Victoria level was followed by a drop till 1890. Later on, the lake level rose and fall in sympathy with the weak solar cycles till 1922. Following the 1957 maximum of the next WG cycle a ~2.5 m sharp rise in Lake Victoria occurred. Again 1997 marked the end of the past WG cycle and the beginning of a new era of low activity solar cycles. As a consequence, the level of Lake Victoria rose sharply by 1.6 m and at present is dropping till the end of cycle 23 leading to drought conditions around 2009±2-3 years. Cyclic lake level will follow cycles 24 and 25 and possibly 26 when solar forcing will come to a holt.

Yousef, Shahinaz M.; Amer, Morsi

2003-09-01

288

Transmission gap, Bragg-like reflection, and Goos-Haenchen shifts near the Dirac point inside a negative-zero-positive index metamaterial slab  

SciTech Connect

Motivated by the realization of the Dirac point (DP) with a double-cone structure for optical field in the negative-zero-positive index metamaterial (NZPIM), the reflection, transmission, and Goos-Haenchen (GH) shifts inside the NZPIM slab are investigated. Due to the linear Dirac dispersion, the transmission as the function of the frequency has a gap, thus, the corresponding reflection has a frequency or wavelength window for the perfect reflection, which is similar to the Bragg reflection in the one-dimensional photonic crystals. Near the DP, the associated GH shifts in the transmission and reflection can be changed from positive to negative with increasing the wavelength. These negative and positive shifts can also be enhanced by transmission resonances when the frequency is far from that at the DP. All these phenomena will lead to some potential applications in the integrated optics and optical devices.

Chen Xi [Department of Physics, Shanghai University, 200444 Shanghai (China); Departamento de Quimica-Fisica, UPV-EHU, Apartado 644, 48080 Bilbao (Spain); Wang Ligang [Department of Physics, Chinese University of Hong Kong, Shatin, New Territories (Hong Kong); Department of Physics, Zhejiang University, Hangzhou 310027 (China); Li Chunfang [Department of Physics, Shanghai University, 200444 Shanghai (China)

2009-10-15

289

Chemotherapeutic agents circumvent emergence of dasatinib-resistant BCR-ABL kinase mutations in a precise mouse model of Philadelphia chromosome-positive acute lymphoblastic leukemia  

PubMed Central

The introduction of cultured p185BCR-ABL-expressing (p185+) Arf ?/? pre-B cells into healthy syngeneic mice induces aggressive acute lymphoblastic leukemia (ALL) that genetically and phenotypically mimics the human disease. We adapted this high-throughput Philadelphia chromosome–positive (Ph+) ALL animal model for in vivo luminescent imaging to investigate disease progression, targeted therapeutic response, and ALL relapse in living mice. Mice bearing high leukemic burdens (simulating human Ph+ ALL at diagnosis) entered remission on maximally intensive, twice-daily dasatinib therapy, but invariably relapsed with disseminated and/or central nervous system disease. Although relapse was frequently accompanied by the eventual appearance of leukemic clones harboring BCR-ABL kinase domain (KD) mutations that confer drug resistance, their clonal emergence required prolonged dasatinib exposure. KD P-loop mutations predominated in mice receiving less intensive therapy, whereas high-dose treatment selected for T315I “gatekeeper” mutations resistant to all 3 Food and Drug Administration–approved BCR-ABL kinase inhibitors. The addition of dexamethasone and/or L-asparaginase to reduced-intensity dasatinib therapy improved long-term survival of the majority of mice that received all 3 drugs. Although non–tumor-cell–autonomous mechanisms can prevent full eradication of dasatinib-refractory ALL in this clinically relevant model, the emergence of resistance to BCR-ABL kinase inhibitors can be effectively circumvented by the addition of “conventional” chemotherapeutic agents with alternate antileukemic mechanisms of action.

Mulder, Heather L.; Calabrese, Christopher R.; Morrison, Jeffrey B.; Rehg, Jerold E.; Relling, Mary V.; Sherr, Charles J.; Williams, Richard T.

2011-01-01

290

Comparisons of line-of-sight water vapor observations using the global positioning system and a pointing microwave radiometer.  

SciTech Connect

Line-of-sight measurements of integrated water vapor from a global positioning system (GPS) receiver and a microwave radiometer are compared. These two instruments were collocated at the central facility of the Department of Energy's Atmospheric Radiation Measurement Program's Southern Great Plains region, near Lamont, Oklahoma. The comparison was made using 47 days of observations in May and June of 2000. Weather conditions during this time period were variable with total integrated water vapor ranging from less than 10 to more than 50 mm. To minimize errors in the microwave radiometer observations, observations were compared during conditions when the liquid water measured by the radiometer was less than 0.1 mm. The linear correlation of the observations between the two instruments is 0.99 with a root-mean-square difference of the GPS water vapor to a linear fit of the microwave radiometer of 1.3 mm. The results from these comparisons are used to evaluate the ability of networks of GPS receivers to measure instantaneous line-of-sight integrals of water vapor. A discussion and analysis is provided regarding the additional information of the water vapor field contained in these observations compared to time- and space-averaged zenith and gradient measurements.

Braun, J.; Rocken, C.; Liljegren, J. C.; Environmental Research; Univ. Corporation for Atmospheric Research

2003-05-01

291

Using Global Positioning System techniques in landslide monitoring  

Microsoft Academic Search

The precise determination of point coordinates with conventional Global Positioning System (GPS) techniques often required observation times of one to several hours. In the last few years, new GPS methods have been developed (among them, the fast-static and real time kinematic), with higher productivity and good theoretical precision. The main objective of this paper is to ascertain the performance of

Josep A. Gili; Jordi Corominas; Joan Rius

2000-01-01

292

The pointing system of the TNA-1500 radio telescope  

NASA Astrophysics Data System (ADS)

The design of the pointing system of the TNA-1500 telescope is described, with attention given to the electric drive of the antenna, the high-precision angular-position meters, and the deformation-compensation system. Test results indicate the good performance of the pointing system.

Poperechenko, B. A.; Gippius, A. A.; Kliuev, O. L.; Sevriukov, B. N.; Lychkin, V. P.; Terekhov, V. M.; Baranov, V. E.

293

Pointing to a target from an upright standing position: anticipatory postural adjustments are modulated by the size of the target in humans.  

PubMed

To examine the influence of the target size onto postural EMG activity, eight subjects performed, from a standing position, rapid and accurate pointings to a target located within reach. The target size was varied across blocks of trials. Hand movement time increased when the target size was decreased. Interestingly, the magnitude of the integrated EMG activity of lower limb muscles (TAi, TFLc, RFi) decreased with a decreasing target size, while that of the erector spinae increased. The effects were observed as early as 200 ms before the hand movement onset. When standing, these early commands could influence the control of the hand during the acceleration phase. The target size was specified within the postural command before any hand movement took place suggesting the characteristics of the pointing task were integrated in a feedforward manner. PMID:15039111

Bonnetblanc, François; Martin, Olivier; Teasdale, Normand

2004-04-01

294

A Position Estimation Based on Tire-Road Contact Points Considering Displacements of Two Concentric Circles on a Circular Fisheye Image  

NASA Astrophysics Data System (ADS)

In this paper, we propose a new method for estimating the positions on a road based on detected tire-road contact points taking the distortion on circular fisheye images into consideration. In our proposed method, we use the distortion parameters of two concentric circles composed of the inner wheel and the outer tire by considering projection system of fisheye lens, and the searching the gray scale profiles in the vertical direction are derived from each pixel that is the outline of the wheel region. The effectiveness of the proposed method is confirmed through experimental results.

Hirose, Kenichi; Toriu, Takashi; Hama, Hiromitsu

295

Back propagation simulations using limited precision calculations  

Microsoft Academic Search

The precision required for neural net algorithms is an important question facing hardware architects. The authors present simulation results that compare floating point and limited precision integer back-propagation simulators. Data sets from the neural network benchmark suite maintained by Carnegie Mellon University were used to compare integer and floating point implementations. The simulation results indicate that integer computation works quite

Jordan L. Holt; Thomas E. Baker

1991-01-01

296

The study of optical feature point imaging gray value automation control method with movement  

Microsoft Academic Search

In order to solve the problem that feature point imaging quality affects the measurement precision of vision system, a method of optical feature point imaging gray value automation control with movement is proposed. The method eliminates the effect of the relative position changes of camera and feature point on imaging gray value by automatic modulating the current in the feature

Changying C. Liu; Qingcheng Huang; Dong Ye; Rensheng Che; Qiaoyu Xu

2005-01-01

297

GOCE Precise Science Orbits  

NASA Astrophysics Data System (ADS)

GOCE (Gravity field and steady-state Ocean Circulation Explorer), as the first ESA (European Space Agency) Earth Explorer Core Mission, is dedicated for gravity field recovery of unprece-dented accuracy using data from the gradiometer, its primary science instrument. Data from the secondary instrument, the 12-channel dual-frequency GPS (Global Positioning System) receiver, is used for precise orbit determination of the satellite. These orbits are used to accu-rately geolocate the gradiometer observations and to provide complementary information for the long-wavelength part of the gravity field. A precise science orbit (PSO) product is provided by the GOCE High-Level Processing Facility (HPF) with a precision of about 2 cm and a 1-week latency. The reduced-dynamic and kinematic orbit determination strategies for the PSO product are presented together with results of about one year of data. The focus is on the improvement achieved by the use of empirically derived azimuth-and elevation-dependent variations of the phase center of the GOCE GPS antenna. The orbits are validated with satellite laser ranging (SLR) measurements.

Bock, Heike; Jäggi, Adrian; Meyer, Ulrich; Beutler, Gerhard; Heinze, Markus; Hugentobler, Urs

298

Development of a micro-depth control system for an ultra-precision lathe using a piezo-electric actuator  

Microsoft Academic Search

Micro-positioning systems using piezo-electric actuators have very wide applications, for example as in ultra-precision machine tools, optical devices and measurement systems In order to keep a high-precision displacement resolution, they use a position sensor and feed back the error. From the practical point of view, high-resolution displacement sensor systems are very expensive and it is difficult to guarantee such sensitive

Jeong-Du Kim; Soo-Ryong Nam

1997-01-01

299

Precision powder feeder  

DOEpatents

A new class of precision powder feeders is disclosed. These feeders provide a precision flow of a wide range of powdered materials, while remaining robust against jamming or damage. These feeders can be precisely controlled by feedback mechanisms.

Schlienger, M. Eric (Albuquerque, NM); Schmale, David T. (Albuquerque, NM); Oliver, Michael S. (Sandia Park, NM)

2001-07-10

300

Energy gradients with respect to atomic positions and cell parameters for the Kohn-Sham density-functional theory at the ? point  

NASA Astrophysics Data System (ADS)

The application of theoretical methods based on density-functional theory is known to provide atomic and cell parameters in very good agreement with experimental values. Recently, construction of the exact Hartree-Fock exchange gradients with respect to atomic positions and cell parameters within the ?-point approximation has been introduced [V. Weber et al., J. Chem. Phys. 124, 214105 (2006)]. In this article, the formalism is extended to the evaluation of analytical ?-point density-functional atomic and cell gradients. The infinite Coulomb summation is solved with an effective periodic summation of multipole tensors [M. Challacombe et al., J. Chem. Phys. 107, 9708 (1997)]. While the evaluation of Coulomb and exchange-correlation gradients with respect to atomic positions are similar to those in the gas phase limit, the gradients with respect to cell parameters needs to be treated with some care. The derivative of the periodic multipole interaction tensor needs to be carefully handled in both direct and reciprocal space and the exchange-correlation energy derivative leads to a surface term that has its origin in derivatives of the integration limits that depend on the cell. As an illustration, the analytical gradients have been used in conjunction with the QUICCA algorithm [K. Németh and M. Challacombe, J. Chem. Phys. 121, 2877 (2004)] to optimize one-dimensional and three-dimensional periodic systems at the density-functional theory and hybrid Hartree-Fock/density-functional theory levels. We also report the full relaxation of forsterite supercells at the B3LYP level of theory.

Weber, Valéry; Tymczak, Christopher J.; Challacombe, Matt

2006-06-01

301

Precision contour gage  

DOEpatents

An apparatus for gaging the contour of a machined part includes a rotary slide assembly, a kinematic mount to move the apparatus into and out of position for measuring the part while the part is still on the machining apparatus, a linear probe assembly with a suspension arm and a probe assembly including as probe tip for providing a measure of linear displacement of the tip on the surface of the part, a means for changing relative positions between the part and the probe tip, and a means for recording data points representing linear positions of the probe tip at prescribed rotation intervals in the position changes between the part and the probe tip. 5 figs.

Bieg, L.F.

1990-12-11

302

Precision contour gage  

DOEpatents

An apparatus for gaging the contour of a machined part includes a rotary slide assembly, a kinematic mount to move the apparatus into and out of position for measuring the part while the part is still on the machining apparatus, a linear probe assembly with a suspension arm and a probe assembly including as probe tip for providing a measure of linear displacement of the tip on the surface of the part, a means for changing relative positions between the part and the probe tip, and a means for recording data points representing linear positions of the probe tip at prescribed rotation intervals in the position changes between the part and the probe tip.

Bieg, Lothar F. (Louisville, CO)

1990-12-11

303

Precision measurements in supersymmetry  

SciTech Connect

Supersymmetry is a promising framework in which to explore extensions of the standard model. If candidates for supersymmetric particles are found, precision measurements of their properties will then be of paramount importance. The prospects for such measurements and their implications are the subject of this thesis. If charginos are produced at the LEP II collider, they are likely to be one of the few available supersymmetric signals for many years. The author considers the possibility of determining fundamental supersymmetry parameters in such a scenario. The study is complicated by the dependence of observables on a large number of these parameters. He proposes a straightforward procedure for disentangling these dependences and demonstrate its effectiveness by presenting a number of case studies at representative points in parameter space. In addition to determining the properties of supersymmetric particles, precision measurements may also be used to establish that newly-discovered particles are, in fact, supersymmetric. Supersymmetry predicts quantitative relations among the couplings and masses of superparticles. The author discusses tests of such relations at a future e{sup +}e{sup {minus}} linear collider, using measurements that exploit the availability of polarizable beams. Stringent tests of supersymmetry from chargino production are demonstrated in two representative cases, and fermion and neutralino processes are also discussed.

Feng, J.L.

1995-05-01

304

State Your Position  

NSDL National Science Digital Library

To navigate, you must know roughly where you stand relative to your designation, so you can head in the right direction. In locations where landmarks are not available to help navigate (in deserts, on seas), objects in the sky are the only reference points. While celestial objects move fairly predictably, and rough longitude is not too difficult to find, it is not a simple matter to determine latitude and precise positions. In this activity, students investigate the uses and advantages of modern GPS for navigation.

Integrated Teaching And Learning Program

305

Probing the metabotropic glutamate receptor 5 (mGlu?) positive allosteric modulator (PAM) binding pocket: discovery of point mutations that engender a "molecular switch" in PAM pharmacology.  

PubMed

Positive allosteric modulation of metabotropic glutamate receptor subtype 5 (mGlu?) is a promising novel approach for the treatment of schizophrenia and cognitive disorders. Allosteric binding sites are topographically distinct from the endogenous ligand (orthosteric) binding site, allowing for co-occupation of a single receptor with the endogenous ligand and an allosteric modulator. Negative allosteric modulators (NAMs) inhibit and positive allosteric modulators (PAMs) enhance the affinity and/or efficacy of the orthosteric agonist. The molecular determinants that govern mGlu? modulator affinity versus cooperativity are not well understood. Focusing on the modulators based on the acetylene scaffold, we sought to determine the molecular interactions that contribute to PAM versus NAM pharmacology. Generation of a comparative model of the transmembrane-spanning region of mGlu? served as a tool to predict and interpret the impact of mutations in this region. Application of an operational model of allosterism allowed for determination of PAM and NAM affinity estimates at receptor constructs that possessed no detectable radioligand binding as well as delineation of effects on affinity versus cooperativity. Novel mutations within the transmembrane domain (TM) regions were identified that had differential effects on acetylene PAMs versus 2-methyl-6-(phenylethynyl)-pyridine, a prototypical NAM. Three conserved amino acids (Y658, T780, and S808) and two nonconserved residues (P654 and A809) were identified as key determinants of PAM activity. Interestingly, we identified two point mutations in TMs 6 and 7 that, when mutated, engender a mode switch in the pharmacology of certain PAMs. PMID:23444015

Gregory, Karen J; Nguyen, Elizabeth D; Reiff, Sean D; Squire, Emma F; Stauffer, Shaun R; Lindsley, Craig W; Meiler, Jens; Conn, P Jeffrey

2013-02-26

306

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

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 calibrated isotopic composition measurements are 0.319876 ± 0.000067, 0.319768 ± 0.000187, and 0.319549 ± 0.000044, respectively. As a result, the atomic weights of chlorine in NIST 975, NIST 975a, and ISL 354 are derived as 35.45284(8), 35.45272(21), and 35.45252(2) individually, which are consistent with the issued values of 35.453(2) by IUPAC in 1999. PMID:23088631

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

2012-11-02

307

A Fortran Multiple-Precision Arithmetic Package  

Microsoft Academic Search

A collection of ANSI Standard Fortran subroutines for performing multiple-precision floating- point arithmetic and evaluating elementary and special functions is described. The subroutines are machine independent and the precision is arbitrary, subject to storage limitations. The design of the package is discussed, some of the algorithms are described, and test results are given. Comments

Richard P. Brent

1978-01-01

308

ARPREC: An Arbitrary Precision Computation Package.  

National Technical Information Service (NTIS)

This paper describes a new software package for performing arithmetic with an arbitrarily high level of numeric precision. It is based on the earlier MPFUN package, enhanced with special IEEE .oating-point numerical techniques and several new functions. T...

D. H. Bailey Y. Hida X. S. Li B. Thompson

2002-01-01

309

Tracking the key point of a building in infrared imaging guidance  

NASA Astrophysics Data System (ADS)

Ground target detection is very important in precise infrared imaging guidance. To address this problem, an accurate tracking algorithm of the key points, i.e., vertex of buildings is proposed. First, the feature points are extracted by Kanade-Lucas-Tomasi (KLT) algorithm, and the template of feature points is updated constantly in the tracking process according to the offset. Then based on the extracted feature points, the key point can be positioned using the geometric relation between the feature points and the key point. Third, the algorithm tracks the feature points and uses the geometric relation to track the key point in the next frame. The experimental results demonstrate the effectiveness of the proposed algorithm in tracking the key point of buildings in front-lower infrared image sequences for long time precise guidance.

Tan, Yi-mei; Zhou, Fu-gen; Jin, Ting

2013-09-01

310

Use of Terrestrial Laser Scanning Technology for Long Term High Precision Deformation Monitoring  

PubMed Central

The paper presents a new methodology for high precision monitoring of deformations with a long term perspective using terrestrial laser scanning technology. In order to solve the problem of a stable reference system and to assure the high quality of possible position changes of point clouds, scanning is integrated with two complementary surveying techniques, i.e., high quality static GNSS positioning and precise tacheometry. The case study object where the proposed methodology was tested is a high pressure underground pipeline situated in an area which is geologically unstable.

Vezocnik, Rok; Ambrozic, Tomaz; Sterle, Oskar; Bilban, Gregor; Pfeifer, Norbert; Stopar, Bojan

2009-01-01

311

Impact on ART initiation of point-of-care CD4 testing at HIV diagnosis among HIV-positive youth in Khayelitsha, South Africa  

PubMed Central

Introduction Despite the rapid expansion of antiretroviral therapy (ART) programmes in developing countries, pre-treatment losses from care remain a challenge to improving access to treatment. Youth and adolescents have been identified as a particularly vulnerable group, at greater risk of loss from both pre-ART and ART care. Point-of-care (POC) CD4 testing has shown promising results in improving linkage to ART care. In Khayelitsha township, South Africa, POC CD4 testing was implemented at a clinic designated for youth aged 12–25 years. We assessed whether there was an associated reduction in attrition between HIV testing, assessment for eligibility and ART initiation. Methods A before-and-after observational study was conducted using routinely collected data. These were collected on patients from May 2010 to April 2011 (Group A) when baseline CD4 count testing was performed in a laboratory and results were returned to the clinic within two weeks. Same-day POC CD4 testing was implemented in June 2011, and data were collected on patients from August 2011 to July 2012 (Group B). Results A total of 272 and 304 youth tested HIV-positive in Group A and Group B, respectively. Group B patients were twice as likely to have their ART eligibility assessed compared to Group A patients: 275 (90%) vs. 183 (67%) [relative risk (RR)=2.4, 95% CI: 1.8–3.4, p<0.0001]. More patients in World Health Organization (WHO) Stage 1 disease (85% vs. 69%), with CD4 counts?350 cells/µL (58% vs. 35%) and more males (13% vs. 7%) were detected in Group B. The proportion of eligible patients who initiated ART was 50% and 44% (p=0.6) in Groups B and A, respectively; and 50% and 43% (p=0.5) when restricted to patients with baseline CD4 count?250 cells/µL. Time between HIV-testing and ART initiation was reduced from 36 to 28 days (p=0.6). Discussion POC CD4 testing significantly improved assessment for ART eligibility. The improvement in the proportion initiating ART and the reduction in time to initiation was not significant due to sample size limitations. Conclusions POC CD4 testing reduced attrition between HIV-testing and assessment of ART eligibility. Strategies to improve uptake of ART are needed, possibly by improving patient support for HIV-positive youth immediately after diagnosis.

Patten, Gabriela EM; Wilkinson, Lynne; Conradie, Karien; Isaakidis, Petros; Harries, Anthony D; Edginton, Mary E; De Azevedo, Virginia; van Cutsem, Gilles

2013-01-01

312

High precision fiber development  

Microsoft Academic Search

The improvement of single-mode precision fiber is critical to the efficient use of these fibers in connectors and to allow for low loss splices. Similarly, the alignment of fibers to integrated optic devices demands high precision. Likewise, the precision of large core multimode fibers affects coupler and connector losses as well as overall optical and physical performance. In accordance with

F. I. Akers; H. D. Shepherd

1981-01-01

313

Precision zero-home locator  

DOEpatents

A zero-home locator includes a fixed phototransistor switch and a moveable actuator including two symmetrical, opposed wedges, each wedge defining a point at which switching occurs. The zero-home location is the average of the positions of the points defined by the wedges.

Stone, W.J.

1983-10-31

314

Apparent precision of GPS radio occultation temperatures  

NASA Astrophysics Data System (ADS)

The abundant atmospheric data provided by radio occultation (RO) via the Global Positioning System satellite network have improved short and long-term forecasts and have demonstrated the potential to provide a long-term, consistent, and independent climate dataset. Previous studies have already verified the consistency and reliability of the RO method, listing a range of precision estimates. Uncertainties arising during temperature retrievals, and confounding effects of atmospheric variability, have made the precision of RO temperature data difficult to determine. In this paper, we introduce the concept of apparent precision, and describe a simple, robust method for estimating the apparent temperature precision using data from the COSMIC project. We examine apparent RO temperature precision by latitude, and find it to be somewhat lower than previous estimates. We attribute this to apparent precision being a function of the true precision plus representativeness errors.

Staten, Paul W.; Reichler, Thomas

2009-12-01

315

Controlling precise movement with stochastic signals.  

PubMed

In a noisy system, such as the nervous system, can movements be precisely controlled as experimentally demonstrated? We point out that the existing theory of motor control fails to provide viable solutions. However, by adopting a generalized approach to the nonconvex optimization problem with the Young measure theory, we show that a precise movement control is possible even with stochastic control signals. Numerical results clearly demonstrate that a considerable significant improvement of movement precisions is achieved. Our generalized approach proposes a new way to solve optimization problems in biological systems when a precise control is needed. PMID:20306201

Rossoni, Enrico; Kang, Jing; Feng, Jianfeng

2010-03-20

316

The distribution of extreme points in best complex polynomial approximation  

Microsoft Academic Search

LetK be a compact point set in the complex plane having positive logarithmic capacity and connected complement. For anyf continuous onK and analytic in the interior ofK we investigate the distribution of the extreme points for the error in best uniform approximation tof onK by polynomials. More precisely, if\\u000a$$A_n (f): = \\\\{ z \\\\in K:|f(z) - p_n^* (f;z)| =

H.-P. Blatt; E. B. Saff; V. Totik

1989-01-01

317

Advanced tracking control of positioning tables  

NASA Astrophysics Data System (ADS)

It is well known that point-to-point positioning can be well achieved by a conventional PID controller. However, precise tracking of preplanned motion trajectories requires more sophisticated model-based control algorithms. This paper presents a study on the design and implementation of precise tracking controllers for positioning tables during high-acceleration high-speed motion. A controller incorporating both acceleration feedforward and robust friction compensation is theoretically analyzed under various operating conditions and model uncertainties. An effective technique for tuning feedback gains was found, allowing the determination of the largest well-damped feedback gains. The control design was tested on an industrial belt-drive high-speed positioning table, and much better results were obtained than those of conventional controllers.

Li, Weiping; Rehani, Manoj

1995-08-01

318

Precision guided parachute LDRD final report.  

National Technical Information Service (NTIS)

This report summarizes the results of the Precision Guided Parachute LDRD, a two year program at Sandia National Laboratories which developed a Global Positioning System (GPS) guided parachute capable of autonomous flight and landings. A detailed computer...

J. C. Gilkey

1996-01-01

319

Hivis: Precision Limitations  

NASA Astrophysics Data System (ADS)

The high-resolution visible and infrared spectrograph (HiVIS) is located in one of the coudé rooms of the air force's AEOS (advanced electro-optical system) telescope, which is a 3.67m telescope situated on the island of Maui. Spectropolarimetric signals are typically on the order of 0.1% of the continuum intensity. Therefore, although spectropolarimetry is a powerful remote-sensing tool, useful for the detection of processes taking place within the stellar environment, it requires a high signal to noise ratio to detect these small signatures as well as the identification of systematic noise in order to achieve the precision necessary to avoid masking polarization signatures. HiVIS uses a new CCID20 detector with bi-directional clocking and charge shuffling capabilities and liquid crystal variable retarders for the purpose of modulating an incoming polarization signature. We present a characterization of the CCID20 detector and the LCVRs, revealing trade-offs and limitations of the rapid modulation process. The preliminary results show that within the range of parameters we expect for observations, the detector is not a major limitation. The liquid crystal variable retarders show the expected correlation between more rapid modulation (increased fraction of time spent switching) and an increase in statistical noise from demodulation. This work was conducted by a Research Experience for Undergraduates (REU) position at the University of Hawai'i's Institute for Astronomy and funded by the NSF.

Nevin, Becky; Harrington, D.

2012-01-01

320

Coherent detection circuit for high precision encoders  

Microsoft Academic Search

Robots and industrial machines today requires high precision of 0.1 ?m, high speed of 30-60 m\\/min, and durability for position sensing. Moreover, being compact in size and low in price is indispensable for practical applications. Inductosyn scale is one of the most widely used position sensors. It can attain either required precision or speed, however, not both of them at

Masanobu Mizoguchi; T. Matsukawa; K. Takeuchi; T. Fukuda

2000-01-01

321

Intelligent Precision Motion Control  

Microsoft Academic Search

Precision engineering [3] has been steadily gathering momentum over the last century in terms of research, development, and application to product innovation. The driving force in this development appears to arise from requirements for much higher performance of products, higher reliability, longer life, lower cost, and miniaturization. In the new millenium, ultra precision manufacture is poised to progress further and

Kok Kiong Tan; Sunan Huang; Ser Yong Lim; Wei Lin

2005-01-01

322

Precision Hinge Mounting Stops.  

National Technical Information Service (NTIS)

The present invention relates to a precision hinge apparatus. To accurately and reproducibly set the angle of a hinge, especially a very small hinge, a precision hinge and angled mounting stops are provided. The device comprises a hinge joint having a fas...

W. H. Nedderman

1999-01-01

323

Precision in liver surgery.  

PubMed

Continuous theoretical and technological progress in the face of increasing expectations for quality health care has transformed the surgical paradigm. The authors systematically review these historical trends and propose the novel paradigm of "precision surgery," featuring certainty-based practice to ensure the best result for each patient with multiobjective optimization of therapeutic effectiveness, surgical safety, and minimal invasiveness. The main characteristics of precision surgery may be summarized as determinacy, predictability, controllability, integration, standardization, and individualization. The strategy of precision in liver surgery is to seek a balance of maximizing the removal of the target lesion, while maximizing the functional liver remnant and minimizing surgical invasiveness. In this article, the authors demonstrate the application of precision approaches in specific settings in complex liver surgery. They propose that the concept of precision surgery should be considered for wider application in liver surgery and other fields as a step toward the ultimate goal of perfect surgery. PMID:23943100

Dong, Jiahong; Yang, Shizhong; Zeng, Jianping; Cai, Shouwang; Ji, Wenbin; Duan, Weidong; Zhang, Aiqun; Ren, Weizheng; Xu, Yinzhe; Tan, Jingwang; Bu, Xiangyang; Zhang, Ning; Wang, Xuedong; Wang, Xianqiang; Meng, Xiangfei; Jiang, Kai; Gu, Wanqing; Huang, Zhiqiang

2013-08-13

324

Low Cost Precision Lander for Lunar Exploration  

NASA Astrophysics Data System (ADS)

For 60 years the US Defense Department has invested heavily in producing small, low mass, precision guided vehicles. The technologies matured under these programs include terrain-aided navigation, closed loop terminal guidance algorithms, robust autopilots, high thrust-to-weight propulsion, autonomous mission management software, sensors, and data fusion. These technologies will aid NASA in addressing New Millennium Science and Technology goals as well as the requirements flowing from the Vision articulated in January 2004. Establishing and resupplying a long term lunar presence will require automated landing precision not yet demonstrated. Precision landing will increase safety and assure mission success. In the DOD world, such technologies are used routinely and reliably. Hence, it is timely to generate a point design for a precise planetary lander useful for lunar exploration. In this design science instruments amount to 10 kg, 16% of the lander vehicle mass. This compares favorably with 7% for Mars Pathfinder and less than 15% for Surveyor. The mission design flies the lander in an inert configuration to the moon, relying on a cruise stage for navigation and TCMs. The lander activates about a minute before impact. A solid booster reduces the vehicle speed to 300-450 m/s. The lander is now about 2 minutes from touchdown and has 600 to 700 m/s delta-v capability, allowing for about 10 km of vehicle divert during terminal descent. This concept of operations is chosen because it closely mimics missile operational timelines used for decades: the vehicle remains inert in a challenging environment, then must execute its mission flawlessly on a moment's notice. The vehicle design consists of a re-plumbed propulsion system, using propellant tanks and thrusters from exoatmospheric programs. A redesigned truss provides hard points for landing gear, electronics, power supply, and science instruments. A radar altimeter and a Digital Scene Matching Area Correlator (DSMAC) provide data for the terminal guidance algorithms. DSMAC acquires high-resolution images for real-time correlation with a reference map. This system provides ownship position with a resolution comparable to the map. Since the DSMAC can sample at 1.5 mrad, any imaging acquired below 70 km altitude will surpass the resolution available from previous missions. DSMAC has a mode where image data are compressed and downlinked. This capability could be used to downlink live images during terminal guidance. Approximately 500 kbitps telemetry would be required to provide the first live descent imaging sequence since Ranger. This would provide unique geologic context imaging for the landing site. The development path to produce such a vehicle is that used to develop missiles. First, a pathfinder vehicle is designed and built as a test bed for hardware integration including science instruments. Second, a hover test vehicle would be built. Equipped with mass mockups for the science payload, the vehicle would otherwise be an exact copy of the flight vehicle. The hover vehicle would be flown on earth to demonstrate the proper function and integration of the propulsion system, autopilots, navigation algorithms, and guidance sensors. There is sufficient delta-v in the proposed design to take off from the ground, fly a ballistic arc to over 100 m altitude, then guide to a precision soft landing. Once the vehicle has flown safely on earth, then the validated design would be used to produce the flight vehicle. Since this leverages the billions of dollars DOD has invested in these technologies, it should be possible to land useful science payloads precisely on the lunar surface at relatively low cost.

Head, J. N.; Gardner, T. G.; Hoppa, G. V.; Seybold, K. G.

2004-12-01

325

Validation of GPS Based Precise Orbits Using SLR Observations  

NASA Astrophysics Data System (ADS)

In this study, the YLPODS (Yonsei Laser-ranging Precision Orbit Determination System) is developed for POD using SLR (Satellite Laser Ranging) NP (Normal Point) observations. The performance of YLPODS is tested using SLR NP observations of TOPEX/POSEIDON and CHAMP satellite. JPL's POE (Precision Orbit Ephemeris) is assumed to be true orbit, the measurement residual RMS (Root Mean Square) and the orbit accuracy (radial, along-track, cross-track) are investigated. The validation of POD using GPS (Global Positioning System) raw data is achieved by YLPODS performance and highly accurate SLR NP observations. YGPODS (Yonsei GPS-based Precision Orbit Determination System) is used for generating GPS based precise orbits for TOPEX/POSEIDON. The initial orbit for YLPODS is derived from the YGPODS results. To validate the YGPODS results the range residual of the first adjustment of YLPODS is investigated. The YLPODS results using SLR NP observations of TOPEX/POSEIDON and CHAMP satellite show that the range residual is less than 10 cm and the orbit accuracy is about 1 m level. The validation results of the YGPODS orbits using SLR NP observations of the TOPEX/POSEIDON satellite show that the range residual is less than 10 cm. This result predicts that the accuracy of this GPS based orbits is about 1m level and it is compared with JPL's POE. Thus this result presents that the YLPODS can be used for POD validation using SLR NP observations such as STSAT-2 and KOMPSAT-5.

Kim, Young-Rok; Park, Eunseo; Park, Sang-Young; Choi, Kyu-Hong; Hwang, Yoola; Kim, Hae-Yeon; Lee, Byoung-Sun; Kim, Jaehoon

2009-03-01

326

Rapid and precise absolute distance measurements at long range  

NASA Astrophysics Data System (ADS)

The ability to determine absolute distance to an object is one of the most basic measurements of remote sensing. High-precision ranging has important applications in both large-scale manufacturing and in future tight formation-flying satellite missions, where rapid and precise measurements of absolute distance are critical for maintaining the relative pointing and position of the individual satellites. Using two coherent broadband fibre-laser frequency comb sources, we demonstrate a coherent laser ranging system that combines the advantages of time-of-flight and interferometric approaches to provide absolute distance measurements, simultaneously from multiple reflectors, and at low power. The pulse time-of-flight yields a precision of 3 µm with an ambiguity range of 1.5 m in 200 µs. Through the optical carrier phase, the precision is improved to better than 5 nm at 60 ms, and through the radio-frequency phase the ambiguity range is extended to 30 km, potentially providing 2 parts in 1013 ranging at long distances.

Coddington, I.; Swann, W. C.; Nenadovic, L.; Newbury, N. R.

2009-06-01

327

High precision calibration for 2D optical standard  

NASA Astrophysics Data System (ADS)

Photomask is a kind of 2-D optical standard with etched orthogonal coordinates made of a glass substrate chrominged or filmed with other metal. In order to solve the problems of measurement and traceability of ultra precision photomasks used in advanced manufacturing industry, 2-D photomask optical standard was calibrated in high precision laser two coordinate standard device. A high precision differential laser interferometer system was used for a length standard, a high magnification optical micro vision system was used for precision optical positioning feedback. In this paper, a image measurement model was purposed; A sampling window auto identification algorithm was designed. Grid stripe image could be identified and aimed at automatically by this algorithm. An edge detection method based on bidirection progressive scanning and 3-sigma rule for eliminating outliers in sampling window was found. Dirty point could be removed with effect. Edge detection error could be lowered. By this means, the measurement uncertainty of 2-D optical standard's ruling span was less than 0.3 micrometer (k=2).

Sun, Shuanghua; Gan, Xiaochuan; Xue, Zi; Ye, Xiaoyou; Wang, Heyan; Gao, Hongtang

2012-10-01

328

Positive Changes in Perceptions and Selections of Healthful Foods by College Students after a Short-Term Point-of-Selection Intervention at a Dining Hall  

ERIC Educational Resources Information Center

|Objective: Determine the effects of a short-term, multi-faceted, point-of-selection intervention on college students' perceptions and selection of 10 targeted healthful foods in a university dining hall and changes in their self-reported overall eating behaviors. Participants: 104 college students, (age 18-23) completed pre-I and post-I surveys.…

Peterson, Sharon; Duncan, Diana Poovey; Null, Dawn Bloyd; Roth, Sara Long; Gill, Lynn

2010-01-01

329

Special techniques in ultra-precision machining  

NASA Astrophysics Data System (ADS)

As the development of ultra-precision machining, the SPDT (single point diamond turning) was applied for the manufacture of a variety of optical components for its high precision , versatility and lower manufacturing cost. Whereas, the improvement of ultra-precision machining is not only related to the most topnotch equipments in the world but also closely linked to the special techniques in the ultra-precision Machining. Therefore, the industrialization and marketization of the ultra-precision machining will not be realized without these special techniques. This paper introduces the principle, trait and application of some important special techniques which can match the SPDT efficaciously, they are FTS, STS, SSS, ACT, VQ, LADT and UADT techniques.

Li, Li; Min, Xu; Chen, Dong; Wang, JunHua

2007-12-01

330

Precision blackbody sources for radiometric standards  

Microsoft Academic Search

The precision blackbody sources developed at the All-Russian Institute for Optical and Physical Mea- surements ~Moscow, Russia! and their characteristics are analyzed. The precision high-temperature graphite blackbody BB22p, large-area high-temperature pyrolytic graphite blackbody BB3200pg, middle- temperature graphite blackbody BB2000, low-temperature blackbody BB300, and gallium fixed-point blackbody BB29gl and their characteristics are described. © 1997 Optical Society of America

V. I. Sapritsky; B. B. Khlevnoy; V. B. Khromchenko; B. E. Lisiansky; S. N. Mekhontsev; U. A. Melenevsky; S. P. Morozova; A. V. Prokhorov; L. N. Samoilov; V. I. Shapoval; K. A. Sudarev; M. F. Zelener

1997-01-01

331

Precision blackbody sources for radiometric standards.  

PubMed

The precision blackbody sources developed at the All-Russian Institute for Optical and Physical Measurements (Moscow, Russia) and their characteristics are analyzed. The precision high-temperature graphite blackbody BB22p, large-area high-temperature pyrolytic graphite blackbody BB3200pg, middle-temperature graphite blackbody BB2000, low-temperature blackbody BB300, and gallium fixed-point blackbody BB29gl and their characteristics are described. PMID:18259361

Sapritsky, V I; Khlevnoy, B B; Khromchenko, V B; Lisiansky, B E; Mekhontsev, S N; Melenevsky, U A; Morozova, S P; Prokhorov, A V; Samoilov, L N; Shapoval, V I; Sudarev, K A; Zelener, M F

1997-08-01

332

The GPS Analysis and Positioning Software (GAPS): A Present and Future Tool for Processing GNSS Data  

Microsoft Academic Search

Precise Point Positioning (PPP) is one of the existing techniques to determine point coordinates using a GNSS receiver. In this technique, observations carried out by a single receiver are used in order to determine the three coordinate components, as well as other parameters, such as the receiver clock error and total neutral atmosphere delay. The technique is said to be

R. Leandro; R. Langley; M. Santos

2007-01-01

333

High-precision method for determing the distance to a point source observed through a turbulent atmosphere, using the variation of the position of the plane of the best speckle sharpness  

NASA Astrophysics Data System (ADS)

This paper described a high-accuracy method for obtaining the distance to a source observed through a turbulent atmosphere. Based on a comparative analysis, the limits of applicability of the proposed method are determined, and the possibility of using the proposed method as a basis for modern optical data processing is demonstrated.

Bezdenezhnykh, I. V.; Sviridov, K. N.; Shumilov, Yu. P.; Bakut, P. A.

1994-03-01

334

Novel method for laser focal point positioning on the cover slip for TPP-based microfabrication and detection of the cured structure under optical microscope  

NASA Astrophysics Data System (ADS)

Detection of a single cured structure in two-photon photopolymerization (TPP) based microstructure fabrication requires the laser focal spot to be exactly positioned on the cover slip. This is due to the fact that if the laser focal position is not exactly on the cover slip, the structure may not stick to the cover slip and flow away with the liquid during the washing and developing stages. In this paper, we report a scheme of laser spot positioning for the implementation of TPP process and the detection of a single cured microstructure under an optical microscope. For this, a novel yet very simple approach is devised and an uncomplicated procedure is developed. Experimental results are also included to prove the worthiness of the devised method.

Najam, Muhammad Tallal Bin; Arif, Khalid Mahmood; Lee, Yong-Gu

2013-04-01

335

Position and velocity sensitivities at the triangular libration points in the restricted problem of three bodies when the bigger primary is an oblate body  

NASA Astrophysics Data System (ADS)

In this paper we have examined the stability of triangular libration points in the restricted problem of three bodies when the bigger primary is an oblate spheroid. Here we followed the time limit and computational process of Tuckness (Celest. Mech. Dyn. Mech. 61, 1-19, 1995) on the stability criteria given by McKenzie and Szebehely (Celest. Mech. 23, 223-229, 1981). In this study it was found that in comparison to other studies the value of the critical mass ? c has been reduced due to oblateness of the bigger primary, i.e. the range of stability of the equilateral triangular libration points reduced with the increase of the oblateness parameter I and hence the order of commensurability was increased.

Hassan, M. R.; Antia, H. M.; Bhatnagar, K. B.

2013-07-01

336

Precision Joining Center.  

National Technical Information Service (NTIS)

The establishment of a Precision Joining Center (PJC) is proposed. The PJC will be a cooperatively operated center with participation from U.S. private industry, the Colorado School of Mines, and various government agencies, including the Department of En...

J. W. Powell

1991-01-01

337

Precision Web Searching.  

National Technical Information Service (NTIS)

Report developed under SBIR contract for topic AF99-136, 'Intelligent Web Assistant'. The technical feasibility of a new approach to precisely searching multiple, distributed, heterogeneous information sources was demonstrated. This new approach combines ...

K. Romanik

2000-01-01

338

Experimental study on the precise orbit determination of the BeiDou navigation satellite system.  

PubMed

The regional service of the Chinese BeiDou satellite navigation system is now in operation with a constellation including five Geostationary Earth Orbit satellites (GEO), five Inclined Geosynchronous Orbit (IGSO) satellites and four Medium Earth Orbit (MEO) satellites. Besides the standard positioning service with positioning accuracy of about 10 m, both precise relative positioning and precise point positioning are already demonstrated. As is well known, precise orbit and clock determination is essential in enhancing precise positioning services. To improve the satellite orbits of the BeiDou regional system, we concentrate on the impact of the tracking geometry and the involvement of MEOs, and on the effect of integer ambiguity resolution as well. About seven weeks of data collected at the BeiDou Experimental Test Service (BETS) network is employed in this experimental study. Several tracking scenarios are defined, various processing schemata are designed and carried out; and then, the estimates are compared and analyzed in detail. The results show that GEO orbits, especially the along-track component, can be significantly improved by extending the tracking network in China along longitude direction, whereas IGSOs gain more improvement if the tracking network extends in latitude. The involvement of MEOs and ambiguity-fixing also make the orbits better. PMID:23529116

He, Lina; Ge, Maorong; Wang, Jiexian; Wickert, Jens; Schuh, Harald

2013-03-01

339

Experimental Study on the Precise Orbit Determination of the BeiDou Navigation Satellite System  

PubMed Central

The regional service of the Chinese BeiDou satellite navigation system is now in operation with a constellation including five Geostationary Earth Orbit satellites (GEO), five Inclined Geosynchronous Orbit (IGSO) satellites and four Medium Earth Orbit (MEO) satellites. Besides the standard positioning service with positioning accuracy of about 10 m, both precise relative positioning and precise point positioning are already demonstrated. As is well known, precise orbit and clock determination is essential in enhancing precise positioning services. To improve the satellite orbits of the BeiDou regional system, we concentrate on the impact of the tracking geometry and the involvement of MEOs, and on the effect of integer ambiguity resolution as well. About seven weeks of data collected at the BeiDou Experimental Test Service (BETS) network is employed in this experimental study. Several tracking scenarios are defined, various processing schemata are designed and carried out; and then, the estimates are compared and analyzed in detail. The results show that GEO orbits, especially the along-track component, can be significantly improved by extending the tracking network in China along longitude direction, whereas IGSOs gain more improvement if the tracking network extends in latitude. The involvement of MEOs and ambiguity-fixing also make the orbits better.

He, Lina; Ge, Maorong; Wang, Jiexian; Wickert, Jens; Schuh, Harald

2013-01-01

340

A novel Position-Based Visual Servoing approach for robust global stability with feature points kept within the Field-of-View  

Microsoft Academic Search

In this paper, we shed new light on PBVS (Position-Based Visual Servoing) by introducing the concept of a 3D (Dimension) visible set for PBVS, which can serve to play exactly the role of the 2D visible set, image plane, for IBVS. Our 3D visible set is convex even in the presence of uncertainties in intrinsic and extrinsic parameters of the

In-Joong Ha; Do-Hwan Park; Jeong-Hun Kwon

2010-01-01

341

Third-order point contact approach for five-axis sculptured surface machining using non-ball-end tools (II): Tool positioning strategy  

Microsoft Academic Search

Based on the mathematical model describing the third-order approximation of the cutter envelope surface according to one given\\u000a cutter location (CL), a tool positioning strategy is proposed for efficiently machining free-form surfaces with non-ball-end\\u000a cutters. The optimal CL is obtained by adjusting the inclination and tilt angles of the cutter until its envelope surface\\u000a and the design surface have the

LiMin Zhu; Han Ding; YouLun Xiong

2010-01-01

342

The Effect of Processing Technique and Reference Frame Definition on Noise in CGPS Position Time Series  

Microsoft Academic Search

In this presentation we investigate the effects of GPS processing techniques and strategies, and the related reference frame realization on the stochastic properties of continuous GPS (CGPS) position time series. It was of particular interest to establish whether and how different GPS processing strategies, e.g. double differencing (DD) and precise point positioning (PPP), the use of different orbit and clock

F. N. Teferle; S. D. Williams; H. P. Kierulf; R. M. Bingley; H. Plag

2005-01-01

343

High precision fiber development  

NASA Astrophysics Data System (ADS)

The improvement of single-mode precision fiber is critical to the efficient use of these fibers in connectors and to allow for low loss splices. Similarly, the alignment of fibers to integrated optic devices demands high precision. Likewise, the precision of large core multimode fibers affects coupler and connector losses as well as overall optical and physical performance. In accordance with the statement of work (SOW), EOPD has evaluated the parameters that affect the fabrication of high precision 100 micrometer core fiber and single-mode precision fiber. ITT EOPD has completed the full dimensional evaluation of precision shrunk, ground, and polished natural fused quartz tubing. Additionally, ITT has verified the od uniformity of precision shrunk, ground, and polished Vycor brand silica glass tubing. Fibers made from preforms utilizing the above substrates met all requirements of this contract. The large core deliverable had a fiber od of 140 micrometers with a fiber core diameter of 100.1 micrometers, well within the limits of the contract. Other measurements showed the core eccentricity to be less than 0.08%; optical loss at 0.85 micrometers was 7.94 dB/km while the NA was 0.29. Measurements of the low NA deliverable revealed an average NA of 0.11, an od of 80.5 micrometers, and a core eccentricity of 0.20%. For the high NA fiber, the NA value ran 0.20; the od was the same as the low NA, 80.5 micrometers, while the core eccentricity ran less than 0.20%.

Akers, F. I.; Shepherd, H. D.

1981-01-01

344

Precision steering of an optical trap by electro-optic deflection  

PubMed Central

We designed, constructed, and tested a single-beam optical trapping instrument employing twin electro-optic deflectors (EODs) to steer the trap in the specimen plane. Compared to traditional instruments based on acousto-optic deflectors (AODs), EOD-based traps offer a significant improvement in light throughput and a reduction in deflection-angle (pointing) errors. These attributes impart improved force and position resolution, making EOD-based traps a promising alternative for high precision nanomechanical measurements of biomaterials.

Valentine, Megan T.; Guydosh, Nicholas R.; Gutierrez-Medina, Braulio; Fehr, Adrian N.; Andreasson, Johan O.; Block, Steven M.

2010-01-01

345

Optimistic Parallelization of Floating-Point Accumulation  

Microsoft Academic Search

Floating-point arithmetic is notoriously non- associative due to the limited precision representation which demands intermediate values be rounded to fit in the available precision. The resulting cyclic dependency in floating-point ac- cumulation inhibits parallelization of the computation, including efficient use of pipelining. In practice, however, we observe that floating-point operations are \\

Nachiket Kapre; André Dehon

2007-01-01

346

[A positioning method of ultrasound probe in MR system].  

PubMed

This paper provides a method of positioning the ultrasound probe in MR system. Machining 6 slots or cylinder perpendicular to the ultrasound probe surface on the edge of ultrasound probe as markers, 12 central cylinder ends are chosen as positioning points. By calculating these positioning points' coordinates in MR's coordinate system, the coordinate transformation between the ultrasound and MR coordinate system can be computed. Furthermore, by taking advantage of redundant information, calculating errors can be reduced and the precision can be improved. PMID:24015606

Wei, Bo; Shen, Guofeng; Chen, Sheng; Zhu, Mengyuan; Su, Zhiqiang; Chen, Yazhu

2013-05-01

347

ACCESS pointing control system  

NASA Astrophysics Data System (ADS)

ACCESS (Actively-Corrected Coronagraph for Exoplanet System Studies) was one of four medium-class exoplanet concepts selected for the NASA Astrophysics Strategic Mission Concept Study (ASMCS) program in 2008/2009 [14, 15]. The ACCESS study evaluated four major coronagraph concepts under a common space observatory. This paper describes the high precision pointing control system (PCS) baselined for this observatory.

Brugarolas, Paul; Alexander, James; Trauger, John; Moody, Dwight; Egerman, Robert; Vallone, Phillip; Elias, Jason; Hejal, Reem; Camelo, Vanessa; Bronowicki, Allen; O'Connor, David; Patrick, Richard; Orzechowski, Pawel; Spittler, Connie; Lillie, Chuck

2010-07-01

348

Conservation of the Conformation and Positive Charges of Hepatitis C Virus E2 Envelope Glycoprotein Hypervariable Region 1 Points to a Role in Cell Attachment  

PubMed Central

Chronic hepatitis C virus (HCV) infection is a major cause of liver disease. The HCV polyprotein contains a hypervariable region (HVR1) located at the N terminus of the second envelope glycoprotein E2. The strong variability of this 27-amino-acid region is due to its apparent tolerance of amino acid substitutions together with strong selection pressures exerted by anti-HCV immune responses. No specific function has so far been attributed to HVR1. However, its presence at the surface of the viral particle suggests that it might be involved in viral entry. This would imply that HVR1 is not randomly variable. We sequenced 460 HVR1 clones isolated at various times from six HCV-infected patients receiving alpha interferon therapy (which exerts strong pressure towards quasispecies genetic evolution) and analyzed their amino acid sequences together with those of 1,382 nonredundant HVR1 sequences collected from the EMBL database. We found that (i) despite strong amino acid sequence variability related to strong pressures towards change, the chemicophysical properties and conformation of HVR1 were highly conserved, and (ii) HVR1 is a globally basic stretch, with the basic residues located at specific sequence positions. This conservation of positively charged residues indicates that HVR1 is involved in interactions with negatively charged molecules such as lipids, proteins, or glycosaminoglycans (GAGs). As with many other viruses, possible interaction with GAGs probably plays a role in host cell recognition and attachment.

Penin, Francois; Combet, Christophe; Germanidis, Georgios; Frainais, Pierre-Olivier; Deleage, Gilbert; Pawlotsky, Jean-Michel

2001-01-01

349

Precision data from LEP  

SciTech Connect

This conference report summarizes recent experimental progress on precise electroweak tests at the e{sup +}e{sup -} collider LEP. These data provide primarily a test of the Z propagator and the Zf{bar f} vertex. However, by imposing certain assumptions on the structure of the underlying theory, they also constrain vector boson self interactions. We review briefly new results concerning the Z line shape, polarization asymmetries and electroweak measurements with heavy quarks. We discuss the consistency of LEP high precision electroweak measurements within themselves with those from other experiments and with the Standard Model. {copyright} 1995 {ital American Institute of Physics.}

Schaile, D. [CERN, CH1211 Geneva (Switzerland)

1995-11-01

350

Points on Computable Curves of Computable Lengths  

NASA Astrophysics Data System (ADS)

A computable plane curve is defined as the image of a computable real function from a closed interval to the real plane. As it is showed by Ko [7] that the length of a computable curve is not necessarily computable, even if the length is finite. Therefore, the set of the computable curves of computable lengths is different from the set of the computable curves of finite lengths. In this paper we show further that the points covered by these two sets of curves are different as well. More precisely, we construct a computable curve K of a finite length and a point z on the curve K such that the point z does not belong to any computable curve of computable length. This gives also a positive answer to an open question of Gu, Lutz and Mayordomo in [4].

Rettinger, Robert; Zheng, Xizhong

351

Precision contour gage  

DOEpatents

An apparatus for gaging the contour of a machined part includes a rotary slide assembly and a linear probe assembly supported by the rotary slide assembly. The linear probe assembly is comprised of a suspension arm and a tip assembly including a probe tip for contacting the part. The suspension arm is supported by the rotary slide assembly and includes a slider portion which is capable of sliding upon a complementary rail located on a rotating platform at the top of the rotary slide assembly. By engagement of the slider with the rail, the linear probe assembly is capable of being positioned with respect to the rotary slide assembly. Repositioning is required when a concave part to be measured is substituted for a convex part or vice versa. A kinematic mount supports the entire contour gaging apparatus. A motor drives the rotary slide assembly, and the motor is controlled by a numerical control apparatus. The rotation of the rotary slide assembly is measured by a digital encoder. The probe tip provides a measure of linear displacement of the tip on the surface of the part. As the rotary slide assembly rotates and as the probe tip contact the part, a series of actual data points are generated representing the actual contour of the part. In a numerical controller, the actual contour is compared with a stored ideal contour, and a disparity between the two is calculated. In real-time, the settings of the machining apparatus may be adjusted by the numerical controller, and additional machining operations can continue until the actual contour is as close to the ideal contour as desired. 4 figs.

Bieg, L.F.

1989-02-09

352

Lean and Agile Precision Manufacturing Systems.  

National Technical Information Service (NTIS)

A quasi-kinematic coupling (QKC) is an alignment interface that can be used to make low-cost assemblies with sub-micron precision and/or sealing contact. Unlike kinematic couplings that rely on point contacts formed by mating balls in v-grooves, quasi-kin...

A. H. Slocum

2002-01-01

353

Spark gap device for precise switching  

Microsoft Academic Search

A spark gap device for precise switching of an energy storage capacitor into an exploding bridge wire load is disclosed. Niobium electrodes having a melting point of 2,415 degrees centigrade are spaced apart by an insulating cylinder to define a spark gap. The electrodes are supported by conductive end caps which, together with the insulating cylinder, form a hermetically sealed

Boettcher

1984-01-01

354

Spark gap device for precise switching  

Microsoft Academic Search

A spark gap device for precise switching of an energy storage capacitor into an exploding bridge wire load is disclosed. Niobium electrodes having a melting point of 2,415 degrees centrigrade are spaced apart by an insulating cylinder to define a spark gap. The electrodes are supported by conductive end caps which, together with the insulating cylinder, form a hermetically sealed

Boettcher; Gordon E

1984-01-01

355

Precise GRACE baseline determination using GPS  

Microsoft Academic Search

Precision relative navigation is an essential aspect of spacecraft formation flying missions, both from an operational and a scientific point of view. When using GPS as a relative distance sensor, dual-frequency receivers are required for high accuracy at large inter-satellite separations. This allows for a correction of the relative ionospheric path delay and enables double difference integer ambiguity resolution. Although

Remco Kroes; Oliver Montenbruck; William Bertiger; Pieter Visser

2005-01-01

356

Integrated Precision Tuning System.  

National Technical Information Service (NTIS)

A brief history of the Precision Integrated Tuner program from its inception to date is given. Some of the more interesting highlights in the evolution of the final design are presented, including a brief outline of the factual data to be presented. A sum...

G. J. Luhowy

1965-01-01

357

Precision liquid level sensor  

DOEpatents

A precision liquid level sensor utilizes a balanced R. F. bridge, each arm including an air dielectric line. Changes in liquid level along one air dielectric line imbalance the bridge and create a voltage which is directly measurable across the bridge. 2 figs.

Field, M.E.; Sullivan, W.H.

1985-01-29

358

Precision Airdrop System SPADES.  

National Technical Information Service (NTIS)

In the Netherlands a cargo precision delivery system for 100 - 1000 kg payloads utilizing ram air parachutes for different weight classes has been developed by Dutch Space in partnership with the National Aerospace Laboratory NLR. The system is based on G...

H. W. Jentink J. W. Wegereef

2006-01-01

359

Precision liquid level sensor  

DOEpatents

A precision liquid level sensor utilizes a balanced R. F. bridge, each arm including an air dielectric line. Changes in liquid level along one air dielectric line imbalance the bridge and create a voltage which is directly measurable across the bridge.

Field, Michael E. (Albuquerque, NM); Sullivan, William H. (Albuquerque, NM)

1985-01-01

360

Precise measurement of positronium  

NASA Astrophysics Data System (ADS)

Positronium is an ideal system for research into bound-state quantum electrodynamics. In this paper, many properties of positronium are precisely measured and compared with theory. Two properties, the lifetime of ortho-positronium and ground-state hyperfine splitting, are discussed.

Namba, Toshio

2012-12-01

361

Precision tip-tilt-piston actuator that provides exact constraint  

DOEpatents

A precision device which can precisely actuate three degrees of freedom of an optic mount, commonly referred to as tip, tilt, and piston. The device consists of three identical flexure mechanisms, an optic mount to be supported and positioned, a structure that supports the flexure mechanisms, and three commercially available linear actuators. The advantages of the precision device is in the arrangement of the constraints offered by the flexure mechanism and not in the particular design of the flexure mechanisms, as other types of mechanisms could be substituted. Each flexure mechanism constrains two degrees of freedom in the plane of the mechanisms and one direction is actuated. All other degrees of freedom are free to move within the range of flexure mechanisms. Typically, three flexure mechanisms are equally spaced in angle about to optic mount and arranged so that each actuated degree of freedom is perpendicular to the plane formed by the optic mount. This arrangement exactly constrains the optic mount and allows arbitrary actuated movement of the plane within the range of the flexure mechanisms. Each flexure mechanism provides a mechanical advantage, typically on the order of 5:1, between the commercially available actuator and the functional point on the optic mount. This improves resolution by the same ratio and stiffness by the square of the ratio.

Hale, Layton C. (Livermore, CA)

1999-01-01

362

Positioning apparatus  

DOEpatents

An apparatus is provided for precisely adjusting the position of an article relative to a beam emerging from a neutron source disposed in a housing. The apparatus includes a support pivotably mounted on a movable base plate and freely suspended therefrom. The support is gravity biased toward the housing and carries an article holder movable in a first direction longitudinally of the axis of said beam and normally urged into engagement against said housing. Means are provided for moving the base plate in two directions to effect movement of the suspended holder in two mutually perpendicular directions, respectively, normal to the axis of the beam.

Vogel, M.A.; Alter, P.

1983-07-07

363

American Precision Museum  

NSDL National Science Digital Library

Housed in the historic Robbins & Lawrence Armory in Windsor, Vermont, the American Precision Museum "celebrates the ingenuity of our mechanical forebears, and explores the effects of their work on everyday lives." Interestingly enough, some of the tools and methods that made mass production possible were developed at this very armory, and the concept of precision manufacturing provides "the foundation for modern industry around the world." First-time visitors should start by viewing the 8.5-minute introductory film on the homepage, as it provides a good overview of the museum. Next, visitors should look over the "Machine Tool Hall of Fame" area. Here they can learn about various inductees, including Frank Lyman Cone, Edward P. Bullard, and William L. Bryant, who developed the technology that made the rapid production of bearing races possible. The site is rounded out by information about visiting the museum, along with a link to their mailing list.

364

Precision Calculation Project Report  

Microsoft Academic Search

The complete list of definitions for quantities relevant in the analysis of SLD\\/LEP-1 results around the Z-resonance is given. The common set of conventions adopted by the programs TOPAZ0 and ZFITTER, following the recommendations of the LEP electroweak working group, is reviewed. The relevance of precision calculations is discussed in detail both for pseudo-observables (PO) and for realistic observables (RO).

Dmitri Bardin; Martin Grunewald; Giampiero Passarino

1999-01-01

365

Precise DC current sensors  

Microsoft Academic Search

Three novel DC current sensors are described. Portable 40 A DC current clamps have resolution of 1 mA and high immunity to unclamped currents and external fields. AC\\/DC comparator with amorphous core may serve for precise measurement of DC currents with AC component up to 1 kHz. Magnetoresistive sensor field has limited accuracy but potential bandwidth from DC to 1

P. Ripka; P. Kejik; P. Kaspar; K. Draxler

1996-01-01

366

Precision surface measurement.  

PubMed

Surface size, geometry and texture are some of the most influential subjects in the fields of precision and ultra-precision engineering, defining the functional interface through which emerging products operate. Next-generation products demand super-smooth surfaces, freeform geometries or even deterministically introduced microstructures to provide functional performance. Technological progress using these surfaces types is possible only if the associated manufacturing processes are rigorously controlled and the surfaces are measurable. Metrology for advanced surfaces is not established. The current state of the art is challenged in respect to (i) surface characteristics, extremity of size, ultra precision, quality, geometric complexity, or combinations of these aspects, and (ii) measurement technology for the manufacturing environment, in particular, online, non-contact, high speed, ease of use, small footprint and robustness. This study addresses the challenges in this subject area and discusses some fundaments and principles derived from interdisciplinary research. The combination of these aspects is enabling the creation of manufacturing-environment-based measurement technology. This is expected to facilitate advanced surface manufacture over a wide range of sectors, including large science programmes and high-technology engineering. PMID:22802503

Jiang, X

2012-08-28

367

Automatic titrator for high precision plutonium assay  

SciTech Connect

Highly precise assay of plutonium metal is required for accountability measurements. We have developed an automatic titrator for this determination which eliminates analyst bias and requires much less analyst time. The analyst is only required to enter sample data and start the titration. The automated instrument titrates the sample, locates the end point, and outputs the results as a paper tape printout. Precision of the titration is less than 0.03% relative standard deviation for a single determination at the 250-mg plutonium level. The titration time is less than 5 min.

Jackson, D.D.; Hollen, R.M.

1986-01-01

368

Precision Assembly with a Magnetically Levitated Wrist  

Microsoft Academic Search

A magnetically levitated six-degree-of-freedom fine motion wrist design based on the prototype magic wrist described by R.H. Hollis et al. (1991) is introduced. Its use for automated assembly, where delicate accommodating motion and precise positioning is required, is discussed. The new wrist is smaller than the prototypes and has several improved features. Parts positioning and assembly strategies are discussed in

Oh Sang-rok; Ralph L. Hollis; S. E. Salcudean

1993-01-01

369

Computation of High-Order Maps to Multiple Machine Precision  

NASA Astrophysics Data System (ADS)

The Beam Dynamics simulation package in COSY INFINITY is built upon a differential algebra data type. With it, it is possible to compute transfer maps or arbitrary systems to arbitrary order. However, this data type is limited by the precision of the underlying floating point number model provided by the computer processor. We will present a method to extend the effective precision of the calculations based purely on standard floating point operations. Those algorithms are then integrated into the differential algebra data type to efficiently extend the available precision, without unnecessarily affecting overall efficiency. To that effect, the precision of each coefficient is adjusted automatically during the calculation. We will then proceed to show the effectiveness of our implementation by calculating high precision maps of combinations of homogeneous dipole segments, for which the exact results are known, and comparing the high precision coefficients with the results produced by the traditional COSY beam physics package.

Wittig, Alexander; Berz, Martin

370

Precision electroweak measurements  

SciTech Connect

Recent electroweak precision measurements fro {ital e}{sup +}{ital e}{sup -} and {ital p{anti p}} colliders are presented. Some emphasis is placed on the recent developments in the heavy flavor sector. The measurements are compared to predictions from the Standard Model of electroweak interactions. All results are found to be consistent with the Standard Model. The indirect constraint on the top quark mass from all measurements is in excellent agreement with the direct {ital m{sub t}} measurements. Using the world`s electroweak data in conjunction with the current measurement of the top quark mass, the constraints on the Higgs` mass are discussed.

Demarteau, M.

1996-11-01

371

How to read floating point numbers accurately  

Microsoft Academic Search

Converting decimal scientific notation into binary floating point is nontrivial, but this conversion can be performed with the best possible accuracy without sacrificing efficiency.Consider the problem of converting decimal scientific notation for a number into the best binary floating point approximation to that number, for some fixed precision. This problem cannot be solved using arithmetic of any fixed precision. Hence

William D. Clinger

2004-01-01

372

How to read floating point numbers accurately  

Microsoft Academic Search

Consider the problem of converting decimal scientific notation for a number into the best binary floating point approximation to that number, for some fixed precision. This problem cannot be solved using arithmetic of any fixed precision. Hence the IEEE Standard for Binary Floating-Point Arithmetic does not require the result of such a conversion to be the best approximation.This paper presents

William D. Clinger

1990-01-01

373

White-Point Preservation Enforces Positivity  

Microsoft Academic Search

It is commonplace to use a linear transform to map device RGBs to XYZs. Two particular types of trans- forms have been developed based on the assumptions that we either maximally ignorant or maximally prescient about the world. Under the maximum ignorance assumption, it is assumed that nothing is known about the spectral statistics of the world and so the

Graham D. Finlayson

1998-01-01

374

The estimate of ballistic trajectory and the analysis of its precision in space for early warning of medium or low orbit satellite  

NASA Astrophysics Data System (ADS)

In this paper, we studied the problem of estimating trajectory parameters of ballistic missile (BM) such as the first detected point and impact position, in space early warning of a single low orbit satellite, and provided corresponding precision analysis. The main idea is that through matching the observation trajectory data to the trajectory equation of free flight phase, first detected point and the main trajectory is determined. Simulation results review that those algorithms in this paper is efficient.

Long, Han; Li, Zhenjie; Yi, Dongyun

2005-11-01

375

Precision flyer initiator  

DOEpatents

A precision flyer initiator forms a substantially spherical detonation wave in a high explosive (HE) pellet. An explosive driver, such as a detonating cord, a wire bridge circuit or a small explosive, is detonated. A flyer material is sandwiched between the explosive driver and an end of a barrel that contains an inner channel. A projectile or ``flyer`` is sheared from the flyer material by the force of the explosive driver and projected through the inner channel. The flyer than strikes the HE pellet, which is supported above a second end of the barrel by a spacer ring. A gap or shock decoupling material delays the shock wave in the barrel from predetonating the HE pellet before the flyer. A spherical detonation wave is formed in the HE pellet. Thus, a shock wave traveling through the barrel fails to reach the HE pellet before the flyer strikes the HE pellet. The precision flyer initiator can be used in mining devices, well-drilling devices and anti-tank devices. 10 figs.

Frank, A.M.; Lee, R.S.

1998-05-26

376

Excite Precision Search  

NSDL National Science Digital Library

Hot on the heels of AltaVista's Raging Search (see the May 5, 2000 Scout Report) comes another returned and (somewhat) slimmed-down search engine that focuses on relevant results. Like Raging Search, Excite's new Precision Search uses Google-style link analysis technology ("Deep Analysis") to help identify the most useful sites. Test queries produced consistently relevant results among the top few returns, though an indication of the number of total returns would be helpful, with two banner ads and (in some but not all cases) a Quick Results box on the left that could be quite handy for consumer-related searching. For instance, a search for "Plymouth" yielded links to research and comparisons, blue book values, financing, and service and repair information in the Quick Results box. I was also pleased to see that clicking on one of the other search categories (category, news, photo, audio/video) instantly produces returns for the original query, though the photo databases available seem somewhat limited compared to, say, AltaVista. While users searching for "official" sites will still do best at Google, those who also search for additional resources such as news, photos, and audio/video content may wish to give Excite Precision a run-through.

377

Precision flyer initiator  

DOEpatents

A precision flyer initiator forms a substantially spherical detonation wave in a high explosive (HE) pellet. An explosive driver, such as a detonating cord, a wire bridge circuit or a small explosive, is detonated. A flyer material is sandwiched between the explosive driver and an end of a barrel that contains an inner channel. A projectile or "flyer" is sheared from the flyer material by the force of the explosive driver and projected through the inner channel. The flyer than strikes the HE pellet, which is supported above a second end of the barrel by a spacer ring. A gap or shock decoupling material delays the shock wave in the barrel from predetonating the HE pellet before the flyer. A spherical detonation wave is formed in the HE pellet. Thus, a shock wave traveling through the barrel fails to reach the HE pellet before the flyer strikes the HE pellet. The precision flyer initiator can be used in mining devices, well-drilling devices and anti-tank devices.

Frank, Alan M. (Livermore, CA); Lee, Ronald S. (Livermore, CA)

1998-01-01

378

Labeling Points with Weights  

Microsoft Academic Search

Abstract. Annotating maps, graphs, and diagrams with pieces of text is an important step in information visualization that is usually referred to as label placement. We define nine label-placement models for labeling points with axis-parallel rectangles given a weight for each point. There are two groups; fixed-position models and slider models. We aim to maximize,the weight sum of those points

Sheung-hung Poon; Chan-su Shin; Tycho Strijk; Takeaki Uno; Alexander Wolff

2003-01-01

379

Precision Bearing Grease Selection Guide.  

National Technical Information Service (NTIS)

The study was initiated to develop a precision bearing grease selection guide. As a pan of this study, forty lubricating greases used in precision bearings, including instrument bearings was evaluated in a comprehensive series of laboratory tests in order...

I. Rhee

2006-01-01

380

Topic in Depth - Precision Machining  

NSDL National Science Digital Library

As technology advances and devices become smaller and more complex, the need for precision manufacturing processes is becoming increasingly important. A number of innovative techniques for precision machining have been developed to enable the construction and operation of such contrivances.

2010-09-06

381

Alloys by precision electrodeposition  

NASA Astrophysics Data System (ADS)

We show that a Cu-Ni alloy film of arbitrary composition may be grown by electrodepositing well-defined submonolayer quantities of Cu and Ni in alternation. Active computer control of the deposition process is used to compensate for undesired electrochemical processes, such as partial redissolution of the Ni. Magnetic measurements were used to characterize alloy homogeneity. With this electrodeposition method it is possible to tailor the composition profile of a film with subnanometer precision. As an example, Cu0.19Ni0.81/Cu0.79Ni0.21 alloy/alloy multilayers were fabricated which gave prominent satellite peaks in high angle x-ray diffraction patterns.

Kazeminezhad, I.; Blythe, H. J.; Schwarzacher, W.

2001-02-01

382

Precision QCD at HERA  

NASA Astrophysics Data System (ADS)

HERA was a high-energy electron/positron proton collider with a centre of mass energy of up to 320 GeV operated until summer 2007. The hadronic final state in the regime of deep-inelastic scattering as well as of photoproduction has been thoroughly investigated over a wide range of phase space with the two multi-purpose detectors H1 and ZEUS. The large available HERA data samples of about 0.5 fb-1 per experiment allowed stringent tests of quantum chromodynamics using a variety of different observables connected to the production of jets and heavy quarks. From the jet production measurements the strong coupling constant ?s has been extracted with high precision. Some of the most recent results of the H1 and ZEUS collaborations are presented in this contribution.

Behr, Jörg

2013-01-01

383

Mathematics for modern precision engineering.  

PubMed

The aim of precision engineering is the accurate control of geometry. For this reason, mathematics has a long association with precision engineering: from the calculation and correction of angular scales used in surveying and astronomical instrumentation to statistical averaging techniques used to increase precision. This study illustrates the enabling role the mathematical sciences are playing in precision engineering: modelling physical processes, instruments and complex geometries, statistical characterization of metrology systems and error compensation. PMID:22802502

Scott, Paul J; Forbes, Alistair B

2012-08-28

384

Precision Spectroscopy of Tellurium  

NASA Astrophysics Data System (ADS)

Tellurium (Te_2) is widely used as a frequency reference, largely due to the fact that it has an optical transition roughly every 2-3 GHz throughout a large portion of the visible spectrum. Although a standard atlas encompassing over 5200 cm^{-1} already exists [1], Doppler broadening present in that work buries a significant portion of the features [2]. More recent studies of Te_2 exist which do not exhibit Doppler broadening, such as Refs. [3-5], and each covers different parts of the spectrum. This work adds to that knowledge a few hundred transitions in the vicinity of 444 nm, measured with high precision in order to improve measurement of the spectroscopic constants of Te_2's excited states. Using a Fabry Perot cavity in a shock-absorbing, temperature and pressure regulated chamber, locked to a Zeeman stabilized HeNe laser, we measure changes in frequency of our diode laser to ˜1 MHz precision. This diode laser is scanned over 1000 GHz for use in a saturated-absorption spectroscopy cell filled with Te_2 vapor. Details of the cavity and its short and long-term stability are discussed, as well as spectroscopic properties of Te_2. References: J. Cariou, and P. Luc, Atlas du spectre d'absorption de la molecule de tellure, Laboratoire Aime-Cotton (1980). J. Coker et al., J. Opt. Soc. Am. B {28}, 2934 (2011). J. Verges et al., Physica Scripta {25}, 338 (1982). Ph. Courteille et al., Appl. Phys. B {59}, 187 (1994) T.J. Scholl et al., J. Opt. Soc. Am. B {22}, 1128 (2005).

Coker, J.; Furneaux, J. E.

2013-06-01

385

Precision, Local Search and Unimodal Functions  

Microsoft Academic Search

We investigate the effects of precision on the efficiency of various local search algorithms on 1-D unimodal functions. We\\u000a present a (1+1)-EA with adaptive step size which finds the optimum in O(log?n) steps, where n is the number of points used. We then consider binary (base-2) and reflected Gray code representations with single bit mutations.\\u000a The standard binary method does

Martin Dietzfelbinger; Jonathan E. Rowe; Ingo Wegener; Philipp Woelfel

2011-01-01

386

Profile Guided Code Positioning  

Microsoft Academic Search

This paper presents the results of our investigation of code positioning techniques using execution profile data as input into the compilation process. The primary objective of the positioning is to reduce the overhead of the instruction memory hierarchy. After initial investigation in the literature, we decided to implement two prototypes for the Hewlett-Packard Precision Architecture (PA-RISC). The first, built on

Karl Pettis; Robert C. Hansen

1990-01-01

387

Precision alignment device  

DOEpatents

Apparatus for providing automatic alignment of beam devices having an associated structure for directing, collimating, focusing, reflecting, or otherwise modifying the main beam. A reference laser is attached to the structure enclosing the main beam producing apparatus and produces a reference beam substantially parallel to the main beam. Detector modules containing optical switching devices and optical detectors are positioned in the path of the reference beam and are effective to produce an electrical output indicative of the alignment of the main beam. This electrical output drives servomotor operated adjustment screws to adjust the position of elements of the structure associated with the main beam to maintain alignment of the main beam. 5 figs.

Jones, N.E.

1988-03-10

388

Precision alignment device  

DOEpatents

Apparatus for providing automatic alignment of beam devices having an associated structure for directing, collimating, focusing, reflecting, or otherwise modifying the main beam. A reference laser is attached to the structure enclosing the main beam producing apparatus and produces a reference beam substantially parallel to the main beam. Detector modules containing optical switching devices and optical detectors are positioned in the path of the reference beam and are effective to produce an electrical output indicative of the alignment of the main beam. This electrical output drives servomotor operated adjustment screws to adjust the position of elements of the structure associated with the main beam to maintain alignment of the main beam.

Jones, Nelson E. (Huntington Beach, CA)

1990-01-01

389

Precision flyer initiator  

SciTech Connect

A propulsion point design is presented for lifting geological samples from Mars. Vehicle complexity is kept low by choosing a monopropellant single stage. Little new development is needed, as miniature pump fed hydrazine has been demonstrated. Loading the propellant just prior to operation avoids structural, thermal, and safety constraints otherwise imposed by earlier mission phases. hardware mass and engineering effort are thereby diminished. The Mars liftoff mass is 7/8 hydrazine, <5% propulsion hardware, and >3% each for the payload and guidance.

Frank, A

1999-04-19

390

Precision cosmological parameter estimation  

NASA Astrophysics Data System (ADS)

Experimental efforts of the last few decades have brought. a golden age to mankind's endeavor to understand tine physical properties of the Universe throughout its history. Recent measurements of the cosmic microwave background (CMB) provide strong confirmation of the standard big bang paradigm, as well as introducing new mysteries, to unexplained by current physical models. In the following decades. even more ambitious scientific endeavours will begin to shed light on the new physics by looking at the detailed structure of the Universe both at very early and recent times. Modern data has allowed us to begins to test inflationary models of the early Universe, and the near future will bring higher precision data and much stronger tests. Cracking the codes hidden in these cosmological observables is a difficult and computationally intensive problem. The challenges will continue to increase as future experiments bring larger and more precise data sets. Because of the complexity of the problem, we are forced to use approximate techniques and make simplifying assumptions to ease the computational workload. While this has been reasonably sufficient until now, hints of the limitations of our techniques have begun to come to light. For example, the likelihood approximation used for analysis of CMB data from the Wilkinson Microwave Anistropy Probe (WMAP) satellite was shown to have short falls, leading to pre-emptive conclusions drawn about current cosmological theories. Also it can he shown that an approximate method used by all current analysis codes to describe the recombination history of the Universe will not be sufficiently accurate for future experiments. With a new CMB satellite scheduled for launch in the coming months, it is vital that we develop techniques to improve the analysis of cosmological data. This work develops a novel technique of both avoiding the use of approximate computational codes as well as allowing the application of new, more precise analysis methods. These techniques will help in the understanding of new physics contained in current and future data sets as well as benefit the research efforts of the cosmology community. Our idea is to shift the computationally intensive pieces of the parameter estimation framework to a parallel training step. We then provide a machine learning code that uses this training set to learn the relationship between the underlying cosmological parameters and the function we wish to compute. This code is very accurate and simple to evaluate. It can provide incredible speed- ups of parameter estimation codes. For some applications this provides the convenience of obtaining results faster, while in other cases this allows the use of codes that would be impossible to apply in the brute force setting. In this thesis we provide several examples where our method allows more accurate computation of functions important for data analysis than is currently possible. As the techniques developed in this work are very general, there are no doubt a wide array of applications both inside and outside of cosmology. We have already seen this interest as other scientists have presented ideas for using our algorithm to improve their computational work, indicating its importance as modern experiments push forward. In fact, our algorithm will play an important role in the parameter analysis of Planck, the next generation CMB space mission.

Fendt, William Ashton, Jr.

2009-09-01

391

Precision galactic structure  

SciTech Connect

Optical and IR surveys in progress or in the planning stages will lead to substantial improvements in our picture of the Milky Way as a consequence of their providing large volumes of data with much improved photometric and positional measurements compared with existing datasets.

Kent, S.M.

2001-01-04

392

PRECISION OF BONE MINERAL DENSITY SCANS AT THE PROXIMAL TIBIA  

Technology Transfer Automated Retrieval System (TEKTRAN)

Clinicians rely on knowledge of instrument precision to determine whether a measured change in bone mineral density (BMD) indicates a significant change in that patient's BMD. Precision errors result from improper positioning, inconsistent analysis, and short and long-term instability in densitomet...

393

Modeling GPS satellite attitude variation for precise orbit determination  

Microsoft Academic Search

High precision geodetic application of the Global Positioning System (GPS) require highly precise ephemerides of the GPS satellites. An accurate model for the non-gravitational forces on the GPS satellites is a key to high quality GPS orbit determination, especially in long arcs. In this paper the effect of the satellite solar panel orientation error is investigated. These effects are approximated

D. Kuang; H. J. Rim; B. E. Schutz; P. A. M. Abusali

1996-01-01

394

Applying spatial analysis for precision conservation across the landscape  

Microsoft Academic Search

Although new technologies such as precision farming will contribute to increasing yields per unit area, similarly soil and water conservation will be instrumental in maintaining these increases in productivity while reducing environmental degradation, off-site transport, and water pollution. Initially, 'precision conservation' was defined as the integration of spatial technologies such as global positioning systems (GPS), remote sensing, and geographic information

J. K. Berry; J. A. Delgado; F. J. Pierce; R. Khosla

395

Modeling GPS satellite attitude variation for precise orbit determination  

Microsoft Academic Search

High precision geodetic applications of the Global Positioning System (GPS) require highly precise ephemerides of the GPS satellites. An accurate model for the non-gravitational forces on the GPS satellites is a key to high quality GPS orbit determination, especially in long arcs. In this paper the effect of the satellite solar panel orientation error is investigated. These effects are approximated

D. Kuang; H. J. Rim; B. E. Schutz; P. A. M. Abusali

1996-01-01

396

Precision robotic control of agricultural vehicles on realistic farm trajectories  

NASA Astrophysics Data System (ADS)

High-precision "autofarming", or precise agricultural vehicle guidance, is rapidly becoming a reality thanks to increasing computing power and carrier-phase differential GPS ("CPDGPS") position and attitude sensors. Realistic farm trajectories will include not only rows but also arcs created by smoothly joining rows or path-planning algorithms, spirals for farming center-pivot irrigated fields, and curved trajectories dictated by nonlinear field boundaries. In addition, fields are often sloped, and accurate control may be required either on linear trajectories or on curved contours. A three-dimensional vehicle model which adapts to changing vehicle and ground conditions was created, and a low-order model for controller synthesis was extracted based on nominal conditions. The model was extended to include a towed implement. Experimentation showed that an extended Kalman filter could identify the vehicle's state in real-time. An approximation was derived for the additional positional uncertainty introduced by the noisy "lever-arm correction" necessary to translate the GPS position measurement at the roof antenna to the vehicle's control point on the ground; this approximation was then used to support the assertion that attitude measurement accuracy was as important to control point position measurement as the original position measurement accuracy at the GPS antenna. The low-order vehicle control model was transformed to polar coordinates for control on arcs and spirals. Experimental data showed that the tractor's control, point tracked an arc to within a -0.3 cm mean and a 3.4 cm standard deviation and a spiral to within a -0.2 cm mean and a 5.3 cm standard deviation. Cubic splines were used to describe curve trajectories, and a general expression for the time-rate-of-change of curve-related parameters was derived. Four vehicle control algorithms were derived for curve tracking: linear local-error control based on linearizing the vehicle about the curve's radius of curvature, linear finite-preview control using discrete linear quadratic tracking, nonlinear local error control based on feedback linearization, and nonlinear finite-preview control using nonlinear optimization techniques. The first three algorithms experimentally demonstrated mean tracking errors between zero and four centimeters and standard deviations of roughly four to ten centimeters. The fourth algorithm was computationally too expensive to implement with current technology. In experiment, the feedback linearization algorithm outperformed the other two control algorithms and also used the most control effort. For control on sloped terrain, a variation on bias estimation (termed slope-adjusted bias estimation) was created, based on the terrain slope information calculated from vehicle attitude measurements. Slope-adjusted bias estimation demonstrated a 25% improvement in the standard deviation of the tractor's row-tracking error over "normal" bias estimation on terrain sloped at grades up to 28%. The CPDGPS attitude information was also used to develop a contour-tracking controller that tracked a contour to within a mean height error of 0.5 cm and a standard deviation of 4.3 cm without any prior knowledge of the terrain. These real-time vehicle control results, applicable to any front-wheel-steered vehicle, demonstrate that accurate real-time control is possible over a variety of trajectories needed in a commercial autofarming system. This research is a significant step towards completely automating tractor control because farmers can now build global trajectories composed of the different types of trajectory "building blocks" developed here. Experimental results demonstrate that farmers can expect precision tracking down to the limit of the GPS position and attitude sensors.

Bell, Thomas

397

A novel target LOS calibration method for IR scanning sensor based on control points  

NASA Astrophysics Data System (ADS)

Space based IR system uses the information of target LOS (line of sight) for target location. Recent researches show that the measuring precision of target LOS is usually determined by measuring precision of platform's position and attitude, and deformation of sensor etc. Most methods for improving target location precision are either through improving platform's position and attitude measuring precision or through calib rating the whole image obtained by IR sensor. With the development of measuring technology, it is harder to make a further improvement on the measuring precision of position and attitude of the platform and the expansion of the sensor view make calibrat ion of the whole image with a larger computation cost. In this paper, a method using control points to calibrate target LOS was proposed. Based on the analysis of the imaging process of the scanning sensor of space based IR system, this paper established a modify model of target LOS based on control points, used a bias filter to estimate the bias value of sensor boresight, and finally achieved the mission of target LOS calibrat ion. Different from the traditional calibration method of remote sensing image, the proposed method only made a correct ion on the LOS of suspicious target, but not established the accurate relationship between the all pixels and their real location, and has a similar calibration performance, but more lower computational complexity.

Xue, Yong-Hong; An, Wei; Zhang, Yin-Sheng; Zhang, Tao

2012-12-01

398

Limitations of a single-point evaluation of anti-MDA5 antibody, ferritin, and IL-18 in predicting the prognosis of interstitial lung disease with anti-MDA5 antibody-positive dermatomyositis.  

PubMed

Autoantibodies against melanoma differentiation-associated gene 5 (MDA5) are important serological markers in dermatomyositis (DM) with rapidly progressive interstitial lung disease (ILD). Recent studies noted that anti-MDA5 antibody (anti-MDA5ab), ferritin, and IL-18 are useful biomarkers for evaluating the responses to treatment and the status of ILD in anti-MDA5ab-positive DM. In this study, we further studied the importance of anti-MDA5ab levels and of ferritin and IL-18 concentrations in our patients. These biomarkers could be sometimes useful for evaluating ILD status and/or predicting the prognosis in patients with anti-MDA5ab-positive DM with several exceptional cases. A single-point evaluation of anti-MDA5ab levels and of ferritin and IL-18 concentrations has limitations in predicting the prognosis of ILD with DM. We consider that the timing of initial therapy and the anti-MDA5ab isotype, in addition to the patient's age, are also crucial factors for predicting the prognosis. PMID:23250474

Muro, Yoshinao; Sugiura, Kazumitsu; Akiyama, Masashi

2012-12-19

399

The Integration of Positioning Technologies for Precise Location ID  

Microsoft Academic Search

With the growing trend towards a world where people, vehicles, and other mobile objects are getting more and more interconnected, location information is increasingly becoming a recognized need for providing rapid and timely information to the mobile workforce. More and more products are present in the market that allows location identifications. In this paper, the key deliverable is the Hierarchical

Tee Yong Chew

400

Point Groups  

NSDL National Science Digital Library

This exercise involves identifying symmetry in crystals and using that information to assign crystals to crystal systems and point groups. Students examine cardboard models and wooden blocks and fill their symmetry elements into a table. Then they figure out what what crystal system and point group each sample belongs to and fill in another table.

Perkins, Dexter

401

The use of Global Positioning System techniques for the continuous monitoring of landslides: application to the Super-Sauze earthflow (Alpes-de-Haute-Provence, France)  

Microsoft Academic Search

Recent researches have demonstrated the applicability of using Global Positioning System (GPS) techniques to precisely determine the 3-D coordinates of moving points in the field of natural hazards. Indeed, the detailed analysis of the motion of a landslide, in particular for a near real-time warning system, requires the combination of accurate positioning in three dimensions (infracentimetric) and fine temporal resolution

J.-P. Malet; O. Maquaire; E. Calais

2002-01-01

402

Human grasp point selection.  

PubMed

When we grasp an object, our visuomotor system has to solve an intricate problem: how to find the best out of an infinity of possible contact points of the fingers with the object? The contact point selection model (CoPS) we present here solves this problem and predicts human grasp point selection in precision grip grasping by combining a few basic rules that have been identified in human and robotic grasping. Usually, not all of the rules can be perfectly satisfied. Therefore, we assessed their relative importance by creating simple stimuli that put them into conflict with each other in pairs. Based on these conflict experiments we made model-based grasp point predictions for another experiment with a novel set of complexly shaped objects. The results show that our model predicts the human choice of grasp points very well, and that observers' preferences for their natural grasp angles is as important as physical stability constraints. Incorporating a human grasp point selection model like the one presented here could markedly improve current approaches to cortically guided arm and hand prostheses by making movements more natural while also allowing for a more efficient use of the available information. PMID:23887046

Kleinholdermann, Urs; Franz, Volker H; Gegenfurtner, Karl R

2013-07-25

403

Better position  

NASA Astrophysics Data System (ADS)

The U.S. Global Positioning System (GPS) will soon become more accurate for civilian users, improving the quality of navigation and of some types of scientific research. The Clinton Administration announced March 29 that within a decade, the federal government will stop degrading the civilian GPS signal and will allow nonmilitary users access to the same clear signals that U.S. troops rely upon.Designed as dual-use system with primary use by the American military, the GPS is a constellation of 24 satellites that allows soldiers to determine their exact positions (in latitude and longitude) anywhere in the world. While the GPS is operated by the Department of Defense (DoD), scientists and adventurous civilians have been able to purchase small, portable GPS devices. However, the U.S. military has kept to itself a capability known as “selective availability” that provides a much more precise signal than is available to the public. According to the White House, that selected signal will be available to all users within 4-10 years.

Carlowicz, Michael

404

Real-time compression of point cloud streams  

Microsoft Academic Search

We present a novel lossy compression approach for point cloud streams which exploits spatial and temporal redundancy within the point data. Our proposed compression framework can handle general point cloud streams of arbitrary and varying size, point order and point density. Furthermore, it allows for controlling coding complexity and coding precision. To compress the point clouds, we perform a spatial

Julius Kammerl; Nico Blodow; Radu Bogdan Rusu; Suat Gedikli; Michael Beetz; Eckehard Steinbach

2012-01-01

405

Precision steering of an optical trap by electro-optic deflection.  

PubMed

We designed, constructed, and tested a single-beam optical trapping instrument employing twin electro-optic deflectors (EODs) to steer the trap in the specimen plane. Compared with traditional instruments based on acousto-optic deflectors (AODs), EOD-based traps offer a significant improvement in light throughput and a reduction in deflection-angle (pointing) errors. These attributes impart improved force and position resolution, making EOD-based traps a promising alternative for high-precision nanomechanical measurements of biomaterials. PMID:18347722

Valentine, Megan T; Guydosh, Nicholas R; Gutiérrez-Medina, Braulio; Fehr, Adrian N; Andreasson, Johan O; Block, Steven M

2008-03-15

406

Metrology with ?CT: precision challenge  

NASA Astrophysics Data System (ADS)

Over the last years computed tomography (CT) with conventional x-ray sources has evolved from imaging method in medicine to a well established technology for industrial applications in the field of material science, microelectronics, geology, etc. By using modern microfocus and nanofocus® X-ray tubes, parts can be scanned with sub-micrometer resolutions. Currently, micro-CT is used more and more as a technology for metrological applications. Especially if complex parts with hidden or difficult accessible surfaces have to be measured, CT offers big advantages comparing with conventional tactile or optical coordinate measuring machines (CMMs): high density of measurement points and fast capturing of the complete sample's geometry. When using this modern technology the question arises how precise a CT based CMM can measure in comparison to conventional CMMs? To characterize the metrological capabilities of a tactile or optical CMM, internationally standardized characteristics like length measurement error and probing error are used. To increase the acceptance of CT as a metrological method, the definition and usage of these parameters is important. In this paper, an overview of the process chain in CT based metrology will be given and metrological characteristics will be described. With the help of a special material standard designed and calibrated by PTB-National Metrology Institute of Germany-the influence of methods for beam hardening correction and for surface extraction on the metrological characteristics will be analyzed. It will be shown that with modern micro-CT systems length measurement error of less than 1?m for an object diameter of 20 mm can be reached.

Suppes, Alexander; Neuser, Eberhard

2008-09-01

407

Precise Exceptions in Asynchronous Processors  

Microsoft Academic Search

The presence of precise exceptions in a processor leads to co mplications in its design. Some re- cent processor architectures have sacrificed this requirem ent for performance reasons at the cost of software complexity. We present an implementation strateg y for precise exceptions in asynchronous processors that does not block the instruction fetch when ex ceptions do not occur; the

Rajit Manohar; Mika Nyström; Alain J. Martin

2001-01-01

408

GPS surveying with 1 mm precision using corrections for atmospheric slant path delay  

Microsoft Academic Search

Multipath and atmospheric effects can limit GPS surveying precision. We surveyed a 43 km baseline using large diameter choke ring antennas to reduce multipath and pointed radiometer and barometric data to correct for atmospheric slant delay. Based on 11 daily solutions, atmospheric slant delay corrections improved vertical precision to 1.2 mm rms and horizontal precision to sub-mm. Applications for high

Chris Alber; Randolph Ware; Christian Rocken; Fredrick Solheim

1997-01-01

409

ARPREC: An arbitrary precision computation package  

SciTech Connect

This paper describes a new software package for performing arithmetic with an arbitrarily high level of numeric precision. It is based on the earlier MPFUN package, enhanced with special IEEE floating-point numerical techniques and several new functions. This package is written in C++ code for high performance and broad portability and includes both C++ and Fortran-90 translation modules, so that conventional C++ and Fortran-90 programs can utilize the package with only very minor changes. This paper includes a survey of some of the interesting applications of this package and its predecessors.

Bailey, David H.; Yozo, Hida; Li, Xiaoye S.; Thompson, Brandon

2002-09-01

410

Dew Point  

NSDL National Science Digital Library

Determine the dew point temperature for your classroom through a hands-on experiment. Use humidity and temperature probes to investigate the temperature at which it would rain in your classroom! Learn about water density and the conditions necessary to produce fog or rain.

Consortium, The C.

2011-12-13

411

Proposal for a CLEO precision vertex detector  

SciTech Connect

Fermilab experiment E691 and CERN experiment NA32 have demonstrated the enormous power of precision vertexing for studying heavy quark physics. Nearly all collider experiments now have or are installing precision vertex detectors. This is a proposal for a precision vertex detector for CLEO, which will be the pre-eminent heavy quark experiment for at least the next 5 years. The purpose of a precision vertex detector for CLEO is to enhance the capabilities for isolating B, charm, and tau decays and to make it possible to measure the decay time. The precision vertex detector will also significantly improve strange particle identification and help with the tracking. The installation and use of this detector at CLEO is an important step in developing a vertex detector for an asymmetric B factory and therefore in observing CP violation in B decays. The CLEO environment imposes a number of unique conditions and challenges. The machine will be operating near the {gamma} (4S) in energy. This means that B's are produced with a very small velocity and travel a distance about {1/2} that of the expected vertex position resolution. As a consequence B decay time information will not be useful for most physics. On the other hand, the charm products of B decays have a higher velocity. For the long lived D{sup +} in particular, vertex information can be used to isolate the charm particle on an event-by-event basis. This helps significantly in reconstructing B's. The vertex resolution for D's from B's is limited by multiple Coulomb scattering of the necessarily rather low momentum tracks. As a consequence it is essential to minimize the material, as measured in radiation lengths, in the beam pip and the vertex detector itself. It is also essential to build the beam pipe and detector with the smallest possible radius.

Not Available

1991-01-01

412

Optimal Centroid Position Estimation  

SciTech Connect

The alignment of high energy laser beams for potential fusion experiments demand high precision and accuracy by the underlying positioning algorithms. This paper discusses the feasibility of employing online optimal position estimators in the form of model-based processors to achieve the desired results. Here we discuss the modeling, development, implementation and processing of model-based processors applied to both simulated and actual beam line data.

Candy, J V; McClay, W A; Awwal, A S; Ferguson, S W

2004-07-23

413

Profile guided code positioning  

Microsoft Academic Search

This paper presents the results of our investigation of code positioning techniques using execution profile data as input into the compilation process. The primary objective of the positioning is to reduce the overhead of the instruction memory hierarchy.After initial investigation in the literature, we decided to implement two prototypes for the Hewlett-Packard Precision Architecture (PA-RISC). The first, built on top

Karl Pettis; Robert C. Hansen; Jack W. Davidson

2004-01-01

414

The Lagrange Points  

ERIC Educational Resources Information Center

|This paper presents a derivation of all five Lagrange points by methods accessible to sixth-form students, and provides a further opportunity to match Newtonian gravity with centripetal force. The predictive powers of good scientific theories are also discussed with regard to the philosophy of science. Methods for calculating the positions of the…

Lovell, M.S.

2007-01-01

415

Vibrational drives for precision instruments  

SciTech Connect

The principles underlying the construction of vibrational drives for precision systems are described. The main characteristics of the drives in the asynchronous and synchronous regimes of motion are presented along with their technical specifications.

Kurilo, R.E.; Syanyunas, G.I.

1994-12-01

416

Image processing in precision agriculture  

Microsoft Academic Search

A brief review of our signal and image processing application in precision agriculture is presented. A method for determining sampling frequency for agriculture data is proposed, and some initial results based on data simulation and image processing are reported

Dragoljub Pokrajac; A. Lazarevic; S. Vucetic; T. Fiez; Z. Obradovic

1999-01-01

417

Vacuum Mechanisms of Nanoscale Precision  

Microsoft Academic Search

The principles of design of vacuum mechanims of nanoscale precision are presented. Physical basics of the mechanisms nanoscale\\u000a precision are discussed. Vacuum multicoordinate drives and manipulators are also shown.\\u000a \\u000a The analysis of vacuum technological equipment and vacuum research equipment shows that the most strict requirements for the\\u000a object transference are in electron beam micro lithography equipment. For example, electron beam

E. A. Deulin; V. P. Mikhailov; Yu. V. Panfilov; R. A. Nevshupa

418

Assessment of Accuracy and Precision  

NASA Astrophysics Data System (ADS)

Volumetric glassware, mechanical pipettes, and balances are used in many analytical laboratories. If the basic skills in the use of this glassware and equipment are mastered, laboratory exercises are easier, more enjoyable, and the results obtained are more accurate and precise. Measures of accuracy and precision can be calculated based on the data generated, given the glassware and equipment used, to evaluate the skill of the user as well as the reliability of the instrument and glassware.

Nielsen, S. Suzanne

419

Precision localization of single atom using Autler-Townes microscopy  

Microsoft Academic Search

Detuning of the classical standing wave field with the atomic transition plays an important role in the characterization of the peaks present in Autler-Townes spontaneous spectrum of a three-level atom. We investigate how this detuning effects the position distribution of the atom and show that we gain a precision in position information of the single atom inside the standing wave

S. Qamar; S.-Y. Zhu; M. S. Zubairy

2000-01-01

420

Precision localization of single atom using Autler–Townes microscopy  

Microsoft Academic Search

Detuning of the classical standing wave field with the atomic transition plays an important role in the characterization of the peaks present in Autler–Townes spontaneous spectrum of a three-level atom. We investigate how this detuning effects the position distribution of the atom and show that we gain a precision in position information of the single atom inside the standing wave

Sajid Qamar; Shi-Yao Zhu; M. Suhail Zubairy

2000-01-01

421

Precise and efficient groundness analysis for logic programs  

Microsoft Academic Search

We show how precise groundness information can be extracted from logic programs. The idea is to use abstract interpretation with Boolean functions as “approximations” to groundness dependencies between variables. This idea is not new, and different classes of Boolean functions have been used. We argue, however, that one class, the positive functions, is more suitable than others. Positive Boolean functions

Kim Marriott; Harald Søndergaard

1993-01-01

422

Ultralightweight telescopes and precision pointers as enabling technologies for small low-cost missions  

Microsoft Academic Search

Very high precision, lightweight optical pointing devices, in conjunction with ultra lightweight telescope assemblies are enabling technolgies for small, low cost space satellite platforms. These platforms do not provide a stable pointing platform. High bandwidth, servo controlled pointers compensate for the platform instabilites. A new generation of high bandwidth, very precise pointers are possible because of very low mass mirrors

Dexter Wang; Michael I. Anapol

1995-01-01

423

Graphing Points  

NSDL National Science Digital Library

Let's learn how to use the lines on graphs (the x & y axis) to plot information. Choose any of the activities below to test your knowledge of identifying the coordinates correctly. Meteoroid Coordinates Soccer Coordinates Donut Coordinates Graphing Points Save the Zogs!-Using Linear Equations Using your coordinate plane knowledge and linear equations help to rescue the Zogs! Can you find the axis for these problems too? What have you noticed about linear equations? What do the lines in linear equations look ...

Izzy

2012-02-07

424

Field Emission Current and Electrical Breakdown by a Pointed Cathode Coated with Carbon-Nano-Tube  

Microsoft Academic Search

Feature of field emission current and electrical breakdown was experimentally investigated for very short gap in the range of 0.1mum to 3mum between a pointed cathode coated with Carbon-Nano-Tube (CNT) and a plane anode in vacuum environment. The experimental setup, which consists of the CNT coated cathode, the stainless steel anode and the precise positioning mechanisms actuated by piezoelectric devices,

Yoshinori Hirata; Masayoshi Teramoto; Mizue Mizoshiri; Ukyo Ikeda; Takayoshi Ohji; Kimihiro Ozaki

2007-01-01

425

Precision visual guidance for agricultural applicator aircraft  

NASA Astrophysics Data System (ADS)

The in-cockpit swath centerline identifier (SCI) for aerial applicators uses differentially corrected global positioning system (GPS) signals to determine precise ground track of an aircraft and provide guidance to the pilot for flying patterns for aerial application of materials such as pesticides, herbicides, and fertilizers. Cross track distance from the swath centerline is provided by a heads up light bar display while detailed navigation, position, and status information is provided on an alphanumeric display on a panel mounted console. This system provides straight line guidance when executing a swath and turn-in guidance when proceeding from one swath to the next. It provides a record of the swaths which were sprayed and logs all of the associated navigation and operational data, including time. In addition, it provides navigation information from base to the fields, between fields, and return. The SCI eliminates the need for flaggers while providing improved accuracy of application. Reduced exposure to liability and improved quality control results as the position, altitude, time, and spray status are logged for post flight analysis. The SCI has been used in commercial agricultural applications. Demonstrations of the SCI showed better precision than anticipated.

Hartt, Joseph R.; Bletzacker, Frank R.; Forgette, T. J.; Vetter, Alan A.

1992-07-01

426

A precision force microscope for biophysics  

NASA Astrophysics Data System (ADS)

Single-molecule force spectroscopy studies have produced rich insights into the unfolding of individual proteins. In a typical force spectroscopy experiment, an atomic force microscope (AFM) tip is coupled to a surface-adsorbed protein and force-extension curves are generated by retracting the tip using a piezoelectric (PZT) stage. Force is measured by cantilever deflection. Extension, or more precisely tip-sample separation, is deduced from the PZT stage position used to control the vertical tip position. Thus, this deduced extension is sensitive to vertical mechanical drift of the AFM assembly. We have previously developed an ultrastable AFM in which the tip and the sample positions are independently measured by, and stabilized with respect to, a pair of laser foci in three dimensions. These lasers establish a local reference frame that is insensitive to long-term mechanical drift of the AFM assembly. We have now extended the ultrastable AFM capabilities into liquid and can routinely mechanically unfold proteins at slow pulling velocities, which allows averaging to increase precision. We can also stop pulling altogether and stabilize the tip-sample separation while measuring force. Using these techniques, we are studying the unfolding and re-folding of bacteriorhodopsin, a model transmembrane protein.

King, Gavin; Churnside, Allison; Perkins, Thomas

2009-11-01

427

Extreme point and halving edge search in abstract order types  

PubMed Central

Many properties of finite point sets only depend on the relative position of the points, e.g., on the order type of the set. However, many fundamental algorithms in computational geometry rely on coordinate representations. This includes the straightforward algorithms for finding a halving line for a given planar point set, as well as finding a point on the convex hull, both in linear time. In his monograph Axioms and Hulls, Knuth asks whether these problems can be solved in linear time in a more abstract setting, given only the orientation of each point triple, i.e., the set?s chirotope, as a source of information. We answer this question in the affirmative. More precisely, we can find a halving line through any given point, as well as the vertices of the convex hull edges that are intersected by the supporting line of any two given points of the set in linear time. We first give a proof for sets realizable in the Euclidean plane and then extend the result to non-realizable abstract order types.

Aichholzer, Oswin; Miltzow, Tillmann; Pilz, Alexander

2013-01-01

428

Precision tool holder with flexure-adjustable, three degrees of freedom for a four-axis lathe  

DOEpatents

A precision tool holder for precisely positioning a single point cutting tool on 4-axis lathe, such that the center of the radius of the tool nose is aligned with the B-axis of the machine tool, so as to facilitate the machining of precision meso-scale components with complex three-dimensional shapes with sub-.mu.m accuracy on a four-axis lathe. The device is designed to fit on a commercial diamond turning machine and can adjust the cutting tool position in three orthogonal directions with sub-micrometer resolution. In particular, the tool holder adjusts the tool position using three flexure-based mechanisms, with two flexure mechanisms adjusting the lateral position of the tool to align the tool with the B-axis, and a third flexure mechanism adjusting the height of the tool. Preferably, the flexures are driven by manual micrometer adjusters. In this manner, this tool holder simplifies the process of setting a tool with sub-.mu.m accuracy, to substantially reduce the time required to set the tool.

Bono, Matthew J. (Pleasanton, CA); Hibbard, Robin L. (Livermore, CA)

2008-03-04

429

High precision electrostatic potential calculations for cylindrically symmetric lenses  

SciTech Connect

A method is developed for a potential calculation within cylindrically symmetric electrostatic lenses using mesh relaxation techniques, and it is capable of considerably higher accuracies than currently available. The method involves (i) creating very high order algorithms (orders of 6, 8, and 10) for determining the potentials at points in the net using surrounding point values, (ii) eliminating the effect of the large errors caused by singular points, and (iii) reducing gradients in the high gradient regions of the geometry, thereby allowing the algorithms used in these regions to achieve greater precisions--(ii) and (iii) achieved by the use of telescopic multiregions. In addition, an algorithm for points one unit from a metal surface is developed, allowing general mesh point algorithms to be used in these situations, thereby taking advantage of the enhanced precision of the latter. A maximum error function dependent on a sixth order gradient of the potential is defined. With this the single point algorithmic errors are able to be viewed over the entire net. Finally, it is demonstrated that by utilizing the above concepts and procedures, the potential of a point in a reasonably high gradient region of a test geometry can realize a precision of less than 10{sup -10}.

Edwards, David Jr. [238 Marylyn Lane, Newark, Vermont 05871 (United States)

2007-02-15

430

Satellite positioning  

NASA Astrophysics Data System (ADS)

Geodetic positioning programs with the U.S. Navy Transit and GPS satellite systems and satellite laser ranging programs are described. As of 1982 the number of Doppler receivers had increased to over 16,000 units, 1000 with two-frequency geodetic apparatus. The Nova 1 satellite, launched in 1981, was a drag-free satellite, incorporating a single-axis disturbance compensation system (DISCOS) to continuously correct track aberrations due to perturbing forces acting on the satellite. One of the Transit system units, Nova 1 lowered the broadcast ephemeris prediction errors to 5-15 m rms, compared to the 5-70 m rms error for the Oscar satellite. The Navstar GPS system is in full engineering development and will lead to an 18 satellite configuration, with four in view from any point on earth. Global positioning accuracies of 10 m have been found in tests. The Lageos, Starlette, beacon Explorer-C, and Geos-3 satellites have been used in laser ranging experiments to measure polar motions by reflecting laser light from the ground off reflectors on the satellite surfaces. NASA is currently moving a transportable laser station to Easter Island to obtain an accuracy of 10 cm.

Hill, R. W.

1983-04-01

431

Automation of Precise Time Reference Stations (PTRS)  

NASA Astrophysics Data System (ADS)

The U.S. Naval Observatory is presently engaged in a program of automating precise time stations (PTS) and precise time reference stations (PTBS) by using a versatile mini-computer controlled data acquisition system (DAS). The data acquisition system is configured to monitor locally available PTTI signals such as LORAN-C, OMEGA, and/or the Global Positioning System. In addition, the DAS performs local standard intercomparison. Computer telephone communications provide automatic data transfer to the Naval Observatory. Subsequently, after analysis of the data, results and information can be sent back to the precise time reference station to provide automatic control of remote station timing. The DAS configuration is designed around state of the art standard industrial high reliability modules. The system integration and software are standardized but allow considerable flexibility to satisfy special local requirements such as stability measurements, performance evaluation and printing of messages and certificates. The DAS operates completely independently and may be queried or controlled at any time with a computer or terminal device (control is protected for use by authorized personnel only). Such DAS equipped PTS are operational in Hawaii, California, Texas and Florida.

Wheeler, P. J.

1985-04-01

432

Precision cleaning apparatus and method  

DOEpatents

A precision cleaning apparatus and method are disclosed. The precision cleaning apparatus includes a cleaning monitor further comprising an acoustic wave cleaning sensor such as a quartz crystal microbalance (QCM), a flexural plate wave (FPW) sensor, a shear horizontal acoustic plate mode (SH--APM) sensor, or a shear horizontal surface acoustic wave (SH--SAW) sensor; and measurement means connectable to the sensor for measuring in-situ one or more electrical response characteristics that vary in response to removal of one or more contaminants from the sensor and a workpiece located adjacent to the sensor during cleaning. Methods are disclosed for precision cleaning of one or more contaminants from a surface of the workpiece by means of the cleaning monitor that determines a state of cleanliness and any residual contamination that may be present after cleaning; and also for determining an effectiveness of a cleaning medium for removing one or more contaminants from a workpiece. 11 figs.

Schneider, T.W.; Frye, G.C.; Martin, S.J.

1998-01-13

433

Precision cleaning apparatus and method  

DOEpatents

A precision cleaning apparatus and method. The precision cleaning apparatus includes a cleaning monitor further comprising an acoustic wave cleaning sensor such as a quartz crystal microbalance (QCM), a flexural plate wave (FPW) sensor, a shear horizontal acoustic plate mode (SH--APM) sensor, or a shear horizontal surface acoustic wave (SH--SAW) sensor; and measurement means connectable to the sensor for measuring in-situ one or more electrical response characteristics that vary in response to removal of one or more contaminants from the sensor and a workpiece located adjacent to the sensor during cleaning. Methods are disclosed for precision cleaning of one or more contaminants from a surface of the workpiece by means of the cleaning monitor that determines a state of cleanliness and any residual contamination that may be present after cleaning; and also for determining an effectiveness of a cleaning medium for removing one or more contaminants from a workpiece.

Schneider, Thomas W. (Albuquerque, NM); Frye, Gregory C. (Cedar Crest, NM); Martin, Stephen J. (Albuquerque, NM)

1998-01-01

434

Point Defects  

NASA Astrophysics Data System (ADS)

Point defects are pervasive. They are present in all materials, as a result of the intrinsic thermodynamic equilibrium and of the inevitable levels of impurities. Indeed, elementary chemical thermodynamics shows that if a defect formation reaction (e.g., Frenkel or Schottky formation as discussed below) is associated with a free energy gD, then the equilibrium mole fraction, xD, of defects is given by: x_D = exp ( { - {g_D }/{{nkT} ), where n is the number of defects created in the defect formation process. The equation shows that xd > 0 for T > 0, and also demonstrates that properties dependent on defects will show "Arrhenius"-like temperature dependence.

Catlow, C. R. A.

435

Precision agriculture and food security.  

PubMed

Precision agriculture comprises a set of technologies that combines sensors, information systems, enhanced machinery, and informed management to optimize production by accounting for variability and uncertainties within agricultural systems. Adapting production inputs site-specifically within a field and individually for each animal allows better use of resources to maintain the quality of the environment while improving the sustainability of the food supply. Precision agriculture provides a means to monitor the food production chain and manage both the quantity and quality of agricultural produce. PMID:20150492

Gebbers, Robin; Adamchuk, Viacheslav I

2010-02-12

436

Microbiopsy/precision cutting devices  

DOEpatents

Devices are disclosed for performing tissue biopsy on a small scale (microbiopsy). By reducing the size of the biopsy tool and removing only a small amount of tissue or other material in a minimally invasive manner, the risks, costs, injury and patient discomfort associated with traditional biopsy procedures can be reduced. By using micromachining and precision machining capabilities, it is possible to fabricate small biopsy/cutting devices from silicon. These devices can be used in one of four ways (1) intravascularly, (2) extravascularly, (3) by vessel puncture, and (4) externally. Additionally, the devices may be used in precision surgical cutting. 6 figs.

Krulevitch, P.A.; Lee, A.P.; Northrup, M.A.; Benett, W.J.

1999-07-27

437

PRECISION RADIAL VELOCITIES WITH CSHELL  

SciTech Connect

Radial velocity (RV) identification of extrasolar planets has historically been dominated by optical surveys. Interest in expanding exoplanet searches to M dwarfs and young stars, however, has motivated a push to improve the precision of near-infrared RV techniques. We present our methodology for achieving 58 m s{sup -1} precision in the K band on the M0 dwarf GJ 281 using the CSHELL spectrograph at the 3 m NASA Infrared Telescope Facility. We also demonstrate our ability to recover the known 4 M{sub JUP} exoplanet Gl 86 b and discuss the implications for success in detecting planets around 1-3 Myr old T Tauri stars.

Crockett, Christopher J.; Prato, L. [Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001 (United States); Mahmud, Naved I.; Johns-Krull, Christopher M. [Department of Physics and Astronomy, Rice University, MS-108, 6100 Main Street, Houston, TX 77005 (United States); Jaffe, Daniel T. [Department of Astronomy, University of Texas, R.L. Moore Hall, Austin, TX 78712 (United States); Beichman, Charles A., E-mail: crockett@lowell.edu, E-mail: lprato@lowell.edu, E-mail: naved@rice.edu, E-mail: cmj@rice.edu, E-mail: dtj@astro.as.utexas.edu [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

2011-07-10

438

Microbiopsy/precision cutting devices  

DOEpatents

Devices for performing tissue biopsy on a small scale (microbiopsy). By reducing the size of the biopsy tool and removing only a small amount of tissue or other material in a minimally invasive manner, the risks, costs, injury and patient discomfort associated with traditional biopsy procedures can be reduced. By using micromachining and precision machining capabilities, it is possible to fabricate small biopsy/cutting devices from silicon. These devices can be used in one of four ways 1) intravascularly, 2) extravascularly, 3) by vessel puncture, and 4) externally. Additionally, the devices may be used in precision surgical cutting.

Krulevitch, Peter A. (Pleasanton, CA); Lee, Abraham P. (Walnut Creek, CA); Northrup, M. Allen (Berkeley, CA); Benett, William J. (Livermore, CA)

1999-01-01

439

Spotted Star Light Curves with Enhanced Precision  

NASA Astrophysics Data System (ADS)

The nearly continuous timewise coverage of recent photometric surveys is free of the large gaps that compromise attempts to follow starspot growth and decay as well as motions, thereby giving incentive to improve computational precision for modeled spots. Due to the wide variety of star systems in the surveys, such improvement should apply to light/velocity curve models that accurately include all the main phenomena of close binaries and rotating single stars. The vector fractional area (VFA) algorithm that is introduced here represents surface elements by small sets of position vectors so as to allow accurate computation of circle-triangle overlap by spherical geometry. When computed by VFA, spots introduce essentially no noticeable scatter in light curves at the level of one part in 10,000. VFA has been put into the Wilson-Devinney light/velocity curve program and all logic and mathematics are given so as to facilitate entry into other such programs. Advantages of precise spot computation include improved statistics of spot motions and aging, reduced computation time (intrinsic precision relaxes needs for grid fineness), noise-free illustration of spot effects in figures, and help in guarding against false positives in exoplanet searches, where spots could approximately mimic transiting planets in unusual circumstances. A simple spot growth and decay template quantifies time profiles, and specifics of its utilization in differential corrections solutions are given. Computational strategies are discussed, the overall process is tested in simulations via solutions of synthetic light curve data, and essential simulation results are described. An efficient time smearing facility by Gaussian quadrature can deal with Kepler mission data that are in 30 minute time bins.

Wilson, R. E.

2012-09-01

440

Using GPS and leveling data in local precise geoid determination and case study  

NASA Astrophysics Data System (ADS)

As an important result of developments in high technology, satellite based positioning system has become to use in geodesy and surveying professions. These developments made the measurement works more accurate, more practical and more economic. Today, one of the most recent used satellite based positioning system is GPS (Global Positioning System) and it serves to a very wide range of geodetic applications from monitoring earth crustal deformations till building the basis for a GIS (Geographical Information Systems). The most efficient way to utilize GPS measurement system for mentioned aims is having a reliable geodetic infrastructure in working area. Geodetic infrastructure is a extraterrestrial and time system and involved 4D geodetic reference networks. The forth element of mentioned geodetic