Sample records for precise point positioning

  1. Surveying using GPS Precise Point Positioning

    Microsoft Academic Search

    Ola OVSTEDAL; Narve Schipper KJORSVIK; Jon Glenn

    The technique of Precise Point Positioning (PPP) is a viable alternative to differential methods for precise positioning using Global Navigation Satellite Systems (GNSS). PPP is very cost effective since there is no need for data from local or regional reference stations. Especially in remote areas the logistic is greatly simplified. The PPP method has a potential for centimetre accuracy for

  2. Precise Point Positioning with Partial Ambiguity Fixing

    PubMed Central

    Li, Pan; Zhang, Xiaohong

    2015-01-01

    Reliable and rapid ambiguity resolution (AR) is the key to fast precise point positioning (PPP). We propose a modified partial ambiguity resolution (PAR) method, in which an elevation and standard deviation criterion are first used to remove the low-precision ambiguity estimates for AR. Subsequently the success rate and ratio-test are simultaneously used in an iterative process to increase the possibility of finding a subset of decorrelated ambiguities which can be fixed with high confidence. One can apply the proposed PAR method to try to achieve an ambiguity-fixed solution when full ambiguity resolution (FAR) fails. We validate this method using data from 450 stations during DOY 021 to 027, 2012. Results demonstrate the proposed PAR method can significantly shorten the time to first fix (TTFF) and increase the fixing rate. Compared with FAR, the average TTFF for PAR is reduced by 14.9% for static PPP and 15.1% for kinematic PPP. Besides, using the PAR method, the average fixing rate can be increased from 83.5% to 98.2% for static PPP, from 80.1% to 95.2% for kinematic PPP respectively. Kinematic PPP accuracy with PAR can also be significantly improved, compared to that with FAR, due to a higher fixing rate. PMID:26067196

  3. Elements of GPS precise point positioning

    NASA Astrophysics Data System (ADS)

    Witchayangkoon, Boonsap

    The International GPS Service (IGS) now regularly makes accurate GPS ephemeris and satellite clock information available over the Internet. The satellite coordinates are given in the International Terrestrial Reference Frame (ITRF). This thesis investigates Precise Point Positioning (PPP) using dual and single-frequency pseudorange and carrier phase observations. Both the static and kinematic modes are investigated. The static PPP solution examples use six-hour data sets from four stations. The observations were made while Selective Availability (SA) was active and after it had been discontinued. The static solutions agree to within 10 cm with published coordinates or with solutions obtained from the Jet Propulsion Laboratory (M) PPP Internet service. The kinematic solutions show a discrepancy of less than one meter, mostly around half a meter. For observations with low multipath, the research shows that single-frequency ionosphere-free PPP solutions are equivalent to the dual-frequency solutions. In case of single-frequency observations the pseudorange dominates the solution. Using a priori tropospheric information does not seem to improve dual-frequency PPP solutions as compared to the case when the vertical tropospheric delay is estimated as part of the Kalman filter solution. However, a priori tropospheric information seems to provide benefits to single-frequency kinematic PPP. The Saastamoinen model is used when computing the zenith tropospheric delay. In all cases, the Neill's mapping function is applied. The studies show high correlation between receiver clock and the up coordinate. The troposphere has a high negative correlation with receiver clock and the up coordinate. However, the troposphere is more correlated with the receiver clock than the up component. All solutions incorporate corrections for solid earth tides, relativity, and satellite antenna phase center offsets. Corrections have not been applied for the phase wind-up angle. The widelane and ionospheric functions are used to detect and fix cycle slips in a semi-graphical manner. Since even a single cycle slip significantly falsifies PPP solutions, it is suggested that between-satellite carrier phases be used as another way of detecting slips (now since SA has been discontinued). The software consists mostly of highly modular Mathcad functions that form an excellent base for continued research of PPP.

  4. Kinematic Precise Point Positioning During Marginal Satellite Availability

    Microsoft Academic Search

    N. S. Kjørsvik; O Øvstedal; J. G. O Gjevestad

    Precise Point Positioning (PPP) is a technique where observations from a single GNSS receiver are used to estimate coordinates\\u000a with precision ranging from centimeters to decimeters. PPP does not rely on data from dedicated reference receivers and is\\u000a logistically a very competitive alternative to differential GNSS methods. In areas with reduced satellite availability the\\u000a geometrical strength of the solution will

  5. Adaptive robust Kalman filtering for precise point positioning

    NASA Astrophysics Data System (ADS)

    Guo, Fei; Zhang, Xiaohong

    2014-10-01

    The optimality of precise point postioning (PPP) solution using a Kalman filter is closely connected to the quality of the a priori information about the process noise and the updated mesurement noise, which are sometimes difficult to obtain. Also, the estimation enviroment in the case of dynamic or kinematic applications is not always fixed but is subject to change. To overcome these problems, an adaptive robust Kalman filtering algorithm, the main feature of which introduces an equivalent covariance matrix to resist the unexpected outliers and an adaptive factor to balance the contribution of observational information and predicted information from the system dynamic model, is applied for PPP processing. The basic models of PPP including the observation model, dynamic model and stochastic model are provided first. Then an adaptive robust Kalmam filter is developed for PPP. Compared with the conventional robust estimator, only the observation with largest standardized residual will be operated by the IGG III function in each iteration to avoid reducing the contribution of the normal observations or even filter divergence. Finally, tests carried out in both static and kinematic modes have confirmed that the adaptive robust Kalman filter outperforms the classic Kalman filter by turning either the equivalent variance matrix or the adaptive factor or both of them. This becomes evident when analyzing the positioning errors in flight tests at the turns due to the target maneuvering and unknown process/measurement noises.

  6. Deterministic and Stochastic Receiver Clock Modeling in Precise Point Positioning

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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.

  7. Experimental assessment of the time transfer capability of precise point positioning (PPP)

    Microsoft Academic Search

    Diego Orgiazzi; Patrizia Tavella; François Lahaye

    2005-01-01

    In recent years, many national timing laboratories have installed geodetic global positioning system (GPS) receivers together with their traditional GPS\\/GLONASS common view (CV) receivers and two way satellite time and frequency transfer (TWSTFT) equipment. A method called precise point positioning (PPP) is in use in the geodetic community allowing precise recovery of geodetic GPS receiver position, clock phase and tropospheric

  8. Development of a Real-Time Single-Frequency Precise Point Positioning System and Test Results

    Microsoft Academic Search

    Yang Gao; Yufeng Zhang; Kongzhe Chen

    2006-01-01

    Precise Point Positioning (PPP) has received wide attention in the past several years as one of the next generation RTK technologies. PPP can offer great flexibility and cost-saving to field positioning work as it can eliminates the need to deploy base stations. Centimetre to decimetre accurate positioning accuracy has been widely demonstrated for PPP using a dual-frequency GPS receiver. The

  9. X-ray stereo photogrammetry locating the precise, three-dimensional position of image points

    Microsoft Academic Search

    L. P. Adams

    1981-01-01

    A method of locating analytically the precise position in the object space of an image point such as a foreign body using\\u000a simple stereo X-ray pictures and digitised co-ordinates of common image points identified in the stereo pictures is described.

  10. Precise point positioning with the BeiDou navigation satellite system.

    PubMed

    Li, Min; Qu, Lizhong; Zhao, Qile; Guo, Jing; Su, Xing; Li, Xiaotao

    2014-01-01

    By the end of 2012, China had launched 16 BeiDou-2 navigation satellites that include six GEOs, five IGSOs and five MEOs. This has provided initial navigation and precise pointing services ability in the Asia-Pacific regions. In order to assess the navigation and positioning performance of the BeiDou-2 system, Wuhan University has built up a network of BeiDou Experimental Tracking Stations (BETS) around the World. The Position and Navigation Data Analyst (PANDA) software was modified to determine the orbits of BeiDou satellites and provide precise orbit and satellite clock bias products from the BeiDou satellite system for user applications. This article uses the BeiDou/GPS observations of the BeiDou Experimental Tracking Stations to realize the BeiDou and BeiDou/GPS static and kinematic precise point positioning (PPP). The result indicates that the precision of BeiDou static and kinematic PPP reaches centimeter level. The precision of BeiDou/GPS kinematic PPP solutions is improved significantly compared to that of BeiDou-only or GPS-only kinematic PPP solutions. The PPP convergence time also decreases with the use of combined BeiDou/GPS systems. PMID:24406856

  11. GPS/GLONASS time offset monitoring based on combined Precise Point Positioning (PPP) approach

    NASA Astrophysics Data System (ADS)

    Huang, G.; Zhang, Q.; Fu, W.; Guo, H.

    2015-06-01

    A new strategy is proposed to monitor GPS/GLONASS time offsets for common navigation users using a combined GPS/GLONASS Precise Point Positioning (PPP) method based on the orbit and clock products of different time scales. The results of the inter-system GPS/GLONASS time offset, the user time offset and the inter-system device delay difference were obtained using the proposed method. The properties of these results were analyzed in terms of the stability, precision and variation characteristics. Moreover, the practicality of the time offset results in an actual navigation application was tested and demonstrated. The results indicate that the monitoring and prediction of the user time offset, but not the inter-system time offset, has important values for navigation users.

  12. Tightly Coupled Integration of Ionosphere-Constrained Precise Point Positioning and Inertial Navigation Systems

    PubMed Central

    Gao, Zhouzheng; Zhang, Hongping; Ge, Maorong; Niu, Xiaoji; Shen, Wenbin; Wickert, Jens; Schuh, Harald

    2015-01-01

    The continuity and reliability of precise GNSS positioning can be seriously limited by severe user observation environments. The Inertial Navigation System (INS) can overcome such drawbacks, but its performance is clearly restricted by INS sensor errors over time. Accordingly, the tightly coupled integration of GPS and INS can overcome the disadvantages of each individual system and together form a new navigation system with a higher accuracy, reliability and availability. Recently, ionosphere-constrained (IC) precise point positioning (PPP) utilizing raw GPS observations was proven able to improve both the convergence and positioning accuracy of the conventional PPP using ionosphere-free combined observations (LC-PPP). In this paper, a new mode of tightly coupled integration, in which the IC-PPP instead of LC-PPP is employed, is implemented to further improve the performance of the coupled system. We present the detailed mathematical model and the related algorithm of the new integration of IC-PPP and INS. To evaluate the performance of the new tightly coupled integration, data of both airborne and vehicle experiments with a geodetic GPS receiver and tactical grade inertial measurement unit are processed and the results are analyzed. The statistics show that the new approach can further improve the positioning accuracy compared with both IC-PPP and the tightly coupled integration of the conventional PPP and INS. PMID:25763647

  13. Further characterization of the time transfer capabilities of precise point positioning (PPP): the Sliding Batch Procedure.

    PubMed

    Guyennon, Nicolas; Cerretto, Giancarlo; Tavella, Patrizia; Lahaye, François

    2009-08-01

    In recent years, many national timing laboratories have installed geodetic Global Positioning System receivers together with their traditional GPS/GLONASS Common View receivers and Two Way Satellite Time and Frequency Transfer equipment. Many of these geodetic receivers operate continuously within the International GNSS Service (IGS), and their data are regularly processed by IGS Analysis Centers. From its global network of over 350 stations and its Analysis Centers, the IGS generates precise combined GPS ephemeredes and station and satellite clock time series referred to the IGS Time Scale. A processing method called Precise Point Positioning (PPP) is in use in the geodetic community allowing precise recovery of GPS antenna position, clock phase, and atmospheric delays by taking advantage of these IGS precise products. Previous assessments, carried out at Istituto Nazionale di Ricerca Metrologica (INRiM; formerly IEN) with a PPP implementation developed at Natural Resources Canada (NRCan), showed PPP clock solutions have better stability over short/medium term than GPS CV and GPS P3 methods and significantly reduce the day-boundary discontinuities when used in multi-day continuous processing, allowing time-limited, campaign-style time-transfer experiments. This paper reports on follow-on work performed at INRiM and NRCan to further characterize and develop the PPP method for time transfer applications, using data from some of the National Metrology Institutes. We develop a processing procedure that takes advantage of the improved stability of the phase-connected multi-day PPP solutions while allowing the generation of continuous clock time series, more applicable to continuous operation/monitoring of timing equipment. PMID:19686979

  14. An Assessment of GPS-based precise point positioning of the low earth-orbiting satellite CHAMP

    Microsoft Academic Search

    Takahiro Yoshioka; Masaaki Murata

    2009-01-01

    Precise point positioning (PPP) with the international GNSS service (IGS) products, which consist of precise orbits and clock correction information, has been demonstrated by several investigators to achieve a centimeter-decimeter level positioning accuracy in real-time for land and aerial vehicular navigation. The purpose of this paper is to present one phase of study conducted at National Defense Academy (NDA) on

  15. Impact of orbit, clock and EOP errors in GNSS Precise Point Positioning

    NASA Astrophysics Data System (ADS)

    Hackman, C.

    2012-12-01

    Precise point positioning (PPP; [1]) has gained ever-increasing usage in GNSS carrier-phase positioning, navigation and timing (PNT) since its inception in the late 1990s. In this technique, high-precision satellite clocks, satellite ephemerides and earth-orientation parameters (EOPs) are applied as fixed input by the user in order to estimate receiver/location-specific quantities such as antenna coordinates, troposphere delay and receiver-clock corrections. This is in contrast to "network" solutions, in which (typically) less-precise satellite clocks, satellite ephemerides and EOPs are used as input, and in which these parameters are estimated simultaneously with the receiver/location-specific parameters. The primary reason for increased PPP application is that it offers most of the benefits of a network solution with a smaller computing cost. In addition, the software required to do PPP positioning can be simpler than that required for network solutions. Finally, PPP permits high-precision positioning of single or sparsely spaced receivers that may have few or no GNSS satellites in common view. A drawback of PPP is that the accuracy of the results depend directly on the accuracy of the supplied orbits, clocks and EOPs, since these parameters are not adjusted during the processing. In this study, we will examine the impact of orbit, EOP and satellite clock estimates on PPP solutions. Our primary focus will be the impact of these errors on station coordinates; however the study may be extended to error propagation into receiver-clock corrections and/or troposphere estimates if time permits. Study motivation: the United States Naval Observatory (USNO) began testing PPP processing using its own predicted orbits, clocks and EOPs in Summer 2012 [2]. The results of such processing could be useful for real- or near-real-time applications should they meet accuracy/precision requirements. Understanding how errors in satellite clocks, satellite orbits and EOPs propagate into PPP positioning and timing results allows researchers to focus their improvement efforts in areas most in need of attention. The initial study will be conducted using the simulation capabilities of Bernese GPS Software and extended to using real data if time permits. [1] J.F. Zumberge, M.B. Heflin, D.C. Jefferson, M.M. Watkins and F.H. Webb, Precise point positioning for the efficient and robust analysis of GPS data from large networks, J. Geophys. Res., 102(B3), 5005-5017, doi:10.1029/96JB03860, 1997. [2] C. Hackman, S.M. Byram, V.J. Slabinski and J.C. Tracey, Near-real-time and other high-precision GNSS-based orbit/clock/earth-orientation/troposphere parameters available from USNO, Proc. 2012 ION Joint Navigation Conference, 15 pp., in press, 2012.

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

    Microsoft Academic Search

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

    1997-01-01

    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

  17. Precise point positioning with quad-constellations: GPS, BeiDou, GLONASS and Galileo

    NASA Astrophysics Data System (ADS)

    Cai, Changsheng; Gao, Yang; Pan, Lin; Zhu, Jianjun

    2015-07-01

    Multi-constellation GNSS precise point positioning (PPP) first became feasible back to 2007 but with only two constellations, namely GPS and GLONASS. With the availability of more satellites and precise orbit and clock products from BeiDou and Galileo, it is possible now to investigate PPP with four constellations, namely GPS, BeiDou, GLONASS and Galileo. This research aims at investigating the quad-constellation PPP for position determination and analyzing its positioning performance. A quad-constellation PPP model is developed to simultaneously process the observations from all the four GNSS systems. The developed model is also applicable to the PPP processing with observations from single, dual or triple constellations. The analysis on PPP accuracy and convergence time is conducted based on data processing results from both static and kinematic tests of single-constellation and multi-constellations. The three-hour static positioning results indicate that the BeiDou-only PPP accuracy is worse than the GPS-only PPP. The RMSs of position errors for BeiDou-only PPP are 5.2 cm, 2.7 cm and 8.3 cm in east, north and up directions while the ones for GPS-only PPP are 3.9 cm, 1.6 cm and 5.7 cm. The GPS/BeiDou PPP improves the positioning accuracy by 28%, 6% and 7% and reduces the convergence time by 26%, 13% and 14% over the GPS-only PPP in three coordinate components, respectively. The GPS/GLONASS PPP achieves slightly better performance than the GPS/BeiDou PPP. The triple-constellation PPP further increases the positioning accuracy and decreases the convergence time over the dual-constellation PPP. The improvement of positioning performance is not significant after adding Galileo due to currently limited number of satellites. Similar to the static positioning, the quad-constellation kinematic PPP also significantly improves the positioning performance in contrast with single-constellation and dual-constellations. The time varying characteristics of the time differences between the four systems are also investigated. The results indicate that the system time differences of GPS with BeiDou, GLONASS and Galileo are very stable over time with STD values of better than 1.1 ns.

  18. Towards PPP-RTK: Ambiguity resolution in real-time precise point positioning

    NASA Astrophysics Data System (ADS)

    Geng, J.; Teferle, F. N.; Meng, X.; Dodson, A. H.

    2011-05-01

    Integer ambiguity resolution at a single station can be achieved by introducing predetermined uncalibrated phase delays (UPDs) into the float ambiguity estimates of precise point positioning (PPP). This integer resolution technique has the potential of leading to a PPP-RTK (real-time kinematic) model where PPP provides rapid convergence to a reliable centimeter-level positioning accuracy based on an RTK reference network. Nonetheless, implementing this model is technically subject to how rapidly we can fix wide-lane ambiguities, stabilize narrow-lane UPD estimates, and achieve the first ambiguity-fixed solution. To investigate these issues, we used 7 days of 1-Hz sampling GPS data at 91 stations across Europe. We find that at least 10 min of observations are required for most receiver types to reliably fix about 90% of wide-lane ambiguities corresponding to high elevations, and over 20 min to fix about 90% of those corresponding to low elevations. Moreover, several tens of minutes are usually required for a regional network before a narrow-lane UPD estimate stabilizes to an accuracy of far better than 0.1 cycles. Finally, for hourly data, ambiguity resolution can significantly improve the accuracy of epoch-wise position estimates from 13.7, 7.1 and 11.4 cm to 0.8, 0.9 and 2.5 cm for the East, North and Up components, respectively, but a few tens of minutes is required to achieve the first ambiguity-fixed solution. Therefore, from the timeliness aspect, our PPP-RTK model currently cannot satisfy the critical requirement of instantaneous precise positioning where ambiguity-fixed solutions have to be achieved within at most a few seconds. However, this model can still be potentially applied to some near-real-time remote sensing applications, such as the GPS meteorology.

  19. Improving the estimation of fractional-cycle biases for ambiguity resolution in precise point positioning

    NASA Astrophysics Data System (ADS)

    Geng, Jianghui; Shi, Chuang; Ge, Maorong; Dodson, Alan H.; Lou, Yidong; Zhao, Qile; Liu, Jingnan

    2012-08-01

    Ambiguity resolution dedicated to a single global positioning system (GPS) station can improve the accuracy of precise point positioning. In this process, the estimation accuracy of the narrow-lane fractional-cycle biases (FCBs), which destroy the integer nature of undifferenced ambiguities, is crucial to the ambiguity-fixed positioning accuracy. In this study, we hence propose the improved narrow-lane FCBs derived from an ambiguity-fixed GPS network solution, rather than the original (i.e. previously proposed) FCBs derived from an ambiguity-float network solution. The improved FCBs outperform the original FCBs by ensuring that the resulting ambiguity-fixed daily positions coincide in nature with the state-of-the-art positions generated by the International GNSS Service (IGS). To verify this improvement, 1 year of GPS measurements from about 350 globally distributed stations were processed. We find that the original FCBs differ more from the improved FCBs when fewer stations are involved in the FCB estimation, especially when the number of stations is less than 20. Moreover, when comparing the ambiguity-fixed daily positions with the IGS weekly positions for 248 stations through a Helmert transformation, for the East component, we find that on 359 days of the year the daily RMS of the transformed residuals based on the improved FCBs is smaller by up to 0.8 mm than those based on the original FCBs, and the mean RMS over the year falls evidently from 2.6 to 2.2 mm. Meanwhile, when using the improved rather than the original FCBs, the RMS of the transformed residuals for the East component of 239 stations (i.e. 96.4% of all 248 stations) is clearly reduced by up to 1.6 mm, especially for stations located within a sparse GPS network. Therefore, we suggest that narrow-lane FCBs should be determined with ambiguity-fixed, rather than ambiguity-float, GPS network solutions.

  20. GPS/GLONASS Combined Precise Point Positioning with Receiver Clock Modeling.

    PubMed

    Wang, Fuhong; Chen, Xinghan; Guo, Fei

    2015-01-01

    Research has demonstrated that receiver clock modeling can reduce the correlation coefficients among the parameters of receiver clock bias, station height and zenith tropospheric delay. This paper introduces the receiver clock modeling to GPS/GLONASS combined precise point positioning (PPP), aiming to better separate the receiver clock bias and station coordinates and therefore improve positioning accuracy. Firstly, the basic mathematic models including the GPS/GLONASS observation equations, stochastic model, and receiver clock model are briefly introduced. Then datasets from several IGS stations equipped with high-stability atomic clocks are used for kinematic PPP tests. To investigate the performance of PPP, including the positioning accuracy and convergence time, a week of (1-7 January 2014) GPS/GLONASS data retrieved from these IGS stations are processed with different schemes. The results indicate that the positioning accuracy as well as convergence time can benefit from the receiver clock modeling. This is particularly pronounced for the vertical component. Statistic RMSs show that the average improvement of three-dimensional positioning accuracy reaches up to 30%-40%. Sometimes, it even reaches over 60% for specific stations. Compared to the GPS-only PPP, solutions of the GPS/GLONASS combined PPP are much better no matter if the receiver clock offsets are modeled or not, indicating that the positioning accuracy and reliability are significantly improved with the additional GLONASS satellites in the case of insufficient number of GPS satellites or poor geometry conditions. In addition to the receiver clock modeling, the impacts of different inter-system timing bias (ISB) models are investigated. For the case of a sufficient number of satellites with fairly good geometry, the PPP performances are not seriously affected by the ISB model due to the low correlation between the ISB and the other parameters. However, the refinement of ISB model weakens the correlation between coordinates and ISB estimates and finally enhance the PPP performance in the case of poor observation conditions. PMID:26134106

  1. Real-time Precise Point Positioning with Ambiguity Resolution for Geosciences

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    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.

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

    PubMed

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

    2012-01-01

    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

  3. Performance Analysis of Several GPS/Galileo Precise Point Positioning Models.

    PubMed

    Afifi, Akram; El-Rabbany, Ahmed

    2015-01-01

    This paper examines the performance of several precise point positioning (PPP) models, which combine dual-frequency GPS/Galileo observations in the un-differenced and between-satellite single-difference (BSSD) modes. These include the traditional un-differenced model, the decoupled clock model, the semi-decoupled clock model, and the between-satellite single-difference model. We take advantage of the IGS-MGEX network products to correct for the satellite differential code biases and the orbital and satellite clock errors. Natural Resources Canada's GPSPace PPP software is modified to handle the various GPS/Galileo PPP models. A total of six data sets of GPS and Galileo observations at six IGS stations are processed to examine the performance of the various PPP models. It is shown that the traditional un-differenced GPS/Galileo PPP model, the GPS decoupled clock model, and the semi-decoupled clock GPS/Galileo PPP model improve the convergence time by about 25% in comparison with the un-differenced GPS-only model. In addition, the semi-decoupled GPS/Galileo PPP model improves the solution precision by about 25% compared to the traditional un-differenced GPS/Galileo PPP model. Moreover, the BSSD GPS/Galileo PPP model improves the solution convergence time by about 50%, in comparison with the un-differenced GPS PPP model, regardless of the type of BSSD combination used. As well, the BSSD model improves the precision of the estimated parameters by about 50% and 25% when the loose and the tight combinations are used, respectively, in comparison with the un-differenced GPS-only model. Comparable results are obtained through the tight combination when either a GPS or a Galileo satellite is selected as a reference. PMID:26102495

  4. The application of GPS precise point positioning technology in aerial triangulation

    NASA Astrophysics Data System (ADS)

    Yuan, Xiuxiao; Fu, Jianhong; Sun, Hongxing; Toth, Charles

    In traditional GPS-supported aerotriangulation, differential GPS (DGPS) positioning technology is used to determine the 3-dimensional coordinates of the perspective centers at exposure time with an accuracy of centimeter to decimeter level. This method can significantly reduce the number of ground control points (GCPs). However, the establishment of GPS reference stations for DGPS positioning is not only labor-intensive and costly, but also increases the implementation difficulty of aerial photography. This paper proposes aerial triangulation supported with GPS precise point positioning (PPP) as a way to avoid the use of the GPS reference stations and simplify the work of aerial photography. Firstly, we present the algorithm for GPS PPP in aerial triangulation applications. Secondly, the error law of the coordinate of perspective centers determined using GPS PPP is analyzed. Thirdly, based on GPS PPP and aerial triangulation software self-developed by the authors, four sets of actual aerial images taken from surveying and mapping projects, different in both terrain and photographic scale, are given as experimental models. The four sets of actual data were taken over a flat region at a scale of 1:2500, a mountainous region at a scale of 1:3000, a high mountainous region at a scale of 1:32000 and an upland region at a scale of 1:60000 respectively. In these experiments, the GPS PPP results were compared with results obtained through DGPS positioning and traditional bundle block adjustment. In this way, the empirical positioning accuracy of GPS PPP in aerial triangulation can be estimated. Finally, the results of bundle block adjustment with airborne GPS controls from GPS PPP are analyzed in detail. The empirical results show that GPS PPP applied in aerial triangulation has a systematic error of half-meter level and a stochastic error within a few decimeters. However, if a suitable adjustment solution is adopted, the systematic error can be eliminated in GPS-supported bundle block adjustment. When four full GCPs are emplaced in the corners of the adjustment block, then the systematic error is compensated using a set of independent unknown parameters for each strip, the final result of the bundle block adjustment with airborne GPS controls from PPP is the same as that of bundle block adjustment with airborne GPS controls from DGPS. Although the accuracy of the former is a little lower than that of traditional bundle block adjustment with dense GCPs, it can still satisfy the accuracy requirement of photogrammetric point determination for topographic mapping at many scales.

  5. A simplified and unified model of multi-GNSS precise point positioning

    NASA Astrophysics Data System (ADS)

    Chen, Junping; Zhang, Yize; Wang, Jungang; Yang, Sainan; Dong, Danan; Wang, Jiexian; Qu, Weijing; Wu, Bin

    2015-01-01

    Additional observations from other GNSS s can augment GPS precise point positioning (PPP) for improved positioning accuracy, reliability and availability. Traditional multi-GNSS PPP model requires the estimation of inter-system bias (ISB) parameter. Based on the scaled sensitivity matrix (SSM) method, a quantitative approach for assessing parameter assimilation, we theoretically prove that the ISB parameter is not correlated with coordinate parameters and it can be assimilated into clock and ambiguity parameters. Thus, removing ISB from multi-GNSS PPP model does not affect coordinate estimation. Based on this analysis, we develop a simplified and unified model for multi-GNSS PPP, where ISB parameter does not need to be estimated and observations from different GNSS systems are treated in a unified way. To verify the new model, we implement the algorithm to the self-developed software to process 1 year GPS/GLONASS data of 53 IGS (International GNSS Service) worldwide stations and 1 month GPS/BDS data of 15 IGS MGEX (Multi-GNSS Experiment) stations. Two types of GPS/GLONASS and GPS/BDS combined PPP solution are performed, one is based on traditional model and the other implements the new model. RMSs of coordinate differences between the two type of solutions are few ?m for daily static PPP and less than 0.02 mm for GPS/GLONASS kinematic PPP in the North, East and Up components, respectively. Considering the millimeter-level precision of current GNSS PPP solutions, these statistics demonstrate equivalent performance of the two solution types.

  6. Rapid re-convergences to ambiguity-fixed solutions in precise point positioning

    NASA Astrophysics Data System (ADS)

    Geng, Jianghui; Meng, Xiaolin; Dodson, Alan H.; Ge, Maorong; Teferle, Felix N.

    2010-12-01

    Integer ambiguity resolution at a single receiver can be achieved if the fractional-cycle biases are separated from the ambiguity estimates in precise point positioning (PPP). Despite the improved positioning accuracy by such integer resolution, the convergence to an ambiguity-fixed solution normally requires a few tens of minutes. Even worse, these convergences can repeatedly occur on the occasion of loss of tracking locks for many satellites if an open sky-view is not constantly available, consequently totally destroying the practicability of real-time PPP. In this study, in case of such re-convergences, we develop a method in which ionospheric delays are precisely predicted to significantly accelerate the integer ambiguity resolution. The effectiveness of this method consists in two aspects: first, wide-lane ambiguities can be rapidly resolved using the ionosphere-corrected wide-lane measurements, instead of the noisy Melbourne-Wübbena combination measurements; second, narrow-lane ambiguity resolution can be accelerated under the tight constraints derived from the ionosphere-corrected unambiguous wide-lane measurements. In the test at 90 static stations suffering from simulated total loss of tracking locks, 93.3 and 95.0% of re-convergences to wide-lane and narrow-lane ambiguity resolutions can be achieved within five epochs of 1-Hz measurements, respectively, even though the time latency for the predicted ionospheric delays is up to 180 s. In the test at a mobile van moving in a GPS-adverse environment where satellite number significantly decreases and cycle slips frequently occur, only when the predicted ionospheric delays are applied can the rate of ambiguity-fixed epochs be dramatically improved from 7.7 to 93.6% of all epochs. Therefore, this method can potentially relieve the unrealistic requirement of a continuous open sky-view by most PPP applications and improve the practicability of real-time PPP.

  7. Precise Point Positioning using Multi-Constellation GNSS Observations for Kinematic Applications

    NASA Astrophysics Data System (ADS)

    Rabbou, Mahmoud Abd; El-Rabbany, Ahmed

    2015-03-01

    Traditional precise point positioning (PPP) is commonly based on un-differenced ionosphere-free linear combination of Global Positioning System (GPS) observations. Unfortunately, for kinematic applications, GPS often experiences poor satellite visibility or weak satellite geometry in urban areas. To overcome this limitation, we developed a PPP model, which combines the observations of three global navigation satellite systems (GNSS), namely GPS, GLONASS and Galileo. Both un-differenced and between-satellite single-difference (BSSD) ionosphere-free linear combinations of pseudorange and carrier phase GNSS measurements are processed. The performance of the combined GNSS PPP solution is compared with the GPS-only PPP solution using a real test scenario in downtown Kingston, Ontario. Inter-system biases between GPS and the other two systems are also studied and obtained as a byproduct of the PPP solution. It is shown that the addition of GLONASS observations improves the kinematic PPP solution accuracy in comparison with that of GPS-only solution. However, the contribution of adding Galileo observations is not significant due to the limited number of Galileo satellites launched up to date. In addition, BSSD solution is found to be superior to that of traditional un-differenced model.

  8. Employing GPS L5 Carrier-Frequency in Precise Point Positioning

    NASA Astrophysics Data System (ADS)

    Spits, J.; Santos, M. C.

    2012-12-01

    Justine Spits and Marcelo C. Santos Dept. of Geodesy and Geomatics Engineering, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 5A3 Tel: (1-506) 453-4698, Email: msantos@unb.ca, jspits@unb.ca Precise Point Positioning (PPP) is a GNSS technique which, in most cases nowadays, makes use of Global Positioning System (GPS) dual-frequency signals. The increasing availability of the new GPS L5 signal brings about the question on how much can PPP benefit if it uses L5 in conjunction with the legacy L1 and L2 signals. This poster discusses this issue. It involves the study of the use of L5 in conjunction with the other GPS signals (L1 and L2) with emphasis on the potentialities associated with the various combinations, such as L1-L5, L2-L5 and L1-L2-L5. These combinations will bring benefits in different ways, for example, for ionospheric delay mitigation, ambiguity resolution, convergence time and accuracy. Simulated L5 data will be used to test the PPP algorithms. Performance will be compared against the current dual-frequency PPP methodology. Justine Spits: Ph.D. (Liège, Belgium); Post-Doctoral Fellow, University of New Brunswick Marcelo. C. Santos: Ph.D. (New Brunswick); Professor, University of New Brunswick

  9. On troposphere delay constraining in real-time GNSS Precise Point Positioning

    NASA Astrophysics Data System (ADS)

    Hadas, Tomasz; Kazmierski, Kamil; Bosy, Jaroslaw

    2015-04-01

    A common procedure in Precise Point Positioning (PPP) is to have the adjustment model accounting for the correction to an a priori value of the total troposphere delay (ZTD) given at the first epoch of data processing, and the troposphere wet delay filter is updated epoch by epoch. This approach requires some time so that a change in satellite geometry allows to efficiently de-correlate among tropospheric delay, receiver clock error and height. Empirical troposphere state models and mapping functions are available, however they may not reflect properly the actual state of the troposphere, especially in severe weather conditions. It might be more appropriate to take advantage on a regional troposphere model derived from near real-time (NRT) processing of GBAS network. To evaluate the impact of troposphere constraining in real-time PPP, one week long period was selected, that was characterized with active troposphere conditions. Using the development version of original GNSS-WARP software, a 1 Hz kinematic positioning was performed for 10 selected Polish GBAS stations using IGS Real-Time Service (RTS) products. Two processing strategies were used, one reflecting the common PPP approach and the second with NRT ZTD to constrain the troposphere delay estimates. GPS only and GPS+GLONASS positioning was performed and analyzed using both strategies. For unconstrained solutions, the convergence time of one hour (GPS only) and 15 minutes (GPS+GLONASS) was reached, providing the sub-decimeter accuracy in horizontal and vertical component. However, for some epochs, and outlying height estimates were observed with the residuals reaching up to 0.5m with the estimated error of 0.2m. At the same time, the unconstrained estimated troposphere delay differs up to 12 cm from the reference NRT ZTD solution. In case the troposphere delay is constrained, all three coordinate components remains accurate and precise for entire processing period after the convergence is reached. From the very beginning of the data processing, the residuals with respect to true receiver position are small. The standard deviation of height component residuals is reduced on average by 40%, however the height are shifted by about 1cm. The results confirm the usefulness of near-real time troposphere delay models in real-time PPP kinematic processing and a significant improvement is noticed in active troposphere conditions.

  10. Integration of GPS Precise Point Positioning and MEMS-Based INS Using Unscented Particle Filter

    PubMed Central

    Abd Rabbou, Mahmoud; El-Rabbany, Ahmed

    2015-01-01

    Integration of Global Positioning System (GPS) and Inertial Navigation System (INS) integrated system involves nonlinear motion state and measurement models. However, the extended Kalman filter (EKF) is commonly used as the estimation filter, which might lead to solution divergence. This is usually encountered during GPS outages, when low-cost micro-electro-mechanical sensors (MEMS) inertial sensors are used. To enhance the navigation system performance, alternatives to the standard EKF should be considered. Particle filtering (PF) is commonly considered as a nonlinear estimation technique to accommodate severe MEMS inertial sensor biases and noise behavior. However, the computation burden of PF limits its use. In this study, an improved version of PF, the unscented particle filter (UPF), is utilized, which combines the unscented Kalman filter (UKF) and PF for the integration of GPS precise point positioning and MEMS-based inertial systems. The proposed filter is examined and compared with traditional estimation filters, namely EKF, UKF and PF. Tightly coupled mechanization is adopted, which is developed in the raw GPS and INS measurement domain. Un-differenced ionosphere-free linear combinations of pseudorange and carrier-phase measurements are used for PPP. The performance of the UPF is analyzed using a real test scenario in downtown Kingston, Ontario. It is shown that the use of UPF reduces the number of samples needed to produce an accurate solution, in comparison with the traditional PF, which in turn reduces the processing time. In addition, UPF enhances the positioning accuracy by up to 15% during GPS outages, in comparison with EKF. However, all filters produce comparable results when the GPS measurement updates are available. PMID:25815446

  11. Effectiveness of Observation-Domain Sidereal Filtering for GPS Precise Point Positioning

    NASA Astrophysics Data System (ADS)

    Atkins, C.; Ziebart, M. K.

    2014-12-01

    Global navigation satellite systems (GNSS) are increasingly being used in earthquake monitoring and tsunami warning systems. However, the ability of GNSS to measure potentially small ground displacements is limited by a number of error sources, one of which is multipath interference, which affects the measurements made by a GNSS receiver.Sidereal filtering is a technique sometimes used to reduce errors caused by multipath in the positioning of static receivers via GPS in particular. It relies upon the receiver and its surrounding environment remaining static from one day to the next and takes advantage of the approximately sidereal repeat time of the GPS constellation geometry. The repeating multipath error can thus be identified, usually in the position domain, and largely removed from the following day.We have developed an observation-domain sidereal filter (ODSF) algorithm that operates on un-differenced ionosphere-free GPS carrier phase observations to reduce errors caused by multipath. It is applied in the context of high-rate 1 Hz precise point positioning (PPP) of a static receiver. An ODSF is able to account for the slightly different repeat times of each GPS satellite, unlike a position-domain sidereal filter, and can hence be more effective at reducing high-frequency multipath error.Using eight-hour long datasets of GPS observations from two different receivers with different antenna types and contrasting environments, the ODSF algorithm is shown overall to yield a position time series 10% to 45% more stable, in terms of Allan deviation, than a position-domain sidereal filter over time intervals of between 20 s and 300 s in length. This would be particularly useful for earthquake and tsunami early warning systems where the accurate measurement of small displacements of the ground over the period of just a few minutes is crucial. However, the sidereal filters have also been applied to a third dataset during which two short episodes of particularly high-frequency multipath error were identified. These two periods are analyzed in detail and illustrate the limitations of using sidereal filters with important implications for other methods of correcting for multipath at the observation level.

  12. Precise Orbit Determination of Low Earth Orbiters with GPS Point Positioning

    Microsoft Academic Search

    Sunil B. Bisnath; Richard B. Langley

    2001-01-01

    Precise orbit determination (POD) of low earth orbiters (LEOs) with GPS is becoming a standard practice in the space science community. The need for such information has been growing rapidly due to such scientific applications as radio occultation and ever increasing demands from engineering applications such as space - based earth sensor positioning. The conventional GPS - based POD strategies

  13. Determination of glacial isostatic adjustment parameters based on precise point positioning using GPS

    NASA Astrophysics Data System (ADS)

    Park, Kwan-Dong

    2000-10-01

    Various error sources affecting the precise point positioning using GPS are addressed and their effects are corrected for to reduce the scatter in the daily station position estimates. Several models of tropospheric wet delay and tropospheric wet delay gradient were tested to find the best model and estimation parameters. Atmospheric and ocean loading effects were also evaluated. It was analyzed how the height estimates are affected by elevation cutoff angle, integer ambiguity fixing, and antenna phase center variations. To characterize the multipath interference at each of 219 global permanent GPS stations, the time-shifted post-fit phase residual was used. This analysis tool was found to be very effective and it verified that the multipath interference is reduced at sites with the choke ring antenna. Among sites with the same antenna type, the multipath effect was highly variable depending on the environment. Sixty permanent GPS sites in the northeastern U.S. are being automatically processed on a daily basis to generate continuous time series of station position estimates for geophysical studies. In the time series, common-mode signals were found and the scatter was significantly reduced when the common-mode signals were removed. For a smaller network of sites, the daily station position repeatability was reduced as much as by 63%. The amount of the scatter reduction was dependent on the inter-site distance. The possible cause of these common mode signals was analyzed by processing GPS data with different GPS satellite orbits. Scalar Empirical Orthogonal Function (EOF) analysis was done to detect the primary mode of variability for a regional network. Horizontal and vertical site velocities determined from GPS measurements of the northeast U.S. permanent stations were used to estimate the parameters of the Glacial Isostatic Adjustment (GIA). On the basis of the long-term and short-term variability of each site, 20 stations were carefully selected out of 60 stations. Three-dimensional deformation rates of the selected 20 stations were used in the weighted least squares adjustment of GIA parameters. The estimated value of the lower mantle viscosity was comparable to the previous result obtained solely with tide gauge data.

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

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaohong; Li, Pan

    2013-06-01

    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.

  15. A closer look at the concept of regional clocks for Precise Point Positioning

    NASA Astrophysics Data System (ADS)

    Weber, Robert; Karabatic, Ana; Thaler, Gottfried; Abart, Christoph; Huber, Katrin

    2010-05-01

    Under the precondition of at least two successfully tracked signals at different carrier frequencies we may obtain their ionosphere free linear combination. By introducing approximate values for geometric effects like orbits and tropospheric delay as well as an initial bias parameter N per individual satellite we can solve for the satellite clock with respect to the receiver clock. Noting, that residual effects like orbit errors, remaining tropospheric delays and a residual bias parameter map into these parameters, this procedure leaves us with a kind of virtual clock differences. These clocks cover regional effects and are therefore clearly correlated with clocks at nearby station. Therefore we call these clock differences, which are clearly different from clock solutions provided for instance by IGS, the "regional clocks". When introducing the regional clocks obtained from real-time data of a GNSS reference station network we are able to process the coordinates of a nearby isolated station via a PPP .In terms of PPP-convergence time which will be reduced down to 30 minutes or less, this procedure is clearly favorable. The accuracy is quite comparable with state of the art PPP procedures. Nevertheless, this approach cannot compete in fixing times with double-difference approaches but the correlation holds over hundreds of kilometers distance to our master station and the clock differences can easily by obtained, even in real-time. This presentation provides preliminary results of the project RA-PPP. RA-PPP is a research project financed by the Federal Ministry for Transport, Innovation and Technology, managed by the Austrian Research Promotion Agency (FFG) in the course of the 6th call of the Austrian Space Application Program (ASAP). RA-PPP stands for Rapid Precise Point Positioning, which denotes the wish for faster and more accurate algorithms for PPP. The concept of regional clocks which will be demonstrated in detail in this presentation is one out of 4 concepts to be evaluated in this project.

  16. GPS Phase-Connected, Precise Point Positioning of Low Earth Orbiters

    Microsoft Academic Search

    Sunil B. Bisnath; Richard B. Langley

    2001-01-01

    A completely geometric approach for precise orbit determination (POD) of low earth orbiter (LEO) spacecraft has been devised by the authors which does not use dynamic models, but only data from the GPS receiver onboard the LEO and the International GPS Service (IGS) precise GPS ephemeris product. The strategy relies on combining the time-continuous measurement strength of the pseudorange and

  17. On the convergence of ionospheric constrained precise point positioning (IC-PPP) based on undifferential uncombined raw GNSS observations.

    PubMed

    Zhang, Hongping; Gao, Zhouzheng; Ge, Maorong; Niu, Xiaoji; Huang, Ling; Tu, Rui; Li, Xingxing

    2013-01-01

    Precise Point Positioning (PPP) has become a very hot topic in GNSS research and applications. However, it usually takes about several tens of minutes in order to obtain positions with better than 10 cm accuracy. This prevents PPP from being widely used in real-time kinematic positioning services, therefore, a large effort has been made to tackle the convergence problem. One of the recent approaches is the ionospheric delay constrained precise point positioning (IC-PPP) that uses the spatial and temporal characteristics of ionospheric delays and also delays from an a priori model. In this paper, the impact of the quality of ionospheric models on the convergence of IC-PPP is evaluated using the IGS global ionospheric map (GIM) updated every two hours and a regional satellite-specific correction model. Furthermore, the effect of the receiver differential code bias (DCB) is investigated by comparing the convergence time for IC-PPP with and without estimation of the DCB parameter. From the result of processing a large amount of data, on the one hand, the quality of the a priori ionosphere delays plays a very important role in IC-PPP convergence. Generally, regional dense GNSS networks can provide more precise ionosphere delays than GIM and can consequently reduce the convergence time. On the other hand, ignoring the receiver DCB may considerably extend its convergence, and the larger the DCB, the longer the convergence time. Estimating receiver DCB in IC-PPP is a proper way to overcome this problem. Therefore, current IC-PPP should be enhanced by estimating receiver DCB and employing regional satellite-specific ionospheric correction models in order to speed up its convergence for more practical applications. PMID:24253190

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

    Microsoft Academic Search

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

    2004-01-01

    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

  19. Non-Linear Filtering for Precise Point Positioning GPS/INS integration

    NASA Astrophysics Data System (ADS)

    Abd Rabbou, M.; El-Rabbany, A.

    2014-11-01

    This research investigates the performance of non-linear estimation filtering for GPS-PPP/MEMS-based inertial system. Although integrated GPS/INS system involves nonlinear motion state and measurement models, the most common estimation filter employed is extended Kalman filter. In this paper, both unscented Kalman filter and particle filter are developed and compared with extended Kalman filter. Tightly coupled mechanization is adopted, which is developed in the raw measurements domain. Un-differenced ionosphere-free linear combination of pseudorange and carrier-phase measurements is employed. The performance of the proposed non-linear filters is analyzed using real test scenario. The test results indicate that comparable accuracy-level are obtained from the proposed filters compared with extended Kalman filter in positioning, velocity and attitude when the measurement updates from GPS measurements are available.

  20. Assessment of precipitable water vapor derived from ground-based BeiDou observations with Precise Point Positioning approach

    NASA Astrophysics Data System (ADS)

    Li, Min; Li, Wenwen; Shi, Chuang; Zhao, Qile; Su, Xing; Qu, Lizhong; Liu, Zhizhao

    2015-01-01

    Precipitable water vapor (PWV) estimation from Global Positioning System (GPS) has been extensively studied and used for meteorological applications. However PWV estimation using the emerging BeiDou Navigation Satellite System (BDS) is very limited. In this paper the PWV estimation strategy and the evaluation of the results inferred from ground-based BDS observations using Precise Point Positioning (PPP) method are presented. BDS and GPS data from 10 stations distributed in the Asia-Pacific and West Indian Ocean regions during the year 2013 are processed using the PANDA (Position and Navigation Data Analyst) software package. The BDS-PWV and GPS-PWV are derived from the BDS-only and GPS-only observations, respectively. The PPP positioning differences between BDS-only and GPS-only show a standard deviation (STD) <1 cm in the east and north components and 1-3 cm in vertical component. The BDS-PWV and GPS-PWV at the HKTU station (Hong Kong, China) is compared with PWV derived from a radiosonde station (about 1 km distance) over a 6-month period. The GPS-PWV shows a good agreement with radiosonde-PWV with a bias of 0.002 mm and a STD of 2.49 mm while BDS-PWV has with a bias of -2.04 mm and STD 2.68 mm with respect to radiosonde-PWV. This indicates that the PWV estimated from the BDS can achieve similar precision as PWV from GPS. The BDS-PWV is compared to GPS-PWV at 10 stations. The mean bias and STD of their differences at 10 stations are 0.78 mm and 1.77 mm, respectively. The mean root mean square (RMS) value is 2.00 mm by considering the GPS-PWV as reference truth. This again confirms that the BDS-PWV has a good agreement with the GPS-PWV. It clearly indicates that the BDS is ready for the high precision meteorological applications in the Asia-Pacific and West Indian Ocean regions and that BDS alone can be used for PWV estimation with an accuracy comparable to GPS.

  1. Impact of mapping functions based on spherical, ellipsoidal, gradient, and 3d atmospheric structures on GPS Precise Point Positioning

    NASA Astrophysics Data System (ADS)

    Nievinski, F. G.; Santos, M. C.

    2008-12-01

    We evaluate the impact of mapping functions developed from different atmospheric structures on precise point positioning. In each case the atmospheric structure is derived from the same Numerical Weather Model (NWM). We compared five different structures -- from simpler to more realistic: spherical concentric, spherical osculating, ellipsoidal, gradient, and 3D -- and a state-of-art mapping function, Vienna Mapping Functions Site (VMF1). We used data from IGS station ALGO. Results correspond to comparisons with the IGS (non- cumulative) weekly solution. The spherical concentric model shows a large (cm-level) bias in the north component. The spherical osculating (and ellipsoidal) model shows an improvement in the up component, by almost one order of magnitude, over that of VMF1. The 3D atmosphere model reduces the horizontal bias to less than 1 mm, but there is no apparent improvement in the vertical position, which we attribute to unaccounted non-tidal atmospheric pressure loading. Finally, the gradient atmosphere shows biases with magnitude in between those of the spherical osculating and 3d models.

  2. Atmosphere Mitigation in Precise Point Positioning Ambiguity Resolution for Earthquake Early Warning in the Western U.S.

    NASA Astrophysics Data System (ADS)

    Geng, J.; Bock, Y.; Reuveni, Y.

    2014-12-01

    Earthquake early warning (EEW) is a time-critical system and typically relies on seismic instruments in the area around the source to detect P waves (or S waves) and rapidly issue alerts. Thanks to the rapid development of real-time Global Navigation Satellite Systems (GNSS), a good number of sensors have been deployed in seismic zones, such as the western U.S. where over 600 GPS stations are collecting 1-Hz high-rate data along the Cascadia subduction zone, San Francisco Bay area, San Andreas fault, etc. GNSS sensors complement the seismic sensors by recording the static offsets while seismic data provide highly-precise higher frequency motions. An optimal combination of GNSS and accelerometer data (seismogeodesy) has advantages compared to GNSS-only or seismic-only methods and provides seismic velocity and displacement waveforms that are precise enough to detect P wave arrivals, in particular in the near source region. Robust real-time GNSS and seismogeodetic analysis is challenging because it requires a period of initialization and continuous phase ambiguity resolution. One of the limiting factors is unmodeled atmospheric effects, both of tropospheric and ionospheric origin. One mitigation approach is to introduce atmospheric corrections into precise point positioning with ambiguity resolution (PPP-AR) of clients/stations within the monitored regions. NOAA generates hourly predictions of zenith troposphere delays at an accuracy of a few centimeters, and 15-minute slant ionospheric delays of a few TECU (Total Electron Content Unit) accuracy from both geodetic and meteorological data collected at hundreds of stations across the U.S. The Scripps Orbit and Permanent Array Center (SOPAC) is experimenting with a regional ionosphere grid using a few hundred stations in southern California, and the International GNSS Service (IGS) routinely estimates a Global Ionosphere Map using over 100 GNSS stations. With these troposphere and ionosphere data as additional observations, we can shorten the initialization period and improve the ambiguity resolution efficiency of PPP-AR. We demonstrate this with data collected by a cluster of Real-Time Earthquake Analysis for Disaster mItigation (READI) network stations in southern California operated by UNAVCO/PBO and SOPAC.

  3. The project RTPPP (Development of a realtime PPP processing facility) is planned to be a followup project of RAPPP (Innovative Algorithms for Rapid Precise Point Positioning),

    E-print Network

    Schuh, Harald

    RTPPP The project RTPPP (Development of a realtime PPP processing facility) is planned to be a followup project of RAPPP (Innovative Algorithms for Rapid Precise Point Positioning), which has RAPPP, the proposed project RTPPP concentrates on the possibilities of the PPP technique within a real

  4. A reactionless precision pointing actuator

    NASA Technical Reports Server (NTRS)

    Wiktor, Peter

    1987-01-01

    The applications, design, control and testing of an actuator that provides the precise motion control of a gimbal platform without torquing against the basebody to which it is attached are described. The reactionless actuator described was given the name reactuator.

  5. High-Precision Platform Positioning with a Single GPS Receiver

    Microsoft Academic Search

    Sunil B. Bisnath; Richard B. Langley

    2001-01-01

    The goal of the research described in this paper is the design of a GPS data processing technique capable of producing high-precision positioning results, regardless of platform dynamics, utilising only a single, high-quality receiver. This is accomplished by combining two processing philosophies: point positioning - making use of precise GPS constellation ephemeris and clock offset information to estimation a single

  6. Shaping a Morphogen Gradient for Positional Precision

    Microsoft Academic Search

    Feng He; Timothy E. Saunders; Ying Wen; David Cheung; Renjie Jiao; Pieter Rein ten Wolde; Martin Howard; Jun Ma

    2010-01-01

    Morphogen gradients, which provide positional information to cells in a developing tissue, could in principle adopt any nonuniform profile. To our knowledge, how the profile of a morphogen gradient affects positional precision has not been well studied experimentally. Here, we compare the positional precision provided by the Drosophila morphogenetic protein Bicoid (Bcd) in wild-type (wt) embryos with embryos lacking an

  7. PRECISION POINTING OF IBEX-Lo OBSERVATIONS

    SciTech Connect

    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

    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.

  8. Algorithms for arbitrary precision floating point arithmetic

    Microsoft Academic Search

    Douglas M. Priest

    1991-01-01

    The author presents techniques for performing computations of very high accuracy using only straightforward floating-point arithmetic operations of limited precision. The validity of these techniques is proved under very general hypotheses satisfied by most implementations of floating-point arithmetic. To illustrate the applications of these techniques, an algorithm is presented which computes the intersection of a line and a line segment.

  9. Precise Applications Of The Global Positioning System

    NASA Technical Reports Server (NTRS)

    Lichten, Stephen M.

    1992-01-01

    Report represents overview of Global Positioning System (GPS). Emphasizes those aspects of theory, history, and status of GPS pertaining to potential utility for highly precise scientific measurements. Current and anticipated applications include measurements of crustal motions in seismically active regions of Earth, measurements of rate of rotation of Earth and orientation of poles, tracking of non-GPS spacecraft in orbit around Earth, surveying, measurements of radio-signal-propagation delays, determinations of coordinates of ground stations, and transfer of precise time signals worldwide.

  10. Micro-Precision Interferometer: Pointing Control System

    NASA Technical Reports Server (NTRS)

    O'Brien, John

    1995-01-01

    This paper describes the development of the wavefront tilt (pointing) control system for the JPL Micro-Precision Interferometer (MPI). This control system employs piezo-electric actuators and a digital imaging sensor with feedback compensation to reject errors in instrument pointing. Stringent performance goals require large feedback, however, several characteristics of the plant tend to restrict the available bandwidth. A robust 7th-order wavefront tilt control system was successfully implemented on the MPI instrument, providing sufficient disturbance rejection performance to satisfy the established interference fringe visibility.

  11. Toward more precise beam position measurements

    SciTech Connect

    Clark, J C; Fessenden, T J; Holmes, C

    1999-05-12

    For the past year or so we have been examining the properties and limitations of the beam bugs in use in the ETA program at LLNL with a view toward improving the accuracy of beam position and current measurements. When considering measurements of beam position, it is very important to distinguish between relative and absolute position measurements. A relative position measurement determines only the amplitude and direction of the motion of the beam within the transport tube. If one knew where the beam was, one could determine its new position. A relative measurement is essentially independent of errors in mechanical fabrication or electrical components. The minimum measurable displacement is only limited by the strength of the electrical signals or the signal to noise ratio of the position signal. An absolute position measurement is much more challenging. All inaccuracies in mechanical components and fabrication, electrical components, installation and assembly errors must be considered and controlled along with the issues common to relative position measurements. However, if the object is to strike a small specific point on a target or pass the beam through a small hole, absolute beam position measurements are required. The following is a summary of our progress including conclusions and recommendations for developments and improvements. This is, of course, only a step in beam bug development and there is plenty of room for others to contribute.

  12. Point Positioning Service for Natural Hazard Monitoring

    NASA Astrophysics Data System (ADS)

    Bar-Sever, Y. E.

    2014-12-01

    In an effort to improve natural hazard monitoring, JPL has invested in updating and enlarging its global real-time GNSS tracking network, and has launched a unique service - real-time precise positioning for natural hazard monitoring, entitled GREAT Alert (GNSS Real-Time Earthquake and Tsunami Alert). GREAT Alert leverages the full technological and operational capability of the JPL's Global Differential GPS System [www.gdgps.net] to offer owners of real-time dual-frequency GNSS receivers: Sub-5 cm (3D RMS) real-time, absolute positioning in ITRF08, regardless of location Under 5 seconds turnaround time Full covariance information Estimates of ancillary parameters (such as troposphere) optionally provided This service enables GNSS networks operators to instantly have access to the most accurate and reliable real-time positioning solutions for their sites, and also to the hundreds of participating sites globally, assuring inter-consistency and uniformity across all solutions. Local authorities with limited technical and financial resources can now access to the best technology, and share environmental data to the benefit of the entire pacific region. We will describe the specialized precise point positioning techniques employed by the GREAT Alert service optimized for natural hazard monitoring, and in particular Earthquake monitoring. We address three fundamental aspects of these applications: 1) small and infrequent motion, 2) the availability of data at a central location, and 3) the need for refined solutions at several time scales

  13. Precision Positioning for Shallow Water Drilling

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

    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.

  14. Precision position-control of piezoelectric actuators using charge feedback

    NASA Astrophysics Data System (ADS)

    Main, John A.; Garcia, Ephrahim; Newton, David V.

    1995-05-01

    The issue of precision position control is critical if piezoelectric actuator technology is to be applied in increasingly demanding applications. In one particular application, the NASA NAOMI project, piezoelectric actuators have been proposed as the pointing and focusing elements for thousands of small mirror-lenslets because of their fast response time and load- carrying ability. In this application the positions of these actuators must be precisely controlled both statically and dynamically to the nanometer level. This requirement necessitates a careful study of the concept and design of the driving electronics of the system. This paper is focused on finding an appropriate method for driving piezoelectric stack actuators for ultraprecision position and motion control. In this paper the theoretical basis of the electrical control of piezoelectric stack actuators is derived using the fundamental physical laws governing dielectrics and piezoceramics. It is shown that the relationships used for voltage control of piezoelectric actuators result from an approximation of the constitutive equations. An exact input/output relationship for piezoelectric actuators is derived and shows that displacement relies fundamentally on charge, not voltage. Experimental verification was obtained to illustrate the differences between driving piezoactuators with voltage control and charge control.

  15. High precision applications of the global positioning system

    NASA Technical Reports Server (NTRS)

    Lichten, Stephen M.

    1991-01-01

    The Global Positioning System (GPS) is a constellation of U.S. defense navigation satellites which can be used for military and civilian positioning applications. A wide variety of GPS scientific applications were identified and precise positioning capabilities with GPS were already demonstrated with data available from the present partial satellite constellation. Expected applications include: measurements of Earth crustal motion, particularly in seismically active regions; measurements of the Earth's rotation rate and pole orientation; high-precision Earth orbiter tracking; surveying; measurements of media propagation delays for calibration of deep space radiometric data in support of NASA planetary missions; determination of precise ground station coordinates; and precise time transfer worldwide.

  16. Design and Analysis of Precise Pointing Systems

    NASA Technical Reports Server (NTRS)

    Kim, Young K.

    2000-01-01

    The mathematical models of Glovebox Integrated Microgravity Isolation Technology (g- LIMIT) dynamics/control system, which include six degrees of freedom (DOF) equations of motion, mathematical models of position sensors, accelerometers and actuators, and acceleration and position controller, were developed using MATLAB and TREETOPS simulations. Optimal control parameters of G-LIMIT control system were determined through sensitivity studies and its performance were evaluated with the TREETOPS model of G-LIMIT dynamics and control system. The functional operation and performance of the Tektronix DTM920 digital thermometer were studied and the inputs to the crew procedures and training of the DTM920 were documented.

  17. A floating-point technique for extending the available precision

    Microsoft Academic Search

    T. J. Dekker

    1971-01-01

    A technique is described for expressing multilength floating-point arithmetic in terms of singlelength floating point arithmetic, i.e. the arithmetic for an available (say: single or double precision) floating-point number system. The basic algorithms are exact addition and multiplication of two singlelength floating-point numbers, delivering the result as a doublelength floating-point number. A straight-forward application of the technique yields a set

  18. Evaluation of precision tilt sensors for measuring telescope position

    Microsoft Academic Search

    Robert I. Kibrick; Lloyd B. Robinson; David J. Cowley

    1995-01-01

    This report describes a method for using precision tilt-sensors to measure the position of an equatorial telescope relative to the local horizontal plane. Unlike conventional systems which measure the telescope position using position encoders coupled to the telescope axes, this method avoids many sources of non-repeatable error, such as hysteresis in the telescope structure due to inelastic flexure of the

  19. High precision pointing system based on Risley prism: analysis and simulation

    NASA Astrophysics Data System (ADS)

    Li, Jin-ying; Peng, Qi; Chen, Ke; Fu, Cheng-yu

    2015-02-01

    This paper presents the key issues for high precision pointing system using Risley prism. An iterative optimization algorithm is proposed to solve the inverse problem of Risley Prism and anti-achromatic Risley Prism. Different error sources, particularly Risley prism's rotation errors and rotation axis jitters are considered. Error propagation formula between pointing accuracy and rotation position is deduced. Finally, a beam steering simulation system including target position creating module, Risley Prism inverse solution module, Risley Prism rotation control module and beam pointing module is established. The simulation results show that it can achieve better than 1 arcsec pointing accuracy.

  20. The Online Positioning User Service: a Web Utility for Precise Geodetic Positioning in the Geosciences

    NASA Astrophysics Data System (ADS)

    Stone, W. A.

    2014-12-01

    Geoscientists often require precise positioning capability to support research. Accurate Global Navigation Satellite System (GNSS) positioning is a specialized skill involving expertise and fraught with accuracy-compromising nuances. With the goal of providing a robust and high accuracy positioning tool and enhanced access to the United States' National Spatial Reference System (NSRS), the nation's fundamental positioning infrastructure, NOAA's National Geodetic Survey (NGS) developed the Online Positioning User Service (OPUS). OPUS is a free Web utility for processing user-submitted GNSS observations and producing geodetic coordinates referenced to both NSRS and a global reference frame. Relying on NGS' national network of GNSS Continuously Operating Reference Stations (CORS), OPUS is a powerful and user-friendly tool for production and scientific research. OPUS is widely used in geomatics professions and holds great, yet not fully tapped, potential for research geoscientists requiring accurate positional information. OPUS became operational in 2002 as a single point processing tool for multi-hour GPS occupations (OPUS-Static). Its capability has since evolved, adding the ability to process short (15 minutes) sessions (OPUS-RapidStatic) and to provide a solution sharing option. All OPUS variations have proven to be popular, with typical monthly submissions now numbering 40,000. In 2014, NGS released a network version of OPUS, OPUS-Projects, the focus of this discussion. Although other versions of OPUS process a single GNSS occupation per submission, OPUS-Projects offers rigorous geodetic network analysis and processing capability by assembling and processing GNSS observations collected over time and at multiple locations. Least squares geodetic network adjustment of included observations results in an optimal set of station coordinates, including their uncertainties and graphical statistical plots, derived from user-submitted observation data, CORS observation data and coordinates, satellite ephemerides, and models. Users have the ability to configure the processing, including tropospheric modeling, definition of observation sessions, network design, adjustment constraints, station descriptive information, and integration with passive geodetic control.

  1. A New Algorithm for GNSS Precise Positioning in Constrained Area

    E-print Network

    Paris-Sud XI, Université de

    to GPS, EGNOS and GALILEO. He is now technical director of M3 Systems and is following M3 Systems' development on GPS, EGNOS and Galileo algorithms and receivers. Recently, he has been particularly involved Point Positioning (PPP) and Real-Time Kinematic (RTK) techniques provide a position estimate

  2. Astrophysical Adaptation of Points, the Precision Optical Interferometer in Space

    NASA Technical Reports Server (NTRS)

    Reasenberg, Robert D.; Babcock, Robert W.; Murison, Marc A.; Noecker, M. Charles; Phillips, James D.; Schumaker, Bonny L.; Ulvestad, James S.; McKinley, William; Zielinski, Robert J.; Lillie, Charles F.

    1996-01-01

    POINTS (Precision Optical INTerferometer in Space) would perform microarcsecond optical astrometric measurements from space, yielding submicroarcsecond astrometric results from the mission. It comprises a pair of independent Michelson stellar interferometers and a laser metrology system that measures both the critical starlight paths and the angle between the baselines. The instrument has two baselines of 2 m, each with two subapertures of 35 cm; by articulating the angle between the baselines, it observes targets separated by 87 to 93 deg. POINTS does global astrometry, i.e., it measures widely separated targets, which yields closure calibration, numerous bright reference stars, and absolute parallax. Simplicity, stability, and the mitigation of systematic error are the central design themes. The instrument has only three moving-part mechanisms, and only one of these must move with sub-milliradian precision; the other two can tolerate a precision of several tenths of a degree. Optical surfaces preceding the beamsplitter or its fold flat are interferometrically critical; on each side of the interferometer, there are only three such. Thus, light loss and wavefront distortion are minimized. POINTS represents a minimalistic design developed ab initio for space. Since it is intended for astrometry, and therefore does not require the u-v-plane coverage of an imaging, instrument, each interferometer need have only two subapertures. The design relies on articulation of the angle between the interferometers and body pointing to select targets; the observations are restricted to the 'instrument plane.' That plane, which is fixed in the pointed instrument, is defined by the sensitive direction for the two interferometers. Thus, there is no need for siderostats and moving delay lines, which would have added many precision mechanisms with rolling and sliding parts that would be required to function throughout the mission. Further, there is no need for a third interferometer, as is required when out-of-plane observations are made. An instrument for astrometry, unlike those for imaging, can be compact and yet scientifically productive. The POINTS instrument is compact and therefore requires no deployment of precision structures, has no low-frequency (i.e., under 100 Hz) vibration modes, and is relatively easy to control thermally. Because of its small size and mass, it is easily and quickly repointed between observations. Further, because of the low mass, it can be economically launched into high Earth orbit which, in conjunction with a solar shield, yields nearly unrestricted sky coverage and a stable thermal environment.

  3. Helicopter precision approach capability using the Global Positioning System

    NASA Technical Reports Server (NTRS)

    Kaufmann, David N.

    1992-01-01

    The period between 1 July and 31 December, 1992, was spent developing a research plan as well as a navigation system document and flight test plan to investigate helicopter precision approach capability using the Global Positioning System (GPS). In addition, all hardware and software required for the research was acquired, developed, installed, and verified on both the test aircraft and the ground-based reference station.

  4. A comparison of four precise global positioning system geodetic receivers

    NASA Technical Reports Server (NTRS)

    Goad, C. C.; Sims, M. L.; Young, L. E.

    1985-01-01

    Four precise global positioning system (GPS) geodetic receivers were operated simultaneously in January and February 1984 over ten baselines ranging in distance from 13 to 1304 km. Several of the baselines had been previously measured using very long baseline interferometry and, therefore, provide very good standards to which the satellite results can be compared. Results of these experiments are presented along with a brief description of each receiver and the associated analysis techniques.

  5. Precise Measurement of the Positive Muon Anomalous Magnetic Moment

    Microsoft Academic Search

    H. N. Brown; G. Bunce; R. M. Carey; P. Cushman; G. T. Danby; P. T. Debevec; M. Deile; H. Deng; W. Deninger; S. K. Dhawan; V. P. Druzhinin; L. Duong; E. Efstathiadis; F. J. Farley; G. V. Fedotovich; S. Giron; F. Gray; D. Grigoriev; M. Grosse-Perdekamp; A. Grossmann; M. F. Hare; D. W. Hertzog; V. W. Hughes; M. Iwasaki; K. Jungmann; D. Kawall; M. Kawamura; B. I. Khazin; J. Kindem; F. Krienen; I. Kronkvist; R. Larsen; Y. Y. Lee; I. Logashenko; R. McNabb; W. Meng; J. Mi; J. P. Miller; W. M. Morse; D. Nikas; C. J. Onderwater; Y. Orlov; C. S. Özben; J. M. Paley; C. Polly; J. Pretz; R. Prigl; G. Zu Putlitz; S. I. Redin; O. Rind; B. L. Roberts; N. Ryskulov; S. Sedykh; Y. K. Semertzidis; Yu. M. Shatunov; E. P. Sichtermann; E. Solodov; M. Sossong; A. Steinmetz; L. R. Sulak; C. Timmermans; A. Trofimov; D. Urner; P. von Walter; D. Warburton; D. Winn; A. Yamamoto; D. Zimmerman

    2001-01-01

    A precise measurement of the anomalous g value, amu = \\\\(g-2\\\\)\\/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron. The result amu+ = 11 659 202\\\\(14\\\\) \\\\(6\\\\)×10-10 (1.3 ppm) is in good agreement with previous measurements and has an error one third that of the combined previous data. The current theoretical value from the standard

  6. Design of a reversible single precision floating point subtractor.

    PubMed

    Anantha Lakshmi, Av; Sudha, Gf

    2014-01-01

    In recent years, Reversible logic has emerged as a major area of research due to its ability to reduce the power dissipation which is the main requirement in the low power digital circuit design. It has wide applications like low power CMOS design, Nano-technology, Digital signal processing, Communication, DNA computing and Optical computing. Floating-point operations are needed very frequently in nearly all computing disciplines, and studies have shown floating-point addition/subtraction to be the most used floating-point operation. However, few designs exist on efficient reversible BCD subtractors but no work on reversible floating point subtractor. In this paper, it is proposed to present an efficient reversible single precision floating-point subtractor. The proposed design requires reversible designs of an 8-bit and a 24-bit comparator unit, an 8-bit and a 24-bit subtractor, and a normalization unit. For normalization, a 24-bit Reversible Leading Zero Detector and a 24-bit reversible shift register is implemented to shift the mantissas. To realize a reversible 1-bit comparator, in this paper, two new 3x3 reversible gates are proposed The proposed reversible 1-bit comparator is better and optimized in terms of the number of reversible gates used, the number of transistor count and the number of garbage outputs. The proposed work is analysed in terms of number of reversible gates, garbage outputs, constant inputs and quantum costs. Using these modules, an efficient design of a reversible single precision floating point subtractor is proposed. Proposed circuits have been simulated using Modelsim and synthesized using Xilinx Virtex5vlx30tff665-3. The total on-chip power consumed by the proposed 32-bit reversible floating point subtractor is 0.410 W. PMID:24455466

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

    USGS Publications Warehouse

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

    2006-01-01

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

  8. High-precision positioning system of four-quadrant detector based on the database query

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Deng, Xiao-guo; Su, Xiu-qin; Zheng, Xiao-qiang

    2015-02-01

    The fine pointing mechanism of the Acquisition, Pointing and Tracking (APT) system in free space laser communication usually use four-quadrant detector (QD) to point and track the laser beam accurately. The positioning precision of QD is one of the key factors of the pointing accuracy to APT system. A positioning system is designed based on FPGA and DSP in this paper, which can realize the sampling of AD, the positioning algorithm and the control of the fast swing mirror. We analyze the positioning error of facular center calculated by universal algorithm when the facular energy obeys Gauss distribution from the working principle of QD. A database is built by calculation and simulation with MatLab software, in which the facular center calculated by universal algorithm is corresponded with the facular center of Gaussian beam, and the database is stored in two pieces of E2PROM as the external memory of DSP. The facular center of Gaussian beam is inquiry in the database on the basis of the facular center calculated by universal algorithm in DSP. The experiment results show that the positioning accuracy of the high-precision positioning system is much better than the positioning accuracy calculated by universal algorithm.

  9. Closed loop high precision position control system with optical scale

    NASA Astrophysics Data System (ADS)

    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

    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.

  10. Electrostatic Microactuators for Precise Positioning of Neural Microelectrodes

    PubMed Central

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

    2006-01-01

    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 ?m. 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

  11. An approach for filtering hyperbolically positioned underwater acoustic telemetry data with position precision estimates

    USGS Publications Warehouse

    Meckley, Trevor D.; Holbrook, Christopher M.; Wagner, C. Michael; Binder, Thomas R.

    2014-01-01

    The use of position precision estimates that reflect the confidence in the positioning process should be considered prior to the use of biological filters that rely on a priori expectations of the subject’s movement capacities and tendencies. Position confidence goals should be determined based upon the needs of the research questions and analysis requirements versus arbitrary selection, in which filters of previous studies are adopted. Data filtering with this approach ensures that data quality is sufficient for the selected analyses and presents the opportunity to adjust or identify a different analysis in the event that the requisite precision was not attained. Ignoring these steps puts a practitioner at risk of reporting errant findings.

  12. High precision pointing with a multiline spectrometer at the VTT

    NASA Astrophysics Data System (ADS)

    Staiger, J.

    2012-12-01

    We are investigating the pointing quality of the VTT, Tenerife under the aspect of suitability for long-term heliosesimological observations. Tests have shown that thermal and mechanical loads within the telescope may create spurious image drifts with shift rates of up to 5 arcsec per hour. During daylong recordings this will reduce significantly the effective size of the field-of-view and may infer artificial lateral movements into the data. The underlying problem that not all image position offsets developing during a measurement may be compensated for is common to most high-resolution solar telescopes independently of the type of pointing system used. We are developing new approaches to address this problem which are to be tested in the near future at the VTT. The simulations established so far show that the problem may be reduced by more than 90 %.

  13. New linear piezomotors for high-force precise positioning applications

    NASA Astrophysics Data System (ADS)

    Le Letty, Ronan; Claeyssen, Frank; Barillot, Francois; Six, Marc F.; Bouchilloux, Philippe

    1998-07-01

    Piezomotors are an increasingly competitive alternative to electromagnetic stepper motors, especially in applications where large bandwidths and/or precise positioning control are desired. Piezomotors use a combination of electromechanical and frictional forces and, compared to conventional electromagnetic motors, have the advantages that no power supply is required to maintain the motor in position and no lubrication is necessary in the device. The operating principle of these motors relies on the use of an ultrasonic vibration, which is created via the piezoelectric effect (at resonance in most cases), in order to generate vibration forces at the `stator/rotor' contact interface. A mechanical preload is also applied at this contact interface and is responsible for the motor's holding force at rest. To meet the specifications of an aerospace application, we developed a new design of Linear PiezoMotors (LPMs). The first prototype we built shows very promising results, and makes the LPM a serious candidate to replace conventional stepper motors. The LPM features the following characteristics: a standing force of 100 N, a blocked force of 37 N, a maximum actuation speed of 23 mm/s, a maximum run of 10 mm, a mass of 500 g, an electrical power of 2.2 W, and a position accuracy superior to 1 micrometers . To our knowledge, the driving force delivered by the LPM has never before been achieved in resonant devices. This paper describes the physical operating principles of the LPM, as well as the modeling tools and experimental techniques we used for its development. Several implementation schemes are also presented and show the wide range of possible applications offered by the linear piezomotor.

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

    PubMed

    Elati, Mohamed; Nicolle, Rémy; Junier, Ivan; Fernández, David; Fekih, Rim; Font, Julio; Képès, François

    2013-02-01

    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. PMID:23241390

  15. Faculty Position in Ultra High Precision Robotics & Manufacturing

    E-print Network

    Candea, George

    , manipulation and metrology systems targeting additive manufacturing; · New kinematics, quasi-perfect guidings, actuators, transmission systems, sensors and methods targeting ultra-high precision additive manufacturing. Specific areas include, but are not limited to: · Design of innovative ultra-high precision machining

  16. Multipliers for Floating-Point Double Precision and Beyond LIP Research Report RR2010-15

    E-print Network

    Paris-Sud XI, Université de

    Multipliers for Floating-Point Double Precision and Beyond on FPGAs LIP Research Report RR2010.Banescu,Radu.Tudoran}@cs.utcluj.ro Abstract--The implementation of high-precision floating-point applications on reconfigurable hardware requires large multipli- ers. Full multipliers are the core of floating-point multipliers. Truncated

  17. Robot positioning based on point-to-point motion capability

    SciTech Connect

    Park, Y. S.; Cho, H. S.; Koh, K. C.

    2000-03-20

    This paper presents an optimal search method for determining the base location of a robot manipulator so that the robot can have a designated point-to-point (PTP) motion capabilities. Based on the topological characterization of the manipulator workspace and the definitions of various p-connectivity, a computational method is developed for enumerating various PTP motion capabilities into quantitative cost functions. Then an unconstrained search by minimizing the cost function yields the task feasible location of the robot base. This methodology is useful for placement of mobile manipulators and robotic workcell layout design.

  18. Intuitionistic Fixed Point Theories for Strictly Positive Operators

    Microsoft Academic Search

    Christian Rüede; Thomas Strahm

    2002-01-01

    In this paper it is shown that the intuitionistic fixed point theory#IDi# (strict) for # times iterated fixed points of strictly positive operatorforms is conservative for negative arithmetic and #02 sentences over thetheory ACA -i # for # times iterated arithmetic comprehension withoutset parameters. This generalizes results previously due to Buchholz[5] and Arai [2].Keywords: Intuitionistic fixed point theories, strictly positive

  19. Optimal Floating-Point Realizations of Finite-Precision Digital Controllers

    E-print Network

    Chen, Sheng

    Optimal Floating-Point Realizations of Finite-Precision Digital Controllers Jun Wu Ý , Sheng Chen Þ-loop stability issue of finite-precision realizations for digital controllers imple- mented in floating-point arithmetic. Unlike the existing methods which only address the effect of the mantissa bits in floating

  20. Kangaroo points and oblique polynomials in resolution of positive characteristic

    E-print Network

    Hauser, Herwig

    2008-01-01

    The article surveys the theory of kangaroo points as they appear in the resolution of singularities in positive characteristic. They represent one of the main obstructions for transcribing the characteristic zero proof of resolution to positive characteristic. Kangaroo points are classified through the concept of oblique polynomials. The results of the article are used in Hironaka's recent program towards the resolution of singularities in positive characteristic.

  1. Strategies for high-precision Global Positioning System orbit determination

    NASA Technical Reports Server (NTRS)

    Lichten, Stephen M.; Border, James S.

    1987-01-01

    Various strategies for the high-precision orbit determination of the GPS satellites are explored using data from the 1985 GPS field test. Several refinements to the orbit determination strategies were found to be crucial for achieving high levels of repeatability and accuracy. These include the fine tuning of the GPS solar radiation coefficients and the ground station zenith tropospheric delays. Multiday arcs of 3-6 days provided better orbits and baselines than the 8-hr arcs from single-day passes. Highest-quality orbits and baselines were obtained with combined carrier phase and pseudorange solutions.

  2. DEVELOPMENTAL TEST AND EVALUATION OF HELICOPTERS USING A PRECISION DIFFERENTIAL GLOBAL POSITIONING SYSTEM

    Microsoft Academic Search

    Mark Hardesty; Mark Metzger; Daphne Fredrickson; Engineer McDonnell; Douglas Helicopter

    Development of new and innovative applications for high precision differential global positioning syst ems (DGPS) has exploded in the last two years. Real-ti me three-dimensional accuracy's of under three centime ters and processed position update rates in excess of four h ertz, along with position update latencies of under eight y milliseconds are now commercially available. Immediate position information of

  3. Precise Viscosity Measurements Very Close to Critical Points

    NASA Technical Reports Server (NTRS)

    Moldover, M. R.; Berg, B.

    1985-01-01

    A torsion oscillator is being developed to measure the viscosity of fluids at moderate temperatures (0-100 C) and pressures (0-10 MPa) at very low frequencies (0.5 Hz) and very low shear rates (0.05/sec). These conditions are required to measure the shear viscosity of fluids extremely close to the critical point. The oscillator, thermostat, vacuum system, and instrumentation were assembled and are undergoing debugging. Preliminary measurements indicate that the system has a noise corresponding to 0.2% of the viscosity of methanol-cyclohexane mixtures near the consolute point.

  4. Precision Pointing for the Laser Interferometry Space Antenna Mission

    NASA Technical Reports Server (NTRS)

    Hyde, T. Tupper; Maghami, P. G.

    2003-01-01

    The Laser Interferometer Space Antenna (LISA) mission is a planned NASA-ESA gravitational wave detector consisting of three spacecraft in heliocentric orbit. Lasers are used to measure distance fluctuations between proof masses aboard each spacecraft to the picometer level over a 5 million kilometer separation. Each spacecraft and its two laser transmit/receive telescopes must be held stable in pointing to less than 8 nanoradians per root Hertz in the frequency band 0.1-100 mHz. The pointing error is sensed in the received beam and the spacecraft attitude is controlled with a set of micro-Newton thrusters. Requirements, sensors, actuators, control design, and simulations are described.

  5. Pointing Control System for a High Precision Flight Telescope

    SciTech Connect

    BENTLEY,ANTHONY E.; WILCOXEN,JEFFREY LEE

    2000-12-01

    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.

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

    USGS Publications Warehouse

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

    1989-01-01

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

  7. Global positioning system measurements for crustal deformation: precision and accuracy.

    PubMed

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

    1989-06-16

    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. PMID:17820661

  8. High precision global positioning system for mining applications

    SciTech Connect

    O`Grady, M. [Trimble Navigation, Ltd., Elgin, IL (United States)

    1997-12-01

    The author discusses today`s satellite technology that has lead to the development of a system that will increase safety and production in surface mining. The Department of Defense is maintaining a satellite system made up of 24 NavStar satellites that allow the use of their frequencies to position equipment anywhere on Earth. The previous satellite system was called the Transit system or Sat-Nav. It consisted of low-orbit satellites (not many up there) that ground-based receivers needed three days of logged data to process sub-meter accuracy positions. With the NavStar network of satellites, centimeter accuracy can be achieved within just a few minutes. Changes to the way one used to survey in the mining industry are being replaced with the Global Positioning System. It has proven to be a system that is more accurate and after the typical learning curve that is required by any new system, will lead to higher productivity; hence, financial rewards are in the immediate future.

  9. OPTIMAL FINITE-PRECISION CONTROLLER REALIZATIONS IN BLOCK-FLOATING-POINT FORMAT

    E-print Network

    Chen, Sheng

    OPTIMAL FINITE-PRECISION CONTROLLER REALIZATIONS IN BLOCK-FLOATING-POINT FORMAT Jun Wu Ý , Sheng (FWL) block-floating-point (BFP) arithmetic and investigates the closed-loop stability issue of finite. Keywords ­ digital controller, finite word length, block-floating-point, closed-loop stability. 1

  10. A precision pointing system for space telescope class optical trackers

    NASA Astrophysics Data System (ADS)

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

    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.

  11. A precision pointing system for space telescope class optical trackers

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  12. PROBLEMS IN ULTRAHIGH PRECISION GPS POSITION ALEKSEI BELTUKOV, JONGHO CHOI, LEONARD HOFFNUNG,

    E-print Network

    PROBLEMS IN ULTRA­HIGH PRECISION GPS POSITION ESTIMATION ALEKSEI BELTUKOV, JONGHO CHOI, LEONARD used to resolve integer ambiguities inherent in the measurements of GPS phase pseudoranges model for testing ambiguity resolution strategies, and discuss optimal satellite selection strategies

  13. Precision Positioning of Hard Disk Drives Using Piezoelectric Actuators With Passive Damping

    Microsoft Academic Search

    K. W. Chan; W. H. Liao; I. Y. Shen

    2008-01-01

    Positioning precision is crucial to today's increasingly high-speed, high-capacity, high-data-density, and miniaturized hard disk drives (HDDs). The demand for higher bandwidth servo systems that can quickly and precisely position the read\\/write head on a high track density becomes more pressing. The idea of applying dual-stage actuators to track servo systems has been studied. However, the current dual-stage actuator design uses

  14. Precise mean sea level measurements using the Global Positioning System

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  15. High-precision three-dimensional coordinate measurement with subwavelength-aperture-fiber point diffraction interferometer

    NASA Astrophysics Data System (ADS)

    Wang, Daodang; Xu, Yangbo; Chen, Xixi; Wang, Fumin; Kong, Ming; Zhao, Jun

    2014-11-01

    To overcome the accuracy limitation due to the machining error of standard parts in measurement system, a threedimensional coordinate measurement method with subwavelength-aperture-fiber point diffraction interferometer (PDI) is proposed, in which the high-precision measurement standard is obtained from the ideal point-diffracted spherical wavefront instead of standard components. On the basis of the phase distribution demodulated from point-diffraction interference field, high-precision three-dimensional coordinate measurement is realized with numerical iteration optimization algorithm. The subwavelength-aperture fiber is used as point-diffraction source to get precise and highenergy spherical wavefront within high aperture angle range, by which the conflict between diffraction wave angle and energy in traditional PDI can be avoided. Besides, a double-iterative method based on Levenbery-Marquardt algorithm is proposed to realize precise reconstruct three-dimensional coordinate. The analysis shows that the proposed method can reach the measurement precision better than microns within a 200×200×300 (in unit of mm) working volume. This measurement method does not rely on the initial iteration value in numerical coordinate reconstruction, and also has high measurement precision, large measuring range, fast processing speed and preferable anti-noise ability. It is of great practicality for measurement of three-dimensional coordinate and calibration of measurement system.

  16. SHAPES - Spatial, High-Accuracy, Position-Encoding Sensor for multi-point, 3-D position measurement of large flexible structures

    NASA Technical Reports Server (NTRS)

    Nerheim, N. M

    1987-01-01

    An electro-optical position sensor for precise simultaneous measurement of the 3-D positions of multiple points on large space structures is described. The sensor data rate is sufficient for most control purposes. Range is determined by time-of-flight correlation of short laser pulses returned from retroreflector targets using a streak tube/CCD detector. Angular position is determined from target image locations on a second CCD. Experimental verification of dynamic ranging to multiple targets is discussed.

  17. AN X-BAND CAVITY FOR A HIGH PRECISION BEAM POSITION MONITOR

    Microsoft Academic Search

    Ronald Johnson; Zenghai Li; Takashi Naito; Jeffrey Rifkin; Stephen Smith; Vernon Smith

    2003-01-01

    The next generation of accelerators will require increasingly precise control of beam position. For example designs for the next linear collider require beam-position monitors (BPMs) with 300 nm resolution. The accelerator designs also place difficult requirements on accuracy and stability. To meet these requirements a cavity BPM operating at 11.424 GHz was designed. The BPM consists of two cavities: an

  18. HIGH PRECISION KINEMATIC POSITIONING USING SINGLE DUAL-FREQUENCY GPS RECEIVER

    Microsoft Academic Search

    Y. Gao; A. Wojciechowski

    Currently, high precision kinematic GPS positioning with centimetre level accuracy can only be carried out using differential GPS (DGPS) positioning techniques which require the deployment of base receiver stations. The requirement to deploy base receiver sta- tions, however, spatially limits the operating range of the rover receiver to about 20 km from the base stations. As a result, it not

  19. Study of precise positioning at L-band using communications satellites

    NASA Technical Reports Server (NTRS)

    1971-01-01

    The L-band positioning experiment is reported which encompassed experiment design, experimentation, and data reduction and analysis. In the experiment the ATS-5 synchronous satellite L-band transponder was used in conjunction with the modified ALPHA 2 navigation receivers to demonstrate the technical capability of precision position fixing for oceanographic purposes. The feasibility of using relative ranging techniques implemented by two identical receiving systems, properly calibrated, to determine a line of position accurately on the surface of the earth was shown. The program demonstrated the level of resolution, repeatibility, precision, and accuracy of existing modest-cost effective navigation equipment. The experiment configuration and data reduction techniques were developed in parallel with the hardware modification tasks. Test results verify the ability of a satellite-based system to satisfy the requirements of precision position fixing.

  20. Adaptive Precision Floating-Point Arithmetic and Fast Robust Geometric Predicates

    Microsoft Academic Search

    Jonathan Richard Shewchuk

    1997-01-01

    .    Exact computer arithmetic has a variety of uses, including the robust implementation of geometric algorithms. This article\\u000a has three purposes. The first is to offer fast software-level algorithms for exact addition and multiplication of arbitrary\\u000a precision floating-point values. The second is to propose a technique for adaptive precision arithmetic that can often speed\\u000a these algorithms when they are

  1. Intuitionistic fixed point theories for strictly positive operators

    E-print Network

    Jäger, Gerhard

    Intuitionistic fixed point theories for strictly positive operators Christian R¨uede Thomas Strahm parameters. This generalizes results previously due to Buchholz [5] and Arai [2]. Keywords: Intuitionistic]. Not long ago it has been observed by Buchholz [5] that the choice of logic is crucial in the context

  2. An Approach for High-precision Stand-alone Positioning in a Dynamic Environment

    NASA Astrophysics Data System (ADS)

    Halis Saka, M.; Metin Alkan, Reha; Ozpercin, Ali?ir

    2015-04-01

    In this study, an algorithm is developed for precise positioning in dynamic environment utilizing a single geodetic GNSS receiver using carrier phase data. In this method, users should start the measurement on a known point near the project area for a couple of seconds making use of a single dual-frequency geodetic-grade receiver. The technique employs iono-free carrier phase observations with precise products. The equation of the algorithm is given below; Sm(t(i+1))=SC(ti)+[?IF (t(i+1) )-?IF (ti)] where, Sm(t(i+1)) is the phase-range between satellites and the receiver, SC(ti) is the initial range computed from the initial known point coordinates and the satellite coordinates and ?IF is the ionosphere-free phase measurement (in meters). Tropospheric path delays are modelled using the standard tropospheric model. To accomplish the process, an in-house program was coded and some functions were adopted from Easy-Suite available at http://kom.aau.dk/~borre/easy. In order to assess the performance of the introduced algorithm in a dynamic environment, a dataset from a kinematic test measurement was used. The data were collected from a kinematic test measurement in Istanbul, Turkey. In the test measurement, a geodetic dual-frequency GNSS receiver, Ashtech Z-Xtreme, was set up on a known point on the shore and a couple of epochs were recorded for initialization. The receiver was then moved to a vessel and data were collected for approximately 2.5 hours and the measurement was finalized on a known point on the shore. While the kinematic measurement on the vessel were carried out, another GNSS receiver was set up on a geodetic point with known coordinates on the shore and data were collected in static mode to calculate the reference trajectory of the vessel using differential technique. The coordinates of the vessel were calculated for each measurement epoch with the introduced method. With the purpose of obtaining more robust results, all coordinates were calculated once again by inversely, i.e. from the last epoch to the first one. In this way, the estimated coordinates were also controlled. The average of both computed coordinates were used as vessel coordinates and then compared with the known-coordinates those of geodetic receiver epoch by epoch. The results indicate that the calculated coordinates from the introduced method are consistent with the reference trajectory with an accuracy of about 1 decimeter. In contrast, the findings imply lower accuracy for height components with an accuracy of about 2 decimeters. This accuracy level meets the requirement of many applications including some marine applications, precise hydrographic surveying, dredging, attitude control of ships, buoys and floating platforms, marine geodesy, navigation and oceanography.

  3. Efficient methods for determining precise orbits of low Earth orbiters using the Global Positioning System

    NASA Astrophysics Data System (ADS)

    Bock, Heike

    The main part of this work dealt with the development and evaluation of efficient methods for precise orbit determination of LEOs. A kinematic approach using GPS zero-difference observations was developed (program LEOKIN) and a procedure for generation of dynamic and reduced-dynamic orbits was presented (program SATORB). The procedures have been tested using long GPS data series gathered by two LEO satellites, namely CHAMP and SAC-C. An external comparison was available for the time interval of the eleven days of the IGS CHAMP test campaign (May 20 to 30, 2001). The orbit solution generated at the Technical University of Munich (TUM), Germany, using the Bernese GPS Software was used for this purpose. The TUM-solution is believed to be one of the best solutions contributing to the IGS test campaign. Comparisons with this solution showed that both our best kinematic trajectory and a post-fit reduced-dynamic orbit based on this kinematic solution compare within an RMS error per coordinate (of a Helmert transformation) of about 10 cm with the TUM-solutions. This indicates that LEO orbits with a quality of about 10 cm result from our analyses. The goal of developing efficient methods for precise orbit determination of LEOs is therefore achieved with the zero-difference kinematic point positioning procedure in LEOKIN and the program SATORB to generate reduced-dynamic orbits. It is worth mentioning that the procedure, when using only code observations as input, results in reduced-dynamic orbits with a qualitiy of already 30 cm RMS.

  4. A device to improve the SNR of the measurement of the positional floating reference point

    NASA Astrophysics Data System (ADS)

    Jiang, Jingying; Rong, Xuzheng; Zhang, Hao; Xu, Kexin

    2013-02-01

    Previous studies have preliminarily validated the floating reference method and shown that it has the potential to improve the accuracy of non-invasive blood glucose sensing by Near-Infrared Spectroscopy. In order to make this method practical, it is necessary to precisely verify and measure the existence and variation features of the positional floating reference point. In this talk, a device which can precisely verify and measure the positional floating reference point is built. Since the light intensity of diffuse reflectance from the tested sample is very weak, a multipath detecting fibers system was built to improve signal-to-noise ratio. In this system, the fibers encircle the light source fiber which is regarded as the reference center of detecting fibers while they are moving. In addition, the position of each fiber is accurately controlled by manual translation stage to keep all detecting fibers always in the same radius around light source fiber. This ensures that received signal is coming from the same radial distance of light source. The variation of signal-to-noise ratio along with the different radial distance was investigated based on experiments. Results show that the application of this device could improve signal-to-noise ratio, and provide a new experimental method for the further study of positional floating reference point.

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

    PubMed Central

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

    2009-01-01

    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

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

    PubMed

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

    2009-01-01

    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

  7. Ultra precision positioning system for servo motor–piezo actuator using the dual servo loop and digital filter implementation

    Microsoft Academic Search

    Heui Jae Pahk; Dong Sung Lee; Jong Ho Park

    2001-01-01

    The ultra precision positioning technique has become one of the important parts in the development of precision machines. For positioning systems having a long stroke with ultra precision, a combined system including a global stage (coarse stage) and a micro stage (fine stage) is designed in this paper. A ball screw based servo motor is used as the global stage

  8. Precise spacecraft position measurement for spaceborne distributed aperture\\/coherent array processing (SDA\\/CAP)

    Microsoft Academic Search

    M. S. Kaplan; P. A. Minthorn

    1986-01-01

    Various precise spacecraft position measurement techniques based on spaceborne distributed aperture\\/coherent array processing (SDA\\/CAP) technology are studied. The implementation of SDA\\/CAP technology to linear beamforming and multistatic synthetic aperture radar techniques is examined. The effects of spacecraft position measurement error on linear beamforming and multistatic aperture radar technique applications of SDA\\/CAP technologies are investigated. An angular dependence is observed between

  9. Tobacco point of sale advertising increases positive brand user imagery

    PubMed Central

    Donovan, R; Jancey, J; Jones, S

    2002-01-01

    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. PMID:12198267

  10. Precise tracking of remote sensing satellites with the Global Positioning System

    Microsoft Academic Search

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

    1990-01-01

    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

  11. Visual servoing is a manipulation control strategy that precisely positions objects using imprecisely calibrated

    E-print Network

    . In its basic form, image­based visual servoing is a purely reactive manipulator motion strategyAbstract Visual servoing is a manipulation control strategy that precisely positions objects using­based manipulation strategies such as visual servoing into robotic systems, a system frame­ work and a task

  12. Innovative High-Precision Position Sensor Systems for Robotic and Automotive Applications

    Microsoft Academic Search

    M. R. Kirchhoff; C. Boese; J. Güttler; M. Feldmann; S. Büttgenbach

    2009-01-01

    Easily integrated high-precision position sensor systems manufactured by means of MEMS technologies are presented in this work. Two contactless working principles, inductive and capacitive, have been brought in operation successfully. The inductive sensors detect the direction of vector magnetic fields. Combined with permanent magnets, they are optimized for high-resolution angular measurements within the joints of parallel robots. The capacitive linear

  13. New fully integrated 3-D silicon Hall sensor for precise angular-position measurements

    Microsoft Academic Search

    F. Burger; P.-A. Besse; R. S. Popovic

    1998-01-01

    A ± 0.3 ° precision in angular-position measurement over a 360 ° rotation has been obtained with a novel fully integrated 3-D magnetic sensor. This low-field sensor, based on buried silicon Hall devices, combines two vertical Hall devices for the planar sensitivity and novel horizontal Hall elements for the orthogonal sensitivity. The advantages of this sensor are its very low

  14. High-Precision Absolute Positioning of Medical Instruments in MRI Systems

    Microsoft Academic Search

    Eric Aboussouan; Sylvain Martel

    2006-01-01

    An absolute positioning technique has been developed for ferromagnetic markers in medical instruments and untethered devices operating in a magnetic resonance imaging (MRI) system. This technique allows high precision 3D readings of the location of the device with respect to the absolute center of the MRI bore. The local magnetic field induced by the device is used as a signature

  15. Precise Positioning of Ocean Bottom Seismometer by Using Acoustic Transponder and CTD

    Microsoft Academic Search

    Hajime Shiobara; Ayako Nakanishi; Hideki Shimamura; Rolf Mjelde; Toshihiko Kanazawa; Eivind W. Berg

    1997-01-01

    We have obtained precise estimates of the position of Ocean Bottom Seismometers (OBS) on the sea bottom. Such estimates are usually uncertain due to their free falling deployment. This uncertainty is small enough, or is correctable, with OBS spacing of more than 10 km usually employed in crustal studies. But, for example, if the spacing is only 200 m for

  16. Compensation of temperature induced position measuring error in the ultra-precision moving robot system

    Microsoft Academic Search

    Jooho Hwang; Chang-Kyu Song; Bang-Won Kim; Chul-Ho Choi

    2008-01-01

    In this paper, for measuring the position error of the ultra precision stage more accurately, the refractive index compensation method is introduced. The wave length of the laser interferometer is compensated using the simultaneously measured the variation of room temperature in the method. In order to investigate the limit of compensation, the stationary test against two fixed reflectors mounted on

  17. 546 precise astrometric positions of minor planets obtained at the GPO telescope of ESO - La Silla.

    NASA Astrophysics Data System (ADS)

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

    1989-12-01

    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.

  18. Positive area and inaccessible fixed points for hedgehogs

    E-print Network

    Biswas, Kingshook

    2010-01-01

    Let f be a germ of holomorphic diffeomorphism with an irra- tionally indifferent fixed point at the origin in C (i.e. f(0) = 0, f'(0) = e 2pi i alpha, alpha in R - Q). Perez-Marco showed the existence of a unique family of nontrivial invariant full continua containing the fixed point called Siegel compacta. When f is non-linearizable (i.e. not holomorphically conjugate to the rigid rotation R_{alpha}(z) = e 2pi i z) the invariant compacts obtained are called hedgehogs. Perez-Marco developed techniques for the construction of examples of non-linearizable germs; these were used by the author to construct hedge- hogs of Hausdorff dimension one, and adapted by Cheritat to construct Siegel disks with pseudo-circle boundaries. We use these techniques to construct hedgehogs of positive area and hedgehogs with inaccessible fixed points.

  19. Precision Pointing Control System (PPCS) system design and analysis. [for gimbaled experiment platforms

    NASA Technical Reports Server (NTRS)

    Frew, A. M.; Eisenhut, D. F.; Farrenkopf, R. L.; Gates, R. F.; Iwens, R. P.; Kirby, D. K.; Mann, R. J.; Spencer, D. J.; Tsou, H. S.; Zaremba, J. G.

    1972-01-01

    The precision pointing control system (PPCS) is an integrated system for precision attitude determination and orientation of gimbaled experiment platforms. The PPCS concept configures the system to perform orientation of up to six independent gimbaled experiment platforms to design goal accuracy of 0.001 degrees, and to operate in conjunction with a three-axis stabilized earth-oriented spacecraft in orbits ranging from low altitude (200-2500 n.m., sun synchronous) to 24 hour geosynchronous, with a design goal life of 3 to 5 years. The system comprises two complementary functions: (1) attitude determination where the attitude of a defined set of body-fixed reference axes is determined relative to a known set of reference axes fixed in inertial space; and (2) pointing control where gimbal orientation is controlled, open-loop (without use of payload error/feedback) with respect to a defined set of body-fixed reference axes to produce pointing to a desired target.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    In this contribution, we present a GPS+GLONASS+BeiDou+Galileo four-system model to fully exploit the observations of all these four navigation satellite systems for real-time precise orbit determination, clock estimation and positioning. A rigorous multi-GNSS analysis is performed to achieve the best possible consistency by processing the observations from different GNSS together in one common parameter estimation procedure. Meanwhile, an efficient multi-GNSS real-time precise positioning service system is designed and demonstrated by using the multi-GNSS Experiment, BeiDou Experimental Tracking Network, and International GNSS Service networks including stations all over the world. The statistical analysis of the 6-h predicted orbits show that the radial and cross root mean square (RMS) values are smaller than 10 cm for BeiDou and Galileo, and smaller than 5 cm for both GLONASS and GPS satellites, respectively. The RMS values of the clock differences between real-time and batch-processed solutions for GPS satellites are about 0.10 ns, while the RMS values for BeiDou, Galileo and GLONASS are 0.13, 0.13 and 0.14 ns, respectively. The addition of the BeiDou, Galileo and GLONASS systems to the standard GPS-only processing, reduces the convergence time almost by 70 %, while the positioning accuracy is improved by about 25 %. Some outliers in the GPS-only solutions vanish when multi-GNSS observations are processed simultaneous. The availability and reliability of GPS precise positioning decrease dramatically as the elevation cutoff increases. However, the accuracy of multi-GNSS precise point positioning (PPP) is hardly decreased and few centimeter are still achievable in the horizontal components even with 40 elevation cutoff. At 30 and 40 elevation cutoffs, the availability rates of GPS-only solution drop significantly to only around 70 and 40 %, respectively. However, multi-GNSS PPP can provide precise position estimates continuously (availability rate is more than 99.5 %) even up to 40 elevation cutoff (e.g., in urban canyons).

  1. Preliminary Results on Setup Precision of Prone-Lateral Patient Positioning for Whole Breast Irradiation

    SciTech Connect

    Veldeman, Liv, E-mail: Liv.Veldeman@uzgent.b [Department of Radiotherapy, Ghent University Hospital, Ghent (Belgium); Speleers, Bruno; Bakker, Marlies; Jacobs, Filip; Coghe, Marc; De Gersem, Werner; Impens, Aline; Nechelput, Sarah; De Wagter, Carlos [Department of Radiotherapy, Ghent University Hospital, Ghent (Belgium)

    2010-09-01

    Purpose: The aim of this study was to develop a rapid and reproducible technique for prone positioning and to compare dose-volume indices in prone and supine positions. Methods and Materials: Eighteen patients underwent computed tomography imaging for radiotherapy planning in prone and supine position. Experience was gained in the first eight patients, which lead to modifications of the Horizon prone breast board (Civco Medical Solutions, Orange City, Iowa, USA) and the patient setup technique. A unilateral breast holder (U-BH) was developed (Van de Velde, Schellebelle, Belgium) to retract the contralateral breast away from the treated breast. The technique was then applied to an additional 10 patients. The setup precision was evaluated using daily cone-beam CT. Results: Modifications to the breast board were made to secure a prone-lateral rather then a pure prone position. We evolved from a classical setup using laser marks on the patients' body to a direct breast setup using marks on the breast only. The setup precision of the direct positioning procedure with the modified breast board and the U-BH is comparable to supine setup data in the literature. Dose-volume indices for heart and lung show significantly better results for prone than for supine position, and dose homogeneity within the treated breast did not differ according to the treatment position. Conclusions: The setup precision of our prone-lateral positioning technique is comparable to supine data in literature. Our data show the advantage of prone radiotherapy to spare the lung and heart. Further research is necessary to reduce the duration of prone setup.

  2. High-Precision Floating-Point Arithmetic in ScientificComputation

    SciTech Connect

    Bailey, David H.

    2004-12-31

    At the present time, IEEE 64-bit floating-point arithmetic is sufficiently accurate for most scientific applications. However, for a rapidly growing body of important scientific computing applications, a higher level of numeric precision is required: some of these applications require roughly twice this level; others require four times; while still others require hundreds or more digits to obtain numerically meaningful results. Such calculations have been facilitated by new high-precision software packages that include high-level language translation modules to minimize the conversion effort. These activities have yielded a number of interesting new scientific results in fields as diverse as quantum theory, climate modeling and experimental mathematics, a few of which are described in this article. Such developments suggest that in the future, the numeric precision used for a scientific computation may be as important to the program design as are the algorithms and data structures.

  3. Precise computer controlled positioning of robot end effectors using force sensors

    NASA Technical Reports Server (NTRS)

    Shieh, L. S.; Mcinnis, B. C.; Wang, J. C.

    1988-01-01

    A thorough study of combined position/force control using sensory feedback for a one-dimensional manipulator model, which may count for the spacecraft docking problem or be extended to the multi-joint robot manipulator problem, was performed. The additional degree of freedom introduced by the compliant force sensor is included in the system dynamics in the design of precise position control. State feedback based on the pole placement method and with integral control is used to design the position controller. A simple constant gain force controller is used as an example to illustrate the dependence of the stability and steady-state accuracy of the overall position/force control upon the design of the inner position controller. Supportive simulation results are also provided.

  4. A high precision position sensor design and its signal processing algorithm for a maglev train.

    PubMed

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

    2012-01-01

    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. PMID:22778582

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

    PubMed Central

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

    2012-01-01

    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. PMID:22778582

  6. AN X-BAND CAVITY FOR A HIGH PRECISION BEAM POSITION MONITOR

    SciTech Connect

    Johnson, R

    2003-12-08

    The next generation of accelerators will require increasingly precise control of beam position. For example designs for the next linear collider require beam-position monitors (BPMs) with 300 nm resolution. The accelerator designs also place difficult requirements on accuracy and stability. To meet these requirements a cavity BPM operating at 11.424 GHz was designed. The BPM consists of two cavities: an xy-cavity tuned to the dipole mode and a phase cavity tuned to the monopole mode. The xy-cavity uses a novel-coupling scheme that (in principal) has zero coupling to the monopole mode. This report will present the mechanical design, simulations, and test results of a prototype BPM. In addition BPM designs with even higher precision will be discussed.

  7. Advanced THz sensor array for precise position and material properties recognition

    NASA Astrophysics Data System (ADS)

    Sešek, Aleksander; Trontelj, Janez; Å vigelj, Andrej

    2014-06-01

    The precise position of objects in the industrial process, assembly lines, conveyers, or processing bins is essential for fast and high quality production. In many robotized setups the material type and its properties are crucial. When several types of materials or parts are used, material recognition is required. Advanced robotics systems depend on various sensors to recognize material properties, and high resolution cameras with expensive laser measuring systems are used to determine the precise object position. The purpose of this paper is to present how the THz sensor and THz waves can be applicable for such precise object position sensing and its material properties in real time. One of the additional features of such a THz sensor array is also the ability to see behind barriers that are transparent for THz waves. This allows the system to obtain precise dimensions, position, and material properties of the object, which are invisible for visible light or anyhow obscured to other vision systems. Furthermore, a 3D THz image of the object can also be obtained and, in cases when a visual picture is available, its fusion with a THz image is possible. In the paper a THz sensor array, operating at a 300GHz central frequency and at room conditions is presented, together with the proposed vision system description. The target is illuminated with a frequency modulated, solid state THz source, and provides output power around 1mW. By mixing of the illuminating and reflected signals, the resulting difference frequency signal is obtained. Its amplitude and phase carry all relevant information of the target. Some measurement results are also shown and discussed.

  8. A mathematical approach for analyzing ultra precision positioning system with compliant mechanism

    Microsoft Academic Search

    S. R. Park; S. H. Yang

    2005-01-01

    A monolithic and symmetric structure is good for reducing mechanical noise, such as thermal and compliant errors. Design and analysis of six-degree freedom ultra precision positioning system with compliant mechanism is described in this paper. An inclined bridge displacement amplifier is developed to achieve out-of-plane motions. A mechanism to amplify displacement is used to overcome short travel range of piezoelectric

  9. Remote Measurement of Breathing Rate in Real Time Using a High Precision, Single-Point Infrared Temperature Sensor

    E-print Network

    O'Kane, Jason

    a high precision, single-point infrared sensor. Remote breathing detec- tion is especially useful-nasal region of the face, continuously targeting and sampling the infrared sensor. The breathing rateRemote Measurement of Breathing Rate in Real Time Using a High Precision, Single-Point Infrared

  10. The Evaluation of Surface Morphology Using Flexure Guided Nano-Positioning System and Ultra-Precision Lathe

    NASA Astrophysics Data System (ADS)

    Kwak, Nam-Su; Kim, Jae-Yeol

    In this study, piezoelectric actuator, Flexure guide, Power transmission element and control method and considered for Nano-positioning system apparatus. The main objectives of this thesis were to develop the 3-axis Ultra-precision stages which enable the 3-axis control by the manipulation of the piezoelectric actuator and to enhance the precision of the Ultra-Precision CNC lathe which is responsible for the ductile mode machining of the hardened-brittle material where the machining is based on the single crystal diamond. Ultra-precision CNC lathe is used for machining and motion error of the machine are compensated by using 3-axis Ultra-precision stage. Through the simulation and experiments on ultra-precision positioning, stability and priority on Nano-positioning system with 3-axis ultra-precision stage and control algorithm are secured by using NI Labview. And after applying the system, is to analyze the surface morphology of the mold steel (SKD61)

  11. Effect of Radio Frequency Interference (RFI) on the Precision of GPS Relative Positioning

    NASA Astrophysics Data System (ADS)

    Idris, A. N.; Sathyamoorthy, D.; Suldi, A. M.; Hamid, J. R. A.

    2014-02-01

    The successful of GPS observations are dependent on several factors between satellite vehicles and GPS receivers, where low GPS power levels have led to the threat of radio frequency interference (RFI) on the GPS signals. This study was conducted to evaluate the effect of RFI on the precision of positions of single and dual frequency receivers through relative positioning technique by taking into consideration the radius of GPS receiver from interference source, length of baseline and response of rejection. Several tests were conducted in real environment by simulating the interference signal towards GPS receivers in the nominated GPS L1 and L2 bands. Calculations were made to indentify the distance and interference signal power between interference source and GPS receiver in order to investigate the level of effect. To be able to study this effect on the precision of GPS positions, the 3D residual positions and geometric dilution of precision (GDOP) have been used. The findings of this study have demonstrated that a sufficient time for the GPS receiver to respond in particular interference signal power level and the radius from the interference source were made as compared to previous work. It was also indicated that the residual positions and GDOPs were affected proportionally when nearly to interference source but not similar for both days due to GPS coverage and other probable errors. Therefore, a good investigation on RFI towards GPS signals should be conducted in secured environment which can control the various GPS error parameters in order to obtain a reliable result on this effect.

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

    NASA Astrophysics Data System (ADS)

    Beran, Tomas

    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 of low-cost, single-frequency GPS receivers in similar applications creates a challenge because of difficulty of handling the ionosphere, multipath and other measurement error sources. Potential use of such receivers to provide horizontal positioning accuracies of a few decimetres, and vertical accuracies of less than two metres, will be examined in this dissertation. Practical applications of post-processed, high-accuracy, single-frequency point positioning include a myriad of terrestrial and space-borne applications, where the size and cost of the GPS unit is an issue. The processing technique uses pseudorange and time-differenced carrier-phase measurements in a sequential least-squares filter. In developing the approach, different techniques were investigated. Ionospheric delay grid maps are used to remove the bulk of the ionospheric error, while tropospheric error is handled by a prediction model. Pseudorange multipath errors are mitigated by means of stochastic modelling and carrier-phase cycle slips are detected and corrupted measurements are removed in a quality-control algorithm. The technique was first tested on L1 measurements extracted from datasets from static, high-quality GPS receivers. Accuracies better than two-decimetres in horizontal components (northing and easting r.m.s.), and three-decimetre accuracies in the vertical component (up-component r.m.s.), were obtained. A test dataset from a stationary low-cost GPS receiver has been processed to demonstrate the difference in data quality. Positioning results obtained are worse than those of a high-quality GPS receiver, but they are still within the few decimetre accuracy level (northing and easting r.m.s.) and less than two metre vertical accuracy level. The use of the technique is not restricted to static applications, and the results of kinematic experiments are also presented. These experiments consist of terrestrial data processing and spaceborne data processing. The kinematic terrestrial tests include processing of single-frequency data from geodetic-quality GPS receiver and low-cost GPS receiver from a moving vehicle. The spaceborne kinematic tests include processing of dual-frequency data from a geodetic-quality GPS receiver on board of a low Earth orbit (LEO) satellite, and processing of the simulated single-frequency data from a low-cost GPS receiver for a future satellite mission. The question whether it is possible to use low-cost GPS receivers for high accuracy GPS positioning has been answered. Contributions to the leading edge research in the area of high precision GPS point positioning have been made. The software that was developed is the only software capable of reliable pseudorange and carrier-phase data processing from low-cost GPS receivers. Its reliability is accomplished through data quality control based on residual outlier detection theory. The implemented algorithm is capable to detect 95% of outliers. Despite the encouraging results the limitations of this technique were found. During the static terrestrial data testing it was found that the presence of multipath has negative impact on the positioning results from low-cost GPS receivers. The kinematic terrestrial data testing is limited to short periods of time when a reliable reference solution is available. The majority of the test results are from terrestrial platforms, because the spaceborne single-frequency point positioning requires more sophisticated ionospheric models than the terrestrial single-frequency point positioning. One example of sophisticated ionospheric model is a global 3D ionospheric model which was tested in this dissertation.

  13. Sliding mode control of magnetic suspensions for precision pointing and tracking applications

    NASA Technical Reports Server (NTRS)

    Misovec, Kathleen M.; Flynn, Frederick J.; Johnson, Bruce G.; Hedrick, J. Karl

    1991-01-01

    A recently developed nonlinear control method, sliding mode control, is examined as a means of advancing the achievable performance of space-based precision pointing and tracking systems that use nonlinear magnetic actuators. Analytic results indicate that sliding mode control improves performance compared to linear control approaches. In order to realize these performance improvements, precise knowledge of the plant is required. Additionally, the interaction of an estimating scheme and the sliding mode controller has not been fully examined in the literature. Estimation schemes were designed for use with this sliding mode controller that do not seriously degrade system performance. The authors designed and built a laboratory testbed to determine the feasibility of utilizing sliding mode control in these types of applications. Using this testbed, experimental verification of the authors' analyses is ongoing.

  14. Testing of an End-Point Control Unit Designed to Enable Precision Control of Manipulator-Coupled Spacecraft

    NASA Technical Reports Server (NTRS)

    Montgomery, Raymond C.; Ghosh, Dave; Tobbe, Patrick A.; Weathers, John M.; Manouchehri, Davoud; Lindsay, Thomas S.

    1994-01-01

    This paper presents an end-point control concept designed to enable precision telerobotic control of manipulator-coupled spacecraft. The concept employs a hardware unit (end-point control unit EPCU) that is positioned between the end-effector of the Space Shuttle Remote Manipulator System and the payload. Features of the unit are active compliance (control of the displacement between the end-effector and the payload), to allow precision control of payload motions, and inertial load relief, to prevent the transmission of loads between the end-effector and the payload. This paper presents the concept and studies the active compliance feature using a simulation and hardware. Results of the simulation show the effectiveness of the EPCU in smoothing the motion of the payload. Results are presented from initial, limited tests of a laboratory hardware unit on a robotic arm testbed at the l Space Flight Center. Tracking performance of the arm in a constant speed automated retraction and extension maneuver of a heavy payload with and without the unit active is compared for the design speed and higher speeds. Simultaneous load reduction and tracking performance are demonstrated using the EPCU.

  15. Highly accelerated simulations of glassy dynamics using GPUs: caveats on limited floating-point precision

    E-print Network

    Peter H. Colberg; Felix Höfling

    2011-01-17

    Modern graphics processing units (GPUs) provide impressive computing resources, which can be accessed conveniently through the CUDA programming interface. We describe how GPUs can be used to considerably speed up molecular dynamics (MD) simulations for system sizes ranging up to about 1 million particles. Particular emphasis is put on the numerical long-time stability in terms of energy and momentum conservation, and caveats on limited floating-point precision are issued. Strict energy conservation over 10^8 MD steps is obtained by double-single emulation of the floating-point arithmetic in accuracy-critical parts of the algorithm. For the slow dynamics of a supercooled binary Lennard-Jones mixture, we demonstrate that the use of single-floating point precision may result in quantitatively and even physically wrong results. For simulations of a Lennard-Jones fluid, the described implementation shows speedup factors of up to 80 compared to a serial implementation for the CPU, and a single GPU was found to compare with a parallelised MD simulation using 64 distributed cores.

  16. Geodetic point positioning with GPS (Global Positioning System) carrier beat phase data from the CASA (Central and South America) Uno experiment

    SciTech Connect

    Malys, S.; Jensen, P.A. (Defense Mapping Agency, Washington, DC (USA))

    1990-04-01

    The Global Positioning System (GPS) carrier beat phase data collected by the TI4100 GPS receiver has been successfully utilized by the US Defense Mapping Agency in an algorithm which is designed to estimate individual absolute geodetic point positions from data collected over a few hours. The algorithm uses differenced data from one station and two to four GPS satellites at a series of epochs separated by 30 second intervals. The precise GPS ephemerides and satellite clock states, held fixed in the estimation process, are those estimated by the Naval Surface Warfare Center (NSWC). Broadcast ephemerides and clock states are also utilized for comparative purposes. An outline of the data corrections applied, the mathematical model and the estimation algorithm are presented. Point positioning results and statistics are presented for a globally-distributed set of stations which contributed to the CASA Uno experiment. Statistical assessment of 114 GPS point positions at 11 CASA Uno stations indicates that the overall standard deviation of a point position component, estimated from a few hours of data, is 73 centimeters. Solution of the long line geodetic inverse problem using repeated point positions such as these can potentially offer a new tool for those studying geodynamics on a global scale.

  17. A polyphenylene dendrimer drug transporter with precisely positioned amphiphilic surface patches.

    PubMed

    Stangenberg, René; Wu, Yuzhou; Hedrich, Jana; Kurzbach, Dennis; Wehner, Daniel; Weidinger, Gilbert; Kuan, Seah Ling; Jansen, Malin Insa; Jelezko, Fedor; Luhmann, Heiko J; Hinderberger, Dariush; Weil, Tanja; Müllen, Klaus

    2015-02-18

    The design and synthesis of a polyphenylene dendrimer (PPD 3) with discrete binding sites for lipophilic guest molecules and characteristic surface patterns is presented. Its semi-rigidity in combination with a precise positioning of hydrophilic and hydrophobic groups at the periphery yields a refined architecture with lipophilic binding pockets that accommodate defined numbers of biologically relevant guest molecules such as fatty acids or the drug doxorubicin. The size, architecture, and surface textures allow to even penetrate brain endothelial cells that are a major component of the extremely tight blood-brain barrier. In addition, low to no toxicity is observed in in vivo studies using zebrafish embryos. The unique PPD scaffold allows the precise placement of functional groups in a given environment and offers a universal platform for designing drug transporters that closely mimic many features of proteins. PMID:25182694

  18. Self-assembly. Selective assemblies of giant tetrahedra via precisely controlled positional interactions.

    PubMed

    Huang, Mingjun; Hsu, Chih-Hao; Wang, Jing; Mei, Shan; Dong, Xuehui; Li, Yiwen; Li, Mingxuan; Liu, Hao; Zhang, Wei; Aida, Takuzo; Zhang, Wen-Bin; Yue, Kan; Cheng, Stephen Z D

    2015-04-24

    Self-assembly of rigid building blocks with explicit shape and symmetry is substantially influenced by the geometric factors and remains largely unexplored. We report the selective assembly behaviors of a class of precisely defined, nanosized giant tetrahedra constructed by placing different polyhedral oligomeric silsesquioxane (POSS) molecular nanoparticles at the vertices of a rigid tetrahedral framework. Designed symmetry breaking of these giant tetrahedra introduces precise positional interactions and results in diverse selectively assembled, highly ordered supramolecular lattices including a Frank-Kasper A15 phase, which resembles the essential structural features of certain metal alloys but at a larger length scale. These results demonstrate the power of persistent molecular geometry with balanced enthalpy and entropy in creating thermodynamically stable supramolecular lattices with properties distinct from those of other self-assembling soft materials. PMID:25908818

  19. Web-Based Integrated Precise Positioning System Design and Testing for Moving Platforms in Offshore Surveying

    Microsoft Academic Search

    Rahmi Nurhan CELIK

    2010-01-01

    SUMMARY Positions of points which are decided to drill exploration wells are defined after some feasibility studies in petroleum exploration activities carried out in offshore sea areas. For the wells that are planned to drill in the offshore sea areas, petroleum platforms (in shallow sea: jack-up platforms, in deep sea: semi-submersible, and in very deep sea: drillship) must be transported

  20. A Precise Position and Attitude Determination System for Lightweight Unmanned Aerial Vehicles

    NASA Astrophysics Data System (ADS)

    Eling, C.; Klingbeil, L.; Wieland, M.; Kuhlmann, H.

    2013-08-01

    In many unmanned aerial vehicle (UAV) applications a direct georeferencing is required. The reason can be that the UAV flies autonomous and must be navigated precisely, or that the UAV performs a remote sensing operation, where the position of the camera has to be known at the moment of the recording. In our application, a project called Mapping on Demand, we are motivated by both of these reasons. The goal of this project is to develop a lightweight autonomously flying UAV that is able to identify and measure inaccessible three-dimensional objects by use of visual information. Due to payload and space limitations, precise position and attitude determination of micro- and mini-sized UAVs is very challenging. The limitations do not only affect the onboard computing capacity, but they are also noticeable when choosing the georeferencing sensors. In this article, we will present a new developed onboard direct georeferencing system which is real-time capable, applicable for lightweight UAVs and provides very precise results (position accuracy ? < 5 cm and attitude accuracy ? < 0.5 deg). In this system GPS, inertial sensors, magnetic field sensors, a barometer as well as stereo video cameras are used as georeferencing sensors. We will describe the hardware development and will go into details of the implemented software. In this context especially the RTK-GPS software and the concept of the attitude determination by use of inertial sensors, magnetic field sensors as well as an onboard GPS baseline will be highlighted. Finally, results of first field tests as well as an outlook on further developments will conclude this contribution.

  1. Improved treatment of global positioning system force parameters in precise orbit determination applications

    NASA Technical Reports Server (NTRS)

    Vigue, Y.; Lichten, S. M.; Muellerschoen, R. J.; Blewitt, G.; Heflin, M. B.

    1993-01-01

    Data collected from a worldwide 1992 experiment were processed at JPL to determine precise orbits for the satellites of the Global Positioning System (GPS). A filtering technique was tested to improve modeling of solar-radiation pressure force parameters for GPS satellites. The new approach improves orbit quality for eclipsing satellites by a factor of two, with typical results in the 25- to 50-cm range. The resultant GPS-based estimates for geocentric coordinates of the tracking sites, which include the three DSN sites, are accurate to 2 to 8 cm, roughly equivalent to 3 to 10 nrad of angular measure.

  2. Position-sensitive ion detection in precision Penning trap mass spectrometry

    NASA Astrophysics Data System (ADS)

    Eitel, G.; Block, M.; Czasch, A.; Dworschak, M.; George, S.; Jagutzki, O.; Ketelaer, J.; Ketter, J.; Nagy, Sz.; Rodríguez, D.; Smorra, C.; Blaum, K.

    2009-07-01

    A commercial, position-sensitive ion detector was used for the first time for the time-of-flight ion-cyclotron resonance detection technique in Penning trap mass spectrometry. In this work, the characteristics of the detector and its implementation in a Penning trap mass spectrometer will be presented. In addition, simulations and experimental studies concerning the observation of ions ejected from a Penning trap are described. This will allow for a precise monitoring of the state of ion motion in the trap.

  3. Precision beam pointing for laser communication system using a CCD-based tracker

    NASA Astrophysics Data System (ADS)

    Chen, Chien-Chung; Ansari, Homayoon; Lesh, James R.

    1993-09-01

    Spatial acquisition and precision beam pointing functions are critical to spaceborne laser communication systems. A recent system study indicated that a single high bandwidth CCD detector can be used to perform both spatial acquisition and tracking functions. Compared to previous lasercom hardware design, the array tracking concept offers reduced system complexity by reducing the number of optical elements in the design. Specifically, the design requires only one detector and one beam steering mechanism. It also provides means to optically close the point-ahead control loop. The technology required for high bandwidth array tracking was examined and shown to be consistent with current state of the art. It is believed that the single detector design can lead to a significantly reduced system complexity and a lower system cost.

  4. Miniature zero-backslash gears and actuators for precision positioning applications

    NASA Astrophysics Data System (ADS)

    Slatter, Rolf; Degen, Reinhard

    2005-07-01

    The Micro Harmonic Drive gear, first invented in 2001 by Micromotion GmbH in co-operation with the Institute for Microtechnology in Mainz, Germany, is already successfully established in a wide variety of precise positioning applications in industrial machines. Based on experience gathered in terrestrial vacuum applications there are now first applications in space mechanisms. The miniature dimensions and low weight enable completely new design solutions for positioning actuators and mechanisms. The paper describes the developments made to qualify the Micro gear for space applications, including extensive tests with various different lubricants. The paper also describes in detail a practical application of the Micro gear in a camera under development by the DLR Institute for Interplanetary Research in Berlin, Germany.

  5. Spacecraft precision entry navigation using an adaptive sigma point Kalman filter bank

    NASA Astrophysics Data System (ADS)

    Heyne, Martin Cornelius

    This work documents the development of a sigma point Kalman filter for the purpose of precision spacecraft navigation during the atmospheric entry, descent and landing phase. The use of the sigma point Kalman filter is driven by the desire to avoid complex partial derivatives associated with the standard extended Kalman filter. The strategy increases the likelihood that the navigation algorithm will be compatible with the Electra. Using Mars Exploration Rover Spirit (MER-A) and the Mars Science Laboratory (MSL) data, experiments were conducted to validate the proposed navigation concept. Beginning at atmospheric entry interface, the hypersonic entry phase is considered and the navigation architecture performance is quantified. Using the sigma point Kalman filter as the main computational unit, a filter bank for environmental parameter identification is investigated. The focus of the investigation is atmospheric parameter identification. The MER-A mission is used to verify the ability of the filter bank to make appropriate selections. The navigation architecture is implemented on the Electra programmable radio, a flight hardware communication node available on spacecraft build for Mars exploration. The investigations show that the sigma point Kalman filter structure is very applicable to the atmospheric entry navigation problem. When used in conjunction with the filter bank concept, the overall navigation architecture is shown to be able to improve navigation accuracy over standard dead-reckoning, while providing robustness to uncertainties in the atmosphere. The navigation algorithm is successfully hosted on the Electra programmable radio and is capable of processing actual MER inertial measurement data.

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

    PubMed

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

    2013-09-01

    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

  7. The Feasibility of the Disturbance Accommodating Controller for Precision Antenna Pointing

    NASA Technical Reports Server (NTRS)

    Gresham, L. L.; Lansing, F. L.; Guiar, C. N.

    1988-01-01

    The objective of this study is to investigate the feasibility of a pointing (position loop) controller for the NASA-JPL Deep Space Network (DSN) antennas using the Disturbance Accommodating Control (DAC) theory. A model that includes state dependent disturbances was developed, and an example demonstrating the noise estimator is presented as an initial phase in the controller design. The goal is to improve pointing accuracy by the removal of the systematic errors caused by the antenna misalignment as well as sensor noise and random wind and thermal disturbances. Preliminary simulation results show that the DAC technique is successful in both cancelling the imposed errors and maintaining an optimal control policy.

  8. Assessment of regional ionosphere model supporting precise positioning for ASG-EUPOS network

    NASA Astrophysics Data System (ADS)

    Krypiak-Gregorczyk, Anna; Wielgosz, Pawel; Jarmo?owski, Wojciech

    2015-04-01

    Since 2008 the Head Office of Geodesy and Cartography in Poland operates a dense active GNSS network - ASG-EUPOS - consisting of over 100 stations. Currently over 60 stations are equipped with GPS+GLONASS receivers, including almost 30 stations with Galileo capability. This greatly improves IPP coverage over Poland and neighboring areas and offers excellent opportunity of providing high resolution and accurate ionosphere model for positioning purposes. In this paper we show performance assessment of a multi-GNSS ionospheric TEC model derived from precise carrier phase GNSS data. The model is based on processing of 170 GNSS stations located in Poland and neighboring countries. In the first step, carrier phase biases are estimated for each satellite arc. In the second step, theses biases are used together with multi-frequency, multi-GNSS carrier phase observations to calculate TEC at IPP locations. Then, the least squares collocation method is applied to provide vertical TEC grid - the TEC model. The TEC grid is used to calculate ionospheric delay corrections. The corrections are then verified by comparison to double differences ionospheric residual derived from GNSS data at selected test baselines. Our results show that the multi-GNSS regional ionospheric TEC model is capable of providing ionospheric corrections that may satisfy precise GNSS positioning requirements.

  9. 1.[14 pts]) a) Convert the following numbers to IEEE single precision floating-point format. Give the

    E-print Network

    Grantner, Janos L.

    set on p. 250 has additional instructions for multiplication (IMUL) and division (IDIV) Revere Polish the following IEEE single-precision floating-point numbers from hex to decimal: (for the final value provide

  10. Track-Level-Compensation Look-Up Table Improves Antenna Pointing Precision

    NASA Technical Reports Server (NTRS)

    Gawronski, W.; Baher, F.; Gama, E.

    2006-01-01

    This article presents the improvement of the beam-waveguide antenna pointing accuracy due to the implementation of the track-level-compensation look-up table. It presents the development of the table, from the measurements of the inclinometer tilts to the processing of the measurement data and the determination of the threeaxis alidade rotations. The table consists of three axis rotations of the alidade as a function of the azimuth position. The article also presents the equations to determine the elevation and cross-elevation errors of the antenna as a function of the alidade rotations and the antenna azimuth and elevation positions. The table performance was verified using radio beam pointing data. The pointing error decreased from 4.5 mdeg to 1.4 mdeg in elevation and from 14.5 mdeg to 3.1 mdeg in cross-elevation. I. Introduction The Deep Space Station 25 (DSS 25) antenna shown in Fig. 1 is one of NASA s Deep Space Network beam-waveguide (BWG) antennas. At 34 GHz (Ka-band) operation, it is necessary to be able to track with a pointing accuracy of 2-mdeg root-mean-square (rms). Repeatable pointing errors of several millidegrees of magnitude have been observed during the BWG antenna calibration measurements. The systematic errors of order 4 and lower are eliminated using the antenna pointing model. However, repeatable pointing errors of higher order are out of reach of the model. The most prominent high-order systematic errors are the ones caused by the uneven azimuth track. The track is shown in Fig. 2. Manufacturing and installation tolerances, as well as gaps between the segments of the track, are the sources of the pointing errors that reach over 14-mdeg peak-to-peak magnitude, as reported in [1,2]. This article presents a continuation of the investigations and measurements of the pointing errors caused by the azimuth-track-level unevenness that were presented in [1] and [2], and it presents the implementation results. Track-level-compensation (TLC) look-up tables were created for the DSS 25, DSS 26, DSS 34, and DSS 55 antennas. To date, the most complete and detailed results were obtained for the DSS 25 and DSS 55 antennas. In this article, for brevity of presentation, we present the DSS 25 antenna results only. 1 Communications Ground Systems Section. The research described in this publication was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  11. An automated focal point positioning and emittance measurement procedure for the interaction point of the SLC

    SciTech Connect

    Phinney, N.; Bambade, P.; Kozanecki, W.; Koska, W.

    1989-08-01

    To achieve maximum luminosity at the SLC, both the electron and positron beams must reach their minimum transverse size within 1 mm of the longitudinal location where the two bunches collide. This paper describes an automated procedure for positioning the focal point of each beam at this collision plant. The technique is based on measurements of the beam size utilizing either secondary emission or bremsstrahlung signals from carbon fibers a few microns in diameter. We have achieved simultaneous and reproducible measurements of the angular speed (/approximately/200 /mu/rad) and the optimum beam spot size (/approximately/2 /mu/m), which when combined yield measurements of the beam emittance consistent with those obtained using conventional profile monitor techniques. 8 refs., 5 figs., 1 tab.

  12. Achieving high-precision pointing on ExoplanetSat: initial feasibility analysis

    NASA Astrophysics Data System (ADS)

    Pong, Christopher M.; Lim, Sungyung; Smith, Matthew W.; Miller, David W.; Villaseñor, Jesus S.; Seager, Sara

    2010-07-01

    ExoplanetSat is a proposed three-unit CubeSat designed to detect down to Earth-sized exoplanets in an orbit out to the habitable zone of Sun-like stars via the transit method. To achieve the required photometric precision to make these measurements, the target star must remain within the same fraction of a pixel, which is equivalent to controlling the pointing of the satellite to the arcsecond level. The satellite will use a two-stage control system: coarse control will be performed by a set of reaction wheels, desaturated by magnetic torque coils, and fine control will be performed by a piezoelectric translation stage. Since no satellite of this size has previously demonstrated this high level of pointing precision, a simulation has been developed to prove the feasibility of realizing such a system. The current baseline simulation has demonstrated the ability to hold the target star to within 0.05 pixels or 1.8 arcseconds (with an 85 mm lens and 15 ?m pixels), in the presence of large reaction wheel disturbances as well as external environmental disturbances. This meets the current requirement of holding the target star to 0.14 pixels or 5.0 arcseconds. Other high-risk aspects of the design have been analyzed such as the effect of changing the guide star centroiding error, changing the CMOS sampling frequency, and reaction wheel selection on the slew performance of the satellite. While these results are promising as an initial feasibility analysis, further model improvements and hardware-in-the-loop tests are currently underway.

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

    SciTech Connect

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

    1995-05-01

    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.

  14. Precise Real-Time Low-Earth-Orbiter Navigation With the Global Positioning System (GPS)

    NASA Astrophysics Data System (ADS)

    Bertiger, W.; Haines, B.; Kuang, D.; Lough, M.; Lichten, S.; Muellerschoen, R. J.; Vigue-Rodi, Y.; Wu, S.

    1999-01-01

    Technology currently is available to support real-time onboard knowledge of the position of a low Earth orbiter at the 5- to 15-m level using the civilian broadcast Global Positioning System (GPS) signal with sophisticated models and filtering techniques onboard the spacecraft. Without these techniques, the standard positioning service yields 50 to 100 m with the current level of selective availability (SA). Proposed augmentations and/or enhancements to the GPS system will make rms accuracies of from 10 centimeters to a few decimeters available to the real-time onboard user. Presently, near-real-time processing of GPS tracking data can routinely provide low-Earth-orbit determination accuracy at the level of 5 cm. Such processing systems can, in fact, be fully automated; recent results from the Jet Propulsion Laboratory (JPL), where ongoing daily processing of low Earth GPS tracking data has been undertaken for several years, are presented in this article, showing orbit determination accuracies at the sub-10-cm level. At the present time, such solutions can be produced with about a 10-h delay after real time, but recent improvements in JPL's processing system soon will enable turnaround at the 1-h level or better for such precise orbit determination. We anticipate that orbit determination at the 1-cm-accuracy level will be demonstrated, with some refinements to the current system, in the not too distant future. Continuing enhancements in the automation of data retrieval and precise orbit processing will result in continuing decreases in latency for ground-based generation of precise orbit products for Earth orbiters. Such ephemerides can be propagated slightly ahead to provide real-time knowledge. However, there are advantages to an onboard, real-time orbit-determination capability. These include unique mission requirements (military, strategic, and scientific), as well as the potential to dramatically lower navigation operations costs through the enabling of a fully autonomous spacecraft. JPL has bee!n actively involved in the development of technology to enable a fully autonomous spacecraft in low Earth orbit. This article includes recent results of analysis of actual and simulated GPS data collected in space that demonstrate that a 10-cm (or better) real-time onboard orbit-determination capability presently is technologically feasible. In addition to space-based data, present-day tests in real time of wide-area differential GPS (WADGPS) on aircraft in real time show upper bounds for space-based users with a global WADGPS at the level of 30-cm-rms horizontal and 60-cm-rms vertical. The article describes several alternative technology road maps that can be followed to make such a capability routinely available to a wide range of low Earth orbiters. The discussion will include the use of wide-area approaches as well as non-WADGPS approaches for achieving this capability. In addition to supporting a sub-10-cm real-time onboard positioning capability in Earth orbit, this system also could support a few-decimeters real-time kinematic positioning for ground, sea, and air users globally.

  15. Spacecraft and mission design for the precision optical INTerferometer in space (POINTS)

    NASA Astrophysics Data System (ADS)

    Schumaker, Bonny L.; Agronin, Michael L.; Chen, Gun-Shing; Ledeboer, W.; Melody, James W.; Noon, D.; Ulvestad, James S.

    1993-09-01

    This paper describes key features of the instrument, spacecraft, and mission design for the Precision Optical INTerferometer in Space (POINTS), which have evolved through studies at the Jet Propulsion Laboratory during the last few years. Design of the flight-system configuration has been driven by several considerations. Since the most ambitious science goals require access to a large portion of the sky most of the time, minimal systematic errors, and a 10-year mission life, a high Earth orbit (higher than 50,000 km) is preferred; the nominal has been taken to be a circular orbit of 100,000-km radius. In order to provide a very uniform thermal environment for the instrument, a solar shield supporting an array of solar cells is mounted on a boom and gimballed along two axes so as to remain pointed at the Sun and to provide constant shade for the entire spacecraft. Silicon cells covering about 85% of the roughly 4.8-m-diameter shield and operating at about 100 deg C could supply sufficient power for a 10-year mission life. A unibody design was selected in which the instrument and spacecraft bus are solidly attached to form a single rigid body. Full pointing freedom for the instrument is provided by articulation of the solar shield about two axes plus roll of the entire spacecraft around the Sun direction. With the high orbit and Sun-facing, geometrically simple spacecraft configuration, the effects of solar radiation pressure--the only significant external disturbance to spacecraft acceleration--can be modeled accurately enough to guarantee no compromise in the accurate velocity determination needed to correct astrometric measurements for stellar aberration.

  16. Dynamic properties of an omni-directional piezoelectric motor for precision position control.

    PubMed

    Jung, Woo-Suk; Kang, Chong-Yun; Paik, Dong-Soo; Vasiljev, Piotr E; Kim, Jeong-Do; Yoon, Seok-Jin

    2009-06-01

    A piezoelectric motor capable of omni-directional movements has been developed to apply for robot joints, eyes, and precision positioning stage. The piezoelectric actuator has a simple structure of a cone type consisting of two piezoelectric ring-typed ceramics with electrodes divided into four segments and stainless steel elastic bodies. Before manufacturing the piezoelectric motor, the admittance characteristics and displacements of the actuator as a function of frequency were simulated. Elliptical motions of the actuator were created at several frequencies between the longitudinal and transverse resonance frequencies. The actual motor with alumina ball exhibited nice performance using a driving circuit with two rotary encoders and a PID controller. The moving element was omni-directionally operated at a driving frequency of 53.8 kHz and an output voltage of 280 V(p-p). The developed motor enables the moving element to move to a desired position with a resolution of 1.2 degrees/pulse, an angular velocity of 4 rad/s, and a thrust force of 200 g. PMID:19395053

  17. Radioisotopic Tie Points of the Quaternary Geomagnetic Instability Time Scale (GITS): How Accurate and Precise?

    NASA Astrophysics Data System (ADS)

    Singer, B. S.

    2014-12-01

    Reversals and excursions of the geomagnetic field are recorded globally by sedimentary and volcanic rocks. These geodynamo instabilities provide a rich set of chronostratigraphic tie points for the Quaternary period that can provide tests of age models central to paleoclimate studies. Radioisotopic dating of volcanic rocks, mainly 40Ar/39Ar dating of lava flows, coupled with astronomically-dated deep sea sediments, reveals 10 polarity reversals and 27 field excursions during the Quaternary (Singer, 2014). A key question concerns the uncertainties associated with radioisotopic dates of those geodynamo instabilities that have been identified both in terrestrial volcanic rocks and in deep sea sediments. These particular features offer the highest confidence in linking 40Ar/39Ar dates to the global marine climate record. Geological issues aside, for rocks in which the build-up of 40Ar by decay of 40K may be overwhelmed by atmospheric 40Ar at the time of eruption, the uncertainty in 40Ar/39Ar dates derives from three sources: (1) analytical uncertainty associated with measurement of the isotopes; this is straightforward to estimate; (2) systematic uncertainties stemming from the age of standard minerals, such as the Fish Canyon sanidine, and in the 40K decay constant; and (3) systematic uncertainty introduced during analysis, mainly the size and reproducibility of procedural blanks. Whereas 1 and 2 control the precision of an age determination, 2 and 3 also control accuracy. In parallel with an astronomical calibration of 28.201 Ma for the Fish Canyon sanidine standard, awareness of the importance of procedural blanks, and a new generation multi-collector mass spectrometer capable of exceptionally low-blank and isobar-free analysis, are improving both accuracy and precision of 40Ar/39Ar dates. Results from lavas recording the Matuyama-Brunhes reversal, the Santa Rosa excursion, and the reversal at the top of the Cobb Mtn subchron demonstrate these advances. Current best ages for these instabilities are 777 ± 2, 932 ± 3, and 1189 ± 1 ka (±1?), respectively. These ages, likely accurate and precise to better than ±0.3%, are identical to those determined from deep sea sediment cores for which high-resolution magnetostratigraphy and O isotope-based age models have been developed (Channell et al., 2010).

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

    NASA Astrophysics Data System (ADS)

    Yan, Su

    2007-12-01

    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.

  19. Eye Position Signal Modulates a Human Parietal Pointing Region during Memory-Guided Movements

    E-print Network

    Andersen, Richard

    location with respect to the head by taking into account the position of the eyes in the orbit (Andersen etEye Position Signal Modulates a Human Parietal Pointing Region during Memory-Guided Movements position of the eyes. Delayed pointing activated a bilateral parietal area in the intraparietal sulcus (r

  20. Multi-Degree-of-Freedom Precision Position Sensing and Motion Control Using TwoAxis Hall-Effect Sensors

    Microsoft Academic Search

    Yusuke Kawato; Won-jong Kim

    2006-01-01

    This paper presents a novel precision position-sensing methodol- ogy using two-axis Hall-effect sensors, where the absolute multi- degree-of-freedom (DOF) positioning of a device above any mag- net matrix is possible. Magnet matrices have a periodic magnetic field about each of its orthogonal axes, which can be modeled using Fourier series. This position-sensing methodology was implemented on a Halbach-magnet-matrix-based magnetic- levitation

  1. The double-helix point spread function enables precise and accurate measurement of 3D single-molecule localization and orientation

    PubMed Central

    Backlund, Mikael P.; Lew, Matthew D.; Backer, Adam S.; Sahl, Steffen J.; Grover, Ginni; Agrawal, Anurag; Piestun, Rafael; Moerner, W. E.

    2014-01-01

    Single-molecule-based super-resolution fluorescence microscopy has recently been developed to surpass the diffraction limit by roughly an order of magnitude. These methods depend on the ability to precisely and accurately measure the position of a single-molecule emitter, typically by fitting its emission pattern to a symmetric estimator (e.g. centroid or 2D Gaussian). However, single-molecule emission patterns are not isotropic, and depend highly on the orientation of the molecule’s transition dipole moment, as well as its z-position. Failure to account for this fact can result in localization errors on the order of tens of nm for in-focus images, and ~50–200 nm for molecules at modest defocus. The latter range becomes especially important for three-dimensional (3D) single-molecule super-resolution techniques, which typically employ depths-of-field of up to ~2 ?m. To address this issue we report the simultaneous measurement of precise and accurate 3D single-molecule position and 3D dipole orientation using the Double-Helix Point Spread Function (DH-PSF) microscope. We are thus able to significantly improve dipole-induced position errors, reducing standard deviations in lateral localization from ~2x worse than photon-limited precision (48 nm vs. 25 nm) to within 5 nm of photon-limited precision. Furthermore, by averaging many estimations of orientation we are able to improve from a lateral standard deviation of 116 nm (~4x worse than the precision, 28 nm) to 34 nm (within 6 nm). PMID:24817798

  2. Hyperspectral Reflectance Signatures and Point Clouds for Precision Agriculture by Light Weight Uav Imaging System

    NASA Astrophysics Data System (ADS)

    Honkavaara, E.; Kaivosoja, J.; Mäkynen, J.; Pellikka, I.; Pesonen, L.; Saari, H.; Salo, H.; Hakala, T.; Marklelin, L.; Rosnell, T.

    2012-07-01

    The objective of this investigation was to study the use of a new type of a low-weight unmanned aerial vehicle (UAV) imaging system in the precision agriculture. The system consists of a novel Fabry-Perot interferometer based hyperspectral camera and a high-resolution small-format consumer camera. The sensors provide stereoscopic imagery in a 2D frame-format and they both weigh less than 500 g. A processing chain was developed for the production of high density point clouds and hyperspectral reflectance image mosaics (reflectance signatures), which are used as inputs in the agricultural application. We demonstrate the use of this new technology in the biomass estimation process, which is based on support vector regression machine. It was concluded that the central factors influencing on the accuracy of the estimation process were the quality of the image data, the quality of the image processing and digital surface model generation, and the performance of the regressor. In the wider perspective, our investigation showed that very low-weight, low-cost, hyperspectral, stereoscopic and spectrodirectional 3D UAV-remote sensing is now possible. This cutting edge technology is powerful and cost efficient in time-critical, repetitive and locally operated remote sensing applications.

  3. A study of attitude control concepts for precision-pointing non-rigid spacecraft

    NASA Technical Reports Server (NTRS)

    Likins, P. W.

    1975-01-01

    Attitude control concepts for use onboard structurally nonrigid spacecraft that must be pointed with great precision are examined. The task of determining the eigenproperties of a system of linear time-invariant equations (in terms of hybrid coordinates) representing the attitude motion of a flexible spacecraft is discussed. Literal characteristics are developed for the associated eigenvalues and eigenvectors of the system. A method is presented for determining the poles and zeros of the transfer function describing the attitude dynamics of a flexible spacecraft characterized by hybrid coordinate equations. Alterations are made to linear regulator and observer theory to accommodate modeling errors. The results show that a model error vector, which evolves from an error system, can be added to a reduced system model, estimated by an observer, and used by the control law to render the system less sensitive to uncertain magnitudes and phase relations of truncated modes and external disturbance effects. A hybrid coordinate formulation using the provided assumed mode shapes, rather than incorporating the usual finite element approach is provided.

  4. Wild Singularities and Kangaroo Points for the Resolution of Singularities in Positive Characteristic

    E-print Network

    Hauser, Herwig

    Wild Singularities and Kangaroo Points for the Resolution of Singularities in Positive which produce under blowup at selected points of the exceptional divisor ­ so called kangaroo points of kangaroo points, giving a complete characterization of both phenomena. This in turn sheds some light

  5. Precise evaluation of GNSS position and latency errors in dynamic agricultural applications

    NASA Astrophysics Data System (ADS)

    Sama, Michael Patrick

    A method for precisely synchronizing an external serial data stream to the pulseper- second (PPS) output signal from a global navigation satellite-based system (GNSS) receiver was investigated. A signal timing device was designed that used a digital signal processor (DSP) with serial inputs and input captures to generate time stamps for asynchronous serial data based on an 58593.75 Hz internal timer. All temporal measurements were made directly in hardware to eliminate software latency. The resolution of the system was 17.1 is, which translated to less than one millimeter of horizontal position error at travel speeds typical of most agricultural operations. The dynamic error of a TTS was determined using a rotary test fixture. Tests were performed at angular velocities ranging from 0 to 3.72 rad/s and a radius of 0.635 m. Average latency from the TTS was shown to be consistently near 0.252 s for all angular velocities and less variable when using a reflector based machine target versus a prism target. Sight distance from the target to the TTS was shown to have very little effect on accuracy between 4 and 30 m. The TTS was determined to be a limited as a position reference for dynamic GNSS and vehicle auto-guidance testing based on angular velocity. The dynamic error of a GNSS receiver was determined using the rotary test fixture and modeled as discrete probability density functions for varying angular velocities and filter levels. GNSS position and fixture data were recorded for angular velocities of 0.824, 1.423, 2.018, 2.618, and 3.222 rad/s at a 1 m radius. Filter levels were adjusted to four available settings including; no filter, normal filter, high filter, and max filter. Each data set contained 4 hours of continuous operation and was replicated three times. Results showed that higher angular velocities increased the variability of the distribution of error while not having a significant effect on average error. The distribution of error tended to change from normal distributions at lower angular velocities to uniform distributions at higher angular velocities. Internal filtering was shown to consistently increase dynamic error for all angular velocities.

  6. Super-resolution for a point source using positive refraction

    NASA Astrophysics Data System (ADS)

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

    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.

  7. Active Noise Control Using Position of Evaluation Point

    NASA Astrophysics Data System (ADS)

    Ikeda, Ikuma; Kijimoto, Shinya; Matsuda, Koichi; Koba, Yosuke; Kageyama, Keitaro

    Active noise control (ANC) in a three-dimensional sound field ( e.g., in an office) is investigated in this paper. As the size of the controlled area generally depends on the wavelength of the target noise, it is difficult to control the noise throughout an entire room using ANC. Instead, a noise control method in the vicinity of a subject's head (referred to as around-head control) is investigated in this paper. To realize around-head control, an evaluation point that mimics head movement is required. However, movement of the evaluation point during control has not been considered in conventional ANC. The authors earlier proposed control using a filter map to solve this problem. In this method, the controlled space is subdivided into small grids, and a filter map is produced by storing and updating filters in each grid. A new method of updating the map is proposed in this paper, in which a reliability index is calculated and used. The effectiveness of the proposed method is shown by numerical simulations using acoustic properties measured in an anechoic chamber.

  8. Precise focus point scenario for a natural Higgs boson in the MSSM

    NASA Astrophysics Data System (ADS)

    Kyae, Bumseok; Shin, Chang Sub

    2014-08-01

    A small Higgs mass parameter mhu2 can be insensitive to various trial heavy stop masses, if a universal soft squared mass is assumed for the chiral superpartners and the Higgs boson at the grand unification (GUT) scale, and a focus point (FP) of mhu2 appears around the stop mass scale. The challenges in the FP scenario are (1) a too heavy stop mass (?5 TeV) needed for the 126 GeV Higgs mass and (2) the too high gluino mass bound (?1.4 TeV). For a successful FP scenario, we consider (1) a superheavy right-hand (RH) neutrino and (2) the first and second generations of hierarchically heavier chiral superpartners. The RH neutrino can move a FP in the higher energy direction in the space of (Q ,mhu2(Q)), where Q denotes the renormalization scale. On the other hand, the hierarchically heavier chiral superpartners can lift up a FP in that space through two-loop gauge interactions. Precise focusing of mhu2(Q) is achieved with the RH neutrino mass of ˜1014 GeV together with an order one (0.9-1.2) Yukawa coupling to the Higgs boson, and the hierarchically heavy masses of 15-20 TeV for the heavier generations of superpartners, when the U(1)R breaking soft parameters m1/2 and A0 are set to be 1 TeV at the GUT scale. Those values can naturally explain the small neutrino mass through the seesaw mechanism, and suppress the flavor violating processes in supersymmetric models.

  9. EFFECTS OF FINITE-PRECISION ARITHMETIC ON INTERIOR-POINT METHODS FOR NONLINEAR PROGRAMMING

    E-print Network

    Wright, Steve

    J. WRIGHT Abstract. We show that the e ects of nite-precision arithmetic in forming and solving : IR n ! IR and g : IR n ! IR m are twice Lipschitz continuously di erentiable functions Contract W-31-109-Eng-38. 1 #12;2 STEPHEN J. WRIGHT uncorrupted by nite precision were taken

  10. Clusterless Decoding of Position from Multiunit Activity Using a Marked Point Process Filter.

    PubMed

    Deng, Xinyi; Liu, Daniel F; Kay, Kenneth; Frank, Loren M; Eden, Uri T

    2015-07-01

    Point process filters have been applied successfully to decode neural signals and track neural dynamics. Traditionally these methods assume that multiunit spiking activity has already been correctly spike-sorted. As a result, these methods are not appropriate for situations where sorting cannot be performed with high precision, such as real-time decoding for brain-computer interfaces. Because the unsupervised spike-sorting problem remains unsolved, we took an alternative approach that takes advantage of recent insights into clusterless decoding. Here we present a new point process decoding algorithm that does not require multiunit signals to be sorted into individual units. We use the theory of marked point processes to construct a function that characterizes the relationship between a covariate of interest (in this case, the location of a rat on a track) and features of the spike waveforms. In our example, we use tetrode recordings, and the marks represent a four-dimensional vector of the maximum amplitudes of the spike waveform on each of the four electrodes. In general, the marks may represent any features of the spike waveform. We then use Bayes's rule to estimate spatial location from hippocampal neural activity. We validate our approach with a simulation study and experimental data recorded in the hippocampus of a rat moving through a linear environment. Our decoding algorithm accurately reconstructs the rat's position from unsorted multiunit spiking activity. We then compare the quality of our decoding algorithm to that of a traditional spike-sorting and decoding algorithm. Our analyses show that the proposed decoding algorithm performs equivalent to or better than algorithms based on sorted single-unit activity. These results provide a path toward accurate real-time decoding of spiking patterns that could be used to carry out content-specific manipulations of population activity in hippocampus or elsewhere in the brain. PMID:25973549

  11. Influence of the shape and position of the preform in the precision forging of a compressor blade

    Microsoft Academic Search

    Mei Zhan; Yuli Liu; He Yang

    2002-01-01

    The influence of the shape and the initial position of the preform in precision forging of a compressor blade has been studied by 3D rigid–viscoplastic finite element method (FEM) in this paper. The results show the following: (1) a short and thick preform results in necking at the arc transition zone between the tenon and the blade body, and at

  12. Precise Gravity Measurements for Lunar Laser Ranging at Apache Point Observatory

    NASA Astrophysics Data System (ADS)

    Crossley, D. J.; Murphy, T.; Boy, J.; De Linage, C.; Wheeler, R. D.; Krauterbluth, K.

    2012-12-01

    Lunar Laser Ranging (LLR) at Apache Point Observatory began in 2006 under the APOLLO project using a 3.5 m telescope on a 2780 m summit in New Mexico. Recent improvements in the technical operations are producing uncertainties at the few-mm level in the 1.5 x 10^13 cm separation of the solar orbits of the Earth and Moon. This level of sensitivity permits a number of important aspects of gravitational theory to be tested. Among these is the Equivalence Principle that determines the universality of free fall, tests of the time variation of the Gravitational Constant G, deviations from the inverse square law, and preferred frame effects. In 2009 APOLLO installed a superconducting gravimeter (SG) on the concrete pier under the main telescope to further constrain the deformation of the site as part of an initiative to improve all aspects of the modeling process. We have analyzed more than 3 years of high quality SG data that provides unmatched accuracy in determining the local tidal gravimetric factors for the solid Earth and ocean tide loading. With on-site gravity we have direct measurements of signals such as polar motion, and can compute global atmospheric and hydrological loading for the site using GLDAS and local hydrology models that are compared with the SG observations. We also compare the SG residuals with satellite estimates of seasonal ground gravity variations from the GRACE mission. Apache Point is visited regularly by a team from the National Geospatial-Intelligence Agency to provide absolute gravity values for the calibration of the SG and to determine secular gravity changes. Nearby GPS location P027 provides continuous position information from the Plate Boundary Observatory of Earthscope that is used to correlate gravity/height variations at the site. Unusual aspects of the data processing include corrections for the telescope azimuth that appear as small offsets at the 1 ?Gal level and can be removed by correlating the azimuth data with the SG residuals.

  13. High-precision position control of a heavy-lift manipulator in a dynamic environment

    E-print Network

    Garretson, Justin R. (Justin Richard)

    2005-01-01

    This thesis considers the control of a heavy-lift serial manipulator operating on the deck of a large ocean vessel. This application presents a unique challenge for high- precision control because the system must contend ...

  14. INTERNATIONAL COMPARISON OF WATER TRIPLE POINT CELLS LEADING TO A MORE PRECISE DEFINITION OF THE KELVIN

    Microsoft Academic Search

    Michael Stock; Stéphane Solve

    The water triple point serves to define the kelvin, the unit of thermodynamic temperature, in the International System of Units (SI) and it is the most important temperature fixed point in the International Temperature Scale of 1990 (ITS-90). The International Bureau of Weights and Measures (BIPM) has carried out an international comparison of water triple point cells from twenty National

  15. Limit Cycles in a Class of Quartic Kolmogorov Model with Three Positive Equilibrium Points

    NASA Astrophysics Data System (ADS)

    Du, Chaoxiong; Liu, Yirong; Zhang, Qi

    2015-06-01

    Limit cycle bifurcation problem of Kolmogorov model is interesting and significant both in theory and applications. In this paper, we will focus on investigating limit cycles for a class of quartic Kolmogorov model with three positive equilibrium points. Perturbed model can bifurcate three small limit cycles near (1, 2) or (2, 1) under a certain condition and can bifurcate one limit cycle near (1, 1). In addition, we have given some examples of simultaneous Hopf bifurcation and the structure of limit cycles bifurcated from three positive equilibrium points. The limit cycle bifurcation problem for Kolmogorov model with several positive equilibrium points are less seen in published references. Our result is good and interesting.

  16. Artificial Immune System and its applications in gps single frequency precise point positioning

    Microsoft Academic Search

    Chengquan Xu; Suxia Xu; Wei Chen

    2008-01-01

    The natural immune system is a robust and powerful information process system that demonstrates features such as distributed control, parallel processing and adaptation. Artificial immune systems (AIS) are machine-learning algorithms that embody some of the principles and attempt to take advantages of the benefits of natural immune systems for use in tackling complex problem domains. Using the artificial immune algorithm

  17. Multi-DOF precision positioning methodology using two-axis Hall-effect sensors

    E-print Network

    Kawato, Yusuke

    2006-08-16

    A novel sensing methodology using two-axis Hall-effect sensors is proposed, where the absolute positioning of a device atop any magnet matrix is possible. This methodology has the capability of micrometer-order positioning resolution as well...

  18. Fast and precise positioning of single cells on planar electrode substrates.

    PubMed

    Thielecke, H; Stieglitz, T; Beutel, H; Matthies, T; Ruf, H H; Meyer, J U

    1999-01-01

    For cell biosensors and for studying neural networks using planar electrode substrates, a suitable technique for positioning single cells on electrodes was needed. We reported a new method for fast and efficient positioning of single cells on ring electrodes by controlled suction through holes. We described the microfabrication of electrode substrates with microholes and the cell positioning procedure. L929 cells and Neuro 2A cells could be positioned in parallel without cell damage. PMID:10576072

  19. Fast and precise positioning of single cells on planar electrode substrates

    Microsoft Academic Search

    H. Thielecke; T. Stieglitz; H. Beutel; T. Matthies; H. H. Ruf; J.-U. Meyer

    1999-01-01

    For cell biosensors and for studying neural networks using planar electrode substrates, a suitable technique for positioning single cells on electrodes was needed. We reported a new method for fast and efficient positioning of single cells on ring electrodes by controlled suction through holes. We described the microfabrication of electrode substrates with microholes and the cell positioning procedure. L929 cells

  20. Precise Determination of Hydrostatic Pressure Correction Coefficient of Triple Point Cell of Water using Cryogenic Current Comparator Bridge

    Microsoft Academic Search

    Masakazu Nakanishi; Hirohisa Sakurai

    2005-01-01

    Applying a cryogenic current comparator bridge to resistance thermometry, the temperature distributions along the thermometer wells of two triple point cells of water are precisely measured using a standard platinum resistance thermometer with low measuring currents of about 0.1 mA. The average hydrostatic pressure coefficient of the two cells calculated from the temperature distributions is -0.854(38) mK\\/m. This value agrees

  1. Importing Prepackaged Software into Lisp: Experience with ArbitraryPrecision FloatingPoint Numbers

    E-print Network

    Fateman, Richard J.

    Importing Pre­packaged Software into Lisp: Experience with Arbitrary­Precision Floating Lisp as a powerful glue for building scientific computing environments. Naturally one then has to address mixing pre­existing (non Lisp) code into this system. We provide a specific example

  2. Efficient methods for determining precise orbits of low Earth orbiters using the Global Positioning System

    Microsoft Academic Search

    Heike Bock

    2003-01-01

    The main part of this work dealt with the development and evaluation of efficient methods for precise orbit determination of LEOs. A kinematic approach using GPS zero-difference observations was developed (program LEOKIN) and a procedure for generation of dynamic and reduced-dynamic orbits was presented (program SATORB). The procedures have been tested using long GPS data series gathered by two LEO

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

    Microsoft Academic Search

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

    2005-01-01

    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

  4. Investigation on a Novel Dual-Grating Macro-Micro Driven High Speed Precision Positioning System for NEMS

    Microsoft Academic Search

    L. N. Sun; D. G. Jie; Y. J. Liu; Z. C. Chen; H. G. Cai

    2006-01-01

    Microelectromechanical system (MEMS) is naturally continuing its downsizing into nanoelectromechanical system (NEMS), but at the same time it is indispensable in the package equipment used for nano-devices packaging in NEMS manufacture. A novel dual-grating macro-micro driven high speed precision XY-stage positioning system is presented in this paper. Combining macro with micro actuator, a system of large workspace and high speed

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

    Microsoft Academic Search

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

    1990-01-01

    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

  6. Evaluation of an off-the-shelf acoustic system for precision positioning of seabed transponders

    Microsoft Academic Search

    Hsin-Hung Chen; Chau-Chang Wang; Jia-Pu Jang

    2010-01-01

    In this study, a commercial off-the-shelf acoustic system with ranging accuracy of 20 centimeters is employed to conduct an experiment of positioning seabed transponders. The feasibility of using a GPS\\/acoustic system with off-the-shelf transponders to achieve centimeter-level positioning accuracy was evaluated. In order to verify the relative positioning accuracy between seabed transponders, a seafloor acoustic transponder (SAT) system was developed.

  7. LDPC decoder with a limited-precision FPGA-based floating-point multiplication coprocessor

    Microsoft Academic Search

    Raymond Moberly; Michael O'Sullivan; Khurram Waheed

    2007-01-01

    Implementing the sum-product algorithm, in an FPGA with an embedded processor, invites us to consider a tradeoff between computational precision and computational speed. The algorithm, known outside of the signal processing community as Pearl's belief propagation, is used for iterative soft-decision decoding of LDPC codes. We determined the feasibility of a coprocessor that will perform product computations. Our FPGA-based coprocessor

  8. Positioning Standardized Acupuncture Points on the Whole Body Based on X-Ray Computed Tomography Images.

    PubMed

    Kim, Jungdae; Kang, Dae-In

    2014-02-01

    Objective: The goal of this research was to position all the standardized 361 acupuncture points on the entire human body based on a 3-dimensional (3D) virtual body. Materials and Methods: Digital data from a healthy Korean male with a normal body shape were obtained in the form of cross-sectional images generated by X-ray computed tomography (CT), and the 3D models for the bones and the skin's surface were created through the image-processing steps. Results: The reference points or the landmarks were positioned based on the standard descriptions of the acupoints, and the formulae for the proportionalities between the acupoints and the reference points were presented. About 37% of the 361 standardized acupoints were automatically linked with the reference points, the reference points accounted for 11% of the 361 acupoints, and the remaining acupoints (52%) were positioned point-by-point by using the OpenGL 3D graphics libraries. Based on the projective 2D descriptions of the standard acupuncture points, the volumetric 3D acupoint model was developed; it was extracted from the X-ray CT images. Conclusions: This modality for positioning acupoints may modernize acupuncture research and enable acupuncture treatments to be more personalized. PMID:24761187

  9. Extreme points of the set of density matrices with positive partial transpose

    E-print Network

    Jon Magne Leinaas; Jan Myrheim; Eirik Ovrum

    2007-04-25

    We present a necessary and sufficient condition for a finite dimensional density matrix to be an extreme point of the convex set of density matrices with positive partial transpose with respect to a subsystem. We also give an algorithm for finding such extreme points and illustrate this by some examples.

  10. Positioning Standardized Acupuncture Points on the Whole Body Based on X-Ray Computed Tomography Images

    PubMed Central

    Kim, Jungdae

    2014-01-01

    Abstract Objective: The goal of this research was to position all the standardized 361 acupuncture points on the entire human body based on a 3-dimensional (3D) virtual body. Materials and Methods: Digital data from a healthy Korean male with a normal body shape were obtained in the form of cross-sectional images generated by X-ray computed tomography (CT), and the 3D models for the bones and the skin's surface were created through the image-processing steps. Results: The reference points or the landmarks were positioned based on the standard descriptions of the acupoints, and the formulae for the proportionalities between the acupoints and the reference points were presented. About 37% of the 361 standardized acupoints were automatically linked with the reference points, the reference points accounted for 11% of the 361 acupoints, and the remaining acupoints (52%) were positioned point-by-point by using the OpenGL 3D graphics libraries. Based on the projective 2D descriptions of the standard acupuncture points, the volumetric 3D acupoint model was developed; it was extracted from the X-ray CT images. Conclusions: This modality for positioning acupoints may modernize acupuncture research and enable acupuncture treatments to be more personalized. PMID:24761187

  11. Freeform Object Positioning by 3D Shape Matching Without Artificial Feature Points

    Microsoft Academic Search

    Joris S. M. Vergeest; Yu Song; D. Hartge

    2004-01-01

    Determining the position and orientation of a workpiece relative to a manufacturing device is a prerequisite for machining path planning. If the workpiece is freeform and if it contains no predefined feature points, then object positioning and tool calibration can be accomplished using shape matching in 3D space. In this paper we study the feasibility and accuracy of non-contact, featureless

  12. Sensor for High Speed, High Precision Measurement of 2-D Positions

    PubMed Central

    Luna, Carlos A.; Lázaro, José L.; Mazo, Manuel; Cano, Angel

    2009-01-01

    A sensor system to measure the 2-D position of an object that intercepts a plane in space is presented in this paper. This sensor system was developed with the aim of measuring the height and lateral position of contact wires supplying power to electric locomotives. The sensor comprises two line-scans focused on the zone to be measured and positioned in such a way that their viewing planes are on the same plane. The report includes a mathematical model of the sensor system, and details the method used for calibrating the sensor system. The procedure used for high speed measurement of object position in space is also described, where measurement acquisition time was less than 0.7 ms. Finally, position measurement results verifying system performance in real time are given. PMID:22291537

  13. Double Precision Hybrid-Mode Floating-Point FPGA CORDIC Coprocessor

    Microsoft Academic Search

    Jie Zhou; Yong Dou; Yuanwu Lei; Jinbo Xu; Yazhuo Dong

    2008-01-01

    FPGA chips have become a promising option for accelerating scientific applications, which involve many floating-point transcendental functions, such as sin, log, exp, sqrt and etc. In this paper, we present a 64-bit ANSI\\/IEEE floating-point CORDIC co-processor on FPGA, providing all known CORDIC functions. And there is no 64-bit CORDIC implementation on FPGA known to us. We propose a hybrid-mode CORDIC

  14. A method of rapidly estimating the position of the laminar separation point

    NASA Technical Reports Server (NTRS)

    Von Doenhoff, Albert E

    1938-01-01

    A method is described of rapidly estimating the position of the laminar separation point from the given pressure distribution along a body; the method is applicable to a fairly wide variety of cases. The laminar separation point is found by the von Karman-Millikan method for a series of velocity distributions along a flat plate, which consist of a region of uniform velocity followed by a region of uniform decreased velocity. It is shown that such a velocity distribution can frequently replace the actual velocity distribution along a body insofar as the effects on laminar separation are concerned. An example of the application of the method is given by using it to calculate the position of the laminar separation point on the NACA 0012 airfoil section at zero lift. The agreement between the position of the separation point calculated according to the present method and that found from more elaborate computations is very good.

  15. An Evaluation of VLBI Observations for the Precise Positioning of the NOZOMI Spacecraft

    NASA Astrophysics Data System (ADS)

    Ryuichi, I.; Mamoru, S.; Hiroo, O.; Yasuhiro, K.; Tetsuro, K.; Takafumi, O.; Makoto, Y.; Nozomi Dvlbi Group,.

    2003-12-01

    We performed more than 30 VLBI experiments for the NOZOMI spacecraft navigation from September 2002 until July 2003. NOZOMI, which means ``Hope'' in Japanese, is the Japan's first Mars probe developed and launched by the Institute of Space and Astronautical Science (ISAS). NOZOMI was originally scheduled to reach its destination in October 1999. However, NOZOMI had to be forced to make extra maneuver due to malfunction of a thruster valve during the powered earth swing-by. As a result, it was found that NOZOMI no longer had enough fuel to inject itself into its scheduled orbit on arrival at Mars. Fortunately, the ISAS mission analysis team succeeded to reschedule its flight plan to meet both fuel and observation conditions. According to the new trajectory strategy, NOZOMI's arrival at Mars is scheduled in the middle of December 2003 through two additional earth swingbys in December 2002 and June 2003. Our main concern was to determine the NOZOMI orbit just before the second earth swingby on June 19, 2003. It was significantly important to get the timing to maneuver the NOZOMI before the swingby. ISAS scientists were afraid that the range and range rate (R&RR) orbit determination might not be available because it was difficult to point the high-gain antenna mounted the spacecraft toward the earth during the period between two swingby events. So we started to support the orbit determination of the NOZOMI using differential VLBI technique since September 2002. These VLBI experiments are also aimed to establish the positioning technology for the interplanetary spacecrafts in realtime. We use nine VLBI antennas in Japan to carry out the VLBI experiments at X-band. Algonquin 46-m of the Space Geodynamics Laboratory (SGL) of CRESTech also participated in the several experiments. We equipped the state of the art ``K5 VLBI system'' to these stations. The K5 system is the multiple PC-based VLBI system equipped with a specific PCI-bus board on the FreeBSD and Linux operating system. The K5 system includes the original software packages which are data sampling and acquisition, real-time IP data transmission, and correlation analysis. For the purpose of analyzing the VLBI observables we are developing the specific VLBI delay model for finite distance radio source. The model is already implemented in the VLBI software package. The package will include the VLBI observation scheduling to take account of the passage of the spacecraft near the quasar line of sight and the propagation delay estimating for the ionosphere and the neutral atmosphere. We can successfully detect fringes of NOZOMI range signal for several baselines using software correlation in spite of weak and narrow-bandwidth signal. We provided 15 VLBI group delay data sets to ISAS to support the orbit determination at the end of May 2003. On the other hand, ISAS scientists have fortunately succeeded to determine the NOZOMI orbit using R&RR observables at the end of May 2003. Preliminary results demonstrate that the VLBI delay residuals are consistent with R&RR observables. However, the rms scatter between them are relatively large up to several tens nanoseconds. We are now evaluating our VLBI data sets by comparing with the R&RR results.

  16. A novel multi-DOF precision positioning methodology using two-axis Hall-effect sensors

    Microsoft Academic Search

    Yusuke Kawato; Won-jong Kim

    2005-01-01

    A novel sensing methodology using two-axis Hall-effect sensors is proposed, where the absolute positioning of a device atop any magnet matrix is possible. This methodology has the capability of micrometer-order positioning resolution as well as unrestricted translational and rotational range in planar 3-DOF (degree-of-freedom) motions, with potential capability of measuring all 6-DOF motions. This paper presents the methodology and preliminary

  17. Precision measurement of energy and position resolutions of the BTeV electromagnetic calorimeter prototype

    NASA Astrophysics Data System (ADS)

    Batarin, V. A.; Brennan, T.; Butler, J.; Cheung, H.; Derevschikov, A. A.; Fomin, Y. V.; Frolov, V.; Goncharenko, Y. M.; Grishin, V. N.; Kachanov, V. A.; Khodyrev, V. Y.; Khroustalev, K.; Konstantinov, A. S.; Kravtsov, V. I.; Kubota, Y.; Leontiev, V. M.; Maisheev, V. A.; Matulenko, Y. A.; Melnick, Y. M.; Meschanin, A. P.; Mikhalin, N. E.; Minaev, N. G.; Mochalov, V. V.; Morozov, D. A.; Mountain, R.; Nogach, L. V.; Ryazantsev, A. V.; Semenov, P. A.; Shestermanov, K. E.; Soloviev, L. F.; Solovianov, V. L.; Stone, S.; Ukhanov, M. N.; Uzunian, A. V.; Vasiliev, A. N.; Yakutin, A. E.; Yarba, J.

    2003-09-01

    The energy dependence of the energy and position resolutions of the electromagnetic calorimeter prototype made of lead tungstate crystals produced in Bogoroditsk (Russia) and Shanghai (China) is presented. These measurements were carried out at the Protvino accelerator using a 1- 45 GeV electron beam. The crystals were coupled to photomultiplier tubes. The dependence of energy and position resolutions on different factors as well as the measured electromagnetic shower lateral profile are presented.

  18. Modelling of differential single difference receiver clock bias for precise positioning

    Microsoft Academic Search

    Xianglin Liu; Christian Tiberius; Kees de Jong

    2004-01-01

    A receiver hardware delay should be seriously considered for time-transfer and determination of ionospheric delay corrections for wide area differential GPS positioning. A receiver hardware delay does not generally effect the common geo-position application, as suitable differences of observations are used, or equivalently, clock error parameters are introduced, epoch-wise, that also absorb the delays. This paper investigates the behavior of

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

    SciTech Connect

    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

    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.

  20. Precision Pointing Control to and Accurate Target Estimation of a Non-Cooperative Vehicle

    NASA Technical Reports Server (NTRS)

    VanEepoel, John; Thienel, Julie; Sanner, Robert M.

    2006-01-01

    In 2004, NASA began investigating a robotic servicing mission for the Hubble Space Telescope (HST). Such a mission would not only require estimates of the HST attitude and rates in order to achieve capture by the proposed Hubble Robotic Vehicle (HRV), but also precision control to achieve the desired rate and maintain the orientation to successfully dock with HST. To generalize the situation, HST is the target vehicle and HRV is the chaser. This work presents a nonlinear approach for estimating the body rates of a non-cooperative target vehicle, and coupling this estimation to a control scheme. Non-cooperative in this context relates to the target vehicle no longer having the ability to maintain attitude control or transmit attitude knowledge.

  1. High-precision position estimation in PET using artificial neural networks

    NASA Astrophysics Data System (ADS)

    Mateo, F.; Aliaga, R. J.; Ferrando, N.; Martínez, J. D.; Herrero, V.; Lerche, Ch. W.; Colom, R. J.; Monzó, J. M.; Sebastiá, A.; Gadea, R.

    2009-06-01

    Traditionally, the most popular technique to predict the impact position of gamma photons on a PET detector has been Anger's logic. However, it introduces nonlinearities that compress the light distribution, reducing the useful field of view and the spatial resolution, especially at the edges of the scintillator crystal. In this work, we make use of neural networks to address a bias-corrected position estimation from real stimulus obtained from a 2D PET system setup. The preprocessing and data acquisition were performed by separate custom boards, especially designed for this application. The results show that neural networks yield a more uniform field of view while improving the systematic error and the spatial resolution. Therefore, they stand as a better performing and readily available alternative to classic positioning methods.

  2. Comparative classification analysis of post-harvest growth detection from terrestrial LiDAR point clouds in precision agriculture

    NASA Astrophysics Data System (ADS)

    Koenig, Kristina; Höfle, Bernhard; Hämmerle, Martin; Jarmer, Thomas; Siegmann, Bastian; Lilienthal, Holger

    2015-06-01

    In precision agriculture, detailed geoinformation on plant and soil properties plays an important role, e.g., in crop protection or the application of fertilizers. This paper presents a comparative classification analysis for post-harvest growth detection using geometric and radiometric point cloud features of terrestrial laser scanning (TLS) data, considering the local neighborhood of each point. Radiometric correction of the TLS data was performed via an empirical range-correction function derived from a field experiment. Thereafter, the corrected amplitude and local elevation features were explored regarding their importance for classification. For the comparison, tree induction, Na?ve Bayes, and k-Means-derived classifiers were tested for different point densities to distinguish between ground and post-harvest growth. The classification performance was validated against highly detailed RGB reference images and the red edge normalized difference vegetation index (NDVI705), derived from a hyperspectral sensor. Using both geometric and radiometric features, we achieved a precision of 99% with the tree induction. Compared to the reference image classification, the calculated post-harvest growth coverage map reached an accuracy of 80%. RGB and LiDAR-derived coverage showed a polynomial correlation to NDVI705 of degree two with R2 of 0.8 and 0.7, respectively. Larger post-harvest growth patches (>10 × 10 cm) could already be detected by a point density of 2 pts./0.01 m2. The results indicate a high potential of radiometric and geometric LiDAR point cloud features for the identification of post-harvest growth using tree induction classification. The proposed technique can potentially be applied over larger areas using vehicle-mounted scanners.

  3. Restoring the Suzaku Source Position Accuracy and Point-Spread Function

    E-print Network

    Yasunobu Uchiyama; Yoshitomo Maeda; Masatoshi Ebara; Ryuichi Fujimoto; Yoshitaka Ishisaki; Manabu Ishida; Ryo Iizuka; Masayoshi Ushio; Hirohiko Inoue; Shunsaku Okada; Hideyuki Mori; Masanobu Ozaki

    2008-03-24

    We present an empirical correction of sky coordinates of X-ray photons obtained with the XIS aboard the Suzaku satellite to improve the source position accuracy and restore the point-spread function (PSF). The XIS images are known to have an uncertainty in position of up to 1 arcmin, and to show considerable degradations of the PSF. These problems are caused by a drifting of the satellite attitude due to thermal distortion of the side panel 7, where the attitude control system is mounted. We found that the position error averaged over a pointing observation can be largely reduced by using the relation between the deviation of the source position in the DETX direction and the ecliptic latitude of the pointing target. We parameterized the wobbling of the source position synchronized with the satellite orbital period with temperatures of onboard radiators and elapsed time since the night-day transition of the spacecraft. We developed software, aeattcor, to correct the image drift using these parameters, and applied it to 27 point-source images. We show that the radius of the 90% error circle of the source position was reduced to 19 arcsec and the PSF was sharpened. These improvements have enhanced the scientific capability of the Suzaku XIS.

  4. Development and deployment of a precision underwater positioning system for in situ laser Raman spectroscopy in the deep ocean

    NASA Astrophysics Data System (ADS)

    White, Sheri N.; Kirkwood, William; Sherman, Alana; Brown, Mark; Henthorn, Richard; Salamy, Karen; Walz, Peter; Peltzer, Edward T.; Brewer, Peter G.

    2005-12-01

    The field of ocean geochemistry has recently been expanded to include in situ laser Raman spectroscopic measurements in the deep ocean. While this technique has proved to be successful for transparent targets, such as fluids and gases, difficulty exists in using deep submergence vehicle manipulators to position and control the very small laser spot with respect to opaque samples of interest, such as many rocks, minerals, bacterial mats, and seafloor gas hydrates. We have developed, tested, and successfully deployed by remotely operated vehicle (ROV) a precision underwater positioner (PUP) which provides the stability and precision movement required to perform spectroscopic measurements using the Deep Ocean Raman In situ Spectrometer (DORISS) instrument on opaque targets in the deep ocean for geochemical research. The positioner is also adaptable to other sensors, such as electrodes, which require precise control and positioning on the seafloor. PUP is capable of translating the DORISS optical head with a precision of 0.1 mm in three dimensions over a range of at least 15 cm, at depths up to 4000 m, and under the normal range of oceanic conditions (T, P, current velocity). The positioner is controlled, and spectra are obtained, in real time via Ethernet by scientists aboard the surface vessel. This capability has allowed us to acquire high quality Raman spectra of targets such as rocks, shells, and gas hydrates on the seafloor, including the ability to scan the laser spot across a rock surface in sub-millimeter increments to identify the constituent mineral grains. These developments have greatly enhanced the ability to obtain in situ Raman spectra on the seafloor from an enormous range of specimens.

  5. Precision measurement of beta-ray end-point energies: 60Co, 137Cs and 204Tl

    Microsoft Academic Search

    J. L. Wolfson; A. J. Collier

    1968-01-01

    Using a high resolving power, iron-free spectrometer, precise measurements have been performed of the end-point energies of the beta-ray spectra from 60Co, 137Cs (low-energy spectrum) and 204Tl. The values obtained were 317.88+\\/-0.10, 511.63+\\/-0.84, and 763.47+\\/-0.22 keV, respectively. The experimental work on which this paper is based was performed by one of us (J.L.W.) during 1964 at the National Research Council

  6. Precise Three-Dimensional Scan-Free Multiple-Particle Tracking over Large Axial Ranges with Tetrapod Point Spread Functions.

    PubMed

    Shechtman, Yoav; Weiss, Lucien E; Backer, Adam S; Sahl, Steffen J; Moerner, W E

    2015-06-10

    We employ a novel framework for information-optimal microscopy to design a family of point spread functions (PSFs), the Tetrapod PSFs, which enable high-precision localization of nanoscale emitters in three dimensions over customizable axial (z) ranges of up to 20 ?m with a high numerical aperture objective lens. To illustrate, we perform flow profiling in a microfluidic channel and show scan-free tracking of single quantum-dot-labeled phospholipid molecules on the surface of living, thick mammalian cells. PMID:25939423

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

    Microsoft Academic Search

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

    1992-01-01

    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

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

    Microsoft Academic Search

    N. Barov; J. S. Kim; A. W. Weidemann; R. H. Miller; C. D. Nantista

    2006-01-01

    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

  9. High-Precision Resonant Cavity Beam Position, Emittance and Third-Moment Monitors

    Microsoft Academic Search

    N. Barov; J. S. Kim; A. W. Weidemann; R. H. Miller; C. D. Nantista

    2005-01-01

    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

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

    Microsoft Academic Search

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

    2000-01-01

    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

  11. MODELLING AND IDENTIFICATION OF A HIGH-PRECISION PLANAR POSITIONING SYSTEM

    E-print Network

    Knobloch,Jürgen

    -- planar positioning system, air bearing, electro magnetic propulsion, physical modelling 1. INTRODUCTION embedded into the stator plate. Currents through those conductors together with the permanent magnets of the slider is 200x200mm2 and the maximal yaw angle is ±0.25 . A number of perma- nent magnets are mounted

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

    Microsoft Academic Search

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

    2000-01-01

    In this paper are presented the design and experimental results of using a shape memory alloy (SMA) wire as an actuator for\\u000a position control of a composite beam. The composite beam is honeycomb structured, having wires of SMA embedded in one of its\\u000a face sheets for the purposes of active actuation. Nickel-titanium SMA wires were chosen as actuating elements due

  13. Precision real-time navigation of LEO satellites using global positioning system measurements

    Microsoft Academic Search

    Oliver Montenbruck; Pere Ramos-Bosch

    2008-01-01

    Continued advancements in remote sensing technology along with a trend towards highly autonomous spacecraft provide a strong\\u000a motivation for accurate real-time navigation of satellites in low Earth orbit (LEO). Global Navigation Satellite System (GNSS)\\u000a sensors nowadays enable a continuous tracking and provide low-noise radiometric measurements onboard a user spacecraft. Following\\u000a the deactivation of Selective Availability a representative real-time positioning accuracy

  14. Extracting Precise (11\\/2-M) Tactical Positioning Data from LF Radio Transmissions

    Microsoft Academic Search

    D. W. Allan; G. R. German; S. F. Smith

    2006-01-01

    This paper describes a series of low-frequency (LF) time-transfer measurements performed during 2005 to support the prototyping of a frequency-agile, programmable-bandwidth radionavigation system, the theater positioning system (TPS), which is being implemented for the U.S. Army to support soldier training and combat systems testing in GPS-denied environments such as dense forests and in urban terrain. The fundamental basis for the

  15. DGPS Kinematic Carrier Phase Signal Simulation Analysis for Precise Velocity and Position Determination

    Microsoft Academic Search

    M. ELIZABETH CANNON; GERARD LACHAPELLE; MICHAEL C. SZARMES; JEFFREY M. HEBERT; JAMES KEITH; SCOTT JOKERST; Holloman Air Force Base

    This paper describes the differential GPS and signal simulator equipment, procedures, and simulated aircraft trajectories used to analyze carrier phase measurements in estimating velocities and 30 positions. A differential GPS simulator system was used to generate CIA-code, P-code, and carrier phase signals from segments of the actual GPS constellation. Two pairs of dual-frequency receivers from different manufacturers were tested. These

  16. Zero-point energies, the uncertainty principle and positivity of the quantum Brownian density operator

    E-print Network

    Allan Tameshtit

    2012-04-09

    High temperature and white noise approximations are frequently invoked when deriving the quantum Brownian equation for an oscillator. Even if this white noise approximation is avoided, it is shown that if the zero point energies of the environment are neglected, as they often are, the resultant equation will violate not only the basic tenet of quantum mechanics that requires the density operator to be positive, but also the uncertainty principle. When the zero-point energies are included, asymptotic results describing the evolution of the oscillator are obtained that preserve positivity and, therefore, the uncertainty principle.

  17. Zero-point energies, the uncertainty principle, and positivity of the quantum Brownian density operator.

    PubMed

    Tameshtit, Allan

    2012-04-01

    High-temperature and white-noise approximations are frequently invoked when deriving the quantum Brownian equation for an oscillator. Even if this white-noise approximation is avoided, it is shown that if the zero-point energies of the environment are neglected, as they often are, the resultant equation will violate not only the basic tenet of quantum mechanics that requires the density operator to be positive, but also the uncertainty principle. When the zero-point energies are included, asymptotic results describing the evolution of the oscillator are obtained that preserve positivity and, therefore, the uncertainty principle. PMID:22680520

  18. Centroid Position as a Function of Total Counts in a Windowed CMOS Image of a Point Source

    SciTech Connect

    Wurtz, R E; Olivier, S; Riot, V; Hanold, B J; Figer, D F

    2010-05-27

    We obtained 960,200 22-by-22-pixel windowed images of a pinhole spot using the Teledyne H2RG CMOS detector with un-cooled SIDECAR readout. We performed an analysis to determine the precision we might expect in the position error signals to a telescope's guider system. We find that, under non-optimized operating conditions, the error in the computed centroid is strongly dependent on the total counts in the point image only below a certain threshold, approximately 50,000 photo-electrons. The LSST guider camera specification currently requires a 0.04 arcsecond error at 10 Hertz. Given the performance measured here, this specification can be delivered with a single star at 14th to 18th magnitude, depending on the passband.

  19. Precise determination of earth's center of mass using measurements from the Global Positioning System

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    Global Positioning System (GPS) data from a worldwide geodetic experiment were collected during a 3-week period early in 1991. Geocentric station coordinates were estimated 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 average geocenter estimates agree to 7-13 cm with geocenter estimates determined from satellite laser ranging, a well-established technique. The RMS of daily GPS geocenter estimates were 4 cm for x and y, and 30 cm for z.

  20. The dynamics of global positioning system orbits and the determination of precise ephemerides

    NASA Technical Reports Server (NTRS)

    Colombo, Oscar L.

    1989-01-01

    The suggestion made on the basis of the analytical orbit perturbation theory that the errors in the ephemerides of the GPS satellites are due mostly to resonant effects that can be corrected by adjusting a few parameters in a empirical acceleration formula is tested using simulations and actual data analysis. Data from the Spring 1985 Experiment were used to calculate improved ephemerides, and these ephemerides were used in the estimation of the coordinates of GPS stations within the continental United States, previously positioned with VLBI. The results of this test support the idea that the errors are mostly of a resonant nature and can be corrected.

  1. Precision pointing of scientific instruments on space station: The LFGGREC perspective

    NASA Technical Reports Server (NTRS)

    Blackwell, C. C.; Sirlin, S. W.; Laskin, R. A.

    1988-01-01

    An application of Lyapunov function-gradient-generated robustness-enhancing control (LFGGREC) is explored. The attention is directed to a reduced-complexity representation of the pointing problem presented by the system composed of the Space Infrared Telescope Facility gimbaled to a space station configuration. Uncertainties include disturbance forces applied in the crew compartment area and control moments applied to adjacent scientific payloads (modeled as disturbance moments). Also included are uncertainties in gimbal friction and in the structural component of the system, as reflected in the inertia matrix, the damping matrix, and the stiffness matrix, and the effect of the ignored vibrational dynamics of the structure. The emphasis is on the adaptation of LFGGREC to this particular configuration and on the robustness analysis.

  2. Precise positioning and compliance synthesis for automatic assembly using Lorentz levitation

    NASA Astrophysics Data System (ADS)

    Hollis, R. L.; Salcudean, S.

    1992-05-01

    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.

  3. Pointed water vapor radiometer corrections for accurate Global Positioning System surveying

    Microsoft Academic Search

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

    1993-01-01

    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

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

    Microsoft Academic Search

    Seiichi Shimada; Yehuda Bock

    1992-01-01

    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

  5. Scaling of distributions of sums of positions for chaotic dynamics at band-splitting points

    E-print Network

    Alvaro Diaz-Ruelas; Miguel Angel Fuentes; Alberto Robledo

    2014-09-26

    The stationary distributions of sums of positions of trajectories generated by the logistic map have been found to follow a basic renormalization group (RG) structure: a nontrivial fixed-point multi-scale distribution at the period-doubling onset of chaos and a Gaussian trivial fixed-point distribution for all chaotic attractors. Here we describe in detail the crossover distributions that can be generated at chaotic band-splitting points that mediate between the aforementioned fixed-point distributions. Self affinity in the chaotic region imprints scaling features to the crossover distributions along the sequence of band splitting points. The trajectories that give rise to these distributions are governed first by the sequential formation of phase-space gaps when, initially uniformly-distributed, sets of trajectories evolve towards the chaotic band attractors. Subsequently, the summation of positions of trajectories already within the chaotic bands closes those gaps. The possible shapes of the resultant distributions depend crucially on the disposal of sets of early positions in the sums and the stoppage of the number of terms retained in them.

  6. High precision micro-scale Hall effect characterization method using in-line micro four-point probes

    Microsoft Academic Search

    D. H. Petersena; O. Hansen; R. Lin; P. F. Nielsen; T. Clarysse; J. Goossens; E. Rosseel; W. Vandervorst

    2008-01-01

    Accurate characterization of ultra shallow junctions (USJ) is important in order to understand the principles of junction formation and to develop the appropriate implant and annealing technologies. We investigate the capabilities of a new micro-scale Hall effect measurement method where Hall effect is measured with collinear micro four-point probes (M4PP). We derive the sensitivity to electrode position errors and describe

  7. Restoring the Suzaku Source Position Accuracy and Point-Spread Function

    E-print Network

    Uchiyama, Yasunobu; Ebara, Masatoshi; Fujimoto, Ryuichi; Ishisaki, Yoshitaka; Ishida, Manabu; Iizuka, Ryo; Ushio, Masayoshi; Inoue, Hirohiko; Okada, Shunsaku; Mori, Hideyuki; Ozaki, Masanobu

    2008-01-01

    We present an empirical correction of sky coordinates of X-ray photons obtained with the XIS aboard the Suzaku satellite to improve the source position accuracy and restore the point-spread function (PSF). The XIS images are known to have an uncertainty in position of up to 1 arcmin, and to show considerable degradations of the PSF. These problems are caused by a drifting of the satellite attitude due to thermal distortion of the side panel 7, where the attitude control system is mounted. We found that the position error averaged over a pointing observation can be largely reduced by using the relation between the deviation of the source position in the DETX direction and the ecliptic latitude of the pointing target. We parameterized the wobbling of the source position synchronized with the satellite orbital period with temperatures of onboard radiators and elapsed time since the night-day transition of the spacecraft. We developed software, aeattcor, to correct the image drift using these parameters, and appl...

  8. Accepted for publication in the 1998 IEEE ICRA Proceedings, Leuven, Belgium, May 16-21 Integrated Precision 3-DOF Position Sensor for Planar Linear Motors

    E-print Network

    Butler, Zack

    with overhead robots to perform precision assembly tasks 2 . Planar linear motors are essentially stepper motors closed-loop control that exploits these abilities of the motor, a planar motor sensor should have micron Precision 3-DOF Position Sensor for Planar Linear Motors Zack J. Butler, Alfred A. Rizzi, and Ralph L

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

    SciTech Connect

    Kim, Wan-Soo; Lee, Dong-Jin; Lee, Sun-Kyu [School of Mechatronics, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of)

    2011-01-15

    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.

  10. Examination about Influence for Precision of 3d Image Measurement from the Ground Control Point Measurement and Surface Matching

    NASA Astrophysics Data System (ADS)

    Anai, T.; Kochi, N.; Yamada, M.; Sasaki, T.; Otani, H.; Sasaki, D.; Nishimura, S.; Kimoto, K.; Yasui, N.

    2015-05-01

    As the 3D image measurement software is now widely used with the recent development of computer-vision technology, the 3D measurement from the image is now has acquired the application field from desktop objects as wide as the topography survey in large geographical areas. Especially, the orientation, which used to be a complicated process in the heretofore image measurement, can be now performed automatically by simply taking many pictures around the object. And in the case of fully textured object, the 3D measurement of surface features is now done all automatically from the orientated images, and greatly facilitated the acquisition of the dense 3D point cloud from images with high precision. With all this development in the background, in the case of small and the middle size objects, we are now furnishing the all-around 3D measurement by a single digital camera sold on the market. And we have also developed the technology of the topographical measurement with the air-borne images taken by a small UAV [1~5]. In this present study, in the case of the small size objects, we examine the accuracy of surface measurement (Matching) by the data of the experiments. And as to the topographic measurement, we examine the influence of GCP distribution on the accuracy by the data of the experiments. Besides, we examined the difference of the analytical results in each of the 3D image measurement software. This document reviews the processing flow of orientation and the 3D measurement of each software and explains the feature of the each software. And as to the verification of the precision of stereo-matching, we measured the test plane and the test sphere of the known form and assessed the result. As to the topography measurement, we used the air-borne image data photographed at the test field in Yadorigi of Matsuda City, Kanagawa Prefecture JAPAN. We have constructed Ground Control Point which measured by RTK-GPS and Total Station. And we show the results of analysis made in each of the 3D image measurement software. Further, we deepen the study on the influence of the distribution of GCP on the precision.

  11. X -Point-Position-Dependent Intrinsic Toroidal Rotation in the Edge of the TCV Tokamak

    NASA Astrophysics Data System (ADS)

    Stoltzfus-Dueck, T.; Karpushov, A. N.; Sauter, O.; Duval, B. P.; Labit, B.; Reimerdes, H.; Vijvers, W. A. J.; Camenen, Y.

    2015-06-01

    Edge intrinsic rotation was investigated in Ohmic L -mode discharges on the Tokamak à Configuration Variable, scanning the major radial position of the X point, RX. Edge rotation decreased linearly with increasing RX, vanishing or becoming countercurrent for an outboard X point, in agreement with theoretical expectations. The core rotation profile shifted fairly rigidly with the edge rotation, changing the central rotation speed by more than a factor of two. Core rotation reversals had little effect on the edge rotation velocity. Edge rotation was modestly more countercurrent in unfavorable than favorable ?B shots.

  12. Effects of Reduced Terrestrial LiDAR Point Density on High-Resolution Grain Crop Surface Models in Precision Agriculture

    PubMed Central

    Hämmerle, Martin; Höfle, Bernhard

    2014-01-01

    3D geodata play an increasingly important role in precision agriculture, e.g., for modeling in-field variations of grain crop features such as height or biomass. A common data capturing method is LiDAR, which often requires expensive equipment and produces large datasets. This study contributes to the improvement of 3D geodata capturing efficiency by assessing the effect of reduced scanning resolution on crop surface models (CSMs). The analysis is based on high-end LiDAR point clouds of grain crop fields of different varieties (rye and wheat) and nitrogen fertilization stages (100%, 50%, 10%). Lower scanning resolutions are simulated by keeping every n-th laser beam with increasing step widths n. For each iteration step, high-resolution CSMs (0.01 m2 cells) are derived and assessed regarding their coverage relative to a seamless CSM derived from the original point cloud, standard deviation of elevation and mean elevation. Reducing the resolution to, e.g., 25% still leads to a coverage of >90% and a mean CSM elevation of >96% of measured crop height. CSM types (maximum elevation or 90th-percentile elevation) react differently to reduced scanning resolutions in different crops (variety, density). The results can help to assess the trade-off between CSM quality and minimum requirements regarding equipment and capturing set-up. PMID:25521383

  13. Line-of-sight kinematics and corrections for fast-steering mirrors used in precision pointing and tracking systems

    NASA Astrophysics Data System (ADS)

    Hilkert, J. M.; Kanga, Gavin; Kinnear, K.

    2014-06-01

    Fast steering mirrors, or FSMs, have been used for several decades to enhance or augment the performance of electrooptical imaging and beam-steering systems in applications such as astronomy, laser communications and military targeting and surveillance systems. FSMs are high-precision, high-bandwidth electro-mechanical mechanisms used to deflect a mirror over a small angular displacement relative to the base it is mounted on which is typically a stabilized gimbal or other primary pointing device. Although the equations describing the line-of-sight kinematics derive entirely from the simple plane-mirror law of reflection, they are non-linear and axis-coupled and these effects increase as the FSM angular displacement increases. These inherent non-linearities and axis-coupling effects can contribute to pointing errors in certain modes of operation. The relevant kinematic equations presented in this paper can be used to assess the magnitude of the errors for a given application and make corrections as necessary.

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

    NASA Astrophysics Data System (ADS)

    Dabove, Paolo; Manzino, Ambrogio Maria

    2015-04-01

    The use of GPS/GNSS instruments is a common practice in the world at both a commercial and academic research level. Since last ten years, Continuous Operating Reference Stations (CORSs) networks were born in order to achieve the possibility to extend a precise positioning more than 15 km far from the master station. In this context, the Geomatics Research Group of DIATI at the Politecnico di Torino has carried out several experiments in order to evaluate the achievable precision obtainable with different GNSS receivers (geodetic and mass-market) and antennas if a CORSs network is considered. This work starts from the research above described, in particular focusing the attention on the usefulness of single frequency permanent stations in order to thicken the existing CORSs, especially for monitoring purposes. Two different types of CORSs network are available today in Italy: the first one is the so called "regional network" and the second one is the "national network", where the mean inter-station distances are about 25/30 and 50/70 km respectively. These distances are useful for many applications (e.g. mobile mapping) if geodetic instruments are considered but become less useful if mass-market instruments are used or if the inter-station distance between master and rover increases. In this context, some innovative GNSS networks were developed and tested, analyzing the performance of rover's positioning in terms of quality, accuracy and reliability both in real-time and post-processing approach. The use of single frequency GNSS receivers leads to have some limits, especially due to a limited baseline length, the possibility to obtain a correct fixing of the phase ambiguity for the network and to fix the phase ambiguity correctly also for the rover. These factors play a crucial role in order to reach a positioning with a good level of accuracy (as centimetric o better) in a short time and with an high reliability. The goal of this work is to investigate about the real effect and how is the contribute of L1 mass-market permanent stations to the CORSs Network both for geodetic and low-cost receivers; in particular is described how the use of the network products which are generated by the network (in real-time and post-processing) can improve the accuracy and precision of a rover 5, 10 and 15 km far from the nearest station. Some tests have been carried out considering different types of receivers (geodetic and mass market) and antennas (patch and geodetic). The tests have been conducted considering several positioning approaches (static, stop and go and real time) in order to make the analysis more complete. Good and interesting results were obtained: the followed approach will be useful for many types of applications (landslides monitoring, traffic control), especially where the inter-station distances of GNSS permanent station are greater than 30 km.

  15. Line photogrammetry: a tool for precise localization of 3D points and lines in automated object reconstruction

    NASA Astrophysics Data System (ADS)

    Guelch, Eberhard

    1995-07-01

    An approach to line photogrammetry using four independent parameters for the representation of a 3D straight line is discussed. The developed algorithm is designed for the reconstruction of objects in map updating from large scale aerial imagery. It allows the introduction of 3D geometric constraints on single and multiple lines in a simultaneous adjustment process. The approach is extended to digital line photogrammetry, by automatically extracting straight line segments with image segmentation methods. The identification of corresponding lines and the 3D constraints are currently provided by the user. In an empirical test it has been shown that line photogrammetry is at least as good as conventional point photogrammetry concerning accuracy and reliability, but with digital line photogrammetry offering a potential automation of the measurement process. Current research involves the development of a multi stage comparator for interactive mapping with a core of line photogrammetry and an automated extraction of straight lines. The final intention is however, to provide the line correspondences and the constraints by automated parsing of image segmentations and to use digital line photogrammetry as a final, precise adjustment process to derive coordinates of lines and corners of buildings with objective quality estimates.

  16. 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...

  17. The fork in the road: HIV as a potential positive turning point and the role of spirituality

    Microsoft Academic Search

    H. Kremer; G. Ironson; L. Kaplan

    2009-01-01

    We interviewed 147 HIV-positive people regarding their key life-changing experiences – involving profound changes in attitudes, behaviors, beliefs (including spiritual beliefs), or self-views – to determine the prominence of HIV as the key positive\\/negative turning point. HIV was the key turning point, for 37% (26% positive, 11% negative), whereas for 63% of our sample it was not. Characteristics associated with

  18. An Experimental Study on the Dependent on the Location for the Precision of the Network-Based RTK-GPS Positioning

    Microsoft Academic Search

    Hiromune Namie; Chunming Fan; Sumio Usui; Akio Yasuda

    2005-01-01

    The precision of a few centimeters can be easily obtained in 2drms of the horizontal positions by RTK-GPS positioning, as the range from a user GPS antenna to the satellite is determined by the phase measurement of the carrier waves. Since December 2000, it has been operated experimentally by the network-based system, known as the area correction parameter FKP (flächen-korrectur-parameter

  19. Optimal design of a double-sided linear motor with a multi-segmented trapezoidal magnet array for a high precision positioning system

    Microsoft Academic Search

    Moon G. Lee; Dae-Gab Gweon

    2004-01-01

    A comparative analysis is performed for linear motors adopting conventional and multi-segmented trapezoidal (MST) magnet arrays, respectively, for a high-precision positioning system. The proposed MST magnet array is a modified version of a Halbach magnet array. The MST array has trapezoidal magnets with variable shape and dimensions while the Halbach magnet array generally has a rectangular magnet with identical dimensions.

  20. X-point-position-dependent intrinsic rotation in the edge of TCV

    NASA Astrophysics Data System (ADS)

    Stoltzfus-Dueck, Timothy

    2014-10-01

    A simple transport-based theoretical model predicts that intrinsic toroidal rotation in the tokamak edge should depend strongly on RX, the major-radial position of the X-point, including a sign change to counter-current rotation for adequately outboard X-point. To test the prediction, an RX scan was conducted in Ohmic L-mode shots on TCV, in both USN and LSN configurations. The strong linear dependence on RX was experimentally observed, with quantitative magnitude corresponding to a realistic value for the theory's corresponding input parameter. Although peaked rotation profiles complicate the comparison of absolute rotation values, the data is consistent with the predicted sign change. The core rotation profile shifted fairly rigidly with the edge rotation value, maintaining a relatively constant core rotation gradient. Core rotation reversals, triggered accidentally in a few shots, had little effect on the edge rotation velocity. Edge rotation was modestly more counter-current in USN than LSN discharges. This work was supported in part by the Swiss National Science Foundation and in part by the European Atomic Energy Community, and is subject to the provisions of the European Fusion Development Agreement.

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

    Microsoft Academic Search

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

    2010-01-01

    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

  2. Design and development of measuring device for beam pointing and positional errors in multi-axes laser interferometric systems

    NASA Astrophysics Data System (ADS)

    Hu, Pengcheng; Zhang, Yifei; Wu, Ting; Yuan, Guibin

    2015-02-01

    The mechanism of Abbe error and cosine error resulting from beam pointing and positional errors in a laser interference measurement system was analyzed, a PSD-based measurement method was proposed to measure both errors simultaneously. A light intensity adaptive measuring device was designed for measurement of pointing and positional errors. Experimental results indicated that the measuring range and resolution of the position deviation could reach +/-4.5mm and 1?m respectively; the angular range and resolution could reach +/-0.112rad and 25?rad.

  3. Positions of equilibrium points for dust particles in the circular restricted three-body problem with radiation

    NASA Astrophysics Data System (ADS)

    Pástor, P.

    2014-11-01

    For a body with negligible mass moving in the gravitational field of a star with one planet in a circular orbit (the circular restricted three-body problem), five equilibrium points exist and are known as the Lagrangian points. The positions of the Lagrangian points are not valid for dust particles because in the derivation of the Lagrangian points it is assumed that no other forces besides the gravitation act on the body with negligible mass. Here, we determined positions of the equilibrium points for the dust particles in the circular restricted three-body problem with radiation. The equilibrium points are located on curves connecting the Lagrangian points in the circular restricted three-body problem. The equilibrium points for Jupiter are distributed in large interval of heliocentric distances due to its large mass. The equilibrium points for the Earth explain a cloud of dust particles trailing the Earth observed with the Spitzer Space Telescope. The dust particles moving in the equilibrium points are distributed in interplanetary space according to their properties.

  4. An electro-thermal bimorph-based microactuator for precise track-positioning of optical disk drives

    Microsoft Academic Search

    J P Yang; X C Deng; T C Chong

    2005-01-01

    Electro-thermal actuations are very attractive since they can generate large deflections and forces with low actuating voltages and their fabrication process is compatible with the general integrated circuit (IC) fabrication process. In this paper, we present a novel electro-thermal bimorph-based microactuator as a precise-tracking positioner for high-density optical disk drives (ODD). In the proposed microactuator, four thermal bimorph cantilevers suspend

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

    NASA Astrophysics Data System (ADS)

    Bock, Yehuda

    1992-08-01

    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.

  6. Precise positioning of a moving object in urban area Michal HODO1, Fabian HINTERBERGER2, Robert WEBER2

    E-print Network

    Schuh, Harald

    raw GPS and GLONASS observations and, via GPRS, 10Hz RTK corrections obtained from the nationwide lasting about 2-hours 6750 RTK positions as well as raw data files for post processing were gained of multipath to harm RTK positioning. Furthermore the presentation discusses other environmental effects like

  7. New Method for Determining Isotopic Values of Glutamic Acid and Phenylalanine for Estimation of Precise Trophic Position in Food Web Studies

    NASA Astrophysics Data System (ADS)

    Kamath, T.; Broek, T.; McCarthy, M.

    2012-12-01

    Compound Specific Isotope Analysis of Amino Acids (CSI-AA) has emerged as a highly precise new method of determining trophic levels of both aquatic and terrestrial organisms. Multiple studies have now shown that ?15N values for glutamic acid (Glu) and phenylalanine (Phe) can be coupled to provide extremely precise estimates of trophic position in diverse food web studies. The standard gas chromatography—isotope ratio mass spectrometer (GC-IRMS) approach is presently limited to a select number of labs since necessary equipment is both expensive and not widely accessible. Furthermore, typical GC-IRMS ?15N precision (±1‰) is significantly lower than usual bulk ?15N values (±0.1‰), thus presenting a considerable setback for precise trophic level calculations. In this study, we develop a new dual-column method to purify Glu and Phe using high performance liquid chromatography (HPLC). Phe is purified using an analytical scale reverse phase column embedded with anionic ion-pairing reagents and collected using automated fraction collection. Glu is separated from the non-polar amino acids using the same column and further purified using a hydrophilic interaction liquid chromatography (HILIC) cation and anion-exchange column and collected via automated fraction collection. Isotopic analysis of the purified AAs is then conducted on an elemental analyzer—isotope ratio mass spectrometer (EA-IRMS). As a test of this method, we present and compare the trophic position of five marine organisms—cyanobacteria, deep-sea bamboo coral, juvenile and adult white sea bass, and harbor seal, calculated using Glu and Phe ?15N values produced by both GC-IRMS and our HPLC-EA-IRMS approach. The preliminary results of this study suggest that the HPLC-EA-IRMS method is a viable alternative to GC-IRMS, which should allow accurate trophic position estimates to be made by more researchers using more readily available instrumentation.

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

    ERIC Educational Resources Information Center

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

    2008-01-01

    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…

  9. Cinderellas and Ugly Ducklings: Positive Turning Points in Students' Educational Careers--Exploratory Evidence and a Future Agenda

    ERIC Educational Resources Information Center

    Yair, Gad

    2009-01-01

    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…

  10. The Mariner Mark II high precision scan actuator - Results of an options trade study covering pointing performance and system-wide impacts

    NASA Technical Reports Server (NTRS)

    Schier, J. Alan; Bell, Charles E.; Agronin, Michael; Socha, Michael

    1988-01-01

    Four actuators considered as candidates to meet the requirements of the Mariner Mark II high-precision scan platform are evaluated with respect to such criteria as the net effect on spacecraft mass, required power, cost, expected pointing performance, operational considerations, and necessary control complexity. A direct drive actuator is found to be the most suitable candidate. It is noted that for missions where reactionless actuation results in a lower spacecraft mass due to propellant savings, the option of using a platform mounted or spacecraft mounted reaction wheel for platform momentum compensation and spacecraft attitude control is attractive.

  11. Design of a One-Third Scale Multi-Tethered Aerostat System for Precise Positioning of a Radio Telescope Receiver

    Microsoft Academic Search

    Casey Lambert; Aaron Saunders; Curran Crawford; Meyer Nahon

    The National Research Council of Canada's Herzberg Institute has proposed a design for a new radio telescope known as the 'Large Adaptive Reflector' (LAR). The LAR telescope is comprised of a 200 m reflector and a receiver held aloft at an altitude of 500 m by a tethered aerostat. The position of the receiver is actively controlled by a series

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

    Microsoft Academic Search

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

    1984-01-01

    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

  13. Optimal design of a double-sided linear motor with a multi-segmented trapezoidal magnet array for a high precision positioning system

    NASA Astrophysics Data System (ADS)

    Lee, Moon G.; Gweon, Dae-Gab

    2004-10-01

    A comparative analysis is performed for linear motors adopting conventional and multi-segmented trapezoidal (MST) magnet arrays, respectively, for a high-precision positioning system. The proposed MST magnet array is a modified version of a Halbach magnet array. The MST array has trapezoidal magnets with variable shape and dimensions while the Halbach magnet array generally has a rectangular magnet with identical dimensions. We propose a new model that can describe the magnetic field resulting from the complex-shaped magnets. The model can be applied to both MST and conventional magnet arrays. Using the model, a design optimization of the two types of linear motors is performed and compared. The magnet array with trapezoidal magnets can produce more force than one with rectangular magnets when they are arrayed in a linear motor where there is a yoke with high permeability. After the optimization and comparison, we conclude that the linear motor with the MST magnet array can generate more actuating force per volume than the motor with the conventional array. In order to satisfy the requirements of next generation systems such as high resolution, high speed, and long stroke, the use of a linear motor with a MST array as an actuator in a high precision positioning system is recommended from the results obtained here.

  14. An abasic site analogue activates a c-Ha-ras gene by a point mutation at modified and adjacent positions.

    PubMed Central

    Kamiya, H; Suzuki, M; Komatsu, Y; Miura, H; Kikuchi, K; Sakaguchi, T; Murata, N; Masutani, C; Hanaoka, F; Ohtsuka, E

    1992-01-01

    Synthetic c-Ha-ras genes with an analogue of an abasic site in the first or the second position of codon 12, or in the second position of codon 61 were constructed and transfected into NIH3T3 cells. The genes with the lesions in codon 12 exhibited more focus formation than a normal c-Ha-ras gene, while the gene with the lesion in codon 61 did not. Transformed cells were isolated from the foci, and the c-Ha-ras genes present in the transformants were analysed. A point mutation to A in the modified position was found most frequently in the cases of ras genes modified in codon 12. Surprisingly, point mutations in the adjacent position were also detected. These results indicate that dTMP, and not dAMP, was mainly incorporated into the sites opposite to the abasic site analogue, and that incorrect deoxynucleotides were incorporated in the position adjacent to the abasic site analogue. Images PMID:1408742

  15. Systematic investigations of the influence of the shape of the profile upon the position of the transition point.

    NASA Technical Reports Server (NTRS)

    Bussmann, K; Ulrich, A

    1947-01-01

    The position of the beginning of transition laminar/turbulent as a function of the thickness and the camber of the profile at various Reynolds numbers and lift coefficients was investigated for a series of Joukowsky profiles. The calculation of the boundary layer was carried out according to the Pohlhausen method which may be continued by a simplified stability calculation according to H. Schlichting. A list of tables is given which permits the reading off of the position of the transition point on suction and pressure side for each Joukowsky profile.

  16. A scheme for reducing the effect of selective availability on precise geodetic measurements from the Global Positioning System

    NASA Technical Reports Server (NTRS)

    Feigl, Kurt L.; King, Robert W.; Herring, Thomas A.; Rothacher, Markus

    1991-01-01

    From March to August 1990, the signals transmitted by the Block II satellites of the GPS were dithered under a policy of 'Selective Availability' (SA). The dithering appears as an about 10 to the -10th deviation of the satellite oscillator frequency, which, when accumulated over several minutes, can produce an error of about 100 cycles in the model for carrier beat phase. Differencing between simultaneously sampling receivers minimizes the error. If, however, the receivers do not sample simultaneously, it is necessary to model the frequency deviation. Such a model is here applied to data collected in March 1990 by TI4100 and Minimac receivers sampling at times separated by 0.92 s. Applying the algorithm significantly improves the rms scatter of the estimated relative position vectors. The rms scatter from a data set including dithered satellites is similar for both simultaneously and nonsimultaneously sampling receivers, a result which indicates that SA can be adequately modeled.

  17. Bounded components of positive solutions of abstract fixed point equations: mushrooms, loops and isolas

    Microsoft Academic Search

    Julián López-Gómez; Marcela Molina-Meyer

    2005-01-01

    In this work a general class of nonlinear abstract equations satisfying a generalized strong maximum principle is considered in order to study the behavior of the bounded components of positive solutions bifurcating from the curve of trivial states (?,u)=(?,0) at a nonlinear eigenvalue ?=?0 with geometric multiplicity one. Since the unilateral theorems of Rabinowitz (J. Funct. Anal. 7 (1971) 487,

  18. On the validity of series expansion being used for the position of a point on a Roche equipotential

    Microsoft Academic Search

    A. K. Lal; S. Saini; C. Mohan; V. P. Singh

    2007-01-01

    The concept of Roche equipotentials has been frequently used in literature to study the problems of rotating stars and stars\\u000a in binary systems. However in spite of using this simplifying concept, it is still not possible to express the position of\\u000a a point in the potential field of such a system in a closed analytic form. In order to carry

  19. Tuning the Dirac point position in Bi(2)Se(3)(0001) via surface carbon doping.

    PubMed

    Roy, Sumalay; Meyerheim, H L; Ernst, A; Mohseni, K; Tusche, C; Vergniory, M G; Menshchikova, T V; Otrokov, M M; Ryabishchenkova, A G; Aliev, Z S; Babanly, M B; Kokh, K A; Tereshchenko, O E; Chulkov, E V; Schneider, J; Kirschner, J

    2014-09-12

    Angular resolved photoemission spectroscopy in combination with ab initio calculations show that trace amounts of carbon doping of the Bi_{2}Se_{3} surface allows the controlled shift of the Dirac point within the bulk band gap. In contrast to expectation, no Rashba-split two-dimensional electron gas states appear. This unique electronic modification is related to surface structural modification characterized by an expansion of the top Se-Bi spacing of ?11% as evidenced by surface x-ray diffraction. Our results provide new ways to tune the surface band structure of topological insulators. PMID:25259997

  20. Extended precision software packages

    NASA Technical Reports Server (NTRS)

    Phillips, E. J.

    1972-01-01

    A description of three extended precision packages is presented along with three small conversion subroutines which can be used in conjunction with the extended precision packages. These extended packages represent software packages written in FORTRAN 4. They contain normalized or unnormalized floating point arithmetic with symmetric rounding and arbitrary mantissa lengths, and normalized floating point interval arithmetic with appropriate rounding. The purpose of an extended precision package is to enable the user to use and manipulate numbers with large decimal places as well as those with small decimal places where precision beyond double precision is required.

  1. Positive fragile X microsatellite associations point to a common mechanism of dynamic mutation evolution

    SciTech Connect

    Brown, W.T.; Zhong, N.; Dobkin, C. [Institute for Basic Research, Staten Island, NY (United States)

    1996-03-01

    We recently reported that the size of fragile X gene (FMR1) triplet repeats and two nearby microsatellites show positive allele-size associations. The larger alleles of microsatellite DXS548, located {approximately}150 kb proximal to the FMR1 CGG repeat, and of FRAXAC1 (AC1), located 7 kb proximal to the FMR1 CGG repeat, tend to occur together, and smaller alleles also tend to occur together. Also, fragile X chromosomes are more commonly found on the larger combined microsatellite-allele haplotypes. We now have extended these observations to include two other nearby repeats, FRAXAC2 (AC2), a complex three-part polymorphism located 12 kb distal, and the FRAXE triplet repeat, located 600 kb distal. We divided the chromosomes into controls with FMR1 repeats of <60 and fragile X chromosomes with repeats {>=}60, since FMR1 alleles with repeats {>=}60 show high intergenerational instability. In the 133 controls, previously analyzed for AGG interspersions, and in 119 fragile X chromosomes, we found that these repeats show nonrandom size associations. To describe this numerically, we calculated correlation coefficients for the repeat lengths. These repeats showed significantly positive correlations with each other. Although FRAXE alleles showed no correlation with the control repeats, they did have positive correlations with fragile X chromosome microsatellites (AC1 and AC2 but not DXS548), which may reflect the larger recombinational distances involved and the possibly more recent origin of the fragile X mutations. The correlations tended to be higher for the number of 3{prime} pure CGGs than for total FMR1 repeats in controls. These findings strengthen our hypothesis that there may be a common underlying mutational mechanism that simultaneously affects these repeat loci. 13 refs., 1 tab.

  2. A Method to Improve the Temperature Distribution of Holder Around the Fixed-Point Cell Position

    NASA Astrophysics Data System (ADS)

    Lim, S. D.; Karmalawi, A. M.; Salim, S. G. R.; Soliman, M. A.; Kim, B. H.; Lee, D. H.; Yoo, Y. S.

    2014-07-01

    The temperature profile along the furnaces used in heating high-temperature fixed points has a crucial impact on the quality and duration of melting plateaux, accordingly the accuracy of thermodynamic temperature determination of such fixed points. This paper describes a simple, yet efficient, approach for improving the temperature uniformity along a cell holder in high-temperature blackbody (HTBB) furnaces that use pyrolytic graphite rings as heating elements. The method has been applied on the KRISS' HTBB furnace. In this work, an ideal solution for arranging the heating elements inside the furnace is presented by which the temperature gradient across the cell holder can be kept as low as possible. Numerical calculations, based on a finite element method, have been carried out to find the best possible arrangement of the rings. This has been followed by measuring the temperature gradient along an empty cell holder to validate our calculations. A temperature gradient of 100 mK has been achieved at over a length of 50 mm within a cell holder of 10 cm in length. It has also been shown that for a 20 cm long holder surrounded by rings with an arbitrary resistance profile, the temperature uniformity can be improved by adding a few "hot" rings around the cell holder.

  3. Bounded components of positive solutions of abstract fixed point equations: mushrooms, loops and isolas

    NASA Astrophysics Data System (ADS)

    López-Gómez, Julián; Molina-Meyer, Marcela

    In this work a general class of nonlinear abstract equations satisfying a generalized strong maximum principle is considered in order to study the behavior of the bounded components of positive solutions bifurcating from the curve of trivial states (?,u)=(?,0) at a nonlinear eigenvalue ?=?0 with geometric multiplicity one. Since the unilateral theorems of Rabinowitz (J. Funct. Anal. 7 (1971) 487, Theorems 1.27 and 1.40) are not true as originally stated (cf. the very recent counterexample of Dancer, Bull. London Math. Soc. 34 (2002) 533), in order to get our main results the unilateral theorem of López-Gómez (Spectral Theory and Nonlinear Functional Analysis, Research Notes in Mathematics, vol. 426, CRC Press, Boca Raton, FL, 2001, Theorem 6.4.3) is required. Our analysis fills some serious gaps existing is some published papers that were provoked by a direct use of Rabinowitz's unilateral theory. Actually, the abstract theory developed in this paper cannot be covered with the pioneering results of Rabinowitz (1971), since in Rabinowitz's context any component of positive solutions must be unbounded, by a celebrated result attributable to Dancer (Arch. Rational Mech. Anal. 52 (1973) 181).

  4. Crustal deformation measurements in central Japan determined by a Global Positioning System fixed-point network

    NASA Technical Reports Server (NTRS)

    Shimada, Seiichi; Bock, Yehuda

    1992-01-01

    Results are presented from temporally dense measurements of crustal deformation associated with the convergence of the Eurasian (EUR), Pacific, North American, and Philippine Sea (PHS) plates, carried out in April 1988 by a 10-station GPS fixed-point network established in central Japan. Using regional orbit relaxation methods, the analysis of the first 17-month data revealed significant horizontal deformation across the Suruga trough. Namely, it was found that a site in the northern tip of PHS plate moved nearly westward with a velocity of 28 +/-5 mm per year, and a site at the southeastern tip of EUR plate moved south-southwestward with a velocity of 18 +/-5 mm per year. A significant vertical uplift with a velocity of 20 mm/yr was detected at a site inland of the Tokai district located in the Akaishi uplift zone and at a site on the Hatsushima Island in Sagami Bay.

  5. Position difference regularity of corresponding R-wave peaks for maternal ECG components from different abdominal points

    NASA Astrophysics Data System (ADS)

    Zhang, Jie-Min; Guan, Qun; Tang, Li-Ming; Liu, Tie-Bing; Liu, Hong-Xing; Huang, Xiao-Lin; Si, Jun-Feng

    2014-01-01

    We collected 343 groups of abdominal electrocardiogram (ECG) data from 78 pregnant women and deleted the channels unable for experts to determine R-wave peaks from them; then, based on these filtered data, the statistics of position difference of corresponding R-wave peaks for different maternal ECG components from different points were studied. The resultant statistics showed the regularity that the position difference of corresponding maternal R-wave peaks between different abdominal points does not exceed the range of 30 ms. The regularity was also proved using the fECG data from MIT—BIH PhysioBank. Additionally, the paper applied the obtained regularity, the range of position differences of the corresponding maternal R-wave peaks, to accomplish the automatic detection of maternal R-wave peaks in the recorded all initial 343 groups of abdominal signals, including the ones with the largest fetal ECG components, and all 55 groups of ECG data from MIT—BIH PhysioBank, achieving the successful separation of the maternal ECGs.

  6. Conceptual design of a high precision dual directional beam position monitoring system for beam crosstalk cancellation and improved output pulse shapes

    SciTech Connect

    Thieberger P.; Dawson, C.; Fischer, W.; Gassner, D.; Hulsart, R.; Mernick, K.; Michnoff, R.; Minty, M.

    2012-04-15

    The Relativistic Heavy Ions Collider (RHIC) would benefit from improved beam position measurements near the interaction points that see both beams, especially as the tolerances become tighter when reducing the beam sizes to obtain increased luminosity. Two limitations of the present beam position monitors (BPMs) would be mitigated if the proposed approach is successful. The small but unavoidable cross-talk between signals from bunches traveling in opposite directions when using conventional BPMs will be reduced by adopting directional BPMs. Further improvements will be achieved by cancelling residual cross-talk using pairs of such BPMs. Appropriately delayed addition and integration of the signals will also provide pulses with relatively flat maxima that will be easier to digitize by relaxing the presently very stringent timing requirements.

  7. Anatomical landmarks for positioning the head in preparation for the transsphenoidal approach: the spheno-sellar point.

    PubMed

    Campero, Alvaro; Socolovsky, Mariano; Torino, Rafael; Martins, Carolina; Yasuda, Alexandre; Rhoton, Albert L

    2009-06-01

    The transnasal approach is the most utilized approach to the sellar region. This study was conducted to identify an anatomical landmark on the lateral surface of the head that corresponds to the midpoint of the sellar floor at the level of sphenoidal rostrum. This point, lined up with the nostril, simulates the surgical path and facilitates the transnasal access to the sella turcica. Four adult, formalin-fixed and silicon-injected cadaveric heads, and ten dried skulls were used for laboratory dissection. The heads and skulls were sectioned along the midline; and the spheno-sellar point, corresponding to the midpoint of the sellar floor at the level of sphenoid rostrum, was determined. The spheno-sellar point was plotted on the lateral surface of the skull, and its position measured relative to the external acoustic meatus. Linking the spheno-sellar point with the nostril created the spheno-nostril line. This line represents the surgical path to be taken for direct access to the sphenoid rostrum, and was used to align the cadaveric heads as in surgery. The endonasal transsphenoidal approach was then utilized in one hundred and two adult patients with sellar lesions, using the spheno-sellar point and the spheno-nostril line as the superficial landmarks to guide the approach. The results of this clinical experience are summarized. The spheno-sellar point was found to be located an average of 40.1 mm (SD+/-2.9 mm) anterior and 23.3 mm (SD+/-3.2 mm) superior to the external acoustic meatus. The spheno-nostril line represents the straight surgical path to the sphenoidal rostrum. This landmark was used in 102 correlative transnasal surgeries for sellar lesions of adult patients, and has allowed an easy and straightforward access to the sella. In only 3 cases with poor pneumatisation of the sphenoid sinus (presellar type), the actual location of the surgical instruments had to be confirmed by fluoroscopy. The application of the spheno-sellar point and the spheno-nostril line is a fast, reliable and very simple way to facilitate transsphenoidal surgery, and their use may avoid complications associated with misdirection of this approach. Its use may be limited in cases of poor pneumatisation of the sphenoid sinus, where fluoroscopic guidance could be necessary as a rule. PMID:19533460

  8. Three dimensional indoor positioning based on visible light with Gaussian mixture sigma-point particle filter technique

    NASA Astrophysics Data System (ADS)

    Gu, Wenjun; Zhang, Weizhi; Wang, Jin; Amini Kashani, M. R.; Kavehrad, Mohsen

    2015-01-01

    Over the past decade, location based services (LBS) have found their wide applications in indoor environments, such as large shopping malls, hospitals, warehouses, airports, etc. Current technologies provide wide choices of available solutions, which include Radio-frequency identification (RFID), Ultra wideband (UWB), wireless local area network (WLAN) and Bluetooth. With the rapid development of light-emitting-diodes (LED) technology, visible light communications (VLC) also bring a practical approach to LBS. As visible light has a better immunity against multipath effect than radio waves, higher positioning accuracy is achieved. LEDs are utilized both for illumination and positioning purpose to realize relatively lower infrastructure cost. In this paper, an indoor positioning system using VLC is proposed, with LEDs as transmitters and photo diodes as receivers. The algorithm for estimation is based on received-signalstrength (RSS) information collected from photo diodes and trilateration technique. By appropriately making use of the characteristics of receiver movements and the property of trilateration, estimation on three-dimensional (3-D) coordinates is attained. Filtering technique is applied to enable tracking capability of the algorithm, and a higher accuracy is reached compare to raw estimates. Gaussian mixture Sigma-point particle filter (GM-SPPF) is proposed for this 3-D system, which introduces the notion of Gaussian Mixture Model (GMM). The number of particles in the filter is reduced by approximating the probability distribution with Gaussian components.

  9. Occult hepatitis B virus coinfection in HIV-positive African migrants to the UK: a point prevalence study

    PubMed Central

    Chadwick, D; Doyle, T; Ellis, S; Price, D; Abbas, I; Valappil, M; Geretti, AM

    2014-01-01

    Objectives Occult (surface antigen-negative/DNA-positive) hepatitis B virus (HBV) infection is common in areas of the world where HBV is endemic. The main objectives of this study were to determine the prevalence of occult HBV infection in HIV-infected African migrants to the UK and to determine factors associated with occult coinfection. Methods This anonymized point-prevalence study identified Africans attending three HIV clinics, focussing on patients naïve to antiretroviral therapy (ART). Stored blood samples were tested for HBV DNA. Prevalence was calculated in the entire cohort, as well as in subpopulations. Risk factors for occult HBV coinfection were identified using logistic regression analysis. Results Among 335 HIV-positive African migrants, the prevalence of occult HBV coinfection was 4.5% [95% confidence interval (CI) 2.8–7.4%] overall, and 6.5% (95% CI 3.9–10.6%) and 0.8% (95% CI 0.2–4.6%) in ART-naïve and ART-experienced patients, respectively. Among ART-naïve anti-HBV core (anti-HBc)-positive patients, the prevalence was 16.4% (95% CI 8.3–25.6%). The strongest predictor of occult coinfection was anti-HBc positivity [odds ratio (OR) 7.4; 95% CI 2.0–27.6]. Median HBV DNA and ALT levels were 54 IU/mL [interquartile range (IQR) 33–513 IU/mL] and 22 U/L (IQR 13–27 U/L), respectively. Conclusions Occult HBV coinfection remains under-diagnosed in African HIV-infected patients in the UK. Given the range of HBV DNA levels observed, further studies are warranted to determine its clinical significance and to guide screening strategies and ART selection in these patients. PMID:24118868

  10. Optical fixing the positions of the off-shore objects applying the method of two reference points

    NASA Astrophysics Data System (ADS)

    Naus, Krzysztof; Szulc, Dariusz

    2014-06-01

    The Paper presents the optical method of fixing the off-shore objects positions from the land. The method is based on application of two reference points, having the geographical coordinates defined. The first point was situated high on the sea shore, where also the camera was installed. The second point was intended for use to determine the topocentric horizon plane and it was situated at the water-level. The first section of the Paper contains the definition of space and disposed therein reference systems: connected with the Earth, water-level and the camera system. The second section of the Paper provides a description of the survey system model and the principles of the Charge Coupled Device - CCD array pixel's coordinates (plate coordinates) transformation into the geographic coordinates located on the water-level. In the final section there are presented the general rules of using the worked out method in the optical system. W artykule przedstawiono optyczn? metod? wyznaczania pozycji obiektów nawodnych z l?du. Oparto j? na dwóch punktach odniesienia o znanych wspó?rz?dnych geograficznych. Pierwszy umiejscowiono wysoko na brzegu morza i przeznaczono do zamontowania kamery. Drugi przeznaczono do okre?lania p?aszczyzny horyzontu topocentrycznego i umiejscowiono na poziomie lustra wody. W pierwszej cz??ci artyku?u zdefi niowano przestrze? i rozmieszczone w niej uk?ady odniesienia: zwi?zany z Ziemi?, poziomem lustra wody i kamer?. Drug? cz??? artyku?u stanowi opis modelu uk?adu pomiarowego oraz zasad transformacji wspó?rz?dnych piksela (t?owych) z matrycy CCD na wspó?rz?dne geograficzne punktu umiejscowionego na poziomie lustra wody. W cz??ci ko?cowej zaprezentowano ogólne zasady wykorzystywania opracowanej metody w systemie optycznym.

  11. Continuous Monitoring of Coastal Erosion in The Inupiat Eskimo Village of Barrow Alaska Using High Precision Differential Global Positioning System (DGPS)

    NASA Astrophysics Data System (ADS)

    Aguirre, A.; Tweedie, C. E.; Brown, J.; Graves, A.

    2006-12-01

    Barrow Environmental Observatory (BEO) is a 7466 acre area that has been set aside for the sole purpose of scientific research and has been under intense studies for over 60 years under different projects. The BEO contains approximately 15 kilometers of coastline of which the majority have been monitored by Jerry Brown to calculate rates at which this is occurring. Coastal erosion is one of the many impacts resulting from global climate change in the Arctic. Sea ice in the Arctic Ocean is decreasing in extent and is also becoming less thick allowing wave height to increase, which in many areas has enhanced coastal erosion. In northern Alaska, the rate of coastal erosion appears to have increased dramatically over the last 50 years. This is cause for concern because of the increased potential damage to property, archeological sites and the ecology of the Arctic system. The central objective of this study was to determine the extent and nature of coastal erosion. In 2003, a new technique was used to monitor the coastal erosion by walking along the coastal bluff and logging Differential Global Positioning Systems (DGPS) coordinates every second. In 2005, two kilometers of the coast was monitored and 15 km was monitored in 2006 using the same technique as in 2003. This new technique of walking the coastal bluff and logging coordinates every second with high precision DGPS is coming out to be a very effective way to monitor coastal dynamics. Previous observations made by Jerry Brown state that at times up to 10m of coastal bluff per year have been lost to erosion. Using DGPS to monitor coastlines allows for application of GIS techniques to calculate area and volumetric rates at which the coastline is being eroded. This project will serve as a continuation of coastal erosion surveys and will be added as legacy data to the Barrow Area Information Database-Internet Map Server (www.baidims.org) .

  12. A surface displacement analysis for Volcan Pacaya from October 2001 through March 2013 by means of 3-D modeling of precise position GPS data

    NASA Astrophysics Data System (ADS)

    Hetland, Brianna R.

    Volcan Pacaya is one of three currently active volcanoes in Guatemala. Volcanic activity originates from the local tectonic subduction of the Cocos plate beneath the Caribbean plate along the Pacific Guatemalan coast. Pacaya is characterized by generally strombolian type activity with occasional larger vulcanian type eruptions approximately every ten years. One particularly large eruption occurred on May 27, 2010. Using GPS data collected for approximately 8 years before this eruption and data from an additional three years of collection afterwards, surface movement covering the period of the eruption can be measured and used as a tool to help understand activity at the volcano. Initial positions were obtained from raw data using the Automatic Precise Positioning Service provided by the NASA Jet Propulsion Laboratory. Forward modeling of observed 3-D displacements for three time periods (before, covering and after the May 2010 eruption) revealed that a plausible source for deformation is related to a vertical dike or planar surface trending NNW-SSE through the cone. For three distinct time periods the best fitting models describe deformation of the volcano: 0.45 right lateral movement and 0.55 m tensile opening along the dike mentioned above from October 2001 through January 2009 (pre-eruption); 0.55 m left lateral slip along the dike mentioned above for the period from January 2009 and January 2011 (covering the eruption); -0.025 m dip slip along the dike for the period from January 2011 through March 2013 (post-eruption). In all bestfit models the dike is oriented with a 75° westward dip. These data have respective RMS misfit values of 5.49 cm, 12.38 cm and 6.90 cm for each modeled period. During the time period that includes the eruption the volcano most likely experienced a combination of slip and inflation below the edifice which created a large scar at the surface down the northern flank of the volcano. All models that a dipping dike may be experiencing a combination of inflation and oblique slip below the edifice which augments the possibility of a westward collapse in the future.

  13. Optimal contributions of head and eye positions to spatial accuracy in man tested by visually directed pointing

    Microsoft Academic Search

    Yves Rossetti; Bruno Tadary; Claude Prablanc

    1994-01-01

    Encoding of visual target location in extrapersonal space requires convergence of at least three types of information: retinal signals, information about orbital eye positions, and the position of the head on the body. Since the position of gaze is the sum of the head position and the eye position, inaccuracy of spatial localization of the target may result from the

  14. Precise Indoor Localization for Mobile Laser Scanner

    NASA Astrophysics Data System (ADS)

    Kaijaluoto, R.; Hyyppä, A.

    2015-05-01

    Accurate 3D data is of high importance for indoor modeling for various applications in construction, engineering and cultural heritage documentation. For the lack of GNSS signals hampers use of kinematic platforms indoors, TLS is currently the most accurate and precise method for collecting such a data. Due to its static single view point data collection, excessive time and data redundancy are needed for integrity and coverage of data. However, localization methods with affordable scanners are used for solving mobile platform pose problem. The aim of this study was to investigate what level of trajectory accuracies can be achieved with high quality sensors and freely available state of the art planar SLAM algorithms, and how well this trajectory translates to a point cloud collected with a secondary scanner. In this study high precision laser scanners were used with a novel way to combine the strengths of two SLAM algorithms into functional method for precise localization. We collected five datasets using Slammer platform with two laser scanners, and processed them with altogether 20 different parameter sets. The results were validated against TLS reference. The results show increasing scan frequency improves the trajectory, reaching 20 mm RMSE levels for the best performing parameter sets. Further analysis of the 3D point cloud showed good agreement with TLS reference with 17 mm positional RMSE. With precision scanners the obtained point cloud allows for high level of detail data for indoor modeling with accuracies close to TLS at best with vastly improved data collection efficiency.

  15. MEASUREMENT AND PRECISION, EXPERIMENTAL VERSION.

    ERIC Educational Resources Information Center

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

    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, (2)…

  16. Visual information throughout a reach determines endpoint precision.

    PubMed

    Ma-Wyatt, Anna; McKee, Suzanne P

    2007-05-01

    People make rapid, goal-directed movements to interact with their environment. Because these movements have consequences, it is important to be able to control them with a high level of precision and accuracy. Our hypothesis is that vision guides rapid hand movements, thereby enhancing their accuracy and precision. To test this idea, we asked observers to point to a briefly presented target (110 ms). We measured the impact of visual information on endpoint precision by using a shutter to close off view of the hand 50, 110 and 250 ms into the reach. We found that precision was degraded if the view of the hand was restricted at any time during the reach, despite the fact that the target disappeared long before the reach was completed. We therefore conclude that vision keeps the hand on the planned trajectory. We then investigated the effects of a perturbation of target position during the reach. For these experiments, the target remained visible until the reach was completed. The target position was shifted at 110, 180 or 250 ms into the reach. Early shifts in target position were easily compensated for, but late shifts led to a shift in the mean position of the endpoints; observers pointed to the center of the two locations, as a kind of best bet on the position of the target. Visual information is used to guide the hand throughout a reach and has a significant impact on endpoint precision. PMID:17109109

  17. Experimental study of the effect of wind on positive and negative corona from a sharp point in a thunderstorm

    Microsoft Academic Search

    F. D'Alessandro

    2009-01-01

    Corona discharge measurements made during a thunderstorm on a mountain at an altitude of almost 3300m above sea level were analyzed for their dependence on the ambient electric field and the local wind speed. The corona current data were taken from an earthed needle point mounted at a height of 3m above the ground. The coronating point was exposed to

  18. The differences in the isoelectric points of biofilm-positive and biofilm-negative Candida parapsilosis strains.

    PubMed

    Ruzicka, Filip; Horka, Marie; Hola, Veronika; Kubesova, Anna; Pavlik, Tomas; Votava, Miroslav

    2010-03-01

    The isoelectric points of 39 Candida parapsilosis strains were determined by means of capillary isoelectric focusing. The value of the isoelectric point corresponded well with cell surface hydrophobicity, as well as with the ability to form biofilm in these yeasts. PMID:20079385

  19. 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

    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

    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…

  20. Precision displacement reference system

    DOEpatents

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

    2000-02-22

    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.

  1. 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)

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

    2005-01-01

    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.

  2. Using Global Positioning System techniques in landslide monitoring

    Microsoft Academic Search

    Josep A. Gili; Jordi Corominas; Joan Rius

    2000-01-01

    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

  3. A study on the influence of operating circuit on the position of emission point of fluorescent lamp

    NASA Astrophysics Data System (ADS)

    Uetsuki, Tadao; Genba, Yuki; Kanda, Takashi

    2009-10-01

    High efficiency fluorescent lamp systems driven by high frequency are very popular for general lighting. Therefore it is very beneficial to be able to predict the lamp's life before the lamp dying, because people can buy a new lamp just before the lamp dying and need not have stocks. In order to judge the lifetime of a lamp it is very useful to know where the emission point is on the electrode filament. With regard to a method for grasping the emission point, it has been reported that the distance from the emission point to the end of the filament can be calculated by measuring the voltage across the filament and the currents flowing in both ends of the filament. The lamp's life can be predicted by grasping the movement of the emission point with operating time. Therefore it is very important to confirm whether the movement of the emission point changes or not when the operating circuit is changed. The authors investigated the difference in the way the emission points moved for two lamp systems which are very popular. One system had an electronic ballast having an auxiliary power source for the heating cathode. Another system had an electronic ballast with no power source, but with a capacitor connected to the lamp in parallel. In this presentation these measurement results will be reported.

  4. Accurate and precise determination of boron isotopic ratios at low concentration by positive thermal ionization mass spectrometry using static multicollection of Cs2BO2+ ions.

    PubMed

    He, Mao-yong; Xiao, Ying-kai; Jin, Zhang-dong; Ma, Yun-qi; Xiao, Jun; Zhang, Yan-ling; Luo, Chong-guang; Zhang, Fei

    2013-07-01

    A static double-collector system for accurate, precise, and rapid boron isotope analysis has been established by employing a newly fixed Faraday H3 and H4 cup enabling simultaneously collected Cs2BO2(+) ion beams (m/z = 308 and 309) on a Finnigan-MAT Triton thermal ionization mass spectrometer of boron (Triton B). The experimental result indicated that Cs2BO2(+) ion beams (m/z = 308 and 309) were simultaneously collected using a fixed Faraday H3 and H4 cup without using the "Zoom Quad" function and reduced accelerating voltage. Furthermore, the method enabled the measurement of samples containing as little as 20 ng of boron. An analysis of the National Institute of Standards and Technology standard reference material (NIST SRM) 951 standard showed external reproducibility (2RSD) of ±0.013‰, ± 0.013‰, and ±0.019‰ for 100, 50, and 20 ng of boron, respectively. The present method of static multicollection of Cs2BO2(+) ions is applicable to a wide field of boron isotopic research that requires high precision and accuracy to analyze samples with low boron concentrations, including pore fluids, foraminifera, rivers, rainwater, and other natural samples. PMID:23718810

  5. Existence of solutions and positive solutions to a fourth-order two-point BVP with second derivative.

    PubMed

    Yao, Qing-Liu

    2004-03-01

    Several existence theorems were established for a nonlinear fourth-order two-point boundary value problem with second derivative by using Leray-Schauder fixed point theorem, equivalent norm and technique on system of integral equations. The main conditions of our results are local. In other words, the existence of the solution can be determined by considering the "height" of the nonlinear term on a bounded set. This class of problems usually describes the equilibrium state of an elastic beam which is simply supported at both ends. PMID:14727313

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

    SciTech Connect

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

    1991-01-01

    An advanced Synthetic Aperture Radar Motion Compensation System has been developed by Sandia National Laboratories (SNL). The system includes a miniaturized high accuracy ring laser gyro inertial measurement unit, a three axis gimbal pointing and stabilization assembly, a differential Global Positioning System (GPS) navigation aiding system, and a pilot guidance system. The system provides several improvements over previous SNL motion compensation systems and is capable of antenna stabilization to less than 0.01 degrees RMS and absolute position measurement to less than 5.0 meters RMS. These accuracies have been demonstrated in recent flight testing aboard a DHC-6-300 Twin Otter'' aircraft.

  7. Response to the DIAC Discussion Paper: "Review of the General Skilled Migration Points Test". Go8 Position Paper

    ERIC Educational Resources Information Center

    Group of Eight (NJ1), 2010

    2010-01-01

    The Group of Eight (Go8) applauds the government's intention to comprehensively reform the skilled migration program, and it welcomes the opportunity to submit this response to the General Skilled Migration (GSM) Points Test Discussion Paper. The Go8 has argued for some time that it is inappropriate to link international education to the skilled…

  8. Arm Position Constraints During Pointing and Reaching in 3-D Space C.C.A.M. GIELEN,1

    E-print Network

    Gielen, C.C.A.M.

    that the orientation of the eyes in of rotational degrees of freedom in the shoulder and elbow during the head et al. 1993). Just as for the eye, Donders' the fully extended arm and for pointing with elbow difference that was found between eye, head,arm movements involving also elbow flexion and extension

  9. Precision laser machining program

    Microsoft Academic Search

    L. N. Durvasula

    2001-01-01

    High brightness, diode pumped solid state laser technology has now progressed to a point that it is envisioned as the next-generation industrial laser. In response, the Precision Laser Machining (PLM) Consortium was formed as part of the US Defense Advanced Research Project Agency (DARPA) Technology Reinvestment Project. The goal of PLM is to develop a new generation of laser machine

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

    Microsoft Academic Search

    John Braun; Christian Rocken; James Liljegren

    2003-01-01

    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

  11. Mapped Landmark Algorithm for Precision Landing

    NASA Technical Reports Server (NTRS)

    Johnson, Andrew; Ansar, Adnan; Matthies, Larry

    2007-01-01

    A report discusses a computer vision algorithm for position estimation to enable precision landing during planetary descent. The Descent Image Motion Estimation System for the Mars Exploration Rovers has been used as a starting point for creating code for precision, terrain-relative navigation during planetary landing. The algorithm is designed to be general because it handles images taken at different scales and resolutions relative to the map, and can produce mapped landmark matches for any planetary terrain of sufficient texture. These matches provide a measurement of horizontal position relative to a known landing site specified on the surface map. Multiple mapped landmarks generated per image allow for automatic detection and elimination of bad matches. Attitude and position can be generated from each image; this image-based attitude measurement can be used by the onboard navigation filter to improve the attitude estimate, which will improve the position estimates. The algorithm uses normalized correlation of grayscale images, producing precise, sub-pixel images. The algorithm has been broken into two sub-algorithms: (1) FFT Map Matching (see figure), which matches a single large template by correlation in the frequency domain, and (2) Mapped Landmark Refinement, which matches many small templates by correlation in the spatial domain. Each relies on feature selection, the homography transform, and 3D image correlation. The algorithm is implemented in C++ and is rated at Technology Readiness Level (TRL) 4.

  12. Quantitative electron paramagnetic resonance (EPR) spectrometry with a TE 104 double rectangular cavity Part 1. A simple alignment procedure for the precision positioning of the sample

    Microsoft Academic Search

    Milan Mazúr; Marián Valko; Robert Klement; Harry Morris

    1996-01-01

    The Bruker TE104 double rectangular cavity is commonly utilized for quantitative electron paramagnetic resonance (EPR) spectrometric measurements. The sample, together with an appropriate standard, can be studied simultaneously within such a cavity under identical states of machine tuning and parameter settings. However, even under such conditions, there still remain sources of error arising from sample size, shape and positioning of

  13. Assessment of residual error in liver position using kV cone-beam computed tomography for liver cancer high-precision radiation therapy

    SciTech Connect

    Hawkins, Maria A. [Radiation Medicine Program, Princess Margaret Hospital, Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Brock, Kristy K. [Radiation Medicine Program, Princess Margaret Hospital, Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Eccles, Cynthia [Radiation Medicine Program, Princess Margaret Hospital, Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Moseley, Douglas [Radiation Medicine Program, Princess Margaret Hospital, Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Jaffray, David [Radiation Medicine Program, Princess Margaret Hospital, Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Dawson, Laura A. [Radiation Medicine Program, Princess Margaret Hospital, Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada)]. E-mail: laura.dawson@rmp.uhn.on.ca

    2006-10-01

    Purpose: To evaluate the residual error in liver position using breath-hold kilovoltage (kV) cone-beam computed tomography (CT) following on-line orthogonal megavoltage (MV) image-guided breath-hold liver cancer conformal radiotherapy. Methods and Materials: Thirteen patients with liver cancer treated with 6-fraction breath-hold conformal radiotherapy were investigated. Before each fraction, orthogonal MV images were obtained during exhale breath-hold, with repositioning for offsets >3 mm, using the diaphragm for cranio-caudal (CC) alignment and vertebral bodies for medial-lateral (ML) and anterior posterior (AP) alignment. After repositioning, repeat orthogonal MV images, orthogonal kV fluoroscopic movies, and kV cone-beam CTs were obtained in exhale breath-hold. The cone-beam CT livers were registered to the planning CT liver to obtain the residual setup error in liver position. Results: After repositioning, 78 orthogonal MV image pairs, 61 orthogonal kV image pairs, and 72 kV cone-beam CT scans were obtained. Population random setup errors ({sigma}) in liver position were 2.7 mm (CC), 2.3 mm (ML), and 3.0 mm (AP), and systematic errors ({sigma}) were 1.1 mm, 1.9 mm, and 1.3 mm in the superior, medial, and posterior directions. Liver offsets >5 mm were observed in 33% of cases; offsets >10 mm and liver deformation >5 mm were observed in a minority of patients. Conclusions: Liver position after radiation therapy guided with MV orthogonal imaging was within 5 mm of planned position in the majority of patients. kV cone-beam CT image guidance should improve accuracy with reduced dose compared with orthogonal MV image guidance for liver cancer radiation therapy.

  14. Analytical formulae to calculate the solid angle subtended at an arbitrarily positioned point source by an elliptical radiation detector

    NASA Astrophysics Data System (ADS)

    Abbas, Mahmoud I.; Hammoud, Sami; Ibrahim, Tarek; Sakr, Mohamed

    2015-01-01

    In this article, we introduce a direct analytical mathematical method for calculating the solid angle, ?, subtended at a point by closed elliptical contours. The solid angle is required in many areas of optical and nuclear physics to estimate the flux of particle beam of radiation and to determine the activity of a radioactive source. The validity of the derived analytical expressions was successfully confirmed by the comparison with some published data (Numerical Method).

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

    Microsoft Academic Search

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

    2001-01-01

    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

  16. A numerical investigation for the optimal positions and weighting coefficients of point dose measurements in the weighted CTDI

    NASA Astrophysics Data System (ADS)

    Choi, Jang-Hwan; Constantin, Dragos; Fahrig, Rebecca

    2015-03-01

    The mean dose over the central phantom plane (i.e., z = 0, dose maximum image) is useful in that it allows us to compare radiation dose levels across different CT scanners and acquisition protocols. The mean dose from a conventional CT scan with table translation is typically estimated by weighted CTDI (CTDIW). However, conventional CTDIW has inconsistent performance, depending on its weighting coefficients ("1/2 and 1/2" or "1/3 and 2/3") and acquisition protocols. We used a Monte Carlo (MC) model based on Geant4 (GEometry ANd Tracking) to generate dose profiles in the central plane of the CTDI phantom. MC simulations were carried out for three different sizes of z-collimator and different tube voltages (80, 100, or 120 kVp), a tube current of 80 mA, and an exposure time of 25 ms. We derived optimal weighting coefficients by taking the integral of the radial dose profiles. The first-order linear equation and the quadratic equation were used to fit the dose profiles along the radial direction perpendicular to the central plane, and the fitted profiles were revolved about the Z-axis to compute the mean dose (i.e., total volume under the fitted profiles/the central plane area). The integral computed using the linear equation resulted in the same equation as conventional CTDIW, and the integral computed using the quadratic equation resulted in a new CTDIW (CTDIMW) that incorporates different weightings ("2/3 and 1/3") and the middle dose point instead of the central dose point. Compared to the results of MC simulations, our new CTDIMW showed less error than the previous CTDIW methods by successfully incorporating the curvature of the dose profiles regardless of acquisition protocols. Our new CTDIMW will also be applicable to the AAPM-ICRU phantom, which has a middle dose point.

  17. An Alternative Empirical Formula for Positive Corona Discharge I-V Characteristics in Point-to-Plate Electrode Geometry

    NASA Astrophysics Data System (ADS)

    A. Azooz, A.; Sabah, I. Waysi

    2014-03-01

    Experimental data are presented for a study on the dependence of the I-V characteristics of the corona discharge on pressure and electrode spacing using point-to-plane electrode configuration. These experimental data are obtained by a fast, automatic computer data-acquisition system. The data are used to suggest an alternative dimensionally self-consistent empirical equation for the parameterization of the I-V curves. The formula eliminates the need for any prior assumptions concerning the inception voltage, as is customary in this type of work.

  18. Precision Nova operations

    SciTech Connect

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

    1995-09-01

    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.

  19. Practicing Precision 

    E-print Network

    Supercinski, Danielle

    2007-01-01

    . These are the growers we want to target next year to improve their water-use efficiency.? PIN is educating agricultural producers about water conservation and irrigation management of various crops, including corn, cotton, grain sorghum, wheat and such winter vegetables... --------------------------------------------- A LEPA (Low Energy Precision Application) irrigation system is used on the PIN cotton field at the Texas A&M University System Agricultural Research and Extension Center at Uvalde along with lysimeters to evaluate crop water use and develop deficit...

  20. Precision tunable resonant microwave cavity

    Microsoft Academic Search

    Shigeo Nakanishi; Frank S. Calco; August R. Scarpelli

    1987-01-01

    A tunable microwave cavity containing ionizable metallic vapor or gases and an apparatus for precisely positioning a microwave coupling tip in the cavity and for precisely adjusting at least one dimension of the cavity are disclosed. With this combined structure, resonance may be achieved with various types of ionizable gases. A coaxial probe extends into a microwave cavity through a

  1. Precision stationkeeping with azimuthing thrusters

    E-print Network

    Doroski, Adam D

    2011-01-01

    Precision positioning of an unmanned surface vehicle (USV) in a nautical environment is a difficult task. With a dual azimuthing thruster scheme, the optimization of thruster outputs uses an online method to minimize the ...

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

    SciTech Connect

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

    2003-05-01

    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.

  3. Role of telecommunications in precision agriculture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Precision agriculture has been made possible by the confluence of several technologies: geographic positioning systems, geographic information systems, image analysis software, low-cost microcomputer-based variable rate controller/recorders, and precision tractor guidance systems. While these techn...

  4. Precision gap particle separator

    DOEpatents

    Benett, William J.; Miles, Robin; Jones, II., Leslie M.; Stockton, Cheryl

    2004-06-08

    A system for separating particles entrained in a fluid includes a base with a first channel and a second channel. A precision gap connects the first channel and the second channel. The precision gap is of a size that allows small particles to pass from the first channel into the second channel and prevents large particles from the first channel into the second channel. A cover is positioned over the base unit, the first channel, the precision gap, and the second channel. An port directs the fluid containing the entrained particles into the first channel. An output port directs the large particles out of the first channel. A port connected to the second channel directs the small particles out of the second channel.

  5. Instrument Attitude Precision Control

    NASA Technical Reports Server (NTRS)

    Juang, Jer-Nan

    2004-01-01

    A novel approach is presented in this paper to analyze attitude precision and control for an instrument gimbaled to a spacecraft subject to an internal disturbance caused by a moving component inside the instrument. Nonlinear differential equations of motion for some sample cases are derived and solved analytically to gain insight into the influence of the disturbance on the attitude pointing error. A simple control law is developed to eliminate the instrument pointing error caused by the internal disturbance. Several cases are presented to demonstrate and verify the concept presented in this paper.

  6. Coupling high resolution 3D point clouds from terrestrial LiDAR with high precision displacement time series from GB-InSAR to understand landslide kinematic: example of the La Perraire instability, Swiss Alps.

    NASA Astrophysics Data System (ADS)

    Michoud, Clément; Baillifard, François; Harald Blikra, Lars; Derron, Marc-Henri; Jaboyedoff, Michel; Kristensen, Lene; Leva, Davide; Metzger, Richard; Rivolta, Carlo

    2014-05-01

    Terrestrial Laser Scanning and Ground-Based Radar Interferometry have changed our perception and interpretation of slope activities for the last 20 years and are now routinely used for monitoring and even early warning purposes. Terrestrial LiDAR allows indeed to model topography with very high point density, even in steep slopes, and to extract 3D displacements of rock masses by comparing successive datasets. GB-InSAR techniques are able to detect mm displacements over large areas. Nevertheless, both techniques suffer of some limitations. The precision of LiDAR devices actually limits its ability to monitor very slow-moving landslides, as well as by the dam resolution and the particular geometry (in azimuth/range) of GB-InSAR data may complicate their interpretations. To overcome those limitations, tools were produced to truly combine strong advantages of both techniques, by coupling high resolution geometrical data from terrestrial LiDAR or photogrammetry with high precision displacement time series from GB-InSAR. We thus developed a new exportation module into the processing chain of LiSAmobile (GB-InSAR) devices in order to wrap radar results from their particular geometry on high resolution 3D point clouds with cm mean point spacing. Furthermore, we also added new importation and visualization functionalities into Coltop3D (software for geological interpretations of laser scanning data) to display those results in 3D and even analyzing displacement time series. This new method has also been optimized to create as few and small files as possible and for time processing. Advantages of coupling terrestrial LiDAR and GB-InSAR data will be illustrated on the La Perraire instability, an active large rockslide involving frequent rockfalls and threatening inhabitant within the Val de Bagnes in the Swiss Alps. This rock mass, monitored by LiDAR and GPS since 2006, is huge enough and long-term movements are big (up to 1.6 m in 6 years) and complex enough to make difficult point cloud comparisons and LiDAR interpretations. Two monitoring campaigns with GB-InSAR devices were later performed and caught mm daily displacements (up to 8 mm in 15 days in September 2011). By coupling both datasets, we were able to clearly identify back scarps, as well as the most active masses within the whole instability, and thus to map limits of the instability and stable parts of the slope. Here the integration and the coupling of ground-based monitoring techniques were necessary to understand the whole landslide kinematic.

  7. Precision laser aiming system

    DOEpatents

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

    2009-04-28

    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.

  8. Optimal Positive Cutoff Points for careHPV Testing of Clinician- and Self-Collected Specimens in Primary Cervical Cancer Screening: an Analysis from Rural China

    PubMed Central

    Kang, Le-Ni; Jeronimo, Jose; Zhao, Fang-Hui; Chen, Wen; Valdez, Melissa; Zhang, Xun; Bansil, Pooja; Paul, Proma; Bai, Ping; Peck, Roger; Li, Jing; Chen, Feng; Stoler, Mark H.

    2014-01-01

    careHPV, a lower-cost DNA test for human papillomavirus (HPV), is being considered for cervical cancer screening in low- and middle-income countries. However, not a single large-scaled study exists to investigate the optimal positive cutoff point of careHPV test. We pooled data for 9,785 women participating in two individual studies conducted from 2007 to 2011 in rural China. Woman underwent multiple screening tests, including careHPV on clinician-collected specimens (careHPV-C) and self-collected specimens (careHPV-S), and Hybrid Capture 2 on clinician-collected specimens (HC2-C) as a reference standard. The primary endpoint was cervical intraepithelial neoplasia grade 3 or more severe (CIN3+) (n = 127), and secondary endpoint was CIN2+ (n = 213). The area under the curves (AUCs) for HC2-C and careHPV-C were similar (0.954 versus 0.948, P = 0.166), and better than careHPV-S (0.878; P < 0.001 versus both). The optimal positive cutoff points for HC2-C, careHPV-C, and careHPV-S were 1.40, 1.74, and 0.85, respectively. At the same cutoff point, careHPV-C was not significantly less sensitive and more specific for CIN3+ than HC2-C, and careHPV-S was significantly less sensitive for CIN3+ than careHPV-C and HC2-C. Raising the cutoff point of careHPV-C from 1.0 to 2.0 could result in nonsignificantly lower sensitivity but significantly higher specificity. Similar results were observed using CIN2+ endpoint. careHPV using either clinician- or self-collected specimens performed well in detecting cervical precancer and cancer. We found that the optimal cutoff points of careHPV were 2.0 on clinician-collected specimens and 1.0 on self-collected specimens. PMID:24671789

  9. Real Sky Tests of Star-Tracker-Based Attitude Determination System for Earth Pointing Spacecraft

    Microsoft Academic Search

    Takanori Iwata; Eiji Hirokawa; Hiroki Hoshino; Takeshi Yoshizawa; Koshi Sato; Isamu Higashino

    2008-01-01

    Earth-pointing and polar-orbiting spacecraft, the Advanced Land Observing Satellite (ALOS), has a precision attitude determination system exploiting measurements of a precision star tracker and an inertial reference unit, and controls its attitude, based on the attitude estimates. The star tracker provides the positions and magnitudes of stars. The attitude control system's computer identifies stars which enter the star tracker's FOV

  10. PRECISION POINTING OF IBEX-Lo OBSERVATIONS

    E-print Network

    Bzowski, M.

    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 ...

  11. Precision guided parachute LDRD final report

    SciTech Connect

    Gilkey, J.C. [Sandia National Labs., Albuquerque, NM (United States). Aided Navigation and Remote Sensing Dept.

    1996-07-01

    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 model of a gliding parachute was developed for software only simulations. A hardware in-the-loop simulator was developed and used for flight package system integration and design validation. Initial parachute drop tests were conducted at Sandia`s Coyote Canyon Cable Facility, followed by a series of airdrops using Ross Aircraft`s Twin Otter at the Burris Ranch Drop Zone. Final flights demonstrated in-flight wind estimation and the capability to fly a commanded heading. In the past, the cost and logistical complexity of an initial navigation system ruled out actively guiding a parachute. The advent of the low-cost, light-weight Global Positioning System (GPS) has eliminated this barrier. By using GPS position and velocity measurements, a guided parachute can autonomously steer itself to a targeted point on the ground through the use of control drums attached to the control lanyards of the parachute. By actively correcting for drop point errors and wind drift, the guidance accuracy of this system should be on the order of GPS position errors. This would be a significant improvement over unguided airdrops which may have errors of a mile or more.

  12. Precision GPS ephemerides and baselines

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Based on the research, the area of precise ephemerides for GPS satellites, the following observations can be made pertaining to the status and future work needed regarding orbit accuracy. There are several aspects which need to be addressed in discussing determination of precise orbits, such as force models, kinematic models, measurement models, data reduction/estimation methods, etc. Although each one of these aspects was studied at CSR in research efforts, only points pertaining to the force modeling aspect are addressed.

  13. Precision Machining

    NSDL National Science Digital Library

    Leske, Cavin.

    Basic machining processes are introduced on a Web site that is devoted to engineering fundamentals (1). Descriptions and illustrations of drilling, turning, grinding, and other common processes are provided for people with little to no prior machining knowledge. A waterjet is a non-traditional machining technology that uses high pressure streams of water with abrasive additives rather than solid cutting instruments to slice through metal and other materials. An in-depth discussion of waterjet operation and applications is available from Southern Methodist University (2). Waterjets are often cited as being much more precise than traditional machining techniques. The Waterjet Video Vault (3) contains clips of waterjet machines in action. The video of the foam cutting procedure is especially interesting, as it shows how quick and accurate the machining process can be. An online guide to cross process machining, which incorporates elements from various conventional and unconventional techniques, is provided by the Mechanical Engineering Department at Columbia University (4). Some remarkable and innovative techniques that have surfaced over the past few years are outlined, including underwater laser machining and plasma-assisted machining. Entirely different and exotic machining techniques are required for creating microelectromechanical systems (MEMS) and other extremely small devices. The Caltech Micromachining Laboratory (5) maintains an archive of research highlights and papers on its homepage, including a paper on a MEMS-driven flapping wing for a palm-sized aerial vehicle. An online article from Modern Machine Shop (6) outlines some new technologies and research in the area of high speed machining. A particularly interesting section of the article describes a system developed at the University of Florida that aims to enable micromachining to achieve rotational speeds of standard machining processes, specifically up to a half million rotations per minute. Cutting edge waterjet innovations are the subject of a February 2003 feature from a publication of the Society of Manufacturing Engineers (7). Extremely high pressure nozzles are being developed to improve cutting speed, and enhanced software for controlling machine movements is also a focus of study. This news article (8) from June 20, 2003 describes an electrochemical machining process that is being used to fabricate complex nanostructures. The work, produced by German and U.S. researchers, has the potential to compete with current lithographic processes.

  14. Modeling the precision and robustness of Hunchback border during Drosophila embryonic development

    Microsoft Academic Search

    Heather Hardway; Bibhash Mukhopadhyay; Timothy Burke; Theron James Hitchman; Robin Forman

    2008-01-01

    During anterior–posterior axis specification in the Drosophila embryo, the Hunchback (Hb) protein forms a sharp boundary at the mid-point of the embryo with great positional precision. While Bicoid (Bcd) is a known upstream regulator for hb expression, there is evidence to suggest that Hb effectively filters out “noisy” data received from varied Bcd gradients. We use mathematical models to explore

  15. Fiber Scrambling for High Precision Spectrographs

    NASA Astrophysics Data System (ADS)

    Kaplan, Zachary; Spronck, J. F. P.; Fischer, D.

    2011-05-01

    The detection of Earth-like exoplanets with the radial velocity method requires extreme Doppler precision and long-term stability in order to measure tiny reflex velocities in the host star. Recent planet searches have led to the detection of so called "super-Earths” (up to a few Earth masses) that induce radial velocity changes of about 1 m/s. However, the detection of true Earth analogs requires a precision of 10 cm/s. One of the largest factors limiting Doppler precision is variation in the Point Spread Function (PSF) from observation to observation due to changes in the illumination of the slit and spectrograph optics. Thus, this stability has become a focus of current instrumentation work. Fiber optics have been used since the 1980's to couple telescopes to high-precision spectrographs, initially for simpler mechanical design and control. However, fiber optics are also naturally efficient scramblers. Scrambling refers to a fiber's ability to produce an output beam independent of input. Our research is focused on characterizing the scrambling properties of several types of fibers, including circular, square and octagonal fibers. By measuring the intensity distribution after the fiber as a function of input beam position, we can simulate guiding errors that occur at an observatory. Through this, we can determine which fibers produce the most uniform outputs for the severest guiding errors, improving the PSF and allowing sub-m/s precision. However, extensive testing of fibers of supposedly identical core diameter, length and shape from the same manufacturer has revealed the "personality” of individual fibers. Personality describes differing intensity patterns for supposedly duplicate fibers illuminated identically. Here, we present our results on scrambling characterization as a function of fiber type, while studying individual fiber personality.

  16. Precision Astrometry with Adaptive Optics

    E-print Network

    P. B. Cameron; M. C. Britton; S. R. Kulkarni

    2008-05-14

    We investigate the limits of ground-based astrometry with adaptive optics using the core of the Galactic globular cluster M5. Adaptive optics systems provide near diffraction-limit imaging with the world's largest telescopes. The substantial improvement in both resolution and signal-to-noise ratio enables high-precision astrometry from the ground. We describe the dominant systematic errors that typically limit ground-based differential astrometry, and enumerate observational considerations for mitigating their effects. After implementing these measures, we find that the dominant limitation on astrometric performance in this experiment is caused by tilt anisoplanatism. We then present an optimal estimation technique for measuring the position of one star relative to a grid of reference stars in the face of this correlated random noise source. Our methodology has the advantage of reducing the astrometric errors as the square root of time and faster than the square root of the number of reference stars -- effectively eliminating noise caused by atmospheric tilt to the point that astrometric performance is limited by centering accuracy. Using 50 reference stars we demonstrate single-epoch astrometric precision of ~ 1 mas in 1 second, decreasing to < 100 microarcseconds in 2 minutes of integration time at the Hale 200-inch telescope. We also show that our astrometry is accurate to <~ 100 microarcseconds for observations separated by 2 months. Finally, we discuss the limits and potential of differential astrometry with current and next generation large aperture telescopes. At this level of accuracy, numerous astrometric applications become accessible, including planet detection, astrometric microlensing signatures, and kinematics of distant Galactic stellar populations.

  17. Precise positions, separations, and position angles of visual binaries

    NASA Astrophysics Data System (ADS)

    Scardia, M.

    1988-11-01

    Astrometric observations of 212 large visual binaries are reported. Data obtained with a GG 495 yellow filter on IIaD photographic plates using the Zen astrograph (aperture 20 cm and focal length 2077 mm) of the Osservatorio Astronomico di Brera during 1985-1986 are presented in extensive tables. The potential significance of these measurements for the catalog being constructed for the Hipparcos space observatory is indicated.

  18. GOCE Precise Science Orbits

    NASA Astrophysics Data System (ADS)

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

    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.

  19. Precision of jaw-closing movements for different jaw gaps.

    PubMed

    Hellmann, Daniel; Becker, Georg; Giannakopoulos, Nikolaos N; Eberhard, Lydia; Fingerhut, Christopher; Rammelsberg, Peter; Schindler, Hans J

    2014-02-01

    Jaw-closing movements are basic components of physiological motor actions precisely achieving intercuspation without significant interference. The main purpose of this study was to test the hypothesis that, despite an imperfect intercuspal position, the precision of jaw-closing movements fluctuates within the range of physiological closing movements indispensable for meeting intercuspation without significant interference. For 35 healthy subjects, condylar and incisal point positions for fast and slow jaw-closing, interrupted at different jaw gaps by the use of frontal occlusal plateaus, were compared with uninterrupted physiological jaw closing, with identical jaw gaps, using a telemetric system for measuring jaw position. Examiner-guided centric relation served as a clinically relevant reference position. For jaw gaps ?4 mm, no significant horizontal or vertical displacement differences were observed for the incisal or condylar points among physiological, fast, and slow jaw-closing. However, the jaw positions under these three closing conditions differed significantly from guided centric relation for nearly all experimental jaw gaps. The findings provide evidence of stringent neuromuscular control of jaw-closing movements in the vicinity of intercuspation. These results might be of clinical relevance to occlusal intervention with different objectives. PMID:24215119

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

    PubMed

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

    2012-12-01

    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

  1. GRATIS: Pointing and Tracking System

    NASA Astrophysics Data System (ADS)

    Seiffert, M. D.; Lubin, P. M.; Craig, W. W.; McLean, R.; Harrison, F.

    1992-12-01

    The Gamma-Ray Arc Minute Telescope Imaging System (GRATIS; see companion paper by Harrison et al.) requires a balloon-borne stabilized platform capable of 20 arc second absolute pointing accuracy. We have developed a system which uses computer-based inertial-guidance control of an azimuth-elevation pointing mechanism for the telescope. An innovative computer-based star pattern recognition system automatically generates drift corrections from an image acquired by a Peltier cooled CCD camera. The inertial guidance system provides three axis pointing information with approximately 12 arc seconds precision. This is a true inertial guidance system with gyros, accelerometers, and an integral navigational processor. The gyros have high relative pointing precision, but a slow drift component degrades their absolute accuracy. Control of the elevation position is accomplished through a torque motor that is directly coupled to the telescope. Azimuth control is accomplished through an active zero-stiction bearing at the top of the gondola and a reaction wheel at the bottom. The pointing system has been fully constructed and tested and has been mated with the telescope. We present the results of an extensive series of tracking tests.

  2. Chapter 16. Precision Mechatronics Precision Mechatronics

    E-print Network

    Chapter 16. Precision Mechatronics 16-1 Precision Mechatronics Academic and Research Staff Prof, April, 2010 #12;Chapter 16. Precision Mechatronics 16-2 RLE Progress Report 152 Amin-Shahidi, D Head for Dimensional Metrology," 2010 IFAC Symposium on Mechatronic Systems, Cambridge, MA, September

  3. Refining WiFi Indoor Positioning Renders Pertinent Deploying Location-Based Multimedia Guide

    Microsoft Academic Search

    Frederic Lassabe; Philippe Canalda; Pascal Chatonnay; Damien Charlet

    2006-01-01

    If outdoor positioning is widely treated and quite precise, indoor or more generally in heterogeneous environment, the positioning (and also mobility prediction) requires consequent devices. The WiFi solution, easy to deploy and cheaper becomes today an alternative. Our refinement approach, which is based on, both a friis calibrated model and the referenced points, makes it competitive. The targeted applications require

  4. Precision powder feeder

    DOEpatents

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

    2001-07-10

    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.

  5. ForceExtension: Extending Isotonic Position-controlled Multi-touch Gestures with Rate-controlled Force Sensing for 3D Manipulation

    E-print Network

    Lindeman, Robert W.

    , rate-control devices such as the IBM TrackPoint [12] eliminate clutching, but suffer from low precisionForceExtension: Extending Isotonic Position-controlled Multi-touch Gestures with Rate-controlled pressure sensing of each touch point on a multi-touch touchpad in addition to position tracking

  6. Precision GPS ephemerides and baselines

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The emphasis of this grant was focused on precision ephemerides for the Global Positioning System (GPS) satellites for geodynamics applications. During the period of this grant, major activities were in the areas of thermal force modeling, numerical integration accuracy improvement for eclipsing satellites, analysis of GIG '91 campaign data, and the Southwest Pacific campaign data analysis.

  7. Precision orbit computations for Starlette

    NASA Technical Reports Server (NTRS)

    Marsh, J. G.; Williamson, R. G.

    1976-01-01

    The Starlette satellite, launched in February 1975 by the French Centre National d'Etudes Spatiales, was designed to minimize the effects of nongravitational forces and to obtain the highest possible accuracy for laser range measurements. Analyses of the first four months of global laser tracking data confirmed the stability of the orbit and the precision to which the satellite's position is established.

  8. The distribution of extreme points in best complex polynomial approximation

    Microsoft Academic Search

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

    1989-01-01

    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)| =

  9. Precision measurements in supersymmetry

    SciTech Connect

    Feng, J.L.

    1995-05-01

    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.

  10. Precision Joining Center

    SciTech Connect

    Powell, J.W.; Westphal, D.A.

    1991-08-01

    A workshop to obtain input from industry on the establishment of the Precision Joining Center (PJC) was held on July 10--12, 1991. The PJC is a center for training Joining Technologists in advanced joining techniques and concepts in order to promote the competitiveness of US industry. The center will be established as part of the DOE Defense Programs Technology Commercialization Initiative, and operated by EG G Rocky Flats in cooperation with the American Welding Society and the Colorado School of Mines Center for Welding and Joining Research. The overall objectives of the workshop were to validate the need for a Joining Technologists to fill the gap between the welding operator and the welding engineer, and to assure that the PJC will train individuals to satisfy that need. The consensus of the workshop participants was that the Joining Technologist is a necessary position in industry, and is currently used, with some variation, by many companies. It was agreed that the PJC core curriculum, as presented, would produce a Joining Technologist of value to industries that use precision joining techniques. The advantage of the PJC would be to train the Joining Technologist much more quickly and more completely. The proposed emphasis of the PJC curriculum on equipment intensive and hands-on training was judged to be essential.

  11. An automatic high precision registration method between large area aerial images and aerial light detection and ranging data

    NASA Astrophysics Data System (ADS)

    Du, Q.; Xie, D.; Sun, Y.

    2015-06-01

    The integration of digital aerial photogrammetry and Light Detetion And Ranging (LiDAR) is an inevitable trend in Surveying and Mapping field. We calculate the external orientation elements of images which identical with LiDAR coordinate to realize automatic high precision registration between aerial images and LiDAR data. There are two ways to calculate orientation elements. One is single image spatial resection using image matching 3D points that registered to LiDAR. The other one is Position and Orientation System (POS) data supported aerotriangulation. The high precision registration points are selected as Ground Control Points (GCPs) instead of measuring GCPs manually during aerotriangulation. The registration experiments indicate that the method which registering aerial images and LiDAR points has a great advantage in higher automation and precision compare with manual registration.

  12. Ultra-precision processes for optics manufacturing

    NASA Technical Reports Server (NTRS)

    Martin, William R.

    1991-01-01

    The Optics MODIL (Manufacturing Operations Development and Integration Laboratory) is developing advanced manufacturing technologies for fabrication of ultra precision optical components, aiming for a ten-fold improvement in precision and a shortening of the scheduled lead time. Current work focuses on diamond single point turning, ductile grinding, ion milling, and in/on process metrology.

  13. Precision tunable resonant microwave cavity

    NASA Technical Reports Server (NTRS)

    Nakanishi, Shigeo (inventor); Calco, Frank S. (inventor); Scarpelli, August R. (inventor)

    1987-01-01

    A tunable microwave cavity containing ionizable metallic vapor or gases and an apparatus for precisely positioning a microwave coupling tip in the cavity and for precisely adjusting at least one dimension of the cavity are disclosed. With this combined structure, resonance may be achieved with various types of ionizable gases. A coaxial probe extends into a microwave cavity through a tube. One end of the tube is retained in a spherical joint attached in the cavity wall. This allows the coaxial probe to be pivotally rotated. The coaxial probe is slideable within the tube thus allowing the probe to be extended toward or retracted from the center of the cavity.

  14. Precise control of flexible manipulators

    NASA Technical Reports Server (NTRS)

    Cannon, R. H., Jr.; Bindford, T. O.; Schmitz, E.

    1984-01-01

    The design and experimental testing of end point position controllers for a very flexible one link lightweight manipulator are summarized. The latest upgraded version of the experimental set up, and the basic differences between conventional joint angle feedback and end point position feedback are described. A general procedure for application of modern control methods to the problem is outlined. The relationship between weighting parameters and the bandwidth and control stiffness of the resulting end point position closed loop system is shown. It is found that joint rate angle feedback in addition to the primary end point position sensor is essential for adequate disturbance rejection capability of the closed loop system. The use of a low order multivariable compensator design computer code; called Sandy is documented. A solution to the problem of control mode switching between position sensor sets is outlined. The proof of concept for endpoint position feedback for a one link flexible manipulator was demonstrated. The bandwidth obtained with the experimental end point position controller is about twice as fast as the beam's first natural cantilevered frequency, and comes within a factor of four of the absolute physical speed limit imposed by the wave propagation time of the beam.

  15. Laser Pointing Determination for ICESat Altimetry

    NASA Astrophysics Data System (ADS)

    Schutz, B. E.; Webb, C.; Bae, S.; Urban, T.

    2004-12-01

    Since its launch aboard the Ice, Cloud, and land Elevation Satellite (ICESat) in January 2003, the Geoscience Laser Altimeter System (GLAS) has produced high-quality elevation profiles for the Greenland and Antarctic ice sheets, as well as for other land and ocean surfaces, during five operational periods. The computation of individual elevations begins with a scalar range, inferred from the time required for a single pulse to travel from a reference point in the GLAS instrument to the surface, and back. This value is then combined with the laser-pointing direction, determined from ground-based processing of data collected by the uniquely designed, on-board Stellar Reference System (SRS). The resulting range vector, together with the geocentric position vector of the GLAS reference point, defines the position and the elevation of the laser spot on the surface. Consequently, while the accuracy of a GLAS-derived elevation depends on the knowledge of the instrument position, as with radar altimeters, it also depends directly on the knowledge of the laser-pointing direction. The position of the GLAS reference point is obtained through ground-based precision orbit determination (POD), using the navigation data collected by the on-board BlackJack GPS receiver. Current assessment of these results suggests that the critical radial component has an accuracy of 2-3 cm, well within the 5-cm requirement. Faced with a number of challenges in the SRS after launch, significant effort has been expended to calibrate the laser-pointing determination. Through a series of refinements in the precision attitude determination (PAD), the resulting pointing solutions have steadily improved the accuracy of the computed elevations, as determined through a variety of calibration/validation techniques. This presentation will highlight the improvements observed for elevation data obtained during the first two operations periods, February-March and September-November 2003.

  16. An improved majority voting algorithm and its application in GPS-based precise orbit determination of LEOs

    Microsoft Academic Search

    Bao-min Han; Yuan-xi Yang; Xiuying Zhu

    2006-01-01

    Precise Orbit Determination (POD) of Low Earth Orbiter satellites (LEOs) based on Point Positioning (PPP) technique utilizing dual-frequency spaceborne GPS observations has become one of the best POD methods at present. Quality control of raw spaceborne GPS observations is very complex but critical for achieving high orbiting accuracy. Among the various existing methods for detecting outliers, the majority-voting algorithm used

  17. Precise Time Synchronization for Wireless Sensor Networks using the

    E-print Network

    Precise Time Synchronization for Wireless Sensor Networks using the Global Positioning System and wall clock time with the aid of the Global Positioning System. Furthermore the proposed approach is.3 The Global Positioning System . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.4 nes

  18. Precision zero-home locator

    DOEpatents

    Stone, W.J.

    1983-10-31

    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.

  19. Precise timing in electric power systems

    Microsoft Academic Search

    Kenneth E. Martin

    1993-01-01

    Precise timing offers a new approach to system-wide controls. It enables measuring the system-wide AC phase as well as timing events and synchronizing controls. the Global Positioning System (GPS) is the first system to provide timing with enough precision to make this approach practical. GPS also provides the wide area of coverage, continuous availability, and high reliability required for power

  20. Active point out-of-plane ultrasound calibration

    NASA Astrophysics Data System (ADS)

    Cheng, Alexis; Guo, Xiaoyu; Zhang, Haichong K.; Kang, Hyunjae; Etienne-Cummings, Ralph; Boctor, Emad M.

    2015-03-01

    Image-guided surgery systems are often used to provide surgeons with informational support. Due to several unique advantages such as ease of use, real-time image acquisition, and no ionizing radiation, ultrasound is a common intraoperative medical imaging modality used in image-guided surgery systems. To perform advanced forms of guidance with ultrasound, such as virtual image overlays or automated robotic actuation, an ultrasound calibration process must be performed. This process recovers the rigid body transformation between a tracked marker attached to the transducer and the ultrasound image. Point-based phantoms are considered to be accurate, but their calibration framework assumes that the point is in the image plane. In this work, we present the use of an active point phantom and a calibration framework that accounts for the elevational uncertainty of the point. Given the lateral and axial position of the point in the ultrasound image, we approximate a circle in the axial-elevational plane with a radius equal to the axial position. The standard approach transforms all of the imaged points to be a single physical point. In our approach, we minimize the distances between the circular subsets of each image, with them ideally intersecting at a single point. We simulated in noiseless and noisy cases, presenting results on out-of-plane estimation errors, calibration estimation errors, and point reconstruction precision. We also performed an experiment using a robot arm as the tracker, resulting in a point reconstruction precision of 0.64mm.

  1. Partially Automated Method for Localizing Standardized Acupuncture Points on the Heads of Digital Human Models

    PubMed Central

    Kim, Jungdae; Kang, Dae-In

    2015-01-01

    Having modernized imaging tools for precise positioning of acupuncture points over the human body where the traditional therapeutic method is applied is essential. For that reason, we suggest a more systematic positioning method that uses X-ray computer tomographic images to precisely position acupoints. Digital Korean human data were obtained to construct three-dimensional head-skin and skull surface models of six individuals. Depending on the method used to pinpoint the positions of the acupoints, every acupoint was classified into one of three types: anatomical points, proportional points, and morphological points. A computational algorithm and procedure were developed for partial automation of the positioning. The anatomical points were selected by using the structural characteristics of the skin surface and skull. The proportional points were calculated from the positions of the anatomical points. The morphological points were also calculated by using some control points related to the connections between the source and the target models. All the acupoints on the heads of the six individual were displayed on three-dimensional computer graphical image models. This method may be helpful for developing more accurate experimental designs and for providing more quantitative volumetric methods for performing analyses in acupuncture-related research. PMID:26101534

  2. Partially Automated Method for Localizing Standardized Acupuncture Points on the Heads of Digital Human Models.

    PubMed

    Kim, Jungdae; Kang, Dae-In

    2015-01-01

    Having modernized imaging tools for precise positioning of acupuncture points over the human body where the traditional therapeutic method is applied is essential. For that reason, we suggest a more systematic positioning method that uses X-ray computer tomographic images to precisely position acupoints. Digital Korean human data were obtained to construct three-dimensional head-skin and skull surface models of six individuals. Depending on the method used to pinpoint the positions of the acupoints, every acupoint was classified into one of three types: anatomical points, proportional points, and morphological points. A computational algorithm and procedure were developed for partial automation of the positioning. The anatomical points were selected by using the structural characteristics of the skin surface and skull. The proportional points were calculated from the positions of the anatomical points. The morphological points were also calculated by using some control points related to the connections between the source and the target models. All the acupoints on the heads of the six individual were displayed on three-dimensional computer graphical image models. This method may be helpful for developing more accurate experimental designs and for providing more quantitative volumetric methods for performing analyses in acupuncture-related research. PMID:26101534

  3. Kinematic precision of gear trains

    NASA Technical Reports Server (NTRS)

    Litvin, F. L.; Goldrich, R. N.; Coy, J. J.; Zaretsky, E. V.

    1982-01-01

    Kinematic precision is affected by errors which are the result of either intentional adjustments or accidental defects in manufacturing and assembly of gear trains. A method for the determination of kinematic precision of gear trains is described. The method is based on the exact kinematic relations for the contact point motions of the gear tooth surfaces under the influence of errors. An approximate method is also explained. Example applications of the general approximate methods are demonstrated for gear trains consisting of involute (spur and helical) gears, circular arc (Wildhaber-Novikov) gears, and spiral bevel gears. Gear noise measurements from a helicopter transmission are presented and discussed with relation to the kinematic precision theory.

  4. Positioning apparatus

    DOEpatents

    Vogel, Max A. (Kennewick, WA); Alter, Paul (Richland, WA)

    1986-01-01

    An apparatus for precisely positioning materials test specimens within the optimum neutron flux path emerging from a neutron source located in a housing. The test specimens are retained in a holder mounted on the free end of a support pivotably mounted and suspended from a movable base plate. The support is gravity biased to urge the holder in a direction longitudinally of the flux path against the housing. Means are provided for moving the base plate in two directions to effect movement of the holder in two mutually perpendicular directions normal to the axis of the flux path.

  5. Precision metering of germinated seeds 

    E-print Network

    Elliot, Gregory Lawrence

    1990-01-01

    Seeds Purpose and Objectives REVIEW OF LITERATURE Precision Planters and Meters for Dry Seeds Trapping Seeds in Cells Trapping Seeds by Air Pressure Using Other Methods for Dry Seeds Planters and Meters for Seeds in Liquid Extruding a Continuous... require only that a certain plant population density be achieved. Willey (1982) points out that this type of crop may be planted with nonprecision planters or broadcast seeders, which control only the rate at which seeds are distributed. However...

  6. Precision extruding deposition and

    E-print Network

    Sun, Wei

    Precision extruding deposition and characterization of cellular poly-e- caprolactone tissue a novel precision extruding deposition (PED) process technique to directly fabricate cellular poly scaffolds is always a challenged subject in regenerative medicine, particularly for load bearing scaffolds

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

    PubMed Central

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

    2013-01-01

    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

  8. Precision agricultural systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Precision agriculture is a new farming practice that has been developing since late 1980s. It has been variously referred to as precision farming, prescription farming, site-specific crop management, to name but a few. There are numerous definitions for precision agriculture, but the central concept...

  9. Precision Capacitor Bank

    Microsoft Academic Search

    A. H. Bushnell; J. B. Ennis; M. Dobrino; P. Gaywood

    2007-01-01

    Summary form only given. High voltage capacitor banks may be required to deliver precise amounts of energy to the load. Various industrial and scientific systems including lasers, magnets and flash lamps may require precise and repeatable energy delivery. This paper discusses the design of capacitor banks to meet these requirements. This includes precise voltage control and stable capacitors. Film capacitors

  10. 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

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

    2010-01-01

    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.…

  11. High precision calibration for 2D optical standard

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    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).

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

    Microsoft Academic Search

    Jong-Yeoun Choi; Sang-Jeong Lee

    2011-01-01

    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

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

    Microsoft Academic Search

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

    2010-01-01

    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. Methods: Pre-survey collected at dining hall in April 2007, followed by 3-week intervention then post-survey

  14. 77 FR 1708 - Cooperative Research and Development Agreement: Technology To Provide Wireless Precise Time...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-11

    ...Technology To Provide Wireless Precise Time; Alternatives to Global Positioning Systems...GPS) as a means of providing precise time. The alternative under consideration is...technical approach for providing precise time using U.S. government facilities...

  15. Enhanced resistive switching phenomena using low-positive-voltage format and self-compliance IrOx/GdOx/W cross-point memories

    PubMed Central

    2014-01-01

    Enhanced resistive switching phenomena of IrOx/GdOx/W cross-point memory devices have been observed as compared to the via-hole devices. The as-deposited Gd2O3 films with a thickness of approximately 15 nm show polycrystalline that is observed using high-resolution transmission electron microscope. Via-hole memory device shows bipolar resistive switching phenomena with a large formation voltage of -6.4 V and high operation current of >1 mA, while the cross-point memory device shows also bipolar resistive switching with low-voltage format of +2 V and self-compliance operation current of <300 ?A. Switching mechanism is based on the formation and rupture of conducting filament at the IrOx/GdOx interface, owing to oxygen ion migration. The oxygen-rich GdOx layer formation at the IrOx/GdOx interface will also help control the resistive switching characteristics. This cross-point memory device has also Repeatable 100 DC switching cycles, narrow distribution of LRS/HRS, excellent pulse endurance of >10,000 in every cycle, and good data retention of >104 s. This memory device has great potential for future nanoscale high-density non-volatile memory applications. PMID:24400888

  16. Low Cost Precision Lander for Lunar Exploration

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    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.

  17. Precise Orbit Determination of BeiDou Navigation Satellite System

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    China has been developing its own independent satellite navigation system since decades. Now the COMPASS system, also known as BeiDou, is emerging and gaining more and more interest and attention in the worldwide GNSS communities. The current regional BeiDou system is ready for its operational service around the end of 2012 with a constellation including five Geostationary Earth Orbit satellites (GEO), five Inclined Geosynchronous Orbit satellites (IGSO) and four Medium Earth orbit (MEO) satellites in operation. Besides the open service with positioning accuracy of around 10m which is free to civilian users, both precise relative positioning, and precise point positioning are demonstrated as well. In order to enhance the BeiDou precise positioning service, Precise Orbit Determination (POD) which is essential of any satellite navigation system has been investigated and studied thoroughly. To further improving the orbits of different types of satellites, we study the impact of network coverage on POD data products by comparing results from tracking networks over the Chinese territory, Asian-Pacific, Asian and of global scale. Furthermore, we concentrate on the improvement of involving MEOs on the orbit quality of GEOs and IGSOs. POD with and without MEOs are undertaken and results are analyzed. Finally, integer ambiguity resolution which brings highly improvement on orbits and positions with GPS data is also carried out and its effect on POD data products is assessed and discussed in detail. Seven weeks of BeiDou data from a ground tracking network, deployed by Wuhan University is employed in this study. The test constellation includes four GEO, five IGSO and two MEO satellites in operation. The three-day solution approach is employed to enhance its strength due to the limited coverage of the tracking network and the small movement of most of the satellites. A number of tracking scenarios and processing schemas are identified and processed and overlapping orbit differences are utilized to qualify the estimated orbits and clocks. 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. For the current tracking network, deploying tracking stations on the eastern side, for example in New Zealand and/or in Hawaii, will significantly reduce along-track biases of GEOs on the same side. The involvement of MEOs and ambiguity-fixing also make the orbits better but rather moderate. Key words: BeiDou, precise orbit determination (POD), tracking network, ambiguity-fixing

  18. Precision luminosity measurements at LHCb

    E-print Network

    LHCb collaboration; R. Aaij; B. Adeva; M. Adinolfi; A. Affolder; Z. Ajaltouni; S. Akar; J. Albrecht; F. Alessio; M. Alexander; S. Ali; G. Alkhazov; P. Alvarez Cartelle; A. A. Alves Jr; S. Amato; S. Amerio; Y. Amhis; L. An; L. Anderlini; J. Anderson; R. Andreassen; M. Andreotti; J. E. Andrews; R. B. Appleby; O. Aquines Gutierrez; F. Archilli; A. Artamonov; M. Artuso; E. Aslanides; G. Auriemma; M. Baalouch; S. Bachmann; J. J. Back; A. Badalov; C. Baesso; W. Baldini; R. J. Barlow; C. Barschel; S. Barsuk; W. Barter; V. Batozskaya; V. Battista; A. Bay; L. Beaucourt; J. Beddow; F. Bedeschi; I. Bediaga; S. Belogurov; K. Belous; I. Belyaev; E. Ben-Haim; G. Bencivenni; S. Benson; J. Benton; A. Berezhnoy; R. Bernet; M. -O. Bettler; M. van Beuzekom; A. Bien; S. Bifani; T. Bird; A. Bizzeti; P. M. Bjørnstad; T. Blake; F. Blanc; J. Blouw; S. Blusk; V. Bocci; A. Bondar; N. Bondar; W. Bonivento; S. Borghi; A. Borgia; M. Borsato; T. J. V. Bowcock; E. Bowen; C. Bozzi; T. Brambach; J. Bressieux; D. Brett; M. Britsch; T. Britton; J. Brodzicka; N. H. Brook; H. Brown; A. Bursche; J. Buytaert; S. Cadeddu; R. Calabrese; M. Calvi; M. Calvo Gomez; P. Campana; D. Campora Perez; A. Carbone; G. Carboni; R. Cardinale; A. Cardini; L. Carson; K. Carvalho Akiba; G. Casse; L. Cassina; L. Castillo Garcia; M. Cattaneo; Ch. Cauet; R. Cenci; M. Charles; Ph. Charpentier; M. Chefdeville; S. Chen; S. -F. Cheung; N. Chiapolini; M. Chrzaszcz; K. Ciba; X. Cid Vidal; G. Ciezarek; P. E. L. Clarke; M. Clemencic; H. V. Cliff; J. Closier; V. Coco; J. Cogan; E. Cogneras; L. Cojocariu; G. Collazuol; P. Collins; A. Comerma-Montells; A. Contu; A. Cook; M. Coombes; S. Coquereau; G. Corti; M. Corvo; I. Counts; B. Couturier; G. A. Cowan; D. C. Craik; M. Cruz Torres; S. Cunliffe; R. Currie; C. D'Ambrosio; J. Dalseno; P. David; P. N. Y. David; A. Davis; K. De Bruyn; S. De Capua; M. De Cian; J. M. De Miranda; L. De Paula; W. De Silva; P. De Simone; C. -T. Dean; D. Decamp; M. Deckenhoff; L. Del Buono; N. Déléage; D. Derkach; O. Deschamps; F. Dettori; A. Di Canto; H. Dijkstra; S. Donleavy; F. Dordei; M. Dorigo; A. Dosil Suárez; D. Dossett; A. Dovbnya; K. Dreimanis; G. Dujany; F. Dupertuis; P. Durante; R. Dzhelyadin; A. Dziurda; A. Dzyuba; S. Easo; U. Egede; V. Egorychev; S. Eidelman; S. Eisenhardt; U. Eitschberger; R. Ekelhof; L. Eklund; I. El Rifai; Ch. Elsasser; S. Ely; S. Esen; H. -M. Evans; T. Evans; A. Falabella; C. Färber; C. Farinelli; N. Farley; S. Farry; RF Fay; D. Ferguson; V. Fernandez Albor; F. Ferreira Rodrigues; M. Ferro-Luzzi; S. Filippov; M. Fiore; M. Fiorini; M. Firlej; C. Fitzpatrick; T. Fiutowski; P. Fol; M. Fontana; F. Fontanelli; R. Forty; O. Francisco; M. Frank; C. Frei; M. Frosini; J. Fu; E. Furfaro; A. Gallas Torreira; D. Galli; S. Gallorini; S. Gambetta; M. Gandelman; P. Gandini; Y. Gao; J. García Pardiñas; J. Garofoli; J. Garra Tico; L. Garrido; D. Gascon; C. Gaspar; R. Gauld; L. Gavardi; A. Geraci; E. Gersabeck; M. Gersabeck; T. Gershon; Ph. Ghez; A. Gianelle; S. Gianì; V. Gibson; L. Giubega; V. V. Gligorov; C. Göbel; D. Golubkov; A. Golutvin; A. Gomes; C. Gotti; M. Grabalosa Gándara; R. Graciani Diaz; L. A. Granado Cardoso; E. Graugés; G. Graziani; A. Grecu; E. Greening; S. Gregson; P. Griffith; L. Grillo; O. Grünberg; B. Gui; E. Gushchin; Yu. Guz; T. Gys; C. Hadjivasiliou; G. Haefeli; C. Haen; S. C. Haines; S. Hall; B. Hamilton; T. Hampson; X. Han; S. Hansmann-Menzemer; N. Harnew; S. T. Harnew; J. Harrison; J. He; T. Head; V. Heijne; K. Hennessy; P. Henrard; L. Henry; J. A. Hernando Morata; E. van Herwijnen; M. Heß; A. Hicheur; D. Hill; M. Hoballah; C. Hombach; W. Hulsbergen; P. Hunt; N. Hussain; D. Hutchcroft; D. Hynds; M. Idzik; P. Ilten; R. Jacobsson; A. Jaeger; J. Jalocha; E. Jans; P. Jaton; A. Jawahery; F. Jing; M. John; D. Johnson; C. R. Jones; C. Joram; B. Jost; N. Jurik; S. Kandybei; W. Kanso; M. Karacson; T. M. Karbach; S. Karodia; M. Kelsey; I. R. Kenyon; T. Ketel; B. Khanji; C. Khurewathanakul; S. Klaver; K. Klimaszewski; O. Kochebina; M. Kolpin; I. Komarov; R. F. Koopman; P. Koppenburg; M. Korolev; A. Kozlinskiy; L. Kravchuk; K. Kreplin; M. Kreps; G. Krocker; P. Krokovny; F. Kruse; W. Kucewicz; M. Kucharczyk; V. Kudryavtsev; K. Kurek; T. Kvaratskheliya; V. N. La Thi; D. Lacarrere; G. Lafferty; A. Lai; D. Lambert; R. W. Lambert; G. Lanfranchi; C. Langenbruch; B. Langhans; T. Latham; C. Lazzeroni; R. Le Gac; J. van Leerdam; J. -P. Lees; R. Lefèvre; A. Leflat; J. Lefrançois; S. Leo; O. Leroy; T. Lesiak; B. Leverington; Y. Li; T. Likhomanenko; M. Liles; R. Lindner; C. Linn; F. Lionetto; B. Liu; S. Lohn; I. Longstaff; J. H. Lopes; N. Lopez-March; P. Lowdon; H. Lu; D. Lucchesi; H. Luo; A. Lupato; E. Luppi; O. Lupton; F. Machefert; I. V. Machikhiliyan; F. Maciuc; O. Maev; S. Malde; A. Malinin; G. Manca; G. Mancinelli; A. Mapelli; J. Maratas; J. F. Marchand; U. Marconi; C. Marin Benito

    2014-12-05

    Measuring cross-sections at the LHC requires the luminosity to be determined accurately at each centre-of-mass energy $\\sqrt{s}$. In this paper results are reported from the luminosity calibrations carried out at the LHC interaction point 8 with the LHCb detector for $\\sqrt{s}$ = 2.76, 7 and 8 TeV (proton-proton collisions) and for $\\sqrt{s_{NN}}$ = 5 TeV (proton-lead collisions). Both the "van der Meer scan" and "beam-gas imaging" luminosity calibration methods were employed. It is observed that the beam density profile cannot always be described by a function that is factorizable in the two transverse coordinates. The introduction of a two-dimensional description of the beams improves significantly the consistency of the results. For proton-proton interactions at $\\sqrt{s}$ = 8 TeV a relative precision of the luminosity calibration of 1.47% is obtained using van der Meer scans and 1.43% using beam-gas imaging, resulting in a combined precision of 1.12%. Applying the calibration to the full data set determines the luminosity with a precision of 1.16%. This represents the most precise luminosity measurement achieved so far at a bunched-beam hadron collider.

  19. Advanced irrigation engineering: Precision and Precise

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Irrigation advances in precision irrigation (PI) or site specific irrigation (SSI) have been considerable in research; however commercialization lags. A primary necessity for PI/SSI is variability in soil texture that affects soil water holding capacity and crop yield. Basically, SSI/PI uses variabl...

  20. High-Precision Computation and Mathematical Physics

    Microsoft Academic Search

    David H. Bailey; Jonathan M. Borwein

    2008-01-01

    At the present time, IEEE 64-bit floating-point arithmetic i s sufficiently accurate for most sci- entific applications. However, for a rapidly growing body of important scientific computing ap- plications, a higher level of numeric precision is required . Such calculations are facilitated by high-precision software packages that include high-level language translation modules to min- imize the conversion effort. This paper

  1. On the range resolution of point targets with FMCW radar systems

    Microsoft Academic Search

    Reinhard Hammel

    1990-01-01

    The spectral analysis of the low pass filtered echo signals of a stationary point target was carried out starting with the precise position of the transmit signal of a Frequency Modulated Continuous-Wave (FMCW) radar operated with sawtooth modulation and assuming a signal transit time which is short compared with the modulation period. It can be stated that the minimum detectable

  2. Increased localization precision by interference fringe analysis

    NASA Astrophysics Data System (ADS)

    Ebeling, Carl G.; Meiri, Amihai; Martineau, Jason; Zalevsky, Zeev; Gerton, Jordan M.; Menon, Rajesh

    2015-06-01

    We report a novel optical single-emitter-localization methodology that uses the phase induced by path length differences in a Mach-Zehnder interferometer to improve localization precision. Using information theory, we demonstrate that the localization capability of a modified Fourier domain signal generated by photon interference enables a more precise localization compared to a standard Gaussian intensity distribution of the corresponding point-spread function. The calculations were verified by numerical simulations and an exemplary experiment, where the centers of metal nanoparticles were localized to a precision of 3 nm.

  3. Increased localization precision by interference fringe analysis.

    PubMed

    Ebeling, Carl G; Meiri, Amihai; Martineau, Jason; Zalevsky, Zeev; Gerton, Jordan M; Menon, Rajesh

    2015-06-01

    We report a novel optical single-emitter-localization methodology that uses the phase induced by path length differences in a Mach-Zehnder interferometer to improve localization precision. Using information theory, we demonstrate that the localization capability of a modified Fourier domain signal generated by photon interference enables a more precise localization compared to a standard Gaussian intensity distribution of the corresponding point-spread function. The calculations were verified by numerical simulations and an exemplary experiment, where the centers of metal nanoparticles were localized to a precision of 3 nm. PMID:25999093

  4. Integrated multidimensional positioner for precision manufacturing

    Microsoft Academic Search

    W-J Kim; N Bhat; T Hu

    2004-01-01

    Reliable low-cost positioning for precision manufacturing processes requiring clean-room, extreme-temperature or vacuum environments is key for microelectronics manufacturing, packaging, machine tool and high-precision inspection industries. The integrated multidimensional positioner presented herein is a major technological breakthrough and may oÄ er competitive advantages in both cost and performance relative to current practices. Speci® cally, this integrated positioner can generate all required

  5. Effect of double-helix point-spread functions on 3D imaging in the presence of spherical aberrations

    Microsoft Academic Search

    Sreya Ghosh; Ginni Grover; Rafael Piestun; Chrysanthe Preza

    2011-01-01

    Double Helix point-spread functions (DH-PSFs), the result of PSF engineering, are used for super resolution microscopy. The DH-PSF design features two dominant lobes in the image plane which rotate with the change in axial (z) position of the light point source. The center of the DH-PSF gives the precise XY location of the point source, while the orientation of the

  6. Precision Cryogenic Dilatometer

    NASA Technical Reports Server (NTRS)

    Dudik, Matthew; Halverson, Peter; Levine-West, Marie; Marcin, Martin; Peters, Robert D.; Shaklan, Stuart

    2005-01-01

    A dilatometer based on a laser interferometer is being developed to measure mechanical creep and coefficients of thermal expansion (CTEs) of materials at temperatures ranging from ambient down to 15 K. This cryogenic dilatometer has been designed to minimize systematic errors that limit the best previously available dilatometers. At its prototype stage of development, this cryogenic dilatometer yields a strain measurement error of 35 ppb or 1.7 ppb/K CTE measurement error for a 20-K thermal load, for low-expansion materials in the temperature range from 310 down to 30 K. Planned further design refinements that include a provision for stabilization of the laser and addition of a high-precision sample-holding jig are expected to reduce the measurement error to 5-ppb strain error or 0.3-ppb/K CTE error for a 20-K thermal load. The dilatometer (see figure) includes a common-path, differential, heterodyne interferometer; a dual-frequency, stabilized source bench that serves as the light source for the interferometer; a cryogenic chamber in which one places the material sample to be studied; a cryogenic system for cooling the interior of the chamber to the measurement temperature; an ultra-stable alignment stage for positioning the chamber so that the sample is properly positioned with respect to the interferometer; and a data-acquisition and control system. The cryogenic chamber and the interferometer portion of the dilatometer are housed in a vacuum chamber on top of a vibration isolating optical table in a cleanroom. The sample consists of two pieces a pillar on a base both made of the same material. Using reflections of the interferometer beams from the base and the top of the pillar, what is measured is the change in length of the pillar as the temperature in the chamber is changed. In their fundamental optical and electronic principles of operation, the laser light source and the interferometer are similar to those described in Common-Path Heterodyne Interferometers (NPO-20786), NASA Tech Briefs, Vol. 25, No. 7 (July 2001), page 12a, and Interferometer for Measuring Displacement to Within 20 pm (NPO- 21221), NASA Tech Briefs, Vol. 27, No. 7 (July 2003), page 8a. However, the present designs incorporate a number of special geometric, optical, and mechanical features to minimize optical and thermal-expansion effects that contribute to measurement errors. These features include the use of low-thermal expansion materials for structural components, kinematic mounting and symmetrical placement of optical components, and several measures taken to minimize spurious reflections of laser beams.

  7. 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

    J.-P. Malet; O. Maquaire; E. Calais

    2002-01-01

    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

  8. Calibration of a high precision rotary table

    NASA Astrophysics Data System (ADS)

    Wang, Heyan; Xue, Zi; Shen, Ni; Huang, Yao

    2015-02-01

    In order to calibrate a high precision rotary table, a calibration system was established to measure the position error and repeatability of rotary table. The position error was measured with a polygon, an index table and an autocollimator to separate the angular error of the polygon from the position error of the rotary table, and the position error of rotary table was calculated using least square method. The rotary table was compensated and calibrated with the position error measured. The repeatability of the rotary table established through 10 times full circle rotations was 0.02 arc second. The measurement results indicated that the combination calibration method was suitable for the calibration of a high precision rotary table. It was found through the analysis that the angular measurement uncertainty was 0.08 arc second.

  9. A Cyclin T1 point mutation that abolishes positive transcription elongation factor (P-TEFb) binding to Hexim1 and HIV tat

    PubMed Central

    2014-01-01

    Background The positive transcription elongation factor b (P-TEFb) plays an essential role in activating HIV genome transcription. It is recruited to the HIV LTR promoter through an interaction between the Tat viral protein and its Cyclin T1 subunit. P-TEFb activity is inhibited by direct binding of its subunit Cyclin T (1 or 2) with Hexim (1 or 2), a cellular protein, bound to the 7SK small nuclear RNA. Hexim1 competes with Tat for P-TEFb binding. Results Mutations that impair human Cyclin T1/Hexim1 interaction were searched using systematic mutagenesis of these proteins coupled with a yeast two-hybrid screen for loss of protein interaction. Evolutionary conserved Hexim1 residues belonging to an unstructured peptide located N-terminal of the dimerization domain, were found to be critical for P-TEFb binding. Random mutagenesis of the N-terminal region of Cyclin T1 provided identification of single amino-acid mutations that impair Hexim1 binding in human cells. Furthermore, conservation of critical residues supported the existence of a functional Hexim1 homologue in nematodes. Conclusions Single Cyclin T1 amino-acid mutations that impair Hexim1 binding are located on a groove between the two cyclin folds and define a surface overlapping the HIV-1 Tat protein binding surface. One residue, Y175, in the centre of this groove was identified as essential for both Hexim1 and Tat binding to P-TEFb as well as for HIV transcription. PMID:24985203

  10. Precise orbit determination for GRACE

    NASA Astrophysics Data System (ADS)

    Kang, Z.; Nagel, P.; Pastor, R.

    2003-04-01

    The twin, co-orbiting GRACE (Gravity Recovery and Climate Experiment) satellites were launched in March 2002. The primary objective of the GRACE mission is to determine the Earth's gravity field and its temporal variations with unprecedented accuracy. To satisfy this objective as well as other applications (e.g. atmospheric profiling by radio occultation), accurate orbits for GRACE are required. This paper describes several results related to the use of the data collected by the GRACE GPS receiver, high precision accelerometer observations and precise attitude data from star trackers in the application of the GRACE Precise Orbit Determination (POD). The orbit accuracy is assessed using a number of tests, which include analysis of GPS tracking observation residuals, Satellite Laser Ranging (SLR) residuals, K-Band Ranging (KBR) residuals and external orbit comparisons. The results show that an accuracy of better than 5 cm in each direction for GRACE orbits can be obtained. The relative accuracy of the two GRACE satellites is about 1 cm in position and 10 micrometers per second in velocity.

  11. Precision tip-tilt-piston actuator that provides exact constraint

    DOEpatents

    Hale, Layton C. (Livermore, CA)

    1999-01-01

    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.

  12. Determination of wheel–rail contact points: comparison between classical and neural network based procedures

    Microsoft Academic Search

    Stefano Falomi; Monica Malvezzi; Enrico Meli; Andrea Rindi

    2009-01-01

    The multibody simulation of railway dynamics needs a reliable efficient method to evaluate the contact points between wheel\\u000a and rail. In this work some methods to evaluate position of contact points are presented. The aim is to develop a method which\\u000a is reliable in terms of precision and can be implemented on-line, assuring a calculation time consistent with real-time calculations

  13. 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)

    Long, Han; Li, Zhenjie; Yi, Dongyun

    2005-11-01

    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.

  14. GPS Position Time Series @ JPL

    NASA Technical Reports Server (NTRS)

    Owen, Susan; Moore, Angelyn; Kedar, Sharon; Liu, Zhen; Webb, Frank; Heflin, Mike; Desai, Shailen

    2013-01-01

    Different flavors of GPS time series analysis at JPL - Use same GPS Precise Point Positioning Analysis raw time series - Variations in time series analysis/post-processing driven by different users. center dot JPL Global Time Series/Velocities - researchers studying reference frame, combining with VLBI/SLR/DORIS center dot JPL/SOPAC Combined Time Series/Velocities - crustal deformation for tectonic, volcanic, ground water studies center dot ARIA Time Series/Coseismic Data Products - Hazard monitoring and response focused center dot ARIA data system designed to integrate GPS and InSAR - GPS tropospheric delay used for correcting InSAR - Caltech's GIANT time series analysis uses GPS to correct orbital errors in InSAR - Zhen Liu's talking tomorrow on InSAR Time Series analysis

  15. Zeptosecond precision pulse shaping.

    PubMed

    Köhler, Jens; Wollenhaupt, Matthias; Bayer, Tim; Sarpe, Cristian; Baumert, Thomas

    2011-06-01

    We investigate the temporal precision in the generation of ultrashort laser pulse pairs by pulse shaping techniques. To this end, we combine a femtosecond polarization pulse shaper with a polarizer and employ two linear spectral phase masks to mimic an ultrastable common-path interferometer. In an all-optical experiment we study the interference signal resulting from two temporally delayed pulses. Our results show a 2?-precision of 300 zs = 300 × 10(-21) s in pulse-to-pulse delay. The standard deviation of the mean is 11 zs. The obtained precision corresponds to a variation of the arm's length in conventional delay stage based interferometers of 0.45 Å. We apply these precisely generated pulse pairs to a strong-field quantum control experiment. Coherent control of ultrafast electron dynamics via photon locking by temporal phase discontinuities on a few attosecond timescale is demonstrated. PMID:21716397

  16. A Precision Vacuum Gauge

    Microsoft Academic Search

    G. C. Fryburg; J. H. Simons

    1949-01-01

    A pressure measuring device of the general type first described by Knudsen has been constructed for obtaining precision measurements of gaseous pressures in the range from 1×10?5 to 10?3 mm of Hg. The instrument has been calibrated, with the aid of a McLeod gauge, in nitrogen, hydrogen, oxygen, methane, ethylene, normal-butane, and iso-butane. The mechanical precision of the instrument seems

  17. Minimum of Geometric Dilution of Precision (GDOP) for five satellites with dual-GNSS constellations

    NASA Astrophysics Data System (ADS)

    Teng, Yunlong; Wang, Jinling; Huang, Qi

    2015-07-01

    The Geometric Dilution of Precision (GDOP) is a term to specify multiplicative effect of the satellite geometry on positioning and timing precision. For positioning, navigation and timing (PNT) applications with multi-GNSS constellations, the lower the GDOP values are, the more accurate the PNT solution is, and thus, the minimum value of GDOP should be discussed. Firstly, this paper analyses the traditional method for calculating the minimum of GDOP for dual-GNSS constellations. Then, from the point of the practical constraints of a GNSS receiver on the earth surface, a new formula for the specific minimum of GDOP together with the design matrix is derived. The minimum of GDOP is expressed as a function with two satellite elevation angles as variables. The numerical experiments have demonstrated the validation of the new formula for the minimum of GDOP.

  18. ACCESS Pointing Control System

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    ACCESS (Actively-Corrected Coronograph 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. The ACCESS study evaluated four major coronograph concepts under a common space observatory. This paper describes the high precision pointing control system (PCS) baselined for this observatory.

  19. Design of a high precision microwave reflector

    Microsoft Academic Search

    E. W. Noller; J. L. Bauer

    1980-01-01

    Development of a high accuracy spherical microwave reflector to support contour RMS and pointing requirements for a new series of space instruments is reported. The reflector system is composed of precision machined aluminum tile reflectors supported from a eutectic coated graphite epoxy structure by flexures. Several basic technologies have been integrated into a manufacturing process that accommodates fabrication techniques of

  20. Testing the precision lightweight GPS receiver

    Microsoft Academic Search

    Barbara Cosentino

    1994-01-01

    Innovative field testing techniques are employed at Holloman Air Force Base to help the Global Positioning System (GPS) NAVSTAR Joint Program Office (JPO) test the precision lightweight GPS receiver (PLGR). Characterizing the PLGR's accuracy in dynamic environments is of prime importance, but testing also prescribes the evaluation of its ability to receive differential GPS corrections, real time, and its electronic

  1. Testing the precision lightweight GPS receiver

    Microsoft Academic Search

    Barbara Cosentino

    1994-01-01

    Innovative field testing techniques are employed at Holloman Air Force Base to help the Global Positioning System (GPS) NAVSTAR Joint Program Office (JPO) test the Precision Lightweight GPS Receiver (PLGR). Characterizing the PLGR's accuracy in dynamic environments is of prime importance but testing also prescribes the evaluation of its ability to receive differential GPS corrections, real time, and its Electronic

  2. Humancentric Applications of Precise Location Based Services

    Microsoft Academic Search

    Laura Perusco; Katina Michael

    2005-01-01

    This paper focuses on the growing need to consider the implications of humancentric applications of precise location based services (LBS). As newer positioning technologies are introduced into the market with a greater level of location accuracy, and existing technologies are utilized in an integrated fashion to overcome limitations, issues pertaining to the use and potential misuse of location information rise

  3. Precision Localization in Monte Carlo Sensor Networks

    Microsoft Academic Search

    Thomas C. Henderson; Edward Grant; Kyle Luthy; Leonardo Mattos; Matt Craver

    2005-01-01

    We have proposed Monte Carlo Sensor Networks as a method to solve certain sensor queries in the presence of noise and partial information. In that work we used very coarse position estimates for enemy agents. Here we propose methods to (1) improve the posterior probability estimates by using a more precise analysis of the sensor range geometry, and (2) help

  4. How Physics Got Precise

    SciTech Connect

    Kleppner, Daniel (MIT) [MIT

    2005-01-19

    Although the ancients knew the length of the year to about ten parts per million, it was not until the end of the 19th century that precision measurements came to play a defining role in physics. Eventually such measurements made it possible to replace human-made artifacts for the standards of length and time with natural standards. For a new generation of atomic clocks, time keeping could be so precise that the effects of the local gravitational potentials on the clock rates would be important. This would force us to re-introduce an artifact into the definition of the second - the location of the primary clock. I will describe some of the events in the history of precision measurements that have led us to this pleasing conundrum, and some of the unexpected uses of atomic clocks today.

  5. Precision Heating Process

    NASA Technical Reports Server (NTRS)

    1992-01-01

    A heat sealing process was developed by SEBRA based on technology that originated in work with NASA's Jet Propulsion Laboratory. The project involved connecting and transferring blood and fluids between sterile plastic containers while maintaining a closed system. SEBRA markets the PIRF Process to manufacturers of medical catheters. It is a precisely controlled method of heating thermoplastic materials in a mold to form or weld catheters and other products. The process offers advantages in fast, precise welding or shape forming of catheters as well as applications in a variety of other industries.

  6. Precision electron polarimetry

    SciTech Connect

    Chudakov, Eugene A. [JLAB

    2013-11-01

    A new generation of precise Parity-Violating experiments will require a sub-percent accuracy of electron beam polarimetry. Compton polarimetry can provide such accuracy at high energies, but at a few hundred MeV the small analyzing power limits the sensitivity. M{\\o}ller polarimetry provides a high analyzing power independent on the beam energy, but is limited by the properties of the polarized targets commonly used. Options for precision polarimetry at ~300 MeV will be discussed, in particular a proposal to use ultra-cold atomic hydrogen traps to provide a 100\\%-polarized electron target for M{\\o}ller polarimetry.

  7. Points of Positive Density for Smooth Functionals

    E-print Network

    Chaleyat-Maurel, Mireille; Nualart, David

    1998-12-03

    ", G = F and p = r, it is clear that the functional #8;" belongs to D1;r and its derivative is given by the formula : D#8;" = m X i=1 SiDF i where the Si verify q Pm i=1 S 2 i #20; 1" . These random variables cancel almost surely outside the set f0 2...

  8. Improving the precision and accuracy of geodetic GPS: Applications to multipath and seismology

    Microsoft Academic Search

    Andria L. Bilich

    2006-01-01

    The Global Positioning System (GPS) enables precise and accurate determination of position anywhere on anywhere on the Earth, a boon to the field of geodesy. Although great advances in geodetic GPS positioning precision and accuracy have been made over the last decade, improvements can still be made. This dissertation addresses GPS positioning error from two different directions---understanding and taking advantage

  9. Precision liquid level sensor

    DOEpatents

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

    1985-01-29

    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.

  10. Precision liquid level sensor

    DOEpatents

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

    1985-01-01

    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.

  11. RADARSAT precision transponder

    Microsoft Academic Search

    R. K. Hawkins; L. D. Teany; S. Srivastava; S. Y. K. Tam

    1997-01-01

    This paper describes the set of four RADARSAT Precision Transponders (RPTs) developed for the Canadian Space Agency for the calibration and qualification of the spaceborne Synthetic Aperture Radar (SAR) carried on the Canadian remote sensing satellite known as RADARSAT, launched in November, 1995. The transponder system block diagram, RF diagram, and specification development are described, as well as the overall

  12. Precision Phase Meter

    Microsoft Academic Search

    D. M. Waters; D. Smith; M. C. Thompson

    1962-01-01

    A precision electromechanical phase meter has been developed to record slow, continuous phase variations often encountered in radio-propagation research. The phase meter will follow phase variations up to several complete cycles unambiguously and small phase variations as fast as 1 cps.

  13. Precision in Stereochemical Terminology

    ERIC Educational Resources Information Center

    Wade, Leroy G., Jr.

    2006-01-01

    An analysis of relatively new terminology that has given multiple definitions often resulting in students learning principles that are actually false is presented with an example of the new term stereogenic atom introduced by Mislow and Siegel. The Mislow terminology would be useful in some cases if it were used precisely and correctly, but it is…

  14. ICESat Precision Orbit Determination

    Microsoft Academic Search

    H. Rim; S. Yoon; C. E. Webb; Y. Kim; B. E. Schutz

    2003-01-01

    Following the successful launch of the Ice, Cloud and land Elevation Satellite (ICESat) on January 13, 2003, 00:45 UTC, the GPS receiver on ICESat was turned on successfully on Jan. 17, 2003. High quality GPS data were collected since then to support Precision Orbit Determination (POD) activities. ICESat carries Geoscience Laser Altimeter System (GLAS) to measure ice-sheet topography and associated

  15. 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

    Muro, Yoshinao; Sugiura, Kazumitsu; Akiyama, Masashi

    2013-03-01

    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

  16. Precise integration for the time-dependent Schrödinger equation

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Li, J.

    2008-02-01

    The precise integration method proposed for linear-invariant dynamical system can give precise numerical result approaching to the exact solution at the integration points. In this paper, a cheap and easy to implement precise integration method for time-dependent Schrödinger equation with periodic Hamiltonians is presented based on Magnus expansion of the solution of the system. The method requires evaluation of only one exponential of matrix, and preserves many of the qualitative properties of the exact solution.

  17. Determination of global positioning system (GPS) receiver clock errors: impact on positioning accuracy

    Microsoft Academic Search

    Ta-Kang Yeh; Cheinway Hwang; Guochang Xu; Chuan-Sheng Wang; Chien-Chih Lee

    2009-01-01

    Enhancing the positioning precision is the primary pursuit of global positioning system (GPS) users. To achieve this goal, most studies have focused on the relationship between GPS receiver clock errors and GPS positioning precision. This study utilizes undifferentiated phase data to calculate GPS clock errors and to compare with the frequency of cesium clock directly, to verify estimated clock errors

  18. Acoustic navigation for ultra-precise seafloor mapping

    Microsoft Academic Search

    Donald M. Hussong; J. Grant Blackinton

    2005-01-01

    Numerous autonomous underwater vehicles (AUVs) are operating with very precise swath bathymetric mapping systems in ocean depths to 3000 m and greater. Although these systems acquire data from positions known to a few centimeters accuracy with respect to the vehicle position, the positioning of the AUVs is generally no better than tens of meters at great depths. Although not yet

  19. 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.

  20. Precision Muon Physics

    E-print Network

    Gorringe, T P

    2015-01-01

    The muon is playing a unique role in sub-atomic physics. Studies of muon decay both determine the overall strength and establish the chiral structure of weak interactions, as well as setting extraordinary limits on charged-lepton-flavor-violating processes. Measurements of the muon's anomalous magnetic moment offer singular sensitivity to the completeness of the standard model and the predictions of many speculative theories. Spectroscopy of muonium and muonic atoms gives unmatched determinations of fundamental quantities including the magnetic moment ratio $\\mu_\\mu / \\mu_p$, lepton mass ratio $m_{\\mu} / m_e$, and proton charge radius $r_p$. Also, muon capture experiments are exploring elusive features of weak interactions involving nucleons and nuclei. We will review the experimental landscape of contemporary high-precision and high-sensitivity experiments with muons. One focus is the novel methods and ingenious techniques that achieve such precision and sensitivity in recent, present, and planned experiment...

  1. SharePoint Basics

    Microsoft Academic Search

    Sahil Malik

    \\u000a In the previous chapter, you configured your basic SharePoint development machine. Before you move any further, ensure that\\u000a you take a snapshot of that machine so you can get back to that position at any point in this book. In this chapter I will\\u000a walk you through the basics of SharePoint. When I say basics, I mean user level features

  2. Precise DC current sensors

    Microsoft Academic Search

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

    1996-01-01

    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

  3. A precision CTD microprofiler

    Microsoft Academic Search

    N. Brown

    1974-01-01

    This paper describes a conductivity-temperature-depth (CTD) system designed for precise fine scale measurements of salinity and temperature in the deep ocean. The conductivity sensor is a miniature (8 mm long, 2 mm I.D.) four electrode cell. Temperature is sensed with a combination of a miniature fast thermistor (30 ms) and a platinum resistance thermometer. The combined outputs of the thermistor

  4. Precision robotic control of agricultural vehicles on realistic farm trajectories

    NASA Astrophysics Data System (ADS)

    Bell, Thomas

    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.

  5. Floating--Point Fused Multiply--Add: Reduced Latency for Floating-Point Addition

    E-print Network

    California at Davis, University of

    Floating--Point Fused Multiply--Add: Reduced Latency for Floating-Point Addition Javier D for the computation of the double--precision floating--point multiply--add fused (MAF) operation A + (B Ã? C) that permits to compute the floating--point addition with lower latency than floating--point multiplication

  6. NULL Convention Floating Point Multiplier

    PubMed Central

    Ramachandran, Seshasayanan

    2015-01-01

    Floating point multiplication is a critical part in high dynamic range and computational intensive digital signal processing applications which require high precision and low power. This paper presents the design of an IEEE 754 single precision floating point multiplier using asynchronous NULL convention logic paradigm. Rounding has not been implemented to suit high precision applications. The novelty of the research is that it is the first ever NULL convention logic multiplier, designed to perform floating point multiplication. The proposed multiplier offers substantial decrease in power consumption when compared with its synchronous version. Performance attributes of the NULL convention logic floating point multiplier, obtained from Xilinx simulation and Cadence, are compared with its equivalent synchronous implementation. PMID:25879069

  7. Design of ultra precision fixtures for nano-manufacturing

    E-print Network

    Mangudi Varadarajan, Kartik, 1981-

    2005-01-01

    This thesis presents the design, modeling, fabrication and experimental validation of an active precision fixturing system called the Hybrid Positioning Fixture (HPF). The HPF uses the principles of exact constraint, ...

  8. High-Precision Computation and Mathematical Physics

    SciTech Connect

    Bailey, David H.; Borwein, Jonathan M.

    2008-11-03

    At the present time, IEEE 64-bit floating-point arithmetic is sufficiently accurate for most scientific applications. However, for a rapidly growing body of important scientific computing applications, a higher level of numeric precision is required. Such calculations are facilitated by high-precision software packages that include high-level language translation modules to minimize the conversion effort. This paper presents a survey of recent applications of these techniques and provides some analysis of their numerical requirements. These applications include supernova simulations, climate modeling, planetary orbit calculations, Coulomb n-body atomic systems, scattering amplitudes of quarks, gluons and bosons, nonlinear oscillator theory, Ising theory, quantum field theory and experimental mathematics. We conclude that high-precision arithmetic facilities are now an indispensable component of a modern large-scale scientific computing environment.

  9. Precision Pointing in the Sky for IBEX Interstellar Flow Observations

    E-print Network

    New Hampshire, University of

    .4 crescent quarter gibbous full AngularPeakSeparation(indegrees) Moon Phase Angular Peak Separation Varies With Moon Phase Moon Simulation Program & Results The moon is much brighter than other objects in the sky so difference between 1st and 3rd quarter phases. · The dark mare on the moon's surface alter the star sensor

  10. All-Electric Spacecraft Precision Pointing using Model Predictive Control

    E-print Network

    Giannitrapani, Antonello

    ) for spacecraft equipped with cold gas and electrothermal xenon microthrusters is presented. The number thrusters, exploiting a common xenon bus shared with the orbit maneuvering system, has been proposed in [3 by cold gas and resistojet thrusters which, besides using a single propellant bus for the whole control

  11. Putting the precision in precision cosmology: How accurate should your data covariance matrix be?

    NASA Astrophysics Data System (ADS)

    Taylor, Andy; Joachimi, Benjamin; Kitching, Thomas

    2013-07-01

    Cosmological parameter estimation requires that the likelihood function of the data is accurately known. Assuming that cosmological large-scale structure power spectra data are multivariate Gaussian distributed, we show that the accuracy of parameter estimation is limited by the accuracy of the inverse data covariance matrix - the precision matrix. If the data covariance and precision matrices are estimated by sampling independent realizations of the data, their statistical properties are described by the Wishart and inverse-Wishart distributions, respectively. Independent of any details of the survey, we show that the fractional error on a parameter variance, or a figure of merit, is equal to the fractional variance of the precision matrix. In addition, for the only unbiased estimator of the precision matrix, we find that the fractional accuracy of the parameter error depends only on the difference between the number of independent realizations and the number of data points, and so can easily diverge. For a 5 per cent error on a parameter error and ND ? 102 data points, a minimum of 200 realizations of the survey are needed, with 10 per cent accuracy in the data covariance. If the number of data points ND ? 102, we need NS > ND realizations and a fractional accuracy of points grows to ND > 104-106, this approach will be problematic. We discuss possible ways to relax these conditions: improved theoretical modelling, shrinkage methods, data compression, simulation and data resampling methods.

  12. Precision Position Tracking in Virtual Reality Environments using Sensor Networks

    Microsoft Academic Search

    Tauseef Gulrez; Manolya Kavakli

    2007-01-01

    In an immersive interactive virtual reality (VR) environment a real human can be incorporated into a virtual 3D scene to navigate a robotic device within that virtual scene. This has useful applications in rehabilitation. The non-destructive nature of VR makes it an ideal testbed for many applications and a prime candidate for use in rehabilitation robotics simulation. The key challenge

  13. Precise Relative Positioning of Formation Flying Spacecraft using GPS

    Microsoft Academic Search

    R. Kroes

    2006-01-01

    Spacecraft formation flying is considered as a key technology for advanced space missions. Compared to large individual spacecraft, the distribution of sensor systems amongst multiple platforms offers improved flexibility, shorter times to mission, and the prospect of being more cost effective. Besides these advantages, satellite formations in low Earth orbit provide advanced science opportunities, such as measuring small scale variations

  14. High precision laser forming for microactuation

    NASA Astrophysics Data System (ADS)

    Folkersma, Ger K. G. P.; Römer, G. R. B. E.; Brouwer, D. M.; Huis in't Veld, A. J.

    2014-03-01

    For assembly of micro-devices, such as photonic devices, the precision alignment of components is often critical for their performance. Laser forming, also known as laser-adjusting, can be used to create an integrated microactuator to align the components with sub-micron precision after bonding. In this paper a so-called three-bridge planar manipulator was used to study the laser-material interaction and thermal and mechanical behavior of the laser forming mechanism. A 3-D Finite Element Method (FEM) model and experiments are used to identify the optimal parameter settings for a high precision actuator. The goal in this paper is to investigate how precise the maximum occurring temperature and the resulting displacement are predicted by a 3-D FEM model by comparing with experimental results. A secondary goal is to investigate the resolution of the mechanism and the range of motion. With the experimental setup we measure the displacement and surface temperature in real-time. The time-dependent heat transfer FEM models match closely with experimental results, however the structural model can deviate more than 100% in absolute displacement. Experimentally, a positioning resolution of 0.1?m was achieved, with a total stroke exceeding 20?m. A spread of 10% in the temperature cycles between several experiments was found, which was attributed to a spread in the surface absorptivity. Combined with geometric tolerances, the spread in displacement can be as large as 20%. This implies that feedback control of the laser power, in combination with iterative learning during positioning, is required for high precision alignment. Even though the FEM models deviate substantially from the experiments, the 3-D FEM model predicts the trend in deformation sufficiently accurate to use it for design optimization of high precision 3-D actuators using laser adjusting.

  15. Precision electroweak measurements

    SciTech Connect

    Demarteau, M.

    1996-11-01

    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.

  16. Precision Robotic Assembly Machine

    ScienceCinema

    None

    2010-09-01

    The world's largest laser system is the National Ignition Facility (NIF), located at Lawrence Livermore National Laboratory. NIF's 192 laser beams are amplified to extremely high energy, and then focused onto a tiny target about the size of a BB, containing frozen hydrogen gas. The target must be perfectly machined to incredibly demanding specifications. The Laboratory's scientists and engineers have developed a device called the "Precision Robotic Assembly Machine" for this purpose. Its unique design won a prestigious R&D-100 award from R&D Magazine.

  17. Precise Measurement for Manufacturing

    NASA Technical Reports Server (NTRS)

    2003-01-01

    A metrology instrument known as PhaseCam supports a wide range of applications, from testing large optics to controlling factory production processes. This dynamic interferometer system enables precise measurement of three-dimensional surfaces in the manufacturing industry, delivering speed and high-resolution accuracy in even the most challenging environments.Compact and reliable, PhaseCam enables users to make interferometric measurements right on the factory floor. The system can be configured for many different applications, including mirror phasing, vacuum/cryogenic testing, motion/modal analysis, and flow visualization.

  18. Software for precise tracking of cell proliferation

    SciTech Connect

    Kurokawa, Hiroshi [Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan) [Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan); School of Life Science, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392 (Japan); Noda, Hisayori [Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan) [Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan); Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Sugiyama, Mayu [Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan) [Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan); School of Life Science, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392 (Japan); Sakaue-Sawano, Asako [Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan) [Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan); Life Function and Dynamics, ERATO, JST, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan); Fukami, Kiyoko [School of Life Science, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392 (Japan)] [School of Life Science, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392 (Japan); Miyawaki, Atsushi, E-mail: matsushi@brain.riken.jp [Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan) [Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan); Life Function and Dynamics, ERATO, JST, 2-1 Hirosawa, Wako-city, Saitama 351-0198 (Japan)

    2012-01-20

    Highlights: Black-Right-Pointing-Pointer We developed software for analyzing cultured cells that divide as well as migrate. Black-Right-Pointing-Pointer The active contour model (Snakes) was used as the core algorithm. Black-Right-Pointing-Pointer The time backward analysis was also used for efficient detection of cell division. Black-Right-Pointing-Pointer With user-interactive correction functions, the software enables precise tracking. Black-Right-Pointing-Pointer The software was successfully applied to cells with fluorescently-labeled nuclei. -- Abstract: We have developed a multi-target cell tracking program TADOR, which we applied to a series of fluorescence images. TADOR is based on an active contour model that is modified in order to be free of the problem of locally optimal solutions, and thus is resistant to signal fluctuation and morphological changes. Due to adoption of backward tracing and addition of user-interactive correction functions, TADOR is used in an off-line and semi-automated mode, but enables precise tracking of cell division. By applying TADOR to the analysis of cultured cells whose nuclei had been fluorescently labeled, we tracked cell division and cell-cycle progression on coverslips over an extended period of time.

  19. Precision manufacturing using LIGA

    SciTech Connect

    Jackson, K.H.; Malek, C.K. [Center for X-ray Optics, Lawrence Berkeley Laboratory, Berkeley, CA 94720 (United States)] [Center for X-ray Optics, Lawrence Berkeley Laboratory, Berkeley, CA 94720 (United States); Bonivert, W.D.; Hruby, J.M.; Hachman, J.T. [Materials Synthesis Department, Sandia National Laboratory, Livermore, CA 94551 (United States)] [Materials Synthesis Department, Sandia National Laboratory, Livermore, CA 94551 (United States); Brennen, R.A.; Wiberg, D.; Hecht, M.H. [Center for Space Microelectronics Technology, Jet Propulsion Laboratory, Pasadena, CA 91109-8099 (United States)] [Center for Space Microelectronics Technology, Jet Propulsion Laboratory, Pasadena, CA 91109-8099 (United States)

    1996-09-01

    Our objective is the fabrication of small high-precision parts using LIGA, which can be used in a variety of industrial applications. LIGA is a combination of deep x-ray lithography, electroplating, and replication processes that enables the fabrication of microstructures with vertical dimensions several millimeters high, lateral dimensions in the micrometer range, and submicron tolerances. On beamline 10.3.2, at the Advanced Light Source (ALS), the Center for X-ray Optics (CXRO) has built an end station suitable for LIGA. The ALS is an excellent source of radiation for this application. The CXRO, in close collaboration with Sandia National Laboratory and the Jet Propulsion Laboratory, has developed the other essential process steps of mask making, resist development, x-ray exposure, and electroplating. This technology provides a powerful tool for mass production and miniaturization of mechanical systems into a dimensional regime not accessible by traditional manufacturing operations. We will present several applications that exploit the characteristics of the LIGA process: the fabrication of magnetic laminations for a high precision stepping motor; miniature octopole lens for advanced e-beam lithography; high-aspect-ratio x-ray collimating grids for astronomy; and microscopic tumblers for nuclear security. {copyright} {ital 1996 American Institute of Physics.}

  20. Progressive Precision Surface Design

    SciTech Connect

    Duchaineau, M; Joy, KJ

    2002-01-11

    We introduce a novel wavelet decomposition algorithm that makes a number of powerful new surface design operations practical. Wavelets, and hierarchical representations generally, have held promise to facilitate a variety of design tasks in a unified way by approximating results very precisely, thus avoiding a proliferation of undergirding mathematical representations. However, traditional wavelet decomposition is defined from fine to coarse resolution, thus limiting its efficiency for highly precise surface manipulation when attempting to create new non-local editing methods. Our key contribution is the progressive wavelet decomposition algorithm, a general-purpose coarse-to-fine method for hierarchical fitting, based in this paper on an underlying multiresolution representation called dyadic splines. The algorithm requests input via a generic interval query mechanism, allowing a wide variety of non-local operations to be quickly implemented. The algorithm performs work proportionate to the tiny compressed output size, rather than to some arbitrarily high resolution that would otherwise be required, thus increasing performance by several orders of magnitude. We describe several design operations that are made tractable because of the progressive decomposition. Free-form pasting is a generalization of the traditional control-mesh edit, but for which the shape of the change is completely general and where the shape can be placed using a free-form deformation within the surface domain. Smoothing and roughening operations are enhanced so that an arbitrary loop in the domain specifies the area of effect. Finally, the sculpting effect of moving a tool shape along a path is simulated.

  1. Precision Muon Physics

    E-print Network

    T. P. Gorringe; D. W. Hertzog

    2015-06-04

    The muon is playing a unique role in sub-atomic physics. Studies of muon decay both determine the overall strength and establish the chiral structure of weak interactions, as well as setting extraordinary limits on charged-lepton-flavor-violating processes. Measurements of the muon's anomalous magnetic moment offer singular sensitivity to the completeness of the standard model and the predictions of many speculative theories. Spectroscopy of muonium and muonic atoms gives unmatched determinations of fundamental quantities including the magnetic moment ratio $\\mu_\\mu / \\mu_p$, lepton mass ratio $m_{\\mu} / m_e$, and proton charge radius $r_p$. Also, muon capture experiments are exploring elusive features of weak interactions involving nucleons and nuclei. We will review the experimental landscape of contemporary high-precision and high-sensitivity experiments with muons. One focus is the novel methods and ingenious techniques that achieve such precision and sensitivity in recent, present, and planned experiments. Another focus is the uncommonly broad and topical range of questions in atomic, nuclear and particle physics that such experiments explore.

  2. 49 CFR 236.334 - Point detector.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...is locked in normal or reverse position, contacts cannot be opened by manually applying force at the closed switch point. Point detector circuit controller shall be maintained so that the contacts will not assume the position corresponding to...

  3. 49 CFR 236.334 - Point detector.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...is locked in normal or reverse position, contacts cannot be opened by manually applying force at the closed switch point. Point detector circuit controller shall be maintained so that the contacts will not assume the position corresponding to...

  4. Mathematics for modern precision engineering.

    PubMed

    Scott, Paul J; Forbes, Alistair B

    2012-08-28

    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

  5. Offered: Offered: Position(s): Position(s)

    E-print Network

    New Hampshire, University of

    training to introduce the basics of a career in the staffing industry -Assigned mentors to guide youCompany: Industry: Website: Majors: Offered: Offered: Position(s): Position(s): Description IT staffing and Global Services for 82% of the Fortune 500. Ranked #1 in the industry by IT Services Business

  6. Offered: Offered: Position(s): Position(s)

    E-print Network

    New Hampshire, University of

    overall impact to company?s profitability ?Run monthly reports supporting Financial Analysts includingCompany: Industry: Website: Majors: Offered: Offered: Position(s): Position(s): Description and creative companies making premium chocolate, with six production sites in Europe, two in the USA

  7. Precision alignment device

    DOEpatents

    Jones, Nelson E. (Huntington Beach, CA)

    1990-01-01

    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.

  8. Precision alignment device

    DOEpatents

    Jones, N.E.

    1988-03-10

    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.

  9. The Precision Formation Flying Integrated Analysis Tool (PFFIAT)

    NASA Technical Reports Server (NTRS)

    Stoneking, Eric; Lyon, Richard G.; Sears, Edie; Lu, Victor

    2004-01-01

    Several space missions presently in the concept phase (e.g. Stellar Imager, Sub- millimeter Probe of Evolutionary Cosmic Structure, Terrestrial Planet Finder) plan to use multiple spacecraft flying in precise formation to synthesize unprecedently large aperture optical systems. These architectures present challenges to the attitude and position determination and control system; optical performance is directly coupled to spacecraft pointing with typical control requirements being on the scale of milliarcseconds and nanometers. To investigate control strategies, rejection of environmental disturbances, and sensor and actuator requirements, a capability is needed to model both the dynamical and optical behavior of such a distributed telescope system. This paper describes work ongoing at NASA Goddard Space Flight Center toward the integration of a set of optical analysis tools (Optical System Characterization and Analysis Research software, or OSCAR) with the Formation J?lying Test Bed (FFTB). The resulting system is called the Precision Formation Flying Integrated Analysis Tool (PFFIAT), and it provides the capability to simulate closed-loop control of optical systems composed of elements mounted on multiple spacecraft. The attitude and translation spacecraft dynamics are simulated in the FFTB, including effects of the space environment (e.g. solar radiation pressure, differential orbital motion). The resulting optical configuration is then processed by OSCAR to determine an optical image. From this image, wavefront sensing (e.g. phase retrieval) techniques are being developed to derive attitude and position errors. These error signals will be fed back to the spacecraft control systems, completing the control loop. A simple case study is presented to demonstrate the present capabilities of the tool.

  10. Gene symbol precision.

    PubMed

    Bennani-Baiti, Barbara; Bennani-Baiti, Idriss M

    2012-01-10

    Several gene databases, including heavily used ones such as the National Center for Biotechnology Information (NCBI) database, erroneously assign, on occasion, literature references to genes or proteins. These mistakes are mostly due to an overlap in gene aliases, whereby two distinct genes share a pseudonym. This is particularly confusing when the gene products have also biological properties in common, are part of signaling pathways that cross-talk to one another, or are regulated by the same effectors. We present examples spanning several research fields including apoptosis, ubiquitin-dependent degradation, signaling by Notch, Wnt, and small G proteins, transporters of glutathione conjugates of electrophiles, and mitochondrial and ribosomal RNA genes. To solve the problem, we argue in favor of including Entrez gene numbers in papers submitted for publication as unique gene identifiers to allow precise identification of genes and species studied. PMID:22019431

  11. Precision tool holder with flexure-adjustable, three degrees of freedom for a four-axis lathe

    DOEpatents

    Bono, Matthew J. (Pleasanton, CA); Hibbard, Robin L. (Livermore, CA)

    2008-03-04

    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.

  12. Precise seabed emplacement of an articulated loading platform in the North Sea

    SciTech Connect

    Noblanc, A.; Schnader, H.E.

    1983-05-01

    The Statfjord B articulated loading platform is a single point mooring (SPM) consisting essentially of three principal components: gravity base, cylindrical column and rotating head. Built in West Germany and assembled in a Norwegian fjord, the unit was towed to the Statfjord B site and installed precisely adjacent to a seabed valve station and a previously laid sealine in August, 1982. Prior to arrival of the SPM at the site two piles had been driven into the seabed adjacent to the subsea valve station against which the SPM's gravity base was to be docked. Two matching guides had been incorporated in the gravity base for the purpose of mating with the piles. The SPM was maneuvered into position and held steady by three tugboats. A diving support vessel moored on location was equipped with two hydraulic heave compensating winches from which wire ropes were led vertically and fed through sheaves on the valve station to the SPM base. By maintaining constant tension on the pull-in wires and slowly paying out the tug towlines the gravity base was positioned precisely with respect to the horizontal axes and heading by mating the guides with the piles. Touchdown and skirt penetration were achieved by controlled ballasting of the column with water. An integrated acoustic transponder system provided precise real time data on SPM position, base and column angles and under-keel clearance. Final approach was monitored by means of closed circuit television (CCTV). This paper describes the technique developed to install the large structure with a very high degree of precision in two horizontal axes and in azimuth.

  13. The GLAS Algorithm Theoretical Basis Document for Precision Orbit Determination (POD)

    NASA Technical Reports Server (NTRS)

    Rim, Hyung Jin; Yoon, S. P.; Schultz, Bob E.

    2013-01-01

    The Geoscience Laser Altimeter System (GLAS) was the sole instrument for NASA's Ice, Cloud and land Elevation Satellite (ICESat) laser altimetry mission. The primary purpose of the ICESat mission was to make ice sheet elevation measurements of the polar regions. Additional goals were to measure the global distribution of clouds and aerosols and to map sea ice, land topography and vegetation. ICESat was the benchmark Earth Observing System (EOS) mission to be used to determine the mass balance of the ice sheets, as well as for providing cloud property information, especially for stratospheric clouds common over polar areas. The GLAS instrument operated from 2003 to 2009 and provided multi-year elevation data needed to determine changes in sea ice freeboard, land topography and vegetation around the globe, in addition to elevation changes of the Greenland and Antarctic ice sheets. This document describes the Precision Orbit Determination (POD) algorithm for the ICESat mission. The problem of determining an accurate ephemeris for an orbiting satellite involves estimating the position and velocity of the satellite from a sequence of observations. The ICESatGLAS elevation measurements must be very accurately geolocated, combining precise orbit information with precision pointing information. The ICESat mission POD requirement states that the position of the instrument should be determined with an accuracy of 5 and 20 cm (1-s) in radial and horizontal components, respectively, to meet the science requirements for determining elevation change.

  14. Determination of the Isosbestic Point in the Absorption Spectra of DNA-Ethidium Bromide Complexes

    NASA Astrophysics Data System (ADS)

    Vardevanyan, P. O.; Élbakyan, V. L.; Shahinyan, M. A.; Minasyants, M. V.; Parsadanyan, M. A.; Sahakyan, N. S.

    2015-01-01

    We propose a procedure for mathematical treatment of the spectra of complexes between ligands and DNA, which allows us to determine the position of the isosbestic point with high precision. As a specific example, we consider the absorption spectra of ethidium bromide complexes titrated against a DNA solution. As a result of using the method, besides the main type of binding we have identified the appearance of additional types of binding between the ethidium bromide and DNA.

  15. Field Emission Current and Electrical Breakdown by a Pointed Cathode Coated with Carbon-Nano-Tube

    Microsoft Academic Search

    Yoshinori Hirata; Masayoshi Teramoto; Mizue Mizoshiri; Ukyo Ikeda; Takayoshi Ohji; Kimihiro Ozaki

    2007-01-01

    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,

  16. Enhanced Signal-Strength-Difference Position Method Based on an Inversion Propagation Model in Cellular Network

    Microsoft Academic Search

    Li Xu; Yuhao Wang; Ye Liu; Ming Wei; Yang Si

    2008-01-01

    This paper develops a simple and efficient position method based on relative signal-strength prediction, which can be got from an inversion propagation model in cellular networks. The inversion propagation model can predict the propagation loss between any two points along the virtual propagation path from the base-station to mobile-station, which precision has been presented in. So the user's location can

  17. Precision flyer initiator

    NASA Astrophysics Data System (ADS)

    Frank, A.

    1999-04-01

    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.

  18. Precision Farming and Precision Pest Management: The Power of New Crop Production Technologies

    PubMed Central

    Strickland, R. Mack; Ess, Daniel R.; Parsons, Samuel D.

    1998-01-01

    The use of new technologies including Geographic Information Systems (GIS), the Global Positioning System (GPS), Variable Rate Technology (VRT), and Remote Sensing (RS) is gaining acceptance in the present high-technology, precision agricultural industry. GIS provides the ability to link multiple data values for the same geo-referenced location, and provides the user with a graphical visualization of such data. When GIS is coupled with GPS and RS, management decisions can be applied in a more precise "micro-managed" manner by using VRT techniques. Such technology holds the potential to reduce agricultural crop production costs as well as crop and environmental damage. PMID:19274236

  19. PLANS '84 - Position Location and Navigation Symposium, San Diego, CA, November 26-29, 1984, Record

    NASA Astrophysics Data System (ADS)

    Questions regarding the applications and equipment of the Global Positioning System (GPS) are discussed, taking into account the use of differential GPS positioning for geodetic applications, the use of Synchromesh for the practical enhancement of GPS service, the synergism of the Global Positioning System and electronic terrain map systems, position location with the NBS/GPS time transfer system, early applications of civil GPS, service outages in GPS associated with satellite failures, precise positioning using a four-channel C/A code GPS receiver, and differential GPS marine navigation. Other topics explored are related to radio navigation systems, mapping and charting, geodesy, the GPS development, strapdown inertial navigation, federal radionavigation policy, marine navigation, aircraft navigation, and the positioning, stabilization, and pointing of space systems. Attention is given to an evaluation of radionavigation systems, control moment gyros for the Space Shuttle, the impact of GPS on ocean surveying, and Kalman filter designs for integrated marine navigation systems.

  20. Precision alignment device

    SciTech Connect

    Jones, N.E.

    1990-03-13

    This patent describes an 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 servo-motor operated adjustment screws to adjust the position of elements of the structure associated with the main beam to maintain alignment of the main beam.

  1. Precise Orbit Determination and Cal\\/Val for GOCE

    Microsoft Academic Search

    Henno Boomkamp; John Dow; Michiel Otten

    In its position as IGS analysis centre, the ESOC navigation Office has extensive expertise in the processing of GPS data for precise orbit determination purposes. On-going developments in this area include the gradual implementation of real-time processing, and the possible incorporation of GPS data from low Earth orbiting satellites in IGS product generation. From this position, and its close interaction

  2. Advanced precision linear stage for industrial automation applications

    Microsoft Academic Search

    Kay-Soon Low; Meng-Teck Keck

    2003-01-01

    In the area of factory automation, accurate positioning systems are increasingly required in various industries to improve the productivity and to lower the manufacturing cost. In this paper, we present a prototype precision linear stage. It has a positioning accuracy of 1 ?m and a peak speed above 1 m\\/s. A permanent magnet DC linear motor has been used in

  3. Precise Truss Assembly Using Commodity Parts and Low Precision Welding

    NASA Technical Reports Server (NTRS)

    Komendera, Erik; Reishus, Dustin; Dorsey, John T.; Doggett, W. R.; Correll, Nikolaus

    2014-01-01

    Hardware and software design and system integration for an intelligent precision jigging robot (IPJR), which allows high precision assembly using commodity parts and low-precision bonding, is described. Preliminary 2D experiments that are motivated by the problem of assembling space telescope optical benches and very large manipulators on orbit using inexpensive, stock hardware and low-precision welding are also described. An IPJR is a robot that acts as the precise "jigging", holding parts of a local structure assembly site in place, while an external low precision assembly agent cuts and welds members. The prototype presented in this paper allows an assembly agent (for this prototype, a human using only low precision tools), to assemble a 2D truss made of wooden dowels to a precision on the order of millimeters over a span on the order of meters. The analysis of the assembly error and the results of building a square structure and a ring structure are discussed. Options for future work, to extend the IPJR paradigm to building in 3D structures at micron precision are also summarized.

  4. Precise Truss Assembly using Commodity Parts and Low Precision Welding

    NASA Technical Reports Server (NTRS)

    Komendera, Erik; Reishus, Dustin; Dorsey, John T.; Doggett, William R.; Correll, Nikolaus

    2013-01-01

    We describe an Intelligent Precision Jigging Robot (IPJR), which allows high precision assembly of commodity parts with low-precision bonding. We present preliminary experiments in 2D that are motivated by the problem of assembling a space telescope optical bench on orbit using inexpensive, stock hardware and low-precision welding. An IPJR is a robot that acts as the precise "jigging", holding parts of a local assembly site in place while an external low precision assembly agent cuts and welds members. The prototype presented in this paper allows an assembly agent (in this case, a human using only low precision tools), to assemble a 2D truss made of wooden dowels to a precision on the order of millimeters over a span on the order of meters. We report the challenges of designing the IPJR hardware and software, analyze the error in assembly, document the test results over several experiments including a large-scale ring structure, and describe future work to implement the IPJR in 3D and with micron precision.

  5. Fiber Scrambling for Extreme Doppler Precision

    NASA Astrophysics Data System (ADS)

    Spronck, Julien; Kaplan, Z.; Fischer, D.

    2011-09-01

    The detection of Earth-like exoplanets with the radial velocity method requires extreme Doppler precision and long-term stability in order to measure tiny reflex velocities in the host star. Recent planet searches have led to the detection of so called “super-Earths” (up to a few Earth masses) that induce radial velocity changes of about 1 m/s. However, the detection of true Earth analogs requires a precision of 10 cm/s. One of the factors limiting Doppler precision is variation in the Point Spread Function (PSF) from observation to observation due to changes in the illumination of the slit and spectrograph optics. Thus, this stability has become a focus of current instrumentation work. Fiber optics have been used since the 1980’s to couple telescopes to high-precision spectrographs, initially for simpler mechanical design and control. However, fiber optics are also naturally efficient scramblers. Scrambling refers to a fiber’s ability to produce an output beam independent of input. Our research is focused on understanding the scrambling properties of fibers with different geometries (circular, square, octagonal), different lengths and fiber sizes. Another important parameter when it comes to fibers is the so-called focal ratio degradation (FRD), which accounts for a different (faster) focal ratio after the fiber than the one sent into the fiber. In this paper, we will present new insight on fiber scrambling, FRD and what we call fiber personality, which describes differing behaviors for supposedly identical fiber.

  6. High precision beam alignment of electromagnetic wigglers

    SciTech Connect

    Ben-Zvi, I.; Qiu, X.Z.

    1993-01-01

    The performance of Free-Electron Lasers depends critically on the quality of the alignment of the electron beam to the wiggler's magnetic axis and the deviation of this axis from a straight fine. The measurement of the electron beam position requires numerous beam position monitors in the wiggler, where space is at premium. The beam position measurement is used to set beam steerers for an orbit correction in the wiggler. The authors propose an alternative high precision alignment method in which one or two external Beam Position Monitors (BPM) are used. In this technique, the field in the electro-wiggler is modulated section by section and the beam position movement at the external BPM is detected in synchronism with the modulation. A beam offset at the modulated beam section will produce a modulation of the beam position at the detector that is a function of the of the beam offset and the absolute value of the modulation current. The wiggler errors produce a modulation that is a function of the modulation current. It will be shown that this method allows the detection and correction of the beam position at each section in the presence of wiggler errors with a good resolution. Furthermore, it allows one to measure the first and second integrals of the wiggler error over each wiggler section. Lastly, provided that wiggler sections can be degaussed effectively, one can test the deviation of the wiggler's magnetic axis from a straight line.

  7. TMDs: Evolution, modeling, precision

    NASA Astrophysics Data System (ADS)

    D'Alesio, Umberto; Echevarría, Miguel G.; Melis, Stefano; Scimemi, Ignazio

    2015-01-01

    The factorization theorem for qT spectra in Drell-Yan processes, boson production and semi-inclusive deep inelastic scattering allows for the determination of the non-perturbative parts of transverse momentum dependent parton distribution functions. Here we discuss the fit of Drell-Yan and Z-production data using the transverse momentum dependent formalism and the resummation of the evolution kernel. We find a good theoretical stability of the results and a final ?2/points ? 1. We show how the fixing of the non-perturbative pieces of the evolution can be used to make predictions at present and future colliders.

  8. Extreme point and halving edge search in abstract order types.

    PubMed

    Aichholzer, Oswin; Miltzow, Tillmann; Pilz, Alexander

    2013-10-01

    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. PMID:24092953

  9. Extreme point and halving edge search in abstract order types

    PubMed Central

    Aichholzer, Oswin; Miltzow, Tillmann; Pilz, Alexander

    2013-01-01

    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. PMID:24092953

  10. Ion source for high-precision mass spectrometry

    DOEpatents

    Todd, P.J.; McKown, H.S.; Smith, D.H.

    1982-04-26

    The invention is directed to a method for increasing the precision of positive-ion relative abundance measurements conducted in a sector mass spectrometer having an ion source for directing a beam of positive ions onto a collimating slit. The method comprises incorporating in the source an electrostatic lens assembly for providing a positive-ion beam of circular cross section for collimation by the slit. 2 figures, 3 tables.

  11. Probabilistic modelling of LORAN-C for non-precision approaches

    E-print Network

    Einhorn, John Kenneth

    1985-01-01

    A mathematical model of the expected position errors encountered from LORAN-C during a non precision approach was formulated. From this, position error ellipses were generated that corresponded to two time difference ...

  12. Precise time dissemination via portable atomic clocks

    NASA Technical Reports Server (NTRS)

    Putkovich, K.

    1982-01-01

    The most precise operational method of time dissemination over long distances presently available to the Precise Time and Time Interval (PTTI) community of users is by means of portable atomic clocks. The Global Positioning System (GPS), the latest system showing promise of replacing portable clocks for global PTTI dissemination, was evaluated. Although GPS has the technical capability of providing superior world-wide dissemination, the question of present cost and future accessibility may require a continued reliance on portable clocks for a number of years. For these reasons a study of portable clock operations as they are carried out today was made. The portable clock system that was utilized by the U.S. Naval Observatory (NAVOBSY) in the global synchronization of clocks over the past 17 years is described and the concepts on which it is based are explained. Some of its capabilities and limitations are also discussed.

  13. Global Positioning System Satellite Selection Method

    NASA Technical Reports Server (NTRS)

    Niles, Frederick A. (Inventor)

    2001-01-01

    The satellite selection method as utilized by the spaceborne Global Positioning System receiver provides navigational solutions and is designed for use in low Earth orbit. The satellite selection method is a robust algorithm that can be used a GPS receiver to select appropriate GPS satellites for use in calculating point solutions or attitude solutions. The method is takes into account the difficulty of finding a particular GPS satellite phase code, especially when the search range in greatly increased due to Doppler shifts introduced into the carrier frequency. The method starts with an update of the antenna pointing and spacecraft vectors to determine the antenna backplane direction. Next, the GPS satellites that will potentially be in view of the antenna are ranked on a list, whereby the list is generated based on the estimated attitude and position of each GPS satellite. Satellites blocked by the Earth are not entered on this list. A second list is created, whereby the GPS satellites are ranked according to their desirability for use in attitude determination. GPS satellites are ranked according to their orthogonality to the antenna backplane, and according to geometric dilution of precision considerations. After the lists are created, the channels of the spaceborne GPS receiver are assigned to various GPS satellites for acquisition and lock. Preliminary Doppler frequencies for searching are assigned to the various channels.

  14. Robust adaptive floating-point geometric predicates

    Microsoft Academic Search

    Johnathan Richard Shewchuk

    1996-01-01

    Fast C implementations of four geometric predicates, the 2D and 3D orientation and incircle tests, are publicly avail- able. Their inputs are ordinary single or double precision floating-point numbers. They owe their speed to two fea- tures. First, they employ new fast algorithms for arbitrary precision arithmetic that have a strong advantage over other software techniques in computations that manipulate

  15. Precision of Four Acoustic Bone Measurement Devices

    NASA Technical Reports Server (NTRS)

    Miller, Christopher; Rianon, Nahid; Feiveson, Alan; Shackelford, Linda; LeBlanc, Adrian

    2000-01-01

    Though many studies have quantified the precision of various acoustic bone measurement devices, it is difficult to directly compare the results among the studies, because they used disparate subject pools, did not specify the estimation methodology, or did not use consistent definitions for various precision characteristics. In this study, we used a repeated measures design protocol to directly determine the precision characteristics of four acoustic bone measurement devices: the Mechanical Response Tissue Analyzer (MRTA), the UBA-575+, the SoundScan 2000 (S2000), and the Sahara Ultrasound Bone Analyzer. Ten men and ten women were scanned on all four devices by two different operators at five discrete time points: Week 1, Week 2, Week 3, Month 3 and Month 6. The percent coefficient of variation (%CV) and standardized coefficient of variation were computed for the following precision characteristics: interoperator effect, operator-subject interaction, short-term error variance, and long-term drift. The MRTA had high interoperator errors for its ulnar and tibial stiffness measures and a large long-term drift in its tibial stiffness measurement. The UBA-575+ exhibited large short-term error variances and long-term drift for all three of its measurements. The S2000's tibial speed of sound measurement showed a high short-term error variance and a significant operator-subject interaction but very good values (less than 1%) for the other precision characteristics. The Sahara seemed to have the best overall performance, but was hampered by a large %CV for short-term error variance in its broadband ultrasound attenuation measure.

  16. Precision of Four Acoustic Bone Measurement Devices

    NASA Technical Reports Server (NTRS)

    Miller, Christopher; Feiveson, Alan H.; Shackelford, Linda; Rianon, Nahida; LeBlanc, Adrian

    2000-01-01

    Though many studies have quantified the precision of various acoustic bone measurement devices, it is difficult to directly compare the results among the studies, because they used disparate subject pools, did not specify the estimation methodology, or did not use consistent definitions for various precision characteristics. In this study, we used a repeated measures design protocol to directly determine the precision characteristics of four acoustic bone measurement devices: the Mechanical Response Tissue Analyzer (MRTA), the UBA-575+, the SoundScan 2000 (S2000), and the Sahara Ultrasound Done Analyzer. Ten men and ten women were scanned on all four devices by two different operators at five discrete time points: Week 1, Week 2, Week 3, Month 3 and Month 6. The percent coefficient of variation (%CV) and standardized coefficient of variation were computed for the following precision characteristics: interoperator effect, operator-subject interaction, short-term error variance, and long-term drift, The MRTA had high interoperator errors for its ulnar and tibial stiffness measures and a large long-term drift in its tibial stiffness measurement. The UBA-575+ exhibited large short-term error variances and long-term drift for all three of its measurements. The S2000's tibial speed of sound measurement showed a high short-term error variance and a significant operator-subject interaction but very good values ( < 1%) for the other precision characteristics. The Sahara seemed to have the best overall performance, but was hampered by a large %CV for short-term error variance in its broadband ultrasound attenuation measure.

  17. The Lagrange Points

    ERIC Educational Resources Information Center

    Lovell, M.S.

    2007-01-01

    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…

  18. Machine automation using RTK GPS positioning

    Microsoft Academic Search

    A. El-Mowafy; M. Al-Musawa

    2009-01-01

    Machine automation is a challenging application that demands real-time positioning at the centimeter-level accuracy for precise jobs in the open fields. This positioning accuracy can be obtained by using a Global Positioning System (GPS) and employing a single reference station or through utilizing the service of a network of multiple reference stations. The paper first addresses the principles of the

  19. Tipping Points

    NASA Astrophysics Data System (ADS)

    Hansen, J.

    2007-12-01

    A climate tipping point, at least as I have used the phrase, refers to a situation in which a changing climate forcing has reached a point such that little additional forcing (or global temperature change) is needed to cause large, relatively rapid, climate change. Present examples include potential loss of all Arctic sea ice and instability of the West Antarctic and Greenland ice sheets. Tipping points are characterized by ready feedbacks that amplify the effect of forcings. The notion that these may be runaway feedbacks is a misconception. However, present "unrealized" global warming, due to the climate system's thermal inertia, exacerbates the difficulty of avoiding global warming tipping points. I argue that prompt efforts to slow CO2 emissions and absolutely reduce non-CO2 forcings are both essential if we are to avoid tipping points that would be disastrous for humanity and creation, the planet as civilization knows it.

  20. Proposal for a CLEO precision vertex detector

    SciTech Connect

    Not Available

    1991-01-01

    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.

  1. Satellite positioning

    NASA Technical Reports Server (NTRS)

    Colombo, Oscar L.; Watkins, Michael M.

    1991-01-01

    Developments in satellite positioning techniques and their applications are reviewed on the basis of the theoretical and practical work published by U.S. researchers in 1987-1990. Current techniques are classified into two main categories: satellite laser tracking and radio tracking. Particular attention is given to the Geoscience Laser Ranging System, the Lunar Laser Ranging concept; GPS ephemerides determination, fiducial networks, and reference frame; static GPS positioning; and kinematic GPS positioning.

  2. Precision on the top mass

    E-print Network

    Stefan Weinzierl

    2015-05-04

    In this talk I will focus on theoretical issues related to high precision determinations of the top mass. Several mass definitions are reviewed and their respective advantages and disadvantages are discussed. Precision determinations of the top mass will require a short-distance mass definition. I will summarise current work in this direction.

  3. Precise Zero Knowledge Silvio Micali

    E-print Network

    Keinan, Alon

    Precise Zero Knowledge Silvio Micali Rafael Pass December 1, 2007 Abstract We put forward the notion of Precise Zero Knowledge and provide its first implementations in a variety of settings under standard complexity assumptions. Whereas the classical notion of Zero Knowledge bounds the knowledge

  4. A precision force microscope for biophysics

    NASA Astrophysics Data System (ADS)

    King, Gavin; Churnside, Allison; Perkins, Thomas

    2009-11-01

    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.

  5. ARPREC: An arbitrary precision computation package

    SciTech Connect

    Bailey, David H.; Yozo, Hida; Li, Xiaoye S.; Thompson, Brandon

    2002-09-01

    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.

  6. Geodetic Satellite Doppler Positioning and Application to Canadian Test Adjustments

    NASA Astrophysics Data System (ADS)

    Kouba, J.

    1980-01-01

    During 1974-6, the Geodetic Survey of Canada established a geodetic control network with spacing between points of about 200-500 km with the use of the satellite-Doppler method. For this application, a unique observation strategy and Doppler data reduction procedures have been developed, by using both precise and broadcast satellite ephemerides. The satellite-Doppler geodetic control has contributed greatly to the readjustment of the Canadian triangulation network, in particular to the datum orientation and positioning. The results have also been useful for geoid studies in Canada. Continuous satellite-Doppler tracking from the two Canadian Tranet stations provides additional information on polar motion and long-term variations of the satellite system, which are important for monitoring and maintaining the related geodetic datum. The basic Doppler control at 200-500 km has been completed and successfully used in the test adjustment of the Canadian geodetic network. Currently, the Doppler method is used for densification at station spacing below 100 km, and in conjunction with the Inertial Survey Systems. A possible difference between Canadian and the U.S. astronomical observations has been encountered. Further research and field programmes are necessary to solve this problem. Permanent Doppler monitoring is viewed as essential for geodetic datum maintenance and determination of time-related aspects of future precise geodetic networks. The research in Canada is directed towards improvements and better understanding of the relation between the different methods of precise global positioning.

  7. GPS - Global Positioning System. Theory and practice

    Microsoft Academic Search

    B. Hofmann-Wellenhof; H. Lichtenegger; J. Collins

    1997-01-01

    This book shows in comprehensive manner how the Global Positioning System (GPS) works. The use of GPS for precise measurements (i.e. surveying) is treated as well as navigation and attitude determination. The basic mathematical models for various modes of GPS operations and detailed explanation of the practical use of GPS are developed precisely in this book. Additionally, the text shows

  8. Precision evaluation for intensive GPS acoustic measurements along Japan trench

    NASA Astrophysics Data System (ADS)

    Kido, M.; Fujimoto, H.; Osada, Y.; Ohta, Y.; Tadokoro, K.; Watanabe, T.; Nagai, S.; Yasuda, K.; Okuda, T.; Yamamoto, J.

    2013-12-01

    After the Tohoku-oki earthquake in 2011, researchers recognized the importance of the state of inter-plate coupling close to the trench for giant earthquakes, in where seafloor geodetic surveys were few or not available. To overcome this limitation, we have developed GPS/acoustic instrument for greater depth up to 6000m, which can cover the region close to the trench for most subduction zones. MEXT, Japan promotes to construct a network of GPS/acoustic survey sites along the Japan trench to elucidate post-seismic behavior after the giant earthquake. In 2012, research group in Tohoku and Nagoya Universities constructed 20 new survey sites along the Japan trench and started their initial positioning. Three to six transponders were installed for each site, which were 86 transponders in total. The network covers large portion of the Japan trench, mainly along the deep land-side of the trench, covering the region of expected significant afterslip as well as of the large coseismic slip. In this year second phase surveys are planned to detect displacement of roughly 1-yesr since the last survey. These are the first intensive surveys that we have never been experienced, and with new survey style. Therefore, in advance to the second phase survey, we summarize the first phase survey in 2012 in the presentation. As one of the most important key to obtain precise positioning of seafloor transponders is how to estimate horizontal variation of sound speed in ocean, which are neglected in the past analysis. For this purpose, some of the sites consist of six transponders, with which such variation can be potentially estimated. For this context, in the second phase surveys, we are going to introduce automatic surface vehicle to enable simultaneous measurement from two points from sea surface, which will provide information of the horizontal variation in sound speed even for three or four transponders. In addition we have made both moving and stationary surveys, in which we can apply couple of analytical techniques to compare the advantages to each other. In this talk, we report the summary of the first phase survey and comparison of the analytical techniques in the precision in positioning.

  9. Improving the precision of astrometry for space debris

    SciTech Connect

    Sun, Rongyu; Zhao, Changyin; Zhang, Xiaoxiang, E-mail: cyzhao@pmo.ac.cn [Key Laboratory of Space Object and Debris Observation, Purple Mountain Observatory, Chinese Academy of Sciences, 2 West Beijing Road, Gulou District, Nanjing 210008 (China)

    2014-03-01

    The data reduction method for optical space debris observations has many similarities with the one adopted for surveying near-Earth objects; however, due to several specific issues, the image degradation is particularly critical, which makes it difficult to obtain precise astrometry. An automatic image reconstruction method was developed to improve the astrometry precision for space debris, based on the mathematical morphology operator. Variable structural elements along multiple directions are adopted for image transformation, and then all the resultant images are stacked to obtain a final result. To investigate its efficiency, trial observations are made with Global Positioning System satellites and the astrometry accuracy improvement is obtained by comparison with the reference positions. The results of our experiments indicate that the influence of degradation in astrometric CCD images is reduced, and the position accuracy of both objects and stellar stars is improved distinctly. Our technique will contribute significantly to optical data reduction and high-order precision astrometry for space debris.

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

    SciTech Connect

    Yan, C.

    1994-09-07

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

  11. Photoswitchable precision glycooligomers and their lectin binding

    PubMed Central

    Ponader, Daniela; Igde, Sinaida; Wehle, Marko; Märker, Katharina; Santer, Mark

    2014-01-01

    Summary The synthesis of photoswitchable glycooligomers is presented by applying solid-phase polymer synthesis and functional building blocks. The obtained glycoligands are monodisperse and present azobenzene moieties as well as sugar ligands at defined positions within the oligomeric backbone and side chains, respectively. We show that the combination of molecular precision together with the photoswitchable properties of the azobenzene unit allows for the photosensitive control of glycoligand binding to protein receptors. These stimuli-sensitive glycoligands promote the understanding of multivalent binding and will be further developed as novel biosensors. PMID:25161717

  12. Position, Navigation, and Timing: GPS Scientific Applications

    NASA Technical Reports Server (NTRS)

    Neilan, Ruth E.

    2008-01-01

    This slide presentation reviews the development and deployment of the Global Positioning System (GPS). This presentation also includes measuring space and time, GPS as a tool for science, development of high precision JPL GPS receivers, and technology and applications developments.

  13. Controller design and implementation for a 6-degree-of-freedom magnetically levitated positioner with high precision 

    E-print Network

    Yu, Ho

    2005-11-01

    This thesis presents the controller design and implementation of a high-precision 6-degree-of-freedom (6-DOF) magnetically levitated (maglev) positioner. This high-precision positioning system consists of a novel ...

  14. Controller design and implementation for a 6-degree-of-freedom magnetically levitated positioner with high precision

    E-print Network

    Yu, Ho

    2005-11-01

    This thesis presents the controller design and implementation of a high-precision 6-degree-of-freedom (6-DOF) magnetically levitated (maglev) positioner. This high-precision positioning system consists of a novel concentrated-field magnet matrix...

  15. TOPAS a new GPS adjustment system for multistation positioning and orbit determination

    NASA Astrophysics Data System (ADS)

    Landau, Herbert

    A new software package is presented for positioning with the Global Positioning System in a multistation/multisession network approach. The program allows the determination of satellite orbits, clock and atmospheric parameters and terrestrial positions by using raw undifferenced carrier phase and code measurements in a sequential approach. All parameters are modelled and determined in an optimal filtering/smoothing technique based on U-D factorization methods resulting in precise terrestrial positions and satellite orbits. The paper describes the software product and the method principally applied. Results of applications of TOPAS to different networks (DOENAV and GINFEST) are presented showing single-day repeatablities of about 5 cm in all components for baselines of 100 to 1600 km length. Comparisons between results obtained by using broadcast and precise ephemeris data and results derived from measurement improved orbital information are made. This shows the influence of the orbit improvement technique used by TOPAS on precise point positioning. Repeatability analysis of multi-day solutions results in accuracies of 0.01 to 0.03 ppm for baselines of 600 to 700 km length.

  16. Parallel multiple precision division by a single precision divisor

    Microsoft Academic Search

    Niall Emmart; Charles Weems

    2011-01-01

    We report an algorithm for division of a multi-precision integer by a single-precision value using a graphics processing unit (GPU). Our algorithm combines a parallel version of Jebelean's exact division algorithm with a left-to-right algorithm for computing the borrow chain, to relax the requirement of exactness. We also employ Takahashi's recently reported cyclic reduction technique [10] for GPU division to

  17. Precision attitude determination for multimission spacecraft

    NASA Technical Reports Server (NTRS)

    Murrell, J. W.

    1978-01-01

    Attitude determination algorithms for a multimission spacecraft are derived and their performance analyzed. The attitude determination system is composed of a strapdown Inertial Reference Unit (IRU), two fixed head star trackers, and an onboard computer. IRU data is processed to maintain real-time knowledge of spacecraft attitude relative to an inertial reference frame. Star tracker data is processed using Kalman filtering techniques to estimate and correct the attitude determination errors and the gyro drift compensation errors. The results of a star availability analysis for stellar, solar and earth pointing missions are presented. Linear covariance analysis techniques are used to evaluate nominal attitude determination performance, the effects of sensor measurement accuracy variations, the effects of errors in knowledge of sensor measurement accuracy, and the effects of star tracker misalignment errors. Results of a nonlinear simulation analysis of attitude determination performance are also presented. These analyses show that precision attitude determination for stellar, solar and earth pointing missions is achieved.

  18. Fine pointing control for free-space optical communication

    NASA Technical Reports Server (NTRS)

    Portillo, A. A.; Ortiz, G. G.; Racho, C.

    2000-01-01

    Free-Space Optical Communications requires precise, stable laser pointing to maintain operating conditions. This paper also describes the software and hardware implementation of Fine Pointing Control based on the Optical Communications Demonstrator architecture.

  19. Precision Measurements at the ILC

    SciTech Connect

    Nelson, T.K.; /SLAC

    2006-12-06

    With relatively low backgrounds and a well-determined initial state, the proposed International Linear Collider (ILC) would provide a precision complement to the LHC experiments at the energy frontier. Completely and precisely exploring the discoveries of the LHC with such a machine will be critical in understanding the nature of those discoveries and what, if any, new physics they represent. The unique ability to form a complete picture of the Higgs sector is a prime example of the probative power of the ILC and represents a new era in precision physics.

  20. Reliable positioning in a sparse GPS network, eastern Ontario

    NASA Astrophysics Data System (ADS)

    Samadi Alinia, H.; Tiampo, K.; Atkinson, G. M.

    2013-12-01

    Canada hosts two regions that are prone to large earthquakes: western British Columbia, and the St. Lawrence River region in eastern Canada. Although eastern Ontario is not as seismically active as other areas of eastern Canada, such as the Charlevoix/Ottawa Valley seismic zone, it experiences ongoing moderate seismicity. In historic times, potentially damaging events have occurred in New York State (Attica, 1929, M=5.7; Plattsburg, 2002, M=5.0), north-central Ontario (Temiskaming, 1935, M=6.2; North Bay, 2000, M=5.0), eastern Ontario (Cornwall, 1944, M=5.8), Georgian Bay (2005, MN=4.3), and western Quebec (Val-Des-Bois,2010, M=5.0, MN=5.8). In eastern Canada, the analysis of detailed, high-precision measurements of surface deformation is a key component in our efforts to better characterize the associated seismic hazard. The data from precise, continuous GPS stations is necessary to adequately characterize surface velocities from which patterns and rates of stress accumulation on faults can be estimated (Mazzotti and Adams, 2005; Mazzotti et al., 2005). Monitoring of these displacements requires employing high accuracy GPS positioning techniques. Detailed strain measurements can determine whether the regional strain everywhere is commensurate with a large event occurring every few hundred years anywhere within this general area or whether large earthquakes are limited to specific areas (Adams and Halchuck, 2003; Mazzotti and Adams, 2005). In many parts of southeastern Ontario and western Québec, GPS stations are distributed quite sparsely, with spacings of approximately 100 km or more. The challenge is to provide accurate solutions for these sparse networks with an approach that is capable of achieving high-accuracy positioning. Here, various reduction techniques are applied to a sparse network installed with the Southern Ontario Seismic Network in eastern Ontario. Recent developments include the implementation of precise point positioning processing on acquired GPS raw data. These are based on precise GPS orbit and clock data products with centimeter accuracy computed beforehand. Here, the analysis of 1Hz GPS data is conducted in order to find the most reliable regional network from eight stations (STCO, TYNO, ACTO, INUQ, IVKQ, KLBO, MATQ and ALGO) that cover the study area in eastern Ontario. In this way, the estimated parameters are the total number of ambiguities and resolved ambiguities, posteriori rms of each baseline and the coordinates for each station and their differences with the known coordinates. The positioning accuracy, the corrections and the accuracy of interpolated corrections, and the initialization time required for precise positioning are presented for the various applications.

  1. Nuclear Positioning

    PubMed Central

    Gundersen, Gregg G.; Worman, Howard J.

    2013-01-01

    SUMMARY The nucleus is the largest organelle and is commonly depicted in the center of the cell. Yet during cell division, migration and differentiation, it frequently moves to an asymmetric position aligned with cell function. We consider the toolbox of proteins that move and anchor the nucleus within the cell and how forces generated by the cytoskeleton are coupled to the nucleus to move it. The significance of proper nuclear positioning is underscored by numerous diseases resulting from genetic alterations in the toolbox proteins. Finally, we discuss how nuclear position may influence cellular organization and signaling pathways. PMID:23498944

  2. Precision and Reproducibility in Biological Patterning

    NASA Astrophysics Data System (ADS)

    Gregor, Thomas; Wieschaus, Eric F.; Bialek, William; Tank, David W.

    2007-03-01

    During embryonic development, information about spatial location is represented by the concentration of various morphogen molecules. The reproducibility and precision of biological pattern formation thus is limited by the accuracy with which these concentration profiles can be established and ``read out'' by their target pathways. We consider four measures of precision for the Bicoid morphogen in the Drosophila embryo: The concentration differences that distinguish neighboring cells, the limits set by the random arrival of Bcd molecules at their targets (which depends on the absolute concentration), the noise in readout of Bcd by the activation of Hunchback, and the reproducibility of Bcd concentration at corresponding positions in multiple embryos. We show, through a combination of different experiments, that all of these quantities are ˜10%. This agreement among different measures of accuracy, which depend on very different molecular mechanisms, indicates that the embryo is not faced with sloppy input signals and noisy readout mechanisms; rather we have to understand how the embryo exerts precise control over absolute concentrations and responds reliably to small changes in these concentrations, down to the limits set by basic physical principles.

  3. ABJM amplitudes and the positive orthogonal Grassmannian

    NASA Astrophysics Data System (ADS)

    Huang, Yu-tin; Wen, CongKao

    2014-02-01

    A remarkable connection between perturbative scattering amplitudes of four dimensional planar SYM, and the stratification of the positive Grassmannian, was revealed in the seminal work of Arkani-Hamed et al. Similar extension for three-dimensional ABJM theory was proposed. Here we establish a direct connection between planar scattering amplitudes of ABJM theory, and singularities thereof, to the stratification of the positive orthogonal Grassmannian. In particular, scattering processes are constructed through on-shell diagrams, which are simply iterative gluing of the fundamental four-point amplitude. Each diagram is then equivalent to the merging of fundamental OG2 orthogonal Grassmannian to form a larger OG k , where 2 k is the number of external particles. The invariant information that is encoded in each diagram is precisely this stratification. This information can be easily read off via permutation paths of the on-shell diagram, which also can be used to derive a canonical representation of OG k that manifests the vanishing of consecutive minors as the singularity of all on-shell diagrams. Quite remarkably, for the BCFW recursion representation of the tree-level amplitudes, the on-shell diagram manifests the presence of all physical factorization poles, as well as the cancellation of the spurious poles. After analytically continuing the orthogonal Grassmannian to split signature, we reveal that each on-shell diagram in fact resides in the positive cell of the orthogonal Grassmannian, where all minors are positive. In this language, the amplitudes of ABJM theory is simply an integral of a product of d log forms, over the positive orthogonal Grassmannian.

  4. Image processing in precision agriculture

    Microsoft Academic Search

    Dragoljub Pokrajac; A. Lazarevic; S. Vucetic; T. Fiez; Z. Obradovic

    1999-01-01

    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

  5. Observational Model for Precision Astrometry with the Space Interferometry Mission

    NASA Technical Reports Server (NTRS)

    Turyshev, Slava G.; Milman, Mark H.

    2000-01-01

    The Space Interferometry Mission (SIM) is a space-based 10-m baseline Michelson optical interferometer operating in the visible waveband that is designed to achieve astrometric accuracy in the single digits of the microarcsecond domain. Over a narrow field of view SIM is expected to achieve a mission accuracy of 1 microarcsecond. In this mode SIM will search for planetary companions to nearby stars by detecting the astrometric "wobble" relative to a nearby reference star. In its wide-angle mode, SIM will provide 4 microarcsecond precision absolute position measurements of stars, with parallaxes to comparable accuracy, at the end of its 5-year mission. The expected proper motion accuracy is around 3 microarcsecond/year, corresponding to a transverse velocity of 10 m/ s at a distance of 1 kpc. The basic astrometric observable of the SIM instrument is the pathlength delay. This measurement is made by a combination of internal metrology measurements that determine the distance the starlight travels through the two arms of the interferometer, and a measurement of the white light stellar fringe to find the point of equal pathlength. Because this operation requires a non-negligible integration time, the interferometer baseline vector is not stationary over this time period, as its absolute length and orientation are time varying. This paper addresses how the time varying baseline can be "regularized" so that it may act as a single baseline vector for multiple stars, as required for the solution of the astrometric equations.

  6. SPOTTED STAR LIGHT CURVES WITH ENHANCED PRECISION

    SciTech Connect

    Wilson, R. E. [Astronomy Department, University of Florida, Gainesville, FL 32611 (United States)

    2012-09-15

    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.

  7. Global Positioning System Antenna Fixed Height Tripod Adapter

    NASA Technical Reports Server (NTRS)

    Dinardo, Steven J.; Smith, Mark A.

    1997-01-01

    An improved Global Positioning em antenna adaptor allows fixed antenna height measurements by removably attaching an adaptor plate to a conventional surveyor's tripod. Antenna height is controlled by an antenna boom which is a fixed length rod. The antenna is attached to one end of the boom. The opposite end of the boom tapers to a point sized to fit into a depression at the center of survey markers. The boom passes through the hollow center of a universal ball joint which is mounted at the center of the adaptor plate so that the point of the rod can be fixed in the marker's central depression. The mountains of the ball joint allow the joint to be moved horizontally in any direction relative to the tripod. When the ball joint is moved horizontally, the angle between the boom and the vertical changes because the boom's position is fixed at its lower end. A spirit level attached to the rod allows an operator to determine when the boom is plumb. The position of the ball joint is adjusted horizontally until the boom is plumb. At that time the antenna is positioned exactly over the center of the monument and the elevation of the antenna is precisely set by the length of the boom.

  8. Position indicator

    DOEpatents

    Tanner, David E. (Poway, CA)

    1981-01-01

    A nuclear reactor system is described in which a position indicator is provided for detecting and indicating the position of a movable element inside a pressure vessel. The movable element may be a valve element or similar device which moves about an axis. Light from a light source is transmitted from a source outside the pressure vessel to a first region inside the pressure vessel in alignment with the axis of the movable element. The light is redirected by a reflector prism to a second region displaced radially from the first region. The reflector prism moves in response to movement of the movable element about its axis such that the second region moves arcuately with respect to the first region. Sensors are arrayed in an arc corresponding to the arc of movement of the second region and signals are transmitted from the sensors to the exterior of the reactor vessel to provide indication of the position of the movable element.

  9. double as compared to farm A. From a financial point of view, the cash flow of farm B is posi-tive within three years whereas on farm A it is negative throughout the period. At the end of

    E-print Network

    Paris-Sud XI, Université de

    double as compared to farm A. From a financial point of view, the cash flow of farm B is posi- tive within three years whereas on farm A it is negative throughout the period. At the end of the period, net results have increased almost fourfold on farm B as compared to farm A. These differences indicate

  10. Profiling floating point value ranges for reconfigurable

    E-print Network

    Kelly, Paul H. J.

    Profiling floating point value ranges for reconfigurable implementation Ashley W Brown, Paul H J of floating-point arithmetic. This paper presents FloatWatch, a dynamic execution profiling tool designed to identify where an application can benefit from reduced precision or re- duced range in floating

  11. Advanced smart structures flight experiments for precision spacecraft

    Microsoft Academic Search

    Keith K. Denoyer; R. Scott Erwin; R. Rory Ninneman

    2000-01-01

    This paper presents an overview as well as data from four smart structures flight experiments directed by the U.S. Air Force Research Laboratory's Space Vehicles Directorate in Albuquerque, New Mexico. The Middeck Active Control Experiment $?Flight II (MACE II) is a space shuttle flight experiment designed to investigate modeling and control issues for achieving high precision pointing and vibration control

  12. An Ultrasonic\\/Optical Pulse Sensor for Precise Distance Measurements

    Microsoft Academic Search

    Darold Wobschall; Ming Zeng; Bhooma Srinivasaraghavan

    2005-01-01

    The combined ultrasonic transit time and optical pulse method described here is an improvement over the standard ultrasonic echo by providing a lower signal loss and more precise location of sensor reference points, specifically the transmitting and receiving transducers. The ultrasonic transit time sensor described here uses only a one-way ultrasonic pulse. The transit time, typically 0.5 to 50 ms,

  13. Use of precision time and time interval (PTTI)

    NASA Technical Reports Server (NTRS)

    Taylor, J. D.

    1974-01-01

    A review of range time synchronization methods are discussed as an important aspect of range operations. The overall capabilities of various missile ranges to determine precise time of day by synchronizing to available references and applying this time point to instrumentation for time interval measurements are described.

  14. High-Precision Time Delay Control with Continuous Phase Shifter for Pump-Probe Experiments Using Synchrotron Radiation Pulses

    SciTech Connect

    Tanaka, Yoshihito [RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Japan Science and Technology Agency, CREST, 5 Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); Ohshima, Takashi [Japan Science and Technology Agency, CREST, 5 Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); RIKEN, XFEL Joint Project/SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Fukuyama, Yoshimitsu; Yasuda, Nobuhiro; Kim, Jungeun; Osawa, Hitoshi; Kimura, Shigeru [Japan Science and Technology Agency, CREST, 5 Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); JASRI/SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Togashi, Tadashi; Hara, Toru [JASRI/SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); RIKEN, XFEL Joint Project/SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Kamioka, Hayato [Japan Science and Technology Agency, CREST, 5 Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai, Tsukuba, Ibaraki 305-8571 (Japan); Moritomo, Yutaka [Japan Science and Technology Agency, CREST, 5 Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); JASRI/SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai, Tsukuba, Ibaraki 305-8571 (Japan); Tanaka, Hitoshi [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai, Tsukuba, Ibaraki 305-8571 (Japan); Takata, Masaki [RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Japan Science and Technology Agency, CREST, 5 Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); JASRI/SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Sengoku, Hidetoshi; Nonoshita, Eiji [Candox Systems Inc., 15-21, Oshiage-cho, Gyoda, Saitama 361-0045 (Japan)

    2010-06-23

    Brilliant pulsed x-ray synchrotron radiation (SR) is useful for pump-probe experiment such as time-resolved x-ray diffraction, x-ray absorption fine structure, and x-ray spectroscopy. For laser pump-SR x-ray probe experiments, short pulsed lasers are generally synchronized to the SR master oscillator controlling the voltage for acceleration of electron bunches in an accelerator, and the interval between the laser and the SR pulses is changed around the time scale of target phenomenon. Ideal delay control produces any time delay as keeping the time-precision and pointing-stability of optical pulses at a sample position. We constructed the time delay control module using a continuous phase shifter of radio frequency signal and a frequency divider, which can produce the delayed trigger pulses to the laser without degradation of the time precision and the pointing stability. A picoseconds time-resolved x-ray diffraction experiment was demonstrated at SPring-8 storage ring for fast lattice response by femtosecond pulsed laser irradiation, and suggested the possibility of accurate sound velocity measurement. A delay control unit operating with subpicosecond precision has also been designed for femtosecond pump-probe experiments using a free electron laser at SPring-8 campus.

  15. High-Precision Time Delay Control with Continuous Phase Shifter for Pump-Probe Experiments Using Synchrotron Radiation Pulses

    NASA Astrophysics Data System (ADS)

    Tanaka, Yoshihito; Ohshima, Takashi; Fukuyama, Yoshimitsu; Yasuda, Nobuhiro; Kim, Jungeun; Osawa, Hitoshi; Kimura, Shigeru; Togashi, Tadashi; Hara, Toru; Kamioka, Hayato; Moritomo, Yutaka; Tanaka, Hitoshi; Takata, Masaki; Sengoku, Hidetoshi; Nonoshita, Eiji

    2010-06-01

    Brilliant pulsed x-ray synchrotron radiation (SR) is useful for pump-probe experiment such as time-resolved x-ray diffraction, x-ray absorption fine structure, and x-ray spectroscopy. For laser pump-SR x-ray probe experiments, short pulsed lasers are generally synchronized to the SR master oscillator controlling the voltage for acceleration of electron bunches in an accelerator, and the interval between the laser and the SR pulses is changed around the time scale of target phenomenon. Ideal delay control produces any time delay as keeping the time-precision and pointing-stability of optical pulses at a sample position. We constructed the time delay control module using a continuous phase shifter of radio frequency signal and a frequency divider, which can produce the delayed trigger pulses to the laser without degradation of the time precision and the pointing stability. A picoseconds time-resolved x-ray diffraction experiment was demonstrated at SPring-8 storage ring for fast lattice response by femtosecond pulsed laser irradiation, and suggested the possibility of accurate sound velocity measurement. A delay control unit operating with subpicosecond precision has also been designed for femtosecond pump-probe experiments using a free electron laser at SPring-8 campus.

  16. Triple Difference Approach to Low Earth Orbiter Precision Orbit Determination

    Microsoft Academic Search

    Jay-Hyoun Kwon; Dorota A. Grejner-Brzezinska; Jae-Hong Yom; Lee-Dong Cheon

    2003-01-01

    A precise kinematic orbit determination (P-KOD) procedure for Low Earth Orbiter(LEO) using the GPS ion-free triple differenced carrier phases is presented. Because the triple differenced observables provide only relative information, the first epoch's positions of the orbit should be held fixed. Then, both forward and backward filtering was executed to mitigate the effect of biases of the first epoch's position.

  17. Future payload isolation and pointing system technology

    NASA Technical Reports Server (NTRS)

    Laskin, R. A.; Sirlin, S. W.

    1986-01-01

    An overview is presented of the technology associated with the precision pointing of future spaceborne science instruments. High-level architectural options for dealing with the precision pointing problem are considered, and a representative NASA mission set for the 1990s is given. Pointing accuracy and stability requirements are extracted from the mission requirements, with the sub-0.1 arcsec stability requirement emerging as the primary driver. The state of the art of current technology is assessed, including an evaluation of gimbal systems, suspension systems, and actuator and sensor component technology. Areas where the technology needs to be pushed to satisfy future requirements are identified, and some promising design options are proposed.

  18. Spatial Regression for Marked Point Processes

    Microsoft Academic Search

    KATJA ICKSTADT; ROBERT L. WOLPERT

    1998-01-01

    SUMMARY In a wide range of applications, dependence on smoothly-varying covariates leads spatial point count intensities to feature positive correlation for nearby loc ations. In applications where the points are \\

  19. GPS surveying with 1 mm precision using corrections for atmospheric slant path delay

    NASA Astrophysics Data System (ADS)

    Alber, Chris; Ware, Randolph; Rocken, Christian; Solheim, Fredrick

    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 precision GPS surveying include deformation monitoring associated with earthquake and volcanic processes, subsidence, isostasy, and sea level measurements; monitoring of atmospheric water vapor for climate and global change research, and to improve the resolution of synthetic aperture radar; calibration of satellite altimeters; and precise satellite orbit determination.

  20. Sources of position-perception error for small isolated targets.

    PubMed

    van der Heijden, A H; van der Geest, J N; de Leeuw, F; Krikke, K; Müsseler, J

    1999-01-01

    It has often been reported that, in the presence of static reference stimuli, briefly presented visual targets are perceived as being closer to the fixation point than they actually are. The first purpose of the present study was to investigate whether the same phenomenon can be demonstrated in a situation without static reference stimuli. Experiment 1, with position naming as the task, showed that such a central shift is also observed under these conditions. This finding is of importance because it completes an explanation for central near-location errors in the partial-report bar-probe task. The second purpose of the present study was to provide an explanation for these central shifts. For this explanation information about the exact size of the central shift is required. In Exps. 2, 3, and 4, with cursor setting as the task, it was attempted to assess more precisely the size of the central shifts. These experiments revealed that two different factors determine the results in cursor setting tasks; a factor "target position" and a factor "cursor position." Experiment 5 showed that it is the point of fixation, not the fixation point, that serves, at least in part, as the reference point in this type of task. All the findings together allow us to conclude that the target positions are underestimated by about 10%. From vision research it is known that saccadic eye movements, performed for bringing a target in the fovea, also show an undershoot of about 10%. It is therefore concluded that the system in charge of saccadic eye movements also provides the metric in visual space within a single eye fixation. PMID:10356970