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1

Precise Point Positioning Using IGS Orbit and Clock Products  

Microsoft Academic Search

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

Jan Kouba; Pierre Héroux

2001-01-01

2

Assessing the Accuracy of the Precise Point Positioning Technique  

NASA Astrophysics Data System (ADS)

The Precise Point Positioning (PPP) GPS data processing technique has developed over the past 15 years to become a standard method for growing categories of positioning and navigation applications. The technique relies on single receiver point positioning combined with the use of precise satellite orbit and clock information and high-fidelity error modelling. The research presented here uniquely addresses the current accuracy of the technique, explains the limits of performance, and defines paths to improvements. For geodetic purposes, performance refers to daily static position accuracy. PPP processing of over 80 IGS stations over one week results in few millimetre positioning rms error in the north and east components and few centimetres in the vertical (all one sigma values). Larger error statistics for real-time and kinematic processing are also given. GPS PPP with ambiguity resolution processing is also carried out, producing slight improvements over the float solution results. These results are categorised into quality classes in order to analyse the root error causes of the resultant accuracies: "best", "worst", multipath, site displacement effects, satellite availability and geometry, etc. Also of interest in PPP performance is solution convergence period. Static, conventional solutions are slow to converge, with approximately 35 minutes required for 95% of solutions to reach the 20 cm or better horizontal accuracy. Ambiguity resolution can significantly reduce this period without biasing solutions. The definition of a PPP error budget is a complex task even with the resulting numerical assessment, as unlike the epoch-by-epoch processing in the Standard Position Service, PPP processing involving filtering. An attempt is made here to 1) define the magnitude of each error source in terms of range, 2) transform ranging error to position error via Dilution Of Precision (DOP), and 3) scale the DOP through the filtering process. The result is a deeper understanding of how PPP works, rather than just the performance of the technique determined from estimated station coordinates. From the above analysis, the limitations of PPP and the source of these limitations are isolated, including site displacement modelling, geometric measurement strength, pseudorange noise and multipath, etc. It is argued that new ambiguity resolution and multi-GNSS PPP processing will only partially address these limitations. Improved modelling is required for: site displacement effects, pseudorange noise and multipath, and code and phase biases. As well, more robust undifferenced-phase ambiguity validation and overall stochastic modelling is required.

Bisnath, S. B.; Collins, P.; Seepersad, G.

2012-12-01

3

Receiver Widelane Analysis and Its Effect on Precise Point Positioning  

NASA Astrophysics Data System (ADS)

Typically, differential carrier-phase-based methods have been used in positioning applications that require high accuracy. The main advantage of differential methods is solving the carrier-phase ambiguities and obtain millimetre-level accuracy carrier-phase measurements. Recent studies showed that it is possible to fix the un-differenced carrier-phase ambiguities into integers which is well-known as un-differenced carrier-phase ambiguity resolution. Unfortunately, the IGS neglects satellite hardware delay during satellite clock corrections estimation process. In case of differential methods, however, this will not affect the user as all common errors between the reference and rover receivers will be cancelled out by. Point positioning, on the other hand, will be affected by neglecting satellite hardware delays as those hardware delays will be lumped into the carrier-phase ambiguities destroying its integer nature. To solve this problem, satellite clock corrections must be estimated based on clock correction for each observable bases. The user, on the other hand, can form the ionosphere-free linear combination and divide and fix its two components, namely widelane and narrowlane. If both ambiguities are successfully fixed, few millimetres level of accuracy measurements are then obtained. In this paper, one month (December, 2013) of GPS data is used to study the receiver widelane bias, its behaviour over time, and receiver dependency are provided. It is shown that the receiver widelane bias is receiver dependent, stable over time for high-grade geodetic receivers. These results are expected to have a great impact on precise point positioning (PPP) conversion time and PPP carrierphase ambiguity resolution.

Elsobeiey, M.

2014-11-01

4

Adaptive robust Kalman filtering for precise point positioning  

NASA Astrophysics Data System (ADS)

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.

Guo, Fei; Zhang, Xiaohong

2014-10-01

5

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

NASA Astrophysics Data System (ADS)

Five days of continuous GPS observation data were collected in the frontal zone of the Amery ice shelf and subsequently post-processed using precise point position (PPP) technology based on precise orbit and clock products from the International GNSS service. The surface ice flow velocity of the observed point was derived from PPP to be 2.25 m/day toward the northeast with an azimuth of 41°. Major semi-diurnal and diurnal oceanic tide constituents could be recovered from the 5 days of PPP-derived height variations and compared well with a hydrodynamic ocean tide model. The PPP technique can replace double-difference GPS positioning in remote or hostile environments, and be used to retrieve the surface ice flow velocity without any reference station. Furthermore, the solution can be derived epoch-by-epoch with accuracy in the centimeters to decimeter range.

Zhang, Xiaohong; Andersen, Ole B.

2006-07-01

6

Precise Point Positioning technique for short and long baselines time transfer  

NASA Astrophysics Data System (ADS)

In this work the clock parameters determination of several timing receivers TTS-4 (AOS), ASHTECH Z-XII3T (OP, ORB, PTB, USNO) and SEPTENTRIO POLARX4TR (ORB, since February 11, 2012) by use of the Precise Point Positioning (PPP) technique were presented. The clock parameters were determined for several time links based on the data delivered by time and frequency laboratories mentioned above. The computations cover the period from January 1 to December 31, 2012 and were performed in two modes with 7-day and one-month solution for all links. All RINEX data files which include phase and code GPS data were recorded in 30-second intervals. All calculations were performed by means of Natural Resource Canada's GPS Precise Point Positioning (GPS-PPP) software based on high-quality precise satellite coordinates and satellite clock delivered by IGS as the final products. The used independent PPP technique is a very powerful and simple method which allows for better control of antenna positions in AOS and a verification of other time transfer techniques like GPS CV, GLONASS CV and TWSTFT. The PPP technique is also a very good alternative for calibration of a glass fiber link PL-AOS realized at present by AOS. Currently PPP technique is one of the main time transfer methods used at AOS what considerably improve and strengthen the quality of the Polish time scales UTC(AOS), UTC(PL), and TA(PL). KEY-WORDS: Precise Point Positioning, time transfer, IGS products, GNSS, time scales.

Lejba, Pawel; Nawrocki, Jerzy; Lemanski, Dariusz; Foks-Ryznar, Anna; Nogas, Pawel; Dunst, Piotr

2013-04-01

7

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

NASA Astrophysics Data System (ADS)

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

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

8

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

NASA Astrophysics Data System (ADS)

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.

Hackman, C.

2012-12-01

9

Near-real-time regional troposphere models for the GNSS precise point positioning technique  

NASA Astrophysics Data System (ADS)

The GNSS precise point positioning (PPP) technique requires high quality product (orbits and clocks) application, since their error directly affects the quality of positioning. For real-time purposes it is possible to utilize ultra-rapid precise orbits and clocks which are disseminated through the Internet. In order to eliminate as many unknown parameters as possible, one may introduce external information on zenith troposphere delay (ZTD). It is desirable that the a priori model is accurate and reliable, especially for real-time application. One of the open problems in GNSS positioning is troposphere delay modelling on the basis of ground meteorological observations. Institute of Geodesy and Geoinformatics of Wroclaw University of Environmental and Life Sciences (IGG WUELS) has developed two independent regional troposphere models for the territory of Poland. The first one is estimated in near-real-time regime using GNSS data from a Polish ground-based augmentation system named ASG-EUPOS established by Polish Head Office of Geodesy and Cartography (GUGiK) in 2008. The second one is based on meteorological parameters (temperature, pressure and humidity) gathered from various meteorological networks operating over the area of Poland and surrounding countries. This paper describes the methodology of both model calculation and verification. It also presents results of applying various ZTD models into kinematic PPP in the post-processing mode using Bernese GPS Software. Positioning results were used to assess the quality of the developed models during changing weather conditions. Finally, the impact of model application to simulated real-time PPP on precision, accuracy and convergence time is discussed.

Hadas, T.; Kaplon, J.; Bosy, J.; Sierny, J.; Wilgan, K.

2013-05-01

10

Enhanced model for precise point positioning with single and dual frequency GPS/Galileo observables  

NASA Astrophysics Data System (ADS)

This paper introduces a newly developed model for both single and dual-frequency precise point positioning (PPP), which combines GPS and Galileo observables. As is well known, a drawback of a single GNSS system is the availability of sufficient number of visible satellites in urban areas. Combining GPS and Galileo systems offers more visible satellites to users, which is expected to enhance the satellite geometry and the overall positioning solution. However, combining GPS and Galileo observables introduces additional biases which require rigorous modelling, including the GPS to Galileo time offset (GGTO) and the inter-system bias. This research introduces a new ionosphere-free linear combination model for GPS/Galileo PPP, which accounts for the additional errors and biases. An additional unknown is introduced in the least-squares estimation model to account for the additional biases of the GPS/Galileo PPP solution. It is shown that a sub-decimeter level positioning accuracy and 20% reduction in the solution convergence time can be achieved with the newly developed GPS/Galileo PPP model.

Afifi, A.; El-Rabbany, A.

2014-11-01

11

Integrity monitoring in real-time precise point positioning in the presence of ionospheric disturbances  

NASA Astrophysics Data System (ADS)

Ionospheric disturbances are characterized as fast and random variability in the ionosphere. Those phenomena are difficult to predict, detect and model. Occurrence of some strong ionospheric disturbances can cause, inter alia degradation and interruption of GNSS signals. Therefore they are especially harmful for real-time applications, as for example Precise Point Positioning (PPP) in real time, where one of the most important requirements is to ensure the high level of reliability. In such applications verification and confirmation of a high trust degree towards the estimated coordinates is a very critical issue. In one of the previous papers (K. Wezka, 2012 -Identification of system performance parameters and their usability) two sets of parameters have been proposed for enhance reliability of the PPP. The first one for data quality control (QC) of the raw GNSS observations and the second one for examination of the quality, robustness and performance of various processing approaches (strategies). To the second group the following parameters has been proposed: accuracy, precision, availability, integrity and convergence time. In consideration of perturbation of GNSS signal resulting from sudden ionospheric disturbances, one of the most important demands is effective autonomous integrity monitoring. The poster presents first preliminary results of the applicability of the proposed parameters in order to ensure the high level of reliability/integrity of GNSS observations and positioning results under the presence of strong ionospheric anomalies. The data-set from continuously operated GNSS station located at high latitude, where ionospheric disturbances occur more frequently, were used for the analysis. Various selected Receiver Autonomous Integrity Monitoring (RAIM) approaches for quality control of the GNSS observables are applied to the data sets recorded under different (low/quite and high) ionospheric activities. Based on those analyses the usability of the proposed parameters is verified.

Wezka, K.; Galas, R.

2013-12-01

12

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

13

Real-time retrieval of precipitable water vapor from GPS precise point positioning  

NASA Astrophysics Data System (ADS)

of precipitable water vapor (PWV) using the Global Positioning System (GPS) has been intensively investigated in the past 2 decades. However, it still remains a challenging task at a high temporal resolution and in the real-time mode. In this study the accuracy of real-time zenith total delay (ZTD) and PWV using the GPS precise point positioning (PPP) technique is investigated. GPS observations in a 1 month period from 20 globally distributed stations are selected for testing. The derived real-time ZTDs at most stations agree well with the tropospheric products from the International Global Navigation Satellite Systems Service, and the root-mean-square errors (RMSEs) are <13 mm, which meet the threshold value of 15 mm if ZTDs are input to numerical weather prediction models. The RMSE of the retrieved PWVs in comparison with the radiosonde-derived values are ?3 mm, which is the threshold RMSE of PWVs as inputs to weather nowcasting. The theoretical accuracy of PWVs is also discussed, and 3 mm quality of PWVs is proved achievable in different temperature and humidity conditions. This implies that the real-time GPS PPP technique can be complementary to current atmospheric sounding systems, especially for nowcasting of extreme weather due to its real-time, all-day, and all-weather capabilities and high temporal resolutions.

Yuan, Yubin; Zhang, Kefei; Rohm, Witold; Choy, Suelynn; Norman, Robert; Wang, Chuan-Sheng

2014-08-01

14

A Fast-Convergence Stream Editor for real-time Precise Point Positioning  

NASA Astrophysics Data System (ADS)

Conventional approaches for Precise Point Positioning (PPP) use the ionosphere-free combination on range and phase observables from dual frequency GNSS receivers to simultaneously estimate position, receiver clock, troposphere delay and phase biases for each satellite epoch by epoch. Implementations of these PPP algorithms for Real time applications show typical initialization and re-convergence times on the order of tens of minutes. We present here a stream editor that pre-cleans satellite observables using an algorithm based on the geometry-free combination of observables to calibrate the dual frequency phase observables in real time. The stream editor computes the best estimation of carrier phase biases and ionospheric delays for each satellite independently, and thus may be used in conjunction with a variety of approaches to Real-Time PPP (RTPPP). The cleaned observables output from the editor provide a significant reduction in filter convergence time in the estimation of position, typically under one minute. The editor has been extensively tested by generating cleaned satellite phase and range observables suitable for use with GIPSY 6.1.2 in both post-processing and real-time modes. Data from site P494, containing surface waves and permanent displacement from the Sierra El Mayor Earthquake (7.1Mw), were computed in post-processing mode and show good agreement with short-baseline differential processing. For real-time applications, time series for 31 sites in the Pacific Northwest are being processed and evaluated by using clock and orbital corrections and differential code biases provided by the Real Time Service (RTS) of the International GNSS Service (IGS). We find that the RMS scatter of these stations' time series are under 3 cm horizontal and less than 5 cm vertical.

Santillan, V. M.; Melbourne, T. I.; Szeliga, W. M.

2013-12-01

15

Triple-frequency GPS precise point positioning with rapid ambiguity resolution  

NASA Astrophysics Data System (ADS)

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

Geng, Jianghui; Bock, Yehuda

2013-05-01

16

Ambiguity resolution in precise point positioning with hourly data for global single receiver  

NASA Astrophysics Data System (ADS)

Integer ambiguity resolution (IAR) can improve precise point positioning (PPP) performance significantly. IAR for PPP became a highlight topic in global positioning system (GPS) community in recent years. More and more researchers focus on this issue. Progress has been made in the latest years. In this paper, we aim at investigating and demonstrating the performance of a global zero-differenced (ZD) PPP IAR service for GPS users by providing routine ZD uncalibrated fractional offsets (UFOs) for wide-lane and narrow-lane. Data sets from all IGS stations collected on DOY 1, 100, 200 and 300 of 2010 are used to validate and demonstrate this global service. Static experiment results show that an accuracy better than 1 cm in horizontal and 1-2 cm in vertical could be achieved in ambiguity-fixed PPP solution with only hourly data. Compared with PPP float solution, an average improvement reaches 58.2% in east, 28.3% in north and 23.8% in vertical for all tested stations. Results of kinematic experiments show that the RMS of kinematic PPP solutions can be improved from 21.6, 16.6 and 37.7 mm to 12.2, 13.3 and 34.3 mm for the fixed solutions in the east, north and vertical components, respectively. Both static and kinematic experiments show that wide-lane and narrow-lane UFO products of all satellites can be generated and provided in a routine way accompanying satellite orbit and clock products for the PPP user anywhere around the world, to obtain accurate and reliable ambiguity-fixed PPP solutions.

Zhang, Xiaohong; Li, Pan; Guo, Fei

2013-01-01

17

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

PubMed

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

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

2013-01-01

18

On the Convergence of Ionospheric Constrained Precise Point Positioning (IC-PPP) Based on Undifferential Uncombined Raw GNSS Observations  

PubMed Central

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

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

2013-01-01

19

Precision Pointing System Development  

SciTech Connect

The development of precision pointing systems has been underway in Sandia's Electronic Systems Center for over thirty years. Important areas of emphasis are synthetic aperture radars and optical reconnaissance systems. Most applications are in the aerospace arena, with host vehicles including rockets, satellites, and manned and unmanned aircraft. Systems have been used on defense-related missions throughout the world. Presently in development are pointing systems with accuracy goals in the nanoradian regime. Future activity will include efforts to dramatically reduce system size and weight through measures such as the incorporation of advanced materials and MEMS inertial sensors.

BUGOS, ROBERT M.

2003-03-01

20

Near real-time and real-time GNSS Precise Point Positioning with external a priori troposphere models  

NASA Astrophysics Data System (ADS)

Precise Point Positioning (PPP) is a positioning technique that uses a single GNSS (Global Navigation Satellite System) receiver that requires external information from analysis of global GNSS permanent network, in particular precise orbits and satellite clocks. This technique is commonly used in post-processing mode and gives results comparable to relative positioning. A shortcoming of this technique is the time required for the solution to converge, which is a main limitation for near real-time and real-time applications. The convergence time depends on the quality of GNSS data, on the accuracy of the a priori parameters and on fast ambiguity resolution. Until recently, near real-time and real-time users were limited in the sources of precise products, since only the predicted part of the ultra-rapid products were available. In 2012, the International GNSS Service (IGS) launched the Real-Time Service (RTS), making available a dedicated set of real-time products, known as IGS-RTS. Nevertheless, there is still no standard procedure for handling the troposphere delay. The a priori troposphere delay, as well as mapping functions, has to be derived from an external source and the adjustment model should account for the correction to an apriori value of the delay. Currently, a number of empirical troposphere state models and mapping functions are available for users in real-time. Near-real time model of troposphere delay can also be determined from the analysis of regional GNSS permanent network. In this paper, we make use of the IGS-RTS along with a number of a priori tropospheric models in order the assess how they influence convergence time and estimated position. For this purpose, we use GPS Analysis and Positioning Software (GAPS) for near-real time processing and GNSS-Wroclaw Algorithms for Real-time Positioning (GNSS-WARP) software for real-time processing of GPS only data together with IGS-RTS precise orbits and satellite clocks. As a priori troposphere model we used GPT together with the Saastamoinen formula, UNB3 model and regional near-real time troposphere model from the analysis of a network of permanent GNSS stations. We combine these models with Niell and VMF mapping functions to compute slant troposphere delays, including those of low-elevation satellites.

Hadas, Tomasz; Santos, Marcelo; Garcia, Alex; Bosy, Jaroslaw; Kaplon, Jan

2014-05-01

21

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

Microsoft Academic Search

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

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

2004-01-01

22

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

23

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

24

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

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 project. The performance of the developed realtime PPP processing facility will be evaluated

Schuh, Harald

25

Ultra-precision positioning assembly  

DOEpatents

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

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

2002-01-01

26

Precision Pointing of IBEX-Lo Observations  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

27

Rubber bearings for precision positioning systems  

E-print Network

In this thesis we investigate the use of thin rubber sheets or laminates of metal and rubber sheets as bearings in precision positioning systems. Such bearings have the potential to replace more conventional flexures ...

Barton Martinelli, Augusto E

2005-01-01

28

Precision of Position Signals for Letters  

PubMed Central

Accurate reading of words and text relies on reliable identification of letters in left to right order. Previous studies have shown that people often make letter-reversal errors when identifying strings of letters away from fixation. These errors contribute to a decline in letter identification performance away from fixation. This study tests the hypothesis that these errors are due to decreased precision (increased position noise) in the coding of letter position in the periphery. To test our hypothesis, we measured observers' performance for identifying pairs of adjacent letters presented within 8 letter positions left and right of fixation. The task was to name the two letters of each pair, from left to right. Responses were scored in two ways for each letter position: (1) letters were identified correctly and in the correct position, and (2) letters were identified correctly but in the wrong position. The ratio of these two scores, when subtracted from 1, gives the empirical rate of mislocation errors. Our primary finding shows that the coding of letter position becomes increasingly imprecise with distance from fixation. A model in which the encoded position of each letter is independent and Gaussian distributed, and in which the spread of the distribution governs the precision of localizing the letter accounts for the empirical rate of mislocation errors. We also found that precision of letter position coding scales with letter size but the precision does not improve with the use of a pre-cue. PMID:19460396

Chung, Susana T.L.; Legge, Gordon E.

2009-01-01

29

A high precision telescope pointing system  

Microsoft Academic Search

A novel method of telescope pointing has been developed based on He-Ne laser interferometric measurements of mirror position. This technique has been applied to a Pfund-type telescope, which consists of a fixed parabolic mirror illuminated by a flat mirror which rotates in altitude and azimuth. If the parabolic mirror is stationary, the angle of pointing depends only on the change

W. C. Danchi; A. Arthur; R. Fulton; M. Peck; B. Sadoulet

1986-01-01

30

Micro-Precision Interferometer: Pointing Control System  

NASA Technical Reports Server (NTRS)

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.

O'Brien, John

1995-01-01

31

Precise Applications Of The Global Positioning System  

NASA Technical Reports Server (NTRS)

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.

Lichten, Stephen M.

1992-01-01

32

Space Telescope precision pointing control system  

NASA Technical Reports Server (NTRS)

The Hubble Space Telescope has the most stringent pointing requirements imposed on any spacecraft to date. The overall HST stability shall not exceed 0.007 arc-seconds rms. The Pointing Control System utilizes fine guidance sensors and rate gyros for attitude reference and rate information. Control torques are provided by reaction wheels. A digital computer collects the sensor data, performs the control law computations, and sends torque commands to the reaction wheels. To attain this precision pointing, improvements were made to the rate gyros to lower their noise characteristics and to the reaction wheels to reduce their emitted vibration levels. The control system design was validated in a test sequence which progressed from model verification tests on an air-bearing to operations-oriented, closed loop testing on the assembled vehicle. A test system is described which allowed the simultaneous production of test case command loads for the flight computer and plots of predicted profiles to assist in test data analysis. Workarounds were required during system test to accommodate gyro biases and noise introduced into the closed loop system. Testing and analysis indicate that the HST will provide the capability to meet the requirements for precision pointing.

Beals, G. A.; Crum, R. C.; Dougherty, H. J.; Hegel, D. K.; Kelley, J. L.

1986-01-01

33

Enhanced precision pointing jitter suppression system  

NASA Astrophysics Data System (ADS)

Space based defense systems, such as a Space Based Laser (SBL), and space based surveillance systems share a common objective: extremely high resolution Line of Sight (LOS) target imaging. In order to achieve the mission objectives, their beam control subsystem must provide precise LOS pointing and tracking capabilities with suppression of LOS jitter. Draper Laboratory has developed concepts and instrumentation that address these needs based upon a stabilized inertial platform mechanization that holds a collimated light source, called the Inertial Pseudo Star Reference Unit (IPSRU). This paper describes the original IPSRU design and a design concept for a new High Performance version of the IPSRU system (HP-IPSRU) that meet the jitter stabilization needs of the SBL. The IPSRU provides an inertially stabilized optical probe beam that provides a precise pointing and tracking reference with nanoradian jitter performance. The IPSRU serves as a master reference for stabilizing imaging and weapon system pointing and tracking. This paper describes the IPSRU system, its measured error allocation and integrated performance. It presents the error budget required to achieving the 5 nrad rms jitter stabilization performance projected to be necessary for an operational Space Based Laser system. A conceptual design for the HP-IPSRU is presented.

Gilmore, Jerold P.; Luniewicz, Michael F.; Sargent, Darryl

2002-06-01

34

Inertial Pointing and Positioning System  

NASA Technical Reports Server (NTRS)

An inertial pointing and control system and method for pointing to a designated target with known coordinates from a platform to provide accurate position, steering, and command information. The system continuously receives GPS signals and corrects Inertial Navigation System (INS) dead reckoning or drift errors. An INS is mounted directly on a pointing instrument rather than in a remote location on the platform for-monitoring the terrestrial position and instrument attitude. and for pointing the instrument at designated celestial targets or ground based landmarks. As a result. the pointing instrument and die INS move independently in inertial space from the platform since the INS is decoupled from the platform. Another important characteristic of the present system is that selected INS measurements are combined with predefined coordinate transformation equations and control logic algorithms under computer control in order to generate inertial pointing commands to the pointing instrument. More specifically. the computer calculates the desired instrument angles (Phi, Theta. Psi). which are then compared to the Euler angles measured by the instrument- mounted INS. and forms the pointing command error angles as a result of the compared difference.

Yee, Robert (Inventor); Robbins, Fred (Inventor)

1998-01-01

35

Precise positioning control of overhead traveling cranes  

NASA Astrophysics Data System (ADS)

The objective of this paper is to present a new control design for precisely controlling overhead traveling cranes using microprocessors. Overhead cranes are widely used in manufacturing factories and are currently controlled by human operators. Automatic control can bring a number of important benefits, but existing algorithms tend to result in steady-state positioning errors in the presence of friction. In the proposed control design, a state feedback control algorithm is used to guarantee stability, a trajectory planner used to avoid saturation, and an additional integral term is used to eliminate steady-state error. Theoretical analysis and experimental implementation on a laboratory crane verifies the effectiveness of the approach.

Li, Weiping; Tang, Qingjie

1995-08-01

36

Precision pointing and control of flexible spacecraft  

NASA Technical Reports Server (NTRS)

The problem and long term objectives for the precision pointing and control of flexible spacecraft are given. The four basic objectives are stated in terms of two principle tasks. Under Task 1, robust low order controllers, improved structural modeling methods for control applications and identification methods for structural dynamics are being developed. Under Task 2, a lab test experiment for verification of control laws and system identification algorithms is being developed. For Task 1, work has focused on robust low order controller design and some initial considerations for structural modeling in control applications. For Task 2, work has focused on experiment design and fabrication, along with sensor selection and initial digital controller implementation. Conclusions are given.

Bantell, M. H., Jr.

1987-01-01

37

Faculty Position in Ultra High Precision Robotics & Manufacturing  

E-print Network

, manipulation and metrology systems targeting additive manufacturing; · New kinematics, quasi-perfect guidings, actuators, transmission systems, sensors and methods targeting ultra-high precision additive manufacturingFaculty Position in Ultra High Precision Robotics & Manufacturing at the Ecole Polytechnique

Candea, George

38

MICRO ACTUATORS FOR PRECISE POSITIONING APPLICATIONS IN A VACUUM  

Microsoft Academic Search

The Micro Harmonic Drive® gear is now established in the precision machine market as an ideal solution for precise positioning applications. This gear is manufactured using a modified LIGA process, called Direct-LIG. This allows the cost-effective production of extremely precise metallic gear components. With a diameter of 10 mm or less and with a tooth module of 34 ?m or

R. Slatter; R. Degen

39

Design and Analysis of Precise Pointing Systems  

NASA Technical Reports Server (NTRS)

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.

Kim, Young K.

2000-01-01

40

Analysis of a method for precisely relating a seafloor point to a distant point on land  

NASA Technical Reports Server (NTRS)

A study of the environmental constraints and engineering aspects of the acoustic portion of a system for making geodetic ties between undersea reference points and others on land is described. Important areas in which to make such observations initially would be from the California mainland out to oceanic points seaward of the San Andreas fault, and across the Aleutian Trench. The overall approach would be to operate a GPS receiver in a relative positioning (interferometric) mode to provide the long range element of the baseline determination (10 to 1,000 km) and an array of precision sea floor acoustic transponders to link the locally moving sea surface GPS antenna location to a fixed sea floor point. Analyses of various environmental constrants (tides, waves, currents, sound velocity variations) lead to the conclusion that, if one uses a properly designed transponder having a remotely controllable precise retransmission time delay, and is careful with regard to methods for installing these on the sea floor, one should, in many ocean locations, be able to achieve sub-decimeter overall system accuracy. Achievements of cm accuracy or better will require additional understanding of time and space scales of variation of sound velocity structure in the ocean at relevant locations.

Spiess, F. N.; Lowenstein, C. D.; Mcintyre, M. O.

1985-01-01

41

Magnetic suspension - The next generation in precision pointing  

NASA Technical Reports Server (NTRS)

Today's large optical experiments, both free-flying and Shuttle-borne, are finding an increasing need for a stable pointing platform in a vibration environment. As the resolution of optical systems has improved, conventional techniques for isolation and pointing have become less attractive. This paper describes the present state of the art in magnetic suspension pointing systems. This technology combines the functions of translational isolation and precision pointing to achieve performance in the 0.01 arcsec range, in the presence of disturbances such as random noise or reaction jet firings. Ongoing technology refinements and their importance to the experiment community are also discussed. The key to these refinements is a high-resolution, vibrating quartz force sensor that will improve pointing stability.

Hamilton, B. J.

1982-01-01

42

New amplified piezoelectric actuator for precision positioning and active damping  

Microsoft Academic Search

Two typical characteristics of direct piezoelectric actuators are displacements of ten micrometers and high stiffnesses. Recently, multilayer actuators have been improved, and they now display strains of approximately 1200 ppm at low excitation levels (less than two hundred volts). Thus, they are well suited to perform precise positioning of optical devices. But for industrial needs, this performance is still insufficient

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

1997-01-01

43

Point Estimation: Odds Ratios, Hazard Ratios, Risk Differences, Precision  

NSDL National Science Digital Library

This site provides a PowerPoint presentation, created by Dr. Elizabeth Garrett-Mayer of Johns Hopkins University, of a lesson and examples of point estimation, odds ratios, hazard ratios, risk differences and precision. The presentations is quite thorough. The author attempts to define, provide examples of, and then show the application of almost every concept. The presentation follows a easily followed and logical order. Mathematical formulas are intertwined within the slides. If further research is necessary, the author has provided a list of references and cites them during the presentation.

Garrett-Mayer, Elizabeth

2009-02-11

44

Astrophysical Adaptation of Points, the Precision Optical Interferometer in Space  

NASA Technical Reports Server (NTRS)

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.

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

45

Design of a reversible single precision floating point subtractor.  

PubMed

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

Anantha Lakshmi, Av; Sudha, Gf

2014-01-01

46

Precision optical angular position marker system for rotating machinery  

NASA Technical Reports Server (NTRS)

An optical system is described which generates one or more markers of the angular shaft position of rotating machinery. The system consists of a light source, an optical cable, a machinery mounted lens assembly, a light detector, and a signal conditioner. Light reflected by targets on the rotor is converted to a digital output signal. The system is highly immune to extreme environments of vibration and temperature and achieved a 0.002 percent precision under operational test conditions.

Barranger, J. P.

1983-01-01

47

Helicopter precision approach capability using the Global Positioning System  

NASA Technical Reports Server (NTRS)

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.

Kaufmann, David N.

1992-01-01

48

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

USGS Publications Warehouse

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

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

2006-01-01

49

The instrument pointing system: Precision attitude control in space  

NASA Astrophysics Data System (ADS)

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

Hartmann, Ralf; Woelker, Albrecht

1990-06-01

50

Closed loop high precision position control system with optical scale  

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

51

Impact of the floating-point precision and interpolation scheme on the results of DNS of  

E-print Network

Impact of the floating-point precision and interpolation scheme on the results of DNS of turbulence of the floating-point precision and interpo- lation scheme on the results of direct numerical simulations (DNS

Grauer, Rainer

52

High precision pointing with a multiline spectrometer at the VTT  

NASA Astrophysics Data System (ADS)

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 %.

Staiger, J.

2012-12-01

53

Precise on-line position measurement for particle therapy  

NASA Astrophysics Data System (ADS)

An on-line beam position monitoring and regular beam stability tests are of utmost importance for the Quality Assurance (QA) of the patient treatment at any particle therapy facility. The Gantry 2 at the Paul Scherrer Institute uses a strip ionization chamber for the on-line beam position verification. The design of the strip chamber placed in the beam in front of the patient allows for a small beam penumbra in order to achieve a high-quality lateral beam delivery. The position error of 1 mm in a lateral plane (plane perpendicular to the beam direction) can result in a dose inhomogeneity of more than 5%. Therefore the goal of Gantry 2 commissioning was to reach a sub-millimeter level of the reconstruction accuracy in order to bring a dose uncertainty to a level of 1%. In fact, we observed that for beams offered by Gantry 2 signal profiles in a lateral plane can be reconstructed with a precision of 0.1 mm. This is a necessary criterion to perform a reliable patient treatment. The front end electronics and the whole data processing sequence have been optimized for minimizing the dead time in between two consecutive spots to about 2 ms: the charge collection is performed in about 1 ms, read-out takes place in about 100?s while data verification and logging are completed in less than 1 ms.

Actis, O.; Meer, D.; König, S.

2014-12-01

54

Precise measurement of the positive muon anomalous magnetic moment.  

PubMed

A precise measurement of the anomalous g value, a(mu) = (g-2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron. The result a(mu+) = 11 659 202(14) (6) x 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 model is a(mu)(SM) = 11 659 159.6(6.7) x 10(-10) (0.57 ppm) and a(mu)(exp) - a(mu)(SM) = 43(16) x 10(-10) in which a(mu)(exp) is the world average experimental value. PMID:11289896

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

2001-03-12

55

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

NASA Astrophysics Data System (ADS)

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

Long, Chang-yu; Zhu, Ji-gui

2013-08-01

56

Robot positioning based on point-to-point motion capability  

SciTech Connect

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.

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

2000-03-20

57

Precision Pointing Control System (PPCS) star tracker test  

NASA Technical Reports Server (NTRS)

Tests performed on the TRW precision star tracker are described. The unit tested was a two-axis gimballed star tracker designed to provide star LOS data to an accuracy of 1 to 2 sec. The tracker features a unique bearing system and utilizes thermal and mechanical symmetry techniques to achieve high precision which can be demonstrated in a one g environment. The test program included a laboratory evaluation of tracker functional operation, sensitivity, repeatibility, and thermal stability.

1972-01-01

58

Precision Positioning and Vibration Measurement Using Intelligent Instrumentation and Simulation Tools  

NSDL National Science Digital Library

The objective of this research is to detail the development of a simple and unique instrumentation for precise micro-measurement as well as vibration measurement in an integrated manufacturing set up that can be demonstrated in a student laboratory. Based on this we propose new research for a smaller embedded measurement unit. All machines have some amount of forced vibration. However, in some cases, this vibration may cause damage to the machinery. Understanding vibration in aerospace applications is critical for any system that will be exposed to vibrating motion. Previously, strain gauges and piezoelectric accelerometers have been adequate for measuring vibration. However due to the increased requirements in performance, these methods are slowly being replaced by laser-based precision instruments. One of the main reasons for this transition is the fact that the equipment in these methods must be mounted on the surface of the object being measured which can result in increasing the mass and altering the frequency, mode shape of the vibrating object. Laser technology is a non-contact measuring method and provides the resolution needed to satisfy the changing requirements. In order to demonstrate precise positioning and motion control for creating and detecting vibrational movements, an experimental test bed was constructed. Software based simulation tools were used to control the positioning system. For vibration monitoring, the vibrating surface was discretely sampled by individual laser pulses and recorded by the position sensitive detector by the generation of pulses whose magnitudes are proportional to the instantaneous surface displacements. With a sufficiently high sampling rate, reconstruction of the vibration wave form is achieved by conducting peak detection of the resultant series of pulses. Vibration sensing by position sensing detector and vibration sensing by interferometry were the two techniques that were experimented with the new micro-positioning system. Three methods of micro-positioning and measurement were experimented; a precision encoder, an optical interferometer and an integrated vision system. Data was collected at successive points along the translation stages. The results showed that the optical interferometer and the encoder produced the most accurate results. It was also observed that significantly higher peak optical power levels of the probe laser pulses lead to proportional enhancement in the position sensitive detector response and remarkable improvement in detection sensitivity. >/br>This paper also outlines the results of the new approach in micro-positioning, displacement creation and vibration sampling in high precision machine tools. Additional results with the prediction of break-through detection in laser drilling manufacturing process has also been documented.

Eppes, Tom; Hill, Jonathan; Shetty, Devdas

2009-10-29

59

Antenna phase center calibration for precise positioning of LEO satellites  

Microsoft Academic Search

Phase center variations of the receiver and transmitter antenna constitute a remaining uncertainty in the high precision orbit\\u000a determination (POD) of low Earth orbit (LEO) satellites using GPS measurements. Triggered by the adoption of absolute phase\\u000a patterns in the IGS processing standards, a calibration of the Sensor Systems S67-1575-14 antenna with GFZ choke ring has\\u000a been conducted that serves as

Oliver Montenbruck; Miquel Garcia-Fernandez; Yoke Yoon; Steffen Schön; Adrian Jäggi

2009-01-01

60

Precision Pointing for the Laser Interferometry Space Antenna Mission  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

61

Precision Pointing for the Laser Interferometry Space Antenna Mission  

NASA Technical Reports Server (NTRS)

This viewgraph presentation discusses requirements for control systems in the design and production of space-based telescopes. Specific topics covered include: pointing control methods, wavefront control methods, vibration control methods and thermal control methods. Control systems on the Hubble Space Telescope and the James Webb Space Telescope are reviewed. Control system requirements for future space telescopes are also mentioned.

Hyde, T. Tupper; Bauer, Frank H. (Technical Monitor)

2003-01-01

62

All-Electric Spacecraft Precision Pointing using Model Predictive Control  

E-print Network

of electric microthrusters pave the way to the successful diffusion of all-electric spacecraft. Since pointing) for spacecraft equipped with cold gas and electrothermal xenon microthrusters is presented. The number [4,5]. Cold gas and electrothermal microthrusters, with thrust levels scaled down to the millinewton

Giannitrapani, Antonello

63

Precise pointing of space telescope using a quadrant detector  

NASA Technical Reports Server (NTRS)

A study was done to evaluate the pointing performance of Space Telescope with a quadrant detector used as the fine guidance sensor. The detector, a quadrant digicon, has been proposed as a replacement detector should unforeseen problems develop with the present baseline interferometer design. The detector model is discussed along with the experimental data from which it was derived.

Strikwerda, T. E.; Strohbehn, K.; Heyler, G. A.

1985-01-01

64

Pointing Control System for a High Precision Flight Telescope  

SciTech Connect

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

BENTLEY,ANTHONY E.; WILCOXEN,JEFFREY LEE

2000-12-01

65

High Precision PSD Guided Robot Localization: Design, Mapping, and Position Control  

E-print Network

that need to be fulfilled (e.g. assembly in the semiconductor indus- try or robot assisted medical surgeryHigh Precision PSD Guided Robot Localization: Design, Mapping, and Position Control Sebastian Blank developed high precision robot localization system employing position sensitive detectors (PSD). A lateral

Berns, Karsten

66

A precision pointing system for space telescope class optical trackers  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

67

Influence of Ephemeris Error on GPS Single Point Positioning Accuracy  

NASA Astrophysics Data System (ADS)

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

Lihua, Ma; Wang, Meng

2013-09-01

68

Precision Pointing Reconstruction and Geometric Metadata Generation for Cassini Images  

NASA Astrophysics Data System (ADS)

Analysis of optical remote sensing (ORS) data from the Cassini spacecraft is a complicated and labor-intensive process. First, small errors in Cassini’s pointing information (up to ~40 pixels for the Imaging Science Subsystem Narrow Angle Camera) must be corrected so that the line of sight vector for each pixel is known. This process involves matching the image contents with known features such as stars, ring edges, or moon limbs. Second, metadata for each pixel must be computed. Depending on the object under observation, this metadata may include lighting geometry, moon or planet latitude and longitude, and/or ring radius and longitude. Both steps require mastering the SPICE toolkit, a highly capable piece of software with a steep learning curve. Only after these steps are completed can the actual scientific investigation begin.We are embarking on a three-year project to perform these steps for all 300,000+ Cassini ISS images as well as images taken by the VIMS, UVIS, and CIRS instruments. The result will be a series of SPICE kernels that include accurate pointing information and a series of backplanes that include precomputed metadata for each pixel. All data will be made public through the PDS Rings Node (http://www.pds-rings.seti.org). We expect this project to dramatically decrease the time required for scientists to analyze Cassini data. In this poster we discuss the project, our current status, and our plans for the next three years.

French, Robert S.; Showalter, Mark R.; Gordon, Mitchell K.

2014-11-01

69

Global positioning system measurements for crustal deformation: Precision and accuracy  

USGS Publications Warehouse

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

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

1989-01-01

70

High precision global positioning system for mining applications  

SciTech Connect

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.

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

1997-12-01

71

Precise mean sea level measurements using the Global Positioning System  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

72

High-precision DEM reconstruction based on airborne LiDAR point clouds  

NASA Astrophysics Data System (ADS)

Airborne LiDAR point clouds have become important data sources for DEM generation recently; however the problem of low precision and low efficiency in DEM production still exists. This paper proposes a new technical scheme for high-precision DEM production based on airborne LiDAR point clouds systematically. Firstly, an elevation and density analysis method is applied to filter out outliers. Secondly, ground points are detected by an improved filter algorithm based on the hierarchical smoothing method. Finally, feature lines are extracted by the planar surface fitting and intersecting method, and a simple data structure of feature lines preserved DEM is proposed to achieve reconstructing high accuracy DEM, combing feature lines with ground points. Experimental results show that the proposed scheme is able to compensate for deficiencies of existing DEM reconstruction techniques and can meet the needs of high precision DEM production based on LiDAR data.

Xu, Jingzhong; Kou, Yuan; Wang, Jun

2014-05-01

73

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

NASA Astrophysics Data System (ADS)

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

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

74

Geo-referencing point clouds with transformational and positional uncertainties  

NASA Astrophysics Data System (ADS)

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

Paffenholz, Jens-André; Bae, Kwang-Ho

2012-03-01

75

Positional information, positional error, and readout precision in morphogenesis: a mathematical framework.  

PubMed

The concept of positional information is central to our understanding of how cells determine their location in a multicellular structure and thereby their developmental fates. Nevertheless, positional information has neither been defined mathematically nor quantified in a principled way. Here we provide an information-theoretic definition in the context of developmental gene expression patterns and examine the features of expression patterns that affect positional information quantitatively. We connect positional information with the concept of positional error and develop tools to directly measure information and error from experimental data. We illustrate our framework for the case of gap gene expression patterns in the early Drosophila embryo and show how information that is distributed among only four genes is sufficient to determine developmental fates with nearly single-cell resolution. Our approach can be generalized to a variety of different model systems; procedures and examples are discussed in detail. PMID:25361898

Tka?ik, Gašper; Dubuis, Julien O; Petkova, Mariela D; Gregor, Thomas

2015-01-01

76

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

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

77

Design of a precision pointing control system for the space infrared telescope facility  

NASA Technical Reports Server (NTRS)

This paper describes the design of a precision pointing control system for the Space Infrared Telescope Facility (SIRTF). Mission requirements and their impact on control system design are discussed along with the original features of the control strategy. Simulation of the total system is described, and the most significant results are presented.

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

1986-01-01

78

Precision absolute measurement and alignment of laser beam direction and position.  

PubMed

For the construction of high-precision optical assemblies, direction and position measurement and control of the involved laser beams are essential. While optical components such as beamsplitters and mirrors can be positioned and oriented accurately using coordinate measuring machines (CMMs), the position and direction control of laser beams is a much more intriguing task since the beams cannot be physically contacted. We present an easy-to-implement method to both align and measure the direction and position of a laser beam using a CMM in conjunction with a position-sensitive quadrant photodiode. By comparing our results to calibrated angular and positional measurements we can conclude that with the proposed method, a laser beam can be both measured and aligned to the desired direction and position with 10 ?rad angular and 3 ?m positional accuracy. PMID:25322238

Schütze, Daniel; Müller, Vitali; Heinzel, Gerhard

2014-10-01

79

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

PubMed

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

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

2009-01-01

80

Positive Point-to-Plane Corona Studies in Air  

Microsoft Academic Search

Formative time lags for the development of the positive point-to-plane corona in dry air were measured oscillographically at pressures ranging from atmospheric to a few centimeters of Hg. Studies with a photomultiplier tube show that the observed formative lags are associated with a filamentary streamer type of corona. These corona formative lags are of the order of 10-7 sec even

M. Menes; L. H. Fisher

1954-01-01

81

Positive area and inaccessible fixed points for hedgehogs  

E-print Network

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.

Biswas, Kingshook

2010-01-01

82

Precise tracking of remote sensing satellites with the Global Positioning System  

Microsoft Academic Search

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

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

1990-01-01

83

High-Precision Floating-Point Arithmetic in ScientificComputation  

SciTech Connect

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.

Bailey, David H.

2004-12-31

84

Clinical precision of myofascial trigger point location in the trapezius muscle  

Microsoft Academic Search

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

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

2001-01-01

85

Applications of inertial-sensor high-inheritance instruments to DSN precision antenna pointing  

NASA Technical Reports Server (NTRS)

Laboratory test results of the initialization and tracking performance of an existing inertial-sensor-based instrument are given. The instrument, although not primarily designed for precision antenna pointing applications, demonstrated an on-average 10-hour tracking error of several millidegrees. The system-level instrument performance is shown by analysis to be sensor limited. Simulated instrument improvements show a tracking error of less than 1 mdeg, which would provide acceptable performance, i.e., low pointing loss, for the Deep Space Network 70-m antenna subnetwork, operating at Ka-band (1-cm wavelength).

Goddard, R. E.

1992-01-01

86

Applications of inertial-sensor high-inheritance instruments to DSN precision antenna pointing  

NASA Technical Reports Server (NTRS)

Laboratory test results of the initialization and tracking performance of an existing inertial-sensor-based instrument are given. The instrument, although not primarily designed for precision antenna pointing applications, demonstrated an on-average 10-hour tracking error of several millidegrees. The system-level instrument performance is shown by analysis to be sensor limited. Simulated instrument improvements show a tracking error of less than 1 mdeg, which would provide acceptable performance, i.e., low pointing loss, for the DSN 70-m antenna sub network, operating at Ka-band (1-cm wavelength).

Goddard, R. E.

1992-01-01

87

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

PubMed Central

High precision positioning technology for a kind of high speed maglev train with an electromagnetic suspension (EMS) system is studied. At first, the basic structure and functions of the position sensor are introduced and some key techniques to enhance the positioning precision are designed. Then, in order to further improve the positioning signal quality and the fault-tolerant ability of the sensor, a new kind of discrete-time tracking differentiator (TD) is proposed based on nonlinear optimal control theory. This new TD has good filtering and differentiating performances and a small calculation load. It is suitable for real-time signal processing. The stability, convergence property and frequency characteristics of the TD are studied and analyzed thoroughly. The delay constant of the TD is figured out and an effective time delay compensation algorithm is proposed. Based on the TD technology, a filtering process is introduced in to improve the positioning signal waveform when the sensor is under bad working conditions, and a two-sensor switching algorithm is designed to eliminate the positioning errors caused by the joint gaps of the long stator. The effectiveness and stability of the sensor and its signal processing algorithms are proved by the experiments on a test train during a long-term test run. PMID:22778582

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

2012-01-01

88

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

PubMed

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

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

2012-01-01

89

Trajectory planning and control for precision positioning table driven by a PMSM  

Microsoft Academic Search

In this paper, we propose a novel trajectory planning method for a precision positioning table driven by a permanent magnet synchronous motor (PMSM). To generate the mechatronic trajectory we develop a real-coded genetic algorithm (RGA) to search for the optimal trajectory for the motion. In this method, we design a high-degree polynomial to compute minimum-energy trajectories, and consider the problem

Yi-Lung Hsu; Ming-Shyan Huang; Rong-Fong Fung

2011-01-01

90

Eye-Position Signals in the Dorsal Visual System Are Accurate and Precise on Short Timescales  

PubMed Central

Eye-position signals (EPS) are found throughout the primate visual system and are thought to provide a mechanism for representing spatial locations in a manner that is robust to changes in eye position. It remains unknown, however, whether cortical EPS (also known as “gain fields”) have the necessary spatial and temporal characteristics to fulfill their purported computational roles. To quantify these EPS, we combined single-unit recordings in four dorsal visual areas of behaving rhesus macaques (lateral intraparietal area, ventral intraparietal area, middle temporal area, and the medial superior temporal area) with likelihood-based population-decoding techniques. The decoders used knowledge of spiking statistics to estimate eye position during fixation from a set of observed spike counts across neurons. Importantly, these samples were short in duration (100 ms) and from individual trials to mimic the real-time estimation problem faced by the brain. The results suggest that cortical EPS provide an accurate and precise representation of eye position, albeit with unequal signal fidelity across brain areas and a modest underestimation of eye eccentricity. The underestimation of eye eccentricity predicted a pattern of mislocalization that matches the errors made by human observers. In addition, we found that eccentric eye positions were associated with enhanced precision relative to the primary eye position. This predicts that positions in visual space should be represented more reliably during eccentric gaze than while looking straight ahead. Together, these results suggest that cortical eye-position signals provide a useable head-centered representation of visual space on timescales that are compatible with the duration of a typical ocular fixation. PMID:23884945

Bremmer, Frank; Krekelberg, Bart

2013-01-01

91

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

92

Precision pointing and tracking through random media by exploitation of the enhanced backscatter phenomenon.  

PubMed

The active illumination of a target through a turbulent medium with a monostatic transmitter-receiver results in a naturally occurring conjugate wave caused by reciprocal scattering paths that experience identical phase variations. This reciprocal path-scattering phenomenon produces an enhanced backscatter in the retroverse direction (precisely along the boresight of the pointing telescope). A dual aperture causes this intensity enhancement to take the form of Young's interference fringes. Interference fringes produced by the reciprocal path-scattering phenomenon are temporally stable even in the presence of time-varying turbulence. Choosing the width-to-separation ratio of the dual apertures appropriately and utilizing orthogonal polarizations to suppress the time-varying common-path scattered radiation allow one to achieve interferometric sensitivity in pointing accuracy through a random medium or turbulent atmosphere. Computer simulations are compared with laboratory experimental data. This new precision pointing and tracking technique has potential applications in ground-to-space laser communications, laser power beaming to satellites, and theater missile defense scenarios. PMID:21102831

Harvey, J E; Reddy, S P; Phillips, R L

1996-07-20

93

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

94

Optimized laser beam widths meter calibration system: precisely positioning of detector measurement plane  

NASA Astrophysics Data System (ADS)

The direct substitution method is used in the laser beam widths meter (usually the laser beam profiler) calibration. The laser beam widths measurement results of device under test (DUT) are compared with those made by the laboratory standard. For most laser beam widths meter, the detector measurement plane is installed inside detector head, so it is difficult to accurately position the measurement plane for both standard and DUT. Depending on the ocular estimation, the difference of measurement plane between standard and DUT is usually controlled within 5mm. For 2.5mrad divergence angle of laser beam, 5mm tolerance will cause an uncertainty of 12.5?m in the beam widths measurement. In the optimized calibration system, a wedge prism placed in the beam path produces a precise beam deflection, which results in the laser spot displacement on the measurement plane. Depending on the measurable displacement of beam centroid position and the beam deflection angle, the distance from the wedge prism to the detector measurement plane is determined. The experimental results show that using the measurement plane positioning method, the difference of measurement plane between standard and DUT is close to 80?m, only contributing an uncertainty of 0.125?m in final result with the same 2.5mrad beam divergence angle. In additional, some factors affecting precisely positioning of measurement plane are analyzed in this paper.

Wang, Yanping; Wang, Qianqian; Ma, Chong

2013-12-01

95

Astrometry with Hubble Space Telescope Fine Guidance Sensor number 3: Position-mode stability and precision  

NASA Technical Reports Server (NTRS)

We report results from a test exploring the long- and short-term astrometric stability of Hubble Space Telescope Fine Guidance Sensor (FGS) #3. A test field was observed 40 times over 522 days to determine the precision and accuracy of FGS astrometry and to measure the character and magnitude of possible secular scale changes. We examine the astrometric data and the associated guide-star data to determine random errors. These data are also explored to find sources of systematic error. After correcting for some systematic effects we obtain a precision of 0.002 arcsec (2 mas) per observation (RSS of x and y). This is relative astrometry within a central 2.5 arcmin FGS field of view for any orientation. We find that the scale varies over time and confirm the sense of the trend with independent data. From the 40 observation sets we produce a catalog of an astrometry test field containing eight stars whose relative positions are known to an average 0.7 and 0.9 mas in x and y. One reference star has a relative parallax of 3.1 plus or minus 0.5 mas. Finally, we report that eleven observation sets acquired over 387 days produce parallaxes and relative positions with 1-mas precision.

Benedict, G. F.; Mcarthur, B.; Nelan, E.; Story, D.; Whipple, A. L.; Jefferys, W. H.; Wang, Q.; Shelus, P. J.; Hemenway, P. D.; Mccartney, J.

1994-01-01

96

An analysis of the double-precision floating-point FFT on FPGAs.  

SciTech Connect

Advances in FPGA technology have led to dramatic improvements in double precision floating-point performance. Modern FPGAs boast several GigaFLOPs of raw computing power. Unfortunately, this computing power is distributed across 30 floating-point units with over 10 cycles of latency each. The user must find two orders of magnitude more parallelism than is typically exploited in a single microprocessor; thus, it is not clear that the computational power of FPGAs can be exploited across a wide range of algorithms. This paper explores three implementation alternatives for the fast Fourier transform (FFT) on FPGAs. The algorithms are compared in terms of sustained performance and memory requirements for various FFT sizes and FPGA sizes. The results indicate that FPGAs are competitive with microprocessors in terms of performance and that the 'correct' FFT implementation varies based on the size of the transform and the size of the FPGA.

Hemmert, K. Scott; Underwood, Keith Douglas

2005-01-01

97

Demonstration of precise estimation of polar motion parameters with the global positioning system: Initial results  

NASA Technical Reports Server (NTRS)

Data from the Global Positioning System (GPS) were used to determine precise polar motion estimates. Conservatively calculated formal errors of the GPS least squares solution are approx. 10 cm. The GPS estimates agree with independently determined polar motion values from very long baseline interferometry (VLBI) at the 5 cm level. The data were obtained from a partial constellation of GPS satellites and from a sparse worldwide distribution of ground stations. The accuracy of the GPS estimates should continue to improve as more satellites and ground receivers become operational, and eventually a near real time GPS capability should be available. Because the GPS data are obtained and processed independently from the large radio antennas at the Deep Space Network (DSN), GPS estimation could provide very precise measurements of Earth orientation for calibration of deep space tracking data and could significantly relieve the ever growing burden on the DSN radio telescopes to provide Earth platform calibrations.

Lichten, S. M.

1991-01-01

98

Piping inspection instrument carriage with precise and repeatable position control and location determination  

DOEpatents

An instrument carriage for inspection of piping comprises front and rear leg assemblies for engaging the interior of the piping and supporting and centering the carriage therein, and an instrumentation arm carried by a shaft system running from the front to rear leg assemblies. The shaft system has a screw shaft for moving the arm axially and a spline gear for moving the arm azimuthally. The arm has a pair of air cylinders that raise and lower a plate in the radial direction. On the plate are probes including an eddy current probe and an ultrasonic testing probe. The ultrasonic testing probe is capable of spinning 360.degree. about its axis. The instrument carriage uses servo motors and pressurized air cylinders for precise actuation of instrument components and precise, repeatable actuation of position control mechanisms.

Hapstack, Mark (North Augusta, SC); Talarek, Ted R. (Augusta, GA); Zollinger, W. Thor (Martinez, GA); Heckendorn, II, Frank M. (Alken, SC); Park, Larry R. (North Augusta, SC)

1994-01-01

99

High-precision measurement of pixel positions in a charge-coupled device.  

PubMed

The high level of spatial uniformity in modern CCD's makes them excellent devices for astrometric instruments. However, at the level of accuracy envisioned by the more ambitious projects such as the Astrometric Imaging Telescope, current technology produces CCD's with significant pixel registration errors. We describe a technique for making high-precision measurements of relative pixel positions. We measured CCD's manufactured for the Wide Field Planetary Camera II installed in the Hubble Space Telescope. These CCD's are shown to have significant step-and-repeat errors of 0.033 pixel along every 34th row, as well as a 0.003-pixel curvature along 34-pixel stripes. The source of these errors is described. Our experiments achieved a per-pixel accuracy of 0.011 pixel. The ultimate shot-noise limited precision of the method is less than 0.001 pixel. PMID:21060522

Shaklan, S; Sharman, M C; Pravdo, S H

1995-10-10

100

Piping inspection instrument carriage with precise and repeatable position control and location determination  

DOEpatents

An instrument carriage for inspection of piping comprises front and rear leg assemblies for engaging the interior of the piping and supporting and centering the carriage therein, and an instrumentation arm carried by a shaft system running from the front to rear leg assemblies. The shaft system has a screw shaft for moving the arm axially and a spline gear for moving the arm azimuthally. The arm has a pair of air cylinders that raise and lower a plate in the radial direction. On the plate are probes including an eddy current probe and an ultrasonic testing probe. The ultrasonic testing probe is capable of spinning 360[degree] about its axis. The instrument carriage uses servo motors and pressurized air cylinders for precise actuation of instrument components and precise, repeatable actuation of position control mechanisms. 8 figures.

Hapstack, M.; Talarek, T.R.; Zollinger, W.T.; Heckendorn, F.M. II; Park, L.R.

1994-02-15

101

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

SciTech Connect

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.

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

1990-04-01

102

Harmonic Oscillators, Heisenberg's Uncertainty Principle and Simultaneous Measurement Precision for Position and Momentum  

E-print Network

There is no question as to the validity of Heisenberg's uncertainty principle, which follows from an abstract analysis of the tenets of quantum mechanics. Herein, however, we reconsider the implications of Heisenberg's Uncertainty Principle for the simultaneous measurement of position and momentum. We show that one can, with a suitable modification of the Fourier transform (which reflects the specifics of the system mass and force constant), obtain a data analysis kernel that enables one to improve significantly the simultaneous measurement precision for position and momentum for the particular harmonic oscillator under study. Our results show that 1) the simultaneous precision for measuring the position and the corresponding momentum depends on the physical parameters of the harmonic oscillator under study 2) one can simultaneously squeeze coherent states by the same amount in both x and wave number, k. The results also suggest that each physical system may, in fact, determine its own optimum transform between representations of non-commuting observables so as to decrease their simultaneous measurement uncertainty limit.

Donald J. Kouri

2014-09-16

103

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

NASA Astrophysics Data System (ADS)

A subroutine for a very-high-precision numerical solution of a class of ordinary differential equations is provided. For a given evaluation point and equation parameters the memory requirement scales linearly with precision P, and the number of algebraic operations scales roughly linearly with P when P becomes sufficiently large. We discuss results from extensive tests of the code, and how one, for a given evaluation point and equation parameters, may estimate precision loss and computing time in advance. Program summary Program title: seriesSolveOde1 Catalogue identifier: AEMW_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEMW_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 991 No. of bytes in distributed program, including test data, etc.: 488116 Distribution format: tar.gz Programming language: C++ Computer: PC's or higher performance computers. Operating system: Linux and MacOS RAM: Few to many megabytes (problem dependent). Classification: 2.7, 4.3 External routines: CLN — Class Library for Numbers [1] built with the GNU MP library [2], and GSL — GNU Scientific Library [3] (only for time measurements). Nature of problem: The differential equation -s2({d2}/{dz2}+{1-?+-?-}/{z}{d}/{dz}+{?+?-}/{z2})?(z)+{1}/{z} ?n=0N vnzn?(z)=0, is solved numerically to very high precision. The evaluation point z and some or all of the equation parameters may be complex numbers; some or all of them may be represented exactly in terms of rational numbers. Solution method: The solution ?(z), and optionally ?'(z), is evaluated at the point z by executing the recursion A(z)={s-2}/{(m+1+?-?+)(m+1+?-?-)} ?n=0N Vn(z)A(z), ?(z)=?(z)+A(z), to sufficiently large m. Here ? is either ?+ or ?-, and Vn(z)=vnz. The recursion is initialized by A(z)=?z?,for n=0,1,…,N ?(z)=A0(z). Restrictions: No solution is computed if z=0, or s=0, or if ?=?- (assuming Re?+?Re?-) with ?+-?- an integer, except when ?+-?-=1 and v =0 (i.e. when z is an ordinary point for z?(z)). Additional comments: The code of the main algorithm is in the file seriesSolveOde1.cc, which "#include" the file checkForBreakOde1.cc. These routines, and the programs using them, must "#include" the file seriesSolveOde1.cc. Running time: On a Linux PC that is a few years old, at y=?{10} to an accuracy of P=200 decimal digits, evaluating the ground state wavefunction of the anharmonic oscillator (with the eigenvalue known in advance); (cf. Eq. (6)) takes about 2 ms, and about 40 min at an accuracy of P=100000 decimal digits. References: [1] B. Haible and R.B. Kreckel, CLN — Class Library for Numbers, http://www.ginac.de/CLN/ [2] T. Granlund and collaborators, GMP — The GNU Multiple Precision Arithmetic Library, http://gmplib.org/ [3] M. Galassi et al., GNU Scientific Library Reference Manual (3rd Ed.), ISBN 0954612078., http://www.gnu.org/software/gsl/

Noreen, Amna; Olaussen, Kåre

2012-10-01

104

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

105

The Feasibility of the Disturbance Accommodating Controller for Precision Antenna Pointing  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

106

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

107

Positional cranial deformity-the parents' point of view.  

PubMed

The parents' point of view regarding positional cranial deformities and helmet therapy has not been the subject of scientific interest yet. However, carer acceptance is a key factor for therapeutic success. We therefore investigated parental perception. The parents of 218 infants were included in a telephone survey; 122 children had undergone helmet therapy and 96 had not. Satisfaction with the outcome, treatment-associated problems, and parental stress were investigated using a structured questionnaire. The great majority (90.8%) of caregivers were satisfied with the outcome, regardless of whether or not helmet therapy was used. Retrospectively, 76% of the parents of infants who had not undergone helmet therapy would decide against helmet therapy again. Therapy was either temporarily stopped (27.0%) or terminated (4.9%) in 31.9% of infants treated with a helmet. Major problems were sweating (51.1%) and skin lacerations (30.9%). The parents indicated minor (54.9%) or even great (25.4%) personal strain. Conflict with others (38.5%), stress for the child (30.3%), and a financial burden (36.9%) were mentioned most frequently. There appear to be more parental problems than expected associated with helmet therapy. Medical experts should take this into consideration. The indication for a helmet should be evaluated critically and the potential parental burdens should be addressed during counselling. PMID:25457830

Kluba, S; Lypke, J; Kraut, W; Peters, J P; Calgeer, B; Haas-Lude, K; Krimmel, M; Reinert, S

2015-01-01

108

Accounting for Galileo–GPS inter-system biases in precise satellite positioning  

NASA Astrophysics Data System (ADS)

Availability of two overlapping frequencies L1/E1 and L5/E5a of the signals transmitted by GPS and Galileo systems offers the possibility of tightly combining observations from both systems in a single observational model. A tightly combined observational model assumes a single reference satellite for all observations from both Galileo and GPS systems. However, when inter-system double-differenced observations are created, receiver inter-system bias is introduced. This study presents the results and the methodology for estimation and accounting for phase and code GPS-Galileo inter-system bias in precise relative positioning. The research investigates the size and temporal stability of the estimated bias for different receiver pairs as well as examines the influence of accounting for the inter-system bias on the user position solution. The obtained numerical results are based on four experiments carried out at different locations and time periods using both real and simulated GNSS data.

Paziewski, Jacek; Wielgosz, Pawel

2015-01-01

109

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

PubMed Central

Miniaturization precision positioning platforms are needed for in situ nanomechanical test applications. This paper proposes a compact precision positioning platform integrating strain gauges and the piezoactuator. Effects of geometric parameters of two parallel plates on Von Mises stress distribution as well as static and dynamic characteristics of the platform were studied by the finite element method. Results of the calibration experiment indicate that the strain gauge sensor has good linearity and its sensitivity is about 0.0468 mV/?m. A closed-loop control system was established to solve the problem of nonlinearity of the platform. Experimental results demonstrate that for the displacement control process, both the displacement increasing portion and the decreasing portion have good linearity, verifying that the control system is available. The developed platform has a compact structure but can realize displacement measurement with the embedded strain gauges, which is useful for the closed-loop control and structure miniaturization of piezo devices. It has potential applications in nanoindentation and nanoscratch tests, especially in the field of in situ nanomechanical testing which requires compact structures. PMID:23012566

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

2012-01-01

110

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

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

111

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

Microsoft Academic Search

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

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

2005-01-01

112

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

SciTech Connect

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

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

1995-05-01

113

A 145-base pair DNA sequence that positions itself precisely and asymmetrically on the nucleosome core.  

PubMed Central

A 145-bp DNA sequence, cloned from Escherichia coli, was reconstituted into nucleosome core particles by a number of methods. The behaviour of the resulting complex upon sucrose gradient sedimentation and nucleoprotein gel electrophoresis closely resembled that of control bulk nucleosome core particles. DNase I digestion of the 32P-end-labelled complex revealed the 10-bp periodicity of cleavages expected for DNA bound on a histone surface. The narrow cleavage sites observed (1 bp wide) imply that the sequence occupies a single preferred position on the nucleosome core, accurate to the level of single base pairs. By relating the digestion pattern observed to the pattern of site protection found for random sequence nucleosomes, the DNA position was found to be offset by 17 bp from that in the normal core particle. A number of experiments argue against the involvement of length or end effects and suggest that it is some feature of the DNA sequence itself that determines this precise positioning of DNA on the nucleosome. Images Fig. 3. Fig. 4. Fig. 5. PMID:6096135

Ramsay, N; Felsenfeld, G; Rushton, B M; McGhee, J D

1984-01-01

114

Deterministic delivery of externally cold and precisely positioned single molecular ions  

E-print Network

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

G. Leschhorn; S. Kahra; T. Schaetz

2011-10-19

115

Precision feature point tracking method using a drift-correcting template update strategy  

NASA Astrophysics Data System (ADS)

We present a drift-correcting template update strategy for precisely tracking a feature point in 2D image sequences in this paper. The proposed strategy greatly extends Matthews et al's template tracking strategy [I. Matthews, T. Ishikawa and S. Baker, The template update problem, IEEE Trans. PAMI 26 (2004) 810-815.] by incorporating a robust non-rigid image registration step used in medical imaging. Matthews et al's strategy uses the first template to correct drifts in the current template; however, the drift would still build up if the first template becomes quite different from the current one as the tracking continues. In our strategy the first template is updated timely when it is quite different from the current one, and henceforth the updated first template can be used to correct template drifts in subsequent frames. The method based on the proposed strategy yields sub-pixel accuracy tracking results measured by the commercial software REALVIZ(R) MatchMover(R) Pro 4.0. Our method runs fast on a desktop PC (3.0 GHz Pentium(R) IV CPU, 1GB RAM, Windows(R) XP professional operating system, Microsoft Visual C++ 6.0 (R) programming), using about 0.03 seconds on average to track the feature point in a frame (under the assumption of a general affine transformation model, 61×61 pixels in template size) and when required, less than 0.1 seconds to update the first template. We also propose the architecture for implementing our strategy in parallel.

Peng, Xiaoming; Ma, Qian; Zhang, Qiheng; Chen, Wufan; Xu, Zhiyong

2009-02-01

116

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

NASA Astrophysics Data System (ADS)

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.

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

2012-07-01

117

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

E-print Network

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

Andersen, Richard

118

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

NASA Astrophysics Data System (ADS)

In this paper the design, modeling and fabrication of a precision MEMS-based clamp with a relatively large clamping force are presented. The purpose of the clamp is to mechanically fix a six-degree-of-freedom (DOF) MEMS-based sample manipulator (Brouwer et al J. Int. Soc. Precis. Eng. Nanotechnol. submitted) once the sample has been positioned in all DOFs. The clamping force is generated by a rotational electrostatic comb-drive actuator and can be latched passively by a parallel plate type electrostatically driven locking device. The clamp design is based on the principles of exact constraint design, resulting in a high actuation compliance (flexibility) combined with a high suspension stiffness. Therefore, a relatively large blocking force of 1.4 mN in relation to the used area of 1.8 mm2 is obtained. The fabrication is based on silicon bulk micromachining technology and combines a high-aspect-ratio deep reactive ion etching (DRIE), conformal deposition of low-pressure chemical vapor deposition (LPCVD) silicon nitride and an anisotropic potassium hydroxide (KOH) backside etching technology. Special attention is given to void reduction of SixNy trench isolation and reduction of heating phenomena during front-side release etching. Guidelines are given for the applied process. Measurements showed that the clamp was able to fix, hold and release a test actuator. The dynamic behavior was in good agreement with the modal analysis.

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

2009-06-01

119

Airborne vector gravimetry using precise, position-aided inertial measurement units  

NASA Astrophysics Data System (ADS)

Vector gravimetry using a precise inertial navigation system continually updated with external position data, for example using GPS, is studied with respect to two problems. The first concerns the attitude accuracy requirement for horizontal gravity component estimation. With covariance analyses in the space and frequency domains it is argued that with relatively stable uncompensated gyro drift, the short-wavelength gravity vector can be estimated without the aid of external attitude updates. The second problem concerns the state-space estimation of the gravity signal where considerable approximations must be assumed in the gravity model in order to take advantage of the ensemble error estimation afforded by the Kalman filter technique. Gauss-Markov models for the gravity field are specially designed to reflect the attenuation of the signal at a specific altitude and the omission of the long-wavelength components from the estimation. With medium accuracy INS/GPS systems, the horizontal components of gravity with wavelengths shorter than 250 km should be estimable to an accuracy of 4-6 mgal (µg); while high accuracy systems should yield an improvement to 1-2 mgal.

Jekeli, Christopher

1994-03-01

120

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

NASA Astrophysics Data System (ADS)

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.

Kyae, Bumseok; Shin, Chang Sub

2014-08-01

121

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

NASA Astrophysics Data System (ADS)

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.

Sama, Michael Patrick

122

High Precision Point-To-Point Maneuvering of an Experimental Structure Subject To Friction Via Adaptive Impulsive Control.  

E-print Network

. Positioning apparatuses include telescopes, anten- nas, machine tools, disk drives and robot arm positioning. Velocity control is also relevant in machine tool, disk drive and robot arm industrial applications which control [3], PID and state feedback linearization control [4] and variable structure control in order

Singh, Tarunraj

123

A Kalman filter implementation for precision improvement in low-cost GPS positioning of tractors.  

PubMed

Low-cost GPS receivers provide geodetic positioning information using the NMEA protocol, usually with eight digits for latitude and nine digits for longitude. When these geodetic coordinates are converted into Cartesian coordinates, the positions fit in a quantization grid of some decimeters in size, the dimensions of which vary depending on the point of the terrestrial surface. The aim of this study is to reduce the quantization errors of some low-cost GPS receivers by using a Kalman filter. Kinematic tractor model equations were employed to particularize the filter, which was tuned by applying Monte Carlo techniques to eighteen straight trajectories, to select the covariance matrices that produced the lowest Root Mean Square Error in these trajectories. Filter performance was tested by using straight tractor paths, which were either simulated or real trajectories acquired by a GPS receiver. The results show that the filter can reduce the quantization error in distance by around 43%. Moreover, it reduces the standard deviation of the heading by 75%. Data suggest that the proposed filter can satisfactorily preprocess the low-cost GPS receiver data when used in an assistance guidance GPS system for tractors. It could also be useful to smooth tractor GPS trajectories that are sharpened when the tractor moves over rough terrain. PMID:24217355

Gomez-Gil, Jaime; Ruiz-Gonzalez, Ruben; Alonso-Garcia, Sergio; Gomez-Gil, Francisco Javier

2013-01-01

124

A Kalman Filter Implementation for Precision Improvement in Low-Cost GPS Positioning of Tractors  

PubMed Central

Low-cost GPS receivers provide geodetic positioning information using the NMEA protocol, usually with eight digits for latitude and nine digits for longitude. When these geodetic coordinates are converted into Cartesian coordinates, the positions fit in a quantization grid of some decimeters in size, the dimensions of which vary depending on the point of the terrestrial surface. The aim of this study is to reduce the quantization errors of some low-cost GPS receivers by using a Kalman filter. Kinematic tractor model equations were employed to particularize the filter, which was tuned by applying Monte Carlo techniques to eighteen straight trajectories, to select the covariance matrices that produced the lowest Root Mean Square Error in these trajectories. Filter performance was tested by using straight tractor paths, which were either simulated or real trajectories acquired by a GPS receiver. The results show that the filter can reduce the quantization error in distance by around 43%. Moreover, it reduces the standard deviation of the heading by 75%. Data suggest that the proposed filter can satisfactorily preprocess the low-cost GPS receiver data when used in an assistance guidance GPS system for tractors. It could also be useful to smooth tractor GPS trajectories that are sharpened when the tractor moves over rough terrain. PMID:24217355

Gomez-Gil, Jaime; Ruiz-Gonzalez, Ruben; Alonso-Garcia, Sergio; Gomez-Gil, Francisco Javier

2013-01-01

125

Displaying Correlations using Position, Motion, Point Size or Point Colour Serge Limoges  

E-print Network

but quite sensitive to the correlation of phase angle. Some of the potential advantages and disadvantages Ware William Knight School of Computer Science University of New Brunswick P.O. Box 4400 Fredericton if a three dimensional cloud of points is rotated and projected onto a flat screen, their three dimensional

Ware, Colin

126

High Precision Pointing of the 16" LX200 GPS U sing TheSky and TPoint  

E-print Network

with the current TPoint model. To do this: 1. Point the telescope to a bright star that is in its internal that allows pointing analysis and improvement for computer controlled telescopes. TPoint allows this improvement by fitting the telescope pointing errors to a geometric equation with six degrees of freedom

Natelson, Douglas

127

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

E-print Network

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 ...

Garretson, Justin R. (Justin Richard)

2005-01-01

128

Precise GPS\\/Acoustic positioning of seafloor reference points for tectonic studies  

Microsoft Academic Search

Global networks for crustal strain measurement provide important constraints for studies of tectonic plate motion and deformation. To date, crustal strain measurements have been possible only in terrestrial settings: on continental plates and island sites within oceanic plates. We report the development of technology for horizontal crustal motion determination at seafloor sites, allowing oceanic plates to be monitored where islands

Fred N Spiess; C. David Chadwell; John A Hildebrand; Larry E Young; George H Purcell; Herb Dragert

1998-01-01

129

Precise GPS/Acoustic Positioning of Seafloor Reference Points for Tectonic Studies  

NASA Technical Reports Server (NTRS)

Global networks for crustal strain measurement provide important constraints for studies of tectonic plate motion and deformation. To date, crustal strain measurements have been possible only in terrestrial settings: on continental plates and island sites within oceanic plates.

Spiess, F. N.; Chadwell, C.; Hildebrand, J. A.; Young, L. E.; Purcell, G. H., Jr.; Dragert, H.

1998-01-01

130

Precision pointing compensation for DSN antennas with optical distance measuring sensors  

NASA Technical Reports Server (NTRS)

The pointing control loops of Deep Space Network (DSN) antennas do not account for unmodeled deflections of the primary and secondary reflectors. As a result, structural distortions due to unpredictable environmental loads can result in uncompensated boresight shifts which degrade pointing accuracy. The design proposed here can provide real-time bias commands to the pointing control system to compensate for environmental effects on pointing performance. The bias commands can be computed in real time from optically measured deflections at a number of points on the primary and secondary reflectors. Computer simulations with a reduced-order finite-element model of a DSN antenna validate the concept and lead to a proposed design by which a ten-to-one reduction in pointing uncertainty can be achieved under nominal uncertainty conditions.

Scheid, R. E.

1989-01-01

131

The effects of atmospheric turbulence on precision optical measurements used for antenna-pointing compensation  

NASA Technical Reports Server (NTRS)

Blind pointing of the Deep Space Network (DSN) 70-meter antennas can be improved if distortions of the antenna structure caused by unpredictable environmental loads can be measured in real-time, and the resulting boresight shifts evaluated and incorporated into the pointing control loops. The measurement configuration of a proposed pointing compensation system includes an optical range sensor that measures distances to selected points on the antenna surface. The effect of atmospheric turbulence on the accuracy of optical distance measurements and a method to make in-situ determinations of turbulence-induced measurement errors are discussed.

Nerheim, N.

1989-01-01

132

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

Microsoft Academic Search

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

Raymond Moberly; Michael O'Sullivan; Khurram Waheed

2007-01-01

133

Tangential derivative of singular boundary integrals with respect to the position of collocation points1  

E-print Network

words: sensitivity analysis, singular boundary integral equations, hypersingular integrals, boundaryTangential derivative of singular boundary integrals with respect to the position of collocation perturbations of the singular point, of boundary integrals having either weak or strong singularity. Both scalar

Paris-Sud XI, Université de

134

Double Precision Hybrid-Mode Floating-Point FPGA CORDIC Coprocessor  

Microsoft Academic Search

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

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

2008-01-01

135

Precise positioning with current multi-constellation Global Navigation Satellite Systems: GPS, GLONASS, Galileo and BeiDou.  

PubMed

The world of satellite navigation is undergoing dramatic changes with the rapid development of multi-constellation Global Navigation Satellite Systems (GNSSs). At the moment more than 70 satellites are already in view, and about 120 satellites will be available once all four systems (BeiDou + Galileo + GLONASS + GPS) are fully deployed in the next few years. This will bring great opportunities and challenges for both scientific and engineering applications. In this paper we develop a four-system positioning model to make full use of all available observations from different GNSSs. The significant improvement of satellite visibility, spatial geometry, dilution of precision, convergence, accuracy, continuity and reliability that a combining utilization of multi-GNSS brings to precise positioning are carefully analyzed and evaluated, especially in constrained environments. PMID:25659949

Li, Xingxing; Zhang, Xiaohong; Ren, Xiaodong; Fritsche, Mathias; Wickert, Jens; Schuh, Harald

2015-01-01

136

Precise positioning with current multi-constellation Global Navigation Satellite Systems: GPS, GLONASS, Galileo and BeiDou  

PubMed Central

The world of satellite navigation is undergoing dramatic changes with the rapid development of multi-constellation Global Navigation Satellite Systems (GNSSs). At the moment more than 70 satellites are already in view, and about 120 satellites will be available once all four systems (BeiDou + Galileo + GLONASS + GPS) are fully deployed in the next few years. This will bring great opportunities and challenges for both scientific and engineering applications. In this paper we develop a four-system positioning model to make full use of all available observations from different GNSSs. The significant improvement of satellite visibility, spatial geometry, dilution of precision, convergence, accuracy, continuity and reliability that a combining utilization of multi-GNSS brings to precise positioning are carefully analyzed and evaluated, especially in constrained environments. PMID:25659949

Li, Xingxing; Zhang, Xiaohong; Ren, Xiaodong; Fritsche, Mathias; Wickert, Jens; Schuh, Harald

2015-01-01

137

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

Microsoft Academic Search

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

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

1990-01-01

138

Impact of Footprint Diameter and Off-Nadir Pointing on the Precision of Canopy Height Estimates from Spaceborne Lidar  

NASA Technical Reports Server (NTRS)

A spaceborne lidar mission could serve multiple scientific purposes including remote sensing of ecosystem structure, carbon storage, terrestrial topography and ice sheet monitoring. The measurement requirements of these different goals will require compromises in sensor design. Footprint diameters that would be larger than optimal for vegetation studies have been proposed. Some spaceborne lidar mission designs include the possibility that a lidar sensor would share a platform with another sensor, which might require off-nadir pointing at angles of up to 16 . To resolve multiple mission goals and sensor requirements, detailed knowledge of the sensitivity of sensor performance to these aspects of mission design is required. This research used a radiative transfer model to investigate the sensitivity of forest height estimates to footprint diameter, off-nadir pointing and their interaction over a range of forest canopy properties. An individual-based forest model was used to simulate stands of mixed conifer forest in the Tahoe National Forest (Northern California, USA) and stands of deciduous forests in the Bartlett Experimental Forest (New Hampshire, USA). Waveforms were simulated for stands generated by a forest succession model using footprint diameters of 20 m to 70 m. Off-nadir angles of 0 to 16 were considered for a 25 m diameter footprint diameter. Footprint diameters in the range of 25 m to 30 m were optimal for estimates of maximum forest height (R(sup 2) of 0.95 and RMSE of 3 m). As expected, the contribution of vegetation height to the vertical extent of the waveform decreased with larger footprints, while the contribution of terrain slope increased. Precision of estimates decreased with an increasing off-nadir pointing angle, but off-nadir pointing had less impact on height estimates in deciduous forests than in coniferous forests. When pointing off-nadir, the decrease in precision was dependent on local incidence angle (the angle between the off-nadir beam and a line normal to the terrain surface) which is dependent on the off-nadir pointing angle, terrain slope, and the difference between the laser pointing azimuth and terrain aspect; the effect was larger when the sensor was aligned with the terrain azimuth but when aspect and azimuth are opposed, there was virtually no effect on R2 or RMSE. A second effect of off-nadir pointing is that the laser beam will intersect individual crowns and the canopy as a whole from a different angle which had a distinct effect on the precision of lidar estimates of height, decreasing R2 and increasing RMSE, although the effect was most pronounced for coniferous crowns.

Pang, Yong; Lefskky, Michael; Sun, Guoqing; Ranson, Jon

2011-01-01

139

Precision telescope pointing and spacecraft vibration isolation for the Terrestrial Planet Finder Coronagraph  

Microsoft Academic Search

The Terrestrial Planet Finder Coronagraph is a visible-light coronagraph to detect planets that are orbiting within the Habitable Zone of stars. The coronagraph instrument must achieve a contrast ratio stability of 2e-11 in order to achieve planet detection. This places stringent requirements on several spacecraft subsystems, such as pointing stability and structural vibration of the instrument in the presence of

Larry Dewell; Nelson Pedreiro; Carl Blaurock; Kuo-Chia Liu; James Alexander; Marie Levine

2005-01-01

140

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

NASA Astrophysics Data System (ADS)

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.

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

2003-12-01

141

Measuring precise sea level from a buoy using the Global Positioning System  

NASA Technical Reports Server (NTRS)

The feasibility of using the Global Positioning System (GPS) for accurate sea surface positioning was examined. An experiment was conducted on the Scripps pier at La Jolla, California from December 13-15, 1989. A GPS-equipped buoy was deployed about 100 m off the pier. Two fixed reference GPS receivers, located on the pier and about 80 km away on Monument Peak, were used to estimate the relative position of the floater. Kinematic GPS processing software, developed at the National Geodetic Survey, and the Jet Propulsion Laboratory's GPS Infrared Processing System software were used to determine the floater position relative to land-fixing receivers. Calculations were made of sea level and ocean wave spectra from GPS measurements. It is found that the 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.

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

1990-01-01

142

Design and precision construction of novel magnetic-levitation-based multi-axis nanoscale positioning systems  

Microsoft Academic Search

This paper presents two novel six-axis magnetic-levitation (maglev) stages capable of nanoscale positioning. These stages have very simple and compact structures, which is advantageous to meet the demanding positioning requirements of next-generation nanomanipulation and nanomanufacturing. Six-axis motion generation is accomplished by the minimum number of actuators and sensors. The first-generation maglev stage, namely the ?-stage, is capable of generating translation

Won-jong Kim; Shobhit Verma; Huzefa Shakir

2007-01-01

143

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

Microsoft Academic Search

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 1–45GeV electron beam. The crystals were coupled to photomultiplier tubes. The dependence of energy and position resolutions on different factors as

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

2003-01-01

144

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

145

Precisely positioned light-induced self-written (LISW) polymeric optical waveguide for optical transceiver module fabrication  

NASA Astrophysics Data System (ADS)

Plastic optical fibers (POFs) are beginning to replace electrical wiring in many automotive and home applications. In view of this, we have reported the inexpensive wavelength-division-multiplexing (WDM) device for POF system using the LISW waveguide. The LISW waveguides are an attractive and a low-cost process for realizing self alignment between a POF and a waveguide. In this study, we have investigated about the method for precisely aligned LISW polymeric optical waveguides by using an "optical solder" effect. The "optical solder" effect makes it possible to realize a waveguide connection between two faced optical fibers by radiating from both sides even if a significant gap and a small degree of misalignment exist. When we utilize POFs with core diameters of 700?m, waveguides are combinable on the condition that an offset is 700?m or less and a gap is from 6mm to 13mm. By applying this effect, we fabricated precisely positioned LISW waveguides for optical devices. The fiber ends were set at certain mounting positions with respect to the LEDs and PDs. And we evaluated the positioning accuracy. The resulting positional accuracy at the extremities of the optical waveguides is less than one-tenth of the optical fiber core diameter. This value is sufficiently accurate to realize passive alignment. And this result creates new possibilities for boosting the yield of optical modules in mass-production.

Matsui, T.; Yamashita, T.; Kagami, M.

2006-10-01

146

FPGA Implementation of a Best-Precision Fixed-Point Digital PID Controller  

Microsoft Academic Search

Proportional-integral-derivative (PID) controllers have been broadly used in many areas. Compared with analog controllers, digital ones by digital signal processor (DSP) or field programmable gate arrays (FPGA) are more stable and easier to adjust parameter. Digital controllers are usually implemented with FPGA for its fast and stable performance. When it is implemented with FPGA, floating-point arithmetic is usually converted to

Yankai Xu; Kai Shuang; Shan Jiang; Xiaoliang Wu

2009-01-01

147

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

NASA Technical Reports Server (NTRS)

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

Lynch, Dana H. (inventor); Gunter, William D. (inventor); Mcalister, Kenneth W. (inventor)

1991-01-01

148

Improvement of a geodetic triangulation through control points established by means of satellite or precision traversing  

NASA Technical Reports Server (NTRS)

Whether any significant increment to accuracy could be transferred from a super-control continental net (continental satellite net or super-transcontinental traverse) to the fundamental geodetic net (first-order triangulation) is discussed. This objective was accomplished by evaluating the positional accuracy improvement for a triangulation station, which is near the middle of the investigated geodetic triangulation net, by using various station constraints over its geodetic position. This investigation on a 1858 kilometer long triangulation chain shows that the super-control net can provide a useful constraint to the investigated geodetic triangulation net, and thus can improve it only when the accuracy of super-control net is at least 1 part in 500,000.

Saxena, N. K.

1972-01-01

149

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

SciTech Connect

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

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

1990-11-01

150

Deploying a Locata network to enable precise positioning in urban canyons  

NASA Astrophysics Data System (ADS)

Locata is a new positioning technology developed by the Locata Corporation. At the beginning of 2007, the Institute of Engineering Surveying and Space Geodesy (IESSG) bought and received a network of Locata transceivers with two rovers. The purpose is to solve the challenges identified when surveying in dense multipath areas (i.e. urban canyons). In this paper, the technology is tested in an urban canyon scenario on the University park at the University of Nottingham. By comparing Locata position solutions with the true positions calculated with a total station and a carrier-phase GPS, the results show that centimetre-level accuracy is achievable in difficult environments in the presence of Wi-Fi signals. The rover’s estimated coordinates may diverge in some cases. Finally, a comparison study shows that Real Time Kinematic GPS and Locata technologies have similar accuracy when both are available.

Montillet, J.-P.; Roberts, G. W.; Hancock, C.; Meng, X.; Ogundipe, O.; Barnes, J.

2009-02-01

151

Beeline RT20 - a Compact, Medium Precision Positioning system with an  

Microsoft Academic Search

Methods that transform phase differences to vehicle orientation are well known in the GPS community. These generally involve some combination of phase measured at multiple antenna\\/receivers such that the phase data from the various receivers is combined and used to generate attitude in an external processor. Usually these systems generate attitude as their primary function and pseudo range position as

Tom Ford; Waldemar Kunysz; Rod Morris; Janet Neumann; Jim Rooney

152

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

Microsoft Academic Search

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

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

1992-01-01

153

The study of precision positions of five planets for shoushi-datong calendar  

NASA Astrophysics Data System (ADS)

Shoushi-Datong calendar is a very important ancient Chinese astronomical calendar,it was applied for over 380 years in the Chinese history. It is introduced to calculate principle and method for the positions of five planets by Shoushi-Datong. It is analysed to produce the reasons for actual motion's errors of five planets computed by Shoushi-Datong calendar. It is discussed to calculate ``ying suo cha'' by Shoushi-Datong calendar and ``centre difference'' by modern astronomy. The daily positions of the five planets (1531) are computed by Shoushi-Datong calendar and modern astronomical method respectively. The computational results are studied by comparative analysis of the mean and actual motion of five planets such as synodic period, backward movement and angular velocity of coition or opposition act.The quantitative analysis are given in this paper.

Zhang, J.

2008-04-01

154

The study of precision positions of five planets for shoushi-datong calendar  

Microsoft Academic Search

Shoushi-Datong calendar is a very important ancient Chinese astronomical calendar,it was applied for over 380 years in the Chinese history. It is introduced to calculate principle and method for the positions of five planets by Shoushi-Datong. It is analysed to produce the reasons for actual motion's errors of five planets computed by Shoushi-Datong calendar. It is discussed to calculate ``ying

J. Zhang

2008-01-01

155

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

Microsoft Academic Search

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

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

156

Precise station positions from VLBI observations to satellites: a simulation study  

NASA Astrophysics Data System (ADS)

Very long baseline interferometry (VLBI) tracking of satellites is a topic of increasing interest for the establishment of space ties. This shall strengthen the connection of the various space geodetic techniques that contribute to the International Terrestrial Reference Frame. The concept of observing near-Earth satellites demands research on possible observing strategies. In this paper, we introduce this concept and discuss its possible benefits for improving future realizations of the International Terrestrial Reference System. Using simulated observations, we develop possible observing strategies that allow the determination of radio telescope positions in the satellite system on Earth with accuracies of a few millimeters up to 1-2 cm for weekly station coordinates. This is shown for satellites with orbital heights between 2,000 and 6,000 km, observed by dense regional as well as by global VLBI-networks. The number of observations, as mainly determined by the satellite orbit and the observation interval, is identified as the most critical parameter that affects the expected accuracies. For observations of global positioning system satellites, we propose the combination with classical VLBI to radio sources or a multi-satellite strategy. Both approaches allow station position repeatabilities of a few millimeters for weekly solutions.

Plank, Lucia; Böhm, Johannes; Schuh, Harald

2014-07-01

157

Distributed position-adaptive UAV radar concepts for building geometries with multiple signal-leakage points  

Microsoft Academic Search

Distributed airborne sensor geometries are considered that are comprised of multiple radar\\/comm transmit and receive nodes. Under this distributed robotic sensor concept, each of these radar transmit\\/receive nodes position-adaptively converge to the vicinity of a signal leakage point. A number of signal leakage point geometries are investigated that conform to geometries for typical building-type structures. The results include a set

Atindra K. Mitra

2006-01-01

158

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

E-print Network

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.

Allan Tameshtit

2012-04-09

159

Dilution of Precision-Based Lunar Navigation Assessment for Dynamic Position Fixing  

NASA Technical Reports Server (NTRS)

The NASA Vision for Space Exploration is focused on the return of astronauts to the Moon. While navigation systems have already been proven in the Apollo missions to the moon, the current exploration campaign will involve more extensive and extended missions requiring new concepts for lunar navigation. In contrast to Apollo missions, which were limited to the near-side equatorial region of the moon, missions under the Exploration Systems Initiative will require navigation on the moon's limb and far-side. As these regions have poor Earth visibility, a navigation system comprised solely of Earth-based tracking stations will not provide adequate navigation solutions in these areas. In this paper, a Dilution of Precision (DoP) based analysis of the performance of a network of Moon orbiting satellites is provided. The analysis extends previous analysis of a Lunar Network (LN) of navigation satellites by providing an assessment of the capability associated with a variety of assumptions. These assumptions are with regard to the navigation receiver and satellite visibility. The assessment is accomplished by making appropriately formed estimates of DoP. Different adaptations of DoP (i.e., GDoP, PDoP, etc.) are associated with a different set of assumptions regarding augmentations to the navigation receiver or transceiver.

Sands, Obed S.; Connolly, Joseph W.; Welch, Bryan W.; Carpenter, James R.; Ely, Todd A.; Berry, Kevin

2006-01-01

160

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

NASA Technical Reports Server (NTRS)

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.

Colombo, Oscar L.

1989-01-01

161

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

162

Precise angular positioning at 6K: the FIFI-LS grating assembly  

NASA Astrophysics Data System (ADS)

The Field Imaging Far Infrared Line Spectrometer (FIFI-LS) obtains spectral data within two wavelength ranges. The observed wavelengths are set by rotating the two diffraction gratings to specific angles. This paper describes on the grating assemblies, designed to rotate and stabilize the gratings. First the assembly itself and its special environment inside FIFI-LS is explained. Then a method is layed out how to monitor the performance of the drive and how to detect upcoming failures before they happen. The last chapter is dedicated to first inflight measurements of the position stability of the grating.

Rebell, Felix; Raab, Walfried; Colditz, Sebastian; Beckmann, Simon; Bryant, Aaron; Fischer, Christian; Fumi, Fabio; Geis, Norbert; Hönle, Rainer; Klein, Randolf; Krabbe, Alfred; Looney, Leslie; Poglitsch, Albrecht; Ragan, Sarah; Savage, Maureen

2014-07-01

163

CIRCLE PATTERNS OF POSITIVELY WEIGHTED DELAUNAY TRIANGULATIONS AS CRITICAL POINTS OF THE  

E-print Network

CIRCLE PATTERNS OF POSITIVELY WEIGHTED DELAUNAY TRIANGULATIONS AS CRITICAL POINTS OF THE HYPERBOLIC is provided and the intersection angles between the potential circumscribed circles of the triangles of a Dalaunay triangulation gives the existence and uniqueness of what we could call an ideal circle pattern

Dimitrov, Nikolay

164

Pointed water vapor radiometer corrections for accurate Global Positioning System surveying  

Microsoft Academic Search

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

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

1993-01-01

165

Design of a precision etalon position control system for a cryogenic spectrometer  

NASA Technical Reports Server (NTRS)

The Upper Atmosphere Research Satellite (UARS) will be launched in 1988 to study the distribution of a series of trace elements in the upper atmosphere and to study atmospheric dynamics. The UARS carries on board a cryogenically cooled infrared spectrometer to measure the concentration of a series of chemical species that are important for understanding the ozone layer in the stratosphere. This device, known as the Cryogenic Limb Array Etalon Spectrometer (CLAES), uses a multiposition filter wheel combined with tilt-scanned Fabry Perot etalons to obtain the high resolution required for these experiments. The CLAES optical system is sealed in a dewar where it is maintained at cryogenic temperatures by a supply of solid hydrogen. Operating temperatures for CLAES range from 130 K at the entrance aperture to 13 K at the focal plane. The design and test of a special control system using a unique actuator concept to provide position and can control for the CLAES etalon are described. Results of performance tests at cryogenic temperatures simulating the CLAES on-orbit environment are discussed.

Aubrun, J. N.; Lorell, K. R.; Zacharie, D. F.; Thatcher, J. B.

1984-01-01

166

Research on acupuncture points and cortical functional activation position in cats by infrared imaging detection  

NASA Astrophysics Data System (ADS)

The research of the brain cognition is mainly to find out the activation position in brain according to the stimulation at present in the world. The research regards the animals as the experimental objects and explores the stimulation response on the cerebral cortex of acupuncture. It provides a new method, which can detect the activation position on the creatural cerebral cortex directly by middle-far infrared imaging. According to the theory of local temperature situation, the difference of cortical temperature maybe associate with the excitement of cortical nerve cells, the metabolism of local tissue and the local hemal circulation. Direct naked detection of temperature variety on cerebral cortex is applied by middle and far infrared imaging technology. So the activation position is ascertained. The effect of stimulation response is superior to other indirect methods. After removing the skulls on the head, full of cerebral cortex of a cat are exposed. By observing the infrared images and measuring the temperatures of the visual cerebral cortex during the process of acupuncturing, the points are used to judge the activation position. The variety in the cortical functional sections is corresponding to the result of the acupuncture points in terms of infrared images and temperatures. According to experimental results, we know that the variety of a cortical functional section is corresponding to a special acupuncture point exactly.

Chen, Shuwang; Sha, Zhanyou; Wang, Shuhai; Wen, Huanming

2007-12-01

167

Analytical expressions for position error in triangulation solution of point in space for several station configurations  

NASA Technical Reports Server (NTRS)

Analytical expressions are derived to first order for the rms position error in the triangulation solution of a point object in space for several ideal observation-station configurations. These expressions provide insights into the nature of the dependence of the rms position error on certain of the experimental parameters involved. The station geometries examined are: (1) the configuration of two arbitrarily located stations; (2) the symmetrical circular configuration of two or more stations with equal elevation angles; and (3) the circular configuration of more than two stations with equal elevation angles, when one of the stations is permitted to drift around the circle from its position of symmetry. The expressions for the rms position error are expressed as functions of the rms line-of-sight errors, the total number of stations of interest, and the elevation angles.

Long, S. A. T.

1974-01-01

168

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

PubMed Central

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

Hämmerle, Martin; Höfle, Bernhard

2014-01-01

169

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

PubMed

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

Hämmerle, Martin; Höfle, Bernhard

2014-01-01

170

Whole-body magnetic resonance imaging featuring moving table continuous data acquisition with high-precision position feedback.  

PubMed

A novel setup for whole-body MR imaging with moving table continuous data acquisition has been developed and evaluated. The setup features a manually positioned moving table platform with integrated phased-array surface radiofrequency coils. A high-precision laser position sensor was integrated into the system to provide real-time positional data that were used to compensate for nonlinear manual table translation. This setup enables continuous 2D and 3D whole-body data acquisition during table movement with surface coil image quality. The concept has been successfully evaluated with whole-body steady-state free precession (TrueFISP) anatomic imaging in five healthy volunteers. Seamless coronal and sagittal slices of continually acquired whole-body data during table movement were accurately reconstructed. The proposed strategy is potentially useful for a variety of applications, including whole-body metastasis screening, whole-body MR angiography, large field-of-view imaging in short bore systems, and for moving table applications during MR-guided interventions. PMID:16086302

Zenge, Michael O; Ladd, Mark E; Vogt, Florian M; Brauck, Katja; Barkhausen, Joerg; Quick, Harald H

2005-09-01

171

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

NASA Astrophysics Data System (ADS)

In this paper, we investigate the existence of positive solutions for the following nonlinear fractional semipositone boundary value problem: D0+?u(t) = -f(t,u),0point theorem in a cone, the existence of many positive solutions are obtained.

Al-Askar, Farah M.

2013-09-01

172

Tunable band gap near the Dirac point in nonlinear negative-zero-positive index metamaterial waveguide  

SciTech Connect

We make theoretical investigations of the nonlinear guided modes near the Dirac point (DP) in nonlinear negative-zero-positive index metamaterial (NZPIM) waveguide. When the nonlinearity is self-focusing, an asymmetric forbidden band exists near the DP that can be modulated by the strength of the nonlinearity. However, the self-defocusing nonlinearity can completely eliminate the asymmetric band gap. We also study the nonlinear surface waves in such nonlinear NZPIM waveguide. These results may predict analogous phenomena in nonlinear graphene.

Shen Ming; Ruan Linxu; Shi Jielong; Wang Qi [Department of Physics, Shanghai University, Shanghai 200444 (China); Wang Xinglin [Department of Applied Mathematics and Physics, Anhui Normal University, Wuhu 241000 (China)

2011-04-15

173

Point of impact : delivering mission essential supplies to the warfighter through the Joint Precision Airdrop System (JPADS)  

E-print Network

The Joint Precision Airdrop System (JPADS) exists to execute logistical resupply operations using fixed and rotary wing air in a safe, effective and precise manner in order to deliver supplies and equipment to intended ...

Eaton, Joshua A. N. (Joshua Andrew Norman)

2012-01-01

174

Steps toward a high precision solar rotation profile: Results from SDO/AIA coronal bright point data  

E-print Network

Coronal bright points (CBP) are ubiquitous small brightenings in the solar corona associated with small magnetic bipoles. We derive the solar differential rotation profile by tracing the motions of CBPs detected by the Atmospheric Imaging Assembly (AIA) instrument aboard the Solar Dynamics Observatory (SDO). We also investigate problems related to detection of coronal bright points resulting from instrument and detection algorithm limitations. To determine the positions and identification of coronal bright points we used a segmentation algorithm. A linear fit of their central meridian distance and latitude versus time was utilised to derive velocities. We obtained 906 velocity measurements in a time interval of only 2 days. The differential rotation profile can be expressed as $\\omega_{rot} = (14.47\\pm 0.10 + (0.6\\pm 1.0)\\sin^{2}(b) + (-4.7\\pm 1.7)\\sin^{4}(b))$\\degr day$^{-1}$. Our result is in agreement with other work and it comes with reasonable errors in spite of the very short time interval used. This wa...

Sudar, Davor; Brajša, Roman; Saar, Steven H

2015-01-01

175

Distributed position-adaptive UAV radar concepts for building geometries with multiple signal-leakage points  

NASA Astrophysics Data System (ADS)

Distributed airborne sensor geometries are considered that are comprised of multiple radar/comm transmit and receive nodes. Under this distributed robotic sensor concept, each of these radar transmit/receive nodes position-adaptively converge to the vicinity of a signal leakage point. A number of signal leakage point geometries are investigated that conform to geometries for typical building-type structures. The results include a set of electromagnetic computations that simulate the signal interaction and signal propagation between multiple leakage points. These signals are simulated via the modeling of materials that enclose "building-type" structures with a series of connected dielectric materials. For example, windows, walls, and doors are each modeled separately by a combination of suitable material properties. Signals from objects that are embedded within these "building-type" structures are also simulated via the development and application of appropriate geometrical and materials models. Analysis of the resulting simulated "leakage signals", that penetrate the surfaces of these "building-type" structures and are scattered from embedded objects within the indoor environment back to the simulated sensor-nodes in the outdoor environment, are presented. Interpretations of these results are included from a signal analysis perspective. These results also include approximate preliminary systems-type calculations with regard to this distributed position-adaptive UAV radar system concept. Potential applications are outdoor-to-indoor detection of objects-of-interest that are within a building via implementation of a intelligent multi-static sensor network.

Mitra, Atindra K.

2006-05-01

176

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...

177

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

178

Career inflection points of women who successfully achieved the hospital CEO position.  

PubMed

Women are significantly underrepresented in hospital CEO positions, and this gender disparity has changed little over the past few decades. The purpose of this study was to analyze the career trajectories of successful female healthcare executives to determine factors that generated inflections in their careers. Using qualitative research methodology, we studied the career trajectories of 20 women who successfully ascended into a hospital CEO position. Our findings revealed 25 inflection points related to education and training, experience, career management, family, networking, and mentorship and sponsorship. We found substantial differences in the career inflection points by functional background. Inflections were more pronounced early in the careers of women in healthcare management, while clinical and administrative support executives experienced more inflections later as they took on responsibilities outside of their professional roles. Only two inflections were common among all the executives: completing a graduate degree and obtaining experience as a chief operating officer. More importantly, our findings show that organizational support factors are critical for the career advancement of women. We conclude with recommendations for individuals in an effort to enhance their career trajectories. We also provide recommended activities for organizations to support the careers of women in healthcare leadership. PMID:25647957

Sexton, Donald W; Lemak, Christy Harris; Wainio, Joyce Anne

2014-01-01

179

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

Microsoft Academic Search

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

S. Malys; P. A. Jensen

1990-01-01

180

Precise positions and optical search for the 38 second X-ray pulsar near OAO 1653-40 and upper limit on X-ray emission from V861 Scorpii  

NASA Technical Reports Server (NTRS)

The region of the binary system V861 Scorpii, whose secondary has been suggested as a black hole candidate, was observed with the HEAO 1 X-ray observatory during an 8-hour pointed observation on September 4, 1978. An upper limit of 1.0 micro Jy (within three standard deviations) is placed on X-ray emission from V861 Sco during this observation. This effectively removes the secondary from the list of black hole candidates. The presence of a 38 sec pulsar in the region is confirmed, precise (0.63 sq arcmin) positions are given, and a search for the optical counterpart is described.

Armstrong, J. T.; Johnston, M. D.; Bradt, H. V.; Doxsey, R. E.; Cowley, A. P.; Griffiths, R. E.; Hesser, J. E.; Schwartz, D. A.

1980-01-01

181

Combined micrococcal nuclease and exonuclease III digestion reveals precise positions of the nucleosome core/linker junctions: implications for high-resolution nucleosome mapping.  

PubMed

Micrococcal nuclease (MNase) is extensively used in genome-wide mapping of nucleosomes but its preference for AT-rich DNA leads to errors in establishing precise positions of nucleosomes. Here, we show that the MNase digestion of nucleosomes assembled on a strong nucleosome positioning sequence, Widom's clone 601, releases nucleosome cores whose sizes are strongly affected by the linker DNA sequence. Our experiments produced nucleosomal DNA sizes varying between 147 and 155 bp, with positions of the MNase cuts reflecting positions of the A?T pairs rather than the nucleosome core/linker junctions determined by X-ray crystallography. Extent of chromatosomal DNA protection by linker histone H1 also depends on the linker DNA sequence. Remarkably, we found that a combined treatment with MNase and exonuclease III (exoIII) overcomes MNase sequence preference producing nucleosomal DNA trimmed symmetrically and precisely at the core/linker junctions regardless of the underlying DNA sequence. We propose that combined MNase/exoIII digestion can be applied to in situ chromatin for unbiased genome-wide mapping of nucleosome positions that is not influenced by DNA sequences at the core/linker junctions. The same approach can be also used for the precise mapping of the extent of linker DNA protection by H1 and other protein factors associated with nucleosome linkers. PMID:23458408

Nikitina, Tatiana; Wang, Difei; Gomberg, Misha; Grigoryev, Sergei A; Zhurkin, Victor B

2013-06-12

182

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

Microsoft Academic Search

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

Gad Yair

2009-01-01

183

Precision Mass Measurements of Short-Lived, Neutron-Rich, R-Process Nuclei About the N=82 Waiting Point  

NASA Astrophysics Data System (ADS)

This thesis details the precision mass measurements of 33 neutron-rich ground-state nuclei and isomeric states that approach or lie on the proposed rapid neutron capture process (r-process) path. For many of the nuclei measured the work presented here will be the rst direct mass measurements of these nuclei, including 130In, 137Sb, 133I, and 134I. The measurements were made using the Canadian Penning Trap mass spectrometer (CPT), located at the ATLAS heavy ion-linac at Argonne National Laboratory. Ground states and isomers have been measured with the CPT at fractional precisions (?m/m) between 10-7, and 10-8. The nuclei were produced at the new CAlifornium Rare Isotope Breeder Upgrade (CARIBU) to ATLAS. Because nuclear masses are required for measuring neutron separation energies, and neutron separation energies are important inputs in r-process network calculations, precision mass measurements are critical for advancing our knowledge of the r-process. This thesis will give the astrophysical motivation for making these mass measurements, the theoretical background behind ion trapping and mass measurements using ion traps, an explanation of the CPT apparatus, the mass measurements themselves, and the results of those measurements as they pertain to r-process network calculations. Results of these mass measurements show significant shifts in the r-process path over a range of temperatures and neutron densities.

Lascar, Daniel David

184

IAIN World Congress, Stockholm, 27-30 October 2009 1 of 1 ULTRA-PRECISE POSITIONING FOR SPORT  

E-print Network

Alpine Ski Team during training. The GPS-GLONASS based sensor has proven to operate very well under the above limitations and is now used operationally by the Canadian Alpine ski team during training, in collaboration with Own The Podium/Ã? Nous le Podium 2010 and Alpine Canada Alpin, an ultra-precise, ultra

Calgary, University of

185

Systems for producing precise movements of a joint over a wide range of speeds and displacements for tests of a static-position sense.  

PubMed

This report describes 3 types of apparatus that were used to produce precise movements of a joint over a wide range of speeds and angles. The designs feature an ability for ultra slow rotation of the joint (fractions of a degree per min) with a minimum of extraneous cues. Two designs use servo-controlled DC motors configured as velocity servos and a third design uses a galvanometer motor configured as a position servo. Originally designed for use with humans in studies of proprioception with the ankle and two joints of the index finger (the metacarpophalangeal joint and proximal interphalangeal joint), the apparatuses should be useful in a variety of applications where precise control of velocity and position is needed. PMID:3573811

Clark, F J; Burgess, R C

1987-03-01

186

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

PubMed

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

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

2011-10-01

187

Precise determination of full matrix of piezo-optic coefficients with a four-point bending technique: the example of lithium niobate crystals.  

PubMed

A recently proposed technique representing a combination of digital imaging laser interferometry with a classical four-point bending method is applied to a canonical nonlinear optical crystal, LiNbO?, to precisely determine a full matrix of its piezo-optic coefficients (POCs). The contribution of a secondary piezo-optic effect to the POCs is investigated experimentally and analyzed theoretically. Based on the POCs thus obtained, a full matrix of strain-optic coefficients (SOCs) is calculated and the appropriate errors are estimated. A comparison of our experimental errors for the POCs and SOCs with the known reference data allows us to claim the present technique as the most precise. PMID:24787189

Krupych, Oleg; Savaryn, Viktoriya; Vlokh, Rostyslav

2014-04-01

188

Stability characteristics of a supersonic boundary layer and their relation to the position of the laminar-turbulent transition point  

NASA Technical Reports Server (NTRS)

By comparing the calculated results with experimental data, it is demonstrated that the position of the laminar-boundary transition point of a boundary layer can be estimated by using the e-exp-n method. The effect of the Mach number, pressure gradient, and heat transfer on the laminar-turbulent transition is discussed. It is found that under conditions of strong cooling, the effect of the pressure gradient on the position of the transition point is less pronounced than in the absence of heat transfer.

Lysenko, V. I.

1987-01-01

189

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)

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.

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

2012-12-01

190

High-precision positioning using a self-sensing piezoelectric actuator control with a differential detection method  

Microsoft Academic Search

We present a self-sensing control method for piezoelectric actuators, which enables high-resolution positioning without an external positioning sensor. One of the present authors previously proposed a self-sensing piezoelectric actuator control system (Kawamata et al. (2008) [1] and Ishikiriyama and Morita (2010) [2]). In the previous studies, a linear relationship between piezoelectric displacement and permittivity change was discovered, and this linear

Hideyuki Ikeda; Takeshi Morita

2011-01-01

191

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

ERIC Educational Resources Information Center

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

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

2008-01-01

192

Common Excess Air Trends in Industrial Boilers with Single-Point Positioning Control and Strategies to Optimize Efficiency  

E-print Network

Common Excess Air Trends in Industrial Boilers with Single-Point Positioning Control and Strategies'Antonio, Energy & Resource Solutions ABSTRACT Industrial boilers are among the most common pieces of energy, process boilers operate at a large range of loading conditions depending on process loads, market

Kissock, Kelly

193

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

Microsoft Academic Search

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

Casey Lambert; Aaron Saunders; Curran Crawford; Meyer Nahon

194

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

Microsoft Academic Search

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

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

1984-01-01

195

Precise measurements of the Bk97249 ground state half-life and the ?--decay end-point energy  

NASA Astrophysics Data System (ADS)

The half-life of the Bk249 ground state was determined by means of ?-ray spectroscopy, following for 728 days the growth of its ?-decaying daughter nuclide Cf249. Using a chemically purified source containing Bk249 and Cs137 nuclides, ?-ray singles measurements were carried out using a 25% coaxial Ge detector. The areas of the strongest 333.37- and 388.17-keV ?-ray peaks, produced in the ? decay of Cf249, and the 661.66-keV peak, produced in the ?- decay of Cs137, were determined. The measured activity of the latter was used to account for geometrical and dead-time corrections to the efficiency of the spectrometer, thus minimizing the systematic uncertainties associated with long-time, ?-ray counting measurements. Using the growth with time of the ratio of the 388.17- and 661.66-keV ?-ray peaks, a value of T1/2=327.2±0.3 d (the uncertainty quoted is one standard deviation, 1?) for the half-life of the Bk249 ground state was determined. The ?--decay end-point energy of Bk249 was measured with a passivated implanted planar silicon detector to be 123.6±0.4 keV.

Chen, J.; Ahmad, I.; Greene, J. P.; Kondev, F. G.

2014-10-01

196

Precision translator  

DOEpatents

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

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

1982-03-09

197

Precision translator  

DOEpatents

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

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

1984-01-01

198

The absolute zero point method to improve the positional accuracy for PDS microdensitometer coordinate system - hardware  

Microsoft Academic Search

The logic circuit design of the absolute zero signal for PDS coordinate system is introduced. The key point is to make use of the phase relation between the zero signal and B-phase signal on the linear optical encoder. A logic circuit is designed to extract the absolute zero signal with a high repeatability of less than 1 mum.

Hui Fang; You-Yi Zhang

1993-01-01

199

Necessary and sufficient conditions for the existence of symmetric positive solutions of multi-point boundary value problems  

Microsoft Academic Search

We study the nonlinear boundary value problem with multi-point boundary condition (|u?|p?1u?)?=f(t,u,u?,u?),t?(0,1),u(2i)(0)=u(2i)(1)=?j=1maiju(2i)(tj),i=0,1. Necessary and sufficient conditions are obtained for the existence of symmetric positive solutions of this problem using fixed point theorems on cones. Applications of our results to the special case where f is a power function of u and its derivatives are also discussed. Moreover, similar conclusions for

John R. Graef; Lingju Kong

2008-01-01

200

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

201

Real-Time Point Positioning Performance Evaluation of Single-Frequency Receivers Using NASA's Global Differential GPS System  

NASA Technical Reports Server (NTRS)

This paper evaluates the performance of a single-frequency receiver using the 1-Hz differential corrections as provided by NASA's global differential GPS system. While the dual-frequency user has the ability to eliminate the ionosphere error by taking a linear combination of observables, the single-frequency user must remove or calibrate this error by other means. To remove the ionosphere error we take advantage of the fact that the magnitude of the group delay in range observable and the carrier phase advance have the same magnitude but are opposite in sign. A way to calibrate this error is to use a real-time database of grid points computed by JPL's RTI (Real-Time Ionosphere) software. In both cases we evaluate the positional accuracy of a kinematic carrier phase based point positioning method on a global extent.

Muellerschoen, Ronald J.; Iijima, Byron; Meyer, Robert; Bar-Sever, Yoaz; Accad, Elie

2004-01-01

202

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

PubMed

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

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

203

A radio optical reference frame. I - Precise radio source positions determined by Mark III VLBI - Observations from 1979 to 1988 and a tie to the FK5  

NASA Technical Reports Server (NTRS)

Observations from 600 Mark III VLBI experiments from 1979 to 1988, resulting in 237,681 acceptable pairs of group delay and phase delay rate observations, have been used to derive positions of 182 extragalactic radio sources with typical formal standard errors less than 1 mas. The sources are distributed fairly evenly above delta = -30 deg, and 70 sources have delta greater than 0 deg. Analysis with different troposphere models, as well as internal and external comparisons, indicates that a coordinate frame defined by this set of radio sources should be reliable at the 1 mas level. The right ascension zero point of this reference frame has been aligned with the FK5 by using the optical positions of 28 extragalactic radio sources whose positions are on the FK5 system. Because of known defects in the knowledge of astronomical constants, daily nutation offsets in longitude and obliquity were determined relative to an arbitrary reference day in the set of experiments.

Ma, C.; Shaffer, D. B.; De Vegt, C.; Johnston, K. J.; Russell, J. L.

1990-01-01

204

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

NASA Technical Reports Server (NTRS)

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.

Shimada, Seiichi; Bock, Yehuda

1992-01-01

205

Three point lead screw positioning apparatus for a cavity tuning plate  

NASA Technical Reports Server (NTRS)

Three lead screws are provided for adjusting the position of a traversing plate. Each of the three lead screws is threaded through a collar that is press fitted through the center of one of three pinion gears. A sun gear meshes with all three pinion gears and transversely moves the three lead screws upon actuation of a drive gear. The drive gear meshes with the sun gear and is driven by a handle or servomotor. When the handle or servomotor rotates the drive gear, the sun gear rotates causing the three pinion gears to rotate, thus, causing transverse movement of the three lead screws and, accordingly, transverse movement of the transversing plate. When the drive gear rotates, the traversing plate is driven in and out of a microwave cavity. Thus, the length or size of the cavity can be tuned while maintaining the traversing plate in an exact parallel relationship with an opposing plate on another end of the cavity.

Calco, Frank S. (inventor)

1993-01-01

206

Development of a simple and rapid method of precisely identifying the position of 10B atoms in tissue: an improvement in standard alpha autoradiography  

PubMed Central

Boron neutron capture therapy (BNCT) can be utilized to selectively kill cancer cells using a boron compound that accumulates only in cancer cells and not in normal cells. Tumor-bearing animals treated by BNCT are routinely used to evaluate long-term antitumor effects of new boron compounds. Alpha-autoradiography is one of the methods employed in the evaluation of antitumor effects. However, a standard alpha-autoradiography cannot detect the microdistribution of 10B because of the difficulty associated with the superposition of a tissue sample image and etched pits on a track detector with the etching process. In order to observe the microdistribution of 10B, some special methods of alpha-autoradiography have been developed that make use of a special track detector, or the atomic force microscope combined with X-ray and UV light irradiation. In contrast, we propose, herein, a simple and rapid method of precisely identifying the position of 10B using the imaging process and the shape of etched pits, such as their circularity, without the need to use special track detectors or a microscope. A brief description of this method and its verification test are presented in this article. We have established a method of detecting the microdistribution of 10B with submicron deviation between the position of etched pits and the position of reaction in a tissue sample, for a given circularity of etched pits. PMID:24142968

Tanaka, Hiroki; Sakurai, Yoshinori; Suzuki, Minoru; Masunaga, Shin-ichiro; Takamiya, Koichi; Maruhashi, Akira; Ono, Koji

2014-01-01

207

Development of a simple and rapid method of precisely identifying the position of 10B atoms in tissue: an improvement in standard alpha autoradiography.  

PubMed

Boron neutron capture therapy (BNCT) can be utilized to selectively kill cancer cells using a boron compound that accumulates only in cancer cells and not in normal cells. Tumor-bearing animals treated by BNCT are routinely used to evaluate long-term antitumor effects of new boron compounds. Alpha-autoradiography is one of the methods employed in the evaluation of antitumor effects. However, a standard alpha-autoradiography cannot detect the microdistribution of (10)B because of the difficulty associated with the superposition of a tissue sample image and etched pits on a track detector with the etching process. In order to observe the microdistribution of (10)B, some special methods of alpha-autoradiography have been developed that make use of a special track detector, or the atomic force microscope combined with X-ray and UV light irradiation. In contrast, we propose, herein, a simple and rapid method of precisely identifying the position of (10)B using the imaging process and the shape of etched pits, such as their circularity, without the need to use special track detectors or a microscope. A brief description of this method and its verification test are presented in this article. We have established a method of detecting the microdistribution of (10)B with submicron deviation between the position of etched pits and the position of reaction in a tissue sample, for a given circularity of etched pits. PMID:24142968

Tanaka, Hiroki; Sakurai, Yoshinori; Suzuki, Minoru; Masunaga, Shin-ichiro; Takamiya, Koichi; Maruhashi, Akira; Ono, Koji

2014-03-01

208

Study of positional dependence of dose to bladder, pelvic wall and rectal points in High-Dose-Rate Brachytherapy in cervical cancer patients  

PubMed Central

The objective of the study is to examine the variation in doses to, Bladder, pelvic wall and Rectal Points when a patient is simulated in Supine (S Position) and Lithotomy M shaped positions (LM Position), respectively as part of Intracavitary Brachytherapy in Cervical Cancer patients. Patients (n = 19) were simulated and orthogonal images were taken in S Position and LM Positions on a physical simulator. Digital orthogonal X-ray images were transferred to Brachyvision Treatment Planning System via Dicom to generate treatment plans. Radio opaque dye of 7 ml was injected into the Foley bulb for identification and digitization of International Commission on Radiological Units and Measurements (ICRU) Bladder point. Pelvic side wall points were marked in accordance with ICRU 38 recommendations. A Rectal tube containing dummy source marker wire was used to identify Rectal Point. Students’t-test was used to analyze the results. Doses in LM Position were lower and statistically significant when compared to S Position for ICRU Bladder Point, pelvic walls and Rectal Point. It was observed that movement of applicator could be the reason for the variations in doses between the two positions. Bladder, pelvic wall and rectal points systematically registered lower doses in LM Position as compared to S Position. PMID:24672152

Talluri, Anil Kumar; Alluri, Krishnam Raju; Gudipudi, Deleep Kumar; Ahamed, Shabbir; Sresty, Madhusudhana M.; Reddy, Aparna Yarrama

2013-01-01

209

Study of positional dependence of dose to bladder, pelvic wall and rectal points in High-Dose-Rate Brachytherapy in cervical cancer patients.  

PubMed

The objective of the study is to examine the variation in doses to, Bladder, pelvic wall and Rectal Points when a patient is simulated in Supine (S Position) and Lithotomy M shaped positions (LM Position), respectively as part of Intracavitary Brachytherapy in Cervical Cancer patients. Patients (n = 19) were simulated and orthogonal images were taken in S Position and LM Positions on a physical simulator. Digital orthogonal X-ray images were transferred to Brachyvision Treatment Planning System via Dicom to generate treatment plans. Radio opaque dye of 7 ml was injected into the Foley bulb for identification and digitization of International Commission on Radiological Units and Measurements (ICRU) Bladder point. Pelvic side wall points were marked in accordance with ICRU 38 recommendations. A Rectal tube containing dummy source marker wire was used to identify Rectal Point. Students't-test was used to analyze the results. Doses in LM Position were lower and statistically significant when compared to S Position for ICRU Bladder Point, pelvic walls and Rectal Point. It was observed that movement of applicator could be the reason for the variations in doses between the two positions. Bladder, pelvic wall and rectal points systematically registered lower doses in LM Position as compared to S Position. PMID:24672152

Talluri, Anil Kumar; Alluri, Krishnam Raju; Gudipudi, Deleep Kumar; Ahamed, Shabbir; Sresty, Madhusudhana M; Reddy, Aparna Yarrama

2013-10-01

210

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

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

211

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

SciTech Connect

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.

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

2012-04-15

212

The Effects of L2C Signal Tracking on High-Precision Carrier Phase GPS Positioning: Implications for the Next Generation of GNSS Systems  

NASA Astrophysics Data System (ADS)

In December 2005, the L2C signal was introduced to improve the accuracy, tracking and redundancy of the GPS system for civilian users. The L2C signal also provides improved SNR data when compared with the L2P(Y) legacy signal. However, GNSS network operators have been hesitant to use the new signal as it is not well determined how positions derived from L2 carrier phase measurements are affected. L2C carrier phase is in quadrature with L2P(Y); some manufacturers correct for this when logging L2C phase while others do not. In cases where both L2C and L2P(Y) are logged simultaneously, translation software must be used carefully in order to select which phase is used in positioning. Modifications were made to UNAVCO's teqc pre-processing software to eliminate confusion, however GNSS networks such as the IGS still suffer occasional data loss due to improperly configured GPS receivers or data flow routines. To date L2C analyses have been restricted to special applications such as snow depth and soil moisture using SNR data, as some high-precision data analysis packages are not compatible with L2C. We use several different methods to determine the effect that tracking and logging L2C has on carrier phase measurements and positioning for various receiver models and configurations. Twenty-four hour zero-length baseline solutions using L2 show sub- millimeter differences in mean positions for both horizontal and vertical components. Direct comparisons of the L2 phase observable from RINEX files with and without the L2C observable show sub-millicycle differences. The magnitude of the variations increased at low elevations. The behavior of the L2P(Y) phase observations or positions from a given receiver were not affected by the enabling of L2C tracking. We find that the use of the L2C-derived carrier phase in real-time applications can be disastrous in cases where receiver brands are mixed between those that correct for quadrature and those that do not (Figure 1). Until standards are implemented for universal phase corrections in either receivers or software the use of L2C should be avoided by real-time network operators. The complexity involved in the adoption of a single new signal on an existing GPS frequency over a period of 7 years has implications for the use of multi-GNSS systems and modernized GPS in geodetic networks.

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

2012-12-01

213

Pregnant women screening positive for depressive symptoms at 24–28 weeks may have increased risk of preterm birth but more precise research is needed  

PubMed Central

Context The prevalence of prenatal depression and anxiety ranges between 5% and 16% and the consequences are extensive.1 In addition to negative maternal effects, research points to detrimental fetal effects, and higher rates of PTB and LBW. Postpartum symptoms of depression and anxiety are often experienced by women prenatally and may lead to maternal suffering and parenting ineffectiveness. Thus, research attention to prenatal and postpartum affective symptoms and their causes is warranted. Methods Straub et al screened a sample of 14 175 pregnant women between 24 and 28 weeks gestation for depressive symptoms using the Edinburgh Postnatal Depression Scale (EPDS). Scores of ?12 or endorsement of the self-harm item identified those at risk. Findings Comparable to past studies, the screen positive rate was 9.1% (N=1298). Multivariate analysis revealed an association between prenatal depression symptoms and PTB adjusting for maternal age, race, history of PTB and insurance status (adjusted OR=1.3). Separate analyses indicated significant effects of depressive symptoms on LBW and small for gestational age (SGA). Commentary Strengths of this study include the large cohort of women screened with immediate follow-up and triage for positive screens. PMID:23525078

Accortt, Eynav Elgavish; Schetter, Christine Dunkel

2014-01-01

214

New fixed point theorems for mixed monotone operators and local existence–uniqueness of positive solutions for nonlinear boundary value problems  

Microsoft Academic Search

In this article we present a new fixed point theorem for a class of general mixed monotone operators, which extends the existing corresponding results. Moreover, we establish some pleasant properties of nonlinear eigenvalue problems for mixed monotone operators. Based on them the local existence–uniqueness of positive solutions for nonlinear boundary value problems which include Neumann boundary value problems, three-point boundary

Chengbo Zhai; Lingling Zhang

2011-01-01

215

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

Microsoft Academic Search

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

Yves Rossetti; Bruno Tadary; Claude Prablanc

1994-01-01

216

A precise calibration of the zero point of the cosmic distance scale from late-type eclipsing binaries in the LMC  

NASA Astrophysics Data System (ADS)

Eclipsing binaries represent one of the most accurate distance measurement tools available. This is especially true for systems composed of late-type stars, for which a reliable surface brightness-color relationship is now at hand. We have discovered 31 G-type eclipsing binary systems in the LMC wading through 100,000 eclipsing systems catalogued by the OGLE project. We have also uncovered two rare and unique systems in which one of the two components is a Cepheid variable. We have collected near-IR photometry and high-resolution spectroscopy from the ground for all the new systems in order to derive orbital and stellar parameters, and distances. Recently, we published the results for the first of our systems, obtaining a distance modulus to the LMC of 18.50 +/- 0.06. We also derived the dynamical mass of a Cepheid variable contained in one of our binaries with an unprecedented accuracy of 1%. We are now in a position to measure the distance to the LMC, the main anchor point of the extragalactic distance scale, with an accuracy of 1%, using the large number of binaries at our disposal. However, our photometric solutions for the eclipsing binaries assume that there is no blending with nearby companions. Therefore, in order to make full use of the very special stellar systems that we have discovered and obtain a very accurate distance to the LMC, we request multi-band, high spatial resolution WFC3 imaging of 11 of the best systems to check for the presence of companions and characterize their spectral energy distribution.

Bresolin, Fabio

2012-10-01

217

Localization precision in stepwise photobleaching experiments.  

PubMed

The precise determination of the position of fluorescent labels is essential for the quantitative study of biomolecular structures by various localization microscopy techniques. Localization by stepwise photobleaching is especially suited for measuring nanometer-scale distances between two labels; however, the precision of this method has remained elusive. Here, we show that shot noise from other emitters and error propagation compromise the localization precision in stepwise photobleaching. Incorporation of point spread function-shaped shot noise into the variance term in the Fisher matrix yielded fundamental Cràmer-Rao lower bounds (CRLBs) that were in general anisotropic and depended on emitter intensity and position. We performed simulations to benchmark the extent to which different analysis procedures reached these ideal CRLBs. The accumulation of noise from several images accounted for the worse localization precision in image subtraction. Propagation of fitting errors compromised the CRLBs in sequential fitting using fixed parameters. Global fitting of all images was also governed by error propagation, but made optimal use of the available information. The precision of individual distance measurements depended critically on the exact bleaching kinetics and was correctly quantified by the CRLBs. The methods presented here provide a consistent framework for quantitatively analyzing stepwise photobleaching experiments and shed light on the localization precision in some other bleaching- or blinking-assisted techniques. PMID:25418097

Schoen, Ingmar

2014-11-01

218

Precision manometer gauge  

DOEpatents

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

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

1982-09-27

219

Precision manometer gauge  

DOEpatents

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

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

1984-01-01

220

Rydberg-Klein-Rees 1-Sigma-positive potential curve turning points for the isotopes of carbon monoxide  

NASA Technical Reports Server (NTRS)

First order RKR turning points were computed for (C-12)O16, (C-12)O17, (C-13)O16, (C-12)O18, and (C-13)O18 for vibrational levels up to v = 40. These turning points should be useful in the numerical computation of matrix elements of powers of the internuclear separation.

Chackerian, C., Jr.; Goorvitch, D.

1982-01-01

221

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

ERIC Educational Resources Information Center

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

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

2012-01-01

222

Precision displacement reference system  

DOEpatents

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

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

2000-02-22

223

A comparison of statistical methods for fitting telescope pointing models  

Microsoft Academic Search

Telescope mount models use a mathematical model to introduce commanded position adjustments to compensate for predictable pointing errors. The parameters of the model are estimated from observed pointing deviations on a set of calibration stars. These calibration measurements generally contain random noise and other features that limit the precision of the parameter estimates and ultimately degrade pointing. This paper compares

Robert L. Meeks

2004-01-01

224

Precision voltage regulator  

NASA Technical Reports Server (NTRS)

Balanced positive and negative voltage output circuit, in which error voltage for control is developed from difference in absolute value of positive and negative voltages referenced to a common point, regulates voltage for use with inertial reference unit. Fast-acting, temperature-compensated, high-gain operational amplifier circuits maintain common point.

Hand, P. J.; Crawford, R. A.

1972-01-01

225

Image Alignment for Precise Camera Fixation and Aim  

Microsoft Academic Search

Two important problems in camera control are how to keep a moving camera fixated on a target point, and how to precisely aim a camera, whose approximate pose is known, towards a given 3D position. This paper describes how electronic image alignment techniques can be used to solve these problems, as well as provide other benefits such as stabilized video.

Lambert E. Wixson; Jayakrishnan Eledath; Michael W. Hansen; Robert Mandelbaum; Deepam Mishra

1998-01-01

226

Effects of age, sex and arm on the precision of arm position sense—left-arm superiority in healthy right-handers  

PubMed Central

Position sense is an important proprioceptive ability. Disorders of arm position sense (APS) often occur after unilateral stroke, and are associated with a negative functional outcome. In the present study we assessed horizontal APS by measuring angular deviations from a visually defined target separately for each arm in a large group of healthy subjects. We analyzed the accuracy and instability of horizontal APS as a function of age, sex and arm. Subjects were required to specify verbally the position of their unseen arm on a 0-90° circuit by comparing the current position with the target position indicated by a LED lamp, while the arm was passively moved by the examiner. Eighty-seven healthy subjects participated in the study, ranging from 20 to 77 years, subdivided into three age groups. The results revealed that APS was not a function of age or sex, but was significantly better in the non-dominant (left) arm in absolute errors (AE) but not in constant errors (CE) across all age groups of right-handed healthy subjects. This indicates a right-hemisphere superiority for left APS in right-handers and neatly fits to the more frequent and more severe left-sided body-related deficits in patients with unilateral stroke (i.e. impaired APS in left spatial neglect, somatoparaphrenia) or in individuals with abnormalities of the right cerebral hemisphere. These clinical issues will be discussed. PMID:24399962

Schmidt, Lena; Depper, Lena; Kerkhoff, Georg

2013-01-01

227

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

Microsoft Academic Search

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

John Braun; Christian Rocken; James Liljegren

2003-01-01

228

Using Global Positioning System techniques in landslide monitoring  

Microsoft Academic Search

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

Josep A. Gili; Jordi Corominas; Joan Rius

2000-01-01

229

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

NASA Astrophysics Data System (ADS)

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).

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

2015-01-01

230

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

applications without position sensing with some success 1 . However, they have not been widely accepted because or proposed to sense the platen teeth magnetically, optically 3 , and capacitively 4 . Of the three sensing modali- ties, magnetic sensing has received the most attention since it takes advantage of the distinct

Butler, Zack

231

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

SciTech Connect

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.

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

232

Adobe photoshop quantification (PSQ) rather than point-counting: A rapid and precise method for quantifying rock textural data and porosities  

NASA Astrophysics Data System (ADS)

Commonly used petrological quantification methods are visual estimation, counting, and image analyses. However, in this article, an Adobe Photoshop-based analyzing method (PSQ) is recommended for quantifying the rock textural data and porosities. Adobe Photoshop system provides versatile abilities in selecting an area of interest and the pixel number of a selection could be read and used to calculate its area percentage. Therefore, Adobe Photoshop could be used to rapidly quantify textural components, such as content of grains, cements, and porosities including total porosities and different genetic type porosities. This method was named as Adobe Photoshop Quantification (PSQ). The workflow of the PSQ method was introduced with the oolitic dolomite samples from the Triassic Feixianguan Formation, Northeastern Sichuan Basin, China, for example. And the method was tested by comparing with the Folk's and Shvetsov's "standard" diagrams. In both cases, there is a close agreement between the "standard" percentages and those determined by the PSQ method with really small counting errors and operator errors, small standard deviations and high confidence levels. The porosities quantified by PSQ were evaluated against those determined by the whole rock helium gas expansion method to test the specimen errors. Results have shown that the porosities quantified by the PSQ are well correlated to the porosities determined by the conventional helium gas expansion method. Generally small discrepancies (mostly ranging from -3% to 3%) are caused by microporosities which would cause systematic underestimation of 2% and/or by macroporosities causing underestimation or overestimation in different cases. Adobe Photoshop could be used to quantify rock textural components and porosities. This method has been tested to be precise and accurate. It is time saving compared with usual methods.

Zhang, Xuefeng; Liu, Bo; Wang, Jieqiong; Zhang, Zhe; Shi, Kaibo; Wu, Shuanglin

2014-08-01

233

Effect of errors in positioning the sampling points on the assessment of the relationships between the remote sensing data and the soil properties  

NASA Astrophysics Data System (ADS)

The stochastic modeling of the shift in coordinates of the sampling points was performed for a typical land plot in Bryansk opolie with the purpose to assess the influence of the accuracy of the sampling point positioning on the predicted properties of the plow horizon. It was proved that, for agro-gray soils, an occasional shift of the sampling points by 2-6 m regarding the coordinates on satellite photographs of superhigh resolution may significantly change the correlation between the soil properties and the brightness in the infrared channel. Based on the modeling data, the 95% confidence interval was estimated for the possible correlation coefficients of such properties of the arable agro-gray soil as the density, moisture, specific surface, carbon, and mobile nitrogen content. The use of the brightness in the infrared channel as a covariate for building charts may noticeably improve the map's quality; however, it may unjustifiably complicate the mapping units delineation.

Samsonova, V. P.; Meshalkina, Yu. L.; Blagoveshchenskii, Yu. N.

2013-05-01

234

Precision Nova operations  

SciTech Connect

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

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

1995-09-01

235

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

PubMed

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

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

2010-12-01

236

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

SciTech Connect

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

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

2003-05-01

237

[Epidemiological, clinical and evolving HIV-positive patients referred to the University Hospital of Point G, Bamako, Mali.  

PubMed

We conduct a longitudinal descriptive study in the department of infectious diseases to CHU of Point G during 18 months. It concerned adult patients referred from another care center. All the patients underwent systematic clinical examination and complementary exploration. Our sample was 352 HIV+ patients, with a mean age of 37.8 ± 9.8 years and a sex ratio (M/F)=0.94 shared among patients receiving ARV treatment (ART-s) and not (n-ART). Delay of reference was 5±4.4 days. All patients benefited from clinical and paraclinical examinations. In both groups patients were mostly from level II. On admission, 132 cases were ART-s (38%). The main reasons for consultation were mainly fever [87.9%, p <0.05] and vomiting [17.4%, p =0.005] in the ART-s. Cough (p=0.9), and diarrhoea (p=0.5] were most noted in the n-TARV no statistically significant (no SS). Other reference reasons were similar in the 2 groups: headache (p=0.4), dyspnea (p=0.1). Selected diagnoses were dominated by tuberculosis (p=0.6) for n-ART no SS. Nontuberculosis infectious pneumonia (p=0.8) and cerebral toxoplasmosis (p=0.8) were comparable in the two groups. Severe systemic bacterial infections occurred more noted in the n-TARV (p=0.7). Malaria has been the main non-AIDS defining disease in the n-ART [-p=0.07] no SS. Patients were seen to late stage a corollary of a more collapsed of immunity in n-ART group [93.3%, p <0.05]. The fatality rate was similar in both groups (43.2%). Pathological factors were mainly tuberculosis (p=0.3) no SS. The factors involved significantly in TARV-s were non-tuberculosis bacterial pneumonia (p=0.001). The hospital mortality of HIV and AIDS is still important. Despite free ARVs and the large number of support center, the delay in diagnosis is a key as well as the lack of monitoring of patients factor. PMID:24363016

Traoré, A M; Minta, D K; Fomba, M; Cissé, H; Diallo, K; Coulibaly, I; Soukho-Kaya, A; Beye, S A; Cissé, T; Dembélé, M; Traoré, H A; Bissagnené, E

2013-12-21

238

Assessment on tracking error performance of Cascade P/PI, NPID and N-Cascade controller for precise positioning of xy table ballscrew drive system  

NASA Astrophysics Data System (ADS)

At present, positioning plants in machine tools are looking for high degree of accuracy and robustness attributes for the purpose of compensating various disturbance forces. The objective of this paper is to assess the tracking performance of Cascade P/PI, Nonlinear PID (NPID) and Nonlinear cascade (N-Cascade) controller with the existence of disturbance forces in the form of cutting forces. Cutting force characteristics at different cutting parameters; such as spindle speed rotations is analysed using Fast Fourier Transform. The tracking performance of a Nonlinear cascade controller in presence of these cutting forces is compared with NPID controller and Cascade P/PI controller. Robustness of these controllers in compensating different cutting characteristics is compared based on reduction in the amplitudes of cutting force harmonics using Fast Fourier Transform. It is found that the N-cascade controller performs better than both NPID controller and Cascade P/PI controller. The average percentage error reduction between N-cascade controller and Cascade P/PI controller is about 65% whereas the average percentage error reduction between cascade controller and NPID controller is about 82% at spindle speed of 3000 rpm spindle speed rotation. The finalized design of N-cascade controller could be utilized further for machining application such as milling process. The implementation of N-cascade in machine tools applications will increase the quality of the end product and the productivity in industry by saving the machining time. It is suggested that the range of the spindle speed could be made wider to accommodate the needs for high speed machining.

Abdullah, L.; Jamaludin, Z.; Rafan, N. A.; Jamaludin, J.; Chiew, T. H.

2013-12-01

239

Precision stationkeeping with azimuthing thrusters  

E-print Network

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 ...

Doroski, Adam D

2011-01-01

240

Precision mechatronics lab robot development  

E-print Network

based mobile robot. The principal goal of this work was the demonstration of the Precision Mechatronics Lab (PML) robot. This robot should be capable of traversing any known distance while maintaining a minimal position error. An optical correction...

Rogers, Adam Gregory

2008-10-10

241

Precision mechatronics lab robot development  

E-print Network

based mobile robot. The principal goal of this work was the demonstration of the Precision Mechatronics Lab (PML) robot. This robot should be capable of traversing any known distance while maintaining a minimal position error. An optical correction...

Rogers, Adam Gregory

2009-05-15

242

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)

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.

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

2014-05-01

243

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...

244

Instrument Attitude Precision Control  

NASA Technical Reports Server (NTRS)

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.

Juang, Jer-Nan

2004-01-01

245

Development of positive antinuclear antibodies and rheumatoid factor in systemic juvenile idiopathic arthritis points toward an autoimmune phenotype later in the disease course  

PubMed Central

Background Systemic juvenile idiopathic arthritis (sJIA) is commonly considered an autoinflammatory disease. However, sJIA patients may develop aggressive arthritis without systemic inflammation later in the disease, resembling an autoimmune phenotype similar to other subtypes of JIA. The objective of this study was to determine whether antinuclear antibodies (ANA) and rheumatoid factor (RF) will develop in patients with sJIA over the course of the disease. Findings A single center sample of sJIA patients with follow-up of more than one year was obtained. A retrospective chart survey was used to extract demographic and clinical data as well as presence and titers of ANA and RF at diagnosis and during follow-up. 32 patients were included in the study, with a median age of 4.2 years and median follow-up of 6.0 years. 8/32 patients had ANA titers???1:80 at diagnosis, with 22/32 patients showing rising ANA titers with titers???1:80 at last follow-up (p =0.001). 10/32 patients had a positive RF at least once during follow-up, compared to 0/32 at diagnosis (p?=?0.001). In 5/10 patients, positive RF was documented at least twice, more than twelve weeks apart. Patients treated with TNF antagonists were not significantly more likely to develop positive ANA titers (p?=?0.425) or positive RF (p?=?0.703). Conclusions Patients with sJIA developed increased ANA titers and positive RF over the course of the disease, independent of treatment with TNF antagonists. This might point towards an autoimmune, rather than an autoinflammatory phenotype later in the course of sJIA. PMID:25114627

2014-01-01

246

Precision laser aiming system  

DOEpatents

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

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

2009-04-28

247

State Your Position  

NSDL National Science Digital Library

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

Integrated Teaching And Learning Program

248

High-Precision Stellar Photometry with the K2 Mission  

NASA Astrophysics Data System (ADS)

The K2 mission is a repurposed use of the Kepler spacecraft to perform high-precision photometry of selected fields in the ecliptic. We have developed an aperture photometry pipeline for K2 data which performs dynamic automated aperture mask selection, background estimation and subtraction, and positional decorrelation to minimize the effects of spacecraft pointing jitter. Here we describe that pipeline and the photometric precision we are capable of achieving with K2, illustrated by application to Campaign 0 data, and suggest future improvements in our algorithm.

Carboneau, Lindsey; Buzasi, Derek L.; Hessler, Carly; Lezcano, Andy; Preston, Heather L.

2015-01-01

249

Ground control requirements for precision processing of ERTS images  

USGS Publications Warehouse

With the successful flight of the ERTS-1 satellite, orbital height images are available for precision processing into products such as 1:1,000,000-scale photomaps and enlargements up to 1:250,000 scale. In order to maintain positional error below 100 meters, control points for the precision processing must be carefully selected, clearly definitive on photos in both X and Y. Coordinates of selected control points measured on existing ½ and 15-minute standard maps provide sufficient accuracy for any space imaging system thus far defined. This procedure references the points to accepted horizontal and vertical datums. Maps as small as 1:250,000 scale can be used as source material for coordinates, but to maintain the desired accuracy, maps of 1:100,000 and larger scale should be used when available.

Burger, Thomas C.

1973-01-01

250

Precision synchrotron radiation detectors  

SciTech Connect

Precision detectors to measure synchrotron radiation beam positions have been designed and installed as part of beam energy spectrometers at the Stanford Linear Collider (SLC). The distance between pairs of synchrotron radiation beams is measured absolutely to better than 28 /mu/m on a pulse-to-pulse basis. This contributes less than 5 MeV to the error in the measurement of SLC beam energies (approximately 50 GeV). A system of high-resolution video cameras viewing precisely-aligned fiducial wire arrays overlaying phosphorescent screens has achieved this accuracy. Also, detectors of synchrotron radiation using the charge developed by the ejection of Compton-recoil electrons from an array of fine wires are being developed. 4 refs., 5 figs., 1 tab.

Levi, M.; Rouse, F.; Butler, J.; Jung, C.K.; Lateur, M.; Nash, J.; Tinsman, J.; Wormser, G.; Gomez, J.J.; Kent, J.

1989-03-01

251

Minimum-energy point-to-point trajectory planning of a simple mechatronic system  

Microsoft Academic Search

In this paper, we propose a novel minimum-energy point-to-point (PTP) trajectory planning method for a simple mechatronic system, which is a one-dimensional precision positioning table driven by a permanent magnet synchronous motor (PMSM). To generate the mechatronic trajectory we develop a real-coded genetic algorithm (RGA) to search for the optimal trajectory for the PTP motion. In this method, we design

Ming-Shyan Huang; Yi-Lung Hsu; Rong-Fong Fung

2011-01-01

252

Precision guided parachute LDRD final report  

SciTech Connect

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.

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

1996-07-01

253

Precision Astrometry With Adaptive Optics  

NASA Astrophysics Data System (ADS)

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 to ˜1/?{t} 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 a single-epoch astrometric precision of ?1 mas in 1 s, decreasing to lsim100 ?as in 2 minutes of integration time at the Hale 200 inch telescope. We also show that our astrometry is accurate to lsim100 ?as 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.

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

2009-01-01

254

Fiber Scrambling for High Precision Spectrographs  

NASA Astrophysics Data System (ADS)

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.

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

2011-05-01

255

Precision contour gage  

DOEpatents

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

Bieg, L.F.

1990-12-11

256

Precision contour gage  

DOEpatents

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

Bieg, Lothar F. (Louisville, CO)

1990-12-11

257

Precision powder feeder  

DOEpatents

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

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

2001-07-10

258

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

PubMed Central

The paper presents a new methodology for high precision monitoring of deformations with a long term perspective using terrestrial laser scanning technology. In order to solve the problem of a stable reference system and to assure the high quality of possible position changes of point clouds, scanning is integrated with two complementary surveying techniques, i.e., high quality static GNSS positioning and precise tacheometry. The case study object where the proposed methodology was tested is a high pressure underground pipeline situated in an area which is geologically unstable. PMID:22303152

Vezo?nik, Rok; Ambroži?, Tomaž; Sterle, Oskar; Bilban, Gregor; Pfeifer, Norbert; Stopar, Bojan

2009-01-01

259

Precision orbit computations for Starlette  

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

260

Precision tunable resonant microwave cavity  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

261

A Fortran Multiple-Precision Arithmetic Package  

Microsoft Academic Search

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

Richard P. Brent

1978-01-01

262

Precision zero-home locator  

DOEpatents

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

Stone, W.J.

1983-10-31

263

Kinematic precision of gear trains  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

264

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

265

Positioning apparatus  

DOEpatents

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.

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

1986-01-01

266

Positioning apparatus  

DOEpatents

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

Vogel, M.A.; Alter, P.

1983-07-07

267

Space telescope pointing control system  

Microsoft Academic Search

The Space Telescope is a free-flying spacecraft designed for Space Shuttle launch. The Space Telescope's pointing control system slews the optical axis from one target star region of the celestial sphere to the next, and maintains precision pointing for the target star for up to 24 hours. The spacecraft digital computer processes the precision attitude and rate sensor data to

H. Dougherty; K. Tompetrini; J. Levinthal; G. Nurre

1982-01-01

268

Space Telescope pointing control  

Microsoft Academic Search

The Space Telescope Pointing Control System is used to slew the optical axis of the telescope from one target star region of the celestial sphere to the next, and to maintain precision pointing on the target star. A digital computer is employed in the processing of attitude and rate sensor data, in order to generate torque commands for the reaction

H. Dougherty; C. Rodoni; K. Tompetrini; A. Nakashima

1983-01-01

269

Space Telescope pointing control  

Microsoft Academic Search

The Space Telescope, a long life, high performance spacecraft deployed by the Space Shuttle, will carry five scientific instruments on its first mission. Its pointing control system will permit target-to-target maneuvering and precision pointing on a target star to support scientific objectives. Spacecraft attitude control is achieved by onboard computer processing of attitude and rate sensor data to generate reaction

H. Dougherty; C. Rodoni; J. Rodden; K. Tompetrini

1984-01-01

270

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

PubMed Central

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

2014-01-01

271

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

PubMed Central

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

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

2013-01-01

272

Hivis: Precision Limitations  

NASA Astrophysics Data System (ADS)

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

Nevin, Becky; Harrington, D.

2012-01-01

273

The effects of incisor inclination changes on the position of point A in Class II division 2 malocclusion using three-dimensional evaluation: a long-term prospective study  

PubMed Central

Objective: The aim of this study was to evaluate change in the sagittal position of point A due to orthodontic treatment by orthodontic community-cone beam computed tomography (CBCT). Materials and methods: 40 subjects (22 males and 18 females) who had Class II division 2 malocclusion were recruited, and 40 subjects (23 males and 17 females) who had minor crowding in the beginning of the treatment and required no or minimal maxillary anterior tooth movement were served as control. The changes in maxillary incisor inclination, sagittal position of point A, SNA angle, and movement of incisor root apex and incisal edge were calculated before and after CBCT treatment. Results: Maxillary incisors were significantly proclined in the study group but not in the control group. This proclination resulted in 2.95 mm backward movement of the root apex and 6.23 mm forward movement of the incisal edge of maxillary incisors. Point A moved 1.24 mm and 0.18 mm backward in the study and control groups, respectively. Incisor root apex and incisal edge almost remained stable in the control group. No significant change was observed in the SNA angle in both the study and control groups. However, the change in SNA between the two groups was found to be significant. Conclusions: Proclination of maxillary incisors with backward movement of incisor root apex caused posterior movement of point A. This posterior movement significantly affects the SNA angle. PMID:25419382

Chen, Qiushuo; Zhang, Caixia; Zhou, Yu

2014-01-01

274

The Position of Proximal Reference Point of Tibia Plateau for Correct Tibial Osteotomy in Total Knee Replacement: Prospective Randomized and 6 Years Follow-up Study  

PubMed Central

Purpose When there is a varus deformity in proximal tibia, the extension of a tibial shaft axis tends to pass through the lateral intercondylar eminence. A prospective randomized study was conducted to find out whether the lateral eminence of tibia could serve as a reference point for proximal tibial osteotomy during total knee arthroplasty and results from 6-years follow up period were reported. Materials and Methods Forty-six patients (50 knees) who received total knee replacement arthroplasty from April to December 2004, were randomly divided into two groups. For a proximal tibial osteotomy, the proximal tibial reference point was located at the center of intercondylar eminence for group I and at the lateral eminence for group II and subsequently, the results were evaluated. Radiologic indices were the angles between the axis of the prosthesis and the mechanical/shaft axes of tibia and angle of the prosthesis in sagittal plane. Clinical indices were pain and function score of American knee society, functional score of Hospital for Special Surgery and range of knee joint motion. Results The angles between the axis of the prostheses and the mechanical/shaft axes of tibia were varus 1.64°/2.12° in group I and valgus 0.57°/0.38° in group II (p=0.589/p=0.558). There were 6 cases of outliers (27.2%) in group 1 and 3 cases (15.0%) in group 2. There was a significant difference in the pain score between group I (82.9) and II (91.4) (p=0.032), respectively. Conclusions By moving the reference point of proximal tibial osteotomy laterally, lower incidence of outlier and residual varus deformity could be achieved. PMID:22570834

Chae, Woo Young

2011-01-01

275

Golgi Positioning  

PubMed Central

The Golgi apparatus in mammalian cells is positioned near the centrosome-based microtubule-organizing center (Fig. 1). Secretory cargo moves inward in membrane carriers for delivery to Golgi membranes in which it is processed and packaged for transport outward to the plasma membrane. Cytoplasmic dynein motor proteins (herein termed dynein) primarily mediate inward cargo carrier movement and Golgi positioning. These motors move along microtubules toward microtubule minus-ends embedded in centrosomes. Centripetal motility is controlled by a host of regulators whose precise functions remain to be determined. Significantly, a specific Golgi receptor for dynein has not been identified. This has impaired progress toward elucidation of membrane-motor-microtubule attachment in the periphery and, after inward movement, recycling of the motor for another round. Pericentrosomal positioning of the Golgi apparatus is dynamic. It is regulated during critical cellular processes such as mitosis, differentiation, cell polarization, and cell migration. Positioning is also important as it aligns the Golgi along an axis of cell polarity. In certain cell types, this promotes secretion directed to the proximal plasma membrane domain thereby maintaining specializations critical for diverse processes including wound healing, immunological synapse formation, and axon determination. PMID:21504874

Yadav, Smita; Linstedt, Adam D.

2011-01-01

276

Disparities in CD4+ T-Lymphocyte Monitoring Among Human Immunodeficiency Virus-Positive Medicaid Beneficiaries: Evidence of Differential Treatment at the Point of Care  

PubMed Central

Background Monitoring of immune function, measured by CD4 cell count, is an essential service for people with Human Immunodeficiency Virus (HIV). Prescription of antiretroviral (ARV) medications is contingent on CD4 cell count; patients without regular CD4 monitoring are unlikely to receive ARVs when indicated. This study assesses disparities in CD4 monitoring among HIV-positive Medicaid beneficiaries. Methods In this retrospective observational study, we examined 24 months of administrative data on 2,250 HIV-positive, continuously-enrolled fee-for-service Medicaid beneficiaries with at least two outpatient healthcare encounters. We used logistic regression to evaluate the association of patient demographics (age, gender, race/ethnicity, and language) with receipt of at least one CD4 test per year, controlling for other potentially confounding variables. Results Having a history of ARV therapy was positively associated with receipt of CD4 tests. We found racial/ethnic, gender, and age disparities in CD4 testing. Among individuals with a history of ARV use, all racial/ethnic groups were significantly less likely to have CD4 tests than White non-Latinos (African Americans, OR = 0.35, p<0.0001; Asian/Pacific Islanders, OR = 0.31, p=0.0047; and, Latinos, OR = 0.42, p<0.0001). Conclusions Disparities in receipt of CD4 tests elucidate one potential pathway for previously reported disparities in ARV treatment. Further qualitative and quantitative research is needed to identify the specific factors that account for these disparities, so that appropriate interventions can be implemented. PMID:25401120

Davis, Anna C.; Watson, Greg; Pourat, Nadereh; Kominski, Gerald F.; Roby, Dylan H.

2014-01-01

277

Precision Pulsar Timing  

NASA Astrophysics Data System (ADS)

P140 continues to set new standards in precision timing, in terms of both the quality and quantity of pulsars timed at the sub-microsecond level. Recent highlights include highest precision timing (74 ns), the best relative timing (pulsar versus pulsar) of 200 ns, new parallaxes, DM variations and outstanding astrometry. P140 has been conducted for more than ten years. We propose to continue this experiment, improving timing methodologies and precision. This unprecedented precision timing baseline provides exciting opportunities to investigate the existence and level of any Gravitational Wave Background and allows pulsar astrometric parameter estimations with unprecedented accuracies in astronomy.

Bailes, Matthew; Ord, Stephen; Manchester, Dick; Verbiest, Joris P. W.; Bhat, Ramesh; Hotan, Aidan; Kulkarni, S. R.; Jacoby, Bryan; Teoh, Albert

2006-04-01

278

Precision autonomous underwater navigation  

E-print Network

Deep-sea archaeology, an emerging application of autonomous underwater vehicle (AUV) technology, requires precise navigation and guidance. As science requirements and engineering capabilities converge, navigating in the ...

Bingham, Brian S. (Brian Steven), 1973-

2003-01-01

279

Precision Optics Curriculum.  

ERIC Educational Resources Information Center

This guide outlines the competency-based, two-year precision optics curriculum that the American Precision Optics Manufacturers Association has proposed to fill the void that it suggests will soon exist as many of the master opticians currently employed retire. The model, which closely resembles the old European apprenticeship model, calls for 300…

Reid, Robert L.; And Others

280

Precision in liver surgery.  

PubMed

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

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

2013-08-01

281

Comparing costs and effectiveness of different starting points for highly active antiretroviral therapy in HIV-positive patients. Evidence from the ICONA cohort.  

PubMed

We evaluated the costs and effectiveness of starting highly active antiretroviral therapy (HAART) at different points during the course of HIV infection, defined on the basis of CD4 T-lymphocytes counts. The study considered 3,250 HAART-naive patients of the Italian Cohort Naive Antiretrovirals (ICONA), enrolled and followed between 1997 and 2002. In correspondence to the thresholds of 500, 350, and 200 CD4 cells/mm(3), we selected immediate and deferred groups accounting for lead-time bias. The effects of immediate vs. deferred treatment on AIDS-free survival and direct health costs were estimated stratifying on the propensity score of immediate HAART initiation. The incremental cost-effectiveness ratio (ICER) and the cost-effectiveness acceptability curve were also obtained. Although immediate HAART initiation did not affect incidence AIDS and death at high CD4 levels, starting HAART with 200-349 CD4 cells/mm(3) rather than deferring it below 200 CD4 cells/mm(3), proved to be cost-effective. PMID:16404620

Merito, Monica; Pezzotti, Patrizio

2006-03-01

282

Precision ozone vapor pressure measurements  

NASA Technical Reports Server (NTRS)

The vapor pressure above liquid ozone has been measured with a high accuracy over a temperature range of 85 to 95 K. At the boiling point of liquid argon (87.3 K) an ozone vapor pressure of 0.0403 Torr was obtained with an accuracy of + or - 0.7 percent. A least square fit of the data provided the Clausius-Clapeyron equation for liquid ozone; a latent heat of 82.7 cal/g was calculated. High-precision vapor pressure data are expected to aid research in atmospheric ozone measurements and in many laboratory ozone studies such as measurements of cross sections and reaction rates.

Hanson, D.; Mauersberger, K.

1985-01-01

283

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

PubMed Central

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

2014-01-01

284

Distribution and mitigation of higher-order ionospheric effects on precise GNSS processing  

NASA Astrophysics Data System (ADS)

Higher-order ionospheric effects (I2+) are one of the main limiting factors in very precise Global Navigation Satellite Systems (GNSS) processing, for applications where millimeter accuracy is demanded. This paper summarizes a comprehensive study of the I2+ effects in range and in GNSS precise products such as receiver position and clock, tropospheric delay, geocenter offset, and GNSS satellite position and clock. All the relevant higher-order contributions are considered: second and third orders, geometric bending, and slant total electron content (dSTEC) bending (i.e., the difference between the STEC for straight and bent paths). Using a realistic simulation with representative solar maximum conditions on GPS signals, both the effects and mitigation errors are analyzed. The usage of the combination of multifrequency L band observations has to be rejected due to its increased noise level. The results of the study show that the main two effects in range are the second-order ionospheric and dSTEC terms, with peak values up to 2 cm. Their combined impacts on the precise GNSS satellite products affects the satellite Z coordinates (up to +1 cm) and satellite clocks (more than ±20 ps). Other precise products are affected at the millimeter level. After correction the impact on all the precise GNSS products is reduced below 5 mm. We finally show that the I2+ impact on a Precise Point Positioning (PPP) user is lower than the current uncertainties of the PPP solutions, after applying consistently the precise products (satellite orbits and clocks) obtained under I2+ correction.

Hernández-Pajares, Manuel; Aragón-Ángel, Àngela; Defraigne, Pascale; Bergeot, Nicolas; Prieto-Cerdeira, Roberto; García-Rigo, Alberto

2014-04-01

285

Precision Segmented Reflectors (PSR)  

NASA Technical Reports Server (NTRS)

Current Precision Segmented Reflectors (PSR) technology development is intended for LDR-like applications: (1) Large segmented reflector systems; (2) Lightweight composite panels at 3 micron root-mean-square (RMS); (3) Precision lightweight structure at 500 microns; (4) Active figure control at 1 micron RMS accuracy; and (5) 5 micron RMS overall surface accuracy. Development of PSR technologies to date has demonstrated the potential of: (1) Lightweight composite panels at 0.1 micron RMS via polishing and re-finishing; (2) Shape control of composite panels by imbedded actuators; (3) Precision lightweight structure at 100 microns or better; and (4) Smart structure strut that can suppress vibrations and change its length.

Lin, Richard Y.

1989-01-01

286

Precision Observational Asteroseismology Using Kepler Spacecraft Data  

NASA Astrophysics Data System (ADS)

The Kepler spacecraft has been constantly observing the same stars since March, 2010 and at this point, nearly 3 years of data are archived for more than a dozen pulsating sdB stars. With better than a 90% duty cycle, and a new observation every minute, more than a million data points per star are available for examination. In this paper, we discuss a few highlights from these data for sdB pulsators, indicating the precision of the measurements and including multiple methods for constraining pulsation modes. These Kepler data represent a shift from observationally underconstrained models to precision observational asteroseismology to which models will struggle to match.

Reed, M.; Foster, H.

2014-04-01

287

Telescope pointing for GOPEX  

NASA Technical Reports Server (NTRS)

In order for photons emitted by the GOPEX lasers to be detected by Galileo's camera, the telescopes at Table Mountain Observatory and Starfire Optical Range had to be pointed in the right direction within a tolerance less than the beam divergence. At both sites nearby stars were used as pointing references. The technical challenge was to ensure that the transmission direction and the star positions were specified in exactly the same coordinate system; given this assurance, neither the uncertainty in the star catalog positions nor the difficulty in offset pointing was expected to exceed the pointing error budget. The correctness of the pointing scheme was verified by the success of GOPEX.

Owen, W. M., Jr.

1993-01-01

288

Observation of NO B2Pi(v = 3)-X2Pi(v = 0) absorptions with 1 + 1 multiphoton ionization - Precision line position measurements and parity assignment of the B2Pi state  

Microsoft Academic Search

Absorptions have been observed in the beta(3,0) band of NO, B2Pi(v = 3)-X2Pi(v = 0) using 1 + 1 multiphoton ionization at photon energies in the 47,801-48,542\\/cm range. Line positions are reported in 10 of the 12 possible branches with an accuracy of 0.05\\/cm, directly traceable to the visible I2 absorption spectrum. A doubling in the beta(3,0) band is explicitly

G. W. Faris; P. C. Cosby

1992-01-01

289

An improved procedure for separation/purification of boron from complex matrices and high-precision measurement of boron isotopes by positive thermal ionization and multicollector inductively coupled plasma mass spectrometry.  

PubMed

In order to eliminate boron loss and potential isotopic fractionation during chemical pretreatment of natural samples with complex matrices, a three-column ion-exchange separation/purification procedure has been modified, which ensures more than 98% recovery of boron from each step for a wide range of sample matrices, and is applicable for boron isotope analysis by both TIMS and MC-ICP-MS. The PTIMS-Cs2BO2(+)-static double collection method was developed, ensuring simultaneous collection of (133)Cs2(11)B(16)O2(+)(m/z 309) and (133)Cs2(10)B(16)O2(+) (m/z 308) ions in adjacent H3-H4 Faraday cups with typical zoom optics parameters (Focus Quad: 15 V, Dispersion Quad: -85 V). The external reproducibilities of the measured (11)B/(10)B ratios of the NIST 951 boron standard solutions of 1000 ng, 100 ng and 10 ng of boron by PTIMS method are ±0.06‰, ±0.16‰ and ±0.25‰, respectively, which indicates excellent precision can be achieved for boron isotope measurement at nanogram level boron in natural samples. An on-peak zero blank correction procedure was employed to correct the residual boron signals effect in MC-ICP-MS, which gives consistent ?(11)B values with a mean of 39.66±0.35‰ for seawater in the whole range of boron content from 5 ppb to 200 ppb, ensuring accurate boron isotope analysis in few ppb boron. With the improved protocol, consistent results between TIMS and MC-ICP-MS data were obtained in typical geological materials within a wide span of ?(11)B values ranging from -25‰ to +40‰. PMID:24725878

Wei, Hai-Zhen; Jiang, Shao-Yong; Hemming, N Gary; Yang, Jing-Hong; Yang, Tao; Wu, He-Pin; Yang, Tang-Li; Yan, Xiong; Pu, Wei

2014-06-01

290

Precision tip-tilt-piston actuator that provides exact constraint  

DOEpatents

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

Hale, Layton C. (Livermore, CA)

1999-01-01

291

The use of Global Positioning System techniques for the continuous monitoring of landslides: application to the Super-Sauze earthflow (Alpes-de-Haute-Provence, France)  

Microsoft Academic Search

Recent researches have demonstrated the applicability of using Global Positioning System (GPS) techniques to precisely determine the 3-D coordinates of moving points in the field of natural hazards. Indeed, the detailed analysis of the motion of a landslide, in particular for a near real-time warning system, requires the combination of accurate positioning in three dimensions (infracentimetric) and fine temporal resolution

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

2002-01-01

292

Chemical patterning on preformed porous silicon photonic crystals: towards multiplex detection of protease activity at precise positions†Electronic supplementary information (ESI) available: SEM images, XPS result and more optical reflectivity data. See DOI: 10.1039/c4tb00281dClick here for additional data file.  

PubMed

Porous silicon (PSi) rugate filters modified with alkyne-terminated monolayers were chemically patterned using a combination of photolithography of photoresist and click chemistry. Two chemical functionalities were obtained by conjugating, via click reactions, ethylene glycol moieties containing two different terminal groups to discrete areas towards the exterior of a PSi rugate filter. The patterning of biological species to the functionalized surface was demonstrated through the conjugation of fluorescein isothiocyanate labelled bovine serum albumin (FITC-BSA). Fluorescence microscopy showed selective positioning of FITC-BSA at discretely functionalized areas. Meanwhile, the optical information from precisely defined positions on the patterned surface was monitored by optical reflectivity measurements. The optical measurements revealed successful step-wise chemical functionalization followed by immobilization of gelatin. Multiplex detection of protease activity from different array elements on the patterned surface was demonstrated by monitoring the blue shifts in the reflectivity spectra resulted from the digestion of gelatin by subtilisin. Precise information from both individual elements and average population was acquired. This technique is important for the development of PSi into a microarray platform for highly parallel biosensing applications, especially for cell-based assays. PMID:24910774

Zhu, Ying; Soeriyadi, Alexander H; Parker, Stephen G; Reece, Peter J; Gooding, J Justin

2014-06-21

293

Precision Electroweak Measurements at FCC-ee  

E-print Network

The prospects for electroweak precision measurements at the Future Circular Collider with electron-positron beams (FCC-ee) are discussed. The Z mass and width, as well as the value of the electroweak mixing angle, can be measured with very high precision at the Z pole thanks to an instantaneous luminosity five to six order of magnitudes larger than LEP. At centre-of-mass energies around 160 GeV, corresponding to the WW production threshold, the W mass can be determined very precisely with high-statistics cross section measurements at several energy points. Similarly, a very precise determination of the top mass can be provided by an energy scan at the $\\mathrm{t \\bar t}$ production threshold, around 350 GeV.

Roberto Tenchini

2014-12-09

294

Precision Electroweak Measurements at FCC-ee  

E-print Network

The prospects for electroweak precision measurements at the Future Circular Collider with electron-positron beams (FCC-ee) are discussed. The Z mass and width, as well as the value of the electroweak mixing angle, can be measured with very high precision at the Z pole thanks to an instantaneous luminosity five to six order of magnitudes larger than LEP. At centre-of-mass energies around 160 GeV, corresponding to the WW production threshold, the W mass can be determined very precisely with high-statistics cross section measurements at several energy points. Similarly, a very precise determination of the top mass can be provided by an energy scan at the $\\mathrm{t \\bar t}$ production threshold, around 350 GeV.

Tenchini, Roberto

2014-01-01

295

Developing Precision Stroke Imaging  

PubMed Central

Stroke experts stand at the cusp of a unique opportunity to advance the care of patients with cerebrovascular disorders across the globe through improved imaging approaches. NIH initiatives including the Stroke Progress Review Group promotion of imaging in stroke research and the newly established NINDS Stroke Trials network converge with the rapidly evolving concept of precision medicine. Precision stroke imaging portends the coming shift to individualized approaches to cerebrovascular disorders where big data may be leveraged to identify and manage stroke risk with specific treatments utilizing an improved neuroimaging infrastructure, data collection, and analysis. We outline key aspects of the stroke imaging field where precision medicine may rapidly transform the care of stroke patients in the next few years. PMID:24715885

Feldmann, Edward; Liebeskind, David S.

2014-01-01

296

Precision electron polarimetry  

SciTech Connect

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.

Chudakov, Eugene A. [JLAB

2013-11-01

297

Precision electron polarimetry  

SciTech Connect

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. Mo/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 Mo/ller polarimetry.

Chudakov, E. [Jefferson Lab 12000 Jefferson Ave, STE 16, Newport News, VA 23606 (United States)

2013-11-07

298

Space Telescope pointing control  

NASA Technical Reports Server (NTRS)

The Space Telescope, a long life, high performance spacecraft deployed by the Space Shuttle, will carry five scientific instruments on its first mission. Its pointing control system will permit target-to-target maneuvering and precision pointing on a target star to support scientific objectives. Spacecraft attitude control is achieved by onboard computer processing of attitude and rate sensor data to generate reaction wheel torque commands. A momentum management control system is provided to desaturate the reaction wheels. This paper discusses the pointing control system and the control hardware investigations and improvements leading to system design.

Dougherty, H.; Rodoni, C.; Rodden, J.; Tompetrini, K.

1984-01-01

299

Precision Information Environments  

E-print Network

Precision Information Environments Unforeseen events, such as the Hudson Bay incident, medium critical information and tools for support. Not all disasters or events that need support are unforeseen Information Environments (PIEs) will provide tailored access to information and decision support capabilities

300

Precision liquid level sensor  

DOEpatents

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

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

1985-01-01

301

Precision liquid level sensor  

DOEpatents

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

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

1985-01-29

302

Precision bolometer bridge  

NASA Technical Reports Server (NTRS)

Prototype precision bolometer calibration bridge is manually balanced device for indicating dc bias and balance with either dc or ac power. An external galvanometer is used with the bridge for null indication, and the circuitry monitors voltage and current simultaneously without adapters in testing 100 and 200 ohm thin film bolometers.

White, D. R.

1968-01-01

303

Targets for Precision Measurements  

E-print Network

The general properties needed in targets (sources) for high precision, high accuracy measurements are reviewed. The application of these principles to the problem of developing targets for the Fission TPC is described. Longer term issues, such as the availability of actinide materials, improved knowledge of energy losses and straggling and the stability of targets during irradiation are also discussed.

Loveland, W; Asner, David M; Baker, R G; Bundgaard, J; Burgett, E; Cunningham, M; Deaven, J; Duke, D L; Greife, U; Grimes, S; Heffer, M; Hill, T; Isenhower, D; Klay, J L; Kleinrath, V; Kornilov, N; Laptev, A B; Massey, T N; Meharchand, R; Qu, H; Ruz, J; Sangiorgio, S; Selhan, B; Snyder, L; Stave, S; Tatishvili, G; Thornton, R T; Tovesson, F; Towell, D; Towell, R S; Watson, S; Wendt, B; Wood, L

2013-01-01

304

Targets for Precision Measurements  

NASA Astrophysics Data System (ADS)

The general properties needed in targets (sources) for high precision, high accuracy measurements are reviewed. The application of these principles to the problem of developing targets for the Fission TPC is described. Longer term issues, such as the availability of actinide materials, improved knowledge of energy losses and straggling and the stability of targets during irradiation are also discussed.

Loveland, W.; Yao, L.; Asner, D. M.; Baker, R. G.; Bundgaard, J.; Burgett, E.; Cunningham, M.; Deaven, J.; Duke, D. L.; Greife, U.; Grimes, S.; Heffner, M.; Hill, T.; Isenhower, D.; Klay, J. L.; Kleinrath, V.; Kornilov, N.; Laptev, A. B.; Massey, T. N.; Meharchand, R.; Qu, H.; Ruz, J.; Sangiorgio, S.; Selhan, B.; Snyder, L.; Stave, S.; Tatishvili, G.; Thornton, R. T.; Tovesson, F.; Towell, D.; Towell, R. S.; Watson, S.; Wendt, B.; Wood, L.

2014-05-01

305

Targets for Precision Measurements  

E-print Network

The general properties needed in targets (sources) for high precision, high accuracy measurements are reviewed. The application of these principles to the problem of developing targets for the Fission TPC is described. Longer term issues, such as the availability of actinide materials, improved knowledge of energy losses and straggling and the stability of targets during irradiation are also discussed.

W. Loveland; L. Yao; David M. Asner; R. G. Baker; J. Bundgaard; E. Burgett; M. Cunningham; J. Deaven; D. L. Duke; U. Greife; S. Grimes; M. Heffer; T. Hill; D. Isenhower; J. L. Klay; V. Kleinrath; N. Kornilov; A. B. Laptev; T. N. Massey; R. Meharchand; H. Qu; J. Ruz; S. Sangiorgio; B. Selhan; L. Snyder; S. Stave; G. Tatishvili; R. T. Thornton; F. Tovesson; D. Towell; R. S. Towell; S. Watson; B. Wendt; L. Wood

2013-03-09

306

Precision flyer initiator  

Microsoft Academic Search

A precision flyer initiator forms a substantially spherical detonation wave in a high explosive (HE) pellet. An explosive driver, such as a detonating cord, a wire bridge circuit or a small explosive, is detonated. A flyer material is sandwiched between the explosive driver and an end of a barrel that contains an inner channel. A projectile or \\

Alan M. Frank; Ronald S. Lee

1998-01-01

307

Precision flyer initiator  

Microsoft Academic Search

A precision flyer initiator forms a substantially spherical detonation wave in a high explosive (HE) pellet. An explosive driver, such as a detonating cord, a wire bridge circuit or a small explosive, is detonated. A flyer material is sandwiched between the explosive driver and an end of a barrel that contains an inner channel. A projectile or ``flyer`` is sheared

A. M. Frank; R. S. Lee

1998-01-01

308

Precision metal molding  

NASA Technical Reports Server (NTRS)

Method provides precise alignment for metal-forming dies while permitting minimal thermal expansion without die warpage or cavity space restriction. The interfacing dowel bars and die side facings are arranged so the dies are restrained in one orthogonal angle and permitted to thermally expand in the opposite orthogonal angle.

Townhill, A.

1967-01-01

309

Precision in Stereochemical Terminology  

ERIC Educational Resources Information Center

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…

Wade, Leroy G., Jr.

2006-01-01

310

Profile guided code positioning  

Microsoft Academic Search

This paper presents the results of our investigation of code positioning techniques using execution profile data as input into the compilation process. The primary objective of the positioning is to reduce the overhead of the instruction memory hierarchy.After initial investigation in the literature, we decided to implement two prototypes for the Hewlett-Packard Precision Architecture (PA-RISC). The first, built on top

Karl Pettis; Robert C. Hansen; Jack W. Davidson

2004-01-01

311

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.

312

Learning precisely timed spikes.  

PubMed

To signal the onset of salient sensory features or execute well-timed motor sequences, neuronal circuits must transform streams of incoming spike trains into precisely timed firing. To address the efficiency and fidelity with which neurons can perform such computations, we developed a theory to characterize the capacity of feedforward networks to generate desired spike sequences. We find the maximum number of desired output spikes a neuron can implement to be 0.1-0.3 per synapse. We further present a biologically plausible learning rule that allows feedforward and recurrent networks to learn multiple mappings between inputs and desired spike sequences. We apply this framework to reconstruct synaptic weights from spiking activity and study the precision with which the temporal structure of ongoing behavior can be inferred from the spiking of premotor neurons. This work provides a powerful approach for characterizing the computational and learning capacities of single neurons and neuronal circuits. PMID:24768299

Memmesheimer, Raoul-Martin; Rubin, Ran; Olveczky, Bence P; Sompolinsky, Haim

2014-05-21

313

Ultra-Precision Optics  

NASA Technical Reports Server (NTRS)

Under a Joint Sponsored Research Agreement with Goddard Space Flight Center, SEMATECH, Inc., the Silicon Valley Group, Inc. and Tinsley Laboratories, known as SVG-Tinsley, developed an Ultra-Precision Optics Manufacturing System for space and microlithographic applications. Continuing improvements in optics manufacture will be able to meet unique NASA requirements and the production needs of the lithography industry for many years to come.

1999-01-01

314

Precise linear sun sensor  

NASA Technical Reports Server (NTRS)

An evaluation of the precise linear sun sensor relating to future mission applications was performed. The test procedures, data, and results of the dual-axis, solid-state system are included. Brief descriptions of the sensing head and of the system's operational characteristics are presented. A unique feature of the system is that multiple sensor heads with various fields of view may be used with the same electronics.

Johnston, D. D.

1972-01-01

315

Exploiting Mixed Precision Floating Point Hardware in Scientific  

E-print Network

such as Field Programmable Gate Arrays (FPGA), Graphical Processing Units (GPU), and the Cell BE processor. Results on modern processor architectures and the Cell BE are presented. Keywords. Iterative refinement/s] [Gflop/s] AMD Opteron 246 2.0 4 8 IBM PowerPC 970 2.5 10 20 Intel Xeon 5100 3.0 12 24 STI Cell BE 3.2 1

Dongarra, Jack

316

Space telescope pointing control system  

NASA Technical Reports Server (NTRS)

The Space Telescope is a free-flying spacecraft designed for Space Shuttle launch. The Space Telescope's pointing control system slews the optical axis from one target star region of the celestial sphere to the next, and maintains precision pointing for the target star for up to 24 hours. The spacecraft digital computer processes the precision attitude and rate sensor data to generate torque commands for the reaction wheels. The pointing control system has four major elements: the command generator, the control system, the attitude reference processing, and momentum management. The emphasis is on relating design requirements to the hardware and software implementation.

Dougherty, H.; Tompetrini, K.; Levinthal, J.; Nurre, G.

1982-01-01

317

Offered: Offered: Position(s): Position(s)  

E-print Network

, industrial, consumer, and portable electronics". The IC group produces power ICs for motor drivers, motor), industrial, automotive and portable electronics markets. Electrical Engineering No Entry LevelCompany: Industry: Website: Majors: Offered: Offered: Position(s): Position(s): Description

New Hampshire, University of

318

Magnetically suspended contact-free linear actuator for precision stage  

Microsoft Academic Search

With the development of precision manufacturing technologies, the importance of precision positioning devices is increasing.\\u000a Conventional actuators, dual stage or mechanically contacting type, have limitation in coping with performance demands. As\\u000a a possible solution, magnetic suspension technology was studied. Such a contact-free system has advantages in terms of high\\u000a accuracy, low production cost and easy adaptability to high precision manufacturing

Sang Heon Lee; Yoon Su Baek

2003-01-01

319

High precision redundant robotic manipulator  

DOEpatents

A high precision redundant robotic manipulator for overcoming contents imposed by obstacles or imposed by a highly congested work space is disclosed. One embodiment of the manipulator has four degrees of freedom and another embodiment has seven degrees of freedom. Each of the embodiments utilize a first selective compliant assembly robot arm (SCARA) configuration to provide high stiffness in the vertical plane, a second SCARA configuration to provide high stiffness in the horizontal plane. The seven degree of freedom embodiment also utilizes kinematic redundancy to provide the capability of avoiding obstacles that lie between the base of the manipulator and the end effector or link of the manipulator. These additional three degrees of freedom are added at the wrist link of the manipulator to provide pitch, yaw and roll. The seven degrees of freedom embodiment uses one revolute point per degree of freedom. For each of the revolute joints, a harmonic gear coupled to an electric motor is introduced, and together with properly designed based servo controllers provide an end point repeatability of less than 10 microns. 3 figs.

Young, K.K.D.

1998-09-22

320

High precision redundant robotic manipulator  

DOEpatents

A high precision redundant robotic manipulator for overcoming contents imposed by obstacles or imposed by a highly congested work space. One embodiment of the manipulator has four degrees of freedom and another embodiment has seven degreed of freedom. Each of the embodiments utilize a first selective compliant assembly robot arm (SCARA) configuration to provide high stiffness in the vertical plane, a second SCARA configuration to provide high stiffness in the horizontal plane. The seven degree of freedom embodiment also utilizes kinematic redundancy to provide the capability of avoiding obstacles that lie between the base of the manipulator and the end effector or link of the manipulator. These additional three degrees of freedom are added at the wrist link of the manipulator to provide pitch, yaw and roll. The seven degrees of freedom embodiment uses one revolute point per degree of freedom. For each of the revolute joints, a harmonic gear coupled to an electric motor is introduced, and together with properly designed based servo controllers provide an end point repeatability of less than 10 microns.

Young, Kar-Keung David (Mountain View, CA)

1998-01-01

321

High-Precision Computation and Mathematical Physics  

SciTech Connect

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.

Bailey, David H.; Borwein, Jonathan M.

2008-11-03

322

Modeling GPS satellite attitude variation for precise orbit determination  

Microsoft Academic Search

High precision geodetic application of the Global Positioning System (GPS) require highly precise ephemerides of the GPS satellites. An accurate model for the non-gravitational forces on the GPS satellites is a key to high quality GPS orbit determination, especially in long arcs. In this paper the effect of the satellite solar panel orientation error is investigated. These effects are approximated

D. Kuang; H. J. Rim; B. E. Schutz; P. A. M. Abusali

1996-01-01

323

The Integration of Positioning Technologies for Precise Location ID  

Microsoft Academic Search

With the growing trend towards a world where people, vehicles, and other mobile objects are getting more and more interconnected, location information is increasingly becoming a recognized need for providing rapid and timely information to the mobile workforce. More and more products are present in the market that allows location identifications. In this paper, the key deliverable is the Hierarchical

Tee Yong Chew

324

Tests of FARICH prototype with precise photon position detection  

NASA Astrophysics Data System (ADS)

In June 2012 a FARICH prototype from Philips Digital Photon Counting (PDPC) based on a photon camera with dimensions of 200×200 mm has been tested at CERN. Remarkable particle separation has been achieved with a 4-layer aerogel sample: the ?/K separation at a 6 GeV/c momentum is 3.5?, the ? / ? separation is 5.3? at 1 GeV/c. The analysis of the data has shown that the main contribution to the accuracy of the ring radius measurement comes from aerogel. The development of focusing aerogels is proceeding in two main directions: tuning of production technology of multilayer blocks and development of a new production method with continuous density (refractive index) gradient along the block depth. The beam test was carried out in December 2012-January 2013 at the electron beam test facility at the VEPP-4 M e+e- collider. The goal of this test was to measure different single layer and focusing aerogel samples, both multilayer and gradient. Aerogel samples were tested with a PDPC FARICH prototype. A part of DPC SPADs in each pixel was disabled to form an active area of 1×1 mm2. The collected data proved that gradient aerogel samples focus Cherenkov light.

Barnyakov, A. Yu.; Barnyakov, M. Yu.; Basok, I. Yu.; Blinov, V. E.; Bobrovnikov, V. S.; Borodenko, A. A.; Buzykaev, A. R.; Danilyuk, A. F.; Degenhardt, C.; Dorscheid, R.; Finogeev, D. A.; Frach, T.; Gulevich, V. V.; Karavicheva, T. L.; Kasyanenko, P. V.; Kononov, S. A.; Korda, D. V.; Kravchenko, E. A.; Kudryavtsev, V. N.; Kurepin, A. B.; Kuyanov, I. A.; Muelhens, O.; Onuchin, A. P.; Ovtin, I. V.; Podgornov, N. A.; Predein, A. Yu.; Prisekin, V. G.; Protsenko, R. S.; Razin, V. I.; Reshetin, A. I.; Schulze, R.; Shekhtman, L. I.; Talyshev, A. A.; Usenko, E. A.; Zwaans, B.

2014-12-01

325

Precision Robotic Assembly Machine  

SciTech Connect

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.

2009-08-14

326

Precision electroweak measurements  

SciTech Connect

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

Demarteau, M.

1996-11-01

327

Precision Robotic Assembly Machine  

ScienceCinema

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.

None

2010-09-01

328

Design of ultra precision fixtures for nano-manufacturing  

E-print Network

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, ...

Mangudi Varadarajan, Kartik, 1981-

2005-01-01

329

Precision flyer initiator  

DOEpatents

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

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

1998-05-26

330

Precision flyer initiator  

DOEpatents

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

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

1998-01-01

331

Overview of the national precision database for ozone  

SciTech Connect

One of the most important ambient air monitoring quality assurance indicators is the precision test. Code of Federal Regulation Title 40, Section 58 (40 CFR 58) Appendix A1 states that all automated analyzers must have precision tests performed at least once every two weeks. Precision tests can be the best indicator of quality of data for the following reasons: Precision tests are performed once every two weeks. There are approximately 24 to 26 tests per year per instrument. Accuracy tests (audits) usually occur only 1--2 times per year. Precision tests and the subsequent statistical tests can be used to calculate the bias in a set of data. Precision test are used to calculate 95% confidence (probability) limits for the data set. This is important because the confidence of any data point can be determined. If the authors examine any exceedances or near exceedances of the ozone NAAQS, the confidence limits must be examined as well. Precision tests are performed by the monitoring staff and the precision standards are certified against the internal agency primary standards. Precision data are submitted by all state and local agencies that are required to submit criteria pollutant data to the Aerometric and Information Retrieval System (AIRS) database. This subset of the AIRS database is named Precision and Accuracy Retrieval Systems (PARS). In essence, the precision test is an internally performed test performed by the agency collecting and reporting the data.

Mikel, D.K.

1999-07-01

332

Topic in Depth - Precision Machining  

NSDL National Science Digital Library

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

333

Precision alignment device  

DOEpatents

Apparatus for providing automatic alignment of beam devices having an associated structure for directing, collimating, focusing, reflecting, or otherwise modifying the main beam. A reference laser is attached to the structure enclosing the main beam producing apparatus and produces a reference beam substantially parallel to the main beam. Detector modules containing optical switching devices and optical detectors are positioned in the path of the reference beam and are effective to produce an electrical output indicative of the alignment of the main beam. This electrical output drives servomotor operated adjustment screws to adjust the position of elements of the structure associated with the main beam to maintain alignment of the main beam. 5 figs.

Jones, N.E.

1988-03-10

334

The Precision Formation Flying Integrated Analysis Tool (PFFIAT)  

NASA Technical Reports Server (NTRS)

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.

Stoneking, Eric; Lyon, Richard G.; Sears, Edie; Lu, Victor

2004-01-01

335

Space Telescope pointing control  

NASA Technical Reports Server (NTRS)

The Space Telescope Pointing Control System is used to slew the optical axis of the telescope from one target star region of the celestial sphere to the next, and to maintain precision pointing on the target star. A digital computer is employed in the processing of attitude and rate sensor data, in order to generate torque commands for the reaction wheels. The System comprises four major elements: a command generator, the electronic control system, attitude update processing, and momentum management. Emphasis is given to control-related flexibility effects of the Space Telescope's solar cell array and vehicle, and the acquisition methodology and development testing employed, in addition to Pointing Control System design features.

Dougherty, H.; Rodoni, C.; Tompetrini, K.; Nakashima, A.

1983-01-01

336

Positions of Uranian satellites.  

NASA Astrophysics Data System (ADS)

Positions of Uranian satellites from 333 photographic plates obtained at the Cassegrain focus of a 1.6 m reflector are given for the oppositions of 1983 through 1988. These positions were reduced using photometric methods and compared with those calculated theoretically calculated from GUST86. The observed minus calculated residuals referred to Oberon, have standard deviations of the order of 0".04 for the four greatest Uranian satellites and 0".09 for Miranda. These residuals for the four satellites are better than the most precise found in the literature.

Veiga, C. H.; Vieira Martins, R.

1994-11-01

337

Prompt and Precise Prototyping  

NASA Technical Reports Server (NTRS)

For Sanders Design International, Inc., of Wilton, New Hampshire, every passing second between the concept and realization of a product is essential to succeed in the rapid prototyping industry where amongst heavy competition, faster time-to-market means more business. To separate itself from its rivals, Sanders Design aligned with NASA's Marshall Space Flight Center to develop what it considers to be the most accurate rapid prototyping machine for fabrication of extremely precise tooling prototypes. The company's Rapid ToolMaker System has revolutionized production of high quality, small-to-medium sized prototype patterns and tooling molds with an exactness that surpasses that of computer numerically-controlled (CNC) machining devices. Created with funding and support from Marshall under a Small Business Innovation Research (SBIR) contract, the Rapid ToolMaker is a dual-use technology with applications in both commercial and military aerospace fields. The advanced technology provides cost savings in the design and manufacturing of automotive, electronic, and medical parts, as well as in other areas of consumer interest, such as jewelry and toys. For aerospace applications, the Rapid ToolMaker enables fabrication of high-quality turbine and compressor blades for jet engines on unmanned air vehicles, aircraft, and missiles.

2003-01-01

338

Electrosurgery with cellular precision.  

PubMed

Electrosurgery, one of the most-often used surgical tools, is a robust but somewhat crude technology that has changed surprisingly little since its invention almost a century ago. Continuous radiofrequency is still used for tissue cutting, with thermal damage extending to hundreds of micrometers. In contrast, lasers developed 70 years later, have been constantly perfected, and the laser-tissue interactions explored in great detail, which has allowed tissue ablation with cellular precision in many laser applications. We discuss mechanisms of tissue damage by electric field, and demonstrate that electrosurgery with properly optimized waveforms and microelectrodes can rival many advanced lasers. Pulsed electric waveforms with burst durations ranging from 10 to 100 micros applied via insulated planar electrodes with 12 microm wide exposed edges produced plasma-mediated dissection of tissues with the collateral damage zone ranging from 2 to 10 microm. Length of the electrodes can vary from micrometers to centimeters and all types of soft tissues-from membranes to cartilage and skin could be dissected in liquid medium and in a dry field. This technology may allow for major improvements in outcomes of the current surgical procedures and development of much more refined surgical techniques. PMID:18270030

Palanker, Daniel V; Vankov, Alexander; Huie, Philip

2008-02-01

339

Precise Truss Assembly using Commodity Parts and Low Precision Welding  

NASA Technical Reports Server (NTRS)

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.

Komendera, Erik; Reishus, Dustin; Dorsey, John T.; Doggett, William R.; Correll, Nikolaus

2013-01-01

340

Precise Truss Assembly Using Commodity Parts and Low Precision Welding  

NASA Technical Reports Server (NTRS)

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.

Komendera, Erik; Reishus, Dustin; Dorsey, John T.; Doggett, W. R.; Correll, Nikolaus

2014-01-01

341

Design, calibration and evaluation of a robotic needle-positioning system for small animal imaging applications  

NASA Astrophysics Data System (ADS)

A needle-positioning robot has been developed for image-guided interventions in small animal research models. The device is designed to position a needle with an error <=100 µm. The robot has two rotational axes (pitch and roll) to control needle orientation, and one linear axis to perform needle insertion. The three axes intersect at a single point to create a remote centre of motion (RCM) that acts as a fulcrum for the orientation of the needle. The RCM corresponds to the skin-entry point of the needle into the animal. The robot was calibrated to ensure that the three axes intersected at a single point defining an RCM and that the needle tip was positioned at the RCM. Needle-positioning accuracy and precision were quantified in Cartesian coordinates at ten target locations in the plane of each rotational axis. The measured needle-positioning accuracy in free space was 54 ± 12 µm for the pitch axis plane and 91 ± 21 µm for the roll axis plane. The measured needle-positioning precision was 15 and 17 µm for the pitch and roll axes planes, respectively. The robot's ability to insert a needle into a tumour in a euthanized mouse was demonstrated.

Waspe, Adam C.; Cakiroglu, H. Jason; Lacefield, James C.; Fenster, Aaron

2007-04-01

342

TMDs: Evolution, modeling, precision  

E-print Network

The factorization theorem for $q_T$ 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 $\\chi^2/{\\rm points}\\lesssim 1$. We show how the fixing of the non-perturbative pieces of the evolution can be used to make predictions at present and future colliders.

Umberto D'Alesio; Miguel G. Echevarría; Stefano Melis; Ignazio Scimemi

2014-10-16

343

The GLAS Algorithm Theoretical Basis Document for Precision Orbit Determination (POD)  

NASA Technical Reports Server (NTRS)

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.

Rim, Hyung Jin; Yoon, S. P.; Schultz, Bob E.

2013-01-01

344

Precision tool holder with flexure-adjustable, three degrees of freedom for a four-axis lathe  

DOEpatents

A precision tool holder for precisely positioning a single point cutting tool on 4-axis lathe, such that the center of the radius of the tool nose is aligned with the B-axis of the machine tool, so as to facilitate the machining of precision meso-scale components with complex three-dimensional shapes with sub-.mu.m accuracy on a four-axis lathe. The device is designed to fit on a commercial diamond turning machine and can adjust the cutting tool position in three orthogonal directions with sub-micrometer resolution. In particular, the tool holder adjusts the tool position using three flexure-based mechanisms, with two flexure mechanisms adjusting the lateral position of the tool to align the tool with the B-axis, and a third flexure mechanism adjusting the height of the tool. Preferably, the flexures are driven by manual micrometer adjusters. In this manner, this tool holder simplifies the process of setting a tool with sub-.mu.m accuracy, to substantially reduce the time required to set the tool.

Bono, Matthew J. (Pleasanton, CA); Hibbard, Robin L. (Livermore, CA)

2008-03-04

345

VideoPoint  

NSDL National Science Digital Library

VideoPoint is a video analysis software package for both Macintosh and Windows based computers that allows you to collect position and time data from digital video in the form of "Video Points." Data is collected by clicking on the location of the items of interest for each frame of a QuickTime movie. These points can be combined to form other calculations such as center of mass locations and distances between points. A demo version of the software is available for download. Video Point's website includes a free resource library which is an online repository of resources, including movies, sample analyses, and activities. The resource library helps to illustrate key concepts in physics.

346

Fellowships & Positions  

Cancer.gov

Fellowships & Positions The NCI Division of Cancer Prevention is part of the National Institutes of Health (NIH), U.S. Department of Health and Human Services. Current Openings Position Title Number of Openings Cancer Prevention Fellowship Program

347

Nursing Positions  

MedlinePLUS

... breast with your other hand. The Clutch or Football Hold This is also a good position for ... same time may also choose this position. The football hold allows babies to take milk more easily — ...

348

Precision space structures  

NASA Technical Reports Server (NTRS)

NASA large space structures efforts to date aimed towards large, flexible antenna-like structures (30-100M) with relatively long wavelengths (1-30cm) and moderate disturbances leading to some structure-control interaction. Potential missions in the OPTICS regime require small reflectors/mirrors, short wavelengths (visible to 100 microns), very tight tolerances in surface, alignment, pointing stability, as well as the potential of considerable on-board disturbances. For optics systems: figure/surface control can be quasi-static, active/passive isolation schemes are possible, vibration control is necessary, and the attitude control system can be low BW - Ground testing of reflectors and mirrors is more feasible than with antennas.

Soosaar, K.

1985-01-01

349

Precision genome editing in plants via gene targeting and piggyBac-mediated marker excision  

PubMed Central

Precise genome engineering via homologous recombination (HR)-mediated gene targeting (GT) has become an essential tool in molecular breeding as well as in basic plant science. As HR-mediated GT is an extremely rare event, positive–negative selection has been used extensively in flowering plants to isolate cells in which GT has occurred. In order to utilize GT as a methodology for precision mutagenesis, the positive selectable marker gene should be completely eliminated from the GT locus. Here, we introduce targeted point mutations conferring resistance to herbicide into the rice acetolactate synthase (ALS) gene via GT with subsequent marker excision by piggyBac transposition. Almost all regenerated plants expressing piggyBac transposase contained exclusively targeted point mutations without concomitant re-integration of the transposon, resulting in these progeny showing a herbicide bispyribac sodium (BS)-tolerant phenotype. This approach was also applied successfully to the editing of a microRNA targeting site in the rice cleistogamy 1 gene. Therefore, our approach provides a general strategy for the targeted modification of endogenous genes in plants. PMID:25284193

Nishizawa-Yokoi, Ayako; Endo, Masaki; Ohtsuki, Namie; Saika, Hiroaki; Toki, Seiichi

2015-01-01

350

Precision genome editing in plants via gene targeting and piggyBac-mediated marker excision.  

PubMed

Precise genome engineering via homologous recombination (HR)-mediated gene targeting (GT) has become an essential tool in molecular breeding as well as in basic plant science. As HR-mediated GT is an extremely rare event, positive-negative selection has been used extensively in flowering plants to isolate cells in which GT has occurred. In order to utilize GT as a methodology for precision mutagenesis, the positive selectable marker gene should be completely eliminated from the GT locus. Here, we introduce targeted point mutations conferring resistance to herbicide into the rice acetolactate synthase (ALS) gene via GT with subsequent marker excision by piggyBac transposition. Almost all regenerated plants expressing piggyBac transposase contained exclusively targeted point mutations without concomitant re-integration of the transposon, resulting in these progeny showing a herbicide bispyribac sodium (BS)-tolerant phenotype. This approach was also applied successfully to the editing of a microRNA targeting site in the rice cleistogamy 1 gene. Therefore, our approach provides a general strategy for the targeted modification of endogenous genes in plants. PMID:25284193

Nishizawa-Yokoi, Ayako; Endo, Masaki; Ohtsuki, Namie; Saika, Hiroaki; Toki, Seiichi

2015-01-01

351

Simplified modeling and generalized predictive position control of an ultrasonic motor.  

PubMed

Ultrasonic motors (USM's) possess heavy nonlinear and load dependent characteristics such as dead-zone and saturation reverse effects, which vary with driving conditions. In this paper, behavior of an ultrasonic motor is modeled using Hammerstein model structure and experimental measurements. Also, model predictive controllers are designed to obtain precise USM position control. Simulation results indicate improved performance of the motor for both set point tracking and disturbance rejection. PMID:15868864

Bigdeli, Nooshin; Haeri, Mohammad

2005-04-01

352

Precision Segmented Reflector figure control system architecture  

NASA Technical Reports Server (NTRS)

A control system architecture for an actively controlled segmented reflector is described along with a design realization for achieving precision alignment of reflector panels. Performance requirements are derived in part from the Large Deployable Reflector, which is a representative mission, and error allocations are made which consider mirror panel surface errors, position measurement and figure estimation, and position control of both quasi-static and dynamic disturbances. The design uses multiple wavelength interferometric edge sensors and voice coil actuators in conjunction with a hybrid control strategy to correct panel position errors. A unit cell shown to be central to the concept is analyzed. The cell integrates the sensing, actuation, and mechanical functions of a control module together with a reflector panel to form a unitized assembly.

Mettler, E.; Eldred, D.; Briggs, C.; Kiceniuk, T.; Agronin, M.

1989-01-01

353

Precision radiotherapy for brain tumors  

PubMed Central

OBJECTIVE: Precision radiotherapy plays an important role in the management of brain tumors. This study aimed to identify global research trends in precision radiotherapy for brain tumors using a bibliometric analysis of the Web of Science. DATA RETRIEVAL: We performed a bibliometric analysis of data retrievals for precision radiotherapy for brain tumors containing the key words cerebral tumor, brain tumor, intensity-modulated radiotherapy, stereotactic body radiation therapy, stereotactic ablative radiotherapy, imaging-guided radiotherapy, dose-guided radiotherapy, stereotactic brachytherapy, and stereotactic radiotherapy using the Web of Science. SELECTION CRITERIA: Inclusion criteria: (a) peer-reviewed articles on precision radiotherapy for brain tumors which were published and indexed in the Web of Science; (b) type of articles: original research articles and reviews; (c) year of publication: 2002-2011. Exclusion criteria: (a) articles that required manual searching or telephone access; (b) Corrected papers or book chapters. MAIN OUTCOME MEASURES: (1) Annual publication output; (2) distribution according to country; (3) distribution according to institution; (4) top cited publications; (5) distribution according to journals; and (6) comparison of study results on precision radiotherapy for brain tumors. RESULTS: The stereotactic radiotherapy, intensity-modulated radiotherapy, and imaging-guided radiotherapy are three major methods of precision radiotherapy for brain tumors. There were 260 research articles addressing precision radiotherapy for brain tumors found within the Web of Science. The USA published the most papers on precision radiotherapy for brain tumors, followed by Germany and France. European Synchrotron Radiation Facility, German Cancer Research Center and Heidelberg University were the most prolific research institutes for publications on precision radiotherapy for brain tumors. Among the top 13 research institutes publishing in this field, seven are in the USA, three are in Germany, two are in France, and there is one institute in India. Research interests including urology and nephrology, clinical neurology, as well as rehabilitation are involved in precision radiotherapy for brain tumors studies. CONCLUSION: Precision radiotherapy for brain tumors remains a highly active area of research and development.

Yan, Ying; Guo, Zhanwen; Zhang, Haibo; Wang, Ning; Xu, Ying

2012-01-01

354

Optical Pointing Sensor  

NASA Technical Reports Server (NTRS)

The optical pointing sensor provides a means of directly measuring the relative positions of JPL s Formation Control Testbed (FCT) vehicles without communication. This innovation is a steerable infrared (IR) rangefinder that gives measurements in terms of range and bearing to a passive retroreflector.

Shields, Joel F.; Metz, Brandon C.

2010-01-01

355

The Lagrange Points  

ERIC Educational Resources Information Center

This paper presents a derivation of all five Lagrange points by methods accessible to sixth-form students, and provides a further opportunity to match Newtonian gravity with centripetal force. The predictive powers of good scientific theories are also discussed with regard to the philosophy of science. Methods for calculating the positions of the…

Lovell, M.S.

2007-01-01

356

Precise wavefunction engineering with magnetic resonance  

E-print Network

Controlling quantum fluids at their fundamental length scale will yield superlative quantum simulators, precision sensors, and spintronic devices. This scale is typically below the optical diffraction limit, precluding precise wavefunction engineering using optical potentials alone. We present a protocol to rapidly control the phase and density of a quantum fluid down to the healing length scale using strong time-dependent coupling between internal states of the fluid in a magnetic field gradient. We demonstrate this protocol by simulating the creation of a single stationary soliton and double soliton states in a Bose-Einstein condensate with control over the individual soliton positions and trajectories, using experimentally feasible parameters. Such states are yet to be realized experimentally, and are a path towards engineering soliton gases and exotic topological excitations.

L. M. Bennie; P. B. Wigley; S. S. Szigeti; M. Jasperse; J. J. Hope; L. D. Turner; R. P. Anderson

2014-12-22

357

Extreme point and halving edge search in abstract order types.  

PubMed

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

Aichholzer, Oswin; Miltzow, Tillmann; Pilz, Alexander

2013-10-01

358

Polyion multilayers with precise surface charge control for antifouling.  

PubMed

We report on a molecular fabrication approach to precisely control surface ? potentials of polymeric thin layers constructed by electrostatic layer-by-layer (LbL) assembly methods. The protocol established allows us to achieve surface isoelectric points (IEP) in the pH range of 6-10. Poly(acrylic acid) (PAA, a weak polyanion) and poly(diallyldimethylammonium chloride) (PDADMAC, a strong polycation) were chosen to build up the bulk films. The weak polycation polyethylenimine (PEI) was applied as a top layer. A unique feature of this approach is that the chemical composition of the top layer is not affected by the manipulation of the ? potential of the films. Surface charge tuning is achieved by controlling the degree of ionization of the weak polyelectrolytes at various pH values and subsequent manipulation of the amount of polyelectrolyte deposited in the penultimate and last layers, respectively. Following assembly and characterization, the films were used as candidates for antifouling surfaces. The fouling behavior of barnacle cyprids and bacteria on the LbL films with similar hydrophilicity and roughness but different surface charge densities were studied. We found that more cyprids of Amphibalanus amphitrite settled on the negatively charged LbL film compared to the neutral or positively charged LbL film. In bacterial adhesion tests employing Pseudomonas, Escherichia coli, and Staphylococcus aureus, more bacteria were observed on the positively charged LbL film compared with the neutral and negatively charged LbL films, possibly as a result of the negative potential of the bacterial cell wall. The procedures proposed allow one to adjust surface isoelectric points of LbL architectures to achieve optimal antifouling performance of a given material taking into account specific pH values of the environment and the character of the fouler. PMID:25485625

Zhu, Xiaoying; Ja?czewski, Dominik; Guo, Shifeng; Lee, Serina Siew Chen; Parra Velandia, Fernando Jose; Teo, Serena Lay-Ming; He, Tao; Puniredd, Sreenivasa Reddy; Vancso, G Julius

2015-01-14

359

PRECISION FARMING FOR NITROGEN MANAGEMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

Approaches to precision nitrogen management vary from region to region depending on crop, soils, landscape, and climate yet all strategies essentially attempt to estimate crop nitrogen demand or plant available nitrogen. In this chapter, we provide case studies that illustrate precision nitrogen ma...

360

Precise-Test-Pulse Generator  

NASA Technical Reports Server (NTRS)

Precise test pulse with stable duration and amplitude needed for calibration of test equipment. Precise-test-pulse generator provides such waveform and has additional desirable features. Circuit produces single test pulses of stable duration and amplitude. Made of commercially available integrated circuits and discrete components.

Eichenberg, Dennis

1994-01-01

361

New Fast Precise Kinematic Surveying Method Using a Single Dual-Frequency GPS Receiver  

E-print Network

New Fast Precise Kinematic Surveying Method Using a Single Dual-Frequency GPS Receiver Zhizhao Liu1 to perform precise surveying using the single dual-frequency Global Positioning System (GPS) receiver. One, fast method that can conduct precise kinematic surveying using a single dual-frequency GPS receiver

Santerre, Rock

362

Constraints on Lava Flow Emplacement Derived From Precision Topographic Measurements  

NASA Astrophysics Data System (ADS)

Precision topography obtained with a Differential Global Positioning System (DGPS) was used to derive constraints on the physical properties of two lava flows on the Big Island of Hawaii. We used a Trimble 4800 DGPS to collect positional information across the lava flows with < 2 cm horizontal and < 4 cm vertical precision (but field tests show that points are usually repeatable to < 1 cm both horizontally and vertically). The DGPS data were overlaid on georeferenced aerial and satellite imaging data, allowing us to correlate the measured topographic points to field notes and photographs, as well as to the local setting evident in the vertical images. We combined field and imaging data for the eastern lobe of the 1907 basalt flow from the southwestern rift zone of Mauna Loa volcano, east of the Ocean View Estates subdivision, and for portions of a grass-covered Pleistocene benmoreite flow near Mana on the western flank of Mauna Kea volcano. Measured physical dimensions of the Hawaiian lava flows obtained from the DGPS data were then used to calculate the yield strength, average effusion rate, and effective viscosity of the lavas using published relationships derived from diverse theories of fluid flow. Yield strengths obtained from three different expressions ranged from 5800 to 56000 Pa for the Mauna Loa basalt flow and from 13000 to 28000 Pa for the Mauna Kea benmoreite flow. Total flow length could not be determined for the Mauna Kea flow, but the entire surface portion of the 1907 flow is well exposed; this allowed us to calculate an average effusion rate of 29 m/s and effective viscosities ranging from 17000 to 280000 Pa-s for this flow, broadly consistent with values published for the 1984 basalt flow from the eastern rift zone of Mauna Loa. These results improve our confidence in being able to derive similar constraints on the likely emplacement conditions of lava flows on other planets, such as the enormous lava flows commonly found on the martian, venusian and lunar surfaces.

Zimbelman, J. R.; Bjonnes, E. E.

2005-12-01

363

ARPREC: An arbitrary precision computation package  

SciTech Connect

This paper describes a new software package for performing arithmetic with an arbitrarily high level of numeric precision. It is based on the earlier MPFUN package, enhanced with special IEEE floating-point numerical techniques and several new functions. This package is written in C++ code for high performance and broad portability and includes both C++ and Fortran-90 translation modules, so that conventional C++ and Fortran-90 programs can utilize the package with only very minor changes. This paper includes a survey of some of the interesting applications of this package and its predecessors.

Bailey, David H.; Yozo, Hida; Li, Xiaoye S.; Thompson, Brandon

2002-09-01

364

Glass ceramic ZERODUR enabling nanometer precision  

NASA Astrophysics Data System (ADS)

The IC Lithography roadmap foresees manufacturing of devices with critical dimension of < 20 nm. Overlay specification of single digit nanometer asking for nanometer positioning accuracy requiring sub nanometer position measurement accuracy. The glass ceramic ZERODUR® is a well-established material in critical components of microlithography wafer stepper and offered with an extremely low coefficient of thermal expansion (CTE), the tightest tolerance available on market. SCHOTT is continuously improving manufacturing processes and it's method to measure and characterize the CTE behavior of ZERODUR® to full fill the ever tighter CTE specification for wafer stepper components. In this paper we present the ZERODUR® Lithography Roadmap on the CTE metrology and tolerance. Additionally, simulation calculations based on a physical model are presented predicting the long term CTE behavior of ZERODUR® components to optimize dimensional stability of precision positioning devices. CTE data of several low thermal expansion materials are compared regarding their temperature dependence between - 50°C and + 100°C. ZERODUR® TAILORED 22°C is full filling the tight CTE tolerance of +/- 10 ppb / K within the broadest temperature interval compared to all other materials of this investigation. The data presented in this paper explicitly demonstrates the capability of ZERODUR® to enable the nanometer precision required for future generation of lithography equipment and processes.

Jedamzik, Ralf; Kunisch, Clemens; Nieder, Johannes; Westerhoff, Thomas

2014-03-01

365

Probabilistic modelling of LORAN-C for non-precision approaches  

E-print Network

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 ...

Einhorn, John Kenneth

1985-01-01

366

Galvanometer deflection: a precision high-speed system.  

PubMed

An X-Y galvanometer deflection system capable of high precision in a random access mode of operation is described. Beam positional information in digitized form is obtained by employing a Ronchi grating with a sophisticated optical detection scheme. This information is used in a control interface to locate the beam to the required precision. The system is characterized by high accuracy at maximum speed and is designed for operation in a variable environment, with particular attention placed on thermal insensitivity. PMID:20165203

Jablonowski, D P; Raamot, J

1976-06-01

367

TerraSAR-X Precise Trajectory Estimation and Quality Assessment  

Microsoft Academic Search

Since the launch of TerraSAR-X on June 15, 2007, the required precise orbit products have been provided by the German Space Operations Center to support operational spaceborne synthetic aperture radar (SAR) and interferometric SAR image processing. The TerraSAR-X precise trajectory is reconstructed solely based on the Global Positioning System (GPS) measurements from a geodetic-grade dual-frequency Integrated Geodetic and Occultation Receiver

Yoke T. Yoon; Michael Eineder; Nestor Yague-Martinez; Oliver Montenbruck

2009-01-01

368

Satellite positioning  

NASA Technical Reports Server (NTRS)

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.

Colombo, Oscar L.; Watkins, Michael M.

1991-01-01

369

Global Positioning System Satellite Selection Method  

NASA Technical Reports Server (NTRS)

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.

Niles, Frederick A. (Inventor)

2001-01-01

370

Precision gravimetric survey at the conditions of urban agglomerations  

NASA Astrophysics Data System (ADS)

Large cities growth and aging lead to the irreversible negative changes of underground. The study of these changes at the urban area mainly based on the shallow methods of Geophysics, which extensive usage restricted by technogenic noise. Among others, precision gravimetry is allocated as method with good resistance to the urban noises. The main the objects of urban gravimetric survey are the soil decompaction, leaded to the rocks strength violation and the karst formation. Their gravity effects are too small, therefore investigation requires the modern high-precision equipment and special methods of measurements. The Gravimetry division of Lomonosov Moscow State University examin of modern precision gravimeters Scintrex CG-5 Autograv since 2006. The main performance characteristics of over 20 precision gravimeters were examined in various operational modes. Stationary mode. Long-term gravimetric measurements were carried at a base station. It shows that records obtained differ by high-frequency and mid-frequency (period 5 - 12 hours) components. The high-frequency component, determined as a standard deviation of measurement, characterizes the level of the system sensitivity to external noise and varies for different devices from 2 to 5-7 ?Gals. Midrange component, which closely meet to the rest of nonlinearity gravimeter drifts, is partially compensated by the equipment. This factor is very important in the case of gravimetric monitoring or observations, when midrange anomalies are the target ones. For the examined gravimeters, amplitudes' deviations, associated with this parameter may reach 10 ?Gals. Various transportation modes - were performed by walking (softest mode), lift (vertical overload), vehicle (horizontal overloads), boat (vertical plus horizontal overloads) and helicopter. The survey quality was compared by the variance of the measurement results and internal convergence of series. The measurement results variance (from ±2 to ±4 ?Gals) and its internal convergence are independent on transportation mode. Actually, measurements differ just by the processing time and appropriate number of readings. Important, that the internal convergence is the individual attribute of particular device. For the investigated gravimeters it varies from ±3 up to ±8 ?Gals. Various stability of the gravimeters location base. The most stable basis (minimum microseisms) in this experiment was a concrete pedestal, the least stable - point on the 28th floor. There is no direct dependence of the measurement results variance at the external noise level. Moreover, the external dispersion between different gravimeters is minimal in the point of the highest microseisms. Conclusions. The quality of the modern high-precision gravimeters Scintrex CG-5 Autograv measurements is determined by stability of the particular device, its standard deviation value and the nonlinearity drift degree. Despite the fact, that mentioned parameters of the tested gravimeters, generally corresponded to the factory characters, for the surveys required accuracy ±2-5 ?Gals, the best gravimeters should be selected. Practical gravimetric survey with such accuracy allowed reliable determination of the position of technical communication boxes and underground walkway in the urban area, indicated by gravity minimums with the amplitudes from 6-8 ?Gals and 1 - 15 meters width. The holes' parameters, obtained as the result of interpretationare well aligned with priori data.

Sokolova, Tatiana; Lygin, Ivan; Fadeev, Alexander

2014-05-01

371

Photoswitchable precision glycooligomers and their lectin binding  

PubMed Central

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

Ponader, Daniela; Igde, Sinaida; Wehle, Marko; Märker, Katharina; Santer, Mark

2014-01-01

372

A precise technique for manufacturing correction coil  

SciTech Connect

An automated method of manufacturing correction coils has been developed which provides a precise embodiment of the coil design. Numerically controlled machines have been developed to accurately position coil windings on the beam tube. Two types of machines have been built. One machine bonds the wire to a substrate which is wrapped around the beam tube after it is completed while the second machine bonds the wire directly to the beam tube. Both machines use the Multiwire[reg sign] technique of bonding the wire to the substrate utilizing an ultrasonic stylus. These machines are being used to manufacture coils for both the SSC and RHIC.

Schieber, L.

1992-01-01

373

A precise technique for manufacturing correction coil  

SciTech Connect

An automated method of manufacturing correction coils has been developed which provides a precise embodiment of the coil design. Numerically controlled machines have been developed to accurately position coil windings on the beam tube. Two types of machines have been built. One machine bonds the wire to a substrate which is wrapped around the beam tube after it is completed while the second machine bonds the wire directly to the beam tube. Both machines use the Multiwire{reg_sign} technique of bonding the wire to the substrate utilizing an ultrasonic stylus. These machines are being used to manufacture coils for both the SSC and RHIC.

Schieber, L.

1992-11-01

374

Impedance Control and Its Relation to Precision in Orofacial Movement  

PubMed Central

Speech production involves some of the most precise and finely timed patterns of human movement. Here, in the context of jaw movement in speech, we show that spatial precision in speech production is systematically associated with the regulation of impedance and in particular, with jaw stiffness—a measure of resistance to displacement. We estimated stiffness and also variability during movement using a robotic device to apply brief force pulses to the jaw. Estimates of stiffness were obtained using the perturbed position and force trajectory and an estimate of what the trajectory would be in the absence of load. We estimated this “reference trajectory” using a new technique based on Fourier analysis. A moving-average (MA) procedure was used to estimate stiffness by modeling restoring force as the moving average of previous jaw displacements. The stiffness matrix was obtained from the steady state of the MA model. We applied this technique to data from 31 subjects whose jaw movements were perturbed during speech utterances and kinematically matched nonspeech movements. We observed systematic differences in stiffness over the course of jaw-lowering and jaw-raising movements that were correlated with measures of kinematic variability. Jaw stiffness was high and variability was low early and late in the movement when the jaw was elevated. Stiffness was low and variability was high in the middle of movement when the jaw was lowered. Similar patterns were observed for speech and nonspeech conditions. The systematic relationship between stiffness and variability points to the idea that stiffness regulation is integral to the control of orofacial movement variability. PMID:19420122

Laboissière, Rafael; Lametti, Daniel R.; Ostry, David J.

2009-01-01

375

Improving the Precision of Astrometry for Space Debris  

NASA Astrophysics Data System (ADS)

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.

Sun, Rongyu; Zhao, Changyin; Zhang, Xiaoxiang

2014-03-01

376

Dew Point  

NSDL National Science Digital Library

Determine the dew point temperature for your classroom through a hands-on experiment. Use humidity and temperature probes to investigate the temperature at which it would rain in your classroom! Learn about water density and the conditions necessary to produce fog or rain.

2012-07-19

377

Precision Instrument and Equipment Repairers.  

ERIC Educational Resources Information Center

Explains the job of precision instrument and equipment repairers, who work on cameras, medical equipment, musical instruments, watches and clocks, and industrial measuring devices. Discusses duties, working conditions, employment and earnings, job outlook, and skills and training. (JOW)

Wyatt, Ian

2001-01-01

378

Image processing in precision agriculture  

Microsoft Academic Search

A brief review of our signal and image processing application in precision agriculture is presented. A method for determining sampling frequency for agriculture data is proposed, and some initial results based on data simulation and image processing are reported

Dragoljub Pokrajac; A. Lazarevic; S. Vucetic; T. Fiez; Z. Obradovic

1999-01-01

379

Precision Medicine and Targeted Therapy  

Cancer.gov

Information about the role that targeted therapies play in precision medicine. Includes how targeted therapies work against cancer, who receives targeted therapies, common side effects, and what to expect when having targeted therapies.

380

Automation of Precise Time Reference Stations (PTRS)  

NASA Astrophysics Data System (ADS)

The U.S. Naval Observatory is presently engaged in a program of automating precise time stations (PTS) and precise time reference stations (PTBS) by using a versatile mini-computer controlled data acquisition system (DAS). The data acquisition system is configured to monitor locally available PTTI signals such as LORAN-C, OMEGA, and/or the Global Positioning System. In addition, the DAS performs local standard intercomparison. Computer telephone communications provide automatic data transfer to the Naval Observatory. Subsequently, after analysis of the data, results and information can be sent back to the precise time reference station to provide automatic control of remote station timing. The DAS configuration is designed around state of the art standard industrial high reliability modules. The system integration and software are standardized but allow considerable flexibility to satisfy special local requirements such as stability measurements, performance evaluation and printing of messages and certificates. The DAS operates completely independently and may be queried or controlled at any time with a computer or terminal device (control is protected for use by authorized personnel only). Such DAS equipped PTS are operational in Hawaii, California, Texas and Florida.

Wheeler, P. J.

1985-04-01

381

High precision electrostatic potential calculations for cylindrically symmetric lenses  

SciTech Connect

A method is developed for a potential calculation within cylindrically symmetric electrostatic lenses using mesh relaxation techniques, and it is capable of considerably higher accuracies than currently available. The method involves (i) creating very high order algorithms (orders of 6, 8, and 10) for determining the potentials at points in the net using surrounding point values, (ii) eliminating the effect of the large errors caused by singular points, and (iii) reducing gradients in the high gradient regions of the geometry, thereby allowing the algorithms used in these regions to achieve greater precisions--(ii) and (iii) achieved by the use of telescopic multiregions. In addition, an algorithm for points one unit from a metal surface is developed, allowing general mesh point algorithms to be used in these situations, thereby taking advantage of the enhanced precision of the latter. A maximum error function dependent on a sixth order gradient of the potential is defined. With this the single point algorithmic errors are able to be viewed over the entire net. Finally, it is demonstrated that by utilizing the above concepts and procedures, the potential of a point in a reasonably high gradient region of a test geometry can realize a precision of less than 10{sup -10}.

Edwards, David Jr. [238 Marylyn Lane, Newark, Vermont 05871 (United States)

2007-02-15

382

GPS - Global Positioning System. Theory and practice  

Microsoft Academic Search

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

B. Hofmann-Wellenhof; H. Lichtenegger; J. Collins

1997-01-01

383

Graphing Points  

NSDL National Science Digital Library

Let's learn how to use the lines on graphs (the x & y axis) to plot information. Choose any of the activities below to test your knowledge of identifying the coordinates correctly. Meteoroid Coordinates Soccer Coordinates Donut Coordinates Graphing Points Save the Zogs!-Using Linear Equations Using your coordinate plane knowledge and linear equations help to rescue the Zogs! Can you find the axis for these problems too? What have you noticed about linear equations? What do the lines in linear equations look ...

Izzy

2012-02-07

384

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

SciTech Connect

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.

Yan, C.

1994-09-07

385

SPOTTED STAR LIGHT CURVES WITH ENHANCED PRECISION  

SciTech Connect

The nearly continuous timewise coverage of recent photometric surveys is free of the large gaps that compromise attempts to follow starspot growth and decay as well as motions, thereby giving incentive to improve computational precision for modeled spots. Due to the wide variety of star systems in the surveys, such improvement should apply to light/velocity curve models that accurately include all the main phenomena of close binaries and rotating single stars. The vector fractional area (VFA) algorithm that is introduced here represents surface elements by small sets of position vectors so as to allow accurate computation of circle-triangle overlap by spherical geometry. When computed by VFA, spots introduce essentially no noticeable scatter in light curves at the level of one part in 10,000. VFA has been put into the Wilson-Devinney light/velocity curve program and all logic and mathematics are given so as to facilitate entry into other such programs. Advantages of precise spot computation include improved statistics of spot motions and aging, reduced computation time (intrinsic precision relaxes needs for grid fineness), noise-free illustration of spot effects in figures, and help in guarding against false positives in exoplanet searches, where spots could approximately mimic transiting planets in unusual circumstances. A simple spot growth and decay template quantifies time profiles, and specifics of its utilization in differential corrections solutions are given. Computational strategies are discussed, the overall process is tested in simulations via solutions of synthetic light curve data, and essential simulation results are described. An efficient time smearing facility by Gaussian quadrature can deal with Kepler mission data that are in 30 minute time bins.

Wilson, R. E. [Astronomy Department, University of Florida, Gainesville, FL 32611 (United States)

2012-09-15

386

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

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

Paris-Sud XI, Université de

387

Abstract. --A lattice defect is characterized by : i) its position and the arrangement of the atoms around it and ii) by its energy levels. We shall consider here only the first point. The atomic defect  

E-print Network

of the atoms around it and ii) by its energy levels. We shall consider here only the first point. The atomic, the characteristics of the X-ray diffraction phenomena are to give only an average view of the environment of the atoms : but recent progresses in the techniques have considerably improved the sensitivity of X-rays

Boyer, Edmond

388

Different approaches to precise wavelength calibration of a flat-field grating spectrometer for laser-produced plasmas  

NASA Astrophysics Data System (ADS)

Accurate mathematical models called one-line calibration and parameter fitting are presented for wavelength calibration of a flat-field grating spectrometer. The models precisely establish the relationship between wavelength and pixel position of the detector, since geometry parameters and the grating equation of the spectrometer are taken into account. Compared with the commonly used polynomial fitting, the models presented here provide more reliable calibration results, especially in the extended region away from the calibration points. In addition to the high precision of calibration, the parameter fitting procedure provides a helpful way to obtain the actual parameters of the spectrometer. Supported by the National Natural Science Foundation of China under Grant Nos 10875109, 10874156, and 11105129.

Xiong, Gang; Zhang, Jiyan; Yang, Guohong; Yang, Jiamin; Li, Hang; Hu, Zhimin; Zhao, Yang; Wei, Minxi; Yi, Tao

2014-06-01

389

Positioning Reduction of Deep Space Probes Based on VLBI Tracking  

NASA Astrophysics Data System (ADS)

In the background of the Chinese Lunar Exploration Project and the Yinghuo Project, through theoretical analysis, algorithm study, software development, data simulation, real data processing and so on, the positioning reductions of the European lunar satellite Smart-1 and Mars Express (MEX) satellite, as well as the Chinese Chang'e-1 (CE-1) and Chang'e-2 (CE-2) satellites are accomplished by using VLBI and USB tracking data in this dissertation. The progress is made in various aspects including the development of theoretical model, the construction of observation equation, the analysis of the condition of normal equation, the selection and determination of the constraint, the analysis of data simulation, the detection of outliers in observations, the maintenance of the stability of the solution of parameters, the development of the practical software system, the processing of the real tracking data and so on. The details of the research progress in this dissertation are written as follows: (1) The algorithm is analyzed concerning the positioning reduction of the deep spacecraft based on VLBI tracking data. Through data simulation, it is analyzed for the effects of the bias in predicted orbit, the white noises and systematic errors in VLBI delays, and USB ranges on the positioning reduction of spacecraft. Results show that it is preferable to suppress the dispersion of positioning data points by applying the constraint of geocentric distance of spacecraft when there are only VLBI tracking data. The positioning solution is a biased estimate via observations of three VLBI stations. For the case of four tracking stations, the uncertainty of the constraint should be in accordance with the bias in the predicted orbit. White noises in delays and ranges mainly result in dispersion of the sequence of positioning data points. If there is the systematic error of observations, the systematic offset of the positioning results is caused, and there are trend jumps in the shape of asymptotic line in the sequence of positioning points. When VLBI stations changed from three to four or vice versa, trend jumps could sometimes exist in the sequence of positioning points. The analysis could be as a reference to the follow-on Chinese Lunar Exploration Project and Yinghuo Project in the positioning reduction of spacecraft. (2) The tracking data of the MEX satellite by the Chinese VLBI Network (CVN) on 2007 May 30 are processed. The results show that using the delays in precision of nanoseconds in the satellite positioning reduction is more effective than the delay rates in precision of picoseconds per second, and the contribution of the delay rates to the positioning is very limited. If the delays and their rates are jointly used in the positioning reduction, the correction to the adopted velocity should also be solved simultaneously with the position parameters. Otherwise the error in the priori velocity would directly influence the positioning precision. In order to improve the positioning precision of Martian satellite, it is very necessary for CVN to actively practice differential VLBI, same beam VLBI and so on. Then the systematic errors and the noise level of observations are further reduced. (3) Through positioning reduction, the trajectory monitoring of pivotal arcs of the CE-1 satellite is accomplished, including the arcs of maneuvers in the approaching stage, lunar capturing stage, circumlunar stage and the stage of controlled landing on the Moon. Especially, based on the tracking observations of radio ranges and VLBI delays of the CE-1 satellite during the controlled landing on the Moon on 2009 March 1, the landing trajectory, the epoch of the landing, and the coordinates of the landing point are determined by positioning reduction. The three-dimensional positioning uncertainty is about 0.55 km. The trace determination of the rover on the lunar surface is made as planned in the follow-on Chinese lunar exploration project. To apply the constraint of geocentric distance is shown to be helpful to improve the positioning precision. It is

Qiao, S. B.

2011-11-01

390

An investigation of pointing postures in a 3D stereoscopic environment.  

PubMed

Many object pointing and selecting techniques for large screens have been proposed in the literature. There is a lack of quantitative evidence suggesting proper pointing postures for interacting with stereoscopic targets in immersive virtual environments. The objective of this study was to explore users' performances and experiences of using different postures while interacting with 3D targets remotely in an immersive stereoscopic environment. Two postures, hand-directed and gaze-directed pointing methods, were compared in order to investigate the postural influences. Two stereo parallaxes, negative and positive parallaxes, were compared for exploring how target depth variances would impact users' performances and experiences. Fifteen participants were recruited to perform two interactive tasks, tapping and tracking tasks, to simulate interaction behaviors in the stereoscopic environment. Hand-directed pointing is suggested for both tapping and tracking tasks due to its significantly better overall performance, less muscle fatigue, and better usability. However, a gaze-directed posture is probably a better alternative than hand-directed pointing for tasks with high accuracy requirements in home-in phases. Additionally, it is easier for users to interact with targets with negative parallax than with targets with positive parallax. Based on the findings of this research, future applications involving different pointing techniques should consider both pointing performances and postural effects as a result of pointing task precision requirements and potential postural fatigue. PMID:25683543

Lin, Chiuhsiang Joe; Ho, Sui-Hua; Chen, Yan-Jyun

2015-05-01

391

Reliable positioning in a sparse GPS network, eastern Ontario  

NASA Astrophysics Data System (ADS)

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.

Samadi Alinia, H.; Tiampo, K.; Atkinson, G. M.

2013-12-01

392

On polyhedra induced by point sets in space  

Microsoft Academic Search

It is well known that one can always polygonize a set of points in the plane (not all on a line), i.e., construct a simple polygon whose vertices are precisely the given points in . For example, the shortest circuit through is a simple polygon. In 1994 Branko Gr¤ unbaum showed that an analogous theorem holds in . More precisely,

Pankaj K. Agarwal; Ferran Hurtado; Godfried T. Toussaint; Joan Trias

2008-01-01

393

Position measurements in the de Broglie-Bohm interpretation of quantum mechanics  

SciTech Connect

The de Broglie-Bohm interpretation of quantum mechanics assigns positions and trajectories to particles. We analyze the validity of a formula for the velocities of Bohmian particles which makes the analysis of these trajectories particularly simple. We apply it to particle detectors of four different types and show that the detectors of three of these types lead to 'surrealistic trajectories', i.e., leave a trace where the Bohmian particle was not present. - Highlights: Black-Right-Pointing-Pointer We perform computer simulation of Bohmian trajectories for position detectors. Black-Right-Pointing-Pointer A simplified velocity formula provides very precise (or exact) Bohmian trajectories. Black-Right-Pointing-Pointer Spin, phase, and Bohmian velocity type detectors exhibit surrealistic trajectories.

Naaman-Marom, Gillie; Erez, Noam; Vaidman, Lev, E-mail: vaidman@post.tau.ac.il

2012-10-15

394

ABJM amplitudes and the positive orthogonal Grassmannian  

NASA Astrophysics Data System (ADS)

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.

Huang, Yu-tin; Wen, CongKao

2014-02-01

395

Point Estimation  

NSDL National Science Digital Library

Created by Kyle Siegrist of the University of Alabama-Huntsville, this is an online, interactive lesson on point estimation. The author provides examples, exercises, and applets about the topic. More specifically, they concern estimators, method of moments, maximum likelihood, Bayes' estimators, best unbiased estimators, and sufficient, complete and ancillary statistics. Additionally, the author provides links to external resources for students looking to engage in a more in-depth study of the topic. This is simply one lesson in a series of seventeen. They are easily accessible as the author has created the site in an online textbook format.

Siegrist, Kyle

2009-02-23

396

Floating point arithmetic in future supercomputers  

NASA Technical Reports Server (NTRS)

Considerations in the floating-point design of a supercomputer are discussed. Particular attention is given to word size, hardware support for extended precision, format, and accuracy characteristics. These issues are discussed from the perspective of the Numerical Aerodynamic Simulation Systems Division at NASA Ames. The features believed to be most important for a future supercomputer floating-point design include: (1) a 64-bit IEEE floating-point format with 11 exponent bits, 52 mantissa bits, and one sign bit and (2) hardware support for reasonably fast double-precision arithmetic.

Bailey, David H.; Barton, John T.; Simon, Horst D.; Fouts, Martin J.

1989-01-01

397

Future payload isolation and pointing system technology  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

398

Precision Placement of Thin Polymeric Silicone Films Within Fabrics  

Microsoft Academic Search

This unique patented technology allows for the precision place ment of thin polymeric films around fibers, crossover points, and filling in or leav ing open interstitial spaces within fabrics. The choice of polymer, substrate, and placement of polymer allows for improvement of properties, such as breathable barrier performance, controlled porosity, resistance to fluids, and adhesion\\/release behavior. This technology has found

Randy Meirowitz

1998-01-01

399

A precision bearing gimbal system for the Teal Ruby program  

NASA Technical Reports Server (NTRS)

A precision bearing gimbal system designed to allow a spaceborne infrared sensor to stare at points on the Earth while in orbit is described. The problems encountered, analytical tools and test methods used, and data applicable to users of similar systems are presented. Assembly procedures, bearing preload effects, moisture control, structural analysis, and noise control are specifically examined.

Lowry, C. H.

1980-01-01

400

Precision cleaning apparatus and method  

DOEpatents

A precision cleaning apparatus and method are disclosed. The precision cleaning apparatus includes a cleaning monitor further comprising an acoustic wave cleaning sensor such as a quartz crystal microbalance (QCM), a flexural plate wave (FPW) sensor, a shear horizontal acoustic plate mode (SH--APM) sensor, or a shear horizontal surface acoustic wave (SH--SAW) sensor; and measurement means connectable to the sensor for measuring in-situ one or more electrical response characteristics that vary in response to removal of one or more contaminants from the sensor and a workpiece located adjacent to the sensor during cleaning. Methods are disclosed for precision cleaning of one or more contaminants from a surface of the workpiece by means of the cleaning monitor that determines a state of cleanliness and any residual contamination that may be present after cleaning; and also for determining an effectiveness of a cleaning medium for removing one or more contaminants from a workpiece. 11 figs.

Schneider, T.W.; Frye, G.C.; Martin, S.J.

1998-01-13

401

Precision cleaning apparatus and method  

DOEpatents

A precision cleaning apparatus and method. The precision cleaning apparatus includes a cleaning monitor further comprising an acoustic wave cleaning sensor such as a quartz crystal microbalance (QCM), a flexural plate wave (FPW) sensor, a shear horizontal acoustic plate mode (SH--APM) sensor, or a shear horizontal surface acoustic wave (SH--SAW) sensor; and measurement means connectable to the sensor for measuring in-situ one or more electrical response characteristics that vary in response to removal of one or more contaminants from the sensor and a workpiece located adjacent to the sensor during cleaning. Methods are disclosed for precision cleaning of one or more contaminants from a surface of the workpiece by means of the cleaning monitor that determines a state of cleanliness and any residual contamination that may be present after cleaning; and also for determining an effectiveness of a cleaning medium for removing one or more contaminants from a workpiece.

Schneider, Thomas W. (Albuquerque, NM); Frye, Gregory C. (Cedar Crest, NM); Martin, Stephen J. (Albuquerque, NM)

1998-01-01

402

PRECISION CHEMICAL ANALYSIS OF SOILS TO SUPPORT PRECISION MANAGEMENT DECISIONS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Technological advances in application of fertilizers and crop cultivars have expanded the potential for more precise management of soil. Resin-extraction, an alternative method of characterizing soils, coupled with inductively coupled plasma (ICP) provides information about the relative activity of ...

403

Microbiopsy/precision cutting devices  

DOEpatents

Devices for performing tissue biopsy on a small scale (microbiopsy). By reducing the size of the biopsy tool and removing only a small amount of tissue or other material in a minimally invasive manner, the risks, costs, injury and patient discomfort associated with traditional biopsy procedures can be reduced. By using micromachining and precision machining capabilities, it is possible to fabricate small biopsy/cutting devices from silicon. These devices can be used in one of four ways 1) intravascularly, 2) extravascularly, 3) by vessel puncture, and 4) externally. Additionally, the devices may be used in precision surgical cutting.

Krulevitch, Peter A. (Pleasanton, CA); Lee, Abraham P. (Walnut Creek, CA); Northrup, M. Allen (Berkeley, CA); Benett, William J. (Livermore, CA)

1999-01-01

404

Microbiopsy/precision cutting devices  

DOEpatents

Devices are disclosed for performing tissue biopsy on a small scale (microbiopsy). By reducing the size of the biopsy tool and removing only a small amount of tissue or other material in a minimally invasive manner, the risks, costs, injury and patient discomfort associated with traditional biopsy procedures can be reduced. By using micromachining and precision machining capabilities, it is possible to fabricate small biopsy/cutting devices from silicon. These devices can be used in one of four ways (1) intravascularly, (2) extravascularly, (3) by vessel puncture, and (4) externally. Additionally, the devices may be used in precision surgical cutting. 6 figs.

Krulevitch, P.A.; Lee, A.P.; Northrup, M.A.; Benett, W.J.

1999-07-27

405

Precision Manipulation with Cooperative Robots  

NASA Technical Reports Server (NTRS)

This work addresses several challenges of cooperative transportThis work addresses several challenges of cooperative transport and precision manipulation. Precision manipulation requires a rigid grasp, which places a hard constraint on the relative rover formation that must be accommodated, even though the rovers cannot directly observe their relative poses. Additionally, rovers must jointly select appropriate actions based on all available sensor information. Lastly, rovers cannot act on independent sensor information, but must fuse information to move jointly; the methods for fusing information must be determined.

Stroupe, Ashley; Huntsberger, Terry; Okon, Avi; Aghzarian, Hrand

2005-01-01

406

Global Positioning System Antenna Fixed Height Tripod Adapter  

NASA Technical Reports Server (NTRS)

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.

Dinardo, Steven J.; Smith, Mark A.

1997-01-01

407

Precision tracking systems for sonobuoys  

Microsoft Academic Search

A system has been developed to track arrays consisting of several sonobuoys deployed for acoustic detection. This navigation technique can be used to track the position of any free-drifting hydrophones. The method, employing bottom-moored acoustic transponders, can provide relative hydrophone positions to within 20 meters. Ultimate geographical positioning is dependent on the accuracy of the primary navigation system available; satellite

R. Spindel; R. Porter

1974-01-01

408

Offered: Offered: Position(s): Position(s)  

E-print Network

profitability and identifying variances Experience ?General Accounting and Financial Analysis experience in this position is responsible for supporting the Finance group in the monthly closings, variance analysis, sales analysis and providing assistance to division Financial Analysts. ?Support Finance group in General

New Hampshire, University of

409

Remote sensing applications for precision agriculture: A learning community approach  

Microsoft Academic Search

Farmers throughout the world are constantly searching for ways to maximize their returns. Remote Sensing, Geographic Information Systems (GIS), and Global Positioning Systems (GPS) may provide technologies needed for farmers to maximize the economic and environmental benefits of precision farming. However, most farmers do not have the skills to utilize these technologies effectively.Through a learning community approach led by the

Santhosh K Seelan; Soizik Laguette; Grant M Casady; George A Seielstad

2003-01-01

410

Precise asymptotics for a type of order statistics  

Microsoft Academic Search

This paper obtains some results on the precise asymptotics for the order statistics generated by the random samples of maximum domain of attraction of the Fréchet distribution, which reveal the relations among the boundary function, weight function, convergence rate and limit position in a uniform form.

Wang Yuebao; Yan Jigao; Yang Yang

2005-01-01

411

Calibration System with Microinch Precision at Temperatures to 500°C  

Microsoft Academic Search

A reference system for the evaluation and calibration of microdisplacement readout systems is described. The basic reference system consists of several pieces of precision readout and positioning equipment, a high temperature test chamber, and a specially designed linkage system. The case temperature of the transducer under calibration is maintained constant to within ±0.5°C for temperatures to 500°C. A quartz and

J. C. Spanner; B. B. Brenden

1964-01-01

412

Combine Harvester Instrumentation System for Use in Precision Agriculture  

Microsoft Academic Search

A crop yield and field performance mapping system for New Holland TC-56 rice combine harvester (RCH) for precision agriculture applications has been developed using LabVIEW. A Dewe-2010 PC data acquisition system has been used as a core unit to collect and store the real time field data from different sensors and a differential global positioning system to determine the exact

Yap Y. Kin; Sudhanshu S. Jamuar; Azmi Yahya

2011-01-01

413

Powered Descent Guidance with General Thrust-Pointing Constraints  

NASA Technical Reports Server (NTRS)

The Powered Descent Guidance (PDG) algorithm and software for generating Mars pinpoint or precision landing guidance profiles has been enhanced to incorporate thrust-pointing constraints. Pointing constraints would typically be needed for onboard sensor and navigation systems that have specific field-of-view requirements to generate valid ground proximity and terrain-relative state measurements. The original PDG algorithm was designed to enforce both control and state constraints, including maximum and minimum thrust bounds, avoidance of the ground or descent within a glide slope cone, and maximum speed limits. The thrust-bound and thrust-pointing constraints within PDG are non-convex, which in general requires nonlinear optimization methods to generate solutions. The short duration of Mars powered descent requires guaranteed PDG convergence to a solution within a finite time; however, nonlinear optimization methods have no guarantees of convergence to the global optimal or convergence within finite computation time. A lossless convexification developed for the original PDG algorithm relaxed the non-convex thrust bound constraints. This relaxation was theoretically proven to provide valid and optimal solutions for the original, non-convex problem within a convex framework. As with the thrust bound constraint, a relaxation of the thrust-pointing constraint also provides a lossless convexification that ensures the enhanced relaxed PDG algorithm remains convex and retains validity for the original nonconvex problem. The enhanced PDG algorithm provides guidance profiles for pinpoint and precision landing that minimize fuel usage, minimize landing error to the target, and ensure satisfaction of all position and control constraints, including thrust bounds and now thrust-pointing constraints.

Carson, John M., III; Acikmese, Behcet; Blackmore, Lars

2013-01-01

414

End points and trial design in geriatric oncology research: a joint European organisation for research and treatment of cancer--Alliance for Clinical Trials in Oncology--International Society Of Geriatric Oncology position article.  

PubMed

Selecting the most appropriate end points for clinical trials is important to assess the value of new treatment strategies. Well-established end points for clinical research exist in oncology but may not be as relevant to the older cancer population because of competing risks of death and potentially increased impact of therapy on global functioning and quality of life. This article discusses specific clinical end points and their advantages and disadvantages for older individuals. Randomized or single-arm phase II trials can provide insight into the range of efficacy and toxicity in older populations but ideally need to be confirmed in phase III trials, which are unfortunately often hindered by the severe heterogeneity of the older cancer population, difficulties with selection bias depending on inclusion criteria, physician perception, and barriers in willingness to participate. All clinical trials in oncology should be without an upper age limit to allow entry of eligible older adults. In settings where so-called standard therapy is not feasible, specific trials for older patients with cancer might be required, integrating meaningful measures of outcome. Not all questions can be answered in randomized clinical trials, and large observational cohort studies or registries within the community setting should be established (preferably in parallel to randomized trials) so that treatment patterns across different settings can be compared with impact on outcome. Obligatory integration of a comparable form of geriatric assessment is recommended in future studies, and regulatory organizations such as the European Medicines Agency and US Food and Drug Administration should require adequate collection of data on efficacy and toxicity of new drugs in fit and frail elderly subpopulations. PMID:24019549

Wildiers, Hans; Mauer, Murielle; Pallis, Athanasios; Hurria, Arti; Mohile, Supriya G; Luciani, Andrea; Curigliano, Giuseppe; Extermann, Martine; Lichtman, Stuart M; Ballman, Karla; Cohen, Harvey Jay; Muss, Hyman; Wedding, Ulrich

2013-10-10

415

Precision Experiments with Ultraslow Muons  

NASA Astrophysics Data System (ADS)

A source of ~105 ultraslow muons (USM) per second (~0.2 eV energy spread and 40 mm source diameter) reported by Miyake et al., and the demonstration of 100 K thermal muonium in vacuum by Antognini, et al., suggest possibilities for substantial improvements in the experimental precisions of the muonium 1S-2S interval and the muon g-2 measurements.

Mills, Allen P.

416

Precision Efficacy Analysis for Regression.  

ERIC Educational Resources Information Center

When multiple linear regression is used to develop a prediction model, sample size must be large enough to ensure stable coefficients. If the derivation sample size is inadequate, the model may not predict well for future subjects. The precision efficacy analysis for regression (PEAR) method uses a cross- validity approach to select sample sizes…

Brooks, Gordon P.

417

Precision Evaluation of Search Engines  

Microsoft Academic Search

In this paper, we present a general approach for statistically evaluating precision of search engines on the Web. Search engines are evaluated in two steps based on a large number of sample queries: (a) computing relevance scores of hits from each search engine, and (b) ranking the search engines based on statistical comparison of the relevance scores. In computing relevance

Yi Shang; Longzhuang Li

2002-01-01

418

Precision Machining Technology. Curriculum Guide.  

ERIC Educational Resources Information Center

This curriculum guide was developed from a Technical Committee Report prepared with the assistance of industry personnel and containing a Task List which is the basis of the guide. It presents competency-based program standards for courses in precision machining technology and is part of the Idaho Vocational Curriculum Guide Project, a cooperative…

Idaho State Dept. of Education, Boise. Div. of Vocational Education.

419

Development of precision dynamic systems  

Microsoft Academic Search

This dissertation presents the development of novel methods, models, and techniques for designing, evaluating, and characterizing the performance of precision dynamic motion control systems. Several areas have been addressed including modeling of advanced actuators, design of novel flexure mechanisms, a dual-stage multi-axis motion control platform and an investigation of the integration and performance of passive damping treatments. Static and dynamic

Shane Chad Woody

2005-01-01

420

Precision Tilt Measurement for Torsion  

E-print Network

torques #12;Torsion Balances: An Introduction Test fundamental physics at macroscopic scale We get much a torsion balance Composition dipole test mass for equivalence principle (to test universality of freefallPrecision Tilt Measurement for Torsion Balance Experiments Scott Yantek California Institute

Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group

421

Drilling Precise Orifices and Slots  

NASA Technical Reports Server (NTRS)

Reaction control thrustor injector requires precisely machined orifices and slots. Tooling setup consists of rotary table, numerical control system and torque sensitive drill press. Components used to drill oxidizer orifices. Electric discharge machine drills fuel-feed orifices. Device automates production of identical parts so several are completed in less time than previously.

Richards, C. W.; Seidler, J. E.

1983-01-01

422

Precise Selenodetic Coordinate System on Artificial Light Refers  

NASA Astrophysics Data System (ADS)

Historically a coordinate system for the Moon was established on the base of telescopic observations from the Earth. As the angular resolution of Earth-to-Space telescopic observations is limited by Earth atmosphere, and is ordinary worse then 1 ang. second, the mean accuracy of selenodetic coordinates is some angular minutes, which corresponds to errors about 900 meters for positions of lunar objects near center of visible lunar disk, and at least twice more when objects are near lunar poles. As there are no Global Positioning System nor any astronomical observation instruments on the Moon, we proposed to use an autonomous light beacon on the Luna-Globe landing module to fix its position on the surface of the moon ant to use it as refer point for fixation of spherical coordinates system for the Moon. The light beacon is designed to be surely visible by orbiting probe TV-camera. As any space probe has its own stars-orientation system, there is not a problem to calculate a set of directions to the beacon and to the referent stars in probe-centered coordinate system during flight over the beacon. Large number of measured angular positions and time of each observation will be enough to calculate both orbital parameters of the probe and selenodetic coordinates of the beacon by methods of geodesy. All this will allow fixing angular coordinates of any feature of lunar surface in one global coordinate system, referred to the beacon. The satellite’s orbit plane contains ever the center mass of main body, so if the beacon will be placed closely to a lunar pole, we shall determine pole point position of the Moon with accuracy tens times better then it is known now. When angular accuracy of self-orientation by stars of the orbital module of Luna-Glob mission will be 6 angular seconds, then being in circular orbit with height of 200 km the on-board TV-camera will allow calculation of the beacon position as well as 6" corresponding to spatial resolution of the camera. It mean that coordinates of the beacon will be determined with accuracy not worse then 6 meters on the lunar surface. Much more accuracy can be achieved if orbital probe will use as precise angular measurer as optical interferometer. The limiting accuracy of proposed method is far above any reasonable level, because it may be sub-millimeter one. Theoretical analysis shows that for achievement of 1-meter accuracy of coordinate measuring over lunar globe it will be enough to disperse over it surface some 60 light beacons. Designed by Lavochkin Association light beacon is autonomous one, and it will work at least 10 years, so coordinate frame of any other lunar mission could use established selenodetic coordinates during this period. The same approach may be used for establishing Martial coordinates system.

Bagrov, Alexander; Pichkhadze, Konstantin M.; Sysoev, Valentin

423

Lidar Systems for Precision Navigation and Safe Landing on Planetary Bodies  

NASA Technical Reports Server (NTRS)

The ability of lidar technology to provide three-dimensional elevation maps of the terrain, high precision distance to the ground, and approach velocity can enable safe landing of robotic and manned vehicles with a high degree of precision. Currently, NASA is developing novel lidar sensors aimed at needs of future planetary landing missions. These lidar sensors are a 3-Dimensional Imaging Flash Lidar, a Doppler Lidar, and a Laser Altimeter. The Flash Lidar is capable of generating elevation maps of the terrain that indicate hazardous features such as rocks, craters, and steep slopes. The elevation maps collected during the approach phase of a landing vehicle, at about 1 km above the ground, can be used to determine the most suitable safe landing site. The Doppler Lidar provides highly accurate ground relative velocity and distance data allowing for precision navigation to the landing site. Our Doppler lidar utilizes three laser beams pointed to different directions to measure line of sight velocities and ranges to the ground from altitudes of over 2 km. Throughout the landing trajectory starting at altitudes of about 20 km, the Laser Altimeter can provide very accurate ground relative altitude measurements that are used to improve the vehicle position knowledge obtained from the vehicle navigation system. At altitudes from approximately 15 km to 10 km, either the Laser Altimeter or the Flash Lidar can be used to generate contour maps of the terrain, identifying known surface features such as craters, to perform Terrain relative Navigation thus further reducing the vehicle s relative position error. This paper describes the operational capabilities of each lidar sensor and provides a status of their development. Keywords: Laser Remote Sensing, Laser Radar, Doppler Lidar, Flash Lidar, 3-D Imaging, Laser Altimeter, Precession Landing, Hazard Detection

Amzajerdian, Farzin; Pierrottet, Diego F.; Petway, Larry B.; Hines, Glenn D.; Roback, Vincent E.

2011-01-01

424

Pitch evaluation of high-precision gratings  

NASA Astrophysics Data System (ADS)

Optical encoders and laser interferometers are two primary solutions in nanometer metrology. As the precision of encoders depends on the uniformity of grating pitches, it is essential to evaluate pitches accurately. We use a CCD image sensor to acquire grating image for evaluating the pitches with high precision. Digital image correlation technique is applied to filter out the noises. We propose three methods for determining the pitches of grating with peak positions of correlation coefficients. Numerical simulation indicated the average of pitch deviations from the true pitch and the pitch variations are less than 0.02 pixel and 0.1 pixel for these three methods when the ideal grating image is added with salt and pepper noise, speckle noise, and Gaussian noise. Experimental results demonstrated that our method can measure the pitch of the grating accurately, for example, our home-made grating with 20?m period has 475nm peak-to-valley uniformity with 40nm standard deviation during 35mm range. Another measurement illustrated that our home-made grating has 40nm peak-to-valley uniformity with 10nm standard deviation. This work verified that our lab can fabricate high-accuracy gratings which should be interesting for practical application in optical encoders.

Lu, Yancong; Zhou, Changhe; Wei, Chunlong; Jia, Wei; Xiang, Xiansong; Li, Yanyang; Yu, Junjie; Li, Shubin; Wang, Jin; Liu, Kun; Wei, Shengbin

2014-11-01

425

Statistics of ionospheric disturbances and their correlation with GNSS positioning errors at high latitudes  

NASA Astrophysics Data System (ADS)

The Rate Of TEC Index (ROTI) is a commonly used measure of ionospheric activity. ROTI values have been computed every 5 min for the year 2012, for 10 receivers at latitudes from 59° to 79° North. We present the results in geomagnetic coordinates, showing that elevated ROTI values occur mainly in the cusp and nightside auroral oval regions. Elevated ROTI values are more common in the cusp, but in the nightside auroral oval they are stronger. To investigate the relation to positioning errors, receiver coordinates were computed using the GIPSY software, for the same receivers and time resolution. We found that there is a strong positive correlation between Precise Point Positioning (PPP) error and ROTI for receivers that are affected by space weather. The 3D position error increases exponentially with increasing ROTI. A statistical analysis presents also the risk of having several satellites observing enhanced ROTI values simultaneously, showing that this risk is greater at high latitudes.

Jacobsen, Knut Stanley; Dähnn, Michael

2014-09-01

426

Spatially modulated illumination microscopy: online visualization of intensity distribution and prediction of nanometer precision of axial distance measurements by computer simulations.  

PubMed

During the last years, measurements considerably beyond the conventional "Abbe-Limit" of optical resolution in far field light microscopy were realized by several light microscopical approaches. Point spread function (PSF) engineering, spectral precision distance microscopy (SPDM), and related methods were used to demonstrate the feasibility of such measurements. SPDM allows the measurement of position and multiple distances between point-like fluorescent objects of different spectral signatures far below the optical resolution criterion as defined by the full width at half maximum of the PSF. Here, we report a software method to obtain online visualization of light distribution in the lateral and axial direction of any object detected in a spatially modulated illumination (SMI) microscope. This strongly facilitates routine application of SMI microscopy. The software was developed using Microsoft Visual C++ running on Windows NT. Furthermore, some aspects of the theoretical limits of the SPDM method were studied by virtual microscopy. For the case of SMI microscopy the precision of axial distance measurements was studied, taking into account photon statistics and image analysis procedures. The results indicate that even under low fluorescence intensity conditions typical for biological structure research, precise distance measurements in the nanometer range can be determined, and that axial distances in the order of 40 nm are detectable with such precision. PMID:11516319

Albrecht, B; Failla, A V; Heintzmann, R; Cremer, C

2001-07-01

427

Performance of a Smart Vibration Isolator for Precision Spacecraft Instruments  

NASA Technical Reports Server (NTRS)

Under the ARPA SMS Partnership Program for Synthesis and Processing of Smart Materials, Lockheed Missiles and Space company, Inc. has developed a demonstration prototype vibration cancelling mount using electrostrictive ceramic and shape-memory alloy actuators. Shape-memory actuators provide an adaptive-passive, self-damping support for isolation, while the electrostrictive actuators are employed to provide force and position control. The demonstration device was designed to address generic requirements for vibration stabilization of precision spacecraft instruments. It is reconfigurable to operate in any of four modes; passive isolation, active-passive isolation using force cancellation, active precision positioning, and active disturbance rejection. The presentation summarizes design of the device design and results of experimental evaluations of the device in isolation (active and passive) and positioning modes. Rejection of payload-borne disturbances is also discussed with reference to predictions from experimentally calibrated simulations. Finally, avenues for further development and refinement of the device are discussed.

Regelbrugge, Marc E.; Carrier, Alain; Dickson, William C.

1996-01-01

428

Satellite positioning  

NASA Astrophysics Data System (ADS)

The Fifth International Geodetic Symposium on Satellite Positioning was held in Las Cruces, N.Mex., March 13-17, 1989. It was cosponsored by the Defense Mapping Agency and the National Geodetic Survey of the National Oceanic and Atmospheric Administration. More than 385 geodesists, engineers, scientists, surveyors, instrument manufacturers, and managers from 32 countries attended the symposium.The keynote address and 96 papers including 9 invited papers and 10 poster papers were presented in the 5-day meeting. In addition, there were three well-attended workshops with lively technical discussions. The invited guest presentations at the symposium luncheon and banquet provided very useful and interesting information.

Stein, William L.; Kumar, Muneendra

429

High precision triangular waveform generator  

DOEpatents

An ultra-linear ramp generator having separately programmable ascending and descending ramp rates and voltages is provided. Two constant current sources provide the ramp through an integrator. Switching of the current at current source inputs rather than at the integrator input eliminates switching transients and contributes to the waveform precision. The triangular waveforms produced by the waveform generator are characterized by accurate reproduction and low drift over periods of several hours. The ascending and descending slopes are independently selectable.

Mueller, Theodore R. (Oak Ridge, TN)

1983-01-01

430

Precision linear ramp function generator  

DOEpatents

A ramp function generator is provided which produces a precise linear ramp unction which is repeatable and highly stable. A derivative feedback loop is used to stabilize the output of an integrator in the forward loop and control the ramp rate. The ramp may be started from a selected baseline voltage level and the desired ramp rate is selected by applying an appropriate constant voltage to the input of the integrator.

Jatko, W. Bruce (Knoxville, TN); McNeilly, David R. (Maryville, TN); Thacker, Louis H. (Knoxville, TN)

1986-01-01

431

Standard 6: Attend to precision  

NSDL National Science Digital Library

This web page from the Inside Mathematics initiative aims to guide and support educators in understanding the sixth CCSS Practice Standard. Instances of teachers engaging students to be mathematically proficient with the capacity to "attend to precision" are described in Classroom Observations and illustrated in video excerpts of fifth grade students discussing how a rule should be written to describe a pattern. The video clips are excerpts from public lesson: "Numerical Patterning" (cataloged separately).

Austin, The C.; Centre, Shell

2012-01-01

432

Method for grinding precision components  

DOEpatents

A method for precision cylindrical grinding of hard brittle materials, such as ceramics or glass and composites comprising ceramics or glass, provides material removal rates as high as 19-380 cm.sup.3 /min/cm. The abrasive tools used in the method comprise a strong, light weight wheel core bonded to a continuous rim of abrasive segments containing superabrasive grain in a dense metal bond matrix.

Ramanath, Srinivasan (Holden, MA); Kuo, Shih Yee (Westboro, MA); Williston, William H. (Holden, MA); Buljan, Sergej-Tomislav (Acton, MA)

2000-01-01

433

Green Solvents for Precision Cleaning  

NASA Technical Reports Server (NTRS)

Aerospace machinery used in liquid oxygen (LOX) fuel systems must be precision cleaned to achieve a very low level of non-volatile residue (< 1 mg0.1 m2), especially flammable residue. Traditionally chlorofluorocarbons (CFCs) have been used in the precision cleaning of LOX systems, specifically CFC 113 (C2Cl3F3). CFCs have been known to cause the depletion of ozone and in 1987, were banned by the Montreal Protocol due to health, safety and environmental concerns. This has now led to the development of new processes in the precision cleaning of aerospace components. An ideal solvent-replacement is non-flammable, environmentally benign, non-corrosive, inexpensive, effective and evaporates completely, leaving no residue. Highlighted is a green precision cleaning process, which is contaminant removal using supercritical carbon dioxide as the environmentally benign solvent. In this process, the contaminant is dissolved in carbon dioxide, and the parts are recovered at the end of the cleaning process completely dry and ready for use. Typical contaminants of aerospace components include hydrocarbon greases, hydraulic fluids, silicone fluids and greases, fluorocarbon fluids and greases and fingerprint oil. Metallic aerospace components range from small nuts and bolts to much larger parts, such as butterfly valves 18 in diameter. A fluorinated grease, Krytox, is investigated as a model contaminant in these preliminary studies, and aluminum coupons are employed as a model aerospace component. Preliminary studies are presented in which the experimental parameters are optimized for removal of Krytox from aluminum coupons in a stirred-batch process. The experimental conditions investigated are temperature, pressure, exposure time and impeller speed. Temperatures of 308 - 423 K, pressures in the range of 8.3 - 41.4 MPa, exposure times between 5 - 60 min and impeller speeds of 0 - 1000 rpm were investigated. Preliminary results showed up to 86 cleaning efficiency with the moderate processing conditions of 323 K, 13.8 MPa, 30 min and 750 rpm.

Grandelli, Heather; Maloney, Phillip; DeVor, Robert; Surma, Jan; Hintze, Paul

2013-01-01

434

Precise mapping of annual river bed changes based on airborne laser bathymetry  

NASA Astrophysics Data System (ADS)

Airborne Laser Bathymtery (ALB) is a method for capturing relatively shallow water bodies from the air using a pulsed green laser (wavelength=532nm). While this technique was first used for mapping coastal waters only, recent progress in sensor technology has opened the field to apply ALB to running inland waters. Especially for alpine rivers the precise mapping of the channel topography is a challenging task as the flow velocities are often high and the area is difficult and/or dangerous to access by boat or by feet. Traditional mapping techniques like tachymetry or echo sounding fail in such situations while ALB provides, both, high spot position accuracy in the cm range and high spatial resolution in the dm range. Furthermore, state-of-the-art ALB systems allow simultaneous mapping of the river bed and the riparian area and, therefore, represent a comprehensive and efficient technology for mapping the entire floodplain area. The maximum penetration depth depends on, both, water turbidity and bottom reflectivity. Consequently, ALB provides the highest accuracy and resolution over bright gravel rivers with relatively clear water. We demonstrate the capability of ALB for precise mapping of river bed changes based on three flight campaigns in April, May and October 2013 at the River Pielach (Lower Austria) carried out with Riegl's VQ-820-G topo-bathymetric laser scanner. Operated at a flight height of 600m above ground with a pulse repetition rate of 510kHz (effective measurement rate 200kHz) this yielded a mean point spacing within the river bed of 20cm (i.e. point density: 25 points/m2). The positioning accuracy of the river bed points is approx. 2-5cm and depends on the overall ranging precision (20mm), the quality of the water surface model (derived from the ALB point cloud), and the signal intensity (decreasing with water depth). All in all, the obtained point cloud allowed the derivation of a dense grid model of the channel topography (0.25m cell size) for all three epochs constituting an excellent basis for, both, the visual and quantitative estimation of the changes over the year. It turned out that even between the April and May flight remarkable differences could be detected although there was no major precipitation event in-between and the flow conditions were entirely below mean flow. In contrast to the moderate changes between April and May, the flood event in June 2013 (HQ1) resulted in a radical change of the river bed topography documented by the October flight. Since the study site (Neubacher Au) is a Natura2000 conservation area, space for a meandering flow is allowed. Entire gravel bars have been removed and new bars were deposited down-stream. Furthermore, the river axis was locally shifted by more than 1m during the flood event. The results demonstrate the high potential of laser bathymetry for precise mapping of river bed changes. This opens new perspectives for the validation of sediment transport models models and a much better understanding of the river morphology (e.g. formation and changes of sand and gravel banks). The traditional approach in sediment transport modelling based on a limited number of cross sections can be completed respectively replaced by a more comprehensive and more reliable concept on the basis of spatial distributed river bed data. Valuable calibration data in a new quality will be available.

Mandlburger, Gottfried; Wieser, Martin; Pfeifer, Norbert; Pfennigbauer, Martin; Steinbacher, Frank; Aufleger, Markus

2014-05-01

435

Applicationsfor2014 5 points 4 points 3 points 2 points 1 point  

E-print Network

(Individual) State Open (Senior State Representation) Coach Career Management Program Australian School Boys/Girls Footballers' Association (A or W League) Member of Australian Team open or underage (all sports) Member of Australian underage team for a particular sport #12;MUSIC Applicationsfor2014 5 points 4 points 3 points 2

New South Wales, University of

436

Photon beam position monitor  

DOEpatents

A photon beam position monitor is disclosed for use in the front end of a beamline of a high heat flux and high energy photon source such as a synchrotron radiation storage ring detects and measures the position and, when a pair of such monitors are used in tandem, the slope of a photon beam emanating from an insertion device such as a wiggler or an undulator inserted in the straight sections of the ring. The photon beam position monitor includes a plurality of spaced blades for precisely locating the photon beam, with each blade comprised of chemical vapor deposition (CVD) diamond with an outer metal coating of a photon sensitive metal such as tungsten, molybdenum, etc., which combination emits electrons when a high energy photon beam is incident upon the blade. Two such monitors are contemplated for use in the front end of the beamline, with the two monitors having vertically and horizontally offset detector blades to avoid blade ''shadowing''. Provision is made for aligning the detector blades with the photon beam and limiting detector blade temperature during operation. 18 figs.

Kuzay, T.M.; Shu, D.

1995-02-07

437

Photon beam position monitor  

DOEpatents

A photon beam position monitor for use in the front end of a beamline of a high heat flux and high energy photon source such as a synchrotron radiation storage ring detects and measures the position and, when a pair of such monitors are used in tandem, the slope of a photon beam emanating from an insertion device such as a wiggler or an undulator inserted in the straight sections of the ring. The photon beam position monitor includes a plurality of spaced blades for precisely locating the photon beam, with each blade comprised of chemical vapor deposition (CVD) diamond with an outer metal coating of a photon sensitive metal such as tungsten, molybdenum, etc., which combination emits electrons when a high energy photon beam is incident upon the blade. Two such monitors are contemplated for use in the front end of the beamline, with the two monitors having vertically and horizontally offset detector blades to avoid blade "shadowing". Provision is made for aligning the detector blades with the photon beam and limiting detector blade temperature during operation.

Kuzay, Tuncer M. (Naperville, IL); Shu, Deming (Darien, IL)

1995-01-01

438

Advanced imaging system for high-precision, high-resolution CCD imaging  

Microsoft Academic Search

The Advanced Imaging System is a slow scan, high precision CCD camera system designed specifically for low noise image acquisition and precise, highly flexible CCD testing and characterization. In addition, the system is designed to allow CCD mosaics to be supported with separate, programmable clock voltages and output amplifier operating points for each device. A high speed digital signal processor

Peter E. Doherty; Gary R. Sims

1991-01-01

439

Benign positional vertigo  

MedlinePLUS

Vertigo - positional; Benign paroxysmal positional vertigo; BPPV: dizziness- positional ... Benign positional vertigo is also called benign paroxysmal positional ... ear has fluid-filled tubes called semicircular canals. When ...

440

Solar system positioning system  

NASA Technical Reports Server (NTRS)

Power-rich spacecraft envisioned in Prometheus initiative open up possibilities for long-range high-rate communication. A constellation of spacecraft on orbits several A.U. from the Sun, equipped with laser transponders and precise clocks can be configured to measure their mutual distances to within few cm. High on-board power can create substantial non-inertial contribution to the spacecraft trajectory. We propose to alleviate this contribution by employing secondary ranging to a passive daughter spacecraft. Such constellation can form the basis of it navigation system capable of providing position information anywhere in the soIar system with similar accuracy. Apart from obvious Solar System exploration implications, this system can provide robust reference for GPS and its successors.

Penanen, Konstantin I.; Chui, Talso

2006-01-01

441

Preliminary Design and Analysis of the GIFTS Instrument Pointing System  

NASA Technical Reports Server (NTRS)

The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) Instrument is the next generation spectrometer for remote sensing weather satellites. The GIFTS instrument will be used to perform scans of the Earth s atmosphere by assembling a series of field-of- views (FOV) into a larger pattern. Realization of this process is achieved by step scanning the instrument FOV in a contiguous fashion across any desired portion of the visible Earth. A 2.3 arc second pointing stability, with respect to the scanning instrument, must be maintained for the duration of the FOV scan. A star tracker producing attitude data at 100 Hz rate will be used by the autonomous pointing algorithm to precisely track target FOV s on the surface of the Earth. The main objective is to validate the pointing algorithm in the presence of spacecraft disturbances and determine acceptable disturbance limits from expected noise sources. Proof of concept validation of the pointing system algorithm is carried out with a full system simulation developed using Matlab Simulink. Models for the following components function within the full system simulation: inertial reference unit (IRU), attitude control system (ACS), reaction wheels, star tracker, and mirror controller. With the spacecraft orbital position and attitude maintained to within specified limits the pointing algorithm receives quaternion, ephemeris, and initialization data that are used to construct the required mirror pointing commands at a 100 Hz rate. This comprehensive simulation will also aid in obtaining a thorough understanding of spacecraft disturbances and other sources of pointing system errors. Parameter sensitivity studies and disturbance analysis will be used to obtain limits of operability for the GIFTS instrument. The culmination of this simulation development and analysis will be used to validate the specified performance requirements outlined for this instrument.

Zomkowski, Paul P.

2003-01-01

442

Satellite positioning systems - Current status and future prospects  

NASA Astrophysics Data System (ADS)

Two categories of satellite systems are discussed: (1) systems such as Navstar/GPS which are dedicated exclusively to position location and are able to achieve high precision; and (2) systems such as Sarsat, Argos, and Geostar-Locstar which combine positioning with communications services and sacrifice precision for increased simplicity and automation. GPS applications include geodetic surveying and differential position determination for mobile units. The Argos system, employing two Tiros-N meteorological satellites, will be used for obtaining environmental data. The Geostar-Locstar system has a <