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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

Flight evaluation of GPS precise point positioning for helicopter navigation  

Microsoft Academic Search

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

Yutaka Shimizu; Masaaki Murata

2007-01-01

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

Local troposphere augmentation for real-time precise point positioning  

NASA Astrophysics Data System (ADS)

The IGS real-time service (RTS) enables real-time precise point positioning (PPP) at a global scale. A long convergence time however is still a challenging factor. In order to reduce the convergence time, external troposphere corrections could be introduced to remove the troposphere effects on the coordinate solution. This paper proposes the use of a local troposphere model to augment real-time PPP. First, undifferenced observations from a network of multiple stations are processed to estimate the station-based troposphere zenith wet delay (ZWD). A set of local troposphere fitting coefficients are then derived using a proposed optimal fitting model. Finally, the determined troposphere fitting coefficients are broadcast to users to reduce the convergence time in the user solution. A continuous operating reference station (CORS) network is utilized to assess the performance of the proposed approach under quiet and active troposphere conditions. The numerical results show that the overall fitting precisions of the local troposphere model can reach 1.42 and 1.05 cm under the two troposphere conditions. The convergence time of the positioning solutions, especially the height solution, can be greatly reduced using the local troposphere model. The horizontal accuracy of 9.2 cm and the vertical accuracy of 10.1 cm are obtainable under the quiet troposphere condition after 20 min of initialization time, compared to the 14.7 cm horizontal and 21.5 cm vertical accuracies in the conventional troposphere estimation approach. Moreover, the horizontal accuracies of 13.0 cm and the vertical accuracies of 12.4 cm have also been obtained after 20 min under the active troposphere condition.

Shi, Junbo; Xu, Chaoqian; Guo, Jiming; Gao, Yang

2014-12-01

5

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

6

A Reference Point-based Precise Relative Positioning Method  

E-print Network

be overcome with the new algorithm, precise relative positioning (PRP), described in this paper. The PRP by using various techniques, for example, the use of other sensors. The PRP has two modes. One is Iono-Free (I-F) PRP, the other one is Carrier-Based (C-B) PRP. The I-F PRP significantly mitigates the effect

Stanford University

7

Precise Point Positioning with the BeiDou Navigation Satellite System  

PubMed Central

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

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

2014-01-01

8

Real-Time IGS products verification in the context of their use in Precise Point Positioning  

NASA Astrophysics Data System (ADS)

Precise Point Positioning (PPP) is a positioning technique of single GNSS receiver which applies high quality products from permanent GNSS observations to utilize the computational potential of global network analysis. Estimated satellite orbits and clocks corrections are introduced into equation system as known parameters. PPP requires the application of precise products, since their quality directly reflects the positioning accuracy. In June 2007 IGS Real-time Pilot Project has started in order to satisfy real-time users, which is especially important for Precise Point Positioning. Currently available streams including precise orbits, clocks and code biases are standardized on RTCM-SC 104 formats and may be used as a substitute for ultra-rapid products. The target combination product performances are 0.3ns for satellite clock accuracy and orbit accuracy at the level of the IGS Ultra predictions with maximum latency of 10s. This study presents the quality assessment of currently available Real-Time IGS products. Long-term test include comparisons of disseminated information with final and high-rate products, stability assessment over time, as well as latency validation of available RTCM streams.

Hadas, Tomasz; Bosy, Jaroslaw; Kaplon, Jan; Sierny, Jan

2013-04-01

9

Tightly coupled integration of ionosphere-constrained precise point positioning and inertial navigation systems.  

PubMed

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

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

2015-01-01

10

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

PubMed

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

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

2009-08-01

11

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

12

Flight Test Evaluation of Precise Point Positioning Techniques Using Optical Ranging  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

13

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

14

Real-time Precise Point Positioning with Ambiguity Resolution for Geosciences  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

15

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

PubMed Central

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

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

2012-01-01

16

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

17

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

18

Employing GPS L5 Carrier-Frequency in Precise Point Positioning  

NASA Astrophysics Data System (ADS)

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

Spits, J.; Santos, M. C.

2012-12-01

19

Combined GPS/GLONASS precise point positioning with fixed GPS ambiguities.  

PubMed

Precise point positioning (PPP) technology is mostly implemented with an ambiguity-float solution. Its performance may be further improved by performing ambiguity-fixed resolution. Currently, the PPP integer ambiguity resolutions (IARs) are mainly based on GPS-only measurements. The integration of GPS and GLONASS can speed up the convergence and increase the accuracy of float ambiguity estimates, which contributes to enhancing the success rate and reliability of fixing ambiguities. This paper presents an approach of combined GPS/GLONASS PPP with fixed GPS ambiguities (GGPPP-FGA) in which GPS ambiguities are fixed into integers, while all GLONASS ambiguities are kept as float values. An improved minimum constellation method (MCM) is proposed to enhance the efficiency of GPS ambiguity fixing. Datasets from 20 globally distributed stations on two consecutive days are employed to investigate the performance of the GGPPP-FGA, including the positioning accuracy, convergence time and the time to first fix (TTFF). All datasets are processed for a time span of three hours in three scenarios, i.e., the GPS ambiguity-float solution, the GPS ambiguity-fixed resolution and the GGPPP-FGA resolution. The results indicate that the performance of the GPS ambiguity-fixed resolutions is significantly better than that of the GPS ambiguity-float solutions. In addition, the GGPPP-FGA improves the positioning accuracy by 38%, 25% and 44% and reduces the convergence time by 36%, 36% and 29% in the east, north and up coordinate components over the GPS-only ambiguity-fixed resolutions, respectively. Moreover, the TTFF is reduced by 27% after adding GLONASS observations. Wilcoxon rank sum tests and chi-square two-sample tests are made to examine the significance of the improvement on the positioning accuracy, convergence time and TTFF. PMID:25237901

Pan, Lin; Cai, Changsheng; Santerre, Rock; Zhu, Jianjun

2014-01-01

20

Combined GPS/GLONASS Precise Point Positioning with Fixed GPS Ambiguities  

PubMed Central

Precise point positioning (PPP) technology is mostly implemented with an ambiguity-float solution. Its performance may be further improved by performing ambiguity-fixed resolution. Currently, the PPP integer ambiguity resolutions (IARs) are mainly based on GPS-only measurements. The integration of GPS and GLONASS can speed up the convergence and increase the accuracy of float ambiguity estimates, which contributes to enhancing the success rate and reliability of fixing ambiguities. This paper presents an approach of combined GPS/GLONASS PPP with fixed GPS ambiguities (GGPPP-FGA) in which GPS ambiguities are fixed into integers, while all GLONASS ambiguities are kept as float values. An improved minimum constellation method (MCM) is proposed to enhance the efficiency of GPS ambiguity fixing. Datasets from 20 globally distributed stations on two consecutive days are employed to investigate the performance of the GGPPP-FGA, including the positioning accuracy, convergence time and the time to first fix (TTFF). All datasets are processed for a time span of three hours in three scenarios, i.e., the GPS ambiguity-float solution, the GPS ambiguity-fixed resolution and the GGPPP-FGA resolution. The results indicate that the performance of the GPS ambiguity-fixed resolutions is significantly better than that of the GPS ambiguity-float solutions. In addition, the GGPPP-FGA improves the positioning accuracy by 38%, 25% and 44% and reduces the convergence time by 36%, 36% and 29% in the east, north and up coordinate components over the GPS-only ambiguity-fixed resolutions, respectively. Moreover, the TTFF is reduced by 27% after adding GLONASS observations. Wilcoxon rank sum tests and chi-square two-sample tests are made to examine the significance of the improvement on the positioning accuracy, convergence time and TTFF. PMID:25237901

Pan, Lin; Cai, Changsheng; Santerre, Rock; Zhu, Jianjun

2014-01-01

21

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

NASA Astrophysics Data System (ADS)

GNSS geodetic positioning using the classical double-difference approach may have some limitations. For example, fixing ambiguities can be challenging for long baselines, while processing short baseline only give the relative displacement between the two stations. In this context and thanks to the continuous improvement of IGS GNSS orbit and clock products, the Precise Point Positioning (PPP) technique appears in the literature as a powerful alternative. If all local Earth deformations are correctly taken into account, residuals of position time series may be used to assess the processing quality in terms of receiver performance and environment, constellation orbits and clocks error projection, and processing options pertinence. The main limitation of most of the current PPP processing strategies is that ambiguities can not be fixed to integer values. However, Mercier et al. (2008) demonstrated that GPS satellite “electronic” biases can be a priori identified in such a way that using a consistent set of GPS orbits, clocks and biases, phase ambiguities recover their integer nature. The CNES-CLS IGS Analysis Center is being providing such set of data since August 2010. This study evaluate the performance of PPP in front of the nowadays requirements of geodesy. We processed data from several IGS sites in order to compute coordinate series on a daily basis but also at higher frequencies (down to 30 second interval). We investigated both the impact of the processing batch duration from hours to several days and the cut-off elevation angle. Various spurious “non geophysical” signals (random, periodic, jumps...)appeared in our series. Especially artificial "midnight jumps" when adopting the usual 24-hours batch solutions (when satellite passes were cut at 0h). The impact of fixing ambiguities on PPP solutions has been investigated. We demonstrate that most of the artifacts affecting “floating” PPP solutions disappeared when ambiguities were fixed.

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

2010-12-01

22

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

PubMed

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

Rabbou, Mahmoud Abd; El-Rabbany, Ahmed

2015-01-01

23

Predicting atmospheric delays for rapid ambiguity resolution in precise point positioning  

NASA Astrophysics Data System (ADS)

Integer ambiguity resolution in precise point positioning (PPP) can shorten the initialization and re-initialization time, and ambiguity-fixed PPP solutions are also more reliable and accurate than ambiguity-float PPP solutions. However, signal interruptions are unavoidable in practical applications, particularly while operating in urban areas. Such signal interruptions can cause discontinuity of carrier phase arc, which introduces new integer ambiguities. Usually it will take approximately 15 min of continuous tracking to a reasonable number of satellites to fix new integer ambiguities. In many applications, it is impractical for a PPP user to wait for such a long time for the re-initialization. In this paper, a method for rapid ambiguity fixing in PPP is developed to avoid such a long re-initialization time. Firstly, the atmospheric delays were estimated epoch by epoch from ambiguity-fixed PPP solutions before the data gap or cycle slip occurs. A random walk procedure is then applied to predict the atmospheric delays accurately over a short time span. The predicted atmospheric delays then can be used to correct the observations which suffer from signal interruptions. Finally, the new ambiguities can be fixed with a distinct WL-LX-L3 (here LX denotes either of L1, L2) cascade ambiguity resolution strategy. Comprehensive experiments have demonstrated that the proposed method and strategy can fix zero-difference integer ambiguities successfully with only a single-epoch observation immediately after a short data gap. This technique works even when all satellites are interrupted at the same time. The duration of data gap bridged by this technique could be possibly extended if a more precise atmospheric delay prediction is found or on-the-fly (OTF) technology is applied. Based on the proposed method, real-time PPP with integer ambiguity fixing becomes more feasible in practice.

Li, Xingxing; Zhang, Xiaohong; Guo, Fei

2014-09-01

24

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

25

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

26

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

27

Precision positioning device  

DOEpatents

A precision positioning device is provided. The precision positioning device comprises a precision measuring/vibration isolation mechanism. A first plate is provided with the precision measuring mean secured to the first plate. A second plate is secured to the first plate. A third plate is secured to the second plate with the first plate being positioned between the second plate and the third plate. A fourth plate is secured to the third plate with the second plate being positioned between the third plate and the fourth plate. An adjusting mechanism for adjusting the position of the first plate, the second plate, the third plate, and the fourth plate relative to each other.

McInroy, John E.

2005-01-18

28

An improved approach to model ionospheric delays for single-frequency Precise Point Positioning  

NASA Astrophysics Data System (ADS)

PPP with low-cost, single-frequency receivers has been receiving increasing interest in recent years because of its large amount of possible users. One crucial issue in single-frequency PPP is the mitigation of ionospheric delays which cannot be removed by combining observations on different frequencies. For this purpose, several approaches have been developed, such as, the approach using ionospheric model corrections with proper weight, the GRAPHIC (Group and Phase Ionosphere Calibration) approach, and the method to model ionospheric delays over a station with a low polynomial or stochastic process. From our investigation on the stochastic characteristics of the ionospheric delay over a station, it cannot be precisely represented by either a deterministic model in the form of a low-order polynomial or a stochastic process for each satellite, because of its strong irregular spatial and temporal variations. Therefore, a novel approach is developed accordingly in which the deterministic representation is further refined by a stochastic process for each satellite with an empirical model for its power density. Furthermore, ionospheric delay corrections from a constructed model using GNSS data are also included as pseudo-observations for a better solution. A large data set collected from about 200 IGS stations over one month in 2010 is processed with the new approach and several commonly adopted approaches for validation. The results show its significant improvements in terms of positioning accuracy and convergence time with a negligible extra processing time, which is also demonstrated by data collected with a low-cost, handheld, single-frequency receiver.

Shi, Chuang; Gu, Shengfeng; Lou, Yidong; Ge, Maorong

2012-06-01

29

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

30

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

31

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

32

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

33

Ambiguity-fixed GPS precise point positioning for earthquake and tsunami early warning in Western North America  

NASA Astrophysics Data System (ADS)

The development of single-receiver integer ambiguity resolution in recent years has made the GPS precise point positioning (PPP) technique a valuable tool in measuring centimeter-level displacements epoch by epoch at a single station. A good application for this technique is identifying ground motions in an earthquake and tsunami early warning system. With a single receiver, PPP with ambiguity resolution can reproduce the positioning accuracy of conventional differential positioning techniques, but does not depend on any nearby reference stations which may also be displaced during an earthquake. As a result, the PPP data processing is more straightforward and efficient, suggesting that onsite displacement estimation can be carried out semi-autonomously at each GPS station and only a small amount of data, i.e. 3D displacements rather than raw measurements in the differential positioning, need to be transmitted to warning centers. Due to these merits and as part of a NASA-sponsored research effort, we have developed an operational real-time PPP system for Western North America, a vast region of tectonic deformation and significant seismic risk. A group of about 75 real-time GPS stations throughout North America and located far from western US coast (>300 km) is employed to estimate satellite-specific corrections (i.e. satellite clocks and fractional-cycle biases) with the predicted satellite orbits provided by the IGS (International GNSS Services). We note that our PPP implementation is challenged by geophysical constraints in North America and so all clients in the zone of deformation are outside the coverage of the reference network, and thus measurement errors originating in the atmosphere, satellite orbits and clocks are less correlated between the reference stations and the PPP clients. Despite this difficulty, the horizontal positioning accuracy at each PPP station is around 1 cm while the vertical better than 5 cm. This accuracy is sufficient to optimally combine the 1-Hz PPP-derived displacements with collocated (100 Hz) accelerometer data using a Kalman filter to estimate total displacement waveforms with millimeter-level accuracy. We also report on the testing of our approach in a simulated real-time environment for the 2006 Mw 6.0 Parkfield and 2010 Mw 7.2 El Mayor-Cucapah earthquakes.

Geng, J.; Bock, Y.; Fang, P.; Haase, J. S.

2012-12-01

34

Rapid earthquake magnitude from real-time GPS precise point positioning for earthquake early warning and emergency response  

NASA Astrophysics Data System (ADS)

For earthquake early warning (EEW) and emergency response, earthquake magnitude is the crucial parameter to be determined rapidly and correctly. However, a reliable and rapid measurement of the magnitude of an earthquake is a challenging problem, especially for large earthquakes (M>8). Here, the magnitude is determined based on the GPS displacement waveform derived from real-time precise point positioning (PPP). The real-time PPP results are evaluated with an accuracy of 1 cm in the horizontal components and 2-3 cm in the vertical components, indicating that the real-time PPP is capable of detecting seismic waves with amplitude of 1cm horizontally and 2-3cm vertically with a confidence level of 95%. In order to estimate the magnitude, the unique information provided by the GPS displacement waveform is the horizontal peak displacement amplitude. We show that the empirical relation of Gutenberg (1945) between peak displacement and magnitude holds up to nearly magnitude 9.0 when displacements are measured with GPS. We tested the proposed method for three large earthquakes. For the 2010 Mw 7.2 El Mayor-Cucapah earthquake, our method provides a magnitude of M7.18±0.18. For the 2011 Mw 9.0 Tohoku-oki earthquake the estimated magnitude is M8.74±0.06, and for the 2010 Mw 8.8 Maule earthquake the value is M8.7±0.1 after excluding some near-field stations. We therefore conclude that depending on the availability of high-rate GPS observations, a robust value of magnitude up to 9.0 for a point source earthquake can be estimated within 10s of seconds or a few minutes after an event using a few GPS stations close to the epicenter. The rapid magnitude could be as a pre-requisite for tsunami early warning, fast source inversion, and emergency response is feasible.

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

2014-05-01

35

System for precise position registration  

DOEpatents

An apparatus for enabling accurate retaining of a precise position, such as for reacquisition of a microscopic spot or feature having a size of 0.1 mm or less, on broad-area surfaces after non-in situ processing. The apparatus includes a sample and sample holder. The sample holder includes a base and three support posts. Two of the support posts interact with a cylindrical hole and a U-groove in the sample to establish location of one point on the sample and a line through the sample. Simultaneous contact of the third support post with the surface of the sample defines a plane through the sample. All points of the sample are therefore uniquely defined by the sample and sample holder. The position registration system of the current invention provides accuracy, as measured in x, y repeatability, of at least 140 .mu.m.

Sundelin, Ronald M.; Wang, Tong

2005-11-22

36

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 RAPPP, the proposed project RTPPP concentrates on the possibilities of the PPP technique within a real

Schuh, Harald

37

Vermessung & Geoinformation 2/2011, P. 114 121, 5 Figs.114 Within the last decade, Precise Point Positioning (PPP) has been discussed by GNSS (Global Navigation Satellite  

E-print Network

, Precise Point Positioning (PPP) has been discussed by GNSS (Global Navigation Satellite System) experts. Fundamentals 1.1 The principle of PPP Compared to the lifetime of Global Navigation Satellite Systems (GNSS reference stations, since the corrections used for PPP are globally valid. Still, PPP is suffering from long

Schuh, Harald

38

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

39

Floating-Point Arithmetic Precision and Accuracy  

E-print Network

Floating-Point Arithmetic Precision and Accuracy With Mathematica Alkis Akritas University is to approximate the real numbers using the finite set of floating-point numbers. Mathematica has two kinds of floating-point numbers: machine- precision numbers and arbitrary-precision numbers. (The precision

Akritas, Alkiviadis G.

40

Vermessung & Geoinformation 2/2011, P. 171 179, 7 Figs. 171171 Precise Point Positioning (PPP) denotes a GNSS (Global Navigation Satellite System) based positioning technique,  

E-print Network

such as the International GNSS Service (IGS). Typically, the ionospheric delay is almost completely eliminated by means) applications IGS has initiated a real-time working group to investigate the feasibility of real-time GNSS data (TUW) to the IGS Real-Time Working Group and with the quality of PPP positioning obtained using the RT

Schuh, Harald

41

Hemispherical resonator gyro for precision pointing applications  

NASA Astrophysics Data System (ADS)

The solid-state Hemispherical Resonator Gyroscope (HRG) uniquely offers the benefits of small size, extremely long life, and ultrahigh reliability for spacecraft pointing and control application. The HRG also offers precision performance which can be scaled through control loop and electronics design tradeoffs. Delco Systems Operations has developed the HRG-based Space Inertial Reference Unit (SIRU), which has been designed to maximize the benefits of small size and high reliability and meet the medium grade performance of most spacecraft. The precision performance required for many imaging spacecraft has been achieved through selected modifications to the SIRU design. The result is a precision pointing IRU which maintains the inherent small-size, high reliability characteristics offered by the solid-state HRG. These attributes enable the weight reduction and life extension of precision imaging spacecraft. Modifications to the SIRU design for precision pointing applications have been implemented and characterized. These modifications and test results are described herein.

Matthews, Anthony D.; Bauer, David A.

1995-06-01

42

Determining Precise Positions of Supernovae  

NASA Astrophysics Data System (ADS)

A 0.25m/0.32m lenseless Schmidt camera mounted piggyback on the University of Rhode Island (URI) astrometric reflector (Penhallow 1978) is used to determine the positions of supernovae within 0.1 second of arc. Measurable 15.5 magnitude images can be obtained on hypered Kodak SR-5 x-ray film in 4 minutes under favorable conditions. Five exposures with about 16 reference stars are normally used.

Penhallow, William S.

1986-12-01

43

Precise positioning of patients for radiation therapy  

Microsoft Academic Search

A number of immobilization schemes which permit precise daily positioning of patients for radiation therapy are discussed. Pretreatment and post-treatment radiographs have been taken with the patient in the treatment position and analyzed to determine the amount of intratreatment movement. Studies of patients in the supine, seated and decubitus positions indicate mean movements of less than 1 mm with a

Lynn J. Verhey; Michael Goitein; Patricia McNulty; John E. Munzenrider; Herman D. Suit

1982-01-01

44

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

45

A miniaturized rotational precision positioning stage  

Microsoft Academic Search

A miniaturized rotational precision positioning stage using the spring-mounted piezoelectric actuators is proposed in this paper. The positioning stage features micro\\/nano-meter order moving ability that is caused by piezoelectric (PZT) impact force, and continuous actuation ability with unlimited rotational displacement that is obtained by the integration of compression spring and PZT actuator. A one-DOF (degree-of-freedom) experimental setup consisting of two

Yung-Tien Liu; Chih-Kuei Wang

2005-01-01

46

Analysis on the positioning precision of CAPS  

NASA Astrophysics Data System (ADS)

As a newly developed satellite positioning system, the Chinese Area Positioning System (CAPS) is a typical direct sequence spread spectrum ranging system like GPS. The positioning precision of such navigation signals depends on many factors, including the pseudo-code rate, the signal to noise ratio, the processing methods for tracking loops and so on. This paper describes the CAPS link budget, the solution approach for CAPS positioning, focusing on the autocorrelation function feature of C/A code signals. The CAPS signal measurement precision is studied by the software approach together with theoretical analysis of the range resolution. Because the conventional Delay Lock Loop (DLL) is vulnerable to the impact of noise, a narrow correlator and multiple correlators as well as the corresponding discrimination methods of phases are proposed, which improves the robustness of DLL and the code-phase resolution of the measurement. The results show that the improvement of the DLL structure and the discrimination method are the most important way to improve the ranging resolution. Theoretical analysis and experimental results show that a CAPS receiver could reach a 20-m positioning precision by using three satellites with a supported height from an altimeter.

Ji, Yuanfa; Sun, Xiyan

2009-03-01

47

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

48

Exploiting Mixed Precision Floating Point Hardware in Scientific  

E-print Network

Exploiting Mixed Precision Floating Point Hardware in Scientific Computations Alfredo BUTTARI of 32-bit and 64-bit floating point arithmetic, the performance of many dense and sparse linear algebra in using the sin- gle precision, floating point data format over the double precision one. Due to more com

Dongarra, Jack

49

Use of GNSS data for Hydrology: Applications of the method PPP (Precise Point Positioning) with integer ambiguities fixing for hydrological studies in the Amazon basin  

NASA Astrophysics Data System (ADS)

Applications of GNSS data is constantly being used in hydrology. One of the key applications is the characterization of river's longitudinal profiles, an information required to develop hydrological and hydrodynamic studies and to evaluate the quality of data obtained through space altimetry techniques. Some factors illustrate the challenge of establishing quality altimetry data from a GNSS receivers to obtain rivers profiles in Amazon Basin. GNSS reference network is sparse, the distance between survey points and reference stations is large, rivers have an extension of several thousands of kilometers. All these factors contribute in limiting the efficiency of classical techniques of GNSS data processing like double difference. In the present work we use the Gins-PC software developed at CNES / GRGS. We discuss the capability of the PPP kinematic with integer ambiguities fixing strategy implemented in GINS-PC in processing GPS data to calculate river's longitudinal profiles in the Amazon Basin. The profiles will be processed using data obtained from GPS receivers on boarding boats along the rivers of Amazon Basin such as Negro river, Madeira river and Amazon/Solimões river. For this purpose, field campaings were conducted between 2005 and 2010 by ANA ( Brazilian National Water Agency), CPRM (Brazilian Geologic Survey), IRD (French Institute of Research by Development), Hybam ( Hydrology of Amazon Basin), PROSUL (Research project by CNPQ/UFRJ) and FOAM (From Ocean to inland waters Altimetry Monitoring) river section project. Under the proposed framework, these profiles will be then compared with profiles obtained by water level variation data using altimetry data from tracks of the Jason-2 and ENVISAT missions. The profiles will be also used to levelling some gauge stations in Amazon Basin and gauge data will be used to obtain a temporal variation of these profiles. However some gauges are strongly affected by charge effects, mainly caused by the hydrological cycle of the Amazon basin. These effects can produce a variation of about 10 cm in amplitude of vertical coordinates also obtained by GPS. Therefore, we use GRACE data to convert the hydrologic load into crustal displacements to remove these effects.

Moreira, D. M.; Calmant, S.; Perosanz, F.; Santos, A.; Santos Da Silva, J.; Seyler, F.; Ramillien, G. L.; Monteiro, A.; Rotunno, O.; Shum, C.

2011-12-01

50

Algorithms for Arbitrary Precision Floating Point Arithmetic \\Lambda  

E-print Network

Algorithms for Arbitrary Precision Floating Point Arithmetic \\Lambda Douglas M. Priest Department to perform computations of very high accuracy using only straightforward floating point arithmetic operations satisfied by most implementations of floating point arithmetic. To illustrate the application

Shewchuk, Jonathan

51

Software Model Checking the Precision of Floating-Point Programs  

E-print Network

1 Software Model Checking the Precision of Floating-Point Programs Franjo Ivanci´c, Malay K. Ganai floating-point standard, and the precision loss incurred in such programs. There have been techniques with floating point operations. We generate a mixed integral-real model that is then analyzed by two backend

Sankaranarayanan, Sriram

52

Precimonious: Tuning Assistant for Floating-Point Precision  

E-print Network

Precimonious: Tuning Assistant for Floating-Point Precision Cindy Rubio-Gonz´alez1 , Cuong Nguyen1.hough@oracle.com ABSTRACT Given the variety of numerical errors that can occur, floating- point programs are difficult developers in tuning the precision of floating-point programs. Precimonious performs a search on the types

California at Berkeley, University of

53

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

54

High-precision positioning stage for microassembly purposes  

NASA Astrophysics Data System (ADS)

In this paper, a LC-SEM will be presented as observation device for micro assembly purposes. Compared to other means of magnification it offers several advantages like, for instance, a large depth of field. A gripper which can be operated inside this LC-SEM has been developed and tested. It can be equipped with an endoscope for additional process observation. Its gripping arms can be changed according to the assembly task. For precise and flexible positioning of the griper a complex 7-axes positioning system has been designed. It can be operated in the LC-SEM too, and offers a tool-center-point movement of the gripper in order to keep all assembly operations in the focus of the SEM. With these devices further study of micro assembly will be possible.

Weck, Manfred; Petersen, Bernd

1999-03-01

55

High precision applications of the global positioning system  

NASA Technical Reports Server (NTRS)

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

Lichten, Stephen M.

1991-01-01

56

Stochastic Optimization of Floating-Point Programs with Tunable Precision  

E-print Network

Stochastic Optimization of Floating-Point Programs with Tunable Precision Eric Schkufza Stanford Stanford University aiken@cs.stanford.edu Abstract The aggressive optimization of floating-point computations is an important problem in high-performance computing. Unfortunately, floating-point instruction

Aiken, Alex

57

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

58

Precision Pointing in the Sky for IBEX Interstellar Flow Observations  

E-print Network

Precision Pointing in the Sky for IBEX Interstellar Flow Observations Conclusions & Goals by the gas and dust in the space between the Sun and other stars (the interstellar medium). The solar wind creates a protective bubble, or `heliosphere' around the solar system, as we travel through the Milky Way

New Hampshire, University of

59

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

60

Precisely detecting atomic position of atomic intensity images.  

PubMed

We proposed a quantitative method to detect atomic position in atomic intensity images from experiments such as high-resolution transmission electron microscopy, atomic force microscopy, and simulation such as phase field crystal modeling. The evaluation of detection accuracy proves the excellent performance of the method. This method provides a chance to precisely determine atomic interactions based on the detected atomic positions from the atomic intensity image, and hence to investigate the related physical, chemical and electrical properties. PMID:25544105

Wang, Zhijun; Guo, Yaolin; Tang, Sai; Li, Junjie; Wang, Jincheng; Zhou, Yaohe

2015-03-01

61

Precision pointing using a dual-wedge scanner  

NASA Astrophysics Data System (ADS)

The calibration and precise pointing of the germanium dual-wedge scanner that is used by an airborne CO2 Doppler lidar is undertaken by a system whose iterative calibration program combines the available data with estimated parameters of the scanner's orientation (relative to the aircraft's inertial navigation system axes). Attention is given to the effects of specific error conditions on program performance, and to the results of the program's application to 1981 flight test data.

Amirault, C. T.; Dimarzio, C. A.

1985-05-01

62

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

63

Reactionless gimbal actuator for precision pointing of large payloads  

NASA Technical Reports Server (NTRS)

A novel actuator for application to precision pointing gimbal systems is described. The new actuator, dubbed the Reactuator, is capable of large output torques for payload pointing while minimizing reaction torques that can excite gimbal support structure. The Reactuator is able to approach reactionless operation by using an integral wheel to absorb the reaction torques. The advantages that result are described through analysis and simulation examples. Methods for designing control algorithms for the Reactuator are discussed and the results of preliminary breadboard tests are presented.

Laskin, R. A.; Kopf, E. H.; Sirlin, S. W.; Spanos, J. T.; Wiktor, P. J.

1988-01-01

64

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

65

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

66

Precise CCD positions of Galilean satellite-pairs  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

67

Precise Measurement of the Positive Muon Anomalous Magnetic Moment  

Microsoft Academic Search

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

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

2001-01-01

68

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

69

Generation of precise point mutation mice by footprintless genome modification.  

PubMed

Point mutation mice are a key tool in the study of biological functions of genomic DNA sequences and the creation of human disease models. These mice are produced by homologous recombination combined with site-specific recombinase, which allows removal of drug selection cassettes. However, the methods currently available leave ectopic sequences in the "inactive" intron region of the targeted genome in addition to the desired mutation. Since recent research suggests that the intron region may actually have some functionality, these sequences could potentially interfere with neighboring gene expression and, as a result, affect the mouse phenotype. To completely avoid this issue, we used the PiggyBac transposon to remove selection cassettes and achieve precise genome modification without leaving behind a footprint. This PiggyBac system allowed us to successfully generate mice carrying an artificially introduced W(v) point mutation in the Kit gene, and these mice were confirmed to have phenotypes identical to spontaneous W(v) mutation mice. Generation of W(v) -mutation corrected mice was also possible, and phenotypes were completely restored. Our footprintless genome modification technology can generate precise point mutation mice with only the desired mutation, and they reflect an accurate phenotype that makes these mice a reliable and "worry-free" research resource. PMID:24265262

Morioka, Yuka; Fujihara, Yoshitaka; Okabe, Masaru

2014-01-01

70

A floating-point/multiple-precision processor for airborne applications  

NASA Technical Reports Server (NTRS)

A compact input output (I/O) numerical processor capable of performing floating-point, multiple precision and other arithmetic functions at execution times which are at least 100 times faster than comparable software emulation is described. The I/O device is a microcomputer system containing a 16 bit microprocessor, a numerical coprocessor with eight 80 bit registers running at a 5 MHz clock rate, 18K random access memory (RAM) and 16K electrically programmable read only memory (EPROM). The processor acts as an intelligent slave to the host computer and can be programmed in high order languages such as FORTRAN and PL/M-86.

Yee, R.

1982-01-01

71

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

72

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

73

Precision optical pointing and tracking from spacecraft with vibrational noise  

NASA Astrophysics Data System (ADS)

The results of an investigation of the performance of three basic precision pointing and tracking control subsystems considered for application to satellite to satellite optical communication missions are discussed. The three-control subsystems include: (1) gyro-stabilized, (2) mass-stabilized and (3) complementary filter. The sources of error included in the analysis included: (1) sensor noise from the optical detector, (2) host satellite baseframe vibrational noise and (3) frictional and bearing noise. The measured vibrational and disturbance data from the LANDSAT satellite was used to generate the power spectral density parameter needed to model the baseframe noise environments of the two satellites used for the evaluation. The results of the study indicate that the 1 microradian rms pointing and tracking accuracy may be achieved with either the gyro-stabilized or the complementary filter approach.

Held, K. J.; Barry, J. D.

1986-01-01

74

Precision positioning system based on intelligent Fuzzy-PID control  

NASA Astrophysics Data System (ADS)

To break through the limitations of static and dynamic characteristics of conventional step motor driven open-loop positioning devices, a two-dimensional precision positioning system with a travel range of 100mm×100mm has been developed. This paper presents its structure, control principle and performance experiments. This system, equipped with cross roller guides working as linear guiding elements, is driven by step motors through ball screw transmission. A threeaxis dual-frequency laser interferometric measurement system is established for real-time measurement and feedback of system's movements in three degrees of freedom (DOF) and an intelligent Fuzzy-PID controller is implemented for this system's motion control. In the controller, the PID module calculates the output from motor drivers and its initial parameters are tuned through expansion of critical proportioning method; the Fuzzy module optimizes PID parameters to fulfill specific requirements of different movement stages. A dead zone control mechanism is developed in this controller to minimize the oscillations around target position. Experimental results indicate that system with Fuzzy-PID controller shows faster response than that with ordinary PID controller. Moreover, with this controller implemented, the developed precision positioning system achieves better repeatability (+/-2?m) and accuracy (+/-2.5?m) within the full range than open-loop system using step motor.

Liu, Zhen; Zhang, Liqiong; Li, Yan

2010-08-01

75

Influence of GPS antenna phase center variation on precise positioning  

NASA Astrophysics Data System (ADS)

The GPS antenna is the connecting element between the GPS satellites and the GPS receiver. It receives the incoming satellite signal and then converts its energy into an electric current, which can be managed by the GPS receiver. The accurate antenna phase center offsets’ values and phase center variation factors are critical issues in GPS precise positioning. Some GPS users simply apply the manufacturer’s recommended offset values which may not match the precise values determined by calibration process. Other users may ignore the phase center correction factors during GPS data processing. In both cases, the resulted coordinates will have errors especially the height component. In this study, some static and kinematic field experiments have been carried out to evaluate the effect of using the manufacturer’s recommended antenna phase offset and ignoring its variation on precise positioning. The GPS data have been post-processed by two commercial software. The results showed that, a significant error may occur in case of disregarding the calibrated values and applying the manufacturer’s recommended ones. Investigation is also made on the effects of mixing different types of antennas. Significant variations are observed on the height components than the associated horizontal component due to phase center variation. The maximum variations are reached about 8 and 4 cm in height and northing components respectively.

EL-Hattab, Ahmed I.

2013-12-01

76

Precise Positioning Control Using Auto-Tuned Fuzzy Logic Controller  

NASA Astrophysics Data System (ADS)

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

Abd-Elhameed, Esam H.; Iwasaki, Makoto

77

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

Microsoft Academic Search

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

Tomas Beran

2008-01-01

78

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

79

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

80

Research on the structure of high-speed large-scale ultra-precision positioning system  

Microsoft Academic Search

According to the needs in such fields as IC manufacturing and ultra-precision machining, a precision positioning system based on macro-micro dual-drive was developed. The macro positioning system is a two dimensional high-speed large-scale precision positioning system based on linear motor drive. The micro positioning system is a low speed ultra-precision positioning system based on the PZT and flexure hinge. The

Chuan Yang; Guang L. Wang; Bi S. Yang; Hai R. Wang

2008-01-01

81

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

82

An optimal GPS data processing technique for precise positioning  

NASA Technical Reports Server (NTRS)

A mathematical formula to optimally combine dual-frequency GPS pseudorange and carrier phase (integrated Doppler) data streams into a single data stream is derived in closed form. The data combination reduces the data volume and computing time in the filtering process for parameter estimation by a factor of 4 while preserving the full data strength for precise positioning. The resulting single data stream is that of carrier phase measurements with both data noise and bias uncertainty strictly defined. With this mathematical formula the single stream of optimally combined GPS measurements can be efficiently formed by simple numerical calculations. Carrier phase ambiguity resolution, when feasible, is strengthened due to the preserved full data strength with the optimally combined data and the resulting longer wavelength for the ambiguity to be resolved.

Wu, Sien-Chong; Melbourne, William G.

1993-01-01

83

Influence of the northern ionosphere on positioning precision  

NASA Astrophysics Data System (ADS)

The results of the analyses of the influence of the northern ionosphere on positioning precision are presented. The analyses rely on studying the repeatability of vectors' coordinates. These vectors were investigated during the ionospheric storms. The GPS permanent observations from the three periods of the ionospheric storms of 1999 were used: 11-16 September, 27-30 September and 10-15 October. The permanent observations from the following IGS/EUREF stations were analyzed: Onsala, Hoefn, Thule, Kiruna, Ny-Alesund, Reykjavik, Tromso and Metsahovi. Their latitude range varies from 57°N to 80°N. Software Bernese ver.4.2 was used for the analysis of the GPS observational data considering 8, 12 and 24 h sessions.

Krankowski, A.; Baran, L. W.; Shagimuratov, I. I.

84

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

USGS Publications Warehouse

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

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

2014-01-01

85

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

86

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

PubMed

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

Sima, Octavian; Arnold, Dirk

2012-09-01

87

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

88

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

89

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

90

Antenna pointing compensation based on precision optical measurement techniques  

NASA Technical Reports Server (NTRS)

The pointing control loops of the Deep Space Network 70 meter antennas extend only to the Intermediate Reference Structure (IRS). Thus, distortion of the structure forward of the IRS due to unpredictable environmental loads can result in uncompensated boresight shifts which degrade blind pointing accuracy. A system is described which can provide real time bias commands to the pointing control system to compensate for environmental effects on blind pointing performance. The bias commands are computed in real time based on optical ranging measurements of the structure from the IRS to a number of selected points on the primary and secondary reflectors.

Schumacher, L. L.; Vivian, H. C.

1988-01-01

91

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

92

Faculty Position in Ultra High Precision Robotics & Manufacturing  

E-print Network

, actuators, transmission systems, sensors and methods targeting ultra-high precision additive manufacturing links to the diverse and well-established local high-technology industry. As a faculty member a curriculum vitae with a list of publications, a concise statement of research and teaching interests

Candea, George

93

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; Bauer, Frank H. (Technical Monitor); Maghami, P. G.

2003-01-01

94

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

95

Precision Pointing for the Laser Interferometer Space Antenna (LISA) Mission  

NASA Technical Reports Server (NTRS)

The Laser Interferometer Space Antenna (LISA) mission is a planned NASA-ESA gravity wave detector consisting of three spacecraft in heliocentric orbit. Lasers are used to measure distance fluctuations between the proof masses aboard the spacecraft to the picometer level over the 5 million kilometer spacing. Each spacecraft and it's 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 mHz to 0.1 Hz. This is accomplished by sensing the pointing error in the received beam and controlling the spacecraft attitude with a set of micronewton thrusters. Requirements, sensors, actuators, control design, and simulations are described in this paper.

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

2003-01-01

96

A precision pointing system for space telescope class optical trackers  

Microsoft Academic Search

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

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

1988-01-01

97

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

98

A study on adaptive load torque observer for robust precision position control of BLDC motor  

Microsoft Academic Search

A new control method for precision robust position control of a brushless DC (BLDC) motor using asymptotically stable adaptive load torque observer is presented in the paper. Precision position control is obtained for the BLDC motor system approximately linearized using the field-orientation method. Many of these drive systems use BLDC motors to avoid backlash. However, the disadvantages of the motor

Jong Sun Ko; Sung Koo Youn; Bimal K. Bose

1999-01-01

99

Master and slave control of a dual-stage for precision positioning  

Microsoft Academic Search

Master\\/slave control of a dual-stage for precision positioning with application to IC production is presented. Configuration and work principle of ultra precision positioning stage are pictured. By adopting merits of both coarse and fine stage, a desired motion control system having the capacity of large workspace with high resolution of motion is enabled. Identification method of mechatronics system such as

Xuedong Chen; Shangying Zhang; Xiulan Bao; Hui Zhao

2008-01-01

100

Development of 3-axis nano stage for precision positioning in lithography system  

Microsoft Academic Search

The precision positioning system requires robust structural design to obtain enough bandwidth and efficient magnetic circuit to have fast access time. In this paper, the 3-axis nano stage was proposed and dynamic characteristics was improved by design of experiments (DOE) based on specifications of our precision positioning device. Finally, it was checked that the designed actuator had the proper dynamic

Dong-Ju Lee; Kang-Nyung Lee; No-Cheol Park; Young-Pil Park; Hyuk Kim; Suk-Won Lee; Hyoung Gil Choi; Moon Gu Lee; Jiho Uh; Jung-Woo Park; Yong-Hwan Choi; Dong-Jin Lee

2005-01-01

101

Laser-interferometer position-feedback for precision machine tools  

SciTech Connect

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

Barkman, W.E.

1980-04-15

102

A precision pointing system for space telescope class optical trackers  

NASA Astrophysics Data System (ADS)

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

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

103

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

104

Application of a novel capacitive sensor in precise positioning systems  

Microsoft Academic Search

This paper presents a comb-finger capacitive displacement sensor used in nano-positioning system. The displacement sensor is designed to develop an integrated implementation platform and to achieve its closed-loop control. In the design, offset constant-tooth, combinations with S-type beams and flexible cantilevers have been adopted to enhance the position range and structure performance. Surface and bulk micromachining technology is employed to

Tao Chen; Liguo Chen; Mingqiang Pan; Lining Sun

2011-01-01

105

High-precision positioning stages for micro- and nanolithography  

Microsoft Academic Search

Low scanning speed as well as hysteresis nonlinearities have been fundamental limitations of scanning probe based micro\\/nano-fabrication techniques. Scanning speeds are typically limited to about 1\\/10th the fundamental vibrational mode of the piezo-positioning system while hysteresis nonlinearities cause significant errors in large- range positioning applications. This paper presents a method to achieve higher scan rates by using inversion of the

Donald Croft; Santosh Devasia

1997-01-01

106

Adaptive Robust Precision Control of Piezoelectric Positioning Stages Jinghua Zhong and Bin Yao  

E-print Network

available nano-positioning stage driven by a piezoelectric actuator with an integrated capacitive positionAdaptive Robust Precision Control of Piezoelectric Positioning Stages Jinghua Zhong and Bin Yao Abstract-- Positioning stages using piezoelectric stack actua- tor (PEA) have very high theoretical

Yao, Bin

107

Precision of robotic guided instrumentation for acetabular component positioning.  

PubMed

Robotic computerized instrumentation that guides bone preparation and cup implantation in total hip arthroplasty was studied. In 38 patients (43 hips) intraoperative cup inclination and anteversion were validated by postoperative CT scans. Planned inclination was 39.9°±0.8° and with robotic instrumentation was 38. 0°±1.6° with no outliers of 5°; on the postoperative CT scan there were 5 outliers (12%). Planned anteversion was 21.2°±2.4° and intraoperatively was 20.7°±2.4° with no outlier of 5°; on the CT there were 7 outliers (16%). The center of rotation (COR) was superior by a mean 0.9±4.2mm and medial by 2.7±2.9mm. This robotic instrumentation achieved precision of inclination in 88%, anteversion in 84% and COR in 81.5%. PMID:25453633

Kanawade, Vaibhav; Dorr, Lawrence D; Banks, Scott A; Zhang, Zenan; Wan, Zhinian

2015-03-01

108

Control-structure interaction in precision pointing servo loops  

NASA Technical Reports Server (NTRS)

The control-structure interaction problem is addressed via stability analysis of a generic linear servo loop model. With the plant described by the rigid body mode and a single elastic mode, structural flexibility is categorized into one of three types: (1) appendage, (2) in-the-loop minimum phase, and (3) in-the-loop nonminimum phase. Closing the loop with proportional-derivative (PD) control action and introducing sensor roll-off dynamics in the feedback path, stability conditions are obtained. Trade studies are conducted with modal frequency, modal participation, modal damping, loop bandwidth, and sensor bandwidth treated as free parameters. Results indicate that appendage modes are most likely to produce instability if they are near the sensor rolloff, whereas in-the-loop modes are most dangerous near the loop bandwidth. The main goal of this paper is to provide a fundamental understanding of the control-structure interaction problem so that it may benefit the design of complex spacecraft and pointing system servo loops. In this framework, the JPL Pathfinder gimbal pointer is considered as an example.

Spanos, John T.

1989-01-01

109

High-precision pointing and attitude estimation and control algorithms for hardware-constrained spacecraft  

E-print Network

The overarching objective of this thesis is to develop algorithms for high-precision pointing and attitude estimation and control on hardware-constrained spacecraft. This includes small spacecraft, where tight mass, volume, ...

Pong, Christopher Masaru

2014-01-01

110

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

111

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

112

Charge sensing of precisely positioned p donors in Si.  

PubMed

Real-time sensing of (spin-dependent) single-electron tunneling is fundamental to electrical readout of qubit states in spin quantum computing. Here, we demonstrate the feasibility of detecting such single-electron tunneling events using an atomically planar charge sensing layout, which can be readily integrated in scalable quantum computing architectures with phosphorus-donor-based spin qubits in silicon (Si:P). Using scanning tunneling microscopy (STM) lithography on a Si(001) surface, we patterned a single-electron transistor (SET), both tunnel and electrostatically coupled to a coplanar ultrasmall quantum dot, the latter consisting of approximately four P donors. Charge transitions of the quantum dot could be detected both in time-averaged and single-shot current response of the SET. Single electron tunneling between the quantum dot and the SET island on a time-scale (? ? ms) two-orders-of-magnitude faster than the spin-lattice relaxation time of a P donor in Si makes this device geometry suitable for projective readout of Si:P spin qubits. Crucial to scalability is the ability to reproducibly achieve sufficient electron tunnel rates and charge sensitivity of the SET. The inherent atomic-scale control of STM lithography bodes extremely well to precisely optimize both of these parameters. PMID:21919458

Mahapatra, Suddhasatta; Büch, Holger; Simmons, Michelle Y

2011-10-12

113

Research on key techniques of nanometer scale macro-micro dual-drive precision positioning  

NASA Astrophysics Data System (ADS)

With the development of science and technology, high precision of positioning platform is needed in many areas, for example, cell fusing in biology and precision surgery in medical area. In such areas, both high efficiency and high precision are needed in some cases, for example, semiconductor processing equipment, super precision lathe etc. In a word, precision positioning platform becomes an important tool in exploring microscope world. Precision positioning platform is a key element in microscope operation. Macro/micro dual-drive precision positioning is a key technique in high-efficiency high-precision area. By such techniques, large distance and high precision can get. In order to realize nanometer scale macro/micro dual-drive precision positioning there are some key problems. First, system structure of macro/micro combination precision positioning platform is worthy to work on. Another key work is realization method of micrometer scale macroscope motion and nanometer scale microscope motion. The third is mechanics, drive, detection and control techniques in nanometer scale positioning of piezoelectric ceramics drive, in which realization of nanometer scale microscope positioning and micro drive is important by solving hysteresis, creep deformation and non-linearity in piezoelectric ceramics driving. To solve hysteresis problem, instead of traditional Preisach algorithm, a new type hysteresis model with simple computation and identification is needed. The inverse model is also easily to get. So we can present new control method to solve hysteresis and creep deformation problem based on this inverse model. Another way, hysteresis and creep deformation problem exist in traditional voltage-feedback power source for piezoelectric ceramics. To solve this problem, a new type current feedback power source for piezoelectric ceramics is presented. In the end, a macro-micro dual-drive super precision positioning mechanism is presented. Combining macro with micro actuator, a system with large workspace and high resolution of motion is presented. The linear direct-drive motor is used in the macroscope motion and high frequency PZT-driven microscope stage is embedded in the motor and compensates the position error. A high-resolution linear encoder is integrated into the closed-loop feedback, which is used to measure the position of the end-effect in microscope scale.

Xie, Xiaohui; Du, Ruxu

2007-12-01

114

High Precision And Miniaturized Mark Position Sensing Methods For 3-D Shape Measurement  

NASA Astrophysics Data System (ADS)

A high precision mark position sensing method for image position sensing detector (PSD) with kaleido scopic mirror tunnel (KM-PSM) is introduced. To increase the image position detecting precision of a sensor element itself, hybrid ( analogue and digital ) type position sensitive device (R-HPSD) is invented. In order to realize high precision and miniaturized 3-D position measuring system, 1-D mark direction sensing method (PM-DSM) which consist of a 1-D image position sensing element, a cylindrical lens and a parallel mirror tunnel is proposed. Furtheremore, an optical range sensing method (RORS) which is suitable to realize a miniaturized optical range sensing probe based on the triangulation, is proposed. In addition, an optical range sensing probe for advanced 3-D coordinates measuring machine is considered.

Idesawa, Masanori

1989-01-01

115

High-Precision Positioning and Real-Time Data Processing of Uav-Systems  

NASA Astrophysics Data System (ADS)

Available micro-sized Unmanned Aerial Vehicles (UAVs) in the civilian domain currently make use of common GPS receivers and do not address scenarios where high-precision positioning of the UAV is an inevitable requirement. However, for use cases such as creating orthophotos using direct georeferencing, an improved positioning needs to be developed. This article analyses the requirements for integrating Real Time Kinematic positioning into micro-sized UAVs. Additionally, it describes the data processing and synchronisation of the high-precision position data for a workflow of orthorectification of aerial imagery. Preliminary results are described for the use case of precision farming. The described approach for positioning has the potential to achieve a positional accuracy of 1-3 cm, which can be considered as adequate for direct georeferencing of aerial imagery.

Rieke, M.; Foerster, T.; Geipel, J.; Prinz, T.

2011-09-01

116

GPS-based orbit determination and point positioning under selective availability  

NASA Technical Reports Server (NTRS)

Selective availability (SA) degrades the positioning accuracy for nondifferential users of the GPS Standard Positioning Service (SPS). The often quoted SPS accuracy available under normal conditions is 100 m 2DRMS. In the absence of more specific information, many prospective SPS users adopt the 100 m value in their planning, which exaggerates the error in many cases. SA error is examined for point positioning and dynamic orbit determination for an orbiting user. To minimize SA error, nondifferential users have several options: expand their field of view; observe as many GPS satellites as possible; smooth the error over time; and employ precise GPS ephemerides computed independently, as by NASA and the NGS, rather than the broadcast ephemeris. Simulations show that 3D point position error can be kept to 30 m, and this can be smoothed to 3 m in a few hours.

Bar-Sever, Yoaz E.; Yunck, Thomas P.; Wu, Sien-Chong

1990-01-01

117

Study of precise positioning at L-band using communications satellites  

NASA Technical Reports Server (NTRS)

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

1971-01-01

118

Robust indoor positioning using differential wi-fi access points  

Microsoft Academic Search

Location positioning systems using wireless area local network (WLAN) infrastructure are considered cost effective and practical solutions for indoor location tracking and estimation. However, accuracy deterioration due to environmental factors and the need for manual offline calibration limit the application of these systems. In this paper, a new method based on differential operation access points is proposed to eliminate the

Ning Chang; Rashid Rashidzadeh; Majid Ahmadi

2010-01-01

119

Concrete embedded RFID for way-point positioning  

Microsoft Academic Search

RFID markers are proving to be a cheap and reliable enabler for indoor positioning applications. Motivated by this we have developed a concrete embeddable passive RFID tag for robust and long-lasting way-point identification. Embedding commercially available passive tags in concrete significantly reduces their read range and hence, usefulness as markers. By appropriate redesign of the antenna and packaging we have

Donnacha Daly; Thomas Melia; Gerard Baldwin

2010-01-01

120

Compressive Sensing Based Positioning Using RSS of WLAN Access Points  

E-print Network

1 Compressive Sensing Based Positioning Using RSS of WLAN Access Points Chen Feng1,2, Wain Sy (RSS)-based localization problem in WLANs us- ing the theory of compressive sensing (CS), which offers theory. In order to mitigate the effects of RSS variations due to channel impediments, the proposed

Valaee, Shahrokh

121

Employing Tropospheric Numerical Weather Prediction Model for High-Precision GNSS Positioning  

NASA Astrophysics Data System (ADS)

In the past few years is increasing the necessity of realizing high accuracy positioning. In this sense, the spatial technologies have being widely used. The GNSS (Global Navigation Satellite System) has revolutionized the geodetic positioning activities. Among the existent methods one can emphasize the Precise Point Positioning (PPP) and network-based positioning. But, to get high accuracy employing these methods, mainly in real time, is indispensable to realize the atmospheric modeling (ionosphere and troposphere) accordingly. Related to troposphere, there are the empirical models (for example Saastamoinen and Hopfield). But when highly accuracy results (error of few centimeters) are desired, maybe these models are not appropriated to the Brazilian reality. In order to minimize this limitation arises the NWP (Numerical Weather Prediction) models. In Brazil the CPTEC/INPE (Center for Weather Prediction and Climate Studies / Brazilian Institute for Spatial Researches) provides a regional NWP model, currently used to produce Zenithal Tropospheric Delay (ZTD) predictions (http://satelite.cptec.inpe.br/zenital/). The actual version, called eta15km model, has a spatial resolution of 15 km and temporal resolution of 3 hours. In this paper the main goal is to accomplish experiments and analysis concerning the use of troposphere NWP model (eta15km model) in PPP and network-based positioning. Concerning PPP it was used data from dozens of stations over the Brazilian territory, including Amazon forest. The results obtained with NWP model were compared with Hopfield one. NWP model presented the best results in all experiments. Related to network-based positioning it was used data from GNSS/SP Network in São Paulo State, Brazil. This network presents the best configuration in the country to realize this kind of positioning. Actually the network is composed by twenty stations (http://www.fct.unesp.br/#!/pesquisa/grupos-de-estudo-e-pesquisa/gege//gnss-sp-network2789/). The results obtained employing NWP model also were compared to Hopfield one, and the results were very interesting. The theoretical concepts, experiments, results and analysis will be presented in this paper.

Alves, Daniele; Gouveia, Tayna; Abreu, Pedro; Magário, Jackes

2014-05-01

122

High-precision image position sensing methods suitable for 3-D measurement  

NASA Astrophysics Data System (ADS)

A high-precision image position sensing method for a position sensitive detector (PSD) with a kaleidoscopic mirror tunnel (KM-PSM) is introduced. In order to increase the relative resolution of the image position detecting element itself, a hybrid type position sensitive device (R-HPSD) has been invented. A 1-D mark direction sensing method (PM-DSM) which consists of a 1-D image position sensing element, a cylindrical lens and a parallel mirror tunnel is proposed for the realization of a high-precision and miniaturized 3-D position measuring system. Furthermore, an optical range sensing method (RORS), which is suitable for realizing a miniaturized optical range sensing probe based on the triangulation, is proposed.

Idesawa, Masanori

123

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

124

Sound and Precise Malware Analysis for Android via Pushdown Reachability and Entry-Point Saturation  

E-print Network

Sound and Precise Malware Analysis for Android via Pushdown Reachability and Entry-Point Saturation dvanhorn@ccs.neu.edu ABSTRACT Sound malware analysis of Android applications is challeng- ing. First Anadroid, a static malware analysis frame- work for Android apps. Anadroid exploits two techniques

Might, Matt

125

FPC: A High-Speed Compressor for Double-Precision Floating-Point Data  

E-print Network

FPC: A High-Speed Compressor for Double-Precision Floating-Point Data Martin Burtscher Paruj the throughput demands of high-performance systems. A comparison with five lossless compression schemes, BZIP2-mean compression ratio. Moreover, FPC provides a guaranteed throughput as long as the prediction tables fit

Burtscher, Martin

126

Theoretical Research on Adjacent Multistation Point Cloud Data Precision Combination in 3D Laser Scanning  

Microsoft Academic Search

Adjacent multi-station rotational scanning the target band with the 3D laser scanner ( Leica ScanStation II ) .acquires the 3D point cloud models of every rotational position. Adjacent multi-station point seriate cloud models have been registered, acquires the correspondent points. Then combines point cloud models with the theory of single strip aerial triangulation, acquires coordinates of cloud models in the

Tianzi Li; Youfeng Zou

2010-01-01

127

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

128

A novel orientation and position measuring system for large & medium scale precision assembly  

NASA Astrophysics Data System (ADS)

In the field of precision assembly of large & medium scale, the orientation and position measurement system is quite demanding. In this paper a novel measuring system, consisting of four motorized stages, a laser rangefinder, an autocollimator and a camera is proposed to assist precision assembly. Through the design of coaxial optical system, the autocollimator is integrated with a laser rangefinder into a collimation rangefinder, which is used for measuring orientation and position synchronously. The laser spot is adopted to guide autocollimation over a large space and assist the camera in finding collimated measurand. The mathematical models and practical calibration methods for measurement are elaborated. The preliminary experimental results agree with the methods currently being used for orientation and position measurement. The measuring method provides an alternative choice for the metrology in precision assembly.

Li, Yuhe; Qiu, Yongrong; Chen, Yanxiang; Guan, Kaisen

2014-11-01

129

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

NASA Astrophysics Data System (ADS)

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

Wittig, Alexander N.

130

Design Considerations for Miniaturized Control Moment Gyroscopes for Rapid Retargeting and Precision Pointing of Small Satellites  

NASA Technical Reports Server (NTRS)

This paper presents the design as well as characterization of a practical control moment gyroscope (CMG) based attitude control system (ACS) for small satellites in the 15-20 kilogram mass range performing rapid retargeting and precision pointing maneuvers. The paper focuses on the approach taken in the design of miniaturized CMGs while considering the constraints imposed by the use of commercial off-the-shelf (COTS) components as well as the size of the satellite. It is shown that a hybrid mode is more suitable for COTS based moment exchange actuators; a mode that uses the torque amplification of CMGs for rapid retargeting and direct torque capabilities of the flywheel motors for precision pointing. A simulation is provided to demonstrate on-orbit slew and pointing performance.

Patankar, Kunal; Fitz-Coy, Norman; Roithmayr, Carlos M.

2014-01-01

131

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

132

Precision beam pointing control with jitter attenuation by optical deflector exhibiting dynamic hysteresis in COIL  

NASA Astrophysics Data System (ADS)

Due to the existence of various disturbances during the lasing process of the chemical oxygen iodine laser (COIL), the optical beam pointing performance is severely degraded. In this paper, an adaptive control methodology is proposed for the precise pointing control of the optical beam with active beam jitter rejection using a giant magnetostrictive optical deflector (GMOD) which exhibits severe dynamic hysteresis nonlinearity. In particular, a least square support vector machine (LS-SVM) based fast compensator is employed to eliminate the dynamic hysteresis without the inverse model construction. Then an improved feedforward adaptive filter is developed to deal with jitter attenuation when the full-coherent reference signal is unavailable. To improve the stability and overall robustness of the controller, especially when a large initial bias exists, a PI controller is placed in parallel with the adaptive filter. Experimental results validate the precise pointing ability of the proposed control method.

Ma, Yan-Hua; Zhang, Zeng-Bao; Zhang, Zhi-Guo; Liu, Qin; He, Xin; Shi, Wen-Bo; Mao, Jian-Qin; Jin, Yu-Qi

2015-02-01

133

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

PubMed Central

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

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

2009-01-01

134

Precision and accuracy of doubly labeled water energy expenditure by multipoint and two-point methods.  

PubMed

Two-point or multipoint, that is the question. Equations are developed to compare the precision and accuracy of energy expenditure, as estimated from doubly labeled water data, when analyzed by the multipoint and two-point methods. The equations convert the enrichments of deuterium and oxygen-18 into their ratio and product, quantities that are less covariant than the two isotopes themselves are. This is important not only for estimating the precision but also as a graphical aid, since the ratios of the enrichments model carbon dioxide production, whereas the enrichment products largely model water turnover. Using data on 12 human subjects from the United Kingdom and The Gambia as examples, the combined precision and accuracy of the multipoint method (CV 3.6%) was found to be appreciably better than the two-point method (CV 5.4%). The bias in the multipoint estimate of body pool size would need to be three times as large as was observed before it canceled out the better precision. PMID:1443129

Cole, T J; Coward, W A

1992-11-01

135

Tobacco point of sale advertising increases positive brand user imagery  

PubMed Central

Objectives: To determine the potential impact of point of sale advertising on adolescents so as to inform changes to the Tobacco Control Act. Design: Participants were randomly assigned to one of two conditions. In the control condition, students were exposed to a photograph of a packet of cigarettes; in the intervention condition, students were exposed to an ad for cigarettes, typical of point of sale advertising posters. All students then rated the brand user on a set of 12 bipolar adjectives. Two brands were used in the study: Benson & Hedges, and Marlboro. Subjects: One hundred year (grade) 6 and 7 students (age range 10–12 years), from four Western Australian metropolitan primary schools, participated in the study. Results: In a majority of the brand user descriptions, the cigarette advertisements increased brand user imagery in a positive way, especially for Benson & Hedges. For example, participants viewing the Benson & Hedges advertisement, as distinct from those viewing the Benson & Hedges pack only, were more likely to describe the Benson & Hedges user as relaxed, interesting, cool, rich, adventurous, and classy. Relative to the Marlboro pack only, the Marlboro ad increased positive perceptions of the Marlboro user on adventurous, interesting, and relaxed. Conclusions: The results presented here support restrictions being placed on advertising at point of sale, since such ads have the potential to increase positive brand user imagery directly in the situation where a product purchase can take place, and hence the potential to increase the likelihood of impulse purchasing. PMID:12198267

Donovan, R; Jancey, J; Jones, S

2002-01-01

136

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

137

Nonlinear control design for a high-precision contactless positioning system using magnetic levitation  

Microsoft Academic Search

This paper presents the implementation of a two degree-of-freedom, high-precision, magnetic-levitation-based positioning system. The apparatus employs one permanent magnet linear synchronous motor and is constructed by Quanser Inc. The paper focuses on the design and testing of a nonlinear controller required for actuating the positioning system. The controller is based on feedback linearization and output regulation. Experimental results show that

Robert Brydon Owen; Manfredi Maggiore; Jacob Apkarian

2005-01-01

138

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

Microsoft Academic Search

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

Kazuaki Itoh; Makoto Iwasaki; Nobuyuki Matsui

2004-01-01

139

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

Microsoft Academic Search

In this paper we propose a hand-held 3D laser scanner composed of an optical head device to extract 3D local surface information and a stereo vision system with subvoxel precision to measure the position and orientation of the 3D optical head. The optical head is manually scanned over the surface object by the operator. The orientation and position of the

Néstor Arias; Néstor Meneses; Jaime Meneses; Tijani Gharbi

2011-01-01

140

Design and kinematics analysis of a 3DOF precision positioning stage  

Microsoft Academic Search

This paper presents a novel 3-DOF precision positioning stage for nanoimprint lithograph (NIL). Due to the advantages such as high positioning accuracy, dexterity, low inertial, and balanced mechanical structure, a piezo-driven flexure-based parallel mechanism is utilized. Based on Pseudo-Rigid-Body modelling theory, the kinematics of the stage is developed by simplifying the single-axis flexure hinges as ideal revolute joints. A modified

Xiaohui Jia; Yanling Tian; Dawei Zhang

2009-01-01

141

A PRECISE POSITION AND ATTITUDE DETERMINATION SYSTEM FOR LIGHTWEIGHT UNMANNED AERIAL VEHICLES  

E-print Network

A PRECISE POSITION AND ATTITUDE DETERMINATION SYSTEM FOR LIGHTWEIGHT UNMANNED AERIAL VEHICLES.wieland)@igg.uni-bonn.de, heiner.kuhlmann@uni-bonn.de KEY WORDS: Unmanned Aerial Vehicle, Direct Georeferencing, RTK-GPS, IMU, Extended Kalman Filtering, Real Time Operating System ABSTRACT: In many unmanned aerial vehicle (UAV

Behnke, Sven

142

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

143

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

Microsoft Academic Search

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

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

1997-01-01

144

Hybrid Cursor Control for Precise and Fast Positioning without Clutching Markus Schlattmann  

E-print Network

that this way some kind of de-clutching mechanism is realized. Originally, PRISM was designed to aid in directHybrid Cursor Control for Precise and Fast Positioning without Clutching Markus Schlattmann technique not incorporating any clutching mechanism. It is a hybrid between proportional and relative cursor

Behnke, Sven

145

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

146

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

147

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

148

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

SciTech Connect

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

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

2010-09-01

149

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. A significant innovation described in this paper is the "Generalized" Dilution of Precision. In the same sense that the various versions of DoP can be represented as a functional of the observability grammian, Generalized DoP is defined as a functional of the sum of observability grammians associated with a batch of radiometric measurements. Generalized DoP extends the DoP concept to cases in which radiometric range and range-rate measurements are integrated over time to develop an estimate of user position (referred to here as a 'dynamic' solution.) Generalized DoP allows for the inclusion of cases in which the receiver location is underdetermined when assessed in the usual 'kinematic' sense. The Generalized DoP concept is thereby a method to assess the navigation capability associated with constellations with sparse coverage. This alleviates the burden of performing a full "covariance analysis" for each point on the surface of the Moon.

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

2006-01-01

150

GA-Based Autonomous Design of Robust Fast and Precise Positioning Considering Machine Stand Vibration Suppression  

NASA Astrophysics Data System (ADS)

This paper presents a novel Genetic Algorithm (GA)-based autonomous compensator design and position command shaping considering the stand vibration suppression for the fast-response and high-precision positioning of mechatronic systems. The positioning system is mainly composed of a robust 2-degrees-of-freedom (2DOF) controller based on the coprime factorization description. The feedback compensator based on H? design framework in the 2DOF controller ensures the robustness against the variations of resonant vibration mode. The feedforward compensator and position command, on the other hand, can be autonomously designed by the optimization capability of GA, in order to achieve the desired positioning performance and to suppress the machine stand vibration. The effectiveness of the proposed optimal design has been verified by experiments using a table drive system with ball screw.

Ito, Kazuaki; Nagata, Ryo; Iwasaki, Makoto; Matsui, Nobuyuki

151

Preliminary assessment of the basic navigation and precise positioning performance of BDS  

NASA Astrophysics Data System (ADS)

Following the general guideline of starting with regional services and then expanding to global services, the BeiDou Navigation Satellite System(BDS) is steadily accelerating the construction. By the end of 2012, the BDS already consists of fourteen networking satellites, including five GEO satellites, five IGSO satellites, and four MEO satellites, and owns full operational capability for China and its surrounding areas. Both basic navigation and precise positioning performance of current BDS (with 5GEO+5IGSO+4MEO satellites) during January to December of 2013 are evaluated in this presentation. In China and its surrounding area, the positioning accuracy using BDS opening service is about 10 meters in both horizontal and vertical direction. Users can get high precise service using BDS only, and both BDS and GPS users can be benefitted from combination of the two systems.

Zhao, Qile; Hu, Zhigang; Li, Min; Guo, Jing; Shi, Chuang; Liu, Jingnan

2014-05-01

152

Advanced THz sensor array for precise position and material properties recognition  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

153

[2-component technic for the production of positioning supports for highly precise radiotherapy].  

PubMed

In many small institutes exact positioning supports could not yet be manufactured for cost and personal reasons. This problem is solved in a simple manner by the use of the described modern synthetics which allow the application of high-precision techniques such as small-field pendulum therapy and isocentric multifield therapy. This system serves the safety of patients and therapists and is meant to prevent recurrences and late damages especially in children. PMID:2799629

Hawliczek, R; Theil, E; Schmidt, W

1989-09-01

154

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

155

Highly accelerated simulations of glassy dynamics using GPUs: Caveats on limited floating-point precision  

NASA Astrophysics Data System (ADS)

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

Colberg, Peter H.; Höfling, Felix

2011-05-01

156

Development of stewart platforms for active vibration isolation and precision pointing  

NASA Astrophysics Data System (ADS)

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

Liu, Lei; Wang, Benli

2007-07-01

157

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

NASA Astrophysics Data System (ADS)

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

Kwak, Nam-Su; Kim, Jae-Yeol

158

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

159

Prediction of CNC Heavy-duty Horizontal Lathe position precision and its application based on evaluation of uncertainty  

Microsoft Academic Search

According to type B evaluation of uncertainty, A method is presented to predict position precision of CNC Heavy-duty Horizontal Lathe. A case studying on X axle feeding system, mathematical model of position precision which is based on standard uncertainty is established. Calculation results are compared with experiment truth-value, model's feasibility is proved. It provides a theoretical basis for further enhance

Sheng Wang

2010-01-01

160

Asynchronous RTK precise DGNSS positioning method for deriving a low-latency high-rate output  

NASA Astrophysics Data System (ADS)

Low-latency high-rate (> 1 Hz) precise real-time kinematic (RTK) can be applied in high-speed scenarios such as aircraft automatic landing, precise agriculture and intelligent vehicle. The classic synchronous RTK (SRTK) precise differential GNSS (DGNSS) positioning technology, however, is not able to obtain a low-latency high-rate output for the rover receiver because of long data link transmission time delays (DLTTD) from the reference receiver. To overcome the long DLTTD, this paper proposes an asynchronous real-time kinematic (ARTK) method using asynchronous observations from two receivers. The asynchronous observation model (AOM) is developed based on undifferenced carrier phase observation equations of the two receivers at different epochs with short baseline. The ephemeris error and atmosphere delay are the possible main error sources on positioning accuracy in this model, and they are analyzed theoretically. In a short DLTTD and during a period of quiet ionosphere activity, the main error sources decreasing positioning accuracy are satellite orbital errors: the "inverted ephemeris error" and the integration of satellite velocity error which increase linearly along with DLTTD. The cycle slip of asynchronous double-differencing carrier phase is detected by TurboEdit method and repaired by the additional ambiguity parameter method. The AOM can deal with synchronous observation model (SOM) and achieve precise positioning solution with synchronous observations as well, since the SOM is only a specific case of AOM. The proposed method not only can reduce the cost of data collection and transmission, but can also support the mobile phone network data link transfer mode for the data of the reference receiver. This method can avoid data synchronizing process besides ambiguity initialization step, which is very convenient for real-time navigation of vehicles. The static and kinematic experiment results show that this method achieves 20 Hz or even higher rate output in real time. The ARTK positioning accuracy is better and more robust than the combination of phase difference over time (PDOT) and SRTK method at a high rate. The ARTK positioning accuracy is equivalent to SRTK solution when the DLTTD is 0.5 s, and centimeter level accuracy can be achieved even when DLTTD is 15 s.

Liang, Zhang; Hanfeng, Lv; Dingjie, Wang; Yanqing, Hou; Jie, Wu

2015-03-01

161

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

162

Single-point position and transition defects in continuous time quantum walks  

E-print Network

We present a detailed analysis of continuous time quantum walks (CTQW) with both position and transition defects defined at a single point in the line. Analytical solutions of both traveling waves or bound states are obtained, which provide valuable insight into the dynamics of CTQW. The number of bound states is found to be critically dependent on the defect parameters, and the localized probability peaks can be readily obtained by projecting the CTQW wavefunction on to these bound states. The interference between two bound states are also observed in the case of a transition defect. The spreading of CTQW probability over the line can be finely tuned by varying the position and transition defect parameters, offering the possibility of precision quantum control of the system.

Zhi-Jian Li; J. B. Wang

2015-02-15

163

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

164

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

PubMed

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

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

2015-02-01

165

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

166

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

NASA Astrophysics Data System (ADS)

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

Heyne, Martin Cornelius

167

High precision analysis of variations in self image quality and position with Multimode Interference (MMI) device width  

NASA Astrophysics Data System (ADS)

Multimode Interference (MMI) device is a useful optical component for optical power splitter/combiner and router applications. In this paper we present high precision calculation results on the optimum position of self-images in an MMI and their variation due to wavelengths, for WDM applications. We show that the commonly used MMI self-image position calculation methods, using the beat length of two lowest order modes or effective MMI width approximation, lead to significant deviations from the optimum self-image position. We calculate the optimum position of the self-image by finding the maximum value of overlap integral of total MMI field, comprised of all MMI modes, with the total field at the input of the MMI device. In addition, for the optimum output power coupling distance for MMI, we calculate the overlap integral of the total MMI field with the output waveguide field. Both these methods give approximately the same optimum length. We obtain up to 60 um difference in optimum self-image position for a Si MMI (width =15 ~ 30 um), and refractive index difference of 0.02 between core and cladding, from the approximations based methods. We also calculate the variation of this image position in 1.50 um to 1.60 um wavelength region. We show that the optimum image position is strongly dependent on wavelength, with up to 100 um variations in this wavelength range. In addition, we show that there is a significant variation in this self image position with MMI widths, at points where a new power carrying mode is added.

Azfar, Talal; Amin, Sundas; Malik, Beena

2012-10-01

168

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

169

Position-sensitive ion detection in precision Penning trap mass spectrometry  

E-print Network

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

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

2009-06-01

170

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

PubMed Central

Integrating the precise GPS carrier phases and INS sensor technologies is a methodology that has been applied indispensably in those application fields requiring accurate and reliable position, velocity, and attitude information. However, conventional integration approaches with a single GPS reference station may not fulfil the demanding performance requirements, especially in the position component, when the baseline length between the reference station and mobile user’s GPS receiver is greater than a few tens of kilometres. This is because their positioning performance is primarily dependent on the common mode of errors of GPS measurements. To address this constraint, a novel GPS/INS integration scheme using multiple GPS reference stations is proposed here that can improve its positioning accuracy by modelling the baseline-dependent errors. In this paper, the technical issues concerned with implementing the proposed scheme are described, including the GPS network correction modelling and integrated GPS/INS filtering. In addition, the results from the processing of the simulated measurements are presented to characterise the system performance. As a result, it has been established that the integration of GPS/INS with multiple reference stations would make it possible to ensure centimetre-level positioning accuracy, even if the baseline length reaches about 100 km. PMID:22163417

Lee, Hungkyu

2010-01-01

171

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

172

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

173

Clinical precision of myofascial trigger point location in the trapezius muscle.  

PubMed

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 within a muscle. This paper details a study wherein four trained clinicians achieved statistically significant reliability (see below) in estimating the precise locations of latent TrPs in the trapezius muscle of volunteer subjects (n=20). To do so, the clinicians trained extensively together prior to the study. The precise anatomic location of each subject's primary TrP was measured in a blinded fashion using a 3 dimensional (3-D) camera system. Use of this measurement system permitted the anatomic co-ordinates of each TrP to be located without providing feedback to subsequent clinicians. The clinicians each used a pressure algometer along with patient feedback to document the sensitivity of each suspected TrP site, however unlike routine clinical practice, the algometry was performed with a double-blinded approach hence the results were only examined post-hoc. At the time of data collection (algometry readings unknown), 16 of the 20 subjects were judged to present with a latent TrP. Subsequently, when subjected to a criterion pressure threshold value of <3.0 kg.cm(-2), 12 of these TrPs were classified as being clinically sensitive. To assess the 3-D measurement precision, and the reliability of the TrP estimates, statistical measures of the SEM and the Generalizability coefficient (G-coeff) were determined for all suspected TrP sites in the superior-inferior, medial-lateral and anterior-posterior directions. The best results were determined by pooling the measurements of all 4 clinicians, however, based upon exceeding a criterion reliability threshold of 80%, the use of just two testers was found to produce reliable results. The two-tester condition yielded a precision of 7.5, 7.6 and 6.5 mm (SEM) with reliability (G-coeff) of 0.92, 0.86 and 0.83, respectively. Given the double-blinded methodology, the use of pressure algometry was also found to demonstrate internal validity. The algometer responses associated with TrP estimates varied inversely with respect to the clinical group's reliability in identify the TrP locations. To summarize, for the trapezius muscle, this study demonstrates that two trained examiners can reliably localize latent TrPs with a precision that essentially approaches the physical dimensions of the clinician's own fingertips. Finally, it should be recognized that the ability to precisely document TrP location appears critical to the success of future studies that may be designed to investigate the etiology and pathogenesis of this commonly diagnosed clinical disorder. PMID:11514085

Sciotti, V M; Mittak, V L; DiMarco, L; Ford, L M; Plezbert, J; Santipadri, E; Wigglesworth, J; Ball, K

2001-09-01

174

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

175

The Position Tracking Control of Precise Servo Systems with Nonlinear Dynamic Friction Using Variable Structure Control and Friction Observer  

NASA Astrophysics Data System (ADS)

A position tracking control schemes on the precise servo system in the presence of nonlinear dynamic friction is proposed. A nonlinear dynamic friction is regarded as the bristle friction model to compensate effects of friction. The conventional VSC method that often has used as a non-model-based friction controller has a poor tracking performance in high-precision position tracking application since it completely cannot compensate the friction effect below a certain precision level. Thus to improve the precise position tracking performance, we propose the VSC method combined with the friction-model-based observer having tunable structure of the transient response. Then this control scheme has a good transient response as well as the high precise tracking performance compared with the conventional VSC system without observer and the control system with similar type of observer. The experiments on the ball-screw drive table with the nonlinear dynamic friction show the feasibility of the proposed control scheme.

Han, Seong-Ik

176

Influence of the TEC fluctuations in the polar region on precise GPS positioning.  

NASA Astrophysics Data System (ADS)

The ionospheric delay is an atmoshperic effect influencing on Global Navigation Satellite System signals. On the one hand it is a factor limiting the accuracy of the GNSS positioning, and on the other it makes satellite observations a very good source of the information on the ionospheric conditions. The degradation of the relative positioning accuracy and reliability can be connected with high gradients of the total electron content or with the TEC fluctuations. The latter of these effects mainly occurs in the equatorial and polar regions. The ionosphere near the geomagnetic poles is characterized by relatively small TEC values in comparison to the other regions. However, the connection between the magnetosphere and ionosphere systems in the polar regions allows particle precipitation and leads to very strong ionospheric dynamics. In this work, performance of the GNSS precise relative positioning under disturbed ionospheric conditions in the northern polar region is studied. The test results are based on processing 24-hour data sets from the selected permanent GPS stations located in Greenland. The studies cover several days of high and low solar activity, and also periods of a geomagnetic storm characterized by intensive TEC fluctuations. The data processing was carried out in static and kinematic modes. The GINPOS software developed at the University of Warmia and Mazury in Olsztyn was used for positioning tests. The study confirms and presents the influence of the ionospheric and geomagnetic activity in the polar region on the results in coordinate and ambiguity domains.

Sieradzki, Rafal; Paziewski, Jacek; Wielgosz, Pawel

2014-05-01

177

On the relation between reliable computation time, float-point precision and the Lyapunov exponent in chaotic systems  

E-print Network

The relation among reliable computation time, Tc, float-point precision, K, and the Lyapunov exponent, {\\lambda}, is obtained as Tc= (lnB/{\\lambda})K+C, where B is the base of the float-point system and C is a constant dependent only on the chaotic equation. The equation shows good agreement with numerical experimental results, especially the scale factors.

PengFei Wang; JianPing Li

2014-10-18

178

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

179

Precision measurement of the positive muon lifetime by the MuLan collaboration  

NASA Astrophysics Data System (ADS)

We report the result of a measurement of the positive muon lifetime ?? to one part-per-million (ppm) by the MuLan collaboration using a low-energy pulsed muon beam and a segmented array of plastic scintillators to record over 2×1012 decay positrons. Two different in-vacuum muon-stopping targets were used in separate data-taking periods. The combined result gives ? (MuLan)=2196980.3(2.2) ps (1 ppm). This measurement of the muon lifetime provides the most precise determination of the Fermi constant, GF (MuLan)=1.1663788(7)×10-5 GeV(0.6 ppm), and will be used to extract the capture rates of the negative muon on the proton and the deuteron in the ongoing MuCap and MuSun experiments.

Tishchenko, V.; MuLan Collaboration

2012-04-01

180

Precise tracking of remote sensing satellites with the Global Positioning System  

NASA Technical Reports Server (NTRS)

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 selected ground locations simultaneously. The GPS orbit solutions are always dynamic, relying on the laws of motion, while the user orbit solution can range from purely dynamic to purely kinematic (geometric). Two variations show considerable promise. The first one features an optimal synthesis of dynamics and kinematics in the user solution, while the second introduces a novel gravity model adjustment technique to exploit data from repeat ground tracks. These techniques, to be demonstrated on the Topex/Poseidon mission in 1992, will offer subdecimeter tracking accuracy for dynamically unpredictable satellites down to the lowest orbital altitudes.

Yunck, Thomas P.; Wu, Sien-Chong; Wu, Jiun-Tsong; Thornton, Catherine L.

1990-01-01

181

A Lane-Level LBS System for Vehicle Network with High-Precision BDS/GPS Positioning  

PubMed Central

In recent years, research on vehicle network location service has begun to focus on its intelligence and precision. The accuracy of space-time information has become a core factor for vehicle network systems in a mobile environment. However, difficulties persist in vehicle satellite positioning since deficiencies in the provision of high-quality space-time references greatly limit the development and application of vehicle networks. In this paper, we propose a high-precision-based vehicle network location service to solve this problem. The major components of this study include the following: (1) application of wide-area precise positioning technology to the vehicle network system. An adaptive correction message broadcast protocol is designed to satisfy the requirements for large-scale target precise positioning in the mobile Internet environment; (2) development of a concurrence service system with a flexible virtual expansion architecture to guarantee reliable data interaction between vehicles and the background; (3) verification of the positioning precision and service quality in the urban environment. Based on this high-precision positioning service platform, a lane-level location service is designed to solve a typical traffic safety problem. PMID:25755665

Guo, Chi; Guo, Wenfei; Cao, Guangyi; Dong, Hongbo

2015-01-01

182

A lane-level LBS system for vehicle network with high-precision BDS/GPS positioning.  

PubMed

In recent years, research on vehicle network location service has begun to focus on its intelligence and precision. The accuracy of space-time information has become a core factor for vehicle network systems in a mobile environment. However, difficulties persist in vehicle satellite positioning since deficiencies in the provision of high-quality space-time references greatly limit the development and application of vehicle networks. In this paper, we propose a high-precision-based vehicle network location service to solve this problem. The major components of this study include the following: (1) application of wide-area precise positioning technology to the vehicle network system. An adaptive correction message broadcast protocol is designed to satisfy the requirements for large-scale target precise positioning in the mobile Internet environment; (2) development of a concurrence service system with a flexible virtual expansion architecture to guarantee reliable data interaction between vehicles and the background; (3) verification of the positioning precision and service quality in the urban environment. Based on this high-precision positioning service platform, a lane-level location service is designed to solve a typical traffic safety problem. PMID:25755665

Guo, Chi; Guo, Wenfei; Cao, Guangyi; Dong, Hongbo

2015-01-01

183

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

NASA Technical Reports Server (NTRS)

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

Likins, P. W.

1975-01-01

184

Precision Measurement of the Position-space Wave Functions of Gravitationally Bound Ultracold Neutrons  

E-print Network

Gravity is the most familiar force at our natural length scale. However, it is still exotic from the view point of particle physics. The first experimental study of quantum effects under gravity was performed using a cold neutron beam in 1975. Following this, an investigation of gravitationally bound quantum states using ultracold neutrons was started in 2002. This quantum bound system is now well understood, and one can use it as a tunable tool to probe gravity. In this paper, we review a recent measurement of position-space wave functions of such gravitationally bound states, and discuss issues related to this analysis, such as neutron loss models in a thin neutron guide, the formulation of phase space quantum mechanics, and UCN position sensitive detectors. The quantum modulation of neutron bound states measured in this experiment shows good agreement with the prediction from quantum mechanics.

Kamiya, Y; Komamiya, S

2015-01-01

185

Deterministic delivery of externally cold and precisely positioned single molecular ions  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

186

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

187

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

NASA Astrophysics Data System (ADS)

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

Yan, Su

2007-12-01

188

Semi-robotic 6 degree of freedom positioning for intracranial high precision radiotherapy; first phantom and clinical results  

Microsoft Academic Search

BACKGROUND: To introduce a novel method of patient positioning for high precision intracranial radiotherapy. METHODS: An infrared(IR)-array, reproducibly attached to the patient via a vacuum-mouthpiece(vMP) and connected to the table via a 6 degree-of-freedom(DoF) mechanical arm serves as positioning and fixation system. After IR-based manual prepositioning to rough treatment position and fixation of the mechanical arm, a cone-beam CT(CBCT) is

Jürgen Wilbert; Matthias Guckenberger; Bülent Polat; Otto Sauer; Michael Vogele; Michael Flentje; Reinhart A Sweeney

2010-01-01

189

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

190

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

191

Precise Gravity Measurements for Lunar Laser Ranging at Apache Point Observatory  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

192

Nonlinear control design techniques for precision formation flying at Lagrange points  

Microsoft Academic Search

Precision spacecraft formation flying is an enabling technology for a variety of proposed space-based observatories, such as NASA's Terrestrial Planet Finder (TPF), the Micro-Arcsecond X-Ray Imaging Mission (MAXIM), and Stellar Imager (SI). This research specifically examines the precision formation flying control architecture, characterizing the relative performance of linear and nonlinear controllers. Controller design is based on a 6DOF control architecture,

Richard J. Luquette

2006-01-01

193

Nonlinear Control Design for a High-Precision Contactless Positioning System Using Magnetic Levitation  

E-print Network

as nanotechnology, probing and inspection systems) where significant speed and precision are required at multiple of freedom (DOF) with significant speed and precision [1]. As new technology causes the dimensions and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, ON M5S 3G4, Canada. Jacob

Maggiore, Manfredi

194

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

E-print Network

We report a measurement of the positive muon lifetime to a precision of 1.0~parts per million (ppm); it is the most precise particle lifetime ever measured. The experiment used a time-structured, low-energy muon beam and a segmented plastic scintillator array to record more than 2 x 10^{12} decays. Two different stopping target configurations were employed in independent data-taking periods. The combined results give tau_{mu^+}(MuLan) = 2196980.3(2.2)~ps, more than 15 times as precise as any previous experiment. The muon lifetime gives the most precise value for the Fermi constant: G_F(MuLan) = 1.1663788 (7) x 10^-5 GeV^-2 (0.6~ppm). It is also used to extract the mu^-p singlet capture rate, which determines the proton's weak induced pseudoscalar coupling g_P.

Webber, D M; ~Peng, Q; Battu, S; Carey, R M; Chitwood, D B; Crnkovic, J; Debevec, P T; Dhamija, S; Earle, W; Gafarov, A; Giovanetti, K; Gorringe, T P; Gray, F E; Hartwig, Z; Hertzog, D W; Johnson, B; Kammel, P; Kiburg, B; Kizilgul, S; Kunkle, J; Lauss, B; Logashenko, I; Lynch, K R; McNabb, R; Miller, J P; Mulhauser, F; Onderwater, C J G; Phillips, J; Rath, S; Roberts, B L; Winter, P; Wolfe, B

2010-01-01

195

Measurement of the positive muon lifetime and determination of the Fermi constant to part-per-million precision.  

PubMed

We report a measurement of the positive muon lifetime to a precision of 1.0 ppm; it is the most precise particle lifetime ever measured. The experiment used a time-structured, low-energy muon beam and a segmented plastic scintillator array to record more than 2×10(12) decays. Two different stopping target configurations were employed in independent data-taking periods. The combined results give ?(?(+)) (MuLan)=2?196?980.3(2.2)??ps, more than 15 times as precise as any previous experiment. The muon lifetime gives the most precise value for the Fermi constant: G(F) (MuLan)=1.166?378?8(7)×10(-5)??GeV(-2) (0.6 ppm). It is also used to extract the ?(-)p singlet capture rate, which determines the proton's weak induced pseudoscalar coupling g(P). PMID:21405320

Webber, D M; Tishchenko, V; Peng, Q; Battu, S; Carey, R M; Chitwood, D B; Crnkovic, J; Debevec, P T; Dhamija, S; Earle, W; Gafarov, A; Giovanetti, K; Gorringe, T P; Gray, F E; Hartwig, Z; Hertzog, D W; Johnson, B; Kammel, P; Kiburg, B; Kizilgul, S; Kunkle, J; Lauss, B; Logashenko, I; Lynch, K R; McNabb, R; Miller, J P; Mulhauser, F; Onderwater, C J G; Phillips, J; Rath, S; Roberts, B L; Winter, P; Wolfe, B

2011-01-28

196

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

SciTech Connect

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

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

2011-01-28

197

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

NASA Astrophysics Data System (ADS)

We report a measurement of the positive muon lifetime to a precision of 1.0 ppm; it is the most precise particle lifetime ever measured. The experiment used a time-structured, low-energy muon beam and a segmented plastic scintillator array to record more than 2×1012 decays. Two different stopping target configurations were employed in independent data-taking periods. The combined results give ??+(MuLan)=2196980.3(2.2)ps, more than 15 times as precise as any previous experiment. The muon lifetime gives the most precise value for the Fermi constant: GF(MuLan)=1.1663788(7)×10-5GeV-2 (0.6 ppm). It is also used to extract the ?-p singlet capture rate, which determines the proton’s weak induced pseudoscalar coupling gP.

Webber, D. M.; Tishchenko, V.; Peng, Q.; Battu, S.; Carey, R. M.; Chitwood, D. B.; Crnkovic, J.; Debevec, P. T.; Dhamija, S.; Earle, W.; Gafarov, A.; Giovanetti, K.; Gorringe, T. P.; Gray, F. E.; Hartwig, Z.; Hertzog, D. W.; Johnson, B.; Kammel, P.; Kiburg, B.; Kizilgul, S.; Kunkle, J.; Lauss, B.; Logashenko, I.; Lynch, K. R.; McNabb, R.; Miller, J. P.; Mulhauser, F.; Onderwater, C. J. G.; Phillips, J.; Rath, S.; Roberts, B. L.; Winter, P.; Wolfe, B.

2011-01-01

198

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

E-print Network

We report a measurement of the positive muon lifetime to a precision of 1.0 parts per million (ppm); it is the most precise particle lifetime ever measured. The experiment used a time-structured, low-energy muon beam and a segmented plastic scintillator array to record more than 2 x 10^{12} decays. Two different stopping target configurations were employed in independent data-taking periods. The combined results give tau_{mu^+}(MuLan) = 2196980.3(2.2) ps, more than 15 times as precise as any previous experiment. The muon lifetime gives the most precise value for the Fermi constant: G_F(MuLan) = 1.1663788 (7) x 10^-5 GeV^-2 (0.6 ppm). It is also used to extract the mu^-p singlet capture rate, which determines the proton's weak induced pseudoscalar coupling g_P.

D. M. Webber; V. Tishchenko; Q. ~Peng; S. Battu; R. M. Carey; D. B. Chitwood; J. Crnkovic; P. T. Debevec; S. Dhamija; W. Earle; A. Gafarov; K. Giovanetti; T. P. Gorringe; F. E. Gray; Z. Hartwig; D. W. Hertzog; B. Johnson; P. Kammel; B. Kiburg; S. Kizilgul; J. Kunkle; B. Lauss; I. Logashenko; K. R. Lynch; R. McNabb; J. P. Miller; F. Mulhauser; C. J. G. Onderwater; J. Phillips; S. Rath; B. L. Roberts; P. Winter; B. Wolfe

2010-12-06

199

The study on precision positioning system of two-dimensional platform based on high speed and large range  

Microsoft Academic Search

The aim of this paper is to improve the positioning accuracy of precision positioning system of two-dimensional based on high speed and large range which is driven by linear motor. According to the influence of intrinsic parameters and external disturbance, a fuzzy-neuron self-adaptive and weighted PID control system has been studied out, among them, intrinsic parameters contain nonlinearity of linear

Chuan Yang; Zhi Zhang; Qiang Zhao

2010-01-01

200

Precise position tracking control based on adaptive neuron PID algorithm for automatic clutch driven by DC motor  

Microsoft Academic Search

For automatic clutch control system, precise and quick position tracking is difficult on account of its nonlinear character. A new clutch actuating mechanism with a whirl spring was devised for torque compensation to reduce the load of DC actuator and improve the dynamic performance of clutch control system firstly, and then a neuron adaptive PID controller with feedforward and adjustable

Xudong Wang; Xianping Xie; Xiaogang Wu; Tengwei Yu

2008-01-01

201

Modeling of a Planar Motion Stage for Precision Positioning Kai Treichel**, Remon Al Azrak*, Johann Reger*, and Kai Wulff*  

E-print Network

. The mover is equipped with permanent magnet arrays (PMAs), hence passive, and suspended by pressurized air, high-precision Lorentz force planar mo- tion stage of linear DC brushless type. We derive physical throughout experiments. The position dependency of the Lorentz forces is reduced by a minimum power

Knobloch,Jürgen

202

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

Microsoft Academic Search

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

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

2009-01-01

203

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

204

Achieving high-precision pointing on ExoplanetSat: Initial feasibility analysis  

E-print Network

ExoplanetSat is a proposed three-unit CubeSat designed to detect down to Earth-sized exoplanets in an orbit out to the habitable zone of Sun-like stars via the transit method. To achieve the required photometric precision ...

Pong, Christopher Masaru

205

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

206

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

207

Constraints on arm position when pointing in three dimensions: Donders' law and the Fick gimbal strategy.  

PubMed

1. While making saccades between targets with the head stationary, eye positions are constrained to two of the possible three degrees of freedom. Classically this constraint has been described by Donders' and Listing's laws. The objective was to determine whether these laws also apply for the straight arm when pointing between different targets. Thus we determined whether the arm adopts only one angular position for every pointing direction (Donders' law) and whether these positions can be described by rotations from a reference position about axes that lie in a plane (Listing's law). 2. The angular positions (orientations) of the arm in three-dimensional space were studied as subjects pointed with a straight arm at different targets. Arm position was measured with the search coil technique by means of coils attached to the back of the hand. Pointing was studied over a range of +/- 45 degrees in all directions from a central target located 45 degrees to the right of the straight-ahead position. 3. The positions of the arm in space were described by quaternion vectors, i.e., a particular position was described in terms of the axis and amplitude of a rotation from a reference position to that position. Using this description, it was found that the straight arm adopted a similar orientation (standard deviations ranged from 2.8 to 4.8 degrees) when pointing at a particular target irrespective of which target from which it had moved. 4. The angular position vectors for arm positions associated with relatively small movements (e.g., less than +/- 30 degrees) lay in a flat surface with minimal torsion. At first sight, this surface appeared to be similar to Listing's plane of the eye. However, for positions associated with larger movements (e.g., +/- 45 degrees) it became apparent that, unlike the eye, the surface deviated from one obeying Listing's law, i.e., it was twisted and showed torsion like that produced by rotations around the horizontal and vertical axes of a Fick gimbal. (The characteristic of a Fick gimbal is that the vertical axis is fixed, whereas the horizontal axis moves with the gimbal.) 5. Although there were differences between subjects, all showed a twisted position vector surface. The twist was always in the same direction, and it was always less than that of a Fick gimbal. 6. This position vector surface had a similar shape whether the arm was stationary or was moving between targets, whether subjects pointed with or without vision, and whether the pointing arm had moved between targets or from a bent-elbow position on the lap.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1527564

Hore, J; Watts, S; Vilis, T

1992-08-01

208

Primal-Dual Interior-Point Methods for Semidefinite Programming in Finite Precision  

Microsoft Academic Search

. Recently, a number of primal-dual interior-point methods for semidefinite programminghave been developed. To reduce the number of floating point operations, each iteration of thesemethods typically performs block Gaussian elimination with block pivots that are close to singularnear the optimal solution. As a result, these methods often exhibit complex numerical properties inpractice.We consider numerical issues related to some of these

Ming Gu

2000-01-01

209

GPS Estimation Algorithms for Precise Velocity, Slip and Racetrack Position Measurements  

Microsoft Academic Search

This paper investigates the use of carrier-phase differential GPS (CDGPS) for race car applications. In particular, experimental results are presented to demonstrate the use of CDGPS to accuratelymeasure several keyparameters of a test vehicle, including the inertial velocity, side-slip, and its precise location. This data is useful as a driver's coaching tool because it can be used to determine what

Nicholas Pohlman; Chan-Woo Park

2002-01-01

210

Robust Output Feedback Trajectory Tracking Control of an Electrodynamic Planar Motion Stage for Precision Positioning  

E-print Network

. For meeting these challenges and still increasing require- ments non contact planar brushless type DC motors contact, high-precision Lorentz force planar motion stage of linear DC brushless type. The control problem/Lorentz motors with three degrees of freedom are widely used as they provide nearly frictionless motion due

Knobloch,Jürgen

211

The International GPS Service (IGS) as a Continuous Reference System for Precise GPS Positioning  

NASA Technical Reports Server (NTRS)

The International GPS Service for Geodynamics (IGS) is an organization which operates under the auspices of the International Association of Geodesy (IAG) and has been operational since January 1994. The primary objective of the IGS is to provide precise GPS data and data products to support geodetic and geophysical research activities.

Neilan, Ruth; Heflin, Michael; Watkins, Michael; Zumberge, James

1996-01-01

212

Control System Design for Stability and Precise Positioning of Atomic Force Microscopy Probe  

Microsoft Academic Search

An atomic force microscopy (AFM) operates by moving the platform to put its probe on the sample surface for measurement or processing. One of its greatest drawbacks is longer waiting time for vibrations to settle and so that the task can be operated. This study investigates the modeling and control of AFM's probe in order to achieve stability and precise

Chung-Feng Jeffrey Kuo; Te-Li Su; Zheng-Lin Li; Chin-Hsun Chiu

2007-01-01

213

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

PubMed

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

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

2007-02-01

214

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

215

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

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

216

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

217

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

218

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

219

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

PubMed

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

Kim, Jungdae; Kang, Dae-In

2014-02-01

220

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

Microsoft Academic Search

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

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

2006-01-01

221

Predictorcorrector algorithms for solving P*-matrix Lcp from arbitrary positive starting points  

Microsoft Academic Search

A new predictor-corrector algorithm is proposed for solving P ()-matrix linearcomplementarity problems. If the problem is solvable, then the algorithm convergesfrom an arbitrary positive starting point (x0; s0). The computational complexity of thealgorithm depends on the quality of the starting point. If the starting point is feasibleor close to being feasible, it has O((1+)pn=ae 0 L)-iteration complexity, where ae 0

Florian A. Potra; Rongqin Sheng

1994-01-01

222

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

223

A magnetic attitude control system for precision pointing of the rolling GP-B spacecraft  

NASA Astrophysics Data System (ADS)

A new algorithm for magnetic attitude control of spinning spacecraft is presented. This algorithm requires real time measurments of the local magnetic field. A Kalman filter type estimator is derived that can obtain the local field by applying dither current to the magnetic rods. This eliminates the need for magnetometers, guaranteeing colocation of sensor and actuator and removing a number of failure modes. An example controller design is presented for the Gravity Probe B spacecraft pointing control. This controller achieves better than 20 milliarcsec pointing accuracy using the magnetic control algorithm without magnetometer measurements.

Parkinson, Bradford W.; Kasdin, N. Jeremy

224

Precise voltage contrast image assisted positioning for in situ electron beam nanolithography for nanodevice fabrication with suspended nanowire structures.  

PubMed

In this paper, we demonstrate precise voltage contrast image positioning for in situ electron beam (e-beam) nanolithography to integrate nanowires into suspended structures for nanoswitch fabrication. The positioning of the deflection electrodes on the nanowires can be well controlled using a precise voltage contrast image positioning technique, where the error can be minimized to about 10 nm. Using such a method, dispersed nanowires can be sandwiched between two layers of resist and suspended by one e-beam nanolithography process without any etching. The in situ e-beam nanolithography eliminates the stage movement error by preventing any movements of the stage during the nanolithography process; hence, a high precision laser stage and alignment marks on the substrate are not needed, which simplifies the traditional e-beam nanolithography process. The nanoswitches fabricated using this method show ON and OFF states with the changes of applied voltages. This simplified process provides an easy, low cost and less time-consuming route to integrating suspended nanowire based structures using a converted field emission scanning electron microscope e-beam system, which can also be customized to fabricate multi-layer structures and a site-specific nanodevice fabrication. PMID:19546502

Long, Renhai; Chen, Jiajun; Lim, Jin-Hee; Wiley, John B; Zhou, Weilie

2009-07-15

225

Precise voltage contrast image assisted positioning for in situ electron beam nanolithography for nanodevice fabrication with suspended nanowire structures  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate precise voltage contrast image positioning for in situ electron beam (e-beam) nanolithography to integrate nanowires into suspended structures for nanoswitch fabrication. The positioning of the deflection electrodes on the nanowires can be well controlled using a precise voltage contrast image positioning technique, where the error can be minimized to about 10 nm. Using such a method, dispersed nanowires can be sandwiched between two layers of resist and suspended by one e-beam nanolithography process without any etching. The in situ e-beam nanolithography eliminates the stage movement error by preventing any movements of the stage during the nanolithography process; hence, a high precision laser stage and alignment marks on the substrate are not needed, which simplifies the traditional e-beam nanolithography process. The nanoswitches fabricated using this method show ON and OFF states with the changes of applied voltages. This simplified process provides an easy, low cost and less time-consuming route to integrating suspended nanowire based structures using a converted field emission scanning electron microscope e-beam system, which can also be customized to fabricate multi-layer structures and a site-specific nanodevice fabrication.

Long, Renhai; Chen, Jiajun; Lim, Jin-Hee; Wiley, John B.; Zhou, Weilie

2009-07-01

226

Design and control of long travel range electromagnetically actuated positioning stage with application to precise machining  

Microsoft Academic Search

This paper proposes a long travel range electromagnetically actuated positioning stage with application to micro machining. Specially, a probe with titanium coating is integrated with an electromagnetically actuated and damped positioning stage to perform millimeter range movement. Here, the developed stage replaces traditional piezoelectric actuators for the purpose of lengthening the motion range while minimizing the complexity of the electrical

Shan-Tsung Lee; Kuan-Lin Huang; Jim-Wei Wu; Li-Chen Fu

2010-01-01

227

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

228

Simultaneous precision positioning and vibration suppression of an intelligent composite satellite structure utilizing piezoelectric sensors and actuators  

NASA Astrophysics Data System (ADS)

Adaptive or intelligent structures which have the capability for sensing and responding to their environment promise a novel approach to satisfying the stringent performance requirements of future space missions. This research effort focuses on the development of a smart thruster mount truss structure with precision positioning and active vibration suppression capability for use in a space satellite. The smart thruster mount would utilize piezoelectric sensors and actuators for precision positioning to provide fine tuning of position tolerance for thruster alignment. The same structure may be used for suppressing the vibration that resonates throughout the spacecraft during thruster firing. This vibration renders sensitive optical or measurement equipment non-operational until the disturbance has dissipated. This smart system approach would greatly enhance mission performance by fine tuning attitude control, potentially eliminating the nonoperational period as well as minimizing fuel consumption utilized for position correction. The configuration of the smart thruster mount truss system is that of a modified Stewart platform. Precision positioning of the truss structure is achieved using active members which extend or contract to tilt the upper platform where the thruster is mounted. An inverse kinematic analysis of a modified Stewart platform has been developed and is used to determine the required axial displacement of the active struts for the desired angular tilt of the smart platform. Experimental data is used to verify the precision positioning capabilities of the active struts. This information demonstrates the ability of the active strut to tilt the top of the smart platform by the required angular displacement. Analytical verification of the vibration suppression capabilities of the active struts in the smart composite platform using finite element analysis is presented. A model of an active strut with surface mounted sensors/actuators was used to develop a vibration suppression scheme. This technique was used successfully to analytically demonstrate both the lateral and axial vibration suppression capability of the active strut. The numerical and experimental results show that the proposed smart platform offers a promising method for achieving fine tuning of positioning tolerances of a thruster as well as minimizing the effect of the disturbance generated during thruster firing.

Doherty, Kathleen Marie

229

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

230

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

231

High-efficiency piezoelectric motor combining continuous rotation with precise control over angular positioning  

NASA Astrophysics Data System (ADS)

The letter describes a piezoelectric motor that combines the merits of piezoelectric materials, such as high power density generated at electromechanical resonance, and a precise control of displacement. The motor utilizes a direct coupling mechanism between the stator and rotor, where a clutch drives the rotor via locking it. The direct coupling makes it possible to transmit the whole power generated in the piezoelectric element to the rotor, and thus achieve the high efficiency of the motor. It also allows the combining of two regimes of operation: continuous rotation and a stepwise motion within a 360° interval with a high resolution of angular displacement.

Glazounov, A. E.; Wang, S.; Zhang, Q. M.; Kim, C.

1999-08-01

232

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

233

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

234

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

235

Measurement of Precision Geometric Distances to Three Anchor Points in the Local Universe  

NASA Technical Reports Server (NTRS)

We proposed a program to measure distances directly with accuracies of 5% to three anchor points in the Local Universe. We planned to accomplish this by conducting Very Long Baseline Interferometry (VLBI) observations of NGC 4258, M 33, and Sgr A*. These distance estimates should have a minimum of systematic uncertainty and can be used to re-calibrate several 'standard candles,' such as Cepheid and RR Lyrae variables. This will place the Galactic and extragalactic distance scales on much firmer ground. The primary contribution of our program will be to provide crucial independent checks and calibrations of extragalactic distance measurements. This will contribute to the ultimate success and impact of the HST Key Project on Extragalactic Distances and the Full-Sky Astrometric Mapping Explorer (FAME). Additionally, since distances are fundamental to astrophysics, our results will affect a large number of general projects on NASA facilities such as the Hubble Space Telescope, Chandra X-ray Observatory, and Next Generation Space Telescope.

Reid, Mark J.

2001-01-01

236

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

237

Precision Positional Data of General Aviation Air Traffic in Terminal Air Space  

NASA Technical Reports Server (NTRS)

Three dimensional radar tracks of general aviation air traffic at three uncontrolled airports are considered. Contained are data which describe the position-time histories, other derived parameters, and reference data for the approximately 1200 tracks. All information was correlated such that the date, time, flight number, and runway number match the pattern type, aircraft type, wind, visibility, and cloud conditions.

Melson, W. E., Jr.; Parker, L. C.; Northam, A. M.; Singh, R. P.

1978-01-01

238

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

239

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

Microsoft Academic Search

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

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

2000-01-01

240

MODELLING AND IDENTIFICATION OF A HIGH-PRECISION PLANAR POSITIONING SYSTEM  

E-print Network

embedded into the stator plate. Currents through those conductors together with the permanent magnets and electromagnetic coupling as a principle of propul- sion. We develop physical models of all components and in-- planar positioning system, air bearing, electro magnetic propulsion, physical modelling 1. INTRODUCTION

Knobloch,Jürgen

241

Comparison of Two Kinds of Large Displacement Precision Parallel Mechanisms for Micro\\/nano Positioning Applications  

Microsoft Academic Search

This paper presents kinematic analysis of two kinds of large displacement parallel platforms for micro\\/nano positioning applications. The kinematics model of the dual parallel mechanism systems is established via the stiffness model of individual wide-range flexure hinge. The displacements of the end platform and the input parameters of prismatic actuators are discussed and the corrected values of input motions are

Yuan Yun; Yangmin Li

2008-01-01

242

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

243

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

244

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

245

Measurement of Precision Geometric Distances to Three Anchor Points in the Local Universe  

NASA Technical Reports Server (NTRS)

Our program, funded by a NASA/SARA 3-yr grant, seeks to provide a much improved foundation of r the extra-galactic distance scale. The goal is to measure geometric distances with accuracies of 5% of better to several anchor points in the Local Universe. There are three objects that we are observing in order to attack this problem: NGC 4258, M 33, and Sgr A*. We plan to provide distance estimates, with a minimum of systematic uncertainty, that can be used to recalibrate several "standard candles," such as Cepheid and RR Lyrae variables. This will place the extragalactic distance scales on much firmer ground. The program will provide crucial, independent checks and calibrations of extragalactic distance measurements, and will contribute to the ultimate success and impact of the HST Key Project on Extragalactic Distances and any future NASA astrometric missions. Additionally, since distances are fundamental to astrophysics, our results will affect a large number of general projects on NASA facilities such s the HST, CXO, and JWST.

Reid, Mark J.

2005-01-01

246

Measurement of Precision Geometric Distances to Three Anchor Points in the Local Universe  

NASA Technical Reports Server (NTRS)

Our program, funded by a NASA/SARA 3-yr grant, is designed to measure distances directly with accuracies of 5% to three anchor points in the Local Universe. We are attacking this problem on three fronts, using Very Long Baseline Interferometry (VLBI) observations of NGC 4258, M 33, and Sgr A*. We plan to provide distance estimates, with a minimum of systematic uncertainty, that can be used to re-calibrate several 'standard candles,' such as Cepheid and RR Lyrae variables. This will place the Galactic and extragalactic distance scales on much firmer ground. The program will provide crucial, independent checks and calibrations of extragalactic distance measurements, and will contribute to the ultimate success and impact of the HST Key Project on Extragalactic Distances, the Full-Sky Astrometric Mapping Explorer (FAME), and any future NASA astrometric missions. Additionally, since distances are fundamental to astrophysics, our results will affect a large number of general projects on NASA facilities such as the HST (Hubble Space Telescope), CXO (Chandra X-Ray Observatory), and NGST (Next Generation Space Telescope).

Reid, Mark J.

2002-01-01

247

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

Microsoft Academic Search

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

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

2000-01-01

248

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

E-print Network

Simulation result of DKF output for a 100-?m step, feedback using DKF output .................................. 73 46 Experimental results when there is no motion at the origin, and FFT results 74 47 Experimental results when there is no motion at the origin... using the fast controller, and FFT results ........................ 76 48 Experimental results of 10-?m steps in Y .................. 82 49 Experimental results of positioning platen in X and Y following a zigzag trajectory...

Kawato, Yusuke

2006-08-16

249

A novel high precision electromagnetic flexure-suspended positioning stage with an eddy current damper  

Microsoft Academic Search

This paper proposes a novel planar electromagnetic-actuated positioning stage. The stage is suspended by the monolithic parallel flexure mechanism, which motion comes from the deformation of the flexure. A linear electromagnetic actuator which consists of a near-uniform magnetic field and four coils is designed and implementation to provide the propelling force for 3-DOF motions. In order to suppress the vibration

Chih-Hsien Lin; Shao-Kung Hung; Mei-Yung Chen; Shan-Tsung Li; Li-Chen Fu

2008-01-01

250

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

251

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

252

Predictorcorrector algorithm for solving P * ( ? )-matrix LCP from arbitrary positive starting points  

Microsoft Academic Search

A new predictor-corrector algorithm is proposed for solvingP\\u000a *(?)-matrix linear complementarity problems. If the problem is solvable, then the algorithm converges from an arbitrary positive\\u000a starting point (x\\u000a 0,s\\u000a 0). The computational complexity of the algorithm depends on the quality of the starting point. If the starting point is feasible\\u000a or close to being feasible, it has\\u000a $$O((1 + \\\\kappa

Florian A. Potra; Rongqin Sheng

1997-01-01

253

Precise GNSS single epoch positioning with multiple receiver configuration for medium-length baselines: methodology and performance analysis  

NASA Astrophysics Data System (ADS)

The configuration of multiple GNSS antennas and receivers on a common moving platform is widely used for attitude determination. This rigid configuration with nearby antennas can form several constraints, which can be used in order to improve the accuracy of the solution. In particular, known baseline length, relationships between ambiguities on different baselines as well as similar tropospheric and ionospheric delays can be applied in the relative positioning model. The objective of the presented research was to develop a method for taking advantage of the abovementioned constraints in order to improve the ambiguity resolution and consequently the performance of the precise GNSS positioning. This study is based on the processing of medium length baselines up to 70?km length in the instantaneous mode. The results show clear improvement in ambiguity resolution domain in comparison to the commonly used ionosphere-weighted troposphere-estimated geometry based model.

Paziewski, Jacek

2015-03-01

254

Precise positioning and compliance synthesis for automatic assembly using Lorentz levitation  

NASA Technical Reports Server (NTRS)

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

Hollis, R. L.; Salcudean, S.

1992-01-01

255

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

256

High precision gravity analysis and hydrological modeling from the Lunar Laser Ranging Observatory at Apache Point, New Mexico  

NASA Astrophysics Data System (ADS)

The NASA-supported Lunar Laser Ranging project (LLR) is located at Apache Point, New Mexico, which strives to precisely measure the orbital distance between the Earth and the Moon in an accuracy of a few millimeters. To archive this objective, LLR project requires precise data on local ground deformation, which is difficult to measure directly. However, the high precision gravity data is the reflection of vertical ground deformation of the Earth, therefore the gravity data is able to contribute to the LLR project. Gravity time series is affected by Earth tides, atmospheric pressure, polar motion, and the most critical effect, local hydrology. In order to isolate pure geodetic variation, these effects must be removed from the data. Thus, the goal of this research is to create models of above effects, especially local hydrology model, in order to isolate the vertical deformation signal. The Earth tides, atmospheric pressure and polar motion effects have been modeled and subtracted from gravity data (2009~2012). The local hydrological model has been created based on the in-situ data, which are rainfall, snowfall and temperature. The correlation coefficient and RMS misfit between the hydrological model and gravity residual (2010~2012) is 0.92 and 1.26 microGal. The instrument drift corrections in 2009 have been reanalyzed after comparing with some global hydrological models. The gravity residual from new corrections showed a correlation coefficient of 0.76 and RMS misfit of 1.25 microGal. The isolated deformation signal was obtained after we subtracted the hydrological effects, and the results can be used for further modeling.

Liang, Jiahao

257

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

258

Arm position constraints during pointing and reaching in 3-D space.  

PubMed

Arm movements in 3-D space were studied to investigate the reduction in the number of rotational degrees of freedom in the shoulder and elbow during pointing movements with the fully extended arm and during pointing movements to targets in various directions and at various distances relative to the shoulder, requiring flexion/extension in the elbow. The postures of both the upper arm and forearm can be described by rotation vectors, which represent these postures as a rotation from a reference position to the current position. The rotation vectors describing the posture of the upper arm and forearm were found to lie in a 2-D (curved) surface both for pointing with the fully extended arm and for pointing with elbow flexion. This result generalizes on previous results on the reduction of the number of degrees of freedom from three to two in the shoulder for the fully extended arm to a similar reduction in the number of degrees of freedom for the upper arm and forearm for normal arm movements involving also elbow flexion and extension. The orientation of the 2-D surface fitted to the rotation vectors describing the position of the upper arm and forearm was the same for pointing with the extended arm and for movements with flexion/extension of the elbow. The scatter in torsion of the rotation vectors describing the position of the upper arm and forearm relative to the 2-D surface was typically 3-4 degrees, which is small considering the range of approximately 180 and 360 degrees for torsional rotations of the upper arm and the forearm, respectively. Donders' law states that arm posture for pointing to a target does not depend on previous positions of the arm. The results of our experiments demonstrate that the upper arm violates Donders' law. However, the variations in torsion of the upper arm are small, typically a few degrees. These deviations from Donders' law have been overlooked in previous studies, presumably because the variations are relatively small. These variations may explain the larger scatter of the rotation vectors for arm movements (3-4 degrees) than reported for the eye (1 degree). Unlike for saccadic eye movements, joint rotations in the shoulder during aiming movements were not all single-axis rotations. On the contrary, the direction of the angular velocity vector varied during the movement in a consistent and reproducible way, depending on amplitude, direction, and starting position of the movement. These results reveal several differences between arm movements during pointing and saccadic eye movements. The implications for our understanding of the coordination of eye and arm movements and for the planning of 3-D arm movements are discussed. PMID:9307103

Gielen, C C; Vrijenhoek, E J; Flash, T; Neggers, S F

1997-08-01

259

Semi-robotic 6 degree of freedom positioning for intracranial high precision radiotherapy; first phantom and clinical results  

PubMed Central

Background To introduce a novel method of patient positioning for high precision intracranial radiotherapy. Methods An infrared(IR)-array, reproducibly attached to the patient via a vacuum-mouthpiece(vMP) and connected to the table via a 6 degree-of-freedom(DoF) mechanical arm serves as positioning and fixation system. After IR-based manual prepositioning to rough treatment position and fixation of the mechanical arm, a cone-beam CT(CBCT) is performed. A robotic 6 DoF treatment couch (HexaPOD™) then automatically corrects all remaining translations and rotations. This absolute position of infrared markers at the first fraction acts as reference for the following fractions where patients are manually prepositioned to within ± 2 mm and ± 2° of this IR reference position prior to final HexaPOD-based correction; consequently CBCT imaging is only required once at the first treatment fraction. The preclinical feasibility and attainable repositioning accuracy of this method was evaluated on a phantom and human volunteers as was the clinical efficacy on 7 pilot study patients. Results Phantom and volunteer manual IR-based prepositioning to within ± 2 mm and ± 2° in 6DoF was possible within a mean(± SD) of 90 ± 31 and 56 ± 22 seconds respectively. Mean phantom translational and rotational precision after 6 DoF corrections by the HexaPOD was 0.2 ± 0.2 mm and 0.7 ± 0.8° respectively. For the actual patient collective, the mean 3D vector for inter-treatment repositioning accuracy (n = 102) was 1.6 ± 0.8 mm while intra-fraction movement (n = 110) was 0.6 ± 0.4 mm. Conclusions This novel semi-automatic 6DoF IR-based system has been shown to compare favourably with existing non-invasive intracranial repeat fixation systems with respect to handling, reproducibility and, more importantly, intra-fraction rigidity. Some advantages are full cranial positioning flexibility for single and fractionated IGRT treatments and possibly increased patient comfort. PMID:20504338

2010-01-01

260

A new sensor system for accurate and precise determination of sediment dynamics and position.  

NASA Astrophysics Data System (ADS)

Sediment transport processes control many significant geomorphological changes. Consequently, sediment transport dynamics are studied across a wide range of scales leading to application of a variety of conceptually different mathematical descriptions (models) and data acquisition techniques (sensing). For river sediment transport processes both Eulerian and Lagrangian formulations are used. Data are gathered using a very wide range of sensing techniques that are not always compatible with the conceptual formulation applied. We are concerned with small to medium sediment grain-scale motion in gravel-bed rivers, and other coarse-grained environments, and: a) are developing a customised environmental sensor capable of providing coherent data that reliably record the motion; and, b) provide a mathematical framework in which these data can be analysed and interpreted, this being compatible with current stochastic approaches to sediment transport theory. Here we present results from three different aspects of the above developmental process. Firstly, we present a requirement analysis for the sensor based on the state of the art of the existing technologies. We focus on the factors that enhance data coherence and representativeness, extending the common practice for optimization which is based exclusively on electronics/computing related criteria. This analysis leads to formalization of a method that permits accurate control on the physical properties of the sensor using contemporary rapid prototyping techniques [Maniatis et al. 2013]. Secondly the first results are presented from a series of entrainment experiments in a 5 x 0.8 m flume in which a prototype sensor was deployed to monitor entrainment dynamics under increasing flow conditions (0.037 m3.s-1). The sensor was enclosed in an idealized spherical case (111 mm diameter) and placed on a constructed bed of hemispheres of the same diameter. We measured 3-axial inertial acceleration (as a measure of flow stress), with sampling frequency 4 to 10Hz, for two different initial positions over a range of slopes (from 0.026 to 0.57). The results reveal forces during the pre-entrainment phase and show the effect of slope on the temporal characteristics of the process. Finally we present results from the simulations using a mathematical framework developed to integrate the inertial-dynamics data (corresponding to the above experimental procedure and sensing conceptualization) [Abeywardana et al. 2012] with the mathematical techniques used in contemporary localization applications [Zanella et al. 2012]. We specifically assess different signal filtering techniques in terms of: a) how informative they are regarding the complexity of sediment movement; and, b) how possible it is to reduce rapidly accumulating errors that occur during sensing and increase positional accuracy. References Maniatis, G.; Hoey, T.; Sventek, J. Sensor Enclosures: Example Application and Implications for Data Coherence. J. Sens. Actuator Netw. 2013, 2, 761-779. Abeywardana, D. K., A. P. Hu, and N. Kularatna. "IPT charged wireless sensor module for river sedimentation detection." Sensors Applications Symposium (SAS), 2012 IEEE. IEEE, 2012. Zannella, Fillipo, and Angelo Cenedese. "Multi-agent tracking in wireless sensor networks: implementation." WSEAS Int. Conf. on Information Technology and Computer Networks (ITCN). 2012.

Maniatis, Georgios; Hoey, Trevor; Sventek, Joseph; Hodge, Rebecca

2014-05-01

261

Development of Electronics for the ATF2 Interaction Point Region Beam Position Monitor  

SciTech Connect

Nanometer resolution beam position monitors have been developed to measure and control beam position stability at the interaction point region of ATF2. The position of the beam has to be measured to within a few nanometers at the interaction point. In order to achieve this performance, electronics for the low-Q IP-BPM was developed. Every component of the electronics have been simulated and checked on the bench and using the ATF2 beam. We will explain each component and define their working range. Then, we will show the performance of the electronics measured with beam signal. ATF2 is a final focus test beam line for ILC in the framework of the ATF international collaboration. The new beam line was constructed to extend the extraction line at ATF, KEK, Japan. The first goal of ATF2 is the acheiving of a 37 nm vertical beam size at focal point (IP). The second goal is to stabilize the beam at the focal point at a few nanometer level for a long period in order to ensure the high luminosity. To achieve these goals a high resolution IP-BPM is essential. In addition for feedback applications a low-Q system is desirable.

Kim, Youngim; /Kyungpook Natl. U.; Heo, Ae-young; /Kyungpook Natl. U.; Kim, Eun-San; /Kyungpook Natl. U.; Boogert, Stewart; /Royal Holloway, U. of London; Honda, Yosuke; /KEK, Tsukuba; Tauchi, Toshiaki; /KEK, Tsukuba; Terunuma, Nobuhiro; /KEK, Tsukuba; May, Justin; /SLAC; McCormick, Douglas; /SLAC; Smith, Tonee; /SLAC

2012-08-14

262

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

263

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

264

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

265

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

266

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

267

Precision pointing thrustor.  

NASA Technical Reports Server (NTRS)

A satellite experiment to test the predicted relativistic precession of a gyroscope moving through a gravitational field has been under development at Stanford University for a number of years. The instruments will be located in a liquid helium bath to insure dimensional stability and to permit using superconducting types of circuitry for readout of the gyro orientation. Heat leaks in the system cause the helium to boil and the resultant helium gas is used for attitude control. The principal subject of the paper is the design and experimental evaluation of an electromagnetically actuated differential thrustor which was built and tested at Stanford University. The results are unique because most propulsion systems operate on-off in order to utilize propellant efficiently. In this case, the gas must flow continually to provide cooling, and the requirements are primarily for low power, small volume, and high reliability.

Bull, J. S.; Debra, D. B.

1973-01-01

268

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

NASA Astrophysics Data System (ADS)

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

Lin, Miao; Denker, Heiner; Müller, Jürgen

2013-04-01

269

Single-element based ultra-wideband antenna array concepts for wireless high-precision 2-D local positioning  

NASA Astrophysics Data System (ADS)

We generally categorize the approaches for ultra-wideband antenna array design, and consequently propose simplified concepts for antenna arrays for a high-precision, ultra-wideband FMCW radar 2-D local positioning system to obtain robustness against multi path interference, perform angle of arrival analysis, as well as instantaneous heading estimation. We focus on low-cost and mechanical robust, industrial-application ready antennas. The antenna arrays are optimized for operation in the 5 GHz to 8 GHz frequency range and are designed towards supporting full omnidirectional 360° as well as partial half-plane direction of arrival estimation. Two different concepts for vehicle- as well as wall-mounted antenna array systems are proposed and discussed. We propose a wideband unidirectional bow-tie antenna array element having 97% impedance and 37% pattern bandwidth and a robust vehicle mounted omnidirectional antenna element having more than 85% impedance and pattern bandwidth.

Gardill, M.; Fischer, G.; Weigel, R.; Koelpin, A.

2013-07-01

270

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

Microsoft Academic Search

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

Gerhard L. Weissler

1943-01-01

271

PT-Symmetric Solutions of Schrödinger Equation with Position-Dependent Mass via Point Canonical Transformation  

NASA Astrophysics Data System (ADS)

PT-symmetric solutions of Schrödinger equation are obtained for the Scarf and generalized harmonic oscillator potentials with the position-dependent mass. A general point canonical transformation is applied by using a free parameter. Three different forms of mass distributions are used. A set of the energy eigenvalues of the bound states and corresponding wave functions for target potentials are obtained as a function of the free parameter.

Tezcan, Cevdet; Sever, Ramazan

2008-05-01

272

PT-symmetric Solutions of Schrödinger Equation with position-dependent mass via Point Canonical Transformation  

E-print Network

PT-symmetric solutions of Schrödinger equation are obtained for the Scarf and generalized harmonic oscillator potentials with the position-dependent mass. A general point canonical transformation is applied by using a free parameter. Three different forms of mass distributions are used. A set of the energy eigenvalues of the bound states and corresponding wave functions for target potentials are obtained as a function of the free parameter.

Cevdet Tezcan

2008-01-01

273

PT-symmetric Solutions of Schrodinger Equation with position-dependent mass via Point Canonical Transformation  

E-print Network

PT-symmetric solutions of Schrodinger equation are obtained for the Scarf and generalized harmonic oscillator potentials with the position-dependent mass. A general point canonical transformation is applied by using a free parameter. Three different forms of mass distributions are used. A set of the energy eigenvalues of the bound states and corresponding wave functions for target potentials are obtained as a function of the free parameter.

Tezcand, Cevdet

2007-01-01

274

PT-symmetric Solutions of Schrodinger Equation with position-dependent mass via Point Canonical Transformation  

E-print Network

PT-symmetric solutions of Schrodinger equation are obtained for the Scarf and generalized harmonic oscillator potentials with the position-dependent mass. A general point canonical transformation is applied by using a free parameter. Three different forms of mass distributions are used. A set of the energy eigenvalues of the bound states and corresponding wave functions for target potentials are obtained as a function of the free parameter.

Cevdet Tezcand; Ramazan Sever

2007-09-18

275

The method of free-positioned point masses — geoid studies on the Gulf of Bothnia  

Microsoft Academic Search

Gravity data inversion methods using spatial source distributions are frequently investigated and applied in Geodesy. Nearly\\u000a all of them construct a fixed geometry for the sources. It was shown that this is not at all necessary. We give an approach\\u000a to the problem of geoid determination based on free-positioned point masses. The algorithm available is extended and refined\\u000a in order

Rüdiger Lehmann

1993-01-01

276

Bowl breakout: Escaping the positive region when searching for saddle points  

NASA Astrophysics Data System (ADS)

We present a scheme improving the minimum-mode following method for finding first order saddle points by confining the displacements of atoms to the subset of those subject to the largest force. By doing so it is ensured that the displacement remains of a local character within regions where all eigenvalues of the Hessian matrix are positive. However, as soon as a region is entered where an eigenvalue turns negative all atoms are released to maintain the ability of determining concerted moves. Applying the proposed scheme reduces the required number of force calls for the determination of connected saddle points by a factor two or more compared to a free search. Furthermore, a wider distribution of the relevant low barrier saddle points is obtained. Finally, the dependency on the initial distortion and the applied maximal step size is reduced making minimum-mode guided searches both more robust and applicable.

Pedersen, Andreas; Luiser, Mathieu

2014-07-01

277

Bowl breakout: Escaping the positive region when searching for saddle points  

SciTech Connect

We present a scheme improving the minimum-mode following method for finding first order saddle points by confining the displacements of atoms to the subset of those subject to the largest force. By doing so it is ensured that the displacement remains of a local character within regions where all eigenvalues of the Hessian matrix are positive. However, as soon as a region is entered where an eigenvalue turns negative all atoms are released to maintain the ability of determining concerted moves. Applying the proposed scheme reduces the required number of force calls for the determination of connected saddle points by a factor two or more compared to a free search. Furthermore, a wider distribution of the relevant low barrier saddle points is obtained. Finally, the dependency on the initial distortion and the applied maximal step size is reduced making minimum-mode guided searches both more robust and applicable.

Pedersen, Andreas [Faculty of Physical Sciences, University of Iceland VR-III, 107 Reykjavík (Iceland); Integrated Systems Laboratory, ETH Zurich, 8092 Zurich (Switzerland); Luiser, Mathieu [Integrated Systems Laboratory, ETH Zurich, 8092 Zurich (Switzerland)

2014-07-14

278

Band-edge positions in G W : Effects of starting point and self-consistency  

NASA Astrophysics Data System (ADS)

We study the effect of starting point and self-consistency within G W on the band-edge positions of semiconductors and insulators. Compared to calculations based on a semilocal starting point, the use of a hybrid-functional starting point shows a larger quasiparticle correction for both band-edge states. When the self-consistent treatment is employed, the band-gap opening is found to result mostly from a shift of the valence-band edge. Within the non-self-consistent methods, we analyse the performance of empirical and nonempirical schemes in which the starting point is optimally tuned. We further assess the accuracy of the band-edge positions through the calculation of ionization potentials of surfaces. The ionization potentials for most systems are reasonably well described by one-shot calculations. However, in the case of TiO2, we find that the use of self-consistency is critical to obtain a good agreement with experiment.

Chen, Wei; Pasquarello, Alfredo

2014-10-01

279

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

280

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

281

Paraxial analysis of three-component zoom lens with fixed distance between object and image points and fixed position of image-space focal point.  

PubMed

This work performs an analysis of basic optical properties of zoom lenses with a fixed distance between object and image points and a fixed position of the image-space focal point. Formulas for the calculation of paraxial parameters of such optical systems are derived and the calculation is presented on examples. PMID:24977815

Miks, Antonin; Novak, Jiri

2014-06-30

282

High-precision satellite positioning system as a new tool to study the biomechanics of human locomotion.  

PubMed

New Global Positioning System (GPS) receivers allow now to measure a location on earth at high frequency (5Hz) with a centimetric precision using phase differential positioning method. We studied whether such technique was accurate enough to retrieve basic parameters of human locomotion. Eight subjects walked on an athletics track at four different imposed step frequencies (70-130steps/min) plus a run at free pace. Differential carrier phase localization between a fixed base station and the mobile antenna mounted on the walking person was calculated. In parallel, a triaxial accelerometer, attached to the low back, recorded body accelerations. The different parameters were averaged for 150 consecutive steps of each run for each subject (total of 6000 steps analyzed). We observed a perfect correlation between average step duration measured by accelerometer and by GPS (r=0.9998, N=40). Two important parameters for the calculation of the external work of walking were also analyzed, namely the vertical lift of the trunk and the velocity variation per step. For an average walking speed of 4.0km/h, average vertical lift and velocity variation were, respectively, 4.8cm and 0.60km/h. The average intra-individual step-to-step variability at a constant speed, which includes GPS errors and the biological gait style variation, were found to be 24. 5% (coefficient of variation) for vertical lift and 44.5% for velocity variation. It is concluded that GPS technique can provide useful biomechanical parameters for the analysis of an unlimited number of strides in an unconstrained free-living environment. PMID:11006399

Terrier, P; Ladetto, Q; Merminod, B; Schutz, Y

2000-12-01

283

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

PubMed

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

Itaguchi, Yoshihiro; Fukuzawa, Kazuyoshi

2013-11-01

284

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

NASA Astrophysics Data System (ADS)

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

Komatsu, K.

2009-12-01

285

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

NASA Astrophysics Data System (ADS)

Context. Coronal bright points (CBP) are ubiquitous small brightenings in the solar corona associated with small magnetic bipoles. Aims: 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 the detection of CBPs resulting from instrument and detection algorithm limitations. Methods: To determine the positions and identification of CBPs we used a segmentation algorithm. A linear fit of their central meridian distance and latitude vs time was used to derive velocities. Results: We obtained 906 velocity measurements in a time interval of only 2 days. The differential rotation profile can be expressed as ?rot = (14.47° ± 0.10° + (0.6° ± 1.0°) sin2(b) = (-4.7° ± 1.7°) sin4(b)) d-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 was made possible by the higher sensitivity and resolution of the AIA instrument compared to similar equipment as well as high cadence. The segmentation algorithm also played a crucial role by detecting so many CBPs, which reduced the errors to a reasonable level. Conclusions: Data and methods presented in this paper show a great potential for obtaining very accurate velocity profiles, both for rotation and meridional motion and, consequently, Reynolds stresses. The amount of CBP data that could be obtained from this instrument should also provide a great opportunity to study changes of velocity patterns with a temporal resolution of only a few months. Other possibilities are studies of evolution of CBPs and proper motions of magnetic elements on the Sun.

Sudar, D.; Skoki?, I.; Brajša, R.; Saar, S. H.

2015-03-01

286

Positive-streamer-like phenomena in point-plane corona gaps: Trichel pulses and high-pressure cathode sheath instabilities  

Microsoft Academic Search

Current pulse shapes have been measured in negative and positive corona discharges mostly in dry air. Negative corona Trichel pulses and pulses corresponding to the primary streamer\\/cathode contact in a positive point-plane gap were found to exhibit remarkable similarities, indicating a positive-streamer-like mechanism for the Trichel pulse development. High-frequency instabilities of the high-pressure filamentary glow discharge, which can be responsible

Mirko Cernák; Tatsuzo Hosokawa; Masayuki Inoshima

1990-01-01

287

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

NASA Astrophysics Data System (ADS)

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

Pástor, P.

2014-11-01

288

Positive-streamer-like phenomena in point-plane corona gaps: Trichel pulses and high-pressure cathode sheath instabilities  

NASA Astrophysics Data System (ADS)

Current pulse shapes have been measured in negative and positive corona discharges mostly in dry air. Negative corona Trichel pulses and pulses corresponding to the primary streamer/cathode contact in a positive point-plane gap were found to exhibit remarkable similarities, indicating a positive-streamer-like mechanism for the Trichel pulse development. High-frequency instabilities of the high-pressure filamentary glow discharge, which can be responsible for the arcing from freshly polished cathodes, were observed and attributed to local positive-streamer-like breakdowns of the cathode sheath.

Cernák, Mirko; Hosokawa, Tatsuzo; Inoshima, Masayuki

1990-07-01

289

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

290

A Search Algorithm for a Class of Optimal Finite-Precision Controller Realization Problems with Saddle Points  

E-print Network

with Saddle Points Jun Wu , Sheng Chen 0, Gang Li § and Jian Chu National Key Laboratory of Industrial implementation can have a serious influence on the actual performance of a digital closed-loop control system [1 critical influence on closed-loop stability [6]­[12]. Typically, these two types of errors are investigated

Chen, Sheng

291

Exact Solutions of the Schr\\"{o}dinger Equation with position-dependent effective mass via general point canonical transformation  

E-print Network

Exact solutions of the Schrodinger equation are obtained for the Rosen-Morse and Scarf potentials with the position-dependent effective mass by appliying a general point canonical transformation. The general form of the point canonical transformation is introduced by using a free parameter. Two different forms of mass distributions are used. A set of the energy eigenvalues of the bound states and corresponding wave functions for target potentials are obtained as a function of the free parameter.

Tezcan, C; Tezcan, Cevdet; Sever, Ramazan

2006-01-01

292

Exact Solutions of the Schrödinger Equation with position-dependent effective mass via general point canonical transformation  

E-print Network

Exact solutions of the Schrodinger equation are obtained for the Rosen-Morse and Scarf potentials with the position-dependent effective mass by appliying a general point canonical transformation. The general form of the point canonical transformation is introduced by using a free parameter. Two different forms of mass distributions are used. A set of the energy eigenvalues of the bound states and corresponding wave functions for target potentials are obtained as a function of the free parameter.

Cevdet Tezcan; Ramazan Sever

2006-04-06

293

Accuracy and precision of point-of-care testing for glucose and prothrombin time at the critical care units  

Microsoft Academic Search

The use of point-of-care testing (POCT) in critical care patient units has continued to increase since the 1980s. This increase is due to the need for prompt therapeutic interventions that may impact mortality and morbidity, and reduce the overall cost of healthcare for critically ill patients. The diagnostic manufacturing industry has risen to this challenge by introducing portable and\\/or handheld

Cecilia Yuoh; M Tarek Elghetany; John R Petersen; Amin Mohammad; Anthony O Okorodudu

2001-01-01

294

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

295

Design and analysis of a novel 6DOF redundant actuated parallel robot with compliant hinges for high precision positioning  

Microsoft Academic Search

This paper presents the design and modeling of a new 6-DOF 8-PSS\\/SPS compliant dual redundant parallel robot with wide-range\\u000a flexure hinges. This robot can achieve either high accurate positioning or rough positioning as well as a 6-DOF active vibration\\u000a isolation and excitation to the payload placed on the moving platform. Adopting a kind of wide-range flexure hinge, we establish\\u000a the

Yuan Yun; Yangmin Li

2010-01-01

296

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

Microsoft Academic Search

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

Dariusz Sawicki

2005-01-01

297

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

298

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

ERIC Educational Resources Information Center

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…

Yair, Gad

2009-01-01

299

Experimental analysis and simulation of nonlinear microscopic behavior of ball screw mechanism for ultra-precision positioning  

Microsoft Academic Search

In this paper, microscopic behavior of a preloaded ball screw supported by ball bearings is discussed based on experimental results and simulation. An experimental apparatus is specially designed and constructed to independently measure the torques of ball screw, ball bearings supporting the screw shaft and driving motor. It is clarified experimentally that the nonlinear microscopic behavior of a positioning mechanism

Shigeo Fukada; Bin Fang; Akira Shigeno

2011-01-01

300

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

301

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

302

A FRAMEWORK FOR POSITION UNCERTAINTY OF UNORGANISED THREE-DIMENSIONAL POINT CLOUDS FROM NEAR-MONOSTATIC LASER SCANNERS USING COVARIANCE ANALYSIS  

Microsoft Academic Search

Position uncertainty is one of the most important quantities of an unorganised three-dimensional point clouds since it provides the confidence level of any parametric estimation such as surface normal vector estimation and the registration of point clouds. We present an explicit form of position uncertainty based on the covariance analysis of a point. In addition, an explicit form of the

Kwang-Ho Bae; David Belton; Derek D. Lichti

2005-01-01

303

A study of the application of differential techniques to the global positioning system for a helicopter precision approach  

NASA Technical Reports Server (NTRS)

The results of a simulation study to define the functional characteristics of a airborne and ground reference GPS receiver for use in a Differential GPS system are doumented. The operations of a variety of receiver types (sequential-single channel, continuous multi-channel, etc.) are evaluated for a typical civil helicopter mission scenario. The math model of each receiver type incorporated representative system errors including intentional degradation. The results include the discussion of the receiver relative performance, the spatial correlative properties of individual range error sources, and the navigation algorithm used to smooth the position data.

Mccall, D. L.

1984-01-01

304

Stable fixed points of the Einstein flow with positive cosmological constant  

E-print Network

We give a concise proof of nonlinear stability for a large class of solutions to the Einstein equations with a positive cosmological constant and compact spatial topology, where the spatial metric is Einstein with either positive or negative Einstein constant. The proof uses the CMC Einstein flow and stability follows by an energy argument. We prove in addition that the development of non-CMC initial data close to the background contains a CMC hypersurface, which in turn implies that stability holds for arbitrary perturbations. Furthermore, we construct a one-parameter family of initial data such that above a critical parameter value the corresponding development is future and past incomplete.

Fajman, David

2015-01-01

305

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

PubMed

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

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

2011-12-01

306

a Precise Measurement of the Position of the Source of Giant and Rapid Variability in the NLS1 13224-3809  

NASA Astrophysics Data System (ADS)

Within a 30 day ROSAT HRI monitoring observations we have detected the strongest persistent X-ray variability known in a Seyfert galaxy. At least 5 giant amplitude variations with a factor of about 60 are visible. Unusually strong relativistic boosting effects provide the most plausible explanation of the X-ray data. We propose to use AXAF for a precise measurement of the position of the source of the strong variability to further proof that the X-rays we measure are associated with the distant galaxy. We expect about 500 HRC photons within 10 ks observing time. We may further improve the HRG position using serendipitous X-ray sources detected previously with the HRI that have counterparts in the Optical.

Predehl, Peter

1999-09-01

307

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

308

The organization of roots of dicotyledonous plants and the positions of control points  

PubMed Central

Background The structure of roots has been studied for many years, but despite their importance to the growth and well-being of plants, most researchers tend to ignore them. This is unfortunate, because their simple body plan makes it possible to study complex developmental pathways without the complications sometimes found in the shoot. In this illustrated essay, my objective is to describe the body plan of the root and the root apical meristem (RAM) and point out the control points where differentiation and cell cycle decisions are made. Hopefully this outline will assist plant biologists in identifying the structural context for their observations. Scope and Conclusions This short paper outlines the types of RAM, i.e. basic-open, intermediate-open and closed, shows how they are similar and different, and makes the point that the structure and shape of the RAM are not static, but changes in shape, size and organization occur depending on root growth rate and development stage. RAMs with a closed organization lose their outer root cap layers in sheets of dead cells, while those with an open organization release living border cells from the outer surfaces of the root cap. This observation suggests a possible difference in the mechanisms whereby roots with different RAM types communicate with soil-borne micro-organisms. The root body is organized in cylinders, sectors (xylem and phloem in the vascular cylinder), cell files, packets and modules, and individual cells. The differentiation in these root development units is regulated at control points where genetic regulation is needed, and the location of these tissue-specific control points can be modulated as a function of root growth rate. In Arabidopsis thaliana the epidermis and peripheral root cap develop through a highly regulated series of steps starting with a periclinal division of an initial cell, the root cap/protoderm (RCP) initial. The derivative cells from the RCP initial divide into two cells, the inner cell divides again to renew the RCP and the other cell divides through four cycles to form 16 epidermal cells in a packet; the outer cell divides through four cycles to form the 16 cells making up the peripheral root cap packet. Together, the epidermal packet and the peripheral root cap packet make up a module of cells which are clonally related. PMID:21118839

Rost, Thomas L.

2011-01-01

309

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

Microsoft Academic Search

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

Oliver Montenbruck; Markus Markgraf

2004-01-01

310

EMAS position statement: The ten point guide to the integral management of menopausal health.  

PubMed

With increased longevity and more women becoming centenarians, management of the menopause and postreproductive health is of growing importance as it has the potential to help promote health over several decades. Women have individual needs and the approach needs to be personalised. The position statement provides a short integral guide for all those involved in menopausal health. It covers diagnosis, screening for diseases in later life, treatment and follow-up. PMID:25757366

Neves-E-Castro, Manuel; Birkhauser, Martin; Samsioe, Goran; Lambrinoudaki, Irene; Palacios, Santiago; Borrego, Rafael Sanchez; Llaneza, Placido; Ceausu, Iuliana; Depypere, Herman; Erel, C Tamer; Pérez-López, Faustino R; Schenck-Gustafsson, Karin; van der Schouw, Yvonne T; Simoncini, Tommaso; Tremollieres, Florence; Rees, Margaret

2015-05-01

311

Tuning the Dirac Point Position in Bi2Se3(0001) via Surface Carbon Doping  

NASA Astrophysics Data System (ADS)

Angular resolved photoemission spectroscopy in combination with ab initio calculations show that trace amounts of carbon doping of the Bi2Se3 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.

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.

2014-09-01

312

Extended precision software packages  

NASA Technical Reports Server (NTRS)

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

Phillips, E. J.

1972-01-01

313

Sensitivity Analysis for Reactor Period Induced by Positive Reactivity Using One-point Adjoint Kinetic Equation  

NASA Astrophysics Data System (ADS)

In order to better predict a kinetic behavior of a nuclear fission reactor, an improvement of the delayed neutron parameters is essential. The present paper specifies important nuclear data for a reactor kinetics: Fission yield and decay constant data of 86Ge, some bromine isotopes, 94Rb, 98mY and some iodine isotopes. Their importance is quantified as sensitivities with a help of the adjoint kinetic equation, and it is found that they are dependent on an inserted reactivity (or a reactor period). Moreover, dependence of sensitivities on nuclear data files is also quantified using the latest files. Even though the currently evaluated data are used, there are large differences among different data files from a view point of the delayed neutrons.

Chiba, G.; Tsuji, M.; Narabayashi, T.

2014-04-01

314

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

315

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

316

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

317

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

318

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

319

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

PubMed Central

When related to a single and good contrast object or a laser spot, position sensing, or sensitive, detectors (PSDs) have a series of advantages over the classical camera sensors, including a good positioning accuracy for a fast response time and very simple signal conditioning circuits. To test the performance of this kind of sensor for microrobotics, we have made a comparative analysis between a precise but slow video camera and a custom-made fast PSD system applied to the tracking of a diffuse-reflectivity object transported by a pneumatic microconveyor called Smart-Surface. Until now, the fast system dynamics prevented the full control of the smart surface by visual servoing, unless using a very expensive high frame rate camera. We have built and tested a custom and low cost PSD-based embedded circuit, optically connected with a camera to a single objective by means of a beam splitter. A stroboscopic light source enhanced the resolution. The obtained results showed a good linearity and a fast (over 500 frames per second) response time which will enable future closed-loop control by using PSD. PMID:23223078

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

2012-01-01

320

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

321

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

322

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

NASA Astrophysics Data System (ADS)

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

Naus, Krzysztof; Szulc, Dariusz

2014-06-01

323

Paraxial analysis of zoom lens composed of three tunable-focus elements with fixed position of image-space focal point and object-image distance.  

PubMed

This work performs a paraxial analysis of three-component zoom lens with a fixed position of image-space focal point and a distance between object and image points, which is composed of three tunable-focus elements. Formulas for the calculation of paraxial parameters of such optical systems are derived and the calculation is presented on examples. PMID:25401855

Miks, Antonin; Novak, Jiri

2014-11-01

324

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

325

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

326

Sensing Position With Approximately Constant Contact Force  

NASA Technical Reports Server (NTRS)

Computer-controlled electromechanical system uses number of linear variable-differential transformers (LVDTs) to measure axial positions of selected points on surface of lens, mirror, or other precise optical component with high finish. Pressures applied to pneumatically driven LVDTs adjusted to maintain small, approximately constant contact forces as positions of LVDT tips vary.

Sturdevant, Jay

1996-01-01

327

Study on Edge Detection of LIDAR Point Cloud  

Microsoft Academic Search

The LIDAR points should be interpolated to grids by the method of the edge detection with images directly. That will damage the position precision of the edge points. This paper proposes methods of using height difference and the spatial structure information of points cloud. The methods transition from 2D level to 3D level, they get a clear edge, retains the

Rongrong Wang; Xudong Lai; Wenguang Hou

2011-01-01

328

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

329

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

Microsoft Academic Search

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

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

2012-01-01

330

Novel active pointing system for point-to-point optical communication  

NASA Astrophysics Data System (ADS)

A unique active pointing system for point-to-point optical communications capitalizes on the limited angular travel requirements to achieve a high angular precision, frictionless, lubrication-free design, at a price point consistent with commercial production. Gimbal components and three design configurations were traded for performance, cost, reliability, and technical risk. A gimbal ring configuration with voice coil actuators, flexure bearings, and LVDT position sensors was selected as the baseline, and prototypes were fabricated and assembled. Servo integration and testing is ongoing, which will be followed by commercial production.

Hiley, David J.; Mecherle, G. Stephen; Decanini, J.

2001-06-01

331

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

332

Precision positioning of a three-axis optical pickup via a double phase-lead compensator equipped with auto-tuned parameters  

Microsoft Academic Search

The objective of this study is to design an intelligent control servo scheme for the three-axis optical pickups employed in\\u000a the next-generation optical disc drives. The three-axis pickup owns the capability to move the lens holder in three directions\\u000a of focusing, tracking and tilting, which is required particularly for higher data-density optical disks and precision measuring\\u000a instruments to annihilate non-zero

Paul C.-P. Chao; Chi-Wei Chiu; Jackal C.-Y. Shen

2010-01-01

333

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

334

Precise tuning technique of frequency conversion crystals of SG facility  

NASA Astrophysics Data System (ADS)

To assure that the frequency conversion crystals of SG facility are always being in the best shot position, and have the highest energy conversion efficiency with various beam conducting directions, we researched the precise tuning technique of frequency conversion crystals with the SG facility. The on-line quick tuning method of target point detecting with preshot was used in precise tuning of crystal match angle, and helped to correct the off-line match angle satisfactorily. With crystal alignment technique and crystal accompany technique, the precise tuning of crystal match angle can assure the crystals to maintain a stable high efficiency in a long experiment period.

Zhang, Fan; Zhong, Wei; Jia, Huai Ting; Wang, YuanCheng; Guo, HuaiWen; Deng, XueWei; Zhou, Wei

2015-02-01

335

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

ERIC Educational Resources Information Center

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

Group of Eight (NJ1), 2010

2010-01-01

336

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

SciTech Connect

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

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

1991-01-01

337

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

338

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

339

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

340

High-precision hydraulic Stewart platform  

NASA Astrophysics Data System (ADS)

We present a novel design for a Stewart platform (or hexapod), an apparatus which performs positioning tasks with high accuracy. The platform, which is supported by six hydraulic telescopic struts, provides six degrees of freedom with 1 ?m resolution. Rotations about user defined pivot points can be specified for any axis of rotation with microradian accuracy. Motion of the platform is performed by changing the strut lengths. Servo systems set and maintain the length of the struts to high precision using proportional hydraulic valves and incremental encoders. The combination of hydraulic actuators and a design which is optimized in terms of mechanical stiffness enables the platform to manipulate loads of up to 20 kN. Sophisticated software allows direct six-axis positioning including true path control. Our platform is an ideal support structure for a large variety of scientific instruments that require a stable alignment base with high-precision motion.

van Silfhout, Roelof G.

1999-08-01

341

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

342

Precision and sensitivity of the measurement of 15N enrichment in D-alanine from bacterial cell walls using positive/negative ion mass spectrometry  

NASA Technical Reports Server (NTRS)

Sensitive detection of cellular components from specific groups of microbes can be utilized as 'signatures' in the examination of microbial consortia from soils, sediments or biofilms. Utilizing capillary gas chromatography/mass spectrometry and stereospecific derivatizing agents, D-alanine, a component localized in the prokaryotic (bacterial) cell wall, can be detected reproducibly. Enrichments of D-[15N]alanine determined in E. coli grown with [15N]ammonia can be determined with precision at 1.0 atom%. Chemical ionization with methane gas and the detection of negative ions (M - HF)- and (M - F or M + H - HF)- formed from the heptafluorobutyryl D-2 butanol ester of D-alanine allowed as little as 8 pg (90 fmol) to be detected reproducibly. This method can be utilized to define the metabolic activity in terms of 15N incorporation at the level of 10(3)-10(4) cells, as a function of the 15N-14N ratio.

Tunlid, A.; Odham, G.; Findlay, R. H.; White, D. C.

1985-01-01

343

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

Microsoft Academic Search

Motivated by the realization of the Dirac point (DP) with a double-cone structure for optical field in the negative-zero-positive index metamaterial (NZPIM), the reflection, transmission, and Goos-Hänchen (GH) shifts inside the NZPIM slab are investigated. Due to the linear Dirac dispersion, the transmission as the function of the frequency has a gap, thus, the corresponding reflection has a frequency or

Xi Chen; Li-Gang Wang; Chun-Fang Li

2009-01-01

344

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

Microsoft Academic Search

Motivated by the realization of the Dirac point (DP) with a double-cone structure for optical field in the negative-zero-positive index metamaterial (NZPIM), the reflection, transmission, and Goos-Haenchen (GH) shifts inside the NZPIM slab are investigated. Due to the linear Dirac dispersion, the transmission as the function of the frequency has a gap, thus, the corresponding reflection has a frequency or

Chen Xi; Wang Ligang; Li Chunfang

2009-01-01

345

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

346

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

347

Mapped Landmark Algorithm for Precision Landing  

NASA Technical Reports Server (NTRS)

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

Johnson, Andrew; Ansar, Adnan; Matthies, Larry

2007-01-01

348

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

NASA Astrophysics Data System (ADS)

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

Chen, Xi; Wang, Li-Gang; Li, Chun-Fang

2009-10-01

349

Transmission gap, Bragg-like reflection, and Goos-H\\"{a}nchen shifts near the Dirac point inside a negative-zero-positive index metamaterial slab  

E-print Network

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

Chen, Xi; Li, Chun-Fang

2009-01-01

350

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

SciTech Connect

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

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

2009-10-15

351

A non-radioactive assay for precise determination of intracellular levels of imatinib and its main metabolite in Bcr-Abl positive cells.  

PubMed

Multidrug resistance (MDR) is often associated with overexpression of the P-glycoprotein (P-gp, ABCB1). It was demonstrated that the P-gp mediated efflux decreases the drug concentration in cancer cells which results in the failure of chemotherapy. However, the MDR phenotype in cancer cells obviously involves various mechanisms. Therefore, if we want to estimate a contribution of the P-gp expression to the MDR phenotype, a clear quantitative relationship between the intracellular drug level and cell sensitivity must be established. To achieve this goal, a sensitive and non-radioactive assay for precise determination of intracellular levels of imatinib and its main metabolite N-desmethyl imatinib (CGP 74588) has been developed. The assay is based on an optimised extraction of cells with 4% formic acid after their separation from the growth medium by centrifugation through a layer of silicone oil. Cell extracts are subsequently analyzed by LC/MS/MS. Calibration curves were linear from 1 to 500 nmol/l for imatinib and from 2 to 500 nmol/l for CGP 74588, with correlation coefficients (r(2)) better than 0.998 and 0.996, respectively. The limit of quantitation (LOQ) was 1 nmol/l for imatinib and 2 nmol/l for CGP 74588. Our method has been successfully applied to the determination of intracellular levels of imatinib in sensitive K562 and their resistant variant, K562/Dox cells. PMID:21238737

Mlejnek, Petr; Novak, Ondrej; Dolezel, Petr

2011-02-15

352

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

353

Practicing Precision  

E-print Network

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

Supercinski, Danielle

2007-01-01

354

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

355

Position-addressable digital laser scanning point fluorescence microscopy with a Blu-ray disk pickup head  

PubMed Central

A compact and position-addressable blue ray scanning microscope (BSM) based on a commercially available Blu-ray disk pickup head (PUH) is developed for cell imaging with high resolution and low cost. The BSM comprises two objective lenses with numerical apertures (NAs) of 0.85 and 0.6 for focusing blue and red laser beams, respectively, on the sample slide. The blue and red laser beams are co-located adjacent to each other and move synchronously. A specially designed sample slide is used with a sample area and an address-patterned area for sample holding and address recognition, respectively. The blue laser beam is focused on the sample area and is used for fluorescent excitation and image capturing, whereas the red laser beam is focused on the address-patterned area and is used for address recognition and dynamic focusing. The address-patterned area is divided into 310 sectors. The cell image of each sector of the sampling area has a corresponding address pattern. Fluorescence images of monkey-derived kidney epithelial cells and fibroblast cells in which the F-actin is stained with fluorophore phalloidin CF 405 are measured by the BSM, with results comparable to those measured by a Leica TCS CP2 confocal microscope. The cell image of an area of interest can be easily tracked based on the coded address, and a large-area sample image can be accurately reconstructed from the sector images. PMID:24575338

Tsai, Rung-Ywan; Chen, Jung-Po; Lee, Yuan-Chin; Huang, Chun-Chieh; Huang, Tai-Ting; Chiang, Hung-Chih; Cheng, Chih-Ming; Lo, Feng-Hsiang; Chang, Sheng-Li; Weng, Kuo-Yao; Chung, Lung-Pin; Chen, Jyh-Chern; Tiao, Golden

2014-01-01

356

Position-addressable digital laser scanning point fluorescence microscopy with a Blu-ray disk pickup head.  

PubMed

A compact and position-addressable blue ray scanning microscope (BSM) based on a commercially available Blu-ray disk pickup head (PUH) is developed for cell imaging with high resolution and low cost. The BSM comprises two objective lenses with numerical apertures (NAs) of 0.85 and 0.6 for focusing blue and red laser beams, respectively, on the sample slide. The blue and red laser beams are co-located adjacent to each other and move synchronously. A specially designed sample slide is used with a sample area and an address-patterned area for sample holding and address recognition, respectively. The blue laser beam is focused on the sample area and is used for fluorescent excitation and image capturing, whereas the red laser beam is focused on the address-patterned area and is used for address recognition and dynamic focusing. The address-patterned area is divided into 310 sectors. The cell image of each sector of the sampling area has a corresponding address pattern. Fluorescence images of monkey-derived kidney epithelial cells and fibroblast cells in which the F-actin is stained with fluorophore phalloidin CF 405 are measured by the BSM, with results comparable to those measured by a Leica TCS CP2 confocal microscope. The cell image of an area of interest can be easily tracked based on the coded address, and a large-area sample image can be accurately reconstructed from the sector images. PMID:24575338

Tsai, Rung-Ywan; Chen, Jung-Po; Lee, Yuan-Chin; Huang, Chun-Chieh; Huang, Tai-Ting; Chiang, Hung-Chih; Cheng, Chih-Ming; Lo, Feng-Hsiang; Chang, Sheng-Li; Weng, Kuo-Yao; Chung, Lung-Pin; Chen, Jyh-Chern; Tiao, Golden

2014-02-01

357

Precision Manipulation with Cooperative Robots  

Microsoft Academic Search

We present a cooperative approach to robotic precision manipulation tasks in the context of autonomous robotic construction. Precision manipulation requires a firm grasp, which constraints the team to rigidly maintain formation during transport and manipulation. A leader\\/follower approach with force sensing to provide relative formation information and vision to provide team position relative to construction components is applied. Our approach

Ashley Stroupe; Terry Huntsberger; Avi Okon; Hrand Aghazarian

358

Precision gap particle separator  

DOEpatents

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

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

2004-06-08

359

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

360

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

361

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

362

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...

363

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

364

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

365

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

366

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,

367

How people achieve their amazing temporal precision in interception.  

PubMed

People can hit rapidly moving balls with amazing precision. To determine how they manage to do so, we explored how various factors that we could manipulate influenced people's precision when intercepting virtual targets. We found that temporal precision was highest for fast targets that subjects were free to intercept wherever they wished. Temporal precision was much poorer when the point of interception was specified in advance. Examining responses to abrupt perturbations of the target's motion revealed that people adjusted where rather than when they would hit the target if given the choice. A model that combines judging how long it will take to reach the target's path with estimating the target's position at that time from its visually perceived position and velocity could account for the observed precision with reasonable values for all the parameters. The model considers all relevant sources of errors, together with the delays with which the various aspects can be adjusted. Our analysis provides a biologically plausible explanation for how light falling on the eye can guide the hand to intercept a moving ball with such high precision. PMID:25767094

Brenner, Eli; Smeets, Jeroen B J

2015-01-01

368

Precision muon lifetime at PSI  

NASA Astrophysics Data System (ADS)

The goal of MuLan, positive muon lifetime measurement, is the measurement of the positive muon lifetime to 1 ppm, which will in turn determine the Fermi coupling constant GF to 0.5 ppm precision. We will describe our experimental efforts and latest achievements.

Mulhauser, Françoise; MuLan Collaboration [1

2006-05-01

369

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

370

Precision Machining  

NSDL National Science Digital Library

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

Leske, Cavin.

371

Precision GPS ephemerides and baselines  

NASA Technical Reports Server (NTRS)

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

1991-01-01

372

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

373

Precision Astrometry with Adaptive Optics  

E-print Network

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

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

2008-05-14

374

Precision Astronomy with Imperfect Deep Depletion CCDs  

NASA Astrophysics Data System (ADS)

While thick CCDs do provide definite advantages in terms of increased quantum efficiency at wavelengths 700 nmprecision determination of the positions, fluxes, and shapes of astronomical objects, and for the precision extraction of features in astronomical spectra. For example, the assumptions of a perfectly rectilinear pixel grid and of an intensity-independent point spread function become increasingly invalid as we push to higher precision measurements. Many of the effects seen in these devices arise from lateral electrical fields within the detector, that produce charge transport anomalies that have been previously misinterpreted as quantum efficiency variations. Performing simplistic flat-fielding therefore introduces systematic errors in the image processing pipeline. One measurement challenge we face is devising a combination of calibration methods and algorithms that can distinguish genuine quantum efficiency variations from charge transport effects. These device imperfections also confront spectroscopic applications, such as line centroid determination for precision radial velocity studies. Given the scientific benefits of improving both the precision and accuracy of astronomical measurements, we need to identify, characterize, and overcome these various detector artifacts. In retrospect, many of the detector features first identified in thick CCDs also afflict measurements made with more traditional CCD detectors, albeit often at a reduced level since the photocharge is subject to the perturbing influence of lateral electric fields for a shorter time interval. I provide a qualitative overview of the physical effects we think are responsible for the observed device properties, and provide some perspective for the work that lies ahead.

Stubbs, Christopher; LSST Sensor Team; PanSTARRS Team

2014-01-01

375

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

PubMed

Because the variation in chlorine isotopic abundances of naturally occurring chlorine bearing substances is significant, the IUPAC Inorganic Chemistry Division, Commission on Isotopic Abundances and Atomic Weights (CIAAW-IUPAC) decided that the uncertainty of atomic weight of chlorine (A(r)(Cl)) should be increased so that the implied range was related to terrestrial variability in 1999 (Coplen, T. B. Atomic weights of the elements 1999 (IUPAC Technical Report), Pure Appl. Chem.2001, 73(4), 667-683; and then, it emphasized that the standard atomic weights of ten elements including chlorine were not constants of nature but depend upon the physical, chemical, and nuclear history of the materials in 2009 (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396). According to the agreement by CIAAW that an atomic weight could be defined for one specified sample of terrestrial origin (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396), the absolute isotope ratios and atomic weight of chlorine in standard reference materials (NIST 975, NIST 975a, ISL 354) were accurately determined using the high-precision positive thermal ionization mass spectrometer (PTIMS)-Cs(2)Cl(+)-graphite method. After eliminating the weighing error caused from evaporation by designing a special weighing container and accurately determining the chlorine contents in two highly enriched Na(37)Cl and Na(35)Cl salts by the current constant coulometric titration, one series of gravimetric synthetic mixtures prepared from two highly enriched Na(37)Cl and Na(35)Cl salts was used to calibrate two thermal ionization mass spectrometers in two individual laboratories. The correction factors (i.e., K(37/35) = R(37/35meas)/R(37/35calc)) were obtained from five cycles of iterative calculations on the basis of calculated and determined R((37)Cl/(35)Cl) values in gravimetric synthetic mixtures. The absolute R((37)Cl/(35)Cl) ratios for NIST SRM 975, NIST 975a, and ISL 354 by the precise calibrated isotopic composition measurements are 0.319876 ± 0.000067, 0.319768 ± 0.000187, and 0.319549 ± 0.000044, respectively. As a result, the atomic weights of chlorine in NIST 975, NIST 975a, and ISL 354 are derived as 35.45284(8), 35.45272(21), and 35.45252(2) individually, which are consistent with the issued values of 35.453(2) by IUPAC in 1999. PMID:23088631

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

2012-12-01

376

Tracking the key point of a building in infrared imaging guidance  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

377

Workpiece fixturing for precision machining  

SciTech Connect

To keep within the tolerances required in precision machining workpiece fixturing has to ensure minimal distortion of the part. Some of the methods used at the Oak Ridge Y-12 Plant are reviewed. Significant factors are discussed and three-point mounting, vacuum fixturing and potting are described.

Barkman, W.E.

1982-04-01

378

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

379

Precision GPS ephemerides and baselines  

NASA Technical Reports Server (NTRS)

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

1992-01-01

380

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

381

Space Technology 7 Disturbance Reduction System - precision control flight Validation  

NASA Technical Reports Server (NTRS)

The NASA New Millennium Program Space Technology 7 (ST7) project will validate technology for precision spacecraft control. The Disturbance Reduction System (DRS) will be part of the European Space Agency's LISA Pathfinder project. The DRS will control the position of the spacecraft relative to a reference to an accuracy of one nanometer over time scales of several thousand seconds. To perform the control, the spacecraft will use a new colloid thruster technology. The thrusters will operate over the range of 5 to 30 micro-Newtons with precision of 0.1 micro- Newton. The thrust will be generated by using a high electric field to extract charged droplets of a conducting colloid fluid and accelerating them with a precisely adjustable voltage. The control reference will be provided by the European LISA Technology Package, which will include two nearly freefloating test masses. The test mass positions and orientations will be measured using a capacitance bridge. The test mass position and attitude will be adjustable using electrostatically applied forces and torques. The DRS will control the spacecraft position with respect to one test mass while minimizing disturbances on the second test mass. The dynamic control system will cover eighteen degrees of freedom: six for each of the test masses and six for the spacecraft. After launch in late 2009 to a low Earth orbit, the LISA Pathfinder spacecraft will be maneuvered to a halo orbit about the Earth-Sun L1 Lagrange point for operations.

Carmain, Andrew J.; Dunn, Charles; Folkner, William; Hruby, Vlad; Spence, Doug; O'Donnell, James; Markley, Landis; Maghami, Peiman; Hsu, Oscar; Demmons, N.; Roy, T.; Gasdaska, C.; Young, J.; Connolly, W.; McCormick, R.; Gasdaska, C.

2005-01-01

382

Precision measurements in supersymmetry  

SciTech Connect

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

Feng, J.L.

1995-05-01

383

Precision requirements do not affect the allocation of visual working memory capacity.  

PubMed

There has been a debate about whether allocation of visual working memory (VWM) capacity was flexible. One of the key points about this issue is whether complexity has an effect on the capacity, and one of the critical features of complex objects is higher requirements on the encoding precision than simple objects. Thus we investigated the influence of precision requirements on the allocation of VWM capacity resources, by comparing VWM capacity under different levels of sample-test similarity in a change-detection task. If the VWM capacity is limited by a fixed number of items, then the capacity should not be affected by precision requirements; however, if the capacity is allocated flexibly, then precision requirements should influence the capacity. Cowan's K and amplitude of contralateral delay activity (CDA) were used as behavioral and neurophysiological measures of VWM capacity, respectively. Cowan's K for high-precision discrimination was calculated on the basis of the accuracy of a small number of large-change trials inserted into high-precision blocks. This approach avoided the confounder of different test-phase difficulties between the low- and high-precision conditions and controlled for errors during the test phase. The results showed no effect of precision requirements on VWM capacity. However, analysis of the late positive component (LPC) amplitude indicated that higher precision requirements indeed caused more top-down control over VWM retention. These results support the hypothesis that VWM is limited by a fixed number of items. PMID:25625356

He, Xu; Zhang, Weiwei; Li, Cuihong; Guo, Chunyan

2015-03-30

384

Precision Joining Center  

SciTech Connect

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

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

1991-08-01

385

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

Microsoft Academic Search

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

Frederic Lassabe; Philippe Canalda; Pascal Chatonnay; Damien Charlet

2006-01-01

386

Pitfalls in precision stereotactic surgery  

PubMed Central

Precision is the ultimate aim of stereotactic technique. Demands on stereotactic precision reach a pinnacle in stereotactic functional neurosurgery. Pitfalls are best avoided by possessing in-depth knowledge of the techniques employed and the equipment used. The engineering principles of arc-centered stereotactic frames maximize surgical precision at the target, irrespective of the surgical trajectory, and provide the greatest degree of surgical precision in current clinical practice. Stereotactic magnetic resonance imaging (MRI) provides a method of visualizing intracranial structures and fiducial markers on the same image without introducing significant errors during an image fusion process. Although image distortion may potentially limit the utility of stereotactic MRI, near-complete distortion correction can be reliably achieved with modern machines. Precision is dependent on minimizing errors at every step of the stereotactic procedure. These steps are considered in turn and include frame application, image acquisition, image manipulation, surgical planning of target and trajectory, patient positioning and the surgical procedure itself. Audit is essential to monitor and improve performance in clinical practice. The level of stereotactic precision is best analyzed by routine postoperative stereotactic MRI. This allows the stereotactic and anatomical location of the intervention to be compared with the anatomy and coordinates of the intended target, avoiding significant image fusion errors. PMID:22826812

Zrinzo, Ludvic

2012-01-01

387

A precise calculation of the Feigenbaum constants  

NASA Astrophysics Data System (ADS)

The Feigenbaum constants arise in the theory of iteration of real functions. We calculate here to high precision the constants ? and ? associated with period-doubling bifurcations for maps with a single maximum of order z, for 2 ? z ? 12 . Multiple-precision floating-point techniques are used to find a solution of Feigenbaum's functional equation, and hence the constants.

Briggs, Keith

1991-07-01

388

Ultra-precision processes for optics manufacturing  

NASA Technical Reports Server (NTRS)

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

Martin, William R.

1991-01-01

389

Precise control of flexible manipulators  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

390

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, William J. (Kansas City, MO)

1986-01-01

391

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

392

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

393

Precise Autohover Control For A Helicopter  

NASA Technical Reports Server (NTRS)

Report describes development and testing of experimental precise autohover control system for helicopter. Attempts to maintain constant horizontal position. Part of continuing effort to develop such systems for next generation of military rotorcraft.

Hindson, W. S.; Tucker, G. E.

1991-01-01

394

MERLIN-2.1 double precision  

NASA Astrophysics Data System (ADS)

MERLIN-2.1 is an adaptation of the MERLIN-2.0 package, mainly designed to run on computers using 32-bit floating point arithmetic. The standard Merlin-2.0 on such machines, achieves a precision of 7 significant digits at most. This is insufficient since in many real problems a higher precision is required. MERLIN-2.1 treats this inadequacy using double precision operations, enhancing so the precision up to about 14 significant digits, in the standard user-friendly Merlin environment.

Papageorgiou, D. G.; Lagaris, I. E.

1990-02-01

395

Precision photometry for planetary transits  

E-print Network

We review the state of the art in follow-up photometry for planetary transit searches. Three topics are discussed: (1) Photometric monitoring of planets discovered by radial velocity to detect possible transits (2) Follow-up photometry of candidates from photometric transit searches to weed out eclipsing binaries and false positives (3) High-precision lightcurves of known transiting planets to increase the accuracy on the planet parameters.

Frederic Pont; Claire Moutou

2007-02-06

396

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

397

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

398

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

ERIC Educational Resources Information Center

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

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

2010-01-01

399

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

PubMed

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

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

2013-01-01

400

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

Microsoft Academic Search

Objective: Determine the effects of a short-term, multi-faceted, point-of-selection intervention on college students’ perceptions and selection of 10 targeted healthful foods in a university dining hall and changes in their self-reported overall eating behaviors. Participants: 104 college students, (age 18–23) completed pre-I and post-I surveys. Methods: Pre-survey collected at dining hall in April 2007, followed by 3-week intervention then post-survey

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

2010-01-01

401

High precision numerical accuracy in physics research  

NASA Astrophysics Data System (ADS)

Concerns arise that the current standard of double-precision floating-point may no longer be sufficient for today's large-scale numerical simulations. One approach to solve this problem will be to switch to a wider floating-point format: the upcoming quadruple-precision standard is introduced and compared to currently available software-based approaches. Another complimentary approach is to use mathematical and algorithmic techniques to improve the accuracy of large floating-point programs and the confidence in the quality of the result.

de Dinechin, Florent; Villard, Gilles

2006-04-01

402

Stereo optical tracker for standoff monitoring of position and orientation  

NASA Astrophysics Data System (ADS)

A Precision Optical Measurement System (POMS) has been designed, constructed and tested for tracking the position (x, y, z) and orientation (roll, pitch, yaw) of models in Boeing's 9-77 Compact Radar Range. A stereo triangulation technique is implemented using two remote sensor units separated by a known baseline. Each unit measures pointing angles (azimuth and elevation) to optical targets on a model. Four different reference systems are used for calibration and alignment of the system's components and two platforms. Pointing angle data and calibration corrections are processed at high rates to give near real-time feedback to the mechanical positioning system of the model. The positional accuracy of the system is +/- .010 inches at a distance of 85 feet while using low RCS reflective tape targets. The precision measurement capabilities and applications of the system are discussed.

Sherman, W. D.; Houk, T. L.; Saint Clair, J. M.; Sjoholm, P. F.; Voth, M. D.

2009-01-01

403

High precision calibration for 2D optical standard  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

404

Low Cost Precision Lander for Lunar Exploration  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

405

Precise Electrochemical Drilling of Repeated Deep Holes  

NASA Technical Reports Server (NTRS)

Tooling enables maintenance of close tolerances. Tooling includes guide that holds electrochemical drilling electrodes in proper relative alinement and guide-positioning fixture clamps directly on reference surfaces of strut. High precision achieved by positioning tooling anew on each strut before drilling: Tolerances of (0.008 mm) maintained in some details.

Kincheloe, J. P.

1985-01-01

406

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+ T-lymphocyte (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 2250 HIV-positive, continuously enrolled, fee-for-service, Medicaid beneficiaries with at least 2 outpatient healthcare encounters. We used logistic regression to evaluate the association of patient demographics (age, gender, race or ethnicity, and language) with receipt of at least 1 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 or ethnic, gender, and age disparities in CD4 testing. Among individuals with a history of ARV use, all racial or ethnic groups were significantly less likely to have CD4 tests than White non-Latinos (African Americans, odds ratio [OR] = 0.35, P < .0001; Asian or Pacific Islanders, OR = 0.31, P = .0047; and Latinos, OR = 0.42, P < .0001). Conclusions ?We identified disparities in receipt of CD4 tests, a finding that may 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

407

3D - Laser Scanning: Integration of Point Cloud and CCD Camera Video Data for the Production of High Resolution and Precision RGB Textured Models: Archaeological Monuments Surveying Application in Ancient Ilida  

Microsoft Academic Search

SUMMARY In this project, techniques of integration of 3D - Laser Scanning point cloud data and the video produced by the CCD camera are explored. This integration is employed to the produc- tion of high - accuracy and resolution RGB textured models and ortho - photo diagrams of archaeological monuments. The \\

Vaios BALIS; Spyros KARAMITSOS; Ioannis KOTSIS; Christos LIAPAKIS

408

Author version of: T. Tsandilas, E. Dubois, and M. Raynal. Modeless Pointing with Low-Precision Wrist Movements, In INTERACT 2013: Proceedings of the 14th IFIP TC13 Con-  

E-print Network

-switching mechanisms. Taking into account elastic properties of the human joints, we investigate designs based on rate control, clutching. 1 Introduction Technology becomes more and more ubiquitous, and a variety of handheld and relative pointing. "Clutching" is a common input recalibration mechanism that allows users to reposition

Paris-Sud XI, Université de

409

Linear Precision for Toric Patches Luis Garcia-Puente  

E-print Network

Linear Precision for Toric Patches Luis Garcia-Puente Department of Mathematics and Statistics Sam Garcia-Puente (SHSU) Linear Precision for Toric Patches Towson University 1 / 19 #12;Bézier curves are control points in some affine space. Luis Garcia-Puente (SHSU) Linear Precision for Toric Patches Towson

Garcia-Puente, Luis David

410

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

411

Hydraulic Cylinder With an Integral Position Indicator  

NASA Technical Reports Server (NTRS)

Linear variable differential transformer (LVDT) incorporated within cylinder of hydraulic actuator gives precise readout of position of piston relative to cylinder. LVDT contained completely within actuator. System requires precise positioning and position readout for computer control of model motions. Minimal space available for motion cylinders, and precise, continuous position readout (with no steps or pulses) required. Device provides continuous and accurate position indication of a hydraulic cylinder by means of integral, coaxially mounted LVDT.

Goodwin, G. O.

1986-01-01

412

Precise Orbit Determination of BeiDou Navigation Satellite System  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

413

Analytic proportional-derivative control for precise and compliant motion  

Microsoft Academic Search

Precise control with proportional-derivative (PD) control generally requires stiffness. The proposed method deter- mines critically damped PD control trajectories that precisely obtain target position and velocity constraints for arbitrary initial conditions. An analytic solution provides the PD control parameters, thereby determining the required impedance. The resulting controller precisely interpolates the target state by solving the full boundary-value problem. Control parameters

Brian F. Allen; Michael Neff; Petros Faloutsos

2011-01-01

414

Profile Guided Code Positioning  

Microsoft Academic Search

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

Karl Pettis; Robert C. Hansen

1990-01-01

415

Precise orbit determination for GRACE  

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

416

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

417

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

418

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

419

A Precise Measurement of a Leonid Meteor  

NASA Astrophysics Data System (ADS)

A measuring engine and a detailed analysis have been applied to the photographs of the Leonid meteor reported by Bishop (2003). The radiant of the meteor has been determined, along with more precise values for the heights and geographic coordinates of the beginning and end points. The green-red-white colour sequence of bright Leonid meteors displayed on photographs is discussed.

Tatum, Jeremy B.; Bishop, Roy

2005-04-01

420

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

421

How Physics Got Precise  

SciTech Connect

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

Kleppner, Daniel (MIT) [MIT

2005-01-19

422

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

423

Positive tensor factorization  

Microsoft Academic Search

A novel fixed point algorithm for positive ten- sor factorization (PTF) is introduced. The update rules efficiently minimize the reconstruction error of a positive tensor over positive factors. Tensors of arbitrary order can be factorized, which extends earlier results in the lit- erature. Experiments show that the factors of PTF are easier to interpret than those produced by methods based

Max Welling; Markus Weber

2001-01-01

424

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

425

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

426

High Precision Astrometry  

NASA Astrophysics Data System (ADS)

This |*|program |*|uses |*|the |*|enhanced |*|astrometric |*|precision |*|enabled |*|by |*|spatial |*|scanning |*|to |*|calibrate |*|remaining |*|obstacles |*|toreaching |*|<<40 |*|microarc|*|second |*|astrometry |*|{<1 |*|millipixel} |*|with |*|WFC3/UVIS |*|by |*|1} |*|improving |*|geometric |*|distor-on |*|2} |*|calibratingthe |*|e|*|ect |*|of |*|breathing |*|on |*|astrometry|*|3} |*|calibrating |*|the |*|e|*|ect |*|of |*|CTE |*|on |*|astrometry, |*|4} |*|characterizing |*|the |*|boundaries |*|andorientations |*|of |*|the |*|WFC3 |*|lithograph |*|cells.

Riess, Adam

2012-10-01

427

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

E-print Network

Company: Industry: Website: Majors: Offered: Offered: Position(s): Position(s): Description.gza.com, to view a listing of current open positions. Resumes may also be sent to humanresources@gza.com GZA

New Hampshire, University of

428

Optimal Centroid Position Estimation  

SciTech Connect

The alignment of high energy laser beams for potential fusion experiments demand high precision and accuracy by the underlying positioning algorithms. This paper discusses the feasibility of employing online optimal position estimators in the form of model-based processors to achieve the desired results. Here we discuss the modeling, development, implementation and processing of model-based processors applied to both simulated and actual beam line data.

Candy, J V; McClay, W A; Awwal, A S; Ferguson, S W

2004-07-23

429

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