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1
Uno, T., and S. Adachi. "Range distance requirements for large antenna measurements." IEEE Transactions on Antennas and Propagation 37, no. 6 (June 1989): 707–20. http://dx.doi.org/10.1109/8.29357.
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Toma, Toma, Bunyamin Rizki Abdillah, and Murni Marlina Simarmata. "Pentingnya Pengukuran Pupil Distance (PD) Secara Tepat Untuk Menjaga Akurasi Distance Vitror (DV) Kacamata." Jurnal Mata Optik 2, no. 2 (July 31, 2021): 19–27. http://dx.doi.org/10.54363/jmo.v2i2.35.
Повний текст джерелаАнотація:
Pupil Distance (PD) is measured in millimetres and even a slight variation can cause a number of vision and eye health problems due to inacurately fitting of Distance Vitror (DV). PD must be paralel to DV, therefore PD measurements must be committed throughtly. It requires comprehensive knowledge and technical skill. With the popularity of buying glasses online, a number of websites have come up with do-it-yourself measurements or apps that will take this measurement for you. The problem is that these are not scientifically accurate measurements and are not being performed by professionals. There is a large margin of error and buyers could end up with glasses that hurt their vision—not correct it.This research is aimed to show ideal procedure that must be committed in producing glasses to avoid inacurate PD measurement. The researcher uses library aprroach to gain related data and informations, then discuss the problem and solution in descriptive approach.
3
Pisani, Marco, Milena Astrua, and Massimo Zucco. "Improved Acoustic Thermometry for Long-Distance Temperature Measurements." Sensors 23, no. 3 (February 2, 2023): 1638. http://dx.doi.org/10.3390/s23031638.
Повний текст джерелаАнотація:
Accurate measurements of long distances (in the order of tens of meters or more) are necessary in manufacturing processes of large structures, as, for example, in the aerospace industry. In the most demanding applications, the goal is to achieve a relative accuracy of 10−7 in the measurement of distances (e.g., 1 µm over 10 m). This goal can be obtained with laser interferometers whose accuracy is based on knowledge of the speed of light, which, in turn, depends on the temperature of air. A thermometer based on the measurement of the speed of sound in air has been realized at INRIM. Its purpose is the measurement of the air temperature along the measurement path of the interferometer with an accuracy of 0.1 °C at distances up to 11 m. The paper describes the principle and the experimental setup of the acoustic thermometer and demonstrates its performance by comparison with calibrated reference platinum resistance thermometers. Furthermore, we demonstrate the potentiality of the method to measure the vertical temperature gradient, which is the main error source in triangulation measurements when using laser trackers.
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Zhang, Chengyang, Xishuang Jing, Siyu Chen, Xuanzhe Ling, Jiarong Zou, and Gang Zhao. "Method of improving large-scale measurement accuracy of laser tracker based on photogrammetry." Measurement and Control 52, no. 9-10 (April 15, 2019): 1220–27. http://dx.doi.org/10.1177/0020294018813644.
Повний текст джерелаАнотація:
Background: When performing the spatial large-scale measurements, the measurement accuracy of laser tracker would decreased with the increase of the measurement distances due to the refraction difference of most optical digital measurement devices. Therefore, this paper proposed a method based on photogrammetry system to improve the large-scale measurement accuracy of the laser tracker. Purpose: The purpose of this method is to improve the large-scale measurement accuracy of the laser tracker by considering the advantages of photogrammetry system such as high measurement accuracy and good portability. Methods: The measurement data from the photogrammetry system would be used as a reference to do correction on measurement results from laser tracker. The coordinate correction method based on Rodrigues’ rotation formula has been discussed. The measurement accuracy of the long-distance point of laser tracker can be significantly improved through the coordinate correction method. Conclusion: Based on the advantages of using photogrammetry system, the proposed method can achieve higher accuracy when measuring the common points at a closer distance than the laser tracker can do when measuring objects far away from instrument. The feasibility of the proposed method has been demonstrated by experiment.
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Sargeant, B., S. Robson, E. Szigeti, P. Richardson, A. El-Nounu, and M. Rafla. "A METHOD TO ACHIEVE LARGE VOLUME, HIGH ACCURACY PHOTOGRAMMETRIC MEASUREMENTS THROUGH THE USE OF AN ACTIVELY DEFORMABLE SENSOR MOUNTING PLATFORM." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B5 (June 15, 2016): 123–29. http://dx.doi.org/10.5194/isprs-archives-xli-b5-123-2016.
Повний текст джерелаАнотація:
When using any optical measurement system one important factor to consider is the placement of the sensors in relation to the workpiece being measured. When making decisions on sensor placement compromises are necessary in selecting the best placement based on the shape and size of the object of interest and the desired resolution and accuracy. One such compromise is in the distance the sensors are placed from the measurement surface, where a smaller distance gives a higher spatial resolution and local accuracy and a greater distance reduces the number of measurements necessary to cover a large area reducing the build-up of errors between measurements and increasing global accuracy. This paper proposes a photogrammetric approach whereby a number of sensors on a continuously flexible mobile platform are used to obtain local measurements while the position of the sensors is determined by a 6DoF tracking solution and the results combined to give a single set of measurement data within a continuous global coordinate system. The ability of this approach to achieve both high accuracy measurement and give results over a large volume is then tested and areas of weakness to be improved upon are identified.
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Sargeant, B., S. Robson, E. Szigeti, P. Richardson, A. El-Nounu, and M. Rafla. "A METHOD TO ACHIEVE LARGE VOLUME, HIGH ACCURACY PHOTOGRAMMETRIC MEASUREMENTS THROUGH THE USE OF AN ACTIVELY DEFORMABLE SENSOR MOUNTING PLATFORM." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B5 (June 15, 2016): 123–29. http://dx.doi.org/10.5194/isprsarchives-xli-b5-123-2016.
Повний текст джерелаАнотація:
When using any optical measurement system one important factor to consider is the placement of the sensors in relation to the workpiece being measured. When making decisions on sensor placement compromises are necessary in selecting the best placement based on the shape and size of the object of interest and the desired resolution and accuracy. One such compromise is in the distance the sensors are placed from the measurement surface, where a smaller distance gives a higher spatial resolution and local accuracy and a greater distance reduces the number of measurements necessary to cover a large area reducing the build-up of errors between measurements and increasing global accuracy. This paper proposes a photogrammetric approach whereby a number of sensors on a continuously flexible mobile platform are used to obtain local measurements while the position of the sensors is determined by a 6DoF tracking solution and the results combined to give a single set of measurement data within a continuous global coordinate system. The ability of this approach to achieve both high accuracy measurement and give results over a large volume is then tested and areas of weakness to be improved upon are identified.
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Yan, Qing-Zeng, Ji Yang, Yang Su, Yan Sun, Ye Xu, Hongchi Wang, Xin Zhou, and Chen Wang. "Improved Measurements of Molecular Cloud Distances Based on Global Search." Astrophysical Journal 922, no. 1 (November 1, 2021): 8. http://dx.doi.org/10.3847/1538-4357/ac214f.
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Abstract The principle of the background-eliminated extinction-parallax (BEEP) method is examining the extinction difference between on- and off-cloud regions to reveal the extinction jump caused by molecular clouds, thereby revealing the distance in complex dust environments. The BEEP method requires high-quality images of molecular clouds and high-precision stellar parallaxes and extinction data, which can be provided by the Milky Way Imaging Scroll Painting (MWISP) CO survey and the Gaia DR2 catalog, as well as supplementary A V extinction data. In this work, the BEEP method is further improved (BEEP-II) to measure molecular cloud distances in a global search manner. Applying the BEEP-II method to three regions mapped by the MWISP CO survey, we collectively measured 238 distances for 234 molecular clouds. Compared with previous BEEP results, the BEEP-II method measures distances efficiently, particularly for those molecular clouds with large angular size or in complicated environments, making it suitable for distance measurements of molecular clouds in large samples.
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Pillarz, Marc, Axel von Freyberg, and Andreas Fischer. "Determination of the mean base circle radius of gears by optical multi-distance measurements." Journal of Sensors and Sensor Systems 9, no. 2 (August 20, 2020): 273–82. http://dx.doi.org/10.5194/jsss-9-273-2020.
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Abstract. The required reliability of wind turbine gearboxes increases the requirements for large gear measurements. Extensive measurements to reliably assess the geometry of large gears in the single micrometer range are necessary. Due to an individually fixed measuring volume, standard methods like coordinate and gear measuring instruments reach their limits for large gears with diameters > 1 m. Therefore, a scalable optical measurement approach consisting of a single sensor in combination with a rotary table for multi-distance measurements with subsequent model-based evaluation of shape parameters of gears is presented. The scalable measurement approach is to be extended to a multisensory system in further work. As a fundamental shape parameter the mean base circle radius using the example of spur gears is determined. The base circle radius is used due to the geometric relationship to further shape parameters for example to the profile slope deviation. The theoretically achievable measurement uncertainty of the mean base circle radius due to sensor noise is estimated to less than 5 µm (k=2) for a small and a large gear, which verifies the scalability of the sensor system. In order to show a general proof of principle, two series of optical measurements on a gear with a diameter of 0.105 m are performed and referenced with a tactile measurement. As a result, random errors of 1.2 µm for k=2 are determined. The remaining systematic deviations to the reference value amount to 4.3 and 1.6 µm, respectively. Hence, the total measurement uncertainty is currently limited by systematic effects, and the defined aim of a total uncertainty of less than 5 µm (k=2) is narrowly missed by 1.5 µm. The random errors of 1.2 µm (k=2) show, however, that an adequate measurement precision is achieved and that the multi-distance measurement approach has the potential to reach the aimed measurement uncertainty with appropriate strategies to compensate for the systematic influences. The experimental and theoretical results prove the principle applicability of the proposed single sensor multi-distance approach for the precise inspection of gears.
9
MAHAL, VERED, and ADY ARIE. "DISTANCE MEASUREMENTS USING FREQUENCY STABILIZED Nd:YAG LASERS." Journal of Nonlinear Optical Physics & Materials 05, no. 03 (July 1996): 543–50. http://dx.doi.org/10.1142/s0218863596000362.
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Two diode-pumped tunable Nd:YAG lasers locked to sub-Doppler transitions of 127I2 and 133 Cs 2 are used as a source for two-wavelength interferometry. The synthetic wavelength, Λ=c/∆ν, is highly stable and accurate, owing to the frequency stability of the locked lasers and the precise determination of the frequency difference Δν between Cs 2 and I 2 transitions. The dense spectra of these molecules allows selection of Λ over a wide range, between 8.5 mm and several meters, thus enabling distance measurements with a large non-ambiguity range. Fringe contrast and phase-shifting methods are used to measure the phase difference. An accuracy of 70 μm is achieved for Λ~19 mm, i.e. Λ/260.
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Garcia Espinilla, Oscar, Irene Sanchez, and Raul Martin. "Intrasession repeatability and agreement of a new method to measure the foveal fixation axis." PeerJ 11 (February 24, 2023): e14942. http://dx.doi.org/10.7717/peerj.14942.
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Purpose Ophthalmic lens adaptation, particularly with progressive addition lenses, requires accurate measurements of the patient nasopupillary distance (NPD) and interpupillary distance (IPD), which are usually collected using the pupil centre as a reference. However, differences between the pupil centre and visual or foveal axis could induce some subsidiary effects of correcting lenses. This study aimed to assess the intrasession repeatability of a new prototype (Ergofocus®; Lentitech, Barakaldo, Spain) that can measure the foveal fixation axis (FFA) distance and assess the agreement with the NPD measurements collected using a traditional method (frame ruler). Methods The FFA at far and near distances was measured three consecutive times in 39 healthy volunteers to determine the intrasession repeatability according to the British Standards Institute and International Organization for Standardization. Additionally, the FFA and NPD (standard frame ruler) were measured in 71 healthy volunteers and compared using Bland–Altman analysis. Two blinded experienced practitioners conducted each FFA and NPD measurement. Results The FFA measurements showed acceptable repeatability at far distances (right eye (RE): Sw = 1.16 ± 0.76 mm and coefficient of variation (CV) = 3.92 ± 2.51%; left eye (LE) Sw = 1.11 ± 0.79 mm and CV = 3.76 ± 2.51%) and at near distances (RE: Sw = 0.97 ± 0.85 mm and CV = 3.52 ± 3.02%; LE: Sw = 1.17 ± 0.96 mm and CV = 4.54 ± 3.72%). Additionally, agreement with the NPD showed large differences at far distances (RE: −2.15 ± 2.34, LoA = −6.73 to 2.43 mm (P < 0.001); LE: −0.61 ± 2.62, LoA = −5.75 to 4.53 mm (P = 0.052)) and near distances (RE: −3.08 ± 2.80, LoA −8.57 to 2.42 mm (P < 0.001); LE: −2.97 ± 3.97, LoA: −10.75 to 4.80 mm (P < 0.001)). Conclusions FFA measurements showed clinically acceptable repeatability at both far and near distances. Agreement with the NPD measured using a standard frame ruler showed significant differences, suggesting that both measurements are not interchangeable in clinical practice to prescribe and center ophthalmic lenses. Further research is necessary to assess the impact of FFA measurement in ophthalmic lens prescriptions.
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Denicke, Eckhard, Gunnar Armbrecht, and Ilona Rolfes. "Radar distance measurements in circular waveguides involving intermodal dispersion effects." International Journal of Microwave and Wireless Technologies 2, no. 3-4 (June 25, 2010): 409–17. http://dx.doi.org/10.1017/s1759078710000413.
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This contribution deals with guided radar distance measurements in the field of industrial tank level control. The aim is to achieve a submillimeter gauging accuracy even when conducting the measurement within a highly dispersive environment of large and thus overmoded circular waveguides. Normally, multimode propagation causes a decrease in measurement precision. Therefore, the effects of intermodal dispersion are fundamentally reviewed and, based on these results, a correlation-based signal processing method is presented. This method is able to exploit the otherwise parasitic dispersion effects to enhance the measurement precision even in constellation with a simple waveguide transition or antenna, respectively. Furthermore, considerations on the mode variety and its influence on the signal complexity as well as investigations on the technique's reliability and accuracy are presented. Measurement results in a frequency range of 8.5–10.5 GHz are provided for three different kinds of waveguide transitions proving the capability of the method.
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Kienle, Patrick, Lorena Batarilo, Markus Akgül, Michael H. Köhler, Kun Wang, Martin Jakobi, and Alexander W. Koch. "Optical Setup for Error Compensation in a Laser Triangulation System." Sensors 20, no. 17 (September 1, 2020): 4949. http://dx.doi.org/10.3390/s20174949.
Повний текст джерелаАнотація:
Absolute distance measurement is a field of research with a large variety of applications. Laser triangulation is a well-tested and developed technique using geometric relations to calculate the absolute distance to an object. The advantages of laser triangulation include its simple and cost-effective setup with yet a high achievable accuracy and resolution in short distances. A main problem of the technology is that even small changes of the optomechanical setup, e.g., due to thermal expansion, lead to significant measurement errors. Therefore, in this work, we introduce an optical setup containing only a beam splitter and a mirror, which splits the laser into a measurement beam and a reference beam. The reference beam can then be used to compensate for different error sources, such as laser beam dithering or shifts of the measurement setup due to the thermal expansion of the components. The effectiveness of this setup is proven by extensive simulations and measurements. The compensation setup improves the deviation in static measurements by up to 75%, whereas the measurement uncertainty at a distance of 1 m can be reduced to 85 μm. Consequently, this compensation setup can improve the accuracy of classical laser triangulation devices and make them more robust against changes in environmental conditions.
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Wang, Wei. "The distance indicators in gamma-ray pulsars." Proceedings of the International Astronomical Union 8, S291 (August 2012): 546–48. http://dx.doi.org/10.1017/s1743921312024829.
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AbstractDistance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars, including 34 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (η=Lγ/Ė) and pulsar parameters, for young radio-selected gamma-ray pulsars with known distance information. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find a strong correlation between η and ζ3, the generation order parameter which reflects γ-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation between η and BLC, the magnetic field at the light cylinder radius, is also found. These correlations can serve as distance indicators in gamma-ray pulsars, to evaluate distances for gamma-selected pulsars. Distances of 35 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. The physical origin of the correlations may be also interesting for pulsar studies.
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Manera, M., W. J. Percival, Ashley Ross, R. Tojeiro, L. Samushia, C. Howlett, M. Vargas-Magaña, and A. Burden. "Understanding Cosmological Measurements with a large number of mock galaxy catalogues." Proceedings of the International Astronomical Union 10, S306 (May 2014): 266–68. http://dx.doi.org/10.1017/s1743921314013738.
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AbstractMock galaxy catalogues are essential to the error analysis of cosmological measurements from big galaxy surveys covering thousands of square degrees in the sky, like BOSS, WiggleZ, DES, or Euclid. The PTHalos mock galaxy catalogues were used in the BOSS survey to analyse the BAO measurement from the CMASS (z∼ 0.57) and LOWZ (z∼ 0.32) galaxy samples, which provided the best estimate to date of the cosmic distance scale from galaxy surveys at these redshifts. We review the PTHalos mocks galaxy catalogues and their key contributions to these analyses.
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WANG, WEI. "DISTANCE INDICATORS OF GAMMA-RAY PULSARS." International Journal of Modern Physics: Conference Series 23 (January 2013): 289–94. http://dx.doi.org/10.1142/s2010194513011483.
Повний текст джерелаАнотація:
Distance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars including 24 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (η = Lγ/Ė) and pulsar parameters for young radio-selected gamma-ray pulsars with known distance information in the first gamma-ray pulsar catalog reported by Fermi/LAT. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find the strong correlation of η – ζ3 a generation order parameter which reflects γ-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation of η – B LC the magnetic field at the light cylinder radius is also found. These correlations would be the distance indicators in gamma-ray pulsars to evaluate distances for gamma-selected pulsars. Distances of 25 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. Physical origin of the correlations may be also interesting for pulsar studies.
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Wang, Tao, Bicong Wang, Yufeng Luo, Hengyu Li, Jinjun Rao, Zhizheng Wu, and Mei Liu. "Accurate Measurements of the Rotational Velocities of Brushless Direct-Current Motors by Using an Ultrasensitive Magnetoimpedance Sensing System." Micromachines 10, no. 12 (December 6, 2019): 859. http://dx.doi.org/10.3390/mi10120859.
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Reports on measurements of the rotational velocity by using giant magnetoimpedance (GMI) sensors are rarely seen. In this study, a rotational-velocity sensing system based on GMI effect was established to measure rotational velocities of brushless direct-current motors. Square waves and sawtooth waves were observed due to the rotation of the shaft. We also found that the square waves gradually became sawtooth waves with increasing the measurement distance and rotational velocity. The GMI-based rotational-velocity measurement results (1000–4300 r/min) were further confirmed using the Hall sensor. This GMI sensor is capable of measuring ultrahigh rotational velocity of 84,000 r/min with a large voltage response of 5 V, even when setting a large measurement distance of 9 cm. Accordingly, the GMI sensor is very useful for sensitive measurements of high rotational velocity.
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Sy, Luke Wicent F., Nigel H. Lovell, and Stephen J. Redmond. "Estimating Lower Limb Kinematics Using a Lie Group Constrained Extended Kalman Filter with a Reduced Wearable IMU Count and Distance Measurements." Sensors 20, no. 23 (November 29, 2020): 6829. http://dx.doi.org/10.3390/s20236829.
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Tracking the kinematics of human movement usually requires the use of equipment that constrains the user within a room (e.g., optical motion capture systems), or requires the use of a conspicuous body-worn measurement system (e.g., inertial measurement units (IMUs) attached to each body segment). This paper presents a novel Lie group constrained extended Kalman filter to estimate lower limb kinematics using IMU and inter-IMU distance measurements in a reduced sensor count configuration. The algorithm iterates through the prediction (kinematic equations), measurement (pelvis height assumption/inter-IMU distance measurements, zero velocity update for feet/ankles, flat-floor assumption for feet/ankles, and covariance limiter), and constraint update (formulation of hinged knee joints and ball-and-socket hip joints). The knee and hip joint angle root-mean-square errors in the sagittal plane for straight walking were 7.6±2.6∘ and 6.6±2.7∘, respectively, while the correlation coefficients were 0.95±0.03 and 0.87±0.16, respectively. Furthermore, experiments using simulated inter-IMU distance measurements show that performance improved substantially for dynamic movements, even at large noise levels (σ=0.2 m). However, further validation is recommended with actual distance measurement sensors, such as ultra-wideband ranging sensors.
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Zucker, Catherine, Joshua S. Speagle, Edward F. Schlafly, Gregory M. Green, Douglas P. Finkbeiner, Alyssa Goodman, and João Alves. "A compendium of distances to molecular clouds in the Star Formation Handbook." Astronomy & Astrophysics 633 (January 2020): A51. http://dx.doi.org/10.1051/0004-6361/201936145.
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Accurate distances to local molecular clouds are critical for understanding the star and planet formation process, yet distance measurements are often obtained inhomogeneously on a cloud-by-cloud basis. We have recently developed a method that combines stellar photometric data with Gaia DR2 parallax measurements in a Bayesian framework to infer the distances of nearby dust clouds to a typical accuracy of ∼5%. After refining the technique to target lower latitudes and incorporating deep optical data from DECam in the southern Galactic plane, we have derived a catalog of distances to molecular clouds in Reipurth (2008, Star Formation Handbook, Vols. I and II) which contains a large fraction of the molecular material in the solar neighborhood. Comparison with distances derived from maser parallax measurements towards the same clouds shows our method produces consistent distances with ≲10% scatter for clouds across our entire distance spectrum (150 pc−2.5 kpc). We hope this catalog of homogeneous distances will serve as a baseline for future work.
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Lavoie, Hugo, Eldon Puckrin, Jean-Marc Thériault, and François Bouffard. "Passive Standoff Detection of SF6 at a Distance of 5.7 km by Differential Fourier Transform Infrared Radiometry." Applied Spectroscopy 59, no. 10 (October 2005): 1189–93. http://dx.doi.org/10.1366/000370205774431007.
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Recent results are presented on the passive detection, identification, and quantification of a vapor cloud of SF6 measured at a horizontal standoff distance of 5.7 km using a dual-beam interferometer optimized for background signal suppression. The measurements were performed at Defense Research and Development Canada (DRDC)–Valcartier during a number of recent open-air experiments. The measurement approach is based on the differential passive standoff detection method that has been developed by DRDC Valcartier during the past few years. This work represents the first such measurement reported in the open literature for a standoff distance as large as 5.7 km. These results clearly demonstrate the capability of the differential radiometry approach to the detection, identification, and quantification of chemical vapor clouds located at long distances from the sensor.
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Kenworthy, W. D’Arcy, Adam G. Riess, Daniel Scolnic, Wenlong Yuan, José Luis Bernal, Dillon Brout, Stefano Casertano, David O. Jones, Lucas Macri, and Erik R. Peterson. "Measurements of the Hubble Constant with a Two-rung Distance Ladder: Two Out of Three Ain’t Bad." Astrophysical Journal 935, no. 2 (August 1, 2022): 83. http://dx.doi.org/10.3847/1538-4357/ac80bd.
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Abstract The three-rung distance ladder, which calibrates Type Ia supernovae (SNe Ia) through stellar distances linked to geometric measurements, provides the highest precision direct measurement of the Hubble constant. In light of the Hubble tension, it is important to test the individual components of the distance ladder. For this purpose, we report a measurement of the Hubble constant from 35 extragalactic Cepheid hosts measured by the SH0ES team, using their distances and redshifts at cz ≤ 3300 km s−1, instead of any more distant SNe Ia, to measure the Hubble flow. The Cepheid distances are calibrated geometrically in the Milky Way, NGC 4258, and the Large Magellanic Cloud. Peculiar velocities are a significant source of systematic uncertainty at z ∼ 0.01, and we present a formalism for both mitigating and quantifying their effects, making use of external reconstructions of the density and velocity fields in the nearby universe. We identify a significant source of uncertainty originating from different assumptions about the selection criteria of this sample, whether distance or redshift limited, as it was assembled over three decades. Modeling these assumptions yields central values ranging from H 0 = 71.7 to 76.4 km s−1 Mpc−1. Combining the four best-fitting selection models yields H 0 = 72.9 − 2.2 + 2.4 as a fiducial result, at 2.4σ tension with Planck. While SNe Ia are essential for a precise measurement of H 0, unknown systematics in these supernovae are unlikely to be the source of the Hubble tension.
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Brett, Caroline E., and Ian J. Deary. "…obtain accurate objective measurements of health at a distance." Health Psychology Update 24, no. 2 (2015): 43–48. http://dx.doi.org/10.53841/bpshpu.2015.24.2.43.
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Large–scale longitudinal studies are an excellent tool for increasing our understanding of the aetiology of health and disease. Obtaining accurate measures of health status is important in these kinds of studies. However, self–report measures of health are subject to bias and obtaining objective health measures can be costly. This paper outlines the process and challenges of designing a home testing kit to enable participants to obtain objective health measures themselves, using the example of a new cohort study, the 6–Day Sample.
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Keenan, Ryan C., Amy J. Barger, and Lennox L. Cowie. "Local Large-Scale Structure and the Assumption of Homogeneity." Proceedings of the International Astronomical Union 11, S308 (June 2014): 295–98. http://dx.doi.org/10.1017/s1743921316010024.
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AbstractOur recent estimates of galaxy counts and the luminosity density in the near-infrared (Keenan et al. 2010, 2012) indicated that the local universe may be under-dense on radial scales of several hundred megaparsecs. Such a large-scale local under-density could introduce significant biases in the measurement and interpretation of cosmological observables, such as the inferred effects of dark energy on the rate of expansion. In Keenan et al. (2013), we measured the K-band luminosity density as a function of distance from us to test for such a local under-density. We made this measurement over the redshift range 0.01 < z < 0.2 (radial distances D ~ 50 - 800 h70−1 Mpc). We found that the shape of the K-band luminosity function is relatively constant as a function of distance and environment. We derive a local (z < 0.07, D < 300 h70−1 Mpc) K-band luminosity density that agrees well with previously published studies. At z > 0.07, we measure an increasing luminosity density that by z ~ 0.1 rises to a value of ~ 1.5 times higher than that measured locally. This implies that the stellar mass density follows a similar trend. Assuming that the underlying dark matter distribution is traced by this luminous matter, this suggests that the local mass density may be lower than the global mass density of the universe at an amplitude and on a scale that is sufficient to introduce significant biases into the measurement of basic cosmological observables. At least one study has shown that an under-density of roughly this amplitude and scale could resolve the apparent tension between direct local measurements of the Hubble constant and those inferred by Planck team. Other theoretical studies have concluded that such an under-density could account for what looks like an accelerating expansion, even when no dark energy is present.
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Li, Ping, and Tianmao Lai. "Influence of Lateral Movement on Level Behavior of Adhesion Force Measured Repeatedly by an Atomic Force Microscope (AFM) Colloid Probe in Dry Conditions." Materials 14, no. 2 (January 13, 2021): 370. http://dx.doi.org/10.3390/ma14020370.
Повний текст джерелаАнотація:
An atomic force microscope (AFM) was operated to repeatedly measure the adhesion forces between a polystyrene colloid probe and a gold film, with and without lateral movement in dry conditions. Experimental results show that the adhesion force shows a level behavior without lateral movement and with a small scan distance: the data points are grouped into several levels, and the adhesion force jumps between different levels frequently. This was attributed to the fact that when the cantilever pulls off the sample, the contact area of the sample is not exactly the same between successive contacts and jumps randomly from one to another. Both lateral velocity and material wear have little influence on level behavior. However, with a medium scan distance, level behavior is observed only for some measurements, and adhesion forces are randomly distributed for the other measurements. With a large scan distance, adhesion forces are randomly distributed for all measurements. This was attributed to the fact that the cantilever pulls off the sample in many different contact areas on the scanning path for large distances. These results may help understand the influence of lateral movement and imply the contribution of asperities to adhesion force.
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Horn, Berthold K. P. "Indoor Localization Using Uncooperative Wi-Fi Access Points." Sensors 22, no. 8 (April 18, 2022): 3091. http://dx.doi.org/10.3390/s22083091.
Повний текст джерелаАнотація:
Indoor localization using fine time measurement (FTM) round-trip time (RTT) with respect to cooperating Wi-Fi access points (APs) has been shown to work well and provide 1–2 m accuracy in both 2D and 3D applications. This approach depends on APs implementing the IEEE 802.11-2016 (also known as IEEE 802.11mc) Wi-Fi standard (“two-sided” RTT). Unfortunately, the penetration of this Wi-Fi protocol has been slower than anticipated, perhaps because APs tend not to be upgraded as often as other kinds of electronics, in particular in large institutions—where they would be most useful. Recently, Google released Android 12, which also supports an alternative “one-sided” RTT method that will work with legacy APs as well. This method cannot subtract out the “turn-around” time of the signal, and so, produces distance estimates that have much larger offsets than those seen with two-sided RTT—and the results are somewhat less accurate. At the same time, this method makes possible distance measurements for many APs that previously could not be used. This increased accessibility can compensate for the decreased accuracy of individual measurements. We demonstrate here indoor localization using one-sided RTT with respect to legacy APs that do not support IEEE 802.11-2016. The accuracy achieved is 3–4 m in cluttered environments with few line-of-sight readings (and using only 20 MHz bandwidths). This is not as good as for two-sided RTT, where 1–2 m accuracy has been achieved (using 80 MHz bandwidths), but adequate for many applications A wider Wi-Fi channel bandwidth would increase the accuracy further. As before, Bayesian grid update is the preferred method for determining position and positional accuracy, but the observation model now is different from that for two-sided RTT. As with two-sided RTT, the probability of an RTT measurement below the true distance is very low, but, in the other direction, the range of measurements for a given distance can be much wider (up to well over twice the actual distance). We describe methods for formulating useful observation models. As with two-sided RTT, the offset or bias in distance measurements has to be subtracted from the reported measurements. One difference is that here, the offsets are large (typically in the 2400–2700 m range) because of the “turn-around time” of roughly 16 μs (i.e., about two orders of magnitude larger than the time of flight one is attempting to measure). We describe methods for estimating these offsets and for minimizing the effort required to do so when setting up an installation with many APs.
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Mironova, M., Guoping Du, and K. Salama. "Measurements of misorientation angles over a large distance in strongly coupled grain boundaries." IEEE Transactions on Appiled Superconductivity 9, no. 2 (June 1999): 1630–33. http://dx.doi.org/10.1109/77.784734.
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Lüttgens, Sylvia, Günter Lüttgens, Anders Thulin, Thierry Paillat, and Gérard Touchard. "Electrostatic Charge Measurements of Droplets of Various Liquids Falling over a Large Distance." Chemical Engineering & Technology 38, no. 7 (April 27, 2015): 1261–68. http://dx.doi.org/10.1002/ceat.201400747.
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Sheng, Ying, Yukun Wang, Siwei Liu, Cuiping Wang, and Juntong Xi. "Large-Scale Measurement Layout Optimization Method Based on Laser Multilateration." Machines 10, no. 11 (October 28, 2022): 988. http://dx.doi.org/10.3390/machines10110988.
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Laser multilateration is a measurement method based on the distance intersection of multiple laser trackers which has been widely used in large-scale measurements. However, the layout of laser trackers has a great impact on the final measurement accuracy. In order to improve the overall measurement accuracy, firstly, a measurement uncertainty model based on laser multilateration is established. Secondly, a fast laser intersection detection constraint algorithm based on a k-DOPS bounding box and an adaptive target ball incident angle constraint detection algorithm are established for large-scale measurement scenes. Finally, the constrained layout optimization of the laser trackers is realized by using an improved cellular genetic algorithm. The results show that the optimized system layout can achieve the full coverage of measurement points and has higher measurement accuracy. Compared with the traditional genetic algorithm, the improved cellular genetic algorithm converges faster and obtains a better position layout.
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Zamora, Iván, Eyglis Ledesma, Arantxa Uranga, and Núria Barniol. "High Accuracy Ultrasound Micro-Distance Measurements with PMUTs under Liquid Operation." Sensors 21, no. 13 (July 1, 2021): 4524. http://dx.doi.org/10.3390/s21134524.
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Ultrasonic systems driven by multi-frequency continuous waves (MFCW) have been used for range distance measurement, offering high accuracy in long and medium range distance estimation. However, the use of continuous waves in very short-distance measurements causes large errors due to multipath reflections. This paper presents a new strategy to estimate very short relative distances with high accuracy based on the use of multi-frequency pulsed waves (MFPW). The proposed strategy allows to avoid the multipath reflections that appear when continuous waves are used, and it improves the achieved accuracy compared to the original MFCW method. To validate it, an 80 µm square AlScN piezoelectric micromachined ultrasonic transducer (PMUT) was chosen as a transmitter while a hydrophone was utilized as a target and receiver, immersed in fluorinert (FC-70) as a propagation medium. Three independent and consecutive tone-burst signals were transmitted successively. The selected frequencies are f1 = 2.3962 MHz, f2 = 2.327 MHz and f3 = 2.1195 MHz, giving first and second-order resolutions of 6.88 and 0.79 µm/°, respectively. Experimental results show a ±6.2 μm measured range error in a range of 3.5 mm, and therefore it represents a good candidate for ultrasound micro-profilometer applications under liquid operation.
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Wang, Shu, Chengyu Zhang, Biwei Jiang, He Zhao, Bingqiu Chen, Xiaodian Chen, Jian Gao, and Jifeng Liu. "Distances to the supernova remnants in the inner disk." Astronomy & Astrophysics 639 (July 2020): A72. http://dx.doi.org/10.1051/0004-6361/201936868.
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Context. Distance measurements of supernova remnants (SNRs) are essential as accurate estimates of physical size, dust masses, and some other properties of SNRs depend critically on accurate distance measurements. However, the determination of SNR distances is still a tough task. Aims. Red clump stars (RCs) have a long history of being used as standard candles. In this work, we take RCs as tracers to determine the distances to a large group of SNRs in the inner disk. Methods. We first selected RC stars based on the near-infrared (IR) color-magnitude diagram. Then the distance to and extinction of RC stars were calculated. To extend the measurable range of distance, we combined near-IR photometric data from the 2MASS survey with the deeper UKIDSS and VVV surveys. With the help of the Gaia parallaxes, we also removed contaminants, including dwarfs and giants. Because an SN explosion compresses the surrounding interstellar medium, the SNR region would become denser and exhibit higher extinction than the surroundings. The distance of an SNR is then recognized by the position where the extinction and its gradient is higher than that of the ambient medium. Results. A total of 63 SNRs distances in the Galactic inner disk were determined and divided into three Levels A, B, and C with decreasing reliability. The distances to 43 SNRs are well determined with reliability A or B. The diameters and dust masses of SNRs were estimated with the obtained distance and extinction.
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Guillory, Joffray, Daniel Truong, and Jean-Pierre Wallerand. "Multilateration with Self-Calibration: Uncertainty Assessment, Experimental Measurements and Monte-Carlo Simulations." Metrology 2, no. 2 (May 11, 2022): 241–62. http://dx.doi.org/10.3390/metrology2020015.
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Large-volume metrology is essential to many high-value industries and contributes to the factories of the future. In this context, we have developed a tri-dimensional coordinate measurement system based on a multilateration technique with self-calibration. In practice, an absolute distance meter, traceable to the SI metre, is shared between four measurement heads by fibre-optic links. From these stations, multiple distance measurements of several target positions are then performed to, at the end, determine the coordinates of these targets. The uncertainty on these distance measurements has been determined with a consistent metrological approach and it is better than 5 µm. However, the propagation of this uncertainty into the measured positions is not a trivial task. In this paper, an analytical solution for the uncertainty assessment of the positions of both targets and heads under a multilateration scenario with self-calibration is provided. The proposed solution is then compared to Monte-Carlo simulations and to experimental measurements: it follows that all three approaches are well agreed, which suggests that the proposed analytical model is accurate. The confidence ellipsoids provided by the analytical solution described well the geometry of the errors.
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Xu, Cheng, Wei Yuan, Axiu Cao, Li Xue, Qiling Deng, Hui Pang, and Yongqi Fu. "Enhancing Multi-Distance Phase Retrieval via Unequal Interval Measurements." Photonics 8, no. 2 (February 12, 2021): 48. http://dx.doi.org/10.3390/photonics8020048.
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In the conventional methods of multi-distance phase retrieval, the diffraction intensity patterns are recorded at equal intervals, which can induce slow convergence or stagnation in the subsequent reconstruction process. To solve this problem, a measurement method with unequal intervals is proposed in this paper. The interval spacings between adjacent measurement planes are decreased gradually. A large gap accelerates retrieval progress, and a short span helps to recover detailed information. The proposed approach makes full use of the available measured dataset and simultaneously generates variations in diversity amplitude, which is a crucial issue for the techniques of multi-image phase retrieval. Both computational simulations and experiments are performed. The results demonstrate that this method can improve the convergence speed by 2 to 3 times and enhance the quality of reconstruction results in comparison to that of the conventional methods.
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Gregori, Amedeo, Emidio Di Giampaolo, Alessandro Di Carlofelice, and Chiara Castoro. "Presenting a New Wireless Strain Method for Structural Monitoring: Experimental Validation." Journal of Sensors 2019 (November 3, 2019): 1–12. http://dx.doi.org/10.1155/2019/5370838.
Повний текст джерелаАнотація:
The structural health monitoring (SHM) of large and complex infrastructures as well as laboratory tests of new structures and materials resorts to strain gauge measurements to check mechanical stress. A wireless measurement of the strain gauge response is desirable in many practical applications to avoid the cost and the difficulty of wiring, particularly in large structures requiring several sensors and in complex objects where the measurement points are difficult to access. In this paper, a wireless strain gauge which is a hybrid between an RFID tag and a usual thin-film resistive strain gauge is experimented. Installation and maintenance problems of the wireless sensor networks are overcome allowing a high level of measurement accuracy, comparable to that of wired strain sensors, together with a long measurement distance. A large set of measurements has been performed using reference specimens and readings in order to validate the sensor and to develop a calibration procedure that makes the sensor suitable for a large number of different applications in civil engineering.
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Strachan, Russell, Kevin Knowles, Nicholas J. Lawson, and Mark V. Finnis. "Force and moment measurements for a generic car model in proximity to a side wall." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 226, no. 10 (May 18, 2012): 1352–64. http://dx.doi.org/10.1177/0954407012443643.
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Force and moment data are presented for an Ahmed reference model with backlight angles of 10°, 25° and 40° at various distances from a side wall. Tests were run at a freestream velocity of 25 m/s and a rolling road provided ground simulation. Six-component force data were recorded and compared with previous experimental data. It is found that the proximity of the side wall causes a general increase in both the lift coefficient and the pitching moment for the Ahmed model, with the increase in the pitching moment becoming more rapid with decreasing wall distance. Increasing the proximity to the wall is further found to increase the overall Ahmed model drag. Furthermore, there is evidence of the breakdown of longitudinal vortices on the near-wall side of the model as the wall-to-model distance decreases, and a large pressure drop on the near-wall model side. This pressure drop increases in magnitude as the wall-to-model distance decreases, before dissipating at wall distances where the boundary layer restricts the flow.
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Xiao, Yuhao, Guijin Wang, Xiaowei Hu, Chenbo Shi, Long Meng, and Huazhong Yang. "Guided, Fusion-Based, Large Depth-of-field 3D Imaging Using a Focal Stack." Sensors 19, no. 22 (November 7, 2019): 4845. http://dx.doi.org/10.3390/s19224845.
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Three dimensional (3D) imaging technology has been widely used for many applications, such as human–computer interactions, making industrial measurements, and dealing with cultural relics. However, existing active methods often require both large apertures of projector and camera to maximize light throughput, resulting in a shallow working volume in which projector and camera are simultaneously in focus. In this paper, we propose a novel method to extend the working range of the structured light 3D imaging system based on the focal stack. Specifically in the case of large depth variation scenes, we first adopted the gray code method for local, 3D shape measurement with multiple focal distance settings. Then we extracted the texture map of each focus position into a focal stack to generate a global coarse depth map. Under the guidance of the global coarse depth map, the high-quality 3D shape measurement of the overall scene was obtained by local, 3D shape-measurement fusion. To validate the method, we developed a prototype system that can perform high-quality measurements in the depth range of 400 mm with a measurement error of 0.08%.
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Marszal, Jacek, and Roman Salamon. "Distance Measurement Errors in Silent Fm-Cw Sonar with Matched Filtering." Metrology and Measurement Systems 19, no. 2 (January 1, 2012): 321–32. http://dx.doi.org/10.2478/v10178-012-0027-6.
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Distance Measurement Errors in Silent Fm-Cw Sonar with Matched Filtering The secretiveness of sonar operation can be achieved by using continuous frequency-modulated sounding signals with reduced power and significantly prolonged repeat time. The application of matched filtration in the sonar receiver provides optimal conditions for detection against the background of white noise and reverberation, and a very good resolution of distance measurements of motionless targets. The article shows that target movement causes large range measurement errors when linear and hyperbolic frequency modulations are used. The formulas for the calculation of these errors are given. It is shown that for signals with linear frequency modulation the range resolution and detection conditions deteriorate. The use of hyperbolic frequency modulation largely eliminates these adverse effects.
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Ngeow, Chow-Choong, Anupam Bhardwaj, Matthew J. Graham, Steven L. Groom, Frank J. Masci, and Reed Riddle. "Zwicky Transient Facility and Globular Clusters: The Period–Luminosity and Period–Wesenheit Relations for Anomalous Cepheids Supplemented with Large Magellanic Cloud Sample." Astronomical Journal 164, no. 5 (October 13, 2022): 191. http://dx.doi.org/10.3847/1538-3881/ac8df2.
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Abstract We present the first gri-band period–luminosity (PL) and period–Wesenheit (PW) relations for the fundamental mode anomalous Cepheids. These PL and PW relations were derived from a combined sample of five anomalous Cepheids in globular cluster M92 and the Large Magellanic Cloud, both of which have distance accurate to ∼1% available from literature. Our g-band PL relation is similar to the B-band PL relation as reported in previous study. We applied our PL and PW relations to anomalous Cepheids discovered in dwarf galaxy Crater II, and found a larger but consistent distance modulus than the recent measurements based on RR Lyrae. Our calibrations of gri-band PL and PW relations, even though less precise due to small number of anomalous Cepheids, will be useful for distance measurements to dwarf galaxies.
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Mandal, N. R., Sharat Kumar, and Pankaj Biswas. "Distortion Measurement of Ship Blocks Using Photogrammetry." Journal of Ship Production and Design 30, no. 02 (May 1, 2014): 58–65. http://dx.doi.org/10.5957/jspd.2014.30.2.58.
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Welding being a transient phenomenon, explicit finite element thermomechanical analysis of large structural units is computationally extremely time-consuming and in general not feasible. Computational methods are available; however, they need to be validated with full-scale shop floor measured data. As of now, it is extremely difficult to do measurements and acquire some tangible data in actual shop floor situation. In the present work, a method was proposed to actually get the dimensions of such large structures through the use of multiple digital photographs of the structure. The photographs were then processed through a software to get to the dimensions of the threedimensional structure. For validating this method of measurement, two test cases were undertaken. First was using a flat surface plate measuring 3.3 m ×1.3 m over which black dots were pasted at predetermined positions. The distances between the dots were measured using a laser distance meter and compared with those obtained through photogrammetry. In the second case, a test sample was fabricated using a 500 m × 500 mm, 8-mm thick mild steel plate and two longitudinal and one transverse stiffener of 75 × 50 × 6 angle sections. Photographs were taken both before and after welding of the stiffeners. This set of photographs was processed to obtain the resulting deformation of the plate resulting from welding of the stiffeners. The distortion obtained through photogrammetry was compared with the distortion shape of the welded panel obtained from finite element analysis using an average plastic strain method. In both cases, the results of photogrammetry compared fairly well with those of laser distance meter measurements and finite element analysis. The proposed method shows great promise toward actual measurement of large blocks of ship structures and thereby satisfactorily validating theoretical methods of distortion prediction of such large structures.
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Skulkin, Sergey P., Victor I. Turchin, and Nikolay I. Kascheev. "RANGE DISTANCE REQUIREMENTS FOR LARGE ANTENNA MEASUREMENTS FOR LINEAR APERTURE WITH UNIFORM FIELD DISTRIBUTION." Progress In Electromagnetics Research M 48 (2016): 87–94. http://dx.doi.org/10.2528/pierm16031604.
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Skulkin, Sergey P., Victor I. Turchin, and Nikolay I. Kascheev. "Range Distance Requirements for Large Antenna Measurements for Square Aperture With Uniform Field Distribution." IEEE Antennas and Wireless Propagation Letters 17, no. 7 (July 2018): 1257–60. http://dx.doi.org/10.1109/lawp.2018.2841645.
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Colombo, Pietro, and Alessandro Fassò. "Quantifying the interpolation uncertainty of radiosonde humidity profiles." Measurement Science and Technology 33, no. 7 (April 6, 2022): 074001. http://dx.doi.org/10.1088/1361-6501/ac5bff.
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Abstract The global climate observing system Reference Upper Air Network (GRUAN) provides reference measurements of the essential climate variables and their measurement uncertainty. An important aspect of the measurement uncertainty is the interpolation uncertainty. This problem arises, for example, when GRUAN processes atmospheric profiles collected by Vaisala RS41 radiosondes. For various reasons, the radiosonde sensor may fail to collect some values along the vertical profile in the atmosphere. As a consequence, estimation techniques to fill the data gaps and to provide an evaluation of the related interpolation uncertainty are welcome. This paper aims to understand and quantify the interpolation uncertainty of the relative humidity (RH). In particular, we consider linear and Gaussian process interpolation either unidimensional or multidimensional. We provide results in terms of interpolation distance in seconds, which measures the distance of an interpolated data from the interpolating data. We also consider measurement altitude and launch site. Although the Gaussian interpolation results to be generally better than linear interpolation, the difference in uncertainty is relatively small. The average column uncertainty difference is in the order of 0.2% and for large data gaps around 0.4%. The interpolation uncertainty is larger in the lower atmosphere. For example at 2–4 km altitude, the uncertainty is around 2% at 10 s distance, around 5% at 40 s and 10% at 90 s. In the upper atmosphere, RH and its uncertainty decrease. For example, at 14–16 km altitude, the latter is smaller than 2% RH at all interpolation distances.
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Li, Xianyou, Ke Xu, and Shun Wang. "Precision Measurement Method of Large Shaft Diameter Based on Dual Camera System." Sensors 22, no. 11 (May 24, 2022): 3982. http://dx.doi.org/10.3390/s22113982.
Повний текст джерелаАнотація:
At present, there is a problem that the measurement accuracy and measurement range cannot be balanced in the measurement of shaft diameter by the machine vision method. In this paper, we propose a large-scale shaft diameter precision measurement method based on a dual camera measurement system. The unified world coordinate system of the two cameras is established by analyzing the dual camera imaging model and obtaining the measurement formula. In order to verify the validity of the proposed method, two black blocks in the calibration plate with a known center distance of 100 mm were measured. The mean value was 100.001 mm and the standard deviation was 0.00039 in 10 measurements. Finally, the proposed system was applied to the diameter measurement of a complexed crankshaft. The mean μ95 values of CMM and the proposed method were ±1.02 μm and ±1.07 μm, respectively, indicating that the measurement accuracy of the proposed method is roughly equal to the CMM.
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DVALI, GIA. "OBSERVABLE CONSEQUENCES OF STRONG COUPLING IN THEORIES WITH LARGE DISTANCE MODIFIED GRAVITY." International Journal of Modern Physics D 16, no. 12a (December 2007): 2013–21. http://dx.doi.org/10.1142/s0218271807011346.
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In this talk, we review theories that modify gravity at cosmological distances, and show that any such theory must exhibit a strong coupling phenomenon. We show that all consistent theories that modify the dynamics of the spin-2 graviton on asymptotically flat backgrounds, automatically have this property. Due to the strong coupling effect, modification of the gravitational force is source-dependent, and for lighter sources sets in at shorter distances. This universal feature makes modified gravity theories predictive and potentially testable by precision gravitational measurements at scales much shorter than the current cosmological horizon.
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Onoue, Yasuhiro, Tomohiro Ishizawa, Toru Danjo, and Teruki Fukuzono. "Proposing a Method to Analyze Slope Displacement Using the Distance Image Data of Depth Camera." Journal of Disaster Research 16, no. 7 (October 1, 2021): 1086–95. http://dx.doi.org/10.20965/jdr.2021.p1086.
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Sediment disasters have occurred with higher frequencies in recent years because of local heavy rains caused by line-shaped precipitation systems and torrential rains accompanying large typhoons. Since rescue operators are constantly under physical risk at disaster sites, there is a need for technologies to predict the occurrence of secondary disasters. The authors research the measurement of slope displacements by focusing on a depth camera that is readily deployable, can be easily set up, and enables monitoring of an extensive area but does not require expert knowledge to carry out measurements. In this process, we confirmed the difficulty of measuring slope changes preceding failure when the depth camera (DC) is set at a distance because of the large measurement errors caused by the limited depth resolution and poor measurement conditions under rainfall. In this study, we propose a new method for analyzing depth image data obtained by a depth camera and verify its validity for displacement measurements. After comparing the previous and proposed methods, we could confirm that the latter enables one to detect slope changes from minute deformations. When compared with the results of extensometers that directly measured the slope, we found that the results displayed similar tendencies of increase. Therefore, by measuring displacements preceding a slope failure using a depth camera and analyzing the depth image data acquired using the proposed method, we found that it is possible to detect minute changes that precede slope failures.
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Xie, Yuyang, Tao Yang, Xiaofeng Wang, Xi Chen, Shuxin Pang, Juan Hu, Anxian Wang, Ling Chen, and Zehao Shen. "Applying a Portable Backpack Lidar to Measure and Locate Trees in a Nature Forest Plot: Accuracy and Error Analyses." Remote Sensing 14, no. 8 (April 8, 2022): 1806. http://dx.doi.org/10.3390/rs14081806.
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Accurate tree positioning and measurement of structural parameters are the basis of forest inventory and mapping, which are important for forest biomass calculation and community dynamics analyses. Portable backpack lidar that integrates the simultaneous localization and mapping (SLAM) technique with a global navigation satellite system receiver has greater flexibility for tree inventory than terrestrial laser scanning, but it has never been used to measure and map forest structure in a large area (>101 hectares) with high tree density. In the present study, we used the LiBackpack DG50 backpack lidar system to obtain the point cloud data of a 10 ha plot of subtropical evergreen broadleaved forest, and applied these data to quantify errors and related factors in the diameter at breast height (DBH) measurements and positioning for more than 1900 individual trees. We found an average error of 4.19 cm in the DBH measurements obtained by lidar, compared with manual field measurements. The incompleteness of the tree stem point clouds was the main factor that caused the DBH measurement errors, and the field DBH measurements and density of the point clouds also had significant impacts. The average tree positioning error was 4.64 m, and it was significantly affected by the distance and route length from the measured trees to the data acquisition start position, whereas it was affected little by the habitat complexity and characteristics of tree stems. The tree positioning measurement error led to increases in the mean value and variability of paired-tree distance error as the sample plot scale increased. We corrected the errors based on the estimates of predictive models. After correction, the DBH measurement error decreased by 31.3%, the tree positioning error decreased by 44.3%, and the paired-tree distance error decreased by 56.3%. As the sample plot scale increased, the accumulated paired-tree distance error stabilized gradually.
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Yıldırım, Akın, Sherry H. Suyu, and Aleksi Halkola. "Time-delay cosmographic forecasts with strong lensing and JWST stellar kinematics." Monthly Notices of the Royal Astronomical Society 493, no. 4 (February 27, 2020): 4783–807. http://dx.doi.org/10.1093/mnras/staa498.
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ABSTRACT We present a joint strong lensing and stellar dynamical framework for future time-delay cosmography purposes. Based on a pixelated source reconstruction and the axisymmetric Jeans equations, we are capable of constraining cosmological distances and hence the current expansion rate of the Universe (H0) to the few per cent level per lens, when high signal-to-noise integral field unit (IFU) observations from the next generation of telescopes become available. For illustrating the power of this method, we mock up IFU stellar kinematic data of the prominent lens system RXJ1131−1231, given the specifications of the James Webb Space Telescope. Our analysis shows that the time-delay distance (DΔt) can be constrained with 3.1 per cent uncertainty at best, if future IFU stellar kinematics are included in the fit and if the set of candidate model parametrizations contains the true lens potential. These constraints would translate to a 3.2 per cent precision measurement on H0 in flat ΛCDM cosmology from the single lens RXJ1131−1231, and can be expected to yield an H0 measure with ≤2.0 per cent uncertainty, if similar gains in precision can be reached for two additional lens systems. Moreover, the angular diameter distance (Dd) to RXJ1131−1231 can be constrained with 2.4 per cent precision, providing two distance measurements from a single lens system, which is extremely powerful to further constrain the matter density (Ωm). The measurement accuracy of Dd, however, is highly sensitive to any systematics in the measurement of the stellar kinematics. For both distance measurements, we strongly advise to probe a large set of physically motivated lens potentials in the future, to minimize the systematic errors associated with the lens mass parametrization.
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Hajra, Rajkumar, Pierre Henri, Xavier Vallières, Marina Galand, Martin Rubin, Bruce T. Tsurutani, Nicolas Gilet, Luca Bucciantini, and Zoltan Nemeth. "Ionospheric total electron content of comet 67P/Churyumov-Gerasimenko." Astronomy & Astrophysics 635 (March 2020): A51. http://dx.doi.org/10.1051/0004-6361/201937022.
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We study the evolution of a cometary ionosphere, using approximately two years of plasma measurements by the Mutual Impedance Probe on board the Rosetta spacecraft monitoring comet 67P/Churyumov-Gerasimenko (67P) during August 2014–September 2016. The in situ plasma density measurements are utilized to estimate the altitude-integrated electron number density or cometary ionospheric total electron content (TEC) of 67P based on the assumption of radially expanding plasma. The TEC is shown to increase with decreasing heliocentric distance (rh) of the comet, reaching a peak value of ~(133 ± 84) × 109 cm−2 averaged around perihelion (rh < 1.5 au). At large heliocentric distances (rh > 2.5 au), the TEC decreases by ~2 orders of magnitude. For the same heliocentric distance, TEC values are found to be significantly larger during the post-perihelion periods compared to the pre-perihelion TEC values. This “ionospheric hysteresis effect” is more prominent in the southern hemisphere of the comet and at large heliocentric distances. A significant hemispheric asymmetry is observed during perihelion with approximately two times larger TEC values in the northern hemisphere compared to the southern hemisphere. The asymmetry is reversed and stronger during post-perihelion (rh > 1.5 au) periods with approximately three times larger TEC values in the southern hemisphere compared to the northern hemisphere. Hemispheric asymmetry was less prominent during the pre-perihelion intervals. The correlation of the cometary TEC with the incident solar ionizing fluxes is maximum around and slightly after perihelion (1.5 au < rh < 2 au), while it significantly decreases at larger heliocentric distances (rh > 2.5 au) where the photo-ionization contribution to the TEC variability decreases. The results are discussed based on cometary ionospheric production and loss processes.
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Reginsson, Gunnar W., and Olav Schiemann. "Pulsed electron–electron double resonance: beyond nanometre distance measurements on biomacromolecules." Biochemical Journal 434, no. 3 (February 24, 2011): 353–63. http://dx.doi.org/10.1042/bj20101871.
Повний текст джерелаАнотація:
PELDOR (or DEER; pulsed electron–electron double resonance) is an EPR (electron paramagnetic resonance) method that measures via the dipolar electron–electron coupling distances in the nanometre range, currently 1.5–8 nm, with high precision and reliability. Depending on the quality of the data, the error can be as small as 0.1 nm. Beyond mere mean distances, PELDOR yields distance distributions, which provide access to conformational distributions and dynamics. It can also be used to count the number of monomers in a complex and allows determination of the orientations of spin centres with respect to each other. If, in addition to the dipolar through-space coupling, a through-bond exchange coupling mechanism contributes to the overall coupling both mechanisms can be separated and quantified. Over the last 10 years PELDOR has emerged as a powerful new biophysical method without size restriction to the biomolecule to be studied, and has been applied to a large variety of nucleic acids as well as proteins and protein complexes in solution or within membranes. Small nitroxide spin labels, paramagnetic metal ions, amino acid radicals or intrinsic clusters and cofactor radicals have been used as spin centres.
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Voirin, Jordan, Carlo F. Manara, and Timo Prusti. "A revised estimate of the distance to the clouds in the Chamaeleon complex using the Tycho–Gaia Astrometric Solution." Astronomy & Astrophysics 610 (February 2018): A64. http://dx.doi.org/10.1051/0004-6361/201731153.
Повний текст джерелаАнотація:
Context. The determination of the distance to dark star-forming clouds is a key parameter to derive the properties of the cloud itself and of its stellar content. This parameter is still loosely constrained even in nearby star-forming regions. Aim. We want to determine the distances to the clouds in the Chamaeleon-Musca complex and explore the connection between these clouds and the large-scale cloud structures in the Galaxy. Methods. We used the newly estimated distances obtained from the parallaxes measured by the Gaia satellite and included in the Tycho–Gaia Astrometric Solution catalog. When known members of a region are included in this catalog we used their distances to infer the distance to the cloud. Otherwise, we analyzed the dependence of the color excess on the distance of the stars and looked for a turn-on of this excess, which is a proxy of the position of the front-edge of the star-forming cloud. Results. We are able to measure the distance to the three Chamaeleon clouds. The distance to Chamaeleon I is 179-10-10+11+11pc, where the quoted uncertainties are statistical and systematic uncertainties, respectively, ~20 pc further away than previously assumed. The Chamaeleon II cloud is located at the distance of 181-5-10+6+11pc, which agrees with previous estimates. We are able to measure for the first time a distance to the Chamaeleon III cloud of 199-7-11+8+12pc. Finally, the distance of the Musca cloud is smaller than 603603-70-92+91+133 pc. These estimates do not allow us to distinguish between the possibility that the Chamaeleon clouds are part of a sheet of clouds parallel to the Galactic plane, or perpendicular to it. Conclusions. We measured a larger distance to the Chamaeleon I cloud than assumed in the past, confirmed the distance to the Chamaeleon II region, and measured for the first time the distance to the Chamaleon III cloud. These values are consistent with the scenario in which the three clouds are part of a single large-scale structure. Gaia Data Release 2 will allow us to put more stringent constraints on the distances to these clouds by giving us access to parallax measurements for a larger number of members of these regions.
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Pillarz, Marc, Axel von Freyberg, and Andreas Fischer. "Gear Shape Parameter Measurement Using a Model-Based Scanning Multi-Distance Measurement Approach." Sensors 20, no. 14 (July 14, 2020): 3910. http://dx.doi.org/10.3390/s20143910.
Повний текст джерелаАнотація:
To reduce wind turbine failures by defective drive trains, deviations in the geometry of large gears (diameter ≳ 1 m) must be extensively determined with single-digit micrometer uncertainties. Fixed measuring volumes limit standard measuring methods like coordinate and gear measuring instruments for large gear measurements. Therefore, a model-based scanning multi-distance measurement approach for gear shape parameters is presented. The measurement approach has a scalable design and consists of a confocal-chromatic sensor, rotary table as a scanning unit and model-based signal processing. A preliminary study on a midsize spur gear demonstrates the general feasibility of the model-based scanning multi-distance measurement approach. As a result, the mean base circle radius as the fundamental gear shape parameter is determined with an uncertainty of <5 μm. The calibration and adjustment of the sensor arrangement were performed with a known calibration gear. Scalability is not experimentally validated in this article. However, simulations verify the scalability of the measurement approach in a first step. For gears with 1 m in diameter and varying tooth flank geometries, the estimated achievable uncertainty of the mean base circle radius is still <5 μm. Therefore, the model-based scanning multi-distance measurement approach is a promising alternative for gear inspection.
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Cabrera, Doreen, Daniel Andres, Philip D. McLoughlin, Lucie Debeffe, Sarah A. Medill, Alastair J. Wilson, and Jocelyn Poissant. "Island tameness and the repeatability of flight initiation distance in a large herbivore." Canadian Journal of Zoology 95, no. 10 (October 2017): 771–78. http://dx.doi.org/10.1139/cjz-2016-0305.
Повний текст джерелаАнотація:
Antipredator behaviours can be lost relatively quickly in populations that are relieved of predation, as is known for several species inhabiting islands. Flight initiation distance (FID) is often studied in the context of island tameness; however, little is known about the factors that influence and maintain FID variation in predation-free populations. Here, we studied FID in foals of an isolated predator-free population of feral horses (Equus caballus L., 1758) on Sable Island, Canada, to determine if FID could be used for research on consistent individual differences in risk aversion and island tameness. In addition to testing for temporal, spatial, and sex effects on FID, we compared repeatability estimates at two temporal scales (within and among days). Similar FID for measurements obtained on the same day and for males and females indicated an absence of short-term desensitization and sex effects. In contrast, FID decreased for measurements made on subsequent days and from east to west, which could reflect habituation to human presence and (or) other temporal and spatial processes. Repeatability was high (0.42 ± 0.06), but tended to decrease with increasing time intervals. This study highlights the potential of FID for individual-based research on the ecology and evolutionary dynamics of risk aversion in predation-free populations.