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1
Özdin, Kamil, Emrah Büyük, Firuz Abdalov, Hüsamettin Bayram, and Ahmet Çini. "Investigation of Spring-Back and Spring-Go of AISI 400 S Sheet Metal in "V" Bending Dies Depending on Bending Angle and Punch Radius." Applied Mechanics and Materials 532 (February 2014): 549–53. http://dx.doi.org/10.4028/www.scientific.net/amm.532.549.
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The components made of steel sheet metal very important in todays industry. In order to be useful, those parts must comply with the design tolerances, such as shape, position and dimensions. The largest problem with the parts bended by using dies is the springing, because it violates the manufacturing tolerances. Therefore, it is vital to know a parts springback and springgo properties in advance, which is mainly dependent on the properties of the sheet metal and bending conditions.In this study, 0.9 mm AISI 400 S steel sheet metal was bended using V dies (30°, 45°and 60°) and punches (2 mm, 4 mm and 6 mm). After being removed from the bending dies,springback rates of the specimens were measured by using optical goniometer. With respect to the bending angles and punch radii, springback and springgo properties of the specimens were recorded by using a spreadsheet software and some figures are obtained.
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Scherllin-Pirscher, B., S. Syndergaard, U. Foelsche, and K. B. Lauritsen. "Generation of a Bending Angle Radio Occultation Climatology (BAROCLIM) and its use in radio occultation retrievals." Atmospheric Measurement Techniques Discussions 7, no. 8 (August 8, 2014): 8193–231. http://dx.doi.org/10.5194/amtd-7-8193-2014.
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Abstract. In this paper, we introduce a bending angle radio occultation climatology (BAROCLIM) based on Formosat-3/COSMIC (F3C) data. This climatology represents the monthly-mean atmospheric state from 2006 to 2012. Bending angles from radio occultation (RO) measurements are obtained from the accumulation of the change in the raypath direction of Global Positioning System (GPS) signals. Best quality of these near-vertical profiles is found from the middle troposphere up to the mesosphere. Beside RO bending angles we also use data from the Mass Spectrometer and Incoherent Scatter Radar (MSIS) model to expand BAROCLIM in a spectral model, which (theoretically) reaches from the surface up to infinity. Due to the very high quality of BAROCLIM up to the mesosphere, it can be used to detect deficiencies in current state-of-the-art analysis and reanalysis products from numerical weather prediction (NWP) centers. For bending angles derived from European Centre for Medium-Range Weather Forecasts (ECMWF) analysis fields from 2006 to 2012, e.g., we find a positive bias of 0.5% to % at 40 km, which increases to more than 2% at 50 km. BAROCLIM can also be used as a priori information in RO profile retrievals. In contrast to other a priori information (i.e., MSIS) we find that the use of BAROCLIM better preserves the mean of raw RO measurements. Global statistics of statistically optimized bending angle and refractivity profiles also confirm that BAROCLIM outperforms MSIS. These results clearly demonstrate the utility of BAROCLIM.
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Scherllin-Pirscher, B., S. Syndergaard, U. Foelsche, and K. B. Lauritsen. "Generation of a bending angle radio occultation climatology (BAROCLIM) and its use in radio occultation retrievals." Atmospheric Measurement Techniques 8, no. 1 (January 9, 2015): 109–24. http://dx.doi.org/10.5194/amt-8-109-2015.
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Abstract. In this paper, we introduce a bending angle radio occultation climatology (BAROCLIM) based on Formosat-3/COSMIC (F3C) data. This climatology represents the monthly-mean atmospheric state from 2006 to 2012. Bending angles from radio occultation (RO) measurements are obtained from the accumulation of the change in the raypath direction of Global Positioning System (GPS) signals. Best quality of these near-vertical profiles is found from the middle troposphere up to the mesosphere. Beside RO bending angles we also use data from the Mass Spectrometer and Incoherent Scatter Radar (MSIS) model (modified for RO purposes) to expand BAROCLIM in a spectral model, which (theoretically) reaches from the surface up to infinity. Due to the very high quality of BAROCLIM up to the mesosphere, it can be used to detect deficiencies in current state-of-the-art analysis and reanalysis products from numerical weather prediction (NWP) centers. For bending angles derived from European Centre for Medium-Range Weather Forecasts (ECMWF) analysis fields from 2006 to 2012, e.g., we find a positive bias of 0.5 to 1% at 40 km, which increases to more than 2% at 50 km. BAROCLIM can also be used as a priori information in RO profile retrievals. In contrast to other a priori information (i.e., MSIS) we find that the use of BAROCLIM better preserves the mean of raw RO measurements. Global statistics of statistically optimized bending angle and refractivity profiles also confirm that BAROCLIM outperforms MSIS. These results clearly demonstrate the utility of BAROCLIM.
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Zeng, Z., S. Sokolovskiy, W. Schreiner, D. Hunt, J. Lin, and Y. H. Kuo. "Ionospheric correction of GPS radio occultation data in the troposphere." Atmospheric Measurement Techniques Discussions 8, no. 7 (July 24, 2015): 7781–803. http://dx.doi.org/10.5194/amtd-8-7781-2015.
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Abstract. For inversions of the GPS radio occultation (RO) data in the neutral atmosphere, this study investigates an optimal transition height for replacing the standard ionospheric correction by the linear combination of the L1 and L2 bending angles with the correction of the L1 bending angle by the L1-L2 bending angle extrapolated from above. The optimal transition height depends on the RO mission (i.e., the receiver and firmware) and is different between rising and setting occultations and between L2P and L2C GPS signals. This height is within the range approximately 10–20 km. One fixed transition height, which can be used for the processing of currently available GPS RO data, can be set to 20 km. Analysis of the L1CA and the L2C bending angles in the presence of a sharp top of the boundary layer reveals differences that can be explained by shifts in the impact parameter. The ionosphere-induced vertical shifts of the bending angle profiles require further investigation.
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Zeng, Z., S. Sokolovskiy, W. Schreiner, D. Hunt, J. Lin, and Y. H. Kuo. "Ionospheric correction of GPS radio occultation data in the troposphere." Atmospheric Measurement Techniques 9, no. 2 (February 3, 2016): 335–46. http://dx.doi.org/10.5194/amt-9-335-2016.
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Abstract. For inversions of the GPS radio occultation (RO) data in the neutral atmosphere, this study investigates an optimal transition height for replacing the standard ionospheric correction using the linear combination of the L1 and L2 bending angles with the correction of the L1 bending angle by the L1–L2 bending angle extrapolated from above. The optimal transition height depends on the RO mission (i.e., the receiver and firmware) and is different between rising and setting occultations and between L2P and L2C GPS signals. This height is within the range of approximately 10–20 km. One fixed transition height, which can be used for the processing of currently available GPS RO data, can be set to 20 km. Analysis of the L1CA and the L2C bending angles shows that in some occultations the errors of standard ionospheric correction substantially increase around the strong inversion layers (such as the top of the boundary layer). This error increase is modeled and explained by the horizontal inhomogeneity of the ionosphere.
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Owen, Frazer N. "The Extended Radio Structure of Quasars." Symposium - International Astronomical Union 119 (1986): 173–79. http://dx.doi.org/10.1017/s0074180900152593.
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Modern radio maps usually allow quasars to be recognized from their radio morphology alone. Most have strong central components, double lobed outer structure and one-sided jets connecting the inner and outer structures. The physics of the sources is poorly understood. The observed bending of the jets, the high minimum pressures observed, and the required energy supply to the lobes are major problems. However, the outstanding problem regarding the extended structure is whether or not this morphology is produced by special relativistic effects or the intrinsic activity level and physics of the radio sources.
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Healy, S. B. "Smoothing radio occultation bending angles above 40 km." Annales Geophysicae 19, no. 4 (April 30, 2001): 459–68. http://dx.doi.org/10.5194/angeo-19-459-2001.
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Abstract. The 'statistically optimal' approach to smoothing bending angles derived from radio occultation (RO) measurements is outlined. This combines a measured bending angle profile with an a priori or background estimate derived from climatology, in order to obtain the most probable bending angle profile. However, the method is only optimal if the error statistics of both the measured and background profiles are known and applied accurately. In this work it is shown that correlations in the background estimate have a significant role in determining the degree of smoothing in the solution. We find that smooth profiles, consistent with the measured values, can be derived if the correlations are approximated analytically with a Gaussian, assuming a scale length of 6km. In regions where the observed and background error levels are comparable, the solutions take the general shape from the background estimate, centred on the observation data. The effects of correlated observation errors are also considered. It is shown that the quality of the temperature retrievals can be significantly affected by the choice of climatology used for background estimate.Key words. Atmosphere composition and structure (pressure, density and temperature) – Radio science (remote sensing)
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Healy, S. B., J. Haase, and O. Lesne. "<i>Letter to the Editor</i>Abel transform inversion of radio occultation measurements made with a receiver inside the Earth’s atmosphere." Annales Geophysicae 20, no. 8 (August 31, 2002): 1253–56. http://dx.doi.org/10.5194/angeo-20-1253-2002.
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Abstract. Radio occultation measurements made with a receiver inside the Earth’s atmosphere can be inverted, assuming local spherical symmetry, with an Abel transform to provide an estimate of the atmospheric refractive index profile. The measurement geometry is closely related to problems encountered when inverting seismic time-travel data and solar occultation measurements, where the Abel solution is well known. The method requires measuring both rays that originate from above and below the local horizon of the receiver. The Abel transform operates on a profile of "partial bending angles" found by subtracting the positive elevation measurement from the negative elevation value with the same impact parameter. In principle, the refractive index profile can be derived from measurements with a single frequency GPS receiver because the ionospheric bending is removed when the partial bending angle is evaluated.Key words. Atmospheric composition and structure (pressure, density and temperature) – Radio science (remote sensing)
9
Pavliuchenko, Pavlo, Marco Teller, Markus Grüber, and Gerhard Hirt. "A Semianalytical Model for the Determination of Bistability and Curvature of Metallic Cylindrical Shells." Journal of Manufacturing and Materials Processing 3, no. 1 (February 27, 2019): 22. http://dx.doi.org/10.3390/jmmp3010022.
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Bistable metal shells with a fully closed unfolded geometry are of great interest as lightweight construction parts which could be transported without housing and unfolded at the construction place. In order to achieve the effect of bistability in metallic shells, residual stresses with a specific distribution along the shell thickness are necessary. These residual stresses can be introduced in bending processes. The tools with specific bending radii are used to influence the curvature of the shell in the different stable states and thus determine whether a completely closed profile can be achieved. In addition to the forming process, the shell thickness and the shell material have an effect on the achievable geometries and stability. In order to manufacture bistable metallic cylindrical shells from different materials and shell thicknesses, it is necessary to be able to determine a promising process sequence and corresponding bending radii in advance. For this reason, this article presents a semianalytical model for the calculation of bistability and final curvatures. This model is applied to an incremental die-bending process using two bending operations with bending radii of 6 to 12 mm and a 0.2 mm thick steel shell of grade 1.1274 (AISI 1095). The calculation results show that bistability cannot be reached for all combinations of the two bending radii. Moreover, the model indicates that a bistable and fully closed shell is only achieved for a bending radii combination of R1 = 6 mm and R2 = 6 mm. With the aim of model verification, experiments with a closed-die incremental bending tool were performed. Calculated and experimental results show good correlation regarding bistability and curvature. In addition, X-ray diffraction measurement of the residual stresses shows a good qualitative agreement regarding the calculated and experimental results.
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Tanaka, Mitsuhiro, Takahiro Namazu, and Shozo Inoue. "OS5-2-1 On-Chip Pure Bending Test for Measuring in-Plane Poisson's Ratio of MEMS Materials." Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2007.6 (2007): _OS5–2–1–1—_OS5–2–1–4. http://dx.doi.org/10.1299/jsmeatem.2007.6._os5-2-1-1.
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Liu, Geng Wu, and Zhen Long Zhong. "Study and Design of Sheet Metal Bending Springback Adjustable Die." Advanced Materials Research 152-153 (October 2010): 1092–96. http://dx.doi.org/10.4028/www.scientific.net/amr.152-153.1092.
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A kind of U type 90°or V type 90°bending springback testing die was set up to discuss the bending springback . The springback of material can be masteried through setting up of bending springback adjusting test die without prior calculation . In order to adjust the bending angle , the T type slide seat and bending press plate were used and the adjusting of bending radii was implemented by replacing the adjusting axis of bending radii. At first, if the springback value of the sheet metal made sure for the die design , then the die was designed , the large of works for repaired and tested die were reduced and it will be the `most convenient for the die designer.
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Biondi, R., T. Neubert, S. Syndergaard, and J. K. Nielsen. "Radio occultation bending angle anomalies during tropical cyclones." Atmospheric Measurement Techniques 4, no. 6 (June 15, 2011): 1053–60. http://dx.doi.org/10.5194/amt-4-1053-2011.
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Abstract. The tropical deep convection affects the radiation balance of the atmosphere changing the water vapor mixing ratio and the temperature of the upper troposphere lower stratosphere. The aim of this work is to better understand these processes and to investigate if severe storms leave a significant signature in radio occultation profiles in the tropical tropopause layer. Using tropical cyclone best track database and data from different GPS radio occultation missions (COSMIC, GRACE, CHAMP, SACC and GPSMET), we selected 1194 profiles in a time window of 3 h and a space window of 300 km from the eye of the cyclone. We show that the bending angle anomaly of a GPS radio occultation signal is typically larger than the climatology in the upper troposphere and lower stratosphere and that a double tropopause during deep convection can easily be detected using this technique. Comparisons with co-located radiosondes, climatology of tropopause altitudes and GOES analyses are also shown to support the hypothesis that the bending angle anomaly can be used as an indicator of convective towers. The results are discussed in connection to the GPS radio occultation receiver which will be part of the Atomic Clock Ensemble in Space (ACES) payload on the International Space Station.
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Biondi, R., T. Neubert, S. Syndergaard, and J. Nielsen. "Radio occultation bending angle anomalies during tropical cyclones." Atmospheric Measurement Techniques Discussions 4, no. 1 (February 28, 2011): 1371–95. http://dx.doi.org/10.5194/amtd-4-1371-2011.
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Abstract. The tropical deep convection affects the radiation balance of the atmosphere changing the water vapor mixing ratio and the temperature of the upper troposphere lower stratosphere. The aim of this work is to better understand these processes and to investigate if severe storms leave a significant signature in radio occultation profiles in the tropical tropopause layer. Using tropical cyclone best track database and data from different GPS radio occultation missions (COSMIC, GRACE, CHAMP, SACC and GPSMET), we selected 1194 profiles in a time window of 3 h and a space window of 300 km from the eye of the cyclone. We show that the bending angle anomaly of a GPS radio occultation signal is typically larger than the climatology in the upper troposphere and lower stratosphere and that a double tropopause during deep convection can easily be detected using this technique. Comparisons with co-located radiosondes, climatology of tropopause altitudes and GOES analyses are also shown to support the hypothesis that the bending angle anomaly can be used as an indicator of convective towers. The results are discussed in connection to the GPS radio occultation receiver which will be part of the Atomic Clock Ensemble in Space (ACES) payload on the International Space Station.
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Zhang, Bohan, Cheng Zhang, Yuchao Wang, Zhe Wang, Chengguo Liu, Daping He, and Zhi P. Wu. "Flexible Anti-Metal RFID Tag Antenna Based on High-Conductivity Graphene Assembly Film." Sensors 21, no. 4 (February 22, 2021): 1513. http://dx.doi.org/10.3390/s21041513.
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We propose a flexible anti-metal radio frequency identification (RFID) tag antenna based on a high-conductivity graphene assembly film (HCGAF). The HCGAF has a conductivity of 1.82 × 106 S m−1, a sheet resistance of 25 mΩ and a thickness of 22 μm. The HCGAF is endowed with high conductivity comparable to metal materials and superb flexibility, which is suitable for making antennas for microwave frequencies. Through proper structural design, parameter optimization, semiautomatic manufacturing and experimental measurements, an HCGAF antenna could realize a realized gain of –7.3 dBi and a radiation efficiency of 80%, and the tag could achieve a 6.4 m read range at 915 MHz on a 20 × 20 cm2 flat copper plate. In the meantime, by utilizing flexible polyethylene (PE) foam, good conformality was obtained. The read ranges of the tags attached to curved copper plates with different bending radii were measured, as well as those of those attached to several daily objects. All the results demonstrate the excellent performance of the design, which is highly favorable for practical RFID anti-metal applications.
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Hummel, C. A. "The Radio Jet of Quasar 0153+744." International Astronomical Union Colloquium 164 (1998): 61–62. http://dx.doi.org/10.1017/s0252921100044535.
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AbstractWe highlight a few aspects of the radio jet of quasar 0153+744. Some challenge the relativistic beaming model to explain a stationary jet of short length and ending in a bright secondary component, extreme bending of the jet, and the lack of any emission on the counter jet side. We discuss a model of a precessing mildly relativistic jet for 0153+744.
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Sol, H., S. Appl, and L. Vicente. "Distortion Effects in BL Lac Radio Jets." Symposium - International Astronomical Union 175 (1996): 477–78. http://dx.doi.org/10.1017/s0074180900081559.
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BL Lac objects often show a quite distorted radio morphology. Almost 75% of the BL Lacs for which the information is available show an apparent misalignment angle ΔPA between the VLBI jet and the large scale radio structure larger than 45 degrees. This can be explained by strong enhancement of slight bending due to projection effects, especially if BL Lacs are the most highly beamed sources. However we recently performed a statistical analysis of misalignment angle histograms for 155 extragalactic radio sources of different types and found that the intrinsic distortion is significantly more important in BL Lacs than in quasars and even CSS sources. Indeed the best fits of the δPA histograms by a simple bend model correspond to γɸ = 123° for BL Lacs, 37° for quasars and 36° for CSS sources, where ɸ and γ are the jet typical intrinsic bend and Lorentz factor within a given class of sources (Appl et al, 1995). If, as currently thought, jets in BL Lacs have smaller Lorentz factors than in quasars, high intrinsic bending and misalignment appear to be the rule in BL Lac sources.
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Gleisner, H., and S. B. Healy. "A simplified approach for generating GNSS radio occultation refractivity climatologies." Atmospheric Measurement Techniques 6, no. 1 (January 22, 2013): 121–29. http://dx.doi.org/10.5194/amt-6-121-2013.
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Abstract. The possibility of simplifying the retrieval scheme required to produce GNSS radio occultation refractivity climatologies is investigated. In a new, simplified retrieval approach, the main statistical analysis is performed in bending angle space and an estimate of the average bending angle profile is then propagated through an Abel transform. The average is composed of means and medians of ionospheric corrected bending angles up to 80 km. Above that, the observed profile is exponentially extrapolated to infinity using a fixed a priori scale height. The new approach circumvents the need to introduce a "statistical optimisation" processing step in which individual bending angle profiles are merged with a priori data, often taken from a climatology. This processing step can be complex, difficult to interpret, and is generally recognised as a potential source of structural uncertainty. The new scheme is compared with the more conventional approach of averaging individual refractivity profiles, produced with the implementation of statistical optimisation used in the EUMETSAT Radio Occultation Meteorology Satellite Application Facility (ROM SAF) operational processing. It is shown that the two GNSS radio occultation climatologies agree to within 0.1% from 5 km up to 35–40 km, for the three months January, February, and March 2011. During this time period, the new approach also produces slightly better agreement with ECMWF analyses between 40–50 km, which is encouraging. The possible limitations of the new approach caused by mean residual ionospheric errors and low observation numbers are discussed briefly, and areas for future work are suggested.
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Gleisner, H., and S. B. Healy. "A simplified approach for generating GNSS radio occultation refractivity climatologies." Atmospheric Measurement Techniques Discussions 5, no. 4 (July 27, 2012): 5245–69. http://dx.doi.org/10.5194/amtd-5-5245-2012.
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Abstract. The possibility of simplifying the retrieval scheme required to produce GNSS radio occultation refractivity climatologies is investigated. In a new, simplified retrieval approach, the main statistical analysis is performed in bending angle space and an estimate of the average bending angle profile is then propagated through an Abel transform. The average is composed of means and medians of ionospheric corrected bending angles up to 80 km. Above that, the observed profile is exponentially extrapolated to infinity using a fixed a priori scale height. The new approach circumvents the need to introduce a "statistical optimization" processing step in which individual bending-angle profiles are merged with a priori data, often taken from a climatology. This processing step can be complex, difficult to interpret, and is generally recognized as a potential source of structural uncertainty. The new scheme is compared with the more conventional approach of averaging individual refractivity profiles, produced with the implementation of statistical optimization used in the EUMETSAT Radio Occultation Meteorology Satellite Application Facility (ROM SAF) operational processing. It is shown that the two GNSS radio occultation climatologies agree to within 0.1% from 5 km up to 35–40 km, for the three months January, February, and March 2011. During this time period, the new approach also produces slightly better agreement with ECMWF analyses between 40–50 km, which is encouraging. The possible limitations of the new approach caused by mean residual ionospheric errors and low observation numbers are discussed briefly, and areas for future work are suggested.
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Aparicio, Josep M., Estel Cardellach, and Hilda Rodríguez. "Information content in reflected signals during GPS Radio Occultation observations." Atmospheric Measurement Techniques 11, no. 4 (April 5, 2018): 1883–900. http://dx.doi.org/10.5194/amt-11-1883-2018.
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Abstract. The possibility of extracting useful information about the state of the lower troposphere from the surface reflections that are often detected during GPS radio occultations (GPSRO) is explored. The clarity of the reflection is quantified, and can be related to properties of the surface and the low troposphere. The reflected signal is often clear enough to show good phase coherence, and can be tracked and processed as an extension of direct non-reflected GPSRO atmospheric profiles. A profile of bending angle vs. impact parameter can be obtained for these reflected signals, characterized by impact parameters that are below the apparent horizon, and that is a continuation at low altitude of the standard non-reflected bending angle profile. If there were no reflection, these would correspond to tangent altitudes below the local surface, and in particular below the local mean sea level. A forward operator is presented, for the evaluation of the bending angle of reflected GPSRO signals, given atmospheric properties as described by a numerical weather prediction system. The operator is an extension, at lower impact parameters, of standard bending angle operators, and reproduces both the direct and reflected sections of the measured profile. It can be applied to the assimilation of the reflected section of the profile as supplementary data to the direct section. Although the principle is also applicable over land, this paper is focused on ocean cases, where the topographic height of the reflecting surface, the sea level, is better known a priori.
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Gorbunov, Michael E., Estel Cardellach, and Kent B. Lauritsen. "Reflected ray retrieval from radio occultation data using radio holographic filtering of wave fields in ray space." Atmospheric Measurement Techniques 11, no. 2 (March 1, 2018): 1181–91. http://dx.doi.org/10.5194/amt-11-1181-2018.
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Abstract. Linear and non-linear representations of wave fields constitute the basis of modern algorithms for analysis of radio occultation (RO) data. Linear representations are implemented by Fourier Integral Operators, which allow for high-resolution retrieval of bending angles. Non-linear representations include Wigner Distribution Function (WDF), which equals the pseudo-density of energy in the ray space. Representations allow for filtering wave fields by suppressing some areas of the ray space and mapping the field back from the transformed space to the initial one. We apply this technique to the retrieval of reflected rays from RO observations. The use of reflected rays may increase the accuracy of the retrieval of the atmospheric refractivity. Reflected rays can be identified by the visual inspection of WDF or spectrogram plots. Numerous examples from COSMIC data indicate that reflections are mostly observed over oceans or snow, in particular over Antarctica. We introduce the reflection index that characterizes the relative intensity of the reflected ray with respect to the direct ray. The index allows for the automatic identification of events with reflections. We use the radio holographic estimate of the errors of the retrieved bending angle profiles of reflected rays. A comparison of indices evaluated for a large base of events including the visual identification of reflections indicated a good agreement with our definition of reflection index.
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Li, Mingzhe, and Xinan Yue. "Statistically analyzing the effect of ionospheric irregularity on GNSS radio occultation atmospheric measurement." Atmospheric Measurement Techniques 14, no. 4 (April 22, 2021): 3003–13. http://dx.doi.org/10.5194/amt-14-3003-2021.
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Abstract. The Global Navigation Satellite System (GNSS) atmospheric radio occultation (RO) has been an effective method for exploring Earth's atmosphere. RO signals propagate through the ionosphere before reaching the neutral atmosphere. The GNSS signal is affected by the ionospheric irregularity including the sporadic E (Es) and F region irregularity mainly due to the multipath effect. The effect of ionospheric irregularity on atmospheric RO data has been demonstrated by several studies in terms of analyzing singe cases. However, its statistical effect has not been investigated comprehensively. In this study, based on the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO data during 2011–2013, the failed inverted RO events occurrence rate and the bending angle oscillation, which is defined as the standard deviation of the bias between the observed bending angle and the National Center for Atmospheric Research (NCAR) climatology model bending angle between 60 and 80 km, were used for statistical analysis. It is found that at middle and low latitudes during the daytime, the failed inverted RO occurrence and the bending angle oscillation show obvious latitude, longitude, and local time variations, which correspond well with the Es occurrence features. The F region irregularity (FI) contributes to the obvious increase of the failed inverted RO occurrence rate and the bending angle oscillation value during the nighttime over the geomagnetic equatorial regions. For high latitude regions, the Es can increase the failed inverted RO occurrence rate and the bending angle oscillation value during the nighttime. There also exists the seasonal dependency of the failed inverted RO event and the bending angle oscillation. Overall, the ionospheric irregularity effects on GNSS atmospheric RO measurement statistically exist in terms of failed RO event inversion and bending angle oscillation. Awareness of these effects could benefit both the data retrieval and applications of RO in the lower atmosphere.
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Määttä, Antti, Kari Mäntyjärvi, and Jussi A. Karjalainen. "Incremental Bending of Ultra-High-Strength Steels." Key Engineering Materials 473 (March 2011): 53–60. http://dx.doi.org/10.4028/www.scientific.net/kem.473.53.
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Utilisation of ultra-high-strength steels (UHS) has increased, particularly in the automotive industry. By using these materials vehicle structures can be lightened. However, one of the problems of UHS is weak formability. Materials fracture easily with small bending radii and the minimum bending radii are rather large. In this study, the tested materials were complex phase (CP) bainitic-martensitic UHS steels (YS/TS 960/1000 and 1100/1250). The steels were incrementally bent with a press brake in the rolling direction and perpendicular to it, and the final bending angle was 90 degrees. The incremental bending angles were 150°, 130°, 110° and 90°. The punch was unloaded after every incremental bending step. The test materials were bent with different bending radii. The aim was to find the minimum bending radius which produces an acceptable bend. Every incremental bend was compared with a bending performed in the traditional manner. The aim of this study was to examine how well the results of incremental bending compare to roll forming. In addition, clarification studies of when the bend started to fracture were made. It is well known that steels are more efficiently bent by roll forming compared with traditional bending. The results presented in this study demonstrate that incremental bending does not produce better results than traditional bending. Nevertheless, it has been shown that the examined steels can be bent incrementally against manufacturer’s recommendations.
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Michalczyk, J., and K. Wojsyk. "Development and Modelling of the Method of Mandrelless Small-Radius Tube Bending / Opracowanie I Modelowanie Sposobu Beztrzpieniowego Gięcia Rur Na Małych Promieniach." Archives of Metallurgy and Materials 60, no. 4 (December 1, 2015): 2797–804. http://dx.doi.org/10.1515/amm-2015-0449.
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The paper reports the results of research aimed at creating theoretical grounds for a new method of mandrelless small-radius tube bending (1.5Dr<Rg<2.5Dr, where Dr- tube diameter, Rg- bending radius). As the result of applying such a methodology it is possible to carry out the bending process (with an angle of up to 180°) and obtain an ovalization and wall thinning in the bending area, which are much smaller than those in currently manufactured products. The currently used bending methods and bending equipment are able to achieve a minimum bending radius not less than three times the tube outer diameter. The research hypothesis has assumed the existence of tube bending methods that are more efficient that those known so far. Than methods do not rely on circular bending contours, but instead they may use other shaping die contours which has not been explored yet. Circular benders used in practice fail in that they do not yield the expected results on small radii and do not control the material flow (do not ensure its correct behaviour) in the bending zone. The literature review has shown that there are currently no theoretical studies, numerical analyses and experimental verifications related to the processes of mandrelless tube bending on small radii, i.e. for 1.5D≤R≥2.5D, where: (R - bending radius, D - tube outer diameter) up to an angle of 180°. Due to the lack of studies on this subject, in their approach to the numerical modelling of the problem, the authors of the paper were guided by their own experience in this field and made every effort to make the numerical model reflect the actual process as accurately as possible. They were only aided by the general knowledge accumulated in the literature on numerical modelling. To sum up, the purpose of the publication is to demonstrate that the change in the die recess towards a shape resembling an ellipse results in a change in the characteristics of metal flow (movement) along the tube perimeter and in a change in the stress characteristics and, as a consequence, a change in the tube cross-section in the bending zone. The research discussed in this paper seeks to establish the correct flow of material in the tube cross-section in the bending zone by determining the most efficient bender recess shape and friction surface forming, which will eliminate the excessive ovalization and upper wall thinning. The expected effect of implementing this bending technology will be increasing the flow capacity in energy systems, which will directly translate into a reduction of atmospheric CO emissions due to the lower energy consumption. In addition, the paper has presented the concepts of tools intended for the experimental verification of tube bending process.
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Burrows, C. P., S. B. Healy, and I. D. Culverwell. "Improving the bias characteristics of the ROPP refractivity and bending angle operators." Atmospheric Measurement Techniques Discussions 7, no. 5 (May 6, 2014): 4439–80. http://dx.doi.org/10.5194/amtd-7-4439-2014.
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Abstract. The bending angle observation operator (forward model) currently used to assimilate radio occultation (RO) data at the Met Office, ECMWF and other centres is the same as is included in the Radio Occultation Processing Package (ROPP), along with the corresponding tangent-linear and adjoint code. The functionality of this package is described in another paper in this issue. The mean bending angle innovations produced with this operator using Met Office background fields show a bias that oscillates with height and whose magnitude peaks between the model levels. These oscillations have been attributed to shortcomings in the assumption of exponentially varying refractivity between model levels. This is used directly in the refractivity operator, and indirectly to produce forward-modelled bending angles via the Abel transform. When the spacing between the model levels is small, this assumption is acceptable, but at stratospheric heights where the model level spacing is large, these biases can be significant, and can potentially degrade analyses. This paper provides physically-based improvements to the functional form of refractivity with height. These new assumptions considerably improve the oscillatory bias, and a number of approaches for practical implementation of the bending angle operator are provided.
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Choi. "Flexural Resistance and Ductility Ratio of Composite Hybrid I-Girder using HSB High Performance Steel in Positive Bending." Journal of Korean Society of Steel Construction 26, no. 3 (2014): 205. http://dx.doi.org/10.7781/kjoss.2014.26.3.205.
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Chyzy, Krzysztof T. "On the Unification of Radio Galaxies and Quasars." Symposium - International Astronomical Union 159 (1994): 501. http://dx.doi.org/10.1017/s0074180900176740.
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A comparison of the projected linear size evolution of extended quasars and radio galaxies are often used as a test of the radio galaxy - quasar unification schemes. If both the mentioned categories of radio sources differ to an observer only due to the various viewing directions, then their radio linear sizes are expected to evolve with redshift in the same way (Gopal-Krishna & Kulkarni, 1992). However, apart from the simplest linear size parameter L we can still determine two independent parameters assessing the asymmetry of the radio structure: Q - the arm lengths ratio; M - misalignment, which measures the apparent bending, and defined as the ratio of the displacement of the core from the source axis to the linear size. The asymmetry parameters Q and M can also be a powerful tool in the consistency test for the orientation based unification scheme as their evolutionary patterns should be the same for radio galaxies and quasars. Contrary to the linear size, they are not sensitive to the simple homological rescaling of the whole structure and hence to the age or expansion velocity of the structure.
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Vespe, Francesco, and Teresa Persia. "Derivation of the Water Vapor Content from the GNSS Radio Occultations Observations." Journal of Atmospheric and Oceanic Technology 23, no. 7 (July 1, 2006): 936–43. http://dx.doi.org/10.1175/jtech1891.1.
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Abstract The present work investigates the possibility of retrieving humidity using the bending angle data obtained from radio occultation of GPS signals without additional external information. In particular, with the proposed approach, the dry pressure profiles are obtained by fitting the bending angles of the outer-troposphere layers (from h = h250K up to the stratopause) using the Hopfield dry atmosphere model. The ground pressure and temperature are the parameters of the model to be estimated. In the second step the humidity profiles are extracted by subtracting the contribution resulting from the dry atmosphere from the measured bending angles. Such derivation implies a complex mathematical treatment of the relationship between the bending angle and the refractivity, which is fully explained herein. Furthermore, the method was applied on Challenging Minisatellite Payload (CHAMP) profiles. The CHAMP profiles are achieved by applying heuristic retrieval algorithms based on the canonical transform. The algorithms are applied to minimize the negative refractivity bias that is observed for low-latitude GNSS RO. Thus, the results are shown and discussed in the second part of the paper. Finally, it is widely discussed how the proposed method is able to retrieve refractivity profiles without using the Abel inversion.
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Lasota, Elżbieta, Witold Rohm, Chian-Yi Liu, and Paweł Hordyniec. "Cloud Detection from Radio Occultation Measurements in Tropical Cyclones." Atmosphere 9, no. 11 (October 25, 2018): 418. http://dx.doi.org/10.3390/atmos9110418.
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Tropical cyclones (TC) are one of the main producers of clouds in the tropics and subtropics. Hence, most of the clouds in TCs are dense, with large water and ice content, and provide conditions conducive to investigate clouds’ impact on Radio Occultation (RO) measurements. Although the RO technique is considered insensitive to clouds, recent studies show a refractivity positive bias in cloudy conditions. In this study, we analyzed the RO bending angle sensitivity to cloud content during tropical cyclone seasons between 2007 and 2010. Thermodynamic parameters were obtained from the ERA-Interim reanalysis, whereas the water and ice cloud contents were retrieved from the CloudSat profiles. Our experiments confirm the positive mean RO refractivity bias in cloudy conditions that reach up to more than 0.5% at the geometric height of around 7 km. A similar bias but larger and shifted up is visible in bending angle anomaly (1.6%). Our results reveal that the influence of clouds is significant and can exceed the RO bending angle standard deviation for 21 out of 50 (42%) investigated profiles. Mean clouds’ impact is detectable between 9.0 and 10.5 km, while, in the case of single events, clouds in most of the observations are significant between 8 and 14 km. Almost 15% of the detectable clouds reach 16 km height, while the influence of the clouds below 5 km is insignificant. For more than half of the significant cases, the detection range is less than 3 km but for one observation this range spreads to 7–8 km.
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Xu, Xu, and Xiaolei Zou. "Global 3D Features of Error Variances of GPS Radio Occultation and Radiosonde Observations." Remote Sensing 13, no. 1 (December 22, 2020): 1. http://dx.doi.org/10.3390/rs13010001.
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Global Positioning System (GPS) radio occultation (RO) and radiosonde (RS) observations are two major types of observations assimilated in numerical weather prediction (NWP) systems. Observation error variances are required input that determines the weightings given to observations in data assimilation. This study estimates the error variances of global GPS RO refractivity and bending angle and RS temperature and humidity observations at 521 selected RS stations using the three-cornered hat method with additional ERA-Interim reanalysis and Global Forecast System forecast data available from 1 January 2016 to 31 August 2019. The global distributions, of both RO and RS observation error variances, are analyzed in terms of vertical and latitudinal variations. Error variances of RO refractivity and bending angle and RS specific humidity in the lower troposphere, such as at 850 hPa (3.5 km impact height for the bending angle), all increase with decreasing latitude. The error variances of RO refractivity and bending angle and RS specific humidity can reach about 30 N-unit2, 3 × 10−6 rad2, and 2 (g kg−1)2, respectively. There is also a good symmetry of the error variances of both RO refractivity and bending angle with respect to the equator between the Northern and Southern Hemispheres at all vertical levels. In this study, we provide the mean error variances of refractivity and bending angle in every 5°-latitude band between the equator and 60°N, as well as every interval of 10 hPa pressure or 0.2 km impact height. The RS temperature error variance distribution differs from those of refractivity, bending angle, and humidity, which, at low latitudes, are smaller (less than 1 K2) than those in the midlatitudes (more than 3 K2). In the midlatitudes, the RS temperature error variances in North America are larger than those in East Asia and Europe, which may arise from different radiosonde types among the above three regions.
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Angling, Matthew J., Sean Elvidge, and Sean B. Healy. "Improved model for correcting the ionospheric impact on bending angle in radio occultation measurements." Atmospheric Measurement Techniques 11, no. 4 (April 18, 2018): 2213–24. http://dx.doi.org/10.5194/amt-11-2213-2018.
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Abstract. The standard approach to remove the effects of the ionosphere from neutral atmosphere GPS radio occultation measurements is to estimate a corrected bending angle from a combination of the L1 and L2 bending angles. This approach is known to result in systematic errors and an extension has been proposed to the standard ionospheric correction that is dependent on the squared L1 ∕ L2 bending angle difference and a scaling term (κ). The variation of κ with height, time, season, location and solar activity (i.e. the F10.7 flux) has been investigated by applying a 1-D bending angle operator to electron density profiles provided by a monthly median ionospheric climatology model. As expected, the residual bending angle is well correlated (negatively) with the vertical total electron content (TEC). κ is more strongly dependent on the solar zenith angle, indicating that the TEC-dependent component of the residual error is effectively modelled by the squared L1 ∕ L2 bending angle difference term in the correction. The residual error from the ionospheric correction is likely to be a major contributor to the overall error budget of neutral atmosphere retrievals between 40 and 80 km. Over this height range κ is approximately linear with height. A simple κ model has also been developed. It is independent of ionospheric measurements, but incorporates geophysical dependencies (i.e. solar zenith angle, solar flux, altitude). The global mean error (i.e. bias) and the standard deviation of the residual errors are reduced from -1.3×10-8 and 2.2×10-8 for the uncorrected case to -2.2×10-10 rad and 2.0×10-9 rad, respectively, for the corrections using the κ model. Although a fixed scalar κ also reduces bias for the global average, the selected value of κ (14 rad−1) is only appropriate for a small band of locations around the solar terminator. In the daytime, the scalar κ is consistently too high and this results in an overcorrection of the bending angles and a positive bending angle bias. Similarly, in the nighttime, the scalar κ is too low. However, in this case, the bending angles are already small and the impact of the choice of κ is less pronounced.
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Burrows, C. P., S. B. Healy, and I. D. Culverwell. "Improving the bias characteristics of the ROPP refractivity and bending angle operators." Atmospheric Measurement Techniques 7, no. 10 (October 9, 2014): 3445–58. http://dx.doi.org/10.5194/amt-7-3445-2014.
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Abstract. The bending angle observation operator (forward model) currently used to assimilate radio occultation (RO) data at the Met Office, the European Centre for Medium-Range Weather Forecasts (ECMWF) and other centres is the same as is included in the Radio Occultation Processing Package (ROPP), along with the corresponding tangent-linear and adjoint code. The functionality of this package will be described in another paper in this issue. The mean bending angle innovations produced with this operator using Met Office background fields show a bias that oscillates with height and whose magnitude peaks between the model levels. These oscillations have been attributed to shortcomings in the assumption of exponentially varying refractivity between model levels. This is used directly in the refractivity operator, and indirectly to produce forward-modelled bending angles via the Abel transform. When the spacing between the model levels is small, this assumption is acceptable, but at stratospheric heights where the model level spacing is large, these biases can be significant, and can potentially degrade analyses. This paper provides physically based improvements to the functional form of refractivity with height. These new assumptions considerably improve the oscillatory bias, and a number of approaches for practical implementation of the bending angle operator are provided.
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Burns, Jack O. "Wide-angle tailed radio galaxies." Canadian Journal of Physics 64, no. 4 (April 1, 1986): 373–77. http://dx.doi.org/10.1139/p86-065.
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In this paper, the properties of a class of extragalactic radio sources associated with dominant cluster galaxies known as wide-angle tails (WATs) are reviewed. The mechanism responsible for forming and, in particular, bending these sources remains controversial nearly 10 years after their discovery. To gain possibly new insight into these radio galaxies, we divide them into three subclasses according to linear size. The smallest WATs are limited in size to the optical extent of the galaxies, are weaker in radio power, and may be bent by dynamic pressure as a result of motion of the radio galaxy about a second large galaxy or subcondensation of galaxies in the cluster. The large, 1-Mpc size WATs are associated with a single, dominant cD galaxy, have only sharp and irregularly placed bends in the jets, and probably interact with clouds in the cluster gas. The moderate-size, symmetrically bent WATs such as 3C 465 may bend and decollimate as a result of the passage of a jet through a sharp pressure gradient, which occurs within the halos of these galaxies.
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Liu, Zhenlu, Zhimin Zhao, Xiaolei Yu, Mengjie Liu, and Rendong Ji. "A novel reverse design method of tag antenna based on image analysis." Journal of Algorithms & Computational Technology 14 (January 2020): 174830262090696. http://dx.doi.org/10.1177/1748302620906969.
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Since the working efficiency of the entire radio frequency identification system depends on the performance of the radio frequency identification tag antenna, the research and design of the tag antenna have received attention, especially for radio frequency identification tags applied to special scenes. We mainly studied the effect of antenna bending on the performance of ultra-high frequency radio frequency identification systems, and combined the bent antenna with the impedance matching loop to achieve impedance matching between the chip and the antenna in the ultra-high frequency band. We analyzed the variation of tag antenna performance with antenna parameters by the simulation software High Frequency Structure Simulator (HFSS). At the same time, we propose a novel antenna reverse design method. Through the analysis of the antenna-specific absorption rate image, the antenna performance intensity is visually reflected. According to the image analysis result, the antenna parameters are corrected to improve the antenna matching performance. This design method is simpler and faster than other methods.
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Sokolovskiy, S., W. Schreiner, C. Rocken, and D. Hunt. "Optimal Noise Filtering for the Ionospheric Correction of GPS Radio Occultation Signals." Journal of Atmospheric and Oceanic Technology 26, no. 7 (July 1, 2009): 1398–403. http://dx.doi.org/10.1175/2009jtecha1192.1.
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Abstract GPS radio occultation remote sensing of the neutral atmosphere requires ionospheric correction of L1 and L2 signals. The ionosphere-corrected variables derived from radio occultation signals—such as the phase, Doppler, and bending angle—are affected by small-scale ionospheric effects that are not completely eliminated by the ionospheric correction. They are also affected by noise from mainly the L2 signal. This paper introduces a simple method for optimal filtering of the L4 = L1 − L2 signal used to correct the L1 signal, which minimizes the combined effects of both the small-scale ionospheric residual effects and L2 noise on the ionosphere-corrected variables. Statistical comparisons to high-resolution numerical weather models from the European Centre for Medium-Range Weather Forecasts (ECMWF) validate that this increases the accuracy of radio occultation inversions in the stratosphere.
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Sievert, Thomas, Joel Rasch, Anders Carlström, and Mats Ingemar Pettersson. "Analysis of reflections in GNSS radio occultation measurements using the phase matching amplitude." Atmospheric Measurement Techniques 11, no. 1 (January 29, 2018): 569–80. http://dx.doi.org/10.5194/amt-11-569-2018.
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Abstract. It is well-known that in the presence of super-refractive layers in the lower-tropospheric inversion of GNSS radio occultation (RO) measurements using the Abel transform yields biased refractivity profiles. As such it is problematic to reconstruct the true refractivity from the RO signal. Additional information about this lower region of the atmosphere might be embedded in reflected parts of the signal. To retrieve the bending angle, the phase matching operator can be used. This operator produces a complex function of the impact parameter, and from its phase we can calculate the bending angle. Instead of looking at the phase, in this paper we focus on the function's amplitude. The results in this paper show that the signatures of surface reflections in GNSS RO measurements can be significantly enhanced when using the phase matching method by processing only an appropriately selected segment of the received signal. This signature enhancement is demonstrated by simulations and confirmed with 10 hand-picked MetOp-A occultations with reflected components. To validate that these events show signs of reflections, radio holographic images are generated. Our results suggest that the phase matching amplitude carries information that can improve the interpretation of radio occultation measurements in the lower troposphere.
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Davtyan, Arman, Dominik Kriegner, Václav Holý, Ali AlHassan, Ryan B. Lewis, Spencer McDermott, Lutz Geelhaar, et al. "X-ray diffraction reveals the amount of strain and homogeneity of extremely bent single nanowires." Journal of Applied Crystallography 53, no. 5 (September 23, 2020): 1310–20. http://dx.doi.org/10.1107/s1600576720011516.
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Core–shell nanowires (NWs) with asymmetric shells allow for strain engineering of NW properties because of the bending resulting from the lattice mismatch between core and shell material. The bending of NWs can be readily observed by electron microscopy. Using X-ray diffraction analysis with a micro- and nano-focused beam, the bending radii found by the microscopic investigations are confirmed and the strain in the NW core is analyzed. For that purpose, a kinematical diffraction theory for highly bent crystals is developed. The homogeneity of the bending and strain is studied along the growth axis of the NWs, and it is found that the lower parts, i.e. close to the substrate/wire interface, are bent less than the parts further up. Extreme bending radii down to ∼3 µm resulting in strain variation of ∼2.5% in the NW core are found.
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Biondi, R., and T. Neubert. "Bending Angle and Temperature Climatologies from Global Positioning System Radio Occultations." Dataset Papers in Geosciences 2013 (March 27, 2013): 1–5. http://dx.doi.org/10.7167/2013/795749.
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The Global Positioning System (GPS) Radio Occultation (OR) technique provides estimates of atmospheric density, temperature, and water vapour content with high vertical resolution, global coverage, and high accuracy. We have used data acquired using this technique in the period 1995–2009 to create a reference climatology of radio occultation bending angle and atmospheric temperature which are used for meteorological studies. The bending angle is interesting because it is a direct measurement and independent of models. It is given with one-degree spatial resolution and 50-meter vertical sampling. In addition, we give the temperature climatology with one-degree spatial resolution and 100-meter vertical sampling. This dataset can be used for several applications including weather forecast, physics of atmosphere, and climate changes. Since the GPS signal is not affected by clouds and the acquisitions are evenly distributed in the globe, the dataset is well suited for studying extreme events (such as convective systems and tropical cyclones) and remote areas.
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Teng, Chuanxin, Fangda Yu, Shijie Deng, Houquan Liu, Libo Yuan, Jie Zheng, and Hongchang Deng. "Displacement Sensor Based on a Small U-Shaped Single-Mode Fiber." Sensors 19, no. 11 (June 3, 2019): 2531. http://dx.doi.org/10.3390/s19112531.
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A simple structure and easily fabricated displacement sensor was proposed and demonstrated based on a bending-induced fiber interferometer. In the design, the fiber interferometer was formed only by bending the single-mode fiber into a small U-shape without splicing, tapering, or heating pre-processing, which effectively reduces the complexity of the fabrication process, greatly enhances the mechanical strength of the sensor, and lowers the cost in the displacement sensing applications. The displacement sensing performances for the sensor with different bending radii of 3.3 mm, 4.4 mm, 5.0 mm, and 6.3 mm were investigated. Experimental results showed that the sensor had a good linear response, and for the bending radii of 3.3, 4.4, 5.0, and 6.3 mm, the proposed sensors showed high sensitivities of 134.3, 105.1, 120.9, and 144.1 pm/μm, respectively.
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Lan, Kuibo, Fei Wang, Qijun Zhang, Zhenqiang Ma, and Guoxuan Qin. "Performance prediction of bended radio-frequency capacitors and inductors on plastic substrates using artificial neural network." Modern Physics Letters B 35, no. 17 (April 9, 2021): 2150288. http://dx.doi.org/10.1142/s0217984921502882.
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Flexible radio-frequency (RF) capacitors and inductors on the plastic substrates have been fabricated and characterized under mechanical bending conditions. A novel method to predict the RF performance for them on different bending states is demonstrated. Artificial neural network (ANN) shows good modeling accuracy for the flexible RF passive components with bending strains from dc to resonant frequency ([Formula: see text] GHz for the capacitor/inductor). More importantly, the automatically generated ANN model, with no need of repeatedly tuning the model parameters, has demonstrated the ability to predict the RF responses for the flexible capacitors and inductors under arbitrary bending conditions with only a few sets of experimental data. Once established, this model can automatically learn the structure of the input date and predict the actual results on specific bending state which can provide an original method to measure the performance for flexible electronics on even extreme bent radius. The ANN model indicates good potential for accurate design, characterization and optimization of the high-performance flexible electronics.
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Scherllin-Pirscher, B., A. K. Steiner, G. Kirchengast, Y. H. Kuo, and U. Foelsche. "Empirical analysis and modeling of errors of atmospheric profiles from GPS radio occultation." Atmospheric Measurement Techniques 4, no. 9 (September 13, 2011): 1875–90. http://dx.doi.org/10.5194/amt-4-1875-2011.
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Abstract. The utilization of radio occultation (RO) data in atmospheric studies requires precise knowledge of error characteristics. We present results of an empirical error analysis of GPS RO bending angle, refractivity, dry pressure, dry geopotential height, and dry temperature. We find very good agreement between data characteristics of different missions (CHAMP, GRACE-A, and Formosat-3/COSMIC (F3C)). In the global mean, observational errors (standard deviation from "true" profiles at mean tangent point location) agree within 0.3% in bending angle, 0.1% in refractivity, and 0.2 K in dry temperature at all altitude levels between 4 km and 35 km. Above 35 km the increase of the CHAMP raw bending angle observational error is more pronounced than that of GRACE-A and F3C leading to a larger observational error of about 1% at 42 km. Above ≈20 km, the observational errors show a strong seasonal dependence at high latitudes. Larger errors occur in hemispheric wintertime and are associated mainly with background data used in the retrieval process particularly under conditions when ionospheric residual is large. The comparison between UCAR and WEGC results (both data centers have independent inversion processing chains) reveals different magnitudes of observational errors in atmospheric parameters, which are attributable to different background fields used. Based on the empirical error estimates, we provide a simple analytical error model for GPS RO atmospheric parameters for the altitude range of 4 km to 35 km and up to 50 km for UCAR raw bending angle and refractivity. In the model, which accounts for vertical, latitudinal, and seasonal variations, a constant error is adopted around the tropopause region amounting to 0.8% for bending angle, 0.35% for refractivity, 0.15% for dry pressure, 10 m for dry geopotential height, and 0.7 K for dry temperature. Below this region the observational error increases following an inverse height power-law and above it increases exponentially. For bending angle and refractivity we also include formulations for error correlations in order to enable modeling of full error covariance matrices for these primary data assimilation variables. The observational error model is the same for UCAR and WEGC data but due to somewhat different error characteristics below about 10 km and above about 20 km some parameters have to be adjusted. Overall, the observational error model is easily applicable and adjustable to individual error characteristics.
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Gorbunov, Michael E., and Gottfried Kirchengast. "Wave-optics uncertainty propagation and regression-based bias model in GNSS radio occultation bending angle retrievals." Atmospheric Measurement Techniques 11, no. 1 (January 10, 2018): 111–25. http://dx.doi.org/10.5194/amt-11-111-2018.
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Abstract. A new reference occultation processing system (rOPS) will include a Global Navigation Satellite System (GNSS) radio occultation (RO) retrieval chain with integrated uncertainty propagation. In this paper, we focus on wave-optics bending angle (BA) retrieval in the lower troposphere and introduce (1) an empirically estimated boundary layer bias (BLB) model then employed to reduce the systematic uncertainty of excess phases and bending angles in about the lowest 2 km of the troposphere and (2) the estimation of (residual) systematic uncertainties and their propagation together with random uncertainties from excess phase to bending angle profiles. Our BLB model describes the estimated bias of the excess phase transferred from the estimated bias of the bending angle, for which the model is built, informed by analyzing refractivity fluctuation statistics shown to induce such biases. The model is derived from regression analysis using a large ensemble of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO observations and concurrent European Centre for Medium-Range Weather Forecasts (ECMWF) analysis fields. It is formulated in terms of predictors and adaptive functions (powers and cross products of predictors), where we use six main predictors derived from observations: impact altitude, latitude, bending angle and its standard deviation, canonical transform (CT) amplitude, and its fluctuation index. Based on an ensemble of test days, independent of the days of data used for the regression analysis to establish the BLB model, we find the model very effective for bias reduction and capable of reducing bending angle and corresponding refractivity biases by about a factor of 5. The estimated residual systematic uncertainty, after the BLB profile subtraction, is lower bounded by the uncertainty from the (indirect) use of ECMWF analysis fields but is significantly lower than the systematic uncertainty without BLB correction. The systematic and random uncertainties are propagated from excess phase to bending angle profiles, using a perturbation approach and the wave-optical method recently introduced by Gorbunov and Kirchengast (2015), starting with estimated excess phase uncertainties. The results are encouraging and this uncertainty propagation approach combined with BLB correction enables a robust reduction and quantification of the uncertainties of excess phases and bending angles in the lower troposphere.
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Xiao, Han, Yu Chun Dang, Shi Hong Zhang, and De Hong Lu. "Numerical Simulation of Bending Angle on Geometric Accuracy of AZ31 Mg Alloy Profile during Warm Bending Process." Advanced Materials Research 482-484 (February 2012): 314–17. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.314.
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A 3D elastic-plastic thermo-mechanical coupled finite element model of AZ31 Mg alloy profile during warm bending process was established. The effect of bending angle on the geometric accuracy of the profile was investigated. The results indicate that with increasing bending angle, the springback angles increase from 7.56° to 8.27°; the bending radii decrease from 90.15 mm to 90.01 mm; the cross-section distortion of the bent profile increases.
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Arola, Anna Maija, Vili Kesti, and Raimo Ruoppa. "The Effect of Punch Radius on the Deformation of Ultra-High Strength Steel in Bending." Key Engineering Materials 639 (March 2015): 139–46. http://dx.doi.org/10.4028/www.scientific.net/kem.639.139.
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Bendability is an important material property for ultra-high strength steel. The bendability of a certain material is expressed as the minimum bending radius Rmin of the inner surface of the bend and expressed in multiples of the sheet thickness. Bendability is limited by either cracking on the surface or the edges of the bend or by surface waviness that usually precedes cracking on the outer surface. Surface waviness is a form of strain localization in bending and the intensity of the phenomenon is dependent on e.g. the punch radius, the lower tool width and the sheet thickness. In this study the bendability of a 960MPa grade steel was investigated using optical strain measurements of three-point bending tests to determine the strain level and the bending angle when localization starts with different punch radii. The unbent samples were marked with a grid using laser marking and the deformation was measured with the GOM ARGUS strain analysis system after bending. The quality of the bend was also evaluated visually. In addition, tensile tests were performed and evaluated with the GOM ARAMIS deformation analysis system to investigate the local mechanical properties of the studied steel. The results of strain measurements and visual evaluation were then compared. It was found that beyond a certain angle the maximum strain across the bend did not significantly change with further increases in the bending angle when the punch radius was at least three times the sheet thickness. But with smaller punch radii the maximum strain increased almost linearly with increasing bending angle until fracture appeared. With the smaller punch radii deformation localizes and surface waviness begins to form in smaller bending angles because the deformation is concentrated in a narrow zone.
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Healy, S. B., and I. D. Culverwell. "A modification to the ionospheric correction method used in GPS radio occultation." Atmospheric Measurement Techniques Discussions 8, no. 1 (January 27, 2015): 1177–201. http://dx.doi.org/10.5194/amtd-8-1177-2015.
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Abstract. A modification to the standard bending angle correction used in GPS radio occultation is proposed. The modified approach should reduce systematic residual ionospheric errors in GPS radio occultation climatologies. A new second order term is introduced in order to account for a known source of systematic error, which is generally neglected. The new term has the form κ(a) × (αL1 (a)-αL1(a))2, where a is the impact parameter, and (αL1, αL2) are the L1 and L2 bending angles, respectively. The variable κ is a weak function of impact parameter, a, but it does depend on a priori ionospheric information. The theoretical basis of the new term is examined. The sensitivity of κ to the assumed ionospheric parameters is investigated in one-dimensional simulations, and it is shown that κ &simeq; 10–20 rad−1. We note that the current implicit assumption is κ = 0, and this is probably adequate for numerical weather prediction applications. However, the uncertainty in κ should be included in the uncertainty estimates for the geophysical climatologies produced from GPS-RO measurements. The limitations of the new ionospheric correction when applied to CHAMP measurements are noted. These arise because of the assumption that the refractive index is unity at the satellite, made when deriving bending angles from the Doppler shift values.
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Cucurull, L., J. C. Derber, R. Treadon, and R. J. Purser. "Preliminary Impact Studies Using Global Positioning System Radio Occultation Profiles at NCEP." Monthly Weather Review 136, no. 6 (June 1, 2008): 1865–77. http://dx.doi.org/10.1175/2007mwr2260.1.
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Abstract Following the successful launch of the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) satellites in April 2006, NCEP’s Environmental Modeling Center (EMC) is planning to use the COSMIC data in its next-generation Global Data Assimilation System. In preparation for the assimilation of GPS radio occultation (RO) data from COSMIC and other missions, NCEP/EMC has developed the infrastructure necessary to use profiles of refractivity and bending angle in an operational framework. In both forward operators, horizontal gradients of refractivity have been neglected and each operator has been tuned with its corresponding quality control checks and error characterization. In this paper, the benefits of the assimilation of profiles of GPS RO on top of the current observations being regularly used in operations are analyzed. In addition, differences between the assimilation of bending angle and refractivity are discussed. To avoid unrealistic increments within the higher model layers, experiments not using GPS RO observations above 30 km are also performed. This stratospheric data assimilation problem was present in earlier experiments with GPS RO data at NCEP/EMC and impacted the forecast in the lower-atmospheric levels as well as the stratosphere. Some characteristics of the assimilation of profiles of bending angle are also discussed. Data from the Challenging Minisatellite Payload (CHAMP) satellite are available in non–real time at NOAA and have been used to perform the experiments examined herein.
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PETIT, J. P., and M. VITON. "GAUGE COSMOLOGICAL MODEL WITH VARIABLE LIGHT VELOCITY: III.: COMPARISON WITH QSO OBSERVATIONAL DATA." Modern Physics Letters A 04, no. 23 (November 10, 1989): 2201–10. http://dx.doi.org/10.1142/s0217732389002471.
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After a complement to previous papers on the gauge invariance of the Boltzmann collisional operator, we compare a recent homogeneous set of data on radio-QSOs, including angular sizes and bending of lobes, with what is expected from either our new cosmological gauge model or several conventional models. It is shown that the new gauge model provides a much better fit to the angular size distribution versus redshift than the Friedman model with q0=1 /2, and similarly to the bending, thanks to crude hypotheses on the mechanisms involved with the formation of jets.
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Anlauf, H., D. Pingel, and A. Rhodin. "Assimilation of GPS radio occultation data at DWD." Atmospheric Measurement Techniques 4, no. 6 (June 17, 2011): 1105–13. http://dx.doi.org/10.5194/amt-4-1105-2011.
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Abstract. We describe the status of the assimilation of bending angles from GPS radio occultations in the 3D-Var for DWD's operational global forecast model GME ("Global Model for Europe"). Experiments show that the assimilation of GPSRO data leads to a significant reduction of biases in the analyses of temperature, humidity and wind in the upper troposphere and the stratosphere, as well as a better r. m. s. fit in the comparison to radiosondes. The impact on forecasts is most prominent in the data sparse Southern Hemisphere, but is also quite notable in the Northern Hemisphere extra-tropics. The positive results found in the impact experiments lead to the implementation of the assimilation of GPS radio occultations from GRACE-A, FORMOSAT-3/COSMIC and GRAS/MetOp-A into the operational suite on 3 August 2010. We also show some initial results from assimilation experiments using radio occultation data from the German research satellite TerraSAR-X.
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Anlauf, H., D. Pingel, and A. Rhodin. "Assimilation of GPS radio occultation data at DWD." Atmospheric Measurement Techniques Discussions 4, no. 2 (March 2, 2011): 1533–54. http://dx.doi.org/10.5194/amtd-4-1533-2011.
Full textAbstract:
Abstract. We describe the status of the assimilation of bending angles from GPS radio occultations in the 3D-Var for DWD's operational global forecast model GME ("Global Model for Europe"). Experiments show that the assimilation of GPSRO data leads to a significant reduction of biases in the analyses of temperature, humidity and wind in the upper troposphere and the stratosphere, as well as a better r. m. s. fit in the comparison to radiosondes. The impact on forecasts is most prominent in the data sparse Southern Hemisphere, but is also quite notable in the Northern Hemisphere extra-tropics, where we also see a slightly positive impact on surface pressure. The positive results found in the impact experiments lead to the implementation of the assimilation of GPS radio occultations from GRACE-A, FORMOSAT-3/COSMIC and GRAS/MetOp-A into the operational suite on 3 August 2010. We also show some initial results from assimilation experiments using radio occultation data from the German research satellite TerraSAR-X.
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Chen, Weiwei, Yongliang Xiong, Xinzhong Li, Ban Zhao, Rui Zhang, and Shaoguang Xu. "Preliminary Validation of Surface Reflections from Fengyun-3C Radio Occultation Data." Remote Sensing 13, no. 10 (May 19, 2021): 1980. http://dx.doi.org/10.3390/rs13101980.
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Fengyun-3C (FY-3C) is a Global Navigation Satellite Systems (GNSS) Radio Occultation (RO) mission founded which was by China on 23 September 2013. In this study, under a specific temporal and spatial domain, we systematically compare FY-3C refractivity profiles with Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) refractivity profiles for the year 2015. The COSMIC profiles used in this study contain reflections, as identified in the Radio Occultation Meteorology Satellite Application Facility (ROM SAF) flag database. From 0 to 25 km altitude, the mean biases and relative standard deviations of the comparisons between FY-3C and COSMIC are less than 1% and 2% when COSMIC profiles present reflected signals. Radio holographic analysis is used to visualize and identify the spectra of FY-3C-reflected signals in the time-frequency domain. It is confirmed that the reflected signals in the lower troposphere and near the surface can be tracked by an FY-3C receiver. Further, most of the FY-3C events that matched with COSMIC reflected events show reflection patterns at a lower height, especially above the ocean’s surface. Under Bouguer’s rule and spherical symmetry assumptions, we reconstructed the reflected bending angle models by Abel transformation, which are valuable for reducing N-bias in the ducting layer. Three examples of FY-3C events show that the reflected bending branch is near the surface. Overall, the reflected signal of FY-3C could be used as a supplementary data portion for FY-3C atmospheric products.
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Shadid, Reem, Mohammad Haerinia, and Sima Noghanian. "Study of Rotation and Bending Effects on a Flexible Hybrid Implanted Power Transfer and Wireless Antenna System." Sensors 20, no. 5 (March 2, 2020): 1368. http://dx.doi.org/10.3390/s20051368.
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We present rotational misalignment and bending effects on a hybrid system to transfer power and data wirelessly for an implantable device. The proposed system consists of a high-frequency coil (13.56 MHz) to transfer power and an ultra-high frequency antenna (905 MHz) for data communication. The system performance and the transmitted power were studied under two misalignment conditions: (1) receiver rotation around itself with reference to the transmitter, and (2) bending of the implanted receiver under three different radii. Implanted receiver was printed on a flexible Kapton substrate and placed inside a layered body tissue model at a 30 mm depth. It is shown that the inductive link is stable under rotational misalignment and three bending conditions, whereas the communication data link is suitable to be used if the rotation angle is less than 75° or larger than 150°. The results show that the resonance frequency varies by 1.6%, 11.05%, and 6.62% for the bending radii of 120 mm, 80 mm, and 40 mm, respectively. Moreover, transmission efficiency varies by 4.3% for the bending radius of 120 mm. Decreasing the bending radius has more effects on antenna transmission efficiency that may cause severe losses in the communication link.