Добірка наукової літератури з теми "Vertical signal attenuation"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся зі списками актуальних статей, книг, дисертацій, тез та інших наукових джерел на тему "Vertical signal attenuation".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Статті в журналах з теми "Vertical signal attenuation"
1
Berne, A., G. Delrieu, and H. Andrieu. "Estimating the Vertical Structure of Intense Mediterranean Precipitation Using Two X-Band Weather Radar Systems." Journal of Atmospheric and Oceanic Technology 22, no. 11 (November 1, 2005): 1656–75. http://dx.doi.org/10.1175/jtech1802.1.
Повний текст джерелаАнотація:
Abstract The present study aims at a preliminary approach of multiradar compositing applied to the estimation of the vertical structure of precipitation—an important issue for radar rainfall measurement and prediction. During the HYDROMET Integrated Radar Experiment (HIRE’98), the vertical profile of reflectivity was measured, on the one hand, with an X-band vertically pointing radar system, and, on the other hand, with an X-band RHI scanning protocol radar. The analysis of the raw data highlights the effects of calibration and attenuation problems affecting the measurements of both radar systems. Once the two radar systems have been intercalibrated, various attenuation correction techniques are applied. The comparison of raw, intercalibrated, and corrected radar measurements for the two radar systems stresses the importance of calibration and attenuation correction. The applied corrections improve the consistency of the vertical profile of reflectivity that is measured by the two radar systems. However, a significant uncertainty remains when strong radar signal attenuations occur.
2
Vaňková, Irena, Keith W. Nicholls, Surui Xie, Byron R. Parizek, Denis Voytenko, and David M. Holland. "Depth-dependent artifacts resulting from ApRES signal clipping." Annals of Glaciology 61, no. 81 (April 2020): 108–13. http://dx.doi.org/10.1017/aog.2020.56.
Повний текст джерелаАнотація:
AbstractSeveral autonomous phase-sensitive radio-echo sounders (ApRES) were deployed at Greenland glaciers to investigate ice deformation. Different attenuation settings were tested and it was observed that, in the presence of clipping of the deramped ApRES signal, each setting produced a different result. Specifically, higher levels of clipping associated with lower attenuation produced an apparent linear increase of diurnal vertical cumulative displacement with depth, and obscured the visibility of the basal reflector in the return amplitude. An example with a synthetic deramped signal confirmed that these types of artifacts result from the introduction of harmonics from square-wave-like features introduced by clipping. Apparent linear increase of vertical displacement with depth occurs when the vertical position of a near-surface internal reflector changes in time. Artifacts in the return amplitude may obscure returns from internal reflectors and the basal reflector, making it difficult to detect thickness evolution of the ice and to correctly estimate vertical velocities. Variations in surface melt during ApRES deployments can substantially modulate the received signal strength on short timescales, and we therefore recommend using higher attenuator settings for deployments in such locations.
3
Shen, Xi, and Defeng David Huang. "Retrieval of Raindrop Size Distribution Using Dual-Polarized Microwave Signals from LEO Satellites: A Feasibility Study through Simulations." Sensors 21, no. 19 (September 24, 2021): 6389. http://dx.doi.org/10.3390/s21196389.
Повний текст джерелаАнотація:
In this paper, a novel approach for raindrop size distribution retrieval using dual-polarized microwave signals from low Earth orbit satellites is proposed. The feasibility of this approach is studied through modelling and simulating the retrieval system which includes multiple ground receivers equipped with signal-to-noise ratio estimators and a low Earth orbit satellite communicating with the receivers using both vertically and horizontally polarized signals. Our analysis suggests that the dual-polarized links offer the opportunity to estimate two independent raindrop size distribution parameters. To achieve that, the vertical and horizontal polarization attenuations need to be measured at low elevation angles where the difference between them is more distinct. Two synthetic rain fields are generated to test the performance of the retrieval. Simulation results suggest that the specific attenuations for both link types can be retrieved through a least-squares algorithm. They also confirm that the specific attenuation ratio of vertically to horizontally polarized signals can be used to retrieve the slope and intercept parameters of raindrop size distribution.
4
Wallis, Rory, and Hyunkook Lee. "Localisation of Vertical Auditory Phantom Image with Band-limited Reductions of Vertical Interchannel Crosstalk." Applied Sciences 10, no. 4 (February 21, 2020): 1490. http://dx.doi.org/10.3390/app10041490.
Повний текст джерелаАнотація:
Direct sound that is captured by the upper layer of a three-dimensional (3D) microphone array is typically regarded as vertical interchannel crosstalk (VIC), since it tends to produce an undesired effect of the sound source image being elevated from the ear-level loudspeaker layer position (0°) in reproduction. The present study examined the effectiveness of band-limited VIC attenuation methods on preventing the vertical image shift problem. In a subjective experiment, five natural sound sources were presented as vertically-oriented phantom images while using two stereophonic loudspeaker pairs elevated at 0° and 30° in front of the listener. The upper layer signal (i.e., VIC) was attenuated in various octave-band-dependent conditions that were based on vertical localisation thresholds obtained from previous studies. The results showed that it was possible to achieve the goal of panning the phantom image at the same height as the image produced by the main loudspeaker layer by attenuating only a single octave band with the centre frequency of 4 kHz or 8 kHz or multiple bands at 1 kHz and above. This has a useful practical implication in 3D sound recording and mixing where a vertically oriented phantom image is rendered.
5
Kosteletskii, Valerii. "Cascade Configuration of Modal Filters for Power Bus Protection in Differential and Common Modes." International Journal of Circuits, Systems and Signal Processing 15 (July 20, 2021): 666–71. http://dx.doi.org/10.46300/9106.2021.15.74.
Повний текст джерелаАнотація:
The paper discusses the results of quasi-static simulation of two modal filter (MF) cascade configurations designed to attenuate an interference pulse in differential and common modes. The geometric parameters of the MF are optimized by heuristic search according to the amplitude minimization condition. The results of calculating the time responses to an ultrashort pulse (USP) and electrostatic discharge (ESD) are presented. The USP attenuation coefficient in the differential mode was 6.84 times for the horizontally placed cascades, and 6.94 times for the vertical configuration. In the common mode, the attenuation coefficient was 7.35 times for the horizontally placed cascades, and 7.57 times for the vertically placed cascades. For ESD, the attenuation coefficients were 1.51 times for the horizontally and 1.55 times for the vertically placed cascades in the differential and common modes. It was found that only the first spike is attenuated by the ESD excitation on the MF
6
Maresh, Jennifer, Robert S. White, Richard W. Hobbs, and John R. Smallwood. "Seismic attenuation of Atlantic margin basalts: Observations and modeling." GEOPHYSICS 71, no. 6 (November 2006): B211—B221. http://dx.doi.org/10.1190/1.2335875.
Повний текст джерелаАнотація:
Paleogene basalts are present over much of the northeastern Atlantic European margin. In regions containing significant thicknesses of layered basalt flows, conducting seismic imaging within and beneath the volcanic section has proven difficult, largely because the basalts severely attenuate and scatter seismic energy. We use data from a vertical seismic profile (VSP) from well 164/07-1 that penetrated [Formula: see text] of basalt in the northern Rockall Trough west of Britain to measure the seismic attenuation caused by the in-situ basalts. The effective quality factor [Formula: see text] of the basalt layer is found from the VSP to be 15–35, which is considerably lower (more attenuative) than the intrinsic attenuation measured on basalt samples in the laboratory. We then run synthetic seismogram models to investigate the likely cause of the attenuation. Full waveform 1D modeling of stacked sequences of lava flows based on rock properties from the same well indicates that much of the seismic attenuation observed from the VSP can be accounted for by the scattering effects of multiple thin layers with high impedance contrasts. Phase-screen seismic modeling of the rugose basalt surface at the top-of-basalt sediment interface, with the magnitude and wavelength of the relief constrained by a 3D seismic survey around the well, suggests that surface scattering from this interface plays a much smaller role than internal scattering in attenuating the seismic signal as it passes through the basalt sequence.
7
Wang, Yanghua. "Stable Q analysis on vertical seismic profiling data." GEOPHYSICS 79, no. 4 (July 1, 2014): D217—D225. http://dx.doi.org/10.1190/geo2013-0273.1.
Повний текст джерелаАнотація:
Vertical seismic profiling (VSP) provides a direct observation of seismic waveforms propagating to various depths within the earth’s subsurface. The [Formula: see text] analysis or attenuation ([Formula: see text]) analysis based on direct comparison between individual waveforms at different depths, however, suffers from the problem of instability commonly due to fluctuations inherent in the frequency spectrum of each waveform. To improve the stability, we considered frequency and time variations and conducted [Formula: see text] analysis on an integrated observation. First, we transformed the time- (or depth-) frequency-domain spectrum to a 1D attenuation measurement with respect to a single variable, the product of time and frequency. Although this 1D measurement has a higher signal-to-noise ratio than the 2D spectrum in the time-frequency domain, it can also be used to further generate a stabilized compensation function. Then, we implemented two [Formula: see text]-analysis methods by data fitting (in a least-squares sense) to either the attenuation measurement or the data-driven gain function. These two methods are theoretically consistent and practically robust for conducting [Formula: see text] analysis on field VSP data.
8
Nikahd, Ali, Mazlan Hashim, and Mohammad Jafar Nazemosadat. "A Review of Uncertainty Sources on Weather Ground-Based Radar for Rainfall Estimation." Applied Mechanics and Materials 818 (January 2016): 254–71. http://dx.doi.org/10.4028/www.scientific.net/amm.818.254.
Повний текст джерелаАнотація:
Efforts in hydrometeorology are concentrated on finding the causes of the ground based radar uncertainty sources for rainfall estimation recently. The error sources are interactions between radar with atmosphere and topography. Radar singly often covers systematic error whereas atmospheric and topographic errors are relevant to location and precipitation pattern. This article reviews uncertainty sources on weather ground-based radar in order to rainfall estimation that have been discussed in nine main categories includes; the range effects, radar signal attenuation, beam blockage, vertical air motion and precipitation drift, ground clutter, anomalous propagation, vertical variability of the precipitation system, variability of the Z-R relationship and bright band. Topographic errors such as ground clutter and beam blockage primarily can be eliminated by attentive in site selection. Atmospheric errors such as vertical air motion and precipitation drift can filter or eliminated by calibration methods. Systematic errors include radar signal attenuation and anomalous propagation is the result of structural changes in the radar waves in space. Thus, this review is explored the characteristics of uncertainty error resources and a comprehensive appraisal of experimental procedures is provided.
9
Borel, Andžej. "DEVELOPMENT AND INVESTIGATION OF INPUT AMPLIFIER FOR THE OSCILOSCOPE." Mokslas - Lietuvos ateitis 12 (January 20, 2020): 1–5. http://dx.doi.org/10.3846/mla.2020.11420.
Повний текст джерелаАнотація:
Digital oscilloscope’s structure has analog signal acquisition circuit, which transforms signal’s amplitude to fit ADC dynamic range. This circuit is commonly called oscilloscope’s vertical or front-end amplifier. Difficulty in designing front-end amplifiers in GHz range largely affects higher frequency range oscilloscope’s price. This work is focused on designing a front-end amplifier using discrete and openly sold components. We propose a design for attenuator, buffer, variable gain circuits. Amplifier’s prototype is designed. Main characteristics of the amplifier were measured. Measured bandwidth is 3 GHz. Amplifier’s gain and attenuation can support vertical scale sensitivity range from 10 mV/div to 1 V/div. Step response distortion is under 10 %. SMD and PTH relay model attenuators were evaluated. In this paper we review oscilloscope’s front-end purpose and structure. We review amplifiers design and provide the results of experimental measurements.
10
Protat, Alain, Surendra Rauniyar, Julien Delanoë, Emmanuel Fontaine, and Alfons Schwarzenboeck. "W-Band (95 GHz) Radar Attenuation in Tropical Stratiform Ice Anvils." Journal of Atmospheric and Oceanic Technology 36, no. 8 (August 2019): 1463–76. http://dx.doi.org/10.1175/jtech-d-18-0154.1.
Повний текст джерелаАнотація:
AbstractAttenuation of the W-band (95 GHz) radar signal by atmospheric ice particles has long been neglected in cloud microphysics studies. In this work, 95-GHz airborne multibeam cloud radar observations in tropical stratiform ice anvils are used to estimate vertical profiles of 95-GHz attenuation. Two techniques are developed and compared, using very different assumptions. The first technique examines statistical reflectivity differences between repeated aircraft passes through the same cloud mass at different altitudes. The second technique exploits reflectivity differences between two different pathlengths through the same cloud, using the multibeam capabilities of the cloud radar. Using the first technique, the two-way attenuation coefficient produced by stratiform ice particles ranges between 1 and 1.6 dB km−1 for reflectivities between 13 and 18 dBZ, with an expected increase of attenuation with reflectivity. Using the second technique, the multibeam results confirm these high attenuation coefficient values and expand the reflectivity range, with typical attenuation coefficient values of up to 3–4 dB km−1 for reflectivities of 20 dBZ. The potential impact of attenuation on precipitating-ice-cloud microphysics retrievals is quantified using vertical profiles of the mean and the 99th percentile of ice water content derived from noncorrected and attenuation-corrected reflectivities. A large impact is found on the 99th percentile of ice water content, which increases by 0.3–0.4 g m−3 up to 11-km height. Finally, T-matrix calculations of attenuation constrained by measured particle size distributions, ice crystal mass–size, and projected area–size relationships are found to largely underestimate cloud radar attenuation estimates.
Дисертації з теми "Vertical signal attenuation"
1
Сальников, Д. С., А. И. Цопа, В. В. Павликов, А. Д. Собколов, and Н. В. Руженцев. "Millimeter-Range Radiometric System for Perspective Problems of Meteorology and Telecommunication." Thesis, Kyiv: Ukraine, 2017. http://openarchive.nure.ua/handle/document/5696.
Повний текст джерелаАнотація:
Short description of new ground radiometric complex,
working on 40 GHz and 94 GHz frequencies and providing
remote continuous measurements of full vertical atmosphere
attenuation, effective temperature values and liquid-water
content of clouds, integral content of vaporous moisture in
atmosphere. The feature of the complex is the availability of
digital signal processing of detected signals mode.
Тези доповідей конференцій з теми "Vertical signal attenuation"
1
Chatellier, Laurence, Valery E. Just, Louis Fournier, Bruno Charbonnier, and Lionel Robillard. "Characterization Improvement Through Signal Processing: Application to Radiography Inspection — 3D Reconstruction." In ASME 2005 Pressure Vessels and Piping Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/pvp2005-71617.
Повний текст джерелаАнотація:
During in-service inspections, experts are faced with the delicate task of establishing a complete diagnosis of defects from radiographs. Should a defect be detected, one must be able to demonstrate that the component still meets regulatory requirements. Thus, it is essential to be able to characterize precisely the defect, especially when the demonstration relies on mechanical calculus. However the characterization of the defect by only g or X-ray is sometimes very difficult, and the justification process can thus be jeopardized. In such cases, signal processing can be very helpful for the interpretation of the data and for the characterization (positioning and sizing) of the defect. This paper presents a 3-D reconstruction processing in hard conditions representatives of pipe inspections: the incidence angle is very reduced and thus the radiographs contain very little information along the vertical direction. The reconstruction process relies on the estimation of the attenuation. It is called inversion because it restores the attenuation from both data and prior information. The method has been tested on radiographs of a block with real defects and the performances were evaluated from a mock-up with several electro-drilled cylindrical defects. Even in the case of limited incidence, the method provides very useful 3D results. Moreover this process can be applied whatever the nature of the source. When a larger source is used in order to inspect thick components, signal processing allows to reduce the inevitable blur which leads to improved accuracy. In conclusion, signal processing and especially 3D reconstruction in the case of radiography can turn out to be a key step fur in-service inspection of major NPP components.
2
Wang, Gong Li, Dean Homan, David Maggs, and David Allen. "A NEW LOOK AT THE DUAL DEPTH OF INVESTIGATION OF LWD PROPAGATION RESISTIVITY LOGGING." In 2021 SPWLA 62nd Annual Logging Symposium Online. Society of Petrophysicists and Well Log Analysts, 2021. http://dx.doi.org/10.30632/spwla-2021-0119.
Повний текст джерелаАнотація:
It is well established that phase shift and attenuation measurements acquired by an electromagnetic propagation tool come with different depths of investigation (DOI). The attenuation measurement sees deeper into the formation than the phase shift measurement. This difference has been reported not only for the 2 MHz propagation resistivity tool, but also for the deep propagation tool that operates at 25 MHz. Although the difference has been demonstrated with modeling, test tank experiments and logs, a complete physical explanation has been notably absent since the introduction of the MHz-frequency propagation logging in 1980s. The question is so intriguing that it has been raised repeatedly over the past decades: what drives the difference of DOI for the two measurements that are acquired with the same electromagnetic field? In this paper, we revisit this problem with an aim of providing a physical insight to bridge the gap between theory and application. This is an extension of our recent work on the theory of apparent conductivity for propagation measurements. We address the problem by applying high-order geometric theory for low-frequency electromagnetic problems in lossy media in conjunction with the Taylor series expansion for the voltage ratio measured by a propagation tool. In so doing, we find that in a resistive formation where the dielectric effect is small: 1) the phase shift measurement is primarily due to the first-order eddy current induced in the formation; 2) in contrast, the leading source of the attenuation measurement is the second-order eddy current. Since the second-order eddy current is more spread out than the first-order eddy current, this explains why the DOI of attenuation resistivity is larger than that of phase shift resistivity. The difference in spatial distribution of two eddy currents is also the reason for the difference of vertical resolution between the two. The same root cause for the difference of DOI and vertical resolution also holds when comparing R-signal and X-signal from induction resistivity logging. Other properties shared by propagation and induction resistivity logging will be discussed, such as skin effect and dielectric effect, as well as their asymptotic properties in high-resistivity formations. We conclude that propagation and induction resistivity logging are essentially similar, even though the two measurement principles may seem rather different.
3
Srinivasa Ramanujam, K., and C. Balaji. "A Fast Polarized Microwave Radiative Transfer Model for a Raining Atmosphere." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22228.
Повний текст джерелаАнотація:
Retrieval of vertical rain structure and hence the estimation of surface rain rate is of central importance to various missions involving remote sensing of the earth’s atmosphere. Typically, remote sensing involves scanning the earth’s atmosphere at visible, infra red and microwave frequencies. While the visible and infra red frequencies can scan the atmosphere with higher spatial resolution, they are not suited for scanning under cloudy conditions as clouds are opaque under these frequencies. However, the longer wavelength microwave radiation can partially penetrate through the clouds without much attenuation thereby making it more suitable for meteorological purposes. The retrieval algorithms used for passive microwave remote sensing involve modeling of the radiation in the earth’s atmosphere where in the clouds and precipitating rain (also known as hydrometeors) emit / absorb / scatter. Additionally, it has been observed that the rain droplets tend to polarize the microwave signal emitted by the earth’s surface. In view of this, the first step in the development of a rainfall retrieval algorithm for any satellite mission is to simulate the radiances (also known as brightness temperatures) that would have been measured by a typical radiometer for different sensor frequencies and resolutions. Towards this, a polarized microwave radiation transfer code has been developed in house for a plane parallel raining atmosphere (henceforth called as forward model) that depicts the physics as seen by a satellite. Physics based retrieval algorithm often involves repeated execution of the forward model for various raining scenario. However, due to the complexity involved in the radiation modeling of the raining atmosphere which is participating in nature, the forward model suffers from the drawback that it requires enormous computational effort. In the present work, a much quicker alternative is proposed wherein the forward model can be replaced with an Artificial Neural Network (ANN) based Fast Forward Model (AFFM). This AFFM can be used in conjunction with an appropriate inverse technique to retrieve the rain structure. Spectral microwave brightness temperatures at frequencies corresponding to the Tropical Rainfall Measuring Mission (TRMM) of National Aeronautics and Space Administration (NASA) and Japan Aerospace Exploration Agency (JAXA) are first simulated using an in-house polarized radiate on transfer code for sixteen past cyclones in the North Indian Ocean region in the period (2000–2005), using the hydrometeor profiles retrieved from the Goddard Profiling Algorithm (GPROF) of the Tropical Rainfall Measuring Mission (TRMM)’s Microwave Imager (TMI). This data is split into two sets: while the first set of data is used for training the network, the remainder of the data is used for testing the ANN. The results obtained are very encouraging and shows that neural network is capable of predicting the brightness temperature accurately with the correlation coefficient of over 99%. Furthermore, the execution of the forward model on an Intel Core 2 Quad 3.0 GHz processor based, 8 GB DDR3 RAM workstation took 3 days, while the AFFM delivers the results in 10 seconds.
4
Zhu, Jun, Yong Die, Yuanshi Tian, and John Zhou. "DECIPHERING THE CAPABILITIES OF LOOK-AHEAD METHODS IN LWD." In 2021 SPWLA 62nd Annual Logging Symposium Online. Society of Petrophysicists and Well Log Analysts, 2021. http://dx.doi.org/10.30632/spwla-2021-0024.
Повний текст джерелаАнотація:
The use of electromagnetic logging tools while drilling to investigate the space in front of the drill-bit and to predict the geologic strata and/or fluid property ahead has been one of the industry-focuses in recent years. The commercial look-ahead tools have two main designs based on the published tool configurations and data-channel definitions. The first type employs combinations of tilted coils to acquire multiple or all components of electromagnetic fields and presents logs defined in novel expressions as functions of these field components. The second kind uses combination of the voltage measurements from orthogonal coils (coils pointing along and perpendicular to tool-axis) and the propagation resistivity logs from coaxial coils of large coil-spacing. This work starts with reviewing the tool physics and the mathematic expressions defining the logs. The look-ahead capabilities are then investigated by considering the case where a borehole is perpendicular to the formation boundaries. It is found that the necessary information for forward detection applications is exclusively from the apparent resistivity logs, not the so-called geo-signals or any other logs. We further explore an ideal scenario, i.e., to detect the presence of a good conductor in front of a high resistivity formation to obtain the asymptotic behaviors for the two measurement types. The asymptotic expressions lay the foundation to understanding the intrinsic differences between the two methods. The insights derived from the theoretical work and the subsequent modeling results for a broad set of models define the response characteristics and the probing capabilities of the look-ahead techniques. It is realized that the look-ahead instrument design can be simplified, such as using only the familiar three-coil coaxial configuration with a suitable long coil-spacing and multiple carefully chosen operating frequencies to achieve a robust detection-distance coverage. It is worth to point out that the commercially available look-ahead services are mainly applicable to vertical and inclined wells so far. For look-ahead applications in horizontal wells, due to the contribution of the geologic and fluid boundaries lateral to the tool and the inhomogeneities ahead of the drill-bit, there is no reliable method yet to simultaneously solve the large number of unknown parameters associated other than some special situations. The look-ahead evaluation in the horizontal wells must be investigated further by understanding the characteristics of exponential attenuation and geometric spreading of the electromagnetic fields in a conductive formation and the inherent relatively poor resolution through combining with other detection physics and the introduction of proper geologic model constraints.