An automatic algorithm for the detection and the characterization of cloud boundaries from BAQUNIN LIDAR signals

2020 ◽  
Author(s):  
AnnaMaria Iannarelli ◽  
Marco Cacciani ◽  
Gabriele Mevi ◽  
Stefano Casadio ◽  
Annalisa Di Bernardino
Keyword(s):  
Boundary Layer ◽  
Temporal Resolution ◽  
Signal To Noise Ratio ◽  
Threshold Value ◽  
Temporal Variations ◽  
Cloud Layer ◽  
Spatial And Temporal Variations ◽  
Quality Analysis ◽  
Signal To Noise ◽  
Noise Ratio

<p>The lidar LIDAR system is widely used in atmospheric aerosol and boundary layer (BL) studies, and for the detection of cloud boundaries. However automatic and accurate identification of cloud top and bottom heights and BL height is not trivial, especially for low signal to noise ratio values, and for cloud layers below the top of BL, because of the disentanglement of cloud and aerosol contribution to LIDAR signal.</p><p>In this work, a signal threshold approach is presented, starting from the Range Corrected Signal (RCS) and using its spatial and temporal variations. The approach has been tested using one year of acquisitions of the elastic LIDAR hosted in the BAQUNIN (Boundary-layer Air QUality analysis using Network of INstruments) Supersite(https://www.baqunin.eu) with a spatial and temporal resolution of 7.5 m and 10 s, respectively.</p><p>A minimum threshold value T<sub>c</sub> applied to the RCS values allows detecting the presence of a cloud layer. This approach could be applied to each type of acquired LIDAR elastic signal, but depends on the specific LIDAR channel characteristics, in particular the signal to noise ratio.</p><p>RCS values obtained for each acquired profile and altitude could be considered as a two-dimensional matrix M. As first step the elements M<sub>ij</sub>>T<sub>c</sub> of this matrix are labeled as possible cloud elements.</p><p>Subsequently, the algorithm excludes from the calculation the elements M<sub>ij </sub>corresponding to spike values or affected by high noise considering the spatial and temporal variations of the RCS. A labeled element is confirmed to be a cloud element if the number of its labeled neighbors is above a selected percentage threshold T<sub>perc.</sub> The grid of elements considered as neighbors can be defined according to spatial and temporal resolution of the LIDAR acquisition.</p><p>Finally, bottom and top of cloud layers are retrieved as the altitude of first and last labeled elements of each cloud layer and profile.</p><p>The accuracy of the results depends on the spatial and temporal resolution of the acquired signal, considering the BAQUNIN LIDAR characteristics the best accuracy is 15 m and 20 s.</p><p>The same approach could be used to distinguish aerosol from cloud layers, using a different threshold value for the aerosol.</p><p>This method was tested for different atmospheric conditions and results are discussed in this work.</p>

scholarly journals Cooperative GPS and Neighbors Awareness Based Device Discovery for D2D Communication in in-Band Cellular Networks

2018 ◽  
Vol 7 (2.29) ◽  
pp. 700 ◽  
Author(s):  
O Hayat ◽  
R Ngah ◽  
Yasser Zahedi
Keyword(s):  
Cellular Networks ◽  
Channel Capacity ◽  
Signal To Noise Ratio ◽  
Threshold Value ◽  
D2d Communication ◽  
Core Network ◽  
New Paradigm ◽  
Signal To Noise ◽  
Device Discovery ◽  
Noise Ratio

Device to Device (D2D) communication is a new paradigm for next-generation wireless systems to offload data traffic. A device needs to discover neighbor devices on the certain channel to initiate the D2D communication within the minimum period. A device discovery technique based on Global Positioning System (GPS) and neighbor awareness base are proposed for in-band cellular networks. This method is called network-centric approach, and it improves the device discovery efficiency, accuracy, and channel capacity. The differential code is applied to measure the signal to noise ratio of each discovered device. In the case that the signal to noise ratio (SNR) of two devices is above a specified threshold value, then these two devices are qualified for D2D communication. Two procedures are explored for device discovery; discovery by CN (core network) and eNB (evolved node B) cooperation with the help of GPS and neighbor awareness. Using ‘Haversine’ formula, SNR base distance is calculated. Results show an increment in the channel capacity relative to SNR obtained for each device.  

Variations in Photoreceptor Response Dynamics Across the Fly Retina

2001 ◽  
Vol 86 (2) ◽  
pp. 950-960 ◽  
Author(s):  
Brian G. Burton ◽  
Ben W. Tatler ◽  
Simon B. Laughlin
Keyword(s):  
Temporal Resolution ◽  
Light Adaptation ◽  
Signal To Noise Ratio ◽  
Calliphora Vicina ◽  
Retinal Neuron ◽  
Response Dynamics ◽  
Signal To Noise ◽  
Spatiotemporal Resolution ◽  
Temporal Properties ◽  
Noise Ratio

Gradients in the spatial properties of retinal cells and their relation to image statistics are well documented. However, less is known of gradients in temporal properties, especially at the level of the photoreceptor for which no account exists. Using light flashes and white-noise-modulated light and current stimuli, we examined the spatial and temporal properties of a single class of photoreceptor (R1–6) within the compound eyes of male blowfly, Calliphora vicina. We find that there is a trend toward higher performance at the front of the eye, both in terms of spatiotemporal resolution and signal-to-noise ratio. The receptive fields of frontal photoreceptors are narrower than those of photoreceptors at the side and back of the eye and response speeds are 20% faster. The signal-to-noise ratio at high frequencies is also greatest at the front of the eye, allowing a 30–40% higher information rate. The power spectra of signals and noise indicate that this elevation of performance results both from shorter responses to individual photons and from a more reliable registration of photon arrival times. These distinctions are characteristic of adaptational changes that normally occur on increasing illumination. However, all photoreceptors were absorbing light at approximately the same mean photon rate during our recordings. We therefore suggest that frontal photoreceptors attain a higher state of light adaptation for a given photon rate. This difference may be achieved by a higher density of (Ca2+ permeable) light-gated channels. Consistent with this hypothesis, membrane-impedance measurements show that frontal photoreceptors have a higher specific conductance than other photoreceptors. This higher conductance provides a better temporal performance but is metabolically expensive. Across the eye, temporal resolution is not proportional to spatial (optical) resolution. Neither is it matched obviously to optic flow. Instead we examine the consequences of an improved temporal resolution in the frontal region for the tracking of small moving targets, a behavior exhibited by male flies. We conclude that the temporal properties of a given class of retinal neuron can vary within a single retina and that this variation may be functionally related to the behavioral requirements of the animal.

Quantitative Analysis of Noise Impact on Duffing Chaotic Detection System Using Lyapunov Characteristic Exponents

2011 ◽  
Vol 130-134 ◽  
pp. 1331-1337
Author(s):  
Wen Jing Hu ◽  
Zhi Zhen Liu ◽  
Zhi Hui Li
Keyword(s):  
Detection System ◽  
Signal To Noise Ratio ◽  
Duffing Oscillator ◽  
Threshold Value ◽  
System State ◽  
Signal To Noise ◽  
Phase Trajectories ◽  
Lyapunov Characteristic Exponents ◽  
Noise Ratio ◽  
System States

Performance of the Duffing oscillator to detect weak signals buried in heavy noise is analyzed quantitatively by LCEs. First in the case of noise, differential equations to compute LCE s are derived using RHR algorithm, so the quantitative criteria to identify system states are obtained. Then using LCEs, the threshold value of the forced periodic term is found accurately. Finally the system state and state change are analyzed using LCEs by keeping the threshold value and varying the noise intensity, and the minimum signal to noise ratio is determined. By contrast of phase trajectories and LCEs, it shows that phase trajectories disturbed by strong noise sometimes are ambiguous to our eyes, but through LCEs, the system state can be identified clearly and quantitatively especially in strong noise background. So the minimum signal to noise ratio can be obtained accurately.

scholarly journals QUALITY ANALYSIS OF GNSS OBSERVATIONS OF REFERENCE STATIONS NETWORK WITH THE TEQC UTILITY

2020 ◽  
Vol 25 (3) ◽  
pp. 72-88
Author(s):  
Vyacheslav E. Tereshchenko ◽  
Keyword(s):  
Signal To Noise Ratio ◽  
Satellite System ◽  
Quality Analysis ◽  
Signal To Noise ◽  
International Gnss Service ◽  
Novosibirsk Region ◽  
Russian State ◽  
Noise Ratio ◽  
Gnss Measurements ◽  
Global Navigation Satellite

The measurements of Global Navigation Satellite System (GNSS) obtained from different reference stations: Novosibirsk Region reference stations network, Russian state reference stations network ‒ Fundamental Astronomical and Geodetic Networks (FAGN) and stations of International GNSS service (IGS) are checked and analyzed. The relevance of the usage of regional (commercial or industrial) reference stations in state foundation geodetic framework for formation of a unified system of coordinate-time and navigation support is shown. The article describes quality analysis results of the GNSS measurements by the main criteria: number of rejected measurements, ionospheric delay, multipath effect, signal-to-noise ratio, receiver clock slips. The main errors affecting satellite measurements are estimated. The conclusions about the possibility of including the Novosibirsk Region reference stations network into one of the levels of the state foundation geodetic framework are drawn. The comparison of quality of the GNSS measurements showed that according to all criteria of quality the GNSS measurements of the Novosibirsk Region reference stations network are not worse than GNSS measurements of FAGN. According to all criteria the GNSS measurements of the Novosibirsk Region reference stations network approximately corresponds to GNSS measurements of IGS stations, except the signal-to-noise ratio criterion.

scholarly journals An Image Filter Based on Multiobjective Genetic Algorithm and Shearlet Transformation

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Zhi-yong Fan ◽  
Quan-sen Sun ◽  
Ze-xuan Ji ◽  
Kai Hu
Keyword(s):  
Genetic Algorithm ◽  
Wavelet Decomposition ◽  
Signal To Noise Ratio ◽  
Target Function ◽  
Threshold Value ◽  
Rician Noise ◽  
Signal To Noise ◽  
Multiobjective Genetic Algorithm ◽  
Noise Ratio ◽  
Magnetic Resonance Imaging Mri

Rician noise pollutes magnetic resonance imaging (MRI) data, making data’s postprocessing difficult. In order to remove this noise and avoid loss of details as much as possible, we proposed a filter algorithm using both multiobjective genetic algorithm (MOGA) and Shearlet transformation. Firstly, the multiscale wavelet decomposition is applied to the target image. Secondly, the MOGA target function is constructed by evaluation methods, such as signal-to-noise ratio (SNR) and mean square error (MSE). Thirdly, MOGA is used with optimal coefficients of Shearlet wavelet threshold value in a different scale and a different orientation. Finally, the noise-free image could be obtained through inverse wavelet transform. At the end of the paper, experimental results show that this proposed algorithm eliminates Rician noise more effectively and yields better peak signal-to-noise ratio (PSNR) gains compared with other traditional filters.

NMR spectroscopy threshold signal-to-noise ratio

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Petar Kolar ◽  
Lovro Blažok ◽  
Dario Bojanjac
Keyword(s):  
Nmr Spectroscopy ◽  
Communication Channel ◽  
Detection System ◽  
Signal To Noise Ratio ◽  
Standard Procedure ◽  
Threshold Value ◽  
Signal To Noise ◽  
Online Questionnaire ◽  
Spectroscopy System ◽  
Noise Ratio

Abstract Ever since noise was spotted and proven to cause problems for the transmission and detection of information through a communication channel, a standard procedure in the process of characterizing a detection system of the communication channel is to determine the level of the lowest detectable signal. In signal processing, this is usually done by determining the so-called threshold signal-to-noise ratio (SNR). This determination is especially important for the communication channels and systems that constantly operate with low-level signals. A good example of such a system is definitely the NMR spectroscopy system. However, to the authors’ knowledge, the threshold SNR value of NMR spectroscopy systems has not been determined yet. That is why the experts in the field of NMR spectroscopy were asked to assess, using an online questionnaire, which SNR level they considered to be the NMR threshold SNR level. Afterwards, the threshold value was calculated from the obtained data. Finally, it was compared to the existing rule of thumb and thus, a conclusion about its legitimacy was made. The described questionnaire is still available online (https://forms.gle/Y9hyDZ1v1iJoEbk27). This enables everyone to form their own opinion about the threshold SNR level, which the authors encourage the readers to do.

scholarly journals Experimental design and stochastic modeling of hydrodynamic wave propagation within cavities for wind tunnel acoustic measurements

2019 ◽  
Vol 18 (8) ◽  
pp. 752-779 ◽  
Author(s):  
Colin P VanDercreek ◽  
Alireza Amiri-Simkooei ◽  
Mirjam Snellen ◽  
Daniele Ragni
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Turbulent Boundary Layer ◽  
Design Of Experiments ◽  
Signal To Noise Ratio ◽  
Spectral Energy ◽  
Measured Signal ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Hydrodynamic Wave

This study investigates how embedding microphones in different cavity geometries along the wall of a wind tunnel reduces the measured turbulent boundary layer pressure fluctuations. The effect of these cavities on the measured signal-to-noise ratio of an acoustic source with flow present was also quantified. Twelve cavity geometries defined by their depths, diameters, chamfer, opening percentage, and mesh covering were tested. The cavity geometries were selected using a design of experiments methodology. The application of design of experiments enabled a statistically sound and efficient test campaign. This was done by applying a D-optimal selection criterion to all potential cavity geometries in order to select 12 cavities to allow for the individual effect of the geometric parameters such as depth and diameter to be quantified with statistical confidence. The resulting wind tunnel test data were fit to a generalized additive model. This approach quantified the relative effect of these parameters on the turbulent boundary layer pressure spectral energy and signal-to-noise ratio while accounting for non-linear frequency dependence. This experimental investigation quantified how much increasing depth reduces the turbulent boundary layer spectral energy and increases signal-to-noise ratio. It also showed that a mesh covering reduces the boundary layer noise by 8 dB. It was also quantified how much reducing the cavity area from the opening of the cavity to the base of the microphone reduces the measured boundary layer spectral energy. Additionally, the model quantified the interactions between the mesh and cavity area as well as the change in area.

Determination of the Best Emulsion for the Microscopy of Crystals

1981 ◽  
Vol 39 ◽  
pp. 32-33
Author(s):  
David A. Grano ◽  
Kenneth H. Downing
Keyword(s):  
Spatial Frequency ◽  
Information Transfer ◽  
Signal To Noise Ratio ◽  
Experimental Situation ◽  
Photographic Emulsion ◽  
Modulation Transfer ◽  
Signal To Noise ◽  
Frequency Space ◽  
Noise Ratio

The retrieval of high-resolution information from images of biological crystals depends, in part, on the use of the correct photographic emulsion. We have been investigating the information transfer properties of twelve emulsions with a view toward 1) characterizing the emulsions by a few, measurable quantities, and 2) identifying the “best” emulsion of those we have studied for use in any given experimental situation. Because our interests lie in the examination of crystalline specimens, we've chosen to evaluate an emulsion's signal-to-noise ratio (SNR) as a function of spatial frequency and use this as our critereon for determining the best emulsion.The signal-to-noise ratio in frequency space depends on several factors. First, the signal depends on the speed of the emulsion and its modulation transfer function (MTF). By procedures outlined in, MTF's have been found for all the emulsions tested and can be fit by an analytic expression 1/(1+(S/S0)2). Figure 1 shows the experimental data and fitted curve for an emulsion with a better than average MTF. A single parameter, the spatial frequency at which the transfer falls to 50% (S0), characterizes this curve.

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