The Impact of Beam Broadening on the Quality of Radar Polarimetric Data

2007 ◽  
Vol 24 (5) ◽  
pp. 729-744 ◽  
Author(s):  
Alexander V. Ryzhkov
Keyword(s):  
Correlation Coefficient ◽  
Cross Correlation ◽  
Horizontal Gradients ◽  
Analytical Formulas ◽  
Radar Resolution ◽  
Differential Reflectivity ◽  
The Impact ◽  
Nonuniform Beam ◽  
Beam Broadening

Abstract The impact of beam broadening on the quality of radar polarimetric data in the presence of nonuniform beam filling (NBF) is examined both theoretically and experimentally. Cross-beam gradients of radar reflectivity Z, differential reflectivity ZDR, and differential phase ΦDP within the radar resolution volume may produce significant biases of ZDR, ΦDP, and the cross-correlation coefficient ρhv. These biases increase with range as a result of progressive broadening of the radar beam. They are also larger at shorter radar wavelengths and wider antenna beams. Simple analytical formulas are suggested for estimating the NBF-induced biases from the measured vertical and horizontal gradients of Z, ZDR, and ΦDP. Analysis of polarimetric data collected by the KOUN Weather Surveillance Radar-1988 Doppler (WSR-88D) demonstrates that frequently observed perturbations of the radial ΦDP profiles and radially oriented “valleys” of ρhv depression can be qualitatively and quantitatively explained using the suggested NBF model.

scholarly journals Impact of Vitiligo on Quality of Life: A Cross-sectional Pilot Study from Western India

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
Vasudha Abhijit Belgaumkar ◽  
Ravindranath Brahmadeo Chavan ◽  
Nitika S Deshmukh ◽  
Nupur Vasudeo Warke
Keyword(s):  
Quality Of Life ◽  
Surface Area ◽  
Correlation Coefficient ◽  
Body Surface Area ◽  
Body Surface ◽  
Western India ◽  
Care Hospital ◽  
Cross Sectional ◽  
The Impact

Background: Vitiligo is a common, acquired, mucocutaneous discoloration characterized by well-circumscribed depigmented macules. It has profound potential for cosmetic disfigurement and social stigma, which is an often neglected aspect of the disease. Objectives: To analyze the impact of vitiligo on the quality of life (Qol) of patients in western India and To determine the contributory factors. Methods: A cross-sectional, observational study was conducted at a tertiary care hospital on 60 patients with vitiligo (were enrolled after informed consent and ethical approval). Basic patient-related (age, gender, socioeconomic status, co-morbidities) and vitiligo-related variables (body surface area involved, stability, duration of disease, treatment modality) were noted. This information were collated with QoL using a standardized questionnaire, the Dermatology Life Quality Index (DLQI). Statistical analysis was performed using Spearman’s rank correlation coefficient, Pearson’s r, unpaired t-test (SPSS version 16). Results: Mean DLQI score of the study sample was 3.15 ± 4.2 (small effect on QoL). The mean DLQI score in females (3.97) was significantly higher than in males (1.92) (P = 0.046). Also, the DLQI demonstrated a significant positive correlation with body surface area involvement (Spearman’s correlation coefficient = 0.306) (P = 0.018). Other factors were not found to affect the DLQI. Conclusions: Various modifiable and non-modifiable factors influence the QoL of vitiligo patients. Gender- associated stigma may be alleviated by counseling and creating awareness, while the body surface area involvement may be addressed by instituting and appropriate treatment. The clinician must be vigilant for any subtle signs of impairment of QoL to enable timely intervention.

Statistical Quality of Spectral Polarimetric Variables for Weather Radar

2012 ◽  
Vol 29 (9) ◽  
pp. 1221-1235 ◽  
Author(s):  
Tian-You Yu ◽  
Xiao Xiao ◽  
Yadong Wang
Keyword(s):  
Radial Velocity ◽  
Correlation Coefficient ◽  
Signal To Noise Ratio ◽  
Weather Radar ◽  
Statistical Quality ◽  
Spectral Signal ◽  
Individual Drop ◽  
Drop Size Distributions ◽  
Differential Reflectivity

Abstract Spectral polarimetry for weather radar capitalizes on both Doppler and polarimetric measurements to reveal polarimetric variables as a function of radial velocity through spectral analysis. For example, spectral differential reflectivity at a velocity represents the differential reflectivity from all the scatterers that have the same radial velocity of interest within the radar resolution volume. Spectral polarimetry has been applied to suppress both ground and biological clutter, retrieve individual drop size distributions from a mixture of different types of hydrometeors, and estimate turbulence intensity, for example. Although spectral polarimetry has gained increasing attention, statistical quality of the estimation of spectral polarimetric variables has not been investigated. In this work, the bias and standard deviation (SD) of spectral differential reflectivity and spectral copolar correlation coefficient estimated from averaged spectra were derived using perturbation method. The results show that the bias and SD of the two estimators depend on the spectral signal-to-noise ratio, spectral copolar correlation coefficient, the number of spectrum average, and spectral differential reflectivity. A simulation to generate time series signals for spectral polarimetry was developed and used to verify the theoretical bias and SD of the two estimators.

Does Religiosity Help Muslims Adjust to Death?: A Research Note

2008 ◽  
Vol 57 (1) ◽  
pp. 113-119 ◽  
Author(s):  
Mohammad Samir Hossain ◽  
Mohammad Zakaria Siddique
Keyword(s):  
End Of Life ◽  
Correlation Coefficient ◽  
Statistical Tests ◽  
Stratified Sampling ◽  
Cross Sectional ◽  
P Values ◽  
Age Range ◽  
The Impact ◽  
Minimum Education

Death is the end of life. But Muslims believe death is an event between two lives, not an absolute cessation of life. Thus religiosity may influence Muslims differently about death. To explore the impact of religious perception, thus religiosity, a cross-sectional, descriptive, analytic and correlational study was conducted on 150 Muslims. Self-declared healthy Muslims equally from both sexes ( N = 150, Age range – 20 to 50 years, Minimum education – Bachelor) were selected by stratified sampling and randomly under each stratum. Subjects, divided in five levels of religiosity, were assessed and scored for the presence of maladjustment symptoms and stage of adjustment with death. ANOVA and correlation coefficient was applied on the sets of data collected. All statistical tests were done at the level of 95% confidence ( P < 0.05). Final results were higher than the table values used for ANOVA and correlation coefficient yielded P values of < 0.05, < 0.01, and < 0.001. Religiosity as a criterion of Muslims influenced the quality of adjustment with death positively. So we hypothesized that religiosity may help Muslims adjust to death.

scholarly journals Close-Range Observations of Tornadoes in Supercells Made with a Dual-Polarization, X-Band, Mobile Doppler Radar

2007 ◽  
Vol 135 (4) ◽  
pp. 1522-1543 ◽  
Author(s):  
Howard B. Bluestein ◽  
Michael M. French ◽  
Robin L. Tanamachi ◽  
Stephen Frasier ◽  
Kery Hardwick ◽  
...  
Keyword(s):  
Correlation Coefficient ◽  
Cross Correlation ◽  
Doppler Radar ◽  
Dual Polarization ◽  
Radar Beam ◽  
X Band ◽  
Close Range ◽  
Debris Cloud ◽  
The Cross ◽  
Differential Reflectivity

Abstract A mobile, dual-polarization, X-band, Doppler radar scanned tornadoes at close range in supercells on 12 and 29 May 2004 in Kansas and Oklahoma, respectively. In the former tornadoes, a visible circular debris ring detected as circular regions of low values of differential reflectivity and the cross-correlation coefficient was distinguished from surrounding spiral bands of precipitation of higher values of differential reflectivity and the cross-correlation coefficient. A curved band of debris was indicated on one side of the tornado in another. In a tornado and/or mesocyclone on 29 May 2004, which was hidden from the view of the storm-intercept team by precipitation, the vortex and its associated “weak-echo hole” were at times relatively wide; however, a debris ring was not evident in either the differential reflectivity field or in the cross-correlation coefficient field, most likely because the radar beam scanned too high above the ground. In this case, differential attenuation made identification of debris using differential reflectivity difficult and it was necessary to use the cross-correlation coefficient to determine that there was no debris cloud. The latter tornado’s parent storm was a high-precipitation (HP) supercell, which also spawned an anticyclonic tornado approximately 10 km away from the cyclonic tornado, along the rear-flank gust front. No debris cloud was detected in this tornado either, also because the radar beam was probably too high.

scholarly journals Derivative of an image that corrupted by additive noise

2019 ◽  
Vol 12 (23) ◽  
pp. 30-35
Author(s):  
Suhad. A. Hamdan
Keyword(s):  
Correlation Coefficient ◽  
Cross Correlation ◽  
Additive Noise ◽  
Original Image ◽  
Noise Parameter ◽  
Dramatic Decline ◽  
Before And After ◽  
Mathematical Equations ◽  
Noise Error

In this paper the behavior of the quality of the gradient that implemented on an image as a function of noise error is presented. The cross correlation coefficient (ccc) between the derivative of the original image before and after introducing noise error shows dramatic decline compared with the corresponding images before taking derivatives. Mathematical equations have been constructed to control the relation between (ccc) and the noise parameter.

scholarly journals Multi-Pulse Diode Rectifier for More-Electric Aircraft Applications: Parallel versus Series Topologies

2017 ◽  
Vol 13 (1) ◽  
pp. 138-144
Author(s):  
Ahmed Hafez ◽  
Ali Yousef
Keyword(s):  
Test Rig ◽  
Grid Systems ◽  
Aircraft Systems ◽  
Electric Aircraft ◽  
Analytical Formulas ◽  
Key Variables ◽  
Set Up ◽  
The Impact ◽  
More Electric Aircraft

This article analyzes thoroughly the performance of the Multi-Pulse Diode Rectifiers (MPDRs) regarding the quality of input/output voltage and currents. Two possible arrangements of MPDRs are investigated: series and parallel. The impact of the DC side connection on the performance of the MPDRs regarding the operation parameters and rectifier indices are comprehensively examined. Detailed analytical formulas are advised to identify clearly the key variables that control the operation of MPDRs. Moreover, comprehensive simulation results are presented to quantify the performance and validate the analytical analysis. Test-rig is set up to recognize the promising arrangement of MPDRs. Significant correlation is there between simulation and practical results. The analytical results are presented for aircraft systems (400Hz), and power grid systems (60Hz). This is to study the impact of voltage and frequency levels on the topology type of MPDRs. In general, each topology shows merits and have limitations.

scholarly journals THE IMPACT OF COVID-19 ON EXCHANGE RATE VOLATILITY: AN ECONOPHYSICS APPROACH

2020 ◽  
Author(s):  
Rui Dias ◽  
◽  
Hortense Santos ◽  
Keyword(s):  
Exchange Rates ◽  
Correlation Coefficient ◽  
Cross Correlation ◽  
Exchange Rate Volatility ◽  
Correlation Coefficients ◽  
Weak Form ◽  
Fluctuation Analysis ◽  
Global Pandemic ◽  
Exchange Markets ◽  
The Impact

This paper aims to analyze the efficiency, in its weak form, between exchange rates, US-RMB, US-EUR, US-JPY, US-MYR, US-PHP, US-SGD, US-THB, US-CHF, US-GBP, in the period from July 1, 2019 to October 27, 2020. To perform this analysis, different approaches were undertaken to assess whether: (i) the impact of the global pandemic created long memories in international foreign exchange markets? The results of the exponents Detrended Fluctuation Analysis (DFA) show that the exchange rates US-THB (0.60), US-MYR (0.59), US-SGD (0. 59), present long memories, to a lesser extent the exchange pairs US-GBP (0.56), US-EUR (0.53). On the other side, exchange rates US-RMB (0. 47), US-JPY (0. 43), US-CHF (0. 46), US-PHP (0. 38) show anti persistence, while the Detrended cross-correlation coefficient (𝑝𝐷𝐶𝐶𝐴) results show 19 average correlation coefficients (≌ 0.333 → ≌ 0.666), 10 weak correlation coefficient (≌ 0,000 → ≌ 0.333), 7 strong non-trend cross correlation coefficients (0.666→ ≌ 1,000). In conclusion, we show that the exchange pairs analyzed show some predictability, that is, there are levels of arbitrage that can be explored by investors; we also found that the exchange rates analyzed have characteristics of diversification, due to the low autocorrelation between markets. The objective of this study was not to analyze abnormal profitability by investors without incurring additional risk.

scholarly journals Spaced-Antenna Interferometry to Detect and Locate Subvolume Inhomogeneities of Reflectivity: An Analogy with Monopulse Radar

2008 ◽  
Vol 25 (11) ◽  
pp. 1921-1938 ◽  
Author(s):  
Guifu Zhang ◽  
Richard J. Doviak
Keyword(s):  
Correlation Function ◽  
Power Spectrum ◽  
Correlation Coefficient ◽  
Wave Scattering ◽  
Cross Correlation ◽  
Phased Array ◽  
Weather Radar ◽  
Individual Object ◽  
Potential Applications ◽  
Nonuniform Beam

Abstract The theory of spaced-antenna interferometry (SAI) is formulated to detect and locate deterministic objects and reflectivity inhomogeneities embedded within the phased-array weather radar’s resolution volume V6 and to improve weather radar performance. An analogy is made between monopulse tracking and SAI. The cross-correlation function and its power spectrum are derived based on wave scattering by a large deterministic object and clusters of randomly distributed precipitation particles. It is shown that nonuniform beam filling leads to an effective narrower beam and an increase in cross-correlation coefficient at zero lag. Hence, an individual object or a subvolume inhomogeneity can be detected and located by SAI. This capability further enhances the potential applications of phased-array weather radar used as a multimission system.

scholarly journals Polarimetric Tornadic Debris Signature Variability and Debris Fallout Signatures

2015 ◽  
Vol 54 (12) ◽  
pp. 2389-2405 ◽  
Author(s):  
Matthew S. Van Den Broeke
Keyword(s):  
Land Cover ◽  
Correlation Coefficient ◽  
Cross Correlation ◽  
Extreme Values ◽  
Life Cycles ◽  
Areal Extent ◽  
Polarimetric Radar ◽  
Horizontal Polarization ◽  
Differential Reflectivity ◽  
Relative Flow

AbstractValues of polarimetric radar variables may vary substantially between and through tornadic debris signature (TDS) events. Tornadoes with higher intensity ratings are associated with higher average and extreme values of reflectivity factor at horizontal polarization ZHH and lower values of copolar cross-correlation coefficient ρhv. Although values of these variables often fluctuate through reported tornado life cycles, ZHH repeatably decreases and ρhv repeatably increases across the volume scan immediately following reported tornado demise. Land cover has a relatively small effect on values of the polarimetric variables within TDSs, although near-radar urban TDSs may exhibit relatively high ZHH values. TDS areal extent is typically larger aloft than near the surface, although this trend may reverse in the most intense tornadoes. Maximum altitude to which a TDS is visible is more strongly a function of tornado intensity than of land cover or ambient shear and instability. Debris often disappears once lofted but may also be observed to spread out downstream with the storm-relative flow or to fall out along the parent storm’s northwest flank in a debris fallout signature (DFS). DFS characteristics, although variable, most commonly include ZHH values of 30–35 dBZ, ρhv values of 0.60–0.80, and values of differential reflectivity ZDR that are repeatably near 0 dB.

scholarly journals Autocorrelation and Cross-Correlation Estimators of Polarimetric Variables

2007 ◽  
Vol 24 (8) ◽  
pp. 1337-1350 ◽  
Author(s):  
Valery M. Melnikov ◽  
Dusan S. Zrnić
Keyword(s):  
Correlation Coefficient ◽  
Cross Correlation ◽  
Radar Data ◽  
Lower Sensitivity ◽  
Noise Levels ◽  
Low Snr ◽  
Interference Signals ◽  
Cross Correlations ◽  
Differential Reflectivity ◽  
Thermal Radiations

Abstract Herein are proposed novel estimators of differential reflectivity ZDR and correlation coefficient ρhv between horizontally and vertically polarized echoes. The estimators use autocorrelations and cross correlations of the returned signals to avoid bias by omnipresent but varying white noise. These estimators are considered for implementation on the future polarimetric Weather Surveillance Radar-1988 Doppler (WSR-88D) network. On the current network the reflectivity factor is measured at signal-to-noise ratios (SNRs) as low as 2 dB and the same threshold is expected to hold for the polarimetric variables. At such low SNR and all the way up to SNR = 15 dB, the conventional estimators of differential reflectivity and the copolar correlation coefficient are prone to errors due to uncertainties in noise levels caused by instability of radar devices, thermal radiations of precipitation and the ground, and wideband radiation of electrically active clouds. Noise variations at SNR less than 15 dB can bias the estimates beyond apparatus accuracy. For brevity the authors refer to the estimators of ZDR and ρhv free from noise bias as the “1-lag estimators” because these are derived from 1-lag correlations. The estimators are quite robust and the only weak assumption for validity is that spectral widths of signals from vertically and horizontally polarized returns are equal. This assumption is verified on radar data. Radar observations demonstrate the validity of these estimator and lower sensitivity to interference signals than the conventional algorithms.

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