scholarly journals Calculation of crosswind integrated concentration by using different dispersion schemes

MAUSAM ◽  
2021 ◽  
Vol 62 (1) ◽  
pp. 51-60
Author(s):  
KHALED S. M. ESSA ◽  
REFAAT A. R. GHOBRIAL ◽  
A. N. MINA ◽  
MAMDOUH HIGAZY
Keyword(s):  
Point Source ◽  
Power Law ◽  
Standard Method ◽  
Gaussian Model ◽  
Plume Rise ◽  
Concentration Data ◽  
Local Dispersion ◽  
Continuous Release ◽  
Statistical Measures ◽  
Theta Method

The Gaussian model is the most extensively used model for local dispersion. The Gaussian formula for a continuous release from a point source (GPM) is integrated to get crosswind integrated concentration. Different schemes such as Irwin, power law, Briggs, Standard method, and split sigma theta method can be used to obtain integrated concentration. Also downwind speed in power law, plume rise and Statistical measures are used in the model to know which is the best scheme agrees with the observed concentration data obtained from Copenhagen, Denmark.

scholarly journals Derivation of the Gaussian plume model in three dimensions

MAUSAM ◽  
2021 ◽  
Vol 65 (1) ◽  
pp. 83-92
Author(s):  
M.M. ABDELWAHAB ◽  
KHALED S.M.ESSA ◽  
H.M. ELSMAN ◽  
A.SH. SOLIMAN ◽  
S.M. ELGMMAL ◽  
...  
Keyword(s):  
Power Law ◽  
Eddy Diffusivity ◽  
Three Dimensions ◽  
Gaussian Plume Model ◽  
Concentration Data ◽  
Plume Model ◽  
Advection Diffusion Equation ◽  
Statistical Measures ◽  
Advection Diffusion ◽  
Gaussian Plume

Gaussian plume model is a common model to study advection diffusion equation which is solved in three dimensions by using Laplace transformation considering constant eddy diffusivity and wind speed power law. Different schemes such as Irwin, Power Law, Briggs and Standard methods are used to obtain crosswind integrated concentration. Statistical measures are used in this paper to know which is the best scheme which agrees with the observed concentration data obtained from Copenhagen, Denmark. The results of model are compared with observed data.

scholarly journals Normative human brain volume growth

2018 ◽  
Vol 21 (5) ◽  
pp. 478-485 ◽  
Author(s):  
Mallory Peterson ◽  
Benjamin C. Warf ◽  
Steven J. Schiff
Keyword(s):  
Human Brain ◽  
Power Law ◽  
Goodness Of Fit ◽  
Brain Volume ◽  
Volume Growth ◽  
Growth Charts ◽  
Brain Growth ◽  
Statistical Measures ◽  
Curve Fit ◽  
Males And Females

OBJECTIVEWhile there is a long history of interest in measuring brain growth, as of yet there is no definitive model for normative human brain volume growth. The goal of this study was to analyze a variety of candidate models for such growth and select the model that provides the most statistically applicable fit. The authors sought to optimize clinically applicable growth charts that would facilitate improved treatment and predictive management for conditions such as hydrocephalus.METHODSThe Weibull, two-term power law, West ontogenic, and Gompertz models were chosen as potential models. Normative brain volume data were compiled from the NIH MRI repository, and the data were fit using a nonlinear least squares regression algorithm. Appropriate statistical measures were analyzed for each model, and the best model was characterized with prediction bound curves to provide percentile estimates for clinical use.RESULTSEach model curve fit and the corresponding statistics were presented and analyzed. The Weibull fit had the best statistical results for both males and females, while the two-term power law generated the worst scores. The statistical measures and goodness of fit parameters for each model were provided to assure reproducibility.CONCLUSIONSThe authors identified the Weibull model as the most effective growth curve fit for both males and females. Clinically usable growth charts were developed and provided to facilitate further clinical study of brain volume growth in conditions such as hydrocephalus. The authors note that the homogenous population from which the normative MRI data were compiled limits the study. Gaining a better understanding of the dynamics that underlie childhood brain growth would yield more predictive growth curves and improved neurosurgical management of hydrocephalus.

scholarly journals Air quality simulations for London using a coupled regional-to-localmodelling system

2018 ◽  
Author(s):  
Christina Hood ◽  
Ian MacKenzie ◽  
Jenny Stocker ◽  
Kate Johnson ◽  
David Carruthers ◽  
...  
Keyword(s):  
Air Quality ◽  
Climate Model ◽  
Coupled Model ◽  
Horizontal Resolution ◽  
Exhaust Emission ◽  
Emission Rates ◽  
Concentration Data ◽  
Local Dispersion ◽  
Diurnal Cycles ◽  
Good Agreement

Abstract. High-resolution and accurate air quality concentration data are needed for detailed exposure and health effects calculations. Simulating such data numerically requires realistic treatment of both local emissions and background concentrations transported from further afield. This study combines regional and urban scale modelling and uses adjusted emission factors for NOx and NO2 and non-exhaust emission rates of PM10 and PM2.5 to reflect real-world emissions more accurately. Three modelling approaches have been used to simulate air quality in 2012 across London: a regional chemistry-climate model with 5 km horizontal resolution and gridded emissions; a local dispersion and chemistry model with explicit road source emissions; and a coupled regional-to-local modelling system combining the two individual models. The performance of each of the models is assessed against measurements from background and near-road sites in London in terms of annual averages, high hourly average concentrations and diurnal cycles. The regional model shows good agreement compared to measurements for background sites for these metrics but under-predicts concentrations of all pollutants except O3 at near-road sites due to the low resolution of input emissions and calculations. The urban model, using measured concentrations as regional background, and the coupled model show similarly good agreement for most pollutants at both background and near-road sites. Using the coupled model, it is estimated that 13 % of the area of London exceeded the EU limit value of 40 µg m−3 for annual average NO2 in 2012.

scholarly journals The angular power spectrum measurement of the Galactic synchrotron emission using the TGSS survey

2017 ◽  
Vol 12 (S333) ◽  
pp. 157-161
Author(s):  
Samir Choudhuri ◽  
Somnath Bharadwaj ◽  
Sk. Saiyad Ali ◽  
Nirupam Roy ◽  
H. T. Intema ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Power Spectrum ◽  
Point Source ◽  
Power Law ◽  
Point Sources ◽  
Synchrotron Emission ◽  
Angular Power Spectrum ◽  
Spectrum Measurement ◽  
Upper Limit ◽  
Sky Survey

AbstractCharacterizing the diffuse Galactic synchrotron emission (DGSE) at arcminute angular scales is needed to remove this foregrounds in cosmological 21-cm measurements. Here, we present the angular power spectrum (Cℓ) measurement of the diffuse Galactic synchrotron emission using two fields observed by the TIFR GMRT Sky Survey (TGSS). We apply 2D Tapered Gridded Estimator (TGE) to estimate the Cℓ from the visibilities. We find that the residual data after subtracting the point sources is likely dominated by the diffuse Galactic synchrotron radiation across the angular multipole range 240 ≤ ℓ ≲ 500. We fit a power law to the measured Cℓ over this ℓ range. We find that the slopes in both fields are consistent with earlier measurements. For the second field, however, we interpret the measured Cℓ as an upper limit for the DGSE as there is an indication of a significant residual point source contribution.

scholarly journals POWER-LAW TEMPLATE FOR INFRARED POINT-SOURCE CLUSTERING

2012 ◽  
Vol 752 (2) ◽  
pp. 120 ◽  
Author(s):  
Graeme E. Addison ◽  
Joanna Dunkley ◽  
Amir Hajian ◽  
Marco Viero ◽  
J. Richard Bond ◽  
...  
Keyword(s):  
Point Source ◽  
Power Law

scholarly journals A MULTI-DOMAIN HYBRID METHOD FOR HEAD-ON COLLISION OF BLACK HOLES IN PARTICLE LIMIT

2011 ◽  
Vol 22 (05) ◽  
pp. 517-541 ◽  
Author(s):  
DEBANANDA CHAKRABORTY ◽  
JAE-HUN JUNG ◽  
GAURAV KHANNA
Keyword(s):  
Finite Difference ◽  
Power Law ◽  
Hybrid Method ◽  
Gaussian Model ◽  
Spectral Domain ◽  
Computational Domain ◽  
Power Law Decay ◽  
Decay Profile ◽  
Singular Source ◽  
Proper Power

A hybrid method is developed based on the spectral and finite-difference methods for solving the inhomogeneous Zerilli equation in time-domain. The developed hybrid method decomposes the domain into the spectral and finite-difference domains. The singular source term is located in the spectral domain while the solution in the region without the singular term is approximated by the higher-order finite-difference method. The spectral domain is also split into multi-domains and the finite-difference domain is placed as the boundary domain. Due to the global nature of the spectral method, a multi-domain method composed of the spectral domain only does not yield the proper power-law decay unless the range of the computational domain is large. The finite-difference domain helps reduce boundary effects due to the truncation of the computational domain. The multi-domain approach with the finite-difference boundary domain method reduces the computational cost significantly and also yields the proper power-law decay. Stable and accurate interface conditions between the finite-difference and spectral domains and the spectral and spectral domains are derived. For the singular source term, we use both the Gaussian model with various values of full width at half-maximum and a localized discrete δ-function. The discrete δ-function was generalized to adopt the Gauss–Lobatto collocation points of the spectral domain. The gravitational waveforms are measured. Numerical results show that the developed hybrid method accurately yields the quasi-normal modes and the power-law decay profile. The numerical results also show that the power-law decay profile is less sensitive to the shape of the regularized δ-function for the Gaussian model than expected. The Gaussian model also yields better results than the localized discrete δ-function.

scholarly journals Instantaneous point source solutions in nonlinear diffusion with nonlinear loss or gain

2000 ◽  
Vol 41 (3) ◽  
pp. 281-300 ◽  
Author(s):  
J. R. Philip
Keyword(s):  
Point Source ◽  
Power Law ◽  
Finite Time ◽  
Nonlinear Diffusion ◽  
Blow Up ◽  
Central Place ◽  
Point Sources ◽  
Nonlinear Loss ◽  
Instantaneous Point ◽  
Central Concentration

AbstractExact solutions are developed for instantaneous point sources subject to nonlinear diffusion and loss or gain proportional to nth power of concentration, with n > 1. The solutions for the loss give, at large times, power-law decrease to zero of slug central concentration and logarithmic increase of slug semi-width. Those for gain give concentration decreasing initially, going through a minimum, and then increasing, with blow-up to infinite concentration in finite time. Slug semi-width increases with time to a finite maximum in finite time at a blow-up. Taken in conjunction with previous studies, these new results provide an overall schema for instantaneous nonlinear diffusion point sources with nonlinear loss or gain for the total range n ≥ 0. Six distinct regimes of behaviour of slug semi-width and concentration are identified, depending on the range of n, 0 ≤ n < 1, n = 1, or n > 1. Three of them are for loss, and three for gain. The classical Barenblatt-Pattle nonlinear instantaneous point-source solutions with material concentration occupy a central place in the total schema.

scholarly journals The 3D Spatial Autocorrelation of the Branching Fractal Vasculature

Acoustics ◽  
2019 ◽  
Vol 1 (2) ◽  
pp. 369-381 ◽  
Author(s):  
Kevin Parker ◽  
Jonathan Carroll-Nellenback ◽  
Ronald Wood
Keyword(s):  
Spatial Autocorrelation ◽  
Autocorrelation Function ◽  
Power Law ◽  
Soft Tissues ◽  
Specific Power ◽  
High Resolution Computed Tomography ◽  
Statistical Measures ◽  
Open Questions ◽  
Wide Range ◽  
Ultrasound Backscatter

The fractal branching vasculature within soft tissues and the mathematical properties of the branching system influence a wide range of important phenomena from blood velocity to ultrasound backscatter. Among the mathematical descriptors of branching networks, the spatial autocorrelation function plays an important role in statistical measures of the tissue and of wave propagation through the tissue. However, there are open questions about analytic models of the 3D autocorrelation function for the branching vasculature and few experimental validations for soft vascularized tissue. To address this, high resolution computed tomography scans of a highly vascularized placenta perfused with radiopaque contrast through the umbilical artery were examined. The spatial autocorrelation function was found to be consistent with a power law, which then, in theory, predicts the specific power law behavior of other related functions, including the backscatter of ultrasound.

scholarly journals Technical Note: Assessing a 24/7 solution for monitoring water quality loads in small river catchments

2011 ◽  
Vol 15 (10) ◽  
pp. 3093-3100 ◽  
Author(s):  
P. Jordan ◽  
R. Cassidy
Keyword(s):  
Point Source ◽  
Integrated Approach ◽  
Technical Note ◽  
Low Flow ◽  
Phosphorus Concentration ◽  
Storm Events ◽  
Concentration Data ◽  
High Discharge ◽  
Sediment Loads ◽  
Source Signals

Abstract. Quantifying nutrient and sediment loads in catchments is difficult owing to diffuse controls related to storm hydrology. Coarse sampling and interpolation methods are prone to very high uncertainties due to under-representation of high discharge, short duration events. Additionally, important low-flow processes such as diurnal signals linked to point source impacts are missed. Here we demonstrate a solution based on a time-integrated approach to sampling with a standard 24 bottle autosampler configured to take a sample every 7 h over a week according to a Plynlimon design. This is evaluated with a number of other sampling strategies using a two-year dataset of sub-hourly discharge and phosphorus concentration data. The 24/7 solution is shown to be among the least uncertain in estimating load (inter-quartile range: 96% to 110% of actual load in year 1 and 97% to 104% in year 2) due to the increased frequency raising the probability of sampling storm events and point source signals. The 24/7 solution would appear to be most parsimonious in terms of data coverage and certainty, process signal representation, potential laboratory commitment, technology requirements and the ability to be widely deployed in complex catchments.

A Stochastic Model for the Transition to Strong Convection

2011 ◽  
Vol 68 (12) ◽  
pp. 2955-2970 ◽  
Author(s):  
Samuel N. Stechmann ◽  
J. David Neelin
Keyword(s):  
Stochastic Model ◽  
Probability Density ◽  
Power Law ◽  
Precipitation Event ◽  
Model Parameters ◽  
External Forcing ◽  
Statistical Measures ◽  
Extreme Precipitation Events ◽  
Exponential Tails ◽  
Strong Convection

Abstract A simple stochastic model is designed and analyzed in order to further understand the transition to strong convection. The transition has been characterized recently in observational data by an array of statistical measures, including (i) a sharp transition in mean precipitation, and a peak in precipitation variance, at a critical value of column water vapor (CWV), (ii) an approximate power law in the probability density of precipitation event size, (iii) exponential tails in the probability density of CWV values, when conditioned on either precipitating or nonprecipitating locations, and (iv) long and short autocorrelation times of CWV and precipitation, respectively, with approximately exponential and power-law decays in their autocorrelation functions, respectively. The stochastic model presented here captures these four statistical features in time series of CWV and precipitation at a single location. In addition, analytic solutions are given for the exponential tails, which directly relates the tails to model parameters. The model parameterization includes three stochastic components: a stochastic trigger turns the convection on and off (a two-state Markov jump process), and stochastic closures represent variability in precipitation and in “external” forcing (Gaussian white noise). This stochastic external forcing is seen to be crucial for obtaining extreme precipitation events with high CWV and long lifetimes, because it can occasionally compensate for the heavy precipitation and encourage more of it. This stochastic model can also be seen as a simplified stochastic convective parameterization, and it demonstrates simple ways to turn a deterministic parameterization—the trigger and/or closure—into a stochastic one.

Sign in / Sign up

Export Citation Format

Share Document