Values Of Dispersion Parameters Research Articles

Method for Estimating the Monetary Benefit of Improving Annual Average Daily Traffic Accuracy in the Context of Road Safety Network Screening

Conventional road safety network screening (NS) relies on measures of historical crash data and annual average daily traffic (AADT) as a measure of exposure to develop safety performance functions. AADT is typically estimated from short-term counts and contains error which can negatively affect NS outcomes and result in the inefficient allocation of safety improvement resources. In this paper, we propose a simulation-based method for quantifying the monetary benefit of improving AADT accuracy. The results of applying the method under various conditions show that crash data sets with higher sample mean and dispersion parameter values are more sensitive to AADT error and consequently benefit more from improving AADT accuracy. The use of the proposed method is illustrated through the application to a real-world example.

Role of rubrene additive for reinforcing the structural, optical, and dispersion properties of polyvinyl alcohol films towards optoelectronic applications

A conventional casting method was used to produce promoted polyvinyl alcohol (PVA) films via rubrene additive. The 1.2 g of PVA dissolved in 120 ml of distilled water and doped with various concentrations (0, 0.1, 0.3 and 0.4 wt%) of rubrene dye. The influence of rubrene dopants on the structural properties of PVA was studied using FTIR and XRD techniques. The semicrystalline nature of the PVA polymer was established by the XRD pattern. FT-IR analysis shows changes in peaks intensities of PVA and their widths are expanded in the presence of rubrene dopants which indicates the interactions between the functional groups of PVA and the rubrene dopants. XRD patterns exhibit the existence of rubrene inside the PVA structure leads to form cross-linking which enhances the amorphous nature within the doped PVA samples. The optical characteristics were investigated using spectrophotometric measurements of transmittance T(λ), reflectance R(λ), and absorbance A(λ) in the spectral range of 200–2500 nm. The indirect and direct optical band-gap values of PVA films decreased from 5.15 eV and 5.69 eV to 3.63 eV and 4.50 eV as rubrene doping ratio was increased from 0 to 0.4 wt%, respectively. The refractive index dispersion region was explained using the single oscillator (Wemple–DiDomenico) model. The extracted values of dispersion energy (Ed), dielectric constant at infinite frequency (ε∞) and lattice dielectric constant (εL) of PVA/rubrene composite films increased from 0.74 eV, 1.31 and 1.35 to 5.35 eV, 3.47 and 4.35; respectively, whereas oscillator energy (Eo) decreased from 2.41eV to 2.17 eV as rubrene contents increased from 0 to 0.4 wt%, respectively. Indeed, these changes in values of dispersion parameters is evidence to the cross-linking bonds between the host polymer and the rubrene dopants. The improvement of optical properties of PVA/rubrene films demonstrates their applicability as eco-friendly packaging materials, particularly in flexible optoelectronic and microelectronic devices.

Geochemical processes in the groundwater of Soubré, Ivory Coast, West Africa: Evidence from 14C, 13C, 18O, 2H and major ions

Characteristics of the bedrock groundwater in the southwestern (SW) Ivory Coast (IC) (5–6°N, 4–7°W) are geochemically less known compared to those in the eastern part of the country. Several main cash crops, such as cocoa, coffee, rubber and palm oil, started being grown in this area twenty years ago because of the migration of agricultural activities from the East to the West of IC; this migration of agricultural activites was tied to climate variability. Within these large land use areas, food crops such as plantain bananas, yams, rice, maize, and vegetables are also grown. In this work, the mineralisation and groundwater pollution from East IC to West IC are studied within groundwater of the Archean and Paleoproterozoïce bedrock aquifers located in the SW IC. Stable isotopes ratios (δ18O, δ2H and δ13C), radiocarbon activity (A14C) and chemical contents (major ions) were measured on a set of 23 groundwater samples. In SW IC, the residence times calculated by an exponential mixing model (EMM) and a dispersion model (DM) with Dispersion Parameter values of 0.05 and 0.5 reveal that the oldest groundwater is located in the aquifer of migmatitic and granulitic gneiss (MiGn aquifer). Recent groundwater is located in the metagranitoid (MetGr) and the metasedimentary rocks (MetSe) aquifers. The most appropriate model to compute residence times is EMM because of the highest proportion of recharge in accordance with the nitrate content in groundwater after 1958, the beginning of Ivorian deforestation. However, this model lead to an overestimate of the residence time of groundwater particularly high in NO3. The oldest age of MiGn groundwater according to EMM calculation is ∼5 ka BP. The MiGn aquifer is less renewed (mean annual renewal rate of 0.03%) followed by those of MetSe (∼2.5 ka BP) and MetGr (∼2 ka BP), with mean annual renewal rates of 0.09% and 0.012%, respectively. Groundwater mineralisation is mainly governed by the hydrolysis of Al-silicates minerals and cultivation practice linked to K and N-fertilisers use, which leads to an increase of Ca, Mg and Na content. The values of TDS ranged from 49.4 to 720.4 mg L−1, which indicates the chemical characteristics of fresh water in SW IC. Most of the studied area groundwater are evaporated, likely due to both climate variability since the last 5 ka BP, delayed infiltration of rainwater which would be caused by impervious sediments covering the hard rock aquifers and agricultural practices affecting the most recently recharged groundwater. River water recharge from irrigation in cultivated areas may be possible. The groundwater with low 14C activities (64.33 pMC) has high residence times and is depleted in 13C content, while that with high 14C activities (99.58 pMC) is enriched in 13C content. This demonstrates that vegetation cover changed from C3 plants or forest (−23.9‰) to C4 plants, savannah or cultivation plants (−12.5‰) similar to those found in the southeastern IC.

Blueshifted dielectric properties and optical conductivity of new nanoscale nickel-(II)-tetraphenyl-21H,23H-porphyrin films as a function of UV illumination for energy storage applications.

Pristine thermally evaporated nickel-(II)-tetraphenyl-21H,23H-porphyrin (NiTPP) thin films are amorphous, but after 4 and 8 h of UV illumination, the films become crystalline with preferred orientations of (112), (103) and (004) and crystallite sizes of (13, 18, 16) and (42, 31, 38) nm after 4 and 8 h, respectively. After UV illumination for 4 and 8 h, the NiTPP thin films are characterized by blueshifted absorption coefficients, increasing the optical and fundamental gap values and decreasing the dispersion parameter values. The dielectric properties display energy storage regions corresponding to the peak values of optical conductivity, which provides an elegant confirmation of the tailoring and tuning of band gaps, energy storage properties and optical conductivity by UV illumination time. Therefore, NiTPP films may be good candidates for environmental and energy storage applications.

Optical properties of Al-doped ZnO thin films obtained by the method of high-frequency magnetron sputtering

The optical constants and thickness of Al-doped ZnO (ZnO:Al(2.5 wt.%)) thin films prepared by high-frequency magnetron sputtering method are determined. ZnO:Al thin films are crystallized in the hexagonal structure from XRD studies. The optical constants and the bandgap of the films under study have been determined. Optical properties (refractive index [Formula: see text], absorption coefficient [Formula: see text], extinction coefficient [Formula: see text], dielectric functions [Formula: see text] and optical conductivity [Formula: see text]) of thin films and thickness [Formula: see text] can be determined from the transmission spectrum. The dispersion of the refractive index was explained using a single oscillator model. Single oscillator energy and dispersion energy are obtained from fitting. Optical parameters of the films were determined using the Cauchy, Sellmeier and Wemple models. The increasing value of dispersion parameter for polycrystalline thin films than for single crystals is observed. The fundamental absorption edge position (3.26 eV) in the transmittance spectrum of studied thin films corresponds to the values that are typical for ZnO:Al compound. No significant increase of the bandgap width was revealed by comparing ZnO:Al thin films with the known results of the optical studies of ZnO thin films. Possible reasons of such behavior were analyzed and the influence of bandgap increase on spectral behavior of optical functions are investigated. The material optical parameters such as normalized integrated transmission, zero and high-frequency dielectric constant, density of state effective mass ratio were also calculated.

Influence of phase transformation on structure–property relationship in quaternary In10Sb10Ag10Se70 chalcogenide films

This work reports the effect of thermal annealing (353–413 K) on structure and physical properties of thermally evaporated In10Ag10Sb10Se70 chalcogenide films. The samples were characterized by X-ray diffraction, transmission electron microscopy, TEM, Raman spectroscopy, optical absorption and photoconductivity measurements. Thermal annealing favours amorphous to polycrystalline structure transition with the growth of Se, AgInSe2 and AgSbSe2 phases. A significant change in position/shape of Raman bands upon annealing has been observed. The indirect optical gap decreases from 1.44 to 0.68 eV while tailing parameter increases with annealing. Photosensitivity decreases from 29.3 to 14.2 with annealing temperature. The decay of photocurrents is well fitted to stretched exponential function; the value of decay time constant increases while local minimum value of dispersion parameter at 353 K has been observed. These results are explained on the basis of amorphous crystalline phase transformation in chalcogenides and are important for developing new materials for emerging technologies.

Application of the Poisson-Tweedie distribution in analyzing crash frequency data

This paper describes a study that applies the Poisson-Tweedie distribution in developing crash frequency models. The Poisson-Tweedie distribution offers a unified framework to model overdispersed, underdispersed, zero-inflated, spatial, and longitudinal count data, as well as multiple response variables of similar or mixed types. The form of its variance function is simple, and can be specified as the mean added to the product of dispersion and mean raised to the power P. The flexibility of the Poisson-Tweedie distribution lies in the domain of P, which includes positive real number values. Special cases of the Poisson-Tweedie distribution models include the linear form of the negative binomial (NB1) model with P equal to 1.0, the geometric Poisson (GeoP) model with P equal to 1.5, the quadratic form of the negative binomial (NB2) model with P equal to 2.0, and the Poisson Inverse Gaussian (PIG) model with P equal to 3.0. A series of models were developed in this study using the Poisson-Tweedie distribution without any restrictions on the value of the power parameter as well as with specific values of the power parameter representing NB1, GeoP, NB2, and PIG models. The effects of fixed and varying dispersion parameters (i.e., dispersion as a function of covariates) on the variance and expected crash frequency estimates were also examined. Three years (2012–2014) of crash data from urban three-leg stop-controlled intersections and urban four-leg signalized intersections in the state of Florida were used to develop the models. The Poisson-Tweedie models or the GeoP models were found to perform better when the dispersion parameter was constant or fixed. With the varying dispersion parameter, the NB2 and PIG models were found to perform better, with both performing equally well. Also, the fixed dispersion parameter values were found to be smaller in the models with a higher value of the power parameter. The variation across the models in their estimates of weight factor, expected crash frequency, and potential for safety improvement of hazardous sites based on the empirical Bayes method was also discussed.

A Simulation-Based Study on the Comparison of Statistical and Time Series Forecasting Methods for Early Detection of Infectious Disease Outbreaks.

Early detection of infectious disease outbreaks is one of the important and significant issues in syndromic surveillance systems. It helps to provide a rapid epidemiological response and reduce morbidity and mortality. In order to upgrade the current system at the Korea Centers for Disease Control and Prevention (KCDC), a comparative study of state-of-the-art techniques is required. We compared four different temporal outbreak detection algorithms: the CUmulative SUM (CUSUM), the Early Aberration Reporting System (EARS), the autoregressive integrated moving average (ARIMA), and the Holt-Winters algorithm. The comparison was performed based on not only 42 different time series generated taking into account trends, seasonality, and randomly occurring outbreaks, but also real-world daily and weekly data related to diarrhea infection. The algorithms were evaluated using different metrics. These were namely, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), F1 score, symmetric mean absolute percent error (sMAPE), root-mean-square error (RMSE), and mean absolute deviation (MAD). Although the comparison results showed better performance for the EARS C3 method with respect to the other algorithms, despite the characteristics of the underlying time series data, Holt–Winters showed better performance when the baseline frequency and the dispersion parameter values were both less than 1.5 and 2, respectively.

A Comparison of Tritium Dispersion Methodology for Accident Analysis in U.S. Department of Energy Complex Facilities

A comparison of three United States (U.S.) Department of Energy (DOE) Standard DOE-STD-3009–2014 dispersion modeling protocol options has been performed assuming a ground-level release of tritium oxide source term. The options are characterized by differing sets of assumptions and inputs that allow incorporating greater user flexibility and realism into the modeling and subsequent analysis. The three options used to evaluate atmospheric dispersion include: (1) Use of U.S. Nuclear Regulatory Commission (NRC) Regulatory Guide 1.145; (2) Application of a DOE-approved toolbox code and application of conservative input parameters; and (3) Use of site-specific methods and parameters as defined in a site/facility specific DOE-approved modeling protocol.Option 1 dose results are the lowest of the three sets of results at close-in distances, but are the highest for distances beyond approximately 3,000 m, reflecting the distance-dependent NRC plume meander model. Option 1 doses also reflect a lower minimum wind speed and consideration of G stability. Option 3 dose results are consistently lower than the Option 2 results by a factor of 2.2 reflecting the higher vertical dispersion values calculated from the crediting site-specific surface roughness. Option 2 and 3 results are obtained with DOE Central Registry computer software reflect default parameters in Option 2, and more site-specific input with Option 3. An averaging time of two hours leads to dose results that are lower than those obtained with an averaging time of three minutes by a factor of 2.5 due to the higher crosswind dispersion parameter values. This effect is due to the larger crosswind dimension of the plume with increasing averaging time using the Gifford meander model. A sensitivity case study indicates appreciable differences are observed between results obtained with the NRC Regulatory Guide 1.145 temperature difference (ΔT) method and those with U.S. Environmental Protection Agency (EPA) EPA-454/R-99–005 methodology for stability class categorization. A second sensitivity case suggests that crediting deposition, hold-up or other retention of tritium may be difficult to defend from a regulatory perspective, recognizing region of transport characteristics and accounting for reemission phenomenon. In terms of recommending one of the three options for modeling tritium releases in Documented Safety Analysis (DSA) applications, the Option 2 approach (Application of a DOE-approved toolbox code and conservative input parameters – without crediting tritium deposition) is the simplest model for source to receptor distances of 500 m or greater. Option 3 requires additional resource commitment and DOE authority approval, but may provide regulatory relief for certain accident scenarios. These recommendations apply to deterministic DSA dispersion analysis but are not extended to best estimate, realistic analyses such as those supporting probabilistic safety analyses.

Charge transport in gap structures based on amorphous Al2O3

The charge transport in amorphous layers of oxide of aluminum Al2O3 in the temperature range T=223-273K is studied. It was found the existence of hopping conduction mechanism in studied layers. The values of dispersion parameter s and activation energy EA are determined.

Bright Solitons on Continuous Wave Background in Blood Vessels

The nonlinear Schrödinger equation (NLSE) with variable coefficients in blood vessels is discussed via an NLSE-based constructive method, and exact solutions are obtained including multi-soliton solutions with and without continuous wave backgrounds. The dynamical behaviors of these soliton solutions are studied. The solitonic propagation behaviors such as restraint and sustainment on continuous wave background are discussed by altering the value of dispersion parameter δ. Moreover, the longitude controllable behaviors are also reported by modulating the dispersion parameter δ. These results are potentially useful for future experiments in various blood vessels.

Systematic study of rapidity dispersion parameter in high energy nucleus–nucleus interactions

A systematic study of rapidity dispersion parameter as a quantitative measure of clustering of particles has been carried out in the interactions of 16 O , 28 Si and 32 S projectiles at 4.5 A GeV/c with heavy ( AgBr ) and light (CNO) groups of targets present in the nuclear emulsion. For all the interactions, the total ensemble of events has been divided into four overlapping multiplicity classes depending on the number of shower particles. For all the interactions and for each multiplicity class, the rapidity dispersion parameter values indicate the occurrence of clusterization during the multiparticle production at Dubna energy. The measured rapidity dispersion parameter values are found to decrease with the increase of average multiplicity for all the interactions. The dependence of rapidity dispersion parameter on the average multiplicity can be successfully described by a relation D(η) = a + b〈ns〉 + c〈ns〉2. The experimental results have been compared with the results obtained from the analysis of Monte Carlo simulated (MC-RAND) events. MC-RAND events show weaker clusterization among the pions in comparison to the experimental data.

Spatial Effects on Zone-Level Collision Prediction Models

A recent study developed a set of zone-level negative binomial collision prediction models to investigate the relationship between various transportation and sociodemographic characteristics and overall roadway safety. The developed models used data from Metro Vancouver, British Columbia, Canada, and considered the effect of Poisson variations and heterogeneity (extra variation) on collision occurrence. This study aims to evaluate spatial effects on the occurrence of collisions and to check whether the inclusion of spatial variables can improve the goodness of fit and inference capability of those previously developed prediction models. Transit-reliant and application-based collision prediction models with spatial correlations were developed by using the WinBUGS software. The convergence of the developed models was tested by trace plots of the parameter estimated, the Brooks–Gelman–Rubin statistics, and ratios of Monte Carlo errors relative to the standard deviations of the estimates. The results showed that incorporation of the spatial correlations affected the parameter estimates, the values of dispersion parameters and intercepts, and also the t-statistics. The effect of the main exposure variable on all of the models for total, severe, and property-damage-only collisions was found to be smaller under spatial models. The smaller values of the exponents of the main exposure variable confirmed the assumption that spatial effects need to be considered in collision prediction models to mitigate any potential bias associated with model misspecification.

Examining the effects of site selection criteria for evaluating the effectiveness of traffic safety countermeasures

The primary objective of this paper is to describe how site selection effects can influence the safety effectiveness of treatments. More specifically, the goal is to quantify the bias for the safety effectiveness of a treatment as a function of different entry criteria as well as other factors associated with crash data, and propose a new method to minimize this bias when a control group is not available. The study objective was accomplished using simulated data. The proposed method documented in this paper was compared to the four most common types of before–after studies: the Naïve, using a control group (CG), the empirical Bayes (EB) method based on the method of moment (EBMM), and the EB method based on a control group (EBCG). Five scenarios were examined: a direct comparison of the methods, different dispersion parameter values of the Negative Binomial model, different sample sizes, different values of the index of safety effectiveness (θ), and different levels of uncertainty associated with the index. Based on the simulated scenarios (also supported theoretically), the study results showed that higher entry criteria, larger values of the safety effectiveness, and smaller dispersion parameter values will cause a larger selection bias. Furthermore, among all methods evaluated, the Naïve and the EBMM methods are both significantly affected by the selection bias. Using a control group, or the EBCG, can mutually eliminate the site selection bias, as long as the characteristics of the control group (truncated data for the CG method or the non-truncated sample population for the EBCG method) are exactly the same as for the treatment group. In practice, finding datasets for the control group with the exact same characteristics as for the treatment group may not always be feasible. To overcome this problem, the method proposed in this study can be used to adjust the Naïve estimator of the index of safety effectiveness, even when the mean and dispersion parameter are not properly estimated.

Suction/injection effects on thermophoresis particle deposition in a non-Darcy porous medium under the influence of Soret, Dufour effects

The effect of suction/injection on thermophoretic particle deposition in free convection on a vertical plate embedded in a fluid saturated non-Darcy porous medium is studied using similarity solution technique. The effect of Soret and Dufour parameters on convective transport, wall thermophoretic deposition velocity, heat transfer and mass transfer is discussed in detail for different values of dispersion parameters, ( Ra γ, Ra ξ ) inertial parameter F and Lewis number Le. The result indicates that in both suction, injection the Soret effect is more influential in increasing the concentration distribution in both aiding as well as opposing buoyancies. Also, it is worth mentioning here that the combined effect of opposing buoyancy and injection will have a more significant effect on the boundary layer thickness. In both the cases, suction as well as injection, magnitude of heat transfer is observed to be more when the second order effects are considered than when they are not. But, mass transfer and the wall thermophoretic deposition velocity V tw becomes less when all effects are considered than when they are not.

Solute Transport Modeling for Urban Drainage Structures

Solute transport and dispersion processes affect the performance of a wide range of water engineering structures. Some urban drainage network models transport the pollutants by advection only, whereas others also account for the effects of dispersion, although there is only limited knowledge regarding appropriate values for dispersion parameters. Computational fluid dynamics (CFD)-based software tools enable engineers to simulate flow patterns and associated pollutant transport mechanisms within both natural and engineered hydraulic structures. It is feasible to use CFD to represent solute transport using two contrasting approaches, an unsteady species (scalar) transport model or a discrete phase (Lagrangian particle tracking) model. This paper outlines these two approaches, using the example of a storage tank to demonstrate, compare, and validate the two approaches, and to explore a number of issues associated with interpretation of the simulation outputs. It is concluded that both CFD-based approaches m...

Thermophoresis particle deposition in a non-Darcy porous medium under the influence of Soret, Dufour effects

Thermophoresis particle deposition in free convection on a vertical plate embedded in a fluid saturated non-Darcy porous medium is studied using similarity solution technique. The effect of Soret and Dufour parameters on concentration distribution, wall thermophoretic deposition velocity, heat transfer and mass transfer is discussed in detail for different values of dispersion parameters (Raγ, Raξ) inertial parameter F and Lewis number Le. The result indicates that the Soret effect is more influential in increasing the concentration distribution in both aiding as well as opposing buoyancies. Also, the non-dimensional heat transfer coefficient and non-dimensional mass transfer coefficient changes according to different values of thermophoretic coefficient k.

Influence of thermoannealing on crystallinity and optical properties of Sb2S3 thin films

AbstractSb2S3 thin films are obtained by evaporating of Sb2S3 powder onto glass substrates maintained at room temperature under pressure of 2×10‐5 torr. The composition of the thin films was determined by energy dispersive analysis of X‐ray (EDAX). The effect of thermal annealing in vacuum on the structural properties was studied using X‐ray diffraction (XRD) technique and scanning electron microscopy (SEM). The as‐deposition films were amorphous, while the annealed films have an orthorhombic polycrystalline structure. The optical constants of as‐deposited and annealed Sb2S3 thin films were obtained from the analysis of the experimental recorded transmission spectral data over the wavelength range 400‐1400 nm. The transmittance analysis allowed the determination of refractive index as function of wavelength. It was found that the refractive dispersion data obeyed the single oscillator model, from which the dispersion parameters (oscillator energy, E0, dispersion energy, Ed) were determined. The static refractive index n(0), static dielectric constant, ε∞, and optical band gap energy, Eg, were also calculated using the values of dispersion parameters. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Solitonic structures in KdV-based higher-order systems

Wave propagation in microstructured materials is studied using a Korteweg–de Vries (KdV)-type nonlinear evolution equation. Due to the microstructure, nonlinear effects are described by a quartic elastic potential and dispersive effects — by both the third- and the fifth-order space derivatives. The problem is solved numerically under harmonic initial condition. For nondispersive materials, the quartic elastic potential, compared with that of the second-order (KdV) one, leads to the formation of two additional discontinuities in the harmonic initial wave profile. This together with the additional dispersive effect is the reason for emerging complicated solitonic structures (train of solitons, train of negative solitons and multiple solitons) depending on the values of dispersion parameters. Chaotic motion results if both the third- and the fifth-order dispersion parameters take the small possible values.

Air quality assessment of the environment over a cement industrial complex

In recent years SO 2, NO χ and SPM (suspended particulate matter) over the industrialized cities of India are showing an increasing tend. Any new industrial sitings are likely to contribute further to the degradation of air quality. Since industrial development has to continue, one must take sufficient safety measures to ensure that our air quality is not impaired. A balanced and scientific approach is required to set up industrial and residential complexes. Various impact assessment studies can be undertaken to study the effect of existing industries by the use of mathematical models. Two different air quality models, IITST and ISI (ASME), have been used to predict monthly averaged SPM concentrations at different receptor points within an area of 10 km radius around the proposed plant. The calm winds which are most frequent in Indian meteorological conditions and whose occurrence at the plant site is about 40% has been given special attention in the IITST model. An important parameter in air quality models is the atmospheric stability which is identified as a key factor in dispersion modelling since the values of dispersion parameters σ y and σ z depend on stability. A number of different approaches, to classify stability class available in the literature, have been intercompared in the present study. In the present work, the meteorological data of four months (25 November 1991 to 31 March 1992), monitored at the site of the upcoming plant, have been analyzed and used.