bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling extreme rainfall data within a catchment region
Authors: Cocchi Daniela , Scagliarini Michele 
Published: January 2003

AbstractThe present work examines the extreme behaviour of monthly rainfall in the Reno River catchment area (Italy). The data are recorded by a network of monitoring sites for which a single model, valid for the whole region, can be built. As a first step, a generalized extreme value (GEV) model is fitted to monthly rainfall maxima for each site. As a further step, we have introduced a second level into the model whereby the GEV site‐specific parameters depend on covariates by means of hyperparameters common to the area. The maximum likelihood method is used for the purposes of estimation. We employed an extra‐sample set of monitoring sites in order to compare the results obtained using the catchment model with the single‐site models estimated by classical one‐level extreme value analysis. Copyright © 2003 John Wiley & Sons, Ltd.
Bootstrap simulations for evaluating the uncertainty associated with peaks‐over‐threshold estimates of extreme wind velocity
Authors: Pandey M. D. , Van Gelder P. H. A. J. M. , Vrijling J. K. 
Published: January 2003

AbstractIn the peaks‐over‐threshold (POT) method of extreme quantile estimation, the selection of a suitable threshold is critical to estimation accuracy. In practical applications, however, the threshold selection is not so obvious due to erratic variation of quantile estimates with minor changes in threshold. To address this issue, the article investigates the variation of quantile uncertainty (bias and variance) as a function of threshold using a semi‐parametric bootstrap algorithm. Furthermore, the article compares the performance of L‐moment and de Haan methods that are used for fitting the Pareto distribution to peak data.The analysis of simulated and actual U.S. wind speed data illustrates that the L‐moment method can lead to almost unbiased quantile estimates for certain thresholds. A threshold corresponding to minimum standard error appears to provide reasonable estimates of wind speed extremes. It is concluded that the quantification of uncertainty associated with a quantile estimate is necessary for selecting a suitable threshold and estimating the design wind speed. For this purpose, semi‐parametric bootstrap method has proved to be a simple, practical and effective tool. Copyright © 2003 John Wiley & Sons, Ltd.
Systematic sample design for the estimation of spatial means
Authors: Ambrosio Flores Luis , Iglesias Martínez Luis , Marín Ferrer Carmen 
Published: January 2003

AbstractThis article develops a practical approach to undertaking systematic sampling for the estimation of the spatial mean of an attribute in a selected area. A design‐based approach is used to estimate population parameters, but it is combined with elements of a model‐based approach in order to identify the spatial correlation structure, to evaluate the relative efficiency of the sample mean under simple random and systematic sampling, to estimate sampling error and to assess the sample size needed in order to achieve a desired level of precision. Using two case studies (land use estimation and weed seedbank in soil) it is demonstrated how the practical basis for the design of systematic samples provided in this work should be applied and it is shown that if the spatial correlation is ignored the sampling error of the sample mean and the sample size needed in order to achieve a desired level of precision with systematic sampling are overestimated. Copyright © 2003 John Wiley & Sons, Ltd.
Extracting quantitative dynamics from 222Rn gaseous emissions of mud volcanoes
Authors: Albarello D. , Lapenna V. , Martinelli G. , Telesca L. 
Published: January 2003

AbstractIn this work we explore the inner time dynamics of 222Rn gaseous emissions of a bubbling mud volcano located in northern Apennines (Italy). In order to discriminate shallow environmental effects, barometric and temperature series have been also monitored and compared with 222Rn data. The Lomb periodogram and the Higuchi techniques have been applied to characterize the time dynamics of the experimental time series. No significant periodicity has been identified and the power spectrum is characterised by a monotonic decrease with frequency f which follows a typical power law (∝f−α). Our findings suggest to consider the 222Rn time series as a realization of an antipersistent stochastic process. This indicates that the dynamics underlying Radon emissions from bubbling mud volcanoes is complex and that a relatively large number of unknown factors control the process. This result discourages the use of bubbling gaseous emissions for the monitoring of geodynamic processes. Copyright © 2003 John Wiley & Sons, Ltd.
Interannual variability in a plankton time series
Authors: Dowd Michael , Martin Jennifer L. , LeGresley Murielle M. , Hanke Alex , Page Fred H. 
Published: January 2003

AbstractTemporal changes in a plankton time series are examined, with an emphasis on interannual variability. A stochastic cycle model is used which describes an annual cycle with a fixed frequency, but a randomly varying amplitude and phase. A state space representation is used with the Kalman filter, and associated fixed‐interval smoother, to provide estimation of the time‐varying state. Parameter estimation relies on maximum likelihood methods. A data set is considered comprised of an irregularly sampled time series of plankton (dinoflagellate) abundance over a 12 year period in the Bay of Fundy, off the east coast of Canada. Analysis of the log10‐transformed data indicated timing changes in the seasonal cycle of up to 23 days. Significant variations in abundance relative to the mean cycle were found for some highly sampled summer periods. Case deletion diagnostics identified two influential observations, one of which has a large impact on the estimated system noise. Examination of the sampling protocol, or monitoring design, indicates the need to reduce the observation error variance in order to improve detection of interannual variations in plankton abundance. Copyright © 2003 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.
Density estimate and its application to analysis of temperature series
Authors: Horová Ivana , Zelinka Jiří , Brázdil Rudolf , Budíková Marie 
Published: January 2003

AbstractNonparametric density estimates attempt to reconstruct the probability density from which a random sample has come, using the sample values and as few assumptions as possible about the density. These methods are smoothing operations on the sample distribution. Methods of kernel estimates represent one of the most effective nonparametric methods. These methods are simple to understand, easy to implement and they have very good mathematical properties. We employed the automatic procedure for the selection of the bandwidth, the kernel and the order of the kernel. This procedure is used for analysis of air temperature fluctuations for series of Central England and Prague–Klementinum in the periods 1661–2000 and 1771–2000, respectively. Graphical representation of the family of estimated densities in three dimensional space provide a better explanation of the long‐term trends in temperature distribution of both series. Copyright © 2003 John Wiley & Sons, Ltd.
System identification of the Vincent Thomas suspension bridge using earthquake records
Authors: Smyth Andrew W. , Pei Jin‐Song , Masri Sami F. 
Published: January 2003

AbstractThe Vincent Thomas Bridge in the Los Angeles metropolitan area, is a critical artery for commercial traffic flow in and out of the Los Angeles Harbor, and is at risk in the seismically active Southern California region, particularly because it straddles the Palos Verdes fault zone. A combination of linear and non‐linear system identification techniques is employed to obtain a complete reduced‐order, multi‐input–multi‐output (MIMO) dynamic model of the Vincent Thomas Bridge based on the dynamic response of the structure to the 1987 Whittier and 1994 Northridge earthquakes.Starting with the available acceleration measurements (which consists of 15 accelerometers on the bridge structure and 10 accelerometers at various locations on its base), an efficient least‐squares‐based time‐domain identification procedure is applied to the data set to develop a reduced‐order, equivalent linear, multi‐degree‐of‐freedom model. Although not the main focus of this study, the linear system identification method is also combined with a non‐parametric identification technique, to generate a reduced‐order non‐linear mathematical model suitable for use in subsequent studies to predict, with good fidelity, the total response of the bridge under arbitrary dynamic environments.Results of this study yield measurements of the equivalent linear modal properties (frequencies, mode shapes and non‐proportional damping) as well as quantitative measures of the extent and nature of non‐linear interaction forces arising from strong ground shaking. It is shown that, for the particular subset of observations used in the identification procedure, the apparent non‐linearities in the system restoring forces are quite significant, and they contribute substantially to the improved fidelity of the model. Also shown is the potential of the identification technique under discussion to detect slight changes in the structure's influence coefficients, which may be indicators of damage and degradation in the structure being monitored. Difficulties associated with accurately estimating damping for lightly damped long‐span structures from their earthquake response are discussed. The technical issues raised in this paper indicate the need for added spatial resolution in sensor instrumentation to obtain identified mathematical models of structural systems with the broadest range of validity. Copyright © 2003 John Wiley & Sons, Ltd.
Flammability of polystyrene layered silicate (clay) nanocomposites: Carbonaceous char formation
Authors: Morgan Alexander B. , Harris Richard H. , Kashiwagi Takashi , Chyall Leonard J. , Gilman Jeffrey W. 
Published: January 2003

AbstractPolymer layered‐silicate (clay) nanocomposites have not only the unique advantage of reduced flammability, but also improved mechanical properties. This is a key advantage over many flame retardants, which reduce flammability but also reduce the mechanical properties of the polymer. In our efforts to further understand the mechanism of flame retardancy with polymer‐clay nanocomposites, we investigated the effect of the clay, the loading level and polymer melt viscosity on the flammability of polystyrene‐clay nanocomposites. The nanoscale dispersion of the clay in the polymer was analysed by wide‐angle X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Cone calorimetry and gasification studies were used to evaluate the flammability of these nanocomposites. There were major reductions in peak heat release rates (HRRs), and increased carbonaceous char formation, for these nanocomposites. It was determined that while the viscosity of the PS nanocomposite played a role in lowering the peak HRR, the clay loading level had the largest effect on peak HRR. Finally, it was found that clay catalysed carbonaceous char formation, and the reinforcement of the char by the clay was responsible for the lowered flammability of these nanocomposites. Published in 2002 by John Wiley & Sons, Ltd.
Short communication: Carbon nanotubes as flame retardants for polymers
Authors: Beyer Günter 
Published: January 2003

AbstractFlame retardant nanocomposites were synthesized by melt‐blending ethylene‐vinyl acetate copolymer (EVA) with multi wall carbon nanotubes. Fire property measurements by cone calorimeter revealed that the incorporation of multi wall carbon nanotubes into EVA significantly reduced the peak heat release rates compared with the virgin EVA. Peak heat release rates of EVA with multi‐wall carbon nanotubes were slightly improved compared with EVA nanocomposites based on modified layered silicates. Char formation is the main important factor for these improvements. There was also a synergistic effect by the combination of carbon nanotubes and organoclays resulting in an overall more perfect closed surface with improved heat release values. Copyright © 2002 John Wiley & Sons, Ltd.
Update for combustion properties of wood components
Authors: Dietenberger Mark 
Published: January 2003

AbstractThe combustion properties of various biomass and wood materials from various references and from our laboratory were reanalysed. The net heat of combustion for cellulosic materials was found to be 13.23 kJ/g times the ratio of stoichiometric oxygen mass to fuel mass, ro, regardless of the material composition. Bomb calorimeter data for original, charred and volatilized material components provide gross heating values, while elemental analysis of the materials for carbon, hydrogen, oxygen and ash provide direct evaluation for ro. We corrected these data as provided in various references by converting gross heating values to lower heating values and converting elemental compositions, char fractions and ro to a moisture‐free and ash‐free basis. Some existing formulae were found to disagree with data from vegetation, charred wood with high ash content, and with volatiles from cellulose treated with the fire retardant NaOH. We also established various functional correlations of ro with elemental compositions, or volatization fractions of untreated and treated materials, or material fractions for cellulose, lignin and extractives, or volatile fractions for tar, combustible gases and inert gases in pure nitrogen carrier gas. An interesting predictive result provides nearly constant heat of combustion while the volatile tar fraction is decreasing and combustible and inert gas fractions are increasing with time during the charring of Douglas‐fir wood. Published in 2002 John Wiley & Sons, Ltd.
Investigation and correlation of manikin and bench‐scale fire testing of clothing systems
Authors: Lee Calvin , Kim Il Young , Wood Alycia 
Published: January 2003

AbstractThe US Army currently has five flame/thermal protective clothing systems to provide protection for soldiers against fire hazards. The protective performance of these clothing systems against burn injuries was investigated in full‐scale manikin tests. The protective performance of fabric layers of these clothing systems was also examined in bench‐scale tests. In addition, air gap thicknesses and distributions of the five clothing systems were determined by using a three‐dimensional laser scanning technique. In this paper, test conditions of the manikin and bench‐scale tests are compared, and the test results are correlated in light of the air gap measurements. The behavior of individual sensors on the manikin with similar test conditions to those of bench‐scale tests are compared with the bench‐scale tests. It is found that if the air gap distribution of a clothing system is known, bench‐scale tests could provide useful information for full‐scale performance, especially bench‐scale tests with zero air gap measurements. Published in 2002 by John Wiley & Sons, Ltd.
Flame height correlation and upward flame spread modelling
Authors: Chung Tsai Kuang‐ , Drysdale Dougal 
Published: January 2003

AbstractPrevious work has demonstrated that flame height is one of the two most important parameters determining the rate of vertical flame spread on a wall. Flame spread models rely on empirical flame height correlations of the form Xf=KQ̇′n, but there have been no carefully controlled experiments designed to establish the validity of such correlations and there are no data for values of Q̇′< c.25 kW/m. Two new sets of data are presented here, one based on experiments with 6 mm thick PMMA slabs (heights 25–250 mm, width 50–150 mm) as the fire source, measuring Q̇′ and Xf simultaneously. This set relates to the early stages of a wall fire when Q̇′< 30 kW/m. The other set of data was obtained with a vertical gas‐fired panel which consisted of an array of 14 independent burners arranged to allow the aspect ratio of the burning surface to be varied. The data confirm that the flame height correlates with Q̇′, but reveal (inter alia) that there are two regions, for values of Q̇′ greater than and less than c. 20 kW/m.An existing upward flame spread model was modified to allow these two correlations to be incorporated to predict the development of a small fire on a vertical surface for these two regions, which would provide more realistic modelling information. Copyright © 2002 John Wiley & Sons, Ltd.
Reducing salinity and organic contaminants in the Pearl Harbor dredged material using soil amendments and plants
Authors: Hue N. V. , Campbell S. , Li Q. X. , Lee C. R. , Fong J. 
Published: January 2003

AbstractPhytoremediation is an emerging technique that can be used to economically remediate sites contaminated with
trace elements and/or man‐made organic contaminants. This technique was used on Pearl Harbor (Oahu,
Hawaii) dredged material (PHDM) containing polycyclic aromatic hydrocarbons (PAHs) and
some heavy metals. The dredged material was first amended with a high‐calcium soil (Waialua
Mollisol) and a biosolids‐based compost at different proportions to yield varying salinity levels. A
mixture that yielded an electrical conductivity (EC, a measure of salinity) of the saturated paste
extract of 15 to 20 dS/m was identified and used to evaluate the salt tolerance of five plant species. Relative
germination and one‐month‐old biomass indicated that common bermuda grass (Cynodon
dactylon), seashore paspalum (Paspalum vaginatum), beach pea
(Vigna marina), and cow pea (Vigna unguiculata) can produce
at least 40 percent of biomass of the control at an EC of approximately 18 dS/m, suggesting the four plants are
relatively salt tolerant. In contrast, Desmodium intortum either did not germinate or died within
two weeks after germination at the same salinity level. A subsequent greenhouse experiment, using mixtures of the
PHDM (0 or 25 percent dry weight), organic amendments (10 percent leucaena green manure or
biosolids‐based compost), and a Mollisol (65 or 90 percent dry weight) in 6‐liter pots
containing 4 kilograms of material yielded the following results: (1) a combination of transplanted
seashore paspalum, seeded bermuda grass, and seeded beach pea was effective in taking up sodium (Na),
thereby reducing salinity and making the medium more amenable to diversified microbes and plants, which may be
effective PAH degraders; (2) total PAH concentration was reduced by about 30 percent after three
months of active plant growth, but degradation of individual PAH members varied significantly, however;
(3) leguminous green manure, as a soil amendment, was more effective than compost for use in bio‐
and/or phyto‐remediations; and (4) soil amendments, when applicable, could supplement
living plants in reducing organic contaminants, such as PAHs. © 2003 Wiley Periodicals, Inc. Reprinted from
Remediation Volume 12, Number 4.
An implicit pseudo‐spectral multi‐domain method for the simulation of incompressible flows
Authors: Droll P. , Schäfer M. , Serre E. , Bontoux P. 
Published: January 2003

AbstractA pseudo‐spectral method for the solution of incompressible flow problems based on an iterative solver involving an implicit treatment of linearized convective terms is presented. The method allows the treatment of moderately complex geometries by means of a multi‐domain approach and it is able to cope with non‐constant fluid properties and non‐orthogonal problem domains. In addition, the fully implicit scheme yields improved stability properties as opposed to semi‐implicit schemes commonly employed. Key components of the method are a Chebyshev collocation discretization, a special pressure–correction scheme, and a restarted GMRES method with a preconditioner derived from a fast direct solver. The performance of the proposed method is investigated by considering several numerical examples of different complexity, and also includes comparisons to alternative solution approaches based on finite‐volume discretizations. Copyright © 2003 John Wiley & Sons, Ltd.
Accurate multi‐level schemes for advection
Authors: Kim Cheolwan 
Published: January 2003

AbstractThe upwind leapfrog method for the advection equation, which is non‐dissipative and very accurate, is extended to higher‐order and multiple dimensions. The higher‐order version is developed by extending the stencil into space and time, and an analysis of the phase error is given. The schemes are then successfully applied to the classical test cases of rotating flow, and to a more realistic problem of non‐uniform advection. Copyright © 2003 John Wiley & Sons, Ltd.
A fourth‐order compact finite difference scheme for the steady stream function–vorticity formulation of the Navier–Stokes/Boussinesq equations
Authors: Tian Zhenfu , Ge Yongbin 
Published: January 2003

AbstractA fourth‐order compact finite difference scheme on the nine‐point 2D stencil is formulated for solving the steady‐state Navier–Stokes/Boussinesq equations for two‐dimensional, incompressible fluid flow and heat transfer using the stream function–vorticity formulation. The main feature of the new fourth‐order compact scheme is that it allows point‐successive overrelaxation (SOR) or point‐successive underrelaxation iteration for all Rayleigh numbers Ra of physical interest and all Prandtl numbers Pr attempted. Numerical solutions are obtained for the model problem of natural convection in a square cavity with benchmark solutions and compared with some of the accurate results available in the literature. Copyright © 2003 John Wiley & Sons, Ltd.
Application of the method of lines to unsteady compressible Euler equations
Authors: Šolín Pavel , Segeth Karel 
Published: January 2003

AbstractIn the sense of method of lines, numerical solution of the unsteady compressible Euler equations in 1D, 2D and 3D is split into three steps: First, space discretization is performed by the first‐order finite volume method using several approximate Riemann solvers. Second, smoothness and Lipschitz continuity of RHS of the arising system of ordinary dimensional equations (ODEs) is analysed and its solvability is discussed. Finally, the system of ODEs is integrated in time by means of implicit and explicit higher‐order adaptive schemes offered by ODE packages ODEPACK and DDASPK, by a backward Euler scheme based on the linearization of the RHS and by higher‐order explicit Runge–Kutta methods. Time integrators are compared from several points of view, their applicability to various types of problems is discussed, and 1D, 2D and 3D numerical examples are presented. Copyright © 2003 John Wiley & Sons, Ltd.
Artificial boundary method for the exterior Stokes flow in three dimensions
Authors: Zheng Chunxiong , Han Houde 
Published: January 2003

AbstractIn this paper, the artificial boundary method is considered for the numerical simulation of the exterior Stokes flow in three dimensions. First, an exact relation between the normal stress and the velocity field is obtained on a spherical artificial boundary. With the relation specified on the artificial boundary, the original problem is reduced to a new one only defined on a finite domain. After that, an variational problem equivalent to the reduced problem is derived. By truncating the series term in the formulation, a sequence of approximate variational problems are obtained, which can then be solved with a suitable finite‐element scheme. Finally, a numerical example is presented to show the performance of the method. Copyright © 2003 John Wiley & Sons, Ltd.