bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of the drawing form and draw ratio on the fiber structure and mechanical properties of CO2‐laser‐heated‐drawn poly(ethylene terephthalate) fibers
Authors: Okumura W. , Ohkoshi Y. , Gotoh Y. , Nagura M. , Urakawa H. , Kajiwara K. 
Published: December 2003

AbstractThe structure, mechanical properties, and thermomechanical properties of poly(ethylene terephthalate) (PET) fibers obtained by laser‐heated drawing were investigated in terms of their dependence on the draw ratio and feed speed and the differences between neck‐drawn fibers and flow‐drawn fibers. The long period at a draw ratio of 6.0 reached 19.0 nm, notably larger than at lower ratios, whereas the tilting angle of the laminar structure was constant at about 60°, regardless of the draw ratio. A maximum value of 15.0 GPa was attained for the initial modulus, and 1.07 GPa was attained for the tensile strength. A higher tensile strength orientation‐induced crystallized fiber at the same initial modulus was obtained from higher molecular weight PET. The relationship between the compliance and molecular orientation of the amorphous phase was studied with a series model of crystalline and amorphous phases. The results revealed that, in the high‐draw‐ratio fibers, the compliance of the amorphous phase decreased with the draw ratio at a higher rate than indicated by extrapolation to intrinsic values. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 79–90, 2004
Analysis of the 1030‐cm−1 band of poly(ethylene terephthalate) fibers using polarized raman microscopy
Authors: Yang Shuying , Michielsen Stephen 
Published: December 2003

AbstractPolarized Raman spectroscopy was used to analyze uniaxially oriented fibers of poly(ethylene terephthalate) (PET) fibers. The second‐order and fourth‐order Legendre polynomials of the orientation distribution function of the 1030‐cm−1 vibrational band were determined to be zero for samples of low‐to‐moderate orientation. Because this band was assigned to the gauche conformation of the ethylene glycol unit, the orientation of the gauche configuration of ethylene glycol units in PET for PET of low‐to‐moderate orientation was random. This was consistent with the assumptions used by Ward and coworkers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 47–52, 2004
Nonlinear conduction in nylon‐6/foliated graphite nanocomposites above the percolation threshold
Authors: Chen Guohua , Weng Wengui , Wu Dajun , Wu Cuiling 
Published: December 2003

AbstractThe nonlinear conduction behavior of composite materials of foliated graphite nanosheets and nylon‐6 subjected to a variable direct‐current electric field has been studied. Corresponding to the onset of the nonlinearity, there is a crossover current density/electric field (or current–voltage) couple. The current density or current decreases as the foliated graphite concentration decreases. Through discussions of the nonlinearities within the frameworks of the two theoretical models, the nonlinear random resistor network and the dynamic random resistor network, it is shown that neither of these models can explain fully the results obtained for this system. On the basis of the microscopic structures and conduction processes of the nanocomposites, it is found that a combination of the models can generally account for the nonlinear characteristics. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 155–167, 2004
An integrated model for statistical and vision monitoring in manufacturing transitions
Authors: Nembhard Harriet Black , Ferrier Nicola J. , Osswald Tim A. , Sanz‐Uribe Juan R. 
Published: December 2003

AbstractManufacturing transitions have been increasing due to higher pressures for product variety. One dimension of this variety is color. A major quality control challenge is to regulate the color by capturing data on color in real‐time during the operation and to use it to assess the opportunities for good parts. Control charting, when applied to a stable state process, is an effective monitoring tool to continuously check for process shifts or upsets. However, the presence of transition events can impede the normal performance of a traditional control chart. In this paper, we present an integrated model for statistical and vision monitoring using a tracking signal to determine the start of the transition and a confirmation signal to ensure that any process oscillation has concluded. We also developed an automated color analysis and forecasting system (ACAFS) that we can adjust and calibrate to implement this methodology in different production processes. We use a color transition process in plastic extrusion to illustrate a transition event and demonstrate our proposed methodology. Copyright © 2003 John Wiley & Sons, Ltd.
Process monitoring for correlated gamma‐distributed data using generalized‐linear‐model‐based control charts
Authors: Jearkpaporn Duangporn , Montgomery Douglas C. , Runger George C. , Borror Connie M. 
Published: December 2003

AbstractA model‐based scheme is proposed for monitoring multiple gamma‐distributed variables. The procedure is based on the deviance residual, which is a likelihood ratio statistic for detecting a mean shift when the shape parameter is assumed to be unchanged and the input and output variables are related in a certain manner. We discuss the distribution of this statistic and the proposed monitoring scheme. An example involving the advance rate of a drill is used to illustrate the implementation of the deviance residual monitoring scheme. Finally, a simulation study is performed to compare the average run length (ARL) performance of the proposed method to the standard Shewhart control chart for individuals. Copyright © 2003 John Wiley & Sons, Ltd.
Using Neural Networks to Detect and Classify Out‐of‐control Signals in Autocorrelated Processes
Authors: Noorossana R. , Farrokhi M. , Saghaei A. 
Published: December 2003

AbstractThis paper presents an artificial neural network model for detecting and classifying three types of non‐random disturbances referred to as level shift, additive outlier and innovational outlier which are common in autocorrelated processes. To the best of our knowledge, this is the first time that a neural network has been considered for simultaneous detection and classification of such non‐random disturbances. An AR (1) model is considered to characterize the quality characteristic of interest in a continuous process where autocorrelated observations are generated over time. The performance of the proposed procedure is evaluated through the use of a numerical example. Preliminary results indicate that the procedure can be used effectively to detect and classify unusual shocks in autocorrelated processes. Copyright © 2003 John Wiley & Sons, Ltd.
Quantifying nitrate retention processes in a riparian buffer zone using the natural abundance of 15N in NO3−
Authors: Dhondt Karel , Boeckx Pascal , Van Cleemput Oswald , Hofman Georges 
Published: December 2003

AbstractQuantifying the relative importance of denitrification and plant uptake to groundwater nitrate retention in riparian zones may lead to methods optimising the construction of riparian zones for water pollution control. The natural abundance of 15N in NO3− has been shown to be an interesting tool for providing insights into the NO3− retention processes occurring in riparian zones. In this study, 15N isotope fractionation (variation in δ15N of the residual NO3−) due to denitrification and due to plant uptake was measured in anaerobic soil slurries at different temperatures (5, 10 and 15°C) and in hydroponic systems with different plant species (Lolium perenne L., Urtica dioica L. and Epilobium hirsutum L.). It was found that temperature had no significant effect on isotope fractionation during denitrification, which resulted in a 15N enrichment factor εD of −22.5 ± 0.6‰. On the other hand, nitrate uptake by plants resulted in 15N isotope fractionation, but was independent of plant species, leading to a 15N enrichment factor εP of −4.4 ± 0.3‰. By relating these two laboratory‐defined enrichment factors to a field enrichment factor for groundwater nitrate retention during the growing season (εR = −15.5 ± 1.0‰), the contribution of denitrification and plant uptake to groundwater nitrate retention could be calculated. The relative importance of denitrification and plant uptake to groundwater nitrate retention in the riparian buffer zone was 49 and 51% during spring, 53 and 47% during summer, and 75 and 25% during autumn. During wintertime, high micropore dissolved organic carbon (DOC) concentrations and low redox potentials due to decomposition of the highly productive riparian vegetation probably resulted in a higher denitrification rate and favoured other nitrate retention processes such as nitrate immobilisation or dissimilatory nitrate reduction to ammonium (DNRA). This could have biased the 15N isotope fractionation and led to a low 15N enrichment factor for groundwater nitrate retention during wintertime (−6.2 ± 0.9‰). In contradiction to what many other studies suggest, it is possible that due to plant decomposition during the winter period other nitrate transformation processes compete with denitrification. Copyright © 2003 John Wiley & Sons, Ltd.
Effect of preparation and preservation procedures on carbon and nitrogen stable isotope determinations from zooplankton
Authors: Feuchtmayr Heidrun , Grey Jonathan 
Published: December 2003

AbstractA literature survey of zooplankton stable isotope studies revealed inconsistencies between authors concerning (a) fixation and (b) allowance for gut clearance of zooplankton prior to δ13C and δ15N determinations. To address whether commonly used preservation techniques induce changes in stable isotope values, fresh lake zooplankton (control) were compared with preserved (ethanol, methanol, formaldehyde, gluteraldehyde, frozen and shock frozen) material. Differences of up to 1.1‰ for carbon and 1.5‰ for nitrogen isotopic signatures were found. Even freezing, the most frequently used method identified from the literature, caused significant changes compared with the control. We advocate the use of fresh material prepared immediately whenever possible, or complementary testing of the preservative method to be used.Larger organisms are routinely eviscerated, or specific tissues are dissected, and analysed for stable isotopes to reduce errors introduced via the gut contents. Yet zooplankton gut clearance is rarely performed: the gut content assumed to be negligible relative to organism mass. Experimental determinations of relative gut mass, from both original and compiled data, range from 1–26% for different zooplankton species. Using reported isotopic values of basal resources from natural systems, we calculated that, when analysing bulk zooplankton, inclusion of the gut mass may introduce substantial errors of >3‰. Thus it appears prudent to perform the simple procedure of gut clearance, especially for copepod species. Copyright © 2003 John Wiley & Sons, Ltd.
Simultaneous measurement of drug metabolic stability and identification of metabolites using ion‐trap mass spectrometry
Authors: Kantharaj E. , Tuytelaars An , Proost Pascale E. A. , Ongel Zuleyha , van Assouw Harrie P. , Gilissen Ron A. H. J. 
Published: December 2003

AbstractThe use of in vitro drug metabolism data in the understanding of in vivo pharmacokinetic, safety and toxicity data has become a large area of scientific interest. This has stemmed from a trend in the pharmaceutical industry to use in vitro data generated from human tissue as a criterion to select compounds for further investigation. As well as measuring metabolic stability in vitro using human liver microsomal preparations, the identification of possible metabolite(s) formed may play a vital role in Hit‐to‐Lead and Lead optimisation processes. The data‐dependent scan function mode with the ion‐trap instrumentation provides the ability to measure the metabolic stability and identification of possible metabolites of a compound. A gradient liquid chromatographic method with a run time of 6 min/injection was developed for this purpose. The approach of simultaneous metabolic stability measurements and rapid identification of metabolites of drugs with high (verapamil), medium (propranolol and cisapride) and low (flunarazine) metabolic stabilities using ion‐trap mass spectrometry is described. The metabolites identified after 15 min incubation for verapamil, propranolol and cisapride are in good agreement with those reported as the major metabolites in human in vivo studies. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of ketones by selected ion flow tube mass spectrometry
Authors: Smith David , Wang Tianshu , Španĕl Patrik 
Published: December 2003

AbstractA selected ion flow tube mass spectrometry (SIFT‐MS) study of the reactions of H3O+, NO+ and O2+. ions with the ketones (M) 2‐heptanone, 2‐octanone, 2‐nonanone, 2‐undecanone and 2‐aminoacetophenone has been conducted in preparation for studies of volatile emissions from bacteria. The H3O+ reactions all proceed rapidly via exothermic proton transfer, producing only MH+ ions that form their monohydrates when water vapour is present in the helium carrier gas. The O2+. reactions proceed rapidly via dissociative charge transfer producing parent cations M+. and some fragment ions. The NO+ reactions form the NO+M adduct ions at rates which are dependent on the pressure of the helium carrier gas. Combining the present NO+ kinetic data with those available from previous SIFT studies, the phenomenon of charge transfer complexing is clearly demonstrated. This results in adduct formation in these NO+/ketone reactions at or near the collisional rate. SIFT‐MS spectra are presented to illustrate the simplicity of SIFT‐MS analysis of ketones using both H3O+ and NO+ precursor ions. Copyright © 2003 John Wiley & Sons, Ltd.
The emergence of a giant component in random subgraphs of pseudo‐random graphs
Authors: Frieze Alan , Krivelevich Michael , Martin Ryan 
Published: December 2003

AbstractLet G be a d‐regular graph G on n vertices. Suppose that the adjacency matrix of G is such that the eigenvalue λ which is second largest in absolute value satisfies λ = o(d). Let Gp with p = α/d be obtained from G by including each edge of G independently with probability p. We show that if α < 1, then whp the maximum component size of Gp is O(log n) and if α > 1, then Gp contains a unique giant component of size Ω(n), with all other components of size O(log n). © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 2004
A stochastic model for solitons
Authors: Itoh Yoshiaki , Mahmoud Hosam M. , Takahashi Daisuke 
Published: December 2003

AbstractThe soliton physics for the propagation of waves is represented by a stochastic model in which the particles of the wave can jump ahead according to some probability distribution. We demonstrate the presence of a steady state (stationary distribution) for the wavelength. It is shown that the stationary distribution is a convolution of geometric random variables. Approximations to the stationary distribution are investigated for a large number of particles. The model is rich and includes Gaussian cases as limit distribution for the wavelength (when suitably normalized). A sufficient Lindeberg‐like condition identifies a class of solitons with normal behavior. Our general model includes, among many other reasonable alternatives, an exponential aging soliton, of which the uniform soliton is one special subcase (with Gumbel's stationary distribution). With the proper interpretation, our model also includes the deterministic model proposed in Takahashi and Satsuma [A soliton cellular automaton, J Phys Soc Japan 59 (1990), 3514–3519]. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 2004
General urn models with several types of balls and Gaussian limiting fields
Authors: Drmota Michael , Gardy Danièle , Gittenberger Bernhard 
Published: December 2003

AbstractWe study a system of m urns, where several types of balls are thrown, and an additive valuation is assigned to each urn depending on its state. Examples are the join models studied in a database context, and some models with two types of balls. The object of our investigation is the evolution of the valuation with time, when a ball is thrown at each time unit. By means of a generating function approach we show the weak convergence of the valuation process to a Gaussian field. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 2004
Modified methodology for computing interference in LEO satellite environments
Authors: Chávez Santiago Raúl , Kontorovitch Valeri Ya. , Lara Barrón Mauricio 
Published: December 2003

AbstractComputing interference is very important in satellite networks design in order to assure the electromagnetic compatibility (EMC) with other radiocommunication systems. There are different methods to compute interference in geostationary (GEO) satellite systems including conventional methods using link budget equations and alternate methods such as increase in noise temperature. However, computing interference in low earth orbit (LEO) systems represents a different problem. Due to the special characteristics of this kind of orbits, the elevation angle at any site changes continuously over time, meaning a time dependent change of the propagation path length between an interfering transmitter and an interfered‐with receiver, and of the discrimination provided by the transmitting and/or the receiving antenna. Thus, conventional interference prediction methods developed for fixed links must be adapted to the case of LEO systems. To overcome this problem a mathematical model that characterizes the path length variations by an average value obtained from the probability density function of the varying distance between an interfering transmitter and an interfered‐ with receiver is proposed in this paper. This average path length enables the use of conventional link budget methods to reduce the computation time for the evaluation of interference in LEO satellite environments. Two practical examples show the possible applications of the proposed model. Copyright © 2003 John Wiley & Sons, Ltd.
On the rain attenuation dynamics: spatial‐temporal analysis of rainfall rate and fade duration statistics
Authors: Panagopoulos Athanasios D. , Kanellopoulos John D. 
Published: December 2003

AbstractKnowledge about the dynamic characteristics of rain attenuation is of utmost importance for many applications in terrestrial and satellite communication systems operating at frequencies above 10 GHz. Long‐term rain rate statistics and rain rate duration statistics are usually available from meteorological data. In this paper, a spatial–temporal analysis is employed in order to evaluate the rain attenuation power spectrum of a terrestrial/satellite path. The predicted power spectrum is compared with experimental data. Based on the spectral analysis of rainfall rate a method for converting rain rate duration statistics to link fade duration statistics is also proposed. Fade duration statistics are presented for terrestrial and satellite links and compared with available experimental data. The agreement between the predicted results and the experimental data has been found to be quite encouraging. Finally, numerical results are presented for various climatic zones, elevation angles and frequencies. Some very useful conclusions concerning the dynamic properties of rain attenuation for a microwave path are deduced. Copyright © 2003 John Wiley & Sons, Ltd.
Freezing height distribution in the tropics
Authors: Thurai Merhala , Deguchi Eri , Iguchi Toshio , Okamoto Ken'ichi 
Published: December 2003

AbstractThe calculation of fade margins required to meet the user‐specified availability criteria needs to take into consideration a number of meteorological factors specific to the earth‐station location. One such factor is the annual average of the freezing level height. Information on this height is available in ITU‐R Recommendation P. 839‐3, which provides contours that are generated on a 1.5° by 1.5° latitude by longitude resolution grid. This paper compares these heights with the bright‐band heights (BBH) obtained from the precipitation radar on‐board the TRMM (Tropical Rainfall Measuring Mission) satellite. Four years of TRMM radar data have been analysed, and their averages are compared within the latitude range covered by the satellite orbit (35°N to 35°S). Comparisons show that the radar bright‐band heights typically occur 300 m below the 0°C isotherm heights. However, results also indicate that this difference may be latitude dependent. Also examined are the year‐to‐year variability and the seasonal variation. In the former case, only 1998 showed BBH values which are somewhat higher in tropical regions, this year having had one of the strongest El Niño events recorded. In the latter case, results show significant seasonal variation, becoming more pronounced at higher latitudes. Copyright © 2003 John Wiley & Sons, Ltd.
A note on non‐parametric ANCOVA for covariate adjustment in randomized clinical trials
Authors: Lesaffre Emmanuel , Senn Stephen 
Published: December 2003

AbstractKoch et al. recently (1998) proposed two covariate‐adjusted approaches for the comparison of continuous, ordinal and binary responses in a randomized clinical trial (Statist. Med. 1998; 17: 1863–1892). The first is a randomization approach while the second assumes that the study is a sample of a population. Here, we study the second approach and consider the simplest cases of two treatments with a continuous response and with a binary response. Koch's second approach will be compared with the classical ANCOVA for a continuous response. From this relationship we demonstrate that Koch's method cannot preserve the probability of the type I error. Simulations with continuous responses as well as with binary outcomes confirm the aforementioned theoretical result on the performance of Koch's method under the null hypothesis of no treatment effect. However, this poses only a problem for relatively small to moderate sample sizes. Further, as specified in the original paper of Koch et al., the first approach does preserve the type I error for any sample size, as the P‐values can be reported in an exact manner (Statist. Med. 1998; 17: 1863–1892). Finally, we propose a correction factor for Koch's test statistic that better preserves the type I error. Copyright © 2003 John Wiley & Sons, Ltd.
Comparison of multiple regression to two latent variable techniques for estimation and prediction
Authors: Wall Melanie M. , Li Ruifeng 
Published: December 2003

AbstractIn the areas of epidemiology, psychology, sociology, and other social and behavioural sciences, researchers often encounter situations where there are not only many variables contributing to a particular phenomenon, but there are also strong relationships among many of the predictor variables of interest. By using the traditional multiple regression on all the predictor variables, it is possible to have problems with interpretation and multicollinearity. As an alternative to multiple regression, we explore the use of a latent variable model that can address the relationship among the predictor variables. We consider two different methods for estimation and prediction for this model: one that uses multiple regression on factor score estimates and the other that uses structural equation modelling. The first method uses multiple regression but on a set of predicted underlying factors (i.e. factor scores), and the second method is a full‐information maximum‐likelihood technique that incorporates the complete covariance structure of the data. In this tutorial, we will explain the model and each estimation method, including how to carry out prediction. A data example will be used for demonstration, where respiratory disease death rates by county in Minnesota are predicted by five county‐level census variables. A simulation study is performed to evaluate the efficiency of prediction using the two latent variable modelling techniques compared to multiple regression. Copyright © 2003 John Wiley & Sons, Ltd.