bluuebunny/crossref_metadata_2025_split huggingface dataset:
Speech recognition under noisy environments using segmental unit input HMM
Authors: Yamamoto Kazumasa , Nakagawa Seiichi 
Published: August 2002

AbstractIn this paper, we apply a segmental unit input HMM to noisy speech recognition. In this modeling, several successive frames are combined and treated as an input vector. We expect that the segmental unit input HMM will be effective for noisy speech recognition because segmental statistics considering correlation between frames reduce noise effects when the correlation of noise between frames is assumed to be small. In recognition experiments, we compared the segmental unit input HMM with a conventional frame‐based HMM and found the segmental unit input HMM to be superior. We also compared the segmental unit input HMM with dynamic cepstral coefficients, which have both static and dynamic features, and found that the segmental unit input HMM is more effective than the dynamic cepstrum. We also combined the segmental unit input HMM with a spectral subtraction method and confirmed the effectiveness of the method. Additionally, in experiments using acoustic models trained with noisy speech, the segmental unit input HMM outperformed the conventional HMM. From these results, we propose PMC for the segmental unit input HMM. Experimental results showed the PMC for segmental unit input HMM offered better recognition performance than the original PMC. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(8): 111–120, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1151
The Winnipeg Principles, WTO and sustainable development: proposed policies for reconciling trade and the environment
Authors: Tisdell Clem 
Published: August 2002

AbstractThere is a widespread belief that the WTO has made virtually no concessions to environmentalists about their concerns arising from free trade and the process of globalization. There are concerns that these processes may undermine prospects for sustainable development. Following the United Nations Conference on Environment and Development held in Rio de Janeiro in 1992, the International Institute for Sustainable Development was established to advocate policies to support sustainable development within Canada and globally. In 1994, it proposed the Winnipeg Principles as a means for reconciling international trade and development so as to achieve sustainable development (IISD, 1994a,b). These seven principles are outlined in this article and assessed. Although the International Institute for Sustainable Development had hoped through these principles to influence the work programme of the Environment and Trade Committee of WTO, it seems to have little effect. Probably if these principles had been seriously considered by WTO, the serious social conflicts which emerged globally at the beginning of this century would have been avoided, and we would be in a better position to understand the complex links between trade, environment and sustainable development and adopt relevant policies. Copyright © 2001 John Wiley & Sons, Ltd and ERP Environment
Determining the role of surfaces and interfaces in the powder metallurgy processing of aluminum alloy powders
Authors: Anderson Iver E. , Foley James C. 
Published: August 2002

AbstractThe current options for solid‐state consolidation processing of powder‐based advanced aluminum alloys have been very limited and complicated, resulting in a segregation of the applications primarily to the aerospace segment. Throughout any consolidation sequence for aluminum powders, the oxide and/or hydroxide films on the typical powder surfaces can interfere with densification and interparticle bonding. In fact, the consolidation sequence for many low‐strength aluminum alloy powder metallurgy parts involves transient liquid‐phase sintering to massively disrupt the powder surfaces, producing improved bonding but introducing a coarsened resolidification microstructure. Although preventing aluminum oxide formation is nearly impossible during aluminum powder production, the gas atomization reaction synthesis (GARS) method—an advanced powder production technique—can modify the oxide coating and enable improved consolidation processing. This report compares the effects of the GARS process and other representative atomization processes on the surface structure and properties of aluminum powders and on their ability to sinter. The powders were characterized with transmission electron microscopy, scanning electron microscopy, Auger electron spectroscopy, quadrapole mass spectroscopy and with a new ultrasonic method for in situ sensing of the evolution of sintering. In general, a marked reduction in the surface film thickness and in the level of chemisorbed moisture and moisture‐borne impurities was observed in the GARS powders. This change in powder surface characteristics also was effective in promoting sintering processes in the GARS powders, as monitored by our new technique. An initial direct comparison of explosivity for the different types of aluminum powder revealed that the GARS powder also had a reduced hazard level. All of these findings indicate that the GARS approach to aluminum powder production may enable mass‐produced lightweight powder metallurgy parts from advanced aluminum alloys with simple consolidation processing techniques. Copyright © 2001 John Wiley & Sons, Ltd.
Error performance analysis of artificial neural networks applied to Rutherford backscattering
Authors: Vieira A. , Barradas N. P. , Jeynes C. 
Published: August 2002

AbstractWe have developed a code based on artificial neural networks (ANN) to analyse Rutherford backscattering data. In particular, we have applied the code to the analysis of germanium implants in silicon substrates. Here, we study the reliability and accuracy of the quantitative results obtained. We first constructed three different training data sets. The first data set was fully general. On the second one, we restricted the experimental conditions to well‐defined values, and on the third we also restricted the implantation parameters (depth and dose of implant) to a narrower range. We then studied the trade‐off between generality and accuracy of the ANNs obtained. Furthermore, for a given architecture we applied two different training processes. The first was backpropagation on the whole data set. In the second we excluded, after an initial training phase, all the training cases with errors double the average and then continued training. Each of the processes was applied to the three different data sets. We report the performance of the ANNs so obtained when applied to real experimental data. Copyright © 2001 John Wiley & Sons, Ltd.
Electron transport in solids for quantitative surface analysis
Authors: Werner Wolfgang S. M. 
Published: August 2002

AbstractThe influence of electron transport on the signal generation process in electron beam techniques is reviewed. A survey of the fundamental physical quantities for the electron–solid interaction is presented and sources for these quantities in the literature as well as semi‐empirical formulae are given. The theoretical approaches used to describe multiple scattering in solids are outlined. These include the partial intensity approach and the continuous slowing down approximation to describe multiple energy losses and the transport approximation to tackle multiple deflections. A detailed description of the Monte Carlo technique is presented because this constitutes an effective means to study transport processes. The different theoretical approaches are illustrated in a survey of applications. These include: quantitative description of the surface sensitivity in Auger and photoelectron spectroscopy; line shape analysis of electron spectra; extracting information on the compositional depth profile from the combined energy/angular distribution in an electron spectrum; quasi‐elastic electron reflection; inelastic electron backscattering; depth distribution of production of x‐rays caused by electron bombardment; and the surface sensitivity in total electron yield electron spectroscopy. These applications demonstrate that the outlined approaches have a broad field of application, not only for electrons with energies ranging from thermal to the relativistic energy range, but also for other microbeam analysis techniques. Copyright © 2001 John Wiley & Sons, Ltd.
Longitudinal profiles of health care providers
Authors: Bronskill Susan E. , Normand Sharon‐Lise T. , Beth Landrum Mary , Rosenheck Robert A. 
Published: August 2002

AbstractProvider profiling is the activity of collecting, comparing and reporting quality of care measures for individuals, groups, agencies and institutions that provide health care services. Univariate provider profiles, such as hospital‐specific mortality rates, have been constructed using cross‐sectional data based on posterior summaries or maximum likelihood estimates. As data continue to be collected over time, the construction and interpretation of longitudinal profiles of health care providers will become increasingly important. Longitudinal series can be used to improve the precision of estimates – a feature that is particularly important for providers who treat a small number of patients per year. We extend and apply hierarchical models to examine and classify provider performance over time using two examples, one in the area of cardiology and the other in mental health. Performance is evaluated using the squared Mahalanobis distance and posterior probabilities based on this distance. By comparing providers based on level and temporal trend simultaneously, conservative but comprehensive assessments of performance are possible. Furthermore, the longitudinal profiles developed are easily interpreted and flexible, making them of practical use to policy‐makers. Copyright © 2002 John Wiley & Sons, Ltd.
A competing risk approach to the analysis of trials of alternative intra‐uterine devices (IUDs) for fertility regulation
Authors: Tai Bee‐Choo , Peregoudov Alexander , Machin David 
Published: August 2002

AbstractThe methods of survival analysis have had a profound influence on the way that studies concerned with the safety and efficacy of intra‐uterine devices (IUDs) for fertility control have been designed, conducted, analysed and reported. For example, the Kaplan–Meier technique has been used to summarize the results of controlled clinical trials of alternative devices and the logrank test used to make any comparisons. A particular feature of IUD studies is the large number of possible causes of failure (reasons for discontinuation of the device). These lead to considerations of competing risks, where in this framework, the discontinuations are considered as competing causes of contraceptive failure. In this context, we compare the net and crude probability estimates of discontinuation rates using continuous time and argue for the routine use of the latter. We use data from a randomized multi‐centre trialon the long‐term safety and efficacy of two IUDs, TCu220C and TCu380A, for illustration. Copyright © 2001 John Wiley & Sons, Ltd.
Jointly modelling the relationship between survival and pulmonary function in cystic fibrosis patients
Authors: Schluchter Mark D. , Konstan Michael W. , Davis Pamela B. 
Published: August 2002

AbstractModelling the relationship between pulmonary function and survival in cystic fibrosis (CF) is complicated by the fact that measures of pulmonary function commonly used such as the forced expiratory volume in one second (FEV1) are measured with error, and patients with the poorest lung function are increasingly censored by death, that is, data are available only for the patients who have survived to the current age. We assume a linear random effects model for FEV1 per cent predicted, where the random intercept and slope of FEV1per cent predicted, along with a specified transformation of the age at death follow a trivariate normal distribution. We illustrate how this model can be used to describe the relationship between age at death and parameters of the individual patient's regression of FEV1per cent predicted versus age, such as the slope and the intercept or true value of FEV1per cent predicted at a given age. We also illustrate how the model provides empirical Bayes estimates of these individual parameters. In particular, we explore how the predicted value of the age at death might be used as a prognostic or severity index. The model and methods are illustrated on a cohort of 188 cystic fibrosis patients with a common genotype (homozygous for the ΔF508 mutation), born on or after 1965 and followed at the CF Center at the Rainbow Babies and Children's Hospital, Cleveland, OH, U.S.A. Copyright © 2002 John Wiley & Sons, Ltd.
Analysis of ambulatory blood pressure monitor data using a hierarchical model incorporating restricted cubic splines and heterogeneous within‐subject variances
Authors: Lambert Paul C. , Abrams Keith R. , Jones David R. , Halligan Aidan W. F. , Shennan Andrew 
Published: August 2002

AbstractHypertensive disorders of pregnancy are associated with significant maternal and foetal morbidity. Measurement of blood pressure remains the standard way of identifying individuals at risk. There is growing interest in the use of ambulatory blood pressure monitors (ABPM), which can record an individual's blood pressure many times over a 24‐hour period. From a clinical perspective interest lies in the shape of the blood pressure profile over a 24‐hour period and any differences in the profile between groups. We propose a two‐level hierarchical linear model incorporating all ABPM data into a single model. We contrast a classical approach with a Bayesian approach using the results of a study of 206 pregnant women who were asked to wear an ABPM for 24 hours after referral to an obstetric day unit with high blood pressure. As the main interest lies in the shape of the profile, we use restricted cubic splines to model the mean profiles. The use of restricted cubic splines provides a flexible way to model the mean profiles and to make comparisons between groups. From examining the data and the fit of the model it is apparent that there were heterogeneous within‐subject variances in that some women tend to have more variable blood pressure than others. Within the Bayesian framework it is relatively easy to incorporate a random effect to model the between‐subject variation in the within‐subject variances. Although there is substantial heterogeneity in the within‐subject variances, allowing for this in the model has surprisingly little impact on the estimates of the mean profiles or their confidence/credible intervals. We thus demonstrate a powerful method for analysis of ABPM data and also demonstrate how heterogeneous within‐subject variances can be modelled from a Bayesian perspective. Copyright © 2001 John Wiley & Sons, Ltd.
The effect of outliers on confidence interval procedures for cost‐effectiveness ratios
Authors: Indurkhya Alka , Gardiner Joseph C. , Luo Zhehui 
Published: August 2002

AbstractCost‐effectiveness ratio (CER) is defined as the ratio of the difference in cost between a test and standard health care programme to the difference in benefit, respectively. Methods to obtain confidence intervals for CERs are either variants of Fieller's method (1954), or bootstrap methods. We study the effect of outliers in cost measures on the precision of confidence interval procedures for CERs. In particular the performance of the procedures under single and multiple case influential deletion diagnostics, respectively, are evaluated. Simulation studies suggest that the bias‐corrected percentile bootstrap procedure gives better precision and coverage under either diagnostic. Copyright © 2001 John Wiley & Sons, Ltd.
Latent class marginal regression models for modelling youthful drug involvement and its suspected influences
Authors: Reboussin Beth A. , Anthony James C. 
Published: August 2002

AbstractIn longitudinal behavioural studies, it is common to have multiple categorical indicators for measuring a theoretical construct of interest. A latent class model is presented that accounts for the structure in a set of correlated, categorical variables measured at discrete time periods, drawing information from these variables to form a smaller number of latent classes. The dependence of the resulting latent class model parameters on suspected factors over time is simultaneously modelled using a baseline‐category logistic regression model. Estimation of the model parameters is achieved using an estimating equations procedure. A motivating example is provided from a longitudinal study of suspected linkages between monitoring or supervision by parents and the occurrence of drug use behaviours in an epidemiologic sample of school‐attending youths. Copyright © 2001 John Wiley & Sons, Ltd.
A flexible design for multiple armed screening trials
Authors: Sargent Daniel J. , Goldberg Richard M. 
Published: August 2002

AbstractThe goal of a screening trial is to examine several treatments with the intention of selecting one or more treatment(s) for further testing. Such a trial frequently occurs in the phase II setting, with the intention that the selected treatment be formally compared to a standard treatment in a phase III clinical trial. In this framework it is not essential that the very best treatment is definitely selected (such a decision would require a formal phase III trial), rather it is important that a substantially inferior treatment is not selected when a superior treatment exists. The level of evidence required to select a treatment based on this standard is lower than the evidence required to definitively order treatments. This paper introduces a flexible design for such trials, the flexibility coming from the use of a particular decision rule. The proposed rule states that if the observed difference in the success rates of the treatments is larger than some prespecified quantity d, then the treatment with the highest observed success rate is selected. However, if the observed difference is less than or equal to d, other factors may be considered in the selection. The goal of this design is to mirror clinical practice, where a treatment's success probability is often only one of many considerations in determining a treatment recommendation for a particular patient. Copyright © 2001 John Wiley & Sons, Ltd.
Optimal continuous sequential boundaries for monitoring toxicity in clinical trials: a restricted search algorithm
Authors: Goldman Anne I. , Hannan Peter J. 
Published: August 2002

AbstractContinuous monitoring of severe adverse experiences can ensure the timely termination of a clinical trial if the therapy is shown to be harmful. In this paper we present methods for choosing a stopping rule for continuous monitoring of toxicity in small trials. They are especially useful for small phase II trials of about 30 patients for monitoring a binary toxicity event that is observed relatively quickly compared to the efficacy outcome. In 1987 Goldman described an algorithm for computing the exact type I error rate (α) and power (1−β) of a specified discrete stopping boundary for sequential monitoring of a study with a fixed maximum number of patients (N) to be enrolled on the experimental therapy. Only an upper boundary was used since trials are only terminated for an excess frequency of toxicity and not for a low rate. By repeated use of this algorithm a stopping rule can be identified which has nearly the chosen level of (α) and a reasonable power depending on the design parameters of the study. The work reported here embeds this earlier algorithm as a subroutine in a larger FORTRAN program which searches all boundaries that fulfil constraints on size and power, as specified by the user. The search is restricted so that only those boundaries with size in a small neighbourhood of the chosen α are examined and displayed if the power is above a set minimum. These restrictions reduce the number of boundaries examined to only 0.4 per cent of all possible boundaries, thus reducing running time to a practical few seconds. Many such boundaries exist, the one with the largest power can then be chosen for monitoring the trial. The average sample number (ASN) and the expected relative loss (ERL) are also computed. The criterion for choosing may also be based on small ASN or low ERL in addition to power and appropriate α. Copyright © 2001 John Wiley & Sons, Ltd.
Variance estimation of a survival function for interval‐censored survival data
Authors: Sun Jianguo 
Published: August 2002

AbstractInterval‐censored survival data often occur in medical studies, especially in clinical trials. In this case, many authors have considered estimation of a survival function. There is, however, relatively little discussion on estimating the variance of estimated survival functions. For right‐censored data, a special case of interval‐censored data, the most commonly used method for variance estimation is to use the Greenwood formula. In this paper we propose a generalization of the Greenwood formula for variance estimation of a survival function based on interval‐censored data. Also a simple bootstrap approach is presented. The two methods are evaluated and compared using simulation studies and a real data set. The simulation results suggest that the methods work well. Copyright © 2001 John Wiley & Sons, Ltd.
Computational tools for exact conditional logistic regression
Authors: Corcoran Chris , Mehta Cyrus , Patel Nitin , Senchaudhuri Pralay 
Published: August 2002

AbstractLogistic regression analyses are often challenged by the inability of unconditional likelihood‐based approximations to yield consistent, valid estimates andp‐values for model parameters. This can be due to sparseness or separability in the data. Conditional logistic regression, though useful in such situations, can also be computationally unfeasible when the sample size or number of explanatory covariates is large. We review recent developments that allow efficient approximate conditional inference, including Monte Carlo sampling and saddlepoint approximations. We demonstrate through real examples that these methods enable the analysis of significantly larger and more complex data sets. We find in this investigation that for these moderately large data sets Monte Carlo seems a better alternative, as it provides unbiased estimates of the exact results and can be executed in less CPU time than can the single saddlepoint approximation. Moreover, the double saddlepoint approximation, while computationally the easiest to obtain, offers little practical advantage. It produces unreliable results and cannot be computed when a maximum likelihood solution does not exist. Copyright © 2001 John Wiley & Sons, Ltd.
Graphical model checking with correlated response data
Authors: Pan Wei , Connett John E. , Porzio Giovanni C. , Weisberg Sanford 
Published: August 2002

AbstractCorrelated response data arise often in biomedical studies. The generalized estimation equation (GEE) approach is widely used in regression analysis for such data. However, there are few methods available to check the adequacy of regression models in GEE. In this paper, a graphical method is proposed based on Cook and Weisberg's marginal model plot. A bootstrap method is applied to obtain the reference band to assess statistical uncertainties in comparing two marginal mean functions. We also propose using the generalized additive model (GAM) in a similar fashion. The proposed two methods are easy to implement by taking advantage of existing smoothing and GAM softwares for independent data. The usefulness of the methodology is demonstrated through application to a correlated binary data set drawn from a clinical trial, the Lung Health Study. Copyright © 2001 John Wiley & Sons, Ltd.