904 resultados para Random coefficient multinomial logit
Resumo:
Perceived depth was measured for three-types of stereograms with the colour/texture of half-occluded (monocular) regions either similar to or dissimilar to that of binocular regions or background. In a two-panel random dot stereogram the monocular region was filled with texture either similar or different to the far panel or left blank. In unpaired background stereograms the monocular region either matched the background or was different in colour or texture and in phantom stereograms the monocular region matched the partially occluded object or was a different colour or texture. In all three cases depth was considerably impaired when the monocular texture did not match either the background or the more distant surface. The content and context of monocular regions as well as their position are important in determining their role as occlusion cues and thus in three-dimensional layout. We compare coincidence and accidental view accounts of these effects. (C) 2002 Elsevier Science Ltd. All rights reserved.
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A two-component survival mixture model is proposed to analyse a set of ischaemic stroke-specific mortality data. The survival experience of stroke patients after index stroke may be described by a subpopulation of patients in the acute condition and another subpopulation of patients in the chronic phase. To adjust for the inherent correlation of observations due to random hospital effects, a mixture model of two survival functions with random effects is formulated. Assuming a Weibull hazard in both components, an EM algorithm is developed for the estimation of fixed effect parameters and variance components. A simulation study is conducted to assess the performance of the two-component survival mixture model estimators. Simulation results confirm the applicability of the proposed model in a small sample setting. Copyright (C) 2004 John Wiley Sons, Ltd.
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New differential linear coherent scattering coefficient, mu(CS), data for four biological tissue types (fat pork, tendon chicken, adipose and fibroglandular human breast tissues) covering a large momentum transfer interval (0.07 <= q <= 70.5 nm(-1)), resulted from combining WAXS and SAXS data, are presented in order to emphasize the need to update the default data-base by including the molecular interference and the large-scale arrangements effect. The results showed that the differential linear coherent scattering coefficient demonstrates influence of the large-scale arrangement, mainly due to collagen fibrils for tendon chicken and fibroglandular breast samples, and triacylglycerides for fat pork and adipose breast samples at low momentum transfer region. While, at high momentum transfer, the mu(CS) reflects effects of molecular interference related to water for tendon chicken and fibroglandular samples and, fatty acids for fat pork and adipose samples. (C) 2009 Elsevier B.V. All rights reserved.
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A new conceptual model for soil pore-solid structure is formalized. Soil pore-solid structure is proposed to comprise spatially abutting elements each with a value which is its membership to the fuzzy set ''pore,'' termed porosity. These values have a range between zero (all solid) and unity (all pore). Images are used to represent structures in which the elements are pixels and the value of each is a porosity. Two-dimensional random fields are generated by allocating each pixel a porosity by independently sampling a statistical distribution. These random fields are reorganized into other pore-solid structural types by selecting parent points which have a specified local region of influence. Pixels of larger or smaller porosity are aggregated about the parent points and within the region of interest by controlled swapping of pixels in the image. This creates local regions of homogeneity within the random field. This is similar to the process known as simulated annealing. The resulting structures are characterized using one-and two-dimensional variograms and functions describing their connectivity. A variety of examples of structures created by the model is presented and compared. Extension to three dimensions presents no theoretical difficulties and is currently under development.
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Calculating the estimated resting energy expenditure (REE) in severely obese patients is useful, but there is controversy concerning the effectiveness of available prediction equations (PE) using body weight (BW). We evaluated the efficacy of REE equations against indirect calorimetry (IC) in severely obese subjects and aimed to develop a new equation based on body composition compartments. One hundred and twenty severely obese patients had their REE measured (MREE) by IC and compared to the most commonly used PE (Harris-Benedict (HB), Ireton-Jones, Owen, and Mifflin St. Jeor). In a random sample (n = 60), a new REE equation based on fat-free mass (FFM) was developed and validated. All PE studied failed to estimate REE in severe obesity (low concordance correlation coefficient (CCC) and limits of agreement of nearly 50% of the sample +/- 10% of MREE). The HB equation using actual BW exhibited good results for all samples when compared to IC (2,117 +/- 518 kcal/day by HB vs. 2,139 +/- 423 kcal/day by MREE, P > 0.01); these results were blunted when patients were separated by gender (2,771 vs. 2,586 kcal/day, P < 0.001 in males and 1,825 vs. 1,939 kcal/day, P < 0.001 in females). A new resting energy expenditure equation prediction was developed using FFM, Horie-Waitzberg, & Gonzalez, expressed as 560.43 + (5.39 x BW) + (14.14 x FFM). The new resting energy expenditure equation prediction, which uses FFM and BW, demonstrates higher accuracy, precision, CCC, and limits of agreement than the standard PE in patients when compared to MREE (2,129 +/- 45 kcal/day vs. 2,139 +/- 423 kcal/day, respectively, P = 0.1). The new equation developed to estimate REE, which takes into account both FFM and BW, provides better results than currently available equations.
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The present study was carried out to evaluate the effectiveness of a specific program regarding the occurrence of vocal attrition symptoms in telemarketers. A total of 71 subjects participated in this study: 28 completed the Vocal Symptoms questionnaire to test its reliability, and 43 were randomly assigned to two groups: an 8-week vocal training group (n = 14) and a no-training control group (n = 29), to evaluate the effectiveness of the training program with this tool. The voice training group also filled in the posttraining questionnaire `Benefits Obtained with Voice Training` (BVT). The vocal training program was not considered effective with regard to the occurrence of vocal symptoms. However, due to a probable increase in symptoms in untrained telemarketers, it can work as a protective factor. According to BVT answers, the vocal training contributed to an improvement in vocal use as a communication tool for telemarketers. Copyright (C) 2009 S. Karger AG, Basel
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Feature selection is one of important and frequently used techniques in data preprocessing. It can improve the efficiency and the effectiveness of data mining by reducing the dimensions of feature space and removing the irrelevant and redundant information. Feature selection can be viewed as a global optimization problem of finding a minimum set of M relevant features that describes the dataset as well as the original N attributes. In this paper, we apply the adaptive partitioned random search strategy into our feature selection algorithm. Under this search strategy, the partition structure and evaluation function is proposed for feature selection problem. This algorithm ensures the global optimal solution in theory and avoids complete randomness in search direction. The good property of our algorithm is shown through the theoretical analysis.
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Objective: Clinical evaluation of the stomatognathic system is indispensable for the diagnosis of orofacial myofunctional disorders. In order to obtain a more precise diagnosis, the protocol of orofacial myofunctional evaluation with scores (OMES protocol) (Int. J. Pediatr. Otorhinolaryngol. 72 (2008) 367-375) was expanded in terms of number of items and scale amplitude. The proposal of this study is to describe the expanded OMES protocol (OMES-E) for the evaluation of children. Validity of the protocol, reliability of the examiners and agreement between them were analyzed, as also were the sensitivity, specificity and predictive values of the instrument. Methods: The sample consisted of videorecorded images of 50 children, 25 boys (mean age = 8.4 years, SD = 1.8) and 25 girls (mean age = 8.2 years, SD = 1.7) selected at random from 200 samples. Three speech therapists prepared for orofacial myofunctional evaluation participated as examiners (E). The OMES and OMES-E protocols were used for evaluation on different days. E1 evaluated all images, E2 analyzed children with recordings from 1 to 25 and E3 analyzed children with recordings from 26 to 50. The validity of OMES-E was analyzed by comparing the instrument to the OMES protocol using the Pearson correlation test complemented with the split-half reliability test (p < 0.05). The linear weighted Kappa coefficient of agreement (Kw`), the sensitivity, specificity and predictive values and the prevalence of OMD were calculated. Results: There was a statistically significant correlation between the OMES and OMES-E protocols (0.79 > r < 0.94, p < 0.01) and a significant test-retest correlation with the OMES-E (0.75 > r < 0.86, p < 0.01), with a reliability range of 0.86-0.93. The correlation and reliability coefficients between examiners were: E1 x E2 (r = 0.74, 0.84), E1 x E3 (r = 0.70, 0.83) (p < 0.01). Kw` coefficients with moderate and good strength predominated. The OMES-E protocol presented mean sensitivity = 0.91, specificity = 0.77, positive predictive value = 0.87 and negative predictive value = 0.85. The mean prevalence of OMD was 0.58. Conclusion: The OMES-E protocol is valid and reliable for orofacial myofunctional evaluation. (C) 2010 Elsevier Ireland Ltd. All rights reserved.
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Objective: In the literature there is no validated instrument for the clinical evaluation of the orofacial myofunctional condition of children that will permit the examiner to express numerically his perception of the characteristics and behaviors observed. The proposal of this study is to describe a protocol for the evaluation of children aged 6-12 years in order to establish relations between the orofacial. myofunctional conditions and numerical scales. The protocol validity, reliability of the examiners and agreement between them was analyzed. Methods: Eighty children aged 6-12 years participated in the study. All were evaluated and 30 were selected at random for the analyses (age range: 72-149 months, mean = 103.3, S.D. = 23.57). Individuals with and without orofacial myofunctional. disorders were included. The examiners were two speech therapists property calibrated in orofacial myofunctional evaluation. Two protocols were constructed. One, based on traditional models, was called traditional orofacial. myofunctional. evaluation (TOME), and the other, with the addition of numerical scales, was called orofacial myofunctional. evaluation with scores (OMES). The clinical conditions included were: appearance, posture and mobility of lips, tongue, cheeks and jaws, respiration, mastication and deglutition. Statistical analysis was performed using the split-half reliability method. Means, standard deviations and the Spearman correlation coefficient were also calculated. Results: There was a statistically significant correlation between the evaluations of 30 children assessed with the TOME and OMES protocols (r = 0.85, p < 0.01). The reliability between protocols was 0.92. The test-retest reliability of the OMES instrument was 0.99 and the correlation was 0.98. Reliability between examiners 1 and 2 using the OMES protocol was 0.99, and the correlation was 0.98 (P < 0.01). Conclusion: The OMES protocot proved to be a valid and reliable instrument for orofacial myofunctional evaluation, permitting the grading of orofacial myofunctional conditions within the limits of the selected items. (c) 2007 Elsevier Ireland Ltd. All rights reserved.
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Most cellular solids are random materials, while practically all theoretical structure-property results are for periodic models. To be able to generate theoretical results for random models, the finite element method (FEM) was used to study the elastic properties of solids with a closed-cell cellular structure. We have computed the density (rho) and microstructure dependence of the Young's modulus (E) and Poisson's ratio (PR) for several different isotropic random models based on Voronoi tessellations and level-cut Gaussian random fields. The effect of partially open cells is also considered. The results, which are best described by a power law E infinity rho (n) (1<n<2), show the influence of randomness and isotropy on the properties of closed-cell cellular materials, and are found to be in good agreement with experimental data. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
Resumo:
A mixture model incorporating long-term survivors has been adopted in the field of biostatistics where some individuals may never experience the failure event under study. The surviving fractions may be considered as cured. In most applications, the survival times are assumed to be independent. However, when the survival data are obtained from a multi-centre clinical trial, it is conceived that the environ mental conditions and facilities shared within clinic affects the proportion cured as well as the failure risk for the uncured individuals. It necessitates a long-term survivor mixture model with random effects. In this paper, the long-term survivor mixture model is extended for the analysis of multivariate failure time data using the generalized linear mixed model (GLMM) approach. The proposed model is applied to analyse a numerical data set from a multi-centre clinical trial of carcinoma as an illustration. Some simulation experiments are performed to assess the applicability of the model based on the average biases of the estimates formed. Copyright (C) 2001 John Wiley & Sons, Ltd.