Search results for "Modeling"
showing 10 items of 4489 documents
Ethyl Hexanoate Transfer Modeling in Carrageenan Matrices for Determination of Diffusion and Partition Properties.
2007
; Aroma compound properties in food matrices, such as volatility and diffusivity, have to be determined to understand the effect of composition and structure on aroma release and perception. This work illustrates the use of mass transfer modeling to identify diffusion and partition properties of ethyl hexanoate in water and in carrageenan matrices with various degrees of structure. The comparison of results obtained with a diffusive model to those obtained with a convective model highlights the importance of considering the appropriate transfer mechanism. Modeling of the preliminary experimental steps ensures correct estimation of the conditions for the main aroma release step. The obtaine…
On dependence of sets of functions on the mean value of their elements
2009
The paper considers, for a given closed bounded set M ⊂ R m and K = (0,1) n ⊂ R n , the set M = {h ϵ L2 (K;R m ) | h(x) ϵ M a.e.x ϵ K} and its subsets It is shown that, if a sequence {hk } ⊂ coM converges to an element hk ϵ M(hk ) there is h‘k ϵ M(ho ) such that h'k - hk → 0 as k → ∞ . If, in addition, the set M is finite or M is the convex hull of a finite set of elements, then the multivalued mapping h → M(h) is lower semicontinuous on coM. First published online: 14 Oct 2010
The project scheduling polyhedron: Dimension, facets and lifting theorems
1993
Abstract The Project scheduling with resource constraints can be formulated as follows: given a graph G with node set N, a set H of directed arcs corresponding to precedence relations, and a set H′ of disjunctive arcs reflecting the resource incompatibilities, find among the subsets of H′ satisfying the resource constraints the set S that minimizes the longest path in graph (N, H ∪ S). We define the project scheduling polyhedron Qs as the convex hull of the feasible solutions. We investigate several classes of inequalities with respect to their facet-defining properties for the associated polyhedron. The dimension of Qs is calculated and several inequalities are shown to define facets. For …
Stabilization and lx -gain analysis of switched positive systems with actuator saturation
2014
This paper is concerned with the problems of stability and l 1 -gain analysis for a class of switched positive systems with time-varying delays and actuator saturation. Firstly, a convex hull representation is used to describe the saturation behavior. By constructing a multiple co-positive Lyapunov functional, sufficient conditions are provided for the closed-loop system to be locally asymptotically stable at the origin of the state space under arbitrary switching. Then, the l 1 -gain performance analysis in the presence of actuator saturation is developed. Finally, two numerical examples are provided to demonstrate the effectiveness of the proposed method.
Enhancement of the Lifetime of Metastable States in Er-Doped Si Nanocrystals by External Colored Noise
2015
The changes in the lifetime of a metastable energy level in Er-doped Si nanocrystals in the presence of an external source of colored noise are analyzed for different values of noise intensity and correlation time. Exciton dynamics is simulated by a set of phenomenological rate equations which take into account all the possible phenomena inherent in the energy states of Si nanocrystals and Er^{3+} ions in the host material of Si oxide. Electronic deexcitation is studied by examining the decay of the initial population of the Er atoms in the first excitation level 4I_{13/2} through fluorescence and cooperative energy transfer upconversion. Our results show that the deexcitation process of th…
Innovation in services through learning in a joint venture
2011
Innovation determines a firm's competitiveness and survival and a joint venture is a fast and effective way to acquire the missing knowledge that partners require to innovate, but ‘knowing how to cooperate’ can be a determining factor in achieving the successful transfer of knowledge. Employing a sample of 81 service-sector firms and using a structural equation modeling methodology, we found a positive and direct impact between the cooperative learning process and partners' commitment to innovation.
Coping and Life Satisfaction in Colombian Older Adults
2021
Background. Effective coping strategies facilitate older adults’ optimal adaptation and contribute to their well-being. Problem-focused strategies are associated with active styles and enhance well-being. This study analyzes the role of coping strategies in Colombian older adults’ subjective well-being (SWB) using structural equation modelling. Additionally, Confirmatory Factor Analyses of the Life Satisfaction Scale and Coping Strategies Questionnaires are performed. Method. A cross-sectional study is conducted with 455 Colombian older adults, ranging from 65 to 92 years old. Results. The results show that problem-focused coping has a positive effect on SWB, whereas emotion-focused coping …
Predicting Well-Being Among the Elderly: The Role of Coping Strategies
2020
Objectives: This study aims to give a wider view on the role of coping strategies on elderly’s well-being, by means of literature-based competitive structural equation models (SEM). Methods: 857 older adults were surveyed with Ryff’s scales of Psychological Well-being and the Coping Strategies Questionnaire. Competitive full SEMs were tested. Results: The best fitting model was the one in which the religious coping dimension was removed, leaving the remaining dimensions defined by problem- and emotion-focused coping, which explained both psychological and subjective well-being factors (χ2(46)=165.910, p<.001; CFI=.906; GFI=.957; RMSEA=.058 [.048, .067]). Discussion: Results pointed the rele…
Different drinking motives, different adverse consequences? Evidence among adolescents from 10 European countries
2017
INTRODUCTION AND AIM: This study, which builds on previous research demonstrating that drinking motives are associated with adverse consequences, investigates the associations between drinking motives and non-alcohol-attributed adverse consequences and disentangles alcohol-related and direct effects. DESIGN AND METHOD: On the basis of a sample of 22 841 alcohol-using 13- to 16-year-olds (50.6% female) from Belgium, Denmark, Estonia, Finland, Ireland, Portugal, Scotland, Slovakia, Switzerland and Wales, structural equation models were used to estimate direct and indirect effects. Additionally, differences across countries were tested in a multigroup analysis. RESULTS: The indirect effect (vi…
Individual, co-active and collective coping and organizational stress: A longitudinal study
2019
This study aims to identify the association between changes in three types of problem-focused coping (individual, organizational co-active and collective) and the change in the appraisal of different facets of employees' stress and the organizational stress climate. These relationships are tested by means of Bayesian Multilevel Structural Equation Modeling and a two-wave panel design. The sample is composed of 525 teachers in 100 schools. Stress experiences and coping behaviors are assessed during the first and third terms of the academic year. The results show that an increase in the use of individual problem-focused coping has little to no effect on the decrease in individual stress appra…