Determination of scattering functions and their effects on remote sensing of turbidity in natural waters

The development of quantitative analytical procedures for relating scattered signals, measured by a remote sensor, was considered. The applications of a Monte Carlo simulation model for radiative transfer in turbid water are discussed. The model is designed to calculate the characteristics of the backscattered signal from an illuminated body of water as a function of the turbidity level, and the spectral properties of the suspended particulates. The optical properties of the environmental waters, necessary for model applications, were derived from available experimental data and/or calculated from Mie formalism. Results of applications of the model are presented

Stratospheric measurement requirements and satellite-borne remote sensing capabilities

The capabilities of specific NASA remote sensing systems to provide appropriate measurements of stratospheric parameters for potential user needs were assessed. This was used to evaluate the capabilities of the remote sensing systems to perform global monitoring of the stratosphere. The following conclusions were reached: (1) The performance of current remote stratospheric sensors, in some cases, compares quite well with identified measurement requirements. Their ability to measure other species has not been demonstrated. (2) None of the current, in-situ methods have the capability to satisfy the requirements for global monitoring and the temporal constraints derived from the users needs portion of the study. (3) Existing, non-remote techniques will continue to play an important role in stratospheric investigations for both corroboration of remotely collected data and in the evolutionary development of future remote sensors

Failure Analysis of Brazed Joints Using the CZM Approach

Brazing, as a type of joining process, is widely used in manufacturing industries to join individual components of a structure. Structural reliability of a brazed assembly is strongly dependent on the joint mechanical properties. In the present work, mechanical reliability of low carbon steel brazed joints with copper filler metal is investigated and a methodology for failure analysis of brazed joints using the cohesive zone model (CZM) is presented. Mechanical reliability of the brazed joints is characterized by strength and toughness. Uniaxial and biaxial strengths of the joints are evaluated experimentally and estimated by finite element method using the ABAQUS software. Microstructural analysis of the joint fracture surfaces reveals different failure mechanisms of dimple rupture and dendritic failure. Resistance of the brazed joints against crack propagation, evaluated by the single-parameter fracture toughness criterion, shows dependency on the specimen geometry and loading configuration. Fracture of the brazed joints and the subsequent ductile tearing process are investigated using a two-parameter CZM. The characterizing model parameters of the cohesive strength and cohesive energy are identified by a four-point bend fracture test accompanied with corresponding FE simulation. Using the characterized CZM, the joint fracture behavior under tensile loading is well estimated. Predictability of the developed cohesive zone FE model for fracture analysis of brazed joints independent of geometry and loading configuration is validated. The developed cohesive zone FE model is extended to fatigue crack growth analysis in brazed joints. A cyclic damage evolution law is implemented into the cohesive zone constitutive model to irreversibly account for the joint stiffness degradation over the number of cycles. Fatigue failure behavior of the brazed joints is characterized by performing fully reversed strain controlled cyclic tests. The damage law parameters are calibrated based on the analytical solutions and the experimental fatigue crack growth data. The characterized irreversible CZM shows applicability to fatigue crack growth life prediction of brazed joints

A feasibility study for a remote laser water turbidity meter

A technique to remotely determine the attenuation coefficient (alpha) of the water was investigated. The backscatter energy (theta = 180 deg) of a pulse laser (lambda = 440 - 660 nm) was found directly related to the water turbidity. The greatest sensitivity was found to exist at 440 nm. For waters whose turbidity was adjusted using Chesapeake Bay sediment, the sensitivity in determining alpha at 440 nm was found to be approximately 5 - 10%. A correlation was also found to exist between the water depth (time) at which the peak backscatter occurs and alpha

Space Station Freedom automation and robotics: An assessment of the potential for increased productivity

This report presents the results of a study performed in support of the Space Station Freedom Advanced Development Program, under the sponsorship of the Space Station Engineering (Code MT), Office of Space Flight. The study consisted of the collection, compilation, and analysis of lessons learned, crew time requirements, and other factors influencing the application of advanced automation and robotics, with emphasis on potential improvements in productivity. The lessons learned data collected were based primarily on Skylab, Spacelab, and other Space Shuttle experiences, consisting principally of interviews with current and former crew members and other NASA personnel with relevant experience. The objectives of this report are to present a summary of this data and its analysis, and to present conclusions regarding promising areas for the application of advanced automation and robotics technology to the Space Station Freedom and the potential benefits in terms of increased productivity. In this study, primary emphasis was placed on advanced automation technology because of its fairly extensive utilization within private industry including the aerospace sector. In contrast, other than the Remote Manipulator System (RMS), there has been relatively limited experience with advanced robotics technology applicable to the Space Station. This report should be used as a guide and is not intended to be used as a substitute for official Astronaut Office crew positions on specific issues

Cohesive zone modeling of fatigue crack growth in brazed joints

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.engfracmech.2014.03.014 © 2014. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Fatigue crack growth in low carbon steel brazed joints with copper filler metal is modeled by an irreversible Cohesive Zone Model. Strain-controlled fatigue tests are performed on the brazed specimens, and the corresponding fatigue crack initiation and propagation lives are recorded. A cyclic damage evolution law is coupled to a bilinear Cohesive Zone Model to irreversibly account for the joint stiffness degradation over the number of cycles. The damage law parameters are calibrated based on Irwin's analytical solution and the experimental fatigue crack growth data. Using the characterized irreversible Cohesive Zone Model, the fatigue crack growth is simulated and the corresponding fatigue crack growth rates are obtained. The agreement between the numerical results and the experimental data shows the applicability of the Cohesive Zone Model to fatigue crack growth analysis and life estimation of brazed joints.Natural Sciences and Engineering Research Council of Canada, NSERC Strategic Grant Progra

Microscopic multicluster description of neutron-halo nuclei with a stochastic variational method

To test a multicluster approach for halo nuclei, we give a unified description for the ground states of $^6$He and $^8$He in a model comprising an $\alpha$ cluster and single-neutron clusters. The intercluster wave function is taken a superposition of terms belonging to different arrangements, each defined by a set of Jacobi coordinates. Each term is then a superposition of products of gaussian functions of the individual Jacobi coordinates with different widths, projected to angular momenta $l=0$ or 1. To avoid excessively large dimensions and ``overcompleteness", stochastic methods were tested for selecting the gaussians spanning the basis. For $^6$He, we were able to calculate ground-state energies that are virtully exact within the subspace defined by the arrangements and $l$ values, and we found that preselected random sets of bases (with or without simulated annealing) yield excellent numerical convergence to this ``exact" value with thoroughly truncated bases. For $^8$He good energy convergence was achieved in a state space comprising three arrangements with all $l=0$, and there are indications showing that the contributions of other subspaces are likely to be small. The $^6$He and $^8$He energies are reproduced by the same effective force very well, and the matter radii obtained are similar to those of other sophisticated calculations.Comment: Latex , 8 figures available on request, ATOMKI-4-1993-

Cohesive zone modeling of ductile tearing process in brazed joints

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.engfracmech.2012.11.018 © 2013. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Ductile tearing process in low carbon steel brazed joints with copper filler metal is studied using the Cohesive Zone Model. The Cohesive Zone Model is characterized by two parameters related to the cohesive strength and cohesive energy. A new method is developed to estimate the Cohesive Zone Model parameters through direct experimental measurements and numerical modeling. The cohesive energy of the brazed joints is obtained from the fracture test results performed on the single-edge notched bend specimens. Based on the obtained cohesive energy parameter, the fracture test is simulated using a cohesive zone finite element model. A unique value for the joint cohesive strength is determined by best fitting the finite element results to the experimental load-crack mouth opening displacement curves. The merit of the characterized Cohesive Zone Model is explored by finite element modeling of the tensile test performed on the single-edge notched tension specimens. The load-crack mouth opening displacement curve obtained from the finite element modeling conforms to the corresponding tensile test results. Furthermore, the effect of the crack tip stress constraint on the plastic zone shape and size is successfully captured by the model. The good agreement between the finite element simulation results and the experimental data demonstrates the applicability of the Cohesive Zone Model for fracture analysis of the brazed joints.Natural Sciences and Engineering Research Council of Canada, NSER

Étude des stratégies linguistiques de locuteurs de français L1 et d'apprenants étrangers lors de la prise de notes en français : perspectives en didactique des langues

Cette thèse se propose d’étudier les différents types de traitement utilisés par des locuteurs de français L1 et des apprenants étrangers de français lors de la prise de notes dans cette langue, à partir du discours oral magistral. Ce travail qui s’inscrit dans une perspective psycholinguistique vise à analyser la conformité et la fidélité sémantique et formelle des textes-cibles (les productions) par rapport au texte-source (le discours émis). Le cadre théorique de la thèse analyse différentes approches et taxinomies relatives aux stratégies communicatives en langue étrangère, notamment celle de Kellerman, dans le but de dégager une typologie des stratégies de traitement à étudier dans les données empiriques relevées. Afin d’étudier l’efficacité des prises de notes des participants à l’enquête observés, nous avons conçu une grille d’analyse intitulée une « grille de matrices » permettant d’analyser d’une part, le discours professoral (par la méthode de l’analyse discursive de Van Dijk) et d’identifier et de quantifier différents procédés audiographiques déployés par les noteurs observés. A l’issue d’analyses portant sur la forme et le fond des textes recueillis, nous avons dégagé des résultats détaillés relatifs à l’efficacité de la prise de notes des participants observés. Au terme des analyses, des propositions didactiques en matière de prise de notes en langue maternelle et étrangère sont formulées.This thesis intends to study different types of treatments used by speakers of French L1 and foreign learners of French for note-taking during an oral lecture in that language. From a psycholinguistic perspective, this assignment aims to analyze compliance and definite semantic fidelity of targets-texts (productions) in comparison with the source-text (the issued speech). The theoretical context of the thesis analyzes different approaches and taxonomies relating to conversational strategies in a foreign language notably that of Kellerman, with the intention of identifying a typology of treatment strategies to be studied in gathered empirical data. To study the effectiveness of the participants’ note-taking, we conceived an analysis grid called “matrix grid” allowing to analyze, on one hand, professorial speech (through the method of the discursive analysis of Van Dijk) and on the other hand, to identify and quantify different audiographique techniques used by examined note takers. After analyzing the form and semantic content of the gathered texts, we formulated detailed results relating to the effectiveness of the examined participants’ note-taking. As a consequence of these analyses, didactic proposals in note-taking in a native or foreign language were formulated

Étude des stratégies linguistiques de locuteurs de français L1 et d'apprenants étrangers lors de la prise de notes en français (perspectives en didactique des langues)

Cette thèse se propose d étudier les différents types de traitement utilisés par des locuteurs de français L1 et des apprenants étrangers de français lors de la prise de notes dans cette langue, à partir du discours oral magistral. Ce travail qui s inscrit dans une perspective psycholinguistique vise à analyser la conformité et la fidélité sémantique et formelle des textes-cibles (les productions) par rapport au texte-source (le discours émis). Le cadre théorique de la thèse analyse différentes approches et taxinomies relatives aux stratégies communicatives en langue étrangère, notamment celle de Kellerman, dans le but de dégager une typologie des stratégies de traitement à étudier dans les données empiriques relevées. Afin d étudier l efficacité des prises de notes des participants à l enquête observés, nous avons conçu une grille d analyse intitulée une grille de matrices permettant d analyser d une part, le discours professoral (par la méthode de l analyse discursive de Van Dijk) et d identifier et de quantifier différents procédés audiographiques déployés par les noteurs observés. A l issue d analyses portant sur la forme et le fond des textes recueillis, nous avons dégagé des résultats détaillés relatifs à l efficacité de la prise de notes des participants observés. Au terme des analyses, des propositions didactiques en matière de prise de notes en langue maternelle et étrangère sont formulées.This thesis intends to study different types of treatments used by speakers of French L1 and foreign learners of French for note-taking during an oral lecture in that language. From a psycholinguistic perspective, this assignment aims to analyze compliance and definite semantic fidelity of targets-texts (productions) in comparison with the source-text (the issued speech). The theoretical context of the thesis analyzes different approaches and taxonomies relating to conversational strategies in a foreign language notably that of Kellerman, with the intention of identifying a typology of treatment strategies to be studied in gathered empirical data. To study the effectiveness of the participants note-taking, we conceived an analysis grid called matrix grid allowing to analyze, on one hand, professorial speech (through the method of the discursive analysis of Van Dijk) and on the other hand, to identify and quantify different audiographique techniques used by examined note takers. After analyzing the form and semantic content of the gathered texts, we formulated detailed results relating to the effectiveness of the examined participants note-taking. As a consequence of these analyses, didactic proposals in note-taking in a native or foreign language were formulated.AIX-MARSEILLE1-Bib.electronique (130559902) / SudocSudocFranceF