Confinement Effects on Non-Reactive and Reactive Transport Processes: Insights from Molecular Dynamics Simulations

Exploring the thermodynamic, structural and transport properties, coupled with the reactivity of complex geo-fluids in porous systems is vital in geochemistry, and it also has repercussions in a variety of fields, most importantly the manufacturing of chemicals in the industry. Experimental and computational studies can shed light on the behaviour of fluids in confinement, thereby providing insights for industrial applications in various areas such as catalysis, gas recovery, separations, and adsorption. This thesis seeks to obtain some fundamental understanding of the behaviour of fluids confined in narrow pores as well as the role of pores in reactive-transport processes by implementing the atomistic molecular dynamics (MD) simulation techniques. In collaboration with experimentalists, validation has been achieved for selected systems. The systems were simulated as confined within a realistic cylindrical pore of diameter ~16 Å carved out of amorphous silica. A series of MD simulations implementing classical force fields were conducted to examine the effect of bulk pressure and water loading on the mobility of propane confined within cylindrical silica pores. The transport properties of propane were found to depend on pressure, as well as on the amount of water present. At high H2O loading, propane transport is hindered by “molecular bridges” formed by water molecules. The results are in quantitative agreement with neutron scattering data conducted for propane-water systems confined in MCM-41–type materials. To investigate the effect of narrow pores on the possible abiotic synthesis of methane in sub-surface conditions, MD simulations implementing the reactive force field (ReaxFF) formalism were performed. Although the ReaxFF force fields were successfully parameterized to describe dynamics of complex reactive chemical systems, the simulation results reveal that they can also be able to reliably predict bulk properties of nonreactive pure fluids (CH4, CO2, H2O, and H2). However, the agreement with both simulations implementing classical force fields and experiments depends strongly on fluids and thermodynamics conditions considered. When ReaxFF molecular dynamics simulations were conducted for CO2 in the presence of excess H2 within the amorphous silica nanopores, no CH4 was obtained at the conditions considered; however, CO was found to be a stable product, suggesting that the silica pore surface facilitates the partial reduction of CO2 to CO. Because the results could be important for CCUS applications, we investigated the wetting properties of calcite in the presence of water and CO2, at various pressures and salt content. Comparison with experiments suggests that much fundamental research is still needed to design safe and reliable geological storage repositories

THE QUALITY WATER ENVIRONMENT HAPPENING OF THE HUONG RIVER IN THE HUE CITY, PERIOD OF 2003-2006

Joint Research on Environmental Science and Technology for the Eart

LEARNING IDIOMS FOR ENGLISH MAJORS: VIETNAMESE STUDENTS’ PERCEPTIONS OF DIFFICULTIES AND LEARNING STRATEGIES

Learning idioms play an influential role in language generally and in English notably. Comprehending idioms assists language learners in integrating culture, enhancing skills, and ameliorating English levels. Numerous studies have analyzed the function of idioms in second language acquisition (Cieślicka, 2015). This study investigates the difficulties and strategies used in learning idioms by English-majored students at a regional public university (PU) in the south of Vietnam. This paper furnishes data showing learners’ perceptions of facing complications and learning methods. The samples consisted of 150 undergraduate EFL students from English-medium instruction programs. The data was analyzed by utilizing descriptive and inferential statistics. The findings reveal that students struggle to understand idiomatic terms without specific, understandable contexts. Furthermore, the results indicate that the most frequently employed strategies are guessing the meaning of idioms, learning idioms through keywords, and learning from a range of sources, particularly via media. The findings also mentioned that low-proficiency and high-proficiency students encounter identical challenges, with no significant differences. The study's results revealed that the majority of students have difficulty acquiring, recognizing, and interpreting idioms. The findings indicated that guessing the implication of idioms is the most used strategy.  Article visualizations

L'autonomisation des apprentissages du français : enjeux et perspectives

Durant ces dernières années, les universités vietnamiennes ont adopté une politique générale d’innovation pour améliorer la qualité de leurs formations. L’évolution vers un système à crédits capitalisables en est un grand projet. Il s’agit d’une nouvelle organisation des activités d’enseignement-apprentissage, réduisant les cours en présentiel et privilégiant l’auto-apprentissage. Les pratiques de formation doivent nécessairement évoluer. Quelles transformations pédagogiques cette situation suppose-t-elle de mettre en œuvre afin de satisfaire aux exigences d’autonomisation du nouveau système à crédits capitalisables ? Dans le cadre de notre cursus de licence (bac+4), qui inclut des formations à l’activité enseignante et à la traduction-interprétation, nous avons initié, depuis 2012, un dispositif qui consiste à décloisonner certaines disciplines dans notre programme et à en restructurer les contenus. Les objectifs du dispositif sont, d’une part, de donner du sens aux contenus enseignés pour améliorer les apprentissages linguistiques et professionnels et, d’autre part, de former nos étudiants à l’autonomie et à la réflexivité.Comment ce dispositif d’enseignement a-t-il été conçu ? Quelle en est la réalisation ? En quoi il contribue à former à la réflexivité et l’autonomie ? Tels sont les éléments analysés dans cet article

On the Discovery of Semantically Meaningful SQL Constraints from Armstrong Samples: Foundations, Implementation, and Evaluation

A database is said to be C-Armstrong for a finite set Σ of data dependencies in a class C if the database satisfies all data dependencies in Σ and violates all data dependencies in C that are not implied by Σ. Therefore, Armstrong databases are concise, user-friendly representations of abstract data dependencies that can be used to judge, justify, convey, and test the understanding of database design choices. Indeed, an Armstrong database satisfies exactly those data dependencies that are considered meaningful by the current design choice Σ. Structural and computational properties of Armstrong databases have been deeply investigated in Codd’s Turing Award winning relational model of data. Armstrong databases have been incorporated in approaches towards relational database design. They have also been found useful for the elicitation of requirements, the semantic sampling of existing databases, and the specification of schema mappings. This research establishes a toolbox of Armstrong databases for SQL data. This is challenging as SQL data can contain null marker occurrences in columns declared NULL, and may contain duplicate rows. Thus, the existing theory of Armstrong databases only applies to idealized instances of SQL data, that is, instances without null marker occurrences and without duplicate rows. For the thesis, two popular interpretations of null markers are considered: the no information interpretation used in SQL, and the exists but unknown interpretation by Codd. Furthermore, the study is limited to the popular class C of functional dependencies. However, the presence of duplicate rows means that the class of uniqueness constraints is no longer subsumed by the class of functional dependencies, in contrast to the relational model of data. As a first contribution a provably-correct algorithm is developed that computes Armstrong databases for an arbitrarily given finite set of uniqueness constraints and functional dependencies. This contribution is based on axiomatic, algorithmic and logical characterizations of the associated implication problem that are also established in this thesis. While the problem to decide whether a given database is Armstrong for a given set of such constraints is precisely exponential, our algorithm computes an Armstrong database with a number of rows that is at most quadratic in the number of rows of a minimum-sized Armstrong database. As a second contribution the algorithms are implemented in the form of a design tool. Users of the tool can therefore inspect Armstrong databases to analyze their current design choice Σ. Intuitively, Armstrong databases are useful for the acquisition of semantically meaningful constraints, if the users can recognize the actual meaningfulness of constraints that they incorrectly perceived as meaningless before the inspection of an Armstrong database. As a final contribution, measures are introduced that formalize the term “useful” and it is shown by some detailed experiments that Armstrong tables, as computed by the tool, are indeed useful. In summary, this research establishes a toolbox of Armstrong databases that can be applied by database designers to concisely visualize constraints on SQL data. Such support can lead to database designs that guarantee efficient data management in practice

Finnish Customer Expectations in Senior Residences on Costa del Sol, Spain : Case: Villa Aurora Company

The number of senior citizens in Finland has been increasing for decades, and this trend is predicted to continue due to the aging of Finnish baby-boom generations. The rise of aging population leads to the increase of demand in living places for senior people. At the same time, more Finnish retirees choose Spain as a destination for their retirement holidays, especially in winter. Another fact is that the hotels in Spain have low occupancy rates during winter. Therefore converting hotels into senior residences, particularly in low season, is likely a solution to maximize hotel facility utility and provide more comfortable living places for Finnish senior people. Throughout this study, the deductive approach is applied with the assistance of qualitative method. The primary data is obtained from interviews with Finnish potential customers and with the director of the case company, and from communications via e-mails with senior residences in Spain. The secondary data is collected from books, journals, previous studies, and reliable Internet sources. The research’s aim is to assist the case company to improve their knowledge about the Finnish market for their new business, senior residences services. In this case, the research provides the findings about Finnish customer expectations towards senior residences. All analyses and recommendations have managed to achieve the research’s objectives and can benefit later researches as a trusted study source. The conclusion is that Finnish customers have various expectations in senior residences in Spain regarding different aspects from services, facilities to locations, staff and price. Further research is necessary to study pricing issues as well as other groups of potential customers

The psychological contract of temporary employees with a university degree in Vietnam

Dissertação de mestrado em Gestão de Recursos HumanosIn Vietnam, graduate employees have entered the labor market with temporary contracts of employment and precarious employment conditions. The psychological contract is currently one of the most interesting research topics; nevertheless this concept is virtually unknown among those responsible for human resources management in Vietnam. Thus, this study was conducted to identify the psychological contract that characterizes the employees with a temporary employment contract, and to describe this reality in the context of Vietnam. The objective of this study is therefore to understand what type of psychological contract is held by Vietnamese employees, with a university degree, working as temporary employees, and to understand how they deal with the broken promises from their employer. The empirical study uses a quantitative methodology. Thus, questionnaire surveys were applied to employees in Ho Chi Minh City, during the month of March 2012. The questionnaire was conducted online and to participate in the research, respondents had to satisfy two criteria: have experience as employees on temporary or short-term contract, and an education level equal or superior to a degree. A total of 106 questionnaires were received. The questionnaire collected information on the expectations held by respondents as to the employment relationship, the degree to which they assessed the fulfillment of these expectations by the employer, and the degree to which they themselves have complied with their obligations, as well as the perception of breach and violation of the psychological contract (PC). The data analysis was performed with the use of the SPSS software program, version 18 (Statistical Package for Social Sciences). The results showed that the graduate employees, with a temporary or short-term employment contract, had a psychological contract (PC) both relational and transactional, and that the two components of the PC were correlated. In addition, respondents also felt a psychological contract breach whenever their employer did not fulfill the promises made to them, and where the break occurred, they experienced a negative emotion, that is, the violation of the PC. The results of this study can be regarded as an initial step to explore the concept of psychological contract in a specific group of employees: the Vietnamese employees with short-term contracts, and with a high educational level.No Vietname, os trabalhadores licenciados têm entrado no mercado de trabalho com um contrato de trabalho temporário e precário em termos de condições de emprego. Apesar do contrato psicológico ser atualmente um dos tópicos de investigação mais interessantes, este conceito é praticamente desconhecido junto dos responsáveis pela gestão de recursos humanos vietnamitas. Deste modo, este estudo foi conduzido com o objetivo de identificar o contrato psicológico que carateriza o trabalhador com um contrato de trabalho temporário, ou de curto-prazo, e para descrever esta realidade no contexto vietnamita. O objetivo deste estudo é assim o de compreender que tipo de contrato psicológico é detido pelos trabalhadores vietnamitas, com o grau de licenciatura, que trabalham como empregados temporários, e perceber como lidam com as promessas não cumpridas pelo empregador. O estudo empírico utiliza uma metodologia do tipo quantitativo. Assim, foram aplicados inquéritos por questionário a trabalhadores na cidade de Ho Chi Minh, durante o mês de Março de 2012. A aplicação do questionário foi realizada online e para poderem participar na investigação os respondentes tinham que satisfazer dois critérios: possuírem experiência como trabalhadores em regime de contrato de trabalho temporário, ou de curto-prazo, e um nível educacional igual ou superior ao grau de licenciado. Foram recebidos um total de 106 questionários. O questionário recolheu informação relativa às expectativas detidas pelos respondentes quanto à relação laboral, o grau em que eles avaliavam o cumprimento dessas expectativas pelo empregador, e o grau em que eles próprios cumpriam com as suas obrigações, bem como a perceção de quebra e violação do contrato psicológico. O tratamento dos dados recolhidos foi realizado com o recurso ao programa de análise de dados estatísticos SPSS, versão 18 (Statistical Package for the Social Sciences). Os resultados revelaram que os empregados licenciados, com um contrato de trabalho temporário, possuíam um contrato psicológico (CP) quer relacional, quer transacional, sendo que ambas as componentes do CP estavam correlacionadas. Além disso, os respondentes também percecionavam quebra do contrato psicológico quando o empregador não cumpria com as promessas, sendo que sempre que ocorria a quebra, eles experimentavam uma emoção negativa, isto é, a violação do CP. Os resultados deste estudo podem ser perspetivados como um passo inicial para explorar o conceito de contrato psicológico num grupo específico de trabalhadores: os trabalhadores vietnamitas, com um contrato temporário, ou de curto-prazo, e com um elevado nível educacional

Comparison of dispersion characteristics of hollow-core photonic crystal fibers filled with aromatic compounds

In this paper, hollow-core photonic crystal fibers (PCFs) infiltrated with benzene and nitrobenzene are designed and investigated. Their dispersion characteristics are numerically simulated. The results show that using the aromatic-compounds-filled hollow core of PCFs makes dispersion curves flat. In addition, the dispersion curves approach the zero-dispersion line closer than previously published dispersion curves of PCFs with toluene, thus significantly improving the supercontinuum generation to create the ultra-flat spectrum expansion

Comparing the effectiveness of online and onsite learning in English proficiency classes: Learners’ perspectives

Online education has significantly gained popularity due to new technology and more importantly, the growing impact of the digitalization of the economy. Despite its prominent advantages such as accessibility, affordability and flexibility, the effectiveness of online education is still a constant debate and needs extensive investigations in different research contexts. This study aimed to evaluate the effectiveness of online learning in comparison to traditional learning in the context of English language teaching. This descriptive study was undertaken with learners of English as a foreign language (EFL) in English proficiency preparation classes, employing an online questionnaire together with final scores of proficiency tests. The results revealed that the participants had relatively positive perceptions towards online learning in all four aspects: course content, teachers, learning environment and course supports. The significant finding was that when comparing the final results of the VSTEP exams, the online learners generally were able to perform better than the learners in traditional classrooms, though the difference was not largely remarkable. Online education in the new normal will continue to excel and the effectiveness of this learning mode certainly needs further investigation from different perspectives

Recherche de manifestation de dimensions supplémentaires dans le canal diphoton avec l'expérience ATLAS au LHC

Cette thèse résume une recherche de manifestations de Grandes Dimensions Supplémentaires (GDS, og Large Extra Dimensions fg en anglais) en utilisant 4.91 fb-1 de données enregistrées en 2011 par le détecteur Atlas installé auprès du collisionneur LHC au CERN. En 2011, le LHC a produit des collisions proton-proton à une énergie dans le centre de masse de sqrt(s)= 7 TeV. Les GDS peuvent potentiellement expliquer une énigme connue sous le nom du problème de la hiérarchie : la grande différence entre l'échelle électrofaible et l'échelle de Planck dans le Modèle Standard (MS). Dans le cadre du modèle ADD (nommé selon les auteurs N. Arkani-Hamed, S. Dimopoulos and G. Dvali) des GDS, les effets de la gravitation quantique deviennent plus forts que dans le MS; potentiellement suffisamment forts pour être observés au LHC. Il y a deux mécanismes de production de gravitons dans les collisions proton-proton : production directe de gravitons et échange virtuel de gravitons. Dans cette thèse, nous présentons une recherche de dimensions supplémentaires via l'effet de l'échange virtuel de gravitons dans l'état final di-photon. Le spectre de masse invariante des événements di-photon est étudié, et un bon accord entre les données et le bruit de fond prédit par le MS est observé. Nous utilisons deux méthodes pour estimer des limites sur l'échelle de Planck fondamentale du modèle ADD : une expérience de comptage et une analyse de la forme du spectre de masse. L'expérience de comptage donne des limites entre 2.62 et 3.92 TeV à 95% C.L., en fonction du nombre de dimensions supplémentaires et du formalisme théorique utilisé. L'analyse de la forme du spectre de masse donne des limites légèrement plus strictes : la limite inférieure sur l'échelle de Planck fondamentale augmente d'un facteur de 1.04.This thesis summarizes a search for manifestations of Large Extra Dimensions (LED) using 4.91fb-1 of data collected in 2011 by the Atlas detector at the LHC collider at CERN. In 2011, the LHC has provided proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV. LED can potentially solve the so-called hierarchy problem, i.e. large apparent difference between two fundamental scales of the Standard Model (SM), the electroweak and the Planck scales. In the context of the ADD model (named after the authors N. Arkani-Hamed, S. Dimopoulos and G. Dvali) of LED, the effects of quantum gravity become much stronger than in the SM; possibly large enough to be observed at the LHC. There are two possibilities of graviton production in proton-proton collisions: direct graviton production and virtual graviton exchange. In this thesis, we present a search for the manifestation of extra dimensions via the effect of virtual graviton exchange on the di-photon final state. The di-photon invariant mass spectrum is studied and found to be in good agreement with SM background expectation. We set limits on the fundamental Planck scale of the ADD model using two different methods: a counting experiment and an analysis of the shape of the di-photon mass spectrum. The counting experiment yields limits between 2.62 and 3.92 TeV at 95% CL, depending on the number of extra dimensions and the theoretical formalism used. The shape analysis yields slightly more stringent limits: the lower limits on the fundamental Planck scale improve by a factor of 1.04.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF