Jean-Marie Basset, Wiebke Wackerow

جامعة الملك عبدالله للعلوم والتقنية · السعودية

The general objective of this thesis is the analysis of selective reactions for group VI grafted metal complexes via methods and principles of SOMC. For this objective, three approaches have been chosen. The first chapter is an introduction to the topic of selectivity in catalysis, emphasizing heterogeneous catalysis and more specifically the different approaches to support catalysts on surfaces. The concept of catalysis by design is introduced as a new way to use the surface as a ligand. Chapter 2 presents the results of a library of well-defined catalysts of group VI with identical catalytic functionality, but different ligand environment. The results reveal, thatmetal-carbynes are able to switch their catalytic reactivity based on the substrate that they are contacted with. The difference in reaction mechanisms and the differingre activities towards the substrates are presented. It can be concluded that the classical ROMP is selectively achieved with cyclic alkene substrates leading to polymers whereas cyclic alkanes yield exclusively higher and lower homologues of the substrate without polymeric products. Chapter 3 presents the study of olefin metathesis of cis-2-pentene with metal-carbynes of group VI, where the selectivity of the catalyst library towards yield of cis-/trans products is analyzed. It is presented, that the ligand environment of the catalysts is showing an influence in the selectivity. Rates of cis/trans isomerization of the products are high and are approaching thermodynamic equilibrium at high conversion. Product isomerization, thermodynamic equilibrium and reactivity differences between liquid phase and gas phase products are analyzed. Chapter 4 presents the full characterization of tungsten-hydrides by selective transformation into tungsten-hydroxides. These newly discovered well-defined tungsten hydroxides are fully characterized by ICP, TEM, DRIFT, double quantum and triple quantum solid-state NMR. The presented results allow to predict that tungsten-hydride son KCC-1700 are present as two distinct species. Catalysis results with cyclooctane show, that due to burial of the complexes in the KCC-1700 surface the tungsten-hydrides are less active towards cyclic alkane metathesis reactions with bulky cyclooctane than the metalcarbyne complexes. Chapter 5 is giving a conclusion of results and an outlook for catalytic applications of the generated tungsten-hydroxides of chapter 4.

إيمان عبدالكريم محمد, ابتسام فارس

كلية التربية-جامعة دمشق · سوريا

عبده بوديلمي, بوبكر زريقات, ياسمين عبد المولى

كلية العلوم الاقتصادية والتجارية وعلوم التسيير-جامعة محمد بوضياف - المسيلة · الجزائر

جمال صبحي نافع, هبه علي عامر حميدان

كلية العلوم التربوية-جامعة القدس المفتوحة · فلسطين

This study aimed to investigate the effect of using the inductive and deductive methods on 7th grade students’ achievement in grammar and their attitudes toward EFL in Bethlehem District in Palestine. To achieve the purpose of the study, the researcher applied the instrumentsto a purposeful sample from 7thgrade students at two schools, one for boys and the other for girls. Two groups, the experimental and the controlled ones were used in this study. The experimental group was taught by the inductive and deductive methods,and the controlled group was taught by the traditional method. To answer the main research question whether the inductive and deductive method are more effective in teaching grammar rather than the traditional way, the researcher used a pre and post-teststo measure students' achievement in grammar.The researcher also designed a questionnaire to measure students' attitudes toward English as foreign language (EFL).In this study, the researcherused the quasi-experimental design and the used Analysis of Covariance(ANCOVA) for measuring the contrast between the experimental and control groups. The research concludedthat there are statistical significant differences between the mean scores of 7thgrade students' achievement in grammar, due to interaction between teaching method and gender and the differences were in favor of male studentswho studied in theexperimental group. Also, the results showed that there are no statistical significant differences between attitudes towards EFL, due to interaction between teaching method and gender. The researcher recommended the needs to train English teachers to use inductive and deductive methods in teaching English grammar to improve both students' attitudes towards EFL and their achievement level. Also, to conduct more researches on other variables and other education levels.

شادن قاطرجي , شواخ الأحمد

كلية الحقوق-جامعة حلب · سوريا

Mehdi Bouskri, Sara Retal

كلية الطب والصيدلة-جامعة محمد الخامس بالرباط · المغرب

Abeer Atef Al Mohtar , Malek Tabbal

كلية العلوم والأداب-الجامعة الأمريكية في بيروت · لبنان

A low-pressure plasma system operating at microwave frequencies (2.45 GHz) in pure oxygen has been developed to perform surface treatment of materials. The aim of this work is to use this plasma reactor to induce the formation of the electrochromic materi

ريم دونية رزاق, عمار القري

كلية العلوم الاقتصادية والتجارية وعلوم التسيير-جامعة عبد الحميد بن باديس مستغانم · الجزائر

تهدف هذه الدراسة إلى دراسة أثر جائحة كوفيد- 19 على التجارة الخارجية من جهة والتي تلعب دوراهاما في الاقتصاد الوطني، عن طريق استيراد ما يحتاجه الاقتصاد من سلع وخدمات، وتصدير الفائض منه.وعلى البطالة من جهة أخرى والتي تعتبر أكثر الظواهر السلبية على اقتصاد أي بلد فهي مؤشر على انحدارالنظام الاقتصادي الى منعرج خطير؛وقد وصلت الدراسة إلى أن الاستيراد والتصدير قد تعرضا للعديد من الخسائر بفعل الأزمة الصحيةالعالمية الحالية، مما تسبب في انخفاض مداخيل كل منهما ؛كما عرفت البطالة ارتفاعا رهيبا بسبب التدابير والإجراءات التي اتخذتها الحكومة الجزائرية للحد منانتشار الفيروس.

Ghada R. Jaber, mured jurdak

الجامعة الأمريكية في بيروت · لبنان

Abdelghafour Herizi, Yahia Oulad Yahia

كلية العلوم والتكنولوجيا-جامعة غرداية · الجزائر

Le travail présenté dans ce mémoire, propose l'étude de la commande vectorielle directe de la machine asynchrone alimentée en tension . La commande vectorielle directe par orientation du flux rotorique sur l'axe d a été exploitée pour améliorer les performances en boucle fermée . Afin on a passé par la suite à la commande vectorielle de la MAS par orientation de flux rotorique, avec un référentiel d-q liée au champ tournant. Les résultats de simulation obtenus montrent la robustesse de la commande vectorielle vis-à-vis les variations de la vitesse et de la charge. Ce mémoire a été finalisé par une conclusion générale qui synthétisera les points les plus marquants de ce mémoire et récapitulera ainsi en gros le travail abordé. (The work presented in this paper, proposes the study of the direct vector control induction motor supplied with voltage. Direct vector control by orientation of the rotor flux of the d-axis has been exploited to improve performance in the closed loop. So we had afterwards to the vector control by the MAS rotor flux orientation, with a d-q reference related rotating field. The simulation results show the robustness of the vector control vis-a-vis the variations of the speed and load. This brief was finalized by a general conclusion that summarize the most salient points of this memory and so wholesale summarize the work discussed.)