Casual and instinctive resemblances between Poe and the Oriental

Thesis (M.A.)--Boston University, 1931. This item was digitized by the Internet Archive

EXPERIMENTAL STUDY OF MULTIPACTOR SUPPRESSION IN DIELECTRIC MATERIALS

International audienceA novel coaxial resonator to investigate two-surface multipactor discharges on metal and dielectric surfaces in the gap region under vacuum conditions (~10-8 mbar) has been developed and tested. The resonator is ~ 100 mm in length with an outer diameter of ~ 60 mm (internal dimensions). A pulsed RF source delivers up to 30 W average power over a wide frequency range 650-900 MHz to the RF resonator. The incident and reflected RF signals are monitored by calibrated RF diodes. An electron probe provides temporal measurements of the multipacting electron current with respect to the RF pulses. In this paper we compare and contrast the results from the RF power tests of the alumina (97.6% Al2O3) and quartz samples without a coating, “the non-coated samples” and the Alumina and quartz samples with a TiN coating in order to evaluate a home made sputtered titanium nitride (TiN) thin layers as a Multipactor suppressor. The effectiveness of this method is presented and discussed in the paper

Field-Assisted DC-Pulsed Cathodes for next generation light sources and accelerators

International audienceThe scope of that contribution is to present the challenges of the next particle sources for accelerators. It is admitted that emittance near Interaction Point (IP) is strongly dominated by the emittance of the low power source. To minimize theBremstrahlung effects in the Interaction Point (IP), we also need extremely low emittance bunches, ultra high brillance, very low charges sub fC, near depopulated attosecond electronic bunches. These produced bunches should fit the entrances of Dielectric Laser Accelerators (DLA) and Laser Plasma Accelerators (LPA).A 20kV DC pulsed sub nanosecond Field Emission Array source with extremely low emittance is considered in order to obtain such results. Firstly, we will describe the DC-pulsed experimental source by blocks. Following that, we will raise more general problems induced by DC-pulsed configuration: thermal transient behaviour of nanostructures, enhancement of plasmons coupling in relation to nanostructured networks, then fast prototyping of cathode geometry will be undertaken using different models. These cathodes are to be fabricated at Orsay.We present the method of curvilinear coordinate calculus, adapted to major classes of nanostructured tips. We define 3 major classes of 3D analytical profiles to emulate experimental conditions (multi-segment, quadratic and exponential one) and apply curvilinear analytical Maxwellsolving to find electrostatic potential around the profile. Our method is concurrent to T-splines for instance, but it is expected to converge faster. Cathode physics will be modelled integrating different phenomenons: photo/thermal/field/emission... Results will be compared to electromagnetic simulations with CST and Astra tools. To conclude, we shall then evaluate the emittance performances planned for a 20keV cathodic source, and its acceptance to the next stages, with the help of some electrostatic focusing. Numerous experimental and theoretical aspects are to be solved

Gestion du capital intellectuel : Le capital intellectuel dans différents domaines et ses composantes

The purpose of our article is to definethe concept of intellectual capital, to talk  about its history, its models of measurement, the components that characterize it, its impact  on organizations, and lastly how it is manifested in different fields and its relationship with  knowledge management , that is all to highlight its importance in an economy dominated by  the creation and diffusion of knowledge, since the role of intellectual capital is indelible,  especially with the increase in overall corporate investment in IC - and because of its  economic characteristics, notably its intangible nature, itss value inscreased, it also has  characteristics that are, by definition, growth-enhancing, and permit to establish evidences of  a link between investment in this intellectual capital to growth and changes in productivity.The purpose of our article is to definethe concept of intellectual capital, to talk  about its history, its models of measurement, the components that characterize it, its impact  on organizations, and lastly how it is manifested in different fields and its relationship with  knowledge management , that is all to highlight its importance in an economy dominated by  the creation and diffusion of knowledge, since the role of intellectual capital is indelible,  especially with the increase in overall corporate investment in IC - and because of its  economic characteristics, notably its intangible nature, itss value inscreased, it also has  characteristics that are, by definition, growth-enhancing, and permit to establish evidences of  a link between investment in this intellectual capital to growth and changes in productivity

RF Coaxial Resonator for Investigating Multipactor Discharges on Metal and Dielectric Surfaces

http://accelconf.web.cern.ch/AccelConf/LINAC2014/html/auth0693.htmTHPP096International audienceMultipactor discharge is a phenomenon in which electrons impact one or more material surfaces in resonance with an alternating electric field. The discharge can occur for a wide range of frequencies, from the MHz range to tens of GHz, and in wide array of geometries if the impacted surface has a secondary electron emission (SEE) yield larger than one. The discharge can take place on a single surface or between two surfaces. A novel coaxial resonator to investigate two-surface multipactor discharges on metal and dielectric surfaces in the gap region under vacuum conditions has been designed and tested. The resonator is ~ 100 mm in length with an outer diameter of ~ 60 mm (internal dimensions). A pulsed RF source delivers up to 30 W average power over a wide frequency range 650-900 MHz to the RF resonator. The incident and reflected RF signals are monitored by calibrated RF diodes. An electron probe provides temporal measurements of the multipacting electron current with respect to the RF power. These experiments were successful in identifying multipacting and allowed us the evaluation of a home made sputtered titanium nitride (TiN) thin layers as a Multipactor suppressor

Mapping boundaries of generative systems for design synthesis

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2007.Page 123 blank.Includes bibliographical references (p. 121-122).Architects have been experimenting with generative systems for design without a clear reference or theory of what, why or how to deal with such systems. In this thesis I argue for three points. The first is that generative systems in architecture are implemented at a skin-deep level as they are only used to synthesize form within confined domains. The second is that such systems can be only implemented if a design formalism is defined. The third is that generative systems can be deeper integrated within a design process if they were coupled with performance-based evaluation methods. These arguments are discussed in four chapters: 1- Introduction: a panoramic view of generative systems in architecture and in. computing mapping their occurrences and implementations. 2- Generative Systems for Design: highlights on integrating generative systems in architecture design processes; and discussions on six generative systems including: Algorithmic, Parametrics, L-systems, Cellular Automata, Fractals and Shape Grammars. 3- Provisional taxonomy: A summery table of systems properties and a classification of generative systems properties as discussed in the previous chapter 4- Conclusion: comments and explanations on why such systems are simplicity implemented within design.by Maher El-Khaldi.S.M

أهمية التقويم الرقمي في تعليم العربية للناطقين بغيرها عن بعد

 تنشغل هذه الورقة بتعليم اللغة العربية عن بعد باستثمار النمط التعليمي الرقمي الذي اعتمد بالتزامن مع جائحة كوفيد-19، كما أنها تهدف إلى تحديد مفهوم التقويم ورصد أنواعه، فضلا عن تقديم أهم محددات ومعايير التقويم الرقمي، علاوة على أنها تبرز الكيفية التي تتم بموجبها عملية بناء وإعداد نموذج تقويم رقمي خاص باللغة العربية موجه لدارسيها الناطقين بغيرها من الأجانب وذلك بالاعتماد على بعض المواقع والتطبيقات التعليمية التفاعلية الإلكترونية. عطفا على ما تقدم، فإن هذه الورقة تنطلق من جملة من التساؤلات الأساسية من أبرزها:كيف يمكن تهيئ تقويم عن بعد يراعي اختلاف المستويات وتكافؤ الفرص - -ما هي التقنيات والوسائل التكنولوجية المتوفرة لتقديم اختبار رقمي وتمريره عن بعد

Analyse et suivi du phénomène de la désertification en Algérie du nord

La présente étude a pour objectif de contribuer au suivi de la désertification au nord d’Algérie par l’utilisation des capteurs MODIS (MODerate resolution Imaging Spectroradiometer) de TERRA. A cet effet, certains paramètres géophysiques (albédo "R0", indice de végétation "NDVI" et température de surface "TS") sont produits régulièrement et couvrent la période de 2000 à 2005. Les combinaisons de ces paramètres deux à deux en particulier R0 -TS ; NDVI-TS et NDVI-R0 ont permis respectivement la caractérisation de l'état hydrique et de l'état de la végétation. La synthèse de l'ensemble des résultats sous un système d’information géographique (SIG), ainsi que leurs confrontations avec d'autres types de données ont permis de dresser des cartes de la sensibilité à la désertification selon cinq degrés (très bon état, bon état, état critique, état dégradé et état très dégradé). Ces résultats montrent qu’environ 75 % des parcours steppiques sont désertifiés ou au seuil de la désertification.The present study aims to work out a methodology based on the use of the sensors such TERRA MODIS (MODerate resolution Imaging Spectroradiometer) in the desertification following and the detection of desertification risk zones in the northern area of Algeria. To this end, some geophysical parameters (albedo "R0", vegetation index "NDVI'' and surface temperature "TS") are produced regularly and cover the period of 2000 to 2005. The combination of these parameters two per two especially R0 -TS, NDVI-TS and R0 - NDVI has allowed respectively the characterization of the hydric and vegetation state. The synthesis of the totality of results under a geographical information system GIS as well as their confrontation with others types of data have allowed to map the desertification risk following five degrees (very high, high, moderated, weak and stable). Our results show that 75 % of the risk zones are already desertify or near of desertification