Auswahl der wissenschaftlichen Literatur zum Thema „MADMAX facility“

Does microcredit have the potential to empower women? Many factors facilitate female empowerment through microcredit. The Department of Samurdhi Development in Sri Lanka provides microcredit programs to enhance the business environment of unemployed women. The Samurdhu microcredit program is designed with training facilities, market facilities, loan cycles, group lending, exposure to credit, and business support facilities. This study will determine the factors for women's empowerment through microcredit facilities in Samurdhi banks for self-employment activities. In this study, women's empowerment at the household level through the microcredit facility of Samurai Bank has been taken into account to analyze the problem identified in this research. This paper illustrates the most significant factors of the microcredit facility granted by the Samurdhi community-based banks for empowering women. The method used to select women beneficiaries is a simple random sampling from the lists of loan applicants in the bank based on 13 Grama Niladhari Divisions, Madame divisional secretariat, Puttalam District, Sri Lanka.241 cross-sectional data was gathered by the questionnaire survey in the Madampe divisional secretariat, Puttalam District in Sri Lanka. The data analysis in this paper revealed that training facilities and market access are the two most significant factors, followed by group lending and exposure to credit components to facilitate women’s empowerment in rural areas. Finally, this paper proposed policy recommendations for policymakers to improve their microcredit policies with several different components.

Cette thèse de doctorat explore la dynamique de propagation des ondes de détente dans les circuits de réacteurs nucléaires, en se concentrant sur une configuration représentative d'un scénario de type Accident par Perte de Réfrigérant Primaire (APRP) dans les Réacteurs à Eau Pressurisée (REP). L'étude examine les charges de pression transitoires sur les structures internes, en particulier le cloisonnement du cœur du réacteur, induites par les ondes de détente générées par la rupture brutale et totale (rupture guillotine) d'une des tuyauteries du circuit primaire de refroidissement du REP. Cette analyse est menée en combinant des mesures expérimentales sur un banc d'essai de géométrie simplifiée mais représentatif du scénario APRP et des simulations numériques. Ces simulations sont réalisées en faisant appel à une hiérarchie de modèles numériques: 1D, 2D axisymétriques et 3D, avec ou sans prise en compte des mécanismes d'interaction fluide-structure. Les modèles 1D incluent des représentations simplifiées ou modèles d'impédance des obstacles présents dans l'écoulement, indispensables pour réduire les coûts de simulation de la propagation des ondes au travers d'un circuit complet. Ces obstacles sont des diaphragmes de diamètre et d'épaisseur variables, représentatifs des singularités géométriques présentes dans les circuits parcourus par les ondes de détente. La comparaison calcul/expérience permet d'évaluer le potentiel prédictif des différentes stratégies mises en oeuvre. Le Chapitre 1 introductif du mémoire détaille le contexte et la motivation de l'étude menée en mettant en évidence l'importance d'une compréhension approfondie des phénomènes physiques associés au scénario APRP et la nécessité de modèles simplifiés pour simuler l'écoulement de fluides dans les géométries complexes d'un REP. Une revue de la littérature récapitule les principaux travaux dans l'analyse par voie numérique des réacteurs nucléaires et les simulations d'écoulement transitoire. Une anlyse des approches numériques développées pour la propagation d'ondes en présence d'obstacles avec description simplifiée est également menée pour des applications hors contexte nucléaire. Les Chapitres 2 et 3 présentent respectivement i) la plateforme expérimentale MADMAX utilisée pour produire les mesures de référence ainsi que l'évolution de ses configurations au cours de la thèse, ii) les modèles disponibles au sein du logiciel EUROPLEXUS et utilisés pour mener les simulations numériques des configurations étudiées expérimentalement. Le Chapitre 4 détaille les résultats des expériences et des simulations de la propagation des ondes de détente à travers un unique diaphragme de géométrie modulaire. L'impact de la géométrie des obstacles sur la propagation des ondes est analysé et les capacités prédictives de modèles numériques de complexité (et de coût) variable sont évaluées pour cette configuration de base. Le Chapitre 5 élargit l'analyse à la configuration complète de MADMAX, incorporant une conduite de dérivation avec plusieurs diaphragmes positionnés dans cette conduite. La comparaison détaillée des données expérimentales et des résultats des simulations révéle un bon accord dans la capture du comportement transitoire et des différentiels de pression entre les conduites du cœur et de la dérivation. Des configurations alternatives de MADMAX sont explorées dans le Chapitre 6, mettant en évidence les effets de variation du nombre des diaphragmes et de leur emplacement. Les expériences sur la plateforme MADMAX et les simulations EUROPLEXUS réalisées dans le présent travail contribuent à une meilleure compréhension des phénomènes d'écoulement transitoire dans les circuits de réacteurs nucléaires. [...]
This doctoral thesis explores the dynamics of rarefaction wave propagation in nuclear reactor circuits, focusing on a configuration representative of a Loss of Coolant Accident (LOCA) scenario in Pressurized Water Reactors (PWRs). The study examines transient pressure loads on internal structures, particularly the reactor core baffle, induced by rarefaction waves generated by the sudden and complete rupture (guillotine break) of one of the pipes in the primary cooling circuit of the PWR. This analysis is conducted by combining experimental measurements on a test bench with simplified geometry but representative of the LOCA scenario and numerical simulations. These simulations employ a hierarchy of numerical models: 1D, 2D axisymmetric, and 3D, with or without taking into account fluid-structure interaction mechanisms. The 1D models include simplified representations or impedance models of the obstacles in the flow, essential for reducing the simulation costs of wave propagation through an entire circuit. These obstacles are orifice plates of varying diameter and thickness, representative of the geometric singularities present in the circuits traversed by rarefaction waves. The comparison between calculations and experiments allows for evaluating the predictive potential of the various strategies implemented. Chapter 1 of the thesis introduces the context and motivation of the study, highlighting the importance of a thorough understanding of the physical phenomena associated with the LOCA scenario and the necessity of simplified models for simulating fluid flow in the complex geometries of a PWR. A literature review summarizes the main works in the numerical analysis of nuclear reactors and transient flow simulations. An analysis of the numerical approaches developed for wave propagation in the presence of obstacles with simplified descriptions is also conducted for applications outside the nuclear context. Chapters 2 and 3 respectively present i) the MADMAX experimental platform used to produce the reference measurements and the evolution of its configurations during the thesis, ii) the models available within the EUROPLEXUS software and used to perform the numerical simulations of the experimentally studied configurations. Chapter 4 details the results of the experiments and simulations of rarefaction wave propagation through a single modular orifice plate. The impact of obstacle geometry on wave propagation is analyzed, and the predictive capabilities of numerical models of varying complexity (and cost) are evaluated for this basic configuration. Chapter 5 expands the analysis to the complete MADMAX configuration, incorporating a by-pass pipe with several orifice plates positioned in this pipe. The detailed comparison of experimental data and simulation results reveals good agreement in capturing transient behavior and pressure differentials between the core and by-pass pipes. Alternative configurations of MADMAX are explored in Chapter 6, highlighting the effects of varying the number and placement of the orifice plates. The experiments on the MADMAX platform and the EUROPLEXUS simulations conducted in this work contribute to a better understanding of transient flow phenomena in nuclear reactor circuits. The proposed calculations/experiments comparisons provide quantitative indications on the predictive capacity of the simulation codes based on the choices of geometric singularity descriptions present in the flow. The thesis conclusion proposes some avenues for future analysis and improvements

In order to enable comparison of Helicon ion thruster performance across different vacuum test facilities, an understanding of the effect of operating pressure on plasma plume properties is required. Plasma property measurements are compared for thruster operation at two separate vacuum facility operating pressures to determine the effect of neutral ingestion on Helicon ion thruster operation. The ion energy distribution function (IEDF), electron temperature, ion number density, and plasma potential are measured along the thruster main axis for a replica of the Madison Helicon eXperiment. Plasma property values recorded at the ‘high-pressure condition’ (3.0×10^(-4) Torr corrected for argon) are compared to values recorded at the ‘low-pressure condition’ (1.2×10^(-5) Torr corrected for argon) for thruster operation at 100 - 500 watts radio frequency forward power, 340 – 700 gauss source region magnetic field strength, and 1.3 - 60 sccm argon volumetric flow rate (0.039-1.782 mg/s). Differences in plasma behavior at the ‘high-pressure condition’ result from two primary neutral-plume interactions: collisions between accelerated beam ions and ingested neutrals leading to a reduction of ion energy and neutral ionization downstream of the thruster exit due to electron-neutral collisions. Electron temperature at higher operating pressures is lowered due to an electron cooling effect resulting from repeated collisions with neutral atoms. Results suggest that Helicon ion thruster plasma properties are greatly influenced when subjected to neutral ingestion.

Abstract A numerical analysis of the hydrodynamic performance of high-speed displacement vessels with and without Hull Vane (HV) is presented in the paper. A Hull Vane is an energy-saving device that is transversely fastened to the vessel’s transom bottom. The pressure differential is the primary reason for the vessel’s decreased pressure drag and trim. The Finite Volume approach employing a standard mesh was used to analyze the hull model utilizing a Hull Vane with various spans. Heave and pitch are the two degrees of freedom taken into account. The high-speed displacement vessel with and without a Hull Vane is subjected to model tests in calm water in the Department of Ocean Engineering’s current towing tank facility at the Indian Institute of Technology, Madras. The effects of span (Length of the HV has been discussed in this paper. The vessel’s performance is significantly influenced by the length of the Hull Vane and limited condition for span has been obtained. The study demonstrates a greater trim reduction due to the lift force produced by the hull vane at the stern of the vessel. The overall resistance coefficient has been decreased to 7%.

Abstract In this paper an attempt has been made to study the effectiveness of interceptor on lift and drag as this device is nowadays used by both partial and dynamic lift crafts. There is change in pressure distribution at the stern region where interceptor is fitted which helps in the lift of vessel. This study focuses on the effect of interceptor in high speed planing hull with 20deg deadrise angle based on experimental, numerical and empirical approaches. Experiments were conducted in the Towing Tank facility, Department of Ocean Engineering at IIT Madras and numerical simulations were carried out in still water condition for the cases of the hull with and without interceptor. Results showed good reduction in resistance and trim of the vessel when fitted with interceptor in planing regime. Savitsky empirical relations for bare hull and Steen empirical equations for hull with interceptor are used to estimate lift and drag on the vessel. The results of this study show that interceptor creates more lift on the vessel due to the pressure created at the stern region which helps in drag reduction and further in better control of trim on the vessel. Measurements were also made to confirm that interceptor has an effect on the dynamic lift of the hull and hence a change in resistance resulting in control of the trim angle.

Demand for renewable energy sources is rapidly increasing since they are able to replace depleting fossil fuels and their capacity to act as a carbon neutral energy source. A substantial amount of such clean, renewable and reliable energy potential exists in offshore winds. The major engineering challenge in establishing an offshore wind energy facility is the design of a reliable and financially viable offshore support for the wind turbine tower. An economically feasible support for an offshore wind turbine is a compliant platform since it moves with wave forces and offer less resistance to them. Amongst the several compliant type offshore structures, articulated type is an innovative one. It is flexibly linked to the seafloor and can move along with the waves and restoring is achieved by large buoyancy force. This study focuses on the experimental investigations on the dynamic response of a three-legged articulated structure supporting a 5MW wind turbine. The experimental investigations are done on a 1: 60 scaled model in a 4m wide wave flume at the Department of Ocean Engineering, Indian Institute of Technology, Madras. The tests were conducted for regular waves of various wave periods and wave heights and for various orientations of the platform. The dynamic responses are presented in the form of Response Amplitude Operators (RAO). The study results revealed that the proposed articulated structure is technically feasible in supporting an offshore wind turbine because the natural frequencies are away from ocean wave frequencies and the RAOs obtained are relatively small.

A compact model of synchrotron accelerator facility is proposed for the treatment of deep seated tumors with proton therapy. The extracted beam from the existing C-30 cyclotron is first injected into the model of synchrotron. The injected beam is specified with its longitudinal plane as well as its horizontal and vertical emittances. For this design to be compatible with the cyclotron C-30 the synchrotron should be kept compact and the number of magnet components must be low. The modeled synchrotron layout is designed using the computer codes MADX and AGILE in order to accelerate the injection proton ions from 30 MeV to a maximum extraction energy of 250 MeV with magnetic rigidity of 2.433 Tm. In this lattice arrangement with phase advance of about 90 degrees in two horizontal and vertical planes doublet cells are utilized. This ring consists of two long straight sections for RF and injection/extraction equipment, as well as four short straight sections. For chromaticity correction two families of sextupoles are used. To prohibit emittance growth, a matching at injection in longitudinal plane was performed. The proton beam energy spread of 2% can be improved to 0.1% at injection by using the designed achromatic system. For the proton beam acceleration a RF cavity with an approximate voltage of 160 volts with a frequency in the range of 2.3 up to 14 MHz is used.