Based on thesis, University of Chicago. / Bibliography: 147-149.

Islam Md. Saiful. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 175-181). / Abstracts in English and Chinese. / Abstract / Abstract in Chinese --- p.ii / Acknowledgements --- p.iii / Note --- p.iv / List of Figures --- p.ix / List of Plates --- p.x / Chapter Chapter One --- Introduction --- p.1 / Statement of the Problem / Literature Review / Chapter - --- "Minority Groups, NGOs and Development Issues" / Chapter - --- Education Among Minority Groups / Chapter - --- Minority Groups as Discriminated and Stigmatized / Chapter - --- Fighting Against Discrimination: The Art of Resistance / Methodology / Chapter - --- Selecting the NGOs / Chapter - --- Finding the Field Site / Chapter - --- Settling / Chapter - --- From Padri through Sir to Dada: Rapport Buildup / Chapter - --- How I Collected Data / Chapter - --- Pains and Pleasures of Fieldwork / Chapter - --- Limitations of the Study / Structure of the Thesis / Chapter Chapter Two --- "Barind Tract of Northwest Bangladesh: The Villages Studied, Ecology and Cultural Mosaic" --- p.37 / The Study Villages: A Brief Profile / Chapter - --- Ruposhi: A Santal Village / Chapter - --- Fulpur: An Oraon Village / Northwest Bangladesh: Ecology and Implications / People of Barind Tract: The Cultural Mosaic / The Santal and the Oraon: From Historical Context to the Present Situation / Chapter Chapter Three --- "NGOs in Bangladesh: Growth, Rhetoric and Realities" --- p.56 / The Growth of NGOs in Bangladesh: A Brief Overview / Chapter - --- NGOs and Their Achievements / Chapter - --- The Rhetoric Behind the Reality: Challenges and problems of the NGOs / Prochesta: A Minority-run NGO / Chapter - --- "Goals, Objectives and Programmes of Prochesta" / Chapter - --- Organizational Structure of Prochesta / Unnoyan: A Bengali-run NGO / Chapter - --- "Vision, Mission and Programmes of Unnoyan" / Chapter - --- Unnoyan: Organizational Structure / Chapter Chapter Four --- "Minority Groups, Economic Livelihood and NGOs" --- p.79 / Agrarian Economy with Single Crop Cultivation / Land Ownership and Patterns of Tenancy / Agriculture and Food Sufficiency: A General Calculation / Supplementing Household Income / Economic Support: The Santal and Prochesta / The Oraon and Unnoyan in Promoting Economic Livelihood / "Minority Groups, Economic Livelihood and the Role of NGOs" / Chapter Chapter Five --- "Education Among Minority Groups: The Santal, The Oraon and The NGOs" --- p.114 / The General Situation of Education Among Minority People in the Study Villages / Dropout From the School: Minority Point of View / Medium of Instruction for Minority Students: The Dilemmas of Monolingualism / The Santal and Prochesta in Promoting Education / "The Oraon, Unnoyan and Education" / Chapter - --- Primary Education for the Oraon Children / Chapter - --- Lahanti: The Adult Education Programme / Chapter - --- Preparing Curriculum in Oraon Language: The Action Research Project / "Minority Groups, Education and the NGOs" / Chapter Chapter Six --- Minority Groups and Fighting Against Discrimination: The Art of Resistance and the Involvement of NGOs --- p.144 / Everyday Discrimination Encountered by Minority People: Nature and Pervasiveness / Fighting Against Discrimination and the Involvement of NGOs / Chapter - --- The Santal and Prochesta in Fighting Against Discrimination / Chapter - --- The Oraon and Unnoyan in Fighting Against Discrimination / Minority Groups and the Role NGOs in Fighting Against Discrimination / Chapter Chapter Seven --- Conclusion --- p.164 / Bibliography --- p.175

La présente étude porte sur l’analyse fondamentale et expérimentale des procédés d’extraction des volatils. Les méthodes conventionnelles d’hydrodistillation et d’entrainement à la vapeur dans l’extraction des composés volatils (huiles essentielles…), impliquent une cinétique ralentie voire bloquée par « le processus paradoxal ». Ce dernier est dû au couplage de la génération interne de vapeur impliquant deux transferts couplés de vapeur (par diffusion) et de chaleur (par conduction). Ces deux transferts sont alors dirigés de la surface d’échange vers l’intérieur. Seul un processus de transfert partiel de la vapeur par front progressif assure l’évolution du processus. La cinétique est ainsi inévitablement lente, générant un niveau élevé de consommation d’énergie et induisant une dégradation potentielle de la matière extraite. Pour faire face à cette situation, une modification du type de transfert est essentielle. Nous avons opté pour un transfert de type Darcy au lieu du transfert de Fick, soit un gradient de pression totale au lieu du gradient de pression partielle comme « driving force ». Nous avons ainsi choisi la Détente Instantanée Contrôlée DIC comme procédé générant, suite à la détente vers le vide, une autovaporisation instantanée couplée à un grand gradient de pression totale de l’intérieur du matériau vers le milieu environnant sous vide. La détente instantanée contrôlée (DIC) a été étudiée, selon la méthodologie des plans d’expériences dans le but d’évaluer l’impact des variables opératoires sur l’extraction et de définir les paramètres optimums. Le nombre de cycles et le temps de traitement ont été pris comme paramètres indépendants. Ces paramètres sont appropriés pour représenter les aspects mécaniques et thermiques du processus DIC. L’extraction directe de l’huile essentielle du bois de santal par DIC-MP, gérée essentiellement par le nombre de cycles, indépendamment du temps de traitement, est une autovaporisation des composés volatils. Cette nouvelle méthode a ensuite été comparée tout au long de sa mise en application à l’hydrodistillation. Alors que la méthode traditionnelle d’extraction de l’huile essentielle du bois de santal requiert 140 h, l’optimisation de la DIC nous a permis de réaliser l’extraction en seulement 6 minutes, avec des rendements pratiquement similaires. Dans un dernier temps, une approche écologique et une compréhension du phénomène mis en jeu pour l’extraction des huiles essentielles par DIC ont été abordées. La rapidité de la procédure, la réduction du coût énergétique et le bon impact environnemental font de la DIC une technique industrielle particulièrement innovante et hautement attrayante. / This study focuses on fundamental analysis and experimental work carried out on extraction via conventional and innovative processes. The extraction of volatile compounds (essential oils ...) through hydrodistillation or steam distillation as conventional methods is slowed or even blocked because of "the paradoxical process". The latter is due to the coupling of vapor and heat transfers, both directed from the exchange surface towards product core. Only partial vapor transfer by progressive forehead ensures the evolution of the process. The kinetics is so inevitably slow, implying high energy consumption and inducing a high degradation of both extracted and residual material. To face this situation, changing the nature of the transfer is essential. We considered the total pressure gradient instead of the vapor pressure gradient as "driving force". Instant Controlled Pressure Drop DIC was used. Instant releasing of high pressure/high pressure towards a vacuum leads to instant autovaporisation, implying a Darcy-type transfer of vapor within the material to the surrounding medium vacuum. Instant Controlled Pressure Drop (DIC) was investigated, according to the Response surface methodology RSM in order to evaluate the impact of process variables on the extraction and to define the optimal settings. The number of treatment cycles and treatment time were taken as independent parameters. These parameters were appropriated to represent both mechanical and thermal impacts of DIC process. Direct extraction of the essential oil of sandalwood DIC-MP, managed primarily by the number of cycles, regardless of treatment time, is an autovaporization of volatile compounds. This new method was then compared throughout its application to steam distillation. While traditional extraction method requires 140 hours, optimized DIC allowed performing essential oil extraction of sandalwood in only 6 minutes, with substantially similar yields. Finally, environment approach and understanding of the phenomena involved in DIC extraction of essential oils were addressed. By dramatically reducing the treatment time and the energy consumption, DIC is a particularly innovative, exceptionally effective and highly attractive environment-friendly essential oil extraction technique.