13 research outputs found
Development of a multi-scale projection method with immersed boundaries for chemically reactive flows and its application to examine flame stabilization and blow-off mechanisms
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 193-201).High-fidelity multi-scale simulation tools are critically important for examining energy conversion processes in which the coupling of complex chemical kinetics, molecular transport, continuum mixing and acoustics play important roles. The objectives of this thesis are: (i) to develop a state-of-the-art numerical approach to capture the wide spectra of spatio-temporal scales associated with reacting flows around immersed boundaries, and (ii) to use this tool to investigate the underlying mechanisms of flame stabilization and blow-off in canonical configurations. A second-order immersed boundary method for reacting flow simulations near heat conducting, grid conforming, solid object has been developed. The method is coupled with a block-structured adaptive mesh refinement (SAMR) framework and a semi-implicit operator-split projection algorithm. The immersed boundary approach captures the flame-wall interactions. The SAMR framework and the operator-split algorithm resolve several decades of length and time efficiently. A novel "buffer zone" methodology is introduced to impose the solid-fluid boundary conditions such that symmetric derivatives and interpolation stencils can be used throughout the interior of the domain, thereby maintaining the order of accuracy of the method. Near an immersed solid boundary, single-sided buffer zones are used to resolve the species discontinuities, and dual buffer zones are used to capture the temperature gradient discontinuities. This eliminates the need to utilize artificial flame anchoring boundary conditions used in existing state-of-the-art numerical methods. As such, using this approach, it is possible for the first time to analyze the complex and subtle processes near walls that govern flame stabilization. The approach can resolve the flow around multiple immersed solids using coordinate conforming representation, making it valuable for future research investigating a variety of multi-physics reacting flows while incorporating flame-wall interactions, such as catalytic and plasma interactions. Using the numerical method, limits on flame stabilization in two canonical configurations: bluff-body and perforated-plate, were investigated and the underlying physical mechanisms were elucidated. A significant departure from the conventional two-zone premixed flame-structure was observed in the anchoring region for both configurations. In the bluff-body wake, the location where the flame is initiated, preferential diffusion and conjugate heat exchange furnish conditions for ignition and enable streamwise flame continuation. In the perforated-plate, on the other hand, a combination of conjugate heat exchange and flame curvature is responsible for local anchoring. For both configurations, it was found that a flame was stable when (1) the local flame displacement speed was equal to the flow speed (static stability), and (2) the gradient of the flame displacement speed normal to its surface was higher than the gradient of the flow speed along the same direction (dynamic stability). As the blow-off conditions were approached, the difference between the former and the latter decreased until the dynamic stability condition (2) was violated. The blowoff of flames stabilized in a bluff-body wake start downstream, near the end of the combustion-products dominated recirculation zone, by flame pinching into an upstream and a downstream propagating sections. The blow-off of flames stabilized in flow perforated-plate wake start in the anchoring region, near the end of the preheated reactants-filled recirculation zone, with the entire flame front convecting downstream. These simulations elucidated the thus far unknown physics of the underlying flame stabilization and blow-off mechanisms, understanding which is crucial for designing flame-holders for combustors that support continuous burning. Such an investigation is not possible without the advanced numerical tool developed in this work. Based on the insight gained from the simulations, analytical models were developed to describe the dynamic response of flames to flow perturbations in an acoustically coupled environment. These models are instrumental in optimizing combustor designs and applying active control to guarantee dynamic stability if necessary.by Kushal Sharad Kedia.Ph. D
Strain effect on electronic and lattice dynamical behaviour of two dimensional Bi, BiAs and BiSb
No full textDesigning liquid repellent surfaces for fabrics, feathers and fog
No full textThesis (Ph. D. in Chemical Engineering Practice)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis. "December 2012."Includes bibliographical references.Omniphobicity refers to a property of surfaces which are not wetted by water, oils, alcohols and other low surface tension liquids. Robust omniphobic surfaces can be applied in many areas including fabrics with chemical / biological protection and dirt / fingerprint resistant touch screens. The main aim of this thesis is to develop rules for the systematic design of omniphobic surfaces with a focus on textiles. First, a design chart is developed to help us understand the impact of surface chemistry and surface topography on the wettability of a textured surface. A smaller characteristic length scale of a re-entrant surface topography, tighter weave and a coating with inherently low wettability are better for producing omniphobic surfaces that resist wetting by liquids with low surface tension. This framework is applied to textile fabrics and bird feathers to test their wettability. Using this framework, wettability of low surface tension liquids on a polyester fabric is tuned or switched using either thermal annealing or biaxial stretching. Army Combat Uniform fabrics are rendered oleophobic, thus opening the way to optimize omniphobic army uniforms. The wettability of molecules similar to fluorodecyl POSS is investigated by measuring the contact angles with liquids of a broad range of surface tension and polarity. Of the molecules tested so far, fluorodecyl POSS has the lowest solid surface energy (9.3 mN/m) and the lowest increment in solid surface energy (7 mN/m). The wetting aspects of the hierarchical topography of bird feathers are captured using contact angle measurements in terms of a spacing ratio. Thermodynamics of the wetting of feathers and the robustness against wetting during the course of a dive are correlated to the wing spreading behavior. Our understanding of surface wettability of woven meshes is applied to optimize their fog collection ability. A business case for fog harvesting is developed and strategies to decrease asset and cash flow risks are proposed. The contributions presented here provide means to better characterize surfaces with complex topography, tune and a priori predict their wettability and recommend a design strategy both at a molecular and a macroscopic level to maximize their non-wettability.by Shreerang S. Chhatre.Ph.D.in Chemical Engineering Practic
Fortune at the Bottom of the Pyramid: An Alternative Perspective
No full textThe Bottom of the Pyramid (BOP) has emerged as one of the dominant ideas in business. Cognizant of the overwhelming attention BOP has attracted and its potential impact on the billions of the poor and on managerial practices, the author analyzes the different aspects of BOP approach on how large corporations can serve low income customers profitably. An attempt is made to provide an alternate perspective on the BOP concept. I argue for the facilitation of selective consumption by the poor by avoiding their undesirable inclusion (marketing products that are not likely to enhance their wellbeing or products that are likely to be abused by them) and exclusion (not offering products that are likely to enhances their wellbeing) in target market selection decisions by the private sector organizations. A framework is presented for assessing the appropriateness of large corporations’ participation in BOP markets. I also emphasize the need to strengthen the role of the poor as a producer for rapid poverty alleviation.
PHARMACEUTICAL AND BIOPHARMACEUTICAL ASPECTS OF QUANTUM DOTS-AN OVERVIEW
No full textIn the twenty-first century, nanotechnology has become cutting-edge technology. It is interdisciplinary and multidisciplinary, covering numerous fields such as medicine, engineering, biology, physics, material sciences, and chemistry. The present work aims to cover the optical properties, method of preparations, surface modifications, bio-conjugation, characterization, stability, and cytotoxicity of quantum dots (QDs).
Articles were reviewed in English literature reporting the pharmaceutical and bio-pharmaceutical aspects of QDs which were indexed in Scopus, web of science, google scholar and PubMed without applying the year of publication criterion.
One significant value of utilizing nanotechnology is that one can alter and control the properties in a genuinely unsurprising way to address explicit applications\u27 issues. In science and biomedicine, the usage of functional nanomaterials has been broadly investigated and has become one of the quick-moving and stimulating research directions. Different types of nanomaterial (silicon nanowires, QDs, carbon nanotubes, nanoparticles of gold/silver) were extensively utilized for biological purposes. Nanomedicine shows numerous advantages in the natural characteristics of targeted drug delivery and therapeutics. For instance, protection of drugs against degradation, improvement in the drug\u27s stability, prolonged circulation time, deceased side effects, and enhanced distribution in tissues. The present review article deals with the quantum dots, their optical properties, method of preparations, surface modifications, bio-conjugation, characterization, stability, and cytotoxicity of quantum dots. The review also discusses various biomedical applications of QDs.
The QDs-based bio-nanotechnology will always be in the growing list of unique applications, with progress being made in specialized nanoparticle development, the detection of elegant conjugation methods, and the discovery of new targeting ligands
Women in forestry in India
No full textThe increasingly visible impact of the fuelwood and fodder crisis on the household has called attention to the need to involve women in forestry planning. In this paper, women have been classified into four groups based on farming system and habitat: tribal women; hill women; plains women; and poor urban women. This paper attempts to make a few basic points. First, it is essential to document women's relationship to forests both in the context of the household and the outside economy. For projects to succeed, the linkages must be drawn between women's roles in the different farming systems, the food supply system, domestic tasks and their income-earning activities. A second major thrust of the paper is to demonstrate that an overriding concern with the impact of the fuelwood and fodder crisis on women as actors in the domestic subsistence economy has blinded planners to their equally important role in the non-domestic forestry economy. The paper also points out the importance of forest resources for poor households and as a source of income for resource-poor women. Finally, through an examination of women's roles in different farming systems, this paper shows women's substantial involvement with forests and makes the case for strengthening their involvement in the entire forestry sector.Forestry,Agricultural Knowledge&Information Systems,Health Monitoring&Evaluation,Environmental Economics&Policies,Crops&Crop Management Systems
The dramaturgy of ritual performances in Indian parliamentary debates
No full textThe content, style and form of MPs' performances on the floor of both Houses of the
Indian Parliament has undergone dramatic change within the last decade. For example,
97% of the productive hours of the Winter (Nov-Dec) 2010 Session were lost due to
intense disruption by MPs across the political spectrum seeking to stall the House.
Moreover, an increasing number of Bills are debated for less than an hour, if at all, on
the floor of Parliament - raising the conceptual question of whether legislation can still
be considered one of parliament's key functions in India. These changes require, at the
very least, an attempt to re-conceptualize the meaning and significance attributed to
various tropes of parliamentary performances, including those which seemingly subvert
all notions of parliamentary procedure, decorum and etiquette. In my thesis, I adopt a
novel interdisciplinary analytical framework, drawing upon performance studies, microsociological
dramaturgy of face-to-face interaction, interpretations of procedural
invocations, rhetorical political analysis and the study of political rituals. My primary
research question was whether the concept of ritual could usefully be mapped onto
performances of debates in the Indian parliamentary context. I then asked what the
significance of the absence or presence of rituals in this context would mean. Two case
were studies selected for this analysis, namely the Prevention of Terrorism Act (2001-
2004) and the Women's Reservation Bill (1996-2011), informed by a more general
ethnography of the Indian Parliament undertaken for this research. Both studies were
chosen using the logic of 'extreme case study selection' as these performances exhibit
extreme forms of dramaturgical violence, protest and polarized rhetoric that is
increasingly reflective of the everyday performances of the Indian Parliament. In my
research, I have adopted an interpretivist-constructivist approach to the ethnographic
method and have conducted two tranches of field research in New Delhi for that
purpose. My analysis demonstrates the presence of a diverse range of rituals of debate
being performed simultaneously during the legislative process within the Indian
Parliament, namely, procedural rituals, interpersonal rituals and disruptive rituals. These
findings corroborate the broader argument that the study of rituals are integral to an
understanding of parliamentary processes. Moreover, instead of dismissing certain
aspects of performance (e.g. physical obstruction of debate) as being symptomatic of
what many scholars have called the 'decline of parliament', my findings support the
cause for re-signifying, or re-reading parliamentary disruption as supporting, rather than
diminishing, the processes of political representation and widening the spectrum of
forms of political action considered as legitimate modes of political deliberation. The
evolution of these newer, sometimes disruptive, forms of representative ritual can be
read into wider processes of vernacularization and mediatization currently transforming
the ethos, identity and modus operandi of the Indian Parliament
BRAINSTORM: A Multi-Institutional Phase 1/2 Study of RRx-001 in Combination With Whole Brain Radiation Therapy for Patients With Brain Metastases
No full text© 2020 The Author(s) Purpose: To determine the recommended phase 2 dose of RRx-001, a radiosensitizer with vascular normalizing properties, when used with whole-brain radiation therapy (WBRT) for brain metastases and to assess whether quantitative changes in perfusion magnetic resonance imaging (MRI) after RRx-001 correlate with response. Methods and Materials: Five centers participated in this phase 1/2 trial of RRx-001 given once pre-WBRT and then twice weekly during WBRT. Four dose levels were planned (5 mg/m2, 8.4 mg/m2, 16.5 mg/m2, 27.5 mg/m2). Dose escalation was managed by the time-to-event continual reassessment method algorithm. Linear mixed models were used to correlate change in 24-hour T1, Ktrans (capillary permeability), and fractional plasma volume with change in tumor volume. Results: Between 2015 and 2017, 31 patients were enrolled. Two patients dropped out before any therapy. Median age was 60 years (range, 30-76), and 12 were male. The most common tumor types were melanoma (59%) and non-small cell lung cancer (18%). No dose limiting toxicities were observed. The most common severe adverse event was grade 3 asthenia (6.9%, 2 of 29). The median intracranial response rate was 46% (95% confidence interval, 24-68) and median overall survival was 5.2 months (95% confidence interval, 4.5-9.4). No neurologic deaths occurred. Among 10 patients undergoing dynamic contrast-enhanced MRI, a reduction in Vp 24 hours after RRx-001 was associated with reduced tumor volume at 1 and 4 months (P ≤.01). Conclusions: The addition of RRx-001 to WBRT is well tolerated with favorable intracranial response rates. Because activity was observed across all dose levels, the recommended phase 2 dose is 10 mg twice weekly. A reduction in fractional plasma volume on dynamic contrast-enhanced MRI 24 hours after RRx-001 suggests antiangiogenic activity associated with longer-term tumor response
