139 research outputs found
Investigating possible mechanisms of Non-Photochemical Laser Induced Nucleation
No full textCrystallization is employed in a wide range of industries but our ability to control it remains far from perfect. New methods are being continuously developed and improved to provide enhanced kinetics and control. Non-photochemical laser induced nucleation (NPLIN) is one of the avenues being looked into extensively since its accidental discovery about two decades ago. Despite providing improved nucleation kinetics and potential polymorph control, the mechanism behind NPLIN is still unknown. Four different theories have been proposed in the literature with varying amounts of agreement betweendifferent research groups.The main aim of this thesis is to try to determine the mechanism behind NPLIN. This report can be divided into two parts, each focusing on a possible mechanism. The first is the optical Kerr effect,which involves investigating the effect of polarization of light on glycine polymorph formed. This is achieved by varying the laser light polarisation and number of pulses for a range of glycine supersaturation. The second part deals with an experimental setup designed to work with microscale volumes. This will give us the capability to isolate the nuclei and observe the events leading up to their formation.For studying the optical Kerr effect, the experiment performed by Sun et al. was repeated. A significant temperature increase inside the solution was obtained because of exposure to a high numberof pulses (600) of infrared light. No dependence of laser light polarization on polymorph formation was found. The polymorph formed by laser is different than that obtained by crash cooling. In thesecond part of the thesis, the attention is shifted towards the role of impurities present in the solution which can also absorb the laser light leading to formation of a cavitation bubble. This possibility wasexamined with the help of the setup mentioned above. It was noted that the crystals were nucleating at multiple points around the laser focus at a distance which is similar to the size of the cavitation bubble previously reported in literature. These observations made can be attributed towards the presence of a bubble.Mechanical Engineerin
Collective excitations in layered materials with momentum-resolved electron energy loss spectroscopy
Get PDFStrong Coulomb interactions are either suspected or known to play a prominent role in material classes such as high temperature superconductors, charge density waves, and Mott insulators among many others. These interactions are quantified by the charge density response function, chi(q,w) (or the closely related inverse dielectric function). The measurement of the energy- and momentum-resolved chi(q,w) over a large phase space of q and w, however, presents a significant experimental challenge. Traditional methods to measure chi(q,w) have suffered from either one or more major drawbacks. To address this problem, the development of a spectroscopic technique, momentum-resolved electron energy loss spectroscopy (M-EELS), was undertaken. Because many of the material classes that exhibit these unusual ground states tend to be layered or quasi-two dimensional, M-EELS presents a promising approach to measuring the energy- and momentum-resolved charge density response. Since the technique is not widely used, however, the M-EELS results obtained as part of this thesis were compared to other probes in the relevant ranges of phase space to ensure consistency. Furthermore, a theoretical framework was worked out to demonstrate explicitly the relationship between the scattering cross section and c(q,w). M-EELS experiments were conducted on a high-temperature superconductor, Bi2Sr2CaCu2O8+d, a charge density wave material, TiSe2, and a topological insulator, Bi2Se3. It was determined that the bosonic origin of quasiparticle kinks often seen in angle-resolved photoemission studies can be identified using M-EELS. Lastly, the observation of a novel electronic collective mode in TiSe2 is presented as strong evidence for an excitonic insulator phase in this compound.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2017-12-01The student, Anshul Kogar, accepted the attached license on 2015-08-28 at 14:26.The student, Anshul Kogar, submitted this Dissertation for approval on 2015-08-28 at 14:40.This Dissertation was approved for publication on 2015-09-08 at 14:22.DSpace SAF Submission Ingestion Package generated from Vireo submission #8678 on 2016-03-08 at 11:05:02Made available in DSpace on 2016-03-08T17:21:39Z (GMT). No. of bitstreams: 2
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Android game development with AppInventor
Get PDFThesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 94).AppInventor is an educational learning tool provided by MIT that allows users to build Android apps without any knowledge of programming. As AppInventor gains popularity amongst educators and students around the world, it will become increasingly important to ensure that the tool offers its users the breadth and depth of app-development functionality they desire. In anticipation of AppInventor's expanding role and influence in educational institutions worldwide (middle schools and high-schools, primarily), this thesis focuses on the age group of 3rd to 12th grade students, and on the topic that is of greatest interest to them: gaming, animation, and graphics. The aim of this thesis is to identify AppInventor's existing capabilities and limitations with respect to game development, and to implement ideas (both pedagogical and technological in nature) that will improve the diversity, complexity, aesthetic appeal, and performance of games that can be built using AppInventor. The author of this thesis believes that if AppInventor's game development capabilities can be augmented, the adoption rate of the tool and its popularity amongst school students will be impacted very positively. In this thesis, the author describes his personal experiences teaching AppInventor game development in India and USA, as well as the limitations (in teaching methodology and in AppInventor's feature set) that he identified through this experience. The author's primary contributions are the development of a hands-on curriculum for a 40-hour AppInventor Game Development course, and the implementation of several new features and components for AppInventor. The author will be traveling to China and India in Summer 2012 to test to what extent his creative curriculum and novel AppInventor modifications facilitate the development of games using AppInventor.by Anshul Bhagi.M.Eng
Interactions between auditory and visual motion mechanisms and the role of attention: psychophysics and quantitative models
No full textThe human brain continuously receives sensory input from the dynamic physical world via various sensory modalities. In many cases, a single physical event generates simultaneous input to more than one modality. For example, a ball hitting the ground generates both visual and auditory input. The human brain has developed mechanisms to take advantage of the correlations between inputs to different modalities to form a uniform and stable percept. Recently, there has been a lot of research interest, psychophysical, neurophysiological and computational, to explore the mechanisms involved in crossmodal interactions in general and auditory-visual interactions in particular.
The current thesis makes three significant contributions to the field of auditory-visual interactions. First, I designed a comprehensive study to psychophysically examine the interactions between auditory and visual motion mechanisms for three different motion configurations: horizontal, vertical and motion-in-depth. I showed that simultaneous presentation of a strong motion signal in one modality influences perception of a weak motion signal in the other modality both when the weak motion in presented in the visual, as well as in the auditory modality. I further observed that crossmodal aftereffects were induced only when subjects adapted to spatial motion in the visual modality and not in the auditory modality. However, adaptation to auditory spectral motion did induce vertical visual motion aftereffects. To my knowledge, this is the first report of auditory-induced visual aftereffects. Second, I conducted psychophysical experiments to study the effects of spectral attention on the visual and the auditory motion mechanisms and showed that there are similar attentional effects on motion mechanisms within the two modalities. Third, I developed a neurophysiologically relevant computational model to provide a possible explanation for crossmodal interactions between the auditory and the visual motion mechanisms. In addition, I developed a model that can explain the observed experimental findings on the role of spectral attention in modulating motion aftereffects. The results obtained from both the model simulations agree very closely with the human behavioral data obtained from the experiments.Ph.D.Includes bibliographical references (p. 139-144)
Development of thermal displays for haptic interfaces
No full textThesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.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 97-102).This thesis studied the effect of different stimulus parameters on the thermal response of the skin. A set of thermal patterns, known as thermal icons, was presented to participants using a thermal display mounted on the hand. The thermal responses of the skin were studied to understand which features of the thermal stimuli were important and could be perceived by users. The effectiveness of these patterns was evaluated for applications involving hand-held and wearable thermal devices. In the first series of experiments, a set of six thermal icons was developed and presented on the thenar eminence and the fingertips. The second experiment was conducted on the wrist with a revised set of thermal icons which had a shorter duration and were presented relative to each participant's baseline skin temperature. The information transfer (IT) values for the thermal icons presented on the wrist-mounted thermal display demonstrated that the information processing capabilities of the thermal sensory system may rival those achieved with vibrotactile inputs. To date, thermal icon studies have only used the temporal properties of stimuli and not the spatial properties. A set of two experiments was conducted to examine how the spatial and temporal properties of thermal stimuli interact. The results showed that the temporal properties of thermal stimulation can influence the perceived location of a thermal stimulus. This space-time dependency for the thermal sensory system provides an extra dimension to use to present information in a thermal display and potentially could result in a display that functionally has a higher spatial resolution than the number of thermal elements would indicate.by Anshul Singhal.S.M
A robust and novel regression based fuzzy time series algorithm for prediction of rice yield
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Mechanic Clues vs. Humanic Clues: Students’ Perception towards Service Quality of Fast Food Restaurants in Taylor's University Campus
No full textAbstractThe college student's market is expanding. Earlier research shows that the common wisdom that college students and fast food go together seems valid. These young adults had formed a substantial market for the fast food industry. Both Mechanic clues and Humanic clues will be used to test the influence on college students’ perception of the service quality of fast food restaurants. The objectives of this study were to gauge the college students’ perception towards fast food restaurant and to determine whether Mechanic clues or Humanic clues have more impact on the perception of college student as service experience which influences the customers’ perception is affected by Mechanic clues and Humanic clues; it effected the emotional perceptions of quality. Consequently, this leads to a quantitative research which examined the combined effects of the physical environment (Mechanic clues) and the behaviour of employees (Humanic clues)
Adoption of software-defined cloud by companies
No full textThe overarching purpose of this research is to explore how Software Defined Cloud (hereafter “SDC”) impacts data innovation or information technology service providers. Additionally, this research considers the qualitative factors to transitioning from traditional to software defined cloud service provision, its configuration and how it can transform cloud. SDC is a cutting edge proposition which will be at the forefront of technology adoption in 2019. Whilst the application of SDC to cloud is in its nascent phases, already it is deemed to be of particular significance within academic literature and by leading industry experts.
This research will be of interest to the academic community, IT managers, IT technicians, cloud architects and industry experts. Deploying semi structured interview to explore the perceptions of industry experts from Irish Data Centres this research finds that the main barriers to adoption are cost and requirement or need SDC. As SDC is considered as big technological setups, not all businesses can afford or find the need to have such big setups installed. The findings of the research are (i) experiences regarding SDC from a cloud supply-side point of view (ii) benefits that the endeavours procure and (iii) eventual fate of this framework when adopted by ventures. The contribution to academic knowledge is distinctly in regards to transition from traditional to software defined cloud service provision, its configuration and how it can transform cloud. Whereas, the contribution to industry is by providing an overview on the working, general design and architecture of software defined cloud, its virtualised network and various other concepts like software defined environment
The finite element based study on active attenuation of structural vibration using porous ferroelectric ceramics
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