506 research outputs found
Self-assembled strained nanostructures for light emission grown using molecular beam epitaxy
Get PDFIII-V nanostructures are widely researched for applications in dislocation-resistant light emitters for photonic integrated circuits, quantum computing and single photon emitters. The 0D nanostructures include quantum dots (QDs), dot in a well (DWELLs), sub-monolayer QDs and droplet epitaxy QDs, while 1D elongated structures include quantum dashes and nanowires (NWs). The optical properties of nanostructures can be controlled through size, composition, strain and band-offsets during epitaxial growth and can be tailored precisely to emit light with photon energies suited to the application, spanning 0.2-2.0 eV. This thesis explores two novel QD based light emitters in the visible and near-infrared wavelength regime. In the first part of the thesis, we demonstrate the growth and characterization of tensile strained Ge QDs and Ge NWs phase segregated in the III-V matrix via Volmer-Weber growth mode emitting at 1200 nm. The second part of the thesis demonstrates the dislocation tolerance of compressively strained InP QDs grown on lattice-matched GaAs and lattice-mismatched Si substrate via Stranski-Krastanov growth mode emitting at 713 nm.
The first part of the thesis explores the growth of tensile strained Ge QDs and NWs phase segregated in the III-V matrix. Epitaxial growth of phase segregated Ge nanostructures embedded within III-V compound semiconductors is a promising way to achieve a high biaxial tensile strain along with precise control of nanostructure density, size and morphology. Here we demonstrate growth of phase-segregated Ge quantum dots (QDs) and compare them to our previously reported Ge nanowires (NWs); both are strained to an In0.52Al0.48As matrix with a high biaxial tensile strain of 3.6%. Despite the similar growth conditions, there exist pronounced differences in the lateral size and planar density of Ge QDs and Ge NWs, with Ge QDs showing significantly larger size, lower density and structural anisotropy along the in-plane [1-10] direction. In addition to the difference in morphology, Ge QDs are shown to be more prone to plastic relaxation by formation of dislocations and stacking faults, which we attribute to their larger in-plane size. Finally, tensile Ge QDs are shown to exhibit strong room-temperature photoluminescence at 1176 nm, which is blueshifted from the case of Ge NWs.
In the second part of the thesis, we demonstrate epitaxial InP QDs on GaAs on Si virtual substrates with room-temperature photoluminescence (PL) intensity nearly identical to those grown on GaAs substrates. The similarity in PL characteristics is remarkable considering that the active region on the GaAs/Si virtual substrate has a threading dislocation density (TDD) of ~3×10^7 cm-2, as compared to the bulk GaAs substrate with TDD 50× improvement in the luminescence intensity of InP QDs annealed at ~700⁰C for 100 minutes without observable structural degradation or blue-shift in the PL spectrum.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-05-01The student, Pankul Dhingra, accepted the attached license on 2019-04-25 at 12:06.The student, Pankul Dhingra, submitted this Thesis for approval on 2019-04-25 at 12:16.This Thesis was approved for publication on 2019-04-25 at 14:10.DSpace SAF Submission Ingestion Package generated from Vireo submission #13914 on 2019-08-22 at 16:23:56Made available in DSpace on 2019-08-23T20:48:26Z (GMT). No. of bitstreams: 2
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Previous issue date: 2019-04-25Embargo set by: Seth Robbins for item 112387
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Foreign Direct Investment Inflows to India
No full text India, without exception, as in case of other developing countries, is eager to prompt its economic growth which compels it to accept and seek assistance of foreign direct investment (FDI). At present, it accounts for 1.25 per cent share of global FDI inflows, 7.18 per cent of Asian inflows and garners more than two third share of FDI inflows to the developing South Asia. Present study traces the history of FDI in India and reveals that actually FDI in India is an evolution since mid-eighteenth century and is an outcome of international and domestic dynamisms. It is not merely a phenomenon of post Independence or post liberalization period. Present study is an effort to examine the growth of FDI inflows to India and some selected representative countries of the developing Asia, through the computation of compound annual growth rates by fitting an exponential function estimated by ordinary least square method. It is detected that during the last three decades, the growth of FDI inflows remained highest in case of India followed by UAE, Turkey and China. What will happen in future is the function of what happened in the past. Believing this, the study has generated the forecasts of FDI inflows to the representative countries of Asia for the period 2009 to 2020, by using Double Exponential Smoothing Model. The adequacy of the model is tested by computing autocorrelation coefficients and Ljung-Box Q statistics. The study revealed that in the ensuing decade, out of all the countries of developing Asia, Saudi Arabia is expected to grow at the fastest pace as far as FDI inflows are concerned. In near future, although the magnitude of FDI inflows may remain highest in case of China but India is expected to leap forward swiftly and attract more than one seventh share of aggregate anticipated inflows to the developing Asia. </jats:p
Management of Meloidogyne incognita and Rotylenchulus reniformis in nursery-beds by soil solarization and organic soil amendment
No full textAccelerating (Compressed) SENSE Scans in MRI
No full textMagnetic Resonance Imaging is a painless procedure to produce high-resolution diagnostic images. Today, it is one of the essential clinical imaging modalities. One of the major challenges involved with this imaging modality is its long scanning time. Parallel imaging in combination with compressed sensing has overcome this challenge to a great extent. As a quid pro quo for this reduced scan time is the increase in image reconstruction time. An extensive research is focused to develop algorithms to make the image reconstruction faster. Fast Iterative Shrinkage Threshold algorithm is one of these algorithms (which is clinically viable) that speeds up the image reconstruction process. The present project focuses to speed up the particular algorithm, fast iterative shrinkage threshold algorithm, by preconditioning the convex optimization problem. This work proposes two new preconditioners, specifically in the context of the given algorithm, but otherwise can be used with different frameworks solving similar problems. The first preconditioner is a degree one polynomial of the system matrix and the second preconditioner is a block diagonal matrix where each block is a circulant matrix. The preconditioners are evaluated using two stopping criteria: residual error and relative error. The computation complexity of both the preconditioners are evaluated by measuring the floating point operations and total time consumption. Additionally, the simulations are performed by undersampling the data at two factors r=2 and r=4. The results indicate that the polynomial preconditioner reduces the overall time by a factor of 0.25 however is computationally expensive to construct. On the other side, block diagonal circulant preconditioner is extremely cheap to construct and evaluate on a vector but does not provide the desired results within the current framework. The study concludes that a suitable preconditioner for FISTA is the one that without affecting the largest eigenvalue of the system matrix improves the condition number and simultaneously is cheap to construct and evaluate.Electrical Engineerin
Understanding Non-Photochemical Laser Induced Nucleation
No full textNucleation is the initial step for the creation of new crystalline phase. A precise control over nucleation and its kinetics is important for both research and industries. Thus, alternative methods are sought after to extend the toolbox for controlling nucleation. In the 1990's, Non-Photochemical Laser Induced Nucleation (NPLIN) was suggested as a promising method to alter the nucleation kinetics. Since then, several reports have demonstrated that NPLIN dramatically reduces the nucleation induction time and controls polymorphism of various fine chemicals relevant for industrial practice. Although different hypotheses have been proposed in literature to explain the experimental observations, the mechanism behind NPLIN is still unknown.The objective of this work is to extend the mechanistic understanding of NPLIN. This has been approached by qualitatively studying the effect of different factors on the nucleation efficiency of the non-photochemical process using unfocused pulsed laser in aqueous supersaturated solution of KCl. The factors investigated include wavelength, peak intensity, supersaturation, mixing, and impurity level of the solution. Each of these parameters are studied using high number of samples (80-100) to generate a robust set of results and to avoid the stochastic nature of nucleation.In a separate series of experiments, an acoustic wave was detected in the solution due to the non-linear interaction of the unfocused laser with the system by measuring the pressure signal with a piezo-electric transducer placed just below the air-liquid interface. Further experiments were executed to understand the nature of the acoustic wave and its influence on NPLIN. The results show that laser could induce nucleation at significantly low peak intensities, much below the previously reported intensity threshold in literature. It is also observed that NPLIN shows a strong dependence on peak intensity, supersaturation, impurity level, and mixing of the solution while the dependence on wavelength was found to be weak. Furthermore, the acoustic wave experiments show that the laser induced pressure fluctuations do not affect the nucleation efficiency of the process. Overall, the results suggest that several mechanisms play a role during laser induced nucleation. To summarize, the research provides a robust analysis of different factors that can influence NPLIN. The results can be further utilized to enhance the understanding and applicability of the process
Evaluation of Centre of Gravity of Four Wheeled Trailer
No full textA four-wheeled trailer with flat platform was designed for fabrication of mobile agro-processing unit. The size of the trailer is 4270 mm x 2135 mm and its wheelbase is 263Omm. The location of the centre of gravity in longitudinal, transverse and vertical direction was determined by weighing method I technique. The total weight and the reaction on rear wheels were measured using a weighbridge. These reactions were used to locate the centre of gravity in longitudinal and transverse directions. The rear wheels were lifted and the net reaction on them was measured. The amount of weight transferred to the front wheels is dependent on the height of the centre of gravity. This concept was used to locate the height of the plane-containing centre of gravity. The centre of gravity was located with reference to the plane containing the wheel axles. It was observed to be 1139 mm behind front wheel axle, 618 mm above the wheel axles and midway (perpendicular to the axles) between the wheels
Influence of protein's molecular weight and polymer's PEG content on protein release from polymeric implants
No full textDe begeleider en/of auteur heeft geen toestemming gegeven tot het openbaar maken van de scriptie.
The supervisor and/or the author did not authorize public publication of the thesis.
Development of Millets and Wheat Based Diabetic Foods
No full textThis Dissertation / Report is the outcome of investigation carried out by the creator(s) / author(s) at the department/division of Central Food Technological Research Institute (CFTRI), Mysore mentioned below in this page
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