105 research outputs found
Experimental Enhancement of Heat Transfer Analysis on Heat Pipe using SiO2 and TiO2 Nano Fluid
No full textThis paper describes the enhancement of thermal performance of heat pipe using SiO2 and TiO2 nano fliuds. The experimentation explains about the effects of heat pipe inclination and heat input on the thermal efficiency and thermal resistance. Heat pipe is an advance type of heat exchanger which transfers huge amount of heat due to the effect of capillary action and phase change heat transfer principle. Recent developments in the heat pipe with high thermal conductivity through nano fluids. This paper reviews, influence of various factors such as heat pipe tilt angle, charged amount of working fluid, nanoparticles type, size, mass volume fraction and its effect on the improvement of thermal efficiency, heat transfer capacity and reduction in thermal resistance. The nano fluid preparation and the analysis of its thermal characteristics also have been reviewed. Arunkumar. G | Dr. P. Navaneetha Krishnan | Dr. T. Senthil Kumar "Experimental Enhancement of Heat Transfer Analysis on Heat Pipe using SiO2 and TiO2 Nano Fluid" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: https://www.ijtsrd.com/papers/ijtsrd13094.pd
Band engineering of metal oxide heterostructures for catalysis applications
No full textSupported metal oxides are used as catalysts for a wide variety of industrially and environmentally important reactions such as the selective oxidation of hydrocarbons and alcohols and the selective catalytic reduction of nitrogen oxides. The support often plays an important role in the activity and selectivity of such catalysts, beyond just the provision of mechanical support and large surface area. V2O5 supported on TiO2 is an example of a catalyst that is widely used, where the synergy between the support and the overlayer is taken advantage of. The support effect has often been ascribed to the electronegativity of the support cation which affects the electron density on the metal–oxygen bond in the overlayer. However, this effect may not hold for thicker overlayers and for doped supports.
In the current work, a model is proposed in which the supported catalyst is considered as a heterostructure. Most metal oxides are (wide band-gap) semiconductors and hence a semiconductor heterojunction is formed when one oxide is deposited on another. This conception of supported oxide catalysts allows for the use of heterojunction physics to predict the electron richness at the surface of the catalyst. Moreover, effect of overlayer thickness and support doping can be easily determined using such a model. Thus quantitative estimates of surface electron richness were obtained for the system of V2O5/TiO2. It is shown that modification of overlayer thickness and the carrier concentration in the support can lead to modification of the surface electron richness (represented by the surface Fermi level) of the catalyst. A semi-empirical model was also developed to relate the Fermi level of oxide catalysts to their activity. Using these models, the quantitative variation of catalytic activity with the heterostructure parameters (overlayer thickness, support carrier concentration) was determined, for the test reaction of partial oxidation of methanol to formaldehyde.
Results from experiments using thin films of polycrystalline oxides (V2O5 supported on TiO2) and methanol oxidation as the test reaction, matched qualitatively with the model predictions. The quantitative enhancement (> 10x) in rate obtained by reducing the overlayer thickness was better than the model predictions. Surface potential measurements combined with kinetic data proved the validity of the model relating Fermi level and catalytic activity, and showed directions for further development of the heterojunction model to predict the surface electron richness.Item withdrawn by Mark Zulauf ([email protected]) on 2012-10-02T14:34:59Z
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An immersed boundary method based on domain decomposition
No full textA novel immersed boundary method based on a domain decomposition approach is proposed in the context of a finite element discretisation method. It is applicable to incompressible flows past rigid, deforming, or moving bodies. In this method, unlike most immersed boundary methods, strong boundary conditions are imposed in the regions of the computational domain that are occupied by the structure. In order to achieve this, the proposed formulation decomposes the computational domain by splitting the finite element test functions into solid and fluid parts. In the continuous Galerkin formulation, this produces a smeared representation of the fluid-structure interface. The absence of an immersed boundary forcing term implies that the method itself has no influence on the CFL stability criterion. Furthermore, the stiffness matrix in the momentum equation is sparser than compared with other forcing immersed boundary methods, and symmetry and positive-definiteness of the Laplacian operator in the pressure equation is preserved. As shown in this paper, stability and accurate imposition of boundary conditions make the method promising for high Reynolds number flows. The method is applied to the simulations of two-dimensional laminar flow over stationary and moving cylinders, as well as a moderately high Reynolds number flow past an aerofoil. Good results are obtained when compared with those from previous experimental and numerical studies.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Wind Energ
Study of a passive pitching rotor using blade element momentum theory coupled to a rigid-body model
No full textMisaligned wind turbine rotors experience uneven loads because of two effects: dissymmetry of lift, and skewed wake effect. Rotor-crafts that have a similar problem introduce various mechanisms to combat this - one of them is to add a δ3-hinge. The hinge provides the blade with an additional degree of freedom to relieve the unbalanced loads; in theory, it is a self-correcting mechanism. In this work, we couple a blade element momentum (BEM) approach for the aerodynamics to a rigid-body model that simulates the hinge rotation. The results from BEM are used to identify the working mechanisms of the hinged rotor and highlight the strengths and weaknesses of such a rotor. Wind Energ
USING THE FROG EPIDERMIS TO UNCOVER DESMOSOME FUNCTION AND REGULATION IN THE DEVELOPING EMBRYO
No full textThe desmosome is one of the major cell adhesion junctions found in the epithelia, heart, and hair follicle. Described as a “rivet” that hold cells together, it provides these tissues with the integrity to withstand the tremendous forces they face in everyday life. Defects in this junction can lead to devastating diseases where patients are susceptible to skin infections and cardiovascular defects. Limited treatments exist for diseases of the desmosome, and strategies do not target all symptoms. Therefore, delineating the function and regulation of desmosomes is of paramount importance for the development of prevention and treatment strategies. The Xenopus laevis has been utilized for the study of embryonic development and tissue movements. This study takes advantage of the frog model to study a key desmosomal protein, desmoplakin (Dsp), in the epidermal development of the embryo. First, Xenopus embryonic epidermis has junctional desmosomes as early as the blastula stages. Desmosomes numbers per junction increase as the embryo develops. Dsp is present in many epidermally-derived structures in the embryo at varying levels. Xenopus embryos deficient in desmoplakin have phenotypic defects in epidermal structures and the heart, mimicking mammalian models. Embryos with reduced Dsp exhibit an increased susceptibility to epidermal damage under applied mechanical forces. Assays also reveal a potential role for desmosomes in radial intercalation, a process through which cells move from the inner to the outer epidermal layers. Embryos with reduced Dsp exhibit a slight reduction in intercalation and defects in intercalating cell types, including multiciliated cells and small secretory cells. Finally, c-Jun N-terminal kinase (JNK) may have a potential role in the regulation of desmosome assembly and adhesion. Embryos with deficient Dsp display a partial recovery of mechanical integrity when treated with a JNK inhibitor
A Study to Assess the Impact of Parental and Peer relationship on School Performance of Adolescents in a Selected School at Madurai, Tamilnadu
No full textA study to assess the impact of parental and peer relationship on school performance of adolescents in a selected school at Madurai, Tamilnadu, was conducted in partial fulfillment of the requirement for award of degree of master of science in nursing under the Tamilnadu Dr.M.G.R. Medical university, Chennai.
OBJECTIVES:
1. To assess the parental relationship among adolescents.
2. To assess the peer relationship among adolescents.
3. To assess the school performance among adolescents.
4. To assess the inter relation between parent relationship, peer relationship and school performance among adolescents.
5. To find out the association between parent relationship, school performance and selected demographic variables such as age, gender, religion, type of family, no of siblings, birth order, father education, father occupation, mother occupation, mother education, family income, more attached to, most time spent with, quality time spent with parents.
HYPOTHESIS:
H1: There will be a significant interrelationship between parental relationship, peer relationship, and school performance of adolescent’s.
H2: There will be a significant association between parent
relationship, peer relationship and school performance with
selected demographic variables such as age, gender, religion, type of family, no of siblings, birth order, father education, father occupation, mother occupation, mother education, family income, more attached to, most time spent with, quality time spent with parents and if single parents, the partners.
RECOMMENDATIONS:
1. This study can be replicated with larger samples.
2. Studies regarding the parent perception about the adolescents' relationship could be done.
3. The comparative study can be conducted in different schools, and different medium of instructions.
4. In-depth studies can be carried out to identify the factors that affect the parental relationship, peer relationship and school performance.
5. This study can be replicated in large sample including the sample from an entire adolescence period as a longitudinal study.
MAJOR FINDINGS OF THE STUDY:
❖ With regard to age, majority (51%) were in the age group of 14 years, (41%) samples were in 15 years, (6%) were in 16 years and (3%) belongs to the age group of 13 years.
❖ Regarding gender, majority (62%) were males and (38%) were Females.
❖ About religion, by large (74%) were hindus, (10%) were muslim, (12.5%) were christian and the rest of (3.3%) were belongs to other religions.
❖ Moving to the family type, (73%) were living in a joint family, (21%) were living in a nuclear family and (6%) were in a extended family type.
❖ About siblings, majority (65%) of family had two child, ,( 28%) of family had one child and remaining (8%) of family had three children's.
❖ With regarding to birth order, majority (55%) of the samples were second child, (39%) were eldest child and (6%) were third child.
❖ In regard education, large (42%) of fathers had primary education, (39%) were illiterates, (10%) had higher secondary school education and (9%) were graduates.
❖ About father occupation, majority (57%) were working as a private employee, (28%) were self employed, (12.5%) were
government employees and remaining (3%) were coolie worker.
❖ Regarding mother occupation, (43%) were self employed, (38%) were home makers, (10%) were working private concern, (7.5%) were government employee and remaining (2%) were coolie workers. Regarding mother occupation 51 [42.5%] majority was self employment.
❖ About mother’s education, (58%) of mother had primary
education, (34%) had higher secondary education, (4%) were
illiterates and remaining (4%) were graduates.
❖ Moving to family income, majority (61%) of family falls under the financial income between Rs.5001 to 7000 per month,(34%) has income of Rs.7001 and above and (6%) has income between Rs.3001 – 5000 per month.
❖ Among 120 samples, majority (52%) were more attached to the mother, (32%) were attached to the friend,(16%) were more attached to the father and remaining (1%) towards the siblings.
❖ Majority (64%) adolescents spent most of their time with mother, (23%) spent their time with friends,(12%) spent their time with father and remaining (1%) spent time with siblings.
❖ Fifty one percent of adolescents occasionally spent the time with parents, (33%) weekly once spent the time with parents.
❖ Majority 84(70%) of the adolescents has moderately favorable relationship, 20(16.6%) has unfavorable relationship and 16 (13.3%) has favorable relationship. In mother relationship, majority 69 (57.5%) of the adolescents has moderately favorable relationship, 26 (21.6%) has favorable relationship and 25 (20.8%) has unfavorable relationship with mother.
❖ With regard, majority 79 (65.8%) of the adolescents had
moderately favorable relationship, 21 (17.5%) had unfavorable relationship and 20 (16.6%) had favorable relationship with peer.
❖ Majority 83(69.2%) of the adolescents had above average in school performance, 30(25.0%) had average and 7 (5.8%) had below average in school performance.
❖ Majority 83 (69.2%) of the adolescents were having above average in school performance, 30 (25.0%) were having average and 7 (5.8%) were having below average in school performance among 120 samples.
❖ There was a negative correlation between the relationship with father, mother relationship and peer relationship.
❖ There was a positive correlation between the relationship with mother, peer relationship and school performance.
❖ There was a positive correlation between the peer relationship and school performance.
❖ There is a significant association between the mother relationship and demographic variable such as father education.
❖ There was a significant association between the school
performance and demographic variable such as gender and father's occupation.
CONCLUSION:
This study has shown that interrelated the parental relationship, peer relationship and school performance are interrelated and essential for adolescent health. Adolescent having trouble in any of these areas may develop problems in other areas also. Adolescents who are positively attached with their mother and peer could be perform better in the school also. Therefore, the nursing interventions aimed at promoting adolescent mental health should target these areas
Mapping the (un)known: Spatially-driven Frameworks for characterization of Disease Heterogeneity
No full textIn recent years, novel treatment approaches such as immunotherapy, where we boost an individual's immune system for better cancer targeting, are being increasingly trialed and adopted for various cancer pathologies. However, immune system function response is highly variable, especially in cancers such as Pancreatic Ductal Adenocarcinoma(PDAC), with many patients either not responding or suffering from adverse effects. Recent work has highlighted the importance of spatial quantification of tumor and immune cell subtypes to provide insights into treatment prognosis. My proposed work involves leveraging machine learning and spatial statistical methods to build frameworks that better characterize the (un)known tumor microenvironment, utilizing the inherent spatial structure extracted from imaging data. We validate these frameworks using commonly accessible histopathological imaging data such as hematoxylin and eosin(H&E)-stained whole slide images and multiplexed immunofluorescence(mIF) images.
For this purpose, I explore three distinct methodological approaches to quantify tumor-immune interactions in a patient cohort consisting of 6 different pancreatic diseases, including PDAC. In the first approach, I utilize the concepts of geographically weighted regression (GWR) and a density function-based classification model to compute a spatially salient construction that can discriminate the six classes of lesions. This framework, GaWRDenMap, showed significant discriminant ability in multiple pairwise comparisons compared to abundance-based metrics, like the Morisita-Horn index. Our framework was able to highly discriminate between PDAC and non-cancerous chronic pancreatitis(CP), which is challenging for pathologists to discern based on the arrangement and structure of the cells under the microscope.
Next, I repurpose an existing discriminative feature-based dictionary learning method to identify sub-regions of the tumor microenvironment representative of the disease. Initial results on mIF images from CP and PDAC patients from the same pancreatic cohort point to the excellent discriminant capabilities of the model while providing a visually interpretable dictionary output representative of the given cohort.
Finally, I propose a novel cell-graph-based Cell-Graph ATtention (CGAT) network for precisely classifying PDAC and its precursor lesions only utilizing available spatial and phenotypic information as input features. The self-attention mechanism facilitates the identification of tissue regions and novel cell-cell interaction patterns characteristic of the disease.
The proposed methods move away from single-number summaries by providing a more comprehensive representation of the state of the microenvironment. This thesis lays the groundwork for adopting these tools into not just exploratory biological research but also as diagnostic tools in the clinical setting
Out of Equilibrium: Modelling and Simulating Traverse
No full textManaging disequilibrium and its consequent traverse is one of the important topics in economic theory. During such traverse, the evolving economic system faces various imbalances and coordination problems that arise within and outside the sys-tem. In order to traverse the disequilibrium, the economic system should innovate, create, and manage its resources in a viable manner. This dissertation reports stud-ies in modelling ‘disequilibrium traverse economies’, in the sense of Hicksian Neo-Austrian, Time-to-Build, theory. In the first chapter, we discuss the origins of traverse analysis and the role of ‘time-to-build’ framework in modelling macro-dynamics. We also provide a review of the literature concerning ‘time-to-build’ tradition in modelling traverse and business cycles. Then, we discuss in detail how this framework actually enters into these models and the assumptions that underpin them. In the second chapter, we provide an overview of different notions of viability, which are widely used in economic literature, and formulate viability conditions for Amendola and Gaffard’s Neo-Austrian model. We then simulate the model, with and without the viability conditions, to study the dynamics of the evolving system. The main aim of this chapter is to explore and analyse the importance of viability creating mechanisms during dynamic traverse.
In chapter three, we analyse some of the classics in business cycle theory and how the ‘time-to-build’ framework plays an important role in modelling economic fluctuations. The contribution of this chapter is to provide insights on various as-sumptions and the choice of mathematical formalisms that underpin these business cycle models. In conclusion, we also suggest that the Neo-Austrian tradition should be placed as a part of the rich tradition of business cycle theory. In the fourth chapter, we take the ‘time-to-build’ model and improve the framework by endogenizing one of the main engines of growth, i.e., innovations, in a non-stochastic, non ad-hoc, manner. We model innovations using Turing Machine metaphor, so that we can encapsulate the intrinsic uncertainties of Research and Development processes in an insightful way. The enhanced ‘time-to-build’ model thus developed is then simulated for various policy parameters, such as - R&D policies, interest rates, and bankruptcy policies, and the resulting traverses are studied. In the last chapter, we provide a comprehen-sive summary of the novel contributions of the dissertation and list some of the future research paths that can be traversed
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Supramolecular Solar Cells
No full textSupramolecular chemistry - chemistry of non-covalent bonds including different type of intermolecular interactions viz., ion-pairing, ion-dipole, dipole-dipole, hydrogen bonding, cation-p and Van der Waals forces. Applications based on supramolecular concepts for developing catalysts, molecular wires, rectifiers, photochemical sensors have been evolved during recent years. Mimicking natural photosynthesis to build energy harvesting devices has become important for generating energy and solar fuels that could be stored for future use. In this dissertation, supramolecular chemistry is being explored for creating light energy harvesting devices. Photosensitization of semiconductor metal oxide nanoparticles, such as titanium dioxide (TiO2) and tin oxide (SnO2,), via host-guest binding approach has been explored. In the first part, self-assembly of different porphyrin macrocyclic compounds on TiO2 layer using axial coordination approach is explored. Supramolecular dye sensitized solar cells built based on this approach exhibited Incident Photon Conversion Efficiency (IPCE) of 36% for a porphyrin-ferrocene dyad. In the second part, surface modification of SnO2 with water soluble porphyrins and phthalocyanine resulted in successful self-assembly of dimers on SnO2 surface. IPCE more than 50% from 400 - 700 nm is achieved for the supramolecular self-assembled heterodimer photocells is achieved. In summary, the axial ligation and ion-pairing method used as supramolecular tools to build photocells, exhibited highest quantum efficiency of light energy conversion with panchromatic spectral coverage. The reported findings could be applied to create interacting molecular systems for next generation of efficient solar energy harvesting devices
Theoretical and Experimental Investigation of Phonon Boundary Scattering in Thin Silicon Membranes
No full textThe thermal transport properties of thin semiconductor membranes play an important role in the performance of many technologies like micro-electronics and solid-state energy conversion. The dominant resistance to heat flow in thin membranes is offered by the scattering of thermal phonons at the membrane boundaries. In this dissertation, we examine the nature of microscopic phonon boundary scattering processes and their effect on the thermal conductivity of the thin membranes using a pump-probe experimental technique and computationally efficient solutions of the phonon Boltzmann transport equation (BTE).
First, we investigate the boundary scattering-limited thermal transport in nanostructures using an efficient variance-reduced Monte Carlo (MC) solution of the BTE to elucidate the impact of specular and diffuse phonon boundary scattering events on the thermal conductivity of the nanostructures. To directly measure the relative frequency of these two boundary scattering events, called the phonon specularity parameter, we design, implement and characterize a non-contact laser-based pump-probe experiment called the transient grating (TG) to perform phonon mode-dependent measurements of the specularity parameter in suspended free-standing thin silicon membranes. We describe the phenomenon of quasiballistic heat conduction, which enables the phonon mode-dependent measurements of the specularity parameter, and derive a transfer function based on the BTE with ab-initio phonon properties as inputs, to connect the specularity parameter with the experimentally measured thermal conductivity of the thin membranes.
Finally, we present the methodology adopted to invert the BTE transfer function to extract the phonon specularity parameter from the thermal conductivity measurements in the TG experiment, while rigorously accounting for the experimental uncertainties. We find that the observed magnitudes and trends of the thermal conductivity of the thin membranes cannot be explained by the 50-year old Ziman's model for the phonon specularity parameter and the Fuchs-Sondheimer theory of phonon boundary scattering. We also find that the partially specular boundary scattering picture of phonon boundary interactions works well for one of the membranes, enabling a direct measurement of the mode-dependent phonon specularity parameter for the first time in an experiment. We discuss the possibility of phonon mode conversion at the boundaries of a few membranes for which the partially specular phonon boundary scattering picture fails to explain the observed thermal conductivity trends. Considering the importance of understanding phonon boundary scattering to engineer and improve nanoscale device performance, we expect that the new experimental and computational tools developed in this work will advance a variety of nanoscale energy applications and further our understanding of nanoscale heat transport.</p
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