161 research outputs found
Fabrication of a Flexible UV Band-Pass Filter Using Surface Plasmon Metal-Polymer Nanocomposite Films for Promising Laser Applications
No full textWe introduce a strategy for the fabrication of silver/polycarbonate (Ag/PC) nanocomposite flexible films of (20 +/- 0.01) mu m thickness with different filling factor of surface plasmon metal using customized solution cast thermal evaporation method. Structural characterizations confirmed the good crystallinity with cubic phase of Ag nanoparticles in PC films. Moreover, the microstructural evolutions of nanocomposite films are investigated by transmission electron microscopy, which indicates that the metal fraction is in the form of fractals. Additionally, the surface plasmonic behavior of nanocomposite films has been explored in detail to examine the distribution of Ag nanoparticles in PC film by spectroscopic technique. Furthermore, the obtained transmittance spectral features of this nanocomposite film are suitable for the applications of band-pass filter at 320 nm UV range, which is highly desirable for a HeCd laser
Performance assessment of vegetable oil based cutting fluids with extreme pressure additive in machining
No full textThe present work focuses on the experimental evaluation of the performance of vegetable
oil based cutting fluids (coconut, canola and sesame oils) with extreme pressure (EP) additive in
machining. Cutting fluids are prepared with three different base oils at three different percentages of
EP additives. Performance of these cutting fluids is assessed by measuring cutting forces, cutting tool
temperature, tool flank wear and surface roughness in turning AISI 1040 steel with coated carbide tool.
Experiments are conducted initially at constant cutting conditions with 5% EP additive in vegetable
oils in order to compare their performance with conventional cutting fluid prepared from soluble oil.
Further evaluation is done by varying percentage of EP additive and cutting conditions as well. The
results indicated that 10% EP additive included in coconut oil based cutting fluid performed better
compared to other vegetable oils and other percentages of EP additive
Multi response optimization for turning aisi 1040 steel with extreme pressure additive Included vegetable oil based cutting fluids using grey relational analysis
No full textThe present work focuses on finding the optimal machining parameters in turning AISI 1040
steel with multiple performance characteristics using Grey-based Taguchi method. The multi-response
problem is converted into an equivalent single-response problem using Grey Relational Analysis
(GRA). A Grey grade obtained from GRA is analysed to get optimal machining parameters using the
Grey grade as the performance index. The performance characteristics selected in this work are cutting
force, cutting tool temperature, tool flank wear and surface roughness. These performance
characteristics are analysed to obtain the optimal machining parameters for type of vegetable oil based
cutting fluid, proportion of extreme pressure (EP) additive, cutting speed and feed. The results reveal
that type of vegetable based cutting fluid is found to be the major factor along with feed, proportion of
EP additive and cutting speed that influences the multiple performance characteristics
A three parameter hyper-Poisson distribution and some of its properties
No full textA new class of distribution is introduced here as a generalization of the well-known hyper-Poisson distribution of Bardwell and Crow (J. Amer. Statist. Associ., 1964) and alternative hyper-Poisson distribution of Kumar and Nair (Statistica, 2012), and derive some of its important aspects such as mean, variance, expressions for its raw moments, factorial moments, probability generating function and recursion formulae for its probabilities, raw moments and factorial moments. The estimation of the parameters of the distribution by various methods are considered and illustrated using some real life data sets. Further, a test procedure is suggested for testing the significance of the additional parameter and a simulation study is carried out for comparing the performance of the estimators
Variations in surface ozone at Nainital : a high-altitude site in the central Himalayas
Get PDFSurface ozone measurements have been made for the first time at Nainital (29.37 degrees N, 79.45 degrees E, 1958 m amsl), a high-altitude site in the central Himalayas, between October 2006 and December 2008. Diurnal variations in ozone do not show the daytime photochemical build-up typical of urban or rural sites. The seasonal variation shows a distinct ozone maximum in late spring (May; 67.2 +/- 14.2 ppbv) with values sometimes exceeding 100 ppbv and a minimum in the summer/monsoon season (August; 24.9 +/- 8.4 ppbv). Springtime ozone values in the central Himalayas are significantly higher than those at another high-altitude site (Mt. Abu) in the western part of India. Seasonal variations in ozone and the processes responsible for the springtime peak are studied using meteorological parameters, insolation, spatial and temporal classifications of air mass trajectories, fire counts, and simulations with a chemical transport model. Net ozone production over the Northern Indian Subcontinent in regionally polluted air masses is estimated to be 3.2 ppbv/day in spring but no clear build-up is seen at other times of year. Annual average ozone values in regionally polluted air masses (47.1 +/- 16.7 ppbv) and on high insolation days (46.8 +/- 17.3 ppbv) are similar. Background ozone levels are estimated to be 30-35 ppbv. Regional pollution is shown to have maximum contribution (16.5 ppbv) to ozone levels during May-June and is about 7 ppbv on an annual basis, while the contribution of long-range transport is greatest during January-March (8-11 ppbv). The modeled stratospheric ozone contribution is 2-16 ppbv. Both the trajectory analysis and the model suggest that the stratospheric contribution is 4-6 ppbv greater than the contribution from regional pollution. Differences in the seasonal variation of ozone over high-altitude sites in the central Himalayas (Nainital) and western India (Mt. Abu) suggest diverse regional emission sources in India and highlight the large spatial and temporal variability in ozone over the Indian region
High-Order Numerical Schemes for Compressible Flows
No full textHigh-order numerical methods for Computational Fluid Dynamics have undergone significant fundamental developments over the last two decades owing to combined efforts from the applied mathematics and engineering communities. Even though low-order numerical methods are still the standard in industry, the increased requirements of engineering applications have led to significant scientific interest in developing efficient and robust numerical methods. Applications that would benefit from high-order numerical methods include Direct Numerical Simulations (DNS), Large Eddy simulations (LES), Computational Aero-Acoustics (CAA) and vortex dominated flows. The objective of this thesis is to successfully implement and validate a fifth order traditional WENO scheme in a finite volume framework, for a solver currently being developed in the Aerodynamics group of TU Delft. A detailed literature study of classical numerical schemes has been performed along with a study of the traditional WENO schemes. The quality of results using the fifth order scheme is studied for a variety of test cases to study the shock capturing ability of the scheme. Implementing the finite volume WENO schemes includes the calculation of numerical flux at cell faces using Gaussian quadrature formulas. The effect of varying the number of Gaussian quadrature points while calculating the numerical flux is investigated. Also, the effect of the approximate Riemann solvers on the quality of results is studied by implementing four different Riemann solvers and studying the results for different test cases using these Riemann solvers. The test cases are governed by the inviscid Euler equations and deals with flow in the compressible regime. They involve shocks, other discontinuities and often also complicated structures in the smooth part of the solution which tests the design of the schemes to be non-oscillatory at the discontinuities and still gives a high order of accuracy in the smooth parts of the flow. Convergence tests of the error for test cases using the linear advection equation is used to study the order of accuracy of the scheme using different number of Gaussian quadrature points. The tests clearly show that the order of accuracy remains the same irrespective of the number of quadrature points used. This result is important as it allows simulation run with just one quadrature point which is less expensive, and saves memory. This result is highly relevant while running test cases for LES where very fine grids have to be used. WENO schemes have been considered to be too dissipative for LES in their traditional form. This is indeed true as seen by Kelvin-Helmholtz type small scale vortices (which are characteristic of high Reynolds number flows), even in the test cases using the inviscid Euler equations, due to the inherent dissipation in the schemes. However, this could be seen as motivation for using the WENO schemes for Implicit LES where no explicit sub-grid scale models are used to represent the unresolved scales. The different Riemann solvers exhibit different levels of dissipation and recommendations are made for the choice of Riemann solvers according to the application.Aerospace EngineeringFlight Performance and Propulsio
Association between Serum Prolactin Levels and Adverse Cardiovascular Events in Chronic Kidney Disease Patients
Get PDFBACKGROUND:
Chronic kidney disease is defined as progressive loss in renal function over a period of months or years leading to failure of excretory, metabolic, synthetic functions resulting in accumulation of non protein nitrogenous substances and present with various numbers of clinical manifestations. Prolactin (PRL) is an anterior pituitary hormone. PRL clearance is evidently reduced in CKD patients and its production is also to an extent altered. Increased level of serum prolactin is in turn associated with essential hypertension, acute component of coronary syndrome, stroke ischemic variety and also in preeclampsia. Elevated levels of serum prolactin which occurs in CKD can also contribute to vascular dearrangements. This might lead to cardiovascular outcomes among CKD patients.
OBJECTIVE:
To study the correlation between serum prolactin level and the adverse cardiovascular events in Chronic Kidney Disease (CKD) patients.
To identify the association between elevated serum prolactin level and carotid intima media thickness (CIMT) in CKD patients
To determine its prognostic outcome
MATERIALS AND METHODS:
It was a prospective and analytical study of 50 patients admitted in our hospital with CKD and its complications. The study period was from Feb 2018 to Feb 2019 after informed consent patients were evaluated with laboratory investigations, clinical examination.
INCLUSION CRITERIA:
1) Age: 35-65 years,
2) Either sex,
3) Known CKD Patients with elevated blood urea creatinine and decreased creatinine clearance,
4) USG evidence of CKD.
(1) Bilateral contracted kidney size <8cm in males and <7cm in females,
(2) Poor cortico medullary differentiation,
(3) Type 2 or type 3 renal parenchymal changes.
EXCLUSION CRITERIA:
1. Patient refusal,
2. Chronic liver disease,
3. Seizure disorder,
4. Thyroid disease patients,
5. Pregnancy,
6. Congenital heart disease, RHD, IF Patients on medications - phenothiazines, haloperidol, TCA, reserpine
RESULT:
In our study among 50 patients with CKD, 28 had raised serum PRL level (about 56% of study population) and among those 28 patients 17 had raised CIMT (about 60.71%). By statistical analysis T test showed a strong correlation for hyperprolactinemia in CKD patients. Chi-square test showed a significant association between hyperprolactinemia and raised CIMT among patients with CKD. By statistical analysis we also found correlation between raised PRL level in CKD patients and T2DM, dyslipidemia and occurrence of CAHD among them.
CONCLUSION:
Serum prolactin levels are raised in patients with CKD. This hyperprolactinemia in CKD patients is associated with increase in the CIMT and occurrence of adverse cardiovascular events among them
Some applications in laser technology
No full textThe discovery of the Photoacoustic (PA) effect was a remarkable
achievement and was relegated to the scientific footnotes of the nineteenth
century. However, after the advent of lasers and sophisticated
electronics this effect was rediscovered and it has established itself
as an important research and analytical tool in numerous areas, including
physics, chemistry, biology and medicine. Quite recently, this phenomenon
has made its impact in the field of laser technology for applications
such as the developments of highly efficient active media for
lasers, high quality optics and sensitive laser power monitoring devices.
This thesis presents the work carried out by the author in this field
during the past few years at the Department of Physics in Cochin University
of Science and Technology.
The studies discussed here are mostly based on the development
of a sensitive PA laser power meter and its various applications using
different laser systems available in the laboratory. This includes the
development of a current regulated CW C0 laser and its application
in material processing. The thesis contains seven chapters which by and large are self
contained with separate abstracts and references. The first chapter
which is divided into two parts presents an introduction to the PA effect
and its present status. Part A reviews the basic theory of laser and
gives a sum mary of various lasers and their applications. Part B presents
a brief description of PA effect and its suitability as a spectroscopic
tool followed by its applications to various branches of science and
technology.Cochin
University of Science and TechnologyDepartment of Physics, Cochin
University of Science and Technolog
Content based Video Retrieval using Improved Gray Level Co-Occurrence Matrix with Region-based Pre Convoluted Neural Network–RPCNN
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