10,351 research outputs found
Machining of Tungsten Heavy Alloy under Cryogenic Environment
AbstractThe machining of tungsten heavy alloy is very difficult as it has high strength and hardness, which requires special cutting tools and cutting process. Though carbide tools are extensively used in conventional cutting, these lead take high machining time and tool failures which cause to decrease in productivity. To overcome the above, special techniques are being practiced in machining of tungsten alloys, one such technique is machining under cryogenic environment. In this paper, liquid nitrogen is used as coolant in machining of tungsten heavy alloys, because it is cost effective, safe, non flammable and environmental friendly gas, in addition to that it cannot contaminate the work piece and no separate mechanism required for disposal. An experimental investigation has been carried out on machining of tungsten heavy alloys by the solid carbide cutting tools under cryogenic and conventional coolants. The material removal rate, surface integrity and cutting forces were studied for both the coolants. The chip morphology also measured for evaluation of shear stress and shear strain. The cryogenic coolant has enhanced the machinability of tungsten heavy alloys. It is observed that the material removal rate was three times higher in cryogenic cooling method when compared with conventional coolant method and the surface finish of the machined surfaces are extremely good and the magnitude of cutting forces are lesser in cryogenic coolant
(Anti)symmetric multivariate trigonometric functions and corresponding Fourier transforms
Four families of special functions, depending on n variables, are studied. We
call them symmetric and antisymmetric multivariate sine and cosine functions.
They are given as determinants or antideterminants of matrices, whose matrix
elements are sine or cosine functions of one variable each. These functions are
eigenfunctions of the Laplace operator, satisfying specific conditions at the
boundary of a certain domain F of the n-dimensional Euclidean space. Discrete
and continuous orthogonality on F of the functions within each family, allows
one to introduce symmetrized and antisymmetrized multivariate Fourier-like
transforms, involving the symmetric and antisymmetric multivariate sine and
cosine functions.Comment: 25 pages, no figures; LaTaX; corrected typo
Computer Literacy for Life Sciences: Helping the Digital-Era Biology Undergraduates Face Today's Research
Computer literacy plays a critical role in today's life sciences research. Without the ability to use computers to efficiently manipulate and analyze large amounts of data resulting from biological experiments and simulations, many of the pressing questions in the life sciences could not be answered. Today's undergraduates, despite the ubiquity of computers in their lives, seem to be largely unfamiliar with how computers are being used to pursue and answer such questions. This article describes an innovative undergraduate-level course, titled Computer Literacy for Life Sciences, that aims to teach students the basics of a computerized scientific research pursuit. The purpose of the course is for students to develop a hands-on working experience in using standard computer software tools as well as computer techniques and methodologies used in life sciences research. This paper provides a detailed description of the didactical tools and assessment methods used in and outside of the classroom as well as a discussion of the lessons learned during the first installment of the course taught at Emory University in fall semester 2009
Antibacterial and analgesic activity of leaves of Lantana camara
The leaves of the plant Lantana camara were extracted with different solvents and screened for their antibacterial and analgesic activities. The chloroform and methanolic extract of the plant Lantana camara has showed the presence of four alkaloid compounds each. Antibacterial activity was evaluated using MIC method against bacteria. The analgesic activity of different extracts of Lantana camara leaves is evaluated by Eddy’s hot plate method where the responses are jumping withdrawal of paws and licking of paws. This study demonstrates that leaf powder of Lantana camara has significant antibacterial and analgesic activities
Frequency-domain study of relaxation in a spin glass model for the structural glass transition
We have computed the time-dependent susceptibility for the finite-size
mean-field Random Orthogonal model (ROM). We find that for temperatures above
the mode-coupling temperature the imaginary part of the susceptibility
obeys the scaling forms proposed for glass-forming liquids.
Furthermore, as the temperature is lowered the peak frequency of
decreases following a Vogel-Fulcher law with a critical temperature remarkably
close to the known critical temperature where the configurational entropy
vanishes.Comment: 7 pages, 4 figures, epl LaTeX packag
Cosmic ray tables - Asymptotic directions, variational coefficients and cut-off rigidities IQSY instruction manual no. 10
Cosmic ray deflections in geomagnetic field, variational coefficients, and diurnal intensity variations - table
P02.179. Effects of an integrated yoga program on mood, perceived stress, quality of life and immune measures in HIV patients: a pilot study
Glassy transition and metastability in four-spin Ising model
Using Monte Carlo simulations we show that the three-dimensional Ising model
with four-spin (plaquette) interactions has some characteristic glassy
features. The model dynamically generates diverging energy barriers, which give
rise to slow dynamics at low temperature. Moreover, in a certain temperature
range the model possesses a metastable (supercooled liquid) phase, which is
presumably supported by certain entropy barriers. Although extremely strong,
metastability in our model is only a finite-size effect and sufficiently large
droplets of stable phase divert evolution of the system toward the stable
phase. Thus, the glassy transitions in this model is a dynamic transition,
preceded by a pronounced peak in the specific heat.Comment: extensively revised, with further simulations of metastability
properties, response to referees tactfully remove
Dynamics of Magnetized Bulk Viscous Strings in Brans-Dicke Gravity
We explore locally rotationally symmetric Bianchi I universe in Brans-Dicke
gravity with self-interacting potential by using charged viscous cosmological
string fluid. We use a relationship between the shear and expansion scalars and
also take the power law for scalar field as well as self-interacting potential.
It is found that the resulting universe model maintains its anisotropic nature
at all times due to the proportionality relationship between expansion and
shear scalars. The physical implications of this model are discussed by using
different parameters and their graphs. We conclude that this model corresponds
to an accelerated expanding universe for particular values of the parameters.Comment: 17 pages, 6 figure
Derivation of a dynamic model of the kinetics of nitrogen uptake throughout the growth of lettuce : calibration and validation
A kinetic model of nitrogen (N) uptake throughout growth was developed for lettuce
cultivated in nutrient solution under varying natural light conditions. The model couples
nitrogen uptake with dry matter accumulation using a two-compartment mechanistic
approach, incorporating structural and non-structural pools. Maximum nitrogen uptake
rates are assumed to decline with shoot dry weight, to allow for the effects of plant
age. The model was parameterized using data from the literature, and calibrated for
differences in light intensity using an optimization algorithm utilizing data from three
experiments in different growing seasons. The calibrated model was validated against
the data from two independent experiments conducted under different light conditions.
Results showed that the model made good predictions of nitrogen uptake by plants from
seedlings to maturity under fluctuating light levels in a glasshouse. Plants grown at a
higher light intensity showed larger maximum nitrogen uptake rates, but the effect of
light intensity declined towards plant maturity
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