1,816 research outputs found
Numerical Computational Technique for Scattering from Underwater Objects
This paper presents a computational technique for mono-static and bi-static scattering from underwater objects of different shape such as submarines. The scatter has been computed using finite element time domain (FETD) method, based on the superposition of reflections, from the different elements reaching the receiver at a particular instant in time. The results calculated by this method has been verified with the published results based on ramp response technique. An in-depth parametric study has been carried out, by considering different pulse frequency, pulse length, pulse type (CW, LFM , SFM), sampling frequency, as well as different size , shape of the scatteringbody and grid size. It has been observed that increasing the pulse frequency, sampling frequency and number of elements leads to improved results. However, good amount of accuracy has been achieved with element size less than one third of wave length. The experimental result of the underwater object has been found very close to the`simulated result. This technique is useful for computing forward scatter for inverse scattering applications and as well as to generate forward scatter of very narrow and wide band signals of any pulse type and shape of body.Defence Science Journal, 2013, 63(1), pp.119-126, DOI:http://dx.doi.org/10.14429/dsj.63.77
Quest for a Universal Cluster Preformation Formula: A new paradigm for estimating the cluster formation energy
This study presents a holistic picture of the preformation of nuclear
clusters with credence to the kinematics of their emissions. Besides the
fitting of the preformation formula to reproduce the experimental half-lives,
we have investigated the interrelationship between the parameters involved in
the cluster decay process for medium, heavy and superheavy nuclei. Based on the
established conceptual findings, we propose a new cluster preformation
probability () formula that incorporates all influential parameters of the
cluster radioactivity and thus has an edge over the existing formulae in the
literature. Further, we hypothesize that a fraction of the decay energy is
needed for cluster formation within the parent nucleus. The proposed formula
opens a new paradigm to separately estimate the energy contributed during the
cluster formation from its emission and thus shows that the contribution of the
Q-value splits into three major parts accounting for the energy contributed
during the cluster preformation, its emission and recoil of the daughter
nucleus. Moreover, the expression is adept at accommodating the theorized
concept of heavy particle radioactivity (HPR). The result reveals that, like
-decay, a proper estimation of the and -value in the cluster
studies are enriched with qualitative information about the nuclear structure.
However, from the analysis, the Geiger-Nuttall law is not the best compromise
in the clustering due to the non-linearity between and
, unlike in -decay. We have demonstrated that with the
inclusion of the proposed formula, the half-life predictions from both
microscopic R3Y and phenomenological M3Y NN potentials closely agree with the
available experimental data and that the slight variation can be traced to
their peculiar barrier characteristics.Comment: 7 pages, 3 figures, Journa
Cluster decay dynamics of Actinides yielding non-Pb-daughter
The cluster dynamics of radioactive nuclei decaying to neighbouring daughter
nuclei of the double magic Sn and Pb is investigated using the
relativistic mean-field (RMF) approach with NL3 parameter set within the
preformed cluster-decay model (PCM). The novel feature of the present study is
the application of the newly derived preformation formula, laying the
groundwork for accessing the break-up of the Q-value: preformation energy,
cluster emission energy and the recoil energy of the daughters formed. The
energy associated with cluster preformation is theoretically quantified for the
first time. This treatment underscores the shell effect, pairing correlation as
well as the blocking of particular orbitals by unpaired nucleons. To ascertain
the applicability of the new formula, the PCM based calculations are carried
out with nuclear potential obtained using the phenomenological M3Y and
microscopic RMF-based R3Y nucleon-nucleon (NN) potentials along with
corresponding densities. We found a marginal variation that can be attributed
to the difference in their barrier properties, however, the predictions for the
case of both M3Y and R3Y potentials are found to agree well with the
experimental half-lives. Although none of the considered reaction systems
yields a double magic daughter nucleus, we found that the kinematics of their
cluster emissions is governed by their proximity to the shell closure. The
deduced systematic of the recoil energy in cluster decays can provide valuable
insight for the synthesis of elements in superheavy mass region in the future.Comment: 10 pages, 5 figures, Journa
Pharmacognostical Study of Dioscorea oppositifolia L.
Extraction of bioactive compounds from medicinal plants permits demonstration of their physiological activity. It also facilitates pharmacology studies leading to discovery of synthesis of more potent drugs. The plant selected in the present study is Dioscorea oppositifolia L. (Dioscoreaceae) which is used traditionally for antiseptics, ulcers and abscesses. The root is chewed to cure toothache and aphthae. The whole plant extract is used for secondary syphilis and Psorasis. The present investigation was intended to evaluate the preliminary phytochemical characters and fluorescence analysis of this species
Synthesis and Structural Analysis of Nanocrystalline MnFe2O4
AbstractNanocrystalline form of manganese ferrite (MnFe2O4) has been synthesized by simple sol-gel auto combustion method using citric acid as chelating agent. The obtained nanocrystalline powders of manganese ferrite were subjected to structural and magnetic measurements. Temperature dependent magnetization was also carried out for the single phase nanocrystalline manganese ferrite and the results have been discussed in detail
Exploring the extended density-dependent Skyrme effective forces for normal and isospin-rich nuclei to neutron stars
We parameterize the recently proposed generalized Skyrme effective force
(GSEF) containing extended density dependence. The parameters of the GSEF are
determined by the fit to several properties of the normal and isospin-rich
nuclei. We also include in our fit a realistic equation of state for the pure
neutron matter up to high densities so that the resulting Skyrme parameters can
be suitably used to model the neutron star with the "canonical" mass (). For the appropriate comparison we generate a parameter set for the
standard Skyrme effective force (SSEF) using exactly the same set of the data
as employed to determine the parameters of the GSEF. We find that the GSEF
yields larger values for the neutron skin thickness which are closer to the
recent predictions based on the isospin diffusion data. The Skyrme parameters
so obtained are employed to compute the strength function for the isoscalar
giant monopole, dipole and quadrupole resonances. It is found that in the case
of GSEF, due to the the larger value of the nucleon effective mass the values
of centroid energies for the isoscalar giant resonances are in better agreement
with the corresponding experimental data in comparison to those obtained using
the SSEF. We also present results for some of the key properties associated
with the neutron star of "canonical" mass and for the one with the maximum
mass.Comment: 45pages, 16 figure
Trace Detection of Nerve Agent Simulant in the Fuel Vapour Environment using Metal Oxide Surface Acoustic Wave E Nose
Nerve agents are often used at the military warfront, where diesel is a very common interferant. In the present work, a group of surface acoustic wave (SAW) sensors, called E-Nose with dissimilar sensing layers is developed for the recognition of the mixture of diesel and dimethyl methylphosphonate (DMMP) vapors. The exposure of DMMP and diesel vapors is kept at ppb and ppm levels respectively. Varied response patterns of DMMP and diesel vapors were obtained by SAW E-nose. Principal component analysis (PCA) has been used to extract features from the response curves of SAW sensors. Artificial Neural Network pattern recognition has been implemented to identify the precise detection of DMMP vapors in the binary mixture of DMMP and diesel. The effect of pre-processing (using PCA) the raw data before feeding it to artificial neural network is also studied
Preformation Probability and Kinematics of Clusters Emission yielding Pb-daughters
In the present study, the newly established preformation formula is applied
for the first time to study the kinematics of the cluster emission from various
radioactive nuclei, especially those decaying to the double-shell closure
Pb nucleus and its neighbours as daughters. The recently proposed
universal cluster preformation formula has been established based on the
concepts that underscore the influence of the mass and charge asymmetry
( and ), cluster mass and the Q-value, paving the way to
quantify the energy contribution during the preformation as well as the
tunnelling process separately. The cluster-daughter interaction potential is
obtained by folding the relativistic mean-field (RMF) densities with the
recently developed microscopic R3Y using the NL and the phenomenological
M3Y NN potentials to compare their adaptability. The penetration probabilities
are calculated from the WKB approximation. With the inclusion of the new
preformation probability , the predicted half-lives from the R3Y and M3Y
interactions are in good agreement with the experimental data. Furthermore, a
careful inspection reflects slight differences in the decay half-lives, which
arise from their respective barrier properties. The for the systems with
the double magic shell closure Pb daughter are found to be relatively
higher with an order of than those with neighbouring Pb-daughter
nuclei. By exploring the contributions of the decay energy, the recoil effect
of the daughter nucleus is appraised, unlike several other conjectures. Thus,
the centrality of the Q-value in the decay process is demonstrated and
re-defined within the preformed cluster-decay model. Besides, we have
introduced a simple and intuitive set of criteria that governs the estimation
of recoil energy in the cluster radioactivity.Comment: 09 Pages, 06 Figures, and 01 Tabl
Theoretical Investigation of α-decay Chains of Fm-isotopes
Background: The theoretical and experimental investigations of decay properties of heavy and superheavy nuclei are crucial to explore the nuclear structure and reaction dynamics.
Purpose: The aim of this study is to probe the α-decay properties of 243Fm and 245Fm isotopic chains using relativistic mean-field (RMF) approach within the framework of preformed cluster-decay model (PCM).
Methods: The RMF densities are folded with the relativistic R3Y NN potential to deduce the nuclear interaction potential between the α particle and daughter nucleus. The penetration probability is calculated within the WKB approximation.
Results: The α-decay half-lives of even-odd 243Fm and 245Fm isotopes and their daughter nuclei are obtained from the preformed cluster-decay model. These theoretically calculated half-lives are found to be in good agreement with the recent experimental measurements.
Conclusions: The novel result here is the applicability of the scaling factor within the PCM as a signature for shell/sub-shell closures in α-decay studies. As such, we have also demonstrated that N=137, 139 and Z=94 corresponding to 231,233Pu could be shell/sub-shell closures. The least T1/2 is found at 243,245Fm which indicate their individual stability and α-decay as their most probable decay mode
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