2,125 research outputs found
COLOR IMAGE QUANTIZATION USING GDBSCAN
Color image quantization is the most widely used techniques in the field of image compression. DBSCAN is a density based data clustering technique. However DBSCAN is widely used for data clustering but not very popular for color image quantization due to some of issues associated with it. One of the problems associated with DBSCAN is that it becomes expensive when used on whole image data and also the noise points been unmapped. In this paper we are proposing a new color image quantization scheme which overcomes these problems. Our proposed algorithm is GDBSCAN (Grid Based DBSCAN) where we first decompose the image data in grids and then apply DBSCAN algorithm on each grid
A New Monte-Carlo Radiative Transfer Simulation of Cyclotron Resonant Scattering Features
We present a new Monte-Carlo radiative transfer code, which we have used to
model the cyclotron line features in the environment of a variable magnetic
field and plasma density. The code accepts an input continuum and performs only
the line transfer by including the three cyclotron resonant processes
(cyclotron absorption, cyclotron emission, cyclotron scattering). Subsequently,
the effects of gravitational red-shift and light bending on the emergent
spectra are computed. We have applied our code to predict the observable
spectra from three different emission geometries; 1) an optically thin slab
near the stellar surface, 2) an accretion mound formed by the accumulation of
the accreted matter, 3) an accretion column representing the zone of a settling
flow onto the star. Our results show that the locally emergent spectra from the
emission volume are significantly anisotropic. However, in the presence of
strong light bending the anisotropy reduces considerably. This averaging also
drastically reduces the strength of harmonics higher than second in the
observable cyclotron spectra. We find that uniform field slabs produce line
features that are too narrow, and mounds with large magnetic distortions
produce features that are too wide compared to the average widths of the
spectral features observed from various sources. The column with a gently
varying (dipole) field produces widths in the intermediate range, similar to
those observed.Comment: 15 pages, 15 figures, Accepted for publication in MNRA
Differential expression of 9-O-acetylated sialoglycoconjugates on leukemic blasts: a potential tool for long-term monitoring of children with acute lymphoblastic leukemia
Earlier studies have demonstrated overexpression of 9-O-acetylated sialoglycoconjugates (9-O-AcSGs) on lymphoblasts, concomitant with high titers of anti-9-O-AcSG antibodies in childhood acute lymphoblastic leukemia (ALL). Our aim was to evaluate the correlation between expression of different 9-O-AcSGs during chemotherapeutic treatment. Accordingly, expression of 9-O-AcSGs on lymphoblasts of ALL patients (n = 70) were longitudinally monitored for 6 years (1997-2002), using Achatinin-H, a 9-O-acetylated sialic acid (9-O-AcSA) binding lectin with preferential affinity for 9-O-AcSGs with terminal 9-O-AcSAα2→6GalNAc. Western blot analysis of patients (n = 30) showed that 3 ALL-specific 9-O-AcSGs (90, 120 and 135 kDa) were induced at presentation; all these bands disappeared after treatment in patients (n = 22) who had disease-free survival. The 90 kDa band persisted in 8 patients who subsequently relapsed with reexpression of the 120 kDa band. FACS analysis revealed that at presentation (n = 70) 90.1 ± 5.0% cells expressed 9-O-AcSGs, which decreased progressively with chemotherapy, remained <5% during clinical remission and reappeared in relapse (80 ± 10%, n = 18). Early clearance of 9-O-AcSG+ cells, during 4-8 weeks of treatment showed a good correlation with low risk of relapse. Sensitivity of detection of 9-O-AcSG+ cells was 0.1%. Numbers of both high- and low-affinity binding sites were maximum at presentation, decreased with treatment and increased again in clinical relapse. We propose that close monitoring of 90 and 120 kDa 9-O-AcSGs may serve as a reliable index for long-term management of childhood ALL and merits therapeutic consideration
Time dependent current in a nonstationary environment: A microscopic approach
Based on a microscopic system reservoir model,where the associated bath is
not in thermal equilibrium, we simulate the nonstationary Langevin dynamics and
obtained the generalized nonstationary fluctuation dissipation relation (FDR)
which asymptotically reduces to the traditional form. Our Langevin dynamics
incorporates non-Markovian process also, the origin of which lies on the
decaying term of the nonstationary FDR. We then follow the stochastic dynamics
of the Langevin particle based on the Fokker-Planck-Smoluchowski description,
in ratchet potential to obtain the steady and time dependent current in an
analytic form. We also examine the influence of initial excitation and
subsequent relaxation of bath modes on the transport of the Langevin particle
to show that the nonequilibrium nature of the bath leads to both strong
non-exponential dynamics as well as nonstationary current.Comment: 10 pages, RevTex4, references updated, final version to appear in
Journal of Mathematical Physic
Kramers turnover in class of thermodynamically open systems: Effect of interplay of nonlinearity and noises
A system-reservoir nonlinear coupling model has been proposed for a situation
where the reservoir is nonlinearly driven by an external Gaussian stationary
noise which exposes the system particles to a nonequilibrium environment. Apart
from the internal thermal noise, the thermodynamically open system encounters
two other noises that are multiplicative in nature. Langevin equation derived
from the resulting composite system contains the essential features of the
interplay between these noise processes. Based on the numerical simulation of
the full model potential, we show that one can recover the turnover features of
the Kramers dynamics even when the reservoir is modulated nonlinearly by an
external noise.Comment: 7 pages, 2 figure
Science with the Daksha High Energy Transients Mission
We present the science case for the proposed Daksha high energy transients
mission. Daksha will comprise of two satellites covering the entire sky from
1~keV to ~MeV. The primary objectives of the mission are to discover and
characterize electromagnetic counterparts to gravitational wave source; and to
study Gamma Ray Bursts (GRBs). Daksha is a versatile all-sky monitor that can
address a wide variety of science cases. With its broadband spectral response,
high sensitivity, and continuous all-sky coverage, it will discover fainter and
rarer sources than any other existing or proposed mission. Daksha can make key
strides in GRB research with polarization studies, prompt soft spectroscopy,
and fine time-resolved spectral studies. Daksha will provide continuous
monitoring of X-ray pulsars. It will detect magnetar outbursts and high energy
counterparts to Fast Radio Bursts. Using Earth occultation to measure source
fluxes, the two satellites together will obtain daily flux measurements of
bright hard X-ray sources including active galactic nuclei, X-ray binaries, and
slow transients like Novae. Correlation studies between the two satellites can
be used to probe primordial black holes through lensing. Daksha will have a set
of detectors continuously pointing towards the Sun, providing excellent hard
X-ray monitoring data. Closer to home, the high sensitivity and time resolution
of Daksha can be leveraged for the characterization of Terrestrial Gamma-ray
Flashes.Comment: 19 pages, 7 figures. Submitted to ApJ. More details about the mission
at https://www.dakshasat.in
Plant-Mediated Synthesis of Silver Nanoparticles: Their Characteristic Properties and Therapeutic Applications
Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an
Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis
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