arXiv subjects

Manoj Kumar

Publications and source records attributed to Manoj Kumar.

At least 91 records · Page 5Linked to original sources

arXiv2018

Approximate ground states of the random-field Potts model from graph cuts

While the ground-state problem for the random-field Ising model is polynomial, and can be solved using a number of well-known algorithms for maximum flow or graph cut, the analogue random-field Potts model corresponds to a multi-terminal flow problem that is known to be NP hard. Hence an efficient exact algorithm is very unlikely to exist. As we show here, it is nevertheless possible to use an embedding of binary degrees of freedom into the Potts spins in combination with graph-cut methods to solve the corresponding ground-state problem approximately in polynomial time. We benchmark this heuristic algorithm using a set of quasi-exact ground states found for small systems from long parallel tempering runs. For not too large number $q$ of Potts states, the method based on graph cuts finds the same solutions in a fraction of the time. We employ the new technique to analyze the breakup length of the random-field Potts model in two dimensions.

cond-mat.dis-nn↗

arXiv2017

Ordering Kinetics in the Random Bond XY Model

We present a comprehensive Monte Carlo study of domain growth in the random-bond XY model with non-conserved kinetics. The presence of quenched disorder slows down domain growth in d = 2; 3. In d = 2, we observe power-law growth with a disorder-dependent exponent on the time-scales of our simulation. In d = 3, we see the signature of an asymptotically logarithmic growth regime. The scaling functions for the real-space correlation function are seen to be independent of the disorder. However, the same does not apply for the two-time autocorrelation function, demonstrating the breakdown of superuniversality.

cond-mat.stat-mech↗

arXiv2017

Enabling Massive Deep Neural Networks with the GraphBLAS

Deep Neural Networks (DNNs) have emerged as a core tool for machine learning. The computations performed during DNN training and inference are dominated by operations on the weight matrices describing the DNN. As DNNs incorporate more stages and more nodes per stage, these weight matrices may be required to be sparse because of memory limitations. The GraphBLAS.org math library standard was developed to provide high performance manipulation of sparse weight matrices and input/output vectors. For sufficiently sparse matrices, a sparse matrix library requires significantly less memory than the corresponding dense matrix implementation. This paper provides a brief description of the mathematics underlying the GraphBLAS. In addition, the equations of a typical DNN are rewritten in a form designed to use the GraphBLAS. An implementation of the DNN is given using a preliminary GraphBLAS C library. The performance of the GraphBLAS implementation is measured relative to a standard dense linear algebra library implementation. For various sizes of DNN weight matrices, it is shown that the GraphBLAS sparse implementation outperforms a BLAS dense implementation as the weight matrix becomes sparser.

cs.DC↗

arXiv2017

Incoherent digital holograms acquired by interferenceless coded aperture correlation holography system without refractive lenses

We present a lensless, interferenceless incoherent digital holography technique based on the principle of coded aperture correlation holography. The acquired digital hologram by this technique contains a three-dimensional image of some observed scene. Light diffracted by a point object is modulated using a random-like coded phase mask (CPM) and the intensity pattern is recorded and composed as a point spread hologram (PSH). A library of PSH is created using the same CPM by moving the pinhole to all possible axial locations. Intensity diffracted through the same CPM from an object placed within the axial limits of the PSH library is recorded by a digital camera. The recorded intensity this time is composed as the object hologram. The image of the object at any axial plane is reconstructed by cross-correlating the object hologram with the corresponding component of the PSH library. The reconstruction noise attached to the image is suppressed by various methods. The reconstruction results of multi-plane and thick objects by this technique are compared with regular lens-based imaging.

physics.optics↗

arXiv2017

Equilibrium structure and off-equilibrium kinetics of a magnet with tunable frustration

We study numerically a two-dimensional random-bond Ising model where frustration can be tuned by varying the fraction $a$ of antiferromagnetic coupling constants. At low temperatures the model exhibits a phase with ferromagnetic order for sufficiently small values of $a$, $a a_a$ an antiferromagnetic phase exists. After a deep quench from high temperatures, slow evolution is observed for any value of $a$. We show that different amounts of frustration, tuned by $a$, affect the dynamical properties in a highly non trivial way. In particular, the kinetics is logarithmically slow in phases with ferromagnetic or antiferromagnetic order, whereas evolution is faster, i.e. algebraic, when spin glass order is prevailing. An interpretation is given in terms of the different nature of phase space.

cond-mat.stat-mech↗

arXiv2017

The Signs in Elliptic Nets

We give a generalization of a theorem of Silverman and Stephens regarding the signs in an elliptic divisibility sequence to the case of an elliptic net. We also describe applications of this theorem in the study of the distribution of the signs in elliptic nets and generating elliptic nets using the denominators of the linear combination of points on elliptic curves.

math.NT↗

arXiv2016

Determination of Surface Morphology of TiO2 nanostructure using synchrotron X-ray standing wave technique

Nanostructures of Titanium oxide (TiO2) are being studied for many promising applications, e.g., solar photovoltaics, solar water splitting for H2 fuel generation etc., due to their excellent photo-catalytic properties. We have synthesized low-dimensional TiO2 nanoparticles by gas phase CW CO2 laser pyrolysis. The laser synthesis process has been optimized for the deposition of highly pure, nearly mono-dispersed TiO2 nanoparticles on silicon substrates. Hard x-ray standing wave-field (XSW) measurements in total reflection geometry were carried out on the BL-16 beamline of Indus-2 synchrotron radiation facility in combination with x-ray reflectivity and grazing incidence x-ray fluorescence measurements for the determination of surface morphology of the deposited TiO2 nanostructures. The average particle size of TiO2 nanostructure estimated using transmission electron microscopy (TEM) was found to closely agree with the XSW and grazing incidence x-ray diffraction (GIXRD) results.

cond-mat.mtrl-sci↗

arXiv2016

Mathematical Foundations of the GraphBLAS

The GraphBLAS standard (GraphBlas.org) is being developed to bring the potential of matrix based graph algorithms to the broadest possible audience. Mathematically the Graph- BLAS defines a core set of matrix-based graph operations that can be used to implement a wide class of graph algorithms in a wide range of programming environments. This paper provides an introduction to the mathematics of the GraphBLAS. Graphs represent connections between vertices with edges. Matrices can represent a wide range of graphs using adjacency matrices or incidence matrices. Adjacency matrices are often easier to analyze while incidence matrices are often better for representing data. Fortunately, the two are easily connected by matrix mul- tiplication. A key feature of matrix mathematics is that a very small number of matrix operations can be used to manipulate a very wide range of graphs. This composability of small number of operations is the foundation of the GraphBLAS. A standard such as the GraphBLAS can only be effective if it has low performance overhead. Performance measurements of prototype GraphBLAS implementations indicate that the overhead is low.

cs.MS↗

arXiv2016

Design and Implementation of an Improved Carry Increment Adder

A complex digital circuit comprises of adder as a basic unit. The performance of the circuit depends on the design of this basic adder unit. The speed of operation of a circuit is one of the important performance criteria of many digital circuits which ultimately depends on the delay of the basic adder unit. Many research works have been devoted in improving the delay of the adder circuit. In this paper we have proposed an improved carry increment adder (CIA) that improves the delay performance of the circuit. The improvement is achieved by incorporating carry look adder (CLA) in the design of CIA contrary to the previous design of CIA that employs ripple carry adder (RCA). A simulation study is carried out for comparative analysis. The coding is done in Verilog hardware description language (HDL) and the simulation is carried out in Xilinx ISE 13.1 environment.

cs.AR↗

arXiv2014

Domain wall motions in perpendicularly magnetized CoFe/Pd multilayer nanowire

Current induced domain wall (DW) motion has been investigated in a 600-nm wide nanowire using multilayer film with a structure of Ta(5 nm)/Pd(5 nm)/[CoFe(0.4 nm)/Pd(1.2 nm)]$_{15}$/Ta(5 nm)in terms of anomalous Hall effect measurements. It is found that motion of DWs can be driven by a current density as low as 1.44$\times$10$^{11}$ A.m$^{-2}$. The effect of the Oersted field ($H_{Oe}$) and spin transfer torque field ($H_{ST}$), which are considered as effective fields for DW motion, has been quantitatively separated from the dependence of depinning fields on the current. The results show that the motion of the walls was essentially dominated by the non-adiabaticity with a high non-adiabatic factor $β$ up to 0.4.

cond-mat.mes-hall↗

arXiv2013

Multi Constraint Satisfying AODV routing using Fuzzy Logic

Mobile Networks are in need of what we call as an e-age. There have been numerous advancements in this field and soft computing has gained roots in this Mobile Ad-hoc Network domain. This documents studies the use of fuzzy logic over Ad Hoc On-Demand Distance vector Routing. The evaluation of the network using fuzzy logic over AODV has been conducted using selective criterion. Both the terms come from two different computing environments, but when combined together can achieve better results; when it comes to QoS based upon selective parameters. The crisp the rules formed in fuzzy logic, better the performance or quality will be achieved in AODV routing mechanism of MANET.

cs.NI↗

arXiv2013

The Wonderful Toy of 20th Century can be a Disaster in 21st Century:Scenario and Policies Regarding Mobile Waste in India

The subscribers base of mobile phones is increasing globally with a rapid rate.The sale of mobile phones has exceeded those of personal computers.India is the second largest telecommunication network in the world in terms of number of wireless connections after China.Telecom companies are ready to tap a large unexplored market in India with lucrative offerings.Smart phones sale are at its peak.3G technology is also ready to play a lead role in mobile revolution.Due to the low average life of the mobile phones,lack of awareness among users and in absence of government policies,mobile waste is accumulating in vast amount in India.Without a proper system of recycling,the unsafe disposal is causing a variety of environmental and health problems.This paper discusses the various issues related to the worldwide growth of mobile phones,the insecure methods of disposal and the regulations and policies in India.We intend to put forward some challenges and advices.

cs.CY↗

arXiv2013

Services in Android can Share Your Personal Information in Background

Mobile phones have traveled a very long journey in a very short span of time since its inception in 1973.This wonderful toy of 20th century has started playing significant role in daily life.More than 5 billion mobile users are there around the world and almost 90 percent of the entire earth is under the mobile coverage now.These days smart phones are equipped with numerous features,faster processors and high storage capacity.Android is a latest trend in this series whose popularity is growing by leaps and bounds.Android has a number of components which helps Application developers to embed distinguish features in applications.This paper explains how the Service component of Android can share your personal information to others without users interaction.

cs.OH↗

arXiv2013

Algorithm and approaches to handle large Data- A Survey

Data mining environment produces a large amount of data, that need to be analyzed, patterns have to be extracted from that to gain knowledge. In this new era with boom of data both structured and unstructured, in the field of genomics, meteorology, biology, environmental research and many others, it has become difficult to process, manage and analyze patterns using traditional databases and architectures. So, a proper architecture should be understood to gain knowledge about the Big Data. This paper presents a review of various algorithms from 1994-2013 necessary for handling such large data set. These algorithms define various structures and methods implemented to handle Big Data, also in the paper are listed various tool that were developed for analyzing them.

cs.DB↗

arXiv2013

DREAM_OLSR PROTOCOL (Distance Routing Effective Algorithm for Mobility - Optimized Link State Routing)

This paper lays down a proposal of protocol named DREAM_OLSR. The protocol has been developed so as to effect current OLSR (RFC 3626) [4] protocol. The protocol establishes an optimized solution hence the name has been manipulated from Open Link State Routing to DREAM Optimized Link State Routing. DREAM specifies Distance Routing Effective Algorithm for Mobility wherein it implements the Distance routing effective algorithm for the optimized solution. This optimization includes higher efficiency and fewer overheads for the MANET.

cs.NI↗

arXiv2012

A New Approach of Improving CFA Image for Digital Camera's

This paper work directly towards the improving the quality of the image for the digital cameras and other visual capturing products. In this Paper, the authors clearly defines the problems occurs in the CFA image. A different methodology for removing the noise is discuses in the paper for color correction and color balancing of the image. At the same time, the authors also proposed a new methodology of providing denoisiing process before the demosaickingfor the improving the image quality of CFA which is much efficient then the other previous defined. The demosaicking process for producing the colors in the image in a best way is also discuss.

cs.CV↗

arXiv2012

On the proficient use of GEV distribution: a case study of subtropical monsoon region in India

The paper deals with the probabilistic estimates of extreme maximum rainfall (Annual basis) in the Ranchi, Jharkhand (India). Extreme Value Distribution family models are tried to capture the uncertainty of data and finally Generalized Extreme Value (GEV) distribution model is found as the best fitted distribution model. The GEV model satisfied the selection criteria [Anderson-Darling test (A-D test or Goodness of fit test) and Normality test (Q-Q plot)], which are adopted under the present study. The return levels are estimated for 5, 10, 50, 100 and 200 years which are consistently increasing for long run in future.

stat.AP↗

arXiv2012

Single bit full adder design using 8 transistors with novel 3 transistors XNOR gate

In present work a new XNOR gate using three transistors has been presented, which shows power dissipation of 550.7272$μ$W in 0.35$μ$m technology with supply voltage of 3.3V. Minimum level for high output of 2.05V and maximum level for low output of 0.084V have been obtained. A single bit full adder using eight transistors has been designed using proposed XNOR cell, which shows power dissipation of 581.542$μ$W. Minimum level for high output of 1.97V and maximum level for low output of 0.24V is obtained for sum output signal. For carry signal maximum level for low output of 0.32V and minimum level for high output of 3.2V have been achieved. Simulations have been performed by using SPICE based on TSMC 0.35$μ$m CMOS technology. Power consumption of proposed XNOR gate and full adder has been compared with earlier reported circuits and proposed circuit's shows better performance in terms of power consumption and transistor count.

cs.OH↗