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Search Results: 1 - 10 of 1242 matches for " Neha Aggarwal "
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A Mid – Point based k-mean Clustering Algorithm for Data mining
Neha Aggarwal,Kirti Aggarwal
International Journal on Computer Science and Engineering , 2012,
Abstract: In k-means clustering algorithm, the number of centroids is equal to the number of the clusters in which data has to be partitioned which in turn is taken as an input parameter. The initial centroids in original k-means are chosen randomly from the given dataset and for the same dataset different clustering results are produced with different randomly chosen initial centroids. This paper presents a solution to this limitation of the original K-means Algorithm.
Texture Classification using Multiresolution Decomposition of Sorted DCT and Fractional DCT Coefficients
Neha Aggarwal,Tarun Kr. Rawat
International Journal of Advanced Electrical and Electronics Engineering , 2012,
Abstract: In this paper, a method is proposed which uses the multiresolution decomposition on the sorted Fractional DCT (FrDCT) and standard DCT coefficients for feature vector extraction of textures. The method shows better classification rates for DCT than conventional DCT based algorithm
Optomechanical effect on the Dicke quantum phase transition and quasi-particle damping in a Bose-Einstein Condensate: A new tool to measure weak force
Neha Aggarwal,Aranya B Bhattacherjee
Physics , 2013, DOI: 10.1080/09500340.2013.836254
Abstract: We make a semi-classical steady state analysis of the influence of mirror motion on the quantum phase transition for an optomechanical Dicke model in the thermodynamic limit. An additional external mechanical pump is shown to modify the critical value of atom-photon coupling needed to observe the quantum phase transition. We further show how to choose the mechanical pump frequency and cavity-laser detuning to produce extremely cold condensates. The present system can be used as a quantum device to measure weak forces.
Simple Pendulum Revisited
Neha Aggarwal,Nitin Verma,P. Arun
Physics , 2004, DOI: 10.1088/0143-0807/26/3/016
Abstract: We describe a 8085 microprocessor interface developed to make reliable time period measurements. The time period of each oscillation of a simple pendulum was measured using this interface. The variation of the time period with increasing oscillation was studied for the simple harmonic motion (SHM) and for large angle initial displacements (non-SHM). The results underlines the importance of the precautions which the students are asked to take while performing the pendulum experiment.
bit.ly/malicious: Deep Dive into Short URL based e-Crime Detection
Neha Gupta,Anupama Aggarwal,Ponnurangam Kumaraguru
Computer Science , 2014,
Abstract: Existence of spam URLs over emails and Online Social Media (OSM) has become a massive e-crime. To counter the dissemination of long complex URLs in emails and character limit imposed on various OSM (like Twitter), the concept of URL shortening has gained a lot of traction. URL shorteners take as input a long URL and output a short URL with the same landing page (as in the long URL) in return. With their immense popularity over time, URL shorteners have become a prime target for the attackers giving them an advantage to conceal malicious content. Bitly, a leading service among all shortening services is being exploited heavily to carry out phishing attacks, work-from-home scams, pornographic content propagation, etc. This imposes additional performance pressure on Bitly and other URL shorteners to be able to detect and take a timely action against the illegitimate content. In this study, we analyzed a dataset of 763,160 short URLs marked suspicious by Bitly in the month of October 2013. Our results reveal that Bitly is not using its claimed spam detection services very effectively. We also show how a suspicious Bitly account goes unnoticed despite of a prolonged recurrent illegitimate activity. Bitly displays a warning page on identification of suspicious links, but we observed this approach to be weak in controlling the overall propagation of spam. We also identified some short URL based features and coupled them with two domain specific features to classify a Bitly URL as malicious or benign and achieved an accuracy of 86.41%. The feature set identified can be generalized to other URL shortening services as well. To the best of our knowledge, this is the first large scale study to highlight the issues with the implementation of Bitly's spam detection policies and proposing suitable countermeasures.
Query Based Duplicate Data Detection on WWW
Ranjna Gupta,Neelam Duhan,,A.K. Sharma,Neha Aggarwal
International Journal on Computer Science and Engineering , 2010,
Abstract: The problem of finding relevant documents has become much more prominent due to the presence of duplicate data on the WWW. This redundancy in results increases the users’ seek time to find the desired information within the search results, while in general most users just want to cull through tens of result pages to find new/different results. The identification of similar or near-duplicate pairs in a large collection is a significant problem with wide-spread applications. Another contemporary materialization of the problem is the efficient identification of near-duplicate Web pages. This is certainly challenging in the web-scale due to the voluminous data. Therefore, a mechanism needs to be introduced for detecting duplicate data so that relevant search results can be provided to the user. In this paper, architecture is being proposed that introduces methods that run online as well as offline on the basis of favored and disfavored user queries to detect duplicates andnear duplicates.
Achieving the Quantum Ground State of a Mechanical Oscillator using a Bose-Einstein Condensate with Back-Action and Cold Damping feedback schemes
Sonam Mahajan,Neha Aggarwal,Aranya B Bhattacherjee,ManMohan
Physics , 2013, DOI: 10.1088/0953-4075/46/8/085301
Abstract: We present a detailed study to show the possibility of approaching the quantum ground-state of a hybrid optomechanical quantum device formed by a Bose-Einstein condensate (BEC) confined inside a high-finesse optical cavity with an oscillatory end mirror. Cooling is achieved using two experimentally realizable schemes: back-action cooling and cold damping quantum feedback cooling. In both the schemes, we found that increasing the two body atom-atom interaction brings the mechanical oscillator to its quantum ground state. It has been observed that back-action cooling is more effective in the good cavity limit while the cold damping cooling scheme is more relevant in the bad cavity limit. It is also shown that in the cold damping scheme, the device is more efficient in the presence of BEC than in the absence of BEC.
Excitations of optomechanically driven Bose-Einstein condensates in a cavity: photodetection measurements
Neha Aggarwal,Sonam Mahajan,Aranya B Bhatttacherjee,Man Mohan
Physics , 2013,
Abstract: We present a detailed study to analyse the Dicke quantum phase transition within the thermodynamic limit for an optomechanically driven Bose-Einstein condensates in a cavity. The photodetection-based quantum optical measurements have been performed to study the dynamics and excitations of this optomechanical Dicke system. For this, we discuss the eigenvalue analysis, fluorescence spectrum and the homodyne spectrum of the system. It has been shown that the normal phase is negligibly affected by the mechanical mode of the mirror while it has a significant effect in the superradiant phase. We have observed that the eigenvalues and both the spectra exhibit distinct features that can be identified with the photonic, atomic and phononic branches. In the fluorescence spectra, we further observe an asymmetric coherent energy exchange between the three degrees of freedom of the system in the superradiant phase arising as a result of optomechanical interaction and Bloch-Siegert shift.
Dynamical Casimir Effect in Superradiant Light Scattering by Bose-Einstein Condensate in an Optomechanical Cavity
Sonam Mahajan,Neha Aggarwal,Aranya B Bhattacherjee,ManMohan
Physics , 2013,
Abstract: We investigate the effects of dynamical Casimir effect in superradiant light scattering by Bose-Einstein condensate in an optomechanical cavity. The system is studied using both classical and quantized mirror motions. The cavity frequency is harmonically modulated in time for both the cases. The main quantity of interest is the number of intracavity scattered photons. The system has been investigated under the weak and strong modulation. It has been observed that the amplitude of the scattered photons is more for the classical mirror motion than the quantized mirror motion. Also, initially, the amplitude of scattered photons is high for lower modulation amplitude than higher modulation amplitude. We also found that the behaviour of the plots are similar under strong and weak modulation for the quantized mirror motion.
Influence of periodically modulated cavity field on the generation of atomic-squeezed states
Neha Aggarwal,Aranya B Bhattacherjee,Arup Banerjee,Man Mohan
Physics , 2013,
Abstract: We investigate the influence of periodically time-modulated cavity frequency on the generation of atomic squeezed states for a collection of N two-level atoms confined in a non-stationary cavity with a moving mirror. We show that the two-photon character of the field generated from the vacuum state of field plays a significant role in producing the atomic or spin squeezed states. We further show that the maximum amount of persistent atomic squeezing is obtained for the initial cavity field prepared in the vacuum state.
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