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Search Results: 1 - 10 of 561 matches for " Avinava Dubey "
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Large-scale randomized-coordinate descent methods with non-separable linear constraints
Sashank Reddi,Ahmed Hefny,Carlton Downey,Avinava Dubey,Suvrit Sra
Mathematics , 2014,
Abstract: We develop randomized (block) coordinate descent (CD) methods for linearly constrained convex optimization. Unlike most CD methods, we do not assume the constraints to be separable, but let them be coupled linearly. To our knowledge, ours is the first CD method that allows linear coupling constraints, without making the global iteration complexity have an exponential dependence on the number of constraints. We present algorithms and analysis for four key problem scenarios: (i) smooth; (ii) smooth + nonsmooth separable; (iii) asynchronous parallel; and (iv) stochastic. We illustrate empirical behavior of our algorithms by simulation experiments.
A non-parametric mixture model for topic modeling over time
Avinava Dubey,Ahmed Hefny,Sinead Williamson,Eric P. Xing
Statistics , 2012,
Abstract: A single, stationary topic model such as latent Dirichlet allocation is inappropriate for modeling corpora that span long time periods, as the popularity of topics is likely to change over time. A number of models that incorporate time have been proposed, but in general they either exhibit limited forms of temporal variation, or require computationally expensive inference methods. In this paper we propose non-parametric Topics over Time (npTOT), a model for time-varying topics that allows an unbounded number of topics and exible distribution over the temporal variations in those topics' popularity. We develop a collapsed Gibbs sampler for the proposed model and compare against existing models on synthetic and real document sets.
Exact and Efficient Parallel Inference for Nonparametric Mixture Models
Sinead A. Williamson,Avinava Dubey,Eric P. Xing
Statistics , 2012,
Abstract: Nonparametric mixture models based on the Dirichlet process are an elegant alternative to finite models when the number of underlying components is unknown, but inference in such models can be slow. Existing attempts to parallelize inference in such models have relied on introducing approximations, which can lead to inaccuracies in the posterior estimate. In this paper, we describe auxiliary variable representations for the Dirichlet process and the hierarchical Dirichlet process that allow us to sample from the true posterior in a distributed manner. We show that our approach allows scalable inference without the deterioration in estimate quality that accompanies existing methods.
Bayesian Nonparametric Kernel-Learning
Junier Oliva,Avinava Dubey,Barnabas Poczos,Jeff Schneider,Eric P. Xing
Statistics , 2015,
Abstract: Kernel methods are ubiquitous tools in machine learning. They have proven to be effective in many domains and tasks. Yet, kernel methods often require the user to select a predefined kernel to build an estimator with. However, there is often little reason for the a priori selection of a kernel. Even if a universal approximating kernel is selected, the quality of the finite sample estimator may be greatly effected by the choice of kernel. Furthermore, when directly applying kernel methods, one typically needs to compute a $N \times N$ Gram matrix of pairwise kernel evaluations to work with a dataset of $N$ instances. The computation of this Gram matrix precludes the direct application of kernel methods on large datasets. In this paper we introduce Bayesian nonparmetric kernel (BaNK) learning, a generic, data-driven framework for scalable learning of kernels. We show that this framework can be used for performing both regression and classification tasks and scale to large datasets. Furthermore, we show that BaNK outperforms several other scalable approaches for kernel learning on a variety of real world datasets.
Multidimensional QSAR Modeling of Amprenavir Derivatives as HIV-Protease Inhibitors  [PDF]
Sonal Dubey, G. Gowtham
Open Journal of Medicinal Chemistry (OJMC) , 2011, DOI: 10.4236/ojmc.2011.11001
Abstract: A computational study has been performed on a series of 55 compounds having (S)-N-(3-(N-(cyclopean- tylmethyl)substituted-phenylsulfonamido)-2-hydroxypropyl)acetamide backbone as HIV-1 protease inhibitors. Various combinations of these specific inhibitors fragments were formed by breaking them at central alicyclic single bonds, while retaining the core. Standard Topomer 3D models were automatically constructed for each fragment, and a set of steric and electrostatic fields was generated for each set of topomers. The models generated showed r2 of 0.811 and crossvalidated r2 (q2) of 0.608. The other method used were Quasar and Raptor based on receptor-modelling concept (6D-QSAR) and this explicitly allows for the simulation of the induced fit, that yielded r2 of 0.574, cross-validated r2 (q2) of 0.504 and predictive r2 (q2) of 0.895 averaged over 200 models. This study has suggested the various type of substituent that can be attached to the core. The information obtained from these 3-D contour maps can be used for the design of amprenavir analogs possessing better protease inhibitory activity.
A new Set Partitioning in Hierarchical (SPIHT) Algorithm and Analysis with Wavelet Filters
Vidhi Dubey,Rahul Dubey
International Journal of Innovative Technology and Exploring Engineering , 2013,
Abstract: Spiht-Set Partitioning in Hierarchical Trees algorithm is widely used as a compression and encoding algorithm for satellite image compression and transmission. Though it provides efficient lossless compression with high PSNR the associated complexity of algorithm is very high which makes it unfeasible for many practical hardware implementations. Based on the SPIHT algorithms, we define two modifications to develop a simpler image coding method. The first concept is obtained from the relationship between the bit-planes and the target bit- rate. The second concept is obtained by applying different wavelet filters. Based on the above mentioned concepts, we can discard the refinement pass and improve the image quality at different target bit-rates. The project implements image codec's based on both the algorithms and compares their performance on the basis of PSNR values. The images used are square grayscale images. The programming is done in java platform
Primary 25-guage transconjunctival sutureless vitrectomy in pseudophakic retinal detachment
Dubey Arvind,Dubey Benu
Indian Journal of Ophthalmology , 2008,
Macular hole surgery.
Dubey Arvind,Dubey Benu
Indian Journal of Ophthalmology , 2004,
A Practical Solution for Location Estimation in Manually Deployed Wireless Sensor Networks  [PDF]
Om Prakash Sahu, Tarun Dubey
Wireless Sensor Network (WSN) , 2011, DOI: 10.4236/wsn.2011.34013
Abstract: This paper addresses the existing research and adds another aspect of functionality by incorporating pertinent sensor nodes to provide a dynamic location discovery and estimation. The software used provides an easy graphical user interface to visualize a particular location in accordance with geographical latitude and longitude. A simple real time location estimation technique is worked out for wireless sensor networks based on manual deployment of sensors. The proposed scheme finds more efficient solutions with less quantity of sensors as compared to existing deployment schemes. The set up is evaluated exclusively in real environments using IRIS sensor nodes supported by a global positioning system module to provide visualization of an outdoor location. The results are offered by Google Earth application.
Effect of Base Width and Stiffness of the Structure on Period of Vibration of RC Framed Buildings in Seismic Analysis  [PDF]
Prakash Sangamnerkar, Sheo Kumar Dubey
Open Journal of Earthquake Research (OJER) , 2015, DOI: 10.4236/ojer.2015.42006
Abstract: Fundamental natural period of vibration T of the building is an important parameter for evaluation of seismic base shear. Empirical equations given in the Indian seismic code for the calculation of the fundamental period of a framed structure, primarily as a function of height, do not consider the effect of stiffness of the structure, base dimensions of the structure, number of panels in both the directions, amount of infill and properties of the infill. The fundamental period can be evaluated using simplified expressions found in codes, which are based on earthquake recordings in existing buildings, laboratory tests, numerical or analytical computations. These technical codes provide expressions which depend on basic parameters such as building height or number of stories. Building periods predicted by these expressions are widely used in practice although it has been observed that there is scope for further improvement in these equations since the height alone is inadequate to explain period variability. It is also known that the period of a RC frame structure differs depending on whether the longitudinal or transverse direction of the structure is considered. The aim of this study is to find the effects of building base width in both the directions, stiffness of the structure etc. and to predict the fundamental period of vibration of reinforced concrete buildings with moment resisting frames (MRF). A few examples of dynamic analysis are presented in this study to show the effect of base dimensions and stiffness of the structure in calculating the time period of the structure. And it is recommended to be incorporated in the formula for evaluating the natural period of vibration of structures.
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