919 research outputs found
Outage Probability of Multiple-Input Single-Output (MISO) Systems with Delayed Feedback
We investigate the effect of feedback delay on the outage probability of
multiple-input single-output (MISO) fading channels. Channel state information
at the transmitter (CSIT) is a delayed version of the channel state information
available at the receiver (CSIR). We consider two cases of CSIR: (a) perfect
CSIR and (b) CSI estimated at the receiver using training symbols. With perfect
CSIR, under a short-term power constraint, we determine: (a) the outage
probability for beamforming with imperfect CSIT (BF-IC) analytically, and (b)
the optimal spatial power allocation (OSPA) scheme that minimizes outage
numerically. Results show that, for delayed CSIT, BF-IC is close to optimal for
low SNR and uniform spatial power allocation (USPA) is close to optimal at high
SNR. Similarly, under a long-term power constraint, we show that BF-IC is close
to optimal for low SNR and USPA is close to optimal at high SNR. With imperfect
CSIR, we obtain an upper bound on the outage probability with USPA and BF-IC.
Results show that the loss in performance due to imperfection in CSIR is not
significant, if the training power is chosen appropriately.Comment: Submitted to IEEE Transactions on Communications Jan 2007, Revised
Jun 2007, Revised Nov 200
Spanning trees short or small
We study the problem of finding small trees. Classical network design
problems are considered with the additional constraint that only a specified
number of nodes are required to be connected in the solution. A
prototypical example is the MST problem in which we require a tree of
minimum weight spanning at least nodes in an edge-weighted graph. We show
that the MST problem is NP-hard even for points in the Euclidean plane. We
provide approximation algorithms with performance ratio for the
general edge-weighted case and for the case of points in the
plane. Polynomial-time exact solutions are also presented for the class of
decomposable graphs which includes trees, series-parallel graphs, and bounded
bandwidth graphs, and for points on the boundary of a convex region in the
Euclidean plane. We also investigate the problem of finding short trees, and
more generally, that of finding networks with minimum diameter. A simple
technique is used to provide a polynomial-time solution for finding -trees
of minimum diameter. We identify easy and hard problems arising in finding
short networks using a framework due to T. C. Hu.Comment: 27 page
INDEMICS: An Interactive High-Performance Computing Framework for Data Intensive Epidemic Modeling
We describe the design and prototype implementation of Indemics (_Interactive; Epi_demic; _Simulation;)—a modeling environment utilizing high-performance computing technologies for supporting complex epidemic simulations. Indemics can support policy analysts and epidemiologists interested in planning and control of pandemics. Indemics goes beyond traditional epidemic simulations by providing a simple and powerful way to represent and analyze policy-based as well as individual-based adaptive interventions. Users can also stop the simulation at any point, assess the state of the simulated system, and add additional interventions. Indemics is available to end-users via a web-based interface.
Detailed performance analysis shows that Indemics greatly enhances the capability and productivity of simulating complex intervention strategies with a marginal decrease in performance. We also demonstrate how Indemics was applied in some real case studies where complex interventions were implemented
Stochastic pump of interacting particles
We consider the overdamped motion of Brownian particles, interacting via
particle exclusion, in an external potential that varies with time and space.
We show that periodic potentials that maintain specific position-dependent
phase relations generate time-averaged directed current of particles. We obtain
analytic results for a lattice version of the model using a recently developed
perturbative approach. Many interesting features like particle-hole symmetry,
current reversal with changing density, and system-size dependence of current
are obtained. We propose possible experiments to test our predictions.Comment: 4 pages, 2 figure
Bicriteria Network Design Problems
We study a general class of bicriteria network design problems. A generic
problem in this class is as follows: Given an undirected graph and two
minimization objectives (under different cost functions), with a budget
specified on the first, find a <subgraph \from a given subgraph-class that
minimizes the second objective subject to the budget on the first. We consider
three different criteria - the total edge cost, the diameter and the maximum
degree of the network. Here, we present the first polynomial-time approximation
algorithms for a large class of bicriteria network design problems for the
above mentioned criteria. The following general types of results are presented.
First, we develop a framework for bicriteria problems and their
approximations. Second, when the two criteria are the same %(note that the cost
functions continue to be different) we present a ``black box'' parametric
search technique. This black box takes in as input an (approximation) algorithm
for the unicriterion situation and generates an approximation algorithm for the
bicriteria case with only a constant factor loss in the performance guarantee.
Third, when the two criteria are the diameter and the total edge costs we use a
cluster-based approach to devise a approximation algorithms --- the solutions
output violate both the criteria by a logarithmic factor. Finally, for the
class of treewidth-bounded graphs, we provide pseudopolynomial-time algorithms
for a number of bicriteria problems using dynamic programming. We show how
these pseudopolynomial-time algorithms can be converted to fully
polynomial-time approximation schemes using a scaling technique.Comment: 24 pages 1 figur
Lightweight Object Detection Ensemble Framework for Autonomous Vehicles in Challenging Weather Conditions
The computer vision systems driving autonomous vehicles are judged by their ability to detect objects and obstacles in the vicinity of the vehicle in diverse environments. Enhancing this ability of a self-driving car to distinguish between the elements of its environment under adverse conditions is an important challenge in computer vision. For example, poor weather conditions like fog and rain lead to image corruption which can cause a drastic drop in object detection (OD) performance. The primary navigation of autonomous vehicles depends on the effectiveness of the image processing techniques applied to the data collected from various visual sensors. Therefore, it is essential to develop the capability to detect objects like vehicles and pedestrians under challenging conditions such as like unpleasant weather. Ensembling multiple baseline deep learning models under different voting strategies for object detection and utilizing data augmentation to boost the models' performance is proposed to solve this problem. The data augmentation technique is particularly useful and works with limited training data for OD applications. Furthermore, using the baseline models significantly speeds up the OD process as compared to the custom models due to transfer learning. Therefore, the ensembling approach can be highly effective in resource-constrained devices deployed for autonomous vehicles in uncertain weather conditions. The applied techniques demonstrated an increase in accuracy over the baseline models and were able to identify objects from the images captured in the adverse foggy and rainy weather conditions. The applied techniques demonstrated an increase in accuracy over the baseline models and reached 32.75% mean average precision (mAP) and 52.56% average precision (AP) in detecting cars in the adverse fog and rain weather conditions present in the dataset. The effectiveness of multiple voting strategies for bounding box predictions on the dataset is also demonstrated. These strategies help increase the explainability of object detection in autonomous systems and improve the performance of the ensemble techniques over the baseline models
Documentation of Wild Edible Plants of Melghat Forest, Dist. Amravati, Maharashtra State, India
An ethnobotanical survey with respect to food plants showed that tribals depend much upon forest products for their various daily needs. Wild edible plants play a significant role in the sustenance of rural life in Melghat. The paper deals with documentation of 42 plant species belonging to 23 families consumed by the tribal and other locals of Melghat area, Dist. Amravati, Maharashtra, India. Plant name, Family, along with their part used, and method of preparation is discussed
Gauge theory of Faddeev-Skyrme functionals
We study geometric variational problems for a class of nonlinear sigma-models
in quantum field theory. Mathematically, one needs to minimize an energy
functional on homotopy classes of maps from closed 3-manifolds into compact
homogeneous spaces G/H. The minimizers are known as Hopfions and exhibit
localized knot-like structure. Our main results include proving existence of
Hopfions as finite energy Sobolev maps in each (generalized) homotopy class
when the target space is a symmetric space. For more general spaces we obtain a
weaker result on existence of minimizers in each 2-homotopy class.
Our approach is based on representing maps into G/H by equivalence classes of
flat connections. The equivalence is given by gauge symmetry on pullbacks of
G-->G/H bundles. We work out a gauge calculus for connections under this
symmetry, and use it to eliminate non-compactness from the minimization problem
by fixing the gauge.Comment: 34 pages, no figure
Development of stability indicating assay method for the simultaneous estimation of Metformin hydrochloride and Glipizide by RP-HPLC method
A simple, sensitive an isocratic RP-HPLC method for the estimation of Metformin Hydrochloride (MET) and Glipizide (GPZ) in combined dosage form using Inertsil C8 column (250.6 mm, 5 ) in an isocratic mode with mobile phase comprising Acetonitrile: Water (70:30) and one drop of Triethylamine. The flow rate was 1.0 ml/min and effluent was monitored at 222 nm. The retention times were found to be 3.40 min for MET and 4.44 min for GPZ. The assay exhibited a linear dynamic range of 100-500 g/ml of MET and 1-5 g/mL for GPZ .The calibration curves were linear (r = 0.9985 for MET and r = 0.9955 for GPZ) over the entire linear range. Recovery was found to be 99.94 % + .17 for MET and 99.61 % + 0.89 for GPZ. % RSD of system precision were observed 0.0429 for MET and 0.7212 for GPZ
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