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1.
The problem of helicopter parameter estimation and blade number selection is addressed. The parameters are estimated based on Maximum Likelihood methods and the corresponding Cramér-Rao bounds are derived. To avoid ambiguities in blade number estimation, we apply information theoretic criteria for blade number selection incorporating alternate penalty functions. We assume that a clutter filter essentially removes all of the clutter and also part of the signal returns, lowering the effective signal-to-noise-ratio. The fractional Fourier transform is used to separate the combined tail and main rotor signals into two different returns, allowing initial estimates of their corresponding rotor parameters. The proposed technique is validated by using returns from a helicopter observed experimentally with a pulse-Doppler radar. 相似文献
2.
It is known that the emission color of Ce3+ doped garnets is strongly redshifted at higher Ce3+ concentrations. In this report, we study the cause of this redshift in Lu3Al5O12:Ce3+ (LuAG:Ce) phosphors. These changes in emission color with Ce3+ concentration are mainly attributed to a combination of inhomogenous broadening for Ce3+ in LuAG and energy transfer from high energy Ce3+ ions to low energy Ce3+ ions. Evidence for inhomogenous broadening and energy transfer is given through time resolved measurements. Potential reasons for inhomogenous broadening of Ce3+ in these phosphors are also discussed. 相似文献
3.
Solid‐state lighting (SSL) technologies such as light emitting diodes (LEDs) have been of interest for the last 15 years. This article focuses on inorganic LED technology and their evolving applications, energy efficiency, and economic impact as well as the effect of thermal management on LED lighting systems. The efficacy of the best commercial 1 W LED packages currently surpasses 120 lm/W, which is more efficient than typical metal‐halide and fluorescent lamps. This high efficacy will eventually allow LED lighting systems to be used in specialty and general illumination applications. However, higher lumen requirements for LED systems will inevitably lead to significant thermal challenges at both the chip and the system level that need to be addressed to enable practical applications at low costs. In this article, the basics of LED lighting will be discussed first. It will be followed by the potential economic benefits for high efficiency LED lighting systems in the general illumination market. We will then discuss the thermal challenges and possible candidate cooling technologies in LED lighting systems. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
4.
Suryaprakash Kompalli Srirangaraj Setlur Venu Govindaraju 《International Journal on Document Analysis and Recognition》2009,12(2):123-138
This paper describes a novel recognition driven segmentation methodology for Devanagari Optical Character Recognition. Prior approaches have used sequential rules to segment characters followed by template matching
for classification. Our method uses a graph representation to segment characters. This method allows us to segment horizontally
or vertically overlapping characters as well as those connected along non-linear boundaries into finer primitive components.
The components are then processed by a classifier and the classifier score is used to determine if the components need to
be further segmented. Multiple hypotheses are obtained for each composite character by considering all possible combinations
of the classifier results for the primitive components. Word recognition is performed by designing a stochastic finite state
automaton (SFSA) that takes into account both classifier scores as well as character frequencies. A novel feature of our approach
is that we use sub-character primitive components in the classification stage in order to reduce the number of classes whereas
we use an n-gram language model based on the linguistic character units for word recognition. 相似文献
5.
Vidya Setlur Tom Lechner Marc Nienhaus Bruce Gooch 《Computer Graphics and Applications, IEEE》2007,27(5):80-88
A nonphotorealistic algorithm for retargeting images adapts large images so that important objects in the image are still recognizable when displayed at a lower target resolution. Unlike existing image manipulation techniques such as cropping and scaling, the retargeting algorithm can handle multiple important objects in an image. To identify the important objects in an image, we must first segment the image. We use mean-shift image segmentation to decompose an image into homogeneous regions. 相似文献
6.
Srirangaraj Setlur Alfred Lawson Venugopal Govindaraju Sargur Srihari 《International Journal on Document Analysis and Recognition》2002,4(3):154-169
This paper describes the issues involved in the design of a system for evaluating improvements in the performance of a real-time
address recognition system being used by the United States Postal Service for processing mail-piece images. Evaluation of
the performance of recognition systems is normally carried out by measuring the performance of the system on a representative
sample of images. Designing a comprehensive and valid testing scenario is a complex task that requires careful attention.
Sampling live mail-stream to generate a deck of images representative of the general mail-stream for testing, truthing (generating
reference data on a significant number of images), grading and evaluation, and designing tools to facilitate these functions
are important topics that need to be addressed. This paper describes the efforts of the United States Postal Service and CEDAR
towards developing an infrastructure for sampling, truthing, and testing of mail-stream images.
Received: July 25, 2000 / Revised version: July 31, 2001 相似文献
7.
8.
Xujun Peng Srirangaraj Setlur Venu Govindaraju Sitaram Ramachandrula 《Pattern recognition letters》2012,33(7):943-950
A boosted tree classifier is proposed to segment machine printed, handwritten and overlapping text from documents with handwritten annotations. Each node of the tree-structured classifier is a binary weak learner. Unlike a standard decision tree (DT) which only considers a subset of training data at each node and is susceptible to over-fitting, we boost the tree using all available training data at each node with different weights. The proposed method is evaluated on a set of machine-printed documents which have been annotated by multiple writers in an office/collaborative environment. The experimental results show that the proposed algorithm outperforms other methods on an imbalanced data set. 相似文献
9.
P. Setlur J.R. Wagner D.M. Dawson E. Marotta 《Mechatronics, IEEE/ASME Transactions on》2005,10(2):210-220
Internal combustion engine thermal management system functionality can be enhanced through the introduction of smart thermostat valves and variable speed electric pumps and fans. The traditional automotive cooling system components include a wax based thermostat valve and crankshaft driven water pump. However, servo-motor driven valves, pumps, and fans can better regulate the engine's coolant fluid flow to realize fuel economy gains and tailpipe emission reductions. To study these cooling system actuators, with accompanying nonlinear control strategy, a scale experimental system has been fabricated which features a smart valve, electric coolant pump, radiator with electric fan, and immersion heater. In this paper, mathematical models will be presented to describe the system's behavior. A nonlinear controller will then be designed for transient temperature tracking. Representative experimental results are presented and discussed to demonstrate the smart valve's operation in maintaining the temperature within a neighborhood of the target value for various scenarios including highway mode, full power with load disturbance, and quick heat. 相似文献
10.
Energy transfer processes in Pr^3 -codoped CaAl12O19crystal from 12 to 290K were studied.Energy transfer from Pr^3 toEr^3 ions in this system was observed,The transfer can partially convert the ^1S0UVfluorescence of Pr^3 into green emission of the characteristic of Er^3 ,The efficiency of the energy transfer was estimated based of the spectroscopic data,The temperature dependence on the transfer was also discussed. 相似文献