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1.
The network scenario is that of an infrastructure IEEE 802.11 WLAN with a single AP with which several stations (STAs) are associated. The AP has a finite size buffer for storing packets. In this scenario, we consider TCP-controlled upload and download file transfers between the STAs and a server on the wireline LAN (e.g., 100 Mbps Ethernet) to which the AP is connected. In such a situation, it is well known that because of packet losses due to finite buffers at the AP, upload file transfers obtain larger throughputs than download transfers. We provide an analytical model for estimating the upload and download throughputs as a function of the buffer size at the AP. We provide models for the undelayed and delayed ACK cases for a TCP that performs loss recovery only by timeout, and also for TCP Reno. The models are validated in comparison with NS2 simulations. 相似文献
2.
Robert Jay Milewski Venu Govindaraju Anurag Bhardwaj 《International Journal on Document Analysis and Recognition》2009,11(4):203-218
A new paradigm, which models the relationships between handwriting and topic categories, in the context of medical forms,
is presented. The ultimate goals are: (1) a robust method which categorizes medical forms into specified categories, and (2)
the use of such information for practical applications such as an improved recognition of medical handwriting or retrieval
of medical forms as in a search engine. Medical forms have diverse, complex and large lexicons consisting of English, Medical
and Pharmacology corpus. Our technique shows that a few recognized characters, returned by handwriting recognition, can be
used to construct a linguistic model capable of representing a medical topic category. This allows (1) a reduced lexicon to
be constructed, thereby improving handwriting recognition performance, and (2) PCR (Pre-Hospital Care Report) forms to be
tagged with a topic category and subsequently searched by information retrieval systems. We present an improvement of over
7% in raw recognition rate and a mean average precision of 0.28 over a set of 1,175 queries on a data set of unconstrained
handwritten medical forms filled in emergency environments.
This work was supported by the National Science Foundation. 相似文献
3.
Huaigu Cao Venu Govindaraju Anurag Bhardwaj 《International Journal on Document Analysis and Recognition》2011,14(2):145-157
With the ever-increasing growth of the World Wide Web, there is an urgent need for an efficient information retrieval system
that can search and retrieve handwritten documents when presented with user queries. However, unconstrained handwriting recognition
remains a challenging task with inadequate performance thus proving to be a major hurdle in providing robust search experience
in handwritten documents. In this paper, we describe our recent research with focus on information retrieval from noisy text
derived from imperfect handwriting recognizers. First, we describe a novel term frequency estimation technique incorporating
the word segmentation information inside the retrieval framework to improve the overall system performance. Second, we outline
a taxonomy of different techniques used for addressing the noisy text retrieval task. The first method uses a novel bootstrapping
mechanism to refine the OCR’ed text and uses the cleaned text for retrieval. The second method uses the uncorrected or raw
OCR’ed text but modifies the standard vector space model for handling noisy text issues. The third method employs robust image
features to index the documents instead of using noisy OCR’ed text. We describe these techniques in detail and also discuss
their performance measures using standard IR evaluation metrics. 相似文献
4.
Research on fine tuning stabilization properties has received attention for more than a decade. This paper presents probabilistic algorithms for fault containment. We demonstrate two exercises in fault containment in a weakly stabilizing system, which expedite recovery from single failures, and confine the effect of any single fault to the constant-distance neighborhood of the faulty process. The most significant aspect of the algorithms is that the fault gap, defined as the smallest interval after which the system is ready to handle the next single fault with the same efficiency, is independent of the network size. We argue that a small fault gap increases the availability of the fault-free system. 相似文献
5.
Most existing solutions to group security in Mobile Ad Hoc Networks (MANETs) rely on a multicast Core Based Tree (CBT) for key distribution. Such solutions, although suitable for systems with low mobility and static characteristics, are unsuitable for dynamic and sparse groups with changing neighborhoods. In this paper, we propose an entirely decentralized key generation mechanism, employing a central trusted entity only during initialization. Using our approach, keys can be established between group members with absolutely no prior communication. The solution relies on threshold cryptography and introduces a novel concept of Node-Group-Key (NGK) mapping. We have provided an extensive analytical model for the computations involved and communication costs and have also provided a lie detection mechanism. Simulation results show appreciable performance improvement and enhanced robustness. 相似文献
6.
M2Tracker: A Multi-View Approach to Segmenting and Tracking People in a Cluttered Scene 总被引:1,自引:0,他引:1
When occlusion is minimal, a single camera is generally sufficient to detect and track objects. However, when the density of objects is high, the resulting occlusion and lack of visibility suggests the use of multiple cameras and collaboration between them so that an object is detected using information available from all the cameras in the scene.In this paper, we present a system that is capable of segmenting, detecting and tracking multiple people in a cluttered scene using multiple synchronized surveillance cameras located far from each other. The system is fully automatic, and takes decisions about object detection and tracking using evidence collected from many pairs of cameras. Innovations that help us tackle the problem include a region-based stereo algorithm capable of finding 3D points inside an object knowing only the projections of the object (as a whole) in two views, a segmentation algorithm using bayesian classification and the use of occlusion analysis to combine evidence from different camera pairs.The system has been tested using different densities of people in the scene. This helps us determine the number of cameras required for a particular density of people. Experiments have also been conducted to verify and quantify the efficacy of the occlusion analysis scheme. 相似文献
7.
Aswin V. Pramod Kumar Pooja Singh Anurag Gupta S. Rayaprol Anjana Dogra 《Journal of Materials Science》2015,50(1):366-373
We report investigations on polycrystalline LaCo1?x Al x O3 (x = 0–0.9) bulk samples. The solid state synthesized samples showed a coexistence of rhombohedral and monoclinic phases in the intermediate concentrations (0.2 ≤ x ≤ 0.5) and pure rhombohedral phase otherwise. The observed effect of Al doping on dc transport has been analysed on the basis of small polaron hopping mechanism. The magnetisation results presented give evidence of weak ferromagnetism and anomalous temperature dependence of coercivity which we associate to the canting of the localised high-spin Co(III) and anti-symmetric exchange interactions at low temperatures. 相似文献
8.
Anurag Dwivedi Mark A. Rodriguez Alastair N. Cormack 《Journal of the American Ceramic Society》1992,75(7):1993-1996
Compositions of La1- x Ba x CuO3 , where x ranges from 0.0 to 0.5, were fired in air, oxygen-enriched air, and oxygen. Studies show that BaO cannot make a solid solution with LaCuO3 without changing the basic structure. The resulting phases, in all attempts, were the binary compounds La2 CuO4 , La1- x Ba x CuO3-δ ( x = 0.2 to 0.5), or their mixtures. All samples showed metallic conductivity. Extra oxygen in the reaction atmosphere appeared to encourage the formation of the LaCuO3 -based phases of La1- x Ba x CuO3-δ ( x = 0.2 or 0.5). We provide a defect-chemical and thermodynamical explanation for this observation. 相似文献
9.
Rakesh Sarin Ajay K. Arora Rajeev Ranjan Anurag A. Gupta Ravinder K. Malhotra 《Lubrication Science》2007,19(2):151-157
Bio‐diesel has been accepted as a renewable liquid biofuel worldwide. In order to ensure customers' acceptance, standardisation and quality assurance are the key factors to the market introduction of bio‐diesel as a transport fuel. Lubricity of bio‐diesel is an important issue and it is well reported that 1–2% bio‐diesel is sufficient to maintain the lubricity of diesel even of very poor lubricity. However, a wide variation in lubricity performance of bio‐diesel from different vegetable oils and sources has been noticed. In addition, on critical examination, it was noticed that the variation in the lubricating performance of bio‐diesel could be better linked to its residual acidity than to variation in fatty acid composition. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
10.
We report room-temperature ferromagnetism of graphitic petal arrays grown on Si substrates by microwave plasma chemical vapor deposition without catalyst. The samples have been characterized by Raman and X-ray photoelectron spectroscopy to confirm the absence of possible ferromagnetic impurities. The petals exhibit ferromagnetic hysteresis with saturation magnetization of ~4.67 emu cm(-3) and coercivity of ~105 Oe at 300 K, comparable to the reported behavior of few-layer graphene. Upon O2 annealing the saturation magnetization and coercivity decreased to 2.1 emu cm(-3) and ~75 Oe respectively. The origin of ferromagnetism is believed to arise from the edge defects and vacancies in the petals. 相似文献