24,158 research outputs found
Sensor Management for Tracking in Sensor Networks
We study the problem of tracking an object moving through a network of
wireless sensors. In order to conserve energy, the sensors may be put into a
sleep mode with a timer that determines their sleep duration. It is assumed
that an asleep sensor cannot be communicated with or woken up, and hence the
sleep duration needs to be determined at the time the sensor goes to sleep
based on all the information available to the sensor. Having sleeping sensors
in the network could result in degraded tracking performance, therefore, there
is a tradeoff between energy usage and tracking performance. We design sleeping
policies that attempt to optimize this tradeoff and characterize their
performance. As an extension to our previous work in this area [1], we consider
generalized models for object movement, object sensing, and tracking cost. For
discrete state spaces and continuous Gaussian observations, we derive a lower
bound on the optimal energy-tracking tradeoff. It is shown that in the low
tracking error regime, the generated policies approach the derived lower bound
Sensor Scheduling for Energy-Efficient Target Tracking in Sensor Networks
In this paper we study the problem of tracking an object moving randomly
through a network of wireless sensors. Our objective is to devise strategies
for scheduling the sensors to optimize the tradeoff between tracking
performance and energy consumption. We cast the scheduling problem as a
Partially Observable Markov Decision Process (POMDP), where the control actions
correspond to the set of sensors to activate at each time step. Using a
bottom-up approach, we consider different sensing, motion and cost models with
increasing levels of difficulty. At the first level, the sensing regions of the
different sensors do not overlap and the target is only observed within the
sensing range of an active sensor. Then, we consider sensors with overlapping
sensing range such that the tracking error, and hence the actions of the
different sensors, are tightly coupled. Finally, we consider scenarios wherein
the target locations and sensors' observations assume values on continuous
spaces. Exact solutions are generally intractable even for the simplest models
due to the dimensionality of the information and action spaces. Hence, we
devise approximate solution techniques, and in some cases derive lower bounds
on the optimal tradeoff curves. The generated scheduling policies, albeit
suboptimal, often provide close-to-optimal energy-tracking tradeoffs
Prawn fishery resources of Cochin backwaters
Increasing utilization of prawns both in the internal and external markets has created a large demand for this commodity in recent years. While efforts arebeing made to meet such demands through more intensified exploitation of the resources from the conventional prawn grounds, often serious shortages of the raw ma terial have been experienced due to the fluctuations in the fishery
Some aspects of prawn culture in the seasonal and perennial fields of Vypeen island
Prawn culture is extensively practised in the paddy fields (seasonal fields)
and other low lying areas (perennial fields) of Vypeen Island. Though the
seasonal fields are found to be more productive, the perennial fields, which are
available for prawn culture throughout the year, are not less important. Prawns
stay for longer time and attains larger size in this type of fields. The average
annual production of prawns is 903.3 and 838.6 kg|ha in the seasonal and perennial
fields respectively. The month-wise catch rates show that higher catch
rate is generally observed in January-iMarch period. Four species of penaeid
prawns, Metapenaeus dobsoni, M. monoceros, Penaeus indicus and P. monodon
constitute the culture fishery of which M. dobsoni contributes more than 50% of
the catch. It is observed that M. dobsoni in the perennial fields grow at an average
rate of 10.0 mm per month. Although, the total expenditure to run the seasonal
field is higher than that of the perennial fields, the net income realised
from the seasonal field is always found to be better. It is therefore concluded
that the paddy field prawn culture is more profitable than the culture of prawns
in perennial fields
Application of Multiprotocol Medical Imaging Communications and an Extended DICOM WADO Service in a Teleradiology Architecture
Multiprotocol medical imaging communication through the Internet is more flexible than the tight DICOM transfers. This paper introduces a modular multiprotocol teleradiology architecture that integrates DICOM and common Internet services (based on web, FTP, and E-mail) into a unique operational domain. The extended WADO service (a web extension of DICOM) and the other proposed services allow access to all levels of the DICOM information hierarchy as opposed to solely Object level. A lightweight client site is considered adequate, because the server site of the architecture provides clients with service interfaces through the web as well as invulnerable space for temporary storage, called as User Domains, so that users fulfill their applications' tasks. The proposed teleradiology architecture is pilot implemented using mainly Java-based technologies and is evaluated by engineers in collaboration with doctors. The new architecture ensures flexibility in access, user mobility, and enhanced data security
A case study of the English language practices of six learners in a desegregated urban South African school.
Faculty of Humanities
School of Education
0516698x
[email protected] research report explores the English language practices of six Grade 10 learners
in a desegregated Johannesburg school as well as the ways in which the learners
position themselves and others as users of English and other languages. The context
of the study is desegregated schooling that is a consequence of the demise of
apartheid with its policies of separation of people on racial and ethnic grounds.
I draw on post-structuralist theorizing of language and identity in thinking about the
relationship between language and identity (Hall, 1992a; Weedon, 1997; Zegeye,
2001) with an emphasis on the productive force of language in constituting identity
(Pennycook, 2004). Also significant in this research report are the hybridity theories
of Bhabha (1994) and Hall (1992b) and their critiques as well as the post-structuralist
concepts of ‘positioning’ (Davis and Harrè, 1990) and ‘investment’ (Norton (Pierce),
1995; 1997). A further important strand in this study are the politics of English as a
global language and language of power.
The overall design of the project is qualitative, using ethnographic methods and
drawing on the traditions of school ethnography. In analyzing the data, I argued that
English constitutes and is experienced as a major part of the participants’ identities. I
also state that through learners’ language practices and positioning of themselves and
others as speakers of language, multiple and at times contradictory identities are
continually being constructed and reconstructed. I also argue that the learners’ desire
to be proficient in English and use of prestigious accents and varieties of English is
not about a simple process of assimilation into dominant discourses. Assimilation as I
contend, takes place under complex processes of contestation and appropriation that
involves constant crossing of borders and authorization of hybridities. I have also
argued that the post-apartheid youth find themselves in a situation where internalised
racialised categories of apartheid ideology continue to be relevant in their
understanding of issues but that they are not constrained by them in their lived
experience of boundary crossing and fashioning of hybrid identities
Studies on riverine flora of Pamba river basin, Kerala
Riparian forests are ecotonal assemblage of aquatic and terrestrial habitats. The composition of riparian forests of Pamba River is an amalgamation of riverine, evergreen, deciduous and wetland flora. The floristic investigation of the riparian forests of Pamba river basin revealed taxonomically 433 species which include 410 angiosperms, 3 gymnosperms and 20 pteridophytes. The dominant families based on the number of species are Poaceae, Euphorbiaceae, Rubiaceae, Cyperaceae and Fabaceae. The flora consists of a diverse blend of 99 evergreen, 36 deciduous, 50 wetland, 15 shola-grassland, 46 cultivated and 44 riverine components. The river basin holds 17.5 % endemism and 17 RET species. The riparian tree species identified in the present investigation are _Barringtonia racemosa_, _Calophyllum inophyllum_, _Crateva magna_, _Dillenia indica_, _Elaeocarpus tuberculatus_, _Garcinia gummi-gutta_, _Humboldtia vahliana_, _Largestromea speciosa_, _Neolamarkia kadamba_, _Ochrenauclea missionis_, _Syzigium salicifolium_, _Talipatri tiliaceaum_ and _Trewia nudiflora_. It is assumed that these potential tree species might have a crucial role to maintain the ecological integrity of the riparian zones and floodplain for the restoration of Pamba river
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