18,227 research outputs found
A topological approach to the problem of searching on a contour map
Topological approach to obtain ground track of aircraft using height over terrain and contour ma
Larvae of the three common North American species of Phylocentropus (Trichoptera: Dipseudopsidae)
The caddisfly genus Phylocentropus includes 7 extant species globally, of which 5 occur in eastern North America and 2 in eastern Asia. Larvae of the 3 most common North American species [Phylocentropus carolinus Carpenter, P. lucidus (Hagen), and P. placidus (Banks)] were associated with identifiable adults and diagnostic characters are described. Larvae ofthese 3 species may be distinguished by overall length of mature larvae, head color pattern, and number of spines on the hind tibiae. Larvae of other species of this genus are unknown
Materials and construction techniques for cryogenic wind tunnel facilities for instruction/research use
The results of the cryogenic wind tunnel program conducted at NASA Langley Research Center are presented to provide a starting point for the design of an instructional/research wind tunnel facility. The advantages of the cryogenic concept are discussed, and operating envelopes for a representative facility are presented to indicate the range and mode of operation. Special attention is given to the design, construction and materials problems peculiar to cryogenic wind tunnels. The control system for operation of a cryogenic tunnel is considered, and a portion of a linearized mathematical model is developed for determining the tunnel dynamic characteristics
Distance and intersection number in the curve graph of a surface
In this work, we study the cellular decomposition of induced by a filling
pair of curves and , , and its connection
to the distance function in the curve graph of a closed orientable
surface of genus . Efficient geodesics were introduced by the first
author in joint work with Margalit and Menasco in 2016, giving an algorithm
that begins with a pair of non-separating filling curves that determine
vertices in the curve graph of a closed orientable surface and
computing from them a finite set of {\it efficient} geodesics. We extend the
tools of efficient geodesics to study the relationship between distance
, intersection number , and . The main result is
the development and analysis of particular configurations of rectangles in
called \textit{spirals}. We are able to show that, in some
special cases, the efficient geodesic algorithm can be used to build an
algorithm that reduces while preserving . At the end of the
paper, we note a connection of our work to the notion of extending geodesics.Comment: 20 pages, 17 figures. Changes: A key lemma (Lemma 5.6) was revised to
be more precise, an irrelevant proposition (Proposition 2.1) and example were
removed, unnecessary background material was taken out, some of the
definitions and cited results were clarified (including added figures,) and
Proposition 5.7 and Theorem 5.8 have been merged into a single theorem,
Theorem 4.
A Hybrid Observer for a Distributed Linear System with a Changing Neighbor Graph
A hybrid observer is described for estimating the state of an channel,
-dimensional, continuous-time, distributed linear system of the form
. The system's state is
simultaneously estimated by agents assuming each agent senses and
receives appropriately defined data from each of its current neighbors.
Neighbor relations are characterized by a time-varying directed graph
whose vertices correspond to agents and whose arcs depict
neighbor relations. Agent updates its estimate of at "event
times" using a local observer and a local parameter
estimator. The local observer is a continuous time linear system whose input is
and whose output is an asymptotically correct estimate of
where a matrix with kernel equaling the unobservable space of .
The local parameter estimator is a recursive algorithm designed to estimate,
prior to each event time , a constant parameter which satisfies the
linear equations , where is a small
positive constant and is the state estimation error of local observer
. Agent accomplishes this by iterating its parameter estimator state
, times within the interval , and by making use of
the state of each of its neighbors' parameter estimators at each iteration. The
updated value of at event time is then . Subject to the assumptions that (i) the neighbor graph
is strongly connected for all time, (ii) the system whose state
is to be estimated is jointly observable, (iii) is sufficiently large, it
is shown that each estimate converges to exponentially fast as
at a rate which can be controlled.Comment: 7 pages, the 56th IEEE Conference on Decision and Contro
Factors in the emergence of infectious diseases.
"Emerging" infectious diseases can be defined as infections that have newly appeared in a population or have existed but are rapidly increasing in incidence or geographic range. Among recent examples are HIV/AIDS, hantavirus pulmonary syndrome, Lyme disease, and hemolytic uremic syndrome (a foodborne infection caused by certain strains of Escherichia coli). Specific factors precipitating disease emergence can be identified in virtually all cases. These include ecological, environmental, or demographic factors that place people at increased contact with a previously unfamiliar microbe or its natural host or promote dissemination. These factors are increasing in prevalence; this increase, together with the ongoing evolution of viral and microbial variants and selection for drug resistance, suggests that infections will continue to emerge and probably increase and emphasizes the urgent need for effective surveillance and control. Dr. David Satcher's article and this overview inaugurate Perspectives, a regular section in this journal intended to present and develop unifying concepts and strategies for considering emerging infections and their underlying factors. The editors welcome, as contributions to the Perspectives section, overviews, syntheses, and case studies that shed light on how and why infections emerge, and how they may be anticipated and prevented
Limits of stakeholder participation in sustainable development : "where facts are few, experts are many"
Extract from: The Mediterranean coastal areas from watershed to the sea : interactions and changes / by L.F. Cassar ... [et al.]. Proceedings of the MEDCORE International conference, Florence, 10th-14th November 2005The notion of including stakeholders, those affected (positively or negatively)
by a sustainable development programme in both its design and implementation,
has become a central concern for those implementing such programmes.
Such an approach is often referred to as âstakeholder participationâ, as âparticipatory
developmentâ or more simply still as âparticipationâ. How best to
achieve this has been the topic of a substantial literature, with a host of different
methodologies presented and promoted. Each has its own advantages
and disadvantages, but there has been surprisingly little discussion in the
sustainable development literature as to the limits and dangers of participation
irrespective of the approach employed to âbestâ facilitate it. Inter-linked
with the limits of participation is the role of specialists and expert opinion
in sustainable development. This paper discusses the results of participatory
exercises conducted in Gozo (Malta) between 2003 and 2005. On the positive
side, participation yielded many useful and interesting insights and invoked
a sense of âinvolvementâ in sustainable development, but there were
problems and these are discussed in this paper. For example, the outcome of
the exercise crucially depends upon representation, and a simplified vision of
âcommunityâ often employed in participation to make it practicable can load
the process in favour of certain stakeholder groups at the expense of others.peer-reviewe
Effect of temperature and relative humidity on the development times and survival of Synopsyllus fonquerniei and Xenopsylla cheopis, the flea vectors of plague in Madagascar
Acknowledgements We would like to thank Dr Lila Rahalison and Jocelyn Ratovonjato for their advice and help during the experiment. We are grateful to the staff of the Plague Unit and the Medical Entomology Unit at the Institut Pasteur de Madagascar, particularly Dr Nohal Elissa. Without their expertise this study would not have been possible. Sincere thanks to Mr Tojo Ramihangihajason for his technical assistance. We are indebted to the Institut Pasteur de Madagascar for an internal grant which facilitated additional laboratory research. Two Wellcome Trust fellowships supported ST during this work (081705 and 095171).Peer reviewedPublisher PD
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Global Preparedness for Public Health
There are many reasons to be interested in public health in China. China is the single most populous nation on earth and was the point of origin for SARS and probably for most pandemic influenza viruses, past and future. In this issue of the Journal, we get a valuable window into the organization of public health emergency preparedness in China in the form of the paper, "Preparing and responding to public health emergencies in China: Results of a focus group study". This paper summarizes the results of focus groups conducted with 47 local- and provincial-level public health officials, and includes some of the most complete information on Chinese public health emergency preparedness at the working level. That makes it an invaluable contribution to the growing literature on public health emergency preparedness
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