142 research outputs found
Local Search in Unstructured Networks
We review a number of message-passing algorithms that can be used to search
through power-law networks. Most of these algorithms are meant to be
improvements for peer-to-peer file sharing systems, and some may also shed some
light on how unstructured social networks with certain topologies might
function relatively efficiently with local information. Like the networks that
they are designed for, these algorithms are completely decentralized, and they
exploit the power-law link distribution in the node degree. We demonstrate that
some of these search algorithms can work well on real Gnutella networks, scale
sub-linearly with the number of nodes, and may help reduce the network search
traffic that tends to cripple such networks.Comment: v2 includes minor revisions: corrections to Fig. 8's caption and
references. 23 pages, 10 figures, a review of local search strategies in
unstructured networks, a contribution to `Handbook of Graphs and Networks:
From the Genome to the Internet', eds. S. Bornholdt and H.G. Schuster
(Wiley-VCH, Berlin, 2002), to be publishe
Searching for the Sunk Cost Fallacy
We seek to isolate in the laboratory factors that encourage and discourage the sunk cost fallacy. Subjects play a computer game in which they decide whether to keep digging for treasure on an island or to sink a cost (which will turn out to be either high or low) to move to another island. The research hypothesis is that subjects will stay longer on islands that were more costly to find. Nine treatment variables are considered, e.g. alternative visual displays, whether the treasure value of an island is shown on arrival or discovered by trial and error, and alternative parameters for sunk costs. The data reveal a surprisingly small and erratic sunk cost effect that is generally insensitive to the proposed psychological drivers.sunk cost fallacy
Searching for the Sunk Cost Fallacy
We seek to isolate in the laboratory factors that encourage and discourage the sunk cost fallacy. Subjects play a computer game in which they decide whether to keep digging for treasure on an island or to sink a cost (which will turn out to be either high or low) to move to another island. The research hypothesis is that subjects will stay longer on islands that were more costly to find. Nine treatment variables are considered, e.g. alternative visual displays, whether the treasure value of an island is shown on arrival or discovered by trial and error, and alternative parameters for sunk costs. The data reveal a surprisingly small and erratic sunk cost effect that is generally insensitive to the proposed psychological drivers.sunk cost fallacy, experimental economics
Economics-Based Optimization of Unstable Flows
As an example for the optimization of unstable flows, we present an
economics-based method for deciding the optimal rates at which vehicles are
allowed to enter a highway. It exploits the naturally occuring fluctuations of
traffic flow and is flexible enough to adapt in real time to the transient flow
characteristics of road traffic. Simulations based on realistic parameter
values show that this strategy is feasible for naturally occurring traffic, and
that even far from optimality, injection policies can improve traffic flow.
Moreover, the same method can be applied to the optimization of flows of gases
and granular media.Comment: Revised version of ``Optimizing Traffic Flow'' (cond-mat/9809397).
For related work see http://www.parc.xerox.com/dynamics/ and
http://www.theo2.physik.uni-stuttgart.de/helbing.htm
Intermittent exploration on a scale-free network
We study an intermittent random walk on a random network of scale-free degree
distribution. The walk is a combination of simple random walks of duration
and random long-range jumps. While the time the walker needs to cover all
the nodes increases with , the corresponding time for the edges displays a
non monotonic behavior with a minimum for some nontrivial value of . This
is a heterogeneity-induced effect that is not observed in homogeneous
small-world networks. The optimal increases with the degree of
assortativity in the network. Depending on the nature of degree correlations
and the elapsed time the walker finds an over/under-estimate of the degree
distribution exponent.Comment: 12 pages, 3 figures, 1 table, published versio
Laparoscopic removal of transmigrated intrauterine contraceptive device from abdomen in an asymptomatic patient
Uterine perforation followed by transmigration of intrauterine contraceptive device to the abdominal cavity is one of the rarest, but most dangerous complication of Copper T. These displaced Copper containing devices can cause chronic inflammatory reaction leading to adhesions, intestinal obstruction and even bowel perforation. Hence removal of these devices once found outside the uterus is recommended. Traditionally, a laparotomy used to be performed owing to the associated inflammation, adhesions and the risks of bowel injury. Laparoscopic removal of these displaced devices is a minimally invasive surgical approach with good results in skilled hands. Authors reported a rare case of misplaced transmigrated intrauterine contraceptive device in a 43-year-old asymptomatic lady. The Copper T had migrated after silent perforation of the uterus and was impacted in the greater omentum. There was evidence of chronic inflammation and small pockets of pus surrounding it. There were flimsy bowel adhesions. The dislodged device was successfully removed laparoscopically along with partial omentectomy without any complications. Regular follow up of patients who have had Copper T insertions and teaching them to feel the thread and report if not felt is essential to diagnose complications early. A transmigrated intrauterine device can be successfully removed laparoscopically
Geochemistry, textural studies and its environmental implications on the core sediment of Kadalundi estuary, Kerala
1536-1544The study area Kadalundi estuary is fully occupied with mangroves, and conserved as a bird sanctuary. In this estuary, systematic studies on sedimentological and geochemical aspects are not done so far. Hence, an attempt has been made in this area to infer the paleoenvironmental significance in this region. A core of length 185 cm was taken and subsampled in 5 cm intervals. The sand-silt-clay analyses indicate higher concentration of sand in the core and overall low calcium carbonate content. The organic matter content is highly concentrated at the top and bottom core, whereas in the middle core it is slightly decreased. The sorting values depict poor sorting which indicates mixed environment condition.i.e, one derived from riverine/aeolian environment and the other derived from marine environment. This is due to the widely varying nature of sediments and change in gradients of the coastaline. The heavy mineral assemblage of the study area shows the distribution of low and high ranked metamorphic and some basic igneous rocks.The presence of a little amount of zircon in the top core implies the influence of marine inputs by reworked sediments. XRF data resembles a sudden rise in the concentration towards the bottom core suggests that the trace elements show a positive relation with silt, clay and organic matter in the sediments. XRD analysis projects the presence of Illite in all the samples suggesting the emergence of estuary into Arabian Sea and the reworking of waves. From the overall study it is concluded that the river discharge from Kadalundi, deposits an additional sub-population of sand with a mean size of sediments from medium to fine grained, where low-energy conditons prevails and accretionary processes are taking place with mixed environments
Search in Power-Law Networks
Many communication and social networks have power-law link distributions,
containing a few nodes which have a very high degree and many with low degree.
The high connectivity nodes play the important role of hubs in communication
and networking, a fact which can be exploited when designing efficient search
algorithms. We introduce a number of local search strategies which utilize high
degree nodes in power-law graphs and which have costs which scale sub-linearly
with the size of the graph. We also demonstrate the utility of these strategies
on the Gnutella peer-to-peer network.Comment: 17 pages, 14 figure
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