2,770 research outputs found
Search in the Universe of Big Networks and Data
Searching in the Internet for some object characterised by its attributes in
the form of data, such as a hotel in a certain city whose price is less than
something, is one of our most common activities when we access the Web. We
discuss this problem in a general setting, and compute the average amount of
time and the energy it takes to find an object in an infinitely large search
space. We consider the use of N search agents which act concurrently. Both the
case where the search agent knows which way it needs to go to find the object,
and the case where the search agent is perfectly ignorant and may even head
away from the object being sought. We show that under mild conditions regarding
the randomness of the search and the use of a time-out, the search agent will
always find the object despite the fact that the search space is infinite. We
obtain a formula for the average search time and the average energy expended by
N search agents acting concurrently and independently of each other. We see
that the time-out itself can be used to minimise the search time and the amount
of energy that is consumed to find an object. An approximate formula is derived
for the number of search agents that can help us guarantee that an object is
found in a given time, and we discuss how the competition between search agents
and other agents that try to hide the data object, can be used by opposing
parties to guarantee their own success.Comment: IEEE Network Magazine - Special Issue on Networking for Big Data,
July-August 201
Signalling Storms in 3G Mobile Networks
We review the characteristics of signalling storms that have been caused by
certain common apps and recently observed in cellular networks, leading to
system outages. We then develop a mathematical model of a mobile user's
signalling behaviour which focuses on the potential of causing such storms, and
represent it by a large Markov chain. The analysis of this model allows us to
determine the key parameters of mobile user device behaviour that can lead to
signalling storms. We then identify the parameter values that will lead to
worst case load for the network itself in the presence of such storms. This
leads to explicit results regarding the manner in which individual mobile
behaviour can cause overload conditions on the network and its signalling
servers, and provides insight into how this may be avoided.Comment: IEEE ICC 2014 - Communications and Information Systems Security
Symposiu
Fine needle aspiration cytology of hepatic metastases of neuroendocrine tumors: A 20âyear retrospective, single institutional study
Background
Fine needle aspiration (FNA) is considered an excellent technique for documenting metastatic neuroendocrine tumors (NETs). This study aims to evaluate the accuracy of FNA in diagnosing metastatic NETs to the liver and determining the grade and origin of these metastases.
Methods
Our laboratory information system was searched from 1997 to 2016 to identify all cases of metastatic NETs to the liver that were sampled by FNA. The cytopathology and surgical pathology reports as well as the patients' electronic medical records were reviewed. The cytohistologic type and grade of the metastatic NETs, as well as the site of the patient's primary were recorded.
Results
Highâgrade NETs, including small cell and poorly differentiated neuroendocrine carcinomas, constituted 62% (167/271) of the cases, while lowâgrade NETs, including well differentiated NET (grade1 and grade 2), pheochromocytomas, paragangliomas, and carcinoid tumors of lung, constituted 38% (104/271) of cases. The most common diagnosis was metastatic small cell carcinoma accounting for 45% (122/271) of cases. The most common primary sites were lung (44%; 119/271) followed by pancreas (19%; 51/271). The FNA diagnosis was confirmed by histopathology in 121 cases that had a concurrent biopsies or resection specimens.
Conclusions
FNA is an accurate method for diagnosing metastatic NETs to the liver. There were significantly more highâgrade (62%) than lowâgrade (38%) metastatic NETs to the liver. In our practice, lung (44%) and pancreas (19%) were the most common primary sites of metastatic NETs involving the liver. In 16% of the cases, a primary site could not be established
A state variable for crumpled thin sheets
Despite the apparent ease with which a sheet of paper is crumpled and tossed
away, crumpling dynamics are often considered a paradigm of complexity. This
complexity arises from the infinite number of configurations a disordered
crumpled sheet can take. Here we experimentally show that key aspects of
crumpling have a very simple description; the evolution of the damage in
crumpling dynamics can largely be described by a single global quantity, the
total length of all creases. We follow the evolution of the damage network in
repetitively crumpled elastoplastic sheets, and show that the dynamics of this
quantity are deterministic, and depend only on the instantaneous state of the
crease network and not at all on the crumpling history. We also show that this
global quantity captures the crumpling dynamics of a sheet crumpled for the
first time. This leads to a remarkable reduction in complexity, allowing a
description of a highly disordered system by a single state parameter. Similar
strategies may also be useful in analyzing other systems that evolve under
geometric and mechanical constraints, from faulting of tectonic plates to the
evolution of proteins
Extending The Lossy Spring-Loaded Inverted Pendulum Model with a Slider-Crank Mechanism
Spring Loaded Inverted Pendulum (SLIP) model has a long history in describing
running behavior in animals and humans as well as has been used as a design
basis for robots capable of dynamic locomotion. Anchoring the SLIP for lossy
physical systems resulted in newer models which are extended versions of
original SLIP with viscous damping in the leg. However, such lossy models
require an additional mechanism for pumping energy to the system to control the
locomotion and to reach a limit-cycle. Some studies solved this problem by
adding an actively controllable torque actuation at the hip joint and this
actuation has been successively used in many robotic platforms, such as the
popular RHex robot. However, hip torque actuation produces forces on the COM
dominantly at forward direction with respect to ground, making height control
challenging especially at slow speeds. The situation becomes more severe when
the horizontal speed of the robot reaches zero, i.e. steady hoping without
moving in horizontal direction, and the system reaches to singularity in which
vertical degrees of freedom is completely lost. To this end, we propose an
extension of the lossy SLIP model with a slider-crank mechanism, SLIP- SCM,
that can generate a stable limit-cycle when the body is constrained to vertical
direction. We propose an approximate analytical solution to the nonlinear
system dynamics of SLIP- SCM model to characterize its behavior during the
locomotion. Finally, we perform a fixed-point stability analysis on SLIP-SCM
model using our approximate analytical solution and show that proposed model
exhibits stable behavior in our range of interest.Comment: To appear in The 17th International Conference on Advanced Robotic
The Role of Supreme Audit Institutions in Improving Citizen Participation in Governance
Supreme Audit Institutions (SAIs) â key government agencies responsible for auditing how public funds are being spent â have been traditionally seen as insulated and technocratic entities serving other government organizations and having little to do with citizens and broader governance issues. This image has been slowly changing around the world in light of the broader transformations in governmentsâ roles, SAIsâ own practices, and increased public participation in governance. This article reviews why and how these changes are happening and barriers to the more productive collaboration between SAIs and the public. The article concludes with implications for practitioners and researchers
Effect of concept map supported teaching approaches from rules to sample and sample to rules to grammar teaching
2nd World Conference on Educational Sciences (WCES-2010) -- FEB 04-08, 2010 -- Bahceschir Univ, Istanbul, TURKEYWOS: 000282002803154In this study, the effect of approach from rules-to-sample and sample-to-rules to the teaching of grammar subjects has been analysed. While treating grammar subjects from rules-to-sample and sample-to-rules learning-teaching process in both approaches are supported by the concept map. Application has been maintained for six weeks and data were obtained by applying more assesment instruments to students taking part in experimental and control groups. In practice, pretest - post test model was applied. At the end of the learning-teaching process, achievements of students have been assesed by a variety of assesment instruments, the data gathered has been analysed with the help of statistical techniques such as one-way variance analysis, "t" test, arithmetic averages. 96 students at the level of fourth grade participated the application process; 30 of them participated application from rules-to-sample; 33 students participated application from sample to rules in an active manner, and 33 students in the control group continued to traditional teaching. Assesments have been analysed and results have been compared. As a result of research, results that participants obtained were compared in terms of variables such as students' participation level to teaching process, the time students spent for learning, students' rememberance level of what they have learned. In terms of foregoing variables, meaningful results were obtained in favor of approach from sample to rule. By taking into account of the results obtained, some suggestions have been done aiming to teaching done by teaching strategies and concept maps. (C) 2010 Elsevier Ltd. All rights reserved
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