Browsing by Subject "Effective solution"

Now showing 1 - 5 of 5

Open Access
Algorithms for sink mobility in wireless sensor networks to improve network lifetime
(Springer, 2012-09) Koç, Metin; Körpeoğlu, İbrahim
Sink mobility is an effective solution in the literature for wireless sensor network lifetime improvement. In this paper, we propose a set of algorithms for sink site determination (SSD) and movement strategy problems of sink mobility. We also present experiment results that compare the performance of our algorithms with other approaches in the literature. © 2012 Springer-Verlag London Limited.
Open Access
Coordinated movement of multiple mobile sinks in a wireless sensor network for improved lifetime
(SpringerOpen, 2015) Koç, M.; Korpeoglu, I.
Sink mobility is one of the most effective solutions for improving lifetime and has been widely investigated for the last decade. Algorithms for single-sink mobility are not directly applied to the multiple-sink case due to the latter’s specific challenges. Most of the approaches proposed in the literature use mathematical programming techniques to solve the multiple-sink mobility problem. However, doing so leads to higher complexities when traffic flow information for any possible sink-site combinations is included in the model. In this paper, we propose two algorithms that do not consider all possible sink-site combinations to determine migration points. We first present a centralized movement algorithm that uses an energy-cost matrix for a user-defined threshold number of combinations to coordinate multiple-sink movement. We also give a distributed algorithm that does not use any prior network information and has a low message exchange overhead. Our simulations show that the centralized algorithm gives better network lifetime performance compared to previously proposed MinDiff-RE, random movement, and static-sink algorithms. Our distributed algorithm has a lower network lifetime than centralized algorithms; sinks travel significantly less than in all the other schemes.
Open Access
Nanosprings harvest light more efficiently
(OSA - The Optical Society, 2015) Khudiyev, T.; Bayındır, Mehmet
Nanotechnology presents versatile architectural designs for the purpose of utilization as a building block of 1D optoelectronic nanodevices because current nanowire-based schemes require more effective solutions for low absorption capacity of nanoscale volumes. We report on the potential of nanospring absorbers as an alternative light-harvesting platform with significant advantages over conventional nanowires. Absorption capacity of nanospring geometry is found to be superior to cylindrical nanowire shape. Unlike nanowires, they are able to trap a larger amount of light thanks to characteristic periodic behavior that boosts light collection for the points matched with Mie resonances. Moreover, nanospring shape supplies compactness to a resulting device with area preservation as high as twofold. By considering that a nanospring array with optimal periods yields higher absorption than individual arrangements and core-shell designs, which further promote light collection due to unique antireflection features of shell layer, these nanostructures will pave the way for the development of highly efficient self-powered nanosystems.
Open Access
RailwayDB: adaptive storage of interaction graphs
(Association for Computing Machinery, 2016) Soulé R.; Gedik, B.
We are living in an ever more connected world, where data recording the interactions between people, software systems, and the physical world is becoming increasingly prevalent. These data often take the form of a temporally evolving graph, where entities are the vertices and the interactions between them are the edges. We call such graphs interaction graphs. Various domains, including telecommunications, transportation, and social media, depend on analytics performed on interaction graphs. The ability to efficiently support historical analysis over interaction graphs requires effective solutions for the problem of data layout on disk. This paper presents an adaptive disk layout called the railway layout for optimizing disk block storage for interaction graphs. The key idea is to divide blocks into one or more sub-blocks. Each sub-block contains the entire graph structure, but only a subset of the attributes. This improves query I/O, at the cost of increased storage overhead. We introduce optimal integer linear program (ILP) formulations for partitioning disk blocks into sub-blocks with overlapping and nonoverlapping attributes. Additionally, we present greedy heuristics that can scale better compared to the ILP alternatives, yet achieve close to optimal query I/O. We provide an implementation of the railway layout as part of RailwayDB—an open-source graph database we have developed. To demonstrate the benefits of the railway layout, we provide an extensive experimental evaluation, including model-based as well as empirical results comparing our approach to baseline alternatives.
Open Access
Understanding the tendency of software development teams to develop software over the cloud
(CEUR-WS, 2016) Çoban, S.; Uçar, Erkan; Chouseinoglou, Oumout; Sevgi, C.; Testik, Murat Caner
Today, Cloud Computing offers attractive and effective solutions for organizations which enable them to decrease IT costs, provide flexibility to ser-vices and make it easier to access IT services -Therefore enable faster market entries. For an organization that decides to make use of Cloud services, there are various factors to evaluate - similar to outsourcing. In this paper, we studied these factors through the literature and then we tried to understand the viewpoints of software developers regarding the existing and possible future usage of Cloud in software development processes. In this context, we prepared a questionnaire based on the findings in the literature and applied it to software development team members working in technoparks in Turkey. We used the dataset which is obtained from this questionnaire to observe the relationship between the tendency of using Cloud in software development processes and the factors effecting them. This research is performed as the first phase of a study with a larger scope, de-signed to forecast the Cloud needs of software developing organizations and it provides important findings. The questionnaire findings also describe the current demographics of software development organizations in Turkish technoparks to-gether with their perception of Cloud services.