Synchronization waves in geometric networks

We report synchronization of networked excitable nodes embedded in a metric space, where the connectivity properties are mostly determined by the distance between units. Such a high clustered structure, combined with the lack of long-range connections, prevents full synchronization and yields instead the emergence of synchronization waves. We show that this regime is optimal for information transmission through the system, as it enhances the options of reconstructing the topology from the dynamics. Measurements of topological and functional centralities reveal that the wave-synchronization state allows detection of the most structurally relevant nodes from a single observation of the dynamics, without any a priori information on the model equations ruling the evolution of the ensembl

Integration versus segregation in functional brain networks

We propose a new methodology to evaluate the balance between segregation and integration in functional brain networks by using singular value decomposition techniques. By means of magnetoencephalography, we obtain the brain activity of a control group of 19 individuals during a memory task. Next, we project the node-to-node correlations into a complex network that is analyzed from the perspective of its modular structure encoded in the contribution matrix. In this way, we are able to study the role that nodes play I/O its community and to identify connector and local hubs. At the mesoscale level, the analysis of the contribution matrix allows us to measure the degree of overlapping between communities and quantify how far the functional networks are from the configuration that better balances the integrated and segregated activit

Insulator materials for interface passivation of Cu(In,Ga)Se2 thin films

In this work, Metal-Insulator-Semiconductor (MIS) structures were fabricated in order to study different types of insulators, namely, aluminum oxide (Al2O3), silicon nitride (Si3Nx) and silicon oxide (SiOx) to be used as passivation layers in Cu(In,Ga)Se2 (CIGS) thin film solar cells. The investigated stacks consisted of SLG/Mo/CIGS/insulator/Al. Raman scattering and Photoluminescence measurements were done to verify the insulator deposition influence on the CIGS surface. In order to study the electrical properties of the CIGS-insulator interface, capacitance vs. conductance and voltage (C-G-V) measurements were done to estimate the number and polarity of fixed insulator charges (Qf). The density of interface defects (Dit) was estimated from capacitance vs. conductance and frequency (C-G-f) measurements. This study evidences that the deposition of the insulators at high temperatures (300 ºC) and the use of sputtering technique cause surface modification on the CIGS surface. We found that, by varying the SiOx deposition parameters, it is possible to have opposite charges inside the insulator, which would allow its use in different device architectures. The material with lower Dit values was Al2O3 when deposited by sputtering.publishe

Data mining application on students' data

AbstractIn today's world, due to the rapid development of technology, the amount of data stored has been constantly increasing in every field. It is intended to obtain meaningful, valuable information that is not previously known from these data by applying data mining techniques.In data mining techniques, association rules are one of the most preferred techniques. Apriori algorithm is the most used one in these association rules. In this work, by being carried out apriori algorithm upon the data of students of Istanbul Eyup I.M.K.B. Vocational Commerce High School, the rules have been produced and from the results obtained the relation between the courses that the students failed have been revealed