Bilgisayar Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/253
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Article Citation - WoS: 8Citation - Scopus: 8Comparative Analysis on Wavelet-Based Detection of Finite Duration Low-Amplitude Signals Related To Ventricular Late Potentials(Iop Publishing Ltd, 2004) Mousa, A; Yilmaz, AVentricular late potentials (VLPs) are considered as a noninvasive marker of patients with myocardial infarction, who are prone to the development of ventricular tachycardia. This paper investigates the effects of variations in physical properties of myocardial infarcts in terms of their effects on the parametric variations in VLP analysis. A sufficiently large set of signals underlining the behavior of physical parameters was employed to represent the effect of physical size, position, orientation and type of infarct. The approximated signals are variations from real electrocardiography signals by adding potentials representing late potentials based on duration, frequency, amplitude and position. The aim is not to exactly model VLP but rather to generate an approximate set of signals to examine the performance of the standard methods for different possibilities in infarct dynamics. We investigate some of the detection approaches together with their related assumptions, and try to pinpoint the drawbacks and inaccuracies of these methods and also their assumptions. The three widely accepted criteria-QRS duration, root-mean-square and duration of the signal at the end of QRS for VLP detection-were used in the investigation. Results from the application of these parameters to the set of signals are presented. In addition we investigate the physical nature of an infarct and list a number of possible reasons that might be the cause of a low success rate for the detection of additive potentials. To improve the performance of the common methods, two more wavelet transform parameters are added to those of the standard methods. The method derived from this analysis is presented as an alternative means for the detection of late signals named as delayed potentials, a more general class that includes VLP as a subset.Article Citation - WoS: 22Citation - Scopus: 21Functionalizing Graphene by Embedded Boron Clusters(Iop Publishing Ltd, 2008) Ozdogan, Cem; Kunstmann, Jens; Fehske, Holger; Quandt, AlexanderWe present a model system that might serve as a blueprint for the controlled layout of graphene based nanodevices. The systems consists of chains of B-7 clusters implanted in a graphene matrix, where the boron clusters are not directly connected. We show that the graphene matrix easily accepts these alternating B-7-C-6 chains and that the implanted boron components may dramatically modify the electronic properties of graphene based nanomaterials. This suggests a functionalization of graphene nanomaterials, where the semiconducting properties might be supplemented by parts of the graphene matrix itself, but the basic wiring will be provided by alternating chains of implanted boron clusters that connect these areas.Article Citation - WoS: 9Citation - Scopus: 11Thermal Stability of Metallic Single-Walled Carbon Nanotubes: an O(N) Tight-Binding Molecular Dynamics Simulation Study(Iop Publishing Ltd, 2007) Suengue, B.; Oezdogan, C.; Dereli, G.; Süngü, B.; Özdoǧan, C.Order(N) tight-binding molecular dynamics (TBMD) simulations are performed to investigate the thermal stability of ( 10, 10) metallic single-walled carbon nanotubes (SWCNTs). Periodic boundary conditions (PBCs) are applied in the axial direction. The velocity Verlet algorithm along with the canonical ensemble molecular dynamics (NVT) is used to simulate the tubes at the targeted temperatures. The effects of slow and rapid temperature increases on the physical characteristics, structural stability and the energetics of the tube are investigated and compared. Simulations are carried out starting from room temperature and the temperature is raised in steps of 300 K. The stability of the simulated metallic SWCNT is examined at each step before it is heated to higher temperatures. The first indication of structural deformation is observed at 600 K. For higher heat treatments the deformations are more pronounced and the bond-breaking temperature is reached around 2500 K. Gradual ( slow) heating and thermal equilibrium ( fast heating) methods give the value of radial thermal expansion coefficient in the temperature range between 300 and 600 K as 0.31 x 10(-5) and 0.089 x 10(-5) K-1, respectively. After 600 K, both methods give the same value of 0.089 x 10(-5) K-1. The ratio of the total energy per atom with respect to temperature is found to be 3 x 10(-4) eV K-1.