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- 저자 : Bayrakdar (검색결과 6 건)
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Bayrakdar, Muhammed Enes Electronics and Telecommunications Research Instit 2020 ETRI Journal Vol.42 No.1
A priority-based data communication approach, developed by employing cognitive radio capacity for sensor nodes in a wireless terrestrial sensor network (TSN), has been proposed. Data sensed by a sensor node-an unlicensed user-were prioritized, taking sensed data importance into account. For data of equal priority, a first come first serve algorithm was used. Non-preemptive priority scheduling was adopted, in order not to interrupt any ongoing transmissions. Licensed users used a nonpersistent, slotted, carrier sense multiple access (CSMA) technique, while unlicensed sensor nodes used a nonpersistent CSMA technique for lossless data transmission, in an energy-restricted, TSN environment. Depending on the analytical model, the proposed wireless TSN environment was simulated using Riverbed software, and to analyze sensor network performance, delay, energy, and throughput parameters were examined. Evaluating the proposed approach showed that the average delay for sensed, high priority data was significantly reduced, indicating that maximum throughput had been achieved using wireless sensor nodes with cognitive radio capacity.
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Ali Bayrakdar,Mine Yaman,Ramazan Ilgün 한국통합생물학회 2015 Animal cells and systems Vol.19 No.5
In this research, we aimed to determine the regional distribution and relative frequency of immunoreactive (IR) endocrine cells of ghrelin, glucagon, somatostatin–14 (SOM–14), neuropeptide Y (NPY), calcitonin-gene-related peptide (CGRP), insulin and galanin in small and large intestines of mole-rats (Spalax leucodon) by using immunohistochemical staining methods. For this purpose, small and large intestine regions of six adult mole-rats were used as material. In the small and large intestines of mole-rats (S. leucodon), ghrelin, glucagon, SOM–14, NPY and CGRP were identified at various frequencies, but insulin and galanin were not detected in this study. Ghrelin-IR cells were only observed in the small intestine. In addition, the existence of positive staining in the cells was decreased while passing from duodenum to ileum. Glucagon-IR cells were mainly detected in the small intestine regions and colon. SOM–14-IR cells were detected throughout the small intestines with a lesser frequency. NPY-IR cells were also detected in the small and large intestines at various frequencies but not in cecum and rectum. CGRP-IR cells were scarce in duodenum and jejunum, but their numbers increased from ileum to colon. In conclusion, the present study revealed the existence and distributions of neuropeptide-secreting endocrine cells in small and large intestines of mole-rats (S. leucodon).
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Muhammed Enes Bayrakdar,Ali Çalhan 한국전자통신연구원 2017 ETRI Journal Vol.39 No.4
In this study, a non-preemptive M/G/1 queueing model of a spectrum handoff scheme for cognitive wireless networks is proposed. Because spectrum handoff gives secondary users an opportunity to carry on their transmissions, it is crucially important to determine the actions of primary users. In our queueing model, prioritized data traffic is utilized to meet the requirements of the secondary users. These users’ packets are categorized into three different priority classes: urgent, real-time, and non-real time. Urgent data packets have the highest priority, while non-real time data packets have the lowest priority. Riverbed (OPNET) Modeler simulation software was used to simulate both reactive and proactive decision spectrum handoff schemes. The simulation results were consistent with the analytical results obtained under different load and traffic conditions. This study also revealed that the cumulative number of handoffs can be drastically decreased by exploiting priority classes and utilizing a decent spectrum handoff strategy, such as a reactive or proactive decision-based strategy.
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The statistical optimization of bacterial cellulose production via semi-continuous operation mode
Ali O¨ zhan Aytekin,Deniz Dilan Demirbag,Tug˘c¸e Bayrakdar 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.37 No.-
Bacterial cellulose (BC) is highly pure and has a higher crystallinity and molecular weight than plantcellulose. Therefore, BC can be used in many different areas such as biotechnology, pharmaceutical,cosmetics. Because of the price of BC, the productivity of BC is an important parameter for industrial scaleapplications. In this study, BC was produced in static culture using a semi-continuous operation mode;the conditions were optimized using response surface methodology (RSM). The collected BC wascharacterized by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM),and tensile strength. Optimization parameters were selected as glucose concentration, surface area/volume ratio, surface area and incubation day intervals. The optimum values for incubation dayintervals, volume changing ratios, glucose concentrations and surface area/volume ratios were 7 days,66%, 50 g/L and 1.22 cm 1, respectively. BC productivity reached 0.284 g/L/day under optimalconditions, while the model equation proposed 0.289 g/L/day. RSM is essential for determining theoptimum values of parameters for BC production compared with the one-variable-at-a-time method. The semi-continuous operation mode is alternative and a good candidate for the industrial scaleproduction of BC.
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Ahmet G¨um¨us¸,G¨ul¸cin Ers¨oz,˙Ibrahim Y¨uceda˘g,S¨umeyye Bayrakdar,S¸ emsettin Altındal 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.5
The dielectric properties of Au/PPy/n-Si metal-polymer-semiconductor (MPS)-type Schottky barrier diodes (SBDs) were investigated by using capacitance-voltage (C-V ) and conductancevoltage (G/!-V ) measurements at various temperatures and voltages at frequencies of 100 kHz and 500 kHz. Both the real and the imaginary parts of the complex dielectric constant and dielectric loss ("0, "00) and of the electric modulus (M0, M00), as well as the conductivity (ac), were found to depend strongly on the temperature and the voltage. Both the C and G/! values increased with increasing applied voltage and had inversion, depletion, and accumulation regions as with a metal-insulator-semiconductor (MIS) type behavior. Both the dielectric constant ("0) and the dielectric loss ("00) increased with increasing temperature and decreased with increasing frequency. The loss tangent (tan ) vs. temperature curve had a peak at about 200 K for both frequencies. The M0 and the M00 values decreased with increasing temperature and became independent of the frequency at high temperatures. The series resistance (Rs) of the diode decreased with increasing temperature for the two frequencies while the ac increased. Such behaviors of the dielectric properties with temperature were attributed to the restructuring and reordering of charges at interface states/traps due to the varying temperature, the interfacial polarization, and the interfacial polymer layer. ln(ac) vs. q/kT plots had two distinct linear regions with different slopes for the two frequencies. Such behaviors of these plots confirmed the existence of two different conduction mechanisms corresponding to low and high temperatures. The values of the activation energy (Ea) were obtained from the slopes of these plots, and its value at low temperatures was considerably lower than that at high temperatures.
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