Baysal, Veli | Özer, Mahmut | Yılmaz, Ergin

Bildiri | 2017 | 2017 Medical Technologies National Conference, TIPTEKNO 20172017-January , pp.1 - 4

In this paper, the effects of autapse (a kind of synapse formed between the axon or soma of a neuron and its own dendrites) on the weak signal detection capacity of a Hodgkin-Huxley (H-H) neuron are investigated. In the study, we consider that the H-H neuron has an inhibitory autapse modeled as a chemical synapse. The subthreshold sine wave is injected to the H-H neuron as a weak signal. Obtained results indicate that inhibitory autapse prominently increases the weak signal detection capacity of a H-H neuron when the proper autaptic time delay and autaptic conductance values are choosen. © 2017 IEEE.

Ergün, Alper | Ceylan, İlhan | Acar, Bahadır | Erkaymaz, Hande

Makale | 2017 | DRYING TECHNOLOGY35 ( 14 ) , pp.1711 - 1720

In this study, a temperature-controlled solar air collector was designed and tested for drying. Solar drying systems have two disadvantages. First one is the lack of ability to store energy and the second one is the lack of temperature control. This study presents the experimental analysis of an air collector that is able to keep the drying air temperature at 40 degrees C even in cases where the level of solar radiation received by the collectors changes. Most of the tests were performed at a solar radiation level ranging from 500 to 900W/m(2) and at an air flow of 3 to 5m/s. The system tested for drying three different crops separa . . .tely performed 21h of a total of 27-h drying period at or above the temperature set of 40 degrees C. The thermodynamic analysis of the relationship between solar radiation, air temperature, flow, and the produced energy was performed. The relationship between productivity, energy produced, and set temperature was analyzed using distribution charts. Moreover, an artificial neural network model was used to estimate outlet air temperature from the solar collectors based on air flow, solar radiation, and outside air temperature Daha fazlası Daha az

Çalım, Ali | Uzuntarla, Muhammet | Özer, Mahmut

Bildiri | 2014 | 2014 22nd Signal Processing and Communications Applications Conference, SIU 2014 - Proceedings , pp.1991 - 1994

In this study, the information coding issue in the nervous system is investigated. By using mathematical equations for modeling the dynamics of the basic units of the system, which are neurons, the information processing performance of the neuron populations is systematically studied. As most of studies in the literature investigate the subject by considering neuron populations as homogenous systems, in this study, the populations are considered as heterogeneous in terms of neuronal excitability. The obtained results demonstrate that considering the heterogeneity of the populations provides significant advantages for the processing . . .of neuronal information. It is shown that the neuron population exhibits maximal performance (resonance) for two different levels of network heterogeneity. Moreover, the influences of other biological parameters, forming the whole system, on this double-resonance phenomenon are investigated. © 2014 IEEE Daha fazlası Daha az

Çalım, Ali | Ağaoğlu, Şükriye Nihal | Uzuntarla, Muhammet

Bildiri | 2017 | 2017 25th Signal Processing and Communications Applications Conference, SIU 2017 , pp.1991 - 1994

Vital functions which take place in the brain are accomplished through synchronized neural activities between interconnected neuronal populations. In healthy and unhealthy nerve system, rhythms in different frequencies can be recognized as they are responsible for neural synchronization. Despite this, in the case of global synchronization where oscillation power is the maximum, as observed in epileptic seizures, neural activity can terminate. In this study, effects of neural network characteristics synchronization emerges from on activity termination are computationally investigated. Stochastic Hodgkin-Huxley (H-H) equations are use . . .d in the simulations. The results show that synchronization increases when neurons have high synaptic conductance and due to this, strong synaptic current neurons exposed to terminates the firings. © 2017 IEEE Daha fazlası Daha az

Erkaymaz, Okan | Palabaş, Tuğba

Bildiri | 2018 | 26th IEEE Signal Processing and Communications Applications Conference, SIU 2018 , pp.1 - 4

Computer assisted automatic diagnostic systems are used for the purpose of speeding up diagnosis and treatment and helping to make the right decision. In this study, cervical cancer is identified using four basic classifiers: Naive Bayes (NB), k-Nearest Neighbor (kNN), Multilayer Perceptron (MLP) and Decision Trees (KA-C4.5) algorithms and random subspaces ensemble algorithm. Gain Ratio Attribute Evaluation (GRAE) feature extraction algorithm is applied to contribute to classification performance. The classification results obtained with all datasets and reduced datasets are compared with respect to performance criteria such as accu . . .racy, Root Mean Square Error (RMSE), Sensitivity, Specificity performance criteria. According to the obtained performance analysis, it is seen that the classification performance with the random subspace ensemble algorithm using the kNN basic classifier on the reduced data set is the highest (%95.51). © 2018 IEEE Daha fazlası Daha az

Akbuğday, Burak | Yılmaz, Ergin

Bildiri | 2019 | TIPTEKNO 2019 - Tip Teknolojileri Kongresi , pp.1 - 4

Obstructive sleep apnea defined as a medical condition caused by loss of muscle tone in upper airway dilator muscles. There are various treatment methods exist for this condition both invasive and non-invasive, but they all have their weaknesses and strengths. Electrical stimulation method seems to be the most promising non-invasive method in terms of efficiency and adherence rate. This study introduces a low-cost, easy-to-use and wireless novel device to treat obstructive sleep apnea based on electrical stimulation method. The developed device uses an accelerometer to track respiration and apnea episodes and when an apnea episode i . . .s detected delivers a small electric current to dilator muscles to make them regain their muscle tone, thus treating obstructive sleep apnea. The device also communicates with a smartphone application to keep a recording of respiration and apnea data to enable further studying of data by medical professionals and researchers. © 2019 IEEE Daha fazlası Daha az

Baysal, Veli | Yılmaz, Ergin

Makale | 2020 | Physica A: Statistical Mechanics and its Applications537 , pp.1 - 4

In this paper, Vibrational Resonance (VR), in which the response of some dynamical systems to a weak, low frequency signal can be enhanced by the optimal amplitude of high frequency signal, is investigated under the effects of electromagnetic induction in both single neurons and small-world networks. We find that the occurrence of VR in single neurons requires less energy in the presence of electromagnetic induction, although the resonant peak of the response reduces. Besides, VR can be obtained in small-world networks both with and without electromagnetic induction. In small-world neuronal networks, the highest resonance peak of VR . . . enhances with an increase in the probability of adding link in case of without electromagnetic induction. On the other hand, with the increasing of the probability of adding link, VR disappears in the presence of relatively strong electromagnetic induction, while it enhances in the presence of relatively weak electromagnetic induction. © 2019 Elsevier B.V Daha fazlası Daha az

Yılmaz, Ergin | Uzuntarla, Muhammet | Özer, Mahmut | Perc, Matjaž

Makale | 2013 | Physica A: Statistical Mechanics and its Applications392 ( 22 ) , pp.5735 - 5741

We study the phenomenon of stochastic resonance in a system of coupled neurons that are globally excited by a weak periodic input signal. We make the realistic assumption that the chemical and electrical synapses interact in the same neuronal network, hence constituting a hybrid network. By considering a hybrid coupling scheme embedded in the scale-free topology, we show that the electrical synapses are more efficient than chemical synapses in promoting the best correlation between the weak input signal and the response of the system. We also demonstrate that the average degree of neurons within the hybrid scale-free network signifi . . .cantly influences the optimal amount of noise for the occurrence of stochastic resonance, indicating that there also exists an optimal topology for the amplification of the response to the weak input signal. Lastly, we verify that the presented results are robust to variations of the system size. © 2013 Elsevier B.V. All rights reserved Daha fazlası Daha az

Baysal, Veli | Yılmaz, Ergin | Özer, Mahmut

Bildiri | 2015 | 2016 MEDICAL TECHNOLOGIES NATIONAL CONFERENCE (TIPTEKNO) , pp.5735 - 5741

In this paper, the effects of autapse (a kind of synapse formed between the axon or soma of a neuron and its own dendrite) on the transmission of weak signal are investigated in scale-free neuronal networks. In the study, we consider that each neuron in the network has an autapse modelled as chemical synapse. Besides, a subthreshold signal are injected to all neurons in the network. When obtained results are analyzed, it is seen that the autaptic conductance has a threshold value. According to this threshold, the effects of autapse on the transmission of weak signal are evaluated within two categories. When conductance of autapse is . . . less than this threshold value, autapses with proper autaptic time delay values slightly increase the transmission of weak signal. When autaptic conductance is bigger than the threshold value, autapses with proper autaptic time deley values prominently block the transmission of weak signal Daha fazlası Daha az

Yılmaz, Ergin | Özer, Mahmut

Makale | 2013 | Physics Letters, Section A: General, Atomic and Solid State Physics377 ( 18 ) , pp.1301 - 1307

We consider a scale-free network of stochastic HH neurons driven by a subthreshold periodic stimulus and investigate how the collective spiking regularity or the collective temporal coherence changes with the stimulus frequency, the intrinsic noise (or the cell size), the network average degree and the coupling strength. We show that the best temporal coherence is obtained for a certain level of the intrinsic noise when the frequencies of the external stimulus and the subthreshold oscillations of the network elements match. We also find that the collective regularity exhibits a resonance-like behavior depending on both the coupling . . .strength and the network average degree at the optimal values of the stimulus frequency and the cell size, indicating that the best temporal coherence also requires an optimal coupling strength and an optimal average degree of the connectivity. © 2013 Elsevier B.V Daha fazlası Daha az

Erkan, Yasemin | Saraç, Zehra | Yılmaz, Ergin

Makale | 2019 | Nonlinear Dynamics95 ( 4 ) , pp.3411 - 3421

By virtue of recent developments in brain measurement technology, it is now recognized that information processing in brain includes not only neurons but also astrocytes. For this reason, to illustrate the effects of astrocyte on information processing in neuronal systems, we research the weak signal detection performance of the Hodgkin–Huxley neuron under the effect of astrocyte. It is found that the weak signal detection performance of the neuron exhibits the stochastic resonance phenomenon depending on noise intensity, where the presence of astrocyte with an optimal coupling strength significantly increases the detection performa . . .nce of the neuron when compared the one without astrocyte. The obtained results also reveal that there is an optimal weak signal frequency ensuring the best detection performance. Besides, we show that the colored noise exhibits a better performance than white Gaussian noise on improving the weak signal detection capacity of the neuron; moreover, the weak signal detection performance of the neuron demonstrates a resonance-like dependence on the correlation time of the noise. Finally, we investigate the effects of calcium channel noise. Although the calcium channel noise generally reduces the weak signal detection performance of the neuron, the optimal coupling strength warranting the best detection performance critically depends on its intensity. © 2019, Springer Nature B.V Daha fazlası Daha az

Baysal, Veli | Yılmaz, Ergin | Özer, Mahmut

Makale | 2017 | Istanbul University - Journal of Electrical and Electronics Engineering17 , pp.3081 - 3085

In this paper, the effects of autapse, a kind of synapse formed between the axon or soma of a neuron and its own dendrite, on the transmission of weak signal are investigated in scale-free neuronal networks. In the study, we consider that each neuron has an autapse modelled as chemical synapse. Then, a weak signal that is thought to carry information or an unwanted activity such as virus is applied to all neurons in the network. It is seen that the autapse with its small conductance values can slightly increases the transmission of weak signal across the network when the autaptic time delay is equal to the intrinsic oscillation peri . . .od of the Hodgkin-Huxley neuron. Interestingly, when the autaptic time delay becomes equal to half of this intrinsic period or its integer multiples the autapse can prominently blocks the weak signal transmission. Also, as the autaptic conductance is increased the weak signal transmission is completely impeded by the autapse with its proper auatptic time delays. One consider that the weak signal is an unwanted or virius threatening the whole network, this autaptic mechanism is an efficient way to protect the network from attacks Daha fazlası Daha az