Koray Gürkan

A spiking and bursting neuron circuit based on memristor

In this paper, we propose two emulator circuits. Firstly, we present a novel memristor emulator based on operational transconductance amplifier (OTA) which is different from classical TiO2 memristor. This memristor emulator has a threshold switching mechanism. Secondly, we create a novel neuron circuit using proposed memristor, which is capable of generating spiking and bursting firing behaviors, with a biologically plausible spike shapes. The behavior of this neuron circuit can be adjusted by changing only one external biasing voltage. This neuron circuit mimics the behavior of cortical neurons, such as regular spiking (RS), intrinsic bursting (IB), chattering (CH) and fast spiking (FS). Proposed emulator circuits are compatible with VLSI systems and they can also be implemented by using discrete circuit components for different applications.

Electric field responsive chitosan–poly(N,N-dimethyl acrylamide) semi-IPN gel films and their dielectric, thermal and swelling characterization

The electroresponsive, dielectric and swelling behavior of semi-interpenetrated polymer network (semi-IPN) gel films prepared from chitosan (CS) and N,N-dimethyl acrylamide (DA) were investigated and compared with those CS film. CS?DA semi-IPN films were also characterized by Fourier transform infrared, x-ray diffraction and differential scanning calorimetry measurements. The electrosensitivity of CS?DA films to an electric field was investigated by determining their bending at 8?V in (0.05?M/0.1?M/0.15?M) NaCl solution. Equilibrium swelling values of CS?DA films both in distilled water and buffer solution with pH?=?2.2 decreased with poly-DA (PDA) content of the films. While the maximum decomposition of CS film took place at about 296??C, the presence of PDA in CS?DA semi-IPN films reduced the thermal stability, and their maximum decomposition temperature shifted from 261 to 240??C with the increase in PDA content. In addition, the PDA network led to a decrease in the dielectric constant (??), dielectric loss (??) and conductance (?) of CS?DA semi-IPN films in the frequency range between 12?Hz and 100?kHz. The values of electric modulus and impedance, and Cole?Cole plots confirmed that the conductance values of CS?DA films are lower than that of CS film. The PDA network also led CS?DA films to respond more slowly to electric field. The increase in NaCl concentration in the bending medium increased the response rate of CS?DA films to an electric field. The final bending angle of all CS?DA films was 90?, and it was not dependent on either NaCl concentration or PDA content of the films.

Design and Experimental Evaluation of Quadrature Oscillator Employing Single FB–VDBA

Abstract This paper presents an attractive and a new voltage-mode quadrature oscillator using a single Fully Balanced-Voltage Differencing Buffer Amplifier (FB-VDBA) as the active element. The circuit structure is very simple, consisting of merely one FB-VDBA, one resistor and two capacitors. The circuit is implemented using the commonly available OPA860 which results in low output impedance and high current drive capability. The proposed circuit also has a suitable architecture for IC production. Experimental results which are matched well with the theoretical assumptions are given.

Simulation and Measurement of Air-Coupled Semi-Circular and Conical PVDF Sensors

For airborne sound navigation and ranging (SONAR) applications, low frequency and broadband transducers are required for the detection of obstacles with high axial resolution. In this paper, electrical and mechanical characteristics of semi-circular sensors and a semi-conical polyvinylidene fluoride (PVDF) sensor are compared through simulations and experiments. First, the implementation of semi-circular transducers and semi-conical transducer is presented. The electrical pulse, sine responses, dielectric impedance spectroscopy, and beam pattern measurements of transducers are achieved and compared. The vibration analysis of produced sensors was performed by a finite-element method and compared with experimental results. Experiments and simulations show that the semi-conical PVDF transducer has a higher bandwidth than the semi-circular transducers and it is suitable for low-frequency airborne pulse-echo ultrasound applications using single pulse or frequency chirped wave transducer.

Wireless 3-axis accelerometer system for measurement of structural displacement

In this study, we present the design of a 3-axis acceleration measurement system that is capable of UTC (Coordinated Universal Time) time-stamping captured from a Global Positioning System (GPS) receiver module. With this achievement, the system is able to monitor and record the 3-axis vibrations with respect to an absolute time rather than the local sensor (and computer) time. Acquired 3-axis acceleration data and UTC are transferred via Bluetooth® protocol and developed software which enables monitoring and recording of UTC and acceleration data on a PC, respectively. For verification and synchronization quality test of acceleration data, shake-table tests were conducted for simulation of structural displacement and the calculated displacements were compared with a displacement sensor of a commercially available shake table system.

VibroCap: A mobility supporting hat for blind

In this paper, we present the VibroCap, a mobility aiding hat which is designed to detect obstacles and alert the visually impaired user. By using low cost PVDF (Polyvinylidene Fluoride) ultrasonic sensors, hat detects obstacles, which are located across the upper part of the human body and cannot normally be detected by white cane. Depending on the distance of the detected obstacle, visually impaired person is informed by three vibration motors placed on the forehead. The design stages and experimental results of the obstacle detection system are presented.

Maximum load behaviour of a fuel cell stack under different ambient temperatures

We studied the full load behavior of a proton exchange membrane fuel-cell(PEMFC) stack at under different ambient temperatures. We switched a load to the FC system and observed the system parameters as FC temperature, current and voltage under two different ambient temperature. We extracted to ambient temperature effects on the power transferred to load. We also investigated the effect of hydrogen tube temperature and hydrogen tube pressure relation on FC system.