Konstantin Nikolic | University of West London (original) (raw)

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Papers by Konstantin Nikolic

F1000Research, Sep 3, 2016

International Conference on Machine Learning, Jun 24, 2016

Research features, Feb 10, 2019

IEEE Conference Proceedings, 2016

Applied system innovation, Aug 17, 2022

Solid-state Electronics, May 1, 1992

Abstract Landsberg, Scholl and Shukla have recently proposed a new model for generation-recombina... more Abstract Landsberg, Scholl and Shukla have recently proposed a new model for generation-recombination kinetics which can be used to explain the origin of chaos in semiconductors. In this paper, steady-states for the Landsberg-Scholl-Shukla (LSS) model are determined and compared with the steady-states arising from the classical (rate equation) model. In the case of cooled p -Ge, both models give a second-order nonequilibrium phase transition, from the nonconducting to the conducting state for the same value of control parameter A. This nonzero stable fixed point, in the case of the LSS model, can lose stability in a way which does not exist in the classical model. This leads to very significant differences between these two models. Furthermore, for the LSS model there is the possibility of extra fixed points appearing.

This paper identifies and addresses key design considerations and trade-offs in the implementatio... more This paper identifies and addresses key design considerations and trade-offs in the implementation of a CMOS high-resolution microheater array for Lab-on-Chip (LOC) applications. Specifically, this is investigated in the context of facilitating the in vitro thermal stimulation of single neurons. The paper analyses the electro-thermal response (by means of COMSOL simulations) and reliability issues (such as melting and electromigration) of different microheater designs. The analysis shows that a small-area heater is more efficient in terms of power, but it has more reliability problems essentially due to electromigration effects. For the proposed heater designs, the expected lifetime is a few days (in continuous operation) in the worst scenario, which is still generally acceptable for LOC applications.

Applied Physics Letters, Jun 17, 1996

We present the current–voltage characteristics of a T-shaped semiconductor electron waveguide str... more We present the current–voltage characteristics of a T-shaped semiconductor electron waveguide structure in the nonlinear regime. This system is interesting as a potential quantum interference transistor. Calculated zero-temperature I–V characteristics are with multiple peaks and exhibit regions of negative-differential resistance. The peak-to-valley ratio has maximum value of 3:1. The calculated values of the transconductance and the differential drain conductance are small, which suggests limited abilities for conventional applications of the transistor.

2022 IEEE Biomedical Circuits and Systems Conference (BioCAS)

2018 IEEE Biomedical Circuits and Systems Conference (BioCAS), 2018

2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2018

Neurostimulations which use High Frequency Alternating Current (HFAC) block show great promise fo... more Neurostimulations which use High Frequency Alternating Current (HFAC) block show great promise for neuromodulatory therapies. Treatments have been developed for various health conditions including obesity and obesity related health risks, and now even stomach cancer treatments are being considered. However the mechanism of the block is still not completely clear, as well as how various neural and electrode parameters affect it. In order to study conduction block during HF stimulation in mammalian axons, we describe a detailed computational model and perform comprehensive simulations. We establish relationships between the blocking frequency and amplitude versus fibre diameter and the distance between the electrode and fibre. We found that only a certain level of depolarisation will universally create a block irrespective of the fibre size, and it is in the range 24–30mV depending on the stimulus frequency. Our study crucially improves our knowledge about this important technique whi...

Investigative Ophthalmology & Visual Science, 2008

Closed loop neuromodulation, where the stimulation is controlled autonomously based on physiologi... more Closed loop neuromodulation, where the stimulation is controlled autonomously based on physiological events, has been more effective than open loop techniques. In the few existing closed loop implementations which have a feedback, indirect non-neurophysiological biomarkers have been typically used (e.g. heart rate, stomach distension). Although these biomarkers enable automatic initiation of neural stimulation, they do not enable intelligent control of stimulation dosage. In this paper, we present a novel closed loop neuromodulation platform based on a dual signal mode that is detecting electrical and chemical signatures of neural activity. We demonstrated it on a case of vagus nerve stimulation (VNS). Vagal chemical (pH) signal is detected and used for initiatisng VNS and vagal compound action potential (CAP) signals are used to determine the stimulation dosage and pattern. Although we used the paradigm of appetite control and neurometabolic therapies, the platform developed here c...

BMC Neuroscience, Dec 1, 2015

Neuromorphic computing is going to be the new standard in low power AI applications. The integrat... more Neuromorphic computing is going to be the new standard in low power AI applications. The integration between new neuromorphic hardware and traditional microcontroller is an open challenge. Here we present an interface board and a communication protocol that allows the communication between different devices using a microcontroller unit (Arduino Due) in the middle. Our compact printed circuit board (PCB) board links different devices as a whole system and provides power supply for the entire system using batteries as power source. Specifically, we have connected a Dynamic Vision Sensor (DVS128), SpiNNaker board and a servo motor, creating a platform for intercepting incoming objects. The data rate of the implemented interface board is 24.64k symbols/s and the latency for generating commands is about 11ms. The complete system is run only by batteries making it very suitable for robotic applications.

In recent years, artificial neural networks (ANNs) have completely changed the field of machine l... more In recent years, artificial neural networks (ANNs) have completely changed the field of machine learning, especially computer vision. The Spike Neural Network (SNN) is biologically more realistic than ANN. It is more hardware-friendly and energy-efficient, and suitable for running on portable devices with weak computing performance. In this paper we aim to classify several Chinese character images based on SNN. The input image is preprocessed by traditional methods (OpenCV) and then it is input into the trained spike neural network to classify the characters. Different hyperparameters configurations are tested reaching an optimal configuration and a classification accuracy rate of 93%.

2018 IEEE International Symposium on Circuits and Systems (ISCAS)

An integrated circuit for real-time, simultaneous recording of electrical and chemical(pH) signat... more An integrated circuit for real-time, simultaneous recording of electrical and chemical(pH) signatures of neural activity is presented. It consists of six recording channels, three for electrical and three for chemical signals. Each channel has a low-noise amplifier which utilizes a new and optimized technique of flicker noise suppression. Our approach is based on a modified switched bias current technique. Both electrical and chemical amplifiers use the same circuit topology and have a common footprint, but the type of amplifier is reconfigured by controlling the bias current, which controls the bandwidth of the amplifier. The chip was fabricated using an AMS 0.35μm and four metal double poly CMOS technology. Measured noise reduction depends on the switching frequency. Bench tests have shown that our technique achieves up to 60% intrinsic 1/f noise suppression by determining an optimal switching frequency, without additional circuit complexity or an increase in transistor and chip area. The amplifier was designed to exhibit a 60 dB closed loop gain for electrical neural signals, and a 20 dB closed loop gain neurochemical signals. Each channel within the design occupied an area of 3.66mm2. This circuit design will be used as an integrated circuit for a real-time bimodal recording of neural activity for closed-loop neuromodulation therapies.

A new technique pertaining to the optical contactless chip-to-board communication using a commerc... more A new technique pertaining to the optical contactless chip-to-board communication using a commercially available CMOS technology is under development. The main concept is to use mid-IR light from a small LED which will enter an IC from the underside, impinge upon one or more pn-junctions and be reflected by a metallic sheet so that it falls on an external, discrete photodetector. After propagation through the doped semiconductor, the light undergoes attenuation due to free carrier absorption. By varying the reverse bias across the pn-junction(s), the depletion region widths are changed and therefore modulation of light intensity can be achieved. Through this scheme, data readout can be realized optically, thus alleviating the need for galvanic contacts (most notably wirebonds).