Elitsa Gieva

Air quality monitoring in urban environments

Air pollution is both an environmental and a social problem, as it leads to a multitude of adverse effects on human health, ecosystems and the climate. Air pollution is one of the largest environmental health risks in Europe today. Quality of the air in city and urban areas is the most important factor that directly influences the incidence of diseases and decreases the quality of life. Taking appropriate decisions in a timely period depends on the measurement and analysis of the parameters of the air, which creates the need for the development of real time air quality monitoring. The use of multi-parameter air quality monitoring systems makes it possible to do a detailed level analysis of major pollutants and their sources. These monitoring systems are important components in many smart city projects for monitoring air quality and for controlling the main pollutant concentrations in urban areas. In this paper we present an approach for cost-effective measurement of relevant environmental parameters, based on a scalable sensor array with integrated amperometric and infrared gas sensors. The device has been tested in the city and the measurement was compared with the output data of the local environmental control authority stations. The preliminary results show that this approach can be used as an economical alternative to the professional grade systems.

Hydrogen bonding networks in transient state of beta-lactamase protein analogous to integrated circuits

Two hydrogen bonding networks (HBN) that are extracted from the β-lactamase protein are presented and studied in the present paper. The HBNs are formed in the active site of ß-lactamase when β-lactamase is in transient state (T1). The hydrogen bonds are modeled as three or four-terminal block elements analogous to classic electrical multi-terminal networks. Each block element is coded in Matlab and described by polynomials. Block elements are then included in a microelectronic circuits analogous to “proton networks”. The dynamic and static simulations with analogous circuits are carried out in Matlab. The results showed an analogy to a current source, amplifier, current mirror, and amplitude limiter.

Microelectronic circuit emulating Hydrogen Bonding Network of Green Fluorescent Protein

Hydrogen Bonding Network in active site of wild type Green Fluorescent Protein during the A→A* state is modeled. A microelectronic equivalent circuit is developed on its basis to emulate the operational principle of the Hydrogen Bonding Network. It is coded in Matlab to investigate its static and dynamic behavior. Output characteristics of static analysis are similar to inversed tunnel diode. The dynamic analysis show that the circuit can operate as amplifier, modulator and amplitude limiter.

Remote ECAD laboratory access for the MSc course ‘Advanced Electronics for information and communication systems’

The paper presents the remote laboratory practice in computer added design of integrated circuits within the European project “Remote-labs Access in Internet-based Performance-Centered Learning Environment for Curriculum Support”. The ECAD laboratory at the Technical University of Sofia implemented a remote access to the professional microelectronics software (very expensive and running only on workstations) and is being used by the students from the MSc degree for working on their projects.

Extraction of solar cell parameters using source measure unit

This paper presents a methodology for parameters extraction of photovoltaic cell based on real measurement. The modeling of equivalent schemes of solar cells is of great importance in order to be included in electric circuits for wireless sensor networks power supply. The parameters extraction of these devices is still a very difficult task, which requires experimental data, computing and modeling. In recent years different analytic, iterative, and evolutionary computational methods have been suggested in various references to extract the parameters of solar cell and modules. This paper presents an innovative approach to estimate model parameters by completely extracting them from real measured data.

Virtual system for analysis of treated water

One of our most vital resources nowadays is fresh water. Water quality refers to the condition of the water, including chemical, biological and physical characteristics with respect to its suitability for a particular purpose. The main purpose of this publication is to set up a virtual system for water analysis in order to measure particular parameters of the water before and after physicochemical treatment. The water is treated with clinoptilolite, which has recently been used for water filtration. It is suitable especially for water treatment due to its ion exchange, absorption properties and high porosity. The main geochemical and technological concerns are how the chemical behavior of natural clinoptilolite affects the quality of different types of water.

Circuit modeling of Green Fluorescent Protein's hydrogen bonding network in cadence

A library of block-elements that mimics the behavior of the hydrogen bonds of Green Fluorescent Protein is created in Cadence for bioelectronics applications. A circuit is designed with these elements that model the architecture and behavior of the analogous hydrogen bonding networks of the protein. The circuit is studied by DC and transient analyses. The DC analysis shows that the output voltage is a linear function of the input voltage and that the output current is a non-linear function of the output voltage. This IV-characteristic clearly shows three operating regions. Depending on the bias points the circuit inspired by the hydrogen bonding networks operates as an amplifier, modulator and amplitude limiter.

COMSOL modeling of Hall sensors efficiency

In this paper we present a finite element analysis routine for modeling of semiconductor Hall sensors. Their efficiency is studied varying the base semiconductor material. More specifically, 2D COMSOL semi-conductor model is initially employed to extract the properties of the conductive channel. Subsequently a 3D COMSOL DC model is used to perform the studies regarding the Hall sensor efficiency. Hall sensors of identical topology and doping levels are studied in a comparative manner.

A microelectronic circuit in CADENCE analogous to michaelis complex of β-lactamase protein

In the present paper a microelectronic circuit in Cadence functionally analogous to Michaelis complex of β-lactamase protein is investigated. The hydrogen bonding networks are described by electrical circuits. Block elements are made for each residue from protein hydrogen bonding networks, which are functionally analogous to residues and describe the proton transport. The block-elements are coded and described in Cadence with polynomials and DC and transient analyses were carried out. The simulation results are compared to electronic circuit and elements.

System for multi-frequency capacitance-voltage characterization

Capacitance measurement at different DC voltage levels, different signal amplitudes and different frequencies, finds extensive application to qualify semiconductor and multiple-layered structures. Generally, the cost of such type instrumentation is in range of several thousand dollars and they are not very popular in the market. In present paper an approach of combining conventional measuring instruments and high-level programming environment is suggested in order to achieve system with complete functionalities for capacitance measurements.