Abstract. In this paper we evaluate characteristics of three optical particulate matter sensors/sizers (OPS): high-end spectrometer 11-D (Grimm, Germany), low-cost sensor OPC-N2 (Alphasense, United Kingdom) and in-house developed MAQS (Mobile Air Quality System), which is based on another low-cost sensor – PMS5003 (Plantower, China), under realistic conditions of strong and mild urban pollution. Results were compared against a reference gravimetric system, based on a Gemini (Dadolab, Italy), 2.3 m3 h−1 air sampler, with two channels (simultaneously measuring PM2.5 and PM10 concentrations). The measurements were performed in Sarajevo, the capital of Bosnia-Herzegovina, from December 2019 until May 2020. This interval is divided into period 1 – strong pollution – and period 2 – mild pollution. The city of Sarajevo is one of the most polluted cities in Europe in terms of particulate matter: the average concentration of PM2.5 during the period 1 was 83 µg m−3, with daily average values exceeding 500 µg m−3. During period 2, the average concentration of PM2.5 was 20 µg m−3. These conditions represent a good opportunity to test optical devices against the reference instrument in a wide range of ambient particulate matter (PM) concentrations. The effect of an in-house developed diffusion dryer for 11-D is discussed as well. In order to analyse the mass distribution of particles, a scanning mobility particle sizer (SMPS), which together with the 11-D spectrometer gives the full spectrum from nanoparticles of diameter 10 nm to coarse particles of diameter 35 µm, was used. All tested devices showed excellent correlation with the reference instrument in period 1, with R2 values between 0.90 and 0.99 for daily average PM concentrations. However, in period 2, where the range of concentrations was much narrower, R2 values decreased significantly, to values from 0.28 to 0.92. We have also included results of a 13.5-month long-term comparison of our MAQS sensor with a nearby beta attenuation monitor (BAM) 1020 (Met One Instruments, USA) operated by the United States Environmental Protection Agency (US EPA), which showed similar correlation and no observable change in performance over time.

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This Publication has to be referred as: AbstractTemperature inversions represent an important element of air pollution in cities situated in natural valleys, such as the Sarajevo Valley. Due to the strong thermal stratification, which acts as a natural lid over the city, air circulation is blocked and pollutants accumulate and stay for much longer time. As a consequence, air pollution in the residential area of the city increases dramatically. Investigation of the temperature inversions in Sarajevo Valley was, for the first time, performed using unmanned aerial vehicles.

Vertical temperature profiles represent a very important factor for various analytical and numerical studies, such as weather forecasts, air pollution models and CFD simulations. These temperature profiles are especially important during the winter periods, when temperature inversions occur. The cities in the natural valleys, such as the city of Sarajevo, B&H, are strongly affected by this phenomenon. In this paper, a method for quantitative characterization of vertical temperature profiles, which is based on the in-house developed data acquisition system and the unmanned aerial vehicle, is presented. Comprehensive calibration and verification procedure was performed and explained in details. Field measurements were focused on the winter period and extreme temperature inversion scenarios. The correlation with the air pollution in the city, for the same period, was discussed as well.

Air pollution with particulate matter (PM) represents major risk for humans' health. Important step towards the solution of the aforementioned problem is the correct measurement of PM concentrations in the air. Commodity (low-cost) sensors are very popular nowadays, since they are affordable and they fit well in the trend called Internet of Things (IoT). However, measurement of PM concentrations in the air is difficult task and low-cost sensors are unable to provide accurate readings out of the box. Thus, advanced calibration is necessary for any application of low-cost dust sensors. In this paper we propose calibration technique and discuss initial results.

The main objective of this research was to propose a light and practical design solution for electric bike front drive with bottom bracket electric motor. The initial design needs to be redesigned so it can enable simultaneous use of the electric drive and pedal drive, with integration of the front gear shifter. After gathering the basic information linked to the problem and inspecting the initial design solution, the assets and flaws have been identified. The CAD models of the considered possible solutions were developed into FEM models which were used for structural analysis in CAD/CAE software system CATIA. On the basis of the FEM analysis and additional criteria, the optimal solution was chosen, and structural optimization, based on FEM model, was performed. A prototype was manufactured and a mounting process in a place of the initial design was performed. Afterwards, electric bike with mounted prototype was tested under real conditions.

In this paper we will look at the one system of ODE and analyze it. We aim to determine the points of equilibrium; examine their character and establish the existence of a bifurcation for the corresponding parameter value. A detailed analysis of local stability was performed for all values of the given parameter. For a certain value of the parameter, the existence of supercritical Hopf bifurcation of the observed system of differential equations has been proved. Also, the existence of a limit cycle that is always stable has been proved.

In this paper, a method for analysis of dynamic characteristics of an electric vehicle is presented. The developed method is completely independent from vehicle's on-board systems and there is no interaction with vehicle's hardware or software. The test vehicle was a semi-custom electric light truck. Dynamic characteristics from realistic test scenario are presented and discussed. Special attention is dedicated to the energy consumption, kinetic energy recuperation and battery behaviour. Some suggestions for future research are proposed as well.