Design of EEG Experiments for Motor Imagery Mental Task Classification
Ivaylo Ivaylov, Agata Manolova, Milena Lazarova

Abstract

The research of Brain-Computer Interface (BCI) and its utilization has significantly raised in the last years. A BCI system perceives and processes brain signals following five data processing stages: signal acquisition, signal preprocessing, data extraction, and data classification and generation of control signals. Brain activity data to be used for BCI systems can be achieved through measurements of induced as well as evoked neuronal activity of the cortex. Motor imagery based BCI is a system wherein a person can generate prompted brain activity with the aid of imagining motor movements. In order to design and develop a BCI system, a relevant dataset is used. The acquisition of a dataset on which the BCI system is based is very important for the overall system performance. Many BCI datasets are available and can be used either for research purposes or for the development of certain BCI system. The paper presents a procedure for the design and conduction of EEG data acquisition for motor imagery mental tasks classification as well experimental results for the usage of the data acquired using different classification approaches.

Keywords
Brain-computer interface, Classification, Electroencephalography, Motor imagery tasks.

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DOI: 10.47978/TUS.2022.72.01.001
 

Aviation Services in Tourism during the COVID-19 Pandemic
Aneta Blazheva, Tasho Tashev and Ivo Draganov

Abstract

In this paper, an investigation is being made over the tendency of air flights rate around the world due to the COVID-19 pandemic in 2020 considering all the negative effects in limiting tourist mobility. There is an attempt to support the customer activities in tourism through travel information portals with suitably extended marketing strategies some of which are being effectively applied in this study. These include but are not limited to active maintenance of Facebook page, weekly Newsletters, and others which prove to be stimulating the user’s interests as some of the presented statistics show.

Keywords
flight reduction, travel, tourism, aviation, COVID-19 pandemic.

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DOI: 10.47978/TUS.2022.72.01.002
 

Analysis of the Real Estate Market in Sofia, Bulgaria, during the COVID-19 pandemic
Marin Marinov, Ivo Draganov

Abstract

In this paper an analysis of the real estate prices in Sofia, Bulgaria for the period from 2019 to 2021 is presented. It is based on observation of the selling rates by type of apartments – with one, two and three bedrooms, and as cumulative entity, over quartiles by 3 months periods, for representative set of neighborhoods, uniformly selected by geographical criteria from the whole city. Approximating price distributions are found on a year basis, evaluated by precision, which reveal new tendencies during the COVID-19 pandemic. Linear regression models are generated from the price series over time for 14 neighborhoods and their predicting capability has been estimated as satisfactory. These models uncover the underlying price change and its rate on a local scale within the city prior and during the pandemic. Cluster models, obtained from the K-means algorithm, of the real estate in low- and high-price groups denote the current layered structure of the market. All obtained results could be useful into building new marketing strategies of the real estate brokerage houses, adequate to the ongoing pandemic situation.

Keywords
real estate, market analysis, Sofia, Bulgaria, pandemic, COVID-19.

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DOI: 10.47978/TUS.2022.72.01.003
 

An Оverview of the Мultipath Тechnologies, their Importance and Types
N. A. Jabbar, G. Lencse

Abstract

One of the challenges for networks that operate according to traditional protocols is to solve the limitations of the single interface or the single path. Especially in mobile phone networks (4G, 5G, and Wi-Fi) and networks that support smart devices, it is an important question, how to take advantage of network resources or distribute traffic between paths and choose the alternative path in case the current path fails. As a result of the rapid development of applications that depend on the multipath interface, a massive increase in traffic has been occurred. The solutions and algorithms that were studied and discussed gave realistic and distinct solutions to increase throughput and reduce delays, which in turn achieves obtaining high-quality data transmission through multiple paths and thus be able to aggregate resources and reduce blocking in the network in terms of QoS (Quality of Service), QoE (Quality of Experience), which allows faster data transfer compared to cases that use a single path. In this paper, we review a set of technologies that provide multipath services (such as MPT, MPTCP, MMPTCP, AOMDV, and OAOMDV) which have been designed and proven through researchers' experiments to be helpful and promising in solving the above problems. Most of these multipath technologies are in the process of being built, some of which need additions to deal with data packets and others to be sufficient and comprehensive facing with the rapid growth of technology.

Keywords
MPT, GRE-in-UDP, MPTCP, Multipath Technology.

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DOI: 10.47978/TUS.2022.72.01.004
 

Abstract

Due to the scarcity of frequencies required to develop digital infrastructure in broadband, can only be offered by releasing frequency bands that are already allocated and utilized by other services. To meet this requirement, the International Telecommunication Union released the terrestrial broadcast spectrum for mobile fixed communications networks in two phases, as known the first and second digital dividends. An upcoming challenge is the effect of the presence of more services in the same or adjacent bands. Hence, it is critical to offer adequate radioprotection against potentially harmful interference in practice, whether on terrestrial television systems or mobile fixed broadband networks in digital dividend bands. This article presents a survey on compatibility studies between mobile fixed communications networks and terrestrial television networks in the 700/800 MHz frequency ranges. We present a brief general overview of the methodologies used to investigate coexistence, including computer simulations, laboratory measurements, and field measurements, as well as a review of the literature relevant to each methodology.

Keywords
Coexistence, Interference, Terrestrial Television, MFCN, 700 MHz

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DOI: 10.47978/TUS.2022.72.01.005
 

A Research and Comparative Analysis of the full Planet Engagement Planetary Gear Train
Angel Alexandrov

Abstract

This article aims to research and classify the full pinion engagement planetary gear train. It can be described as a type of gear train in which each planet gear is arranged in such a way so that it is engaged with the adjacent planets forming a closed meshed loop.  It can be also described as “full planetary engagement gearbox” or “constrained planetary gearbox” An overview of the literature is conducted aiming to compare the “full pinion engagement planetary gear train” with its closest type of planetary gear train designs and other geared systems. The comparison will include planetary gearbox and constrained gear systems specific- assembly and neighbor conditions, center distance relations as well as a short analysis of the characteristics and uses of each design. The article will also include an overview of a manufactured prototype using the full planet engagement concept and a theoretical analysis of the potential uses of such geartrains.

Keywords
Planetary gearbox, full engagement, double pinion planetary gearbox, constrained planetary gear system, torque split transmission

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DOI: 10.47978/TUS.2022.72.01.006
 

Pade Series Approximation of Static Nondifferentiable Nonlinearities
Kamen Perev

Abstract

This paper considers the problem of smooth function approximation of certain nondifferentiable nonlinear characteristics by applying Pade series. Unified approach for this approximation is presented, which is based on using the ideal relay characteristic to describe the nonlinear effect of the approximated nonlinearity. The ideal relay serves as a switching device to carry out changes in the nonlinear element behavior. The main idea of the presented approach is to transform the problem of smooth function approximation of certain nonlinear characteristics to the problem of smooth function approximation of the ideal relay characteristic. The jumping in the relay behavior is replaced by parameterized hyperbolic tangent function, which on its own turn is described in terms of an exponential function. Furthermore, Pade series is used to approximate the exponential function in the hyperbolic tangent expression. Some popular nonlinear characteristics are considered and the approximation mechanism is explained by considering different ranges of operation for the input argument. The approximation power is increased by using parametrization of the hyperbolic tangent function.
 

Keywords
Hyperbolic tangent function, ideal relay, nondifferentiable nonlinearities, Pade series, smooth function approximation

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DOI: 10.47978/TUS.2022.72.01.007