Vilnius Gediminas Technical University
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The Influence of the Participation of Non-Resident Drivers on Roundabout Capacity
No full textProcedures for the calculation of capacity of all types of unsignalized intersections, therefore roundabouts as well, represents a combination of the empirical model (exponential regression) and the likelihood of accepting time gaps in the priority flow by drivers who perform a minor manoeuvre. The values of the critical headway, as the minimum necessary time gap for performing the wanted minor manoeuvre, and the follow-up headway, have been given as the recommendations in the existing methodologies for capacity calculation, depending on the type of the manoeuvre. In traffic flow theory it has been known that drivers’ behaviour influences the capacity of roads and intersections, and the assessment of that influence is done through the adoption or correction of the values of certain parameters. At unsignalized intersections the influence of drivers’ behaviour is reflected through the values of critical headway and follow-up headway. The acceptance of the value of time gaps, i.e., the value of the critical headway and follow-up headway, depends on drivers’ knowledge of local conditions. This paper presents the parameter values of critical headway and follow-up headway for resident and non-resident drivers based on the analysis and statistical processing of research results. The research was conducted at four roundabouts in four towns in Bosnia and Herzegovina, and the total number of vehicles covered by the research is 31,053. In that way, it has been confirmed that the capacity of roundabouts depends on the behaviour of the alleged groups of drivers, i.e., with the increase of the level of participation of non-resident drivers in traffic flow, the roundabout capacity decreases. The model for determining the influence of non-resident drivers on the roundabout capacity was created by using multiple linear regression. If the proposed model in the procedures of traffic planning is applied, the influence of roundabouts on the level of service, sustainability, and the emission of Green House Gases (GHG) can be realistically assessed and perceived in accordance with the expected participation of resident and non-resident drivers.This article belongs to the Special Issue Sustainable Mobility: Social, Technological and Environmental Issue
Bond Mutual Funds vs. Bond Exchange Traded Funds: Evaluation of Risk Adjusted Performance
No full textGrowing acceptance of passive bond exchange traded funds (ETFs) and actively managed bond mutual funds has exposed the need to find a divide between these two comparatively similar types of instrument. This paper provides a comparative analysis of actively managed bond funds and passive bond ETFs in the context of multiple criteria. The research of risk-adjusted performance of a sampled group of bond funds and ETFs using the TOPSIS multi-criteria decision-making method revealed that actively managed bond funds have a modest advantage over passive bond ETFs. Moreover, the final findings indicate the funds’ performance dependability on portfolio composition by fixed income sector.This article belongs to the Special Issue Rational Decision Making in Risk Managemen
Building Information Modeling (BIM) for structural engineering: a bibliometric analysis of the literature
No full textBuilding information modeling (BIM) is transforming the way of work across the architecture, engineering, and construction
(AEC) industry, where BIM offers vast opportunities for improving performance. BIM is therefore an area of great interest across
the AEC industry in general and for the structural engineering field in particular. *is paper is aimed at providing a broad picture
of published papers that relate BIM with structural engineering. *is overview will enhance understanding of the state of the
research work on this subject, drawing upon bibliometric analysis of 369 papers. Findings provide an updated picture of how nowavailable studies that link BIM developments and applications in structural engineering are distributed chronologically, across
journals, authors, countries, and institutions. Detailed analyses of citation networks present the cooccurrence map of keywords,
citation patterns of journals and articles, the most cited journals, and the top 15 most cited articles on BIM in the area of structural
engineering. Discussions demonstrate that research on BIM applications for structural engineering has been constantly growing
with a sudden increase after 2014. *is study reveals that research attempts on this area have been dominated by exploring generic
issues of BIM like information management; however, technical issues of structural engineering, to be resolved through BIM
capabilities, have remained overlooked. Moreover, the research work in this area is found to be conducted largely in isolation,
comprising disjointed and fragmented research studies. Gaps and important areas for future research include modeling of
structural components, automation of the assembly sequence, planning and optimization of off-site construction, and dynamic
structural health monitoring
Application of thermodynamic analysis for thermohydrodynamic loops systems
Get PDFDisertacijoje, naudojant taikomosios termodinaminės analizės metodus, nagrinėjamos termohidrodinaminių kontūrų sistemos efektyvumo didinimo problemos. Šio darbo tikslas – sukurti termohidrodinaminių kontūrų sistemos sezoninio termodinaminio efektyvumo nustatymo metodą ir suformuluoti metodiką siekiant sistemingai didinti sezoninį efektyvumą. Sukurto metodo ir metodikos taikymo sritis – tiriamoji veikla ir inžinerinė praktika – orientuota į tvarių energinių sistemų kūrimą, eksploataciją ir tobulinimą. Disertacijoje taip pat siekiama sumažinti atotrūkį tarp tiriamojoje mokslinėje ir inžinerinėje praktikoje naudojamų taikomosios termodinaminės analizės metodų.
Darbo tikslui pasiekti, sprendžiami keli pagrindiniai uždaviniai: termodinaminės analizės taikymo problematikos identifikavimas, termodinaminio sezoninio efektyvumo (TSE) vertinimo metodo sudarymas, modeliavimui reikalingo detalumo lygio identifikavimas ir TSE tobulinimo metodikos sudarymas eliminuojant kritinius trukdžius.
Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai ir vienuolika priedų.
Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai.
Pirmasis skyrius skirtas literatūros apžvalgai ir analizei. Skyriaus pabaigoje formuluojamos išvados ir tikslinami disertacijos uždaviniai.
Antrajame skyriuje pateiktas termodinaminio sezoninio efektyvumo nustatymo metodas, skirtas apskaičiuoti specifinius efektyvumo atvejus, ir sezoninio efektyvumo gerinimo metodika.
Trečiajame skyriuje pateikiama tiriamos sistemos analizės pavyzdys, iliustruojantis TSE nustatymo ir jo tobulinimo metodų funkcionalumą.
Disertacijos tema paskelbti 9 straipsniai: 2 – Clarivate Analytics Web of Science duomenų bazėse referuojamuose leidiniuose, turinčiuose citavimo rodiklį (Martinaitis et al. 2017, Januševičius et. al 2019), 1 – tarptautinių konferencijų leidiniuose, referuojamuose Clarivate Analytics duomenų bazėje Proceedings (Januševičius et al. 2014a). 6 – kitų tarptautinių duomenų bazių leidiniuose (Januševičius et al. 2016; Januševičius et al. 2015; Januševičius, Streckienė 2015; Januševičius, Streckienė 2013; Bielskus et al. 2013). 2 – konferencijų pranešimų medžiagoje (Januševičius et al. 2014a, Januševičius et al. 2014b). Disertacijos tema perskaityti 3 pranešimai tarptautinėse konferencijose Lietuvoje, Latvijoje ir Jungtinėje Karalystėje
Vidutinių dažnių 5G belaidžių tinklų galios stiprintuvų tyrimas
Get PDFThis dissertation addresses the problems of ensuring efficient radio fre-quency transmission for 5G wireless networks. Taking into account, that the next
generation 5G wireless network structure will be heterogeneous, the device
density and their mobility will increase and massive MIMO connectivity
capability will be widespread, the main investigated problem is formulated –
increasing the efficiency of portable mid-band 5G wireless network CMOS power amplifier with impedance matching networks.
The dissertation consists of four parts including the introduction, 3 chapters, conclusions, references and 3 annexes.
The investigated problem, importance and purpose of the thesis, the ob-ject of the research methodology, as well as the scientific novelty are de-fined in the
introduction. Practical significance of the obtained results, defended state-ments and the structure of the dissertation are also included.
The first chapter presents an extensive literature analysis. Latest ad-vances in the structure of the modern wireless network and the importance of the power amplifier in the radio frequency transmission chain are de-scribed in detail. The latter is followed by different power amplifier archi-tectures, parameters and their improvement techniques. Reported imped-ance matching network design methods are also discussed. Chapter 1 is concluded distinguishing the possible research vectors and defining the problems raised in this dissertation.
The second chapter is focused around improving the accuracy of de-signing lumped impedance matching network. The proposed methodology of estimating lumped inductor and capacitor parasitic parameters is dis-cussed in detail provi-ding complete mathematical expressions, including a summary and conclusions.
The third chapter presents simulation results for the designed radio fre-quency power amplifiers. Two variations of Doherty power amplifier archi-tectures are presented in the second part, covering the full step-by-step de-sign and simulation process. The latter chapter is concluded by comparing simulation and
measurement results for all designed radio frequency power amplifiers.
General conclusions are followed by an extensive list of references and a list of 5 publications by the author on the topic of the dissertation.
5 papers, focusing on the subject of the discussed dissertation, have been
published: three papers are included in the Clarivate Analytics Web of Sci-ence database with a citation index, one paper is included in Clarivate Ana-lytics Web of Science database Conference Proceedings, and one paper has been published in unreferred international conference preceedings. The au-thor has also made
9 presentations at 9 scientific conferences at a national and international level.Dissertatio
Informacijos saugos reikalavimų harmonizavimo, analizės ir įvertinimo automatizavimas
Get PDFThe growing use of Information Technology (IT) in daily operations of enterprises requires an ever-increasing level of protection over organization’s assets and information from unauthorised access, data leakage or any other type of information security breach. Because of that, it becomes vital to ensure the necessary level of protection. One of the best ways to achieve this goal is to implement controls defined in Information security documents. The problems faced by different organizations are related to the fact that often, organizations are required to be aligned with multiple Information security documents and their requirements. Currently, the organization’s assets and information protection are based on Information security specialist’s knowledge, skills and experience. Lack of automated tools for multiple Information security documents and their requirements harmonization, analysis and visualization lead to the situation when Information security is implemented by organizations in ineffective ways, causing controls duplication or increased cost of security implementation. An automated approach for Information security documents analysis, mapping and visualization would contribute to solving this issue. The dissertation consists of an introduction, three main chapters and general conclusions. The first chapter introduces existing Information security regulatory documents, current harmonization techniques, information security implementation cost evaluation methods and ways to analyse Information security requirements by applying graph theory optimisation algorithms (Vertex cover and Graph isomorphism). The second chapter proposes ways to evaluate information security implementation and costs through a controls-based approach. The effectiveness of this method could be improved by implementing automated initial data gathering from Business processes diagrams. In the third chapter, adaptive mapping on the basis of Security ontology is introduced for harmonization of different security documents; such an approach also allows to apply visualization techniques for harmonization results presentation. Graph optimization algorithms (vertex cover algorithm and graph isomorphism algorithm) for Minimum Security Baseline identification and verification of achieved results against controls implemented in small and medium-sized enterprises were proposed. It was concluded that the proposed methods provide sufficient data for adjustment and verification of security controls applicable by multiple Information security documents.Dissertatio
Atstumo tarp pagrindinių plyšių armuoto betono elementuose modelis
Get PDFThe intention of the present study is to develop a unified approach for serviceability analysis reinforced concrete tensile and flexural elements, with a focus on mean crack spacing. The current research is mainly quantitative in nature, with the development of the strain compliance approach based on collected data of 170 tensile and 96 flexural specimens. Furthermore, statistical analysis and individual physical parameter impact on the crack spacing and accuracy in general are provided. The key feature of the proposed strain compliance concept is the merging of two distinct cracking analysis methods, referred to as the stress transfer and the mean deformation approaches. Compatibility is ensured by equating the mean reinforcement strains, as estimated by the referred techniques individually. Thus, the lack of knowledge on the spatial strain distribution in the mean deformation approach is addressed by the stress transfer technique, which contains such knowledge.
The technique has been derived for tensile elements with the inclusion of a reference element notion, that is defined by reference values of bar diameter and reinforcement ratio. Moreover, the mean crack spacing must also be known. Consequently, the bond stresses can be evaluated for this reference case and the predictions can then be extended to alternative configurations of ratios of reinforcement and bar diameters.
The concept has been extended with modifications to the assumed strain profile for flexural elements. The notion of the reference element has been eliminated with bond stresses accounted for directly from selected models, such as design codes. A central zone concept is introduced, which governs the averaged behaviour of the reinforcement strains within the middle between consecutive primary cracks. A constitutive length model was derived. In-depth comparisons with experimental data and parametric investigations were carried out.
With the rise of machine learning in the field of civil engineering, it is imperative that research stays ahead of the trend to be able to analyse the implications. A multipurpose study was carried out, resulting in the development of an artificial neural network for estimating the spacing between cracks with very good generalisation abilities, good adequacy in terms of accuracy and consistency. Incidentally, the gathered experimental data was validated for robustness and the general features of the strain compliance method were found to be in good agreement with the neural network predictions and the experimental results.
The research concludes with the validation of the strain compliance technique as a more adequate approach in terms of scatter and accuracy than the present design codes. Moreover, the concept has been shown to be mechanically sound.Dissertatio
The influence of semi-active suspension adjustment on vehicle body pitch oscillations
No full textIn this paper the relation between semi-active suspension characteristics and vertical oscillations of the vehicle body on road
roughness is analysed. During experimental tests, the damping of semi-active suspension was changed while measuring vehicle's
sprung and unsprung mass vertical accelerations, pitch rate, which were transformed into a frequency domain for further analysis. The
results of the experimental tests were compared to the simulations using the semi-active dynamic model. Validation has shown that
model can be used to analyse the influence of semi-active suspension parameters on vehicle oscillations over the entire range of semiactive suspension settings. The comparison of experimental and theoretical simulation showed that semi-active suspension settings
have influence on longitudinal oscillations of the sprung mass and it should be estimated in related researches of modern suspension
The Possibilities of Paper Sludge Waste (PSw) Utilization in Cement Materials
Get PDFThe paper production is developed throughout the world, therefore, more paper sludge waste (PSw) is accumulating. The aim of this work was to determine the properties of PSw burned at 900 °C and its impact on physical–mechanical properties of cementitious matrix and evaluate its usage/utilization possibilities in cementitious materials. For the implementation of the aim, cement-based specimens were prepared and their –mechanical properties were determined. Specimens from five compositions were formed, with 2.5%, 5%, 7.5%, and 10% of the cement by weight replaced with PSw. When 5% of the cement was replaced with PSw, the compressive strength increased by approximately 7%, although density and ultrasound velocity slightly decreased (up to 1.5%). When 7.5% PSw was added, the compressive strength of the specimens decreased. To summarize, it can be stated that up to 5% PSw may be utilized/used for the preparation of cementitious mixtures. The usage of the waste allows environment conservation, reduced amount of cement in mixtures, and improvement of properties of cementitious materials.This article belongs to the Proceedings of Innovations-Sustainability-Modernity-Openness Conference (ISMO’19), Bialystok, Poland, 22–23 May 201
Analysis of Dynamic Parameters of a Railway Bridge
No full textThis article analyses the dispersion of vibration accelerations of a railway bridge during the passage of a train, and presents an analysis of their parameters after the application of the theory of covariance functions. The measurements of vibration accelerations at the fixed points of the beams of the overlay of the bridge were recorded in the time scale as digital arrays (matrices). The values of inter-covariance functions of the arrays of data of measurements of digital vibration accelerations and the values of auto-covariance functions of the individual arrays, changing the quantization interval in the time scale, were calculated. The compiled software Matlab 7 in the operator package environment was used in calculations. This article aims at determining the interdependencies of results of vibrations of bridge points rather than at the impact which a train makes on a bridge without emphasizing the modal parameters of the bridge. The aforementioned interdependencies make it possible to predict the results of hard-to-reach points.This article belongs to the Section Acoustics and Vibration