New doctoral dissertations

June 15, 2023
VILNIUS TECH Library invites you to follow the published new dissertations. Two dissertations are presented today:

The dissertation „Research of improvement of non-alloy steel surface hardness and stiffness by laser treatment“ („Nelegiruotojo plieno paviršiaus kietumo ir standumo didinimo lazerinio apdorojimo metodu tyrimai“) prepared by VILNIUS TECH, Oleksandr Kapustynskyi. The dissertation was prepared in 2018–2023, supervisor Assoc. Prof. Dr Nikolaj Višniakov.

The dissertation was defended at the public meeting of the Dissertation Defense Council of the Scientific Field of Materials Engineering in the Senate Hall of Vilnius Gediminas Technical University at 10 a. m. on 15 June 2023.

The dissertation deals with the development of new metal processing technologies that enable to control and improve the microstructure and properties of the metals. Laser treatment is one such modern technique. The dissertation aims to determine the laser processing effect on the surface of a thin sheet of non-alloy structural steel. The research aims to solve one of the critical problems in diversifying the use of thin-sheet steel products in the industry by developing laser-processing technology for the creation of structural strengthening ribs, which can significantly affect the overall strength and stiffness of metal parts. The proposed solutions will help solve the problems of using thin-sheet metal products in the industry by increasing the stiffness with preserving the original design parameters (e.g., the product’s size, shape, and weight). This will save production time and resources due to the reduced number of technological and maintenance operations compared to traditional methods of increasing the stiffness of thin-sheet metals, where designing methods are based on the relationship between a construction geometry and its stiffness. The introductory chapter discusses the research aim and objectives. It also describes the research methodology, its scientific novelty, and the practical significance of the results. The introduction closes by presenting the author’s publications and conference papers on the dissertation’s topic and structure. The first chapter reviews the existing methods of increasing the hardness and stiffness of thin-sheet steel products. It also overviews the microstructure and the possibility of increasing the mechanical strength and hardness of the non-alloy steel. At the end of the chapter, the conclusions of the literature review are formulated, and the essential tasks of the dissertation are specified. The second chapter describes the materials and laboratory equipment used in the research work. This includes the methodology of microstructure analysis, mechanical properties testing, surface laser processing technology, calculating laser processing parameters, and modeling bending and tensile cases. The third chapter presents the results of the analysis of surface layer microstructure and phase composition, mechanical properties, calculation and selection of laser processing parameters, modeling of bending and tensile of treated thin-sheet samples, analysis of the importance of laser processing depth, and direction of processing, geometry, and direction of processing, and location of reinforcement areas. Six articles on the topic of the dissertation have been published, and the research results have been presented at nine scientific conferences in Lithuania and abroad.

Doctoral dissertation readers can search via VILNIUS TECH Virtual Library.


The dissertation „Research into variability of permanent magnet synchronous motor parameters by magnetic field modelling“ („Sinchroninio variklio su nuolatiniais magnetais parametrų kitimo tyrimas modeliuojant magnetinį lauką“) prepared by VILNIUS TECH, Justas Dilys. The dissertation was prepared in 2017–2023, supervisors Supervisors: Prof. Dr Algirdas Baškys, Prof. Dr Voitech Stankevič. Consultant Dr Habil. Marcin Morawiec.

The dissertation was defended at the public meeting of the Dissertation Defence Council of the Scientific Field of Electrical and Electronic Engineering in the Senate Hall of Vilnius Gediminas Technical University at 2 p. m. on 15 June 2023.

The dissertation deals with permanent magnet synchronous motors (PMSM) classical control theory and also by applying magnetic field theory approach. The purpose of the thesis is to create the mathematical model of the PMSM based on analytical equations of magnetic field accounting torque ripple, inductance distributions and back electromotive force, to develop the measurement system for direct measurement of magnetic flux density and to propose PMSM parameter estimation method. In order to solve the stated problem and reach the goal following main tasks of the thesis are formulated: create PMSM model based on the analytical equations of magnetic flux density; develop vector control method of PMSM and investigate it experimentally; develop PMSM parameter estimation method; develop and implement a magnetic flux density measurement system; perform experimental measurement of magnetic flux density of PMSM using the developed system. The dissertation consists of the introduction, three chapters, general conclusions, references, and the list of scientific publications of the author on the topic of the dissertation. The introduction discusses the research problem, the relevance of the dissertation, the object of the research, formulates the aim and tasks, de- scribes the research methodology, the scientific novelty of the dissertation, de- fended statements and the practical value of the research findings. At the end of the introduction, the dissertation and the structure of the dissertation are provided. The first chapter reviews the PMSM design, rotor and stator types, magnetic field analytical solutions for predicting magnetic flux in the PMSM and magnetic field measurement systems. The second chapter presents an analysis of the following topics of PMSM’s magnetic field distribution: the field created only by the rotor (open-circuit) and the field created only by the stator (armature reaction). Next, the effect of the stator slot on the magnetic field distribution is analysed. Finally, the enhanced PMSM model concept is stated based on magnetic field analysis. The third chapter presents the magnetic flux density measurement systems and compares the experimental results with the simulation results obtained using the proposed enhanced PMSM model. The main results of the dissertation were published in seven scientific publications: four in the Clarivate Analytics Web of Science database with an impact factor and three in other databases. The results were presented at eight scientific conferences.

Doctoral dissertation readers can search via VILNIUS TECH Virtual Library.

Related news

From biological bridges to living facades: how civil engineers are reshaping cities
From biological bridges to living facades: how civil engineers are reshaping cities
Modern buildings are no longer made of concrete and steel alone. Biology, artificial intelligence, and sustainable technologies are becoming an integral part of construction, transforming the way cities are designed and built. As technology advances and environmental awareness grows, civil engineers are developing innovative materials and construction methods that are more sustainable, durable, and environmentally responsible. One of these innovators is Assoc. Prof. Dr. Ronaldas Jakubovskis, a researcher at the Faculty of Civil Engineering at VILNIUS TECH, whose work is helping shape the future of urban environments. Turning Research into Real-World Structures Assoc. Prof. Dr. Ronaldas Jakubovskis serves as a Senior Researcher at the Laboratory of Innovative Building Structures, where his work focuses on developing advanced structural solutions through experimental testing, laboratory research, and numerical modelling. However, innovation rarely begins with a completely new idea. According to Dr. Jakubovskis, much of the research process is dedicated to analysing existing materials and construction technologies to understand how they can be improved. [caption id="attachment_88679" align="alignnone" width="2560"] Ronaldas Jakubovskis[/caption] „The most rewarding moment is when years of laboratory research become a real structure that can be built and experienced in a natural environment,“ he says. Although he works in academia, Dr. Jakubovskis sees himself primarily as a civil engineer supporting other civil engineers. While structural designers and project managers oversee the overall design of buildings and infrastructure – determining layouts, dimensions, and cost-effective construction solutions – researchers provide the specialised expertise needed to develop new materials and solve complex engineering challenges. „Practising engineers often don't have enough time to investigate highly specialised solutions or explore entirely new materials – that's where we come in. Sometimes we analyse complex structural behaviour through numerical modelling, and sometimes we investigate how emerging materials can be applied in construction. In my opinion, research engineers don't quite fit the traditional stereotype of scientists wearing white lab coats or solving abstract equations all day. Our work is highly practical—we often design, manufacture, and physically test new structural systems ourselves.“ Engineering That Leaves a Visible Legacy Among the projects he is most proud of is the Biological Bridge installed at the Kairėnai Botanical Garden, as well as the Living Concrete wall currently being developed for the rooftop of the Lithuanian National Drama Theatre. Both projects demonstrate how engineering can merge sustainability, science, and architectural design. „These projects represent the culmination of years of laboratory work and numerical modelling. They are demonstration structures that show what is possible when innovative materials meet advanced engineering. I also value their aesthetic qualities. Designing complex organic forms allows you to feel a little like a sculptor creating a work of art.“ Looking ahead, Dr. Jakubovskis believes his greatest achievements are still to come. His long-term vision is to create buildings with façades intentionally designed to be colonised by living organisms, allowing them to interact naturally with their environment while providing ecological and functional benefits. [caption id="attachment_88005" align="alignnone" width="2560"] Ronaldas Jakubovskis[/caption] „We are currently developing larger demonstration projects, seeking research funding, and expanding international collaborations. I believe that within the next five years, we'll be able to stand in front of one of these buildings and say: this is a significant achievement.“ A Profession That Will Still Matter in 100 Years For Dr. Jakubovskis, choosing civil engineering was an easy decision. Since childhood, he enjoyed watching buildings rise from the ground and observing construction sites and heavy machinery. „You don't need extraordinary dreams to become a civil engineer. If you want to build, you become an engineer. It's not like travelling to space or conducting research in Antarctica.“ What motivates him most is the opportunity to create structures that remain valuable for decades – or even centuries. „Every civil engineer feels proud when driving past a bridge or building they helped design, and they will always point it out to everyone in the car,“ he says with a smile. His own career began in structural design after completing his third year of university. He later pursued doctoral studies focusing on the cracking behaviour and deformation of reinforced concrete structures before returning to industry. Eventually, an invitation to rejoin VILNIUS TECH brought him back to academia. „I came back, and today I'm doing exactly what I truly enjoy.“ Advice for Future Engineers As both a researcher and lecturer at the Faculty of Civil Engineering, Dr. Jakubovskis emphasises that a university education is essential for anyone pursuing a career in civil engineering. „It would be extremely difficult to master this profession through self-study alone. Should you begin with theoretical mechanics, mechanics of materials, or structural mechanics? University programmes are carefully designed so that knowledge develops step by step, preparing graduates to become highly qualified professionals.“ He also offers practical advice to prospective students: „Don't be afraid of mechanics, physics, or mathematics. Every semester, identify a few key subjects, understand them thoroughly, and make sure you truly master them. Once those foundations are in place, everything else builds naturally.“ Industry Investing in Future Engineers Preparing the next generation of civil engineers is a shared responsibility between universities and industry. As digitalisation, artificial intelligence, and emerging technologies continue to reshape construction, employers increasingly recognise the importance of investing in future talent. The Faculty of Civil Engineering at VILNIUS TECH enjoys long-standing partnerships with the Lithuanian Builders Association (LSA) and the Lithuanian Association of Civil Engineers (LSIS), both of which actively support education and professional development. The Faculty's industry partners – including Hanner, Gilesta, and Alvora – offer scholarships to first-year Civil Engineering students, helping talented young people begin their studies. Other partners, such as Naresta, PST Group, HSC Baltic, and numerous construction companies, contribute by delivering guest lectures, presenting real-life projects, and inviting students to construction sites, where they gain first-hand experience of modern engineering practice. These close collaborations ensure that VILNIUS TECH programmes remain aligned with industry needs while providing students with practical knowledge, professional skills, and valuable connections long before graduation. Learn more about Civil Engineering studies at VILNIUS TECH and discover how you can help shape the cities of tomorrow.
More
Discover JSTOR: Explore Scholarly Journals and Primary Sources
Discover JSTOR: Explore Scholarly Journals and Primary Sources
With exams behind you and more time available for independent exploration, we invite you to take advantage of VILNIUS TECH’s subscribed database, the JSTOR Archival Journals and Primary Sources Collection. This collection offers not only scholarly articles but also original historical documents, images, primary sources, manuscripts, plant specimens, cultural heritage objects, and other unique materials. JSTOR also provides access to more than 4,000 academic journals covering a wide range of subjects, including literature, history, politics, psychology, economics, business, life sciences, natural sciences, the arts, and more. By combining scholarly articles and primary sources on a single platform, JSTOR makes it easier to discover new research perspectives, uncover unexpected connections across disciplines, and enrich both study and research activities. What can you discover in JSTOR? Nineteenth-century pamphlets on technological innovations and social change. Historical letters, speeches, and documents. Millions of plant specimens from around the world. Photographs, maps, and 3D models of cultural heritage objects. Works of art, posters, and historical photographs. More than 4,000 academic journals across a wide range of disciplines. Access is available from VILNIUS TECH computer network or via VPN. As a security measure, two-factor authentication is additionally required (i.e. verification from mobile device app or by call).
More