New doctoral dissertation

December 20, 2023
VILNIUS TECH Library invites you to follow the published new dissertations. The dissertation „Investigation of the inkjet printing process, evaluating the dynamics of the ink and the properties of specific printing surfaces“ („Rašalinio spausdinimo proceso tyrimas, įvertinant rašalo dinamiką ir specifinių spausdinimo paviršių savybes“) prepared by VILNIUS TECH, Tim Tofan. The doctoral dissertation was prepared at Vilnius Gediminas Technical University in 2019–2023., Supervisor – Assoc. Prof. Dr Raimondas Jasevičius.

The dissertation was defended at the public meeting of the Dissertation Defence Council of the Scientific Field of Mechanical Engineering in the SRA-I Meeting Hall of Vilnius Gediminas Technical University at 10 a.m. on 20 December 2023.

The most well-known and commonly used printing techniques made the inkjet printing technology more popular among manufacturers for its simplicity and flexibility. Demand for printing products is increasing in such areas as textile printing, microchip production and personalised production, raising quality requirements. Thus, inkjet printing is continuously enhancing its capabilities. With the printing market expected to grow, there are many propositions to improve the productivity of inkjet process. The dissertation aims to study the dynamics of an inkjet droplet at different stages of its formation, considering its interaction with the surface to improve the quality and speed of high-class inkjet printing and improve inkjet printhead testing applications. The present dissertation reviews theoretical and numerical techniques of inkjet printing process modelling by applying the Computational Fluid Dynamics (CFD) module using the finite elements method. Inkjet printing inks are calculated as Newtonian fluid. The ink flow is modelled by the incompressible Navier–Stokes equations. The presented simulation model is solved using a level set method to determine the ink and air interface. Experimental investigation results are reported on the inkjet printing process colour reproduction on different linen fabrics, and modelling results are given for droplet ejecting, printing and interaction processes with the flat surface and the interaction with the inkjet droplet with physically treated polymer surfaces. Based on systematic and analysed numerical simulations of research on the operation of inkjet printing heads, Article 1 describes the inkjet print-head models, which analyse how different inks impact droplet formation and movement at different time steps. Article 2 presents an experimental realisation of colour reproduction by inkjet printing possibilities on different materials in different printing settings. Article 3 presents the physical and numerical experiments on the impact characteristics of inkjet printhead droplets with flat surfaces. Different surface treatment methods were investigated to increase droplet adhesion with flat surfaces. Article 4 investigates the numerical model of the print head modelled in three-dimensional space. Various parameters of drop formation and fall were experimentally determined with a change in the time of the excitation impulse. A numerical analysis was carried out regarding the influence of the excitation time on the droplet formation and further movement. The supplemented articles were published in four peer-reviewed scientific journals listed in the Clarivate Analytics Web of Science database with an impact factor. The study results were presented at three international conferences.

Doctoral dissertation readers can search via VILNIUS TECH Virtual Library.

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Time-resistant student love: Emilija and Marius found each other at VILNIUS TECH
Time-resistant student love: Emilija and Marius found each other at VILNIUS TECH
Love from university days does not rust - this is something the heroes of this article unanimously agree on. For them, VILNIUS TECH (then Vilnius Gediminas Technical University) provided not only education, a circle of long-lasting friends, and countless beautiful memories, but also love.  Emilija Gaveniene and Marius Gavenas not only met here, but also got engaged during the diploma awarding ceremony - an event later even broadcasted on national television.  First of all, tell us how you met each other and your love story began. Emilija: Our story began completely by chance. In the summer of 2013, after finishing school, I received a call from the Student Representation of the Faculty of Transport Engineering. They invited me, a first-year student, to a freshmen camp. Without much hesitation, I agreed, although I had been admitted to the Entertainment Industries study program at the Faculty of Creative Industries. I clearly remember seeing Marius on the main university stairs when I arrived - his appearance and self-confidence caught my attention. At the first-year student camp, there was a presentation of the student representation. After the event, we sat together on a bench and talked for about half an hour about the representation and life choices. After the camp, we each returned to our student routine, until we met again on May 8, 2015, at the student representation anniversary. That evening we danced, and since then we’ve been inseparable. Marius: Emilija still does not believe it, but I noticed her during the very first introduction game at the freshmen camp in Aukstadvarys. The shy Samogitian girl somehow caught my attention, and in the evening sitting on the bench was not quite as accidental as it seems. Marius, you proposed during the graduation ceremony. Why did you decide to propose in this way? Were you nervous in front of such a large audience? Marius: It turned out that this proposal perfectly summarized the study cycle. We met on Emilija’s first day at the university and committed to each other on the last. I was not only studying but also actively involved in the student representation, so I felt a special connection to the Alma Mater. [caption id="attachment_122391" align="alignnone" width="2048"] Emilija ir Marius[/caption] As for the idea itself, I was never afraid of attention, and I was not scared by it until the very last moment. Only when I was already kneeling and people started cheering did I become very emotional, and I am not even sure if I managed to say the standard “Will you marry me?” Also, I must thank the university staff who encouraged me when I doubted whether it was a good idea. Emilija, was this move unexpected? Or did you suspect something? Emilija: At that time we were living separately, so it was a complete surprise. We had been together for about three years, so I secretly sometimes dreamed about engagement. The only small hint was that the evening before the proposal Marius asked what my favorite song was. But I really could not have guessed it would happen during the graduation ceremony. Your proposal video became very popular on social media and was even featured in various media outlets. Did this bring additional emotions? Emilija: The emotions were overflowing! We also received a lot of media attention - we were shown on LRT news, on the show “Good Morning, Lithuania,” and radio stations called us. We were happy to share our joy. Marius: The attention was unexpected. When planning it, I definitely did not think it would become so public. Friends joked that I should have put an advertisement on my back and monetized it. How did your story continue? Emilija: Soon after the engagement we moved in together into our first shared apartment. A year later, in 2018, we had a big wedding, where Marius prepared a slideshow presentation telling our story. It was the highlight of the celebration. Later we bought our first home, and five years later we had our daughter Beata. She fills our lives daily with laughter, joy, and maturity. [caption id="attachment_122387" align="alignnone" width="1361"] Emilija ir Marius[/caption] How do you live now? How has your love grown? What is your professional field? Emilija: We are currently in a mature stage of love - family health and peace have become the most important things. We enjoy parenthood but still make time for each other. Our daughter Beata is 2.5 years old, so we are growing together with her. I recently returned from maternity leave and work as a senior customer service manager at Lindstrom. Like many mothers, I combine work and family. Marius: A friend wished us at our wedding: “May you always have something to look forward to.” That really helps. We have future plans and are moving toward them. Thanks to Emilija’s enthusiasm, we travel a lot, and traveling strengthens our relationship and deepens love. Professionally, I develop technical sales projects, where my engineering education and confidence gained in student representation help a lot. Do you think university love really does not rust? Do you know other couples who met at university and are still together? Emilija: I think we are living proof that it truly does not rust - on the contrary, it only gets stronger. We have many friends who also met at university and are still together. [caption id="attachment_122393" align="alignnone" width="1707"] Emilija ir Marius Gavėnai su dukrele[/caption] Marius: Where else do people meet anyway? What would you wish to the VILNIUS TECH community as former students? Emilija: We wish current and future students to be curious, active, and boldly engage in university life. Do not overthink every life choice, but rather enjoy everyday life - you never know where or when you might meet your life partner. Marius: I highly recommend using student status. While being a student, a lot is allowed and much is forgiven, so it is the best time to try yourself in different fields, go on Erasmus+ exchange, work different jobs, and try hobbies. Prepared by: Egle Kirliauskaite-Blazeviciene Photos: from personal archive
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