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Valikoivan lasersulatuksen vaikutus Ti-6Al-4V-titaaniseoksen mekaaniseen suorituskykyyn
No full textAinetta lisäävä valmistus (engl. additive manufacturing, AM) on moderni valmistustekniikka, jossa kappaleet valmistetaan suoraan 3D-mallin perusteella, lisäämällä materiaalia kerros kerrokselta. Valikoiva lasersulatus (engl. selective laser melting, SLM) on tehokas metallien ainetta lisäävä valmistustekniikka, jonka suurimpia etuja koneenrakennuksessa ovat muun muassa geometrinen joustavuus, ylivoimainen suunnittelun vapaus, materiaalihukan vähentäminen ja nopea prototyyppien valmistus. Menetelmän käyttöön liittyy myös haasteita, koska valmistettavien kappaleiden mekaanisia ominaisuuksia on vaikeaa ennustaa. AM-valmistusprosessi ja prosessiparametrit vaikuttavat materiaalin käytökseen, eikä historian aikana kertynyttä tietoa perinteisistä valmistusmenetelmistä voida soveltaa. Kestävien rakenteiden valmistaminen tehokkaasti, ekologisesti ja kustannustehokkaasti on haastava tehtävä, jonka merkitys korostuu tulevaisuuden insinöörityössä. Tämän työn näkökulmana analysoitiin, miten valikoivan lasersulatuksen valmistusprosessi ja prosessiparametrit vaikuttavat Ti-6Al-4V-titaaniseoksen mekaaniseen suorituskykyyn.
Työ on luonteeltaan kirjallisuuskatsaus, jonka avulla pyrittiin vastaamaan, miten Ti-6Al-4V-konerakenteiden mekaanista suorituskykyä voidaan optimoida. Työ koostuu kolmesta osasta. Työn ensimmäisessä osassa käsitellään valikoivan lasersulatuksen toimintaperiaatetta, menetelmän laitteistoa, menetelmään liittyviä yleisimpiä virheitä sekä titaanin soveltuvuutta tähän valmistusmenetelmään. Työn toisessa osassa analysoidaan valikoivan lasersulatuksen energia-, skannaus- ja jälkikäsittelyparametreja. Kattavaa aineistoa käyttäen työn toisessa osassa pyritään tunnistamaan valmistusprosessista merkittäviä prosessiparametrien valintakriteerejä, joita noudattamalla voidaan valmistaa kestäviä rakenteita säännöllisemmin. Työn kolmannessa osassa käydään läpi analyysin perusteella saadut tulokset ja prosessiparametrien valintakriteerit.
Tutkimuksen perusteella voidaan todeta, että tärkein mekaaniseen suorituskykyyn vaikuttava tekijä on valmistettavien rakenteiden tiheys. Tiheyden ohella isotrooppiset materiaaliominaisuudet tukevat merkittävästi rakenteiden mekaanista suorituskykyä. Korkean tiheyden ja isotrooppisien materiaaliominaisuuksien avulla on mahdollista saavuttaa korkea myötö- ja murtolujuus, sitkeys sekä väsymisenkesto. Huolellisesti optimoitujen prosessiparametrien avulla valmistettujen SLM-tulosteiden mekaaniset ominaisuudet ylittävät perinteisillä valmistusmenetelmillä valmistettujen kappaleiden mekaaniset ominaisuudet.Additive manufacturing (AM) is a modern manufacturing technique where parts are made directly from a 3D model by adding material layer by layer. Selective laser melting (SLM) is an efficient additive manufacturing technique for metals, which main advantages in mechanical engineering include geometric flexibility, superior freedom of design, reduced material wastage and rapid prototyping. It also presents challenges due to the difficulty in predicting the mechanical properties of the manufactured parts. The AM-manufacturing process and process parameters affect material behavior, and the knowledge accumulated historically from traditional manufacturing methods cannot be applied. Manufacturing durable structures efficiently, ecologically and cost-effectively is a challenging task that will become even more important in future engineering. The perspective of this work was to analyze how the manufacturing process and process parameters of selective laser melting affect the mechanical performance of Ti-6Al-4V.
This work is a literature review, which aims to answer the question of how to optimize the mechanical performance of Ti-6Al-4V machine structures. The work consists of three parts. The first part of the work deals with the principle of selective laser melting, the equipment used in the process, the most common defects associated with the process, and the suitability of Titanium for SLM-process. The second part of the thesis analyses the energy, scanning, and post-processing parameters of selective laser melting. Using comprehensive data, the second part of the work aims to identify important process parameter selection criteria in the manufacturing process that can be used to produce durable structures more regularly. In the third part of the work, the results of the analysis and the selection criteria for the process parameters are discussed.
The study shows that the main factor influencing mechanical performance is density. High density and isotropic material properties make it possible to achieve high yield and fracture strength, toughness, and fatigue resistance. The mechanical properties of SLM-parts produced with carefully optimized process parameters exceed those parts produced by conventional manufacturing methods
Studying the migration of FGFR3-TACC3 fusion-positive glioblastoma cells in a 3D collagen hydrogel matrix
Get PDFGlioblastoma (GBM) is the most common and aggressive type of primary brain cancer in adults. Its highly invasive nature makes treatment challenging. Among the genetic alterations associated with GBM, the FGFR3-TACC3 gene fusion has recently been identified as a recurrent oncogenic driver that promotes tumour progression. However, its precise functional role in tumour cell migration, particularly within physiologically relevant 3D environments, remains partially unresolved.
This thesis aimed to investigate the impact of FGFR3-TACC3 fusion on glioblastoma cell migration within a three-dimensional (3D) collagen hydrogel model under different culture conditions. SNB19-derived glioblastoma cell lines overexpressing FGFR3-TACC3, wild-type FGFR3, or control vectors were cultured as spheroids in ultra-low attachment (ULA) plates and embedded in a collagen hydrogel matrix to assess their migration behaviour. Over seven days, spheroid morphology, growth, and migration were monitored using bright-field imaging under a nutrient-rich condition and two distinct nutrient-deprived environments followed by stimulation with fibroblast growth factor (FGF).
The results showed that all SNB19-derived GBM cell lines formed viable spheroids and exhibited consistent migratory patterns within the 3D collagen matrix. FGFR3-TACC3 fusion-positive cells exhibited significantly enhanced migration compared to control and wild-type FGFR3 (WT-FGFR3) overexpressing cells, as revealed by increased radial dispersion.
In conclusion, the present study established and characterized a functional and physiologically relevant 3D in vitro model to study FGFR3-TACC3 fusion-driven invasion in glioblastoma. Further work may be required to optimise this 3D model, for instance, by incorporating patient-derived cells, co-culturing with immune or stromal cells, or integrating hypoxic gradients, to facilitate a deeper exploration of the molecular mechanisms governing the enhanced aggressiveness of FGFR3-TACC3 fusion-positive glioblastomas. Interestingly, this study paves the way for future research on targeted therapies to combat the invasive potential of FGFR3-TACC3 fusion-positive glioblastoma cells
Design of a Synthesizable Operational Amplifier Built With Standard Cell Cmos Inverters
No full textThis thesis presents the design and evaluation of an operational amplifier (op-amp) constructed entirely with CMOS inverters. First, the design has been evaluated using basic CMOS inverters, and then the design has been implemented and proven in simulations using only standard cell CMOS inverters in a 22nm process. Traditional op-amp architectures rely on differential pairs, current mirrors, and complex biasing networks, all of which face challenges in modern low-voltage, deep sub-micron nodes. These challenges include reduced power efficiency, limited scalability, and difficulty integrating into digital design flows.
The op-amp presented in this work uses cascaded stages of the Nauta circuit, imple mented with CMOS inverters with the goal of achieving a fully synthesizable design. The design process involves single-stage analysis using only inverter multiplier ad justments (as would be done in a digital flow), followed by cascading, compensation and stability tuning for high-speed operation.
The first iteration achieves an open-loop gain (Aol) of 52dB, a gain-bandwidth product (GBW) of 1.52GHz, a phase margin (PM) of 45°, and a common-mode re jection ratio (CMRR) of 65dB at frequencies below 3MHz, and 49dB at 100MHz. The differential slew rate is 86V/µs under a 0.9V supply.
The second iteration using only standard cells achieves an Aol of 44dB, a GBW of 1.1GHz, a PM of 56°, and a CMRR of 43.6dB at frequencies below 3MHz, and 43.6dB at 100MHz. The differential slew rate is 147V/µs
Teräsrakenteiden konepajakustannusten arviointi piirrepohjaisella laskentamenetelmällä
No full textTässä diplomityössä tutkittiin piirrepohjaisen kustannuslaskentamenetelmän soveltuvuutta teräsrunkojen konepajakustannusten arviointiin suunnittelun alkuvaiheessa. Työn taustalla on tarve kehittää tarkempi ja aikaisessa vaiheessa hyödynnettävä kustannuslaskentamenetelmä, joka ei ole riippuvainen valmiista valmistussuunnitelmista.
Tutkimuksen päätavoitteena oli selvittää, voidaanko rakenteen piirteisiin perustuvalla laskentamallilla tuottaa luotettavaa kustannustietoa ennen lopullisten valmistusratkaisujen määrittämistä. Työssä hyödynnettiin Haapion kehittämää piirrepohjaista kustannuslaskentamenetelmää ja siihen liittyvää laskentamallia, joka sisältää kustannusfunktiot eri valmistusvaiheille, näitä funktioita päivitettiin nykyaikaisilla hinta- ja palkkatiedoilla, ja malliin tehtiin myös sisällöllisiä muutoksia. Esimerkiksi sinkopuhallus muutettiin manuaaliseen raesuihkupuhallukseen ja hitsausvaiheisiin lisättiin jigissä suoritettava puikkohitsaus, jota alkuperäinen malli ei sisältänyt. Kuljetus- ja asennuskustannukset puolestaan jätettiin tarkastuksen ulkopuolelle, koska tutkimuksen rajaus kohdistui konepajavalmistukseen.
Työssä mallinnettiin esimerkkikohteena teräsrunkoinen teollisuushalli, ja kustannuslaskenta toteutettiin kahdelle rakennekokoonpanolle: mastopilarille ja putkipalkkiristikolle. Kustannuslaskenta perustui mallinnettuihin rakenteen piirteisiin, jotka liitettiin yksityiskohtaisiin kustannusfunktioihin. Näiden avulla arvioitiin tuotantoaikaa ja valmistuskustannukset vaiheittain. Herkkyysanalyysi toi esiin materiaalikustannusten merkittävän vaikutuksen kokonaiskustannuksiin.
Työ osoittaa, että piirrepohjainen kustannuslaskenta voi toimia tehokkaana suunnittelun tukivälineenä erityisesti eri rakenneratkaisuiden kustannusvaikutusten hahmottamisessa ja rakenteiden kustannusten optimoinnissa.
Mallin kehittämisen yhteydessä havaittiin, että tarkempaa kustannusten laskentaa varten tarvitaan tietoa valmistavasta konepajasta sekä jatkuvaa kustannustietojen päivittämistä. Lisäksi laskentaprosessin automatisointi parantaisi merkittävästi mallin käytettävyyttä ja tehokkuutta erityisesti suunnittelun aikaisissa vaiheissa.In this master’s thesis, the applicability of a feature-based cost estimation method for assessing workshop manufacturing costs of steel structures in the early design stages was investigated. The motivation behind the work stems from the need to develop a more accurate cost estimation method that can be utilized early in the design process and is not dependent on finalized production plans.
The main objective of the study was to determine whether a feature-based cost model could provide reliable cost information before the final manufacturing decisions are made. The study utilized the feature-based cost estimation method developed by Haapio and the associated cost model. which includes cost functions were updated with current price and wage data, and the model was also modified content-wise. For example, blasting was replaced with manual abrasive blasting, and stick welding performed in jigs was added to the welding phases, which was not included in the original model. Transport and installation costs were excluded from the scope of study, as it focused specifically on workshop manufacturing.
A steel-framed industrial hall was modeled as a case example, and cost estimation was carried out for two structural assemblies: a cantilevered column and a tubular truss beam. The cost estimation was based on the modeled features of the structure, which were linked to detailed cost functions. These functions were used to estimate production time and manufacturing costs step-by-step. A sensitivity analysis revealed the significant impact of material costs on total expenses.
The study demonstrates that feature-based cost estimation can serve as an effective design support tool, especially in visualizing the cost implications of different structural solutions and optimizing the costs of structures.
During the development of the model, it was noted that more accurate cost estimation requires information about the specific manufacturing workshop and continuous updating of cost data. Furthermore, automating the calculation process would significantly enhance the usability and efficiency of the model, particularly in the early stages of design
A comprehensive review on biological methanation processes: from gaseous feedstocks to biomethane
No full textBiological methanation is a process that utilizes methanogenic archaea as catalysts to convert carbon dioxide (CO2) and hydrogen (H2) to methane (CH4). The process can be carried out in various ways: in-situ, i.e. within a biogas digestor fed with organic feedstocks and H2, ex-situ, i.e. in a reactor fed with CO2-rich gas and H2, or in a microbial electrosynthesis reactor, where the reducing equivalents for CO2 reduction are provided with cathode electrode. This review shortly presents the key metabolic pathways involved in biological methanation and the different process options, including microbial electrosynthesis, and examines in detail the significance of the CO2 and H2 sources and the availability and composition of these gas streams, and presents results from life cycle assessment (LCA) of biological methanation processes. The focus of the review is on biogenic CO2. When planning biological methanation, it is crucial to carefully evaluate the options of transferring CO2 and/or H2 or producing H2 where CO2 is produced in terms of cost and feasibility. The continuous versus intermittent availability of CO2 and H2 as well as the potential presence of impurities in the CO2-rich gases can impact the efficiency of the biological methanation process. Specifically, impurities such as nitrogen and sulfur oxides, hydrogen sulfide and heavy metals can negatively impact the biological methanation process. Several LCA studies have demonstrated that biological methanation significantly reduces the greenhouse gas emissions and improves climate impacts, when renewable energy is used for H2 generation and natural gas replacement is considered.Peer reviewe
1D Light-Emitting MAPbBr<sub>3</sub> Perovskite Encapsulated in Carbon Nanotubes
No full textThe instability and broad optical features of perovskites limit the full realization of their unique optoelectronic potential. In this study, a novel MAPbBr3@SWCNTs hybrid material is presented, in which methylammonium lead bromide perovskite (MAPbBr3) is successfully encapsulated in single-walled carbon nanotubes (SWCNTs), fabricated in the form of thin films. Encapsulation enables the formation of 1D perovskite structures with narrowband light-emission, confined within a protective carbon nanoshell. A thorough investigation is conducted into the hybrid material's structure, linear optical properties, ultrafast carrier dynamics, and THz conductivity. The encapsulation preserves the distinct characteristics of both MAPbBr3 and SWCNTs while introducing novel optoelectronic effects, including the tuning and spectral unification of perovskite photoluminescence (PL), as well as doping-induced modifications to SWCNT carrier relaxation dynamics. Furthermore, the observation of negative photoconductivity (NPC) response of MAPbBr3@SWCNTs thin films highlights the potential of this innovative material as a strong candidate for future energy-efficient photodetectors, optoelectronic switches, neuromorphic computing devices, photovoltaic enhancers, and flexible electronics.Peer reviewe
”Jokuhan täyttää sen tyhjiön” : Asiantuntijoiden kokemuksia julkisena asiantuntijana toimimisesta korona-aikana
No full textPostural Control as a Risk Factor for Noncontact Anterior Cruciate Ligament Injury in Youth Female Basketball and Floorball Athletes
No full textThe aim of this study was to investigate whether postural control was associated with an increased risk of future noncontact ACL injury in youth female basketball and floorball athletes. Data collection on 189 youth female basketball and floorball athletes was performed during a 3-year period. The modified Star Excursion Balance Test (mSEBT), single-leg drop-down test, and single-leg stance tests on a balance platform were used to measure postural control. In the mSEBT, performance in the anteromedial, medial, and posteromedial directions, as well as the corresponding composite score, were recorded. In balance platform tests, the mediolateral and anteroposterior velocity, velocity moment, and side length of a square representing 90% of postural sway were measured. Relative limb asymmetry and bilateral limb mean results for these variables were calculated and used as predictor variables in Cox regression analysis. Noncontact ACL injuries and individual exposure hours were prospectively recorded throughout the follow-up. Twelve noncontact ACL injuries occurred. Greater limb asymmetry in the posteromedial direction [HR 1.18 (95% CI 1.05–1.32)] and composite score [HR 1.17 (95% CI 1.01–1.36)] on the mSEBT were associated with an increased risk of noncontact ACL injury. No statistically significant associations were found in the other directions for the mSEBT or any of the balance-platform-generated variables. Dynamic postural control, measured by limb asymmetry in the mSEBT, was associated with future ACL injury. Prevention programs for noncontact ACL injury could benefit from exercises directed toward correcting limb asymmetries in dynamic postural control in youth female basketball and floorball athletes.Peer reviewe
Impact of replacing Na<sup>+</sup> with Ag<sup>+</sup> on the optical and spectroscopic properties of Er<sup>3+</sup>-doped tellurite glasses
No full textEr3+ doped tellurite glasses have attracted significant interest due to their broad emission band at 1.5 µm, the telecommunication window. Among them, the glasses in the TeO2-ZnO-Na2O system are particularly suitable for waveguide fabrication using ion exchange. This study investigates the impact of substituting Na2O with Ag2O in the tellurite glass doped with Er3+ ions on its optical and spectroscopic properties, as well as its chemical durability when immersed in AgNO3-KNO3-NaNO3 molten salt baths, usually used for Ag+-Na+ exchange. The replacement of Na2O with Ag2O leads to an increase in thermal stability and refractive index due to the depolymerization of the glass network. When immersed in Ag-containing salt baths, the glass surface reacts with the molten salt bath, the reaction of which depends on the glass and molten salt bath composition. Diffusion of Ag+ and preferential etching of TeO2 can be obtained, as well as surface crystallization. The glass with the composition 80 TeO2 – 10 ZnO – 10 Na2O (in mol%) was found to be the most stable in the molten salt bath probably due to its polymerized network and so the most suitable glass for ion exchange processes and waveguide fabrication.Peer reviewe