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Opis: Traditional prosthetic liners are often limited in customization due to constraints in manufacturing processes and materials. Typically made from non-compressible elastomers, these liners can cause discomfort through uneven contact pressures and inadequate adaptation to the complex shape of the residual limb. This study explores the development of bioinspired cellular metamaterial prosthetic liners, designed using additive manufacturing techniques to improve comfort by reducing contact pressure and redistributing deformation at the limb–prosthesis interface. The gyroid unit cell was selected due to its favorable isotropic properties, ease of manufacturing, and ability to distribute loads efficiently. Following the initial unit cell identification analysis, the results from the uniaxial compression test on the metamaterial cellular samples were used to develop a multilinear material model, approximating the response of the metamaterial structure. Finite Element Analysis (FEA) using a previously developed generic limb–liner–socket model was employed to simulate and compare the biomechanical behavior of these novel liners against conventional silicone liners, focusing on key parameters such as peak contact pressure and liner deformation during donning, heel strike, and the push-off phase of the gait cycle. The results showed that while silicone liners provide good overall contact pressure reduction, cellular liners offer superior customization and performance optimization. The soft cellular liner significantly reduced peak contact pressure during donning compared to silicone liners but exhibited higher deformation, making it more suitable for sedentary individuals. In contrast, medium and hard cellular liners outperformed silicone liners for active individuals by reducing both contact pressure and deformation during dynamic gait phases, thereby enhancing stability. Specifically, a medium-density liner (10% infill) balanced contact pressure reduction with low deformation, offering a balance of comfort and stability. The hard cellular liner, ideal for high-impact activities, provided superior shape retention and support with lower liner deformation and comparable contact pressures to silicone liners. The results show that customizable stiffness in cellular metamaterial liners enables personalized design to address individual needs, whether focusing on comfort, stability, or both. These findings suggest that 3D-printed metamaterial liners could be a promising alternative to traditional prosthetic materials, warranting further research and clinical validation
Ključne besede: bioinspired design, metamaterial model, cellular structure, additive manufacturing, lower-limb prosthetic, 3D printing, finite element method
Objavljeno v DKUM: 19.09.2024; Ogledov: 0; Prenosov: 0
Celotno besedilo (8,88 MB)
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Opis: Diplomsko delo se osredotoča na raziskovanje ene najpomembnejših transformacij v sodobni avtomobilski industriji – prehoda na električna vozila in trajnostno mobilnost. Avtomobilska industrija se sooča z velikimi pritiski za zmanjšanje emisij toplogrednih plinov, zaradi česar so proizvajalci avtomobilov prisiljeni spremeniti svoje poslovne modele, da ostanejo konkurenčni in relevantni na trgu. V tem kontekstu smo v tem delu preučili podjetje Volkswagen, enega izmed vodilnih svetovnih proizvajalcev avtomobilov, ki se je prav tako znašel na tej prelomni točki. Volkswagen se je po tej točki znašel na položaju, kjer je bila sprememba nujna za ponovno pridobitev zaupanja potrošnikov in izboljšanje svoje tržne pozicije. Podjetje se je odzvalo z ambiciozno strategijo prehoda na električna vozila, ki vključuje visoke investicije v raziskave in razvoj, vzpostavitev gigatovarn za proizvodnjo baterij ter preoblikovanje svoje ponudbe vozil. V središču te strategije je bila uvedba serije električnih vozil ID, ki so ključnega pomena za prihodnjo rast in uspešnost podjetja. V raziskavi smo analizirali, kako so te inovacije v poslovnem modelu vplivale na Volkswagnovo konkurenčnost, finančne kazalnike in tržni položaj. Ugotovili smo, da je podjetje s temi spremembami ne le uspelo obdržati svojo tržno pozicijo, temveč jo je tudi okrepilo, kar se kaže v povečanju prodaje električnih vozil, izboljšanju bruto marže. Prehod na trajnostno mobilnost je Volkswagnu omogočil, da se prilagodi novim tržnim razmeram in se postavi kot pionir na področju trajnostnih tehnologij. Diplomsko delo prav tako opozarja na nekatere ključne izzive, s katerimi se Volkswagen in širša avtomobilska industrija soočata pri tem prehodu. Mednje sodijo visoki stroški prehoda na nove tehnologije, negotovosti glede prihodnje regulative ter potreba po hitrem prilagajanju na digitalizacijo in avtonomno vožnjo. Kljub tem izzivom delo izpostavlja, kako lahko podjetja z inovativnimi poslovnimi modeli ne le preživijo, temveč tudi uspevajo v dobi disruptivnih sprememb.
Ključne besede: Poslovni model, inovacija, Volkswagen, avtomobilska industrija
Objavljeno v DKUM: 10.09.2024; Ogledov: 83; Prenosov: 69
Celotno besedilo (1,71 MB)

Opis: Type 2 diabetes mellitus is a complex multifactorial disease of epidemic proportions. It involves genetic and lifestyle factors that lead to dysregulations in hormone secretion and metabolic homeostasis. Accumulating evidence indicates that altered mitochondrial structure, function, and particularly bioenergetics of cells in different tissues have a central role in the pathogenesis of type 2 diabetes mellitus. In the present study, we explore how mitochondrial dysfunction impairs the coupling between metabolism and exocytosis in the pancreatic alpha and beta cells. We demonstrate that reduced mitochondrial ATP production is linked with the observed defects in insulin and glucagon secretion by utilizing computational modeling approach. Specifically, a 30-40% reduction in alpha cells' mitochondrial function leads to a pathological shift of glucagon secretion, characterized by oversecretion at high glucose concentrations and insufficient secretion in hypoglycemia. In beta cells, the impaired mitochondrial energy metabolism is accompanied by reduced insulin secretion at all glucose levels, but the differences, compared to a normal beta cell, are the most pronounced in hyperglycemia. These findings improve our understanding of metabolic pathways and mitochondrial bioenergetics in the pathology of type 2 diabetes mellitus and might help drive the development of innovative therapies to treat various metabolic diseases.
Ključne besede: pancreatic endocrine cells, mathematical model, mitochondrial dysfunction, cellular bioenergetics, diabetes, glucagon, insulin
Objavljeno v DKUM: 03.09.2024; Ogledov: 47; Prenosov: 3
Celotno besedilo (1,63 MB)
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Opis: This in-depth study explores the intricate dynamics of reflective materials, emphasizing their impact on the indoor thermal environment and urban heat island (UHI) mitigation. Examining diffuse highly reflective (DHR), general reflective (GR), and retro-reflective (RR) materials on a simplified building model during summer days, the research utilizes outdoor experiments to analyze air and surface temperatures, as well as solar radiation. Prioritizing key metrics—mean radiant temperature (MRT), operative temperature (OT), and solar reflectance (ρ)—the study uncovers nuanced distinctions in DHR, GR, and RR materials. Solar reflectance calculations consistently show higher values for DHR and RR materials compared to GR material, highlighting reflectance's pivotal role in influencing surface temperatures and indoor thermal environment. When evaluating the impact of exterior wall materials on building temperatures, RR material with a 76% reflectance performs similarly to DHR material (82%). Notably, with a 6% lower reflectance in RR, the temperature contrast between external and internal walls is only about 1.5 °C at its maximum, underscoring RR's effectiveness as an outer wall material for UHI mitigation and building energy conservation, surpassing both DHR and GR materials.
Ključne besede: urban heat island, reflective materials, indoor thermal environment, solar reflectance, simplified building model
Objavljeno v DKUM: 23.08.2024; Ogledov: 110; Prenosov: 6
Celotno besedilo (4,82 MB)

Opis: In order to ensure efficient wastewater treatment and seawater desalination, adequate modeling and optimization of the forward osmosis (FO) process has the potential to be very helpful. This paper deals with the FO model parameters calibration and FO process optimization by a gradient-based optimization method. For this purpose, an upgraded FO model, which involves temperature- and agent-dependent parameters, was developed. The FO model calibration was done using NaCl as agents in draw solution, while MgCl2 was used for model validation. The agreements between simulated and measured FO performance were satisfactory; relative index of agreement are higher than 0.99. By using the proposed FO model, the optimization of FO process conditions was performed with various definitions of the objective and constraint functions. In case of maximizing the water flux, minimizing reverse solute flux, and fulfilling the required constraints, the ratio of water flux and reverse solute flux increased up to 40 % for NaCl and up to 20 % for MgCl2; meanwhile the effective osmotic pressure difference was improved 2-times for NaCl and up to 3.8-times for MgCl2. The optimization process proved to be stable and efficient and can easily be adapted or upgraded for more complex dynamic FO modeling.
Ključne besede: forward osmosis, modeling, model and process parameters, calibration procedure, gadient-based optimization
Objavljeno v DKUM: 23.08.2024; Ogledov: 67; Prenosov: 8
Celotno besedilo (12,72 MB)