Yes / In recent years 3D printing has gained popularity amongst industry professionals and hobbyists alike, with many new types of Fused Filament Fabrication (FFF) apparatus types becoming available on the market. A massively overlooked component of FFF is the requirement for a simple method to calculate the geometries of polymer depositions extruded during the FFF process. Manufacturers have so far achieved adequate methods to calculate tool-paths through so called slicer software packages which calculate the required velocities of extrusion from prior knowledge and data. Presented here is a method for obtaining a series of equations for predicting height, width and cross-sectional area values for given processing parameters within the FFF process for initial laydown on to a glass surface.

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No description available.

Climate change and rising temperatures is a well-known problem. To tackle global warming a transition from fossil fuels to renewable and reliable energy sources is necessary. Hydrogen, in fuel cells, is proposed to replace diesel and gasoline in the transport sector. Hydrogen is a pure fuel and the fuel cells only emit water and heat as a byproductbyproduct. Combined with electric motors, the hydrogen fuel cell can be 2-3 times more efficient compared to combustion engines fueled by gasoline. The performance of the fuel cell is affected by how the individual parts of the cell are designed. There are some difficulties in manufacturing complex geometries which requires require a forming in more than one step.  The goal isis to investigate, with the help of COMSOL Multiphysics software, how the performance of the fuel cell is affected by the shaped geometry at the cathode side of the flow plate. A numerical model is developeding will be made with varying parameters on the measurement of the cross-sections of the channels where pressure drop and flow distribution for ten different geometries isarewill be investigated. The model iswas built in the COMSOL Multiphysics 6.1 Software and includes a three-dimensional geometry consisting of a gas channel and a gas diffusion layer. The flow is laminar and the gas diffusion layer is set as a porous medium.  The results show that geometries with less sharp edges have lower pressure drops and more uniform flow distribution compared to geometries with sharper edges. The geometry with the sharpest edges has the highest pressure drop of 4.8 Pa/mm and the geometry with rounder edges has the lowest of 3.8 Pa/mm. A relationship between pressure drop and cross-sectional area can be found. With increasing radius and increasing cross-sectional area will the pressure drop decrease. The Reynolds number is higher for sharper geometries since the average velocity in the channels is higher, which also gives a lower friction factor. The length of the top flat becomes less for rounder geometries, which positively affects uniform flow distribution. The geometries with rounder edges have the most uniform distribution at the top of the gas diffusion layer and the sharpest geometry has the least uniform distribution. The deviation from the mean velocity is lower for sharper geometries, mainly because the velocities in the gas diffusion layer are lower. Sensitivity analysis was made over the mass flow rate and mesh, showing that the pressure drop is proportional to the mass flow rate and it becomes higher with less fine mesh.  Less fine mesh also gives lower velocities in the gas diffusion layer. Further studies can be made on how the gas diffusion layer behaves in the fuel cell when adding clamping force to the stack when putting it together and investigate if and how it affects pressure drop and flow distribution. The environmental benefit can be crucial if the performance of the fuel cells improves and motivates the investments which is are needed for, among other things, the infrastructure. / Klimatförändringar och stigande temperaturer är ett välkänt problem. För att ta itu med den globala uppvärmningen är en övergång från fossila bränslen till förnybara och pålitliga energikällor nödvändigt. Vätgas,  går bland annat att användas ii bland annat bränsleceller och , skulle kunna ersätta diesel och bensin inom transportsektorn. Vätgas är ett rent bränsle och bränslecellerna släpper bara ut vatten och värme som biprodukter. I kombination med elmotorer kan vätgasbränslecellen vara 2–3 gånger mer effektiva jämfört med förbränningsmotorer som drivs av bensin. Bränslecellens prestanda påverkas av hur de enskilda delarna av cellen är utformade. Det finns vissa svårigheter att tillverka komponenter med komplexa geometrier som kräver formning i fler än ett steg. Målet är att med hjälp av programvaran COMSOL Multiphysics undersöka hur bränslecellens prestanda påverkas av den formade geometrin på katodsidan av flödesplattan. En numerisk modellering kommer att utförasgöras utifrån med varierande parametrar därpå måtten hos kanalernas tvärsnitt varieras. Tdär tryckfall och flödesfördelning hos tio olika geometrier kommer att undersökas. Modellen byggdes i COMSOL Multiphysics 6.1 Software och inkluderar en tredimensionell geometri bestående av en gaskanal och ett gasdiffusionsskikt. Flödet är laminärt och gasdiffusionsskiktet antas vara ett poröst medium. Resultaten visar att geometrier med mindre skarpa kanter ger lägre tryckfall och jämnare flödesfördelning jämfört med geometrier med skarpare kanter. Geometrin med skarpast kanter har det högsta tryckfallet på 4.8 Pa/mm och geometrin med rundare kanter har ett tryckfall på 3.8 Pa/mm. Ett samband mellan tryckfall och tvärsnittsarea kan hittas då ökad radie och ökad tvärsnittsarea ger en minskning i tryckfall. Reynoldstalet är högre för skarpare geometrier eftersom medelhastigheten i kanalerna är högre, vilket också ger en lägre friktionsfaktor. Längden på toppen av kanalerna blir mindre för rundare geometrier, vilket påverkar flödesfördelningen positivt. Geometrierna med rundare kanter har den mest jämna fördelningen i toppen av gasdiffusionsskiktet och den skarpaste geometrin har den minst jämna fördelningen. Avvikelsen från medelhastigheten är lägre för skarpare geometrier, främst på grund av att hastigheterna i gasdiffusionslagret är lägre. Känslighetsanalys gjordes över storleken på massflödet och noggrannheten i meshen, vilket visar att tryckfallet är proportionellt mot massflödet och att det blir högre med mindre noggrann mesh. Mindre noggrann mesh ger också lägre hastigheter i gasdiffusionsskiktet. Ytterligare studier kan göras om hur gasdiffusionslagret beter sig i bränslecellen vid sammanpressning av alla delar i cellen och undersöka om och hur det påverkar tryckfall och flödesfördelning. Fördelen för miljönMiljönyttan kan vara stor om bränslecellernas prestanda förbättras och på så vis kan motivera de investeringar som behövs för utbyggnaden av bland annat infrastrukturen.

Using the concept of bone functional adaptation, this study analyzes femoral and humeral cross-sectional properties of human skeletal materials from Morton Shell Mound on the Louisiana coast. This work helps fill a gap in such analyses in the southern U.S. and contributes to an understanding of the functional adaptation of the human skeleton. Properties were compared to those of other prehistoric Southeastern fisher-hunter-gatherers from Gold Mine, Plash Island, and several Georgia coast sites to assess mobility and activity patterns among inland and coastal groups. Less sexual dimorphism of femoral midshaft shape among coastal Morton and Plash, compared to inland Gold Mine, indicates lower terrestrial logistic mobility. Greater robusticity (not significant) in coastal samples is linked to an expanded subpersiosteum, rather than terrestrial logistic mobility. Both coastal and inland samples exhibit round humeral shape, typical of fisher-hunter-gatherers.

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Locomotion is one of the most important qualities of man and has always been associated with survival, foraging ans subsistence. During the course of evolution, men and women developed some form of gender specialization which resulted in different level of mobility between the sexes. Throughout history, the types of subsistence have changed and the degree of sedentism has increased. However, despite all the changes in subsistence, gender specialization and bone robusticity sexual dimorphism in the robusticity of the lower limb bones remained surprisingly stable. Is it possible that women load lower limb bones differenty than men (e.i. due to different body proportions)? The aim of this work is to determine wheter there is sexual dimorphism between the sexes of the recent living population in the cross-sectional properties of the tibia and in the load on the tibia during running. In this work we used images of the tibia from magnetic resonance imaging and kinematic and kinetic data during the run of 20 probands. By using musculoskeletal modeling we estimated the bending moment acting at 50 % of the tibial length as well as the angle of action of this moment. After adjusting for size, no significant difference was found in the results of cross-sectional geometry of the bone in any of the monitored...

There is an understanding among biological anthropologists that long bone epiphyseal shape is highly regulated by genetic and biomechanical factors. Conversely, long bone diaphyseal geometry and robusticity have been shown to respond to activity in life. The current study examined the assumption of epiphyseal consistency by exploring the relationship between a well established bony response to activity (Cross-Sectional Geometry) and shape change among the proximal humerus and femur. Long bone samples were taken from four hunter-gatherer populations: the Andaman Islanders, the Indian Knoll, Point Hope Alaskans, and the Sadlermiut. Shape was measured through landmark configurations placed on the proximal end of a total of 91 humeri and 84 femora. Cross-sectional Geometry measures (J) were taken from each specimen, as well. Principal Component Analyses were conducted on the landmark shape data to determine where the shape variation was occurring among the sample. These Principal Components were then compared via Bivariate Regression to the J values taken from the diaphysis. Significant relationships occurred between the development of the lesser tubercle and an increase in J among the humerus sample. Significant relationships were also found among the femur sample; as when J increased the proximal epiphyses were more likely to be more gracile, and the space between the femoral head and the greater trochanter increased. The humerus results indicated a more robust proximal epiphysis in groups with activities that rely heavily on the upper body, such as rowing, swimming, and harpooning. The femur results were more complex, as the relationship between activity and proximal shape is likely heavily influenced by a genetically predetermined body shape. These results indicated that there is a relationship between activity and proximal epiphyseal shape, but that it, like all relationships, is complex, and comprised of multiple factors. Ultimately, proximal long bone shape is the result of multiple influences including, activity, genetics, population adaptation, health, and many more. Future research should focus on determining if the relationship between activity and shape exists among other populations, and when and where it begins during growth and development. / Graduate

L’analyse biomécanique peut être utilisée pour comprendre et interpréter l’impact de la mobilité et du climat sur la morphologie squelettique des populations humaines préhistoriques en mesurant les propriétés mécaniques des os longs. Le comportement et le climat font parties de plusieurs facteurs non-génétiques qui peuvent avoir un impact sur l’adaptation fonctionnelle osseuse en influençant les charges mécaniques sur le squelette et déclenchant le processus de modelage osseux. Cette étude se concentre sur les changements au niveau macrostructural des os longs : les propriétés mécaniques sont ainsi calculées sur plusieurs sections en coupe afin de mesurer la robustesse et la géométrie diaphysaire. Mon projet consiste à développer une collection de référence incluant quatre populations holocènes du Nord du Canada dont les Inuit Sadlermiut et trois échantillons d’Euro-Canadiens venant de Notre-Dame, Pointe-aux-Trembles et Sainte-Marie. L’objectif est de contrôler pour différents facteurs environnementaux afin de mieux comprendre l’effet de la mobilité et le climat sur la morphologie squelettique humaine. Les propriétés mécaniques d’os longs incluant l’humérus, le fémur et le tibia sont mesurées par tomodensitométrie quantitative périphérique (pQCT). Ces données sont ensuite incluses dans une méta-analyse dont les données sont tirées de la littérature scientifique, comparant d’autres populations archéologiques qui avaient différents modes de subsistance et habitaient diverses zones climatiques. Les données démontrent que les Inuit Sadlermiut ont des membres supérieurs et inférieurs plus robustes que trois échantillons de populations d’Euro-Canadiens qui ne diffèrent pas l’un de l’autre. La robustesse squelettique chez les Sadlermiut proviendrait de leur haut niveau d’activité physique nécessité par leur mode de vie de chasseur-cueilleur dans un climat rude et froid. De plus, la méta-analyse portant sur la mobilité a déterminé que le type et l’intensité des charges mécaniques habituelles ont une influence importante sur la morphologie des membres supérieurs et inférieurs tandis que celle portant sur le climat démontre qu’une relation est significative avec l’humérus. Ainsi, ce projet atteste que le processus de modelage osseux est multifactoriel et que le degré d’influence des facteurs comportementaux et environnementaux n’est pas uniforme sur le squelette. / Biomechanical analyses have been used to study the impact of mobility and climate on the skeletal morphology of past human populations through the measure of the cross-sectional geometry of long bones. Behavior and climate are one of the many non-genetic factors that can impact bone functional adaptation by influencing mechanical loads on the skeleton and triggering the bone modeling process. The present study focuses on the structural changes occurring at the macrolevel of long bones, more specifically robusticity and shape, by calculating mechanical properties at several cross-sectional locations. This project consists of creating a reference collection using four Holocene populations from northern Canada including Sadlermiut Inuit and three Euro-Canadian samples from Notre-Dame, Pointe-aux-Trembles and Sainte-Marie. The objective is to control for different environmental factors to better understand the impact of mobility and climate on human postcranial morphology. Cross-sectional properties were measured in the humerus, femur and tibia using a portable peripheral quantitative computed tomography (pQCT). These data were then input into a meta-analysis that included data, drawn from the scientific literature, from other archaeological populations with different modes of subsistence and inhabiting various climate types. The results showed that Sadlermiut Inuit had more robust upper and lower limbs than all three samples of Euro-Canadians who did not differ significantly from one another. The high measures of robusticity among Sadlermiut were attributed to the strenuous physical activity demanded by their hunting and gathering mode of subsistence in cold and harsh environmental conditions. Furthermore, the meta-analysis on mobility demonstrated that the type and intensity of habitual mechanical loading on the skeleton has a significant influence on the upper and lower limbs whereas the meta-analysis pertaining to climate only had a significant relationship with the humerus. Essentially, this project highlights the multifactorial nature of the bone modeling process and that the level of influence of behavioral versus climatic factors is not uniform throughout the skeleton.

An ongoing debate concerning Neandertal ecology is whether or not they utilized long range weaponry. The anteroposteriorly expanded cross-section of Neandertal humeri have led some to argue they thrusted their weapons, while the rounder cross-section of Late Upper Paleolithic modern human humeri suggests they threw their weapons. We test the hypothesis that Neandertal humeri were built to resist strains engendered by thrusting rather than throwing using finite element models of one Neandertal, one Early Upper Paleolithic (EUP) human and three recent human humeri, representing a range of cross-sectional shapes and sizes. Electromyography and kinematic data and articulated skeletons were used to determine muscle force magnitudes and directions during three positions of spear throwing and three positions of spear thrusting. Maximum von Mises strains were determined at the 35% and 50% cross-sections of all models. During throwing and thrusting, von Mises strains produced by the Neandertal humerus fell roughly within or below those produced by the modern human humeri. The EUP humerus performed similarly to the Neandertal, but slightly poorer during spear thrusting. This implies the Neandertal and EUP human humeri were just as well adapted at resisting strains during throwing as recent humans and just as well or worse adapted at resisting strains during thrusting as recent humans. We also did not find any correlation between strains and biomechanical metrics used to measure humeral adaptation in throwing and thrusting (retroversion angle, Imax/Imin, J). These results failed to support our hypothesis and suggest they were capable of using long distance weaponry.