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In modern forestry, two types of machines are generally used for thinning, harvesters and forwarders. These machines are large and weigh several tens of tons, this means that they damage the ground when they drive around in the woods. AirForestry is a startup company that focuses on manufacturing lightweight and electric forest machines that will do much less damage due to the lower weight. As their ambition is to develop an all-electric harvester, high efficiency in the work process is required to be competitive. The purpose of this thesis was to find which factors affect the debranching process and to find what approximate effect the harvester head's drive motors would need to have to achieve a stable debranching process. If the results of the research were successful, a new knife design would be developed for thinning. The work carried out began with a planning report which included introduction, literature study and method was written. The method chosen was to first develop a test rig to be able to measure what amount of work and what maximum impact force a single branch would need to be cut. Afterwards a study of branches and their distribution on trees in the thinning phase were conducted. The branch distribution and the data from the test rig, would make it possible to estimate the energy required to cut down a tree. Impact forces along the tree provide an opportunity to not only estimate the life cycle of the knives but also an analysis of how the remaining units hold. The branching process was assumed to be affected by both the design of the knives and which branches are present and how these are placed. The literature study showed that frozen wood gives higher forces when sheared, so it was investigated as well. The test rig was designed as a guillotine to make it easy to manufacture and due to potential energy being the only source of energy to power the rig. The work of cutting a branch was measured with a high-speed camera and the maximum impact force was measured with an accelerometer. Different knife designs were tested together with different angles and branch types. All variables tested in the rig were performed on several different branch diameters. The study of branch distribution along the tree was done on trees that were considered to be in the thinning stage and all branches with a diameter greater than 5 mm were noted together with distance and whether it was dead or not. The test rig's test data were later used in a multiple linear regression to determine if a variable effect of not. The regression was then used to estimate the power required to debranch a pine to be 3.1 kW and 6.6 kW for a spruce. Only the diameter of the branches and the tree sort could be proven to have a statistically significant effect on both the work required and the maximum impact force. / I det moderna skogsbruket används i regel två maskintyper vid gallring, skördare och skotare. Dessa maskiner är stora och väger flera tiotals ton vilket gör att de skadar marken när de kör ute i skog och mark. AirForestry är ett startupbolag som riktar in sig på att tillverka lättviktiga och elektriska skogsmaskiner som ska göra mycket mindre skada på grund av deras lägre vikt. Då deras ambition är att utveckla en helelektrisk skördare, krävs en energieffektiv process för att kunna vara konkurrenskraftiga. Målet med detta arbete var att hitta vilka faktorer som påverkar avgreningsprocessen samt hitta vilken ungefärlig effekt skördaraggregatets drivmotorer skulle behöva ha för att uppnå en stabil avgrening. Om resultatet av forskningen var lyckat skulle en ny knivdesign tas fram anpassad för gallring. Arbetet som utfördes började med en planeringsrapport där introduktion, litteraturstudie och metod skrevs. Metoden som valdes var att först utveckla en testrigg för att kunna mäta vilket arbete och vilken maximal slagkraft en gren skulle behöva för att kapas. En studie av grenar och dess distribution på träd i gallringsfasen skulle tillsammans med data från testriggen göra att energin som krävs att ta ner ett träd kan uppskattas. Slagkrafter längs med trädet ger en möjlighet att inte bara uppskatta knivarnas livscykel utan även en analys på hur resterande aggregat håller. Avgreningsprocessen antogs påverkas av både knivarnas design och vilka grenar som finns samt hur dessa är placerade. Litteraturstudien visade på att fryst trä ger högre krafter vid skjuvning, därför undersöktes det med. Testriggen konstruerades som en giljotin för att göra den enkel att tillverka och för att endast potentiell energi används för att driva riggen. Arbetet för att kapa en kvist mättes med höghastighetskamera och maximal slagkraft mättes med en accelerometer. Olika knivdesigner testades tillsammans med olika infallsvinklar och grentyper. Alla variabler som testades i riggen utfördes på flera olika kvistdiametrar. Studien av grenars distribution längs med trädet gjordes på träd som ansågs vara i gallringsstadiet och alla grenar med diameter större än 5 mm noterades tillsammans med avstånd och om den var död eller ej. Testriggens testdata användes senare i en multipel linjär regression för att kunna bestämma vilka variabler som påverkar. Regressionen användes sedan till att uppskatta effekt som krävs till 3.1 kW för en tall och 6.6 kW för en gran. Endast grenarnas diameter och trädsort kunde med statistik säkerställas påverka både arbetet som krävs samt maximala slagkraften.

<p>Highly shear-thinning polymers that can easily flow upon the application of shear but form gels at rest have multiple potential applications in the eye. In the front of the eye, a formulation that can easily be administered via a conventional eye dropper but form a gel within the tear film once applied would be beneficial for prolonging drug release at the front of the eye, either alone or as a medium for entrapping nanoparticles or nano-objects loaded with drugs. In the back of the eye, vitreous substitutes that can be administered through a narrow gauge needle (and, ideally, removed via the same) may be beneficial for retinal surgeries.</p> <p>The overall objective of the proposed research is to chemically modify PVP through grafting strategies to improve its viscometric and mucoadhesive properties while maintaining the beneficial properties, which make it useful in ophthalmic applications.</p> <p>N-vinylpyrrolidone is copolymerized with N-vinylformamide to produce a functionalized grafting platform P(VP-co-VF), which is then grafted with low concentrations of short hydrophobic grafts to introduce non-Newtonian flow profile to the precursor.</p> <p>For applications at the back of the eye, the hydrophobic grafted PVP can be injected into the vitreous cavity of the eye in a liquid form to form subsequently a gel-like substance and function as a substitute for the vitreous humour. For application at the front of the eye, the shear thinning properties of hydrophobic-grafted PVP is combined with the mucoadhesive properties of phenylboronic acids (PBA) to improve the bioavailability of the drugs delivered to the front of the eye with eye drops.</p> <p>Rheological characterization of the solutions has shown the potential to form gel-like materials via hydrophobic associations without sacrificing the facile injectability of the material. Targeted gelation and mucoadhesion properties can be obtained by the synthesis of polymers with desired PBA and hydrophobic graft contents.</p> / Master of Applied Science (MASc)

The instability mechanism of the shear-thinning and shear-thickening fluids pasta circular cylinder is studied using linear theory. The shear-dependent viscosityis modeled by the Carreau-law where the rheological parameters, the power-index and the material time constant are chosen in the range 0.4 &lt; n &lt; 1.75 and0.1 &lt; λ &lt; 100. A second order finite-difference code is used for the simulationof cylinder flow in which the Immersed Boundary Technique is implemented torepresent the cylinder surface on a Cartesian mesh. The critical Reynolds num-ber for the onset of instability is reported for a range of rheological parameters.Structural sensitivity analysis based on the idea of ”wavemaker” is performedto identify the core of the instability. Perturbation kinetic energy budget is alsoconsidered to examine the physical mechanism of the instability. The charac-teristics of base-flow: drag coefficient, size of recirculation bubble and viscositydistribution are presented to provide useful knowledge about shear-thinning ef-fect in flow past a cylinder.