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1031 Uppsatser om Degradation rate - Sida 9 av 69
Hur påverkar naturvårdsåtgärder mängden av vedlevande insekter : Manuellt dödade träd vs självdöda
Today?s forest managers implement a large number of methods to increase the amount of dead wood in Swedish forests. They use everything from high cutting of trees to girdling trees and burning forests. However, implementation of these measures without proper knowledge of their consequences is a common problem. This study has been performed to increase knowledge about two of these measures, girdling and high cutting, and how these actions affect the number of wood-living insects living on dead trees.
Studieavbrott vid distansutbildning
Uppsatsen är producerat och examinerad under 2007.
Pilotmodeller till flygmekanisk simulator för JAS 39 Gripen
AbstractSAAB has for a long time used user controlled pilot models in ARES. ARES is a simulation tool used in the desktop environment for simulations and calculations of the JAS 39 Gripen fighter and other aircraft. ARES stands for ?Aircraft Rigid body Engineering Simulation?. To work with these pilot models has been both time-consuming and inefficient.
Utveckling av en metod och en utrustning för mätning av bränslesprayers rörelsemängd
A new type of device for measuring thev m& ?rate of fuel sprays from a diesel fuel injector has been developed and the various steps in the development are described. The device works by deflecting all of the sprays from the injector at the same time by using a bell shaped deflector. A load cell consisting of a machined steel part with strain gauges mounted on it measures the resulting force. The shape of the curvature in the deflector bell shape has been evaluated by photographing the flow in a 2D?version of the curve shape.
Sex differences in feeding visit rates in Northern Wheatears Oenanthe oenanthe
AbstractThe Northern Wheatear (Oenanthe oenanthe) is a small insectivorous passerine bird living in open landscapes. Both parents feed the brood of approximately five chicks, but little is known about how each sex allocates their feeding effort. In this study I investigate feeding nest visit differences between male and female Northern Wheatears relative to the age of the chicks, the number of chicks and the quality of the territory for 17 pairs from 2008-2010. Data were collected using automated data loggers to record nest visitation rates during chick feeding, and the sex was determined from nest video cameras. I also examine if the parents? rate of feeding visits changes over the nestling period.
Fortsatt gran eller självföryngrad björk efter stormfällning? : en ekonomisk analys
The southern part of Sweden, Skåne, is frequently exposed to storms causing great damage to Norway spruce (Picea abies L. Karst.) stands. A storm during the winter 1999/2000 raised the attention of the problem. A lot of forest owners got large areas of spruce stands wind thrown during this storm. Can naturally regenerated birch (Betula sp.) be an alternative on these wind-exposed sites? This was the main question I was facing when discussilig the problems with Esben Möller Madsen, Söderåsens forest district.
The aim of this master thesis was to present an economic analysis of Norway spruce versus
birch.
Röjningsförbandets betydelse för avverkningsekonomin i södra Sverige :
The aim of this work is to demonstrate how the net present value (NPV) at the time of the first thinning depends on the spacing after pre-commercial thinning, and show how net value from first thinning in same stand is influenced.
This study is performed with models based on non-distant dependent growth models for single trees. Two different growth models have been used, one for cleaning (pre-commercial thinning) and one for thinning. The first one yields stem density distributed over diameter classes. In the second one, (the thinning model), it is possible to choose when thinning should be done, the thinning method, thinning grade and numbers of thinning.
Oljetemperaturens inverkan på motoroljans degradering i lastbil
The market for heavy duty engines is constantly requiring engines that should be more andmore powerful, while still maintaining low fuel consumption. As a result of increasing enginepower, the engine and coolant temperature increases as well due to insufficient coolingperformance (because of design issues, cost etc.).Also, emission legislations, both current and future, require more and more measures to betaken by engine manufacturers. One way of meeting the legislations is the use of cooled EGR(Exhaust Gas Recirculation), which also lead to increased coolant temperatures.Both these factors also naturally lead to increased engine oil temperatures, the consequencesof which are not thoroughly investigated.This thesis project aims to investigate effects of high temperatures on engine oil degradation,with focus on the greatest degradation process: oxidation. To do this several engine runs havebeen performed on a 310 hp engine with EGR to see what happens to the engine oil in a realengine when exposed to high temperatures. During the tests oil samples have been taken andanalysed for important parameters.As a complement to these engine tests some laboratory oxidation testing have also beenperformed, to be able to compare engine test data with laboratory tests.One goal of the project was to try to formulate an empirical oxidation model, which would beable to predict oil oxidation levels in an engine, given any running parameters.
Hållfasthetsegenskaper i gjutjärn : tensile properties of cast iron
In the last few years people have become more and more aware of how humanity is affecting the climate. In the direction of reducing the greenhouse gases is to design engines with higher tensile properties and reduced weight, in order to achieve lower fuel consumption and cleaner fuel incineration in today's truck engines.In order to achieve these requirements it?s necessary to increase the combustion pressure in the engine. This requires higher tensile properties and high thermal conductivity of the engine material. The department of Component Technology at the University of Jönköping in collaboration with Volvo Powertrain AB, Scania CV AB and DAROS Piston Rings AB has been commissioned to develop this material and to find knowledge of material properties used in truck engines and piston rings used for marine applications.The purpose with this work is to analyze the tensile properties of a series of cast iron, cast under different metallurgical conditions.Four different series of cast irons have been analyzed from four points of view, carbon concentration, nodularity, amount inoculation and cooling rate.After the tensile test all specimen data was analyzed in a mathematic calculation program called Matlab 2006a.
Hur påverkar ålder och fetthalt laxsmoltens utvandring till havet?
AbstractPrevious studies have shown that wild smolt have 2.5-4.5 times higher survival rate than smolt grown in culture and that starved reared smolt behave more like wild born smolt. The purpose of this project was to study whether there are differences in migration patterns and survival during migration to the coast between wild and reared smolt and between different types of reared smolt.In 2009, 25 smolts in three different groups were tagged with acoustic transmitters: Wild Born, conventionally reared 2-year and 1 ?year old smolt. For the 2010 trial there was also added a group of reared 2 ?year old smolt that were starved before release.
Tungmetaller i lakvatten : avskiljning med mineraliska filtermaterial
Four different kinds of filter-materials with reactive surfaces have been studied concerning their capacity to absorb heavy metals in leachate from a municipal waste deposit. The heavy metals studied were: lead, cadmium, copper, mercury, chromium, nickel and zinc. The leachate contains high levels of dissolved organic carbon (DOC) and has a high pH-value along with a high buffer capacity. These characteristics of the leachate make it difficult to remove pollutants and require efficient filters. The filters that were examined in the report are blast-furnace slag with CaO, sand covered with iron oxides, olivine and nepheline.
Wii Sports och Sport : En jämförelse av fysiska och emotionella skillnader och likheter i träningsspel jämfört med riktig träning
AimThe purpose of this study is to compare the level of activity between playing wii Sports Tennis and wii Sports boxing, and the usual sports, and to see how the two variants are perceived.Issues:- How much strain ratio and energy consumption it gives to exercise wii sports compared with the playing of sport for real?- How do the test participants experience the different tests?- How are the two wii sports games against each other in terms of activity and fitness in the school environment?MethodThis is an experimental study in which 10 test participants (5 men and 5 women) have carried out four different physical tests. The tests consisted of either playing an exergame or playing a sport for 25 minutes. Physical activity was measured during the test using a heart rate monitor. All test participants completed all tests in the same order.
Påverkas röstkällans egenskaper av förändrad stående kroppshållning? En experimentell studie av otränade mansröster
The aim of this study was to investigate whether a direct shift inpostural alignment results in changes in voice source characteristics. Ninemales with untrained voices were recorded standing in ideal posturalalignment and in the deviant postures swayback and kyphosis characterizedby extended hips and a slump back respectively. The voice source wasderived from the audio signal by inverse filtering. The parameters pulseamplitude, maximal flow declination rate, level difference between the firstand second voice source partials, closed quotient and the normalizedamplitude quotient in relation to subglottal pressure were compared betweenideal postural alignment and swayback and kyphosis respectively. Resultsindicate an impact of changed postural alignment on the voice source.Swayback posture gave significantly less pulse amplitude and maximal flowdeclination rate and significantly higher subglottal pressures thus resulting ina less effective phonation.
Feromoninnehållande substansers effekt på hjärtfrekvensen hos kvigor i östrus och diöstrus :
With increased milkproduction in our dairy cattle, comes a risk for a reduced fertility. Studies performed on animals and humans have shown that it is possible to manipulate the oestrous cycle through exposure to pheromones. This means that pheromones could potentionally be used to make reproduction more efficient. To evaluate the bioactivity of the substances in question, there is need for a bioassay. In insects, pheromones can induce a changed cardiac activity.
Fast etableringsställe : En skatteplanerares dröm?
This master?s thesis will examine the concept of ?fixed establishment? in VAT-law. The concept can be found in the new EC-directive on the common system of value added tax, however it has existed for thirty years in previous directives. Despite this, the legislator has never provided a proper definition of the concept. Its meaning has therefore evolved through the case-law of the ECJ.The Court has put forward a number of criteria which are all to be met if a fixed establishment is to be at hand.