Characterization of benthic communities at Loki’s Castle vent field using a photomosaic

Postponed access: the file will be accessible after 2022-08-30Loki’s Castle was the first black smoker hydrothermal vent field to be discovered on the Arctic Mid-Ocean Ridge (AMOR), and is known to host a specialized and highly endemic fauna. Despite being studied since its discovery in 2008 there are still knowledge gaps, especially regarding the diversity and spatial distribution of the faunal community. The increasing interest in opening areas at the AMOR to deep sea mining makes it crucial to gather baseline data from the sites that could be affected, including Loki’s Castle. The purpose of this thesis was to characterize the abundance, diversity and spatial distribution of the benthic megafauna community at Loki’s Castle and to investigate the influence of abiotic factors on this community. To achieve this, an ortophotomosaic created from seafloor images of the area was used to annotate and quantify all visible fauna. These observations were analyzed together with pre-existing data of abiotic parameters (temperature and heat flux) and topographic variables (slope, aspect and roughness) from the vent field, using a multivariate analytical framework. A total of 14743 observations were recorded, and 20 morphospecies belonging to eight different phyla were identified. There were statistically significant differences between diffuse venting areas, focused venting areas and peripheral areas in density, diversity and morphospecies distribution. The diffuse venting site called the Barite field supports a diverse and dense community of organisms. Some of these, such as the tubeworm Sclerolinum contortum, are dependent on symbiosis with chemosynthetic bacteria, while others are likely influenced by a facilitating cascade where S. contortum is the primary foundation species. Temperature and slope were found to significantly influence the spatial distribution of most of the prominent morphospecies, total abundance and species richness. However, most of the species distributions could not be explained by temperature and slope, and it is likely that other biological and abiotic factors such as food availability, competition, predation, substrate and hydrothermal fluid composition also contribute to the observed patterns. This hypothesis should be investigated in future experimental studies. A seabed mining event at or near Loki’s Castle could change the benthic megafaunal community through elimination of vital habitat and alteration of the hydrothermal circulation from vents. This thesis provides baseline knowledge that can be useful in assessing how the benthic megafaunal community will be impacted by a possible future mining event.Masteroppgave i biologiBIO399MAMN-BIOMAMN-HAVS

Advanced technology for minimum weight pressure vessel system

Bosses were made of fiber/resin composite materials to evaluate their potential in lightweight pressure vessels. An approximate 25% weight savings over the standard aluminum boss was achieved without boss failures during burst tests. Polymer liners and metal liners are used in fiber composite pressure vessels for containment of gases. The internal support of these liners required during the filament winding process has previously been provided by dissolvable salt mandrels. An internal pressurization technique has been developed which allows overwinding the liner without other means of support and without collapse. Study was made of several additional concepts including styrene/Saran, styrene/flexible epoxy

Deciphering acoustic emission signals in drought stressed branches: the missing link between source and sensor

When drought occurs in plants, acoustic emission (AE) signals can be detected, but the actual causes of these signals are still unknown. By analyzing the waveforms of the measured signals, it should, however, be possible to trace the characteristics of the AE source and get information about the underlying physiological processes. A problem encountered during this analysis is that the waveform changes significantly from source to sensor and lack of knowledge on wave propagation impedes research progress made in this field. We used finite element modeling and the well-known pencil lead break source to investigate wave propagation in a branch. A cylindrical rod of polyvinyl chloride was first used to identify the theoretical propagation modes. Two wave propagation modes could be distinguished and we used the finite element model to interpret their behavior in terms of source position for both the PVC rod and a wooden rod. Both wave propagation modes were also identified in drying-induced signals from woody branches, and we used the obtained insights to provide recommendations for further AE research in plant science

Hvordan samsvarer eiendomsskatten med boligprisene? : en empirisk analyse av Grimstad kommune

Masteroppgave i økonomi og administrasjon – Universitetet i Agder 2014Formålet med oppgaven har vært å undersøke hvordan eiendomsskatten samsvarer medboligprisene. For å studere dette, ble det samlet inn relevant informasjon om boliger som blesolgt i Grimstad kommune i perioden mars 2011 – mars 2014. Datamaterialet er hentet fraEiendomsverdi, skattelisten for Grimstad kommune 2014 og Eiendomspulsen (finn.no).Oppgaven starter med en generell beskrivelse av Grimstad og eiendommene i kommunen.Videre redegjøres det for relevant informasjon om eiendomsbeskatning i Norge, hvor detavsluttes med spesifikk informasjon om eiendomsskatten i Grimstad.Teorikapittelet tar for seg litteratur som vurderer forekomsten av eiendomsskatt. Ved studietav eiendomsskatt er det tre ulike teoretiske retninger: det tradisjonelle synet, det nye synet ogbrukeravgiftssynet. Videre følger en kort beskrivelse av den hedonistiske prisfunksjonen.Kapittelet avsluttes med formulering av hypoteser omkring enkelte attributter som kan habetydning for boligprisene og eiendomsskatten.For å gjennomføre analysen ble det samlet inn ca. 1300 observasjoner av solgte boliger iGrimstad kommune i perioden mars 2011 – mars 2014. Etter datarensing bestod utvalget av910 observasjoner som har dannet grunnlag for hypotesetestingen. Attributter som antas å habetydning for boligprisene og eiendomsskatten er boligareal, tomteareal, alder, boligtype,eierform, lokalisering og salgstidspunkt. En detaljer presentasjon av alle variablene som erinkludert i analysen presenteres i kapittel 4.Det gis en kort beskrivelse av både enkel og multippel regresjonsanalyse, etterfulgt avdobbeltlogaritmisk og semi-logaritmisk regresjonsanalyse. En grundig økonometriskregresjonsanalyse gjennomføres for tre forskjellige modeller: modell for boligprisene, modellfor eiendomsskatten og modell for faktisk versus korrekt eiendomsskatt. Den semilogaritmiskeregresjonsmetoden viser seg å være den metoden som beskriver datamaterialetbest for samtlige modeller, og blir således brukt i videre analyse. Kontrollhypotesene testes ogdet konkluderes med at samtlige av attributtene opptrådde som forventet. Etter en nærmereanalyse av modellen for faktisk versus korrekt eiendomsskatt, konkluderes det med ateiendomsskatten ikke samsvarer med boligprisene

High-performance fiber/epoxy composite pressure vessels

Activities described include: (1) determining the applicability of an ultrahigh-strength graphite fiber to composite pressure vessels; (2) defining the fatigue performance of thin-titanium-lined, high-strength graphite/epoxy pressure vessel; (3) selecting epoxy resin systems suitable for filament winding; (4) studying the fatigue life potential of Kevlar 49/epoxy pressure vessels; and (5) developing polymer liners for composite pressure vessels. Kevlar 49/epoxy and graphite fiber/epoxy pressure vessels, 10.2 cm in diameter, some with aluminum liners and some with alternation layers of rubber and polymer were fabricated. To determine liner performance, vessels were subjected to gas permeation tests, fatigue cycling, and burst tests, measuring composite performance, fatigue life, and leak rates. Both the metal and the rubber/polymer liner performed well. Proportionately larger pressure vessels (20.3 and 38 cm in diameter) were made and subjected to the same tests. In these larger vessels, line leakage problems with both liners developed the causes of the leaks were identified and some solutions to such liner problems are recommended

A new methodology for automating acoustic emission detection of metallic fatigue fractures in highly demanding aerospace environments: An overview

The acoustic emission (AE) phenomenon has many attributes that make it desirable as a structural health monitoring or non-destructive testing technique, including the capability to continuously and globally monitor large structures using a sparse sensor array and with no dependency on defect size. However, AE monitoring is yet to fulfil its true potential, due mainly to limitations in location accuracy and signal characterisation that often arise in complex structures with high levels of background noise. Furthermore, the technique has been criticised for a lack of quantitative results and the large amount of operator interpretation required during data analysis. This paper begins by introducing the challenges faced in developing an AE based structural health monitoring system and then gives a review of previous progress made in addresing these challenges. Subsequently an overview of a novel methodology for automatic detection of fatigue fractures in complex geometries and noisy environments is presented, which combines a number of signal processing techniques to address the current limitations of AE monitoring. The technique was developed for monitoring metallic landing gear components during pre-flight certification testing and results are presented from a full-scale steel landing gear component undergoing fatigue loading. Fracture onset was successfully identify automatically at 49,000 fatigue cycles prior to final failure (validated by the use of dye penetrant inspection) and the fracture position was located to within 10. mm of the actual location

Acoustic emission source characterisation using evolutionary optimisation

When a crack initiates and grows in a metal or composite structure, for example, due to high cycle fatigue, the crack propagation gives rise to acoustic emissions (AE)-ultrasonic waves travelling through the structure. Because the presence and rate of growth of any cracks are important pieces of information about the condition or health of the structure, the monitoring of AE activity using sensors mounted on its surface is a potentially useful technique of structural health monitoring. In tests, acoustic emissions are often simulated by breaking a pencil lead against the surface of the structure in a standardised way (a "Hsu-Nielsen" source), but the forces that this imparts are not well understood at present. The current paper proposes a new evolutionary optimisation-based approach to source characterisation. The principle is to introduce a parametrised representation of a general source and then identify the parameters that allow the source to best match responses measured elsewhere on the structure. The predicted responses are modelled using a local interaction simulation approach (LISA) algorithm to simulate the propagation of the ultrasonic waves. The approach is validated here using experiments on AE propagation in thin plate-like structures, where the ultrasound propagates as Lamb waves. Three separate case studies are proposed here. In the first case, an idealised point source is simulated using laser-generated ultrasound, and the optimisation algorithm uses a two-dimensional LISA model. A differential evolution optimisation scheme is used to find the optimal profile of forcing to match the simulation with experiment. In the second case, the two-dimensional LISA approach is used to characterise the forces associated with standard pencil lead breaks. The final study addresses the full three-dimensional wave propagation. Because of the computational expense of the latter calculation, the LISA algorithm is implemented using a CUDA graphics card computer system

Improved Signal-to-noise Wideband Acoustic/ultrasonic Contact Displacement Sensors for Wood and Polymers

Research leading to a significant improvement in the signal-to-noise sensitivity of wideband acoustic/ultrasonic contact displacement sensors for wood and polymers is described. Design principles for such high-sensitivity sensors are reviewed. Comparisons of response between ceramic and polymer piezoelectric elements are made on low modulus specimens, A new, practical high-sensitivity sensor is characterized and its signal-to-noise sensitivity is compared to that of an existing commercial wide band displacement sensor. The comparisons were made for polymer, maple, and redwood samples. Optimization of the piezoelectric element in the new sensor is considered. The typical increased sensitivity of the new sensor is about 30 dB over the existing commercial sensor