Glacial geomorphology of the central Barents Sea Implications for the dynamic deglaciation of the Barents Sea Ice Sheet

Contemporary climate change has resulted in great uncertainty in how glaciers and ice sheets around the Earth might evolve. It has long been appreciated that the contemporary West Antarctic Ice Sheet (WAIS) shares many similarities with the former Barents Sea Ice Sheet (BSIS). Therefore, an increasing number of studies have sought to investigate the Barents Sea glacial record to better understand marine-based glaciation. This paper reports the analysis of a new high-resolution bathymetric survey covering ~ 55,000 km2 in the central Barents Sea. The relative chronologies of newly-mapped glacial landforms such as mega-scale glacial lineations, grounding-zone wedges, moraines, and crevasse-squeeze ridges are used to reconstruct the ice sheet dynamics in the central Barents Sea. Our results show that the ice sheet responded dynamically with different periods of retreat, advance, and stagnation observed. These new landform records have been integrated with other geomorphological records in order to reconstruct the retreat pattern of the BSIS between 17–14 ka, when the Fennoscandian Ice Sheet is thought to have uncoupled from the BSIS. Our data shows that the dynamic drawdown of the ice sheet saddle by ice streams was probably the primary mechanism in separating the two ice sheets. After the ice sheets uncoupled, the BSIS is shown to have retreated episodically with several periods of relative stability. Geomorphological records such as those from the BSIS can be used to constrain ice sheet modelling and will help to develop a clearer understanding of marine-based glaciation and the role of ice streams in driving ice sheet evolution.</p

Early Quaternary sedimentary processes and palaeoenvironments in the central North Sea

A number of elongate trough-like features are observed in the early Quaternary succession of the central North Sea basin. A definitive model of formation for the features remains unclear but the troughs may aid in our understanding of the depositional environment of the early Quaternary. In total, 380 troughs were mapped over 11 000 km2 using continuous 3D seismic data and analysed in conjunction with well log data and understanding of the probable palaeogeographical context. The troughs were formed in a marine setting on the slope of a large clinoform set during a period of rapid progradation. The geometry and infill of the troughs, as well as the marine setting, strongly support a model of repeated density-driven downslope flows which excavate and then infill the troughs perpendicular to the strike of the slope. A subset of the troughs are observed to form parallel to the strike in such a way that cannot be easily explained by downslope processes alone. A number of possible models are considered for the formation of these along-slope troughs; here we conclude that the most likely scenario involves modification of the downslope flows by currents which divert the features along-slope while maintaining the erosive nature of the flow

The early Quaternary North Sea Basin

The onset of the Quaternary (2.58 Ma) corresponds to significant paleo-environmental events, such as the intensification and southward extension of Northern Hemisphere glaciation. In the North Sea Basin a significant late Cenozoic succession has been identified as a high-resolution archive of paleo-environmental changes during the Pliocene and Pleistocene. However, the identification of the base of the Quaternary has been a long-standing issue owing to lack of stratigraphic calibration. This study incorporates continuous, regional 3D seismic data with high-quality chronostratigraphic markers to map the base-Quaternary surface at high resolution across the entire North Sea. Depth conversion, backstripping, seismic geomorphology and sedimentation rate calculations are integrated to analyse the paleogeographical evolution of the North Sea Basin and its infill of c. 83 × 103 km3 of northward prograding marine to deltaic sediments. The basin is 600 km long from SSE to NNW and largely localized above residual topography of the Mesozoic graben system. During the earliest Quaternary (2.58 – 2.35 Ma) paleo-water depths were c. 300 ± 50 m and solid sedimentation rates (calculated from 0% porosity) c. 32 km3 ka−1. The base-Quaternary provides an important marker for further studies of the changing environment of the Quaternary of NW Europe as well as resource and shallow geohazard analysis. Supplementary material: A base Quaternary two-way travel time structure map is available at https://doi.org/10.6084/m9.figshare.c.390034

Modelling and Robust Control of Production Force of a Wave Energy Converter

Lifesaver is a point-absorber wave energy converter developed by Fred. Olsen. She is currently deployed off the coast of England for pre-commercial testing. Lifesaver consists of a toroidal floater supporting three Power-Take Off (PTO) units moored separately to the seabed. The mooring lines are kept taut by electrical generators.Large force oscillations have been encountered in the mooring lines during testing. The source of force oscillations is identified as velocity fluctuations in the PTO drive train due to sudden saturation of generator torque. The unfavorable transient response is a result of low stiffness in the mooring line combined with large inertia in the drive train. A numerical model of the mooring line and PTO unit is developed for use in control system development. The system dynamics are identified through a frequency analysis of a linearized model. Based on these findings a Kalman filter observer is developed to estimate force and force gradient from the angular velocity of the electrical generator. Three different controllers are proposed to mitigate the undesirable force oscillations. The first prevents sudden saturation by limiting the generator force gradient, and should be straight-forward to implement. Proportional-derivative (PD) feedback of the rope force is enabled by the Kalman filter, and is shown to effectively mitigate the unwanted behavior. However, PD feedback reduces the stability margin of the controller and must be implemented with care. A control algorithm using hysteresis is explored. The hysteretic controller behaves in a predictable and similar manner independent of the incoming wave, and has the potential of increasing robustness during high sea states. Real-time optimization of the main control parameter using extremum seeking is explored. The algorithm may be used to track a time-varying optimum due to changes in sea state. The adaptation rate is limited by the high peak-to-average power ratio of Lifesaver

Geothermal Energy at Oslo Airport Gardermoen

Rock Energy is a Norwegian company with a patented solution for drilling deep geothermal wells, for exploitation of deep geothermal energy from Hot Dry Rocks. The concept involves a drilled sub-surface heat exchanger, referred to as cross wells. The concept is well suited for production of heat for direct heat applications. In this thesis an analysis of the existing district heating plant at Oslo Airport Gardermoen has been conducted, together with examining possibilities of implementing geothermal energy as base load at the plant. A geothermal design that could meet the needs of the district heating plant has been established, and for evaluating the geothermal system in an environmental perspective an analysis based on LCA methodology has been conducted. Hafslund operates two district heating centrals at Gardermoen (Gardermoen heating central and a smaller mobile central) for which both have been analyzed to determine the potential for implementing deep geothermal energy as base load for the systems. Gardermoen heating central is connected to the airport and to the area close to the airport. This central is again connected to the mobile heating central, which is situated near the industrial estate south-east of the airport. Based on Hafslund s production data from February 2011 to January 2012, a heat load duration curve for the two existing centrals have been established. When adding the two curves together the duration curve show a maximum load of 25,7 MW at present, and a yearly energy production of 74 GWh. The mobile central accounts for only 7,2% of the total load and heat production at present.Future heat demand in the Gardermoen area is expected to increase beyond existing capacity. Hafslund is therefore considering to increase the capacity of both their district heating centrals. The enlargement plans involves that the heating central will be expanded to a design load of 37,4 MW (24 MW at present), while the mobile central need to be increased to a design load of 15,2 MW (1,7 MW at present). Assessment of the geothermal installation showed that it is preferable to include the geothermal system in the base load of the mobile central. The additional geothermal capacity will cover 10 MW, and thus deliver 65% of the required heat load and 90% of the energy production from the mobile central. The geothermal installation was designed using the spreadsheet Geocalc . The outputs from Geocalc are used in an analysis of the environmental performance of the designed system through a Life Cycle Assessment (LCA). LCA introduces a technique to assess environmental impacts associated with all stages of a product s life from cradle to grave . The report aims at giving normative results for the environmental impacts of a geothermal installation at Gardermoen. The method provides the ability to quantitatively compare results to other sources of heat provision processes for district heating. It is important to emphasize that the analysis has provided an overview of the potential environmental impact, and not necessarily the actual results of environmental consequences. The system analyzed has a thermal output of 10 MW, lifetime of 30 years, 5000 annual operating hours. The functional unit of district heating produced is kWh. The analysis is based on the main contributing processes to construction, operation and demolition of Rock Energy s geothermal system. The district heating grid is not included in the analysis, as it is already in place at the site. Each contributing process has been systematically validated. It is however uncertainties associated with the data collection mainly due to contradictory information gathered. The information considered to be mostly uncertain is the energy consumption used for drilling purposes.Possible scenarios for the energy supply to drilling were established. These scenarios were simulated in a system model in Excel. The model is based on data and information gathered from existing literature, the database Ecoinvent, published reports and personal communication with drilling experts and specialists within the relevant fields of study. The results are assessed for the following impact categories: Climate change, metal depletion, fossil depletion, terrestrial acidification and freshwater eutrophication. The evaluated potential energy sources for the drilling operation are electricity from the Norwegian grid, electricity from the European grid, and diesel. The climate change category has especially been in focus when conducting the simulations and this category shows large spread in the results, from 0,9993 g CO2-eq/kWh for the best scenario to 23,6 g CO2-eq/kWh for the worst scenario. As expected, the analysis concludes that electricity from the Norwegian grid for the drilling is preferable. For a geothermal system in Europe, the results show that it would be advantageous to use diesel as energy supply for the drilling operation instead of European electricity mix, for which the emissions are doubled.For the metal depletion impact category, the variation of energy supply to drilling cause the least fluctuation. This is also the only impact category where the Norwegian electricity mix has higher impacts than for the diesel consumption. This can be explained by the infrastructure related to electricity transmission. The results of the study have been compared to other heat sources for district heating (waste incineration, biofuel and solar thermal). The comparison shows that from an LCA perspective geothermal energy based on Rock Energy s concept is an environmentally friendly energy supplier for district heating. The studies compared are however based on varying assumptions, and thus a generalized conclusion cannot be drawn from this

Hybrid and nonhybrid control barrier functions for constraint satisfaction in dynamical systems: Applied to safe motion control of autonomous vessels

Control barrier functions (CBFs) enable constraint satisfaction in controlled dynamical systems, by mapping state constraints into state-dependent input constraints. CBFs may then be synthesized with any nominal control law by solving an optimization problem that finds the safe input that is closest to the nominal control input (by some appropriate measure). First-order CBFs are applicable for systems where the control input appears in the first time derivative of the controlled output. High-order CBFs (HOCBFs) extend the notion of CBFs to systems of any order, following a procedure reminiscent of the recursive design of a control Lyapunov function in backstepping. Augmenting CBFs with logic variables that may change value instantaneously result in hybrid CBF formulations. This thesis studies hybrid and nonhybrid control barrier functions (CBFs) for continuous-time systems, with contributions to both theory and applications. Two distinct robustness results for CBF-based control strategies are established: robustness towards bounded disturbances, and robustness towards arbitrarily small perturbations when employing discontinuous safeguarding control laws. Robustness of discontinuous CBF-based control strategies for control-affine systems is established, in the sense that the CBF-induced stability properties are retained under Krasovskii regularization. This result alleviates the need of establishing continuity properties of optimization-based control laws frequently employed together with CBFs. The result on robustness towards bounded disturbances is stated in the form of sufficient conditions for input-to-state stability (ISS) of nonhybrid HOCBFinduced systems with respect to the safe set, i.e., the subset of the state space where safety constraints are satisfied. This ISS result is established by constructing a vector comparison system from the worst-case evolution of the HOCBF along the disturbed system. Sufficient conditions for uniform global asymptotic stability (UGAS) of the safe set follow as a corollary from the sufficient condition for ISS. Both the ISS and UGAS results apply to closed, but not necessarily compact, safe sets. The distinction between compact and noncompact sets is important in context of HOCBFs, since the safe set defined by HOCBFs is often noncompact. Hybrid CBFs enable solving control problems that are not solvable by continuous control. Such control problems are frequently encountered in obstacle avoidance problems, since decisiveness with respect to turning direction of the vehicle is required either for task completion or for safety. This thesis proposes to construct hybrid CBFs by combining multiple CBF-like functions defining partially overlapping safe sets. Among the main contributions is a recursive design procedure for constructing hybrid HOCBFs, thereby extending hybrid CBFs to systems with high-order safety constraints. The theoretical results are complemented by several novel CBF-based control designs: Two hybrid CBF designs for safe motion control are proposed. The first ensures robust safety for vessels required to maintain a nonzero forward speed, whereas the second robustly resolves deadlocks that arise for CBF-based control strategies applied to obstacle avoidance. A dynamic maneuvering guidance scheme for path-following and obstacle avoidance is also proposed. The guidance scheme reactively generates a safe trajectory for autonomous for autonomous vessels to follow. Modifying the desired path itself, as opposed to forcing vessels to deviate from the path, avoids integral windup in adaptive control schemes that rely on integrating the tracking error. The thesis also motivates the use of CBF-based control strategies for constraint satisfaction in oscillatory mechanical systems, using a wave energy converter as a case study

The Economics of Technology Stock Prices An empirical study of the relationship between macroeconomic variables and the Norwegian technology index

Many of today's largest and most influential companies are in the technology sector. In recent years, these firms have experienced enormous growth in their stock price. For investors, this has been an excellent opportunity to make abnormal returns by investing in technology stocks. In the same period as the technology stock prices increased, there also were major changes in the economic environment. This suggests that the macroeconomic development has an impact of the prices of technology stocks. The purpose of our thesis is therefore to examine the relationship between chosen economic variables and the performance of the Oslo Stock Exchange technology index by answering the following research question: How do macroeconomic determinants affect the development of the Norwegian technology index? To answer the research question, we use quarterly time series data over a period spanning from 2000-2021. Based on earlier research and economic theory, seven macroeconomic variables are included. These are the 3-month NIBOR rate, inflation, the oil price, NOK/USD exchange rate, gross domestic product per capita, gross fixed capital formation and credit to the private sector. Previous literature has to a large extent examined the relationship between macroeconomic factors and the market as a whole. Our research differs from previous literature by focusing on the development of one specific sector. This can contribute to explain how the economics of technology stock prices differ from the overall stock market and how investors can exploit these differences to decide how and when to invest in the technology sector. The results of our analysis confirm that there exists a relationship between the macroeconomic factors and the Norwegian technology index. Several different relationships are found in our models. However, both models suggested a significant relationship from the 3-month NIBOR rate, inflation, the oil price and exchange rate to the value of the technology index, making those relationships robust. Investors should therefore be aware of the development of these factors when investing in the Norwegian technology stock market. Further, our analysis found no relationships from the technology index to any of the macroeconomic variables, implying that the index is a bad indicator for predicting the development of the macroeconomic variables.nhhma

Effects of exercise intensity and nutrition advice on myocardial function in obese children and adolescents: a multicentre randomised controlled trial study protocol.

INTRODUCTION: The prevalence of paediatric obesity is increasing, and with it, lifestyle-related diseases in children and adolescents. High-intensity interval training (HIIT) has recently been explored as an alternate to traditional moderate-intensity continuous training (MICT) in adults with chronic disease and has been shown to induce a rapid reversal of subclinical disease markers in obese children and adolescents. The primary aim of this study is to compare the effects of HIIT with MICT on myocardial function in obese children and adolescents. METHODS AND ANALYSIS: Multicentre randomised controlled trial of 100 obese children and adolescents in the cities of Trondheim (Norway) and Brisbane (Australia). The trial will examine the efficacy of HIIT to improve cardiometabolic outcomes in obese children and adolescents. Participants will be randomised to (1) HIIT and nutrition advice, (2) MICT and nutrition advice or (3) nutrition advice. Participants will partake in supervised exercise training and/or nutrition sessions for 3 months. Measurements for study end points will occur at baseline, 3 months (postintervention) and 12 months (follow-up). The primary end point is myocardial function (peak systolic tissue velocity). Secondary end points include vascular function (flow-mediated dilation assessment), quantity of visceral and subcutaneous adipose tissue, myocardial structure and function, body composition, cardiorespiratory fitness, autonomic function, blood biochemistry, physical activity and nutrition. Lean, healthy children and adolescents will complete measurements for all study end points at one time point for comparative cross-sectional analyses. ETHICS AND DISSEMINATION: This randomised controlled trial will generate substantial information regarding the effects of exercise intensity on paediatric obesity, specifically the cardiometabolic health of this at-risk population. It is expected that communication of results will allow for the development of more effective evidence-based exercise prescription guidelines in this population while investigating the benefits of HIIT on subclinical markers of disease. TRIAL REGISTRATION NUMBER: NCT01991106

An integrated model of clastic injectites and basin floor lobe complexes: implications for stratigraphic trap plays

Injectites sourced from base-of-slope and basin-floor parent sandbodies are rarely reported in comparison to submarine slope channel systems. This study utilises the well-constrained palaeogeographic and stratigraphic context of three outcrop examples exposed in the Karoo Basin, South Africa, to examine the relationship between abrupt stratigraphic pinchouts in basin-floor lobe complexes, and the presence, controls, and character of injectite architecture. Injectites in this palaeogeographic setting occur where there is: (i) sealing mudstone both above and below the parent sand to create initial overpressure; (ii) an abrupt pinchout of a basin-floor lobe complex through steep confinement to promote compaction drive; (iii) clean, proximal sand beds aiding fluidisation; and (iv) a sharp contact between parent sand and host lithology generating a source point for hydraulic fracture and resultant injection of sand. In all outcrop cases, dykes are orientated perpendicular to palaeoslope, and the injected sand propagated laterally beneath the parent sand, paralleling the base to extend beyond its pinchout. Understanding the mechanisms that determine and drive injection is important in improving the prediction of the location and character of clastic injectites in the subsurface. Here, we highlight the close association of basin-floor stratigraphic traps and sub-seismic clastic injectites, and present a model to explain the presence and morphology of injectites in these locations