Magnus Thor Jonsson

Structural analysis of a transform fault-rift zone junction in North Iceland

Abstract On the north coast of Iceland, the rift zone in North Iceland is shifted about 120 km to the west where it meets with, and joins, the mid-ocean Kolbeinsey ridge. This shift occurs along the Tjornes fracture zone, an 80-km-wide zone of high seismicity, which is an oblique (non-perpendicular) transform fault. There are two main seismic lineaments within the Tjornes fracture zone, one of which continues on land as a 25-km-long WNW-trending strike-slip fault. This fault, referred to as the Husavik fault, meets with, and joins, north-trending normal faults of the Theistareykir fissure swarm in the axial rift zone. The most clear-cut of these junctions occurs in a basaltic pahoehoe lava flow, of Holocene age, where the Husavik fault joins a large normal fault called Gudfinnugja. At this junction, the Husavik fault strikes N55°W, whereas Gudfinnugja strikes N5°E, so that they meet at an angle of 60°. The direction of the spreading vector in North Iceland is about N73°W, which is neither parallel with the strike of the Husavik fault nor perpendicular to the strike of the Gudfinnugja fault. During rifting episodes there is thus a slight opening on the Husavik fault as well as a considerable dextral strike-slip movement along the Gudfinnugja fault. Consequently, in the Holocene lava flow, there are tension fractures, collapse structures and pressure ridges along the Husavik fault, and pressure ridges and dextral pull-apart structures subparallel with the Gudfinnugja fault. The 60° angle between the Husavik strike-slip fault and the Gudfinnugja normal fault is the same as the angle between the Tjornes fracture zone transform fault and the adjacent axial rift zones of North Iceland and the Kolbeinsey ridge. The junction between the faults of Husavik and Gudfinnugja may thus be viewed as a smaller-scale analogy to the junction between this transform fault and the nearby ridge segments. Using the results of photoelastic and finite-element studies, a model is provided for the tectonic development of these junctions. The model is based on an analogy between two offset cuts (mode I fractures) loaded in tension and segments of the axial rift zones (or parts thereof in the case of the Husavik fault). The results indicate that the Tjornes fracture zone in general and the Husavik fault in particular, developed along zones of maximum shear stress. Furthermore, the model suggests that, as the ridge-segments propagate towards a zero-underlapping configuration, the angle between them and the associated major strike-slip faults gradually increases. This conclusion is supported by the trends of the main seismic lineaments of the Tjornes fracture zone.

Genetic production systems for intelligent problem solving

The paper discusses an evolutionary knowledge approach to intelligent problem solving. A rule-based production system is used to model the problem and the means by which the problem space should be searched. Search heuristics are modelled as production rules. These rules are redundant as there may be more than one view on the best method for building solutions. Some rules may have complex reasoning for their actions, others have none. Deciding which rule is most appropriate is solved by a genetic algorithm and ultimately only the ‘fitter’ rules will survive. The approach eliminates the necessity of designing problem specific search or variation operators, leaving the genetic algorithm to process patterns independent of the problem at hand. Learning methods and how they aid evolution is also discussed: they are Lamarckian learning and the Baldwin effect. The approach is tested on a scheduling problem.

An Approach to Optimum Route and Site Selection of a Steam Gathering System for Geothermal Power Plants Using Multiple Weight Distance Transform

This article proposes a new approach to select the location for separators and routes for two phase flow pipelines in a geothermal steam gathering system. Multiple weight distance transform is presented and used to find the optimum location of site for a steam separator based on the flow capacity of geothermal wells. The routes are monotonic and the incline is slight in order to minimize the pressure drop and the slug flow conditions in the pipeline. A map with weighted distance for five wells shows the accessible area and the route from each well is calculated. The optimum site location reduces the total pipe length from all wells by 9%.

Specified Maintenance of Steam Turbines in Geothermal Power Plants

In a geothermal power plant the working fluid used to produce electricity is often wet steam composed of corrosives chemicals. In this situation, more frequent maintenance of the equipment is required. By constructing an overview for maintenance in geothermal power plants and how it can be done with minimum power outages and cost, the geothermal energy can be made more competitive in comparison to other energy resources.This work is constructed as a part of a project, which has the aim of mapping the maintenance management system at the Hellisheiði geothermal power plant in Iceland. The object of the project is to establish Reliability Centered Maintenance (RCM) program for Hellisheiði power plant that can be utilized to establish efficient maintenance management procedures. The focus of this paper is to examine the steam turbines, which have been defined as one of the main subsystems of the power plant at Hellisheiði. A close look will be taken at the maintenance needed for the steam turbines by studying for example which parts break down and how frequently they fail.The local ability of the staff to repair or construct turbine parts on-site is explored. The paper explores how the maintenance and condition monitoring is carried out today and what can be improved in order to reduce cost.The data collected is analyzed using Failure Mode and Effect Analysis (FMEA) in order to get an overview of the system and to help organizing maintenance and condition monitoring of the power plant in the future. Furthermore, the paper presents an overview of currently employed maintenance methods at Hellisheiði power plant, the domestic ability for maintaining and repairing steam turbines and the power plant’s need for repairs.The results show that the need for maintenance of the geothermal steam turbines at Hellisheiði power plant is high and that on-site maintenance and repairs can decrease the cost.Copyright

Pipe Route Design Using Variable Topography Distance Transforms

In this paper the Variable Topography Distance Transform method (VTDT) is used to find optimal paths across physical landscapes for pipelines carrying a two-phase geothermal fluid. The method incorporates constraints such as obstacles, land costs, building costs, variable gradients, height, and environmental issues in the route selection process. The method is an expanded form of Distance Transform algorithms that are used in image processing. It offers a way to look at land surfaces as a slope-adjusted 2-D model rather than as a more complex and computationally intensive 3-D model. The VTDT method works with a digital representation, called a Digital Elevation Model (DEM), of the landscape in question. The method is then tested on the route design for pipelines carrying a two-phase geothermal fluid at the Hellisheidi Power Plant in Iceland, which is currently (early 2005) in the design and construction phase.Copyright

Thermoelectric-Based Power Generator for Powering Microcontroller Based Security Camera

This paper presents the design, implementation and evaluation of a thermoelectric-based point of use power generation system with no moving parts. The power system was designed to be robust and stable, capable of being clamped onto the outer wall of a hot steam pipe with a temperature of over 160°C using only heat pipes and natural convection of ambient air for cooling.Several systems were built and tested. One system was built and tested at the Cooper Union in New York City. The power generation was evaluated for different ambient and steam pipe temperatures. The other systems were attached to an 85°C geothermal hot water pipe and a 100–120°C geothermal steam pipe in Iceland. The Cooper Union system was used to power two microcontroller based security cameras, one with wireless LAN and another with cellular connectivity. Additional testing of the PV voltage controller and the generator were conducted in Iceland.The results show that the system can be used to power surveillance systems, even in remote locations without access to the electrical grid. Because the system does not require grid access, it will run constantly, and hence improve security. Furthermore, the unit’s power generation is greater in colder environments that substantially degrade battery performance.Copyright

Seismic Design of Geothermal Pipeline Supports

Seismic loading is a critical factor in the structural design of piping systems for geothermal power plants in Iceland. It has been shown that the design of piping systems which is based on response spectrum static analysis can lead to overdesigned systems. The loading on the supports will be overestimated and, hence, the supports tend to be too stiff. This increased stiffness both increases the cost and reduces the quality of the seismic design. The systems response is highly dependent on the support stiffness. In this work, the design of a typical expansion loop with respect to seismic loading is discussed, with the goal being to minimize the loading from the ground acceleration. A typical pipe support is modelled, and its stiffness characteristics are evaluated and optimized. Finally, recommendations are made for improvements in pipeline support design.Copyright

Evolution of Gene Coordination Networks

A new model for the incorporation of learning with simulated evolution is presented. The model uses gene coordination networks to control gene expression. Alleles at a locus compete for expression by matching up to the network. Reinforcement is achieved through choice dynamics where gene expression will be decided by competing environmental states. The result is a epistasis model containing both plasticity and mean loci. Solutions obtained are adaptive in the sense that any changes in the environment will bring about a spontaneous self-organization in the pattern of gene expression resulting in a solution with (near) equivalent fitness. Additionally the model makes the search for structures through neutral or near neutral mutation possible. The model is tested on two standard job-shop scheduling problems which demonstrate the novelty of the approach.

Cumulant Based Modal Parameter Extraction of Structures

This paper describes a nonlinear deterministic estimator based on cumulants for the extraction of modal parameters. The signal analysed is composed of multiple exponentially damped real sinusoids in unknown additive noise. Cumulants reduce significantly the effects of noise and are also an efficient way of compressing the sampled data. In modal analysis a sensor may be unable to detect some modes of vibration due to its location. Cumulants estimated from real data sampled at different locations and instances are added directly together. This average cumulant function will contain the eigenvalues for all excited modes of vibration. Finding the frequencies and corresponding damping factors is therefore reduced to solving a single average cumulant function. The performance of the proposed estimator is examined and compared with the Eigensystem Realization Algorithm via simulations.