Multiagent negotiation for fair and unbiased resource allocation

This paper proposes a novel solution for the n agent cake cutting (resource allocation) problem. We propose a negotiation protocol for dividing a resource among n agents and then provide an algorithm for allotting portions of the resource. We prove that this protocol can enable distribution of the resource among n agents in a fair manner. The protocol enables agents to choose portions based on their internal utility function, which they do not have to reveal. In addition to being fair, the protocol has desirable features such as being unbiased and verifiable while allocating resources. In the case where the resource is two-dimensional (a circular cake) and uniform, it is shown that each agent can get close to l/n of the whole resource.Utility theory ; Utility function ; Bargaining ; Artificial intelligence ; Resource allocation ; Multiagent system

Mechanisms of serpentinization and some geochemical effects

The thesis is presented as a collection of three scientific papers dealing with the chemical and mechanical feedbacks accompanying hydration processes in ultramafic rocks. The first paper deals with the petrological and chemical effects associated with the hydration of ultramafic rocks in the Leka Ophiolite Complex. Although, major elements present in the ultramafic rocks do not seem to be mobile on the regional scale during hydration, textural evidence shows that Fe, Mn and Ca can be transported along grain-scale distances and play an important role in the formation of metamorphic minerals. Textural observations and equilibrium thermodynamic calculations help constrain the sequence of phase transitions through the evolution of the ultramafic rocks during hydration. An important outcome of the serpentinization reactions is the volume change occurring in the affected rocks which may cause deformation. A key observation is that the major volume changes taking place in the dunites occur after the hydration of the orthopyroxenite dykes, i.e. at lower temperatures. The second paper deals with the fracturing of the orthopyroxenite dykes as a response to the stresses set up during the expansion of the dunites. The fracture patterns in the dykes have been statistically characterized as hierarchical patterns which are dominated by four-sided polygons. The fractures in such patterns develop sequentially and later fractures develop orthogonally to earlier fractures. A fragmentation model was also developed to provide insight into the number of generations of fractures in the observed patterns and the initial fracture lengths. An important observation is that the thickness of the orthopyroxenite dykes controls the density of fractures in the dyke. A 2-D FEM model was developed to study the effect of layer thickness on the fracture spacing within a layer with perfectly welded interfaces. The model shows that there exists a critical fracture spacing to layer thickness ratio (0.8-1.0) below which the horizontal stress component turns compressive, i.e. no tensile fractures can form. However, field data shows that the fracture spacing to layer thickness ratios in the orthopyroxenite dykes are below the critical value with the mean value of 0.45±0.2. The third paper investigates the effect of friction along the dyke-dunite interface on the fracture spacing to layer thickness ratios. Results from a 1-D FDM model of a layer with frictional interfaces shows that the minimum fracture spacing to layer thickness ratio is directly dependent on the ratio of the tensile and shear strength of the material. The ratios obtained for a layer with frictional interfaces can be as low as 0.10 and are in agreement with field observations

SILLi 1.0: A 1D Numerical Tool Quantifying the Thermal Effects of Sill Intrusions

Igneous intrusions in sedimentary basins may have a profound effect on the thermal structure and physical properties of the hosting sedimentary rocks. These include mechanical effects such as deformation and uplift of sedimentary layers, generation of overpressure, mineral reactions and porosity evolution, and fracturing and vent formation following devolatilization reactions and the generation of CO2 and CH4. The gas generation and subsequent migration and venting may have contributed to several of the past climatic changes such as the end-Permian event and the Paleocene-Eocene Thermal Maximum. Additionally, the generation and expulsion of hydrocarbons and cracking of pre-existing oil reservoirs around a hot magmatic intrusion is of significant interest to the energy industry. In this paper, we present a user-friendly 1D FEM based tool, SILLi, which calculates the thermal effects of sill intrusions on the enclosing sedimentary stratigraphy. The model is accompanied by three case studies of sills emplaced in two different sedimentary basins, the Karoo Basin in South Africa and the Vøring Basin offshore Norway. Input data for the model is the present-day well log or sedimentary column with an Excel input file and includes rock parameters such as thermal conductivity, total organic carbon (TOC) content, porosity, and latent heats. The model accounts for sedimentation and burial based on a rate calculated by the sedimentary layer thickness and age. Erosion of the sedimentary column is also included to account for realistic basin evolution. Multiple sills can be emplaced within the system with varying ages. The emplacement of a sill occurs instantaneously. The model can be applied to volcanic sedimentary basins occurring globally. The model output includes the thermal evolution of the sedimentary column through time, and the changes that take place following sill emplacement such as TOC changes, thermal maturity, and the amount of organic and carbonate-derived CO2. The TOC and vitrinite results can be readily benchmarked within the tool to present-day values measured within the sedimentary column. This allows the user to determine the conditions required to obtain results that match observables and leads to a better understanding of metamorphic processes in sedimentary basins

Application of A Distributed Nucleus Approximation In Grid Based Minimization of the Kohn-Sham Energy Functional

In the distributed nucleus approximation we represent the singular nucleus as smeared over a smallportion of a Cartesian grid. Delocalizing the nucleus allows us to solve the Poisson equation for theoverall electrostatic potential using a linear scaling multigrid algorithm.This work is done in the context of minimizing the Kohn-Sham energy functionaldirectly in real space with a multiscale approach. The efficacy of the approximation is illustrated bylocating the ground state density of simple one electron atoms and moleculesand more complicated multiorbital systems.Comment: Submitted to JCP (July 1, 1995 Issue), latex, 27pages, 2figure

Multiagent negotiation for fair and unbiased resource allocation

This paper proposes a novel solution for the n agent cake cutting (resource allocation) problem. We propose a negotiation protocol for dividing a resource among n agents and then provide an algorithm for allotting portions of the resource. We prove that this protocol can enable distribution of the resource among n agents in a fair manner. The protocol enables agents to choose portions based on their internal utility function, which they do not have to reveal. In addition to being fair, the protocol has desirable features such as being unbiased and verifiable while allocating resources. In the case where the resource is two-dimensional (a circular cake) and uniform, it is shown that each agent can get close to l/n of the whole resource