Relativistic Brownian Motion

Stimulated by experimental progress in high energy physics and astrophysics, the unification of relativistic and stochastic concepts has re-attracted considerable interest during the past decade. Focusing on the framework of special relativity, we review, here, recent progress in the phenomenological description of relativistic diffusion processes. After a brief historical overview, we will summarize basic concepts from the Langevin theory of nonrelativistic Brownian motions and discuss relevant aspects of relativistic equilibrium thermostatistics. The introductory parts are followed by a detailed discussion of relativistic Langevin equations in phase space. We address the choice of time parameters, discretization rules, relativistic fluctuation-dissipation theorems, and Lorentz transformations of stochastic differential equations. The general theory is illustrated through analytical and numerical results for the diffusion of free relativistic Brownian particles. Subsequently, we discuss how Langevin-type equations can be obtained as approximations to microscopic models. The final part of the article is dedicated to relativistic diffusion processes in Minkowski spacetime. Due to the finiteness of velocities in relativity, nontrivial relativistic Markov processes in spacetime do not exist; i.e., relativistic generalizations of the nonrelativistic diffusion equation and its Gaussian solutions must necessarily be non-Markovian. We compare different proposals that were made in the literature and discuss their respective benefits and drawbacks. The review concludes with a summary of open questions, which may serve as a starting point for future investigations and extensions of the theory.Comment: review article, 159 pages, references updated, misprints corrected, App. A.4. correcte

Prototype of HIL Test Platform for Autonomous USV - Simulation and Visualization of Vessel Surroundings

This thesis considers the simulation and visualization of the maritime surroundings of unmanned surface vehicles (USVs) in a Hardware-In-the-Loop (HIL) simulator. The development of the simulator was conducted as two master's projects, and resulted in the first prototype of a HIL simulator meant for verification testing of two USVs developed by Kongsberg Maritime AS in cooperation with Norwegian Defense Research Establishment (FFI). The two USVs are called Odin and Jolner, where Odin is the primary target of the HIL simulator. The simulator consists of 3 main software modules: the Surroundings simulator, the Dynamics simulator and a graphical user interface (GUI), where the modeling and simulation of the dynamics of the USVs are considered in Ødegaard (2017). The desired sensor systems to simulate in the Surroundings simulator are an Automatic Identification System (AIS) and a dedicated target detection module (TDM), which is a sensor fusion of AIS, radar and Light Detection and Ranging (LiDAR) sensors. An investigation of these sensor systems and how they can be simulated with appropriate levels of sensor noise are considered. A basic sensor fusion algorithm is applied to artificial data from AIS, radar and LiDAR to make an educated guess in regards to the performance of the TDM, which is currently under development at FFI. Possible simulation scenarios and objects to include in the simulations are discussed, with emphasis on usefulness in regards to the current development stage of Odin. The Surroundings simulator is implemented based on this discussion and the investigation of the relevant sensor systems. A GUI is also implemented, with real-time plots and visualization of the simulation in both 2D and 3D. The functionality of the HIL simulator in its entirety is demonstrated through an example, simulating Odin in an open sea scenario under presence of icebergs and other vessels. Odin navigates in the simulated environment using thrust inputs as logged from a real, unrelated mission. Unfortunately, the control system and the TDM of Odin is still under development, so the Surroundings simulator could not be tested with the real control system in the loop. It is, however, implemented simple motion control, which enabled testing of the Dynamics simulator against Odin's control system. This is proven successful in Ødegaard (2017), and indicates that the interface between the simulator and the control system works as intended. It is hence expected that the simulator in its entirety will provide a complete and functional HIL simulator platform for Odin and Jolner when their respective control systems are ready to receive data from the sensor systems considered in this thesis

Å finne og gi mening. En casestudie om mellomlederes prosess med å finne og gi mening i endring

Temaet for denne masteravhandlingen er mellomlederes prosess med å finne og gi mening i endringsprosesser. Oppgaven stiller spørsmålet om hvorvidt det er en sammenheng mellom mellomledere sin prosess med å finne mening i en endring, og hvordan mellomlederne støtter de ansatte ved å gi mening til endring. Hensikten er å bidra med en økt innsikt innenfor forskningsfeltene mellomledere, endring og meningsdannelse, ettersom det etterlyses av flere forskere (Balogun, 2003; Rouleau, 2005; Raelin & Cataldo, 2011, Filstad, 2014; Hope 2015). Studien tar utgangspunkt en kvalitativt case, der syv avdelingsledere innenfor hjemmetjenesten i seksjon for helse og omsorg i Tromsø kommune har blitt intervjuet ved bruk av dybdeintervjuer. Funnene fra denne avhandlingen viser at seks av syv intervjuobjekter har en klar sammenheng mellom egen prosess med å finne mening i en endring, og hvordan de hjelper sine ansatte ved å gi mening til endring. Avhandlingen finner at dersom en mellomleder har en aktiv prosess med selv å finne mening, har de også en aktiv prosess med å hjelpe sine ansatte å gi mening, mens intervjuobjektene som har en passiv prosess med å finne mening, har en passiv atferd ovenfor de ansatte. Et annet interessant funn er at de avdelingslederne som har en ambivalent affektiv reaksjon på endring, altså at de gir uttrykk for både positive og negative følelser i forbindelse med endring, har en aktiv prosess med å hjelpe sine ansatte å gi mening til endring. De mellomlederne som har en utpreget positiv eller negativ affektiv reaksjon på endring, har en passiv prosess med å hjelpe sine ansatte gjennom endring