The electrodynamic coupling between the auroral ionosphere and the magnetosphere is the main subject of this thesis. Satellite measurements of electric and magnetic fields and of charged particles are used to explore three distinct plasma boundaries, magnetically linked to the nightside auroral ionosphere. These boundaries are the inner edge of the plasma sheet (PS), and the inner and the outer edges of the plasma sheet boundary layer (PSBL). Strong ionospheric electric fields with amplitudes up to 400 mV/m may be observed in the subauroral ionosphere, in the vicinity of the ionospheric projection of the PS inner edge. Intense and dynamic auroral electric fields with local magnitudes up to 150 mV/m associated with upward ion beams and field-aligned currents are observed for the events treated here, at the inner and outer boundaries of the PSBL at an altitude of about 4-5 Earth radii, well above the acceleration region. Subauroral and auroral electric fields are the two main subjects of this thesis. Subauroral ion drifts (SAID) are associated with poleward electric fields, occurring predominantly in the premidnight region during the substorm recovery phase. The recently revealed abnormal subauroral ion drifts (ASAID) are associated with equatorward electric fields, occurring during extended periods of low auroral activity. The results indicate that the generation mechanism of SAID can neither be regarded as a pure voltage generator nor a pure current generator, but having certain characteristics of both generator types. Ionospheric feedback appears to play a major role for the development and maintenance of the SAID electric fields. The formation of ASAID is proposed to result from the proximity and interaction between different plasma boundaries of the innermost magnetosphere during extended periods of low auroral activity. The auroral electric fields observed in the upward current region at the PSBL inner and outer edges are associated with upward parallel electric fields, which partially decouple the high-altitude electric fields from the ionosphere. This is in contrast to the subauroral electric fields which are coupled. Multi-point measurements provided by the Cluster mission show that the observed electric fields are highly variable in space and time, revealing various types of acceleration processes. However, they appear to be tied to the boundary where they are originally formed. A case is  presented where they are associated with large electromagnetic energy fluxes directed upward away from the ionosphere. The interaction between the magnetosphere and ionosphere, being more pronounced at plasma boundary regions, is important for the understanding of the formation and regulation of the highly structured auroral electric fields observed in the upward current region. / QC 20100727

A detailed characterization of the proton and neutron induced radiation environment onboard Columbus and the International Space Station (ISS) has been carried out using the Geant4 Monte Carlo particle transport toolkit. Dose and dose equivalent rates, as well as penetrating particle spectra corresponding to incident trapped protons, GCR protons, SPE protons and cosmic ray albedo neutrons are presented. These results are based on detailed Geant4 geometry models of Columbus and ISS, comprising a total of about 750 and 350 geometry volumes, respectively. Additionally, the physics models of Geant4 have been validated with respect to space radiation shielding applications. Geant4 physics configurations based on the “Binary Cascade” and “Bertini Cascade” models of hadronic reactions were found to adequately model the particle interactions of the relevant space radiation fields. Other studied Geant4 models of hadronic reactions were found to be unsatisfactory for this application. Calculated trapped proton dose rates are found to be strongly dependent on ISS altitude. Dose rates for different locations inside the Columbus cabin are presented, as well as for different models of the incident space radiation flux. Dose rates resulting from incident anisotropic trapped protons are found to be lower, or equal to, those of omnidirectional models. The anisotropy induced by the asymmetric shielding distribution of Columbus/ISS is also studied. GCR proton dose rates are presented, and it is demonstrated that the presence of thick shielding may increase the dose rate. A possible problem using Geant4 for future studies of effects induced by high-energy GCR ions is discussed. The dose rate due to cosmic ray albedo neutrons is demonstrated to be negligible. The calculated trapped proton dose rates are 120 μGy/d and 79 μGy/d for solar minimum and maximum conditions, respectively. GCR dose rates are estimated based on calculated GCR proton dose rates to 161 μGy/d and 114 μGy/d, respectively. These dose rates are found to be compatible with experimental measurements. / QC 20110125

The Earth ionosphere is a highly inhomogeneous medium containing electron density irregularities of various scales, from hundreds of kilometers to tens of centimeters. Understanding the mechanisms responsible for their formation is an important task for various practical applications such as communication, navigation, and safe satellite operation. Of special interest are the decameter irregularities that are abundant at E region heights of ~ 100 120 km. These are excited when enhanced electric field and plasma drifts are setup in the ionosphere. This thesis is aimed at studying the physics of decameter irregularity formation at E region heights with a focus on the extreme conditions of very strong electric fields (plasma flows) of > 50 mV/m (1000 m/s) for which the so called Farley-Buneman (FB) plasma instability is the dominating mechanism of irregularity excitation. The relationship between the irregularity velocity and plasma drift is investigated by considering data of the SuperDARN radar located at Stokkseyri, Iclenad. The radar detects echoes from the irregularities and is thus capable of measuring their velocity. The DMSP satellites measure the plasma drifts in situ at heights of ~ 800 km, but these measurements can be projected onto E region heights at high latitudes. By comparing the radar and satellite data in one direction, we show that irregularity velocity is smaller than the plasma drift by a factor of 2 3 with the stronger difference at faster flows. This contrasts with the theoretical expectation for the velocity to be close to 400 m/s, the nominal ion-acoustic speed at electrojet heights. A two-dimensional comparison is performed by considering a subset of the observations for which the HF echo velocity showed a cosine type variation with the radar look direction. This class of echoes is consistent with predictions of recent theories of the Farley-Buneman instability, but the irregularity velocity magnitude was found to be smaller than the ion-acoustic speed with occasional occurrence of velocities as small as 100 m/s. This implies that either recent theories of the Farley-Buneman instability should be modified or that the typical height of HF echoes is typically below 100 km. Various other properties of decameter irregularities are investigated and discussed in view of the existing theories.

Trade shows, a powerful tool to introduce and sell products and services, need to attract, hold, persuade and inform visitors. In trade shows, well-designed social spaces can facilitate active communications and interactions between exhibitors and visitors. Besides being amenities to retain visitors, social spaces can balance or re-stimulate visitors’ emotion. Based on the interdisciplinary exploration of urbanism, environmental psychology, and exhibition design, the practicum proposes a new strategy of organization for exhibition layout, structured by social spaces in various scales and levels. Case studies of existing trade shows identify the context and design factors in existing social spaces. The understanding of human behaviour and activities determines an appropriate configuration of social spaces. Systematic programming will delineate the context relating to the practicum topic. The final product is to find appropriate solutions and approachable settings to develop effective social spaces within a public trade show, improving the comprehensive quality of exhibitions. / February 2005

Sylvia Plath’s poetry has received considerable critical attention with respect to a wide range of themes and critical approaches. Variously labeled feminist, political, mythical and suicidal, Plath has been subject to enormous biographical scrutiny but the critical responses available today offer increasingly nuanced understandings of Plath’s work.  However, sufficient attention has not been given to the significant prevalence of images of places and spaces in Plath’s poetry. With particular focus on a selection of poems from The Collected Poems, this thesis argues that the personae in the poems confront “infelicitous places” and that the poems resonate with a tension between place (here referring to a space that is delimited by certain values) and space (in the sense of an expansion without the restrictions of place). What I here refer to as infelicitous place can be understood as an inversion of Gaston Bachelard’s conception of “felicitous space” and accounts for the way in which places in Plath’s poetry are marred with anxiety and ambivalence as opposed to Bachelard’s benevolent, protective spaces. The places and spaces in the poems are dealt with in relation to the notion of infelicitous place, as well as the significance of walls and the affinity between place and poetics.

The Earth ionosphere is a highly inhomogeneous medium containing electron density irregularities of various scales, from hundreds of kilometers to tens of centimeters. Understanding the mechanisms responsible for their formation is an important task for various practical applications such as communication, navigation, and safe satellite operation. Of special interest are the decameter irregularities that are abundant at E region heights of ~ 100 120 km. These are excited when enhanced electric field and plasma drifts are setup in the ionosphere. This thesis is aimed at studying the physics of decameter irregularity formation at E region heights with a focus on the extreme conditions of very strong electric fields (plasma flows) of > 50 mV/m (1000 m/s) for which the so called Farley-Buneman (FB) plasma instability is the dominating mechanism of irregularity excitation. The relationship between the irregularity velocity and plasma drift is investigated by considering data of the SuperDARN radar located at Stokkseyri, Iclenad. The radar detects echoes from the irregularities and is thus capable of measuring their velocity. The DMSP satellites measure the plasma drifts in situ at heights of ~ 800 km, but these measurements can be projected onto E region heights at high latitudes. By comparing the radar and satellite data in one direction, we show that irregularity velocity is smaller than the plasma drift by a factor of 2 3 with the stronger difference at faster flows. This contrasts with the theoretical expectation for the velocity to be close to 400 m/s, the nominal ion-acoustic speed at electrojet heights. A two-dimensional comparison is performed by considering a subset of the observations for which the HF echo velocity showed a cosine type variation with the radar look direction. This class of echoes is consistent with predictions of recent theories of the Farley-Buneman instability, but the irregularity velocity magnitude was found to be smaller than the ion-acoustic speed with occasional occurrence of velocities as small as 100 m/s. This implies that either recent theories of the Farley-Buneman instability should be modified or that the typical height of HF echoes is typically below 100 km. Various other properties of decameter irregularities are investigated and discussed in view of the existing theories.

Cables are an integral part of many engineering systems; thus, the control of cables and systems containing cables is an important problem to address. This thesis proposes to use command shaping techniques to reduce command-induced vibration in two cabled systems, a tower crane and an electrodynamic tethered satellite system in low Earth orbit. Systems containing cables often exhibit important nonlinear dynamics, which complicates the application of command shaping. As a first step to demonstrate the effectiveness of command shaping techniques for nonlinear cabled systems, nonlinear tower crane dynamics are investigated. A novel command generation technique for the slewing of tower cranes is presented, and experimental results demonstrate its increased effectiveness. Once improvement of tower crane dynamics has been demonstrated, space tether dynamics are considered. Electrodynamic tethers have the promise to become invaluable propulsive actuators for orbit boost and station keeping. Using electrodynamic tethers, it is possible to boost orbits without the use of propellant because electrical energy is used to produce a Lorentz force that creates orbit boost. Furthermore, electrodynamic tether deboost makes it possible to accelerate the deorbiting of spent rocket stages and other space debris to reduce clutter in the space environment. Unfortunately, the Lorentz force pushes transversely on the cable tether, thereby producing a significant amount of vibration and libration. This thesis proposes to use command shaping techniques to reduce the command-induced vibration from a boosting operation. Intelligent command generation will significantly reduce the amount of tether libration and string vibration. First, flexible tether dynamics in a constant, circular orbit are investigated. The work is then expanded to include the effects of orbit boosting. The robustness of the command generation techniques is established through numerical simulation.

Radiation risks to humans in space will be better understood if ground-based mixed field irradiations are developed and used to measure the overall effectiveness of proposed space radiation shielding. The space environment is composed of wide range of particles containing various energies. Existing measurements illustrate the properties of galactic cosmic rays (GCR) in particle fluence and species. However, it is nearly impossible to simulate a radiation environment corresponding to both properties at once. Since the final objective of this thesis research is to understand radiation risks, and radiation risks are more directly related to the energy deposited in the human tissue than to fluence and charge, the more likely goal would be reproducing the linear energy transfer (LET) spectrum found in the GCR. The purpose of this thesis research is to use a Monte Carlo transport code to study the fragmentation of a combined iron and proton beam source using a multi-depth moderator block to reproduce the LET component of the GCR. To study mixed-field radiation exposures, the Monte Carlo transport code - Particle and Heavy Ion Transport code System (PHITS) will be used. Calculations showed it is necessary to design a moderator block that contains two different thicknesses - one with a length less than 23 cm and one with a length greater than 23 cm. The thinner moderator will allow high-Z particles to pass through and produce heavy-ion fragments that contribute mostly in the high-LET range. The thicker moderator will stop most of fragments and only allow lighter ions to penetrate and contribute to the mid-range and low-LET portion of the GCR spectrum. Since iron beams along will not produce enough low-LET particles, proton beams were employed to increase the abundance of the low-LET portion of the GCR spectrum. After series of studies, it was concluded that a 17 cm and 49 cm thickness will be most effective. The initial conclusion of this project was that it is possible to produce the GCR environment using a multi-depth moderator block and a combined iron and proton beam.

The limit of bandwidth efficiency is well known in wireless radio communication. Therefore, making use of bandwidth efficiently is very important. Among various technologies which can increase the bandwidth efficiency, space-time coding system is very popular technology recently. In this article, we¡¦ll discuss three common schemes in ST system¡GSpace-Time Trellis Coding (STTC), Space-Time Block Coding (STBC) and Differential Space-Time Block Coding (DSTBC). First, we¡¦ll introduce the basic model of ST systems in chapter 2. And in chapter 3, the error probability, which is a close form, of STBC and DSTBC systems in slow fading channel will be derived, according to the derivation of error probability in multi-channel communication systems¡i10¡j. Then, the channel model will be defined as a fast fading channel and the error probability of STBC system in this channel model will be derived in chapter 4. Furthermore, we¡¦ll derive the error probability of STBC system in multi-path slow fading channel. Finally, we¡¦ll make a conclusion to the works we did in this article. The contribution of this article are¡G1. We derive a bit error probably which is a close form of STBC and DSTBC systems in slow fading channel. 2. We analyze the performace of STBC system in fast fading channel and derive a bit error probability in this case. 3. We analyze the performance of STBC system in multi-path slow fading channel and get a result that the diversity gain will increase when use the RAKE receiver mentioned in this article.

<p>Waves in the mHz frequency range are a prominent feature in the terrestrial magnetosphere. In this frequency range the waves have wavelengths comparable to the lengths of the geomagnetic field lines. The waves are then standing waves along closed field lines with endpoints in the southern and northern ionosphere. Waves play an important role in the distribution of energy in the magnetosphere and mHz waves can accelerate electrons to MeV energies and have been proposed as a driver of auroral arcs. They can also be used as a diagnostic tool for determining the plasma density. There are two important classes of these low frequency waves. One has large azimuthal wavelength and is usually associated with driving mechanisms outside the magnetosphere, such as the Kelvin-Helmholtz instability at the magnetopause. The other has small azimuthal wavelength and is associated with plasma instabilities inside the magnetosphere. Both types of waves are studied in this thesis with an emphasis on the small azimuthal wavelength waves. For the type of wave with large azimuthal wavelength there is however, a considerable debate about the driving mechanism. One recently suggested driver is coherent magnetohydrodynamic waves in the solar wind. Part of this thesis studies this experimentally and we conclude that, at least on some occasions, this driving mechanism come into play. The Cluster satellites are used to study the morphology of the waves. We demonstrate the ability of Cluster to determine the azimuthal wave number of the waves and also how the structure along the magnetic field lines can be determined. This gives information regarding the harmonic number of the standing waves, which in turn says something about the driver of the waves. We also look at possible excitation mechanisms for the small azimuthal wavelength waves.</p>