This thesis addresses solitary waves and their significance for auroral particle acceleration, coronal heating and incoherent scatter radar spectra. Solitary waves are formed due to a balance of nonlinear and dispersive effects. There are several nonlinearities present in ideal magnetohydrodynamics (MHD) and dispersion can be introduced by including theHall termin the generalised Ohm’s law. The resulting system of equations comprise the classical ideal MHD waves, whistlers, drift waves and solitarywave solutions. The latter reside in distinct regions of the phase space spanned by the speed and the angle (to the magnetic field) of the propagating wave. Within each region, qualitatively similar solitary structures are found. In the limit of neglected electron intertia, the solitary wave solutions are confined to two regions of slow and fast waves, respectively. The slow (fast) structures are associated with density compressions (rarefactions) and positive (negative) electric potentials. Such negative potentials are shown to accelerate electrons in the auroral region (solar corona) to tens (hundreds) of keV. The positive electric potentials could accelerate solar wind ions to velocities of 300–800 km/s. The structure widths perpendicular to themagnetic field are in the Earth’s magnetosphere (solar corona) of the order of 1–100 km (m). This thesis also addresses a type of incoherent scatter radar spectra, where the ion line exhibits a spectrally uniform power enhancement with the up- and downshifted shoulder and the spectral region in between enhanced simultaneously and equally. The power enhancements are one order of magnitude above the thermal level and are often localised to an altitude range of less than 20 km at or close to the ionospheric F region peak. The observations are well-described by a model of ion-acoustic solitary waves propagating transversely across the radar beam. Two cases of localised ion line enhancements are shown to occur in conjunction with auroral arcs drifting through the radar beam. The arc passages are associated with large gradients in ion temperature, which are shown to generate sufficiently high velocity shears to give rise to growing Kelvin-Helmholtz (K-H) instabilities. The observed ion line enhancements are interpreted in the light of the low-frequency turbulence associated with these instabilities. / Denna avhandling handlar om solitära vågor och deras roll i norrskensacceleration och koronaupphettning, samt deras signatur i spektra uppmätta med inkoherent spridningsradar. Solitära vågor bildas genom en balans mellan ickelinjära och dispersiva effekter. Ickelinjäriteter finns det gott om i ideal magnetohydrodynamik (MHD) och dispersion kan införas genom att inkludera Halltermen i den generaliserade Ohms lag. Det resulterande ekvationssystemet omfattar de klassiska vågorna inom ideal MHD, visslare, driftvågor och solitära vågor. De sistnämnda återfinns i väldefinierade områden i fasrummet som spänns upp av farten och vinkeln (mot magnetfältet) för den propagerande vågen. Inom varje sådant område återfinns kvalitativt lika solitära våglösningar. Om man försummar elektronernas tröghet begränsas de solitära våglösningarna till två områden med långsamma respektive snabba vågor. De långsamma (snabba) strukturerna är associerade med täthets-kompressioner (förtunningar) och positiva (negativa) elektriska potentialer. De negativa potentialerna visas kunna accelerera elektroner i norrskensområdet (solens korona) till tiotals (hundratals) keV medan de positiva potentialerna accelererar solvindsjoner till hastigheter på 300–800 km/s. Strukturbredderna vinkelrät mot magnetfältet är i jordens magnetosfär (solens korona) av storleksordningen 1–100 km (m). Denna avhandling tar även upp en typ av inkoherent spridningsradarspektra, där jonlinjen uppvisar en spektralt uniform förstärkning. Detta innebär att den upp- och nedskiftade skuldran och spektralbandet däremellan förstärks simultant och i lika hög grad. Effektförstärkningen är en storleksordning över den termiska nivån och är ofta lokaliserad till ett höjd-intervall av mindre än 20 km nära jonosfärens F-skiktstopp. Observationerna beskrivs väl av en modell med solitära vågor som propagerar transversellt genom radarstrålen. Två fall av lokaliserade jonlinjeförstärkningar visas sammanfalla med att norrskensbågar driver genom radarstrålen. I samband med bågarnas passage uppmäts stora gradienter i jontemperatur, vilket visas skapa tillräckligt kraftiga hastighetsskjuvningar för att Kelvin-Helmholtz-instabiliteter ska tillåtas växa. De observerade jonlinjeförstärkningarna tolkas i skenet av den lågfrekventa turbulensen som är kopplad till dessa instabiliteter.

Today, the growing and aging population, and the rise of new global threats on human health puts an increasing demand on the healthcare system and calls for preventive actions. To make existing medical treatments more efficient and widely accessible and to prevent the emergence of new threats such as drug-resistant bacteria, improved diagnostic technologies are needed. Potential solutions to address these medical challenges could come from the development of novel lab-on-chip (LoC) for point-of-care (PoC) diagnostics. At the same time, the increasing demand for sustainable energy calls for the development of novel approaches for energy conversion and storage systems (ECS), to which micro- and nanotechnologies could also contribute. This thesis has for objective to contribute to these developments and presents the results of interdisciplinary research at the crossing of three disciplines of physics and engineering: electrokinetic transport in fluids, manufacturing of micro- and nanofluidic systems, and surface control and modification. By combining knowledge from each of these disciplines, novel solutions and functionalities were developed at the macro-, micro- and nanoscale, towards applications in PoC diagnostics and ECS systems. At the macroscale, electrokinetic transport was applied to the development of a novel PoC sampler for the efficient capture of exhaled breath aerosol onto a microfluidic platform. At the microscale, several methods for polymer micromanufacturing and surface modification were developed. Using direct photolithography in off-stoichiometry thiol-ene (OSTE) polymers, a novel manufacturing method for mold-free rapid prototyping of microfluidic devices was developed. An investigation of the photolithography of OSTE polymers revealed that a novel photopatterning mechanism arises from the off-stoichiometric polymer formulation. Using photografting on OSTE surfaces, a novel surface modification method was developed for the photopatterning of the surface energy. Finally, a novel method was developed for single-step microstructuring and micropatterning of surface energy, using a molecular self-alignment process resulting in spontaneous mimicking, in the replica, of the surface energy of the mold. At the nanoscale, several solutions for the study of electrokinetic transport toward selective biofiltration and energy conversion were developed. A novel, comprehensive model was developed for electrostatic gating of the electrokinetic transport in nanofluidics. A novel method for the manufacturing of electrostatically-gated nanofluidic membranes was developed, using atomic layer deposition (ALD) in deep anodic alumina oxide (AAO) nanopores. Finally, a preliminary investigation of the nanopatterning of OSTE polymers was performed for the manufacturing of polymer nanofluidic devices. / <p>QC 20140509</p> / Rappid / NanoGate / Norosensor

This essay uses frame analysis to study changes in the descriptions of the hymen in Swedish printed press from 1989-2015. The study shows that the traditional story about the hymen has significant power in the dominant culture and affects the idea of what the hymen is and what is believed to be its functions. The study also showcases how our ideas about the hymen are socially constructed since the descriptions can shift widely but still be considered as the truth. The concept of the hymen has gone through a change over time, from a story of a hymen that breaks during first intercourse, to the hymen being a myth that doesn’t exist at all, to then emerge into the idea of the vaginal corona – another version of a hymen that is different from the traditional image. The study also shows that the traditional frame for describing the hymen does live on, and that the vaginal corona has not replaced the idea of the traditional hymen.

Made available in DSpace on 2016-03-15T19:35:52Z (GMT). No. of bitstreams: 1 DENIS PAVEL CABEZAS HUAMAN.pdf: 1718725 bytes, checksum: b98f52c6b4dac9b37a33cc5bc62d871e (MD5) Previous issue date: 2015-03-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The project aims to study the disturbances (responses) of the low solar atmosphere caused by solar flares, using H&#945;, 30 THz (10 &#956;m), UV/EUV, soft and hard X-rays observations, and a wide range of radio waves emissions (microwaves, millimeter, sub-millimeter). This set of multispectral data enabled us to (i) examine in detail various aspects of the phenomena, (ii) determine the origin of the radio emission during the gradual phase, and therefore (iii) understand the mechanism of the particles acceleration. The data we used for the completion of this study are based on H&#945; and 30 THz (10 &#956;m) observations, made by the high cadence flare imaging system installed at OSM4 and CASLEO5 observatories, additionally data from HASTA (H-Alpha Solar Telescope for Argentina) telescope installed at OAFA6 observatory. In the sub-millimeter and millimeter domain at 212, 405 GHz and 45, 90 GHz, were from SST (Solar Sub-millimeter Telescope) and from POEMAS (POlarization Emission of Millimeter Activity at the Sun) solar radio telescopes, respectively. Complementary radio observations in the microwave range (0.2-15 GHz) from RSTN (Radio Solar Telescope Network) were considered. In addition, solar observations obtained by RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager), Fermi and GOES (Geostationary Operational Environmental Satellite) satellites in X-ray channels, and from AIA (Atmospheric Imaging Assembly) and HMI (Helioseismic and Magnetic Imager) instruments, onboard the SDO (Solar Dynamics Observatory) satellite, respectively. / O trabalho tem como objetivo estudar as perturbações da baixa atmosfera solar produzidas pelas explosões solares, usando observações em H&#945;, 30 THz (10 &#956;m), UV/EUV, raios X e uma ampla faixa de emissões em ondas de rádio (microondas, milimétrica, submilimétrica); com o propósito de determinar a natureza dos processos físicos envolvidos. Este conjunto de dados multiespectrais nos permitiu (i) analisar os diferentes aspectos das explosões tanto na fase impulsiva como gradual, (ii) determinar a origem da emissão em rádio durante a fase gradual, e consequentemente (iii) entender melhor os mecanismos de aceleração das partículas. Os dados em H&#945; e 30 THz foram fornecidos pelo sistema de aquisição de dados com alta resolução temporal, instalado nos observatórios OSM1 e CASLEO2, adicionalmente dados do telescópio HASTA (H-Alpha Solar Telescope for Argentina) instalado no observatório OAFA3. Enquanto as observações em rádio, os dados foram do rádio polarímetro POEMAS (POlarization Emission of Millimeter Activity at the Sun) nas frequências de 45 e 90 GHz, do telescópio SST (Sub-millimeter Solar Telescope) nas frequências 212 e 405 GHz, ambos instalados no CASLEO. Dados na faixa de microondas (0,2-15 GHz) obtidos pela rede RSTN (Radio Solar Telescope Network). Além disso, foram considerados observações do Sol obtidas pelos satélites RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager), Fermi e GOES (Geostationary Operational Environmental Satellite) para raios X, e dos instrumentos AIA (Atmospheric Imaging Assembly), HMI (Helioseismic and Magnetic Imager), a bordo do satélite SDO (Solar Dynamics Observatory), respectivamente.

Les régions d’interface du Soleil de la photosphère à la chromosphère et au delà de la basse couronne ont été étudiées à partir des spectres éclairs. Les éclipses sont les plus adaptées à ce type d’observation, car l’occultation a lieu en dehors de l’atmosphère terrestre et sont exemptes de lumière parasite. Les images Extrême-UV des régions du limbe obtenues récemment dans l’espace sont analysés avec des modèles hydrostatiques à une dimension, comme les modèles VAL, mais cette méthode ne tient pas compte du phénomène d’émergence du champ magnétique, associé au réseau chromosphérique qui est responsable de: i) les spicules et le milieu interspiculaire, ii) les jets coronaux et macrospicules. Un saut de température de 0.01 à 1 MK est observé autour de 2 Mm d’altitude plus loin, et produit plus loin le flot du vent solaire permanent. Le processus de chauffage responsable du saut de température et la source du vent solaire ne sont pas encore compris. Dans cette thèse, nous traitons ces problèmes à partir de spectres éclairs récents réalisés avec les technologies actuelles de détecteurs CCD rapides, images d’éclipse en lumière blanche et des images EUV obtenues avec des instruments de missions spatiales. Nous illustrons les mécanismes des émissions des raies à faible potentiel de première ionisation (FIP) présents dans les basses couches de l’atmosphère solaire. Nous identifions plus précisément les raies à bas FIP à la fois dans les interfaces, à l’intérieur et en dehors des protubérances. Nous caractérisons en détail les enveloppes d’hélium et la région de l’interface solaire. Nous discutons de l'enrichissement de la couronne en éléments low FIP. / The solar interface region from the photosphere to the chromosphere and to the lower corona has been studied using flash spectra obtained during solar total eclipses. Eclipses are very favourable for this type of observation as the occultation takes place outside the Earth atmosphere and are free of parasitic scattered light. Independently, EUV filtergrams of the limb region obtained in space were analyzed using one dimensional hydrostatic models like the VAL models but this method ignores the ubiquitous magnetic field emergence phenomenon associated with the chromospheric network and responsible for: i) spicules and interspicular regions, ii) coronal jets and macrospicules. The components of the solar interface region are dynamical and different type of waves and magnetic reconnections are suggested to be at work. A jump of temperature from 0.01 to 1 MK is observed near the 2 Mm heights and higher, further producing a permanent solar wind flow. The heating processes responsible for this temperature jump and for the flow are not yet fully understood. In this thesis, we reconsider these problems on the basis of original, superior flash spectra which benefit from present technology such as CCD detectors, white light (W-L) eclipse images and new EUV images obtained with space-borne instruments. We illustrate the mechanisms of low First Ionisation Potential (FIP) emission lines present in the low layers of the solar atmosphere and interfaces. We identify more precisely low FIP lines both inside and nearby prominences. We characterize in detail the He shells and the solar interface region. We discuss the enrichment of low FIP elements in the corona.

The developments of new types of conductors and increase of voltage level have driven the need to carry out research on evaluating overhead line acoustic noise. The surface potential gradient of a conductor is a critical design parameter for planning overhead lines, as it determines the level of corona loss (CL), radio interference (RI), and audible noise (AN). The majority of existing models for surface gradient calculation are based on analytical methods which restrict their application in simulating complex surface geometries. This thesis proposes a novel method which utilizes both analytical and numerical procedures to predict the surface gradient. Stranding shape, proximity of tower, protrusions and bundle arrangements are considered within this model. One of UK National Grid's transmission line configurations has been selected as an example to compare the results for different methods. The different stranding shapes are a key variable in determining dry surface fields. The dynamic behaviour of water droplets subject to AC electric fields is investigated by experiment and finite element modelling. The motion of a water droplet is considered on the surface of a metallic sphere. To understand the consequences of vibration, the FEA model is introduced to study the dynamics of a single droplet in terms of phase shift between vibration and exciting voltage. Moreover, the evolution of electric field within the whole cycle of vibration is investigated. The profile of the electric field and the characteristics of mechanical vibration are evaluated. Surprisingly the phase shift between these characteristics results in the maximum field occurring when the droplet is in a flattened profile rather than when it is ‘pointed’.Research work on audible noise emitted from overhead line conductors is reviewed, and a unique experimental set up employing a semi-anechoic chamber and corona cage is described. Acoustically, this facility isolates undesirable background noise and provides a free-field test space inside the anechoic chamber. Electrically, the corona cage simulates a 3 m section of 400 kV overhead line conductors by achieving the equivalent surface gradient. UV imaging, acoustic measurements and a partial discharge detection system are employed as instrumentation. The acoustic and electrical performance is demonstrated through a series of experiments. Results are discussed, and the mechanisms for acoustic noise are considered. A strategy for evaluating the noise emission level for overhead line conductors is developed. Comments are made on predicting acoustic noise from overhead lines. The technical achievements of this thesis are summarized in three aspects. First of all, an FEA model is developed to calculate the surface electric field for overhead line conductors and this has been demonstrated as an efficient tool for power utilities in computing surface electric field especially for dry condition. The second achievement is the droplet vibration study which describes the droplets' behaviour under rain conditions, such as the phase shift between the voltage and the vibration magnitude, the ejection phenomena and the electric field enhancement due to the shape change of droplets. The third contribution is the development of a standardized procedure in assessing noise emission level and the characteristics of noise emissions for various types of existing conductors in National Grid.

Globalt har hela världens befolkning påverkats både ekonomiskt och psykiskt av coronaviruset SARS-CoV-2, som har drabbat så många människor med covid-19 att det klassas som en pandemi. Strax efter pandemins utbrott upptäcktes det att viruset utsöndras från avföring och ut i spillvattennätet som leder till reningsverken. Då virusmängden ökar i avloppsvattnet ökar även covid-19 fallen i samhället. Ökning av virusmängd i avloppsvatten kan nämligen signalera om att det förekommer smittspridning i samhället. Avloppsvattenbaserad övervakning kan dock användas som komplement till andra teststrategier vilket EU-kommissionen har nämnt i en rekommendation. Trender kan analyseras för att i ett tidigt skede informera sjukvård och regioner om ökad smittspridning.  På Kungsängens reningsverk i Västerås kommun har Mälarenergi analyserat avloppsvattnet för att ta reda på om ökning av virus i avloppsvatten kan indikera på ökad smittspridning i Västerås kommun. De har samlat in proverna och skickat det till SGS Analytics AB Sweden som har analyserat proverna med RT-qPCR. CT-värdena har normaliserats med vattenflöden. Korrelationstest har gjorts mellan virusmängd i avloppsvattnet och covid-19 fall, dödsfall samt IVA-fall. Det fanns ett signifikant svagt negativt samband mellan virusmängd i avloppsvatten och covid-19 fall per vecka. Mellan virusmängd och IVA-fall eller dödsfall fanns inget samband. Det finns en del felkällor som kan ha påverkat virusmängden. Vid höga vattenflöden kan PCR inhibitorer från tillskottsvatten och lakvatten ha påverkat CT-värdena. Värdena är höga på sommaren trots att covid-19 fall, dödsfall och IVA-fall var som lägst. Inhibitorer skapar direkt eller indirekt högre CT-värden vilket tolkas som lägre virusmängder.

The main subject of the final thesis is to find a suitable method for measuring the partial discharge (PD) in the dielectric of high-voltage capacitor. In the theoretical part of my thesis contains from the mechanisms of origin and the harmful effects of partial discharge at high voltage insulation of capacitor. It describes the global galvanic method of partial discharge measurement, the principle of cascade voltage multiplier, its main components are high-voltage capacitor and diode, facilities quality measurement of capacitors for voltage multipliers, advantages and disadvantages and principles of HIPOTRONICS DDX-8003 with the pulse discrimination system. In the experimental part of the diploma thesis is familiar with the diagnostics of high – voltage capacitors by means of laboratory measurements on the electronic bridge and with the help of partial discharge measurement system. Design of suitable electrode arrangement is described which eliminates the influence of corona which makes it impossible to measure partial discharges and the dissipation factor (tg ). Analysis data from measurement and determination of quality level, eventual degradation of measured capacitors. The result of this project should be designed the methodology for finding of poor – quality capacitors in order to increase the reliability of the voltage multiplier.

The main subject of the final thesis is to find a suitable method for measuring the partial discharge (PD) in the dielectric of high-voltage capacitor. In the theoretical part of thesis contains from the mechanisms of origin and the harmful effects of partial discharge at high voltage insulation of capacitor. It describes the global galvanic method of partial discharge measurement, the principle of cascade voltage multiplier, its main components (high-voltage capacitor and diode). Nowadays are presented the possibilities of measuring the quality of capacitors for voltage multipliers. In the experimental part of the diploma thesis is familiar with the diagnostics of high – voltage capacitors by means of laboratory measurements on the electronic bridge and with the help of partial discharge measurement system. It describes the design of a suitable electrode arrangement that eliminates the influence of the corona, which makes it impossible to measure partial discharges and the dissipation factor tg . The thesis analyzes the obtained data from measurements and determines the quality level or the degradation of the measured capacitors. The result of the project should be designed the methodology for finding poor quality capacitors in order to increase the reliability of the voltage multiplier.

Gasisolierte Systeme im Gleichspannungsbetrieb vereinen für Anwendungen moderner Energieübertragung die Forderungen nach kleinräumigen Anlagen und verlustarmem Energietransport über große Entfernungen. Für einen zuverlässigen und sicheren Betrieb muss das Verhalten der eingesetzten Gas-Feststoff-Isolierung im technologischen System bis an die Grenzen des Isolationsvermögens bekannt sein. Gegenstand der vorliegenden Arbeit ist deshalb das Überschlagsverhalten von Gas-Feststoff-Isoliersystemen unter Gleichspannungsbelastung. Dabei stehen zwei wesentliche Einflussfaktoren im Vordergrund: die Temperatur, motiviert durch reale Stromwärmeverluste, und eine feste Störstelle auf der Gas-Feststoff-Grenzfläche, motiviert durch in der Praxis nicht völlig auszuschließende, metallische Partikel. Die Effekte dieser beiden Parameter auf die Feldverteilung, die Oberflächen- und Raumladungsbildung sowie das Isolationsvermögen bei Gleichspannung werden zunächst in zwei Versuchsanordnungen separat experimentell untersucht. Anschließend wird deren Zusammenwirken und gegenseitige Beeinflussung im Gesamtsystem analysiert. Die betriebsbedingte Erwärmung der Leiter gasisolierter Systeme führt zu einer inhomogenen Temperaturverteilung, die sich auf die Eigenschaften der Isolierstoffe Gas und Epoxidharz auswirkt. Die von der Temperatur abhängige Leitfähigkeit der Feststoffisolatoren führt zu einer temperaturabhängigen Feldverteilung, bei der sich der Ort der Höchstfeldstärke verschiebt. Dabei kann sich der Absolutwert der Höchstfeldstärke erhöhen und somit das Isolationsvermögen verringern. Gleichzeitig weist das Isoliergas nahe des erwärmten Leiters lokal eine geringere Dichte und damit eine geringere dielektrische Festigkeit auf. Die thermisch bedingte Minderung des Isolationsvermögens bei Gleichspannung beträgt in der untersuchten Anordnung (25 ... 35) %. In den schwach inhomogenen Feldern gasisolierter Anlagen erweisen sich metallische Partikel auf Isolatoren ab drei Millimetern Länge als besonders kritisch. Bei einem Gasdruck unterhalb von 0,3 MPa setzen an den Partikelspitzen zum Teil bereits ab 50 % der Durchschlagsspannung ohne Partikel Teilentladungen ein, sodass die Koronastabilisierung zu einer vergleichsweise hohen Überschlagsspannung führt. Durch diese stabilen Glimmentladungen kann die Störstelle bei Gleichspannung durch die üblichen Detektionsverfahren jedoch nicht zweifelsfrei nachgewiesen werden. Oberhalb von 0,3 MPa treten vor dem Überschlag keine Teilentladungen auf. Aufgrund der fehlenden Koronastabilisierung kann die Isolationsfestigkeit durch einen erhöhten Gasdruck nicht oder nur stark unterproportional gesteigert werden. Die mit der Modellanordnung gewonnenen Erkenntnisse sind nachweislich auf Isolatoren kommerzieller Anlagen übertragbar. Das in der vorliegenden Arbeit untersuchte Überschlagsverhalten von Gas-Feststoff-Isoliersystemen unter Gleichspannungsbelastung wird maßgeblich durch die Temperaturverteilung und durch feste Störstellen auf der Grenzfläche beeinflusst. Oberflächen- und Raumladungen verändern das üblicherweise ohmsch-kapazitiv beschriebene Verhalten des Isolierstoffsystems bei Gleich- und Mischspannungsbelastung. Der Einfluss zusätzlicher Ladungsträger auf die stark temperaturabhängige Feldumbildung demonstriert, dass das Isoliergas in diesem Fall mit teilchendichte- und feldstärkeabhängigen Drift- und Diffusionsprozessen zur Modellierung des transienten Verhaltens von Gleichspannungssystemen berücksichtigt werden muss. Die Untersuchung des Systemverhaltens an den Grenzen des Isolationsvermögens ist wichtiger Bestandteil bei der Entwicklung innovativer Technologien der modernen Energieübertragung bei steigender Übertragungsleistung. / DC operated gas-insulated systems combine the demand for space saving installations and lowloss energy transport over long distances for applications of recent energy transmission. In order to ensure a reliable and safe operation, the behaviour of the gas-solid insulation, which is used in the technological system, has to be known up to the limits of the insulation properties. Hence, this thesis deals with the flashover behaviour of gas-solid insulation systems under DC voltage stress. Thereby, it focuses on two main influence factors: the temperature, due to real current heat losses, and an adhesive defect on the gas-solid interface, due to metallic particles that cannot be fully excluded in practice. Firstly, it is investigated experimentally in two test arrangements, how each parameter separately affects the electrical field distribution, the surface and volume charge accumulation and the insulation performance under DC voltage stress. Following that, their interaction and mutual influence is analysed in the whole system. Due to operating currents, the heating of the conductors in gas-insulated systems causes an inhomogeneous temperature distribution, that affects the properties of the insulating materials gas and epoxy resin. The temperature-dependent conductivity of the solid insulators leads to a temperature-dependent field distribution. Thereby, the location of the highest field strength is shifted. Since the absolute value of the highest field strength can increase, the insulation performance can decrease. Simultaneously, the insulating gas close to the heated conductor locally has a lower gas density and therefore a lower dielectric strength. The thermal related reduction of the insulation performance under DC voltage stress amounts to (25 ... 35) % in the investigated arrangement. Metallic particles, with a length of more than three millimetres and adhering on spacers, turn out to be particularly critical in the weakly inhomogeneous field of gas-insulated systems. At pressures below 0,3 MPa, partial discharges at the particle tips partly ignite already at 50 %of the breakdown voltage without a particle. The corona stabilisation leads to a relatively high flashover voltage. However, due to these stable glow discharges under DC voltage stress, the defect can not be unequivocally proven by usual detection methods. Above 0,3 MPa, no partial discharges occur before the flashover. Due to the missing corona stabilisation, with a higher gas pressure, the insulation strength is not or only disproportionately low increasing. The findings gained with the model arrangement are evidently applicable to spacers of commercial installations. The flashover behaviour of gas-solid insulation systems under DC voltage stress, examined in this thesis, is influenced significantly by the temperature distribution and adhesive particles on the interface. Surface and volume charges change the generally resistive-capacitive described behaviour of the insulation system under DC and superimposed voltage stress. The influence of additional charge carriers on the strongly temperature-dependent field transition demonstrates, that in this case, the insulating gas with its drift and diffusion processes, depending on the particle density and the field strength, has to be considered, when modelling the transient behaviour of DC operated systems. Investigating the system behaviour to the limits of the insulation properties is a crucial element of developing innovative technologies of the modern energy transmission at increasing transmissions powers.