In the present thesis it could be demonstrated that strong exciton coupling does not only occur between same type of chromophores but also between chromophores with different excited state energies. The coupling significantly influences the optical absorption properties of the heterostacks comprising merocyanine and perylene bisimide dyes, respectively, and is an indication for coherent energy transfer between the chromophores. In addition, bis(merocyanine)-C60 conjugates have been synthesized, which self-assemble in non-polar solvents resulting in well-defined supramolecular p/n-heterojunctions in solution. These model systems enabled femtosecond transient absorption studies on the photoinduced electron transfer process, which is a key step for the formation of charge carriers in organic solar cells. / In der vorliegenden Doktorarbeit konnte gezeigt werden, dass eine starke Exzitonenkopplung nicht nur zwischen gleichen Chromophoren, sondern auch zwischen Chromophoren mit unterschiedlichen Energien der angeregten Zustände möglich ist. Diese beeinflusst maßgeblich die Absorptionsspektren der Heterostapel bestehend aus Merocyanin- bzw. Perylenbisimidfarbstoffen und deutet außerdem auf einen kohärenten Energientransfer zwischen den Chromophoren hin. Weiterhin wurden Bis(merocyanin)-C60-Konjugate synthetisiert, die in unpolaren Lösungsmitteln selbst assemblieren und auf diese Weise wohldefinierte supramolekulare p/n-Heterogrenzflächen gebildet werden. An diesen wurde mithilfe von femtosekundenaufgelöster transienter Absorptionsspektroskopie der photoinduzierte Elektronentransfer untersucht, was ein wichtiger Schritt bei der Erzeugung von Ladungsträgern in organischen Solarzellen darstellt.

By taking human perception into account in computer graphics, time and processing power may be utilised more efficiently when modelling and rendering scenes. Exploring possibilities for reducing the complexity of forest scenes is particularly interesting because of the geometric complexity of trees, the effects of which are compounded by dense, large-scale forests. Most studies of rendering simplifications for forests concern level-of-detail methods, simplifying scenes in areas where simplifications are less perceptible to the viewer. The present study instead approaches the topic by considering that humans, to certain extents, are insensitive to the exact composition of objects in aggregates. In forest scenes that use a variety of geometrically different trees, this can be utilised to favour the geometrically simpler tree. A perceptual study was conducted to explore how perceptive viewers are to the ratio between trees, in forest scenes that feature two geometrically different tree models. Specifically, the tree models varied in leaf and branch density. The impacts of forest density, layout and camera angle were studied. Overall, it was found that density and layout had significant effects on thresholds measured for participants’ perceptiveness of ratio, while camera angle had little impact. The results indicate that the ratio between two different tree models can be skewed considerably in favour of the geometrically simpler model, without participants detecting changes. These findings provide some guidelines for reducing polygon count in forest scenes while preserving appearance. Motivated by these findings, the educational part of this study considers the role of perceptual topics in computer graphics courses. Specifically, the study focuses on the inclusion of perceptual topics in introductory computer graphics courses at Swedish universities, as well as the attitudes of computer graphics educators toward teaching perception. 22 course syllabuses at 12 Swedish universities were collected and analysed. Interviews were conducted with three computer graphics educators, while 13 educators responded to an online survey. The results present a diverse set of approaches and attitudes toward perception among educators, signifying that the role of perception in computer graphics education is uncertain. Perceptual topics were included in about half of the surveyed courses, with teaching approaches ranging from marginally including perceptual topics, to fully dedicated lectures, though perception was rarely mentioned in the intended learning outcomes of courses. Overall, approaches seemed influenced mainly by the background of the student group, educators’ own biases and experiences, as well as challenges posed by needing to address foundational skills such as programming. By investigating perceptual thresholds through a psychophysical experiment and exploring pedagogical practices in relation to perceptual topics in computer graphics courses, this study links empirical research with pedagogy, highlighting the role of perception in computer graphics from different perspectives. / Genom att ta hänsyn till mänsklig perception i datorgrafik kan tid och processorkraft utnyttjas mer effektivt vid modellering och rendering av scener. Att utforska möjligheter för att minska komplexiteten i skogsscener är särskilt intressant, på grund av den geometriska komplexiteten hos träd, vars effekt förvärras av täta, storskaliga skogar. De flesta studier av renderingsförenklingar för skogar rör detaljnivåmetoder (eng: level-of-detail), förenklingar av scener i områden där ändringar är mindre märkbara för betraktaren. Denna studie närmar sig istället ämnet genom att ta hänsyn till att människor, i viss utsträckning, är okänsliga för den exakta sammansättningen av objekt i aggregat. I skogsscener som använder en mängd geometriskt olika träd kan detta utnyttjas för att gynna det geometriskt enklare trädet. En perceptuell studie genomfördes för att undersöka hur medvetna personer är om förhållandet mellan träd i virtuella skogsscener betraktat ovanifrån, där två geometriskt olika trädmodeller använts. Specifikt studerades effekterna av skogstäthet, trädplacering och kameravinkel på uppfattningsförmåga. Det visade sig att täthet och placering hade betydande effekter på tröskelvärden som mättes för deltagarnas uppfattning om förhållandet, medan kameravinkeln hade liten inverkan. Resultaten indikerar att förhållandet kan förskjutas avsevärt till förmån för den geometriskt enklare trädmodellen, utan att deltagarna upptäcker förändringar. Sammantaget erbjuder dessa resultat några riktlinjer för att minska antalet polygoner i storskaliga skogsscener sett från luften, samtidigt som scenernas utseenden bevaras. Motiverad av dessa fynd överväger den pedagogiska delen av denna studie rollen av perceptuella ämnen i datorgrafikkurser. Specifikt fokuserar studien på inkluderingen av perceptuella ämnen i kurser på introduktionsnivå vid svenska universitet, samt attityder till att undervisa om perception bland lärare som undervisar om datorgrafik. 22 kursplaner vid 12 svenska universitet samlades in och analyserades. Intervjuer genomfördes med tre pedagoger, medan 13 pedagoger svarade på en enkät. Resultaten presenterar en mångsidig uppsättning tillvägagångssätt och attityder till perception bland lärare, vilket indikerar att perceptionens roll i datorgrafikutbildning är vag. Perceptuella ämnen inkluderades i ungefär hälften av de undersökta kurserna, även om perception sällan nämns i kursernas lärandemål. Undervisningsmetoderna innefattande perception sträckte sig från marginell inkludering, till dedikerade föreläsningar. Sammantaget verkade tillvägagångssätten främst påverkas av studenternas bakgrund, lärares egna fördomar och erfarenheter, såväl som utmaningar som uppstår genom att behöva ägna tid åt grundläggande färdigheter som programmering.

Idag är energieffektivitet en viktig fråga, nya bostäder har höga krav på energieffektivitet och miljömedvetenhet, kraven är betydligt högre än för 40 år sedan. Många av de äldre flerbostadshusen bygger på en annan princip av ventilation än den som används i nya bostadsprojekt idag, denna typ kallas självdrag och systemet är inte energieffektivt. I nya flerbostadshus är däremot ventilationssystemet ofta av typen FTX och det är ett system som är mycket energieffektivt. Rapporten är en undersökning till hur modern ventilationsteknik kan användas i äldre typer av flerbostadshus, skapar ny teknik en reducerad kostnad i längden och kan den upplevda komforten förbättras med moderna system?Resultatet av ett ventilationsbyte från självdrag till FTX kommer att innebära en energibesparing i fastigheten om den optimeras efter FTX-systemet. Med filtrerade system blir även luftkvaliteten betydligt bättre än tidigare / Energy efficiency is an important question today. New buildings have high demands of energy efficiency and environmental awareness, the demands are signinficantly higher today than 40 years ago. Many older apartment complexes have another kind of ventilation than the kind that is used in new apartment complexes today, this old kind is called natural ventilation and the system is not energy efficient. The type of ventilation that is used in the new apartment complexes is often mechanical ventilation with heat recovery, which is energy efficient.This study is an investigation in how modern ventilation technology can be used in older apartment complexes, will new technology reduce the cost in the long-run, and can the experienced comfort be improved with modern systems?The result of a change in ventilation from natural ventilation to mechanical ventilation with heat recovery will result in energy savings if the building is optimized for the new system. The air quality in the building will improve with a filtered ventilation system.

Yes / This paper investigates the bond performance of recycled coarse aggregate (RCA) concrete with un-corroded/corroded reinforcing steel bars, with the main parameters being RCA content, corrosion level, bar diameter and embedment length. For this purpose, 60 pull-out specimens containing different percentages of RCA (i.e. 0%, 25%, 50% and 100%) and steel bars of two diameters (12 and 20 mm) and different embedment lengths were tested. In order to establish various levels of corrosion, specimens were exposed to an electrochemical corrosion for 2, 5, 10 and 15 days. The bond strength between RAC concrete and un-corroded/corroded steel are compared to current codes and equations proposed by other researchers. Experimental results showed that larger corrosion rate of steel bars was observed with the increase of the replacement level of RCA due to its high porosity and water absorption. The use of RCA had a slight influence on bond strength for un-corroded specimens compared to that obtained from conventional concrete. Furthermore, the bond strength of RCA concrete was strongly affected by corrosion products; bond strength slightly enhanced for up to about 2% corrosion rate, and then significantly decreased as the corrosion time further increased, similar to that of conventional concrete. However, the rate of bond degradation between RCA concrete and corroded steel bars was much faster than that observed in corroded conventional concrete.

In dieser Doktorarbeit wurde gezeigt, dass die sehr begehrte J-Aggregation funktionaler Perylenbisimid-Chromophore durch geeignetes Design der monomeren Bausteine erreicht werden kann. Hierzu war einerseits die Selbstanordnung durch ein Zusammenwirken von Wasserstoffbrücken und Pi-Pi-Wechselwirkungen zu begünstigen, und andererseits eine Anordnung in kolumnaren Stapeln zu verhindern, was durch Kern-Verdrillung mittels sterisch anspruchsvollen Substituenten gelang. Desweiteren gaben Selbstanordnungsstudien neue Einblicke in den dynamischen Aggregationsprozess niedrigdimensionaler langgestreckter Aggregate mit stark exzitonisch gekoppelten Chromophoren. Die Beziehung zwischen bekannten Cyaninfarbstoffen, wie der von THIATS mit dem vorliegenden PBI 1a wurde durch Absorptions- und Fluoreszenzspektroskopie bei Tieftemperaturen von 5 K bis Raumtemperatur untersucht. Die vormals beispiellosen funktionalen Eigenschaften der PBI-Aggregate, welche aus der J-artigen exzitonischen Kopplung herrühren, sind vielversprechend für die Anwendung in optoelektronischen Bauteilen und für die Photovoltaik. / In conclusion, the present thesis demonstrates that the highly desired J-type aggregation of functional perylene bisimide chromophores can be achieved by proper design of monomeric building blocks that direct self-assemble by mutual effects of hydrogen bonding and pi-pi interaction, and on the other hand, are prevented to assemble in columnar stacks owing to their twisted pi-conjugated core and sterically demanding substituents. Furthermore, the self-assembly studies gave new insights into the dynamic aggregation process of low-dimensional extended assemblies with strongly excitonically coupled chromophores. The relationship between commonly known cyanine dye aggregates like that of THIATS and that of the present PBI 1a was investigated by absorption and fluorescence spectroscopy at low temperatures down to 5 K. The formerly unprecedented functional properties of PBI aggregates that are expressed in J-type excitonic coupling hold promise for application in optoelectronic and photovoltaic devices.

Due to the importance of a correct tree placement and the wear that occurs to equalizer bars inharvester heads, Komatsu Forest AB in Umeå was interested if the bar could be replaced with ahydraulic system. According to Komatsu, the problems were that the equalizer bars that are responsible forsynchronizing the delimbing knives and feeding mechanism add weight, take up space and have atendency to break before their life expectancy. Some harvester heads do not possess equalizer barsbut this complicates tree length and diameter measurements, risks increasing wear to parts of theharvester head not designed to be in contact with the trees and makes cutting the tree correctlymore difficult during certain actions. Thus, Komatsu saw a potential opportunity to increase thefeeding mechanisms performance and life span through a hydraulic solution. In this thesis, a literature study investigating practiced solutions to similar systems as well asa previous study by Komatsu in the subject are included. Furthermore, the product design process,implementation and verification of the solution are covered. The resulting solution included two Parker A2N0029D2H Series 3000 accumulators and fourParker DSH083NV valves, coupled in parallel pairs to create two arrangements of the final conceptsystem, “Half Control Remastered”; “regenerative coupling force distributor” and “shut off valveflow divider”. During the testing both the Regen and shut off function, mounted on a Komatsu C164harvester head, were observed to help during tree picking, grasping and feeding, but both functions,unfortunately, had disadvantages. The Regen function was unstable since hydraulic flow occurredfrom one cylinder to the other, and the Shut off function was imprecise because it became “choppy”with increased accuracy. While testing the system arranged with the Shut off function in the forest,it assisted during slow feeding as well as feeding while simultaneously forcing rotation, where theharvester head tended to drop trees. However, the system did little to no difference as soon thedelimbing knives were deployed. The results that are revealed in this thesis are difficult to evaluate, since Scandinavian forestharvester drivers do not challenge the harvester head in a way for the hydraulic equalizer barsystem to assist to its full potential. To conclude, the system shows promise to meet Komatsu’sperformance requirements but further testing and development is necessary for it to become refinedenough to implement in their mass produced harvester heads.

Diss. (sammanfattning) Stockholm : Stockholms universitet, 2009. / Härtill 4 uppsatser.

Industrial wastewater, such as the effluents from textile and garment companies, may contain toxic organic pollutants, which resist conventional wastewater treatment. Their complete and environmentally friendly degradation requires innovative technologies. Photocatalysis, an advanced oxidation process, can serve this purpose. Since 1972, when the photocatalytic activity of titanium dioxide was first noticed, photocatalysis has drawn the attention of scientists and engineers but it has not yet been widely applied in industrial practice. This is mainly related to the challenges of up-scaling from laboratory experiments to large production sites. The main goal of this thesis is to develop a concept of nanoparticle-based photocatalysis for the treatment of wastewater. Ideally, process parameters should be adjustable and process conditions should be well-defined. These constraints are prerequisite for establishing process models and comparing the photocatalytic efficiency of different photocatalysts or for different pollutants. More importantly, the configuration should be scalable, in order to cover a wide spectrum of applications. In response to these requirements, this thesis introduces a new reactor concept for photocatalytic wastewater treatment, which relies on finely dispersed photocatalysts as well as uniform and defined process conditions with regard to illumination and flow. The concept was realized in a photocatalytic setup with an illuminated flow reactor. The flow channel has a rectangular cross section and meanders in a plane exposed to two dimensional illumination. Crucial process parameters, e.g., volumetric flow rate and light intensity, can be adjusted in a defined manner. This facilitates the study on the photocatalytic degradation of different organic pollutants in the presence of various photocatalytic materials under arbitrary illumination. The thesis provides a comprehensive description of the operational procedures necessary to run photocatalytic reactions in the experimental setup. It includes three main steps: i) dispersion of photocatalysts, ii) equilibration with respect to pollutant adsorption and iii) accomplishing the photocatalytic reaction. Samples are collected in a mixing tank for online or offline analysis. The proceeding decrease in the concentration of organic pollutant is used to assess the activity of the photocatalytic materials. A particular focus lies on the first of these steps, the dispersion of photocatalysts, because it is ignored in most studies. Typically, photocatalysts are in an aggregated state. The thesis demonstrates that type, intensity and energy of dispersion exert a crucial influence on size and morphology of the photocatalyst particles and, thus, on their optical properties and, accordingly, macroscopic photocatalytic behavior. Apart from this, a proper dispersion is necessary to reduce speed of gravitational solid-liquid separation, at best, to prevent catalyst sedimentation and to avoid misleading results. The photocatalytic performance was intensively investigated for the color removal of a model dye substance, methylene blue. Commercial titanium dioxide nanoparticles, widely explored in literature, were used as a photocatalyst. Their characteristics (size, morphology, stability and optical properties) were determined. Photocatalytic experiments were carried out under UV irradiation. Influences of different factors, including the concentration of the photocatalyst, the concentration of the organic compounds, light intensity, optical pathlength and pH were examined. The degradation was quantified via the decrease of methylene blue concentration. This conversion is, however, an immediate result influenced by all process parameters, e.g., the volume, the light intensity, the optical pathlength. Hence, kinetic models on macroscopic and microscopic levels are established. Normalizations with respect to process conditions are proposed. The apparent reaction kinetics are traced back to volume- and intensity-related reaction rate constants, and the reaction rate constant at the illuminated surface of the reactor. Additionally, the model is modified to be used for time-variant UV intensities, as encountered for solar photocatalysis. These achievements allow for a comparison of the experimental results from different laboratories. Moreover, they are prerequisite for the translation of laboratory results into large scale plants. Selected case studies for further applications are introduced. The photocatalytic degradation of different organic molecules (one antibiotic and two commercial dyes) with different photocatalytic materials (commercial nanomaterials and self-synthesized magnetic particles) under artificial or natural light sources was performed. Additionally, photocatalysis was studied in a realistic application. Preliminary tests with dye solutions of a textile company in Danang, Vietnam, impressively showed the feasibility of wastewater treatment by means of photocatalysis. Based on the reported capacity of wastewater in the current treatment plant of the company, the necessary process parameters were assessed. The rough estimation showed that photocatalysis can improve the working ability of the current wastewater treatment plant. In conclusion, this thesis presents a concept for wastewater treatment by slurry photocatalysis. As the process conditions are adjustable and definable, the process can be ideally performed in laboratories for research purposes, where different materials need to be tested and the working volume can be lower than hundreds of milliliters. The photocatalytic configuration is expected to work with a capacity of hundreds of liters, although appropriate experimental evidences are reserved for further up-scaling studies.

I dagens samhälle ligger stort fokus på energianvändningen för bostäder och kommersiella fastigheter. Energianvändningen beskriver inte bara en byggnads energibehov, utan också miljö- och ekonomiska aspekter. Flerbostadshus är en del av Sveriges bostad- och servicesektor, som utgör 40 % av Sveriges totala energianvändning (Henning, 2017). Ventilationssystem i flerbostadshus utgör således en betydande del av fastighetens energianvändning och måste därför ständigt effektiviseras för att tjäna ett hållbart samhälle. I nuläget är den verkliga energianvändningen för ett flertal av JM:s driftsatta FTX-aggregat (till- och frånluftssystem med värmeåtervinning) okänd. Detta på grund av att tillgängliga energiberäkningar och deklarationer redovisar byggnadens totala energianvändning uppdelat i fyra huvudkategorier; uppvärmning, komfortkyla, tappvatten och byggnadens fastighetsenergi. Energianvändningen för ventilationssystemet framgår inte specifikt från dessa beräkningar, utan delas in i kategorierna uppvärmning och byggnadens fastighetsenergi. Rapporten undersöker, under perioden mars – juni 2018, energianvändningen för totalt elva stycken FTX-aggregat i två av JM:s projekt i Stockholm, Kista Torn och Nya Kvarnen 2. Undersökningens syfte är att försöka beräkna den verkliga energianvändningen för dessa FTX-aggregat. Energiberäkningar har genomförts med värden hämtade från egna samt tidigare utförda mätningar, som jämförts med projekterade värden. Resultatet indikerar att den genomsnittliga energianvändningen för FTX-aggregaten i Kista Torn är ca 120 000 kWh/år. Den större delen av energianvändningen går åt till att värma tilluften. Undersökningen visar på att den genomsnittliga temperaturverkningsgraden är ca 7 % lägre än den projekterade verkningsgraden. De beräkningar som genomförts visar även att uppvärmningskostnaden har ökat med ca 150 000 kr/år, i jämförelse med de projekterade värdena. Det beror till stor del på den minskade temperaturverkningsgraden, men också på grund av förändrade luftflöden i aggregaten. Undersökningen i Nya Kvarnen 2 har inte kunnat göras lika omfattande. Beräkningarna som genomförts här tyder på att energianvändningen uppgår till ca 61 000 kWh/år och aggregat. Tillförlitligheten av beräkningarna störs dock av att inga egna mätningar kunde utföras, att dokumentationen var bristfällig, samt att övervakningssystemet SCADA redovisade orimliga värden. Slutsatsen för rapporten indikerar att den verkliga energianvändningen för FTX-aggregaten generellt är högre än vad som tidigare projekterats. Energianvändningen varierar markant beroende på luftflöden och temperaturverkningsgrad. Störst påverkan på energianvändningen har dock temperaturverkningsgraden. Det visade sig att temperaturverkningsgraden vara svår att bestämma, då många felkällor och faktorer påverkar framtagningen, samt att resultatet varierar beroende på vald mätmetod. För bättre kontroll på energianvändning rekommenderas fler och mer kontinuerligt genomförda mätningar. Alternativt skulle övervakningsprogrammet SCADA kunna användas i större utsträckning för beräkning av energianvändning, förutsatt att precisionen och placering av temperaturgivare förbättras. / In today's society the energy use within residential and commercial real estate is of great importance. Energy use does not only describe a building's energy needs, but also its environmental and economic aspects. Apartment buildings are a part the Swedish residential and service sector, which constitutes 40 % of Sweden's total energy use (Henning, 2017). The ventilation system in apartment buildings makes up a significant part of the property's energy use, it must therefore continuously be improved to work towards a more sustainable society. The actual energy use for several of JM's powered air assemblies is unknown today. Energy calculations and declarations show that the building's total energy use is divided into four main categories; heating, comfort cooling, tap water and property energy. The energy use of the ventilation system is not made apparent in these aforementioned calculations since it is distrubuted into two of the main categories, heating and property energy. The report examines the energy use for a total of eleven air assemblies within two of JM's projects in Stockholm, Kista Torn and Nya Kvarnen 2. The purpose of the study is to find the actual energy use of these air assemblies. Energy calculations will be carried out using values ​​taken from our own and previously performed measurements, which will be compared to expected projected data. The result indicate that the average energy use of the air assemblies in Kista Tower is approximately 120 000 kWh/year. The majority of the energy use goes to heating the supply air. The study shows that the average heat recovery efficiency is circa 7 % lower than the projected efficiency. The calculations show that the cost of heating has increased by approximately 150 000 SEK/year compared to projected data. This is largely due to the reduced heat recovery efficiency but partly due to changes in the airflow within the air assemblies. The study made in Nya Kvarnen 2 was not as extensive, although calculations of energy use have been carried out. These calculations show an energy use of approximately 61 000 kWh/year for each separate air assembly. The reliability of these numbers is considered low because no control measurements could be made. The documentation was inadequate along with the monitoring system, SCADA, which reported unrealistic values. The conclusion of the report shows that the actual energy use of the air assemblies is in general higher than expected. The energy use varies depending on the airflow and heat recovery efficiency, however the greatest impact comes from the heat recovery efficiency in the air assemblies. Heat recovery efficiency was proven difficult to determine because of the multiple sources and factors affecting the measurement. This made the results fluctuate greatly depending on the method chosen of calculating the heat recovery efficiency. To oversee the actual energy use in these air assemblies, more frequent measurements are recommended. Alternatively, the SCADA monitoring program could be used to calculate the energy use, but to do so the accuracy and placement of temperature sensors needs to be improved.

This work offers a concept to predict and comprehend the electronic excited states in regular aggregates formed of quasi-one-dimensional organic materials. The tight face-to-face stacking of the molecules justifies the idealization of the crystals and clusters as weakly interacting stacks with leading effects taking place within the columnar sub-structures. Thus, the concept of the small radius exciton theory in linear molecular chains was adopted to examine the excitonic states. The excited states are composed of molecular excitations and nearest neighbor charge transfer (CT) excitations. We analyzed the structure and properties of the excited states which result from the coupling of Frenkel and CT excitons of arbitrary strength in finite chains with idealized free ends. With the help of a partially analytical approach to determine the excitonic states of mixed Frenkel CT character by introducing a complex wave vector, two main types of states can be distinguished. The majority of states are bulk states with purely imaginary wavevector. The dispersion relation of these state matches exactly the dispersion relation known from the infinite chain. The internal structure of the excitons in infinite chains is directly transferred to the bulk states in finite chains. TAMM-like surface states belong to the second class of states. Owing to the damping mediated by a a non-vanishing real part of the wavevector, the wave function of the surface states is localized at the outermost molecules. The corresponding decay length is exclusively determined by the parameterization of the coupling and is independent of the system size. It can therefore be assigned as a characteristic quantum length which plays a vital role for the understanding of system-dependent behavior of the states. The number and type of surface states occurring is predicted for any arbitrary coupling situation. The different nature of bulk and surface states leads to distinct quantum confinement effects. Two regimes are distinguished. The first regime, the case of weak confinement, is realized if the chain length is larger than the intrinsic length. Both kinds of states arrange with the system size according to their nature. Derived from the excitonic states of the infinite chain, the bulk states preserve their quasi-particle character in these large systems. Considered as a quasi-particle confined in box, they change their energy with the system size according to the particle-in-a-box picture. The surface states do not react to a change of the chain length at all, since effectively only the outermost molecules contribute to the wavefunction. The second regime holds if the states are strongly confined, i.e., the system is smaller than the intrinsic length. Both types of states give up their typical behavior and adopt similar properties. / Diese Arbeit unterbreitet ein Konzept, um elektronische Anregungszustände in Aggregaten quasi-eindimensionaler organischer Materialien vorherzusagen und zu verstehen. Die dichte Packung der Moleküle rechtfertigt die Idealisierung der Kristalle bzw. Cluster als schwach wechselwirkende Stapel, wobei die führenden Effekte innerhalb der Molekülstapel zu erwarten sind. Zur Beschreibung der exzitonischen Zustände wurde das Konzept der 'small radius'-Exzitonen in linearen Molekülketten angewandt. Die elektronischen Zustände sind dabei aus molekularen (Frenkel) und nächsten Nachbarn 'charge-transfer' (CT) Anregungen zusammengesetzt. Die Struktur und Eigenschaften der Zustände wurden für beliebige Kopplungsstärken zwischen Frenkel- und CT Anregungen in Ketten mit idealisierten freien Enden für beliebiger Längen analysiert. Der entwickelte, überwiegend analytische Zugang, welcher auf der Einführung eines komplexen Wellenvektors beruht, ermöglicht die Unterscheidung zweier grundsätzlicher Zustandstypen. Die Mehrheit der Zustände sind Volumenzustände mit rein imaginärem Wellenvektor. Die zugehörige Dispersionsrelation entspricht exakt der Dispersionsrelation der unendlichen Kette mit äquivalenten Kopplungsverhältnissen. Die interne Struktur der Exzitonen der unendlichen Kette wird auf die Volumenzustände der endlichen Kette direkt übertragen. Der zweite grundlegende Zustandstyp umfaßt Tamm-artige Oberflächenzustände. Aufgrund der durch einen nichtverschwindenden reellen Anteil des Wellenvektors hervorgerufenen Dämpfung sind die Wellenfunktionen der Oberflächenzustände an den Randmolekülen lokalisiert. Die entsprechende Dämpfungslänge ist ausschließlich durch die Parametrisierung der Kopplungen bestimmt und ist somit unabhängig von der Kettenlänge. Sie kann daher als intrinische Quantenlänge interpretiert werden, welche von essentieller Bedeutung für das Verständnis systemgrößenabhängigen Verhaltens ist. Sowohl die Anzahl als auch die Art der Oberflächenzustände kann für jede Kopplungssituation vorhergesagt werden. Die unterschiedliche Natur der Volumen- und Oberflächenzustände führt auf ausgeprägte 'Quantum confinement' Effekte. Zwei Regime sind zu unterscheiden. Im Falle des ersten Regimes, dem schwachen 'Confinement', ist die Kettenlänge größer als die intrinsische Länge. Beide Zustandarten reagieren auf eine Veränderung der Kettenlänge gemäß ihrer Natur. Aufgrund ihrer Verwandschaft mit den Bandzuständen der unendlichen Kette bewahren die Volumenzustände ihren Quasiteilchen-Charakter. Aufgefaßt als Quasiteilchen, erfahren sie in endlichen Systemen eine energetische Verschiebung gemäß dem Potentialtopf-Modell. Oberflächenzustände zeigen keine Reaktion auf veränderte Kettenlängen, da effektiv nur die Randmoleküle zur Wellenfunktion beitragen. Es findet ein Übergang zum zweiten Regime (starkes 'Confinement') statt, sobald die Kettenlänge kleiner als intrinsische Quantenlänge wird. Beide Zustandsarten geben ihr typisches Verhalten auf und werden mit abnehmender Kettenlänge zunehmend ähnlicher.