[pt] A óptica de espaço livre (FSO), inicialmente estudada na década de 60, está atraindo atenção no contexto dos sistemas 5G+, que exige tecnologias de back-hauling sem fio com taxas de dados extremamente altas em distâncias de poucos quilômetros. A atual falta de um modelo global de perda de percurso para FSO motiva o estudo do comportamento do enlace óptico sob diferentes condições atmosféricas. Esta tese trata do desenvolvimento de modelos para prever a atenuação devido a neblina e chuva para projetar enlaces FSO em tecnologias 5G e além. Estudamos os bancos de dados de medições de superfície disponíveis em todo o mundo como referência para analisar as respostas do FSO considerando os dados disponíveis de longo prazo e descobrimos que o maior impacto na visibilidade em todo o mundo é causado por neblina, neve e chuva. Assim, selecionamos neblina e chuva como o foco deste estudo. Vários modelos de perda de percurso, baseados na visibilidade, são avaliados através de uma abordagem analítica. Propomos modelos de limite inferior e superior para estimar a atenuação específica devido ao nevoeiro considerando incertezas quanto à sensibilidade da atenuação específica, gama, em função da visibilidade em 1.550 micrômetros e o melhor ajuste aos resultados do modelo microfísico. Com relação à atenuação causada pela chuva, estudamos modelos disponíveis na literatura para enlaces de micro-ondas e os modificamos para aplicação em enlaces FSO. Quando os efeitos de espalhamento múltiplo são considerados, foi encontrada uma redução significativa na atenuação da chuva. Construímos a partir dos modelos, um método para combinar estatisticamente a atenuação em enlaces FSO causada por diferentes condições climáticas. O desempenho dos enlaces ópticos é avaliado em termos do máximo comprimento do enlace em relação à disponibilidade sob quatro condições climáticas: (i) somente chuva, (ii) somente neblina, (iii) chuva e neblina, e (iv) e todas as condições. Finalmente, eventos experimentais para os enlaces FSO e mmWave implementados no campus Leonardo do Politecnico di Milano são classificados e analisados dependendo do efeito atmosférico estudado: chuva estratiforme, chuva convectiva, chuva leve, vento, neblina pesada, neve e outros. / [en] Free-space optics (FSO), initially studied in the 60s, is attracting attention in the frame of 5G+ systems, which demands wireless back-hauling technologies with extremely high data rates over distances up to a few kilometers. The current lack of a global path loss model for FSO motivates studying the optical link s behavior under different atmospheric conditions. This thesis deals with the development of models for predicting the attenuation due to fog and rain for designing FSO links in 5G and beyond technologies. We study extensive surface measurement databases worldwide as a benchmark for analyzing FSO responses considering available long-term data. We find that the highest impact on visibility worldwide is caused by fog, snow, and rain. Thus, we select fog and rain as the focus of this study. Several path loss models based on visibility are assessed. We propose lower and upper-bound models to estimate the specific attenuation, gamma, due to fog which considers uncertainties as the sensitivity of gamma to the visibility at 1.550 µm and a micro-physical model of fog. Regarding attenuation caused by rain, we study models available in the literature for microwave links and modify them for application to FSO. When the multiple scattering effects are considered, a significant reduction in the rain attenuation has been found. From the findings, we build a method to statistically combine the attenuation effects on FSO caused by different weather conditions. The performance of FSO links is assessed in terms of the maximum link range against availability under four weather conditions: (i) rain only, (ii) fog only, (iii) rain and fog, and (iv) all conditions. Finally, experimental events for FSO and mmWave links implemented at Leonardo Campus of Politecnico di Milano are classified and analyzed depending on the studied atmospheric effects: stratiform rain, convective rain, light rain, wind, heavy fog, snow, and others.

The aim of this thesis is to present the situation of the intravenous drug-users (IDUs) living with HIV in Romania, with a focus on Bucharest. The study follows the IDUs experiences from the environment they live in, to the day-to-day examples of structural violence they face. The questions followed regard the lives of the IDUs in Romania, as well as how they are handled by various authorities and institutions’ representatives such as medical staff in hospitals, the national healthcare system, social workers, law enforcement representatives and other public servants. The fieldwork was conducted around Bucharest through the use of observation while volunteering on outreach with an NGO, and interviews in the form of life histories in a hospital, as research methods. The thesis offers a background look at the communist and transition periods that influenced everyday life in today’s Romania. I argue that because of the stigma attached to them for being part of risk groups, the IDUs face many different forms of structural violence. Whether it comes to governmental authorities, law enforcement or medical staff, the IDUs, as well as other vulnerable risk group members, are continuously pushed outside of society through various measures. This creates a continuous state of isolation from which they cannot remove themselves without outsider help.

In the wake of the COVID-19 pandemic and working from home conditions, hybrid work is becoming an increasingly common practice among companies. However, the mix of employees working from home and from the office creates a new environment for communication between employees and supervisors. Physical interactions in the office have proved to be important in allowing employees to present themselves and their work to colleagues and supervisors. Thus, the aim of this study is to investigate how hybrid work affects employees’ opportunities to make themselves and their work visible on equal terms. The method used is semi-structured interviews with employees and supervisors at two large Swedish companies. Results show that employees use continuous dialog, fostering close relations, and supporting colleagues to create favorable impressions in the hybrid workplace. These impression management tactics were motivated by both wanting to look good, as well as do good in the organization. Supervisors likewise agree these behaviors create favorable impressions, although supervisors are more likely to acknowledge behaviors that directly or indirectly assist the supervisors’ work. The study identified four aspects that affect employees’ impression management: routines for mutual meetings, trust and openness within the group, transparency in the work environment, and informal channels for interactions. The results indicate that a hybrid workplace with equal opportunities for managing impressions will decrease the risk of employees experiencing impression management as a sacrifice. However, the biggest challenge to create equal opportunities was identified as providing adequate informal channels for interaction - both generally in the remote environment, as well as informal channels that connect to the wider organization and higher ups in the physical office. / I kölvattnet av COVID-19-pandemin och påtvingat hemarbete, har hybridarbete blivit en alltmer vanligt förekommande arbetsform bland företag. Däremot skapar blandningen av att medarbetare arbetar delvis hemifrån och delvis från kontoret nya förutsättningar för kommunikation medarbetare emellan och med ens chefer. Fysiska interaktioner på kontoret har tidigare visats vara viktigt för medarbetare för att framställa sig själva och sitt arbete inför kollegor och chefer. Denna studie ämnar därav besvara hur hybridarbete påverkar medarbetares möjligheter att på lika villkor synliggöra sig själva och sitt arbete. Metoden som används är semistrukturerade intervjuer med medarbetare och chefer på två stora svenska företag. Resultaten visar att medarbetarna använder kontinuerlig dialog, främjande av närhet, och att stötta kollegor för att inge positiva intryck på den hybrida arbetsplatsen. Dessa taktiker för att skapa intryck motiveras både av viljan att se bra ut, och att göra gott för organisationen. Cheferna instämmer med att dessa beteenden skapar ett positivt intryck, även om cheferna är mer troliga att uppmärksamma beteenden som direkt eller indirekt underlättar deras arbete. Studien identifierar fyra aspekter som påverkar medarbetarnas möjligheter att skapa intryck: rutiner för gemensamma träffar, tillit och öppenhet, transparens i arbetsmiljön, samt informella kontaktvägar. Resultaten indikerar att en hybrid arbetsplats med jämlika möjligheter för medarbetarna att skapa intryck minskar risken av att medarbetarna uppfattar sina ansträngningar som uppoffringar. Däremot identifierades den största utmaningen i att skapa jämlika förutsättningar som att förse medarbetarna med lämpliga informella kontaktvägar - både generellt i distansarbetet, men även informella kontaktvägar till den större organisationen och högre uppsatta chefer på kontoret.

This thesis will investigate the relationship between lighting and perception of safety through a case study. The main focus of this study is outdoor lighting with consideration of gender equality and perception of safety. Although street lighting is generally recognized as the most important environmental features that influences subjective perception of safety after dark, there is still lack of knowledge regarding the needed quality of light for this purpose and how it may influence perceived safety. Literature review indicates that effect of light on perceived safety works through two different mechanisms: natural surveillance and social integration. The main focus of this thesis is on natural surveillance. Indeed, light by increasing visibility in interaction with presence of people, enhance possibilities of natural surveillance. Based on literature review, a tool has been developed to have a more specific examination of visibility.Besides, the women’s safety audit (WSA) diagnostic tool is used as a qualitative data collection tool to identify unsafe spots in the chosen area by 10 local female participants. The chosen area is a residential area in Eskilstuna city, called Årby neighbourhood. All the participants were asked to determine unsafe spots from their perspective in the chosen area during an exploratory night walk. In the next step, the identified unsafe spots are analysed by means of the developed tool in terms of visibility.The result of this thesis supports the previous findings regarding the relationship between visibility and safety perception. Results show that urban settings with low level of prospect (obstructed view), high level of entrapment (escape difficulty), high level of concealment (lots of hiding spots), lack of illuminated visual spatial boundaries (sky plane, vertical plane and ground plane), low level of facial recognition and obstacle detection, low level of illumination of path, high level of glare and varied lighting distribution are judged as the most unsafe by women. In addition, the study revealed that illuminated ground plane has the minimum impact on sense of safety in comparison with other safety-related environmental factors. Consequently, this study highlighted that standards and guidelines, which are related to ground plane, are not very beneficial for improving perception of safety.

Trygghetsarbete ärnågot som både statliga myndigheter och kommuner intresserar sig för. Kommunernämner gärna i sina översiktsplaner att trygghetsfrämjande åtgärder ska vidtasoch att områden ska utvecklas med hänsyn till tryggheten. Hur dettatrygghetsarbete tar sig form i den fysiska miljön är mindre tydligt och syftetmed denna studie har således varit att ta fram aspekter som går att arbeta medför att främja trygghet. Dessa aspekter har sedan använts för att analyseratorg i Stockholm stad, Nacka kommun och Vaxholm stad för att se hur väl torgensvarar mot dessa aspekter. Aspekterna som tagits fram med hjälp av enlitteraturstudie och den fallstudie som har utförts har sedan legat till grundför att ta fram tips för hur trygga torg kan utformas.Litteraturstudien ledde till att fem aspekter av stor betydelse för trygghetentogs fram: närhet till andra människor, synlighet och överblickbarhet,belysning, grönska och skötsel av allmän plats. Inget av de torg som omfattadesav fallstudien uppnådde samtliga trygghetsaspekter, men vissa uppfyllde fler änandra. Utöver de slutsatser som har dragits kring vilka aspekter som är trygghetsfrämjandeså ledde studien till slutsatser kring vilka torg som uppfyller vilka aspekter.Slutligen ledde studien fram till konkreta förbättringsförslag för trygghetenpå de torg som fallstudien omfattade och handfasta tips för hur torg kanutformas med hänsyn till trygghet / Working with perceived safety is something that both government agencies and municipalities are interested in. Municipalities gladly mention in their general plans that perceived safety actions is something that should be prioritised and that new areas should be developed with regard to the perceived safety. Exactly how these perceived safety actions takes shape in the physical environment is less clear and the purpose has thus been to identify aspects that are possible to work with and that promotes the perceived safety. The identified aspects have then been used to analyse squares in Stockholm stad, Nacka kommun and Vaxholm stad to see how well these places correspond to the these aspects. Tips on how squares that are perceived as safe was then formulated based on the case study and the aspects that was identified in the literature study.The literature study led to the identification of five aspects with great significance to the perceived safety: closeness to other people, visibility and overview, lightning, greenery and maintenance of public space. None of the observed squares fulfill all the aspects, but some fulfill more than others. Other than the conclusions that were drawn concerning which aspects that are promoting for the perceived safety, the study also led to conclusions regarding which squares that fulfill which aspects. Finally the study led to improvement-proposals for perceived safety on the squares of the case study and concrete tips on how squares can be designed with regard to perceived safety.

Supply chain visibility (SCV) has been gaining attention as a key for supply chainperformance. The key characteristics of SCV are information accessibility, accuracy,timeliness, completeness and usage, all of which aid in the enhancement ofoperational and strategic supply chain activities. Despite the increasing acceptanceof the importance of SCV, knowledge regarding SCV is scattered. There is a needfor knowledge regarding the conditions affecting the realisation of SCV, whichmotivates this thesis.The thesis contains three research questions. First, it identifies andcategorises the conditions affecting SCV to provide a holistic view of SCV. Second,given the role of SCV in decision making, it investigates what supply chaininformation is important for SCV from a supply practitioner’s point of view. Third,it explores the possibilities and challenges of implementing technologies toimprove SCV in practice.The findings include a holistic framework on SCV based on the literature andempirical research. The framework categorises the factors affecting SCV and itsoutcome as antecedents, barriers and challenges and drivers and effects. Amongthe identified essential supply chain information for SCV, there is a consensus thatdata regarding deliveries, deviations, supplier capabilities, inventories andcapacities are the most important. In terms of approaching SCV in practice, thisthesis identifies the steps for translating SCV problem areas into technologicalsolutions to enhance supply chain performance. However, the full SCV effort willrequire a focus on people, processes and technology. Given its role in decisionmaking and performance, SCV is difficult yet important to implement.This thesis outlines four main academic contributions: i) adding to theacademic research and detailing the need for more research on SCV, ii) a state-ofthe-art understanding of SCV, iii) empirically exploring the factors influencing SCVand iv) confirming and adding to previous research on the technologies for SCV.For supply chain practitioners, the present thesis offers guidance and insights toplan, implement and further enhance SCV to attain increased levels of supply chainperformance. / Synlighet i försörjningskedjor, s.k. Supply Chain Visibility (SCV), har fått ökaduppmärksamhet för sin betydelse för försörjningskedjors prestanda. För att nå SCVhar olika egenskaper hos information mellan försörjningsleden pekats ut:tillgänglighet, noggrannhet, aktualitet, fullständighet och användbarhet. Alla dessaegenskaper stödjer förbättring av både operativa och strategiska aktiviteter iförsörjningskedjor. Även om värdet av SCV generellt sett är oomtvistat, ärkunskapen kring SCV inte samlad. Det finns ett ökat behov av kunskap omförutsättningar och förhållanden som påverkar hur vi kan nå synlighet iförsörjningskedjor, vilket är motivet till denna avhandling.Avhandlingen bygger på tre forskningsfrågor. Den första identifierar ochkategoriserar förhållanden som påverkar SCV med avsikt att ge en holistisk syn.Den andra frågan undersöker, utgående från relaterade beslut som ska fattas,vilken information för SCV som är viktig för försörjningskedjors intressenter. Dentredje utforskar möjligheterna och utmaningarna med att implementerateknologier för att förbättra SCV i praktiken.Resultaten inkluderar ett holistiskt ramverk av SCV baserat på litteratur ochempirisk forskning. Ramverket kategoriserar de faktorer som påverkar SCV ochdess utfall, som förutsättningar, barriärer och utmaningar, drivkrafter och effekter.Rörande den information som är viktig vid SCV, är bilden att leverans, avvikelse,leverantörskapacitet, lager och kapacitetsrelaterade data är viktigast. För attförverkliga SCV i praktiken, introduceras steg för att översätta problemområdenrelaterad till SCV till tekniska lösningar, allt i syfte att stimuleraförsörjningskedjors prestanda. Dock kräver SCV en gedigen insats med fokus påmänniskor, processer och teknologier.Denna avhandling tillför i huvudsak fyra akademiska bidrag: i) ett bidrag tillden akademiska forskningen och detaljerat behov rörande fortsatt forskning inomSCV, ii) en övergripande sammanställning av kunskapsfronten rörande SCV, iii) ettempiriskt utforskande av faktorer som påverkar SCV och iv) en bekräftelse och ettbidrag till tidigare forskning om teknologierna för SCV. För industriella aktörer,tillför denna avhandling vägledning och insikter för att planera, etablera,implementera och ytterligare förbättra SCV.

Many of the languages in the world are currently dying at an alarming rate. One of these languagesis Eldalian. It is a small language spoken by about 2,500 people in the village of Älvdalen in theDalarna county of Sweden. Despite shrinking numbers, attitudes towards the language remain highand people are increasingly identifying themselves with the language.Through qualitative datacollection and by using the analytical frameworks of framing as well as place-making to examinethe issues, this thesis details the relationship between the language and its speakers with a focus onthe speakers. Based on the ethnographic accounts and the subsequent analysis, this thesis pointstowards how the change in attitudes regarding the language during the 20th century led to adecrease in the presence of the language is viewed as the main reason why the language is where itis today; with Swedish having replaced the language in most public settings. To change this, therevitalisation movement strives to increase the value of the language by “framing” it in variouscontexts, arguing for its existence, and enriching its usage through values that can be found indifferent contexts. Furthermore, this leads to an engagement with the place-making of Älvdalen bywhich the language is “imbued” into the place through signs and the content production of thosewho live village; increasing its presence by placing it firmly in the Älvdalen setting. Hence,Elfdalian is currently situated in the middle between the “private” to “public”.

[EN] In this thesis, we consider two problems: we first explore the application of visibility graphs for describing the orbits of a discrete dynamical system that is governed by a fractional version of the logistic equation. We also study how to use this type of graphs to study response time series from the perspective of psychology. The preliminaries and introduction of these visibility graphs are presented in Chapter 1, where we revisit some basic facts from network science related to them. In the first part of this thesis, we analyze a phenomenon of mathematical nature. Wu and Baleanu introduced a fractional discrete dynamical system inspired by the fractional difference logistic equation. In order to study the trajectories of this model under this perspective of network science, in Chapter 2, we first review the most used fractional derivatives (Riemann-Liouville, Caputo, and Gründwald-Letnikov). Later, we show how to consider discrete fractional derivatives. Within our work, we present an alternative way of deducing the governing equation with respect to the one shown by Wu and Baleanu. We revisit the Wu-Baleanu equation in Chapter 3, focused on the visibility graphs of trajectories generated under different values of the scaling factor and the fractional exponent. We also study the existing connections between these parameters and the fitting with the degree distribution of the corresponding visibility graphs. When chaos is present, we link them with the exponent obtained when fitting the degree distribution to a power-law of the form x^(¿¿). With this approach, we provide an integrated vision of the dynamics of a family of fractional discrete dynamical systems that cannot be obtained from single Feigenbaum diagrams computed for each scaling factor and fractional exponent. We also connect the power-law exponent of the degree distribution fitting with the Shannon entropy of the visibility graphs degree distribution. In the second part, we analyze the response times of students to a binary decision task from the perspective of network science. We analyze the properties of the natural visibility graphs associated with their reaction time series. We observe that the degree distribution of these graphs usually fits a power-law distribution p(x) = x^(¿¿). We study the range in which parameter ¿ occurs and the changes of this exponent with respect to the age and gender of the students. Besides, we also study the links between the parameter ¿ and the ex-Gaussian distribution parameters that best fits each subject's response times. Finally, we outline some conclusions and perspectives of future research in both parts in Chapter 6. / [ES] En esta tesis, hemos considerado dos problemas: primero exploramos la aplicación de los grafos de visibilidad para describir las órbitas de un sistema dinámico discreto que está gobernado por una versión fraccionaria de la ecuación logística. Además, también estudiamos cómo usar este tipo de grafos para estudiar series temporales de tiempos de respuesta desde una perspectiva psicológica. Los preliminares, así como una introducción a estos grafos de visibilidad, se presentan en el Capítulo 1, donde revisitamos algunos hechos básicos de la ciencia de redes relacionados con dichos grafos. En la primera parte de esta tesis, analizamos un fenómeno de naturaleza matemática. Wu y Baleanu introdujeron un sistema dinámico discreto fraccionario inspirado en la ecuación logística con derivadas fraccionarias. Con el propósito de estudiar las trayectorias de este modelo desde la perspectiva de la ciencia de redes, en el Capítulo 2, primero revisamos las derivadas fraccionarias más utilizadas (Riemann-Liouville, Caputo y Gründwald-Letnikov). Posteriormente, mostramos cómo considerar derivadas fraccionarias discretas. En nuestro trabajo, presentamos una forma alternativa de deducir la ecuación gobernante con respecto a la presentada por Wu y Baleanu. Revisitamos la ecuación de Wu-Baleanu en el Capítulo 3, centrado en los grafos de visibilidad de trayectorias generadas a partir de distintos valores del factor de escala y del exponente fraccionario. También estudiamos la existencia de conexiones entre estos parámetros y el ajuste de la distribución de los grados de los correspondientes grafos de visibilidad. Cuando el caos está presente, los enlazamos con el exponente obtenido al ajustar la distribución de los grados a una ley de potencias de la forma x^(¿¿). A través de este enfoque, proporcionamos una visión integrada de la dinámica de una familia de sistemas dinámicos discretos fraccionarios que no se pueden obtener a partir de diagramas de Feigenbaum individuales calculados para cada factor de escala y exponente fraccionario. Además, relacionamos el exponente de la ley de potencias del ajuste de la distribución de grados con la entropía de Shannon de la distribución de grados de los grafos de visibilidad. En la segunda parte, analizamos el tiempo de respuesta de un grupo de estudiantes que realizaron una tarea de decisión binaria desde la perspectiva de la ciencia de redes. Estudiamos las propiedades de los grafos de visibilidad natural asociados con sus correspondientes series de tiempos de respuesta. Observamos que la distribución de los grados de estos grafos normalmente sigue una distribución ley de potencias p(x) = x^(¿¿). Analizamos el rango en el cual el parámetro ¿ se mueve y los cambios de este exponente con respecto a la edad y el sexo de los estudiantes. Por otro lado, también estudiamos la relación entre el parámetro ¿ y los parámetros de la distribución ex-Gaussiana que mejor se ajusta al tiempo de respuesta de cada sujeto. Finalmente, destacamos algunas conclusiones y perspectivas de investigación futura en ambas líneas de trabajo en el Capítulo 6. / [CAT] En aquesta tesi, hem considerat dos problemes: primer explorem l'aplicació dels grafs de visibilitat per a descriure les òrbites d'un sistema dinàmic discret que està governat per una versió fraccionària de l'equació logística. A més a més, també estudiem com emprar aquest tipus de grafs per a analitzar sèries temporals de temps de resposta des d'una perspectiva psicològica. Els preliminars, així com una introducció a aquests grafs de visibilitat, es presenten al Capítol 1, on revisitem alguns fets bàsics de la ciència de xarxes relacionats amb ells. En la primera part d'aquesta tesi, analitzem un fenomen de naturalesa matemàtica. Wu i Baleanu van introduir un sistema dinàmic discret fraccionari inspirat en l'equació logística amb derivades fraccionàries. Amb el fi d'estudiar les trajectòries d'aquest model des d'una perspectiva de la ciència de xarxes, en el Capítol 2, primer revisem les derivades fraccionàries més utilitzades (Riemann-Liouville, Caputo i Gründwald-Letnikov). Posteriorment, mostrem com considerar derivades fraccionàries discretes. Al nostre treball, presentem una forma alternativa de deduir l'equació governant respecte a la presentada per Wu i Baleanu. Revisitem l'equació de Wu-Baleanu al Capítol 3, focalitzat en els grafs de visibilitat de trajectòries generades a partir de valors diferents del factor d'escala i de l'exponent fraccionari. També estudiem l'existència de connexions entre aquests paràmetres i l'ajust de la distribució dels graus dels corresponents grafs de visibilitat. Quan el caos hi és, els enllacem amb l'exponent que hem obtés en ajustar la distribució dels graus a una llei de potències de la forma x^(¿¿). Des d'aquesta perspectiva, proporcionem una visió integrada de la dinàmica d'una família de sistemes dinàmics discrets fraccionaris que no es poden obtenir a partir de diagrames de Feigenbaum individuals calculats per a cada factor d'escala i exponent fraccionari. A més a més, relacionem l'exponent de la llei de potències de l'ajust de la distribució de graus amb l'entropia de Shannon de la distribució de graus dels grafs de visibilitat. A la segona part, analitzem el temps de resposta d'un grup d'estudiants que realitzaren una tasca de decisió binària des del punt de vista de la ciència de xarxes. Estudiem les propietats dels grafs de visibilitat natural associats amb les seues corresponents sèries temporals de temps de resposta. Observem que la distribució dels graus d'aquests grafs normalment segueix una distribució llei de potències p(x) = x^(¿¿). Analitzem el rang en què el paràmetre ¿ es mou i els canvis d'aquest exponent respecte a l'edat i el sexe dels estudiants. D'altra banda, també estudiem la relació entre el paràmetre ¿ i els paràmetres de la distribució ex-Gaussiana que millor fita el temps de resposta de cada subjecte. Finalment, destaquem algunes conclusions i perspectives d'investigació futura en ambdues línies de treball en el Capítol 6. / Mira Iglesias, A. (2021). Applications of Visibility Graphs for the representation of Time Series [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/176012

This study applied the impression management theory in the context of social networking to investigate the generalized research question of this dissertation which is "Do active social media presence and various privacy concerns influence online behaviors of students on social media?" The results and conclusions are presented via the conduct of three different studies and the summary provides insights and explain the overall contribution of the research. For each study we developed a research model for which data was collected separately for each of these models. Hypotheses of each model were tested by partial least squares- structural equation modeling techniques using SmartPLS 2.0. Our findings confirm the hypotheses and showed that all the predictors positively influence online social networking behaviors. Active social media presence is operationalized as predictors such as SNS stalking awareness, Selective disclosure, desired differential persona, impression motivation, and information trustworthiness. Privacy concerns have been operationalized as SNS privacy awareness, technology awareness. Online behaviors have been operationalized as responsible image and reckless image.

In den letzten Jahren erfreuen sich komplexe Netzwerke einer zunehmenden Beliebtheit, um Zusammenhänge und Strukturen in hoch-dimensionalen Datensätzen zu analysieren. Im Unterschied zu vielen anderen Forschungsgebieten wurden sie jedoch selten auf Paläoklima-Daten angewandt, obwohl die steigende Anzahl an veröffentlichen Zeitreihen die Nutzung effizienter Methoden multivariater Analyse ermöglicht. Die Resultate der wenigen Studien, in denen Netzwerkmethoden und Paläoklima-Daten kombiniert wurden, sind außerdem geprägt von niedriger Robustheit und hohen Unsicherheiten. Dies steht im Zusammenhang zu der niedrigen Anzahl und Auflösung der Zeitreihen als auch den Unsicherheiten, die den meisten Paläoklima-Rekonstruktionen zu eigen sind. In dieser Doktorarbeit schlage ich verschiedene Wege vor, um diese Probleme zu überwinden, indem verlässlichere, quantitative Resultate ermöglicht werden, unter anderem indem die Datenunsicherheiten explizit in die Analyse mit einbezogen werden. Zu diesem Zweck präsentiere ich vier Fallstudien mit einem Fokus auf zwei Zeiträume, das späte Holozän (die letzten zweitausend Jahre) und den Übergang von der letzten Kaltzeit zur aktuellen Warmzeit, die letzte glaziale Termination. Alle diese Studien legen einen räumlichen Fokus auf den Nordatlantik, eine Schlüsselregion globaler Klimavariabilität. Ich beschränke mich hierbei auf zwei Methoden, eine der netzwerkbasierten Zeitreihenanalyse, Sichtbarkeitsgraphen genannt, und eine der räumlichen Analyse, sogenannte Klimanetzwerke. Neben Erweiterungen von existierende Methoden, schlage ich auch neue Wege vor, um verlässliche Resultate auch für Zeitreihen mit hohen Unsicherheiten zu erhalten. Diese Fallstudien demonstrieren, dass Netzwerkmethoden auch für die Analyse von Paläoklima-Daten nützlich sein können. Sie sind daher ein weiterer Schritt hin zu einer künftigen Anwendung durch eine größere Anzahl an Forschenden. / In recent years, complex networks have become an increasingly popular tool to analyse relationships and structures in high-dimensional data sets in a variety of research fields. They have, however, rarely been applied to paleoclimate data sets, even though the growing number of published records demands efficient tools of multivariate analysis. The few published results that combine network methods and paleoclimate proxies are often not robust or have high uncertainty levels, linked tothe low dimensionality, resolution and the large uncertainties of most particulate time series. In this thesis, I propose several ways to overcome these issues in order to obtain reliable and quantitative results from network based tools by taking the particularities of paleoclimate data into account. For this purpose, I present four case studies, focusing on two time periods, the late Holocene (last two millennia) and the transition from the last ice age to the recent warm period, the last deglaciation. These studies are all related to the North Atlantic, a key region in multi-decadal to millennial scale climate variability. I primarily use two methods, one of network based time series analysis named visibility graphs and one of spatial analysis, so called limate networks. I have both further developed existing methods, but also propose new ways to yield reliable results when dealing with highly uncertain paleoclimate data. The case studies demonstrate the usefulness of network based data analysis to study patterns of regional climate variability. Hence, this work is another step in bringing network based approaches to a larger audience and towards a wider application of these methods.