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The article processing charge was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 491192747 and the Open Access Publication Fund of Humboldt-Universität zu Berlin., In this paper we extend the use of a relational approach to simulation modelling, a widely used knowledge practice in sustainability science. Among modellers, there is awareness that model results can only be interpreted in view of the assumptions that inform model construction and analysis, but less systematic questioning of those assumptions. Moreover, current methodological discussions tend to focus on integrating social and ecological dynamics or diverse knowledges and data within a model. Yet choices regarding types of modelling, model structure, data handling, interpretation of results and model validation are not purely epistemic. They are entangled with values, contexts of production and use, power relations, and pragmatic considerations. Situated Modelling extends a relational understanding of the world to scientific knowledge production and with that to modelling itself in order to enable a systematic interrogation of these choices and to research social-ecological transformations relationally. To make tangible the situatedness of simulation modelling, we build on existing practices and describe the situatedness of three distinct modelling approaches. We then suggest four guiding principles for Situated Modelling: 1. attending to the apparatus of knowledge production that is socially and materially embedded and produced by e.g. research infrastructures, power relations, and ways of thinking; 2. considering how agency is distributed between model, world, data, modeller in model construction; 3. creating heterogenous collectives which together occupy the formerly individualised subject position; and 4. using agonism as an epistemic virtue to retain and work with significant differentiations of social-ecological dynamics throughout the modelling process., Peer Reviewed

Popular methods to quantify transmitted data quality are the Age of Information (AoI), the Query Age of Information (QAoI), and the Age of Incorrect Information (AoII). We consider these metrics in a point-to-point wireless communication system, where the transmitter monitors a process and sends status updates to a receiver. The challenge is to decide on the best time for an update, balancing the transmission energy and the age-based metric at the receiver. Due to the inherent risk of high age-based metric values causing complications such as unstable system states, we introduce the new concept of risky states to denote states with high age-based metric. We use this new notion of risky states to quantify and minimize this risk of experiencing high age-based metrics by directly deriving the frequency of risky states as a novel risk-metric. Building on this foundation, we introduce two risk-sensitive strategies for AoI, QAoI and AoII. The first strategy uses system knowledge, i.e., channel quality and packet arrival probability, to find an optimal strategy that transmits when the age-based metric exceeds a tunable threshold. A lower threshold leads to higher risk-sensitivity. The second strategy uses an enhanced Q-learning approach and balances the age-based metric, the transmission energy and the frequency of risky states without requiring knowledge about the system. Numerical results affirm our risk-sensitive strategies' high effectiveness.

Several areas of wireless networking, such as wireless sensor networks or the Internet of Things, require application data to be distributed to multiple receivers in an area beyond the transmission range of a single node. This can be achieved by using the wireless medium’s broadcast property when retransmitting data. Due to the energy constraints of typical wireless devices, a broadcasting scheme that consumes as little energy as possible is highly desirable. In this article, we present a novel multi-hop data dissemination protocol called BTP. It uses a game-theoretical model to construct a spanning tree in a decentralized manner to minimize the total energy consumption of a network by minimizing the transmission power of each node. Although BTP is based on a game-theoretical model, it neither requires information exchange between distant nodes nor time synchronization during its operation, and it inhibits graph cycles effectively. The protocol is evaluated in Matlab and NS-3 simulations and through real-world implementation on a testbed of 75 Raspberry Pis. The evaluation conducted shows that our proposed protocol can achieve a total energy reduction of up to 90% compared to a simple broadcast protocol in real-world experiments.

Purpose Antibody assays against SARS-CoV-2 are used in sero-epidemiological studies to estimate the proportion of a population with past infection. IgG antibodies against the spike protein (S-IgG) allow no distinction between infection and vaccination. We evaluated the role of anti-nucleocapsid-IgG (N-IgG) to identify individuals with infection more than one year past infection. Methods S- and N-IgG were determined using the Euroimmun enzyme-linked immunosorbent assay (ELISA) in two groups: a randomly selected sample from the population of Stuttgart, Germany, and individuals with PCR-proven SARS-CoV-2 infection. Participants were five years or older. Demographics and comorbidities were registered from participants above 17 years. Results Between June 15, 2021 and July 14, 2021, 454 individuals from the random sample participated, as well as 217 individuals with past SARS-CoV-2 infection. Mean time from positive PCR test result to antibody testing was 458.7 days (standard deviation 14.6 days) in the past infection group. In unvaccinated individuals, the seroconversion rate for S-IgG was 25.5% in the random sample and 75% in the past infection group (P = < 0.001). In vaccinated individuals, the mean signal ratios for S-IgG were higher in individuals with prior infection (6.9 vs 11.2; P = < 0.001). N-IgG were only detectable in 17.1% of participants with past infection. Predictors for detectable N-IgG were older age, male sex, fever, wheezing and in-hospital treatment for COVID-19 and cardiovascular comorbidities. Conclusion N-IgG is not a reliable marker for SARS-CoV-2 infection after more than one year. In future, other diagnostic tests are needed to identify individuals with past natural infection.

Wireless backhauling at millimeter-wave frequencies (mmWave) in static scenarios is a well-established practice in cellular networks. However, highly directional and adaptive beamforming in today's mmWave systems have opened new possibilities for self-backhauling. Tapping into this potential, 3GPP has standardized Integrated Access and Backhaul (IAB) allowing the same base station serve both access and backhaul traffic. Although much more cost-effective and flexible, resource allocation and path selection in IAB mmWave networks is a formidable task. To date, prior works have addressed this challenge through a plethora of classic optimization and learning methods, generally optimizing a Key Performance Indicator (KPI) such as throughput, latency, and fairness, and little attention has been paid to the reliability of the KPI. We propose Safehaul, a risk-averse learning-based solution for IAB mmWave networks. In addition to optimizing average performance, Safehaul ensures reliability by minimizing the losses in the tail of the performance distribution. We develop a novel simulator and show via extensive simulations that Safehaul not only reduces the latency by up to 43.2% compared to the benchmarks but also exhibits significantly more reliable performance (e.g., 71.4% less variance in achieved latency)., Comment: To appear in Proceedings of IEEE INFOCOM 2023

Enabling quantum switches (QSs) to serve requests submitted by quantum end nodes in quantum communication networks (QCNs) is a challenging problem due to the heterogeneous fidelity requirements of the submitted requests and the limited resources of the QCN. Effectively determining which requests are served by a given QS is fundamental to foster developments in practical QCN applications, like quantum data centers. However, the state-of-the-art on QS operation has overlooked this association problem, and it mainly focused on QCNs with a single QS. In this paper, the request-QS association problem in QCNs is formulated as a matching game that captures the limited QCN resources, heterogeneous application-specific fidelity requirements, and scheduling of the different QS operations. To solve this game, a swap-stable request-QS association (RQSA) algorithm is proposed while considering partial QCN information availability. Extensive simulations are conducted to validate the effectiveness of the proposed RQSA algorithm. Simulation results show that the proposed RQSA algorithm achieves a near-optimal (within 5%) performance in terms of the percentage of served requests and overall achieved fidelity, while outperforming benchmark greedy solutions by over 13%. Moreover, the proposed RQSA algorithm is shown to be scalable and maintain its near-optimal performance even when the size of the QCN increases., Comment: 6 pages, 4 figures

The problem of coordinated data collection is studied for a mobile crowdsensing (MCS) system. A mobile crowdsensing platform (MCSP) sequentially publishes sensing tasks to the available mobile units (MUs) that signal their willingness to participate in a task by sending sensing offers back to the MCSP. From the received offers, the MCSP decides the task assignment. A stable task assignment must address two challenges: the MCSP's and MUs' conflicting goals, and the uncertainty about the MUs' required efforts and preferences. To overcome these challenges a novel decentralized approach combining matching theory and online learning, called collision-avoidance multi-armed bandit with strategic free sensing (CA-MAB-SFS), is proposed. The task assignment problem is modeled as a matching game considering the MCSP's and MUs' individual goals while the MUs learn their efforts online. Our innovative "free-sensing" mechanism significantly improves the MU's learning process while reducing collisions during task allocation. The stable regret of CA-MAB-SFS, i.e., the loss of learning, is analytically shown to be bounded by a sublinear function, ensuring the convergence to a stable optimal solution. Simulation results show that CA-MAB-SFS increases the MUs' and the MCSP's satisfaction compared to state-of-the-art methods while reducing the average task completion time by at least 16%.

Wissen als Praxis zu begreifen, ist in der Europäischen Ethnologie heute selbstverständlich. Erkenntnisse der Wissenschafts- und Technikforschung, feministischer Kritiken und praxistheoretischer Entwicklungen haben sich produktiv mit fachlichen Problematisierungen von Rationalität, materieller und epistemischer Kultur verbunden. Im Zuge dieser Entwicklungen ist zunehmend die Performativität von Wissenspraktiken betont worden, d. h. ihre notwendigerweise immer auch gestaltende Weltwirksamkeit. Dies wiederum hat Anthropolog*innen ermutigt, verstärkt mit ethnografischen Methoden zu experimentieren, um eben jene Weltwirksamkeit besser kontrollieren bzw. entfalten zu können. Konzepte von Wissenstransfer und mode 2 Wissensproduktion sind ersetzt worden durch Interventionen, Ko-Produktion/Kreation/Design, Kollaboration, experimental entanglement und Ko-Laboration. Uns interessiert in diesem Beitrag die Frage, was diese Entwicklung praktisch für ethnografische Theorieproduktion bedeutet. Wir entwickeln unsere Argumentation an vier Forschungsfeldern, die derzeit in unserem Labor ethnografisch im Rahmen von fortgeschrittenen Dissertationsprojekten bearbeitet werden: Genesungsbegleitung in psychiatrischen Kliniken (Schmid), Praktiken des Plattformwirtschaftens in digitalen start-up Ökosystemen (Josties), Offener Dialog in der Psychiatrie als prozessuale Therapieform (Cubellis) und Skalierung in Modellen für Mensch-Umwelt Beziehungen (Klein). Wir legen besonderen Wert auf das gemeinschaftliche "Fügen" von Theorie und Reflexivität und beleuchten fallübergreifend drei Fragen genauer: Welche Konsequenzen hat die Verteilung von epistemischer Handlungsträgerschaft für ethnografische Theoriebildung? Wie müssen Differenzierungen in ko-laborativer Forschung kuratiert werden? Wo liegen Herausforderungen, Grenzen und Risiken dieser Herangehensweise?, To understand knowledge as practice is taken for granted in European Ethnology today. Insights from science and technology studies, feminist critique and developments in practice theory have productively combined with disciplinary problematizations of rationality, materiality and epistemic culture. In the course of these developments, the performativity of knowledge practices has been increasingly emphasized, i. e. their worlding capacity. This, in turn, has encouraged anthropologists to experiment more with ethnographic methods in order to better understand and develop this worlding capacity. Concepts of knowledge transfer and mode 2 knowledge production have been replaced by approaches of intervention, co-production/creation/design, collaboration, experimental entanglement and co-laboration. In this contribution, we are interested in the question of what this development means in practice for ethnographic theory building. We develop our argument across four research fields that are currently being ethnographically studied in our laboratory in the context of advanced dissertation projects: Peer support in psychiatric clinics (Schmid), economic and management practices in digital start-up ecosystems (Josties), open dialogue in psychiatry (Cubellis) and scaling in models of human-environment relations (Klein). We place special emphasis on the joint "assembling" of theory and reflexivity and take a closer look at three questions across all cases: What consequences does the distribution of epistemic agency have for ethnographic theory building? How do differentiations in co-laborative research have to be curated? What are the challenges, limits and risks of this approach?

The phase III study was designed to compare event-free survival (EFS) after treosulfan-based conditioning with a widely applied reduced-intensity conditioning (RIC) busulfan regimen in older or comorbid patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) undergoing allogeneic hematopoietic cell transplantation (HCT). A previously reported confirmatory interim analysis of the randomized clinical study including 476 patients demonstrated statistically significant noninferiority for treosulfan with clinically meaningful improvement in EFS. Here, the final study results and pre-specified subgroup analyses of all 570 randomized patients with completed longer-term follow-up are presented. Patients presenting HCT-specific comorbidity index >2 or aged >= 50 years were randomly assigned (1:1) to intravenous (IV) fludarabine with either treosulfan (30 g/m(2) IV) or busulfan (6.4 mg/kg IV) after stratification by disease risk group, donor type, and participating institution. The primary endpoint was EFS with disease recurrence, graft failure, or death from any cause as events. EFS of patients (median age 60 years) was superior after treosulfan compared to RIC busulfan: 36-months-EFS rate 59.5% (95% CI, 52.2-66.1) vs. 49.7% (95% CI, 43.3-55.7) with a hazard ratio (HR) of 0.64 (95% CI, 0.49-0.84), p = 0.0006. Likewise, overall survival (OS) with treosulfan was superior compared to busulfan: 36-month-OS rate 66.8% vs. 56.3%; HR 0.64 (95% CI, 0.48-0.87), p = 0.0037. Post hoc analyses revealed that these differences were consistent with the confirmatory interim analysis, and thereby the treosulfan regimen appears particularly suitable for older AML and MDS patients.

The optimal offloading of tasks in heterogeneous edge-computing scenarios is of great practical interest, both in the selfish and fully cooperative setting. In practice, such systems are typically very large, rendering exact solutions in terms of cooperative optima or Nash equilibria intractable. For this purpose, we adopt a general mean-field formulation in order to solve the competitive and cooperative offloading problems in the limit of infinitely large systems. We give theoretical guarantees for the approximation properties of the limiting solution and solve the resulting mean-field problems numerically. Furthermore, we verify our solutions numerically and find that our approximations are accurate for systems with dozens of edge devices. As a result, we obtain a tractable approach to the design of offloading strategies in large edge-computing scenarios with many users., Comment: Accepted to GLOBECOM 2022

Device-to-device (D2D) communication is an innovative solution for improving wireless network performance to efficiently handle the ever-increasing mobile data traffic. Communication takes place directly between two devices that are in each other’s transmission range. So far, research has focused on the technical challenges of implementing this technology and assumes a user’s general willingness to participate as forwarder in this technology. However, this simplifying assumption is not realistic, as willingness to participate in D2D communication can vary depending on the user. In this work, we consider the scenario that a user can act as a forwarder for a receiver who is not directly or insufficiently reached by the base station and accordingly has no or poor Internet connection. We take a user-centric approach and investigate the willingness to provide an Internet connection as a forwarder. We are the first to investigate user preferences for D2D communication using a choice-based conjoint analysis. Our results, based on a representative sample of potential users (N=181), show that the social relationship between the potential forwarder and the receiver has the greatest impact on the potential forwarder’s decision to provide an Internet connection to the receiver, accepting sacrifices in terms of additional battery consumption and reduced own service performance. In a detailed segment analysis, we observe significant preference differences depending on smartphone usage behavior and user age. Taking the corresponding preferences into account when matching forwarders and receivers can further increase technology adoption.

Background Further improvement of preparative regimens before allogeneic haemopoietic stem cell transplantation (HSCT) is an unmet medical need for the growing number of older or comorbid patients with acute myeloid leukaemia or myelodysplastic syndrome. We aimed to evaluate the efficacy and safety of conditioning with treosulfan plus fludarabine compared with reduced-intensity busulfan plus fludarabine in this population. Methods We did an open-label, randomised, non-inferiority, phase 3 trial in 31 transplantation centres in France, Germany, Hungary, Italy, and Poland. Eligible patients were 18-70 years, had acute myeloid leukaemia in first or consecutive complete haematological remission (blast counts <5% in bone marrow) or myelodysplastic syndrome (blast counts <20% in bone marrow), Karnofsky index of 60% or higher, and were indicated for allogeneic HSCT but considered at an increased risk for standard myeloablative preparative regimens based on age (>= 50 years), an HSCT-specific comorbidity index of more than 2, or both. Patients were randomly assigned (1:1) to receive either intravenous 10 g/m(2) treosulfan daily applied as a 2-h infusion for 3 days (days -4 to -2) or 0.8 mg/kg busulfan applied as a 2-h infusion at 6-h intervals on days -4 and -3. Both groups received 30 mg/m(2) intravenous fludarabine daily for 5 days (days -6 to -2). The primary outcome was event-free survival 2 years after HSCT. The non-inferiority margin was a hazard ratio (HR) of 1.3. Efficacy was assessed in all patients who received treatment and completed transplantation, and safety in all patients who received treatment. The study is registered with EudraCT (2008-002356-18) and ClinicalTrials.gov (NCT00822393). Findings Between June 13, 2013, and May 3, 2016,476 patients were enrolled (240 in the busulfan group received treatment and transplantation, and in the treosulfan group 221 received treatment and 220 transplanation). At the second preplanned interim analysis (Nov 9, 2016), th

In this paper we present the impact of acoustic resonances excited by electrostriction in BST thin-films on the Q-factor of a varactor in the GHz range. By changing the process-parameter substrate to target distance while sputtering the thin-films, we observe a change in the acoustic resonance frequencies. To characterize the material properties which determine the acoustic resonance frequencies a model based on a 1D acoustic transmission line is used. The extracted material properties results in a proportional dependency to the changed process parameter. For verification of the acoustic transmission line model 3D simulations have been performed which show good agreement to the line model for lower resonance frequencies, where the difference at higher frequencies becomes significant due to additional higher order modes.

This paper studies video streaming from a source to multiple receivers in wireless networks. The video is streamed with the help of intermediate users who forward the video to others. Two main challenges affect user satisfaction in this network. The users usually have 1) different willingness to contribute (forwarding the video), and; 2) different preferences regarding the video quality. To overcome the challenges, we propose a framework based on an incentive/taxation mechanism in which the forwarding users, depending on their spent energy, are paid by their corresponding receivers. The video is layered such that the more video layers are received, the higher the quality-of-experience (QoE) and the higher the price. Using a decentralized game-theoretic algorithm, we define a user-specific utility function whose maximization determines the number of video layers a user wishes to receive. The utility function captures the user's preferences including the importance of the video quality to her and her willingness to contribute. Our model supports the multicast transmission by which the receivers can use a common forwarder and share the cost. The simulation results show that the proposed model not only provides a higher QoE for the users compared to the preference-agnostic models but also improves the network social-welfare.

We study multi-hop data-dissemination in a wireless network from one source to multiple nodes where some of the nodes of the network act as re-transmitting nodes and help the source in data dissemination. In this network, we study two scenarios; i) the transmitting nodes do not need an incentive for transmission and ii) they do need an incentive and are paid by their corresponding receiving nodes by virtual tokens. We investigate two problems; P1) network power minimization for the first scenario and P2) social cost minimization for the second scenario, defined as the total cost paid by the nodes of the network for receiving data. In this paper, to address P1 and P2, we propose centralized and decentralized approaches that determine which of the nodes of the network should act as transmitting nodes, find their transmit powers and their corresponding receiving nodes. For the sake of energy efficiency, in our model, we employ maximal-ratio combining (MRC) at the receivers so that a receiver can be served by multiple transmitters. The proposed decentralized approach is based on a non-cooperative cost-sharing game (CSG). In our proposed game, every receiving node chooses its respective transmitting nodes and consequently, a cost is assigned to it according to the power imposed on its chosen transmitting nodes. We discuss how the network is formed in a decentralized way, find the action of the nodes in the game and show that, despite being decentralized, the proposed game converges to a stable solution. To find the centralized global optimum, which is a benchmark to our decentralized approach, we use a mixed-integer-liner-program (MILP). Simulation results show that our proposed decentralized approach outperforms the conventional algorithms in terms of energy efficiency and social cost while it can address the need for an incentive for collaboration., Comment: 14 pages, 7 figures

Millimeter-wave (mmWave) communication plays a vital role to efficiently disseminate large volumes of data in beyond-5G networks. Unfortunately, the directionality of mmWave communication significantly complicates efficient data dissemination, particularly in multicasting, which is gaining more and more importance in emerging applications (e.g., V2X, public safety). While multicasting for systems operating at lower frequencies (i.e., sub-6GHz) has been extensively studied, they are sub-optimal for mmWave systems as mmWave has significantly different propagation characteristics, i.e., using the directional transmission to compensate for the high path loss and thus promoting spectrum sharing. In this paper, we propose novel multicast scheduling algorithms by jointly exploiting relaying and spatial sharing gains while aiming to minimize the multicast completion time. We first characterize the min-time mmWave multicasting problem with a comprehensive model and formulate it with an integer linear program (ILP). We further design a practical and scalable distributed algorithm named mmDiMu, based on gradually maximizing the transmission throughput over time. Finally, we carry out validation through extensive simulations in different scales and the results show that mmDiMu significantly outperforms conventional algorithms with around 95% reduction on multicast completion time., Comment: 11 pages

Andreas Baranowski,1 Ludwig Schlemmer,1 Katharina Förster,1 Ekaterina Slotina,1 Tim Mickan,1 Sebastian Truffel,1 Anja Klein,1 Stefan G Mattyasovszky,1 Alexander Hofmann,1,2 Ulrike Ritz,1 Pol M Rommens11Department of Orthopaedics and Traumatology, Biomatics Group, University Medical Centre of the Johannes Gutenberg University, Mainz, Germany; 2Department of Traumatology and Orthopaedics 1, Westpfalz-Medical Centre Kaiserslautern, Kaiserslautern, GermanyBackground: After a trauma, exuberant tissue healing with fibrosis of the joint capsule can lead to posttraumatic joint stiffness (PTJS). Losartan and atorvastatin have both shown their antifibrotic effects in different organ systems.Objective: The purpose of this study was the evaluation of the influence of losartan and atorvastatin on the early development of joint contracture. In addition to joint angles, the change in myofibroblast numbers and the distribution of bone sialoprotein (BSP) were assessed.Study design and methods: In this randomized and blinded experimental study with 24 rats, losartan and atorvastatin were compared to a placebo. After an initial joint injury, rat knees were immobilized with a Kirschner wire. Rats received either losartan, atorvastatin or a placebo orally daily. After 14 days, joint angle measurements and histological assessments were performed.Results: Losartan increased the length of the inferior joint capsule. Joint angle and other capsule length measurements did not reveal significant differences between both drugs and the placebo. At cellular level both losartan and atorvastatin reduced the total number of myofibroblasts (losartan: 191±77, atorvastatin: 98±58, placebo: 319±113 per counting field, p<0.01) and the percentage area of myofibroblasts (losartan: 2.8±1.8% [p<0.05], atorvastatin: 2.5±1.7% [p<0.01], vs control [6.4±4%], respectively). BSP was detectable in equivalent amounts in t

The increasing demand for diverse, mobile applications with various degrees of Quality of Service requirements meets the increasing elasticity of on-demand resource provisioning in virtualized cloud computing infrastructures. This paper provides a dynamic optimization approach for enhanced cloud infrastructures, based on the concept of cloudlets, which are located at hotspot areas throughout a metropolitan area. In conjunction, we consider classical remote data centers that are rigid with respect to QoS but provide nearly abundant computation resources. Given fluctuating user demands, we optimize the cloudlet placement over a finite time horizon from a cloud infrastructure provider's perspective. By the means of a custom tailed heuristic approach, we are able to reduce the computational effort compared to the exact approach by at least three orders of magnitude, while maintaining a high solution quality with a moderate cost increase of 5.8% or less.

We study multi-hop broadcast in wireless networks with one source node and multiple receiving nodes. The message flow from the source to the receivers can be modeled as a tree-graph, called broadcast-tree. The problem of finding the minimum-power broadcast-tree (MPBT) is NP-complete. Unlike most of the existing centralized approaches, we propose a decentralized algorithm, based on a non-cooperative cost-sharing game. In this game, every receiving node, as a player, chooses another node of the network as its respective transmitting node for receiving the message. Consequently, a cost is assigned to the receiving node based on the power imposed on its chosen transmitting node. In our model, the total required power at a transmitting node consists of (i) the transmit power and (ii) the circuitry power needed for communication hardware modules. We develop our algorithm using the marginal contribution (MC) cost-sharing scheme and show that the optimum broadcast-tree is always a Nash equilibrium (NE) of the game. Simulation results demonstrate that our proposed algorithm outperforms conventional algorithms for the MPBT problem. Besides, we show that the circuitry power, which is usually ignored by existing algorithms, significantly impacts the energy-efficiency of the network., Comment: 33 pages including references, figures, and tables

Diese Arbeit basiert auf einer explorierenden ethnografischen Forschung bei einer interdisziplinären Forschungsgruppe, die mathematische Modelle und Computersimulationen komplexer sozio-ökologischer Transformationen entwickelt. Die detaillierte empirische Beschreibung von Wissenspraxen in der Modellierung trägt zu ihrem grundlegenden Verständnis seitens der Sozialanthropologie und Wissenschaft- und Technikforschung bei. Dabei werden Konzepte wie Bifurkation, Irreversibiltätsgrade und Alignment (Ausrichtung) operationalisiert. Theoretisch Diskussionen betreffen die Kollektivität wissenschaftlicher Praxis, die Epistemologie von Computersimulationen, Materialität in Experimenten, Laborstudien und Ontologie. Modellkonstruktion und –läufe können als Prozess beschrieben werden, in dem Modellformate durch materiell-semiotische Praxen – vereinfachen, experimentieren, und visualisieren – iterativ und kontinuierlich aufeinander ausgerichtet werden. Die verschiedenen Praxen sind dabei mit bestimmten Formaten jeweils besonders verbunden. Das Konzept des Formats verdeutlicht dabei die verschiedenen Arten und Weisen in denen ein Modell in alltäglichen Praxen hervorgebracht wird: als Gleichungen und Computercode, als Visualisierung, Plot, Text, oder mentales Modell. Dabei trägt jedes Format etwas Eigenes zu dem Modell bei, in einer Art des produktiven nicht-ausgerichtet Seins. Schließlich werden den Modellen zugrunde liegende epistemologische und ontologische Annahmen über „das Soziale“, „das Natürliche“ und „das Hybride“ als separaten Sphären problematisiert – ein nötiger Schritt, um die drängenden hybriden, sozio-ökologischen Prozessen des Anthropozäns zu verstehen. Mit Bezug auf eine „Bayessche Anthropologie“ (Kockelman) wird versuchsweise eine alternative Rahmung dieser ontologischen Annahmen und der aus ihnen folgenden Probleme des Schlussfolgerns vorgeschlagen., This thesis builds on exploratory ethnographic research with an interdisciplinary research group that constructed mathematical models and computer simulations of complex socio-ecological transformations. In giving a detailed and empirically grounded account of modelling practices in a specific setting this work develops a basic understanding of modelling practices from the perspective of social anthropology and Science and Technology Studies. It operationalizes several concepts such as bifurcation, degree of irreversibility and alignment. Theoretical discussions concern collectivity in scientific practice, epistemology of computer simulations, materiality in experiments, laboratory studies and ontology. Building and running models can be described as a process of iteratively and continuously aligning model formats through material-semiotic practices of simplification, experimentation and visualization. These practices are each related to some model formats more than to others. The notion of “format” captures the different ways in which “the model” appears in everyday practices: as equations and code, but also as visualizations, plots of model output, descriptive text in a paper and as mental models. In a productive misalignment, each format contributes something particular to the model. Finally, this work problematizes underlying epistemological and ontological assumptions about “the social”, “the natural” and “the hybrid” as separate spheres, which is necessary in order to come to terms with hybrid, socio-ecological processes as they become more and more pressing in the Anthropocene. With reference to “Bayesian Anthropology” (Kockelman) it tentatively suggests an alternative framing of these ontological assumptions and the resulting problems of inference.

In mobile crowdsourcing (MCS), mobile users accomplish outsourced human intelligence tasks. MCS requires an appropriate task assignment strategy, since different workers may have different performance in terms of acceptance rate and quality. Task assignment is challenging, since a worker's performance (i) may fluctuate, depending on both the worker's current personal context and the task context, (ii) is not known a priori, but has to be learned over time. Moreover, learning context-specific worker performance requires access to context information, which may not be available at a central entity due to communication overhead or privacy concerns. Additionally, evaluating worker performance might require costly quality assessments. In this paper, we propose a context-aware hierarchical online learning algorithm addressing the problem of performance maximization in MCS. In our algorithm, a local controller (LC) in the mobile device of a worker regularly observes the worker's context, her/his decisions to accept or decline tasks and the quality in completing tasks. Based on these observations, the LC regularly estimates the worker's context-specific performance. The mobile crowdsourcing platform (MCSP) then selects workers based on performance estimates received from the LCs. This hierarchical approach enables the LCs to learn context-specific worker performance and it enables the MCSP to select suitable workers. In addition, our algorithm preserves worker context locally, and it keeps the number of required quality assessments low. We prove that our algorithm converges to the optimal task assignment strategy. Moreover, the algorithm outperforms simpler task assignment strategies in experiments based on synthetic and real data., Comment: 18 pages, 10 figures

We consider an energy harvesting (EH) transmitter communicating with a receiver through an EH relay. The harvested energy is used for data transmission, including the circuit energy consumption. As in practical scenarios, the system state, comprised by the harvested energy, battery levels, data buffer levels, and channel gains, is only partially observable by the EH nodes. Moreover, the EH nodes have only outdated knowledge regarding the channel gains for their own transmit channels. Our goal is to find distributed transmission policies aiming at maximizing the throughput. A channel predictor based on a Kalman filter is implemented in each EH node to estimate the current channel gain for its own channel. Furthermore, to overcome the partial observability of the system state, the EH nodes cooperate with each other to obtain information about their parameters during a signaling phase. We model the problem as a Markov game and propose a multi-agent reinforcement learning algorithm to find the transmission policies. We show the trade-off between the achievable throughput and the signaling required, and provide convergence guarantees for the proposed algorithm. Results show that even when the signaling overhead is taken into account, the proposed algorithm outperforms other approaches that do not consider cooperation.

Content caching in small base stations or wireless infostations is considered to be a suitable approach to improve the efficiency in wireless content delivery. Placing the optimal content into local caches is crucial due to storage limitations, but it requires knowledge about the content popularity distribution, which is often not available in advance. Moreover, local content popularity is subject to fluctuations since mobile users with different interests connect to the caching entity over time. Which content a user prefers may depend on the user's context. In this paper, we propose a novel algorithm for context-aware proactive caching. The algorithm learns context-specific content popularity online by regularly observing context information of connected users, updating the cache content and observing cache hits subsequently. We derive a sublinear regret bound, which characterizes the learning speed and proves that our algorithm converges to the optimal cache content placement strategy in terms of maximizing the number of cache hits. Furthermore, our algorithm supports service differentiation by allowing operators of caching entities to prioritize customer groups. Our numerical results confirm that our algorithm outperforms state-of-the-art algorithms in a real world data set, with an increase in the number of cache hits of at least 14%., Comment: 32 pages, 9 figures, to appear in IEEE Transactions on Wireless Communications, see http://doi.org/10.1109/TWC.2016.2636139

In this paper, we propose a novel algorithm to maximize the sum rate in interference-limited scenarios where each user decodes its own message with the presence of unknown interferences and noise considering the signal-to-interference-plus-noise-ratio. It is known that the problem of adapting the transmit and receive filters of the users to maximize the sum rate with a sum transmit power constraint is non-convex. Our novel approach is to formulate the sum rate maximization problem as an equivalent multi-convex optimization problem by adding two sets of auxiliary variables. An iterative algorithm which alternatingly adjusts the system variables and the auxiliary variables is proposed to solve the multi-convex optimization problem. The proposed algorithm is applied to a downlink cellular scenario consisting of several cells each of which contains a base station serving several mobile stations. We examine the two cases, with or without several half-duplex amplify-and-forward relays assisting the transmission. A sum power constraint at the base stations and a sum power constraint at the relays are assumed. Finally, we show that the proposed multi-convex formulation of the sum rate maximization problem is applicable to many other wireless systems in which the estimated data symbols are multi-affine functions of the system variables., Comment: 24 pages, 5 figures

A computational algorithm is presented for the Bayesian Cramer-Rao lower bound (BCRB) in filtering applications with measurement noise from mixture distributions with jump Markov switching structure. Such mixture distributions are common for radio propagation in mixed line- and non-line-of-sight environments. The newly derived BCRB is tighter than earlier more general bounds proposed in literature, and thus gives a more realistic bound on actual estimation performance. The resulting BCRB can be used to compute a lower bound on root mean square error of position estimates in a large class of radio localization applications. We illustrate this on an archetypical tracking application using a nearly constant velocity model and time of arrival observations.

[ANGLÈS] In this thesis, a scenario consisting of two-pairs of multi-antenna mobile stations performing bidirectional communications through a multi-antenna relay station is considered. First, different approaches for the relay station transceive filter design based on zero-forcing and the minimization of the mean square error are described. Second, a protocol to obtain channel state information (CSI) using pilot-assisted channel estimation in a multi-user two-way relaying network is introduced. In addition, an error model describing the influence of the imperfect transceive beamforming at the relay station and the imperfect self-interference cancellation at the mobile stations is presented. Finally, simulations are used to evaluate the impact of imperfect CSI on the achievable data rates., [CASTELLÀ] En esta tesis, se considera un escenario que consta de dos pares de estaciones móviles equipadas con múltiples antenas que realizan una comunicación bidireccional a través de una estación de relevo multi-antena. En primer lugar, se describen diferentes diseños de los filtros en la estación relieve, basados en los criterios del forzador de ceros y la minimización del error cuadrático medio. En segundo lugar, se introduce un protocolo para obtener la información del estado del canal (CSI) con la ayuda de señales piloto o referencia en una red Multi-user Two-Way relaying. Además, se presenta un modelo de error que describe la influencia de un Beamforming imperfecto en la estación relevo, así como de una imperfecta cancelación de la auto-interferencia en las estaciones móviles. Finalmente, se llevan a cabo simulaciones para evaluar el impacto de la CSI imperfecta sobre las tasas de datos alcanzables., [CATALÀ] En aquesta tesi, es considera un escenari que consta de dos parells d'estacions mòbils equipades amb múltiples antenes que realitzen una comunicació bidireccional a través d'una estació de relleu multiantena. En primer lloc, es descriuen diferents dissenys dels filtres a l'estació relleu, basats en els criteris del forçador de zeros i la minimització de l'error quadràtic mitjà. En segon lloc, s'introdueix un protocol per obtenir la informació de l'estat del canal (CSI) amb l'ajuda de senyals pilot o referència en una xarxa Multi-user Two-Way relaying. A més, es presenta un model d'error que descriu la influència d'un Beamforming imperfecte a l'estació relleu, així com d'una imperfecta cancel·lació de l'autointerferència en les estacions mòbils. Finalment, es duen a terme simulacions per avaluar l'impacte de la CSI imperfecta sobre els volums de dades assolibles.

GINSENG

In this paper we are concerned with nonlinear systems subject to a conditionally linear, Gaussian sub-structure. This structure is often exploited in high-dimensional state estimation problems using the marginalized (aka Rao-Blackwellized) particle filter. The main contribution in the present work is to show how an efficient filter can be derived by exploiting this structure within the auxiliary particle filter. Based on a multisensor aircraft tracking example, the superior performance of the proposed filter over conventional particle filtering approaches is demonstrated.

Die stetige Entwicklung intelligenter Sensorsysteme erlaubt die Automatisierung und Verbesserung komplexer Prozess- und Geschäftsentscheidungen in vielfältigen Anwendungsszenarien. Sensoren können zum Beispiel zur Bestimmung optimaler Wartungstermine oder zur Steuerung von Produktionslinien genutzt werden. Ein grundlegendes Problem bereitet dabei die Sensordatenqualität, die durch Umwelteinflüsse und Sensorausfälle beschränkt wird. Ziel der vorliegenden Arbeit ist die Entwicklung eines Datenqualitätsmodells, das Anwendungen und Datenkonsumenten Qualitätsinformationen für eine umfassende Bewertung unsicherer Sensordaten zur Verfügung stellt. Neben Datenstrukturen zur effizienten Datenqualitätsverwaltung in Datenströmen und Datenbanken wird eine umfassende Datenqualitätsalgebra zur Berechnung der Qualität von Datenverarbeitungsergebnissen vorgestellt. Darüber hinaus werden Methoden zur Datenqualitätsverbesserung entwickelt, die speziell auf die Anforderungen der Sensordatenverarbeitung angepasst sind. Die Arbeit wird durch Ansätze zur nutzerfreundlichen Datenqualitätsanfrage und -visualisierung vervollständigt.

The multiple access solution in an IMT-Advanced mobile radio system has to meet challenging requirements such as high throughput, low delays, high flexibility, good robustness, low computational complexity, and a high power efficiency, especially in the uplink. In this paper, a novel multiple access scheme for uplinks denoted as B-IFDMA is presented. We show that this scheme is able to provide equal or better error rate performance than the Single-Carrier Frequency Division Multiple Access (SCFDMA) schemes IFDMA and LFDMA, when considering realistic channel estimation performance at the receiver and no reliable channel state information at the transmitter. We also show that B-IFDMA provides better amplifier efficiency than OFDMA and can provide better end-to-end energy efficiency than IFDMA and LFDMA. Moreover, the scheme shows a promisingly high robustness to frequency-offsets and Doppler spread. Thus, this scheme can be regarded as a promising solution for the uplink of future mobile radio systems., Special Issue on 3GPP LTE and LTE Advanced

Sensors in smart-item environments capture data about product conditions and usage to support business decisions as well as production automation processes. A challenging issue in this application area is the restricted quality of sensor data due to limited sensor precision and sensor failures. Moreover, data stream processing to meet resource constraints in streaming environments introduces additional noise and decreases the data quality. In order to avoid wrong business decisions due to dirty data, quality characteristics have to be captured, processed, and provided to the respective business task. However, the issue of how to efficiently provide applications with information about data quality is still an open research problem. In this article, we address this problem by presenting a flexible model for the propagation and processing of data quality. The comprehensive analysis of common data stream processing operators and their impact on data quality allows a fruitful data evaluation and diminishes incorrect business decisions. Further, we propose the data quality model control to adapt the data quality granularity to the data stream interestingness.

Most of the currently deployed wireless sensor networks applications do not require performance control. The goal of the GINSENG project is sensor networks that meet application-specific performance targets, in particular with respect to latency and reliability. We present scenarios within the GALP oil re¿nery where the system will be deployed and some initial technical insights with respect to deterministic communication.

In this paper we are concerned with nonlinear systems subject to a conditionally linear, Gaussian sub-structure. This structure is often exploited in high-dimensional state estimation problems using the marginalized (aka Rao-Blackwellized) particle filter. The main contribution in the present work is to show how an efficient filter can be derived by exploiting this structure within the auxiliary particle filter. Based on a multisensor aircraft tracking example, the superior performance of the proposed filter over conventional particle filtering approaches is demonstrated., CADICS

In this paper we present the impact of acoustic resonances excited by electrostriction in BST thin-films on the Q-factor of a varactor in the GHz range. By changing the process-parameter substrate to target distance while sputtering the thin-films, we observe a change in the acoustic resonance frequencies. To characterize the material properties which determine the acoustic resonance frequencies a model based on a 1D acoustic transmission line is used. The extracted material properties results in a proportional dependency to the changed process parameter. For verification of the acoustic transmission line model 3D simulations have been performed which show good agreement to the line model for lower resonance frequencies, where the difference at higher frequencies becomes significant due to additional higher order modes.

In smart item environments, multitude of sensors are applied to capture data about product conditions and usage to guide business decisions as well as production automation processes. A big issue in this application area is posed by the restricted quality of sensor data due to limited sensor precision as well as sensor failures and malfunctions. Decisions derived on incorrect or misleading sensor data are likely to be faulty. The issue of how to efficiently provide applications with information about data quality (DQ) is still an open research problem. In this paper, we present a flexible model for the efficient transfer and management of data quality for streaming as well as static data. We propose a data stream metamodel to allow for the propagation of data quality from the sensors up to the respective business application without a significant overhead of data. Furthermore, we present the extension of the traditional RDBMS metamodel to permit the persistent storage of data quality information in a relational database. Finally, we demonstrate a data quality metadata mapping to close the gap between the streaming environment and the target database. Our solution maintains a flexible number of DQ dimensions and supports applications directly consuming streaming data or processing data filed in a persistent database.

Although approximate query processing is a prominent way to cope with the requirements of data analysis applications, current database systems do not provide integrated and comprehensive support for these techniques. To improve this situation, we propose an SQL extension---called SQL/S---for approximate query answering using random samples, and present a prototypical implementation within the engine of the open-source database system Derby---called Derby/S. Our approach significantly reduces the required expert knowledge by enabling the definition of samples in a declarative way; the choice of the specific sampling scheme and its parametrization is left to the system. SQL/S introduces new DDL commands to easily define and administrate random samples subject to a given set of optimization criteria. Derby/S automatically takes care of sample maintenance if the underlying dataset changes. Finally, samples are transparently used during query processing, and error bounds are provided. Our extensions do not affect traditional queries and provide the means to integrate sampling as a first-class citizen into a DBMS.

Das vorliegende Heft „Strövtåg i nordisk språkvetenskap“ enthält neun der Beiträge von Teilnehmerinnen und Teilnehmern des sechsten studentischen Kolloquiums in skandinavistischer Sprachwissenschaft. Als ein Ergebnis der Zusammenarbeit zwischen dem Institut für Nordische Sprachen der Universität Stockholm und dem Nordeuropa-Institut der Humboldt-Universität zu Berlin findet das Kolloquium seit 1996 jährlich statt. Es hat sich als ein Rahmen für die Förderung des wissenschaftlichen Nachwuchses bewährt. Austragungsort des nunmehr sechsten Treffens war Stockholm. Teilnehmerinnen und Teilnehmer dieses Kolloquiums waren Josefin Bloch, Charlotta Brylla, Sven Lange, Yvonne Lindqvist, Rune Palm (Stockholm) sowie Irina Enders, Piret Frädrich, Anja Klein, Kristina Kotcheva, Jurij Kusmenko und Michael Rießler (Berlin). Wir bedauern, die Beiträge von Piret Frädrich und Yvonne Lindqvist nicht einschließen zu können. Traditionell erscheinen die Beiträge des Colloquiums in den „Kleinen Schriften des Nordeuropa-Instituts“. Und – inzwischen fast ebenso traditionell – lädt auch dieses Heft ein zu einem nordistischen smörgåsbord. Die Artikel spiegeln dabei die große Bandbreite der linguistischen Forschung innerhalb beider Institute wider: Die Beiträge behandeln Themen aus der Lexikologie, Semantik, Morphologie sowie Kontaktlinguistik, wobei sowohl synchrone als auch diachrone Analysen präsentiert werden. Smaklig måltid!, Not Reviewed