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Peak-to-Average Ratio Reduction for MIMO and Multi-user OFDM Systems
No full textA major drawback of MIMO-OFDM systems is its high Peak-to-Average Ratio (PAR). The signal is clipped when the peak values are higher than the linear operation range of non-linear devices. In order to avoid clipping the signal above a certain threshold, measure must be taken to limit all peaks crossing the threshold value. In this thesis, we therefore investigate and address the PAR problem of different MIMO-OFDM scenarios and provide countermeasures to limit the peak excursions in MIMO-OFDM systems.
First, we extend the Tone-Reservation algorithm for PAR reduction of MIMO-OFDM systems. For a point-to-point scenario, a spiky function is generated on the weakest eigenchannel not suited for data transmission. This spiky function is then iteratively used for PAR reduction of the transmit signal. For a multi-user broadcast scenario, the spiky function is generated on a small percent of tones reserved on all spatial dimensions, in the conventional manner. This spiky function is then used to limit the peak excursions of the transmit signal.
Second, we introduce a novel Least-Squares iterative PAR reduction algorithm for MIMO-OFDM
scenarios. For a P2P scenario, the weakest eigenchannel is used to approximate the peak excursions on the remaining spatial dimensions in a least-squares fashion. This model function is then added to the transmit signal for PAR reduction. The algorithm is thoroughly investigated in terms of the capacity loss and the mean power increase due to the modeled function. Moreover, for a broadcast scenario, we consider that one user is inactive and the channel associated to it is not used. This inactive channel is then used to approximate and model the peak excursions on the remaining spatial dimensions in the similar fashion.
In a further part of this thesis, we consider PAR reduction using Trellis Shaping for single antenna systems. We concatenate an optimized irregular LDPC code with Trellis Shaping for PAR reduction
A Theory and Practice of Coexistence: Improving Coexistence Orientation through Mixed-Model Encounters between Jews and Palestinians in Israel
No full textPlanned encounters between members of groups in conflict aiming to contribute to reconciliation have long been practiced in regions of intractable conflicts. However, there is an evident scarcity of rigorous experimental studies, and there have been almost no assessment of the durability of the effects after participants return to their communities. Addressing these deficits, this thesis examines the effectiveness of a two-day encounter program for Jewish and Palestinian youth in Israel. This program uses a mixed model approach by integrating techniques focusing on harmony and coexistence, with ones emphasizing differences and disagreements. To properly compensate for selection bias, this quasi-experimental study utilized the Solomon Four Group Design, with delayed posttests to assess intermediate- and long-term effects (total N = 938). It assessed the impact of the encounters on Coexistence Orientation (CO), a hierarchical index with emotional, cognitive, motivational, behavioral, and political domains of attitudes that are associated with coexistence, a minimally acceptable state of post-conflict positive relations. The results indicate that the encounters had a significant positive effect on CO in both groups. The effects were stronger for participants who exhibited low motivation to take part in encounters at baseline, compared to participants who were highly motivated for the activity. The analysis of pretesting effects indicated possible reactive but not interactive effects, largely ruling out the possibility of pretest sensitization. Finally, there was limited evidence that the encounters have durable effect on the examined variables, and most effects completely faded in the range of one year after the encounter.Considering these results, it is recommended that practitioners use various means to increase hope among participants, and create opportunities for follow-up activities that may increase the sustainability and durability of revealed positive effects
Interarts Aesthetics in Latin-American Avant-Garde. On Creative Constructionism in Xul Solar, Vicente Huidobro and Joaquín Torres-García.
No full textThe present investigation traces the theoretical and productive interrelations between the Latin-American writers-artists Xul Solar (1887 – 1963), Vicente Huidobro (1893 - 1948) and Joaquín Torres-García (1874 -1949). This work demonstrates the existence of a Creative- Creationist aesthetic shared by the three authors based on a) the recuperation of the rational elements found in Pre-Colombian art, b) a common theory of inter-artistic translatability, c) the fusion of the processes of creation and construction and d) a transformation of the concept of writing derived from interartistic exploration in the fields of painting and poetry.
By exploring elements that have been left unattended in previous works concerned with the Latin-American Avant-Garde, this investigation proposes an alternative to the mapping of the continent as divided in open and closed regions, offering a less antagonistic panorama of the cultural and artistic interchanges that took place in the region during the first half of the twentieth century. The programs of social and spiritual transformation, as well as the structured and anti-colonialist recuperation of Mesoamerican and South-American cosmology found in the work of these authors, provide a renewed and more comprehensive image of the formal, programmatic and spiritual direction taken by Latin-American Avant-Garde.
Furthermore, by a close comparative reading of key works which had not been interpreted with the adequate tools of analysis until now, such as San Signos and Grafias from Xul Solar, the Poèmes Peints of Vicente Huidobro and the rustic illustrated books of Torres- García and his constructive ink drawings, it will be demonstrated that the Creative-Constructive aesthetic is a revaluation of articulated and visual languages, embracing new systems of writing which anticipate conceptualism and post-structural theory
Rare earth elements and Yttrium (REY) in natural waters and the potential impact of polar rivers on the REY distribution in seawater
No full textRivers are the major source of many trace elements, such as rare earth elements (REE; or REY if yttrium is included) to the oceans. While many studies focus on the REY behavior and distribution in natural terrestrial waters, little is known about the impact of glacial meltwaters on the seawater distribution of particle-reactive elements, such as REY, due to (i) a practically non-existing data base with regard to REY distribution in glacial meltwaters and (ii) a lack of knowledge about the behavior of those REY that are truly dissolved and those that are bound to inorganic (nano-) particles during estuarine mixing of polar rivers with seawater.
This thesis is structured as a compilation of seven independently published and submitted manuscripts and manuscripts in preparation, covering the topics of REY behavior and distribution in arctic rivers from southern Iceland and western Greenland, and the arctic estuarine mixing between glacial-fed river waters and seawater. Furthermore, the interplay between surface-scavenging and solution-complexation of REY in presence of the siderophore Desferrioxamine B (DFOB) is studied in two different incubation experiments. The first incubation experiments were performed to investigate the impact of DFOB on the mobilization of REE from volcanic ash particles into river water from Iceland and the second incubation experiments studied the competitive complexing behavior of surface-complexation of REY onto manganese (hydr-)oxides and of solution-complexation of DFOB-REY complexes. Additionally, a study comparing natural and anthropogenically influenced aquatic systems is included and is focusing on the strong increase of anthropogenic gadolinium levels in tap water of Berlin, Germany, from 2009 to 2012
Adaptive Predictive Control by Open-Loop- Feedback-Optimal Controller for Cultivation Processes
No full textProcess description, optimization and control using mathematical models are an innovative and efficient approach in the process development. And the development of mathematical models is also time and cost consuming.The use of a highly adaptive general model for bio-processes can reduce the time for modeldevelopment. Because it takes only the adjustment of model parameters to achieve the adaptation of a process model to a new organism or product. Development of a general process model with high adaptability was one of the main goals of "ProTool". A general process model is not bound to a certain cell line and microorganism, but adapts itself to a variety of organisms and different scenarios. This process model will be used for data interpretation, process monitoring, recipe optimization and the verification of control concepts as well as the basis of a virtual bioreactor.
Correspondingly, the development of an advanced controller to achieve an optimized process
control adapting the general model (named as the open-loop-feedback-optimal(OLFO) controller) was another main goal of "ProTool", which is also the core task of my dissertation. A structured model consisting of four biomass compartments is working as the general model which is able to describe the cultivation of different organisms. Based on this model, online parameter identification is carried out periodically with the actual process data collected from the plant and laboratory analysis. And the new estimated process parameters and the updated process state variables are used in calculating an optimal control profile. The model parameters are updated at desired period using the extended database to reduce the plant model mismatch to improve the performance of the optimizer.
This work outlines the advantages to apply the OLFO controller in fermentation processes. The results obtained in both simulation and real processes show the efficiency of the OLFO controller for online fermentation process control
Information Causality in the Prediction of Stochastic Networks
No full textNumerous real world systems of major interest are modeled as sets of analog continuous stochastic processes with delayed and varying causal relationships.
Yet, studying their dynamics becomes often difficult, as it involves sensing, understanding and predicting a system of inter-dependent random variables in a given context and over time.
In the present work we develop a systematic, rigorous and efficient framework to structurally characterize and forecast the future states of such systems in a scalable manner. In particular we use an improved maximum spanning tree method to capture the causal dependence structure based on directed information theory. To this end we address the sparsity problem in information causality estimation in general, and directed information in particular and propose a new method that identifies and eliminates redundant calculations. To predict the behavior of child nodes based on their inferred causal parents we use a linear model aiming to capture the closest approximation of functional relations. Further dependencies are accounted for using causal conditional information and potential links that improve child nodes estimation are added. The result is a comprehensive and scalable approach to understanding and predicting large sets of inter-dependent narrowband processes, as we demonstrate on several synthetic datasets
Electronic properties of low-dimensional materials under mechanical deformation
No full textLow-dimensional materials utilized in nanoelectronics, inevitably undergo structural deformations during the device manufacturing processes. These mechanical deformations can significantly modify the intrinsic electronic properties of the materials. Therefore, the optimal design of electronic devices at nanometric scale demands a deep understanding of the effects of mechanical deformations on the electric structure of the nanosystems. In addition, the interplay between mechanical and electronic properties can advantageously be used to tune the material characteristics for optimizing the device performance.
In this work, mechanical deformations were deliberately introduced to low-dimensional materials as a strategy to tune their electronic properties. In particular, elastic deformations of carbon nanotubes, graphene, metal organic frameworks (MOFs), and SiGe thin films were simulated using quantum mechanical methods. The results from these simulations indicate that the elastic indentation applied to metallic carbon nanotubes and graphene do not change their metallic character, whereas in the case of semiconducting carbon tubes, the same type of deformation reduces significantly their intrinsic band gap, by up to 60%. Nevertheless, no transport channels for the conductance are opened due to these reversible structural distortions. Further, applying uniaxial strain to a particular type of metal organic frameworks, namely MOF-2, results in a decrease in the effective mass of the charge carriers, which can be understood as an enhancement of their charge carrier mobility. In the case of SiGe monolayers, elastic strain induces a band inversion between the valence and conduction bands, causing a nontrivial topological phase transition
Visual Analysis of Multi-run Spatio-temporal Simulation Data
No full textMulti-run simulations are widely used to investigate how the simulated processes evolve depending on varying initial conditions in different fields of sciences, such as astrophysics, ballistics, and oceanography. This kind of experiments is typically executed using high-performance computers and generates a large amount of data to analyze. The main goals of this work are an efficient visualization of multi-run time-varying spatial data, pairwise and ensemble-wise comparison of simulations, as well as simulation feature detection and investigation, and exploration and classification of simulation results. Also, this work aims generalization of developing approaches to be applicable for data of any spatial configuration and of a multi-field nature. This work introduces a number of approaches and tools, which can significantly improve an analysis of multi-run time-varying spatial data on all data aggregation levels from a field distribution of an single time frame up to overview of the whole simulations ensemble. To investigate a single-field spatial data a new isocontour based similarity measure is introduced. For an interactive visualization and for detailed comparative analysis of multi-field spatial data algorithms for a splat-based progressive rendering of continuous scatterplots are developed. For a comparative visualization of multi-run and multi-field spatio-temporal simulation data a new visualization technique, called multi-run similarity plots, is introduced. For an overview of a multi-run and multi-field spatio-temporal simulation data on a highest aggregation levels two histogram based visualizations are proposed. Finally, a scheme of a top-down analysis of a multi-run spatio-temporal simulation data is introduced. In this work an application on the real world data sets, results of a user study and evaluation by the domain experts, as well as detailed discussions about scalability of the methods, their efficiency and restrictions, are presented
Managing Sino-European FDI: Perceptions of psychic distance and culture
No full textThis PhD thesis investigates the concept of "psychic distance" in international business contexts and looks at managers' perceptions of psychic distance and culture between home and host country. Psychic distance is defined by international business scholars as the existing perceived distance between the characteristics of the firm's home country and the characteristics of the firm's host country. Psychic distance is operationalized as a multi-dimensional construct including "culture" and other eleven dimensions (Child et al., 2009). Building on Child et al.'s (2009) studies, this thesis focuses on psychic distance and culture in the context of green tech Sino-European FDI. It is part of a wider EU Marie Curie project on Partnering Opportunities between Europe and China in the Renewable Energy and Environmental industry (POREEN). This thesis is structured in four papers and preceded by an introduction.
As about culture, main findings show that managers' perceptions vary over time, between the pre- and post-market entry operations. With respect to psychic distance, by conducting a "static" and a "dynamic" analysis this paper shows the (mis)match of managers' perceptions in time between these two operations. Findings also show that the cultural dimension is the most important one within the psychic distance construct, according to both European and Chinese managers.
Contributions and research implications are illustrated in the conclusion before the Appendix, which contains the material used to collect data
Polynomial endomorphisms having coefficients in finitely generated Z-algebras.
No full textThis thesis is divided into five chapters. Except for the last chapter we focused on prime characteristic. Let k be a field. Understanding the automorphism group of affine k-varieties, in particular the automorphism group GA_n(k) of affine n-space k^n, is a key problem in algebraic geometry. In order to understand GA_n(C) it turns out to be useful (due to reduction-mod-p techniques) to understand GA_n(F_q), which is an important object in itself. In chapter 2 we first show that a large class of potentially non-tame maps in GA_n(F_q) are inside the profinite tame group PTA_n(F_q) (i.e. are "profinitely tame"). Then we analyze the group of invertible elements in PMA_n(F_q), as this is the "world" in which PGA_n(F_q) and PTA_n(F_q) live in. We also study the "distance" between PTA_n(F_q) and PGA_n(F_q).
In chapter 3 we mainly give a new formulation of the Jacobian conjecture (denoted by curly JC). We do some explicit examples in order to point out that JC might do what it claims. We show that this new formulation of the Jacobian conjecture coincides with the regular formulation in case the field is of characteristic zero. We also present two surjectivity conjectures. We use them to conjecturally prove various basic properties of JC.
In chapter 4 we unite both the Gupta and Asanuma result for the counter example to cancellation for affine 3-space in one result.
Let R be a ring containing the field of rationals Q and define the group SA_n(A)={F\in GA_n(A) | detJac(F)=1}. Van den Essen, Maubach and Vénéreau prove that the map SA_n([R[x])--->SA_n(R[x]/(x^m)) is surjective. This result has strong consequences in three papers by Van den Essen etal, Adrien Dubouloz etal and Joost Berson. In chapter 5 we extend this result