Browsing by Department "KTH Royal Institute of Technology"
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Item Adhesion properties of regenerated lignocellulosic fibres towards poly(lactic acid) microspheres assessed by colloidal probe technique(2018-12-15) Colson, Jérôme; Pettersson, Torbjörn; Asaadi, Shirin; Sixta, Herbert; Nypelö, Tiina; Mautner, Andreas; Konnerth, Johannes; University of Natural Resources and Life Sciences; KTH Royal Institute of Technology; Department of Bioproducts and Biosystems; School of Chemical Engineering; Chalmers University of Technology; University of ViennaIn the field of polymer reinforcement, it is important to understand the interactions involved between the polymer matrix and the reinforcing component. This paper is a contribution to the fundamental understanding of the adhesion mechanisms involved in natural fibre reinforced composites. We report on the use of the colloidal probe technique for the assessment of the adhesion behaviour between poly(lactic acid) microspheres and embedded cross-sections of regenerated lignocellulosic fibres. These fibres consisted of tailored mixtures of cellulose, lignin and xylan, the amount of which was determined beforehand. The influence of the chemical composition of the fibres on the adhesion behaviour was studied in ambient air and in dry atmosphere. In ambient air, capillary forces resulted in larger adhesion between the sphere and the fibres. Changing the ambient medium to a dry nitrogen atmosphere allowed reducing the capillary forces, leading to a drop in the adhesion forces. Differences between fibres of distinct chemical compositions could be measured only on freshly cut surfaces. Moreover, the surface energy of the fibres was assessed by inverse gas chromatography. Compared to fibres containing solely cellulose, the presence of lignin and/or hemicellulose led to higher adhesion and lower surface energy, suggesting that these chemicals could serve as natural coupling agents between hydrophobic and hydrophilic components.Item Analysis of pandemic outdoor recreation and green infrastructure in Nordic cities to enhance urban resilience(Nature Publishing Group, 2022-10-03) Fagerholm, Nora; Samuelsson, Karl; Eilola, Salla; Giusti, Matteo; Hasanzadeh, Kamyar; Kajosaari, Anna; Koch, Daniel; Korpilo, Silviya; Kyttä, Marketta; Legeby, Ann; Liu, Yu; Præstholm, Søren; Raymond, Christopher; Rinne, Tiina; Olafsson, Anton Stahl; Barthel, Stephan; University of Turku; University of Gävle; Planning and Transportation; KTH Royal Institute of Technology; University of Helsinki; University of Copenhagen; Department of Built EnvironmentRecent empirical research has confirmed the importance of green infrastructure and outdoor recreation to urban people’s well-being during the COVID-19 pandemic. However, only a few studies provide cross-city analyses. We analyse outdoor recreation behaviour across four Nordic cities ranging from metropolitan areas to a middle-sized city. We collected map-based survey data from residents (n = 469–4992) in spring 2020 and spatially analyse green infrastructure near mapped outdoor recreation sites and respondents’ places of residence. Our statistical examination reveals how the interplay among access to green infrastructure across cities and at respondents’ residential location, together with respondents’ socio-demographic profiles and lockdown policies or pandemic restrictions, affects outdoor recreation behaviour. The results highlight that for pandemic resilience, the history of Nordic spatial planning is important. To support well-being in exceptional situations as well as in the long term, green infrastructure planning should prioritise nature wedges in and close to cities and support small-scale green infrastructure.Item Antichiral and nematicity-wave superconductivity(American Physical Society, 2019-06-27) Barkman, Mats; Zyuzin, Alexander A.; Babaev, Egor; KTH Royal Institute of Technology; Centre of Excellence in Quantum Technology, QTF; Department of Applied PhysicsLarkin-Ovchinnikov superconducting state has spontaneous modulation of Cooper pair density, while Fulde-Ferrell state has a spontaneous modulation in the phase of the order parameter. We report that a quasi-two-dimensional Dirac metal, under certain conditions has principally different inhomogeneous superconducting states that by contrast have spontaneous modulation in a submanifold of a multiple-symmetries-breaking order parameter. The first state we find can be viewed as a nematic superconductor where the nematicity vector spontaneously breaks rotational and translational symmetries due to spatial modulation. The other demonstrated state is a chiral superconductor with spontaneously broken time-reversal and translational symmetries. It is characterized by an order parameter, which forms a lattice pattern of alternating chiralities.Item Asymptotic Reverse-Waterfilling Characterization of Nonanticipative Rate Distortion Function of Vector-Valued Gauss-Markov Processes with MSE Distortion(2019-01-18) Stavrou, Photios A.; Charalambous, Themistoklis; Charalambous, Charalambos D.; Loyka, Sergey; Skoglund, Mikael; KTH Royal Institute of Technology; Department of Electrical Engineering and Automation; University of Cyprus; University of OttawaWe analyze the asymptotic nonanticipative rate distortion function (NRDF) of vector-valued Gauss-Markov processes subject to a mean-squared error (MSE) distortion function. We derive a parametric characterization in terms of a reverse-waterfilling algorithm, that requires the solution of a matrix Riccati algebraic equation (RAE). Further, we develop an algorithm reminiscent of the classical reverse-waterfilling algorithm that provides an upper bound to the optimal solution of the reverse-waterfilling optimization problem, and under certain cases, it operates at the NRDF. Moreover, using the characterization of the reverse-waterfilling algorithm, we derive the analytical solution of the NRDF, for a simple two-dimensional parallel Gauss-Markov process. The efficacy of our proposed algorithm is demonstrated via an example.Item Automated defect detection in digital radiography of aerospace welds using deep learning(SPRINGER HEIDELBERG, 2022-04) Tyystjärvi, Topias; Virkkunen, Iikka; Fridolf, Peter; Rosell, Anders; Barsoum, Zuheir; Trueflaw Ltd.; Department of Mechanical Engineering; GKN Aerospace Engine Systems; KTH Royal Institute of TechnologyAerospace welds are non-destructively evaluated (NDE) during manufacturing to identify defective parts that may pose structural risks, often using digital radiography. The analysis of these digital radiographs is time consuming and costly. Attempts to automate the analysis using conventional computer vision methods or shallow machine learning have not, thus far, provided performance equivalent to human inspectors due to the high reliability requirements and low contrast to noise ratio of the defects. Modern approaches based on deep learning have made considerable progress towards reliable automated analysis. However, limited data sets render current machine learning solutions insufficient for industrial use. Moreover, industrial acceptance would require performance demonstration using standard metrics in non-destructive evaluation, such as probability of detection (POD), which are not commonly used in previous studies. In this study, data augmentation with virtual flaws was used to overcome data scarcity, andcompared with conventional data augmentation. A semantic segmentation network was trained to find defects from computed radiography data of aerospace welds. Standard evaluation metrics in non-destructive testing were adopted for the comparison. Finally, the network was deployed as an inspector’s aid in a realistic environment to predict flaws from production radiographs. The network achieved high detection reliability and defect sizing performance, and an acceptable false call rate. Virtual flaw augmentation was found to significantly improve performance, especially for limited data set sizes, and for underrepresented flaw types even at large data sets. The deployed prototype was found to be easy to use indicating readiness for industry adoption.Item Building performance indicators and IEQ assessment procedure for the next generation of EPC-s(EDP SCIENCES, 2021-03-29) Võsa, Karl Villem; Ferrantelli, Andrea; Tzanev, Dragomir; Simeonov, Kamen; Carnero, Pablo; Espigares, Carlos; Escudero, Miriam Navarro; Quiles, Pedro Vicente; Andrieu, Thibault; Battezzati, Florian; Cordeiro, Katia; Allard, Francis; Magyar, Zoltan; Turturiello, Giusy; Piterà, Luca Alberto; D'Oca, Simona; Willems, Eric; Veld Op 'T, Peter; Litiu, Andrei Vladimir; Lungu, Cǎtǎlin; Catalina, Tiberiu; Kurnitski, Jarek; Tallinn University of Technology; Center For Energy Efficiency EnEffect; Valencia Institute of Building; Spanish Technical Association of Air Conditioning and Refrigeration; Plateform technologique batiment durable; Comfort Consulting Ltd.; Associazione Italiana Condizionamento dell'Aria Riscaldamento Refrigerazione; Huygen Engineers and Consultants; KTH Royal Institute of Technology; Asociatia Inginerilor de Instalatii din Romania; Department of Civil EngineeringIn the current implementation of EPC-s, the assessment focus is purely on the energy consumption data. For the next generation of EPC-s, new performance indicators are proposed to address relevant building performance aspects, such as sustainability, productivity and market value. These indicators would enable evidence-based decision-making processes and facilitate the delivery of renovation triggers. Within the EPC framework, the problem is not the availability of such performance indicators, but the assessment effort required. Only easily available data can justifiably be introduced to bulk EPC-s, either as direct complementary input or as a performance indicator. Availability of such data was analysed from case studies that included EPC-s from 11 EU member states, mainly non-residential buildings. Analysed data included relevant HVAC information such as ventilation air flows, heating and cooling set-points and installed power, but also output data, such as EPC classes, net and primary energy need and GHG emissions. Based on our findings, we outlined two different development paths-one for existing buildings and one for new buildings and major renovations. Two categories of complementary indicators to energy are proposed-IEQ and power indicators.Item Causal analysis, Correlation-Response, and Dynamic cavity(2016-04-06) Aurell, Erik; Ferraro, Gino Del; Department of Computer Science; KTH Royal Institute of Technology; Department of Applied PhysicsThe purpose of this note is to point out analogies between causal analysis in statistics and the correlation-response theory in statistical physics. It is further shown that for some systems the dynamic cavity offers a way to compute the stationary state of a non-equilibrium process effectively, which could then be taken an alternative starting point of causal analysis.Item Cavity master equation for the continuous time dynamics of discrete-spin models(2017-05-12) Aurell, E.; Del Ferraro, Gino; Dominguez, E.; Mulet, R.; Centre of Excellence in Computational Inference, COIN; KTH Royal Institute of Technology; University of Havana; Department of Applied Physics; Department of Computer ScienceWe present an alternate method to close the master equation representing the continuous time dynamics of interacting Ising spins. The method makes use of the theory of random point processes to derive a master equation for local conditional probabilities. We analytically test our solution studying two known cases, the dynamics of the mean-field ferromagnet and the dynamics of the one-dimensional Ising system. We present numerical results comparing our predictions with Monte Carlo simulations in three different models on random graphs with finite connectivity: the Ising ferromagnet, the random field Ising model, and the Viana-Bray spin-glass model.Item The chaos in calibrating crop models(ELSEVIER SCI LTD, 2021-11) Wallach, Daniel; Palosuo, Taru; Thorburn, Peter; Hochman, Zvi; Gourdain, Emmanuelle; Andrianasolo, Fety; Asseng, Senthold; Basso, Bruno; Buis, Samuel; Crout, Neil; Dibari, Camilla; Dumont, Benjamin; Ferrise, Roberto; Gaiser, Thomas; Garcia, Cecile; Gayler, Sebastian; Ghahramani, Afshin; Hiremath, Santosh; Hoek, Steven; Horan, Heidi; Hoogenboom, Gerrit; Huang, Mingxia; Jabloun, Mohamed; Jansson, Per Erik; Jing, Qi; Justes, Eric; Kersebaum, Kurt Christian; Klosterhalfen, Anne; Launay, Marie; Lewan, Elisabet; Luo, Qunying; Maestrini, Bernardo; Mielenz, Henrike; Moriondo, Marco; Nariman Zadeh, Hasti; Padovan, Gloria; Olesen, Jørgen Eivind; Poyda, Arne; Priesack, Eckart; Pullens, Johannes Wilhelmus Maria; Qian, Budong; Schütze, Niels; Shelia, Vakhtang; Souissi, Amir; Specka, Xenia; Srivastava, Amit Kumar; Stella, Tommaso; Streck, Thilo; Trombi, Giacomo; Wallor, Evelyn; Wang, Jing; Weber, Tobias K.D.; Weihermüller, Lutz; de Wit, Allard; Wöhling, Thomas; Xiao, Liujun; Zhao, Chuang; Zhu, Yan; Seidel, Sabine J.; INRAE; Luke Natural Resources Institute Finland; CSIRO; Arvalis Institut du Végétal; Technical University of Munich; Michigan State University; University of Nottingham; University of Florence; University of Liege; University of Bonn; University of Hohenheim; University of Southern Queensland; Department of Computer Science; Wageningen University and Research Centre; University of Florida; China Agricultural University; KTH Royal Institute of Technology; Ottawa Research and Development Centre; Centre de coopération internationale en recherche agronomique pour le développement (CIRAD); Leibniz Centre for Agricultural Landscape Research; Jülich Research Centre; Swedish University of Agricultural Sciences; Hillridge Technology Pty Ltd; Institute for Crop and Soil Science; CNR-ENEA-EURATOM Association; Aarhus University; Kiel University; Helmholtz Zentrum München - German Research Center for Environmental Health; Technische Universität Dresden; University of Carthage; Nanjing Agricultural UniversityCalibration, the estimation of model parameters based on fitting the model to experimental data, is among the first steps in many applications of process-based models and has an important impact on simulated values. We propose a novel method of developing guidelines for calibration of process-based models, based on development of recommendations for calibration of the phenology component of crop models. The approach was based on a multi-model study, where all teams were provided with the same data and asked to return simulations for the same conditions. All teams were asked to document in detail their calibration approach, including choices with respect to criteria for best parameters, choice of parameters to estimate and software. Based on an analysis of the advantages and disadvantages of the various choices, we propose calibration recommendations that cover a comprehensive list of decisions and that are based on actual practices.Item Characterization of silver nanowire layers in the terahertz frequency range(MDPI AG, 2021-12-01) Przewłoka, Aleksandra; Smirnov, Serguei; Nefedova, Irina; Krajewska, Aleksandra; Nefedov, Igor S.; Demchenko, Petr S.; Zykov, Dmitry V.; Chebotarev, Valentin S.; But, Dmytro B.; Stelmaszczyk, Kamil; Dub, Maksym; Zasada, Dariusz; Lisauskas, Alvydas; Oberhammer, Joachim; Khodzitsky, Mikhail K.; Knap, Wojciech; Lioubtchenko, Dmitri; Military University of Technology Warsaw; KTH Royal Institute of Technology; Department of Electronics and Nanoengineering; Institute of High Pressure Physics; Saratov State University; St. Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO); Institute of Semiconductor Physics NASU; Vilnius UniversityThin layers of silver nanowires are commonly studied for transparent electronics. However, reports of their terahertz (THz) properties are scarce. Here, we present the electrical and optical properties of thin silver nanowire layers with increasing densities at THz frequencies. We demonstrate that the absorbance, transmittance and reflectance of the metal nanowire layers in the frequency range of 0.2 THz to 1.3 THz is non-monotonic and depends on the nanowire dimensions and filling factor. We also present and validate a theoretical approach describing well the experimental results and allowing the fitting of the THz response of the nanowire layers by a Drude–Smith model of conductivity. Our results pave the way toward the application of silver nanowires as a prospective material for transparent and conductive coatings, and printable antennas operating in the terahertz range—significant for future wireless communication devices.Item Cometary plasma science: Open science questions for future space missions(Springer Netherlands, 2021) Goetz, C.; Gunell, H.; Volwerk, M.; Beth, A.; Eriksson, A.; Galand, M.; Henri, P.; Nilsson, H.; Wedlund, C. Simon; Alho, M.; Andersson, L.; Andre, N.; De Keyser, J.; Deca, J.; Ge, Y.; Glassmeier, K. H.; Hajra, R.; Karlsson, T.; Kasahara, S.; Kolmasova, I.; LLera, K.; Madanian, H.; Mann, I.; Mazelle, C.; Odelstad, E.; Plaschke, F.; Rubin, M.; Sanchez-Cano, B.; Snodgrass, C.; Vigren, E.; Technical University of Braunschweig; Umeå University; Austrian Academy of Sciences; Imperial College London; Uppsala University; CNRS; Esa Kallio Group; University of Colorado Boulder; IRAP; Royal Belgian Institute for Space Aeronomy; Chinese Academy of Sciences; National Atmospheric Research Laboratory; KTH Royal Institute of Technology; University of Tokyo; Czech Academy of Sciences; Southwest Research Institute; UiT The Arctic University of Norway; University of Bern; University of Leicester; University of Edinburgh; Department of Electronics and NanoengineeringComets hold the key to the understanding of our Solar System, its formation and its evolution, and to the fundamental plasma processes at work both in it and beyond it. A comet nucleus emits gas as it is heated by the sunlight. The gas forms the coma, where it is ionised, becomes a plasma, and eventually interacts with the solar wind. Besides these neutral and ionised gases, the coma also contains dust grains, released from the comet nucleus. As a cometary atmosphere develops when the comet travels through the Solar System, large-scale structures, such as the plasma boundaries, develop and disappear, while at planets such large-scale structures are only accessible in their fully grown, quasi-steady state. In situ measurements at comets enable us to learn both how such large-scale structures are formed or reformed and how small-scale processes in the plasma affect the formation and properties of these large scale structures. Furthermore, a comet goes through a wide range of parameter regimes during its life cycle, where either collisional processes, involving neutrals and charged particles, or collisionless processes are at play, and might even compete in complicated transitional regimes. Thus a comet presents a unique opportunity to study this parameter space, from an asteroid-like to a Mars- and Venus-like interaction. The Rosetta mission and previous fast flybys of comets have together made many new discoveries, but the most important breakthroughs in the understanding of cometary plasmas are yet to come. The Comet Interceptor mission will provide a sample of multi-point measurements at a comet, setting the stage for a multi-spacecraft mission to accompany a comet on its journey through the Solar System. This White Paper, submitted in response to the European Space Agency’s Voyage 2050 call, reviews the present-day knowledge of cometary plasmas, discusses the many questions that remain unanswered, and outlines a multi-spacecraft European Space Agency mission to accompany a comet that will answer these questionsby combining both multi-spacecraft observations and a rendezvous mission, and at the same time advance our understanding of fundamental plasma physics and its role in planetary systems.Item Compressible flow simulations of voiced speech using rigid vocal tract geometries acquired by MRI(ASA/CSSA/SSSA, 2019-04-01) Schickhofer, Lukas; Malinen, Jarmo; Mihaescu, Mihai; KTH Royal Institute of Technology; Department of Mathematics and Systems AnalysisVoiced speech consists mainly of the source signal that is frequency weighted by the acoustic filtering of the upper airways and vortex-induced sound through perturbation in the flow field. This study investigates the flow instabilities leading to vortex shedding and the importance of coherent structures in the supraglottal region downstream of the vocal folds for the far-field sound signal. Large eddy simulations of the compressible airflow through the glottal constriction are performed in realistic geometries obtained from three-dimensional magnetic resonance imaging data. Intermittent flow separation through the glottis is shown to introduce unsteady surface pressure through impingement of vortices. Additionally, dominant flow instabilities develop in the shear layer associated with the glottal jet. The aerodynamic perturbations in the near field and the acoustic signal in the far field are examined by means of spatial and temporal Fourier analysis. Furthermore, the acoustic sources due to the unsteady supraglottal flow are identified with the aid of surface spectra, and critical regions of amplification of the dominant frequencies of the investigated vowel geometries are identified.Item Concise and interpretable multi-label rule sets(Springer, 2023-12) Ciaperoni, Martino; Xiao, Han; Gionis, Aristides; Department of Computer Science; Helsinki Institute for Information Technology (HIIT); KTH Royal Institute of Technology; Department of Computer ScienceMulti-label classification is becoming increasingly ubiquitous, but not much attention has been paid to interpretability. In this paper, we develop a multi-label classifier that can be represented as a concise set of simple “if-then” rules, and thus, it offers better interpretability compared to black-box models. Notably, our method is able to find a small set of relevant patterns that lead to accurate multi-label classification, while existing rule-based classifiers are myopic and wasteful in searching rules, requiring a large number of rules to achieve high accuracy. In particular, we formulate the problem of choosing multi-label rules to maximize a target function, which considers not only discrimination ability with respect to labels, but also diversity. Accounting for diversity helps to avoid redundancy, and thus, to control the number of rules in the solution set. To tackle the said maximization problem, we propose a 2-approximation algorithm, which circumvents the exponential-size search space of rulesusing a novel technique to sample highly discriminative and diverse rules. In addition to our theoretical analysis, we provide a thorough experimental evaluation and a case study, which indicate that our approach offers a trade-off between predictive performance and interpretability that is unmatched in previous work.Item Dense Subset Sum may be the hardest(2016-02-01) Austrin, Per; Kaski, Petteri; Koivisto, Mikko; Nederlof, Jesper; KTH Royal Institute of Technology; Department of Computer Science; Helsinki Institute for Information Technology HIIT; Eindhoven University of Technology; Ollinger, Nicolas; Vollmer, HeribertThe Subset Sum problem asks whether a given set of n positive integers contains a subset of elements that sum up to a given target t. It is an outstanding open question whether the O∗(2n/2)-time algorithm for Subset Sum by Horowitz and Sahni [J. ACM 1974] can be beaten in the worst-case setting by a "truly faster", O∗(2(0.5-δ)n)-time algorithm, with some constant δ > 0. Continuing an earlier work [STACS 2015], we study Subset Sum parameterized by the maximum bin size β, defined as the largest number of subsets of the n input integers that yield the same sum. For every ∈ > 0 we give a truly faster algorithm for instances with β ≤ 2(0.5-∈)n, as well as instances with β ≥ 20.661n. Consequently, we also obtain a characterization in terms of the popular density parameter n/log2 t: if all instances of density at least 1.003 admit a truly faster algorithm, then so does every instance. This goes against the current intuition that instances of density 1 are the hardest, and therefore is a step toward answering the open question in the affirmative. Our results stem from a novel combinatorial analysis of mixings of earlier algorithms for Subset Sum and a study of an extremal question in additive combinatorics connected to the problem of Uniquely Decodable Code Pairs in information theory.Item Determination and Evaluation of Landslide-Prone Regions of Isparta (Turkey): An Urban Planning View(MDPI AG, 2023-10) Keçik, Aynur Uluç; Çiftçi, Canan; Gülcen Eren, Şirin; Diş, Aslı Tepecik; Rizzo, Agatino; Süleyman Demirel University; KTH Royal Institute of Technology; Department of ArchitectureLandslides represent a significant hazard affecting human life and property and threaten the sustainability of human settlements. They are among the most critical threats after earthquakes in Turkey. In 2020, 107 landslide events occurred in Turkey. Implementing proper policies, strategies, and tools for landslide risk mitigation remains challenging for urban planning institutions. In the plan preparation phase, urban planners and plan-making authorities, agencies, or institutions may overlook landslide risks due to a lack of data or related studies. Therefore, this article aims to develop a novel spatial analysis for identifying landslide-prone areas at the provincial level from an urban planning perspective. The analysis is compared to the approved upper-scale plan, and the results are used to build a more robust understanding of landslide risks for sustainable urban development. Isparta Province is selected as the study area, as it has active landslide areas. The methods used include a literature survey including internet sources, newspapers, plans, articles, and other research projects and a case study utilizing a GIS spatial analysis. The spatial analysis using GIS is based on three landslide inventories currently available in Turkey. This spatial analysis is developed to determine landslide-prone regions by considering thematic layers, triggering factors, and vulnerability inputs. As a result of this analysis, five landslide-prone areas in Isparta Province are determined. When these regions are compared to the upper-scale plan that covers the province, it is found that land use and planning decisions have neglected landslide risks, and urban areas are at high landslide risk. Several specific principles and strategies, such as a spatial inventory database and an integrated planning approach including landslide-prone areas, are stated with a reliable spatial analysis to assess landslide-prone areas on a regional scale, which can be applied later in any city and region of Turkey.Item A Digitalized Property Formation Process?: Comparative study of legal qualifications in Finland and Sweden(2020) Ekbäck, Peter; Riekkinen, Kirsikka; KTH Royal Institute of Technology; Real Estate; Department of Built Environment; Hepperle, Erwin; Paulsson, Jenny; Maliene, Vida; Mansberger, Reinfried; Auzins, Armands; Valciukiene, JolantaDigitalization and automation of different elements of the land development process are frequent and highlighted phenomena in both Finland and Sweden. Several projects focus on standardization of spatial data, electronic transactions of real property, physical plans in digital format, etc. The focus of most projects is on technical and organizational aspects of these potential developments. Legal features do occur, but are mostly devoted to protection of personal data and privacy. The emphasis in this study is on legal structures and relationships in real property law, applicable in property formation processes. The objective is to compare the legal system for property formation in Finland and Sweden concerning potentials and obstructions for digi-talization and automation of the legal process for examination and adjudication. Apart from some minor obstacles, the findings indicate that the Swedish legal system for property for-mation, to a larger degree, suffers from a complex interconnection between the legislation on real property formation and the public regulation of permitted land uses. This intercon-nection is not present in all processes in the Finnish system, which will simplify the road towards digitalization of the property formation process in Finland.Item Discovering conflicting groups in signed networks(Morgan Kaufmann Publishers, 2020) Tzeng, Ruo-Chun; Ordozgoiti Rubio, Bruno; Gionis, Aristides; KTH Royal Institute of Technology; Adj. Prof. Gionis Aris group; Department of Computer ScienceSigned networks are graphs where edges are annotated with a positive or negative sign, indicating whether an edge interaction is friendly or antagonistic. Signed networks can be used to study a variety of social phenomena, such as mining polarized discussions in social media, or modeling relations of trust and distrust in online review platforms. In this paper we study the problem of detecting k conflicting groups in a signed network. Our premise is that each group is positively connected internally and negatively connected with the other k−1 groups. An important aspect of our formulation is that we are not searching for a complete partition of the signed network, instead, we allow other nodes to be neutral with respect to the conflict structure we are searching. As a result, the problem we tackle differs from previously studied problems, such as correlation clustering and k-way partitioning. To solve the conflicting-group discovery problem, we derive a novel formulation in which each conflicting group is naturally characterized by the solution to the maximum discrete Rayleigh's quotient (\maxdrq) problem. We present two spectral methods for finding approximate solutions to the \maxdrq problem, which we analyze theoretically. Our experimental evaluation shows that, compared to state-of-the-art baselines, our methods find solutions of higher quality, are faster, and recover ground truth conflicting groups with higher accuracy.Item A Distributed Mode Selection Scheme for Full-Duplex Device-to-Device Communication(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019-10-01) Penda, Demia Della; Wichman, Risto; Charalambous, Themistoklis; Fodor, Gabor; Johansson, Mikael; KTH Royal Institute of Technology; Risto Wichman Group; Distributed and Networked Control Systems; Department of Electrical Engineering and AutomationNetworks with device-to-device (D2D) technology allow for two possible communication modes: traditional communication via the base station, and direct communication between the users. Recent studies show that in-band full-duplex (IBFD) operations can be advantageously combined with D2D communication to improve the spectral efficiency. However, no algorithms for selecting the communication mode of mobile users in IBFD networks have yet appeared in the literature. In this paper, we design a distributed mode selection scheme for users in D2D-enabled IBFD networks. The proposed scheme maximizes the users' prob-ability of successful communication by leveraging only existing signaling mechanisms.Item District heating driven membrane distillation for advanced flue gas condensate treatment in combined heat and power plants(ELSEVIER SCI LTD, 2021-04-10) Noor, Imtisal-e−; Martin, Andrew; Dahl, Olli; KTH Royal Institute of Technology; Department of Bioproducts and BiosystemsThis investigation involves recent work on developing membrane distillation (MD) as a novel separation technology for flue gas condensate treatment in combined heat and power (CHP) applications. Flue gas condensate samples were obtained from municipal solid waste and bio-fuel fired CHP facilities and were tested in laboratory-scale air gap MD equipment. Separation efficiencies and other water quality parameters were measured, and the outcomes show that high-quality clean condensate can be recovered, i.e., conductivity <5 mS/m; total organic carbon <2 ppm; total hardness <0.15 °dH; pH ∼7.5; and turbidity <1 FNU. Strict discharge limits for cadmium could not be achieved in all trials. This aspect is examined in further detail with respect to potential mechanisms attributed to the non-ideal separation of contaminants below the parts per billion limit. Beyond this, an industrial scale district heating driven membrane distillation system was designed and analyzed. The estimated annual thermal energy demand was 88 GWh for treating 500,000 m3 of flue gas condensate per year, with an expected clean condensate cost of around 2.6 $/m3.Item Dynamic capacity sharing based energy saving market for MNOs(2017-12) Hossain, M.M.; Cavdar, Cicek; Jäntti, Riku; KTH Royal Institute of Technology; Department of Communications and NetworkingAs the larger share of total energy consumed by mobile network operators (MNOs) is wasted in order to ensure coverage, three to five MNOs covering the same geographical area results in enormous energy waste. In order to cater for the data tsunami with almost zero marginal revenue, required densification of cells are not sustainable from both Capex and Opex perspective. Even with densification of networks, it is hard to satisfy the performance requirement of the cell edge users due to interference. However, the performance can be upgraded as well as energy can be saved by the offloading of the cell edge users to other MNOs if regulator and MNOs resort to appropriate mechanism. In our previous work, we proposed a double auction based energy saving market mechanism where MNOs participate in bidding to share coverage and capacity in order to save energy, especially during low to medium load. Unlike previous work, in this paper we use this mechanism that involve cell level bidding, i.e., cells bid for each user which not only allows total offloading of the cells at the low load but also offloading of cell edge users among the MNOs during high load. As a result, the energy saving potential becomes very high also at high load conditions along with improvement in performance of cell edge users.
