2019 - Repozytorium publikacji - Politechnika Gdańska

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Things You Might Not Know about the k-Nearest Neighbors Algorithm
- Aleksandra Karpus
- Marta Raczyńska
- Adam Przybyłek
2019
Recommender Systems aim at suggesting potentially interesting items to a user. The most common kind of Recommender Systems is Collaborative Filtering which follows an intuition that users who liked the same things in the past, are more likely to be interested in the same things in the future. One of Collaborative Filtering methods is the k Nearest Neighbors algorithm which finds k users who are the most similar to an active user and then it computes recommendations based on the subset of users. The main aim of this paper is to compare two implementations of k Nearest Neighbors algorithm, i.e. from Mahout and LensKit libraries, as well as six similarity measures. We investigate how implementation differences between libraries influence optimal neighborhood size k and prediction error. We also show that measures like F1-score and nDCG are not always a good choice for choosing the best neighborhood size k. Finally, we compare different similarity measures according to the average time of generating recommendations and the prediction error.
Threat intelligence platform for the energy sector
- Rafał Leszczyna
- Michał Wróbel
2019 Pełny tekst SOFTWARE-PRACTICE & EXPERIENCE
In recent years, critical infrastructures and power systems in particular have been subjected to sophisticated cyberthreats, including targeted attacks and advanced persistent threats. A promising response to this challenging situation is building up enhanced threat intelligence that interlinks information sharing and fine-grained situation awareness. In this paper a framework which integrates all levels of threat intelligence i.e. strategic, tactical, operational and technical is presented. The platform implements the centralised model of information exchange with peer-to-peer interactions between partners as an option. Several supportive solutions were introduced, including anonymity mechanisms or data processing and correlation algorithms. A data model that enables communication of cyberincident information, both in natural language and machine-readable formats was defined. Similarly, security requirements for critical components were devised. A pilot implementation of the platform was developed and deployed in the operational environment, which enabled practical evaluation of the design. Also the security of the anonymity architecture was analysed.
Three Editions of Inter-University Studies on Space and Satellite Technology. Candidate and/vs. Graduate, a Case Study
- Zbigniew Łubniewski
- Przemysław Falkowski-Gilski
- Marek Chodnicki
- Andrzej Stepnowski
2019 Pełny tekst
Currently, there is a growing demand for most up-to-date academic courses that will fulfil the needs of modern society. Each candidate has to make choices and judgements carefully, in order to succeed on the market. This is particularly important when educating individuals with different backgrounds, especially on an inter-university course in the field of space sciences and technology. This paper describes a case study carried out on a group of candidates and graduates from different editions of Space and Satellite Technologies interdisciplinary master studies at Gdansk University of Technology as well as two maritime universities in Gdynia. The education process itself is realized in cooperation with business partners. The paper provides both qualitative and quantitative data, considering the whole group and particular individuals. In addition, some examples of individual achievements of outstanding students are presented.
TIME- AND FREQUENCY-DOMAIN QUASI-2D SMALL-SIGNAL MOSFET MODELS
- Wiesław Kordalski
- Tomasz Stefański
- Damian Trofimowicz
2019 Pełny tekst
A novel approach to small-signal MOSFET modeling is presented in this book. As a result, time- and frequency-domain physics-based quasi-2D NQS four-terminal small-signal MOSFET models are proposed. The time-domain model provides the background to a novel DIBL-included quasi‑2D NQS four-terminal frequency-domain small-signal MOSFET model. Parameters and electrical quantities of the frequency-domain model are described by explicit functions. The models take into account: the velocity saturation effect of carriers in the channel, the dependence of the mobility on the electric field, the electrical coupling between the perturbed charge in the channel and the gate and the body, local variations in the channel thickness, and the DIBL effect. Derivation of the models is based on an analysis of a current density vector field and the following newly introduced phenomena: gradual channel detachment effect (GCDE), channel thickness modulation effect CTME), and channel-lengthening effect (CLE). A set of partial differential equations for the new physics-based small-signal MOSFET models is derived. The set consists of a quasi-2D small-signal continuity equation, a quasi-2D small-signal Poisson’s equation, and a quasi-2D small-signal transport equation. All the equations give a mathematical description of the behavior of the carriers in the channel and charges in the gate and the body. A set of supplementary equations for coupling and non-capacitive displacement currents in the MOSFET under dynamic operation is also derived. Based on the quasi‑2D dc MOSFET representation, a useful formula for the gate-to-body capacitance Cgb is derived, and some rules dealing with channel-to-gate and channel-to-body coupling currents are established. Only reciprocal capacitances are present in these models. The quasi-2D approach to the MOSFET modeling shows that two types of waves can propagate from the source to the drain, i.e., a longitudinal wave of disturbance in the carrier density and a transverse wave of disturbance in the channel thickness. It is shown that the magnitudes of both gate and body transadmittances are decreasing functions of frequency. The new frequency-domain small-signal MOSFET model has been successfully verified experimentally up to 30 GHz. The model parameters have realistic values. The new model is valid from zero Hz to well above the cut-off frequency fT. Each model parameter describes some physical phenomenon.
Time domain model of the resonance-based electromagnetic pulses emission system
- Mikołaj Nowak
- Kazimierz Jakubiuk
- Daniel Kowalak
- Mirosław Wołoszyn
2019 Pełny tekst ITM Web of Conferences
In the literature, the emission properties of the electromagnetic field pulse systems based on high voltage antennas (HVR) have been widely described. In order to increase the emission efficiency by extending duration and increasing amplitude of the impulse it is possible to use a resonance system tuned to the parameters of the signal shaped in the pulse forming circuit. The synthesis of a time-domain simulation model of a complex electromagnetic pulses emission system and its verification by experimental research has been presented in this paper.
Time travel without paradoxes: Ring resonator as a universal paradigm for looped quantum evolutions
- Marek Czachor
2019 Pełny tekst PHYSICS LETTERS A
A ring resonator involves a scattering process where a part of the output is fed again into the input. The same formal structure is encountered in the problem of time travel in a neighborhood of a closed timelike curve (CTC). We know how to describe quantum optics of ring resonators, and the resulting description agrees with experiment. We can apply the same formal strategy to any looped quantum evolution, in particular to the time travel. The argument is in its essence a topological one and thus does not refer to any concrete geometry. It is shown that the resulting paradigm automatically removes logical inconsistencies associated with chronology protection, provided all input-output relations are given by unitary maps. Examples of elementary loops and a two-loop time machine illustrate the construction. In order to apply the formalism to quantum computation one has to describe multi-qubit systems interacting via CTC-based quantum gates. This is achieved by second quantization of loops. An example of a multiparticle system, with oscillators interacting via a time machine, is explicitly calculated. However, the resulting treatment of CTCs is not equivalent to the one proposed by Deutsch in his classic paper [1].
Time-current tripping curves of arc fault detection devices
- Stanisław Czapp
2019 Automatyka Elektryka Zakłócenia
Tripping curves of arc fault detection devices, in accordance with PN-EN 62606 “General requirements for arc fault detection devices” have been presented in the paper. Consequently the most fundamental differences in arc fault detection devices tripping compared to circuit-breakers and residual current devices have been indicated.
TiO2 nanotube arrays-based reactor for photocatalytic oxidation of parabens mixtures in ultrapure water: Effects of photocatalyst properties, operational parameters and light source
- J Gomes
- J Lincho
- M Domingues
- M Gmurek
- Paweł Mazierski
- Adriana Zaleska-Medynska
- Tomasz Klimczuk
- R. M. Quinta-Ferreira
- R. C. Martins
- Marta Gmurek
2019 SCIENCE OF THE TOTAL ENVIRONMENT
Self-organized TiO2 nanotubes as immobilized photocatalysts were evaluated in detail for the photocatalytic degradation of parabens mixtures from ultrapure water. This kind of approach can be a very suitable option for emerging contaminants degradation considering the possibility of the catalyst reuse and recovery which will be simpler than when catalytic powders are used. The anodization method was applied for the TiO2 nanotubes production under different preparation voltages (20, 30 and 40 V). These preparation conditions are important on the morphological characteristics of nanotubes such as length, as well as internal and external diameters. The photocatalytic efficiency was dependent on the materials preparation voltages. The photocatalytic oxidation was evaluated using two different irradiation sources, namely UVA and sunlight. These irradiation sources were evaluated for parabens mixture degradation using different number of catalytic plates. The increase of the number of plates improved the parabens degradation possibly due to the availability of more active sites which can be relevant for the hydroxyl radical's generation. The effect of the reactor design was also evaluated using sunlight irradiation. The configuration, position and solar concentrators can be important for the performance of degradation. The mechanism of degradation was analysed through by-products formation under sunlight irradiation. The main responsible for parabens degradation was hydroxyl radical. Decarboxylation, dealkylation and hydroxylation seem to be the most important reactional steps for the mixture decontamination.
Titania Nanofiber Scaffolds with Enhanced Biointegration Activity—Preliminary In Vitro Studies
- Michalina Ehlert
- Katarzyna Roszek
- Tomasz Jędrzejewski
- Michał Bartmański
- Aleksandra Radtke
2019 Pełny tekst INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
The increasing need for novel bone replacement materials has been driving numerous studies on modifying their surface to stimulate osteogenic cells expansion and to accelerate bone tissue regeneration. The goal of the presented study was to optimize the production of titania-based bioactive materials with high porosity and defined nanostructure, which supports the cell viability and growth. We have chosen to our experiments TiO2 nanofibers, produced by chemical oxidation of Ti6Al4V alloy. Fibrous nanocoatings were characterized structurally (X-ray diraction (XRD)) and morphologically (scanning electron microscopy (SEM)). The wettability of the coatings and their mechanical properties were also evaluated. We have investigated the direct influence of the modified titanium alloy surfaces on the survival and proliferation of mesenchymal stem cells derived from adipose tissue (ADSCs). In parallel, proliferation of bone tissue cells—human osteoblasts MG-63 and connective tissue cells - mouse fibroblasts L929, as well as cell viability in co-cultures (osteoblasts/ADSCs and fibroblasts/ADSCs has been studied. The results of our experiments proved that among all tested nanofibrous coatings, the amorphous titania-based ones were the most optimal scaolds for the integration and proliferation of ADSCs, fibroblasts, and osteoblasts. Thus, we postulated these scaolds to have the osteopromotional potential. However, from the co-culture experiments it can be concluded that ADSCs have the ability to functionalize the initially unfavorable surface, and make it suitable for more specialized and demanding cells.
Titania Nanotubes/Hydroxyapatite Nanocomposites Produced with the Use of the Atomic Layer Deposition Technique: Estimation of Bioactivity and Nanomechanical Properties
- Aleksandra Radtke
- Michalina Ehlert
- Tomasz Jędrzejewski
- Beata Sadowska
- Marzena Więckowska-Szakiel
- Jani Holopainen
- Mikko Ritala
- Markku Leskelä
- Michał Bartmański
- Marek Szkodo
- Piotr Piszczek
2019 Pełny tekst Nanomaterials
Titanium dioxide nanotubes/hydroxyapatite nanocomposites were produced on a titanium alloy (Ti6Al4V/TNT/HA) and studied as a biocompatible coating for an implant surface modification. As a novel approach for this type of nanocomposite fabrication, the atomic layer deposition (ALD) method with an extremely low number of cycles was used to enrich titania nanotubes (TNT) with a very thin hydroxyapatite coating. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for determination of the structure and the surface morphology of the fabricated nanocoatings. The biointegration activity of the layers was estimated based on fibroblasts’ proliferation on the TNT/HA surface. The antibacterial activity was determined by analyzing the ability of the layers to inhibit bacterial colonization and biofilm formation. Mechanical properties of the Ti6Al4V/TNT/HA samples were estimated by measuring the hardness, Young’s module, and susceptibility to scratching. The results revealed that the nanoporous titanium alloy coatings enriched with a very thin hydroxyapatite layer may be a promising way to achieve the desired balance
Titanium Scaffolds – Hopes and Limitations
- Magda Dziaduszewska
- Andrzej Zieliński
2019 Pełny tekst American Journal of Biomedical Science & Research
The state-of-art on titanium scaffolds is briefly reviewed. The real hopes from medicine associated with scaffolds are indicated. The limitations of different scaffolds associated with their mechanical, chemical and biological properties are discussed. The great importance of titanium scaffolds is demonstrated as the materials of high biocompatibility and corrosion resistance, fair mechanical properties and important biological behaviour.
To meet or to connect? Face-to-face contacts vs ICT in cluster organisations
- Anna Lis
- Adrian Lis
2019 Pełny tekst Engineering Management in Production and Services
The main purpose of the paper is to explore how cluster organisations (COs) take advantage of direct (F2F) and indirect (ICT) contacts in fulfilling their main roles. The paper addresses the research question: “How important are Information and Communication Technologies at each level of advancement of cluster cooperation?” The research was conducted in 2016 in four purposefully selected cluster organisations representing metal and ICT industry. The basic method of data collection was an in-depth individual interview. The authors applied the qualitative content analysis as the procedure to analyse the interviews. The research sample comprised of 30 cluster members. The research was based on an original theoretical concept referring to the trajectory of the development of cooperative relationships in cluster organisations. Four levels of development of cluster cooperation as well as three main roles of cluster organisation were distinguished. At each level, COs play one of three identified roles: a direct resource supplier (providing access to resources), a broker (facilitating resource exchanges) and an integrator (integrating into different dimensions), which gives a total of 12 specific roles. The research has shown that both direct and indirect contacts were significant both in fulfilling the roles assigned to the cluster organisations as well as in developing the cluster cooperation. It has been also observed that ICT importance was slightly different at each level of a CO’s development. Only in one identified role (at level II: Process integrator) the importance of ICT tools was at least as great as F2F contacts. The research study contributes to the literature which refers to the question of face-to-face contacts established in geographical proximity versus the ones set up by using Information and Communication Technologies in cluster organisations. It was noticed that even though ICT plays a significant role in the functioning of COs, they cannot replace face-to-face contacts. They can only be their important complement at every level of CO development. There are also some limitations connected with the qualitative approach, which does not allow the author to generalise the findings. The first limitation is the small research sample. The second limitation is the subjectivity characterising qualitative research, mainly due to the applied techniques of data collection and analysis.
Topological Model of an Electromagnetic Environment Inside a Ship for Electromagnetic Compatibility (EMC) Analysis
- Ryszard Katulski
- Rafał Namiotko
2019 Pełny tekst Applied Sciences-Basel
The mutual electromagnetic (EM) interactions between electrical and electronic devices in a segmented space, such as a ship's environment, ared described. Firstly, the topological structure of a ship's segmented internal environment, which consists of many electrical screening walls (shielding planes), is presented. Then, taking into account the ship's topological structure, a general description of the EM disturbance distribution, called the ship's topological electromagnetic compatibility (EMC) model, is formulated using matrix expressions. This model includes EM disturbances that radiate from a ship's own internal sources (located under the main deck) and/or external sources (located above the main deck), and/or that radiate from extraneous external sources, i.e. from other ships and/or aircrafts. A description of the model for an example EMC ship scenario and a partial verification of its measurements are shown and discussed. Finally, a discussion of the usefulness of the proposed model in an analysis of a ship,s EMC conditions concludes of the study.
Towards a Smart Sustainable City Roadmap
- Gabriela Viale Pereira
- Elsa Estevez
- Robert Krimmer
- Marijn Janssen
- Tomasz Janowski
2019 Pełny tekst
This workshop of the CAP4CITY (Erasmus+ Strengthening Governance Capacity for Smart Sustainable Cities) project is to promote and stimulate the discussion and networking in the area of Digital Government. Smart Sustainable Cities and related concepts of Digital, Intelligent and Smart Cities represent a progression of how cities around the world apply digital technology to serve their populations, pursue sustainable socio-economic development, and transform themselves in the process, and require strong capacity for public governance in the digital world. In order to identify the gaps concerning missing knowledge and training needs in this area we propose to validate a Smart Sustainable Cities roadmap through a scenario-building approach.
Towards Digital Anti-Corruption Typology for Public Service Delivery
- Fredrick Mutungi
- Rehema Baguma
- Tomasz Janowski
2019 Pełny tekst
Digital anti-corruption refers to a family of digital technology tools that are used to fight corruption. Many such tools have not performed well in practice due to their non-alignment with forms of corruption they are supposed to fight against and persistence of corruption-enabling conditions. The aim of this paper is to contribute to filling this gap by offering a typology of digital anti-corruption in public service delivery that can be used to decide what digital measures should be applied to fight against specific forms of corruption or address specific corruption-enabling conditions. The typology also highlights that digital technology can both assist in corrupt practices e.g. theft of digital personal records, and aid the fight against corruption e.g. mobile channels to report incidents of corruption, automated audits of transaction records to uncover fraudulent payments, or service automation to replace discretionary decision making by public officials with rule-based automated decision-making. The typology is grounded in research and policy literature, validated using real-life examples from East Africa, and instantiated to the public health sector. The paper concludes by presenting a range of scenarios for using the typology and offers some recommendations for public authorities.
Towards Experience-Based Smart Product Design for Industry 4.0
- Muhammad Bilal
- Syed Imran
- Cesar Sanin
- Edward Szczerbicki
2019 Pełny tekst CYBERNETICS AND SYSTEMS
This paper presents the concept of smart virtual product development (SVPD) system capable of supporting industrial product development process. It enhances the decision making process during different stages and activities involved in product development i.e. product design, manufacturing, and its inspection planning. The enhancement is achieved by using the explicit knowledge of formal past decision events, which are captured, stored, and recalled in the form of set of experiences. The basic description and principle of the approach are introduced first, and then the porotype version of the system is developed and tested. Working of the design knowledge management module of the system is demonstrated with the case study, which verifies the feasibility of the proposed approach. The presented system successfully supports smart product design and it can play a vital role in Industry 4.0 development.
Towards Knowledge Formalization and Sharing in a Cognitive Vision Platform for Hazard Control (CVP-HC)
- Caterine De
- Cesar Sanin
- Edward Szczerbicki
2019
Hazards are present in all workplaces and can result in serious injuries, short and long-term illnesses, or death. In this context, management of safety is essential to ensure the occupational health of workers. Aiming to assist the safety manage-ment process, especially in industrial environments, a Cognitive Vision Platform for Hazard Control (CVP-HC) has been proposed. The CVP-HC is a scalable yet adaptable system capable of working in a variety of video analysis scenarios (generality) whilst meeting specific safety requirements of companies by modify-ing its behavior accordingly. To meet generality, the platform is based on the Set of Experience Knowledge Structure (SOEKS) and Decisional DNA (DDNA). To ensure scalability and adaptability the publishing/subscribe interaction scheme (a loosely coupled communication model) is used over the Robot Operating Sys-tem (ROS) framework.
Towards semantic-rich word embeddings
- Grzegorz Beringer
- Mateusz Jabłoński
- Piotr Januszewski
- Andrzej Sobecki
- Julian Szymański
2019 Pełny tekst Annals of Computer Science and Information Systems
In recent years, word embeddings have been shown to improve the performance in NLP tasks such as syntactic parsing or sentiment analysis. While useful, they are problematic in representing ambiguous words with multiple meanings, since they keep a single representation for each word in the vocabulary. Constructing separate embeddings for meanings of ambiguous words could be useful for solving the Word Sense Disambiguation (WSD) task. In this work, we present how a word embeddings averagebased method can be used to produce semantic-rich meaning embeddings. We also open-source a WSD dataset that was created for the purpose of evaluating methods presented in this research.
Towards understanding the role of peroxide initiators on compatibilization efficiency of thermoplastic elastomers highly filled with reclaimed GTR
- Aleksander Hejna
- Marek Klein
- Mohammad Saeb
- Krzysztof Formela
2019 POLYMER TESTING
Thermoplastic elastomers based on recycled high density polyethylene (rHDPE) and styrene-butadiene-styrene (SBS) block copolymer were highly filled with reclaimed ground tire rubber (RR). The impact of various organic peroxides (dicumyl peroxide (DCP), benzoyl peroxide (BP) and di-tert-butyl peroxide (DB)), applied as free-radical initiators, on the processing, structure and performance properties of rHDPE/SBS/RR blends was investigated. It was found that, regardless of peroxide type, their application resulted in decrease of the sol fraction, which indicated increase of cross-link density. This was confirmed by the reduced flowability of material, expressed by noticeable changes in melt flow index that decreased in the order BP > DB > DCP. The most beneficial changes were observed for application of DCP, which led to 80% increase of tensile strength, 40% reduction of permanent set and 25% increase of hardness. Moreover, thermal stability of analyzed thermoplastic elastomers was significantly improved with onset of thermal decomposition shifted by over 40 °C. Scanning electron microscope images revealed enhancement of interactions at the interphase due to increased cross-link density, which had direct influence on the mechanical properties of thermoplastic elastomers. The results showed that that processing and mechanical performance of obtained thermoplastic elastomers can be easily engineered by suitable selection of organic peroxide.
Toxoplasma gondii Tetravalent Chimeric Proteins as Novel Antigens for Detection of Specific Immunoglobulin G in Sera of Small Ruminants
- Lucyna Holec-Gąsior
- Bartłomiej Ferra
- Weronika Grąźlewska
2019 Pełny tekst Animals
The detection of Toxoplasma gondii infection in small ruminants has important significance for public health and veterinary medicine. This study, for the first time, describes the reactivity of four tetravalent chimeric proteins (AMA1N-SAG2-GRA1-ROP1, AMA1C-SAG2-GRA1-ROP1, AMA1-SAG2-GRA1-ROP1, and SAG2-GRA1-ROP1-GRA2) containing immunodominant regions from the AMA1 (apical membrane antigen 1), SAG2 (surface antigen 2), GRA1 (dense granule antigen 1), GRA2 (dense granule antigen 2), and ROP1 (rhoptry antigen 1) with specific IgG antibodies from the sera of small ruminants with the use of an indirect enzyme-linked immunosorbent assay (ELISA). The reactivity of individual chimeric antigens was analyzed in relation to the results obtained in IgG ELISA based on a Toxoplasma lysate antigen (TLA). All chimeric proteins were characterized by high specificity (between 96.39% to 100%), whereas the sensitivity of the IgG ELISAs was variable (between 78.49% and 96.77%). The highest sensitivity was observed in the IgG ELISA test based on the AMA1-SAG2-GRA1-ROP1. These data demonstrate that this chimeric protein can be a promising serodiagnostic tool for T. gondii infection in small ruminants.