2020 - Repozytorium publikacji - Politechnika Gdańska

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Smart Services for Improving eCommerce
- Andrzej Sobecki
- Julian Szymański
- Henryk Krawczyk
- Higinio Mora-Mora
- David Gil
2020
The level of customer support provided by the existing eCom-merce solutions assumes that the person using the functionality of theshop has sufficient knowledge to decide on the purchase transaction. Alow conversion rate indicates that customers are more likely to seekknowledge about the particular product than finalize the transaction.This is facilitated by the continuous development of customers’ digi-tal competencies, resulting in the increasing popularity of web servicesenabling the exchange of information, e.g. through social networks. Cur-rently the user act with eCommerce platform like a source of informa-tion. At the same time, he or she usually use more than one source ofinformation e.g., web portals, social networks, etc. The existing onlineshops seem unsuited to these trends because they remain simple tradingplatforms without integration with external web services and sources ofknowledge. New categories of smart services are suggested, enabling thenewly implemented eCommerce network platform to enhance the offeredknowledge and reduce the abandonment of the platform by the user. Ourempirical studies show an increase in the conversion rate in the case ofshops which increased the level of customer support using the proposedmodel of integration.
SMART SHOP SERVICES FOR BUILDING CUSTOMER-ORIENTED SCENARIOS
- Henryk Krawczyk
- Andrzej Sobecki
2020 Pełny tekst TASK Quarterly
The shops of today mostly support the customer by offering him or her products based on basic relationships between products viewed or ordered by users with similar tastes. This common approach may fail in many cases especially when the user does not have sufficient knowledge about the market, or when he or she wants to build a set of products in more than one shop. New categories of smart shop services are proposed in order to execute such customer-oriented scenarios where recommended products do meet mutual dependencies with products previously ordered by the customer. An attempt is made to collect additional information about the behavior of users (from past and current contexts) and represent it in a targeted graph called the customer-oriented scenario. Four types of such scenarios are distinguished depending on how many shops have been visited by the user before buying the expected products and how many products the user wants to buy. Moreover, the proposed scenario model provides the possibility of showing which services had been used by the user before the selection was made. Customer-oriented scenarios may be created post factum based on event data logs or before the user will use the shop, which means that it can be arranged which information, knowledge sources (internal or external), products or categories should be suggested in some context of the user’s decision. The possibility of leveraging additional smart services into a traditional trading platform may help users, especially when they want to implement a complex scenario and order many products with mutual dependencies or in a situation when the user wants to understand the market before buying something. Using internal and external services allows creating a network for distributing knowledge focused on the actual customer context in a shop.
Smart Virtual Product Development (SVPD): Experience Based Product Development System for Industry 4.0
- Muhammad Bilal
- Cesar Sanin
- Edward Szczerbicki
2020
This chapter presents the concept of smart virtual product development (SVPD) system capable of supporting industrial product development. It enhances the decision making process during various activities involved in product development i.e. product design, manufacturing, and inspection planning. This is achieved by using the explicit knowledge of past formal decision events, which are captured, stored, and recalled in the form of set of experiences (SOEs). The basic description and principles of approach are introduced first, and then the prototype version of the system is developed and tested. Working of the design knowledge management module and manufacturing capability analysis and process planning module of the system are demonstrated with the case study, which verifies the feasibility of the proposed approach. The presented system successfully supports smart product design and manufacturing, and it can play a vital role in Industry 4.0.
Smart Virtual Product Development (SVPD) System to Support Product Inspection Planning in Industry 4.0
- Muhammad Ahmed
- Cesar Sanin
- Edward Szczerbicki
2020 Pełny tekst Procedia Computer Science
This paper presents the idea of supporting product inspection planning process during the early stages of product life cycle for the experts working on product development. Aim of this research is to assist a collaborative product development process by using Smart Virtual Product Development (SVPD) system, which is based on Set of Experience Knowledge Structure (SOEKS) and Decisional DNA (DDNA). The proposed system is developed to support three key aspects of industrial product development i.e. design, manufacturing, and product inspection. Therefore, it comprises of three main modules; design knowledge management (DKM), manufacturing capability and process planning (MCAPP), and product inspection planning (PIP). It collects, stores, and uses experiential knowledge from formal decisional events in the form of set of experience (SOE). This research enlightens the working mechanism of the PIP module, and shows how experiential knowledge related to product inspection can be used during the early stages of product development process. This experiential knowledge is extracted and stored from similar products having some common features and functions. First, the basic description and principles of the approach are introduced, then the prototype version of the system is developed and tested for product inspection planning (PIP) module for the case study, which verifies the feasibility of the proposed approach. The presented system successfully supports smart manufacturing and can play a vital role in Industry 4.0.
Social benefits valuation of hosting non-mega sporting events
- Krystian Zawadzki
2020 Pełny tekst International Journal of Event and Festival Management
Purpose In the study, an attempt was made to estimate the social benefits resulting from three non-mega sporting events organized in Ergo Arena located on the border of two cities in Poland. By attributing a value to intangible social benefits, the intangible effect was determined and compared to the expenditure incurred in the construction of Ergo Arena Hall. Design/methodology/approach In order to value social intangible effects of three non-mega sporting events the Contingent Valuation Method was applied. Each time, the Contingent Valuation Method study covered the area of the two cities: Gdańsk and Sopot and was conducted on a sample of 500 people – 250 per city. The mean values of Willingness-to-Pay were used in order to obtain aggregate values of intangible benefits. Finally, the aggregate results were compared to expenditure incurred in connection with the construction of Ergo Arena Hall. Findings It appeared that intangible effects were eagerly valued by the residents of Gdańsk and Sopot. The aggregated value of all three sporting events was estimated at PLN 8.8 million. The obtained results question the equal share of both cities in financing but confirm that under certain circumstances, hosting non-mega sporting events may justify the use of public funds. In the case of the two cities, the reasonable reason for the employment of public means is the size of Gdańsk compared to Sopot. Originality/value The paper fulfils the research gap which arises regarding Willingness-to-Pay in estimating the intangible social effects of non-mega sporting events and considering these effects in the net effect valuation. The findings have implications for policy makers since they show to what extent it may be justified to use public means in order to host non-mega sporting events.
Soft Sensor Application in Identification of the Activated Sludge Bulking Considering the Technological and Economical Aspects of Smart Systems Functioning
- Bartosz Szeląg
- Jakub Drewnowski
- Grzegorz Łagód
- Dariusz Majerek
- Ewa Dacewicz
- Francesco Fatone
2020 Pełny tekst SENSORS
The paper presented the methodology for the construction of a soft sensor used for activated sludge bulking identification. Devising such solutions fits within the current trends and development of a smart system and infrastructure within smart cities. In order to optimize the selection of the data-mining method depending on the data collected within a wastewater treatment plant (WWTP), a number of methods were considered, including: artificial neural networks, support vector machines, random forests, boosted trees, and logistic regression. The analysis conducted sought the combinations of independent variables for which the devised soft sensor is characterized with high accuracy and at a relatively low cost of determination. With the measurement results pertaining to the quantity and quality of wastewater as well as the temperature in the activated sludge chambers, a good fit can be achieved with the boosted trees method. In order to simplify the selection of an optimal method for the identification of activated sludge bulking depending on the model requirements and the data collected within the WWTP, an original system of weight estimation was proposed, enabling a reduction in the number of independent variables in a model— quantity and quality of wastewater, operational parameters, and the cost of conducting measurements.
Soft-mode enhanced type-I superconductivity in LiPd2Ge
- Karolina Górnicka
- Gabriel Kuderowicz
- Elizabeth M. Carnicom
- Kamil Kutorasiński
- Bartlomiej Wiendlocha
- Robert J. Cava
- Tomasz Klimczuk
2020 Pełny tekst PHYSICAL REVIEW B
The synthesis, crystal structure, and physical properties (magnetization, resistivity, heat capacity) in combination with theoretical calculations of the electronic structure and phonon properties are reported for intermetallic compounds LiPd2X (X = Si, Ge, and Sn). LeBail refinement of powder x-ray diffraction data confirms that all compounds belong to the Heusler family (space group Fm-3m, No. 225). The lattice parameter increases with atomic size of X, and its value varies from a = 5.9059(4) Å for LiPd2Si and a = 6.0082(3) Å for LiPd2Ge, to a = 6.2644(1) Å for LiPd2Sn. The first compound, LiPd2Si, has apparently not been previously reported. All measured quantities demonstrate that LiPd2Ge exhibits superconductivity below Tc = 1.96 K and the normal and superconducting-state data indicate that it is a weak-strength type-I superconductor (C/γ Tc = 1.38) with electron-phonon coupling constant λe−p = (0.53 − 0.56). LiPd2Si and LiPd2Sn are not superconducting above 1.68 K. The experimental observations are supported by theoretical calculations which show that LiPd2Ge has the highest computed λe−p and Tc of the group. A strong softening of the acoustic phonon mode is calculated, and in the case of X = Ge and Sn, imaginary phonon frequencies were computed. The soft mode is most pronounced in the case of LiPd2Ge, which suggests its correlation with superconductivity.
Solvent dependency of carbon dioxide Henry's constant in aqueous solutions of choline chloride-ethylene glycol based deep eutectic solvent
- Ali Reza Harifi-Mood
- Fereshteh Mohammadpour
- Grzegorz Boczkaj
2020 Pełny tekst JOURNAL OF MOLECULAR LIQUIDS
The Henry's constants of carbon dioxide absorbed in aqueous solutions of ethaline (choline chloride-ethylene glycol) were determined for temperatures ranging from 303.15 to 323.15 K based on solubility measurement at CO2 pressure ranging from 0 to 6 bar (0.6 MPa). These studies revealed that the Henry's constant increased with the increase of temperature. Data indicated the highest capacity of CO2 absorption is obtained for ethaline and the lowest temperature dependency of absorption capacity is reported for aqueous solution of ethaline based deep eutectic solvent (0.3 mol fraction of water). The dependence of Henry's constant on solvent composition and solvent properties was investigated using preferential solvation model and linear free energy relationship method. Results showed that CO2 was preferentially solvated by ethaline in aqueous solution. Furthermore it revealed that solute-solvent interactions related to the scale of hydrogen bond donor ability of the solvent were the main parameter which controls the solubility of CO2 in the studied system. Presented methodology is useful for selection of best absorbent composition for systems of hot off-gases treatment. Interesting and practical results obtained in this work, indicated that precisely selected composition of the deep eutectic solvent based absorbent provide low sensitivity of the treatment performance in respect to the temperature of the treated gas.
Solvent Impact on the Diversity of Products in the Reaction of Lithium Diphenylphosphide and a Ti(III) Complex Supported by a tBu2P–P(SiMe3) Ligand
- Aleksandra Ziółkowska
- Natalia Szynkiewicz
- Jerzy Pikies
- Łukasz Ponikiewski
2020 Pełny tekst INORGANIC CHEMISTRY
We present two important trends in the reactivity ofthe titanium complex [MeNacNacTi(Cl){η2-P(SiMe3)-PtBu2}](MeNacNac− = [Ar]NC(Me)CHC(Me)N[Ar]; Ar = 2,6-iPr2Ph)with nucleophilic reagents RLi (R = Ph2P,tBuO, (Me3Si)2N, andtBu2N) depending on the reaction medium. Reaction in nonpolarsolvent (toluene) leads to three main products: via an autoredoxprocess and nucleophilic substitution at the Ti-atom to afford theTi(IV) complex [MeNacNacTi(R){η2-P-PtBu2}] (1for R = PPh2),via the elimination of Me3SiR to afford Ti(III) complex[MeNacNacTi(Cl){η2-P-PtBu2}]−[Li(12-crown-4)2]+(2), and via2e−reduction process to afford new ionic complex [{ArNC(Me)-CHC(Me)}TiNAr{η1-P(SiMe3)-PtBu2}]−[Li(12-crown-4)2]+(3). Quite differently, the complex [MeNacNacTi(Cl){η2-P(SiMe3)-PtBu2}] reacts with Ph2PLi in THF, unexpectedly yielding two new, four-coordinate Ti(IV) imido complexes4a[{ArNC(Me)CHC(H)(Me)-P(PtBu2)}TiNAr(Cl)]−[Li(12-crown-4)2]+·(toluene)2and4b[{ArNC(CH2)CHC(Me)-P(PtBu2)}TiNAr-(Cl)]−[Li(12-crown-4)2]+·(Et2O). Complex2dissolved in THF converts to4aand4b.1,2,3,4a, and4bwere characterized by X-ray diffraction.1,4a, and4bwere also fully characterized by multinuclear NMR spectroscopy.
Some Security Features of Selected IoT Platforms
- Robert Kałaska
- Paweł Czarnul
2020 Pełny tekst TASK Quarterly
IoT (Internet of Things) is certainly one of the leading current and future trends for processing in the current distributed world. It is changing our life and society. IoT allows new ubiquitous applications and processing, but, on the other hand, it introduces potentially serious security threats. Nowadays researchers in IoT areas should, without a doubt, consider and focus on security aspects. This paper is aimed at a high-level review of the existing IoT enabling standalone middleware solutions and frameworks in terms of potential application areas, architecture and components, communication APIs as well as support for key security features including access control, support against attacks on service, device authorization and data filtering. On the one hand, it allows the developer to choose the middleware best matching their needs. On the other hand, it can serve as a starting point for further research on middleware security features based on the provid ed security related open areas and challenges.
Sophistication assessment of existing FEM models of orbital blowout trauma: Is models valuation justified?
- Marcin Zmuda Trzebiatowski
- Andrzej Skorek
2020 Journal of Stomatology Oral and Maxillofacial Surgery
After a thorough study of the work entitled “Development and validation of an optimized finite element model of the human orbit”, some doubts aroused concerning the sophistication assessment of the existing finite element method (FEM) models of orbital blow-out. Although the work was unquestionably innovative, and the results were not only fascinating but also invaluable, the authors stated that their model was the most sophisticated one ever developed to their best knowledge. Hence, the purpose of this letter is to consider whether and upon what circumstances FEM models valuation may be justified.
Spatial and vertical distribution analysis of heavy metals in urban retention tanks sediments: a case study of Strzyza Stream
- Nicole Nawrot
- Ewa Wojciechowska
- Karolina Matej-Łukowicz
- Jolanta Walkusz-miotk
- Ksenia Pazdro
2020 Pełny tekst ENVIRONMENTAL GEOCHEMISTRY AND HEALTH
Concentrations of seven heavy metals (HMs): Zn, Cu, Pb, Cd, Ni, Cr, and Fe in core samples of bottom sediments from four retention tanks (RTs) located along the Strzyza Stream in northern Poland (Gdansk) were measured to obtain a general view of sediment quality. The recognition of contamination and potential environmental impacts is the main aim of this paper. A total of 96 sediment samples were collected from eight sampling sites at depths of 0–2 cm, 8–10 cm, 16–18 cm, 24–26 cm. Concentrations of Cu, Zn, Pb, Fe, Ni, and Cr were measured with AAS while Cd concentration was measured with ICP-MS. Granulometric analyses with normalized sieve apertures were carried out. Geochemical indices: enrichment factor, anthropogenic factor, and modified degree of contamination (mCd) were used to assess the contamination level. Concentrations of HMs in sediments changed in the range: Cu (3.24–119 mg/kg d.w.), Zn (12.5–584 mg/kg d.w.), Pb (4.91–309 mg/kg d.w.), Cd (0.003–0.716 mg/kg d.w.), Ni (1.57–25.8 mg/kg d.w.), Cr (2.45–74.5 mg/kg d.w.), and Fe (3993–63817 mg/kg d.w.). The sequential extraction verified the bonding of HMs with non-mobile fractions. Geochemical indices showed widespread pollution by Cu, Pb, Cd, and Zn. Cluster and factor analysis distinguished three related subgroups of HMs: Pb, Ni–Cr, and Fe–Cd–Cu–Zn, suggesting possible common source of each subgroup. Strongly contaminated sediments were distinguished in sediment cores in two middle stream RTs characterized by intense urbanization in their direct catchments.
Spatial Differences in the Chemical Composition of Surface Water in the Hornsund Fjord Area: A Statistical Analysis with A Focus on Local Pollution Sources
- Krystyna Kozioł
- Ruman Marek
- Filip Pawlak
- Stanisław Chmiel
- Żaneta Polkowska
2020 Pełny tekst Water
Surface catchments in Svalbard are sensitive to external pollution, and yet what is frequently considered external contamination may originate from local sources and natural processes. In this work, we analyze the chemical composition of surface waters in the catchments surrounding the Polish Polar Station in Svalbard, Hornsund fjord area. We have pooled unpublished and already published data describing surface water composition in 2010, related to its pH, electrical conductivity (EC), metals and metalloids, total organic carbon (TOC) and selected organic compound concentrations, including persistent organic pollutants (POPs) and surfactants. These data were statistically analyzed for spatial differences, using Kruskal–Wallis ANOVA and principal component analysis (PCA), with distance from the station in the PCA approximating local human activity impact. The geological composition of the substratum was found to be a strong determinant of metal and metalloid concentrations, sufficient to explain significant differences between the studied water bodies, except for the concentration of Cr. The past and present human activity in the area may have contributed also to some of the polycyclic aromatic hydrocarbons (PAHs), although only in the case of naphthalene can such an effect be confirmed by an inverse correlation with distance from the station. Other likely factors contributing to the chemical concentrations in the local waters are marine influence, long-range pollution transport and release from past deposition in the environment.
Special Issue: “Non-Destructive Testing of Structures”
- Magdalena Rucka
2020 Pełny tekst Materials
The Special Issue “Non-Destructive Testing of Structures” has been proposed to present recent developments in the field of diagnostics of structural materials and components in civil and mechanical engineering. The papers highlighted in this editorial concern various aspects of non-invasive diagnostics, including such topics as condition assessments of civil and mechanical structures and connections of structural elements, the inspection of cultural heritage monuments, the testing of structural materials, structural health monitoring systems, the integration of non-destructive testing methods, advanced signal processing for the non-destructive testing of structures (NDT), damage detection and damage imaging, as well as modeling and numerical analyses for supporting structural health monitoring (SHM) systems.
Special Issue: Recent Advances in Corrosion Science
- Jacek Ryl
2020 Pełny tekst Materials
The dynamic development of the global industry and growing demand for new material technologies generates constantly increasing problems regarding premature material degradation and the requirement to determine corrosion mechanisms and to develop new protection/evaluation approaches. This Special Issue, “Recent Advances in Corrosion Science”, brings together fourteen articles and one review, providing a snapshot of the recent activity and development in this field.
Speciation of heavy metals in bottom sediments of drinking water reservoir for Gdansk, Poland – changes over the 14 years
- Eliza Kulbat
- Aleksandra Sokołowska
2020 Desalination and Water Treatment
There was conducted a comparative study of the concentrations of heavy metals (Zn, Cu, Pb, and Cd) in the surface layer of sediments collected in two investigation periods: 1999–2000 and 2013. Theresults demonstrated that the degree of metals pollution decreased over time. The contamina-tion factors (Cf) calculated for Zn, Cu, Pb, and Cd were respectively 3.63, 3.86, 3.23, and 3.25 in the first period of research and 1.35, 3.42, 1.98, and 1.43 in the second one. The metal speciation analysis indicated that Zn was mainly associated with the Fe–Mn oxides fraction and the residual fraction, and Cu – with the residual fraction and the organic fraction in both periods of investigation, while the percentage of geochemical fractions in binding of Pb and Cd changed in time. The share of fractions Fe–Mn oxides/carbonate increased in the case of Pb, and carbonate/exchangeable fractions in the case of Cd. The risk assessment code (RAC) decreased in the following order: Cd>Zn>Pb>Cu and was higher in 2013 - it achieved the very high-risk category in the case of Cd. Thus, despite the decrease of sediment pollution, RAC for Cd increased due to changed geochemical speciation.
Spectroscopic Optical Coherence Tomography for Thin Layer and Foil Measurements
- Aleksandra Kamińska
- Marcin Strąkowski
- Jerzy Pluciński
2020 Pełny tekst SENSORS
The main goal of this research was to assess if it is possible to evaluate the thickness of thin layers (both thin films on the surface and thin layers below the surface of the tested object) and foils using optical coherence tomography (OCT) for thickness assessment under the resolution of the standard commercially available OCT measurement system. In the proposed solution, light backscattered from the evaluated thin layer has been expressed as a multiple beam interference. Therefore, the OCT system was modeled as a two-beam interferometer (e.g., Michelson), in which one beam propagates from the reference arm and the other comes from a Fabry–Pérot interferometer. As a consequence, the mathematical model consists of the main Michelson interferometer, in which the measuring arm represents the Fabry–Pérot interferometer. The parameters of the layer (or foil) are evaluated by analyzing the minimum value of the interference contrast. The model developed predicts the behavior of the thin layers made from different materials (with different refractive indexes) with different thickness and located at different depths. To verify the correctness of the proposed model, an experiment with a wedge cell has been carried out. The wedge cell was shifted across the scanning beam using a linear translation stage with a micrometer screw under the scanning head. The relationship between the thickness of the gap of the wedge cell and the OCT output signal is presented. For the additional verification of the proposed model, the results of the measurements of the thickness of the thin foil were compared with the theoretical results of the simulations. The film thickness was evaluated based on the calculated positions of the minimum value of interference contrast. A combination of the standard potentialities of OCT with the proposed approach to analyzing the signal produces new metrological possibilities. The method developed allows us to evaluate thickness under the resolution of the system and the location of the layer as well. This produces the possibility of measuring a layer which is covered by another layer. Moreover, it is possible to create a thickness map with high sensitivity to thickness changes. These experiments and simulations are the culmination of preliminary research for evaluating the potential of the proposed measurement method.
Spectroscopic studies of Nb-doped tricalcium phosphate glass-ceramics prepared by sol-gel method
- Wojciech Korzeniewski
- Agnieszka Witkowska
- Maciej Manecki
2020 Synchrotron Radiation in Natural Science
Calcium-phosphate based glasses and glass-ceramics play a crucial role in the tissue engineering development. Apart from their high biocompatibility and excellent ability to undergo varying degrees of resorbability1, they exhibit relatively high bioactivity and due to that they are commonly used as bone and dental implants. A substantial research effort is devoted to improve calcium-phosphate materials physico-chemical properties by tuning their degree of crystallinity and doping them with metal ions is one of the mostly researched strategies. The results found in the literature show that synthesized CaOP2O5-Nb2O5 compounds exhibit a good biocompatibility, very low cytotoxicity in respect to calciumphosphate doped with other metals and additionally can enhance human osteoblast function2,3. As of today structure of these materials is not thoroughly described. Therefore, the detailed structural investigation by means of spectroscopic studies, i.e. FTIR spectroscopy, Raman spectroscopy, XAFS spectroscopy, XPS and EDX, together with SEM imaging, XRD and BET surface area measurements, was realized to shed light on the relationship between materials structure and the presence of dopant. In this work, we show the results obtained for bioactive glass-ceramics, prepared via simple sol-gel method, with Ca/(P+Nb) molar ratio equal to 1.5 and with relative Nb contents of 0 mol% and 10 mol% of P. XRD patterns analysis shows that samples consist of tricalcium phosphate and hydroxyapatite phase. Raman spectra analysis confirms the incorporation of Nb into the material structure. Moreover, niobium doping leads to an increase in degree of crystallinity and crystallite size of the sample. Stoichiometry of the ceramics is as intended. Additionally, there is a greater proportion of carbonate groups in the doped material than in the undoped one (FTIR, Raman spectroscopy), and all samples exhibit calcium deficiency on the surface (XPS). XAFS analysis shows presence of octahedral coordination of niobium ions, with average oxidation state around +4.5 and XPS analysis indicates that on the sample surface the contribution of Nb+5 ions is greater than Nb+4 ions. Additionally it can be concluded, that Nb accumulates on materials surface.
Spinon excitations in the quasi-one-dimensional S=12 chain compound Cs4CuSb2Cl12
- Thao Tran
- Chris A. Pocs
- Yubo Zhang
- Michał Winiarski
- Jianwei Sun
- Minhyea Lee
- Tyrel McQueen
2020 Pełny tekst PHYSICAL REVIEW B
The spin−1/2 Heisenberg antiferromagnetic chain is ideal for realizing one of the simplest gapless quantum spin liquids (QSLs), supporting a many-body ground state whose elementary excitations are fractional fermionic excitations called spinons. Here we report the discovery of such a one-dimensional (1D) QSL in Cs4CuSb2Cl12. Compared to previously reported S=1/2 1D chains, this material possesses a wider temperature range over which the QSL state is stabilized. We identify spinon excitations extending at T>0.8K, with a large T-linear contribution to the specific heat, γ=31.5(2)mJmol−1K−2, which contribute itinerantly to thermal transport up to temperatures as high as T=35K. At T=0.7K, we find a second-order phase transition that is unchanged by a μ0H=5T magnetic field. Cs4CuSb2Cl12 reveals new phenomenology deep in the 1D QSL regime, supporting a gapped QSL phase over a wide temperature range compared to many other experimental realizations.
Spirala 2 (wg Ulama) z cyklu No Quick Response
- Krzysztof Wróblewski
2020
Spirala 2 (wg Stanisława Ulama) Obraz odnosi się do modelu matematycznego nazywanego Spiralą Ulama, który polega na okrężnym zapisie w polu kwadratu liczb naturalnych od 1 do nieskończoności. Taki zapis uwidacznia szczególne wzory, które powstają z położenia liczb pierwszych (niepodzielnych). Liczby pierwsze tworzą ciągi mniej lub bardziej regularne w układzie diagonalnym, poziomym i pionowym. W obrazie Spirala 2 wykorzystany został zestaw liczb od 1 do 1600. Położenia liczb pierwszych są malowane czernią i bielą, natomiast położenie pozostałych liczb kolorami podstawowymi i pochodnymi w różnej tonacji. Kolory "wędrują" progresywnie za liczbami po kształcie spirali. Sekwencyjny rytm przerywany jest położeniem liczby pierwszej. W wyniku tego zabiegu samorzutnie powstają grupy różnych form i kolorów, przy czym żadna z nich nie jest dominująca w całości układu. Poszczególne kształty są tylko cząstkami większej całości. W spirali Ulama podobnie jak w ciągu Fibonacciego występuje rodzaj harmonijnej jedności. Krzysztof Wróblewski