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  • Non-Linear Interaction of Harmonic Waves in a Quasi-Isentropic Flow of Magnetic Gas
    • Anna Perelomova
    2020 Pełny tekst Archives of Acoustics

    The diversity of wave modes in the magnetic gas gives rise to a wide variety of nonlinear phenomenaassociated with these modes. We focus on the planar fast and slow magnetosound waves in the geometryof a flow where the wave vector forms an arbitrary angleθwith the equilibrium straight magnetic field.Nonlinear distortions of a modulated signal in the magnetic gas are considered and compared to thatin unmagnetised gas. The case of acoustical activity of a plasma is included into consideration. Theresonant three-wave non-collinear interactions are also discussed. The results depend on the degree ofnon-adiabaticity of a flow,θ, and plasma-β.

  • Nonlinear numerical simulation of earthquake-induced pounding between timber frame buildings
    • Wojciech Migda
    • Marcin Szczepański
    • Natalia Lasowicz
    • Anna Jakubczyk-Gałczyńska
    • Robert Jankowski
    2020 AIP Conference Proceedings

    Earthquakes may induce serious dynamic loads acting on buildings, which can lead to damage or even destruction of the whole structure. In densely populated areas, it is quite common that buildings are located very close one to another which can result in pounding between them during ground motions. Due to the environmental awareness, multi-story timber frame buildings are gaining popularity and therefore there is a need to investigate the effects of structural collisions on seismic response of such buildings. In this paper, the results of advanced numerical FEM simulation, focused on inter-story pounding between two adjacent multi-story timber frame buildings, are presented. The results of the study show that structural interactions have a significant influence on the overall response of buildings exposed to damaging seismic excitations. Moreover, due to deformability of buildings made of wood, pounding may change response of such buildings much more, as compared to steel, reinforced concrete or masonry structures. Finally, the results confirm that the use of the nonlinear FEM with detailed representation of material and geometric structural properties can be considered as the effective approach in obtaining the accurate response of colliding timber frame buildings during earthquakes

  • Nonlocal Vibration of Carbon/Boron-Nitride Nano-hetero-structure in Thermal and Magnetic Fields by means of Nonlinear Finite Element Method
    • Hamid M. Sedighi
    • Mohammad Malikan
    • Ali Valipour
    • Krzysztof Kamil Żur
    2020 Pełny tekst Journal of Machinery Manufacture and Reliability

    Hybrid nanotubes composed of carbon and boron-nitride nanotubes have manifested as innovative building blocks to exploit the exceptional features of both structures simultaneously. On the other hand, by mixing with other types of materials, the fabrication of relatively large nanotubes would be feasible in the case of macroscale applications. In the current article, a nonlinear finite element formulation is employed to deal with the nonlocal vibrational behavior of carbon/boron-nitride nano-hetero-tubes in the presence of magneto-thermal environment. Euler-Bernoulli beam model in conjunction with the Eringen's nonlocal theory of elasticity is adopted to derive the governing equation of motion. In order to conduct a nonlinear frequency analysis, the von-Kármán nonlinearity associated with moderate rotations is also considered. It is well-known that temperature gradients can significantly change the dynamic behavior of nanotubes. On the other hand, the coefficients of thermal expansions of carbon and boron-nitride nanotubes are quite different which may affect the structural stability of hybrid nanotubes. Hence, to explore the vibration characteristic of such composite structures, the influence of magneto-thermal environment is also taken into account. Finally, the eigenvalue analysis is performed to exhibit the nonlinear mode shapes and natural frequencies of the system due to initial displacement. It is expected that the recognition of dynamic behavior of such hybrid nanotubes may open the doors to the creative design of next-generation nanodevices.

  • Nonreciprocal cavities and the time-bandwidth limit: comment
    • Kosmas L. Tsakmakidis
    • Yun You
    • Tomasz Stefański
    • Linfang Shen
    2020 Pełny tekst Optica

    In their paper in Optica 6, 104 (2019), Mann et al. claim that linear, time-invariant nonreciprocal structures cannot overcome the time-bandwidth limit and do not exhibit an advantage over their reciprocal counterparts, specifically with regard to their time-bandwidth performance. In this Comment, we argue that these conclusions are unfounded. On the basis of both rigorous full-wave simulations and insightful physical justifications, we explain that the temporal coupled-mode theory, on which Mann et al. base their main conclusions, is not suited for the study of nonreciprocal trapped states, and instead direct numerical solutions of Maxwell’s equations are required. Based on such an analysis, we show that a nonreciprocal terminated waveguide, resulting in a trapped state, clearly outperforms its reciprocal counterpart; i.e., both the extraordinary time-bandwidth performance and the large field enhancements observed in such modes are a direct consequence of nonreciprocity.

  • Non-Salient Brushless Synchronous Generator Main Exciter Design for More Electric Aircraft
    • Filip Kutt
    • Michał Michna
    • Grzegorz Kostro
    2020 Pełny tekst ENERGIES

    This paper presents a prototype of high speed brushless synchronous generators (BSG) design for the application in autonomous electric power generation systems (e.g., airplane power grid). Commonly used salient pole field of the main generator part of BSG was replaced with a prototype non-salient pole field. The main objective of the research is an investigation into the advantages and disadvantages of a cylindrical field of the main generator part of BSG over the original salient pole field. The design process of the prototype generator is presented with a focus on the electromagnetic and mechanical finite element method (FEM) analysis. The measurements of prototype and commercial BSG were conducted for the nominal speed of 8 krpm. The advantages and disadvantages of the proposed solution were established based on measurements in load and no-load conditions.

  • Non-standard contact conditions in generalized continua: microblock contact model for a Cosserat body
    • Maciej Lewandowski-Szewczyk
    • S. Stupkiewicz
    2020 Pełny tekst INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES

    Generalized continuum theories involve non-standard boundary conditions that are associated with the additional kinematic variables introduced in those theories, e.g., higher gradients of the displacement field or additional kinematic degrees of freedom. Accordingly, formulation of a contact problem for such a continuum necessarily requires that adequate contact conditions are formulated for the additional kinematic variables and/or for the respective generalized tractions. In this paper, we address several related open problems, namely, how to enhance the classic contact conditions to include the effects of the additional kinematic variables, how to link the enhanced contact model to the underlying microstructure of the solid, and how to do it in a consistent manner. As a first step towards a new class of contact models for generalized continua, a microblock contact model is derived for a Cosserat solid based on simple micromechanical considerations. To illustrate the non-trivial effects introduced by the non-standard boundary conditions, the problem of compression of an infinite strip with nonaligned microblocks is considered, and the analytical solution is derived for the corresponding boundary layers. A Hertz-like contact problem is also solved numerically with the focus on non-standard features of the solution and on the related size effects.

  • Normy i szkolenia z normalizacji w Bibliotece PG
    • Janusz Waluszko
    2020 Pismo PG

    Tekst omawia znaczenie norm dla studentów i naukowców oraz szkolenia z normalizacji organizowane przez Bibliotekę Politechniki Gdańskiej

  • Novel 1,2,4-Oxadiazole Derivatives in Drug Discovery
    • Karol Biernacki
    • Mateusz Daśko
    • Olga Ciupak
    • Konrad Kubiński
    • Janusz Rachoń
    • Sebastian Demkowicz
    2020 Pełny tekst Pharmaceuticals

    Abstract: Five-membered 1,2,4-oxadiazole heterocyclic ring has received considerable attention because of its unique bioisosteric properties and an unusually wide spectrum of biological activities. Thus, it is a perfect framework for the novel drug development. After a century since the 1,2,4-oxadiazole have been discovered, the uncommon potential attracted medicinal chemists’ attention, leading to the discovery of a few presently accessible drugs containing 1,2,4-oxadiazole unit. It is worth noting that the interest in a 1,2,4-oxadiazoles’ biological application has been doubled in the last fifteen years. Herein, after a concise historical introduction, we present a comprehensive overview of the recent achievements in the synthesis of 1,2,4-oxadiazole-based compounds and the major advances in their biological applications in the period of the last five years as well as brief remarks on prospects for further development.

  • Novel ABTS-dot-blot method for the assessment of antioxidant properties of food packaging
    • Barbara Kusznierewicz
    • Hanna Staroszczyk
    • Edyta Malinowska-Pańczyk
    • Karol Parchem
    • Agnieszka Bartoszek-Pączkowska
    2020 Pełny tekst Food Packaging and Shelf Life

    The new ABTS-dot-blot method for the direct determination of antioxidant activity of active packaging that is in contact with foodstuffs has been developed. The usefulness of the new method was verified with the use of agarose, pork gelatin, bacterial cellulose and cellulose-chitosan films with incorporated standard antioxidant – Trolox or plant phytochemicals derived from three types of berry juices (chokeberry, blue-berried honeysuckle, rowanberry) or green tea. The plant components used for preparation of films were characterized by antioxidant profiling with the use of HPLC coupled with post-column derivatization with ABTS. The most abundant antioxidants were polyphenols, mainly anthocyanins, hydroxycinnamates and flavan-3-ols. The antioxidant properties of different types of films studied were evaluated by typical cuvette spectrophotometric ABTS test or by the novel method employing ABTS radical stabilised in an agarose gel. The results obtained for the Trolox containing films showed quantitative linear relationship between antioxidant content and the degree of ABTS bleaching in agarose gel. The results of both standard spectrophotometric method as well as ABTS-dot-blot approach indicated that gelatin, bacterial cellulose and chitosan on their own possessed antioxidant activity, which was substantially increased (6–10 times) by the addition of phytochemicals during film preparation. The highest antioxidant activity was observed for microbial cellulose films, which were prepared on the basis of material obtained during the kombucha drink production.

  • Novel application of dynamic electrochemical impedance monitoring to a cataphoretic coating process
    • Kazimierz Darowicki
    • Paweł Ślepski
    • Michał Szociński
    2020 Pełny tekst PROGRESS IN ORGANIC COATINGS

    The paper presents a novel method of on-line impedance monitoring of cataphoretic coating application process. Utilization of dynamic electrochemical impedance spectroscopy (DEIS) overcame the fundamental problem connected with non-stationarity of the aforementioned coating deposition process, which eliminates classical impedance spectroscopy technique from a real-time description of cataphoresis. The paper illustrates selected examples of potentialities of DEIS regarding the characterization of the cataphoretic coating process. Acquired instantaneous impedance spectra enabled on-line insight into impedance changes upon steel substrate polarization duration, thus visualizing coating application progress. DEIS allowed estimation of the time necessary for the coating/steel substrate system to achieve a steady state after polarization switch off. The proposed approach seems to be a step towards real-time monitoring of electrophoretic coating application and offers a potential for improved process control and optimization.

  • Novel approach to interference analysis of glucose sensing materials coated with Nafion
    • Adrian Olejnik
    • Jakub Karczewski
    • Anna Dołęga
    • Katarzyna Siuzdak
    • Katarzyna Grochowska
    2020 BIOELECTROCHEMISTRY

    A gold-based sensing platform, TiND | AuNP | Nafion, was prepared as an exemplary electrode material exhibiting a response to glucose in a neutral solution. The change of electrochemical properties after exposure to glucose and interference compounds such as vitamin C, glycine, urea, paracetamol and acetylsalicylic acid was tested.

  • Novel Class of Proton Conducting Materials—High Entropy Oxides
    • Maria Gazda
    • Tadeusz Miruszewski
    • Daniel Jaworski
    • Aleksandra Dorota Mielewczyk-Gryń
    • Wojciech Skubida
    • Sebastian Lech Wachowski
    • Piotr Winiarz
    • Kacper Dzierzgowski
    • Marcin Stanisław Łapiński
    • Iga Szpunar
    • Ewa Dzik
    2020 Pełny tekst ACS Materials Letters

    Here, for the first time, we present data on proton conductivity of high-entropy, single-phase perovskites. The BaZr0.2Sn0.2Ti0.2Hf0.2Ce0.2O3−δ, BaZr0.2Sn0.2Ti0.2Hf0.2Y0.2O3−δ, BaZr1/7Sn1/7Ti1/7Hf1/7Ce1/7Nb1/7Y1/7O3−δ, and BaZr0.15Sn0.15Ti0.15Hf0.15Ce0.15Nb0.15Y0.10O3−δ single-phase perovskites were synthesized. Before electrical measurements, materials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The following experimental results demonstrated that studied high-entropy perovskites are proton conductors: (1) The observed mass increase upon the switch from dry to wet atmosphere confirmed the water incorporation into materials structure. (2) The electrochemical impedance spectroscopy (EIS) revealed that the total conductivity increased while its activation energy decreased in the presence of water vapor in the atmosphere. (3) The conductivity in atmosphere humidified with H2O and D2O differed one from another, showing typical of proton conductors isotope effect in high-entropy oxides.

  • Novel Fault Identification for Electromechanical Systems via Spectral Technique and Electrical Data Processing
    • Tomasz Ciszewski
    • Len Gelman
    • Andrew Ball
    2020 Pełny tekst Electronics

    It is proposed, developed, investigated, and validated by experiments and modelling for the first time in worldwide terms new data processing technologies, higher order spectral multiple correlation technologies for fault identification for electromechanical systems via electrical data processing. Investigation of the higher order spectral triple correlation technology via modelling has shown that the proposed data processing technology effectively detects component faults. The higher order spectral triple correlation technology successfully applied for rolling bearing fault identification. Experimental investigation of the technology has shown, that the technology effectively identifies rolling bearing fault by electrical data processing at very early stage of fault development. Novel technology comparisons via modelling and experiments of the proposed higher order spectral triple correlation technology and the higher order spectra technology show the higher fault identification effectiveness of the proposed technology over the bicoherence technology.

  • Novel MNZ-type microwave sensor for testing magnetodielectric materials
    • Abhishek Jha
    • Nicolò Delmonte
    • Adam Lamęcki
    • Michał Mrozowski
    • Maurizzio Bozzi
    2020 Pełny tekst Scientific Reports

    A novel microwave sensor with the mu-near-zero (MNZ) property is proposed for testing magnetodielectric material at 4.5 GHz. The sensor has a double-layer design consisting of a microstrip line and a metal strip with vias on layers 1 and 2, respectively. The proposed sensor can detect a unit change in relative permittivity and relative permeability with a difference in the operating frequency of 45 MHz and 78 MHz, respectively. The MNZ sensor is fabricated and assembled on two layers of Taconic RF-35 substrate, with thicknesses of 0.51 mm and 1.52 mm, respectively, for the measurement of the sample under test using a vector network analyzer. The dielectric and magnetic properties of two standard dielectric materials (Taconic CER-10 and Rogers TMM13i) and of yttrium–gadolinium iron garnet are measured at microwave frequencies. The results are found to be in good agreement with the values available in the literature, which shows the applicability of the prototype for sensing of magnetodielectric materials.

  • Novel N-(aryl/heteroaryl)-2-chlorobenzenesulfonamide derivatives: synthesis and anticancer activity evaluation
    • Anita Bułakowska
    • Jarosław Sławiński
    • Kamila Siedlecka-Kroplewska
    • Grzegorz Stasiłojć
    • Marcin Serocki
    • Mateusz Heldt
    2020 BIOORGANIC CHEMISTRY

    A new series of N-(aryl/heteroaryl)-2-chlorobenzenesulfonamide derivatives 4-21 have been synthesized, and evaluated at the National Cancer Institute (USA) for their in vitro activities against a panel of 60 different human cancer cell lines. Among them, compounds 16, 20 and 21 exhibited remarkable cytotoxic activity against numerous human cancer cell lines. We found that sulfonamide derivative 21 appeared to be more selective than compounds 16 and 20. In comparison to compounds 16 and 20 it showed higher cytotoxic activity against A549 non-small cell lung adenocarcinoma and HCT-116 colon carcinoma cells and was less toxic to HEK-293 human embryonic kidney cells and HaCaT immortalized human keratinocytes. Treatment of A549 and HCT-116 cells with compound 21 resulted in the G0/G1-cell cycle arrest with a concomitant increase in p53 and p21 protein levels. Moreover, compound 21 led to ATP depletion and disruption of the mitochondrial membrane potential in both studied cell lines. Our results suggest that 2,4-dichloro-N-(quinolin-8-yl and/or 1H-indazol-7-yl)benzenesulfonamides serve as novel promising anticancer agents.

  • Novel tetrahedral cobalt(II) silanethiolates: structures and magnetism
    • Daria Kowalkowska-Zedler
    • Natalia Nedelko
    • Katarzyna Kazimierczuk
    • Pavlo Aleshkevych
    • Renata Łyszczek
    • Anna Ślawska-waniewska
    • Agnieszka Pladzyk
    2020 Pełny tekst RSC Advances

    Three heteroleptic complexes of Co(II) tri-tert-butoxysilanethiolates have been synthesized with piperidine [Co{SSi(OtBu)3}2(ppd)2] 1, piperazine [Co{SSi(OtBu)3}2(NH3)]2(μ-ppz)·2CH3CN 2, and N-ethylimidazole [Co{SSi(OtBu)3}2(etim)2] 3. The complexes have been characterized by a single-crystal X-ray, revealing their tetrahedral geometry on Co(II) coordinated by two nitrogen and two sulfur atoms. Complexes 1 and 3 are mononuclear, whereas 2 is binuclear. The spectral properties and thermal properties of 1–3 complexes were established by FTIR spectroscopy for solid samples and TGA. The magnetic properties of complexes 1, 2, and 3 have been investigated by static magnetic measurements and X-band EPR spectroscopy. These studies have shown that 1 and 3, regardless of the similarity in structure of CoN2S2 cores, demonstrate different types of local magnetic anisotropy. Magnetic investigations of 2 reveal the presence of weak antiferromagnetic intra-molecular Co(II)–Co(II) interactions that are strongly influenced by the local magnetic anisotropy of individual Co(II) ions.

  • Nowa koncepcja płaszczowo-rurowego wymiennika ciepła z techniką strugową w rurach pęku
    • Jan Wajs
    • Roksana Bochniak
    2020

    W pracy przedstawiono nowe podejście do implementacji techniki strugowej w wymiennikach cylindrycznych. Obiektem badań jest opatentowana konstrukcja płaszczowo-rurowego wymiennika ciepła z techniką strugową obecną w rurach pęku. Generatorem strug są perforowane wkłady rurowe, w których średnica pojedynczego otworu wynosi 1.3 mm. Dla poprawy kompaktowości tego wymiennika, perforowane wkłady wykonano w technologii minikanałowej – ich średnica wewnętrzna wynosi 2 mm. Omówiono budowę i zasadę działania wymiennika, przedstawiono stanowisko pomiarowe do prowadzenia badań cieplno-przepływowych oraz omówiono wyniki wstępnych badań konwekcji jednofazowej w układzie gaz-ciecz. Wyniki te posłużyły do weryfikacji korelacji dostępnych w literaturze przedmiotu.

  • Nowoczesne metody termografii w systemie monitorowania stanu sieci przesyłowych
    • Filip Ratkowski
    • Krzysztof Szuchnik
    2020 Wiadomości Elektrotechniczne

    W artykule przedstawiono obecnie stosowane metody inspekcji termowizyjnej, skupiając się na prewencyjnej diagnostyce stanu sieci przesyłowej. Badanie termowizyjne ma różne wymiary wpływu na efektywność energetyczną. Z jednej strony wykorzystuje się ją do inspekcji szczelności termoizolacji budynków, wpływając na świadomość, że „najtańsza energia to ta zaoszczędzona”, z drugiej strony jest narzędziem dla operatorów sieci dystrybucyjnych i przesyłowych, zmniejszając prawdopodobieństwo zawodności elementów infrastruktury elektroenergetycznej. Przy zwiększającym się sektorze usług inspekcji termowizyjnych, wywołanym dostępnością kamer termowizyjnych i możliwości z nimi związanymi, takimi jak: termowizyjny skaning laserowy, kolejnym krokiem jest implementacja danych o stanie temperatury obiektu w cyklu życia obiektu w BIM i CMS.

  • Nuclear Magnetic Resonance Metabolomics Reveals Qualitative and Quantitative Differences in the Composition of Human Breast Milk and Milk Formulas
    • Dorota Garwolińska
    • Weronika Hewelt-Belka
    • Agata Kot-Wasik
    • Ulrik Kræmer Sundekilde
    2020 Pełny tekst Nutrients

    Commercial formula milk (FM) constitutes the best alternative to fulfill the nutritional requirements of infants when breastfeeding is precluded. Here, we present the comparative study of polar metabolite composition of human breast milk (HBM) and seven different brands of FM by nuclear magnetic resonance spectroscopy. The results of the multivariate data analysis exposed qualitative and quantitative differences between HBM and FM composition as well as within FM of various brands and in HBM itself (between individual mothers and lactation period). Several metabolites were found exclusively in HBM and FM. Statistically significant higher levels of isoleucine and methionine in their free form were detected in FM samples based on caprine milk, while FM samples based on bovine milk showed a higher level of glucose and galactose in comparison to HBM. The results suggest that the amelioration of FM formulation is imperative to better mimic the composition of minor nutrients in HBM.

  • Numerical analyses of novel prefabricated structural wall panels in residential buildings based on laboratory tests in scale 1:1
    • Łukasz Skarżyński
    • Ireneusz Marzec
    • Krzysztof Drąg
    • Andrzej Tejchman-Konarzewski
    2020 Pełny tekst European Journal of Environmental and Civil Engineering

    The paper presents experimental and numerical investigations on novel prefabricated composite building wall panels for residential building constructions. The wall panels were composed of reinforced concrete ribbed elements with the core from the EPS foam as the thermal insulation. The wall panels in the full-scale 1:1 were subjected to vertical loads. In the first step, the experiments were analysed with simple usual static methods. Next they were analysed numerically using the finite element method based on two different constitutive continuum models for concrete. First, an elasto-plastic model with the Drucker-Prager criterion defined in compression and with the Rankine criterion defined in tension was used. Second, a coupled elasto-plastic damage formulation based on the strain equivalence hypothesis was used. In order to properly describe strain localization in concrete, both models were enhanced in a softening regime by a characteristic length of micro-structure by means of a non-local theory. A satisfactory agreement between the experiments and FE analyses was achieved. In addition, the FE results with the non-local approach were compared with the crack band model.

  • Numerical analysis of high temperature minichannels heat exchanger performance
    • Jan Wajs
    • Tomasz Kura
    • Dariusz Mikielewicz
    • Elżbieta Fornalik-Wajs
    • Jarosław Mikielewicz
    2020

    Nowadays, the most difficult technological challenge in energy sector is connected with the gas micro-CHP units, dedicated to the distributed power generation. They are expected to be of high efficiency and at the same time of compact in size. Regarding the first reason, significant increase in microturbine efficiency can only be achieved by increase in the engine operating temperature. Therefore, one of the critical elements in such installation is the recuperator, which contributes to the overall microturbine efficiency in considerable part. Taking into account the system size and its efficiency, only the compact heat exchangers with passive techniques of the heat transfer intensification can fulfil strict requirements. Very promising are the cylindrical/plate heat exchangers with minichannels or heat exchangers with jets/microjets technology. In the paper an own construction of plate heat exchanger with minichannels, proposed for high-efficiency gas microturbine engines with external combustion chamber is considered. It consists of a set of steel plates with the channels of rectangular crossection, with 3 mm width and 1.5 mm depth. This unit can be supplied with air at temperature about 1000 C and transfer the thermal energy to air at temperature close to the ambient level. A numerical model was developed for the entire unit and validated with the experimental results, coming from the analysis conducted on the prototype in the “cold” conditions (at 18 C) and normal operating conditions (at 957 C). The experimental and numerical results, referring to the pressure drop, agreed within 2%-14% range, while referring to the heat rate – within 1%-7% range. Analysis of local thermal and hydraulic results was a source of few ideas, concerning an optimization of the heat exchanger construction, oriented at the improvement of its performance.

  • Numerical investigation on behaviour of cylindrical steel tanks during mining tremors and moderate earthquakes
    • Daniel Burkacki
    • Michał Wójcik
    • Robert Jankowski
    2020 Earthquakes and Structures

    Cylindrical steel tanks are important components of industrial facilities. Their safety becomes a crucial issue since any failure may cause catastrophic consequences. The aim of the paper is to show the results of comprehensive FEM numerical investigation focused on the response of cylindrical steel tanks under mining tremors and moderate earthquakes. The effects of different levels of liquid filling, the influence of non-uniform seismic excitation as well as the aspects of diagnosis of structural damage have been investigated. The results of the modal analysis indicate that the level of liquid filling is really essential in the structural analysis leading to considerable changes in the shapes of vibration modes with a substantial reduction in the natural frequencies when the level of liquid increases. The results of seismic and paraseismic analysis indicate that the filling the tank with liquid leads to the substantial increase in the structural response under ground motions. It has also been observed that the peak structural response values under mining tremors and moderate earthquakes can be comparable to each other. Moreover, the consideration of spatial effects related to seismic wave propagation leads to a considerable decrease in the structural response under non-uniform seismic excitation. Finally, the analysis of damage diagnosis in steel tanks shows that different types of damage may induce changes in the free vibration modes and values of natural frequencies.

  • Numerical Solution of the Two-Dimensional Richards Equation Using Alternate Splitting Methods for Dimensional Decomposition
    • Dariusz Gąsiorowski
    • Tomasz Kolerski
    2020 Pełny tekst Water

    Research on seepage flow in the vadose zone has largely been driven by engineering and environmental problems affecting many fields of geotechnics, hydrology, and agricultural science. Mathematical modeling of the subsurface flow under unsaturated conditions is an essential part of water resource management and planning. In order to determine such subsurface flow, the two-dimensional (2D) Richards equation can be used. However, the computation process is often hampered by a high spatial resolution and long simulation period as well as the non-linearity of the equation. A new highly efficient and accurate method for solving the 2D Richards equation has been proposed in the paper. The developed algorithm is based on dimensional splitting, the result of which means that 1D equations can be solved more efficiently than as is the case with unsplit 2D algorithms. Moreover, such a splitting approach allows any algorithm to be used for space as well as time approximation, which in turn increses the accuracy of the numerical solution. The robustness and advantages of the proposed algorithms have been proven by two numerical tests representing typical engineering problems and performed for typical properties of soil.

  • Numerical solutions for blood flow in elastic vessels
    • Henryk Leszczyński
    • Artur Poliński
    • Monika Wrzosek
    2020 MATHEMATICAL METHODS IN THE APPLIED SCIENCES

    We consider the differential–algebraic system for the blood flow and pressure in the systemic arteries. By the operator splitting method, we transform the system into the hyperbolic one, introduce the bicharacteristics, and perform the time–space nonuniform discretization, obtaining the innovative difference scheme. Our results are illustrated with numerical experiments.

  • Numerical Study of Concrete Mesostructure Effect on Lamb Wave Propagation
    • Beata Zima
    • Rafał Kędra
    2020 Pełny tekst Materials

    The article presents the results of the numerical investigation of Lamb wave propagation in concrete plates while taking into account the complex concrete mesostructure. Several concrete models with randomly distributed aggregates were generated with the use of the Monte Carlo method. The influence of aggregate ratio and particle size on dispersion curves representing Lamb wave modes was analyzed. The results obtained for heterogeneous concrete models were compared with theoretical results for homogeneous concrete characterized by the averaged macroscopic material parameters. The analysis indicated that not only do the averaged material parameters influence the dispersion solution, but also the amount and size of aggregate particles. The study shows that Lamb waves propagate with different velocities in homogeneous and heterogeneous models and the difference increases with aggregate ratio and particle size, which is a particularly important observation for wave-based diagnostic methods devoted to concrete structures.

  • Numerical Study on Seismic Response of a High-Rise RC Irregular Residential Building Considering Soil-Structure Interaction
    • Tomasz Falborski
    2020

    The objective of the present study is to investigate the importance of soilstructure interaction effects on the seismic response of a high-rise irregular reinforced-concrete residential building. In order to conduct this research, a detailed three-dimensional structure model was subjected to various earthquake excitations, also including a strong mining tremor. Soil-foundation flexibility was represented using the spring-based solutions, incorporating foundation springs and dashpots. For each soil type analyzed in this study, the foundation stiffness was calculated using the static stiffness, embedment correction factors, and dynamic stiffness modifiers. The influence of diverse soil conditions (represented by their average effective profile velocities and shear moduli) on the dynamic characteristics (e.g. fundamental vibration period) and seismic response (e.g. peak lateral accelerations) of the structure model was investigated and discussed. The numerical analysis results clearly demonstrate that the seismic performance of the building to the strong earthquake shaking can be significantly affected by the soil-structure interaction effects.

  • O analizach kratownicy ze ściskanym pasem dolnym
    • Marcin Krajewski
    2020 Inżynieria i Budownictwo

    Praca poświęcona jest analizom stateczności kratownicy poddanej obciążeniu skierowanemu pionowo ku górze. Przedstawione zostały badania wpływu stężeń usytuowanych w pasie górnym na nośność wyboczeniową konstrukcji. Przedstawiony został model zastępczy kratownicy w formie ściskanego pasa dolnego na podłożu sprężystym. Analizie poddano również wpływ sztywności skrętnej podpór skrajnych na wartość obciążenia krytycznego.

  • O historii i działalności Katedry Konstrukcji Metalowych Politechniki Gdańskiej
    • Piotr Iwicki
    2020 Pełny tekst Inżynieria i Budownictwo

    W artykule przedstawiono prowadzone w Katedrze Konstrukcji Metalowych badania naukowe, współpracę z przemysłem i działalność dydaktyczną od czasu jej powstania w 1945 r. po dzień dzisiejszy.

  • O nadjeżdżającej rewolucji w transporcie
    • Paweł Gora
    2020 Pełny tekst Pismo PG

    1,3 miliona – tyle osób rocznie na świecie ginie w wypadkach drogowych. Ponad 20 milionów zostaje rannych! 4 miliardy złotych – prawie tyle rocznie tracą kierowcy w 7 największych miastach w Polsce z powodu korków (a są to jedynie szacowane koszty straconego czasu i paliwa, bez uwzględnienia np. negatywnego wpływu na środowisko). Czy możemy coś z tym zrobić?

  • O średniowiecznej architekturze zakonów żebraczych w Chełmnie. Na marginesie tomu pierwszego "Księgi klasztorów ziemi chełmińskiej w średniowieczu"
    • Piotr Samól
    2020 Pełny tekst Zapiski Historyczne. Poświęcone Historii Pomorza i Krajów Bałtyckich

    Celem artykułu było przedstawienie wyników wieloletnich badań autora nad architekturą zakonów żebraczych w Chełmnie i polemika z ustaleniami najnowszej publikacji na ten temat. Autor, historyk architektury, prowadził kwerendy archiwalne i badania terenowe w Chełmnie od 2010 r. zbierając obszerny materiał źródłowy o kościołach świętych Piotra i Pawła (dominikanów) oraz świętych Mikołaja i Jakuba (franciszkanów). Na jego podstawie podjął polemikę z ustaleniami najnowszej monografii dotyczącej budownictwa klasztornego na ziemi chełmińskiej autorstwa Moniki Jakubek-Raczkowskiej, Juliusza Raczkowskiego i Piotr Olińskiego. Artykuł został podzielony na cztery części. W pierwszej z nich omówiono konieczność sprzężenia metod historycznych i architektonicznych, które pozwalają traktować zabytek jak źródło historyczne. Wskazano na niewykorzystane dotychczas źródła z archiwów polskich i niemieckich, które pozwalają doprecyzować historię budowlana założeń zakonów żebraczych w Chełmnie. Druga część dotyczy różnic w ustaleniach na temat kościoła dominikańskiego. Autor odnosi się w niej do podnoszonych w „Księdze klasztorów ziemi chełmińskiej w średniowieczu” wątpliwości, co do interpretacji wyników jego badań z 2014 r. Krótki przegląd stanu badań zestawiono z analizowanymi śladami materialnymi (wynikami badań architektonicznych), co pozwoliło falsyfikować wiele formułowanych w przeszłości hipotez na temat jego rozwoju przestrzennego. W trzeciej części omówiono możliwości rekonstrukcji układu przestrzennego średniowiecznego klasztoru predykantów oraz podstawowe fazy przebudowy w okresie nowożytnym, które poprzedziły rozbiórkę w latach trzydziestych XIX w. Ustalenia te są szczególnie ważne dla prowadzonych w przyszłości badań archeologicznych. Odstąpiono od przedstawienia historii budowlanej całego kościoła świętych Mikołaja i Jakuba, ponieważ jego złożona materia jest przedmiotem osobnego opracowania monograficznego. Ostatnia, czwarta część zawiera uwagi na temat lektoriów w świątyniach dominikanów i franciszkanów w Chełmnie. Ważnym elementem jest przedstawiona autorska dokumentacja śladów architektonicznych, pominięta w dotychczasowej literaturze przedmiotu. Opisane wyżej badania historyczne i architektoniczne skłaniają do refleksji nad metodą badań obiektów historycznych, które wymagają dobrego rozpoznania źródeł – zarówno pisanych, jak i architektonicznych. Ustalenia mają zastosowanie nie tylko w historii architektury, ale i dyscyplinach pokrewnych.

  • O wymiarowaniu kształtowników giętych na zimno według eurokodów i norm amerykańskich.
    • Patryk Deniziak
    2020 Pełny tekst Inżynieria i Budownictwo

    Nośne konstrukcje z kształtowników giętych na zimno były wykorzystywane w przemyśle lotniczym i motoryzacyjnym od początku XX w. W obiektach budowlanych początkowo pełniły one rolę elementów konstrukcyjnych drugorzędnych, takich jak ościeżnice czy elementy ścian działowych. Obecnie są stosowane również jako główne elementy nośne w halach przemysłowych (słupy, wiązary, konstrukcje wsporcze dźwignic). Pręty cienkościenne, ze względu na dużą smukłość ścianek, są wrażliwe na zjawisko utraty stateczności. W niniejszym artykule przedstawiono główne założenia i różnice pomiędzy dwiema metodami wymiarowania prętów cienkościennych: metoda amerykańska oraz europejska.

  • Obraz olejny, 100x180 cm, Bez tytułu
    • Jan Buczkowski
    2020

    Prezentacja obrazu na wystawie w Centrum Sztuki Współczesnej Łaźnia w Gdańsku

  • Obtaining and Characterization of the PLA/Chitosan Foams with Antimicrobial Properties Achieved by the Emulsification Combined with the Dissolution of Chitosan by CO2 Saturation
    • Szymon Mania
    • Karolina Partyka
    • Joanna Pilch
    • Ewa Augustin
    • Mateusz Cieślik
    • Jacek Ryl
    • Jia-Rong Jinn
    • Ya-Jane Wang
    • Anna Michałowska
    • Robert Tylingo
    2020 Pełny tekst

    A new method of obtaining functional foam material has been proposed. The materials were created by mixing the poly lactic acid (PLA) solution in chloroform, chitosan (CS) dissolved in water saturated with CO2 and polyethylene glycol (PEG), and freeze-dried for removal of the solvents. The composite foams were characterized for their structural (SEM, FT-IR, density, porosity), thermal (DSC), functional (hardness, elasticity, swelling capacity, solubility), and biological (antimicrobial and cytotoxic) properties. Chitosan in the composites was a component for obtaining their foamed form with 7.4 to 22.7 times lower density compared to the neat PLA and high porosity also confirmed by the SEM. The foams had a hardness in the range of 70–440 kPa. The FT-IR analysis confirmed no new chemical bonds between the sponge ingredients. Other results showed low sorption capacity (2.5–7.2 g/g) and solubility of materials (less than 0.2%). The obtained foams had the lower Tg value and improved ability of crystallization compared to neat PLA. The addition of chitosan provides the bacteriostatic and bactericidal properties against Escherichia coli and Staphylococcus aureus. Biocompatibility studies have shown that the materials obtained are not cytotoxic to the L929 cell line

  • Occurrences, sources, and transport of organochlorine pesticides in the aquatic environment of Antarctica
    • Joanna Potapowicz
    • Dimitra Lambropoulou
    • Christina Nannou
    • Krystyna Kozioł
    • Żaneta Polkowska
    2020 Pełny tekst SCIENCE OF THE TOTAL ENVIRONMENT

    We review information on the concentration levels of organochlorine pesticides in the abiotic aquatic environment (in seawater, sea ice, surface freshwater, snow, firn, and glacial ice) and the organisms inhabiting those, in Antarctica. Particular attention is given to the environmental fate of these pollutants, which modifies their impact on the organisms living in the Antarctic. OCPs have been delivered to the Antarctic environment mainly via long-range transport from inhabited areas, and due to their long accumulation they are sometimes reemitted from melting cryosphere. Since climate change is forecasted to intensify, the release of anthropogenic pollutants from increased seasonal thaw may prove its importance for the future state of this unspoiled environment. However, the limited estimations of the OCPs storage magnitude in the Antarctic cryosphere are relatively crude and may err significantly towards higher values. The OCPs are already present in different types of animal tissues at every trophic level, where they may cause negative effects such as reproductive disorders, decreased survival rates, and an increased parasitic load. Therefore, it is important to continuously monitor OCP concentrations in various elements of the Antarctic environment and the fate of these pollutants, taking into account their global and local sources, including the remobilization from frozen state.

  • Ocena jakości superkondensatorów wybranymi metodami, wykorzystując zjawiska losowe i badania rozkładu temperatury
    • Stanisław Galla
    • Arkadiusz Szewczyk
    • Janusz Smulko
    2020 Pełny tekst Przegląd Elektrotechniczny

    W artykule przedstawiono metody analizy jakości wykonania próbek superkondensatorów na podstawie pomiarów szumów generowanych w ich strukturach oraz rozkładów temperatury na ich powierzchni. Prezentowane metody zostały porównane z obecnie stosowanymi parametrami oceny jakości tych elementów. Wyniki uzasadniają wprowadzenie dodatkowych parametrów, pozwalających oceniać jakość superkondensatorów.

  • Ocena klimatu akustycznego w przestrzeni pasażerskiej elektrycznego zespołu trakcyjnego serii EN57
    • Roksana Licow
    • Dominika Szabłowska
    2020 Pełny tekst Pojazdy Szynowe

    W pracy przedstawiono wyniki badań poziomów dźwięku w przestrzeni pasażerskiej elektrycznego zespołu trakcyjnego (EZT) serii EN57 podczas postoju, rozruchu, jazdy oraz hamowania. Badania przeprowadzono na podstawie autorskiej metodyki badawczej bazując na normie PNEN ISO 3381:Kolejnictwo. Akustyka. Pomiar hałasu wewnątrz pojazdów szynowych. Badania przeprowadzono na linii kolejowej nr 250 od przystanku Gdańsk Śródmieście do stacji Rumia. Celem badań była ocena klimatu akustycznego w przestrzeni pasażerskiej elektrycznego zespołu trakcyjnego serii EN57, trójmiejskiej szybkiej kolei miejskiej linii S2 Gdańsk Śródmieście – Rumia. Wyniki przeprowadzonej analizy wskazały na miejsca potencjalnie zagrożone wyższymi poziomami dźwięków niż pozostałe oraz wpływ tych poziomów dźwięku na pasażerów korzystających z transportu publicznego jakim jest EZT serii EN57 w Trójmieście.

  • Ocena komfortu pieszego na kładkach. Case study
    • Anna Banaś
    2020 Pełny tekst Builder

    Trend w projektowaniu nowych kładek dla pieszych wymaga, aby były one coraz bardziej „wyszukane” i lekkie. Bardzo często jednak z tego powodu obiekty te mają pierwszą częstotliwość giętną pomostu zbliżoną do wymuszenia chodem pieszego. W niniejszej pracy przedstawiono trzy konstrukcje kładek dla pieszych. Każda z nich znalazła się w innej grupie narażenia na wystąpienie drgań rezonansowych, z uwagi na pierwszą częstotliwość drgań giętnych pomostu. Przeprowadzone badania pokazały, że kładka nad drogą S8, która znajdowała się w wysokiej grupie ryzyka, bez względu na sposób wymuszenia spełnia najwyższy poziom komfortu. W przypadku kładki w Bydgoszczy, która znalazła się w średniej grupie ryzyka poziomy przyspieszeń były znacznie większe. Przy wymuszeniach synchronicznych zapewniały często tylko minimalny komfort jej użytkownikom. W przypadku kładki w Gdyni, mimo stosunkowo wysokiej wartości częstotliwości drgań własnych i niskiego ryzyka wystąpienia rezonansu, nawet dla bardzo małych grup pieszych przyspieszenia były na bardzo wysokim poziomie. Kładka w normalnych warunkach eksploatacji zapewnia minimalny komfort użytkownikom. Przy wymuszeniach synchronicznych poziom komfortu jest już jednak nieakceptowalny. Przeprowadzone analizy i badania pokazują, że jednym z kluczowych elementów etapu projektowania jest analiza dynamiczna.

  • Ocena stopnia denaturacji oraz zawartości hydroksyproliny w kosmetycznej bazie kolagenowej.
    • Szymon Mania
    2020

    W ramach zadania wykonano pomiary oraz opracowano wyniki dotyczące określenia temperatury denaturacji oraz zawartości hydroksyproliny w bazie kolagenowej.

  • Ocena zagrożenia korozyjnego zbiorników na terenie modernizowanego Terminala Paliw LOTOS w Piotrkowie Trybunalskim.
    • Krzysztof Żakowski
    • Kazimierz Darowicki
    • Łukasz Gaweł
    • Tadeusz Sonneck
    2020

    Zbadano zagrożenie korozyjne nowo budowanych zbiorników na terenie modernizowanego terminala paliw. Oceny dokonano na podstawie badań agresywności korozyjnej pobranych próbek gruntu oraz wykonanych pomiarów terenowych. Uzyskane wyniki będą wykorzystane przy projektowaniu systemu ochrony katodowej nowych zbiorników podziemnych.

  • Od postawy prozdrowotnej w stoczni jachtowej do ograniczania zagrożeń na stanowisku pracy formierza-laminiarza
    • Anna Dembicka
    • Katarzyna Mołas
    2020 Pełny tekst Problemy Jakości

    Tematyka zdrowia i bezpieczeństwa pracowników, coraz częściej popularyzowana w świecie biznesu, nadal stanowi dość mało rozpoznany obszar działalności polskich przedsiębiorstw. Niniejszy artykuł porusza ważką kwestię promocji zdrowia w miejscu pracy jako czynnika zwiększającego efektywność pracy oraz jego wpływ na osiąganie wysokiej jakości produktu. Publikacja omawia znaczenie postawy prozdrowotnej i sposobów jej kształtowania w przemyśle jachtowym na przykładzie pracy formierza-laminiarza. Uszczegółowionej analizie poddana zostaje kwestia zmniejszania uciążliwości i szkodliwości czynników występujących podczas naprawy błędów powstających w procesie laminowania jachtu. Artykuł wieńczą propozycje możliwych do wdrożenia aktywności prozdrowotnych zarówno w pracy, jak i poza miejscem pracy. Publikacja wchodzi w skład cyklu prezentującego różne aspekty zarządzania procesowego w przemyśle stoczni jachtowych. Artykuł koncentruje się na procesie zarządzania kapitałem ludzkim w świetle orientacji prozdrowotnej.

  • Oddziaływanie elektronów z wybranymi prekursorami metalicznych i półprzewodnikowych nanostruktur wytwarzanych za pomocą skupionych wiązek elektronowych
    • Sylwia Stefanowska-Tur
    2020 Pełny tekst

    Praca poświęcona jest oddziaływaniom elektronów z prostymi prekursorami metody FEBID. W szczególności wyznaczono oraz przeanalizowano całkowite przekroje czynne na rozpraszanie elektronów funkcji energii dla wybranych cząsteczek: SnCl4, TiCl4, C(CH3)4, Si(CH3)4 oraz Ge(CH3)4, C5H6. W ramach pracy badano korelacje pomiędzy wartościami całkowitych przekrojów czynnych, a wybranymi fizykochemicznymi wielkościami charakteryzującymi badane związki, takimi jak statyczna dipolowa polaryzowalność elektryczna oraz elektryczny moment dipolowy. Szczególną uwagę zwrócono na wpływ metylacji, w tetraedrycznych związkach węgla, krzemu i germanu, na efektywność procesu rozpraszania elektronów. Zbadano wpływ zmiany zarówno atomu centralnego, jak i zamiany atomów zewnętrznych w cząsteczce tetraedrycznej, na zależność energetyczną całkowitego przekroju czynnego. Przeprowadzone badania przyczyniają się do lepszego zrozumienia oddziaływania elektronów z cząsteczkami zawierającymi atomy C, Si, Ge, Sn oraz Ti.

  • Oko, obraz olejny na płótnie
    • Krzysztof Wróblewski
    2020

    Krzysztof Wróblewski w 1992 roku rozpoczął komponowanie symetrycznych obrazów składających się z realistycznych i abstrakcyjnych powierzchni. Połowę obrazu stanowią zawsze układy trójkątów. Relacje pomiędzy realizmem i abstrakcją oraz współzależność malarstwa i fotografii są kluczowymi zagadnieniami w jego twórczości. Jego prace często tworzą cykle tematyczne. Obraz pt. Oko prezentowany na 11. Charytatywnej Aukcji Sztuki Współczesnej Aperio należy do jednego z tych cyklów i jest charakterystyczny dla twórczości artysty.

  • Określenie przyczyn korozji śrub napędowych ORP Drużno.
    • Krzysztof Żakowski
    • Stefan Krakowiak
    2020

    Przedmiotem ekspertyzy było określenie przyczyn korozji śrub napędowych na okręcie ORP Drużno oraz wskazanie zaleceń odnośnie ograniczenia czynników powodujących ich korozję.

  • On Applications of Elements Modelled by Fractional Derivatives in Circuit Theory
    • Jacek Gulgowski
    • Tomasz Stefański
    • Damian Trofimowicz
    2020 Pełny tekst ENERGIES

    In this paper, concepts of fractional-order (FO) derivatives are reviewed and discussed with regard to element models applied in the circuit theory. The properties of FO derivatives required for the circuit-level modeling are formulated. Potential problems related to the generalization of transmission-line equations with the use of FO derivatives are presented. It is demonstrated that some formulations of FO derivatives have limited applicability in the circuit theory. Out of the most popular approaches considered in this paper, only the Grünwald–Letnikov and Marchaud definitions (which are actually equivalent) satisfy the semigroup property and are naturally representable in the phasor domain. The generalization of this concept, i.e., the two-sided fractional Ortigueira–Machado derivative, satisfies the semigroup property, but its phasor representation is less natural. Other ideas (including the Riemann–Liouville and Caputo derivatives—with a finite or an infinite base point) seem to have limited applicability.

  • On Applications of Fractional Derivatives in Circuit Theory
    • Jacek Gulgowski
    • Tomasz Stefański
    2020

    In this paper, concepts of fractional-order (FO) derivatives are discussed from the point of view of applications in the circuit theory. The properties of FO derivatives required for the circuit-level modelling are formulated. Potential problems related to the generalization of transmission line equations with the use of FO derivatives are presented. It is demonstrated that some of formulations of the FO derivatives have limited applicability in the circuit theory. That is, the Riemann-Liouville and Caputo derivatives with finite base point have a limited applicability whereas the Grünwald-Letnikov and Marchaud derivatives lead to reasonable results of the circuit-level modelling.

  • On Applications of Fractional Derivatives in Electromagnetic Theory
    • Jacek Gulgowski
    • Tomasz Stefański
    2020 Pełny tekst

    In this paper, concepts of fractional-order (FO) derivatives are analysed from the point of view of applications in the electromagnetic theory. The mathematical problems related to the FO generalization of Maxwell's equations are investigated. The most popular formulations of the fractional derivatives, i.e., Riemann-Liouville, Caputo, Grünwald-Letnikov and Marchaud definitions, are considered. Properties of these derivatives are evaluated. It is demonstrated that some of formulations of the FO derivatives have limited applicability in the electromagnetic theory. That is, the Riemann-Liouville and Caputo derivatives with finite base point have a limited applicability whereas the Grünwald-Letnikov and Marchaud derivatives lead to reasonable generalizations of Maxwell's equations.

  • On coertia and inertia in aspects of Natanson’s nonlinear extended thermodynamics
    • Janusz Badur
    • Paweł Ziółkowski
    • Tomasz Kowalczyk
    • Sylwia Gotzman
    • Daniel Sławiński
    • Tomasz Ochrymiuk
    • Marcin Daniel Lemański
    • Rafał Hyrzyński
    • Bartosz Kraszewski
    • Mateusz Bryk
    • Michał Stajnke
    • Piotr Józef Ziółkowski
    2020 Pełny tekst

    In this article, the previously underrepresented contributions of Natanson to the field of thermodynamics have been presented. In order to identify a source of irreversibility at Nature, Natanson introduced the concept of Coertia, which is similar to inertia. Natanson’s Coertia is a fundamental property of space that is responsible for every irreversible phenomena in matter, as well as in the electromagnetic and gravitational fields. We focus on the mathematical reconstruction of a few of his principal ideas that until now have been neglected by the literature. To set these ideas in proper epistemological order, we thought it would be valuable to first revalue and reconstruct some missing parts of the proceedings process by Ladislavus Natanson constructed their thermodynamics. We also aimed to present Natanson’s achievements against the background of modern continuum mechanics, exemplifying old but still relevant approaches. We propose that Natanson’s ideas were ahead of their time by about one century. Give that scientist was educated in the scientific royal way: chemistry, through mechanic of solid and fluid, thermodynamics, electro-chemistry, electrodynamics, early quantum and relativistic mechanics, we can closely compare their conceptions and solutions. Natanson was in strong opposition with Newtonian mechanisms, the Maupertuis least action principle formed the basis of his activities, which they were developing as a sum of elementary quantum actions.

  • On Computationally-Efficient Reference Design Acquisition for Reduced-Cost Constrained Modeling and Re-Design of Compact Microwave Passives
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    2020 Pełny tekst IEEE Access

    Full-wave electromagnetic (EM) analysis has been playing a major role in the design of microwave components for the last few decades. In particular, EM tools allow for accurate evaluation of electrical performance of miniaturized structures where strong cross-coupling effects cannot be adequately quantified using equivalent network models. However, EM-based design procedures (parametric optimization, statistical analysis) generate considerable computational expenses. These can be mitigated using fast surrogate models, yet their construction is hindered by the curse of dimensionality but also the utility requirements: a practically useful model needs to cover sufficiently broad ranges of geometry/material parameters as well as operating conditions. The recently proposed constrained modeling methods—both forward and inverse—work around the above issues by setting up the surrogate only in the relevant regions of the parameter space, i.e., containing designs that are of high quality with respect to the assumed performance measures. The model domain is established using pre-optimized sets of reference points. The high cost of generating such designs may significantly diminish the computational savings achieved by operating in confined domains. This paper discusses a technique for fast reference design acquisition, involving inverse gradients, and expedited local refinement aided by the response feature technology. The presented approach is validated using a branch-line coupler and miniaturized rat-race coupler. It is also demonstrated to considerably reduce the cost of constructing performance-driven surrogates as well as setting up efficient procedures for fast geometry scaling of microwave components.

  • On description of periodic magnetosonic perturbations in a quasi-isentropic plasma with mechanical and thermal losses and electrical resistivity
    • Anna Perelomova
    2020 Pełny tekst PHYSICS OF PLASMAS

    Magnetosonic periodic perturbations in a uniform and infinite plasma model are considered. Damping due to compressional viscosity, electrical resistivity, and thermal conduction are taken into account, as well as some heating–cooling function, which may destroy the isentropicity of wave perturbations. The wave vector forms arbitrary angle h with the equilibrium straight magnetic field, and all perturbations are functions of time and longitudinal coordinate. Variable h and plasma- b bring essential difficulties in the description of magnetosonic perturbations, which may be fast or slow. Wave damping of each kind depends differently on h and plasma- b . Longitudinal velocity, which is periodic at any distance from an exciter, is analytically constructed. It approximates the exact solution with satisfactory accuracy.

  • On design and analysis of flow characteristics of the last stage of gas-steam turbine
    • Stanisław Głuch
    • Paweł Ziółkowski
    • Łukasz Witanowski
    • Michał Stjanke
    • Piotr Józef Ziółkowski
    • Janusz Badur
    2020 Pełny tekst

    Research regarding blade design and analysis of flow have been conducted for over a century. Meanwhile new concepts and design approaches were created and improved. Advancements in information technologies allowed to introduce computational fluid dynamics (CFD) and computational flow mechanics (CFM). Currently a combination of mentioned methods is used for design of turbine blades. These methods enabled us to improve flow efficiency and strength of turbine blades. This paper relates to a new type turbine which is in the phase of theoretical analysis, because the working fluid is a mixture of steam and gas generated in wet combustion chamber. Conception of this cycle and thermodynamic calculations are presented in previous papers, therefore the main aim of this article is design and analysis of flow characteristics of the last stage of gas-steam turbine. When creating the spatial model, the atlas of profiles of reaction turbine steps was used. In this paper results of CFD calculations of twisting of the last stage are presented. Blades geometry and the computational mesh are also presented. Triangles of velocity for selected dividing sections are presented. It is worth noting that the velocity along the pitch diameter varies greatly. Near the root it shows an action triangle, on the other hand, near the tip it presents a reaction type of triangle. Velocity fields and pressure fields show the flow characteristics of the last stage of gas-steam turbine. The net efficiency of the cycle is estimated as 54.35% regarding to enthalpy drop, however, the net efficiency taking into account the mechanical power determined from the stage theory is equal 52.61%.