2021 - Repozytorium publikacji - Politechnika Gdańska

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3D DEM SIMULATIONS OF BASIC GEOTECHNICAL TESTS WITH EARLY DETECTION OF SHEAR LOCALIZATION.
- Aleksander Grabowski
- Michał Nitka
2021 Pełny tekst Studia Geotechnica et Mechanica
W artykule przedstawiono rezultaty numeryczne dla podstawowych testów geotechnicznych: testu trójosiowego ściskania oraz w aparacie bezpośredniego ścinania dla piasku bez kohezji. Wszystkie testy zostały wykonane w 3D, a piasek został wymodelowany w postaci kulek wraz z momentami symulującymi nieregularny kształt ziarna. Podczas badań sprawdzono wpływ parametrów fizycznych (m. in. początkowy wskaźnik porowatości, obciążenie pionowe przyłożone do próbki) na zachowanie się materiału sypkiego. Nacisk położono na analizę zachowań materiału pozwalających jako pierwszych przewidzieć miejsce wystąpienia strefy ścięcia. Na poziomie ziarna zbadano m. in. obroty cząsteczek, porowatość, fluktuacje oraz rozkład sił. Na podstawie otrzymanych rezultatów wyłonione zostały predyktory pozwalające najwcześniej wykryć powstającą strefę ścięcia.
3D DEM simulations of monotonic interface behaviour between cohesionless sand and rigid wall of different roughness
- Aleksander Grabowski
- Michał Nitka
- Andrzej Tejchman-Konarzewski
2021 Pełny tekst Acta Geotechnica
Artykuł omawia wyniki metodą elementów dyskretnych (DEM) dotyczace zachowania się strefy kontaktu między bezkohezyjnym piaskiem a sztywną scianą o różnej szorstkości. Obliczenia wykonano dla dla różnej wysokości, nachylenia i rozstawu rowków wzdłuż sciany, które symulowały jej szorstkość. W symulacjach zmieniano dodatkowo ciśnienie pionowe i początkowy wskaźnik porowatosci piasku. Nacisk położono na wpływ szorstkości na mobilizowany kąt tarcia i strefę ścinania oraz związki między przemieszczeniami a obrotami cząstek oraz naprężeniami ścinających i momentami naprężeniowymi wzdłuż ściany.
3D Scanning of Semitransparent Amber with and without Inclusions
- Adam Kaczmarek
- Jacek Lebiedź
- Jakub Jaroszewicz
- Wojciech Święszkowski
2021
This paper is concerned with making 3D scans of semitransparent ambers with and without inclusions. The paper presents results of using a variety of devices applied for this purpose. Equipment used in the experiments includes a 3D laser scanner, a structured light scanner, a stereo camera, a camera array and a tomograph. The main object used in the experiment was an amber with a fossil of a lizard. The paper shows possibilities of acquiring the 3D structure of fossils embedded in semitransparent material which interfere with the measurement performed by 3D scanning equipment. Moreover, the paper shows the application of results of 3D scanning as the 3D scan of a lizard was reconstructed in a virtual reality cave making it possible to visualize in detail its shape and texture.
A 95-Year-Old Concrete Arch Bridge: From Materials Characterization to Structural Analysis
- Andrzej Ambroziak
- Maciej Malinowski
2021 Pełny tekst Materials
The structural analysis of a 95-year-old concrete arch bridge located in Jagodnik (Poland) is performed in this paper, in order to check its behavior under today’s traffic loads. The mechanical properties of both the concrete and the reinforcement are investigated by testing cores and bar stubs extracted from the bridge. Structural analysis confirms that the bridge meets today’s load requirements in terms of bearing capacity, serviceability state, and that the adopted structural improvements (a new deck slab on top of the existing structure and a layer of mortar to protect the surface of the old concrete) are effective. In this way, the 95-year-old arch bridge was given a new life. The structural improvements show how combining numerical modelling and laboratory tests can contribute to the preservation of an old—though fairly simple—and valuable structure, otherwise destined to demolition, with both environmental and economic benefits.
A Assessment of Management Efficiency in Local Administrative Offices: Case Study Poland
- Mariola Grzebyk
- Agata Pierścieniak
- Małgorzata Stec
2021 Lex Localis-Journal of Local Self-Government
The analysis of management efficiency is an important element in evaluating the functioning of public administration from an economic point of view. In order to achieve greater efficiency of the management process, and thus the quality in public administration, it is important to analyze and evaluate its elements. Modern research usually covers individual elements, parts of the management process. However, the current study proposes a comprehensive approach to this process. The objective of the article is the evaluate levels of management efficiency of local government offices using a single synthetic indicator and also to identify areas that hinder management efficiency. The study applies the institutional analysis methodology, adjusting it to the needs of the article. The article postulates that areas that call for immediate changes in Poland's local government offices should include such areas as strategic and financial management, invigorating economic development, project management and public service offers. Any changes thus introduced in these areas may enhance improvements in management processes, effectiveness and efficiency of activities, the quality of the office's functioning, organizational development, which togethr indirectly affects local development.
A case study of robust sliding mode control applied to inverted pendulum on a cart
- Mateusz Czyżniewski
- Rafał Łangowski
- Dawid Klassa
- Mateusz Matwiszyn
2021 Pełny tekst
A control problem of an inverted pendulum on a cart has been addressed in this paper. In particular, a synthesis of alternative sliding mode control for stabilisation of an inverted pendulum at an upper equilibrium point has been investigated. Hence, the feasibility of implementing the developed control system, taking into account primarily the friction of the cart against the gantry and the limited length of the gantry, in a real plant has been given. The proposed control system has been tested by simulation in Matlab/Simulink environment and satisfactory performance of its operation has been obtained.
A chemo-mechano-thermodynamical contact theory for adhesion, friction, and (de)bonding reactions
- Roger Sauer
- Thang X. Duong
- Kranthi K. Mandadapu
2021 Pełny tekst MATHEMATICS AND MECHANICS OF SOLIDS
This work presents a self-contained continuum formulation for coupled chemical, mechanical, and thermal contact interactions. The formulation is very general and, hence, admits arbitrary geometry, deformation, and material behavior. All model equations are derived rigorously from the balance laws of mass, momentum, energy, and entropy in the framework of irreversible thermodynamics, thus exposing all the coupling present in the field equations and constitutive relations. In the process, the conjugated kinematic and kinetic variables for mechanical, thermal, and chemical contact are identified, and the analogies between mechanical, thermal, and chemical contact are highlighted. Particular focus is placed on the thermodynamics of chemical bonding distinguishing between exothermic and endothermic contact reactions. Distinction is also made between long-range, non-touching surface interactions and short-range, touching contact. For all constitutive relations, examples are proposed and discussed comprehensively with particular focus on their coupling. Finally, three analytical test cases are presented that illustrate the thermo-chemo-mechanical contact coupling and are useful for verifying computational models. Although the main novelty is the extension of existing contact formulations to chemical contact, the presented formulation also sheds new light on thermo-mechanical contact, because it is consistently derived from basic principles using only a few assumptions.
A Comparability of Renal Length and Volume Measurements in MRI and Ultrasound in Children
- Dominik Świętoń
- Weronika Bernard
- Małgorzata Grzywińska
- Piotr Czarniak
- Agata Durawa
- Mariusz Kaszubowski
- Maciej Piskunowicz
- Edyta Szurowska
2021 Pełny tekst Frontiers in Pediatrics
Introduction: Despite the significant increase in use of magnetic resonance imaging (MRI) in children, there is still a lack of normal reference values of renal size in this method and reference values are being interpolated from the ultrasound (US) studies. The study provides comparative analysis of agreement in renal length and volume measurements between MRI and ultrasound. Materials and Methods: Ninety-three children with a mean age of 8.0 ± 6.0 years, who had undergone both renal US and MRI exams, were included in the study. Participants were divided into three subgroups; each kidney was considered separately. Group 1 included 106 kidneys without any anomalies. Group 2 comprised 48 kidneys with a dilated collecting system. Group 3 included 32 kidneys with a duplicated collecting system. Measurements were taken in three dimensions, and renal volume was calculated from the ellipsoid formula. Results: We found no significant difference between US and MRI measurements in Group 1 and Group 2. In Group 3, the difference between measurements in both imaging methods was significant. The mean difference varied from 0.05% in Group 1, 2.95% in Group 2, to 4.99% in Group 3. Conclusion: The US and MRI are comparable methods in renal size measurements. The interpolation of sonographic renal length and volume reference values to the MRI in the pediatric population is justified, as there is a strong agreement between both methods. Both methods can be used interchangeably for following up of the renal size changes in the pediatric population.
A comparative performance assessment of a hydrodynamic journal bearing lubricated with oil and magnetorheological fluid
- F. Quinci
- Wojciech Litwin
- Michał Wodtke
- R. van den Nieuwendijk
2021 Pełny tekst TRIBOLOGY INTERNATIONAL
This work presents the investigation results of a journal bearing lubricated with magnetorheological fluid that is activated by a local constant magnetic field to vary both the local flow resistance and pressure. The bearing performance is assessed via Finite Element Modelling (FEM) and results are corroborated by experiments. The FEM model uses the Bingham model to describe the fluid film. A dedicated test rig is used to assess the hydrodynamic behavior of the bearing with magnetorheological fluid, and the results are compared with the same geometrical bearing lubricated with oil. Thicker fluid films at low speeds, beneficial pressure distribution, and higher friction losses under all operating conditions are observed in the bearing with magnetorheological fluid compared to the oil lubrication.
A competition between two- and three-body dissociation channels in photo-double-ionization of tetrahydro-2H-pyran and 3,4-dihydro-2H-pyran molecules
- Tomasz Wąsowicz
- Antti Kivimäki
- Robert Richter
2021
Various molecules possess structures consisting of the heterocyclic rings containing oxygen atoms. These substances often play a significant role in many different fields of chemistry, medicine, and biology. Due to a specific atomic composition and bond arrangement, many of these molecules retain unique electronic properties, which may be probed by diverse spectroscopic techniques, including those utilizing synchrotron radiation. In particular, the photoelectron-photoion coincidence (PEPICO) technique provides detailed information about the presence of specific bonds, the reactivity of these molecules, as well as their electronic structure and decomposition mechanisms.
A Comprehensive Analysis of Deep Neural-Based Cerebral Microbleeds Detection System
- Maria Ferlin
- Michał Grochowski
- Arkadiusz Kwasigroch
- Agnieszka Mikołajczyk
- Edyta Szurowska
- Małgorzata Grzywińska
- Agnieszka Sabisz
2021 Pełny tekst Electronics
Machine learning-based systems are gaining interest in the field of medicine, mostly in medical imaging and diagnosis. In this paper, we address the problem of automatic cerebral microbleeds (CMB) detection in magnetic resonance images. It is challenging due to difficulty in distinguishing a true CMB from its mimics, however, if successfully solved it would streamline the radiologists work. To deal with this complex three-dimensional problem we propose a machine learning approach based on a 2D Faster RCNN network. We aimed to achieve a reliable system, i.e. with balanced sensitivity and precision. Therefore, we have researched and analysed, among others impact of the way the training data are provided to the system, their pre-processing, the choice of model and its structure and also the ways of regularisation. Furthermore, we also carefully analysed the network predictions and proposed an algorithm for its post-processing. The proposed approach enabled for obtaining high precision (89.74\%), sensitivity (92.62\%), and F1 score (90.84\%). The paper presents the main challenges connected with automatic cerebral microbleeds detection, its deep analysis and developed system. The conducted research may significantly contribute to automatic medical diagnosis.
A Comprehensive Experimental and Theoretical Study on the[{(η5-C5H5)2Zr[P(µ-PNEt2)2P(NEt2)2P]}2O Crystalline System
- Agnieszka Łapczuk-Krygier
- Katarzyna Kazimierczuk
- Jerzy Pikies
- Mar Ríos-Gutiérrez
2021 Pełny tekst MOLECULES
The structure of tetraphosphetane zirconium complex C52H100N8OP10Zr21 was determined by single crystal X-ray diffraction analysis. The crystal belongs to the monoclinic system, space group P21/c, with a = 19.6452(14), b = 17.8701(12), c = 20.7963(14)Å, α = γ = 90°, β = 112.953(7)°, V = 6722.7(8)Å3, Z = 4. The electronic structure of the organometallic complex has been characterized within the framework of Quantum Chemical Topology. The topology of the Electron Localization Function (ELF) and the electron density according to the Quantum Theory of Atoms in Molecules (QTAIM) show no covalent bonds involving the Zr atom, but rather dative, coordinate interactions between the metal and the ligands. This is the first reported case of a Zr complex stabilized by an oxide anion, anionic cyclopentadienyl ligands and rare tetraphosphetane anions.
A Comprehensive Investigation of Knowledge Management Publications
- Rodrigo Oliveira de Castro
- Cesar Sanin
- Andrew Levula
- Edward Szczerbicki
2021 Pełny tekst
Recent trends in knowledge management (KM) have increasingly indicated a lack of agreement, integration and classification between different KM domains. As such, experts are inadequately equipped when attempting to classify KM into their specific areas that could effectively contribute to a technocratic approach behind the organizational strategy. This paper illustrates a method of classifying KM publications by using a scheme that assists technocratic developments to explicitly expresses knowledge using a clearly defined approach. A classification method is applied using a taxonomy template to perform procedures and as a result offers an alternative approach for the classification and organization of KM publications. A series of 180 KM publications produced over the past 15 years was analyzed using the proposed taxonomy framework. The results highlighted that there were two key categories: Conceptual and Empirical which helps to explain the existing discrepancies found in KM. This enables the reuse and sharing of this new classification approach to provide guidance for academics and practitioners.
A comprehensive survey on low-cost ECG acquisition systems: Advances on design specifications, challenges and future direction
- Nasir Faruk
- Abubakar Abdulkarim
- Ifada Emmanuel
- Yusuf Y. Folawiyo
- Kayode S. Adewole
- Hammed Mojeed
- Abdukareem A. Oloyede
- Lukman A. Olawoyin
- Ismaeel A. Sikiru
- Musa Nehemiah
- Abdulsalam Ya'u Gital
- Haruna Chiroma
- James A. Ogunmodede
- Mubarak Almutairi
- Ibraheem A. Katibi
2021 Biocybernetics and Biomedical Engineering
Availability of low-cost, reliable, and portable Electrocardiography (ECG) devices is still very important in the medical world today. Despite the tremendous technological advancement, Cardiovascular Diseases (CVDs) remain a serious health burden claiming millions of lives on an annual basis globally. This is more prevalent in Low and Middle-Income Countries (LMICs) where there are huge financial instability and lack of critical infrastructure and support services for the health care system. Efforts aimed at reducing the prevalence of CVDs are confounded by late diagnosis, frequently, caused by lack of access to or non-availability of basic diagnostic modalities such as the ECG. Hence effective mitigation of the effect of CVDs in LMICs depend on the development of such devices at low-cost with reliability, accuracy and energy efficiency. This paper therefore, was developed to understand the state of the art of low-cost ECG acquisition systems with respect to design features and system capabilities for different use cases. In addition, different design options and taxonomies of available low-cost ECG devices, case studies reports of efficacy tests have been provided. The paper proposes a generalised ECG framework and provides implementation challenges and open research directions that should be considered when developing such devices for proper management of CVDs.
A device for measuring heat flux on a rocket skin surface
- Adam Dąbrowski
- Róża Pietruszewska
- Szymon Krawczuk
2021 Pełny tekst
A novel method for measuring heat flux on a surface is presented. It is an extensive upgrade of currently known heat flux sensors used mostly in civil engineering. As the thermal environment of launchers, especially sounding rocket can have an enormous negative effect on payload, careful considerations have to be taken in the process of preparing insulation. Usually, thermal data provided by the launch vehicle manufacturer is limited only to temperature ranges, sometimes time plot. However, temperature is a very local phenomenon, and depends heavily on multiple factors such as launch configuration, insulation material, convection coefficient, air pressure, etc. Technical standards such as ECSS-E-HB-31-03A – Thermal analysis handbook incourages to perform thermal Coupled Launch Analysis (CLA) prior to launch. Access to precise boundary conditions is limiting verification of such results. The heat flux density on rocket skin varies greatly during course of flight, as the vehicle traverses layers of atmoshpere of various density with various velocities. Furthermore, it is difficult to determine the vector of heat flow a priori. These problems are handled in the design of new heat flux sensor. Due to special design, a 1D homogenous heat flow is enforced which allows easy model estimation and simplifies future calculations. As a result, no complicated finite element analysis is required and apparent heat flux density values can be calculated in real time by a simple embedded system with little computation power. A crucial element is dimensioning the sensor to match the launcher. The most important criteria are proper range of measurement (no saturation) and appropriate sensivity. The physics of the sensor has been carefully examined by various means including: analytical calculations, finite differences model and finite element analysis. The results of these calculations are verified with flights on AMBER and REXUS rockets. The device has a commercialization purpose for any launcher. The data it provides enables for more precise design of future payload, such as insulation thickness optimisation or material choice. Preliminary results from sounding rocket flights will be presented.
A dynamic vehicle-bridge model based on the modal identification results of an existing EN57 train and bridge spans with non-ballasted tracks
- Marek Szafrański
2021 Pełny tekst MECHANICAL SYSTEMS AND SIGNAL PROCESSING
This paper addresses the methodology of the bridge-vehicle dynamic model definition based on the free response measurements of an existing train and existing bridge spans. In the case of the railway vehicle, the methodology uses the impulse excitations of a single car by means of the wedge method. In the case of the bridge spans, free responses are collected after the passages of trains. The global modal parameters (frequencies and modal damping) of both structures are identified using two modal identification techniques, i.e., the eigensystem realization algorithm (ERA) and the peak picking method (PP). A simplified single-suspension model of the vehicle with 11 global dof’s is proposed that can be useful in the bridge-vehicle interaction analysis. Two steel spans having non-ballasted tracks are the bridge structures. Field tests are conducted to identify the modal parameters and validate the numerical models. Finally, numerical simulations of the train passing over the bridges are compared with the in situ measurements performed under operating conditions.
A general approach to study molecular fragmentation and energy redistribution after an ionizing event
- Ewa Erdmann
- Néstor Aguirre
- Suvasthika Indrajith
- Jacopo Chiarinelli
- Alicja Domaracka
- Patrick Rousseau
- Bernd Alan Huber
- Paola Bolognesi
- Robert Richter
- Lorenzo Avaldi
- Sergio Díaz-Tendero
- Manuel Alcamí
- Marta Łabuda
2021 Pełny tekst PHYSICAL CHEMISTRY CHEMICAL PHYSICS
We propose to combine quantum chemical calculations, statistical mechanical methods, and photoionization and particle collision experiments to unravel the redistribution of internal energy of the furan cation and its dissociation pathways. This approach successfully reproduces the relative intensity of the different fragments as a function of the internal energy of the system in photoelectron–photoion coincidence experiments and the different mass spectra obtained when ions ranging from Ar+ to Xe25+ or electrons are used in collision experiments. It provides deep insights into the redistribution of the internal energy in the ionized molecule and its influence on the dissociation pathways and resulting charged fragments. The present pilot study demonstrates the efficiency of a statistical exchange of excitation energy among various degrees of freedom of the molecule and proves that the proposed approach is mature to be extended to more complex systems.
A High-Arctic flow-through lake system hydrochemical changes: Revvatnet, southwestern Svalbard (years 2010–2018)
- Marek Ruman
- Klaudia Kosek
- Krystyna Kozioł
- Michał Ciepły
- Katarzyna Kozak-Dylewska
- Żaneta Polkowska
2021 Pełny tekst CHEMOSPHERE
Lake ecosystems are strongly coupled to features of their surrounding landscapes such as geomorphology, lithology, vegetation and hydrological characteristics. In the 2010–2018 summer seasons, we investigated an Arctic flow-through lake system Revvatnet, located in the vicinity of the coastal zone of Hornsund fjord in Svalbard, characterising its hydrological properties and the chemical composition of its waters. The lake system comprises of a small upper lake and a large lower one, the latter cone-shaped, with −29.1 m maximum depth. With near-neutral pH (full range 6.5–8.4) and low EC (7–147 μS cm-1), the lake has rather similar characteristics to many Arctic lakes. Metal and metalloid concentrations were either similar across the lake system or increased downstream (except Zn, which has important ore-bearing veins in the upper part of the catchment), which is consistent with the likely slow dissolution of suspended particles within the lakes. The ΣPAHs concentrations ranged from <MDL to 2151 ng L-1, and according to the indicator PAHs concentration ratios, they originated from a mixture of combustion processes (they were not petrogenic). Principal component analysis showed that seasonal variability was the most characteristic feature of the chemical composition of these waters, although there appear to be consistent changes with time (sampling year) as well. Future research should explore the occurrence of high maxima in the concentrations of priority pollutants, such as PAHs, metals and metalloids (e.g. As).
A hyperelastic model for soils with stress-induced and inherent anisotropy
- Marcin Cudny
- Katarzyna Staszewska
2021 Pełny tekst Acta Geotechnica
In this paper, modelling of the superposition of stress-induced and inherent anisotropy of soil small strain stiffness is8presented in the framework of hyperelasticity. A simple hyperelastic model, capable of reproducing variable stress-induced9anisotropy of stiffness, is extended by replacement of the stress invariant with mixed stress–microstructure invariant to10introduce constant inherent cross-anisotropic component. A convenient feature of the new model is low number of material11constants directly related to the parameters commonly used in the literature. The proposed description can be incorporated12as a small strain elastic core in the development of some more sophisticated hyperelastic-plastic models of overconsoli-13dated soils. It can also be used as an independent model in analyses involving small strain problems, such as dynamic14simulations of the elastic wave propagation. Various options and features of the proposed anisotropic hyperelastic model15are investigated. The directional model response is compared with experimental data available in the literature.
A measurement method for lossy capacitive relative humidity sensors based on a direct sensor-to-microcontroller interface circuit
- Zbigniew Czaja
2021 Pełny tekst MEASUREMENT
A new time-domain measurement method for determining the capacitance and resistance values of lossy relative humidity capacitive sensors is presented. The method is based on a direct sensor-to-microcontroller interface for microcontrollers with internal analog comparators and timers. The interface circuit consists only of four reference resistors (two reference resistors if a microcontroller includes a voltage reference source), a given sensor and a microcontroller. A systematic error correction algorithm based on a correction dictionary and the M-multiple measurement approach are also proposed in the paper. Experimental investigations were carried out using a prototype device based on an 8-bit ATXmega32A4 microcontroller. The experimental research confirmed that the relative errors of measurement of capacitance introduced by the interface circuit are less than 0.71% (for capacitance values 100 – 286 pF), and the relative errors of measurement of resistance are less than 0.74% (for resistance values 1 – 10 MOhm).