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  • 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).

  • A MEASUREMENT SYSTEM FOR MONITORING CARDIOVASCULAR EVENTS IN SYNCOPE PATIENTS
    • Michał Pietrewicz
    • Katarzyna Mazur
    • Ewa Wagner-Wysiecka
    2021

    Syncope phenomena is an abrupt and transient loss of consciousness leading to interruption of awareness of one’s surroundings and falls with risk of injury. Syncope is often followed by complete and usually rapid spontaneous recovery. It is said that half of all individuals experience syncopal event at least once during their life. The condition can occur at any age and happens in people with and without other medical problems. The underlying mechanism is global hypoperfusion of both the cerebral cortices or focal hypoperfusion of the reticular activating system. Decreased cerebral perfusion is common to most causes of syncope. Cessation of a cerebral perfusion for even a short time, as 3-5 seconds, could result in syncope. Decreased cerebral perfusion may occur as a result of decreased both cardiac output or systemic vascular resistance. There are several different types of syncope which derive from different etiologies such as the neurally-mediated (reflex) syncope, orthostatic hypotension which may be caused by dehydration or due to medication and the cardiovascular derived syncopal events which are most dangerous ones. The most common syncope event is called vasovagal syncope. Such commonfaint may be experienced by normal persons with no evidence of any heart disease. Vasovagal syncope is the most common cause of such phenomena in young adults. As in other forms of neurally-mediated reflex syncope, it is due to systemic hypotension resulting in a transient period of inadequate cerebral blood flow. Vasovagal syncope can be preceded by such symptoms as pallor, nausea, sweating or heart palpitations. It often occurs when person is exposed to the prolonged standing, heat, emotional stress, trauma or pain etc. During and after the syncopal event the headache, confusion, discomfort and chest pain may occur, but there are many events that end up with no side effects at all. Overall, even if the syncopal event may have no side effects, it impacts patient quality of life and often may lead to dramatic consequences of self-injury or risk of danger for surrounding people (e.g. syncopal event occurring while driving a car). Monitoring cardiovascular events in syncope patients is tough and challenging issue.

  • A Method for Underwater Wireless Data Transmission in a Hydroacoustic Channel under NLOS Conditions
    • Jerzy Mizeraczyk
    • Ryszard Studanski,
    • Andrzej Zak
    • Agnieszka Czapiewska
    2021 Pełny tekst SENSORS

    Wireless data transmission in the hydroacoustic channel under non-line-of-sight (NLOS) propagation conditions, for example, during a wreck penetration, is difficult to implement reliably. This is mostly due to the multipath propagation, which causes a reduction in the quality of data reception. Therefore, in this work an attempt has been made to develop a reliable method of wireless underwater communication test it under the NLOS conditions. In our method, we used multiple frequency-shift keying (MFSK) modulation, sending a single bit on two carriers, and diversity combining. The method was tested in laboratory conditions which simulated underwater signal propagation during the penetration of the wreck. The propagation conditions were investigated by determining the impulse responses at selected measurement points using the correlation method. Additionally, for comparison, the data transmission quality was determined by the bit error rate (BER) under the same conditions using direct sequence spread spectrum (DSSS) and binary phase shift keying (BPSK) modulation. The obtained results confirmed the usefulness of the application of the developed method for wireless data transmission in a hydroacoustic channel under NLOS conditions.

  • A method of predicting the best conditions for large-size workpiece clamping to reduce vibration in the face milling process
    • Krzysztof Kaliński
    • Natalia Stawicka-Morawska
    • Marek Galewski
    • Michał Mazur
    2021 Pełny tekst Scientific Reports

    The paper presents an innovative method of solving the problem of vibration suppression during milling of large-size details. It consists in searching for the best conditions for clamping the workpiece based on a rapid modal identification of the dominant natural frequencies only and requires repetitive changes in the tightening torque of the clamping screws. Then, by estimating the minimum work of the cutting forces acting in the direction of the width of the cutting layer, it is possible to predict the best fixing of the workpiece. Application of the method does not require the creation and identification of a computational model of the process or preliminary numerical simulations. The effectiveness of this method was confirmed by the evaluation of the Root Mean Square (RMS) of the vibration level in the time domain observed during the actual face milling process. The worst results were obtained for the configuration of supports tightened with a torque of 90–110 Nm, and the best—with a torque of 50 Nm.

  • A Microwave Sensor with Operating Band Selection to Detect Rotation and Proximity in the Rapid Prototyping Industry
    • Abhishek Jha
    • Adam Lamęcki
    • Michał Mrozowski
    • Bozzi Maurizio
    2021 Pełny tekst IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS

    This paper presents a novel sensor for detecting and measuring angular rotation and proximity, intended for rapid prototyping machines. The sensor is based on a complementary split-ring resonator (CSRR) driven by a conductor-backed coplanar waveguide. The sensor has a planar topology, which makes it simple and cost-effective to produce and accurate in measuring both physical quantities. The sensor has two components, a rotor, and a stator: the first of these can rotate around its axis and translate along the plane normal to the ground. A detailed theoretical and numerical analysis, along with a circuit model, of the unique sensor design is presented. The proposed sensor exhibits linear response for measuring angular rotation and proximity in the range of 30×60 degrees and 0-200 μm. Another distinctive feature of the rotation and proximity sensor is the wide frequency band of applicability, which is an integral part of its novel design and is implemented through various dielectric material loadings on the CSRR. The stator was fabricated on RF-35 substrate, while the CSRR-based rotor was fabricated on TLY-5 and RF-35 substrates. The angular rotation, the proximity, the operating band selection, and the sensitivity were measured using a vector network analyzer and were found to be good matches to the simulated and theoretical result

  • A Model-Order Reduction Approach for Electromagnetic Problems With Nonaffine Frequency Dependence
    • Grzegorz Fotyga
    2021 Pełny tekst IEEE Access

    The aim of this paper is to present a novel model-order reduction (MOR) technique for the efcient frequency-domain nite-element method (FEM) simulation of microwave components. It is based on the standard reduced-basis method, but the subsequent expansion frequency points are selected following the so-called sparsied greedy strategy. This feature makes it especially useful to perform a fast-frequency sweep of problems that lead to systems of equations exhibiting a nonafne frequency dependence. This property appears, for example, when the excitation of the problem is characterized by a frequency-dependent waveguide mode pattern, or when the computational domain includes materials with frequency-dependent permittivity or permeability tensors. Moreover, the new MOR scheme can be also used to accelerate the frequency sweep of problems with many excitations, for which the standard reduction algorithms tend to be time-consuming. Its effectiveness and accuracy is veried through analysis of three microwave structures: planar microstrip branch-line coupler, three-port waveguide junction with ferrite post, and an eighth-order dual-mode waveguide lter.

  • A multi-criteria decision model for the introduction of electric storage multiple units on the partially electrified Gdynia-Hel railway
    • Natalia Karkosińska-Brzozowska
    • Paweł Stromski
    • Dariusz Karkosiński
    2021 Pełny tekst Pojazdy Szynowe

    : In this article a multi-criteria study of the use of independently powered electric multiple units on the partially electrified Gdynia Główna - Hel line was carried out. The use of (currently used) diesel and, as an alternative, electric and electric multiple units with an electric energy storage was considered. The analysis was carried out on the basis of three criteria for assessing the route service options, i.e. environmental, economic, operational and economic investment criteria. A multi-criteria decision model was developed for the analysis and a comparative analysis of the considered options for servicing the Gdynia Główna - Hel route was carried out. As part of the environmental criterion, it was found that the most environmentally friendly use of storage units. As part of the operational economic criterion, it was shown that the storage units have the lowest operating costs. The analysis as part of the investment cost criterion showed that the lowest investment costs are characteristic of route operation with the use of combustion units. The highest investment costs are related to the route operation by classic electric units, which is associated with the complete electrification of the line.

  • A new 1-nitro-9-aminoacridine derivative targeting yeast topoisomerase II able to overcome fluconazole-resistance
    • Kamila Rząd
    • Ewa Paluszkiewicz
    • Iwona Gabriel
    2021 BIOORGANIC & MEDICINAL CHEMISTRY LETTERS

    Fungal resistance remains a significant threat and a leading cause of death worldwide. Thus, overcoming microbial infections have again become a serious clinical problem. Although acridine derivatives are widely analyzed as anticancer agents, only a few reports have demonstrated their antifungal activity. In an effort to develop biologically active antifungals, twelve novel C-857 (9-(2′ -hydroxyethylamino)-1-nitroacridine) and C-1748 (9-(2′ -hydroxyethylamino)-4-methyl-1-nitroacridine) derivatives were synthesized. The evaluation of biological properties suggests that starting compounds: C-1748, C-857 and IE3 (2-[(4-methyl-1-nitroacridin-9- yl)amino]ethyl lysinate), IE4 (2-[(1-nitroacridin-9-yl)amino]ethyl lysinate) antifungal mode of action differ from that determined for IE5 (N′ -{3-[(4-methyl-1-nitroacridin-9-yl)amino]propyl}lysinamide), IE6 (N′ -{3-[(1-nitroacridin-9-yl)amino]propyl}lysinamide) and IE10 (3,3′ -Bis-(1-nitroacridin-9-ylamino) aminoethylaminoethylaminoethylamine). Although MIC values determined for the latter were higher, in contrast to C-857 and C-1748, newly synthesized IE5, IE6 and IE10 reduced C. albicans hyphal growth in different inducing media. Those compounds also exhibited antibiofilm activity, whereas IE10 was the most effective. Moreover, only IE6 exhibited antifungal activity against fluconazole resistant C. albicans strains with MICs values in the range of 16–64 μg mL- 1. Our results also indicate that, in contrast to other analyzed derivatives, novel synthetized compounds IE6 and IE10 with antifungal activity target yeast topoisomerase II activity.

  • A New Adaptive Method for the Extraction of Steel Design Structures from an Integrated Point Cloud
    • Paweł Burdziakowski
    • Angelika Zakrzewska
    2021 Pełny tekst SENSORS

    The continuous and intensive development of measurement technologies for reality modelling with appropriate data processing algorithms is currently being observed. The most popular methods include remote sensing techniques based on reflected-light digital cameras, and on active methods in which the device emits a beam. This research paper presents the process of data integration from terrestrial laser scanning (TLS) and image data from an unmanned aerial vehicle (UAV) that was aimed at the spatial mapping of a complicated steel structure, and a new automatic structure extraction method. We proposed an innovative method to minimize the data size and automatically extract a set of points (in the form of structural elements) that is vital from the perspective of engineering and comparative analyses. The outcome of the research was a complete technology for the acquisition of precise information with regard to complex and high steel structures. The developed technology includes such elements as a data integration method, a redundant data elimination method, integrated photogrammetric data filtration and a new adaptive method of structure edge extraction. In order to extract significant geometric structures, a new automatic and adaptive algorithm for edge extraction from a random point cloud was developed and presented herein. The proposed algorithm was tested using real measurement data. The developed algorithm is able to realistically reduce the amount of redundant data and correctly extract stable edges representing the geometric structures of a studied object without losing important data and information. The new algorithm automatically self-adapts to the received data. It does not require any pre-setting or initial parameters. The detection threshold is also adaptively selected based on the acquired data.

  • A New Approach to the PWM Modulation for the Multiphase Matrix Converters Supplying Loads with Open-End Winding.
    • Paweł Szczepankowski
    • Natalia Strzelecka
    • Enrique Romero-Cadaval
    2021 Pełny tekst ENERGIES

    This article presents three variants of the Pulse Width Modulation (PWM) for the Double Square Multiphase type Conventional Matrix Converters (DSM-CMC) supplying loads with the open-end winding. The first variant of PWM offers the ability to obtain zero value of the common-mode voltage at the load's terminals and applies only six switches within the modulation period. The second proposal archives for less Total Harmonic Distortion (THD) of the generated load voltage. The third variant of modulation concerns maximizing the voltage transfer ratio, minimizing the number of switching, and the common-mode voltage cancellation. The discussed modulations are based on the concept of sinusoidal voltage quadrature signals, which can be an effective alternative to the classic space-vector approach. In the proposed approach, the geometrical arrangement of basic vectors needed to synthesize output voltages is built from the less number of vectors, which is equal to the number of the matrix converter's terminals. The PWM duty cycle computation is performed using only a second-order determinant of the voltages coordinate matrix without using trigonometric functions. A new approach to the PWM duty cycles computing and the load voltage synthesis by 5x5 and 12x12 topologies has been verified using the PSIM simulation software.

  • A new concept of contemporary marketing
    • Anna Drapińska
    2021

    Purpose: This conceptual paper aims to propose a new concept of marketing that responds well to the needs of a changing world, taking into account the continuous development of the service economy and the revolution in the development of the Internet and related tools. Methodology/Approach: The proposed concept is based on well-researched theories: service marketing, experience marketing, relationship marketing and digital marketing (4.0). An in-depth review of marketing literature has been conducted. The proposed concept uses such terms as interactions, relationships, experiences, and digital marketing. Findings: The main achievement is a new concept of contemporary marketing. Its essence is the creation by organizations of long-term relationships with customers, through interactions and consistent customer experiences both in the offline and online world. Originality/value: The paper proposes a new look at contemporary marketing, indicates its elements and essence and contributes both to the development of the theory and research in marketing.

  • A New Direct-Sequence Spread Spectrum Signal Detection Method for Underwater Acoustic Communications in Shallow-Water Channel
    • Iwona Kochańska
    2021 Pełny tekst Vibrations in Physical Systems

    Direct-Sequence Spread Spectrum (DSSS) is one of the modulation and coding techniques used in Underwater Acoustic Communication (UAC) systems for reliable data transmision even at low signal levels. However, in a shallow water channel, there is a strong multipath propagation which causes a phase fluctuation of the received signal, affecting the performance of the spread-spectrum system. The article presents a differential method for DSSS signal detection. It is based on the calculation of the correlation coefficient of adjacent segments of signal at the output of filter matched to the spreading sequence used in the transmitter. A positive value of the correlation coefficient means that a given modulation symbol carries the same information bit as the previous one; a negative value means that the opposite bit has been transmitted. The reliability of the proposed method has been compared to classical method of DSSS signal detection, which consists in detecting the information directly from the signal at the output of the matched filter. Simulation and measurement tests of underwater acoustic communications in strong multipath propagation conditions have shown that the proposed method allows obtaining lower values of the DSSS transmission Bit Error Rate (BER) than the classical detection technique while maintaining the same data transmission rate.

  • A new multi-process collaborative architecture for time series classification
    • Zhiwen Xiao
    • Xingtao Xu
    • Haoxi Zhang
    • Edward Szczerbicki
    2021 Pełny tekst KNOWLEDGE-BASED SYSTEMS

    Time series classification (TSC) is the problem of categorizing time series data by using machine learning techniques. Its applications vary from cybersecurity and health care to remote sensing and human activity recognition. In this paper, we propose a novel multi-process collaborative architecture for TSC. The propositioned method amalgamates multi-head convolutional neural networks and capsule mechanism. In addition to the discovery of the temporal relationship within time series data, our approach derives better feature extraction with different scaled capsule routings and enhances representation learning. Unlike the original CapsNet, our proposed approach does not need to reconstruct to increase the accuracy of the model. We examine our proposed method through a set of experiments running on the domain-agnostic TSC benchmark datasets from the UCR Time Series Archive. The results show that, compared to a number of recently developed and currently used algorithms, we achieve 36 best accuracies out of 128 datasets. The accuracy analysis of the proposed approach demonstrates its significance in TSC by offering very high classification confidence with the potential of making inroads into plentiful future applications.

  • A note on the applications of artificial intelligence in the hospitality industry: preliminary results of a survey
    • Joanna Citak
    • Mieczysław Owoc
    • Paweł Weichbroth
    2021 Pełny tekst

    Intelligent technologies are widely implemented in different areas of modern society but specific approaches should be applied in services. Basic relationships refer to supporting customers and people responsible for services offering for these customers. The aim of the paper is to analyze and evaluate the state-of-the art of artificial intelligence (AI) applications in the hospitality industry. Our findings show that the major deployments concern in-person customer services, chatbots and messaging tools, business intelligence tools powered by machine learning, and virtual reality & augmented reality. Moreover, we performed a survey (n = 178), asking respondents about their perceptions and attitudes toward AI, including its implementation within a hotel space. The paper attempts to discuss how the hotel industry can be motivated by potential customers to apply selected AI solutions. In our opinion, these results provide useful insights for understanding the phenomenon under investigation. Nevertheless, since the results are not conclusive, more research is still needed on this topic. Future studies may concern both qualitative and quantitative methods, devoted to developing models that: a) quantify the potential benefits and risks of AI implementations, b) determine and evaluate the factors affecting the AI adoption by the customers, and c) measure the user (guest) experience of the hotel services, fueled by AI-based technologies.

  • A Novel Versatile Decoupling Structure and Expedited Inverse-Model-Based Re-Design Procedure for Compact Single-and Dual-Band MIMO Antennas
    • Muhammad Abdullah
    • Sławomir Kozieł
    2021 Pełny tekst IEEE Access

    Multiple-input multiple-output (MIMO) antennas are considered to be the key components of fifth generation (5G) mobile communications. One of the challenges pertinent to the design of highly integrated MIMO structures is to minimize the mutual coupling among the antenna elements. The latter arises from two sources, the coupling in the free space and the coupling currents propagating on a ground plane. In this paper, an array of H-shaped parasitic patches is proposed as a decoupling structure for compact MIMO antennas to reduce propagation of the coupling currents on a shared ground plane. The proposed decoupling structure is generic, and it can be applied to different antenna configurations as demonstrated in the work. Furthermore, it is employed to develop a new high-performance compact dual-band MIMO structure featuring acceptable level of element coupling at both operating frequencies. The design is validated both numerically and experimentally. The mutual coupling levels are less than -17 dB and -20 dB, with the total efficiency of 89% and 90%, and the realized gain of 6.6 dB and 7 dB at the two resonant frequencies of 5 GHz and 6 GHz, respectively. Topological complexity of the compact MIMO systems featuring elaborated decoupling structures, a large number of geometry parameters, as well as the necessity of handling multiple performance figures, constitute the major challenges of antenna design, in particular, its re-design for various specifications. To alleviate these difficulties, the paper also provides a procedure for rapid geometry scaling of the dual-band MIMO antennas. Our approach is based on inverse surrogate modeling methods, and results in numerically-derived expressions that enable a precise control over the operating antenna bands within broad ranges thereof (from 4 GHz to 8 GHz for the lower band, and from 1.1 to 1.3 ratio of the upper to lower operating frequency). The aforementioned procedure is accompanied by an optimization-based design refinement scheme. A practical utility of the procedure is corroborated using multiple verification case studies as well as physical measurements of the antenna designed for the exemplary set of performance specifications.

  • A Panel Analysis of the Impact of Green Transformation and Globalization on the Labor Share in the National Income
    • Małgorzata Gawrycka
    • Anna Szymczak
    2021 Pełny tekst ENERGIES

    This study aims to examine the impact of green transition and globalization processes on changes in the labour share. The study covers 76 national economies diversified in development, global production share and energy transition stage from 2000 to 2018. Based on the Total Economy Database data, panel models of the relationship between green transition, globalization and the labour share in the national income were estimated. The conducted Breusch–Pagan and Hausman tests proved the validity of using fixed-effects models. We confirmed the research hypothesis that the openness of the economy contributes to a decline in the labour share. The openness of the economy resulting from globalization reduces the labour share in the national income. We do not confirm hypotheses that suggest energy transition contributes to a reduction in the labour share and that the labour share will decline in the post-crisis period due to the lower bargaining power of workers. Changes in the labour share should be of interest to government representatives who influence the shape and implementation of economic policy, especially in employment policy, education, and investment policy, mainly aimed at the green transformation.

  • A Pilot Study on Machining Difficult-to-Cut Materials with the Use of Tools Fabricated by SLS Technology
    • Mariusz Deja
    • Dawid Zieliński
    2021 Pełny tekst Materials

    The growing use of contemporary materials in various industrial sectors, such as aerospace, automotive, as well as the oil and gas industry, requires appropriate machining methods and tools. Currently, apart from the necessity to obtain high-dimensional and shape accuracy, the efficiency and economic aspects of the selected manufacturing process are equally important, especially when difficult-to-cut materials, such as hard and brittle ceramics, have to be machined. In the research presented in this paper, a prototype tool fabricated from polyamide powder by the SLS method was used in flat-lapping of Al2O3 ceramics, showing the promising potential and efficacy of rapid tooling and manufacturing in the area of abrasive machining. The influence of the selected input process factors, such as machining time, the type of abrasive suspension, kinematic parameters, and unit pressure, on technological effects, was analyzed. The microscopic observations of the active surface of the prototype tool showed its reinforcement with loose diamond abrasive particles (size D107), resulting in the effective material removal and improved surface finish of Al2O3 ceramic samples. The directions for further development of tools fabricated by the SLS method for applications in abrasive machining were also envisaged by the authors.

  • A pilot study to assess manufacturing processes using selected point measures of vibroacoustic signals generated on a multitasking machine
    • Mariusz Deja
    • Roksana Licow
    2021 Pełny tekst INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY

    The article presents the method for the evaluation of selected manufacturing processes using the analysis of vibration and sound signals. This method is based on the use of sensors installed outside the machining zone, allowing to be used quickly and reliably in real production conditions. The article contains a developed measurement methodology based on the specific location of microphones and vibration transducers mounted on the tested object, in this case on a four-axis CNC ST20Y Haas lathe. A mobile phone was integrated into the measuring system and used to control the measurement process. The results from the analysis of vibration and sound signals recorded during different machining operations are presented. They refer to selected working conditions of a machine tool depending on switching the coolant supply on or off and different machine loads caused by various technological processing as well as the various speed of the positioning movements. The analysis was carried out using selected point measures describing the vibroacoustic signals. The synthesis conducted on the basis of results from the experiments indicates the validity of using vibration and acoustic signals, recorded outside the machining area, to evaluate material removal processes that are diverse in terms of kinematics and processing conditions. It indicates the possibility of using proposed point measures of vibroacoustic signals in the diagnostic aspects of the machine tools to achieve high dimension and shape accuracy and to evaluate the condition of the technological devices in terms of their optimal efficiency. Presented methodology can be used as a supporting tool in the CAD/CAM software for a better selection of appropriate cutting parameters and for a wireless control of manufacturing systems consisting of several machine tools.

  • A Qualitative Study on Non-functional Requirements in Agile Software Development
    • Aleksander Jarzębowicz
    • Paweł Weichbroth
    2021 Pełny tekst IEEE Access

    Widespread use of agile software development (ASD) methods can be observed nowadays. Non-functional requirements (NFRs) are often reported to be a problematic issue for agile projects, since ASD methods tend to neglect NFRs while focusing on incremental delivery of functional features. Despite that, only very few studies have explored the requirements engineering practices used in ASD and dedicated particularly to NFRs. Objective: We aimed to identify and investigate the practices used in industrial ASD projects to identify, elicit and document NFRs. Method: We conducted a systematic literature review (SLR) and used its findings to prepare an interview guide. We then conducted a series of semi-structured interviews with 10 experienced practitioners. Results: The SLR revealed a number of strategies related to the timing of NFR identification as well as 13 elicitation practices and 20 documentation techniques. At least some of these findings show discrepancies between ASD theory and practice. The interviews provided a more in-depth understanding of the practices used, and their context. The main findings from the interviews include: practitioners' attempts to start identifying NFRs early in the project, a lack of elicitation techniques aimed at NFRs only, and different choices about documentation techniques, including the additional techniques introduced to cope specifically with NFRs. Conclusions: It was not confirmed that requirements engineering activities related to NFRs are perceived by ASD practitioners as a problem, as they developed effective practices to deal with this issue. Moreover, our findings show that different approaches to NFRs can be used and give satisfactory results.

  • A review of recent advances in the single- and multi-degree-of-freedom ultrasonic piezoelectric motors
    • Roland Ryndzionek
    • Łukasz Sienkiewicz
    2021 Pełny tekst ULTRASONICS

    In this paper a comprehensive review of recent studies on the ultrasonic piezoelectric motors is presented. The analytical, numerical and experimental analysis. In further sections, classification methods of piezoelectric motors, survey criteria and three main groups of ultrasonic piezoelectric motors with examples have been presented and described. Finally, the conclusions and future research perspectives have been proposed.

  • A Review of Reduction Methods of Impact of Common-Mode Voltage on Electric Drives.
    • Marek Turzyński
    • Piotr Musznicki
    2021 Pełny tekst ENERGIES

    In this survey paper, typical solutions that focus on the reduction in negative effects resulting from the common-mode voltage influence in AC motor drive applications are re-examined. The critical effectiveness evaluation of the considered methods is based on experimental results of tests performed in a laboratory setup with an induction machine fed by an inverter. The capacity of a common-mode voltage level reduction and voltage gradient du/dt limitation is discussed to extend motor bearings’ lifetime and increase motor windings’ safety. The characteristic features of the described solutions are compared and demonstrated using laboratory results.

  • A Review of Traffic Analysis Attacks and Countermeasures in Mobile Agents' Networks
    • Rafał Leszczyna
    2021

    For traditional, message-based communication, traffic analysis has been already studied for over three decades and during that time various attacks have been recognised. As far as mobile agents’ networks are concerned only a few, specific-scope studies have been conducted. This leaves a gap that needs to be addressed as nowadays, in the era of Big Data, the Internet of Things, Smart Infrastructures and growing concerns for privacy, the subject gains particular importance. This paper presents the results of a literature study that aimed at identifying traffic analysing attacks and countermeasures in mobile agents’ networks. No limiting assumptions are made in regard to the complexity or size of agent networks. Also, various types of attackers’ configurations have been analysed and referred to each attack. The results enable building appropriate threat models for cybersecurity management or when designing new security solutions.

  • A review on application of artificial neural network (ANN) for performance and emission characteristics of diesel engine fueled with biodiesel-based fuels
    • Anh Tuan Hoang
    • Sandro Nižetić
    • Hwai Chyuan Ong
    • Wiesław Tarełko
    • Van Viet Pham
    • Tri Hieu Le
    • Minh Quang Chau
    • Xuan Phuong Nguyen
    2021 Sustainable Energy Technologies and Assessments

    Biodiesel has been emerging as a potential and promising biofuel for the strategy of reducing toxic emissions and improving engine performance. Computational methods aiming to offer numerical solutions were inevitable as a study methodology which was sometimes considered the only practical method. Artificial neural networks (ANN) were data-processing systems, which were used to tackle many issues in engineering and science, especially in some fields where there was a failure of the conventional modeling approaches. Thus, it was believed that the best choice was the development of a novel approach like the ANN model to anticipate engine performance and exhaust emissions with high accuracy. In this review paper, the structure and applicability of the ANN model were comprehensively evaluated. More importantly, the use of ANN with trained, tested, and validated data was introduced to determine the performance and emission characteristics of a diesel engine fueled with biodiesel-based fuel. In general, the ANN model could supply a relatively high determination coefficient as compared between predicted results and experimental data, showing that the ANN model could have a good ability to predict the engine behaviors with an accuracy higher than 95%.

  • A review on recent advances in the application of biosurfactants in wastewater treatment
    • Surya Teja Malkapuram
    • Vikrant Sharma
    • Sarang P. Gumfekar
    • Shirish H. Sonawane
    • Shriram Sonawane
    • Grzegorz Boczkaj
    • Murali Mohan Seepana
    2021 Pełny tekst Sustainable Energy Technologies and Assessments

    Microorganisms produce a variety of non-conventional surface-active molecules, known as biosurfactants. The biosurfactants find diverse applications in the oil industry, agriculture, emulsifiers, and wastewater treatment, to name a few. Since they are produced from microbes, advantages such as biodegradability, lower toxicity, and environmental compatibility can be leveraged compared to the chemical surfactants. Recently, biosurfactants found potential usability in treating wastewater generated from various domestic, industrial, and agricultural sources. The application of biosurfactants in wastewater treatment is mainly due to their excellent foaming ability, specific activity, and high selectivity under wide operation window of temperature, pH, and salinity. Wastewater treatment with use of low cost biosurfactant is one of the important suitable goal in treating the wastewater since biosurfactants can be produced from cheap material and cause less damage to the environment by replacing surfactants produced from petroleum crude. This review focuses on the recent developments in biosurfactant production using waste materials such as food and agricultural residues, industrial waste, and animal waste and their application in wastewater treatment processes such as contaminant degradation, oil–water separation, heavy metal removal, and effluent flotation. The characteristics of the biosurfactants produced from cheap materials are compared with that of synthetic surfactants. In fact, the characteristics of both types of surfactants are found to be similar. The ability of biosurfactants for pollution removal from wastewater is extensively reviewed and presented. Finally, the review also evaluates the economic feasibility of biosurfactant production on commercial scale and their industrial scale wastewater treatment application.

  • A selection of PID type controller settings via LQR approach for two-wheeled balancing robot
    • Krzysztof Laddach
    • Mateusz Czyżniewski
    • Rafał Łangowski
    2021 Pełny tekst

    The problem of PID type controller tuning has been addressed in this paper. In particular, a method of selection of PD settings based on the solution of linear–quadratic optimisation problem using the energy criterion has been investigated. Thus, the possibility of transforming optimal settings of the linear–quadratic regulator into the settings of the controller in the classical control system has been given. The presented methodology has been used during synthesis of control system for a two–wheeled balancing robot. Finally, the performance of the proposed control system has been validated by simulation in Matlab/Simulink environment with the use of a two–wheeled balancing robot model.

  • A Self-Adaptive Complex Root Tracing Algorithm for the Analysis of Propagation and Radiation Problem
    • Sebastian Dziedziewicz
    • Rafał Lech
    • Piotr Kowalczyk
    2021 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION

    An improved complex root tracing algorithm for radiation and propagation issues is proposed. The approach is based on a self-adaptive discretization of Cauchy’s argument principle for a C × R space and requires a reduced number of function calls in comparison to other procedures presented in the literature. A few different examples concerning propagation and radiation problems have been considered to verify the validity and efficiency of the proposed technique.

  • A sense of security and freedom in a residential environment
    • Antoni Taraszkiewicz
    • Karolina Taraszkiewicz
    2021 Pełny tekst World Transactions on Engineering and Technology Education

    The article is based on the results of a survey carried out among students of architecture faculties in several countries, which examined the students’ knowledge of shaping the housing environment in such a way as to enable them to fulfil two basic and, at the same time, seemingly mutually exclusive psychological needs of a person: a sense of security and a sense of freedom. In examining these issues, particular emphasis was placed on the possibility of creating such methods of architectural education that would make students - future engineers - aware of the necessity to understand the needs of the human psyche, and provide an opportunity to develop design skills to create a space that meets those needs. This kind of architectural education is part of the search for an answer to an important question today: how in the contemporary world, in a constantly transformed environment, can a person retain their own identity, find a place to live, find their own existential space?

  • A Series-Inclined-Slot-Fed Circularly Polarized Antenna for 5G 28-GHz Applications
    • Ubaid Ullah
    • Muath Al-hasan
    • Sławomir Kozieł
    • Ismail Mabrouk
    2021 Pełny tekst IEEE Antennas and Wireless Propagation Letters

    This letter presents the design of a single-point-fed, geometrically simple circularly polarized (CP) antenna for 28 GHz Ka-band applications. The proposed antenna is based on a straight microstrip line printed on one side and coupled with the nearly square patches through a 45-degree inclined V-shape slot aperture on the other side. In order to generate circular polarization, the fundamental radiating mode is degenerated at a slightly different frequency by aligning the patch edges parallel to each arm of the V-slot with orthogonal arms. This configuration yields a relatively small size (10 mm × 27.7 mm), wideband, and high-gain right-hand circularly polarized antenna operating at 28 GHz. The impedance bandwidth of the proposed antenna is from 27.2 GHz to 30.35 GHz and the 3 dB axial ratio (AR) bandwidth from 27.3 GHz to 29.7 GHz with excellent directional characteristics in the broadside direction. The peak realized gain is approximately 11.65 dBic. The performance characteristics in terms of the impedance matching, AR, gain and efficiency of the antenna for wearable applications are also investigated both numerically and experimentally. For practical applications, the small size of the structure allows for implementing the systems that consist of more than one antenna for mobility.

  • A ship domain-based model of collision risk for near-miss detection and Collision Alert Systems
    • Rafał Szłapczyński
    • Joanna Szłapczyńska
    2021 Pełny tekst RELIABILITY ENGINEERING & SYSTEM SAFETY

    The paper presents a new model of ship collision risk, which utilises a ship domain concept and the related domain-based collision risk parameters. An encounter is here described by five variables representing: degree of domain violation (DDV), relative speed of the two vessels, combination of the vessels’ courses, arena violations and encounter complexity. As for the first three variables, their values can be directly computed based on positions, courses and speeds of two vessels. The last two variables require decomposing a close quarters situation into phases. For this purpose the method utilizes a number of auxiliary parameters derived from the concept of ship domain: time of domain violation (TDV), time of domain exit (TDE), timespan of close quarters situation and vessels’ proximity, which is quantified based on the ship arena. The formulas and algorithms for determining all variables’ values are provided in detail. Once all the values are computed, the final collision risk assessment is made. Possible applications of the presented model include: AIS-based near-miss detection, Collision Alert Systems (CAS) and collision avoidance decision support systems (DSS). Case studies for those applications are provided, including examples of encounter classification and quantification of collision risk.

  • A Simple Neural Network for Collision Detection of Collaborative Robots
    • Michał Czubenko
    • Zdzisław Kowalczuk
    2021 Pełny tekst SENSORS

    Due to the epidemic threat, more and more companies decide to automate their production lines. Given the lack of adequate security or space, in most cases, such companies cannot use classic production robots. The solution to this problem is the use of collaborative robots (cobots). However, the required equipment (force sensors) or alternative methods of detecting a threat to humans are usually quite expensive. The article presents the practical aspect of collision detection with the use of a simple neural architecture. A virtual force and torque sensor, implemented as a neural network, may be useful in a team of collaborative robots. Four different approaches are compared in this article: auto-regressive (AR), recurrent neural network (RNN), convolutional long short-term memory (CNN-LSTM) and mixed convolutional LSTM network (MC-LSTM). These architectures are analyzed at different levels of input regression (motor current, position, speed, control velocity). This sensor was tested on the original CURA6 robot prototype (Cooperative Universal Robotic Assistant 6) by Intema. The test results indicate that the MC-LSTM architecture is the most effective with the regression level set at 12 samples (at 24 Hz). The mean absolute prediction error obtained by the MC-LSTM architecture was approximately 22 Nm. The conducted external test (72 different signals with collisions) shows that the presented architecture can be used as a collision detector. The MC-LSTM collision detection f1 score with the optimal threshold was 0.85. A well-developed virtual sensor based on such a network can be used to detect various types of collisions of cobot or other mobile or stationary systems operating on the basis of human-machine interaction.

  • A Simulation Model for Risk and Pricing Competition in the Retail Lending Market
    • Błażej Kochański
    2021 Pełny tekst FINANCE A UVER-CZECH JOURNAL OF ECONOMICS AND FINANCE

    We propose a simulation model of the retail lending market with two types of agents: borrowers searching for low interest rates and lenders competing through risk-based pricing. We show that individual banks observe adverse selection, even if every lender applies the same pricing strategy and a credit scoring model of comparable discrimination power. Additionally, the model justifies the reverse-S shape of the response rate curve. According to the model, the benefits of even small increases in the discrimination power of credit scoring are substantial. This effect is more pronounced if the number of offers checked by the applicants before making a decision increases. The simulations illustrate the trade-off between profitability, market share, and credit loss rates. The profit-maximising strategy is to set interest rates slightly lower than the competition; the excessive price reduction turns out to be counterproductive. At the same time, there exists a niche for higher yield players.

  • A Single-Carrier-Based Pulse-Width Modulation Template for Cascaded H-Bridge Multilevel Inverters
    • Charles Ikechukwu Odeh
    • Arkadiusz Lewicki
    • Marcin Morawiec
    2021 Pełny tekst IEEE Access

    Multiplicity of the triangular carrier signals is a criterion for the extension of sinusoidal pulsewidth modulation, SPWM, to a number of output voltage levels per phase-leg in cascaded H-bridge (CHB) multilevel inverter (MLI). Considering medium and high voltage applications where appreciable number of output voltage levels from CHB MLI is needed, commensurate high number of carrier signals in either classical level- or phase-shifted SPWM scheme for this inverter is inevitable. High-quality output waveforms from CHB MLI system demands precise synchronization of these multi-carrier signals. Sampling issues, memory constraints and computational delays pose difficulties in achieving this synchronization for real-time digital implementation. This study presents a PWM template for CHB MLI. The developed control concept generates adequate modulation templates for CHB inverter wherein a sinusoidal modulating waveform is modified to fit in a single triangular carrier signal range. These templates can be used on CHB inverter of any level with no further control modification. Nearly even distribution of switching pulses, equal sharing of the overall real power among the constituting power switches and enhanced output voltage quality were achieved with the proposed modulation. For a 3-phase, 7-level CHB, simulation and experimental results, for an R-L load, were presented.