2020 - Repozytorium publikacji - Politechnika Gdańska

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1D convolutional context-aware architectures for acoustic sensing and recognition of passing vehicle type
- Adam Kurowski
- Szymon Zaporowski
- Andrzej Czyżewski
2020
A network architecture that may be employed to sensing and recognition of a type of vehicle on the basis of audio recordings made in the proximity of a road is proposed in the paper. The analyzed road traffic consists of both passenger cars and heavier vehicles. Excerpts from recordings that do not contain vehicles passing sounds are also taken into account and marked as ones containing silence. The neural network architecture employed for these tasks is a 1D convolutional network. Two types of classifiers are tested: one analyzing only the current audio frame and one analyzing three consecutive audio frames that allow us to take into account the context of the middle frame occurrence. The neural network is trained on datasets derived for four frame lengths, namely 50 ms, 100 ms, 200 ms, and 400 ms. Results of statistical analysis of both network classification accuracy are presented. The context-aware variant of a neural network performed better in a statistically significant manner for three out of four investigated frame lengths
3D mesoporous α-Co(OH)2 nanosheets electrodeposited on nickel foam: A new generation of macroscopic cobalt-based hybrid for peroxymonosulfate activation
- Ruixia Yuan
- Minglang Jiang
- Simeng Gao
- Zhaohui Wang
- Huaiyuan Wang
- Grzegorz Boczkaj
- Zhanjian Liu
- Jun Ma
- Zhijun Li
2020 CHEMICAL ENGINEERING JOURNAL
Cobalt-based catalysts with high stability and facile recovery for heterogeneous peroxymonosulfate (PMS) activation are still rather sparse and therefore highly desirable. Herein, 3D mesoporous α-Co(OH)2 nanosheets was created on robust nickel foam (NF) via facile electrodeposition approach at 6 mA/cm2 for only 400 s. Almost complete removal of phenol can be achieved within 7 min with a degradation rate of 0.39 min−1, 2 times higher than that with ever-prevalent Co3O4 derived from direct calcination of α-Co(OH)2/NF. This can be attributed to the hydrotalcite-like hexagonal structure of α-Co(OH)2 with large interlayer spacing for enhancing the catalytic performance. The low activation energy of Co(OH)2/NF (53.8 kJ/mol) indicates its lower reaction energy barrier for PMS activation. Moreover, the influences of electrodeposition parameters (i.e. current density, deposition time), PMS dosage, initial pH and coexisting anions (HCO3−, SO42−, Cl−) on the phenol degradation were systematically evaluated. The recycling tests revealed the prominent stability of Co(OH)2/NF. The quenching tests verified that SO4− radicals acted as the predominant reactive species for phenol decomposition. The possible reaction mechanisms were proposed based on the intermediates identification. The findings of this work suggest the great potentials of the 3D macroscopic Co(OH)2/NF in water purification, and open up new avenues for scalable preparing recyclable heterogeneous catalysts.
3D PCB package for GaN inverter leg with low EMC feature
- Paweł Derkacz
- Piotr Chrzan
- Pierre-Olivier Jeannin
- Piotr Musznicki
- Mickael Petit
- Jean-Luc Schanen
2020 Pełny tekst
This paper presents the adaptation of a 3D integration concept previously used with vertical devices to lateral GaN devices. This 3D integration allows to reduce loop inductance, to ensure more symmetrical design with especially limited Common Mode emission, thanks to a low middle point stray capacitance. This reduction has been achieved by both working on the power layout and including a specific shield between the devices and the heatsink. The performances of this 3D layout have been verified in comparison with a more conventional 2D implementation, using both simulations and measurements.
3D POINT-CLOUD SPATIAL EXPANSION BY TOTAL LEAST-SQUARES LINE FITTING
- Paweł S. Dąbrowski
- Marek Zienkiewicz
2020 PHOTOGRAMMETRIC RECORD
Point-cloud spatial expansion (PCSE) allows the creation of a new pointcloud form that presents an alternative geometry of an entire object in a single spatial view. Spatial expansion facilitates the analysis process and introduces an additional spatial parameter describing the point cloud. An important element of the PCSE method is determining the position of the axis of symmetry of a symmetrical object: the procedure for determining the parameters of this axis (set of cross-sectional centres) of the object’s point cloud by the total least-squares method is presented. The estimation results were used to create a spatial expansion of the point cloud of a cylindrical object, demonstrating the usefulness of total least-squares fitting to the PCSE method.
3D Vision System for a Robotic Arm Based on Equal Baseline Camera Array
- Adam Kaczmarek
2020 Pełny tekst JOURNAL OF INTELLIGENT & ROBOTIC SYSTEMS
This paper presents a lightweight 3D vision system called Equal Baseline Camera Array (EBCA). EBCA can work in different light conditions and it can be applied for measuring large range of distances. The system is a useful alternative to other known distance measuring devices such as structured-light 3D scanners, time-of-flight cameras, Light Detection and Ranging (LIDAR) devices and structure from motion techniques. EBCA can be mounted on a robotic arm without putting significant load on its construction. EBCA consists of a central camera and a ring of side cameras. The system uses stereo matching algorithms to acquire disparity maps and depth maps similarly as in case of using stereo cameras. This paper introduces methods of adapting stereo matching algorithms designed for stereo cameras to EBCA. The paper also presents the analysis of local, semi-global and global stereo matching algorithms in the context of the EBCA usage. Experiments show that, on average, results obtained from EBCA contain 37.49% less errors than the results acquired from a single stereo camera used in the same conditions.
45 lat minęło - kolejne spotkanie technologów na Wydziale Mechanicznym
- Adam Barylski
2020 Pismo PG
Omówiono przebieg Jubileuszowego Zjazdu Absolwentów Wydziału Mechanicznego Politechniki Gdańskiej, którzy ukończyli studia wiosną i jesienią w roku 1974.
60 GHz Microstrip Van Atta Arrays for Millimeter Wave Identification and Localization
- Kamil Trzebiatowski
- Mateusz Rzymowski
- Łukasz Kulas
- Krzysztof Nyka
2020 Pełny tekst
In this paper performance comparison of co-polarized and cross-polarized microstrip Van Atta arrays working in the 60 GHz frequency range is presented. They can be treated as simple chipless RFID tags with frequency response based identification. Tags with three different nominal resonance frequencies of 57, 62 and 67 GHz are designed by scaling optimized base model. Designed 62 GHz co-polarized and cross-polarized arrays with four interconnected pairs of elementary antenna arrays have small dimensions of 20 x 18 mm and 36 x 23 mm, and exhibit RCS levels of –20 and -22 dBsm, respectively. The influence of number of interconnected antennas on the radar cross-section (RCS) of the tag is investigated. Frequency responses of the tags are also examined and compared for both types of tags with 0.80 GHz (co-polarized) and 2.10 GHz (cross-polarized) 3 dB bandwidth of the RCS response at 60 degree interrogation angle.
70 LAT PRAKTYKI POMIAROWEJ W OCENIE WŁAŚCIWOŚCI UZIEMIEŃ METODĄ UDAROWĄ
- Stanisław Wojtas
- Marek Wołoszyk
- Marek Olesz
2020 Pełny tekst Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej
Przedstawiono liczącą ok. 70 lat historię prac związanych z rozwojem sposobów oceny uziemień wykorzystujących metodę udarową. Pierwsze prace związane z tym zagadnieniem zostały rozpoczęte w połowie ubiegłego wieku na Politechnice Gdańskiej z inicjatywy profesora Stanisława Szpora. Omówiono metodę pomiaru, stosowane kolejne generacje mierników, możliwości oceny uziemień i różne definicje normalizacyjne opisujące właściwości uziemienia mierzone przy prądach udarowych o czasie czoła zbliżonym do czasu rzeczywistego wyładowania piorunowego.
A 1-nS 1-V Sub-1-µW Linear CMOS OTA with Rail-to-Rail Input for Hz-Band Sensory Interfaces
- Jacek Jakusz
- Waldemar Jendernalik
- Grzegorz Blakiewicz
- Miron Kłosowski
- Stanisław Szczepański
2020 Pełny tekst SENSORS
The paper presents an operational transconductance amplifier (OTA) with low transconductance (0.62–6.28 nS) and low power consumption (28–270 nW) for the low-frequency analog front-ends in biomedical sensor interfaces. The proposed OTA implements an innovative, highly linear voltage-to-current converter based on the channel-length-modulation effect, which can be rail-to-rail driven. At 1-V supply and 1-Vpp asymmetrical input driving, the linearity error in the current-voltage characteristics is 1.5%, while the total harmonic distortion (THD) of the output current is 0.8%. For a symmetrical 2-Vpp input drive, the linearity error is 0.3%, whereas THD reaches 0.2%. The linearity is robust for the mismatch and the process-voltage-and-temperature (PVT) variations. The temperature drift of transconductance is 10 pS/°C. The prototype circuit was fabricated in 180-nanometer CMOS technology.
A Comparison of Empirical Correlations of Viscosity and Thermal Conductivity of Water-Ethylene Glycol-Al2O3 Nanofluids
- Dorota Sawicka
- Janusz Cieśliński
- Sławomir Smoleń
2020 Pełny tekst Nanomaterials
Because of their superb thermal conductivity, nanofluids are seen as new generation of cooling mediums in many engineering applications. It is well established that even a small amount of nanoparticles mixed with a base fluid may result in distinct thermal conductivity enhancement. On the other hand, addition of nanoparticles to the base fluid results in its substantial viscosity increase. Therefore, it is very dicult to evaluate the relative importance of viscosity and thermal conductivity of the nanofluid on convective heat transfer performance. In order to estimate such resultant impact properly, it is necessary to develop reliable correlation equations for predictions of these two thermophysical properties of nanofluids. In this paper, the thermal conductivity and dynamic viscosity of five fluids, i.e., pure water, ethylene glycol (EG) and three mixtures of water and EG with volume ratio of 40:60, 50:50 and 60:40 have been experimentally determined. The aforementioned fluids served as base fluids in nanofluids with Al2O3 nanoparticles at the concentration of 0.01%, 0.1% and 1% by weight. A set of 20 correlations for prediction of thermal conductivity and dynamic viscosity of base fluids and corresponding nanofluids has been developed. Moreover, present results have been confronted with literature data and predictions made by use of carefully selected recognized literature correlations.
A comprehensive assessment of environmental pollution by means of heavy metal analysis for oysters' reefs at Hab River Delta, Balochistan, Pakistan
- Sadar Aslam
- Malik Wajid Hussain Chan
- Ghazala Siddiqui
- Grzegorz Boczkaj
- Syed Jamil Hasan Kazmi
- Mohib Reza Kazmi
2020 MARINE POLLUTION BULLETIN
The heavy metal pollution status of oyster reefs has been assessed with respect to ten metals pollutants in seawater, sediments, and tissues of above two oysters (soft tissues and shells) for assessing the pollution status in a short food chain in Hab River Delta. The results showed that heavy metals accumulated in M. bilineata were higher than those in M. cuttackensis. Simultaneously, the population of M. bilineata species has been ironically decreasing as a results of high pollution. The determined concentrations revealed a significant differences in their profiles among sediments, seawater and bioaccumulation in tissues and shells of two native oysters. The present study also compared these metal concentrations with national and international database by applying different pollution indices. Heavy metals in all samples were above the national environmental quality standards (NEQS-Pakistan). High level of pollution with an alarming condition of Hab River Delta need more attention for coastal management.
A comprehensive evaluation of flexible FDM/FFF 3D printing filament as a potential material in medical application
- Agnieszka Haryńska
- Iga Carayon
- Paulina Kosmela
- Kamil Szeliski
- Marcin Łapiński
- Marta Pokrywczyńska
- Justyna Kucińska-Lipka
- Helena Janik
2020 Pełny tekst EUROPEAN POLYMER JOURNAL
The use of FDM/FFF in 3D printing for medical sciences is becoming common. This is due to the high availability and decent price of both 3D printers and filaments useful for FDM/FFF. Currently, researchers' attention is focused mainly on the study of medical filaments based on PLA, PCL or their modifications. This contributes to insufficient diversity of medical-grade filaments on the market. Moreover, due to the lack of specified standards for filaments testing, manufacturers often provide merely the characteristics of the raw materials, which were used for filaments fabrication. This lack of comprehensive data can be problematic when viewed as medical-grade material. As a consequence of this overview, we have performed a comprehensive evaluation of a flexible medical-grade filament for FDM/FFF 3DP - Bioflex® (Filoalfa). We have performed complex characterization through a variety of methods and techniques including spectroscopic analysis (FTIR, Raman), dynamic mechanical analysis (DMA), thermal properties (DSC, TGA), rheological characteristic (MFR). In the next step, printed Bioflex® samples were utilized to characterize the material behaviour after the 3D printing process. The mechanical analysis allowed to estimate how the material strength decreases after the printing process according to the values given in the technical data sheet. The contact angle measurements determined wettability of the Bioflex® printouts. Performed series of in vitro studies were carried out to assess its potential as implantable structures. In conclusion, 3D printing process did not affect the printouts biocompatibility (ISO 10993:5). Accelerated degradation studies indicated elevated hydrolysis resistance of printed samples. In turn, performed incubation in simulated body fluid (SBF) solution, revealed carbonated hydroxyapatite (HAp) deposition on printouts surface indicating their bioactive properties. Thus, studied filament seems to be a suitable candidate for further development of FDM/FFF 3DP structures for advanced biological and medical application.
A concept of zero-dimensional and three-dimensional thermodynamic modelling of steam storage in a steam cycle
- Paweł Ziółkowski
2020
This work presents the thermodynamic model of steam storage in a steam cycle. The innovative steam storage is an integral part of the unit and thus responds quickly to changes in load. This enhances the primary control reserve while maintaining high efficiency of energy conversion. With regard to power plants, it improves the operational safety of generation units, as it prevents boiler and turbines overload in the case of steep reduction in the load. A steam power plant able to swiftly adjust its generation to load changes becomes more competitive on the capacity market due to improve its dynamic characteristics. The relative disadvantage of the steam storage is its limited capacity. Therefore, the article includes a comprehensive assessment of the power plant parameters that will allow developing guidelines and recommendations to determine the optimal operation modes of the steam accumulator for the case of the underlying reference process. This will also take into account changing ambient conditions and current operational requirements. Therefore, it is necessary to use zero-dimensional modelling (0D) which relates to the design level strictly focused on thermodynamic parameters at specific points in the thermodynamic cycle. However, the three-dimensional approach, which allows determining temperature fields, displacements and stresses in relevant space is used for more accurate analysis. This paper also presents the relationship between the different approaches in relation to steam storage. The steam accumulator itself will be analysed in detail by means of Thermal-FSI (Fluid Solid Interaction) based on flow models with phase transitions induced both by change of pressure and temperature. Computational Solid Dynamics (CSD) models will be included to obtain the thermal and mechanical stresses. The mathematical modelling of complex physical phenomena in the steam storage is of increasing interest, particularly with regard to energy storage in the steam cycle. However, taking into account zero-dimensional modelling it is possible to show that charging the energy storage leads to a load reduction of up to 6.5%. On the other hand, discharging the energy storage can produce an additional net power of up to 4.1%. However, a new three-dimensional FSI analyses are necessary.
A Conformal Circularly Polarized Series-Fed Microstrip Antenna Array Design
- Stanislav Ogurtsov
- Sławomir Kozieł
2020 Pełny tekst IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
A conformal circularly polarized series-fed microstrip array design for broadside radiation is presented. The array aperture under design is conformal to a cylindrical surface of a given radius. The approach we present primarily addresses focusing of the circularly polarized major lobe of the conformal array by proper dimensioning of the aperture spacings. The proposed analytical models yield the values of the element spacings within the series-fed conformal array aperture, and elementspecific spacings of the patch radiators within each circularly polarized element. These spacings are critical to produce a broadside circularly polarized major lobe at the design frequency. Subsequently, each array element is equipped with an in-line matching quarter wave transformer. Measured characteristics of the X-band conformal array validate the proposed design approach.
A continual model of a damaged medium used for analyzing fatigue life of polycrystalline structural alloys under thermal–mechanical loading
- Ivan Volkov
- Leonid Igumnov
- Francesco dell'Isola
- Svetlana Litvinchuk
- Victor Eremeev
2020 Pełny tekst CONTINUUM MECHANICS AND THERMODYNAMICS
The main physical laws of thermal–plastic deformation and fatigue damage accumulation processes in polycrystalline structural alloys under various regimes of cyclic thermal–mechanical loading are considered. Within the framework of mechanics of damaged media, a mathematical model is developed that describes thermal–plastic deformation and fatigue damage accumulation processes under low-cycle loading. The model consists of three interrelated parts: relations defining plastic behavior of the material, accounting for its dependence on the failure process; evolutionary equations describing damage accumulation kinetics; a strength criterion of the damaged material. The plasticity model based on the notion of yield surface and the principle of orthogonality of the plastic strain vector to the yield surface is used as defining relations. This version of defining equations of plasticity describes the main effects of the deformation process under monotone cyclic, proportional and nonproportional loading regimes. The version of kinetic equations of damage accumulation is based on introducing a scalar parameter of damage degree and energy principles, and account for the main effects of nucleation, growth and merging of microdefects under arbitrary regimes of low-cycle loading. The strength criterion of the damaged material is based on reaching a critical value of the damage degree. The results of numerically modeling cyclic thermal–plastic deformation and fatigue damage accumulation in heat-resistant alloys (Nimonic 80A, Haynes 188) under combined thermal–mechanical loading are presented. Special attention is paid to the issues of modeling the processes of cyclic thermal–plastic deformation and fatigue damage accumulation for complex deformation processes accompanied by the rotation of the main stress and strain tensor areas. It is shown that the present damaged medium model accurately enough for engineering purposes describes the processes of cyclic isothermal and nonisothermal deformation and fatigue damage accumulation under combined thermal–mechanical loading and makes it possible to evaluate low-cycle fatigue life of heat-resistant alloys under arbitrary deformation trajectories.
A Critical Reanalysis of Uncontrollable Washboarding Phenomenon in Metal Band Sawing
- Kazimierz Orłowski
- Michał Dobrzyński
- Grzegorz Gajowiec
- Marcin Lackowski
- Tomasz Ochrymiuk
2020 Pełny tekst Materials
The article analyzes the cutting process of hard bars. Investigations conducted in industrial conditions demonstrated the presence of surface errors in the machined workpieces in the form of washboard patterns. The purpose of this study was to analyze the results of cutting on band sawing machines with different band saw blades. The cutting processes were conducted on three different horizontal band sawing machine types. Analyzed material was an alloy steel Ø40 mm rod with a hardened surface covered with a thin layer of chromium. The hardness of the outer layer was 547 HV with a core hardness of 180 HV. The surface topography measurements of the processed workpieces were carried out with the 3D Optical Profiler, which supplied information on the irregularities of the processed material texture. In each of the analyzed cases, a corrugated surface was obtained after sawing, which is the effect of the occurrence of the washboarding phenomenon, despite the fact that the teeth of each band saw had variable pitches. The washboarding phenomenon when cutting rods with hard surfaces is caused by the phenomenon of wave regeneration. Despite the use of variable pitch saw blades, the cutting process results in rippling of the sawn surface, which is caused by the high hardness of the outer layer of the workpiece, as well as by the type of tool with spring setting of teeth.
A Development of a Capacitive Voltage Divider for High Voltage Measurement as Part of a Combined Current and Voltage Sensor
- Roman Hrbac
- Vaclav Kolar
- Mikołaj Bartłomiejczyk
- Tomas Mlcak
- Petr Orsag
- Jakub Vanc
2020 Pełny tekst Elektronika Ir Elektrotechnika
This article deals with the development of capacitive voltage divider for high voltage measurements and presents a method of analysis and optimization of its parameters. This divider is a part of a combined voltage and current sensor for measurements in high voltage power networks. The sensor allows continuous monitoring of the network distribution status and performs a quick diagnosis and location of possible network failures. Deployment of these devices will support semi-autonomous control of power networks and it can be considered as a step from traditional power grids toward smart grids. This is a worldwide trend connected with increasing number of renewable energy sources and plug-in electric vehicles as described in. In this way, it contributes to the reliability of the distribution network. Together with automated control techniques and fault location methods, it enables its self-healing capability. The following characteristics required for the sensor include: current measurement error up to 2 %, voltage measurement error up to 0.5 %, and power measurement error up to 5 %. At the same time, it is necessary that the sensor is cost-effective - relatively cheap. There were selected capacitors made in series production for the capacitive divider designing. The capacitive voltage divider was tested in terms of time and temperature stability; the results are described in the paper. Then, the method of mathematical correction of a temperature dependence of the capacitive voltage divider was suggested and tested.
A Finer Point on Vision
- Karolina Zielińska-Dąbkowska
2020 Lighting Design and Application
As an IES Member, I look forward to each issue of LD+A and read them with great interest as they are often very informative. To my surprise, the Research article (May 2019, p. 76) has an error which should be corrected.
A five-year retrospective study shows increasing rates of antimicrobial drug resistance in Cabo Verde for both Staphylococcus aureus and Escherichia coli
- Tamar Monteiro
- Magdalena Wysocka
- Elena Tellez
- Ofelia Monteiro
- Luzia Spencer
- Elisa Veiga
- Sandra Monteiro
- Carine De Pina
- Deisy Goncalves
- Sandrine De Pina
- Ludgero Correia
- Joao Moreno
- Teresa Conceicao
- Marta Aires De Sousa
- Herminia De Lencastre
- Laura J Gray
- Manish Pareek
- David R Jenkins
- Sandra Beleza
- Marco R Oggioni
- Isabel Ines Araujo
2020 Pełny tekst Journal of Global Antimicrobial Resistance
Objectives Data on baseline drug resistance is important in informing future antimicrobial stewardship programs. So far, no data on the antimicrobial drug resistance of clinical isolates was available for the African archipelago of Cabo Verde. Methods We have performed a retrospective analysis over five-years (2013-17) of the antimicrombial drug susceptibility profiles of clinical isolates in the two main hospitals of Cabo Verde. For Escherichia coli and Staphylococcus aureus, representing respectively 47% and 26% of all clinical isolates, the antimicrobial drug resistance profile was reported for six representative drugs. Results For E. coli we detected an increase in resistance to ampicillin, amoxicillin/clavulanic acid, ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole and for S. aureus to methicillin, erythromycin and trimethoprim-sulfamethoxazole. This increase in both the most commonly isolated bacterial pathogens is of alarm as it might compromise empirical treatment in a setting with limited access to laboratory testing. Conclusions When compared to the published low resistance rates in carriage isolates, the more alarming situation in clinical isolates for S. aureus might encourage antimicrobial stewardship programs to reduce MRSA in the hospital settings, possibly as part of the Cabo Verdean national plan against antimicrobial drug resistance.
A Flexible Nafion Coated Enzyme‐free Glucose Sensor Based on Au‐dimpled Ti Structures
- Adrian Olejnik
- Katarzyna Siuzdak
- Jakub Karczewski
- Katarzyna Grochowska
2020 ELECTROANALYSIS
The detection of glucose at low concentrations using electrochemical sensors is of great importance due to the possibility of using different human body fluids than blood, such as e.g. urine, saliva, sweat or tears. The interest behind those biofluids is related to their utility in non-invasive sugar determination. In this work, we present flexible, fully biocompatible electrode material based on Au nanoparticles immobilized onto titanium dimples. Au Ti heterostructures were obtained via electrochemical anodization of titanium foil in presence of fluoride anions followed by chemical etching, magnetron sputtering of gold and subsequent thermal dewetting in continuous regime. In the last step of fabrication, electrodes were modified by permselective Nafion membrane. The selection of the best electrode material among different configurations was carried out basing on the electrochemical activity in the contact with 5 mM glucose dissolved in neutral air-saturated 0.1 M PBS. For the 10 nm Au dewetted gold film, limit of detection of 30 μM and high sensitivity of 93 mAcm 2mM 1 were achieved. Application of Nafion membrane caused complete inhibition of the impact of various interference species onto the glucose detection. Good selectivity and repeatability combined with the resistance to prolonged mechanical stress suggest that prepared material can be used in noninvasive glucose sensig