Publications Repository - Gdańsk University of Technology

Page settings

polski
Publications Repository
Gdańsk University of Technology

Show publications from the year

Publications from the year 2022

Show all
  • Effect of slag coal ash and foamed glass on the mechanical properties of two-stage concrete
    • Hakim S. Abdelgader
    • Marzena Kurpińska
    • Mugahed Amran
    2022 Materials Today: Proceedings

    Two-stage concrete (TSC) is known by various names such as colcrete, Polcrete, preplaced aggregate concrete and prepacked concrete. It is different from traditional concrete in two fundamental ways, namely method of construction and mix proportion. Two-stage concrete (TSC) is defined as firstly, coarse aggregates are placed into the formwork and grout is applied to fill in the between coarse aggregate particles voids. Secondly, the percentage of coarse aggregates in the mix proportion of TSC is higher than that in normal concrete. The typical value is about 60% as compared with 40% in traditional concrete. As coarse aggregates are preplaced first, they can occupy up to 60–70% of the total volume. As coarse aggregates are not involved in the mixing process, TSC is environmentally friendly with lesser consumption of energy. With a higher content of aggregates, TSC reduces the use of cement by 20–30% and may minimize the temperature rise. Engineering properties of TSC, including its stress–strain relationship, is mainly governed by the properties of coarse aggregates as stress is transferred from the skeleton of aggregates to hardened grout. Main advantages of TSC include a higher volume of coarse aggregates and the ability to use larger size coarse aggregates. The latter also reduces the cost of crushing. TSC has beneficial properties such as low drying shrinkage, high bonding strength, high modulus of elasticity, and excellent durability. The method of TSC has proved particularly useful in a number of applications like underwater construction, and masonry repair, where placement by conventional methods is extremely difficult. The method is also applicable in case of massive concrete where low heat of hydration is required. It is studied the feasibility of casting two stage concrete with 100% steel slag as coarse aggregate. In term of formulation, to adopt two stage concreting method we could minimize the risk of concrete bleeding and segregation due to high water absorption and quite high density of slag aggregate. The effect of slag coal ash and foamed glass on the mechanical properties of two-stage concrete has rarely been reported. Thus, the development of an eco-efficient alkali-activated grout for two-stage concrete is a new research topic that has no robust results to draw solid conclusions and it should blaze the track towards a cleaner production of building materials with outstanding sustainability.

  • Effect of temperature change on refractive index of an egg white and yolk: a preliminary study
    • Patryk Sokołowski
    2022 Full text Photonics Letters of Poland

    In this article, the refractive index of an egg white and yolk depending on temperature in range 30 - 47 °C over 1550 nm was determined. The measurement head was constructed as fiber optic Fabry-Perot interferometer with interference between polished fiber end-face and aluminum weighing dish. The measurement setup has been made of an optical spectrum analyzer, a superluminescent diode with a central wevelength of 1550 nm, 2:1 fiber coupler and heat plate.

  • Effect of the ionic liquids on extraction of aromatic and sulfur compounds from the model petrochemical stream
    • Wiśniewski Piotr
    • Konrad Bołoz
    • Anna Wiśniewska
    • Zbigniew Dąbrowski
    • Dominika Kubica
    • Justyna Łuczak
    • Urszula Domańska
    2022 FLUID PHASE EQUILIBRIA

    Suitability of a imidazolium ionic liquids (ILs) as solvents in dearomatization and desulfurization in the ternary systems and in a model multicomponent systems has been analyzed. With this aim, ternary liquid-liquid phase equilibrium data (LLE) have been obtained for ternary mixtures of {IL + benzene, or toluene, or thiophene, or 2-butanethiol + hexane}, or {IL + benzene + 2-methylpentane} at T = 298.15 K and ambient pressure, as well as for multicomponent systems –model petrochemical stream {IL + model stream (benzene, toluene, thiophene, 2-butanethiol) + hexane} at T = 303.15 K and ambient pres- sure. Two ILs have been studied: 1-ethyl-3-methylimidazolium thiocyanate, [EMIM][SCN] and 1-ethyl- 3-methylimidazolium dicyanamide, [EMIM][DCA]. The values of solute distribution ratio and selectivity have been evaluated. It has been shown that ILs investigated in this work are able to extract sulfur com- pounds in preference to benzene and toluene. The solute distribution ratios for both ILs are similar. The selectivity of the aromatic and sulfur compounds are higher for [EMIM][SCN]. The best distribution ratio ( > 1.98) and selectivity ( > 242) was observed for thiophene extracted from the model stream 1:1.

  • Effect of Tool Positioning Factors on the Strength of Dissimilar Friction Stir Welded Joints of AA7075-T6 and AA6061-T6
    • Amir Ghiasvand
    • Saja Mohammed Noori
    • Wanich Suksatan
    • Jacek Tomków
    • Shabbir Memon
    • Hesamoddin Aghajani Derazkola
    2022 Full text Materials

    Friction Stir Welding (FSW) is a solid-state bonding technique. There are many direct and indirect factors affecting the mechanical and microstructural properties of the FSW joints. Tool offset, tilt angle, and plunge depth are determinative tool positioning in the FSW process. Investigating the effect of these factors simultaneously with other parameters such as process speeds (rotational speed and translational speed) and tool geometry leads to a poor understanding of the impact of these factors on the FSW process. Because the three mentioned parameters have the same origin, they should be studied separately from other process parameters. This paper investigates the effects of tilt angle, plunge depth, and tool offset on Ultimate Tensile Stress (UTS) of joints between AA6061-T6 and AA7075-T6. To design the experiments, optimization, and statistical analysis, Response Surface Methodology (RSM) has been used. Experimental tests were carried out to find the maximum achievable UTS of the joint. The optimum values were determined based on the optimization procedure as 0.7 mm of tool offset, 2.7 degrees of tilt angle, and 0.1 mm of plunge depth. These values resulted in a UTS of 281 MPa. Compared to the UTS of base metals, the joint efficiency of the optimized welded sample was nearly 90 percent.

  • Effect of tube bundle arrangement on performance of shell-and-tube latent heat storage system
    • Maciej Fabrykiewicz
    • Janusz Cieśliński
    2022

    This work presents the results of experimental investigation on charging and discharging of latent heat storage systems (LHSS) in the form of shell-and-tube heat exchangers with a variable arrays of the tube bundles. The tests included two tube arrangements – in-line and triangular (staggered), a variable number of tubes in a bundle, two pitch ratios, and different tube positions in a bundle. Three commercial products (LTP56, RT54HC, P1808) from the group of aliphatic hydrocarbons were used as PCM. Systematic experimental studies have shown that regardless of the type of the tested PCM, the shortest charging / discharging rates for the tested LHSS were achieved for a bundle of 7 tubes in a staggered arrangement and a pitch ratio of 4.5.

  • Effect of Tube Bundle Arrangement on the Performance of PCM Heat Storage Units
    • Maciej Fabrykiewicz
    • Janusz Cieśliński
    2022 Full text ENERGIES

    The results of comprehensive study on charging and discharging of latent heat storage systems (LHSS) are presented. The multi tube shell-and-tube unit with a variable layouts of the tube bundles are examined. Two tube arrangements – in-line and staggered are tested. A variable number of tubes and different tube positions in a bundle are investigated. Moreover, two pitch ratios are studied. Three commercially available substances are used as phase change material (PCM). The results show that increasing the number of tubes reduces both charging and dis-charging times. It is found that for a bundle of 7 tubes with the pitch ratio s/d=4.5, the in-line tube arrangement results in shorter charging time, but the discharging time is shorter for staggered tube arrangement.

  • Effectiveness of a dual surface modification of metallic interconnects for application in energy conversion devices
    • Łukasz Mazur
    • Justyna Ignaczak
    • Maciej Bik
    • Sebastian Molin
    • Maciej Sitarz
    • Aleksander Gil
    • Tomasz Brylewski
    2022 Full text INTERNATIONAL JOURNAL OF HYDROGEN ENERGY

    A dual surface modification of an SOFC metallic interconnect with a Gd2O3 layer and an MnCo2O4 coating was evaluated. The tested samples were oxidized for 7000 h in air at 1073 K. Oxidation products were characterized using XRD, SEM-EDS, and confocal Raman imaging, and ASR was measured. The effect of gadolinium segregation at grain boundaries in Cr2O3 was evaluated using S/TEM-EDS. Area specific-resistance was measured and fuel cell tests investigating electrochemical performance and Cr contamination of electrodes were also performed. The results show that the proposed dual modification was more advantageous than either modification applied separately. The fuel cell tests performed after aging in humidified hydrogen at 1073 K and involving an actual interconnect made of this dual-modified material showed that after 250 h of aging its electrochemical parameters were nearly identical to those of the non-aged reference electrode. Moreover, the modification protected the electrodes from Cr poisoning.

  • Effectiveness of Random Field Approach in Serviceability Limit State Analysis of Strip Foundation
    • Karol Winkelmann
    • Kamil Żyliński
    • Aleksandra Korzec
    • Jarosław Górski
    2022 Full text Geotechnical and Geological Engineering

    This work conducts a probabilistic inquiry on how the variability of the parameter defining soil deformability affects the settlement of the foundation located on the soil. The analysis addresses the random foundation model to relevantly estimate the probability of allowable deflection exceedance. The constitutive model parameter is based either on a single random variable or a random field. The computations incorporate direct Monte Carlo sampling and the variance reduction techniques, i.e. Stratified Sampling and Latin Hypercube Sampling. The work focuses on soil parameter modelling by random fields defined by various correlation functions. One of the analytical means is the application of a non-homogeneous function capable of reflecting the soil strata. The probabilistic methods proposed in the paper are tested on a standard example of a foundation strip featuring load eccentricity. It is proved that the modelling mode of the soil—a single variable or a random field—substantially affects the results, i.e. foundation settlements. It was detected that incorporating random fields in soil analysis allows for a valid reliability assessment of a foundation in respect to Serviceability Limit State. The relevantly adjusted correlation functions of random fields allow for a realistic subsoil analysis even in the case of a limited in situ measurement database.

  • Effects of Column Base Flexibility on Seismic Response of Steel Moment-Frame Buildings
    • Tomasz Falborski
    • Ahmad Hassan
    • Amit Kanvinde
    2022

    Steel Moment Resisting Frames (SMRFs) are very popular lateral load resisting systems in many seismically active regions. However, their seismic response is strongly dependent on the rotational fixity of column base connections. Despite many studies (both experimental and numerical) in this particular area, available approaches for estimating column base flexibility have been validated only against laboratory test data. In the present paper these approaches are examined based on strong motion recordings from two instrumented SMRF buildings in California (CA) to introduce best practices for seismic response simulation. Three-dimensional simulation models are constructed for these buildings, including the gravity framing and non-structural stiffness. For each building, the base fixities are parametrically varied. These include pinned and fixed bases, as well as intermediate fixities determined from previously developed models that are appropriate for simulating the specific types of base connections used in the buildings. The simulated response of these buildings is compared to strong motion recordings to propose optimal approaches for simulating rotational fixity of column base connections.

  • Effects of full displacement pile installation on the stress and deformation state of surrounding soil: review
    • Worku Firomsa Kabeta
    2022 Full text Archives of Civil Engineering

    Several field and model tests have been conducted to investigate the impact of pile installation on bearing capacity. However, little is known about how piles behave during installation, how they interact with the surrounding soil, and how this affects sandy soil properties. This review paper investigates the effect of pile driving on surrounding sandy soil as it compacts sandy soil near to the pile. For this purpose, various related literature was studied based on the observation of the pile installation effect on earth pressure or lateral stress, relative density, and pore water pressure in the sandy soil. A change in the deformation and stress state of surrounding sandy soil due to pile driving was presented. The installation of fully displacement piles can lead to significant stresses and deformations in the surrounding sandy soil. This is one of the main causes of uncertainty in the design and analysis of pile foundations. According to this study, the sandy soil around the pile is compacted during pile driving, resulting in lateral and upward displacement. This leads to the densification effect of pile driving on loose sandy soil. Sandy soil improvement with driven piles depends on pile shape, installation method, and pile driving sequences. This study concludes that in addition to its advantages of transferring superstructure load to deep strata, the increased relative density of loose sand, the change in the horizontal stress, and the influence of compaction on the sandy soil parameters during pile driving should be considered during pile design and analysis.

  • Effects of La0.8Sr0.2MnO3 and Ag electrodes on bismuth-oxide-based low-temperature solid electrolyte oxygen generators
    • Jeng-Ting Tsai
    • Sea-Fue Wang
    • Yung-Fu Hsu
    • Piotr Jasiński
    2022 CERAMICS INTERNATIONAL

    In this study, La0.8Sr0.2MnO3 (LSM) was used as the ceramic electrode in a (Bi1.50Y0.50)0.98Zr0.04O3+δ (BYO)-based solid electrolyte oxygen generator (SEOG) and its performance was compared with that of a previously studied high-fire Ag electrode. Among La0.6Sr0.4Co0.2Fe0.8O3, LaNi0.6Fe0.4O3, Cu1.4Mn1.6O4, and LSM materials, only LSM materials did not trigger any chemical reaction or interdiffusion with BYO at temperatures up to 900 °C. Two cell designs, Cell A, with a Bi1.71Nb0.25Ba0.04O3+δ (BBNO) interlayer and high-fire Ag electrode, and Cell B, with an LSM-BYO composite electrode, were obtained in this study. The cells were sandwiched between two modular SUS 316 planar interconnects using a ZnO–SiO2–Al2O3 glass sealant to form the SEOG device. Although Cells A and B possessed similar ohmic resistance (Ro) values, the polarization resistance (Rp) values of Cell A were 3.6 times larger than those of Cell B. Furthermore, the stability study of the cells operated at 600 °C for 12 h revealed that Ro increased from 0.79 to 3.17 Ω cm2 and Rp from 3.12 to 12.58 Ω cm2 for the Cell A, while Ro increased from 0.76 to 0.77 Ω cm2 and Rp from 0.87 to 1.12 Ω cm2 for the Cell B. Therefore, minor variations in the Ro and Rp of Cell B indicate the excellent stability of the electrode. The degradation of Cell A was caused by the migration of Ag and formation of voids and cracks adjacent to the anode/electrolyte interface under the DC field. Furthermore, the Cell A experienced a decrease in faradaic efficiency for current densities greater than 0.20 A cm−2 owing to the partial decomposition of BYO at the cathode. In contrast, the Cell B generated an oxygen flux of 1.29 cm⋅min−1 at 600 °C. In addition, the faradaic efficiency of Cell B remained consistent for current densities up to 0.35 A cm−2. Therefore, the SEOG using LSM-BYO as the cell electrode exhibited excellent stability and electrochemical performance.

  • Effects of Ni-NCAL and Ni–Ag electrodes on the cell performances of low-temperature solid oxide fuel cells with Sm0.2Ce0·8O2-δ electrolyte at various temperatures
    • Sea-Fue Wang
    • Yi-Le Liao
    • Yung-Fu Hsu
    • Piotr Jasiński
    2022 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY

    Three low-temperature solid oxide fuel cells are built using Sm0.2Ce0·8O2-δ (SDC) as the electrolyte. Cell A is symmetrical and features Ni–LiNi0.8Co0·15Al0·05O2 (Ni–NCAL) electrodes, Cell B comprises a Ni–NCAL anode and a Ni–Ag cathode, and Cell C is fabricated using a Ni–NCAL cathode and a Ni–Ag anode. The ohmic resistance and polarization resistance (Rp) of Cells B and C are significantly higher than those of Cell A. The reduction of NCAL at the anodes of Cells A and B yields LiOH and Li2CO3 phases, and the Ni particles generated on the surfaces of the NCAL particles improve the catalytic activity of the cells. Li2CO3–LiOH melts at temperatures >450 °C and penetrates the porous SDC electrolyte layer, causing its densification and abnormal grain growth and increasing its ionic conductivity to >0.2 S/cm at low temperatures. The high open-circuit voltages (OCVs) (0.970–1.113 V) of the cells during electrochemical measurements are ascribed to the Li2CO3–LiOH phase which serves as an electron-blocking layer for the SDC electrolytes. As the reduction of NCAL approaches completion, the anode comprises only Ni phase, which hinders the charge transfer process. The triple-phase-boundary (TPB) area at cathode of Cell B is significantly lower than that of Cell A; therefore, the catalytic activity of Cell B for the oxygen reduction reaction is lower than that of Cell A. Consequently, the maximum power density (MPD) of Cell B is less than half of that of Cell A. The large Rp value of Cell C is ascribed to its low TPB area at Ni–Ag anode which has no reaction with H2 during operation. No visible sintering of the SDC electrolyte layer is observed for Cell C; therefore, its ionic conductivity is considerably smaller than those of the electrolyte layers of Cells A and B. The OCVs of Cell C (0.281–0.495 V) are significantly lower than the typical OCVs of ceria-based SOFCs. This is attributed to the porous SDC electrolyte layer of Cell C. The large Rp values and the low OCVs contribute to the low MPDs of Cell C at various temperatures.

  • Effects of Noncontact Shoulder Tool Velocities on Friction Stir Joining of Polyamide 6 (PA6)
    • Raheem Al-Sabur
    • Hassanein I. Khalaf
    • Aleksandra Świerczyńska
    • Grzegorz Rogalski
    • Hesamoddin Aghajani Derazkola
    2022 Full text Materials

    In this study, the effects of the traverse and rotational velocities of the noncontact shoulder tool on the heat generation and heated flux during the friction stir joining of high-density polyamide 6 (PA6) polymer were investigated. The computational fluid dynamics (CFD) method was employed to simulate the thermomechanical phenomena during the friction stir joining (FSJ) process of PA6. A developed model was used to consider the void formation and thermochemical properties of PA6. The surface and internal heat flow, material flow, and geometry of the joint were simulated, and an experimental study evaluated the simulation results. The simulation results indicated that the stir zone formed was smaller than regular joints with a noncontact shoulder tool. Despite the polymer’s traditional FSJ, heat generation and material flow do not differ significantly between advancing and retreating sides. On the other hand, the surface flow is not formed, and the surface temperature gradient is in a narrow line behind the tool. The material velocity increased at higher rotational speed and lower transverse velocity and in the stir zone with more giant geometry forms. The maximum generated heat was 204 C, and the maximum material velocity was predicted at 0.44 m/s in the stir zone, achieved at 440 rpm and 40 mm/min tool velocities.

  • Effects of Post-Harvest Elicitor Treatments with Ultrasound, UV- and Photosynthetic Active Radiation on Polyphenols, Glucosinolates and Antioxidant Activity in a Waste Fraction of White Cabbage (Brassica oleracea var. capitata)
    • Randi Seljåsen
    • Barbara Kusznierewicz
    • Agnieszka Bartoszek-Pączkowska
    • Jørgen Mølmann
    • Ingunn M. Vågen
    2022 Full text MOLECULES

    Biosynthesis of phytochemicals in leaves of Brassica can be initiated by abiotic factors. The aim of the study was to investigate elicitor treatments to add value to waste of cabbage. A leaf waste fraction from industrial trimming of head cabbage was exposed to UV radiation (250–400 nm, 59 and 99 kJ m-2, respectively), photosynthetic active radiation (PAR, 400–700 nm, 497 kJ m-2), and ultrasound in water bath (35 kHz, at 15, 30 and 61 kJ l-1 water), in order to improve nutraceutical concentration. UV was more effective than PAR to increase the level of flavonols (2 to 3-fold higher) and hydroxycinnamate monosaccharides (1 to 10-fold higher). PAR was three times as effective as UV to increase anthocyanins. Interaction of PAR +UV increased antioxidant activity (30%), the content of five phenolics (1.4 to 10-fold higher), and hydroxycinnamic monosaccharides (compared with PAR or UV alone). Indoles were reduced (40–52%) by UV, but the other glucosinolates (GLS) were unaffected. Ultrasound did not influence any parameters. The results are important for white cabbage by-products by demonstrating that UV + PAR can be successfully used as an effectual tool to increase important phenolics and antioxidant activity of waste fraction leaves without an adverse effect on the main GLS.

  • Effects of Surface Energy and Surface Residual Stresses on Vibro-Thermal Analysis of Chiral, Zigzag, and Armchair Types of SWCNTs Using Refined Beam Theory
    • Subrat Kumar Jena
    • S. Chakraverty
    • Mohammad Malikan
    • Francesco Tornabene
    2022 Full text MECHANICS BASED DESIGN OF STRUCTURES AND MACHINES

    In this article, vibration characteristics of three different types of Single-Walled Carbon Nanotubes (SWCNTs) such as armchair, chiral, and zigzag carbon nanotubes have been investigated considering the effects of surface energy and surface residual stresses. The nanotubes are embedded in the elastic substrate of the Winkler type and are also exposed to low and high-temperature environments. A new refined beam theory namely, one-variable shear deformation beam theory has been combined with Hamilton’s principle to develop the governing equations of the proposed model. The size-dependent behavior of the SWCNTs is addressed by Eringen’s nonlocal elasticity theory whereas the model is investigated analytically by employing Navier’s technique. Also, a parametric study has been conducted to analyze the effects of various scaling parameters such as small scale parameter, temperature change, thermal environments, Winkler modulus, and length of the beam. The results are also validated with previously published articles in special cases witnessing robust agreement.

  • Effects of UV light irradiation on fluctuation enhanced gas sensing by carbon nanotube networks
    • Katarzyna Drozdowska
    • Adil Rehman
    • Aleksandra Krajewska
    • Dmitri V. Lioubtchenko
    • Krystian Pavłov
    • Sergey Rumyantsev
    • Janusz Smulko
    • Grzegorz Cywiński
    2022 Full text SENSORS AND ACTUATORS B-CHEMICAL

    The exceptionally large active surface-to-volume ratio of carbon nanotubes makes it an appealing candidate for gas sensing applications. Here, we studied the DC and low-frequency noise characteristics of a randomly oriented network of carbon nanotubes under NO2 gas atmosphere at two different wavelengths of the UV light-emitting diodes. The UV irradiation allowed to sense lower concentrations of NO2 (at least 1 ppm) compared to dark conditions. Our experimental studies confirmed that the flicker noise of resistance fluctuations under UV irradiation significantly enhanced the sensing characteristics of nanotube networks at low concentrations. We observed a dominating 1/f-like noise component below 1 kHz. The sensitivity of nanotube networks was higher for shorter wavelength, whereas drift in the resistance was smaller for longer wavelength. The measurements under the NO2 gas atmosphere revealed a remarkable reduction in DC resistance drift of the nanotube network between consecutive cycles of gas sensing. This phenomenon was explained via absorption-desorption of NO2 gas molecules on nanotubes surface. Since small concentrations of NO2 pose a threat to the ecosystem, these results might play a significant role in the development of sensitive nanotubes-based photo-activated gas sensors.

  • Efficacy of intralesional bleomycin in treatment resistant viral warts
    • Martyna Sławińska
    • Jakub Żółkiewicz
    • Krzysztof Pastuszak
    • Klaudia Zawadzka
    • Monika Sikorska
    • Roman Nowicki
    • Michał Sobjanek
    2022 Full text Przegląd Dermatologiczny

    Introduction Optimal management of treatment-refractory viral warts caused by human papillomavirus is unknown. One of the treatment methods is intralesional bleomycin solution. Objective To determine risk factors for resistant viral warts (not responding to conventional treatments for ≥ 6 months), to determine the effectiveness and safety of intralesional bleomycin in a group of patients with viral warts resistant to conventional treatment methods, and to assess the utility of dermoscopy in monitoring treatment effects during intralesional bleomycin therapy. Material and methods The study group consisted of consecutive 12 adult patients with resistant viral warts treated with intralesional bleomycin (0,5 U/ml) at the Department of Dermatology, Venereology and Allergology, Medical University of Gdansk between July 2019 and December 2021. Inclusion criteria were age > 18 and previous unsuccessful treatment of viral warts with ≥ 2 methods used according to guidelines over a period of 6 months. The control group consisted of 8 adult patients who presented with viral warts of the total duration of less than 6 months with no previous treatment, and qualified for cryotherapy. Results Bleomycin showed 100% efficacy. Except for periprocedural pain, no side effects were observed. Dermoscopy proved to be effective in clinical evaluation of patients, as it allowed to differentiate wart remnants from eschar observed after bleomycin injection. In one patient we observed CD4+ lymphocytopenia at the inclusion stage, and no other risk factors of resistant warts could be identified, however a relatively small number of patients studied could influence this observation. Conclusions Intralesional bleomycin may be considered as possible therapeutic option in patients with therapy-resistant viral warts.

  • Efficiency evaluation of graduation process in Australian public universities
    • Andrzej Szuwarzyński
    2022 Full text Economic Research-Ekonomska Istrazivanja

    First-year attrition and on-time graduation are key challenges for contemporary universities, which determine their efficiency. Based on the benefit of the doubt approach, this study reports the efficiency of the graduation process in 37 Australian public universities. The super-efficiency model extended by restrictions on virtual weights is used. The proposed model considers the attrition rate and the on-time graduation rate separately for domestic and overseas students and other variables, like student-staff ratio, the share of full-time students and the share of online students. Some additional factors are included, such as the university's affiliation with a grouping, the year of the university founding and basic data on the subject mix of universities courses, explaining the rankings created. The analysis indicates that research-oriented universities achieve better results and overseas students perform better than domestic ones. Also, it can be seen that the universities dealing with large-scale online learning are underperformed. The obtained results allow all stakeholders to understand better the efficiency of the graduation process. The main findings are consistent with research published elsewhere.

  • Efficiency of exciton splitting in organic photovoltaic cells within EQE spectrum
    • Grażyna Jarosz
    • Ryszard Signerski
    • Rafał Marczyński
    2022 Full text APPLIED SURFACE SCIENCE

    The paper presents a procedure of estimating the efficiency of exciton splitting at ED/EA interface. The procedure consists in evaluation of splitting of excitons into electron-hole pairs on the basis of the external quantum efficiency spectra of planar cells and spectra of absorbance of active organic layers. The fitting parameters are the exciton splitting probabilities at ED/EA interface. The presented procedure was applied to two different photovoltaic systems: ITO/MoO3/DBP/PTCBI/BCP/Ag and ITO/MoO3/DBP/F16ZnPc/BCP/Ag with quite similar energy diagrams at the ED/EA interface. The analysis performed led us to the conclusion that only the DBP/PTCBI interface can be considered attractive for organic photovoltaics and organic photodetection, while the DBP/F16ZnPc interface does not show any favourable properties for such applications.

  • Efficient and robust quadratures for isogeometric analysis: Reduced Gauss and Gauss–Greville rules
    • Z. Zou
    • T.j.r. Hughes
    • M.a. Scott
    • D. Miao
    • Roger Sauer
    2022 Full text COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING

    This work proposes two efficient quadrature rules, reduced Gauss quadrature and Gauss–Greville quadrature, for isogeometric analysis. The rules are constructed to exactly integrate one-dimensional B-spline basis functions of degree p, and continuity class C^{p−k}, where k is the highest order of derivatives appearing in the Galerkin formulation of the problem under consideration. This is the same idea we utilized in Zou et al. (2021), but the rules therein produced negative weights for certain non-uniform meshes. The present work improves upon Zou et al. (2021) in that the weights are guaranteed to be positive for all meshes. The reduced Gauss quadrature rule is built element-wise according to the element basis degree and smoothness. The Gauss– Greville quadrature rule combines the proposed reduced Gauss quadrature and Greville quadrature Zou et al. (2021). Both quadrature rules involve many fewer quadrature points than the full Gauss quadrature rule and avoid negative quadrature weights for arbitrary knot vectors. The proposed quadrature rules are stable and accurate, and they can be constructed without solving nonlinear equations, therefore providing efficient and easy-to-use alternatives to full Gauss quadrature. Various numerical examples, including curved shells, demonstrate that they achieve good accuracy, and for p = 5 and 6 eliminate locking.