Ghazanfar Mehboob, K. Nadeem, A. Iqbal, Gohar Mehboob, Shahnawaz Hussain, Mohamed Ragab, Mazhar Iqbal, S. Ajmal, Adel El-Marghany
Abstract The present study investigates the temperature-dependent magnetic (MT) properties of CoCr2O4/(SiO2)y (y = 0 and 0.8) nanoparticles. Nanoparticles were synthesised by using the conventional sol–gel technique. The X-ray diffraction (XRD) method confirmed the normal spinel structure of CoCr2O4 nanoparticles. The main peak analysis of the XRD pattern using Debye–Scherrer’s formula probes the mean crystallite sizes for coated and uncoated nanoparticles, and the sizes based on which the probes have been carried out amount to 19 nm and 28 nm, respectively. The transmission electron microscopy (TEM) image showed the non-spherical shape of these nanoparticles. Field-cooled (FC) and zero field-cooled (ZFC) MT plots were taken by using a superconducting quantum interference device (SQUID) magnetometer. Pure CoCr2O4 nanoparticles showed the ferrimagnetic transition at Curie temperature (Tc = 99 K) on an applied field (H) of 50 Oe. Tc decreased up to 95 K with the increase in 80% SiO2 concentration in CoCr2O4 nanoparticles. For pure samples, conical spiral temperature (TS) and lock-in transition temperature (TL) remain unchanged with increasing magnetic field because of strong spin–lattice coupling. However, for 80% SiO2 impurity, the decrease in Tc was attributed to the reduction in surface disorder with a minor decline in TS and TL. The Ms declined with a decrease in temperature because of the existence of stiffed/strong conical spin-spiral and lock-in states in pure CoCr2O4 nanoparticles, while nanoparticles with 80% coating SiO2 concentration showed abnormal behavior. The coercivity increases with a decrease in temperature due to a decrease in thermal fluctuations at low temperatures for both samples. The fitting of coercivity (Hc) versus temperature plot by using Kneller’s law has given the values of coercivity constant (α) and coercivity at average blocking temperature (TB) for both samples, which are α = 0.54, TB = 75 K and α = 1.59, TB = 81 K, respectively. Hence, the increase in the concentration of SiO2 decreased nanoparticles size and surface disorder in CoCr2O4 nanoparticles while enhancing Ms below spin-spiral state ordering.
{"title":"The Study of Temperature-Dependent Magnetic Properties Variation in CoCr2O4 Nanoparticles with (y = 0.8) and Without Coating Concentration of Non-Magnetic (SiO2)y","authors":"Ghazanfar Mehboob, K. Nadeem, A. Iqbal, Gohar Mehboob, Shahnawaz Hussain, Mohamed Ragab, Mazhar Iqbal, S. Ajmal, Adel El-Marghany","doi":"10.2478/ama-2023-0062","DOIUrl":"https://doi.org/10.2478/ama-2023-0062","url":null,"abstract":"Abstract The present study investigates the temperature-dependent magnetic (MT) properties of CoCr2O4/(SiO2)y (y = 0 and 0.8) nanoparticles. Nanoparticles were synthesised by using the conventional sol–gel technique. The X-ray diffraction (XRD) method confirmed the normal spinel structure of CoCr2O4 nanoparticles. The main peak analysis of the XRD pattern using Debye–Scherrer’s formula probes the mean crystallite sizes for coated and uncoated nanoparticles, and the sizes based on which the probes have been carried out amount to 19 nm and 28 nm, respectively. The transmission electron microscopy (TEM) image showed the non-spherical shape of these nanoparticles. Field-cooled (FC) and zero field-cooled (ZFC) MT plots were taken by using a superconducting quantum interference device (SQUID) magnetometer. Pure CoCr2O4 nanoparticles showed the ferrimagnetic transition at Curie temperature (Tc = 99 K) on an applied field (H) of 50 Oe. Tc decreased up to 95 K with the increase in 80% SiO2 concentration in CoCr2O4 nanoparticles. For pure samples, conical spiral temperature (TS) and lock-in transition temperature (TL) remain unchanged with increasing magnetic field because of strong spin–lattice coupling. However, for 80% SiO2 impurity, the decrease in Tc was attributed to the reduction in surface disorder with a minor decline in TS and TL. The Ms declined with a decrease in temperature because of the existence of stiffed/strong conical spin-spiral and lock-in states in pure CoCr2O4 nanoparticles, while nanoparticles with 80% coating SiO2 concentration showed abnormal behavior. The coercivity increases with a decrease in temperature due to a decrease in thermal fluctuations at low temperatures for both samples. The fitting of coercivity (Hc) versus temperature plot by using Kneller’s law has given the values of coercivity constant (α) and coercivity at average blocking temperature (TB) for both samples, which are α = 0.54, TB = 75 K and α = 1.59, TB = 81 K, respectively. Hence, the increase in the concentration of SiO2 decreased nanoparticles size and surface disorder in CoCr2O4 nanoparticles while enhancing Ms below spin-spiral state ordering.","PeriodicalId":44942,"journal":{"name":"Acta Mechanica et Automatica","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139195960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Michał Kolankowski, Michał Banach, R. Piotrowski, Tomasz Ujazdowski
Abstract The wastewater treatment plant (WWTP) is a complex system due to its non-linearity, time-variance and multiple time scales in its dynamics among others. The most important control parameter in a WWTP is the dissolved oxygen (DO) concentration. The tracking problem of the DO concentration is one of the most fundamental issues in biological wastewater treatment. Proper control of DO concentration is necessary to achieve adequate biological conditions for microorganisms in the WWTP. Aeration is an important process to achieve those conditions, but it is expensive. It was performed using an aeration system, which includes blowers, pipelines and diffusers. This paper presents a new approach to designing a non-linear control system for controlling DO concentration using an adaptive backstepping algorithm. A model of biological processes and aeration system were applied in designing the control system. Simulation tests of the control system were performed and very good results on control were obtained. The proposed solution has proved to be effective and computationally efficient.
{"title":"A New Approach to Designing Control of Dissolved Oxygen and Aeration System in Sequencing Batch Reactor by Applied Backstepping Control Algorithm","authors":"Michał Kolankowski, Michał Banach, R. Piotrowski, Tomasz Ujazdowski","doi":"10.2478/ama-2023-0070","DOIUrl":"https://doi.org/10.2478/ama-2023-0070","url":null,"abstract":"Abstract The wastewater treatment plant (WWTP) is a complex system due to its non-linearity, time-variance and multiple time scales in its dynamics among others. The most important control parameter in a WWTP is the dissolved oxygen (DO) concentration. The tracking problem of the DO concentration is one of the most fundamental issues in biological wastewater treatment. Proper control of DO concentration is necessary to achieve adequate biological conditions for microorganisms in the WWTP. Aeration is an important process to achieve those conditions, but it is expensive. It was performed using an aeration system, which includes blowers, pipelines and diffusers. This paper presents a new approach to designing a non-linear control system for controlling DO concentration using an adaptive backstepping algorithm. A model of biological processes and aeration system were applied in designing the control system. Simulation tests of the control system were performed and very good results on control were obtained. The proposed solution has proved to be effective and computationally efficient.","PeriodicalId":44942,"journal":{"name":"Acta Mechanica et Automatica","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139187792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Beata Maciejewska, S. Hożejowska, M. Grabowski, M. Poniewski
Abstract This paper deals with boiling heat transfer in the flow of water through an asymmetrically heated horizontal rectangular mini-channel. The mini-channel was made by gluing three transparent glass plates and a copper block. Through the glass window, the variable along the length of the mini-channel two-phase flow structures were recorded to determine local values of the void fraction. Four resistance heaters were attached to the copper block, powered by direct current, generating the heat initiating the flow boiling inside the channel. During the experiment, the following were measured: water volumetric flow rate, inlet pressure with pressure drop, inlet and outlet water temperature, copper block temperatures at three points inside its body, voltage and current supplied to the heaters. Stationary and laminar fluid flow with low Reynolds numbers were assumed in the mathematical model of heat transfer in selected elements of the measuring module. The temperature distributions in the copper block and flowing water were described by the appropriate energy equations: the Laplace equation for the copper block and the Fourier–Kirchhoff equation with parabolic fluid velocity for the flowing water. These equations were supplemented with a set of boundary conditions based on measurement data; moreover, data from experimental studies were the basis for numerical calculations and their verification. Two-dimensional temperature distributions of the copper block and water were calculated with the Trefftz method (TM). The main objective of this study was to determine the heat transfer coefficient on the contact surface of the copper block and water, which was calculated from the Robin boundary condition. The results of the calculations were compared with the results of numerical simulations performed using the Simcenter STAR-CCM+ software, obtaining consistent values. Computational fluid dynamics (CFD) simulations were verified based on experimental data including void fraction and temperature measurements of the copper block and flowing water.
{"title":"Numerical Analysis of the Boiling Heat Transfer Coefficient in the Flow in Mini-Channels","authors":"Beata Maciejewska, S. Hożejowska, M. Grabowski, M. Poniewski","doi":"10.2478/ama-2023-0069","DOIUrl":"https://doi.org/10.2478/ama-2023-0069","url":null,"abstract":"Abstract This paper deals with boiling heat transfer in the flow of water through an asymmetrically heated horizontal rectangular mini-channel. The mini-channel was made by gluing three transparent glass plates and a copper block. Through the glass window, the variable along the length of the mini-channel two-phase flow structures were recorded to determine local values of the void fraction. Four resistance heaters were attached to the copper block, powered by direct current, generating the heat initiating the flow boiling inside the channel. During the experiment, the following were measured: water volumetric flow rate, inlet pressure with pressure drop, inlet and outlet water temperature, copper block temperatures at three points inside its body, voltage and current supplied to the heaters. Stationary and laminar fluid flow with low Reynolds numbers were assumed in the mathematical model of heat transfer in selected elements of the measuring module. The temperature distributions in the copper block and flowing water were described by the appropriate energy equations: the Laplace equation for the copper block and the Fourier–Kirchhoff equation with parabolic fluid velocity for the flowing water. These equations were supplemented with a set of boundary conditions based on measurement data; moreover, data from experimental studies were the basis for numerical calculations and their verification. Two-dimensional temperature distributions of the copper block and water were calculated with the Trefftz method (TM). The main objective of this study was to determine the heat transfer coefficient on the contact surface of the copper block and water, which was calculated from the Robin boundary condition. The results of the calculations were compared with the results of numerical simulations performed using the Simcenter STAR-CCM+ software, obtaining consistent values. Computational fluid dynamics (CFD) simulations were verified based on experimental data including void fraction and temperature measurements of the copper block and flowing water.","PeriodicalId":44942,"journal":{"name":"Acta Mechanica et Automatica","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139189095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The current study is a semi-analytical analysis of the vibratory behaviour of a rigid vertical rotor, supported by a new hydrostatic squeeze film damper (HSFD), consisting of four hydrostatic pads fed through four single-action membrane-type variable-flow restrictors. The Reynolds equation based on the Newtonian theory of lubrication is used and then adapted to our work, which is solved semi-analytically. In this paper, we study the effect of different parameters, the eccentricity, membrane geometry coefficient, pressure ratio and rotational speed, on the main characteristics of a four-pad HSFD. From the simulation results, we observed that at the critical speed, the rigid rotor fed by membrane restrictor shows a decrease in transmitted forces, a decrease in vibration response and good system stability as compared with a similar rotor fed by capillary restrictor. From the results reported in this work, we observed good agreement between our study and other works.
{"title":"Semi-Analytical Analysis of a Rigid Rotor Mounted on Four-Pad Hydrostatic Squeeze Film Damper with Single-Action Membrane-Type Restrictors","authors":"Ahmed Kechra, Ahmed Bouzidaine","doi":"10.2478/ama-2023-0059","DOIUrl":"https://doi.org/10.2478/ama-2023-0059","url":null,"abstract":"Abstract The current study is a semi-analytical analysis of the vibratory behaviour of a rigid vertical rotor, supported by a new hydrostatic squeeze film damper (HSFD), consisting of four hydrostatic pads fed through four single-action membrane-type variable-flow restrictors. The Reynolds equation based on the Newtonian theory of lubrication is used and then adapted to our work, which is solved semi-analytically. In this paper, we study the effect of different parameters, the eccentricity, membrane geometry coefficient, pressure ratio and rotational speed, on the main characteristics of a four-pad HSFD. From the simulation results, we observed that at the critical speed, the rigid rotor fed by membrane restrictor shows a decrease in transmitted forces, a decrease in vibration response and good system stability as compared with a similar rotor fed by capillary restrictor. From the results reported in this work, we observed good agreement between our study and other works.","PeriodicalId":44942,"journal":{"name":"Acta Mechanica et Automatica","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139187788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Piotr Radomski, Paweł Ziółkowski, Dariusz Mikielewicz
Abstract This work introduces the theoretical method of metallic nanoparticles’ (NPs’) heat and mass transfer where the particles are coated on a surface (base), together with considering the case wherein nanoparticles move freely in a pipe. In order to simulate the heat transfer, energy and radiative transfer equations are adjusted to the considered issue. NPs’ properties are determined following the nanofluidic theories, whereas absorption and scattering coefficients are described using either Mie-Lorenz theory or Rayleigh-Drude approximation. Thermal boundary conditions are implemented based on the microscale heat transfer and Smoluchowski theory. Results are compared with the classical Fourier transport differential solutions that have been adjusted to laser irradiation.
{"title":"Energy Conversion in Systems-Contained Laser-Irradiated Metallic Nanoparticles – Comparison of Results from Analytical Solutions and Numerical Methods","authors":"Piotr Radomski, Paweł Ziółkowski, Dariusz Mikielewicz","doi":"10.2478/ama-2023-0063","DOIUrl":"https://doi.org/10.2478/ama-2023-0063","url":null,"abstract":"Abstract This work introduces the theoretical method of metallic nanoparticles’ (NPs’) heat and mass transfer where the particles are coated on a surface (base), together with considering the case wherein nanoparticles move freely in a pipe. In order to simulate the heat transfer, energy and radiative transfer equations are adjusted to the considered issue. NPs’ properties are determined following the nanofluidic theories, whereas absorption and scattering coefficients are described using either Mie-Lorenz theory or Rayleigh-Drude approximation. Thermal boundary conditions are implemented based on the microscale heat transfer and Smoluchowski theory. Results are compared with the classical Fourier transport differential solutions that have been adjusted to laser irradiation.","PeriodicalId":44942,"journal":{"name":"Acta Mechanica et Automatica","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139187933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Modified LCD-based method was used to print three-dimensional (3D) elements. This innovative method combines printing the external shell and filling, thus obtaining mould by casting resin. In order to compare the properties of prints obtained with this method with the ones fabricated in a standard procedure, we conducted bending tests of vertically/horizontally printed and shell-printed cast specimens. The shell-cast samples showed higher flexural strength and larger values of apparent Young’s modulus. The presented results also concern the kinetics of curing samples obtained with different fabrication routes.
{"title":"An Innovative Approach to Fabrication With Photo-Cured Resins by Shell-Printed-Core-Casting","authors":"Emil Szymczyk, M. Rećko, K. Dzierżek, K. Sapiołko","doi":"10.2478/ama-2023-0056","DOIUrl":"https://doi.org/10.2478/ama-2023-0056","url":null,"abstract":"Abstract Modified LCD-based method was used to print three-dimensional (3D) elements. This innovative method combines printing the external shell and filling, thus obtaining mould by casting resin. In order to compare the properties of prints obtained with this method with the ones fabricated in a standard procedure, we conducted bending tests of vertically/horizontally printed and shell-printed cast specimens. The shell-cast samples showed higher flexural strength and larger values of apparent Young’s modulus. The presented results also concern the kinetics of curing samples obtained with different fabrication routes.","PeriodicalId":44942,"journal":{"name":"Acta Mechanica et Automatica","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45985734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The widespread use of battery-powered electronic devices creates the need to develop methods to extend their maximum operating time. This can be achieved by using ambient energy, which would otherwise be dissipated. The conversion of energy, usually mechanical energy, into electric energy takes place in energy harvesters. Energy harvester systems based on a dielectric elastomer (DE) are a relatively new field that is being constantly developed. Due to their features, dielectric elastomer generators (DEGs) may complement the currently dominant piezoelectric harvesters. The major feature of employing a hyperelastic material is that it allows relatively large displacements to be utilised for generating energy, which is impossible in the case of piezoceramics. This article presents a DEG designed to operate under uniaxial tensile loads and which has a multilayer structure, describes the general operating principles of a DEG, explains the construction and assembly process of the investigated design and shows the electric circuit necessary to properly direct current flow during the DEG operation. The experimental part consists of two series of tests based on a central composite design (CCD). The objective of the first part was to map a capacitance response surface of the DEG in the selected range of the cyclic mechanical load. The second part concerned the amount of generated energy for the specific load case as a function of operating voltages. The result of the work is the formulation of regression models that allow the characteristics of the presented DEG design to be identified.
{"title":"Experimental Investigation of a Uniaxial Dielectric Elastomer Generator","authors":"W. Sikora","doi":"10.2478/ama-2023-0058","DOIUrl":"https://doi.org/10.2478/ama-2023-0058","url":null,"abstract":"Abstract The widespread use of battery-powered electronic devices creates the need to develop methods to extend their maximum operating time. This can be achieved by using ambient energy, which would otherwise be dissipated. The conversion of energy, usually mechanical energy, into electric energy takes place in energy harvesters. Energy harvester systems based on a dielectric elastomer (DE) are a relatively new field that is being constantly developed. Due to their features, dielectric elastomer generators (DEGs) may complement the currently dominant piezoelectric harvesters. The major feature of employing a hyperelastic material is that it allows relatively large displacements to be utilised for generating energy, which is impossible in the case of piezoceramics. This article presents a DEG designed to operate under uniaxial tensile loads and which has a multilayer structure, describes the general operating principles of a DEG, explains the construction and assembly process of the investigated design and shows the electric circuit necessary to properly direct current flow during the DEG operation. The experimental part consists of two series of tests based on a central composite design (CCD). The objective of the first part was to map a capacitance response surface of the DEG in the selected range of the cyclic mechanical load. The second part concerned the amount of generated energy for the specific load case as a function of operating voltages. The result of the work is the formulation of regression models that allow the characteristics of the presented DEG design to be identified.","PeriodicalId":44942,"journal":{"name":"Acta Mechanica et Automatica","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42382224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The article presents the results of experimental research and simulation analyses of the influence of slip velocity, normal pressures and vibration frequency on the effectiveness of friction force reduction carried out in sliding motion in the presence of forced tangential vibrations. In experimental studies, changes in the driving force were measured during the slip of the upper body over the vibrating lower body. The direction of these vibrations was parallel both to the contact plane and to the direction of movement of the shifted body. The simulation tests were carried out in the Matlab/Simulink environment through the use of numerical procedures that were specially created for this purpose. Dynamic friction models considering the tangential compliance of contact and the phenomenon of pre-sliding displacement were used for calculations. The paper presents the designated values of the so-called coefficient of average friction force reduction in sliding motion for the following friction pairs: steel C45–steel C45, steel C45–cast iron GGG40 and steel C45–polytetrafluoroethy-lene PTFE (Teflon). The results of numerical analyses were in good agreement with those of experimental tests. A significant dependence of the level of average friction force reduction on the frequency of forced vibrations, sliding velocity as well as the kind of sliding pair material, and normal pressures was shown.
{"title":"Effectiveness of Friction Force Reduction in Sliding Motion Depending on the Frequency of Longitudinal Tangential Vibrations, Sliding Velocity and Normal Pressure","authors":"Mariusz Leus, P. Gutowski, Marta Rybkiewicz","doi":"10.2478/ama-2023-0057","DOIUrl":"https://doi.org/10.2478/ama-2023-0057","url":null,"abstract":"Abstract The article presents the results of experimental research and simulation analyses of the influence of slip velocity, normal pressures and vibration frequency on the effectiveness of friction force reduction carried out in sliding motion in the presence of forced tangential vibrations. In experimental studies, changes in the driving force were measured during the slip of the upper body over the vibrating lower body. The direction of these vibrations was parallel both to the contact plane and to the direction of movement of the shifted body. The simulation tests were carried out in the Matlab/Simulink environment through the use of numerical procedures that were specially created for this purpose. Dynamic friction models considering the tangential compliance of contact and the phenomenon of pre-sliding displacement were used for calculations. The paper presents the designated values of the so-called coefficient of average friction force reduction in sliding motion for the following friction pairs: steel C45–steel C45, steel C45–cast iron GGG40 and steel C45–polytetrafluoroethy-lene PTFE (Teflon). The results of numerical analyses were in good agreement with those of experimental tests. A significant dependence of the level of average friction force reduction on the frequency of forced vibrations, sliding velocity as well as the kind of sliding pair material, and normal pressures was shown.","PeriodicalId":44942,"journal":{"name":"Acta Mechanica et Automatica","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43729937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Berrabah, A. Attia, Daoudi Mohammed Habib, D. Ouzandja
Abstract Using the Beni Behdel dam and the El Mefrouch dam as example studies, this paper intends to clearly demonstrate how modeling of the interactions between rock foundations and dams impacts the modal behavior of these two multi-arch dams. The uniqueness of this study is that the modal behavior of each dam is represented in terms of related parameters (period, participation factor, ratio, and effective mass), and more precisely in terms of ratio (defined as the ratio between the participation factor of the mode i and the maximum participation factor), as opposed to other works that have expressed this behavior in terms of frequency. In this article, stiff rock foundation, massless rock foundation, and massed rock foundation are the three methods used to simulate dynamic interactions. The investigated dams are three-dimensionally simulated using the ANSYS finite elements code. The modeling of the rock foundation–dam interaction has an effect on the fundamental mode value, its location, and the related parameters, according to the results. Furthermore, it is found that the upstream–downstream direction is not always the most important direction for dams and that interaction modeling influences the resonance bandwidth, which affects the forecast of the resonance phenomenon.
{"title":"Effect of Dam–Rock Foundation Interaction Modeling on the Modal Ratio-Related Quantity of Beni Behdel and ‘El Mefrouch Multi-Arch Dams","authors":"A. Berrabah, A. Attia, Daoudi Mohammed Habib, D. Ouzandja","doi":"10.2478/ama-2023-0052","DOIUrl":"https://doi.org/10.2478/ama-2023-0052","url":null,"abstract":"Abstract Using the Beni Behdel dam and the El Mefrouch dam as example studies, this paper intends to clearly demonstrate how modeling of the interactions between rock foundations and dams impacts the modal behavior of these two multi-arch dams. The uniqueness of this study is that the modal behavior of each dam is represented in terms of related parameters (period, participation factor, ratio, and effective mass), and more precisely in terms of ratio (defined as the ratio between the participation factor of the mode i and the maximum participation factor), as opposed to other works that have expressed this behavior in terms of frequency. In this article, stiff rock foundation, massless rock foundation, and massed rock foundation are the three methods used to simulate dynamic interactions. The investigated dams are three-dimensionally simulated using the ANSYS finite elements code. The modeling of the rock foundation–dam interaction has an effect on the fundamental mode value, its location, and the related parameters, according to the results. Furthermore, it is found that the upstream–downstream direction is not always the most important direction for dams and that interaction modeling influences the resonance bandwidth, which affects the forecast of the resonance phenomenon.","PeriodicalId":44942,"journal":{"name":"Acta Mechanica et Automatica","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48655779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jagoda Kurowiak, A. Mackiewicz, T. Klekiel, R. Będziński
Abstract The appropriate development and customisation of the stent to the urethral tissues requires the determination of many factors such as strength and degradation. Given the distinctive conditions of urethral tissues, it is important that the design of the stent be properly developed. The selection of a stent material requires knowing its material characteristics and verifying that they are suitable for the future implantation site. In the present study, the development of a polydioxanone (PDO)-based stent was undertaken. The PDO material was fabricated using an additive technique – 3D printing. Then, in vitro tests were performed to determine the degradation time of the material under conditions simulating an aggressive urinary environment. The changes in the parameters of mechanical properties before and after the degradation period were determined, and the changes in the structure of the material before and after degradation were observed. Numerical analysis was performed for the proposed stent design. The results showed that PDO has good mechanical properties, but its degradation time is too short to be used in a urethral stent. Among the innovations of the studies conducted are bending strength tests, which is not a frequently considered aspect so far.
{"title":"Material Characteristic of an Innovative Stent for the Treatment of Urethral Stenosis","authors":"Jagoda Kurowiak, A. Mackiewicz, T. Klekiel, R. Będziński","doi":"10.2478/ama-2023-0055","DOIUrl":"https://doi.org/10.2478/ama-2023-0055","url":null,"abstract":"Abstract The appropriate development and customisation of the stent to the urethral tissues requires the determination of many factors such as strength and degradation. Given the distinctive conditions of urethral tissues, it is important that the design of the stent be properly developed. The selection of a stent material requires knowing its material characteristics and verifying that they are suitable for the future implantation site. In the present study, the development of a polydioxanone (PDO)-based stent was undertaken. The PDO material was fabricated using an additive technique – 3D printing. Then, in vitro tests were performed to determine the degradation time of the material under conditions simulating an aggressive urinary environment. The changes in the parameters of mechanical properties before and after the degradation period were determined, and the changes in the structure of the material before and after degradation were observed. Numerical analysis was performed for the proposed stent design. The results showed that PDO has good mechanical properties, but its degradation time is too short to be used in a urethral stent. Among the innovations of the studies conducted are bending strength tests, which is not a frequently considered aspect so far.","PeriodicalId":44942,"journal":{"name":"Acta Mechanica et Automatica","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46504373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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