Artykuły naukowe (WEl)

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Open Access
Comparison of frequency domain methods for discrete-time, linear time-varying system with invariant eigenvalues
(International Society for Advanced Research, 2007-10) Orlowski, Przemyslaw; Institute of Control Engineering Szczecin University of Technology
The main aim of this paper is to compare and evaluate frequency methods applicable for discrete-time (DT) linear time-varying (LTV) systems, in particular: two-dimensional (time, frequency) transfer function (2D-TF), timeaveraged 2D-TF and approximated Bode diagrams calculated using SVD-DFT approach and power spectral density (PSD) properties. The main evaluation criteria is possible applicability to feedback system stability analysis. The paper begins from short theoretical background of frequency methods applicable for LTV systems. Further properties of these methods are compared and discussed on the basis of particular case of parameter controlled switching DT LTV system.
Open Access
E-Beam Effects on Poly(Xylitol Dicarboxylate-co-diol Dicarboxylate) Elastomers Tailored by Adjusting Monomer Chain Length
(MDPI, 2021-04-02) Piątek-Hnat, Marta; Bomba, Kuba; Kowalski-Stankiewicz, Janusz P.; Pęksiński, Jakub; Kozłowska, Agnieszka; Sośnicki, Jacek G.; Idzik, Tomasz J.; Schmidt, Beata; Kowalczyk, Krzysztof; Walo, Marta; Mikołajczak, Grzegorz; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; Pomeranian Medical University in Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; Institute of Nuclear Chemistry and Technology,Warszawa; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin
Poly(xylitol dicarboxylate-co-diol dicarboxylate) elastomers can by synthesized using wide variety of monomers with different chain lengths. Obtained materials are all biodegradable, thermally stable elastomers, but their specific properties like glass transition temperature, degradation susceptibility, and mechanical moduli can be tailored for a specific application. Therefore, we synthesized eight elastomers using a combination of two dicarboxylic acids, namely suberic and sebacic acid, and four different diols, namely ethanediol, 1,3-propanediol, 1,4-buanediol, and 1,5- pentanediol. Materials were further modified by e-beam treatment with a dose of 100 kGy. Materials both before and after radiation modification were tested using tensile tests, gel fraction determination, 1H NMR, and 13C NMR. Thermal properties were tested by Differential Scanning Calorimetry (DSC), Dynamic Thermomechanical Analysis (DMTA) and Thermogravimetric Analysis (TGA). Degradation susceptibility to both enzymatic and hydrolytic degradation was also determined.
Open Access
Effect of E-Beam Irradiation on Thermal and Mechanical Properties of Ester Elastomers Containing Multifunctional Alcohols
(MDPI, 2020-05-02) Piątek-Hnat, Marta; Bomba, Kuba; Pęksiński, Jakub; Kozłowska Agnieszka; Sośnicki, Jacek G.; Idzik, Tomasz J.; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin
The aim of this work was to investigate the thermal and mechanical properties of novel, electron beam-modified ester elastomers containing multifunctional alcohols. Polymers tested in this work consist of two blocks: sebacic acid–butylene glycol block and sebacic acid–sugar alcohol block. Di erent sugar alcohols were utilized in the polymer synthesis: glycerol, sorbitol, xylitol, erythritol, and mannitol. The polymers have undergone an irradiation procedure. The materials were irradiated with doses of 50 kGy, 100 kGy, and 150 kGy. The expected e ect of using ionizing radiation was crosslinking process and improvement of the mechanical properties. Additionally, a beneficial side e ect of the irradiation process is sterilization of the a ected materials. It is also worth noting that the materials described in this paper do not require either sensitizers or cross-linking agent in order to perform radiation modification. Radiation-modified poly(polyol sebacate-co-butylene sebacate) elastomers have been characterized in respect to the mechanical properties (quasi-static tensile tests), cross-link density, thermal properties (Di erential Scanning Calorimetry (DSC)), chemical properties: Fourier transform infrared spectroscopy (FTIR), and wettability (water contact angle). Poly(polyol sebacate-co-butylene sebacate) preopolymers were characterized with nuclear magnetic resonance spectroscopy (1HNMRand 13C NMR) and gel permeation chromatography (GPC). Thermal stability of cross-linked materials (directly after synthesis process) was tested with thermogravimetric analysis (TGA).
Open Access
An extension of Nyquist feedback stability for linear time-varying, discrete-time systems
(International Journal of Factory Automation, Robotics and Soft Computing, 2007) Orlowski, Przemyslaw; Institute of Control Engineering, Szczecin University of Technology
The paper concerns on extending the classical Nyquist theorem to stability analysis of linear time-varying (LTV) discrete-time (DT) feedback control systems. Frequency methods, are well- known tool for analysis and synthesis for linear time-invariant systems. Unfortunately, the methods cannot be applied for LTV systems. The main objective is to show that Bode plots approximated using SVD-DFT are adequate methods for evaluating stability margins as well as external stability for LTV systems. We assume discrete-time state space models with time dependent system matrices defined on a finite time horizon. To solve the problem we employ discrete Fourier transform and singular value decomposition of a system matrix operator as well as properties of power spectral density.
Open Access
Influence of e-beam irradiation on the physicochemical properties of poly(polyol succinate-co-butylene succinate) ester elastomers
(2020-07-17) Piątek-Hnat, Marta; Bomba, Kuba; Pęksiński, Jakub; Kozłowska, Agnieszka; Sośnicki, Jacek G.; Idzik, Tomasz J.; Piwowarska, Danuta; Janik, Jolanta; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin
The purpose of this research was synthesis and electron beam modification of novel ester elastomers consisting of sugar alcohol–succinic acid block and butylene glycol–succinic acid block. Four di erent alditols were used in the synthesis—sorbitol, erythritol, xylitol, and glycerol. The materials were irradiated with doses of 50, 100, and 150 kGy in order to determine which dose is the most beneficial. As expected, irradiation of the materials has led to the cross-link density becoming higher and improvement of the mechanical properties. Additionally, the materials were also sterilized in the process. The great advantage of elastomers described in the paper is the fact that they do not need chemical cross-linking agents or sensitizers in order to undergo radiation modification. The following tests were performed on cross-linked poly(polyol succinate-co-butylene succinate) elastomers: quasi-static tensile test, determination of cross-link density, di erential scanning calorimetry (DSC), dynamic thermomechanical analysis (DMTA), wettability (water contact angle), and Fourier transform infrared spectroscopy (FTIR). In order to confirm successful synthesis, prepolymers were analyzed by nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR).
Open Access
Physical Effects of Radiation Modification of Biodegradable Xylitol-Based Materials Synthesized Using a Combination of Different Monomers
(MDPI, 2021-03-26) Piątek-Hnat, Marta; Bomba, Kuba; Kowalski-Stankiewicz, Janusz P.; Pęksiński, Jakub; Kozłowska, Agnieszka; Sośnicki, Jacek G.; Idzik, Tomasz J.; Schmidt, Beata; Kowalczyk, Krzysztof; Walo, Marta; Kochmańska, Agnieszka; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; Pomeranian Medical University in Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; Institute of Nuclear Chemistry and Technology,Warszawa; West Pomeranian University of Technology, Szczecin
There is a possibility of obtaining xylitol-based elastomers sharing common characteristics of biodegradability, thermal stability, and elastomeric behavior by using monomers with different chain-lengths. Therefore, we have synthesized eight elastomers using a combination of four different diols (ethanediol, 1.3-propanediol, 1.4-buanediol, and 1.5-pentanediol) and two different dicarboxylic acids (succinic acid and adipic acid). The obtained materials were further modified by performing e-beam treatment with a dose of 100 kGy. Materials both before and after radiation modification were tested by DSC, DMTA, TGA, tensile tests, gel fraction determination, hydrolytic and enzymatic degradation tests, 1H NMR and 13C NMR and FTIR.
Open Access
Porównanie systemów sterowania zapasami ze zmiennym opóźnieniem dostaw i zaburzonym zapotrzebowaniem: cyklicznego oraz z regulatorem PD i predyktorem Smitha
(Społeczna Akademia Nauk, 2016) Orłowski, Przemysław; Chołodowicz, Ewelina; Zachodniopomorski Uniwersytet Technologiczny w Szczecinie; Zachodniopomorski Uniwersytet Technologiczny w Szczecinie
In this paper, we use a mathematical model of an inventory system with time-varying delivery delay and two control systems in order to compare their properties with different variance of noise for the goods flow optimization problem in the inventory systems. Control systems structures based on mathematical discrete equations are given for optimization: a Periodic Inventory System with adaptive maximal inventory level and Proportional-derivative Inventory Control System with Smith predictor and adaptive reference stock proposed by the authors in previous works. Parameters were selected for each of the control system structures through solving bictriterial optimization task for a specific scenario of variable market demand using SPEA2 in Matlab/Simulink. In this article, we mainly highlight which control structure reaches better performance taking account probabilistic disturbance in market demand.
Open Access
Structure and Properties of Biodegradable Poly (Xylitol Sebacate-Co-Butylene Sebacate) Copolyester
(MDPI, 2020-03-28) Piątek-Hnat, Marta; Bomba, Kuba; Pęksiński, Jakub; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin
In this work, a bio-based copolyester with good mechanical properties was synthesized and characterized in terms of structure, main properties and biodegradability Determining the chemical structure of such materials is important to understand their behavior and properties. Performing an extraction of insoluble cross-linked polymer using di erent solvents allowed us to analyze how the polymer behaves when subjected to di erent chemical environments, and to obtain soluble samples suitable for more in-depth analysis. Chemical structure of poly (xylitol sebacate-co-butylene sebacate) was determined by a 1H NMR and FTIR analysis of both prepolymer gel sample and samples obtained by extraction of cross-linked polymer using di erent solvents. Block structure of the copolymer was confirmed by both NMR and DSC. Gel fraction, swelling value, water contact angle, and mechanical properties were also analyzed. Biodegradability of this material was confirmed by performing enzymatic and hydrolytic degradation. Synthesizing sugar-alcohol based copolyester using three monomers leads to obtaining a material with interesting chemical structure and desirable mechanical properties comparable to conventional elastomers.
Open Access
Synthesis and Selected Properties of Ester Elastomer Containing Sorbitol
(MDPI, 2020-02-29) Piątek-Hnat, Marta; Bomba, Kuba; Pęksiński, Jakub; West Pomeranian University of Technology in Szczecin. Faculty of Chemical Technology and Engineering; West Pomeranian University of Technology in Szczecin. Faculty of Chemical Technology and Engineering; West Pomeranian University of Technology in Szczecin. Faculty of Electrical Engineering
The aim of this work was synthesizing ester elastomers, using sorbitol as a monomer obtainable from renewable sources. Three polymers were synthesized, utilizing three di erent polycondensation times. Their mechanical and thermal properties were examined and compared. Poly(sorbitol sebacate-co-butylene sebacate) elastomers were synthesized as a result of polycondensation reaction, using sebacic acid, butylene glycol and sorbitol as monomers. Resulting materials had good mechanical properties and a cross-linked structure. Such elastomers are susceptible to hydrolytic degradation which has been confirmed in earlier studies. This paper shows that the material synthesized utilizing a 3.5 h polycondensation time has the most desirable mechanical and thermal properties, and the reaction is characterized by the highest degree of conversion of substrates.
Open Access
Tailoring the Physico-chemical Properties of Poly(xylitol-dicarboxylate-co-butylene dicarboxylate) Polyesters by Adjusting the Cross-Linking Time
(MDPI, 2020-07-03) Piątek-Hnat, Marta; Sładkiewicz, Paulina; Bomba, Kuba; Pęksiński, Jakub; Kozłowska, Agnieszka; Sośnicki, Jacek G.; Idzik, Tomasz J.; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin; West Pomeranian University of Technology, Szczecin
Determining the cross-linking time resulting in the best achievable properties in elastomers is a very important factor when considering their mass production. In this paper, five biodegradable polymers were synthesized—poly(xylitol-dicarboxylate-co-butylene dicarboxylate) polymers, based on xylitol obtained from renewable sources. Five di erent dicarboxylic acids with even numbers of carbon atoms in the aliphatic chain were used: succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid. Samples were taken directly after polycondensation (prepolymer samples) and at di erent stages of the cross-linking process. Physiochemical properties were determined by a gel fraction test, di erential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), quasi-static tensile tests, nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR), and an in vitro biodegradation test. The best cross-linking time was determined to be 288h. Properties and degradation time can be tailored for specific applications by adjusting the dicarboxylic acid chain length.
Open Access
Zastosowanie sterowania feedback-feedforward i predyktora Smitha do optymalizacji przepływu towarów w magazynie ze zmiennym w czasie opóźnieniem
(Społeczna Akademia Nauk, 2016) Orłowski, Przemysław; Zachodniopomorski Uniwersytet Technologiczny w Szczecinie
The paper proposes the use of the automatic control system to control the system for supplementary orders for the warehouse in the presence of time-varying market demand and time-varying delay. A discrete-time, time-varying dynamic model of the ware-house system is assumed for the analysis. For the given model it is proposed a feedback-feedforward control system with the Smith predictor. The settings of the control system are evaluated by minimizing cost function using particle swarm optimization. The work contains the results of calculations and computer simulations for the assumed scenario for the market demand.

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