Wyniki wyszukiwania - Biblioteka Nauki

1

The functional atom of tribology and its application

100%

Kandeva M. , Manolova-Daneva M.

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2009

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tom Vol. 44, nr 4

29-39

EN

The notion "functional atom" (FA) was created in the Center of Tribology at the Technical University of Sofia, in the field of tribology as interdisciplinary science. The functional atom is formed of 3 components similarly to the basic contact system "body-contact-counterbody". This notion assigns the central role of contacts in the interaction of bodies in nature, techniques and society. The idea for the FA is expressed in the fact that its two alternatives "body" and "counterbody" do not interact directly, but through the third body - the contact between them, and the contact networks in the whole functional space of the atom. Six postulates as basis of the model, theory and application of FA are formulated in the pressent work. The application of FA is illustrated with concrete examples: the development of the macrostructure of tribology as interdisciplinary science; formulation and using of General law of the contact interaction of bodies in the functional space of tribology - friction, wear, lubrication, contact deformation, contact conductance and capillarity. Other illustrations and applications of the model of FA in triboecology, tribotechnologies, engineering education, etc.

2

Characteristics and biological properties of ferulic acid

100%

Dędek K. , Rosicka-Kaczmarek J. , Nebesny E. , Kowalska G.

Biotechnology and Food Science

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2019

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tom Vol. 83, nr 1

71--85

EN

The interest in the properties of hydroxycinnamic acids with health-promoting properties is constantly increasing. That is why more and more research is being conducted to better understand these properties. Ferulic acid, FA (4-hydroxy-3-methoxycinnamic acid) is a derivative of hydroxycinnamic acid found in the plant tissue. It is possible to find him among others in bran cereal, popcorn bamboo shoots, and coffee. According to available literature data ferulic acid has a lot of biological properties, particularly appreciated in medicine. Its bioactive properties effectively contribute to the fight against diseases described as a civilization, including neurodegenerative diseases that increase the incidence. As reported the World Alzheimer Report, the number of people with dementia progression in 2016 exceeded 47.5 million, of which 33.5 million were diagnosed with Alzheimer's disease. According to the WHO estimates, this number will triple by 2050. The manuscript presents health-promoting properties of FA on the example of its antioxidant, antidiabetic, hepatoprotective, anti-atherosclerotic, neuroprotective, antineoplastic and antibacterial properties. In addition, the reaction of its synthesis in plants and in-vivo metabolization have been explained. The collected data suggest that bioactive FA molecules can effectively reduce the risk of civilization diseases and significantly reduce the level of oxidative stress contributing to the formation of neurodegenerative diseases.

3

ZrO2 Gelcast Foams Coated with Apatite Layers

85%

Potoczek M. , Kocyło E. , Krauz M. , Tłuczek A.

Archives of Metallurgy and Materials

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2020

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tom Vol. 65, iss. 2

885--891

EN

In this work, gel-casting of foams method was used to produce ZrO2 porous ceramics. The obtained foams with total porosity of 89.5 vol% were composed of approximately spherical cells having the mean diameter of 537 ± 153 μm interconnected by circular cell windows having the mean diameter of 152 ± 82 μm. Next, the ZrO2 foams were coated with fluorapatite (FA) and hydroxyapatite (HA) layers by slurry infiltration. The intermediate fluorapatite (FA) layer was introduced to prevent the chemical reactions between ZrO2 and HA at high temperatures during sintering process. The ZrO2 samples containing only HA coatings, were also tested, for comparison. The obtained ceramic biomaterials were subjected to in vitro tests in the simulated body fluid (SBF) solution. The results show that the ZrO2 foams with FA/HA layers possessed better bioactivity than the foams with the HA/HA coating.

4

Prediction of microstructural evolution in fly ash-modified cementitious system: A computational study

85%

Yadeta A. E. , Goyal P. K. , Sarkar R.

Materials Science Poland

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2023

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tom Vol. 41, No. 4

68--77

EN

The intricate interaction between supplementary cementitious materials (SCMs) and cementitious systems profoundly influences the performance and sustainability of cementitious composites. This study explores the microstructural evolution of fly ash (FA)-modified cement paste by employing a three-dimensional cement hydration and microstructure development (CEMHYD3D) modeling package. Through comprehensive simulations, the influence of varying FA content on hydration phase evolution and pore structure within the cementitious system is revealed. As the proportion of FA within the cementitious mixtures increases, there is a substantial enhancement in the rate of hydration. Notably, the incorporation of FA introduces a significant augmentation in the hydration rate, a phenomenon with potential implications for the long-term performance of FA-modified cementitious materials. The prediction results also highlight that increasing FA substitution in cement leads to finer and more interconnected pore networks due to the pozzolanic reaction. These perceptions hold significant implications for optimizing cementitious mixes and advancing sustainable construction practices. The model-predicted results have been validated with experiments, and they are successful in predicting the microstructural evolution in FA-modified cement paste. In summary, the prediction model bridges the theoretical and practical implementation gaps by providing a thorough understanding of the microstructural evolution of FA-modified cement paste. Furthermore, it provides invaluable guidance for tailoring FA-blended cement compositions, thus promoting their enhanced performance and sustainability in the realm of cementitious materials.

5

Inicjalizacja segmentacji k-means uwzględniająca rozkład gęstości pikseli

80%

Świta R. , Suszyński Z.

Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej

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2014

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tom Nr 6

89--98

PL

Artykuł przedstawia modyfikację inicjalizacji KKZ algorytmu k-means, uwzględniającą, oprócz wzajemnych odległości środków segmentów, również rozkład gęstości pikseli. Funkcja gęstości piksela jest sumą odwrotności odległości piksela od pozostałych i jest poddawana oszacowaniu na podstawie odległości piksela od wartości średniej i wariancji wartości pikseli. W eksperymentach segmentacji podlegały cztery różne sekwencje obrazów termicznych uzyskanych metodą termografii aktywnej. Pomimo dodatkowych obliczeń podczas inicjalizacji, metoda wykazała szybszą zbieżność algorytmu z czasami bardzo podobnymi do inicjalizacji KKZ, ale mniejszym błędem końcowym segmentacji.

EN

This article presents a modification for the KKZ initialization of the k-means segmentation algorithm, which, in addition to the mutual distance of segments, takes into account the density of pixels. Pixel density is expressed asa sum of the inverse of the pixel’s distance to the other pixels and is subjected to estimation based on the distance from the mean and variance of the pixel values. In the experiments, four different sequences of thermal images were used, obtained using active thermography. Despite the additional calculations during initialization, method showed a faster convergence of the algorithm, with processing times very similar to the KKZ initialization, but with a lower final segmentation error.

6

Synthesis of Reconfigurable Multiple Shaped Beams of a Concentric Circular Ring Array Antenna Using Evolutionary Algorithms

71%

Dubey S. K. , Mandal D.

Journal of Telecommunications and Information Technology

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2023

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tom nr 1

8--17

EN

The approach described in this paper uses evolutionary algorithms to create multiple-beam patterns for a concentric circular ring array (CCRA) of isotropic antennas using a common set of array excitation amplitudes. The flat top, cosec2, and pencil beam patterns are examples of multiple-beam patterns. All of these designs have an upward angle of θ = 0◦. All the patterns are further created in three azimuth planes (φ = 0◦, 5◦, and 10◦). To create the necessary patterns, non-uniform excitations are used in combination with evenly spaced isotropic components. For the flat top and cosecant-squared patterns, the best combination of common components, amplitude and various phases is applied, whereas the pencil beam pattern is produced using the common amplitude only. Differential evolutionary algorithm (DE), genetic algorithm (GA), and firefly algorithm (FA) are used to generate the best 4-bit discrete magnitudes and 5-bit discrete phases. These discrete excitations aid in lowering the feed network design complexity and the dynamic range ratio (DRR). A variety of randomly selected azimuth planes are used to verify the excitations as well. With small modifications in the desired parameters, the patterns are formed using the same excitation. The results proved both the efficacy of the suggested strategy and the dominance of DE over GA as well as FA.

7

Use of waste paper ash or wood ash as substitution to fly ash in production of geopolymer concrete

71%

Owaid H. M. , Al-Rubaye M. M. , Al-Baghdadi H. M.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2021

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tom Vol. 30, No. 3

464--476

EN

Large quantities of paper and wood waste are generated every day, the disposal of these waste products is a problem because it requires huge space for their disposal. The possibility of using these wastes can mitigate the environmental problems related to them. This study presents an investigation on the feasibility of inclusion of waste paper ash (WPA) or wood ash (WA) as replacement materials for fly ash (FA) class F in preparation geopolymer concrete (GC). The developed geopolymer concretes for this study were prepared at replacement ratios of FA by WPA or WA of 25, 50, 75 and 100% in addition to a control mix containing 100% of FA. Sodium hydroxide (NaOH) solutions and sodium silicate (Na2SiO3) are used as alkaline activators with 1M and 10M of sodium hydroxide solution.The geopolymer concretes have been evaluated with respect to the workability, the compressive strength, splitting tensile strength and flexural strength. The results indicated that there were no significant differences in the workability of the control GC mix and the developed GC mixes incorporating WPA or WA. Also, the results showed that, by incorporating of 25–50% PWA or 25% WA, the mechanical properties (compressive strength, splitting tensile strength and flexural strength) of GC mixes slightly decreased. While replacement with 75–100% WPA or with 50–100% WA has reduced these mechanical properties of GC mixes. As a result, there is a feasibility of partial replacement of FA by up to 50% WPA or 25% WA in preparation of the geopolymer concrete.

8

A parametric testing of the firefly algorithm in the determination of the optimal osmotic drying parameters of mushrooms

71%

Yeomans J. S.

Journal of Artificial Intelligence and Soft Computing Research

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2014

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tom Vol. 4, No. 4

257--256

EN

The Firefly Algorithm (FA) is employed to determine the optimal parameter settings in a case study of the osmotic dehydration process of mushrooms. In the case, the functional form of the dehydration model is established through a response surface technique and the resulting mathematical programming is formulated as a non-linear goal programming model. For optimization purposes, a computationally efficient, FA-driven method is used and the resulting optimal process parameters are shown to be superior to those from previous approaches. The final section of this study provides a computational experimentation performed on the FA to analyze its relative sensitivity over a range of the two key parameters that most influence its running time.

9

Joint optimization of redundancy and maintenance staff allocation for multi-state series-parallel systems

57%

Liu Y. , Huang H. Z. , Wang Z. , Li Y. F. , Zhang X. L.

Eksploatacja i Niezawodność

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2012

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tom Vol. 14, No. 4

312-318

EN

Multi-state system (MSS), as a kind of complex system consisting of elements with different performance levels, widely exists in engineering practices. In this paper, redundancy and maintenance staff allocation problems for repairable MSS with series-parallel configuration are considered simultaneously. The traditional redundancy allocation problem (RAP) for MSS always assumes that maintenance resources are unlimited. However in many practical situations, maintenance resources are limited due to the budget and/or time. To maximize the system availability under a certain demand, there are two feasible ways: (1) designing an optimal system configuration with available elements, and (2) allocating more maintenance staffs to reduce waiting time for repair. With the assistance of Markov queue model, the availabilities of identical version elements with the pre-assigned number of maintenance staffs can be evaluated. The universal generation function (UGF) is employed to assess the availability of entire MSS under a certain demand. Two optimization formulas considering the limited maintenance resources are proposed. One regards the limitation of maintenance resources as a constraint, and the other considers minimizing the total system cost including both the system elements and maintenance staff fees. The system redundancy and staffs allocation strategies are jointly optimized under required availability. A numerical case is presented to illustrate the efficiency of the proposed models. The Firefly Algorithm (FA), which is a recently developed metaheuristic optimization algorithm, is employed to seek the global optimal strategy.

PL

Systemy wielostanowe (multi-state systems, MSS), stanowiące typ złożonych systemów zbudowanych z elementów o różnym poziomie wydajności, znajdują szerokie zastosowanie w praktyce inżynierskiej. W prezentowanej pracy podjęto rozważania łączące zagadnienia alokacji nadmiarowości oraz alokacji pracowników służb utrzymania ruchu w naprawialnych systemach MSS o konfiguracji szeregowo-równoległej. Tradycyjnie ujmowane zagadnienie alokacji nadmiarowości (redundancy allocation problem, RAP) w systemach MSS zawsze zakłada, że środki obsługi są nieograniczone. Jednakże w wielu sytuacjach praktycznych, środki obsługi mogą być ograniczone budżetem i/lub czasem. Istnieją dwa możliwe sposoby maksymalizacji gotowości systemu przy określonym zapotrzebowaniu użytkowników: (1) zaprojektowanie optymalnej konfiguracji systemu z wykorzystaniem dostępnych elementów oraz (2) alokowanie większej liczby pracowników obsługi w celu zmniejszenia czasu oczekiwania na naprawę. Dostępność jednakowych wersji elementów przy wcześniej określonej liczbie pracowników obsługi oceniano za pomocą modelu kolejek Markowa. Uniwersalną funkcję generacyjną (UGF) wykorzystano do oceny gotowości całego systemu MSS przy określonym zapotrzebowaniu. Zaproponowano dwa równania optymalizacyjne uwzględniające ograniczone środki obsługi. W jednym z nich ograniczoność środków obsługi potraktowano jako ograniczenie (constraint), natomiast drugie równanie dotyczyło minimalizacji całkowitych kosztów systemu włącznie z kosztami elementów systemu oraz płacą pracowników służb utrzymania ruchu. Strategie alokacji nadmiarowości systemu oraz alokacji pracowników poddano jednoczesnej optymalizacji z uwzględnieniem wymaganej gotowości. Wydajność proponowanych modeli zilustrowano przykładem numerycznym. Poszukiwania optymalnej strategii globalnej prowadzono przy pomocy niedawno opracowanego metaheurystycznego algorytmu optymalizacyjnego znanego jako algorytm świetlika (Firefly Algorithm, FA).