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JournalISSN: 0239-7528

Bulletin of The Polish Academy of Sciences-technical Sciences 

De Gruyter Open
About: Bulletin of The Polish Academy of Sciences-technical Sciences is an academic journal published by De Gruyter Open. The journal publishes majorly in the area(s): Linear system & Computer science. It has an ISSN identifier of 0239-7528. It is also open access. Over the lifetime, 1806 publications have been published receiving 19302 citations.


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Journal ArticleDOI
TL;DR: In this paper, the effects of high temperature on concrete have been investigated, including changes taking place in cement paste, aggregates, as well as the interaction of these two constituents, that result in changes of mechanical and physical characteristics of concrete.
Abstract: The paper presents the impact of high temperature on cement concrete. The presented data have been selected both from the author's most recent research and the published literature in order to provide a brief outline of the subject. The effect of a high temperature on concrete covers changes taking place in cement paste, aggregates, as well as the interaction of these two constituents, that result in changes of mechanical and physical characteristics of concrete. This paper presents the effects of a high temperature on selected physical properties of concrete, including colour change, thermal strain, thermal strains under load, and transient thermal strains. In addition, changes to mechanical properties are discussed: stress-strain relationship, compressive strength, and modulus of elasticity. Moreover, the phenomenon of explosive spalling and the main factors that affect its extent are analysed in light of the most recent research. Interest in the behaviour of concrete at a high temperature mainly results from the many cases of fires taking place in buildings, high-rise buildings, tunnels, and drilling platform structures. During a fire, the temperature may reach up to 1100 ◦ C in buildings and even up to 1350 ◦ C in tunnels, lead- ing to severe damage in a concrete structure (1). However, in some special cases, even much lower temperature, may cause explosive destruction of concrete, thus endangering the bear- ing capacity of the concrete element. Nevertheless, concrete is considered a construction material that satisfactorily preserves its properties at high temperature. Owing to concrete's fairly low coefficient of thermal conductivity, the movement of heat through concrete is slow, and thus reinforced steel, which is sensitive to high temperature, is protected for a relatively long period of time. When concrete is heated under conditions of fire, the increase in temperature in the deeper layers of the ma- terial is progressive, but because this process is slow, signifi- cant temperature gradients are produced between the concrete member's surface and core inducing additional damage to the element. Fundamental issues related to the impact of high temperature on concrete involve identification of the complex changes that take place in concrete while heated. This con- cerns both the physical and chemical changes taking place in the cement matrix, as well as the phenomena involved in mass movement (gases and liquids). The analysis is complicated due to the fact that cement concrete is a composite consisting of two substantially different constituents: cement paste and aggregates. The effects of the various changes taking place in heated concrete are the alterations of its physical, thermal, and mechanical properties. Research has demonstrated (1, 2), that changes in the strength of concrete as a function of tem- perature are related to, inter alia, concrete composition the type of aggregate used, the water/cement ratio, the presence of pozzolana additives, etc. Important factors are also the rate of heating and the time of concrete exposure to high tempera- ture. The increase in temperature results in water evaporation, C-S-H gel dehydration, calcium hydroxide and calcium alu- minates decomposition, etc. Along with the increase in tem- perature, changes in the aggregate take place. Due to those changes, concrete strength and modulus of elasticity gradu- ally decreases, and when the temperature exceeds ca. 300 ◦ C, the decline in strength becomes more rapid. When the 500 ◦ C threshold is passed, the compressive strength of concrete usu- ally drops by 50% to 60%, and the concrete is considered fully damaged. The Eurocode method of calculating the load- bearing capacity of reinforced concrete members subjected to a fire is based on this assumption. In the 500 ◦ C isotherm method, sections of concrete surface where the temperature had exceeded 500 ◦ C are omitted from the calculations (3).

318 citations

Journal Article
TL;DR: This paper deals with general pure active filters for power conditioning, and specific hybridactive filters for harmonic filtering of three-phase diode rectifiers, as well as traditional passive filters.
Abstract: Unlike traditional passive filters, modern active filters have the following multiple functions; harmonic filtering, damping, isolation and termination, reactive-power control for power factor correction and voltage regulation, load balancing, voltage-flicker reduction, and/or their combinations. Significant cost reductions in both power semiconductor devices and signal-processing devices have inspired manufactures to put active filters on the market. This paper deals with general pure active filters for power conditioning, and specific hybrid active filters for harmonic filtering of three-phase diode rectifiers, as well as traditional passive filters.

232 citations

Journal ArticleDOI
TL;DR: In this article, the authors present some recent results in the area of application of fractional order system models for real-world phenomena such as ultracapacitor and beam heating.
Abstract: . This paper presents some recent results in the area of application of fractional order system models. After the introduction to the dynamic systems modelling with the fractional order calculus the paper concentrates on the possibilities of using this approach to the modelling of real-world phenomena. Two examples of such systems are considered. First one is the ultracapacitor where fractional order models turn out to be more precise in the wider range of frequencies than other models used so far. Another example is the beam heating problem where again the fractional order model allows to obtain better modelling accuracy. The theroetical models were tested experimentally and the results of these experiments are described in the paper.

185 citations

Journal Article
TL;DR: In this article, the authors present general information on LTCC materials, manufacturing processes and properties of fired modules, and a short information is given on other LTCC applications, and the research and development on the LTCC sensors and microsystems carried out in the Laboratory of Thick Film Microsystems at Wroclaw University of Technology is described in detail.
Abstract: The paper presents general information on LTCC materials, manufacturing processes and properties of fired modules. A Multichip Module package has been the main application of Low Temperature Cofired Ceramic (LTCC) technology. Recently, this technology is also used for production of sensors, actuators and microsystems. The research and development on the LTCC sensors and microsystems carried out in the Laboratory of Thick Film Microsystems at Wroclaw University of Technology are presented. LTCC microfluidic system is described in detail. Moreover, a short information is given on other LTCC applications .

185 citations

Journal ArticleDOI
TL;DR: This article studies the differential-geometrical structure of a manifold induced by a divergence function, which consists of a Riemannian metric, and a pair of dually coupled affine connections, which are studied in information geometry.
Abstract: Measures of divergence between two points play a key role in many engineering problems. One such measure is a distance function, but there are many important measures which do not satisfy the properties of the distance. The Bregman divergence, KullbackLeibler divergence and f -divergence are such measures. In the present article, we study the differential-geometrical structure of a manifold induced by a divergence function. It consists of a Riemannian metric, and a pair of dually coupled affine connections, which are studied in information geometry. The class of Bregman divergences are characterized by a dually flat structure, which is originated from the Legendre duality. A dually flat space admits a generalized Pythagorean theorem. The class of f -divergences, defined on a manifold of probability distributions, is characterized by information monotonicity, and the Kullback-Leibler divergence belongs to the intersection of both classes. The f -divergence always gives the α-geometry, which consists of the Fisher information metric and a dual pair of ±α-connections. The α-divergence is a special class of f -divergences. This is unique, sitting at the intersection of the f -divergence and Bregman divergence classes in a manifold of positive measures. The geometry derived from the Tsallis q-entropy and related divergences are also addressed.

169 citations

Performance
Metrics
No. of papers from the Journal in previous years
YearPapers
202390
202134
202076
201976
201897
2017100