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1.
Slip modeling in timber-framed walls with wood-based or fibre-plaster sheathing boards
Miroslav Premrov, Peter Dobrila, Branko Bedenik, Igor Špacapan, 2007, izvirni znanstveni članek

Opis: The paper provides mathematical modelling for prefabricated timber-framed walls composed of a timber frame and two different types of sheathing boards. Since by wood-based boards (WBB) the tensile strength is similar to the compressive one, there are practically no cracks appearing in the boards. On the other hand, in case of fibre-plaster sheathing boards (FPB) the tensile strength is approximately 10-times lower than the compressive one and therefore cracks in the tensile diagonal boardćs direction usually appear. Based on analysis of experimental research results [1] special approximate mathematical models have been developed. The models enable simultaneously to consider the flexibility of mechanical fasteners in the connecting areas, as well as possible cracks appearing in the tensile area of the sheathing boards.
Ključne besede: civil engineering, timber structures, walls, CFRP strips, carbon fibre-reinforced polymer, mathematical modelling
Objavljeno: 31.05.2012; Ogledov: 1155; Prenosov: 22
URL Povezava na celotno besedilo

2.
Mathematical modelling of timber-framed walls strengthened with CFRP strips
Miroslav Premrov, Peter Dobrila, 2008, izvirni znanstveni članek

Opis: This paper provides mathematical modelling for prefabricated timber-framed walls composed of a timber frame and fibre-plaster boards. Because the tensile strength of the fibre-plaster boards is approximately 10-times lower than the compressive one, it is convenient to strengthen the boards in their tensile diagonal direction with carbon fibre-reinforced polymer (CFRP) strips, which are glued to the boards. Based on analysis of experimental research results [7] special approximate mathematical models have been developed. The models enable simultaneously to consider the influence of inserted CFRP strips, flexibility of mechanical fasteners in the connecting areas and any appearing of tensile cracks in the coating boards.
Ključne besede: civil engineering, timber structures, frame walls, fibre-plaster boards, steel reinforcement, CFRP strips, mathematical modelling
Objavljeno: 01.06.2012; Ogledov: 1168; Prenosov: 50
URL Povezava na celotno besedilo

3.
Modelling of fastener flexibility in CFRP strengthened timber-framed walls using modified [gamma]-method
Miroslav Premrov, Peter Dobrila, 2008, izvirni znanstveni članek

Opis: The paper provides semi-analytical modelling for prefabricated timber-framed walls using the modified ▫$/gamma$▫-method. The walls are composed of a timber frame and gypsum plasterboards (GPB) which are flexibly connected to the timber frame. Because the tensile strength of the GPB is approximately 10-times lower than the compressive one, it is convenient to strengthen the boards in their tensile diagonal direction with carbon fibre-reinforced polymer (CFRP) strips, which are glued to the boards. Additionally, in the proposed mathematical model the classical beam theory is used taking into account a fasteners' flexibility in the timber frame - GPB connecting area, as well as crack appearing in the GPB and an influence of the inserted CFRP strips. Therefore the CFRP strip contribution is considered with a modified slip modulus which results in the fictive increased stiffness coefficient of the fasteners.
Ključne besede: civil engineering, timber structures, frame walls, fibre-plaster boards, steel reinforcement, CFRP strips, carbon fibre-reinforced polymer, mathematical modelling
Objavljeno: 01.06.2012; Ogledov: 1279; Prenosov: 14
URL Povezava na celotno besedilo

4.
Approximate analytical solutions for diagonal reinforced timber-framed walls with fibre-plaster coating material
Miroslav Premrov, Peter Dobrila, Branko Bedenik, 2004, izvirni znanstveni članek

Opis: This paper provides approximate analytical solutions for diagonally reinforced timber-framed panel walls usually used as main bearing capacity elements in the construction of prefabricated timber structures. These walls can be mathematically treated as composite elements made of a timber frame and fibre-plaster boards as a coating material. As boards are the weakest part of the system they are reinforced with steel diagonals. The proposed approximate analytical models with the fictitious thickness and width of fibre-plaster boards enable simultaneously to consider the influence of inserted steel diagonals, flexibility of mechanical fasteners between the boards and the timber frame and any appearing cracks in the tensile area of the fibre-plaster boards. The obtained numerical results show good agreement with the measured experimental results.
Ključne besede: civil engineering, timber structures, panel walls, fibre-plaster boards, steel reinforcement, steel diagonals, mathematical modelling
Objavljeno: 01.06.2012; Ogledov: 1223; Prenosov: 42
URL Povezava na celotno besedilo

5.
Optimal kinematic design of a link-drive mechanism with prescribed velocity characteristics
Bojan Vohar, Karl Gotlih, Jože Flašker, 2003, kratki znanstveni prispevek

Opis: The paper presents an example of a link-drive mechanism for a deep drawing mechanical press. Because of its characteristics such a drive is much more appropriate than conventional crankshaft or eccentric drive. The existing design of the drive has proved unsatisfactory and does not meet all the demands and constraints, which are ideal for deep drawing process. Optimization of the drive is therefore necessary. The intention is to achieve the required velocity characteristics in a defined area of movement. Firstly, the drive is analyzed and a mathematical model is made and prepared for optimization procedure. The process is time-dependent, so it cannot be used directly in the optimization algorithm. Mathematical model is transformed intoa form suitable for the standard non-linear optimization procedure and then optimization is carried out. The method used is sequential quadratic programming. The final objective of the optimization process is to find such dimensions of link-drive members that the given requirements are satisfied in the best possible manner.
Ključne besede: mechanics, dynamics of mechanical systems, closed kinematic chains, mathematical modelling, non-linear optimization, drive optimization, drive dimensioning, kinematic analysis, link-drive mechanism, deep drawing press
Objavljeno: 01.06.2012; Ogledov: 1338; Prenosov: 69
URL Povezava na celotno besedilo

6.
Reinforced prefabricated timber shear walls
Miroslav Premrov, Peter Dobrila, 2002, izvirni znanstveni članek

Opis: The paper presents results of shear-bending experiments performed on panel shear walls used as load-carrying capacity walls in the construction of prefabricated timber structures. The aim of research is to determine the difference in resistance and ductility between panel shear walls, reinforced with two different methods. While the first, reinforcing with additional fiberboard, was not improve resistance and especially ductility in the contended sense, we tried to find a solution by inserting diagonal steel strips, which were fixed to the timber frame. Additionally, analytical solutions of those by mathematical modeling with the fictive thickness and height of fiber-plaster boards are proposed. Presented design models are simple and show a good coincidence with the measured results.
Ključne besede: timber structures, shear walls, shear bending tests, mathematical modelling
Objavljeno: 01.06.2012; Ogledov: 1137; Prenosov: 18
URL Povezava na celotno besedilo

7.
Role of cascades in converting oscillatory signals into stationary step-like responses
Marko Marhl, Vladimir Grubelnik, 2007, izvirni znanstveni članek

Opis: In biological signal transduction pathways intermediates are often oscillatory and need to be converted into smooth output signals at the end. We show by mathematical modelling that protein kinase cascades enable converting oscillatory signals into sharp stationary step-like outputs. The importance of this result is demonstrated for the switch-like protein activation by calcium oscillations, which is of biological importance for regulating different cellular processes. In addition, we found that protein kinase cascades cause memory effects in the protein activation, which might be of a physiological advantage since a smaller amount of calcium transported in the cell is required for an effective activation of cellular processes.
Ključne besede: physics, calcium oscillations, mathematical modelling, calcium, calcium oscillations, sygnalling cascade, protein kinase cascades, signal transduction, ultrasensitivity, biochemical switch, cellular dynamics
Objavljeno: 07.06.2012; Ogledov: 985; Prenosov: 24
URL Povezava na celotno besedilo

8.
Theoretical and experimental investigation of calcium-contraction coupling in airway smooth muscle
Prisca Mbikou, Aleš Fajmut, Milan Brumen, Etienne Roux, 2006, izvirni znanstveni članek

Opis: We investigated theoretically and experimentally the ▫$Ca^{2+}$▫-contraction couplingin rat tracheal smooth muscle. ▫$[Ca^{2+}]_i$▫, isometric contraction and myosin light chain (MLC) phosphorylation were measured in response to 1 mM carbachol. Theoretical modeling consisted in coupling a model of ▫$Ca^{2+}-dependent$▫ MLC kinase (MLCK) activation with a four-state model of smooth muscle contractile apparatus. Stimulation resulted in a short-time contraction obtained within 1 min, followed by a long-time contraction up to the maximal force obtained in 30 min. ML-7 and Wortmannin (MLCK inhibitors) abolished the contraction. Chelerythrine (PKC inhibitor) did not change the short-time, but reduced the long-time contraction. ▫$[Ca^{2+}]_i$▫ responses of isolated myocytes recorded during the first 90 s consisted in a fast peak, followed by a plateau phase and, in 28 % of the cells, superimposed ▫$Ca^{2+}$▫ oscillations. MLC phosphorylation was maximal at 5 s and then decreased, whereas isometric contraction followed a Hill-shaped curve. The model properlypredicts the time course of MLC phosphorylation and force of the short-time response. With oscillating ▫$Ca^{2+}$▫ signal, the predicted force does not oscillate. According to the model, the amplitude of the plateau and the frequency of oscillations encode for the amplitude of force, whereas the peak encodes for force velocity. The long-time phase of the contraction, associated with a second increase in MLC phosphorylation, may be explained, at least partially, by MLC phosphatase (MLCP) inhibition, possibly via PKC inhibition.
Ključne besede: biophysics, mathematical modelling, modelling, calcium oscillations, contractions, force development, muscle cells, smooth muscles, myosin kinase
Objavljeno: 07.06.2012; Ogledov: 886; Prenosov: 44
URL Povezava na celotno besedilo

9.
Modeling of molecular and cellular mechanisms involved in [Ca sup 2+] signal encoding in airway myocytes
Marko Marhl, Denis Noble, Etienne Roux, 2006, pregledni znanstveni članek

Opis: In airway myocytes signal transduction via cytosolic calcium plays an important role. In relation with experimental results we review models of basic molecular and cellular mechanisms involved in the signal transduction from the myocyte stimulation to the activation of the contractile apparatus. We concentrate on mechanisms for encoding of input signals into Ca2+ signals and the mechanisms for their decoding. The mechanisms are arranged into a general scheme of cellular signaling, the so-called bow-tie architecture of signaling, in which calcium plays the role of a common media for cellular signals and links the encoding and decoding part. The encoding of calcium signals in airway myocytes is better known and is presented in more detail. Inparticular, we focus on three recent models taking into account the intracellular calcium handling and ion fluxes through the plasma membrane. Themodel of membrane conductances was originally proposed for predicting membrane depolarization and voltage-dependent Ca2+ influx triggered by initialcytosolic Ca2+ increase as observed on cholinergic stimulation. Cellular models of intracellular Ca2+ handling were developed to investigate the role of a mixed population of InsP3 receptor isoforms and the cellular environment in the occurrence of Ca2+ oscillations, and the respective role ofthe sarcoplasmic reticulum, mitochondria, and cytosolic Ca2+-binding proteins in cytosolic Ca2+ clearance. Modeling the mechanisms responsible for the decoding of calcium signals is developed in a lesser extent; however, the most recent theoretical studies are briefly presented in relation with the known experimental results.
Ključne besede: biophysics, mathematical modelling, modelling, calcium oscillations, contractions, airway smooth muscle cells, muscle cells, smooth muscles, encoding, decoding, bow-tie structures
Objavljeno: 07.06.2012; Ogledov: 1003; Prenosov: 13
URL Povezava na celotno besedilo

10.
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