Thin-film-induced morphological instabilities over calcite surfaces

Precipitation of calcium carbonate from water films generates fascinating calcite morphologies that have attracted scientific interest over past centuries. Nowadays, speleothems are no longer known only for their beauty but they are also recognized to be precious records of past climatic conditions, and research aims to unveil and understand the mechanisms responsible for their morphological evolution. In this paper, we focus on crenulations, a widely observed ripple-like instability of the the calcite–water interface that develops orthogonally to the film flow. We expand a previous work providing new insights about the chemical and physical mechanisms that drive the formation of crenulations. In particular, we demonstrate the marginal role played by carbon dioxide transport in generating crenulation patterns, which are indeed induced by the hydrodynamic response of the free surface of the water film. Furthermore, we investigate the role of different environmental parameters, such as temperature, concentration of dissolved ions and wall slope. We also assess the convective/absolute nature of the crenulation instability. Finally, the possibility of using crenulation wavelength as a proxy of past flows is briefly discussed from a theoretical point of view.

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Studies of Viscoelastic Relaxation of Some Nitrile Rubbers under Compressive Stress

Rubber Chemistry and Technology ◽

10.5254/1.3535185 ◽

1977 ◽

Vol 50 (5) ◽

pp. 906-914 ◽

Cited By ~ 2

Author(s):

B. Stenberg ◽

J. F. Jansson

Keyword(s):

Stress Relaxation ◽

Point Of View ◽

Relaxation Behavior ◽

Relaxation Processes ◽

Theoretical Point ◽

Stress Relaxation Behavior ◽

Physical Mechanisms ◽

Viscoelastic Stress Relaxation ◽

Nitrile Rubbers ◽

Relaxation Curves

Abstract Stress relaxation in rubbers is usually supposed to be due to chemical aging phenomena of a mainly elastic material. Considerable physical viscoelastic processes can, however, be observed in the rubbery region, depending upon the type of rubber, crosslink density, type of crosslink, filler, and so on. Thus, in chemical stress relaxation experiments chemical and physical mechanisms are superimposed and can seldom be distinguished. Stress relaxation curves registered at different temperatures contain contributions from both types of mechanism. From a practical, as well as a theoretical, point of view it is therefore essential to find methods of distinguishing between the two relaxation processes. This would be possible if the relaxation curves were obtained during periods of time so short that the chemical relaxation can be neglected. The long-term physical relaxation is then obtained by shifting the curves by, for instance, the method of reduced variables. This technique has been utilized by Curro and Salazar. We now present an alternative procedure by which the physical viscoelastic stress relaxation behavior is determined from dynamic data. The physical relaxation curves are calculated from values of E′(ω) and E″(ω) obtained at different frequencies and temperatures. In this method of determining the physical relaxation, no change of sample is needed, nor is it necessary to allow the sample to relax between measurements. The stress relaxation behavior under compression of three nitrile rubbers has been studied, and it is shown that physical mechanisms dominate just above room temperature, while chemical mechanisms dominate at higher temperatures.

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Timber Auctions in the Context of the Modern Auction Theory

Voprosy Ekonomiki ◽

10.32609/0042-8736-2007-3-86-94 ◽

2007 ◽

pp. 86-94

Author(s):

A. Manakov

Keyword(s):

Theoretical Analysis ◽

Auction Theory ◽

Point Of View ◽

Theoretical Point ◽

English Auction ◽

Analysis And Evaluation

The article provides theoretical analysis and evaluation of the timber auctions reforms in Russia. The author shows that the mechanism of the "combined auctions", which functioned until recently, is more appropriate from the theoretical point of view (and from the point of view of the Russian practice) as compared to the officially approved format of the English auction.

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A novel cryptosystem based on abstract automata and Latin cubes

Studia Scientiarum Mathematicarum Hungarica ◽

10.1556/012.2015.52.2.1309 ◽

2015 ◽

Vol 52 (2) ◽

pp. 221-232

Author(s):

Pál Dömösi ◽

Géza Horváth

Keyword(s):

Block Cipher ◽

Finite Automata ◽

Theoretical Background ◽

Point Of View ◽

Theoretical Point ◽

Transition Matrices ◽

Encryption And Decryption ◽

Secret Keys ◽

Automata Network ◽

Fully Functioning

In this paper we introduce a novel block cipher based on the composition of abstract finite automata and Latin cubes. For information encryption and decryption the apparatus uses the same secret keys, which consist of key-automata based on composition of abstract finite automata such that the transition matrices of the component automata form Latin cubes. The aim of the paper is to show the essence of our algorithms not only for specialists working in compositions of abstract automata but also for all researchers interested in cryptosystems. Therefore, automata theoretical background of our results is not emphasized. The introduced cryptosystem is important also from a theoretical point of view, because it is the first fully functioning block cipher based on automata network.

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Graffiti als Version und Subversion–Praxen kultureller Re-Regulierung und die Möglichkeit von Gratiforschung

Zeitschrift für Ästhetik und Allgemeine Kunstwissenschaft ◽

10.28937/1000106165 ◽

2010 ◽

Vol 55 (2) ◽

pp. 11-25 ◽

Cited By ~ 1

Author(s):

Bernd Dollinger

Keyword(s):

Social Life ◽

Point Of View ◽

Theoretical Point ◽

Research Practice ◽

Wird Eine ◽

Multiple Perspectives

Der Beitrag geht von Versuchen aus, integrative Perspektiven einer überaus heterogenen Graffitiforschung zu bestimmen. In Auseinandersetzung insbesondere mit Bruno Latours Ansatz des »Iconoclash« wird eine kulturtheoretische Referenz bestimmt, die Graffiti als Version identifiziert, d. h. als semiotisch orientierte Veränderung räumlich situierter Ordnungs- und Regulierungspraxen. Ihnen kann, wenn auch nicht zwingend, eine subversive Qualität zukommen. Durch die Ausrichtung am Konzept einer Version wird beansprucht, Forderungen einer normativ weitgehend abstinenten, nicht-essentialistischen und für komplexe Fragen der Identitäts- und Raumpolitik offenen Forschungspraxis einzulösen.<br><br>The contribution attempts to integrate multiple perspectives of current largely heterogeneous graffiti scholarship. Referring to Bruno Latour’s concept »iconoclash«, we discuss graffiti from a cultural-theoretical point of view as a »version«. It appears as a semiotically oriented modification of spatially situated practices that regulate social life. Often, but not necessarily, these practices involve subversive qualities. The concept of »version« facilitates a non-normative and non-essentialist strategy of research. This enables an explorative research practice in which the complex matters of identity and space politics that are associated with graffiti can be addressed.

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How Digital Inclusion Increase Opportunities for Young People: Case of NEETs from Bulgaria, Romania and Turkey

Sustainability ◽

10.3390/su13147894 ◽

2021 ◽

Vol 13 (14) ◽

pp. 7894

Author(s):

Gabriela Neagu ◽

Muhammet Berigel ◽

Vladislava Lendzhova

Keyword(s):

Data Analysis ◽

Rural Areas ◽

Secondary Data ◽

Point Of View ◽

Multidimensional Analysis ◽

Theoretical Point ◽

Digital Inclusion ◽

Virtual Mobility ◽

Alternative Research ◽

High Share

This paper examines the perspectives of rural NEETs in the information society. Our analysis focuses on the situation of three European countries—Bulgaria, Romania, and Turkey—characterized by a high share of rural areas and a population of NEETs. From a methodological point of view, we use alternative research methods (secondary data analysis) with statistical methods (simple linear regression). From a theoretical point of view, we will opt for a multidimensional analysis perspective: the theory of digital divide, digital inclusion, virtual mobility, etc. Through data analysis, we expect to obtain a more complete and detailed picture of the ICT situation in rural areas (level of digital skills, level of digital inclusion) to demonstrate the importance of ICT in optimizing virtual mobility for the living conditions of the population, especially the NEET population.

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Verbena officinalis Verbenaceae (Lamiales): a new plant model system for phyllotaxis research

Journal of Plant Research ◽

10.1007/s10265-021-01288-2 ◽

2021 ◽

Author(s):

Beata Zagórska-Marek ◽

Magdalena Turzańska ◽

Klaudia Chmiel

Keyword(s):

Vascular System ◽

Cumulative Effect ◽

Point Of View ◽

Theoretical Point ◽

Inflorescence Axis ◽

Organ Identity ◽

Lateral Organ ◽

Complex Relationships ◽

Secondary Transitions

AbstractPhyllotactic diversity and developmental transitions between phyllotactic patterns are not fully understood. The plants studied so far, such as Magnolia, Torreya or Abies, are not suitable for experimental work, and the most popular model plant, Arabidopsis thaliana, does not show sufficient phyllotactic variability. It has been found that in common verbena (Verbena officinalis L.), a perennial, cosmopolitan plant, phyllotaxis differs not only between growth phases in primary transitions but also along the indeterminate inflorescence axis in a series of multiple secondary transitions. The latter are no longer associated with the change in lateral organ identity, and the sequence of phyllotactic patterns is puzzling from a theoretical point of view. Data from the experiments in silico, confronted with empirical observations, suggest that secondary transitions might be triggered by the cumulative effect of fluctuations in the continuously decreasing bract primordia size. The most important finding is that the changes in the primary vascular system, associated with phyllotactic transitions, precede those taking place at the apical meristem. This raises the question of the role of the vascular system in determining primordia initiation sites, and possibly challenges the autonomy of the apex. The results of this study highlight the complex relationships between various systems that have to coordinate their growth and differentiation in the developing plant shoot. Common verbena emerges from this research as a plant that may become a new model suitable for further studies on the causes of phyllotactic transitions.

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Modeling and theoretical description of magnetic hybrid materials—bridging from meso- to macro-scales

Physical Sciences Reviews ◽

10.1515/psr-2019-0088 ◽

2020 ◽

Vol 0 (0) ◽

Cited By ~ 1

Author(s):

Andreas M. Menzel ◽

Hartmut Löwen

Keyword(s):

Colloidal Particles ◽

Colloidal Particle ◽

Theoretical Description ◽

Point Of View ◽

Material Behavior ◽

Theoretical Point ◽

Mechanical Stiffness ◽

Theoretical Approaches ◽

Theoretical Predictions ◽

Particle Level

Abstract Magnetic gels and elastomers consist of magnetic or magnetizable colloidal particles embedded in an elastic polymeric matrix. Outstanding properties of these materials comprise reversible changes in their mechanical stiffness or magnetostrictive distortions under the influence of external magnetic fields. To understand such types of overall material behavior from a theoretical point of view, it is essential to characterize the substances starting from the discrete colloidal particle level. It turns out that the macroscopic material response depends sensitively on the mesoscopic particle arrangement. We have utilized and developed several theoretical approaches to this end, allowing us both to reproduce experimental observations and to make theoretical predictions. Our hope is that both these paths help to further stimulate the interest in these fascinating materials.

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New Deterministic Mathematical Model for Estimating the Useful Energy Output of a Medium-Sized Solar Domestic Hot Water System

Energies ◽

10.3390/en14102753 ◽

2021 ◽

Vol 14 (10) ◽

pp. 2753

Author(s):

Miroslaw Zukowski ◽

Walery Jezierski

Keyword(s):

Thermal Power ◽

Optimization Procedure ◽

Climatic Conditions ◽

Point Of View ◽

Hot Water ◽

Energy Output ◽

Daily Consumption ◽

Software Environment ◽

Optical Efficiency ◽

Domestic Hot Water

According to the authors of this paper, the mathematical point of view allows us to see what sometimes cannot be seen from the designer’s point of view. The aim of this study was to estimate the influence of the most important parameters (volume of heat storage tanks, daily consumption of domestic hot water, optical efficiency, heat loss coefficient, and total area of a solar collector) on the thermal power output of solar domestic hot water (SDHW) system in European climatic conditions. Three deterministic mathematical models of these relationships for Madrid, Budapest, and Helsinki were created. The database for the development of these models was carried out using computer simulations made in the TRNSYS software environment. The SDHW system located at the Bialystok University of Technology (Poland) was the source of the measurement results used to validate the simulation model. The mathematical optimization procedure showed that the maximum annual useful energy output that can be obtained from 1 m2 of gross collector area is 1303 kWh in the case of Madrid, 918.5 kWh for Budapest, and 768 kWh for Helsinki weather conditions.

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The expectation marker of course in a cross-linguistic perspective

Languages in Contrast ◽

10.1075/lic.4.1.03sim ◽

2004 ◽

Vol 4 (1) ◽

pp. 13-43 ◽

Cited By ~ 8

Author(s):

Anne-Marie Simon-Vandenbergen ◽

Karin Aijmer

Keyword(s):

English Learners ◽

Native Speakers ◽

Point Of View ◽

Theoretical Point ◽

Pragmatic Markers ◽

Semantic Fields ◽

Explanatory Account ◽

Semantics And Pragmatics ◽

Multilingual Corpus ◽

Core Meaning

The study of of course presented in this article has an applied, a descriptive and a theoretical aim. Since of course proves to be very frequent in English, learners will need to know what meanings the item has and in what pragmatic contexts it is used. It has indeed been shown that some learners tend to use of course in contexts where it is felt by native speakers to be inappropriate. In order to explain such inappropriate uses we need detailed descriptions of the semantics and pragmatics of of course. From a theoretical point of view such multifunctional items raise the question of whether semantic polysemy or pragmatic polysemy is the best explanatory account. It is argued in this paper that empirical cross-linguistic work can contribute to providing answers to all three research questions. First, the study of correspondences and differences between languages with regard to the meanings and uses of pragmatic markers is a necessary step in the explanation of learner problems. Second, the bidirectional approach to equivalents, which involves going back and forth from sources to translations, enables us to show to what extent the equivalents have partially overlapping pragmatic functions. An in-depth comparison of the semantic fields in which the translation equivalents operate is the ultimate goal. Third, the translation method helps to see to what extent a core meaning account is justified. In this paper three languages are brought into the picture, viz. English, Swedish and Dutch. The cross-linguistic data have been gathered from three translation corpora, i.e. the English-Swedish Parallel Corpus, the Oslo Multilingual Corpus and the Namur Triptic Corpus.

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Transformation of the Flow Regime of a Large Allochthonous River in Central Europe—An Example of the Vistula River in Poland

Water ◽

10.3390/w12020507 ◽

2020 ◽

Vol 12 (2) ◽

pp. 507 ◽

Cited By ~ 1

Author(s):

Dariusz Wrzesiński ◽

Leszek Sobkowiak

Keyword(s):

Flow Regime ◽

Annual Cycle ◽

River Flow ◽

Hydrological Cycle ◽

Temporal Structure ◽

Flow Characteristics ◽

Point Of View ◽

Theoretical Point ◽

Vistula River ◽

Basin Water

Identification of river flow regime and its possible changes caused by natural factors or human activity is one of major issues in modern hydrology. In such studies different approaches and different indicators can be used. The aim of this study is to determine changes in flow regime of the largest river in Poland—the Vistula, using new, more objectified coefficients and indices, based on data recorded in 22 gauges on the Vistula mainstream and 38 gauges on its tributaries in the multi-year period 1971–2010. The paper consists of three main parts: in the first part, in order to recognize changes in the flow regime characteristics along the Vistula, data from gauges located on the river mainstream were analyzed with the help of the theory of entropy. In the second part gauging stations on the Vistula mainstream and its tributaries were grouped; values of the newly introduced pentadic Pardé’s coefficient of flow (discharge) (PPC) were taken as the grouping criterion. In the third part of the study a novel method of determining river regime characteristics was applied: through the recognition of the temporal structure of hydrological phenomena and their changes in the annual cycle sequences of hydrological periods (characteristic phases of the hydrological cycle) on the Vistula River mainstream and its tributaries were identified and their occurrence in the yearly cycle was discussed. Based on the detected changes of the 73-pentad Pardé’s coefficients of flow four main types of rivers were distinguished. Transformation of the flow regime was reflected in the identified different sequences of hydrological periods in the average annual cycle. It was found that while transformation of the Vistula River regime occurred along its whole course, the most frequent changes were detected in its upper, mountainous reaches, under the influence of the flow characteristics of its tributaries. This allowed the Vistula to be considered the allochthonous river. These findings are interesting not only from a theoretical point of view, but they also can be valuable to stakeholders in the field of the Vistula River basin water management and hydrological forecasting, including flood protection, which has recently become a matter of growing concern due to the observed effects of climate change and human impact.

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