bluuebunny/crossref_metadata_2025 huggingface dataset:
The Gravitational Wave Signal from Core-collapse Supernovae
Authors: Morozova Viktoriya , Radice David , Burrows Adam , Vartanyan David
Published: June 2018

We study gravitational waves (GWs) from a set of 2D multigroup neutrino radiation hydrodynamic simulations of core-collapse supernovae (CCSNe). Our goal is to systematize the current knowledge about the post-bounce CCSN GW signal and recognize the templatable features that could be used by the ground-based laser interferometers. We demonstrate that, starting from ∼400 ms after core bounce, the dominant GW signal represents the fundamental quadrupole (l = 2) oscillation mode (f-mode) of the proto–neutron star (PNS), which can be accurately reproduced by a linear perturbation analysis of the angle-averaged PNS profile. Before that, in the time interval between ∼200 and ∼400 ms after bounce, the dominant mode has two radial nodes and represents a g-mode. We associate the high-frequency noise in the GW spectrograms above the main signal with p-modes, while below the dominant frequency there is a region with very little power. The collection of models presented here summarizes the dependence of the CCSN GW signal on the progenitor mass, equation of state, many-body corrections to the neutrino opacity, and rotation. Weak dependence of the dominant GW frequency on the progenitor mass motivates us to provide a simple fit for it as a function of time, which can be used as a prior when looking for CCSN candidates in the LIGO data.
How Galaxies Form Stars: The Connection between Local and Global Star Formation in Galaxy Simulations
Authors: Semenov Vadim A. , Kravtsov Andrey V. , Gnedin Nickolay Y.
Published: June 2018

Using a suite of isolated L
⋆ galaxy simulations, we show that global depletion times and star-forming gas mass fractions in simulated galaxies exhibit systematic and well-defined trends as a function of the local star formation efficiency per freefall time,

, strength of stellar feedback, and star formation threshold. We demonstrate that these trends can be reproduced and explained by a simple physical model of global star formation in galaxies. Our model is based on mass conservation and the idea of gas cycling between star-forming and non-star-forming states on certain characteristic timescales under the influence of dynamical and feedback processes. Both the simulation results and our model predictions exhibit two limiting regimes with rather different dependencies of global galactic properties on the local parameters. When

is small and feedback is inefficient, the total star-forming mass fraction,

, is independent of

and the global depletion time,

, scales inversely with

. When

is large or feedback is very efficient, these trends are reversed:

 ∝ 

and

is independent of

but scales linearly with the feedback strength. We also compare our results with the observed depletion times and mass fractions of star-forming and molecular gas and show that they provide complementary constraints on

and the feedback strength. We show that useful constraints on

can also be obtained using measurements of the depletion time and its scatter on different spatial scales.
Keck/Palomar Cosmic Web Imagers Reveal an Enormous Lyα Nebula in an Extremely Overdense Quasi-stellar Object Pair Field at z = 2.45
Authors: Cai Zheng , Hamden Erika , Matuszewski Matt , Prochaska J. Xavier , Li Qiong , Cantalupo Sebastiano , Battaia Fabrizio Arrigoni , Martin Christopher , Neill James D. , O’Sullivan Donal , Wang Ran , Moore Anna , Morrissey Patrick
Published: June 2018

Enormous Lyα nebulae (ELANe) represent the extrema of Lyα nebulosities. They have detected extents of >200 kpc in Lyα and Lyα luminosities >1044 erg s−1. The ELAN population is an ideal laboratory to study the interactions between galaxies and the intergalactic/circumgalactic medium (IGM/CGM) given their brightness and sizes. The current sample size of ELANe is still very small, and the few z ≈ 2 ELANe discovered to date are all associated with local overdensities of active galactic nuclei (AGNs). Inspired by these results, we have initiated a survey of ELANe associated with quasi-stellar object (QSO) pairs using the Palomar and Keck Cosmic Web Imagers (PCWI/KCWI). In this Letter, we present our first result: the discovery of ELAN0101+0201 associated with a QSO pair at z = 2.45. Our PCWI discovery data shows that, above a 2σ surface brightness of 1.2 × 10−17 erg s−1 cm−2 arcsec−2, the end-to-end size of ELAN0101+0201 is ≳232 kpc. We have conducted follow-up observations using KCWI, resolving multiple Lyα emitting sources within the rectangular field of view of ≈130 × 165 projected kpc2, and obtaining their emission line profiles at high signal-to-noise ratios (S/Ns). Combining both KCWI and PCWI, our observations confirm that ELAN0101+0201 resides in an extremely overdense environment. Our observations further support that a large amount of cool (T ∼ 104 K) gas could exist in massive halos (M ≳1013
M
⊙) at z ≈ 2. Future observations on a larger sample of similar systems will provide statistics of how cool gas is distributed in massive overdensities at high redshift and strongly constrain the evolution of the intracluster medium.
Tuberculosis in the Prisons in the Republic of Macedonia, 2008-2017
Authors: Ilievska-Poposka Biljana , Zakoska Maja , Pilovska-Spasovska Karolina , Simonovska Ljiljana , Mitreski Vladimir
Published: June 2018

BACKGROUND: Tuberculosis (TB) is a major health problem in penitentiary institutions (prisons), and its prevalence was reported to be multiple times higher compared to that of the general population. Conditions such as overcrowding, malnutrition and limited access to medical care which often exist in prisons increase the risk of reactivation, transmission and poor prognosis of tuberculosis disease among inmates.AIM: The main objective of this study was to present the epidemiological situation of TB in the prisons from 2008 till 2017 in the Republic of Macedonia (RM).PATIENTS AND METHODS: There are 13 different penitentiary institutions in the RM with a total capacity to house 2600 prisons inmates. Management of TB in the prisons is part of the National TB program in RM, and the Institute for Lung Diseases and Tuberculosis in Skopje is in charge of it. All prisoners with TB in the RM are registered in the Central Register for TB within this Institute. We use the data from the Central Register, and with the method of description, we present the epidemiological data and clinical characteristics of the prisoners about TB in prisons in RM for 10 years’ period.RESULTS: From 2008 till 2017 there were 58 TB cases registered in prisons in total. The absolute number of TB cases in the prisons is not big, but the incidence rate is higher than 100/100,000 population, or several times bigger than in the general population (except in 2012 and 2016). In 2017 there were 10 TB cases registered in the prisons with an incidence rate of 323.9/100,000 population which is many times higher than in the general population in RM. The majority of inmates with TB were young men with risk factors for TB infection or TB disease before incarceration such as drug abuse, alcohol, smoking, but there was no association with HIV infection. The most of the patients diagnosed in prison were new cases (54), secondary TB due to reactivation from the latent TB infection or secondary TB due to the environment. From 2008-2017 there were 82.75% successfully treated TB cases in the prisons, and there were no cases of multi-drug resistant tuberculosis (MDR-TB).CONCLUSION: The results from our study showed that the TB control in the prisons in RM is good with satisfactory treatment outcome. On the other hand, the high incidence rate showed that the prisons in RM provide conditions for TB transmission and with other additional risk factors present place for high TB prevalence. The study findings can be used for planning more effective TB control interventions for the prison population in RM.
Phylogeography, species delimitation and population structure of a Western Australian short-range endemic mite harvestman (Arachnida: Opiliones: Pettalidae: Karripurcellia)
Authors: Schwentner Martin , Giribet Gonzalo
Published: June 2018

The mite harvestmen of the genusKarripurcelliaGiribet, 2003 are endemic to the tall, wet eucalypt forests of south-western Western Australia, a region known as a hotspot for biodiversity. Currently, there are two accepted species,K.peckorumGiribet, 2003 andK.sierwaldaeGiribet, 2003, both with type localities within the Warren National Park. We obtained 65COImtDNA sequences from across the entire distributional range of the genus. These sequences, falling into two to three geographically separate groups, probably correspond to two species. Morphologically, all of the studied specimens correspond toK.peckorum, suggesting cryptic speciation within that species. A few common haplotypes occur in more than one population, but most haplotypes are confined to a single population. As a result, populations are genetically differentiated and gene flow after initial colonization appears to be very limited or completely lacking. Our study provides another example of short-range endemism in an invertebrate from the south-western mesic biome.
La sécurisation de la frontière ou l’apparition de territoires-frontières
Authors: Moullé François
Published: June 2018

Les frontières Schengen sont aujourd’hui bousculées par les tensions géopolitiques internationales et les flux migratoires internationaux. Nous nous intéressons aux processus de transformation des modalités de contrôles aux frontières pour comprendre comment le territoire est utilisé par les pouvoirs publics pour garantir à la fois les fonctions de filtres et celles permettant la fluidité des échanges. Chaque fonction de la frontière est localisée sur le lieu où elle pourra être utilisée de manière performante, les lieux de la coopération ne seront pas ceux des échanges ou ceux du contrôle. Nous assistons donc à un éclatement spatial de la frontière s’organisant en système frontalier, fruit d’une co-construction de la frontière, entre les différents acteurs, notamment publics et privés mais aussi de part et d’autre de la frontière, pour optimiser la frontière dans sa dualité ouverture-sécurité.
Le Maup et l’insoluble question de frontière optimale
Authors: Gbenyo Koffi , Dubé Jean
Published: June 2018

L’article propose une façon simple de tester la présence du problème d’unité d’aire modifiable sur un ensemble d’indicateurs spatiaux locaux calculés à partir de micro-données d’emplois par établissement dans la province du Québec en 2011. À partir de la localisation des ports du Québec, l’application construit les indicateurs sélectionnés en effectuant un ensemble de délimitations spatiales avec des cercles de rayons variant de 250 à 10 000 mètres. La stabilité de ces indicateurs est ensuite testée afin d’identifier un point de rupture permettant de déterminer une distance « optimale ». Les résultats confirment la difficulté d’établir une limite géographique unique permettant d’obtenir des résultats stables, confirmant une fois de plus la difficulté de résoudre en totalité le problème d’unité d’aire modifiable. S’il est possible d’identifier des points de rupture servant à décrire des logiques territoriales spécifiques aux régions portuaires, l’article montre comment les micro-données spatiales peuvent être mobilisées pour définir des territoires d’études.
Les courtiers bordelais, intermédiaires de commerce du vin aux xvii e - xviii e siècles
Authors: Lachaud-Martin Stéphanie
Published: June 2018

Le système du courtage des vins en France aux xvii e  et xviii e  siècles reste soumis à des édits royaux mais aussi à des particularités régionales, liées à leur origine urbaine ancienne. Ainsi, si le courtage officiel disparaît en Champagne et en Bourgogne dans la seconde moitié du xviii e  siècle, au profit des commissionnaires, il n’en est pas de même en Bordelais. Plus encore, les courtiers y ont occupé une véritable place dans la définition des hiérarchies et des qualités des vins, grâce à une recomposition complexe du corps des courtiers qui a été partagé entre les courtiers royaux et les courtiers brevetés mais qui s’est maintenu à une place importante, malgré l’activité de commissionnaires officieux, appelés courtiers volants. Il faut ici y voir un faisceau d’explications, en lien avec la professionnalisation du corps des courtiers en vin bordelais, mais aussi en rapport avec la mutation quantitative et qualitative du marché des vins. En effet, la bonne connaissance par les courtiers du vignoble et des vins, mais aussi leur rôle de défense des producteurs et de la qualité des productions de l’arrière-pays viticole constitue un déterminant essentiel du maintien du courtage en Bordelais, au-delà des mises en cause de la seconde moitié du xviii e  siècle.
Marx et Allah. Les gauches alternatives françaises face à l’islam, de Mai 1968 au 11 septembre 2001
Authors: Ferhat Ismail
Published: June 2018

La question de l’islam suscite des passions particulièrement fortes dans le monde politique français, et ce depuis plusieurs décennies. Au sein des gauches alternatives (c’est-à-dire les forces de gauche se situant en dehors des organisations et courants traditionnels des gauches françaises), ce sujet a entraîné de nombreuses dis­­cussions, oppositions et évolutions. Cet article, mené à partir d’un travail de dépouillement d’archives, de littérature grise, de publications et de programmes, souhaite comprendre comment cette sensibilité, parfois présentée comme plus favorable à cette religion que le reste du monde politique français, a pensé son rapport avec l’islam. Il étudie une période allant de 1968, moment de retour d’influence des gauches alternatives, à 2001 et les attentats sur le sol américain. Durant celle-ci, ces forces politiques ont progressivement remplacé la figure du « travailleur immigré » par celle de « musulman ». Or, cette mutation était fondamentale : elle posait la question, difficile, d’un passage d’une catégorie socio-économique à un groupe religieux, peu pensé par des approches largement inspirées du mouvement ouvrier et du marxisme. Cette évolution a été différente selon les sensibilités des gauches alternatives. Celles-ci ont généré un vaste spectre de réponses, allant d’une hostilité déclarée au religieux à une volonté de se rapprocher de l’islam, y compris politique. Ces réponses ont été largement influencées par le contexte international, entraînant des difficultés récurrentes à circonscrire le sujet au seul cadre français.
Les Misérables, « un livre de charité » ?
Authors: Scepi Henri
Published: June 2018

Cet article se propose de reprendre la question de la charité telle qu’elle est formulée et déployée dans  Les Misérables  afin de la resituer d’abord dans le cadre d’une pensée critique et dynamique – une pensée non dogmatique – qui s’efforce de cerner et d’évaluer l’action de bienfaisance et la philosophie morale qui l’inspire non plus comme la déduction d’une  vertu , mais comme le produit d’un agir historique, d’une pratique qui s’inscrit et se développe dans le champ d’une anthropologie sociale et politique. C’est à l’affirmation d’un droit redéfini à l’abri des théologies et des églises que travaille le discours de l’écrivain. Une relation spécifique avec le lecteur s’y rattache – de même qu’une fonction de la littérature – comme fiction et pensée – s’y renforce dans l’invention conjointe d’une exigence de liberté et d’un devoir de fraternité assignables à l’humain conçu comme progrès et transcendance de l’Histoire.
De Baudelaire à Villiers : les envers ironiques de la charité
Authors: Noiray Jacques
Published: June 2018

Baudelaire et Villiers de l’Isle-Adam portent sur l’acte charitable et celui qui l’accomplit un regard qui diffère de l’habituel concert de louanges et ne va pas sans ironie. Ce qui est d’abord critiqué, c’est l’hypocrisie charitable, et surtout la bonne conscience qui accompagne la charité. La charité vraie devrait reposer sur un échange équitable que l’aumône d’argent ne permet pas. Cet échange passe par le regard. La relation qui s’établit est alors de sympathie, mais surtout de curiosité. Liée à l’imagination, la curiosité est inséparable de l’acte poétique. Charité et poésie, sous le signe de l’imagination, tendent à se confondre dans la création d’une légende de l’être souffrant qui devient pour le poète plus vraie que la réalité même. Mais comme elle est acte d’amour, la relation charitable devient aussi désir de projection dans autrui et de possession d’autrui. Elle s’apparente à une prostitution. Elle se charge de sensualité et même de cruauté. Dans un monde marqué par la malédiction de la Chute, seule l’ironie peut qualifier une charité dégradée qui ne peut aboutir qu’au grotesque. C’est ce qu’expriment Baudelaire et Villiers, l’un dans « Assommons les pauvres », l’autre dans « Les délices d’une bonne œuvre ».
De l’allégorie à la scène de genre : peindre la charité en acte
Authors: Saint-Martin Isabelle
Published: June 2018

En un siècle où rivalisent le catholicisme des œuvres et les philosophies humanitaires, l’image de la Charité associe la référence à la plus haute vertu théologale et la vision d’une piété en acte proposée en modèle aux fidèles. Ainsi, pour traiter de la charité comme amour de Dieu et amour du prochain, le répertoire de l’allégorie, qui inspire encore la République de Daumier, ouvre aussi à la figure de la fraternité chère au christianisme social. Dans les peintures du quotidien, à côté d’innombrables scènes d’aumônes, certaines représentations de la pauvreté laissent parfois apparaître, à travers le contraste entre nantis et démunis, une critique sous-jacente. Parce que les enjeux sont vifs tant sur le plan social que théologique, le motif de la Charité semble apte à brouiller les frontières ; alors que la hiérarchie des genres se trouble, l’allégorie ressurgit parfois derrière le pittoresque.
Quelques enjeux du mot « influence » vers 1800
Authors: Naïm Jérémy
Published: June 2018

Vers 1800, le mot « influence » connut une vogue soudaine dans l'écriture lettrée. En quelques années, le mot était passé du discours astrologique au discours historique et moral pour dire l'emprise d'un homme ou d'un livre sur l'opinion. Il allait bientôt devenir le mot décisif de l'histoire littéraire. Cet article revient sur l'histoire de cette transition et ses conséquences sur la notionalisation de l'« influence », en s'arrêtant en particulier sur le débat entre Bonald, Barante et Mme de Staël à propos des rapports entre littérature et société.
The Suitability of Fly Ash for Use in Concrete According to EN 450 Based on their Particle Size
Authors: Ťažký Martin , Labaj Martin , Hela Rudolf
Published: June 2018

The by-products of energy industry are nowadays often affected by new limits governing the production of harmful gases discharged into the air. These stricter and stricter criteria are often met by electricity producers by changing the combustion process in thermal power plants itself. Nowadays, the SNCR (selective non-catalytic reduction) application is quite common in the combustion process in order to help reduce the nitrogen oxide emission. This article deals with the primary measures of thermal power plants, which in particular consist of a modified treatment of raw materials (coal) entering the combustion process. These primary measures then often cause the formation of fly ash with unsuitable fineness for the use in concrete according to EN 450. The paper presents the comparison of the physico-mechanical parameters of several fly ashes with a different fineness values. The primary task is to assess the impact of non-suitable granulometry in terms of EN 450 on the other physico-mechanical parameters of fly ashes sampled within the same thermal power plant. Several fly ashes produced in the Czech Republic and surrounding countries were evaluated in this way.
Effect of Hardening Accelerators and other Chemical Admixtures on the Properties of a Quick-Setting Mixture
Authors: Khamatova Alsu , Yakovlev Grigory Ivanovich , Khozin Vadim , Pervushin Grigory Nikolaevich
Published: June 2018

The physicochemical and physicomechanical properties of quick-setting compositions based on fine-grained electric steelmaking slag (ESS) produced by Izhstal PJSC, Russia, have been examined. The study also focuses on the processes of interaction of the components of the compositions based on ESS in combination with hardening accelerators (Li2CO3, K2SO4) and plasticizing additives (SP-1, Melflux 2651F). It has been found that mechanoactivation of the composition improves the hydration in comparison with chemical admixtures. This can be proved by the obtained results of the setting and testing timing of the mechanical properties of the mixture. Plasticizers being added, the setting time increases at the average by 2.3 times, and accelerators being added, by 2 times compared with the mechanically activated composition. The influence of mechanoactivation on the strength of the compositions has been described. In comparison with the plasticized composition, the strength increases by 10%, while using accelerators – by 30%. Thus, the most effective way of producing a dry mixture with the properties of quick setting and hardening is a short-term mixed grinding of all its components, which makes it possible to exclude accelerating chemical admixtures and plasticizing additives in the mixture. Also, grinding positively affects the strength gain of quick-setting compositions while reducing the gypsum content to 5%.
Decorative Coating Based on Composite Cement-Silicate Matrix
Authors: Shaybadullina Arina , Ginchitskaya Yuliya , Smirnova Olga
Published: June 2018

The designed is a cement-silicate coating based on liquid sodium glass and Portland cement, modified with a complex ultra-and nanodispersed additive that includes titanium dioxide, expanded perlite sand and a dispersion of multilayered carbon nanotubes. The advantage of the designed coating is the use of Portland cement as a silicizer instead of conventionally used zinc oxide. The presented cement-silicate coating is water resistant, steam and gas proof, has good adhesion to the base and an increased durability, providing 4-5 times longer service life than those of the existing analogs. The presence of multilayered carbon nanotubes in the coating leads to the absorption of technogenic electromagnetic emission, and ultradisperse titanium dioxide promotes self-cleaning of the coating surface due to the photocatalysis effect. Expanded pearlite sand makes the coating surface textured when applying it to the base. The cement-silicate coating is used for facades decorative finishing of buildings made of ceramic bricks, cement concrete and plastered surfaces.
Influence of the Maximum Aggregate Grain Size on the Modulus of Elasticity and on the Parameters of the Acoustic Emission of Concrete Exposed to High Temperatures
Authors: Topolář Libor , Kocáb Dalibor , Hoduláková Michaela , Halamová Romana
Published: June 2018

Several very large and tragic fires of buildings have occurred recently, drawing attention to the issues of fire resistance of buildings (especially high-rise buildings and tunnels) and of building materials. For cement-based composites, it is essential to comprehensively understand the behaviour of their internal structures when exposed to high temperatures. This paper deals with the changes of the physical properties of concrete with different aggregate grain sizes when exposed to high temperatures. The emphasis is placed on the changes of the static and dynamic modulus of elasticity as an important parameter in assessing the behaviour of structures or their parts. During the test of the static modulus of elasticity, the acoustic emission method was also used as its results may reveal the behaviour of the internal structure of the material during mechanical loading.
High Strain Rate Compressive Behavior of Micro-Fibre Reinforced Fine Grained Cementitious Composite
Authors: Drdlová Martina , Popovič Miloslav , Čechmánek René
Published: June 2018

This paper presents an experimental study on the high strain rate compressive behavior of micro-fibre reinforced ultrahigh performance cementitious composite, which is intended to be used as a matrix for slurry infiltrated fibre concrete (SIFCON). Cementitious composite specimens with 5 different types of microfibres, namely aramid, carbon, wollastonite, polypropylene and glass in amounts of 1.5-2.0% by volume were prepared and investigated. Split Hopkinson pressure bar (SHPB) equipment was used to determine the cementitious composite behavior at strain rates up to 1600 s-1. Quasistatic tests were performed, as well and ratios of these properties at high strain rates to their counterparts at static loading were compared. The dynamic increase factors were calculated. Strain rate sensitivity was observed - compressive strength was found to be increased with strain rate for all tested specimens. Peak stress values, critical compressive strain and post peak behaviour varies for specimens with different micro-fibre reinforcement, which allows to find the optimal reinforcement for high strain rate impacted structures.
Physical Properties of Selected Silicates for a Long-Term Heat Container
Authors: Šťastník Stanislav , Vala Jiří , Šot František
Published: June 2018

Implementation of high temperature solar reservoirs is associated with problems related to the physical properties of materials, especially with temperature resistance of the material at temperature changes, with high heat capacity, with high thermal conductivity and with material fire resistance. In the case of silicate materials, more specific materials with favourable physical properties are available, which can be used for the construction of high temperature containers. The basic prerequisite for designing such container is the knowledge of the physical properties of the heat storage core and the thermal insulation ability of container cladding layers.The paper deals with the problem of identification of material properties of silicates in the wide temperature range up to 800 °C, using the standard measurement methodology, improved by additional temperature recording at a defined distance from the thermal source during the dynamic thermal development of the linear thermal source, well-known as the hot wire method.
Porous Systems Based on Alkali-Activated Fly Ash
Authors: Kejík Pavel , Bílek Jr. Vlastimil , Bulejko Pavel , Hajzler Jan , Březina Matěj , Galvánková Lucie , Kalina Lukáš
Published: June 2018

This paper studies possibilities of alkali-activated fly ash (AAFA) for the preparation of systems with preserved certain porosity level. Such systems would be used for example as filtration barriers, which are commonly prepared by both energetically and economically expensive sintering process at high temperatures. Porosity preservation was facilitated by the use of only coarse fraction from fly ash particles together with the use of low water to fly ash ratio and pressure compaction. Two different doses of sodium hydroxide were used to alkali activate fly ash. Prepared specimens were moist cured at 95 °C for 24 hours. Porosity and binder phase among the fly ash grains were investigated using scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and capillary flow porosimetry (CFP). The results showed that it is possible to prepare AAFA-based porous systems and modify their properties by changing the activator dose.
Modifying Stucco Mortars with Additions of Sulphoaluminate Cement and Aluminate Cement
Authors: Brachaczek Wacław
Published: June 2018

Stucco products due to the specific nature should be characterized by a short time of the beginning and end of setting, low shrinkage, good adhesion to the substrates and workability at running. The type of cement used has a significant influence on this parameter. The change in the physical properties of stucco mortars in which Portland cement was gradually replaced with AliCem sulphoaluminate cement and Górkal 70 aluminate cement. For this purpose, two sets of samples were prepared, in the first set the percentage of Górkal 70 cement in relation to the entire cement was 15, 20, 25, 30 and 33%, in the second set the percentage of Alicem cement was 25, 50, 75 and 100%. The research results indicate that both cements significantly shortened the setting time of the mortars, reduced the shrinkage and improved adhesion to the substrates.
The Impact of Addition of Fibers on Reducing the Shrinkage Cracks in Multilayer Renovation Plasters
Authors: Kaczmarczyk Marcin
Published: June 2018

Renovation plasters need to be characterized by high porosity, appropriate pore size distribution and the ability to transport and accumulate mineral salts. In addition, they must perform functions of a regular plaster. One of the main features that every plaster should have is the resistance to shrinkage cracks. For salt-absorbing plasters, the need to use multiple layers necessitates an in-depth research of this phenomenon. The shrinkage crack formation is determined by the bending strength of mortars. This feature can be adjusted with the addition of different types of fibers. This paper presents a study on the change in bending and compressive strength of renovation plasters with the addition of 6 mm fibers. 0.05, 0.10, 0.15, 0.20% of polyethylene fibers and 0.10, 0.20, 0.30, 0.40% of glass and basalt fibers by mass ratio to dry mix were used. The results were referenced to mortars without fibers. Significant changes in mechanical properties were observed. Compression and bending strength increases with the fiber addition, reaching maximum values at 0.15% for PE and 0.20% for glass and basalt fibers. The best results were obtained for the latter ones.
The Combined Effect of the Plasticizer and Multi-Walled Carbon Nanotubes on the Cement Hydration Products
Authors: Skripkiūnas Gintautas , Yakovlev Grigory Ivanovich , Karpova Ekaterina , Gordina Anastasiya Fedorovna , Shaybadullina Arina
Published: June 2018

There are many research devoted to the influence of carbon nanotubes (CNT) on the structure and properties of cement systems. In the course of this research, the combined influence of of multi-walled carbon nanotubes (MWCNT) and polycarboxylate (PCE) plasticizer on the products of hydration and the properties of hardened cement paste was investigated. The strength characteristics of nanomodified hardened cement paste and the hydration products were determined by the usage of modern methods of physico-mechanical and physico-chemical analyses. Based on the physico-chemical investigations, it was concluded the necessity of additional experiments, associated primary with questions of uniform distribution of the nanostructures and their chemical interactions with another components of admixture and cement system.
Comparison of Automated Concrete Shrinkage Measurement Methods
Authors: Osuská Lucia , Novosad Petr , Labaj Martin
Published: June 2018

Volumetric changes are deformation properties of concrete that are caused by external or internal forces and can be reversible or irreversible. Relatively significant and irreversible volumetric changes occur during the hydration of clinker minerals during the first stages concrete setting and hardening. From the “real-world” point of view, the volumetric changes associated with drying are the most important – these take place when the leftover mixing water evaporates. The current legislation addresses the volumetric changes of concrete relatively briefly and the calculations of the assumed autogenous shrinkage according to Eurocode 2 are generally related only to the concrete’s strength class, not to the composition of the concrete mixture. The principle of determination of volumetric changes is classified by the standard ČSN 73 1320, which requires the measuring devices with an accuracy of at least 1∙10-5 of expected proportional deformation.
In this experiment, the volumetric changes of the concrete will be monitored by two different measurement methods. Several different test mixtures will be prepared to monitor these changes continuously with an automatic measuring device. In one case, the measurement will take place from the point of fresh concrete and, in the case of the others, immediately after the acquisition of the handling strength, i.e. from the age of 1 day.
Use of Undersize Fractions of Refractory Claystone for Grog Manufacturing in Shaft Kilns
Authors: Nevřivová Lenka
Published: June 2018

Refractory aluminosilicate grogs are made by firing refractory clays and claystones. They are fired predominantly in rotary or shaft kilns. Prior to firing in shaft kilns, particles of claystone smaller than 35 mm are separated These fine fractions cannot be processed in a shaft kiln, since they lower the quality and homogeneity of firing. However, these claystones can be briquetted into larger pieces (5 – 6 cm), which can be easily fired in shaft kilns. It is possible to modify the raw material by adding correcting materials or other types of clay. This method can then be used for making special grogs. The paper discusses the possibilities of manufacturing grog with an increased Al2O3 content with undersize fractions of claystone mined in Březinka. The research focused on the influence of raw material water content and compacting pressure on the final properties of fireclay grog, and determining the influence of firing temperature on the properties of the grog.
The Evaluation of the Effect of Crystallization Additives on Long Term Durability of Cement Composites
Authors: Dufka Ámos , Melichar Tomáš
Published: June 2018

The article deals with the influence of crystallization additives on the life of self-compacting concrete (so-called SCC concrete), which are exposed to chemically aggressive environments. The focus is not only on the effect of the crystallization additive on the characteristics of the capillary-pore structure of SCC concrete, but especially long life durability of self-compacting concrete (two years expozition). The effect of individual types of aggressive environment is assessed on the basis of a set of physico-mechanical and physico-chemical analyzes.
The Influence of Concentrations of Cement Particles on Rheological Behavior and Thixotropy of Portland Cement Paste
Authors: Macijauskas Mindaugas , Skripkiūnas Gintautas
Published: June 2018

The influence of concentration of cement particles φc on rheological behavior (flow behavior, dynamic yield stress, plastic viscosity) and thixotropy of the Portland cement CEM I 42.5 R paste was investigated in this research. Also, thixotropy was evaluated by index of reversible structure of Portland cement paste. Concentration of cement particles φc ranged from 0.434 to 0.518. Investigation was carried out using rotational rheometer Rheotest RN4.1 with coaxial cylinders. The tests revealed that as φc decreases from 0.518 to 0.434, rheological behavior of Portland cement paste is improved: yield stress decreases from 12.7 Pa to 7.1 Pa as well as plastic viscosity – from 4.3 Pa·s to 0.88 Pa·s. The exponential correlation between φc and index of reversible structure of Portland cement paste was found. As φc decreases from 0.518 to 0.434, index of reversible structure of Portland cement paste, which describes a thixotropy, decreases from 5291 Pa·min to 977 Pa·min.
Durability Assessment of Cement Matrices for Neutralization Sludge Disposing
Authors: Dohnalkova Bozena , Drochytka Rostislav
Published: June 2018

The paper deals with durability assessment of different cement matrices for disposing of hazardous waste – neutralization sludge from physical chemical processing from an active industrial source. The durability of the matrices is estimated on the basis of laboratory testing results of compressive strength and leachability tests those indicate the possibility of matrices to bind the hazardous substances inside matrices. These tests were performed on the matrices after different time period.
Possibilities of Experimental Determinations of the Modulus of Elasticity in the early Stage of Ageing of Cement Composites
Authors: Halamová Romana , Kocáb Dalibor , Kucharczyková Barbara , Daněk Petr , Misák Petr
Published: June 2018

This paper deals with the possibilities of experimental determination of the dynamic and static modulus of elasticity of fine-grained cement composites in the early stage of setting and hardening - up to 72 hours. Several cement pastes and cement mortars were produced for the purpose of this experiment. The measurement of the modulus of elasticity on the manufactured cement-based composites was carried out in the first 24 hours, each time only by the ultrasonic pulse velocity test using the innovative Vikasonic instrument. In the following 48 hours, the resonance method and the static load test were employed. The results of the pilot measurement and particularly the assessment of the possibilities of determination of the moduli of elasticity are presented in this paper.
Properties of Aerial Lime-Based Mortars with Chitosan Ethers
Authors: Žižlavský Tomáš , Vyšvařil Martin , Bayer Patrik , Rovnaníková Pavla
Published: June 2018

This paper studies the possibility of usage of chitosan derivatives (hydroxypropyl chitosan (HPCH) and carboxymethyl chitosan (CMCH)) as admixtures for aerial lime-based mortars. The physical-mechanical properties were studied on the specimens prepared with constant water/binder ratio and binder/aggregate ratio 1:3 by weight using siliceous sand with the grain size up to 4 mm and doses of admixture ranging between 0.5 and 10‰. The properties were studied on the specimens up to 365 days. The addition of admixtures improves workability of mortar, but in the early stages also decreases strengths of mortars, especially the compressive strength. The addition of HPCH significantly reduces the bulk densities of specimens, while CMCH decreases them just slightly. With the increasing amount of time, the difference in strengths between reference and tested mortars decreases, reaching the similar values after 90 days of curing time. The further ageing causes additional growth of strengths with a significantly higher increase in the case of CMCH.
Alkali-Sulfate Activated Blended Portland Cements
Authors: Kryvenko Pavlo V. , Sanytsky Myroslav , Kropyvnytska Tetiana
Published: June 2018

Early strength of the blended Portland cements containing granulated blast furnace slag and natural pozzolanas (zeolite tuff, etc.) can be enhanced by the alkali-sulfate activation. High early strength of the blended Portland cements as a result of alkali-sulfate activation can be attributed to acceleration of pozzolanic reaction at the early stages and formation of more quantities of ettringite at the early stages of structure formation. The results of the study showed that with high amounts of sodium sulfate in the alkali-sulfate activator, contents of gypsum dihydrate as a setting regulator of the blended Portland cements could be reduced. The effect of sodium sulfate activator on properties of the blended Portland cements was studied and the results are discussed.
Rock Mass Strength Estimation Using Structural Factor Based on Statistical Strength Theory
Authors: Babets Dmytro
Published: June 2018

Quantitative estimation of scale effect is a complex problem which contained many uncertainties and should be solved using probability calculus and statistical approach. This paper aims to derive the structural factor according statistical strength theory involving discontinuity surface conditions account to estimate the design rock mass strength. A short review of scale effect estimation techniques based on statistical strength theory is given. A new method of structural factor evaluation is proposed. This technique allows accounting discontinuity conditions by changing the variation of tested specimen random sample. A function that describes the decreasing of strength due to poor discontinuity surface quality is introduced to correct the initial and central statistical moments of strength random distribution. The evaluation of the joints condition function based on analysis of the results of uniaxial compressive strength tests and petrographic structure of specimens is shown. Improving the statistical approach of structural factor evaluating increase the accuracy of the rock mass strength assessment and allow avoiding costly modifications of the mining excavation support design. A case of rock mass strength estimation under conditions of coal mine “Komsomolets Donbassa” according to proposed statistical method is studied.
Technological Solutions for the Realization of NGH-Technology for Gas Transportation and Storage in Gas Hydrate Form
Authors: Pedchenko Mykhailo , Pedchenko Larysa , Nesterenko Tetiana , Dyczko Artur
Published: June 2018

The technology of transportation and storage of gas in a gas-hydrated form under atmospheric pressure and slight cooling – the maximum cooled gas-hydrated blocks of a large size covered with a layer of ice are offered. Large blocks form from pre-cooled mixture of crushed and the granulated mass of gas hydrate. The technology of forced preservation gas hydrates with ice layer under atmospheric pressure has developed to increase it stability. The dependence in dimensionless magnitudes, which describes the correlation-regressive relationship between the temperature of the surface and the center gas hydrate block under its forced preservation, had proposed to facilitate the use of research results. Technology preservation of gas hydrate blocks with the ice layer under atmospheric pressure (at the expense of the gas hydrates energy) has designed to improve their stability. Gas hydrated blocks, thus formed, can are stored and transported during a long time in converted vehicles without further cooling. The high stability of gas hydrate blocks allows to distributed in time (and geographically) the most energy expenditure operations – production and dissociation of gas hydrate. The proposed technical and technological solutions significantly reduce the level of energy and capital costs and, as a result, increase the competitiveness of the stages NGH technology (production, transportation, storage, regasification).
Physical and Chemical Methods of Methane Utilization in Ukrainian Coal Mines
Authors: Maksymova Ella , Ovchynnikov Mykola , Lysenko Roman , Kostrytska Svitlana
Published: June 2018

Associated gas of coal and minor oil deposits emitting into the atmosphere is considered to be valuable energy resource requiring proper utilization both from the economic and environmental viewpoints. It is proposed to develop mobile gas-hydrate plants to utilize associated gas of mines and minor oil and gas deposits. Hydrogenerating technology to collect and utilize coalmine methane immediately at the degassing wells of coal mines and oil extraction platform has been developed. Thermobaric parameters along with physical and chemical effect upon hydrate-formation process have been substantiated and selected. Certain degree of mechanical impact as well as magnetic field and ultrasound influence upon the process of hydrate formation has been proved. The technology will make it possible to obtain end product within the degassing area for its further transportation to consumers at long distances.
Influence of Dispersed Systems on Exploratory Well Drilling
Authors: Dudlia Mykola , Pinka Jan , Dudlia Kateryna , Rastsvietaiev Valerii , Sidorova Marina
Published: June 2018

Results of theoretical, laboratory and stand study which enabled to recommend solutions of surface active substances while well drilling, taking into account mining and geological conditions of a number of Ukrainian regions are given. It was determined that addition of surface active substances to the drilling fluid during rotary drilling by hard-face and diamond cores makes it possible to increase drilling rate.
Automated Monitoring of Physical Processes of Formation of Burden Material Surface and Gas Flow in Blast Furnace
Authors: Golovchenko Anatoliy , Pazynich Yuliya , Potempa Michał
Published: June 2018

The paper is devoted to the issues of energy saving automatic control of radial burden distribution in the blast furnace throat. The main idea consists in control with prediction of the control resulting on the basis of automatic monitoring of burden surface texture. The paper develops the mathematic description of burden surface texture on the blast furnace throat by means of substantiation of minimum quantity of general indicators of the mixture being closely related to the main parameters of blast furnace processes. It is the first time that the optimum value of hoper depth in burden surface at 0.14 – 0.2 of throat diameter determined, the methods of its stabilization at the rate are substantiated, the new regularity of burden surface formation on the operating blast furnace throat is shown as consisting in the fact that the hoper depth on the surface is mainly changed responding the process of material charge rather than bulk material descent after the charge. It was also substantiated for the first time that radioisotopic methods for current control of burden distribution on the blast furnace throat provide timely formation of control actions for gas flow stabilization. The principle of self-tuning was theoretically substantiated for monitoring system of gamma profilometer responding to the monitoring conditions with respect to high penetration and random character of gamma rays. The principle enables significant improvement of accuracy, quick-response and radiological safety of gamma profilometer operation. The possibility of determination of burden surface texture on the throat of operating blast furnace and distribution of burden components according to infrared radiation of the surface without application of radiation hazardous monitoring means was proved for the first time.
Coal Seam Gasification in Faulting Zones (Heat and Mass Balance Study)
Authors: Lozynskyi Vasyl , Dichkovskiy Roman , Saik Pavlo , Falshtynskyi Volodymyr
Published: June 2018

In this article, the mass and heat balance calculations of underground coal gasification process for thin coal seams in faulting zones of Lvivskyi coal basin (Ukraine) are defined. The purpose of the research is to establish regularities of heat and mass balance changes in faulting zones influence due to usage air and oxygen-enriched blast. A comprehensive methodology that included analytical calculations is implemented in the work. The output parameters of coal gasification products for the Lvivvyhillia coal mines are detailed. The heat balance is performed on the basis of the mass balance of underground coal gasification analytical results and is described in detail. Interpretations based on the conducted research and investigation are also presented. Conclusions regarding the implementation of the offered method are made on the basis of undertaken investigations. According to conducted research the technology of underground coal gasification can be carry out in the faulting zone of stable geodynamic and tectonic activity. The obtained results with sufficient accuracy in practical application will allow consume coal reserves in the faulting zones using environmentally friendly conversion technology to obtain power and chemical generator gas, chemicals and heat.
Physico-Mechanical and Chemical Characteristics of Amber
Authors: Malanchuk Zynovii , Moshynskyi Viktor , Malanchuk Yevhenii , Korniienko Valerii
Published: June 2018

Amber of amber-bearing deposits in Rivne-Volyn region of Ukraine has been analyzed. Relying upon instrumental techniques, physical and chemical as well as spectral analyses, and geological prospecting of the deposits, chemical composition and ultimate composition of amber occurring at the territory of Klesiv deposit (Ukraine, Rivne Region, Sarny District) have been identified. Klesiv amber contains the greatest part of inclusions; it contains 18 chemical elements. Basing upon the performed geological cross-section it has been determined that the amber occur in sandy soil and sandy-shale soil. The depth is insignificant – from 1 m to 10 – 15 m. Moreover, to determine the cost, experimental technique has been developed. The technique involves classification of the amber fragments according to their form, dimensions, and colour. Lithologic-and-facies sections of sites of Klesiv deposit have been obtained.