A damage model with non-convex free energy for quasi-brittle materials

A state coupling between the hydrostatic (volumetric) and deviatoric parts of the free energy is introduced in a damage mechanics model relevant for the quasi-brittle materials. It is shown that it describes the large dilatancy of concrete under compression and the different localization angles and damage levels in tension and compression. A simple isotropic description is used, although similar ideas can be extended to anisotropic damage. The model is identified with respect to tensile and compression tests and validated on bi-compression and bi-tension. Fully written in three dimensions under the framework of thermodynamics of irreversible processes, it allows further developments within a finite element code

An exploratory social network analysis of academic research networks

For several decades, academics around the world have been collaborating with the view to support the development of their research domain. Having said that, the majority of scientific and technological policies try to encourage the creation of strong inter-related research groups in order to improve the efficiency of research outcomes and subsequently research funding allocation. In this paper, we attempt to highlight and thus, to demonstrate how these collaborative networks are developing in practice. To achieve this, we have developed an automated tool for extracting data about joint article publications and analyzing them from the perspective of social network analysis. In this case study, we have limited data from works published in 2010 by England academic and research institutions. The outcomes of this work can help policy makers in realising the current status of research collaborative networks in England

Parametri sušenja koštičavog voća

The paper presents the study results on technical and technological parameters in the process of low-temperature drying of stone fruit (plum and apricot) under both laboratory conditions and in a multi-purpose prototype dryer intended for plant material drying. The experimental investigations comprised flow and thermal measurements, technological and kinetic drying parameters. Major emphasis was on temperature and relative humidity of the drying agent and moisture and temperature of the dried material, as well as the drying rate. According to the results obtained, the preheating period was 2-3 hours depending on the type of the material and the drying regime i.e. on the condition of the drying agent. Maximum plum drying rate was recorded 2 h after the beginning of the process and amounted to about 1.15 kg w/kg d.b.h. In the case of apricot drying, maximum drying rate was approx. 0.45 kgw/kg d.b.h. and was registered only 4 hours after the beginning of the drying process, which differed from the plum drying rate under approximately equal drying regime. In addition, the apricot drying kinetics curve differed in shape from the plum drying kinetics curve. The obtained quality of both dried fruits under low-temperature drying conditions was found to meet standard requirements to a great extent primarily respecting sugar and acid loss and the fact that there was no odor or contamination of the fruit. The results obtained showed that, in addition to the technical designs of the drying system, the fruit drying process was found to be significantly affected by how the process itself the duration of which could be reduced, was being managed.U radu su prikazani rezultati istraživanja tehničko tehnoloških parametara procesa niskotemperatuskog sušenja plodova koštičavog voća (šljiva i kajsija). Eksperimentalna istraživanja sprovedena na laboratorijskoj instalaciji i na prototipskoj univerzalnoj sušari namenjenoj za sušenje biljnih materijala, obuhvatila su strujnotermička merenja, parametre kinetike procesa i tehnološke parametre sušenja. Posebno su analizirani temperatura i relativna vlažnost agensa sušenja, vlažnost i temperatura materijala za sušenje kao i brzina sušenja. Rezultati pokazuju da period pregrevanja materijala iznosi od 2-3 h, što je uslovljeno vrstom materijala i režimom sušenja tj. stanjem agensa sušenja. Maksimalna brzina sušenja plodova šljive nastaje nakon 2 h i iznosi oko 1,15 kg w/kg s.m.h. Kod sušenja plodova kajsija maksimalna brzina sušenja iznosi približno 0,45 kgw/kg s.m.h. i pojavljuje se tek nakon 4 časa od početka procesa u čemu se razlikuje od brzine sušenje plodova šljive za približno isti režim sušenja. Pored toga, kriva kinetike sušenja kajsija ima drugačiji oblik u odnosu na krivu sušenja šljiva. Ostvaren kvalitet obe vrste osušenih plodova sa navedenim niskotemperaturskim režimima u velikoj meri odgovara standardima pre svega u pogledu gubitka šećera i kiselina, kao i odsustva bilo kakvih mirisa i zagađenosti plodova. Dobijeni rezultati ukazuju da, pored tehničkih rešenja sistema za sušenje, na uspeh procesa značajan uticaj ima i samo vođenje procesa čije se trajanje može redukovati

The role of a historical comic book in the contemporary world

Засоби масової інформації називають «Четвертою владою», тому що вони мають величезний вплив на людей. Комічна книга – не виключення. Влада використала її в якості засобу формування громадської думки, як про минулий час, так і про сьогодення. За допомогою комічної книги видно як влада захотіла, щоб вони були сприйняті потенційним читачем. Зокрема уряди Польської Народної Республіки охоче використовували комічну книгу, щоб впливати на суспільство, особливо на молодь з метою ідеологічної обробки.Средства массовой информации называют «Четвертой властью», потому что они имеют огромное влияние на людей. Комическая книга – не исключение. Власти использовали ее в качестве средства формирования общественного мнения, как о прошедшем времени, так и о настоящем. С помощью комической книги видно как власти захотели, чтобы они были восприняты потенциальным читателем. В частности правительства Польской Народной Республики охотно использовали комическую книгу, чтобы влиять на общество, особенно на молодежь с целью идеологической обработки.The mass media are called «the forth estate» because they have an enormous influence on people. A comic book is not an exception. The authorities used it as a way of shaping citizens’ opinions about the past as well as the current reality. It presented facts as the authorities wanted them to be perceived by a potential reader. Especially the governments of PRL willingly used a comic book to create desired behaviours and attitude of the society, particularly its younger part prone for indoctrination

Visualisation and les simulation of cavitation cloud formation and collapse in an axisymmetric geometry

Visualisation and Large Eddy Simulations (LES) of cavitation inside the apparatus previously developed by Franc (2011) for surface erosion acceleration tests and material response monitoring are presented. The experimental flow configuration is a steady-state closed loop flow circuit where pressurised water, flowing through a cylindrical feed nozzle, is forced to turn 90° and then, move radially between two flat plates towards the exit of the device. High speed images show that cavitation is forming at the round exit of the feed nozzle. The cavitation cloud then grows in the radial direction until it reaches a maximum distance where it collapses. Due to the complexity of the flow field, direct observation of the flow structures was not possible, however vortex shedding is inferred from relevant simulations performed for the same conditions. Despite the axisymmetric geometry utilized, instantaneous pictures of cavitation indicate variations in the circumferential direction. Image post-processing has been used to characterize in more detail the phenomenon. In particular, the mean cavitation appearance and the cavity length have been estimated, showing good correlation with the erosion zone. This also coincides with the locations of the maximum values of the standard deviation of cavitation presence. The dominant frequency of the ‘large-scale’ cavitation clouds has been estimated through FFT. Cloud collapse frequencies vary almost linearly between 200 and 2000 Hz as function of the cavitation number and the downstream pressure. It seems that the increase of the Reynolds number leads to a reduction of the collapse frequency; it is believed that this effect is due to the agglomeration of vortex cavities, which causes a decrease of the apparent frequency. The results presented here can be utilized for validation of relevant cavitation erosion models which are currently under development

Approximation of holomorphic mappings on strongly pseudoconvex domains

Let D be a relatively compact strongly pseudoconvex domain in a Stein manifold, and let Y be a complex manifold. We prove that the set A(D,Y), consisting of all continuous maps from the closure of D to Y which are holomorphic in D, is a complex Banach manifold. When D is the unit disc in C (or any other topologically trivial strongly pseudoconvex domain in a Stein manifold), A(D,Y) is locally modeled on the Banach space A(D,C^n)=A(D)^n with n=dim Y. Analogous results hold for maps which are holomorphic in D and of class C^r up to the boundary for any positive integer r. We also establish the Oka property for sections of continuous or smooth fiber bundles over the closure of D which are holomorphic over D and whose fiber enjoys the Convex approximation property. The main analytic technique used in the paper is a method of gluing holomorphic sprays over Cartan pairs in Stein manifolds, with control up to the boundary, which was developed in our paper "Holomorphic curves in complex manifolds" (Duke Math. J. 139 (2007), no. 2, 203--253)