Physical space description of decorated quasicrystals

In this paper the systematic method of dealing with the arbitrary decorations of quasicrystals is presented. The method is founded on the average unit cell formalism and operates in the physical space only, where each decorating atom manifests itself just by an additional component of the displacement density function in the average unit cell. Such approach allows us to use almost all classical crystallography algorithms for structure refining based on experimental data and may meaningly decrease the number of parameters which have to be fit. Further help for such analysis may be the use of proposed recently average Patterson function, here applied to decorated sets. As an example we present a description of a class of decorated quasicrystals based on Sturmian sequence of two interatomic spacings: we calculate explicitly structure factor, the shape of average Patterson function and give an algorithm for pattern analysis.Comment: 17 pages, 5 figure

Life times and chirality of spin-waves in antiferromagnetic and ferromagnetic FeRh: time depedent density functional theory perspective

The study of the spin excitations in antiferromagnetic (AFM) and ferromagnetic (FM) phases of FeRh is reported. We demonstrate that although the Fe atomic moments are well defined there is a number of important phenomena absent in the Heisenberg description: Landau damping of spin waves, large Rh moments induced by the AFM magnons, the formation of the optical magnons terminated by Stoner excitations. We relate the properties of the spin-wave damping to the features of the Stoner continuum and compare the chirality of the spin excitations in AFM, FM and paramagnetic (PM) systems.Comment: 5 pages, 5 figures, submitted to PR

Periodic diffraction patterns for 1D quasicrystals

A simple model of 1D structure based on a Fibonacci sequence with variable atomic spacings is proposed. The model allows for observation of the continuous transition between periodic and non-periodic diffraction patterns. The diffraction patterns are calculated analytically both using ``cut and project'' and ``average unit cell'' methods, taking advantage of the physical space properties of the structure.Comment: 17 pages, 6 figures, the language was polished. References added: [18], [23] & [28]. Paper accepted to Acta Physica Polonica

Finite element models for predicting crack growth characteristics in composite materials

Two dimensional and quasi-three dimensional, linear elastic finite element models for the prediction of crack growth characteristics, including crack growth direction, in laminated composite materials are presented. Mixed mode crack growth in isotropic materials, unidirectional and laminated composites is considered. The modified crack closure method is used to predict the applied load level for crack extension and two failure theories, modifications of the point stress and the Hashin failure criteria, are proposed to predict the direction of crack extension in composites. Comparisons are made with the Tsai-Wu failure criterion and the Sih strain energy density criterion as well as with experimental results. It is shown that the modified versions of point stress and Hashin criteria compare well with experiment

First-principles perspective on magnetic second sound

The fluctuations of the magnetic order parameter, or longitudinal spin excitations, are investigated theoretically in the ferromagnetic Fe and Ni as well as in the antiferromagnetic phase of the pnictide superconductor FeSe. The charge and spin dynamics of these systems is described by evaluating the generalized charge and spin density response function calculated from first-principles linear response time dependent density functional theory within adiabatic local spin density approximation. We observe that the formally non-interacting Kohn-Sham system features strong coupling between the magnetization and charge dynamics in the longitudinal channel and that the coupling is effectively removed upon the inclusion of the Coulomb interaction in the charge channel and the resulting appearance of plasmons. The longitudinal spin fluctuations acquire a collective character without the emergence of the Goldstone boson, similar to the case of paramagnon excitations in non-magnetic metals like Pd. In ferromagnetic Fe and Ni the longitudinal spin dynamics is governed by interactions between low-energy intraband electron-hole pairs while in quasi two dimensional antiferromagnet FeSe it is dominated by the interband transitions with energies of the order of exchange splitting. In the later material, the collective longitudinal magnetization fluctuations feature well defined energies and long life times for small momenta and appear below the particle-hole continuum. The modes become strongly Landau-damped for growing wave-vectors. We relate our theoretical findings to existing experimental spin-polarized electron energy loss spectroscopy results. In bulk bcc Fe, the longitudinal magnetic modes appear above the typical energies of transverse spin-waves, have energies comparable with the Stoner spin-flip excitation continuum, and are order of magnitude less energetic than the charge dynamics.Comment: 20 pages with 13 color figure

From Crowdsourcing to Citizensourcing

The dynamic development of the outsourcing sector led the definition and evolution of hitherto unusual or niche areas of operations. Accordingly, the companies are looking for strategies and solutions to obtain tangible results. An example of the strategy based on the business website and based on external sources of knowledge are crowdsourcing and citizensourcing allowing the involvement of a wide range of stakeholders and to create and achieve a new spectrum of activity.Dynamiczny rozwój sektora outsourcingowego doprowadził do zdefiniowania i ewolucji dotychczas nietypowych lub niszowych obszarów działalności. W związku z tym firmy poszukują strategii i rozwiązań umożliwiających uzyskiwanie konkretnych wyników. Przykładem strategii opartej na narzędziach internetowych i zewnętrznych źródłach wiedzy są crowdsourcing i citizensourcing, które umożliwiają zaangażowanie szerokiej gamy interesariuszy oraz tworzenie i osiąganie nowego zakresu działalności

Lexical Approach to Cultural Aspects of Death in the Old Frisian Writings

Death as a phenomenon was in Germanic culture both feared, celebrated and respected. Personalized, it was supposed to take the deceased to the afterlife world. That is why the way somebody lost his life or the circumstances of his death were very significant. After the introduction of Christianity, death was treated as the end of the worldly life and the beginning of the eternal life in haven or eternal damnation. Church’s teachings were reflected in the mediaeval legal codes, which tried to keep a tight rein on the society and regulate the earlier dominating tribal laws. The main task of the study constitutes the linguistic analysis of the notion of death on the basis of the Old Frisian texts. The first part of the paper focuses on the cultural treatment of death by Frisians in the past. Here, the death as an ultimate and natural end of life is counterpoised to the death that is conceived as a consequence of punishment or murder. The second part of the paper provides the analysis of the vocabulary taken from the texts included in two manuscripts, the Rüstring and Brokmer Manuscript (both edited by Buma (1949 – 1963)), connected with the account of death. Here, the preference for the choice of lexical means which are present in these texts is detected and estimated. Expressions referring to death as a punishment are compared with those connected the natural decease of family members or nobilities

Testing of nanostructure within active carbons particles

Activation process with water-steam of carbonaceous precursors leading to the production of active carbons is noncatalytic reaction, which takes place in a gas-solid system. Transport phenomena within porous particles depend strongly on the internal structure of the particles. Not too much experimental work has been done to understand how the tortuosity and hence effective diffusivity within the pore space are affected by the pore size distribution, pore shape, and nanostructure (micro- and mesopores). The activating gas in the process is thought to penetrate the particle as a result of diffusion accompanied by chemical reactions, the gas concentration decreasing with distance from the external surface. Moreover, the activation reaction is endothermic and this leads to temperature decrease in the reaction zone while heat energy flows slowly to the deeper layers of the particle. Because of these factors, the activating of carbonaceous substance is a function particle radius. Active carbons (A-type, Poland) and N (Norit 2RL type, Holland) were subjected to abrasion in a spouted bed. A method of successive removal of the layers from the carbon particles was applied. A diagram of the experimental equipment is shown in Fig 1 For core samples of active carbons so obtained, physicochemical properties were determined from densities measurements and by adsorption technique. It has been shown found that there exists a correlation between the properties of samples obtained via abrasion technique, to the position within the active carbon particles. Anisotropy of nanostructure is due to conversion of the carbonaceous substance which reduces radially from the outer surface the particle to its inner core

Frisians in Roman Britain in the Light of the Available Epigraphic Sources

The paper discusses the notion of Frisian presence in both the Roman Britain and the Roman army. It investigates the available Latin sources, which provide us with certain amount of information concerning Frisians’ role, significance and distribution during the period of the Roman ruling. Finally, the author tries, on the basis of the available resources, to draw some conclusions regarding the perception of Frisians by both Romans and Brits. All the analyzed materials are taken from the extensive database of the Roman Inscriptions that are to be found in Britain, which is an invaluable source of knowledge of the military tradition of the Roman Empire and the units serving on the Isles. The paper aims at showing the importance of Frisian participation in both Roman invasion and the Adventus Saxonum. It tries to shed a new light on the perception of not only Frisians but all the Germanic tribes