28,782 research outputs found

    Two-dimensional negative donors in magnetic fields

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    A finite-difference solution of the Schroedinger equation for negative donor centers D^- in two dimensions is presented. Our approach is of exact nature and allows us to resolve a discrepancy in the literature on the ground state of a negative donor. Detailed calculations of the energies for a number of states show that for field strengths less than \gamma=0.117 a.u. the donor possesses one bound state, for 0.117<\gamma<1.68 a.u. there exist two bound states and for field strengths \gamma>1.68 a.u. the system possesses three bound states. Further relevant characteristics of negative donors in magnetic fields are provided.Comment: 7 pages, 1 figur

    Topological events on wave dislocation lines: birth and death of small loops, and reconnection

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    In three-dimensional space, a wave dislocation, that is, a quantized (optical) vortex or phase singularity, is a line zero of a complex scalar wavefunction. As a 'time' parameter varies, the topology of the vortex can change by encounter with a line of vanishing vorticity (curl of the current associated with the wavefunction). An isolated critical point of the field intensity, sliding along the zero-vorticity line like a bead on a wire, meets the vortex as it encounters the line, and so participates in the singular event. Local expansio n and gauge and coordinates transformations show that the vortex topology can change generically by the appearance or disappearance of a loop, or by the reconnection of branches of a pair of hyperbolas

    Physical Vacuum Properties and Internal Space Dimension

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    The paper addresses matrix spaces, whose properties and dynamics are determined by Dirac matrices in Riemannian spaces of different dimension and signature. Among all Dirac matrix systems there are such ones, which nontrivial scalar, vector or other tensors cannot be made up from. These Dirac matrix systems are associated with the vacuum state of the matrix space. The simplest vacuum system realization can be ensured using the orthonormal basis in the internal matrix space. This vacuum system realization is not however unique. The case of 7-dimensional Riemannian space of signature 7(-) is considered in detail. In this case two basically different vacuum system realizations are possible: (1) with using the orthonormal basis; (2) with using the oblique-angled basis, whose base vectors coincide with the simple roots of algebra E_{8}. Considerations are presented, from which it follows that the least-dimension space bearing on physics is the Riemannian 11-dimensional space of signature 1(-)& 10(+). The considerations consist in the condition of maximum vacuum energy density and vacuum fluctuation energy density.Comment: 19 pages, 1figure. Submitted to General Relativity and Gravitatio

    A GROOVE Solution for the BPMN to BPEL Model Transformation

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    In this paper we present a solution of a model transformation between two standard languages for business process modeling BPMN and BPEL, using the GROOVE tool set. GROOVE is a tool for graph transformations that uses directed, edge labelled simple graphs and the SPO approach [Ren04]. Given a graph grammar (G, P), composed of a start graph G and a set of production rules P, the tool allows to compute a labelled transition system (LTS) corresponding to all possible derivations in this grammar. The tool is freely available for download. The latest version and documentation can be found on the website http://sourceforge.net/projects/groove. The graph grammar presented here as well as detailed description of the sample realization to the case study is available in the attachment

    Time evolution of MX-80 bentonite geochemistry under thermo-hydraulic gradients

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    Indexación: Web of ScienceTwo 20-cm long columns of MX-80 bentonite compacted at a nominal dry density of 1.7 g/cm(3) with a water content of 17% were tested in thermo-hydraulic (TH) cells with the aim of simulating the conditions of a sealing material in a nuclear waste repository. On top of the columns a hydration surface simulated the host rock supplying groundwater and at the bottom a heater simulated the waste canister. The tests comprised two phases: a heating phase and a 'heating + hydration' phase. The temperatures at the ends of the columns were set during the last phase to 30 degrees C at the top and 140 degrees C at the bottom, respectively. The thermo-hydraulic treatment resulted in major changes along the bentonite columns. These changes led to significant gradients along the column with respect to the physical state (water content, dry density) and geochemistry of the bentonite. Smectite dissolution processes occurred. As a result, colloids were probably produced, particularly in the more hydrated areas. In the warmest part of the columns precipitation of carbonates took place, caused by their solubility decrease with temperature and the evaporation. The increase in water content reduced the ionic strength of the pore water in the more hydrated areas where species such as gypsum were dissolved. The solubilized ions were transported towards the bottom of the columns; Na+, Ca+, Mg2+ and SO42- moved at a similar rate and K+ and Cl- moved farther. These solubilized ions precipitated in the form of salts farther away along the columns as the test was longer. The TH treatment implied the loss of exchangeable positions in the smectite, particularly towards the heater. The cation exchange complex was also modified.http://www.ingentaconnect.com/content/minsoc/cm/2016/00000051/00000002/art0000

    On abolishing symmetry requirements in the formulation of a five-level selective harmonic elimination pulse-width modulation technique

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    Selective harmonic elimination pulse width modulation (SHE-PWM) techniques offer a tight control of the harmonic spectrum of a given voltage waveform generated by a power electronic converter along with a low number of switching transitions. These optimal switching transitions can be calculated through Fourier theory, and for a number of years quarter-wave and half-wave symmetries have been assumed when formulating the problem. It was shown recently that symmetry requirements can be relaxed as a constraint. This changes the way the problem is formulated, and different solutions can be found without a compromise. This letter reports solutions to the switching transitions of a five-level SHE-PWM when both the quarter- and half-wave symmetry are abolished. Only the region of high-modulation indices is reported since the low-modulation indices region requires a unipolar waveform to be realized. Selected simulation and experimental results are reported to show the effectiveness of the proposed method

    Scale-dependent stochastic quantization

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    Based on the wavelet-defined multiscale random noise proposed in [Doklady Physics 2003, v.48, 478], a multiscale version of the stochastic quantization procedure is considered. A new type of the commutation relations emerging from the multiscale decomposition of the operator-valued fields is derivedComment: Talk at FFP6 International Conference, Udine, Italy, Sep 2004. LaTeX, 7 pages, 5 eps figure

    Анатомы - лечащие врачи папства (обзор литературы)

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    Стаття присвячена анатомам, які були особистими лікарями Пап Римських у різний час: М. Р. Коломбо (1515-1559), Г. Б. Канано (1515-1579), Г. C. Аранзі (1530-1589), К. Варолій (1543- 1575), А. Чезальпіно (1525-1603), М. Мальпігі (1628-1694), Дж. M. Ланцізі (1654-1720) та Дж. Флайяні (1739-1808). Подається інформація про їх внесок у розвиток медицини та короткі біографічні данні. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/31507Статья посвящена анатомам, которые были лечащими врачами Пап Римских в разные годы: М. Р. Коломбо (1515-1559), Г. Б. Канано (1515-1579), Г. C. Аранзи (1530-1589), К. Варолий (1543- 1575), А. Чезальпино (1525-1603), М. Мальпиги (1628-1694), Дж. M. Ланцизи (1654-1720) и Дж. Флайяни (1739-1808). Рассказывается об их вкладе в развитие медицины и короткие биографические данные. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/31507Article is about anatomists, who were papal physicians: M.R. Colombo (c.1515-1559), G.B. Canano (1515-1579), G.C. Aranzi (1530-1589), C. Varolio (1543-1575), A. Cesalpino (1525- 1603), M. Malpighi (1628-1694), G.M. Lancisi (1654-1720) and G. Flaiani (1739-1808). Their contribution into anatomy and brief biographical information are given. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3150
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