Stress concentration and effective mechanical properties of plates with doubly periodic systems of enforced holes

Використовуючи модифікацію методу граничних елементів, розглянуто подвійно періодичні системи отворів довільної форми із тонкими замкненими та розімкненими накладками. Обчислено концентрацію напружень та ефективні механічні характеристики таких композицій для різних відстаней між круговими отворами, відносних жорсткостей накладки та характеристик анізотропії матеріалу матриці.Modern high-tech devices and machines are designed using mainly composite materials, since the latter are lightweight and provide desired rigidity and durability. A lot of attention is paid to the usage of perforated plates, in which edges of the holes are enforced by thin overlays. Therefore, this study is concerned with the analysis of doubly periodic sets of enforced holes. Based on the previously developed boundary element technique for doubly periodic problems and models of thin overlays, the efficient approach is developed for studying effective properties and stress concentration in perforated plates with enforced holes. The enforcements can be both closed and opened. First an infinite plate with doubly periodic fully enforced holes is considered. With the increase of the relative rigidity of an overlay, effective elastic moduli of the perforated plate expectedly increase. The smaller is the distance between holes the higher is the increase in effective elastic moduli. It is clear, that in the case of holes without enforcement (or an overlay of a very small rigidity) the closer are the holes, the lower are effective properties of the plate. For an anisotropic plate with holes the increase in rigidity of isotropic overlays gives different change in elastic moduli in different directions. The growth of the effective modulus in a direction perpendicular to fibers is the highest. The thinner is an overlay the more evident is an influence of its bending not only on the effective properties of the composite, but also on the maximal Mises stress in it. In particular, local maxima of Mises stress increases with the decrease of the thickness of enforcements. With the increase in the relative rigidity of overlays the longitudinal force and bending moment in each overlay also increase. The higher is the distance between holes the higher are the force and bending moment. This behavior should be accounted for during the design of perforated composite plates. Also the plate with a doubly periodic set of holes with a square lattice is considered. The edge of each hole is conditionally divided into six symmetric and identical parts, three of which are enforced with overlays. For the considered geometrical configuration of the opened reinforcements one of the effective moduli practically does not change with an increase in the rigidity of overlays. At the same time this increase significantly influences another elastic modulus and also effective shear modulus. This behavior is explained by the fact that selected arrangement of overlays “works” for tension/compression in one direction better than in other. Therefore, the usage of opened overlays allows changing effective properties of the perforated plate in the given direction, thus, establishing the desired anisotropy of the material. The numerical data obtained using proposed boundary element approach was verified by the commercial finite element software. Relative deviation of both approaches did not exceed 3 %. However, the advantages of the proposed approach are obvious, since it requires only boundary mesh, and no periodic boundary conditions are required to imposed, as they are already incorporated in the boundary integral equations used

A holomorphic representation of the Jacobi algebra

A representation of the Jacobi algebra $\mathfrak{h}_1\rtimes \mathfrak{su}(1,1)$ by first order differential operators with polynomial coefficients on the manifold $\mathbb{C}\times \mathcal{D}_1$ is presented. The Hilbert space of holomorphic functions on which the holomorphic first order differential operators with polynomials coefficients act is constructed.Comment: 34 pages, corrected typos in accord with the printed version and the Errata in Rev. Math. Phys. Vol. 24, No. 10 (2012) 1292001 (2 pages) DOI: 10.1142/S0129055X12920018, references update

Pamela: development of the RF system for a non-relativistic non-scaling FFAG

The PAMELA project(Particle Accelerator For MEdical Applications) currently consists of the design of a particle therapy facility. The project, which is in the design phase, contains Non-Scaling FFAG, particle accelerator capable of rapid beam acceleration, giving a pulse repetition rate of 1kHz, far beyond that of a conventional synchrotron. To realise the repetition rate, a key component of the accelerator is the rf accelerating system. The combination of a high energy gain per turn and a high repetition rate is a significant challenge. In this paper, options for the rf system of the proton ring and the status of development are presented

Accelerator system for the PRISM based muon to electron conversion experiment

The next generation of lepton flavor violation experiments need high intensity and high quality muon beams. Production of such beams requires sending a short, high intensity proton pulse to the pion production target, capturing pions and collecting the resulting muons in the large acceptance transport system. The substantial increase of beam quality can be obtained by applying the RF phase rotation on the muon beam in the dedicated FFAG ring, which was proposed for the PRISM project.This allows to reduce the momentum spread of the beam and to purify from the unwanted components like pions or secondary protons. A PRISM Task Force is addressing the accelerator and detector issues that need to be solved in order to realize the PRISM experiment. The parameters of the required proton beam, the principles of the PRISM experiment and the baseline FFAG design are introduced. The spectrum of alternative designs for the PRISM FFAG ring are shown. Progress on ring main systems like injection and RF are presented. The current status of the study and its future directions are discussed.Comment: Studies performed within the PRISM Task Force initiativ

Raman fingerprints of ultrasmall nanodiamonds produced from adamantane

The synthesis of ultrasmall (2-5 nm) nanodiamonds purely from adamantane at pressure of 12 GPa is reported. Their structural features have been studied by Raman spectroscopy. The unusual vibration band containing a number of pronounced maxima at about 1147, 1245, 1344, and 1456 cm-1 was detected in Raman spectra. The band is confidently identified with the bending vibrational modes of CHx groups terminating the nanodiamonds surface. Excessively intense mode at 1344 cm-1 is explained by its coupling with the 1328 cm-1 diamond phonons. The Raman band found is proposed to be used for express recognition of ultrasmall nanodiamonds produced from adamantane and other hydrocarbons with a high hydrogen content. Moreover, polarized CH bonds on a diamond surface are sensitive to environmental conditions. This opens up opportunities for using the diamond produced from adamantane as ultrasmall nanosensors in biology, chemistry, and medicineComment: 12 pages, 6 figure

Conceptual design of a nonscaling fixed field alternating gradient accelerator for protons and carbon ions for charged particle therapy

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.The conceptual design for a nonscaling fixed field alternating gradient accelerator suitable for charged particle therapy (the use of protons and other light ions to treat some forms of cancer) is described.EPSR

‘Sons of athelings given to the earth’: Infant Mortality within Anglo-Saxon Mortuary Geography

FOR 20 OR MORE YEARS early Anglo-Saxon archaeologists have believed children are underrepresented in the cemetery evidence. They conclude that excavation misses small bones, that previous attitudes to reporting overlook the very young, or that infants and children were buried elsewhere. This is all well and good, but we must be careful of oversimplifying compound social and cultural responses to childhood and infant mortality. Previous approaches have offered methodological quandaries in the face of this under-representation. However, proportionally more infants were placed in large cemeteries and sometimes in specific zones. This trend is statistically significant and is therefore unlikely to result entirely from preservation or excavation problems. Early medieval cemeteries were part of regional mortuary geographies and provided places to stage events that promoted social cohesion across kinship systems extending over tribal territories. This paper argues that patterns in early Anglo-Saxon infant burial were the result of female mobility. Many women probably travelled locally to marry in a union which reinforced existing social networks. For an expectant mother, however, the safest place to give birth was with experience women in her maternal home. Infant identities were affected by personal and legal association with their mother’s parental kindred, so when an infant died in childbirth or months and years later, it was their mother’s identity which dictated burial location. As a result, cemeteries central to tribal identities became places to bury the sons and daughters of a regional tribal aristocracy

Glucosinolates in leaves of Moringa species grown and disseminated in Niger

Moringa leaves rank first among the most widely consumed leafy vegetables in Niger. Glucosinolate contents in leaves of five accessions of three Moringa species (M. oleifera, M. stenopetala and M. peregrina) ranged from 2.65 μmol/g in old leaves of M. stenopetala (Ethiopian-1) to 28.62 μmol/g in young leaves of M. oleifera (ICG-42). An Indian introduction, PKM-1 (M. oleifera) gave maximum leaf yield (7.5 t/ha) and had maximum consumer preference than the local (M. oleifera) and Ethiopian-1 (M. stenopetala) genotypes. Large scale dissemination of PKM-1 and use of other species under different production systems are described