Efficient semi-analytical integration of vortex sheet influence in 3D vortex method

The original numerical scheme is developed for vortex sheet intensity computation for 3D incompressible flow simulation using meshless Lagrangian vortex methods. It is based on tangential components of the velocity boundary condition satisfaction on the body surface instead of widespread condition for normal components. For the body triangulated surface the corresponding integral equation is approximated by the system of linear algebraic equations, which dimension is doubled number of triangular panels. Vortex layer intensity on the panels assumed to be piecewise-constant. The coefficients of the matrix are expressed through double integrals over the influ- ence and control panels. When these panels have common edge or common vertex these integrals become improper. In order to compute them it is necessary to exclude the sin- gularities, i.e., to split the integrals into regular and singular parts. Regular parts are expressed by smooth functions, so they can be integrated numerically with high precision by using Gaussian quadrature formulae. For singular parts exact analytical integration formulae are derived. The developed approach allows to raise significantly the accuracy of vortex layer in- tensity computation in vortex method for flow simulation around arbitrary 3D bodies. The test problem of flow simulation around the sphere is considered. The exact analyt- ical solution is known for it, and the developed numerical scheme provides more accurate results in comparison with ‘classical’ 3D vortex method, especially when non-uniform un- structured triangular meshes are used for bodies surface representation. It allows to use arbitrary triangular mesh on body surface and to refine mesh near sharp edges, what is especially important for flow simulation around bodies with complicated geometry

Lagrangian vortex loops method for hydrodynamic loads computation in 3D incompressible flows

A new approach is developed for incompressible 3D flow simulation around bodies by Lagrangian vortex method. Closed vortex loops are considered as vortex elements, which are generated on all the body surface and provide the satisfaction of the no-slip boundary condition. The procedure of double layer potential density reconstruc- tion is considered, which consists of two steps. Firstly, the integral equation with respect to vortex sheet intensity is solved, which expresses the equality between the tangential components of flow velocity limit value and the body surface velocity. It is solved by using Galerkin approach. Secondly, the least-squares procedure is implemented, which permits to find nodal values of the double layer potential density. It is shown that the developed algorithm makes it possible to improve significantly the quality of solution for the bodies with very complicated geometry and low-quality surface meshes. The combination of this approach with vortex wake modelling with vortex loops, permits to simulate unsteady flows with higher resolution with acceptable numerical complexity. It can be useful for CFD applications and visual effects reproducing in computer graphics

Accurate solution of the boundary integral equation in 2d lagrangian vortex method for flow simulation around curvilinear airfoils

The problem of numerical solution of the boundary integral equation is considered for 2D case. Viscous vortex domains (VVD) method is used for flow simulation, so vorticity is generated on the whole surface line of the airfoil, and there are a lot of vortex elements close to the airfoil. The aim of the research is to provide high accuracy of numer- ical solution of the integral equation; at the same time the computational complexity of the numerical algorithm should be at rather low level. The third-order accuracy numerical scheme, based on piecewise-quadratic solution representation on the curvilinear panels is presented, approximate analytic expressions are obtained for the matrix coefficients. These schemes work perfect in the case of potential flow simulation, when vorticity is absent and also when vortex elements are placed rather far from the airfoil surface line. A trivial way to the accuracy improvement for the closely located vortices, which consists in extremely fine surface line discretization, leads to unacceptably high numerical complexity of the algorithm. This problem is solved by developing semi-analytical correcti- on procedure which makes it possible to achieve high accuracy at extremely coarse surface line discretization. For example, in the model problem of flow simulation around elliptical airfoil with 2:1 semiaxes ratio only 20 panels are required to achieve the error level less than 1 % for arbitrary position of the vortex element in the flow

Policies and reporting guidelines for small biopsy specimens of mediastinal masses

目前，胸腺恶性肿瘤治疗方案大多是根据术\ud 后病理确定，然而，多数临床治疗决策需要在术前\ud 通过活检小标本的病理报告来制定。所以，术前活\ud 检小标本的正确获取和病理解读对治疗决策的制定\ud 显得非常重要[1]。这些标本包括细针活检标本，带\ud 芯穿刺活检标本和手术切取活检标本[2-7]。由于胸\ud 腺肿瘤的病理诊断对组织的获取方法和获取量都有较高\ud 的要求，加之对病理的描述也没有统一的标准，使得小\ud 标本在诊断胸腺瘤方面存在诸多问题。为此，ITMIG在\ud 病理科医生和外科医生回顾相关文献和提出初步建议的\ud 基础上，经集体讨论制定了活检规范操作流程，提出了\ud 对纵隔肿物小活检标本处理和病理报告的建议。旨在为\ud 术前患者的治疗提供一个统一和具有循证医学证据的方\ud 法；同时，将有利于全球数据之间的比较和开展合作研\ud 究，充分利用医疗资源

Performance correlation between YBa2Cu3O7-δ coils and short samples for coil technology development

A robust fabrication technology is critical to achieve the high performance in YBa Cu O (YBCO) coils as the critical current of the brittle YBCO layer is subject to the strain-induced degradation during coil fabrication. The expected current-carrying capability of the magnet and its temperature dependence are two key inputs to the coil technology development. However, the expected magnet performance is not straightforward to determine because the short-sample critical current depends on both the amplitude and orientation of the applied magnetic field with respect to the broad surface of the tape-form conductor. In this paper, we present an approach to calculate the self-field performance limit for YBCO racetrack coils at 77 and 4.2 K. Critical current of short YBCO samples was measured as a function of the applied field perpendicular to the conductor surface from 0 to 15 T. This field direction limited the conductor critical current. Two double-layer racetrack coils, one with three turns and the other with 10 turns, were wound and tested at 77 and 4.2 K. The test coils reached at least 80% of the expected critical current. The ratio between the coil critical currents at 77 and 4.2 K agreed well with the calculation. We conclude that the presented approach can determine the performance limit in YBCO racetrack coils based on the short-sample critical current and provide a useful guideline for assessing the coil performance and fabrication technology. The correlation of the coil critical current between 77 K and 4.2 K was also observed, allowing the 77 K test to be a cost-effective tool for the development of coil technology. 2

Experimental Demonstration of Nanolaser with sub-μ\muA Threshold Current

We demonstrate a photonic crystal nanolaser exhibiting an ultra-low threshold of 730 nA at telecom wavelengths. The laser can be directly modulated at 3 GHz at an energy cost of 1 fJ/bit. This is the lowest threshold reported for any laser operating at room temperature and facilitates low-energy on-chip links.Comment: 3 pages with 2 figure

Characterization of insulating coatings for wind-and-react coil fabrication

Electrical insulation breakdown between conductor and coil parts and structures is a limiting factor in the performance of high-field magnets. We have evaluated various insulation coatings for possible application in both Nb Sn and Bi-2212 coil fabrication. Such coatings must be robust to maintain structural integrity and provide adequate voltage standoff after the wind-and-react coil fabrication process. Such processes are characterized by reaction temperatures of 650°C in an inert atmosphere for Nb Sn and 890°C in a pure oxygen atmosphere for Bi-2212, and down to cryogenic temperatures when coils are in service. We present a method of testing standardized samples and report the performance characteristics of oxide layers produced (or applied) by plasma-spray, surface conversion, and "paintable" coatings in common areas of voltage breakdown in coil parts. We also address material compatibility and durability during high-temperature heat treatment and cryogenic shock. Suitable coatings selected in the testing process will be instrumental in improving the performance of future wind-and-react coils. © 2014 AIP Publishing LLC. 3

Why pinning by surface irregularities can explain the peak effect in transport properties and neutron diffraction results in NbSe2 and Bi-2212 crystals?

The existence of a peak effect in transport properties (a maximum of the critical current as function of magnetic field) is a well-known but still intriguing feature of type II superconductors such as NbSe2 and Bi-2212. Using a model of pinning by surface irregularities in anisotropic superconductors, we have developed a calculation of the critical current which allows estimating quantitatively the critical current in both the high critical current phase and in the low critical current phase. The only adjustable parameter of this model is the angle of the vortices at the surface. The agreement between the measurements and the model is really very impressive. In this framework, the anomalous dynamical properties close to the peak effect is due to co-existence of two different vortex states with different critical currents. Recent neutron diffraction data in NbSe2 crystals in presence of transport current support this point of view

Micrografía cuantitativa y perfiles de HPLC y FTIR de Melissa officinalis y Nepeta cataria (Lamiaceae) de Argentina

Melissa officinalis L., so called "Melissa" or "Toronjil", is a perennial aromatic herb, whose leaves are used in traditional medicine as a carminative, digestive and sedative, both in simple as in mixtures. Meanwhile, Nepeta cataria L., commonly called "Cat mint" or "Toronjil", with some similar properties, often replacing M. officinalis in the market, although their chemical composition is not completely matched, and contains an iridoid potentially toxic (nepetalactone). It is therefore necessary to establish diacritic parameters to differentiate these species, both at crude drug level, mixtures and extracts. Samples from various sources in Argentina were studied and documental specimens are preserved in the Herbarium UNSL. Anatomical sections were analyzed, and quantitative micrographic parameters were obtained, together with HPLC and FTIR spectra from methanolic and aqueous lyophilized extracts. Significant differences were detected in the prevailing smell foliage, morphology of leaves and inflorescences, trichomata type, palisade ratio, veinlet termination number, rosmarinic acid concentration (with distinctive HPLC profiles), and the CO/CH relationships obtained by FTIR from the extracts, that together allow adequate differentiation of both drugs, even when they were ground or powdered.Melissa officinalis L., llamada vulgarmente "melisa" o "toronjil", es una hierba perenne, aromática, cuyas hojas son empleadas en medicina popular como carminativo, digestivo y sedante, tanto en droga simple como en asociación. Por su parte Nepeta cataria L., llamada vulgarmente "menta de los gatos" y también "toronjil", con algunas propiedades similares, sustituye con frecuencia a M. officinalis en el mercado, aunque su composición química no es del todo coincidente y contiene un iridoide potencialmente tóxico (nepetalactona). Por ello es necesario establecer parámetros diacríticos para diferenciar ambas especies, a nivel de droga cruda, mezclas y extractos. Fueron estudiados especímenes de diversas procedencias en Argentina, y los ejemplares documentales son conservados en el Herbario UNSL. Se analizaron cortes anatómicos, se registraron los parámetros micrográficos cuantitativos y se obtuvieron espectros de HPLC y FTIR a partir de extractos metanólicos y acuosos liofilizados. Fueron detectadas diferencias significativas entre ambas especies en cuanto al aroma prevaleciente del follaje, la exomorfología de hojas e inflorescencias, los tipos tricomáticos, la relación de empalizada, el número de terminales de nerviación, la concentración de ácido rosmarínico (con perfiles HPLC distintivos), y las relaciones CO/CH obtenidas por FTIR a partir de los extractos, caracteres que en conjunto permiten una diferenciación adecuada de ambas drogas, aún cuando se presenten molidas o reducidas a polvo.Fil: Petenatti, Marta E.. Universidad Nacional de San LuisFil: Gette, María A.. Universidad Nacional de San LuisFil: Camí, Gerardo E.. Universidad Nacional de San LuisFil: Popovich, Mariana C.. Universidad Nacional de San LuisFil: Marchevsky, Eduardo J.. Universidad Nacional de San LuisFil: Del Vitto, Luis A.. Universidad Nacional de San LuisFil: Petenatti, Elisa M.. Universidad Nacional de San Lui

V-I characteristics in the vicinity of order-disorder transition in vortex matter

The shape of the V-I characteristics leading to a peak in the differential resistance r_d=dV/dI in the vicinity of the order-disorder transition in NbSe2 is investigated. r_d is large when measured by dc current. However, for a small Iac on a dc bias r_d decreases rapidly with frequency, even at a few Hz, and displays a large out-of-phase signal. In contrast, the ac response increases with frequency in the absence of dc bias. These surprisingly opposite phenomena and the peak in r_d are shown to result from a dynamic coexistence of two vortex matter phases rather than from the commonly assumed plastic depinning.Comment: 12 pages 4 figures. Accepted for publication in PRB rapi