Orthotropic rotation-free thin shell elements

A method to simulate orthotropic behaviour in thin shell finite elements is proposed. The approach is based on the transformation of shape function derivatives, resulting in a new orthogonal basis aligned to a specified preferred direction for all elements. This transformation is carried out solely in the undeformed state leaving minimal additional impact on the computational effort expended to simulate orthotropic materials compared to isotropic, resulting in a straightforward and highly efficient implementation. This method is implemented for rotation-free triangular shells using the finite element framework built on the Kirchhoff--Love theory employing subdivision surfaces. The accuracy of this approach is demonstrated using the deformation of a pinched hemispherical shell (with a 18{\deg} hole) standard benchmark. To showcase the efficiency of this implementation, the wrinkling of orthotropic sheets under shear displacement is analyzed. It is found that orthotropic subdivision shells are able to capture the wrinkling behavior of sheets accurately for coarse meshes without the use of an additional wrinkling model.Comment: 10 pages, 8 figure

Tokolyse bei vorzeitiger Wehentätigkeit

Zusammenfassung : Im September 2006 wurde die Leitlinie 015/025 "Medikamentöse Wehenhemmung bei drohender Frühgeburt" (http://www.dggg.de, http://www.awmf-online.de) publiziert. Sie zeigt den Korridor auf, innerhalb dessen die Verwendung von Tokolytika bei vorzeitiger Wehentätigkeit dem derzeitigen Stand der Wissenschaft und der sog. guten klinischen Praxis entspricht. Fenoterol, Atosiban, Indometacin und Nifedipin sind äquieffektiv, unterscheiden sich aber im Nebenwirkungsprofil, Kontraindikationen, Kosten und Zulassung. Erläutert werden die Empfehlungen, zusammengefasst werden die wesentlichen Ziele der medikamentösen Wehenhemmung: Durchführung der Lungenreifeprophylaxe bei drohender Frühgeburt, Schwangerschaftsverlängerung bei vorübergehenden Ursachen vorzeitiger Wehentätigkeit (z.B. Durchführung einer Cerclage, Pyelonephritis) sowie Ermöglichung des Transportes der Schwangeren in ein Perinatalzentru

Collapse of orthotropic spherical shells

We report on the buckling and subsequent collapse of orthotropic elastic spherical shells under volume and pressure control. Going far beyond what is known for isotropic shells, a rich morphological phase space with three distinct regimes emerges upon variation of shell slenderness and degree of orthotropy. Our extensive numerical simulations are in agreement with experiments using fabricated polymer shells. The shell buckling pathways and corresponding strain energy evolution are shown to depend strongly on material orthotropy. We find surprisingly robust orthotropic structures with strong similarities to stomatocytes and tricolpate pollen grains, suggesting that the shape of several of Nature's collapsed shells could be understood from the viewpoint of material orthotropy.Comment: 7 pages, 5 figure

Subdivision Shell Elements with Anisotropic Growth

A thin shell finite element approach based on Loop's subdivision surfaces is proposed, capable of dealing with large deformations and anisotropic growth. To this end, the Kirchhoff-Love theory of thin shells is derived and extended to allow for arbitrary in-plane growth. The simplicity and computational efficiency of the subdivision thin shell elements is outstanding, which is demonstrated on a few standard loading benchmarks. With this powerful tool at hand, we demonstrate the broad range of possible applications by numerical solution of several growth scenarios, ranging from the uniform growth of a sphere, to boundary instabilities induced by large anisotropic growth. Finally, it is shown that the problem of a slowly and uniformly growing sheet confined in a fixed hollow sphere is equivalent to the inverse process where a sheet of fixed size is slowly crumpled in a shrinking hollow sphere in the frictionless, quasi-static, elastic limit.Comment: 20 pages, 12 figures, 1 tabl

Half-Life of 14^{14}O

We have measured the half-life of $^{14}$O, a superallowed $(0^{+} \to 0^{+})$ $\beta$ decay isotope. The $^{14}$O was produced by the $^{12}$C($^{3}$He,n)$^{14}$O reaction using a carbon aerogel target. A low-energy ion beam of $^{14}$O was mass separated and implanted in a thin beryllium foil. The beta particles were counted with plastic scintillator detectors. We find $t_{1/2} = 70.696\pm 0.052$ s. This result is $1.5\sigma$ higher than an average value from six earlier experiments, but agrees more closely with the most recent previous measurement.Comment: 10 pages, 5 figure

Energy-efficiency improvements for optical access

This article discusses novel approaches to improve energy efficiency of different optical access technologies, including time division multiplexing passive optical network (TDM-PON), time and wavelength division multiplexing PON (TWDM-PON), point-to-point (PTP) access network, wavelength division multiplexing PON (WDM-PON), and orthogonal frequency division multiple access PON (OFDMA-PON). These approaches include cyclic sleep mode, energy-efficient bit interleaving protocol, power reduction at component level, or frequency band selection. Depending on the target optical access technology, one or a combination of different approaches can be applied

Respect for Form as Substance in U.S. Taxation of International Trusts

...we might decide that the attribution rule should not be applied so broadly, or so automatically. But how would such a system be devised by regulation? The attribution rule could be applied to trusts in which the discretion of the trustee is very limited and the beneficial interests so clearly ascertainable that the trust is, for all practicable purposes, transparent. That is, however, only a small universe of cases. This leads to the further conclusion that the attribution rule has to be applied based on a facts and circumstances determination of the beneficial interest in each case. Yet that seems the antithesis of an attribution rule, and the factual inquiry would necessarily require a thorough examination of governing trust law and corporate law in almost every case. That process would be difficult enough if it were Delaware law at issue. Applying non-U.S. trust law and non-U.S. corporate law would be much more cumbersome. Assessing the element of tax avoidance motivation in the structure in order to test the bona fide nature of the trustee\u27s role would further add to the burden of the inquiry. The search for a satisfactory system seems fruitless

Pulse shape analysis in segmented detectors as a technique for background reduction in Ge double-beta decay experiments

The need to understand and reject backgrounds in Ge-diode detector double-beta decay experiments has given rise to the development of pulse shape analysis in such detectors to discern single-site energy deposits from multiple-site deposits. Here, we extend this analysis to segmented Ge detectors to study the effectiveness of combining segmentation with pulse shape analysis to identify the multiplicity of the energy deposits.Comment: 12 pages, 13 figures, will be submitted to NI

Acute Polyhydramnios Complicating Twin Pregnancies

Acute polyhydramnios in the second trimestr is a typical complication in monozygous twin pregnancies. It is caused by a feto-fetal transfusion with anemia on the donor and polycytemia on the recipient twin. Contrary to the chronic hydramnios, there is no increase in malformations. In view of the high mortality rate (100%, according to most authors), the clinical management has to be reconsidered. During the years 1979 to 1983, 10 cases of acute polyhydramnios have been observed at the University Hospital in Zurich. This corresponds to an incidence of 9% in our twin population. All cases investigated were MZ twin pregnancies. With the exception of one patient, who underwent an abortion, all women were hospitalized, had bed rest and received recurrent removals of amniotic fluid and prophylactic tocolysis. The mean gestational age at the time of diagnosis was 23 4/7 weeks and at delivery 30 3/7 weeks. In two cases - one of which is presented in detail - with an unintentional puncture of a placental vessel, the recurrence of the hydramnios did not appear. Eight of 18 newborns survived. No malformations were found. Bed rest, tocolysis and recurrent amniocenteses seem to have a positive influence on the prolongation and outcome of the gestation in acute polyhydramnio