A rotation-free beam element for beam and cable analyses

The rotation-free or RF element method represents a non-conventional finite element method in which the rotations are not used as dofs and the element interpolation domains are overlapping. Its obvious advantage is that the complication of finite rotations can be avoided. In this paper, the relatively unexplored RF plane beam element recently formulated by the authors in the course of developing a RF triangle for thin-shell analyses is revisited. Comparing with other RF plane beam elements, the present one is simple and physical yet its accuracy remains competitive. Using a corotational approach and the small strain assumption, its tangent bending stiffness matrix can be approximated by a constant matrix which does not require updating in geometric nonlinear analyses. The element is here extended to spatial cable analyses in which the torsional stiffness can often be neglected and the sectional properties are isotropic. Under the same nodal distributions, it is seen that the present element can tolerate much larger load increment and time step under static and dynamic analyses, respectively, than the two-node thin beam finite element.postprin

Drape simulation using solid-shell elements and adaptive mesh subdivision

In this paper, 4-node quadrilateral and 3-node triangular solid-shell elements are applied to drape simulations. With locking issues alleviated by the assumed natural strain method and plane-stress enforcement, static and dynamic drape problems are attempted by the quadrilateral element. If the drape is deep and the mesh density is inadequate, non-realistic sharp folds are predicted due to the non-physical interpenetration of top and bottom element surfaces. To avoid the interpenetration, a reversible adaptive subdivision based on the 1–4 splitting method is developed. To ensure displacement compatibility among elements at different subdivision levels, macro-transition elements are formed by quadrilateral and triangular solid-shell elements. To reduce the dynamic oscillation induced by newly inserted nodes, the discrete Kirchhoff condition is employed to determine the related nodal variables. Dynamic drape examples using adaptive meshing are presented. It can be seen that the predictions look realistic and deep drapes can be predicted with the interpenetration avoided yet the required number of nodes can be kept relatively small.postprin

Stabilized Plane and Axisymmetric Lobatto Finite Element Models

High order elements are renowned for their high accuracy and convergence. Among them, Lobatto spectral finite elements are commonly used in explicit dynamic analyses as their mass matrices when evaluated by the Lobatto integration rule are diagonal. While there are numerous advanced first and second order elements, advanced high order elements are rarely seen. In this paper, generic stabilization schemes are devised for the reduced integrated plane and axisymmetric elements. Static and explicit dynamic tests are considered for evaluating the relatively merits of the stabilized and conventional elements. The displacement errors of the stabilized elements are less than those of the conventional Lobatto elements. When the material is nearly incompressible, the stabilized elements are also more accurate in terms of the energy error norm. This advantage is of practical importance for bio-tissue and hydrated soil analyses.postprin

Modified and Trefftz unsymmetric finite element models

The unsymmetric finite element method employs compatible test functions but incompatible trial functions. The pertinent 8-node quadrilateral and 20-node hexahedron unsymmetric elements possess exceptional immunity to mesh distortion. It was noted later that they are not invariant and the proposed remedy is to formulate the element stiffness matrix in a local frame and then transform the matrix back to the global frame. In this paper, a more efficient approach will be proposed to secure the invariance. To our best knowledge, unsymmetric 4-node quadrilateral and 8-node hexahedron do not exist. They will be devised by using the Trefftz functions as the trial function. Numerical examples show that the two elements also possess exceptional immunity to mesh distortion with respect to other advanced elements of the same nodal configurations.postprin

Geochemistry of the Panzhihua Mafic Layered Intrusion (SW China): Petrogenetic Implications for its Giant V-Ti-Magnetite Deposit

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Provenance and tectonic setting of the Neoproterozoic Yanbian Group, western Yangtze Block (SW China)

Tectonic evolution of the Yangtze Block of South China during Neoproterozoic time has been a major focus of debate and is important in the reconstruction of the Rodinian supercontinent. The Yanbian Group in the western margin of the Yangtze Block is a well-preserved Neoproterozoic volcanic-sedimentary sequence and provides a rare opportunity to examine the provenance and tectonic setting. It consists of a lower part composed of ∼1500 m thick basaltic lavas and an upper part of ∼3500 m thick flysch deposits. The flysch sequence contains typical deep marine turbidites consisting mainly of fine-grained volcaniclastic sandstones and mudstones, indicating a submarine fan depositional system. Detrital zircon dating yields ages ranging from ca. 865 Ma to 1000 Ma with two peaks at ca. 900 Ma and 920 Ma, respectively. The Yanbian Group is intruded by the ∼860 Ma Guandaoshan dioritic pluton, constraining its depositional age at ca. 870 Ma. The sandstones contain abundant feldspar and lithic fragments with minor amounts of quartz and have an average composition of Q 16F 35L 49, suggesting a proximal source and an undissected to transitional arc setting. The lithic fragments in the sandstones point to andesitic and felsic volcanic rock sources. The sandstones and mudstones have intermediate SiO 2/Al 2O 3 (typically 3-6), high Fe 2O 3 + MgO contents (5-12 wt%), and moderate to high K 2O/Na 2O ratios (generally 0.1-1 and 1-10 for sandstones and mudstones, respectively). In comparison with average upper continental crust, they show strong negative Nb-Ta anomalies, slight depletion of Zr-Hf, La and Th, but moderate enrichment of V, Cr, Ni, and Sc. These rocks show LREE enrichment (La/Yb N = 5.3-7.4) with flat HREE, and pronounced negative Eu anomalies (Eu/Eu * = 0.6-0.74) in chondrite-normalized REE patterns, similar to post-Archean shales. Geochemical data for these rocks suggest an arc setting and intermediate-felsic volcanic source, consistent with a back-arc basin scenario for the basaltic lavas in the lower Yanbian Group. Together with regional geological evidence, the turbidites of the Yanbian Group strongly support a model in which the western margin of the Yangtze Block was a major magmatic arc, active probably from ∼920 Ma to 740 Ma, a period of more than 180 million years. © 2008 Elsevier B.V. All rights reserved.postprin

Apollonian metric, uniformity and Gromov hyperbolicity

The main purpose of this paper is to investigate the properties of a mapping which is required to be roughly bilipschitz with respect to the Apollonian metric (roughly Apollonian bilipschitz) of its domain. We prove that under these mappings the uniformity, phi-uniformity and delta-hyperbolicity (in the sense of Gromov with respect to quasihyperbolic metric) of proper domains of are invariant. As applications, we give four equivalent conditions for a quasiconformal mapping which is defined on a uniform domain to be roughly Apollonian bilipschitz, and we conclude that phi-uniformity is invariant under quasimobius mappings

Evaluation of analgesic, anti-inflammatoryand antipyretic activities of the ethanol extract from Speranskia tuberculate

Background: Speranskia tuberculata (Bunge) Baill, has been used to prevent and treat many diseases in Chinese folk medicine, nevertheless, few investigations had been reported.Materials and Methods: Animals were orally administered STE at the doses of 125, 250, 500 mg/kg. The analgesic effect was estimated in mice by hot-plate test and the acetic acid-induced writhing test. The anti-inflammatory effect was assessed using rat paw edema model elicited by fresh egg white and the mouse ear edema model caused by dimethylbenzene. The antipyretic effect was determined using the lipopolysaccharide (LPS)-induced rat fever model. In addition, the acute oral toxicity of STE was studied.Results: STE significantly and dose-dependently reduced the number of writhing responses in mice, prolonged reaction time of mice against heat stimulation, depressed egg white-induced paw edema in rats and the dimethylbenzene-caused ear edema in mice, but did not alleviate LPS-induced pyrexia in rats. No death of mice was observed when orally administered STE up to 52.8 g/kg (approximately 2080 times of clinical dose used).Conclusion: STE possesses evident analgesic and anti-inflammatory activities, but has no antipyretic effect. Furthermore STE has a favorable safety. These findings support the applications of Speranskia tuberculata as an analgesic and anti-inflammatory drug in folk medicine.Key Words: Herb, pain, inflammation, Pyrexia, Safet

Suboptimal health: a new health dimension for translational medicine

Background One critical premise of disease-related biomarkers is the definition of the counterpart normality. Contrary to pre-clinical models that can be carefully tailored according to scientific need, heterogeneity and uncontrollability is the essence of humans in health studies. Fully characterization of consistent parameters that define the normal population is the basis to individual differences normalization irrelevant to a given disease process. Self claimed normal status may not represent health because asymptomatic subjects may carry chronic diseases or diseases at their early stage such as cancer, diabetes and hypertension. Methods This paper exemplifies the characterization of the suboptimal health status (SHS) which represents a new public health problem in a population with ambiguous health complaints such as general weakness, unexplained medical syndrome and chronic fatigue. We applied clinical informatics approaches and developed a questionnaire for measuring SHS. The validity and reliability of this approach were evaluated in a small pilot study and then in a cross-sectional study of 3,405 individuals. Results The final questionnaire congregated into a score (SHSQ-25) which could significantly distinguish among several abnormal conditions. Conclusion SHSQ-25 could be used as a translational medicine instrument for health measuring in the general population

Developing a voltage-stability-constrained security assessment system part I: Determination of power system voltage security operation limits

The method for determining the voltage security operation limits in a practical voltage security analysis (VSA) system based on VSAT software for large power systems is introduced in this paper. These operation limits include bus voltage limits, branch/corridor transfer power limits and P-load limit of the whole system. The voltage security operation limits are determined by the most critical contingency among the studied contingency set. The most critical contingency determines the P-load limit of the whole system, and all kinds of operation parameter limits are operation parameter values corresponding to this P-load limit under pre-contingency. An operation parameter limit is upper limit if the function relationship between this operation parameter and load power is an increasing curve, or lower limit if the function relationship between this operation parameter and load power is an decreasing curve. These operation parameter limits are helpful for operators to monitor the system operation state. © 2005 IEEE.published_or_final_versio