Optimization of lumping schemes for plane square quadratic finite element in elastodynamics

The effectiveness of explicit direct time-integration methods is conditioned by using diagonal mass matrix which entails significant computational savings and storage advantages. In recent years many procedures that produced diagonally lumped mass matrices were developed. For example, the row sum method and diagonal scaling method (HRZ procedure) can be mentioned. In this paper, the dispersive properties of different lumping matrices with variable mass distribution for the plane square 8-node serendipity elements are investigated. The dispersion diagrams for such lumping matrices are derived for various Courant numbers, wavelengths and the directions of wave propagation

Simultaneous Border-Collision and Period-Doubling Bifurcations

We unfold the codimension-two simultaneous occurrence of a border-collision bifurcation and a period-doubling bifurcation for a general piecewise-smooth, continuous map. We find that, with sufficient non-degeneracy conditions, a locus of period-doubling bifurcations emanates non-tangentially from a locus of border-collision bifurcations. The corresponding period-doubled solution undergoes a border-collision bifurcation along a curve emanating from the codimension-two point and tangent to the period-doubling locus here. In the case that the map is one-dimensional local dynamics are completely classified; in particular, we give conditions that ensure chaos.Comment: 22 pages; 5 figure

Dispersion of elastic waves in the contact–impact problem of a long cylinder

AbstractNumerical dispersion of two-dimensional finite elements was studied. The outcome of the dispersion study was verified by the numerical and analytical solutions to the longitudinal impact of two long cylindrical bars. In accordance with the results of the dispersion analysis it was demonstrated that the quadratic elements showed better accuracy than the linear ones

Corrosion and Electrochemical Properties of Laser-Shock-Peening-Treated Stainless Steel AISI 304L in VVER Primary Water Environment

Laser Shock Peening (LSP) is a surface treatment technique for metallic materials. It induces plastic deformation at the surface of up to around 1 mm in depth. This process introduces residual stresses that lead to strain hardening, and potentially improvements in fatigue, stress corrosion cracking (SCC) and general corrosion behaviour in many, but not all, corrosive media. In this paper, two specimens made of AISI 304L stainless steel, one LSP-treated and one un-treated, were tested at 280 °C and 8 MPa in VVER (or PWR) primary circuit water chemistry using in situ Electrochemical Impedance Spectroscopy (EIS). This experiment serves to qualify the influence of LSP on the changes in corrosion behaviour in high-temperature, high-density water. The residual stress (RS) measurement of the surface showed a compression RS. Before LSP treatment, RS at the surface was 52.2 MPa in the rolling direction 0°RD and 10.42 MPa in the transverse rolling direction 90°RD. After the treatment, surface RS was −175.27 MPa and −183.51 MPa for Scan and TScan directions, respectively. The effect of compressive RS at the surface was studied and showed an increase in corrosion rate. The analysis of oxide layer by SEM revealed differences between LSP-treated and untreated AISI 304L specimens and their connection to corrosion rates

Mitochondrial DNA diversity in the Kuna Amerinds of Panama

Mitochondrial DNA (mtDNA) haplotype diversity was determined for 63 Chlbcha-speaking Kuna Amerinds sampled widely across their geographic range in eastern Panama^ The Kuna data were compared with mtDNA control region I sequences from two neighboring Chibchan groups, the Ngdb6 and the Huetar; two Amerind groups located at the northern and southern extremes of Amerind distribution, the Nuu-ChahNulth of the Pacific Northwest and the Chilean Mapuche; and with a single Na-Dene group, the Haida of the Pacific Northwest. The Kuna exhibited low levels of mitochondrial diversity as had been reported for the other two Chibchan groups and, furthermore, carried only two of the four Amerind founding lineages first reported by Schurr and coworkers (4m. J. Hum. Genet. 1990; 46: 613-623). We posit that speakers of modern Chibchan languages (henceforth referred to as the Chibcha) passed through a population bottleneck caused either by ethnogenesls from a small founding population and/or subsequent European conquest and colonization. Using the approach of Harpending etal. (Curr. Anthropol. 1993; 34: 483-496), we estimated a Chibchan population bottleneck and subsequent expansion approximately 10 000 years before present, a date consistent with a bottleneck at the time of Chibchan ethnogenesis. The low mtDNA diversity of Kuna Amerinds, as opposed to the generally high levels of mtDNA variation detected in other Amerind groups, demonstrates the need for adequate sampling of cultural or racial groups when attempting to genetically characterize human populations.Mitochondrial DNA (mtDNA) haplotype diversity was determined for 63 Chlbcha-speaking Kuna Amerinds sampled widely across their geographic range in eastern Panama^ The Kuna data were compared with mtDNA control region I sequences from two neighboring Chibchan groups, the Ngdb6 and the Huetar; two Amerind groups located at the northern and southern extremes of Amerind distribution, the Nuu-ChahNulth of the Pacific Northwest and the Chilean Mapuche; and with a single Na-Dene group, the Haida of the Pacific Northwest. The Kuna exhibited low levels of mitochondrial diversity as had been reported for the other two Chibchan groups and, furthermore, carried only two of the four Amerind founding lineages first reported by Schurr and coworkers (4m. J. Hum. Genet. 1990; 46: 613-623). We posit that speakers of modern Chibchan languages (henceforth referred to as the Chibcha) passed through a population bottleneck caused either by ethnogenesls from a small founding population and/or subsequent European conquest and colonization. Using the approach of Harpending etal. (Curr. Anthropol. 1993; 34: 483-496), we estimated a Chibchan population bottleneck and subsequent expansion approximately 10 000 years before present, a date consistent with a bottleneck at the time of Chibchan ethnogenesis. The low mtDNA diversity of Kuna Amerinds, as opposed to the generally high levels of mtDNA variation detected in other Amerind groups, demonstrates the need for adequate sampling of cultural or racial groups when attempting to genetically characterize human populations

Measurement of velocity profiles in a stratified pipe flow recirculatory shear zone using laser flow visualization

Argonne National Laboratory is studying pipe-flow/plenum thermal-plume interactions induced by a pipe-to-plenum temperature difference. Under these conditions a pipe-flow-generated thermal plume is produced in the plenum and a stratified recirculation zone is produced in the pipe resulting in cold fluid being drawn out of the plenum into the bottom of the horizontal pipe conveying hot fluid into the plenum. These phenomena produce plenum wall and pipe nozzle thermal distributions conductive to detrimental structural thermal stresses. In order to study these phenomena studies are being conducted in the ANL Buoyancy Effects Tank (BET), a 3.41-m/sup 3/ plenum containing cold water which is interfaced with a horizontal transparent pipe conveying hot water into the plenum

Dynamics of a cantilever beam with piezoelectric sensor: Parameter identification

This work has been supported by the grant 23-06220S of the Czech Science Foundation within institutional support RVO:61388998

The Acidic Tail of the Cdc34 Ubiquitin-conjugating Enzyme Functions in Both Binding to and Catalysis with Ubiquitin Ligase SCFC^(dc4*)

Ubiquitin ligases, together with their cognate ubiquitin-conjugating enzymes, are responsible for the ubiquitylation of proteins, a process that regulates a myriad of eukaryotic cellular functions. The first cullin-RING ligase discovered, yeast SCF^(Cdc4), functions with the conjugating enzyme Cdc34 to regulate the cell cycle. Cdc34 orthologs are notable for their highly acidic C-terminal extension. Here we confirm that the Cdc34 acidic C-terminal tail has a role in Cdc34 binding to SCF^(Cdc4) and makes a major contribution to the submicromolar K_m of Cdc34 for SCF^(Cdc4). Moreover, we demonstrate that a key functional property of the tail is its acidity. Our analysis also uncovers an unexpected new function for the acidic tail in promoting catalysis. We demonstrate that SCF is functional when Cdc34 is fused to the C terminus of Cul1 and that this fusion retains partial function even when the acidic tail has been deleted. The Cdc34-SCF fusion proteins that lack the acidic tail must interact in a fundamentally different manner than unfused SCF and wild type Cdc34, demonstrating that distinct mechanisms of E2 recruitment to E3, as is seen in nature, can sustain substrate ubiquitylation. Finally, a search of the yeast proteome uncovered scores of proteins containing highly acidic stretches of amino acids, hinting that electrostatic interactions may be a common mechanism for facilitating protein assembly