Genome sequencing reveals extraordinary cephalic horns in the Madagascan dung beetle genus Helictopleurus (Coleoptera, Scarabaeinae) : insight from a revision of fungicola species group

In this study, we test and corroborate the phylogenetic position of Heterosyphus within Helictopleurus using mitogenomes and nuclear loci. Our recent samplings revealed that males of the former Heterosyphus sicardi Paulian, 1975 (today under Helictopleurus d'Orbigny, 1915) have extraordinary bilateral clypeal horns which are exclusive within the genus. We provide a taxonomic review of the fungicola species group of Helictopleurus and discuss the systematic position of H. sicardi within the group. The male phenotype of H. sicardi is described and photographs of the body and genitalia of the members of the fungicola group are given, as well as a diagnostic key to species of the group. Helictopleurus fungicola peyrierasi is considered to be a distinct species within the genus (H. peyrierasi stat. rest.). Helictopleurus pluristriatus d'Orbigny, 1915 syn. nov. is established as a junior synonym of H. fungicola (Fairmaire, 1899).Peer reviewe

The effect of friction stir welding tool wear on the weld quality of aluminum alloy AMg5M

Friction stir welding (FSW) tool wear has been studied from the standpoint of tribological layer generation and interaction of this layer with the tool’s metal. It was shown that during FSW on aluminum alloy the latter adheres to the tool’s working surface and then iron/aluminum reaction diffusion is initiated under the conditions of high mechanical stress and temperature. Since diffusion along the former austenite grain boundaries is much faster than volume diffusion, an intermetallic compound is formed inside the tool’s metal thus causing embrittlement and pulling out the tool’s metal fragments

Friction stir processing on carbon steel

Friction stir processing of medium carbon steel samples has been carried out using a milling machine and toolsmade of cemented tungsten carbide. Samples have been machined from 40 and 40X steels. The tools have been made inthe shape of 5u5u1.5 mm and 3u3u1.5 mm tetrahedrons. The microstructure of stirred zone has been obtained using thesmaller tool and consists of fine recrystallized 2–3 Pm grains, whereas the larger tool has produced the “onion-like”structures comprising hard quenched “white” 500–600 MPa layers with 300–350 MPa interlayers of bainite needles. Themean values of wear intensity obtained after measuring the wear scar width were 0.02 mm/m and 0.001 mm/m for nonprocessedand processed samples, respectively

Plastic strain arrangement in copper single crystals in sliding

Deformation of tribologically loaded contact zone is one of the wear mechanisms in spite of the fact that no mass loss may occur during this process. Generation of optimal crystallographic orientations of the grains in a polycrystalline materials (texturing) may cause hardening and reducing the deformation wear. To reveal the orientation dependence of an individual gain and simplify the task we use copper single crystals with the orientations of the compression axis along [11 1] and [110]. The plastic deformation was investigated by means of optical, scanning electron microscopy and EBSD techniques. It was established that at least four different zones were generated in the course of sliding test, such as non-deformed base metal, plastic deformation layer sliding, crystalline lattice reorientation layer and subsurface grain structure layer. The maximum plastic strain penetration depth was observed on [110]-single crystals. The minimum stability of [11 1]-crystals with respect to rotation deformation mode as well as activation of shear in the sliding contact plane provide for rotation deformation localization below the worn surface. The high-rate accumulation of misorientations and less strain penetration depth was observed on [11 1]-crystals as compared to those of [110]-oriented ones

Identification of conditions for nanostructured burnishing and subsurface shear instability

Numerical as well as physical modeling of nanostructuring burnishing has been carried out to find out the process parameter limiting levels, which serve both to provide appropriate surface quality and positive deformation-induced structural modification of the subsurface layers as well as to avoid shear instability in the subsurface layers of burnished metal. The effects of load, burnishing speed, tool tip material, tool pass number and tribological transfer on the burnished surface roughness have been elucidated by the example of quenched and tempered steel 20X (EN 20Cr4). It was shown that overloading results in quasi-viscous flow of the subsurface material, deterioration of the surface and ruining the positive effect of nanostructuring burnishing

Radiographic detection of defects in friction stir welding on aluminum alloy AMg5M

In order to reveal weld defects specific to friction stir welding we undertook radiographic inspection of AMg5M aluminum alloy welded joints. Weld defects in the form of voids have been revealed in the weld obtained under the non-optimal rotation and feed rate. Both shape and size of these defects have been confirmed by examining metallographically successive sections prepared in the weld plane as well as in the plane transversal to the tool feed direction. Linear defects have been also found in the sections that are not seen in the radiographic images. Both the preferable localization and origination of the defects have been analyzed

Fast Traveling-Wave Reactor of the Channel Type

The main aim of this paper is to solve the technological problems of the TWR based on the technical concept described in our priority of invention reference, which makes it impossible, in particular, for the fuel claddings damaging doses of fast neutrons to excess the ~200 dpa limit. Thus the essence of the technical concept is to provide a given neutron flux at the fuel claddings by setting the appropriate speed of the fuel motion relative to the nuclear burning wave. The basic design of the fast uranium-plutonium nuclear traveling-wave reactor with a softened neutron spectrum is developed, which solves the problem of the radiation resistance of the fuel claddings material.Comment: 18 pages, 5 figures, 2 table

High repetition rate multi-similariton laser

We present the numerical demonstration of an harmonically mode-locked multi-similariton laser supporting a low jitter, stable train of self similar high repetition rate pulses exploiting, as mode-locking mechanism, the principle of dissipative Faraday instability (DFI) induced by zigzag modulation of spectral losses [1, 2]. At variance with the theoretical and experimental studies on the DFI [1, 2], where the amplification was distributed along the fiber, we propose here a lumped amplification scheme suitable for a more flexible design of mode-locked lasers pumped by rare-earth gain medium (Erbium, Ytterbium). We have considered an unidirectional all normal dispersion ring resonator with two lumped amplifying sections separated by two passive nonlinear dispersive fibers. Just before each amplifying section is located a spectral filter. The two filters differ by having the transmittance profile respectively blue- and red-detuned relatively to the amplifiers central frequency. The detuned spectral filters provide the necessary periodic zigzag modulation of the spectral losses needed to trigger the DFI. The CW operation of the laser is unstable and the growth of spectral sidebands results in a temporal modulation of the field temporal profile leading to the formation of a pulse train with repetition rate corresponding to the instability frequency around 0.1 THz and pulse duration of about 3 ps. Propagation in the fibers has been modeled using the generalized nonlinear Schrödinger equation and the lumped amplification by a saturable gain term with spectral bandwidth typical of rare-earth amplifiers

Ultrasonic phase array and eddy current methods for diagnostics of flaws in friction stir welds

The feasibility of the defect detection in friction stir welds of aluminum alloys with the use of two different non-destructive testing (NDT) methods has been studied. We have used the following NDT techniques: ultrasonic phase array and eddy current methods. A metallographic examination was chosen as the third method. The weld flaws such as kissing bond boundaries, lack of penetration, voids and cracks have been successfully detected using the ultrasonic phase array technique. The eddy current method enabled the detection of a weld root flaw