A numerical study of dust explosion properties of hydrogen storage alloy materials

Hydrogen as a clean fuel has gained increased attention in the recent years and considerable research is being undertaken to develop hydrogen storage technologies. Hydrogen storage using metal hydride is one such technology. Hydride materials, used in hydrogen storage technologies, in powder form can be an explosion hazard and testing these materials using standard techniques is also difficult. Research reported in this paper is an attempt to develop numerical methods to obtain explosion properties of such materials. In this work a one dimensional transport-type model is presented to simulate the dust explosion process in a closed 20-L spherical vessel. Transport equations for energy, species and particle volume fraction are solved with the finite difference method, whilst velocity distribution and pressure are updated with numerical integration of the continuity equation. The model is first validated with experimental data and then applied to simulate the explosion process of an AB2-type alloy powder used for hydrogen storage. Two kinetic models accounting for the particle burning mechanism are investigated in the current study. One is based on an Arrhenius surface reaction law, the other is based on a simplified diffusion-type d2 law. The former is found to be better in terms of prediction of the deflagration indices. This work is of great significance in safety assessment of new hydrogen storage materials in the processes of their production, storage and transportation

RECENT CASE NOTES

<p><i>Notes</i>: H-sites and L-sites refer to high-tide-zone sites and low-tide-zone sites, respectively.</p><p>Results of <i>t</i>-test for effects of different stands on aboveground net primary production (ANPP), soil pH, total carbon (TC), organic and inorganic carbon (SOC and SIC, 0–100 cm), and SMBC.</p

1. スポロトリコーシス5例(第443回千葉医学会例会 第16回千葉皮膚科臨床談話会)

A potential stable stem-loop structure in the 5’-terminal sequence (left) and a triple stem-loop structure in 3’-terminal sequences (right) were predicted with a RNA structure software. (PDF 60 kb

Neighboring Heteroatom Effect Unique to Aqueous Aldol Reactions of Water-Insoluble Substrates

The reactions of ketones and aldehydes in the presence of Li⁺ and in the presence or absence of PTC mediated by water were performed to produce aldol products. Several advantages of the aqueous reactions over organic solvent-mediated ones have been demonstrated including higher yields, shorter reaction times, simpler purifications, and better functional group tolerance. Some reactions that do not take place in organic solvents have been realized in water. The successes are attributed to the neighboring heteroatom effect. In the aqueous aldol condensations, Li₂CO₃ was an efficient catalyst, and therefore base-liable groups such as epoxides, esters, and silyl groups could survive. For heteroaromatic ethanones, the aqueous aldol reactions were accomplished without PTC to give β-hydroxyketones in good yields. The water-mediated condensations of aldosyl hemiacetals with aromatic ketones led to a new carbohydrate-derived skeleton in quantitative yields. To some extent, this research has expanded the applicablities of aldol condensations and reactions

High-cycle fatigue induced twinning in CoCrFeNi high-entropy alloy processed by laser powder bed fusion additive manufacturing

High-cycle fatigue (R=0.1, room temperature) induced microstructural evolution in a laser powder bed fusion (L-PBF) additively manufactured quaternary CoCrFeNi high-entropy alloy (HEA) was studied. The as-built material exhibited a combined and texture and high proportion of low-angle boundaries. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) revealed that deformation twinning occurred under the high-cycle fatigue of σmax= 450 MPa (Nf=1.06 ×105), but not for the stress level of 300 MPa and 200 MPa. The deformation twins led to the cyclic softening, as manifested by the continuous increase of maximum strain under the stress-controlled fatigue, and the hardness increased by ∼80 HV0.2 in the post-fatigued condition. EBSD revealed that both the and orientations were favorable for the twin formation. Given that the size of grains with the and orientations was twice larger than those of the other orientations, the grain size effect on twin formation could play a certain role. High-resolution TEM revealed that the full dislocations, lattice distortion, stacking faults, and partial dislocations were associated with the twin, cellular and labyrinth wall-like dislocation structures. The underlying mechanism for the formation of nano-twins during high-stress fatigue involved the dissociation of 1/2 full dislocations to 1/6 partial ones. Moreover, the dislocation cell structure as observed in the as-built condition evolved into sub-grains after the high-cycle fatigue loading, with the immensely dense dislocations at the sub-grain boundary

Drying-Mediated Assembly of Colloidal Nanoparticles into Large-Scale Microchannels

Large-scale highly ordered microchannels were spontaneously and rapidly created by simply drying the colloidal nanoparticle suspension on a rigid substrate. Interestingly, free evaporation of colloidal suspension yielded radially aligned microchannels, while constrained evaporation that was rendered by the use of confined geometries composed of either two nearly parallel plates or a slide placed perpendicular to a rigid substrate imparted the formation of periodic arrays of parallel microchannels in a controllable manner. The microchannels were formed as a result of the competition between stress relaxation due to crack opening that ruptured the film and stress increase due to the loss of solvent. Quite intriguingly, these patterned microchannels can be exploited as templates to craft well-ordered metallic stripes. This facile and scalable approach may offer a new paradigm of producing microscopic patterns over large areas with unprecedented regularity at low cost that can serve as scaffolds for use in microelectronics and microfluidic-based biochips, among other areas

Schaetzung der Verkehrsbeziehungen bei unvollstaendiger Information und deren Anwendung bei der Verkehrssteuerung

Available from TIB Hannover: F02B909 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

An Efficient Strategy for Self-Assembly of DNA-Mimic Homochiral 1D Helical Cu(II) Chain from Achiral Flexible Ligand by Spontaneous Resolution

Four helical copper complexes Cu­[N­(CN)₂]₂­(Hhmp) (<b>1</b>), {Cu­[N­(CN)₂]₂­(Hhmp)}_∞ (<b>2</b>), (l-{Cu₄[N­(CN)₂]₂­(hmp)₄­(CH₃COO)₂·​CH₃CN}_∞ (<b>3a</b>), and d-{Cu₄[N­(CN)₂]₂­(hmp)₄­(CH₃COO)₂·​CH₃CN}_∞ (<b>3b</b>) (Hhmp = 2-(hydroxy­methyl)­pyridine) have been prepared toward a mimic DNA structure. By changing the solvent and supplementary ligand, the structures can be successfully tuned from quasi-double-helical (complex <b>1</b>) to racemic 1D single helix (complex <b>2</b>), then the right (<b>3a</b>)-/left (<b>3b</b>)-handed double helices. The topologies of <b>3a</b> and <b>3b</b> may be considered as a mimic of DNA, where the Cu–O bonds between the two strands replace the hydrogen-bonding interactions in DNA. Solid-state circular dichroism spectra confirmed that <b>3a</b> and <b>3b</b> are optically active, respectively. Magnetic measurements for <b>1</b>–<b>3</b> indicated all complexes to be antiferromagnetic interactions. The best fitting results to the magnetic susceptibilities were <i>J</i> = −0.80 cm^–1, <i>g</i> = 2.11 for <b>1</b> and <i>J</i>₁ = −9.22 cm^–1, <i>J</i>₂ = 3.56 cm^–1, <i>J</i>₃ = −9.49 cm^–1, <i>g</i> = 2.27 for <b>3</b>

Methane Dissociation on Li‑, Na‑, K‑, and Cu-Doped Flat and Stepped CaO(001)

We report the results of density-functional theory calculations for the dissociative adsorption of methane (DAM) on CaO(001) doped with Li, Na, K, and Cu. The presence of these dopants lowers the energy of oxygen-vacancy formation, increases the energy of the DAM reaction, and lowers the activation energy for DAM. We performed the same calculations for a stepped CaO(001) surface doped with Na and found that Na prefers being located at a step and the activation energy for DAM is lower at this step than on the doped, flat surface. We propose that such trends are valid for all oxides doped with lower-valence dopants

A Bridge Role Metric Model for Nodes in Software Networks

<div><p>A bridge role metric model is put forward in this paper. Compared with previous metric models, our solution of a large-scale object-oriented software system as a complex network is inherently more realistic. To acquire nodes and links in an undirected network, a new model that presents the crucial connectivity of a module or the hub instead of only centrality as in previous metric models is presented. Two previous metric models are described for comparison. In addition, it is obvious that the fitting curve between the results and degrees can well be fitted by a power law. The model represents many realistic characteristics of actual software structures, and a hydropower simulation system is taken as an example. This paper makes additional contributions to an accurate understanding of module design of software systems and is expected to be beneficial to software engineering practices.</p></div