Failure mode of laser welds in lap-shear specimens of high strength low alloy (HSLA) steel sheets is investigated in this paper. The experiments for laser welds in lap-shear specimens under ...quasi-static loading conditions are briefly reviewed first. The experimental results showed that the laser welds failed in a ductile necking/shear failure mode and the ductile failure was initiated at a distance away from the crack tip near the boundary of the base metal and heat affected zone. In order to understand the failure mode of these welds, finite element analyses under plane strain conditions were conducted to identify the effects of the different plastic behaviors of the base metal, heat affected zone, and weld zone as well as the weld geometry on the ductile failure. The results of the reference finite element analysis based on the homogenous material model show that the failure mode is most likely to be a middle surface shear failure mode in the weld. The results of the finite element analysis based on the multi-zone non-homogeneous material models show that the higher effective stress–plastic strain curves of the weld and heat affected zones and the geometry of the weld protrusion result in the necking/shear failure mode in the load carrying sheet. The results of another finite element analysis based on the non-homogeneous material model and the Gurson yield function for porous materials indicate that the consideration of void nucleation and growth is necessary to identify the ductile failure initiation site that matches well with the experimental observations. Finally, the results of this investigation indicate that the failure mode of the welds should be examined carefully and the necking/shear failure mode needs to be considered for development of failure or separation criteria for welds under more complex loading conditions.
Direct numerical simulation is performed for quenching of a hot plate in liquid jet impingement. The flow and thermal characteristics associated with the quenching process, which includes film ...boiling in the fluid region as well as transient conduction in the solid region, are investigated by solving the conservation equations of mass, momentum and energy in the liquid, gas and solid phases. The liquid–vapor and liquid–air interfaces are tracked by the sharp-interface level-set method modified to treat the effect of phase change. The computations demonstrate that the boiling curve of wall heat flux versus temperature does not depend on the transient or steady-state heating conditions. The effects of initial solid temperature and solid properties on the quenching characteristics are quantified.
Summary
Research activities devoted to the development of noble metal‐free electrocatalysts have expanded and still require large energy input to drive the oxygen evolution reaction (OER). A key ...challenge to improve the efficiency of water electrolysis systems is to develop efficient and robust electrocatalysts for water splitting. We propose a simple strategy to construct a nanostructure composed of zeolitic imidazolate framework (ZIF)‐67 grafted onto vanadium‐doped nickel hydroxide (Ni‐V) microflowers (MFs). In this integrated structure, the ZIF‐67 polyhedrons were well assembled on the surface of the Ni‐V MFs (ie, Z‐67/Ni‐V), thus enhancing the OER kinetics as a result of the interaction between Ni‐V and Co and increasing the electrocatalytic activity. In addition, the Z‐67/Ni‐V nanostructure is an efficient catalyst that exhibits improved surface area and pore volume. The Z‐67/Ni‐V nanostructures demonstrated greater OER electrocatalytic activity for alkaline water electrolysis and improved structural stability. Compared to their bare Ni‐V‐hydroxide counterparts, the Z‐67/Ni‐V nanostructure reveals an exceptionally low overpotential of 320 mV with a low Tafel slope of 71 mV dec−1 and remarkable long‐standing stability at current density of 10 mA cm−2.
In this study, we designed and developed an efficient electrocatalyst for the ternary composite of ZIF‐67‐embedded vanadium‐doped Ni(OH)2 (Z‐67/Ni‐V) nanostructures by simple hydrothermal and room‐temperature methods. The Z‐67/Ni‐V nanostructure exhibited a low Tafel slope of 71 mV dec‐1 and low overpotential of 320 mV at a current density of 10 mA cm‐2. Z‐67/Ni‐V nanostructures showed excellent OER electrocatalytic activity and remarkable long‐term stability for alkaline water electrolysis. The proposed strategy is suitable for microbial fuel cells, and photoelectrochemical applications.
Binary vapor liquid equilibrium data were measured for the carbon dioxide + tetrahydrofuran system at five temperatures from (311.01 to 331.33) K. A circulating type apparatus with on-line gas ...chromatography was used in this study. The measured data were correlated well by the Peng−Robinson equation of state with van der Waals one fluid mixing rules.
Nowadays, the development of various electricity generation methods via dynamic water motions has been intensively focused on. While verifying the exact electricity generation mechanism, another ...important task of making full use of the electricity generated by the solid-liquid interaction is being considered. Herein, we demonstrated a self-powered illuminating glucose sensor with high sensitivity (∼ 22.61 V·M−1) and selectivity, and a wide detection range (0.5–100 mM), utilizing the electricity generated from the water infiltration into a glycine-coated porous CuO nanowires film. Fundamentally, the sensing mechanism could be comprehensively verified by an ionovoltaic effect that attributes the electricity generation to the adsorption/desorption of ions or protons at the solid-liquid interface. As the concentration of adsorbed glucose increases, the generated open-circuit voltage decreases accordingly. Moreover, by selectively turning on LEDs with different threshold voltages, the glucose concentration that is harmful to the human body is successfully distinguished. Overall, the self-powered illuminating sensor platform utilizing electricity generated by the water-infiltration phenomenon provides the feasibility of novel biosensors.
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•A self-powered illuminating glucose sensor (glycine-coated porous CuO nanowires film) utilizing electricity generated from the water-infiltration phenomenon was demonstrated.•The glycine-coated porous CuO nanowires film could selectively bind with glucose molecules.•The relationship between electricity generation and the concentration of glucose molecules was thoroughly verified by the ionovoltaic effect.
We expanded the application of endothelin-1 (EDN1) by treating human mesenchymal stem cell (hMSC) organotypic spinal cord slice cultures with EDN1. EDN1-treated hMSCs significantly enhanced neuronal ...outgrowth. The underlying mechanism of this effect was evaluated via whole-genome methylation. EDN1 increased whole-genome demethylation and euchromatin. To observe demethylation downstream of EDN1, deaminases and glycosylases were screened, and APOBEC1 was found to cause global demethylation and OCT4 gene activation. The sequence of methyl-CpG-binding domain showed similar patterns between EDN1- and APOBEC1-induced demethylation. SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin subfamily A member 4 (SMARC A4) and SMARC subfamily D, member 2 (SMARC D2) were screened via methyl-CpG-binding domain sequencing as a modulator in response to EDN1. Chromatin immunoprecipitation of the H3K9me3, H3K27me3, and H3K4me4 binding sequences on the APOBEC1 promoter was analyzed following treatment with or without siSMARC A4 or siSMARC D2. The results suggested that SMARC A4 and SMARC D2 induced a transition from H3K9me3 to H3K4me3 in the APOBEC1 promoter region following EDN1 treatment. Correlations between EDN1 pathways and therapeutic efficacy in hBM-MSCs were determined in a sciatic nerve injury mouse model. Thus, EDN1 may be a useful novel-concept bioactive peptide and biomaterial component for improving hMSC regenerative capability.
This paper describes an experimental approach to evaluate the effective doses of space radiations at high-altitude by combining the measured data from the Liulin-6K spectrometer loaded onto the ...air-borne RC-800 cockpit and the calculated data from CARI-6M code developed by FAA. In this paper, 15 exposed dose experiments for the flight missions at a highaltitude above 10 km and 3 experiments at a normal altitude below 4 km were executed over the Korean Peninsula in 2012. The results from the high-altitude flight measurements show a dramatic change in the exposed doses as the altitude increases The effective dose levels (an average of 15.27 μSv) of aircrew at the high-altitude are an order of magnitude larger than those (an average of 0.30 μSv) of the normal altitude flight. The comparison was made between the measure dose levels and the calculated dose levels and those were similar each other. It indicates that the annual dose levels of the aircrew boarding RC- 800 could be above 1 mSv. These results suggest that a proper procedure to manage the exposed dose of aircrew is required for ROK Air Force.
Efficient differentiation of pluripotent stem cells (PSCs) into cardiac cells is essential for the development of new therapeutic modalities to repair damaged heart tissue. We identified a novel cell ...surface marker, the G protein-coupled receptor lysophosphatidic acid receptor 4 (LPAR4), specific to cardiac progenitor cells (CPCs) and determined its functional significance and therapeutic potential. During in vitro differentiation of mouse and human PSCs toward cardiac lineage, LPAR4 expression peaked after 3−7 days of differentiation in cardiac progenitors and then declined. In vivo, LPAR4 was specifically expressed in the early stage of embryonal heart development, and as development progressed, LPAR4 expression decreased and was non-specifically distributed. We identified the effective agonist octadecenyl phosphate and a p38 MAPK blocker as the downstream signal blocker. Sequential stimulation and inhibition of LPAR4 using these agents enhanced the in vitro efficiency of cardiac differentiation from mouse and human PSCs. Importantly, in vivo, this sequential stimulation and inhibition of LPAR4 reduced the infarct size and rescued heart dysfunction in mice. In conclusion, LPAR4 is a novel CPC marker transiently expressed only in heart during embryo development. Modulation of LPAR4-positive cells may be a promising strategy for repairing myocardium after myocardial infarction.
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To effectively achieve cardiac differentiation from pluripotent stem cells, the discovery of new markers is essential. Lee et al. discovered a new cardiac progenitor cell marker, LPAR4, and its modulation showed functional significance during cardiac differentiation, providing new insight into cell-free cardiac repair by modulating LPAR4-positive cells in the heart.
It is well known that there are many 2-torsion elements in the classical knot concordance group. On the other hand, it is not known if there is any torsion element in the rational knot concordance ...group \(\mathcal{C}_\mathbb{Q}\). Cha defined the algebraic rational concordance group \(\mathcal{AC}_\mathbb{Q}\), an analogue of the classical algebraic concordance group, and showed that \(\mathcal{AC}_\mathbb{Q}\cong\mathbb{Z}^\infty\oplus\mathbb{Z}_2^\infty\oplus\mathbb{Z}_4^\infty\). The knots that represent 2-torsions in \(\mathcal{AC}_\mathbb{Q}\) potentially have order \(2\) in \(\mathcal{C}_\mathbb{Q}\). In this paper, we provide an obstruction for knots of order \(2\) in \(\mathcal{AC}_\mathbb{Q}\) from being of finite order in \(\mathcal{C}_\mathbb{Q}\). Moreover, we give a family consisting of such knots that generates an infinite rank subgroup of \(\mathcal{C}_\mathbb{Q}\). We also note that Cha proved that in higher dimensions, the algebraic rational concordance order is the same as the rational knot concordance order. Our obstruction is based on the localized von Neumann \(\rho\)-invariant.
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