289 research outputs found
Mechanical response of a triply periodic minimal surface cellular structures manufactured by selective laser melting
No full textCellular structures with controllable mechanical properties and porous architecture are the most promising candidates for many applications such as bone implants. Selective laser melting (SLM), one of the additive manufacturing (AM) technologies, enables manufacturing of space filling lattice structures with exceptional load bearing efficiency, customizable stiffness, controllable cell topology, cell size, and porosity. In this work, Schoen Gyroid (SG) unit cell, a triply periodic minimal surface (TPMS) structure, was used to design the cellular structures. As opposed to many other types of unit cells, SG has superior characteristics of self-supporting and high manufacturability for AM technologies. The titanium alloy (Ti–6Al–4V) SG cellular structures were manufactured by SLM. Finite element (FE) method was employed to predict the elastic modulus, compressive yield strength and stress/strain distributions of the SG cellular structures, and the failure occurrence mechanisms were analyzed. The FE results were compared with the experimental data. The results show that through FE method, the mechanical responses of the SG cellular structures can be accurately described and it is possible to customize the mechanical properties of SLM-produced titanium alloy TPMS lattices
8-Bit Adder and Subtractor with Domain Label Based on DNA Strand Displacement
No full textDNA strand displacement, which plays a fundamental role in DNA computing, has been widely applied to many biological computing problems, including biological logic circuits. However, there are many biological cascade logic circuits with domain labels based on DNA strand displacement that have not yet been designed. Thus, in this paper, cascade 8-bit adder/subtractor with a domain label is designed based on DNA strand displacement; domain t and domain f represent signal 1 and signal 0, respectively, instead of domain t and domain f are applied to representing signal 1 and signal 0 respectively instead of high concentration and low concentration high concentration and low concentration. Basic logic gates, an amplification gate, a fan-out gate and a reporter gate are correspondingly reconstructed as domain label gates. The simulation results of Visual DSD show the feasibility and accuracy of the logic calculation model of the adder/subtractor designed in this paper. It is a useful exploration that may expand the application of the molecular logic circuit
A self-regulated interface toward highly reversible aqueous zinc batteries
No full textFirst published: 15 January 2022Aqueous zinc batteries, that demonstrate high safety and low cost, are considered promising candidates for large-scale energy storage. However, Zn anodes suffer from rapid performance deterioration due to the severe Zn dendrite growth and side reactions. Herein, with a low-cost ammonium acetate (NH₄OAc) additive, a self-regulated Zn/electrolyte interface is built to address these problems. The NH₄⁺ induces a dynamic electrostatic shielding layer around the abrupt Zn protuberance to make the Zn deposition uniform, and the OAc⁻ acts as an interfacial pH buffer to suppress the proton-induced side reactions and the precipitation of insoluble by-products. As a result, in the electrolyte with the NH₄OAc additive, Zn anodes exhibit a long cycling stability of 3500 h at 1 mA cm⁻², an impressive cumulative areal capacity of 5000 mAh cm⁻² at 10 mA cm⁻², and a high Coulombic efficiency of ≈99.7%. A prototype full cell coupled with a NH₄V₄O₁₀ cathode performs much better in terms of capacity retention than the additive-free case. The findings pave the way for developing practical Zn batteries.Daliang Han, Zhenxing Wang, Haotian Lu, Huan Li, Changjun Cui, Zhicheng Zhang, Rui Sun, Chuannan Geng, Qinghua Liang, Xiaoxia Guo, Yanbing Mo, Xing Zhi, Feiyu Kang, Zhe Weng, and Quan-Hong Yan
Expansion and equality in Chinese higher education
No full textWhat is the relationship between the fast expansion of higher education and the equality of college enrollment opportunity in China? Based on the data from four large-scale surveys on college graduates in China, this paper explores this question by conducting empirical analysis on the family occupational, educational, regional, and economic status through descriptive and regression analyses. The result shows: Firstly, quantitatively speaking, enrollment opportunities have equalized in some aspects as well as unequalized in some others. The percentage of students from medium and inferior occupational families and the percentage of female students have increased, while the percentage of students from families with low academic qualification has not changed much more; but the percentage of students from county and below has obviously decreased. Secondly, qualitatively speaking, enrollment opportunity inequality has deepened continuously. Students with better family occupational, educational, regional, and economic status and male students have more chances to enter elite universities, and those groups have become more and more advantaged with the passing of time. (C) 2014 Elsevier Ltd. All rights reserved.Education & Educational [email protected]
Optical singularity assisted method for accurate parameter detection of step-shaped nanostructure in coherent Fourier scatterometry
No full textAccurate determination of the physical parameters of nanostructures from optical far-field scattering is an important and challenging topic in the semiconductor industry. Here, we propose a novel metrology method to determine simultaneously the height and side-wall angle of a step-shaped silicon nanostructure. By employing an optical singular beam into a typical coherent Fourier scatterometry system, both parameters can be retrieved through analyzing the intensity profile of the far-field scattering pattern. The use of singular beam is shown to be sensitive to slight changes of the parameters of the step. By changing the relative direction between the singularity and structure, the height and side-wall angle can both be retrieved with high precision. This new method is robust, simple, and can provide valuable means for micro-and-nano- metrologies.ImPhys/Optic
Additive Manufacturing of Metallic Materials: Structures, Properties and Methodologies
No full textAdditive manufacturing (AM) is a crucial aspect of contemporary science and engineering, enabling the layer-by-layer production of components [...
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