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[en] The antiferromagnetic/ferromagnetic NiO/CoFe bilayers are prepared by radio frequency magnetron sputtering method. Magnetization hysteresis curves were measured by a vibrating sample magnetometer (VSM). The exchange bias fields Hex of NiO/CoFe bilayers are studied by using different substrates and sputtering Ar gas pressures. When the glass, Si (100), Si (110) and Si (111) substrates are used, the exchange bias fields of the bilayers are different. The Hex is also influenced because of different sputtering Ar gas pressures. The crystal texture and surface roughness of the samples were analyzed by using X-ray diffraction (XRD) and atom force microscope (AFM). It is found that the exchange bias field strongly depends on the NiO/CoFe interface roughness. With the increase of the interface roughness, the exchange bias field Hex of NiO/CoFe bilayers decreases. It is not dependent on the existence of NiO (111) texture which is the spin uncompensated plane, believed to strongly correlate with exchange bias field according to the traditional understanding for the anisotropic exchange biasing mechanism. These results cannot be explained by the ideal interface model and Mauri et al.'s interfacial antiferromagnetic domain wall model, but the random-field model can interpret the results
[en] Highlights: •The catalytic effect of TPP on the reaction of CNE and DOPO is revealed. •The reaction condition is determined by APC. •The decomposition mechanism of DOPO in air and nitrogen is proposed. •The flame-retardant mechanism of DOPO beneath or at the edge of flame is proposed. -- Abstract: Phosphorus-containing epoxy resins were synthesized by o-cresol-novolac epoxy resin (CNE) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) catalyzed by triphenyl phosphine (TPP). The reaction was characterized by FTIR, differential scanning calorimeter(DSC), Advanced Polymer Chromatography (APC) and HCl/acetone titration method. The results showed that the reaction of CNE and DOPO completed in 2 h at 130 °C with 1.5%TPP and the activation energy reduced from 162 kJ/mol to113 kJ/mol. The thermal properties and flame retardancy of the phosphorus-containing epoxy resins cured by phenol formaldehyde novolac resin(PN) were investigated by simultaneous thermal analyzer, cone calorimeter, limiting oxygen index (LOI) and vertical burning test (UL-94). The results revealed that the DOPO groups decomposed into phosphoric or polyphosphoric acid in air and decomposed into PO free radicals in nitrogen. The epoxy thermoset with 1.5% phosphorus content achieved UL94 V-1 rating and LOI 27% and the epoxy thermoset with 2.4% phosphorus content achieved UL94 V-0 rating and LOI 31%. The morphology of residues after cone calorimeter test was observed by scanning electron microscope (SEM). The results showed that the char of DOPO-CNE(2%P)/PN and DOPO-CNE(3%P)/PN present a compact and continuous surface.
[en] Based on the moving least square (MLS) approximations and the boundary integral equations (BIEs), a meshless algorithm is presented in this paper for elliptic Signorini problems. In the algorithm, a projection operator is used to tackle the nonlinear boundary inequality conditions. The Signorini problem is then reformulated as BIEs and the unknown boundary variables are approximated by the MLS approximations. Accordingly, only a nodal data structure on the boundary of a domain is required. The convergence of the algorithm is proven. Numerical examples are given to show the high convergence rate and high computational efficiency of the presented algorithm. (general)
[en] Risk-informed Technical Specification (RITS) and Risk-Managed Technical Specification (RMTS) Technologies has important significance in the operation and safety management of nuclear power plants. In this paper, the technology connotation of RITS and RMTS is introduced, the application of PSA technology in RITS and RMTS and relevant issues are studied and discussed. (authors)
[en] Based on an improved random number generator which is designed mainly by Gauss error function and digital discarding technology, a multi-rounds image encryption algorithm is proposed and implemented in this paper. The structure of the thesis is mainly composed of three modules: The first one is the random number generation module, and the second one is the pixel encryption module and the last one is the algorithm implementation module. First, the chaotic sequence derived from a first-order time-delay differential equation is mapped to another sequence by using the improved Gauss error function, and then the data are truncated and recombined to obtain the random numbers. After scrambling the pixels of the original image by using the generated random numbers, the first round encrypted pixels can be obtained by performing XOR operation between the scrambled pixel sequence and another sequence which derived from the improved random number generator. And then, the generator is used for the next round encryption after selecting an encrypted pixel value of the previous round. Finally, the implementation methods of encryption algorithm in embedded hardware are discussed, and two prototypes are developed on STM32. Simulation experiments demonstrate that this cryptosystem is secure enough to resist brute force attacks, differential attacks, entropy attacks, and statistical attacks. In addition, the cryptosystem has high key sensitivity and large key space.
[en] In this study, three "1"8F-labeled crown ether fused anilinoquinazoline derivatives (["1"8F]11a-c) were synthesized and evaluated as potential tumor imaging probes. The biodistribution results of ["1"8F]11b were good. Compared with ["1"8F]-fludeoxyglucose and l-["1"8F]-fluoroethyltyrosine in the same animal model, ["1"8F]11b had better tumor/brain, tumor/muscle, and tumor/blood uptake ratios. Overall, these results suggest that ["1"8F]11b is promising as a tumor imaging agent for positron emission tomography. (author)
[en] Lithium metal is recognized as one of the most promising anode materials owing to its ultrahigh theoretical specific capacity and low electrochemical potential. Nonetheless, dendritic Li growth has dramatically hindered the practical applications of Li metal anodes. Realizing spherical Li deposition is an effective approach to avoid Li dendrite growth, but the mechanism of spherical deposition is unknown. Herein, a diffusion-reaction competition mechanism is proposed to reveal the rationale of different Li deposition morphologies. By controlling the rate-determining step (diffusion or reaction) of Li deposition, various Li deposition scenarios are realized, in which the diffusion-controlled process tends to lead to dendritic Li deposition while the reaction-controlled process leads to spherical Li deposition. This study sheds fresh light on the dendrite-free Li metal anode and guides to achieve safe batteries to benefit future wireless and fossil-fuel-free world. (© 2020 Wiley‐VCH Verlag GmbH and Co. KGaA, Weinheim)
[en] High-energy-density Li metal batteries suffer from a short lifespan under practical conditions, such as limited lithium, high loading cathode, and lean electrolytes, owing to the absence of appropriate solid electrolyte interphase (SEI). Herein, a sustainable SEI was designed rationally by combining fluorinated co-solvents with sustained-release additives for practical challenges. The intrinsic uniformity of SEI and the constant supplements of building blocks of SEI jointly afford to sustainable SEI. Specific spatial distributions and abundant heterogeneous grain boundaries of LiF, LiNO, and LiO effectively regulate uniformity of Li deposition. In a Li metal battery with an ultrathin Li anode (33 μm), a high-loading LiNiCoMnO cathode (4.4 mAh cm), and lean electrolytes (6.1 g Ah), 83 % of initial capacity retains after 150 cycles. A pouch cell (3.5 Ah) demonstrated a specific energy of 340 Wh kg for 60 cycles with lean electrolytes (2.3 g Ah). (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
[en] Lithium metal is used to achieve high-energy-density batteries due to its large theoretical capacity and low negative electrochemical potential. The introduction of quasi-solid electrolytes simultaneously overcomes the safety problems induced by the liquid electrolytes and the high interfacial resistance issues confronted by all solid-state electrolytes. In-depth investigations involving interfacial behaviors in quasi-solid lithium metal batteries are inadequate. Herein an ultrathin LiOCl quasi-solid-state electrolyte layer (500 nm thickness) is used to cover a lithium anode. The polarization of the anode is remarkably reduced by introducing the LiOCl quasi-solid-state electrolyte. In contrast to the decomposition of solvents in a standard electrolyte (EC-DEC,1.0 m LiPF), the established quasi-solid-state electrolyte interfaces can significantly inhibit the decomposition of solvents when the cut-off voltage is 4.5 V. (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
[en] The persistent efforts to reveal the formation and evolution mechanisms of solid electrolyte interphase (SEI) are of fundamental significance for the rational regulation. In this work, through combined theoretical and experimental model investigations, we elucidate that the electric double layer (EDL) chemistry at the electrode/electrolyte interface beyond the thermodynamic stability of electrolyte components predominately controls the competitive reduction reactions during SEI construction on Li metal anode. Specifically, the negatively-charged surface of Li metal will prompt substantial cation enrichment and anion deficiency within the EDL. Necessarily, only the species participating in the solvation shell of cations could be electrostatically accumulated in proximity of Li metal surface and thereafter be preferentially reduced during sustained dynamic cycling. Incorporating multi-valent cation additives to more effectively drag the favorable anionic SEI enablers into EDL is validated as a promising strategy to upgrade the Li protection performance. The conclusions drawn herein afford deeper understandings to bridge the EDL principle, cation solvation, and SEI formation, shedding fresh light on the targeted regulation of reactive alkali metal interfaces. (© 2020 Wiley‐VCH GmbH)