Thermodynamic property of ternary compound MgCaSi: A study from ab initio Debye-Grüneisen model

The thermodynamic properties of MgCaSi and its mother phase Ca₂Si are comparatively investigated from ab initio calculations and quasi-harmonic Debye-Grüneisen model. At 0 K, MgCaSi is more thermodynamically stable. Under high temperature, the advantage of higher thermodynamically stability of MgCaSi is reduced, originating from the less negative entropy contribution because the thermodynamic entropy of MgCaSi increases more slowly with temperature and the entropy values are slightly smaller. With increasing temperature, the anti-softening ability for MgCaSi is slightly smaller due to the slightly faster decrease trend of bulk modulus than that of Ca₂Si, although the bulk modulus of MgCaSi is higher in the whole temperature range considered. The thermal expansion behaviors of both MgCaSi and Ca₂Si exhibit similar increase trend, although thermal expansion coefficient of MgCaSi is slightly lower and the increases is slightly slower at lower temperature. The isochoric heat capacity and isobaric heat capacity of MgCaSi and Ca₂Si rise nonlinearly with temperature, and both are close to the Dulong–Petit limit at high temperature due to the negligibly small electronic contribution. The Debye temperature of both phases decrease with increasing temperature, and the downtrend for MgCaSi is slightly faster. However, MgCaSi possess slightly higher Debye temperature, implying the stronger chemical bonds and higher thermal conductivity than the mother phase Ca₂Si. The Grüneisen parameter of MgCaSi and Ca₂Si increase slightly with temperature, the values of MgCaSi are slightly larger. The investigation of electronic structures shows that with substitution of partial Ca by Mg in Ca₂Si, the stronger MgSi, MgCa and SiSi covalent bonds are formed, and plays a very significant role for the structural stability and mechanical properties.     

A comparative study of NdY-Fe-B magnet and NdCe-Fe-B magnet

Low cost and high abundance rare earth elements Y and Ce have attracted tremendous interests of the industrial and scientific societies for fabricating the highly cost-performance efficient rare earth permanent magnets. However, the effect of separate replacement of Nd by Y or Ce on the performances of NdFeB-type magnet under the same atomic ratio and preparation conditions is still unclear. In this work, we systematically investigated the magnetic properties, thermal stabilities and service performances of (Nd_0.8Y_0.2)_13.80Fe_balAl_0.24Cu_0.1B_6.04 (atomic fraction, denoted as 20Y) and (Nd_0.8Ce_0.2)_13.80Fe_balAl_0.24Cu_0.1B_6.04 (atomic fraction, denoted as 20Ce) magnets. The results demonstrate that the μ₀M_r, μ₀H_c and (BH)_max of 20Y magnet are respectively 1.325 T, 1.173 T and 343.467 kJ/m³, which are comprehensively higher than those of 20Ce magnet (μ₀M_r = 1.310 T, μ₀H_c = 0.948 T, (BH)_max = 321.105 kJ/m³). Moreover, the 20Y magnet has higher thermal stability compared with 20Ce magnet which is favorable for the magnetic performances at elevated temperatures. The investigation of microstructure and elemental distribution indicates that the excellent magnetic performances of NdY-Fe-B magnet can be attributed not only to the preferable intrinsic properties 4πM_s, H_a and T_c of Y₂Fe₁₄B, but also to the in-situ core–shell structure of the 2:14:1 matrix phase grain with Y-rich core and Nd-rich shell, along with the thicker grain boundary layer between the adjacent matrix phase grains in NdY-Fe-B magnet. Furthermore, the 20Y magnet exhibits better mechanical property and higher corrosion resistance than 20Ce magnet, which are helpful for prolonging the service life of the magnet in practical application.     

Stability of antioxidant peptides from duck meat after post‐mortem ageing

The stability of antioxidant peptides from aged duck meat during processing and simulated gastrointestinal digestion was investigated. The antioxidant peptides preserved a high stability in the presence of diverse NaCl or upon various time heating. The antioxidant activities were strengthened by the addition of 4–8% glucose or by heating at 100 °C, whereas they were lost under alkaline conditions. During in vitro digestion, the antioxidant activities increased with pepsin treatment but then decreased following trypsin digestion. Pepsin hydrolysed peptides into short fragments and results in the increased exposure of internal hydrophobic amino acids. With further treatment by trypsin, peptides can be hydrolysed completely and more free amino acids were released, leading to the decline in surface hydrophobicity. These variations might be responsible for the change in antioxidant activity during in vitro digestion. The antioxidant peptides from aged duck with high stability can be used as functional food ingredients to improve human health.     

酸奶粉产品稳定性研究

为确定产品的保质期,研究产品在加速试验、常温保存试验及低温保存试验的活菌数的变化及对发酵酸奶的影响.结果表明:经过3个月的加速试验,样品的活菌数下降3个数量级,发酵酸奶不成功.在常温试验中.活菌数下降1个数量级,样品发酵酸奶质量略有降低.而低温下,经过18个月保存活菌数才下降1个数量级,发酵酸奶的影响不大.初步评价产品在常温下的保质期为5个月～6个月.对于舍有益生菌的产品建议采用低温保存及冷链运输.     

Submarine Magnetic Field Extrapolation Based on Boundary Element Method

In order to master the magnetic field distribution of submarines in the air completely and exactly and study the magnetic stealthy performance of submarine, a mathematic model of submarine magnetic field extrapolation is built based on the boundary element method （BEM）. An experiment is designed to measure three components of magnetic field on the envelope surface surrounding a model submarine. The data in different heights above the model submarine are obtained by use of tri-axial magnetometers. The results show that this extrapolation model has good stabilities and high accuracies compared the measured data with the extrapolated data. Moreover, the model can reflect the submarine magnetic field distribution in the air exactly, and is valuable in practical engineering.     

利用缓冲质子源制作LiNbO3光波导:光学特性及稳定性研究

利用缓冲质子源(苯甲酸中掺入一定量的苯甲酸锂)在Z切LiNbO3基底上制作了质子交换平面光波导，得到了不同掺杂摩尔分数(0．5％，1．0％和1．5％)的缓冲质子源质子交换波导的有效扩散系数及折射率分布。随着质子源中苯甲酸锂的摩尔含量逐渐增加，质子交换的有效扩散系数呈指数衰减，同时波导表面折射率增量线性递减。研究了有效折射率的稳定性特征，并与用纯苯甲酸制作的光波导进行了比较，发现利用缓冲质子源制作的LiNbO3光波导的稳定性明显优于纯苯甲酸制作的光波导。     

Boosting Perovskite Solar Cells Performance and Stability through Doping a Poly‐3(hexylthiophene) Hole Transporting Material with Organic Functionalized Carbon Nanostructures

Perovskite solar cells (PSCs) are demonstrating great potential to compete with second generation photovoltaics. Nevertheless, the key issue hindering PSCs full exploitation relies on their stability. Among the strategies devised to overcome this problem, the use of carbon nanostructures (CNSs) as hole transporting materials (HTMs) has given impressive results in terms of solar cells stability to moisture, air oxygen, and heat. Here, the use of a HTM based on a poly(3‐hexylthiophene) (P3HT) matrix doped with organic functionalized single walled carbon nanotubes (SWCNTs) and reduced graphene oxide in PSCs is proposed to achieve higher power conversion efficiencies (η = 11% and 7.3%, respectively) and prolonged shelf‐life stabilities (480 h) in comparison with a benchmark PSC fabricated with a bare P3HT HTM (η = 4.3% at 480 h). Further endurance test, i.e., up to 3240 h, has shown the failure of all the PSCs based on undoped P3HT, while, on the contrary, a η of ≈8.7% is still detected from devices containing 2 wt% SWCNT‐doped P3HT as HTM. The increase in photovoltaic performances and stabilities of the P3HT‐CNS‐based solar cell, with respect to the standard P3HT‐based one, is attributed to the improved interfacial contacts between the doped HTM and the adjacent layers.     

Development of Dual-light Path Monitoring System of Optical Thin-film Thickness

The accurate monitoring of optical thin-film thickness is a key technique for depositing optical thin-film. For existing coating equipments, which are low precision and automation level on monitoring thin-film thickness, a new photoelectric control and analysis system has been developed. In the new system, main techniques include a photoelectric system with dual-light path, a dual-lock-phase circuit system and a comprehensive digital processing-control-analysis system. The test results of new system show that the static and dynamic stabilities and the control precision of thin-fihn thickness are extremely increased. The standard deviation of thin-film thickness, which indicates the duplication of thin-film thick-ness monitoring, is equal to or less than 0.72%. The display resolution limit on reflectivity is 0.02%. In the system, the linearity of drift is very high, and the static drift ratio approaches zero.     

基于（16,8）准循环码的星载FPGA有限状态机容错设计

有限状态机作为星载数字系统实现控制逻辑的重要手段,其稳定性直接影响系统的正常运行. 空间辐射环境所造成的单粒子翻转效应会导致有限状态机不稳定. 目前常用的容错方法适于处理状态机的1位翻转错误,而具有高可靠性要求的系统还需要能处理2位翻转错误. 基于（16,8）准循环码的有限状态机容错设计方法,可实时纠正1位或2位翻转错误,检测到3位翻转错误,使有限状态机拥有更高的可靠性. 此方法同时具有硬件易实现,系统延时小等优点.