Effect of nanoalumina on fatigue characteristics of fiber metal laminates

The fatigue life enhancement of fiber metal laminates (FMLs) through embedment of nanofiller into the epoxy has not reported hitherto, and it is the subject of this investigation. Due to its outstanding mechanical properties, nanoalumina is chosen as filler to enhance the fatigue life of FMLs. Tension-tension low cycle fatigue tests were conducted at various stress levels with different percentage of nanofillers, at constant frequency and stress ratio. The results showed that the fatigue characteristics of nano-modified FMLs outclassed the neat epoxy FMLs, and the 0.1-wt percentage of nanoalumina is found to be optimum. Improvement in fatigue life of FML is around 46%, 45% and 94% at a stress level of 50%, 60% and 70% of ultimate tensile strength (UTS) respectively at optimum nanoalumina. The great enhancement in fatigue life is attributed to the combined effect of interfacial strengthening, crack bridging, and pullout of nanoalumina, as evident from macro-to nano-scale fractography.     

两参数拉普拉斯BS疲劳寿命分布的统计分析

研究了两参数拉普拉斯BS疲劳寿命分布LBS(α,β)的极大似然估计，指出了原文献中的错误；给出了几种参数点估计的方法，通过Monte-Carlo模拟,比较了各方法的优劣，其中，对数矩估计方法精度较高；还讨论了参数的近似区间估计，比较了2种方法参数α的近似区间估计精度。     

Non-parametric estimation of the generalized past entropy function with censored dependent data

The generalized past entropy function introduced by Gupta and Nanda (2002) is viewed as a dynamic measure of uncertainty in past life. This measure finds applications in modeling past life time data. In the present work we provide non-parametric kernel-type estimator for the generalized past entropy function based on censored data. Asymptotic properties of the estimator are established under suitable regularity conditions. Simulation studies are carried out using the Monte Carlo method.     

A Study on the Fatigue Life of the Laser Additive Manufactured Metallic Material北大核心CSCD

随着军用飞机上越来越多的结构件使用增材制造（AM）技术成形,对增材制造材料和结构疲劳特性的研究就变得十分迫切.为了研究激光增材制造（选区激光熔化成形,SLM）铝合金以及钛合金的疲劳寿命特性,设计了一系列带各种结构细节的模拟试验件,进行常幅谱和随机谱下的试验,统计分析了各组试验的基本可靠性寿命,并得到了可靠度安全寿命曲线.断口分析发现铝合金试验件缺陷较多,存在混合失效特征,而钛合金试验件疲劳分散性较锻件大.     

Application of Pomegranate by-Products in Muscle Foods: Oxidative Indices,Colour Stability,Shelf Life and Health Benefits

In recent years, considerable importance is given to the use of agrifood wastes as they contain several groups of substances that are useful for development of functional foods. As muscle foods are prone to lipid and protein oxidation and perishable in nature, the industry is in constant search of synthetic free additives that help in retarding the oxidation process, leading to the development of healthier and shelf stable products. The by-products or residues of pomegranate fruit (seeds, pomace, and peel) are reported to contain bioactive compounds, including phenolic and polyphenolic compounds, dietary fibre, complex polysaccharides, minerals, vitamins, etc. Such compounds extracted from the by-products of pomegranate can be used as functional ingredients or food additives to harness the antioxidant, antimicrobial potential, or as substitutes for fat, and protein in various muscle food products. Besides, these natural additives are reported to improve the quality, safety, and extend the shelf life of different types of food products, including meat and fish. Although studies on application of pomegranate by-products on various foods are available, their effect on the physicochemical, oxidative changes, microbial, colour stabilizing, sensory acceptability, and shelf life of muscle foods are not comprehensively discussed previously. In this review, we vividly discuss these issues, and highlight the benefits of pomegranate by-products and their phenolic composition on human health.     

核心素养视域下化学与生活深度融合的教学*——以“碳酸钠和碳酸氢钠的性质及应用”为例

当前“碳酸钠和碳酸氢钠”的教学中,注重2者性质的分析比较,缺少对2者在生活应用的关注和亲身实践,学生无法切身感受碳酸钠与碳酸氢钠的实用价值。在核心素养视域下,化学教学应注意与生活深度融合。通过课前设置项目式学习和实践;课中汇报实践成果、进行实验探究、解决真实情境问题,使化学与生活深度融合,帮助学生深刻理解“碳酸钠和碳酸氢钠的性质及应用”,发展学生的学科核心素养,落实教、学、评一致性的要求。     

Ultralong Life Symmetric Potassium Ion Batteries Using a Bipolar Cr/Ti Based Layered Material

Based on low cost and earth abundance potassium resources, potassium-ion batteries have been regarded as the potential candidate for large-scale energy storage applications for renewable energy and smart grid. Although some earlier works have proposed reversible insertion/extraction of K⁺ ions in K cells, their cycle instability is insufficient for the further application of potassium-ion batteries. Herein, we report a symmetric potassium-ion battery with ultralong life employing a bipolar Cr/Ti based layered oxide, which contains two electrochemically active transition metals with the redox couples of Cr⁴⁺/Cr³⁺ and Ti⁴⁺/Ti³⁺ working on the ca-thode and anode side, respectively. Moreover, the (de)intercalation process in the structure and the in-situ electrochemical exchange process are investigated by ex-situ XRD. As a result, the symmetric cell based on the obtained K-based bipolar layered material exhibits a reversible capacity of 102 mA·h/g between 0.5 V and 3.5 V at 20 mA/g, an ultralong cycle life of 2000 cycles with a capacity retention of 80% and high rate capabilities. The outstanding cycling stability and rate performance endow this work with promising advantages for the future development of the novel energy storage system.     

Application of the phase‐type mortality law to life contingencies and risk management

The class of phase‐type distributions has recently gained much popularity in insurance applications due to its mathematical tractability and denseness in the class of distributions defined on positive real line. In this paper, we show how to use the phase‐type mortality law as an efficient risk management tool for various life insurance applications. In particular, pure premiums, benefit reserves, and risk‐loaded premiums using CTE for standard life insurance products are shown to be available in analytic forms, leading to efficient computation and straightforward implementation. A way to explicitly determine provisions for adverse deviation for interest rate and mortality is also proposed. Furthermore, we show how the interest rate risk embedded in life insurance portfolios can be analyzed via interest rate sensitivity index and diversification index which are constructed based on the decomposition of portfolio variance. We also consider the applicability of phase‐type mortality law under a few non‐flat term structures of interest rate. Lastly, we explore how other properties of phase‐type distributions may be applied to joint‐life products as well as subgroup risk ordering and pricing within a given pool of insureds. Copyright © 2017 John Wiley & Sons, Ltd.     

Developing the roots of modelling conceptions: ‘mathematical modelling is the life of the world’

A study conducted with 25 Year 6 primary school students investigated the potential for a short classroom intervention to begin the development of a Modelling conception of mathematics on the way to developing a sense of mathematics as a way of thinking about life. The study documents the developmental roots of the cognitive activity, actions and conceptions of both modelling and mathematics that these beginners to modelling displayed. Understanding the conceptions of mathematics that students might hold or be developing and how these can be influenced in early schooling are essential ingredients in any plans for introducing modelling seriously into primary school classrooms. The majority of the students (22/25) were identified as displaying a developing conception of modelling as a way of problem handling. The three other students displayed the developmental roots of a way of understanding the world conception of modelling. These three students also displayed a Modelling conception of mathematics with one showing indications of developing towards a Life conception of mathematics.     

Pot life extension of hydroxyl terminated polybutadiene based solid propellant binder system by tailoring the binder polymer microstructure

A possibility of extending the pot life of the HTPB-TDI based propellant binder system without adverse modification of mechanical properties is explored in the present study. It is proposed that by tailoring functionality distribution of the base HTPB polymer and changing the binder composition concurrently, the pot life of the binder system can be extended while the mechanical characteristics are kept within the acceptability window. Using an existing empirical relationship between fraction of high molecular weight (Fh) in HTPB and r-value corresponding to a more optimized set of mechanical properties, the r-values were calculated for different HTPB resins. HTPB resins with widely varying fractions of high molecular weight (Fh) were chosen and binder networks were prepared at different r values. Viscosity build up and chemical kinetics were studied for different formulations. From the studies, it is shown that the extension of pot-life is achievable by about 150 minutes without sacrificing the mechanical characteristics.