基于数理统计的航材备件预测方法研究

备件预测是航空公司备件订货和供货方零部件生产计划的基础,本文提出以数理统计方法来判断附件寿命分布形式,对附件寿命和故障率进行估算,并据此给出航材备件需求量及其保障率预测模型,并运用实例进行了验证。     

平台本体的可靠性评估及其应用

平台本体的可靠性评估是用来验证其抽样数据是否符合其指标要求的一种方法。本文就平台本体的可靠性指标验证问题,进行了威布尔寿命型产品可靠性的讨论,阐述了新的可靠性评估方法的理论推导,它对比原始的可靠性评估方法更加准确和充分。最后将其应用在某型号平台本体的可靠性试验数据上并计算出结果,能够验证该平台本体满足控制系统的指标要求。     

以学期总结与规划为抓手的学生工作模式研究

从个性化教育的需要出发,提出基于学期总结与规划的因材施教法学生工作研究的新思路,旨在通过学期总结与规划为抓手和因材施教法相结合指导学生大学生活规划,通过学生书写每学期总结与下学期规划以及老师的一对一辅导,把握学生的个性化特征和潜质,帮助学生认知自我,因材施教,实现学生主观志趣与其个性特质的统一,跟踪学生的发展轨迹,并及时进行调整。结果表明,该工作模式操作性强,学生认可度高,有助于学生形成正确的人生观和做好人生规划。     

Soybean cultivation for Bioregenerative Life Support Systems (BLSSs): The effect of hydroponic system and nitrogen source

Soybean [Glycine max (L.) Merr.] is one of the plant species selected within the European Space Agency (ESA) Micro-Ecological Life Support System Alternative (MELiSSA) project for hydroponic cultivation in Biological Life Support Systems (BLSSs), because of the high nutritional value of seeds. Root symbiosis of soybean with Bradirhizobium japonicum contributes to plant nutrition in soil, providing ammonium through the bacterial fixation of atmospheric nitrogen. The aim of this study was to evaluate the effects of two hydroponic systems, Nutrient Film Technique (NFT) and cultivation on rockwool, and two nitrogen sources in the nutrient solution, nitrate (as Ca(NO₃)₂ and KNO₃) and urea (CO(NH₂)₂), on root symbiosis, plant growth and seeds production of soybean. Plants of cultivar ‘OT8914’, inoculated with B. japonicum strain BUS-2, were grown in a growth chamber, under controlled environmental conditions.     

民用飞机机身蒙皮对接结构疲劳分析及试验

在对细节疲劳额定值(DFR)方法深入研究的基础上,对 MA700飞机机身蒙皮典型对接结构进行了疲劳寿命分析,确定了该结构的载荷传递及一系列修正系数,得到了结构疲劳寿命分析结果.     

Characteristics of the soil-like substrates produced with a novel technique combining aerobic fermentation and earthworm treatment

The soil-like substrate (SLS) technique is key for improving the closure of bioregenerative life support system (BLSS) by recycling the inedible biomass of higher plants. In this study, a novel SLS technique (NSLST) was proposed: aerobic fermentations at 35 °C for 1 day, then 60 °C for 6 days, finally 30 °C for 3 days, followed by earthworm treatment for 70 days. Comparing with the original SLS technique (OSLST), its process cycle was 13 days shorter, and the dry weight loss rate (81.1%) was improved by 24.77%. The cellulose and lignin degradation rates were 96.6% and 94.6%. The concentrations of available N, P and K in mature SLS were respectively 776.1 mg/L, 348.0 mg/L and 7943.0 mg/L. Low CH₄ and NH₃ production was observed, but no accumulation. According to the seed germination test, the SLSs were feasible for plant growth. This investigation will provide a preliminary foundation for BLSS design.     

Remaining useful life prediction of aircraft lithium-ion batteries based on F-distribution particle filter and kernel smoothing algorithm

As an emergency and auxiliary power source for aircraft, lithium (Li)-ion batteries are important components of aerospace power systems. The Remaining Useful Life (RUL) prediction of Li-ion batteries is a key technology to ensure the reliable operation of aviation power systems. Particle Filter (PF) is an effective method to predict the RUL of Li-ion batteries because of its uncertainty representation and management ability. However, there are problems that particle weights cannot be updated in the prediction stage and particles degradation. To settle these issues, an innovative technique of F-distribution PF and Kernel Smoothing (FPFKS) algorithm is proposed. In the prediction stage, the weights of the particles are dynamically updated by the F kernel instead of being fixed all the time. Meanwhile, a first-order independent Markov capacity degradation model is established. Moreover, the kernel smoothing algorithm is integrated into PF, so that the variance of the parameters of capacity degradation model keeps invariant. Experiments based on NASA battery data sets show that FPFKS can be excellently applied to RUL prediction of Li-ion batteries.     

Selection and hydroponic growth of potato cultivars for bioregenerative life support systems

As part of the ESA-funded MELiSSA program, Ghent University and the Université catholique de Louvain investigated the suitability, growth and development of four potato cultivars in hydroponic culture under controlled conditions with the aim to incorporate such cultivation system in an Environmental Control and Life Support System (ECLSS). Potato plants can fulfill three major functions in an ECLSS in space missions: (a) fixation of CO₂ and production of O₂, (b) production of tubers for human nutrition and (c) production of clean water after condensation of the water vapor released from the plants by transpiration. Four cultivars (Annabelle, Bintje, Desiree and Innovator) were selected and grown hydroponically in nutrient film technique (NFT) gullies in a growth chamber under controlled conditions. The plant growth parameters, tuber harvest parameters and results of tuber nutritional analysis of the four cultivars were compared. The four potato cultivars grew well and all produced tubers. The growth period lasted 127 days for all cultivars except for Desiree which needed 145 days. Annabelle (1.45 kg/m²) and Bintje (1.355 kg/m²) were the best performing of the four cultivars. They also produced two times more tubers than Desiree and Innovator. Innovator produced the biggest tubers (20.95 g/tuber) and Desiree the smallest (7.67 g/tuber). The size of Annabelle and Bintje potatoes were intermediate. Bintje plants produced the highest total biomass in term of DW. The highest non-edible biomass was produced by Desiree, which showed both the highest shoot and root DW. The manual length and width measurements were also used to predict the total tuber mass. The energy values of the tubers remained in the range of the 2010 USDA and Souci-Fachmann-Kraut food composition databases. The amount of Ca determined was slightly reduced compared to the USDA value, but close to the Souci-Fachmann-Kraut value. The concentration of Cu, Zn and P were high compared to both databases.     

Acceptance sampling plan of accelerated life testing for lognormal distribution under time-censoring

Lognormal distribution is commonly used in engineering.It is also a life distribution of important research values.For long-life products follow this distribution,it is necessary to apply accelerated testing techniques to product demonstration.This paper describes the development of accelerated life testing sampling plans(ALSPs)for lognormal distribution under time-censoring conditions.ALSPs take both producer and consumer risks into account,and they can be designed to work whether acceleration factor(AF)is known or unknown.When AF is known,life testing is assumed to be conducted under accelerated conditions with time-censoring.The producer and consumer risks are satisfied,and the size of test sample and the size of acceptance number are optimized.Then sensitivity analyses are conducted.When AF is unknown,two or more predetermined levels of accelerated stress are used.The sample sizes and sample proportion allocated to each stress level are optimized.The acceptance constant that satisfies producer and consumer risk is obtained by minimizing the generalized asymptotic variance of the test statistics.Finally,the properties of the two ALSPs(one for known-AF conditions and one for unknownAF conditions)are investigated to show that the proposed method is correct and usable through numerical examples.     

相同设备在不同试验条件下试验图谱选择方法

同一机载设备可能安装在同一飞机的不同位置,而不同位置可能具有不同振动试验要求。为合理选择典型振动试验条件,使同状态机载设备既能经受考核验证又能满足产品互换性要求,以累计疲劳损伤理论为基础,以仿真为手段,以试验为验证,研究了不同试验条件对产品寿命的影响,并以产品寿命为依据,得出了试验条件的选择方法。