微分学基本定理在极限计算中的应用

本文讨论了微分学的基本定理在极限求解过程中的三种应用,总结了一些简化极限运算的方法。     

积分计算中的几种方法

本文主要是应用积分上限函数的构造，建立了相应的公式。从而解决了一些定积分的繁难计算。其次，给出了一个定积分不等式的证明与三重积分计算的方法。     

CFD predictions of LBO limits for aero-engine combustors using fuel iterative approximation

Lean blow-out (LBO) is critical to operational performance of combustion systems in propulsion and power generation. Current predictive tools for LBO limits are based on decadesold empirical correlations that have limited applicability for modern combustor designs. According to the Lefebvre’s model for LBO and classical perfect stirred reactor (PSR) concept, a load parameter (LP) is proposed for LBO analysis of aero-engine combustors in this paper. The parameters contained in load parameter are all estimated from the non-reacting flow field of a combustor that is obtained by numerical simulation. Additionally, based on the load parameter, a method of fuel iterative approximation (FIA) is proposed to predict the LBO limit of the combustor. Compared with experimental data for 19 combustors, it is found that load parameter can represent the actual combustion load of the combustor near LBO and have good relativity with LBO fuel/air ratio (FAR). The LBO FAR obtained by FIA shows good agreement with experimental data, the maximum prediction uncertainty of FIA is about ±17.5%. Because only the non-reacting flow is simulated, the time cost of the LBO limit prediction using FIA is relatively low (about 6 h for one combustor with computer equipment of CPU 2.66 GHz · 4 and 4 GB memory), showing that FIA is reliable and efficient to be used for practical applications.     

极大值Ⅰ型—正态模式结构可靠性的近似置信下限

对于两个分布参数都未知的极大值Ⅰ型－正态模型，在结构强度的方差比应力的方差大得多的条件下，给出了它的结构可靠性的近似置信下限。     

Feasibility study of astronaut standardized career dose limits in LEO and the outlook for BLEO

Cosmic Study Group SG 3.19/1.10 was established in February 2013 under the aegis of the International Academy of Astronautics to consider and compare the dose limits adopted by various space agencies for astronauts in Low Earth Orbit. A preliminary definition of the limits that might later be adopted by crews exploring Beyond Low Earth Orbit was, in addition, to be made. The present paper presents preliminary results of the study reported at a Symposium held in Turin by the Academy in July 2013. First, an account is provided of exposure limits assigned by various partner space agencies to those of their astronauts that work aboard the International Space Station. Then, gaps in the scientific and technical information required to safely implement human missions beyond the shielding provided by the geomagnetic field (to the Moon, Mars and beyond) are identified. Among many recommendations for actions to mitigate the health risks potentially posed to personnel Beyond Low Earth Orbit is the development of a preliminary concept for a Human Space Awareness System to: provide for crewed missions the means of prompt onboard detection of the ambient arrival of hazardous particles; develop a strategy for the implementation of onboard responses to hazardous radiation levels; support modeling/model validation that would enable reliable predictions to be made of the arrival of hazardous radiation at a distant spacecraft; provide for the timely transmission of particle alerts to a distant crewed vehicle at an emergency frequency using suitably located support spacecraft. Implementation of the various recommendations of the study can be realized based on a two pronged strategy whereby Space Agencies/Space Companies/Private Entrepreneurial Organizations etc. address the mastering of required key technologies (e.g. fast transportation; customized spacecraft design) while the International Academy of Astronautics, in a role of handling global international co-operation, organizes complementary studies aimed at harnessing the strengths and facilities of emerging nations in investigating/solving related problems (e.g. advanced space radiation modeling/model validation; predicting the arrivals of Solar Energetic Particles and shocks at a distant spacecraft). Ongoing progress in pursuing these complementary parallel programs could be jointly reviewed bi-annually by the Space Agencies and the International Academy of Astronautics so as to maintain momentum and direction in globally progressing towards feasible human exploration of interplanetary space.     

三参数幂函数回归分析

本文给出了一种三参数幂函数回归分析方法。根据该方法, 可以通过散点试验测定高置信度、高可靠度的三参数幂函数性能曲线。它不但适用于异方差情况, 而且与传统的成组试验法相比, 既可节省大量试件又具有更高的精度。      

Weibull分布定时无失效数据可靠性分析方法

定时无失效数据的处理是当前工程中亟需解决的问题.为此,提出一种Weibull分布定时无失效数据可靠性分析方法,在形状参数下限已知的情况下,给出了可靠度和使用寿命的单侧置信下限,从而能够根据定时无失效数据对产品进行高置信水平的可靠性评定.大量Monte Carlo模拟验证结果表明,该方法既可以充分利用定时无失效数据,又能对Weibull分布无失效数据进行累加,所以增大了信息量,提高了预测精度.文中给出某型号高压容器定时无失效寿命试验数据的计算实例.      

机匣包容性的贝叶斯评价方法

用击穿率描述机匣包容性,知识状态曲线表达击穿率评价结果。针对实际评价中有关知识和信息逐步完善的特点,运用贝叶斯理论,研究出一个动态递推的评价方法。解决了贝叶斯方法实用中难题：如何简易地确定先验的贝塔分布。     

正态分布定时无失效数据可靠性分析方法

定时无失效是指产品试验到预定的时间未发生失效的情况,定时无失效数据的处理是当前工程中亟需解决的问题.为此,提出一种正态分布定时无失效数据可靠性分析方法,该方法能够根据定时无失效数据对产品进行高置信水平的可靠性评定.分别针对标准差或标准差上限已知的情况进行了详细讨论,给出了可靠度和使用寿命的单侧置信下限.并结合某型号卫星推力器脉冲点火试验得到的定时无失效数据,进行了分析计算,结果表明本方法既可以充分利用定时无失效数据,又能最大化发挥对数正态分布置信下限较高的优点,且计算简单,便于工程应用.      

基于Driscoll凹腔稳焰模型的超声速燃烧火焰稳定尺度效应研究

为了研究超声速燃烧室尺度放大后,保持火焰稳定边界相对于基准燃烧室不变,凹腔火焰稳定器几何参数应遵循何种放大准则的问题,基于已有的Driscoll凹腔稳焰数学模型,采用典型的单凹腔矩形截面燃烧室作为基准燃烧室,分别计算基准燃烧室在贫燃和富燃状态时的火焰稳定准则数DaNP,再按照燃烧室尺度放大定义写出尺度放大燃烧室的稳焰准则数表达式Da''NP,将稳焰边界不变作为约束条件,构建尺度放大准则方程式DaNP= Da''NP,求解准则方程式获得凹腔几何参数放大准则表达式,绘制准则特性曲线,分析归纳近似准则,并通过数值计算方法初步验证准则的有效性。采用Driscoll凹腔稳焰模型的尺度效应分析结果表明,燃烧室放大一定倍数n后,无法通过调整凹腔长度和深度放大倍数k1和k2使得贫燃熄火边界保持不变;但是,可以通过调整参数k1和k2使得富燃熄火边界保持不变,此时凹腔几何参数遵循的放大准则近似为 k1≈k2≈n1/4。