Investigating the Desirability of Navy Aircraft Service Life Extension Programs

Building on prior work on optimal replacement of aging aircraft, this paper presents three methodologies to evaluate prospective aviation Service Life Extension Programs (SLEPs) and applies these methodologies to US Navy F/A-18E/F data. While considerable uncertainty remains as to the values of key parameters (e.g. the cost of F/A-18E/F SLEPs), the preponderance of the evidence available at this juncture favors undertaking SLEPs on F/A-18E/Fs rather than replacing them with new Joint Strike Fighters.     

A lagrangean relaxation algorithm for the constrained matrix problem

We present variants of a convergent Lagrangean relaxation algorithm for minimizing a strictly convex separable quadratic function over a transportation polytope. The algorithm alternately solves two “subproblems,” each of which has an objective function that is defined by using Lagrange multipliers derived from the other. Motivated by the natural separation of the subproblems into independent and very easily solved “subsubproblems,” the algorithm can be interpreted as the cyclic coordinate ascent method applied to the dual problem. We exhibit our computational results for different implementations of the algorithm applied to a set of large constrained matrix problems.     

复杂形状薄壁零件加工的综合质量控制

首先分析了加工时零件表面热量场和加工参数、余量场之间的关系;利用数字扫描及滤波的方法建立起复杂形面零件的数学模型;以此为基础,在加工过程中,对零件的几何质量和表面层质量进行了综合控制。研究表明,该方法是提高飞行器发动机中高负载复杂形状薄壁零件可靠性和寿命的有效新途径。