高空通风活门内流场特性数值模拟和试验验证

为准确掌握大通风量条件下高空通风活门工作特性,以高空通风活门为研究对象开展流场特性数值仿真分析技术研 究,对不同膜盒间隙的高空通风活门内部流场进行对比分析,获得了不同入口质量流量条件下高空通风活门的压降特性曲线。结 合滑油系统附件试验器改造,利用小量程与大量程体积流量计组合形式实现纯空气体积流量的测量,开展了高空通风活门压降试 验,并将试验结果与数值仿真分析结果进行对比验证。结果表明：仿真分析结果与试验结果吻合较好,流场特性仿真分析方法可 用于高空通风活门压降特性预测,现有高空通风活门在不同膜盒间隙下内流场特性相似,其压降主要集中于膜盒间隙处,改善膜 盒间隙处结构,可有效降低压降。     

Cooling and lubrication techniques in grinding:A state-of-the-art review,applications, and sustainability assessment

Grinding technology is an essential manufacturing operation, in particular, when a component with a superfinishing and an ultra-resolution is yearned. Meeting the required strict quality checklist with maintaining a high level of productivity and sustainability is a substantive issue. The recent paper outlines the lubrication and cooling technologies and mediums that are used for grinding. Furthermore, it provides a basis for a critical assessment of the different lubrication/cooling techniques ...     

卫星在轨推进剂补加量测量方法精度研究

卫星在轨推进剂补加量的精确测量技术是在轨补加任务的关键技术之一。本文结合型号攻关结果，提出2种在轨推进剂补加量测量方法数学模型，分别是压力-体积-温度(PVT)法和超声波流量计法。首先，PVT法是一种通过补加前后受体卫星贮箱剩余量反算补加量的间接测量方法，而超声波流量计法是利用超声波顺逆流相位差进行测量的直接测量方法;其次，在推进剂补加量测量模型的基础上，进一步通过取变分的手段提出2种模型的精度分析解析模型，解析的精度分析模型不仅可用于定性分析影响测量精度的因素，还可量化评价各个因素对测量精度的影响;最后，利用现有在研单机的精度水平及精度分析解析模型分析了2种方法的测量精度，验证了方法的有效性。     

Cooperative differential games guidance laws for multiple attackers against an active defense target

This paper is concerned with a scenario of multiple attackers trying to intercept a target with active defense. Three types of agents are considered in the guidance: The multiple attackers, the target and the defender, where the attackers aim to pursuit the target from different directions and evade from the defender simultaneously. The guidance engagement is formulated in the framework of a zero-sum two-person differential game between the two opposing teams, such that the measurements on the m...     

民用航空发动机润滑系统适航审定技术分析

润滑系统对航空发动机的润滑、散热、清洁、防腐等有重要作用,润滑系统的安全影响着发动机整体的安全.研究发动机润滑系统的审定基础与安全性对我国自主研制发动机润滑系统十分重要.首先对航空发动机润滑系统涉及的适航条款及标准规范进行分析,再针对润滑系统的功能和部件故障模式及影响分析(failure mode and effect...     

Cramér-rao lower bound for pulsar rotation parameters estimation with X-ray pulsar observation data

In this paper, the Cramér-Rao Lower Bound (CRLB) for estimating the rotation parameters of pulsars using X-ray pulsar observation data is deduced, and the calculation equation is presented. In order to verify the correctness of the deduced equation, we use the X-ray pulsar observation data to estimate pulsar rotation parameters, and obtain the root mean square error (RMSE) of the estimated pulsar rotation parameters through conducting repeated experiments. The experimental results suggest that when the observation time increases, the RMSE gradually approaches the estimated CRLB, and that when the observation time is 2.4 × 10⁶ s, the error between the RMSE of pulsar frequency estimation and the CRLB stays at 10^?11 order of magnitude. This verifies that the CRLB expression deduced in this paper is the theoretical lower bound for estimating pulsar rotation parameters. The deduced CRLB in this paper helps determine the minimum variance estimator for pulsar rotation parameter estimation using X-ray pulsar data, providing a benchmark for the comparison between the minimum variance estimator and other estimators.     

Formation control for networked multiagent systems with a minimum energy constraint

Minimum-energy formation achievement problems for networked multiagent systems are investigated, where information networks with leaderless and leader-follower structures are respectively addressed and information networks are randomly switching. The critical feature of this work is that the energy constraint is minimum in the sense of the linear matrix inequality, but limited-budget control and guaranteed-cost control cannot realize a minimum-energy formation. Firstly, the leaderless minimum-energy formation control problem is converted into an asymptotic stability one via a nonsingular transformation and state space decomposition, and based on linear matrix inequality techniques, sufficient conditions for analysis and design of leaderless minimum-energy formation achievement are proposed, respectively, which can be solved by the generalized eigenvalue method. Then, main results of minimum-energy formation achievement of leaderless networked multiagent systems are extended leader-follower networked multiagent systems, where the asymmetric property of the leader-follower information network is well dealt with by two nonsingular transformations. Finally, two simulation examples are shown to verify the main results for minimum-energy formation achievements of leaderless and leader-follower networked multiagent systems, respectively.