A model of flow separation controlled by dielectric barrier discharge

Flow separation,as an aerodynamic phenomenon,occurs in specific conditions.The conditions are studied in a wind tunnel on different airfoils.The phenomenon can be delayed or suppressed by exerting an external momentum to the flow.Dielectric barrier discharge actuators arranged in a row of 8 and perpendicular to the flow direction can delay flow separation by exerting the momentum.In this study,a mathematical model is developed to predict a parameter,which is utilized to represent flow separation on an NACA0012 airfoil.The model is based on the neurofuzzy method applied to experimental datasets.The neuro model is trained in different flow conditions and the parameter is measured by pressure sensors.     

Theory and detection scheme of seismic EM signals transferred into the atmosphere from the oceanic and continental lithosphere

Due to the compound structure of the medium and large portions of energy transferred, a seismic excitation in the oceanic or continental lithosphere disturbs all types of geophysical fields. To investigate the problem of electromagnetic (EM) disturbances in the atmosphere from the seismically activated lithosphere, we have formulated two mathematical models of interaction of fields of different physical nature resulting in arising of the low-frequency (from 0.1 to 10 Hz by amplitude of a few hundreds of pT) EM signals in the atmosphere. First we have considered the EM field generation in the moving oceanic lithosphere and then in the moving continental one. For both cases, the main physical principles and geological data were applied for formulation of the model and characteristics of the computed signals of different nature agree with measurements of other authors. On the basis of the 2D model of the seismo-hydro-EM-temperature interaction in the lithosphere–Ocean–atmosphere domain, a block-scheme of a multisensory vertically distributed (from a seafloor up to the ionosphere) tsunami precursors’ detection system is described. On the basis of the 3D model of the seismo-EM interaction in a lithosphere–atmosphere domain, we explain why Prof. Kopytenko (Inst. IZMIRAN of Russian Acad. Sci.) and co-authors were able to estimate location of the future seismic epicenter area from their magnetic field measurements in the atmosphere near the earth’s surface.     

径向全跳动误差的理论研究

叙述了直角坐标采样时 ,径向全跳动误差的最小二乘评定法数学模型 ,并用计算机进行仿真研究。结果表明 ,所建立的数学模型具有编程简单 ,计算准确度较高等特点。所建立的数学模型为研制形位误差虚拟测量系统提供了理论基础     

Supercomputer modeling of hydrogen combustion in rocket engines

Hydrogen being an ecological fuel is very attractive now for rocket engines designers. However, peculiarities of hydrogen combustion kinetics, the presence of zones of inverse dependence of reaction rate on pressure, etc. prevents from using hydrogen engines in all stages not being supported by other types of engines, which often brings the ecological gains back to zero from using hydrogen. Computer aided design of new effective and clean hydrogen engines needs mathematical tools for supercomputer modeling of hydrogen–oxygen components mixing and combustion in rocket engines.The paper presents the results of developing verification and validation of mathematical model making it possible to simulate unsteady processes of ignition and combustion in rocket engines.     

An aviation oxygen supply system based on a mechanical ventilation model

At high altitudes, an Aviation Oxygen Supply System(AOSS) protects pilots from low pressure and hypoxia by continuously providing oxygen corresponding to the pilots' dynamic respiratory properties.An AOSS mainly consists of oxygen supercharging machines which are used in a high-altitude flight cabin to supply pressurized oxygen to pilots.Therefore, it is of great significance to study the airflow dynamic characteristics of an AOSS for safe, continuous, and efficient oxygen supply.In this paper, an AOSS is firstly simplified and considered as a mechanical ventilation system.Then, its corresponding mathematical model is constructed.Next, to verify the mathematical model, a prototype AOSS with a lung simulator is proposed for an experimental study.Afterwards, to build a foundation for the optimization of the AOSS, the airflow dynamic characteristics of an aircraft are analyzed, and the effects of key parameters on the respiration system are researched.Through experimental and simulation studies, it can be concluded that the mathematical model is effective.Subsequently, for stability during the respiration process, we consider setting the equivalent throttling areas of the inspiration and expiration pipelines smaller within certain limits; additionally, an excessively high oxygen supply pressure will disturb smooth airflow, and in a low-pressure environment, the pressure can be 84 cm H_2O lower than the standard atmospheric pressure.This research can be referred to in the design of an oxygen supply system and the study on optimization of airflow dynamic characteristics.     

导弹系统贮存可靠性预测的数学模型

本文研究了贮存环境对导弹系统贮存可靠性的影响问题。提出了合理的数学模型。在产品的固有贮存寿命为指数分布情况下，得到了在定期检测修复条件下，产品的贮存寿命分布。并以此为依据研究了贮存寿命数据的统计方法。作为一个实例分析，本文对于导弹系统的某部件给出了实用的贮存可靠度预测模型。所用估计方法简单易行，有较强的实用性。数值结果表明预测模型有较好的预测精度     

面对面平行度误差的数学模型

简要地叙述了面对面平行度误差的正交最小二乘评定法和最小条件评定法,并分别建立了评定面对面平行度误差的数学模型。该原理可扩展到其他平行度误差的评定。     

渗碳层浓度分布的数学模型及计算机仿真

利用微分方程的数值解法，建立了气体渗碳过程中渗层碳浓度分布的数学模型，并利用所得数学模型进行计算机仿真，研究表明，该模型计算结果与实际结果吻合良好。     

疲劳试验中的数据处理

从疲劳试验工作的实际出发，介绍与疲劳问题有关的数理统计方法。该方法使分散性很大的疲劳试验结果得以合理处理，从而可准确地提供试验数据，供作材料疲劳鉴定与疲劳寿命估算之用。     

一种修正的次优子集多项式回归法

提出以集合论为工具建立在抽象代数理论基础上的修正次优子集多项式回归法，对回归过程的主要内容进行了充分的数学描述和讨论，给出了一个重要的定理和推论。理论分析和实际计算发现，利用本文提出的修正次优子集回归法对给定的任意精度都可求出最佳逼近结果。