水平同心旋转套筒内的混合对流

 用数值模拟法研究了水平同心套筒内、外筒加热旋转时的流动和传热特性,提出了旋转流抑制自然对流的物理机制,进一步验证了对流换热可比拟为具有内热源的导热问题。     

边界弹性支撑板固有振动分析的一种解析方法

板的挠曲面微分方程与振型函数方程在数学上具有相同的形式，在力学上又具有相同的意义。这种可比拟性使得利用贝蒂功互等定理对板的固有振动进行研究成为可能。该文给出了求解矩形板的通用基本解，并对对边简支矩形板分别具有均匀的一般弹性边界支撑和弹性嵌固支撑时的固有振动进行了讨论，得到了解析形式的频率方程。     

MS中的自然数系统

首先给出了中介逻辑ＭＬ的二值子系统Ｆ＾ＩＭＬ，说明了它与经典二值逻辑的子系统Ｆ＾Ｉ同构。其次，利用中介公理集合论ＭＳ的相关理论，构造了ＭＳ中的自然数系统，证明了Ｐｅａｎｏ５条公理为ＭＳ中的定理。最后指出以此五条性质为公理、并以Ｆ＾ＩＭ为配套逻辑，在ＭＳ中可推出自然数的所有性质。     

超临界自然层流翼型NPU-L72513的风洞试验研究

超临界自然层流翼型具有很好的应用前景。西北工业大学翼型研究中心设计的我国第一个超临界自然层流翼型 NPU-L72513在 CARDC 高速所的跨声速风洞进行了试验,证明超临界自然层流翼型 NPU-L72513具有优良气动特性,其设计是成功的。同时说明我国已初步具有自行设计超临界自然层流翼型和进行相应风洞试验的能力。     

倾转旋翼机传动系统多状态响应特性研究

以倾转旋翼机发动机短舱内的传动系统为研究对象,根据设计的传动结构建立了它的动力学模型和动态响应方程,分析了倾转旋翼机旋翼在起降、巡航和过渡三种状态下的激励特性,并针对三种状态下旋翼激励的特点对传动系统动态响应进行了数值求解,最后研究了传动系统中齿轮啮合的动载系数的变化特点,并对系统的共振频率进行了探讨.研究工作对倾转旋翼机的传动系统的可靠性分析和动态优化设计等均有参考意义.      

“双顺差”下中国经济隐含的危机

中国的国际收支正处于“双顺差”阶段,一些学者认为“双顺差”是中国经济迅速腾飞的必经阶段,而另一些学者提出“双顺差”正给中国带来巨大的福利损失。文章对“双顺差”的成因进行分析,指出“双顺差”使中国经济孕育的风险增加,环境污染加剧,资源和能源耗竭速度加快,企业遭遇贸易争端的风险增加,政府储备机构承受的风险越来越高。要控制和缓解“双顺差”带来的危机,可采取以下对策：优化利用外资结构,提高外商投资的门槛;优化和提升出口产品结构,禁止战略性资源出口;扩大内需,降低中国经济的对外贸易依存度;适当放松资本管制,但要抑制非法资本的流入;制定鼓励进口的政策,扩大进口贸易。     

飞机发动机冷气道与隔热层的耦合传热分析

数值研究了某飞机发动机外侧冷气道与隔热层的耦合传热过程。采用低雷诺数k-ε模型与SIMPLEC算法计算通道内可压缩变物性气流的湍流对流换热,采用蒙特卡罗法求解通道壁面间的辐射换热。通道内气流湍流对流换热、壁面间辐射换热与隔热层内导热耦合求解。通过模拟计算,分析了通道与隔热层的耦合传热机制,考察了相关参数的影响。结果表明,在所考虑的通道结构与空气流条件下,冷气道外环壁面的温度高于气流温度,气流对内外环壁面均起冷却作用;在隔热层参数不变条件下,壁面间的辐射换热与气流的对流冷却是该传热过程的控制机制,增大冷气流量、降低壁面发射率均可显著降低隔热层的外壁面温度。     

Relationship of the diffuse aurora and SAR arc dynamics to substorms and storms

Investigation results of a diffuse aurora (DA) and stable auroral red (SAR) arc dynamics based on spectrophotometric observations at the Yakutsk meridian (199°E geomagnetic longitude) are presented. The relationship of an equatorward extension of DA in the 557.7 nm emission to a substorm growth phase during the magnetospheric convection intensification after the turn of IMF B_Z to the south is shown. The formation of SAR arc during the substorm expansion phase is investigated. The association of SAR arc dynamics with the development of asymmetric ring current (substorm injection) during the main phase of a storm is analyzed. It is shown how the pulsating precipitations of energetic ring current particles develop in the outer plasmasphere based on photometric observations.     

伸展垂直薄片非定常层流自然对流的群论分析

用Ｍｏｒｇａｎ的双参数变换群理论，对磁场作用下的伸展垂直薄片的不可压缩非定常层流自然对流边界层流动进行相似性分析，得到了三种情况下的相似性解方程组。并在不同的Ｐｒ，Ｎｍ，Ｆｃ和ｒ下，用四阶龙格－库塔法进行了数值求解，得到了速度和温度分布，并给出了一组相似性解的结果。     

Convection of liquid with internal heat release in a rotating container

The convection of heat-generating fluid in a rotating horizontal cylinder is experimentally investigated. The threshold of convection excitation, the structure of convective flows and the heat transfer in the cylinder depending on the heat release capacity, liquid viscosity and aspect ratio of the cavity are studied. It is found that the average convection is excited by the thermovibrational mechanism —the gravity force, rotating in the cavity frame, produces the oscillations of non-isothermal fluid relative to the wall, which in turn result in excitation of mean convective flows. It is shown that the structure of convective flows depends on the dimensionless velocity of rotation. At relatively low rotation velocity the convection develops in the form of a periodic system of vortices regularly distributed along the cylinder axis. The threshold of excitation (critical value of vibration parameter) of three-dimensional vortex structures grows with rotation velocity. Above some definite rotation velocity the convection develops as two-dimensional rolls parallel to the axis of rotation. The threshold of two-dimensional structures excitation does not depend on the rotation velocity. Besides the structure of thermal convective flows the analysis of the relatively weak currents generated by the inertial waves below the threshold of convection is performed.