基于灰色预测的加速试验机理一致性判定方法

确定失效机理一致性条件是保证加速试验正确性的前提之一.由于现有的一致性判定方法只能利用加速试验数据,不能指导加速试验设计,因此需要一种基于强化试验数据的一致性判定方法.针对工程中强化试验数据少的特点,选取可以处理少数据的灰色预测,给出了一致性判定的新方法及流程.该方法通过将灰色预测中的GM(1,1)和等维新息模型相结合,找出强化试验数据的趋势改变点,在加速试验之前得到机理一致性变化的条件.通过在加速度计中的应用案例,验证了该方法的可行性.     

基于拉格朗日拟序结构的局部激励流动分离控制有效性分析方法

从流体输运角度提出了用于局部周期激励流动分离控制有效性研究的数值分析方法。基于有限时间不变流形理论建立用于非定常流动的流体输运分析方法,并采用数值方法从非定常流场中提取得到吸引拉格朗日拟序结构（LCSs）和排斥LCSs描述流体输运行为。通过对局部周期激励的流动分离控制规律的研究,结果表明存在三种与激励频率相关的影响翼型气动特性的流体输运模式,其中在锁频激励下吸引LCSs在前缘形成的尖楔结构有效增强主流与分离区流体的物质交换,减小翼面流动分离区的面积,显著提高翼型升力。     

多斜孔壁与机加环气膜冷却燃烧室面换热特性数值研究

数值研究了在燃烧室实际工作条件下,多斜孔壁冷却燃烧室和机加环气膜冷却燃烧室的流动、换热特性,比较分析了内、外壁温度场以及冷却流量的变化.研究发现,采用多斜孔壁后,壁面冷却效果得到强化,相比机加环气膜冷却燃烧室,燃烧室前段壁温略有升高,而后段受到气膜冷却效果增强的影响,壁面温度有所降低,壁面温度梯度明显减小.流量系数明显减小,冷却空气量降低23%,用于组织燃烧用气量增加.多斜孔壁冷却技术可以为高温升燃烧室的发展提供有效的冷却技术.      

Model for induced ionization by galactic cosmic rays in the Earth atmosphere and ionosphere

The ionization profiles produced by galactic cosmic rays in the Earth atmosphere and ionosphere are obtained on the basis of Monte Carlo simulations. Cascade processes in the atmosphere are simulated using CORSIKA 6.52 code with FLUKA 2006 and QGSJET II hadronic interaction subroutines. Proton induced showers are considered using a realistic atmospheric model (US Standard Atmosphere). The energy deposit from different components is taken into account, namely electromagnetic, hadron and muon components. The curvature of the atmosphere is considered in the computer code. On the basis of the computed ionization yield function the ion pair production rate in the atmosphere is obtained for different conditions and locations. The model is applicable to the entire atmosphere, from ground level to upper atmosphere. Several applications of the obtained results are discussed. The Monte Carlo simulation model considers nuclear interactions below the altitude of 35 km. It is compared with analytical–numerical electron production rate model. The latter model which takes into account the electromagnetic interactions above altitudes of 35 km has two main regions of application: above 50 km (thin target model) and between 35 and 50 km (intermediate target model). A good agreement between the CORSIKA results and analytical–numerical model results is found above altitude of 35 km.     

密集型阵列冲击射流换热特性实验

设计了多种不同几何参数的阵列射流冲击孔实验件,利用红外热像仪对其冲击冷却进行了热像显示实验,获得了冲击射流雷诺数和几何参数对局部对流换热特性的影响规律.结果表明:①对流换热系数随着射流雷诺数R_ej的增加而逐渐增大;②随着孔间距的或者冲击间距的增大,冲击冷却的对流换热效果逐渐减弱;③当孔间距与孔径之比在3～5时,顺排阵列射流的强化换热效果优于叉排,而当孔间距与孔径之比为2时,在阵列射流上游叉排排布的强化换热效果优于顺排,而在下游则顺排排布的强化换热效果占优.      

A Simulation of the Mid-and Low-latitude Ionospheric Electric Fields

A theoretical model of ionospheric electric fields at mid- and low-latitudes is developed. In the geomagnetic dipolar coordinate system, the ionospheric dynamo equations were solved, and the ionospheric electric potential and electric field were derived respectively. Major parameters for the model inputs, such as the neutral winds, the densities and temperatures of electron, ions and neutrals, are obtained from empirical models. The global ionospheric electrical potential and field at mid- and low-latitudes derived from our model are largely in agreement with the results presented by other authors and the empirical model. Using our model, it is found that the diurnal component of the HWM93 wind mainly contributed to the formation of the vertical electric field, while the semidiurnal component mainly contributed to the zonal electric field. Finally, by adjustment of the input F region winds and conductivities, most discrepancies between our model and the empirical one can be eliminated, and it is proved that the F region dynamo is the most significant contribution to the electric fields.      

Analysis of post-sunset F-region vertical plasma drifts during Counter Electrojet days using multi frequency HF Doppler Radar

In this paper, through a case study, an attempt has been made to bring out the relationship between post noon E-region electric field and post sunset F-region vertical plasma drift on quiet time Counter Electrojet (CEJ) days. Study carried out using the data from a multi frequency HF Doppler Radar and Digital Ionosonde located over Trivandrum (8.5° N; 77° E; 0.5° N dip lat.) a geomagnetic dip equatorial station in India during quite time CEJ days of the years 2004 and 2006, revealed some interesting aspects of the E region electrodynamics and post sunset F region electrodynamics. It has been observed that, in contrast to the normal electrojet (EEJ) days, the Pre-Reversal Enhancement (PRE) is either weakened or inhibited on CEJ days and the field reversal takes place much earlier than that on a normal day. It is suggested that even after the effects of the field reversal ceases to show up in the ground magnetic data, the reversed field may persist and shows up as a decrease in the PRE experienced by the F-region. In other words, the study indicates that the EEJ associated electrodynamics have a significant role in controlling the PRE.     

Equatorial Ionospheric Anomaly (EIA) and comparison with IRI model during descending phase of solar activity (2005–2009)

The ionospheric variability at equatorial and low latitude region is known to be extreme as compared to mid latitude region. In this study the ionospheric total electron content (TEC), is derived by analyzing dual frequency Global Positioning System (GPS) data recorded at two stations separated by 325 km near the Indian equatorial anomaly region, Varanasi (Geog latitude 25°, 16^/ N, longitude 82°, 59^/ E, Geomagnetic latitude 16°, 08^/ N) and Kanpur (Geog latitude 26°, 18^/ N, longitude 80°, 12^/ E, Geomagnetic latitude 17°, 18^/ N). Specifically, we studied monthly, seasonal and annual variations as well as solar and geomagnetic effects on the equatorial ionospheric anomaly (EIA) during the descending phase of solar activity from 2005 to 2009. It is found that the maximum TEC (EIA) near equatorial anomaly crest yield their maximum values during the equinox months and their minimum values during the summer. Using monthly averaged peak magnitude of TEC, a clear semi-annual variation is seen with two maxima occurring in both spring and autumn. Results also showed the presence of winter anomaly or seasonal anomaly in the EIA crest throughout the period 2005–2009 only except during the deep solar minimum year 2007–2008. The correlation analysis indicate that the variation of EIA crest is more affected by solar activity compared to geomagnetic activity with maximum dependence on the solar EUV flux, which is attributed to direct link of EUV flux on the formation of ionosphere and main agent of the ionization. The statistical mean occurrence of EIA crest in TEC during the year from 2005 to 2009 is found to around 12:54 LT hour and at 21.12° N geographic latitude. The crest of EIA shifts towards lower latitudes and the rate of shift of the crest latitude during this period is found to be 0.87° N/per year. The comparison between IRI models with observation during this period has been made and comparison is poor with increasing solar activity with maximum difference during the year 2005.     

空间碳纤维壳结构导热增强方法试验研究

为提高空间碳纤维复合材料壳结构的导热能力,降低热控设计难度,并提高热控系统可靠性,设计了包含贴覆石墨高导热膜材料以及在外部包覆的多层隔热组件内增加高导热膜等在内的3种导热增强措施,分别按这3种方法制作了试件,并增加了对照组,进行了真空热试验。试验结果表明,贴覆石墨高导热膜材料的方法使碳纤维壳结构试件的当量导热系数增大了7倍,相较其他方法具有明显优势。若该方法与包覆含有高导热膜夹层的多层隔热组件的方法协同使用,可以取得更好的效果。     

超声速非平衡电离磁流体动力技术实验系统

介绍了超声速非平衡电离磁流体动力技术实验系统的设计思想和组成,设计、制作了马赫数为3.5的吸气式双喉道风洞,采用以陶瓷板为阻挡介质的电容耦合射频阻挡放电,实现了超声速流场中大体积、连续、稳定、均匀等离子体的产生.主要结论有:实验测试风洞稳定工作时间为18s,稳定运行时实验段静压为650Pa;电容耦合射频放电典型工作状态下,通过伏安诊断法测出超声速条件下等离子体的电导率为1.27×10-3S/m.