Variation of ionospheric total electron content in Taiwan region of the equatorial anomaly from 1994 to 2003

The ionospheric total electron content (TEC) in the northern hemispheric equatorial ionospheric anomaly (EIA) region is studied by analyzing dual-frequency signals of the Global Position System (GPS) acquired from a chain of nine observational sites clustered around Taiwan (21.9–26.2°N, 118.4–112.6°E). In this study, we present results from a statistical study of seasonal and geomagnetic effects on the EIA during solar cycle 23: 1994–2003. It is found that TEC at equatorial anomaly crests yield their maximum values during the vernal and autumnal months and their minimum values during the summer (except 1998). Using monthly averaged I_c (magnitude of TEC at the northern anomaly crest), semi-annual variations is seen clearly with two maxima occurring in both spring and autumn. In addition, I_c is found to be greater in winter than in summer. Statistically monthly values of I_c were poorly correlated with the monthly Dst index (r = −0.22) but were well correlated with the solar emission F_10.7 index (r = 0.87) for the entire database for the period during 1994–2003. In contrast, monthly values of I_c were correlated better with Dst (r ? 0.72) than with F_10.7 (r ? 0.56) in every year during the low solar activity period (1994–1997). It suggests that the effect of solar activity on I_c is a longer term (years), whereas the effect of geomagnetic activity on I_c is a shorter term (months).     

空气循环制冷游离水与空气分离方法的探讨与研究

本文分析了空气循环制冷技术的原理以及技术应用于地面设备的特点，针对外界高温、高湿的大气条件下制冷过程中游离水与空气的分离问题给出了新的有效的解决办法。     

Global characteristics of ionospheric electric fields and disturbances during the first hours of magnetic storms

The ionospheric plasma density can be significantly disturbed during magnetic storms. In the conventional scenario of ionospheric storms, the negative storm phases with plasma density decreases are caused by neutral composition changes, and the positive storm phases with plasma density increases are often related to atmospheric gravity waves. However, recent studies show that the global redistribution of the ionospheric plasma is dominated primarily by electric fields during the first hours of magnetic storms. In this paper, we present the measurements of ionospheric disturbances by the DMSP satellites and GPS network during the magnetic storm on 6 April 2000. The DMSP measurements include the F region ion velocity and density at the altitude of ∼840 km, and the GPS receiver network provides total electron content (TEC) measurements. The storm-time ionospheric disturbances show the following characteristics. The plasma density is deeply depleted in a latitudinal range of ∼20° over the equatorial region in the evening sector, and the depletions represent plasma bubbles. The ionospheric plasma density at middle latitudes (20°–40° magnetic latitudes) is significantly increased. The dayside TEC is increased simultaneously over a large latitudinal range. An enhanced TEC band forms in the afternoon sector, goes through the cusp region, and enters the polar cap. All the observed ionospheric disturbances occur within 1–5 h from the storm sudden commencement. The observations suggest that penetration electric fields play a major role in the rapid generation of equatorial plasma bubbles and the simultaneous increases of the dayside TEC within the first 2 h during the storm main phase. The ionospheric disturbances at later times may be caused by the combination of penetration electric fields and neutral wind dynamo process.     

Generation of secondary waves due to intensive large-scale AGW traveling

By using data from GPS receivers we detected huge-amplitude solitary large-scale traveling acoustic-gravity waves (LS AGW) which manifested themselves as perturbations of total electron content (TEC) of duration of about 40 min. Originated in the auroral area after significant alterations of geomagnetic field intensity during geomagnetic storms on 29–30 October 2003, LS disturbances propagated with a velocity about 1000–1200 m/s and caused generation of secondary small-scale (SS) waves with time period of 2–10 min. Such SS structure followed the solitary intensive AGW at a distance more than 4000 km. However, we observed such phenomenon only within the territory with high values of “vertical” TEC and steep gradients of TEC. Apparently, these conditions are necessary for generation of SS waves due to propagation of LS AGW.     

U形管内含水航空燃油流动及换热特性数值模拟

为探究航空发动机燃油管路内流动及换热特性,建立发动机外部U形燃油管路含水燃油离散相模型（DPM）进行数值模 拟。结果表明：体积含水率（≤10%）越高,U形管全管段的压降梯度越大,换热系数越高;流动分离、迪恩涡、离心力作用和油水两 相相互作用导致流动阻力增大,是弯管段压降梯度明显大于一般直管的主要原因。不同流量条件下：迪恩涡引起的燃油横向输运 和二次流流速分布对弯管段的周向换热不均现象影响较大,弯管内、外侧的换热系数大小关系可以根据弯管段迪恩数判定。环境 温度不变,流量越大,U形管全管段压降越高,沿程换热系数越大,且含水率越高,流量对压降梯度的影响越明显;流量不变,环境 温度越低,U形管全管段压降越高,沿程换热系数越小。     

吸雨对压气机叶栅气动性能影响的实验研究

针对雨水会导致飞机发动机非正常运行的实际问题,以某压气机静叶叶栅为对象开展了压气机吸雨实验,探究了0.5马赫数和同一进口总压条件下不同来流含水量对压气机气动性能的影响。实验结果表明：来流水滴在压气机叶栅中会发生充分破碎,不同含水量来流破碎后水滴粒径基本一致,极限水滴破碎粒径约为13.3 μm。随来流含水量增加,叶栅压力面静压基本不变,吸力面静压升高,因此叶片载荷系数降低。同时,总压损失系数随含水量增大而增大,当含水量为6.41%时,相对于干空气流动,总压损失系数大致上增加了一倍。另外,来流含水量对叶栅落后角和气流转折角的影响主要体现在叶栅的尾缘附近,其中压力面侧壁附近角度变化范围为1°～3°。由实验结果推测雨水影响压气机叶栅气动性能的机理为：雨水进入叶栅中发生充分破碎,消耗主流部分动能,使得来流总压沿着流动方向不断降低,来流含水量越大总压降低越多;破碎后水滴沉积在叶栅表面,在主流剪切力、壁面摩擦力和水膜表面张力共同作用下形成溪流流动,引起表面静压变化。     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

EFFECT OF LASER CLADDING ON HYDROGEN EMBRITTLEMENT RESISTANCE OF AUSTENITIC STAINLESS STEEL

SupportedbyEngineeringPhysicsFoundationofChineseAcademyAusteniticstainlesssteels(ASS)areextenisivelyusedinnuclear,chemicalandotherin-dustriesbecauseoftheirrelativelybetterhydrogencompatibilityandcorrosionresistance.However,manyresearchers'workhasshownthatpronouncedhydrogen-inducedlossofductiLity,e.g.hydrogenembrittlement(HE),oftenoccursinthosekindsofmaterialswhenex-posedtohightemperature,highpressuregaseoushydrogen['~'J.Moreover,theyarepronetopittingcorrosion,intergranularcorrosionandinte…     

Fe含量对2219铝合金锻件焊接组织与性能的影响

为研究杂质Fe元素对2219铝合金及其焊接接头的组织、性能以及电化学腐蚀性能等的影响,采用力学拉伸、焊接试验以及金相和扫描电镜等分析测试方法,对0.15%(w)至0.01%(w)等不同Fe元素含量的2219铝合金锻件进行实验研究和分析。研究表明:2219铝合金中经热变形加工存在网络状Al_2Cu变成颗粒状和纤维状的Al_7Cu_2(Fe,Mn)相,随着Fe含量由0.15%(w)降低至0.01%(w),合金固溶时效后的Al_7Cu_2(Fe,Mn)相显著减少,锻件强度和塑性显著提高;合金焊接接头断口由脆性断裂逐渐转变为韧窝尺寸细小的韧性断裂,尤其对于延伸率,提高至近1.4倍,强度和塑性显著提高;合金的自腐蚀电流逐渐减小,单位面积上的线性极化电阻增大,合金焊接接头的耐腐蚀性能显著提高。     

置氢钛合金粉末模压成形-烧结改性机理

采用置氢TC4钛合金粉末模压成形+保护气氛下烧结工艺,研究了置氢TC4合金粉末模压成形-烧结后合金的组织性能的变化规律,提出了采用置氢钛合金粉末成形与钛合金热氢处理技术相结合的新工艺路线制备合金.结果表明:随着置氢量的增加和烧结温度的升高,置氢TC4合金粉末模压成形烧结体致密度均呈逐渐增高趋势;烧结体组织由明显的魏氏体...