发动机燃烧室内壁材料热环境的气动热试验模拟技术研究

利用超声速矩形湍流导管和等离子电弧加热器模拟了发动机燃烧室内流和高超声速飞行器外壁面外流热环境,进行了平板表面冷壁热流测量和燃烧室内壁材料考核试验。结果表明:由于辐射换热的影响,在选取的两个典型来流条件下,发动机燃烧室内流热环境下的冷壁热流比外流热环境下的高出21%和40%,但是冷壁热流的增量基本相当,约为0.70~0.80MW/m²。随着冷壁热流的增加,辐射换热产生的热流增量的影响力会逐渐减小。材料考核时,相同配方的C/SiC复合材料在内流热环境下的表面温度高出约400℃,背面温度高出约90℃,这种差异对于发动机燃烧室内壁面材料考核至关重要,必须在材料考核试验中加以考虑。      

客运索道防雷分类方法

根据索道所处的极易遭受雷击的独特环境、信息系统的电子器件对雷电干扰极其敏感以及索道接地效果恶劣且泄放电流不畅的实际情况,引进现行其他行业成熟防雷技术原则,提出定量计算方法进行索道防雷分类。如果能够利用监测的雷暴日数Td、结合实际环境特征分段选取合适的校正系数k,计算索道年预计雷击次数N值会更趋向真实可靠。     

Records of the Moon‐forming impact and the 470 Ma disruption of the L chondrite parent body in the asteroid belt from U‐Pb apatite ages of Novato (L6)

Novato, a newly observed fall in the San Francisco Bay area, is a shocked and brecciated L6 ordinary chondrite containing dark and light lithologies. We have investigated the U‐Pb isotope systematics of coarse Cl‐apatite grains of metamorphic origin in Novato with a large geometry ion microprobe. The U‐Pb systematics of Novato apatite reveals an upper intercept age of 4472 ± 31 Ma and lower intercept age of 473 ± 38 Ma. The upper intercept age is within error identical to the U‐Pb apatite age of 4452 ± 21 Ma measured in the Chelyabinsk LL5 chondrite. This age is interpreted to reflect a massive collisional resetting event due to a large impact associated with the peak arrival time at the primordial asteroid belt of ejecta debris from the Moon‐forming giant impact on Earth. The lower intercept age is consistent with the most precisely dated Ar‐Ar ages of 470 ± 6 Ma of shocked L chondrites, and the fossil meteorites and extraterrestrial chromite relicts found in Ordovician limestones with an age of 467.3 ± 1.6 Ma in Sweden and China. The lower intercept age reflects a major disturbance related to the catastrophic disruption of the L chondrite parent body most likely associated with the Gefion asteroid family, which produced an initially intense meteorite bombardment of the Earth in Ordovician period and reset and degassed at least approximately 35% of the L chondrite falls today. We predict that the 470 Ma impact event is likely to be found on the Moon and Mars, if not Mercury.     

两类γ暴的谱形和光变曲线的统计差异的K-S检验

最近的研究表明：短γ射线暴（γ暴）的辐射特性和长γ暴的前两秒的辐射特征相似，这引发了对以前争论的问题，即：这两类暴是否是本质上相同的暴？本文主要对和γ暴谱形和光变曲线有关的两个量的分布进行了K—S检验。分析表明：这两类暴的分布是不同的，这和广为接受的两类γ暴事件产生于不同机制的观点是一致的。     

EFFECTS OF WATER TABLE AND NITROGEN ADDITION ON CO2 EMISSION FROM WETLAND SOIL

Soil respiration is a main dynamic process of carbon cycle in wetland. It is important to contribute to global climate changes. Water table and nutritious availability are significant impact factors to influence responses of CO₂ emission from wetland soil to climate changes. Twenty-four wetland soil monoliths at 4 water-table positions and in 3 nitrogen status have been incubated to measure rates of CO₂ emission from wetland soils in this study. Three static water-table controls and a fluctuant water-table control, with 3 nitrogen additions in every water-table control, were carried out. In no nitrogen addition treatment, high CO₂ emissions were found at a static low water table (I) and a fluctuant water table (IV), averaging 306.7mg/(m²·h) and 307.89mg/(m²·h), respectively, which were 51%–57% higher than that at static high water table (II and III). After nitrogen addition, however, highest CO₂ emission was found at II and lowest emission at III. The results suggested that nutritious availability of wetland soil might be important to influence the effect of water table on the CO₂ emission from the wetland soil. Nitrogen addition led to enhancing CO₂ emissions from wetland soil, while the highest emission was found in 1N treatments other than in 2N treatments. In 3 nutritious treatments, low CO₂ emissions at high water tables and high CO₂ emissions at low water tables were also observed when water table fluctuated. Our results suggested that both water table changes and nutritious imports would effect the CO₂ emission from wetland. Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 90211003) and the Knowledge Innovation Program of Chinese Academy of Sciences (No. KACX3-SW-332) Biography: YANG Ji-song (1978-), male, a native of Chengwu of Shandong Province, Ph.D. candidate, specialized in environmental ecology and wetland biogeochemistry. E-mail: yangjisong@neigae.ac.cn     

太阳黑子相对数的分维研究

本文用非线性动力系统理论控制了现代太阳周（１８５０年１月－１９９２年５月）黑子相对数月平均变化的动力行为和可预报性，计算了它的分维数。结果表明，太阳黑子数月均变化是一个复杂的低维浑沌系统，可用有限个参数描述，所需变量至少为３个，最多为７个，本文还讨论了黑子数月均值的可预报时间尺度，平均可预报时间尺度为１５０个月，本文建议利用最小二乘直线拟合的最小方差来判定最佳无标度区，所得分维数较客观，并简要讨论     

南极纳尔逊冰帽的雪层及其成冰作用研究

纳尔逊冰帽雪—粒雪的演化依赖于融水渗浸冻结作用下的暖变质过程。积雪的密实化过程的快慢,取决于温度条件和融水的参与程度,以及自身的物理状况。粒雪的密实化过程表现为均匀且变幅小。纳尔逊冰帽成冰深度在23～25m,成冰历时17～19年。成冰带分为暖渗浸—重结晶带,渗浸—冻结带,消融带。     

Can the bump in the composite spectrum of GRB 910503 be an emission line feature of gamma-ray bursts？

Appearing in the composite spectral data of BATSE, EGRET and COMPTEL for GRB 910503, there is a bump at around 1600 keV. We perform a statistical analysis on the spectral data, trying to find out if the bump could be accounted for by a blue-shifted and significantly broadened rest frame line due to the Doppler effect of an expanding fireball surface. We made an F-test and adopted previously proposed criteria. The study reveals that the criteria are well satisfied and the feature can be interpreted as the blue shifted 6.4 keV line. Prom the fit with this line taken into account, we find the Lorentz factor of this source to be P = 116-9+9 (at the 68% confident level,△x2 = 1) and the rest frame spectral peak energy to be E0,p- 2.96-0.18+0.24 keV. Although the existence of the emission line feature requires other independent tests to confirm, the analysis suggests that it is feasible to detect emission line features in the high energy range of GRB spectra when taking into account the Doppler effect of fireball expansion.