大连地区大雾特征

选取2007年2月和4月出现在大连及其沿海地区的两次大雾过程, 采用GTS1型数字式探空仪探测资料、常规观测资料和NCEP/NCAR再分析资料, 对其环境场、热力和动力作用等进行诊断分析。结果表明:大雾期间, 中高纬度地区高空纬向暖干气流和对流层中下层西南暖湿气流, 为大雾形成提供了有利的水汽和风场条件。低层大气稳定层结的建立及暖干空气与雾层的上下叠置, 有利于大雾的维持。黄渤海的海温作用使冬季地面冷高压进一步增温变性, 有利于辐射雾形成发展, 使春季的暖气团冷却凝结, 有利于平流冷却雾的生成维持。伴有冷平流东移南下的偏北风是促使持续大雾消散的动力因子。     

Rapid development of the great Millennium eruption of Changbaishan (Tianchi) Volcano,China/North Korea: Evidence from U–Th zircon dating

The Changbaishan (Tianchi) volcano extending across the border of northeast China and North Korea erupted ~ 100 km³ peralkaline rhyolites around 1000 AD. This Millennium eruption of the Changbaishan volcano is one of the two largest explosive eruptions in the past 2000 years. Here we report the results of uranium–thorium dating of zircons from the Changbaishan volcanic rocks. Our data indicate that the rhyolitic magmas were stored in the crust for only 8.2 ± 1.2 ka prior to eruption. Based on titanium-in-zircon geothermometer and alkali feldspar-glass geothermometer, the rhyolitic magmas were formed at a relatively low temperature (~ 740 ± 40 °C). This storage time is very short compared with other large volume catastrophic silicic eruptions. This work demonstrates that peralkaline rhyolitic magmas from the Changbaishan volcano can develop into a catastrophic eruptive phase quite quickly.     

Reconstruction of nonmonotonic electron density profiles of the Martian topside ionosphere

One of the problems in reconstructing the real ionosphere from an ionogram is the occurrence of a ‘valley,’ where electron density decreases with altitude and make a non-monotonic profile. For the case of the Earth ionosphere, the ordinary and extraordinary ray data, accompanied with an empirical model, based on the observations, are necessary to obtain a mathematical solution for a ‘valley,’ such as the region between the E and F layers. MARSIS/MEX is a topside sounder designed to observe the ionosphere of Mars. Some ‘valley’ structures were found in the ionograms measured by MARSIS. The echoes of the extraordinary ray are not available owing to the absence of the strong magnetic field on Mars. Therefore, it is difficult to have a mathematical solution for the valleys in the Martian ionosphere. In this paper, a least square method with a simple model is presented to solve the ‘valley’ problem in the topside ionosphere of Mars. The electron density profiles with ‘valleys’ observed by the Radio Occultation experiment onboard MGS are used to rebuild the virtual depths at MARSIS frequencies. The reconstructed electron density profile by the least square method with a simple model from the rebuilt virtual depth curve is compared with the original electron density profile. It is proved that this method can reproduce small valleys in the profile of the Martian ionosphere well.     

Parameters optimization based on the combination of localization and auto-calibration of SWAT model in a small watershed in Chinese Loess Plateau

This study simulated the watershed flow and sediment responses based on calibration of the SWAT model in the semi-arid Chinese Loess Plateau (LP) where soil erosion intensively occurs. After the model’s initiation and manual modification, a 7-year inconsecutively observed flow and sediment data from 1984 to 1990 was used to analyze the model’s application in the selected watershed called AJW in the Chinese LP region. The model procedure included sensitivity analysis, parameter calibration and model validation. The best parameter set was finally determined based on the combination of parameter localization and auto-calibration. Then the model was assessed for its accuracy based on the NSE estimation, resulting in 0.77 and 0.67 for calibration and 0.46 and 0.32 for validation on simulations for flow and sediment, respectively, which is a moderately satisfactory accuracy among the applications of the SWAT model. Annual watershed assessment on flow and sediment with the calibrated SWAT model resulted in a multiyear averaged annual runoff coefficient of about 2.7% and an erosion modulus of 797 t/(km²·a⁻¹) in the AJW, indicating a beneficial consequence from the implementation of the historical soil and water conservations.     

高精度时间频率基准辅助GPS定位的研究与实现

介绍一种基于压控振荡器和GPS技术的时间频率基准，实现可编程脉冲、频率输出，达到了长期稳定性与短期稳定性兼优的目的。     

珠江三角洲地震次生灾害初步研究

介绍了地震后可能引发的地震火灾、爆炸等次生灾害；讨论了地震火灾及损失的影响因素；根据次生灾害源的分布，初步定性预测它们可能带来的损失及影响。     

甘肃公婆泉铜矿成矿地质特征及矿床成因

公婆泉铜矿位一塔里木－中朝板块中段过渡类型区岛弧环境中。矿床产于钙碱系列中酸性浅成一超浅成相斑岩体内、矿床受斑岩体、古火山机构和区域北西西向主干断裂控制。据容矿岩石、矿石矿物、微量元素、硫、铝、氧、氢、碳同位素、包体地球化学、稀土元素分析研究，认为矿床具矿化蚀变多阶段、矿质多来源的成矿特点。属中高温气成热液－海相火山斑岩矿床。