西南岩溶山区生态危机与反贫困的可持续发展文化反思

西南岩溶山区生态环境退化严重、贫困人口集中。文章探讨民族传统文化观念在岩溶山区经济活动中的作用,力图寻找岩溶山区生态恶化和贫困的深层次原因,指出岩溶山区存在的山地文化封闭性和典型的贫困文化特性及不合理的现代性转换导致区域生态恶化和可持续发展的滞后。岩溶山区应通过生态恢复模式示范建设、开展参与式社区资源管理、改善居民聚居点环境来实现文化创新和文化整合,实现传统性与现代性的深层次互动与接纳,拓宽现代性生长的内在精神空间,变外源性的“输血”机制为内源性的“造血”机制,从而使岩溶山区实现可持续发展。     

Reflections and standing waves on the Tianlai cylinder array

In 21 cm intensity mapping,the spectral smoothness of the foreground is exploited to separate it from the much weaker 21 cm signal.However,the non-smooth frequency response of the instrument complicates this process.Reflections and standing waves generate modulations on the frequency response.Here we report the analysis of the standing waves in the bandpass of the signal channels of the Tianlai Cylinder Array.By Fourier transforming the bandpass into the delay time domain,we find various standing waves generated on the telescope.A standing wave with time delay at~142 ns is most clearly identified which is produced in the 15-meter feed cable.We also identify a strong peak at a shorter delay ofτ<50 ns,which may be a mix of the standing wave between the reflector and feed,and the standing wave on the 4 m intermediate frequency(IF)cable.We also show that a smoother frequency response could be partially recovered by removing the reflection-inducted modulations.However,the standing wave on the antenna is direction-dependent,which poses a more difficult challenge for high precision calibration.     

Development and calibration of the Moon-based EUV camera for Chang'e-3

The process of development and calibration for the first Moon-based extreme ultraviolet(EUV) camera to observe Earth's plasmasphere is introduced and the design, test and calibration results are presented. The EUV camera is composed of a multilayer film mirror, a thin film filter, a photon-counting imaging detector, a mechanism that can adjust the direction in two dimensions, a protective cover, an electronic unit and a thermal control unit. The center wavelength of the EUV camera is 30.2 nm with a bandwidth of 4.6 nm. The field of view is 14.7° with an angular resolution of 0.08°, and the sensitivity of the camera is 0.11 count s-1Rayleigh-1. The geometric calibration, the absolute photometric calibration and the relative photometric calibration are carried out under different temperatures before launch to obtain a matrix that can correct geometric distortion and a matrix for relative photometric correction,which are used for in-orbit correction of the images to ensure their accuracy.     

大气CO2浓度非均匀动态分布条件下的气候模拟

利用现有大气本底站的大气CO₂浓度观测信息,综合考虑不同经济区划与土地覆盖类型对应的CO₂浓度差异及其季节变化规律,构建模式区域内以月为单位的网格化大气CO₂浓度非均匀动态分布数据模型.由此数据模型驱动RegCM4-CLM3.5区域气候模式运行,对东亚区2000年3月—2009年2月之间的气候变化特征进行了模拟,进而对大气CO₂浓度非均匀动态分布可能引起的区域气候效应进行了初步研究.结果表明:目前气候模式中CO₂浓度的常态均匀分布假设可能将温室效应夸大了10%左右.对大气CO₂浓度非均匀动态分布影响气温变化的可能机制进行研究表明:CO₂的自身效应(改变大气透射率)并不是导致Exp2试验温度降低的主要原因.大气CO₂浓度的变化影响了大气与植物胞间CO₂分压差,陆地植被通过改变气孔阻力适应这种变化,气孔阻力的变化直接影响到植物与大气间水分的交换,这种作用一方面通过蒸发冷却改变环境温度,另一方面,蒸发水分改变了近地面层湿度,进而水汽扩散到空中影响低云的分布.冬季,植物处于非生长季,对大气CO₂浓度变化响应微弱,湿度和低云变化不明显;夏季,植物生长旺盛,由CO₂生理学强迫激发的云反馈效应强烈,其效果是使中低云趋于增加,进而减弱了到达对流层低层的太阳短波辐射,造成温室效应减弱.     

24kaB.P.以来青藏高原中部湖泊演化及古降水量研究———以兹格塘错与错鄂为例

古湖泊砂砾堤研究表明,24kaB.P.,兹格塘错、错鄂分别存在10m、30m(高出现代湖面)的高湖面,湖泊面积分别可达272km2、220km2,是现代湖泊的1.42、3.12倍.与此相比,9.0-6.0kaB.P.湖面略低;在兹格塘错,古湖泊高出现代湖面8m,面积约为246km2,比现代大56km2;在错鄂,古湖面高出现代12m,面积约为138km2.基于Kutzbach水能联合方程,利用逐次逼近法取得有关参数,重建的各流域上述各时期的降水量分别可达(400±20)mm/a (兹格塘错 24kaB.P.)、(535±20)mm/a (错鄂 24kaB.P.)、(370±20)mm/a (兹格塘错 9.0-6.0kaB.P.)、(470±20)mm/a (错鄂 9.0-6.0kaB.P.).     

Satellite RFI mitigation on FAST

As the most sensitive single-dish radio telescope,the Five-hundred Aperture Spherical radio Telescope(FAST)is very susceptive to radio frequency interference(RFI)from active radio services.Moreover,due to the rapid development of space applications and research,satellite interference has become one of the main RFI sources for FAST,particularly at the L band.Therefore,we have developed several measures to mitigate satellite RFI.On the one hand,an antenna with 4.5-meter diameter has been constructed and installed at the FAST site to detect the satellite interference in the frequency band between 1 to 5 GHz.Meanwhile,we have developed a satellite RFI database based on the FAST sky coverage,the observing frequency bands,and known satellite systems.By combining the satellite RFI monitoring antenna and the database,we have established a satellite RFI mitigation system.With this system,we can not only track satellites to collect their characteristics and update the database but also help the observer to program the observing plan by predicting satellite interference.During the practical observation of FAST at the L band,the feasibility of this system to mitigate satellite RFI has been proved.In particular,the system effectively avoids strong satellite interference from entering the main beam of the telescope and causing receiver saturation.