Environmental degradation in the Hexi Corridor region of China over the last 50 years and comprehensive mitigation and rehabilitation strategies

The regional hydrology and ecosystems of the Hexi Corridor region of northwestern China have changed over the last half century under the driving force of intense human activity and regional climate changes. Streamflow issuing from mountains in the eastern section of the Corridor by way of the Shiyang River has decreased significantly. Annual mountain outflow from the Heihe and Shule Rivers in the central and western portions of the Corridor, respectively, have tended to increase; however, their downstream discharge has decreased sharply. These lower reaches clearly display anthropogenic hydrological features. Water salinization and pollution have worsened. Presently, up to 208 km of river courses exhibit the poorest water pollution grades of IV and V. Overall, the forested area in the south Qilian Mountain region has decreased by 16.5% in the last 50 years, but has recently begun to show a gradual increase. However, natural desert forests in the northern portion of the Hexi Corridor have continued in a trend of degradation and rapid disappearance, with 3431 km² lost in Minqin and Ejin counties alone. Grasslands have been progressively degraded and their area decreased such that grasslands in the Hexi Corridor region only cover 46.86% of their former area. Desertification has been exacerbated and the grasslands' stock capacity reduced. In the Hexi Corridor region desertification has proceeded swiftly over the last 50 years, reaching, in the early 1980s, a maximum annual rate of 2.15% of total initial grassland area. However, from the late 1980s through the 1990s their desertification rate has dropped significantly. A unified watershed-scale plan for water use and management in different regions of the Hexi Corridor, considering water demands for economic development as well as ecosystem maintenance and remediation, must be implemented. The improved and ultimate sustainability of regional development for the Hexi Corridor is linked to following ecological criteria in exploiting land resources, and to systematically protect ecosystem function, allowing for sound ecosystem development.     

垂直基准定义及联接

介绍了利用地球位模型、地面重力资料、GPS和水准测量结果确定定全球高程基准及局部性垂直基准联接的基本原理和方法 ,给出了计算公式 ,并列出了国际上有关研究所获得的主要成果 ,最后对我国所需要进行的相关研究工作提出了建议     

Effects of altitude on critical ionization velocity experiments in space

The efficiency with which critical ionization velocity (CIV) discharges can be generated in space experiments is affected by the altitude at which the experiments are conducted. At around 500 km higher plasma density enhances plasma lower hybrid instability, momentum coupling efficiency, and charge exchange which is needed for seed ionization. At higher altitudes where atomic hydrogen and helium become the dominant ambient neutral species, the conditions for CIV discharge may improve considerably because less energy is lost to atmospheric ionization, even though the ambient density is reduced.     

JT-1型晶体管特性图示仪无阶梯波故障分析

针对ＪＴ－１型晶体管特性图示仪可能出现的无阶梯波故障，通过对故障特征及其思路和检修流程的分析，提出了仪器的简化框图及用示波器观察的关键点波形。     

柴达木北缘奥陶纪火山作用与构造机制

柴达木北缘奥陶系海相火山岩（洋脊及洋岛火山岩组合）是柴北缘奥陶纪古洋盆存在的重要证据。奥陶纪末期，柴北缘洋盆逐渐闭合，洋壳自南向北下插到祁连陆块之下。大洋消失后，俯冲作用携带柴达木陆块继续下插，祁连陆块则自北向南道冲到柴达木陆块之上，柴北缘成为陆－陆碰撞型造山带。从而在柴达木北缘地区，自北而南形成了祁连超叠壳楔、柴北缘碰撞混杂岩带以及柴达木俯冲壳楔的三单元结构模式。     

五大连池和宽甸地幔包体的惰性气体同位素特征——MORB型地幔和交代型地幔

黑龙江五大连池科洛和辽宁宽甸的碱性玄武岩中地幔包体的惰性气体同位素的地球化学特征研究表明,东北地区表现了地幔的不均匀性。五大连池地区的地幔包体中的~3He/~4He 比为4.5～5.3R_4,明显低于 MORB 的值,具有被交代的大陆富集地幔特征。氩同位素~(40)Ar/~(36)Ar 比的变化在557～4005。结合玄武岩和地幔包体的矿物学特征和微量元素地球化学特征,显示五大连池地区的岩浆源区可能遭受过来自壳源物质或和古俯冲事件有关的富 H_2O-CO_2流体的交代作用,辽宁宽甸黄椅山的样品~3He/~4He 比为7.30～7.52R_A,氩同位素~(40)Ar/~(36)Ar 比的范围在1496～7677。宽甸黄椅山地区的则显示了具亏损地幔 MORB 的特点,反映了未经地壳组分改造的大陆地幔的特征。本文通过对两种不同类型的地幔岩的研究,认为东北地区大陆地幔存在 MORB 型亏损地幔和交代型地慢两种类型,反映了各自不同的演化机理。     

Geopolymer formation and its unique properties

The characteristic property of naturally-occurring geopolymers is a high content of humic materials that are recognized by the nitrogen function. Through a simulated geopolymerization, biopolymers with non-nitrogen function, such as xanthan gum, were found to have the characteristics of humic acid by means of UV–Vis spectrometry. This fact ascertains that any kind of biopolymer may naturally transform to a geopolymer. A geopolymer is a type of crosslinked long-chain compound, built in three-dimensional structures whose property is immune to microbial degradation. A crosslinked biopolymer was shown to have the same characterization as a geopolymer that has a long life due to its crosslinking capacity and anti-microbial properties. In this study, the formation of petroleum-based geopolymers (e.g., kerogen) was introduced. This study may elucidate the structure of geomacromolecules and the mechanism of their formation, closely related with crosslink reaction between inorganic and organic molecules. This will further change the conventional definition of geopolymer that involves only the inorganic geopolymer.     

Sulfur electronic environments in α-NiS and β-NiS: examination of the relationship between coordination number and core electron binding energies

X-ray photoelectron spectra have been obtained under the same experimental conditions for synthetic α-NiS and natural β-NiS in order to establish any difference in S electronic environment, and to test the proposition that S core electron binding energies increase measurably with coordination number when the same metal is in different sulfide structures or lattice sites. The Ni and S electronic environments in the two NiS structures have been further probed by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and the NEXAFS spectra interpreted by reference to spectra simulated by ab initio calculations. The photoelectron and NEXAFS spectra for freshly prepared surfaces of α-NiS and β-NiS were found to be similar, with only subtle differences in electronic environment evident in the experimental and simulated NEXAFS spectra. The measured and calculated core electron binding energies did not support the previously postulated relationship between S coordination number and electron binding energies.     

Geology and Mineralogy of the Baolun Hydrothermal Gold Deposit in the Hainan Island, South China

Abstract. The Baolun quartz vein type Au deposit, is located at the southwestern Hainan Island. It occurs next to a Triassic ilmenite-series/S-type syenogranite complex. A ⁴⁰Ar/³⁹Ar plateau age for muscovite from the master orebody is dated to be 219.4±0.6 Ma, suggesting that the gold deposit genetically related to the granite pluton. In the Baolun mining area, orebodies of auriferous quartz vein and wall rock alteration occur in NNW-striking fracture zones hosted by weakly metamorphosed turbidite of the Lower Silurian age. Eight fracture zones, 400∼1300 m long and 10∼30 m wide, have been identified. The five fracture zones of them form orebodies. The ores are mainly of quartz vein type. More than 20 orebodies in shapes of vein and lens of 195∼751 m in length and 0.20∼7.49 m in thickness are known, and 14 of them occur in the No. 1 vein belt. Silicification, sericitization and pyritization are closely related to the Au mineralization. The ores exhibit commonly 1.54∼29.48 g/t in Au grade, partially >98 g/t. The master orebody is 720 m long and 2.62 m thick in average, with 9.53∼29.27 g/t Au. Gold reserves of more than 70 t have been proven by geological exploration. More than 20 metallic minerals including native gold and sulfides such as pyrite, pyrrhotite, chalcopyrite, and others are identified to be formed in four ore-forming stages: (1) Au-coarse grain quartz stage, (2) Au-fine grained quartz stage, (3) Au-bismuthide-bismuth sulfosalt-sulfide-quartz stage, and (4) calcite-sulfide-quartz stage. The Au mineralization in this deposit occurred mainly in the first three stages. A variety of Bi- and Te-bearing minerals is closely associated with native gold suggesting that the mineralization may take place in a relatively high temperature.     

A deterministic linearized recurrent neural network for recognizing the transition of rainfall–runoff processes

Characterizing the dynamic relationship between rainfall and runoff is a highly interesting modeling problem in hydrology. This study develops a deterministic linearized recurrent neural network (denoted as DLRNN) that deals with the system’s nonlinearity by recalibration at each time interval, and relates the weights of DLRNN to unit hydrographs in order to describe the transition of the rainfall–runoff processes. Case studies of 38 events, from 1966 to 1997, are implemented in the Wu-Tu watershed of Taiwan, where the runoff path-lines are short and steep. A comparison between the DLRNN and a feed-forward neural network demonstrates the advantage of DLRNN as a dynamic system model. It is concluded that DLRNN shows superiority in the performance of rainfall–runoff simulations and the ability to recognize transitions in hydrological processes.