利辛ML4．6地震与蒙城地电阻率变化特征

以消除年变化等短周期变化后的数据做为当月正常值,利用实测的月均值与正常值之比即月干扰比率、偏差等指标,突出反映月观测值在当月受到综合干扰因素影响的大小。从而突出地震前短临地电阻率异常。     

辽宁海城-岫岩地区尾波Q值研究

本文利用Sato单次散射模型,研究1999年至2007年辽宁海城-岫岩地区尾波Q值随时间的变化情况及1999年岫岩5.4级地震和2000年5.1级两次中强地震发生阶段该地区的尾波Q值变化。计算结果表明:该区在地震活跃阶段,Qc值随时间变化起伏较大,平均值相对较高,在岫岩5.4级主震前有短时升高现象,之后Qc值并没有明显的降低,直到强余震序列结束之后Qc值逐步降低,趋于平稳,通过对比该区在地震活跃阶段与平静阶段的Qc值变化,可以为未来该区的强震预测提供参考依据。     

Asymmetric variability between maximum and minimum temperatures in Northeastern Tibetan Plateau: Evidence from tree rings

Ecological systems in the headwaters of the Yellow River, characterized by hash natural environmental conditions, are very vulnerable to climatic change. In the most recent decades, this area greatly attracted the public's attention for its more and more deteriorating environmental conditions. Based on tree-ring samples from the Xiqing Mountain and A'nyêmagên Mountains at the headwaters of the Yellow River in the Northeastern Tibetan Plateau, we reconstructed the minimum temperatures in the winter half year over the last 425 years and the maximum temperatures in the summer half year over the past 700 years in this region. The variation of minimum temperature in the winter half year during the time span of 1578―1940 was a relatively stable trend, which was followed by an abrupt warming trend since 1941. However, there is no significant warming trend for the maximum temperature in the summer half year over the 20th century. The asymmetric variation patterns between the minimum and maximum temperatures were observed in this study over the past 425 years. During the past 425 years, there are similar variation patterns between the minimum and maximum temperatures; however, the minimum temperatures vary about 25 years earlier compared to the maximum temperatures. If such a trend of variation patterns between the minimum and maximum temperatures over the past 425 years continues in the future 30 years, the maximum temperature in this region will increase significantly.     

Late Eocene pollen records and palaeoenvironmental changes in northern Tibetan Plateau

The Eocene palaeovegetation landscape and palaeoclimate reconstructed from the pollen records in the Jiuquan Basin, northwest China provide some important information on the early uplift of the Tibetan Plateau and the origin and evolution of the aridification in northwest China. The records show the arid-semiarid scrubs with open forest palynofloras controlled by the subtropical high existed in northwest China during the 40.2–33.4 Ma. Four pollen assemblages are found: Nitrariadites-Cheno-podipollis-Pinaceae assemblage (40.2–37.9 Ma) is followed by Chenopodipollis-Nitrariadites assemblage (37.9–34.6 Ma), Pinuspollenites & Abietineaepollenites-Chenopodipollis assemblage (34.6–33.9 Ma), and Chenopodipollis-Nitrariadites assemblage (33.9–33.4 Ma). The percentage of thermophilic types is in anti-correlation with that of the dry types, which means the palaeoclimate is relatively warm-wet or cold-dry during most of that time. Such aridity may be related to the water vapor reduction and the planetary wind system movement northward in response to the cooling caused by small-ephemeral ice-sheets. Supported by the National Key Program for Developing Basic Sciences (Grant No. 2005CB422001), the National Science Foundation of China (Grant Nos. 40334038, 40421101) and the President Fund of Chinese Academy of Sciences     

筒仓与地基相互作用对支承柱端弯矩的影响

对钢筋混凝土柱承式筒仓动力时程分析表明,场地类别对支承柱端弯矩的变化有重要影响,在软弱场地上柱顶弯矩绝对值大于柱底弯矩绝对值;整体性较好的基础可以明显改善支承柱的受力,支承柱合理增设赘余杆也可以改善柱顶受力;文中提出了柱端弯矩增大系数及取值,以考虑地基与结构的相互作用.     

旅游地地方感的游客认知研究

体现旅游地地方特征的元素是各种类型旅游体验设计的源泉,引导不同文化背景的游客进行体验认知.形成游客的综合体验感.地方感包含了地方的客观特征和人们的主观认知两方面,而旅游地地方感的认知由地方认同和地方依赖两方面构成:其中地方认同主要来源于游客对地方独特性的感官、情感,以及对地方原真性的思考体验:地方依赖则主要来源于游客对地方依赖性的功能要素的体验.本文归纳旅游地地方感的构成要素,构建了由3大部分、11个因子构成的游客地方感认知测量的指标体系,通过问卷调查对游客的地方感认知进行定量调查.基于调查数据统计得到所有因子的评价得分,采用皮尔森相关分析的方法分析所有凶子之间的相关关系,归纳得到游客地方感认知的规律,以便为旅游地开发、规划、管理提供参考.     

Adsorption kinetics, isotherm, and thermodynamic studies of adsorption of pollutant from aqueous solutions onto humic acid

In the present study,humic acid was used as an adsorbent for the investigation of the adsorption kinetics,isotherms,and thermo-dynamic parameters of hexavalent chromium from aqueous solution at varying pH,temperatures,and concentrations.Adsorption isotherms and equilibrium adsorption capacities were determined by the fittings of the experimental data to three well-known iso-therm models:Langmuir,Freundlich,and Redlich-Peterson.The results showed that the Langmuir and Redlich-Peterson models appear to fit the adsorption better than did the Freundlich adsorption model for the adsorption of chromium onto humic acid.The equilibrium constants were used to calculate thermodynamic parameters such as the change of free energy,enthalpy,and entropy.The derived adsorption constants (logaL) and their temperature dependencies from Langmuir isotherm have been used to calculate the corresponding thermodynamic quantities such as the free energy of adsorption,heat,and entropy of adsorption.The thermo-dynamic data indicate that Cr (VI) adsorption onto humic acid is entropically driven and characterized by physical adsorption.     

Impact of human activities on soil respiration: A review

Soil respiration is one of the primary fluxes of carbon between soils and the atmosphere.It is produced by rhizosphere respiration and soil microbial respiration.Soil respiration is not only affected by environmental factors,but also changes with the hu-man-induced disturbances of ecosystems.Land-use,the measures of land management,the pollution of soil,and so on can affect soil respiration and change the soil efflux.According to some research,the authors summed up their impacts on soil respiration by human activities through land-use changes and land-management measures among agroecosystem,grassland ecosystem,and for-est ecosystem.The results showed that (1) when adding fertilization to farmland,the soil respiration will increase;(2) fenced land can decrease soil respiration,while soil respiration in the grazed land at a grassland ecosystem will decline with the increasing of grazing intensity;(3) with grassland fertilization;farmland cultivation;fire,fertilization,and cutting of forest,conflicting results were found in the changes of soil respiration.Perhaps plant species,site condition,and measurement season can lead to different results on soil respiration.     

Successful vegetative propagation by stem cuttings of Tetraena mongolica Maxim.

Techniques have been developed for the vegetative propagation of Tetraena mongolica,a rare and endangered species endemic to the western Ordos Plateau in the northcentral portion of China.The purpose of the study was to investigate the rooting characteris-tics of the plant species from the aspects of length and ages of cuttings,external hormone concentration,leaf retention,cutting orientations,and cutting positions.The results obtained from the experiments indicated that the rooting ratio of 2-year or 3-year old cuttings was larger than more than of 4-year old cuttings.The influence of external hormone concentration on rooting was ob-vious;the rooting ratio of cuttings was increased by external hormone treatment,especially when treated by ABT1(ABT No.1 Rooting Powder) 50 mg/L for 3 hours,in which case,the rooting ratio reached 91 percent.Leaf retention influenced rooting sig-nificantly;the rooting rate of cuttings became greater as the leaf retention increased.There was no significant difference in rooting capability between south and north orientations of the ortets.The rooting ratio of the cuttings obtained from the distal portions of shoots was significantly larger than those obtained from the middle and the basal portions of the shoots.On day three after treat-ment,calluses started appearing at the incisions of some cuttings dipped in 500 mg/L IAA(indole acetic acid).Most cuttings were healed or swelled,and 6 percent of cuttings rooted on day 6 after treatment.Higher rooting period occurred 7-10 days after the experiment was set up.     

S-wave velocity structure beneath Changbaishan volcano inferred from receiver function

The S wave velocity structure in Changbaishan volcanic region was obtained from teleseismic receiver func-tion modeling. The results show that there exist distinct low velocity layers in crust in volcano area. Beneath WQD station near to the Tianchi caldera the low velocity layer at 8 km depth is 20 km thick with the lowest S-wave velocity about 2.2 km/s. At EDO station located 50 km north of Tianchi caldera,no obvious crustal low velocity layer is detected. In the volcanic re-gion,the thickness of crustal ...