中国西南地区晚二叠世泥炭地净初级生产力及其控制因素

米兰科维奇旋回理论是古环境研究中重要的时间“度量”工具.文中以贵州普安糯东17号煤层和云南富源天佑10号煤层为例,对晚二叠世煤层的地球物理测井信号进行频谱分析,以获得其中的米兰科维奇轨道周期参数.研究发现,测井信号所反映出的煤层灰分含量变化受泥炭地发育时期的米兰科维奇轨道周期(123 ka(偏心率):35.6 ka(斜...     

Preservation of earthen heritage sites on the Silk Road,northwest China from the impact of the environment

The Silk Road played an important role in the economic and cultural exchanges between central China, Europe and Central Asia. A number of heritage sites with significant values still remain throughout the Gobi Desert and other desert regions in Northwest China. Most of the heritage sites composed of adobeern materials and the earthen structures have been impacted by adverse environmental conditions for thousands of years causing severe damage with only a small proportion of the structures left surviving to the present day. Analysis of the main environmental factors affecting the heritage sites such as temperature difference, wind storms, rain storms, and the freeze–thaw process and a study of the mechanism of the deterioration are the main topics presented in this paper. The authors have concluded that a Potassium–Silica solution PS invented by one of the authors has been effective in improving the intrinsic properties of heritage site earthen structures with regard to reducing the impact of environmental damage. The results of comparative tests show that samples treated by using the PS solution have performed well, particularly in protecting structures from aeolian erosion and heavy rainfall. Some findings on the effect of PS treatment on earthen structures at heritage sites are discussed in detail in the present paper.     

欠发达地区农户消费行为空间结构演变特征——以湖北省黄冈市为例

农户消费活动空间是乡村空间结构的一种表现和组成部分,在受到乡村已有的物质空间和社会空间结构影响的同时,也不断塑造并形成新的乡村空间结构.在对湖北黄冈二程镇8个村100家农户的访谈和问卷调查的基础上,总结了农户消费行为空间结构演变的一般规律和影响机制.研究结构表明:10年来,农户消费的平均空间距离总体上有缩短趋势;农户消...     

Changes in stream flow regime in headwater catchments of the Yellow River basin since the 1950s

The headwater catchments of the Yellow River basin generate over 35% of the basin's total stream flow and play a vital role in meeting downstream water resources requirements. In recent years the Yellow River has experienced significant changes in its hydrological regime, including an increased number of zero‐flow days. These changes have serious implications for water security and basin management. We investigated changes in stream flow regime of four headwater catchments since the 1950s. The rank‐based non‐parametric Mann–Kendall test was used to detect trends in annual stream flow. The results showed no significant trend for the period 1956 to 2000. However, change‐point analysis showed that a significant change in annual stream flow occurred around 1990, and hence the stream‐flow data can be divided into two periods: 1956–1990 and 1991–2000. There was a considerable difference in average annual stream flow between the two periods, with a maximum reduction of 51%. Wet‐season rainfall appears to be the main factor responsible for the decreasing trend in annual stream flow. Reductions in annual stream flow were associated with decreased interannual variability in stream flow. Seasonal stream flow distribution changed from bimodal to unimodal between the two periods, with winter stream flow showing a greater reduction than other seasons. Daily stream flow regime represented by flow duration curves showed that all percentile flows were decreased in the second period. The high flow index (Q₅/Q₅₀) reduced by up to 28%, whereas the reduction in the low flow index (Q₉₅/Q₅₀) is more dramatic, with up to 100% reduction. Copyright © 2006 John Wiley & Sons, Ltd.     

Sustainable land use planning based on ecological health

This paper, taking Beiwenquan Town of Beibei, Chongqing as an example, assessed the impacts of land use on ecological health by comprehensive index method, and discussed methodological system of sustainable land use planning based on ecological health. Results indicated that: 1) From 1992 to 2002, land use changes focused on 12 patterns with the total conversion area of 92.11%, which were related to cultivated land, residential and industrial-mining area, and orchard land. Urbanization and economic reconstruction with the leading driving forces. 2) There was obvious difference of the areas of ecotypes driven by land use change in wide valley and mild slope between 1992 and 2002, while there were little or no difference in steep slope and very steep slope. 3) Both of the conditions of ecological health in 1992 and 2002 were sound, and the ecotypes focused on the types of health and sub-health. But, health ecosystem in 1992, with an area of 764.64ha, accounting for 38.51% of the total evaluation area, was better than that in 2002, with an area of 636.10ha, accounting for 34.19% of the total evaluation area. 4) The ecotypes involved into different ranges have already degenerated, due to humankind’s disturbance, while the conditions of ecological health in the same range in 1992, regardless of stability and reconstruction, were better than that in 2002. 5) The planning scenario based on ecological health was accorded with the practice condition of Beiwenquan Town: 388.29ha of cultivated land could meet the Beiwenquan demand of food and byproduct; 1045.26ha of forest land area, the Beiwenquan demand of ecological health; and 1004.73ha of the residential and industrial-mining area, the Beiwenquan building demand. 6) Sustainable land use planning based on ecological health had higher useful value, because it not only stood to ecological theory, but also satisfied the development demand of society and economy. Foundation item: Under the auspices of the Key Project of Science and Technology of the Ministry of Education (No. 03111) and Incubation Fund Project of Science and Technology Committee of Chongqing (No. 017079) Biography: SHAO Jing-an (1976-), male, a native of Bozhou of Anhui Province, Ph.D., specialized in land use and eco-environmental evolution. E-mail: shaojinganswau@yahoo.com.cn     

The optical spectral slope variability of 17 blazars

Many quasi-simultaneous optical observations of 17 blazars are obtained from previous papers published over the last 19 years in order to investigate the spectral slope variability and understand the radiation mechanism of blazars. The long-period dereddened optical spectral slopes are calculated. We analyse the average spectral slope distribution, which suggests that the spectra of flat spectrum radio quasars (FSRQs) and high energy peaked BL Lac objects (HBLs) are probably deformed by other emission components. The average spectral slopes of low energy peaked BL Lac objects(LBLs), which scatter around 1.5, show a good accordance with the synchrotron self-Compton (SSC) loss-dominated model. We present and discuss the variability between the spectral slope and optical luminosity. The spectra of all HBLs and LBLs get flatter when they turn brighter, while for FSRQs this trend does not exist or may even be reversed. This phenomenon may imply that there is a thermal contribution to the optical spectrum for FSRQs. For the FSRQ 1156+295, there is a hint that the slope gets flatter at both the brightest and faintest states. Our result shows that three subclasses locate in different regions in the pattern of slope variability indicator versus average spectral slope. The relativistic jet mechanism is supported by the significant correlation between the optical Doppler factor and the average spectral slope.     

冰雹文献主题词词频统计与分析

作者就美国气象学会编辑出版的“气象学和地球天体物理学文摘”（Ｍｅｔｅｏ－ｒｏｌｏｇｉｃａｌ＆ＧｅｏａｓｔｒｏｐｈｙｓｉｃａｌＡｂｓｔｒａｃｔｓ，简称Ｍ．Ｇ．Ａ）所附的主题词索引中，对冰雹、雹块和雹暴等主题词在近１５年中出现的次数（即频率），进行了统计和分析，以此反映各国对冰雹研究的状况和今后发展趋势     

马氏珠母贝黄壳色选系F1和养殖群体形态性状比较

<正>马氏珠母贝(Pinctada martensii)是我国南方养殖的一种重要经济贝类,长期以来一直是我国主要的海水育珠的主要贝类,用马氏珠母贝育珠是广东、广西和海南沿海部分地区经济发展的支柱性产业。近年来,我国海水珍珠的质量出现明显滑坡,严重地削弱了在国际市场上的竞争力。为提高海水珍珠质量和在国际市场上的竞争力,国内科技工作者已经进行了大量的研究工作,这些工作主要包括对马氏珠母贝养殖群体性状的改良、育珠技术的优化和海水珍珠形成机理的研究[1-5]。     

Modelling of elastoplastic damage in concrete due to desiccation shrinkage

We present a numerical modelling of elastoplastic damage due to drying shrinkage of concrete in the framework of mechanics of partially saturated porous media. An elastoplastic model coupled with isotropic damage is first formulated. Two plastic flow mechanisms are involved, controlled by applied stress and suction, respectively. A general concept of net effective stress is used in take into account effects of capillary pressure and material damage on stress‐controlled plastic deformation. Damage evolution depends both on elastic and plastic strains. The model's parameters are determined or chosen from relevant experimental data. Comparisons between numerical simulations and experimental data are presented to show the capacity of model to reproduce mains features of concrete behaviour under mechanical loading and during drying shrinkage of concrete. An example of application concerning drying of a concrete wall is finally presented. The results obtained allow to show potential capacity of proposed model for numerical modelling of complex coupling processes in concrete structures. Copyright © 2002 John Wiley & Sons, Ltd.     

Textural research on the main source of the Changjiang River

The Chinese people began to research the main source of the Changjiang (Yangtze) River 2,400 years ago. Limited by the scientific level, they did not discover it. The Tuotuo River was determined as the main source of the Changjiang River in the 1970s. However, this was not correct, because when comparing the length of the Tuotuo River with the Dam River, the glacier length at the headwaters was added to the Tuotuo River, resulting in that the Tuotuo River is 1 km longer than the Dam River, keeping in mind that the glacier can not be regarded as part of the river. In the summer of 1986, we investigated the source of the Changjiang River, we accurately measured the length of both the Tuotuo and Dam rivers, we discovered that the Dam River was 353.1 km long, and the Tuotuo River was 346.3 km long, the Dam River thus being 6.8 km longer than the Tuotuo River. The discharge of the Dam River is 196.18 m³/sec., 2.6 times as large as that of the Tuotuo River, that of the Tuotuo River is 75.10 m³/ sec. The drainage area of the Dam River is 1.8 times as larger as that of the Tuotuo River; the drainage area of the Dam River is 30,715.7 km², the Tuotuo River is 16,691.0 km². Through synthetic analysis of the factors mentioned above, we came to the conclusion that the main source of the Changjiang River is the Dam River instead of the Tuotuo River.