Application of micropolar plasticity to post failure analysis in geomechanics

A micropolar elastoplastic model for soils is formulated and a series of finite element analyses are employed to demonstrate the use of a micropolar continuum in overcoming the numerical difficulties encountered in application of finite element method in standard Cauchy–Boltzmann continuum. Three examples of failure analysis involving a deep excavation, shallow foundation, and a retaining wall are presented. In all these cases, it is observed that the length scale introduced in the polar continuum regularizes the incremental boundary value problem and allows the numerical simulation to be continued until a clear collapse mechanism is achieved. The issue of grain size effect is also discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

A relationship between solar activity and frequency of natural disasters in China

The relationship between the length of the solar cycle, a good indicator of long-term change in solar activity, and natural disasters (drought, flood, and strong earthquakes) in China during the last 108 years is analyzed. The results suggest that the length of solar cycle may be a useful indicator for drought/flood and strong earthquakes. When the solar activity strengthens, we see the length of the solar cycle shorten and more floods occur in South China and frequent strong earthquakes happen in the Tibetan Plateau,but the droughts in East China as well as the strong earthquakes in Taiwan and at the western boundary of China are very few. The opposite frequencies occur when the solar activity weakens. The current study indicates that the solar activity may play an important role in the climate extremes and behavior in the lithosphere.     

Comparisons between the reproductive biology of black bream Acanthopagrus butcheri (Teleostei: Sparidae) in four estuaries with widely differing characteristics

The reproductive biology of Acanthopagrus butcheri has been studied in the permanently open Swan River and intermittently open Moore River estuaries on the lower west coast of Australia (31--32 °S) and in the permanently open Nornalup Walpole and normally closed Wellstead estuaries on the southern coast of Western Australia (34--35 °S). Trends exhibited by gonadosomatic indices, gonadal maturity stages and the sizes and developmental stages of the oocytes demonstrate that A. butcher typically spawns in spring and early summer. However, spawning occurred in salinities ranging from as low as 3.5-8 g L^–1 in the Moore River Estuary to as high as 41-45 g L^–1 in the Wellstead Estuary. Furthermore, water temperatures during spawning were greater in the two northern estuaries (19.7--28.5 °C) than in the two southern and cooler estuaries (17.5--23.4 °C). Histological studies strongly indicate that A. butcheri spawn more than once in a breeding season and demonstrate that the development of its oocytes exhibits group synchrony sensu de Vlaming (1983). The ages and total lengths at which, on average, female and male A. butcheri both first attain maturity in the Swan River Estuary were ca 2 years and ca 215 mm. However, the age at which individual fish in that system reach maturity was influenced by body size. This suggests that the attainment of first maturity at an older age but smaller length in the Moore River and Nornalup Walpole estuaries than is the case in the Swan River Estuary is a consequence of the slower growth rates of A. butcheri in those estuaries. The combination of the young age (ca 2 years) but small length (ca 145 mm) at which maturity is first attained in the Wellstead Estuary could have resulted from selection pressures brought about by high mortality rates and/or heavy fishing pressure in this estuary. The mean fecundity of A. butcheri, based on the combined number of yolk vesicle and yolk granule oocytes found in ovaries just prior to the onset of spawning, was 1580 × 10³. The significance of the sizes at first maturity, minimum legal length for capture, mesh selectivity data and closure of certain regions of estuaries to fishing for the management of the recreational and commercial fishery for A. butcheri is discussed.     

A greenhouse study on root dynamics of cactus pears, Opuntia ficus-indica and O. robusta

Over the last 10 years a great interest in spineless cactus pear was shown in the drier areas in terms of both fresh fruit and fodder production. However, there is a lack of knowledge on quantitative data on root dynamics of these plants needed to fully understand its potential under water limiting conditions. This study aimed at quantifying the effects of water stress on the growth of tap roots, side roots and rain roots of the species Opuntia ficus-indica (L.) Miller (cultivar Morado—green cladode) and O. robusta Wendl. (cultivar Monterey—blue cladode). One-year-old cladodes were planted in root boxes and pots (2002/2003 season) that were kept in the greenhouse at day/night temperatures of 25–30 °C/15–18 °C. Placing the cladodes flat on the soil, more areoles came in contact with the soil and therefore more roots developed in both species with an average of only 3.4% areole complexes not rooting. Each areole complex formed on average 3 roots. The highest daily tap root growth was 42 and 36 mm for O. ficus-indica and O. robusta, respectively. Tap root growth increased in the morning with water stress for both species but decreased in the afternoon. Side root growth increased with water stress, with that of O. robusta more per tap root than O. ficus-indica. O. robusta showed a finer root system than O. ficus-indica. The side roots grew as much as 8 and 5 mm per day for O. ficus-indica and O. robusta, respectively. Whitish rain roots developed on the established roots within the first hour after rewetting the soil and grew for only 3 days. Rain roots grew up to 7 and 5 mm within a day for O. ficus-indica and O. robusta, respectively. Considering all studied aspects of their roots systems, O. robusta appears to be better adapted to drought (less sensitive to water stress) than O. ficus-indica.     

应用地震资料设计水平井轨迹

应用三维地震资料设计水平井的轨迹,用人工合成记录标定层位和岩性并进行精细的构造解释和储层横向预测,对测区速度场进行研究,利用Geoquest 人机联作解释系统编绘层拉平图、转弯测线剖面图,不整合面构造图,各套油层顶面构造图,沿地层倾向设计水平井的轨迹.经两口井钻探,钻遇不整合面的误差0.19%—0.39%,一口井平均钻遇油层204m,相当9口直井的效益.用地震资料设计巷道水平井的关键是油层标定、深度标定和确定油层走向,用人机联作系统绘制水平切片图、反射波振幅图、油层顶构造图,设计了在油层内钻探的巷道井.经钻探,钻遇不整合面的误差0.07%,在真厚度8.23m 的油层内钻进563m.     

Single-Link Cluster Method to Identify Foreshocks and Aftershocks

Based on Single-Link Cluster (SLC) analysis,a new method to identify the foreshocks andaftershocks of a strong shock from the earthquake catalogue and then to form a sequencecatalogue has been proposed in this paper.In the SLC frame,there are many chains formedby links with lengths shorter than or equal to the characteristic length Lc.It is defined thatwhen some of these chains connect with a strong shock,the seismic events on such chainsfirm a sequence with the strong shock.In this sequence,the strong shock is the main shock;the events preceding the main shock are foreshocks and those following the main shock areaftershocks.By using this method,the foreshocks and aftershocks associated with the M_s7.4Haicheng earthquake and with the strong shocks of M_s≥6.0 in the top area of Kunlun-AltunArc were identified and sequence catalogues for these strong shocks were set up.     

我国沿海棘头梅童鱼（Collichthys lucidus）群体遗传结构的AFLP分析

利用AFLP技术分析了我国沿海棘头梅童鱼8个地理群体（山东荣成、江苏南通、启东、上海芦潮港、浙江温州、瑞安、福建福州和广州番禺）的遗传结构特征。10对引物组合在8个群体160尾个体中共扩增出272个位点,多态位点72个,多态位点比例为26．47％。8个地理群体的多态位点比例、Nei遗传多样性指数分别为8．82％-15．...     

川滇地区地震活动单键群分析

利用单键群（即ＳＬＣ）分析方法,通过有关ＳＬＣ特征参量的时间滑移分析,结合１９７０年以来的区域地震活动和构造环境,分析了川滇西部地区的地震活动。较之７０年代和８０年代,９０年代的地震活动在总体上是处于中等强度的活动水平。文章认为,ＳＬＣ方法考虑了地震事件的时空关联性,可以用来分析地震活动趋势,是研究地震活动性的有用工具。     

以菏泽地震为例探讨地震学综合预测方法

在前人提出的地震预测方法基础上提出一种地震学综合预测方法。 首先利用动态图像方法(地震条带与地震空区)大致确定潜在地震危险区; 然后利用中、 强地震产生的库仑应力确定孕震区; 最后利用地震矩快速释放模型和相关长度增长模型判断孕震区是否进入短临状态。 在地震三要素预测中, 发挥地震学典型预测方法的优势, 并且对相关性较小的预测方法的预测结论相互对比、 印证, 以便得出更可靠的预测结果。 文中还利用这种综合预测方法对1983年菏泽5.9级做了简略研究, 结果表明这种综合预测方法的预测结果和菏泽地震基本上是一致的。