AQUIFER PARAMETERS FROM CONSTANT DRAWDOWN NONSTEADY-LEAKY TYPE CURVES1

ABSTRACT: A drain function and set of type curves were defined for the mathematical solution that represents one-dimensional flow under nonsteady conditions in a leaky aquifer for the constant drawdown boundary condition. A match point procedure was developed for determining the aquifer parameters transmissivity, storage coefficient, and leakance based on the drain function and type curves. Use of the procedure is illustrated by an example that utilizes simulated aquifer drawdowns and flowrate data. The drain function and type curves developed in this investigation include the effects of leakage for the constant drawdown boundary condition, which is not included in the existing drain function and type curve found in the literature. Thus, a new set of type curves was developed that can be used to analyze drawdowns for one-dimensional flow in a leaky aquifer with constant drawdown at a line sink. Applications would include flow to a canal or river, drainage of agricultural lands, and dewatering associated with strip mining operations.     

冲压件的特征识别技术研究

特征识别是指从产品中识别出具有一定工程意义的几何形状，即特征信息的过程。作为CAD与CAPP间的智能接口，特征识别技术对实现CAD／CAPP／CAM的集成具有重要意义。针对冲压零件，尤其是带体积成形的冲压件的特点，提出了一种新型的冲压特征识别算法，并对特征识别中的难点-特征相交问题提出基于痕迹的冲压件相交特征识别方法。     

Individual variation and prior experience affect the discrimination of a brood-parasite by its subsocial beetle host

In birds, host experience can modify response to parasites but nothing similar is known for insects. We studied two desert tenebrionid beetles, the subsocial host Parastizopus armaticeps and its obligate and ubiquitous brood-(clepto)parasite Eremostibes opacus, which mimics the hosts odour spectrum. Nearly 10% of host burrows in the field (n=214) remain unparasitised even after introducing E. opacus experimentally (n=22). In discrimination tests, 7% of naive host beetles eject the parasite, showing individual variation in olfactory discrimination ability. To test for effects of prior breeding experience, naive (first time) or experienced (second time) breeders with or without prior parasite contact were confined with E. opacus at breeding onset, their behaviour recorded and parasite number counted on breeding completion. More first- than second-time breeding pairs completely excluded the parasite and second-time breeders with no prior contact with E. opacus had fewer parasites than any others. These pairs increased burrow-guarding dramatically, mostly during early reproduction, this being the best predictor of parasite number. Prolonged guarding, however, must be traded-off against other brood-care behaviours. Hence, it might pay breeding pairs to take the risk of accepting some parasites breeding within their burrow, and we expect this effect will be more pronounced if poor feeding and digging conditions are taken into account. This might explain why apparently 90% of the P. armaticeps breeding burrows in the field contain at least one parasitic E. opacus.Communicated by D. Gwynne     

Do changes in risk-taking affect habitat shifts of sticklebacks?

The distribution of individuals is often the outcome of conflicting demands, such as between predator avoidance and reproduction. A factor that has seldom been considered in studies on habitat choice is time-dependent changes in risk-taking. We investigated the distribution of threespine sticklebacks, Gasterosteus aculeatus, over two breeding seasons and found it to change with time towards shallower areas with a more open habitat structure. Shallow and structurally less complex habitats were probably favorable due to a higher reproductive rate, but costly due to an increased risk of predation. Contrary to expectation, changing predation pressure was not a predictor of the shift in habitat use and, thus, not the proximate cue. Instead date was the main predictor. This suggests that increased risk-taking in relation to predation contributed to the habitat shift. The possibility was supported by a laboratory experiment that showed sticklebacks to take larger risks and prefer more predator-exposed areas at the end of the season than at the start of the season. These results demonstrate that temporal changes in risk-taking occur and can influence habitat choice, which points to the importance of considering risk-taking, in addition to predation pressure, when studying the effect of predators on distribution.Communicated by J. Krause     

International externalities, strategic interaction, and domestic politics

Domestic politics can sometimes play an influential role when externalities have strategic and international implications. If voters delegate the choice to policymakers and if individual countries independently determine their environmental policy using a consumption tax on the emissions generating good, the result could be an outcome that is inferior to the one preferred by the median voter in the absence of delegation. On the other hand, if the international externality is unilateral in nature, rather than reciprocal, we find that delegation is largely irrelevant, since voters’ choice of policymaker is no longer strategic in character. Similarly, if voters anticipate policymakers successfully coordinating their policies at a later stage, there also will be no difference between the policymakers’ and the median voters’ aggregate weighting of environmental emissions.     

镧、锌及其交互作用对浮萍活性氧清除系统的影响

以浮萍(Lemnaminor)为材料,研究La、Zn及其交互作用对体内活性氧清除系统的影响,单独施加20mg·L-1的La或Zn对浮萍都有明显的伤害作用,且Zn的毒性远大于La。La、Zn复合处理不同程度地减弱各自的毒性,表现为植株叶绿素含量、蛋白质含量及过氧化氢酶(CAT)活性下降减缓;谷胱甘肽(GSH)、抗坏血酸(AsA)含量提高;超氧化物歧化酶(SOD)活性增强;过氧化物酶(POD)活性降低。各处理对浮萍的毒性由大到小的顺序依次为:Zn、La、Zn+La。     

A Minimal Model of Adiabatic Isotherms Surfacing in Very Shallow Waters

Based on a phenomenology that is rather frequent in the Gulf of Trieste (Northern Adriatic Sea), we analytically model the short time evolution of the temperature field inside a shallow layer of coastal water induced by a sudden offshore wind. In particular, we reproduce in a very simple way the unsteady surfacing of the isotherms forced by the marine current circulating in a vertical plane perpendicular to the coastline. The model is in agreement with the observations of a significant event recorded on 25 June, 2002 in the Gulf of Trieste.     

Random binary matrices in biogeographical ecology—Instituting a good neighbor policy

Binary matrices originating from presence/absence data on species (rows) distributed over sites (columns) have been a subject of much controversy in ecological biogeography. Under the null hypothesis that every matrix is equally likely, the distributions of some test statistics measuring co-occurrences between species are sought, conditional on the row and column totals being fixed at the values observed for some particular matrix. Many ad hoc methods have been proposed in the literature, but at least some of them do not provide uniform random samples of matrices. In particular, some swap algorithms have not accounted for the number of neighbors each matrix has in the universe of matrices with a set of fixed row and column sums. We provide a Monte-Carlo method using random walks on graphs that gives correct estimates for the distributions of statistics. We exemplify its use with one statistic.     

The curve of ion exchange ratio(%)-pH of the interaction between suspended particles with Cd(II) in the Yellow River

The curve of ion exchange ratio(%)-pH of the interactionbetween suspended particles with Cd(II) in the Yellow River wasstudied. The effects of lysine on this curve have been alsoinvestigated. The results showed that (1) Cadmium in Cd(OH)+ formin the suspended particles exchanges with the cations.The exchangeratio of Cd2+ is nearly at its greatest value in the range of pH(8.0-8.5) in natural aquatic system; (2) Ion exchange ratiodecreases as the concentration of Cd2+ raises from 8.9×10-6 mol/L to 2x8.9 x 10-6mol/L; (3) At the lysine concentration of 6.8x10-6 mol/L, it can promote the ion exchange ratio; (4) Adsorption of thesuspended particles to cadmium is weaker in seawater and Jin ShaRiver than in the Yellow River.     

成矿流体地球化学界面:Ⅱ组成及标志

本文主要介绍了地球化学界面的三个组成部分 (环境条件突变界面、流体性质演化界面、流体 -环境作用界面 ) ,地球化学界面的标志及识别方法