Optimal yield level of bilinear seismic isolation devices

The yield level of an insulator is one of the important parameters which are related to responses and absorbing energy under seismic input energy in isolated structures. The purpose of this paper is to determine the optimal ratios of yield force of the isolator (Q_y) to the total weight of the structures (W). To obtain the optimal ratio, 1044 two-degree-of-freedom isolated bridge models, which have bilinear isolators, were selected. These 2-DOF isolated bridge models with superstructure isolation can consider pier flexibility and various parameters of the isolator. Two formulas for determining the optimal yield ratio are proposed and compared with the previous researches. RAE (the ratio of absorbed energy by the isolator to the total input energy) is related directly to structural responses, and Optimal Yield Ratio (OYR), defined as a yield ratio at maximum RAE, can be obtained from the relationship between RAE and Q_y/W. Here, we found that RAE is a reliable factor to evaluate OYR, and it is proportional to earthquake amplitudes under the same kinds of earthquake loadings. Using the proposed formulas, OYR is determined and the optimal yield force of the isolator can be obtained easily and reliably at a seismic isolation design stage. Copyright © 1999 John Wiley & Sons, Ltd.     

径流量干旱指数在河西走廊灌区的应用

利用径流量干旱指数以及河西地区的酒泉、张掖和武威的春小麦单产资料,探讨干旱指数的等级与去趋势春小麦产量之间的关系.研究结果表明,径流量干旱指数与河西灌溉区春小麦气候产量呈反位相的变化趋势.因此,可利用径流量干旱指数的变化来预测该地区未来春小麦产量变化趋势.     

用气象卫星资料估算吉林省主要农作物产量

净第一性生产力（Npp）分析是全球变化研究中广为利用的方法,利用气象卫星资料获得年际植被指数（Iv）估算Npp建立不同作物的Npp与其产量的关系模型,即可实现对粮食总产和不同作物产量的估算。文中介绍了应用净第一性生产力遥感（NPP—RS）模型对吉林省粮食总产和主要作物产量进行估算的方法。采用NPP—RS模型,对1995～2000年吉林省的粮食总产及主要农作物玉米、水稻产量进行了动态估算。对粮食总产估产的平均相对误差为13．6％,玉米的平均相对误差为17．6％,水稻的平均相对误差为6．7％。要提高用此方法进行遥感估产的精度,还需要对当年的种植制度、种植结构的变化有所了解,注意当年的灾情,增加灾害影响系数。     

气象条件对奶牛产奶量的影响及对策

在分析奶牛产奶量时间和空间分布的基础上,将乌兰浩特市全市产奶量和乌兰哈达奶牛场观测站产奶量与乌兰浩特市气象资料进行相关分析,确定了影响当地牛奶产量的关键气象因子和关键时期。结果表明,温度是当地春秋季节和冬季影响奶牛产奶量的主要限制因子,其次是气压和相对湿度,而降雨量和日照时数的影响不明显。     

深部开采底板隔水关键层受局部高承压水作用破坏理论分析

大量实测地质资料与防治水实践证实,深部煤层开采底板含水层存在大量的局部高承压水区域,在强开采扰动下极易诱发底板突水灾害。基于“下三带”、“关键层”理论,将局部高承压水与底板隔水关键层简化为圆筒力学模型,分析研究隔水关键层在局部高承压水作用下的屈服破坏机制,得到了隔水关键层发生屈服的4个临界水压值公式;对各临界水压值进行区间划分,分析不同区间隔水关键层的屈服状态,确定了局部高承压水致使隔水关键层屈服破坏两个阶段的水压判据平衡方程,得出了奥陶系顶部岩层作为隔水关键层剩余隔水能力的计算表达式,并反演得到了开采深度上限、下限公式。结合九龙矿深部开采实际,对所建力学模型进行了验证与应用,进而提出了防止局部高承压水致灾的相关措施,对实现深部煤层安全带压开采具有重要的理论指导意义。     

中西太平洋金枪鱼围网高产渔区年间变化及其原因分析

金枪鱼类是中西太平洋海域重要的经济鱼种,其中鲣产量约占到总产量的50%。本研究利用1995-2010年16年的中西太平洋（20°S~20°N,120°E~155°W）鲣围网生产统计数据和Niño3.4海区（5°S~5°N,120°~170°W）海表温度异常数据,对这16年鲣产量最高的十大渔区（5°×5°）进行时空格局分析,讨论渔场分布差异及CPUE与ENSO指数的关系。结果表明:16年间十大作业渔区主要分布在5°S~5°N、130°~175°E区域,这十大渔区产量占总产量的比重达47.5%,其中5°S~0°、155°~160°E,0°~5°N、130°~135°E,0°~5°N、135°~140°E及5°S~0°、160°~165°E等4个渔区产量占高产渔区产量的比重均超过10%,是中西太平洋重要的鲣产区。高产渔区的分布受海表温度影响较大,在厄尔尼诺时期,高产渔区分布明显偏东,主要分布在155°~180°E海域;在拉尼娜时期,高产渔区分布明显偏西,主要分布在130°~160°E海域。     

Rheological behavior of dredged slurries at high water contents

Each year in the world, there is significant amount of dredged slurries generated during geotechnical jobs. In the slurry storage process, the rheological behavior is a key factor affecting the motion of dredged slurries. To gain better understanding on this behavior, experiments on dredged slurries with different liquid limits are conducted using rotary viscometer. It has been found that, as water content increases, slurry property can change from Bingham plastic fluids to Newtonian fluids. In log–log coordinates, their corresponding yield stress and plastic viscosity are in linear relationship with their water contents and the intersection of these two lines can be treated as the turning point which is 4.7 times the liquid limit. The yield stress and plastic viscosity of different dredged slurries can be normalized efficiently using normalized water content. So, in this paper, a new quantitative prediction method for yield stress and plastic viscosity is proposed, which is effective for use in alkined modes of motion, is proposed.     

The Fractal Characteristics of Drainage Networks and Erosion Evolution Stages of Ten Kongduis in the Upper Reaches of the Yellow River,China

The fractal characteristics of drainage in the ten kongduis of the upper Yellow River were obtained using the box counting dimension, and the evolution stages of the watershed topography were defined by different ranges of the fractal dimensions of river networks (Dg). The results show that the fractal scaleless range of the Maobula River is 20–370 m based on a combination of artificial judgment, correlation coefficient test and fitting error. Other kongduis show good fractal characteristics in this fractal scaleless range as well. The box counting dimension can be used as a quantitative index of watershed topography fractal characteristics. The fractal dimension of stream networks is independent of the threshold contributing area used for extracting the drainage networks from the DEM. The values of Dg in the upper ten kongduis are in the range of 1.08?1.14. Both the runoff yield and the sediment yield are positively and linearly related with Dg. The positive relation between the sediment yield and Dg reflects the effect of landform features on sediment yield in the young and/or mature stages of landform evolution of the study area. By revising the critical value of Dg, the value of Dg of the basin in the young evolution stage is less than 1.06, while it is more than 1.06 for the basin in mature or old evolution stage. The upper ten kongduis are in the mature stage of landform evolution.     

Numerical modeling of water yield of mine in Yangzhuang Iron Mine,Anhui Province of China

This study develops a three-dimensional heterogeneous numerical model to simulate the water inrush process and predict the water yield for mineral exploration in Yangzhuang Iron Mine in Anhui Province. To identify the hydrogeological parameters of the aquifer in the study area, the model was calibrated and validated using the observed heads through the integrated trial-and-error and automated techniques. Also, the sensitivity analysis of the model was performed to evaluate the uncertainty associated with the calibrated model. According to the mine construction plan at different mining levels of -500 m, -600 m, and -700 m, the calibrated model was then applied to predict the water yields dependent on the different mining levels. As indicated by the prediction results, the numerical simulation model can systematically describe the groundwater system in the mining area and determine the source of water inrush in this iron mine. In conclusion, numerical analyses carried out in this study can provide guidance to decision-makers in balancing the iron ore mining and mine dewatering in the future.     

基于旁压试验土体弹塑性本构模型初探

在大量旁压试验数据分析的基础上,通过曲线拟合,建立了旁压试验弹塑性阶段曲线的椭圆方程,利用土体SMP屈服准则和Rowe流动法则,推导出土体塑性阶段应力增量与应变增量间关系矩阵。在弹性阶段,假设土体应力-应变服从广义虎克定律,建立了基于旁压试验的土体弹塑性本构模型。编制了相应的计算程序,将文中模型计算结果与实际旁压试验曲线进行对比,初步验证了模型的正确性。将本构模型编译为ABAQUS自定义材料子程序UMAT,通过有限元对比分析,文中模型计算变形较弹性模型小,较摩尔-库仑模型大,与模型建立的假设一致。基于旁压试验的土体弹塑性本构模型参数少,且易于获取,便于在实际工程中应用。