Effects of the improper modeling of viscous damping on the first-mode and higher-mode dominated responses of base-isolated buildings

In many finite element platforms, a classical global damping matrix based on the elastic stiffness of the system (including isolators) is usually developed as part of the solution to the equations of motion of base-isolated buildings. The conducted analytical and numerical investigations illustrate that this approach can lead to the introduction of unintended damping to the first and higher vibration modes and the spurious suppression of the respective structural responses. A similar shortcoming might be observed even when a nonclassical damping model (ie, an assembly of the superstructure and isolation system damping sub-matrices) is used. For example, the use of Rayleigh damping approach to develop the superstructure damping sub-matrix can lead to the undesired addition of damping to the isolated mode arising from the mass-proportional component of the superstructure damping. On the other hand, the improper use of nonclassical stiffness-proportional damping (eg, determining the proportional damping coefficient, β_k , based on the first mode) can result in assigning significant damping to the higher-modes and the unintended mitigation of the higher-mode responses. Results show that a nonclassical stiffness-proportional model in which β_k is determined based on the second modal period of a base-isolated building can reasonably specify the intended damping to the higher modes without imparting undesirable damping to the first mode. The nonclassical stiffness-proportional damping can be introduced to the numerical model through explicit viscous damper elements attached between adjacent floors. In structural analysis software such as SAP2000®, the desired nonclassical damping can be also modeled through specifying damping solely to the superstructure material.     

基于伪随机信号的磁电法渗漏模型试验

磁电法是近些年在国内兴起的一种电磁勘探方法,该方法在探测地下渗流等长走向的良导地质体方面具有技术优势,但是其抗干扰能力差,易受外部噪声影响,一直未能推广.近年来,伪随机信号在物探领域开始广泛应用,该技术通过对冲激响应及阶跃响应进行卷积运算来达到降噪目的 ,可极大地提升抗干扰能力,因此,本文结合磁电法的勘探原理及伪随机辨...     

张掖市水资源实物型投入产出表的编制应用

实物型投入产出模型更适合用于核算与量化分析经济系统与资源环境间直接及间接的耦合关联。采用Helga Weisz的方法,通过价值型向实物型表转换,编制完成张掖市实物型投入产出表。基于实物型投入产出模型,对张掖市各部门水资源利用在社会经济系统中迁移特点和部门关联程度及乘数进行分析。结果表明：实物表为我们提供了新的分析视角,此方法的应用在资源环境领域的应用具有相当的适用价值。间接需求对水资源影响不容忽视,每个部门的乘数作用很大程度影响该部门在虚拟水战略中的地位和作用。畜牧业、制造业、建筑业在张掖市水资源利用部门关联中作用突出,应作为水资源的社会化管理重点关注的部门。     

Biomass strategies for climate policies?

Abstract

This paper discusses the results of the BEAP linear programming model that has been developed to study the optimal use of biomass and land for greenhouse gas emission reduction, notably the competition between food production, biomass production for energy and materials and afforestation. The model results suggest up to 100 EJ biomass use in case of global policies (about 20% of global primary energy use). The biomass is used for industrial and residential heating, transportation fuels and as a feedstock for plastics. In the electricity markets competing emission reduction options are more cost-effective than biomass. In case the Kyoto protocol is continued beyond 2010 the developed countries can rely in 2020–2030 on afforestation and land use change credits from developing countries, without any major use of other emission reduction strategies. However, in case of a planning perspective of more than half a century bioenergy is preferred instead of afforestation. The results indicate a limited impact on global agricultural trade, but food demand may be affected by CO₂ policies.     

化探渗滤异常找矿方法探讨--以云南巧家茂租铅锌矿区为例

传统的化探异常提取方法对埋深较大的隐伏矿床的弱异常难以突现,文章选择云南巧家茂租铅锌矿区作为研究试验区,将遥感影像信息与勘查地球化学方法相结合,通过对渗滤异常特征进行研究,选择有利的指示元素,运用地球化学多元分析,实现对渗滤异常的弱异常信息进行增强。该方法对主攻矿床类型明确,探测深度及找矿难度较大的地区的找矿工作有较好的指导作用。     

应用综合勘查方法分析平朔安太堡三号井工矿突水原因

平朔公司安太堡三号井工矿2007年3月在首采工作面辅运顺槽掘进时,迎头冒顶突水,初期突水量达6000～8000m^3/d,将1289．16m标高以下淹没。在分析研究区地层、构造及水文地质条件的基础上,对沙沟河道进行了渗漏观测,对地表排污水、沟水和井下突水点的水质进行了分析化验,有针对性的布置了6条物探线,最后进行了钻孔验证,综合分析认为突水水源主要为大沙沟河道的侧向补给,突水通道为NW向的强风化带。提出了加大井下排水,地表对大沙沟河进行土工膜防渗处理的综合治理措施。     

“双端封堵侧漏技术”在探测大采深工作面煤层底板裂隙中的应用

我国浅部煤层的储量在近几年内大量减少,为满足工业生产,人民生活的需要,开采深部煤层成为势在必行的发展趋势,但是,深部采区条件较为复杂,尤其是在华北石炭-二叠型煤田内,底板奥灰水,溶岩水一直都限制着煤层的开采,底板突水占整个煤矿事故中90%以上的比例。大采深工作面受底板承压水的威胁较大,采动造成的裂隙一旦与导升带相连通,形成一导水通道,则会造成底板突水。双端封堵侧漏技术通过将整个钻孔细分为若干单位段,通过测试每一单位段前后两次漏水的差异,从而确定受回采影响下底板的裂隙发育情况和最大发育深度。     

淮南矿区新集二矿1煤地面排水钻孔的设计施工

新集二矿的主采煤层位于山西组的底部,受到下伏太原组岩溶裂隙含水层的威胁。为缓解井下的防治水压力．采用了在地面施工排水孔的防治水思路。根据钻孔的位置及地层情况,采用了泥浆循环钻进与空气潜孔锤钻进相结合的方法。由于在钻孔施工过程中,发生了泥浆向巷道渗漏的情况,为保证钻孔施工安全及井下生产安全而对钻孔设计深度进行了调整,从而顺利的完成了该孔的钻探施工任务。此孔的成功,可为类似地区施工矿井防治水钻探工程提供借鉴。     

天山北麓玛纳斯河流域山间洼地地下水库的形成机理与开发利用的意义

天山北麓玛纳斯河流域山问洼地位于低山丘陵区山前坳陷带的南部，该区褶皱、断裂、近NS向次级张性断裂与平移构造以及山间洼地的第四系沉积物发育．山区地表水流经该段入渗，加之南部中山区的侧向补给形成山间洼地地下水库．正确认识玛纳斯河流域山间洼地地下水库的形成机理并对其进行合理的开发利用，对解决玛纳斯河流域季节性缺水及枯水年缺水有重要意义．笔应用构造及地表水由山区水站至山口渠首站实测流量损失的研究成果，揭示了玛纳斯河流域山间洼地地下水库的形成及调蓄作用，并概算了补给量，为今后开发利用山间洼地地下水库水资源提供了依据．     

How soil texture,channel shape and cross-sectional area affect moisture dynamics and water loss in irrigation channels

To enhance the utilization efficiency of farmland irrigation water and reduce the leakage of water conveyance channels, the leakage process of channels was simulated dynamically. The simulated results were compared with data measured in laboratory experiments, and the performance of the model was evaluated. The results indicated that the simulated values of the model were consistent with the observation values, and the R² values varied between 0.91 and 0.99. In addition, based on the laboratory experiments, a water supply system (Mariotte bottles) and soil box were built using plexiglass. Three influencing factors, namely, the channel form, soil texture and channel cross-sectional area, were varied to observe and calculate the resulting cumulative infiltration amount, infiltration rate and wetting front migration distance. HYDRUS-3D software was used to solve the three-dimensional soil water movement equation under different initial conditions. The results demonstrated that the U-shaped channel was more effective than the trapezoidal channel in increasing the utilization efficiency of the water resources. A U-shaped channel with a small channel cross-sectional area should be adopted and the soil particle size should be prioritized in the construction of water conveyance channels for farmlands. The simulation results were in agreement with the observed results, which indicates that HYDRUS-3D is a reliable tool that can accurately simulate the soil moisture movement in water conveyance channels. The research results can provide a reference for the design and operation of farmland irrigation systems.