生态城市建设土地利用评价——以扬州市为例

本文从土地资源禀赋、土地利用效益、土地保护水平三个方面,初步建立了生态城市建设土地利用评价指标体系,并以扬州市为研究案例,得出扬州市2000～2008年的土地利用与保护综合水平。研究结果表明:2000年,扬州市土地利用与保护综合评价分值为52.9,处于生态恢复阶段中的治理小于破坏阶段;自2000～2008年扬州市土地利用与保护综合水平随时间呈递增趋势,特别是2004年以来递增速度明显加快,到2008年扬州市土地利用与保护综合分值为74.7,处于生态恢复阶段的末期,即将跨入生态保育阶段。最后,根据评价结论,提出了今后一段时期扬州生态城市建设土地利用与保护的建议。     

辽中地区矿业城市生态系统脆弱性研究

辽中地区矿业城市是中国重要的能源生产和重工业基地,研究其生态系统脆弱性有助于改善该区域环境恶化、生态系统失调的状况,为其可持续发展提供决策依据。基于矿业城市复合生态系统内涵,建立了辽中地区矿业脆弱性评价指标体系,提出生态系统协调度,并设定了其脆弱性和协调性分级标准。结果表明:2005年,辽中地区矿业城市生态系统脆弱性处于亚稳定状态,主要限制因子为资源匹配指数、环境质量指数和经济发展指数;辽中地区矿业城市生态系统间处于亚协调状态,其中本溪略低于亚协调,处于低度失调状态。鞍山的资源匹配指数处于较失调状态,抚顺、本溪的资源匹配指数处于失调状态,抚顺、本溪的经济发展指数处于较失调状态,是限制整个生态系统协调发展的主要原因。该评价模型较真实的反映了辽中地区矿业城市生态系统脆弱性、协调性状况,并且提出了制约其发展主要限制因子。     

初论紫金山铜金矿床超临界成矿流体系统

紫金山矿床是我国东南沿海发现的大型金铜矿床.在分析超临界成矿流体系统形成的区域地质背景和研究成矿物理化学条件的基础上,探讨了超临界成矿流体系统形成的动力学条件,提出该系统的成矿机理:与燕山晚期酸性火山-侵入岩浆有关的金铜矿床是在上地幔隆起、张性或向张性过渡背景下形成的,酸性岩浆经熔体-流体分离作用形成的岩浆热液与大气降水混合,经水-岩作用等复杂的输运和化学反应耦合过程的动力学产物.     

Implementation of online model updating in hybrid simulation

Hybrid simulation combines numerical and experimental methods for cost‐effective, large‐scale testing of structures under simulated earthquake loading. Structural system level response can be obtained by expressing the equation of motion for the combined experimental and numerical substructures, and solved using time‐stepping integration similar to pure numerical simulations. It is often assumed that a reliable model exists for the numerical substructures while the experimental substructures correspond to parts of the structure that are difficult to model. A wealth of data becomes available during the simulation from the measured experiment response that can be used to improve upon the numerical models, particularly if a component with similar structural configuration and material properties is being tested and subjected to a comparable load pattern. To take advantage of experimental measurements, a new hybrid test framework is proposed with an updating scheme to update the initial modeling parameters of the numerical model based on the instantaneously‐measured response of the experimental substructures as the test progresses. Numerical simulations are first conducted to evaluate key algorithms for the selection and calibration of modeling parameters that can be updated. The framework is then expanded to conduct actual hybrid simulations of a structural frame model including a physical substructure in the laboratory and a numerical substructure that is updated during the tests. The effectiveness of the proposed framework is demonstrated for a simple frame structure but is extendable to more complex structural behavior and models. Copyright © 2013 John Wiley & Sons, Ltd.     

张家口地下热水资源成因探讨

张家口地热资源丰富，通过对区内地热成矿机制，成矿规律的分析认为，以祁吕系为主的多构造体系复合部位控制了本区地下热水的形成与分布，本区地下热水是大气降水经深循环而成，经计算深循环的深度达为2600m，张家口南部地区有很多个热水异常点，是具有远景意义的地热区。     

上海地区扁铲侧胀试验计算地基承载力的探讨

通过对扁铲侧胀试验和试验机理的研究和对试验指数的对比分析 ,提出了用扁铲侧胀试验计算地基承载力的方法 ;利用上海地区部分重大工程中的扁铲侧胀试验数据 ,在与室内土工试验、静力触探试验及十字板剪切试验的相关分析的基础上 ,经数理统计后给出了上海地区用扁铲侧胀试验计算地基承载力的经验公式。最后 ,通过与室内土工试验、静力触探试验和十字板剪切试验计算的地基承载力对比 ,分析了本经验公式计算地基承载力的精度。研究分析表明 ,可以用扁铲侧胀试验计算地基承载力     

基于内模原理的汽车主动悬挂系统的减振控制

研究路面粗糙度扰动作用下的汽车主动悬挂系统的减振控制问题。首先简化单自由度四分之一悬挂系统模型,建立路面粗糙度扰动模型。然后基于内模原理设计汽车主动悬挂系统的减振控制结构,并利用线性系统的极点配置方法设计系统的减振控制律。最后利用数字仿真验证了减振控制律的有效性。     

A stability analysis of a conduit flow model for lava dome eruptions

Periodic variations in magma discharge rate and ground deformation have been commonly observed during lava dome eruptions. We performed a stability analysis of a conduit flow model by Barmin et al. [Barmin, A., Melnik, O., Sparks, R.S.J., 2002. Periodic behavior in lava dome eruptions. Earth and Planetary Science Letters 199 (1-2), 173–184], in which the periodic variations in magma flow rate and chamber pressure are reproduced as a result of the temporal and spatial changes of the magma viscosity controlled by the kinetics of crystallization. The model is reduced to a dynamical system where the time derivatives of the magma flow rate (dQ/dt) and the chamber pressure (dP/dt) are functions of Q and P evaluated at a shifted time t − t_?. Here, the time delay t_? represents the time for the viscosity of fluid particle to increase in a conduit. The dynamical system with time delay is approximated by a simple two-dimensional dynamical system of Q and P where t_? is given as a parameter. The results of our linear stability analyses for these dynamical systems indicate that the transition from steady to periodic flow depends on nonlinearities in the steady state relation between Q and P. The steady state relation shows a sigmoidal curve in Q − P phase plane; its slope has negative values at intermediate flow rates. The steady state solutions become unstable, and hence P and Q oscillate periodically, when the negative slope of the steady state relation ([dP/dQ]_S) exceeds a critical value; that is [dP/dQ]_S < − t_?γ/(2V_ch), where V_ch is the chamber volume and γ is an elastic constant which is related to the rigidity of chamber wall. We also found that the period and the pattern of oscillation of the conduit flow primarily depend on a quantity defined by LV_ch/r⁴, where L is the conduit length and r is the conduit radius.     

Determination of allowable subgrade frost heave with the pavement roughness index in numerical analysis

Frost heave is an upward swelling of soil during cryogenic conditions in cold regions. It is caused by the accumulation of ice crystals in subgrade soil, which grow upwards when freezing temperatures penetrate into the subgrade. This study establishes the allowable soil subgrade frost heave based on the roughness standard of asphalt pavement in China, and aims to balance the pavement design and frost heave resistance of subgrades in cold regions. We formulated a mechanical model of pavement supported by the boundary conditions of differential frost heave, based on the elastic layered system theory. The differential soil subgrade frost heave was modeled as a sinusoidal function, and the allowable frost heave and the roughness index were modeled as the displacement boundaries for the top and bottom of the pavement structure. Then the allowable frost heave was back-calculated according to the roughness standard. Numerical results show that the allowable frost heave depends on the pavement structure, material properties, the highway grade, and other factors. In order to ensure that the actual soil subgrade frost heave is lower than the allowable frost heave, pavement structures and materials need to be selected and designed carefully. The numerical method proposed here can be applied to establish the frost heave resistance of subgrade when the pavement structure and materials are determined.     

Mechanical properties of calcareous silts in a hydraulic fill island-reef

Abstract

The mechanical characteristics of calcareous silt interlayers play an important role in the stability of island-reef foundations. Direct shear and consolidation tests were performed to study the relationship between the mechanical properties and the physical parameters of calcareous silt. Based on the consolidation test results and analysis of the settling examples, different calculation methods for soil settling were compared. The results show the following. (1) The relationship between the cohesion and water content of calcareous silt can be represented by an M-shaped curve. The water contents corresponding to the two peaks of the M-type curve increase with increasing dry density. (2) When the dry density is less than 1.33?g/cm³, increasing the density significantly improves the internal friction angle of calcareous silts. When the dry density of the calcareous silt is greater than 1.33?g/cm³, the internal friction angle is affected by both the dry density and the water content. (3) The shear strength decreases when the water content exceeds the optimum level. (4) The compressive modulus of calcareous silt is larger than that of terrigenous silt. Specifically, it decreases with decreasing dry density and increasing water content. (5) The stepwise loading method should be used to estimate the soil settling before fill engineering construction.