耗散结构理论在土壤科学上应用途径的探索

本文根据耗散结构的基本理论，结合生产实践经验，提出了表征土壤肥力的非线性微分方程：＝（Ｋ－ｂ）ｘ－βｘ２Ｘ─土壤生物活性，ｔ─时间，Ｋ─生物繁殖系数，ｂ─生物死亡系数，β─生物饱和系数．解这个并不复杂的非线性微分方程，便可知道土壤是处于热力学分枝，还是耗散结构分枝．这对研究土壤肥力的动态变化、土壤肥力的分类、土壤的管理、土壤退化的防止等方面有着无法预测的应用前景．     

人地协同论：可持续发展模型构建的基础

人地协同论是在陆地系统科学、非线性系统理论基础上建立起来的关于可持续发展的一个数理模型,它以社会与自然的交互作用、交界面性质及其演化规律为研究对象。本文根据系统生态学理论,提出了关于可持续生存的数学定义。     

NONLINEAR MODELING AND PREDICTION OF A RIVER FLOW SYSTEM1

ABSTRACT: Model estimation and prediction of a river flow system are investigated using nonlinear system identification techniques. We demonstrate how the dynamics of the system, rainfall, and river flow can be modeled using NARMAX (Nonlinear Autoregressive Moving Average with eXogenuous input) models. The parameters of the model are estimated using an orthogonal least squares algorithm with intelligent structure detection. The identification of the nonlinear model is described to represent the relationship between local rainfall and river flow at Enoree station (inputs) and river flow at Whitmire (output) for a river flow system in South Carolina.     

海上溢油扩散图像处理的非线性方法研究

针对海上溢油应急处理问题,本文主要对溢油的初级行为--扩散进行探讨.提出了采用溢油扩散图像来预测溢油扩散未来发展趋势的3步非线性处理过程,即图像边缘检测、面积计算和面积预测,对这一过程中应采用的方法进行了分析与比较.并以奥里油在静止海水中扩散为范例,在MATLAB环境下,利用非线性方法对扩散图像进行边缘监测,通过对梯度算子阀值的调整来计算完整的油膜覆盖面积,并将其计算结果进行BP神经网络预测.结果表明:采用Roberts边缘算子可以得到很好的边缘检测结果,采用BP神经网络获得的面积预测结果与实验结果吻合程度较好.     

爆破地震波作用下尾矿坝的有限元动力分析

为了了解某钼矿进行爆破采矿是否会对近距离的尾矿坝产生破坏作用,结合实际勘探资料,在二维静力非线性有限元分析的基础上,进行爆破地震波作用下坝体的动力反应分析,综合研究了动位移、动应力和加速度时程等关键物理量变化的规律性,并在此基础上进一步结合试验资料对坝体进行了液化判断及稳定性分析。分析结果表明,该钼矿在规定的爆心距、药量范围内进行爆破采矿时,相邻的尾矿坝是安全稳定的。本文的研究结果对爆破设计、现场采矿及尾矿坝体运行维护均具有一定的指导意义。     

钢筋混凝土箱型高墩双向拟静力试验研究

随着高墩大跨桥梁的广泛应用,其抗震问题也越来越突出。本文主要考虑轴压比、长细比的影响,进行了6个钢筋混凝土薄壁箱型高墩缩尺模型的双向拟静力试验,以及反复荷载作用下的非线性分析。研究表明:①钢筋混凝土薄壁箱型高墩柱在多维荷载共同作用下,主要发生典型的弯曲破坏,但剪切作用也不容忽视;②墩柱的破坏受到不同方向耦合作用的显著影响,尤其是抗弯刚度小的一侧受到的影响更大,较早就出现开裂,提前进入塑性发展阶段;③非线性有限元计算的滞回曲线、骨架曲线等与试验结果基本吻合;④建立了考虑轴压比、长细比影响的钢筋混凝土薄壁箱型高墩的双向荷载—位移恢复力模型,该模型基本能够反映钢筋混凝土薄壁箱型高墩的抗震性能,可供钢筋混凝土箱型高墩柱及高墩桥梁结构的抗震设计和动力计算参考。     

A mathematical approach for retrofit and optimization of total site steam distribution networks

This paper presents a generic mathematical model for retrofitting the steam power plants in an industrial site. The industrial sector under review consists of one steel mill, one oil refinery, and several petrochemical plants, where only small-scale steam integration has been implemented before this study. The relevant unit models in a typical steam power plant are established, and the steam plant retrofit problem is formulated as a mixed-integer nonlinear program (MINLP). Feasible retrofit alternatives suggested by experienced field engineers are investigated in sequence to examine the revenue of those possible modifications. The first scenario examines operational optimization of existent plants; the second option allows installation of one new turbine and replacement of several boilers and turbines with lower efficiency; the third scenario considers using a steam ejector to upgrade the disqualified import steam in the oil refinery. The significant merits from these three retrofit alternatives show that the proposed MINLP formulation has been a great help to enhance the inter-plant steam integration in an industrial sector.     

阿克苏河年径流变化的非线性特征

以阿克苏河流域的托什干河、库玛拉克河和阿克苏河干流为例,基于1957-2008年的径流序列,运用小波分析和R/S分析方法分析了阿克苏河径流过程的非线性特征,揭示了流域径流的变化规律,得出以下结论:①库玛拉克河、托什干河及阿克苏河干流的年径流序列均呈增加的趋势,且都以20世纪80年代后期为分界点分为两个阶段:前期径流较少,处于枯水期;后期径流较多,处于丰水期。②阿克苏河流域年径流量变化存在较长周期,长周期中又包含着短周期;其中,18 a和22 a的周期贯穿于整个时间序列,为流域径流的第一主周期。③流域内三条河流各个时段径流量的Hurst指数值几乎都大于0.5,表明流域径流的时间序列具有长期持续的特征;从各条河流最后一个时段的Hurst指数可以推断,在2008年后的一段时间里流域径流量将会继续保持增加趋势。     

考虑非线性吸附时溶质在有限厚度粘土中的一维扩散解

在采用非线性分段式吸附等温模式的基础上,建立了溶质在粘土中的一维扩散模型,在考虑有限厚度边界及土中溶质背景浓度的条件下得到了相应的解.模型引入了移动边界以说明当溶质在粘土孔隙水中的浓度达到某一较高值后,阻滞因子将发生显著变化.算例分析表明,该模型和考虑经典非线性吸附等温线得到的结果相差不大,这进一步说明了该模型的合理性.考虑非线性吸附效应对溶质迁移有重要影响.在较高溶质浓度下采用线性吸附等温模式会得到偏不安全的结果.该解相对较简单,并可用于验证各种数值模型、拟合试验数据等.     

CHAOTIC FORECASTING OF DISCHARGE TIME SERIES: A CASE STUDY1

ABSTRACT: This paper considers the problem of forecasting the discharge time series of a river by means of a chaotic approach. To this aim, we first check for some evidence of chaotic behavior in the dynamic by considering a set of different procedures, namely, the phase portrait of the attractor, the correlation dimension, and the largest Lyapunov exponent. Their joint application seems to confirm the presence of a nonlinear deterministic dynamic of chaotic type. Second, we consider the so‐called nearest neighbors predictor and we compare it with a classical linear model. By comparing these two predictors, it seems that nonlinear river flow modeling, and in particular chaotic modeling, is an effective method to improve predictions.