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31.
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《The Professional geographer》1986,38(3):291-295
Geographic Software Reviewed in this article: APPLEPIPS IBM EDUCATIONAL SOFTWARE SERIES: EARTH SCIENCE SERIES . Moisture in the Atmosphere, Hydrologic Cycle, Surface Water and Ground Water. MINI-MAX MULTIMAP . Barry R. Cohen . Planning Data Systems WORLD GEOGRAPHY SERIES, U.S. GEOGRAPHY QUIZ, U.S. GEOGRAPHY ADVENTURE 相似文献
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P.?KnabnerEmail author B.?A.?Igler K.?U.?Totsche P.?DuChateau 《Computational Geosciences》2005,9(4):203-217
Accurate identification of interactions of reactive solutes with porous media constituents is necessary for reliable risk
assessment studies and the development of efficient sanitation strategies. Standard parameter estimation procedures bear a
number of unsolved problems with respect to uniqueness and identifiability. This paper presents a new approach for the identification
of nonlinear interaction parameters of column outflow experiments. The procedure requires no a priori assumptions on the shape
of the underlying interaction process functions. Employing experimental data sets on cadmium and anthracene breakthrough as
case studies, possible applications of the new approach will be shown, and its features will be discussed. Error analysis
based on singular value decomposition of the sensitivity matrix quantifies the identification error. Identification procedures
without a priori shape information are superior to fixed parametrizations in diagnostic investigations, especially in cases
without reliable a priori knowledge on the sorptive interactions. 相似文献
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提出一种新的基于马尔可夫随机场(Markov Random Field,MRF)的图像分割算法。根据Gibbs分布与MRF的等价性,图像分割问题转换为后验能量函数最小化所对应的标号问题。该文采用图割技术的-αexpansion算法进行后验能量函数的局部最优化,并通过近似于最大期望(EM)算法的迭代过程估算数据模型中的参数。对合成图像和遥感图像的分割实验表明,该方法的运算时间和分割精度都能达到满意的效果。 相似文献
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Chih Ted YANG Francisco J. M. SIMES Borland Prof. of Water Resources Director of Hydroscience Training Center Department of Civil Environmental Engineering Colorado State University Fort Collins CO - U. S. A. Research Hydrologist US Geological Survey Geomorphology Sediment Transport Laboratory Technology Drive Suite Golden CO U. S. A. 《国际泥沙研究》2008,23(3):197-211
GSTARS is a series of computer models developed by the U.S. Bureau of Reclamation for alluvial river and reservoir sedimentation studies while the authors were employed by that agency. The first version of GSTARS was released in 1986 using Fortran IV for mainframe computers. GSTARS 2.0 was released in 1998 for personal computer application with most of the code in the original GSTARS revised, improved, and expanded using Fortran IV/77. GSTARS 2.1 is an improved and revised GSTARS 2.0 with graphical user interface. The unique features of all GSTARS models are the conjunctive use of the stream tube concept and of the minimum stream power theory. The application of minimum stream power theory allows the determination of optimum channel geometry with variable channel width and cross-sectional shape. The use of the stream tube concept enables the simulation of river hydraulics using one-dimensional numerical solutions to obtain a semi-two- dimensional presentation of the hydraulic conditions along and across an alluvial channel. According to the stream tube concept, no water or sediment particles can cross the walls of stream tubes, which is valid for many natural rivers. At and near sharp bends, however, sediment particles may cross the boundaries of stream tubes. GSTARS3, based on FORTRAN 90/95, addresses this phenomenon and further expands the capabilities of GSTARS 2.1 for cohesive and non-cohesive sediment transport in rivers and reservoirs. This paper presents the concepts, methods, and techniques used to develop the GSTARS series of computer models, especially GSTARS3. 相似文献
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The classical performance index optimization control algorithm is considered in order to check the real optimality of the control procedure; the basic steps for the optimal algorithm are reviewed, and the equation for the optimal control force derived. It is shown that the optimality conditions cannot be met with regard to the performance index, unless one is concerned with simple free oscillations. It is proved that in this case on one side the optimal control turns out to be of the linear closed‐loop type, yielding explicit optimal control coefficients, and on the other side that no solution can exist of the optimal problem for a generic forcing function. It is concluded that one is forced to calibrate the control force for free oscillations, and that the reliability of the index procedure mainly rests on some implicit expectation that linear control can be calibrated in the absence of the external disturbance and that it works under forced oscillations as well. Furthermore, the problem of delayed active control, with reference to a s.d.o.f. system controlled by a closed‐loop linear algorithm and under the action of a dynamic forcing function is investigated. In particular, the effects produced on the response of the structure by the introduction in the control law of assessed critical values of time delay are analysed and the comparison is proposed between the numerical results that one gets by adopting two different procedures (on one hand the above‐mentioned optimal linear control law and on the other hand the constrained minimization of the structural response norm) to compensate for time lag occurring in the actuation of the active control servomechanisms. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
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本文以分层均匀"多层介质模型"为依据,正演模拟多炮人工地面地震记录.其观测方式为:三炮位置分别在1500m,2500m,3500m处;道检距25m,140道(或道检距5m,700道),偏移距1000 m.为提高地震反射层析成像的精度,运用"走时最小纵横波速度层析成像"与"波形基本解纵横波速度层析成像"相结合的方法,反演... 相似文献