ANALYSIS OF DRIVING FORCES ON THE CHANGE OF HISTORICAL FARMLAND USE IN SHANDONG PROVINCE DURING THE QING DYNASTY (1644-1911)     

ZHANG Xue-in  GE Quan-heng  ZHENG Jing-un 《中国地理科学(英文版)》2003,13(3)

1INTRODUCTIONTheIGBP-IHDP(InternationalGeosphere-BiosphereProgramme,andInternationalHumanDimensionPro-gramme)jointproject—LUCC(landuse/coverchange)isaninterdisciplinaryprogramdesignedtoimprovetheunderstandingofthedynamicsofland-useandland-coverchangeasinputstoandconsequencesofglobalenvironmentalchangeandsustainabledevelopment(CHARLOTTE,2002).Inparticularthedifferentbio-geochemicalmodeling(e.g.theglobalcarboncycle)ac-tivitiesandcomparativestudies,suchasthoseconduct-edbyIGBP-G…  相似文献   

ANALYSIS OF DRIVING FORCES ON THE CHANGE OF HISTORICAL FARMLAND USE IN SHANDONG PROVINCE DURING THE QING DYNASTY （1644-1911）     

ZHANGXue-qin GEQuan-sheng ZHENGJing-yun 《中国地理科学(英文版)》2003,13(3):207-215

How land-cover has been changed by human use over the last 300 years is one of the five overarching questions guiding the Land-use/Cover Change (LUCC) Science/Research Plan. China has variety of historical docu-ments providing unique data superiority. So the characteristics of farmland area in Shandong Province during the Qing Dynasty (1644-1911) are summarized firstly: 1) the rising trend of farmland area was striking; 2) farmland area had re-markable fluctuation; 3) farmland area per capita decreased dramatically; 4) wasteland reclamation index increased rapidly. Then, the driving forces of farmland area change are analyzed. It is concluded that natural and human factors are jointly influential. Among the driving forces, human dimensions are the main factors of farmland area change,which direct the general tendency of the changes mentioned above. And the natural factors influence the stability of farmland area as well. Variation of the natural factors would act as the major contributory factor to farmland area change during years or periods of abrupt climatic changes, or during the intensive occurring periods of natural hazards.Besides, the passive aspects of human factors, such as war chaos also influenced the fluctuation of the farmland area.This research indicates that it is feasible to study the land-use/cover change by Chinese historical literatures, which has huge potential to provide a comprehensive picture of the growing dominance of human land-use and land-cover pat-terns that can be used in many global change research oroiects.  相似文献   

Robe's restricted three-body problem revisited     

A. R. Plastino  A. Plastino 《Celestial Mechanics and Dynamical Astronomy》1995,61(2):197-206

Robe's restricted three-body problem is reanalyzed with a view to incorporate a new assumption, namely that the configuration of the fluid body is that described by an hydrostatic equilibrium figure (Roche's ellipsoid). In the concomitant gravitational field a full treatment of the buoyancy force is given. The pertinent equations of motion are derived, the linear stability of the equilibrium solution is studied and the connection between the effect of the buoyancy forces and a perturbation of the Coriolis force is pointed out.  相似文献   

The linearisation of three dimensional drag force in random seas with current     

R.S. Langley 《Applied Ocean Research》1984,6(3):126-131

A frame invariant linearisation method for three-dimensional drag force in random seas with current is presented. Numerical results are compared with those obtained from a commonly used linearisation method which is based on a non-frame invariant approximation to the drag force. Significant differences are discovered and the present method is found to show closer agreement with computed time histories of the true drag force.  相似文献   

Wave-Current Forces on Vertical Cylinders in Side-by-Side Arrangement for Irregular Waves Combined With Opposing Current     

Li Yucheng Wang Fenglong Professor  Dalian University of Technology  Dalian Senior Engineer  Dalian University of Technology  Dalian 《中国海洋工程》1993,(1)

- The wave-current forces on vertical piles in side-by-side arrangement induced by irregular waves with opposing current are investigated experimentally in this paper. The characteristics in both time and frequency domain of in-line, lift and resultant forces are analyzed. The grouping effect coefficients of inline, lift and resultant forces on piles related to KC number and relative spacing parameters are given. These results are compared with those in the case of irregular waves combined with following currents. It is found that the results in these two cases are quite different. The range of KC number tested is 10- 60, the range of Reynolds number is (0.55-3.43) ×104.  相似文献   

Experimental study of reflection coefficient and wave forces acting on perforated caisson     

Chen Xuefeng  Li Yucheng  Sun Dapeng  Chen Renyou 《海洋学报(英文版)》2002,21(3):451-460

The reflection coefficient and the total horizontal forces of regular waves acting on theperforated caisson are experimentally investigated. The empirical relationship between reflection coefficient and the ratio of the total horizontal forces acting on the perforated caisson to those on solid vertical walls with the relative chamber width, relative water depth and porosity of perforated wall, etc. are given. Moreover, the results of the ratio of the total horizontal forces are also compared with formulas given by Chinese Harbour Design Criteria and Takahashi, which may be useful for the practical engineering application.  相似文献   

Numerical Analysis of Wave Forces on Arbitrarily Shaped Multi-Pillars Over Varying Topography     

Zhang Libang Research Engineer  First Institute of Oceanography  Qingdao 《中国海洋工程》1991,(4)

The modified hybrid element method (MHEM) is utilized to predict and analyze wave forces on arbitrarily shaped multiple bodies. This method can be applied to waves of all water depths, i. e. shallow, intermediate, and deep waters, on slowly varying seabed. The MHEM employs the ICCG method to save CPU and storage, thus the computation of wave forces for large multi-body systems can be carried out on microcomputers. Numerical results of the present method are compared with experimental data and other solutions. It is shown that the MHEM provides more accurate solutions of the wave forces than other numerical methods do. Therefore, the methodology presented herein can be used in the design of coastal and ocean structures.  相似文献   

Low-frequency damping of a moored semisubmersible obtained from simulated extinction tests and mean wave drift forces     

T.E. Schellin  A. Kirsch 《Applied Ocean Research》1989,11(4):202-211

Low-frequency damping of a moored semisubmersible drilling platform was obtained from numerical extinction tests simulated in still water and in regular waves and from mean wave drift forces calculated at zero forward speed. The influence of drag forces was represented by the modified Morison equation. The platform as used for the 18th ITTC Comparative Mooring Study was analyzed in irregular beam waves. The computed time series of sway as well as the corresponding sway response spectrum compared favourably with model test measurements, demonstrating that this procedure to determine low-frequency damping can be effective.  相似文献   

Wave-Current Forces on Small Square Cylinders (Part I)     

Li Yucheng  He Ming Professor  Dalian University of Technology  Dalian Former master student  Dalian University of Technology  Dalian 《中国海洋工程》1994,(3)

-Based on the extended Morison Equation and model tests, the in-line forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in detail in this paper. The hydrodynamic coefficient CD and Cu related to KC number and the effect of direction of wave incidence are also given, which can be used in engineering practice.  相似文献   

Modelling of flow around a near-bed pipeline with a spoiler   总被引：1，自引：0，他引：1  

L. Cheng  L. W. Chew 《Ocean Engineering》2003,30(13):1595-1611

Flow around a pipeline with and without a spoiler near a smooth wall is simulated by solving the Navier–Stokes equations. Finite-difference formulation with a second-order upwind scheme in a curvilinear coordinate system is employed. The influences of the spoiler on hydrodynamic forces, pressure distribution, vortex shedding frequency, velocity profile under the pipe, as well as shear stress on the wall are investigated. The attachment of a spoiler significantly increases drag, root-mean-square (RMS) lift, flow through the gap between the pipe and the wall and shear stress on the seabed around the pipe. The spoiler also generates a non-zero mean downward force on the pipeline, which may enhance the self-burial of the pipeline.  相似文献