نتایج جستجو برای: 20th century
تعداد نتایج: 117401 فیلتر نتایج به سال:
We studied five lower forest–grassland ecotones in the Darhad Valley in northern Mongolia and investigated the effects of 20th Century grazing regimes and changes in grazing management on ecotone dynamics at a local scale. A total of 2968 Siberian larch (Larix sibirica) trees were cored and tree-age distribution was constructed to determine 20th Century tree establishment. Tree age and location...
The control problem and Dynamic programming is a powerful tool in economics and management. We review the dynamic programming problem from its beginning up to its present stages. A problem which was involved in physics and mathematics in I 7” century led to a branch of mathematics called calculus of variation which was used in economic, and management at the end of the first quarter of the 20” ...
ences is that of a “field,” which, together with appropriate mathematical operations on fields, is used to express the physical conservation laws of nature, such as conservation of mass, momentum, charge, etc. Fields were first introduced by the great 19th-century British scientist Michael Faraday to represent the intensity and direction of the force experienced by a small charged particle in t...
This paper analyzes the major historical milestones in the study of normal and abnormal personality, from antiquity up until the 20th century. Special attention is paid to the interaction between dimensional and typological approaches, which was a major issue during the preparation of DSM-5. Theories of personality started with the humoral theory of Greek medicine. Pinel, and later Esquirol and...
Military service requires individuals who are free from ill-health and who are physically and mentally robust, and throughout history those who have become unfit for service have been discharged on medical grounds. This paper uses published historical records to examine trends in the rate of discharge for six key conditions for the period 1861-1998 and to draw conclusions. In the late 19th and ...
Six Earth system models of intermediate complexity that are able to simulate interaction between atmosphere, ocean, and land surface, were forced with a scenario of land cover changes during the lastmillennium. In response to historical deforestation of about 18 million sq km, themodels simulate a decrease in globalmean annual temperature in the range of 0.13–0.25 C. The rate of this cooling ac...
Forced and unforced ocean temperature changes in Atlantic and Pacific tropical cyclogenesis regions.
Previous research has identified links between changes in sea surface temperature (SST) and hurricane intensity. We use climate models to study the possible causes of SST changes in Atlantic and Pacific tropical cyclogenesis regions. The observed SST increases in these regions range from 0.32 degrees C to 0.67 degrees C over the 20th century. The 22 climate models examined here suggest that cen...
Urban vegetation is of key importance because a large proportion of the human population lives in cities. Nevertheless, urban vegetation is understudied outside central Europe and particularly, little is known about the flora of tropical Asian, African and Latin American cities. We present an estimate of how the vegetation has changed in the city of San José, Costa Rica, after about one century...
[1] We used a simulated data set of hydro-climatological variables to examine for 20th century trends in soil moisture, runoff, and drought characteristics over the conterminous United States (U.S.). An increasing trend is apparent in both model soil moisture and runoff over much of the U.S., with a few decreasing trends in parts of the Southwest. The trend patterns were qualitatively similar t...
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