River Changes Research Articles

Modeling the Process of Critical Exhaustion of Oxygen in a River Caused by Exponential Source of Pollution

The analysis and improvement of the river's change dynamics are critical to the global investigation of water quality issues. This study investigates the mathematical model representation of one dimension of a pair of advection-dispersion equations. These equations pertain to the concentrations of both pollutants and dissolved oxygen. Certain terms, which demonstrate an increase in the decay rate of pollution through exponential sources and assume a decreasing river's cross-sectional measurement, lead to the diminished oxygen levels observed in this study. The crucial points are demonstrated using both analytical and numerical analysis of the steady-state model, which allows for examining multiple situations about the elimination of oxygen and aquatic survival in a river with severe pollution.

EVALUATION OF IMPACT ON DIADROMOUS FISHES BY CHANGES IN BOTH SEA AND RIVER WATER TEMPERATURE

EVALUATION OF IMPACT ON DIADROMOUS FISHES BY CHANGES IN BOTH SEA AND RIVER WATER TEMPERATURE

Tone River's Changes, Bank Protection and Water System

Tone River's Changes, Bank Protection and Water System

Settlement Patterns, Chiefdom Variability, and the Development of Early States in North China

In the third millennium B.C., the Longshan culture in the Central Plains of northern China was the crucial matrix in which the first states evolved from the basis of earlier Neolithic societies. By adopting the theoretical concept of the chiefdom and by employing the methods of settlement archaeology, especially regional settlement hierarchy and rank-size analysis, this paper introduces a new approach to research on the Longshan culture and to inquiring about the development of the early states in China. Three models of regional settlement pattern correlating to different types of chiefdom systems are identified. These are: (1) the centripetal regional system in circumscribed regions representing the most complex chiefdom organizations, (2) the centrifugal regional system in semi-circumscribed regions indicating less integrated chiefdom organization, and (3) the decentralized regional system in noncircumscribed regions implying competing and the least complex chiefdom organizations. Both external and internal factors, including geographical condition, climatic fluctuation, Yellow River's changing course, population movement, and intergroup conflict, played important roles in the development of complex societies in the Longshan culture. As in many cultures in other parts of the world, the early states in China emerged from a system of competing chiefdoms, which was characterized by intensive intergroup conflict and frequent shifting of political centers. However, what is unusual about the Chinese case is the fact that the earliest states did not develop from the most complex of the chiefdom organizations, but from the least complex chiefdom systems then existing there.