Final Narrative Report

Northern Mariana IslandsCultural Assets Restoration and Education Strategy or CNMI CARESInstitute of Museum and Library ServicesJoeten-Kiyu Public Librar

Reseñas 33/2 (2000)

To analyze the dynamics of small, spherical, rigid bubbles in a certain class of turbulent shear flows dominated by large scale coherent vortical structures, we model the plane free shear layer with a periodic array of Stuart vortices. The equation of motion of the bubbles is then integrated numerically to obtain the Lagrangian description of the bubbles, the long-term dynamics of which depends on the free-stream Reynolds number, the Stokes number, the gravitational field, and the strength of the vortices. Depending on the values of these four parameters, it is found that either there exists a stable equilibrium point near the center of each vortex, where bubble accumulation occurs, or all bubbles escape from captivity by the vortices. In the limiting case of dominant viscous drag forces, an Eulerian description of the "bubble flow field" is derived. Furthermore, the divergence of this flow field is negative in the neighborhood of a vortex center, where it achieves its minimum. This indicates that bubbles accumulation may indeed exist, and thus qualitatively confirms the more general numerical results obtained without the assumption of dominant viscous drag forces

Spatial Configurations of Water Management at an Early Angkorian Capital - Combining GPR and TerraSAR-X Data to Complement an Archaeological Map

Hariharalaya was a medieval political centre of the eighth–ninth century ce, located on the northern shore of Lake Tonle Sap in Cambodia. Mapped in detail in the 1990s by means of aerial photographs and ground surveys, more recently ground-penetrating radar (GPR) and high-resolution satellite synthetic aperture radar (SAR) were applied to further interpret this complex archaeological landscape. In combination with remote sensing imagery, the two radiofrequency-based imaging techniques were used to complement the existing archaeological maps. The area housed an extensive low-density urban complex of earthen mounds and ponds, approximately 5 × 5 km square and centring on the Bakong, an early Angkorian state temple, crossed and encircled by a mostly disconnected water-management network of embankments and canals. Extensive GPR surveys, conducted predominantly on the existing small roads and paths criss-crossing the landscape, appraise the visible archaeological features with subsurface information. The analysis verifies the existence of channels and embankments, complementing the information with depth and width. The identification of additional, now desiccated, canals and river channels assisted in connecting a number of already mapped archaeological features, and helped to distinguish possible later additions, thereby untangling the water-management network. Spotlight TerrSAR-X satellite data together with satellite images of the visual spectrum complemented the analysis, by providing information about water saturation in areas inaccessible to ground surveys, marking out palaeochannels and providing clues about the landscape before development took place. This three-dimensional interpretation informs on the functioning of this particular early Angkorian hydraulic system, adding to the understanding of water management in medieval Southeast Asia.FdA – Publicaties niet-programma gebonde