The effects of anthropogenic impact on plant and soil cover in Mongolia.
Under the prevailing variable natural conditions nomadic pastoralism was the most suitable form of land use in Mongolia and the neighboring countries in the past. Furthermore, small areas were used for agriculture in some regions. Therefore, anthropogenic influence was present throughout history. In the forest steppe zone this led to the disappearance of forest sites which then gave way to meadow steppe. The severe impact on the natural pastures by continuous increase of livestock herding and other human activities was perceptible during the socialist period. But since the 1990s, after the transition to market economy, this impact has increased greatly and a great number of degradation features and irreversible damages in the plant and soil cover can be observed now. Especially in the vicinity of the Mongolian capital Ulaanbaatar, along the north-south road corridor from Russia to the Chinese border, but also in some western regions of the country herders concentrate their livestock in search for better marketing opportunities. Especially there, the vegetation in vast areas is overgrazed by biting and trampling to such an extent that its regeneration is endangered. Degraded and devastated pasture types with a decrease of valuable forage plants and a high increase of ruderal elements can be found in these grasslands. Characteristic sequences of pasture degradation are presented here. The degradation effects steppes and desert steppes as well as reed, mire, and meadow vegetation in the river valleys and lowlands. In the desert regions saxaul vegetation is especially threatened. In some cases after degradation of the plant cover these degradation processes effect soil cover, too. Impacts on soil cover caused by ploughing of virgin land, by ploughing of long term used arable land, and by irrigation are the main reasons for soil degradation. Also recreational activities in the vicinity of settlement centers and traffic along the tracks lead to detrimental vegetation and soil cover changes. Unsystematic forest clearing goes on at a high level and often results in irreversible soil degradation.
Landscape Classification using Principal Component Analysis and Fuzzy Classification: Archaeological Sites and their Natural Surroundings in Central Mongolia
The middle and upper Orkhon Valley in Central Mongolia (47.5°N, 102.5°E) hosts a multitude of diverse archaeological features. Most of them – including the well-known ancient cities of Karakorum and Karabalgasun – have only rarely been described in their geographical setups. The aim of this study is to describe, classify and analyse their surrounding landscapes and consequently characterise these sites geographically. This analysis is based on freely available raster datasets that offer information about topography, surface reflectance and derivatives. Principal component analysis is applied as a dimensional reduction technique. Subsequently, a fuzzy-logic approach leads to a classification scheme in which archaeological features are embedded and therefore distinguishable. A distinct difference in preferences regarding to choose a site location can be made and confirmed by semiautomatic analysis, comparing burial and ritual places and settlements. Walled enclosures and settlements are connected to planar steppe regions, whereas burial and ritual places are embedded in mountainous and hilly environments.
Computational fluid dynamics as a development tool for rotary blood pumps.
Computational fluid dynamics (CFD) is beginning to significantly impact the development of biomedical devices, in particular rotary cardiac assist devices. The University of Pittsburgh's McGowan Center for Artificial Organ Development has extensively used CFD as the primary tool to analyze and design a novel axial flow blood pump having a magnetically suspended rotor. The blood-contacting surfaces of the pump were developed using a design strategy based on CFD that involved closely coupling a Navier-Stokes solver to a parameterized geometry modeler and advanced mesh movement techniques. CFD-based blood damage models for shear-induced hemolysis as well as surrogate functions describing thrombosis potential were employed to help guide design improvements. This CFD-based design approach resulted in the timely development of a pump subjected to multiple geometric refinements without building expensive physical prototypes for each design iteration. A physical prototype of the final improved pump was fabricated and experimentally analyzed using particle imaging flow visualization. The CFD predicted results correlated well with the experimental data including pressure-flow (H-Q) performance and specific flow field features. It is estimated that the present CFD-based design approach shortened the overall design time frame from an order of years to months.