Ambiguity as Grasp: The Reworking of Sense

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111788/1/jccm12080.pd

Study on Cr-rare Earth-boronizing of the Steel 45 at Low Temperature

AbstractThe Cr-Rare earth-boronized layers were fabricated on the steel 45 at 650°C for 6h. The microstructure, phase composition, microhardness and tribological properties were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness tester and wear tester. The results showed the Cr-Rare earth-boronized layer was composed of single Fe2B phase. A sawtooth morphology was obtained in the Cr-Rare earth-boronized layer and the microstructure of the Cr-Rare earth-boronized layer was compact and dense. The thickness of the boride layer is about 23μm. The boride tooth was thin and straight. The microhardness of the Cr-Rare earth-boronized layer was 1200HV∼1700HV, and first increased with the increase of distance from surface and then decreased when the distance from surface is longer than 7.5μm. The hardness gradient of the boride layer is lessened. The wear resistance of steel 45 is greatly improved by Cr-Rare earth-boronizing

Impacts of land use and cover changes on the hydrology of Gumara catchment, Ethiopia

Land use and cover changes (LUCC) are continuous phenomena often driven by natural or anthropogenic factors. In Ethiopia, a conversion of forest and grass lands into cultivated and urbanized lands has been reported. While such changes are known to have multidirectional impact on river flows, erosion and sedimentation, environment and socio-economic situation within a catchment, there is a lack of assessment on the scale and rate of these changes, and consequent impacts. This study quantifies the rate of LUCC in the Gumara River catchment (1413 km2), an important tributary to Lake Tana in northwest Ethiopia. The Landsat images of three years (1986, 2001 and 2015) were processed, and a supervised classification method was used for the LULC classification. An extensive field survey generated over 150 ground truth points, used in the classification and accuracy assessment process. Then, a conceptual rainfall-runoff model (HBV) was applied to assess the impact on water balance components - evapotranspiration, soil moisture and groundwater recharge, and runoff. A reasonably reliable LULC classification was achieved, with overall efficiency of 90%. In 1986, the area under forest and grass land was about 11% and 18%, respectively, which reduced to 5% and 10%, respectively, in 2015. In contrast, cultivated land increased from 70% in 1986 to 72% in 2015. The successfully calibrated and validated HBV model, against observed streamflow, indicated only a slight change in the water balance components (±5%). In general, the observed LULC changes seemingly caused an increase in soil moisture and recharge, and a decrease in evapotranspiration. Consequently, streamflow showed a slight increase, though not as significant as expected in the light of LULC changes. The uncertainties involved in the LULC impact modelling process are also discussed in this paper. This application also highlighted the limitations of conceptual models, like HBV, that represent LULC in a much simplified manner, in adequately simulating the hydrological response under LULC change scenarios

Spark plasma sintering of damage tolerant and machinable YAM ceramics

Single-phase Y4Al2O9 (YAM) powders were synthesized via solid-state reaction starting from nano-sized Al2O3 and Y2O3. Fully dense (99.5%) bulk YAM ceramics were consolidated by spark plasma sintering (SPS) at 1800 ℃. We demonstrated the excellent damage tolerance and good machinability of YAM ceramics. Such properties are attributed to the easy slipping along the weakly bonded crystallographic planes, resulting in multiple energy dissipation mechanisms such as transgranular fracture, shear slipping and localized grain crushing