The Potential Use of Osl Properties of Quartz in Investigating Fluvial Processes on the Catchment of River Mureş, Romania

To understand the functioning of fluvial systems it is important to investigate dynamics of sediment transport and the source of sediments. In case of reconstructing past processes these studies must be accompanied by the numerical dating of sediment samples. In this respect optically stimulated luminescence is a widely used technique, by which the time of sediment deposition can be directly dated. Recently, in various fluvial environments it has been shown that certain luminescence properties of minerals, and especially that of quartz, can be applied as indicators of fluvial erosion and/or sediment provenance. These properties are residual luminescence (or residual dose) and luminescence sensitivity of quartz grains. However, the values of the parameters above are affected by various factors, the importance of which is under debate. The present study therefore aims to assess these factors along a ~560 km long reach of River Mureş (Maros) a relatively large river with a compound surface lithology on its catchment. The research focused on the sandy fraction of modern sediments, collected from the main river and from three tributaries alike. This way not only longitudinal downstream changes, but the influence of tributaries could also be studied. Based on the data, both investigated parameters show a great variation, which can be attributed to the lithological differences of subcatchments and geomorphological drivers, such as erosional activity and potential number of sedimentary cycles, and human activity. However, relationships are not entirely clear and are influenced by the maximum grain size of the samples investigated, and the recycling of previously laid deposits with different properties. Still, when performing detailed dating studies, and tracing sediments from certain parts of the catchment luminescence properties can be a useful tool in the future.

Iso-Planar Feed Vector-Fields-Based Streamline Tool Path Generation for Five-Axis Compound Surface Machining With Torus-End Cutters

This paper presents a new vector-field-based streamline smoothing method in the parametric space and a tool orientation optimization technique for five-axis machining of complex compound surfaces with torus-end cutters. Iso-planar tool path is widely used in the machining of various types of surfaces, especially for the compound surface with multiple patches, but the operations of intersecting the compound surface with a series of planes have depended considerably on the complicated optimization methods. Instead of intersecting the surface directly with planes, a novel and effective tool path smoothing method is presented, based on the iso-planar feed vector fields, for five-axis milling of a compound surface with torus-end cutters. The iso-planar feed vector field in the parametric domain is first constructed in the form of stream function that is used to generate the candidate streamlines for tool path generation. Then, a G1 blending algorithm is proposed to blend the vector fields within the adjacent parametric domains to ensure smooth transition of cross-border streamlines. Based on the smoothened streamlines in the parametric domains, pathlines along with their correspondent side sizes are selected as desirable tool paths. Concerning a high performance machining, detailed computational techniques to determine the tool axis orientation are also presented to ensure, at each cutter contact (CC) point, the torus-end cutter touches the part surface closely without gouging. Both the computational results and machined examples are demonstrated for verification and validation of the proposed methods.

Strontium-Substituted Hydroxyapatite Nanocrystals Synthesized in Ultrasonic Field: Use for Protein Adsorption

Hydroxyapatite Ca10(PO4)6(OH)2 (HAP) is widely applied in a biomaterial because of its excellent biocompatibility and bioactivity. However, all properties of HAP, especially the adsorption properties can be tailored by modifying the composition with ionic substitutions. Among many cations that can substitute for calcium in the structure of HAP, strontium is a kind of essential trace elements in human body. It has been known as one of the cationic substitute for calcium in the HAP lattice. The strontium-substituted hydroxyapatite (Sr-HAP) is formed when strontium is doped in HAP structure. The bioactivity, biocompatibility, and adsorption properties are improved when the original lattice of HAP is destroyed. In this study, we focus on synthesis of strontium-substituted HAP nanocrystals in ultrasonic field which is a mild and simple synthesis method. The Sr-HAP with different Sr contents was synthesized. The effects of reaction temperature, sintering temperature and reaction time on protein adsorption of Sr-HAP were studied. In addition, the crystalline phase, chemical compound, surface area and morphology were characterized by XRD, FTIR, TEM and BET. The results indicate that the original lattice of HAP was destroyed and the structure of HAP doped with strontium formed. Sr-HAP with smaller crystal size, larger specific surface area and homogeneous distribution was prepared. Especially, it has great adsorption to target protein, bovine serum albumin (BSA).