Mineralogy and geochemistry of fine-grained Dahab stream sediments, Southeastern Sinai, Egypt: emphasis on the intergrowths of Fe–Ti oxides

Mineralogical and geochemical characteristics of stream sediments collected from 30 stations in the Dahab-Wadi Kid area(southeastern Sinai,Egypt)are presented.The studied sediments contain considerable amounts of heavy minerals,including abundant Fe–Ti oxides,with up to 25.94%index figure that measures the relative abundance of heavy minerals to light minerals.Immaturity of the sediments and nature of Fe–Ti oxide intergrowths,in addition to some non-opaque heavy minerals,indicate multiple provenances with contributions from a variety of Neoproterozoic mafic to felsic intrusions.Appreciable amounts of heavy minerals are derived from schists that belong to the so-called Wadi Kid volcanosedimentary group.Owing to the considerable contribution of the felsic intrusions represented by within-plate granites,the sediments are enriched in REE-bearing minerals(e.g.,monazite,cerianite,La-cerianite and allanite),V-bearing thorite,zircon,and a ZrO_(2) phase.The majority of Fe–Ti oxides are derived from the mafic intrusions,and they show evidence of pre-,syn-and post-depositional phases of alteration and formation of intergrowths.As to the geochemical signature of the bulk silt fraction,there is remarkable enrichment of LREEs with distinct negative Eu anomaly,and this supports dominance of a provenance dominated by felsic intrusions(i.e.,the A-type within-plate granite and associated pegmatites).Also,the felsic provenance is responsible for slight abnormality of ∑PU+Th content(up to~37 ppm)and few anomalous samples bear uraniferous zircon and Ce-type monazite.The present paper sheds light on the fertility of the Dahab stream sediments in some economic minerals for possible future exploitation,not for gold only,but for potential REEbearing minerals that are needed for a wide spectrum of modern technological industries.

PRODUCT IMAGE RETRIEVAL BASED ON CO-FEATURES OF THE OBJECT

In this paper, we propose a product image retrieval method based on the object contour corners, image texture and color. The product image mainly highlights the object and its background is very simple. According to these characteristics, we represent the object using its contour, and detect the corners of contour to reduce the number of pixels. Every corner is described using its approximate curvature based on distance. In addition, the Block Difference of Inverse Probabilities (BDIP) and Block Variation of Local Correlation (BVLC) texture features and color moment are extracted from image's HIS color space. Finally, dynamic time warping method is used to match features with different length. In order to demonstrate the effect of the proposed method, we carry out experiments in Mi-crosoft product image database, and compare it with other feature descriptors. The retrieval precision and recall curves show that our method is feasible.

Processing of metastable beta titanium alloy:Comprehensive study on deformation behaviour and exceptional microstructure variation mechanisms

Thermomechanical processing(TMP)is especially crucial for metastableβtitanium alloys,which has received significant attention in the community for a long time.In this contribution,the processing-responding behaviour including microstructure evolution process,texture variation mechanism,and un-derlying deformation process of powder metallurgy Ti-5553 alloy in a wide processing parameter range was comprehensively investigated.Thermal physical simulation was performed on the alloy at temper-atures ranging from 800℃ to 1100℃,and strain rates between 0.001 s^(−1) and 10 s^(−1),to varied defor-mation degrees of 20%-80%height reduction.It was found that the processing parameters(i.e.temper-ature,strain rate,and deformation degree)are influential on the deformation process and resultant mi-crostructure.Varied microstructural evolution processes forβphase including flow localization,dynamic recovery,dynamic recrystallization,and grain coarsening are activated in different processing domains,while different evolution mechanisms forαphase including dynamic precipitation,phase separation,dy-namic coarsening,and mechanical shearing also play their roles under different processing conditions.In particular,four exceptional evolution mechanisms ofαprecipitation which have not been previously reported in titanium alloys were discovered and clearly demonstrated,more specifically,they are multi-interior twinning,internal compositing,layered coarsening and selective diffusion-actuated separation.After the establishment of comprehensive microstructural evolution mechanism maps,the guidance for precise processing and the knowledge reserve extension for deformation process of metastableβtita-nium alloys can be effectively achieved.