A polycrystalline 1.5% Ho: YAG fiber with a diameter of 31 µm was prepared. Surface roughness from grain boundary grooving was reduced by polishing, which decreased the fiber scattering coefficient from 76 m-1 to 35 m-1. Lasing tests were done on this fiber with a SF57 Schott glass cladding. Lasing was confirmed by spectrum narrowing with threshold pump power lower than 500 mW and a slope efficiency of 7%. To our knowledge, this is the first lasing demonstration from a small diameter polycrystalline ceramic fiber.
The main aim of this research is to define the mineralogical composition of recent sediments deposited around the Al-Teeb river basin in eastern Missan, trying to determine the provenance or the source of these sediments. The study area represents the southeastern edge of the Mesopotamian Plain and is part of it. Quaternary deposits cover most of the area. It is clayey with old sea and river deposits and part of aeolian deposits. These sediments cover 95% of the study area, while the older rocks, which date back to the Tertiary (Late Miocene – Pliocene), exposed in the area east and northeast of the Al-Teeb area, made up hills which back to the undifferentiated Pliocene Mukdadiya and Bai-Hassan formations. The light components of these sediments consist mainly of quartz, feldspars (potash and plagioclase feldspar), sedimentary rock fragments (carbonate rock fragments, chert rock fragments, evaporates fragments), igneous rock fragments, and metamorphic rock fragments The heaviest minerals are opaque, amphiboles, pyroxenes, chlorite, epidotes, biotite, garnet, muscovite, zircon, kyanite, staurolite, and rutile. These sediments are typically formed by sedimentary rocks (single or many cycles), low and high-rank metamorphic rocks, acidic and basic igneous rocks, and pegmatite rocks. The high percentage of opaque heavy minerals in clastic sediment refers to unstable clastic sediments. The stability issue to the areas during the study shows that there are significant variances over the several places, indicating dissimilar sources and types of source rocks
The main goal of this research paper is to investigate the response of the RC rectangular columns under loading simultaneously exposed to fire by using experimental study. The number of test columns were seventeenth columns. The dimension for these columns was 1600mm for length and 150mmx150mm for the cross-section. The columns were tested under axial load with two different types of eccentricity 60 mm 100mm, while the third type of loading is tested as a beam. The eccentric compression load was applied by using top and bottom cap with a column bracket. The eccentric load was applied simultaneously with fire. The test was performed under a high temperature of (400°C, 600°C, and 900°C) on the side of a compression face. At each temperature burning, cooling by two techniques of cooling, and normal cooling (by open air) and fast cooling (by direct water). The experimental results show decreasing in ultimate load capacity with increasing of temperature burning, ultimate load, load-deflection curve, strain profile, neutral axis, moment-curvature, and ductility.
A silicon carbide‐based ceramic, containing 50 vol% SiC, 35 vol% ZrB2, and 15 vol% ZrC was plasma arc welded to produce continuous fusion joints with varying penetration depth. The parent material was preheated to 1450°C and arc welding was successfully implemented for joining of the parent material. A current of 138 A, plasma flow rate of ~1 L/min or ~0.5 L/min, and welding speed of ~8 cm/min were utilized for repeated joining, with full penetration fusion zones along the entire length of the joints. Solidification was determined to occur through the crystallization of β‐SiC (3C), then the simultaneous solidification of SiC and ZrB2, and lastly through the simultaneous solidification of SiC, ZrB2, and ZrC through a ternary eutectic reaction. The ternary eutectic composition was determined to be 35.3 ± 2.2 vol% SiC, 39.3 ± 3.8 vol% ZrB2, and 25.4 ± 3.0 vol% ZrC. A dual fusion zone microstructure was always observed due to convective melt pool mixing. The SiC content at the edge of the fusion zone was 57 vol%, while SiC content at the center of the fusion zone was 42 vol% although the overall SiC content was still nominally 50 vol% throughout the entire fusion zone.
Current research into fibers for laser applications is ongoing due to the ability of fibers to eliminate freespace optics, along with being smaller, lighter and more powerful than slab lasers [1]. Current fiber lasers use silica glass cores, however mechanical failure and thermal lensing are significant problems. Yttrium aluminum garnet (Y 3 Al 5 O 12 , YAG) is currently being considered as a host material for highenergy fiber lasers as it has much higher thermal conductivity, a higher laser damage threshold, a lower peak stimulated Brillouin Scattering, and does not photodarken. Researchers have produced both single crystal and polycrystalline YAG fibers, with a variety of cladding materials; the processing steps have evolved to improve fiber quality and minimize optical propagation losses [2]. The fibers used in this work were prepared using commercially available YAG powder (Nanocerox, Ann Arbor, MI), Methocel TM as a binder (E4M grade, Dow, Midland, MI), Glycerol as a plasticizer (Sigma-Aldrich, St. Louis, MO), and deionized water. The powder was heat treated to remove organic contaminants and then powder ball milled to de-agglomerate. Any ball milling impurities were separated by centrifugation. The mixture was extruded using 20-35MPa through a 50μm diameter nozzle and dried overnight. These were then burned out at 600°C and densified between 1500-1750°C [3].
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