Configuration and installation design of optical diagnostic systems on KSTAR

The optical diagnostic system of KSTAR consists of visible diagnostics including toroidal and poloidal Hα monitors, a visible survey spectrometer, and filterscopes. A re-entrant cassette made of stainless steel, containing five optical quartz windows has been developed to allow easy access of the visible diagnostics to the plasma. The configuration and manufacturing design of the diagnostic cassette and the installation of optical diagnostic systems within the cassette are described. The structural and thermal analysis of the diagnostic cassette and in situ calibration of optical diagnostics have also been performed. The optical lens system showed good image quality by spot diagram analysis.     

Response surface optimization of the purification process of cyclotrimethylenetrinitramine explosive via digestion in binary solvent mixtures of acetone/water

The present study introduces a new route for the purification of cyclotrimethylenetrinitramine (RDX) explosive containing cyclotetramethylenetetranitramine (HMX) impurity, based on the digestion of crude materials in the binary solvent of acetone/water. Here, first, the solubility data, enthalpy of dissolution and mixing of RDX and HMX were determined experimentally in binary solvent. Then, the effects of various factors on the purification of RDX were studied statistically via response surface methodology (RSM) experimental design. In this technique, unlike the solubility data, unexpectedly HMX was dissolved with higher ratio and solid RDX was obtained with purity >99.5 wt.% and improved crystal morphology.     

Effects of Welding and rotational speeds on the Microstructure and Hardness of Friction Stir Welded Single-Phase Brass

This study focuses on the effects of rotational and welding speeds on the microstructure and hardness of joints in friction stir welded single-phase brass. Welds were achieved under low heat input conditions at rotational and welding speeds of 400-800 r/min and 100-300 mm/min, respectively. In order to characterize the obtained welds, optical microscopy and Vickers hardness measurements were taken on the weld cross sections. According to the obtained results, increasing the welding speed and/or decreasing the rotational speed caused the grain size of the stir zone to decrease and, hence, improved the average hardness of this region. These results are discussed with respect to the interplay between the welding parameters and the peak temperature in the weld thermal cycle.     

Using ARB process as a solution for dilemma of Si and SiCp distribution in cast Al-Si/SiCp composites

A major challenge in achieving the best potential of SiC_p-reinforced aluminum composites is to homogeneously disperse SiC particles within the aluminum alloys. The presence of coarse Si fibers with non-uniform distribution in cast Al-Si alloys, which may lead to poor mechanical properties, is another important problem that limits the application of these alloys. In order to eliminate these problems, accumulative roll bonding (ARB) process was used in this study as a very effective method for improving the microstructure and mechanical properties of the Al356/SiC_p composite. It was found that when the number of ARB cycles was increased, the uniformity of the Si and SiC_p in the aluminum matrix improved, the Si particles became finer and more spheroidal, the free zones of Si and SiC particles disappeared, the porosity of composite decreased, the bonding quality between SiC_p and matrix improved, and therefore mechanical properties of the composites were improved. The microstructure of the manufactured Al356/SiC_p composite after six ARB cycles indicated a completely modified structure so that its tensile strength and elongation values reached 318 MPa and 5.9%, which were 3.1 and 3.7 times greater than those of the as-cast composite, respectively.     

The influence of nanocrystalline state of iron on the corrosion inhibitor behavior in aqueous solution

Effect of grain size reduction on the electrochemical and corrosion behavior of iron of different grain sizes (32–320 nm) produced by direct and pulsed current electrodeposition was characterized using Tafel polarization curves and electrochemical impedance spectroscopy (EIS). The grain size of deposits was determined by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The most intensive first-order peak (110) of the XRD patterns was taken for detailed analysis using a Gaussian fitting curve. The electrochemical tests were carried out in electrolyte 30 mg L⁻¹ NaCl + 70 mg L⁻¹ Na₂SO₄ + 250 mg L⁻¹ NaNO₂ aqueous solution. It was found that the corrosion potential and corrosion current density significantly changed as the microstructure morphology was changed. Results obtained from electrochemical tests suggested that the inhibition effect and corrosion protection of sodium nitrite inhibitor in near-neutral aqueous solutions increased as the grain size decreased from submicrocrystalline to nanocrystalline. This was attributed to the excess free energy, and concomitantly the increased number of the active sites caused by higher grain boundary and triple junction content in the nanocrystalline surface, which provides sites for electrochemical activity, and effect of sodium nitrite, was more pronounced.     

Flavonone 3-hydroxylase Relieves Bacterial Leaf Blight Stress in Rice via Overaccumulation of Antioxidant Flavonoids and Induction of Defense Genes and Hormones

Efficient accumulation of flavonoids is important for increased tolerance to biotic stress. Although several plant defense mechanisms are known, the roles of many pathways, proteins, and secondary metabolites in stress tolerance are unknown. We generated a flavanone 3-hydroxylase (F3H) overexpressor rice line and inoculated Xanthomonas Oryzae pv. oryzae and compared the control and wildtype inoculated plants. In addition to promoting plant growth and developmental maintenance, the overexpression of F3H increased the accumulation of flavonoids and increased tolerance to bacterial leaf blight (BLB) stress. Moreover, leaf lesion length was higher in the infected wildtype plants compared with infected transgenics. Kaempferol and quercetin, which scavenge reactive oxygen species, overaccumulated in transgenic lines compared with wildtypes in response to pathogenic infection, detected by scanning electron microscopy and spectrophotometry. The induction of F3H altered the antioxidant system and reduced the levels of glutathione peroxidase activity and malondialdehyde (MDA) contents in the transgenic lines compared with the wildtypes. Downstream gene regulation analysis showed that the expression of F3H increased the regulation of flavonol synthase (FLS), dihydroflavonol 4-reductase (DFR), and slender rice mutant (SLR1) during BLB stress. The analysis of SA and JA signaling revealed an antagonistic interaction between both hormones and that F3H induction significantly promoted SA and inhibited JA accumulation in the transgenic lines. SA-dependent nonexpressor pathogenesis-related (NPR1) and Xa1 showed significant upregulation in the infected transgenic lines compared with the infected control and wildtype lines. Thus, the overexpression of F3H was essential for increasing BLB stress tolerance.     

Lean blowoff of bluff body stabilized flames: Scaling and dynamics

This paper overviews the dynamics of bluff body stabilized flames and describes the phenomenology of the blowoff process. The first section of the paper provides an overview of the fluid mechanics of the non-reacting and reacting bluff body wake flow. It highlights the key features of the flow (the boundary layer, separated shear layer, and wake), the flow instabilities that influence each of these features, and the influences of the flame on these instabilities. A key point from these studies is the large differences between the non-reacting wake (dominated by an absolutely unstable, sinuous instability associated with vortex shedding from the bluff body) and the reacting wake of high dilatation ratio flames. The latter are dominated by the lower intensity, convective instability of the shear layer. Very low dilatation ratio flames begin to approach the behavior of the non-reacting wake, as might be expected.