Face-centered Orthorhombic Research Articles

Study on the Microstructure, Mechanical Properties, and Corrosion Behavior of 900 °C-Annealed CoCrFeMnNiSix (X = 0, 0.3, 0.6, 0.9) High-Entropy Alloys.

In this study, a series of CoCrFeMnNiSix (x = 0, 0.3, 0.6, 0.9) high-entropy alloys (HEAs) were prepared by suspension melting of cold crucible, annealed at 1000 °C, and then quenched at 900 °C. The changes in the microstructure of the HEAs after the addition of Si were analyzed using X-ray diffraction (XRD), metallographic microscope, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). The hardness, room-temperature friction, and wear behavior, room-temperature compressive properties, and corrosion resistance of the annealed CoCrFeMnNiSix HEAs were also studied. The results show that when the Si content is 0 and 0.3, the annealed CoCrFeMnNiSix HEA exhibits a single face-centered cubic (FCC) structure. As the silicon content increases, a face-centered orthorhombic (FCO) phase appears. At a Si content of 0.9, a hexagonal close-packed (HCP) phase is observed. After heat treatment, the hardness of the CoCrFeMnNiSix HEAs increases continuously with the addition of Si. The HEA with a Si content of 0.9 achieves the highest hardness of 974.8 ± 30.2 HV. The HEA with a Si content of 0.6 reaches the highest compressive strength and yield strength, which are 1990.3 MPa and 1327.5 MPa. When the Si content is 0.9, the HEA shows the smoothest surface after wear, with the best wear resistance, achieving a value of 0.21 mm-1. In the CoCrFeMnNiSix HEAs after 900 °C heat treatment, the HEA with a Si content of 0.6 exhibits the lowest self-corrosion current density of 0.23 µA/cm2 and the highest pitting potential of 157.65 mV, indicating the best corrosion resistance.

Structure of Coulomb Crystals in Cylindrical Discharge Plasmas Under Gravity and Microgravity

Structures of Coulomb crystals were analyzed in cylindrical discharge plasmas under gravity and microgravity by using an apparatus similar to the PK-4 on the International Space Station (ISS). Under gravity, layers of cylindrical dust clouds were found to locally form the lattices of the face-centered orthorhombic (FCO) structure, which is a deformation from the face-centered-cubic structure. We also observed that the average density increases with the size of dust clouds. Under microgravity, the structure could be regarded as an assembly of linear chains along the cylinder axes. At the same time, the interparticle distance and the plasma parameters measured by a double-probe method indicated that the structure was formed not only from the wake potential but also from mutual interactions between dust particles in neighboring chains.

Phase transitions of NbHx (1 ≤ x ≤ 2) from first principles calculation

First-principles calculation reveals that the face-centered cubic (FCC) structure of NbH1 and NbH1.25 is energetically unstable and will automatically transform to the face-centered tetragonal (FCT) structure, and that the intrinsic composition range of the FCT → FCC transition of NbHx phases is 1.5 ≤ x < 2.0. Calculations also show that FCC is the most stable structure of NbHx under high pressure, and that the face-centered orthorhombic (FCO) and FCT structures of each NbH1 and NbH1.25 as well as FCT and FCC of each NbH1.5 and NbH1.75 are very close to each other in terms of the behaviors of phase transition and electronic structure. In addition, Poisson's ratio and density of states are discussed, respectively, to provide a fundamental understanding of various phase transitions in NbHx (1 ≤ x ≤ 2) phases.

Motion-compensated interpolation for face-centered-orthorhombic sampled video sequence

Face-centered orthorhombic (FCO) sampling can be implemented more easily on CMOS image sensors than on other video acquisition devices. The sampling efficiency of FCO is the highest among all three-dimensional (3D) sampling schemes. However, interpolation of FCO-sampled data is inevitable in bridging human perception and machine-vision algorithms. In this letter, the concept of motion compensation is borrowed from deinterlacing, which displays interlaced videos on progressively scanned devices. The combination of motion estimation based on intrafield interpolated frames and motion-compensated interfield interpolation is found to provide the best performance by evaluating different combinations of motion estimation and interpolation.

Impact of Film Thickness on the Morphology of Mesoporous Carbon Films Using Organic−Organic Self-Assembly

Mesoporous polymer and carbon thin films are prepared by the organic-organic self-assembly of an oligomeric phenolic resin with an amphiphilic triblock copolymer template, Pluronic F127. The ratio of resin to template is selected such that a body-centered cubic (Im3m) mesostructure is formed in the bulk. However, well-ordered mesoporous films are not always obtained for thin films (<100 nm), and this behavior is found to be directly correlated with the initial phenolic resin to template ratio. Furthermore, the symmetry of ordered phases is highly dependent on the number of layers of spheres in the film: Monolayers and bilayers are characterized by hexagonal close-packed (HCP) symmetry, while films with approximately 5 layers of spheres exhibit a mixture of HCP and face-centered orthorhombic (FCO) structures. Ultrathick films having more than 30 layers of spheres are similar to the bulk body-centered cubic symmetry with a preferential orientation of the closest-packed (110) plane parallel to the substrate. Film thickness and initial composition of the carbonizable precursors in the template are critical factors in determining the morphology of mesoporous carbon films. These results provide insight into why difficulties have been reported in producing ultrathin ordered mesoporous carbon films using cooperative organic-organic self-assembly.

画像処理・符号化とアプリケーション スケーラブル映像符号化のための動き補償時空間非分離フィルタリング

The use of a novel motion compensated spatio-temporal nonseparable filter (MCSTF) is proposed for scalable video coding. This filter is an alternative to the present motion-compensated temporal filtering (MCTF), a fundamental component for scalable video coding in the next generation. MCTF improve the coding efficiency and provide the temporal scalability. We classify MCSTF as a non-separable sub-sampling version of MCTF, and it provides interlaced pictures as intermediate video sequence by using a spatio-temporal split process. Furthermore, its 1/3-transform structure, which excludes the lifting-update-step, significantly suppresses the PSNR fluctuation that occurs when the existing MCTF technique is used. Our proposed system suppresses PSNR fluctuation with a higher average PSNR than the existing MCTF. Two types of sub-sampling lattices were investigated: the vertical-temporal (VT) quincunx and the face-centered orthorhombic (FCO) ones. Experimental results with entropy coded scalar quantization show the signifaicance of our proposed technique.

Parametric Bernstein polynomial for least squares design of 3-D wavelet filter banks

The design of nonseparable three-dimensional (3-D) biorthogonal wavelet filter banks is addressed in this paper. The sampling is on the face centered orthorhombic (FCO) lattice and the ideal low-pass filter's passband shape is the truncated octahedron (TRO). We introduce a 3-D parametric Bernstein polynomial that preserves biorthogonality and gives a good approximation to the TRO shape. Furthermore, filters with arbitrarily flat frequency response for giving regular wavelet systems are readily obtainable. The free parameters of the Bernstein polynomial can be chosen to sharpen the frequency response of the filter. A least squares approach is employed for the design of the parameters. The design process is efficient as it involves solving linear equations and is noniterative. This approach provides a trade-off mechanism between the sharpness of roll-off and the degree of flatness.