STRUCTURE DETERMINATION OF KANGLEMEISU A BY X-RAY DIFFRACTION METHOD

Kanglemeisu A (C50H63O19N·CH3OH) is the product of an actinomyces species from a soil sample gathered in China. Kanglemeisu A belongs to the triclinic system, space group P1,unit cell:a=12.760（3）, b=10.287（2）, c=9.926（2） , α=88.39（2）,β=78.64（2）, γ=89.14（2）. RANTAN direct method is used to solve the structure.The final discrepancy factor is R=0.0689, after atom coordinates and temperature factors have been refined with full matrix least squares.The structure skeleton consists of four parts, the naphthalene nucleus connected to the 5-membered ring, a 17-membered ring connected to C2, a dimethyl butane diacid extended out from C20, β-D-3,4-OO’ methylenedigitoxose passing through an oxygen bridge O6 and linked to C27 of ansa ring.

The determination of the crystal struoure of tetra-potassium uranyl tricarbonate by powder X-ray diffraction method

A uranyl compound, K_4UO_2(CO_3)_3 has been characterized by powder X-ray diffraction method. M. W.=606.46, monoclinic, C2/c (No. 15), a=1.0240(7), b=0.9198(4), c=1.2222(12)nm, β=95.12(4)°,V=1.1466(5)nm^3, Z=4, D_m=3.468g/cm^3, D_c=3.513g/cm~, λ(Cu Kα_1)=O.1540598nm, T=298K. The structure was solved by heavy atom method and Fourier synthesis, and refined by full- matrix least-squares method to R=0.1185 for 275 reflections. The uranium (Ⅵ) atom is in an eight-coordinate distorted hexagonal-bipyramidal environment with creasy fan shape. The linear uranyl group approaches to perpendicular to the equatorial plane in which three carbonate groups are chelated. U(Ⅵ) has two linear oxygen atoms closer to it (U-O=0.1767 (5) nm) than six other neighbours (U-O ranging from 0.2516 to 0.2568nm). The distances between carbon atoms and uncoordinated oxygen atoms are 0.122 (1) and 0.123(1) nm, which are distinctly different from those between carbon and coordinated oxygen atoms (mean 0.134(6) nm). This fact reveals the non-eq- uivalence of one oxygen atom to the other two in each carbonate. In K_4UO_2(CO_3)_3, the O-O dis- tance for the adjacent carbonate groups is 0.2794(4)nm approaching to the sum of Van der Waals radii of two oxygen atoms. The K-O distances vary between 0.2667 and 0.3131nm, and each anion is immediately surrounded by six potassium ions, only four of which can be considered to belong to the same structural formula unit, and they are symmetrically located above and below the equatorial plane.

Comparative Study on the Defects of Kaolinite from America,Brazil and China Applied for Paper Coating：XRD and Refinement by Rietveld Method

Three kaolinite samples applied for paper coating were collected from America（KA）,Brazil（KB）,and China（KC）,respectively.Parameters such as average bond length of Si-O and Al-O（1（Si-O） and1（（Al-O）））,tetrahedral rotation angles（α）,changes of tetrahedral flattemng angles（τ） and octahedral flattemng angles（ψ） comparative to ideal angle,particle layer thickness（T） and basal z corrugation（Δz） were analyzed by XRD and Rietveld method.The experimental results indicated that △z（KA）〉△z（KC）〉△z（KB）.KB has a regular structure and KA has a disorder structure,α（KA）〉α（KC）〉α（KB）,△τ（KA）〉△τ（KC）〉△τ（KB）,and △ψ（KA）〉△ψ（KB）〉△ψ（KC）.KA has unstable tetrahedron and octahedron.KB and KC have stable tetrahedron and octahedron,respectively.In the process of manufacture,kaolinite structure may be broken from places with unstable tetrahedron and octahedron.l（Si-O）（KA） 〉l（Si-O）（KB）〉l（Si-O）（KC） and 1（A1-O）KA〉1（A1-O）（KC）〉1（A1-O）（KB）.What only considered is the effect of bond length,KA may be most easily broken in the manufacture.Compared with bond lengths of KA and KB,Si-O,and Al-O of KB and KC may be easily broken,respectively.T（KA）

Possible Relevance of the Allende Meteorite Conditions in Prebiotic Chemistry: An Insight into the Chondrules and Organic Compounds

The study of the mineral and organic content of the Allende meteorite is important for our understanding of the molecular evolution of the universe as well as the ancient Earth. Previous studies have characterized the magnetic minerals present in ordinary and carbonaceous chondrites, providing information on the evolution of magnetic fields. The interaction of organic compounds with magnetic minerals is a possible source of chemical diversity, which is crucial for molecular evolution. Carbon compounds in meteorites are of great scientific interest for a variety of reasons, such as their relevance to the origins of chirality in living organisms. This study presents the characterization of organic and mineral compounds in the Allende meteorite. The structural and physicochemical characterization of the Allende meteorite was accomplished through light microscopy, powder X-ray diffraction with complementary Rietveld refinement, Raman and infrared spectroscopy, mass spectrometry, scanning electron microscopy, and atomic force microscopy using magnetic signal methods to determine the complex structure and the interaction of organic compounds with magnetic Ni-Fe minerals. The presence of Liesegang-like patterns of chondrules in fragments of the Allende structure may also be relevant to understanding how the meteorite was formed. Other observations include the presence of magnetic materials and nanorod-like solids with relatively similar sizes as well as the heterogeneous distribution of carbon in chondrules. Signals observed in the Raman and infrared spectra resemble organic compounds such as carbon nanotubes and peptide-like molecules that have been previously reported in other meteorites, making the Mexican Allende meteorite a feasible sample for the study of the early Earth and exoplanetary bodies.

Residual Stress Distribution of Asymmetric Quenching in Al-Zn-Mg-Cu Aluminum Alloy Plate

The residual stress distribution for two strategies of asymmetric quenching in Al-Zn-Mg-Cu aluminum alloy plates has been simulated using the finite element method. The results show that for asymmetric quenching between the upper and lower surfaces, the through-thickness asymmetric quenching residual stress distribution lies between the two distributions corre-sponding to the heat transfer coefficients on the upper and lower surfaces respectively. The surface and central stress magnitudes are equal to the average of the stress magnitudes corresponding to the two heat transfer coefficients. For asymmetric quenching of a single surface, the surface stress distribution is the same as the heat transfer coefficient distribution and the stress magnitude is equal to the stress magnitude corresponding to the average value of the heat transfer coefficients at each location. However, the center quench residual stress distribution is approximately uniform and the stress magnitude is equal to the average of the stress magnitudes corresponding to the maximum and minimum heat transfer coefficients.

Analysis on Microstructure and Misorientation of Ultrathin Hot Strip of Low Carbon Steel Produced by Compact Strip Production

The microstructure and misorientation of ultrathin hot strip were analyzed by CSP technology using electron back scattered diffraction (EBSD) method and Autoforge finite element program. The experimental results showed that the finishing hot rolling microstructures were the mixture of recrystallized and deformed austenite. After phase transformation, ferrite grains embody substructures and dislocations, leading to the high strength and relatively low elongation rate of the ultrathin hot strip. The FEM simulation of strain mode and distribution in deformation area has been fulfilled. The simulation results are in good agreement with the theoretical analysis and experimental results.

A method based on diffraction theory for predicting 3D focusing performance of compound refractive X-ray lenses

A method based on the diffraction theory for estimating the three-dimensional (3D) focusing performance of the compound refractive X-ray lenses is presented in this paper. As a special application, the 3D X-ray intensity distribution near the focus is derived for a plano-concave compound refractive X-ray lens. Moreover, the computer codes are developed and some results of 3D focusing performance for a compound refractive X-ray lens with Si material are shown and discussed.

Time domain simulations of radiation and diffraction by a Rankine panel method

The radiation and the diffraction of a ship with a forward speed are studied by using a time domain Rankine panel method. The free surface conditions are linearized onto an undisturbed free surface based on the double body flow. The linearized body boundary condition is applied on the mean wetted hull surface. The fluid domain boundary is discretized by a collection of quadric panels. The unknown quantities, including the free surface elevation, the normal flux over the free surface and the potential on the fluid domain boundary, are determined at each time step. The numerical results are compared with experimental data and other numerical solutions, showing satisfactory agreements.

Effect of diffraction on the ultrasonic velocity measuredby the pulse interference method in VHF range

The effect of diffraction on the ultrasonic velocity measured by the pulse interference method has been investigated in VHF range theoretically and experimentally. Two silicate glasses are taken as the specimens, their frequency dependences of longitudinal velocities are measured in the frequency range of 50-350 MHz, and the phase advances of ultrasonic signals caused by diffraction effect are calculated using A. O. Williams' theoretical expression. For the velocity error due to diffraction effect, the experimental results are in good agreement with the theoretical prediction. It has been shown that the velocity error due to diffraction effect is directly proportional to dθ21 (f)/df, whereθ21 (f) is the phase advances difference between the two partial reflection signals used in velocity measurement and f is the ultrasonic frequency.

Design of a grating by a joint optimization method for a phase-shifting point diffraction interferometer

A grating is an important element of a phase-shifting point diffraction interferometer, and the grating constant and duty cycle have a great impact on the interferometer, so the design of a grating becomes significant. In order to measure the projection objective with a numerical aperture of 0.2, we present a joint optimization method of a pinhole and grating based on scalar diffraction and the finite difference time domain method. The grating constant and the film thickness are selected, and the duty cycle of the grating is optimized. The results show that in the grating processing the material chromium is adopted, the thickness is 200 nm, and the grating constant is 15 μm. When the duty cycle is 55%, the interference fringe contrast is the greatest. The feasibility of the design result is further verified by experiment.

Double-slit diffraction of terahertz wave generated by tilted-pulse-front pumping

We propose a spatial diffraction diagnostic method via inserting a millimeter-gap double slit into the collimated terahertz beam to monitor the minute variation of the terahertz beam in strong-field terahertz sources,which is difficult to be resolved in conventional terahertz imaging systems.To verify the method,we intentionally fabricate tiny variations of the terahertz beam through tuning the iris for the infrared pumping beam before the tilted-pulse-front pumping setups.The phenomena can be well explained by the theory based on the tilted-pulse-front technique and terahertz diffraction.

Low-cost method of fabricating large-aperture,high efficiency,Fresnel diffractive membrane optic using a modified moir technique

To reduce the cost and achieve high diffraction efficiency, a modified moir@ technique for fabricating a large- aperture multi-level Fresnel membrane optic by a novel design of alignment marks is proposed. The modified moire fringes vary more sensitively with the actual misalignment. Hence, the alignment accuracy is significantly improved. Using the proposed method, a 20 μm thick, four-level Fresnel diffractive polyimide membrane optic with a 200 mm diameter is made, which exhibits over 62% diffraction efficiency into the ＋1 order, and an efficiency root mean square of 0.051.

Electromagnetic wave absorption in reduced graphene oxide functionalized with Fe3O4/Fe nanorings

We report the preparation of nanocomposites of reduced graphene oxide with embedded Fe3O4/Fe nanorings （FeNR@rGO） by chemical hydrothermal growth. We illustrate the use of these nanocomposites as novel electromagnetic wave absorbing materials. The electromagnetic wave absorption properties of the nanocomposites with different compositions were investigated. The preparation procedure and nanocomposite composition were optimized to achieve the best electromagnetic wave absorption properties. Nanocomposites with a GO：cx-Fe203 mass ratio of 1：1 prepared by annealing in HdAr for 3 h exhibited the best properties. This nanocomposite sample （thickness = 4.0 mm） showed a minimum reflectivity of -23.09 dB at 9.16 GHz. The band range was 7.4-11.3 GHz when the reflectivity was less than -10 dB and the spectrum width was up to 3.9 GHz. These figures of merit are typically of the same order of magnitude when compared to the values shown by traditional ferric oxide materials. However, FeNR@rGO can be readily applied as a microwave absorbing material because the production method we propose is highly compatible with mass production standards.

Effects of doping Fe cations on crystal structure and thermal expansion property of Yb_2Mo_3O_(12)

Crystal structures and thermal expansion properties of Yb2-xFexMo3O12（x=0.0,0.6,1.0,1.1,1.4） solid solutions have been studied by X-ray powder diffraction（XRPD） at different temperatures.Rietveld analysis of the XRPD data shows that Yb2-xFexMo3O12 solid solutions adopt orthorhombic structure and have variable thermal expansion coefficients controlled by the ratio of Yb^3＋ to Fe^3＋.Yb2Mo3O12 shows anisotropic negative thermal expansion property,induced by the reductions in average Yb-O-Mo angle and average apparent Mo2-O bond length with increasing temperatures.As more Yb^3＋ substituted by Fe^3＋,the linear thermal expansion coefficients of Yb2-xFexMo3O12 increase from negative to positive.A near-zero thermal expansion coefficient of 0.55×10^-6K^-1 for Yb0.6Fe1.4Mo3O12 is observed in the temperature range of 573-873 K.

Lattice parameters of Ti–4Al–2V alloy with thermal oxidation

In this study, the effect of thermal oxidation on the lattice parameters of Ti-4Al-2V alloy was studied.Samples were oxidized at 450, 600 and 650 °C for 1-7 h in electric furnace under air atmosphere. The lattice parameters were determined using the Cohen method as a function of oxidation time at each temperature. The lattice parameters of as-received alloy are calculated as a = 0.29289 nm and c = 0.46652 nm. The thermal oxidation at 450 °C results in a gradual increase in a-parameter, whereas it goes through a maximum at higher temperatures（600 and 700 °C）. The results show that these maximums are reduced to an approximately constant value after a long-time oxidation. The c-parameter generally increases over the whole treatment condition. It is believed that these variations could be due to the dissolution of oxygen atoms in octahedral sites of hcp lattice of titanium.