飞机跑道胶痕的自动识别系统设计与实现

为了减轻机场跑道除胶工作人员的劳动强度,提高除胶工作效率,文章提出了一种基于机器视觉的胶痕自动查找和识别方法,设计了基于ARM单片机控制的图像无线采集和基于PC机控制的图像接收、图像预处理和图像识别系统。文章通过分析预处理后的数据特点,确定了基于细胞神经网络算法的胶痕识别算法,然后在MATLAB仿真环境下确定了该算法的最优模型和参数,最后在Visual C++ 6.0环境下完成了该算法的程序编译,调试并完成了对胶痕的自动识别过程。理论仿真和程序测试的结果证明了文章提出的方法在胶痕自动识别系统中的可行性,也为机场特种设备的无人化和智能化提供了参考。     

The Proton NMR and Structures of Dimethyl and Diethyl Dichalcogenides

The proton NMR spectra of dimethyl dichalcogenides and diethyl dichalcogenides were measured. The experimental results do not show the evidence for the existence of rotational isomerism in each molecules.     

Novel 1122 thallium cuprates showing high Tc superconductivity: TlCa1-xY,Ba2Cu2O y,T,1-xPb x CaSr2Cu2O y and TlCa0.5Ln0.5Sr2Cu2O y

Substitution of Ca by Y in TlCaBa₂Cu₂O _y does not favour superconductivity, but substitution of Tl by Pb or of Ca by Ln (Ln = Y or rare earth) in TlCaSr₂Cu₂O _y results in high T_c superconductivity (T_c π 60–90 K). TlCa_1-xLn _x Sr₂Cu₂O _y is a new series of high T_c superconductors, but the x = 0.0 composition does not exhibit bulk superconductivity.     

Effects of RE2O3 (RE = Tm, Sc, Yb) addition on the superconducting properties of ErBa2Cu3Oy

We investigated the effects of added Tm₂O₃, Sc₂O₃, and Yb₂O₃ on the superconducting properties of sintered Er123 samples. Tm₂O₃ addition caused the least T_c degradation, exhibiting a T_c above 90 K even for 17 vol% addition. Samples with added Sc₂O₃ maintained a T_c at above 90 K up to an addition of 7.2 vol%, while Yb₂O₃-containing samples showed a monotonic decrease in T_c with increased vol% of added Yb₂O₃. Tm₂O₃-containing samples exhibited a slight increase in J_c(0.1 T)/J_c(0) and had constant J_c values even for 17 vol% addition. XRD and SEM results indicate that the Tm₂O₃ is very stable in the superconducting matrix.     

A new high-pressure polymorph of Ti2O3: implication for high-pressure phase transition in sesquioxides

The post-corundum phase transition has been investigated in Ti₂O₃ on the basis of synchrotron X-ray diffraction in a diamond anvil cell and transmission electron microscopy. The new polymorph of Ti₂O₃ was found at about 19 GPa and 1850 K, and this phase was stable even at about 40 GPa. A new polymorph of Ti₂O₃ can be indexed on a Pnma orthorhombic cell, and the unit-cell parameters are a=7.6965 (19) Å, b=2.8009 (9) Å, c=7.9300 (23) Å, V=170.95 (15) Å³ at 19 GPa, and a=7.8240 (2) Å, b=2.8502 (1) Å, c=8.1209 (3) Å, V=181.10 (1) Å³ at ambient conditions. The Birch–Murnaghan equation of state yields K ₀=206 (3) GPa and K′₀=4 (fixed) for corundum phase, and K ₀=296 (4) GPa and K′₀=4 (fixed) for the post-corundum phase. The molar volume decreases by 12% across the phase transition at around 20 GPa. The structural identification was carried out on a recovered sample by the Rietveld method, and a new polymorph of Ti₂O₃ can be identified as Th₂S₃-type rather than U₂S₃-type structure. The transition from corundum-type to Th₂S₃-type structure accompanies the drastic change of the form of polyhedron: from TiO₆ octahedron in the corundum-type to TiO₇ polyhedron in the Th₂S₃-type structures.     

Thermally stimulated luminescence from alkaline earth borates

The thermally stimulated luminescence from XB₂O₄ (X=Ca,Sr,Ba) has been investigated. The results on CaB₂O₄ and SrB₂O₄ are being reported here for the first time. In both cases, the emission is found to be quite intense, contrary to the case with BaB₂O₄. The presence of two peaks in the glow curves is noted over the temperature range of 300-570 K. The emission spectra corresponding to both the peaks have been observed to be identical, consisting of two broad emissions, one in the UV and other in the blue-green regions. The emission is apparently quite different from that of BaB₂O₄ in which case only very weak emission spreading over a broad wavelength range around 410 nm is observed. This result has been understood in terms of the overlap between the excitation and the emission spectra.     

Relation between highT c superconductivity and structure: A study of Ba3+x Cu6O14+δ and YBa2Cu3O7−δ systems

Superconductivity is found in tetragonal La_3−x Ba_3+x Cu₆O_14+δ and La, Ba)_6−x Sr _x Cu₆O_14+δ even though they do not possess Cu-O chains or the K₂NiF₄ structure. Resistivity measurements confirm the occurrence of a transformation from chain-superconductivity to sheet-superconductivity in YBa₂Cu₃O_7−δ as δ is varied in the range 0.0–0.5. Contribution No. 481 from the Solid State and Structural Chemistry Unit     

The stability, frontier orbitals, bond character, and static linear polarizability of the fluorinated fullerene H20@C80F60

This paper uses the density functional theory under generalised gradient approximation to analyse the stability,frontier orbitals,bond character,and static linear polarizability of H20@C80F60,which has not been isolated,as well as those of the synthesised H 20 @C 80 H 60.The H20@C80F60 should be considerably stable by analysing its energy and aromaticity.The inside H and outside X will play different role in the chemical reaction involving H 20 @C 80 X 60(X=H and F).The covalence of C-H bond is in the order that the inside C-H bond of H20@C80F60 > the inside C-H bond of H 20 @C 80 H 60 > the outside C-H bond of H 20 @C 80 H 60,whereas the C-F bond of H20@C80F60 have both the covalent and ionic characters.The static linear polarizabilities of C 80 and H 20 @C 80 X 60(X=H and F) are all isotropic.     

Investigations of oxide superconductors by x-ray absorption,photoemission and cognate spectroscopies

X-ray absorption spectra, X-ray photoelectron spectra and Auger spectra of cuprate superconductors are discussed. The studies establish the absence of Cu³⁺ for all practical purposes, but point out the importance of oxygen holes. X-ray photoelectron spectra of BaBi_0.25Pb_0.75O₃ and related compounds are also examined.     

Optical properties of Mn-activated Na2SnF6 and Cs2SnF6 red phosphors

Alkaline hexafluorostantanate red phosphors Na₂SnF₆:Mn⁴⁺ and Cs₂SnF₆:Mn⁴⁺ are synthesized by chemical reaction in HF/NaMnO₄ (CsMnO₄)/H₂O₂/H₂O mixed solutions immersed with tin metal. X-ray diffraction patterns suggest that the synthesized phosphors have a tetragonal symmetry with the space group D_4h¹⁴ (Na₂SnF₆:Mn⁴⁺) and a trigonal symmetry with the space group D_3d³ (Cs₂SnF₆:Mn⁴⁺). Photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and the Raman scattering techniques are used to investigate the optical properties of the phosphors. The Franck-Condon analysis of the PLE data yields the Mn⁴⁺-related optical transitions to occur at ∼2.39 and ∼2.38 eV (⁴A_2g→⁴T_2g) and at ∼2.83 and ∼2.76 eV (⁴A_2g→⁴T_1g) for Na₂SnF₆:Mn⁴⁺ and Cs₂SnF₆:Mn⁴⁺, respectively. The crystal field parameters (Dq) of the Mn⁴⁺ ions in the Na₂SnF₆ and Cs₂SnF₆ hosts are determined to be ∼1930 and ∼1920 cm⁻¹, respectively. Temperature-dependent PL measurements are performed from 20 to 440 K in steps of 10 K, and the obtained results are interpreted by taking into account the Bose-Einstein occupation factor. Comprehensive discussion is given on the phosphorescent properties of a family of Mn⁴⁺-activated alkaline hexafluoride salts.     

相变存储材料Ge1Sb2Te4和Ge2Sb2Te5薄膜的结构和电学特性研究

采用射频磁控溅射方法制备了两种用于相变存储器的Ge₁Sb₂Te₄和Ge₂Sb₂Te₅相变薄膜材料,对其结构、电学输运性质和恒温下电阻随时间的变化关系进行了比较和分析.X射线衍射(XRD)和原子力显微镜(AFM)的结果表明:随着退火温度的升高,Ge₁Sb₂Te₄薄膜逐步晶化,由非晶态转变为多晶态,表面出现均匀的、 关键词： 硫系相变材料 1Sb₂Te₄')" href="#">Ge₁Sb₂Te₄ 2Sb₂Te₅')" href="#">Ge₂Sb₂Te₅     

Preparation and magnetic properties of BaFe12O19/Ni0.8Zn0.2Fe2O4 nanocomposite ferrite

Nanocomposite of hard (BaFe₁₂O₁₉)/soft ferrite (Ni_0.8Zn_0.2Fe₂O₄) have been prepared by the sol–gel process. The nanocomposite ferrite are formed when the calcining temperature is above 800 °C. It is found that the magnetic properties strongly depend on the presintering treatment and calcining temperature. The “bee waist” type hysteresis loops for samples disappear when the presintering temperature is 400 °C and the calcination temperature reaches 1100 °C owing to the exchange-coupling interaction. The remanence of BaFe₁₂O₁₉/Ni_0.8Zn_0.2Fe₂O₄ nanocomposite ferrite with the mass ratio of 5:1 is higher than a single phase ferrite. The specific saturation magnetization, remanence magnetization and coercivity are 63 emu/g, 36 emu/g and 2750 G, respectively. The exchange-coupling interaction in the BaFe₁₂O₁₉/Ni_0.8Zn_0.2Fe₂O₄ nanocomposite ferrite is discussed.     

The high pressure synthesis of the graphitic form of C3N4

Abstract

Basing on “ab-initio” calculations, C₃N₄ was claimed to be an ultra-hard material with a bulk-modulus close to that of diamond. Five different structural varieties were announced: the graphitic form, the zinc blende structure, the α and β forms of Si₃N₄ and another form, isostructural with the high pressure variety of Zn₂Si0₄.

Using the same strategy as that developed for diamond or c-BN synthesis, it appears that the graphitic form could be an appropriate precursor for preparing the 3D varieties. Two main problems characterize the C₃N₄ synthesis: (-) the temperature should be reduced in order to prevent nitrogen loss, (-) the reactivity of the precursors should be improved.

Consequently, we have developed a new process using the solvothermal decomposition of organic precursors containing carbon and nitrogen in the presence of a nitriding solvent. The resulting material, with a composition close to C₃N₄, has been characterized by different physico-chemical techniques.     

Bi0.5Ba0.5Fe0.5Ti0.49Nb0.01O3热敏陶瓷的微结构和电学性能研究

采用固相合成工艺,制备了Bi_05Ba_05Fe_05Ti_049Nb_001O₃（BBFTN）热敏陶瓷,借助X射线衍射仪、扫描电子显微镜、阻温测试仪和交流阻抗谱考察其微结构、直流电阻、介电特性、阻抗和电学模量方面的电学性能. 结果表明：BBFTN材料依然为立方钙钛矿结构,平均晶粒尺寸约为10 μm,晶格常数相对于BaTiO₃的晶格常数有所变大;室温电 关键词： 05Ba_05Fe_05Ti_049Nb_001O₃')" href="#">Bi_05Ba_05Fe_05Ti_049Nb_001O₃ 微结构 电学性能     

Synthesis,crystal structure and magnetic properties of Yb8Ag18.5Al47.5, Yb2Pd2Cd and Yb1.35Pd2Cd0.65

We report the synthesis of three new Yb-based compounds, Yb₈Ag_18.5Al_47.5 (Yb₈Cu₁₇Al₄₉-type, tetragonal tI74–I4/mmm), Yb₂Pd₂Cd (Mo₂B₂Fe-type, tetragonal tP10-P4/mbm) and Yb_1.35Pd₂Cd_0.65 (MnCu₂Al-type, cubic cF16–Fm3¯m). The crystal symmetry of these compounds has been determined and the complete structural characterisation carried out by single crystal and powder diffraction techniques. Two symmetry in-equivalent sites are available for the Yb ions in Yb₈Ag_18.5Al_47.5 and Yb_1.35Pd₂Cd_0.65. The 4f levels of the Yb ions are appreciably hybridised in Yb₈Ag_18.5Al_47.5 and to a lesser extent in Yb₂Pd₂Cd as inferred from the magnetisation and heat capacity data. Signatures of heavy fermion behaviour are observed in the heat capacity data of Yb₂Pd₂Cd in which the heat capacity, C/T, increases at low temperatures attaining a value of ≈600 mJ/mol K² at 1.8 K. The electrical resistivity of Yb₂Pd₂Cd follows a linear variation with temperature, T, between 1.4 and 5 K, thus indicating a possible non-Fermi liquid behaviour. In contrast, Yb ions are trivalent in Yb_1.35Pd₂Cd_0.65 and order magnetically near 1.4 K.     

Group Classification of Biological Tissues by Infrared Spectroscopy

Infrared spectra of rat tissues, RNA tumor virus (Rauschler) and pure RNA and DNA are examined by the technique of frustrated multiple internal reflection (FMIR). An attempt has been made to characterize biologically important tissue components on the basis of infrared spectral analysis and published literature on the subject.

Under the conditions described, rat tissues may be grouped according to their infrared spectra. The spectral differences in vivo between normal and N-nitroso-dimethylamine (DMN)-injected rat liver have been presented to show the usefulness of the FMIR technique for rapid detection of induced changes in the tissue composition.     

Influence of postdeposition annealing on structural properties and electrical characteristics of thin Tm2O3 and Tm2Ti2O7 dielectrics

We describe the structural properties and electrical characteristics of thin thulium oxide (Tm₂O₃) and thulium titanium oxide (Tm₂Ti₂O₇) as gate dielectrics deposited on silicon substrates through reactive sputtering. The structural and morphological features of these films were explored by X-ray diffraction, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and atomic force microscopy, measurements. It is found that the Tm₂Ti₂O₇ film annealed at 800 °C exhibited a thinner capacitance equivalent thickness of 19.8 Å, a lower interface trap density of 8.37 × 10¹¹ eV⁻¹ cm⁻², and a smaller hysteresis voltage of ∼4 mV than the other conditions. We attribute this behavior to the Ti incorporated into the Tm₂O₃ film improving the interfacial layer and the surface roughness. This film also shows negligible degrees of charge trapping at high electric field stress.     

The nature of antimony-enriched surface layer of Fe-Sb mixed oxides

Antimony segregation is a common feature in Fe-Sb mixed oxides, which have been widely applied as catalysts in selective oxidation and ammoxidation reactions. This paper attempts to shed a light on the cause of such a common feature and on the nature of the antimony-enriched surface layer over FeSbO₄ by means of XPS surface analysis. Single-phase FeSbO₄ samples prepared by different methods were studied, and the antimony in their surface layer is a mixture of both Sb⁵⁺ and Sb³⁺ rather than single Sb⁵⁺. Their surface composition is close to FeSb₂O₆, which could be described as (FeSbO₄)(Sb₂O₄)_δ, δ = 0.5, and it is not “Fe(II)Sb(V)₂O₆” as suggested in literature. Fe-Sb mixed oxides with Sb/Fe > 1 (mol/mol) are mixtures of FeSbO₄ and Sb₂O₄, and the surface of FeSbO₄ grains would be a layer of (FeSbO₄)(Sb₂O₄)_δ, δ ≥ 0.5. Fe-Sb mixed oxides with Sb/Fe < 1 are mixtures of FeSbO₄ and Fe₂O₃, and the surface of FeSbO₄ grains would be a layer of (FeSbO₄)(Sb₂O₄)_δ, δ ≤ 0.5, but the remaining Fe₂O₃ would be encapsulated by a layer of FeSbO₄.     

Magneto-transport properties of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction

Hole-doped rare-earth manganite La_0.7Ca_0.3MnO₃ and the electron-doped manganite La_0.7Ce_0.3MnO₃ both show a metal-insulator transition around 250 K associated with a ferromagnetic transition and colossal magnetoresistance. In an earlier publication we have reported the rectifying characteristic of La_0.7Ca_0.3MnO₃/SrTiO₃/La_0.7Ce_0.3MnO₃ tunnel junction at room temperature, showing that it is possible to fabricate a diode out of the polaronic insulator regime of doped manganites. Here we report the magneto-transport properties of such a tunnel junction above and below the metal-insulator transition. We show, from the large positive magnetoresistance of the tunnel junction at low temperature, that La_0.7Ce_0.3MnO₃ could be a minority spin carrier ferromagnet. The implication of this observation is discussed.     

Constituted oxides/nitrides on nitriding 304, 430 and 17-4 PH stainless steel in salt baths over the temperature range 723 to 923 K

The progressively developed oxides and nitrides that form on nitriding 304, 430 and 17-4 PH stainless steel are analysed by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) in this study. The experimental results show that the Cr contents and matrix structures (ferrite, austenite and martensite) play an important role in forming FeCr₂O₄, Cr₂O₃ and Fe₂O₃ oxides as well as nitrides. After a short immersion time, oxides of Cr₂O₃ and FeCr₂O₄ form in nitride films on 304 stainless steel samples. Fe₂O₃ oxide will subsequently form following an increasing immersion time. For the 430 stainless steel, Cr₂O₃ predominately forms after a short dipping time which hinders the growth of the nitride layer. As a result, this sample had the thinnest nitride film of the three for a given immersion time. After the formation of oxides, both CrN and Cr₂N were detected near the surface of the nitride films of three samples while Cr₂N phases formed in the deeper zone. The greatest amount of Fe₂O₃ oxide among the three samples was obtained on the nitriding 17-4 PH stainless steel which also had a high intensity count of N 1s.