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Low-temperature heat capacities and standard molar enthalpy of formation of pyridine-2,6-dicarboxylic acid

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Chinese Physics B 2010年第6期19卷 188-194页

作者：杨伟伟邸友莹孔玉霞谭志诚 College of Chemistry and Chemical Engineering Liaocheng University Thermochemistry Laboratory Dalian Institute of Chemical PhysicsChinese Academy of Sciences

This paper reports that the low-temperature heat capacities of pyridine-2,6-dicarboxylic acid were measured by a precision automatic calorimeter over a temperature range from 78 K to 380 K. A polynomial equation of heat capacities as a function of temperature was fitted by the least-squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at intervals of 5 K. The constant-volume energy of combustion of the compound was determined by means of a precision rotating-bomb combustion calorimeter. The standard molar enthalpy of combustion of the compound was derived from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound was calculated from a combination of the datum of the standard molar enthalpy of combustion of the compound with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.

关键词： pyridine-2,6-dicarboxylic acid adiabatic calorimetry low-temperature heat capacity standard molar enthalpy of formation

Structure and electrochemical properties of LaMgNi4-xCox(x=0-0.8)hydrogen storage electrode alloys

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Rare Metals 2018年第3期37卷 249-256页

作者： Tai Yang Ting-Ting Zhai Ze-Ming Yuan Wen-Gang Bu Yan Qi Yang-Huan Zhang Functional Materials Research Institute Central Iron and SteelResearch Institute Beijing 100081 China Key Laboratory of Integrated Exploitation of Baiyun Obo Multi-Metal Resources Inner Mongolia University of Science andTechnology Baotou 014010 China

LaMgNi（4-x）Cox（x = 0-0.8） electrode alloys used for MH/Ni batteries were prepared by induction melting. The structures and electrochemical hydrogen storage properties of the alloys were investigated in detail.X-ray diffraction（XRD） and scanning electron microscopy（SEM） analysis show that LaMgNi4 phase and LaNi5 phase are obtained. The lattice parameters of the two phases increase first and then decrease with Co content *** electrochemical properties of the alloy electrodes were measured by means of simulated battery tests. Results show that the addition of Co does not change the discharge voltage plateau of the alloy electrodes. However, the maximum discharge capacity increases from 319.9 mAh·g^-1（x = 0）to 347.5 mAh·g^-1（x = 0.4） and then decreases to331.7 mAh·g^-1（x = 0.8）. The effects of Co content on electrochemical kinetics of the alloy electrodes were also performed. The high rate dischargeability（HRD） first increases and then decreases with Co content increasing and reaches the maximum value（95.0 %） when x = 0.4. Test results of the electrochemical impedance spectra（EIS）,potentiodynamic polarization curves and constant potential step measurements of the alloy electrodes all demonstrate that when Co content is 0.4 at%, the alloy exhibits the best comprehensive electrochemical properties.

关键词： Hydrogen storage alloy Element substitution Phase structure Electrochemical performances Kinetics

Ultrastructural studies of seed coat and cotyledon during rapeseed maturation

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Journal of Integrative Agriculture 2021年第5期20卷 1239-1249页

作者： CAO Jian-bo HE Li-min Chinedu Charles NWAFOR QIN Li-hong ZHANG Chun-yu SONG Yan-tun HAO Rong Key Laboratory of Arable Land Conservation(Middle and Lower Reaches of Yangtse River) Ministry of Agriculture and Rural Affairs/Hubei Key Laboratory of Soil Environment and Pollution Remediation/College of Resources and EnvironmentHuazhong Agricultural UniversityWuhan 430070P.R.China Public Laboratory of Electron Microscopy Huazhong Agricultural UniversityWuhan 430070P.R.China national Key Laboratory of Crop Genetic Improvement/College of Plant science and Technology Huazhong Agricultural UniversityWuhan 430070P.R.China

Brassica napus L.(***)is an important oil crop worldwide and it rapidly accumulates oil at late stage of seed ***,little is known about the cellular mechanism of oil accumulation and seed color changes during the late stage of rapeseed ***,we analyzed the ultrastructure of seed coat,aleurone and cotyledon in embryos of *** from 25 to 70 days after flowering(DAF).The pigments,which were deposited on the cell wall of palisade cells in seed coat,determined dark black color of *** chloroplasts degenerated into non-photosynthetic plastids which caused the green cotyledon to turn into *** chloroplasts in aleurone and cotyledon cells respectively degenerated into remnants without inner and outer envelope membranes and ecoplasts with intact inner and outer envelope *** 40 to 70 DAF,there were degraded chloroplasts without thylakoid,oil bodies contacting with plastids or protein bodies,big starch deposits of chloroplasts degrading into small particles then disappearing,and small endoplasmic reticulum(ER)in aleurone and cotyledon ***,there were decreases of chlorophyll content and dramatic increases of oil content in *** results suggested that the rapid oil accumulation was independent on the NADPH synthesized by photosynthesis of chloroplasts and probably utilized other sources of reductant,such as the oxidative pentose phosphate pathway during the late stage of rapeseed *** triacylglycerol assembly presumably utilizes the enzymes in the plastid,cytosol or oil body of cotyledon and aleurone cells.

关键词： rapeseed seed coat plastid development oil synthesis ultrastructure

Thermal cycling performance of La_(2)Ce_(2)O_(7)/YSZ TBCs with Pt/Dy co-doped NiAl bond coat on single crystal superalloy

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Rare Metals 2021年第9期40卷 2568-2578页

作者： Zi-Min Zhou Hui Peng Lei Zheng Hong-Bo Guo Sheng-Kai Gong School of Materials science and Engineering Beihang UniversityBeijing 100191China Beijing Key Laboratory for Advanced Functional Material and Thin Film Technology Beihang UniversityBeijing 100191China Key Laboratory of Aerospace Materials and Performance(Ministry of Education) Beihang UniversityBeijing 100191China

Thermal barrier coatings(TBCs) consisting ofLa_(2)Ce_(2)O_(7)(LCO) and Y_(2)O_(3)-stabilized-ZrO_(2)(YSZ) doubleceramic layer and Dy/Pt co-doped NiAl bond coat were produced by electron beam physical vapor deposition(EBPVD). Thermal cyclic performance of the TBCs was evaluated by flame shock testing at 1300 ℃. For comparison, the TBCs with a undoped NiAl bond coat were also studied. The microstructural evolution and failure mechanisms of the above TBCs during thermal cycling were investigated. Spallation failure of the TBCs with the undoped bond coat occurs after around 500 cycles by cracking at the interface between YSZ ceramic layer and thermally grown oxides(TGO) layer. The TBCs with Pt/Dy modified bond coat reveal improved interface bonding even after 1200 thermal cycles, whereas some delamination cracks are presented in the LCO layer. On the other hand,the Pt/Dy modified bond coat effectively suppresses the formation of the needle-like topologically closed packed phases(TCP) in the single crystal superalloy.

关键词： Thermal barrier coatings NiAl bond coat Pt/Dy co-doping Electron beam physical vapor deposition Thermal cycling Interdiffusion

Optical emission spectroscopy diagnosis of energetic Ar ions in synthesis of SiC polytypes by DC arc discharge plasma

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Nano Research 2018年第3期11卷 1470-1481页

作者： Jian Gao Lei Zhou Jingshuang Liang Ziming wang Yue Wu Javid Muhammad Xinglong Dong Shouzhe Li Hongtao yu Xie Quan Key Laboratory of Materials Modification by Laser Ion and Electron Beams (Ministry of Education) School of Materials Science and Engineering Dalian University of Technology Dalian 116024 China School of Physics Dalian University of Technology Dalian 116024 China Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education) School of Environmental Science and Technology Dalian University of Technology Dalian 116024 China

Silicon carbides are basilic ceramics with proper bandgaps （2.4-3.3 eV） and unique optical properties. SiC@C monocrystal nanocapsules with different morphologies, sizes, and crystal types were synthesized via the fast and facile direct current （DC） arc discharge plasma method. The influence of Ar atmosphere on the formation of nanocrystal SiC polytypes was investigated by optical emission spectroscopy （OES） diagnoses on the arc discharge plasma. Boltzmann＇s plot was used to estimate the temperatures of plasma containing different Ar concentrations as 10,582 K （in 2 × 10^4 Pa of Ar partial pressure） and 14,523 K （in 4 × 10^4 Pa of Ar partial pressure）. It was found that higher energy state of plasma favors the ionization of carbon atoms and promotes the formation of α-SiC, while β-SiC is generally coexistent. Heat-treatment in air was applied to remove the carbon species in as-prepared SiC nanopowders. Thus, the intrinsic characters of SiC polytypes reappeared in the ultraviolet-visible （UV-vis） light absorbance. It was experimentally revealed that the direct bandgap of SiC is 5.72 eV, the indirect bandgap of β-SiC （3C） is 3.13 eV, and the indirect bandgap of α-SiC （6H） is 3.32 eV; visible quantum confinement effect is predicted for these polytypic SiC nanocrystals.

关键词： SiC polytype nanostructures direct current (DC) arcdischarge plasma optical emission spectroscopy(OES)

Influence Diagnostics in Partially Varying-Coefficient Models

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Acta Mathematicae Applicatae Sinica 2007年第4期23卷 619-628页

作者： Chun-xia Zhang Chang-lin Mei Jiang-she Zhang School of science Xi'an Jiaotong University Xi'an Shaanxi 710049 China

When a real-world data set is fitted to a specific type of models, it is often encountered that one or a set of observations have undue influence on the model fitting, which may lead to misleading conclusions. Therefore, it is necessary for data analysts to identify these influential observations and assess their impact on various aspects of model fitting. In this paper, one type of modified Cook＇s distances is defined to gauge the influence of one or a set observations on the estimate of the constant coefficient part in partially varying- coefficient models, and the Cook＇s distances are expressed as functions of the corresponding residuals and leverages. Meanwhile, a bootstrap procedure is suggested to derive the reference values for the proposed Cook＇s distances. Some simulations are conducted, and a real-world data set is further analyzed to examine the performance of the proposed method. The experimental results are satisfactory.

关键词： Partially varying-coefficient model influential observation Cook's distance cross-validation

Crystal structure and thermochemical properties of bis(1-octylammonium) tetrachlorochromate phase change materials

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Chinese Physics B 2012年第8期21卷 126-133页

作者：卢冬飞邸友莹何东华 Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology College of Chemistry and Chemical EngineeringLiaocheng University

A new crystalline complex （C8H17NH3）2CdCI4（s）（abbreviated as CsCd（s）） is synthesized by liquid phase reaction. The crystal structure and composition of the complex are determined by single crystal X-ray diffraction, chemical analysis, and elementary analysis. It is triclinic, the space group is P-1 and Z = 2. The lattice potential energy of the title complex is calculated to be UpoT （CsCd（s））=978.83 ***^-1 from crystallographic data. Low-temperature heat capacities of the complex are measured by using a precision automatic adiabatic calorimeter over a temperature range from 78 K to 384 K. The temperature, molar enthalpy, and entropy of the phase transition for the complex are determined to be 307.3±0.15 K, 10.15±0.23 ***^-1, and 33.054-0.78 J.K^-***^-1 respectively for the endothermic peak. Two polynomial equations of the heat capacities each as a function of temperature are fitted by using the leastsquare method. Smoothed heat capacity and thermodynamic functions of the complex are calculated based on the fitted polynomials.

关键词： bis(1-octylammonium) tetrachlorochromate X-ray crystallography phase change materials low-temperature heat capacity solid-solid phase transition

A novel dense descriptor based on structure tensor voting for multi-modal image matching

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Chinese Journal of Aeronautics 2020年第9期33卷 2408-2419页

作者： Jiazhen LU Maoqing HU Jing DONG Songlai HAN Ang SU School of Aeronautics and Astronautics Central South UniversityChangsha 410083China Aerospace science and Engineering National University of Defense TechnologyChangsha 410073China

Automatic and robust matching of multi-modal images can be challenging owing to the nonlinear intensity differences caused by radiometric variations among these *** address this problem,a novel dense feature descriptor and improved similarity measure are proposed for enhancing the matching *** proposed descriptor is built on a voting scheme of structure tensor that can effectively capture the geometric structural properties of *** is not only illumination and contrast invariant but also robust against the degradation caused by significant ***,the similarity measure is improved to adapt to the reversal of orientation caused by the intensity inversion between multi-modal *** proposed dense feature descriptor and improved similarity measure enable the development of a robust and practical templatematching algorithm for multi-modal *** verify the proposed algorithm with a broad range of multi-modal images including optical,infrared,Synthetic Aperture Radar(SAR),digital surface model,and map *** experimental results confirm its superiority to the state-of-the-art methods.

关键词： Dense feature descriptor Remote sensing images Similarity measurement Structure tensor Template matching

Asymptotic Formulae for Brillouin Index on Riemannian Manifolds

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Acta Mathematica Sinica,English Series 2007年第7期23卷 1297-1302页

作者： Wen Xiang SUN LMAM School of Mathematical SciencesPeking University

We establish several asymptotic formulae for Brillouin index on fiat tori. As an application of these formulae it is proved that the topological entropy of a geodesic flow on a fiat torus is zero.

关键词： flat torus Brillouin index geodesic flow topological entropy