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Chemical Bond Analysis of Single Crystal Growth of Magnesium Oxide

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Journal of Rare Earths 2006年第z1期24卷 245-248页

作者： Zhang xu xue Dongfeng State Key Laboratory of Fine Chemicals Department of Materials Science and Chemical Engineering School of Chemical Engineering Dalian University of Technology Dalian 116012 China State Key Laboratory of Fine Chemicals Department of Materials Science and Chemical Engineering School of Chemical Engineering Dalian University of Technology Dalian 116012 China

Starting from the crystallographic structure of magnesium oxide (MgO), both the chemical bond model of solids and Pauling's third rule (polyhedral sharing rule) were employed to quantitatively analyze the chemical bonding structure of constituent atoms and single crystal growth. Our analytical results show that MgO single crystals prefer to grow along the direction and the growth rate of the {100} plane is the slowest one. Therefore, the results show that the {100} plane of MgO crystals can be the ultimate morphology face, which is in a good agreement with our previous experimental results. The study indicate that the structure analysis is an effective tool to control the single-crystal growth.

关键词： magnesium oxide crystal structure chemical bond

Bonding Energy and Growth Habit of Lithium Niobate Single Crystals

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Journal of Rare Earths 2006年第z1期24卷 241-244页

On the basis of crystallographic structure of lithium niobate (LN), the bonding energy was quantitatively calculated by the bond valence sum model, which was employed to investigate the crystal growth. A possible relationship between the crystal growth habit and chemical bonding energy of LN crystals are found. It is found that the higher the bond energy, the slower the growth rate, and the more important the plane. The analytical results indicate that (012) plane is the most influential face for the LN crystal growth, which consists well with the standard card (JCPDS Card: 20-0631) and our previous experimental observation. The current work shows that the chemical bond analysis of LN crystals allows us to predict its growth habit and thus to obtain the expected morphology during the spontaneous growth.

关键词： lithium niobate chemical bond bonding energy growth habit

Crystallographic Analysis of Tapering of ADP Crystallites

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Journal of Rare Earths 2006年第z1期24卷 228-232页

作者： xu Dongli xue Dongfeng State Key Laboratory of Fine Chemicals Department of Materials Science and Chemical Engineering School of Chemical Engineering Dalian University of Technology Dalian 116012 China State Key Laboratory of Fine Chemicals Department of Materials Science and Chemical Engineering School of Chemical Engineering Dalian University of Technology Dalian 116012 China

On the basis of crystallographic characteristics of ADP (ammonium dihydrogen phosphate) crystals and the selected growth conditions, the growth habit of ADP crystals was studied. In comparison with pyramidal planes, the growth rate of prismatic faces is slower and more sensitive to the additives and impurities for ADP crystals. When the supersaturation is low, the advance of growth steps on prismatic face can be blocked by ethanol or impurities, the crystal morphology is changed from the tetragonal prism to shuttle (i.e., the tapered shape). The tapering formation of ADP crystallites was structurally studied in a novel view.

关键词： crystal structure chemical bond growth habit ADP hydrogen bond tapering

Chemical Bond Calculations of Crystal Growth of KDP and ADP

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Journal of Rare Earths 2006年第z1期24卷 144-148页

A novel method was proposed to calculate the crystal morphology (or growth habit) on the basis of chemical bond analysis. All constituent chemical bonds were distinguished as relevant and independent bonds according to their variations during the crystallization process. By employing the current method, the influence of specific growth conditions on the crystal morphology can be considered in the structure analysis process. The ideal morphologies of both KDP (KH2PO4) and ADP (NH4H2PO4) crystals were calculated and compared with our obtained crystallites at room temperature, which validates the present calculation method very well.

关键词： chemical bond crystal morphology bond valence crystal surface crystal growth

Squeezed State Caused by Inverse of Photon Creation Operator

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Communications in Theoretical Physics 2006年第2期45卷 332-334页

作者： xu xue-Fen Department of Basic Courses Jiangsu Teachers University of Technology Changzhou 213001 China

Using the photon creation operator＇s eigenstate theory we derive the normally ordered expansion of inverse of the squeezed creation operator. It turns out that using this operator a kind of excitation on the squeezed... 详细信息

关键词： inverse of creation operator squeezed state normal ordering

Hermitian Operators Conjugate to Two-Mode Number-Difference Operator Studied in Entangled State Representation

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Communications in Theoretical Physics 2008年第10期50卷 979-982页

作者： xu xue-Fen School of Mathematics and Physics Jiangsu Teachers University of Technology Changzhou 213001 China

In similar to the derivation of phase angle operator conjugate to the number operator by Arroyo Carrasco-Moya Cessay we deduce the Hermitian phase operators that are conjugate to the two-mode number-difference operatorand the three-mode number combination *** is shown that these operators are on the same footing in theentangled state representation as the one of Turski in the coherent state representation.

关键词： phase operator entangled state representation number-difference operator

Three-Mode Cyclic Squeezed States Constructed via EPR Entangled State

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Communications in Theoretical Physics 2007年第5期47卷 905-908页

作者： xu xue-Fen Department of Basic Courses Jiangsu Teachers University of Technology Changzhou 213001 China

We construct the three-mode cyclic squeezed states and analyze its squeezing property by using the technique of integration within an ordered product of operators and the natural representation of the two-mode squeezi... 详细信息

关键词： three-mode cyclic squeezed state EPR entangled state

Influence Factors for Impact Actions and Transient Trajectories of Fan Blades after Fan Blade Out in Typical 2-Shaft High Bypass Ratio Turbofan Engine

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Journal of Thermal Science 2022年第1期31卷 96-110页

作者： xu xue LI Hongxin FENG Guoquan Shenyang Engine Research Institute Aero Engine Corporation of ChinaShenyang 110015China Corporation Headquarter Aero Engine Corporation of ChinaBeijing 100097China

To enhance the understanding of design characters, which have prominent influences during the fan blade out event, a simplified geometrical and dynamic analysis method was derived, and a typical 2-shaft high bypass ratio turbofan engine was selected and modeled. Based on analytical deriving and engineering experience learned from the real engine failure case, three determinative impact actions were recognized from the fan blade out process. The transient trajectories of these impact actions were researched in analytical method, and then thickness of acoustic lining, quantity of fan blades and threshold load of structural fuse were analyzed as key design characters. 36 serialized fan blade out transient dynamic simulations were conducted by using the 2-shaft high bypass ratio turbofan engine model within different combinations of the three key design factors. The results from geometrical and dynamic analysis matched mainly well with the results from simulations. Characteristic phenomenon in simulation can be explained theoretically. Five conclusions can be summarized from these results. (1) If thickness fan acoustic lining was thinner, the deviation between simplified analytical calculation and simulation were not outstanding to predict Blade-Casing the first impact time and angular position. (2) An appropriate thickness of acoustic lining could make a lower impact stress of fan casing at the first impact. (3) Different thickness of acoustic linings leaded to two impact modes for blade 2, which were tip impact and root impact. (4) Different impact conditions between blade 1 and blade 2 caused remarkable speed components distinction of blade 1, and leaded to a wide range of transient trajectory of blade 1 during FBO event. (5) Thicker acoustic lining in this research can usually find the porper threshold loads setting, which can give a satisfactory outbound vibration. Two details were raised for further research, which were impact behavior of composite material fan bl

关键词： fan blade out transient trajectory design character structural fuse high bypass ratio turbofan

Compound extreme events in Yarlung Zangbo River Basin from 1977 to 2018

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Water Science and Engineering 2023年第1期16卷 36-44页

作者： Zong-xue xu Rui Zhang College of Water Sciences Beijing Normal UniversityBeijing 100875China Beijing Key Laboratory of Urban Hydrological Cycle and Sponge City Technology Beijing 100875China

Extreme climate events threaten human health,economic development,and *** studies have been conducted on extreme precipitation and temperature changes in the Yarlung Zangbo River Basin(YZRB).However,little attention has been paid to compound climate *** this study,the variations of wet/warm compound extreme events in summer and dry/cold compound extreme events in winter over the past 42 years in the YZRB were investigated using eight extreme climate indices that were estimated using monthly temperature and precipitation *** results showed that the numbers of frost days and ice days tended to decrease on the spatiotemporal scale,while the maximum values of daily maximum temperature and daily minimum temperature exhibited increasing *** frequency of wet/warm compound extreme events was significantly higher from 1998 to 2018 than from 1977 to ***/cold compound extreme events became less frequent from 1998 to 2018 than from 1977 to *** rate of increase of wet/warm compound extreme events was about ten times the absolute rate of decrease of dry/cold compound extreme *** regard to the spatial pattern,the frequency of wet/warm compound extreme events increased significantly in almost all parts of the YZRB,while that of dry/cold compound extreme events decreased across the *** study helps to improve our understanding of the changes in compound precipitation and temperature extremes in the YZRB from a multivariable perspective.

关键词： Climate change Extreme events Precipitation Temperature Yarlung Zangbo River Basin