基于LabVIEWTM7 Express绘制二元金属相图的虚拟仪器

设计开发了基于LabVIEW^TM7 Express自动绘制二元金属相图的虚拟仪器系统。实验表明：利用LabVIEW开发绘制相图的虚拟仪器,编程直观高效,仪器面板友好、易操作、功能易扩展;避免了人工数据记录、处理、绘图的烦琐和人为误差,还可利用LabVIEW强大的数据处理功能对实验数据做深层次处理,大大提高实验结果的准确性和重现性。用该虚拟仪器自动绘制的Pb—Sn金属相图,其低共熔点与文献值比较相对误差为-0．219％,结果令人满意。     

Calculation of ternary fluoride glass compositions

The recent discovery of a new family of non-oxide glasses based on mixtures of ZrF₄ or HfF₄ with other metallic fluorides by M. Poulain and coworkers offers great potential in optical fiber, window and source/detector application. Due to the limited phase diagram data available for the binary, ternary and multicomponent fluoride systems currently employed to synthesize these glasses most of the progress in identifying new compositions has proceeded along empirical lines. In order to remedy this situation, the CALPHAD method for coupling phase diagram and thermochemical data has been applied to develop a data base covering metallic fluorides. The objective is to permit computation of multicomponent phase diagrams which can be used to identify the composition range where the liquid is most stable. The latter offers opportunities for glass formation as demonstrated by predictions of new metallic glasses. Currently the data base covers combinations of 0.2 ZrF₄(ZF), 0.25 LaF ₃(LF) 0.333 BaF₂(BF), 0.333 PbF₂(PF), 0.5 NaF(NF), 0.5RbF(RF), O.5CsF(CF) and 0.5 KF(KF) which have been developed along the lines described earlier for III–V, II–VI and SIALON systems. These results were used to generate computed liquidus contours in LF-ZF-BF and BF-ZF-NF to disclose the range of composition in which the liquid has the greatest stability. These compositions agree well with those in which Poulain and coworkers have discovered glass formation.     

Thermodynamic assessment of the V–Zn system supported by key experiments and first-principles calculations

The V–Zn system was investigated by a combination of CALPHAD modeling with key experiments and first-principles calculations. Based on a critical literature review, one diffusion couple and nine alloys were designed to reinvestigate the stabilities of the phases reported in the literature. The samples were annealed and cooled under different conditions, followed by examination with X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray spectrometry. Four phases ((V), (Zn), V Zn₃ and V ₄Zn₅) were confirmed to exist in the phase diagram, while V Zn₁₆ and V ₃Zn were not observed. By means of first-principles calculations, the enthalpies of formation for V Zn₃ and V ₄Zn₅ were computed to be −4.55 kJ mol-atoms⁻¹ and −4.58 kJ mol-atoms⁻¹, respectively. A set of self-consistent thermodynamic parameters for this system was obtained by considering the reliable experimental phase diagram data and the enthalpies of formation acquired from first-principles calculations. The calculated V–Zn phase diagram agrees well with the experimental data.     

Thermodynamic modeling of the Sn–V binary system

The Sn–V binary system was thermodynamically modeled using the CALPHAD approach combined with first-principles calculations. The predicted Gibbs free energy of the end-members in sublattice models of “ V ₃Sn” phase by the first-principles calculations was used to describe the lattice stabilities. A set of thermodynamic parameters for the Sn–V system was obtained using the PanOptimizer program in Pandat software. The calculated phase diagram and thermodynamic properties agree well with the reported experimental data.     

用浓度比较法自动绘制综合平衡电位-pH图

将所有溶液态物质作为一个整体,绘制Ｍ－Ｈ２Ｏ体系综合平衡电位－ｐＨ图,任何非溶液相物质Ｘｊ优势区的边界线可简单地通过比较与Ｘｊ呈平衡的所有溶液态物质的总浓度ΣＣｉ和任一给定总浓度「Ｍ」Ｔ的大小来确定。当体系中所有固相和气相优势区的边界线确定之后,剩余的区域就是溶液相物质的优势区。     

Calculation of the T-X phase diagram for a mixture of liquid crystals

In this study we calculate the T-X phase diagram for a mixture of liquid crystals. In this calculation we use a mean field theory. We fit our calculated phase line equations to the experimental data from the literature. There is a very good agreement between our calculated and the experimentally observed phase diagram.     

Solution of gradually varied flow problems using the direct step method with the IBM PC Lotus 1-2-3 system

A soft ware package based on the Lotus 1-2-3 is developed to solve the Gradually Varied Flow (G.V.F.) problem using the direct step method. The information needed (e.g. normal depth, critical depth and G.V.F. depths) is determined first. Flow profile classification is subsequently checked to identify the type of profile. Finally, the profile length is computed and tabulated. In addition, the Lotus printgraph capabilities are used to provide a graphical representation of the G.V.F. profile, the bed slope and the normal and critical depths.The PC adaptation of the direct step method is documented. A schematic diagram of the direct step method, the spread sheet layouts and Listings of the Lotus MACROS used to facilitate the calculations are presented.     

Altera MAX V CPLD的工程设计应用及系统开发

本文阐述了Altera MAX V最小系统从硬件原理图到PCB设计、从软件QuartusII编写VHDL到Modelsim-Al-tera的软件仿真,以及最终的程序下载到开发板上的整个工程设计调试过程,为后续的Altera MAX V工程设计应用提供技术参考和支持.     

Thermodynamic modeling of the V–Si system supported by key experiments

The V–Si system is reassessed based on a critical literature review involving recently reported data and the present experimental data. These new data include the thermodynamic stability of V ₆Si₅ and the enthalpies of formation for the compounds calculated by first-principles method. Two alloys were prepared in the region of (Si)+V Si₂ and annealed at 1273 K for 14 days. After X-ray diffraction (XRD) and chemical analysis of these alloys were performed, the eutectic reaction (L⇔(Si)+V Si₂) temperature was determined by differential thermal analysis (DTA). Self-consistent thermodynamic parameters for the V–Si system were obtained by optimization of the selected experimental values. The calculated phase diagram and thermodynamic properties agree well with the experimental ones. Noticeable improvements have been made, compared with the previous assessments.     

Thermodynamic assessment of the Au–Ni system

The phase diagram and thermodynamic properties of the Au–Ni system have been assessed from experimental thermodynamic and phase diagram data by means of the CALPHAD method. A consistent set of thermodynamic parameters for each phase was obtained. Good agreement is reached between the calculated and experimental results. The calculated congruent point is 1214.3 K and 42.6 at.% Ni and the critical point of the miscibility gap is 1089.5 K and 73.0 at.% Ni.     

Assessment and development of snowmelt retrieval algorithms over Antarctica from K-band spaceborne brightness temperature (1979-2008)

Results from several previously published algorithms for wet snow detection in Antarctica from K-band spaceborne brightness temperature are compared and evaluated vs. estimates of wet snow conditions from ground measurements. In addition, a new physically-driven algorithm, in which the detectable liquid water content is assumed constant, is proposed and assessed. All algorithms are also evaluated by analyzing their results during collapses of ice shelves. Two algorithms are selected for deriving updated trends of melting index (MI, the number of melting days times the area subject to melting) between 1979 and 2008 over the whole Antarctica and at sub-continental scales. In the first algorithm wet snow is identified when brightness temperature exceeds the mean of winter brightness temperature plus 30 K and the second is the new model-based approach described here. Both negative and positive MI trends are obtained, depending on the algorithm used. A high number of melting days (up to 100 days) are detected over the Wilkins ice shelf, the Peninsula and the George VI ice shelf. Over East Antarctica, the West and Amery ice shelves are subject to melting for a maximum of approximately 50 days. Positive trends of number of melting days are detected over most of the West Antarctica, with peak values up to 1.2 days/year over the Larsen C ice shelf, 1.8 days/year over the George VI ice shelf and 0.55 days/year over the Wilkins ice shelf area. The correlation between MI values and December-January (DJ) averaged air/surface temperature over selected locations show values ranging between ∼ 0.8 and ∼ 0.4. Results suggest that a 1 °C increase in the monthly averaged DJ air/surface temperature corresponds to an average MI increase of approximately 2·10⁶ × km² × day.     

Measurement and calculation of the phase diagram of the Licl-BaCl2-SrCl2 system

The liquidas surface of the ternary LiCl-BaCl₂ SrCl₂ system has been measured by a DTA technique. A complete critical literature assessment and coupled thermodynamic/phase diagram analysis of the 3 binarv sub-systems has been performed. The ternary phase diagram was calculated from the assessed binary thermodynamic properties. Agreement between the calculated and measured ternary liquidus surfaces is good. The estimated accuracy of the calculated diagrams is ±5° for the binaries and ±10° for the ternary.     

CALPHAD应用于有机体系热力学相平衡/相图的计算

相图是一种化学图形,必须通过数学模型的方式才能实现其广泛的应用.而此前固-液平衡相图的计算多采用理想模型或经验模型,前者完全忽视了真实溶液的非理想性,后者的计算结果则可能是对相图完全不合理的预测.因此,为了充分考虑体系的非理想性以获得更为准确真实的相图,采用热力学模型,借助专业的金属及无机物材料的相图计算软件Thermo-Calc,设计实现了获得非理想有机体系中组分作用参数及平衡相图的软件计算方法.利用该计算方法,选择合理的热力学模型,成功地模拟出了二甲苯异构体系二元、三元及二氯苯异构体二元系的固-液平衡相图,模拟结果与文献的实验数据吻合程度较高,且相比于理想状态下的二甲苯三元系相图,正规溶液状态下的相图更能体现真实体系中组分间的作用对体系相平衡温度的影响.该软件计算方法具有较高的自动化程度,在实验数据非常有限的情况下,能够非常精确的模拟出各种无机或有机体系的相图及其它热力学性质,为化学热力学研究提供了一种新的、适用范围广、功能强大的研究手段.     

Thermodynamic study of the Al-Ga-As-Ge system

Using a thermodynamic approach, the phase diagram of gallium-aluminium-arsenicgermanium system has been established for liquid phase epitaxy applications. The calculated phase diagram is compared with experimental information. It is found that at 1073 K and at a given aluminium concentration in the liquid phase, the solubility of arsenic and the distribution coefficient of aluminium have a very low variation when large amounts of germanium are added (up to x^L_Ge = 0.6).     

The Sn-In-Zn system-application of calphad technique to phase diagram measurement

The phase diagram of one promising lead-free solder system---the In-Sn-Zn system was well constructed by using accurate experimental methods in conjunction with CALPHAD technique. This work is a good example to show that the CALPHAD technique is very useful for phase diagram measurements, especially for those systems with a lot of experimental difficulties. The ternary interaction parameter of the Sn-In-Zn liquid phase was also calculated based on our experimental data and thermodynamic properties from the literatures.     

Calculation of phase diagrams using partial phase diagram data

The interaction parameters for various phases were calculated using binary phase diagram data. Since two equilibrium compositions of a binary tie line have some errors in their measurements, a particular attention was paid to the effect of a small variation of the equilibrium compositions on the fluctuation in the calculated free energy curves. From this investigation, it was recommended that the widest possible tie line or tie lines located in the central region of a phase diagram be used to calculate the interaction parameters. Based on these facts, the interaction parameters for various phases in the Ti-W, Pd-W, Zr-W and Hf-W systems were estimated, which were subsequently used to calculate the phase diagrams of the above systems.