二元HFCs和HCs均相共沸物的预测方法研究

本文提供了一种直接预测HFCs(氢氟烃)和HCs(烃)二元均相共沸物的方法.本方法基于UNIFAC和Wilson活度系数模型,无需实验数据.先由UNIFAC模型获得Wilson二元相互作用系数,然后对热力学关系式进行简单的化简,应用牛顿迭代法对二元混合物压力求极值,从而获得共沸组分.实例计算显示,预测结果与实验数据具有良好的一致性.     

含醇二元体系表面张力预测模型

表面张力是重要的物性参数之一,与人们的生产生活密切相关.醇类及其混合物具有重要的工业应用价值.含醇混合物作为特殊的缔合体系,由于氢键的存在,性质复杂.本文应用密度梯度理论结合比容平移后的Peng-Robinson状态方程,回归了醇、水纯净物的作用因子关联式系数,建立了混合物的表面张力预测模型,计算了含醇二元缔合体系的表面张力,该模型不含有任何需要混合物表面张力实验数据回归确定的经验可调参数,对绝大多数含醇混合物具有很好的通用性和计算精度.     

CO2水合物在电解质溶液中的相平衡预测

关于二氧化碳水合物基础物性的研究,对二氧化碳置换开采天然气水合物和工业废气二氧化碳的深海埋藏具有重要意义。本文在Van der Waals-Platteeuw理论和Pizter的电解质模型的基础上,考虑了电解质和温度对二氧化碳在水中溶解度的影响,从理论上对水合物相平衡模型进行了修正,提高了预测的精度。本文预测了二氧化碳水合物在NaCl、KCl、CaCl₂、MgCl₂的一元及二元溶液体系中的相平衡条件,预测的最大压力误差7.92%,平均压力误差在1%～3%之间。结果表明,本文的理论预测结果和实验数据吻合较好。     

一般流体及含超临界组元混合物表面张力密度梯度理论模型

表面张力是非常重要的物性参数之一,特别对于沸腾和凝结换热的计算是必不可少的.但目前的研究成果主要集中于纯物质,对有重要工程应用前景的混合工质研究还很少.本文应用密度梯度理论,结合比容平移后的Peng-Robinson方程建立了混合物的表面张力模型,该模型不含有任何需要表面张力实验数据回归确定的经验可调系数.计算结果表明,本文建立的模型具有很好的通用性和计算精度,能在广泛的温度范围内较好地再现一般流体混合物和含超临界组元混合物的表面张力数据.     

天然气组元及其混合物的黏度计算

本文利用自由体积理论(FVT)并结合相关混合规则建立了一种可以预测天然气组元及其混合物黏度的计算模型。在对实验数据进行收集整理的基础上,通过对实验数据的回归计算确定了9种天然气基础组元的FVT模型参数,模型计算结果与实验数据之间的平均绝对相对偏差(AARD)小于2.8%。针对天然气组元的二元及多元混合物,本文利用FVT结合适当的混合规则对其黏度进行了预测,模型计算值与实验数据之间的AARD小于7.41%。     

氢氟烃二元混合工质的组分分析

气相色谱法是最常用的混合工质组元浓度分析方法。针对氢氟烃二元混合物的特点,本文搭建了气相色谱法混合工质组分分析实验台,测定了9种氢氟烃二元混合物组元质量分数与峰面积百分比的对应关系。讨论了气相色谱法混合工质组分分析的理论方法,比较了2种标准曲线函数模型对实验数据的再现精度,本文提出的校正因子为变量的模型对实验数据的再现性较好,平均绝对偏差小于±0.25%,满足热物性研究对混合物组元成分分析的实验要求。     

微通道内不混溶气液两相二氧化碳界面动力学行为的格子Boltzmann研究

将高精度的二氧化碳状态方程与气液两相流格子Boltzmann方法中的伪势模型耦合,研究微通道内二氧化碳气液两相流动的界面动力学行为,包括二氧化碳气泡和液滴的分裂、合并、变形,以及气液两相二氧化碳在演化过程中的质量交换.研究发现：当分裂和合并行为达到平衡,并且两相之间不发生质量交换时流动达到稳态.稳态时的流型主要依赖于表面张力,惯性力,管道的润湿性,以及初始体积分数.当表面张力较大时,微通道内形成的二氧化碳气泡或液滴会收缩成圆形,此时二氧化碳气泡或液滴会堵塞微通道,形成段塞流;随着表面张力的减小,形成的气泡或液滴不容易收缩,在微通道内更容易发生变形,出现泡状流或环状流.当壁面润湿性为强疏水性时,二氧化碳在微通道中的流动为环状流,其它润湿性下,流型为段塞流.体积分数较小时,二氧化碳两相流动的流型为段塞流,体积分数较大时,流型为环状流.     

乙二醇/水与丙三醇/水体系的焓浓图与(火用)浓图

本文基于乙二醇/水与丙三醇/水两组二元体系在不同温度下的实验数据,对超额焓数据应用局部作用模型拟合,并分析拟合效果与拟合参数变化情况,发现Wilson模型拟合效果较好.通过Wilson方程的活度系数表达形式,推算了两组体系的气液平衡,并进而计算了两组体系的焓浓图与(火用)浓图.     

化学动力学模型预测H_2/CO燃烧的不确定性分析

本文采用数据协同方法,研究了由于模型参数和实验测量不确定度传递导致的H_2/CO详细化学动力学模型预测的不确定性。研究发现在数据集中增加一组H_2/O_2/CO_2混合物在1.5 MPa时层流火焰传播速度实验测量值,数据集出现不一致,并分析了两种有可能导致数据集不一致的原因。研究结果还表明,选择性的增加实验目标,能有效地约束模型参数不确定性空间,提高模型预测性能,并为实验研究提供引导.     

生物柴油及与正丁醇混合物的热物性实验研究

本文测量了常压下生物柴油及其与正丁醇混合物的密度、黏度和表面张力数据,温度范围分别为278~363K、313~363 K、293~353 K。对于密度测量,生物柴油的质量分数分别为80%、60%、50%、40%、20%;对于黏度测量,生物柴油的质量分数分别为80%、50%。同时采用不同模型对生物柴油及其与正丁醇二元混合物的密度、黏度、表面张力实验数据进行拟合,结果显示良好,拟合模型与实验数据的最大标准偏差分别为0.01%、1.56%、0.14%。     

混合工质HFC134a/HCs替代R502的性能分析

针对目前R502主流替代工质R507和R404A存在的温室效应指数高、与矿物油互溶性差等缺点,提出了环保性能更好的三组近共沸混合工质R134a/R290、R134a/R1270和R134a/R290/R1270作为R502新型替代工质;并对其热物性、循环性能、安全性能和溶油性进行了计算分析。结果表明：除了压缩机排气温度偏高,这三组R134a/HCs混合工质的其它主要循环性能参数如压缩机压力比、容积制冷量和系统性能系数COP都优于R507和R404A,并且从理论上讲不存在可燃可爆的危险,同时可以与矿物油互溶,在替代R502方面更具有优势,其中R134a/R290/R1270在高热负荷下的综合性能最优良。     

碳氢化合物/HFC227ea二元系的PVTx实验研究

对定容式 ＰＶＴｘ实验装置的恒温、测温和测压系统进行了改进，温度和压力基本测量精度提高到±５ｍＫ和±０．４ ｋＰａ．对 ＨＣ１２７０／ＨＦＣ２２７ｅａ、ＨＣ２９０／ＨＦＣ２２７ｅａ和 ＨＣ１７０／ＨＦＣ２２７ｅａ二元物系进行了 ＰＶＴｘ实验研究．     

Chiral perturbation theory for fDS/FD and BBS/BB

The decay constants for D and D_s mesons, denoted f_D and f_DS respectively, are equal in the SU(3)_V limit, as are the hadronic amplitudes for and mixing. The leading SU(3)_V violating contribution to (F_DS/F_D) and to the ration of hadronic matrix elements relevant for and mixing amplitudes are calculated in chiral perturbatiion theory. We discuss the formalism needed to include both meson and anti-meson fields in the heavy quark effective theory.     

Near-infrared bands of S2: 3Πgi-3Σu+ system

Vibrational and rotational analyses of the near-infrared bands of S₂ lying in the region 7440–8085 Å are reported. They form a new band system involving a ${}^3\text{Π}{}_{\mathrm{gi}}\text{-}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ transition and arise from the same initial ³Π_gi state of the ³Π_gi-³Δ_ui band system reported earlier. The analyses of the bands of this system due to the isotopic molecules ³²S³⁴S and ³⁴S₂ are also reported.     

Magnetism in nanometer-thick TiOx/Co/TiOx/TiN/Si multilayered structures

Most studies on Co-doped TiO₂ system were focused on thin films grown by MBE-based methods. In this work we report the ferromagnetism of nanometer-thick-layered TiO₂/Co/TiO₂/TiN film grown on Si substrate by conventional magnetron sputtering. For the growth of TiO₂ on silicon, a non-oxide thermally stable material, TiN, was introduced to prevent Ti penetration into the Si substrate. Structural, magnetic, and transport measurements respectively by Raman, SQUID and Hall effect show that our samples are n-type semiconductors and exchange bias effect due to exchange coupling between Co and interfacial CoO. For the rapid vacuum annealed specimen, we found an enhanced loss and a Perminvar-type constricted hysteresis loop, which attributed to pinning of domain walls due to an induced anisotropy by the pair ordering in the metallic alloy of Co-Ti-Si.     

Spinor techniques for calculating pp → W±/Z0 + jets

We present techniques which enable one to calculate quickly the amplitudes for many scattering processes in the high-energy limit. As an illustration of the method, these are applied to the diagrams for $\text{p}\text{p}\text{→}\text{V}\text{+ 0, 1}\text{or}\text{2}\text{jets}$, where V = W^± or Z⁰. The form of the results lends itself to immediate numerical evaluation.     

The decay processes Λ8Li → π− + 8Be1 (∼ 17 MeV)

The branching ratio is calculated for _Λ⁸Li decay to the (2⁺) ⁸Be¹ states near 17 MeV, using intermediate coupling wave functions for _Λ⁸Li and for the relevant ⁸Be¹ states. It is pointed out that this ratio is sensitive primarily to a mixing angle ? in the _Λ⁸Li wave function. Within one standard deviation, the data allow two ranges (+0.05 to +0.25 rad and +1.10 to +1.25 rad) for the value of ?. The further requirement that there also be acceptable agreement between the angular distribution expected for the subsequent ${}^8\text{Be}{}^1\text{(? 17}\text{MeV → 2}{}^4\text{He}$ decay and the data, shifts these allowed ranges for ?, to (+0.13 to 0.40) rad and (+0.9 to +1.2) rad. It is predicted that the dominant transition should be to ⁸Be¹ (16.6 MeV), as is observed to be the case, rather than to ⁸Be¹ (16.9 MeV). The interpretation of these values for ? is discussed in some detail and their implications for intermediate coupling shell-model calculations of Λ-hypernuclear wave functions are considered.     

The 5T2g → 5Eg absorption in MgO: Fe2+

At helium temperatures two sharp lines at 9350 and 9510 cm^?1 have been observed for the first tune on the low-energy side of the broad double-peaked absorption corresponding to the ${}^5\text{T}{}_{\mathrm{2g}}\text{→}{}^5\text{E}{}_{\mathrm{g}}$ transition in Fe²⁺ at the octahedral site in MgO. The lower energy line has a half width of 4 cm^?1; Zeeman measurements show that it is of magnetic dipole origin. The Zeeman spectra are consistent with those expected for a pure electronic transition from the (⁵T_2g)T_2g ground state to the ⁵E_g excited state. The second line, with a halfwidth of ~ 35 cm^?1, a vibrational sideband.     

Electrical property of HfOxNy-HfO2-HfOxNy sandwich-stack films

The effects of HfO_xN_y on the electrical property of HfO_xN_y-HfO₂-HfO_xN_y sandwich-stack (signed as SS) films were investigated. Excellent electrical performances were achieved in SS films, with a high dielectric constant of 16 and a low leakage current of ∼2 × 10⁻⁸ A/cm² at 1 MV/cm. Schottky (SK) emission and Frenkel-Poole (PF) emission are found to be the dominant mechanisms for the current conduction behavior. After a long time stress, the flat-band voltage shift in the SS film is much smaller than that in a pure HfO_xN_y film indicating fewer charge traps existed in the SS film. Based on the experiments, the new SS structure is more favorable for the improvement of electrical performances than a pure HfO_xN_y or HfO₂ structure.