气液固三相相平衡热力学模型与计算方法

原油中含有大量的高分子有机固相物质，因此，要准确地描述油气体系相平衡，必须对气液固三相相平衡进行研究，在对高分子有机烃类沥青沉降机理有了一定的认识的基础上，提出了大的交互作用系数，可以描述沥青与原油中轻质不相容性的程度。根据对油气烃类混合物体系的一般性认识与提出的沥青组分特征化方法，导出了与之相应的有其自身特殊性的气液沥青三相相平衡物料平衡方程组，用考虑沥青沉降三相闪蒸数值算法，对沥青沉降进行有效的理化模拟计算，此外，结合实例分析，给出了沥青质参考逸度的计算，饱和压力和沉降量的拟合方法。     

The Effect of the Estimation on Goodness‐of‐Fit Tests in Time Series Models

Abstract. We analyze, by simulation, the finite‐sample properties of goodness‐of‐fit tests based on residual autocorrelation coefficients (simple and partial) obtained using different estimators frequently used in the analysis of autoregressive moving‐average time‐series models. The estimators considered are unconditional least squares, maximum likelihood and conditional least squares. The results suggest that although the tests based on these estimators are asymptotically equivalent for particular models and parameter values, their sampling properties for samples of the size commonly found in economic applications can differ substantially, because of differences in both finite‐sample estimation efficiencies and residual regeneration methods.     

现代数值计算与模拟技术在大学物理中的应用

讨论了现代数值计算与模拟技术在大学物理中的应用，并给出了两个具体应用的实例．     

Al/Fe2O3反应合成材料热力学

运用CALPHAD技术，基于多组元多相复杂平衡体系的吉布斯自由能最小化原理，用大型集成数据库F^*A^*C^*T系统，考察了铝和氧化铁经典反应体系的热力学规律。针对材料的反应合成技术，计算了化学计量铝和氧化铁体系以及各种产物中物种的相变情况；分析了原料初始温度、配料比和SiO2含量对绝热温度和平衡组成的影响。     

风管摩擦阻力的直接计算方法

提出用高精度的反映密度、黏度和温度关系的经验公式和Colebrook公式计算风管摩擦阻力系数的方法。分析和算例表明，用该方法计算，计算结果比采用常用工程设计方法更为准确，为应用计算机进行风道设计提供了直接、简便的方法。     

储层压力与天然气分布关系——以鄂北塔巴庙地区上古生界储层为例

通过分析塔巴庙地区储层压力的分布特征，建立了研究区泥岩压实曲线，并对影响和控制该区储层压力的主要因素和机理进行了探讨，对“欠压实”剩余压力、生气增压、抬升引起的降压进行了定量计算。分析结果表明，晚三叠-早白垩世末“欠压实”作用和晚侏罗-早白垩世末烃源岩大量生烃作用使塔巴庙地区上古生界形成异常高压；晚白垩系构造抬升降压，使得现今储层为正常-低异常压力。同时证实了“欠压实”对天然气有压力封盖作用，天然气都分布在最大“欠压实”幅度以下的储层当中。烃源岩生气高峰为晚侏罗-早白垩世末，但天然气大规模运移是在晚白垩世，方向以沿过剩压力梯度降低较快的方向（太原-山西组至下石盒子组）垂向运移，通道主要为裂缝，运移的动力主要为异常高压。由于储层致密，聚集成藏能量有限，造成天然气充注不足、气水分异不好、含气饱和度低。     

Research on Marine Boiler＇s Pressurized Combustion and Heat Transfer

The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat transfer theorem. A correction for the heat calculation method for pressurized furnace is made on the basis of the normal pressure case. The correction takes the effect of pressurizing into account. The results show that the correction is reasonable and the method is applicable to combustion and heat transfer of the marine supercharged boiler.     

The Minimum PAPR Code for OFDM Systems

In this letter, a block code that minimizes the peak‐to‐average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals is proposed. It is shown that peak envelope power is invariant to cyclic shift and codeword inversion. The systematic encoding rule for the proposed code is composed of searching for a seed codeword, shifting the register elements, and determining codeword inversion. This eliminates the look‐up table for one‐to‐one correspondence between the source and the coded data. Computer simulation confirms that OFDM systems with the proposed code always have the minimum PAPR.     

Calculation of the Thermodynamic Properties of Diatomic Substances Based on the Ornstein-Zernike Equation

The new method of calculation of intermolecular distribution functions is used to calculate various thermodynamic properties of diatomic substances (oxygen, nitrogen, ethane). Good agreement is demonstrated between the calculation and experimental data.     

Emission of trace toxic metals during pulverized fuel combustion of Czech coals

A study of the trace elements emission (As, Se, Cd, Co, Cr, Cu, Zn, Hg, Tl, Pb, Ni, Sn, Sb, V, Mn and Fe) from pulverized coal combustion has been made at six heating and power stations situated in the Czech Republic. The amount of chlorine in coal has considerable influence on volatilization of some elements such as Zn, Cu, Pb, Hg and Tl, which is explained by the formation of thermodynamically stable compounds of these elements with chlorine. Generally, the affinities for Cl follows the order Tl > Cu > Zn > Pb > Co > Mn > Sn > Hg. The experimental data indicates enrichment of some of the trace toxic elements in the emissions (Cu, Zn, As, Se, Cd, Sn, Sb, Hg and Pb) and good agreement was obtained by thermodynamic equilibrium calculations with a few exceptions. In the case of Fe, Mn, Co, Cr and Sn calculated values are overestimated in the bottom ash and there are zero predicted amounts of these elements in the fly ash. In comparison, the results from experiments show up to 80% of these elements retained in fly ash. This implies that there exist additional steps leading to the enrichment by Fe, Mn, Co, Cr and Sn of small particles. Such mechanisms could include the ejection during devolatilization of small inorganic particles from the coal of bottom ash particles, or disintegration of the char containing these metals to small particles of fly ash. On the other hand, there are slightly overestimated or similar values of relative enrichment factors for As, V, Cu, Cd, Sb, Tl and Pb in the fly ashes and zero predicted values for bottom ashes. Our experimental results show about 5% or less of these elements are retained in bottom ashes, so they probably remain in the bottom ash inside unburned parts of coal. Copyright © 2003 John Wiley & Sons, Ltd.