Calculation of the Phase Equilibrium of CO_2–Hydrocarbon Binary Mixtures by PR-BM EOS and PR EOS

The phase equilibrium data of CO_2 –hydrocarbon binary mixtures are important for the design and operation of CO_2 flooding, coal liquefaction, and supercritical extraction processes. Numerous pieces of binary phase equilibrium data have been obtained. Thus, models for the accurate calculation of binary and multicomponent mixtures must be developed on the basis of existing data. In this work, 3578 vapor–liquid phase equilibrium data points for 10 CO_2 –hydrocarbon binary mixtures, including CO_2 –butane, CO_2 –pentane, CO_2 –isopentane, CO_2 –hexane, CO_2 –benzene, CO_2 –heptane, CO_2 –octane, CO_2 –nonane, CO_2 –decane, and CO_2 –undecane, were collected. The PR and PR-BM equations of state(EOS) in combination with relevant mixing rules were used to calculate the phase equilibrium data of the CO_2 –hydrocarbon binary mixtures. The binary interaction parameter k ij in the PR EOS was temperature independent, whereas parameters in the PR-BM EOS were functions of temperature. Thus, the phase equilibrium data and other thermodynamic properties of the binary and multicomponent mixtures at different temperatures and pressures can be calculated by using the parameters obtained in this work. The PR-BM EOS performed better than the PR EOS, and the average absolute deviations over the temperature range of 255.98–408.15 K calculated by the PR EOS and PR-BM EOS were less than 5.74% and 3.36%, respectively. The results calculated by the two EOS were compared with those calculated by other models, such as PPR78, PR + LCVM + UNIFAC, KIE + PR EOS + HV, and PSRK. The phase equilibrium data of CO_2 –butane–decane, CO_2 –hexane–decane, and CO_2 –octane–decane ternary mixtures were calculated by the two EOS. The average overall deviations for the CO_2 mole fractions calculated by the two EOS were less than 7.66%.     

Kinetics of esterification of 2-keto-L-gulonic acid with methanol catalyzed by cation exchange resin

The kinetics of esterification of 2-keto-L-gulonic acid with methanol in the liquid phase catalyzed by cation exchange resin, D001, was studied. The experiments were carried out in a stirred batch reactor at 318, 323, 328, 333, 338, 341 K under atmospheric pressure, It is found that the speed of rotating rate has no effect on the esterification rate in the range of 300-500 r/min and the effect of internal mass transfer resistance is not obvious. The effects of temperature and catalyst loading on the reaction rate were researched under the condition of eliminating the effect of diffusion. The rate was found to increase with the increase of the temperature and catalyst loading. The experimental data were correlated with a kinetic model based on the pseudo- homogeneous catalysis, The kinetic equation for describing the reaction catalyzed by cation exchange resin was developed, The experimental data are in good agreement with the model     

浅谈在大学英语教学中培养学生的创新能力

大学英语的教学目标应该是在提高大学生英语知识水平和英语技能的过程中全面提高学生的内在素质,培养他们的创新能力。本文将重点探讨如何通过英语课堂上的多种活动实现英语学习目标,培养学生的创新能力。     

谈历法在历史教学中的作用

中国古籍浩若烟海。我们阅读、整理和研究这些古籍时,总要遇到有关时间的概念,即纪年、纪日等历法问题。古今历法不同,且古籍中纪年、纪日等常用天干、地支表示,或用别名代替,这就给后学者欲弄清某一历史现象的确切时间造成很大困难。必须将之换算成公历年、月、日,方可读懂古籍,加深对历史现象的认识,有利于学习与研究。所以,历法在历史及相关学科的教学中具有重要作用,掌握有关历法知识及干支公元换算等运用是学习与研究历史的一把钥匙。同时要破除迷信,树立科学的历史观。     

柯达、富士对图书馆数字时代变革的启示

本文以柯达、富士两个影像行业巨头在数字化时代所面临的不同境遇为切入点,结合当今数字化阅读和数字化出版的发展状况,分析了图书馆在数字时代,应当避免柯达那样的保守态度,而应像富士那样采取积极进取的态度应对数字化时代的发展变革,加快发展数字图书馆建设。     

浅谈承德丹霞奇观的成因

承德丹霞奇观是在地球形成以后随之形成承德古陆,再由后期沉积下来的侏罗纪沉积地层承德砂砾岩被地质运动向上推移经过崩塌、风化、地震等形成了形状各异的承德丹霞奇观.     

Covariate Measurement Error Correction for Student Growth Percentiles Using the SIMEX Method

In this study, we examined the impact of covariate measurement error (ME) on the estimation of quantile regression and student growth percentiles (SGPs), and find that SGPs tend to be overestimated among students with higher prior achievement and underestimated among those with lower prior achievement, a problem we describe as ME endogeneity in this article. We proceeded to assess the effect of covariate ME correction on SGP estimation at two levels—the individual (student) and the aggregate (classroom). Our ME correction approach was limited to the simulation‐extrapolation method known as SIMEX. For both the individual and aggregate SGP, we find SIMEX effective in bias reduction. Further, because SIMEX is especially effective in reducing SGP bias for students with very high or very low prior achievement, it significantly weakens the ME endogeneity. SIMEX is also effective in reducing the MSE of aggregate SGP, provided that the students are sorted to some extent on their latent prior achievement. Our empirical study confirms the pattern of the simulation results: SIMEX mainly affects the mean SGP of classes in the highest and lowest quintiles of the prior score distribution, and significantly lowers the correlation between class SGP and prior achievement.     

用教育起点公平的政策理念解决异地高考问题

城市化过程中社会流动人口不断增加,如何解决随迁子女升学的异地高考问题日益迫切。2013年是异地高考破冰标志性的一年,各地方政府在中央政策的宏观指导下纷纷出台细则并实施,然而备受瞩目的异地高考政策却引发社会舆论更为广泛的争议,不同利益群体的家长,都用教育公平的话语来评价异地高考相关政策的合理性。切实解决异地高考问题,需要以教育起点公平的理念为政策导向。     

A molecular biological study on identification of common septicemia bacteria using 16s–23s rRNA gene spacer regions

In the search for a rapid and reliable method for identification of bacteria in blood and cerebrospinal fluid , we developed a unified set of primers and used them under polymerase chain reaction(PCR) to amplify the spacer regions between the 16s and 23s genes in the prokaryotic rRNA genetic loci . Spacer regions within these loci showed a significant level of length and sequence polymorphism across most of the species lines. A generic pair of priming sequences was selected from highly conserved sequences in the 16s and 23s genes occurring adjacent to these polymorphic regions. This single set of primers and reaction conditions were used for the amplification of the 16s-23s spacer regions for 61 strains of standard bacteria and corresponding clinical isolates belonging to 20 genera and 27 species, including Listeria, Staphylococcus and Salmonella species, et al. When the spacer amplification products were resolved by electrophoresis, the resulting patterns could be used to distinguish most of the bacteria species within the test group, and the amplification products of the clinical isolates clustered at the standard species level. Some species presenting similar pattern were further analyzed by HinfI or AluI digestion or DNA clone and sequences analysis in order to establish the specific 16s-23s rRNA gene spacer regions map. Analysis of 42 blood specimens from septicemic neonates and 6 CSF specimens from suspected purulent meningitis patients by bacterial culture and PCR-RFLP(Restriction Fregament Length Polymorphism) showed that 15 specimens of blood culture were positive(35.7%) in the 42 septicemic neonates; 27 specimens were positive(64.2%) by PCR, and that the positive rate by PCR was significantly higher than that by blood culture(P<0.01). Among the 6 CSF specimens, one specimen found positive by blood culture was also positive by PCR, two found negative by blood culture showed positive by PCR; all three were S.epidermidis according to the DNA map. One C.neoformans found positive by blood culture showed negative by PCR. The remaining two specimens were both negative by PCR and blood culture. These results indicated that the method of detecting bacterial 16s-23s rRNA spacer regions using PCR and RFLP techniques was rapid, sensitive and specific in the detection of bacterial infections; and so, has very important application in the clinical diagnosis of sepsis in neonates.     

《中国图书馆分类法》（第五版）U大类的修订分析

分析《中国图书馆分类法》第五版的类目变化情况,对其中U类（交通运输）的修订特点进行分析,将其类目设置与第四版进行对比,并指出图书馆标引人员在查找交通运输类相关资料时应注意的问题。