碱水驱组分输运过程有效性研究

建立了碱水驱组分孔隙输运数学模型,将模型中所需的物化参数描述为驱油剂浓度相关的函数,用“有效驱替带”量化和分析了吸附、驱油剂段塞尺寸、驱替速度、扩散弥散等因素对碱组分输运过程有效性的影响机理。在此基础上,进一步分析了大庆油田ASP复合驱用碱剂NaOH在孔隙输运过程中的有效性和持久性,并对模拟软件进行了实验验证,它们具有很好的一致性。经过实验验证的模拟软件,不仅可代替部分实验室流动实验和辅助机理分析,而且可以为碱水驱和ASP复合驱工程工艺方案设计和动态监测提供指导。     

Salmonella Enteritidis Surveillance by Egg Immunology: Impact of the Sampling Scheme on the Release of Contaminated Table Eggs

Design of surveillance programs to detect infections could benefit from more insight into sampling schemes. We address the effect of sampling schemes for Salmonella Enteritidis surveillance in laying hens. Based on experimental estimates for the transmission rate in flocks, and the characteristics of an egg immunological test, we have simulated outbreaks with various sampling schemes, and with the current boot swab program with a 15‐week sampling interval. Declaring a flock infected based on a single positive egg was not possible because test specificity was too low. Thus, a threshold number of positive eggs was defined to declare a flock infected, and, for small sample sizes, eggs from previous samplings had to be included in a cumulative sample to guarantee a minimum flock level specificity. Effectiveness of surveillance was measured by the proportion of outbreaks detected, and by the number of contaminated table eggs brought on the market. The boot swab program detected 90% of the outbreaks, with 75% fewer contaminated eggs compared to no surveillance, whereas the baseline egg program (30 eggs each 15 weeks) detected 86%, with 73% fewer contaminated eggs. We conclude that a larger sample size results in more detected outbreaks, whereas a smaller sampling interval decreases the number of contaminated eggs. Decreasing sample size and interval simultaneously reduces the number of contaminated eggs, but not indefinitely: the advantage of more frequent sampling is counterbalanced by the cumulative sample including less recently laid eggs. Apparently, optimizing surveillance has its limits when test specificity is taken into account.     

Individual Prior Information in a Physiological Model of 2H8-Toluene Kinetics: An Empirical Bayes Estimation Strategy

Physiologically-based toxicokinetic (PBTK) models are widely used to quantify whole-body kinetics of various substances. However, since they attempt to reproduce anatomical structures and physiological events, they have a high number of parameters. Their identification from kinetic data alone is often impossible, and other information about the parameters is needed to render the model identifiable. The most commonly used approach consists of independently measuring, or taking from literature sources, some of the parameters, fixing them in the kinetic model, and then performing model identification on a reduced number of less certain parameters. This results in a substantial reduction of the degrees of freedom of the model. In this study, we show that this method results in final estimates of the free parameters whose precision is overestimated. We then compared this approach with an empirical Bayes approach, which takes into account not only the mean value, but also the error associated with the independently determined parameters. Blood and breath ²H₈-toluene washout curves, obtained in 17 subjects, were analyzed with a previously presented PBTK model suitable for person-specific dosimetry. Model parameters with the greatest effect on predicted levels were alveolar ventilation rate Q_PC, fat tissue fraction V_FC, blood-air partition coefficient K_b, fraction of cardiac output to fat Q_a/co and rate of extrahepatic metabolism V_max-p. Differences in the measured and Bayesian-fitted values of Q_PC, V_FC and K_b were significant (p < 0.05), and the precision of the fitted values V_max-p and Q_a/co went from 11 ± 5% to 75 ± 170% (NS) and from 8 ± 2% to 9 ± 2% (p < 0.05) respectively. The empirical Bayes approach did not result in less reliable parameter estimates: rather, it pointed out that the precision of parameter estimates can be overly optimistic when other parameters in the model, either directly measured or taken from literature sources, are treated as known without error. In conclusion, an empirical Bayes approach to parameter estimation resulted in a better model fit, different final parameter estimates, and more realistic parameter precisions.     

投入产出分析的几种系数矩阵在管理和经济分析中的作用

综合评价投入产出分析的几种系数矩阵在经济指标分析、经济效益分析和经济预测中的作用。提出投资系数矩阵的近似构造法,改进了利润作为目标函数的优化模型和推广了数学增量模型,并通过矩阵变换法从一个投入产出分析系数矩阵生成另一个相似的投入产出分析系数矩阵。     

迁移在数学教学中的应用

本文分析了影响学习迁移的主要因素，并从加强新旧知识联系、揭示知识之间异同、提高知识概括水平三个方面论述了迁移在数学教学中的应用，以促进数学知识的迁移．     

学生"数学分析"课程成绩与电类基础课成绩相关性实证分析

文章统计了电子工程系2002、2003级数学分析课程各分数段的学生在四门电类主干课中的成绩分布情况,分析了学生"数学分析"课程成绩与电类基础课成绩的相关性.分析表明,学生对数学分析以及数学类课程的学习理解程度直接影响着专业基础课的学习.     

如何在教学中提高大学生的数学素质

论述了提高大学生数学素质的重要性，指出了当前教学中不利于提高大学生数学素质的一些问题，并提供了解决问题的对策。     

拉格朗日法对溜管输送混凝土流变数学模型探讨

考虑溜管中混凝土重力与管壁的摩擦力，运用拉格朗日法建立了在重力作用下混凝土在软管溜筒中流变的数学模型，运用牛顿迭代求解，并将计算结果与输送情况作了比较。     

《微积分与数学模型》教材编写基本思想

《微积分与数学模型》教材是用以替代原《高等数学》教材的。该教材产生于以“启发应用意识,提高应用能力”为宗旨的、针对非数学专业的多项教学改革项目。文章介绍其编写基本思路为：在强调直观的基础上,改善对数学原理的叙述,并在强调思想性与综合性的基础上模块式地融入数学建模内容。文章还对改革内容进行了具体介绍。     

国内IT产品营销渠道选择研究

营销渠道建设对企业至关重要。针对IT产业大块区域市场的定性描述,建立相应的教学模型并得出渠道选择结论。