Nonparametric estimation of a survival function under progressive Type-I multistage censoring

Failure time data subject to three progressive Type-I multistage censoring schemes are studied. Product limit estimators are proposed for the estimation of the survival function. It is shown that the resulting estimators are asymptotically equivalent to the corresponding estimators where the data are subject to a random iid right censoring scheme. Many well-known results on confidence bands and tests for randomly right censored data hold for these progressive censoring schemes.     

杏仁露稳定性的提高

提出了用离心沉淀率判断杏仁露稳定性的方法，研究了稳定剂、乳化剂、络合物的种类及配比等对提高杏仁露稳定性的影响，其结果表明：稳定剂以ＰＧＡ效果最佳，ＣＭＣ、海藻酸钠次之；乳化剂用蔗糖酯、单甘酯复配ＨＬＢ＝１０为最好；络合剂中，三聚磷钠的稳定效果比柠檬酸钠好．     

锅炉给水泵的振动监测

给出了火电站单元机组锅炉给水泵的振动分析频段及主要故障，推荐了锅炉给水泵的预警和报警振动电平及振动烈度标准，阐述了锅炉给水泵振动数据的分析处理方法．     

A Systematic Approach to Determining the Identifiability of Multistage Carcinogenesis Models

Multistage clonal expansion (MSCE) models of carcinogenesis are continuous‐time Markov process models often used to relate cancer incidence to biological mechanism. Identifiability analysis determines what model parameter combinations can, theoretically, be estimated from given data. We use a systematic approach, based on differential algebra methods traditionally used for deterministic ordinary differential equation (ODE) models, to determine identifiable combinations for a generalized subclass of MSCE models with any number of preinitation stages and one clonal expansion. Additionally, we determine the identifiable combinations of the generalized MSCE model with up to four clonal expansion stages, and conjecture the results for any number of clonal expansion stages. The results improve upon previous work in a number of ways and provide a framework to find the identifiable combinations for further variations on the MSCE models. Finally, our approach, which takes advantage of the Kolmogorov backward equations for the probability generating functions of the Markov process, demonstrates that identifiability methods used in engineering and mathematics for systems of ODEs can be applied to continuous‐time Markov processes.     

直线电机抽油泵流场数值研究

将直线电机置于井下，直接驱动柱塞泵举升原油，有利于提高系统效率和节能。根据直线电机抽油泵结构，结合柱塞和阀球运动模型，运用动网格技术和自编程UDF模块对Fluent进行二次开发，实现了柱塞和阀球运动与流场的耦合求解。可以确定泵筒内任意计算时刻流场状态，揭示了柱塞往复运动过程中泵筒内部流场演化、阀球运动和流场特性。计算结果与实验结果吻合较好，为研究新型抽油泵提供了参考和依据。     

对《化工原理》中离心泵安装高度计算中有关问题的探讨

本文对教材 《化工原理》 在离心泵安装高度计算中存在的问题进行了归纳和讨论，并提出了相应的观点。     

Hormesis Without Cell Killing

Stochastic two-stage clonal expansion (TSCE) models of carcinogenesis offer the following clear theoretical explanation for U-shaped cancer dose-response relations. Low doses that kill initiated (premalignant) cells thereby create a protective effect. At higher doses, this effect is overwhelmed by an increase in the net number of initiated cells. The sum of these two effects, from cell killing and cell proliferation, gives a U-shaped or J-shaped dose-response relation. This article shows that exposures that do not kill, repair, or decrease cell populations, but that only hasten transitions that lead to cancer, can also generate U-shaped and J-shaped dose-response relations in a competing-risk (modified TSCE) framework where exposures disproportionately hasten transitions into carcinogenic pathways with relatively long times to tumor. Quantitative modeling of the competing effects of more transitions toward carcinogenesis (risk increasing) and a higher proportion of transitions into the slower pathway (risk reducing) shows that a J-shaped dose-response relation can occur even if exposure increases the number of initiated cells at every positive dose level. This suggests a possible new explanation for hormetic dose-response relations in response to carcinogenic exposures that do not have protective (cell-killing) effects. In addition, the examples presented emphasize the role of time in hormesis: exposures that monotonically increase risks at younger ages may nonetheless produce a U-shaped or J-shaped dose-response relation for lifetime risk of cancer.     

参数曲线在水泵叶轮设计中的应用

针对水泵设计所需的曲线及其特点，采用B样条和参数样条曲线对设计型线进行建模，根据设计准则和实践经验进行调整、修改和优化。基于曲线的参数化建模，从理论上推导出轴面流线和流线展开线的数学模型。改变了传统手工设计方法计算机化的常规做法，为在真正意义上实现水泵计算机辅助设计提供了理论基础和实现方法。     

Some aspects of maximum likelihood estimation of multistage cancer dose-response odels with application

Quantitative cancer dose-response models play an important role in cancer risk assessment. They also play a role in regulatory processes associated with potential occupational or environmental exposures. The multistage model is currently the most widely used cancer dose-response model. This paper describes the construction of the likelihood function in the special case of the multistage cancer dose-response models. The concavity of the likelihood function is also established. A criterion is developed to determine the degree of the polynomial portion of the multistage model. Finally, the restricted and unrestricted maximum likelihood estimators are considered and applied to some experimental data sets.     

土壤源热泵系统的应用与经济性分析

介绍了土壤源热泵的工作原理,根据工程周围的环境,地质条件,对抚顺市某垂直埋管式地源热泵系统工程的实例进行了分析。并将垂直埋管式地源热泵空调系统与燃油锅炉+冷水机组空调系统进行了经济分析比较。结果表明,土壤源热泵系统初投资高出燃油锅炉+冷水机组空调系统约4倍,而土壤源热泵系统要比燃油锅炉+冷水机组空调系统节省约63%的全年运行费用,其中夏季节省约21.5%的运行费用,冬季节省运行费用较大约为67.9%。土壤源热泵系统初投资回收期短,经济可行性好。