Mixed-effects Models with Skewed Distributions for Time-varying Decay Rate in HIV Dynamics

After initiation of treatment, HIV viral load has multiphasic changes, which indicates that the viral decay rate is a time-varying process. Mixed-effects models with different time-varying decay rate functions have been proposed in literature. However, there are two unresolved critical issues: (i) it is not clear which model is more appropriate for practical use, and (ii) the model random errors are commonly assumed to follow a normal distribution, which may be unrealistic and can obscure important features of within- and among-subject variations. Because asymmetry of HIV viral load data is still noticeable even after transformation, it is important to use a more general distribution family that enables the unrealistic normal assumption to be relaxed. We developed skew-elliptical (SE) Bayesian mixed-effects models by considering the model random errors to have an SE distribution. We compared the performance among five SE models that have different time-varying decay rate functions. For each model, we also contrasted the performance under different model random error assumptions such as normal, Student-t, skew-normal, or skew-t distribution. Two AIDS clinical trial datasets were used to illustrate the proposed models and methods. The results indicate that the model with a time-varying viral decay rate that has two exponential components is preferred. Among the four distribution assumptions, the skew-t and skew-normal models provided better fitting to the data than normal or Student-t model, suggesting that it is important to assume a model with a skewed distribution in order to achieve reasonable results when the data exhibit skewness.     

大型航空制造企业技术改造项目管理新模式

技术改造及其项目管理是大型航空制造企业经营管理活动中的重要任务之一。企业通过技术 改造项目改进生产条件和生产工艺,增强军民用航空产品的研制能力。论文根据技改项目管 理的特点,运用系统动力学方法建立技改项目全生命周期动力学模型,对技改项目生命周期 的全过程进行动态仿真,为管理者提供信息和决策支持。最后,结合工作流技术的优点,建 立了基于工作流技术的技改项目管理协同平台原型     

Vulnerabilities and risks in population and environment studies

In the study of risks , different sciences use the same category in different ways, each related to its own ontological assumptions. But many of these fields communicate very little with one another. This article seeks to approximate two of these areas of study that have shown similar concerns and that can mutually strengthen one another, namely, geography and demography. Geography was one of the first disciplines to include risk in its environmental dimension and has had broad experience in simultaneously focusing on social and natural dynamics. Demography, on the other hand, faces greater difficulties because only recently has it incorporated the environmental dimension into its scientific scope. Both have brought the concept of vulnerability into their conceptual framework as complementary to that of risk. Geographers understand vulnerability as a more symbiotic form of the relationship between society and nature, whereas demographers give it a strong socioeconomic component. In this regard, the conceptual discussion on risks and vulnerabilities, in its attempt at approximating these two fields, is a way of conceptually advancing and strengthening the different approaches to empirical work, especially in population–environment studies which is the common ground for the dialogue between the two disciplines.

Population Density is a Key Factor in Declining Human Fertility

In studying the complex determinants of human fertility, social scientists have given little attention to population density, although reproduction has been shown to be density-dependent for a wide variety of other species. Using fixed effects models on the time series of 145 countries and controlling for key social and economic variables, we find a consistent and significant negative relationship between human fertility and population density. Moreover, we find that individual fertility preferences also decline with population density. These findings suggest that population density should be included as a variable in future studies of fertility determinants.

基于系统动力学的普惠性学前教育服务监管研究

随着国家对于二孩、三孩生育政策的放开,提升普惠性学前教育服务的质量,加强普惠性学前教育服务的监管显得尤为重要。文章建构了普惠性幼儿园、政府和入园幼儿家庭三方参与的演化博弈模型,并结合系统动力学方法进行仿真分析,解析各参与主体的动态演化过程及相关变量因素对演化策略的影响。研究表明：在普惠性学前教育服务监管中,演化系统最终会实现(政府积极监管、普惠性幼儿园自律、入园幼儿家庭监督)均衡状态,多个外部变量的共同作用决定着三方参与主体的策略选择;在博弈过程中,政府发挥着显著的主导作用,普惠性幼儿园和入园幼儿家庭的策略选择明显受到政府影响,入园幼儿家庭监督对普惠性幼儿园的策略选择存在明显的间接影响。之后从提升政府的监管效能、建立科学合理的激励与惩罚机制、重视入园幼儿家庭的监督等层面给出了对策建议。     

中国省际人口流动与 人力资本流动差异性分析

人力资本流动与人口流动相关却不相同,本文采用2010-2016年全国流动人口动态监测数据,从流动方向和流动强度两方面对我国省际人口流动引致的人力资本流动现象加以研究。结果表明从流动方向分析,各省人口净流动方向基本呈现时间一致性并且流入流出区域具有稳定性。在调查期间人口净流出省份为16个,人口净流入省份为15个,没有明显变化。人力资本净流向与人口净流向完全一致,但省际人口净流向与高级人力资本净流向并不完全一致,山西、广西、重庆等省市的高级人力资本净流向始终与总人力资本净流向相反。本文采用流出流入比率和迁移选择中心两种指标测算人力资本流动强度,结果基本一致。人力资本流动中心与人口流动中心分布均较为固定。2010年人力资本流动强度最大的省份在2016年的流动强度也更强,流动强度在省际呈现惯性和马太效应。人力资本流入最强地区包括北京、天津、上海三个直辖市,人力资本流出最强省份始终包括安徽、四川、河南等省份。以人力资本流出弹性衡量人力资本流出强度与人口流出强度的相对强弱,东部地区、东北地区省份人力资本的流出强度始终大于人口流出强度,西部地区省份差异较大。考虑各省近五年经济增长状况,人口流动或者人力资本流动对经济增长的影响是非线性的。     

户籍地禀赋与流入地融合 ——流动人口定居意愿影响因素研究

定居意愿是衡量流动人口转向稳定生活状态的重要指标,实则包含了居留意愿和落户意愿两方面的内容。基于2017年全国流动人口卫生计生动态监测数据,通过建立多项Logistic回归模型的方法,重点从与制度结构相关的“户籍地禀赋”与“流入地融合”两个维度,分析流动人口“居留-落户”的定居意愿状况及其影响因素。研究结果表明,户籍地禀赋性因素的“回流”效应和流入地融合性因素的“拉动”效应对流动人口不同层面定居意愿的影响存在差异:与责任、情感、伦理相关的户籍地禀赋性因素以及与经济融入、社会与文化接纳相关的流入地融合性因素对流动人口居留意愿的影响比较显著;与财富价值相关的户籍地禀赋性因素以及与城乡区位相关的流入地融合性因素对流动人口落户意愿的影响比较显著;制度融入因素、生活融入因素、身份认同因素则对两个维度的定居意愿都产生了显著影响。因此,对于具有定居意愿的流动人口,政府应该努力实现基本公共服务的全覆盖,激发流动人口参与社会建设、增强对流入地的身份认同与文化接纳等融合水平;对于没有定居意愿的流动人口,也需为其“回流”后在户籍地的再次融入提供良好的制度保障环境。     

The potential of online social networking data for augmenting the study of high-risk personal networks among young men who have sex with men at-risk for HIV

Capturing dynamics in high-risk personal networks is essential for preventing HIV transmission. Online social networking data offer incentive to augment traditional selfreported approaches for network enumeration. To explore what online networks reveal about dynamics among high-risk associates, we examine the relationship between egocentric confidant and sex networks and personal Facebook friendship networks of a cohort of young Black men who have sex with men. Although overlap exists between self-reported and Facebook associates, the stabilities of each were unrelated. Confidants who were also Facebook friends with a respondent were, however, more likely to be retained. Thus, Facebook networks contain stable confidants.