热阻力概念的修正及计算方法

以隧道火灾为背景,对一维加热管流中的热阻力进行了研究。通过压力场数值模拟与理论分析,直接证实了热阻力的存在,并表明传统概念上的热阻力明显大于实际的能量损失。根据能量方程提出水平无粘管流的热阻力应等于气流经过加热区的全压力降,而非静压力降;等截面管流的热阻力大小应为传统热阻力值的1/2。这一修正使热阻力概念具有了严格的流体力学意义。在定义新的热阻力系数基础上,建立了2个热阻力系数表达式及低马赫数条件下热阻力的近似表达式。将该近似表达式与热损失方程进行对比,表明两者在低马赫数条件下具有一致性。研究成果进一步发展了热阻力理论体系,对隧道火灾及其它相关工程热物理问题的研究与应用都具有重要价值。     

Assessing the Effects of Alternative Setback Channel Constraint Scenarios Employing a River Meander Migration Model

River channel migration and cutoff events within large river riparian corridors create heterogeneous and biologically diverse landscapes. However, channel stabilization (riprap and levees) impede the formation and maintenance of riparian areas. These impacts can be mitigated by setting channel constraints away from the channel. Using a meander migration model to measure land affected, we examined the relationship between setback distance and riparian and off-channel aquatic habitat formation on a 28-km reach of the Sacramento River, California, USA. We simulated 100 years of channel migration and cutoff events using 11 setback scenarios: 1 with existing riprap and 10 assuming setback constraints from about 0.5 to 4 bankfull channel widths (bankfull width: 235 m) from the channel. The percentage of land reworked by the river in 100 years relative to current (riprap) conditions ranged from 172% for the 100-m constraint setback scenario to 790% for the 800-m scenario. Three basic patterns occur as the setback distance increases due to different migration and cutoff dynamics: complete restriction of cutoffs, partial restriction of cutoffs, and no restriction of cutoffs. Complete cutoff restriction occurred at distances less than about one bankfull channel width (235 m), and no cutoff restriction occurred at distances greater than about three bankfull widths (∼700 m). Managing for point bars alone allows the setbacks to be narrower than managing for cutoffs and aquatic habitat. Results suggest that site-specific “restriction of cutoff” thresholds can be identified to optimize habitat benefits versus cost of acquired land along rivers affected by migration processes.     

Getting caught up in the game: managing non-formal dynamics in the remediation of contaminated sediments in Oslo harbor

This study aims at describing, analyzing and evaluating the relation between management styles and process dynamics of a complex planning process confronted with unexpected dynamics. The development of an aquatic disposal site for dredged contaminated sediments in Oslo was managed by a project management style focused on timely and cost-effective implementation. Coupling the remediation project with another infrastructural project and the actual construction of the site led to unexpected dynamics in terms of resistance and controversy. Project management had difficulties in adjusting its style accordingly, resulting in even more delay and resistance. Managing complex planning projects requires a style suitable to the characteristics of the project and the capability of adjusting it to changing circumstances. The paper concludes with some explanations why it is difficult to change management styles in complex planning and implementation processes and complexity-embracing approaches to deal with this.     

The role of periodic boundary forcing in plankton pattern formation

We consider one and two-dimensional minimal models in plankton dynamics. The influence of oscillating boundary forcing functions as agents for triggering pattern formation is discussed. In particular it is found that in these conditions population waves arise for one dimensional models, while for two dimensional models, different amplitudes and frequencies in the boundary forcing generate definite patterns, mimicking the boundary term. This happens even though the model we investigate is very simple. The emergence of these features is an interesting metaphor for the fundamental biological problem of how pattern formation processes may be inevitable in natural heterogeneous ecosystems.     

计算毒理学在内分泌干扰物筛选上的应用和展望

内分泌干扰物通过干扰内分泌系统导致多种疾病,如生殖疾病、肥胖症甚至癌症。然而,面对环境中大量潜在的内分泌干扰物,传统的体外、体内评估方法由于成本高、耗时长等问题,难以实现内分泌干扰物的高通量筛查。计算毒理学逐渐发展成为被美国环保局(Environmental Protection Agency,EPA)、经济合作与发展组织(Organization for Economic Co-operation and Development,OECD)等机构所推荐的内分泌干扰物筛选与预测方法。本文综述了计算毒理学在内分泌干扰物筛选上的进展,主要包括分子对接和分子动力学模拟的应用,并对有害结局路径(adverse outcome pathway,AOP)的方法进行介绍和展望。     

Element patterns in albatrosses and petrels: Influence of trophic position, foraging range, and prey type

We investigated the concentrations of 22 essential and non-essential elements among a community of Procellariiformes (and their prey) to identify the extent to which trophic position and foraging range governed element accumulation. Stable isotope analysis (SIA) was used to characterise trophic (δ¹⁵N) and spatial patterns (δ¹³C) among species. Few consistent patterns were observed in element distributions among species and diet appeared to be highly influential in some instances. Arsenic levels in seabird red blood cells correlated with δ¹⁵N and δ¹³C, demonstrating the importance of trophic position and foraging range for arsenic distribution. Arsenic concentrations in prey varied significantly across taxa, and in the strength of association with δ¹⁵N values (trophic level). In most instances, element patterns in Procellariiformes showed the clearest separation among species, indicating that a combination of prey selection and other complex species-specific characteristics (e.g. moult patterns) were generally more important determining factors than trophic level per se.     

氟苯胺好氧生物降解性能的研究

利用驯化污泥研究了邻氟苯胺、对氟苯胺、2,4-二氟苯胺的好氧生物降解性能.结果表明,3种氟苯胺的好氧生物降解性能从高到低依次为对氟苯胺、邻氟苯胺和2,4-二氟苯胺.降解动力学分析表明,除2,4-二氟苯胺在实验质量浓度8.56 mg/L时为一级反应,其他为零级反应;且它们的降解规律都符合Monod方程;30 ℃、振荡速率140 r/min为氟苯胺的最佳降解条件.同时研究了共基质条件下葡萄糖和苯胺对2,4-二氟苯胺的好氧降解的影响,葡萄糖的引入有促进作用,而苯胺只在一定浓度范围内有促进作用.氟苯胺的生产废水与生活污水合并处理以及多种组分混合废水处理是可行的.     

地下水环境中甲基叔丁基醚运移过程的动力学模型

建立了地下水环境中甲基叔丁基醚(MTBE)运移过程的变系数动力学模型,并对模型进行了验证和参数灵敏度分析.模拟结果表明,地下水流速和阻滞系数对于MTBE的运移过程影响最为显著,而水动力弥散系数的影响较小,忽略其变化不会对预测地下水环境中污染物运移的环境动力学行为造成太大误差.由此得到的结论可定量研究MTBE在地下水环境中的对流.扩散特征,还可为MTBE污染地下水的预测预报、修复治理等研究提供科学依据.     

煤矿安全生产中人的行为影响因子系统动力学(SD)仿真分析

在构建影响人的安全行为因素因果关系的基础上,运用系统动力学(SD)理论和方法,对影响人的安全行为关键因素进行动态预测,并通过仿真计算、对比分析安全投入增加对系统安全水平的影响。应用该方法建立的煤矿生产中人的安全行为指标水平模型,以求证安全投入与人的安全行为水平的相关性,为煤矿安全管理决策提供一种新的思路,亦有助于政府和煤矿企业科学地明确安全投入方向,降低人因事故率,提高煤矿生产的安全水平。     

高速公路安全水平仿真分析

为深入研究高速公路安全系统,用系统动力学(SD)方法分析驾驶员、车辆、道路、应急救援等组成要素以及环境、管理等影响因素之间的关系,建立高速公路安全系统因果关系模型和存量流量模型。用层次分析法(AHP)确定各影响因素的权重。以三福高速公路为例,用Vensim软件模拟高速公路运营期间系统安全的变化情况。结果表明,在该高速公路运营期间,系统安全与车辆安全度呈先上升后下降的趋势、道路安全度呈下降趋势、驾驶员安全度与应急救援能力呈上升趋势。通过与实际数据对比,验证了模型的有效性。