基于低碳视角的天津市能源结构系统动力学分析

全球气候变化和温室气体的大量排放已成为国际社会广泛关注的问题,能源结构调整是应对这一问题行之有效的手段。通过对天津市能源结构进行研究,从低碳角度出发,以改善天津以煤为主的能源供给结构、提高能源利用效率、缓解能源供应压力、减少环境污染和生态破坏为目的,应用系统动力学对天津市能源结构的未来发展情况进行模拟,通过对非低碳模式、低碳模式和强化低碳模式3种模拟方案下能源消耗情况和温室气体排放的比较,找出适合天津市能源结构调整的最佳模式。     

潮河流域降雨径流事件污染物输出特征

在半干旱半湿润地区,非点源养分污染的发生主要由降水径流事件驱动,伴随这些短暂脉冲事件流失的养分量决定着一年总的污染排放负荷,因此研究汛期降雨径流事件下水体污染动态特征是半干旱半湿润地区污染负荷模拟及控制的关键.以北京市密云水库上游的潮河流域为研究区域,2018年和2019年汛期进行古北口站和下会站的降雨径流过程水质水量同步监测.结果表明：①监测的3场降雨事件（E1、E2和E3）中,E1的降雨量和强度最大,相应的流量和污染物浓度最高;②不同降雨事件下,污染物浓度及其变化不同.大暴雨事件和暴雨事件（E1、E3）下,总氮（TN）、氨氮（NH₄⁺-N）、硝氮（NO₃^--N）、总磷（TP）和悬浮物（TSS）的浓度与流量变化过程相似;大雨事件下（E2）,总氮（TN）、氨氮（NH₄⁺-N）、总磷（TP）和悬浮物（TSS）的浓度与流量变化过程相似,硝氮（NO₃^--N）浓度变化与流量相反;③不同降雨事件下,不同形态污染物浓度及其变化不同.降雨侵蚀强烈（E1、E2）,颗粒态污染物浓度变化明显,与悬浮物（TSS）呈显著正相关关系;降雨未引起土壤侵蚀（E3）,氮磷形态以溶解态氮（TDN）和溶解态磷（TDP）为主,浓度变化主要与流量有关;④不同降雨事件下,不同站点的流量和污染物浓度不同.强降雨侵蚀事件在古北口表现更明显,引起流量和总磷（TP）、悬浮物（TSS）的变化幅度更大.以上结果可以用来确定降雨事件引发的非点源污染物输出特征,为该地区的汛期水质预测与控制提供参考.     

Modeling the effects of production pressure on safety performance in construction projects using system dynamics

Introduction: Construction incidents occur due to system failures, not due to a single factor such as unsafe behavior or condition. Therefore, construction safety should be investigated using a systematic view capable of illustrating the complex nature of incidents. Construction projects are also often behind their planned schedule and suffer from various pressures caused by contractual deadlines or clients. Previous studies demonstrated that such pressures negatively affect safety performance; however, the process of how production pressure influences safety performance is not fully investigated. Method: The present research aimed to understand the feedback mechanism of how production pressure interactively affects safety performance and safety-related managerial components in a construction project. Ground theory method (GTM) is used to create a conceptual causal loop diagram that shows the relationship between incident rate and other variables such as labor hour, actual and planned progress, safety climate, rework, and safety training. Moreover, a power plant construction project was used as a case study to practically investigate the conceptual model; a case study is employed to build a System Dynamics (SD) model. The simulation model was then validated using behavior reproduction and sensitivity analysis. Results: The results of the inequality statistics show that the simulation model can be used to forecast trends in the incident rate.     

Optimization of dilution ventilation layout design in confined environments using Computational Fluid Dynamics (CFD)

Dilution ventilation systems have been widely used to control the airborne toxic and explosive material in confined spaces. Layout design of dilution ventilation is critical to industrial hygiene control and ventilation efficiency. A properly designed dilution ventilation system can significantly improve the safety of confined workshops and maintain a comfortable work condition. In this work, Computational Fluid Dynamics (CFD) has been used to analyze the performance of dilution ventilation system in the confined workshop environment. Seven different ventilation layouts are proposed to evaluate ventilation performance of different installation layouts. Carbon monoxide (CO), which has the similar density as air, is selected as the sample contaminant to conduct steady-state CFD simulations. The simulation results of different layouts are examined and compared to get the optimal layout design for the best contaminant control. Results have shown that the layout with two opposite inlets has the highest ventilation efficiency among seven proposed layouts. This work can serve as a reference to increase dilution ventilation efficiency and minimize the energy cost in general confined areas.     

Hydrogen inhibition in wet dust removal systems by using L-aspartic: A feasible way of hydrogen explosion control measures

Alloy dust generated from automobile wheel hub grinding, after entering the wet dust collector, will react with water to produce hydrogen, thus exposing the entire ventilation and dust removal system to potential hydrogen explosion. In this paper, the inhibition mechanism and kinetic characteristics of different concentrations of L-Aspartic acid (L-Asp) on the reaction of Al_0.9Mg_0.1 alloy with water were studied with respect to adsorption morphology, chemical kinetic modeling and molecular dynamics (MD), using L-Asp as the environmentally-safe hydrogen inhibitor. The results show that within a given temperature interval, the hydrogen production rate of Al_0.9Mg_0.1 alloy dust decreases with increasing L-Asp concentration. When the L-Asp concentration exceeds 1.0g/L, the hydrogen evolution rate is almost zero. The calculated results of chemical kinetics agree with the Langmuir adsorption model, confirming that L-Asp is an ideal monolayer physical adsorption system on the surface of alloy particles. The FTIR and MD simulation results show that –NH₂ and –COOH groups in L-Asp molecules contribute greatly to the adsorption. The research results of this paper can help fundamentally avoid hydrogen generation in wet dust collectors and guarantee intrinsic safety.     

A framework to measure the wildness of managed large vertebrate populations

As landscapes continue to fall under human influence through habitat loss and fragmentation, fencing is increasingly being used to mitigate anthropogenic threats and enhance the commercial value of wildlife. Subsequent intensification of management potentially erodes wildness by disembodying populations from landscape-level processes, thereby disconnecting species from natural selection. Tools are needed to measure the degree to which populations of large vertebrate species in formally protected and privately owned wildlife areas are self-sustaining and free to adapt. We devised a framework to measure such wildness based on 6 attributes relating to the evolutionary and ecological dynamics of vertebrates (space, disease and parasite resistance, exposure to predation, exposure to limitations and fluctuations of food and water supply, and reproduction). For each attribute, we set empirical, species-specific thresholds between 5 wildness states based on quantifiable management interventions. We analysed data from 205 private wildlife properties with management objectives spanning ecotourism to consumptive utilization to test the framework on 6 herbivore species representing a range of conservation statuses and commercial values. Wildness scores among species differed significantly, and the proportion of populations identified as wild ranged from 12% to 84%, which indicates the tool detected site-scale differences both among populations of different species and populations of the same species under different management regimes. By quantifying wildness, this framework provides practitioners with standardized measurement units that link biodiversity with the sustainable use of wildlife. Applications include informing species management plans at local scales; standardizing the inclusion of managed populations in red-list assessments; and providing a platform for certification and regulation of wildlife-based economies. Applying this framework may help embed wildness as a normative value in policy and mitigate the shifting baseline of what it means to truly conserve a species.     

高温下环状五肽构象的分子模拟

运用能量优化和随机动力学模拟了高温下环状五肽的构象,通过能量优化产生粗结构,实现了对此粗结构的随机动力学模拟。结果表明,对本文的研究对象,该模拟方法是高效合理的,该方法提供了一种生物分子结构和功能研究的新思路,模拟结果对从分子水平上揭示高温环境下生物分子的空间结构提供了理论依据,并可应用于生物分子结构和功能的研究中。     

燃烧、爆炸过程复杂性行为的非线性动力学(Ⅰ)

从非线性动力学观点,总结了燃烧和爆炸系统的多种复杂现象。指出了其非线性现象之间的对应关系。提出了从非线性即从“系统”、“全局或大范围”、“演化”及“统一”地观点认识燃烧和爆炸现象的观点。     

水稻根系中多环芳烃的动态变化

水稻根系的多环芳烃浓度随着水稻的生长不断变化,呈现出初期逐渐升高,到成熟期趋于稳定的一般趋势.幼穗期、乳熟期、蜡熟期、完熟期和枯熟期水稻根系的多环芳烃总含量(PAH15)平均分别为464、969、592、1075 ng·g-1和1059ng·g-1,并主要由3环化合物组成.根系的脂含量、比表面和生物量等指标对根系多环芳烃的变化起到了一定影响.其中,脂含量和比表面的影响比生物量的影响更为显著.随着水稻的成熟,水稻土多环芳烃含量逐渐降低,而5、6环化合物的比例逐渐增加.水稻根系和水稻土中的多环芳烃含量之间存在明显的负相关关系.     

旱地和淹水土壤中DDT的降解及DDMU和DDMS的形成趋势

在水稻和黑麦草2种栽培条件下,研究了新施入土壤中的工业DDT及微量老化残留DDT的降解,以及二级降解物DDMS和DDMU的形成动态.结果表明,DDT在旱地土壤中降解缓慢,其一级降解物DDE和DDD检出量略有增加,二级降解物DDMU和DDMS的形成极为有限,到试验终止时(黑麦草生长128 d)二者检出量仅为20 ng·g^-1.DDT在淹水土壤中可迅速降解,84 d后DDT残留量仅为施入量的2％左右,维持在70～80 ng·g^-1的水平;随DDT的降解,其一级降解物DDD检出量增加,在第84 d达峰值,DDD检出量的峰值与DDT的谷值时间基本吻合;同时DDMS和DDMU检出量也明显增加,在84 d时达到峰值,分别为28和115 ng·g^-1.未发现不同土壤条件对微量老化残留DDT降解动态或降解物形成产生影响.因此,淹水条件极利于新施入DDT在土壤中的降解并形成DDMS,但不能通过改变土壤水分条件来促进老化残留DDT降解.