危化品事故情景推演网络构建及关键节点分析*

为有效应对危化品事故发生与演变时存在的动态性及不确定性问题,基于事故演变过程中的关键情景状态及对应孕灾环境、应急活动和处置目标等要素,引入动态贝叶斯网络方法,构建危化品事故情景推演网络,并结合复杂网络知识,对孕灾环境和应急活动2类事故影响因素节点进行敏感性和重要度分析。结果表明:情景推演网络计算的情景节点概率符合事故发生的实际情况,能够对危化品事故在不同孕灾环境和应急救援下的演变路径进行推演,并且分析得到燃烧物、消防力量、火场环境和建筑密度等关键影响因素节点,研究结果可为事故处理提供应急辅助决策支持。     

掘进面出风口风流与风幕调控下的粉尘分布响应曲面优化研究*

为了解决煤矿掘进面风筒出风口参数不能动态变化,而传统风幕全断面控尘效果不理想引起的粉尘浓度高等问题,通过分析风幕和出风口参数对粉尘分布规律的影响,以此得到合理的出风口风流与风幕综合调控方案,降低粉尘浓度。以陕西神木柠条塔煤矿N1212巷道为研究对象,利用Fluent软件建立出风口风流与风幕综合调控的粉尘场有限元模型,设计出风口风流及风幕综合调控响应曲面实验,得到最佳综合调控方案为:风幕射流出口宽度为0.16 m,风幕射流出口速度为6 m/s,出风口口径为0.9 m,出风口右偏角度为3°。搭建相似模拟实验平台来验证最佳综合调控方案,研究结果表明:调控后回风侧行人呼吸处和司机位置处粉尘平均浓度分别降低89%和81%,有效改善掘进面作业环境。     

五氯酚胁迫对转基因杨树光合光响应特性的影响

以从美国引入的转基因杨树(Populus deltoides×nigra,DN34)为材料,设置0、50、100 mg·kg~(-1)三个五氯酚胁迫质量分数开展温室盆栽试验,利用Li-6400便携式光合作用测量系统研究五氯酚污染胁迫下转基因杨树对光强的生理响应.结果表明:与对照相比,相同光强下50和100 mg·kg~(-1)质量分数的五氯酚胁迫均降低了转基因杨树叶片的净光合速率(P_n)、蒸腾速率(T_r)、胞间CO_2摩尔分数(C_i)和气孔导度(G_s).因此高质量分数五氯酚比低质量分数五氯酚对转基因杨树光合作用产生更大的抑制响应.     

Role of competition in phytoplankton population for the occurrence and control of plankton bloom in the presence of environmental fluctuations

Termination of harmful algal blooms (HABs) and coexistence of phytoplankton–zooplankton populations are of great importance to human health, ecosystem, environment, tourism and fisheries. In this paper, we propose a three component model consisting of non-toxic phytoplankton (NTP), toxin producing phytoplankton (TPP) and zooplankton (Z). The growth of zooplankton species is assume to reduce due to toxic chemicals released by TPP population. We have extended the model proposed by Chattopadhyay et al. [Chattopadhyay, J., Sarkar, R.R., Pal, S., 2004. Mathematical modelling of harmful algal blooms supported by experimental findings. Ecol. Comp. 1, 225–235] by including competition terms between TPP and NTP. We observe the effect of competition factors both in the presence and absence of the environmental fluctuation. From our field as well as model analysis we observe that competition helps in the coexistence of the species, but if the effect of competition is very high on the TPP population, it results in planktonic bloom. It is shown that the coexistence equilibrium loses its stability when the competition coefficient crosses a critical value and resulting Hopf-bifurcation around the positive equilibrium depicting oscillations phenomena of the populations.     

Confidence limits on one-stage model parameters in benchmark risk assessment

In modern environmental risk analysis, inferences are often desired on those low dose levels at which a fixed benchmark risk is achieved. In this paper, we study the use of confidence limits on parameters from a simple one-stage model of risk historically popular in benchmark analysis with quantal data. Based on these confidence bounds, we present methods for deriving upper confidence limits on extra risk and lower bounds on the benchmark dose. The methods are seen to extend automatically to the case where simultaneous inferences are desired at multiple doses. Monte Carlo evaluations explore characteristics of the parameter estimates and the confidence limits under this setting.

响应面法优化低频超声协同H2O2降解偶氮染料酸性绿B

以酸性绿B染料废水为研究对象,在单因素试验的基础上,选择染料废水初始pH和H₂O₂投加量及超声功率为自变量,以酸性绿B降解率为响应值,采用响应面分析法研究各自变量及其交互作用对酸性绿B超声降解的影响,并通过回归方程求解和响应曲面分析,得到二次多项式回归方程的预测模型. 结果表明,染料废水初始pH和H₂O₂投加量及超声功率与染料降解率存在显著的相关性. 确定酸性绿B废水超声降解优化条件:初始ρ(酸性绿B)为100 mg/L,初始pH和超声功率分别为4.43和216 W,H₂O₂投加量为1.77 mL. 在该优化条件下,酸性绿B的降解率可达93.34%.经试验验证,实际值与模型预测值拟合性良好,偏差仅为3.48%.      

高速铁路声屏障

提出我国高速铁路(铁路客运专线)声屏障主要结构形式和应有的性能。重点分析高速列车气动力的形成、影响因素、计算方法及其对声屏障的作用。提出了高速铁路声屏障的设计要点及其对声屏障的设计建造的建议。     

响应面法优化阴阳极同时作用电化学法处理染料废水

在自制电化学反应器中,以甲基橙模拟染料废水为处理对象,采用Box-Behnken Design响应面法研究了影响阴阳极同时作用电化学法处理染料废水的因素及其交互作用。实验得出各因素对废水脱色率影响的大小顺序为：电流密度> Fe³⁺浓度>Cl^-浓度。各因素之间的交互作用对废水脱色率影响的大小顺序为：电流密度和Fe³⁺浓度>电流密度和Cl^-浓度>Fe³⁺浓度和Cl^-浓度。优化结果表明：Fe³⁺浓度为1.02 mmol/L、Cl^-浓度为10.96 mmol/L、电流密度为11.52 mA/cm²时,最佳脱色率为94.67%。阴阳极同时作用电化学法对甲基橙去除效果显著。     

滨海平原咸水入侵灾害动态监测及综合减灾对策研究——以潍河下游平原为例

海（咸）水入侵是现代社会中典型的资源－环境－灾害问题,准确掌握咸水入侵动态变化的规律和信息,是进行预测、预报、减灾、防灾的科学基础和工作依据。据此,本文为咸水入侵的实时监测、分析、预测以及减灾方案决策与评估等提供了一个完善系统,并且提出了咸水入侵防治途径及综合减灾对策。     

NATURAL RESTABILIZATION OF STREAM CHANNELS IN URBAN WATERSHEDS1

ABSTRACT: Stream channels are known to change their form as a result of watershed urbanization, but do they restabilize under subsequent conditions of constant urban land use? Streams in seven developed and developing watersheds (drainage areas 5–35 km²) in the Puget Sound lowlands were evaluated for their channel stability and degree of urbanization, using field and historical data. Protocols for determining channel stability by visual assessment, calculated bed mobility at bankfull flows, and resurveyed cross‐sections were compared and yielded nearly identical results. We found that channel restabilization generally does occur within one or two decades of constant watershed land use, but it is not universal. When (or if) an individual stream will restabilize depends on specific hydrologic and geomorphic characteristics of the channel and its watershed; observed stability is not well predicted by simply the magnitude of urban development or the rate of ongoing land‐use change. The tendency for channel restabilization suggests that management efforts focused primarily on maintaining stability, particularly in a still‐urbanizing watershed, may not always be necessary. Yet physical stability alone is not a sufficient condition for a biologically healthy stream, and additional rehabilitation measures will almost certainly be required to restore biological conditions in urban systems.