基于Verhulst模型的新建隧道顶板下沉预测研究

隧道顶板下沉量预测对隧道安全施工十分重要.通过分析隧道下沉过程,指出其具有"S"型曲线特征,探讨了采用Verhulst模型进行隧道顶板下沉预测的适用性和可行性,并运用MATLAB软件开发相关程序,模拟遵赤高速公路中枢隧道YK39+134.6断面沉降过程,获得相应的预测方程.通过对比其预测结果、回归分析预测结果和实测值,发现该模型的顶板沉降预测值与实测值最接近,证实运用灰色Verhulst模型预测隧道顶板沉降量是合理、可行的.     

水处理滤料填充床流动电位测定的可行性研究

根据流动电位与ζ电位的关系,设计研制了一台测定滤料表面流动电位的装置,并测定了石英砂、核桃壳、沸石滤料的流动电位.研究滤料流动电位的稳定时间及压差对稳定时间的影响,并讨论电解质溶液pH值对滤料流动电位的影响.结果表明,1)pH=7.0、压差为2 cm水柱时,石英砂、核桃壳和沸石流动电位的稳定时间分别为45 min、60 min和120 min;2)压差越大,各滤料流动电位的稳定时间越短,因此在保证水流流态为层流条件下,应尽量在大压差条件下测定流动电位;3)随着电解质溶液pH值的升高,各滤料流动电位由正值向负值转变,其中石英砂滤料的等电点约在pH=5.0,核桃壳和沸石滤料约在pH=3.0.可见,研究滤料表面的流动电位对提高过滤效率以及开发改性滤料十分重要.     

Atmospheric mercury concentrations and speciation measured from 2004 to 2007 in Reno, Nevada, USA

Atmospheric elemental, reactive and particulate mercury (Hg) concentrations were measured north of downtown Reno, Nevada, USA from November 2004 to November 2007. Three-year mean and median concentrations for gaseous elemental Hg (Hg⁰) were 1.6 and 1.5 ng m⁻³ (respectively), similar to global mean Hg⁰ concentrations. The three-year mean reactive gaseous Hg (RGM) concentration (26 pg m⁻³) was higher than values reported for rural sites across the western United States. Well defined seasonal and daily patterns in Hg⁰ and RGM concentrations were observed, with the highest Hg⁰ concentrations measured in winter and early morning, and RGM concentrations being greatest in the summer and mid-afternoon. Elevated Hg⁰ concentrations in winter were associated with periods of cold, stagnant air; while a regularly observed early morning increase in concentration was due to local source and surface emissions. The observed afternoon increase and high summer values of RGM can be explained by in situ oxidation of gaseous Hg⁰ or mixing of RGM derived from the free troposphere to the surface. Because both of these processes are correlated with the same environmental conditions it is difficult to assess their overall contribution to the observed trends.     

Effect of the milling solution on lead stabilization in municipal solid waste incinerator fly ash during the milling processes

The wet milling process had been found to effectively stabilize lead in fly ash. This study adopts this method and looks at the effect of different milling solutions to improve the efficiency of lead stabilization. Different milling solutions (water, phosphoric acid and ethanol) and different milling times (1, 24, 48 and 96 h) were selected as parameters. Since lead oxide can be identified by XRD in this experiment’s samples, 5% lead oxide was added to the extracted mixed fly ash to make instrumental analysis easier. The experimental results indicate that the effect of stabilization of lead after milling could exceed 96%. During milling with water, considerable lead leached into the water in the initial stage (1 h) of the process, but a stable level was reached as the milling time increased. After milling with ethanol and 0.2 M phosphoric acids, the efficiency could exceed 93% after 1 h of milling time. The results of the sequential extraction procedure (SEP) results show that the residual fraction could be increased from 8.93% to 56.16% when a 0.2 M phosphoric acid solution was used. Clearly the choice of an appropriate milling solution can enhance lead stabilization in the fly ash.     

Real-world vehicle emissions: a summary of the Seventeenth Coordinating Research Council On-Road Vehicle Emissions Workshop

The Coordinating Research Council, Inc. (CRC) held its 17th On-Road Vehicle Emissions Workshop in March 2007, where results of the most recent on-road vehicle emissions research were presented. We summarize ongoing work from researchers who are engaged in improving our understanding of the role and contribution of mobile sources to ambient air quality and emission inventories. Participants in the Workshop discussed efforts to improve mobile source emission models, light- and heavy-duty vehicle emissions measurements, on- and off-road emissions measurements, effects of fuels and lubricating oils on emissions, as well as emerging issues and topics for future research.     

Innovation in the Knowledge Age: implications for collaborative science

Current trends validate the notion that multifaceted, multimodal interdisciplinary collaborations lead to increased research productivity in publications and citations, compared to those achieved by individual researchers. Moreover, it may be that scientific breakthroughs are increasingly achieved by interdisciplinary research teams. Nonetheless, despite the perceived importance of collaboration and its bibliometric benefits, today’s scientists are still trained to be autonomous, work individually, and encourage their graduate students to do the same—perpetuating values which impede the creation of collaborative space between disciplines. As a consequence, scientists working in teams typically report serious obstacles to collaboration. This paper builds off of recent recommendations from a 2015 National Academies report on the state of team science which emphasizes greater definition of roles, responsibility, accountability, goals, and milestones. However, these recommendations do not address the subjective, relational components of collaboration which can drive innovation and creativity. The relational side of collaboration is key to understanding the capacity and capabilities of the knowledge workers, such as scientists and engineers, who comprise interdisciplinary research teams. The authors’ recommendations, grounded in organizational communication and knowledge worker literature, include a renewed focus on the process of organizing through communication rather than focusing on organization as an outcome or consequence of teamwork, leading and cultivating team members rather than managing them, and the need to address self-driven, rather than external, motivations to engage in knowledge work.     

Global change impacts on the Upper Danube Catchment (Central Europe): a study of participatory modeling

Participatory modeling (PM) has become an essential concept in environmental impact assessment and planning in the field of water resources. In this paper, we focus on the use of PM to support the development of the integrated regional modeling system DANUBIA as a scientific concept to analyze the previously unknown impacts of global change, i.e., the combined effects of climate, demographic, economic, social and ecological change, on the Upper Danube Catchment (Germany). We use this case study to examine the specific conditions for PM in the field of complex integrated models on a regional scale. We describe the stepwise PM process and discuss the respective results, focusing on (1) the stakeholder dialogue’s contribution in supporting the development of new, complex modeling systems, particularly on a regional scale, (2) conditions of stakeholder involvement in issues related to the distant future, such as climate change impacts on regional water availability, and (3) limitations of PM and scientists’ motivation to carry out participatory research at all. We conclude that the PM process was not entirely successful in improving the scientific quality and practical applicability of the developed models because the process goals were manifold and overambitious, and the definition of the problem of “global change impacts on a regional scale” was too weak and uncertain to allow for a clear common objective of modelers and stakeholders. We claim that there is a lack of incentives for scientists, particularly natural scientists, to commit to PM activities.     

Multiresidue analysis of organophosphate and pyrethroid pesticides in duplicate-diet solid food by pressurized liquid extraction

An analytical method was developed for determining organophosphate pesticides (OPP) and pyrethroid pesticides (PYR) in duplicate-diet solid food. The method consisted of pressurized liquid extraction (PLE) with dichloromethane followed by cleanup with gel permeation and solid phase extraction columns and gas chromatography/mass spectrometry (GC/MS) analysis. Quantitative recoveries (73–117 %) of the target pesticides were obtained for spiked duplicate-diet food samples. The percent standard deviation (% RSD) of replicate food samples was within ± 20 %. Another method was developed for determining a common OPP metabolite, 3, 5, 6-trichloro-2-pyridinol (TCP) in duplicate-diet food. The method consisted of a PLE with methanol followed by liquid-liquid partitioning, derivatization, and GC/MS analysis. Recoveries of TCP ranged from 83 to 101 % for spiked duplicate-diet food samples. The % RSD of replicate food samples was within ± 15 %. The results confirmed that these methods are reliable and robust, and that they can be used in routine analysis. In addition, a storage stability study for a common OPP, chlorpyrifos (CPF), in solid food samples was performed. The fortified ¹⁵N-¹³C-labeled CPF was stable over 16 mo storage at ?20° C in the dark. The developed analytical methods were successfully applied to 278 duplicate-diet food samples from preschool children, demonstrating that these methods are robust and suitable for routine analysis in future exposure monitoring studies.     

2001~2017年中国建设用地时空分异特征

在快速城市化进程中，我国建设用地急剧扩张，分析建设用地在时间和空间上的变化规律及其原因，对促进我国土地资源的可持续利用具有重要指导意义。基于2001、2006、2011、2017年四期MODIS Land Cover（MCD12Q1）产品数据，结合经济数据和地貌类型数据，研究中国不同经济区和不同地貌类型区的建设用地扩张的时空变化特征，结果表明：（1）全国建设用地在2001~2006、2006~2011、2011~2017年3时期扩张强度逐渐变弱，扩张速度逐渐变慢。（2）2001~2017年建设用地扩张主要发生在东部地区，该地区扩张强度最强、扩张速度最快。3时期内东部地区建设用地扩张强度逐渐变弱，扩张速度逐渐变慢；中部地区扩张强度逐渐变强，扩张速度逐渐变快；西部地区扩张强度先变弱后趋于稳定，扩张速度逐渐变慢；东北地区扩张强度先变弱后趋于稳定，扩张速度先变快后变慢。（3）2001~2017年建设用地扩张主要发生在平原地区，扩张强度最强，丘陵地区扩张速度最快；平原地区建设用地扩张强度逐渐变弱，扩张速度逐渐变慢；丘陵地区扩张强度先变弱后变强，扩张速度先变慢后变快；山地地区扩张强度逐渐变强，扩张速度先变快后变慢；高原地区扩张强度逐渐变强，扩张速度逐渐变快。从研究结果可知，不同经济区建设用地扩张强度和速度具有差异性，主要受不同时期国家相应的区域政策影响；不同地貌类型对建设用地扩张的时空特征也会产生影响。