On the effectiveness of mitigation strategies for cryogenic applications

The need for sustainable energy sources, as well as the current energetic crisis involving the majority of markets, has promoted the use of cryogenic liquefaction for the transportation and storage of natural gas (i.e., LNG). To guarantee the development of a robust and safe infrastructure, a complete understanding of the main phenomena occurring at low temperatures is paramount. In this sense, the largest grey areas are the characterization of the combustion at low-initial temperature and the interactions between water and cryogenic liquid. For these reasons, this work presents an experimental campaign on the possible mitigation strategies for the mitigation of consequences related to the accidental release of LNG. Particular emphasis was posed on the direct and indirect effects of water on cryogenic pool fire. The former resulted in a significant increase in the dimensions of fire (∼+50%) and burning rate (∼300%) with respect to the case with no direct contact between water and LNG, whereas the latter generated an abrupt decrease in the measured temperatures (<100 °C). The use of an emergency flare to empty an LNG tank was tested, as well. The spatial distribution of temperature was monitored along with the time to guarantee the safe operability of this equipment in the case of LNG combustion. The explanations for the observed phenomena and trends were provided, allowing for the development of safe procedures for the emergency response related to cryogenic fuels.     

Association analysis of accident factors in petrochemical storage tank farms

In order to identify and clarify the association between the factors leading to accidents in a petrochemical tank area, this study analyzes investigation reports of 212 petrochemical tank farm accidents and combines this with the “association rule” mining and science related to complex networks. The main risk factors are determined and a risk factor data set is constructed; 75 association rules are extracted from the factor data set based on the Apriori algorithm. Then the obtained association rules are used to construct an accident factors network of the petrochemical storage tank area, and the topology characteristics of the network are further analyzed to reveal the importance of factors. Factors with large node degree, betweenness, and clustering coefficients are obtained, such as “violation of operating regulations”, “high concentration of flammable gas in the air”, “lack of experience and professional skills”, etc. These factors play an important role in the formation and development of accidents. The results also show that the accident cause network of the petrochemical storage tank area has a small average shortest path length and a large cluster coefficient, indicating a relatively close connection between the accident factors. The contributions of this study is not only extracting the hidden relationships among contributory factors to tank farm accidents using association analysis, but also revealing which factors are more important for the tank farm safety through the complex network.     

公共池塘资源可持续管理的理论框架

由于自然科学和社会科学的学科视角和研究方法各异,使得我们对公共池塘资源管理问题的理解不够系统和全面。论文在综述公共池塘资源和社会-生态系统管理理论的基础上,辨析了公共池塘资源和社会-生态系统的概念;从识别影响公共池塘资源可持续管理的变量出发,梳理了社会-生态系统分析框架的演变及其局限性,指出社会-生态系统可持续发展分析框架为地理学、 生态学、 经济学、 自然资源学、 社会学等学科的交流和融合提供了统一的平台,并为资源管理、 政策分析和案例比较分析等的理论和方法提供了新的研究思路。该框架对现阶段我国资源管理政策的制定有重要借鉴意义。     

Influence assessment of inlet parameters on thermal risk and productivity: Application to the epoxidation of vegetable oils

The influence of inlet parameters on the production and thermal risk of complex chemical systems can be cumbersome to evaluate. To determine the optimum safe operating conditions, one needs to solve complex differential equations derived from energy and material balances. This robust approach cannot be made on-site, and it is essential to propose simplest tools to evaluate rapidly the performance and safety of some operating conditions. This is the aim of this paper that establishes explicit relationships between the production and thermal risk parameters, and the inlet parameters. In addition, it also proposes a Pareto chart that can be used to make the tradeoff between safety and performance. Such relationships and chart were developed for the production of epoxidized cottonseed oil under isoperibolic and semi-batch mode. The kinetic model developed by Zheng et (Zheng et al., 2016). was used. First, a numerical approach, i.e., least square method, was used to find explicit relationships between thermal risk parameters, production parameters and six inlet parameters. The use of such an approach allows a better understanding of this process. Second, safety and performance indicators are proposed and discussed to evaluate the operating conditions thanks to a simple and intuitive schema. Besides, this approach can be used to find the optimum conditions more rapidly.     

我国VOCs污染治理监管存在的问题及对策

VOCs是细颗粒物(PM_2.5)和臭氧(O3)形成的重要前体物,通过梳理我国VOCs治理相关的法律、政策、标准,并结合重点区域的调研情况,分析了我国VOCs治理监管存在的法律法规与标准体系不健全、执法监管能力建设不足、企业全过程精细化管控不到位等问题,提出应进一步健全法律法规与标准体系,建立智能监管技术与人工智能应用体系,加强全过程精细化管控等对策建议。     

Recognizing reflexivity among conservation practitioners

When deciding how to conserve biodiversity, practitioners navigate diverse missions, sometimes conflicting approaches, and uncertain trade-offs. These choices are based not only on evidence, funders’ priorities, stakeholders’ interests, and policies, but also on practitioners’ personal experiences, backgrounds, and values. Calls for greater reflexivity—an individual or group's ability to examine themselves in relation to their actions and interactions with others—have appeared in the conservation science literature. But what role does reflexivity play in conservation practice? We explored how self-reflection can shape how individuals and groups conserve nature. To provide examples of reflexivity in conservation practice, we conducted a year-long series of workshop discussions and online exchanges. During these, we examined cases from the peer-reviewed and gray literature, our own experiences, and conversations with 10 experts. Reflexivity among practitioners spanned individual and collective levels and informal and formal settings. Reflexivity also encompassed diverse themes, including practitioners’ values, emotional struggles, social identities, training, cultural backgrounds, and experiences of success and failure. Reflexive processes also have limitations, dangers, and costs. Informal and institutionalized reflexivity requires allocation of limited time and resources, can be hard to put into practice, and alone cannot solve conservation challenges. Yet, when intentionally undertaken, reflexive processes might be integrated into adaptive management cycles at multiple points, helping conservation practitioners better reach their goals. Reflexivity could also play a more transformative role in conservation by motivating practitioners to reevaluate their goals and methods entirely. Reflexivity might help the conservation movement imagine and thus work toward a better world for wildlife, people, and the conservation sector itself.     

矿井主风机不停风倒机系统最优控制研究

为解决矿井停机切换主要通风机过程中引起的井下风量波动很大,易造成瓦斯积聚等引发的安全问题,提出1种基于智能控制的主通风机稳风切换系统.建立动态风机倒机数学模型,提出基于改进粒子群算法优化的模糊自适应PID的控制方法,并应用MATLAB进行仿真实验,结果表明:控制方法控制效果明显,在系统运行的120 s内,井下风量波动始...     

Thermal interaction analysis in pipeline systems: A case study

The assessment of the consequences of high pressure releases of flammable gases is a fundamental requirement for the safe design and operation of industrial installations, plants and pipework. A scenario of interest concerns a high pressure jet-fire following the ignition of a gas jet release which results in a thermal loading to the surroundings and possibly leads to accident escalation.

In the present paper, a case study is presented: two parallel-laid natural gas pipelines have been considered, the accidental scenarios which may possibly occur as a consequence of a pipeline failure have been discussed and the thermal effects caused by the jet-fire developing from different rupture sizes have been assessed.

Three scenarios have been analyzed, considering the pipelines being within a highly congested area: (i) large failure and vertical jet with detached flame; (ii) small failure with jet fire directly impinging on the parallel pipeline; (iii) small failure with pipeline engulfed within fire.

Once the temperature gradient through the pipeline wall has been found, the stresses deriving from pressure load and steel differential expansion have been analytically calculated and compared with the yielding stresses at the temperature achieved by the pipeline wall.

In the first scenario the pipeline is able to resist without major problems; in the second case the pipeline rupture is likely to occur; in the third scenario the pipeline resists to the applied loads but with a low margin to yielding.

It is understood that the analysis results are very much dependent on the utilized hypotheses, therefore a sensitivity analysis was performed in order to assess the variation of the results as a function of the variation of problem data; this analysis identifies the large influence of the parameters on the final result.     

大型蚤在线生物监测系统研究

近年来,世界范围内突发性废水泄漏事件频发,在引起人们对水质问题恐慌的同时,也促进了饮用水在线监测与早期污染预警系统的发展。生物监测可以对污染环境下多污染物的联合毒性进行有效评估,具有传统化学监测所不具备的优点,已成为判定水质是否对水生生物存在影响、是否符合人类安全饮用的有效依据和手段。介绍了大型蚤在线生物监测系统的多通道流通生物测试室和生物传感器系统,并对世界范围内的研究与应用情况做了研究综述。目前,采用大型蚤作为指示生物的在线监测系统已在饮用水水质监测方面成功实现,但其在工业废水接管过程中毒性评估和早期预警的研究和应用上尚有不足,有待更加深入地探讨与研究。     

Archetypes of famine and response

Famines have long been characterised by rapidly shifting dynamics: sudden price spirals, sharp increases in mortality, the media frenzy that often accompanies such spikes, the swift scaling up of aid flows, and a subsequent decline in interest. In arguing that these aspects of famine have been largely ignored in recent years due to attention to the famine process', this paper attempts to make these dynamics more explicit by applying systems thinking. It uses standard archetypes of systems thinking to explain six situations—watch, price spiral, aid magnet, media frenzy, overshoot, and peaks—that are present in many famine contexts. It illustrates their application with examples from crises in Ethiopia, Malawi, Niger, and Sudan. The paper contends that the systems approach offers a tool for analysing the larger patterns in famines and for pinpointing the most appropriate responses to them, based on an awareness of the dynamics of the crises.