煅烧温度及冷却条件对造纸污泥灰火山灰活性的影响

通过结合水率和水泥胶砂强度实验,研究了煅烧温度、冷却方式对造纸污泥灰火山灰活性的影响,并结合X射线衍射、红外光谱、扫描电镜对污泥灰矿物组成、化学结构及微观形貌进行了研究。结果表明：高温煅烧和水淬处理均可有效提高造纸污泥的火山灰活性,最合理的煅烧温度为950 ℃左右;当煅烧温度从450 ℃提高至850 ℃,污泥灰主要矿物为方解石、石英、利蛇纹石、刚玉和硅灰石,温度升高至950 ℃、1 050 ℃,方解石衍射峰消失,弥散峰增强,污泥灰微观结构变得疏松,大部分晶体转变为玻璃体;相比空气冷却,水淬急冷处理的污泥灰含有更多玻璃体及微观孔隙,火山灰活性更高。     

Impact of local flame quenching on the flame acceleration in H2-CO-air mixtures in obstructed channels

In accident scenarios originating from weak ignition, flame acceleration preconditions the fresh gas ahead of the flame front and provides the necessary conditions for deflagration-to-detonation transition to occur. Strong shear layers, which form at the rear edge of obstacles in the accelerated flow of fast flames, isolate fresh gas pockets. Vortices in the intense shear layer have the potential to locally quench the flame, limiting the integral heat release and delaying the onset of detonation.This study investigates the potential of local turbulent quenching in H${}_2$-CO-air mixtures. First, the presence of locally reduced heat release is visualized in highly resolved simulations for H${}_2$-air and H${}_2$-CO-air flames. Efficient simulation methods are of great importance for risk analysis studies. In connection with the results from highly resolved simulations this justifies a more detailed look at RANS-based combustion models for said flames. Thus, three different treatments of turbulent quenching are investigated, in which the geometrical configuration (blockage ratio and obstacle spacing) and the geometry size is varied.The results indicate that quenching does not need to be considered in RANS-based combustion models for H${}_2$-CO-air flames in explosion scenarios. But since quenching does eventually occur at very high turbulence intensities, the authors suggest limiting the flame turbulence interaction to flame stretch values obtained from 1D counter-flow flame simulations with detailed chemistry.     

Rethinking the native range concept

A species is not native outside its native range, but native range is not precisely defined. The invasion literature contains wide discussion of the core concepts such as naturalization, invasiveness, and ecological impact, but the concept of native range has received so little attention that a formal definition does not exist. I considered, among other impediments to a formal definition of native range, the sometimes arbitrariness of the spatial and temporal limits assigned to native range. Broad questions that remain include whether invasion theory can be used to define the native range for species without non-native ranges.     

What is a static head measurement? Evaluating structural error and implications for regional groundwater modeling

Most groundwater modelers avoid using static heads measured from active production wells because they can introduce a bias into model calibration. However, in the deep confined Cambrian-Ordovician Sandstone Aquifer System in the Central Midcontinent of North America, dedicated observation wells are sparse and remote from areas of most concentrated pumping. As a result, in areas where drawdown is the greatest and modeling is most needed, only static heads from production wells are available for calibration. This paper evaluates two leading sources of discrepancies in using production well data, spatial and temporal structural error (S.E.). A simple Theis solution is used to evaluate the potential magnitude of spatial S.E. when calibrating a regional MODFLOW model with coarse cell resolution. Despite theoretical analyses indicating that spatial S.E. could be significant, statistical analysis of the model results suggests that temporal S.E. is dominant. Long (ranging over decades) or frequent (monthly) head datasets are key in understanding temporal S.E., to better capture water-level variability. In this study, the range in static head observations impacted estimates of the remaining time a well could extract water from the aquifer by 0.1 to 16.0 years. This uncertainty in future water supply is highly relevant to stakeholders and must be assessed in hydrographs depicting risk.     

Disentangling the causes of protected‐species bycatch in gillnet fisheries

Gillnet fisheries are widely thought to pose a conservation threat to many populations of marine mammals, seabirds, and turtles. Gillnet fisheries also support a significant proportion of small‐scale fishing communities worldwide. Despite a large number of studies on protected‐species bycatch in recent decades, relatively few have examined the underlying causes of bycatch and fewer still have considered the issue from a multitaxon perspective. We used 3 bibliographic databases and one search engine to identify studies by year of publication and taxon. The majority of studies on the mechanisms of gillnet bycatch are not accessible through the mainstream published literature. Many are reported in technical papers, government reports, and university theses. We reviewed over 600 published and unpublished studies of bycatch in which causal or correlative factors were considered and identified therein 28 environmental, operational, technical, and behavioral factors that may be associated with high or low bycatch rates of the taxa. Of the factors considered, 11 were associated with potential bycatch reduction in 2 out of the 3 taxa, and 3 factors (water depth, mesh size, and net height) were associated with trends in bycatch rate for all 3 taxa. These findings provide a basis to guide further experimental work to test hypotheses about which factors most influence bycatch rates and to explore ways of managing fishing activities and improving gear design to minimize the incidental capture of species of conservation concern while ensuring the viability of the fisheries concerned.     

某输出缓冲器的失效分析

本文通过对某输出缓冲器在质量一致性检验中的ESD考核环节失效的情况进行分析,找到了产品测试系统的异常情况,通过此次分析,进一步发现该产品的ESD保护设计一直以来存在的问题。文中不仅给出了失效机理,同时提出了改进措施并加以验证。此次失效分析对于同类器件的ESD保护设计,提高其可靠性具有一定的借鉴意义。     

硫磺研磨起电特性的研究

工业生产硫磺粉的过程中,由于静电等因素导致生产过程中容易发生燃烧爆炸事故。本文就是为硫磺粉的生产安全进行基础研究。国内硫磺粉爆炸事故几乎一个月发生一次,给设备和人员带来很大的安全威胁。不同材料的特性是不同的,摩擦产生静电的情况也不一样,本实验主要研究硫磺粉和粉碎设备中主要材料摩擦产生静电的情况,了解硫磺粉的静电特性,为减少静电的产生或者消除静电寻找途径。硫磺粉碎设备———机械磨中主要的材料类型是不锈钢、刚玉和碳化钨,用这三种材料制成的研磨罐对硫磺粉进行研磨,测试表明硫磺全部带负电荷,碳化钨罐研磨起电效率最高,刚玉罐起电效果最小,静电量会随着时间的增加达到平衡。用不同粒径的硫磺粉进行研磨,实验表明粒径较大的硫磺粉比粒径小的硫磺粉产生的静电略少。     

聚烯烃工业粉尘静电爆炸的危险与应对策略

随着我国聚烯烃粉体生产的迅猛发展,粉体生产过程中的静电爆炸事故也相应增多。该文介绍了国外粉尘静电爆炸研究的进展和国内粉尘静电爆炸事故的主要现象。近期国外的研究特点主要是逐渐采用工业规模的实验装置取代实验室的基础研究,着重开展了料仓放电的危险研究和与放电燃爆有关的基础研究,包括安全评价和工业控制条件的推荐研究。国内粉尘静电爆炸事故主要存在的现象有设计缺欠或不合理,装置扩能改造时忽视了脱挥或通风的配套改造,处理不合格料或过渡时应急处理不当,操作失误或不规范,破坏料仓通风控制,料位计选型不当,增加高能放电引燃几率。针对分析出的问题和现象,文章提出了查清运行装置的具体事故隐患,进行防止聚烯烃料仓粉尘静电爆炸的可接受研究和可操作性研究,开展粉尘静电爆炸的危险教育,提高员工的安全意识和应急处理能力等应对策略。     

紫外老化微塑料衍生DOM理化特性及其与磺胺嘧啶、铜的络合机制

微塑料在老化过程中所释放的溶解性有机质(MPDOM)可与有机污染物、重金属等污染物发生络合反应,影响污染物的迁移转化.选取聚对苯二甲酸乙二醇酯(PET)和聚苯乙烯(PS)两种微塑料,利用荧光猝灭法及多种光谱分析技术和方法,同时结合Ryan-Weber模型,探究了MPDOM的光谱特性以及MPDOM与磺胺嘧啶(SDZ)、铜离子(Cu²⁺)的络合机制.紫外-可见吸收光谱分析结果表明,老化后两种MPDOM的相对分子量减小、芳香性及腐殖化程度增加,芳环上的羧基、羰基、羟基及酯类取代基增多.MPDOM与SDZ、 Cu²⁺的荧光猝灭均属于静态猝灭,猝灭后两种MPDOM的芳香性和腐殖化程度相近,相对分子质量相当.三维荧光光谱结合平行因子分析法共鉴定出两种类腐殖质组分和一种类蛋白质组分.同步荧光光谱分析结果表明,两种MPDOM均以类蛋白组分优先与SDZ发生反应,与Cu²⁺反应时更为敏感.结合Ryan-Weber模型可知,两种猝灭体系均以类腐殖质组分与PET-DOM的结合能力更高,但总体来说SDZ猝灭体系中MPDOM的结合能力要强于Cu     

城市黑臭河道夏季产甲烷通量研究——以南宁市朝阳溪为例

利用静态箱法测定城市黑臭河道!南宁市朝阳溪夏季产甲烷通量,结果表明朝阳溪是重要的甲烷排放源,夏季甲烷排放通量平均值为12.2mg/(m2·h),上游、中游、下游排放通量变化不显著。利用偏最小二乘法进行相关性分析可得,甲烷通量与温度、化学需氧量、底泥有机碳呈显著正相关,与溶解氧呈显著负相关,与总氮、氨氮、总磷、pH相关性较小。