不同基质浓度对ANAMMOX菌短期储存的影响

在15℃±1℃条件下,将厌氧氨氧化菌混培物分别置于基质浓度为0、60、120 mg·L~(-1)添加比例为1∶1的NH+4-N和NO-2-N环境中短期(15 d)储存,探究不同基质浓度对厌氧氨氧化污泥短期保存及恢复的影响.经过短期储存后进行恢复实验,结果表明,1、2、3号反应器(分别对应0、60、120 mg·L~(-1)基质浓度中储存的厌氧氨氧化菌混培物)中的厌氧氨氧化活性分别下降41. 8%、17. 4%、33. 4.%,1、3号分别由于过度内源呼吸和高基质浓度抑制,导致活性下降较大,2号反应器由于基质浓度相对合适,避免了过度内源呼吸和高基质浓度抑制,使得菌种活性在该基质浓度下保留较好;储存期间,3个反应器内均发生内源呼吸消耗自身有机物的情况,导致EPS含量下降50. 9%、41. 7%、23. 7%和粒径下降31. 6%、16. 7%、8. 2%,表明在基质匮乏期菌体通过内源呼吸的方式维持自身的活性,较高的基质浓度可以在一定程度上延缓内源呼吸过程;在恢复期间,3个反应器分别经过15、10、7 d实现脱氮性能和厌氧氨氧化活性的恢复,表明同菌种增殖富集相比,原系统通过菌种活性增强的方式脱氮性能恢复更快.     

基于GRACE数据的中国水储量变化特征分析

论文以中国2003—2015年GRACE水储量数据、GLDAS-Noah地表蒸散发数据、地面实测降水数据为数据源,基于Theil-Sen Median 趋势分析和Mann-Kendall检验法,分析了中国水储量、降水量以及蒸散发量的变化趋势及相关关系,并利用经验正交函数（EOF）分析了中国水储量变化时空分布特征,结果表明：1） 2006年以后中国整体水储量年际变化剧烈,且降水和蒸散发可以识别水储量异常时段内的特征信息;2） 2003—2015年全国各地水储量、降雨量和蒸散发量变化空间分布差异明显;3） 全国共有18.6%的地区气候因素对水储量变化的方差解释量超过50%,主要位于中国东北、东南沿海、四川盆地、青海高原以及新疆西北部地区;4） EOF分解的GRACE水储量各主成分信息可以表征研究时段内中国地区整体和局部的水储量时空变化特征。     

Prevention of gasoline vapor explosions in portable fuel containers

Portable Fuel Containers (PFCs) made for consumer use can, under unusual circumstances, develop a flammable atmosphere in the container headspace. In order to prevent an inadvertent ignition from causing flame propagation into this headspace and a subsequent explosion or flame jetting, PFC manufacturers are developing prototype Flame Mitigation Devices (FMDs) for installation in the PFC. A test method is described in this paper to determine if the installed FMD will indeed prevent flame entry into the PFC in a high-challenge flame propagation scenario. The method entails the use of a butane-air mixture ignited in a 5 cm diameter, 12 cm long tube attached to either the container neck or a spout on the container neck. Two concept FMD designs have successfully prevented repeated attempts at flame propagation into the PFC and have also produced encouraging results in tests for fuel flow restriction, duel dispensing nozzle friction, and prolonged fuel exposure. Versions of these tests are currently being promulgated in a draft ASTM standard on PFC FMDs.     

Ignition temperatures of dust layers and bulk storages in hot environments

In many industrial installations, particulate solids (cereals, agri-food products, coal, plants, etc.) are stored or processed. Self-heating of these products, which can lead to fires and explosions, can occur in a variety of situations. Examples include large storage at room temperature, formation of a layer on a hot surface, layer deposited on a surface – insulating or conductive – in a hot environment or even storage of product exposed to heating on one side.The main parameters that determine the occurrence of self-heating are the size of the container, the temperature, the residence time and the characteristics of the product. Depending on the type of situation encountered and these implementation conditions, the analysis of self-heating risks must be based on specific models and/or parameters.This paper presents the different variants and combinations of the theoretical model from the theory of thermal runaway to represent self-heating, taking into account in particular the symmetry or asymmetry of heating, reagent consumption and boundary conditions. It also discusses their adaptation to the previous identified industrial situations.Nine products were chosen to be representative of those used in the different considered industrial situations. They were subjected to self-heating basket tests in isothermal ovens in order to determine the parameters for applying the described theoretical models. These results were compared with the results of self-heating tests in layers of different thicknesses in a hot environment, on an insulating or conductive plate, using a specially developed test protocol, as well as with the results of standardized tests of minimum ignition temperature in 5 mm layers.This led to the proposal of the most appropriate theoretical model to represent the self-heating phenomenon for each of the four identified industrial situations.This analysis can promote better design of industrial equipment and production conditions (temperatures, volumes or product flows …) in order to prevent fires and explosions.     

基于维纳过程的MEMS陀螺仪贮存寿命评估

目的 针对MEMS陀螺仪在步进应力加速试验条件下获取的性能退化数据,提出基于维纳过程的贮存寿命评估方法及其模型准确度检验方法。方法 首先,确定温度为影响MEMS陀螺仪性能退化的主要环境因素,采用步进温度应力加速试验的方式获取其性能退化数据。其次,分析各项性能参数的演变规律,确定标度因数为表征产品性能退化的特征性能参数。最后,采用漂移维纳过程对标度因数退化轨迹进行建模,并外推得到常温条件下的贮存寿命。结果 采用留一法对模型精度进行验证,模型准确度最低为86.44%。可靠度水平为0.95时,常温贮存(25 ℃)条件下的寿命评估结果为50.02 a。结论 基于维纳过程建立的性能退化模型的准确度在85%以上,该模型可应用于指定贮存条件下MEMS陀螺仪的性能退化预测及贮存寿命评估。     

相变储能光伏太阳能热泵干燥系统的研究

建立了相变储能光伏太阳能热泵干燥系统实验平台,介绍了系统的运行方式以及太阳能光伏集热蒸发器与直流压缩机的匹配计算,最后对实验数据进行了分析。结果表明,太阳能辐照量为800 W/m~2、光伏集热蒸发器面积为12 m~2的条件下,系统制热功率为10 k W,太阳能光伏集热蒸发器发电量为6.2 k W·h,大于直流压缩机的耗电量,满足供电要求;实验所得系统COP为3.25。相变储能可以解决太阳辐照波动导致的系统运行不稳定问题,具有显著的节能性和环保性。     

某型硬质泡沫塑料弹架结构长贮特性和本构关系研究

目的研究一类硬质泡沫塑料弹架结构的贮存特性和本构关系。方法首先对结构试件进行高温压缩蠕变试验,然后对压缩后试件蠕变性能进行分析,得到材料高温压缩蠕变曲线,在此基础上用WLF方程对试件的贮存寿命进行评估,推算出试件达到特定蠕变量所需时间。结果基于试验所得材料应力-应变曲线,用数值拟合的方法建立了试件材料的压缩本构关系。结论证实了在高温压缩蠕变试验过程中材料本构关系未发生变化,研究结果可为后续型号结构试件寿命评估和失效机理研究提供参考。     

中国西南喀斯特森林土壤有机碳空间变化及影响因素

喀斯特地区土壤碳储量及其影响因素的认识是评估我国陆地土壤生态系统碳汇能力不可或缺的内容。本文通过对中国西南北起秦岭北坡南至中越边境一条剖面上土壤有机碳的分析,研究了喀斯特森林0~10cm土壤有机碳空间变化及其控制因素。研究发现西南地区土壤有机碳含量和碳密度平均为32.3 g/kg和33.1t/hm2。无论是在整个西南区还是其省市范围内,二者均低于非喀斯特森林土壤。通径分析表明,影响喀斯特表层土壤碳含量和密度的主要因素有土壤容重、地形海拔和有机质C/N;粘粒含量和年平均气温的影响很小,而降水量仅在地处最北部的陕西省构成了土壤碳密度的影响因素。此现象与世界许多地区特别是高纬度地区形成鲜明对比。本研究结果表明,不同区域/气候带土壤碳库的主要影响因素会存在很大差异,这对认识气候变化背景下土壤碳库的反馈作用具有重要意义。     

长期施肥对棕壤有机碳储量及固碳速率的影响

利用棕壤肥料长期定位试验,研究了不同施肥条件下棕壤有机碳在0~60 cm土层的含量和储量特征以及土壤固碳速率.试验共设6个处理,即氮磷肥有机肥配施(M_2NP)、氮肥有机肥配施(M_2N)、单施有机肥(M_2)、单施氮肥(N)、氮磷肥配施(NP)和不施肥处理(CK).结果表明:经过31年长期不同施肥,各处理土壤有机碳(SOC)含量和储量的剖面分布均呈现随土层深度增加而显著降低的规律.本试验条件下M_2NP、M_2N、M_2、NP、N、CK处理的耕层有机碳富集系数分别为0.465、0.455、0.407、0.48_2、0.393、0.471,表明耕层土壤对有机碳的保持强度最强.在0~60 cm土层土壤有机碳储量表现为M_2NP、M_2NM_2、NPNCK,有机肥和化肥配施能够显著提高土壤有机碳含量和储量.与试验前相比,CK处理各土层土壤有机碳含量和储量均显著降低.各处理碳库管理指数(CPMI)表现为M_2NPM_2NM_2NNPCK.分析不同施肥处理土壤固碳速率可知,与试验前相比,CK处理表现为碳的净释放,固碳速率达-401.4 kg·hm~(-_2)·a~(-1);固碳速率最高的为M_2NP,M_2N,分别达到489kg·hm~(-_2)·a~(-1)、440._2 kg·hm~(-_2)·a~(-1).综合结果表明,化肥、有机肥配施所产生交互效应更有利于棕壤有机碳储量的增加及固碳速率的提高.     

Catastrophic Reproductive Failure, Terrestrial Survival, and Persistence of the Marbled Salamander

Abstract:  Wide variation in reproductive success is common among amphibians that breed in seasonal ponds, but persistence of adults can buffer against these fluctuations, particularly for long-lived species. We hypothesized that the frequent episodes of catastrophic failure of the marbled salamander ( Ambystoma opacum ) enhance the importance of high terrestrial survival. At Rainbow Bay in South Carolina reproductive success was poor (<1 metamorph/breeding female) in nearly half of the 22 years that the species bred. Complete failure occurred in 6 of 22 years. To study catastrophic failure, we adapted an age-structured, individual-based model with density-dependent growth and survival of larvae. The model was based on extensive data from local field studies and experiments. With consistently good survival in the pond stages, the simulated population required survival probabilities in the upland stages (juveniles and adults) near 0.5/year to persist and near 0.8/year to achieve the increases observed. Catastrophic failure, occurring randomly with probability 0.5/year, created additional fluctuations in the population, raised the thresholds of survival required for persistence, and caused extinction under conditions that were otherwise favorable. The marbled salamander at Rainbow Bay is not at great risk of extinction because of catastrophic failure, but the risk increases dramatically if life span is decreased or frequency of failure is increased. Any reduction in terrestrial survival will have deleterious consequences by reducing the breeding populations at equilibrium, even if it does not jeopardize persistence. Our model provides assessments of risk that can be applied to poorly studied species with similar life histories, such as the endangered flatwoods salamander ( A. cingulatum ).