永磁铁近场等效阻尼计算分析

目的探究相对速度对等效电涡流阻尼效应的影响规律。方法利用解析法和有限元法分别分析了柱塞型电涡流吸振器的动态电磁场分布和电涡流等效阻尼效应,并基于有限元法分析了永磁铁在不同运动速度下的等效阻尼效应。结果有限元法求解电涡流等效阻尼的精度更高,相对运动速度对等效电涡流阻尼系数有相应非线性影响规律。结论解析法认为的恒定磁场实际中是不存在的,等效电涡流分布和强度高度依赖于磁装置的运动特性。     

基于PT-IE的区域性企业整体应急准备能力评估分析

针对传统评估方法在评价区域性企业整体应急能力的过程中未考虑评价者心理偏好与风险因素之间的关系,提出了1种基于前景理论(PT)与信息熵(IE)的评价模型,并设计了企业生产安全事故应急准备能力评价体系。首先以区属整体企业为单位构建心理损益矩阵,然后运用信息熵理论修正指标权重结构,最后依据前景理论计算得出各区、各指标的综合前景值并以此分析排序。实例表明:影响各区企业整体应急水平的共性问题在于应急组织体系不完善和应急救援力量不足,该模型对政府监管部门有针对性的分析和加强地区企业整体应急建设水平具有一定的指导意义。     

A system dynamics urban water management model for Macau, China

Urban water resources have been facing significant pressure from population growth, urbanization, and climate change. A system dynamics urban water management model was proposed to simulate the dynamic interactions between urban water demands and society, economy, climate, and water conservation. The residents'' water conservation willingness was incorporated in the model and water-saving effects were quantified. The simulation results for Macau showed that population size was the main driving force for urban water demand. The change of temperature and precipitation has obvious effects on the landscape water demand. The water demand output is sensitive to the change in population, per capita demand, and temperature. Increased precipitation will reduce urban water demand and increased economic growth will increase water demand. By implementing integrated water conservation measures and improved water conservation willingness, water demand could be reduced by 17.5%.     

初始pH值和物料配比对高温混料厌氧发酵进程的影响

为了研究高温条件下初始p H对厌氧发酵进程的影响,以猪粪、玉米秸秆为发酵原料,设置3种比例(干物质质量比30∶70、50∶50、70∶30)下6个水平(6.0、6.5、7.0、7.5、8.0的初始p H值以及一个不调控初始p H的处理作为对照)进行批次发酵试验.结果表明,初始p H值和物料配比都会显著影响厌氧发酵过程的启动时间和甲烷产量.当初始p H值为7.0时,VS降解率趋于稳定.COD去除率随着粪便含量的增加而逐渐降低.高温猪粪玉米秸秆混合发酵最佳挥发性脂肪酸(VFA)/碱度比值范围为0.05~0.3;猪粪可以作为一种缓冲材料,适量添加可增大消化系统的缓冲能力.通过建模优化,预测出当初始p H值为6.95、猪粪/玉米秆为70∶30时,可得到每克挥发性固体最大理论单位甲烷产量169.22 m L·g-1.     

Water uptake of multicomponent organic mixtures and their influence on hygroscopicity of inorganic salts

The hygroscopic behaviors of atmospherically relevant multicomponent water soluble organic compounds(WSOCs) and their effects on ammonium sulfate(AS) and sodium chloride were investigated using a hygroscopicity tandem differential mobility analyzer(HTDMA) in the relative humidity(RH) range of 5%–90%. The measured hygroscopic growth was compared with predictions from the Extended-Aerosol Inorganics Model(E-AIM) and Zdanovskii–Stokes–Robinson(ZSR) method. The equal mass multicomponent WSOCs mixture containing levoglucosan, succinic acid, phthalic acid and humic acid showed gradual water uptake without obvious phase change over the whole RH range. It was found that the organic content played an important role in the water uptake of mixed particles.When organic content was dominant in the mixture(75%), the measured hygroscopic growth was higher than predictions from the E-AIM or ZSR relation, especially under high RH conditions. For mass fractions of organics not larger than 50%, the hygroscopic growth of mixtures was in good agreement with model predictions. The influence of interactions between inorganic and organic components on the hygroscopicity of mixed particles was related to the salt type and organic content. These results could contribute to understanding of the hygroscopic behaviors of multicomponent aerosol particles.     

改性生物炭对Ni~(2+)和Cu~(2+)的吸附

以废弃松木屑为原料制备了生物炭,采用六亚甲基四胺(HMTA)和/或CO2对其进行改性,并将其用于水中Ni2+和Cu2+的吸附。表征结果显示,以HMTA和CO2共同改性的生物炭BC1的表面积最小但表面含氧官能团含量最高。实验结果表明:生物炭经改性后,其吸附性能明显提高,且以BC1为最优;在不调节溶液p H、初始重金属离子质量浓度为50 mg/L、吸附剂加入量分别为2.0 g/L和1.0 g/L、吸附时间分别为360 min和240 min的优化条件下,BC1对Ni2+和Cu2+的去除率分别达到99.81%和95.88%;改性生物炭对Ni2+和Cu2+的吸附过程可以用Langmuir等温吸附模型来描述,而其吸附动力学具有拟二级动力学方程特征。     

Accumulation and phytotoxicity of technical hexabromocyclododecane in maize

To investigate the accumulation and phytotoxicity of technical hexabromocyclododecane(HBCD)in maize,young seedlings were exposed to solutions of technical HBCD at different concentrations.The uptake kinetics showed that the HBCD concentration reached an apparent equilibrium within 96 hr,and the accumulation was much higher in roots than in shoots.HBCD accumulation in maize had a positive linear correlation with the exposure concentration.The accumulation of different diastereoisomers followed the orderγ-HBCDβ-HBCDα-HBCD.Compared with their proportions in the technical HBCD exposure solution,the diastereoisomer contribution increased forβ-HBCD and decreased forγ-HBCD in both maize roots and shoots with exposure time,whereas the contribution ofα-HBCD increased in roots and decreased in shoots throughout the experimental period.These results suggest the diastereomer-specific accumulation and translocation of HBCD in maize.Inhibitory effects of HBCD on the early development of maize followed the order of germination rateroot biomass≥root elongationshoot biomass≥shoot elongation.Hydroxyl radical(OH)and histone H2AX phosphorylation(γ-H2AX)were induced in maize by HBCD exposure,indicative of the generation of oxidative stress and DNA double-strand breaks in maize.An OH scavenger inhibited the expression ofγ-H2AX foci in both maize roots and shoots,which suggests the involvement of OH generation in the HBCD-induced DNA damage.The results of this study will offer useful information for a more comprehensive assessment of the environmental behavior and toxicity of technical HBCD.     

臭气强度在恶臭污染物环境空气影响中的应用研究

以兰州某石化公司化工污水处理厂恶臭治理项目为例,在确定恶臭气体的污染源源强的基础上,采用AERMOD模式预测污染物扩散情况。结果表明,添置除臭装置后,NH3的臭气浓度减少了90%,VOCs的臭气浓度减少了88%。同时,当恶臭污染物浓度达到环境质量浓度标准时,NH3的臭气强度为1．40级,VOCs的臭气强度为0．82级,人们仍能感觉到气味。因此石化企业在进行恶臭治理过程中需综合考虑污染物的环境空气质量浓度标准和臭气强度,以期改善环境空气质量。     

Association between population density and infection rate suggests the importance of social distancing and travel restriction in reducing the COVID-19 pandemic

Environmental Science and Pollution Research - Currently, 2019-nCoV has spread to most countries of the world. Understanding the environmental factors that affect the spread of the disease COVID-19...