长直水平管道中铝粉/空气混合物爆炸试验研究

在长为32.4 m,内径为0.199 m的大型长直水平管道中对铝粉/空气两相流的爆炸过程进行了试验研究.试验初始压力为0.14MPa,初始温度为20℃,水平布置17个传感器对试验数据进行测量记录.采用40J电火花进行点火,对铝粉/空气混合物燃烧转爆轰过程(DDT)进行分析,并对不同质量浓度时混合物的燃爆情况进行比较.结果表明:铝粉质量浓度为184 g/m3时,铝粉/空气混合物未被引燃;铝粉质量浓度为230 g/m3时,水平管道末端刚好进入爆轰阶段,此质量浓度为该条件下燃烧转爆轰的最低临界质量浓度;质量浓度为276g/m3、367 g/m3、459 g/m3 505g/m3、551 g/m3、643 g/m3时,均能在此水平管道内完成爆燃向爆轰的转变,并且能够自持.铝粉/空气混合物爆轰的最优质量浓度为551 g/m3.对质量浓度为505 g/m3时的铝粉/空气混合物的燃烧转爆轰过程进行分析,进入爆轰阶段后,多相燃料空气混合物爆轰超压和速度曲线呈现随距离传播不断振荡,但均值稳定的典型特征,其爆轰波胞格尺寸λ约为0.486m.     

拟南芥硫酯酶基因(atfata)在大肠杆菌中的表达及其对游离脂肪酸合成的影响

硫酯酶催化脂酰ACP(酰基载体蛋白)水解生成游离脂肪酸和ACP载体蛋白,能够解除脂肪酸合成与磷脂合成的偶联,是获得游离脂肪酸的关键基因.将拟南芥的硫酯酶基因atfata克隆到原核表达载体pET30a上,在大肠杆菌BL21(DE3)中成功表达了His-tag融合蛋白,经SDS-PAGE检测获得特异性表达条带.对该重组菌株进行摇瓶发酵实验,GC-MS检测表明其与对照菌株脂肪酸组成并未发生变化;但其脂肪酸产量达到232.06 mg/L,比对照菌株提高了70%;同时胞外游离脂肪酸产量达到了33 mg/L,占总脂肪酸含量的15%,是野生菌株胞外脂肪酸产量的7倍.图3表2参17     

Effect of Na+ impregnated activated carbon on the adsorption of NH4+-N from aqueous solution

Two kinds of activated carbons modified by Na+ impregnation after pre-treatments involving oxidation by nitric acid or acidification by hydrochloric acid (denoted as AC/N-Na and AC/HCl-Na, respectively), were used as adsorbents to remove NH4+-N. The surface features of samples were investigated by BET, SEM, XRD and FT-IR. The adsorption experiments were conducted in equilibrium and kinetic conditions. Influencing factors such as initial solution pH and initial concentration were investigated. A possible mechanism was proposed. Results showed that optimal NH4+-N removal efficiency was achieved at a neutral pH condition for the modified ACs. The Langmuir isotherm adsorption equation provided a better fit than other models for the equilibrium study. The adsorption kinetics followed both the pseudo second-order kinetics model and intra-particle kinetic model. Chemical surface analysis indicated that Na+ ions form ionic bonds with available surface functional groups created by pre-treatment, especially oxidation by nitric acid, thus increasing the removal efficiency of the modified ACs for NH4+-N. Na+-impregnated ACs had a higher removal capability in removing NH4+-N than unmodified AC, possibly resulting from higher numbers of surface functional groups and better intra-particle diffusion. The good fit of Langmuir isotherm adsorption to the data indicated the presence of monolayer NH4+-N adsorption on the active homogenous sites within the adsorbents. The applicability of pseudo second-order and intra-particle kinetic models revealed the complex nature of the adsorption mechanism. The intra-particle diffusion model revealed that the adsorption process consisted not only of surface adsorption but also intra-particle diffusion.     

Modeling study on the roles of the deposition and transport of PM2.5 in air quality changes over central-eastern China

The role of PM_2.5 (particles with aerodynamic diameters ≤ 2.5 µm) deposition in air quality changes over China remains unclear. By using the three-year (2013, 2015, and 2017) simulation results of the WRF/CUACE v1.0 model from a previous work (Zhang et al., 2021), a non-linear relationship between the deposition of PM_2.5 and anthropogenic emissions over central-eastern China in cold seasons as well as in different life stages of haze events was unraveled. PM_2.5 deposition is spatially distributed differently from PM_2.5 concentrations and anthropogenic emissions over China. The North China Plain (NCP) is typically characterized by higher anthropogenic emissions compared to southern China, such as the middle-low reaches of Yangtze River (MLYR), which includes parts of the Yangtze River Delta and the Midwest. However, PM_2.5 deposition in the NCP is significantly lower than that in the MLYR region, suggesting that in addition to meteorology and emissions, lower deposition is another important factor in the increase in haze levels. Regional transport of pollution in central-eastern China acts as a moderator of pollution levels in different regions, for example by bringing pollution from the NCP to the MLYR region in cold seasons. It was found that in typical haze events the deposition flux of PM_2.5 during the removal stages is substantially higher than that in accumulation stages, with most of the PM_2.5 being transported southward and deposited to the MLYR and Sichuan Basin region, corresponding to a latitude range of about 24°N-31°N.     

Fringe View: Problems and Construction of Human Settlement Environment for Village-in-City

1 INTRODUCTIONAs a special pattern of community in city, "village-in-city"has objectively existed for many years, but it is only inrecent years that the phenomenon of "village-in-city" hasreally aroused the attention of scholars, government andmedia. The attention of government and media is mainlyfocused on the urban managerial problems that areproduced by "village-in-city", while the academic circlestry to explain the phenomenon of "village-in-city" andput forward measures in the academic…     

Polycyclic aromatic hydrocarbons in farmland soils around main reservoirs of Jilin Province,China: occurrence,sources and potential human health risk

Study on the occurrence, sources and potential human health risk of polycyclic aromatic hydrocarbons in farmland soils around reservoirs is of great significance for the people drinking water security. In the present study, representative farmland soil samples around main reservoirs of Jilin Province, China, were investigated for 16 PAHs. The total concentrations of 16 priority PAHs in 32 farmland soil samples ranged from 602.12 to 1271.87 ng/g, with an arithmetic average of 877.23 ng/g, and the sum of seven carcinogenic PAH concentrations ranged from 30.07 to 710.02 ng/g, with a mean value of 229.04 ng/g. The 3-ring and 4-ring PAHs were major exist and account for 45.78 and 32.03%, respectively. Non-cancer and cancer risk of pollutants were calculated, and the results indicate that the complex PAHs in farmland soils were not considered to pose significant health effects. The isomer ratios Fla/(Fla + Pyr) and BaA/(BaA + Chr) show that the PAHs in soils were generally derived from biomass and coal combustion.     

Enhanced styrene recovery from waste polystyrene pyrolysis using response surface methodology coupled with Box–Behnken design

A work applied response surface methodology coupled with Box–Behnken design (RSM-BBD) has been developed to enhance styrene recovery from waste polystyrene (WPS) through pyrolysis. The relationship between styrene yield and three selected operating parameters (i.e., temperature, heating rate, and carrier gas flow rate) was investigated. A second order polynomial equation was successfully built to describe the process and predict styrene yield under the study conditions. The factors identified as statistically significant to styrene production were: temperature, with a quadratic effect; heating rate, with a linear effect; carrier gas flow rate, with a quadratic effect; interaction between temperature and carrier gas flow rate; and interaction between heating rate and carrier gas flow rate. The optimum conditions for the current system were determined to be at a temperature range of 470–505 °C, a heating rate of 40 °C/min, and a carrier gas flow rate range of 115–140 mL/min. Under such conditions, 64.52% WPS was recovered as styrene, which was 12% more than the highest reported yield for reactors of similar size. It is concluded that RSM-BBD is an effective approach for yield optimization of styrene recovery from WPS pyrolysis.     

A geospatial model of forest dynamics with controlled trend surface

This paper proposes a method of controlled trend surface to simultaneously account for large-scale spatial trends and non-spatial local effects. With this method, a geospatial model of forest dynamics was developed for the Alaska boreal forest from 446 constantly monitored permanent sample plots. The geospatial component of this model represented large-scale spatial trends in recruitment, diameter growth, and mortality. The model was tested on two sets of validation plots which represented temporal and spatial extensions of the current sample coverage. The results suggest that the controlled trend surface model was generally more accurate than both the non-spatial and conventional trend surface models. With this model, we mapped the forest dynamics of the entire Alaska boreal region by aggregating predicted stand states across the region. It was predicted that under current conditions of climate and natural disturbances, most of the Alaska boreal forest region may undergo a major shift from deciduous-dominant to conifer-dominant, with an average increase of 0.33 m² ha year⁻¹ in basal area over the Twenty-First Century.     

电子垃圾拆解地翠鸟对多氯联苯的累积及风险评估

粗犷的电子垃圾拆解活动已造成当地野生生物多氯联苯(PCBs)严重污染,但PCBs在野生鸟类中的生物累积特征及潜在的毒害作用研究较少。本研究采集了广东省某电子垃圾拆解地翠鸟(Alcedo atthis)及其食物(各种小型鱼类)样品,研究翠鸟对PCBs的累积特征、生物放大效应及毒性风险。翠鸟肌肉中PCBs中值含量为220μg·g~(-1)脂重,比其他报道值高1~3个数量级。计算的生物放大因子(BMF)显示,大部分PCB单体的BMF值都大于1,表明翠鸟对PCBs具有生物放大效应。计算的共面PCBs毒性当量(TEQs)范围为39~23 600 pg·g~(-1)湿重,已经达到或超过了影响某些鸟类生殖或发育障碍的报道值。上述结果表明,电子垃圾拆卸活动已经造成了当地翠鸟PCBs严重污染,PCBs污染物对电子垃圾拆解地翠鸟及其他野生生物的毒性效应尚需进一步研究。     

电石渣中杂质对亚硫酸钙氧化及石膏浆液脱水性能影响

为了考察电石渣中杂质(Na2S、SiO2及铁、镁、铝的氧化物等)在湿法烟气脱硫过程中对亚硫酸钙氧化及石膏浆液脱水性能的影响,通过建立亚硫酸钙氧化反应装置,对亚硫酸钙氧化及石膏浆液脱水过程进行了研究。研究表明:浆液中Na2S浓度越高,亚硫酸钙氧化受到的抑制作用越明显,Na2S浓度高于10.0 mmol/L时,浆液中亚硫酸根几乎不发生氧化反应,石膏平均粒径随Na2S浓度增加呈先降低后增大趋势。浆液中SiO2不影响亚硫酸钙氧化,但是浓度低于0.5 g/L时,石膏粒径分布更加集中,更有利于提高石膏浆液脱水性能。浆液中Fe2O3的存在有利于亚硫酸钙氧化,浓度在0.5～1.0 g/L时,对石膏浆液脱水性能有明显的改善作用。浆液中MgO、Al2O3的存在,对亚硫酸钙氧化影响不大,但降低了石膏浆液脱水性能。