给水管网中污染物在管垢上的累积和释放

给水管网中,管垢是各种污染物的源和汇,但目前污染物在管垢中的累积释放特征尚缺乏系统研究.本文以实际的城市供水管网的球墨铸铁管和灰口铸铁管为对象,一方面采用扫描电镜(SEM)、能谱分析(EDS)、晶体衍射结构分析(XRD)等手段对其管垢进行表征,另一方面运用管段滞流反应器研究了三氯甲烷、铅、锰和锌等污染物滞流状态下在管垢上累积和释放特征.结果表明:同为铸铁管,使用一定年限后,管垢成分有所差异,灰口管管垢量较大,具有明显的锈蚀和管瘤出现,成分以二氧化硅、金属复合氧化物为主,而球墨管管垢量较小,以二氧化硅为主;随着初始浓度的提高,管垢对污染物的累积量逐步提高,对于三氯甲烷,其吸附量和释放量都非常低,而对于Pb、Mn和Zn 3种金属,管垢的吸附量远大于释放量,说明在实验条件下它们易累积不易释放,但水质条件的改变有可能引起大规模释放.研究结果对饮用水管网生物化学安全提出了更高的要求,为管网的饮用水安全保障提供了理论依据.     

The Thermodynamic Performance of a Double-Acting Traveling-Wave Thermoacoustic Engine with Liquid-Water Piston

A double-acting traveling-wave thermoacoustic engine with liquid-water piston (DTTELP) was proposed by the authors. This article conducted numerical simulation on its performance for the cases of with and without acoustical loads. The effects of mean working pressure and water-piston mass on its non-load performance were firstly discussed. Then, the output performance of this novel thermoacoustic engine under fixed heating temperature was analyzed. Also, influences of different heating temperatures on the performance of this engine were discussed. According to the simulation, the novel double-acting thermoacoustic heat engine (TTHE) is very efficient and a maximum thermal efficiency can reach about 51% when the heating temperature is 1500 K.     

A novel approach combining bootstrapped non-intrusive reduced order models and unscented transform for the robust and efficient CFD analysis of accidental gas releases in congested plants

The risk assessment for safety-critical, complex systems is a very challenging computational problem when it is performed with high-fidelity models, e.g. CFD, like in the case of accidental gas releases in congested systems. Within this framework, a novel CFD approach, named Source Box Accident Model, has been recently proposed to efficiently model such phenomena by splitting the simulation of the gas release and its subsequent dispersion in the system in two steps. In this view, the present paper proposes a non-intrusive, Proper Orthogonal Decomposition-Radial Basis Functions reduced order model that exploits the two-step nature of the SBAM approach, to mimic the behaviour of the original, long-running CFD model code at a significantly lower computational cost. Moreover, the paper presents a methodology combining the bootstrap and unscented transform approaches to efficiently assess the ROM uncertainty in the safety-critical simulation output quantities of interest, e.g. the flammable volume. The results obtained in a test case involving a high pressure, accidental gas release in an off-shore Oil & Gas plant are in very satisfactory agreement with those produced by CFD, with a relative error smaller than 10% and a reduction in the computational time of about three orders of magnitude.     

Strategic 3-hydroxy-2-butanone release in the dominant male lobster cockroach, <Emphasis Type="Italic">Nauphoeta cinerea</Emphasis>

In the lobster cockroach Nauphoete cinerea, the dominant–subordinate hierarchy formed via the agonistic interactions is unstable, and changes in rank order are common. Our previous results showed that in the first encounter fight during initial rank formation, microgram levels of 3H-2B are released by the aggressive posture (AP)-adopting dominant male. In the present study, the pattern of daily pheromone (3H-2B) release during the domination period and on the day of rank switch, rank duration, and rank switch frequency were investigated in three-male groups and six-male groups to examine the effect of higher frequency of agonistic encounters. The results showed that, in the three-male groups (50-day observation period), daily 3H-2B release rate was not constant, but fluctuated, the average duration of dominant rank was 16.6 ± 2.0 days, rank switch occurred in 58.8% of groups, and the frequency of rank switching (average number of rank switches/group/50 days) was 1.4 ± 0.2. For the six-male groups (30-day observation period), the daily 3H-2B release rate also fluctuated, but the duration of dominant rank was significantly shorter at 4.2 ± 0.6 days, rank switch occurred in 100% of groups, and the frequency of rank switching (average number of rank switches/group/30 days) was significantly higher at 6.9 ± 0.6. The results for both sets of male groups showed that as a new rank formed (either on the first encounter day or on the day of rank switching), the dominant status was significantly associated with a higher 3H-2B release rate. In the animal kingdom, fighting usually involves communication or the exchange of signals, and the results of this study indicated that the fluctuating daily 3H-2B release rate adopted by the dominants is a kind of strategic release and the 3H-2B release rate is a signal used to determine dominance.     

纳米SiO2和发泡剂对聚氨酯防火涂料阻燃性能的影响

近几年来我国火灾的严重性已使木材阻燃成为一项紧迫任务.为了提高马尾松胶合板的阻燃性能,以聚氨酯为对象,采用HRR3热释放率系统、HC-2氧指数测定仪等测定了涂覆膨胀型纳米聚氨酯防火涂料的马尾松胶合板的燃烧热释放率和氧指数,分析了纳米SiO2以及各种发泡剂对聚氨酯防火涂料阻燃性能的影响,并分析它们的阻燃机理.结果表明,在聚氨酯防火涂料中加入纳米SiO2,可使涂覆的胶合板燃烧失重和炭化体积明显降低,有效地提高阻燃性能,纳米SiO2用量以3%为宜.加入发泡剂可进一步提高涂料的阻燃效果和氧指数值.复合发泡剂比单一发泡剂效果好.在8种试验方案中,用尿素-双氰胺按1∶3的质量比组成的复合发泡剂阻燃效果最优,在HRR3热释放率系统测试中,涂覆的胶合板着火燃烧时间最长(69 s),达最高热释放率时间最短(130 s),热释放率峰值最低(53.45 kW/m2),氧指数值最高(55).     

缓释复合肥在不同土壤水分条件下氨挥发特性研究

采用"通气法"室内培养试验研究了非包膜缓释复合肥(SRF)在不同土壤水分条件下的氨挥发损失状况和动力学特性以及盆栽试验条件下水稻生长和氮素利用效率.结果表明,SRF在淹水条件下氨挥发比不淹水处理提前3～4d到达峰值;且峰值和累积氨挥发量也比不淹水培养条件下高.与普通复合肥(CCF)相比,缓释复合肥的氨挥发损失量显著降低,不淹水条件下比等氮量CCF减少氨挥发50.6%和22.8%,淹水条件下比等氮量CCF减少氨挥发24.2%和10.4%,但是其氨挥发损失显著高于包膜缓释肥料(CRF).SRF的氨累积挥发量随施肥水平的增加而增大,其动力学特性可用一级动力学方程、Elovich方程和抛物线扩散方程定量描述.SRF、CCF和CRF各施肥处理在淹水条件下的水稻植株生物量分别比不淹水条件增加67.86%、78.25%和48.75%;氮素利用率分别比不淹水处理增加57.73%、80.70%和12.06%.在不淹水和淹水2种土壤水分条件下,施用SRF处理氮素利用率分别比CCF增加59.10%和10.40%.SRF能够降低氨挥发,提高植株生物量和氮素利用率.     

Controlled-release formulations of cyromazine-lignin matrix coated with ethylcellulose

An encapsulation system was developed and designed to give long-lasting effectiveness of the insect growth regulator cyromazine. Cyromazine was incorporated in lignin-poly (ethylene glycol) (PE) controlled-release formulations by means of a melting process. The basic formulation [lignin (65%)–PE (20%)–cyromazine (15%)] was coated in a Wurster-type fluidized-bed equipment using two different amounts of ethylcellulose. That of the highest one was modified by the addition of a plasticizer, dibutyl sebacate (DBS). The effect on cyromazine release rate caused by the incorporation of ethylcellulose and DBS in lignin-PE formulation was studied by immersion of the granules in water under static conditions. Using an empirical equation, the time taken for 50% of the active ingredient to be released into water (T₅₀) was calculated. From the analysis of the T₅₀ values, the influence of ethylcellulose appears clearly defined, observing a delay in release rate of cyromazine with respect to the basic lignin-PE formulation. In addition, the granules coated with ethylcellulose and the plasticizer lead the slowest release rate into water. The release of cyromazine into water is controlled by a diffusion mechanism. The thickness and permeability of the coating film are the most important factors that affect cyromazine release.     

Qualitative and quantitative determination of heavy metals in waste cellular phones

Twenty four waste cellular phones, manufactured between 2002 and 2011, were selected in order to determine the total heavy metal content in each of their parts (printed circuit boards (PCBs), plastic housing (PH) and liquid crystal display monitors (LCDs)) and compare the results with the permissible limits set by the 2003 Directive on Restriction of Hazardous Substances (RoHS). All the selected samples were pulverized and digested with strong acids. Inductively coupled plasma-mass spectrometry was used to measure the heavy metal content in each sample. The results revealed that concentration levels of the examined heavy metals were higher in PCBs, followed by PH and LCD in that particular order (PCB > PH > LCD). With the exception of Pb and Cr present in PCBs of mobile phones released before the year 2006, all the other metal concentrations were according to the Directive. Concentration levels of Cd, Hg were lower than the permissible limits set by the EU, either before or after the validity of the 2003 RoHS Directive. Considering their significant heavy metal content, coupled with their large quantities produced worldwide in an annual rate, waste cellular phones need to be treated under an environmentally sound management scheme, prioritizing recycling and at the same time eliminating the possibility of any harm.     

Liquid balance monitoring inside conventional,Retrofit, and bio-reactor landfill cells

The Outer Loop landfill bioreactor (OLLB) in Louisville, KY, USA has been the site of a study to evaluate long-term bioreactor performance at a full-scale operational landfill. Three types of landfill units were studied including a conventional landfill (Control cell), a new landfill area that had an air addition and recirculation piping network installed as waste was being placed (As-Built cell), and a conventional landfill that was modified to allow for liquids recirculation (Retrofit cell). During the monitoring period, the Retrofit, Control, and As-Built cells received 48, 14, and 213 L Mg^?1 (liters of liquids per metric ton of waste), respectively. The leachate collection system yielded 60, 57 and 198 L Mg^?1 from the Retrofit, Control, and As-Built cells, respectively. The head on liner in all cells was below regulatory limits. In the Control and As-Built cells, leachate head on liner decreased once waste placement stopped. The measured moisture content of the waste samples was consistent with that calculated from the estimate of accumulated liquid by the liquid balance. Additionally, measurements on excavated solid waste samples revealed large spatial variability in waste moisture content. The degree of saturation in the Control cells decreased from 85% to 75%. The degree of saturation increased from 82% to 83% due to liquids addition in the Retrofit cells and decreased back to 80% once liquid addition stopped. In the As-Built cells, the degree of saturation increased from 87% to 97% during filling activities and then started to decrease soon after filling activities stopped to reach 92% at the end of the monitoring period. The measured leachate generation rates were used to estimate an in-place saturated hydraulic conductivity of the MSW in the range of 10^?8 to 10^?7 m s^?1 which is lower than previous reports. In the Control and Retrofit cells, the net loss in liquids, 43 and 12 L Mg^?1, respectively, was similar to the measured settlement of 15% and 5–8% strain, respectively (Abichou et al., 2013). The increase in net liquid volume in the As-Built cells indicates that the 37% (average) measured settlement strain in these cells cannot be due to consolidation as the waste mass did not lose any moisture but rather suggests that settlement was attributable to lubrication of waste particle contacts, softening of flexible porous materials, and additional biological degradation.     

太湖内源释放及营养盐输运研究

从对流-扩散方程出发,通过公式推导,建立了包含底泥污染的水流-水质模型,对模型进行了率定和验证后,应用于太湖.该模型将湖泊水相和内源悬移相污染作为一个整体,结合污染物在悬移泥沙上的各种迁移过程,研究了太湖总氮、总磷内源释放的分布和数量,过程中考虑了悬移泥沙的各种影响因素,得到了较理想的模拟结果,当风速≤3.5 m/s时,冲刷和悬移造成的内源污染物释放量较小,内源污染物释放主要通过泥-水界面的静态释放;当风速>3.5 m/s时,冲刷和悬移造成的内源污染物释放量随风速增加迅速增大.通过计算得出2001年太湖内源释放的总氮为3.0万t,总磷为0.8万t.