Effects of soiling and cleaning on the reflectance and solar heat gain of a light-colored roofing membrane

A roof with high solar reflectance and high thermal emittance (e.g., a white roof) stays cool in the sun, reducing cooling power demand in a conditioned building and increasing summertime comfort in an unconditioned building. The high initial solar reflectance of a white membrane roof (circa 0.8) can be lowered by deposition of soot, dust, and/or biomass (e.g., fungi or algae) to about 0.6; degraded solar reflectances range from 0.3 to 0.8, depending on exposure. We investigate the effects of soiling and cleaning on the solar spectral reflectances and solar absorptances of 15 initially white or light-gray polyvinyl chloride membrane samples taken from roofs across the United States. Black carbon and organic carbon were the two identifiable strongly absorbing contaminants on the membranes. Wiping was effective at removing black carbon, and less so at removing organic carbon. Rinsing and/or washing removed nearly all of the remaining soil layer, with the exception of (a) thin layers of organic carbon and (b) isolated dark spots of biomass. Bleach was required to clear these last two features. At the most soiled location on each membrane, the ratio of solar reflectance to unsoiled solar reflectance (a measure of cleanliness) ranged from 0.41 to 0.89 for the soiled samples; 0.53 to 0.95 for the wiped samples; 0.74 to 0.98 for the rinsed samples; 0.79 to 1.00 for the washed samples; and 0.94 to 1.02 for the bleached samples. However, the influences of membrane soiling and cleaning on roof heat gain are better gauged by fractional variations in solar absorptance. Solar absorptance ratios (indicating solar heat gain relative to that of an unsoiled membrane) ranged from 1.4 to 3.5 for the soiled samples; 1.1 to 3.1 for the wiped samples; 1.0 to 2.0 for the rinsed samples; 1.0 to 1.9 for the washed samples; and 0.9 to 1.3 for the bleached samples.     

MnO2.CuO／Al2O3催化剂上CO的常温催化氧化研究

本文研究了CO常温氧化的催化剂——MnO_2·CuO/Al_2O_3。考察了活性组分MnO_2,CuO的相对百分含量,浸渍溶液的酸度、焙烧温度、反应温度等因素对催化剂活性的影响。发现催化剂的活性与其差热分析的脱水峰及分解反应(MnO_2→Mn_2O_3)的峰温存在一定的对应关系。     

SeaWiFS资料水色辐射模式验证的研究

从１９９４ 年～１９９７ 年，作者对杭州湾与长江口海区、台湾至吕宋以东海区和渤海海区，进行了多次光谱测量和同步取样试验，将试验所得资料经计算机处理，确定了三种验证区域各种水色要素与遥感光谱值之间的关系，提出适用于我国验证区域各种水色的验证模式。其各水色模式验证偏差均小于２０％ ，并适用于我国海域ＳｅａＷｉＦＳ水色遥感应用。     

Driver speed selection on high-speed two-lane highways: Comparing speed profiles between uniform and differential speed limits

Objective: Although a considerable amount of prior research has investigated the impacts of speed limits on traffic safety and operations, much of this research, and nearly all of the research related to differential speed limits, has been specific to limited access freeways. The unique safety and operational issues on highways without access control create difficulty relating the conclusions from prior freeway-related speed limit research to 2-lane highways, particularly research on differential limits due to passing limitations and subsequent queuing. Therefore, the objective of this study was to assess differences in driver speed selection with respect to the posted speed limit on rural 2-lane highways, with a particular emphasis on the differences between uniform and differential speed limits.

Methods: Data were collected from nearly 59,000 vehicles across 320 sites in Montana and 4 neighboring states. Differences in mean speeds, 85th percentile speeds, and the standard deviation in speeds for free-flowing vehicles were examined across these sites using ordinary least squares regression models.

Results: Ultimately, the results of the analysis show that the mean speed, 85th percentile speed, and variability in travel speeds for free-flowing vehicles on 2-lane highways are generally lower at locations with uniform 65 mph speed limits, compared to locations with differential limits of 70 mph for cars and 60 mph for trucks.

Conclusions: In addition to posted speed limits, several site characteristics were shown to influence speed selection including shoulder widths, frequency of horizontal curves, percentage of the segment that included no passing zones, and hourly volumes. Differences in vehicle speed characteristics were also observed between states, indicating that speed selection may also be influenced by local factors, such as driver population or enforcement.     

嘉兴夏季臭氧污染的近地层垂直变化特征

基于2018年浙江省嘉兴市14个环境国控站点的O₃历史资料与气象要素,研究O₃与气象要素的关系,并结合差分吸收臭氧雷达的垂直臭氧探测资料,分析近地层O₃廓线变化特征.结果表明,嘉兴地区发生高浓度O₃污染的关键气象要素为24~36℃的大气温度和36%~77%的相对湿度,24℃以上的大气温度与77%以下的相对湿度可作为启动预警O₃污染的气象指标.差分吸收臭氧雷达监测结果显示,无论O₃超标天与清洁天,在垂直方向上其浓度随高度先升后降,在600~800m范围出现峰值;O₃污染时段,在中午到午后低空形成持续向下的O₃输送带,这种低空O₃与地表O₃的叠加机制加重地表O₃污染程度,导致地表O₃超标与低空高浓度相伴出现;其廓线日变化规律表现出800m以下浓度在夜间和凌晨梯度不显著,日出后近地层O₃随时间快速增加,中午和午后持续高值,傍晚随时间逐渐下降的特征.后向轨迹分析表明,10,500,1000m高度层的气流后向轨迹聚类有相似性,500m处沿闽浙海岸线的轨迹簇对应O₃较10m处来自海上的轨迹簇高,这与500m处前体物输送堆积和紫外线辐射增强有关.污染过程近地层气流来向紧贴地面,但中高层有明显下沉气流使得O₃前体物在500m附近堆积,是造成2个典型污染过程中垂直方向上O₃高值出现在500m左右的原因之一.     

土壤冻融对溶解性有机质与菲结合的影响

以沈阳市公园土壤和道路边土壤中的溶解性有机质(DOM)为研究对象,利用荧光淬灭法测定DOM与菲的结合常数(K),考察了冷冻温度、融化温度、冷冻时间和冻融次数对其光谱学特性及其与菲的结合常数(K)的影响,并结合相关性矩阵分析K与其他参数的关系.结果表明:冻融处理条件下,K值与溶解性有机碳含量(DOC)显著负相关(p0.01),与254 nm处的紫外吸光系数(a_(254))和单位浓度DOC的254 nm的紫外吸光值(SUVA)显著正相关(p0.01).城市公园土壤DOM和城市道路边土壤DOM的K值都是3.5×10~4L·kg~(-1),经过冷冻温度、冷冻时间和冻融次数相同的冻融处理后,城市公园土壤DOM的K值始终高于城市道路边土壤DOM,这是由于冻融导致城市土壤DOM的芳香性高于城市道路边土壤DOM,而分子量小于城市道路边土壤DOM.经过冻融作用二者的K值变化范围分别为1.6×10~5～8.4×10~5L·kg~(-1)和1.5×10~5～3.7×10~5L·kg~(-1),冻融作用使二者的K值都增大一个数量级.这一方面会增强固相土壤中多环芳烃的溶出和迁移,另一方面也会降低多环芳烃的生物可利用性.     

Evaluating the blue-light hazard from solid state lighting

Purpose. New light sources including light-emitting diodes (LEDs) have elicited questions about retinal damage, including the blue-light hazard. Some organizations have recommended avoiding using LEDs with correlated color temperatures exceeding 3000?K, since they tend to produce greater short-wavelength energy. This article provides quantitative comparisons among light sources and use cases as they affect the blue-light hazard. Methods. The spectral radiant power characteristics of incandescent, fluorescent, LED and daylight sources were evaluated in terms of blue-light hazard using standard procedures for phakic, aphakic and pseudophakic eyes. Results. Under most use cases, LEDs do not exhibit greater risk for the blue-light hazard than other sources (e.g., incandescent). Because they generally produce little to no ultraviolet energy, LEDs often present less risk to aphakic eyes. Conclusions. LEDs present no special concerns for the blue-light hazard over some other common sources in typical use cases because photophobic responses limit exposure to bright sources. Where photophobic responses might not occur (e.g., eye surgery patients or premature infants) or where individuals suppress these responses (e.g., stage actors), caution is necessary. Evidence remains inconsistent regarding the risk of human retinal damage from long-term exposures to light insufficient to reach acute blue-light hazard thresholds.     

Advanced treatment of municipal wastewater by nanofiltration: Operational optimization and membrane fouling analysis

Municipal sewage from an oxidation ditch was treated for reuse by nanofiltration (NF) in this study. The NF performance was optimized, and its fouling characteristics after different operational durations (i.e., 48 and 169 hr) were analyzed to investigate the applicability of nanofiltration for water reuse. The optimum performance was achieved when transmembrane pressure = 12 bar, pH = 4 and flow rate = 8 L/min using a GE membrane. The permeate water quality could satisfy the requirements of water reclamation for different uses and local standards for water reuse in Beijing. Flux decline in the fouling experiments could be divided into a rapid flux decline and a quasi-steady state. The boundary flux theory was used to predict the evolution of permeate flux. The expected operational duration based on the 169-hr experiment was 392.6 hr which is 175% longer than that of the 48-hr one. High molecular weight (MW) protein-like substances were suggested to be the dominant foulants after an extended period based on the MW distribution and the fluorescence characteristics. The analyses of infrared spectra and extracellular polymeric substances revealed that the roles of both humic- and polysaccharide-like substances were diminished, while that of protein-like substances were strengthened in the contribution of membrane fouling with time prolonged. Inorganic salts were found to have marginally influence on membrane fouling. Additionally, alkali washing was more efficient at removing organic foulants in the long term, and a combination of water flushing and alkali washing was appropriate for NF fouling control in municipal sewage treatment.     

Spatial effects and strategic behavior in a multiregional transboundary pollution dynamic game

We analyze a transboundary pollution differential game where pollution control is spatially distributed among a number of agents with predetermined spatial relationships. The analysis emphasizes, first, the effects of the different geographical relationships among decision makers; and second, the strategic behaviour of the agents. The dynamic game considers a pollution stock (the state variable) distributed among one large region divided in subregions which control their own emissions of pollutants. The emissions are also represented as distributed variables. The dynamics of the pollution stock is defined by a parabolic partial differential equation. We numerically characterize the feedback Nash equilibrium of a discrete-space model that still captures the spatial interactions among agents. We evaluate the impact of the strategic and spatially dynamic behaviour of the agents on the design of equilibrium environmental policies.     

Implications of network particle tracking (NPT) for ecological model interpretation

Network particle tracking (NPT), building on the foundation of network environ analysis (NEA), is a new development in the definition of coherence relations within and between connected systems. This paper evaluates three ecosystem models in a comparison of throughflow- and storage-based NEA and NPT. Compartments in models with high indirect effects and Finn cycling showed low correlation of NEA storage and throughflow with particle repeat visits and numbers of particles in compartments at steady state. Conversely, the correlation between NEA and NPT results was high with two models having lower indirect effects and Finn cycling. Analysis of ecological orientors associated with NEA showed NPT to fully support conventional NEA results when the common conditions of donor control and steady state are satisfied. Particle trajectories are recorded in the new concept of a particle “passport”. Ability to track and record particle in-system histories enables views of multiple scales and opens the possibility of making pathway-dependent modeling decisions. NPT may also enable modeling of time, allowing integration of Newtonian, organismal and stochastic modeling perspectives in a single comprehensive analysis.