散装预拌砂浆与传统自拌砂浆优缺点对比分析以及使用过程中需改进的几点意见

预拌砂浆作为一项绿色建材得到政府和社会的认同,预拌砂浆采用密闭容器进行运输和现场存储,以往施工现场砂浆搅拌过程中的扬尘满天飞情况可以基本杜绝,符合北京市地方标准绿色施工管理规程(DB11/513-2008)中"施工现场易飞扬细颗粒散体材料,应密闭存放"的规定。密封运输、密封储存,减少浪费,减少扬尘,真正做到文明施工;精确搅拌使用,施工质量容易控制;加快施工速度,节约成本。但是使用过程中还存在一些需改进的地方,文中详细介绍。     

Design of three-dimensional gradient nonwoven composites with robust dust holding capacity for air filtration

Air pollution has seriously threatened public health in developing countries. However, it is still a big challenge for fabricating a filter with high filtration efficiency, low air resistance, and long service life. Herein, we report a facile strategy to fabricate a multilayered nonwoven composite with a functionally gradient structure for air filtration by a combined method of needle-punch, melt blown, and corona charging techniques. Our integrated multilayer needle-punched/melt blown composite filter could achieve a high filtration efficiency up to 99.52 ± 0.01%, a low pressure drop of 136.87 ± 0.49 Pa, and a satisfied quality factor of 0.03898 ± 0.0001 Pa⁻¹ for sodium chloride particles with an aerodynamic diameter of 0.26 μm at the airflow rate of 85 L min⁻¹. More importantly, the resultant filter exhibited a large dust holding capacity of 23.5 ± 0.41 g m⁻², which indicates a long service life. It is expected that our multilayer needle-punched/melt blown composite fabric may not only serve as a good candidate for air filtration, but also provide a new sight for designing the air filtration materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47827.     

利用矿山固体废物料固结矿区路面的试验研究

白云鄂博西矿铁矿尾矿泥和甩尾碎石是矿山选矿厂排放的主要固体废弃物。利用尾矿泥代替砂、甩尾碎石代替级配碎石，采用碾压混凝土工艺进行矿区路面修筑，是改善矿区运输道路路况，延长汽车使用寿命的根本性措施。试验取得了其最佳含水量和最大比重的指标，28 d抗压强度达到18 MPa以上。工业试验路面选择在矿区主运输坡道上，一共做了4块,路面总长66.5 m，宽9.0 m，面积约600 m2，用料量共计165 t。根据路面混凝土芯样强度试验结果,尾矿泥碾压混凝土平均强度在18 MPa以上。     

Seasonality of meningitis in Africa and climate forcing: aerosols stand out

Bacterial meningitis is an ongoing threat for the population of the African Meningitis Belt, a region characterized by the highest incidence rates worldwide. The determinants of the disease dynamics are still poorly understood; nevertheless, it is often advocated that climate and mineral dust have a large impact. Over the last decade, several studies have investigated this relationship at a large scale. In this analysis, we scaled down to the district-level weekly scale (which is used for in-year response to emerging epidemics), and used wavelet and phase analysis methods to define and compare the time-varying periodicities of meningitis, climate and dust in Niger. We mostly focused on detecting time-lags between the signals that were consistent across districts. Results highlighted the special case of dust in comparison to wind, humidity or temperature: a strong similarity between districts is noticed in the evolution of the time-lags between the seasonal component of dust and meningitis. This result, together with the assumption of dust damaging the pharyngeal mucosa and easing bacterial invasion, reinforces our confidence in dust forcing on meningitis seasonality. Dust data should now be integrated in epidemiological and forecasting models to make them more realistic and usable in a public health perspective.     

Phosphorus flame retardants in indoor dust and their relation to asthma and allergies of inhabitants

Organophosphate esters are used as additives in flame retardants and plasticizers, and they are ubiquitous in the indoor environment. Phosphorus flame retardants (PFRs) are present in residential dust, but few epidemiological studies have assessed their impact on human health. We measured the levels of 11 PFRs in indoor floor dust and multi‐surface dust in 182 single‐family dwellings in Japan. We evaluated their correlations with asthma and allergies of the inhabitants. Tris(2‐butoxyethyl) phosphate was detected in all samples (median value: 580 μg/g in floor dust, 111 μg/g in multi‐surface dust). Tris(2‐chloro‐iso‐propyl) phosphate (TCIPP) was detected at 8.69 μg/g in floor dust and 25.8 μg/g in multi‐surface dust. After adjustment for potential confounders, significant associations were found between the prevalence of atopic dermatitis and the presence of TCIPP and tris(1,3‐dichloro‐2‐propyl) phosphate in floor dust [per log₁₀‐unit, odds ratio (OR): 2.43 and 1.84, respectively]. Tributyl phosphate was significantly associated with the prevalence of asthma (OR: 2.85 in floor dust, 5.34 in multi‐surface dust) and allergic rhinitis (OR: 2.55 in multi‐surface dust). PFR levels in Japan were high compared with values reported previously for Europe, Asia‐Pacific, and the USA. Higher levels of PFRs in house dust were related to the inhabitants' health status.     

金凤煤矿泡沫除尘技术研究及应用

针对金凤煤矿12煤煤层厚度较薄,开采时产生大量粉尘的问题,采用泡沫除尘技术降低粉尘浓度。通过对泡沫降尘技术的机理进行分析,并结合该技术在金凤煤矿12煤实际应用情况,得出:采用泡沫除尘技术大大降低了工作面掘进时产生的粉尘,取得了非常好的除尘效果,明显改善了井下的生产作业环境。     

Influence of temperature and application rate on efficacy of a diatomaceous earth formulation against Tribolium castaneum adults

Unsanitary storage bins can harbor grain-infesting insects, including the red flour beetle, Tribolium castaneum (Herbst). In a previous study involving heat treatment of empty bins, temperatures in the range of 50–55 °C for 2–4 h were effective in completely killing stored-product insects. Previous research in flour mills showed improved efficacy in killing stored-product insects by using diatomaceous earth (DE) dusts at temperatures below 50 °C. In the current study, the efficacy of a diatomaceous earth formulation (DiaFil^® 610) applied to concrete arenas, to simulate floor of empty bins, was examined at three application rates (0, 2.5 and 5.0 g/m²) to control T. castaneum adults at five constant temperatures (28, 36, 42, 44, and 46 °C). Ten adults of T. castaneum were placed on individual untreated and DE-treated concrete arenas for 4, 8, 12, and 24 h at each of the five temperatures. The efficacy of DE against T. castaneum adults increased with an increase in temperature and exposure time. Generally more adults died at 5.0 g/m² when compared with 2.5 g/m². In 2.5 and 5.0 g/m² DE treatments, exposure for 12 h at a temperature of 42 °C resulted in 73–77% mortality of adults with 100% mortality observed after 24 h. At 44 and 46 °C, 100% mortality of adults was observed after 24 h of exposure at both DE rates. At these two temperatures, the high mortality in untreated arenas (controls) at 8, 12, and 24 h exposures ranged from 27 to 100% confounding the true effects of DE. Our results suggest that combined use of DE and temperatures below 50 °C can be used as an integrated approach for controlling insects in empty bins prior to storage of newly-harvested grain.     

Floor dust erosion during early stages of coal dust explosion development

An ignition of methane and air can generate enough air flow to raise mixtures of combustible coal and rock dust. The expanding high temperature combustion products ignite the suspended dust mixture and will continue to propagate following the available combustible fuel supply. If the concentration of the dispersed rock dust is sufficient, the flame will stop propagating. Large-scale explosion tests were conducted within the National Institute for Occupational Safety and Health (NIOSH) Lake Lynn Experimental Mine (LLEM) to measure the dynamic pressure history and the post-explosion dust scour depth. The aim of this effort is to provide quantitative data on depth of dust removal during the early stages of explosion development and its relationship to the depth of floor dust collected for assessing the incombustible content most likely to participate in the combustion process. This experimental work on dust removal on is not only important for coal mine safety but also for industrial dust explosions.     

Silica/mullite fiber composite membrane with double-layer structure for efficient sub-micrometer dust removal

Here, we developed silica/mullite fiber composite membranes with double-layer structure by a simple vacuum procedure for the removal of sub-micrometer dust. The support with three-dimensional skeleton structure exhibited high porosity (higher than 90%), low density (lower than 0.25?g/cm³) and high compressive strength (higher than 0.55?MPa) at 1000?°C. By controlling the mass ratio of silica sol to mullite fiber, we can obtain uniform and complete filtering layers with different thicknesses. The composite membranes exhibited high PM filtration efficiency with 99% for 1–10?µm, 97% for 0.5?µm and 90% for 0.3?µm. These samples had high air flow with very low pressure drop (lower than 600?Pa when airflow velocity reached 1?m/s). These results indicated that the silica/mullite fiber composite membranes were very promising for PM pollution control in the field of hot gas filtration.     

基于微生物灭活芽孢的矿冶粉尘清洁皂的制备及性能研究

矿冶粉尘给一线工人皮肤健康带来严重威胁。通过添加微生物灭活芽孢于清洁皂中,研究了不同芽孢添加量对清洁皂去污能力的影响,对比了硅藻土、活性炭和芽孢添加皂在粉尘去污和重金属去除方面的异同,并通过感官评价测试了三种皂在皮肤清洁方面的效果。结果表明,添加硅藻土可以达到80%的粉尘去除率。而活性炭尽管比表面积高,但微粒细小同样易于吸附于手掌纹理中,造成二次污染,故去除率最低。在基础皂中添加1%(w/w)灭活芽孢对粉尘污染的去污率达到了95%,二次洗涤可将重金属去除率从90%提高到95%以上。感官评价中,黑色活性炭的吸附作用造成了清洗后的手掌依然不够干净,观感最差;硅藻土皂的清洁效果接近日常家用皂,观感居中;而芽孢皂的清洁效果最明显,观感最佳。