Particle number size distribution and new particle formation: New characteristics during the special pollution control period in Beijing

New particle formation is a key process in shaping the size distribution of aerosols in the atmosphere.We present here the measurement results of number and size distribution of aerosol particles (10-1...     

Sewage sludge disintegration by high-pressure homogenization: A sludge disintegration model

High-pressure homogenization (HPH) technology was applied as a pretreatment to disintegrate sewage sludge. The effects of homogenization pressure, homogenization cycle number, and total solid content on sludge disintegration were investigated. The sludge disintegration degree (DDCOD), protein concentration, and polysaccharide concentration increased with the increase of homogenization pressure and homogenization cycle number, and decreased with the increase of sludge total solid (TS) content. The maximum DDCOD of 43.94% was achieved at 80 MPa with four homogenization cycles for a 9.58 g/L TS sludge sample. A HPH sludge disintegration model of DD_COD= kN^aP^b was established by multivariable linear regression to quantify the effects of homogenization parameters. The homogenization cycle exponent a and homogenization pressure exponent b were 0.4763 and 0.7324 respectively, showing that the effect of homogenization pressure (P) was more significant than that of homogenization cycle number (N). The value of the rate constant k decreased with the increase of sludge total solid content. The specific energy consumption increased with the increment of sludge disintegration efficiency. Lower specific energy consumption was required for higher total solid content sludge.     

Size distributions of aerosol and water-soluble ions in Nanjing during a crop residual burning event

To investigate the impact on urban air pollution by crop residual burning outside Nanjing, aerosol concentration, pollution gas concentration, mass concentration, and water-soluble ion size distribution were observed during one event of November 4-9, 2010. Results show that the size distribution of aerosol concentration is bimodal on pollution days and normal days, with peak values at 60-70 and 200-300 nm, respectively. Aerosol concentration is 10⁴ cm^-3. nm^-1 on pollution days. The peak value of spectrum distribution of aerosol concentration on pollution days is 1.5-3.3 times higher than that on a normal day. Crop residual burning has a great impact on the concentration of fine particles. Diurnal variation of aerosol concentration is trimodal on pollution days and normal days, with peak values at 03:00, 09:00 and 19:00 local standard time. The first peak is impacted by meteorological elements, while the second and third peaks are due to human activities, such as rush hour traffic. Crop residual burning has the greatest impact on SO₂ concentration, followed by NO₂, O₃ is hardly affected. The impact of crop residual burning on fine particles (< 2.1 μm) is larger than on coarse particles (> 2.1 μm), thus ion concentration in fine particles is higher than that in coarse particles. Crop residual burning leads to similar increase in all ion components, thus it has a small impact on the water-soluble ions order. Crop residual burning has a strong impact on the size distribution of K⁺, Cl^-, Na⁺, and F^- and has a weak impact on the size distributions of NH₄⁺, Ca²⁺, NO₃^- and SO₄^2-.     

Natural Movements of Tagged Beavers in Tyva

Ninety-three beavers were tagged in 1998–2000 on the Azas River (Tyva Republic), and 28 returns were obtained within one to two years. The results of the study indicated that, unfavorable environment notwithstanding, most beavers did not move outside their settlements. Animals under two years of age were especially active. Females were more resident, whereas males migrated over longer distances. The section of the Azas River with numerous rapids was not an insuperable obstacle for the animals; genetic exchange between the upper and lower subpopulations was found to occur through this section.     

THE IMPORTANCE OF ACCURATE CURVE NUMBERS IN THE ESTIMATION OF STORM RUNOFF1

ABSTRACT: Storm runoff as calculated by the runoff curve number method is shown to be of varying sensitivity to both input rainfall and curve number. Using an assumed input error of 10%, a runoff error chart is given. Up to about 9 inches of rainfall, runoff is more sensitive to curve number than to rainfall. The importance of accurate curve number selection in this range is stressed.     

最优指标法在环境监测优化布点中的应用

采用最优指标法对郑州市17个大气环境采样点的监测数据进行优选,得到的优化点位基本能反映城市空气质量的总体情况,可以达到环境监测优化布点的目的.     

基于UAHP的采空区稳定性模糊综合评判

为准确评判矿山采空区稳定性等级,通过分析采空区稳定性各影响因素,确定地质、水文、采空区几何参数、环境等4个2级指标为影响其稳定性的主要因素。运用层次分析法(AHP)并结合模糊数学理论,建立采空区稳定性2级模糊综合评判模型。用区间数表示评判结果,分析处理评判矩阵得到专家评判的相似度和差异度,进而获取专家评判的可信度,建立基于不确定型层次分析法(UAHP)的采空区稳定性模糊评判方法。实例计算结果表明:在Ⅰ级评判指标中,地质构造、周围开采影响、地下水活动程度、跨度对采空区稳定性影响较大;用该采空区的稳定性等级为Ⅱ级。用该方法能得出各影响因素的综合权重,准确评判采空区稳定性等级。     

GB/T 7702-2008《煤质颗粒活性炭试验方法》标准的研究

通过对GB/T 7702-2008《煤质颗粒活性炭试验方法》的修订,研究了国际上先进国家的ASTM、JIS、ГОСТ同类标准内容。本系列标准除等同采用部分国际先进标准外,还结合本国特点增加了部分国外标准没有的内容,同时着重对碘吸附值测定进行了深入研究,确定了国际先进的碘吸附值试验方法。     

Why do male Callosobruchus maculatus beetles inseminate so many sperm?

Male Callosobruchus maculatus F. (Coleoptera: Bruchidae) inseminate more sperm than females can effectively store in their spermathecae. This study examines the adaptive significance of excess sperm transfer by measuring components of male and female reproductive success in response to manipulating the number of sperm inseminated. The number of sperm transferred during copulation was reduced from 56,000 ±4,462 to 8,700±1,194 by sequentially mating males to virgin females. Reducing the number of sperm inseminated by the first male to mate had no effect on the extent of sperm precedence, but reducing the number of sperm inseminated by the second male resulted in a significant reduction in the extent of sperm precedence. When large numbers of sperm are inseminated the remating refractory period of females is increased. These results indicate that males transferring large numbers of sperm during copulation have a two-fold advantage at fertilization; they are more effective at preempting previously stored sperm and they are likely to father more offspring by delaying the time of female remating. The transfer of excess sperm does not appear to serve as nonpromiscuous male mating effort; the number of eggs laid, their fertility and the subsequent survival of zygotes were unaffected by manipulating the number of sperm inseminated. The underlying mechanisms of sperm precedence were also examined. Simple models of sperm displacement failed to accurately predict the patterns of sperm precedence observed in this species. However, the results do not provide conclusive evidence against the models but rather serve to highlight our limited understanding of the movement of sperm within the female's reproductive tract.     

浅谈代数问题中的数形结合

对数与形的结合在代数解题中的广泛应用作了一些归纳和扩充,主要概括了它在求函数值域与极值(最值)、解不等式(不等式组)、解方程(方程组)三个方面的应用.通过一些典型例题,提出了相应的方法与常用的技巧,因此,数与形不再是分离的主体,而是紧密地结合在一起,并渐渐形成了许多新型数学分支.