多孔喷嘴PM10-PM2.5串级冲击式大气采样器的研制及应用

多孔喷嘴冲击式大气采样器广泛应用于大气环境监测,相对于单孔喷嘴采样器,它具有压差小、相同空气雷诺数下采样流量大等特点.利用Marple的冲击理论,设计了一种中流量PM10-PM2.5串级冲击式大气采样器,采样流量为100L/min.用该采样器进行实地测量,通过PM2.5/PM10的比值分析,该采样器测量的PM2.5/PM10数据基本与文献报道一致.     

Beryllium Concentrations in Ambient Air and Its Source Identification

Beryllium concentrations in atmospheric particulate and soil samples in and around a Beryllium Processing Facility (BPF) have been measured. The mean air concentration level of beryllium in and around the fence line of the BPF is 0.48 ± 0.43 ng m^-3 (n = 397) and is mostly influenced by diurnaland seasonal changes. The observed air concentration levelswere well below the prescribed ambient air quality (AAQ)standard of 10 ng m^-3. The soil concentration levels ofberyllium in the study area were found to be in the range of 1.42–2.75 g g^-1. The mass median aerodynamic diameter (MMAD)of beryllium aerosols in ambient air was found to be 6.9 m.Source identification using the Enrichment Factor (EF) approachindicates soil as the predominant contributory source for air concentrations at the site.     

Determining straining of Escherichia coli from breakthrough curves

Though coliform bacteria are used world wide as an indication of faecal pollution, the parameters determining the transport of Escherichia coli in aquifers are relatively unknown, especially for the period after the clean bed collision phase brought about by prolonged infiltration of waste water. In this research, the breakthrough curves of E. coli after total flushing of 50-200 pore volumes were studied for various influent concentrations in various sediments at different pore water flow velocities. The results indicated that straining in Dead End Pores (DEPs) was an important process that dominated bacteria breakthrough in fine-grained sediment (0.06-0.2 mm). The filling of the DEP space with bacteria took 5-65 pore volumes and was dependent on concentration. Column breakthrough curves were modelled and from this the DEP volumes were determined. These volumes (0.21-0.35% of total column volume) corresponded well with values calculated with a formula based on purely geometrical considerations and also with values calculated with a pore size density function. For this function the so-called Van Genuchten parameters of the sediments used in the experiments were determined. The results indicate that straining might be a dominant process affecting colloid transport in the natural environment and therefore it is concluded that proper knowledge of the pore size distribution is crucial to an understanding of the retention of bacteria.     

冲裁模刃口尺寸及公差的自动标注与修改

根据冲裁模刃口尺寸及公差的确定原则和计算公式 ,提出了切实可行的人机交互式的自动标注和修改冲裁模刃口尺寸及公差的方法     

“后桥”专机流水线排风除尘系统设计

通过治理某厂差动齿轮箱壳体流水线中各类机床在生产过程中产生的金属粉尘，介绍了排风除尘系统的吸尘罩设计，排风量计算，风管管路布置以及除尘器和风机的选用等，系统运行结果表明，达到设计要求。     

Ti-Nb微合金钢焊接粗晶热影响区组织及韧性

喷锌、喷铝、喷锌铝合金三种保护层材料在青海格尔木盐水湖进行1年暴露试验，采用电化学方法研究了该金属喷涂层材料的腐蚀情况，并将其与碳钢的实验结果相对照，初步探讨了其耐蚀机理。     

Cation exchange capacities of soil organic matter fractions in a Ferric Lixisol with different organic matter inputs

Soil organic matter (SOM) has an important effect on the physicochemical status of highly weathered soils in the tropics. This work was conducted to determine the contribution of different SOM fractions to the cation exchange capacity (CEC) of a tropical soil and to study the effect of organic matter inputs of different biochemical composition on the CEC of SOM. Soil samples were collected from a 20-year-old arboretum established on a Ferric Lixisol, under seven multipurpose tree species: Afzelia africana, Dactyladenia barteri, Gliricidia sepium, Gmelina arborea, Leucaena leucocephala, Pterocarpus santalinoides, and Treculia africana. Fractions were obtained by wet sieving and sedimentation after ultrasonic dispersion. Relationships between CEC and pH were determined using the silver thiourea-method and were described by linear regression. The CEC of the fractions smaller than 0.053 mm was inversely related to their particle size: clay (<0.002 mm)>fine silt (0.002–0.02 mm)>coarse silt (0.02–0.053 mm), except for the soils under T. africana, D. barteri, and L. leucocephala, where the CEC of the fine silt fraction was highest or comparable to the CEC of the clay fraction. The clay and fine silt fractions were responsible for 76–90% of the soil CEC at pH 5.8. The contribution of the fine silt fraction to the CEC at pH 5.8 ranged from 35 to 50%, which stressed the importance of the fine silt fraction for the physicochemical properties of the soil. Differences in CEC between treatments for the whole soil and the fractions could be explained by the differences in carbon content. Except for the intercept for the clay fraction, SOM had a significant (P<0.001) contribution to both the intercepts (=estimated CEC at pH 0) and slopes (=pH-dependent charge) of the CEC–pH relationships for the whole soil and the fractions. The CEC of SOM at pH 5.8 varied between 283 cmol_c kg⁻¹ C for particulate organic matter, and 563 cmol_c kg⁻¹ C for the fine silt fraction. The biochemical composition of the organic inputs did not have an important effect on the CEC of SOM. In total, SOM was responsible for 75–85% of the CEC of these soils.     

普通旋风除尘器结构尺寸优化设计

以Ｌｅｉｔｈ设计法为基础，考虑除尘效率和压降等因素的影响，以除尘效率为理想目标，以一些流体力学特性和实际限制、经验值为约束，建立数学模型，用数学规划论的方法进行旋风除尘器结构尺寸的优化，以此设计的旋风除尘器应用到现场既可节约投资，又可降低能耗，设计方法通用性好．     

Chemical composition of aerosols in winter/spring in Beijing

In 1999 aerosol samples were collected by cascade at Meteorological Tower in Beijing.The 12 group aerosol samples obtained were analyzed using PIXE method,which resulted in 20 elemental concentrations and size distribution of elemental concentrations.From the observation,the elemental concentrations,size distribution of elemental concentrations and their variations are analyzed.It shows that concentrations of most elements in aerosols increase greatly compared with those in the past except that the concentrations of V,K,Sr,and the source of aerosols has changed greatly in the past decade.Fine mode aerosols increase more rapidly in the past decade,which may be due to the contribution of coal combustion and automobile exhaust.Pb contait in aerosol is much higher than that at the beginning of 1980s,and has a decreasing trend in recent years because of using non-leaded gasoling.     

五台山春季气溶胶传输特征

基于气溶胶监测仪Grimm180观测的2018年3~5月山西省五台山气溶胶数浓度和质量浓度数据,以及对应时段的美国国家环境预报中心（NCEP）提供的全球资料同化系统（GDAS）数据,利用聚类分析和潜在源贡献因子分析（PSCF）等方法,研究五台山春季气溶胶数浓度和质量浓度的统计特征,分析影响五台山气溶胶浓度变化的主要传输路径,以及潜在的贡献源区.结果表明,影响春季五台山气溶胶变化的主要传输路径有6类,其中,第1,4,2,5类传输路径均为西北和偏西方向,占总轨迹62.5%,而第3,6类传输路径则为偏南和偏东方向,占总轨迹的24.7%.对不同传输路径进行统计分析,发现第1,4类传输路径对粗粒径PN₁₀、PN_>10数浓度和PM₁₀质量浓度影响最大,其潜在贡献源区主要位于内蒙古西部和陕北黄土高原一带,PSCF值在局部地区达到了0.6以上.第6,3类路径对细粒径的数浓度PN_0.5、PN_1.0和PM_1.0质量浓度影响较大,其潜在贡献源区主要位于山西中南部、陕西中部、京津冀地区中部以及河南北部区域,部分地区PSCF值达到0.8以上.细粒径的PSCF高值区主要位于五台山的偏东和偏南方向,传输高度在2km以下.随着粒径的增加,PSCF高值区变为西北和东南方向,传输高度到达了自由对流层2~4km,且通过西北地区自由对流层的输送占比逐渐增大,PSCF高值区距离五台山站也越来越远.