自控式变频器供电的交流矿井提升机

直至目前为止,生产能力较大的竖井提升机几乎全部采用直流电动机驱动。由于现代调节技术以及电子控制和监视装置的发展,直流驱动装置业已达到很高的技术水平,而且安全可靠。为使提升机生产运行更加安全可靠,维护量最小,不断提高驱动功率,以及近年来能源费用急剧上涨等多方面的原因,促使人们寻求其它可能的驱动技术。自控式变频器供电的交流电动机与新型定向励磁的旋转矢     

An extension of ASM2d including pH calculation

This paper presents an extension of the Activated Sludge Model No. 2d (ASM2d) including a chemical model able to calculate the pH value in biological processes. The developed chemical model incorporates the complete set of chemical species affecting the pH value to ASM2d describing non-equilibrium biochemical processes. It considers the system formed by one aqueous phase, in which biochemical processes take place, and one gaseous phase, and is based on the assumptions of instantaneous chemical equilibrium under liquid phase and kinetically governed mass transport between the liquid and gas phase. The ASM2d enlargement comprises the addition of every component affecting the pH value and an ion-balance for the calculation of the pH value and the dissociation species. The significant pH variations observed in a sequencing batch reactor operated for enhanced biological phosphorus removal were used to verify the capability of the extended model for predicting the dynamics of pH jointly with concentrations of acetic acid and phosphate. A pH inhibition function for polyphosphate accumulating bacteria has also been included in the model to simulate the behaviour observed. Experimental data obtained in four different experiments (with different sludge retention time and influent phosphorus concentrations) were accurately reproduced.     

测定岩石三轴压缩强度建议方法(修订)

1.范围和序言本方法叙述三种不同类型的三轴压缩试验。这些试验都是测定圆柱形岩石试样以围压作为函数的强度。这三类试验的区别在于获得强度包络线的方式有所不同(图1a—c)。第1类试验(“单个破坏状态试验”)包络线上的每个破坏点(峰值强度)是由若干个岩样的试验获得的(图1a);而第Ⅱ类试验(多级破坏状态试验)(图1b)和第Ⅲ类试验(连续破坏状态试验) (图1c)的包络线是用一个试验采用逐级或连续加载的方法获得的。因此从     

Selective adsorption of p-chloronitrobenzene from aqueous mixture of p-chloronitrobenzene and o-chloronitrobenzene using HZSM-5 zeolite

The selective adsorption of p-chloronitrobenzene (p-CNB) using zeolite as the adsorbent from an aqueous mixture containing p-CNB and o-chloronitrobenzene (o-CNB) was investigated. The maximum adsorption amounts of p-CNB in HZSM-5 zeolite were found to be approximately 4 molecules per unit cell (mol/uc) at all adsorption temperatures investigated. The maximum adsorption amounts of o-CNB in HZSM-5 zeolite were, however, markedly lower than those of p-CNB at different adsorption temperatures. Diffusion results revealed that the diffusivity of p-CNB at 300K was about 100 times higher than that of o-CNB in HZSM-5 zeolite. The remarkable difference in the adsorption amounts and diffusivities between p-CNB and o-CNB resulted in separation factors of 463.6, 96.8 and 21.9 for p-CNB at 278, 300 and 323 K, respectively, indicating a selective adsorption of p-CNB in HZSM-5 zeolite from the aqueous mixture of p- and o-CNB.     

Lead contamination in tap water of households with children in Lower Saxony, Germany

Lead has numerous acute and chronic adverse effects on human beings. This is especially true for infants and children. The main path of lead ingestion in children can be different according to housing and living situation. The intake of lead through drinking water is commonly due to metal corrosion. The users plumbing can be an important factor. In recent years, many lead pipes in Germany have been replaced by pipes made of an alternative material. The aim of this study is to assess the present state of drinking water contamination and the resulting exposure of infants to lead. For this purpose mothers of new-born babies were offered a free examination of their drinking water. After a written declaration of consent had been obtained and after the infant in question had reached an age of 3 months, a stagnation sample of cold tap-water after overnight stagnation together with a random daytime sample was obtained from the family. The collected samples were analysed by atomic absorption spectrometry for their lead concentration. In total, 1485 samples from households were collected. Of the 1434 stagnation samples, 3.1% had lead concentrations greater than 0.01 mg/l (recommended limit of the WHO) and 0.6% had concentrations above the limit of the German drinking water regulation (0.04 mg/l). The values for the 1474 random daytime samples were 2.1% above 0.01 mg/l and 0.2% greater than 0.04 mg/l, respectively. By region, the areas Bovenden, Friedland, Duderstadt, Northeim and Rosdorf were particularly affected. The highest measured concentrations of lead in the stagnation samples were 0.11 mg/l and 0.15 mg/l in the random daytime samples, respectively.     

Distribution of selected anthropogenic radionuclides (137Cs, 238Pu, (239,240)Pu and 241Am) in marine sediments with emphasis on the Spitsbergen-Bear Island area

Measurements of anthropogenic radionuclides in marine sediments can provide good estimates of past and present radioactive contamination of the marine environment. The Barents Sea is one of the world's richest ocean areas, and it is therefore of major interest for Norwegian fisheries to document the levels of radioactive contamination of this and adjacent ocean areas. In this study, concentrations of 137Cs, 238Pu, (239,240)Pu and 241Am were measured in marine sediments collected mainly in the Spitsbergen-Bear Island region. Additional samples collected in the deep Norwegian Sea and near the Greenland ice-edge have been included for comparison. The highest radionuclide levels were found near Spitsbergen, reaching over 50% higher than in adjacent areas. Determinations of the mineral content and particle size distribution indicate a relation between the content of clay minerals and radionuclide levels. The present study confirms earlier observations of elevated levels of 137Cs in sediments in the Spitsbergen-Bear Island area and documents elevated levels of 238Pu, (239,240)Pu and 241Am in these sediments. Using an exponential curve fit based on determinations of unsupported 210Pb in sediment cores, sedimentation rates of 0.28, 0.05 and 0.26 cm year(-1) were calculated at locations south of Spitsbergen, near the Greenland ice-edge and in the deep Norwegian Sea, respectively.     

用动测法预测桩的承载力

本文介绍一种根据应力波理论预测桩的动承载力的新方法。有关测量桩侧及极端阻力的应用方法及理论根据也分别予以讨论。虽然CASE法和CAFWAP分析法已广泛应用于预测桩的承载力,但并未考虑桩的频率特牲。由于锤击力的频率和桩的反射波频率彼此存在很大的差异,在打桩过程中用CASE法难以预测土的阻力。将桩的响应频率低的同样测量频率用于入射波和反射波,以预测打桩时上的阻力。结果发现,本文所述方法与CAPWAP分析法预测的承载力几乎相等。     

Quantifying inequality in health in the absence of a natural reference group

When quantifying inequality in health, the excess fraction (i.e. the proportional reduction in the outcome in question that would occur if all groups had the same, lowest, risk rate) is an appealing measure. If the population contains a natural, healthiest reference group, the excess fraction is straightforward to estimate. In the absence of an a priori reference group, calculating the excess fraction requires reflection, since using the group with the lowest observed risk rate as reference can lead to erroneous conclusions. This paper proposes a simple simulation procedure for calculating the excess fraction, without fixing a reference group.     

Paleonutritional analysis of the pre-Hispanic population from Fuerteventura (Canary Islands)

In this study, from histological and chemical perspectives, we analyse the human remains belonging to the pre-Hispanic inhabitants from Fuerteventura (one of the Canary Islands) and compare the results with those obtained on a sample of pre-Hispanic inhabitants from Gran Canaria (Canary Islands). We observe that trabecular bone mass was normal in the samples from Fuerteventura except for an elderly woman; this result is in sharp contrast with the decreased bone mass observed in the population from Gran Canaria. The pre-Hispanic population from Fuerteventura showed lower bone strontium, Sr/Ca ratio, and bone barium, but slightly higher bone copper, than that from Gran Canaria. All these data indicate a greater consumption of marine products by the population of Fuerteventura. The high prevalence of osteoporosis observed in the population from Gran Canaria may be interpreted as a consequence of protein-calorie malnutrition, a condition which seemed to be not so prevalent in the population of Fuerteventura.