长列高强螺栓接头传力特性的有限元数值模拟

为研究摩擦型高强螺栓连接接头的传力特性与应力状态,采用通用有限元软件ANSYS建立三维有限元实体模型,对东江大桥中14个不同的螺栓连接接头进行了细致的有限元数值模拟分析。重点研究了长列螺栓群各排螺栓传力比、栓孔应力集中系数,高强螺栓的应力状态以及孔前传力系数等参数的变化规律,明确提出了各参数的取值范围,可为该类型节点的设计验算提供参考。     

丙烯腈、醋酸乙烯酯分析新方法的研究

本文研究一种一次性即可快速有效测试釜内和空间丙烯腈、醋酸乙烯酯浓度的新方法。摒弃了先前在测定丙烯腈、醋酸乙烯酯浓度时必须两种物质分别独立操作的方法,既减轻了工人的劳动强度,又为公司节约了资金。本方法适于腈纶生产厂釜内和空间丙烯腈、醋酸乙烯酯浓度的测试。     

Concentration-dependent response of estrone-degrading bacterial community in activated sludge analyzed by microautoradiography-fluorescence in situ hybridization

Inefficient removal of estrone (E1) in wastewater treatment plants (WWTPs) causes feminizing effects in male aquatic creatures. As E1 is mainly removed by biodegradation, investigation of E1 degradation is important to determine better removal strategies. Using microautoradiography-fluorescence in situ hybridization (MAR-FISH), we demonstrated that the structures of [³H]E1-incorporating bacterial communities were different at different E1 concentrations applied to activated sludge. At 200 μg/L E1, almost all [³H]E1-incorporating cells were associated with either Betaproteobacteria or Gammaproteobacteria (60% and 40% of MAR (+) cells, respectively). The proportion of Betaproteobacteria and Gammaproteobacteria in the total number of [³H]E1-incorporating cells decreased as the concentration of E1 decreased. In contrast, the proportion of Alphaproteobacteria in the total number of [³H]E1-incorporating cells increased as the concentrations of E1 decreased. At the lowest applied concentration (540 ng/L), almost all the [³H]E1-incorporating cells were Alphaproteobacteria (96%). The results of MAR-FISH applied to sludge samples collected from various plant locations and activated sludge processes, and during different seasons also demonstrated the high contribution of Alphaproteobacteria to the entire E1-degrading bacterial community (50.4 ± 11% of the total number of [³H]E1-incorporating cells) at 1 μg/L E1. Since the E1 concentration in domestic wastewater is at sub-μg/L levels, the key E1 degraders in activated sludge of domestic WWTPs are probably be Alphaproteobacteria. All [³H]E1-incorporating Alphaproteobacteria were hybridized with probe ALF968. Few MAR (+) cells were Sphingomonadales. An E1-degrading bacterial community at low E1 concentration appeared to consist of diverse bacterial groups of Alphaproteobacteria. This study suggested that substrate concentration is an essential factor for revealing E1-degrading bacteria in complex communities.     

Concentrations of ultrafine particles at a highway toll collection booth and exposure implications for toll collectors

Research regarding the magnitude of ultrafine particle levels at highway toll stations is limited. This study measured ambient concentrations of ultrafine particles at a highway toll station from October 30 to November 1 and November 5 to November 6, 2008. A scanning mobility particle sizer was used to measure ultrafine particle concentrations at a ticket/cash tollbooth. Levels of hourly average ultrafine particles at the tollbooth were about 3-6 times higher than those in urban backgrounds, indicating that a considerable amount of ultrafine particles are exhausted from passing vehicles. A bi-modal size distribution pattern with a dominant mode at about < 6 nm and a minor mode at about 40 nm was observed at the tollbooth. The high amounts of nanoparticles in this study can be attributed to gas-to-particle reactions in fresh fumes emitted directly from vehicles. The influences of traffic volume, wind speed, and relative humidity on ultrafine particle concentrations were also determined. High ambient concentrations of ultrafine particles existed under low wind speed, low relative humidity, and high traffic volume. Although different factors account for high ambient concentrations of ultrafine particles at the tollbooth, measurements indicate that toll collectors who work close to traffic emission sources have a high exposure risk.     

Combined exposure to cyanobacterial biomass, lead and the Newcastle virus enhances avian toxicity

Under environmental conditions, wild birds can be exposed to multiple stressors including natural toxins, anthropogenic pollutants and infectious agents at the same time.This experimental study was successful in testing the hypothesis that adverse effects of cyanotoxins, heavy metals and a non-pathogenic immunological challenge combine to enhance avian toxicity. Mortality occurred in combined exposures to naturally occurring cyanobacterial biomass and lead shots, lead shots and Newcastle vaccination as well as in single lead shot exposure. Mostly acute effects around day 10 were observed. On day 30 of exposure, there were no differences in the liver accumulation of lead in single and combined exposure groups. Interestingly, liver microcystin levels were elevated in birds co-exposed to cyanobacterial biomass together with lead or lead and the Newcastle virus. Significant differences in body weights between all Pb-exposed and Pb-non-exposed birds were found on days 10 and 20. Single exposure to cyanobacterial biomass resulted in hepatic vacuolar dystrophy, whereas co-exposure with lead led to more severe granular dystrophy. Haematological changes were associated with lead exposure, in particular. Biochemical analysis revealed a decrease in glucose and an increase in lactate dehydrogenase in single and combined cyanobacterial and lead exposures, which also showed a decreased antibody response to vaccination.The combined exposure of experimental birds to sub-lethal doses of individual stressors is ecologically realistic. It brings together new pieces of knowledge on avian health. In light of this study, investigators of wild bird die-offs should be circumspect when evaluating findings of low concentrations of contaminants that would not result in mortality on a separate basis. As such it has implications for wildlife biologists, veterinarians and conservationists of avian biodiversity.     

Modeling and experimental validation of overpotentials of a direct ethanol fuel cell

Direct ethanol fuel cell (DEFC) is a promising power source for future use in portable electronic equipments. In general, the power density obtained in DEFC is lower than that of direct methanol fuel cell. In the present study, various losses in DEFC are estimated by performing experiments with the prepared membrane electrode (MEA) to obtain current–voltage characteristics and comparing it with the prediction of mathematical model. MEA for the DEFC is prepared using Pt–Ru (40:20 by wt.%)/C as anode catalyst, Pt–black as cathode catalyst with 1 mg/cm² of loadings and cast Nafion^® (SE5112, DuPont) ionomer as proton exchange membrane. The mathematical model for DEFC is developed considering different overpotentials. The activation overpotential term is formulated considering ethanol electrooxidation mechanism proposed in literature and Butler–Volmer equation. The ohmic overpotential is modeled based on proton conductivity of Nafion^® membrane and ohmic losses at the electrodes, current collectors and electrode–current collector interfaces. The concentration overpotential is formulated using Fick's law, modified Butler–Volmer equation and transport process through electrodes and electrocatalyst layers. The experiment data on current–voltage characteristics is predicted by the model with reasonable agreement and the influence of ethanol concentration and temperature on the performance of DEFC is captured by the model.     

Application of ECT to solid concentration measurements during granular flow in a rectangular model silo

The paper presents results of concentration changes in cohesionless sand during dynamic mass flow in a rectangular model silo composed of a bin and hopper. Electrical capacitance tomography (ECT) was used. Sensors were located outside the silo along both the periphery and height. Local horizontal one-dimensional and cross-sectional two-dimensional evolutions of solid concentrations in dry sand during silo discharge were determined. The first ones were estimated from the raw data and the latter were obtained with the aid of the reconstructed data using a Linear Back Projection algorithm (LBP) to solve an inverse problem. Experiments in a model silo were carried out with two different initial sand densities and wall roughness grades. The measured results with ECT were compared with corresponding ones obtained with a Particle Image Velocimetry (PIV) method.     

Dye binary mixture formulation by means of derivative ratio spectra of the Kubelka–Munk function

In this study, a new method is introduced for the determination of dye concentration in fabrics dyed with bicomponent dye mixtures. The reflectance spectra of the samples dyed with different binary mixtures of dyes were recorded between 400 and 700 nm. The obtained spectra were divided by a standard spectrum of each of the components in the mixtures and the derivative spectra were calculated. The amounts of dyes were determined by measurements in suitably selected wavelengths in the acquired derivative ratio spectra. The obtained results indicate that the developed derivative ratio spectra method is more accurate than the normal Kubelka–Munk method. The proposed derivative method is simple, accurate, and suitable for quantitative analysis of samples dyed with binary mixed shades. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2010     

简化RP-HPLC法同时测定茶碱和可可碱的含量

确定了同时测定茶碱和可可碱含量的HPLC条件:Symmetry C18柱,乙腈-水(10∶90)为流动相,检测波长275 nm,流速1 mL/min。在此条件下茶碱(THO)的线性回归方程为y=3.186×106x-1.025×105,r=0.999 9);可可碱(TB)回归方程:y=3.011×106x-4.092×104(r=0.999 8),进样量分别在0.09~1.35μg和0.036~0.36μg范围内与峰面积值呈良好线性关系。     

电解除油工艺的改进

在传统的"三碱"电解除油工艺基础上,研究一种新的工艺.该工艺通过添加一定量的发泡剂与消泡剂,组合成一种自消泡电解除油体系.该体系能够有效屏蔽电解除油过程中由阴、阳极析出的氢气、氧气以及由此所带出的碱雾,并有效降低溶液组分中"三碱"的质量浓度,从而降低空气中的碱值,改善车间生产环境.