Enhanced photocatalysis of pentachlorophenol by metal-modified titanium (IV) oxide

The effects of four metals (Ag, Au, Pt, and Cu) doped on TiO2 on the photocatalysis of pentachlorophenol (PCP) were investigated. The results of this study indicated that all four metals-doped TiO2 catalysts were able to enhance the efficiency of PCP photocatalysis with an optimum metallic content of 0.1 wt%. For the metal-doped TiO2 samples (Au, Pt, and Cu), the patterns of light absorption were significantly extended toward visible light spectra in the wavelengths between 400 and 800 nm. The photocatalysis of PCP was pH dependent with the maximum degradation rate achieved in the solution at pH 3. The formation of chloride ion corresponded with the concentration of PCP degraded which confirmed that dechlorination was the major pathway of PCP photocatalysis. The overall toxicities of PCP samples were reduced with the extension of light exposure using the microtox test. The results of PCP photocatalysis are also discussed based on the characteristics of metal/TiO2 including X-ray differential (XRD) patterns, Brunquer Emmett Teller (BET) specific area analysis, and Ultra Violet (UV)-Vis absorption spectra.     

Adsorption characteristics of benzene on biosolid adsorbent and commercial activated carbons

This study selected biosolids from a petrochemical waste-water treatment plant as the raw material. The sludge was immersed in 0.5-5 M of zinc chloride (ZnCl2) solutions and pyrolyzed at different temperatures and times. Results indicated that the 1-M ZnCl2-immersed biosolids pyrolyzed at 500 degrees C for 30 min could be reused and were optimal biosolid adsorbents for benzene adsorption. Pore volume distribution analysis indicated that the mesopore contributed more than the macropore and micropore in the biosolid adsorbent. The benzene adsorption capacity of the biosolid adsorbent was 65 and 55% of the G206 (granular-activated carbon) and BPL (coal-based activated carbon; Calgon, Carbon Corp.) activated carbons, respectively. Data from the adsorption and desorption cycles indicated that the benzene adsorption capacity of the biosolid adsorbent was insignificantly reduced compared with the first-run capacity of the adsorbent; therefore, the biosolid adsorbent could be reused as a commercial adsorbent, although its production cost is high.     

Pozzolanic reactivity of the synthetic slag from municipal solid waste incinerator cyclone ash and scrubber ash

This study investigates the pozzolanic reactions and compressive strength of the blended cement manufactured using synthetic slag obtained from municipal solid waste incinerator (MSWI) cyclone ash and scrubber ash as partial replacement of portland cement. The synthetic slag was made by co-melting the MSWI scrubber ash and cyclone ash mixtures at 1400 degrees C for 30 min. Following pulverization, the different types of slag were blended with cement as cement replacement at ratios ranging from 10 to 40 wt %. The synthetic slag thus obtained was quantified, and the characteristics of the slag-blended cement pastes were examined. These characteristics included the pozzolanic activity, compressive strength, hydration activity, crystal phases, species, and microstructure at various ages. The 90-day compressive strength developed by slag-blended cement pastes with 10 and 20 wt % of the cement replaced by the synthetic slag outperformed ordinary portland cement by 1-7 MPa. X-ray diffraction species analyses indicated that the hydrates in the slag-blended cement pastes were mainly portlandite, the calcium silicate hydrate gels, and calcium aluminate hydrate salts, similar to those found in ordinary portland cement paste. Differential thermal and thermogravimetric analysis also indicated that the slag reacted with portlandite to form calcium silicate hydrate gels.     

造船用双角钢式脚手架的危险点电测

对角钢式脚手架进行应力测试和理论计算研究.采用电测法测试了危险截面的应力大小及分布规律.结果表明,2、4测点是危险点;采用斜弯曲理论进行理论计算,所得结论与实验测试是一致的,其中2点受拉应力作用.上述分析为脚手架的设计、制作和安全使用提供了强度分析依据.同时还对脚手架其他安全问题进行了讨论.     

Quantitative indicator of homeostatic risk perception in car following

Driving behavior is largely affected by the risk perception of drivers. On the basis of risk homeostasis theory, we regard that drivers may adjust car movement according to the perceived risks fluctuating around a target level. However, the manner by which risk perception is quantified remains unclear. We propose assumptions on the quantitative indicators of risk perception and identify a suitable quantitative indicator of risk perception in car-following process. Three risk indicators are discussed, i.e. time-to-collision (TTC), time headway (TH), and safety margin (SM). Using homeostatic features as bases, we found that SM more suitably quantifies homeostatic risk perception than TTC or TH does. Data collected from video drive recorders installed in taxis operating in Beijing are used to analyze the target risk level of SM (desired SM, or DSM) of professional drivers during the car-following process. The data collected by Ahn et al. (2004) to verify Newell’s model are converted into DSM data to further analyze the target risk level of general drivers. The DSM histogram of professional drivers shows that the standard deviation of the DSM value is 0.115, with a mean value of 0.862 and a total distribution close to the normal distribution. For a general driver, the mean value of DSM is 0.896, which is higher than that of professional drivers. This research may shed lights on the understanding of driving behavior.     

Biohydrogen production using waste activated sludge as a substrate from fructose-processing wastewater treatment

Biohydrogen production by dark fermentation in a series of batch tests under different environmental control conditions was evaluated to determine the optimal initial cultivation pH and temperature for a continuous-flow kinetic test to validate the kinetic model system. The waste activated sludge (WAS) from fructose-processing manufacturing was used as the model substrate for biohydrogen production. The batch experiments for biohydrogen production were conducted in a 6 l bioreactor. Fifteen batch kinetic tests were investigated when pH was controlled at 6, 7, 8 and 9 as well as the temperature was controlled at 37 °C, 45 °C and 55 °C, respectively. The experimental results indicated that the optimal operational condition for hydrogen production occurred while pH was 7 and temperature was 55 °C with the highest hydrogen production of 7.8 mmol. The optimal recovery time for hydrogen was 25 h in the batch experiments. Furthermore, the kinetic test of biohydrogen production was performed by anaerobic mixed microbial culture in the continuous-flow experiment when pH and temperature was maintained at 7 and 55 °C. Approximately 60% and 7% of substrate solution was converted into acetate and hydrogen, respectively, at the steady state. Roughly only 0.77% and 2.7% of substrate solution was converted into propionate and butyrate, respectively, at a steady-state condition. The experimental and modeling approaches presented in this study could be employed for the design of pilot-scale and full-scale anaerobic biohydrogen fermentors using food-processing waste activated sludge (WAS) as a substrate solution.     

基于满意度的热风炉变论域模糊控制

针对热风炉具有参数时变、强干扰、非线性等特点,其最佳空燃比难以确定的问题,提出一种基于模糊满意度的变论域模糊控制方法。首先通过在线获得加热过程的状态参数,采用满意度函数对空燃比进行评价,并将该评价结果和炉温变化作为变论域模糊控制方法的输入来实时获取最优的空燃比值,从而保证热风炉炉温的温度控制。实际运行结果证实了该系统的有效性。     

可燃气体燃爆特性综合试验装置构建与甲烷试验

为研究半开敞空间内可燃气体爆炸过程,设计带有泄压面的气体爆炸室,并在此基础上构建一套可燃气体燃爆特性综合试验装置。运用该试验装置,研究预混塔内甲烷气体分层现象以及甲烷爆炸浓度与最小点火能之间的变化规律。甲烷分层试验结果表明:静置一段时间后,预混塔中甲烷浓度随高度的增加而增大。最小点火能试验结果显示,当甲烷的试验爆炸体积分数在10%～13%时,其浓度与点火能之间呈现比较平缓的变化关系,而当其体积分数小于10%或大于13%时,浓度稍微变化,其点火能将发生明显变化。     

基于数值模拟的城市中心区风环境研究

利用CFD软件对长沙市中心区典型区域的风环境进行了三维数值模拟研究。结果表明,城市建筑群布局不当会造成多方面不利影响:如建筑群内局部地区气流不畅,污染物难以扩散,影响市民身体健康;街道峡谷风使得行人行动不便,冬季热舒适感差;复杂的风环境可能造成建筑构件的损坏乃至脱落,对地面行人的安全造成威胁;建筑围护结构渗透风增加造成建筑能耗的增加。在城市规划和建设中,中心区风环境状况要引起足够的重视,在建设之前要进行风环境模拟与评估。     

跨座式单轨交通人身安全雷电防护分析

针对跨座式单轨交通列车遭受雷击时列车内的人员安全性,本文通过对列车内人员不接触与列车金属外壳直接连接的金属构件和接触与列车金属外壳直接连接的金属构件两种情况进行计算分析,得出第一种情况下,人员是完全安全的;第二种情况下,人员可能会有像蜜蜂刺痛或烟头灼痛的感觉,但不威胁生命安全。