The oxidation of trace organic impurities in ultrapure water by ultraviolet light (UV), ozone, and the combination of UV/ozone
is investigated. The emphasis is on the development of a global model to simulate the process that take place in the typical
oxidation reactors used in ultrapure water plants. The study also focuses on reaction mechanism for oxidation of multi-component
organic impurities. Eighteen organic model compounds are chosen as representative contaminants. The results demonstrate and
confirm a significant synergistic effect between UV and ozone oxidation. A mechanism for the synergistic oxidation of organic
impurities is proposed and validated with experimental data. The combination of the reaction and the reactor models is used
to determine the fundamental kinetic parameters involved in the three oxidation processes.
Received: 3 July 1998 / Accepted: 4 September 1998 相似文献
Objective: On 2-lane roads, discomfort glare can cause annoyance, discomfort, inconvenience, stress, and fatigue to drivers, posing a risk of accidents. The aim of this study is to evaluate discomfort glare from the headlamps of cars widely used in Iran.
Methods: The discomfort glare of new vehicles including Pride Saba model GTX, Pride Model 131SL, Samand Soren, Peugeot 405, Megane, and Peugeot Pars was examined at distances of 5 to 100 m at a background luminance of 50 cd/m2 (late twilight/early dawn lighting) and 1 cd/m2 (nighttime) using Schmidt-Clausen and Bindels model and de Boer's subjective scale.
Results: According to the de Boer scale, at a background luminance of 50 cd/m2, the discomfort glare for all studied vehicles was between 1.98 and 4.05 in high-beam mode and between 3.5 and 5.4 in low-beam mode. At a background luminance of 1 cd/m2, discomfort glare was between 0.41 and 2.48 in high-beam mode and between 1.93 and 3.84 in low-beam mode. In high-beam mode, the average levels of discomfort glare of these vehicles gradually increased when the distance between cars was reduced by up to about 20 m. In low-beam mode, there was no discomfort glare up to a vehicle distance of 40 m. In addition, at an angle of 1.15°–5.73° between the line of sight and light of vehicles in high-beam mode, the level of discomfort glare was increased, but at an angle of 5.73°–22.9° the level of discomfort glare was reduced. In low-beam mode at an angle of 2.86°–22.9°, the level of discomfort glare was almost identical. The results show that in high-beam mode and with a 100-m distance between vehicles as well as in low-beam mode at intervals of less than 40 m between cars, discomfort glare is created.
Conclusion: It can be concluded that by providing solutions such as installing road lighting system, an increase in luminance of roads, separating or widening road lanes, increasing the lateral distance between vehicles, and increasing the angle between lighted vehicles and drivers can noticeably reduce discomfort glare. 相似文献
Environmental Science and Pollution Research - Peridotite and serpentinites can be used to sequester CO2 emissions through mineral carbonation. Olivine dissolution rate is directly proportional... 相似文献
The goal of the research was to determine the limits and conditions in which the sheet hydroforming process provides a significant advantage over stamping in deep drawing of AA5754 aluminum sheets. Specifically, the maximum draw depth achievable by stamping, warm stamping (WF), sheet hydroforming (SHF), and sheet thermo-hydroforming (THF) of AA5754 aluminum alloy were quantified through experimental and computational modeling. A limited number of forming experiments were conducted with AA5754 aluminum sheets using a cylindrical punch and counteracting fluid at different temperatures and pressures. Several parameters, such as force–displacement, hydroforming pressure and temperature, and the maximum draw depth prior to wrinkling or tearing were measured during the forming process to make comparisons with simulations. The computational study included the simulation of stamping, WF, SHF and THF of AA5754 aluminum sheet with the LS-Dyna code, and the Barlat 2000-2d yield function with temperature-dependent coefficients. To predict the onset of wrinkling and tearing, the numerically generated, temperature-dependent forming limit diagrams (FLDs) based on the Barlat 2000-2d yield function were used. It was found that compared with stamping, SHF and THF can achieve more than 100% deeper draw depths with AA5754 aluminum sheet. The stamping simulations were used also to calculate the optimum blank size and die corner radii for the limiting draw ratio (LDR). The LDR was found to be very sensitive to the punch and die corner radii used in the experiments, which represent the curvature of character lines in an actual part. The LDR for AA5754 aluminum sheet was found to be 1.33 and 2.21 for sharp and round die corner radii, respectively. Overall, it was concluded that SHF is most ideal for deep drawing of aluminum sheets with sharp radii features. With the additional drawability provided by SHF, the automotive industry would be able to make difficult-to-form aluminum parts that cannot be stamped without product concessions such as increasing the die radii. 相似文献
Introduction. This study examined whether cognitive symptoms and health-related quality of life can be affected by welding fume exposure. Method. Participants consisted of welders (n?=?40) and welder assistants (n?=?25) from welding units as the exposed group, and office workers (n?=?44) as the non-exposed group. All participants were studied using ambient air monitoring and two types of questionnaires: the Cognitive Failures Questionnaire (CFQ) and the 36-item Short Form Health Survey (SF-36). Results. Welders and welder assistants were exposed to higher concentrations of all airborne metals than office employees, except for aluminum and chromium (p?0.05). Mean (95% confidence interval) CFQ score was higher in welders (26.42 (12.74)) compared with welder assistants (22.68 (14.37)) and the non-exposed group (21.38 (8.75)), although these differences were not statistically significant. Mean total score of the SF-36 significantly differed among the three groups (p?0.05) and welders had the lowest score (M (SD)?=?54.84 (17.88)). The relationships between total CFQ score and the measured concentration of nickel at peak work rate was significant for welders. Conclusion. Cognitive symptoms and health-related quality of life were not related to the measures of welding fume exposure and further research should be performed to find other influencing factors. 相似文献
Light extinction, which is the extent of attenuation of light signal for every distance traveled by light in the absence of special weather conditions (e.g., fog and rain), can be expressed as the sum of scattering and absorption effects of aerosols. In this paper, diurnal and seasonal variations of the extinction coefficient are investigated for the urban areas of Tehran from 2007 to 2009. Cases of visibility impairment that were concurrent with reports of fog, mist, precipitation, or relative humidity above 90 % are filtered. The mean value and standard deviation of daily extinction are 0.49 and 0.39 km?1, respectively. The average is much higher than that in many other large cities in the world, indicating the rather poor air quality over Tehran. The extinction coefficient shows obvious diurnal variations in each season, with a peak in the morning that is more pronounced in the wintertime. Also, there is a very slight increasing trend in the annual variations of atmospheric extinction coefficient, which suggests that air quality has regressed since 2007. The horizontal extinction coefficient decreased from January to July in each year and then increased between July and December, with the maximum value in the winter. Diurnal variation of extinction is often associated with small values for low relative humidity (RH), but increases significantly at higher RH. Annual correlation analysis shows that there is a positive correlation between the extinction coefficient and RH, CO, PM10, SO2, and NO2 concentration, while negative correlation exists between the extinction and T, WS, and O3, implying their unfavorable impact on extinction variation. The extinction budget was derived from multiple regression equations using the regression coefficients. On average, 44 % of the extinction is from suspended particles, 3 % is from air molecules, about 5 % is from NO2 absorption, 0.35 % is from RH, and approximately 48 % is unaccounted for, which may represent errors in the data as well as contribution of other atmospheric constituents omitted from the analysis. Stronger regression equation is achieved in the summer, meaning that the extinction is more predictable in this season using pollutant concentrations. 相似文献
Ionic liquids (ILs) have been accepted as ‘green’ alternatives to the organic solvents in a range of synthesis, catalysis
and electrochemistry, because of their distinctive chemical and physical properties. In this investigation, N,N′-(pyromellitoyl)-bis-l-tyrosine dimethyl ester as a chiral bioactive diphenolic monomer was prepared in three steps. The polycondensation of this
monomer with various aromatic and aliphatic diisocyanates such as 4,4′-methylene-bis-(4-phenylisocyanate) (6a), toluylene-2,4-diisocyanate (6b), isophorone diisocyanate (6c) and hexamethylene diisocyanate (6d) were carried out in the presence of tetrabutylammonium bromide as a molten IL under microwave irradiation conditions and
was compared with polymerization in traditional solvent like N-methyl-2-pyrrolidone. The results show that IL efficiently absorbs microwave energy, thus leading to a very high heating
rate. Thus IL method is safe and green since toxic and volatile organic solvents were eliminated. All of the novel poly(urethane-imides)
(PUIs) showed good solubility in various organic solvents. The obtained new polymers were characterized with FT-IR, 1H-NMR, elemental and thermogravimetric analysis techniques. Thermogravimetric analysis (TGA) of two representative PUIs demonstrated
that they are rather thermally stable. In vitro toxicity studies showed that the synthetic materials are biologically active
and they are nontoxic to microbial growth then could be classified as bioactive and biodegradable compounds. 相似文献
Nanoparticles are not specifically targeted in conventional treatment schemes; consequently, typical wastewater treatment systems are ineffective for nanoparticles removal. With rapidly increasing concern over their health effects, improved understanding of nanoparticle transport and retention in porous media filters is critical because of its application in new wastewater treatment methods and for assessment of the fate of the discharged nanoparticles in soil. In this study, a unique and robust integrated method is developed and validated. Experimentally, this approach uses an on-line, real-time, and in situ method for measuring nanoparticle retention dynamics, eliminating the laborious and less accurate sampling and off-line analysis. The data analysis part is a process simulator which provides both kinetic properties of the retention process as well as the overall capacity and loading. This technique is validated by application to the transport and retention of TiO2 nanoparticles in two vastly different porous filtration media—activated carbon and sand. TiO2 retained concentrations ranged from 0.24 to 0.37 mg g?1 for activated carbon and 0.01–0.014 mg g?1 for sand. The integrated method presented here is useful for both comparison of the filtration effectiveness of various porous materials as well as for process optimization and scale-up for industrial applications. 相似文献