Modeling and physical interpretation of photocatalytic oxidation efficiency in indoor air applications

Volatile organic compounds (VOCs) are the major pollutants in indoor air, which significantly impact indoor air quality (IAQ). As a promising technique to remove VOCs, photocatalytic oxidation (PCO) takes the advantages of oxidation of a large range of VOCs with low energy consumption. In this study, the mass transports and reaction mechanism involved in the PCO process have been studied. In addition, the kinetic models of PCO on the different conditions of elementary reactions have been critically reviewed. Moreover, the factors that may affect the efficiency of PCO were interpreted based on the established fundamental mechanism of PCO. Some recommendations were made for future work to improve the efficiency of PCO system for building applications.     

Application of a molecular biology concept for the detection of DNA damage and repair during UV disinfection

As nucleic acids are major targets in bacteria during standardised UV disinfection (254 nm), inactivation rates also depend on bacterial DNA repair. Due to UV-related DNA modifications, PCR-based approaches allow for a direct detection of DNA damage and repair during UV disinfection. By applying different primer sets, the correlation between amplicon length and PCR amplification became obvious. The longer the targeted DNA fragment was, the more UV-induced DNA lesions inhibited the PCR. Regeneration of Pseudomonas aeruginosa, Enterococcus faecium, and complex wastewater communities was recorded over a time period of 66 h. While phases of intensive repair and proliferation were found for P. aeruginosa, no DNA repair was detected by qPCR in E. faecium. Cultivation experiments verified these results. Despite high UV mediated inactivation rates original wastewater bacteria seem to express an enhanced robustness against irradiation. Regeneration of dominant and proliferation of low-abundant, probably UV-resistant species contributed to a strong post-irradiation recovery accompanied by a selection for β-Proteobacteria.     

Photoinitiated oxidation of geosmin and 2-methylisoborneol by irradiation with 254 nm and 185 nm UV light

The degradation of geosmin and 2-methylisoborneol (2-MIB) by UV irradiation at different wavelengths was investigated under varying boundary conditions. The results showed that conventional UV radiation (254 nm) is ineffective in removing these compounds from water. In contrast to the usual UV radiation UV/VUV radiation (254 + 185 nm) was more effective in the removal of the taste and odour compounds. The degradation could be described by a simple pseudo first-order rate law with rate constants of about 1.2 × 10⁻³ m² J⁻¹ for geosmin and 2-MIB in ultrapure water. In natural water used for drinking water abstraction the rate constants decreased to 2.7 × 10⁻⁴ m² J⁻¹ for geosmin and 2.5 × 10⁻⁴ m² J⁻¹ for 2-MIB due to the presence of NOM. Additionally, the formation of the by-product nitrite was studied. In the UV/VUV irradiation process up to 0.6 mg L⁻¹ nitrite was formed during the complete photoinitiated oxidation of the odour compounds. However, the addition of low ozone doses could prevent the formation of nitrite in the UV/VUV irradiation experiments.     

斜长角闪岩累积损伤特性的围压效应研究

利用带围压装置的SHPB设备对不同围压等级下斜长角闪岩在冲击荷载循环作用下动态力学性能进行试验研究,通过对试验过程的能量计算和不同循环作用次数下试件应力-应变曲线的分析,研究斜长角闪岩在冲击荷载循环作用下的累积比能量吸收值与入射能量,损伤度与围压等参量之间的关系。研究结果表明,当入射波能量相同时,斜长角闪岩的比能量吸收值随围压的增加而减小,且斜长角闪岩的比能量吸收值与围压和入射波能量具有良好的规律性。当围压逐渐增大时,斜长角闪岩损伤度的增加随累积比能量吸收值增加的趋势变缓,即围压越高,试件达到相同损伤度所需耗散的能量越多。得到损伤度D与累积比能量吸收值和围压之间的关系表达式。     

Spatially distributed damage in sandstone under stress-freeze-thaw coupling conditions

In the present study, we tried to understand the spatially distributed damage in sandstone samples under the coupled stress-freeze-thaw (SFT) conditions. Firstly, uniaxial compressive stresses (i.e. 0 MPa, 10 MPa, 20 MPa, and 25 MPa) were applied to the samples, and then freeze-thaw (FT) cycles (0, 8, 16, and 24) were performed on the uniaxially stressed samples to realize the SFT coupling. Next, real-time CT scanning was conducted to observe the induced damage. The total porosity was introduced to quantitatively evaluate the damage degree. The local porosity variation, with the distance from the center of the sandstone sample, was analyzed to understand the spatial distribution of damage. Finally, the coupling effects of SFT on the damage gradient were discussed. The results indicate that the porosity rises with FT cycles, and the applied stresses can accelerate the increase in porosity. The damage increases exponentially with the distance from the center of the sample. The damage presents a spatial gradient distribution, not the commonly used uniform distribution in various studies. The damage gradient increases with FT cycles, and the increasing rate in damage gradient decreases at uniaxial stress of 0 MPa and 10 MPa first, but the increasing rate in damage gradient increases with FT cycles then at stress increasing to 20 MPa.     

不同加载方式下实腹式型钢混凝土T形截面柱损伤试验研究

为研究不同加载方式下实腹式型钢混凝土T形截面柱沿腹板方向的损伤演化规律,设计并制作了10根缩尺比为1/2、剪跨比为2.5的型钢混凝土T形截面柱,变化参数为轴压比、配钢率及加载制度。基于试验成果,对单调荷载及低周反复荷载作用下T形截面柱的荷载 位移曲线及能量耗散能力进行了分析。结果表明：从初始加载到失效,型钢混凝土T形截面柱的损伤过程可分为5个阶段,分别为无损阶段、轻微损伤阶段、损伤稳步发展阶段、严重损伤阶段和破坏阶段;与单调加载相比,随着位移幅值的增大与荷载循环次数的增加,T形截面柱的承载力、极限变形能力和极限耗能能力均有不同程度的降低。在试验研究的基础上,考虑荷载循环次数、位移幅值与极限承载能力的动态关系以及加载路径对T形截面柱损伤的影响,建立了由最大变形与滞回耗能双参数组合的非线性损伤模型,并验证了该模型的合理性。     

强震下钢框架动力时程分析模型应用对比分析

为比较几种有限元模型计算钢框架动力时程分析的精度以及效率,采用通用有限元软件ABAQUS,分别建立壳单元模型、多尺度模型、考虑损伤退化的纤维梁模型以及不考虑损伤退化的传统两折线模型,比较几种模型在计算结构变形、结构破坏形态等方面的特征,检验等效本构模型的计算精度,深入探讨考虑损伤退化对钢框架抗震性能的影响。同时,对比几种模型的计算效率,考察等效本构模型的改良作用。研究结果表明:在一开始损伤退化没有出现的时候,四种模型的计算结果基本一致。一旦由于塑性应变累积导致损伤退化的发生,考虑损伤退化的纤维模型、壳单元模型和多尺度模型的计算结果吻合良好,说明等效本构模型能够反映结构出现损伤对结构变形的放大作用。而没有考虑损伤退化的两折线杆系模型与三者的计算结果差别较大,计算得到的变形结果偏小,低估了结构的层间位移角和层位移,导致计算结果偏于不安全。计算效率上,等效本构模型的计算时间远小于壳单元模型和多尺度模型,比两折线模型略高,实现计算精度和计算效率的平衡。     

Photocatalysis of p-chlorobenzoic acid in aqueous solution under irradiation of 254 nm and 185 nm UV light

The photolytic and photocatalytic degradation of p-chlorobenzoic acid (p-CBA) in aqueous solution were investigated using two kinds of low-pressure mercury lamps: one emitted at 254 nm and the other emitted at 254 nm and 185 nm. Both the photolytic and photocatalytic degradations of p-CBA followed pseudo first-order reaction rate form. The rate constants decreased with increase of initial concentration in VUV and TiO2/VUV. The TiO2/VUV was the most efficient process, in which rate constants was 3.0-6.5 times as that in TiO2/UV depending on the initial concentration. The gas bubbling efficiently improved the mass transfer and the kind of bubbling gas had evident influence on the reaction rate except in UV photolysis. TOC reduction rate was greatly reduced in VUV and TiO2/VUV processes when bubbled with nitrogen gas, it was no more than one third of that when bubbled with oxygen, however, the degradation rate of p-CBA was not affected by bubbled nitrogen so greatly.     

Stability analysis of surrounding rock mass in underground powerhouse considering damage effect of microfractures

A high-precision microseismic(MS) monitoring system was built to monitor surrounding rock microfractures in the underground powerhouse on the left bank of Shuangjiangkou Hydropower Station. The surrounding rock damage area with spatiotemporal clustering of MS activities was studied for qualitative analysis of the damage mechanism of surrounding rock microfractures, based on the source parameters of MS events. The surrounding rock microfracture scale characterized by the source radius of MS event...     

The effect of a photocatalytic air purifier on indoor air quality quantified using different measuring methods

The effect on indoor air quality of an air purifier based on photocatalytic oxidation (PCO) was determined by different measuring techniques: sensory assessments of air quality made by human subjects, Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) and chromatographic methods (Gas Chromatography/Mass Spectrometry and High-Pressure Liquid Chromatography with UV detection). The experiment was conducted in a simulated office, ventilated with 0.6 h⁻¹, 2.5 h⁻¹ and 6 h⁻¹, in the presence of additional pollution sources (carpet, chipboard and linoleum). At the lowest air change rate, additional measurements were made with no pollution sources present in the office. All conditions were tested with the photocatalytic air purifier turned on and off. The results show that operation of the air purifier in the presence of pollutants emitted by building materials and furniture improves indoor air quality, as documented by sensory assessments made by human subjects. It also reduces concentrations of many chemical compounds present in the air as documented by the PTR-MS technique. For the lowest ventilation, results from measurements using the chromatographic methods have similar tendency, however many of the 50 compounds that were targeted for analysis were not detected at all, independent of whether the purifier was on or off. For the two conditions with higher ventilation the results were inconclusive.     

单轴循环冲击下岩石的动力学特性及其损伤模型研究

利用改进的大直径SHPB试验装置,对花岗岩试件进行单轴循环冲击压缩试验,分析花岗岩在循环冲击载荷下的力学特性及能量吸收规律。通过基于Weibull分布的动态统计损伤模型计算岩石的累积损伤,结合试验曲线分析岩石累积损伤的演化规律。研究结果表明：随着冲击载荷循环作用次数的增加,变形模量变小,试件的屈服应变增大,峰值应力呈降低趋势。岩石的累积比能量吸收值随着冲击次数的增加而增大,且试件破坏前其值增加缓慢,试件破坏时其值急剧增大。基于Weibull分布的动态损伤本构模型的计算曲线与试验曲线具有较好的一致性,该模型能反映岩石的强度与应变、应变率的关系。累积损伤随着循环冲击次数的增加而增大,其增加速率由小变大,试件破坏前累积损伤的增加较为平缓,其主要增量由最后一次冲击破坏产生。     

爆破动荷载作用下围岩累积损伤效应声波测试研究

基于声波测试原理,利用RSM-SY5智能型声波仪,对厂坝铅锌矿某巷道围岩在爆破动荷载作用下产生的累积损伤效应进行了现场试验研究。研究表明:既有开挖爆破对巷道围岩的影响深度为0.8～1.2 m,根据钻孔的深度,在3.5～4.8 m深度的岩体内进行爆破累积损伤效应研究是可行的;随着爆破次数的不断增加,岩体声波速度逐渐降低,损伤度D呈现出非线性累积规律;随着与爆源距离的增大,岩体爆破损伤程度减小,累积损伤效应逐渐变得不明显;水平和垂直方向测试结果存在较大差异,说明爆破作用下岩体损伤具有各向异性的特征。爆破装药位置和药量对岩体损伤累积规律有一定的影响。装药区段范围内的岩体损伤程度最严重,装药量越大,岩体损伤程度也越大。测试成果为进一步的岩体力学参数研究和地下洞室稳定性分析提供了参考依据。     

A methodology for evaluating dynamic responses of steel columns subjected to blast load under different situations

In recent studies, the uniform simplified distribution blast load and numerical simulation have proven to be prevalent in the use of investigating structural components dynamic behaviour during blast events, whilst neglecting the negative phase pressure. This study compares the steel column's response during the total pressure period to that of its response during only the positive stage. Moreover, the real blast pressure has varying values depending on the point distance and explosion incident angle. The real blast load curve was derived by using a specialised program to calculate pressure at different points on the steel column vertical line; and the results were used to compare its impact with the uniform and concentrated cases. Also ABAQUS finite element code was used to check the validity of the single-degree-of-freedom (SDOF) analysis method when the column is subjected to axial and transverse blast loads. The obtained results show the SDOF inability through dynamic reaction calculations. In addition, SDOF has limitations in dealing with dynamic steel response when the axial load ratio was greater than 0.5. Damage prediction methods and equations were introduced through different concepts and the ductility ratio was used to estimate the damage level of 100 kg TNT at 4.5 m stand-off distance. The strain rate effects were included in the material with different scenarios based on the dynamic increase factor.     

Effects of UV 254 irradiation on residual chlorine and DBPs in chlorination of model organic-N precursors in swimming pools

Ultraviolet (UV) irradiation is commonly applied as a secondary disinfection process in chlorinated pools. UV-based systems have been reported to yield improvements in swimming pool water and air chemistry, but to date these observations have been largely anecdotal. The objectives of this investigation were to evaluate the effects of UV irradiation on chlorination of important organic-N precursors in swimming pools.Creatinine, L-arginine, L-histidine, glycine, and urea, which comprise the majority of the organic-N in human sweat and urine, were selected as precursors for use in conducting batch experiments to examine the time-course behavior of several DBPs and residual chlorine, with and without UV₂₅₄ irradiation. In addition, water samples from two natatoria were subjected to monochromatic UV irradiation at wavelengths of 222 nm and 254 nm to evaluate changes of liquid-phase chemistry. UV₂₅₄ irradiation promoted formation and/or decay of several chlorinated N-DBPs and also increased the rate of free chlorine consumption. UV exposure resulted in loss of inorganic chloramines (e.g., NCl₃) from solution. Dichloromethylamine (CH₃NCl₂) formation from creatinine was promoted by UV exposure, when free chlorine was present in solution; however, when free chlorine was depleted, CH₃NCl₂ photodecay was observed. Dichoroacetonitrile (CNCHCl₂) formation (from L-histidine and L-arginine) was promoted by UV₂₅₄ irradiation, as long as free chlorine was present in solution. Likewise, UV exposure was observed to amplify cyanogen chloride (CNCl) formation from chlorination of L-histidine, L-arginine, and glycine, up to the point of free chlorine depletion. The results from experiments involving UV irradiation of chlorinated swimming pool water were qualitatively consistent with the results of model experiments involving UV/chlorination of precursors in terms of the behavior of residual chlorine and DBPs measured in this study.The results indicate that UV₂₅₄ irradiation promotes several reactions that are involved in the formation and/or destruction of chlorinated N-DBPs in pool settings. Enhancement of DBP formation was consistent with a mechanism whereby a rate-limiting step in DBP formation was promoted by UV exposure. Promotion of these reactions also resulted in increases of free chlorine consumption rates.     

热氧老化沥青多次损伤-愈合性能

为研究沥青在多次损伤条件下的愈合性能,采用动态剪切流变(DSR)仪中的时间扫描模式对沥青进行损伤-愈合循环加载试验,以沥青愈合期间的复数模量恢复程度(即愈合指数)为愈合指标,分析了不同热氧老化程度下70~#基质沥青与SBS改性沥青多次损伤-愈合性能规律,并结合沥青傅里叶红外光谱(FTIR)试验,以特征官能团峰面积比定量分析了沥青功能基团的组成和含量对其自愈能力的影响.结果表明:沥青愈合指数随损伤-愈合次数的增加而减小,首次损伤时沥青愈合指数减小程度最大.老化程度对沥青愈合指数影响显著,表现为老化程度越高愈合指数越小.SBS改性沥青多次损伤-愈合和老化后的愈合性能均优于70~#基质沥青,SBS改性剂可增强沥青的抗疲劳损伤能力和抗老化能力.沥青中大分子含量越高,分子扩散速率越慢,自愈能力越弱;轻长型分子含量越高,分子扩散速率越快,自愈能力越强.     

不同养护条件对钢矿粉掺合料活化效应的影响研究

制备了钢矿粉复合掺合料,通过测试掺合料胶砂活性指数和混凝土抗压强度,研究标准养护和蒸汽养护对钢矿粉掺合料活化效应的影响,并对不同养护条件下掺合料混凝土的胶凝系数K进行对比。结果表明:不论是胶砂活性还是混凝土强度,蒸汽养护更有利于体系中水化反应,高温条件下矿粉和激发剂中的活性物质能更大程度地参与活化反应,加速水化产物的生成,使体系的活性和强度大幅度提高;胶凝系数K也侧面证实了这一观点:在蒸养条件下K值比标准养护条件的高,说明蒸汽养护时钢矿粉掺合料对混凝土强度贡献更大。     

Effect of different organotins on DNA of mollusk (Scapharca inaequivalvis) erythrocytes assessed by the comet assay

The alkaline comet assay, employing a single-cell gel-electrophoresis, is a rapid, simple and sensitive technique for visualizing and measuring DNA damage leading to strand breakage in individual cells. In this study, we report data about the effect of different organotin compounds (MBTC, DBTC and TBTC) on DNA from erythrocytes of the Scapharca inaequivalvis bivalve mollusc. Our results show significant DNA damage after 30 min in vitro incubation with 10microM of organotins. Since TBTC turned out to be the most genotoxic compound, followed by MBTC and DBTC, we exposed the molluscs to 50ppb of TBTC for 11 days. A significant increase of comet parameters was measured in our experimental conditions. The use of the comet test as a high-throughput screening assay to monitor the effect of environmental pollutants on marine organisms has been proposed.     

Feasibility investigation for a bridge damage identification method through moving vehicle laboratory experiment

This paper investigated the feasibility of the pseudo-static damage identification method derived from a bridge–vehicle interaction system through a moving vehicle laboratory experiment. The element stiffness index, defined as the ratio of flexural rigidity of a damaged member to that of an intact member, serves as the damage indicator. Three vehicle models and two travelling speeds were considered in the experiment to examine the effect of vehicle's dynamic characteristic and travelling speed on identified results. It is demonstrated that locations and severities of damages are detectable using the proposed method in spite of the probable changes of roadway roughness and environmental conditions. In addition, adopting higher vehicle speed as well as the vehicle with frequency close to that of the bridge increased the probability of detecting damages.     

不同竖向荷载下PHC管桩水平承载性能研究

在桩基设计中通常分别确定单桩的竖向和水平向承载力,而不考虑竖向荷载与水平荷载之间的相互作用对桩承载力的影响,这显然不能反映桩的真实受力状况。本文通过现场的载荷试验,分析了PHC管桩在不同竖向荷载下的水平承载性能,利用有限元软件ANSYS对该实例进行数值模拟,结果表明：在先施加竖向荷载再施加水平荷载时,存在一个最优的竖向...     

一种基于冲击响应的装配式板梁桥铰接缝病害动力评估方法

提出一种基于冲击响应频响函数和模型修正理论的装配式板梁桥铰接缝病害动力评估方法。将铰接缝整体平均刚度作为待识别变量,以特定频率段内的频响函数相关性指数构造目标函数,改进既有的有限元模型修正技术,从而实现对病害铰接缝的定位以及损伤程度的定量识别。数值分析结果表明：利用文中所提方法可实现对全桥多个铰接缝不同程度病害的同步识别,且计算效率高;所提方法抗噪能力较强,可保证收敛到全局最优解;冲击荷载施加位置和测点布置位置对病害识别结果影响较小。对某装配式板梁桥进行现场动力试验,更新改造前后评估结果与桥梁实际状态相符,从而从实际应用角度证明所提方法的可靠性和实用性。