Robust active control against wind-induced structural vibrations

Slender flexible structures are vulnerable to vibrations under wind loads. The dynamic model of a frame-like structure is obtained by finite element approximation in this paper and used further for the design of an active control mechanism. The behavior of the structure is described by simplified linear equations. A linear quadratic regulator and an H₂ optimal control method are used for the suppression of the extended vibration effects. Structured uncertainties are considered to reflect the errors between the model and the reality. To accommodate directly the plant uncertainties and to obtain a best possible performance in the face of uncertainties a robust H_∞ optimal control for active control structure is used. The two latter robust controllers take into account as well incompleteness of the measured information, a fact that cannot be neglected in civil engineering, and lead to applicable designs of smart structures. The numerical simulation shows that vibrations can be suppressed by means of the proposed methods.     

A new method to calculate wind profile parameters of the wind tunnel boundary layer

This paper introduces a new method to process wind profile data of simulated atmospheric boundary layer flows in the wind tunnel so as to obtain the two important wind profile parameters—the surface roughness length z₀ and the friction velocity u_*. Instead of using the wind speed profile, the turbulent intensity profile of the turbulent surface layer, which is measured with a single probe hot-wire anemometer, is used to calculate the surface roughness length z₀. Then, the calculated surface roughness length z₀ is substituted into the mean wind speed profile of the constant flux layer to calculate friction velocity u_*. From our results this method is better than the simple regression method using the wind speed profile, which has been widely used.     

Efficiency and energy requirements for the transformation of organic micropollutants by ozone, O3/H2O2 and UV/H2O2

The energy consumptions of conventional ozonation and the AOPs O₃/H₂O₂ and UV/H₂O₂ for transformation of organic micropollutants, namely atrazine (ATR), sulfamethoxazole (SMX) and N-nitrosodimethylamine (NDMA) were compared. Three lake waters and a wastewater were assessed. With p-chlorobenzoic acid (pCBA) as a hydroxyl radical (^•OH) probe compound, we experimentally determined the rate constants of organic matter of the selected waters for their reaction with ^•OH (k_OH,DOM), which varied from 2.0 × 10⁴ to 3.5 × 10⁴ L mgC⁻¹ s⁻¹. Based on these data we calculated ^•OH scavenging rates of the various water matrices, which were in the range 6.1-20 × 10⁴ s⁻¹. The varying scavenging rates influenced the required oxidant dose for the same degree of micropollutant transformation. In ozonation, for 90% pCBA transformation in the water with the lowest scavenging rate (lake Zürich water) the required O₃ dose was roughly 2.3 mg/L, and in the water with the highest scavenging rate (Dübendorf wastewater) it was 13.2 mg/L, corresponding to an energy consumption of 0.035 and 0.2 kWh/m³, respectively. The use of O₃/H₂O₂ increased the rate of micropollutant transformation and reduced bromate formation by 70%, but the H₂O₂ production increased the energy requirements by 20-25%. UV/H₂O₂ efficiently oxidized all examined micropollutants but energy requirements were substantially higher (For 90% pCBA conversion in lake Zürich water, 0.17-0.75 kWh/m³ were required, depending on the optical path length). Energy requirements between ozonation and UV/H₂O₂ were similar only in the case of NDMA, a compound that reacts slowly with ozone and ^•OH but is transformed efficiently by direct photolysis.     

Simultaneous abiotic reduction-biotic oxidation in a microbial-MnO2-catalyzed Fenton-like system

The possibility of simultaneous activity of superoxide-mediated transformations and heterotrophic aerobic bacterial metabolism was investigated in catalyzed H₂O₂ propagations (CHP; i.e., modified Fenton's reagent) systems containing Escherichia coli. Two probe compounds were used: glucose for the detection of heterotrophic metabolism of E. coli, and tetrachloromethane (CCl₄) for the detection of superoxide generated in a MnO₂-catalyzed CHP system. In the MnO₂-catalyzed CHP system without bacteria, only CCl₄ loss was observed; in contrast, only glucose degradation occurred E. coli systems without CHP reagents. In combined microbial-MnO₂ CHP reactions, loss of both probes was observed. Glucose assimilation decreased and CCl₄ transformation increased as a function of H₂O₂ concentration. Central composite rotatable experimental designs were used to determine that the conditions providing maximum simultaneous abiotic-biotic reactions were a biomass level of 10⁹ CFU/mL, 0.5 mM H₂O₂, and 0.5 g MnO₂. These results demonstrate that bacterial metabolism can occur in the presence of superoxide-mediated transformations. Such coexisting reactions may occur when H₂O₂ is injected into MnO₂-rich regions of the subsurface as a microbial oxygen source or for in situ oxidation; however, process control of such coexisting transformations may be difficult to achieve in the subsurface due to heterogeneity. Alternatively, hybrid abiotic reduction-biotic oxidation systems could be used for the treatment of industrial effluents or dilute solvent wastes that contain traces of highly halogenated compounds.     

Robust control of civil structures with parametric uncertainties through D‐K iteration

Active control is an alternative method to suppress the civil structural vibration, which is more effective than the passive control or strengthening the structural components. The performance of active control is dependent on the control strategy and the accuracy of the structural model. However, there always exist some uncertainties in the model, such as mass, damping and stiffness uncertainties. This paper presents a robust H_∞ controller design for civil structures with consideration of the parametric uncertainties. The formulation to extract the parametric uncertainties from the structural model matrices is proposed through the linear fractional transformations approach. The robust H_∞ controller design for the civil structures with the parametric uncertainties is achieved through the D‐K iteration method. The linear matrix inequality is then used in the H_∞ optimization procedure of the D‐K iteration. The robustness of the controller is first numerically validated by a four‐story building example and then experimentally corroborated by a shaking table test of a two‐story frame with one active mass damper. The results show that the robust H_∞ controller can consider the parametric uncertainties in the civil structural model and achieve the robust performance. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigating synergism during sequential inactivation of MS-2 phage and Bacillus subtilis spores with UV/H2O2 followed by free chlorine

A sequential application of UV as a primary disinfectant with and without H₂O₂ addition followed by free chlorine as secondary, residual disinfectant was performed to evaluate the synergistic inactivation of selected indicator microorganisms, MS-2 bacteriophage and Bacillus subtilis spores. No synergism was observed when the UV irradiation treatment was followed by free chlorine, i.e., the overall level of inactivation was the same as the sum of the inactivation levels achieved by each disinfection step. With the addition of H₂O₂ in the primary UV disinfection step, however, enhanced microbial inactivation was observed. The synergism was observed in two folds manners: (1) additional inactivation achieved by hydroxyl radicals generated from the photolysis of H₂O₂ in the primary UV disinfection step, and (2) damage to microorganisms in the primary step which facilitated the subsequent chlorine inactivation. Addition of H₂O₂ in the primary disinfection step was also found to be beneficial for the degradation of selected model organic pollutants including bisphenol-A (endocrine disruptor), geosmin (taste and odor causing compound) and 2,4-D (herbicide). The results suggest that the efficiency of UV/free chlorine sequential disinfection processes, which are widely employed in drinking water treatment, could be significantly enhanced by adding H₂O₂ in the primary step and hence converting the UV process to an advanced oxidation process.     

Comparative effect of simulated solar light,UV, UV/H2O2 and photo-Fenton treatment (UV–Vis/H2O2/Fe) in the Escherichia coli inactivation in artificial seawater

Innovative disinfection technologies are being studied for seawater, seeking a viable alternative to chlorination. This study proposes the use of H₂O₂/UV₂₅₄ and photo-Fenton as disinfection treatment in seawater. The irradiations were carried out using a sunlight simulator (Suntest) and a cylindrical UV reactor. The efficiency of the treatment was compared for Milli-Q water, Leman Lake water and artificial seawater. The presence of bicarbonates and organic matter was investigated in order to evaluate possible effects on the photo-Fenton disinfection treatment. The photo-Fenton treatment, employing 1 mg L⁻¹ Fe²⁺ and 10 mg L⁻¹ of H₂O₂, led to the fastest bacterial inactivation kinetics. Using H₂O₂/UV₂₅₄ high disinfection rates were obtained similar to those obtained with photo-Fenton under UV₂₅₄ light. In Milli-Q water, the rate of inactivation for Escherichia coli was higher than in Leman Lake water and seawater due to the lack of inorganic ions affecting negatively bacteria inactivation. The presence of bicarbonate showed scavenging of the OH^• radicals generated in the treatment of photo-Fenton and H₂O₂/UV₂₅₄. Despite the negative effect of inorganic ions, especially HCO₃^-, the disinfection treatments with AOPs in lake water and seawater improved significantly the disinfection compared to light alone (simulated sunlight and UV₂₅₄). In the treatment of photo-Fenton with simulated sunlight, dissolved organic matter had a beneficial effect by increasing the rate of inactivation. This is associated with the formation of Fe³⁺-organo photosensitive complexes leading to the formation of ROS able to inactivate bacteria. This effect was not observed in the photo-Fenton with UV₂₅₄. Growth of E. coli surviving in seawater was observed 24 and 48 h after treatment with UV light. However, growth of surviving bacteria was not detected after photo-Fenton with UV₂₅₄ and H₂O₂/UV₂₅₄ treatments.     

Evaluation of a quantitative H2S MPN test for fecal microbes analysis of water using biochemical and molecular identification

The sensitivity and specificity of the H₂S test to detect fecal bacteria in water has been variable and uncertain in previous studies, partly due to its presence-absence results. Furthermore, in groundwater samples false-positive results have been reported, with H₂S-positive samples containing no fecal coliforms or Escherichia coli. False-negative results also have been reported in other studies, with H₂S-negative samples found to contain E. coli. Using biochemical and molecular methods and a novel quantitative test format, this research identified the types and numbers of microbial community members present in natural water samples, including fecal indicators and pathogens as well as other bacteria. Representative water sources tested in this study included cistern rainwater, a protected lake, and wells in agricultural and forest settings. Samples from quantitative H₂S tests of water were further cultured for fecal bacteria by spread plating onto the selective media for detection and isolation of Aeromonas spp., E. coli, Clostridium spp., H₂S-producers, and species of Salmonella and Shigella. Isolates were then tested for H₂S production, and identified to the genus and species level using biochemical methods. Terminal Restriction Fragment Length Polymorphisms (TRFLP) was the molecular method employed to quantitatively characterize microbial community diversity. Overall, it was shown that water samples testing positive for H₂S bacteria also had bacteria of likely fecal origin and waters containing fecal pathogens also were positive for H₂S bacteria. Of the microorganisms isolated from natural water, greater than 70 percent were identified using TRFLP analysis to reveal a relatively stable group of organisms whose community composition differed with water source and over time. These results further document the validity of the H₂S test for detecting and quantifying fecal contamination of water.     

Stress redistribution and ground arch development during tunneling

Three-dimensional stress adjustment caused by tunneling is related with ground arching development. Investigating the development of ground arching by stress redistribution during tunneling is presented. A three-dimensional numerical simulation model was developed to gain understanding of adjustment of tunneling stress. Vertical stress adjustments σ_ZZ above the tunnel roof during tunneling are analyzed, using four different cover depths H and four lateral pressure coefficients K. Shift of the inflection points of σ_ZZ-depth curves above the tunnel roof during tunneling can be a reliable index to show the development of ground arching.     

An alternative model for evaluating sustainable urbanization

In recent years, there has been rapid urbanization worldwide, resulting in both benefits and problems. Sustainable urbanization has become an important aspect in promoting sustainable development. Existing studies have introduced various methodologies to guide urbanization towards sustainable practices. The application of these methods has contributed to improving urban sustainability. To further support the effective applications of the principles of sustainable urbanization, a tool is needed to evaluate whether a particular process of urbanization is sustainable. In this paper, we introduce an alternative model for evaluating sustainable urbanization by investigating the relationship between urbanization and urban sustainability. The practice of sustainable urbanization is defined as a dynamic process that enables urban sustainability to improve or to maintain a certain level of practice. By employing this definition, we introduce a sustainable urbanization elasticity coefficient e_SU, which is defined by two parameters: urbanization velocity (V_μR) and urban sustainability velocity (V_μS). The sustainability of an urbanization process is measured by the value of e_SU or read from the V_μR-V_μS coordinate. A case study demonstrates the application of the measure e_SU and the V_μR-V_μS coordinate. The proposed model is an effective tool to help policy makers understand whether the urbanization processes they support are sustainable and thus whether to correct practices. The model also allows comparison of different urbanization practices and thereby encourages the sharing of successful experiences.     

An integrated approach to identify the influential priority of the factors governing anaerobic H2 production by mixed cultures

An integrated approach incorporating response surface methodology, grey relational entropy, and fuzzy analytic hierarchy process is established to prioritize the influence of main factors governing the anaerobic H₂ production process and their influential priority. Response surface methodology is employed to design experiments, and the grey relational entropy is used to evaluate the influential grade of the three input factors, i.e., pH, temperature and initial substrate concentration (S_ini), on the H₂ yield, maximum H₂ production rate and volatile fatty acid yield. In addition, through a combination of grey relational entropy, fuzzy analytic hierarchy process, which is used to determine the weight, and accelerating genetic algorithm, which is employed to minimize the nonlinear function in fuzzy analytic hierarchy process, the overall H₂ production process performance could be comprehensively evaluated. The results show that pH is the most important factor influencing the yields of H₂ and volatile fatty acids, while S_ini has the most significant effect on the maximum H₂ production rate. Compared to pH and S_ini, temperature has a less important effect on the overall H₂ production reactor performance. This approach provides an appropriate way to identify the influential priority of input factors and to evaluate the overall performance for the anaerobic H₂ production process, and it can also be used for other complex biological and non-biological wastewater treatment systems.     

Greywater treatment by UVC/H2O2

Greywater treatment by UVC/H₂O₂ was investigated with regard to the removal of chemical oxygen demand (COD). A COD reduction from 225 to 30 mg l⁻¹ (overall removal of 87%) was achieved after settling overnight and subsequent irradiation for 3 h with 10 mM H₂O₂. Most of the contaminants were removed by oxidation since only 13% COD was removed by settlement.The removal of COD in the greywater followed a second-order kinetic equation, r = 0.0637[COD][H₂O₂], up to 10 mM H₂O₂. A slightly enhanced COD removal was observed at the initial pH of 10 compared with pH 3 and 7. This was attributed to the dissociation of H₂O₂ to O₂H⁻. The treatment was not affected by total concentration of carbonate (c_T) of at least 3 mM, above which operation between pH 3 and 5 was essential. The initial biodegradability of the settled greywater (as BOD₅:COD) was 0.22. After 2 h UVC/H₂O₂ treatment, a higher proportion of the residual contaminants was biodegradable (BOD₅:COD = 0.41) which indicated its potential as a pre-treatment for a biological process.     

Robust control of plate vibration via active constrained layer damping

In this paper, the theoretical modeling of a plate partially treated with active constrained layer damping (ACLD) treatments and its vibration control in an H_∞ approach is discussed. Vibration of the flat plate is controlled with patches of ACLD treatments, each consisting of a viscoelastic damping layer which is sandwiched between the piezo-electric constrained layer and the host plate. The piezo-electric constrained layer acts as an actuator to actively control the shear deformation of the viscoelastic damping layer according to the vibration response of the plate excited by external disturbances. In the first part of this paper, the Mindlin–Reissner plate theory is adopted to express the shear deformation characteristics of the viscoelastic damping layer, meanwhile GHM (Golla–Hughes–McTavish) model of viscoelastic damping material and FEM (finite element model) are incorporated to describe the dynamics of the plate partially treated with ACLD treatment. In the second part, particular emphasis is placed on the vibration control of the first four modes of the treated plate using H_∞ robust control method. For this purpose, an H_∞ robust controller is designed to accommodate uncertainties of the ACLD parameters, particularly those of the viscoelastic damping core which arise from the variation of the operation temperature and frequency. Disturbances and measurement noise are rejected in the closed loop by H_∞ robust controller. In the experimental validation, external disturbances of different types are employed to excite the treated plate. The results of the experimental clearly demonstrate that the proposed modeling method is correct and the ACLD treatments are very effective in fast damping out the structural vibration as compared to the conventional passive constrained layer damping (PCLD).     

A study on the relationship between biodegradability enhancement and oxidation of 1,4-dioxane using ozone and hydrogen peroxide

Advanced oxidation involving O₃/H₂O₂ was used to eliminate 1,4-dioxane and to enhance the biodegradability of dioxane-contaminated water. Oxidation experiments were carried out in a bubble column reactor operating in fed-batch. The rate of dioxane removal and enhancement in biodegradability was investigated at hydrogen peroxide to ozone ratios between 0 and 0.6 mol:mol and pH between 5 and 11. A theoretical model was also applied to predict the experimental data and to investigate the effects of dioxane concentration, pH, and H₂O₂ concentration. The model predictions fit the experimental data well and there was a linear correlation between dioxane oxidation and BOD enhancement. At low dioxane concentrations, the oxidation rate was first order and it gradually approached zero order with increasing dioxane concentration. Also, the biodegradability of the solution increased with pH up to about 9 and it stayed constant with further pH increase. Hydrogen peroxide initially enhanced dioxane removal and biodegradability enhancement of the solution. However, at H₂O₂:O₃ ratios greater than about 0.4-0.45 mol:mol, i.e. about 2.90 mM for H₂O₂ concentration, H₂O₂ had negative impacts and resulted in reduced dioxane removal and biodegradability increase.     

The effect of UV/H2O2 treatment on disinfection by-product formation potential under simulated distribution system conditions

Advanced oxidation with ultraviolet light and hydrogen peroxide (UV/H₂O₂) produces hydroxyl radicals that have the potential to degrade a wide-range of organic micro-pollutants in water. Yet, when this technology is used to reduce target contaminants, natural organic matter can be altered. This study evaluated disinfection by-product (DBP) precursor formation for UV/H₂O₂ while reducing trace organic contaminants in natural water (>90% for target pharmaceuticals, pesticides and taste and odor producing compounds and 80% atrazine degradation). A year-long UV/H₂O₂ pilot study was conducted to evaluate DBP precursor formation with varying water quality. The UV pilot reactors were operated to consistently achieve 80% atrazine degradation, allowing comparison of low pressure (LP) and medium pressure (MP) lamp technologies for DBP precursor formation. Two process waters of differing quality were used as pilot influent, i.e., before and after granular activated carbon adsorption. DBP precursors increased under most of the conditions studied. Regulated trihalomethane formation potential increased through the UV/H₂O₂ reactors from 20 to 118%, depending on temperature and water quality. When Post-GAC water served as reactor influent, less DBPs were produced in comparison to conventionally treated water. Haloacetic acid (HAA5) increased when conventionally treated water served as UV/H₂O₂ pilot influent, but only increased slightly (MP lamp) when GAC treated water served as pilot influent. No difference in 3-day simulated distribution system DBP concentration was observed between LP and MP UV reactors when 80% atrazine degradation was targeted.     

Fenton-like initiation of a toluene transformation mechanism

In Fenton-driven oxidation treatment systems, reaction intermediates derived from parent compounds can play a significant role in the overall treatment process. Fenton-like reactions in the presence of toluene or benzene, involved a transformation mechanism that was highly efficient relative to the conventional Fenton-driven mechanism. A delay in hydrogen peroxide (H₂O₂) reaction occurred until the complete or near-complete transformation of toluene or benzene and involved the simultaneous reaction of dissolved oxygen. This highly efficient transformation mechanism is initiated by Fenton-like reactions, and therefore dependent on conventional Fenton-like parameters. Results indicated that several potential parameters and mechanisms did not play a significant role in the transformation mechanism including electron shuttles, Fe chelates, high valent oxo-iron complexes, anionic interferences in H₂O₂ reaction, and H₂O₂ formation. The Fenton-like initiation, formation, and propagation of a reaction intermediate species capable of transforming toluene, while simultaneously inhibiting H₂O₂ reaction is the most viable mechanism.     

Drinking water and biofilm disinfection by Fenton-like reaction

A Fenton-like disinfection process was conducted with Fenton's reagent (H₂O₂) at pH 3 or 5 on autochthonous drinking water biofilms grown on corroded or non-corroded pipe material. The biofilm disinfection by Fenton-like oxidation was limited by the low content of iron and copper in the biomass grown on non-corroded plumbing. It was slightly improved by spiking the distribution system with some additional iron source (soluble iron II or ferrihydrite particles appeared as interesting candidates). However successful in situ disinfection of biofilms was only achieved in fully corroded cast iron pipes using H₂O₂ and adjusting the pH to 5. These new results provide additional support for the use of Fenton's processes for cleaning drinking water distribution systems contaminated with biological agents or organics.     

Hydrogen peroxide-assisted low pressure UV photodegradation of atrazine in aqueous solution

Aqueous solutions of atrazine (ATZ, 2-chloro-4-ethylamino-6-isopropylamino-1, 3, 5-triazine) were photolysed (λ = 254 nm) by low pressure UV/H₂O₂ process (LP/UV/H₂O₂) under a variety of parameters including hydrogen peroxide, the initial concentration of ATZ, pH, and humic acid. The results show that the most favourable reaction condition appears to be a moderate concentration of H₂O₂ from 100 mg/L to 120 mg/L. The presence of humic acid in the solution has a negative impact on the LP/UV/H₂O₂ treatment because of scavenging effects. Ninety percent of ATZ is destroyed in one hour under the optimum conditions. In this study, LP/UV/ H₂O₂ treatment of ATZ yielded several organic by products which are identified, including DIA, DEA, OHDIA, OHDEA, DAA and OAAT. They are quantified over the range of treatment tested and the ATZ degradation scheme is proposed combined with by products information.     

Sorption of ionized and neutral emerging trace organic compounds onto activated sludge from different wastewater treatment configurations

The objective of this study was to examine sorption of a suite of 19 trace organic contaminants (TOrCs) to activated sludge. Compounds examined in this study included neutral, nonionized TOrCs as well as acidic TOrCs which may carry a negative charge and basic TOrCs which may carry a positive charge at the pH of wastewater. These TOrCs were evaluated to examine how sorptive behavior might differ for TOrCs in different states of charge. Additionally, multiple sludges from geographically and operationally different wastewater treatment plants were studied to elicit how solid-phase characteristics influence TOrC sorption. Characterization of sludge solids from 6 full scale treatment facilities and 3 bench-scale reactors showed no significant difference in fraction organic carbon (f_oc) and cation exchange capacity (CEC). Sorption experiments demonstrated that sorption of TOrCs also exhibits little variation between these different sludges. Organic carbon normalized partition coefficients (log K_oc) were determined as a measure of sorption, and were found to correlate well with octanol-water partition coefficients (log K_ow) for nonionized TOrCs, and log D_ow for anionic TOrCs where log D_ow is greater than 2. These data were used to construct a linear free energy relationship (LFER), which was comparable to existing LFERs for sorption onto sludge. No trend in sorption was apparent for the remaining anionic TOrCs or for the cationic TOrCs. These data suggest that predicting sorption to activated sludge based on K_ow values is a reasonable approach for neutral TOrCs using existing LFERs, but electrostatic (and likely other) interactions may govern the sorptive behavior of the charged organic chemicals to sludge.     

The effect of ceiling configurations on indoor air motion and ventilation flow rates

The purpose of this paper is to evaluate the effects of a building parameter, namely ceiling configuration, on indoor natural ventilation. The computational fluid dynamics (CFD) code Phoenics was used with the RNG k–? turbulence model to study wind motion and ventilation flow rates inside the building. All the CFD boundary conditions were described. The simulation results were first validated by wind tunnel experiment results in detail, and then used to compare rooms with various ceiling configurations in different cases. The simulation results generated matched the experimental results confirming the accuracy of the RNG k–? turbulence model to successfully predict indoor wind motion for this study. Our main results reveal that ceiling configurations have certain effects on indoor airflow and ventilation flow rates although these effects are fairly minor.