Abstract:In order to study the effect of different volumetric exchange rates (VER) on the granulation and stable operation of SNAD sludge, two lab-scale SBR reactors, with a 37.5% VER (R1) and 75% VER (R2), were comparably analyzed. Experimental results demonstrated that the granulation of R1 could be achieved in 36 days, was 12 days faster than R2. Meanwhile, a relatively lower sludge loss rate of R1 was obtained. The nitrogen removal rate (R_NR), R_AO and R_AN in R1 were 0.356 g·L^-1·d^-1, 0.113 0 and 0.080 9 g·g^-1·d^-1, respectively; while that of R2 was 0.248 g·L^-1·d^-1, 0.093 6 and 0.070 5 g·g^-1·d^-1, respectively. This confirmed that a lower VER reduced the loss of floc sludge, and further declined the granulation period. Moreover, a lower VER not only enhanced the activity of ammonia-oxidizing and anaerobic ammonia-oxidizing bacteria, but also suppressed nitrite-oxidizing bacteria, was benefit for a stable and efficient removal performance of the SNAD granular sludge.

Abstract:To identify the foulants for ultrafiltration of Dongjiang River water, as well as their fouling process, hydrophobicity and molecular weight distribution of feed, permeate and chemical washing solution were analyzed both in rainy and dry season. High performance size exclusion chromatography (HPSEC) combined with peak fitting was employed as a tool to separate water sample into portions with different molecular weights. The results showed that biopolymers (98 ku), humic substances (1 200 u), building blocks (610 u) and low molecular-weight neutrals (270 u) were the main components in raw water from Dongjiang River, in which the amount of biopolymers and humic substances was higher in rainy season than that in dry season. More importantly, biopolymer and low molecular-weight neutrals were identified the main foulants in total and irreversible fouling during ultrafiltration of Dongjiang River water in both dry and rainy seasons. Furthermore, fitness between fouling data and four classic filtration modeling indicated that cake layer blocking by biopolymer and standard blocking by low molecular-weight neutrals caused fouling during ultrafiltration of Dongjiang River.

Abstract:The aim of the present study was to investigate the effect of pre-treatment with humic acids on the activity of nitrifying bacteria (ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB)) in activated sludge processes. Varied concentration of HA (0, 80, 160, 240 mg/L) were applied to pretreat (24 h) three different sludges, including complete nitrification activated sludge with low/high activity (Sc₁/Sc₂), and the partial nitrification activated sludge (Sp). The results showed that the nitrate accumulation rate (R_NA) of Sc₁ increased significantly from 10.73 % to 53.93% after pretreatment with 80 mg/L of HA (50 mg/gMLVSS), simultaneously the ammonia oxidation rates (R_AO) changed insignificantly. In terms of Sc₂, neither the R_AO nor the R_NA changed under each tested condition. For Sp, no NO₃^--N accumulation was observed after the pretrement, which demonstrated that the HA pretreatment did not destruct its partial nitrification performance. In conclusion, HA pretreatment improved the activity of NOB which with low overall nitrification activity, while exhibited insignificant improvement on AOB activity.

Abstract:The aim of this work is to investigate the effect of potassium permanganate (KMnO₄) on the photocatalytic degradation of hexafluorobisphenol A (BPAF) by peroxymonosulfate (PMS). The influences of the experimental conditions such as PMS and permanganate dosage, solution pH were analyzed. Furthermore, the process for the oxidative removal of BPAF in natural water was confirmed and its efficiency compared with that of UV/PMS process. Results showed that KMnO₄ had a positive effect on the BPAF degradation in the UV/PMS process. The degradation efficiency was increased with the increase of PMS dosage. With the dosage of KMnO₄ increased from 0 to 1.5 μmol/L, the optimum removal efficiency of BPA obtained when PMS was 1 mmol/L. Further addition of KMnO₄, however, had no significant promotion on the extent of BPAF oxidation efficiency. BPAF degradation rate inhibited with increasing the pH under acidic condition, while promoted significantly under alkaline condition. The BPAF removal percentage in UV/PMS/KMnO₄ was about 12%-14% higher than in UV/PMS system in actual water. The mechanism of the synergetic combination of PMS with KMnO₄ for BPA degradation under the UV irradiation indicated that the catalytic oxidation of some reactive manganese intermediates generated in the UV/PMS/Mn(Ⅶ) process.

Abstract:To investigate the aging characteristics of the ultrafiltration membrane used in water treatment, the polyvinylidenefluoride (PVDF) ultrafiltration membrane was aged with sodium hydroxide (NaOH), sodium carbonate(Na₂CO₃), sodium hypochlorite (NaClO), hydrochloric acid (HCl) and citric acid (H₃Cit), respectively. The effect of low-concentration cleaning agents on the aging of the PVDF membrane was investigated, with the analyzing of the parameters of pure water flux, total organic carbon (TOC) rejection, tensile strength, field emission scanning electron microscopy (FESEM), contact angle and fourier transform infrared (FTIR). Experimental result shows that acid, alkali and oxidant, especially NaOH and NaClO, changed the structure and performance of the PVDF ultrafiltration membrane. After exposed to NaOH, Na₂CO₃ and NaClO for 75 days, the total organic carbon (TOC) rejection efficiencies decrease from 36% to 15%, 27% and 17%, respectively. Compared to the virgin membrane, the tensile strength and ultimate elongation of the membrane which aged 15 days with NaOH declines by 11% and 20%, respectively. The negative effect of alkali and oxidant on mechanical performance and TOC rejection was higher than that of HCl and H₃Cit, and the decreasing of hydrophilicity of the membrane exposed to NaClO is more significant than that of the other cleaning agents. The dehydrofluorination, which can generate of C＝C and C＝O bond, is one of the most important reasons that caused the ageing of PVDF membrane.

Abstract:GO/CoFe₂O₄ was synthesized by coprecipitation to remove the environmental pollutants efficiently in the water. Dibutyl phthalate (DBP) was removed using the GO/CoFe₂O₄-catalyzed peroxymonosulfate (PMS). GO/CoFe₂O₄ was characterized by SEM, TEM, XPS and XRD. DBP removal efficiency was studied under different conditions in the water. The results showed that, at room temperature, the removal rate of DBP in the anometer spinel granulated GO/CoFe₂O₄/PMS oxidation reaction system, with the initial DBP concentration of 2 μmol/L, catalysts dosage of 0.1 g/L, PMS concentration of 20 μmol/L and pH of 7.0. The removal efficiency of DBP only decreased 5% after 5 times. The new composite catalyst had a potential engineering application prospect due to its high efficiency and easy recovery.

Abstract:In order to study the effect of carbon resources on the operational performance of denitrifying sulfide removal process, the removal efficiency of sulfide, nitrate and organic carbon was investigated in UASB reactor, using sodium acetate and phenol as the carbon resources respectively. Meanwhile batch cultivation experiment was applied to study the degradation and conversion of carbon, nitrate and sulfide. The results showed that the removal efficiency of NO₃^--N, S^2-and Ac^--C would reach 93%, 90% and 99% under a 2.5-10 h HRT, respectively, using sodium acetate as carbon source. Under such condition the accumulation rate of elemental sulfur remained stable at about 41%. For a comparison, the removal efficiency of NO₃^--N, S^2- and C₆H₅O^--C was 67%, 85% and 50% respectively using phenol as carbon resource (10 h HRT), however the sulfide was converted to sulfate completely and no elemental sulfur accumulated. The results of batch cultivation experiment showed that the oxidation rates of S^2-, acetates and S⁰ displayed in such order: q_S^2- > q_Acetate > q_S⁰ when the sodium acetate was used as carbon resource; however, the oxidation rates of S^2-, phenol and S⁰ using the phenol as carbon resource distributed in the trend of q_S^2- > q_S⁰ > q_Phenol.

Abstract:Microbial electrochemical systems (MESs) suffer deterioration in power generation and wastewater treatment in practical application. In order to improve the performance of MESs when treating medium and high strength wastewater containing fermentative substrates, a continuous stirred microbial electrochemical reactor (CSMER) was developed by integrating MES and continuous stirred tank reactor (CSTR). Maximum power densities of (583±9), (562±7), (533±10) and (572±6) mW·m^-2 were obtained by each separate cell of CSMER under continuous feeding mode (HRT=12 h) at COD concentration of 6 000 mg·L^-1. COD removal and methane production rate of CSMER were (87.1±1.1)% and (1.48±0.15) L·L^-1·d^-1, which increased by 61.6% and 244.2% in comparison with those of a control CSTR. Pyrosequencing analysis showed that the dominant genera in CSMER_CMZ were Clostridium (10.0%), Acidaminococcus (11.7%) and Lactococcus (10.8%), which were fermentative bacteria. The microbial electrochemical zone (MEZ) was dominated by Geobacter (14.5%), which was the most predominant known exoelectrogen. Due to the relatively complicated bacterial communities, the CSMER possessed high abundance both in acetoclastic methanogens (52.2%) and hydrogenotrophic methanogens (47.1%). Syntrophic process occurred between anaerobic digestion in the CMZ and current generation in the MEZ contributed to its better performance.

Abstract:In order to know the interaction effects between biofilm and chlorine decay, influences of chlorine residual on biofilm formation and chlorine decay rules under the existence of biofilm were investigated through static and dynamic simulation in simulated pipelines. Three kinds of pipe materials (cast iron, PE, stainless steel) and 3 chlorine dosage (1, 3, 4 mg/L) were chosen. Results show that chlorine decay and biofilm development interacted, and the specific results are as follows. With the increase of chlorine, biomass decreases in PE and stainless steel, while increases in cast iron; with the existence of biofilm, chlorine decay could be divided into two parts: fast decay (0-30 min) and stable decay (after 30 min). Cast iron influences chlorine decay seriously, followed by PE, and the effects of stainless steel is minimum. Influence of biological diversity on chlorine decay is not obvious, while biomass is closely related with chlorine decay. Velocity and chlorine dosage influenced chlorine decay evidently. This research could support disinfection, chlorine decay modeling and water quality security in water distribution network

Abstract:To effectively control the urban pipeline leakage, the study combines minimum night flow with pressure-driven leakage hydraulic model to calculate the leakage coefficient of network nodes and establish an enhanced hydraulic model considering pressure dependent leakage terms. The model uses the genetic algorithm to solve the problem, taking the minimized pipeline leakage loss as the objective function, the maximum installed number of the pressure reducing valve, the node pressure flow equation, and the maximum allowable leakage rate as the constraint conditions, to find out the installation number and locations of the pressure reducing valves. The one which costs the least is chosen from all the feasibilities as the optimal solution, and HJ area partition is taken as an example to illustrate in detail the calculation procedures of the decision support model. Our study possesses the guiding significance for the control of the actual pipeline leakage.

Abstract:Considering the insufficiency of the present international study on the quantification of water pipeline leakage, and the deficiencies of the existing common methods of leakage calculation, this study combines Kalman filtering algorithm commonly used in the area of information control to build state equation and observation equation of pipeline leakage model. The simulation experiment of pipeline leakage calculation based on Kalman filtering algorithm conducted in the laboratory proved the feasibility of the model. Our study provides a powerful basis for policy-makings of water supply network management, leakage reduction, and improvement of leakage control level

Abstract:To solve the deficiency of organic pollutants removal in traditional technologies, UV/persulfate (PS) process was employed to remove diclofenac, one of the typical pharmaceuticals and personal care products. The effect of various factors including initial diclofenac concentration, persulfate dosage, pH, inorganic anions and humic acidon the diclofenac degradation by UV/PS process was investigated. The proposed degradation pathways of intermediate products after reaction were also analyzed. The results showed that diclofenac degradation fitted the pseudo-first-order kinetics well (R²≥0.95). With the increase of the initial diclofenac concentration, the pseudo-first-order-constant gradually decreased. And the degradation rate of diclofenac quickly increased with the increase of the PS dosage. Different pH environment influenced the degradation rate of diclofenac to a certain extent. For the pH ranging from acidic to alkaline conditions, the degradation rate of diclofenac has an obvious increase. Inorganic anions in the solution had different degree of impact on the diclofenac degradation. The existence of bicarbonate ion accelerated the degradation but chloride ions had an adverse effect. Additionally, the existence of humic acid had an inhibition effect on the removal of diclofenac. Sulfate radicals activated by UV may react with diclofenac molecules, thereby removing carboxyl or hydroxyl herein. The main intermediate products were 2, 6-dichlorodiphenylamine, 1-(2, 6-dichlorophenyl)-2-indolinone, 2-indolinone and aldehydes or something

Abstract:Focused on the potential threat of the membrane fouling to the bio-safety of the drinking water in the second water supply, this study investigated the effect of shock chlorine and chloramine disinfection on the total Bacteria, Escherichia Coli and Heterotrophic (HPC) bacteria as well as the structure of the biofilm in the BAR-simulated secondary water supply system. The results showed that the number of microbes in the biofilm reached maximum on the 80^th day and soon it fluctuated smoothly. The Firmicutes, Proteobacteria and Bacteroidetes were predominant bacteria by Metagenomic approaches. The effect of chlorine and chloramine disinfection on the biofilm was related to the concentration of the disinfectant as well as the concentration and time(CT). At the same CT value, higher concentration of Chlorine and chloramine had more effective disinfection. Comparison and analysis found that in low concentrations, compared to chloramine, chlorine is more effective to total Bacteria and Escherichia Coli, while less effective to HPC. However, in high concentrations, chlorine and chloramine own nearly the same inactivated effect. When the concentration of chlorine and chloramine was 3.0 mg/L and the CT value was 300-400 mg·min/L, the inactivation rate of total Bacteria, Escherichia Coli and HPC was as high as 95%. Scanning Electron Microscope(SEM) images of biofilm surface plot analysis illustrated that the structure of biofilm was damaged seriously, and shock chlorine disinfection, compared to chloramine, possessed less impact to the structure and reduction degree of the biofilm and was hence more conducive to the biofilm control

Abstract:To analyze the effect of protein electrical property to hydration in ultrafiltration, the characteristics of the interaction forces of PVDF-BSA and BSA-BSA (Bovine Serum Albumin) changing with different ionic strengths were separately investigated, as BSA was positively, neutrally and negatively charged. In accordance with the potential variation of Zeta, the mechanism of how the protein electrical property affected hydration was illustrated. When BSA was positively charged, the interaction force increased with the increase of ionic strength, mainly due to that the positively charged BSA could not trigger hydration, and electrostatic force was the main factor controlling membrane fouling. When BSA was neutrally and negatively charged, a large number of hydrated cations adsorbed and accumulated on membrane surfaces of BSA and PVDF, and the increase of the ionic strength would trigger the repelling force of PVDF-BSA and BSA-BSA, and hence the membrane fouling was reduced remarkably. In addition, the hydration phenomenon was more easily observed in BSA isoelectric point

Abstract:To investigate the effect of aluminum additive on the formation of granular aerobic sludge, PAC and aluminum sulfate were added into different SBR reactors to strengthen the granular sludge during the period of 10^th to 16^th day, and the chemical characteristics of granules cultivated with different coagulants were analyzed. Meanwhile the content and distribution changes of aluminum in the sludge were evaluated. Experimental results showed that aluminum coagulants additive could significantly accelerate the formation of granules and influence the chemical structure of sludge EPS. Once dosing terminated, the quality of Al in the granules cultivated with PAC decreased from 30.46% to 0.43% during the 16^th to 29^th day operation. Meanwhile, for the aluminum sulfate enhanced granules, the Al content decreased from 45.69% to 13.29%. Hydrolysis products of PAC mainly distributed in the periphery of flocs and the aluminum content of sludge was eventually below the limit of detection after granulation. However, aluminum sulfate fully contacted with flocs after polymerization and hydrolysis, and then concentrated in the center of granular after maturation. Above results demonstrated that aluminum coagulants played different roles in the granulation process. For PAC, the promotion of EPS secretion enhanced the aerobic granulation and then the microorganism aggregated; while a nucleation is formed after aluminum sulfate additive, leading to an increasing of EPS content

Abstract:In order to study photo-Fenton performance of Fe₃O₄ nanospheres, monodispersed Fe₃O₄ nanospheres with a mean diameter of 200 nm were successfully synthesized by a solvothermal method at 200 ℃. As-synthesized Fe₃O₄ nanospheres show excellent photo-Fenton efficiency on the degradation of methylene blue(MB), and the degradation rate was over 95%. Besides, the catalyst was easy to recycle with only a piece of magnet, and the recovery rate can be more than 85%. Moreover, the catalyst can be regenerated with the ultrasonic treatment, and the degradation performance almost remains unchanged. In addition, the degradation efficiency varies with the amount of hydrogen peroxide applied and the pH value of the reaction system. After intensive investigation, the reaction efficiency performs best with 15 mL hydrogen peroxide added in acid atmosphere.

Abstract:A pump start-stops optimization method was proposed to realize the frequent start-stops in rainwater pump station. Through analyzing the design parameters and operation principles, the optimization model of pump start water level was obtained by SWMM(storm water management model) and PSO(particle swarm optimization algorithm). The feasibility of the optimization method was verified by comparing with manual debugging method. The research results show that the optimization method can minimize the start-stop frequency, achieve a better effect of bump start-stops and get rid of the complex manual debugging process, which will provide reference for the pumping water level selection of rainwater pumping stations

Abstract:The iTRAQ techniques were used to separate and identify milk fat globule membrane proteins(MFGMPs) from bovine and buffalo milk to compare the differences among composition, contents and functional properties of them. MFGMPs were separated and analyzed by Nano-HPLC tandem MS (MS/MS) analysis coupled with Q-Exactive. The results showed that 424 proteins were identified (FDR≤0.01%). The contents of 146 proteins were significantly different between MFGMPs bovine and buffalo in these identified proteins. Among these different proteins, there were 20 up regulated proteins and 25 down regulated proteins by two times (buffalo/bovine). The contents of sodium phosphate solute carrier protein and γ-glutamyl transpeptidase are significantly higher in buffalo MFGMPs than in bovine MFGMPs. The two proteins possess carriers and catalytic activities, and serve as the basic composition of biosynthesis and metabolism. The contents of xanthine oxidoreductase and butyrophilin are significantly higher in bovine MFGMPs than in buffalo MFGMPs. The two proteins, identified as binding protein, can inhibit the growth of tumor cell. The results showed that the significant differences of content existed in some functional protein between the MFGMPs of buffalo and bovine

Abstract:Rapid urbanization contributes to unique local climate. This paper proposed an integrated climatic evaluation method by combining a thermal environmental evaluation model and the geographical information system. The air temperature (T_a), urban heat island intensity (UHII), and the outdoor thermal comfort index (OUT-SET^*) were selected as evaluation parameters. A planned region area in Dagang District of Guangzhou was adopted as a case study, the climatic parameter calculations and spatial visualization under multiple urban blocks were conducted. Results showed that daily average T_a varied between 27.73 ℃ and 29.96 ℃, the average UHII varied between -0.48 ℃ and 2.2 ℃, while OUT-SET^* varied between 29.05 ℃ and 33.44 ℃. By referring to the land use map and spatial distribution maps of green coverage ratio and building floor area ratio, these climatic parameters were influenced in different extent by underlying surface characteristic parameters. By quantitative linear correlation analysis between these parameters, it revealed that UHII had significant negative correlations with both the green coverage ratio and building floor area ratio, the correlation coefficients of which were -0.433 and -0.490, respectively. OUT-SET^* had significant negative correlation with the building floor area ratio and weak negative correlation with green coverage ratio, the correlation coefficients of which were -0.295 and -0.790, respectively

Abstract:Carbon dioxide (CO₂) capture, utilization and storage, as an emerging technology that can help reduce coal chemical plant greenhouse gas emission by large scale, have drawn significant attention. Pipeline transportation is an essential part of the technology, but high cost has greatly limited its application. Therefore the main objective is to develop an optimization model for supporting CO₂ pipeline transportation system planning to reduce the overall carbon capture utilization and storage (CCUS) system cost by optimizing key technology process of a CO₂ transportation system. The developed model was further applied to Shaanxi Yanchang's CCUS project for planning its CO₂ transportation system. The results indicated that in case of low demand of CO₂ storage, a gas-phase CO₂ pipeline transportation system coupled with in-situ compression and injection was recommended. In the case of high demand of CO₂ storage, this study would recommend a super-critical / density phase transportation system which could have lower system cost than gas phase pipeline system as the cost for compression at the site of storage can be saved

Abstract:In order to provide effective guidance to the construction and to ensure the safety of workers, numerical simulations were performed on distributions of airflow, temperature fields, oxygen content, and carbon dioxide content during the process of mechanical ventilation using the CFD software. The results demonstrated that, in the course of mechanical ventilation, compared with the pipe trench, the recovery of environmental condition such as temperature and gas volume fraction including oxygen and carbon dioxide were more rapid in the heat chamber. The air flow was mainly along the bottom of the pipe trench and the air velocity at the top of the pipe trench was small because of the internal structure and thermal lift in the pipe trench. For the pipe aforementioned, when the ventilation volume was 6 000, 8 000, 10 000, 12 000, 14 000 m³·h^-1, the minimum ventilation time needed should not be less than45, 32, 22, 15, 10 minutes, respectively. In practical operation, oxygen content at the top of the central part of the trench should be regarded as the key parameter to evaluate the ventilation effects

Abstract:To improve the respirable dust diffusion model in the fully mechanized working face, based on the theoretical model of aerosol mechanics and fluid dynamics and combined with the actual environment, the respirable dust diffusion model was established by coupling two dust sources of the frame shift and cutting coal. In this process, the treatment of two-time respirable dust was mirror image method. In order to solve the turbulent diffusion coefficient and longitudinal dispersion coefficient of the mathematical model, the experimental site was set up by the ratio of 3:1. Then some experiments were carried out and gradient descent method was used for parameter estimation. Turbulence coefficient value was applied to calculate the respirable dust mass concentration. Then comparing theoretical value with experimental value, results showed that: in the 258 sampling points, the average absolute error rate is 29.66%. It indicated the reliability of the theoretical model, which can be used to predict the dust mass concentration in the actual underground space

Abstract:To research fume-drainage time of tunnel after blasting, the formula of removal law of blasting fume in tunnel is deduced. Through calculating the grey correlation degree of influential factors of fume-drainage time, the ranking results of sensitive degree of main influential factors are: distance of entrance to tunnel face (0.827) > distance of duct to tunnel face(0.738) > air flow in duct(0.628) > initial volumetric concentration of CO in blasting fume(0.547). Blasting fume monitoring tests were conducted in tunnel to study the fume-drainage time when the distance of duct to tunnel face L_O are respectively 10, 15, 20, 25, 30 m and the distance of entrance to tunnel face L_P are respectively 40, 60, 80, 100, 120 m under the condition of forced ventilation. Research findings reveal that: fume-drainage time increases with the longer distance of entrance to tunnel face. The fitting result of the both is linear relation; fume-drainage time shows nonlinear rise with the addition of the distance of duct to tunnel face. The fitting result of fume-drainage coefficient c and L_O is linear relation, and calculation formulas of fume-drainage time in different working condition are concluded. Verification of equation is carried out in 5 tested similar tunnels. And relative errors are respectively 6.1%, 3.8%, 5.4%, 8.8%, 9.3%, which have remarkable accuracy and reliability

Abstract:Multi-ribbed wall structure (MRWs) is composed of densely distributed ribbed frames, including ribbed beams and columns, and autoclaved aerated concrete (AAC) is filled inside the ribbed frames. Because of the special production process, there is a bonded interface of which property is still undefined between ribbed frames and infilled AAC. To study the properties of bonded interface of ordinary concrete and AAC, the experimental study is necessary on the material level. On the background of multi-ribbed composite wall structure, the slant shear test was used to measure the bonded interface properties of ordinary concrete and AAC. This paper analyzed the influence of bonded interface joint angle to interfacial strength and proposed the failure envelope of bonded interface. Based on test results, the equation between τ_n and σ_n of the bond failure envelope is fitted which provides a valuable basis of theoretical and numerical solutions for mechanical properties of multi-ribbed composite wall structures

Abstract:Cracks in soils provide significant preferential pathways for contaminant transport and rainfall infiltration, and water exchange between the cracks and soil matrix is crucial to estimate the preferential flow, which is often quantitatively described by a water exchange ratio. Current studies on the water exchange ratio mainly focus on the crack in sand, but the water exchange ratio between the crack and clay is still unclear. A novel experimental setup was designed with advanced water content and suction measuring system to investigate the water exchange of the deformable cracks in clays. Results show that the water exchange ratio is the highest at the initial stage and decreases with decreasing suction in the clay. The hydraulic conductivity of the crack-clay interface is about one order of magnitude larger than that of the saturated soil matrix. With different initial volumetric water content of soils, the water exchange ratio between crack and soil gradually decreases to 7×10^-6 s^-1 in the process of the infiltration experiments

Abstract:The objective of this paper is to investigate the cavity stability around an under-water vehicle in the water flow. The water tunnel experiment for the cavity around the vehicle was investigated. The experiment was carried out to study cavity developing, break-off and shedding with different cavitation number. The experiment also studied the velocity of shedding cavity and the pressure of the vehicle surface. The mechanism of gas control and cavitation stability was obtained. The results show that the transparent cavity increases gradually with ventilation. Re-entrant jet appears and moves back to the front of the vehicle under adverse pressure gradient at the closure of the cavity. The transparent cavity in front of it is replaced by opaque one gradually at the same time. The shedding cavity rolls up and large cavity vortexes sheds toward downstream. When the re-entrant jet arrives at the forepart of the vehicle, the cavity boundaries become wavy. The characteristics of cavity developing and shedding vary as cavitation number is changed. When the cavitation number is bigger, it is found that the shedding generally contains two processes: cavity break-off and cavity shedding. With the decrease in the cavitation number, the shedding contains three processes: cavity break-off, conjunction and cavity shedding. The average shedding speeds decrease with the decreasing of the cavitation number. The experimental results also show that the pressure signals at different instants destabilize on the vehicle surface; fluctuant pressure peak is detected at the closure region of the cavity. Surface pressure fluctuations occur on the vehicle surface with the cavity shedding

Abstract:A finite-time disturbance observer-based nonsingular terminal sliding mode control strategy is proposed for flexible hypersonic vehicle (FHV) with mismatched uncertainties. First of all, by considering the effects of flexible modes as uncertainties, the control-oriented model, which is convenient for controller design, is obtained by simplification of the FHV model. Then, the lumped uncertainties are estimated by finite-time disturbance observer. Afterwards, a novel nonsingular terminal sliding surface containing the disturbance estimations is designed, which can transform the high-order mismatched uncertainties into first-order matched uncertainties. Then the controller is developed. The stability of the closed-loop system is guaranteed by Lyapunov theory. Simulation results show that the proposed controller is effective in suppressing the mismatched uncertainties and has achieved stable tracking of velocity and altitude

Abstract:To address the issue of the sub-bottom profile layer extraction in complex circumstance, this paper proposes a new demarcating method based on constraint of image information entropy. Firstly, the image of sub-bottom is divided into different blocks; then, the information entropy in each block is calculated and a relation model of information entropy and significant parameters are established according to drilling data; finally, the whole sub-bottom profiling is demarcated according to the model. It is revealed that this method has overcome the shortcomings of existing methods, realized the self-adapting and exacted demarcation of sub-bottom layers. The experiment has gained the same accuracy as the depth and thickness of layers got by drilling data.

Abstract:This paper is intended to study the impacts of information guidance system on driving behavior at intersections. Using the structural equation model (SEM) and the improved technology acceptance model (TAM), a method was proposed to analyze the impacts on the driving behavior. On the basis of literature review, the factors that affect drivers' preference to the guidance information at intersections were determined. The factors can be divided into individual factors, system (or information) factors, and environmental factors. 1 544 valid samples were obtained with the preference survey of the drivers in Beijing, and the proposed model was examined and refined. Then, statistical methods were used to verify the hypothesis of the proposed model. The results have shown that perceived usefulness of the information, credibility of the information, and traffic conditions mainly affect the drivers' preference to the guidance information. The study provides supports to improve the efficiency of the information guidance system

Abstract:Wet and dry depositions serve as important factors affecting the distributions, transport, and transfer of persistent organic pollutants (POPs) in atmosphere. On the one hand, wet and dry depositions can wipe out POPs, such as polybrominated diphenyl ethers (PBDEs) in the atmosphere, but on the other hand, these POPs become important source for contamination when they enter water, sediment, and soil. This paper summarized the worldwide study on dry and wet depositions of PBDEs in the atmosphere, including the composition of PBDEs in air and rain water, wet and dry deposition fluxes, scavenging ratio, and dry deposition velocity, etc. The wet and dry deposition patterns of PBDEs in the atmosphere were described for the first time using chemical partitioning space map (CPSM), and the comparison with the published data indicated that CPSM would properly describe the partitioning behavior for PBDEs-gaseous phase was major portion for BDE-47, and particulate phase the dominant for BDE-209 in both dry and wet depositions. A summary and future development on wet and dry deposition of PBDEs also have been provided