Abstract:The experiment was to explore the effect of different SRT on the nitrogen removal efficiency and kinetic characteristics of AnAOB by studying the variation of nitrite removal loads (N_r), nitrite sludge loads (N_s) and kinetic characteristics with gradient decrease of SRT in a SBR. The results showed that with SRT decreasing from 21 d to 12 d, N_r decreased from 0.590 kg/(m³·d) to 0.493 kg/(m³·d) while N_s increased from 0.178 kg/(kg·d) to 0.297 kg/(kg·d), and the N-removal performance of the whole system was reduced but the N-removal efficiency of unit mass of AnAOB was significantly improved. The Monod model can well simulate the kinetic behavior of AnAOB at different SRT. The maximum specific degradation rate (v_max) increased from 0.406 d^-1 to 0.826 d^-1 and the semi-saturated constant (K_s) increased from 23.3 mg/L to 95.3 mg/L, which indicated that gradiently decreasing SRT can screen and purify AnAOB with faster grow rate, while the affinity for the substrate gradually deteriorated and the stability decreased.

Abstract:In order to study the feasibility of anaerobic ammonia oxidation(Anammox) process in Waste Water Treatment Plant(WWTP), lab-scale Anammox reactor was employed in municipal WWTP. NaNO₂ was added into the sewage effluent treated by A/O process in WWTP to serve as substance to start up Anammox filter reactor. In order to investigate the performance of Anammox process in engineering application, sewage effluent treated by A/O and nitrification process was served as inflow after the successful start-up of reactor. From the 106th to the 144th day, the maximal ammonia and total nitrogen concentrations in effluent were 4.1 and 13.4 mg/L with water temperature vary from 15 to 20 ℃ and the nitrogen concentration in effluent fitted the national 1A discharge standard of pollutants for municipal wastewater treatment plant. From the 168th to the 204th day, the reactor was running in the winter. When water temperature varied from 12 to 15 ℃, nitrogen concentration in effluent fitted the standard with the strategy of prolonging HRT. From the 222th to the 240th day, when the water temperature reduced to 10-12 ℃, NaHCO₃ was added in inflow at a concentration of 125 mg/L. Nitrogen removal rate increasd 40 percents and the ammonia and total nitrogen in effluent was 1.4 and 13.6 mg/L. Nitrogen concentration in effluent reached the national 1A discharge standard of pollutants for municipal wastewater treatment plant in winter. The thickness of biomembrane increased continuely in the whole process of filter column and finally reached 113 μm. Ammonia anaerobic oxidation loading rate was greater than 5 kg/(kgMLSS·d) and Anammox process operated efficiently and stably.

Abstract:The short-term and long-term effects of Cu nanoparticles (NPs) on partial nitrification (PN) process were studied in SBR. The ammonia oxidation rate, nitrogen removal and sludge property were analyzed within exposure of different concentrations of Cu NPs. The short-term result suggested that the Cu NPs with 1 mg/L was beneficial for PN process, while the NPs in 3-30 mg/L significantly inhibit PN. As a result, the ammonia oxidation rate decreased to 21.9%-44.9% of the initial value. When the Cu NPs was 50 mg/L, the PN process was enhanced, which was mainly because the aggregation reduced the actual concentration of NPs acting on the microorganisms. Long-term exposure within low Cu NPs (1 mg/L) could also suppress the PN process, and the ammonia removal efficiency decreased to 44.8% from 91%. The ammonia-oxidizing bacteria was more severe to the Cu NPs than nitrite-oxidizing bacteria. After the long-term exposure, the copper and extracellular polymeric substance in sludge both increased, and then decreased when no Cu NPs was added to the PN system anymore. Cu NPs performed a significant effect on microbial activity, nitrogen removal ability and sludge property.

Abstract:The purpose of this article was to investigate the kinetics, oxidation products and reaction pathways for the degradation of flame retardant tetrachlorobisphenol A (TCBPA) by aqueous potassium permanganate. Experiments were conducted to examine the reaction kinetics of potassium permanganate with TCBPA under the condition with potassium permanganate in excess over a wide pH range, determine the brominated oxidation products and theorize the reaction pathways of TCBPA by aqueous potassium permanganate using liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). The results showed that the degradation of TCBPA followed the second-order kinetics and the rate constants (40.1-981.7 L/(mol·s)) increased with the increase of pH and reached the maximum near the pK_a (7.5/8.5) of TCBPA, after which they decreased gradually. Four chlorinated oxidation products were detected by the precursor scan approach of liquid chromatography tandem mass spectrometry (LC-MS/MS-PIS), the oxidation products of m/z 219/221(Ⅰ), 201/203(Ⅱ), 379/381/383/385(Ⅲ&Ⅲ′), 523/525/527/529/531/533(Ⅳ), respectively. Reaction pathways mainly involves the initial one-electron oxidation of TCBPA to phenolic radical and subsequent release and further reactions of 2, 6-dibromo-4-isopropylphenol carbocation intermediate, leading to the formation of 4-(2-hydroxyisopropyl)-2, 6-dibromophenol and 4-isopropylene-2, 6-dibromophenol) as well as two polymeric products(Ⅲ&Ⅲ′and Ⅳ).

Abstract:The aim of this work is to investigate the effect of chitosan on improving the performance of the conventional coagulation-dissolved air flotation (DAF) process during the treatment of low temperature and low turbidity of Huaihe River water. Comparative tests using chitosan as coagulant aid or bubble surface modifier were conducted. NOM in samples was fractionated based on hydrophobicity and molecular weight. The trihalomethane and haloacetic acid formation potentials in each fraction and their removal efficiency were also evaluated. The results showed that when chitosan was used as a coagulant aid, DAF exhibited obvious selectivity in the removal of NOM fractions. The hydrophobic organic matters with high molecular weight were removed preferentially. A novel, functionalized bubble surface can be obtained in DAF by dosing chitosan in recycle water. Decreasing the pH of the recycle water from 7.0 to 5.5 (less than the pKa of chitosan) improved the removal of hydrophilic NOM fractions with low molecular weight by chitosan-modified bubbles. Most chitosan molecules were adhered onto the bubble surfaces and there was no obvious increase in the zeta potentials of the floated water. In addition, the enhanced reduction of trihalomethane and haloacetic acid precursors were also observed. Bubble surface modification provides an alternative approach for DAF to promote the removal of NOM from surface water.

Abstract:Electroplating wastewater often contains such complex agents as EDTA and some heavy metals exist in complexing form, which present great challenge for heavy metal removal. Given the low cost and satisfying effect of microelectrolytic method in processing complex wastewater, iron-copper microelectrolysis was adopted to treat the EDTA complex copper solution. Analysis of the change of metal ions and the infrared spectrum of the precipitates during microelectrolysis showed that the major changes occurred were iron dissolution, increased concentration of Fe²⁺ and Fe³⁺, decreased Cu²⁺ concentration, accompanied by a slight decrease in EDTA concentration and the formation of Fe(OH)₃ precipitate. MINTEQ software was used to simulate the complex morphological distribution. The results show that the addition of Fe³⁺ can make Cu²⁺ into a free state. The larger the Fe³⁺/Cu²⁺ is, the lower the pH is, hence the better the removal effect. The addition of Fe²⁺ under alkaline conditions can make Cu²⁺ become Cu(OH)₂. The greater the Fe²⁺/Cu²⁺ is, the higher the pH is, the better the removal effect. Combining with the experimental and simulation results, it can be concluded that the desorption of Fe³⁺ under acidic conditions and the reduction of free Cu²⁺ by iron scrap are the main reasons for the removal of Cu²⁺-EDTA by microelectrolysis.

Abstract:To eliminate N₂O emission or utilize it for energy recovery, a laboratory-scale SBR inoculated with common activated sludge with acetate and nitrate additions decoupled, was conducted for endogenous denitrification running with anaerobic/anoxic cycles without DPAOs. During one cycle, approximately 50% of nitrate was converted to nitrite, N₂O emission rate increased with nitrite accumulation, and 2.04% of removed nitrogen was emitted as nitrous oxide (N₂O). Batch tests were conducted to compare the emission of N₂O that was influenced by external carbon source dosage (C/N was 0, 0.75 and 2.50) using nitrite as the electron acceptor before and after poly-β-hydroxybutyrate (PHB) was synthesized.The results showed that, the N₂O emission was slightly decreased with the increase of total carbon source, and the N₂O conversion ratio was between 0.24% and 1.61%. 15.90% of N₂O conversion ratio was obtained in the absence of external organic carbon, the maximum N₂O emission rate was 71.29 μg/(min·g), and the N₂O emission was 14-26 times higher than that of the other batch test results, indicating that when the PHB was the sole electron donor, the endogenous denitrification could produce more N₂O using nitrite as the electron acceptor.

Abstract:To further remove the organic pollutants residual in the biologically pretreated coal chemical industry wastewater, three-dimensional electro-Fenton system was established by involving Fe loaded sludge deserved activated carbon (SAC-Fe) from sewage and waste iron sludge, and was introduced in the advanced treatment of biologically pretreated coal chemical industry wastewater. Process parameters were optimized by response surface methodology (RSM) coupled with central composite design, and the catalytic reaction mechanism involved in system was discussed. Results show that SAC-Fe exhibited high adsorption performance to the pollutants in the wastewater. The maximum adsorption content calculated with Langmuir model was 101.1 mg/g. The optimal process parameters were determined as 16.78 mA/cm² of current density, 14.75 mmol/L of equivalent Fe content and pH 3.92, with the observed TOC removal efficiency of 67.12%. The catalytic reaction mechanism was discussed based on the analysis of H₂O₂ and ·OH contents and adsorption effect. SAC-Fe exhibited high electro-catalytic activity in three-dimensional electro-Fenton system. SAC-Fe as catalytic particle electrode significantly promoted the production amount and rate of H₂O₂ and ·OH. Adsorption effect improved ·OH and organics removals. Thus three-dimensional electro-Fenton with SAC-Fe as catalytic particle electrode exerted excellent performance in the advanced treatment of coal chemical industry wastewater.

Abstract:The work is to investigate the degradation of TBBPA and its toxicity controlling by ferrate(Ⅵ) oxidizing technology. The effects of oxidant dosage and solution pH on TBBPA degradation was evaluated through the beaker tests. The variation and controlling of the acute and chronic toxicity was investigated, and the possible degradation mechanism was proposed. The results of the experiments showed that, TBBPA could be effectively degraded by ferrate(Ⅵ) oxidation. When the concentrations of ferrate(Ⅵ) and TBBPA were both 0.15 mg/L, TBBPA could be thoroughly degraded under different pH (6.0-9.0) conditions. The acute and chronic toxicity of water samples, enhanced at the initial reaction stage due to the accumulation of more toxic organic intermediates, could be impressively controlled by ferrate(Ⅵ) oxidizing technology with the prolonging of the reaction time. The optimum pH was 8.0, under which condition the acute and chronic toxicity were decreased to 0.02 TU and 10.5 TU respectively. The analysis of mechanism showed that the degradation pathway of TBBPA mainly included the addition reaction, the beta scission, the deprotonating reaction and the debromination reaction.

Abstract:A novel water supply network model, pipeline dual graph (PDG), is proposed for structure measurement and robustness analysis of water supply networks using complex network theory. If water pipes of same diameter and material are sequentially connected in rather small angle changes, this model takes them as a unified entity called pipeline. A PDG is an undirected graph constructed by taking every pipeline as a node and inserting a link between two nodes corresponding to a couple of intersected pipelines. Structure measurement for 3 Chinese cities' water supply networks shows that pipeline dual graphs are scale-free networks. Attack simulations using 3 strategies based on scale-free network robustness analysis methods were designed and conducted. Experimental results indicated that structural change processes of these networks were similar under different attack strategies, which all consisted of the initial phase, the splitting phase and the collapsing phase. However, every network entered the splitting phase and the collapsing phase at a distinctly different speed. Among the 3 strategies, the strategy based on node degree had the greatest impact on water supply networks, followed by the strategy based on betweenness, while random attacks had the least influence. Highly connected pipelines are critical and vulnerable components. Structure measurement and attack simulations prove that spectral gap and node removal rate while entering the splitting phase can be adopted as important indicators for evaluating the reliability of water supply networks. The proposed reliability analysis method based on PDG model can be used to guide design and operation of water supply networks.

Abstract:Aiming to treat pharmaceutical wastewater containing pollutants that are difficult to be biodegraded, and deal with the inhomogeneous temperature and big attrition rate during the microwave regeneration of activated carbon, this study adopted a method, using a mixture of activated carbon and expanded graphite as AC-EG adsorption materials, to adsorb and treat the wastewater of a pharmaceutical factory after biochemical treatment. Based on the component analysis of wastewater from a pharmaceutical company, the adsorption thermodynamics and dynamics mechanism of pollutants in pharmaceutical wastewater adsorbed by adsorption material was studied, and the effect of microwave regeneration was investigated. The results showed that the wastewater contained a variety of unbiodegradable pollutants like pyridine, amide, azole, pyrazine and so on. The removal rate of COD in wastewater reached 58.25% when adsorbent was a mixture of activated carbon and 15% expanded graphite. The adsorption process, which AC-EG with 15wt% expanded graphite adsorbed pollutants in pharmaceutical wastewater, is an exothermic physical adsorption which follows Freundlich model (ΔH=-16.918 kJ/mol), and its entropy reduced(ΔS=-54 J/(mol·K)). Its kinetics model was relatively consistent with the second-order equation. A mixture of activated carbon and expanded graphite was heated and adsorbed microwave radiation more uniformly. With the increase of expanded graphite's doping amount, the adsorbent regeneration rate increased and the attrition rate declined.

Abstract:With high purity graphite becoming an important raw material in modern science, technology and industrial development, more and more fluoride-containing wastewater will be produced.The accurate monitor plays an important role in the control of the industry's environmental impact. It is found that fluorine ion concentration measured by fluoride ion selective electrode increased with the increasing of dilution ratio in graphite refining wastewater measurement. Reasons like dissolution of suspended calcium fluoride micro-crystal, the interference of impurity ions and the effect of ionic strength were analyzed through water quality analysis and theoretical calculation. Ion chromatography was used to check the result of experiments. Results show that the release of fluorine ion with complexing state from masking agent of TISAB is the main reason of what was found in the experiment. The fluorine ion concentration of graphite refining wastewater is about 0 to 30 mg/L.The water needs to be diluted 100 times when the fluoride ion concentration is measured by the national standard method.

Abstract:The emission factor method is often used to estimate the atmospheric pollution intensity in the past, in which exists a few defects such as the lack of emission source category, the complex computing and the suspicious atmospheric emission data sources on account of social enterprises' stealing pollutant emission. This study established the simple and rapid-computing atmospheric pollution emission intensity estimation model by using all urban areas' air quality data under high levels of pollution weather. Tyson polygon is adopted to define the regional characteristic length and air box model estimation method is used to determine the source of emissions of pollutants at a high rate of computing speed in this study. Simulation results indicated that the estimated emission intensity of NO_x, SO₂ and CO in the study area is 436.33, 154.82 and 8 566.82 t/d. According to the model accuracy test, the relative error of intermediate value is below 30% which indicates that the atmospheric emission intensity Algorithm can be used in simulation and prediction of regional atmospheric pollutants emission.

Abstract:To find the optimal parameters of least squares vector machine(LSSVM), the daily water demand forecasting method based on self-adaptive differential evolution(SADE) and LSSVM was proposed. The main influencing factors of daily water consumption were determined using improved rough set algorithm, and the correlation analysis on daily water consumption series was conducted. SADE was applied to optimize the parameters of LSSVM to build SADELSSVM-based forecasting model. The case study shows that compared with self-adaptive GA(SAGA) and differential evolution(DE), SADE has stronger global search ability and faster evolution speed, and the proposed model has better prediction performance than SAGALSSVM-based model and DELSSVM-based model.

Abstract:China actively promotes the construction of 3 million square kilometers of marine territory, and is vigorously building the Xisha and Nansha islands in the south China sea at present. The climate of islands and reefs in the sea is quite different from that of continent, and is featured by high temperature, high humidity and intense radiation. Combined with the fact of scarce resources on the island, it is inevitable to research and develop low-energy buildings under this special climatic conditions. In order to determine the characteristics of the low-energy building envelope suitable for island-reef climate, this paper analyzes the characteristics of marine climate by taking the measured data of Xisha as an example. To study the influence law of window-to-wall ratio (WWR) on energy consumption, this paper dynamically simulates the annual refrigeration consumption of one hotel to be built on the island. Results show that moisture load accounts for about 40% of the total cooling load. In summer, the total cooling load of the west room is the highest, south room the lowest. Once WWR increases 0.1, the energy consumption increases 3-5 kWh per unit area, but the variety of WWR in west and east takes big effects on building energy consumption than that in south and north. The fractional energy saving of the comprehensive sunshade is 7%, the best of all. The results of this study are intended to provide a reference for the reasonable value of WWR in the South China sea.

Abstract:Personal control behavior has potentials for both saving energy and maintaining comfort of human body. However, few studies are found on the influence of personal control behavior on thermal comfort in hot and humid environment. In this study, a series of experiments of personal-controlled desk fan were conducted in a hot and humid environment. In total, 24 subjects were invited to participate in the experiments and they experienced the environments which were set at 26, 28, and 30 ℃ with fixed or free-controlled local air flow, respectively. The experiment analyzed the comfort of the subjects under different working conditions. The results show that the use of desk fan significantly improved the subjects' thermal comfort. And the individual control behavior can not only lead to a better thermal comfort situation, but also show potential in energy-saving. When the subjects could freely control the fan, the thermal sensation is very close to neutral, and the average power of fans is at the lowest level.

Abstract:A large number of radiating facilities in turbine house cause tremendous afterheat gathering at the top of the house. While existed studies focus more on afterheat removal in summer, much less has been studied about the afterheat recovery in winter. In order to verify the feasibility of this self-balanced heating scheme in turbine house, CFD simulation was used to analyze it. A geometric model was set up according to actual spatial structure of the turbine house, and calculation was fulfilled with structural mesh. Two presetting heating schemes were compared and the optimized scheme that used airflow of jet tuyere instead of direct jet flow was proposed. The results indicated that the self-balanced heating scheme could meet the heating requirements and reduce the number of radiators; ventilation quantity of scheme 2 was better considering the efficiency of energy saving and heating. In addition, the airflow of jet tuyere was superior to that of direct jet flow, and it also improved the air distribution of the working layer, thereby achieving better heating effect. This paper provides a useful reference for heating design of large plants in cold area from the perspective of waste heat utilization.

Abstract:Thermodynamic vent system (TVS) is deemed as an efficient pressure control technique for long-term on-orbit storage of cryogenic propellants through fluid mixing and a combination of throttling and heat exchanging before venting. To conduct further study on the performance of tank pressure control by TVS under non-uniform heat flux, the effect of non-uniform heat flux (vapor heating only, liquid heating only and one side wall heating for both vapor and liquid) on self-pressurization characteristics and mass loss has been investigated experimentally on a TVS simulator, which works at room temperature and with R141b as the working fluid. The tank pressure rising rate, TVS operation performance, and vent mass loss of different heating condition were compared in detail. The results showed that under the condition of vapor heating mode, the rising rate of the tank pressure is the fastest, the TVS operation frequency and vent mass loss are the highest. However, under the condition of liquid heating mode, the rising rate of the tank pressure is the slowest, the TVS operation frequency and vent mass loss are the lowest, which decreased by 42%, 29% and 33%, respectively, compared with the liquid heating mode. Considering the overall effect by the pressure rising rate, the thermal stratification of the fluid and the vent mass loss, the internal wall surface of the tank is better to have hydrophilic treatment or to integrate capillary structures to avoid direct heating of the ullage in micro-gravity environment.

Abstract:When the side-by-side offloading operation is carried out between FLNG and LNGC, strong hydrodynamic interactions will be induced by the two hulls. The weather vane effect of single point mooring system has attracted most focuses on the analysis of side-by-side configuration in head waves. Nevertheless, the influence of oblique waves on the motion responses of the side-by-side system cannot be ignored. This article investigates the hydrodynamic responses of the side-by-side system through theoretical analysis method and model testing method. Based on the 3-D potential theory and artificial damping-lid method applied on the gap surface between two vessels, the gap water resonance and linear hydrodynamic performances of side-by-side FLNG and LNGC are studied under oblique and head waves. Middle-field method is adopted to calculate the second-order hydrodynamic parameters, and reveal the influence of wave directions on the mean drift forces of both vessels. Investigation shows that the change of wave directions within a certain range does not influence the value selection of the free surface damping, while imposes influence on the mode and amplitude of gap water resonance. The variation of wave directions affects the shielding effect between FLNG and LNGC, and the motion responses of LNGC are greatly suppressed by FLNG under oblique waves. Besides, the main components of mean drift forces on the two vessels change accordingly under different wave directions.

Abstract:In order to identify the effect of fill layout and water flow rate distribution on the cooling performance of cooling tower, a three-dimensional numerical model was established based on prototype of No.6 Cooling Tower in the Second Phase of Guohua Ninghai Power Plant in Zhejiang Province. Loading the mass, momentum, energy equation was computed by using user defined function. The comparision with the field measurement data proves the accuracy of the numerical calculation result. The effects of three kinds of fills and five kinds of fills layouts on cooling performance of super-large cooling tower weve compared and analyzed. It is found that compared with biphasic wave and double oblique wave, the cooling efficiency of S wave is optimal. For S wave, based on the dimensionless radius $ \check{r}$≤0.39 (inner zone), 0.39 < $ \check{r}$≤0.70 (middle zone) and 0.70 < $ \check{r}$≤1 (outer zone), the outlet water temperature of non-uniform layout 1.25-1.5-1.25 m is 0.66 K lower than the outlet water temperature of the uniform fill layout pattern 1.5 m. It is shown that the decreased fill height in inner and outer zones results in a higher air velocity and more uniform distribution of air velocity. In addition, increasing the salinity of cooling water made the outlet water temperature of three kinds of fills improve by about 2 K. It is indicated that the rise of outlet water temperature is related to the nature of seawater itself, and fill types has little impact on outlet water temperature.

Abstract:To investigate the bond behavior between corroded steel bars and high-strength recycled concrete, a central pull-out test was carried on 36 specimens which were produced by electricity to accelerate corrosion. In this paper, the design parameters comprises replacement rate of recycled coarse aggregate, rebar shape, rebar diameter, anchorage length and corrosion rate of rebar. Based on the test results, the bond failure forms of specimens and the influences of each design parameter on the bond behavior between corroded steel bars and high-strength recycled concrete were analyzed. The results indicate that there are three failure forms in the failure process, including steel bar pull-off, steel bar pull-out and concrete splitting. The bond strength between high-strength recycled concrete and corroded rebar is obviously higher than that of corroded plain round bar. The bond strength decreases with the increase of replacement rate of recycled coarse aggregate, rebar diameter, anchorage length, and corrosion rate of rebar. When the bar corrosion rate reaches a certain value, the reduction of bond strength is not obvious.

Abstract:To investigate the nonlinear properties of concrete under multiaxial cyclic loading, an improved bounding surface model was presented for concrete within the framework of elastoplastic and bounding surface theory. The yield surface is closed and smooth, and in tensile and compressive meridan planes, the yield surface is a pear shape. The shape of bounding surface is similar to yield surface. The first stress invariant and the strain deviation were adoped as the independent variables in the yield function and as the differential variable in the loading and unloading criteria. Based on the similarity of the shape between yield and bounding surfaces, the mapping relations were determined by proportional relations. According to the mapping rules, there always was an image stress point on the bounding surface for a current stress point on the yield surface. The two points had the same normal direction for corresponding surfaces, and a nonassociated flow was adopted to describe the plastic deformation. For the experimental results of concrete specimens under monotonic and cyclic loading along the compression direction in the deviatoric plane, the proposed model was used to simulate the results numerically. The calculated results agree well with experimental data. The model can describe the pre-failure and post-failure stress-strain curve and describe the shear dilatancy of concrete.

Abstract:To investigate the influence of corrosion on the bond performance between steel bar and concrete, twenty central pull-out test specimens were cast. Pull-out tests were conducted to study the bond behavior between concrete and steel bar corroded using current accelerate method with the expected mass loss of 0%, 0.5%, 1%, 2%, 5%. The variation of the bond performance between steel bar and concrete caused by steel bar corrosion was explained according to the change of steel bar geometrical characters and concrete strength in the whole corrosion process and the influence of corrosion rate on bond stiffness was studied by method of secant bond stiffness. The variation law of cracking due to corrosion expansion, bond stiffness and failure mode with various corrosion levels were studied. The test results show that bond strength and bond stiffness increase at the beginning and then decrease with the corrosion increasing. The degeneration of bond stiffness related to the appearance of cracking due to corrosion expansion. A simplified two-stage test model and conservative model partly available for reference to similar projects were proposed. A bond-slip constitutive relation with different corrosion rates was proposed based on two-stage model.

Abstract:Test data of reinforced masonry shear walls failed in shear with thickness of 290 mm under cyclic load were employed to establish a criterion for judging the failure loads of reinforced masonry shear walls based on stress state. The relationship between the structural stress state and external load was deduced, and the concept of bearing capacity envelop was introduced based on the failure mechanics of the wall at different stages. By combining the stress state-load relationship with the bearing capacity envelop, a stress state-based criterion was established to judge the crack, failure and ultimate loads of shear walls, which was validated through the comparison between the calculated results and the test results. The proposed criterion provides a new way for structural analysis and extents the application of test data.

Abstract:To investigate the regularity of energy evolution in the process of rock loading with imperfect bounding surface, uniaxial cyclic loading and unloading compressive tests were conducted on granite with mineral bonding slope, during which its acoustic emission was detected. It concludes that: 1) The "Effective energy ratio" (defined as cumulative elastic energy / input rock total energy) can be used as a token of rock energy storage level, which can also indirectly reflect the internal structure of the rock as the stress state changes. 2) The test object's acoustic emission energy release rate at the bonding surface of the test object was higher than that at peak intensity during the loading process. Acoustic emission at the site of bond surface release was short and strong, and the duration of acoustic emission at peak intensity was long but the acoustic emission and energy release rate was lower than that at bond surface failure. 3) No acoustic emission phenomenon occurred in the unloading process with low stress level or such phenomenon could be ignored. However, when the stress reached a certain level, where the elastic energy of granite accumulation exceeded the dissipation energy of local damage, short and intense brittle failure occurred during unloading. 4) The "AE detection efficiency" (cumulative AE / cumulative dissipation energy) is defined based on the fact that AE energy is part of the dissipative energy. It was found that "AE detection efficiency" decreased during the compaction phase and increased in the elastic phase. It reached peak value when the bonding surface was partially destroyed. After that, it tended to decrease until the peak intensity of bonding surface was reached. 5) From the energy point of view, the stress level corresponding to unloading rupture is lower than the loading strength, but it should not be lower than the stress level corresponding to the elastic energy which is equal to the dissipation energy at peak intensity.

Abstract:In order to obtain users' actual emotional status effectively and promote a harmonious human-computer interaction experience, combined with the AVS emotional space and big five personality theory, this paper proposes an incremental emotion mapping model based on Gauss mixture model. First of all, with three attributes in AVS emotional space (A, V, S) coordinate, the emotional probability value and space distribution is calculated with Gauss mixture model. Secondly, based on differences of individual users, analytic hierarchy method was used to study the relationship between big five personality and emotional attributes, personalized cognitive parameters of the user was obtained, and the realization of emotional mapping results with personalized knowledge were achieved. Then, incremental learning method was applied to get real-time correction of the spatial distribution of emotion type, thus ensuring the high accuracy of emotional classification. Finally, the experimental results show that this method has a high degree of consistency with the real emotional state of the user, and also has good adaptability.

Abstract:To improve the weldability of the Tin Free Steel, the granular chromium coatings were obtained on the steel by intermittent electrodeposit. The morphology and structure of the granular chromium were investigated and analyzed with scanning electron microscopy (SEM), X-ray diffraction (XRD), and the chromium content of the coatings were measured by the coulomb electrolysis method. The weldability of TFS was evaluated by measuring the contact resistance and observing the welding surface. Experimental results showed that the granular chromium distribute on the platelike chromium evenly. As the current interruption time extends, the density of the granular chromium gradually increases, while the welding resistance decreases. Compared with continuous electrodeposit, the preferred orientation of Cr (211) plane appears on the granular chromium prepared by intermittent electrodeposit. The chromium content of coating prepared by intermittent electroplating was higher than that of the continuous plating under the same charge amount. When the current is interrupted, the discontinuous oxide film is formed to make the layered chromium partially passivated, and the active point preferentially discharges to form dispersed granular chromium. When the pressure keeps constant, the contact resistance of the granular chromium coating is much smaller than that of the conventional chromium coating, and under same welding current, the former can be welded while the latter can't. During the current interruption, the presence of partial passivation contributes to the formation of granular chromium, which improves the weldability of TFS.

Abstract:To investigate the invasion effects of electric bicycles on motor vehicle traffic flow at an urban signalized intersection, a model was developed for the heterogeneous traffic flow of motor vehicles and electric bicycles. This model introduces the gap force, car-following force and repulsive forces into the original social force model to describe the characteristics of the heterogeneous traffic flow, and was calibrated and validated by using real data. Then, the influences of the the number of electric bicycles in queue and arrival rate of the electric bicycles on the flow rate and average speed of the motor vehicle traffic flow were analyzed. The calibration results showed that the e_MAE, e_MARE and U values for the flow rate and average speed calculated by the proposed model were less than 12%, which indicates that the proposed model can reflect the characteristics of the heterogeneous traffic flow with low errors. When the number of queuing electric bicycles is more than 20, appropriate traffic organization and control methods should be adopted to reduce the conflicts between electric bicycles and motor vehicles. Allowing electric bicycles to pass 2 or 3 seconds ahead of green signal or moving forward the stopping line for them may increase the capacity of the intersection for motor vehicles.

Abstract:Less attention devoting to the disposal of sewage sludge in China in the past decades led to unproper treatment of huge quantity of sewage sludge, which caused serious environmental problems. Since tremendous distribution of the enriched heavy metals in sewage sludge restricted its final land disposal, thus how those heavy metals are adsorbed onto the sludge has been highly concerned. Extracellular polymeric substances (EPS), mainly composed of protein, humic acid, polysaccharides, etc., is the main components of sludge organics. EPS traditionally exhibites a porous polymeric structure, and those polarity heavy metals can be easily adsorbed onto the adsorption sites (such as carboxyl and hydroxyl groups) which existes on the surface of EPS. Overall, the physicochemical structural characteristics of EPS significantly affects the adsorbing processes of heavy metals. In this study, we firstly gave a brief introduction to the current status of sludge treatment and disposal in China. Then, effect of the compositions and structures of sludge EPS on heavy metals adsorption was analyzed and the potential adsorption sites were summarized. Moreover, the analyzing approaches for studying the heavy metals adsorption processes were comparably evaluated. Finally, suggestions on the future research was raised pertinently.