Abstract:To accurately determine the limit carrying capacity of reinforced concrete slabs, based on the classical yield-line theory and previously proposed stress failure criterion, this paper presents the modified segment equilibrium method which incorporated the effect of the tensile membrane action. Additionally, the nonlinear finite element procedure was established according to the flat shell element and elastic-plastic theory. The two methods were used to calculate the limit load carrying capacity of reinforced concrete two-way slabs, and comparison between the calculated results and experimental results were conducted. This study shows that the two methods were clearly capable of predicting the load carrying capacity of the concrete slabs with reasonable accuracy, because the tensile membrane action was taken into account in the two models. Compared with the finite element model, the present method has strong engineering application value, due to its simple principle.

Abstract:To investigate the stability of the new full steel undersize-log formwork with early-removal substructure, 4-bay-5-row which were made up of the logs and steel tubes as a test unit were prepared to study the compressive failure test. The loading patterns and time which affected the substructure were considered, the supports force and deformation were analyzed, and the failure modes that were out-plane bucking and strength failure were observed in some members. The experimental results show that the pouring concrete actual speed should not too fast, and speeding up the turnover time of this formwork is available to reinstate the stress of this log. The members during pour concrete should be monitored. The structural measures and horizontal restraints of joints are absolutely essential, and the logs which are serious imperfection can obviously decrease the stability of the new formwork, so that attention should be paid to the weak parts of the installation location.

Abstract:To determine the shear-resistance performance and deformability of 290 mm-width fully grouted reinforced concrete masonry (FGRM) shear walls under different failure modes, ten full-scale walls were tested firstly under low cyclic reversed lateral loads simulated by a 1 000 kN jack providing constant axial load and a 630 kN servo controlled hydraulic actuator producing low cyclic reversed lateral loads. The seismic performance of walls bearing compress, shear and flexure is studied. Meanwhile, the skeleton curves of FGRM shear walls based on the data recorded in the tests are investigated considering different factors including the axial compressive stress, the horizontal reinforcement, the vertical reinforcement, et al. It is demonstrated that, firstly, both the shear and deformation capacity can be improved as the axial compressive stress increases within a certain range. Secondly, the impact of horizontal reinforcement on the shear-resistant performance of walls is related to failure modes of the wall. Compared with the flexural failure mode, a much higher shear capacity but a worse ductility is derived in a shear failure mode when the walls are confirmed with higher horizontal reinforcement. Finally, the wall shear capacity is influenced significantly by the vertical reinforcement whose effects on ductility are associated with the applied axial stress.

Abstract:Biological manganese removal process has a problem of long start-up period, when it is adopted to purify groundwater containing high concentration of iron, manganese and ammonia nitrogen. In order to investigate the effect of circulation reflux on start-up, three starting modes with varying reflux ratio, constant reflux ratio and no reflux were adopted in three same filters. Results showed that the total iron, manganese and ammomia nitrogen in effluent of the three filters was below 0.3 mg/L, 0.05 mg/L and 0.2 mg/L on 1,1 and 82 day, respectively; Variation of iron, manganese and ammonia nitrogen removal along the filter showed that the iron was removed mainly in the depth of 0-0.4 m, the manganese was adsorbed by manganese sand at the beginning and biological manganese removal was improved gradually after ammonia nitrogen reduced to be low enough. The circulation reflux is an effective way to shorten the start-up period of biological manganese removal process with high concentration of iron, manganese and ammonia nitrogen.

Abstract:To investigate bacterial community structure and biodiversity of a CANON reactor that was operated stably at room temperature, total DNA was extracted from the biofilm for PCR-DGGE analysis. The results of microbial community analysis showed that the ammonia oxidizing bacteria Nitrosomonas and Nitrosospira, together with the anaerobic ammonia oxidizing bacteria Candidatus Brocadia and Candidatus Kuenenia were detected as the functional bacteria while nitrite-oxidizing bacteria (NOB) was not found in the CANON system, and the biodiversity of AOB was significantly higher than anammox bacteria. Besides, some other bacteria like Shewanella, Pseudomonas, Ignatzschineria, Dechloromonas and some uncultured bacterium related to Clostridia, α-Proteobacteria and Bacillales also existed in the reactor.

Abstract:To investigate the effect of different environmental factors on the efficiency of denitrifying phosphorus removal bacteria (DPB), anaerobic/oxic/anoxic reactor (A/O/A-SBR) was used to culture the granular sludge. By designing the orthogonal test, the overall investigation of the biological nitrogen and phosphorus removal efficiency of DPB under various carbon source, carbon concentration, inlet water temperature and pH value was carried out. The results show that: when carbon source is sodium propionate, COD concentration is 400 mg/L, inlet water temperature is 25 ℃, and pH value is 7, the COD degradation efficiency of DPB is the highest; when carbon source is sodium propionate, COD concentration is 400 mg/L, inlet water temperature is 15 ℃, pH value is 7, the nitrogen removal efficiency of DPB is the highest; when carbon source is sodium acetate, COD concentration is 400 mg/L, inlet water temperature is 25 ℃, pH value is 8, the removal efficiency of soluble P is best. Temperature is the most influential factor for the COD and nitrogen removal, while the influence of pH is the minimum. The most influential factor for phosphorus removal of DPB is pH, and carbon source affects the minimum.

Abstract:An mesophilic upflow anaerobic sludge bed (UASB) reactor treating sugar refinery wastewater with an influent COD 20 000 mg·L-1 and HRT 8 h was introduced, and the impact of pH on its performance and hydrogen-producing acetogens and methanogens were investigated. The results showed that the pH in the UASB dropped from 6.8-7.4 to 5.7-6.7 when the influent pH decreased from 6.9 to 5.4, resulting in a reduction in COD removal by 23.3％ and a propionate increase in effluent by 3.9 times. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) of sampled sludge indicated that the diversity of hydrogen-producing acetogens in the UASB was remarkably lower than that of the methanogens. The distribution and dominance of hydrogen-producing acetogens had been observably influenced by the dropped pH. The dominance of propionate-oxidizing bacteria (Pelotomaculum), represented by band Eub 19, were significantly reduced in approach acid condition, while acetotrophic methanogens and the dominant hydrogenotrophic methanogens stood steadily. Furthermore, the dominance of some acid-tolerant hydrogenotrophic methanogens such as Methanobacterium ferruginis and uncultured Methanobrevibacter were enhanced observably following the drop in pH. These results suggested that hydrogen-producing acetogens seemed to be more susceptible to pH than methanogens.

Abstract:To improve the photocatalytic efficiency of TiO₂ for bromate removal, TiO₂ modified with Pt was prepared by impregnation method. The photocatalytic activity of Pt/TiO₂ for bromate removal was studied. The effects of Pt loading, calcination temperature, pH, dissolved oxygen, organic matter on the photocatalytic activity for bromate removal were explored under ultraviolet illumination(365 nm), and the photocatalytic kinetics was also investigated. The results showed that the photosensitization of PtCl₄ significantly improved the photocatalytic activity of TiO₂, and the activity of Pt/TiO₂ was affected by Pt loading, calcination temperature, pH, dissolved oxygen and organic matter. An optimum content of Pt was 0.01％, the optimal calcination temperature was 400 ℃, the activity was increased quickly with a decrease of pH and inhibited by dissolved oxygen and ethanol. The photocatalytic kinetics followed the first-order kinetic equation.

Abstract:In order to provide reference for using the unconventional meteorological data in environmental prediction, based on AERMOD model,the standard meteorological scenario and NCEP meteorological scenarios were constructed by using the 2011 Harbin station-observed data and NCEP reanalyzed data, and the d index and relative error on pollutant prediction concentration between NCEP meteorological scenarios and standard meteorological scenario were analyzed. The results show that the NCEP high altitude meteorological data, cloud data can be used in atmospheric environment prediction, but the NCEP data cannot replace the ground automatic weather station data for atmospheric environment prediction.

Abstract:To improve the accuracy of disturbances detection and localization, a new approach based on Hyperbolic S-transform (HST) is constructed in this paper. After the modular matrix of power quality signal is calculated by the HST, the disturbance is detected and located by the sum of amplitudes of each sample point. The sum of amplitude is processed by threshold at first. Then, the points with the peak value are extracted for disturbances detection. The experimental results show that the new method realizes the accurate detection and localization of 7 types of disturbances including voltage sag, swell, interruption, pulse, spike, notch and transient. The simulation on ideal signals proves that the new method has the good adaptability and noise intensity. The extent of disturbances parameters has little impact on this proposed method. The method is very satisfied for disturbances location in real power system.

Abstract:According to relatively large measurement error of one pair pole axial-flux resistance resolver, a multipole axial-flux reluctance resolver is put forward, which could solve the problem of the high-order harmonic interference and the influence of stator eccentricity and rotor eccentricity on precision. By using calculus method, the mathematics model of this new reluctance resolver is calculated. The validity and feasibility of design proposal are tested by finite element analysis. The analysis results show that the high order harmonic of output voltage makes voltage waveform distortion and causes errors, in which the third harmonic ratio accounts for a large proportion of total harmonic distortion rate. By optimizing the rotor structure, the third harmonic of output voltage is weakended so that the measurement error of the multipole axial-flux reluctance resolver is effectively reduced.

Abstract:As the traditional elevator traffic pattern recognition exists mode lag and it is difficult to adapt the performance requirements of group control system for the new type of twin elevator, this paper presents an elevator traffic mode prediction method which is based on traffic flow prediction. The support vector machine(SVM) is used for elevator traffic flow prediction, the BP neural network for elevator traffic flow pattern recognition and the genetic algorithms(GA) is adopted to optimize the BP neural network. Meanwhile, by fusing elevator traffic flow prediction and traffic pattern recognition together, the neural network is utilized to recognize the pattern of the predicted traffic flow again, thereby the pattern prediction is realized. Research results show that the traffic pattern of predicted traffic flow is consistent with the traffic pattern of actual traffic flow,which verifies the accuracy of traffic pattern prediction, avoids the defect of mode lag and provides a theoretical basis for engineering application of twin elevator group control system.

Abstract:In order to clarify the main affecting factors under the environment of traffic electronic enforcement, on basis of traffic investigation, the effects of the aspects of electronic enforcement, traffic marking, vehicle type and service level at intersection on traffic violation were analyzed by generalized estimation equations. The result showed that the electronic enforcement and traffic marking affected traffic violation significantly, and the cross-effect analysis of automated enforcement and traffic marking showed that the electronic enforcement could restrain traffic violation obviously when the traffic marking was complete. The complete traffic marking was the basic guarantee to achieve the original purpose of electronic enforcement building, it had an important role to restrain traffic violations and improve road traffic safety level under the environment of electronic enforcement.

Abstract:By analytical model based on the patch-corridor model in landscape ecology, the quantitative benchmark data of the mining brownfield ecological restoration is deduced, and it would be become unbroken red line in the planning design. The forest area for ecological species perching can’t be less than 1.5 km², and the area less than 30 km² should be mainly used for afforestation. The natural state of the site boundary should be kept, the shape index should be added and the fences should not be built. The width of ecological corridor should not be less than 60 m, the pollution sources such as tailing heap and so on should be covered by vegetation, and the width of buffer strips can’t be less than the minimum allowable value. All of these could become theoretical foundation in the project design, thus, we could ensure the mine parks based on mining brownfields become genuine ecological civiization construction project, and could prevent predatory secondary development.

Abstract:To study the mechanical behavior of concrete filled steel tube columns subjected to compression-bending-torsion combined load, based on the general finite element program ABAQUS, the suitable material constitutive equations including concrete damage plastic model and steel perfect elastic-plastic model, boundary conditions and combined load conditions were chosen and applied, then the “shell-solid” refined model of concrete filled steel tube columns was established. A good agreement could be observed between the predicted results and test results, and both the stress-strain state of the steel and concrete and the global torsion moment versus rotation angle relations could be obtained, showing that the “shell-solid” refined model had high precisions, and the comprehensive results of concrete filled steel tubes subjected to torsion could be obtained.

Abstract:For solving the difficulties in evaluation of the pile tip embedded depth for a long pile and depth of a deep embedded defect, the parallel seismic test is proposed in this paper. A simplified theoretical model of pile-soil system is established to determinate embedded depths of the pile tip and defect. Three-dimensional (3-D) axisymmetric finite element models were established for comparison of the parallel seismic (PS) and the reflected wave (RW) tests for piles. It was found that the RW test was suitable for determination tip embedded depth of a non-long pile and a non-deep embedded defect of a pile. Exponential amplification could be employed to deal with such difficulties, but still there were uncertainties existing in practical application. Compared to RW test, PS test is much less affected by pile length and depth-to-diameter ratio, and has advantages in identifying the embedded depth and degree of a defect as well as the embedded depth of the pile tip.

Abstract:Bond properties between reactive powder concrete and steel bar are studied through beam bond tests, and compared with C40 concrete. It is showed that, the bond stress-slip curve tendency of the two concretes is similar, and the compressive strength and bond strength of reactive powder concrete are much larger than that of C40 concrete. The ultimate bond stress of reactive powder concrete τu is about three times of C40 concrete, the responding slip su is about twice of that of C40 concrete, and the relative bond strength τu/fcu is about 1.6 times of that of C40 concrete. The bond mechanism between reactive powder concrete and steel bar is analyzed according to the test curve and failure mode, at the same time, an empirical formula including multifactor are established through statistical regression, and a simplified four-line bond stress-slip model is established that can provide a reference for engineering design.

Abstract:To explore the seismic performance of reactive powder concrete (RPC) column, the quasi-static test of 18 RPC columns are carried out. The factors affecting the column failure patterns, hysteretic characteristics, skeleton curves, rigidity, bearing capacity and ductility were analyzed in this paper, which included axial compression ratio, longitudinal reinforcement ratio, stirrup ratio and steel fiber volume content. The results show that, the bearing capacity of reinforced RPC columns increases, but the ductility decreases with the increase of axial compression ratio. The bearing capacity and displacement ductility coefficient of reinforced RPC columns significantly increases with the increase of longitudinal reinforcement. The stirrup ratio has large influence on the hysteretic behavior of reinforced RPC columns and the skeleton curve flattens out as load exceeds the peak point. The steel fiber volume content has large influence on fracture process of RPC columns, with the increase of steel fiber content, and the ductility of reinforced RPC columns can be improved to a certain extent.

Abstract:The adsorption and biodegradability of thefive estrogens, including estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-estradiol and 17α-ethynylestradiol (EE2), by four kinds of activated sludge collected from sewage treatment plants in Hong Kong and Shenzhen are characterized. A pretreatment method of Liquid-liquid-extraction and the GC-MS measurement were applied for determining concentrations of residual estrogens. Adsorption equilibrium could be achieved in around 30 min-1 h and the residual estrogen in adsorption control sets kept relatively stable with no significant difference among different sludges. The average adsorption amount of EE2 and 17α-E2 were estimated at 2.6 and 2.5 μg per mg MLVSS, while E1, E2 and E3 had average adsorption amounts of 1.6,1.7 and 0.9 μg·mg-1. The average biodegradation rate of E1, E2, E3,7α-E2 and EE2 was 6,2, 0,5 and 13 μg·L-1·d-1, respectively under aerobic conditions. The half lives of E1, E2, E3,7α-E2 and EE2 by the four sludges were estimated at 14.9 h, 0.9 h, 4.3 h, 4.7 h and 18.9 d in average. The adsorption amount of E3 was lower than other estrogens, which might be due to its polar structure. EE2 was the hardest to digest. The sludge AS2, nitrifying activated sludge (NAS), was more effective in transforming EE2 than that of other three sludges, which might be closely related to the nitrifiers in NAS.

Abstract:In order to quantitatively analyze the multipath error COMPASS navigation signal with MBOC modulation, this paper introduces the principle of the multiplexed binary offset carrier(MBOC), establishes the corresponding multipath signal model, and achieves the formulas of the code tracking error and carrier phase error due to multipath signals using early minus late power (EMLP) discriminator and arctangent discriminator. The multipath performance of MBOC modulated signal is simulated under different multipath-to-direct ratio, correlator spacing, front-end bandwidth, and code tracking error is analyzed in the presence of noise interference. The simulation results demonstrate the corresponding multipath error envelope decreases with multipath to direct ratio decreasing from -3 dB to -6 dB. When MDR is a constant, the multipath error can be well suppressed by applying narrow correlator technology and wider receiver front-end bandwidth. Code tracking error decreases to 0 as the carrier to noise ratio increasing in the presence of noise interference.