Showing papers in "Journal of Central South University in 2013"

Improving performance of recycled aggregate concrete with superfine pozzolanic powders

Abstract: Phosphorous slag (PHS), ground granulated blast-furnace slag (GGBS) and fly ash (FA) were used as replacements of Portland cement to modify the microstructure of recycled aggregate concrete (RAC). A new manufacturing method named “W3T4” was proposed to improve the performances of interfacial transition zone (ITZ) between recycled aggregate and mortar. The mechanical properties and the durability of RAC were tested, which show that this new manufacturing method improves the properties of RAC, and the GGBS with finest size makes a great contribution to the performance of RAC due to its better filling effect and much earlier pozzolanic reaction. Combined with GGBS, the effects of PHS on the retardation of setting time can be alleviated and the synergistic effect helps to make a more compact RAC. For the RAC with 25% of the recycled aggregate (RA) replacement and 10% PHS + 10% GGBS additives, the compressive strength increases by 25.4%, but the permeability decreases by 64.3% with respect to the reference concrete made with nature aggregates. The micro-mechanisms of these improvements were investigated by the scanning electron microscope (SEM). The SEM images show that the new manufacturing method, adding superfine pozzolanic powders and super-plasticizer benefits, makes a much denser ITZ in RAC.

Mobile robot path planning based on adaptive bacterial foraging algorithm

Abstract: The utilization of biomimicry of bacterial foraging strategy was considered to develop an adaptive control strategy for mobile robot, and a bacterial foraging approach was proposed for robot path planning. In the proposed model, robot that mimics the behavior of bacteria is able to determine an optimal collision-free path between a start and a target point in the environment surrounded by obstacles. In the simulation, two test scenarios of static environment with different number obstacles were adopted to evaluate the performance of the proposed method. Simulation results show that the robot which reflects the bacterial foraging behavior can adapt to complex environments in the planned trajectories with both satisfactory accuracy and stability.

Cr(III) adsorption by sugarcane pulp residue and biochar

Abstract: A batch experiment was conducted to investigate the adsorption of trivalent chromium (Cr(III)) from aqueous solutions by sugarcane pulp residue (SPR) and biochar. The results show that Cr(III) adsorption by SPR and biochar is highly pH-dependent and Cr(III) adsorption amount increases with the increase of pH. The adsorption kinetics of Cr(III) fits well with the pseudo-second-order model. The maximum Cr(III) adsorption capacities of 15.85 mg/g and 3.43 mg/g for biochar and SPR were calculated by Langmuir model. This indicates that biochar has a larger ability for Cr(III) adsorption than SPR. The free energy change value (ΔG) reveals a spontaneous sorption process of Cr(III) onto SPR and non-spontaneous sorption process onto biochar. The entropy change (ΔS) and enthalpy change (ΔH) are found to be 66.27 J/(mol·K) and 17.13 kJ/mol for SPR and 91.59 J/(mol·K) and 30.875 kJ/mol for biochar which further reflect an affinity of Cr(III) onto SPR and biochar. It is suggested that biochar has potential to be an efficient adsorbent in the removal of Cr(III) from industrial wastewater.

A genetic algorithm for community detection in complex networks

Abstract: A new genetic algorithm for community detection in complex networks was proposed. It adopts matrix encoding that enables traditional crossover between individuals. Initial populations are generated using nodes similarity, which enhances the diversity of initial individuals while retaining an acceptable level of accuracy, and improves the efficiency of optimal solution search. Individual crossover is based on the quality of individuals’ genes; all nodes unassigned to any community are grouped into a new community, while ambiguously placed nodes are assigned to the community to which most of their neighbors belong. Individual mutation, which splits a gene into two new genes or randomly fuses it into other genes, is non-uniform. The simplicity and effectiveness of the algorithm are revealed in experimental tests using artificial random networks and real networks. The accuracy of the algorithm is superior to that of some classic algorithms, and is comparable to that of some recent high-precision algorithms.

Inhibition effect of a synthesized N , N′ -bis(2-hydroxybenzaldehyde)-1, 3-propandiimine on corrosion of mild steel in HCl

Abstract: The corrosion inhibition of mild steel in 1 mol/L HCl by N, N′-bis (2-hydroxybenzaldehyde)-1, 3-propandiimine (2-HBP) has been investigated by using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and chronoamperometry measurements. The experimental results suggest that this compound is an excellent corrosion inhibitor for mild steel and the inhibition efficiency increases with the increase in inhibitor concentration. Polarization curves reveal that this organic compound is a mixed type inhibitor. The effect of temperature on the corrosion behavior of mild steel with the addition of the Schiff base was studied in the temperature range from 25 °C to 65 °C. The experimentally obtained adsorption isotherms follow the Langmuir equation. Activation and thermodynamic adsorption parameters such as Ea, ΔH, ΔS, Kads and ΔGads were calculated by the corrosion currents at different temperatures and using the adsorption isotherm. The morphology of mild steel surface in the absence and presence of 2-HBP was examined by atomic force microscope (AFM) images.

Optimization of suspension system of off-road vehicle for vehicle performance improvement

Abstract: Vehicle suspension design includes a number of compromises to provide good leveling of stability and ride comfort. Optimization of off­road vehicle suspension system is one of the most effective methods, which could considerably enhance the vehicle stability and controllability. In this work, a comprehensive optimization of an off­read vehicle suspension system model was carried out using software ADAMS. The geometric parameters of suspension system were optimized using genetic algorithm (GA) in a way that ride comfort, handling and stability of vehicle were improved. The results of optimized suspension system and variations of geometric parameters due to road roughness and different steering angles were presented in ADAMS and the results of optimized and conventional suspension systems during various driving maneuvers were compared. The simulation results indicate that the camber angle variations decrease by the optimized suspension system, resulting in improved handling and ride comfort characteristics.

A strength reduction method based on double reduction parameters and its application

Abstract: In the traditional strength reduction method, the cohesion and the friction angle adopt the same reduction parameter, resulting in equivalent proportional reduction. This method does not consider the different effects of the cohesion and friction angle on the stability of the same slope and is defective to some extent. Regarding this defect, a strength reduction method based on double reduction parameters, which adopts different reduction parameters, is proposed. The core of the double-parameter reduction method is the matching reduction principle of the slope with different angles. This principle is represented by the ratio of the reduction parameter of the cohesion to that of the friction angle, described as η. With the increase in the slope angle, η increases; in particular, when the slope angle is 45°, η is 1.0. Through the matching reduction principle, different safety margin factors can be calculated for the cohesion and friction angle. In combination with these two safety margin factors, a formula for calculating the overall safety factor of the slope is proposed, reflecting the different contributions of the cohesion and friction angle to the slope stability. Finally, it is shown that the strength reduction method based on double reduction parameters acquires a larger safety factor than the classic limit equilibrium method, but the calculation results are very close to those obtained by the limit equilibrium method.

Effect of landform on aerodynamic performance of high-speed trains in cutting under cross wind

Abstract: The effects of the different landforms of the cutting leeward on the aerodynamic performance of high-speed trains were analyzed based on the three-dimensional, steady, and incompressible Navier-Stokes equation and k-ɛ double-equation turbulent model. Results show that aerodynamic forces increase with the cutting leeward slope decreasing. The maximum adding value of lateral force, lift force, and overturning moment are 147%, 44.3%, and 107%, respectively, when the slope varies from 0.67 to −0.67, and the changes in the cutting leeward landform have more effects on the aerodynamic performance when the train is running in the line No. 2 than in the line No. 1. The aerodynamic forces, except the resistance force, sharply increase with the slope depth decreasing. By comparing the circumstance of the cutting depth H= −8 m with that of H=8 m, the resistance force, lateral force, lift force, and overturning moment increase by 26.0%, 251%, 67.3% and 177%, respectively. With the wind angle increasing, the resistance force is nonmonotonic, whereas other forces continuously rise. Under three special landforms, the changes in the law of aerodynamic forces with the wind angle are almost similar to one another.

Optimizing rhamnolipid production by Pseudomonas aeruginosa ATCC 9027 grown on waste frying oil using response surface method and batch-fed fermentation

Abstract: Rhamnolipid production by Pseudomonas aeruginosa ATCC 9027 with waste frying oil as sole carbon source was studied using response surface method. Cultures were incubated in shaking flask with temperature, NO3− and Mg2+ concentrations as the variables. Meanwhile, fed-batch fermentation experiments were conducted. The results show that the three variables are closely related to rhamnolipid production. The optimal cultivation conditions are of 6.4 g/L NaNO3, 3.1 g/L MgSO4 at 32 °C, with the maximum rhamnolipid production of 6.6 g/L. The results of fed-batch fermentation experiments show that feeding the oil in two batches can enhance rhamnolipid production. The best time interval is 72 h with the maximum rhamnolipid production of 8.5 g/L. The data are potentially useful for mass production of rhamnolipid on oil waste with this bacterium.

Triaxial creep tests of weak sandstone from fracture zone of high dam foundation

Abstract: The lithology of fracture zone which was developed at the dam foundation of a hydropower station is weak sandstone with poor integrity and pore cementation contact Its creep properties have a significant impact on the deformation and stability of the dam Based on the characteristics of loose organizational structure, high moisture content and poor mechanical properties, the triaxial compression tests and creep tests were carried out, respectively The results show significant non-linear, low strength and no obvious strength peaks Both axial and lateral strains are achieved more than 3% when the tests are failed The weak sandstone has a significant creep property, but only transient and steady state appear under low stress Increased stress causes creep intensified and lateral strain gradually exceeds axial strain In the failure stage, it has characteristics of large axial plastic deformation, obvious volumetric ductility dilation and large steady creep rate The accelerated creep appears shortly after transient loading under confining of pressures 10 MPa and 15 MPa Therefore, an improved Burgers creep model considering the non-linear characteristics of weak sandstone is built based on hyperbolic equation and the creep parameters are identified This model can well describe the creep properties of weak sandstone

A system combining microbial fuel cell with photobioreactor for continuous domestic wastewater treatment and bioelectricity generation

Abstract: A coupled system consisting of an upflow membrane-less microbial fuel cell (upflow ML-MFC) and a photobioreactor was developed, and its effectiveness for continuous wastewater treatment and electricity production was evaluated. Wastewater was fed to the upflow ML-MFC to remove chemical oxygen demand (COD), phosphorus and nitrogen with simultaneous electricity generation. The effluent from the cathode compartment of the upflow ML-MFC was then continuously fed to an external photobioreactor for removing the remaining phosphorus and nitrogen using microalgae. Alone, the upflow ML-MFC produces a maximum power density of 481 mW/m(3), and obtains 77.9% COD, 23.5% total phosphorus (TP) and 97.6% NH4 (+)-N removals. When combined with the photobioreactor, the system achieves 99.3% TP and 99.0% NH4 (+)-N total removal. These results show both the effectiveness and the potential application of the coupled system to continuously treat domestic wastewater and simultaneously generate electricity and biomass.

Effects of H3PO4 and Ca(H2PO4)2 on mechanical properties and water resistance of thermally decomposed magnesium oxychloride cement

Abstract: The effects of H3PO4 and Ca(H2PO4)2 on compressive strength, water resistance, hydration process of thermally decomposed magnesium oxychloride cement (TDMOC) pastes were studied. The mineral composition, hydration products and hydration heat release were analyzed by XRD, FT-IR, SEM and TAM air isothermal calorimeter, etc. After being modified by H3PO4 and Ca(H2PO4)2, the properties of the TDMOC are improved obviously. The compressive strength increases from 14.8 MPa to 48.1 MPa and 37.1 MPa, respectively. The strength retention coefficient (K n ) increases from 0.38 to 0.99 and 0.94, respectively. The 24 h hydration heat release decreases by 10% and 4% and the time of hydration peak appearing is delayed from 1 h to about 10 h. The XRD, FT-IR and SEM results show that the main composition is 5Mg(OH)2·MgCl2·8H2O in the modified TDMOC pastes. The possible mechanism for the strength enhancement was discussed. The purposes are to extend the potential applications of the salt lake magnesium resources and to improve the mechanical properties of TDMOC.

Analysis of inhibition of concrete steel-rebar corrosion by Na2Cr2O7 concentrations: Implications for conflicting reports on inhibitor effectiveness

Abstract: Corrosion test data were measured using non-destructive electrochemical techniques and analysed for studying inhibition effectiveness by different concentrations of Na2Cr2O7 on the corrosion of concrete steel-rebar in NaCl and in H2SO4 media. For these, specifications of ASTM G16-95 R04 were combined with the normal and the Gumbel probability density functions as model analytical methods for addressing issues of conflicting reports of inhibitor effectiveness that had generated concerns. Results show that reinforced concrete samples admixed with concentrations having 4 g (0.012 7 mol), 8 g (0.025 4 mol) and 6 g (0.019 1 mol) Na2Cr2O7 exhibited, in that order, high inhibition effectiveness, with respective efficiency, η, of (90.46±1.30)%, (88.41±2.24)% and (84.87±4.74)%, in the NaCl medium. These exhibit good agreements within replicates and statistical methods for the samples. Also, optimal inhibition effectiveness model in the H2SO4 medium was exhibited by 8 g (0.025 4 mol) Na2Cr2O7 concentration having η=(78.44±1.10)%. These bear implications for addressing conflicting test data in the study of effective inhibitors for mitigating steel-rebar corrosion in aggressive environments.

Cracking process of rock mass models under uniaxial compression

Abstract: Anisotropic strength and deformability of the rock mass with non-persistent joints are governed by cracking process of the rock bridges. The dependence of cracking process of jointed rock masses on the two important geometrical parameters, joint orientation and joint persistence, was studied systematically by carrying out a series of uniaxial compression tests on gypsum specimens with regularly arranged multiple parallel pre-existing joints. According to crack position, mechanism and temporal sequence, seven types of crack initiations and sixteen types of crack coalescences, were identified. It was observed that both tensile cracks and shear cracks can emanate from the pre-existing joints as well as the matrix. Vertical joints were included and coplanar tensile cracks initiation and coalescence were observed accordingly. For specimen with joint inclination angle β=75°, it was found that collinear joints can be linked not only by coplanar shear cracks but also by mixed tensile-shear cracks, and that a pair of them can form a small rotation block. Seven failure modes, including axial cleavage, crushing, crushing and rotation of new blocks, stepped failure, stepped failure and rotation of new blocks, shear failure along a single plane and shear failure along multiple planes, were observed. These modes shift gradually in accordance with the combined variation of joint orientation and joint persistence. It is concluded that cracking process and failure modes are more strongly affected by joint orientation than by joint persistence, especially when joint inclination angle is larger than 45°. Finally, variations of macroscopic mechanical behaviors with the two geometrical parameters, such as patterns of the complete axial stress-axial strain curves, peak strength and elastic modulus, are summarized and their mechanisms are successfully explained according to their different cracking process.

Effect of cyclic drying and wetting on engineering properties of heavy metal contaminated soils solidified/stabilized with fly ash

Abstract: Solidification/stabilization (S/S) is one of the most effective methods of dealing with heavy metal contaminated soils. The effects of cyclic wetting and drying on solidified/stabilized contaminated soils were investigated. A series of test program, unconfined compressive strength (UCS) test, TCLP leaching test and scanning electron microscopy (SEM) test, were performed on lead and zinc contaminated soils solidified/stabilized by fly ash. Test results show that UCS and the leaching characteristics of heavy metal ions of S/S contaminated soils are significantly improved with the increase of fly ash content. UCS of S/S soils firstly increases with the increase of the times of drying and wetting cycles, after reaching the peak, it decreases with it. When the pollutant content is lower (1 000 mg/kg), the TCLP concentration first slightly decreases under cyclic drying and wetting, then increases, but the change is minor. The TCLP concentration is higher under a high pollutant content of 5 000 mg/kg, and increases with the increase of the times of drying and wetting cycles. The results of scanning electron microscopy (SEM) test are consistent with UCS tests and TCLP leaching tests, which reveals the micro-mechanism of the variations of engineering properties of stabilized contaminated soils after drying and wetting cycles.

Evolution of distribution and content of water in cement paste by low field nuclear magnetic resonance

Abstract: The low field nuclear magnetic resonance (NMR), as a nondestructive and noninvasive technique, was employed to investigate the water distribution and content in cement paste with different water-to-cement ratio (w/c ratio) during early and later hydration stages. From the water distribution spectrum deduced from relaxation time distribution in paste, it is suggested that the water fills in the capillary pores at initial period, and then diffuses to the mesopores and gel pores in hydration products with the hydration proceeding. The decrease of peak area in water distribution spectrum reflects the transformation from physically bound water to chemically bound water. In addition, based on the connection between relaxation time and pore size, the relative content changes of water in various states and constrained in different types of pores were also measured. The results demonstrate that it is influenced by the formation of pore system and the original water-to-cement ratio in the paste. Consequently, the relative content of capillary water is dropped to less than 2% in the paste with low w/c ratio of 0.3 when being hydrated for 1 d, while the contents are still 16% and 36% in the pastes with w/c ratios of 0.4 and 0.5, respectively.

Multi-line code: A low complexity revocable fingerprint template for cancelable biometrics

Abstract: A low computational cost cancelable fingerprint template, namely the multi-line codes was proposed. The formulation of a single-line code involves the inspection of minutiae distribution along a straight line constructed based on the reference minutia. Multi-line code is introduced to elevate the performance by combining several single-line codes. Experiments were carried out on a few FVC databases. It has been proven that the proposed method yields relatively low computational complexity as compared to existing minutiae distribution-based methods, while preserving the performance. The equal error rate obtained for FVC2002 DB1 is 4.69% in stolen-key case, and the total arithmetic operations utilized are 14 520 additions and zero multiplication.

Optimization of process parameters to maximize ultimate tensile strength of friction stir welded dissimilar aluminum alloys using response surface methodology

Abstract: Aluminium alloys generally present low weldability by traditional fusion welding process. Development of the friction stir welding (FSW) has provided an alternative improved way of producing aluminium joints in a faster and reliable manner. The quality of a weld joint is stalwartly influenced by process parameter used during welding. An approach to develop a mathematical model was studied for predicting and optimizing the process parameters of dissimilar aluminum alloy (AA6351 T6-AA5083 H111) joints by incorporating the FSW process parameters such as tool pin profile, tool rotational speed welding speed and axial force. The effects of the FSW process parameters on the ultimate tensile strength (UTS) of friction welded dissimilar joints were discussed. Optimization was carried out to maximize the UTS using response surface methodology (RSM) and the identified optimum FSW welding parameters were reported.

Failure mode classification of reinforced concrete column using Fisher method

Abstract: In order to apply the performance-based seismic design, an engineer must first find out whether the column is expected to fail in shear before or after flexural yielding. According to column failure characteristics and failure mode of reinforced concrete column, the UW-PEER structure performance database was discussed and analyzed. In order to investigate the relevance of failure mode and factors such as longitudinal reinforcement ratio, transverse reinforcement ratio, hoop spacing to depth ratio, aspect ratio, shearing resistance demand to shear capacity ratio and axial load ratio, Fisher’s discriminant analysis (FDA) of the above factors was carried out. A discriminant function was developed to identify column failure mode. Results show that three factors, i.e., Vp/Vn, hoop spacing to depth ratio and aspect ratio have important influence on the failure mode. The failure mode has less to do with longitudinal reinforcement ratio, transverse reinforcement ratio and axial load ratio. Through using these three factors and the model proposed, over 85.6% of the original grouped cases were correctly classified. The value of coefficient of Vp/Vn is the largest, which means that discriminant equation is most sensitive to the shearing resistance demand to shear capacity ratio.

Long term performance of warm mix asphalt versus hot mix asphalt

Abstract: The fatigue behavior, indirect tensile strength (ITS) and resilient modulus test results for warm mix asphalt (WMA) as well as hot mix asphalt (HMA) at different ageing levels were evaluated Laboratory-prepared samples were aged artificially in the oven to simulate short-term and long term ageing in accordance with AASHTO R30 and then compared with unaged specimens Beam fatigue testing was performed using beam specimens at 25 °C based on AASHTO T321 standard Fatigue life, bending stiffness and dissipated energy for both unaged and aged mixtures were calculated using four-point beam fatigue test results Three-point bending tests were performed using semi-circular bend (SCB) specimens at −10 °C and the critical mode I stress intensity factor KI was then calculated using the peak load obtained from the load-displacement curve It is observed that Sasobit and Rheofalt warm mix asphalt additives have a significant effect on indirect tensile strength, resilient modulus, fatigue behavior and stress intensity factor of aged and unaged mixtures

Solution of Terzaghi one-dimensional consolidation equation with general boundary conditions

Abstract: Boundary conditions for the classical solution of the Terzaghi one-dimensional consolidation equation conflict with the equation’s initial condition. As such, the classical initial-boundary value problem for the Terzaghi one-dimensional consolidation equation is not well-posed. Moreover, the classical boundary conditions of the equation can only be applied to problems with either perfectly pervious or perfectly impervious boundaries. General boundary conditions are proposed to overcome these shortcomings and thus transfer the solution of the Terzaghi one-dimensional consolidation equation to a well-posed initial boundary value problem. The solution for proposed general boundary conditions is validated by comparing it to the classical solution. The actual field drainage conditions can be simulated by adjusting the values of parameters b and c given in the proposed general boundary conditions. For relatively high coefficient of consolidation, just one term in series expansions is enough to obtain results with acceptable accuracy.

Crack detection of reinforced concrete bridge using video image

Abstract: With the digital image technology, a crack detection method of reinforced concrete bridge was studied for the performance assessment. The effects including the image gray level, pixel rate, noise filter, and edge detection were analyzed considering cracks qualities. A computer program was developed by visual C++6.0 programming language to detect the cracks, which was tested by 15 cases of bridge video images. The results indicate that the relative error is within 6% for cracks larger than 0.3 mm cracks and it is less than 10% for crack width between 0.2 mm and 0.3 mm. In addition, for the crack below 0.1 mm, the relative error is more than 30% because the bridge is in safe stage and it is very difficult to detect the actual width of crack.

Genetic algorithm tuned PI controller on PMSM simplified vector control

Abstract: A simple control structure in servo system is occasionally needed for simple industrial application which precise and high control performance is not exessively important so that the cost production can be reduced efficiently. Simplified vector control, which has simple control structure, is utilized as the permanent magnet synchronous motor control algorithm and genetic algorithm is used to tune three PI controllers used in simplified vector control. The control performance is obtained from simulation and investigated to verify the feasibility of the algorithm to be applied in the real application. Simulation results show that the speed and torque responses of the system in both continuous time and discrete time can achieve good performances. Furthermore, simplified vector control combined with genetic algorithm has a similar performance with conventional field oriented control algorithm and possible to be realized into the real simple application in the future.

Finite element analysis on thermal upheaval buckling of submarine burial pipelines with initial imperfection

Abstract: In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and prevent the solidification of the wax fraction. The pipeline containing hot oil will expand longitudinally due to the rise in temperature. If such expansion is resisted, for example by frictional effects over a kilometer or so of pipeline, compressive axial stress will be built up in the pipe-wall. The compressive forces are often so large that they induce vertical buckling of buried pipelines, which can jeopardize the structural integrity of the pipeline. A typical initial imperfection named continuous support mode of submarine pipeline was studied. Based on this type of initial imperfection, the analytical solution of vertical thermal buckling was introduced and an elastic-plasticity finite element analysis (FEA) was developed. Both the analytical and the finite element methodology were applied to analyze a practice in Bohai Gulf, China. The analyzing results show that upheaval buckling is most likely to build up from the initial imperfection of the pipeline and the buckling temperature depends on the amplitude of initial imperfection. With the same amplitude of initial imperfection, the triggering temperature difference of upheaval buckling increases with covered depth of the pipeline, the soil strength and the friction between the pipeline and subsoil.

Vacuum preloading combined electroosmotic strengthening of ultra-soft soil

Abstract: To assess the effectiveness of vacuum preloading combined electroosmotic strengthening of ultra-soft soil and study the mechanism of the process, a comprehensive experimental investigation was performed. A laboratory test cell was designed and applied to evaluate the vacuum preloading combined electroosmosis. Several factors were taken into consideration, including the directions of the electroosmotic current and water induced by vacuum preloading and the replenishment of groundwater from the surrounding area. The results indicate that electroosmosis together with vacuum preloading improve the soil strength greatly, with an increase of approximately 60%, and reduce the water content of the soil on the basis of consolidation of vacuum preloading, however, further settlement is not obvious with only 1.7 mm. The reinforcement effect of vacuum preloading combined electroosmosis is better than that of electroosmosis after vacuum preloading. Elemental analysis using X-ray fluorescence proves that the soil strengthening during electroosmotic period in this work is mainly caused by electroosmosis-induced electrochemical reactions, the concentrations of Al2O3 in the VPCEO region increase by 2.2%, 1.5%, and 0.9% at the anode, the midpoint between the electrodes, and the cathode, respectively.

Degradation of aniline by Fe2+-activated persulfate oxidation at ambient temperature

Abstract: The aniline degradation by persulfate activated with ferrous ion (Fe2+) was investigated in batch reactor at ambient temperature. The experimental factors in aqueous solutions including persulfate concentration, Fe2+ concentration, pH and ionic strength level were discussed. It is demonstrated that, aniline degradation rate increases with increasing persulfate concentration, but much more ferrous ion inhibits the aniline degradation. When the aniline concentration is 0.10 mmol/L, the maximum aniline degradation occurs at the S2O8 2− to Fe2+ molar ratio of 250/5 at pH 7.0. In the pH range of 5.0–8.5, increasing pH causes higher aniline degradation. What’s more, the increase of ionic strength in solution causes inhibiting in the reaction. Produced intermediates during the oxidation process were identified using gas chromatography-mass spectrometry (GC-MS) technology. And degradation pathways of aniline were also tentatively proposed.

Applicability of small resistance fastener on long-span continuous bridges of high-speed railway

Abstract: Ballastless tracks have been widely applied in high-speed railway (HSR) The adaptability research between continuous welded rails (CWR) and long-span bridges of HSR is of great practical engineering significance Based on the HSR long-span continuous bridges, the integrative spatial finite element model of track-bridge-pier-foundation system was established with the nonlinear spring element simulating the longitudinal resistance between track and bridge Comparative study on the various additional longitudinal forces of CWR using the common fasteners and small resistance fasteners was carried out Analysis results indicate that the additional expansion forces and additional rail-breaking forces in long-span ballastless continuous girders can be reduced evidently by 40%–50% after adopting small resistance fasteners, but lead to greater rail broken gap The small resistance fasteners have little influence on the additional force only caused by vertical load, but can reduce the additional force caused by vertical load combined with braking load by over 10% Besides, transient analysis method is proved to be more accurate and safe in calculating additional longitudinal forces when the train running or braking on the bridge, compared with the traditional static method

Pressure-impulse diagram with multiple failure modes of one-way reinforced concrete slab under blast loading using SDOF method

Abstract: Two loosely coupled single degree of freedom (SDOF) systems were used to model the flexural and direct shear responses of one-way reinforced concrete slabs subjected to explosive loading. Blast test results show that the SDOF systems are accurate in predicting the failure mode of the slab under blast loads by incorporating the effects of the strain rate effect caused by rapid load application. Based on different damage criteria, pressure-impulse (P-I) diagrams of the two failure modes were analyzed with the SDOF systems. The effects of span length, concrete strength, and reinforcement ratio of the slab on the P-I diagram were also investigated. Results indicate that a slab tends to fail in direct shear mode when it is of a smaller span length and tends to fail in flexure mode when it is of a larger span length. With the increase of the concrete strength or reinforced ratio, both the flexure and shear capacity increase. Based on numerical results, a simplified method and a semi analytical equation for deriving the P-I diagram are proposed for different failure modes and damage levels.

Multidisciplinary design optimization on production scale of underground metal mine

Abstract: In order to ensure overall optimization of the underground metal mine production scale, multidisciplinary design optimization model of production scale which covers the subsystem objective function of income of production, safety and environmental impact in the underground metal mine was established by using multidisciplinary design optimization method. The coupling effects from various disciplines were fully considered, and adaptive mutative scale chaos immunization optimization algorithm was adopted to solve multidisciplinary design optimization model of underground metal mine production scale. Practical results show that multidisciplinary design optimization on production scale of an underground lead and zinc mine reflect the actual operating conditions more realistically, the production scale is about 1.25 Mt/a (Lead and zinc metal content of 160 000 t/a), the economic life is approximately 14 a, corresponding coefficient of production profits can be increased to 15.13%, safety factor can be increased to 5.4% and environmental impact coefficient can be reduced by 9.52%.

Effect of static transmission error on dynamic responses of spiral bevel gears

Abstract: The effect of static transmission error on nonlinear dynamic response of the spiral bevel gear system combining with time-varying stiffness and backlash was investigated. Firstly, two different control equations of the spiral bevel gear model were adopted, where the static transmission error was expressed in two patterns as predesigned parabolic function and sine function of transmission errors. The dynamic response, bifurcation map, time domain response, phase curve and Poincare map were obtained by applying the explicit Runge-Kutta integration routine with variable-step. A comparative study was carried out and some profound phenomena were detected. The results show that there are many different kinds of tooth rattling phenomena at low speed. With the increase of speed, the system enters into stable motion without any rattling in the region (0.72, 1.64), which indicates that the system with predesigned parabolic function of transmission error has preferable capability at high speed.