A new method called mixed Lagrangian and Eulerian method (MiLE method) was used to simulate the thermomechanical behavior during continuous casting process of steel YF45MnV. The simulation results are basically in agreement with the measured data. The delaying period at the beginning of solidification is about 0.1 in square root of solidification time which is agreement with the data in literatures, and shell thickness increases in linear relation to square root of solidification time. The bloom surface temperature decreases gradually as the casting proceeds. The effective stress in the corner is much larger than that in the mid-face. The corner area is the dangerous zone of cracking. The effects of mold flux break temperature on the air gap and hot tearing indicator were also modeled. The model predicts that the bloom surface temperature increases with the increase of the mold flux break temperature, but the heat flux decreases with the increase of the mold flux break temperature. The hot tearing indicator is much smaller when the mold flux break temperature is higher.

The solid state interdiffusion between NiFe₂O₄ and NiO in nitrogen atmosphere was studied by means of diffusion couple technique. NiFe₂O₄/NiO diffusion couple with plane interfaces was made by clamping method and sintering at 1 300 °C for 10 h. Scanning electronic microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS) were used to analyze the microstructure and phase composition of the diffusion couples. The results indicate that a porous layer of uniform thickness forms along the NiFe₂O₄/NiO bonding interface and exhibits a deep penetration in the NiFe₂O₄ due to the Kirkendall effect. Furthermore, SEM observations reveal that the needle-like nickel ferrite precipitates form in NiO near the interface and the formation mechanism of them are inferred to be diffusion type solid-state phase changes.

The contents of Mg, Al, Si, Ti, Cr, Mn, Fe, Co, Cu, Ga, As, Se, Cd, Sb, Pb and Bi in high purity nickel were determined by high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). The sample was dissolved in HNO₃ and HCl by microwave digestion. Most of the spectral interferences could be avoided by measuring in the high resolution mode. The matrix effects because of the presence of excess HCl and nickel were evaluated. Correction for matrix effects was made using Sc, Rh and Tl as internal standards. The optimum conditions for the determination were tested and discussed. The detection limits range from 0.012 to 1.76 μg/g depending on the type of elements. The applicability of the proposed method is also validated by the analysis of high purity nickel reference material (NIST SRM 671). The relative standard deviation (RSD) is less than 3.3%. Results for determination of trace elements in high purity nickel were presented.

In order to reduce the oxidizing and volatilizing caused by Mg element in the traditional methods for synthesizing Mg₂Si_1−xSn_x (x=0.2, 0.4, 0.6, 0.8) solid solutions, microwave irradiation techniques were used in preparing them as thermoelectric materials. Structure and phase composition of the obtained materials were investigated by X-ray diffraction (XRD). The electrical conductivity, Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 750 K. It is found that Mg₂Si_1−xSn_x solid solutions are well formed with excessive content of 5% (molar fraction) Mg from the stoichiometric Mg₂Si_1−xSn_x under microwave irradiation. A maximum dimensionless figure of merit, ZT, of about 0.26 is obtained for Mg₂Si_1−xSn_x solid solutions at about 500 K for x=0.6.

The photo absorbing, photo transmitting and photoluminescence performances of TiO₂ photocatalysts compounded with V₂O₅ or WO₃ were investigated by UV-Vis spectra, transmitting spectra, and PL spectra, respectively. The energy band structures of TiO₂ photocatalysts were analyzed. The photocatalytic activities of the TiO₂ photocatalysts were investigated by splitting of water for O₂ evolution. The results indicate that the band gaps of WO₃ and V₂O₅ are about 2.8 and 2.14 eV, respectively, and the band gap of rutile TiO₂ is about 3.08 eV. Speeds of water splitting for 2%WO₃-TiO₂ and 8%V₂O₅-TiO₂ photocatalysts are 420 and 110 μmol/(L·h), respectively, under UV light irradiation. V₂O₅ and WO₃ compounded with suitable concentration can improve the photocatalytic activity of TiO₂ with Fe³⁺ as electron acceptor.

To develop an effective process for titanium powders production, a calciothermic reduction process of pigment titanium dioxide (w(TiO₂)>98%), based on the preform reduction process (PRP), was investigated by means of XRD, SEM and EDS. In this process, the mixture of TiO₂ powder and CaCl₂ was pressed into pieces as feed preform and was reduced by calcium vapor. Titanium powders was recovered after leaching from the reduced preform with hydrochloric acid and deionized water. The results indicate when the mass ratio of CaCl₂ to TiO₂ is about 1:4 and at a constant temperature of 1 273 K for 6 h in vacuum furnace, titanium powders with 99.55% purity by EDS analysis and irregular shape (8–15 μm in particle size) are obtained.

A thermodynamics analysis on the leaching process of selenium residue and discussion on the behaviors of aqueous ionic in the leaching process were carried out. Through thermodynamical calculation, the values of ΔG_T^Θ and relevant potential expressions were obtained. According to these thermodynamical data, the φ-pH diagrams of Se-H₂O system at 298 and 373 K were obtained; Simultaneously, the φ-pH diagrams of SO₂-H₂O and SO₂-Se-H₂O systems were drawn at 298 K. With increasing the temperature, the stable regions of HSeO₃⁻, SeO₃²⁻ and SeO₄²⁻ in the φ-pH diagram of Se-H₂O system become gradually large, but the limits of pH in the stable region become gradually small. The stability area of reduction precipitation in the SO₂-Se-H₂O system was finally determined. The results of oxidization leaching experiments of selenium residue indicate that when the mass ratio of selenium residue to sodium chlorate is 2, the concentration of sulfuric acid is 300 g/L and the residue is agitated for 3 h at leaching temperature of 80 °C, the leaching rate of selenium could reach 97.76 %. The experimental results conform the calculated results by φ-pH diagram. The selenium reduction precipitation in oxidization-leaching solution was analyzed under the conditions of acidity of 150 g/L, the sodium sulphite concentration of 35 g/L at the reductive temperature of 23 °C for 120 min. And this demonstrates the thermodynamics analysis.

Using Schiff base as a phase transfer catalyst, ethoxycarbonyl isothiocyanate was synthesized by reacting ethyl chloroformate with sodium thiocyanate. In order to get the best synthetic technology, an orthogonal test (L₉(3⁴)) was applied. The results show that reaction temperature, reaction time, content of catalyst and molar ratio of sodium thiocyanate to ethyl chloroformate are the main factors influencing the yield. The four factors chosen for the present investigation are based on the results of a single-factor test. The optimum synthetic technology is determined as follows: reaction temperature 35 °C, reaction time 3 h, the content of catalyst (molar fraction based on ethyl chloroformate) 1.5% and molar ratio of sodium thiocyanate to ethyl chloroformate 1.1. Under the optimized synthetic technology, the experimental yield reaches 96.8%.

The stability of ionic liquid additive 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO₄) during zinc electrowinning from acidic sulfate solution was investigated by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. Compared with the traditional industrial additives, gelatine and gum arabic, [BMIM]HSO₄ has more excellent chemical and thermal stabilities. The inhibition effects of gelatine and gum arabic on the zinc electrocrystallization are observed to markedly weaken due to their part degradation after 12 h longtime successive electrolysis and high temperature (90 °C) treatments. In contrast, the activity of [BMIM]HSO₄ is practically unaffected after 24 h longtime successive electrolysis and high temperature treatments. These results are corroborated with the corresponding morphological analysis of the cathodic deposits.

Good understanding of relationship between parameters of vehicle, terrain and interaction at the interface is required to develop effective navigation and motion control algorithms for autonomous wheeled mobile robots (AWMR) in rough terrain. A model and analysis of relationship among wheel slippage (S), rotation angle (θ), sinkage (z) and wheel radius (r) are presented. It is found that wheel rotation angle, sinkage and radius have some influence on wheel slippage. A multi-objective optimization problem with slippage as utility function was formulated and solved in MATLAB. The results reveal the optimal values of wheel-terrain parameters required to achieve optimum slippage on dry sandy terrain. A method of slippage estimation for a five-wheeled mobile robot was presented through comparing the odometric measurements of the powered wheels with those of the fifth non-powered wheel. The experimental result shows that this method is feasible and can be used for online slippage estimation in a sandy terrain.

Before the task of autonomous underwater vehicle (AUV) was implemented actually, its semi-physical simulation system of pipeline tracking had been designed. This semi-physical simulation system was used to test the software logic, hardware architecture, data interface and reliability of the control system. To implement this system, the whole system plan, including interface computer and the methods of pipeline tracking, was described. Compared to numerical simulation, the semi-physical simulation was used to test the real software and hardware more veritably. In the semi-physical simulation system, tracking experiments of both straight lines and polygonal lines were carried out, considering the influence of ocean current and the situation of buried pipeline. The experimental results indicate that the AUV can do pipeline tracking task, when angles of pipeline are 15°, 30°, 45° and 60°. In the ocean current of 2 knots, AUV could track buried pipeline.

Straightening machine is widely used for improving the quality of the defective mild steel plates. In general, the capacity of straightening machine is affected by material properties, the initial shape of the incoming plate and the plastic ratio. The mechanics model describing the capacity of the machine was developed. The deviation of the straightening capacity curves was studied. Then, the presented model was evaluated by comparative study to filed production data. Finally, the influences of overstretch, straightening speed, strengthening coefficient, elastic modulus, width of the plate on the straightening capacity were studied. It is convenient to determine whether the plate can be straightened or not by a series of straightening capacity curves. The straightening speed, width of the plate and elastic modulus of the material are more sensitive to the straightening capacity than the strengthening coefficient.

A novel 6-PSS flexible parallel mechanism was presented, which employed wide-range flexure hinges as passive joints. The proposed mechanism features micron level positioning accuracy over cubic centimeter scale workspace. A three-layer back-propagation (BP) neural network was utilized to the kinematics analysis, in which learning samples containing 1 280 groups of data based on stiffness-matrix method were used to train the BP model. The kinematics performance was accurately calculated by using the constructed BP model with 19 hidden nodes. Compared with the stiffness model, the simulation and numerical results validate that BP model can achieve millisecond level computation time and micron level calculation accuracy. The concept and approach outlined can be extended to a variety of applications.

The robust control problem for a class of underactuated mechanical systems called acrobots is addressed. The goal is to drive the acrobots away from the straight-down position and balance them at the straight-up unstable equilibrium position in the presence of parametric uncertainties and external disturbance. First, in the swing-up area, it is shown that the time derivative of energy is independent of the parameter uncertainties, but exogenous disturbance may destroy the characteristic of increase in mechanical energy. So, a swing-up controller with compensator is designed to suppress the influence of the disturbance. Then, in the attractive area, the control problem is formulated into a H_∞ control framework by introducing a proper error signal, and a sufficient condition of the existence of H_∞ state feedback control law based on linear matrix inequality (LMI) is proposed to guarantee the quadratic stability of the control system. Finally, the simulation results show that the proposed control approach can simultaneously handle a maximum ±10% parameter perturbation and a big disturbance simultaneously.

The theoretical study of a semi-active predictive control (SAPC) system with magnetorheological (MR) dampers to reduce the responses of seismically excited structures was presented. The SAPC scheme is based on a prediction model of the system response to obtain the control actions by minimizing an object function, which has a function of self-compensation for time delay occurring in real application. A double-ended shear mode combined with a valve mode MR damper, named MRF-04K damper, with the maximum force of 20 kN was designed and manufactured, and parameters of the Bouc-Wen hysteresis model were determined to portray the behavior of this damper. As an example, a 5-story building frame equipped with 2 MRF-04K dampers was presented to demonstrate the performance of the proposed SAPC scheme for addressing time delay and reducing the structural responses under different earthquakes. Comparison with the uncontrolled structure, the passive-off and passive-on cases indicates that both the peak and the norm values of structural responses are all clearly reduced, and the SAPC scheme has a better performance than the two passive cases.

A finite element model for the supercavitating underwater vehicle was developed by employing 16-node shell elements of relative degrees of freedom. The nonlinear structural dynamic response was performed by introducing the updated Lagrangian formulation. The numerical results indicate that there exists a critical thickness for the supercavitating plain shell for the considered velocity of the vehicle. The structure fails more easily because of instability with the thickness less than the critical value, while the structure maintains dynamic stability with the thickness greater than the critical value. As the velocity of the vehicle increases, the critical thickness for the plain shell increases accordingly. For the considered structural configuration, the critical thicknesses of plain shells are 5 and 7 mm for the velocities of 300 and 400 m/s, respectively. The structural stability is enhanced by using the stiffened configuration. With the shell configuration of nine ring stiffeners, the maximal displacement and von Mises stress of the supercavitating structure decrease by 25% and 17% for the velocity of 300 m/s, respectively. Compared with ring stiffeners, longitudinal stiffeners are more significant to improve structural dynamic performance and decrease the critical value of thickness of the shell for the supercavitating vehicle.

A novel discrete-time reaching law was proposed for uncertain discrete-time system, which contained process noise and measurement noise. The proposed method reserves all the advantages of discrete-time reaching law, which not only decreases the band width of sliding mode and strengthens the system robustness, but also improves the dynamic performance and stability capability of the system. Moreover, a discrete-time sliding mode control strategy based on Kalman filter method was designed, and Kalman filter was employed to eliminate the influence of system noise. Simulation results show that there is no chattering phenomenon in the output of controller and the state variables of controlled system, and the proposed algorithm is also feasible and has strong robustness to external disturbances.

The traditional prediction methods of element yield rate can be divided into experience method and data-driven method. But in practice, the experience formulae are found to work only under some specific conditions, and the sample data that are used to establish data-driven models are always insufficient. Aiming at this problem, a combined method of genetic algorithm (GA) and adaptive neuro-fuzzy inference system (ANFIS) is proposed and applied to element yield rate prediction in ladle furnace (LF). In order to get rid of the over reliance upon data in data-driven method and act as a supplement of inadequate samples, smelting experience is integrated into prediction model as fuzzy empirical rules by using the improved ANFIS method. For facilitating the combination of fuzzy rules, feature construction method based on GA is used to reduce input dimension, and the selection operation in GA is improved to speed up the convergence rate and to avoid trapping into local optima. The experimental and practical testing results show that the proposed method is more accurate than other prediction methods.

A high-speed corner detection algorithm based on fuzzy ID3 decision tree was proposed. In the algorithm, the Bresenham circle with 3-pixel radius was used as the test mask, overlapping the candidate corners with the nucleus. Connected pixels on the circle were applied to compare the intensity value with the nucleus, with the membership function used to give the fuzzy result. The pixel with maximum information gain was chosen as the parent node to build a binary decision tree. Thus, the corner detector was derived. The pictures taken in Fengtai Railway Station in Beijing were used to test the method. The experimental results show that when the number of pixels on the test mask is chosen to be 9, best result can be obtained. The corner detector significantly outperforms existing detector in computational efficiency without sacrificing the quality and the method also provides high performance against Poisson noise and Gaussian blur.

In order to form an algorithm for distribution network routing, an automatic routing method of distribution network planning was proposed based on the shortest path. The problem of automatic routing was divided into two steps in the method: the first step was that the shortest paths along streets between substation and load points were found by the basic ant colony algorithm to form a preliminary radial distribution network, and the second step was that the result of the shortest path was used to initialize pheromone concentration and pheromone updating rules to generate globally optimal distribution network. Cases studies show that the proposed method is effective and can meet the planning requirements. It is verified that the proposed method has better solution and utility than planning method based on the ant colony algorithm.

In order to improve image quality, a novel Retinex algorithm for image enhancement was presented. Different from conventional algorithms, it was based on certain defined points containing the illumination information in the intensity image to estimate the illumination. After locating the points, the whole illumination image was computed by an interpolation technique. When attempting to recover the reflectance image, an adaptive method which can be considered as an optimization problem was employed to suppress noise in dark environments and keep details in other areas. For color images, it was taken in the band of each channel separately. Experimental results demonstrate that the proposed algorithm is superior to the traditional Retinex algorithms in image entropy.

An improved speech absence probability estimation was proposed using environmental noise classification for speech enhancement. A relevant noise estimation approach, known as the speech presence uncertainty tracking method, requires seeking the “a priori” probability of speech absence that is derived by applying microphone input signal and the noise signal based on the estimated value of the “a posteriori” signal-to-noise ratio (SNR). To overcome this problem, first, the optimal values in terms of the perceived speech quality of a variety of noise types are derived. Second, the estimated optimal values are assigned according to the determined noise type which is classified by a real-time noise classification algorithm based on the Gaussian mixture model (GMM). The proposed algorithm estimates the speech absence probability using a noise classification algorithm which is based on GMM to apply the optimal parameter of each noise type, unlike the conventional approach which uses a fixed threshold and smoothing parameter. The performance of the proposed method was evaluated by objective tests, such as the perceptual evaluation of speech quality (PESQ) and composite measure. Performance was then evaluated by a subjective test, namely, mean opinion scores (MOS) under various noise environments. The proposed method show better results than existing methods.

By combing the properties of chaos optimization method and genetic algorithm, an adaptive mutative scale chaos genetic algorithm (AMSCGA) was proposed by using one-dimensional iterative chaotic self-map with infinite collapses within the finite region of [−1, 1]. Some measures in the optimization algorithm, such as adjusting the searching space of optimized variables continuously by using adaptive mutative scale method and making the most circle time as its control guideline, were taken to ensure its speediness and veracity in seeking the optimization process. The calculation examples about three testing functions reveal that AMSCGA has both high searching speed and high precision. Furthermore, the average truncated generations, the distribution entropy of truncated generations and the ratio of average inertia generations were used to evaluate the optimization efficiency of AMSCGA quantificationally. It is shown that the optimization efficiency of AMSCGA is higher than that of genetic algorithm.

Let p(s, δ) be a sphere plant family described by the transfer function set where the coefficients of the denominator and numerator polynomials are affine in a real uncertain parameter vector δ satisfying the euclidean norm constraint ‖δ‖<δ. The concept of stabilizability radius of P(s, δ) is introduced which is the norm bound δ_s for δ such that every member plant of P(s, δ) is stabilizable if and only if ‖δ‖<δ_s. The stabilizability radius can be simply interpreted as the ‘largest sphere’ around the nominal plant P(s, 0) such that P(s, δ) is stabilizable. The numerical method and the analytical method are presented to solve the stabilizability radius calculation problem of the sphere plants.

A water balance has a significant impact on the overall system performance in proton exchange membrane fuel cell. An actual fuel cell application has a dynamic electrical load which means also dynamic electrical current. Therefore, since this electrical current is known, the water production from the fuel cell reaction is also able to be predicted. As long as the fuel cell water transportation model is provided, the present liquid water inside the porous medium is also able to be modeled. A model of the liquid water saturation level in a fuel cell in unsteady load condition was proposed. This model is a series of the water transportation model of water saturation level for the final output of proton exchange membrane (PEM) fuel cell to predict the flooding or drying of PEM fuel cell. The simulation of vehicle fuel cell in different dynamic load profiles and different inlet air conditions was done using this model. The simulation result shows that PEM fuel cell with different dynamic load profiles has different liquid water saturation level profiles. This means that a dynamic load fuel cell requires also a dynamic input air humidification.

The pressure characteristics inside single loop oscillating heat pipe (OHP) having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed. Distilled water was used as working fluid inside the OHP with different filling ratios of 40%, 60% and 80% of total inside volume. Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency. And the pressure frequency also depends upon the evaporator temperature that is maintained in the range of 60–96 °C. Piezoresistive absolute pressure sensor (Model-Kistler 4045A5) was used to take data. The investigation shows that the filling ratio of 60% gives the highest inside pressure magnitude at maximum number of pressure frequency at any of set evaporator temperature and the lowest heat flow resistance is achieved at 60% filling ratio.

Taking the ratio of heat transfer area to net power and heat recovery efficiency into account, a multi-objective mathematical model was developed for organic Rankine cycle (ORC). Working fluids considered were R123, R134a, R141b, R227ea and R245fa. Under the given conditions, the parameters including evaporating and condensing pressures, working fluid and cooling water velocities were optimized by simulated annealing algorithm. The results show that the optimal evaporating pressure increases with the heat source temperature increasing. Compared with other working fluids, R123 is the best choice for the temperature range of 100–180 °C and R141b shows better performance when the temperature is higher than 180 °C. Economic characteristic of system decreases rapidly with the decrease of heat source temperature. ORC system is uneconomical for the heat source temperature lower than 100 °C.

By establishing the numerical model in the vertical plane and the similar model in the horizontal plane of gas flow in goaf, the influence of high drainage roadway or drilling on the gas seepage field was analyzed, and the extraction mechanism was clarified. On this basis, the academic thought of directional long drilling group instead of high drainage roadway was put forward. And then using complex function theory, the permeation mechanical model of drilling group with circle distribution in the mining-induced fracture zone was established to explore the coupling relationship between the drilling quantity, extraction volume and the equivalent extraction rate of single drilling. Finally, combined with the concrete geological production conditions, the main parameters of directional long drilling group were determined. The distance between the drilling group center and the air-return roadway is 24 m, the height is 18 m, and the three drillings are in an approximate equilateral triangle distribution with a space of 8 m. The equivalent extraction square is 4.15 m². It is shown that the effect of directional long drilling group is evident. The gas content in the upper corner is controlled below 0.95%, the content in the tail roadway is kept below the alarm value, and the content is over 50% in the drill, realizing the secure and effective extraction of coal and gas.

The circle geometric constraint model (CGCM) was put forward for resolving the open-pit mine ore-matching problems (OMOMP). By adopting the approaches of graph theory, block model of blasted piles was abstracted into a set of nodes and directed edges, which were connected together with other nodes in the range of circle constraints, to describe the mining sequence. Also, the constructing method of CGCM was introduced in detail. The algorithm of CGCM has been realized in the DIMINE system, and applied to a short-term (5 d) program calculation for ore-matching of a cement limestone mine in Hebei Province, China. The applications show that CGCM can well describe the mining sequence of ore blocks and its mining geometric constraints in the process of mining blasted piles. This model, which is applicable for resolving OMOMP under complicated geometric constraints with accurate results, provides effective ways to solve the problems of open-pit ore-matching.

Microseismic effects during the transmission of seismic waves in coal and rock mass associated with mining operation were studied by on-site blasting tests and microseismic monitoring in LW704 of Southern Colliery, Australia, by using spread velocities, amplitudes and frequency contents as the main analysis parameters. The results show that the average P-wave velocity, mean values of combined maximal amplitudes and frequencies of the first arrivals are all reduced significantly along with goaf expanding and intensity weakening of overlying strata during mining process. A full roof fracturing can make the average P-wave velocities, combined maximal amplitudes and frequencies of first arrivals reduce to about 69.8%, 92.2% and 60.0%, respectively. The reduction of the above seismic parameters reveals dynamic effects of the variation of strata structure and property to the wave transmission and energy dissipation of blasting wave. The research greatly benefits further study on stability of surrounding rock under the destructive effort by mine tremor, blasting, etc, and provides experimental basis for source relocation and parameter optimization of seismic monitoring as well.

The mechanism of high pressure roll grinding on improvement of compression strength of oxidized hematite pellets was researched by considering their roasting properties. The results indicate that oxidized hematite pellets require higher preheating temperature and longer preheating time to attain required compression strength of pellets compared with the common magnetite oxidized pellets. It is found that when the hematite concentrates are pretreated by high pressure roll grinding (HPRG), the compression strengths of preheated and roasted oxidized hematite pellets get improved even with lower preheating and roasting temperatures and shorter preheating and roasting time. The mechanism for HPRG to improve roasting properties of oxidized pellets were investigated and the cause mainly lies in the increase of micro-sized particles and the decrease of dispersion degree for hematite concentrates, which promotes the hematite concentrate particles to be compacted, the solid-phase crystallization, and finally the formation of Fe₂O₃ bonding bridges during subsequent high temperature roasting process.

The chemical fractions, i.e., water soluble (WS), exchangeable (Ex), carbonate (Car), weakly organic (WO), Fe-Mn oxide (FMO), strongly organic (SO), residual (Res) fraction, of Pb in irrigated soils in South China were investigated by a modified Tessier sequential extraction technique. The results show that the chemical fraction of Pb in soil is mainly the Res fraction and followed by FMO fraction, and the WS, WO, FMO, and SO fractions in topsoils (0–10 cm) are higher than those in subsoils (30–40 cm). The sum of contents of WS and Ex fractions (S_WE) in topsoils is significantly positively related with that in subsoils, indicating the strong mobility of Pb in WS and Ex fractions in soils, and the S_WE in soils is higher than the German trigger value for the transfer path soil-plant, indicating the high bioavailability of Pb in soils of this area. Fortunately, S_WE and the ratio of WS and Ex fractions (R_WE) to the sum of all fractions generally decrease with the soil depth in soil profile and the R_WE in soil profile is lower than 0.5%, indicating the low pollution risk for Pb in groundwater. In addition, soil particles, pH and Fe₂O₃ play an important role in the impact of mobility and chemical fractions of Pb in soils.

The types, composition and physico-chemical conditions of primary fluid inclusions were researched. The results show that the primary fluid inclusions contain vapor and liquid phase type (Type I), daughter mineral-bearing type (Type II) and pure liquid phase type (Type III). The compositions of vapor are mainly H₂O and CO₂ with a tiny amounts of CH₄ and H₂; the liquid phase mainly contains Mg²⁺, Ca²⁺, Na⁺, K⁺, Cl⁻ and SO₄²⁻, and w(Na⁺)/w(K⁺)>1; the homogenization temperatures of the primary fluid inclusions can be divided into 190–250 °C, 250–340 °C and 360–420 °C, corresponding to the salinities of 4%–9%, 9%–14%, and 14%–20.43% (NaCl equivalent mass fraction), respectively. The mineralization process can be divided into three episodes: the silicatization stage, the quartz-sulfide stage, and the carbonatization stage, and all of them are associated with the ore-forming hydrothermal fluid activity. The origin of the hydrothermal fluid is from magmatic water mainly, and later it mixes with the groundwater and meteoric water, which lead to the decrease of temperature and salinity. The decrease of salinity, temperature and pressure are the main causes of the metallogenic elements unloading and enriching in the favorable position.

Samples were collected from two core sediments (C1 and C2) of Xiangjiang River, Chang-Zhu-Tan region, Hunan Province, China. The heavy metal contents are relatively higher, especially for the surface or near the surface layers. The calculated anthropogenic factor values indicate that all the heavy metals except for Cr in the core samples are enriched, especially for Cd, with the maximum enriching coefficients of 119.44, and 84.67 in C1 and C2, respectively. The correlation of heavy metals with sulphur indicates that they are precipitated as metal sulphides. Correlation matrix shows significant association between heavy metals and mud. Factor analysis identifies that signified anthropogenic activities affect the region of Xiangjiang River.

Simulations of undrained tests were performed in a periodic cell using three dimensional (3D) discrete element method (DEM) program TRUBAL. The effective undrained stress paths are shown to be qualitatively similar to published physical experimental results of cohesionless media such as sand. Liquefaction and temporary liquefaction are observed for very loose samples and medium loose samples, respectively. A new micromechanical parameter is proposed to identify whether liquefaction or temporary liquefaction occurs in terms of a redundancy factor. The relationship of redundancy factor and average coordination number is derived theoretically. It is demonstrated that the phase transition dividing the solid-like behaviour and liquid-like behaviour is associated with a redundancy factor of 1, which corresponds to an average coordination number slightly above 4.

Considering three longitudinal displacement functions and uniform axial displacement functions for shear lag effect and uniform axial deformation of thin-walled box girder with varying depths, a simple and efficient method with high precision to analyze the shear lag effect of thin-walled box girders was proposed. The governing differential equations and boundary conditions of the box girder under lateral loading were derived based on the energy-variational method, and closed-form solutions to stress and deflection corresponding to lateral loading were obtained. Analysis and calculations were carried out with respect to a trapezoidal box girder under concentrated loading or uniform loading and a rectangular box girder under concentrated loading. The analytical results were compared with numerical solutions derived according to the high order finite strip element method and the experimental results. The investigation shows that the closed-form solution is in good agreement with the numerical solutions derived according to the high order finite strip method and the experimental results, and has good stability. Because of the shear lag effect, the stress in cross-section centroid is no longer zero, thus it is not reasonable enough to assume that the strain in cross-section centroid is zero without considering uniform axial deformation.

A new approach is proposed to analyze the settlement behavior for single pile embedded in layered soils. Firstly, soil layers surrounding pile shaft are simulated by using distributed Voigt model, and finite soil layers under the pile end are assumed to be virtual soil-pile whose cross-section area is the same as that of the pile shaft. Then, by means of Laplace transform and impedance function transfer method to solve the static equilibrium equation of pile, the analytical solution of the displacement impedance function at the pile head is derived. Furthermore, the analytical solution of the settlement at the head of single pile is theoretically derived by virtue of convolution theorem. Based on these solutions, the influences of parameters of soil-pile system on the settlement behavior for single pile are analyzed. Also, comparison of the load-settlement response for two well-instrumented field tests in multilayered soils is given to demonstrate the effectiveness and accuracy of the proposed approach. It can be noted that the presented solution can be used to calculate the settlement of single pile for the preliminary design of pile foundation.

In order to establish a rapid method for regional slope stability analysis under rainfall, matric suction and seepage force were taken into account after obtaining explicit solution of infiltration depth. Moreover, simplified analysis model under 3D condition was put forward based on identification and division of slope units, as well as modification of sliding direction of each column. The result shows that explicit solution of infiltration depth is of good precision; for the given model, safety factors without taking seepage force into account are 1.82–2.94 times higher; the stagnation point of slope angle is located approximately in the range of (45°, 50°); the safety factor changes insignificantly when wetting front is deeper than 2 m; when matric suction changes in the specified range, the maximum variations of safety factor are less than 0.5, which proves that matric suction plays an insignificant role in maintaining slope stability compared to the slope angle and infiltration depth. Incorporated with geographic information system, a practical application of regional slope stability assessment verifies the applicability of the proposed method.

Blast vibration analysis is one of the important foundations for studying the control technology of blast vibration damage. According to blast vibration live data that have been collected and the characteristics of short-time non-stationary random signals, the wavelet packet energy spectrum analysis for blast vibration signal has made by wavelet packet analysis technology and the signals were measured under different explosion parameters (the maximal section dose, the distance of blast source to measuring point and the section number of millisecond detonator). The results show that more than 95% frequency band energy of the signals s1–s8 concentrates at 0–200 Hz and the main vibration frequency bands of the signals s1–s8 are 70.313–125, 46.875–93.75, 15.625–93.75, 0–62.5, 42.969–125, 15.625–82.031, 7.813–62.5 and 0–62.5 Hz. Energy distributions for different frequency bands of blast vibration signal are obtained and the characteristics of energy distributions for blast vibration signal measured under different explosion parameters are analyzed. From blast vibration signal energy, the decreasing law of blast seismic waves measured under different explosion parameters was studied and the wavelet packet analysis is an effective means for studying seismic effect induced by blast.

The initiation and evolution of short-pitch corrugation in Beijing metro line 4 was studied from the viewpoint of wheelset vibration. A three-dimensional elastic model was set up. Numerical simulations were undertaken with this model to analyze the corrugation by the wheelset vertical vibration and torsional vibration. Based on numerical results, the relation between rail corrugation and wheelset vibration, and the relation between the position of electromotor and wheelset vibration were indicated. It is found that avoiding the wheelset-rail resonance is one method of controlling the rail short-pitch corrugation and solving the vibration and noise problem in metro lines.

A new cascade control program was proposed based on modified internal model control to handle stable, unstable and integrating processes with time delay. The program had totally four controllers of which the secondary loop had two controllers and the primary loop had two controllers. The two secondary loop controllers were designed using IMC technique. They were decoupled completely and could be adjusted independently, which avoided the undesirable influence on performance of the primary controllers. The main controller in the primary loop was devised as a PID using the method of minimum sensitivity, which could guarantee not only the nominal performance but also the robust stability of the system. A setpoint filter was added in the primary loop to improve the tracking performance. All the controllers of the two closed-loops were designed analytically, and could be adjusted and optimized by single parameter respectively. Simulations were carried out on three various processes with time delay, and the results show that the proposed method can provide a better performance of both set-point tracking and disturbance rejection and robustness against parameters perturbation.

To determine how bus stop design influences mixed traffic operation near Chinese bus stops, a new theoretical method was developed by using additive-conflict-flows procedure. The procedure was extended from homogeneous traffic flow to mixed traffic flow. Based on the procedure and queuing theory, car capacity and speed models were proposed for three types of bus stops including curbside, bus bay and bicycle detour. The effects of various combinations of bus stop type, traffic volume, bus dwell time, and berth number on traffic operations were investigated. The results indicate that traffic volume, bus dwell time and berth number have negative effects on traffic operations for any type of bus stops. For different types of bus stops, at car volumes above approximately 200 vehicles per hour, the bus bay and bicycle detour designs provide more benefits than the curbside design. As traffic volume increases, the benefit firstly increases in uncongested conditions and then decreases in congested conditions. It reaches the maximum at car volumes nearly 1 100 vehicles per hour. The results can be used to aid in the selection of a preferred bus stop design for a given traffic volume in developing countries.