The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine, and the forming of 6063 rod extrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of 25 on the platform of DEFORM 2D successfully. From the compression experimental results, the flow stress model of this Al alloy is obtained which could be the constitutive equation in the simulation of low-temperature high-speed extrusion process. From the numerical simulation results, there is a higher strain concentration at the entrance of the die and the exit temperature reaches up to 522 °C in low-temperature high-speed extrusion, which approaches to the quenching temperature of the 6063 Al alloy. The results show that the low-temperature high-speed extrusion method as a promsing one can reduce energy consumption effectively.

The electronic structures and elastic properties of Al-doped MoSi₂ were calculated using the plane wave pseudo-potential method based on the density functional theory, in which the generalized-gradient approximation (GGA) was used to describe the exchange-correlation potential. Starting from the elastic constants, bulk modulus, shear modulus, elastic modulus and Poisson ratio of Al-doped MoSi₂ were obtained by using the Hill method. The results indicate that conductivity of Al-doped MoSi₂ is improved to some extent in comparison with that of pure MoSi₂ due to the orbit hybridization of Mo 4d, Al 3p and Si 3p electrons. In addition, calculations show that the elastic modulus and the brittleness of Al-doped MoSi₂ are smaller than those of pure MoSi₂, which implies that it is feasible to toughen MoSi₂ by doping Al. The agreement of the conclusion with experiment shows that the present theory is reasonable.

Carbon spheres with size of 50–300 nm were synthesized via a solvent-thermal reaction with calcium carbide and chloroform as reactants in a sealed autoclave. The morphologies and microstructures of carbon spheres before and after high temperature treatment (HTT) were characterized by X-ray diffractometry (XRD), scanning electronic microscopy (SEM), energy diffraction spectroscopy (EDS), and transmission electron microscopy (TEM). The formation mechanism of carbon spheres was discussed. The results indicate that the carbon spheres convert to hollow polyhedron through HTT. Carbon spheres are composed of entangled and curve graphitic layers with short range order similar to cotton structure, and carbon polyhedron with dimension of 50–250 nm and shell thickness of 15–30 nm. The change of solid spheres to hollow polyhedron with branches gives a new evidence for formation mechanism of hollow carbon spheres.

The distribution and magnitude of surface and subsurface stresses of the single-layer sprayed-coatings on monolithic substrates were investigated by finite element method (FEM). The models of coating configurations with different thicknesses and elastic modulus ratios of coating to substrate were introduced, and the effects of thickness and elastic modulus ratio on the stresses were addressed. The calculation results show that the coating/substrate interface shear stress obviously decreases with increasing coating thickness, due to the location of the maximum shear stress moving away from the coating/substrate interface. At the same time, the magnitude of von Mises stress also declines in the case of thicker coatings. However, the high elastic modulus ratio results in extremely high maximum shear stress and the severe discontinuity of the von Mises stress curves, which leads to the intensive stress concentration on the coating/substrate interface. So the coating configurations with the larger coating thickness and lower difference of elastic modulus between coating and substrate exhibit excellent resistant performance of rolling contact fatigue (RCF).

The cooperative effect of laser surface texturing (LST) and double glow plasma surface alloying on tribological performance of lubricated sliding contacts was investigated. A Nd:YAG laser was used to generate microdimples on steel surfaces. Dimples with the diameter of 150 μm and the depth of 30–35 μm distributed circumferentially on the disc surface. The alloying element Cr was sputtered to the laser texturing steel surface by double glow plasma technique. A deep diffusion layer with a thickness of 30 μm and a high hardness of HV900 was formed in this alloy. Tribological experiments of three types of samples (smooth, texturing and texturing + alloying) were conducted with a ring-on-disc tribometer to simulate the face seal. It is found that, in comparison with smooth steel surfaces, the laser texturing samples significantly reduce the friction coefficient. Moreover, the lower wear rate of the sample treated with the two surface techniques is observed.

Based on the steady-state strain measured by single-pass hot compression tests, the method by a double-pass hot compression testing was developed to measure the metadynamic-recrystallization kinetics. The metadynamic recrystallization behavior of low-alloy steel Q345B during hot compression deformation was investigated in the temperature range of 1 000–1 100 °C, the strain rate range of 0.01–0.10 s⁻¹ and the interpass time range of 0.5–50 s on a Gleeble-3500 thermo-simulation machine. The results show that metadynamic recrystallization during the interpass time can be observed. As the deformation temperature and strain rate increase, softening caused by metadynamic recrystallization is obvious. According to the data of thermo-simulation, the metadynamic recrystallization activation energy is obtained to be Q_md=100.674 kJ/mol and metadynamic recrystallization kinetics model is set up. Finally, the error analysis of metadynamic recrystallization kinetics model proves that the model has high accuracy (correlation coefficient R=0.988 6).

Hydration products and morphology characteristics of C₃A (tricalcium aluminate)-CaCO₃-H₂O system were studied by means of XRD, DSC, FTIR spectrum analysis and SEM. The results indicate that, the new phases, i.e., C₃A·0.5CaCO₃·0.5Ca(OH)₂·11.5H₂O and C₃A·CaCO₃·11H₂O are found in this system due to the activity of CaCO₃; the formation of C₄AH₁₃ and C₂AH₈ is prohibited and the generation of C₃AH₆ is delayed in the early hydration process. C₃A·0.5CaCO₃·0.5Ca(OH)₂·11.5H₂O is not stable and will be totally transferred within 24 h; C₃A·CaCO₃·11H₂O exists stably once formation, and its flake-like crystalline phases in the early hydration transform to long rod shape, and to finally fine-needle at 28 d.

The wettability, surfactivity and the correlation between wettability and surfactivity of sodium diethylhexylphosphate, sodium diethylhexyl polyoxyethylene phosphate and their complex in NaOH solutions were studied. A complex alkali resistant phosphate surfactant with good permeability was prepared. The wettability of surfactants was investigated by measuring the immersion time, sinking time and capillary effects of nature cotton grey fabric in NaOH solutions. The surfactivity of the surfactants was characterized by measuring the surface tension. The effect of the complex on the surface appearance of cotton grey fabric was also investigated with a scanning electron microscope (SEM). The results show that all the surfactants exhibit good wettability for cotton grey fabric in 0.5–5.0 mol/L of NaOH solutions, the complex system exhibits better wettability in 5.0–7.0 mol/L of NaOH solutions, in comparison with either corresponding single surfactant component employed, and wettability is well correlative with the surfactivities of the surfactant. SEM images indicate that the cotton grey fabric is well wetted by the alkaline surfactant solution and the quality of fabric is improved.

A new additive of sodium hexametaphosphate (SHMP) was introduced to the paste of zinc electrode, with the purpose of preventing the zinc active materials from agglomerating and improving the stability of batteries. The properties of the zinc electrodes were characterized by scanning electron microscopy (SEM), constant current charge/discharge measurement, self-discharge test and hydrogen collection experiment. The photographs of zinc electrode show that SHMP can significantly break up the agglomeration, uniformize the particle distribution and increase the surface area, which are advantageous to improve the electrochemical performance of zinc electrode. The experimental battery shows a 97 times cycling life and a 30.2% remaining capacity after 4 d storage. The hydrogen collection experimental results indicate that the SHMP can decrease the ratio of hydrogen evolution. Therefore, the corrosion of zinc electrode is suppressed and the charge/discharge efficiency is enhanced.

A new multifunctional mPEG-b-PAA-grafted chitosan copolymer possessing amino and carboxyl groups, mPEG-b-PAA-g-CHI (compound 6), was designed for a potential application in gene/drug delivery and synthesized by the methods of reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylic acid (AA) and grafting reaction of a biodegradable chitosan (CHI) derivative. Completion of the reactions and characterization of the resulting compounds were demonstrated by ¹H NMR, FTIR and gel permeation chtomatography (GPC) studies. The results show that the molar ratio of amino groups to carboxyl groups in the copolymer (compound 6) is 0.41:0.59.

Using carbon felt, polytetrafluoroethylene latex and powder catalyst to assembly a light energy conversion device, the photocatalytic activity of catalyst 2.0%WO₃-TiO₂ (2%WO₃ compounding TiO₂) with oxygen vacancies was studied through the water splitting for O₂ evolution, using a high pressure mercury lamp as the light source and Fe³⁺ as the electron acceptor in two different devices: an ordinary photolysis device with catalyst powder suspending through a magnetic stirrer and a self-assembly light energy conversion device. The results show that after 12 h irradiation, the photocatalytic activity of 2.0%WO₃-TiO₂ with oxygen vacancies in the self-assembly light energy conversion device is higher than that of the ordinary photolysis device, and the amount of oxygen evolution is about 12 and 9 mmol/L respectively in these two devices. After 12 h, the rates of O₂ evolution are slow in each device and the photocatalyst almost loses the photoactivity in the ordinary photolysis device. So, compared with the ordinary photocatalytic device, the rate of oxygen evolution and the life time of the catalyst are improved in the self-assembly light energy conversion device.

The research on the rock burst prediction was made on the basis of seismology, rock mechanics and the data from Dongguashan Copper Mine (DCM), the deepest metal mine in China. The seismic responses to mining in DCM were investigated through the analyses of the spatio-temporal distribution of hypocenters, apparent stress and displacement of seismic events, and the process of the generation of hazardous seismicity in DCM was studied in the framework of the theory of asperity in the seismic source mechanism. A method of locating areas with hazardous seismicity and a conceptual model of hazardous seismic nucleation in DCM were proposed. A criterion of rockburst prediction was analyzed theoretically in the framework of unstable failure theories, and consequently, the rate of change in the ratio of the seismic stiffness of rock in a seismic nucleation area to that in surrounding area, dS/dt, is defined as an index of the rockburst prediction. The possibility of a rockburst will increase if dS/dt>0, and the possibility of rock burst will decrease if dS/dt<0. The correctness of these methods is demonstrated by analyses of rock failure cases in DCM.

In light of the problems of low-quality and low degree of comprehensive utilization of Guangdong muscovite-type kaolin, the reasons affecting the quality of kaolin were found to be a small amount of maroon powdery goethite adhering to the surface of kaolin and minor muscovite affecting the firing whiteness of products. The ores were dealt with by using the new combined process of attritioning-classification-bleaching and flotation. The separation of kaolin from muscovite, quartz and feldspar can come true through the new process. The high-quality kaolin with the firing whiteness of 91% can be obtained, and the muscovite is comprehensively recovered by adopting the key technology of flotation. The content of high-purity muscovite produced is over 99%. The muscovite discarded by original process can be comprehensively recovered.

A gram negative bacterium, named JDC-16, which can grow well on the substrate of phthalic acid esters (PAEs) as the sole source of carbon and energy, was isolated from river sludge. Based on the morphology, physiological and biochemical properties and analysis of 16S rRNA gene sequence, it was preliminarily identified belonging to the genus Acinetobacter. The result of substrates utilization range indicates that strain JDC-16 can utilize a variety of phthalates except for diisononyl phthalate (DINP). The degradation tests using diethyl phthalate (DEP) as the model compound show that the optimal pH and temperature for DEP degradation by Acinetobacter sp. JDC-16 is 8.0 and 35 °C, respectively. Meanwhile, degradation kinetics under various initial concentrations of DEP reveals that substrate depletion curves fit well with the modified Gompertz model with high correlation coefficient (R²>0.99). Furthermore, the substrate induction test indicates that DEP-induction can apparently shorten the lag phase and enhance the degradation rate. This work highlights the potential of this isolate for bioremediation of phthalates-contaminated environments.

Physical and chemical properties of electric arc furnace (EAF) dust from Tianjin seamless Pipe Company were measured and analyzed. The zinc leaching tests in alkaline medium were carried out under variation of leaching agent concentration, leaching temperature, leaching cumulative time and solid-to-liquid ratio. The thermodynamics and kinetics of the zinc leaching process were also analyzed. The results show that the EAF dust contains 10% (mass fraction) zinc and the median particle size is 0.69 μm. The zinc recovery of 73.4% is obtained under the condition of 90 °C, 6 mol/L NaOH, and 60 min leaching time. With the increase of concentration of NaOH and the cumulative time, zinc leaching will be significantly increased. The kinetics study demonstrates that the leaching reaction is chemically controlled and the reaction activation energy is 15.73 kJ/mol.

The isotherm, mechanism and kinetics of carbon tetrachloride (CT) adsorption by polyacrylonitrile-based activated carbon fiber (PAN-ACF) were investigated in batch reactors and a continuous flow reactor, and the regeneration of PAN-ACF was also studied. Freundlich and Dubinin-Radushkevich (D-R) adsorption equations can well describe the adsorption isotherm. CT is mainly adsorbed on the exterior surface of PAN-ACF with low boundary layer effect and rate-controlling step of intra-particle diffusion. The adsorption dynamics in the batch reactor well fits with the pseudo-first-order model, and the breakthrough curves in the continuous flow reactor can be well described by the Yoon-Nelson model. The ACF can be recycled through thermal regeneration, whereas the adsorption capacity decreases from 7.87 to 4.98 mg/g after the fourth regeneration. 78%–94% of CT can be removed from the wastewater of a fluorine chemical plant on a pilot scale, which confirms the efficacy of ACF under industrial conditions. The results indicate that PAN-ACF is applicable to CT removal from wastewater.

The effectiveness of a magnetic ion exchange resin (MIEX) for the treatment of Hongze Lake water in China was evaluated. The kinetics of natural organic matter (NOM) removal at various MIEX doses and contact time, multiple-loading experiments, impacts of MIEX prior to coagulation on coagulant demands and the effectiveness of combination of MIEX, pre-chlorination and coagulation were investigated. Kinetic experimental results show that more than 80% UV₂₅₄ and 67% dissolved organic carbon (DOC) from raw water can be removed by the use of MIEX alone. 94% sulfate, 69% nitrate and 98% bromide removals are obtained after the first use of MIEX in multiple-loading experiments. It is suggested that MIEX can be loaded up to 1 250 bed volume (BV, volume ratio of tested water to resin) or more without saturation when regarding organics removal as a target. MIEX can remove organics to a greater extend than coagulation and lower the coagulant demand when combining with coagulation. Chlorination experimental results show that MIEX can remove 57% chlorine demand and 77% trihalomethane formation potential (THMFP) for raw water. Pre-chlorination followed by MIEX and coagulation can give additional organic and THMFP removals. The results suggest that MIEX provides a new method to solve the problem algae reproduction.

A novel type of metal oxide/activated carbon catalyst was prepared by sol-gel method for the hydrolysis of carbonyl sulfide (COS). The influences of the calcination temperature, additive content (2.5%–10.0% Fe₂O₃, mass fraction) and the basic density of the activation process were thoroughly investigated. The surface of catalysts was characterized by Boehm titration. The products were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The results show that catalysts with 2.5%–5.0% Fe₂O₃ after calcining at 500 °C have superior activity. The conversion rate of COS increases with increasing the relative density of basic capacity loaded onto activated carbon(AC), and the activity follows the order: KOH>Na₂CO₃>NaHCO₃. Boehm titration data clearly show that the total acidity increases (from 0.06 to 0.48 mmol/g) and the basic groups decrease (from 0.78 to 0.56 mmol/g) after COS hydrolysis and H₂S adsorption. The XPS results show that the product of H₂S may be absorbed by the interaction with metal compounds and O₂ to form sulfate (171.28 eV) and element sulfur (164.44 eV), which lead to catalysts poisoning.

To deploy sensor nodes over the area of interest, a scheme, named node scattering manipulation, was proposed. It adopted the following method: during node scattering, the initial states of every node, including the velocity and direction, were manipulated so that it would land in a region with a certain probability; every sensor was relocated in order to improve the coverage and connectivity. Simultaneously, to easily analyze the process of scattering sensors, a trajectory model was also proposed. Integrating node scattering manipulation with trajectory model, the node deployment in wireless sensor network was thoroughly renovated, that is, this scheme can scatter sensors. In practice, the scheme was operable compared with the previous achievements. The simulation results demonstrate the superiority and feasibility of the scheme, and also show that the energy consumption for sensors relocation is reduced.

According to the concept of virtual bending force, a rational explanation for SHOHET’s model was presented. Considering the deformation characters of the work rolls in four-high mill, the deformation model of the work roll was regarded as a cantilever beam and new influence coefficients were deduced. The effect of the bending force was taken into account independently. Therefore, the contribution to work roll deflection caused by rolling load, rolling pressure between rolls and bending force can be got from the new formulas. To validate the accuracy of the formulas, the results obtained from the new formulas were compared with those from SHOHET’s formulas. It is found that they highly coincide, which illustrates that the formulas are reliable.

An analytical algorithm was presented for the exact computation of the probability distribution of the project completion time in stochastic networks, where the activity durations are mutually independent and continuously distributed random variables. Firstly, stochastic activity networks were modeled as continuous-time Markov process with a single absorbing state by the well-know method of supplementary variables and the time changed from the initial state to absorbing state is equal to the project completion time. Then, the Markov process was regarded as a special case of Markov skeleton process. By taking advantage of the backward equations of Markov skeleton processes, a backward algorithm was proposed to compute the probability distribution of the project completion time. Finally, a numerical example was solved to demonstrate the performance of the proposed methodology. The results show that the proposed algorithm is capable of computing the exact distribution function of the project completion time, and the expectation and variance are obtained.

A 512-bit EEPROM IP was designed by using just logic process based devices. To limit the voltages of the devices within 5.5 V, EEPROM core circuits, control gate (CG) and tunnel gate (TG) driving circuits, DC-DC converters: positive pumping voltage (V_PP=4.75 V), negative pumping voltage (V_NN=−4.75 V), and V_NNL(=V_NN/2) generation circuit were proposed. In addition, switching powers CG high voltage (CG_HV), CG low voltage (CG_LV), TG high voltage (TG_HV), TG low voltage (TG_LV), V_{NNL_CG} and V_{NNL_TG} switching circuit were supplied for the CG and TG driving circuit. Furthermore, a sequential pumping scheme and a new ring oscillator with a dual oscillation period were proposed. To reduce a power consumption of EEPROM in the write mode, the reference voltages V_{REF_VPP} for V_PP and V_{REE_VNN} for V_NN were used by dividing V_DD (1.2 V) supply voltage supplied from the analog block in stead of removing the reference voltage generators. A voltage level detector using a capacitive divider as a low-power DC-DC converter design technique was proposed. The result shows that the power dissipation is 0.34 μW in the read mode, 13.76 μW in the program mode, and 13.66 μW in the erase mode.

In the process of numerical control machining simulation, the workpiece surface is usually described with the uniform triangular mesh model. To alleviate the contradiction between the simulation speed and accuracy in this model, two improved methods, i.e., the local refinement triangular mesh modeling method and the adaptive triangular mesh modeling method were presented. The simulation results show that when the final shape of the workpiece is known and its mathematic representation is simple, the local refinement triangular mesh modeling method is preferred; when the final shape of the workpiece is unknown and its mathematic description is complicated, the adaptive triangular mesh modeling method is more suitable. The experimental results show that both methods are more targeted and practical and can meet the requirements of real-time and precision in simulation.

To preserve the original signal as much as possible and filter random noises as many as possible in image processing, a threshold optimization-based adaptive template filtering algorithm was proposed. Unlike conventional filters whose template shapes and coefficients were fixed, multi-templates were defined and the right template for each pixel could be matched adaptively based on local image characteristics in the proposed method. The superiority of this method was verified by former results concerning the matching experiment of actual image with the comparison of conventional filtering methods. The adaptive search ability of immune genetic algorithm with the elitist selection and elitist crossover (IGAE) was used to optimize threshold t of the transformation function, and then combined with wavelet transformation to estimate noise variance. Multi-experiments were performed to test the validity of IGAE. The results show that the filtered result of t obtained by IGAE is superior to that of t obtained by other methods, IGAE has a faster convergence speed and a higher computational efficiency compared with the canonical genetic algorithm with the elitism and the immune algorithm with the information entropy and elitism by multi-experiments.

An approach for parameter estimation of proportional-integral-derivative (PID) control system using a new nonlinear programming (NLP) algorithm was proposed. SQP/IIPM algorithm is a sequential quadratic programming (SQP) based algorithm that derives its search directions by solving quadratic programming (QP) subproblems via an infeasible interior point method (IIPM) and evaluates step length adaptively via a simple line search and/or a quadratic search algorithm depending on the termination of the IIPM solver. The task of tuning PI/PID parameters for the first- and second-order systems was modeled as constrained NLP problem. SQP/IIPM algorithm was applied to determining the optimum parameters for the PI/PID control systems. To assess the performance of the proposed method, a Matlab simulation of PID controller tuning was conducted to compare the proposed SQP/IIPM algorithm with the gain and phase margin (GPM) method and Ziegler-Nichols (ZN) method. The results reveal that, for both step and impulse response tests, the PI/PID controller using SQP/IIPM optimization algorithm consistently reduce rise time, settling-time and remarkably lower overshoot compared to GPM and ZN methods, and the proposed method improves the robustness and effectiveness of numerical optimization of PID control systems.

A unilateral self-locking mechanism (USM) was proposed to increase the tractive ability of the inchworm in-pipe robots for pipeline inspection. The USM was basically composed of a cam, a torsional spring and an axis. The self-locking and virtual work principles were applied to studying the basic self-locking condition of the USM. In order to make the cooperation between the crutch and telescopic mechanism more harmonical, the unlocking time of the USM was calculated. A set of parameters were selected to build a virtual model and fabricate a prototype. Both the simulation and performance experiments were carried out in a pipe with a nominal inside diameter of 160 mm. The results show that USM enables the robot to move quickly in one way, and in the other way it helps the robot get self-locking with the pipe wall. The traction of the inchworm robot can rise to 1.2 kN, beyond the limitation of friction of 0.497 kN.

In order to extract froth morphological feature, a bubble image adaptive segmentation method was proposed. Considering the image’s low contrast and weak froth edges, froth image was coarsely segmented by using fuzzy c means (FCM) algorithm. Through the attributes of size and shape pattern spectrum, the optimal morphological structuring element was determined. According to the optimal parameters, some image noises were removed with an improved area opening and closing by reconstruction operation, which consist of image regional markers, and the bubbles were finely separated from each other by watershed transform. The experimental results show that the structural element can be determined adaptively by shape and size pattern spectrum, and the froth image is segmented accurately. Compared with other froth image segmentation method, the proposed method achieves much high accuracy, based on which, the bubble size and shape features are extracted effectively.

High dimensional data clustering, with the inherent sparsity of data and the existence of noise, is a serious challenge for clustering algorithms. A new linear manifold clustering method was proposed to address this problem. The basic idea was to search the line manifold clusters hidden in datasets, and then fuse some of the line manifold clusters to construct higher dimensional manifold clusters. The orthogonal distance and the tangent distance were considered together as the linear manifold distance metrics. Spatial neighbor information was fully utilized to construct the original line manifold and optimize line manifolds during the line manifold cluster searching procedure. The results obtained from experiments over real and synthetic data sets demonstrate the superiority of the proposed method over some competing clustering methods in terms of accuracy and computation time. The proposed method is able to obtain high clustering accuracy for various data sets with different sizes, manifold dimensions and noise ratios, which confirms the anti-noise capability and high clustering accuracy of the proposed method for high dimensional data.

A series of centrifuge model tests of sandy slopes were conducted to study the dynamic behavior of pile-reinforced slopes subjected to various motions. Time histories of accelerations, bending moments and pile earth pressures were obtained during excitation of the adjusted El Centro earthquake and a cyclic motion. Under a realistic earthquake, the overall response of the pile-reinforced slope is lower than that of the non-reinforced slope. The histories of bending moments and dynamic earth pressures reach their maximums soon after shaking started and then remain roughly stable until the end of shaking. Maximum moments occur at the height of 3.5 m, which is the deeper section of the pile, indicating the interface between the active loading and passive resistance regions. The dynamic earth pressures above the slope base steadily increase with the increase of height of pile. For the model under cyclic input motion, response amplitudes at different locations in the slope are almost the same, indicating no significant response amplification. Both the bending moment and earth pressure increase gradually over a long period.

In order to numerically simulate the failure process of rock and concrete under uniaxial tension, an improved method of selecting the mechanical properties of materials was presented for the random mechanic parameter model based on the mesoscopic damage mechanics. The product of strength and elastic modulus of mesoscale representative volume element was considered to be one of the mechanical property parameters of materials and assumed to conform to specified probability distributions to reflect the heterogeneity of mechanical property in materials. With the improved property parameter selection method, a numerical program was developed and the simulation of the failure process of the rock and concrete specimens under static tensile loading condition was carried out. The failure process and complete stress-strain curves of a class of rock and concrete in stable fracture propagation manner under uniaxial tension were obtained. The simulated macroscopic mechanical behavior was compared with the available laboratory experimental observation, and a reasonable agreement was obtained. Verification shows that the improved parameter selection method is suitable for mesoscopic numerical simulation in the failure process of rock and concrete.

A simplified method was proposed for the design of concrete lining in underground rock cavern/tunnel against shock loading. The loading may result from the detonation of explosives on ground surface or ground penetration projectiles exploding adjacent to the cavern/tunnel. The resulting problem necessitates the solution of the dynamics of a beam loaded by a transient pressure uniformly distributed over the span. According to mechanical characteristics of the system with rock bolt and shotcrete, a dynamic support design method based on equivalent single degree of freedom (SDOF) was put forward. The SDOF method was applied to obtaining the maximum displacement at the mid-span of the beam, which is often the controlling factor in the blast-resistant design. In the formulation of the problem, the proposed method combines the phenomena of spalling and structural dynamics theory. An example is provided to demonstrate the applicability of this simplified method.

In order to investigate the influence of intermediate principal stress on the stress-strain and strength behaviour of a coarse-grained soil, a series of true triaxial tests were performed. The tests were conducted in a recently developed true triaxial apparatus with constant minor principal stress σ₃ and constant value of intermediate principal stress ratio b=(σ₂−σ₃)/(σ₁−σ₃) (σ₁ is the vertical stress, and σ₂ is the horizontal stress). It is found that the intermediate principal strain, ɛ₂, increases from negative to positive value with the increase of parameter b from zero to unity under a constant minor principal stress. The minor principal strain, ɛ₃, is always negative. This implies that the specimen exhibits an evident anisotropy. The relationship between b and friction angle obtained from the tests is different from that predicted by LADE-DUNCAN and MATSUOKA-NAKAI criteria. Based on the test results, an empirical equation of g(b) that is the shape function of the failure surface on π-plane was presented. The proposed equation is verified to be reasonable by comparing the predicted results using the equation with true triaxial test results of soils, such as coarse-grained soils in this study, sands and gravels in other studies.

The effects of fire exposure, reinforcement ratio and the presence of axial load under fire on the seismic behavior of reinforced concrete (RC) shear walls were investigated. Five RC shear walls were tested under low cyclic loading. Prior to the cyclic test, three specimens were exposed to fire and two of them were also subjected to a constant axial load. Test results indicate that the ultimate load of the specimen with lower reinforcement ratio is reduced by 15.8% after exposure to elevated temperatures. While the reductions in the energy dissipation and initial stiffness are 59.2% and 51.8%, respectively, which are much higher than those in the ultimate load. However, this deterioration can be slowed down by properly increasing reinforcement due to the strength and stiffness recovery of steel bars after cooling. In addition, the combined action of elevated temperatures and axial load results in more energy dissipation than the action of fire exposure alone.

The impact of vibrations due to underground trains on Beijing metro line 15 on sensitive equipment in the Institute of Microelectronics of Tsinghua University was discussed to propose a viable solution to mitigate the vibrations. Using the state-of-the-art three-dimensional coupled periodic finite element-boundary element (FE-BE) method, the dynamic track-tunnel-soil interaction model for metro line 15 was used to predict vibrations in the free field at a train speed of 80 km/h. Three types of tracks (direct fixation fasteners, floating slab track and floating ladder track) on the Beijing metro network were considered in the model. For each track, the acceleration response in the free field was obtained. The numerical results show that the influence of vibrations from underground trains on sensitive equipment depends on the track types. At frequencies above 10 Hz, the floating slab track with a natural frequency of 7 Hz can be effective to attenuate the vibrations.

The influence of heterogeneity on mechanical and acoustic emission characteristics of rock specimen under uniaxial compress was studied with numerical simulation methods. Weibull distribution function was adopted to describe the mesoscopic heterogeneity of rocks. The failure process of heterogeneous rock specimen under uniaxial loading was simulated using FLAC^3D software. Five schemes were adopted to investigate the influence of heterogeneity. The results demonstrate that as the homogeneity increases, the peak strength and brittleness of rocks increase, and the macro elastic modulus improves as well. Heterogeneity has great influence on macro elastic modulus and strength when the homogeneity coefficient is less than 20.0. The volume expansion is not so obvious when the homogeneity increases. As the homogeneity coefficient increases the acoustic emissions modes change from swarm shock to main shock. When the homogeneity coefficient is high, the cumulative acoustic emission events-axial strain curve is gentle before the rock failure. The numerical results agree with the previously numerical results and earlier experimental measurements.